WorldWideScience

Sample records for hexavalent cr crvi

  1. Biodegradation of the metallic carcinogen hexavalent chromium Cr(VI) by an indigenously isolated bacterial strain

    National Research Council Canada - National Science Library

    Das, Alok Prasad; Mishra, Susmita

    2010-01-01

    Hexavalent chromium [Cr(VI)], a potential mutagen and carcinogen, is regularly introduced into the environment through diverse anthropogenic activities, including electroplating, leather tanning, and pigment manufacturing...

  2. Biodegradation of the metallic carcinogen hexavalent chromium Cr(VI by an indigenously isolated bacterial strain

    Directory of Open Access Journals (Sweden)

    Das Alok

    2010-01-01

    Full Text Available Background : Hexavalent chromium [Cr(VI], a potential mutagen and carcinogen, is regularly introduced into the environment through diverse anthropogenic activities, including electroplating, leather tanning, and pigment manufacturing. Human exposure to this toxic metal ion not only causes potential human health hazards but also affects other life forms. The World Health Organization, the International Agency for Research on Cancer, and the Environmental Protection Agency have determined that Cr(VI compounds are known human carcinogens. The Sukinda valley in Jajpur District, Orissa, is known for its deposit of chromite ore, producing nearly 98% of the chromite ore in India and one of the prime open cast chromite ore mines in the world (CES, Orissa Newsletter. Materials and Methods: Our investigation involved microbial remediation of Cr(VI without producing any byproduct. Bacterial cultures tolerating high concentrations of Cr were isolated from the soil sample collected from the chromite-contaminated sites of Sukinda, and their bioaccumulation properties were investigated. Strains capable of growing at 250 mg/L Cr(VI were considered as Cr resistant. Results: The experimental investigation showed the maximum specific Cr uptake at pH 7 and temperature 30oC. At about 50 mg/L initial Cr(VI concentrations, uptake of the selected potential strain exceeded 98% within 12 h of incubation. The bacterial isolate was identified by 16S rRNA sequencing as Brevebacterium casei. Conclusion: Results indicated promising approach for microbial remediation of effluents containing elevated levels of Cr(VI.

  3. Simultaneously photocatalytic treatment of hexavalent chromium (Cr(VI)) and endocrine disrupting compounds (EDCs) using rotating reactor under solar irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Youngji [Korea Institute of Energy Research, New and Renewable Energy Research Division, Hydrogen Laboratory, 152 Gajeong-ro, Yuseong-gu, Daejeon 305-343 (Korea, Republic of); Yonsei University, Department of Chemical and Biomolecular Engineering, 134 Shinchon-dong, Seodaemun-gu, Seoul 120-749 (Korea, Republic of); Joo, Hyunku [Korea Institute of Energy Research, New and Renewable Energy Research Division, Hydrogen Laboratory, 152 Gajeong-ro, Yuseong-gu, Daejeon 305-343 (Korea, Republic of); Her, Namguk [Korea Army Academy at Young-Cheon, Department of Chemistry and Environmental Science, 135-1 Changhari, Kokyungmeon, Young-cheon, Gyeongbuk 770-849 (Korea, Republic of); Yoon, Yeomin [University of South Carolina, Department of Civil and Environmental Engineering, Columbia, SC 29208 (United States); Sohn, Jinsik [Kookmin University, School of Civil and Environmental Engineering, 77 Jeongneung-ro, Seongbuk-gu, Seoul 136-702 (Korea, Republic of); Kim, Sungpyo [Korea University, Department of Environmental Engineering, Sejong 339-700 (Korea, Republic of); Yoon, Jaekyung, E-mail: jyoon@kier.re.kr [Korea Institute of Energy Research, New and Renewable Energy Research Division, Hydrogen Laboratory, 152 Gajeong-ro, Yuseong-gu, Daejeon 305-343 (Korea, Republic of)

    2015-05-15

    Highlights: • Self-rotating reactor including TiO{sub 2} NTs is applied under solar irradiation. • Simultaneously photocatalysis of Cr(VI) and EDCs is observed to be up to 95%. • Photocatalytic reactions of Cr(VI) and EDCs are favorable under acidic pH. • Charge interaction and hole scavenge between TiO{sub 2} and pollutants are synergy factors. - Abstract: In this study, simultaneous treatments, reduction of hexavalent chromium (Cr(VI)) and oxidation of endocrine disrupting compounds (EDCs), such as bisphenol A (BPA), 17α-ethinyl estradiol (EE2) and 17β-estradiol (E2), were investigated with a rotating photocatalytic reactor including TiO{sub 2} nanotubes formed on titanium mesh substrates under solar UV irradiation. In the laboratory tests with a rotating type I reactor, synergy effects of the simultaneous photocatalytic reduction and oxidation of inorganic (Cr(VI)) and organic (BPA) pollutants were achieved. Particularly, the concurrent photocatalytic reduction of Cr(VI) and oxidation of BPA was higher under acidic conditions. The enhanced reaction efficiency of both pollutants was attributed to a stronger charge interaction between TiO{sub 2} nanotubes (positive charge) and the anionic form of Cr(VI) (negative charge), which are prevented recombination (electron–hole pair) by the hole scavenging effect of BPA. In the extended outdoor tests with a rotating type II reactor under solar irradiation, the experiment was extended to examine the simultaneous reduction of Cr(VI) in the presence of additional EDCs, such as EE2 and E2 as well as BPA. The findings showed that synergic effect of both photocatalytic reduction and oxidation was confirmed with single-component (Cr(VI) only), two-components (Cr(VI)/BPA, Cr(VI)/EE2, and Cr(VI)/E2), and four-components (Cr(VI)/BPA/EE2/E2) under various solar irradiation conditions.

  4. Removal of hexavalent chromium [Cr(VI)] from aqueous solutions by the diatomite-supported/unsupported magnetite nanoparticles.

    Science.gov (United States)

    Yuan, Peng; Liu, Dong; Fan, Mingde; Yang, Dan; Zhu, Runliang; Ge, Fei; Zhu, JianXi; He, Hongping

    2010-01-15

    Diatomite-supported/unsupported magnetite nanoparticles were prepared by co-precipitation and hydrosol methods, and characterized by X-ray diffraction, nitrogen adsorption, elemental analysis, differential scanning calorimetry, transmission electron microscopy and X-ray photoelectron spectroscopy. The average sizes of the unsupported and supported magnetite nanoparticles are around 25 and 15 nm, respectively. The supported magnetite nanoparticles exist on the surface or inside the pores of diatom shells, with better dispersing and less coaggregation than the unsupported ones. The uptake of hexavalent chromium [Cr(VI)] on the synthesized magnetite nanoparticles was mainly governed by a physico-chemical process, which included an electrostatic attraction followed by a redox process in which Cr(VI) was reduced into trivalent chromium [Cr(III)]. The adsorption of Cr(VI) was highly pH-dependent and the kinetics of the adsorption followed a pseudo-second-order model. The adsorption data of diatomite-supported/unsupported magnetite fit well with the Langmuir isotherm equation. The supported magnetite showed a better adsorption capacity per unit mass of magnetite than unsupported magnetite, and was more thermally stable than their unsupported counterparts. These results indicate that the diatomite-supported/unsupported magnetite nanoparticles are readily prepared, enabling promising applications for the removal of Cr(VI) from aqueous solution.

  5. Cathodic reduction of hexavalent chromium [Cr(VI)] coupled with electricity generation in microbial fuel cells.

    Science.gov (United States)

    Wang, Gang; Huang, Liping; Zhang, Yifeng

    2008-11-01

    A novel approach to Cr(VI)-contaminated wastewater treatment was investigated using microbial fuel cell technologies in fed-batch mode. By using synthetic Cr(VI)-containing wastewater as catholyte and anaerobic microorganisms as anodic biocatalyst, Cr(VI) at 100 mg/l was completely removed during 150 h (initial pH 2). The maximum power density of 150 mW/m(2) (0.04 mA/cm(2)) and the maximum open circuit voltage of 0.91 V were generated with Cr(VI) at 200 mg/l as electron acceptor. This work verifies the possibility of simultaneous electricity production and cathodic Cr(VI) reduction.

  6. A plan for study of hexavalent chromium, CR(VI) in groundwater near a mapped plume, Hinkley, California, 2016

    Science.gov (United States)

    Izbicki, John A.; Groover, Krishangi

    2016-01-22

    The Pacific Gas and Electric Company (PG&E) Hinkley compressor station, in the Mojave Desert 80 miles northeast of Los Angeles, is used to compress natural gas as it is transported through a pipeline from Texas to California. Between 1952 and 1964, cooling water used at the compressor station was treated with a compound containing chromium to prevent corrosion. After cooling, the wastewater was discharged to unlined ponds, resulting in contamination of soil and groundwater in the underlying alluvial aquifer (Lahontan Regional Water Quality Control Board, 2013). Since 1964, cooling-water management practices have been used that do not contribute chromium to groundwater.In 2007, a PG&E study of the natural background concentrations of hexavalent chromium, Cr(VI), in groundwater estimated average concentrations in the Hinkley area to be 1.2 micrograms per liter (μg/L), with a 95-percent upper-confidence limit of 3.1 μg/L (CH2M-Hill, 2007). The 3.1 μg/L upper-confidence limit was adopted by the Lahontan Regional Water Quality Control Board (RWQCB) as the maximum background concentration used to map the plume extent. In response to criticism of the study’s methodology, and an increase in the mapped extent of the plume between 2008 and 2011, the Lahontan RWQCB (Lahontan Regional Water Quality Control Board, 2012) agreed that the 2007 PG&E background-concentration study be updated.The purpose of the updated background study is to evaluate the presence of natural and man-made Cr(VI) near Hinkley, Calif. The study also is to estimate natural background Cr(VI) concentrations in the aquifer upgradient and downgradient from the mapped Cr(VI) contamination plume, as well as in the plume and near its margins. The study was developed by the U.S. Geological Survey (USGS) in collaboration with a technical working group (TWG) composed of community members, the Independent Review Panel (IRP) Manager (Project Navigator, Ltd.), the Lahontan RWQCB, PG&E, and consultants for PG&E.&E.

  7. New approach in modeling Cr(VI) sorption onto biomass from metal binary mixtures solutions

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Chang [College of Environmental Science and Engineering, Anhui Normal University, South Jiuhua Road, 189, 241002 Wuhu (China); Chemical Engineering Department, Escola Politècnica Superior, Universitat de Girona, Ma Aurèlia Capmany, 61, 17071 Girona (Spain); Fiol, Núria [Chemical Engineering Department, Escola Politècnica Superior, Universitat de Girona, Ma Aurèlia Capmany, 61, 17071 Girona (Spain); Villaescusa, Isabel, E-mail: Isabel.Villaescusa@udg.edu [Chemical Engineering Department, Escola Politècnica Superior, Universitat de Girona, Ma Aurèlia Capmany, 61, 17071 Girona (Spain); Poch, Jordi [Applied Mathematics Department, Escola Politècnica Superior, Universitat de Girona, Ma Aurèlia Capmany, 61, 17071 Girona (Spain)

    2016-01-15

    In the last decades Cr(VI) sorption equilibrium and kinetic studies have been carried out using several types of biomasses. However there are few researchers that consider all the simultaneous processes that take place during Cr(VI) sorption (i.e., sorption/reduction of Cr(VI) and simultaneous formation and binding of reduced Cr(III)) when formulating a model that describes the overall sorption process. On the other hand Cr(VI) scarcely exists alone in wastewaters, it is usually found in mixtures with divalent metals. Therefore, the simultaneous removal of Cr(VI) and divalent metals in binary mixtures and the interactive mechanism governing Cr(VI) elimination have gained more and more attention. In the present work, kinetics of Cr(VI) sorption onto exhausted coffee from Cr(VI)–Cu(II) binary mixtures has been studied in a stirred batch reactor. A model including Cr(VI) sorption and reduction, Cr(III) sorption and the effect of the presence of Cu(II) in these processes has been developed and validated. This study constitutes an important advance in modeling Cr(VI) sorption kinetics especially when chromium sorption is in part based on the sorbent capacity of reducing hexavalent chromium and a metal cation is present in the binary mixture. - Highlights: • A kinetic model including Cr(VI) reduction, Cr(VI) and Cr(III) sorption/desorption • Synergistic effect of Cu(II) on Cr(VI) elimination included in the model • Model validation by checking it against independent sets of data.

  8. Novel reduction of Cr(VI) from wastewater using a naturally derived microcapsule loaded with rutin-Cr(III) complex.

    Science.gov (United States)

    Qi, Yun; Jiang, Meng; Cui, Yuan-Lu; Zhao, Lin; Liu, Shejiang

    2015-03-21

    The harmfulness of carcinogenic hexavalent chromium (Cr(VI)) is dramatically decreased when Cr(VI) is reduced to trivalent chromium (Cr(III)). Rutin, a natural flavonoid, exhibits excellent antioxidant activity by coordinating metal ions. In this study, a complex containing rutin and Cr(III) (rutin-Cr(III)) was synthesized and characterized. The rutin-Cr(III) complex was much easier to reduce than rutin. The reduction of the rutin-Cr(III) complex was highly pH-dependent, with 90% of the Cr(VI) being reduced to Cr(III) in 2h under optimal conditions. A biodegradable, sustained-release system encapsulating the rutin-Cr(III) complex in a alginate-chitosan microcapsule (rutin-Cr(III) ACMS) was also evaluated, and the reduction of Cr(VI) was assessed. This study also demonstrated that low-pH solutions increased the reduction rate of Cr(VI). The environmentally friendly microcapsules can reduce Cr(VI) for prolonged periods of time and can easily biodegrade after releasing the rutin-Cr(III) complex. Given the excellent performance of rutin-Cr(III) ACMS, the microcapsule system represents an effective system for the remediation of Cr(VI) pollution.

  9. Removal of Cr(VI) from groundwater by Fe(0)

    Science.gov (United States)

    Gao, Yanjiao; Liu, Rui

    2016-12-01

    This research was conducted to investigate the treatment of hexavalent chromium (Cr(VI)) by iron powder (Fe(0)) columns of simulated permeable reactive barriers with and without calcium carbonate (CaCO3). Two columns filled with Fe(0) were used as Cr(VI) removal equipment running at a flow velocity of 10 ml/min at room temperature. After 200 days running of the two columns, the results showed that Fe(0) was an effective material for Cr(VI) reduction with an average removal rate of above 84.6%. The performance of Column 2 with CaCO3 was better than Column 1 without CaCO3 in terms of average Cr(VI) removal rate. The presence of CaCO3 buffered the increasing pH caused by Fe(0) corrosion in Column 2 and enhanced the removal rate of Column 2. Scanning Electron Microscopy (SEM) images of Fe(0) in the three stages of running of the two columns illustrated that the coat layer of Column 1 was a little thicker than that of Column 2. Energy-dispersive spectrometry (EDS) results showed that the surface of Fe(0) of Column 2 contained more chromium elements. Raman spectroscopy found that all iron oxide was generated on the Fe(0) surface of Column 1 and Column 2 and chromium class objects were only detected on Fe(0) surface in Column 2.

  10. Modeling of kinetics of Cr(VI) sorption onto grape stalk waste in a stirred batch reactor.

    Science.gov (United States)

    Escudero, Carlos; Fiol, Nuria; Poch, Jordi; Villaescusa, Isabel

    2009-10-15

    Recently, Cr(VI) removal by grape stalks has been postulated to follow two mechanisms, adsorption and reduction to trivalent chromium. Nevertheless, the rate at which both processes take place and the possible simultaneity of both processes has not been investigated. In this work, kinetics of Cr(VI) sorption onto grape stalk waste has been studied. Experiments were carried out at different temperatures but at a constant pH (3+/-0.1) in a stirred batch reactor. Results showed that three steps take place in the process of Cr(VI) sorption onto grape stalk waste: Cr(VI) sorption, Cr(VI) reduction to Cr(III) and the adsorption of the formed Cr(III). Taking into account the evidences above mentioned, a model has been developed to predict Cr(VI) sorption on grape stalks on the basis of (i) irreversible reduction of Cr(VI) to Cr(III) reaction, whose reaction rate is assumed to be proportional to the Cr(VI) concentration in solution and (ii) adsorption and desorption of Cr(VI) and formed Cr(III) assuming that all the processes follow Langmuir type kinetics. The proposed model fits successfully the kinetic data obtained at different temperatures and describes the kinetics profile of total, hexavalent and trivalent chromium. The proposed model would be helpful for researchers in the field of Cr(VI) biosorption to design and predict the performance of sorption processes.

  11. Modelling Cr(VI) removal by a combined carbon-activated sludge system

    Energy Technology Data Exchange (ETDEWEB)

    Orozco, A. Micaela Ferro [Centro de Investigacion y Desarrollo en Criotecnologia de Alimentos (CIDCA), CONICET, Fac. de Cs. Exactas, UNLP. 47 y 116 (B1900AJJ), La Plata (Argentina); Contreras, Edgardo M. [Centro de Investigacion y Desarrollo en Criotecnologia de Alimentos (CIDCA), CONICET, Fac. de Cs. Exactas, UNLP. 47 y 116 (B1900AJJ), La Plata (Argentina)], E-mail: econtrer@quimica.unlp.edu.ar; Zaritzky, Noemi E. [Centro de Investigacion y Desarrollo en Criotecnologia de Alimentos (CIDCA), CONICET, Fac. de Cs. Exactas, UNLP. 47 y 116 (B1900AJJ), La Plata (Argentina); Fac. de Ingenieria, UNLP. 47 y 1 (B1900AJJ), La Plata (Argentina)

    2008-01-15

    The combined carbon-activated sludge process has been proposed as an alternative to protect the biomass against toxic substances in wastewaters; however, the information about the effect of powdered-activated carbon (PAC) addition in activated sludge reactors for the treatment of wastewaters containing Cr(VI) is limited. The objectives of the present study were: (a) to evaluate the removal of hexavalent chromium by (i) activated sludge microorganisms in aerobic batch reactors, (ii) powdered-activated carbon, and (iii) the combined action of powdered-activated carbon and biomass; (b) to propose mathematical models that interpret the experimental results. Different Cr(VI) removal systems were tested: (S1) biomass (activated sludge), (S2) PAC, and (S3) the combined activated carbon-biomass system. A Monod-based mathematical model was used to describe the kinetics of Cr(VI) removal in the system S1. A first-order kinetics with respect to Cr(VI) and PAC respectively, was proposed to model the removal of Cr(VI) in the system S2. Cr(VI) removal in the combined carbon-biomass system (S3) was faster than both Cr(VI) removal using PAC or activated sludge individually. Results showed that the removal of Cr(VI) using the activated carbon-biomass system (S3) was adequately described by combining the kinetic equations proposed for the systems S1 and S2.

  12. Remediation of Cr(VI) contaminated soil using long-duration sodium thiosulfate supported by micro–nano networks

    Energy Technology Data Exchange (ETDEWEB)

    He, Lulu [School of Life Sciences, Anhui Agricultural University, Hefei 230036 (China); Key Laboratory of Ion Beam Bioengineering, Hefei Institutes of Physical Science, Chinese Academy of Sciences and Anhui Province, Hefei, Anhui 230031 (China); Wang, Min; Zhang, Guilong [Key Laboratory of Ion Beam Bioengineering, Hefei Institutes of Physical Science, Chinese Academy of Sciences and Anhui Province, Hefei, Anhui 230031 (China); Bioenergy Forest Research Center of State Forestry Administration, Hefei 230031 (China); Qiu, Guannan [Key Laboratory of Ion Beam Bioengineering, Hefei Institutes of Physical Science, Chinese Academy of Sciences and Anhui Province, Hefei, Anhui 230031 (China); Cai, Dongqing, E-mail: dqcai@ipp.ac.cn [Key Laboratory of Ion Beam Bioengineering, Hefei Institutes of Physical Science, Chinese Academy of Sciences and Anhui Province, Hefei, Anhui 230031 (China); Bioenergy Forest Research Center of State Forestry Administration, Hefei 230031 (China); Wu, Zhengyan, E-mail: zywu@ipp.ac.cn [Key Laboratory of Ion Beam Bioengineering, Hefei Institutes of Physical Science, Chinese Academy of Sciences and Anhui Province, Hefei, Anhui 230031 (China); Bioenergy Forest Research Center of State Forestry Administration, Hefei 230031 (China); Zhang, Xin, E-mail: xinzhang@ahau.edu.cn [School of Life Sciences, Anhui Agricultural University, Hefei 230036 (China)

    2015-08-30

    Highlights: • This work aims to develop a long-duration remediation agent (LRA). • LRA was obtained using Na{sub 2}S{sub 2}O{sub 3} supported by attapulgite (ATP) micro–nano networks. • ATP micro–nano networks was induced by high-energy electron beam irradiation. • LRA can effectively control the migration of Cr(VI) and reducing Cr(VI) to Cr(III). • LRA displayed high performance on the remediation of heavy metal contaminated soil. - Abstract: In this work, a long-duration remediation agent (LRA) on hexavalent chromium (Cr(VI)) was developed using sodium thiosulfate (ST) supported by attapulgite (ATP) micro–nano networks induced through high-energy electron beam (HEEB) irradiation. The ATP networks could effectively reduce the leaching amount of Cr(VI) in soil. More importantly, the ATP networks could significantly control the leaching behavior of ST, and then prolong the duration and increase the reduction efficiency of ST on Cr(VI). As a result, LRA displayed high performance on controlling the migration of Cr(VI) and reducing Cr(VI) to Cr(III). Additionally, pot experiment indicated that LRA could effectively decrease the absorbed amount of Cr(VI) in corn, and reduce the inhibition effect of Cr(VI) on the growth of corn. Therefore, this work could provide a facile approach to remediate the Cr(VI)-contaminated soil and lower the harmful effect of Cr(VI) on crop.

  13. Cr(VI) Adsorption on Red Mud Modified by Lanthanum: Performance, Kinetics and Mechanisms.

    Science.gov (United States)

    Cui, You-Wei; Li, Jie; Du, Zhao-Fu; Peng, Yong-Zhen

    Water pollution caused by the highly toxic metal hexavalent chromium (Cr(VI)) creates significant human health and ecological risks. In this study, a novel adsorbent was used to treat Cr(VI)-containing wastewater; the adsorbent was prepared using red mud (RM) generated from the alumina production industry and the rare earth element lanthanum. This study explored adsorption performance, kinetics, and mechanisms. Results showed that the adsorption kinetics of the RM modified by lanthanum (La-RM), followed the pseudo-second-order model, with a rapid adsorption rate. Cr(VI) adsorption was positively associated with the absorbent dose, pH, temperature, and initial Cr(VI) concentration; coexisting anions had little impact. The maximum Cr(VI) adsorption capacity was 17.35 mg/g. Cr(VI) adsorption on La-RM was a mono-layer adsorption pattern, following the Langmuir isotherm model. Thermodynamic parameters showed the adsorption was spontaneous and endothermic. The adsorption of Cr(VI) on La-RM occurred as a result of LaOCl formation on the RM surface, which in turn further reacted with Cr(VI) in the wastewater. This study highlighted a method for converting industrial waste into a valuable material for wastewater treatment. The novel absorbent could be used as a potential adsorbent for treating Cr(VI)-contaminating wastewater, due to its cost-effectiveness and high adsorption capability.

  14. Cr(VI) Adsorption on Red Mud Modified by Lanthanum: Performance, Kinetics and Mechanisms

    Science.gov (United States)

    Cui, You-Wei; Li, Jie; Du, Zhao-Fu; Peng, Yong-Zhen

    2016-01-01

    Water pollution caused by the highly toxic metal hexavalent chromium (Cr(VI)) creates significant human health and ecological risks. In this study, a novel adsorbent was used to treat Cr(VI)-containing wastewater; the adsorbent was prepared using red mud (RM) generated from the alumina production industry and the rare earth element lanthanum. This study explored adsorption performance, kinetics, and mechanisms. Results showed that the adsorption kinetics of the RM modified by lanthanum (La-RM), followed the pseudo-second-order model, with a rapid adsorption rate. Cr(VI) adsorption was positively associated with the absorbent dose, pH, temperature, and initial Cr(VI) concentration; coexisting anions had little impact. The maximum Cr(VI) adsorption capacity was 17.35 mg/g. Cr(VI) adsorption on La-RM was a mono-layer adsorption pattern, following the Langmuir isotherm model. Thermodynamic parameters showed the adsorption was spontaneous and endothermic. The adsorption of Cr(VI) on La-RM occurred as a result of LaOCl formation on the RM surface, which in turn further reacted with Cr(VI) in the wastewater. This study highlighted a method for converting industrial waste into a valuable material for wastewater treatment. The novel absorbent could be used as a potential adsorbent for treating Cr(VI)-contaminating wastewater, due to its cost-effectiveness and high adsorption capability. PMID:27658113

  15. Cr(VI) occurrence and geochemistry in water from public-supply wells in California

    Science.gov (United States)

    Izbicki, John; Wright, Michael; Seymour, Whitney A.; McCleskey, R. Blaine; Fram, Miranda S.; Belitz, Kenneth; Esser, Bradley K.

    2015-01-01

    Hexavalent chromium, Cr(VI), in 918 wells sampled throughout California between 2004 and 2012 by the Groundwater Ambient Monitoring and Assessment-Priority Basin Project (GAMA-PBP) ranged from less than the study reporting limit of 1 microgram per liter (μg/L) to 32 μg/L. Statewide, Cr(VI) was reported in 31 percent of wells and equaled or exceeded the recently established (2014) California Maximum Contaminant Level (MCL) for Cr(VI) of 10 μg/L in 4 percent of wells. Cr(VI) data collected for regulatory purposes overestimated Cr(VI) occurrence compared to spatially-distributed GAMA-PBP data. Ninety percent of chromium was present as Cr(VI), which was detected more frequently and at higher concentrations in alkaline (pH ≥ 8), oxic water; and more frequently in agricultural and urban land uses compared to native land uses. Chemical, isotopic (tritium and carbon-14), and noble-gas data show high Cr(VI) in water from wells in alluvial aquifers in the southern California deserts result from long groundwater-residence times and geochemical reactions such as silicate weathering that increase pH, while oxic conditions persist. High Cr(VI) in water from wells in alluvial aquifers along the west-side of the Central Valley results from high-chromium in source rock eroded to form those aquifers, and areal recharge processes (including irrigation return) that can mobilize chromium from the unsaturated zone. Cr(VI) co-occurred with oxyanions having similar chemistry, including vanadium, selenium, and uranium. Cr(VI) was positively correlated with nitrate, consistent with increased concentrations in areas of agricultural land use and mobilization of chromium from the unsaturated zone by irrigation return.

  16. Cr(VI) reduction at rutile-catalyzed cathode in microbial fuel cells

    Energy Technology Data Exchange (ETDEWEB)

    Li, Yan; Lu, Anhuai; Ding, Hongrui; Yan, Yunhua; Wang, Changqiu; Zen, Cuiping; Wang, Xin [The Key Laboratory of Orogenic Belts and Crustal Evolution, School of Earth and Space Sciences, Peking University, Beijing 100871 (China); Jin, Song [MWH Americas, 3665 JFK Parkway, Suite 206, Fort Collins, CO 80525 (United States); Department of Civil and Architectural Engineering, University of Wyoming, Laramie, WY 82071 (United States)

    2009-07-15

    Cathodic reduction of hexavalent chromium (Cr(VI)) and simultaneous power generation were successfully achieved in a microbial fuel cell (MFC) containing a novel rutile-coated cathode. The selected rutile was previously characterized to be sensitive to visible light and capable of both non-photo- and photocatalysis. In the MFCs containing rutile-coated cathode, Cr(VI) was rapidly reduced in the cathode chamber in presence and absence of light irradiation; and the rate of Cr(VI) reduction under light irradiation was substantially higher than that in the dark. Under light irradiation, 97% of Cr(VI) (initial concentration 26 mg/L) was reduced within 26 h, which was 1.6 x faster than that in the dark controls in which only background non-photocatalysis occurred. The maximal potential generated under light irradiation was 0.80 vs. 0.55 V in the dark controls. These results indicate that photocatalysis at the rutile-coated cathode in the MFCs might have lowered the cathodic overpotential, and enhanced electron transfer from the cathode to Cr(VI) for its reduction. In addition, photoexcited electrons generated during the cathode photocatalysis might also have contributed to the higher Cr(VI) reduction rates when under light irradiation. This work assessed natural rutile as a novel cathodic catalyst for MFCs in power generation; particularly it extended the practical merits of conventional MFCs to cathodic reduction of environmental contaminants such as Cr(VI). (author)

  17. Integrated reduction/oxidation reactions and sorption processes for Cr(VI) removal from aqueous solutions using Laminaria digitata macro-algae

    OpenAIRE

    Dittert, Ingrid M.; Pina, Frederico; Souza,Selene M. A. Guelli U. de; Botelho, Cid??lia M.S.; Vilar, V??tor J.P.; Boaventura, Rui A.R.; Souza, Ant??nio Augusto U. de; Silva, Eduardo A.B. da; Brand??o, Heloisa de Lima

    2015-01-01

    The main goal of this work was the valorization of seaweed Laminaria digitata, after acid pre-treatment, for the remediation of hexavalent chromium solutions. The Cr(VI) removal efficiency by the protonated biomass was studied as a function of different parameters, such as contact time, pH, biomass and Cr(VI) concentration, and temperature. Cr(VI) removal is based on a complex mechanism that includes a reduction of Cr(VI) to Cr(III), through the oxidation of biomass at acidic medi...

  18. Air Force Successes and Challenges in Cr(VI) Elimination

    Science.gov (United States)

    2011-05-10

    Cr(VI) has been used for 40+ years and is an excellent corrosion inhibitor • Cr(VI) compounds are highly toxic • National & International...use of Cr(VI) • Suitable Substitutes for Specific Applications are being Actively Sought 3 Chrome Reduction Plan Description: • Reduce Cr(VI) and...ion vapor deposited Al, and Cd coatings 2. Use trivalent chromium [Cr(III)] conversion coating (CC) on Dipsol IZ- C17+ zinc- nickel (Zn-Ni) coating

  19. Cr(VI) Adsorption on Red Mud Modified by Lanthanum: Performance, Kinetics and Mechanisms

    OpenAIRE

    Cui, You-Wei; Li,Jie; Du, Zhao-Fu; Peng, Yong-Zhen

    2016-01-01

    Water pollution caused by the highly toxic metal hexavalent chromium (Cr(VI)) creates significant human health and ecological risks. In this study, a novel adsorbent was used to treat Cr(VI)-containing wastewater; the adsorbent was prepared using red mud (RM) generated from the alumina production industry and the rare earth element lanthanum. This study explored adsorption performance, kinetics, and mechanisms. Results showed that the adsorption kinetics of the RM modified by lanthanum (La-RM...

  20. Development of mathematical models for insitu bioremediation of Cr(VI) contaminated Aquifers

    Science.gov (United States)

    Vairavan, S.; Philip, L.; Bhallamudi, M. S.

    2009-12-01

    Hexavalent Chromium (Cr(VI)) is a contaminant of significant concern due to its carcinogenic and mutagenic property in mammals. Cr(VI) abatement in aquifers can be achieved by reducing chromium from its hexavalent state to trivalent state because Cr(III) is less toxic, insoluble and immobile compared to Cr(VI). Reduction of Cr(VI) by Fe(II)/S2- present in mineral deposits followed by precipitation as hydroxides and/or sulfides and adsorption of Cr(VI) over mineral deposits in the geological formations are predominant mechanisms which account for the natural attenuation of Cr(VI) inside an aquifer. Once the Cr(VI) concentration goes beyond the carrying capacity of the aquifer, it can be cleaned by constructing a Permeable Reactive Barrier (PRB) perpendicular to the direction of the flow of groundwater or by introducing Injection Wells (IW) along the direction of flow. In both the above mentioned cases addition of chemical reductants results in high costs. On the other hand, bacterial biotransformation of Cr(VI) in presence of organic matter seems to be a viable and eco friendly option for remediation of chromium contaminated aquifers. Enhancement of biotransformation of hexavalent chromium is expected in the presence of soil microbes such as Sulfate Reducing Bacteria (SRB) and Iron Reducing Bacteria (IRB) along with Chromium Reducing Bacteria (CRB). Groundwater usually contains sulfate and iron (dissolution from the mineral deposits) which can act as electron acceptor for IRB and SRB metabolism and yield biogenic reductants such as Fe2+, and S2- which abiotically reduce Cr(VI) to Cr(III). The objective of the present work is to understand the effect of different electron acceptors on Cr(VI) reduction and to model the fate and transport of Cr(VI) in an aquifer. Batch studies were conducted to estimate biokinetic parameters such as maximum specific growth rate (µmax), half saturation constant (Ks), yield coefficient (YT) and inhibition constant (Ki). Transformation

  1. Speciation of Cr(VI) in environmental samples in the vicinity of the ferrochrome smelter.

    Science.gov (United States)

    Sedumedi, Hilda N; Mandiwana, Khakhathi L; Ngobeni, Prince; Panichev, Nikolay

    2009-12-30

    The impact of ferrochrome smelter on the contamination of its environment with toxic hexavalent chromium, Cr(VI), was assessed by analyzing smelter dusts, soil, grass and tree barks. For the separation of Cr(VI) from Cr(III), solid samples were treated with 0.1M Na(2)CO(3) and filtered through hydrophilic PDVF 0.45 microm filter prior to the determination of Cr(VI) by electrothermal atomic absorption spectrometry (ET-AAS). Ferrochrome smelter dust was found to contain significant levels of Cr(VI), viz. 43.5 microg g(-1) (cyclone dust), 2710 microg g(-1) (fine dust), and 7800 microg g(-1) (slimes dust) which exceeded the maximum acceptable risk concentration (20 microg g(-1)). The concentration of Cr(VI) in environmental samples of grass (3.4+/-0.2), soil (7.7+/-0.2), and tree bark (11.8+/-1.2) collected in the vicinity of the chrome smelter were higher as compared with the same kind of samples collected from uncontaminated area. The results of the investigation show that ferrochrome smelter is a source of environmental pollution with contamination factors of Cr(VI) ranging between 10 and 50.

  2. Speciation of Cr(VI) in environmental samples in the vicinity of the ferrochrome smelter

    Energy Technology Data Exchange (ETDEWEB)

    Sedumedi, Hilda N. [Department of Chemistry, Tshwane University of Technology, P.O. Box 56208, Arcadia, 0007, Pretoria (South Africa); Mandiwana, Khakhathi L., E-mail: MandiwanaKL@tut.ac.za [Department of Chemistry, Tshwane University of Technology, P.O. Box 56208, Arcadia, 0007, Pretoria (South Africa); Ngobeni, Prince; Panichev, Nikolay [Department of Chemistry, Tshwane University of Technology, P.O. Box 56208, Arcadia, 0007, Pretoria (South Africa)

    2009-12-30

    The impact of ferrochrome smelter on the contamination of its environment with toxic hexavalent chromium, Cr(VI), was assessed by analyzing smelter dusts, soil, grass and tree barks. For the separation of Cr(VI) from Cr(III), solid samples were treated with 0.1 M Na{sub 2}CO{sub 3} and filtered through hydrophilic PDVF 0.45 {mu}m filter prior to the determination of Cr(VI) by electrothermal atomic absorption spectrometry (ET-AAS). Ferrochrome smelter dust was found to contain significant levels of Cr(VI), viz. 43.5 {mu}g g{sup -1} (cyclone dust), 2710 {mu}g g{sup -1} (fine dust), and 7800 {mu}g g{sup -1} (slimes dust) which exceeded the maximum acceptable risk concentration (20 {mu}g g{sup -1}). The concentration of Cr(VI) in environmental samples of grass (3.4 {+-} 0.2), soil (7.7 {+-} 0.2), and tree bark (11.8 {+-} 1.2) collected in the vicinity of the chrome smelter were higher as compared with the same kind of samples collected from uncontaminated area. The results of the investigation show that ferrochrome smelter is a source of environmental pollution with contamination factors of Cr(VI) ranging between 10 and 50.

  3. Cr(VI) reduction in wastewater using a bimetallic galvanic reactor

    Energy Technology Data Exchange (ETDEWEB)

    Lugo-Lugo, Violeta [Centro Conjunto de Investigacion en Quimica Sustentable UAEM-UNAM, Universidad Autonoma del Estado de Mexico, Facultad de Quimica. Paseo Colon interseccion Paseo Tollocan S/N. C.P. 50120, Toluca (Mexico); Barrera-Diaz, Carlos, E-mail: cbarrera@uaemex.mx [Centro Conjunto de Investigacion en Quimica Sustentable UAEM-UNAM, Universidad Autonoma del Estado de Mexico, Facultad de Quimica. Paseo Colon interseccion Paseo Tollocan S/N. C.P. 50120, Toluca (Mexico); Bilyeu, Bryan [Xavier University of Louisiana, Department of Chemistry, 1 Drexel Drive, New Orleans, LA 70125 (United States); Balderas-Hernandez, Patricia [Centro Conjunto de Investigacion en Quimica Sustentable UAEM-UNAM, Universidad Autonoma del Estado de Mexico, Facultad de Quimica. Paseo Colon interseccion Paseo Tollocan S/N. C.P. 50120, Toluca (Mexico); Urena-Nunez, Fernando [Instituto Nacional de Investigaciones Nucleares, A.P. 18-1027, Col. Escandon, Delegacion Miguel Hidalgo, C.P. 11801, Mexico, D.F. (Mexico); Sanchez-Mendieta, Victor [Centro Conjunto de Investigacion en Quimica Sustentable UAEM-UNAM, Universidad Autonoma del Estado de Mexico, Facultad de Quimica. Paseo Colon interseccion Paseo Tollocan S/N. C.P. 50120, Toluca (Mexico)

    2010-04-15

    The electrochemical reduction of Cr(VI)-Cr(III) in wastewater by iron and copper-iron bimetallic plates was evaluated and optimized. Iron has been used as a reducing agent, but in this work a copper-iron galvanic system in the form of bimetallic plates is applied to reducing hexavalent chromium. The optimal pH (2) and ratio of copper to iron surface areas (3.5:1) were determined in batch studies, achieving a 100% reduction in about 25 min. The Cr(VI) reduction kinetics for the bimetallic system fit a first order mechanism with a correlation of 0.9935. Thermodynamic analysis shows that the Cr(VI) reduction is possible at any pH value. However, at pH values above 3.0 for iron and 5.5 for chromium insoluble species appear, indicating that the reaction will be hindered. Continuous column studies indicate that the bimetallic copper-iron galvanic system has a reduction capacity of 9.5890 mg Cr(VI) cm{sup -2} iron, whereas iron alone only has a capacity of 0.1269 mg Cr(VI) cm{sup -2}. The bimetallic copper-iron galvanic system is much more effective in reducing hexavalent chromium than iron alone. The exhausted plates were analyzed by SEM, EDS, and XRD to determine the mechanism and the surface effects, especially surface fouling.

  4. Cr(Vi) reduction capacity of activated sludge as affected by nitrogen and carbon sources, microbial acclimation and cell multiplication

    Energy Technology Data Exchange (ETDEWEB)

    Ferro Orozco, A.M., E-mail: mferro@cidca.org.ar [Centro de Investigacion y Desarrollo en Criotecnologia de Alimentos (CIDCA) CCT La Plata CONICET - Fac. de Cs. Exactas, UNLP. 47 y 116 (B1900AJJ) La Plata (Argentina); Contreras, E.M.; Zaritzky, N.E. [Centro de Investigacion y Desarrollo en Criotecnologia de Alimentos (CIDCA) CCT La Plata CONICET - Fac. de Cs. Exactas, UNLP. 47 y 116 (B1900AJJ) La Plata (Argentina); Fac. de Ingenieria, UNLP. 47 y 1 (B1900AJJ) - La Plata (Argentina)

    2010-04-15

    The objectives of the present work were: (i) to analyze the capacity of activated sludge to reduce hexavalent chromium using different carbon sources as electron donors in batch reactors, (ii) to determine the relationship between biomass growth and the amount of Cr(VI) reduced considering the effect of the nitrogen to carbon source ratio, and (iii) to determine the effect of the Cr(VI) acclimation stage on the performance of the biological chromium reduction assessing the stability of the Cr(VI) reduction capacity of the activated sludge. The highest specific Cr(VI) removal rate (q{sub Cr}) was attained with cheese whey or lactose as electron donors decreasing in the following order: cheese whey {approx} lactose > glucose > citrate > acetate. Batch assays with different nitrogen to carbon source ratio demonstrated that biological Cr(VI) reduction is associated to the cell multiplication phase; as a result, maximum Cr(VI) removal rates occur when there is no substrate limitation. The biomass can be acclimated to the presence of Cr(VI) and generate new cells that maintain the ability to reduce chromate. Therefore, the activated sludge process could be applied to a continuous Cr(VI) removal process.

  5. Cr(VI reduction by cell-free extract of thermophillic Bacillus fusiformis NTR9

    Directory of Open Access Journals (Sweden)

    Pranee Pattanapipitpaisal

    2013-08-01

    Full Text Available Residual chromium compounds in discharged effluents is a serious problem, due to hexavalent chromium or chromate[Cr(VI] being extremely toxic and showing mutagenic and carcinogenic effects on biological systems. The bacterial enzymaticCr(VI reduction can occur and this could be an effective method of detoxifying Cr(VI polluted effluent. The present studycharacterized Cr(VI reductase activity of cell-free extracts (CFE of thermophilic chromate-reducing bacteria, Bacillusfusiformis NTR9. Results showed that the optimum temperature and pH for Cr(VI reductase activity of CFE was 80°C andpH 7, respectively. The reductase activity remained at 60.34% and 26.44% after 30 minutes of exposure to 70 and 90°C,respectively, suggesting a heat stable enzyme. Moreover, the enzyme was resistant under acidic and neutral condition but itsstability was decreased under alkaline condition. The Cr(VI reductase activity of CFE was enhanced when exposed in Cu2+and Fe3+ by 188.19% and 180.38%, respectively. The Cr(VI reductase activity could be reduced to 72.19% and 8.95% in thepresence of Mn2+ and Ag+, respectively. Mg2+, Zn2+, As3+ and electron acceptors like sulfate and nitrate had no affect on Cr(VIreductase activity. The external electron donors (glucose, glycerol, citrate, malate, succinate, and acetate, but not NADHwere essential to improve the chromate reductase activity of NTR9 strain. The chromate reductase was mainly associatedwith the soluble fraction in the cytoplasm of the bacterial cell. The molecular weight of the enzyme was 20 KDa. The resultsshowed that Cr(VI reductase could be a good candidate for detoxification of Cr(VI in industrial effluents.

  6. Characterizing toxic Cr(VI) contamination in chromite mine overburden dump and its bacterial remediation.

    Science.gov (United States)

    Dhal, B; Das, N N; Thatoi, H N; Pandey, B D

    2013-09-15

    Cr(VI) generated due to natural oxidation of chromite mineral present in chromite mine overburden (COB) dumps of Sukinda, India, has been characterized by different physico-chemical methods. The Cr(VI) was found to be associated with goethite matrix at a contamination level of 500 mg Cr(VI)kg(-1) of COB. Bacillus sp. isolated from the overburden sample exhibiting high tolerance to the hexavalent chromium, was used for the remediation of Cr(VI) in the overburden. The process was optimized while varying the parameters such as pH (2-9), pulp density (10-60%) and temperature (25-40 °C). Optimal reduction of more than 98% of Cr(VI) in the COB sample was achieved in 16 h at pH∼7.0 and 60% pulp density with the Bacillus sp. (4.05 × 10(7)cells mL(-1)) in absence of media. The exponential rate equation yielded rate constant value of 2.14 × 10(-1)h(-1) at 60% pulp density. The mode of bio-reduction of Cr(VI) in the overburden sample was established by FT-IR, XRD, EPMA and SEM-EDS studies.

  7. Reduction of Cr(VI) to Cr(III) using silicon nanowire arrays under visible light irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Fellahi, Ouarda [Institut d' Electronique, de Microélectronique et de Nanotechnologie (IEMN), UMR CNRS 8520, Avenue Poincaré—BP 70478, 59652 Villeneuve d' Ascq Cedex (France); Centre de Recherche en Technologie des Semi-conducteurs pour l' Energétique-CRTSE 02, Bd Frantz Fanon, BP. 140, Alger 7 Merveilles (Algeria); Barras, Alexandre [Institut d' Electronique, de Microélectronique et de Nanotechnologie (IEMN), UMR CNRS 8520, Avenue Poincaré—BP 70478, 59652 Villeneuve d' Ascq Cedex (France); Pan, Guo-Hui [State Key Laboratory of Luminescence and Applications, Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, 3888 Dong Nanhu Road, Changchun 130033 (China); Coffinier, Yannick [Institut d' Electronique, de Microélectronique et de Nanotechnologie (IEMN), UMR CNRS 8520, Avenue Poincaré—BP 70478, 59652 Villeneuve d' Ascq Cedex (France); Hadjersi, Toufik [Centre de Recherche en Technologie des Semi-conducteurs pour l' Energétique-CRTSE 02, Bd Frantz Fanon, BP. 140, Alger 7 Merveilles (Algeria); Maamache, Mustapha [Laboratoire de Physique Quantique et Systèmes Dynamiques, Département de Physique, Université de Sétif, Sétif 19000 (Algeria); Szunerits, Sabine [Institut d' Electronique, de Microélectronique et de Nanotechnologie (IEMN), UMR CNRS 8520, Avenue Poincaré—BP 70478, 59652 Villeneuve d' Ascq Cedex (France); and others

    2016-03-05

    Highlights: • Cr(VI) reduction to Cr(III) using silicon nanowires decorated with Cu nanoparticles. • The reduction takes place at room temperature and neutral pH under visible light. • The photocatalytic reduction was enhanced by addition of adipic or citric acid. - Abstract: We report an efficient visible light-induced reduction of hexavalent chromium Cr(VI) to trivalent Cr(III) by direct illumination of an aqueous solution of potassium dichromate (K{sub 2}Cr{sub 2}O{sub 7}) in the presence of hydrogenated silicon nanowires (H-SiNWs) or silicon nanowires decorated with copper nanoparticles (Cu NPs-SiNWs) as photocatalyst. The SiNW arrays investigated in this study were prepared by chemical etching of crystalline silicon in HF/AgNO{sub 3} aqueous solution. The Cu NPs were deposited on SiNW arrays via electroless deposition technique. Visible light irradiation of an aqueous solution of K{sub 2}Cr{sub 2}O{sub 7} (10{sup −4} M) in presence of H-SiNWs showed that these substrates were not efficient for Cr(VI) reduction. The reduction efficiency achieved was less than 10% after 120 min irradiation at λ > 420 nm. Addition of organic acids such as citric or adipic acid in the solution accelerated Cr(VI) reduction in a concentration-dependent manner. Interestingly, Cu NPs-SiNWs was found to be a very efficient interface for the reduction of Cr(VI) to Cr(III) in absence of organic acids. Almost a full reduction of Cr(VI) was achieved by direct visible light irradiation for 140 min using this photocatalyst.

  8. Biological Cr(VI) removal using bio-filters and constructed wetlands.

    Science.gov (United States)

    Michailides, Michail K; Sultana, Mar-Yam; Tekerlekopoulou, Athanasia G; Akratos, Christos S; Vayenas, Dimitrios V

    2013-01-01

    The bioreduction of hexavalent chromium from aqueous solution was carried out using suspended growth and packed-bed reactors under a draw-fill operating mode, and horizontal subsurface constructed wetlands. Reactors were inoculated with industrial sludge from the Hellenic Aerospace Industry using sugar as substrate. In the suspended growth reactors, the maximum Cr(VI) reduction rate (about 2 mg/L h) was achieved for an initial concentration of 12.85 mg/L, while in the attached growth reactors, a similar reduction rate was achieved even with high initial concentrations (109 mg/L), thus confirming the advantage of these systems. Two horizontal subsurface constructed wetlands (CWs) pilot-scale units were also built and operated. The units contained fine gravel. One unit was planted with common reeds and one was kept unplanted. The mean influent concentrations of Cr(VI) were 5.61 and 5.47 mg/L for the planted and unplanted units, respectively. The performance of the planted CW units was very effective as mean Cr(VI) removal efficiency was 85% and efficiency maximum reached 100%. On the contrary, the unplanted CW achieved very low Cr(VI) removal with a mean value of 26%. Both attached growth reactors and CWs proved efficient and viable means for Cr(VI) reduction.

  9. Integrated Ecogenomics Study for Bioremediation of Cr(VI) at Hanford 100H Area

    Energy Technology Data Exchange (ETDEWEB)

    Chakraborty, Romy; Chakraborty, Romy

    2008-08-12

    Hexavalent chromium is a widespread contaminant found in groundwater. In order to stimulate microbially mediated Cr(VI)-reduction, a poly-lactate compound was injected into Cr(VI)-contaminated aquifers at site 100H at Hanford. Investigation of bacterial community composition using high-density DNA microarray analysis of 16S rRNA gene products revealed a stimulation of Pseudomonas, Desulfovibrio and Geobacter species amongst others. Enrichment of these organisms coincided with continued Cr(VI) depletion. Functional gene-array analysis of DNA from monitoring well indicated high abundance of genes involved in nitrate-reduction, sulfate-reduction, iron-reduction, methanogenesis, chromium tolerance/reduction. Clone-library data revealed Psedomonas was the dominant genus in these samples. Based on above results, we conducted lab investigations to study the dominant anaerobic culturable microbial populations present at this site and their role in Cr(VI)-reduction. Enrichments using defined anaerobic media resulted in isolation of an iron-reducing, a sulfate-reducing and a nitrate-reducing isolate among several others. Preliminary 16S rDNA sequence analysis identified the isolates as Geobacter metallireducens, Pseudomonas stutzeri and Desulfovibrio vulgaris species respectively. The Pseudomonas isolate utilized acetate, lactate, glycerol and pyruvate as alternative carbon sources, and reduced Cr(VI). Anaerobic washed cell suspension of strain HLN reduced almost 95?M Cr(VI) within 4 hr. Further, with 100?M Cr(VI) as sole electron-acceptor, cells grew to 4.05 x 107 /ml over 24 h after an initial lag, demonstrating direct enzymatic Cr(VI) reduction coupled to growth. These results demonstrate that Cr(VI)-immobilization at Hanford 100H site could be mediated by direct microbial metabolism in addition to indirect chemical reduction of Cr(VI) by end-products of microbial activity.

  10. miR-3940-5p enhances homologous recombination after DSB in Cr(VI) exposed 16HBE cell.

    Science.gov (United States)

    Li, Yang; Hu, Guiping; Li, Ping; Tang, Shichuan; Zhang, Ji; Jia, Guang

    2016-02-17

    Hexavalent chromium (Cr(VI)) is a well-recognized human carcinogen, yet the molecular mechanisms by which cause human cancer are still not well understood. MicroRNAs (miRNAs), which are small non-coding RNAs, are involved in carcinogenesis and DNA damage repair. Previous occupational population study showed that hexavalent chromium (Cr(VI)) downregulated plasma miR-3940-5p level, and a low miR-3940-5p level was associated with high XRCC2 expression in lymphocytes, indicating that miR-3940-5p maybe play a protective effect in Cr(VI) induced DNA damage. Here we investigated miR-3940-5p expression and its roles in DNA repair in Cr(VI)-treated 16HBE cells. miR-3940-5p change was detected by qRT-PCR. Rad51 foci formation and double strand break (DSB) were investigated to assess homologous recombination repair (HR) capacity by Immunofluorescent assay and Neutral Comet assay. XRCC2 expression was also evaluated after miRNA oligonucleotides transfection using Western blot. Cr(VI) treatment suppressed miR-3940-5p level in 16HBE cells. miR-3904-5p mimic downregulated XRCC2 expression. As a result, the formation of Rad51-foci was inhibited and DSB repair was prolonged. The results indicate that miR-3940-5p plays a protective effect in Cr(VI) induced DNA damage.

  11. Simultaneous determination of Cr(III) and Cr(VI) in tannery wastewater using low pressure ion chromatography combined with flow injection spectrophotometry

    Science.gov (United States)

    Chen, Shujuan; Zhang, Xinshen; Yu, Lingyun; Wang, Li; Li, Hui

    2012-03-01

    Trivalent and hexavalent chromium have been successfully separated and determined using low pressure ion chromatography combined with flow injection spectrophotometric analysis (LPIC-FIA). A column packed with crosslinking starch microspheres was used for on-line separation of Cr(III) from Cr(VI) in a flow-injection system because of its absorptive effect on Cr(III). To determine the concentration of Cr(III) and Cr(VI) in samples, we used 3.0 mmol/L nitric acid to elute adsorbed Cr(III) from the column and then used ceric sulfate-sulfuric acid as oxidant to convert all Cr(III) into Cr(VI). Then, Cr(VI) directly came from the samples and Cr(VI) came from Cr(III) successively formed a amaranthine complex with diphenycarbazide and the complex shows a maximum absorption at 530 nm. Analytical parameters including the concentration of eluent and oxidant solution, oxidizing temperature, length of oxidizing reaction coil, reaction coil and injection coil, interfering effects, etc., were optimized. The limit of detection was 1.25 μg/L for Cr(VI) and 3.76 μg/L for Cr(III). The linear relationship between absorption with the concentration of Cr(VI) and Cr(III) was 0.001-1.000 mg/L and 0.030-1.000 mg/L with correlation coefficients of 0.9995 and 0.9994, respectively. The relative standard deviation of Cr(VI) and Cr(III) was 1.21% and 1.66%, respectively (n = 10). Major cations and anions did not show any interference. We validated this method through certified reference materials and through measuring the recovery in tannery wastewater.

  12. Biosensing and bioremediation of Cr(VI) by cell free extract of Enterobacter aerogenes T2.

    Science.gov (United States)

    Panda, Jigisha; Sarkar, Priyabrata

    2014-01-01

    Hexavalent chromium or Cr(VI) enters the environment through several anthropogenic activities and it is highly toxic and carcinogenic. Hence it is required to be detected and remediated from the environment. In this study, low-cost and environment-friendly methods of biosensing and bioremediation of Cr(VI) have been proposed. Crude cell free extract (CFE) of previously isolated Enterobacter aerogenes T2 (GU265554; NII 1111) was prepared and exploited to develop a stable biosensor for direct estimation of Cr(VI) in waste water, by using three electrodes via cyclic voltammetry. For bioremediation studies, a homogeneous solution of commercially available sodium alginate and CFE was added dropwise in a continuously stirred calcium chloride solution. Biologically modified calcium alginate beads were produced and these were further utilized for bioremediation studies. The proposed sensor showed linear response in the range of 10-40 μg L(-1) Cr(VI) and the limit of detection was found to be 6.6 μg L(-1) Cr(VI). No interference was observed in presence of metal ions, e.g., lead, cadmium, arsenic, tin etc., except for insignificant interference with molybdenum and manganese. In bioremediation studies, modified calcium alginate beads showed encouraging removal rate 900 mg Cr(VI)/m(3) water per day with a removal efficiency of 90%, much above than reported in literature. The proposed sensing system could be a viable alternative to costly measurement procedures. Calcium alginate beads, modified with CFE of E. aerogenes, could be used in bioremediation of Cr(VI) since it could work in real conditions with extraordinarily high capacity.

  13. Bio-reduction of Cr(VI) by exopolysaccharides (EPS) from indigenous bacterial species of Sukinda chromite mine, India.

    Science.gov (United States)

    Harish, R; Samuel, Jastin; Mishra, R; Chandrasekaran, N; Mukherjee, A

    2012-07-01

    Chrome mining activity has contributed intensively towards pollution of hexavalent chromium around Sukinda Valley, Orissa, India. In an attempt to study the specific contribution of exopolysaccharides (EPS) extracted from indigenous isolates towards Cr(VI) reduction, three chromium (VI) tolerant strains were isolated from the effluent mining sludge. Based on the tolerance towards Cr(VI) and EPS production capacity, one of them was selected for further work. The taxonomic identity of the selected strain was confirmed to be Enterobacter cloacae (showing 98% similarity in BLAST search to E. cloacae) through 16S rRNA analysis. The EPS production was observed to increase with increasing Cr(VI) concentration in the growth medium, highest being 0.078 at 100 mg/l Cr(VI). The extracted EPS from Enterobacter cloacae SUKCr1D was able to reduce 31.7% of Cr(VI) at 10 mg/l concentration, which was relevant to the prevailing natural concentrations at Sukinda mine effluent sludge. The FT-IR spectral studies confirmed the surface chemical interactions of hexavalent chromium with EPS.

  14. Can iron oxides remove Cr(VI) from drinking water at sub-ppb levels?

    Science.gov (United States)

    Kaprara, Efthymia; Simeonidis, Konstantinos; Samaras, Petros; Zouboulis, Anastasios; Mitrakas, Manassis

    2013-04-01

    Hexavalent chromium [Cr(VI)] has long been recognized as a potential carcinogen via inhalation, in contrast to trivalent chromium [Cr(III)] which is 100 times less toxic and also a necessary nutrient, essential to human glucidic metabolism. Nowadays there is an increasing concern that Cr(VI) is also carcinogenic by the oral route of exposure, while an increased number of publications indicate that Cr(VI) is a common natural pollutant. Hexavalent chromium formation is attributed to natural oxidation of Cr(III) in ultramafic derived soils and ophiolithic rocks. To verify this theory, drinking water samples were collected from targeted areas of Greece e.g. areas in which the geological background is predominated by ultramafic minerals and the water supply depends mainly on groundwater resources. Valuable guide for the samples collection was the geological map of Greece and emphasis was given to regions where the natural occurrence of Cr(VI) is thought to be more possible. A wide range of Cr concentrations (2-100 μg/L) were detected in the areas studied, with most of them ranging below the current limit of 50 μg/L, and the Cr(VI) concentration being more than 90% of the total. Since the Cr(VI) affects significant part of population worldwide, a debate was established concerning the enforcement of stringent regulation, which also demands the drinking water treatment processes re-evaluation in view of Cr(VI) removal at sub-ppb level. In this regard, adsorption has evolved as the front line of defense for chromium removal. The motivation of this work was to investigate the efficiency of iron oxides for the adsorption of Cr(VI) from drinking water and its removal at sub-ppb levels. The adsorbents examined included iron oxy-hydroxides and magnetite prepared using common low cost iron salts. Their effectiveness as Cr(VI) adsorbents was evaluated through the decrease of a Cr(VI) concentration of 100μg/L prepared in NSF water at pH 7. Preliminary batch experiments did not

  15. Use of Variamine Blue dye in Spectrophotometric determination of Water Soluble Cr(VI in Portland Cement

    Directory of Open Access Journals (Sweden)

    Devesh K. Sharma

    2015-12-01

    Full Text Available Variamine blue dye as chromogenic reagent was used for Portland cement samples in determination of soluble hexavalent chromium. This method was based on the reaction of Cr(VI with potassium iodide in acidic medium to liberate iodine, which oxidized variamine blue to form a violet colored species having an absorption maximum 556 nm. The extraction of soluble Cr(VI for quantification in cement was done according to European method. The validity of this method was thoroughly examined by comparing with standard DPC method as well as the accuracy of the method was checked using a standard reference material of National Institute of Standards & Technology (NIST, USA.

  16. Tea waste biomass activated carbon electrode for simultaneous removal of Cr(VI) and fluoride by capacitive deionization.

    Science.gov (United States)

    Gaikwad, Mahendra S; Balomajumder, Chandrajit

    2017-10-01

    Capacitive deionization is promising less energy based desalination technique to achieve pure water. In the present study microporous activated carbon was prepared from tea waste biomass by chemical and thermal modification. Further TWBAC was used for preparation of the electrode. The TWBAC electrode was applied in the self-made CDI set up for simultaneous removal of hexavalent chromium [Cr(VI)] and fluoride (F) form mixed feed solution of Cr(VI) and F. The performance of TWBAC electrode was found effective for simultaneous removal of Cr(VI) and F from mixed feed solution. The maximum electrosorption capacity of Cr(VI) and F were found 0.77 and 0.74 mg g(-1) for 10 mg L(-1) and 2.83 and 2.49 mg g(-1) for 100 mg L(-1) mixed feed solution respectively. The higher removal of Cr(VI) was found due to the electrosorption selectivity of the divalent CrO4(2-) is higher than that of the monovalent F(-). Multicomponent isotherm modeling and kinetic study were carried out in this study. TWBAC CDI electrode could be useful for treatment of a low concentrated Cr(VI) and F containing wastewater. Copyright © 2017 Elsevier Ltd. All rights reserved.

  17. Interaction of Cr(VI) reduction and denitrification by strain Pseudomonas aeruginosa PCN-2 under aerobic conditions.

    Science.gov (United States)

    He, Da; Zheng, Maosheng; Ma, Tao; Li, Can; Ni, Jinren

    2015-06-01

    Inhibition of efficient denitrification in presence of toxic heavy metals is one of the current problems encountered in municipal wastewater treatment plants. This paper presents how to remove hexavalent chromium (Cr(VI)) and nitrate simultaneously by the novel strain Pseudomonas aeruginosa PCN-2 under aerobic conditions. The capability of strain PCN-2 for Cr(VI) and nitrate reduction was confirmed by PCR analysis of gene ChrR, napA, nirS, cnorB, nosZ, while Cr(VI) reduction was proved via an initial single-electron transfer through Cr(V) detection using electron paramagnetic resonance. Experimental results demonstrated that Cr(VI) and nitrate reduction by strain PCN-2 was much faster at pH 8-9 and higher initial cell concentration. However, increasing Cr(VI) concentration would inhibit aerobic denitrification process and result in an significant delay of nitrate reduction or N2O accumulation, which was attributed to competition between three electron acceptors, i.e., Cr(VI), O2 and nitrate in the electron transport chain.

  18. Optimizing the application of magnetic nanoparticles in Cr(VI) removal

    Science.gov (United States)

    Simeonidis, Konstantinos; Kaprara, Efthymia; Mitrakas, Manassis; Tziomaki, Magdalini; Angelakeris, Mavroidis; Vourlias, Georgios; Andritsos, Nikolaos

    2013-04-01

    The presence of heavy metals in aqueous systems is an intense health and environmental problem as implied by their harmful effects on human and other life forms. Among them, chromium is considered as an acutely hazardous compound contaminating the surface water from industrial wastes or entering the groundwater, the major source of drinking water, by leaching of chromite rocks. Chromium occurs in two stable oxidation states, Cr(III) and Cr(VI), with the hexavalent form being much more soluble and mobile in water having the ability to enter easily into living tissues or cells and thus become more toxic. Despite the established risks from Cr(VI)-containing water consumption and the increasing number of incidents, the E.U. tolerance limit for total chromium in potable water still stands at 50 μg/L. However, in the last years a worldwide debate concerning the establishment of a separate and very strict limit for the hexavalent form takes place. In practice, Cr(VI) is usually removed from water by various methods such as chemical coagulation/filtration, ion exchange, reverse osmosis and adsorption. Adsorption is considered as the simplest method which may become very effective if the process is facilitated by the incorporation of a Cr(VI) to Cr(III) reduction stage. This work studies the potential of using magnetic nanoparticles as adsorbing agents for Cr(VI) removal at the concentration levels met in contaminated drinking water. A variety of nanoparticles consisting of ferrites MFe2O4 (M=Fe, Co, Ni, Cu, Mn, Mg, Zn) were prepared by precipitating the corresponding bivalent or trivalent sulfate salts under controlled acidity and temperature. Electron microscopy and X-ray diffraction techniques were used to verify their crystal structure and determine the morphological characteristics. The mean particle size of the samples was found in the range 10-50 nm. Batch Cr(VI) removal tests were performed in aqueous nanoparticles dispersions showing the efficiency of ferrite

  19. Ultra-trace level speciated isotope dilution measurement of Cr(VI) using ion chromatography tandem mass spectrometry in environmental waters.

    Science.gov (United States)

    Mädler, Stefanie; Todd, Aaron; Skip Kingston, H M; Pamuku, Matt; Sun, Fengrong; Tat, Cindy; Tooley, Robert J; Switzer, Teresa A; Furdui, Vasile I

    2016-08-15

    The reliable analysis of highly toxic hexavalent chromium, Cr(VI), at ultra-trace levels remains challenging, given its easy conversion to non-toxic trivalent chromium. This work demonstrates a novel analytical method to quantify Cr(VI) at low ngL(-1) concentration levels in environmental water samples by using speciated isotope dilution (SID) analysis and double-spiking with Cr(III) and Cr(VI) enriched for different isotopes. Ion chromatography tandem mass spectrometry (IC-MS/MS) was used for the analysis of Cr(VI) as HCrO4(-) → CrO3(-). Whereas the classical linear multipoint calibration (MPC) curve approach obtained a method detection limit (MDL) of 7ngL(-1) Cr(VI), the modified SID-MS method adapted from U. S. EPA 6800 allowed for the quantification of Cr(VI) with an MDL of 2ngL(-1) and provided results corrected for Cr(VI) loss occurred after sample collection. The adapted SID-MS approach proved to yield more accurate and precise results than the MPC method, allowed for compensation of Cr(VI) reduction during sample transportation and storage while eliminating the need for frequent external calibration. The developed method is a complementary tool to routinely used inductively-coupled plasma (ICP) MS and circumvents typically experienced interferences.

  20. Optimizing magnetic nanoparticles for drinking water technology: The case of Cr(VI)

    Energy Technology Data Exchange (ETDEWEB)

    Simeonidis, K., E-mail: ksime@physics.auth.gr [Department of Mechanical Engineering, School of Engineering, University of Thessaly, Volos 38334 (Greece); Kaprara, E. [Department of Chemical Engineering, Aristotle University of Thessaloniki, Thessaloniki 54124 (Greece); Samaras, T.; Angelakeris, M.; Pliatsikas, N.; Vourlias, G. [Department of Physics, Aristotle University of Thessaloniki, Thessaloniki 54124 (Greece); Mitrakas, M. [Department of Chemical Engineering, Aristotle University of Thessaloniki, Thessaloniki 54124 (Greece); Andritsos, N. [Department of Mechanical Engineering, School of Engineering, University of Thessaly, Volos 38334 (Greece)

    2015-12-01

    The potential of magnetite nanoparticles to be applied in drinking water treatment for the removal of hexavalent chromium is discussed. In this study, a method for their preparation which combines the use of low-cost iron sources (FeSO{sub 4} and Fe{sub 2}(SO{sub 4}){sub 3}) and a continuous flow mode, was developed. The produced magnetite nanoparticles with a size of around 20 nm, appeared relatively stable to passivation providing a removal capacity of 1.8 μg Cr(VI)/mg for a residual concentration of 50 μg/L when tested in natural water at pH 7. Such efficiency is explained by the reducing ability of magnetite which turns Cr(VI) to an insoluble Cr(OH){sub 3} form. The successful operation of a small-scale system consisting of a contact reactor and a magnetic separator demonstrates a way for the practical introduction and recovery of magnetite nanoparticles in water treatment technology. - Highlights: • Iron sulfates were used for the kilogram scale production of Fe{sub 3}O{sub 4} nanoparticles. • Studied particles showed a Cr(VI) removal capacity of 2 μg/mg in natural water. • Cr(VI) uptake is mostly based on its reduction and precipitation as Cr(OH){sub 3}. • A continuous flow reactor–magnetic separator operated with nanoparticles.

  1. Kinetics of Cr(III) and Cr(VI) removal from water by two floating macrophytes.

    Science.gov (United States)

    Maine, M A; Hadad, H R; Sánchez, G; Caffaratti, S; Pedro, M C

    2016-01-01

    The aim of this work was to compare Cr(III) and Cr(VI) removal kinetics from water by Pistia stratiotes and Salvinia herzogii. The accumulation in plant tissues and the effects of both Cr forms on plant growth were also evaluated. Plants were exposed to 2 and 6 mg L(-1) of Cr(III) or Cr(VI) during 30 days. At the end of the experiment, Cr(VI) removal percentages were significantly lower than those obtained for Cr(III) for both macrophytes. Cr(III) removal kinetics involved a fast and a slow component. The fast component was primarily responsible for Cr(III) removal while Cr(VI) removal kinetics involved only a slow process. Cr accumulated principally in the roots. In the Cr(VI) treatments a higher translocation from roots to aerial parts than in Cr(III) treatments was observed. Both macrophytes demonstrated a high ability to remove Cr(III) but not Cr(VI). Cr(III) inhibited the growth at the highest studied concentration of both macrophytes while Cr(VI) caused senescence. These results have important implications in the use of constructed wetlands for secondary industrial wastewater treatment. Common primary treatments of effluents containing Cr(VI) consists in its reduction to Cr(III). Cr(III) concentrations in these effluents are normally below the highest studied concentrations in this work.

  2. Total Reducing Capacity in Aquifer Minerals and Sediments: Quantifying the Potential to Attenuate Cr(VI) in Groundwater

    Energy Technology Data Exchange (ETDEWEB)

    Sisman, S. Lara [Univ. of Virginia, Charlottesville, VA (United States); Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL)

    2015-07-20

    Hexavalent chromium, Cr(VI), is present in the environment as a byproduct of industrial processes. Due to its mobility and toxicity, it is crucial to attenuate or remove Cr(VI) from the environment. The objective of this investigation was to quantify potential natural attenuation, or reduction capacity, of reactive minerals and aquifer sediments. Samples of reduced-iron containing minerals such as ilmenite, as well as Puye Formation sediments representing a contaminated aquifer in New Mexico, were reacted with chromate. The change in Cr(VI) during the reaction was used to calculate reduction capacity. This study found that minerals that contain reduced iron, such as ilmenite, have high reducing capacities. The data indicated that sample history may impact reduction capacity tests due to surface passivation. Further, this investigation identified areas for future research including: a) refining the relationships between iron content, magnetic susceptibility and reduction capacity, and b) long term kinetic testing using fresh aquifer sediments.

  3. Drying Effects on Corrosion Properties of Cr(VI) and Cr(III) Treated Electrogalvanized Steel

    NARCIS (Netherlands)

    Zhang, X.; Van den Bos, C.; Sloof, W.G.; Hovestad, A.; Terryn, H.; De Wit, J.H.W.

    2006-01-01

    Drying effects on corrosion performance of Cr(VI)- and Cr(III)-treated electro-galvanized steel have been studied in NaCl solution using potentiodynamic measurements and electrochemical impedance spectroscopy (EIS). The Cr(VI) and the Cr(III) treated specimens were dried at three different

  4. Drying Effects on Corrosion Properties of Cr(VI) and Cr(III) Treated Electrogalvanized Steel

    NARCIS (Netherlands)

    Zhang, X.; Van den Bos, C.; Sloof, W.G.; Hovestad, A.; Terryn, H.; De Wit, J.H.W.

    2006-01-01

    Drying effects on corrosion performance of Cr(VI)- and Cr(III)-treated electro-galvanized steel have been studied in NaCl solution using potentiodynamic measurements and electrochemical impedance spectroscopy (EIS). The Cr(VI) and the Cr(III) treated specimens were dried at three different temperatu

  5. The influence of Chromium supplied by tanning and wet finishing processes on the formation of cr(vi in leather

    Directory of Open Access Journals (Sweden)

    W. F. Fuck

    2011-06-01

    Full Text Available Chromium used in leather manufacturing can be oxidized from the trivalent to the hexavalent state, causing environmental concerns. In this study, the influence of Cr(III from tanning, deacidification pH, fatliquors, chrome retanning and vegetable retanning on the formation of Cr(VI in leather was analyzed by comparing natural and aged samples. In wet-blue leather, even after aging and in fatliquored leathers that did not suffer the aging process, the presence of Cr(VI was always below the detection limit of 3 mg/kg. Considering the presence of Cr(VI, the supply of chromium during the retanning step had a more significant effect than during the tanning. In the fatliquoring process with sulfites, fish and synthetic fatliquor leather samples contained Cr(VI when aged, and the highest concentration detected was 26.7 mg/kg. The evaluation of Cr(VI formation led to recommendations for regulation in the leather industry.

  6. Computational and Experimental Simulations of Cr(VI) Remediation via In Situ Reduction in an Alluvial Aquifer at Hinkley, California

    Science.gov (United States)

    Bobb, C.; Miller, L. G.; Kent, D. B.; Maher, K.

    2015-12-01

    The accumulation of hexavalent chromium (Cr(VI)) in groundwater due to natural and human-induced processes poses a significant health threat as Cr(VI) is both a carcinogen and mutagen. Anthropogenic Cr(VI) contamination has compromised drinking water in the alluvial aquifer underlying the town of Hinkley, CA and extensive in-situ remediation (ISR) is underway to mitigate the threat to residents. ISR capitalizes on the redox sensitivity of chromium by using ethanol to reduce soluble, toxic, Cr(VI) to insoluble and non-hazardous Cr(III). However, the sequence of reduction reactions that occurs within the aquifer is not well understood. Therefore, we use computer-modeled and experimental redox titrations to examine how pH, oxygen supply, mineral surface chemistry, agitation, and microbial activity impact the reduction of Cr(VI) by ethanol. We further use experimental titrations to confirm the validity of our modeled results. Aqueous and gaseous phases are monitored throughout the experiment to track changes in pH, dissolved oxygen, CO2, Mn(II), Fe(II), and SO42-. Aqueous Fe(II) is a dominant control on Cr(VI) reduction; thus the cycling of Fe in the system must be considered. Our modeled results show that reductive dissolution of manganese oxides and Fe(III) (oxy)hydroxides increases pH, making sulfate reduction thermodynamically favorable. Simultaneous Fe(III) and sulfate reduction allows precipitation of iron sulfide minerals, limiting the available Fe(II) to reduce Cr(VI). Computational model results indicate that elevated organic buffer (HEPES, MOPS, EPPS) concentrations are required to maintain pH values below 8.8 where simultaneous reduction of Fe(III) and SO42- during ethanol oxidation becomes thermodynamically favorable. Microbial activity within the aquifer may also play a significant role in the transfer of electrons from ethanol to the terminal electron acceptors.

  7. Effect of genotype, Cr(III and Cr(VI on plant growth and micronutrient status in Silene vulgaris (Moench

    Directory of Open Access Journals (Sweden)

    A. E. Pradas-del-Real

    2013-06-01

    Full Text Available Chromium released into the environment from industrial activities has become an important environmental concern. Silene vulgaris has been proven to be tolerant to many heavy metals, so it is considered an interesting species in the revegetation and restoration of polluted soils, but no information is available about its response to Cr. The objective of this work was to study uptake and influence on plant growth of Cr(III and Cr(VI in six genotypes (four hermaphrodites and two females of S. vulgaris from different sites of Madrid (Spain. Plants were treated for 12 days with 60 µM of Cr(III or Cr(VI in semihydroponics. Dry weights, soil-plant analysis development values (SPAD reading with chlorophylls and micronutrient and total Cr concentrations were determined. Metal uptake was higher in presence of Cr(VI than of Cr(III and poorly translocated to the shoots. In both cases S. vulgaris did not show visual toxicity symptoms, biomass reduction, or differences among SPAD values as consequence of Cr additions. However genotypes SV36 and SV38 showed Fe and Mn imbalance. This is the first report on the relatively good performance of hermaphrodite and female S. vulgaris genotypes in Cr uptake and physiological traits, but further studies will be necessary to elucidate the mechanisms by which the gender may influence these variables. S. vulgaris presented high diversity at genotypic level; the treatment with hexavalent Cr increased the differences among genotypes so the use of cuttings from an homogeneous genotype seems to be an adequate method for the study of this species.

  8. Cr(VI) and Cr(III)-Based Conversion Coatings on Zinc

    NARCIS (Netherlands)

    Zhang, X.

    2005-01-01

    With the aims of understanding the protective mechanism of chromate conversion coatings and developing alternatives to chromate treatments, the physical natures and corrosion properties of Cr(VI) and Cr(III) treated zinc have been investigated in this work. The Cr(VI) treatments were carried out in

  9. Cr(VI) and Cr(III)-Based Conversion Coatings on Zinc

    NARCIS (Netherlands)

    Zhang, X.

    2005-01-01

    With the aims of understanding the protective mechanism of chromate conversion coatings and developing alternatives to chromate treatments, the physical natures and corrosion properties of Cr(VI) and Cr(III) treated zinc have been investigated in this work. The Cr(VI) treatments were carried out in

  10. Hybrid materials: Magnetite-Polyethylenimine-Montmorillonite, as magnetic adsorbents for Cr(VI) water treatment.

    Science.gov (United States)

    Larraza, Iñigo; López-Gónzalez, Mar; Corrales, Teresa; Marcelo, Gema

    2012-11-01

    Hybrid materials formed by the combination of a sodium rich Montmorillonite (MMT), with magnetite nanoparticles (40 nm, Fe(3)O(4) NPs) coated with Polyethylenimine polymer (PEI 800 g/mol or PEI 25000 g/mol) were prepared. The intercalation of the magnetite nanoparticles coated with PEI among MMT platelets was achieved by cationic exchange. The resulting materials presented a high degree of exfoliation of the MMT sheets and a good dispersion of Fe(3)O(4) NPs on both the surface and among the layers of MMT. The presence of amine groups in the PEI structure not only aids the exfoliation of the MMT layers, but also gives to the hybrid material the necessary functionality to interact with heavy metals. These hybrid materials were used as magnetic sorbent for the removal of hexavalent chromium from water. The effect that pH, Cr(VI) concentration, and adsorbent material composition have on the Cr(VI) removal efficiency was studied. A complete characterization of the materials was performed. The hybrid materials showed a slight dependence of the removal efficiency with the pH in a wide range (1-9). A maximum amount of adsorption capacity of 8.8 mg/g was determined by the Langmuir isotherm. Results show that these hybrid materials can be considered as potential magnetic adsorbent for the Cr(VI) removal from water in a wide range of pH.

  11. Cr(VI) uptake mechanism of Bacillus cereus.

    Science.gov (United States)

    Chen, Zhi; Huang, Zhipeng; Cheng, Yangjian; Pan, Danmei; Pan, Xiaohong; Yu, Meijuan; Pan, Zhiyun; Lin, Zhang; Guan, Xiong; Wu, Ziyu

    2012-04-01

    In this study, we investigated the Cr(VI) uptake mechanism in an indigenous Cr(VI)-tolerant bacterial strain -Bacillus cereus through batch and microscopic experiments. We found that both the cells and the supernatant collected from B. cereus cultivation could reduce Cr(VI). The valence state analysis revealed the complete transformation from Cr(VI) into Cr(III) by living B. cereus. Further X-ray absorption fine structure and Fourier transform infrared analyses showed that the reduced Cr(III) was coordinated with carboxyl and amido functional groups from either the cells or supernatant. Scanning electron microscopy and atomic force microscopy observation showed that noticeable Cr(III) precipitates were accumulated on bacterial surfaces. However, Cr(III) could also be detected in bacterial inner portions by using transmission electron microscopy thin section analysis coupled with energy dispersive X-ray spectroscopy. Through quantitative analysis of chromium distribution, we determined the binding ratio of Cr(III) in supernatant, cell debris and cytoplasm as 22%, 54% and 24%, respectively. Finally, we further discussed the role of bacterium-origin soluble organic molecules to the remediation of Cr(VI) pollutants.

  12. Integrated Cr(VI) removal using constructed wetlands and composting.

    Science.gov (United States)

    Sultana, Mar-Yam; Chowdhury, Abu Khayer Md Muktadirul Bari; Michailides, Michail K; Akratos, Christos S; Tekerlekopoulou, Athanasia G; Vayenas, Dimitrios V

    2015-01-08

    The present work was conducted to study integrated chromium removal from aqueous solutions in horizontal subsurface (HSF) constructed wetlands. Two pilot-scale HSF constructed wetlands (CWs) units were built and operated. One unit was planted with common reeds (Phragmites australis) and one was kept unplanted. Influent concentrations of Cr(VI) ranged from 0.5 to 10mg/L. The effect of temperature and hydraulic residence time (8-0.5 days) on Cr(VI) removal were studied. Temperature was proved to affect Cr(VI) removal in both units. In the planted unit maximum Cr(VI) removal efficiencies of 100% were recorded at HRT's of 1 day with Cr(VI) concentrations of 5, 2.5 and 1mg/L, while a significantly lower removal rate was recorded in the unplanted unit. Harvested reed biomass from the CWs was co-composted with olive mill wastes. The final product had excellent physicochemical characteristics (C/N: 14.1-14.7, germination index (GI): 145-157%, Cr: 8-10mg/kg dry mass), fulfills EU requirements and can be used as a fertilizer in organic farming. Copyright © 2014 Elsevier B.V. All rights reserved.

  13. Nitrate Enhanced Microbial Cr(VI) Reduction-Final Report

    Energy Technology Data Exchange (ETDEWEB)

    John F. Stolz

    2011-06-15

    A major challenge for the bioremediation of radionuclides (i.e., uranium, technetium) and metals (i.e., Cr(VI), Hg) is the co-occurrence of nitrate as it can inhibit metal transformation. Denitrification (nitrate reduction to dinitrogen gas) is considered the most important ecological process. For many metal and metalloid reducing bacteria, however, ammonia is the end product through respiratory nitrate reduction (RNRA). The focus of this work was to determine how RNRA impacts Cr(VI) transformation. The goal was to elucidate the specific mechanism(s) that limits Cr(VI) reduction in the presence of nitrate and to use this information to develop strategies that enhance Cr(VI) reduction (and thus detoxification). Our central hypothesis is that nitrate impacts the biotransformation of metals and metalloids in three ways 1) as a competitive alternative electron acceptor (inhibiting transformation), 2) as a co-metabolite (i.e., concomitant reduction, stimulating transformation), and 3) as an inducer of specific proteins and pathways involved in oxidation/reduction reactions (stimulating transformation). We have identified three model organisms, Geobacter metallireducens (mechanism 1), Sulfurospirillum barnesii, (mechasism 2), and Desulfovibrio desulfuricans (mechanisms 3). Our specific aims were to 1) investigate the role of Cr(VI) concentration on the kinetics of both growth and reduction of nitrate, nitrite, and Cr(VI) in these three organisms; 2) develop a profile of bacterial enzymes involved in nitrate transformation (e.g., oxidoreductases) using a proteomic approach; 3) investigate the function of periplasmic nitrite reductase (Nrf) as a chromate reductase; and 4) develop a strategy to maximize microbial chromium reduction in the presence of nitrate. We found that growth on nitrate by G. metallireducens was inhibited by Cr(VI). Over 240 proteins were identified by LC/MS-MS. Redox active proteins, outer membrane heavy metal efflux proteins, and chemotaxis sensory

  14. Microbial community changes during sustained Cr(VI) reduction at the 100H site in Hanford, WA

    Energy Technology Data Exchange (ETDEWEB)

    Chakraborty, Romy; Brodie, Eoin L; Faybishenko, Boris; Piceno, Yvette M; Tom, Lauren; Choudhuri, Swati; Beller, Harry R; Liu, Jenny; Torok, Tamas; Joyner, Dominique C; Joachimiak, Marcin P; Zhou, Aifen; Van Nostrand, Joy D; Zhou, Joe; Long, Phil E; Newcomer, Darrell R; Andersen, Gary L; Hazen, Terry C.

    2010-05-17

    Hexavalent Chromium is a widespread contaminant found in soil, sediment, and groundwater. In order to stimulate microbially-mediated reduction of Cr(VI), a poly-lactate compound (HRC) was injected into the Chromium-contaminated aquifer at the Hanford (WA) 100H site in 2004. Cr(VI) concentrations rapidly declined to below the detection limit and remained so for more than three years after injection. Based on the results of the bacterial community composition using high-density DNA 16S rRNA gene microarrays, we observed the community to transition through denitrifying, ironreducing and sulfate-reducing populations. As a result, we specifically focused isolation efforts on three bacterial species that were significant components of the community. Positive enrichments in defined anaerobic media resulted in the isolation of an iron-reducing Geobacter metallireducens-like isolate, a sulfate-reducing Desulfovibrio vukgaris-like strain and a nitrate-reducing Pseudomonas stutzeri-like isolate among several others. All of these isolates were capable of reducing Cr(VI) anoxically and have been submitted for genome sequencing to JGI. To further characterize the microbial, and geochemical mechanisms associated with in situ Cr(VI) reduction at the site, additional HRC was injected in 2008. The goal was to restimulate the indigenous microbial community and to regenerate the reducing conditions necessary for continued Cr(VI) bio-immobilization in the groundwater. Analysis of the microbial populations post-injection revealed that they recovered to a similar density as after the first injection in 2004. In this study, we present the results from our investigation into microbially-mediated Cr(VI) reduction at Hanford, and a comparison of the microbial community development following two HRC injections four years apart.

  15. Cr isotope fractionation factors for Cr(VI) reduction by a metabolically diverse group of bacteria

    Science.gov (United States)

    Basu, Anirban; Johnson, Thomas M.; Sanford, Robert A.

    2014-10-01

    Reduction of Cr(VI) is an important process that determines the geochemical behavior, mobility and bioavailability of Cr in both terrestrial and marine environments. Many metabolically diverse microorganisms possess Cr(VI) reduction capacity. Cr(VI) reduction fractionates Cr isotopes and thus 53Cr/52Cr ratios can be used to monitor Cr(VI) reduction and redox conditions. The magnitude of isotopic fractionation (ε) for a variety of microbial reduction mechanisms must be known for accurate interpretation of observed shifts in 53Cr/52Cr ratios. We determined isotopic fractionation factors for Cr(VI) reduction by metal reducers Geobacter sulfurreducens and Shewanella sp. strain NR, a denitrifying soil bacterium Pseudomonas stutzeri DCP-Ps1, and a sulfate reducer Desulfovibrio vulgaris. All bacteria investigated in this study produced significant Cr isotope fractionation. The fractionation (ε) for G. sulfurreducens, Shewanella sp. (NR), P. stutzeri DCP-Ps1, and D. vulgaris were -3.03‰ ± 0.12‰, -2.17‰ ± 0.22‰, -3.14‰ ± 0.13‰, and -3.01‰ ± 0.11‰, respectively. Despite differences in microbial strains in this study, the ε did not vary significantly except for Shewanella sp. (NR). Our results suggest that strong isotopic fractionation is induced during Cr(VI) reduction under electron donor poor (∼300 μM) conditions.

  16. Assessment of genotoxic potential of Cr(VI) in the mouse duodenum: an in silico comparison with mutagenic and nonmutagenic carcinogens across tissues.

    Science.gov (United States)

    Thompson, Chad M; Gregory Hixon, J; Proctor, Deborah M; Haws, Laurie C; Suh, Mina; Urban, Jonathan D; Harris, Mark A

    2012-10-01

    In vitro studies on hexavalent chromium [Cr(VI)] indicate that reduced forms of this metal can interact with DNA and cause mutations. Recently, Cr(VI) was shown to induce intestinal tumors in mice; however, Cr(VI) elicited redox changes, cytotoxicity and hyperplasia - suggesting involvement of tissue injury rather than direct mutagenesis. Moreover, toxicogenomic analyses indicated limited evidence for DNA damage responses. Herein, we extend these toxicogenomic analyses by comparing the gene expression patterns elicited by Cr(VI) with those of four mutagenic and four nonmutagenic carcinogens. To date, toxicogenomic profiles for mutagenic and nonmutagenic duodenal carcinogens do not exist, thus duodenal gene changes in mice were compared to those elicited by hepatocarcinogens. Specifically, duodenal gene changes in mice following exposure to Cr(VI) in drinking water were compared to hepatic gene changes previously identified as potentially discriminating mutagenic and nonmutagenic hepatocarcinogens. Using multivariate statistical analyses (including logistic regression classification), the Cr(VI) gene responses clustered apart from mutagenic carcinogens and closely with nonmutagenic carcinogens. These findings are consistent with other intestinal data supporting a nonmutagenic mode of action (MOA). These findings may be useful as part of a full weight of evidence MOA evaluation for Cr(VI)-induced intestinal carcinogenesis. Limitations to this analysis will also be discussed.

  17. Investigations of HRC®-Stimulated Bioreduction of Cr(VI) at Hanford 100H

    Energy Technology Data Exchange (ETDEWEB)

    Hazen, T.C.; Faybishenko, B.; Joyner, D.; Borglin, S.; Brodie, E.; Hubbard, S.; Williams, K.; Peterson, J.; Wan, J.; Tokunaga, T.; Firestone, M.; Long, P.E.; Resch, C.T.; Cantrell, K.; Newcomer, D.; Koenigsberg, S.; Willet, A.

    2006-04-05

    Hypothesis: Lactate (Hydrogen Release Compound-HRC{trademark}) injection into chromium contaminated groundwater through an injection well will cause indirect or direct bioreduction of chromate [Cr(VI)] and precipitation of insoluble species of [Cr(III)] on soil particles, probably catalyzed at oxide surfaces, at the field scale. Objective: Assess the potential for immobilizing and detoxifying chromium-contaminated groundwater using lactate-stimulated bioreduction of Cr(VI) to Cr(III) at the Hanford Site's 100-H Area field site. Types of Research: A three-well system (injection well and upgradient and downgradient monitoring wells) was used for conducting the in situ biostimulation and monitoring. To assess the pre- and post-injection test groundwater conditions, we used an integrated monitoring approach, involving hydraulic, geochemical, microbial, and geophysical techniques and analytical methods, as well as conducted five Br-tracer injection tests and four pumping tests (concurrently with the Br-tracer tests). Groundwater biostimulation was conducted by injection of 40 lbs of {sup 13}C-labeled HRC into the injection well (over the depth interval from 44-50 ft) on 8/3/2004, followed by low-flow pumping (1.2 to 2.5 l/min) through the downgradient well (to ensure capture of groundwater flow lines passing through the injection well) for 27 days. Main Results: Although the total microbial population in sediments is relatively low (<10{sup 5} cells g{sup -1}) under background conditions, which is likely insufficient for direct enzymatic Cr(VI) reduction, several types of bacteria, e.g., Bacillus/Arthrobacter and Geobacter, are present in the Hanford sediments, which are known to reduce or sorb hexavalent chromium. The HRC injection stimulated microbial cell counts to reach the maximum of 2 x 10{sup 7} cells g{sup -1} 13-17 days after the injection, and generated highly reducing conditions. Geochemical and isotopic observations confirmed microbial metabolism of HRC

  18. Microbial reduction of hexavalent chromium by landfill leachate.

    Science.gov (United States)

    Li, Yarong; Low, Gary K-C; Scott, Jason A; Amal, Rose

    2007-04-02

    The reduction of hexavalent chromium (Cr(VI)) in municipal landfill leachates (MLL) and a non-putrescible landfill leachate (NPLL) was investigated. Complete Cr(VI) reduction was achieved within 17 days in a MLL when spiked with 100 mg l(-1) Cr(VI) or less. In the same period, negligible Cr(VI) reduction was observed in NPLL. In MLL, Cr(VI) reduction was demonstrated to be a function of initial Cr(VI) concentration and bacterial biomass and organic matter concentrations. The bacteria were observed to tolerate 250 mg l(-1) Cr(VI) in MLL and had an optimal growth activity at pH 7.4 in a growth medium. The MLL also possessed an ability to sequentially reduce Cr(VI) over three consecutive spiking cycles.

  19. Removal of Cr(VI) from wastewaters at semi-industrial electrochemical reactors with rotating ring electrodes

    Energy Technology Data Exchange (ETDEWEB)

    Rodriguez R, Miriam G. [Depto. Energia, Universidad Autonoma Metropolitana-Azcapotzalco, Av. San Pablo 180, Azcapotzalco, CP 07740, Mexico D.F. (Mexico); Mendoza, Victor [Depto. Electronica, Universidad Autonoma Metropolitana-Azcapotzalco, Av. San Pablo 180, Azcapotzalco, CP 07740, Mexico D.F. (Mexico); Puebla, Hector [Depto. Energia, Universidad Autonoma Metropolitana-Azcapotzalco, Av. San Pablo 180, Azcapotzalco, CP 07740, Mexico D.F. (Mexico); Martinez D, Sergio A. [Depto. Energia, Universidad Autonoma Metropolitana-Azcapotzalco, Av. San Pablo 180, Azcapotzalco, CP 07740, Mexico D.F. (Mexico)], E-mail: samd@correo.azc.uam.mx

    2009-04-30

    In Mexico, most of the electroplating and textile industries are small facilities and release relatively large amounts of hexavalent chromium (Cr(VI)) in surface waters. In this work, the results obtained during the operation of a batch reactor with a capacity of 170 L, and three electrochemical flow reactors-in-series system with a total capacity of 510 L (both using iron rotating ring electrodes to remove Cr(VI) from wastewaters) are presented. The reactors were scaled up from a laboratory reactor to a semi-industrial level, based on the similarity (dynamical, geometrical and electrochemical). An empirical Cr(VI) removal model was validated in batch and continuous reactors at different operating conditions. Cr(VI) concentration of the industrial wastewaters was reduced from about 500 mg/L to values lower than 0.5 mg/L. A very important parameter that affects the process is the pH, which affects the solubility of the Fe(III). Finally, the electrochemical treated wastewater can be reused.

  20. A novel modified graphene oxide/chitosan composite used as an adsorbent for Cr(VI) in aqueous solutions.

    Science.gov (United States)

    Zhang, Li; Luo, Hanjin; Liu, Peipei; Fang, Wei; Geng, Junjie

    2016-06-01

    A novel adsorbent for removal of hexavalent chromium (Cr(VI)) from aqueous solutions has been successfully prepared by modifying graphene oxide/chitosan composite with disodium ethylenediaminetetraacetate (EDTA-2Na) (GEC). This modified composite was characterized by various technologies; including scanning electron microscopy (SEM), Transmission Electron Microscopy (TEM), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR). Batch adsorption experiments were carried out to evaluate the adsorption of Cr(VI) by GEC under different conditions. The results indicate that the adsorption of Cr(VI) on GEC was highly pH-dependent, with the highest adsorption capacity (86.17mg/g) occurring at pH 2. The kinetics of adsorption exhibited pseudo-second-order behavior. The adsorption data were well described by the Freundlich isotherm model. The adsorption capacity increased with increasing temperature. The calculated thermodynamic parameters indicate that the adsorption is a spontaneous, endothermic and feasible process. The further regeneration experiments showed the adsorption capacity of GEC for Cr(VI) decreased 5% after 7 times reuse, indicating the potential of the as-prepared material for practical application.

  1. Biosorption of Cr(VI)_ and Cr(III)_Arthrobacter species

    CERN Document Server

    Gelagutashvili, E; Gurielidze, M

    2011-01-01

    The biosorption of Cr(VI)_ and Cr(III)_ Arthrobacter species (Arthrobacter globiformis and Arthrobacter oxidas) was studied simultaneous application dialysis and atomic absorption analysis. Also biosorption of Cr(VI) in the presence of Zn(II) during growth of Arthrobacter species and Cr(III) in the presence of Mn(II) were discussed. Comparative Cr(VI)_ and Cr(III)_ Arthrobacter species shown, that Cr(III) was more effectively adsorbed by both bacterium than Cr(VI). The adsorption capacity is the same for both the Chromium-Arthrobacter systems. The biosorption constants for Cr(III) is higher than for Cr(VI) 5.7-5.9- fold for both species. Comparative Freundlich biosorption characteristics Cr(VI) Arthrobacter species of living and dry cells shown, that capacity(n) is in both cases the same(1.25,1.35). Dry cells have larger biosorption constant for both species, than living cells. Biosorption characteristics (K) and (n) for A. oxidas are without Mn(II) and in the presence of Mn(II) 2.6 x 10-4 (K), 1.37 (n) and 2...

  2. Specification of the Operational Parameters Contribution in the Efficiency of TiO2-P25 Nanoparticles in the Photocatalytic Removal of Cr(VI by Taguchi Method

    Directory of Open Access Journals (Sweden)

    Maryam SabonianSchoolari

    2014-12-01

    Full Text Available Chromium exists in environment both as trivalent [Cr(III] and hexavalent [Cr(VI] forms. However, hexavalent form is five hundred times more toxic than the trivalent form. Heterogeneous photocatalysis processes, using aqueous suspensions of semiconductors, have received considerable attention in the removal of toxic metals from aqueous media. In this work the nanoparticles of TiO2-P25 in the form of slurry were used for photoreduction of Cr(VI to the less harmful Cr(III. The process has been conducted in different operational conditions such as different initial concentrations of Cr(VI, dosage of photocatalyst, irradiation times, irradiation intensities of light and pH. For the optimization of the process Taguchi experimental design was used. The results of optimization using the Taguchi method, indicated that the pH with 28%, initial concentration of Cr(VI with 26.99% and dosage of TiO2 nanocatalyst with 20.53% have the most effects among the selected factors. The intensity of UV light irradiation has the least effect on the efficiency of the process.

  3. Impact of Fe(III) as an effective electron-shuttle mediator for enhanced Cr(VI) reduction in microbial fuel cells: Reduction of diffusional resistances and cathode overpotentials

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Qiang [Key Laboratory of Industrial Ecology and Environmental Engineering, Ministry of Education (MOE), School of Environmental Science and Technology, Dalian University of Technology, Dalian 116024 (China); Huang, Liping, E-mail: lipinghuang@dlut.edu.cn [Key Laboratory of Industrial Ecology and Environmental Engineering, Ministry of Education (MOE), School of Environmental Science and Technology, Dalian University of Technology, Dalian 116024 (China); Pan, Yuzhen [College of Chemistry, Dalian University of Technology, Dalian 116024 (China); Quan, Xie [Key Laboratory of Industrial Ecology and Environmental Engineering, Ministry of Education (MOE), School of Environmental Science and Technology, Dalian University of Technology, Dalian 116024 (China); Li Puma, Gianluca, E-mail: g.lipuma@lboro.ac.uk [Environmental Nanocatalysis & Photoreaction Engineering, Department of Chemical Engineering, Loughborough University, Loughborough LE11 3TU (United Kingdom)

    2017-01-05

    Highlights: • Fe(III) shuttles electrons for enhanced reduction of Cr(VI) in MFCs. • The coulombic efficiency increases by 1.6 fold in the presence of Fe(III). • The reduction of Cr(VI) occurs via an indirect Fe(III) mediation mechanism. • Fe(III) decreases the diffusional resistances and the cathode overpotentials. - Abstract: The role of Fe(III) was investigated as an electron-shuttle mediator to enhance the reduction rate of the toxic heavy metal hexavalent chromium (Cr(VI)) in wastewaters, using microbial fuel cells (MFCs). The direct reduction of chromate (CrO{sub 4}{sup −}) and dichromate (Cr{sub 2}O{sub 7}{sup 2−}) anions in MFCs was hampered by the electrical repulsion between the negatively charged cathode and Cr(VI) functional groups. In contrast, in the presence of Fe(III), the conversion of Cr(VI) and the cathodic coulombic efficiency in the MFCs were 65.6% and 81.7%, respectively, 1.6 times and 1.4 folds as those recorded in the absence of Fe(III). Multiple analytical approaches, including linear sweep voltammetry, Tafel plot, cyclic voltammetry, electrochemical impedance spectroscopy and kinetic calculations demonstrated that the complete reduction of Cr(VI) occurred through an indirect mechanism mediated by Fe(III). The direct reduction of Cr(VI) with cathode electrons in the presence of Fe(III) was insignificant. Fe(III) played a critical role in decreasing both the diffusional resistance of Cr(VI) species and the overpotential for Cr(VI) reduction. This study demonstrated that the reduction of Cr(VI) in MFCs was effective in the presence of Fe(III), providing an alternative and environmentally benign approach for efficient remediation of Cr(VI) contaminated sites with simultaneous production of renewable energy.

  4. In Situ Long-Term Reductive Bioimmobilization of Cr(VI) in Groundwater Using Hydrogen Release Compound

    Energy Technology Data Exchange (ETDEWEB)

    Faybishenko, Boris; Hazen, Terry C.; Long, Philip E.; Brodie, Eoin L.; Conrad, Mark S.; Hubbard, Susan; Christensen, John N.; Joyner, Dominique; Borglin, Sharon; Chakraborty, Romy; Williams, Kenneth H.; Peterson, John E.; Chen, Jinsong; Brown, Shaun T.; Tokunaga, Tetsu K.; Wan, Jiamin; Firestone, Mary; Newcomer, Darrell R.; Resch, Charles T.; Cantrell, Kirk J.; Willett, Anna; Koenigsberg, Stephen

    2008-11-15

    Here we describe a novel approach for, and present evidence of the effectiveness of, long-term, in situ bioimmobilization of toxic and soluble Cr(VI) in groundwater using a 13C-labeled slow-release polylactate. A field experiment was conducted at Hanford (Washington), the U.S. Department of Energy nuclear site. A combination of in situ hydrogeological, geophysical, geochemical, and microbiological measurements and analyses of water samples and sediments provided detailed and reliable description of in situ biogeochemical processes. The results of this experiment show that a single lactate injection into Cr(VI)-contaminated groundwater stimulates an average increase in biomass by up to 50 times, from—5∙105 to 2.5∙107 cells/mL. The results also show a depletion of terminal electron acceptors O2, NO3-, and SO42- , and an increase in Fe2+. The biogeochemical processes, including the reaction of ferrous ion with hexavalent Cr, cause the formation of nontoxic and insoluble trivalent Cr precipitates. Cr(VI) concentration in the lactate injection well has remained below the background concentration in downgradient monitoring wells and below the drinking water standards for 3 years. The current studies suggest that Cr(VI) biogeochemical immobilization under these conditions may be fairly resilient, the applicability and degree of resilience under different redox conditions at this and other contaminated sites is currently under study.

  5. Development of iron-based nanoparticles for Cr(VI) removal from drinking water

    Science.gov (United States)

    Simeonidis, K.; Tziomaki, M.; Angelakeris, M.; Martinez-Boubeta, C.; Balcells, Ll.; Monty, C.; Mitrakas, M.; Vourlias, G.; Andritsos, N.

    2013-01-01

    A great deal of research over recent decades has been motivated by the requirement to lower the concentration of chromium in drinking water. This study has been conducted to determine the feasibility of iron-based nanoparticles for chromium removal from contaminated water. Single Fe, Fe3O4 and binary Fe/Fe3O4 nanoparticles were grown at the 45-80 nm size range using the solar physical vapor deposition technique and tested as potential hexavalent chromium removing agents from aqueous solutions. Due to their higher electron donation ability compared to the Fe3O4 ones, single Fe nanoparticles exhibited the highest Cr(VI) removal capacity of more than 3 µg/mg while maintaining a residual concentration 50 µg/L, equal to the regulation limit for drinking water. In combination to their facile and fast magnetic separation, the applicability of the studied particles in water treatment facilities should be considered.

  6. Development of iron-based nanoparticles for Cr(VI removal from drinking water

    Directory of Open Access Journals (Sweden)

    Vourlias G.

    2013-01-01

    Full Text Available A great deal of research over recent decades has been motivated by the requirement to lower the concentration of chromium in drinking water. This study has been conducted to determine the feasibility of iron-based nanoparticles for chromium removal from contaminated water. Single Fe, Fe3O4 and binary Fe/Fe3O4 nanoparticles were grown at the 45-80 nm size range using the solar physical vapor deposition technique and tested as potential hexavalent chromium removing agents from aqueous solutions. Due to their higher electron donation ability compared to the Fe3O4 ones, single Fe nanoparticles exhibited the highest Cr(VI removal capacity of more than 3 µg/mg while maintaining a residual concentration 50 µg/L, equal to the regulation limit for drinking water. In combination to their facile and fast magnetic separation, the applicability of the studied particles in water treatment facilities should be considered.

  7. Application of termite nest for adsorption of Cr(VI).

    Science.gov (United States)

    Araújo, B R; Reis, J O M; Rezende, E I P; Mangrich, A S; Wisniewski, A; Dick, D P; Romão, L P C

    2013-11-15

    This work proposes the use of tree termite nest as an adsorbent for the reduction/removal of Cr(VI) present in aqueous solution. In laboratory experiments, adsorption of Cr(VI) was sensitive to pH in the range investigated (2-5), with maximum adsorption capacity achieved at pH 2 (3.70 ± 0.04 mg g(-1), representing 93.2% removal of Cr). The termite nest was characterized by off-line pyrolysis GC/MS (py-GC/MS), infrared spectroscopy (FTIR), and electron paramagnetic resonance spectroscopy (EPR). Pyrolysis of the adsorbent produced a complex mixture of aromatic compounds, including the guaiacyl and syringilic derivatives that are characteristic of lignocellulosic materials. Infrared spectroscopy revealed deprotonation of the carboxylic acid group of the biomass with increasing pH, which was associated with a decrease in the capacity for adsorption of Cr(VI). The EPR g-factor for the termite nest samples varied between 2.0037 and 2.0038, indicating the presence of organic free radicals that were responsible for the redox reaction. A second line with g-factor values of 1.9790, only observed for the samples after contact with Cr(VI) solutions at different pH values, was assigned to Cr(III)-Cr(III) exchange coupled pairs, which explained the capacity of the adsorbent to retain a large portion of the Cr(III) ions produced after reduction of Cr(VI) to Cr(III). Fixed-bed column experiments showed that the termite nest had a maximum adsorption capacity of 18.60 mg Cr g(-1), an adsorption efficiency varying between 60.8 and 97.4%, and a desorption efficiency varying between 54.5 and 91.4%, for three successive cycles. The adsorbent presented excellent performance in the removal of chromium under acidic conditions, with the advantage that it could be regenerated and reused. Copyright © 2013 Elsevier Ltd. All rights reserved.

  8. Biological and chemical removal of Cr(VI) from waste water: cost and benefit analysis.

    Science.gov (United States)

    Demir, Aynur; Arisoy, Münevver

    2007-08-17

    The objective of the present study is cost and benefit analysis of biological and chemical removal of hexavalent chromium [Cr(VI)] ions. Cost and benefit analysis were done with refer to two separate studies on removal of Cr(VI), one of heavy metals with a crucial role concerning increase in environmental pollution and disturbance of ecological balance, through biological adsorption and chemical ion-exchange. Methods of biological and chemical removal were compared with regard to their cost and percentage in chrome removal. According to the result of the comparison, cost per unit in chemical removal was calculated 0.24 euros and the ratio of chrome removal was 99.68%, whereas those of biological removal were 0.14 and 59.3% euros. Therefore, it was seen that cost per unit in chemical removal and chrome removal ratio were higher than those of biological removal method. In the current study where chrome removal is seen as immeasurable benefit in terms of human health and the environment, percentages of chrome removal were taken as measurable benefit and cost per unit of the chemicals as measurable cost.

  9. Elucidating the mechanism of Cr(VI) formation upon the interaction with metal oxides during coal oxy-fuel combustion.

    Science.gov (United States)

    Chen, Juan; Jiao, Facun; Zhang, Lian; Yao, Hong; Ninomiya, Yoshihiko

    2013-10-15

    The thermodynamics underpinning the interaction of Cr-bearing species with basic metal oxides, i.e. K2O, Fe2O3, MgO and CaO, during the air and oxy-fuel combustion of coal have been examined. The synchrotron-based X-ray adsorption near-edge spectroscopy (XANES) was used for Cr speciation. For the oxides tested, Cr(VI) formation is dominated by the reduction potential of the metals. The oxides of Ca(2+) with high reduction potential favored the oxidation of Cr(III), same for K(+). The other two basic metals, Fe2O3 and MgO with lower reduction potentials reacted with Cr(III) to form the corresponding chromites at the temperatures above 600°C. Coal combustion experiments in drop-tube furnace have confirmed the rapid capture of Cr vapors, either trivalent or hexavalent, by CaO into solid ash. The existence of HCl in flue gas favored the vaporization of Cr as CrO2Cl2, which was in turn captured by CaO into chromate. Both Fe2O3 and MgO exhibited less capability on scavenging the Cr(VI) vapor. Particularly, MgO alone exhibited a low capability for capturing the vaporized Cr(III) vapors. However, its co-existence with CaO in the furnace inhibited the Cr(VI) formation. This is beneficial for minimizing the toxicity of Cr in the coal combustion-derived fly ash.

  10. High performance NiFe layered double hydroxide for methyl orange dye and Cr(VI) adsorption.

    Science.gov (United States)

    Lu, Yi; Jiang, Bin; Fang, Liang; Ling, Faling; Gao, Jiemei; Wu, Fang; Zhang, Xihua

    2016-06-01

    The NiFe layered double hydroxides (LDHs) with different mole ratio of Ni/Fe (4:1, 3:1, 7:3 and 1:1) were prepared by a simple coprecipitation method. The adsorption performance were evaluated by the removal of methyl orange (MO) dye and hexavalent chromium(VI) heavy metal ion. It is found that Ni4Fe1-LDH can remove more than 92% of MO in 10 min at the 10 mg/L MO initial concentration, and 97% of Cr(VI) in 1 h at 4 mg/L Cr2O7(2-) initial concentration. The saturated adsorption capacity of Ni4Fe1-LDH is found to be as large as 205.76 mg/g for MO and 26.78 mg/g for Cr(VI). The adsorption behavior of this new adsorbent is fitted well with Langmuir isotherm and the pseudo-second-order kinetic model, indicative of a monolayer and chemical adsorption that synergistically originates from exchangeable anions mechanism and layer charge density. Due to the excellent removal capacity of MO and Cr(VI), the NiFe-LDHs could be a promising adsorbent for wastewater treatment.

  11. Proteomic analysis of chromium stress and sulfur deficiency responses in leaves of two canola (Brassica napus L.) cultivars differing in Cr(VI) tolerance.

    Science.gov (United States)

    Yıldız, Mustafa; Terzi, Hakan

    2016-02-01

    Sulfur (S) is an essential macronutrient for plant growth and development, and it plays an essential role in response to environmental stresses. Plants suffer with combined stress of S deficiency and hexavalent chromium [Cr(VI)] in the rhizosphere. Little is known about the impact of S deficiency on leaf metabolism of canola (Brassica napus L.) under Cr(VI) stress. Therefore, this study is the first to examine the effects of Cr(VI) stress and S deficiency in canola at a molecular level. A comparative proteomic approach was used to investigate the differences in protein abundance between Cr-tolerant NK Petrol and Cr-sensitive Sary cultivars. The germinated seeds were grown hydroponically in S-sufficient (+S) nutrient solution for 7 days and then subjected to S-deficiency (-S) for 7 days. S-deficient and +S seedlings were then exposed to 100μM Cr(VI) for 3 days. Protein patterns analyzed by two-dimensional electrophoresis (2-DE) revealed that 58 protein spots were differentially regulated by Cr(VI) stress (+S/+Cr), S-deficiency (-S/-Cr) and combined stress (-S/+Cr). Of these, 39 protein spots were identified by MALDI-TOF/TOF mass spectrometry. Differentially regulated proteins predominantly had functions not only in photosynthesis, but also in energy metabolism, stress defense, protein folding and stabilization, signal transduction, redox regulation and sulfur metabolism. Six stress defense related proteins including 2-Cys peroxiredoxin BAS1, glutathione S-transferase, ferritin-1, l-ascorbate peroxidase, thiazole biosynthetic enzyme and myrosinase-binding protein-like At3g16470 exhibited a greater increase in NK Petrol. The stress-related proteins play an important role in the detoxification of Cr(VI) and maintaining cellular homeostasis under variable S nutrition.

  12. Mechanism of Cr(VI) adsorption by coir pith studied by ESR and adsorption kinetic.

    Science.gov (United States)

    Suksabye, Parinda; Nakajima, Akira; Thiravetyan, Paitip; Baba, Yoshinari; Nakbanpote, Woranan

    2009-01-30

    The oxidation state of chromium in coir pith after Cr(VI) adsorption from aqueous solution was investigated using electron spin resonance (ESR). To elucidate the mechanism of chromium adsorption on coir pith, the adsorption studies of Cr(VI) onto lignin, alpha-cellulose and holocellulose extracted from coir pith were also studied. ESR signals of Cr(V) and Cr(III) were observed in coir pith adsorbed Cr(VI) at solution pH 2, while ESR spectra of lignin extracted from coir pith revealed only the Cr(III) signal. In addition, ESR signal of Cr(V) was observed in alpha-cellulose and holocellulose extracted from coir pith adsorbed Cr(VI). These results confirmed that lignin in coir pith reduced Cr(VI) to Cr(III) while alpha-cellulose and holocellulose extracted from coir pith reduced Cr(VI) to Cr(V). The Cr(V) signal exhibited in ESR of alpha-cellulose and holocellulose might be bound with glucose in cellulose part of coir pith. In addition, xylose which is main in pentosan part of coir pith, indicated that it is involved in form complex with Cr(V) on coir pith. The adsorption kinetic of Cr(VI) from aqueous solution on coir pith was also investigated and described well with pseudo second order model. ESR and desorption experiments confirmed that Cr(VI), Cr(V) and Cr(III), exist in coir pith after Cr(VI) adsorption. The desorption data indicated that the percentage of Cr(VI), Cr(V) and Cr(III) in coir pith were 15.63%, 12.89% and 71.48%, respectively.

  13. Mechanism of Cr(VI) adsorption by coir pith studied by ESR and adsorption kinetic

    Energy Technology Data Exchange (ETDEWEB)

    Suksabye, Parinda [Joint Graduate School of Energy and Environment, King Mongkut' s University of Technology Thonburi, 91 Pracha-Utit Road, Bangmod, Thungkru, Bangkok 10140 (Thailand); Nakajima, Akira [Division of Chemistry, Department of Medical Science, Faculty of Medicine, University of Miyazaki, Kiyotake, Miyazaki 889 1692 (Japan); Thiravetyan, Paitip [Division of Biotechnology, School of Bioresources and Technology, King Mongkut' s University of Technology Thonburi, 83 Moo.8 Thakham, Bangkhuntien, Bangkok 10150 (Thailand)], E-mail: paitip.thi@kmutt.ac.th; Baba, Yoshinari [Department of applied Chemistry, Faculty of Technology, University of Miyazaki, Gakuen-Kibabadai, Miyazaki 889 2192 (Japan); Nakbanpote, Woranan [Pilot Plant Development and Training Institute, King Mongkut' s University of Technology Thonburi, 83 Moo.8 Thakham, Bangkhuntien, Bangkok 10150 (Thailand)

    2009-01-30

    The oxidation state of chromium in coir pith after Cr(VI) adsorption from aqueous solution was investigated using electron spin resonance (ESR). To elucidate the mechanism of chromium adsorption on coir pith, the adsorption studies of Cr(VI) onto lignin, {alpha}-cellulose and holocellulose extracted from coir pith were also studied. ESR signals of Cr(V) and Cr(III) were observed in coir pith adsorbed Cr(VI) at solution pH 2, while ESR spectra of lignin extracted from coir pith revealed only the Cr(III) signal. In addition, ESR signal of Cr(V) was observed in {alpha}-cellulose and holocellulose extracted from coir pith adsorbed Cr(VI). These results confirmed that lignin in coir pith reduced Cr(VI) to Cr(III) while {alpha}-cellulose and holocellulose extracted from coir pith reduced Cr(VI) to Cr(V). The Cr(V) signal exhibited in ESR of {alpha}-cellulose and holocellulose might be bound with glucose in cellulose part of coir pith. In addition, xylose which is main in pentosan part of coir pith, indicated that it is involved in form complex with Cr(V) on coir pith. The adsorption kinetic of Cr(VI) from aqueous solution on coir pith was also investigated and described well with pseudo second order model. ESR and desorption experiments confirmed that Cr(VI), Cr(V) and Cr(III), exist in coir pith after Cr(VI) adsorption. The desorption data indicated that the percentage of Cr(VI), Cr(V) and Cr(III) in coir pith were 15.63%, 12.89% and 71.48%, respectively.

  14. Chromium sorption and Cr(VI) reduction to Cr(III) by grape stalks and yohimbe bark.

    Science.gov (United States)

    Fiol, Núria; Escudero, Carlos; Villaescusa, Isabel

    2008-07-01

    In this work, two low cost sorbents, grape stalks and yohimbe bark wastes were used to remove Cr(VI) and Cr(III) from aqueous solutions. Batch experiments were designed to obtain Cr(VI) and Cr(III) sorption data. The mechanism of Cr(III) and Cr(VI) removal and Cr(VI) reduction to Cr(III) by the two vegetable wastes, has been investigated. Fourier transform infrared rays (FTIR) and X-ray photoelectron spectroscopy (XPS) analysis on solid phase were performed to determine the main functional groups that might be involved in metal uptake and to confirm the presence of Cr(III) on the sorbent, respectively. Results put into evidence that both sorbents are able to reduce Cr(VI) to its trivalent form.

  15. Hexavalent Chromium Reduction under Fermentative Conditions with Lactate Stimulated Native Microbial Communities

    OpenAIRE

    Somenahally, Anil C.; Mosher, Jennifer J; Tong Yuan; Mircea Podar; Phelps, Tommy J.; Brown, Steven D.; Yang, Zamin K.; Hazen, Terry C.; Arkin, Adam P.; Palumbo, Anthony V.; Joy D Van Nostrand; Jizhong Zhou; Elias, Dwayne A.

    2013-01-01

    Microbial reduction of toxic hexavalent chromium (Cr(VI)) in-situ is a plausible bioremediation strategy in electron-acceptor limited environments. However, higher [Cr(VI)] may impose stress on syntrophic communities and impact community structure and function. The study objectives were to understand the impacts of Cr(VI) concentrations on community structure and on the Cr(VI)-reduction potential of groundwater communities at Hanford, WA. Steady state continuous flow bioreactors were used to ...

  16. Removal of Cr(VI) by zero-valent, iron-encapsulated alginate beads

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Xue Song; Tang, Yu Jun; Chen, Li Fang; Li, Fei Yan; Wan, Wen Ya; Tan, Ye Bin [Department of Chemical Engineering, Huaihai Institute of Technology, Jiangsu (China)

    2010-03-15

    Zero-valent, iron-encapsulated alginate beads were synthesized and were applied for the removal of Cr(VI) from aqueous solutions. The effects of several important parameters including solution pH, contact time, initial concentration and reaction temperature on Cr(VI) removal levels were investigated in batch studies. An initial solution pH of 1.0 was seen to be most favorable for Cr(VI) removal. The removal process was quick and almost 80% of the removal was attained within 60 min. The kinetic data followed the second-order equation well. The Cr(VI) removal was almost reaction temperature-independent and decreased with an increase in Cr(VI) initial concentration. The removal of Cr(VI) by iron-encapsulated alginate beads was found to be significantly higher than that of non-encapsulated alginate beads. (Abstract Copyright [2010], Wiley Periodicals, Inc.)

  17. Cr(VI) reduction by gluconolactone and hydrogen peroxide, the reaction products of fungal glucose oxidase: Cooperative interaction with organic acids in the biotransformation of Cr(VI).

    Science.gov (United States)

    Romo-Rodríguez, Pamela; Acevedo-Aguilar, Francisco Javier; Lopez-Torres, Adolfo; Wrobel, Kazimierz; Wrobel, Katarzyna; Gutiérrez-Corona, J Félix

    2015-09-01

    The Cr(VI) reducing capability of growing cells of the environmental A. tubingensis Ed8 strain is remarkably efficient compared to reference strains A. niger FGSC322 and A. tubingensis NRRL593. Extracellular glucose oxidase (GOX) activity levels were clearly higher in colonies developed in solid medium and in concentrated extracts of the spent medium of liquid cultures of the Ed8 strain in comparison with the reference strains. In addition, concentrated extracts of the spent medium of A. tubingensis Ed8, but not those of the reference strains, exhibited the ability to reduce Cr(VI). In line with this observation, it was found that A. niger purified GOX is capable of mediating the conversion of Cr(VI) to Cr(III) in a reaction dependent on the presence of glucose that is stimulated by organic acids. Furthermore, it was found that a decrease in Cr(VI) may occur in the absence of the GOX enzyme, as long as the reaction products gluconolactone and hydrogen peroxide are present; this conversion of Cr(VI) is stimulated by organic acids in a reaction that generates hydroxyl radicals, which may involve the formation of an intermediate peroxichromate(V) complex. These findings indicated that fungal glucose oxidase acts an indirect chromate reductase through the formation of Cr(VI) reducing molecules, which interact cooperatively with other fungal metabolites in the biotransformation of Cr(VI).

  18. Polypyrrole-coated halloysite nanotube clay nanocomposite: synthesis, characterization and Cr(VI) adsorption behaviour

    CSIR Research Space (South Africa)

    Ballav, N

    2014-12-01

    Full Text Available in nature. XPS study confirmed the adsorption of Cr(VI) onto the NC where some part of Cr(VI) reduced to Cr(III) by electron-rich PPy moiety. The desorption study suggested that the nanocomposite (NC) can be reused three times without loss of its original...

  19. A simple Cr(VI)–S(IV)–O{sub 2} system for rapid and simultaneous reduction of Cr(VI) and oxidative degradation of organic pollutants

    Energy Technology Data Exchange (ETDEWEB)

    Yuan, Yanan; Yang, Shaojie [Department of Environmental Science, Hubei Key Lab of Biomass Resource Chemistry and Environmental Biotechnology, School of Resources and Environmental Science, Wuhan University, 430079 (China); Zhou, Danna, E-mail: zdncug@163.com [Faculty of Material Science and Chemistry, China University of Geosciences, Wuhan 430074 (China); Wu, Feng [Department of Environmental Science, Hubei Key Lab of Biomass Resource Chemistry and Environmental Biotechnology, School of Resources and Environmental Science, Wuhan University, 430079 (China)

    2016-04-15

    Highlights: • Rapid and simultaneous reduction of Cr(VI) and degradation of organic pollutants occur. • Oxysulfur radicals generated in Cr(VI)–S(IV)–O{sub 2} system oxidize the organic pollutants. • Acidic pH facilitates the reactions from both directions of reduction and oxidation. • Degradation potential of aromatic amines depends on the substituted groups. • Cr(VI)–S(IV)–O{sub 2} system is promising for “waste control by waste”. - Abstract: Hexavalent chromium (Cr(VI)), a heavy-metal contaminant, can be easily reduced to less toxic trivalent chromium (Cr(III)) by sulfite ions (S(IV)). However, S(IV) has not drawn as much attention as the ferrous ion has. We report herein a novel Cr(VI)–S(IV)–O{sub 2} system containing sulfite ions that rapidly and simultaneously reduces Cr(VI) and oxidize organic pollutants in the presence of oxygen in aqueous solutions. This Cr(VI)–S(IV)-O{sub 2} system contains the initiator Cr(VI), the reductant S(IV), and the oxidant O{sub 2}, which produce oxysulfur radicals (mainly SO{sub 4}·{sup −} and SO{sub 5}·{sup −}) and hydroxyl radicals (OH·). The Cr(VI)/S(IV) molar ratio, pH, and oxygen content play important roles in the entire reaction system. Acidic conditions (pH 3.0) facilitated degradation of organic compounds and reduction of Cr(VI) as well. In addition, experiments of rapid degradation of several kinds of organic pollutants such as azo dye (acid orange 7, AO7), aniline, phenol, bisphenol A etc were also conducted. Preliminary results show that the removal rates of the analogs of phenols or aromatic amines in this Cr(VI)–S(IV)–O{sub 2} system have a relationship with the electronic parameters (Hammett constant, σ) of the substituted groups. Thus, the Cr(VI)–S(IV)–O{sub 2} system, provides an excellent strategy of “waste control by waste” for removing multiple industrial contaminants.

  20. Synthesis of novel aminated cellulose microsphere adsorbent for efficient Cr(VI) removal

    Science.gov (United States)

    Yu, Tianlin; Liu, Siqi; Xu, Min; Peng, Jing; Li, Jiuqiang; Zhai, Maolin

    2016-08-01

    A novel aminated cellulose microsphere adsorbent (CVN) was successfully prepared by radiation-induced graft polymerization of vinylbenzyl chloride (VBC) onto cellulose microsphere (CMS), followed by amination. Micro-FTIR, XPS and SEM confirmed the structure of CVN. The adsorption behavior of Cr(VI) onto CVN from solution was well fitted by the pseudo-second order kinetic model. The isothermal adsorption of Cr(VI) was observed at pH 4.68 with adsorption capacity of 129 mg/g in accordance with Langmuir thermal model, and the removal of Cr(VI) from solution could be 91% at a low amount (20 mg) of adsorbent. The best pH for adsorption of Cr(VI) was nearly 3.08, and with the increasing of temperature, the adsorption capacity of Cr(VI) increased. XPS analysis confirmed the adsorption mechanism of Cr(VI) was ion-exchange mechanism, while common co-ions such as Na+, Mg2+, Cu2+, Ca2+, Zn2+, Ni2+, Cl-, NO3- has no significant effect on the adsorption capacity of Cr(VI), and the Cr(VI) removal of 80% still could be obtained compared with that of fresh CVN adsorbent. Finally, spent CVN could be regenerated under 2 mol/L NaCl. The work indicated that aminated cellulose adsorbent could be prepared successfully by radiation-induced grafting and amination and CVN is a promising bio-adsorbent in the removing Cr(VI) from waste water.

  1. Cr(VI) formation during ozonation of Cr-containing materials in ...

    African Journals Online (AJOL)

    2011-10-14

    Oct 14, 2011 ... iron particles can reduce Cr(VI) to Cr(III) in aqueous medium. Pulverising time ... incorporating a Bruker AXS XFlash® 5010 Detector x-ray. EDS system ... determined with UV-visible spectrophotometry as described by McElroy ...

  2. Optimizing magnetic nanoparticles for drinking water technology: The case of Cr(VI).

    Science.gov (United States)

    Simeonidis, K; Kaprara, E; Samaras, T; Angelakeris, M; Pliatsikas, N; Vourlias, G; Mitrakas, M; Andritsos, N

    2015-12-01

    The potential of magnetite nanoparticles to be applied in drinking water treatment for the removal of hexavalent chromium is discussed. In this study, a method for their preparation which combines the use of low-cost iron sources (FeSO4 and Fe2(SO4)3) and a continuous flow mode, was developed. The produced magnetite nanoparticles with a size of around 20 nm, appeared relatively stable to passivation providing a removal capacity of 1.8 μg Cr(VI)/mg for a residual concentration of 50 μg/L when tested in natural water at pH7. Such efficiency is explained by the reducing ability of magnetite which turns Cr(VI) to an insoluble Cr(OH)3 form. The successful operation of a small-scale system consisting of a contact reactor and a magnetic separator demonstrates a way for the practical introduction and recovery of magnetite nanoparticles in water treatment technology.

  3. Microstructural analyses of Cr(VI) speciation in chromite ore processing Residue (COPR)

    Energy Technology Data Exchange (ETDEWEB)

    CHRYSOCHOOU, MARIA; FAKRA, SIRINE C .; Marcus, Matthew A.; Moon, Deok Hyun; Dermatas, Dimitris

    2010-03-01

    The speciation and distribution of Cr(VI) in the solid phase was investigated for two types of chromite ore processing residue (COPR) found at two deposition sites in the United States: gray-black (GB) granular and hard brown (HB) cemented COPR. COPR chemistry and mineralogy were investigated using micro-X-ray absorption spectroscopy and micro-X-ray diffraction, complemented by laboratory analyses. GB COPR contained 30percent of its total Cr(VI) (6000 mg/kg) as large crystals(>20 ?m diameter) of a previously unreported Na-rich analog of calcium aluminum chromate hydrates. These Cr(VI)-rich phases are thought to be vulnerable to reductive and pH treatments. More than 50percent of the Cr(VI) was located within nodules, not easily accessible to dissolved reductants, and bound to Fe-rich hydrogarnet, hydrotalcite, and possibly brucite. These phases are stable over a large pH range, thus harder to dissolve. Brownmilleritewasalso likely associated with physical entrapment of Cr(VI) in the interior of nodules. HB COPR contained no Cr(VI)-rich phases; all Cr(VI) was diffuse within the nodules and absent from the cementing matrix, with hydrogarnet and hydrotalcite being the main Cr(VI) binding phases. Treatment ofHBCOPRis challenging in terms of dissolving the acidity-resistant, inaccessible Cr(VI) compounds; the same applies to ~;;50percent of Cr(VI) in GB COPR.

  4. Evaluation of the Effectiveness of Cr(VI) Biostimulation in Groundwater at Hanford 100H Site

    Science.gov (United States)

    Faybishenko, B.; Hazen, T. C.; Brodie, E.; Joyner, D.; Borglin, S.; Hanlon, J.; Conrad, M.; Tokunaga, T.; Wan, J.; Hubbard, S.; Williams, K. H.; Peterson, J. E.; Firestone, M.; Andersen, G.; Desantis, T.; Long, P. E.; Newcomer, D. R.; Resch, C. T.; Willett, A.; Koenigsberg, S.

    2006-05-01

    To demonstrate the feasibility of a cost-effective field-scale bioimmobilization of Cr(VI) in contaminated groundwater, using a slow release polylactate, Hydrogen Release Compound (HRCTM), we have conducted a pilot study at the Hanford 100H field site. To assess the pre- and post-injection test groundwater conditions, we used an integrated monitoring approach, involving hydraulic, geochemical, microbial, and geophysical techniques and analytical methods, as well as conducted five Br-tracer injection tests and four pumping tests (concurrently with the Br-tracer tests). Although the total microbial population in sediments is Hanford sediments, which are known to reduce or sorb hexavalent chromium. Groundwater biostimulation was conducted by injection of 18.2 kg of 13C-labeled HRC into the injection well (over the depth interval from 13.4-15.2 m) on 8/3/2004. Pumping from the downgradient monitoring well (located 5 m from the injection well) started immediately after the injection, and continued for 27 days. We determined that the HRC injection stimulated microbial cell counts to reach the maximum of 2×107cells g-1 13-17 days after the injection, and generated highly reducing conditions: DO dropped from 8.2 mg/l to non-detect, redox potential - from 240 to -130 mV, and pH - from 8.9 to 6.5. Monitoring of δ13C ratios in dissolved inorganic carbon confirmed microbial metabolism of HRC. The total Cr concentration in the monitoring well decreased by a factor of 4 compared to that under background conditions. The Cr(VI) concentration in the monitoring and pumping wells decreased below the drinking water maximum contaminant limit and remained below background concentrations even after 1.5 years, when redox conditions and microbial densities had returned to background levels. The presence of Fe(II) in groundwater may also account for the continued reduction of Cr(VI). The results of geophysical (radar and seismic) cross-borehole tomography were used to detect the movement

  5. Occurrence of Cr(VI) in drinking water of Greece and relation to the geological background.

    Science.gov (United States)

    Kaprara, E; Kazakis, N; Simeonidis, K; Coles, S; Zouboulis, A I; Samaras, P; Mitrakas, M

    2015-01-08

    This study provides a survey on potential Cr(VI) exposure attributed to drinking water in Greece. For this reason, a wide sampling and chemical analysis of tap waters from around 600 sites, supplied by groundwater resources, was conducted focusing on areas in which the geological substrate is predominated by ultramafic minerals. Results indicate that although violations of the current chromium regulation limit in tap water are very rare, 25% of cases showed Cr(VI) concentrations above 10 μg/L, whereas Cr(VI) was detectable in 70% of the samples (>2 μg/L). Mineralogy and conditions of groundwater reservoirs were correlated to suggest a possible Cr(VI) leaching mechanism. Higher Cr(VI) values are observed in aquifers in alluvial and neogene sediments of serpentine and amphibolite, originating from the erosion of ophiolithic and metamorphic rocks. In contrast, Cr(VI) concentration in samples from ophiolithic and metamorphic rocks was always below 10 μg/L due to both low contact time and surface area, as verified by low conductivity and salt concentration values. These findings indicate that under specific conditions, pollution of water by Cr(VI) is favorable by a slow MnO2-catalyzed oxidation of soluble Cr(III) to Cr(VI) in which manganese products [Mn(III)/Mn(II)] are probably re-oxidized by oxygen. Copyright © 2014 Elsevier B.V. All rights reserved.

  6. Removal of Cr(VI) from aqueous solution by fungal biomass

    Energy Technology Data Exchange (ETDEWEB)

    Ahluwalia, Sarabjeet Singh [Department of Biotechnology, General Shivdev Singh Diwan Gurbachan Singh Khalsa College, Patiala, Punjab (India); Goyal, Dinesh [Department of Biotechnology and Environmental Sciences, Thapar University, Patiala, Punjab (India)

    2010-10-15

    Chromium compounds are released by industrial processes including leather production, mining, petroleum refining, in textile industry and dyeing. They are a significant threat to the environment and public health because of their toxicity. Removal of hexavalent chromium by living biomass of different fungi was effective in the order of Aspergillus terricola>Aspergillus niger>Acremonium strictum>Aureobasidium pullulans>Paecilomyces variotii>Aspergillus foetidus>Cladosporium resinae>Phanerochaete chrysosporium. Non-living dried fungal biomass showed higher potential for metal removal than living cells. Among all fungi dead biomass of P. chrysosporium, C. resinae and P. variotii had the maximum specific chromium uptake capacity, which was 11.02, 10.69 and 10.35 mg/g of dry biomass respectively at pH 4.0-5.0 in batch sorption. Removal of Cr(VI) by P. chrysosporium from multi-metallic synthetic solution as well as chrome effluent was significant by bringing down the residual concentration to 0.1 mg/L in the effluent, which falls within the permissible range and its removal was not affected by the presence of other metal ions such as Fe, Zn and Ni. Fourier transform infrared spectral analysis revealed the presence of carboxylate (C=O) and amine (-NH{sup +}{sub 3}-NH{sup +}{sub 2}) functional groups commonly present on the cell surface of all fungi, with possible involvement in chromium binding. The result indicates that non-living fungal biomass either obtained as a by-product of fermentation industry or mass produced using inexpensive culture media can be used for bioremediation of Cr(VI) from chrome effluent on large scale. (Copyright copyright 2010 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  7. Sequential Process Combination of Photocatalytic Oxidation and Dark Reduction for the Removal of Organic Pollutants and Cr(VI) using Ag/TiO2.

    Science.gov (United States)

    Choi, Yeoseon; Koo, Min Seok; Bokare, Alok D; Kim, Dong-Hyo; Bahnemann, Detlef W; Choi, Wonyong

    2017-04-04

    We investigated a sequential photocatalysis-dark reaction, wherein organic pollutants were degraded on Ag/TiO2 under UV irradiation and the dark reduction of hexavalent chromium (Cr(VI)) was subsequently followed. The photocatalytic oxidation of 4-chlorophenol (4-CP), a test organic substrate, induced the generation of degradation intermediates and the storage of electrons in Ag/TiO2 which were then utilized for reducing Cr(VI) in the postirradiation period. The dark reduction efficiency of Cr(VI) was much higher with Ag/TiO2 (87%), compared with bare TiO2 (27%) and Pt/TiO2 (22%). The Cr(VI) removal by Ag/TiO2 (87%) was contributed by adsorption (31%), chemical reduction by intermediates of 4-CP degradation (26%), and reduction by electrons stored in Ag (30%). When formic acid, humic acid or ethanol was used as an alternative organic substrate, the electron storage effect was also observed. The postirradiation removal of Cr(VI) on Ag/TiO2 continued for hours, which is consistent with the observation that a residual potential persisted on the Ag/TiO2 electrode in the dark whereas little residual potential was observed on bare TiO2 and Pt/TiO2 electrodes. The stored electrons in Ag/TiO2 and their transfer to Cr(VI) were also indicated by the UV-visible absorption spectral change. Moreover, the electrons stored in the preirradiated Ag/TiO2 reacted with O2 with showing a sign of low-level OH radical generation in the dark period.

  8. Single-step synthesis of magnetic chitosan composites and application for chromate (Cr(VI)) removal

    Institute of Scientific and Technical Information of China (English)

    杨卫春; 唐琼芝; 董舒宇; 柴立元; 王海鹰

    2016-01-01

    Magnetic chitosan composites (Fe3O4@chitosan) were synthesized in one single-step, characterized and applied in Cr(VI) removal from water. With the increase of loading proportion of chitosan, Cr(VI) adsorption capacity of Fe3O4@chitosan composites increased from 10.771 to 21.040 mg/g. The optimum adsorption capacities of Cr(VI) on Fe3O4@chitosan-3 were found in a pH range of 3.0−5.0. Kinetic study results show that the adsorption process follows pseudo-second-order model, indicating that the rate-limiting step in the adsorption of Cr(VI) involves chemisorptions. Moreover, FT-IR spectra analysis confirms that the amine and hydroxyl groups of chitosan are predominantly responsible for binding. Results from this work demonstrate that the prepared Fe3O4@chitosan composites possess great potential in Cr(VI) removal from contaminated water.

  9. Removal of Cr(VI from aqueous solution using Bacillus subtilis, Pseudomonas aeruginosa and Enterobacter cloacae

    Directory of Open Access Journals (Sweden)

    P. Sethuraman,

    2010-06-01

    Full Text Available The objective of this study is to investigate the removal efficiency of Cr(VI by Bacillus subtilis, Pseudomonas aeruginosa and Enterobacter cloacae from aqueous solution under different process conditions. Batch mode experiments were carried out as a function of solution pH, biosorbent dosage, Cr(VI concentration and contact time.The FT-IR spectra and SEM analysis of the biosorbent were recorded to analyse the number and position of the functional groups available for the binding of Cr(VI ions and to study the morphology of biosorbent. The batch isothermal equilibrium data were analyzed with Freundlich and Langmuir isotherm models. The kinetic models were examined with pseudo first order and pseudo second order kinetics. The results revealed that the Cr(VI is considerably adsorbed on bacterial biomass and it could be an economical method for the removal of Cr(VI from aqueous solution.

  10. Ultratrace Determination of Cr(VI) and Pb(II) by Microsample Injection System Flame Atomic Spectroscopy in Drinking Water and Treated and Untreated Industrial Effluents

    Science.gov (United States)

    Baig, Jameel Ahmed; Kazi, Tasneem Gul; Elci, Latif; Afridi, Hassan Imran; Khan, Muhammad Irfan; Naseer, Hafiz Muhammad

    2013-01-01

    Simple and robust analytical procedures were developed for hexavalent chromium (Cr(VI)) and lead (Pb(II)) by dispersive liquid-liquid microextraction (DLLME) using microsample injection system coupled with flame atomic absorption spectrophotometry (MIS-FAAS). For the current study, ammonium pyrrolidine dithiocarbamate (APDC), carbon tetrachloride, and ethanol were used as chelating agent, extraction solvent, and disperser solvent, respectively. The effective variables of developed method have been optimized and studied in detail. The limit of detection of Cr(VI) and Pb(II) were 0.037 and 0.054 µg/L, respectively. The enrichment factors in both cases were 400 with 40 mL of initial volumes. The relative standard deviations (RSDs, n = 6) were DLLME were estimated by the analysis of Cr(VI) and Pb(II) in industrial effluent wastewater by standard addition method (recoveries >96%). The proposed method was successfully applied to the determination of Cr(VI) and Pb(II) at ultratrace levels in natural drinking water and industrial effluents wastewater of Denizli. Moreover, the proposed method was compared with the literature reported method. PMID:24163779

  11. Toxic effects of Cr(VI) and Cr(III) on energy metabolism of heterotrophic Euglena gracilis.

    Science.gov (United States)

    Jasso-Chávez, Ricardo; Pacheco-Rosales, Angélica; Lira-Silva, Elizabeth; Gallardo-Pérez, Juan Carlos; García, Noemí; Moreno-Sánchez, Rafael

    2010-11-15

    To assess the toxic effect of Cr on energy metabolism, heterotrophic Euglena gracilis was grown in a medium that prompts high yield biomass and in the presence of different Cr(VI) or Cr(III) concentrations. The cell growth IC₅₀ value was 12 and >250μM for Cr(VI) and Cr(III), respectively; in these cells chromium was accumulated and a fraction compartmentalized into mitochondria, and synthesis of cysteine and glutathione was induced. Respiration of control isolated mitochondria was strongly inhibited by added Cr(VI) or Cr(III) with L-lactate or succinate as substrates. In turn, cellular and mitochondrial respiration, respiratory Complexes I, III and IV, glycolysis and cytosolic NAD(+)-alcohol and -lactate dehydrogenases from cells cultured with Cr(VI) were significantly lower than control, whereas AOX and external NADH dehydrogenase activities were unaltered or increased, respectively. Addition of Cr(VI) or Cr(III) to isolated mitochondria or cytosol from control- or Cr(VI)-grown cells induced inhibition of respiration, respiratory Complexes III, IV and AOX, and glycolytic pyruvate kinase; whereas Complex I, external NADH dehydrogenase, and other glycolytic enzymes were unaffected. Protein contents of mitochondrial Complexes I, III, IV and V, and ANT were diminished in Cr(VI)-grown cells. Decreased respiration and glycolysis induced by Cr(VI) resulted in lower cellular ATP content. Results suggested that Cr(VI) cytotoxicity altered gene expression (as widely documented) and hence enzyme content, and induced oxidative stress, but it was also related with direct enzyme inhibition; Cr(III) was also cytotoxic although at higher concentrations. These findings establish new paradigms for chromium toxicity: Cr(VI) direct enzyme inhibition and non-innocuous external Cr(III) toxicity.

  12. Reduction and removal of Cr(VI) from aqueous solutions using modified byproducts of beer production.

    Science.gov (United States)

    Cui, Haojie; Fu, Minglai; Yu, Shen; Wang, Ming Kuang

    2011-02-28

    Biosorption, as an effective and low-cost technology treating industrial wastewaters containing Cr(VI), has become a significant concern worldwide. In this work, acid-modified byproducts of beer production (BBP) were used to remove Cr(VI) from aqueous solutions. Removal of Cr(VI) increases as the pH is decreased from 4.0 to 1.5, but the maximum of total Cr removal is obtained in a pH range from 2.0 to 2.5. Nearly 60% of the initial Cr(VI) (100 mg L(-1)) was adsorbed or reduced to Cr(III) within the first 10 min at pH 2.0. The Cr(VI) removal capability of acid-modified BBP materials was almost completely retained after regenerating with acid. FT-IR and XPS spectra revealed that carboxylate and carboxyl groups on the surface of modified BBP materials play a major role in Cr(VI) binding and reduction, whereas amide and other groups play a minor role in the Cr(VI) removal process.

  13. Synchrotron Spectroscopic Studies of the Reaction of Cleaved Pyrite ( {FeS2}) Surfaces with Cr(VI) Solutions

    Science.gov (United States)

    Doyle, C. S.; Kendelewicz, T.; Bostick, B. C.; Brown, G. E.

    2002-12-01

    Pyrite is one of the most common sulfide ores, and the separation of valuable sulfide minerals from it has been an area of considerable interest for a long time. This extraction has led to a large quantity of pyrite waste, typically remaining in mine tailings piles which can interact with oxygen and surface water. The oxidation of pyrite under these conditions leads to the commonly known environmental problem of acid mine drainage, with acidification of surface waters, and the release of potentially toxic metals remaining within the pyrite matrix. A microscopic understanding of this oxidation process is extremely important and has been the aim of a number of studies. We apply the methods of synchrotron based surface science to this problem, utilizing surface sensitive photoemission and X-ray absorption spectroscopy to study the surface species present on the pyrite surface at the initial stages of oxidation. We have reacted pyrite surfaces with solutions containing chromate. Chromium exists in solution in two principal valence states, trivalent Cr(III) and hexavalent Cr(VI). Hexavalent chromium is itself considered an environmental problem due to its high toxicity and solubility, and thus mobility, whilst trivalent chromium is much less toxic and relatively insoluble. Hexavalent chromate is a strong oxidizing agent, and will react rapidly with the pyrite surface allowing the identification of oxidized iron and sulfur surface species. The possibility of using pyrite as a means of reducing chromate, and at the same time using chromate to passivate the pyrite surface to further oxidation through the buildup of a non-reactive iron-chromium (oxy)hydroxide layer will be investigated. The work was performed on rods cut from a natural pyrite single crystal from the Logroño region of Spain. The rods were then fractured over a reaction vessel, producing a fresh (100) surface for each experiment. The pyrite surfaces were reacted with 50 μM Cr(VI) solutions for 5 minutes at

  14. Reduction of Cr(VI) in simulated groundwater by FeS-coated iron magnetic nanoparticles.

    Science.gov (United States)

    Gong, Yanyan; Gai, Longshuang; Tang, Jingchun; Fu, Jie; Wang, Qilin; Zeng, Eddy Y

    2017-10-01

    FeS-coated iron (Fe/FeS) magnetic nanoparticles were easily prepared, characterized, and applied for Cr(VI) removal in simulated groundwater. TEM, XRD, and BET characterization tests showed that FeS coating on the surface of Fe(0) inhibited the aggregation of Fe(0) and that Fe/FeS at a S/Fe molar ratio of 0.207 possessed a large surface area of 62.1m(2)/g. Increasing the S/Fe molar ratio from 0 to 0.138 decreased Cr(VI) removal by 42.8%, and a further increase to 0.207 enhanced Cr(VI) removal by 63% within 72h. Moreover, Fe/FeS inhibited the leaching of Fe, reducing the toxicity of the particles. Mechanistic analysis indicated that Fe(0), Fe(2+), and S(2-) were synergistically involved in the reduction of Cr(VI) to nontoxic Cr(III), which further precipitated as (CrxFe1-x)(OH)3 and Cr(III)-Fe-S. The process of Cr(VI) sorption by Fe/FeS (S/Fe=0.207) was fitted well with a pseudo-second-order kinetic model, and the isotherm data were simulated by Langmuir isotherm model with a maximum sorption capacity of 69.7mg/g compared to 48.9mg/g for Fe(0). Low pH and initial Cr(VI) concentration favored Cr(VI) removal. Continuous fixed bed column studies showed that simulated permeable reactive barriers (PRB) with Fe/FeS was considerably effective for in situ removal of Cr(VI) from groundwater. This study demonstrated the high potential of Fe/FeS for Cr(VI) immobilization in water, groundwater, and soil. Copyright © 2017 Elsevier B.V. All rights reserved.

  15. Adsorption of Cr(VI) from synthetic solutions and electroplating wastewaters on amorphous aluminium oxide.

    Science.gov (United States)

    Alvarez-Ayuso, E; García-Sánchez, A; Querol, X

    2007-04-02

    The adsorption behaviour of amorphous aluminium oxide was studied with respect to Cr(VI) in order to consider its application to purify electroplating wastewaters. A batch method was employed using Cr(VI) concentrations ranged from 10 to 200mg/l. The Langmuir model was found to describe the adsorption process well, offering a maximum adsorption capacity of 78.1mg/g. The effect of ionic strength (0-0.1M KNO(3)), pH (3-9) and competitive solutes (molar ratio [Cr(VI)]/[SO(4)(2-)]=1 and 100) on the retention process was evaluated. Cr(VI) adsorption on amorphous aluminium oxide appeared to be dependent on ionic strength with a more pronounced effect in acid conditions. Conversely, adsorption was not affected by pH in acid medium, but decreased when pH sifted to alkaline values. The presence of SO(4)(2-) greatly reduced Cr(VI) removal across the entire pH range when both solutes were present in similar concentrations. Amorphous aluminium oxide also showed a high adsorption capacity when used in the purification of Cr(VI) electroplating wastewaters. The adsorbent doses required to attain more than 90% of Cr(VI) removal varied between 1 and 5 g/l depending on Cr(VI) concentration in wastewaters.

  16. Efficient removal and environmentally benign detoxification of Cr(VI) in aqueous solutions by Zr(IV) cross-linking chitosan magnetic microspheres.

    Science.gov (United States)

    Chen, Xiumei; Zhang, Wengang; Luo, Xueli; Zhao, Fan; Li, Yixuan; Li, Ronghua; Li, Zhonghong

    2017-10-01

    Zirconium(IV) cross-linking chitosan (CTS) magnetic microspheres (Fe3O4@Zr-CTS) as a recoverable adsorbent were synthesized through the coordination reaction between zirconium oxychloride and CTS biopolymeric matrix for efficient adsorption and simultaneous detoxification of hexavalent chromium, Cr(VI), in aqueous solutions. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) confirmed the formation of core@shell magnetite microspheres. X-ray photoelectron spectroscopy (XPS), and Fourier transform infrared spectroscopy (FT-IR) verified the crosslinking of Zr(IV) to CTS on the microspheres. Batch Cr(VI) adsorption performances of the resultant Fe3O4@Zr-CTS microspheres revealed that the maximum adsorption capacity of 280.97 mg/g were achieved under pH 4.0 at 298 K. The XPS analyses indicated that 61.1% of the adsorbed Cr(VI) was reduced to Cr(III) due to the oxidization of alcoholic groups on C-6 in CTS which served as electron donors to carbonyl groups. The adsorbent showed preferential Cr(VI) adsorption with the existence of co-existing cations (K(+), Na(+), Cu(2+), Zn(2+), Ca(2+), Mg(2+)) and anions (NO3(-), Cl(-), SO4(2-), CO3(2-)). The adsorbent exhibited excellent reusability, lower the effluent Cr(VI) contents down to the ppb level, which satisfied the drinking water standard recommended by the World Health Organization and was a promising candidate for water purification. Copyright © 2017. Published by Elsevier Ltd.

  17. Graphene based anticorrosive coatings for Cr(VI) replacement.

    Science.gov (United States)

    Aneja, Karanveer S; Bohm, Sivasambu; Khanna, A S; Bohm, H L Mallika

    2015-11-14

    Corrosion has been a perennial issue of concern for the steel industry. Chromate conversion coatings are well known pre-treatment coatings for steel but due to environmental concerns and legislations, their use has been restricted. The industrial community, pegged by these legislations, has been long demanding an economically viable and eco-friendly pre-treatment coating alternative, without having to compromise on the durability and corrosion performance of the overall coating system. The present study focuses on evaluation of graphene as an anticorrosive alternative to Cr(VI) based coatings. Graphene, produced by a high shear liquid exfoliation route, upon functionalisation, provides a conductive and nearly impermeable barrier coating. On electrochemical and coating performance evaluation of this coating system, a dramatic improvement in corrosion resistance is observed. The study confirms the environment friendly corrosion protection of steel using functionalised graphene coating.

  18. Reductive precipitation and removal of Cr(VI) from groundwaters by pipe flocculation-microfiltration.

    Science.gov (United States)

    Stylianou, Stylianos; Simeonidis, Konstantinos; Mitrakas, Manassis; Zouboulis, Anastasios; Ernst, Mathias; Katsoyiannis, Ioannis A

    2017-08-25

    Chromium (Cr(VI)) is a very toxic and carcinogenic element, which is widely present in groundwaters, mainly due to geogenic conditions. The limit of Cr(VI) in drinking water is expected to be reduced to 10 μg/L in both the USA and the European Union. Recent literature findings indicated that the most efficient process in reducing Cr(VI) levels to below 10 μg/L proved to be Cr(VI) reduction by Fe(II), by applying a molar ratio Fe(II)/Cr(VI) of around 9. In the present work, we investigated the reduction of Cr(VI) by Fe(II) in pipe flocculation reactors followed by filtration of insoluble products by microfiltration. The proposed technology involves re-circulation of a part of the sludge in the pipe reactors, in order to improve kinetics and efficiency of the process. The obtained results showed that with a Fe(II) dose of around 1 mg/L, Cr(VI) was reduced to below 10 μg/L, by even an initial concentration as high as 300 μg/L of Cr(VI), corresponding to a molar ratio Fe(II)/Cr(VI) of around 3, thus reducing the overall quantity of reductive reagents and of the produced sludge. This ratio was also confirmed by the XPS analysis, which also showed that Cr(VI) was reduced to Cr(III) and then precipitated either as Cr(OH)3 or associated with the produced iron oxides.

  19. Thermodynamic analysis of Cr(VI) extraction using TOPO impregnated membranes

    Energy Technology Data Exchange (ETDEWEB)

    Praveen, Prashant; Loh, Kai-Chee, E-mail: chelohkc@nus.edu.sg

    2016-08-15

    Highlights: • Cr(VI) extraction by extractant impregnated membranes (EIM) was investigated. • EIM exhibited high extraction efficiency, mass transfer rate and stability. • Mass transfer mechanism was proposed based on kinetics and equilibrium data. • Uptake of Cr(VI) by EIMs was endothermic and spontaneous. • Cr(VI) extraction by EIMs was dominated by physical interactions. - Abstract: Solid/liquid extraction of Cr(VI) was accomplished using trioctylphosphine oxide impregnated polypropylene hollow fiber membranes. Extraction of 100–500 mg/L Cr(VI) by the extractant impregnated membranes (EIM) was characterized by high uptake rate and capacity, and equilibrium was attained within 45 min of contact. Extraction equilibrium was pH-dependent (at an optimal pH 2), whereas stripping using 0.2 M sodium hydroxide yielded the highest recovery of 98% within 60 min. The distribution coefficient was independent of initial Cr(VI) concentration, and the linear distribution equilibrium isotherm could be modeled using Freundlich isotherm. The mass transfer kinetics of Cr(VI) was examined using pseudo-second-order and intraparticle diffusion models and a mass transfer mechanism was deduced. The distribution coefficient increased with temperature, which indicated endothermic nature of the reaction. Enthalpy and entropy change during Cr(VI) extraction were positive and varied in the range of 37–49 kJ/mol and 114–155 J/mol, respectively. The free energy change was negative, confirming the feasibility and spontaneity of the mass transfer process. Results obtained suggest that EIMs are efficient and sustainable for extraction of Cr(VI) from wastewater.

  20. Cr(VI) adsorption and reduction by humic acid coated on magnetite.

    Science.gov (United States)

    Jiang, Wenjun; Cai, Quan; Xu, Wei; Yang, Mingwei; Cai, Yong; Dionysiou, Dionysios D; O'Shea, Kevin E

    2014-07-15

    Easily separable humic acid coated magnetite (HA-Fe3O4) nanoparticles are employed for effective adsorption and reduction of toxic Cr(VI) to nontoxic Cr(III). The adsorption and reduction of Cr(VI) is effective under acidic, neutral, and basic pH conditions. The chromium adsorption nicely fits the Langmuir isotherm model, and the removal of Cr(VI) from aqueous media by HA-Fe3O4 particles follows pseudo-second-order kinetics. Characterization of the Cr-loaded HA-Fe3O4 materials by X-ray absorption near edge structure spectroscopy (XANES) indicates Cr(VI) was reduced to Cr(III) while the valence state of the iron core is unchanged. Fe K-edge extended X-ray absorption fine structure spectroscopy (EXAFS) and X-ray diffraction measurements also indicate no detectable transformation of the Fe3O4 core occurs during Cr(VI) adsorption and reduction. Thus, suggesting HA on the surface of HA-Fe3O4 is responsible for the reduction of Cr(VI) to Cr(III). The functional groups associated with HA act as ligands leading to the Cr(III) complex via a coupled reduction-complexation mechanism. Cr K-edge EXAFS demonstrates the Cr(III) in the Cr-loaded HA-Fe3O4 materials has six neighboring oxygen atoms likely in an octahedral geometry with average bond lengths of 1.98 Å. These results demonstrate that easily separable HA-Fe3O4 particles have promising potential for removal and detoxification of Cr(VI) in aqueous media.

  1. Dynamic single-interface hollow fiber liquid phase microextraction of Cr(VI) using ionic liquid containing supported liquid membrane.

    Science.gov (United States)

    Pimparu, Rungaroon; Nitiyanontakit, Sira; Miró, Manuel; Varanusupakul, Pakorn

    2016-12-01

    The concept of dynamic single-interface hollow fiber membrane liquid-phase microextraction (HF-LPME), where the target analyte was extracted on-line and eluted inside the lumen of the HF membrane, was explored. An ionic liquid containing supported liquid membrane was used for the trace determination of Cr(VI) as a model compound. Since the extraction took place on-line inside the hollow fiber membrane, the mass transfer behavior was described and discussed in comparison with the conventional HF-LPME. The extraction efficiency was improved by a recirculation configuration of the sample solution at relatively high sampling flow rates as a result of the increased effective contact area. The positive pressure observed to be built up during extraction was overcome by a flow-balancing pressure design. The dynamic single-interface HF-LPME method with an enrichment factor of 41, a detection limit of 1.2µgL(-1) and determination limit of 4.0µgL(-1) was successfully applied to the reliable determination of Cr(VI) from environmental water samples. The quantification limit is below the maximum contaminant level in drinking water, set at 10µgL(-1) of hexavalent chromium by the California Environmental Protection Agency.

  2. Reduction of Cr(VI) to Cr(III) by wetland plants: Potential for in situ heavy metal detoxification

    Energy Technology Data Exchange (ETDEWEB)

    Lytle, C.M.; Qian, J.H.; Hansen, D.; Zayed, A.; Terry, N. [Univ. of California, Berkeley, CA (United States). Dept. of Plant and Microbial Biology; Lytle, F.W. [The EXAFS Co., Pioche, NV (United States); Yang, N. [Sandia National Labs., Livermore, CA (United States)

    1998-10-15

    Reduction of heavy metals in situ by plants may be a useful detoxification mechanism for phytoremediation. Using X-ray spectroscopy, the authors show that Eichhornia crassipes (water hyacinth), supplied with Cr(VI) in nutrient culture, accumulated nontoxic Cr(III) in root and shoot tissues. The reduction of Cr(VI) to Cr(III) appeared to occur in the fine lateral roots. The Cr(III) was subsequently translocated to leaf tissues. Extended X-ray absorption fine structure of Cr in leaf and petiole differed when compared to Cr in roots. In roots, Cr(III) was hydrated by water, but in petiole and more so in leaf, a portion of the Cr(III) may be bound to oxalate ligands. This suggests that E. crassipes detoxified Cr(VI) upon root uptake and transported a portion of the detoxified Cr to leaf tissues. Cr-rich crystalline structures were observed on the leaf surface. The chemical species of Cr in other plants, collected from wetlands that contained Cr(VI)-contaminated wastewater, was also found to be Cr(III). The authors propose that this plant-based reduction of Cr(VI) by E. crassipes has the potential to be used for the in situ detoxification of Cr(VI)-contaminated wastestreams.

  3. Assessment of the mutagenic potential of Cr(VI) in the oral mucosa of Big Blue® transgenic F344 rats.

    Science.gov (United States)

    Thompson, Chad M; Young, Robert R; Suh, Mina; Dinesdurage, Harshini R; Elbekai, Reem H; Harris, Mark A; Rohr, Annette C; Proctor, Deborah M

    2015-08-01

    Exposure to high concentrations of hexavalent chromium [Cr(VI)] in drinking water was associated with an increased incidence of oral tumors in F344 rats in a 2-year cancer bioassay conducted by the National Toxicology Program. These tumors primarily occurred at 180 ppm Cr(VI) and appeared to originate from the gingival mucosa surrounding the upper molar teeth. To investigate whether these tumors could have resulted from a mutagenic mode of action (MOA), a transgenic mutation assay based on OECD Test Guideline 488 was conducted in Big Blue(®) TgF344 rats. The mutagenic oral carcinogen 4-nitroquinoline-1-oxide (4-NQO) served as a positive control. Mutant frequency was measured in the inner gingiva with adjacent palate, and outer gingiva with adjacent buccal tissue. Exposure to 10 ppm 4-NQO in drinking water for 28 days increased mutant frequency in the cII transgene significantly, from 39.1 ± 7.5 × 10(-6) to 688 ± 250 × 10(-6) in the gingival/buccal region, and from 49.8 ± 17.8 × 10(-6) to 1818 ± 362 × 10(-6) in the gingival/palate region. Exposure to 180 ppm Cr(VI) in drinking water for 28 days did not significantly increase the mutant frequency in the gingival/buccal (44.4 ± 25.4 × 10(-6)) or the gingival/palate (57.8 ± 9.1 × 10(-6)) regions relative to controls. These data indicate that high (∼180,000 times expected human exposure), tumorigenic concentrations of Cr(VI) did not significantly increase mutations in the gingival epithelium, and suggest that Cr(VI) does not act by a mutagenic MOA in the rat oral cavity.

  4. Duodenal crypt health following exposure to Cr(VI): Micronucleus scoring, γ-H2AX immunostaining, and synchrotron X-ray fluorescence microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Thompson, Chad M.; Wolf, Jeffrey C.; Elbekai, Reem H.; Paranjpe, Madhav G.; Seiter, Jennifer M.; Chappell, Mark A.; Tappero, Ryan V.; Suh, Mina; Proctor, Deborah M.; Bichteler, Anne; Haws, Laurie C.; Harris, Mark A.

    2015-08-01

    Lifetime exposure to high concentrations of hexavalent chromium [Cr(VI)] in drinking water results in intestinal damage and an increase in duodenal tumors in B6C3F1 mice. To assess whether these tumors could be the result of a direct mutagenic or genotoxic mode of action, we conducted a GLP-compliant 7-day drinking water study to assess crypt health along the entire length of the duodenum. Mice were exposed to water (vehicle control), 1.4, 21, or 180 ppm Cr(VI) via drinking water for 7 consecutive days. Crypt enterocytes in Swiss roll sections were scored as normal, mitotic, apoptotic, karyorrhectic, or as having micronuclei. A single oral gavage of 50 mg/kg cyclophosphamide served as a positive control for micronucleus induction. Exposure to 21 and 180 ppm Cr(VI) significantly increased the number of crypt enterocytes. Micronuclei and γ-H2AX immunostaining were not elevated in the crypts of Cr(VI)-treated mice. In contrast, treatment with cyclophosphamide significantly increased numbers of crypt micronuclei and qualitatively increased γ-H2AX immunostaining. Synchrotron-based X-ray fluorescence (XRF) microscopy revealed the presence of strong Cr fluorescence in duodenal villi, but negligible Cr fluorescence in the crypt compartment. Together, these data indicate that Cr(VI) does not adversely effect the crypt compartment where intestinal stem cells reside, and provide additional evidence that the mode of action for Cr(VI)-induced intestinal cancer in B6C3F1 mice involves chronic villous wounding resulting in compensatory crypt enterocyte hyperplasia.

  5. Speciated isotope dilution analysis of Cr(III) and Cr(VI) in water by ICP-DRC-MS.

    Science.gov (United States)

    Ma, H-L; Tanner, P A

    2008-10-19

    An isotope dilution method has been developed for the speciation analysis of chromium in natural waters which accounts for species interconversions without the requirement of a separation instrument connected to the mass spectrometer. The method involves (i) in-situ spiking of the sample with isotopically enriched chromium species; (ii) separation of chromium species by precipitation with iron hydroxide; (iii) careful measurement of isotope ratios using an inductively coupled plasma mass spectrometer (ICP-MS) with a dynamic reaction cell (DRC) to remove isobaric polyatomic interferences. The method detection limits are 0.4 microg L(-1) for Cr(III) and 0.04 microg L(-1) for Cr(VI). The method is demonstrated for the speciation of Cr(III) and Cr(VI) in local nullah and synthetically spiked water samples. The percentage of conversion from Cr(III) to Cr(VI) increased from 5.9% to 9.3% with increase of the concentration of Cr(VI) and Cr(III) from 1 to 100 microg L(-1), while the reverse conversion from Cr(VI) to Cr(III) was observed within a range between 0.9% and 1.9%. The equilibrium constant for the conversion was found to be independent of the initial concentrations of Cr(III) and Cr(VI) and in the range of 1.0 (at pH 3) to 1.8 (at pH 10). The precision of the method is better than that of the DPC method for Cr(VI) analysis, with the added bonuses of freedom from interferences and simultaneous Cr(III) determination.

  6. Correlation between bulk- and surface chemistry of Cr-tanned leather and the release of Cr(III) and Cr(VI)

    Energy Technology Data Exchange (ETDEWEB)

    Hedberg, Yolanda S., E-mail: yolanda@kth.se [KTH Royal Institute of Technology, School of Chemical Science and Engineering, Department of Chemistry, Division of Surface and Corrosion Science, SE-10044 Stockholm (Sweden); Institute of Environmental Medicine, Karolinska Institutet, Box 210, SE-17177 Stockholm (Sweden); Lidén, Carola, E-mail: carola.liden@ki.se [Institute of Environmental Medicine, Karolinska Institutet, Box 210, SE-17177 Stockholm (Sweden); Odnevall Wallinder, Inger, E-mail: ingero@kth.se [KTH Royal Institute of Technology, School of Chemical Science and Engineering, Department of Chemistry, Division of Surface and Corrosion Science, SE-10044 Stockholm (Sweden)

    2014-09-15

    Graphical abstract: - Highlights: • Released reducing/complexing leather-specific species can reduce released Cr(VI). • No co-released species enable the formation of Cr(VI) in solution. • The major Cr species released from leather in phosphate buffer was Cr(III) (>82%). • No Cr(VI) was released into artificial sweat. - Abstract: About 1–3% of the adult general population in Europe is allergic to chromium (Cr). The assessment of the potential release of Cr(III) and Cr(VI) from leather is hence important from a human health and environmental risk perspective. The Cr(VI) content in leather was recently restricted in the European Union. The aim of this study was to assess possible correlations between the bulk and surface chemistry of leather, released Cr(III) and Cr(VI), and capacities of co-released leather specific species to reduce and complex released Cr. Four differently tanned leathers were characterized by scanning electron microscopy with energy dispersive spectroscopy, X-ray photoelectron spectroscopy, attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy, and the diphenylcarbazide colorimetric method. Their characteristics were compared with results on Cr(III) and Cr(VI) release into artificial sweat (ASW, pH < 6.5) and phosphate buffer (PB, pH 7.5–8.0), measured by means of spectrophotometry and atomic absorption spectroscopy. Co-released leather-specific species were shown to reduce Cr(VI), both in ASW and in PB. Their reduction capacities correlated with findings of the surface content of Cr and of released Cr. Leather samples without this capacity, and with less aromatic surface groups visible by ATR-FTIR, revealed Cr(VI) both at the surface and in solution (PB)

  7. Cr(VI) removal from aqueous solution by activated carbon coated with quaternized poly(4-vinylpyridine).

    Science.gov (United States)

    Fang, Jun; Gu, Zhimang; Gang, Dianchen; Liu, Chongxuan; Ilton, Eugene S; Deng, Baolin

    2007-07-01

    A composite sorbent (GAC-QPVP) was prepared by coating poly(4-vinylpyridine) onto a granular activated carbon, followed by cross-linking and quaternization processes. The sorbent was characterized by scanning electron microscopy, point of zero charge measurement, and BET analysis. Batch experiments with variable pH, ionic strength, and concentrations of Cr(VI), sorbent, and competing anions were conducted to evaluate the selective sorption of Cr(VI) from aqueous solutions. The results showed that Cr(VI) sorption rates could be described by a reversible second-order kinetics, and equilibrium uptake of Cr(VI) increased with decreasing pH, decreasing ionic strength, and increasing sorbent concentration. The estimated maximum equilibrium uptake of chromium was 53.7 mg/g at pH = 2.25, 30.7 mg/g at pH = 3.65, and 18.9 mg/g at pH = 6.03, much higher than the maximum capacity of PVP-coated silica gel, an adsorbent for Cr examined previously. When compared with the untreated granular activated carbon, sorption onto GAC-QPVP resulted in much less Cr(VI) reduction and subsequent release of Cr(III). The effect of phosphate, sulfate, and nitrate was minor on the selective sorption of Cr(VI). An ion exchange model that was linked with aqueous speciation chemistry described Cr(VI) sorption reasonably well as a function of pH, ionic strength, and Cr(VI) concentration. Model simulations suggested that sorbed Cr(VI) was partially reduced to Cr(III) on the sorbent when pH was less than 4. The presence of Cr(III) on the sorbent was confirmed by the X-ray photoelectron spectroscopic analysis. Overall, the study has demonstrated that GAC-QPVP can effectively remove Cr(VI) from aqueous solutions under a wide range of experimental conditions, without significant Cr(III) release associated with the virgin GAC treatment.

  8. New low cost sorbents for Cr(VI – batch and column experiments

    Directory of Open Access Journals (Sweden)

    Šillerová H.

    2013-04-01

    Full Text Available The use of agricultural byproducts and industrial biowaste materials has been shown to be an attractive technique for removing Cr(VI from contaminated waste waters. In this study, used brewers draff, peat moss, sawdust, grape stalks and husks were investigated as novel biosorbents for Cr(VI. The material was tested in two different modifications. The material was dried, cut and sieved and part of it was subjected to acid (2 M H2SO4 and alkali (0.5 M NaOH pre-treatments to remove starch, proteins and sugars. Fourier transform infrared rays analysis on solid phase (FTIR-ATR was used to determine the main functional groups that might control the metal uptake. Batch experiments were performed at different pH values (3, 4.5, 6 and at various initial concentration of Cr(VI (25–2012;250 mg L−1. Two equilibrium empirical models, Langmuir and Freundlich, were used to describe Cr(VI adsorption. In order to identify possible reduction processes, ion exchange separation on the AG1-X8 resin was used to separate the anionic Cr(VI and the reduced cationic Cr(III from the aqueous phase after biosorption. As expected, Cr(VI removal was pH-dependent and fitted well both the Langmuir and Freundlich isotherm models. The ion exchange separation showed that Cr(VI reduction had occurred in the solution during biosorption. The efficiency of draff as a biosorbent was comparable (or even higher to highly organic materials (e.g., composted peat showing its potential application for Cr(VI decontamination.

  9. Soil microbial community response to hexavalent chromium in planted and unplanted soil.

    Science.gov (United States)

    Ipsilantis, Ioannis; Coyne, Mark S

    2007-01-01

    Theories suggest that rapid microbial growth rates lead to quicker development of metal resistance. We tested these theories by adding hexavalent chromium [Cr(VI)] to soil, sowing Indian mustard (Brassica juncea), and comparing rhizosphere and bulk soil microbial community responses. Four weeks after the initial Cr(VI) application we measured Cr concentration, microbial biomass by fumigation extraction and soil extract ATP, tolerance to Cr and growth rates with tritiated thymidine incorporation, and performed community substrate use analysis with BIOLOG GN plates. Exchangeable Cr(VI) levels were very low, and therefore we assumed the Cr(VI) impact was transient. Microbial biomass was reduced by Cr(VI) addition. Microbial tolerance to Cr(VI) tended to be higher in the Cr-treated rhizosphere soil relative to the non-treated systems, while microorganisms in the Cr-treated bulk soil were less sensitive to Cr(VI) than microorganisms in the non-treated bulk soil. Microbial diversity as measured by population evenness increased with Cr(VI) addition based on a Gini coefficient derived from BIOLOG substrate use patterns. Principal component analysis revealed separation between Cr(VI) treatments, and between rhizosphere and bulk soil treatments. We hypothesize that because of Cr(VI) addition there was indirect selection for fast-growing organisms, alleviation of competition among microbial communities, and increase in Cr tolerance in the rhizosphere due to the faster turnover rates in that environment.

  10. Adsorption studies on fruits of Gular (Ficus glomerata): Removal of Cr(VI) from synthetic wastewater

    Energy Technology Data Exchange (ETDEWEB)

    Rao, Rifaqat A.K., E-mail: rakrao1@rediffmail.com [Environmental Research Laboratory, Department of Applied Chemistry, Faculty of Engineering and Technology, Aligarh Muslim University, Aligarh 202002, UP (India); Rehman, Fouzia [Environmental Research Laboratory, Department of Applied Chemistry, Faculty of Engineering and Technology, Aligarh Muslim University, Aligarh 202002, UP (India)

    2010-09-15

    The adsorption of Cr(VI) was studied in batch system using fruits of Ficus glomerata as adsorbent. The effect of temperature, pH, initial Cr(VI) concentration and time was investigated. Scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR) was used to investigate surface morphology and active functional groups present on the adsorbent surface. Thermodynamic parameters like free energy change ({Delta}G{sup 0}), enthalpy ({Delta}H{sup 0}) and entropy ({Delta}S{sup 0}) indicate the spontaneous, endothermic and increased randomness nature of Cr(VI) adsorption. Equilibrium data were fitted well with Langmuir isotherm at 50 deg. C. The magnitude of mean free energy indicates chemical nature of adsorption. The breakthrough and exhaustive capacities were found to be 5 and 23.1 mg g{sup -1} respectively. The applicability of the adsorbent has been demonstrated by removing Cr(VI) from electroplating wastewater.

  11. Biosorption of Cr(VI from Aqueous Solution Using Murraya koenigii (Curry tree Stems

    Directory of Open Access Journals (Sweden)

    Selvaraj Suresh

    2016-12-01

    Full Text Available In the present work, the sorption capacity of Murraya Koenigii Stems (MKST, an agricultural waste, is identified for the removal of Cr(VI from aqueous solution and the effect of different process parameters likes pH and adsorbent dosage were studied. pH 1 is observed to be the optimum pH for Cr(VI sorption onto the biosorbent. The equilibrium data of Cr(VI sorption fit well with the Langmuir model with a monolayer sorption capacity of 12.25 mg/g. The results show that the metal ion interacts strongly with the biosorbent and can be effectively used in the removal of Cr(VI from aqueous solution. DOI: http://dx.doi.org/10.17807/orbital.v0i0.867

  12. Removal of Cr(VI from Aqueous Environments Using Micelle-Clay Adsorption

    Directory of Open Access Journals (Sweden)

    Mohannad Qurie

    2013-01-01

    Full Text Available Removal of Cr(VI from aqueous solutions under different conditions was investigated using either clay (montmorillonite or micelle-clay complex, the last obtained by adsorbing critical micelle concentration of octadecyltrimethylammonium ions onto montmorillonite. Batch experiments showed the effects of contact time, adsorbent dosage, and pH on the removal efficiency of Cr(VI from aqueous solutions. Langmuir adsorption isotherm fitted the experimental data giving significant results. Filtration experiments using columns filled with micelle-clay complex mixed with sand were performed to assess Cr(VI removal efficiency under continuous flow at different pH values. The micelle-clay complex used in this study was capable of removing Cr(VI from aqueous solutions without any prior acidification of the sample. Results demonstrated that the removal effectiveness reached nearly 100% when using optimal conditions for both batch and continuous flow techniques.

  13. Effects of Cu(II on the Adsorption Behaviors of Cr(III and Cr(VI onto Kaolin

    Directory of Open Access Journals (Sweden)

    Juanjuan Liu

    2016-01-01

    Full Text Available The adsorption of Cr(III or Cr(VI in the absence and presence of Cu(II onto kaolin was investigated under pH 2.0–7.0. Results indicated that the adsorption rate was not necessarily proportional to the adsorption capacity. The solutions’ pH values played a key role in kaolin zeta potential (ζ, especially the hydrolysis behavior and saturation index of heavy metal ions. In the presence of Cu(II, qmixCr(III reached the maximum adsorption capacity of 0.73 mg·g−1 at pH 6.0, while the maximum adsorption capacity for the mixed Cr(VI and Cu(II system (qmixCr(VI was observed at pH 2.0 (0.38 mg·g−1. Comparing the adsorption behaviors and mechanisms, we found that kaolin prefers to adsorb hydrolyzed products of Cr(III instead of Cr3+ ion, while adsorption sites of kaolin surface were occupied primarily by Cu(II through surface complexation, leading to Cu(II inhibited Cr(VI adsorption. Moreover, Cr(III and Cr(VI removal efficiency had a positive correlation with distribution coefficient Kd. Cr(III and Cr(VI removal efficiency had a positive correlation with distribution coefficient Kd and that of adsorption affinities of Cr(III or Cr(VI on kaolin was found to be Kd Cr(III Kd Cr(VI-Cu(II.

  14. Adsorption behavior of carboxylated cellulose nanocrystal-polyethyleneimine composite for removal of Cr(VI) ions

    Science.gov (United States)

    Liu, Chao; Jin, Ru-Na; Ouyang, Xiao-kun; Wang, Yang-Guang

    2017-06-01

    In this study, a composite adsorbent (CCN-PEI) composed of carboxylated cellulose nanocrystals (CCN) and polyethyleneimine (PEI) was prepared through an amidation reaction between the carboxyl groups of the CCN and the amine groups of the PEI. The adsorption performance of the CCN-PEI was tested by removing Cr(VI) ions from aqueous solutions. The physicochemical properties of the CCN and the Cr(VI) ion-loaded CCN-PEI were studied using scanning electron microscopy (SEM), transmission electron microscopy, Fourier-transform infrared spectroscopy, and X-ray photoelectron spectroscopy. To investigate the adsorption kinetics of Cr(VI) ions onto this newly developed CCN-PEI, we performed experiments under different adsorption conditions, by varying the contact time, solution pH, initial Cr(VI) ion concentration, and adsorption temperature. The prepared CCN-PEI exhibited an encouraging uptake capacity of 358.42 mg × g-1. The adsorption process was fast: within the first 100 min, Cr(VI) ion adsorption onto the CCN-PEI was about 65%, and the adsorption equilibrium was reached within 250 min. Kinetics experiments indicated that the adsorption process could be described by a pseudo-second-order kinetic model. Furthermore, our adsorption equilibrium data fit the Langmuir isotherms well. The calculated thermodynamic parameters, such as the free energy change (ΔG = -2.93 kJ × mol-1), enthalpy change (ΔH = -5.69 kJ × mol-1), and entropy change (ΔS = -9.14 kJ × mol-1), indicate that the adsorption of Cr(VI) ions onto CCN-PEI was a spontaneous exothermic process. Regeneration tests indicated that CCN-PEI showed good durability and good efficiency for repeated Cr(VI) adsorptions. Based on the results obtained in this work, it can be concluded that CCN-PEI is a potentially effective adsorbent for removing Cr(VI) ions from aqueous solutions.

  15. Optimum Conditions for the Removal of Cr(VI using Modified Eucalyptus Bark

    Directory of Open Access Journals (Sweden)

    Fenjie Niu

    2014-10-01

    Full Text Available The aims of this study were response surface modeling and optimization of Cr(VI removal from solution using formaldehyde-modified eucalyptus bark. A high removal rate of Cr(VI was achieved under the conditions of low adsorbent dosing quantity and high initial concentration of Cr(VI. Analysis of variance showed a high multiple coefficient of determination (R2=0.9875, adjusted determination coefficient (R2Adj=0.9714, and the good second order regression equation. The initial concentration of Cr(VI was 40.15 mg/L, adsorbent dosing quantity 3.40 g/L, and initial reaction pH 2.78, and the largest removal rate was 99.998% under the optimum reaction conditions. Langmuir and Freundlich isothermal models described well adsorption of Cr(VI by the modified stringy bark. Adsorption kinetics studies showed that the adsorption was controlled by multiple factors, dominated by chemical adsorption. The adsorption was found to be spontaneous and endothermic, with △G0 0, and △S0 > 0. Adsorption of Cr(VI by formaldehyde-modified stringy bark was partly controlled by REDOX reactions. The adsorbents were characterized by SEM and FTIR.

  16. Cr(VI) retention and transport through Fe(III)-coated natural zeolite.

    Science.gov (United States)

    Du, Gaoxiang; Li, Zhaohui; Liao, Libing; Hanson, Renee; Leick, Samantha; Hoeppner, Nicole; Jiang, Wei-Teh

    2012-06-30

    Cr(VI) is a group A chemical based on the weight of evidence of carcinogenicity. Its transport and retention in soils and groundwater have been studied extensively. Zeolite is a major component in deposits originated from volcanic ash and tuff after alteration. In this study, zeolite aggregates with the particle size of 1.4-2.4mm were preloaded with Fe(III). The influence of present Fe(III) on Cr(VI) retention by and transport through zeolite was studied under batch and column experiments. The added Fe(III) resulted in an enhanced Cr(VI) retention by the zeolite with a capacity of 82mg/kg. The Cr(VI) adsorption on Fe(III)-zeolite followed a pseudo-second order kinetically and the Freundlich adsorption isotherm thermodynamically. Fitting the column experimental data to HYDRUS-1D resulted in a retardation factor of 3 in comparison to 5 calculated from batch tests at an initial Cr(VI) concentration of 3mg/L. The results from this study showed that enhanced adsorption and retention of Cr(VI) may happen in soils derived from volcanic ash and tuff that contains significant amounts of zeolite with extensive Fe(III) coating. Copyright © 2012 Elsevier B.V. All rights reserved.

  17. Adsorption of Cr(VI onto Hybrid Membrane of Carboxymethyl Chitosan and Silicon Dioxide

    Directory of Open Access Journals (Sweden)

    Yanling Deng

    2017-01-01

    Full Text Available In this study, a new adsorbent material was synthesized by using carboxymethyl chitosan and silicon dioxide. The hybrid membrane was used as an adsorbent for the removal of Cr(VI from aqueous solutions. The adsorption potential of Cr(VI by the hybrid materials was investigated by varying experimental conditions such as pH, contact time, and the dosage of the hybrid membrane. Adsorption isotherms of Cr(VI onto the hybrid membrane were studied with varying initial concentrations under optimum experiment conditions. The surface property of the hybrid membrane was characterized by SEM (scanning electron microscope and Fourier transform infrared spectrometer (FTIR. The concentrations of Cr(VI in solution are determined by ICP-AES (inductively coupled plasma atomic emission spectrometry. The present study investigates the adsorption mechanisms of Cr(VI onto the hybrid membrane. The results provide new insight, demonstrating that the modified hybrid membrane can be an efficient adsorbent for Cr(VI from the aqueous solution.

  18. Characteristics of Amine Surfactant Modified Peanut Shell and Its Sorption Property for Cr(VI)

    Institute of Scientific and Technical Information of China (English)

    岳敏; 张猛; 刘斌; 许醒; 李小明; 岳钦艳; 马春元

    2013-01-01

    Modified peanut shell (MPS) was prepared by amination reaction with peanut shell (PS) as the starting material. The sorption of Cr(VI) oxyanions on MPS in static and column tests were investigated. In addition, the sorption isotherm and kinetic models were applied to confirm the sorption capacity and the sorption mechanisms. BET surface area analysis showed the physicochemical characteristics of the samples. The results of zeta potential, Fourier transform infrared (FT-IR) and Raman spectra analysis illustrated that chemical adsorption and ion ex-change are the potential sorption mechanism. The static sorption test showed that the maximum sorption capacity (qmax) of MPS for Cr(VI) increased with temperature, which indicated that the Cr(VI) sorption process was endo-thermic. The saturated sorption capacity of Cr(VI) in the column sorption test was 138.34 mg·g-1, which accounted for 93.9%of the qmax at 25 °C. The regeneration capacity of MPS was evaluated using HCl solution as an eluent. The high regeneration efficiency (82.6%) validated the dominance of the ion exchange mechanism in the Cr(VI) sorption process with Cl-ions displacing Cr(VI) oxyanion on MPS. The Langmuir isotherm model showed a higher correlation coefficient than the other adsorption isotherm models. And in the kinetic study, a pseudo-second-order model fit the data best.

  19. Reduction of Cr(VI) and survival in Cr-contaminated sites by Caulobacter crescentus

    Science.gov (United States)

    Hu, P.; Chakraborty, R.; Brodie, E. L.; Andersen, G. L.; Hazen, T. C.

    2008-12-01

    The Caulobacter spp. is known to be able to live in low-nutrient environments, a characteristic of most heavy metal-contaminated sites. Recent studies have shown that Caulobacter crescentus can grow in chemically defined medium containing up to 1 mM uranium. Whole-genome transcriptional analysis and electron microscopic imaging of heavy metal stresses in Caulobacter crescentus also provided insight and evidence that the bacterium used an array of defensive mechanisms to deal with heavy metal stresses. In addition to up-regulated enzymes protecting against oxidative stress, DNA repair and down-regulated potential chromium transport, one of the major gene groups respond to chromium stress is "electron transport process and cytochrome oxidases", including cytochrome c oxidases, raising the possibility that the cells can employ the cytochromes to reduce chromium. Analysis of the microbial community at the chromium contaminated DOE site at Hanford, WA revealed the presence of Caulobacter spp. As an oligotroph, Caulobacter can play a significant role in chromium reduction in the environment where the nutrients are limited. This result was confirmed by both 16S rDNA based microarray (Phylochip) as well as by MDA-based clone library data. Based on these results we further investigated the capability of this organism to reduce Cr(VI) using the well known model strain Caulobacter crescentus CB15N. Preliminary cell suspension experiments were set up with glucose as the electron donor and Cr(VI) as the electron acceptor in phosphate based M2 salts buffer. After 22 hours almost 27% of Cr(VI) was reduced in the incubations containing active cells relative to the controls containing heat killed cells. Also, in another set of controls with no electron acceptor added, cells showed no increase in cell density during that time demonstrating that the reduction of Cr(VI) by cells of Caulobacter was due to biological activity. Future experiments will investigate the components

  20. Polyaniline coating with various substrates for hexavalent chromium removal

    Science.gov (United States)

    Qiu, Bin; Xu, Cuixia; Sun, Dezhi; Wang, Qiang; Gu, Hongbo; Zhang, Xin; Weeks, Brandon L.; Hopper, Jack; Ho, Thomas C.; Guo, Zhanhu; Wei, Suying

    2015-04-01

    Hexavalent chromium (Cr(VI)) contamination is increasingly serious in surface water and groundwater, therefore, its removal attracts increasing attention due to its highly toxic to human health. The cost effective and sustainable adsorbents are urgently needed for the remediation of Cr(VI) pollution. Polyanline (PANI), a conductive polymer, has demonstrated a great performance on Cr(VI) removal. But the recycling is the challenge for its application due to its small size. The PANI coating with various substrates is an effective approach to solve this problem. The synthesis methods and applications of the PANI coated magnetic Fe3O4, carbon fabric and cellulose composites for the Cr(VI) removal were reviewed. Finally, this review analyzed the Cr(VI) removal mechanisms by the PANI composites considering the substrate and the PANI coating.

  1. Correlation between bulk- and surface chemistry of Cr-tanned leather and the release of Cr(III) and Cr(VI).

    Science.gov (United States)

    Hedberg, Yolanda S; Lidén, Carola; Odnevall Wallinder, Inger

    2014-09-15

    About 1-3% of the adult general population in Europe is allergic to chromium (Cr). The assessment of the potential release of Cr(III) and Cr(VI) from leather is hence important from a human health and environmental risk perspective. The Cr(VI) content in leather was recently restricted in the European Union. The aim of this study was to assess possible correlations between the bulk and surface chemistry of leather, released Cr(III) and Cr(VI), and capacities of co-released leather specific species to reduce and complex released Cr. Four differently tanned leathers were characterized by scanning electron microscopy with energy dispersive spectroscopy, X-ray photoelectron spectroscopy, attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy, and the diphenylcarbazide colorimetric method. Their characteristics were compared with results on Cr(III) and Cr(VI) release into artificial sweat (ASW, pHleather-specific species were shown to reduce Cr(VI), both in ASW and in PB. Their reduction capacities correlated with findings of the surface content of Cr and of released Cr. Leather samples without this capacity, and with less aromatic surface groups visible by ATR-FTIR, revealed Cr(VI) both at the surface and in solution (PB).

  2. Effective Management of Hexavalent Chromium (Cr+6) in DoD Organic and Inorganic Coatings Operations

    Science.gov (United States)

    2014-11-19

    Vinay V. Gadkari Battelle gadkariv@battelle.org 614-424-5751 Effective Management of Hexavalent Chromium (Cr+6) in DoD Organic and Inorganic...Coatings Operations Enhancing worker safety by minimizing health risks in hexavalent chromium environment 1 11/19/2014 John T. Stropki Battelle ...ADDRESS(ES) Battelle ,505 King Avenue,Columbus,OH,43201 8. PERFORMING ORGANIZATION REPORT NUMBER 9. SPONSORING/MONITORING AGENCY NAME(S) AND ADDRESS(ES

  3. Ultratrace Determination of Cr(VI and Pb(II by Microsample Injection System Flame Atomic Spectroscopy in Drinking Water and Treated and Untreated Industrial Effluents

    Directory of Open Access Journals (Sweden)

    Jameel Ahmed Baig

    2013-01-01

    Full Text Available Simple and robust analytical procedures were developed for hexavalent chromium (Cr(VI and lead (Pb(II by dispersive liquid-liquid microextraction (DLLME using microsample injection system coupled with flame atomic absorption spectrophotometry (MIS-FAAS. For the current study, ammonium pyrrolidine dithiocarbamate (APDC, carbon tetrachloride, and ethanol were used as chelating agent, extraction solvent, and disperser solvent, respectively. The effective variables of developed method have been optimized and studied in detail. The limit of detection of Cr(VI and Pb(II were 0.037 and 0.054 µg/L, respectively. The enrichment factors in both cases were 400 with 40 mL of initial volumes. The relative standard deviations (RSDs, were 96%. The proposed method was successfully applied to the determination of Cr(VI and Pb(II at ultratrace levels in natural drinking water and industrial effluents wastewater of Denizli. Moreover, the proposed method was compared with the literature reported method.

  4. Synthesis and application of magnetic hydrogel for Cr(VI) removal from contaminated water

    KAUST Repository

    Tang, Samuel C N

    2010-11-01

    Many magnetic adsorbents reported in the literature, such as iron oxides, for Cr(VI) removal have been found effective only in low pH environments. Moreover, the application of polymeric hydrogels on heavy metal removal has been hindered by difficulties in separation by filtration. In this study, a magnetic cationic hydrogel was synthesized for Cr(VI) removal from contaminated water, making use of the advantages of magnetic adsorbents and polymeric hydrogels. The magnetic hydrogel was produced by imbedding 10-nm γ-Fe2O 3 nanoparticles into the polymeric matrix via radical polymerization. Characterization of the hydrogel was undertaken with Fourier transform infrared and vibrating sample magnetometer; swelling properties were tested and anionic adsorption capacity was evaluated. The magnetic hydrogel showed a superior Cr(VI) removal capacity compared to commercial products such as MIEX®. Cr(VI) removal was independent of solution pH. Results show that Cr(VI) removal kinetics was improved drastically by grinding the bulk hydrogel into powder form. At relevant concentrations, common water anions (e.g., Cl-, SO4 2-, PO4 3-) and natural organic matter did not exhibit significant inhibition of Cr(VI) adsorption onto the hydrogel. Results of vibrating sample magnetometer indicate that the magnetic hydrogel can be easily separated from treatment systems. Regeneration of the magnetic hydrogel can be easily achieved by washing the Cr(VI)-loaded hydrogel with 0.5 M NaCl solution, with a recovery rate of about 90% of Cr(VI). © Copyright 2010, Mary Ann Liebert, Inc. 2010.

  5. Biosorption of Cr(III), Cr(VI), Cu(II) ions by intact cells of Spirulina platensis

    OpenAIRE

    Gelagutashvili, E.; Bagdavadze, N.; Rcheulishvili, A.

    2017-01-01

    The absorption characteristics of Cr(III), Cr(VI), Cu(II) ions on intact living cells Spirulina platensis (pH9.6) were studied by using a UV-VIS spectrophotometer. Also biosorption of these ions with cyanobacteria Spirulina platensis were studied using equilibrium dialysis and atomic absorption analysis.It was shown, that the absorption intensity of Spirulina platensis decreases, when Cr(III), Cr(VI), Cu(II) ions are added. Significant difference between the absorption intensity for Cu(II) Sp...

  6. Distinguished Cr(VI) capture with rapid and superior capability using polydopamine microsphere: Behavior and mechanism.

    Science.gov (United States)

    Zhang, Qingrui; Li, Yixuan; Yang, Qinggang; Chen, He; Chen, Xinqing; Jiao, Tifeng; Peng, Qiuming

    2017-08-26

    Toxic heavy metal containing Cr(VI) species is a serious threat for ecological environment and human beings. In this work, a new mussel-inspired polydopamine microsphere (PDA-sphere) is prepared through in situ oxidative polymerization at air condition with controllable sizes. The adsorption of Cr(VI) ions onto PDA-sphere is highly pH dependent with the optimal pH ranging from 2.5 to 3.8. A rapid Cr(VI) removal can approach in 8min for equilibrium. More importantly, the prepared materials exhibit a remarkable sorption selectivity, coexisting SO4(2-), NO3(-) and Cl(-) ions at high levels; The applicability model further proves its effective performances with treated capacity of 42,000kg/kg sorbent, and the effluent can be reduced from 2000ppb to below 50ppb, which meets the drinking water criterions recommended by WHO. 1kg sorbent can also purify approximately 100t Cr(VI) contaminated wastewaters basing on the wastewater discharges of China. Such capacity for application ranks the top level for Cr(VI) removal. Additionally, the exhausted materials can be well regenerated by binary alkaline and salts mixtures. Such efficient adsorption can be ascribed to the well-dispersed morphology as well as the strong affinity between Cr(VI) and catechol or amine groups by XPS investigation. All the results suggest that polydopamine microspheres may be ideal materials for Cr(VI) treatment in waters. Copyright © 2017 Elsevier B.V. All rights reserved.

  7. Removal of Cr(VI from Aqueous Solution Using Modified Pomegranate Peel : Equilibrium and Kinetic Studies

    Directory of Open Access Journals (Sweden)

    Tariq S. Najim

    2009-01-01

    Full Text Available The present investigation deals with the utilization of modified pomegrenate peel (MPGP and formaldehyde modified pomegrenate peel (FMPGP as adsorbents for the removal of chromium Cr(VI from aqueous solution. A series of experiments were conducted in a batch system to evaluate the effect of system variables. The effect of pH, initial Cr(VI concentration, contact time, adsorbent dosage and temperature were considered. The optimal pH values of Cr(VI removal by MPGP and FMPGP were 2.0 and 3.0 respectively. The time required for equilibrium was found to be about 100 minutes. The initial Cr(VI concentration and adsorbent dosage was found to have large effect on the adsorption of Cr(VI. The maximum uptake capacities were 13.01 and 22.28 mg of Cr(VI per gram of MPGP and FMPGP respectively. Adsorption kinetic data were tested using pseudo-first order, pseudo-second order, Elovich and intra-particle diffusion models. Kinetic studies showed that the adsorption followed a pseudo second order reaction due to the high correlation coefficient and the agreement between the experimental and calculated values of qe.The adsorption may follow intraparticle diffusion as well, due to the highest values of rate constants for the surface adsorption and intraparticle diffusion kinetic models, the higher values of rate constants are related to an improved bonding between Cr(VI ions and adsorbent particle.The Dubinin-radushkevich, Freundlich and Tempkin models were the closest fit for the equilibrium data of MPGP and FMPGP.

  8. Differential Isotopic Fractionation during Cr(VI) Reduction by an Aquifer-Derived Bacterium under Aerobic versus Denitrifying Conditions

    Energy Technology Data Exchange (ETDEWEB)

    Han, R.; Qin, L.; Brown, S. T.; Christensen, J. N.; Beller, H. R.

    2012-01-27

    We studied Cr isotopic fractionation during Cr(VI) reduction by Pseudomonas stutzeri strain RCH2. Finally, despite the fact that strain RCH2 reduces Cr(VI) cometabolically under both aerobic and denitrifying conditions and at similar specific rates, fractionation was markedly different under these two conditions (ε was ~2‰ aerobically and ~0.4‰ under denitrifying conditions).

  9. Reduction of Hexavalent Chromium Using Sorbaria sorbifolia Aqueous Leaf Extract

    Directory of Open Access Journals (Sweden)

    Shashi Prabha Dubey

    2017-07-01

    Full Text Available Aqueous plant leaves extract (PLE of an abundant shrub, Sorbaria sorbifolia, was explored for the reduction of hexavalent chromium, Cr(VI, to trivalent chromium, Cr(III. The effect of contact time, pH, PLE quantity, ionic strength, hardness, temperature and effective initial Cr(VI ion concentration were tested; Cr(VI reduction followed the pseudo-first order rate kinetics and maximum reduction was observed at pH 2. Significantly, Cr(VI reduction efficacies varied from 97 to 66% over the pH range of 2 to 10, which bodes well for PLE to be used for the reduction of Cr(VI also at a higher pH. PLE-mediated Cr(VI reduction displays considerable efficiency at various ionic strengths; however, hardness strongly affects the reduction ability. Higher temperature significantly enhances the Cr(VI reduction. This study reveals the potential use of PLE as a green reducing agent in aqueous extract for the efficient reduction of Cr(VI to Cr(III.

  10. Biotreatment of Cr(VI) contaminated waters by sulphate reducing bacteria fed with ethanol

    Energy Technology Data Exchange (ETDEWEB)

    Pagnanelli, F., E-mail: francesca.pagnanelli@uniroma1.it [Department of Chemistry, Sapienza University of Rome, P.le Aldo Moro 5, 00185 Rome (Italy); Cruz Viggi, C., E-mail: carolina.cruzviggi@uniroma1.it [Department of Chemistry, Sapienza University of Rome, P.le Aldo Moro 5, 00185 Rome (Italy); Cibati, A., E-mail: alessio.cibati@uniroma1.it [Department of Chemistry, Sapienza University of Rome, P.le Aldo Moro 5, 00185 Rome (Italy); Uccelletti, D., E-mail: daniela.uccelletti@uniroma1.it [Department of Biology and Biotechnology, Sapienza University of Rome, P.le A. Moro 5, 00185 Rome (Italy); Toro, L., E-mail: luigi.toro@uniroma1.it [Department of Chemistry, Sapienza University of Rome, P.le Aldo Moro 5, 00185 Rome (Italy); Palleschi, C., E-mail: claudio.palleschi@uniroma1.it [Department of Biology and Biotechnology, Sapienza University of Rome, P.le A. Moro 5, 00185 Rome (Italy)

    2012-01-15

    Highlights: Black-Right-Pointing-Pointer Use of ethanol as electron donor for sulphate-reducing bacteria for the treatment of Cr(VI). Black-Right-Pointing-Pointer Isolation of contribution in Cr removal (adsorption vs. bioprecipitation). Black-Right-Pointing-Pointer Bioassessment of the process effectiveness by ecotoxicological in vivo tests using C. elegans. - Abstract: Biological treatment of Cr(VI) contaminated waters was performed in fixed bed reactors inoculated with SRB (sulphate-reducing bacteria) growing on ethanol. Treatment efficiency was evaluated by checking chemical abatement of Cr(VI) and by ecotoxicological tests using the nematode Caenorhabditis elegans. A preliminary comparison between ethanol and lactate was performed, denoting that using ethanol, the same values of final sulphate abatement were obtained. In addition ethanol showed to be a substrate more competitive than lactate in kinetic terms. Fixed bed column reactors were continuously fed with a solution containing sulphates (3 g L{sup -1}), ethanol (1.5 g L{sup -1}) and Cr(VI) (50 mg L{sup -1}). At steady state the column inoculated with SRB removed 65 {+-} 5% of sulphate and 95 {+-} 5% of chromium. Bioactive removal mechanisms predominated over biosorption. Diminution of Cr(VI) toxicity was assessed by using the nematode C. elegans as a test organism showing that the survival of nematodes was 20% in the presence of the untreated influent and raised up to 53% when the nematodes were exposed to the treated effluent.

  11. Facile synthesis of boehmite/PVA composite membrane with enhanced adsorption performance towards Cr(VI).

    Science.gov (United States)

    Luo, Lei; Cai, Weiquan; Zhou, Jiabin; Li, Yuanzhi

    2016-11-15

    A novel boehmite/PVA composite membrane (BPCM) with remarkably enhanced adsorption performance towards Cr(VI) was successfully synthesized from Al(NO3)3·9H2O using HAc as the peptizing agent via a facile sol-gel method. The physicochemical properties of the BPCM, the boehmite powder (BP) without PVA and a commercial boehmite powder (CBP) were comparatively characterized by XRD, TGA-DSC, FT-IR and XPS. Batch adsorption experiments showed that the adsorption performance of the BPCM is much better than those of BP and CBP. Its adsorption process was well described by the pseudo-second-order kinetic model, and its equilibrium data fit the Langmuir isotherm well with a maximum adsorption capacity of 36.41mgg(-1). Its interference adsorption experiment in presence of coexisting anions showed that SO4(2-) and HPO4(2-) have greater effect than those of the Cl(-), F(-), C2O4(2-) and HCO3(-). A three step action mechanism including adsorption of Cr(VI) anions, complexation between Cr(VI) anions and the functional groups on the surface of BPCM, and the reduction of Cr(VI) to Cr(III) was proposed to illustrate the adsorption process. This efficient film could be easily separated after adsorption, exhibiting great potential for the removal of Cr(VI) from aqueous solution, and other fields of environmental remediation.

  12. Cr(VI) induces the decrease of ATP level and the increase of apoptosis rate mediated by ROS or VDAC1 in L-02 hepatocytes.

    Science.gov (United States)

    Yuan, Yang; Ming, Zen; Gong-Hua, Hu; Lan, Guan; Lu, Dai; Peng, Li; Feng, Jing; Cai-Gao, Zhong

    2012-09-01

    The present study explored the ability of the voltage-dependent anion channel 1 (VDAC1) mRNA and ROS levels to modulate the effects of hexavalent chromium Cr(VI) on the adenosine triphosphate (ATP) level and the rate of apoptotic cell death. Cultured L-02 cells were pretreated with 20mM N-acetyl-cysteine (NAC) for 24h or transiently transfected with small interfering RNAs targeting VDAC1 (siVDAC1) for 48h; cells that were not pretreated were used as the control. The cells were subsequently treated with 0, 2, 8, or 32μM Cr(VI) for 24h. Then, levels of VDAC1 mRNA, ROS, and ATP and the apoptosis rate were measured by reverse-transcription quantitative PCR, fluorometry, a bioluminescence assay, and flow cytometry, respectively. The results showed that Cr(VI) at 32μM led to increase in the ROS level, VDAC1 mRNA expression, and the apoptosis rate and a decrease in the ATP level; pretreatment with NAC led to the down-regulation in the levels of ROS, VDAC1 mRNA and apoptosis and the significant up-regulation in the ATP levels. Interestingly, after the pretreatment with siVDAC1 to inhibit VDAC1 mRNA expression, the increased apoptosis rates and decreased ATP levels were reversed as well. These results suggested that changes in the ROS or VDAC1 mRNA levels were associated with changes in the ATP level and apoptosis rate. Furthermore, correlation analysis confirmed the association between both the ROS and VDAC1 levels and both the ATP level and the apoptosis rate. In conclusion, Cr(VI) induced ROS- and VDAC1-mediated decreases in ATP levels and increases in the apoptosis rate.

  13. Cytotoxic and genotoxic potential of Cr(VI), Cr(III)-nitrate and Cr(III)-EDTA complex in human hepatoma (HepG2) cells.

    Science.gov (United States)

    Novotnik, Breda; Ščančar, Janez; Milačič, Radmila; Filipič, Metka; Žegura, Bojana

    2016-07-01

    Chromium (Cr) and ethylenediaminetetraacetate (EDTA) are common environmental pollutants and can be present in high concentrations in surface waters at the same time. Therefore, chelation of Cr with EDTA can occur and thereby stable Cr(III)-EDTA complex is formed. Since there are no literature data on Cr(III)-EDTA toxicity, the aim of our work was to evaluate and compare Cr(III)-EDTA cytotoxic and genotoxic activity with those of Cr(VI) and Cr(III)-nitrate in human hepatoma (HepG2) cell line. First the effect of Cr(VI), Cr(III)-nitrate and Cr(III)-EDTA on cell viability was studied in the concentration range from 0.04 μg mL(-1) to 25 μg mL(-1) after 24 h exposure. Further the influence of non-cytotoxic concentrations of Cr(VI), Cr(III)-nitrate and Cr(III)-EDTA on DNA damage and genomic stability was determined with the comet assay and cytokinesis block micronucleus cytome assay, respectively. Cell viability was decreased only by Cr(VI) at concentrations above 1.0 μg mL(-1). Cr(VI) at ≥0.2 μg mL(-1) and Cr(III) at ≥1.0 μg mL(-1) induced DNA damage, while after Cr(III)-EDTA exposure no formation DNA strand breaks was determined. Statistically significant formation of micronuclei was induced only by Cr(VI) at ≥0.2 μg mL(-1), while no influence on the frequency of nuclear buds nor nucleoplasmic bridges was observed at any exposure. This study provides the first evidence that Cr(III)-EDTA did not induce DNA damage and had no influence on the genomic stability of HepG2 cells.

  14. Adsorption of Cr(VI) from aqueous solutions by staphylococcus aureus biomass

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Xue Song; Li, Yuan; Huang, Li Ping; Chen, Jing [Department of Chemical Engineering, Huaihai Institute of Technology, Lianyungang, Jiangsu (China)

    2010-06-15

    Staphylococcus aureus has not been used to remove Cr(VI) ions from aqueous solutions. In the present study, biosorption experiments for Cr(VI) were investigated using S. aureus biomass isolated from activated sludge, Lianyungang Dapu sewage treatment plant, China. The effects of solution pH, contact time reaction temperature and ionic strength on Cr(VI) uptake were studied. The biomass was characterized by energy dispersive X-ray spectroscopy and Fourier transform infrared spectrometer. The applicability of the Langmuir and Freundlich models was tested. The correlation coefficients (R) of both models were higher than 0.9. The maximum adsorption capacity was found to be 27.36 mg/g for Cr(VI) at 20 C. The adsorption process was quick and found to follow the pseudo-second-order equation. The optimum adsorption was achieved at pH 2. The adsorption was strongly dependent on NaCl concentrations as well as on reaction temperature. The S. aureus biomass could serve as adsorbent to remove Cr(VI) from industrial effluents. (Abstract Copyright [2010], Wiley Periodicals, Inc.)

  15. Cr(VI) reduction and Cr(III) immobilization by Acinetobacter sp. HK-1 with the assistance of a novel quinone/graphene oxide composite.

    Science.gov (United States)

    Zhang, Hai-Kun; Lu, Hong; Wang, Jing; Zhou, Ji-Ti; Sui, Meng

    2014-11-04

    Cr(VI) biotreatment has attracted a substantial amount of interest due to its cost effectiveness and environmental friendliness. However, the slow Cr(VI) bioreduction rate and the formed organo-Cr(III) in solution are bottlenecks for biotechnology application. In this study, a novel strain, Acinetobacter sp. HK-1, capable of reducing Cr(VI) and immobilizing Cr(III) was isolated. Under optimal conditions, the Cr(VI) reduction rate could reach 3.82 mg h(-1) g cell(-1). To improve the Cr(VI) reduction rate, two quinone/graphene oxide composites (Q-GOs) were first prepared via a one-step covalent chemical reaction. The results showed that 2-amino-3-chloro-1,4-naphthoquinone-GO (NQ-GO) exhibited a better catalytic performance in Cr(VI) reduction compared to 2-aminoanthraquinone-GO. Specifically, in the presence of 50 mg L(-1) NQ-GO, a Cr(VI) removal rate of 190 mg h(-1) g cell(-1), which was the highest rate obtained, was achieved. The increased Cr(VI) reduction rate is mainly the result of NQ-GO significantly increasing the Cr(VI) reduction activity of cell membrane proteins containing dominant Cr(VI) reductases. X-ray photoelectron spectroscopy analysis found that Cr(VI) was reduced to insoluble Cr(III), which was immobilized by glycolipids secreted by strain HK-1. These findings indicate that the application of strain HK-1 and NQ-GO is a promising strategy for enhancing the treatment of Cr(VI)-containing wastewater.

  16. As(V), Cr(III) and Cr(VI) sorption on biochars and soil

    Science.gov (United States)

    Diamadopoulos, Evan; Agrafioti, Evita; Kalderis, Dimitrios

    2014-05-01

    The use of biochar, as a cost effective sorbent for heavy metal removal from contaminated water and soils is becoming a very promising practice. In this study, rice husk, the organic fraction of solid wastes, as well as sewage sludge were used as precursors for biochar production. The first was chosen as one of the most abundant types of biomass worldwide and the other two in order to find alternative innovative uses of these wastes. A series of batch kinetic and equilibrium (sorption and desorption) experiments was conducted using As(V), Cr(III) and Cr(VI) as adsorbates. The specific heavy metals were chosen in order to assess biochars removal capacity towards both anionic and cationic metals. Apart from biochars, a sandy loam soil was also used as adsorbent for metal removal. Knowing the separate behavior of biochars and soil towards metal sorption, it could be the first step in explaining the fate of heavy metals in a biochar amended soil. The kinetic study showed that, for all adsorbents and metals examined, sorption can be well described by the pseudo-second order kinetic model. What is more, simulation of sorption isotherms gave a better fit for the Freundlich model, possibly due to the heterogeneous surface of the initial biomasses and the fine aggregates that soil consists of. Based on the equilibrium study, the materials examined removed more than 95% of the initial Cr(III). This is possibly related to the electrostatic interactions between adsorbents negative surface charge and Cr(III) cations. However, removal rates for As(V) and Cr(VI) anions were significantly lower. Biochar derived from sewage sludge was efficient in removing 89% of Cr(VI) and 53% of As(V). Its ash high Fe2O3 content may have enhanced metal adsorption via precipitation. Soil was the most effective material for the removal of As(V), yet it could not strongly retain metal anions compared to biochars, as a significant amount of the adsorbed metal was released during desorption

  17. Removal of aqueous chromate [Cr(VI)] through photocatalysis by using TiO2-coated silica granules.

    Science.gov (United States)

    Saeki, Kazutoshi; Kadono, Mayumi; Nabeshima, Akiko

    2010-01-01

    The aim of this study was to determine the optimal conditions for the treatment of chromate [Cr(VI)]- contaminated water by UV photocatalysis using synthesized TiO(2)-coated silica granules (phi 1.7-4.0 mm) containing 12.4% of TiO(2) in a batch method. The effect of the volume of the solution on Cr(VI) removal was investigated in the photocatalysis process by using 10 g of TiO(2)-coated silica granules in water samples with a constant initial Cr(VI) concentration of 5 mg L(-1). In a 10-mL solution, Cr(VI) concentrations were observed to decrease below the detection limit (photocatalysis process to remove Cr(VI) using 10 g of TiO(2)-coated granules did not fluctuate with the solution volume for samples with a constant initial Cr(VI) concentration. The lower the initial pH of the solution, the greater was the amount of Cr(VI) removed from the solution. The addition of chloride ions to the solutions accelerated the removal of Cr(VI) by UV photocatalysis. Ten grams of TiO(2)-coated silica granules were repeatedly used to the 300-min treatment of the Cr(VI) solution (10 mL, 6 mg L(-1)) till seven cycles. After four cycles of UV photocatalysis, Cr(VI) was completely removed from all the solutions. After the fifth cycle, the Cr(VI) removal capacity of the UV photocatalysis process decreased with the repeated use of the catalyst.

  18. Introduction of Hydrogen Peroxide as an Oxidant in Flow Injection Analysis: Speciation of Cr(III) and Cr(VI)

    DEFF Research Database (Denmark)

    Andersen, Jens Enevold Thaulov

    1998-01-01

    Hydrogen peroxide was used as an oxidant in Flow Injection Analysis (FIA). The formation of gaseous components during the analysis was suppressed by maintaining a concentration lower than 0.15% of hydrogen peroxide in 0.1 M NaOH. By this method Cr(III) was oxidised on-line to Cr(VI) which...

  19. Microbial reduction of hexavalent chromium under vadose zone conditions.

    Science.gov (United States)

    Oliver, Douglas S; Brockman, Fred J; Bowman, Robert S; Kieft, Thomas L

    2003-01-01

    Hexavalent chromium [Cr(VI)] is a common contaminant associated with nuclear reactors and fuel processing. Improper disposal at facilities in and and semiarid regions has contaminated underlying vadose zones and aquifers. The objectives of this study were to assess the potential for immobilizing Cr(VI) using a native microbial community to reduce soluble Cr(VI) to insoluble Cr(III) under conditions similar to those in the vadose zone, and to evaluate the potential for enhancing biological Cr(VI) reduction through nutrient addition. Batch microcosm and unsaturated flow column experiments were performed. Native microbial communities in subsurface sediments with no prior Cr(VI) exposure were shown to be capable of Cr(VI) reduction. In both the batch and column experiments, Cr(VI) reduction and loss from the aqueous phase were enhanced by adding high levels of both nitrate (NO3-) and organic C (molasses). Nutrient amendments resulted in up to 87% reduction of the initial 67 mg L(-1) Cr(VI) in an unsaturated batch experiment. Molasses and nitrate additions to 15 cm long unsaturated flow columns receiving 65 mg L(-1) Cr(VI) resulted in microbially mediated reduction and immobilization of 10% of the Cr during a 45-d experiment. All of the immobilized Cr was in the form of Cr(III), as shown by XANES analysis. This suggests that biostimulation of microbial Cr(VI) reduction in vadose zones by nutrient amendment is a promising strategy, and that immobilization of close to 100% of Cr contamination could be achieved in a thick vadose zone with longer flow paths and longer contact times than in this experiment.

  20. Removal of Cr(VI) from aqueous solution by adsorption onto activated carbon.

    Science.gov (United States)

    Selvi, K; Pattabhi, S; Kadirvelu, K

    2001-10-01

    Activated carbon (AC) prepared from coconut tree sawdust was used as an adsorbent for the removal of Cr(VI) from aqueous solution. Batch mode adsorption studies were carried out by varying agitation time, initial Cr(VI) concentration, carbon concentration and pH. Langmuir and Freundlich adsorption isotherms were applied to model the adsorption data. Adsorption capacity was calculated from the Langmuir isotherm and was 3.46 mg/g at an initial pH of 3.0 for the particle size 125-250 microm. The adsorption of Cr(VI) was pH dependent and maximum removal was observed in the acidic pH range. Desorption studies were carried out using 0.01-1 M NaOH solutions.

  1. Phyto-remediation potential of Ipomoea aquatica for Cr(VI) mitigation.

    Science.gov (United States)

    Weerasinghe, Aruni; Ariyawnasa, Sanduni; Weerasooriya, Rohan

    2008-01-01

    Phyto-remedial efficiency of Ipomoea aquatica was examined at different experimental conditions for a period of 3 months. This plant was selected due to its easy establishment, tolerance and growing easiness. In all trials, the I. aquatica was grown in coir dust to ensure an inert medium. Essential growth nutrients were supplied externally using Albert solution. Once plant growth conditions were fixed, the model system was spiked with Cr(VI) solution in the range of 7-90 ppm. Up to 28 ppm Cr(VI), I. aquatica exhibits uniform absorption characteristics showing over 75% removal of added Cr(VI). At this stage I. aquatica was not affected and it showed no toxicity symptoms. Therefore, it is suited as a potential phyto-remediant. Further I. aquatica is a vegetable particularly in Asian region; therefore caution has to be taken when selecting it for human consumption due to its high chromium accumulation capacity.

  2. Speciation of Cr(III) and Cr(VI) after column solid phase extraction on Amberlite XAD-2010.

    Science.gov (United States)

    Bulut, V N; Duran, C; Tufekci, M; Elci, L; Soylak, M

    2007-05-08

    A speciation procedure for Cr(III) and Cr(VI) based on column solid phase extraction on Amberlite XAD-2010 and flame atomic absorption spectrometry combination. Cr(VI) was quantitatively recovered on Amberlite XAD-2010 resin at pH range of 2.0-3.0 as its diethyldithiocarbamate complex, while the recoveries of Cr(III) was below 5%. The influences of the various parameters including amounts of the reagents, eluent type and its volume, sample volume, etc., on the quantitative recoveries were examined. The interference of matrix and coexistent elements for method were studied. The detection limit (corresponding to three times the standard deviation of the blank) and the enrichment factor for Cr(VI) were found to be 1.28 microg/L and 25, respectively. To verify the accuracy of the method, drinking water certified reference material (CRM-TMDW-500) was analyzed and the results obtained were in good agreement with the certified value. The proposed method has been successfully applied to the speciation of Cr(III) and Cr(VI) in water samples and preconcentration of total chromium in environmental samples.

  3. About the performance of Sphaerotilus natans to reduce hexavalent chromium in batch and continuous reactors

    Energy Technology Data Exchange (ETDEWEB)

    Caravelli, Alejandro H., E-mail: alejandrocaravelli@hotmail.com [Centro de Investigacion y Desarrollo en Criotecnologia de Alimentos (CIDCA), CCT - CONICET - La Plata. Fac., Ciencias Exactas, Universidad Nacional de La Plata, 47 y 116 La Plata (1900) (Argentina); Zaritzky, Noemi E., E-mail: zaritzky@ing.unlp.edu.ar [Centro de Investigacion y Desarrollo en Criotecnologia de Alimentos (CIDCA), CCT - CONICET - La Plata. Fac., Ciencias Exactas, Universidad Nacional de La Plata, 47 y 116 La Plata (1900) (Argentina); Fac. de Ingenieria, Universidad Nacional de La Plata, 48 y 115 La Plata (1900) (Argentina)

    2009-09-15

    The hexavalent chromium biological reduction constitutes a safe and economical detoxification procedure of wastewaters containing Cr(VI). However, little research has been done to evaluate Cr(VI) tolerance and reduction capacity of microbial cultures under different growth conditions. The aims of this work were (a) to evaluate the capacity of Sphaerotilus natans to reduce Cr(VI) to Cr(III) in a continuous system limited in carbon and energy source or in nitrogen source, (b) to evaluate the toxic effect of Cr(VI) on this microorganism, (c) to carry out a complete analysis of Cr(VI) reduction by S. natans not only in continuous regime but also in batch system, and (d) to model the obtained results mathematically. S. natans exhibited great resistance to Cr(VI) (19-78 mg l{sup -1}) and optimal growth in continuous and batch systems using a mineral medium supplemented only with citric acid as organic substrate. In carbon- and energy-limited continuous systems, a maximum percentual decrease in Cr(VI) by 13% was reached for low influent Cr(VI) concentration (4.3-5.32 mgCr(VI) l{sup -1}); the efficiency of the process did not notoriously increase as the length of cellular residence time was increased from 4.16 to 50 h. A nitrogen-limited continuous operation with a cellular residence time of 28.5 h resulted in a Cr(VI) decrease of approximately 26-32%. In batch system, a mathematical model allowed to predict the Cr(VI) concentration as a function of time and the ratio between the initial Cr(VI) concentration and that of the biomass. High concentrations of initial Cr(VI) and biomass produced the highest performance of the process of Cr(VI) reduction reached in batch system, aspects which should be considered in detoxification strategies of wastewaters.

  4. Modeling of Cr(VI) Bioreduction Under Fermentative and Denitrifying Conditions

    Science.gov (United States)

    Molins, S.; Steefel, C.; Yang, L.; Beller, H. R.

    2011-12-01

    The mechanisms of bioreductive immobilization of Cr(VI) were investigated by reactive transport modeling of a set of flow-through column experiments performed using natural Hanford 100H aquifer sediment. The columns were continuously eluted with 5 μM Cr(VI), 5 mM lactate as the electron donor, and selected electron acceptors (tested individually). Here we focus on the two separate experimental conditions that showed the most removal of Cr(VI) from solution: fermentation and denitrification. In each case, a network of enzymatic and abiotic reaction pathways was considered to interpret the rate of chromate reduction. The model included biomass growth and decay, and thermodynamic limitations on reaction rates, and was constrained by effluent concentrations measured by IC and ICP-MS and additional information from bacterial isolates from column effluent. Under denitrifying conditions, Cr(VI) reduction was modeled as co-metabolic with nitrate reduction based on experimental observations and previous studies on a denitrifying bacterium derived from the Hanford 100H aquifer. The reactive transport model results supported this interpretation of the reaction mechanism and were used to quantify the efficiency of the process. The models results also suggest that biomass growth likely relied on a nitrogen source other than ammonium (e.g. nitrate). Under fermentative conditions and based on cell suspension studies performed on a bacterial isolate from the columns, the model assumes that Cr(VI) reduction is carried out directly by fermentative bacteria that convert lactate into acetate and propionate. The evolution to complete lactate fermentation and Cr(VI) reduction took place over a week's time and simulations were used to determine an estimate for a lower limit of the rate of chromate reduction by calibration with the flow-through column experimental results. In spite of sulfate being added to these columns, sulfate reduction proceeded at a slow rate and was not well

  5. Studies on Cr(VI) removal from aqueous solutions by nanotitania under visible light and dark conditions

    Indian Academy of Sciences (India)

    Madona Lien Paul; Jastin Samuel; Rajdeep Roy; Natarajan Chandrasekaran; Amitava Mukherjee

    2015-04-01

    The current study deals with Cr(VI) removal by nanotitania under fluorescent light and dark conditions. The equilibrium removal capacities, 85.85 and 59.4 mg of Cr(VI)g−1 of nanoparticle were noted for nanotitania interacted under light and dark conditions, respectively, at optimized conditions (pH: 7.0, contact time: 30 min, initial Cr(VI) concentration: 20 mg l−1, nanoparticle dosage: 0.1 g l−1). Under both the conditions, the equilibrium removal data fitted well with the Langmuir isotherm model. The nanotitania followed a second-order kinetics under light condition whereas a pseudo-second-order kinetics was observed under dark condition. The surface characterization of nanotitania was carried out by zeta potential measurement and transmission electron microscope (TEM). Fourier transform infrared (FT-IR) studies carried out under light and dark conditions indicate the interaction of surface functional groups to Cr(VI). Cr(VI) removal study carried out in the Cr(VI)–Cr(III) mixture showed a decrease in Cr(VI) removal capacity with increase in Cr(III) concentration. A 92% regeneration of nanoparticle was observed indicating efficient reusability of the system. The applicability of the nanotitania in Cr(VI) contaminated water was studied by spiking Cr(VI) in natural water matrices like ground water and lake water.

  6. Combined adsorption and reduction of Cr(VI) from aqueous solution on polyaniline/multiwalled carbon nanotubes composite

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Jiahong; Yin, Xiaolong; Ma, Hongrui [Shannxi University of Science and Technology, Xi' an (China); Tang, Wei [Shaanxi Research Institute of Agricultural Products Processing Technology, Xi' an (China)

    2015-09-15

    Polyaniline/multiwalled carbon nanotube (PANI-MWCNT) was prepared by bounding polyaniline on the surface of oxidized multiwalled carbon nanotube. The structure and surface properties of synthesized composites were characterized by Fourier transformed infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), transmission electron microscope (TEM), and its adsorption capability for aqueous Cr(VI) was also studied. Characterized results showed that polyaniline was successfully anchored on the surface of MWCNT. From adsorption experiments the maximum adsorption amount of Cr(VI) onto PANI-MWCNTs was 28.25, 31.75 and 36.76 mg·g{sup -1} at 15, 25 and 35 .deg. C. Thermodynamic parameters showed that the Cr(VI) adsorption process was endothermic, spontaneous and feasible. Cr(VI) adsorption followed pseudo-second-order kinetics. Cr(VI) adsorption on the adsorbent decreases with increasing solution pH. The presence of anions in solution almost has no effect on Cr(VI) adsorption, indicating good selectivity. XPS analysis confirms that electrostatic interaction, reduction and chelation contribute to enhanced Cr(VI) removal. Cr(VI) loaded absorbent can be readily desorbed in 0.1mol·L{sup -1} of NaOH solution, and the desorption rate was 84.12%.

  7. Determination of thermodynamic parameters of Cr(VI) adsorption from aqueous solution onto Agave lechuguilla biomass

    Energy Technology Data Exchange (ETDEWEB)

    Romero-Gonzalez, J. [Environmental Science and Engineering, University of Texas at El Paso, El Paso, TX 79968 (United States); Peralta-Videa, J.R. [Department of Chemistry, University of Texas at El Paso, El Paso, TX 79968 (United States); Rodriguez, E. [Environmental Science and Engineering, University of Texas at El Paso, El Paso, TX 79968 (United States); Ramirez, S.L. [Department of Chemistry, University of Texas at El Paso, El Paso, TX 79968 (United States); Gardea-Torresdey, J.L. [Environmental Science and Engineering, University of Texas at El Paso, El Paso, TX 79968 (United States) and Department of Chemistry, University of Texas at El Paso, El Paso, TX 79968 (United States)]. E-mail: jgardea@utep.edu

    2005-04-15

    The temperature dependence of the Cr(VI) bioadsorption and its possible reduction to Cr(III) by Agave lechuguilla biomass were studied. The experimental data obtained in batch experiments at different temperatures were fitted to the Langmuir and Freundlich isotherms to obtain the characteristic parameters of each model. The adsorption equilibrium data fitted well with the Freundlich model. The average model parameters calculated from Freundlich's isotherms (adsorption capacity K{sub F} = 4 . 10{sup -2} mol . g{sup -1} and an average adsorption intensity value n = 13.07) showed that A. lechuguilla can be considered as an effective biomaterial for Cr(VI) removal from aqueous solution. Thermodynamic parameters ({delta}G{sup .}, {delta}H{sup .}, and {delta}S{sup .}) for Cr(VI) adsorption determined in the temperature range from (283 to 313) K suggest that a portion of Cr(VI) may be bound to functional groups on the surface of the adsorbent and then reduced to Cr(III). Additionally, the parameters of the Dubinin-Radushkevick equation indicated that the sorption of chromium species onto lechuguilla biomass mainly proceeds through binding surface functional groups.

  8. Adsorption behavior and mechanism of Cr(VI) using Sakura waste from aqueous solution

    Energy Technology Data Exchange (ETDEWEB)

    Qi, Wenfang [School of Environmental Science and Engineering, Tianjin University, Tianjin 300072 (China); Zhao, Yingxin, E-mail: yingxinzhao@tju.edu.cn [School of Environmental Science and Engineering, Tianjin University, Tianjin 300072 (China); Tianjin Engineering Center of Urban River Eco-Purification Technology, Tianjin 300072 (China); Zheng, Xinyi [School of Environmental Science and Engineering, Tianjin University, Tianjin 300072 (China); Ji, Min [School of Environmental Science and Engineering, Tianjin University, Tianjin 300072 (China); Tianjin Engineering Center of Urban River Eco-Purification Technology, Tianjin 300072 (China); Zhang, Zhenya [Graduate School of Life and Environmental Sciences, University of Tsukuba, Tsukuba 3058572 (Japan)

    2016-01-01

    Graphical abstract: The main chemical components of Sakura leaves are cellulose 16.6%, hemicellulose 10.4%, lignin 18.3%, ash 11.4%, and others 43.3%. The adsorption capacity of Cr(VI) onto Sakura leaves can achieve 435.25 mg g{sup −1}, much higher than other similar agroforestry wastes. - Highlights: • Sakura leaves were prepared to remove Cr(VI) from aqueous solution. • The maximum adsorption capacity of Cr(VI) reached 435.25 mg g{sup −1}. • Cr(VI) adsorption fitted pseudo-second-order kinetic model. • Isotherm models indicated Cr(VI) adsorption occurred on a monolayer surface. • The influence order of coexisting ions followed PO{sub 4}{sup 3−} > SO{sub 4}{sup 2−} > Cl{sup −}. - Abstract: A forestall waste, Sakura leave, has been studied for the adsorption of Cr(VI) from aqueous solution. The materials before and after adsorption were characterized by X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR). To investigate the adsorption performance of Sakura waste, batch experiments were conducted under different adsorbent dosage, contact time, initial concentration of Cr(VI), and co-existing ions. Results showed the data fitted pseudo-second-order better than pseudo-first-order kinetic model. Equilibrium data was analyzed with Langmuir, Freundlich and Redlich–Peterson isotherm models at temperature ranges from 25 °C to 45 °C. The maximum adsorption capacity from the Langmuir model was 435.25 mg g{sup −1} at pH 1.0. The presence of Cl{sup −}, SO{sub 4}{sup 2−} and PO{sub 4}{sup 3−} would lead to an obvious negative effect on Cr(VI) adsorption, and their influence order follows PO{sub 4}{sup 3−} > SO{sub 4}{sup 2−} > Cl{sup −}. The study developed a new way to reutilize wastes and showed a great potential for resource recycling.

  9. The applications of populus fiber in removal of Cr(VI) from aqueous solution

    Science.gov (United States)

    Li, Miaomiao; Gong, Yumei; Lyu, Aichao; Liu, Yuanfa; Zhang, Hong

    2016-10-01

    The surface modification of natural materials to be applied in removal of Cr(VI) from aqueous solutions has attracted much attention. A natural sorbent for Cr(VI) based on natural populus fibers (PF) is prepared by transforming the cyano groups (AN) in polyacrylonitriles (PAN) grafted from PF into amidoxime groups (AO), which has strong ability to attract and chelate heavy metal ions. The prepared sorbent is characterized by Fourier Transform Infrared Spectra (FT-IR), thermogravimetric analysis (TGA), solid-state nuclear magnetic resonance (13C NMR) and scanning electron microscope (SEM). As potassium dichromate solution (K2Cr2O7) is used as a target solution for detecting adsorption capacity of the sorbent, the adsorption kinetics of the sorbent for chromiun is consistent with the pseudo-second-order kinetic model by analyzing the adsorption amount as a function of the sorbent dispersed duration in solution at pH = 2. The expected adsorption mechanism is that the Cr(VI) in anionic ions Cr2O72- and HCrO4- are adsorbed through electrostatic attraction but when Cr(VI) is reduced to Cr(III) by AO, the electronegative nitrogen and oxygen in AO chelate it through coordination bond. The as-prepared PF derivant with high adsorption efficiency of chromium 180.5 mg/g (3.47 mmol/g), low cost, reusability and greenly preparation process suggests that the development of natural PF as a sorbent in removal of Cr(VI) from aqueous solutions is a destined significant approach.

  10. Oxidative Stress Markers and Histological Analysis in Diverse Organs from Rats Treated with a Hepatotoxic Dose of Cr(VI): Effect of Curcumin.

    Science.gov (United States)

    García-Niño, Wylly Ramsés; Zatarain-Barrón, Zyanya Lucía; Hernández-Pando, Rogelio; Vega-García, Claudia Cecilia; Tapia, Edilia; Pedraza-Chaverri, José

    2015-09-01

    Hexavalent chromium [Cr(VI)] compounds are extremely toxic and carcinogenic. Despite the vast quantity of reports about Cr(VI) toxicity, the information regarding its effects when it is intraperitoneally (i.p.) administered is still limited. In contrast, it has been shown that curcumin prevents hepatotoxicity induced by a single intraperitoneal injection of 15 mg/kg body weight (b.w.) of potassium dichromate (K2Cr2O7). This study aims to evaluate oxidative stress markers, the activity of antioxidant enzymes, and the potential histological injury in brain, heart, lung, kidney, spleen, pancreas, stomach, and intestine from rats treated with a hepatotoxic dose of K2Cr2O7 (15 mg/kg b.w.), and the effect of curcumin pretreatment. Rats were divided into four groups: control, curcumin, K2Cr2O7, and curcumin+K2Cr2O7. At the end of the treatment, plasma and ascites fluid were collected and target organs were dissected out for biochemical and histological analysis. K2Cr2O7 induced hepatotoxicity but failed to induce in all the other studied organs either oxidative or histological injury, since levels of malondialdehyde (MDA), glutathione (GSH), and the activity of superoxide dismutase (SOD), catalase (CAT), and related GSH enzymes were unchanged. As expected, curcumin was safe. Lack of K2Cr2O7-induced toxicity in those target organs could be due to the following: (1) route of administration, (2) absorption through the portal circulation, (3) lower dose than needed, (4) short time of exposure, or (5) repeated doses are required to produce damage. Thus, the intraperitoneal injection of 15 mg/kg of K2Cr2O7, that is able to induce hepatotoxicity, was unable to induce histological and oxidative damage in other target organs.

  11. The use of Sn(II) oxy-hydroxides for the effective removal of Cr(VI) from water: Optimization of synthesis parameters.

    Science.gov (United States)

    Kaprara, Efthimia; Tziarou, Nafsika; Kalaitzidou, Kyriaki; Simeonidis, Konstantinos; Balcells, Lluis; Pannunzio, Elisa V; Zouboulis, Anastasios; Mitrakas, Manassis

    2017-12-15

    The development of a novel adsorbent based on Sn(II) oxy-hydroxide nanoparticles and the optimization of main synthesis parameters was examined for the efficient removal of hexavalent chromium at low residual concentration levels. The aqueous hydrolysis of Sn(II) salts in a continuous-flow process was evaluated as an effective method to synthesize an appropriate material able to operate both as an electron donor for Cr(VI) reduction, and provide a suitable crystal structure that favors strong complexation with the formed Cr(III) species. Experimental results revealed that the main hydrolysis parameters, such as pH value and tin origin/source, can be used to determine the chemical formula of the produced materials and thereby, eventually improve their uptake capacity for Cr(VI). Among the tested sorbent materials, the synthetic nanostructured hydroromarchite, Sn6O4(OH)4, prepared by the hydrolysis of SnCl2 in a highly acidic environment (pH2), was deemed the best sorbent material and it was further investigated for its Cr(VI) uptake performance under reliable conditions (column experiments) for drinking water treatment. Specifically, Rapid Small-Scale (laboratory) Column Tests indicated that aggregates of the Sn6O4(OH)4 nanomaterial can achieve a maximum uptake capacity of around 19mg/g, keeping the levels of outflow Cr(VI) below 10μg/L during the treatment of natural-like water at pH7. The high efficiency is mainly attributed to the stabilization of Sn(II) content in nanoparticles, as well as the improved surface charge density, reaching 1.0mmol[OH(-)]/g, whereas the obtained thermodynamic data indicate a combined reduction-sorption process. The latter aspect was further verified by XPS, showing that even in the highly-loaded sorbent materials with adsorbed chromium, its trivalent form is the predominant one. These specific characteristics suggest that the product is a more favorable candidate for wider applications in water treatment units, regarding Cr(VI

  12. Biological detoxification of Cr(VI) using wood-husk immobilized Acinetobacter haemolyticus

    Energy Technology Data Exchange (ETDEWEB)

    Zakaria, Zainul Akmar; Zakaria, Zainoha [Department of Chemistry, Faculty of Science, Universiti Teknologi Malaysia, 81310 Skudai, Johor (Malaysia); Surif, Salmijah [Department of Environmental Sciences, Faculty of Science and Technology, Universiti Kebangsaan Malaysia, 43600 Bangi, Selangor (Malaysia); Ahmad, Wan Azlina [Department of Chemistry, Faculty of Science, Universiti Teknologi Malaysia, 81310 Skudai, Johor (Malaysia)], E-mail: azlina@kimia.fs.utm.my

    2007-09-05

    Acinetobacter haemolyticus, a Gram-negative aerobic locally isolated bacterium, immobilized on wood-husk showed the ability to detoxify Cr(VI) to Cr(III). Wood-husk, a natural cellulose-based support material, packed in an upward-flow column was used as support material for bacterial attachment. Around 97% of the Cr(VI) in wastewater containing 15 mg L{sup -1} of Cr(VI) was reduced at a flow rate of 8.0 mL min{sup -1}. The wastewater containing Cr(VI) was added with liquid pineapple wastewater as nutrient source for the bacteria. Electron microscopic examinations of the wood-husk after 42 days of column operation showed gradual colonization of the wood-husk by bacterial biofilm. The use of 0.1% (v/v) formaldehyde as a disinfecting agent inhibited growth of bacteria present in the final wastewater discharge. This finding is important in view of the ethical code regarding possible introduction of exogenous bacterial species into the environment.

  13. Removal of hexavalent chromium upon interaction with biochar under acidic conditions: mechanistic insights and application.

    Science.gov (United States)

    Choudhary, Bharat; Paul, Debajyoti; Singh, Abhas; Gupta, Tarun

    2017-07-01

    Chromium pollution of soil and water is a serious environmental concern due to potential carcinogenicity of hexavalent chromium [Cr(VI)] when ingested. Eucalyptus bark biochar (EBB), a carbonaceous black porous material obtained by pyrolysis of biomass at 500 °C under oxygen-free atmosphere, was used to investigate the removal of aqueous Cr(VI) upon interaction with the EBB, the dominant Cr(VI) removal mechanism(s), and the applicability to treat Cr(VI)-contaminated wastewater. Batch experiments showed complete removal of aqueous Cr(VI) at pH 1-2; sorption was negligible at pH 1, but ~55% of total Cr was sorbed onto the EBB surface at pH 2. Detailed investigations on unreacted and reacted EBB through Fourier transform infrared spectroscopy and X-ray photoelectron spectrometry (XPS) indicate that the carboxylic groups in biochar played a dominant role in Cr(VI) sorption, whereas the phenolic groups were responsible for Cr(VI) reduction. The predominance of sorption-reduction mechanism was confirmed by XPS studies that indicated ~82% as Cr(III) and ~18% as Cr(VI) sorbed on the EBB surface. Significantly, Cr(VI) reduction was also facilitated by dissolved organic matter (DOM) extracted from biochar. This reduction was enhanced by the presence of biochar. Overall, the removal of Cr(VI) in the presence of biochar was affected by sorption due to electrostatic attraction, sorption-reduction mediated by surface organic complexes, and aqueous reduction by DOM. Relative dominance of the aqueous reduction mechanism depended on a critical biochar dosage for a given electrolyte pH and initial Cr(VI) concentration. The low-cost EBB developed here successfully removed all Cr(VI) in chrome tanning acidic wastewater and Cr(VI)-contaminated groundwater after pH adjustment, highlighting its potential applicability in effective Cr(VI) remediation.

  14. Utility of Ochrobactrum anthropi YC152 in a Microbial Fuel Cell as an Early Warning Device for Hexavalent Chromium Determination

    OpenAIRE

    Guey-Horng Wang; Chiu-Yu Cheng; Man-Hai Liu; Tzu-Yu Chen; Min-Chi Hsieh; Ying-Chien Chung

    2016-01-01

    Fast hexavalent chromium (Cr(VI)) determination is important for environmental risk and health-related considerations. We used a microbial fuel cell-based biosensor inoculated with a facultatively anaerobic, Cr(VI)-reducing, and exoelectrogenic Ochrobactrum anthropi YC152 to determine the Cr(VI) concentration in water. The results indicated that O. anthropi YC152 exhibited high adaptability to pH, temperature, salinity, and water quality under anaerobic conditions. The stable performance of t...

  15. Microbial reduction of hexavalent Chromium under vadose zone conditions

    Energy Technology Data Exchange (ETDEWEB)

    Oliver, D S.(unknown); Brockman, Fred J.(BATTELLE (PACIFIC NW LAB)); Bowman, Robert (VISITORS); Kieft, Thomas L.(BATTELLE (PACIFIC NW LAB))

    2003-01-01

    Hexavalent chromium[Cr(VI)] is a common constituent of wastes associated with nuclear reactor operation and fuel processing. Improper disposal at facilities in arid and semi-arid regions has led to contamination of underlying vadose zones and aquifers. The objectives of this study were to assess the potential for immobilizing Cr(VI) contamination using a native microbial community to reduce soluble Cr(VI) to insoluble Cr(III) under conditions similar to those found in the vadose zone, and to evaluate the potential for enhancing biological reduction of Cr(VI) through the addition of nutrients. Batch microcosm and unsaturated flow column experiments were performed. Native microbial communities in subsurface sediments with no prior Cr(VI) exposure were shown to be capable of Cr(VI) reduction. In both the batch and column experiments, Cr(VI) reduction and loss from the aqueous phase were enhanced by adding high levels of both nitrate (NO3-) and organic carbon (molasses). Nutrient amendments resulted in up to 87% Cr(VI) reduction in unsaturated batch experiments. Molasses and nitrate additions to 15-cm length unsaturated flow columns receiving 65 mg L-1 Cr(VI) resulted in microbially mediated reduction and immobilization of 10% of the Cr during a 45-day experiment. All of the immobilized Cr was in the form of Cr (III), as shown by XANES analysis. This suggests that biostimulation of microbial Cr(VI) reduction in vadose zones by nutrient amendment is a promising strategy; and that immobilization of close to 100% of Cr contamination could be achieved in a thick vadose zone with longer flow paths and longer contact times than in this experiment.

  16. Improvement on Simultaneous Determination of Cr(III) and Cr(VI) by Capillary Electrophoresis and Chemiluminescence Detection

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    A sensitive method for the simultaneous determination of Cr(III) and Cr(VI) using in-capillary reaction capillary electrophoresis separation and chemiluminescence detection was developed. The procedures were designed as follows: The sample, hydrochloric acid and sodium hydrogen sulfite solution segments were injected sequentially into the capillary. The reaction of Cr(VI) reduced to Cr(III) by HSO3- occurred inside the capillary after applying the running voltage. According to the migration time difference of both Cr(III) ions moving towards to the cathode (detection end), they could be separated and determined. The limits of detection for chromium(III) and chromium(VI) (S/N = 3) were 6.0(10-13 mol/L (12 zmol) and 1.9(10-11 mol/L (380 zmol), respectively.

  17. Cr(VI) adsorption from electroplating plating wastewater by chemically modified coir pith.

    Science.gov (United States)

    Suksabye, Parinda; Thiravetyan, Paitip

    2012-07-15

    Coir pith samples were chemically modified by grafting with acrylic acid for the removal of Cr(VI) from electroplating wastewater. The presence of acrylic acid on the coir pith surface was verified by a scanning electron microscope with an electron dispersive x-ray spectrometer (SEM/EDX), Fourier transform infrared spectroscopy (FTIR) and thermogravimetry (TG). The carbonyl groups (C==O) from the carboxylic acids (COOH) increased on the coir pith surface after grafting with acrylic acid. In addition, the thermal stability of the acrylic acid-grafted coir pith also improved. The optimum conditions for grafting the acrylic acid on the coir pith consisted of 2 M acrylic acid and 0.00125 M ceric ammonium nitrate (CAN, as an initiator). The maximum Cr(VI) removal (99.99 ± 0.07%) was obtained with the following conditions: a 1.3% (w/v) dosage of acrylic acid-grafted coir pith, a system pH of 2, a contact time of 22 h, a temperature of 30 °C, a particle size of <150 μm and an initial Cr(VI) of 1,171 mg l(-1). At system pH of 2, Cr(VI) in the HCrO(4)(-) form can be adsorbed with acrylic acid-grafted coir pith via an electrostatic attraction. The adsorption isotherm of 2 M acrylic acid-grafted coir pith exhibited a good fit with the Langmuir isotherm. The maximum Cr(VI) adsorption capacity of the 2 M acrylic acid-grafted coir pith was 196.00 mg Cr(VI) g(-1) adsorbent, whereas for coir pith without grafting, the maximum Cr(VI) removal was 165.00 mg Cr(VI) g(-1) adsorbent. The adsorption capacity of the acrylic acid-grafted coir pith for Cr(VI) was higher compared to the original coir pith. This result was due to the enhancement of the carbonyl groups on the coir pith surface that may have involved the mechanism of chromium adsorption. The X-ray absorption near edged structure (XANES) and desorption studies suggested that most of the Cr(III) that presented on the acrylic acid-grafted coir pith was due to the Cr(VI) being reduced to Cr(III) on the adsorbent surface. FTIR

  18. Magnetic vinylphenyl boronic acid microparticles for Cr(VI) adsorption: Kinetic, isotherm and thermodynamic studies

    Energy Technology Data Exchange (ETDEWEB)

    Kara, Ali, E-mail: akara@uludag.edu.tr [Uludag University, Faculty of Arts and Science, Department of Chemistry, 16059 Bursa (Turkey); Demirbel, Emel [Uludag University, Faculty of Arts and Science, Department of Chemistry, 16059 Bursa (Turkey); Tekin, Nalan [Kocaeli University, Faculty of Arts and Science, Department of Chemistry, 41380 Kocaeli (Turkey); Osman, Bilgen; Beşirli, Necati [Uludag University, Faculty of Arts and Science, Department of Chemistry, 16059 Bursa (Turkey)

    2015-04-09

    Highlights: • Cr(VI) can oxidize biological molecules and be one of the most harmful substance. • Magnetic seperation techniques are used on different applications in many fields. • Magnetic systems can be used for rapid and selective removal as a magnetic processor. • We investigate properties of both new material and other magnetic adsorbents reported in the literatures on the adsorption of Cr(VI) ions. • No researchments were reported on adsorption of Cr(VI) with magnetic vinylphenyl boronic acid microparticles. - Abstract: Magnetic vinylphenyl boronic acid microparticles, poly(ethylene glycol dimethacrylate(EG)–vinylphenyl boronic acid(VPBA)) [m-poly(EG–VPBA)], produced by suspension polymerization and characterized, was found to be an efficient solid polymer for Cr(VI) adsorption. The m-poly(EG–VPBA) microparticles were prepared by copolymerizing of ethylene glycol dimethylacrylate (EG) with 4-vinyl phenyl boronic acid (VPBA). The m-poly(EG–VPBA) microparticles were characterized by N{sub 2} adsorption/desorption isotherms, electron spin resonance (ESR), X-ray diffraction (XRD), fourier transform infrared spectroscopy (FTIR), thermal gravimetric analysis (TGA), elemental analysis, scanning electron microscope (SEM) and swelling studies. The m-poly(EG–VPBA) microparticles were used at adsorbent/Cr(VI) ion ratios. The influence of pH, Cr(VI) initial concentration, temperature of the removal process was investigated. The maximum removal of Cr(VI) was observed at pH 2. Langmuir isotherm and Dubinin–Radushkvich isotherm were found to better fit the experiment data rather than Fruendlich isotherm. The kinetics of the adsorption process of Cr(VI) on the m-poly(EG–VPBA) microparticles were investigated using the pseudo first-order, pseudo-second-order, Ritch-second-order and intraparticle diffusion models, results showed that the pseudo-second order equation model provided the best correlation with the experimental results. The thermodynamic

  19. Chitosan/mangiferin particles for Cr(VI) reduction and removal.

    Science.gov (United States)

    Sampaio, Caroline de G; Frota, Lucas S; Magalhães, Herbert S; Dutra, Lilian M U; Queiroz, Danilo C; Araújo, Rinaldo S; Becker, Helena; de Souza, José R R; Ricardo, Nágila M P S; Trevisan, Maria T S

    2015-07-01

    In this work, chitosan/mangiferin particles (CMP) were prepared by spray-drying technique and characterized by SEM, DLS, FTIR, HPLC-UV and adsorption studies to investigate a possible application as a preventive material in cases of human and animal contamination with Cr(VI). CMP presented sizes ranging from nano to micrometers. Chitosan and mangiferin (MA) presence in the powder was confirmed by FTIR and MA quantification (136 μg/mg) was performed using a calibration curve prepared by HPLC-UV. Adsorption capacity of Cr(VI) onto CMP was compared with chitosan and investigated in a batch system by considering the effects of various parameters like contact time, initial concentration of adsorbent and pH. Cr(VI) removal is pH dependent and it was found to be maximum at pH 5.0. The results showed that CMP has a potential application as a preventive material in cases of human or animal contamination with Cr(VI).

  20. Adsorption of Cr(VI) from aqueous solutions by spent activated clay.

    Science.gov (United States)

    Weng, Chih-Huang; Sharma, Y C; Chu, Sue-Hua

    2008-06-30

    Adsorption of Cr(VI) onto spent activated clay (SAC), a waste produced from an edible oil refinery company, was investigated for its beneficial use in wastewater treatment. After pressure steam treatment, SAC was used as an adsorbent. The adsorption kinetic data were analyzed and fitted well in a pseudo-first-order equation and the rate of removal was found to speed up with decreasing pH and increasing temperature. Activation energy for the adsorption process was found to be 4.01-5.47 kcal/K mol. The Langmuir adsorption isotherm was used to fit the equilibrium data and the effect of pH, temperature and ionic strength were studied. The maximum adsorption capacities for Cr(VI) ranged from 0.743 to 1.422 mg/g for temperature between 4 and 40 degrees C under a condition of pH 2.0. The studies conducted show the process of Cr(VI) removal to be spontaneous at high temperature and endothermic in nature. From the waste utilization and environment point of view, the work carried out is important and useful. Results obtained can serve as baseline data for designing a treatment process using this low-cost adsorbent for the treatment of wastewater rich in Cr(VI).

  1. Aqueous solubility of Cr(VI) compounds in ferrochrome bag filter ...

    African Journals Online (AJOL)

    Aqueous solubility of Cr(VI) compounds in ferrochrome bag filter dust and the implications thereof. ... off-gas of the high-temperature processes, which are cleaned by means of venturi scrubbers or bag filter dust (BFD) systems. ... Article Metrics.

  2. Adsorption of Cr(VI) and Pb(II) from aqueous solution using agricultural solid waste.

    Science.gov (United States)

    Geetha, A; Sivakumar, P; Sujatha, M; Palanisamy, P N

    2009-04-01

    Areca nut shell, an agricultural solid waste by-product, has been studied for the removal of heavy metals Cr(VI) and Pb(II) from aqueous solution. Parameters, such as equilibrium time, effect of initial metal ion concentration, effect of pH on the removal, were analyzed. An initial pH of 4.0 was found most favourable for Cr(VI) removal and 5.0 for Pb(II) removal. Two theoretical isotherm models, namely Langmuir and Freundlich, were analyzed for the applicability of the experimental data. The Langmuir adsorption capacity (Q0) was calculated. The results of thermodynamic parameters suggest the exothermic nature of the adsorption. The desorption studies were carried out using dilute hydrochloric acid. Maximum desorption of 88% for Cr(VI) and 91% for Pb(II) were achieved. Areca nut shell waste, the low cost adsorbent is found to be effective in the removal of Cr(VI) and Pb(II) ions, and hence it can be applied for the removal of heavy metals from industrial wastewater.

  3. The surface characteristics of hyperbranched polyamide modified corncob and its adsorption property for Cr(VI)

    Science.gov (United States)

    Lin, Hai; Han, Shaoke; Dong, Yingbo; He, Yinhai

    2017-08-01

    A low-cost anion adsorbent for Cr(VI) effectively removing was synthesized by hyperbranched polyamide modified corncob (HPMC). Samples were characterized by Brunauer-Emmett-Teller (BET) surface area analysis, field-emission scanning electron microscopy (FE-SEM) with energy-dispersive X-ray spectroscopy, Fourier transform infrared (FTIR) and zeta potential analysis. Kinetics, isotherms and thermodynamics studies of HPMC for Cr(VI) adsorption were investigated in batch static experiments, in the temperature range of 25-45 °C, pH = 2.0. Results showed that the adsorption was rapid and stable, with the uptake capacity higher than 80% after 30 min. Adsorption behavior and rate-controlling mechanisms were analyzed using three kinetic models (pseudo-first order, pseudo-second order, intra-particle kinetic model). Kinetic studies showed that the adsorption of HPMC to Cr(VI) relied the pseudo-second-order model, and controlled both by the intra-particle diffusion and film diffusion. Equilibrium data was tested by Langmuir and Freundlich adsorption isotherm models. Langmuir model was more suitable to indicate a homogeneous distribution of active sites on HPMC and monolayer adsorption. The maximum adsorption capacity from the Langmuir model, qmax, was 131.6 mg/g at pH 2.0 and 45 °C for HPMC. Thermodynamic parameters revealed spontaneous and endothermic nature of the Cr(VI) adsorption onto HPMC.

  4. Preparation of activated carbon from corn cob and its adsorption behavior on Cr(VI) removal.

    Science.gov (United States)

    Tang, Shuxiong; Chen, Yao; Xie, Ruzhen; Jiang, Wenju; Jiang, Yanxin

    2016-01-01

    Operation experiments were conducted to optimize the preparation of activated carbons from corn cob. The Cr(VI) adsorption capacity of the produced activated carbons was also evaluated. The impact of the adsorbent dosage, contact time, initial solution pH and temperature was studied. The results showed that the produced corn cob activated carbon had a good Cr(VI) adsorptive capacity; the theoretical maximum adsorption was 34.48 mg g(-1) at 298 K. The Brunauer-Emmett-Teller and iodine adsorption value of the produced activated carbon could be 924.9 m(2) g(-1) and 1,188 mg g(-1), respectively. Under the initial Cr(VI) concentration of 10 mg L(-1) and the original solution pH of 5.8, an adsorption equilibrium was reached after 4 h, and Cr(VI) removal rate was from 78.9 to 100% with an adsorbent's dosage increased from 0.5 to 0.7 g L(-1). The kinetics and equilibrium data agreed well with the pseudo-second-order kinetics model and the Langmuir isotherm model. The equilibrium adsorption capacity improved with the increment of the temperature.

  5. Biosorption of Cr(VI from Aqueous Solutions Using Trametes Versicolor Polyporus Fungi

    Directory of Open Access Journals (Sweden)

    M. Venkata Subbaiah

    2008-01-01

    Full Text Available Removal of chromium(VI from aqueous solution was studied using abundantly available trametes versicolor polyporus fungi as biosorbing medium under equilibrium and column flow conditions. Various sorption parameters such as contact time, effect of pH, concentration of Cr(VI and amount of biomass on the adsorption capacity of the biosorbent were studied. The equilibrium adsorption data were fitted to Freundlich and Langmuir adsorption isotherm models and the model parameters are evaluated. In addition, the data were used to predict the kinetics of adsorption. The results indicated that the adsorption of Cr(VI on fungi followed second order kinetics. The column flow adsorption data were used to predict break through curves. The fungi loaded with Cr(VI was regenerated with 0.1 M NaOH solution and the regenerated biomass was used in the subsequent adsorptiondesorption cycles. The experimental results demonstrated that the trametes versicolor polyporus fungi could be used as sorbent for immobilizing Cr(VI.

  6. Cr(VI) generation during sample preparation of solid samples – A ...

    African Journals Online (AJOL)

    2009-05-15

    May 15, 2009 ... ing of hazardous water-soluble materials such as Cr(VI) into the groundwater. .... with a Pharmacia Biotech Ultrospec 3 000 uv/visible spectro- photometer. Analysis was ..... and digital size analyses of Kemi chromite, Finland. Miner. Eng. 16 ... lization of Soluble Wastes Generated in the South African Ferro-.

  7. Exposure to particulate hexavalent chromium exacerbates allergic asthma pathology

    Energy Technology Data Exchange (ETDEWEB)

    Schneider, Brent C. [Department of Microbiology, Immunology and Tropical Medicine, The George Washington University, Washington, DC 20037 (United States); Department of Pharmacology and Physiology, The George Washington University, Washington, DC 20037 (United States); Constant, Stephanie L. [Department of Microbiology, Immunology and Tropical Medicine, The George Washington University, Washington, DC 20037 (United States); Patierno, Steven R. [Department of Pharmacology and Physiology, The George Washington University, Washington, DC 20037 (United States); GW Cancer Institute, The George Washington University, Washington, DC 20037 (United States); Jurjus, Rosalyn A. [Department of Anatomy and Regenerative Biology, The George Washington University, Washington, DC 20037 (United States); Ceryak, Susan M., E-mail: phmsmc@gwumc.edu [Department of Pharmacology and Physiology, The George Washington University, Washington, DC 20037 (United States)

    2012-02-15

    Airborne hexavalent chromate, Cr(VI), has been identified by the Environmental Protection Agency as a possible health threat in urban areas, due to the carcinogenic potential of some of its forms. Particulate chromates are produced in many different industrial settings, with high levels of aerosolized forms historically documented. Along with an increased risk of lung cancer, a high incidence of allergic asthma has been reported in workers exposed to certain inhaled particulate Cr(VI) compounds. However, a direct causal association between Cr(VI) and allergic asthma has not been established. We recently showed that inhaled particulate Cr(VI) induces an innate neutrophilic inflammatory response in BALB/c mice. In the current studies we investigated how the inflammation induced by inhaled particulate Cr(VI) might alter the pathology of an allergic asthmatic response. We used a well-established mouse model of allergic asthma. Groups of ovalbumin protein (OVA)-primed mice were challenged either with OVA alone, or with a combination of OVA and particulate zinc chromate, and various parameters associated with asthmatic responses were measured. Co-exposure to particulate Cr(VI) and OVA mediated a mixed form of asthma in which both eosinophils and neutrophils are present in airways, tissue pathology is markedly exacerbated, and airway hyperresponsiveness is significantly increased. Taken together these findings suggest that inhalation of particulate forms of Cr(VI) may augment the severity of ongoing allergic asthma, as well as alter its phenotype. Such findings may have implications for asthmatics in settings in which airborne particulate Cr(VI) compounds are present at high levels. -- Highlights: ► Allergic asthma correlated with exposure to certain inhaled particulate chromates. ► Direct causal association between Cr(VI) and allergic asthma not established. ► Cr exacerbated pathology and airway hyperresponsiveness in an OVA-challenged mouse. ► Particulate Cr(VI

  8. Simultaneous determinations of Cr(VI) and Cr(III) by ion-exclusion/cation-exchange chromatography with an unmodified silica-gel column.

    Science.gov (United States)

    Hirata, Shizuko; Kozaki, Daisuke; Sakanishi, Kinya; Nakagoshi, Nobukazu; Tanaka, Kazuhiko

    2010-01-01

    In order to characterize the ion-exclusion and cation-exchange properties of an unmodified silica-gel column, the retention behaviors of Cr(VI) and Cr(III) ions were investigated using a Develosil 30-5 (150 x 4.6 mm i.d.) in the acidic region. Cr(VI) was separated from other anions by an ion-exclusion and ion-adsorption mechanism, and Cr(III) was separated from other cations with a cation-exchange mechanism. When using 2.0 mM oxalic acid (pH 2.6) as an eluent, a good separation of Cr(VI) and Cr(III) was obtained using conductimetric detection in 12 min. The method was successfully applied to the simultaneous determinations of Cr(VI) and Cr(III) added into tap-water and river-water samples.

  9. Biosorption Potential of Bacillus salmalaya Strain 139SI for Removal of Cr(VI from Aqueous Solution

    Directory of Open Access Journals (Sweden)

    Arezoo Dadrasnia

    2015-12-01

    Full Text Available The present study investigated the biosorption capacity of live and dead cells of a novel Bacillus strain for chromium. The optimum biosorption condition was evaluated in various analytical parameters, including initial concentration of chromium, pH, and contact time. The Langmuir isotherm model showed an enhanced fit to the equilibrium data. Live and dead biomasses followed the monolayer biosorption of the active surface sites. The maximum biosorption capacity was 20.35 mg/g at 25 °C, with pH 3 and contact time of 50 min. Strain 139SI was an excellent host to the hexavalent chromium. The biosorption kinetics of chromium in the dead and live cells of Bacillus salmalaya (B. salmalaya 139SI followed the pseudo second-order mechanism. Scanning electron microscopy and fourier transform infrared indicated significant influence of the dead cells on the biosorption of chromium based on cell morphological changes. Approximately 92% and 70% desorption efficiencies were achieved using dead and live cells, respectively. These findings demonstrated the high sorption capacity of dead biomasses of B. salmalaya 139SI in the biosorption process. Thermodynamic evaluation (ΔG0, ΔH0, and ΔS0 indicated that the mechanism of Cr(VI adsorption is endothermic; that is, chemisorption. Results indicated that chromium accumulation occurred in the cell wall of B. salmalaya 139SI rather than intracellular accumulation.

  10. An assessment of the environmental toxicity of hexavalent chromium in fish

    NARCIS (Netherlands)

    Putte, van der I.

    1981-01-01

    At present chromium is a common contaminant in surface waters in many countries. In water the metal may be present in the trivalent form (CrIII) or in the hexavalent form (CrVI), the latter of which is more toxic to aquatic organisms.The investigations presented in this thesis were aimed at a thorou

  11. An assessment of the environmental toxicity of hexavalent chromium in fish

    NARCIS (Netherlands)

    Putte, van der I.

    1981-01-01

    At present chromium is a common contaminant in surface waters in many countries. In water the metal may be present in the trivalent form (CrIII) or in the hexavalent form (CrVI), the latter of which is more toxic to aquatic organisms.
    The investigations presented in this thesis

  12. Photoreduction of Cr(VI Ions in Aqueous Solutions by UV/TiO2 Photocatalytic Processes

    Directory of Open Access Journals (Sweden)

    Chih Ming Ma

    2012-01-01

    Full Text Available This study discussed the photoreduction of Cr(VI ions in aqueous solutions by UV/TiO2 photocatalytic processes under various operational factors. Experimental results showed that the removal rate of Cr(VI increased with decreasing solution pH values and with increasing dosages of organic compounds, indicating that the recombination rate of electrons and h+ can be retarded in the reaction systems by the addition of the scavenger, thus raising the reaction rate of Cr(VI. The relationship of the chemical reaction rate of Cr(VI, TiO2 dosage, and changes of Cr(VI concentration was expressed by the pseudo-first-order kinetic equation. Comparing the experimental results of two different doping metals in modified TiO2 photoreduction systems, the removal rate of Cr(VI by the Ag/TiO2 process is larger, possibly because the electron transferring ability of Ag is superior to that of Cu. However, the photoreduction rates of Cr(VI by modified UV/TiO2 processes are worse than those by a nonmodified commercial UV/TiO2 process.

  13. Application of Scallop shell-Fe3O4 nanoparticles for the removal of Cr(VI) from aqueous solutions.

    Science.gov (United States)

    Mohagheghian, Azita; Vahidi-Kolur, Robabeh; Pourmohseni, Melina; Yang, Jae-Kyu; Shirzad-Siboni, Mehdi

    2017-05-01

    In this study, removal of Cr(VI) by Scallop shell-Fe3O4 nanoparticles was investigated with variation of pH, adsorbent dosage, initial Cr(VI) concentration, ionic strength and temperature. Coating of Fe3O4 nanoparticles onto Scallop shell was identified by Fourier transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy and energy dispersive X-ray analysis. The maximum adsorption was observed at pH 3. Removal efficiency of Cr(VI) was increased with increasing adsorbent dosage, but was decreased with increasing initial Cr(VI) concentration and temperature. Removal efficiency of Cr(VI) was decreased in the presence of sulfate and carbonate ions. Adsorption kinetic study revealed that a pseudo-second order model better described the removal data than a pseudo-first order model and an intra-particle diffusion model. Maximum adsorption capacity was estimated to be 34.48 mg/g. Thermodynamic studies indicated that adsorption of Cr(VI) onto Scallop shell-Fe3O4 nanoparticles occurred via an exothermic (ΔH = -320.88 KJ mol(-1)) process. Adsorption efficiency of Cr(VI) by Scallop shell-Fe3O4 nanoparticles was maintained even after eight successive cycles.

  14. Engineering biogenic magnetite for sustained Cr(VI) remediation in flow-through systems.

    Science.gov (United States)

    Crean, Daniel E; Coker, Victoria S; van der Laan, Gerrit; Lloyd, Jonathan R

    2012-03-20

    In this work, we report a route to enhance the reactivity and longevity of biogenic magnetite in Cr(VI) remediation under continuous-flow conditions by combining functionalization of the biomagnetite surface with a precious metal catalyst, nanoscale palladium, and exposure to formate. Column influent conditions were varied to simulate oxic, anoxic, and nitrate cocontaminated environments. The addition of sodium formate as an electron donor for Pd-functionalized magnetite increased capacity and longevity allowing 80% removal of Cr(VI) after 300 h in anoxic conditions, whereas complete breakthrough occurred after 60 h in anoxic nonformate and nonfunctionalized systems. Removal of Cr(VI) was optimized under anoxic conditions, and the presence of oxidizing agents results in a modest loss in reductive capacity. Examination of reacted Pd-functionalized magnetite reveals close association of Fe with Cr, suggesting that Pd-coupled oxidation of formate serves to regenerate the reactive surface. XMCD studies revealed that Cr(III) is partially substituted for Fe in the magnetite structure, which serves to immobilize Cr. No evidence for a mechanistic interference by nitrate cocontamination was observed, suggesting that this novel system could provide robust, effective and sustained reduction of contaminants, even in the presence of common oxidizing cocontaminants, outperforming the reductive capacity of nonfunctionalized biogenic magnetite.

  15. Flow-through Column Experiments and Modeling of Microbially Mediated Cr(VI) Reduction at Hanford 100H

    Science.gov (United States)

    Yang, L.; Molins, S.; Beller, H. R.; Brodie, E. L.; Steefel, C.; Nico, P. S.; Han, R.

    2010-12-01

    Microbially mediated Cr(VI) reduction at the Hanford 100H area was investigated by flow-through column experiments. Three separate experiments were conducted to promote microbial activities associated with denitrification, iron and sulfate reduction, respectively. Replicate columns packed with natural sediments from the site under anaerobic environment were injected with 5mM Lactate as the electron donor and 5 μM Cr(VI) in all experiments. Sulfate and nitrate solutions were added to act as the main electron acceptors in the respective experiments, while iron columns relied on the indigenous sediment iron (and manganese) oxides as electron acceptors. Column effluent solutions were analyzed by IC and ICP-MS to monitor the microbial consumption/conversion of lactate and the associated Cr(VI) reduction. Biogeochemical reactive transport modeling was performed to gain further insights into the reaction mechanisms and Cr(VI) bioreduction rates. All experimental columns showed a reduction of the injected Cr(VI). Columns under denitrifying conditions showed the least Cr(VI) reduction at early stages (cell growth, and the smallest change in Cr(VI) concentrations during the course of the experiment. In contrast, columns under sulfate-reducing/fermentative conditions exhibited the greatest Cr(VI) reduction capacity. Two sulfate columns evolved to complete lactate fermentation with acetate and propionate produced in the column effluent after 40 days of experiments. These fermenting columns showed a complete removal of injected Cr(VI), visible precipitation of sulfide minerals, and a significant increase in effluent Fe and Mn concentrations. Reactive transport simulations suggested that direct reduction of Cr(VI) by Fe(II) and Mn(II) released from the sediment could account for the observed Cr(VI) removal. The biogeochemical modeling was employed to test two hypotheses that could explain the release of Fe(II) and Mn(II) from the column sediments: 1) acetate produced by lactate

  16. Room temperature ionic liquids enhanced the speciation of Cr(VI) and Cr(III) by hollow fiber liquid phase microextraction combined with flame atomic absorption spectrometry

    Energy Technology Data Exchange (ETDEWEB)

    Zeng, Chujie, E-mail: cjzeng@126.com [Department of Chemistry and Material, Yulin Normal College, Yulin, Guangxi 537000 (China); Lin, Yao; Zhou, Neng; Zheng, Jiaoting; Zhang, Wei [Department of Chemistry and Material, Yulin Normal College, Yulin, Guangxi 537000 (China)

    2012-10-30

    Highlights: Black-Right-Pointing-Pointer First reported enhancement effect of RTILs in HF-LPME for the speciation of chromium. Black-Right-Pointing-Pointer The addition of RTILs led to 3.5 times improvement of the sensitivity of Cr(VI). Black-Right-Pointing-Pointer The proposed method is a simplicity, sensitivity, low cost, green method. - Abstract: A new method for the speciation of Cr(VI) and Cr(III) based on enhancement effect of room temperature ionic liquids (RTILs) for hollow fiber liquid phase microextraction (HF-LPME) combined with flame atomic absorption spectrometry (FAAS) was developed. Room temperature ionic liquids (RTILs) and diethyldithiocarbamate (DDTC) were used enhancement reagents and chelating reagent, respectively. The addition of room temperature ionic liquids led to 3.5 times improvement in the determination of Cr(VI). In this method, Cr(VI) reacts with DDTC yielding a hydrophobic complex, which is subsequently extracted into the lumen of hollow fiber, whereas Cr(III) is remained in aqueous solutions. The extraction organic phase was injected into FAAS for the determination of Cr(VI). Total Cr concentration was determined after oxidizing Cr(III) to Cr(VI) in the presence of KMnO{sub 4} and using the extraction procedure mentioned above. Cr(III) was calculated by subtracting of Cr(VI) from the total Cr. Under optimized conditions, a detection limit of 0.7 ng mL{sup -1} and an enrichment factor of 175 were achieved. The relative standard deviation (RSD) was 4.9% for Cr(VI) (40 ng mL{sup -1}, n = 5). The proposed method was successfully applied to the speciation of chromium in natural water samples with satisfactory results.

  17. Enhanced removal of toxic Cr(VI) in tannery wastewater by photoelectrocatalysis with synthetic TiO2 hollow spheres

    Science.gov (United States)

    Zhao, Yang; Chang, Wenkai; Huang, Zhiding; Feng, Xugen; Ma, Lin; Qi, Xiaoxia; Li, Zenghe

    2017-05-01

    Owing to the acute toxicity and mobility, the Cr(VI) in tannery wastewater is a huge threat to biological and environmental systems. Herein, an effective photoelectrocatalytic reduction of Cr(VI) was carried out by applying electric field to photocatalysis of as-prepared TiO2 spheres. The synthesis of spherical TiO2 catalytic materials with hollow structure and high surface areas was based on a self-assembly process induced by a mixture of organic acetic acid and ethanol. The possible formation mechanism of TiO2 spheres was proposed and verified by acid concentration-dependent and temperature-dependent experiments. It was found that the reaction rate constant of photoelectrocatalytic reduction of Cr(VI) exhibited an almost 3 fold improvement (0.0362 min-1) as compared to that of photocatalysis (0.0126 min-1). As a result, the mechanism of photoelectrocatalytic reduction of Cr(VI) was described according to the simultaneous determination of Cr(VI), Cr(III) and total Cr in the system. In addition, the effect of pH value and voltage of potential were also discussed. Moreover, this photoelectrocatalysis with TiO2 hollow spheres exhibited excellent activity for reduction of Cr(VI) in actual tannery wastewater produced from three different tanning procedures. These attributes suggest that this photoelectrocatalysis has strong potential applications in the treatment of tannery pollutants.

  18. USE OF MICRO X-RAY ABSORPTION SPECTROSCOPY AND DIFFRACTION TO DELINEATE Cr(VI) SPECIATION IN COPR

    Energy Technology Data Exchange (ETDEWEB)

    CHRYSOCHOOU, M.; MOON, D. H.; FAKRA, S.; MARCUS, M.; DERMATAS, D.; CHRISTODOULATOS, C.

    2010-06-22

    The speciation of Cr(VI) in Cromite Ore Processing Residue was investigated by means of bulk XRD, and a combination of micro-XRF, -XAS and -XRD at the Advanced Light Source (ALS), Berkeley, CA, U.S.A.. Bulk XRD yielded one group of phases that contained explicitly Cr(VI) in their structure, Calcium Aluminum Chromium Oxide Hydrates, accounting for 60% of the total Cr(VI). Micro-analyses at ALS yielded complimentary information, confirming that hydrogarnets and hydrotalcites, two mineral groups that can host Cr(VI) in their structure by substitution, were indeed Cr(VI) sinks. Chromatite (CaCrO4) was also identified by micro-XRD, which was not possible with bulk methods due to its low content. The acquisition of micro-XRF elemental maps enabled not only the identification of Cr(VI)-binding phases, but also the understanding of their location within the matrix. This information is invaluable when designing Cr(VI) treatment, to optimize release and availability for reduction.

  19. Recovery of hexavalent chromium from water using photoactive TiO2-montmorillonite under sunlight

    Directory of Open Access Journals (Sweden)

    Ridha Djellabi

    2016-04-01

    Full Text Available Hexavalent chromium was removed from water under sunlight using a synthesized TiO2-montmorillonite (TiO2-M employing tartaric acid as a hole scavenger. Cr(VI species was then reduced to Cr(III species by electrons arising from TiO2 particles. After that, the produced Cr(III species  was transferred to montmorillonite  due to electrostatic attractions leading to  set free TiO2 particles for a further Cr(VI species reduction. Furthermore, produced Cr(III, after Cr(VI reduction, does not  penetrate into the solution. The results indicate that no dark adsorption of Cr(VI species on TiO2-M is present, however, the reduction of Cr(VI species under sunlight increased strongly as a function of tartaric acid concentration up to 60 ppm, for which the extent of reduction is maximum within 3 h. On the other hand, the reduction extent of Cr(VI species is maximum with an initial concentration of Cr(VI species lower than 30 ppm by the use of 0.2 g/L of TiO2-M. Nevertheless, the increase of the Cr(VI initial concentration led to increase the amount of Cr(VI species reduced (capacity of reduction until a Cr(VI concentration of 75 and 100 ppm, for which  it remained constant at around 221 mg/g. For comparison, the increase of Cr(VI species concentration in the case of the commercial TiO2 P25 under the same conditions exhibited its deactivation when the reduced amount decreased from 198.1 to 157.6 mg/g as the concentration increased from 75 to 100 ppm.

  20. Adsorption and reduction: combined effect of polyaniline emeraldine salt for removal of Cr(VI) from aqueous medium

    Indian Academy of Sciences (India)

    PURNIMA BARUAH; DEBAJYOTI MAHANTA

    2016-06-01

    In this study, we have reported the removal of Cr(VI) ions by polyaniline (PANI) particles from aqueous medium. PANI in its emeraldine salt (ES) form can interact with Cr(VI), which is present as HCrO$^{−}_4$ in two ways. The adsorption of HCrO$^{−}_4$ ions due to the electrostatic interaction between partially positively charged PANI backbone and Cr(VI) anions causes the major portion of Cr(VI) removal and a small portion of Cr(VI) is reduced to Cr(III) by PANI (ES). The adsorption follows Langmuir adsorption isotherm and second-order kinetic model. It is observed that the removal of Cr(VI) is negligibly effected by the presence of other anions in the aqueous medium. The adsorption capacity of PANI (ES) is found to be 123 mg g$^{−1}$, which is very high compared to activated carbonbased materials. The adsorbed anions can be desorbed by converting PANI emeraldine salt (ES) to PANI emeraldinebase (EB). The EB form of PANI can be converted into ES form by treating with acid, which can be reused as adsorbent. It is important to note that the PANI (ES) is oxidized by HCrO$^{−}_4$ ions which decrease the hydrophilicity of thesurface of PANI particles. This causes the decrease in adsorption capacity of recycled PANI.

  1. The oxidative degradation of polystyrene resins on the removal of Cr(VI) from wastewater by anion exchange.

    Science.gov (United States)

    Xiao, Ke; Xu, Fuyuan; Jiang, Linhua; Dan, Zhigang; Duan, Ning

    2016-08-01

    Cr(VI) is a powerful oxidant and is capable of oxidizing most of the organic materials. Therefore, it is possible for Cr(VI) to oxidize the polymeric resins and change the sorption properties of the resins on the removal of Cr(VI) from wastewater by anion exchange. In this study, three polystyrene resins (D201, D202, and D301) with different functional groups (-N(+)(CH3)3, -N(+)(CH3)2(C2H4OH), and N(CH3)2) were assessed on oxidation stability for Cr(VI) removal from wastewater in fixed-bed column experiments. After a 10-cycle operation, due to the oxidation of the resin, the sorption capacity of D201, D202, and D301 resins decreased by 23.5, 29.3, and 17.3%, when approximately 20-34%, 31-50%, and 18-30% of Cr(VI) was reduced to Cr(III) during each cycle respectively. The results of the Fourier transform infrared spectroscopy (FT-IR) showed that both the cleavage of CN and the formation of CO bonds occurred on the polystyrene resins during the Cr(VI) removal process. The resin simulation experiments further validated the oxidation of CC and CN bonds connected with phenethyl groups. Based upon the results from column operations and the resin simulated experiments, the oxidation mechanism of the polystyrene resin was proposed.

  2. Natural and induced reduction of hexavalent chromium in soil

    Science.gov (United States)

    Leita, Liviana; Margon, Alja; Sinicco, Tania; Mondini, Claudio; Valentini, Massimiliano; Cantone, Pierpaolo

    2013-04-01

    Even though naturally elevated levels of chromium can be found naturally in some soils, distressing amounts of the hexavalent form (CrVI) are largely restricted to sites contaminated by anthropogenic activities. In fact, the widespread use of chromium in various industries and the frequently associated inadequate disposal of its by-products and wastes have created serious environmental pollution problems in many parts of the world. CrVI is toxic to plants, animals and humans and exhibits also mutagenic effects. However, being a strong oxidant, CrVI can be readily reduced to the much less harmful trivalent form (CrIII) when suitable electron donors are present in the environment. CrIII is relatively insoluble, less available for biological uptake, and thus definitely less toxic for web-biota. Various electron donors in soil can be involved in CrVI reduction in soil. The efficiency of CrVI reducing abiotic agents such as ferrous iron and sulphur compounds is well documented. Furthermore, CrVI reduction is also known to be significantly enhanced by a wide variety of cell-produced monosaccharides, including glucose. In this study we evaluated the dynamics of hexavalent chromium (CrVI) reduction in contaminated soil amended or not with iron sulphate or/and glucose and assessed the effects of CrVI on native or glucose-induced soil microbial biomass size and activity. CrVI negatively affected both soil microbial activity and the size of the microbial biomass. During the incubation period, the concentration of CrVI in soil decreased over time whether iron sulphate or/and glucose was added or not, but with different reduction rates. Soil therefore displayed a natural attenuation capacity towards chromate reduction. Addition of iron sulphate or/and glucose, however, increased the reduction rate by both abiotic and biotic mechanisms. Our data suggest that glucose is likely to have exerted an indirect role in the increased rate of CrVI reduction by promoting growth of

  3. A novel method for amino starch preparation and its adsorption for Cu(II) and Cr(VI)

    Energy Technology Data Exchange (ETDEWEB)

    Dong Aiqin, E-mail: aegean.dong@gmail.com [Department of Chemistry, College of Science, Jiangxi Agricultural University, Zhimin Road, Nanchang 330045 (China); Xie Jie [Institute of Soil and Fertilizer and Environmental and Resources studies, Jiangxi Academy of Agricultural Sciences, Nanchang 330200 (China); Wang Wenmin; Yu Liping; Liu Qian [Department of Chemistry, College of Science, Jiangxi Agricultural University, Zhimin Road, Nanchang 330045 (China); Yin Yeping [Department of Chemistry, College of Science, Huazhong Agricultural University, Wuhan 430070 (China)

    2010-09-15

    A novel method was proposed to prepare amino starch by reacting ethylenediamine with previously synthesized dialdehyde starch. Different factors affecting the preparation, i.e., ethylenediamine concentration, ethylenediamine:dialdehyde starch molar ratio, pH, duration and temperature have been studied. The modified starch was characterized by IR spectroscopy, elemental analysis, X-ray diffraction and differential scanning calorimetry. The amino starch derivatives were evaluated as adsorbents. The adsorption activity for heavy metals such as Cu(II) and Cr(VI) by crosslinked amino starch was studied in terms of adsorption amount, kinetics and isotherm; and adsorbent reuse were also studied. Adsorption processes for Cu(II) and Cr(VI) on crosslinked amino starch fit a Langmuir isotherm, and adsorption for Cu(II) and Cr(VI) from aqueous solution was endothermic reactions. Crosslinked amino starch was very effective for the adsorption of Cu(II) and Cr(VI), and efficient in capacity, recycled.

  4. Magnetic vinylphenyl boronic acid microparticles for Cr(VI) adsorption: kinetic, isotherm and thermodynamic studies.

    Science.gov (United States)

    Kara, Ali; Demirbel, Emel; Tekin, Nalan; Osman, Bilgen; Beşirli, Necati

    2015-04-09

    Magnetic vinylphenyl boronic acid microparticles, poly(ethylene glycol dimethacrylate(EG)-vinylphenyl boronic acid(VPBA)) [m-poly(EG-VPBA)], produced by suspension polymerization and characterized, was found to be an efficient solid polymer for Cr(VI) adsorption. The m-poly(EG-VPBA) microparticles were prepared by copolymerizing of ethylene glycol dimethylacrylate (EG) with 4-vinyl phenyl boronic acid (VPBA). The m-poly(EG-VPBA) microparticles were characterized by N2 adsorption/desorption isotherms, electron spin resonance (ESR), X-ray diffraction (XRD), fourier transform infrared spectroscopy (FTIR), thermal gravimetric analysis (TGA), elemental analysis, scanning electron microscope (SEM) and swelling studies. The m-poly(EG-VPBA) microparticles were used at adsorbent/Cr(VI) ion ratios. The influence of pH, Cr(VI) initial concentration, temperature of the removal process was investigated. The maximum removal of Cr(VI) was observed at pH 2. Langmuir isotherm and Dubinin-Radushkvich isotherm were found to better fit the experiment data rather than Fruendlich isotherm. The kinetics of the adsorption process of Cr(VI) on the m-poly(EG-VPBA) microparticles were investigated using the pseudo first-order, pseudo-second-order, Ritch-second-order and intraparticle diffusion models, results showed that the pseudo-second order equation model provided the best correlation with the experimental results. The thermodynamic parameters (free energy change, ΔG(0) enthalpy change, ΔH(0); and entropy change, ΔS(0)) for the adsorption have been evaluated.

  5. Dispersion-free solvent extraction of Cr(VI) from acidic solutions using hollow fiber contactor.

    Science.gov (United States)

    Alguacil, Francisco J; Alonso, Manuel; Lopez, Félix A; Lopez-Delgado, Aurora; Padilla, Isabel

    2009-10-15

    The use of dispersión-free solvent extraction, through microporous hydrophobic membrane has been investigated. The hollow fiber contactor, with surface area of 1.4 m2 was used to extract Cr(VI) (0.005-0.12 g/L from aqueous sulphuric acidic media (pH 2.5-4.2 +/- 0.05). Several parameters such as extractant concentration, feed acidity and metal concentration in the initial aqueous solution were investigated. Results revealed that 15% v/v Cyanex 923 in Exxsol D-100 as organic phase and feed in the 2.5 pH range, gave optimum extraction (exceeding 95%) of Cr(VI) and it was possible to strip using 10 g/L hydrazine sulfate (also with recoveries exceeding 95%). In this step, Cr(VI) is immediately reduced to the less hazardous Cr(III) state. Results also showed that under the various experimental conditions, chromium(VI) extraction was rate-controlled by the interfacial reaction on the membrane surface. Typical overall mass transfer coefficients values are 4.2 x 10(-5) and 3.6 x 10(-6) cm/s for extraction and stripping operations, respectively.

  6. Removal of chromium from Cr(VI) polluted wastewaters by reduction with scrap iron and subsequent precipitation of resulted cations.

    Science.gov (United States)

    Gheju, M; Balcu, I

    2011-11-30

    This work presents investigations on the total removal of chromium from Cr(VI) aqueous solutions by reduction with scrap iron and subsequent precipitation of the resulted cations with NaOH. The process was detrimentally affected by a compactly passivation film occurred at scrap iron surface, mainly composed of Cr(III) and Fe(III). Maximum removal efficiency of the Cr(total) and Fe(total) achieved in the clarifier under circumneutral and alkaline (pH 9.1) conditions was 98.5% and 100%, respectively. The optimum precipitation pH range which resulted from this study is 7.6-8.0. Fe(total) and Cr(total) were almost entirely removed in the clarifier as Fe(III) and Cr(III) species; however, after Cr(VI) breakthrough in column effluent, chromium was partially removed in the clarifier also as Cr(VI), by coprecipitation with cationic species. As long the column effluent was free of Cr(VI), the average Cr(total) removal efficiency of the packed column and clarifier was 10.8% and 78.8%, respectively. Our results clearly indicated that Cr(VI) contaminated wastewater can be successfully treated by combining reduction with scrap iron and chemical precipitation with NaOH.

  7. Optimizing Cr(VI) and Tc(VII) remediation through nano-scale biomineral engineering

    Energy Technology Data Exchange (ETDEWEB)

    Cutting, R. S.; Coker, V. S.; Telling, N. D.; Kimber, R. L.; Pearce, C. I.; Ellis, B.; Lawson, R; van der Laan, G.; Pattrick, R.A.D.; Vaughan, D.J.; Arenholz, E.; Lloyd, J. R.

    2009-09-09

    To optimize the production of biomagnetite for the bioremediation of metal oxyanion contaminated waters, the reduction of aqueous Cr(VI) to Cr(III) by two biogenic magnetites and a synthetic magnetite was evaluated under batch and continuous flow conditions. Results indicate that nano-scale biogenic magnetite produced by incubating synthetic schwertmannite powder in cell suspensions of Geobacter sulfurreducens is more efficient at reducing Cr(VI) than either biogenic nano-magnetite produced from a suspension of ferrihydrite 'gel' or synthetic nano-scale Fe{sub 3}O{sub 4} powder. Although X-ray Photoelectron Spectroscopy (XPS) measurements obtained from post-exposure magnetite samples reveal that both Cr(III) and Cr(VI) are associated with nanoparticle surfaces, X-ray Magnetic Circular Dichroism (XMCD) studies indicate that some Cr(III) has replaced octahedrally coordinated Fe in the lattice of the magnetite. Inductively Coupled Plasma-Atomic Emission Spectrometry (ICP-AES) measurements of total aqueous Cr in the associated solution phase indicated that, although the majority of Cr(III) was incorporated within or adsorbed to the magnetite samples, a proportion ({approx}10-15 %) was released back into solution. Studies of Tc(VII) uptake by magnetites produced via the different synthesis routes also revealed significant differences between them as regards effectiveness for remediation. In addition, column studies using a {gamma}-camera to obtain real time images of a {sup 99m}Tc(VII) radiotracer were performed to visualize directly the relative performances of the magnetite sorbents against ultra-trace concentrations of metal oxyanion contaminants. Again, the magnetite produced from schwertmannite proved capable of retaining more ({approx}20%) {sup 99m}Tc(VII) than the magnetite produced from ferrihydrite, confirming that biomagnetite production for efficient environmental remediation can be fine-tuned through careful selection of the initial Fe(III) mineral

  8. Effects of hexavalent chromium on performance and microbial community of an aerobic granular sequencing batch reactor.

    Science.gov (United States)

    Wang, Zichao; Gao, Mengchun; She, Zonglian; Jin, Chunji; Zhao, Yangguo; Yang, Shiying; Guo, Liang; Wang, Sen

    2015-03-01

    The performance and microbial community of an aerobic granular sequencing batch reactor (GSBR) were investigated at different hexavalent chromium (Cr(VI)) concentrations. The COD and NH4 (+)-N removal efficiencies decreased with the increase in Cr(VI) concentration from 0 to 30 mg/L. The specific oxygen utilization rate (SOUR) decreased from 34.86 to 12.18 mg/(g mixed liquor suspended sludge (MLSS)·h) with the increase in Cr(VI) concentration from 0 to 30 mg/L. The specific ammonium oxidation rate (SAOR), specific nitrite oxidation rate (SNOR), and specific nitrate reduction rate (SNRR) decreased with the increase in Cr(VI) concentration, whereas the SNRR was always higher than the sum of SAOR and SNOR at 0-30 mg/L Cr(VI). The scanning electron micrographs (SEM) showed some undefined particles on the surface of filamentous bacteria that might be the chelation of chromium and macromolecular organics at 30 mg/L Cr(VI). The denaturing gradient gel electrophoresis (DGGE) profiles revealed that some microorganisms adapting to high Cr(VI) concentration gradually became the predominant bacteria, while others without Cr(VI)-tolerance capacity tended to deplete or weaken. Some bacteria could tolerate the toxicity of high Cr(VI) concentration in the aerobic GSBR, such as Propionibacteriaceae bacterium, Ochrobactrum anthropi, and Micropruina glycogenica.

  9. Effective Adsorption/Reduction of Cr(VI) Oxyanion by Halloysite@Polyaniline Hybrid Nanotubes.

    Science.gov (United States)

    Zhou, Tianzhu; Li, Cuiping; Jin, Huiling; Lian, Yangyang; Han, Wenmei

    2017-02-22

    Halloysite@polyaniline (HA@PANI) hybrid nanotubes are synthesized by the in situ chemical polymerization of aniline on halloysite clay nanotubes. By facilely tuning the dopant acid, pH, and apparent weight proportion for aniline (ANI) and halloysite (HA) nanotubes in the synthesis process, PANI with tuned oxidation state, doping extent, and content are in situ growing on halloysite nanotubes. The reaction system's acidity is tuned by dopant acid, such as HCl, H2SO4, HNO3, and H3PO4. The adsorption result shows the fabricated HA@PANI hybrid nanotubes can effectively adsorb Cr(VI) oxyanion and the adsorption ability changes according to the dopant acid, pH, and apparent weight proportion for ANI and HA in the synthesis process. Among them, the HA@PANI fabricated with HCl as dopant acid tuning the pH at 0.5 and 204% apparent weight proportion for ANI and HA (HP/0.5/204%-HCl) shows the highest adsorption capacity. The adsorption capacity is in accordance well with the doping extent of PANI in HA@PANI. Furthermore, when HP/0.5/204%-HCl is redoped with HNO3, H2SO4, and H3PO4, the adsorption capacity declines, implying the dopant acid in the process of redoping exhibits a marked effect on Cr(VI) oxyanion adsorption for the HA@PANI hybrid nanotubes. HP/0.5/204%-HCl and HP/0.5/204%-H3PO4 have demonstrated good regenerability with an above 80% removal ratio after four cycles. Moreover, the HA@PANI adsorbent has better sedimentation ability than that of pure PANI. The adsorption behavior is in good agreement with Langmuir and pseudo second-order equations, indicating the adsorption of HA@PANI for Cr(VI) oxyanion is chemical adsorption. FT-IR and XPS of HA@PANI after Cr(VI) oxyanion adsorption indicate that the doped amine/imine groups (-NH(+)/═N(+)- groups) are the main adsorption sites for the removal of Cr(VI) oxyanion by electrostatic adsorption and reduction of the adsorbed Cr (VI) oxyanion to Cr(III) simultaneously.

  10. Nitrification inhibition by hexavalent chromium Cr(VI)--Microbial ecology, gene expression and off-gas emissions.

    Science.gov (United States)

    Kim, Young Mo; Park, Hongkeun; Chandran, Kartik

    2016-04-01

    The goal of this study was to investigate the responses in the physiology, microbial ecology and gene expression of nitrifying bacteria to imposition of and recovery from Cr(VI) loading in a lab-scale nitrification bioreactor. Exposure to Cr(VI) in the reactor strongly inhibited nitrification performance resulting in a parallel decrease in nitrate production and ammonia consumption. Cr(VI) exposure also led to an overall decrease in total bacterial concentrations in the reactor. However, the fraction of ammonia oxidizing bacteria (AOB) decreased to a greater extent than the fraction of nitrite oxidizing bacteria (NOB). In terms of functional gene expression, a rapid decrease in the transcript concentrations of amoA gene coding for ammonia oxidation in AOB was observed in response to the Cr(VI) shock. In contrast, transcript concentrations of the nxrA gene coding for nitrite oxidation in NOB were relatively unchanged compared to Cr(VI) pre-exposure levels. Therefore, Cr(VI) exposure selectively and directly inhibited activity of AOB, which indirectly resulted in substrate (nitrite) limitation to NOB. Significantly, trends in amoA expression preceded performance trends both during imposition of and recovery from inhibition. During recovery from the Cr(VI) shock, the high ammonia concentrations in the bioreactor resulted in an irreversible shift towards AOB populations, which are expected to be more competitive in high ammonia environments. An inadvertent impact during recovery was increased emission of nitrous oxide (N2O) and nitric oxide (NO), consistent with recent findings linking AOB activity and the production of these gases. Therefore, Cr(VI) exposure elicited multiple responses on the microbial ecology, gene expression and both aqueous and gaseous nitrogenous conversion in a nitrification process. A complementary interrogation of these multiple responses facilitated an understanding of both direct and indirect inhibitory impacts on nitrification.

  11. Effective adsorption of Cr(VI) on mesoporous Fe-functionalized Akadama clay: Optimization, selectivity, and mechanism

    Science.gov (United States)

    Ji, Min; Su, Xiao; Zhao, Yingxin; Qi, Wenfang; Wang, Yue; Chen, Guanyi; Zhang, Zhenya

    2015-07-01

    A Japanese volcanic soil, Akadama clay, was functionalized with metal salts (FeCl3, AlCl3, CaCl2, MgCl2, MnCl2) and tested for Cr(VI) removal from aqueous solution. FeCl3 was selected as the most efficient activation agent. To quantitatively investigate the independent or interactive contribution of influencing factors (solution pH, contact time, adsorbent dose, and initial concentration) to Cr(VI) adsorption onto Fe-functionalized AC (FFAC), factorial experimental design was applied. Results showed initial concentration contributed most to adsorption capacity of Cr(VI) (53.17%), followed by adsorbent dosage (45.15%), contact time (1.12%) and the interaction between adsorbent dosage and contact time (0.37%). The adsorption showed little dependence on solution pH from 2 to 8. Adsorption selectivity of Cr(VI) was evaluated through analyzing distribution coefficient, electrical double layer theory, as well as the valence and Pauling's ionic radii of co-existing anions (Cl-, SO42-, and PO43-). EDX and XPS analyses demonstrated the adsorption mechanism of Cr(VI) onto FFAC included electrostatic attraction, ligant exchange, and redox reaction. Improved treatment for tannery wastewater shows a potential application of FFAC as a cost-effective adsorbent for Cr(VI) removal.

  12. Scaling Effects of Cr(VI) Reduction Kinetics. The Role of Geochemical Heterogeneity

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Li [Pennsylvania State Univ., State College, PA (United States); Li, Li [Pennsylvania State Univ., State College, PA (United States)

    2015-10-22

    The natural subsurface is highly heterogeneous with minerals distributed in different spatial patterns. Fundamental understanding of how mineral spatial distribution patterns regulate sorption process is important for predicting the transport and fate of chemicals. Existing studies about the sorption was carried out in well-mixed batch reactors or uniformly packed columns, with few data available on the effects of spatial heterogeneities. As a result, there is a lack of data and understanding on how spatial heterogeneities control sorption processes. In this project, we aim to understand and develop modeling capabilities to predict the sorption of Cr(VI), an omnipresent contaminant in natural systems due to its natural occurrence and industrial utilization. We systematically examine the role of spatial patterns of illite, a common clay, in determining the extent of transport limitation and scaling effects associated with Cr(VI) sorption capacity and kinetics using column experiments and reactive transport modeling. Our results showed that the sorbed mass and rates can differ by an order of magnitude due to of the illite spatial heterogeneities and transport limitation. With constraints from data, we also developed the capabilities of modeling Cr(VI) in heterogeneous media. The developed model is then utilized to understand the general principles that govern the relationship between sorption and connectivity, a key measure of the spatial pattern characteristics. This correlation can be used to estimate Cr(VI) sorption characteristics in heterogeneous porous media. Insights gained here bridge gaps between laboratory and field application in hydrogeology and geochemical field, and advance predictive understanding of reactive transport processes in the natural heterogeneous subsurface. We believe that these findings will be of interest to a large number of environmental geochemists and engineers, hydrogeologists, and those interested in contaminant fate and transport

  13. Polymer based nanocomposites for the removal of Cr(VI) from water

    CSIR Research Space (South Africa)

    Setshedi, K

    2012-10-10

    Full Text Available , As, Fe? Abandoned mines Acid mine drainage Wastewater discharge to surface water Industrialization & Heavy-metals ? The problem Health effects ? CSIR 2012 Slide 5 Drinking water containing Heavy metals (even at low concentrations) can cause... :Polymer based NC Cr(VI) ? spiked waterWater bath shaker Sorption kinetics study: -Determination of reaction kinetic parameters Sorption isotherms Sorption kinetics Batch equilibrium and kinetics 0 1 2 3 4 5 6 In te n si ty / a .u . 2...

  14. Metal (Hydr)oxides for the removal of Cr(VI) from drinking water: a XAFS study

    Science.gov (United States)

    Pinakidou, F.; Kaprara, E.; Katsikini, M.; Paloura, E. C.; Simeonidis, K.; Mitrakas, M.

    2016-05-01

    The reduction mechanism and adsorption behaviour of Cr(VI) onto Tin(II) oxy- hydroxides are investigated using Cr-K edge X-ray absorption fine structure (XAFS) spectroscopies. The synthesis of the Sn oxy-hydroxide proceeds via hydrolysis of SnSO4. The successful reduction of Cr(VI) was identified by the analysis of the Cr-K edge XANES spectra where only Cr(III) species in octahedral sites are detected. According to the Cr-K edge EXAFS analysis results, Cr(III) forms bidentate inner sphere (binuclear (2C) and mononuclear (2E)) complexes. However, the surface coverage of Cr affects the type of Cr(III)-complexes formed: as the Cr-loading increases, Cr(III)-oxy-anions preferentially sorb in a “combined” 2C and 1V configuration, at the expense of the existing 2E sorption geometry.

  15. Synthesis of assorted metal ions anchored alginate bentonite biocomposites for Cr(VI) sorption.

    Science.gov (United States)

    Gopalakannan, Venkatrajan; Periyasamy, Soodamani; Viswanathan, Natrayasamy

    2016-10-20

    Biocomposites were synthesized by dispersing bentonite (Bent) clay in a biopolymer namely alginate (Alg) and cross-linked with bi (Ca(2+)), tri (Ce(3+)) and tetravalent (Zr(4+)) metal ions viz., Ca@AlgBent, Ce@AlgBent and Zr@AlgBent composites respectively. The synthesized biocomposites were characterized by various instrumental techniques like FTIR, SEM and EDAX. Cr(VI) sorption capacities (SCs) of the biocomposites Ca@AlgBent, Ce@AlgBent and Zr@AlgBent were examined by batch process. Various adsorption influencing factors viz., contact time, dosage of the sorbent, pH of the medium, temperature, presence of common co-ions and initial Cr(VI) concentration were studied. Freundlich, Langmuir and Dubinin-Radushkevich (D-R) isotherm models were adopted to examine the adsorption equilibrium. Kinetics of the sorption process was carried out by pseudo-first-order and pseudo-second-order models. The nature of the sorption process was explained using thermodynamic parameters like ΔS°, ΔG° and ΔH° and a possible mechanism for the sorption of Cr(VI) onto the biocomposites was given. The application of the biocomposites at field conditions was also examined by testing it with industrial water. The regeneration studies were carried to know about the reusability of the biocomposites.

  16. The bark of holm oak (Quercus ilex, L.) for airborne Cr(VI) monitoring.

    Science.gov (United States)

    Minganti, Vincenzo; Drava, Giuliana; De Pellegrini, Rodolfo; Anselmo, Marco; Modenesi, Paolo; Malaspina, Paola; Giordani, Paolo

    2015-01-01

    In this work, the bark of holm oak was used as a bioindicator to study the atmospheric distribution of Cr(VI). The chosen method (alkaline extraction and atomic absorption determination) was found in the literature, adapted for use with the matrix involved, and validated. The method had some limits, but provided an excellent estimation of Cr(VI) concentrations with good sensitivity and a reasonable time of analysis and cost. Thirty-four samples of holm oak collected in three areas characterised by different possible sources of pollution (the area near a former chromate production plant, an urban area, and a rural "reference" area) were analysed, obtaining concentrations ranging from 1.54 to 502 μg g(-1) near the industrial plant, ranging from 0.22 to 1.35 μg g(-1) in the urban area, and mostly below the detection limit (0.04 μg g(-1)) in the rural area. The bark of holm oak proved to be a good bioindicator to detect Cr(VI) in the environment. The extraction procedure followed by atomic absorption analysis is simple, provides good sensitivity, and it is suitable for environmental studies.

  17. Radiation-induced graft copolymerization of dimethylaminoethyl methacrylate onto graphene oxide for Cr(VI) removal

    Science.gov (United States)

    Ma, Hui-Ling; Zhang, Youwei; Zhang, Long; Wang, Liancai; Sun, Chao; Liu, Pinggui; He, Lihua; Zeng, Xinmiao; Zhai, Maolin

    2016-07-01

    Dimethylaminoethyl methacrylate (DMAEMA)-grafted graphene oxide hybrid materials (GO-g-P) were fabricated using γ-ray irradiation at ambient temperature. The morphology and structure of GO-g-P were characterized by Fourier-transform infrared spectroscopy (FT-IR), X-ray photoelectron (XPS), thermogravimetric analysis (TGA) and X-ray diffraction (XRD). It was confirmed that DMAEMA was grafted successfully on the surface of graphene sheet. The grafting yield of GO-g-P increased with monomer concentration (0-2.5 mol L-1) and dose (0-40 kGy). The resulting adsorbent (GO-g-P) with amine groups was highly efficient for removing Cr(VI) from its acidic aqueous solution and could be easily separated by filtration. The optimum pH for Cr(VI) removal was observed at pH 1.1 and the Cr(VI) uptake of GO-g-P at this pH was 82.4 mg g-1.

  18. Biosorption of Cr(VI from AqueousSolution Using New Adsorbent: Equilibrium and Thermodynamic Study

    Directory of Open Access Journals (Sweden)

    Israa G. Zainal

    2010-01-01

    Full Text Available Biosorption is one such emerging technology which utilized naturally occurring waste materials to sequester heavy metals from polluted water. In the present study cinnamon was utilized for Cr(VI removal from aqueous solutions.It was found that a time of two hours was sufficient for sorption to attain equilibrium. The optimum pH was 2 for Cr(VI removal. Temprature has little influence on the biosorption process. The Cr(VI removal decreased with increase in temperature. The biosorption data was well fitted to Dubinin - Radushkevich (D-R, Freundlich and Tempkin adsorption isotherm models, although the correlation coefficient of Langmuir model was high but the calculated adsorption capacity did not agree with the experimental. The thermodynamic study reveals that the biosorption process is spontaneous and the spontaneity decreased with temperature increase and the process is exothermic accompanied by highly ordered adsorbate at the solid liquid interface. ΔH° values were negative and lie in the range of physical adsorption.

  19. Hexavalent Chromium Reduction under Fermentative Conditions with Lactate Stimulated Native Microbial Communities

    Energy Technology Data Exchange (ETDEWEB)

    Somenahally, Anil C [ORNL; Mosher, Jennifer J [ORNL; Yuan, Tong [University of Oklahoma; Phelps, Tommy Joe [ORNL; Brown, Steven D [ORNL; Yang, Zamin Koo [ORNL; Hazen, Terry C [ORNL; Arkin, Adam [Lawrence Berkeley National Laboratory (LBNL); Palumbo, Anthony Vito [ORNL; Van Nostrand, Dr. Joy D. [Oklahoma University; Zhou, Jizhong [University of Oklahoma; Elias, Dwayne A [ORNL

    2013-01-01

    Microbial reduction of toxic hexavalent chromium (Cr(VI)) in-situ is a plausible bioremediation strategy in electron-acceptor limited environments. However, higher [Cr(VI)] may impose stress on syntrophic communities and impact community structure and function. The study objectives were to understand the impacts of Cr(VI) concentrations on community structure and on the Cr(VI)-reduction potential of groundwater communities at Hanford, WA. Steady state continuous flow bioreactors were used to grow native communities enriched with lactate (30 mM) and continuously amended with Cr(VI) at 0.0 (No-Cr), 0.1 (Low-Cr) and 3.0 (High-Cr) mg/L. Microbial growth, metabolites, Cr(VI), 16S rRNA gene sequences and GeoChip based functional gene composition were monitored for 15 weeks. Temporal trends and differences in growth, metabolite profiles, and community composition were observed, largely between Low-Cr and High-Cr bioreactors. In both High-Cr and Low-Cr bioreactors, Cr(VI) levels were below detection from week 1 until week 15. With lactate enrichment, native bacterial diversity substantially decreased as Pelosinus spp., and Sporotalea spp., became the dominant groups, but did not significantly differ between Cr concentrations. The Archaea diversity also substantially decreased after lactate enrichment from Methanosaeta (35%), Methanosarcina (17%) and others, to mostly Methanosarcina spp. (95%). Methane production was lower in High-Cr reactors suggesting some inhibition of methanogens. Several key functional genes were distinct in Low-Cr bioreactors compared to High-Cr. Among the Cr resistant microbes, Burkholderia vietnamiensis, Comamonas testosterone and Ralstonia pickettii proliferated in Cr amended bioreactors. In-situ fermentative conditions facilitated Cr(VI) reduction, and as a result 3.0 mg/L Cr(VI) did not impact the overall bacterial community structure.

  20. Hexavalent chromium reduction under fermentative conditions with lactate stimulated native microbial communities.

    Science.gov (United States)

    Somenahally, Anil C; Mosher, Jennifer J; Yuan, Tong; Podar, Mircea; Phelps, Tommy J; Brown, Steven D; Yang, Zamin K; Hazen, Terry C; Arkin, Adam P; Palumbo, Anthony V; Van Nostrand, Joy D; Zhou, Jizhong; Elias, Dwayne A

    2013-01-01

    Microbial reduction of toxic hexavalent chromium (Cr(VI)) in-situ is a plausible bioremediation strategy in electron-acceptor limited environments. However, higher [Cr(VI)] may impose stress on syntrophic communities and impact community structure and function. The study objectives were to understand the impacts of Cr(VI) concentrations on community structure and on the Cr(VI)-reduction potential of groundwater communities at Hanford, WA. Steady state continuous flow bioreactors were used to grow native communities enriched with lactate (30 mM) and continuously amended with Cr(VI) at 0.0 (No-Cr), 0.1 (Low-Cr) and 3.0 (High-Cr) mg/L. Microbial growth, metabolites, Cr(VI), 16S rRNA gene sequences and GeoChip based functional gene composition were monitored for 15 weeks. Temporal trends and differences in growth, metabolite profiles, and community composition were observed, largely between Low-Cr and High-Cr bioreactors. In both High-Cr and Low-Cr bioreactors, Cr(VI) levels were below detection from week 1 until week 15. With lactate enrichment, native bacterial diversity substantially decreased as Pelosinus spp., and Sporotalea spp., became the dominant groups, but did not significantly differ between Cr concentrations. The Archaea diversity also substantially decreased after lactate enrichment from Methanosaeta (35%), Methanosarcina (17%) and others, to mostly Methanosarcina spp. (95%). Methane production was lower in High-Cr reactors suggesting some inhibition of methanogens. Several key functional genes were distinct in Low-Cr bioreactors compared to High-Cr. Among the Cr resistant microbes, Burkholderia vietnamiensis, Comamonas testosterone and Ralstonia pickettii proliferated in Cr amended bioreactors. In-situ fermentative conditions facilitated Cr(VI) reduction, and as a result 3.0 mg/L Cr(VI) did not impact the overall bacterial community structure.

  1. Hexavalent chromium reduction under fermentative conditions with lactate stimulated native microbial communities.

    Directory of Open Access Journals (Sweden)

    Anil C Somenahally

    Full Text Available Microbial reduction of toxic hexavalent chromium (Cr(VI in-situ is a plausible bioremediation strategy in electron-acceptor limited environments. However, higher [Cr(VI] may impose stress on syntrophic communities and impact community structure and function. The study objectives were to understand the impacts of Cr(VI concentrations on community structure and on the Cr(VI-reduction potential of groundwater communities at Hanford, WA. Steady state continuous flow bioreactors were used to grow native communities enriched with lactate (30 mM and continuously amended with Cr(VI at 0.0 (No-Cr, 0.1 (Low-Cr and 3.0 (High-Cr mg/L. Microbial growth, metabolites, Cr(VI, 16S rRNA gene sequences and GeoChip based functional gene composition were monitored for 15 weeks. Temporal trends and differences in growth, metabolite profiles, and community composition were observed, largely between Low-Cr and High-Cr bioreactors. In both High-Cr and Low-Cr bioreactors, Cr(VI levels were below detection from week 1 until week 15. With lactate enrichment, native bacterial diversity substantially decreased as Pelosinus spp., and Sporotalea spp., became the dominant groups, but did not significantly differ between Cr concentrations. The Archaea diversity also substantially decreased after lactate enrichment from Methanosaeta (35%, Methanosarcina (17% and others, to mostly Methanosarcina spp. (95%. Methane production was lower in High-Cr reactors suggesting some inhibition of methanogens. Several key functional genes were distinct in Low-Cr bioreactors compared to High-Cr. Among the Cr resistant microbes, Burkholderia vietnamiensis, Comamonas testosterone and Ralstonia pickettii proliferated in Cr amended bioreactors. In-situ fermentative conditions facilitated Cr(VI reduction, and as a result 3.0 mg/L Cr(VI did not impact the overall bacterial community structure.

  2. Enhanced Cr(VI) reduction and As(III) oxidation in ice phase: Important role of dissolved organic matter from biochar

    Energy Technology Data Exchange (ETDEWEB)

    Dong, Xiaoling [Department of Soil and Water Science, University of Florida, Gainesville, FL 32611 (United States); Ma, Lena Q., E-mail: lqma@ufl.edu [State Key Laboratory of Pollution Control and Resource Reuse, School of the Environment, Nanjing University, Jiangsu 210046 (China); Department of Soil and Water Science, University of Florida, Gainesville, FL 32611 (United States); Gress, Julia; Harris, Willie [Department of Soil and Water Science, University of Florida, Gainesville, FL 32611 (United States); Li, Yuncong [Soil and Water Science Department, Tropical Research and Education Center, University of Florida, Homestead, FL 33031-3314 (United States)

    2014-02-01

    Graphical abstract: - Highlights: • Biochar-derived dissolved organic matter (DOM) effectively reduced Cr(VI) and oxidized As(III). • Cr(VI) and As(III) could serve as a redox couple. • Cr(VI) and As(III) redox conversion was more effective in the ice phase than aqueous phase. • FTIR and ESR showed that biochar DOM served as both electron donor and acceptor. - Abstract: This study evaluated the impact of DOM from two biochars (sugar beet tailing and Brazilian pepper) on Cr(VI) reduction and As(III) oxidation in both ice and aqueous phases with a soil DOM as control. Increasing DOM concentration from 3 to 300 mg C L{sup −1} enhanced Cr(VI) reduction from 20% to 100% and As(III) oxidation from 6.2% to 25%; however, Cr(VI) reduction decreased from 80–86% to negligible while As(III) oxidation increased from negligible to 18–19% with increasing pH from 2 to 10. Electron spin resonance study suggested semiquinone radicals in DOM were involved in As(III) oxidation while Fourier transform infrared analysis suggested that carboxylic groups in DOM participated in both Cr(VI) reduction and As(III) oxidation. During Cr(VI) reduction, part of DOM (∼10%) was oxidized to CO{sub 2}. The enhanced conversion of Cr(VI) and As(III) in the ice phase was due to the freeze concentration effect with elevated concentrations of electron donors and electron acceptors in the grain boundary. Though DOM enhanced both Cr(VI) reduction and As(III)oxidation, Cr(VI) reduction coupled with As(III) oxidation occurred in absence of DOM. The role of DOM, Cr(VI) and/or As(III) in Cr and As transformation may provide new insights into their speciation and toxicity in cold regions.

  3. Fabrication of a TiO2-BDD heterojunction and its application as a photocatalyst for the simultaneous oxidation of an azo dye and reduction of Cr(VI).

    Science.gov (United States)

    Yu, Hongbin; Chen, Shuo; Quan, Xie; Zhao, Huimin; Zhang, Yaobin

    2008-05-15

    A TiO2-boron doped diamond (TiO2-BDD) heterojunction was employed as a photocatalyst to simultaneously oxidize an azo dye C.I. reactive yellow 15 (RY15) and reduce hexavalent chromium (Cr(VI)). This heterojunction was fabricated first by depositing a BDD film on a Ti sheet in a hot filament chemical vapor deposition reactor, followed by covering a layer of TiO2 in a metal-organic chemical vapor deposition system. The morphology of this heterojunction was characterized by using a scanning electron microscope (SEM). X-ray diffraction (XRD), Raman spectroscopy, and current-voltage (I-V) measurement were used to characterize its structures. Additionally, the characterization of surface photovoltage showed that the TiO2-BDD heterojunction exhibited a higher photovoltage response and a better ability for charge separation than the photocatalyst of TiO2 directly deposited on a Ti sheet (TiO2-Ti). The photocatalytic experiments revealed that the kinetic constants for the oxidation of RY15 and the reduction of Cr(VI) were, respectively, increased by 85 and 71% when the photocatalyst of TiO2-Ti was replaced by the TiO2-BDD heterojunction. Meanwhile, a significant synergy was confirmed in the simultaneous oxidation of RY15 and reduction of Cr(VI). The enhanced photocatalytic ability of the TiO2-BDD composite could be attributed to the heterojunction. The possible photocatalytic mechanism was also discussed.

  4. Biosorption of Cr(VI) and As(V) at high concentrations by organic and inorganic wastes

    Science.gov (United States)

    María Rivas Pérez, Ivana; Paradelo Núñez, Remigio; Nóvoa Muñoz, Juan Carlos; Arias Estévez, Manuel; José Fernández Sanjurjo, María; Álvarez Rodríguez, Esperanza; Núñez Delgado, Avelino

    2016-04-01

    The potential reutilization of several wastes as biosorbents for As(V) and Cr(VI) has been assessed in batch-type experiments. The materials studied were one inorganic: mussel shell, and three organic: pine bark, oak ash and hemp waste. Batch experiments were performed in order to determine the removal capacity of the wastes under conditions of high As(V) and Cr(VI) loads. For this, 3 g of each waste material were added with 30 mL NaNO3 0.01 M dissolutions containing 0, 0.5, 1.5, 3 and 6 mmol As(V) L-1 or Cr(VI) L-1, prepared from analytical grade Na2HAsO4 or K2Cr2O7. The resulting suspensions were shaken for 24 h, centrifuged and filtered. Once each batch experiment corresponding to the sorption trials ended, each individual sample was added with 30 mL of NaNO3 0.01 M to desorb As(V) or Cr(VI), shaken for 24 h, centrifuged and filtered as in the sorption trials. Oak ash showed high sorption (>76%) and low desorption (hemp waste (98%) with very low desorption (hemp waste and mussel shell, that presented very low Cr(VI) sorption (<10%). Sorption data for both elements were better described by the Freundlich than by the Langmuir model. The variable results obtained for the removal of the two anionic contaminants for a given sorbent suggest that different mechanisms govern removal from the solution in each case. In summary, oak ash would be an efficient sorbent material for As(V), but not for Cr(VI), while pine bark would be the best sorbent for Cr(VI) removal.

  5. Enhanced removal of trace Cr(VI) from neutral and alkaline aqueous solution by FeCo bimetallic nanoparticles.

    Science.gov (United States)

    Qin, Nannan; Zhang, Ya; Zhou, Hongjian; Geng, Zhigang; Liu, Gang; Zhang, Yunxia; Zhao, Huijun; Wang, Guozhong

    2016-06-15

    The reactivity of zero valent iron (Fe(0)) for removing Cr(VI) is self-inhibiting under neutral and alkaline conditions, due to the precipitation of ferrous hydroxide on the surface of Fe(0). To overcome this difficulty, we incorporated a second metal (Co) into Fe(0) to form FeCo bimetallic nanoparticles (FeCo BNPs), which can achieve higher activity and significant improvement in the reaction kinetics for the removal of Cr(VI) compared with Fe(0). The FeCo BNPs were synthesized by a hydrothermal reduction method without using any templates. The characterization analysis indicated that the products were highly uniform in large scale with 120-140 nm size in diameter. The obtained FeCo BNPs exhibited a remarkable removal ability for Cr(VI) in the pH range of 5.3-10.0. Especially, FeCo BNPs were able to reduce trace Cr(VI) (1.0 mg L(-1), pH=7.5) down to about 0.025 mg L(-1) within 1h. XPS analysis confirmed that Cr(VI) was reduced to Cr(III) by FeCo BNPs, while Fe and Co was oxidized, implying a chemical reduction process. The enhanced removal of trace Cr(VI) could be originated from the introduction of Co, which not only served as a protecting agent against surface corrosion by galvanic cell effect, but also enhanced the efficient flow of electron transfer between iron and Cr(VI). All the results primarily imply that FeCo BNPs can be employed as high efficient material for wastewater treatment. Copyright © 2016 Elsevier Inc. All rights reserved.

  6. Synthesis, characterization and application of Lagerstroemia speciosa embedded magnetic nanoparticle for Cr(VI) adsorption from aqueous solution.

    Science.gov (United States)

    Srivastava, Shalini; Agrawal, Shashi Bhushan; Mondal, Monoj Kumar

    2017-05-01

    Lagerstroemia speciosa bark (LB) embedded magnetic nanoparticles were prepared by co-precipitation of Fe(2+) and Fe(3+) salt solution with ammonia and LB for Cr(VI) removal from aqueous solution. The native LB, magnetic nanoparticle (MNP), L. speciosa embedded magnetic nanoparticle (MNPLB) and Cr(VI) adsorbed MNPLB particles were characterized by SEM-EDX, TEM, BET-surface area, FT-IR, XRD and TGA methods. TEM analysis confirmed nearly spherical shape of MNP with an average diameter of 8.76nm and the surface modification did not result in the phase change of MNP as established by XRD analysis, while led to the formation of secondary particles of MNPLB with diameter of 18.54nm. Characterization results revealed covalent binding between the hydroxyl group of MNP and carboxyl group of LB particles and further confirmed its physico-chemical nature favorable for Cr(VI) adsorption. The Cr(VI) adsorption on to MNPLB particle as an adsorbent was tested under different contact time, initial Cr(VI) concentration, adsorbent dose, initial pH, temperature and agitation speed. The results of the equilibrium and kinetics of adsorption were well described by Langmuir isotherm and pseudo-second-order model, respectively. The thermodynamic parameters suggest spontaneous and endothermic nature of Cr(VI) adsorption onto MNPLB. The maximum adsorption capacity for MNPLB was calculated to be 434.78mg/g and these particles even after Cr(VI) adsorption were collected effortlessly from the aqueous solution by a magnet. The desorption of Cr(VI)-adsorbed MNPLB was found to be more than 93.72% with spent MNPLB depicting eleven successive adsorption-desorption cycles. Copyright © 2016. Published by Elsevier B.V.

  7. RDT&E Progress and Plansfor Hexavalent Chromium (Cr6+)

    Science.gov (United States)

    2011-05-12

    Inhibitors Function (Project WP-1620) Project Team – Main Performers ● Dr. Gerald S. Frankel and Dr. Rudolph G. Buchheit Fontana Corrosion Center, The...qualification ● Dr. Joseph Osborne, The Boeing Company  Co-PI, coating system integration, coating and surface prep development, Cr and Cd replacement

  8. Polyurethane-Keratin Membranes: Structural Changes by Isocyanate and pH, and the Repercussion on Cr(VI Removal

    Directory of Open Access Journals (Sweden)

    María D. Manrique-Juárez

    2013-01-01

    Full Text Available Keratin has the capacity to interact with metal ions. In order to take advantage of this potential, a novel membrane with polyurethane and keratin has been developed and studied for removal of Cr(VI from aqueous solution. Physicochemical and morphological properties of these hybrid membranes were studied, varying synthesis parameters such as the type of isocyanate and pH in keratin solution. The effects of using diphenyl-methane-diisocyanate or toluene-diisocyanate and modifying the pH in keratin solutions were evaluated by scanning electron microscopy, Fourier transform infrared spectroscopy, and dynamical mechanical analysis. Results show that pH has a strong influence on morphology and on Cr(VI removal efficiency. When pH in keratin solution is low (2.5, the protein separates from water, and a more closed cell in the membrane is obtained affecting its mechanical properties. The removal efficiency of Cr(VI was also assessed at different pH values of chromium solutions. These results show that when pH of the Cr solution is acidic (at 1.5, the Cr(VI removal percentages increase significantly, reaching up to a 58%. Thus this paper demonstrates the successful combination of synthetic and natural polymers depending on the process parameters to be applied in the critical purpose of remediation of Cr(VI contamination.

  9. ZnO-PLLA Nanofiber Nanocomposite for Continuous Flow Mode Purification of Water from Cr(VI

    Directory of Open Access Journals (Sweden)

    T. Burks

    2015-01-01

    Full Text Available Nanomaterials of ZnO-PLLA nanofibers have been used for the adsorption of Cr(VI as a prime step for the purification of water. The fabrication and application of the flexible ZnO-PLLA nanofiber nanocomposite as functional materials in this well-developed architecture have been achieved by growing ZnO nanorod arrays by chemical bath deposition on synthesized electrospun poly-L-lactide nanofibers. The nanocomposite material has been tested for the removal and regeneration of Cr(IV in aqueous solution under a “continuous flow mode” by studying the effects of pH, contact time, and desorption steps. The adsorption of Cr(VI species in solution was greatly dependent upon pH. SEM micrographs confirmed the successful fabrication of the ZnO-PLLA nanofiber nanocomposite. The adsorption and desorption of Cr(VI species were more likely due to the electrostatic interaction between ZnO and Cr(VI ions as a function of pH. The adsorption and desorption experiments utilizing the ZnO-PLLA nanofiber nanocomposite have appeared to be an effective nanocomposite in the removal and regeneration of Cr(VI species.

  10. Chromium Biosorption from Cr(VI) Aqueous Solutions by Cupressus lusitanica Bark: Kinetics, Equilibrium and Thermodynamic Studies

    Science.gov (United States)

    Netzahuatl-Muñoz, Alma Rosa; Cristiani-Urbina, María del Carmen; Cristiani-Urbina, Eliseo

    2015-01-01

    The present study investigated the kinetics, equilibrium and thermodynamics of chromium (Cr) ion biosorption from Cr(VI) aqueous solutions by Cupressus lusitanica bark (CLB). CLB total Cr biosorption capacity strongly depended on operating variables such as initial Cr(VI) concentration and contact time: as these variables rose, total Cr biosorption capacity increased significantly. Total Cr biosorption rate also increased with rising solution temperature. The pseudo-second-order model described the total Cr biosorption kinetic data best. Langmuir´s model fitted the experimental equilibrium biosorption data of total Cr best and predicted a maximum total Cr biosorption capacity of 305.4 mg g-1. Total Cr biosorption by CLB is an endothermic and non-spontaneous process as indicated by the thermodynamic parameters. Results from the present kinetic, equilibrium and thermodynamic studies suggest that CLB biosorbs Cr ions from Cr(VI) aqueous solutions predominantly by a chemical sorption phenomenon. Low cost, availability, renewable nature, and effective total Cr biosorption make CLB a highly attractive and efficient method to remediate Cr(VI)-contaminated water and wastewater. PMID:26352933

  11. Chromium Biosorption from Cr(VI Aqueous Solutions by Cupressus lusitanica Bark: Kinetics, Equilibrium and Thermodynamic Studies.

    Directory of Open Access Journals (Sweden)

    Alma Rosa Netzahuatl-Muñoz

    Full Text Available The present study investigated the kinetics, equilibrium and thermodynamics of chromium (Cr ion biosorption from Cr(VI aqueous solutions by Cupressus lusitanica bark (CLB. CLB total Cr biosorption capacity strongly depended on operating variables such as initial Cr(VI concentration and contact time: as these variables rose, total Cr biosorption capacity increased significantly. Total Cr biosorption rate also increased with rising solution temperature. The pseudo-second-order model described the total Cr biosorption kinetic data best. Langmuir´s model fitted the experimental equilibrium biosorption data of total Cr best and predicted a maximum total Cr biosorption capacity of 305.4 mg g(-1. Total Cr biosorption by CLB is an endothermic and non-spontaneous process as indicated by the thermodynamic parameters. Results from the present kinetic, equilibrium and thermodynamic studies suggest that CLB biosorbs Cr ions from Cr(VI aqueous solutions predominantly by a chemical sorption phenomenon. Low cost, availability, renewable nature, and effective total Cr biosorption make CLB a highly attractive and efficient method to remediate Cr(VI-contaminated water and wastewater.

  12. Chromium Biosorption from Cr(VI) Aqueous Solutions by Cupressus lusitanica Bark: Kinetics, Equilibrium and Thermodynamic Studies.

    Science.gov (United States)

    Netzahuatl-Muñoz, Alma Rosa; Cristiani-Urbina, María del Carmen; Cristiani-Urbina, Eliseo

    2015-01-01

    The present study investigated the kinetics, equilibrium and thermodynamics of chromium (Cr) ion biosorption from Cr(VI) aqueous solutions by Cupressus lusitanica bark (CLB). CLB total Cr biosorption capacity strongly depended on operating variables such as initial Cr(VI) concentration and contact time: as these variables rose, total Cr biosorption capacity increased significantly. Total Cr biosorption rate also increased with rising solution temperature. The pseudo-second-order model described the total Cr biosorption kinetic data best. Langmuir´s model fitted the experimental equilibrium biosorption data of total Cr best and predicted a maximum total Cr biosorption capacity of 305.4 mg g(-1). Total Cr biosorption by CLB is an endothermic and non-spontaneous process as indicated by the thermodynamic parameters. Results from the present kinetic, equilibrium and thermodynamic studies suggest that CLB biosorbs Cr ions from Cr(VI) aqueous solutions predominantly by a chemical sorption phenomenon. Low cost, availability, renewable nature, and effective total Cr biosorption make CLB a highly attractive and efficient method to remediate Cr(VI)-contaminated water and wastewater.

  13. Biodegradation of hexavalent chromium (Cr+6) in wastewater using Pseudomonas sp. and Bacillus sp. bacterial strains

    Energy Technology Data Exchange (ETDEWEB)

    Qasim, Muhammad [Department of Chemical Engineering, American University of Sharjah (United Arab Emirates)

    2013-07-01

    The recovery of toxic metal compounds is a deep concern in all industries. Hexavalent chromium is particularly worrying because of its toxic influence on human health. In this paper, biodegradation of hexavalent chromium (Cr+6) present in wastewater has been studied using two different bacterial strains; Pseudomonas sp. and Bacillus sp. A chemostat (with and without recycle of cells) with 10 L liquid culture volume was used to study the substrate and the biomass cell concentrations with time. Also, the degree of substrate conversion was studied by the varying the dilution rate as an independent parameter. The dilution rate (ratio of feed flow rate to the culture volume) was varied by varying the feed volumetric rate from 110-170 mL/h for inlet hexavalent chromium concentrations of 70 mg/dm3. The results show that a chemostat with recycle gives a better performance in terms of substrate conversion than a chemostat without a recycle. Moreover, the degree of substrate conversion decreases as the dilution rate is increased. Also, Bacillus sp. was found to give higher conversions compared to pseudomonas sp.

  14. On the passivation mechanism of Fe3O4 nanoparticles during Cr(VI) removal from water: A XAFS study

    Science.gov (United States)

    Pinakidou, F.; Katsikini, M.; Simeonidis, K.; Kaprara, E.; Paloura, E. C.; Mitrakas, M.

    2016-01-01

    X-Ray Absorption Spectroscopies (XAFS) are employed in order to gather a thorough insight on the uptake mechanism of Cr(VI) by Fe3O4 nanoparticles under water treatment conditions. The XANES measurements identify that the reducing potential of Fe3O4 activates the precipitation of Cr(VI) in the form of insoluble and non-toxic Cr(III). However, electron donation from Fe(II) is responsible for its gradual consumption, resulting in the presence of a surface maghemite layer and the formation of structural vacancies. EXAFS analysis reveal that adsorption of Cr(III)-oxyanions occurs on sorption sites provided by the vacancies in the maghemite layer, where Cr(III) is involved in a bidentate binuclear (2E) geometry with Fe-octahedra while it also forms monodentate (1V) complexes with the Fe(III)O4 tetrahedra. The surface maghemitization along with the reduced Cr(III) adsorption into the vacancies, tracks the degree of Cr-reduction, since this surface structural modifications hinder Cr(VI) access to the Fe(II) ions of the magnetite nanoparticles. Thus, high surface coverage leads to the passivation of the reduction ability since physisorbed Cr(VI) is also detected through the formation of outer sphere complexes.

  15. Selective Reduction of Cr(VI in Chromium, Copper and Arsenic (CCA Mixed Waste Streams Using UV/TiO2 Photocatalysis

    Directory of Open Access Journals (Sweden)

    Shan Zheng

    2015-02-01

    Full Text Available The highly toxic Cr(VI is a critical component in the Chromated Copper Arsenate (CCA formulations extensively employed as wood preservatives. Remediation of CCA mixed waste and discarded treated wood products is a significant challenge. We demonstrate that UV/TiO2 photocatalysis effectively reduces Cr(VI to less toxic Cr(III in the presence of arsenate, As(V, and copper, Cu(II. The rapid conversion of Cr(VI to Cr(III during UV/TiO2 photocatalysis occurs over a range of concentrations, solution pH and at different Cr:As:Cu ratios. The reduction follows pseudo-first order kinetics and increases with decreasing solution pH. Saturation of the reaction solution with argon during UV/TiO2 photocatalysis had no significant effect on the Cr(VI reduction demonstrating the reduction of Cr(VI is independent of dissolved oxygen. Reduction of Cu(II and As(V does not occur under the photocatalytic conditions employed herein and the presence of these two in the tertiary mixtures had a minimal effect on Cr(VI reduction. The Cr(VI reduction was however, significantly enhanced by the addition of formic acid, which can act as a hole scavenger and enhance the reduction processes initiated by the conduction band electron. Our results demonstrate UV/TiO2 photocatalysis effectively reduces Cr(VI in mixed waste streams under a variety of conditions.

  16. Selective reduction of Cr(VI) in chromium, copper and arsenic (CCA) mixed waste streams using UV/TiO2 photocatalysis.

    Science.gov (United States)

    Zheng, Shan; Jiang, Wenjun; Rashid, Mamun; Cai, Yong; Dionysiou, Dionysios D; O'Shea, Kevin E

    2015-02-03

    The highly toxic Cr(VI) is a critical component in the Chromated Copper Arsenate (CCA) formulations extensively employed as wood preservatives. Remediation of CCA mixed waste and discarded treated wood products is a significant challenge. We demonstrate that UV/TiO2 photocatalysis effectively reduces Cr(VI) to less toxic Cr(III) in the presence of arsenate, As(V), and copper, Cu(II). The rapid conversion of Cr(VI) to Cr(III) during UV/TiO2 photocatalysis occurs over a range of concentrations, solution pH and at different Cr:As:Cu ratios. The reduction follows pseudo-first order kinetics and increases with decreasing solution pH. Saturation of the reaction solution with argon during UV/TiO2 photocatalysis had no significant effect on the Cr(VI) reduction demonstrating the reduction of Cr(VI) is independent of dissolved oxygen. Reduction of Cu(II) and As(V) does not occur under the photocatalytic conditions employed herein and the presence of these two in the tertiary mixtures had a minimal effect on Cr(VI) reduction. The Cr(VI) reduction was however, significantly enhanced by the addition of formic acid, which can act as a hole scavenger and enhance the reduction processes initiated by the conduction band electron. Our results demonstrate UV/TiO2 photocatalysis effectively reduces Cr(VI) in mixed waste streams under a variety of conditions.

  17. Remediation of hexavalent chromium spiked soil by using synthesized iron sulfide particles.

    Science.gov (United States)

    Li, Yujie; Wang, Wanyu; Zhou, Liqiang; Liu, Yuanyuan; Mirza, Zakaria A; Lin, Xiang

    2017-02-01

    Carboxymethyl cellulose (CMC) stabilized microscale iron sulfide (FeS) particles were synthesized and applied to remediate hexavalent chromium (Cr(VI)) spiked soil. The effects of parameters including dosage of FeS particles, soil moisture, and natural organic matter (NOM) in soil were investigated with comparison to iron sulfate (FeSO4). The results show that the stabilized FeS particles can reduce Cr(VI) and immobilize Cr in soil quickly and efficiently. The soil moisture ranging from 40% to 70% and NOM in soil had no significant effects on Cr(VI) remediation by FeS particles. When molar ratio of FeS to Cr(VI) was 1.5:1, about 98% of Cr(VI) in soil was reduced by FeS particles in 3 d and Cr(VI) concentration decreased from 1407 mg kg(-1) to 16 mg kg(-1). The total Cr and Cr(VI) in Toxicity Characteristic Leaching Procedure (TCLP) leachate were reduced by 98.4% and 99.4%, respectively. In FeS particles-treated soil, the exchangeable Cr fraction was mainly converted to Fe-Mn oxides bound fraction because of the precipitation of Cr(III)-Fe(III) hydroxides. The physiologically based extraction test (PBET) bioaccessibility of Cr was decreased from 58.67% to 6.98%. Compared to FeSO4, the high Cr(VI) removal and Cr immobilization efficiency makes prepared FeS particles a great potential in field application of Cr(VI) contaminated soil remediation. Copyright © 2016 Elsevier Ltd. All rights reserved.

  18. Versatility of Streptomyces sp. M7 to bioremediate soils co-contaminated with Cr(VI) and lindane.

    Science.gov (United States)

    Aparicio, JuanDaniel; Solá, María Zoleica Simón; Benimeli, Claudia Susana; Amoroso, María Julia; Polti, Marta Alejandra

    2015-06-01

    The aim of this work was to study the impact of environmental factors on the bioremediation of Cr(VI) and lindane contaminated soil, by an actinobacterium, Streptomyces sp. M7, in order to optimize the process. Soil samples were contaminated with 25 µg kg(-1) of lindane and 50 mg kg(-1) of Cr(VI) and inoculated with Streptomyces sp. M7. The lowest inoculum concentration which simultaneously produced highest removal of Cr(VI) and lindane was 1 g kg(-1). The influence of physical and chemical parameters was assessed using a full factorial design. The factors and levels tested were: Temperature: 25, 30, 35°C; Humidity: 10%, 20%, 30%; Initial Cr(VI) concentration: 20, 50, 80 mg kg(-1); Initial lindane concentration: 10, 25, 40 µg kg(-1). Streptomyces sp. M7 exhibited strong versatility, showing the ability to bioremediate co-contaminated soil samples at several physicochemical conditions. Streptomyces sp. M7 inoculum size was optimized. Also, it was fitted a model to study this process, and it was possible to predict the system performance, knowing the initial conditions. Moreover, optimum temperature and humidity conditions for the bioremediation of soil with different concentrations of Cr(VI) and lindane were determined. Lettuce seedlings were a suitable biomarker to evaluate the contaminants mixture toxicity. Streptomyces sp. M7 carried out a successful bioremediation, which was demonstrated through ecotoxicity test with Lactuca sativa.

  19. Evaluation of the bioremoval of Cr(VI) and TOC in biofilters under continuous operation using response surface methodology.

    Science.gov (United States)

    Leles, Daniela M A; Lemos, Diego A; Filho, Ubirajara C; Romanielo, Lucienne L; de Resende, Miriam M; Cardoso, Vicelma L

    2012-06-01

    In the present study, the bioremoval of Cr(VI) and the removal of total organic carbon (TOC) were achieved with a system composed by an anaerobic filter and a submerged biofilter with intermittent aeration using a mixed culture of microorganisms originating from contaminated sludge. In the aforementioned biofilters, the concentrations of chromium, carbon, and nitrogen were optimized according to response surface methodology. The initial concentration of Cr(VI) was 137.35 mg l(-1), and a bioremoval of 85.23% was attained. The optimal conditions for the removal of TOC were 4 to 8 g l(-1) of sodium acetate, >0.8 g l(-1) of ammonium chloride and 60 to 100 mg l(-1) of Cr(VI). The results revealed that ammonium chloride had the strongest effect on the TOC removal, and 120 mg l(-1) of Cr(VI) could be removed after 156 h of operation. Moreover, 100% of the Cr(VI) and the total chromium content of the aerobic reactor output were removed, and TOC removals of 80 and 87% were attained after operating the anaerobic and aerobic reactors for 130 and 142 h, respectively. The concentrations of cells in both reactors remained nearly constant over time. The residence time distribution was obtained to evaluate the flow through the bioreactors.

  20. Adsorption of Cr(VI) using cellulose microsphere-based adsorbent prepared by radiation-induced grafting

    Science.gov (United States)

    Li, Cancan; Zhang, Youwei; Peng, Jing; Wu, Hao; Li, Jiuqiang; Zhai, Maolin

    2012-08-01

    Cellulose microsphere (CMS) adsorbent was prepared by radiation-induced grafting of dimethylaminoethyl methacrylate (DMAEMA) onto CMS followed by a protonation process. The FTIR spectra analysis proved that PDMAEMA was grafted successfully onto CMS. The adsorption of Cr(VI) onto the resulting adsorbent was very fast, the equilibrium adsorption could be achieved within 15 min. The adsorption capacity strongly depended on the pH of the solution, which was attributed to the change of both the existed forms of Cr(VI) and the tertiary-ammonium group of PDMAEMA grafted CMS with the pH. A maximum Cr(VI) uptake (ca. 78 mg g-1) was obtained as the pH was in the range of 3.0-6.0. However, even in strong acid media (pH 1.3), the adsorbents still showed a Cr(VI) uptake of 30 mg g-1. The adsorption behavior of the resultant absorbent could be described with the Langmuir mode. This adsorbent has potential application for removing heavy metal ion pollutants (e.g. Cr(VI)) from wastewater.

  1. Radiation-induced graft polymerization for the preparation of a highly efficient UHMWPE fibrous adsorbent for Cr(VI) removal

    Science.gov (United States)

    Gao, Qianhong; Hua, Jiangtao; Li, Rong; Xing, Zhe; Pang, Lijuan; Zhang, Mingxing; Xu, Lu; Wu, Guozhong

    2017-01-01

    A novel fibrous adsorbent containing amine and quaternary ammonium groups was prepared by radiation-induced graft of glycidyl methacrylate (GMA) onto ultra-high molecular weight polyethylene (UHMWPE) fiber and further modifying with triethylenetetramine (TETA) and glycidyl trimethylammonium chloride (GTA). The ATR-IR spectra and SEM observation demonstrated that amine and quaternary ammonium groups were immobilized onto the surface of UHMWPE fiber. The principal factors affecting the adsorption of Cr(VI) ions have been investigated including pH of the aqueous solution, contact time, temperature and coexisting anions. This novel fibrous adsorbent could effectively adsorb Cr(VI) in the range of pH 1-9, and the maximum adsorption capacity reached 295 mg/g at pH 3 and 25 °C based on the Langmuir isotherm. It was found that adsorption equilibrium could be achieved within 2 h for initial Cr(VI) of 100 mg/L, following the pseudo-second order model. The effect of coexisting anions (including SO42-, H2PO4-, NO3-and Cl-) on the uptake of Cr(VI) was investigated in detail. Additionally, the adsorption saturated fiber could be regenerated by soaking in 0.5 mol/L NaOH solution, and the adsorption performance of this adsorbent could be maintained at 90% after eight cycles of adsorption-desorption. ATR-IR and XPS analysis revealed that Cr(VI) ions were adsorbed on the fiber adsorbent through ion exchange mechanism.

  2. Utility of Ochrobactrum anthropi YC152 in a Microbial Fuel Cell as an Early Warning Device for Hexavalent Chromium Determination

    Directory of Open Access Journals (Sweden)

    Guey-Horng Wang

    2016-08-01

    Full Text Available Fast hexavalent chromium (Cr(VI determination is important for environmental risk and health-related considerations. We used a microbial fuel cell-based biosensor inoculated with a facultatively anaerobic, Cr(VI-reducing, and exoelectrogenic Ochrobactrum anthropi YC152 to determine the Cr(VI concentration in water. The results indicated that O. anthropi YC152 exhibited high adaptability to pH, temperature, salinity, and water quality under anaerobic conditions. The stable performance of the microbial fuel cell (MFC-based biosensor indicated its potential as a reliable biosensor system. The MFC voltage decreased as the Cr(VI concentration in the MFC increased. Two satisfactory linear relationships were observed between the Cr(VI concentration and voltage output for various Cr(VI concentration ranges (0.0125–0.3 mg/L and 0.3–5 mg/L. The MFC biosensor is a simple device that can accurately measure Cr(VI concentrations in drinking water, groundwater, and electroplating wastewater in 45 min with low deviations (<10%. The use of the biosensor can help in preventing the violation of effluent regulations and the maximum allowable concentration of Cr(VI in water. Thus, the developed MFC biosensor has potential as an early warning detection device for Cr(VI determination even if O. anthropi YC152 is a possible opportunistic pathogen.

  3. Utility of Ochrobactrum anthropi YC152 in a Microbial Fuel Cell as an Early Warning Device for Hexavalent Chromium Determination.

    Science.gov (United States)

    Wang, Guey-Horng; Cheng, Chiu-Yu; Liu, Man-Hai; Chen, Tzu-Yu; Hsieh, Min-Chi; Chung, Ying-Chien

    2016-08-16

    Fast hexavalent chromium (Cr(VI)) determination is important for environmental risk and health-related considerations. We used a microbial fuel cell-based biosensor inoculated with a facultatively anaerobic, Cr(VI)-reducing, and exoelectrogenic Ochrobactrum anthropi YC152 to determine the Cr(VI) concentration in water. The results indicated that O. anthropi YC152 exhibited high adaptability to pH, temperature, salinity, and water quality under anaerobic conditions. The stable performance of the microbial fuel cell (MFC)-based biosensor indicated its potential as a reliable biosensor system. The MFC voltage decreased as the Cr(VI) concentration in the MFC increased. Two satisfactory linear relationships were observed between the Cr(VI) concentration and voltage output for various Cr(VI) concentration ranges (0.0125-0.3 mg/L and 0.3-5 mg/L). The MFC biosensor is a simple device that can accurately measure Cr(VI) concentrations in drinking water, groundwater, and electroplating wastewater in 45 min with low deviations (<10%). The use of the biosensor can help in preventing the violation of effluent regulations and the maximum allowable concentration of Cr(VI) in water. Thus, the developed MFC biosensor has potential as an early warning detection device for Cr(VI) determination even if O. anthropi YC152 is a possible opportunistic pathogen.

  4. Facile preparation of amino functionalized graphene oxide decorated with Fe3O4 nanoparticles for the adsorption of Cr(VI)

    Science.gov (United States)

    Zhao, Donglin; Gao, Xuan; Wu, Changnian; Xie, Rong; Feng, Shaojie; Chen, Changlun

    2016-10-01

    A novel ternary magnetic composite consisting of graphene oxide (GO), diethylenetriamine and Fe3O4 nanoparticles (AMGO) were synthesized by a facile one-step reaction route and characterized. The AMGO was applied as a magnetic adsorbent for the Cr(VI) removal from aqueous solutions and the magnetic separation process only took 40 s. The maximum adsorption capacity of the AMGO for Cr(VI) was 123.4 mg/g, displaying a high efficiency for the removal of Cr(VI), which was much higher than that of MGO. The removal process was pH dependence, endothermic and spontaneous. The pseudo-second-order model described well the adsorption kinetic data and the Langmuir isotherm model fitted the experimental data better than the Freundlich isotherm model. XPS analysis revealed that the Cr(VI) was reduced to the low-toxicity Cr(III) during the adsorption process. Both the Cr(VI) adsorption and subsequent reduction of adsorbed Cr(VI) to Cr(III) contributed to the Cr(VI) removal. In addition, the excellent reproducibility indicate that the AMGO may be a promising adsorption material for the separation and preconcentration of Cr(VI) ions from aqueous solutions in environmental pollution cleanup.

  5. Hexavalent chromium exposure and control in welding tasks.

    Science.gov (United States)

    Meeker, John D; Susi, Pam; Flynn, Michael R

    2010-11-01

    Studies of exposure to the lung carcinogen hexavalent chromium (CrVI) from welding tasks are limited, especially within the construction industry where overexposure may be common. In addition, despite the OSHA requirement that the use of engineering controls such as local exhaust ventilation (LEV) first be considered before relying on other strategies to reduce worker exposure to CrVI, data on the effectiveness of LEV to reduce CrVI exposures from welding are lacking. The goal of the present study was to characterize breathing zone air concentrations of CrVI during welding tasks and primary contributing factors in four datasets: (1) OSHA compliance data; (2) a publicly available database from The Welding Institute (TWI); (3) field survey data of construction welders collected by the Center for Construction Research and Training (CPWR); and (4) controlled welding trials conducted by CPWR to assess the effectiveness of a portable LEV unit to reduce CrVI exposure. In the OSHA (n = 181) and TWI (n = 124) datasets, which included very few samples from the construction industry, the OSHA permissible exposure level (PEL) for CrVI (5 μg/m(3)) was exceeded in 9% and 13% of samples, respectively. CrVI concentrations measured in the CPWR field surveys (n = 43) were considerably higher, and 25% of samples exceeded the PEL. In the TWI and CPWR datasets, base metal, welding process, and LEV use were important predictors of CrVI concentrations. Only weak-to-moderate correlations were found between total particulate matter and CrVI, suggesting that total particulate matter concentrations are not a good surrogate for CrVI exposure in retrospective studies. Finally, in the controlled welding trials, LEV reduced median CrVI concentrations by 68% (p = 0.02). In conclusion, overexposure to CrVI in stainless steel welding is likely widespread, especially in certain operations such as shielded metal arc welding, which is commonly used in construction. However, exposure could be

  6. Biogenic nano-magnetite and nano-zero valent iron treatment of alkaline Cr(VI) leachate and chromite ore processing residue.

    Science.gov (United States)

    Watts, Mathew P; Coker, Victoria S; Parry, Stephen A; Pattrick, Richard A D; Thomas, Russell A P; Kalin, Robert; Lloyd, Jonathan R

    2015-03-01

    Highly reactive nano-scale biogenic magnetite (BnM), synthesized by the Fe(III)-reducing bacterium Geobacter sulfurreducens, was tested for the potential to remediate alkaline Cr(VI) contaminated waters associated with chromite ore processing residue (COPR). The performance of this biomaterial, targeting aqueous Cr(VI) removal, was compared to a synthetic alternative, nano-scale zero valent iron (nZVI). Samples of highly contaminated alkaline groundwater and COPR solid waste were obtained from a contaminated site in Glasgow, UK. During batch reactivity tests, Cr(VI) removal from groundwater was inhibited by ∼25% (BnM) and ∼50% (nZVI) when compared to the treatment of less chemically complex model pH 12 Cr(VI) solutions. In both the model Cr(VI) solutions and contaminated groundwater experiments the surface of the nanoparticles became passivated, preventing complete coupling of their available electrons to Cr(VI) reduction. To investigate this process, the surfaces of the reacted samples were analyzed by TEM-EDX, XAS and XPS, confirming Cr(VI) reduction to the less soluble Cr(III) on the nanoparticle surface. In groundwater reacted samples the presence of Ca, Si and S was also noted on the surface of the nanoparticles, and is likely responsible for earlier onset of passivation. Treatment of the solid COPR material in contact with water, by addition of increasing weight % of the nanoparticles, resulted in a decrease in aqueous Cr(VI) concentrations to below detection limits, via the addition of ⩾5% w/w BnM or ⩾1% w/w nZVI. XANES analysis of the Cr K edge, showed that the % Cr(VI) in the COPR dropped from 26% to a minimum of 4-7% by the addition of 5% w/w BnM or 2% w/w nZVI, with higher additions unable to reduce the remaining Cr(VI). The treated materials exhibited minimal re-mobilization of soluble Cr(VI) by re-equilibration with atmospheric oxygen, with the bulk of the Cr remaining in the solid fraction. Both nanoparticles exhibited a considerable capacity

  7. Proteomic Characterization of Cr(VI) resistent Bacteria In Wastewater Effluents

    DEFF Research Database (Denmark)

    Koçberber Kılıç, nur; Kjeldal, Henrik; Lolas, Ihab Bishara Yousef;

    The emergence of micropollutants or heavy metals in natural matrices such as soil, sediments and water has been an issue of increasing concern in recent years. Cr(VI) is widely used by industries such as leather tanning, electroplating, wood preservation, manufacture of alloys and corrosion...... inhibitor in conventional and nuclear power plants. Bioremediation, i.e. microbiological decontamination can eliminate these compounds and this study illuminate several mechanisms of the degradation pathways or resistence mechanisms. Bacterial strains able to degrade or tolerate extreme concentrations...

  8. Single-Cell Imaging and Spectroscopic Analyses of Cr(VI) Reduction on the Surface of Bacterial Cells

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Yuanmin; Sevinc, Papatya C.; Belchik, Sara M.; Fredrickson, Jim K.; Shi, Liang; Lu, H. Peter

    2013-01-22

    We investigate single-cell reduction of toxic Cr(VI) by the dissimilatory metal-reducing bacterium Shewanella oneidensis MR-1 (MR-1), an important bioremediation process, using Raman spectroscopy and scanning electron microscopy (SEM) combined with energy-dispersive X-ray spectroscopy (EDX). Our experiments indicate that the toxic and highly soluble Cr(VI) can be efficiently reduced to the less toxic and non-soluble Cr2O3 nanoparticles by MR-1. Cr2O3 is observed to emerge as nanoparticles adsorbed on the cell surface and its chemical nature is identified by EDX imaging and Raman spectroscopy. Co-localization of Cr2O3 and cytochromes by EDX imaging and Raman spectroscopy suggests a terminal reductase role for MR-1 surface-exposed cytochromes MtrC and OmcA. Our experiments revealed that the cooperation of surface proteins OmcA and MtrC makes the reduction reaction most efficient, and the sequence of the reducing reactivity of the MR-1 is: wild type > single mutant @mtrC or mutant @omcA > double mutant (@omcA-@mtrC). Moreover, our results also suggest that the direct microbial Cr(VI) reduction and Fe(II) (hematite)-mediated Cr(VI) reduction mechanisms may co-exist in the reduction processes.

  9. Low temperature reduction of hexavalent chromium by a microbial enrichment consortium and a novel strain of Arthrobacter aurescens

    Directory of Open Access Journals (Sweden)

    Thompson Vicki S

    2006-01-01

    Full Text Available Abstract Background Chromium is a transition metal most commonly found in the environment in its trivalent [Cr(III] and hexavalent [Cr(VI] forms. The EPA maximum total chromium contaminant level for drinking water is 0.1 mg/l (0.1 ppm. Many water sources, especially underground sources, are at low temperatures (less than or equal to 15 Centigrade year round. It is important to evaluate the possibility of microbial remediation of Cr(VI contamination using microorganisms adapted to these low temperatures (psychrophiles. Results Core samples obtained from a Cr(VI contaminated aquifer at the Hanford facility in Washington were enriched in Vogel Bonner medium at 10 Centigrade with 0, 25, 50, 100, 200, 400 and 1000 mg/l Cr(VI. The extent of Cr(VI reduction was evaluated using the diphenyl carbazide assay. Resistance to Cr(VI up to and including 1000 mg/l Cr(VI was observed in the consortium experiments. Reduction was slow or not observed at and above 100 mg/l Cr(VI using the enrichment consortium. Average time to complete reduction of Cr(VI in the 30 and 60 mg/l Cr(VI cultures of the consortium was 8 and 17 days, respectively at 10 Centigrade. Lyophilized consortium cells did not demonstrate adsorption of Cr(VI over a 24 hour period. Successful isolation of a Cr(VI reducing organism (designated P4 from the consortium was confirmed by 16S rDNA amplification and sequencing. Average time to complete reduction of Cr(VI at 10 Centigrade in the 25 and 50 mg/l Cr(VI cultures of the isolate P4 was 3 and 5 days, respectively. The 16S rDNA sequence from isolate P4 identified this organism as a strain of Arthrobacter aurescens, a species that has not previously been shown to be capable of low temperature Cr(VI reduction. Conclusion A. aurescens, indigenous to the subsurface, has the potential to be a predominant metal reducer in enhanced, in situ subsurface bioremediation efforts involving Cr(VI and possibly other heavy metals and radionuclides.

  10. Selective removal of Cr(VI) from aqueous solution by polypyrrole/2,5-diaminobenzene sulfonic acid composite.

    Science.gov (United States)

    Kera, Nazia H; Bhaumik, Madhumita; Ballav, Niladri; Pillay, Kriveshini; Ray, Suprakas Sinha; Maity, Arjun

    2016-08-15

    A polypyrrole/2,5-diaminobenzenesulfonic acid (PPy/DABSA) composite, synthesised by the in situ oxidative polymerization of pyrrole in the presence of DABSA, was studied as an adsorbent for the removal of Cr(VI) from aqueous solution. The structure and morphology of the composite were investigated by ATR-FTIR, FE-SEM, EDX, TGA, XRD and XPS studies. The adsorption of Cr(VI) by PPy/DABSA composite was highly pH dependent and optimum removal was achieved at pH 2. Adsorption of Cr(VI) was confirmed by EDX and XPS studies. The isotherm data fitted the linear Langmuir model well, with a maximum adsorption capacity of 303mg/g at 25°C. Thermodynamic parameters (ΔG°, ΔH° and ΔS°) were calculated using isotherm data and confirmed that the adsorption process was spontaneous and endothermic. Adsorption kinetics was best described by the pseudo-second-order model. The activation energy of the adsorption process suggested that Cr(VI) was chemisorbed by PPy/DABSA composite. PPy/DABSA composite could be used for three consecutive adsorption-desorption cycles without loss of its original adsorption capacity. Highly selective removal of Cr(VI) was observed even when co-existing ions such as Cu(2+), Zn(2+), Ni(2+), Cl(-), SO4(2)(-) and NO3(-) were present in the solution. In summary, the potential of PPy/DABSA composite for remediating industrial wastewater contaminated by Cr(VI) has been demonstrated.

  11. Catalytic role of Cu(II) in the reduction of Cr(VI) by citric acid under an irradiation of simulated solar light.

    Science.gov (United States)

    Li, Ying; Chen, Cheng; Zhang, Jing; Lan, Yeqing

    2015-05-01

    The catalytic role of Cu(II) in the reduction of Cr(VI) by citric acid with simulated solar light was investigated. The results demonstrated that Cu(II) could significantly accelerate Cr(VI) reduction and the reaction obeyed to pseudo zero-order kinetics with respect to Cr(VI). The removal of Cr(VI) was related to the initial concentrations of Cu(II), citric acid, and the types of organic acids. The optimal removal of Cr(VI) was achieved at pH 4, and the rates of Cu(II) photocatalytic reduction of Cr(VI) by organic acids were in the order: tartaric acid (two α-OH groups, two -COOH groups)>citric acid (one α-OH group, three -COOH groups)>malic acid (one α-OH group, two -COOH groups)>lactic acid (one α-OH group, one -COOH group)≫succinic acid (two -COOH groups), suggesting that the number of α-OH was the key factor for the reaction, followed by the number of -COOH. The formation of Cu(II)-citric acid complex could generate Cu(I) and radicals through a pathway of metal-ligand-electron transfer, promoting the reduction of Cr(VI). This study is helpful to fully understanding the conversion of Cr(VI) in the existence of both organic acids and Cu(II) with solar light in aquatic environments.

  12. Effect of Cr(VI) concentration on gas and particle production during iron oxidation in aqueous solutions containing Cl(-) ions.

    Science.gov (United States)

    Ahn, Hyangsig; Jo, Ho Young; Ryu, Ji-Hun; Koh, Yong-Kwon

    2017-02-01

    Zero-valent iron (ZVI) is commonly used as a medium in permeable reactive barriers (PRBs) because of its high reducing ability. The generation of H2 gas in PRBs, however, can decrease the permeability of PRBs and reduce the contact area between the PRB and contaminated groundwater. This study investigated the effect of the initial Cr(VI) concentration ([Cr(VI)init]) in aqueous solutions containing Cl(-) ions on the generation of H2 gas. ZVI chips were reacted in reactors with 0.5-M NaCl solutions with [Cr(VI)init] ranging between 51 and 303 mg/L. The initial pH was set at 3. The oxidation of ZVI chips by Cr(VI) in aqueous solutions containing Cl(-) ions produced H2 gas and particles (Fe(III)-Cr(III)(oxy)hydroxides). The Cr(VI) removal from aqueous solutions increased as the [Cr(VI)init] increased, as did H2 gas generation. The positive effect of [Cr(VI)init] on H2 gas generation might be due to an increase in the redox potential gradient as [Cr(VI)init] increases. This increased gradient would enhance H(+) ion penetration through the passive film (Fe(III)-Cr(III)(oxy)hydroxides), which formed on the ZVI surface, by diffusion from the solution to pits beneath the passive film.

  13. Innovative Use of Cr(VI) Plume Depictions and Pump-and-Treat Capture Analysis to Estimate Risks of Contaminant Discharge to Surface Water at Hanford Reactor Areas

    Energy Technology Data Exchange (ETDEWEB)

    Miller, Chuck W.; Hanson, James P.; Ivarson, Kristine A.; Tonkin, M.

    2015-01-14

    The Hanford Site nuclear reactor operations required large quantities of high-quality cooling water, which was treated with chemicals including sodium dichromate dihydrate for corrosion control. Cooling water leakage, as well as intentional discharge of cooling water to ground during upset conditions, produced extensive groundwater recharge mounds consisting largely of contaminated cooling water and resulted in wide distribution of hexavalent chromium (Cr[VI]) contamination in the unconfined aquifer. The 2013 Cr(VI) groundwater plumes in the 100 Areas cover approximately 6 km2 (1500 acres), primarily in the 100-HR-3 and 100-KR-4 groundwater operable units (OUs). The Columbia River is a groundwater discharge boundary; where the plumes are adjacent to the Columbia River there remains a potential to discharge Cr(VI) to the river at concentrations above water quality criteria. The pump-and-treat systems along the River Corridor are operating with two main goals: 1) protection of the Columbia River, and 2) recovery of contaminant mass. An evaluation of the effectiveness of the pump-and-treat systems was needed to determine if the Columbia River was protected from contamination, and also to determine where additional system modifications may be needed. In response to this need, a technique for assessing the river protection was developed which takes into consideration seasonal migration of the plume and hydraulic performance of the operating well fields. Groundwater contaminant plume maps are generated across the Hanford Site on an annual basis. The assessment technique overlays the annual plume and the capture efficiency maps for the various pump and treat systems. The river protection analysis technique was prepared for use at the Hanford site and is described in detail in M.J. Tonkin, 2013. Interpolated capture frequency maps, based on mapping dynamic water level observed in observation wells and derived water levels in the vicinity of extraction and injection wells

  14. Investigation of Hexavalent Chromium Flux to Groundwater at the 100-C-7:1 Excavation Site

    Energy Technology Data Exchange (ETDEWEB)

    Truex, Michael J.; Vermeul, Vincent R.; Fritz, Brad G.; Mackley, Rob D.; Horner, Jacob A.; Johnson, Christian D.; Newcomer, Darrell R.

    2012-11-16

    Deep excavation of soil has been conducted at the 100-C-7 and 100-C-7:1 waste sites within the 100-BC Operable Unit at the Department of Energy (DOE) Hanford Site to remove hexavalent chromium (Cr(VI)) contamination with the excavations reaching to near the water table. Soil sampling showed that Cr(VI) contamination was still present at the bottom of the 100-C-7:1 excavation. In addition, Cr(VI) concentrations in a downgradient monitoring well have shown a transient spike of increased Cr(VI) concentration following initiation of excavation. Potentially, the increased Cr(VI) concentrations in the downgradient monitoring well are due to Cr(VI) from the excavation site. However, data were needed to evaluate this possibility and to quantify the overall impact of the 100-C-7:1 excavation site on groundwater. Data collected from a network of aquifer tubes installed across the floor of the 100-C-7:1 excavation and from temporary wells installed at the bottom of the entrance ramp to the excavation were used to evaluate Cr(VI) releases into the aquifer and to estimate local-scale hydraulic properties and groundwater flow velocity.

  15. Cr(VI) removal from aqueous solution by thermophilic denitrifying bacterium Chelatococcus daeguensis TAD1 in the presence of single and multiple heavy metals.

    Science.gov (United States)

    Li, Han; Huang, Shaobin; Zhang, Yongqing

    2016-09-01

    Cr(VI) pollution is increasing continuously as a result of ongoing industrialization. In this study, we investigated the thermophilic denitrifying bacterium Chelatococcus daeguensis TAD1, isolated from the biofilm of a biotrickling filter used in nitrogen oxides (NOX) removal, with respect to its ability to remove Cr(VI) from an aqueous solution. TAD1 was capable of reducing Cr(VI) from an initial concentration of 10 mg/L to non-detectable levels over a pH range of 7-9 and at a temperature range of 30-50°C. TAD1 simultaneously removed both Cr(VI) and NO3 (-)-N at 50°C, when the pH was 7 and the initial Cr(VI) concentration was 15 mg/L. The reduction of Cr(VI) to Cr(III) correlated with the growth metabolic activity of TAD1. The presence of other heavy metals (Cu, Zn, and Ni) inhibited the ability of TAD1 to remove Cr(VI). The metals each individually inhibited Cr(VI) removal, and the extent of inhibition increased in a cooperative manner in the presence of a combination of the metals. The addition of biodegradable cellulose acetate microspheres (an adsorption material) weakened the toxicity of the heavy metals; in their presence, the Cr(VI) removal efficiency returned to a high level. The feasibility and applicability of simultaneous nitrate removal and Cr(VI) reduction by strain TAD1 is promising, and may be an effective biological method for the clean-up of wastewater.

  16. On-line Speciation of Cr(III) and Cr(VI) by Flow Injection Analysis With Spectrophotometric Detection and Chemometrics

    DEFF Research Database (Denmark)

    Diacu, Elena; Andersen, Jens Enevold Thaulov

    2003-01-01

    A flow injection system has been developed, for on-line speciation. of Cr(III) and Cr(VI) by the Diphenylcarbazide (DPC) method with H2O2 oxidation followed by spectrophotometric detection at the 550 nm wavelength. The data thus obtained were subjected to a chemometric analysis (PLS), which showe...

  17. Effects of Surface Treatment of Activated Carbon on Its Surface and Cr(VI) Adsorption Characteristics

    Energy Technology Data Exchange (ETDEWEB)

    Park, Soo Jin; Jang, Yu Sin [Advanced Materials Division., Korea Research Institute of Chimical Technology, Taejon (Korea)

    2001-04-01

    In this work, the effect of surface treatments on activated carbons (ACs) has been studied in the context of gas and liquid adsorption behaviors. The chemical solutions used in this experiment were 35% sodium hydroxide, and these were used for the acidic and basic treatments, respectively. The surface properties have been determined by pH, acid-base values, and FT-IR. The adsorption isotherms of Cr(VI) ion on activated carbons have been studied with the 5 mg/l concentration at ambient temperature. N{sub 2} adsorption isotherm characteristics, which include the specific surface area, micro pore volume, and microporosity, were determined by BET and Boer's-plot methods. In case of the acidic treatment of activated carbons, it was observed that the adsorption of Cr(VI) ion was more effective due to the increase acid value (or acidic functional group) of activated carbon surfaces. However, the basic treatment on activated carbons was caused no significant effects, probably due to the decreased specific surface area and total pore volume. 27 refs., 7 figs., 4 tabs.

  18. Chromium(VI) bioremoval by pseudomonas bacteria: role of microbial exudates for natural attenuation and biotreatment of Cr(VI) contamination

    Energy Technology Data Exchange (ETDEWEB)

    Dogan, N.M.; Dodge, C.; Kantar, C.; Gulcan, S.; Yilmaz, B.C.; Mazmanci, M.A.

    2011-02-14

    Laboratory batch and column experiments were conducted to investigate the role of microbial exudates, e.g., exopolymeric substance (EPS) and alginic acid, on microbial Cr(VI) reduction by two different Pseudomonas strains (P. putida P18 and P. aeuroginosa P16) as a method for treating subsurface environment contaminated with Cr(VI). Our results indicate that microbial exudates significantly enhanced microbial Cr(VI) reduction rates by forming less toxic and highly soluble organo-Cr(III) complexes despite the fact Cr(III) has a very low solubility under the experimental conditions studied (e.g., pH 7). The formation of soluble organo-Cr(III) complexes led to the protection of the cells and chromate reductases from inactivation. In systems with no organic ligands, soluble organo-Cr(III) end products were formed between Cr(III) and the EPS directly released by bacteria due to cell lysis. Our results also provide evidence that cell lysis played an important role in microbial Cr(VI) reduction by Pseudomonas bacteria due to the release of constitutive reductases that intracellularly and/or extracellularly catalyzed the reduction of Cr(VI) to Cr(III). The overall results highlight the need for incorporation of the release and formation of organo-Cr(III) complexes into reactive transport models to more accurately design and monitor in situ microbial remediation techniques for the treatment of subsurface systems contaminated with Cr(VI).

  19. Chromium(VI) Bioremoval by Pseudomonas Bacteria: Role of Microbial Exudates for Natural Attenuation and Biotreatment of Cr(VI) Contamination

    Energy Technology Data Exchange (ETDEWEB)

    N Mercan Dogan; C Kantar; S Gulcan; C Dodge; B Coskun Yilmaz; M Ali Mazmanci

    2011-12-31

    Laboratory batch and column experiments were conducted to investigate the role of microbial exudates, e.g., exopolymeric substance (EPS) and alginic acid, on microbial Cr(VI) reduction by two different Pseudomonas strains (P. putida P18 and P. aeuroginosa P16) as a method for treating subsurface environment contaminated with Cr(VI). Our results indicate that microbial exudates significantly enhanced microbial Cr(VI) reduction rates by forming less toxic and highly soluble organo-Cr(III) complexes despite the fact Cr(III) has a very low solubility under the experimental conditions studied (e.g., pH 7). The formation of soluble organo-Cr(III) complexes led to the protection of the cells and chromate reductases from inactivation. In systems with no organic ligands, soluble organo-Cr(III) end products were formed between Cr(III) and the EPS directly released by bacteria due to cell lysis. Our results also provide evidence that cell lysis played an important role in microbial Cr(VI) reduction by Pseudomonas bacteria due to the release of constitutive reductases that intracellularly and/or extracellularly catalyzed the reduction of Cr(VI) to Cr(III). The overall results highlight the need for incorporation of the release and formation of organo-Cr(III) complexes into reactive transport models to more accurately design and monitor in situ microbial remediation techniques for the treatment of subsurface systems contaminated with Cr(VI).

  20. Chromium(VI) bioremoval by Pseudomonas bacteria: role of microbial exudates for natural attenuation and biotreatment of Cr(VI) contamination.

    Science.gov (United States)

    Dogan, Nazime Mercan; Kantar, Cetin; Gulcan, Sibel; Dodge, Cleveland J; Yilmaz, Banu Coskun; Mazmanci, Mehmet Ali

    2011-03-15

    Laboratory batch and column experiments were conducted to investigate the role of microbial exudates, e.g., exopolymeric substance (EPS) and alginic acid, on microbial Cr(VI) reduction by two different Pseudomonas strains (P. putida P18 and P. aeuroginosa P16) as a method for treating subsurface environment contaminated with Cr(VI). Our results indicate that microbial exudates significantly enhanced microbial Cr(VI) reduction rates by forming less toxic and highly soluble organo-Cr(III) complexes despite the fact Cr(III) has a very low solubility under the experimental conditions studied (e.g., pH 7). The formation of soluble organo-Cr(III) complexes led to the protection of the cells and chromate reductases from inactivation. In systems with no organic ligands, soluble organo-Cr(III) end products were formed between Cr(III) and the EPS directly released by bacteria due to cell lysis. Our results also provide evidence that cell lysis played an important role in microbial Cr(VI) reduction by Pseudomonas bacteria due to the release of constitutive reductases that intracellularly and/or extracellularly catalyzed the reduction of Cr(VI) to Cr(III). The overall results highlight the need for incorporation of the release and formation of organo-Cr(III) complexes into reactive transport models to more accurately design and monitor in situ microbial remediation techniques for the treatment of subsurface systems contaminated with Cr(VI).

  1. Preparation of Fe3O4@Ag SERS substrate and its application in environmental Cr(VI) analysis.

    Science.gov (United States)

    Du, Jingjing; Jing, Chuanyong

    2011-06-01

    A novel sensitive and recyclable SERS substrate which can actively concentrate chromate (Cr(VI)) in water and substantially enhance Raman signal was synthesized as uniform Fe(3)O(4)@Ag nanoparticles. The surface morphology, structure, and magnetic properties were characterized using transmission electron microscopy, atomic force microscopy, X-ray powder diffraction, X-ray photoelectron spectroscopy, and vibrating sample magnetometry analysis. The closely spaced Fe(3)O(4)@Ag substrate with a core-shell structure exhibited a 25 nm surface roughness. The high saturation magnetization at 48.35 emu g(-1) enabled the complete and rapid separation of the substrate from the solution. The sensitivity and reproducibility of the substrate were confirmed using a common SERS probe molecule, rhodamine 6G. SERS spectra of Cr(VI) in simulated and real contaminated water showed that the symmetric stretching vibrations of Cr-O occurred at 796 cm(-1). This SERS peak area exhibited a linear dependence (R(2)=0.9992) on the Cr(VI) concentration between 5 and 100 μg L(-1). Coexisting anions such as sulfate, nitrate, chloride, carbonate, and humic acid could decrease the sensitivity of the SERS analysis. However, the adverse effect of the competing ions may be eliminated by proper dilution of the raw sample. This study provides a reliable method for qualitative and quantitative analysis of Cr(VI).

  2. Site-specific functionalization for chemical speciation of Cr(III) and Cr(VI) using polyaniline impregnated nanocellulose composite: equilibrium, kinetic, and thermodynamic modeling

    Science.gov (United States)

    Jain, Priyanka; Varshney, Shilpa; Srivastava, Shalini

    2017-07-01

    Site-specific functionalizations are the emergent attention for the enhancement of sorption latent of heavy metals. Limited chemistry has been applied for the fabrication of diafunctionalized materials having potential to tether both environmentally stable oxidation states of chromium (Cr(III) and Cr(VI). Polyaniline impregnated nanocellulose composite (PANI-NCC) has been fabricated using click chemistry and explored for the removal of Cr(III) and Cr(VI) from hydrological environment. The structure, stability, morphology, particle size, surface area, hydrophilicity, and porosity of fabricated PANI-NCC were characterized comprehensively using analytical techniques and mathematical tools. The maximum sorption performance of PANI-NCC was procured for (Cr(III): 47.06 mg g-1; 94.12 %) and (Cr(VI): 48.92 mg g-1; 97.84 %) by equilibrating 0.5 g sorbent dose with 1000 mL of 25 mg L-1 chromium conc. at pH 6.5 and 2.5 for Cr(III) and Cr(VI), respectively. The sorption data showed a best fit to the Langmuir isotherm and pseudo-second-order kinetic model. The negative value of ∆ G° (-8.59 and -11.16 kJ mol-1) and ∆ H° (66.46 × 10-1 and 17.84 × 10-1 kJ mol-1), and positive value of ∆ S° (26.66 and 31.46 J mol-1K-1) for Cr(III) and Cr(VI), respectively, reflect the spontaneous, feasibility, and exothermic nature of the sorption process. The application of fabricated PANI-NCC for removing both the forms of chromium in the presence of other heavy metals was also tested at laboratory and industrial waste water regime. These findings open up new avenues in the row of high performance, scalable, and economic nanobiomaterial for the remediation of both forms of chromium from water streams.

  3. Impact of Cr(VI) on P removal performance in enhanced biological phosphorus removal (EBPR) system based on the anaerobic and aerobic metabolism.

    Science.gov (United States)

    Fang, Jing; Sun, Pei-de; Xu, Shao-juan; Luo, Tao; Lou, Ju-qing; Han, Jing-yi; Song, Ying-qi

    2012-10-01

    Influence of Cr(VI) on P removal in enhanced biological phosphorus removal (EBPR) system was investigated with respect to the composition of poly-phosphate-accumulating organisms (PAOs) and glycogen accumulating organisms (GAOs), the transformation of poly-β-hydroxyalkanoates (PHA) and glycogen, enzymes' activities, and the intracellular Cr. Whether EBPR system could revive after Cr(VI) shock was also explored. Results showed P removal performance was completely inhibited by Cr(VI) with the concentration more than 5 mg L(-1). PAOs were more sensitive to Cr(VI) than GAOs and the other bacteria were. PHA consumption, glycogen synthesis and adenylate kinase's activity had been inhibited by 5 mg L(-1) Cr(VI). Both adenylate kinase's activity and P removal efficiency were negatively correlated with the intracellular Cr. Recovery experiments revealed that P removal performance with 5 mg L(-1) Cr(VI) shock could revive after a 2-day recovery treatment, while systems with high level Cr(VI) (20 and 60 mg L(-1)) shock could not. Copyright © 2012 Elsevier Ltd. All rights reserved.

  4. Removal of Cr(VI Species from Aqueous Solution by Different Nanoporous Materials

    Directory of Open Access Journals (Sweden)

    Mohammad Ghashghaee

    2016-10-01

    Full Text Available Background: The removal of toxic metals from sewage and wastewaters is one of the most important concerns in the twenty first century. The removal of poisonous Cr(VI from aqueous solution by different low-cost available nanoporous adsorbents was investigated in the present study. Methods: Fumed silica, bentonite (BN, hydrotalcite (HT, MCM-41, Na-Y, mordenite (MOR and SAPO-34 were used at different adsorbent-to-metal ion ratios. Two predominant species of Cr were considered including chromate and hydrogen chromate ions. Results: Both HT and Na-Y adsorbed the toxic bichromate ions more favorably than other sorbents. Overall, the efficiency of the Cr removal followed the sequence of HT > SAPO-34 > MOR > MCM-41 > Na-Y > silica > BN. Because of its surface chemistry, HT with an uptake of 65.2 mg/g showed the highest toxic abatement among the seven adsorbents investigated under the acidic conditions, followed by the microporous materials SAPO-34 and MOR with uptakes of 41.2 and 41.0 mg/g, respectively. Conclusion: Both HT and Na-Y adsorbed the toxic bichromate ions more favorably than other sorbents. The high pore volume and the apparent surface area of a non-functionalized MCM-41 were not effective in the adsorption of Cr compounds. Overall, HT was the best choice owing to its appropriate surface chemistry with respect to the Cr oxygenates.

  5. Synergy of photocatalysis and adsorption for simultaneous removal of Cr(VI) and Cr(III) with TiO₂ and titanate nanotubes.

    Science.gov (United States)

    Liu, Wen; Ni, Jinren; Yin, Xiaochen

    2014-04-15

    An one-step efficient simultaneous removal of Cr(VI) and Cr(III) was achieved with mixture of TiO₂ and titanate nanotubes (TNTs). Unlike the conventional two-step Cr removal with a first photocatalytic reduction of Cr(VI) and a subsequent adsorption of Cr(III), the proposed single process significantly reduced reaction time (over 50%). The synergy of photocatalysis and adsorption played an important role in enhancing Cr removal process. The synergetic mechanism was interpreted and indirectly confirmed with H₂O₂ variation during photocatalysis. The instant transfer of the reduced Cr from TiO₂ surface to TNTs interlayer greatly promoted the release of photocatalytic sites of TiO₂, which in turn considerably enhanced photocatalytic activity of TNTs by inhibiting electron-hole pairs recombination. The optimum condition for the whole process was at pH 5. Adsorption of Cr(III) was primarily in the interlayer of TNTs at pH ≤ 5. However, higher pH would lead to precipitation of Cr(OH)₃ onto TNTs as observed by X-ray photoelectron spectroscopy (XPS). Addition of Ca(2+) could promoted photocatalysis owing to its ionic bridging function and form of ≡TiOH(+)-Cr(VI)-Ca(2+)-Cr(VI) linkages, while SO₄(2-) only slightly inhibited photo-reduction of Cr(VI), indicating good synergy of photocatalysis and adsorption even at high ionic strength of electrolyte. Besides, the desorbed TNTs could be easily regenerated by remedying the damaged tubular structure and reused for Cr removal with excellent performance. The outstanding synergetic effects with essential explanation of the mechanism make this study not only fundamentally important but also potentially practical applicable.

  6. Impact of wastewater derived dissolved organic carbon on reduction, mobility, and bioavailability of As(V) and Cr(VI) in contaminated soils.

    Science.gov (United States)

    Kunhikrishnan, Anitha; Choppala, Girish; Seshadri, Balaji; Wijesekara, Hasintha; Bolan, Nanthi S; Mbene, Kenneth; Kim, Won-Il

    2017-01-15

    In this work, the effects of various wastewater sources (storm water, sewage effluent, piggery effluent, and dairy effluent) on the reduction, and subsequent mobility and bioavailability of arsenate [As(V)] and chromate [Cr(VI)] were compared using both spiked and field contaminated soils. Wastewater addition to soil can increase the supply of carbon, nutrients, and stimulation of microorganisms which are considered to be important factors enhancing the reduction of metal(loid)s including As and Cr. The wastewater-induced mobility and bioavailability of As(V) and Cr(VI) were examined using leaching, earthworm, and soil microbial activity tests. The rate of reduction of As(V) was much less than that of Cr(VI) both in the presence and absence of wastewater addition. Wastewater addition increased the reduction of both As(V) and Cr(VI) compared to the control (Milli-Q water) and the effect was more pronounced in the case of Cr(VI). The leaching experiment indicated that Cr(VI) was more mobile than As(V). Wastewater addition increased the mobility and bioavailability of As(V), but had an opposite effect on Cr(VI). The difference in the mobility and bioavailability of Cr(VI) and As(V) between wastewater sources can be attributed to the difference in their dissolved organic carbon (DOC) content. The DOC provides carbon as an electron donor for the reduction of As(V) and Cr(VI) and also serves as a complexing agent thereby impacting their mobility and bioavailability. The DOC-induced reduction increased both the mobility and bioavailability of As, but it caused an opposite effect in the case of Cr.

  7. Characterization of the effect of Cr(VI) on humoral innate immunity using Drosophila melanogaster.

    Science.gov (United States)

    Pragya, P; Shukla, A K; Murthy, R C; Abdin, M Z; Kar Chowdhuri, D

    2015-11-01

    With the advancement of human race, different anthropogenic activities have heaped the environment with chemicals that can cause alteration in the immune system of exposed organism. As a first line of barrier, the evolutionary conserved innate immunity is crucial for the health of an organism. However, there is paucity of information regarding in vivo assessment of the effect of environmental chemicals on innate immunity. Therefore, we examined the effect of a widely used environmental chemical, Cr(VI), on humoral innate immune response using Drosophila melanogaster. The adverse effect of Cr(VI) on host humoral response was characterized by decreased gene expression of antimicrobial peptides (AMPs) in the exposed organism. Concurrently, a significantly decreased transcription of humoral pathway receptors (Toll and PGRP) and triglyceride level along with inhibition of antioxidant enzyme activities were observed in exposed organism. This in turn weakened the immune response of exposed organism that was manifested by their reduced resistance against bacterial infection. In addition, overexpression of the components of humoral immunity particularly Diptericin benefits Drosophila from Cr(VI)-induced humoral immune-suppressive effect. To our knowledge, this is the first report regarding negative impact of an environmental chemical on humoral innate immune response of Drosophila along with subsequent protection by AMPs, which may provide novel insight into host-chemical interactions. Also, our data validate the utility and sensitivity of Drosophila as a model that could be used for screening the possible risk of environmental chemicals on innate immunity with minimum ethical concern that can be further extrapolated to higher organisms. © 2014 Wiley Periodicals, Inc.

  8. Geophysical Monitoring of Cr(VI) Bioreduction at the Hanford 100H Site

    Science.gov (United States)

    Hubbard, S.; Peterson, J.; Chen, J.; Williams, K. H.; Conrad, M.; Faybishenko, B.; Long, P.; Willett, A.; Hazen, T.

    2005-12-01

    The efficacy of in-situ remediation of contaminated groundwater using injected chemical or biological amendments depends on the ability to effectively distribute the amendments within the contaminated aquifer and to understand the role of heterogeneity on remediation processes. In this study, we investigate the use of geophysical data for providing such information in association with a Cr(VI) bioreduction experiment at the Hanford 100H Site in Southeastern Washington State. Seismic and radar tomographic data were initially used with borehole flowmeter data in a principle components analysis to estimate hydrogeological zonation at the site. Subsequently, pumping was initiated to create a steady state flowfield between an injection and monitoring well, and a slow-release polylactate amendment (HRCTM , Regenesis, Ltd) was injected into a sandy formation to reduce Cr(VI) into insoluble Cr(III) complexes. Laboratory analyses were performed to assess the expected geophysical responses to the injectate, as well as to the formation of gasses and precipitates that often form during such biostimulation procedures. Field-scale, time-lapse tomographic data as well as wellbore geochemical data were collected during and after the cessation of pumping. These datasets were jointly used to assess the spatio-temporal changes in the subsurface system associated with the biostimulation, such as the distribution of an amendment 'plume' and a reaction halo. In agreement with the laboratory experiments, the field-scale geophysical data were useful for detecting chemical transformations associated with the biostimulation. The study also indicated that heterogeneity plays a role in controlling both the amendment distribution and the biostimulation processes. This study suggests that high resolution, field-scale, cross-borehole geophysical techniques hold significant potential for monitoring biostimulation efficacy and for investigating the role of heterogeneity on remediation processes.

  9. Colloidal Surface Active Maghemite Nanoparticles for Biologically Safe Cr(VI) Remediation: from Core-Shell Nanostructures to Pilot Plant Development.

    Science.gov (United States)

    Magro, Massimiliano; Domeneghetti, Stefania; Baratella, Davide; Jakubec, Petr; Salviulo, Gabriella; Bonaiuto, Emanuela; Venier, Paola; Malina, Ondřej; Tuček, Jiří; Ranc, Václav; Zoppellaro, Giorgio; Zbořil, Radek; Vianello, Fabio

    2016-09-26

    The present study is aimed at the exploration of achievable improvements for Cr(VI) ex situ and in situ water remediation by using novel naked colloidal maghemite (γ-Fe2 O3 ) nanoparticles (surface active maghemite nanoparticles, SAMNs). The reliability of SAMNs for Cr(VI) binding and removal was demonstrated, and SAMN@Cr(VI) complex was characterized, as well as the covalent nature of the absorption was unequivocally proved. SAMNs were structurally and magnetically well conserved after Cr(VI) binding. Thus, in consideration of their affinity for Cr(VI) , SAMNs were exploited in a biological model system, mimicking a real in situ application. The assay evidenced a progressive reduction of revertant colonies of Salmonella typhimurium TA100 strain, as maghemite nanoparticles concentration increased, till the complete suppression of Cr(VI) mutagen effect. Finally, an automatic modular pilot system for continuous magnetic removal and recovery of Cr(VI) from water is proposed. SAMNs, thanks to their colloidal, binding, and catalytic properties, represent a promising tool as a reliable nanomaterial for water remediation by Cr(VI) . © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  10. Removal of As(V), Cr(III) and Cr(VI) from aqueous environments by poly(acrylonitril-co-acrylamidopropyl-trimethyl ammonium chloride)-based hydrogels.

    Science.gov (United States)

    Dudu, Tuba Ersen; Sahiner, Mehtap; Alpaslan, Duygu; Demirci, Sahin; Aktas, Nahit

    2015-09-15

    Cationic poly(Acrylonitril-co-Acrylamidopropyl-trimethyl Ammonium Chloride) (p(AN-co-APTMACl)) hydrogels in bulk were synthesized by using acrylonitrile (AN) and 3-acrylamidopropyl-trimethyl ammonium chloride (APTMACl) as monomers. The prepared hydrogels were exposed to amidoximation reaction to replace hydrophobic nitrile groups with hydrophilic amidoxime groups that have metal ion binding ability. Those replacements were increased the hydrogels absorption capacity for As(V) and Cr(VI). Langmuir and Freundlich isotherms equations were utilized to obtain the best-fitted isotherm model for the absorption of the ions at different metal ion concentrations. The absorption data of As(V) ion were fitted well to Freundlich isotherm while those of Cr(VI) and Cr(III) ions were fitted well to Langmuir isotherm. The maximum absorption of poly(3-acrylamidopropyl-trimethyl ammonium chloride (p(APTMACl)) and amid-p(AN-co-APTMACl) macro gels were 22.39 mg and 21.83 mg for As(V), and 30.65 mg and 18.16 mg for Cr(VI) ion per unit gram dried gel, respectively. Kinetically, the absorption behaviors of Cr(III) and Cr(VI) ions were fitted well to a pseudo 2nd-order kinetic model and those of As(V) ions were fitted well to a pseudo 1st order kinetic model.

  11. IN VITRO Cr(VI SPECIATION IN SYNTHETIC SALIVA AFTER RELEASING FROM ORTHODONTIC BRACKETS USING SILICA-APTES SEPARATION AND GF AAS DETERMINATION

    Directory of Open Access Journals (Sweden)

    Maciel S. Luz

    Full Text Available A method for Cr(VI speciation in synthetic saliva after releasing from orthodontic brackets, using silica nanoparticles organofunctionalized with (3-aminopropyltriethoxysilane (APTES for Cr(III/Cr(VI separation and GF AAS determination is proposed. Under the optimized conditions, Cr(VI speciation was performed using 150 mg of silica organofunctionalized with 2.0% (v v-1 of APTES at pH 8. It was observed different sensitivity when calibrations of GF AAS were performed using Cr(III or Cr(VI as standard solutions. Consequently, calibrations using stoichiometric mixtures (Cr(III + Cr(VI were used for total Cr determination and calibration using Cr(VI was used only for the determination of this specie. The reliability of the proposed silica-APTES separation procedure and GF AAS determination was checked by addition of both species in synthetic saliva. Recoveries ranging from 97 to 110% were obtained. The repeatability, based on the relative standard deviation (RSD inter days was less than 6%. A corrosion test was carried out on 20 orthodontic brackets from two different models, after immersion in synthetic saliva (pH=6.0 at 37 °C with agitation (125 rpm for 24 h. It was observed that about 40% of the total chromium released from the analyzed orthodontic brackets was Cr(VI.

  12. Selective removal of Cr(VI) from aqueous solution by polypyrrole/2,5-diaminobenzene sulfonic acid composite

    CSIR Research Space (South Africa)

    Kera, Nazia H

    2016-08-01

    Full Text Available was spontaneous and endothermic. Adsorption kinetics was best described by the pseudo-second-order model. The activation energy of the adsorption process suggested that Cr(VI) was chemisorbed by PPy/DABSA composite. PPy/DABSA composite could be used for three...

  13. Highly effective removal of toxic Cr(VI) from wastewater using sulfuric acid-modified avocado seed

    CSIR Research Space (South Africa)

    Bhaumik, M

    2014-01-01

    Full Text Available to 200 °C. The presence of oxo-functional groups on the ASSA surface was confirmed by ATR-FTIR and XPS studies. Adsorption of Cr(VI) onto ASSA was highly pH dependent and found to be an optimum at pH 2.0. Adsorption isotherm results suggested...

  14. In situ long-term reductive bioimmobilization of Cr(VI) in groundwater using hydrogen release compound.

    Science.gov (United States)

    Faybishenko, Boris; Hazen, Terry C; Long, Philip E; Brodie, Eoin L; Conrad, Mark E; Hubbard, Susan S; Christensen, John N; Joyner, Dominique; Borglin, Sharon E; Chakraborty, Romy; Williams, Kenneth H; Peterson, John E; Chen, Jinsong; Brown, Shaun T; Tokunaga, Tetsu K; Wan, Jiamin; Firestone, Mary; Newcomer, Darrell R; Resch, Charles T; Cantrell, Kirk J; Willett, Anna; Koenigsberg, Stephen

    2008-11-15

    The results of a field experiment designed to test the effectiveness of a novel approach for long-term, in situ bioimmobilization of toxic and soluble Cr(VI) in groundwater using a hydrogen release compound (HRC)--a slow release glycerol polylactate--are described. The field experiment was conducted at the Hanford Site (Washington), a U.S. Department of Energy nuclear production facility, using a combination of hydrogeological, geophysical, geochemical, and microbiological measurements and analyses of water samples and sediments. The results of this experiment show that a single HRC injection into groundwater stimulates an increase in biomass, a depletion of terminal electron acceptors O2, NO3-, and SO4(2-), and an increase in Fe2+, resulting in a significant decrease in soluble Cr(VI). The Cr(VI) concentration has remained below the background concentration in the downgradient pumping/ monitoring well, and below the detection limit in the injection well for more than 3 years after the HRC injection. The degree of sustainability of Cr(VI) reductive bioimmobilization under different redox conditions at this and other contaminated sites is currently under study.

  15. Grafting of β-cyclodextrin to magnetic graphene oxide via ethylenediamine and application for Cr(VI) removal.

    Science.gov (United States)

    Wang, Hui; Liu, Yun-guo; Zeng, Guang-ming; Hu, Xin-jiang; Hu, Xi; Li, Ting-ting; Li, Hua-ying; Wang, Ya-qin; Jiang, Lu-hua

    2014-11-26

    A novel β-cyclodextrin (β-CD) polymer adsorbent named β-cyclodextrin/ethylenediamine/magnetic graphene oxide (CD-E-MGO) was synthesized for decontamination of Cr(VI) from aqueous solution. The sorption kinetics, isotherms and thermodynamics, as well as the effects of pH, aniline and ionic strength on the sorption process were investigated. The results indicated that CD-E-MGO could effectively remove Cr(VI) from aqueous solution and the sorption data could be well described by pseudo-second-order and Langmuir models. The intraparticle diffusion study indicated that intraparticle diffusion was not the only rate-limiting step. Thermodynamic parameters revealed that the sorption reaction was an endothermic and spontaneous process. The decontamination of Cr(VI) was influenced by solution pH and ionic strength. In the system with aniline, the Cr(VI) sorption was improved at low pH values but reduced at high pH values. These results are important for estimating and optimizing the removal of metal ions by CD-E-MGO composite.

  16. Use of a Ferrous Sulfate - Sodium Dithionite Blend to Treat a Dissolved Phase Cr(VI) Plume

    Science.gov (United States)

    A field study was conducted to evaluate the use of a combination of sodium dithionite and ferrous sulfate in creating an in situ redox zone for treatment of a dissolved phase Cr(VI) plume at a former industrial site. The reductant blend was injected into the path of a dissolved ...

  17. Study of the adsorption of Cr(VI) by tannic acid immobilised powdered activated carbon from micro-polluted water in the presence of dissolved humic acid.

    Science.gov (United States)

    Gong, Xujin; Li, Weiguang; Wang, Ke; Hu, Jinhua

    2013-08-01

    The adsorption of Cr(VI) (0.500 mg/L) onto food-grade tannic-acid immobilised powdered activated carbon (TA-PAC) in the presence of dissolved humic acid (DHA) was investigated at 280 K as a function of pH, along with the adsorption capacities and the adsorption isotherms for chromium ions. The results showed that the presence of DHA improved the adsorption capacities of Cr(VI) and its reduction product (Cr(III)) over a wide pH range (4.0-8.0). The main mechanism for metal-DHA complexation in the Cr(VI) system was the reduction of Cr(VI) followed by complexation between Cr(III) and DHA. The Freundlich isotherms yielded the best fits to all data (R(2)=0.9951, qm=5.639 mg/g) in the presence of DHA. The adsorption mechanisms of Cr(VI) onto TA-PAC in the presence of DHA were summarized into three categories: (i) binding by anion adsorption, (ii) Cr(VI) reduction followed by Cr(III) adsorption, and (iii) adsorption of Cr(III)-DHA complexes.

  18. Radiation induced environmental remediation of Cr(VI) heavy metal in aerated neutral solution under simulated industrial effluent

    Energy Technology Data Exchange (ETDEWEB)

    Djouider, Fathi; Aljohani, Mohammed S. [King Abdulaziz Univ., Jeddah (Saudi Arabia). Nuclear Engineering Dept.

    2017-08-01

    Cr(VI) compounds are major water contaminants in most industrial effluents, due to their carcinogenicity, while Cr(III) is an important element for human metabolism. In a previous work, we showed that Cr(VI) was radiolytically reduced to Cr(III) by the CO{sub 2}{sup -.} radical at pH 3 N{sub 2}O-saturated solution in the presence of formate. Here in the present work, this removal was investigated by steady state irradiation and pulse radiolysis in aerated solution at neutral pH, which is close to natural conditions in most wastewaters, where the reducing agent is the superoxide radical anion O{sub 2}{sup -.} The degradation of Cr(VI) increased linearly with the absorbed dose and was significantly enhanced by the added formate but not by the radiolitically produced hydrogen peroxide at this pH. The rate constant for this reduction was found to be 1.28 x 10{sup 8} M{sup -1} s{sup -1} and the absorption spectrum of Cr(V) transient species was obtained. A partial recovery of Cr(VI) is observed over a period of ca. 5 ms following a second order kinetics with a rate constant 8.0 x 10{sup 6} M{sup -1} s{sup -1}. These outcomes suggest that gamma-irradiation of Cr(VI)-contaminated wastewaters and industrial effluents in presence of formate can be simple, effective and economical means for the remediation of this major contaminant.

  19. One-pot synthesis of Mn-doped TiO2 grown on graphene and the mechanism for removal of Cr(VI) and Cr(III).

    Science.gov (United States)

    Chen, Zengping; Li, Yaru; Guo, Meng; Xu, Fengyun; Wang, Peng; Du, Yu; Na, Ping

    2016-06-05

    Mn-doped TiO2 grown on reduced graphene oxide(rGO) was synthesized by one-pot hydrothermal method and the photocatalytic removal of Cr by the material was investigated under sunlight. The materials were characterized by a combination of scanning electron microscopy, transmission electron microscopy, X-ray diffraction, thermogravimetric analysis, Brunauer-Emmett-Teller method, UV-vis diffuse reflectance spectra, photoluminescence spectra, electrochemical impedance spectroscopy and X-ray photoelectron spectroscopy. Cr(total) removal efficiency of the material is 97.32% in 30min and 99.02% in 60min under sunlight irradiation, as the initial concentration of Cr(VI) is 20mg/L. The high photocatalytic activity under visible light is considered mainly due to the Mn-doping, and rGO plays an important role in the synergetic effect of adsorption and photocatalysis to sustain the high efficient removal of Cr(VI) and Cr(III). Cr(VI) adsorbed on the surface of rGO is reduced to Cr(III) by photo electrons which are transported through rGO, and the reaction product Cr(III) continues to be adsorbed. The process contributes to the release of abundant photocatalytic sites of Mn-TiO2 and improves photocatalytic efficiency. The excellent adsorption and photocatalytic effect with the explanation of the synergetic mechanism are very useful not only for fundamental research but also for the potential practical applications.

  20. Epithelial–mesenchymal transition during oncogenic transformation induced by hexavalent chromium involves reactive oxygen species-dependent mechanism in lung epithelial cells

    Energy Technology Data Exchange (ETDEWEB)

    Ding, Song-Ze, E-mail: dingsongze@hotmail.com [Department of Internal Medicine, Henan Provincial People’s Hospital, Zhengzhou University, Wei-Wu Road, Zhengzhou, Henan 450000 (China); Graduate Center for Toxicology, College of Medicine, University of Kentucky, Lexington, KY 40536 (United States); Yang, Yu-Xiu; Li, Xiu-Ling [Department of Internal Medicine, Henan Provincial People’s Hospital, Zhengzhou University, Wei-Wu Road, Zhengzhou, Henan 450000 (China); Michelli-Rivera, Audrey [Graduate Center for Toxicology, College of Medicine, University of Kentucky, Lexington, KY 40536 (United States); Han, Shuang-Yin [Department of Internal Medicine, Henan Provincial People’s Hospital, Zhengzhou University, Wei-Wu Road, Zhengzhou, Henan 450000 (China); Wang, Lei; Pratheeshkumar, Poyil; Wang, Xin; Lu, Jian; Yin, Yuan-Qin; Budhraja, Amit; Hitron, Andrew J. [Graduate Center for Toxicology, College of Medicine, University of Kentucky, Lexington, KY 40536 (United States)

    2013-05-15

    Hexavalent chromium [Cr(VI)] is an important human carcinogen associated with pulmonary diseases and lung cancer. Exposure to Cr(VI) induces DNA damage, cell morphological change and malignant transformation in human lung epithelial cells. Despite extensive studies, the molecular mechanisms remain elusive, it is also not known if Cr(VI)-induced transformation might accompany with invasive properties to facilitate metastasis. We aimed to study Cr(VI)-induced epithelial–mesenchymal transition (EMT) and invasion during oncogenic transformation in lung epithelial cells. The results showed that Cr(VI) at low doses represses E-cadherin mRNA and protein expression, enhances mesenchymal marker vimentin expression and transforms the epithelial cell into fibroblastoid morphology. Cr(VI) also increases cell invasion and promotes colony formation. Further studies indicated that Cr(VI) uses multiple mechanisms to repress E-cadherin expression, including activation of E-cadherin repressors such as Slug, ZEB1, KLF8 and enhancement the binding of HDAC1 in E-cadherin gene promoter, but DNA methylation is not responsible for the loss of E-cadherin. Catalase reduces Cr(VI)-induced E-cadherin and vimentin protein expression, attenuates cell invasion in matrigel and colony formation on soft agar. These results demonstrate that exposure to a common human carcinogen, Cr(VI), induces EMT and invasion during oncogenic transformation in lung epithelial cells and implicate in cancer metastasis and prevention. - Graphical abstract: Epithelial–mesenchymal transition during oncogenic transformation induced by hexavalent chromium involves reactive oxygen species-dependent mechanisms in lung epithelial cells. - Highlights: • We study if Cr(VI) might induce EMT and invasion in epithelial cells. • Cr(VI) induces EMT by altering E-cadherin and vimentin expression. • It also increases cell invasion and promotes oncogenic transformation. • Catalase reduces Cr(VI)-induced EMT, invasion and

  1. Progress in Cr(VI) Adsorption Agents%Cr(VI)吸附剂研究进展

    Institute of Scientific and Technical Information of China (English)

    阮子宁; 刘强; 姚金水; 刘钦泽

    2015-01-01

    Heavy metal pollution not only threatens the sustainable development of the natural environment, but also is a severe challenge to human health. Because of long duration and great harm for environment, Cr(VI) has attracted more and more attention. For providing a reference to solve the problem of environmental pollution, especially water pollution problem caused by heavy metal chromium ions, the classification and characteristics of Cr(VI) adsorption materials, especially the application of polymer materials in adsorption and separation of Cr(VI) are introduced, and the Cr(VI) adsorption kinetics models and the isothermal equations of adsorption process with Langmuir model, Freundlich model as the examples are described briefly.%重金属污染不仅威胁着自然环境的持续发展,也对人类健康提出了严峻的考验。其中,六价铬因为环境污染持续久,危害大,更是得到各国研究者的重视。各种吸附材料对于六价铬的移除能力以及移除机理不尽相同。本文主要介绍了 Cr(VI)吸附材料分类及其特点,重点分析了聚合物吸附材料在吸附和分离 Cr(VI)方面的应用进展,并简要介绍了 Cr(VI)吸附过程中的吸附动力学模型和等温方程式,以 Langmuir 和 Freundlich模型等为例加以说明,为解决重金属铬离子引起的环境污染尤其水污染问题提供借鉴。

  2. Application of Chromium Stable Isotopes to the Evaluation of Cr(VI) Contamination in Groundwater and Rock Leachates from Central Euboea, the Assopos Basin and Thebes Valley (Greece)

    Science.gov (United States)

    Frei, R.; Frei, K. M.; Economou-Eliopoulos, M.; Atsarou, C.; Koilakos, D.

    2014-12-01

    In order to identify the source(s) of toxic Cr(VI) prevalent in drinking and irrigation waters of Central Euboea (CE), the Assopos Basin (AB) and the Thebes Valley (TV;Greece), we have analyzed stable Cr isotopes, together with major and trace elements in porous, karstic and ultramafic mélange-hosted aquifers and groundwaters, ultramafic rocks from the hinterlands and soil samples from cultivated sites of this region. In addition we complemented our data with experimentally produced water leachates of rocks and soils. Mg/Ca ratios >1 in much of the water samples indicate the influence of ultramafic rocks which dominate the geology on the geochemical composition of the groundwaters. Elevated Cr(VI) concentrations in experimental soil leachates, compared to those in rock pulp leachates, can be potentially explained by the presence of larger amounts of Fe(II) and lower amounts of Mn(IV) in the country rocks. Factor analysis on the 17 water samples from TV indicates a strong relationship between Na, Cl-, and Cr(VI), and also points to an aversion of Cr(VI) to nitrates (fertilizer-sewage sourced) and its independency from Mg and SiO2. Assuming that redox processes produce significant Cr isotope fractionation (groundwater δ53Cr values range between +0.62 and +1.99‰), the compilation of the analytical data suggests that the dominant cause of Cr isotope fractionation is post-mobilization reduction of Cr(VI). However, the lack of a clear negative relationship between Cr(VI) concentrations and δ53Cr values may reflect that other processes complicate this interpretation. The variation in δ53Cr values, together with the results from the experimentally produced ultramafic rock pulp leachates, imply initial oxidative mobilization of Cr(VI) from the ultramafic host rocks, followed by reductive processes, as the main reason for the toxicity of the groundwaters. Using a Rayleigh distillation model and different fractionation factors of Cr(VI) reduction valid for aqueous Fe

  3. Sorption of Cr(VI) by Amberlite XAD-7 resin impregnated with brilliant green and its determination by quercetin as a selective spectrophotometric reagent.

    Science.gov (United States)

    Hosseini, Mohammad Saeid; Hosseini-Bandegharaei, Ahmad; Raissi, Haidar; Belador, Foroogh

    2009-09-30

    A new chelating polymeric sorbent as an extractant-impregnated resin (EIR) has been developed using brilliant green (BG) and Amberlite XAD-7 resin. The BG-impregnated resin showed superior binding affinity for Cr(VI) in the presence of many co-existing ions and no considerable interference was observed. The influence of various physicochemical parameters on the recovery of Cr(VI) were optimized by both static and dynamic methods. The Langmuir adsorption isotherm gave a satisfactory fit of the equilibrium data. The kinetic studies performed for Cr(VI) sorption revealed that 93%, which confirmed accuracy of the measurements.

  4. Origin of hexavalent chromium in groundwater

    DEFF Research Database (Denmark)

    Kazakis, N.; Kantiranis, N.; Kalaitzidou, K.

    2017-01-01

    Hexavalent chromium constitutes a serious deterioration factor for the groundwater quality of several regions around the world. High concentrations of this contaminant have been also reported in the groundwater of the Sarigkiol hydrological basin (near Kozani city, NW Greece). Specific interest....... Accordingly, detailed geochemical, mineralogical, hydro-chemical, geophysical and hydrogeological studies were performed on the rocks, soils, sediments and water resources of this basin. Cr(VI) concentrations varied in the different aquifers, with the highest concentration (up to 120 μg L− 1) recorded...

  5. Low temperature reduction of hexavalent chromium by a microbial enrichment consortium and a novel strain of Arthrobacter aurescens

    OpenAIRE

    Thompson Vicki S; Apel William A; Horton Rene' N; Sheridan Peter P

    2006-01-01

    Abstract Background Chromium is a transition metal most commonly found in the environment in its trivalent [Cr(III)] and hexavalent [Cr(VI)] forms. The EPA maximum total chromium contaminant level for drinking water is 0.1 mg/l (0.1 ppm). Many water sources, especially underground sources, are at low temperatures (less than or equal to 15 Centigrade) year round. It is important to evaluate the possibility of microbial remediation of Cr(VI) contamination using microorganisms adapted to these l...

  6. Disruption of putrescine biosynthesis in Shewanella oneidensis enhances biofilm cohesiveness and performance in Cr(VI) immobilization.

    Science.gov (United States)

    Ding, Yuanzhao; Peng, Ni; Du, Yonghua; Ji, Lianghui; Cao, Bin

    2014-02-01

    Although biofilm-based bioprocesses have been increasingly used in various applications, the long-term robust and efficient biofilm performance remains one of the main bottlenecks. In this study, we demonstrated that biofilm cohesiveness and performance of Shewanella oneidensis can be enhanced through disrupting putrescine biosynthesis. Through random transposon mutagenesis library screening, one hyperadherent mutant strain, CP2-1-S1, exhibiting an enhanced capability in biofilm formation, was obtained. Comparative analysis of the performance of biofilms formed by S. oneidensis MR-1 wild type (WT) and CP2-1-S1 in removing dichromate (Cr2O7(2-)), i.e., Cr(VI), from the aqueous phase showed that, compared with the WT biofilms, CP2-1-S1 biofilms displayed a substantially lower rate of cell detachment upon exposure to Cr(VI), suggesting a higher cohesiveness of the mutant biofilms. In addition, the amount of Cr(III) immobilized by CP2-1-S1 biofilms was much larger, indicating an enhanced performance in Cr(VI) bioremediation. We further showed that speF, a putrescine biosynthesis gene, was disrupted in CP2-1-S1 and that the biofilm phenotypes could be restored by both genetic and chemical complementations. Our results also demonstrated an important role of putrescine in mediating matrix disassembly in S. oneidensis biofilms.

  7. A novel solid phase extraction procedure on Amberlite XAD-1180 for speciation of Cr(III), Cr(VI) and total chromium in environmental and pharmaceutical samples.

    Science.gov (United States)

    Narin, Ibrahim; Kars, Ayse; Soylak, Mustafa

    2008-01-31

    Due to the toxicity of chromium, species depend on their chemical properties and bioavailabilities, speciation of chromium is very important in environmental samples. A speciation procedure for chromium(III), chromium(VI) and total chromium in environmental samples is presented in this work, prior to flame atomic absorption spectrometric determination of chromium. The procedure is based on the adsorption of Cr(III)-diphenylcarbazone complex on Amberlite XAD-1180 resin. After oxidation of Cr(III), the developed solid phase extraction system was applied to determinate the total chromium. Cr(III) was calculated as the difference between the total Cr content and the Cr(VI) content. The analytical conditions for the quantitative recoveries of Cr(VI) on Amberlite XAD-1180 resin were investigated. The effects of some alkaline, earth alkaline, metal ions and also some anions were also examined. Preconcentration factor was found to be 75. The detection limits (LOD) based on three times sigma of the blank (N: 21) for Cr(VI) and total chromium were 7.7 and 8.6 microg/L, respectively. Satisfactory results for the analysis of total chromium in the stream sediment (GBW7310) certified reference material for the validation of the presented method was obtained. The procedure was applied to food, water and pharmaceutical samples successfully.

  8. Unraveling the mechanism responsible for the contrasting tolerance of Synechocystis and Synechococcus to Cr(VI): Enzymatic and non-enzymatic antioxidants

    Energy Technology Data Exchange (ETDEWEB)

    Gupta, Alka [Molecular Biology Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400085 (India); Ballal, Anand, E-mail: aballal@barc.gov.in [Molecular Biology Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400085 (India); Homi Bhabha National Institute, Training School Complex, Anushakti Nagar, Mumbai 40085 (India)

    2015-07-15

    Highlights: • Cr(VI) accumulation generates higher ROS in Synechocystis than in Synechococcus. • Synechococcus exhibits better photosynthetic activity in response to Cr(VI). • Synechococcus has higher enzymatic/non-enzymatic antioxidants than Synechocystis. • Synechococcus shows better tolerance to other oxidative stresses than Synechocystis. • Differential detoxification of ROS is responsible for the contrasting tolerance to Cr(VI) - Abstract: Two unicellular cyanobacteria, Synechocystis and Synechococcus, showed contrasting tolerance to Cr(VI); with Synechococcus being 12-fold more tolerant than Synechocystis to potassium dichromate. The mechanism responsible for this differential sensitivity to Cr(VI) was explored in this study. Total content of photosynthetic pigments as well as photosynthetic activity decreased at lower concentration of Cr(VI) in Synechocystis as compared to Synechococcus. Experiments with {sup 51}Cr showed Cr to accumulate intracellularly in both the cyanobacteria. At lower concentrations, Cr(VI) caused excessive ROS generation in Synechocystis as compared to that observed in Synechococcus. Intrinsic levels of enzymatic antioxidants, i.e., superoxide dismutase, catalase and 2-Cys-peroxiredoxin were considerably higher in Synechococcus than Synechocystis. Content of total thiols (both protein as well as non-protein) and reduced glutathione (GSH) was also higher in Synechococcus as compared to Synechocystis. This correlated well with higher content of carbonylated proteins observed in Synechocystis than Synechococcus. Additionally, in contrast to Synechocystis, Synechococcus exhibited better tolerance to other oxidative stresses like high intensity light and H{sub 2}O{sub 2}. The data indicate that the disparity in the ability to detoxify ROS could be the primary mechanism responsible for the differential tolerance of these cyanobacteria to Cr(VI)

  9. Silicon-mediated alleviation of Cr(VI) toxicity in wheat seedlings as evidenced by chlorophyll florescence, laser induced breakdown spectroscopy and anatomical changes.

    Science.gov (United States)

    Tripathi, Durgesh Kumar; Singh, Vijay Pratap; Prasad, Sheo Mohan; Chauhan, Devendra Kumar; Kishore Dubey, Nawal; Rai, Awadhesh Kumar

    2015-03-01

    Silicon (Si)-mediated alleviation of Cr(VI) toxicity was examined in wheat seedlings using an in vivo approach that involves chlorophyll fluorescence, laser induced breakdown spectroscopy (LIBS) and anatomical changes. Exposure to Cr(VI) significantly reduced the growth and photosynthetic activities (chlorophyll fluorescence) in wheat which was accompanied by remarkable accumulation of this element in tissues. However, addition of Si to the growth medium alleviated the effects of Cr(VI). The LIBS spectra were used as a fingerprint of the elemental compositions in wheat seedlings, which showed a reduction in Cr accumulation following Si addition. Nutrient element levels (Ca, Mg, K and Na) declined in wheat following the addition of Cr (VI), as recorded by LIBS and inductively coupled plasma atomic emission spectroscopy (ICAP-AES). However, addition of Si along with Cr(VI) increased the contents of nutrient elements in wheat. LIBS, ICAP-AES and AAS showed a similar distribution pattern of elements measured in wheat. Anatomical observations of leaf and root revealed that Cr(VI) affected internal structures while Si played a role in protection from toxic effects. The results showed the suitability of chlorophyll fluorescence as a parameter and appropriateness of LIBS technique and anatomical procedures to elucidate Si-mediated alleviation of Cr(VI) toxicity. Furthermore, our results suggest that the measured parameters and techniques can be used non-invasively for monitoring the growth of crops under different environmental conditions. Copyright © 2014 Elsevier Inc. All rights reserved.

  10. A facile, versatile approach to hydroxyl-anchored metal oxides with high Cr(VI) adsorption performance in water treatment

    Science.gov (United States)

    Ma, Ji; Zuo-Jiang, SiZhi; He, Yunhao; Sun, Qinglei; Wang, Yunguo; Liu, Wei; Sun, Shuangshuang; Chen, Kezheng

    2016-11-01

    In this study, a facile and versatile urea-assisted approach was proposed to synthesize Chinese rose-like NiO, pinecone-like ZnO and sponge-like CoO adsorbents. The presence of urea during syntheses endowed these adsorbents with high concentration of surface hydroxyl groups, which was estimated as 1.83, 1.32 and 4.19 mmol [OH-] g-1 for NiO, ZnO and CoO adsorbents, respectively. These surface hydroxyl groups would facilitate the adsorption of Cr(vi) species (e.g. HCrO4-, Cr2O72- and CrO42-) from wastewater by exchanging with hydroxyl protons or hydroxide ions, and hence result in extremely high maximum adsorbed amounts of Cr(vi), being 2974, 14 256 and 408 mg g-1 for NiO, ZnO and CoO adsorbents in the pH range of 5.02-5.66 at 298 K, respectively. More strikingly, the maximum adsorbed amounts of Cr(vi) would be greatly enhanced as the adsorbing temperature is increased, and even amount to 23 411 mg g-1 for ZnO adsorbents at 323 K. Based on the kinetics and equilibrium studies of adsorptive removal of Cr(vi) from wastewater, our synthetic route will greatly improve the adsorptivity of the as-synthesized metal-oxide adsorbents, and hence it will shed new light on the development of high-performance adsorbents.

  11. Male reproductive toxicity of CrVI: In-utero exposure to CrVI at the critical window of testis differentiation represses the expression of Sertoli cell tight junction proteins and hormone receptors in adult F1 progeny rats.

    Science.gov (United States)

    Kumar, Kathiresh M; Aruldhas, Mariajoseph Michael; Banu, Sheerin L; Sadasivam, Balaji; Vengatesh, Ganapathy; Ganesh, Karthik M; Navaneethabalakrishnan, Shobana; Navin, Ajith Kumar; Michael, Felicia Mary; Venkatachalam, Sankar; Stanley, Jone A; Ramachandran, Ilangovan; Banu, Sakhila K; Akbarsha, Mohammad Abdulkader

    2017-02-10

    The effect of gestational exposure to CrVI (occupational/environmental pollutant and target to Sertoli cells(SC)) was tested in a rat model during the testicular differentiation from the bipotential gonad may interrupt spermatogenesis by disrupting SC tight junctions(TJ) and it's proteins and hormone receptors. Pregnant Wistar rats were exposed to 50/100/200ppm CrVI through drinking water during embryonic days 9-14. On Postnatal day 120, testes were subjected to ion exchange chromatographic analysis and revealed increased level of CrIII in SCs and germ cells, serum and testicular interstitial fluid(TIF). Microscopic analyses showed seminiferous tubules atrophy and disruption of SC TJ, which also recorded decreased testosterone in TIF. mRNA and Protein expression analyses attested decreased level of Fshr, Ar, occludin and claudin-11 in SCs. Immunofluorescent detection revealed weak signal of TJ proteins. Taken together, we concluded that gestational exposure to CrVI interferes with the expression of SC TJ proteins due to attenuated expression of hormone receptors.

  12. TREATMENT OF HEXAVALENT CHROMIUM IN CHROMITE ORE PROCESSING SOLID WASTE USING A MIXED REDUCTANT SOLUTION OF FERROUS SULFATE AND SODIUM DITHIONITE

    Science.gov (United States)

    We developed a method for disseminating ferrous iron in the subsurface to enhance chemical reduction of hexavalent chromium (Cr(VI)) in a chromite ore processing solid waste derived from the production of ferrochrome alloy. The method utilizes ferrous sulfate (FeSO4) in combinati...

  13. AN IN SITU PERMEABLE REACTIVE BARRIER FOR THE TREATMENT OF HEXAVALENT CHROMIUM AND TRICHLOROETHYLENE IN GROUNDWATER:VOLUME 2 PERFORMANCE MONITORING

    Science.gov (United States)

    A 46 m long, 7.3 m deep, and 0.6 m wide permeable subsurface reactive wall was installed at the U.S. Coast Guard (USCG) Support Center, near Elizabeth City, North Carolina, in June 1996. The reactive wall was designed to remediate hexavalent chromium [Cr(VI)] contaminated ground ...

  14. AN IN-SITU PERMEABLE REACTIVE BARRIER FOR THE TREATMENT OF HEXAVALENT CHROMIUM AND TRICHLOROETHYLENE IN GROUND WATER: VOLUME 1 DESIGN AND INSTALLATION

    Science.gov (United States)

    A 46 m long, 7.3 m deep, and 0.6 m wide permeable subsurface reactive wall was installed at the U.S. Coast Guard (USCG) Support Center, near Elizabeth City, North Carolina, in June 1996. The reactive wall was designed to remediate hexavalent chromium [Cr(VI)] contaminated ground ...

  15. Accumulation and effects of Cr(VI) in Japanese medaka (Oryzias latipes) during chronic dissolved and dietary exposures.

    Science.gov (United States)

    Chen, Hongxing; Mu, Lei; Cao, Jinling; Mu, Jingli; Klerks, Paul L; Luo, Yongju; Guo, Zhongbao; Xie, Lingtian

    2016-07-01

    Chromium (Cr) is an essential metal and a nutritional supplement for both human and agricultural uses. It is also a pollutant from a variety of industrial uses. These uses can lead to elevated Cr levels in aquatic environments, where it can enter and affect aquatic organisms. Its accumulation and subsequent effects in fish have received relatively little attention, especially for chronic exposure. In the present study, Japanese medaka were chronically exposed to dissolved or dietary Cr(VI) for 3 months. Cr accumulation in liver, gills, intestine, and brain was evaluated. Effects on the antioxidant system, nervous system (acetylcholinesterase, AChE), digestive system (α-glucosidase, α-Glu), and tissue histology (liver and gills) were also assessed. Cr accumulation was observed in the intestine and liver of fish exposed to Cr-contaminated brine shrimp. However, chronic dissolved Cr exposure led to significant Cr accumulation in all organs tested. Analysis of the subcellular distribution of Cr in medaka livers revealed that 37% of the Cr was present in the heat stable protein fraction. The dissolved Cr exposure had pronounced effects on the antioxidant system in the liver, with an elevated ratio of reduced glutathione/oxidized glutathione (GSH/GSSG) and decreases in GSH and glutathione S-transferase (GST). The α-Glu activity in the intestine was significantly inhibited. In addition, Cr exposure caused histopathological alterations in the gills and liver. In general, the effects of dietary Cr were relatively minor, possible due to the much lower accumulation in the fish. Our results imply that Japanese medaka accumulate Cr mainly via uptake of dissolved Cr(VI).

  16. Effect of acclimatization on hexavalent chromium reduction in a biocathode microbial fuel cell.

    Science.gov (United States)

    Wu, Xiayuan; Zhu, Xujun; Song, Tianshun; Zhang, Lixiong; Jia, Honghua; Wei, Ping

    2015-03-01

    A simple acclimatization method for the reduction of hexavalent chromium (Cr(VI)) at a biocathode by first enriching an exoelectrogenic biofilm on a microbial fuel cell (MFC) anode, followed by direct inversion of the anode to function as the biocathode, has been established. This novel method significantly enhanced the Cr(VI) reduction efficiency of the MFC, which was mainly attributed to the higher microbial density and less resistive Cr(III) precipitates on the cathode when compared with a common biocathode acclimatization method (control). The biocathode acclimatization period was shortened by 19days and the Cr(VI) reduction rate was increased by a factor of 2.9. Microbial community analyses of biocathodes acclimatized using different methods further verified the feasibility of this electrode inversion method, indicating similar dominant bacteria species in biofilms, which mainly consist of Gamma-proteobacteria and Bacteria.

  17. Sorption of lindane to river biofilms, suspended particles and sediments in the presence and absence of Cr(VI) and As(V)

    Science.gov (United States)

    Guo, Z.; Dong, D.; Hua, X.; Lan, X.; Liang, D.

    2013-12-01

    Few study has focused on the effects of Cr(VI) and As(V) which are often in the form of anionic groups in natural aquatic environment on the sorption of dissolved hydrophobic organic pollutants (HOPs) onto natural solid materials from water. In this study, we compared the sorption thermodynamics of lindene as a model dissolved HOP on biofilms, suspended particles and surface sediments collected from the same river in the presence and absence of Cr(VI) and As(V). Visual MINTEQ (version 3.0) was applied to calculate Cr(VI) and As(V) species in the sorption system. CrO42- (89%) was the main Cr(VI) species and HAsO42- (78%) and H2AsO4- (22%) were the As(V) species. Compared with Freundlich and the dual reactive domain model, linear model gave a better fit for the lindane sorption isotherms on the biofilms, particles and sediments (Fig.1). For the lindane sorption on the biofilms, the linear model distribution coefficient (KL) were reduced by 48.0% and 47.6% in the presence of Cr(VI) and As(V), respectively; For that on the suspended particles, KL were reduced by 6.2% and 10.8%, respectively; For the sediments, KL were reduced by 30.2% and 34.5%, respectively. In general, the presence of Cr(VI) and As(V) inhibited lindane sorption onto the three solids and inhibition level decreased in the order biofilms > sediments > particles. In contrast to the promotion of metal cations on the dissolved HOPs sorption onto natural solid materials, anionic Cr(VI) and As(V) groups suppressed the sorption. This indicated that anionic Cr(VI) and As(V) groups might occupy some sorption sites on solids and then occurred competitive sorption with lindane. Taking account of the errors in experiment, effects on the sorption between Cr(VI) and As(V) has no significant difference. This shown that the type of metal has little effect on the HOPs sorption onto natural solids. This result was consistent with that in other related studis. In addition, we inferred that the differences of component

  18. Hexavalent chromium reduction and energy recovery by using dual-chambered microbial fuel cell.

    Science.gov (United States)

    Gangadharan, Praveena; Nambi, Indumathi M

    2015-01-01

    Microbial fuel cell (MFC) technology is utilized to treat hexavalent chromium (Cr(VI)) from wastewater and to generate electricity simultaneously. The Cr(VI) is bioelectrochemically reduced to non-toxic Cr(III) form in the presence of an organic electron donor in a dual-chambered MFC. The Cr(VI) as catholyte and artificial wastewater inoculated with anaerobic sludge as anolyte, Cr(VI) at 100 mg/L was completely removed within 48 h (initial pH value 2.0). The total amount of Cr recovered was 99.87% by the precipitation of Cr(III) on the surface of the cathode. In addition to that 78.4% of total organic carbon reduction was achieved at the anode chamber within 13 days of operation. Furthermore, the maximum power density of 767.01 mW/m² (2.08 mA/m²) was achieved by MFCs at ambient conditions. The present work has successfully demonstrated the feasibility of using MFCs for simultaneous energy production from wastewater and reduction of toxic Cr(VI) to non-toxic Cr(III).

  19. The Growth of Gypsum in the Presence of Hexavalent Chromium: A Multiscale Study

    Directory of Open Access Journals (Sweden)

    Juan Morales

    2016-03-01

    Full Text Available The sorption of dissolved inorganic pollutants into the structure of minerals is an important process that controls the mobility and fate of these pollutants in the Earth’s crust. It also modifies the surface structure and composition of the host mineral, affecting its crystallization kinetics. Here, we investigate the effect of hexavalent chromium, Cr(VI, on the nucleation and growth of gypsum by conducting two types of experiments: (i in situ atomic force microscopy (AFM observations of the growth of gypsum {010} surfaces in the presence of Cr(VI and (ii gypsum precipitation experiments by mixing aqueous solutions containing variable amounts of Cr(VI. Gypsum precipitation is progressively delayed when occurring from solutions bearing increasing Cr(VI concentrations. Chemical analyses of gypsum precipitates show that gypsum incorporates small Cr(VI amounts that correlate with the content of this ion in the aqueous solution. Gypsum cell parameters variation reflects this incorporation. At the molecular scale, Cr(VI induces a slowdown of step advance rates on gypsum {010} surfaces accompanied by the roughening of nanostep edges and the so-called “template effect”. This effect involves the reproduction of the original nanotopography after the completion of individual advancing monolayers and appears as a general nanoscale phenomenon occurring during growth of solid solutions from aqueous solutions even in the case of compositionally-restricted solid solutions.

  20. Biological groundwater treatment for chromium removal at low hexavalent chromium concentrations.

    Science.gov (United States)

    Mamais, Daniel; Noutsopoulos, Constantinos; Kavallari, Ioanna; Nyktari, Eleni; Kaldis, Apostolos; Panousi, Eleni; Nikitopoulos, George; Antoniou, Kornilia; Nasioka, Maria

    2016-06-01

    The objective of this work is to develop and evaluate biological groundwater treatment systems that will achieve hexavalent chromium reduction and total chromium removal from groundwater at hexavalent chromium (Cr(VI)) groundwater concentrations in the 0-200 μg/L range. Three lab-scale units operated, as sequencing batch reactors (SBR) under aerobic, anaerobic and anaerobic-aerobic conditions. All systems received groundwater with a Cr(VI) content of 200 μg/L. In order to support biological growth, groundwater was supplemented with milk, liquid cheese whey or a mixture of sugar and milk to achieve a COD concentration of 200 mg/L. The results demonstrate that a fully anaerobic system or an anaerobic-aerobic system dosed with simple or complex external organic carbon sources can lead to practically complete Cr(VI) reduction to Cr(III). The temperature dependency of maximum Cr(VI) removal rates can be described by the Arrhenius relationship. Total chromium removal in the biological treatment systems was not complete because a significant portion of Cr(III) remained in solution. An integrated system comprising of an anaerobic SBR followed by a sand filter achieved more than 95% total chromium removal thus resulting in average effluent total and dissolved chromium concentrations of 7 μg/L and 3 μg/L, respectively.

  1. Studies of kinetic of Cr(VI) adsorption in chitosan magnetic particles by radiochemistry method; Estudo da cinetica de adsorcao de Cr(VI) em particulas magneticas de quitosana pelo metodo radioquimico

    Energy Technology Data Exchange (ETDEWEB)

    Rodriguez, Levi S.; Yamaura, Mitiko; Camilo, Ruth L. [Instituto de Pesquisas Energeticas e Nucleares (IPEN), Sao Paulo, SP (Brazil)]. E-mail: lsrodri@ipen.br; Landgraf, Fernando J.G. [Instituto de Pesquisas Tecnologicas (IPT), Sao Paulo, SP (Brazil)]. E-mail: landgraf@ipt.br

    2005-07-01

    There are a number of processes which are used for remove or recovery metals from waters and waste waters. However, such processes are expensive and sometimes ineffective, especially when metals are present in solution at very low concentrations. Alternative and more efficient processes than ones usually employed are being intensively investigated as sorption. Biosorption of metals is already sufficiently known and its mechanisms have been intensely studied. Therefore, the efficiency and the mechanism of Cr(VI) ions uptake in chitosan magnetic particles obtained by suspension crosslinking technique were studied. These particles were spherical in shape and had a high porosity degree, a low saturation magnetization and a low percentage of swelling. The Cr(VI) ions uptake onto chitosan magnetic particles followed a mechanism of second order, suggesting chemical adsorption. (author)

  2. Statistical optimization of process parameters for the simultaneous adsorption of Cr(VI) and phenol onto Fe-treated tea waste biomass

    Science.gov (United States)

    Gupta, Ankur; Balomajumder, Chandrajit

    2017-06-01

    In this study, simultaneous removal of Cr(VI) and phenol from binary solution was carried out using Fe-treated tea waste biomass. The effect of process parameters such as adsorbent dose, pH, initial concentration of Cr(VI) (mg/L), and initial concentration of phenol (mg/L) was optimized. The analysis of variance of the quadratic model demonstrates that the experimental results are in good agreement with the predicted values. Based on experimental design at an initial concentration of 55 mg/L of Cr(VI), 27.50 mg/L of phenol, pH 2.0, 15 g/L adsorbent dose, 99.99% removal of Cr(VI), and phenol was achieved.

  3. The involvement of ATP sulfurylase in Se(VI) and Cr(VI) reduction processes in the fission yeast Schizosaccharomyces pombe.

    Science.gov (United States)

    Raspor, P; Fujs, S; Banszky, L; Maraz, A; Batic, M

    2003-11-01

    The response of Schizosaccharomyces pombe towards the oxyanions selenate [Se(VI)] and dichromate [Cr(VI)] was investigated in order to establish the involvement of the yeast ATP sulfurylase in their reduction. An ATP sulfurylase-defective/selenate-resistant mutant of S. pombe (B-579 Se(R) -2) and an ATP sulfurylase-active/selenate-sensitive strain of S. pombe (B-579 Se(S)) were included in this study. The inhibitory effect of Se(VI) and Cr(VI) oxyanions on growth and bioaccumulation was measured. The sensitive strain showed natural sensitivity to selenate while the resistant mutant tolerated a 100-fold higher concentration of selenate. These results indicate that selenate toxicity to microorganisms is connected with the reduction of selenate to selenite. Both strains showed similar sensitivity to Cr(VI) and in this study there was no evidence that ATP sulfurylase participates in the reduction process of Cr(VI).

  4. Abatement of toxicity of effluents containing Cr(VI) by heterogeneous photocatalysis. Toxicity assessment by AMPHITOX assay.

    Science.gov (United States)

    Hojman, Jonatan Y; Meichtry, J Martín; Litter, Marta I; Pérez Coll, Cristina S

    2015-12-01

    Toxicity of a Cr(VI) solution before and after treatment by TiO2 heterogeneous photocatalysis (HP) was performed with AMPHITOX bioassay. Changes in toxicity on Rhinella arenarum larvae for 10-d were monitored after exposure to an untreated Cr(VI) solution and to the same solution after HP treatment. The HP treatment of a 41.60 mg L(-1) Cr(VI) solution reduced to 37.5% the concentration of the metal ion. A 10-fold reduction in toxicity at acute exposure (72 h) and 150-fold reduction in toxicity after 240 h was found. Further, the LOEC value increased from 0.001% for the untreated solution to 0.153% after HP treatment. Moreover, the safe concentration in untreated solution corresponded to 0.0001% sample, and it was 0.01% after the treatment, i.e., 100 times higher. A saving of water of about 100,000 L per L of effluent would be possible through dilution to allow safer concentrations for discharge; the saving would reach the highest value (1,000,000 L per L) at 240 h. Sub-lethal effects were completely absent in larvae exposed to the treated solution. The AMPHITOX test allowed to detect chronic effects at low Cr concentrations, i.e. at environmentally relevant levels.

  5. A revised model of ex-vivo reduction of hexavalent chromium in human and rodent gastric juices

    Energy Technology Data Exchange (ETDEWEB)

    Schlosser, Paul M., E-mail: schlosser.paul@epa.gov; Sasso, Alan F.

    2014-10-15

    Chronic oral exposure to hexavalent chromium (Cr-VI) in drinking water has been shown to induce tumors in the mouse gastrointestinal (GI) tract and rat oral cavity. The same is not true for trivalent chromium (Cr-III). Thus reduction of Cr-VI to Cr-III in gastric juices is considered a protective mechanism, and it has been suggested that the difference between the rate of reduction among mice, rats, and humans could explain or predict differences in sensitivity to Cr-VI. We evaluated previously published models of gastric reduction and believe that they do not fully describe the data on reduction as a function of Cr-VI concentration, time, and (in humans) pH. The previous models are parsimonious in assuming only a single reducing agent in rodents and describing pH-dependence using a simple function. We present a revised model that assumes three pools of reducing agents in rats and mice with pH-dependence based on known speciation chemistry. While the revised model uses more fitted parameters than the original model, they are adequately identifiable given the available data, and the fit of the revised model to the full range of data is shown to be significantly improved. Hence the revised model should provide better predictions of Cr-VI reduction when integrated into a corresponding PBPK model. - Highlights: • Hexavalent chromium (Cr-VI) reduction in gastric juices is a key detoxifying step. • pH-dependent Cr-VI reduction rates are explained using known chemical speciation. • Reduction in rodents appears to involve multiple pools of electron donors. • Reduction appears to continue after 60 min, although more slowly than initial rates.

  6. Statistical design of experiments as a tool for optimizing the batch conditions to Cr(VI) biosorption on Araucaria angustifolia wastes.

    Science.gov (United States)

    Brasil, Jorge L; Ev, Ricardo R; Milcharek, Caroline D; Martins, Lucas C; Pavan, Flavio A; dos Santos, Araci A; Dias, Silvio L P; Dupont, Jairton; Zapata Noreña, Caciano P; Lima, Eder C

    2006-05-20

    In order to reduce the total number of experiments for achieving the best conditions for Cr(VI) uptake using Araucaria angustifolia (named pinhão) wastes as a biosorbent, three statistical design of experiments were carried out. A full 2(4) factorial design with two blocks and two central points (20 experiments) was experimented (pH, initial metallic ion concentration-C(o), biosorbent concentration-X and time of contact-t), showing that all the factors were significant; besides, several interactions among the factors were also significant. These results led to the performance of a Box-Behnken surface analysis design with three factors (X, C(o) and t) and three central points and just one block (15 experiments). The performance of these two statistical designs of experiments led to the best conditions for Cr(VI) biosorption on the pinhão wastes using a batch system, where: pH 2.0; C(o) = 1200 mg l(-1) Cr(VI); X = 1.5 g l(-1) of biosorbent; t = 8 h. The maximum Cr(VI) uptake in these conditions was 125 mg g(-1). After evaluating the best Cr(VI) biosorption conditions on pinhão wastes, a new Box-Behnken surface analysis design was employed in order to verify the effects of three concomitant ions (Cl(-), NO(3)(-) and PO(4)(3-)) on the biosorption of Cr(VI) as a dichromate on the biosorbent (15 experiments). These results showed that the tested anions did not show any significant effect on the Cr(VI) uptake by pinhão wastes. In order to evaluate the pinhão wastes as a biosorbent in dynamic system, a glass column was fulfilled with pinhão wastes (4.00 g) as biosorbent, and it was fed with 25.0 mg l(-1) Cr(VI) at pH 2.0 and 2.5 ml min(-1). The breakpoint was attained when concentrations of effluent of the column attained the value of 0.05 mg l(-1) Cr(VI) using 5550 ml of the metallic ion solution. In these conditions, the biosorbent was able to remove completely Cr(VI) from aqueous solution with a ratio of Cr(VI) effluent volume/biosorbent volume of 252.3.

  7. A Conceptual model of coupled biogeochemical and hydrogeological processes affected by in situ Cr(VI) bioreduction in groundwater at Hanford 100H Site

    OpenAIRE

    Faybishenko, B.; Long, P. E.; Hazen, T C; Hubbard, S.S.; Williams, K.H.; Peterson, J. E.; Chen, J.; E.V. Volkova; Newcomer, D.R.; Resch, C.T.; Cantrell, K.; Conrad, M.S.; Brodie, E. L.; Joyner, D.C.; Borglin, S.E.

    2006-01-01

    The overall objective of this presentation is to demonstrate a conceptual multiscale, multidomain model of coupling of biogeochemical and hydrogeological processes during bioremediation of Cr(VI) contaminated groundwater at Hanford 100H site. A slow release polylactate, Hydrogen Release Compound (HRCTM), was injected in Hanford sediments to stimulate immobilization of Cr(VI). The HRC injection induced a 2-order-of-magnitude increase in biomass and the onset of reducing biogeochemical con...

  8. Flow injection on-line preconcentration of low levels of Cr(VI) with detection by ETAAS

    DEFF Research Database (Denmark)

    Som-aum, Waraporn; Liawruangrath, Saisunee; Hansen, Elo Harald

    2002-01-01

    A flow injection (FI) on-line sorption preconcentration procedure utilizing a packed column reactor and combined with electrothermal atomic absorption spectrometry (ETAAS) is proposed for the determination of low levels of Cr(VI) in water samples. Polytetrafluoroethylene (PTFE) beads packed...... in a mini-column is used as sorbent material. The complex formed between Cr(VI) and ammonium pyrrolidine dithiocarbamate (APDC) is sorbed on the PTFE beads, and is subsequently eluted by an air-monosegmented discrete zone of absolute ethanol (35mul), the analyte being quantified by ETAAS....... The preconcentration procedure using the proposed column significantly enhances the preconcentration efficiency as compared with the preconcentration approach incorporating an open tubular PTFE knotted reactor (KR). Comparing the two procedure for equal surface sorption area, the advantages of using a packed column...

  9. Polyaniline-modified 3D-flower-like molybdenum disulfide composite for efficient adsorption/photocatalytic reduction of Cr(VI).

    Science.gov (United States)

    Gao, Yang; Chen, Changlun; Tan, Xiaoli; Xu, Huan; Zhu, Kairuo

    2016-08-15

    Polyaniline (PANI) was modified onto 3D flower-like molybdenum disulfide (MoS2) to prepare a novel organic-inorganic hybrid material, PANI@MoS2. PANI@MoS2 was characterized by scanning and transmission electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction and thermogravimetric analysis. The results indicate that PANI was modified onto MoS2. PANI@MoS2 was applied as an adsorbent to remove Cr(VI) from aqueous solutions, and the adsorption isotherms fit well to the Langmuir model; the maximum removal capacity of Cr(VI) by PANI@MoS2 was 526.3 and 623.2mg/g at pH 3.0 and 1.5, respectively. PANI@MoS2 exhibited an enhanced removal capacity of Cr(VI) in comparison with bare MoS2 and other adsorbents. The adsorption of Cr(VI) on PANI@MoS2 might be attributed to the complexation between the amine and imine groups on the surface of PANI@MoS2 with Cr(VI). This study implies that the hybrid material PANI@MoS2 is a potential adsorbent for Cr(VI) removal from large volumes of aqueous solutions. Copyright © 2016 Elsevier Inc. All rights reserved.

  10. Visible-light-induced photocatalytic reduction of Cr(VI) with coupled Bi2O3/TiO2 photocatalyst and the synergistic bisphenol A oxidation.

    Science.gov (United States)

    Yang, Juan; Dai, Jun; Li, Jiantong

    2013-04-01

    Coupled Bi2O3/TiO2 photocatalysts were fabricated by sol-gel and hydrothermal methods and characterized using various spectroscopy techniques. Photocatalytic reduction of Cr(VI) in aqueous solution, together with the synergistic effect of photodegradation of bisphenol A (BPA), was investigated using these coupled Bi2O3/TiO2 under visible-light irradiation. Coupling of Bi2O3 inhibited the phase transformation from anatase to rutile and extended absorption region to visible light. Bi ions did not enter TiO2 lattice and were more likely to bond with oxygen atoms to form Bi2O3 on the surface of TiO2. Photovoltage signals in visible range revealed the effective interfacial charge transfer between Bi2O3 and TiO2. Two percent Bi2O3/TiO2 exhibited the highest photocatalytic activity of visible-light-induced reduction of Cr(VI). The addition of BPA effectively increased the photocatalytic reduction of Cr(VI). Simultaneously, the presence of Cr(VI) promoted the degradation of BPA, which was demonstrated by the investigation of TOC removal yield and generated intermediates. A possible mechanism of photocatalytic reduction of Cr(VI) and degradation of BPA in Bi2O3/TiO2 system was proposed. The synergistic effect, observed between reduction of Cr(VI) and degradation of BPA, provides beneficial method for environmental remediation and purification of the complex wastewater.

  11. Utilization of waste product (tamarind seeds) for the removal of Cr(VI) from aqueous solutions: equilibrium, kinetics, and regeneration studies.

    Science.gov (United States)

    Gupta, Suresh; Babu, B V

    2009-07-01

    In the present study, an adsorbent was prepared from tamarind seeds and used after activation for the removal of Cr(VI) from aqueous solutions. The tamarind seeds were activated by treating them with concentrated sulfuric acid (98% w/w) at a temperature of 150 degrees C. The adsorption of Cr(VI) was found to be maximum at low values of initial pH in the range of 1-3. The adsorption process of Cr(VI) was tested with Langmuir, Freundlich, Redlich-Peterson, Koble-Corrigan, Tempkin, Dubinin-Radushkevich and Generalized isotherm models. Application of the Langmuir isotherm to the system yielded a maximum adsorption capacity of 29.7 mg/g at an equilibrium pH value ranging from 1.12 to 1.46. The adsorption process followed second-order kinetics and the corresponding rate constants obtained were 2.605 x 10(-3), 0.818 x 10(-3), 0.557 x 10(-3) and 0.811 x 10(-3) g/mg min(-1) for 50, 200, 300 and 400 mg/L of initial Cr(VI) concentration, respectively. The regenerated activated tamarind seeds showed more than 95% Cr(VI) removal of that obtained using the fresh activated tamarind seeds. A feasible solution is proposed for the disposal of the contaminants (acid and base solutions) containing high concentrations of Cr(VI) obtained during the regeneration (desorption) process.

  12. Optimization of Cr(VI biosorption onto Aspergillus niger using 3-level Box-Behnken design: Equilibrium, kinetic, thermodynamic and regeneration studies

    Directory of Open Access Journals (Sweden)

    Naba Kumar Mondal

    2017-06-01

    Full Text Available Heavy metal biosorption is an efficient technology for the decontamination of metal from industrial waste water. The present study focused on exploration of Aspergillus niger towards removal of Cr(VI from aqueous solution. The influence of different experimental parameters—initial pH, adsorbent dose, initial concentration, contact time, shaking speed, temperature, and their combined effect during Cr(VI adsorption—was investigated by means of response surface methodology based on four factorial Box–Behnken experimental design. Optimized values of initial Cr(VI concentration, pH, adsorbent dose, and contact time were found as 33.33 mg/L, 4.6, 1.0 g/L, and 48.45 min, respectively. A. niger showed the highest adsorption capacity 11.792 mg/g at initial pH 2.0. Equilibrium data fitted well to the Temkin and Freundlich isotherms. Cr(VI biosorption showed Pseudo-second order rate kinetics. The activation energy of the adsorption was estimated as 2.9 × 10−3 kJ/mol. Thermodynamics properties of the Cr(VI biosorption was spontaneous in nature. Desorption study showed that nearly 94% of the Cr(VI adsorbed on A. niger could be desorbed using 0.5 M EDTA.

  13. Hexavalent chromium reduction with scrap iron in continuous-flow system. Part 2: Effect of scrap iron shape and size.

    Science.gov (United States)

    Gheju, M; Balcu, I

    2010-10-15

    Hexavalent chromium reduction with scrap iron has the advantage that two wastes are treated simultaneously. The reduction of hexavalent chromium by scrap iron was investigated in continuous system, using as reducing agent the following scrap iron shapes and sizes: (1) spiral fibers, (2) shavings, and (3) powder. The shape and size of scrap iron were found to have a significant influence on chromium and iron species concentration in column effluent, on column effluent pH and on Cr(VI) reduction mechanism. While for large scrap iron particles (spiral fibers) homogeneous reduction is the dominant Cr(VI) reduction process, for small scrap iron particles (powder) heterogeneous reduction appears to be the dominant reaction contributing to Cr(VI) reduction. All three shapes and sizes investigated in this work have both advantages and disadvantages. If found in sufficient quantities, scrap iron powder seem to be the optimum shape and size for the continuous reduction of Cr(VI), due to the following advantages: (1) the greatest reduction capacity, (2) the most important pH increase in column effluent (up to 6.3), (3) no chromium was detected in the column effluent during the first 60 h of the experiment, and (4) the lowest steady-state Cr(VI) concentration observed in column effluent (3.7 mg/L). But, despite of a lower reduction capacity in comparison with powder particles, spiral fibers and shavings have the advantage to result in large quantities from the mechanic processing of steel.

  14. Reduction of hexavalent chromium by a novel Ochrobactrum sp. - microbial characteristics and reduction kinetics.

    Science.gov (United States)

    Narayani, M; Vidya Shetty, K

    2014-04-01

    A Gram negative hexavalent chromium (Cr(VI)) reducing bacteria, Ochrobactrum sp. Cr-B4 (genbank accession number: JF824998) was isolated from the aerator water of an activated sludge process of a wastewater treatment facility of a dye and pigment based specialty chemical industry. It showed a resistance for 1000 mg L(-1) Cr(VI). It exhibited resistance against other heavy metal ions like Ni(2+) (900 mg L(-1) ), Cu(2+) (500 mg L(-1) ), Pb(2+) (800 mg L(-1) ), and Cd(2+) (250 mg L(-1) ), Zn(2+) (700 mg L(-1) ), Fe(3+) (800 mg L(-1) ), and against selected antibiotics. Cr-B4 could efficiently reduce 200 mg L(-1) Cr(VI) completely in nutrient and LB media and could convert Cr(VI) to Cr(III) efficiently. Cr(VI) reduction in nutrient media followed allosteric enzyme kinetics with Km values of 59.39 mg L(-1) and Vmax values of 47.03 mg L(-1)  h(-1) . The reduction in LB media followed Michaelis-Menten kinetics with Km values of 99.52 mg L(-1) and Vmax of 77.63 mg L(-1)  h(-1) . Scanning electron micrograms revealed the presence of extracellular polymeric secretions.

  15. Simultaneous extraction of Cr(VI) and Cu(II) from humic acid with new synthesized EDTA derivatives.

    Science.gov (United States)

    Zhang, Tao; Wu, Ying-Xin; Huang, Xiong-Fei; Liu, Jun-Min; Xia, Bing; Zhang, Wei-Hua; Qiu, Rong-Liang

    2012-07-01

    Soil washing is one of the few permanent treatment alternatives for removing metal contaminants. Ethylenediaminetetraacetic acid and its salts (EDTA) is very effective at removing cationic metals and has been utilized globally. However it is ineffective for anionic metal contaminants or metals bound to soil organic matter. The simultaneous removal of cationic and anionic metal contaminants by soil washing is difficult due to differences in their properties. The present study evaluated the potential of a washing process using two synthesized EDTA-derivatives, C(6)HEDTA (2,2'-((2-((carboxymethyl)(2-(hexanoyloxy)ethyl)amino)ethyl)azanediyl)diacetic acid) and C(12)HEDTA (2,2'-((2-((carboxymethyl) (2-(dodecanoyloxy)ethyl)amino)ethyl)azanediyl)diacetic acid), which consist of a hydrophilic polycarboxylic moiety and a hydrophobic moiety with a monoalkyl ester group. A series of equilibrium batch experiments at room temperature were conducted to investigate the efficacy of C(6)HEDTA and C(12)HEDTA as extractants for both oxyanion Cr(VI) and cationic Cu(II). Results showed that either C(6)HEDTA or C(12)HEDTA can extract both Cr(VI) and Cu(II) from humic acid simultaneously. However, C(6)HEDTA was less effective for Cr(VI) probably because it has no surface activities to increase solubility of humic acid, like C(12)HEDTA. Extraction of Cr(VI) was mainly attributed to the decreased surface tension and enhanced solubility of organic matter. Extraction of Cu(II) was attributed to both the Cu(II) chelation and enhanced solubility of humic acid. It was demonstrated that the hydrophilic polycarboxylic moiety of C(12)HEDTA chelates cations while the monoalkyl ester group produces surface active properties that enhance the solubility of humic acid.

  16. Environmental remediation of Cr(VI) solutions by photocatalytic reduction using Ag–Er(OH){sub 3} nanocomposite

    Energy Technology Data Exchange (ETDEWEB)

    Malkhasian, Aramice Y.S., E-mail: amalkhasian10@gmail.com [Chemistry Department, Faculty of Science, King Abdulaziz University, P.O. Box 80203, Jeddah 21589 (Saudi Arabia); Mohamed, Reda M. [Chemistry Department, Faculty of Science, King Abdulaziz University, P.O. Box 80203, Jeddah 21589 (Saudi Arabia); Advanced Materials Department, Central Metallurgical R& D Institute, CMRDI, P.O. Box 87 Helwan, Cairo (Egypt); Center of Excellence in Environmental Studies, King Abdulaziz University, P.O. Box 80216, Jeddah 21589 (Saudi Arabia)

    2015-05-25

    Highlights: • Ag/Er(OH){sub 3} nanoparticles were used for photocatalytic reduction of Cr(VI). • Photocatalytic reduction of Cr(VI) was dependent on wt% of Ag. • Catalyst re-use revealed the present photocatalyst remain effective and active after five cycles. - Abstract: A hydrothermal method was use to prepare Er(OH){sub 3} nanoparticles, and a photoassisted deposition method was used to deposit silver onto the surface of those nanoparticles. Er(OH){sub 3} and Ag/Er(OH){sub 3} nanocomposites were characterized by BET, XRD, XPS, PL, UV–Vis and TEM measurements. The photocatalytic performance of the nanoparticles with respect to the photocatalytic reduction of chromium(VI) under UV light irradiation was determined. The results reveal that the silver particles were well dispersed onto the surface of the Er(OH){sub 3} nanoparticles. Additionally, the surface area of the Ag/Er(OH){sub 3} nanocomposites was observed to be smaller than that of the Er(OH){sub 3} nanoparticles due to the blocking of some pores of the Er(OH){sub 3} nanoparticles by the deposition of silver particles. The Ag/Er(OH){sub 3} nanocomposites (0.15 wt%) exhibit the lowest band gap and highest photocatalytic activity for the reduction of Cr(VI). The photocatalytic performance of the 0.15 wt% Ag/Er(OH){sub 3} nanocomposites was stable after the reuse of the nanoparticles for the reduction of Cr(VI) after five uses.

  17. Impregnation synthesis of TiO{sub 2}/hydroniumjarosite composite with enhanced property in photocatalytic reduction of Cr(VI)

    Energy Technology Data Exchange (ETDEWEB)

    Xu, Junjun [Department of Environmental Engineering, College of Resources and Environmental Sciences, Nanjing Agricultural University, Nanjing 210095 (China); Xu, Zhihui, E-mail: xuzhihui@njau.edu.cn [Department of Chemistry, College of Science, Nanjing Agricultural University, Nanjing 210095 (China); Zhang, Ming [Department of Environmental Engineering, College of Resources and Environmental Sciences, Nanjing Agricultural University, Nanjing 210095 (China); Xu, Jiangyan [Department of Chemistry, College of Science, Nanjing Agricultural University, Nanjing 210095 (China); Fang, Di, E-mail: Di.Fang@njau.edu.cn [Department of Environmental Engineering, College of Resources and Environmental Sciences, Nanjing Agricultural University, Nanjing 210095 (China); Ran, Wei [Department of Environmental Engineering, College of Resources and Environmental Sciences, Nanjing Agricultural University, Nanjing 210095 (China)

    2015-02-15

    In this paper, a series of novel TiO{sub 2}/hydroniumjarosite composite photocatalysts were synthesized by deposition–precipitation method. XRD, UV–vis DRS, TEM, BET, PL spectra and EIS were used to characterize the composite photocatalysts. The photocatalytic performance of the composite catalysts were examined on the Cr(VI) reduction under ultraviolet irradiation in aqueous suspension. The results show that TiO{sub 2}/hydroniumjarosite composites exhibit enhanced photocatalytic activity with a maximum reduction rate of 98.0%, while the Cr(VI) reduction efficiency is only 36.0% over P25 under the same conditions. The increased light absorption intensity and the decreased electron–hole pair recombination rate in TiO{sub 2} with the introduction of hydroniumjarosite are responsible for better catalytic property of TiO{sub 2}/hydroniumjarosite catalysts. It would be of great promise for the industrial application of this catalyst with high potocatalytic performance to reduce Cr(VI) for wastewater treatment. - Highlights: • TiO{sub 2}/hydroniumjarosite with different TiO{sub 2} content was prepared using deposition–precipitation method. • The sample prepared with the TiO{sub 2}/Fe{sup 3+} mole ratio of 75:25 exhibited the highest catalytic efficiency. • The enhanced catalytic activity can be attributed to the formation of TiO{sub 2}/hydroniumjarosite heterostructure.

  18. Studies on biosorption of Cr(VI) on a green resin: dry cow dung powder and tracer technique

    Energy Technology Data Exchange (ETDEWEB)

    Barot, N.S.; Bagla, H.K. [Kishinchand Chellaram College, Mumbai (India). Nuclear and Radiochemistry Dept.

    2012-07-01

    The present investigation entails the application of dry cow dung powder (DCP) as an indigenous, inexpensive and eco-friendly material for the removal of Cr(VI) from aqueous medium. Batch biosorption experiments were conducted employing {sup 51}Cr(VI) as a tracer and the effect of various process parameters such as optimum pH, temperature, amount of resin, time of equilibration, agitation speed, concentration of metal ions and interfering effect of different salts etc. were studied. The kinetic studies were carried out employing various models but the best fitting was given by Lagergren Pseudo-second order model with high correlation coefficient R{sup 2} value of 0.997 and adsorption capacity of 10.20 mg/g. The thermodynamic parameters for biosorption were evaluated as {Delta}G = -2.837 kJ/mol, {Delta}H = -4.757 kJ/mol and {Delta}S = 16.64 J/mol K, which indicated spontaneous and exothermic process with high affinity of DCP for Cr(VI). Many naturally available materials are used for the biosorption of heavy metal pollutants, where most of them are physically or chemically modified. In this research work, DCP has been utilized without any pre or post chemical treatment. Thus it manifests the principle of green chemistry and proves to be an eco-friendly resin. (orig.)

  19. Removal of aqueous Hg(II) and Cr(VI) using phytic acid doped polyaniline/cellulose acetate composite membrane.

    Science.gov (United States)

    Li, Renjie; Liu, Lifen; Yang, Fenglin

    2014-09-15

    Conductive composite membrane-phytic acid (PA) doped polyaniline (PANI)/cellulose acetate (CA) (PANI-PA/CA) was prepared in a simple and environmental-friendly method, in which aniline was blended with CA/PA solution and polymerized before the phase conversion. The resultant composite membranes were characterized by SEM, EDX, FTIR-ATR, BET and electrical resistance measurements. When used as adsorbent for Hg(II) and Cr(VI) ions, the prepared composite membrane exhibits excellent adsorption capability. The adsorption of Hg(II) and Cr(VI) follows a pseudo-second-order kinetic model and best fits the Langmuir isotherm model, with the maximum adsorption capacity reaching 280.11 and 94.34 mg g(-1), respectively. The heavy metal loaded composite membrane can be regenerated and reused after treatment with acid or alkali solution, making it a promising and practical adsorbent for Hg(II) and Cr(VI) removal. Tests with river water were also carried out, indicating good performance and application.

  20. Absorption of Cr(VI) onto amino-modified titanate nanotubes using 2-bromoethylamine hydrobromide through SN2 reaction.

    Science.gov (United States)

    Niu, Guanjun; Liu, Wen; Wang, Ting; Ni, Jinren

    2013-07-01

    Unlike the complex reaction of grafting amino groups using harmful organic solvents, we proposed an environmental friendly method for effective amino grafting on titanate nanotubes (TNTs) with 2-Bromoethylamine hydrobromide (2-Bh) through a two-step SN2 reaction in pure water solution. The amino-modified titanate nanotubes (TNTs-RNH2) were characterized by Transmission electron microscope, X-ray diffraction, X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy. Under optimal conditions, the molar ratio of NaOH/2-Bh was 1.2 for step 1 and 1.3 for step 2 with corresponding reaction time of 12h and 24h, respectively. The adsorption isotherm of Cr(VI) onto TNTs-RNH2 well fits Langmuir model with maximal adsorption capacity of 69.1 mg/g, which is almost five times larger than that of fresh TNTs. The slight decrease in adsorption capacity with NO3(-) concentration was attributed to competition from ions, suppression of electric double layer and changes of Cr(VI) speciation. The wide adsorption pH range was due to much larger point of zero charge (8.2) and electrostatic attraction between positively charged TNTs-RNH2 and Cr(VI) with different speciations. The products could be well reused due to simple desorption at pH 10 with about 20% loss of the adsorption capacity after three recycles without any regeneration treatment.

  1. Removal of Cr(VI) and As(V) ions from aqueous solutions by polyacrylate and polystyrene anion exchange resins

    Science.gov (United States)

    Jachuła, Justyna; Hubicki, Zbigniew

    2013-09-01

    The sorption of Cr(VI) and As(V) from the aqueous solutions with the polyacrylate anion exchangers of the strong base functional groups Amberlite IRA 458 and Amberlite IRA 958 was studied. The studies were carried out by the static-batch method. The concentration of Cr(VI) and As(V) ions in the aqueous solution was determined by the UV-VIS spectrophotometer. The influence of several parameters was studied with respect to sorption equilibrium. The phase contact time and the concentration affect the sorption process. The equilibrium state was established already after 15 min of phase contact time. Maximum uptake of Cr(VI) and As(V) occurred at pH 5 and 10, respectively. The determined kinetic parameters imply that the sorption process proceeds according to the equation type of pseudo second-order. Sorption equilibrium data were correlated with the Langmuir and Freundlich isotherms. Removal of As(V) ions on macroporous Amberlite IRA 900 decreased about 12 % in presence of other anions (Cl-, NO3 -, SO4 2-) in the solution. The sorption was temperature dependent.

  2. Simultaneous removal of Cr(VI) and 4-chlorophenol through photocatalysis by a novel anatase/titanate nanosheet composite: Synergetic promotion effect and autosynchronous doping

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Wen, E-mail: wzl0025@auburn.edu [Jiangsu Key Laboratory of Atmospheric Environment Monitoring and Pollution Control, School of Environmental Science and Engineering, Nanjing University of Information Science and Technology, Nanjing 210044 (China); The Key Laboratory of Water and Sediment Sciences, Ministry of Education, Department of Environmental Engineering, Peking University, Beijing 100871 (China); Environmental Engineering Program, Department of Civil Engineering, Auburn University, Auburn, AL 36849 (United States); Sun, Weiling [The Key Laboratory of Water and Sediment Sciences, Ministry of Education, Department of Environmental Engineering, Peking University, Beijing 100871 (China); Borthwick, Alistair G.L. [School of Engineering, The University of Edinburgh, The King’s Buildings, Edinburgh EH9 3JL (United Kingdom); Wang, Ting [The Key Laboratory of Water and Sediment Sciences, Ministry of Education, Department of Environmental Engineering, Peking University, Beijing 100871 (China); Li, Fan [Environmental Engineering Program, Department of Civil Engineering, Auburn University, Auburn, AL 36849 (United States); Guan, Yidong, E-mail: yidongguan@nuist.edu.cn [Jiangsu Key Laboratory of Atmospheric Environment Monitoring and Pollution Control, School of Environmental Science and Engineering, Nanjing University of Information Science and Technology, Nanjing 210044 (China); Environmental Engineering Program, Department of Civil Engineering, Auburn University, Auburn, AL 36849 (United States)

    2016-11-05

    Highlights: • TNS composed of anatase and titanate synthesized via a facile one-step method. • Cr(VI) and 4-CP can be simultaneously removed by TNS through photocatalysis. • Photocatalytic efficiencies of Cr(VI) and 4-CP greatly enhanced when coexisting. • Synergetic promotion effect occurs due to separation of electron-hole pairs. • Autosynchronous doping after Cr(III) adsorption leads to narrowed energy gap. - Abstract: Clean-up of wastewaters with coexisting heavy metals and organic contaminants is a huge issue worldwide. In this study, a novel anatase/titanate nanosheet composite material (labeled as TNS) synthesized through a one-step hydrothermal reaction was demonstrated to achieve the goal of simultaneous removal of Cr(VI) and 4-cholophenol (4-CP) from water. TEM and XRD analyses indicated the TNS was a nano-composite of anatase and titanate, with anatase acting as the primary photocatalysis center and titanate as the main adsorption site. Enhanced photocatalytic removal of co-existent Cr(VI) and 4-CP was observed in binary systems, with apparent rate constants (k{sub 1}) for photocatalytic reactions of Cr(VI) and 4-CP about 3.1 and 2.6 times of that for single systems. In addition, over 99% of Cr(VI) and 4-CP was removed within 120 min through photocatalysis by TNS at pH 7 in the binary system. Mechanisms for enhanced photocatalytic efficiency in the binary system are identified as: (1) a synergetic effect on the photo-reduction of Cr(VI) and photo-oxidation of 4-CP due to efficient separation of electron-hole pairs, and (2) autosynchronous doping because of reduced Cr(III) adsorption onto TNS. Furthermore, TNS could be efficiently reused after a simple acid-base treatment.

  3. The Adsorption of Cr(VI Using Chitosan-Alumina Adsorbent

    Directory of Open Access Journals (Sweden)

    Darjito Darjito

    2013-12-01

    Full Text Available Chitosan as adsorbent has been used widely, however it was not effective yet for metal ions adsorption in industrial scale. In acidic condition, chitosan’s active site tends to decrease. This drawback can was solved by coating of chitosan active site on alumina. This paper discloses to overcome that limitation. The charateristic of the active side was analysed by FTIR spectrometry toward vibration N-H group at 1679.15 cm-1, C=O group of oxalate at 1703.30 cm-1, and Al-O group of alumina at 924.07 cm-1. The adsorption capacity of the developed adsorbent was tester to adsorb Cr(VI ions under various of pH value such as 1, 2, 3, 4, 5, 6, and 7. The contact time affect toward the adsorption was also reported in 20, 30, 40 50, 60, 70, and 80 minute. In addition, the concentration effects (100, 200, 300, 400, 500, and 600 ppm was also studied. Chromium (VI was measured using spectronic-20. Adsorption capacity was obtained at 66.90 mg/g under optimum conditions pH 2, and contact time 60 minute, respectively.

  4. Geophysical monitoring of hydrological and biogeochemical transformations associated with Cr(VI) bioremediation.

    Science.gov (United States)

    Hubbard, Susan S; Williams, Ken; Conrad, Mark E; Faybishenko, Boris; Peterson, John; Chen, Jinsong; Long, Phil; Hazent, Terry

    2008-05-15

    Understanding how hydrological and biogeochemical properties change over space and time in response to remedial treatments is hindered by our ability to monitor these processes with sufficient resolution and over field relevant scales. Here, we explored the use of geophysical approaches for monitoring the spatiotemporal distribution of hydrological and biogeochemical transformations associated with a Cr(VI) bioremediation experiment performed at Hanford, WA. We first integrated hydrological wellbore and geophysical tomographic data sets to estimate hydrological zonation at the study site. Using results from laboratory biogeophysical experiments and constraints provided by field geochemical data sets, we then interpreted time-lapse seismic and radar tomographic data sets, collected during thirteen acquisition campaigns over a three year experimental period, in terms of hydrological and biogeochemical transformations. The geophysical monitoring data sets were used to infer: the spatial distribution of injected electron donor; the evolution of gas bubbles; variations in total dissolved solids (nitrate and sulfate) as a function of pumping activity; the formation of precipitates and dissolution of calcites; and concomitant changes in porosity. Although qualitative in nature, the integrated interpretation illustrates how geophysical techniques have the potential to provide a wealth of information about coupled hydrobiogeochemical responses to remedial treatments in high spatial resolution and in a minimally invasive manner. Particularly novel aspects of our study include the use of multiple lines of evidence to constrain the interpretation of a long-term, field-scale geophysical monitoring data set and the interpretation of the transformations as a function of hydrological heterogeneity and pumping activity.

  5. Enhancement of Cr(VI) Ion Removal Using Nanochitosan Coated on Bituminous Activated Carbon.

    Science.gov (United States)

    Chooaksorn, Wanida; Nitisoravut, Rachnarin; Polprasert, Chongrak; Babel, Sandhya; Laohhasurayotin, Kritapas; Kangwansupamonkon, Wiyong

    2016-11-01

      Bituminous activated carbon (AC) has been widely used as a sorbent for adsorption of non-polar species, but its performance for removal of ionic species such as heavy metals has not been as efficient. In this study, AC was modified with chitosan nanoparticles (CN) using facile methods of dip coating and wet impregnation. The CN-coated AC demonstrated an increase in Cr(VI) removal efficiency in both kinetics and adsorption capacity. The adsorption capacity of the CN-coated AC (mg/g) was more than twice that of the uncoated AC (36.36 mg/g), or pure chitosan (32.57 mg/g). The sizes of the synthesized CN (160-2,000 nm) can be controlled by varying the concentration of the chitosan/reagents used. The adsorption isotherms are better described using the Freundlich rather than the Langmuir model and are in agreement with the heterogeneity of the surfaces. Adsorption kinetics followed that of the pseudo-second-order kinetics, suggesting chemisorption as a rate limiting step.

  6. Adsorption and Reduction of Hexavalent Chromium on the Surface of Vivianite at Acidic Environment

    Science.gov (United States)

    HA, S.; Hyun, S. P.; Lee, W.

    2016-12-01

    Due to the rapid increase of chemical use in industrial activities, acid spills have frequently occurred in Korea. The acid spill causes soil and water acidification and additional problems such as heavy metal leaching from the soil. Hexavalent chromium (Cr(VI)) is relatively mobile in the environment and toxic and mutagenic. Monoclinic octa-hydrated ferrous phosphate, vivianite, is one of commonly found iron-bearing soil minerals occurring in phosphorous-enriched reducing environments. We have investigated reductive sorption of Cr(VI) on the vivianite surfaces using batch experimental tests under diverse groundwater conditions. Cr(VI) (5 mg/L) was added in 6.5 g/L vivianite suspension buffered at pH 5, 7, and 9, using 0.05 M HEPES or tris buffer solution, to check the effect of pH on the reductive sorption of Cr(VI) on the vivianite surface. The aqueous Cr(VI) removal was fastest at pH 5, followed by pH 7, and pH 9. The effect of ionic strength on the removal kinetics of Cr(VI) was negligible. It could be subsequently removed via sorption and reduction on the surface of vivianite of which reactive chemical species could be aqueous Fe(II), iron oxides, and metavivianite. Adsorption test was conducted using the same amount of Cr(III) to check the selectivity of chromium species on the vivianite surface for the reductive adsorption. Through Cr extraction test, amount of strong-bound Cr to vivianite is similar for Cr(III) and Cr(VI) injection but amount of weak-bound Cr is bigger for Cr(VI) injection. Reaction mechanism for the sorption and reductive transformation of Cr(VI) to Cr(III) species at reactive sites of vivianite surface are discussed based on surface complexation modeling and K-edge Fe X-ray absorption near edge structure (XANES) results. Since vivianite is reacted with Cr(VI), two smooth peaks of absorption edge changed to one sharp peak. Pre-edge that contains 1s-3d transition information tends to show high peak when reaction time is increased and pH is

  7. Hexavalent chromium removal in contaminated water using reticulated chitosan micro/nanoparticles from seafood processing wastes.

    Science.gov (United States)

    Dima, Jimena Bernadette; Sequeiros, Cynthia; Zaritzky, Noemi E

    2015-12-01

    Chitosan particles (CH) were obtained from seafood processing wastes (shrimp shells) and physicochemically characterized; deacetylation degree of CH was measured by Infrared Spectroscopy (FTIR) and potentiometric titration; polymer molecular weight was determined by intrinsic viscosity measurements. Reticulated micro/nanoparticles of chitosan (MCH) with an average diameter close to 100nm were synthesized by ionic gelation of chitosan using tripolyphosphate (TPP), and characterized by SEM, size distribution and Zeta-potential. Detoxification capacities of CH and MCH were tested analyzing the removal of hexavalent chromium Cr(VI) from contaminated water, at different initial chromium concentrations. The effect of pH on adsorption capacity of CH and MCH was experimentally determined and analyzed considering the Cr(VI) stable complexes (anions) formed, the presence of protonated groups in chitosan particles and the addition of the reticulating agent (TPP). Chitosan crosslinking was necessary to adsorb Cr(VI) at pHremoved from the solution was reduced and bound to the MCH as Cr(III). The reduction of toxic Cr(VI) to the less or nontoxic Cr(III) by the reticulated chitosan micro/nanoparticles can be considered a very efficient detoxification technique for the treatment of Cr(VI) contaminated water. Copyright © 2015 Elsevier Ltd. All rights reserved.

  8. Chromium in exhaled breath condensate (EBC), erythrocytes, plasma and urine in the biomonitoring of chrome-plating workers exposed to soluble Cr(VI).

    Science.gov (United States)

    Goldoni, Matteo; Caglieri, Andrea; De Palma, Giuseppe; Acampa, Olga; Gergelova, Petra; Corradi, Massimo; Apostoli, Pietro; Mutti, Antonio

    2010-02-01

    Chromium (Cr) levels measured in exhaled breath condensate (EBC-Cr) and urine (Cr-U) at the beginning and end of working shifts were related to those measured in erythrocytes (Cr-RBC) and plasma in 14 non-smoking male chrome-plating workers exposed to Cr(VI) in soluble aerosol form who did not report any significant current or past respiratory disease. Cr-U mainly correlated with Cr-P (Cr in plasma) at the end of the working shift (r(2) = 0.59, p < 0.01), whereas Cr-RBC correlated with EBC-Cr (r(2) = 0.32, p < 0.05); at the beginning of the shift, the only significant correlation was between Cr-U and Cr-RBC (r(2) = 0.74, p < 0.01). The clearance of Cr(iii) arising from Cr(VI) reduction was rapid, thus making Cr-U and Cr-P ideal biomarkers of the most recent exposure, whereas Cr-RBC may represent the fraction of Cr(VI) that reaches the bloodstream in non-reduced form and therefore depends on the airway inhaled dose represented by EBC-Cr. Cr-RBC clearance is slower and not only involves the free diffusion of Cr(iii) from RBC to plasma, but probably also involves more complicated kinetic phenomena involving other tissues and organs, which may explain the correlation between Cr-RBC and Cr-U and the lack of correlation Cr-RBC and Cr-P at least 36 h after the last exposure. In conclusion, our findings reinforce the idea that measuring Cr in EBC can significantly contribute to traditional biomonitoring by providing specific information at the target organ level and integrating our knowledge of Cr toxicokinetics.

  9. Long-term effect of low concentration Cr(VI) on P removal in granule-based enhanced biological phosphorus removal (EBPR) system.

    Science.gov (United States)

    Fang, Jing; Su, Bin; Sun, Peide; Lou, Juqing; Han, Jingyi

    2015-02-01

    In light of the fact that most wastewater in China contained both industrial and domestic wastewater, a 52-d systematical investigation was conducted on the long-term effect of low concentration Cr(VI) (0.3-0.8 mg L(-1)) on P removal performance of granule-based EBPR system in this study. The mechanisms were likewise discussed. Results showed that high Cr(VI) concentration (⩾0.5 mg L(-1)) could significantly inhibit P removal, while this phenomenon was not found when Cr(VI) concentration was less than (or equal to) 0.4 mg L(-1). Most of the granules was disintegrated and filamentous bacteria overgrew inducing sludge bulking occurred at 0.7 mg L(-1) Cr(VI). During the exposure test, the abundance of poly-phosphate-accumulating organisms (PAOs) significantly decreased while the populations of glycogen accumulating organisms (GAOs) and other bacteria increased. Both production and degradation of poly-β-hydroxyakanoates (PHAs) were apparently inhibited. An improved polysaccharide/protein (PS/PN) ratio was observed with the increasing Cr(VI) concentration, implying excessive polysaccharide was secreted by microorganisms to support its resistance to the toxicity of Cr(VI). Besides, good linear regression between PS/PN ratio and the granule size (R(2)=-0.86, p<0.01) was obtained, indicating that high PS/PN was adverse to granule stability. Correlation analysis indicated that the accumulation of granules intracellular Cr was directly responsible for the observed inhibitory effect on P removal process. The long-term Cr(VI) treatment had irreversible effects on granule-based EBPR system as it could not revive after a 16-d recovery process. Copyright © 2014 Elsevier Ltd. All rights reserved.

  10. Preparation of Polyacrylonitrile/Ferrous Chloride Composite Nanofibers by Electrospinning for Efficient Reduction of Cr(VI).

    Science.gov (United States)

    Zhou, Shilin; Liu, Fang; Zhang, Qian; Chen, Bor-Yann; Lin, Chin-Jung; Chang, Chang-Tang

    2015-08-01

    In this study, A novel adsorbent material of polyacrylonitrile (PAN)/ferrous chloride (FeCl2) composite nanofibers is prepared by electrospinning, a simple and effective method. The obtained composite nanofibers have a non-uniform morphology and structure and a large specific surface area of 13.8 m2 g-1. Fourier transform infrared spectroscopy (FTIR) revealed that Fe2+ was successful introduced into the composite nanofibers. Furthermore, the PAN/FeC12 composite nanofibers exhibited excellent performance in Cr removal, especially when reacted with reduction from a Cr(VI) standard containing solution, which has much faster removal efficiency than the previous report of Lin et al. (2011). The results of the adsorption isotherm show that the data fitted well to the Langmuir isotherm model. The maximum adsorption of chromium ions composite nanofibers is 108 mgCr/gFeCl2. An attempted model prediction of the transient dynamics of adsorption-desorption elucidated the feasible kinetic analysis of Cr6+ from the PAN/FeCl2 composite nanofibers. This kinetic modeling can be used both for adsorption of heavy metals wastewater and for organic-adsorption and biosorption of diverse wastewaters. The PAN/FeCl2 composite nanofibers producted in this study exhibit high efficiency in Cr(VI) removal from wastewater, and may be used as a reference for future investigation.

  11. Simultaneous removal of Cr(VI) and 4-chlorophenol through photocatalysis by a novel anatase/titanate nanosheet composite: Synergetic promotion effect and autosynchronous doping.

    Science.gov (United States)

    Liu, Wen; Sun, Weiling; Borthwick, Alistair G L; Wang, Ting; Li, Fan; Guan, Yidong

    2016-11-05

    Clean-up of wastewaters with coexisting heavy metals and organic contaminants is a huge issue worldwide. In this study, a novel anatase/titanate nanosheet composite material (labeled as TNS) synthesized through a one-step hydrothermal reaction was demonstrated to achieve the goal of simultaneous removal of Cr(VI) and 4-cholophenol (4-CP) from water. TEM and XRD analyses indicated the TNS was a nano-composite of anatase and titanate, with anatase acting as the primary photocatalysis center and titanate as the main adsorption site. Enhanced photocatalytic removal of co-existent Cr(VI) and 4-CP was observed in binary systems, with apparent rate constants (k1) for photocatalytic reactions of Cr(VI) and 4-CP about 3.1 and 2.6 times of that for single systems. In addition, over 99% of Cr(VI) and 4-CP was removed within 120min through photocatalysis by TNS at pH 7 in the binary system. Mechanisms for enhanced photocatalytic efficiency in the binary system are identified as: (1) a synergetic effect on the photo-reduction of Cr(VI) and photo-oxidation of 4-CP due to efficient separation of electron-hole pairs, and (2) autosynchronous doping because of reduced Cr(III) adsorption onto TNS. Furthermore, TNS could be efficiently reused after a simple acid-base treatment.

  12. Identification and geochemical modeling of processes controlling leaching of Cr(VI) and other major elements from chromite ore processing residue

    Science.gov (United States)

    Geelhoed, Jeanine S.; Meeussen, Johannes C. L.; Hillier, Stephen; Lumsdon, David G.; Thomas, Rhodri P.; Farmer, John G.; Paterson, Edward

    2002-11-01

    Chromite ore processing residue (COPR) contains very high levels of chromium as Cr(III) and Cr(VI) and has a pH of ˜11.5 to 12. Millions of tonnes of COPR have in the past been deposited in urban areas. We have studied the factors that control leaching of Cr(VI), Ca, Al, Si, and Mg from COPR by means of batch experiments, mineralogical characterization of COPR via X-ray powder diffraction and scanning electron microscopy, and chemical equilibrium modeling. Batch experiments at a range of pH values and two liquid:solid ratios showed that mineral solubility control exists for aqueous concentrations of Cr(VI) above pH 10. Calculations indicate that the solid phases that control the solubility of Cr(VI) at pH values above 11 are Cr(VI)-substituted hydrogarnet (Ca 3Al 2(H 4O 4,CrO 4) 3) and Cr(VI)-hydrocalumite (Ca 4Al 2(OH) 12CrO 4·6 H 2O), a layered double-hydroxide clay with chromate anions held in the interlayers. In the pH range 9.5 to 11, the description of the Cr(VI) concentration in solution was strongly improved by the incorporation in the model of Cr(VI)-ettringite (Ca 6Al 2(OH) 12(CrO 4) 3·26 H 2O), which precipitates as a secondary phase when hydrocalumite dissolves. The proposed model for leaching of COPR at high pH includes Cr(VI)-bearing hydrogarnet, Cr(VI)-hydrocalumite, Cr(VI)-ettringite, brucite, calcite, Ca 2Al 2(OH) 10·3 H 2O, CaH 2SiO 4, and gehlenite hydrate (Ca 2Al 2(OH) 6SiO 8H 8·H 2O). The model accurately predicts the concentrations of Cr(VI), Ca, Al, Si, and Mg in solution in the pH range 10 to 12 as well as the pH-buffering behavior. Below pH 8, a decrease in the Cr(VI) concentration in solution is observed, which may be attributed to sorption of chromate onto freshly precipitated Al and Fe hydroxide surfaces. Sulfate and carbonate show the same type of behavior as chromate. The chemistry of COPR shows similarities with cement and high-pH municipal waste incinerator bottom ash.

  13. Chi-square analysis of the reduction of ATP levels in L-02 hepatocytes by hexavalent chromium

    Directory of Open Access Journals (Sweden)

    Yang Yuan

    2012-06-01

    Full Text Available This study explored the reduction of adenosine triphosphate (ATP levels in L-02 hepatocytes by hexavalent chromium (Cr(VI using chi-square analysis. Cells were treated with 2, 4, 8, 16, or 32 μM Cr(VI for 12, 24, or 36 h. Methyl thiazolyl tetrazolium (MTT experiments and measurements of intracellular ATP levels were performed by spectrophotometry or bioluminescence assays following Cr(VI treatment. The chi-square test was used to determine the difference between cell survival rate and ATP levels. For the chi-square analysis, the results of the MTT or ATP experiments were transformed into a relative ratio with respect to the control (%. The relative ATP levels increased at 12 h, decreased at 24 h, and increased slightly again at 36 h following 4, 8, 16, 32 μM Cr(VI treatment, corresponding to a "V-shaped" curve. Furthermore, the results of the chi-square analysis demonstrated a significant difference of the ATP level in the 32-μM Cr(VI group (P < 0.05. The results suggest that the chi-square test can be applied to analyze the interference effects of Cr(VI on ATP levels in L-02 hepatocytes. The decreased ATP levels at 24 h indicated disruption of mitochondrial energy metabolism and the slight increase of ATP levels at 36 h indicated partial recovery of mitochondrial function or activated glycolysis in L-02 hepatocytes.

  14. Reduction of Hexavalent Chromium Using L-Cysteine Capped Nickel Nanocatalysts

    Directory of Open Access Journals (Sweden)

    Razium Ali Soomro

    2013-06-01

    Full Text Available The aim of this study was to reduce the highly toxic hexavalent chromium Cr(VI into less toxic chromium Cr(III species by using nickel nanoparticles (Ni NPs as catalysts in order to provide safety to the aqueous environment. In the first phase Ni NPs were synthesized in ethylene glycol and capped with l-cysteine by a modified microwave irradiation method using NaOH as the accelerator. The formed Ni NPs were characterized by various techniques such as UV-Visible spectroscopy, Fourier Transform Infra-red (FTIR spectroscopy and Scanning Electron Microscopy (SEM. In the second phase the formed Ni NPs were immobilized on glass surfaces and employed as catalyst for the reduction of Cr(VI ions. According to observations, 99% reduction of Cr(VI ions was achieved in the presence of 0.5 mg of Ni NPs catalyst in just five minutes as compared to nickel powder that showed only 16% reduction in 15 minutes. The study has a great impact on the aqueous pollution control of Cr(VI especially caused by the discharge of waste water from several industries utilizing Cr(VI containing salt as one of the essential gradients.

  15. Removal of hexavalent chromium by using red mud activated with cetyltrimethylammonium bromide.

    Science.gov (United States)

    Li, Deliang; Ding, Ying; Li, Lingling; Chang, Zhixian; Rao, Zhengyong; Lu, Ling

    2015-01-01

    The removal of hexavalent chromium [Cr(VI)] from aqueous solution by using red mud activated with cetyltrimethylammonium bromide (CTAB) was studied. The optimum operation parameters, such as CTAB concentration, pH values, contact time, and initial Cr(VI) concentration, were investigated. The best concentration of CTAB for modifying red mud was found to be 0.50% (mCTAB/VHCl,0.6 mol/L). The lower pH (Red mud activated with CTAB can greatly improve the removal ratio of Cr(VI) as high as four times than that of original red mud. Adsorption equilibrium was reached within 30 min under the initial Cr(VI) concentration of 100 mg L(-1). The isotherm data were analysed using Langmuir and Freundlich models. The adsorption of Cr(VI) on activated red mud fitted well to the Langmuir isotherm model, and the maximum adsorption capacity was estimated as 22.20 mg g(-1) (Cr/red mud). The adsorption process could be well described using the pseudo-second-order model. The result shows that activated red mud is a promising agent for low-cost water treatment.

  16. Improved Bi Film Wrapped Single Walled Carbon Nanotubes for Ultrasensitive Electrochemical Detection of Trace Cr(VI)

    Science.gov (United States)

    Zhou, Shilin; Xue, Zi-Ling; Xu, Lina; Gu, Yingying; Miao, Yuqing

    2014-01-01

    We report here the successful fabrication of an improved Bi film wrapped single walled carbon nanotubes modified glassy carbon electrode (Bi/SWNTs/GCE) as a highly sensitive platform for ultratrace Cr(VI) detection through catalytic adsorptive cathodic stripping voltammetry (AdCSV). The introduction of negatively charged SWNTs extraordinarily decreased the size of Bi particles to nanoscale due to electrostatic interaction which made Bi(III) cations easily attracted onto the surface of SWNTs in good order, leading to higher quality of Bi film deposition. The obtained Bi/SWNTs composite was well characterized with electrochemical impedance spectroscopy (EIS), scanning electron microscopy (SEM), the static water contact angle and the voltammetric measurements. The results demonstrates the improvements in the quality of Bi film deposited on the surface of SWNTs such as faster speed of electron transfer, more uniform and smoother morphology, better hydrophilicity and higher stripping signal. Using diethylene triaminepentaacetic acid (DTPA) as complexing ligand, the fabricated electrode displays a well-defined and highly sensitive peak for the reduction of Cr(III)-DTPA complex at −1.06 V (vs. Ag/AgCl) with a linear concentration range of 0–25 nM and a fairly low detection limit of 0.036 nM. No interference was found in the presence of coexisting ions, and good recoveries were achieved for the analysis of a river sample. In comparison to previous approaches using Bi film modified GCE, the newly designed electrode exhibits better reproducibility and repeatability towards aqueous detection of trace Cr(VI) and appears to be very promising as the basis of a highly sensitive and selective voltammetric procedure for Cr(VI) detection at trace level in real samples. PMID:24771881

  17. Improved Bi Film Wrapped Single Walled Carbon Nanotubes for Ultrasensitive Electrochemical Detection of Trace Cr(VI).

    Science.gov (United States)

    Ouyang, Ruizhuo; Zhang, Wangyao; Zhou, Shilin; Xue, Zi-Ling; Xu, Lina; Gu, Yingying; Miao, Yuqing

    2013-12-15

    We report here the successful fabrication of an improved Bi film wrapped single walled carbon nanotubes modified glassy carbon electrode (Bi/SWNTs/GCE) as a highly sensitive platform for ultratrace Cr(VI) detection through catalytic adsorptive cathodic stripping voltammetry (AdCSV). The introduction of negatively charged SWNTs extraordinarily decreased the size of Bi particles to nanoscale due to electrostatic interaction which made Bi(III) cations easily attracted onto the surface of SWNTs in good order, leading to higher quality of Bi film deposition. The obtained Bi/SWNTs composite was well characterized with electrochemical impedance spectroscopy (EIS), scanning electron microscopy (SEM), the static water contact angle and the voltammetric measurements. The results demonstrates the improvements in the quality of Bi film deposited on the surface of SWNTs such as faster speed of electron transfer, more uniform and smoother morphology, better hydrophilicity and higher stripping signal. Using diethylene triaminepentaacetic acid (DTPA) as complexing ligand, the fabricated electrode displays a well-defined and highly sensitive peak for the reduction of Cr(III)-DTPA complex at -1.06 V (vs. Ag/AgCl) with a linear concentration range of 0-25 nM and a fairly low detection limit of 0.036 nM. No interference was found in the presence of coexisting ions, and good recoveries were achieved for the analysis of a river sample. In comparison to previous approaches using Bi film modified GCE, the newly designed electrode exhibits better reproducibility and repeatability towards aqueous detection of trace Cr(VI) and appears to be very promising as the basis of a highly sensitive and selective voltammetric procedure for Cr(VI) detection at trace level in real samples.

  18. Development of a standard reference material for Cr(vi) in contaminated soil

    Science.gov (United States)

    Nagourney, S.J.; Wilson, S.A.; Buckley, B.; Kingston, H.M.S.; Yang, S.-Y.; Long, S.E.

    2008-01-01

    Over the last several decades, considerable contamination by hexavalent chromium has resulted from the land disposal of Chromite Ore Processing Residue (COPR). COPR contains a number of hexavalent chromium-bearing compounds that were produced in high temperature industrial processes. Concern over the carcinogenic potential of this chromium species, and its environmental mobility, has resulted in efforts to remediate these waste sites. To provide support to analytical measurements of hexavalent chromium, a candidate National Institute of Standards and Technology (NIST) Standard Reference Material?? (SRM 2701), having a hexavalent chromium content of approximately 500 mg kg -1, has been developed using material collected from a waste site in Hudson County, New Jersey, USA. The collection, processing, preparation and preliminary physico-chemical characterization of the material are discussed. A two-phase multi-laboratory testing study was carried out to provide data on material homogeneity and to assess the stability of the material over the duration of the study. The study was designed to incorporate several United States Environmental Protection Agency (USEPA) determinative methods for hexavalent chromium, including Method 6800 which is based on speciated isotope dilution mass spectrometry (SIDMS), an approach which can account for chromium species inter-conversion during the extraction and measurement sequence. This journal is ?? The Royal Society of Chemistry 2008.

  19. Hexavalent chromium is cytotoxic and genotoxic to hawksbill sea turtle cells

    Energy Technology Data Exchange (ETDEWEB)

    Wise, Sandra S., E-mail: sandra.wise@maine.edu [Wise Laboratory of Environmental and Genetic Toxicology, University of Southern Maine, Science Building, 96 Falmouth Street, Portland, ME 04103 (United States); Maine Center for Toxicology and Environmental Health, University of Southern Maine, Science Building, 96 Falmouth Street, Portland, ME 04103 (United States); Department of Applied Medical Science, University of Southern Maine, Science Building, 96 Falmouth Street, Portland, ME 04103 (United States); Xie, Hong, E-mail: hongxie@usm.maine.edu [Wise Laboratory of Environmental and Genetic Toxicology, University of Southern Maine, Science Building, 96 Falmouth Street, Portland, ME 04103 (United States); Maine Center for Toxicology and Environmental Health, University of Southern Maine, Science Building, 96 Falmouth Street, Portland, ME 04103 (United States); Department of Applied Medical Science, University of Southern Maine, Science Building, 96 Falmouth Street, Portland, ME 04103 (United States); Fukuda, Tomokazu, E-mail: tomofukuda009@gmail.com [Graduate School of Agricultural Sciences, Tohoku University, Laboratory of Animal Breeding and Genetics, Second Research Building, Rm 112, 1-1 Amamiyamachi, Aoba-ku, Sendai 981-8555 (Japan); Douglas Thompson, W., E-mail: dougt@usm.maine.edu [Maine Center for Toxicology and Environmental Health, University of Southern Maine, Science Building, 96 Falmouth Street, Portland, ME 04103 (United States); Department of Applied Medical Science, University of Southern Maine, Science Building, 96 Falmouth Street, Portland, ME 04103 (United States); and others

    2014-09-01

    Sea turtles are a charismatic and ancient ocean species and can serve as key indicators for ocean ecosystems, including coral reefs and sea grass beds as well as coastal beaches. Genotoxicity studies in the species are absent, limiting our understanding of the impact of environmental toxicants on sea turtles. Hexavalent chromium (Cr(VI)) is a ubiquitous environmental problem worldwide, and recent studies show it is a global marine pollutant of concern. Thus, we evaluated the cytotoxicity and genotoxicity of soluble and particulate Cr(VI) in hawksbill sea turtle cells. Particulate Cr(VI) was both cytotoxic and genotoxic to sea turtle cells. Concentrations of 0.1, 0.5, 1, and 5 μg/cm{sup 2} lead chromate induced 108, 79, 54, and 7% relative survival, respectively. Additionally, concentrations of 0, 0.1, 0.5, 1, and 5 μg/cm{sup 2} lead chromate induced damage in 4, 10, 15, 26, and 36% of cells and caused 4, 11, 17, 30, and 56 chromosome aberrations in 100 metaphases, respectively. For soluble Cr, concentrations of 0.25, 0.5, 1, 2.5, and 5 μM sodium chromate induced 84, 69, 46, 25, and 3% relative survival, respectively. Sodium chromate induced 3, 9, 9, 14, 21, and 29% of metaphases with damage, and caused 3, 10, 10, 16, 26, and 39 damaged chromosomes in 100 metaphases at concentrations of 0, 0.25, 0.5, 1, 2.5, and 5 μM sodium chromate, respectively. These data suggest that Cr(VI) may be a concern for hawksbill sea turtles and sea turtles in general. - Highlights: • Particulate Cr(VI) is cytotoxic and clastogenic to hawksbill sea turtle cells. • Soluble Cr(VI) is cytotoxic and clastogenic to hawksbill sea turtle cells. • Cr(VI) may be a risk factor for hawksbill sea turtle health.

  20. Statistical Analysis of Main and Interaction Effects on Cu(II) and Cr(VI) Decontamination by Nitrogen-Doped Magnetic Graphene Oxide

    Science.gov (United States)

    Hu, Xinjiang; Wang, Hui; Liu, Yunguo

    2016-10-01

    A nitrogen-doped magnetic graphene oxide (NMGO) was synthesized and applied as an adsorbent to remove Cu(II) and Cr(VI) ions from aqueous solutions. The individual and combined effects of various factors (A: pH, B: temperature, C: initial concentration of metal ions, D: CaCl2, and E: humic acid [HA]) on the adsorption were analyzed by a 25-1 fractional factorial design (FFD). The results from this study indicated that the NMGO had higher adsorption capacities for Cu(II) ions than for Cr(VI) ions under most conditions, and the five selected variables affected the two adsorption processes to different extents. A, AC, and C were the very important factors and interactions for Cu(II) adsorption. For Cr(VI) adsorption, A, B, C, AB, and BC were found to be very important influencing variables. The solution pH (A) was the most important influencing factor for removal of both the ions. The main effects of A-E on the removal of Cu(II) were positive. For Cr(VI) adsorption, the main effects of A and D were negative, while B, C, and E were observed to have positive effects. The maximum adsorption capacities for Cu(II) and Cr(VI) ions over NMGO were 146.365 and 72.978 mg/g, respectively, under optimal process conditions.

  1. Synthesis of mesoporous magnetic gamma-Fe2O3 and its application to Cr(VI) removal from contaminated water.

    Science.gov (United States)

    Wang, Peng; Lo, Irene M C

    2009-08-01

    In this study, mesoporous magnetic iron-oxide (gamma-Fe(2)O(3)) was synthesized as an adsorbent for Cr(VI) removal. For material synthesis, mesoporous silica (KIT-6) was used as a hard template and to drive iron precursor into KIT-6, a 'greener', affinity based impregnation method was employed, which involved using a nonpolar solvent (xylene) and led to recycling of the solvent. The results of Cr(VI) removal experiments showed that the synthesized mesoporous gamma-Fe(2)O(3) has a Cr(VI) adsorption capacity comparable with 10nm nonporous gamma-Fe(2)O(3) but simultaneously has a much faster separation than 10nm nonporous gamma-Fe(2)O(3) in the presence of an external magnetic field under the same experimental conditions. Cr(VI) adsorption capacity onto the mesoporous gamma-Fe(2)O(3) increased with decreasing solution pH and could be readily regenerated. Therefore, mesoporous gamma-Fe(2)O(3) presents a reusable adsorbent for a fast, convenient, and highly efficient removal of Cr(VI) from contaminated water.

  2. Statistical Analysis of Main and Interaction Effects on Cu(II) and Cr(VI) Decontamination by Nitrogen–Doped Magnetic Graphene Oxide

    Science.gov (United States)

    Hu, Xinjiang; Wang, Hui; Liu, Yunguo

    2016-01-01

    A nitrogen–doped magnetic graphene oxide (NMGO) was synthesized and applied as an adsorbent to remove Cu(II) and Cr(VI) ions from aqueous solutions. The individual and combined effects of various factors (A: pH, B: temperature, C: initial concentration of metal ions, D: CaCl2, and E: humic acid [HA]) on the adsorption were analyzed by a 25−1 fractional factorial design (FFD). The results from this study indicated that the NMGO had higher adsorption capacities for Cu(II) ions than for Cr(VI) ions under most conditions, and the five selected variables affected the two adsorption processes to different extents. A, AC, and C were the very important factors and interactions for Cu(II) adsorption. For Cr(VI) adsorption, A, B, C, AB, and BC were found to be very important influencing variables. The solution pH (A) was the most important influencing factor for removal of both the ions. The main effects of A–E on the removal of Cu(II) were positive. For Cr(VI) adsorption, the main effects of A and D were negative, while B, C, and E were observed to have positive effects. The maximum adsorption capacities for Cu(II) and Cr(VI) ions over NMGO were 146.365 and 72.978 mg/g, respectively, under optimal process conditions. PMID:27694891

  3. On the removal of hexavalent chromium from a Class F fly ash.

    Science.gov (United States)

    Huggins, F E; Rezaee, M; Honaker, R Q; Hower, J C

    2016-05-01

    Coarse and fine samples of a Class F fly ash obtained from commercial combustion of Illinois bituminous coal have been exposed to two long-term leaching tests designed to simulate conditions in waste impoundments. ICP-AES analysis indicated that the coarse and fine fly ash samples contained 135 and 171mg/kg Cr, respectively. Measurements by XAFS spectroscopy showed that the ash samples originally contained 5 and 8% of the chromium, respectively, in the hexavalent oxidation state, Cr(VI). After exposure to water for more than four months, the percentage of chromium as Cr(VI) in the fly-ash decreased significantly for the coarse and fine fly-ash in both tests. Combining the XAFS data with ICP-AES data on the concentration of chromium in the leachates indicated that, after the nineteen-week-long, more aggressive, kinetic test on the coarse fly ash, approximately 60% of the Cr(VI) had been leached, 20% had been reduced to Cr(III) and retained in the ash, and 20% remained as Cr(VI) in the ash. In contrast, during the six-month-long baseline test, very little Cr was actually leached from either the coarse or the fine fly-ash (ash was retained in the ash in that form, while the remainder, 34% and 80%, respectively, was reduced and retained in the ash as Cr(III). The results are interpreted as indicating that Cr(VI) present in Class F fly-ash can be reduced to Cr(III) when in contact with water and that such chemical reduction can compete with physical removal of Cr(VI) from the ash by aqueous leaching.

  4. Potential of modified iron-rich foundry waste for environmental applications: Fenton reaction and Cr(VI) reduction.

    Science.gov (United States)

    Oliveira, Patrícia E F; Oliveira, Leandro D; Ardisson, José D; Lago, Rochel M

    2011-10-30

    A magnetic fraction (15%) from a waste of foundry sand (WFS), composed of sand, carbon, bentonite clay and iron (10%) was modified by thermal treatment at 400, 600 and 800°C under inert atmosphere. Mössbauer analyses showed that the thermal treatment increased the amount of Fe(3)O(4) from 25 to 55% by reduction of Fe(2)O(3) and highly dispersed Fe(3+) by the carbon present in the waste. The Fe(3)O(4) caused a significant increase on the activity of two important reactions with application in environmental remediation: the Fenton oxidation of indigo carmine dye with H(2)O(2) and the reduction of Cr(VI) to Cr(III). The magnetic fraction of WFS was also mixed with hematite (Fe(2)O(3)) and thermally treated at 400, 600 and 800°C. This treatment produced large amounts of surface Fe(3)O(4) and increased substantially the rate of Fenton reaction as well as Cr(VI) reduction. This reactivity combined with the presence of carbon (an adsorbent for organic contaminants), bentonite clay (an adsorbent for metallic contaminants) and the granulometry/packing/hydrodynamic features make WFS a promising material for use in reactive permeable barriers.

  5. Improvement of simultaneous Cr(VI) and phenol removal by an immobilised bacterial consortium and characterisation of biodegradation products.

    Science.gov (United States)

    Ontañon, Ornella M; González, Paola S; Barros, Germán G; Agostini, Elizabeth

    2017-07-25

    Microbial bioremediation emerged some decades ago as an eco-friendly technology to restore polluted sites. Traditionally, the search for microorganisms suitable for bioremediation has been based on the selection of isolated strains able to remove a specific type of pollutant. However, this strategy has now become obsolete, since co-pollution is a global reality. Thus, current studies attempt to find bacterial cultures capable of coping with a mixture of organic and inorganic compounds. In this sense, the bacterial consortium SFC 500-1 has demonstrated efficiency for Cr(VI) and phenol removal, both of which are found in many industrial wastewaters. In the present study, the ability of SFC 500-1 for simultaneous removal was improved through its entrapment in a Ca-alginate matrix. This strategy led to an increased removal of Cr(VI), which was partially reduced to Cr(III). Immobilised cells were able to tolerate and degrade phenol up to 1,500mg/l at high rates, forming catechol and cis,cis-muconate as oxidation intermediates. Successful removal potential through 5 cycles of reuse, as well as after long-term storage, was another important advantage of the immobilised consortium. These characteristics make SFC 500-1 an interesting system for potential application in the biotreatment of co-polluted effluents. Copyright © 2017. Published by Elsevier B.V.

  6. Cr(VI) and COD removal from landfill leachate by polyculture constructed wetland at a pilot scale.

    Science.gov (United States)

    Madera-Parra, C A; Peña, M R; Peña, E J; Lens, P N L

    2015-09-01

    Four subsurface horizontal-flow constructed wetlands (CWs) at a pilot scale planted with a polyculture of the tropical plants Gynerium sagittatum (Gs), Colocasia esculenta (Ce) and Heliconia psittacorum (He) were evaluated for 7 months. The CW cells with an area of 17.94 m(2) and 0.60 m (h) each and 0.5 m of gravel were operated at continuous gravity flow (Q = 0.5 m(3) day(-1)) and a theoretical HRT of 7 days each and treating landfill leachate for the removal of filtered chemical oxygen demand (CODf), BOD5, TKN, NH4 (+), NO3 (-), PO4 (3-)-P and Cr(VI). Three CWs were divided into three sections, and each section (5.98 m(2)) was seeded with 36 cuttings of each species (plant density of six cuttings per square metre). The other unit was planted randomly. The final distributions of plants in the bioreactors were as follows: CW I (He-Ce-Gs), CW II (randomly), CW III (Ce-Gs-He) and CW IV (Gs-He-Ce). The units received effluent from a high-rate anaerobic pond (BLAAT®). The results show a slightly alkaline and anoxic environment in the solid-liquid matrix (pH = 8.0; 0.5-2 mg L(-1) dissolved oxygen (DO)). CODf removal was 67 %, BOD5 80 %, and TKN and NH4 (+) 50-57 %; NO3 (-) effluents were slightly higher than the influent, PO4 (3-)-P (38 %) and Cr(VI) between 50 and 58 %. CW IV gave the best performance, indicating that plant distribution may affect the removal capacity of the bioreactors. He and Gs were the plants exhibiting a translocation factor (TF) of Cr(VI) >1. The evaluated plants demonstrated their suitability for phytoremediation of landfill leachate, and all of them can be categorized as Cr(VI) accumulators. The CWs also showed that they could be a low-cost operation as a secondary system for treatment of intermediated landfill leachate (LL).

  7. Facile preparation of magnetic mesoporous MnFe2O4@SiO2-CTAB composites for Cr(VI) adsorption and reduction.

    Science.gov (United States)

    Li, Na; Fu, Fenglian; Lu, Jianwei; Ding, Zecong; Tang, Bing; Pang, Jiabin

    2017-01-01

    Chromium-contaminated water is regarded as one of the biggest threats to human health. In this study, a novel magnetic mesoporous MnFe2O4@SiO2-CTAB composite was prepared by a facile one-step modification method and applied to remove Cr(VI). X-ray diffraction, scanning electron microscopy, transmission electron microscopy, specific surface area, and vibrating sample magnetometer were used to characterize MnFe2O4@SiO2-CTAB composites. The morphology analysis showed that the composites displayed a core-shell structure. The outer shell was mesoporous silica with CTAB and the core was MnFe2O4 nanoparticles, which ensured the easy separation by an external magnetic field. The performance of MnFe2O4@SiO2-CTAB composites in Cr(VI) removal was far better than that of bare MnFe2O4 nanoparticles. There were two reasons for the effective removal of Cr(VI) by MnFe2O4@SiO2-CTAB composites: (1) mesoporous silica shell with abundant CTA(+) significantly enhanced the Cr(VI) adsorption capacity of the composites; (2) a portion of Cr(VI) was reduced to less toxic Cr(III) by MnFe2O4, followed by Cr(III) immobilized on MnFe2O4@SiO2-CTAB composites, which had been demonstrated by X-ray photoelectron spectroscopy results. The adsorption of Cr(VI) onto MnFe2O4@SiO2-CTAB followed the Freundlich isotherm model and pseudo-second-order model. Tests on the regeneration and reuse of the composites were performed. The removal efficiency of Cr(VI) still retained 92.4% in the sixth cycle. MnFe2O4@SiO2-CTAB composites exhibited a great potential for the removal of Cr(VI) from water.

  8. MIL-53(Fe) as a highly efficient bifunctional photocatalyst for the simultaneous reduction of Cr(VI) and oxidation of dyes

    Energy Technology Data Exchange (ETDEWEB)

    Liang, Ruowen; Jing, Fenfen; Shen, Lijuan; Qin, Na; Wu, Ling, E-mail: wuling@fzu.edu.cn

    2015-04-28

    Highlights: • Fe(III)-based MOF was firstly applied to the photocatalytic reduction reaction. • MIL-53(Fe) exhibited an outstanding photocatalytic activity for reduction of Cr(VI). • A first systematic study of the Fe(III)-based MOF as bifunctional photocatalyst. • Dyes and Cr(VI) could be also converted simultaneously over MIL-53(Fe). • MIL-53(Fe) was performed a stable and reusable visible-light-driven photocatalyst. - Abstract: A bifunctional photocatalyst-Fe-benzenedicarboxylate (MIL-53(Fe)) has been synthesized successfully via a facile solvothermal method. The resulting MIL-53(Fe) photocatalyst exhibited an excellent visible light (λ ≥ 420 nm) photocatalytic activity for the reduction of Cr(VI), the reduction rate have reached about 100% after 40 min of visible light irradiation, which has been more efficient than that of N-doped TiO{sub 2} (85%) under identical experimental conditions. Further experimental results have revealed that the photocatalytic activity of MIL-53(Fe) for the reduction of Cr(VI) can be drastically affected by the pH value of the reaction solution, the hole scavenger and atmosphere. Moreover, MIL-53(Fe) has exhibited considerable photocatalytic activity in the mixed systems (Cr(VI)/dyes). After 6 h of visible light illumination, the reduction ratio of Cr(VI) and the degradation ratio of dyes have been exceed 60% and 80%, respectively. More significantly, the synergistic effect can also be found during the process of photocatalytic treatment of Cr(VI) contained wastewater under the same photocatalytic reaction conditions, which makes it a potential candidate for environmental restoration. Finally, a possible reaction mechanism has also been investigated in detail.

  9. Hexavalent chromium induces energy metabolism disturbance and p53-dependent cell cycle arrest via reactive oxygen species in L-02 hepatocytes.

    Science.gov (United States)

    Xiao, Fang; Feng, Xiaotao; Zeng, Ming; Guan, Lan; Hu, Qingqing; Zhong, Caigao

    2012-12-01

    Hexavalent chromium [Cr(VI)] has become a non-negligible pollutant in the world. Cr(VI) exposure leads to severe damage to the liver, but the mechanisms involved in Cr(VI)-mediated toxicity in the liver are unclear. The present study aimed to explore whether Cr(VI) induces energy metabolism disturbance and cell cycle arrest in human L-02 hepatocytes. We showed that Cr(VI) inhibited state 3 respiration, respiratory control rate (RCR), and subsequently induced energy metabolism disturbance with decreased ATP production. Interestingly, cell cycle analysis by flow cytometry and protein expression analysis by western blotting revealed that low dose of Cr(VI) (4 uM) exposure induced S phase cell cycle arrest with decreased mediator of replication checkpoint 1 (Mrc1) and cyclin-dependent kinase 2 (CDK2), while higher doses of Cr(VI) (16, 32 uM) exposure resulted in G2/M phase arrest with decreased budding uninhibited by benzimidazoles-related 1 (BubR1) and cell division cycle 25 (CDC25). Mechanism study revealed that Cr(VI) decreased the activities of mitochondrial respiratory chain complex (MRCC) I and II, thus leading to ROS accumulation. Moreover, inhibiting ROS production by antioxidant N-acetyl-L-cysteine (NAC) rescued Cr(VI)-induced ATP depletion and cell cycle arrest. ROS-mediated p53 activation was found to involve in Cr(VI)-induced cell cycle arrest, and p53 inhibitor Pifithrin-α (PFT-α) rescued Cr(VI)-induced reduction of check point proteins Mrc1 and BubR1, thus inhibiting cell cycle arrest. In summary, the present study provides experimental evidence that Cr(VI) leads to energy metabolism disturbance and p53-dependent cell cycle arrest via ROS in L-02 hepatocytes.

  10. Influence of rhamnolipids, produced by Pseudomonas aeruginosa NCAIM(P, B001380 on Cr(VI removal capacity in liquid medium

    Directory of Open Access Journals (Sweden)

    Avramović Nataša S.

    2013-01-01

    Full Text Available Pseudomonas aeruginosa NCAIM(P, B001380, a propitious bacterial strain isolated from mineral cutting oil was identified to be chromium tolerant and a producer of biosurfactant rhamnolipid (RL with potential application in heavy metal bioremediation. Culture growth, RL production and Cr(VI removal capacity of the strain in the presence of 50 mg L-1 (I and 100 mg L-1 of Cr(VI (II were studied. Maximum of RL production were found in the late-stationary phase at 72 h for both Cr(VI-amended cultures: I (236 mg L-1 and II (160 mg L-1, as well as the maximum of Cr(VI removal capacity: 70 % (I and 57 % (II. The amount of Cr in RL preparation II was 22 mg mg-1 determined by flame atomic absorption spectroscopy (FAAS. Appearance of a new band at 914 cm-1 in infrared (IR spectrum of RL (II indicated a significant proof for possible coordination of CrO42-ion with RL. The effect of Cr(VI on monorhamnolipids (RL1 and dirhamnolipids (RL2 distribution and its ratio were studied by electrospray ionization mass spectrometry (ESI-MS. An increase was observed in a RL2/RL1 ratio for II compared to control.

  11. Study on multielemental speciation analysis of Cr(VI), As(III) and As(V) in water by advanced hyphenated technique HPLC/ICP-DRC-MS. Fast and reliable procedures.

    Science.gov (United States)

    Marcinkowska, Monika; Komorowicz, Izabela; Barałkiewicz, Danuta

    2015-11-01

    Analytical procedures for multielemental speciation analysis of arsenite - As(III), arsenate - As(V) and hexavalent chromium - Cr(VI) in water using high performance liquid chromatography inductively coupled plasma mass spectrometry (HPLC/ICP-DRC-MS) hyphenated technique have been developed. A dynamic reaction cell (DRC) for spectral interferences elimination has been involved in the experiment. Application of oxygen and ammonia as reaction gases in the DRC under various conditions has been verified. Optimization of the following chromatographic conditions: mobile phase composition, concentration of particular components, mobile phase pH and flow rate, injection volume and column temperature, has been conducted. Species separation has been carried out on anion-exchange chromatographic column using isocratic elution with: 22 mM (NH4)2HPO4, 25 mM NH4NO3 (for procedure A) and 22 mM (NH4)2HPO4, 65 mM NH4NO3 (for procedure B) as mobile phases. Detection limits (LD) for procedure A were 0.16 µg L(-1), 0.090 µg L(-1), 0.073 µg L(-1), and for procedure B were 0.14 µg L(-1), 0.062 µg L(-1), 0.15 µg L(-1) for As(III), As(V) and Cr(VI), respectively. Linearity was tested at two concentration ranges of: (0.5-10.0) µg L(-1) for procedure A and (5-50) µg L(-1) for procedure B, and showed correlation coefficients for each of the analytes to be above 0.999. Repeatability values obtained for spiked real water samples were in the range of (4.2-7.6)% and (2.0-2.4)% for procedure A and B respectively. Accuracy was calculated based on the analysis of spiked real water samples at three concentration levels. Obtained recoveries were from 94% to 102%.

  12. Determination of hexavalent chromium concentration in industrial waste incinerator stack gas by using a modified ion chromatography with post-column derivatization method.

    Science.gov (United States)

    Miyake, Yuichi; Tokumura, Masahiro; Iwazaki, Yuta; Wang, Qi; Amagai, Takashi; Horii, Yuichi; Otsuka, Hideyuki; Tanikawa, Noboru; Kobayashi, Takeshi; Oguchi, Masahiro

    2017-06-16

    An ion chromatography with post-column derivatization with 1,5-diphenylcarbazide (IC-DPC) analytical method was modified to enable measurement of trace-level hexavalent chromium (Cr(VI)) in air. One of the difficulties in determining trace levels of Cr(VI) in air with conventional IC-DPC methods is co-elution of the solvent and ion peaks due to high concentrations of ionic compounds in the extract. However, by using gradient elution rather than isocratic elution we were able to fully resolve the Cr(VI) ion peak from the solvent peak without the need for diluting the extract, which would have reduced the minimum quantifiable level of the method. With this method, we were able to detect Cr(VI) in air at concentrations of 5.3ng/m(3) (assuming a sampling volume of 1m(3) and a final solution volume of 10mL). Recovery tests at three different concentrations of Cr(VI) (50, 250, 1000ng) were performed with or without fly ash; recovery rates at all the concentrations of Cr(VI), with or without fly ash, ranged from 68% to 110% (mean±relative standard deviation, 96%±11%), and there were no differences in recovery rates with respect to the presence or absence of fly ash. Finally, we used the developed method to determine the concentration of Cr(VI) in stack gases collected from eight industrial waste incinerators located in Japan. The concentration of Cr(VI) in the stack gases ranged from below the method quantification limit to 3100ng/m(3). The highest concentrations of Cr(VI) detected in the stack gases were two to three orders of magnitude higher than that in ambient air in Japan. Copyright © 2017 Elsevier B.V. All rights reserved.

  13. A study of low-cost adsorbent materials for removing Cr(VI from aqueous waste effluent Estudio de materiales adsorbentes de bajo costo para remover Cr(VI de efluentes acuosos

    Directory of Open Access Journals (Sweden)

    Castillo Serna Elianna

    2011-05-01

    Full Text Available  

    The present paper shows very high potential for two types of solid (a commercial alumina and material obtained by composting, i.e. matured compost on Cr(VI adsorption/elimination in aqueous solution using a concentration range close to those previously detected in waste-water from Colombian industries. Both had important properties for eliminating Cr(VI, the compost being more important as it represents low-cost material. Optimal conditions for chromium adsorption on alumina and compost were established. Initial Cr(VI alumina concentration was 10 mgL-1, with 100 mL/g volume of solution per adsorbent mass, pH=2.0, 1 hour equilibrium time and 150 rpm stirring. For compost, initial Cr(VI concentration was = 3 mg L-1, 50 mL/g volume of solution per adsorbent mass, pH=2.5, 3 hour equilibrium time and 150 rpm stirring. The experiments showed that compost adsorption properties could be enhanced by adding small quantities of alumina. Compost could thus be chosen as a promising material for use in bioremediation chromium-containing waste water in a management programme for using solid waste in for minimising environmental impact.

     

     

    Influence of TiO2 hollow sphere size on its photo-reduction activity for toxic Cr(VI) removal.

    Science.gov (United States)

    Cai, Jiabai; Wu, Xueqing; Zheng, Fengying; Li, Shunxing; Wu, Yaling; Lin, Yanping; Lin, Liting; Liu, Biwen; Chen, Qiaoying; Lin, Luxiu

    2017-03-15

    After polystyrene@titanium dioxide (PS@TiO2) composite with different size was calcined at designated temperature, TiO2 hollow sphere with controllable size was obtained for high efficient photo-reduction of Cr(VI). The feature of the TiO2 hollow sphere was investigated by SEM, TEM, XRD, UV-Vis, and photoluminescence. The photo-reduction of Cr(VI) were measured for the performance assessment of the TiO2 hollow sphere, Cr(VI) was used as an electron acceptor. After irradiation for 2h, the photo-reduction rate of Cr(VI) (pH=2.82) for TiO2(450nm) was 96%, which exhibited an increase of 5% and 8% compared with TiO2(370nm) and TiO2(600nm). The absorption edges of TiO2 hollow sphere (450nm) was largest with the increasing of hollow sphere size from 370 to 600nm. The optimal hollow sphere size of TiO2 was 450nm for the photo-reduction of Cr(VI), because the light-harvesting efficiency (the best of absorption edge) and photo-generated electron-hole separation rate (the best of photo-reduction rate) of TiO2 hollow sphere were controlled by its hollow sphere size. In addition, we find that the behavior of the hydrogen production was inhibited by the coexistence Cr(VI) solution. This study can improve our understanding of the mechanism for the activity enhancement by the optimal hollow sphere size of TiO2.

  14. In Situ Spectral Kinetics of Cr(VI) Reduction by c-Type Cytochromes in A Suspension of Living Shewanella putrefaciens 200

    Science.gov (United States)

    Liu, Tongxu; Li, Xiaomin; Li, Fangbai; Han, Rui; Wu, Yundang; Yuan, Xiu; Wang, Ying

    2016-07-01

    Although c-type cytochromes (c-Cyts) mediating metal reduction have been mainly investigated with in vitro purified proteins of dissimilatory metal reducing bacteria, the in vivo behavior of c-Cyts is still unclear given the difficulty in measuring the proteins of intact cells. Here, c-Cyts in living Shewanella putrefaciens 200 (SP200) was successfully quantified using diffuse-transmission UV/Vis spectroscopy due to the strong absorbance of hemes, and the in situ spectral kinetics of Cr(VI) reduction by c-Cyts were examined over time. The reduced product Cr(III) observed on the cell surface may play a role in inhibiting the Cr(VI) reduction and reducing the cell numbers with high concentrations (>200 μM) of Cr(VI) evidenced by the 16S rRNA analysis. A brief kinetic model was established with two predominant reactions, redox transformation of c-Cyts and Cr(VI) reduction by reduced c-Cyts, but the fitting curves were not well-matched with c-Cyts data. The Cr(III)-induced inhibitory effect to the cellular function of redox transformation of c-Cyts was then added to the model, resulting in substantially improved the model fitting. This study provides a case of directly examining the reaction properties of outer-membrane enzyme during microbial metal reduction processes under physiological conditions.

  15. Biochemical and molecular mechanisms involved in simultaneous phenol and Cr(VI) removal by Acinetobacter guillouiae SFC 500-1A.

    Science.gov (United States)

    Ontañon, Ornella M; González, Paola S; Agostini, Elizabeth

    2015-09-01

    Bioremediation has emerged as an environmental friendly strategy to deal with environmental pollution. Since the majority of polluted sites contain complex mixtures of inorganic and organic pollutants, it is important to find bacterial strains that can cope with multiple contaminants. In this work, a bacterial strain isolated from tannery sediments was identified as Acinetobacter guillouiae SFC 500-1A. This strain was able to simultaneously remove high phenol and Cr(VI) concentrations, and the mechanisms involved in such process were evaluated. The phenol biodegradation was catalized by a phenol-induced catechol 1,2-dioxygenase through an ortho-cleavage pathway. Also, NADH-dependent chromate reductase activity was measured in the cytosolic fraction. The ability of this strain to reduce Cr(VI) to Cr(III) was corroborated by detection of Cr(III) in cellular biomass after the removal process. While phenol did not affect significantly the chromate reductase activity, Cr(VI) was a major disruptor of catechol dioxygenase activity. Nevertheless, this activity was high even in presence of high Cr(VI) concentrations. Our results suggest the potential application of A. guillouiae SFC 500-1A for wastewaters treatment, and the obtained data provide the insights into the removal mechanisms, dynamics, and possible limitations of the bioremediation.

  16. Combination of cathodic reduction with adsorption for accelerated removal of Cr(VI) through reticulated vitreous carbon electrodes modified with sulfuric acid–glycine co-doped polyaniline

    Energy Technology Data Exchange (ETDEWEB)

    Mo, Xi [College of Environmental Science and Engineering, Hunan University, Changsha 410082 (China); Key Laboratory of Environmental Biology and Pollution Control (Hunan University), Ministry of Education, Changsha 410082 (China); Yang, Zhao-hui, E-mail: yzh@hnu.edu.cn [College of Environmental Science and Engineering, Hunan University, Changsha 410082 (China); Key Laboratory of Environmental Biology and Pollution Control (Hunan University), Ministry of Education, Changsha 410082 (China); Xu, Hai-yin; Zeng, Guang-ming; Huang, Jing; Yang, Xia; Song, Pei-pei; Wang, Li-ke [College of Environmental Science and Engineering, Hunan University, Changsha 410082 (China); Key Laboratory of Environmental Biology and Pollution Control (Hunan University), Ministry of Education, Changsha 410082 (China)

    2015-04-09

    Highlights: • RVC/PANI-SA-GLY electrode was applied as a novel electrode material for accelerated removal of Cr(VI). • Faster reduction kinetics of Cr(VI) was observed by RVC/PANI-SA-GLY electrode when compared with RVC/PANI-SA and RVC electrode. • Cr(VI) removal experienced an adsorption-reduction system built by RVC/PANI-SA-GLY electrode. • The stability of RVC/PANI-SA-GLY electrode was relatively satisfactory. - Abstract: Improving the reduction kinetics is crucial in the electroreduction process of Cr(VI). In this study, we developed a novel adsorption–electroreduction system for accelerated removal of Cr(VI) by employing reticulated vitreous carbon electrode modified with sulfuric acid–glycine co-doped polyaniline (RVC/PANI-SA-GLY). Firstly, response surface methodology confirmed the optimum polymerization condition of co-doped polyaniline for modifying electrodes (Aniline, sulfuric acid and glycine, respectively, of 0.2 mol/L, 0.85 mol/L, 0.93 mol/L) when untraditional dopant glycine was added. Subsequently, RVC/PANI-SA-GLY showed higher Cr(VI) removal percentages in electroreduction experiments over RVC electrode modified with sulfuric acid doped polyaniline (RVC/PANI-SA) and bare RVC electrode. In contrast to RVC/PANI-SA, the improvement by RVC/PANI-SA-GLY was more significant and especially obvious at more negative potential, lower initial Cr(VI) concentration, relatively less acidic solution and higher current densities, best achieving 7.84% higher removal efficiency with entire Cr(VI) eliminated after 900 s. Current efficiencies were likewise enhanced by RVC/PANI-SA-GLY under quite negative potentials. Fourier transform infrared (FTIR) and energy dispersive spectrometer (EDS) analysis revealed a possible adsorption–reduction mechanism of RVC/PANI-SA-GLY, which greatly contributed to the faster reduction kinetics and was probably relative to the absorption between protonated amine groups of glycine and HCrO{sub 4}{sup −}. Eventually, the

  17. Algae decorated TiO2/Ag hybrid nanofiber membrane with enhanced photocatalytic activity for Cr(VI) removal under visible light

    OpenAIRE

    WANG, L.; Zhang, C; Gao, F.; MAILHOT, G; Pan, G

    2016-01-01

    Algae as an abundant natural biomass, more attention has been paid to explore its potential application in environmental pollutants treatment. This work prepared the algae-TiO2/Ag bionano hybrid material by loading algae cells on the ultrafine TiO2/Ag chitosan hybrid nanofiber mat. For the first time, the synergistic photocatalytic effect of fresh algae and TiO2/Ag nanomaterial was investigated by removal of Cr(VI). The addition of algae significantly improved the photo-removal of Cr(VI) in t...

  18. Algae decorated TiO2/Ag hybrid nanofiber membrane with enhanced photocatalytic activity for Cr(VI) removal under visible light

    OpenAIRE

    Wang, L; Zhang,C.; Gao, F.; Mailhot, G.; Pan, G.

    2016-01-01

    Algae as an abundant natural biomass, more attention has been paid to explore its potential application in environmental pollutants treatment. This work prepared the algae-TiO2/Ag bionano hybrid material by loading algae cells on the ultrafine TiO2/Ag chitosan hybrid nanofiber mat. For the first time, the synergistic photocatalytic effect of fresh algae and TiO2/Ag nanomaterial was investigated by removal of Cr(VI). The addition of algae significantly improved the photo-removal of Cr(VI) in t...

  19. Pseudo-emulsion based hollow fibre strip dispersion (PEHFSD) technique for permeation of Cr(VI) using Cyanex-923 as carrier.

    Science.gov (United States)

    Sonawane, Jagannath V; Pabby, Anil K; Sastre, Ana M

    2010-02-15

    Pseudo-emulsion based hollow fibre strip dispersion (PEHFSD) technique is investigated for the permeation-separation of chromium from hydrochloric acid media. The permeation of Cr(VI) is investigated in relation to various experimental variables: hydrodynamic conditions, the concentration of Cr(VI) and HCl in the feed phase, Cyanex-923 concentration, hydrazine sulphate as the stripping agent in the pseudo-emulsion phase. The performance of the PEHFSD was analyzed and optimum conditions are suggested for chromium separation from simulated industrial waste in a hydrochloric acid media.

  1. Hexavalent chromium removal from wastewater using aniline formaldehyde condensate coated silica gel.

    Science.gov (United States)

    Kumar, P Albino; Ray, Manabendra; Chakraborty, Saswati

    2007-05-08

    A resinous polymer, aniline formaldehyde condensate (AFC) coated on silica gel was used as an adsorbent in batch system for removal of hexavalent chromium from aqueous solution by considering the effects of various parameters like reaction pH, dose of AFC coated silica gel, initial Cr(VI) concentration and aniline to formaldehyde ratio in AFC synthesis. The optimum pH for total chromium [Cr(VI) and Cr(III)] adsorption was observed as 3. Total chromium adsorption was second order and equilibrium was achieved within 90-120 min. Aniline to formaldehyde ratio of 1.6:1 during AFC synthesis was ideal for chromium removal. Total chromium adsorption followed Freundlich's isotherm with adsorption capacity of 65 mg/g at initial Cr(VI) 200mg/L. Total chromium removal was explained as combinations of electrostatic attraction of acid chromate ion by protonated AFC, reduction of Cr(VI) to Cr(III) and bond formation of Cr(III) with nitrogen atom of AFC. Almost 40-84% of adsorbed chromium was recovered during desorption by NaOH, EDTA and mineral acids. AFC coated silica gel can be effectively used for treatment of chromium containing wastewaters as an alternative.

  2. Preparation Behavior of the Mg-Fe Hydrotalcite by Urea Method and Its Cr(VI) Sorption Property.

    Science.gov (United States)

    Xu, Sheng; Liao, MengChen; Zeng, HongYan; Liu, XiaoJun; Zhu, PeiHan; Chen, ChaoRong; Duan, HengZhi

    2016-03-01

    The hydrotalcite of Mg6Fe2(OH)16CO3 x 4.5H2O were synthesized using urea method by adjusting the initial pH and urea amount in the reaction solution. The results showed that the co-precipitation of Mg2+ with Fe3+ cations formed Mg-Fe LDH occurring at pH 8.48-9.35. The pH played a crucial role in the Mg-Fe LDH precipitation by controlling urea/Fe3+ molar ratio in the reaction solution at 105 degrees C. The optimized urea/Fe3+ molar ratio was 12.0, where the relative yield of the Mg-Fe LDH was 80.0% and the Mg-Fe LDH was highly crystalline with small particle sizes (1-2 μm). The affinity of the Mg-Fe mixed oxide (Mg-Fe LDO) with Cr(VI) was studied as a function of contact time, initial pH, temperature of the solutions and calcined time of Mg-Fe LDH. The adsorption conditions were optimized using response surface methodology. The maximum adsorption capacity of 38.86 mg/g was achieved at 85 min with the conditions of initial pH 5.5, temperature 55 degrees C and calcined time 4 h. It was concluded that the Mg-Fe LDO can be used as an adsorbent to removal Cr(VI) in aqueous solutions.

  3. Sulfuric acid doped poly diaminopyridine/graphene composite to remove high concentration of toxic Cr(VI).

    Science.gov (United States)

    Dinda, Diptiman; Kumar Saha, Shyamal

    2015-06-30

    Sulfuric acid doped diaminopyridine polymers are synthesized in situ on graphene oxide surface via mutual oxidation-reduction technique. Exploiting large and highly porous surface, we have used this polymer composite as an adsorbent to remove high concentration of toxic Cr(VI) from water. It shows very high adsorption capacity (609.76 mg g(-1)) during removal process. The composite takes only 100 min to remove high concentration of 500 mg L(-1) Cr(VI) from water. Interesting features for this material is the enhancement of removal efficiency at lower acidic condition due to the formation of acid doped emeraldine salt during polymerization. XPS and AAS measurements reveal that our prepared material mainly follows reduction mechanism at higher acidic condition while anions exchange mechanism at lower acidic condition during the removal experiments. Good recycling ability with ∼ 92% removal efficiency after fifth cycle is also noticed for this material. Easy preparation, superior stability in acidic condition, remarkable removal efficiency and excellent recycling ability make this polymer composite an efficient material for modern filtration units in waste water purification. Copyright © 2015 Elsevier B.V. All rights reserved.

  4. Synthesis of porous Fe3O4 hollow microspheres/graphene oxide composite for Cr(vi) removal.

    Science.gov (United States)

    Liu, Mancheng; Wen, Tao; Wu, Xilin; Chen, Changlun; Hu, Jun; Li, Jie; Wang, Xiangke

    2013-10-01

    A composite of porous Fe3O4 hollow microspheres/graphene oxide (Fe3O4/GO) has been fabricated through a facile self-assembly approach. Driven by the mutual electrostatic interactions, the amine-functionalized Fe3O4 microspheres prepared by a hydrothermal method and then modified by 3-aminopropyltrimethoxysilane were decorated with negatively-charged GO sheets. The Fe3O4 microspheres were hollow with porous surfaces and the surfaces were successfully modified with the amine, which was confirmed by Fourier transform infrared spectroscopy. The specific saturation magnetization of Fe3O4/GO was 37.8 emu g(-1). The sorption performance of Fe3O4/GO for Cr(vi) was evaluated. The maximum sorption capacity for Cr(vi) on Fe3O4/GO was 32.33 mg g(-1), which was much higher than that of Fe3O4 microspheres. The GO sheets could not only prevent agglomeration of the Fe3O4 microspheres and enable a good dispersion of these oxide microspheres, but also substantially enhance the specific surface area of the composite. The Fe3O4/GO composite may be a promising sorption material for the separation and preconcentration of heavy metal ions from aqueous solutions in environmental pollution cleanup.

  5. Isolation and characterization of Cr(VI)-reducing actinomycetes from estuarine sediments.

    Science.gov (United States)

    Terahara, Takeshi; Xu, Xudan; Kobayashi, Takeshi; Imada, Chiaki

    2015-04-01

    Bioremediation technologies have strong potential use in the less costly and more environmentally friendly removal of highly toxic hexavalent-chromium (Cr(VI)) compared with physicochemical technologies. Several Cr(VI)-reducing bacteria have been isolated; however, there are few studies on Cr(VI)-resistant and Cr(VI)-reducing actinomycetes. In this study, Cr(VI)-reducing actinomycetes were screened from estuarine, marine, and terrestrial samples on the basis of Cr(VI)-resistant and Cr(VI)-reducing ability. Of the 80 Streptomyces-like strains isolated, 20 strains were found to be resistant to 50 mg/l of Cr(VI). In addition, two strains isolated from the estuarine sediment of Tokyo Bay were found to be resistant to a concentration of 150 mg/l of Cr(VI). Furthermore, one Cr(VI)-reducing strain was found to remove 60 mg/l of Cr(VI) within 1 week and was identified as Streptomyces thermocarboxydus based on 16S rRNA gene analysis. The comparative evaluation with the type strain S. thermocarboxydus NBRC 16323 showed that our isolated strain had higher ability to grow at 27 °C and reduce Cr(VI) at a NaCl concentration of 6.0 % at 27 °C compared with the type strain NBRC 16323. These results indicate that our isolated strain have a potential ability to remove Cr(VI) from contaminated, highly saline sources without heating.

  6. Formaldehyde-Assisted Isolation of Regulatory Elements (FAIRE analysis uncovers broad changes in chromatin structure resulting from hexavalent chromium exposure.

    Directory of Open Access Journals (Sweden)

    Jerald L Ovesen

    Full Text Available The ability of chromatin to switch back and forth from open euchromatin to closed heterochromatin is vital for transcriptional regulation and genomic stability, but its dynamic structure is subject to disruption by exposure to environmental agents such as hexavalent chromium. Cr(VI exposure disrupts chromatin remodeling mechanisms and causes chromosomal damage through formation of free radicals, Cr-DNA adducts, and DNA-Cr-protein cross-links. In addition, acute, high-concentration, and chronic, low-concentration exposures to Cr(VI lead to significantly different transcriptional and genomic stability outcomes. We used mouse hepatoma Hepa-1c1c7 cells to investigate how transcriptional responses to chromium treatment might correlate with structural chromatin changes. We used Formaldehyde-Assisted Isolation of Regulatory Elements (FAIRE analysis coupled with deep sequencing to identify regions of the genome that may switch between open and closed chromatin in response to exposure to varying Cr(VI concentrations. At either Cr(VI concentration, chromatin domains surrounding binding sites for AP-1 transcription factors become significantly open, whereas BACH2 and CTCF binding sites are open solely at the low and high concentrations, respectively. Parallel gene expression profiling using RNA-seq indicates that the structural chromatin changes caused by Cr(VI affect gene expression levels in the target areas that vary depending on Cr(VI concentration, but show no correlation between global changes in the overall transcriptional response and Cr(VI concentration. Our results suggest that FAIRE may be a useful technique to map chromatin elements targeted by DNA damaging agents for which there is no prior knowledge of their specificity, and to identify subsequent transcriptomic changes induced by those agents.

  7. Groundwater contaminated with hexavalent chromium [Cr (VI]: a health survey and clinical examination of community inhabitants (Kanpur, India.

    Directory of Open Access Journals (Sweden)

    Priti Sharma

    Full Text Available BACKGROUND: We assessed the health effects of hexavalent chromium groundwater contamination (from tanneries and chrome sulfate manufacturing in Kanpur, India. METHODS: The health status of residents living in areas with high Cr (VI groundwater contamination (N = 186 were compared to residents with similar social and demographic features living in communities having no elevated Cr (VI levels (N = 230. Subjects were recruited at health camps in both the areas. Health status was evaluated with health questionnaires, spirometry and blood hematology measures. Cr (VI was measured in groundwater samples by diphenylcarbazide reagent method. RESULTS: Residents from communities with known Cr (VI contamination had more self-reports of digestive and dermatological disorders and hematological abnormalities. GI distress was reported in 39.2% vs. 17.2% males (AOR = 3.1 and 39.3% vs. 21% females (AOR = 2.44; skin abnormalities in 24.5% vs. 9.2% males (AOR = 3.48 and 25% vs. 4.9% females (AOR = 6.57. Residents from affected communities had greater RBCs (among 30.7% males and 46.1% females, lower MCVs (among 62.8% males and less platelets (among 68% males and 72% females than matched controls. There were no differences in leucocytes count and spirometry parameters. CONCLUSIONS: Living in communities with Cr (VI groundwater is associated with gastrointestinal and dermatological complaints and abnormal hematological function. Limitations of this study include small sample size and the lack of long term follow-up.

  8. The recovery and recycling of Cr(VI) from waste streams

    Energy Technology Data Exchange (ETDEWEB)

    Hendou, M. [Lacaze S.A., Leyme (France); Solozabal, R. [INASMET, San Sebastian (Spain); Dalrymple, I. [EA Technology, Capenhurst, Chester (United Kingdom)

    2001-07-01

    The objective of the multi-party project discussed in this paper is to develop a process for the recovery of hexavalent chromium waste from dilute waste streams resulting from industrial processes such as chromium electroplating, conversion coating and surface etching of metal and polymer surfaces. Hexavalent chromium is highly toxic and processes currently in use require specialised waste treatment, including the addition of chemical reagents. Development of a clean electrochemical process would allow removal of the chromium from the dilute effluents without the addition of chemical reagents, and permit it to be recycled directly for use in the surface treatment baths used in manufacturing process lines. This paper describes the recovery and recycling methods, and associated technologies, and outlines the advantages and benefits expected from the new method.

  9. Adsorption of hexavalent chromium onto sisal pulp/polypyrrole composites

    Science.gov (United States)

    Tan, Y. Y.; Wei, C.; Gong, Y. Y.; Du, L. L.

    2017-02-01

    Sisal pulp/polypyrrole composites(SP/PPy) utilized for the removal of hexavalent chromium [Cr(VI)] from wastewater, were prepared via in-situ chemical oxidation polymerization approach. The structure and morphology of the SP/PPy were analyzed by polarizing optical microscopy (POM), field-emission scanning electron microscopy (SEM)), Energy-dispersive X-ray spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS), the results indicated SP could be efficient dispersion of PPy. The hexavalent chromium adsorption results indicate adsorption capacity of the SP/PPy were dependent on the initial pH, with an optimum pH of 2.0. The sorption kinetic data fitted well to the pseudo-second order model and isotherm data fitted well to the Langmuir isotherm model. The maximum adsorption capacity determined from the Langmuir isotherm is 336.70 mg/g at 25° C.

  10. Protein expression on Cr resistant microorganism using electrophoresis method

    Directory of Open Access Journals (Sweden)

    SAJIDAN

    2009-01-01

    Full Text Available Fatmawati U, Suranto, Sajidan. 2009. Protein expression on Cr resistant microorganism using electrophoresis method. Nusantara Bioscience 1: 31-37. Hexavalent chromium (Cr(VI is known as toxic heavy metals, so the need is reduced to Cr(III is much less toxicity. Pseudomonas aeruginosa, Pseudomonas putida, Klebsiella pneumoniae, Pantoea sp. and Saccharomyces cerevisiae are resistant Cr(VI microorganism and have ability to reduce Cr(VI. The aim of this research is to know ability of microorganism to reduce Cr(VI and to know protein band pattern between Cr(VI resistant microorganism and non resistant microorganism which inoculated on LB broth. SDS-PAGE was used to indentify protein expression. While, Cr(VI concentration was identified by 1.5 diphenylcarbazide method. The quantitative data was analyzed by two factorial ANOVA that continued with DMRT at 1% level test. The qualitative data i.e. protein expression analyzed by relative mobility (Rf. The results showed that the ability of microorganisms to reduce Cr(VI at initial concentration of 0.5 ppm, 1 ppm, 5 ppm and 10 ppm may vary, the average percentage of the ability of each microorganism in reducing Cr(VI is P. putida (65% > S. cerevisiae (64.45% >. P. aeruginosa (60.73% > Pantoea sp. (50.22% > K. pneumoniae (47.82% > without microorganisms (34.25%. The adding microorganisms have significantly influenced toward reduction of Cr(VI. The SDS-PAGE shows that protein expression between resistant and not resistant microorganisms are no different, but resistant microorganisms have more protein (protein band is thicker.

  11. Removal of Cr(VI) from Aqueous Solution Using Activated Cow Dung Carbon.

    Science.gov (United States)

    Das; Mahapatra; Pradhan; Das; Thakur

    2000-12-15

    Removal of hexavalent chromium from aqueous medium by using activated cow dung carbon was studied. Cow dung was carbonized and activated by treating with concentrated H(2)SO(4) followed by heating for 24 h at 120 degrees C. The extent of adsorption was studied as a function of pH, contact time, amount of adsorbent, concentration of adsorbate, and temperature. At lower pH (Press.

  12. Fe/Al bimetallic particles for the fast and highly efficient removal of Cr(VI) over a wide pH range: Performance and mechanism

    Energy Technology Data Exchange (ETDEWEB)

    Fu, Fenglian, E-mail: fufenglian2006@163.com [School of Environmental Science and Engineering, Guangdong University of Technology, Guangzhou 510006 (China); Environmental Engineering and Science Program, Department of Biomedical, Chemical and Environmental Engineering (DBCEE), University of Cincinnati, OH 45221-0012 (United States); Cheng, Zihang [School of Environmental Science and Engineering, Guangdong University of Technology, Guangzhou 510006 (China); Dionysiou, Dionysios D., E-mail: dionysios.d.dionysiou@uc.edu [Environmental Engineering and Science Program, Department of Biomedical, Chemical and Environmental Engineering (DBCEE), University of Cincinnati, OH 45221-0012 (United States); Tang, Bing [School of Environmental Science and Engineering, Guangdong University of Technology, Guangzhou 510006 (China)

    2015-11-15

    Highlights: • Bimetallic particles with different Fe/Al mass ratios were prepared. • High removal rate of Cr(VI) was achieved in acidic, neutral, and alkaline pH. • No total iron ions at pH 3.0–11.0 and nearly no Al{sup 3+} at pH 3.0–7.0 were released. • Galvanic cell effect and high specific surface area contributed to Cr(VI) removal. - Abstract: The iron/aluminum (Fe/Al) bimetallic particles with high efficiency for the removal of Cr(VI) were prepared. Fe/Al bimetallic particles were characterized by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), SEM mapping, X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). SEM mapping showed that the core of bimetal was Al, and the planting Fe was deposited on the surface of Al. In acidic and neutral conditions, Fe/Al bimetal can completely remove Cr(VI) from wastewater in 20 min. Even at pH 11.0, the Cr(VI) removal efficiency achieved was 93.5%. Galvanic cell effect and high specific surface area are the main reasons for the enhanced removal of Cr(VI) by bimetallic particles. There were no iron ions released in solutions at pH values ranging from 3.0 to 11.0. The released Al{sup 3+} ions concentrations in acidic and neutral conditions were all less than 0.2 mg/L. The bimetal can be used 4 times without losing activity at initial pH 3.0. XPS indicated that the removed Cr(VI) was immobilized via the formation of Cr(III) hydroxide and Cr(III)–Fe(III) hydroxide/oxyhydroxide on the surface of Fe/Al bimetal. The Fe/Al bimetallic particles are promising for further testing for the rapid and effective removal of contaminants from water.

  13. Differential uptake and transport of trivalent and hexavalent chromium by tumbleweed (Salsola kali).

    Science.gov (United States)

    Gardea-Torresdey, J L; de la Rosa, G; Peralta-Videa, J R; Montes, M; Cruz-Jimenez, G; Cano-Aguilera, I

    2005-02-01

    Experiments were conducted to determine the differential absorption of Cr species by tumbleweed (Salsola kali) as well as the effect of this heavy metal on plant growth and nutrient uptake. Tumbleweed seeds were grown in an agar-based media containing different concentrations of either Cr(III) or Cr(VI). The results demonstrated that the uptake of Cr was influenced by the Cr concentration in the growth medium and the speciation of this heavy metal. When supplied in the hexavalent form, the concentration of Cr in the different plant parts (2900, 790, and 600 mg kg(-1) for roots, stems, and leaves, respectively) was between 10 and 20 times higher than the amounts found when Cr was supplied in the trivalent form. In addition, it was found that in most of the experiments, Cr(III) exhibited more toxic effects on tumbleweed plants than Cr(VI). The size of roots of plants grown in 20 mg L(-1) Cr(III) were significantly smaller (p < 0.05) than those grown in 20 mg L(-1) Cr(VI). Plants exposed to 20 mg L(-1) Cr(III) produced shoots significantly shorter (p < 0.05) compared with the size of control plants and with those grown in 20 mg L(-1) Cr(VI). In addition, the absorption of macronutrients and microelements was in general lower when the plants were grown in the medium containing Cr(III). The amounts of Cr concentrated in the aerial plant parts under experimental conditions may indicate tumbleweed as a new option for the phytoremediation of Cr-contaminated soil.

  14. Fe/Al bimetallic particles for the fast and highly efficient removal of Cr(VI) over a wide pH range: Performance and mechanism.

    Science.gov (United States)

    Fu, Fenglian; Cheng, Zihang; Dionysiou, Dionysios D; Tang, Bing

    2015-11-15

    The iron/aluminum (Fe/Al) bimetallic particles with high efficiency for the removal of Cr(VI) were prepared. Fe/Al bimetallic particles were characterized by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), SEM mapping, X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). SEM mapping showed that the core of bimetal was Al, and the planting Fe was deposited on the surface of Al. In acidic and neutral conditions, Fe/Al bimetal can completely remove Cr(VI) from wastewater in 20 min. Even at pH 11.0, the Cr(VI) removal efficiency achieved was 93.5%. Galvanic cell effect and high specific surface area are the main reasons for the enhanced removal of Cr(VI) by bimetallic particles. There were no iron ions released in solutions at pH values ranging from 3.0 to 11.0. The released Al(3+) ions concentrations in acidic and neutral conditions were all less than 0.2mg/L. The bimetal can be used 4 times without losing activity at initial pH 3.0. XPS indicated that the removed Cr(VI) was immobilized via the formation of Cr(III) hydroxide and Cr(III)-Fe(III) hydroxide/oxyhydroxide on the surface of Fe/Al bimetal. The Fe/Al bimetallic particles are promising for further testing for the rapid and effective removal of contaminants from water. Copyright © 2015 Elsevier B.V. All rights reserved.

  15. Effects of Cr(III) and CR(VI) on nitrification inhibition as determined by SOUR, function-specific gene expression and 16S rRNA sequence analysis of wastewater nitrifying enrichments

    Science.gov (United States)

    The effect of Cr(III) and Cr(VI) on ammonia oxidation, the transcriptional responses of functional genes involved in nitrification and changes in 16S rRNA level sequences were examined in nitrifying enrichment cultures. The nitrifying bioreactor was operated as a continuous react...

  16. Immobilization of Cr(Vi) as a contaminant from soil by iron compounds; Inmovilizacion de Cr(VI) como contaminante del suelo por compuestos de hierro

    Energy Technology Data Exchange (ETDEWEB)

    Marin A, M. de J.; Romero G, E. T. [ININ, Carretera Mexico-Toluca s/n, Ocoyoacac 52750, Estado de Mexico (Mexico); Reyes G, L. R. [Universidad Autonoma del Estado de Hidalgo, Centro de Investigacion en Ciencias de la Tierra, Carretera Pachuca-Tulancingo Km. 4.5, Pachuca 42184, Hidalgo (Mexico)], e-mail: elizabeth.romero@inin.gob.mx

    2008-07-01

    The objective of this research was to determine the physicochemical and surface properties of Fe{sup 0} and FeS to select the appropriate radioactive material for use in the design of artificial barriers or walls and remove Cr (Vi). The physicochemical characterization was carried out of iron: Fe{sup 0} and FeS, using scanning electron microscopy of high vacuum, X-ray diffraction and thermal gravimetric analysis techniques. As for the characterization of the surface, was used to determine the surface area, point of zero charge, density of active sites and kinetics of moisture. We obtained a solution of Cr (Vi) by elution of deionized water on the pollution land of Buenavista, Guanajuato. The concentration of Cr (Vi) from a stock solution was 55.56 mg / L determined by UV-Vis spectrophotometry. Stripping or maximum immobilization of Cr (Vi) with Fe{sup 0} (material chosen by their physicochemical and surface properties) was 68.25% using Fe{sup 0}, at a concentration less than 0.1, ph equal to 3 and a contact time of 24 hours. (Author)

  17. Facile synthesis of porous single crystalline ZnO nanoplates and their application in photocatalytic reduction of Cr(VI) in the presence of phenol

    Energy Technology Data Exchange (ETDEWEB)

    Jin, Zhen [Research Center for Biomimetic Functional Materials and Sensing Devices, Institute of Intelligent Machines, Chinese Academy of Sciences, Hefei, Anhui 230031 (China); Zhang, Yong-Xing [School of Physics and Electronic Information, Huaibei Normal University, Huaibei, Anhui 235000 (China); Meng, Fan-Li; Jia, Yong; Luo, Tao; Yu, Xin-Yao; Wang, Jin; Liu, Jin-Huai [Research Center for Biomimetic Functional Materials and Sensing Devices, Institute of Intelligent Machines, Chinese Academy of Sciences, Hefei, Anhui 230031 (China); Huang, Xing-Jiu, E-mail: xingjiuhuang@iim.ac.cn [Research Center for Biomimetic Functional Materials and Sensing Devices, Institute of Intelligent Machines, Chinese Academy of Sciences, Hefei, Anhui 230031 (China)

    2014-07-15

    Graphical abstract: - Highlights: • Porous single crystalline ZnO nanoplates were successfully synthesized. • The nanoplates were with 12 nm in thickness and tens nanometers in pore size. • A synergistic effect of enhanced Cr(VI) photoreduction and phenol degradation was observed. • A possible reaction mechanism was discussed. - Abstract: Porous single crystalline ZnO nanoplates were successfully synthesized through a facile and cost-effective hydrothermal process at low temperature condition, followed by annealing of the zinc carbonate hydroxide hydrate precursors. The as-prepared products were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and Brunauer–Emmett–Teller (BET) measurements. The porous single crystalline ZnO nanoplates are with 12 nm thickness and pore ranging from 10 nm to several tens of nanometers. The porous structure of the ZnO nanoplates caused large amount of surface defects which worked as photogenerated holes’ shallow trappers and largely restrained the recombination of photogenerated electrons and holes, resulting in a significantly high photocatalytic activity and durability toward the photoreduction of Cr(VI) under UV irradiation. Moreover, a synergistic effect, that is, increased photocatalytic reduction of Cr(VI) and degradation of phenol, can be observed. Furthermore, the synergistic photocatalytic mechanism has also been discussed. Those results present an enlightenment to employ porous single crystalline nanomaterials to remove Cr(VI) and organic pollutants simultaneously.

  18. Iminodiacetic acid functionalized cation exchange resin for adsorptive removal of Cr(VI), Cd(II), Ni(II) and Pb(II) from their aqueous solutions.

    Science.gov (United States)

    Misra, R K; Jain, S K; Khatri, P K

    2011-01-30

    Iminodiacetic acid functionality has been introduced on styrene-divinyl benzene co-polymeric beads and characterized by FT-IR in order to develop weak acid based cation exchange resin. This resin was evaluated for the removal of different heavy metal ions namely Cd(II), Cr(VI), Ni(II) and Pb(II) from their aqueous solutions. The results showed greater affinity of resin towards Cr(VI) for which 99.7% removal achieved in optimal conditions following the order Ni(II)>Pb(II)>Cd(II) with 65%, 59% and 28% removal. Experiments were also directed towards kinetic studies of adsorption and found to follow first order reversible kinetic model with the overall rate constants 0.3250, 0.2393, 0.4290 and 0.2968 for Cr(VI), Ni(II), Pb(II) and Cd(II) removal respectively. Detailed studies of Cr(VI) removal has been carried out to see the effect of pH, resin dose and metal ion concentration on adsorption and concluded that complexation enhanced the chromium removal efficacy of resin drastically, which is strongly pH dependent. The findings were also supported by the comparison of FT-IR spectra of neat resin with the chromium-adsorbed resin.

  19. One-Step Synthesis of Hierarchical Micro-Mesoporous SiO2/Reduced Graphene Oxide Nanocomposites for Adsorption of Aqueous Cr(VI

    Directory of Open Access Journals (Sweden)

    Guiyun Yi

    2017-01-01

    Full Text Available A novel micro-mesostructured SiO2/reduced graphene oxide (RGO nanocomposite was successfully synthesized by means of simple one-step hydrothermal method under acidic conditions using tetraethoxysilane (TEOS and graphene oxide (GO as the raw material. The nanocomposites were characterized by TEM, XRD, FT-IR, TG-DSC, and N2 adsorption-desorption. The results showed that GO was partially reduced to RGO without adding any reducing agent and SiO2 nanoparticles (ca. 10 nm were uniformly anchored on the surface of RGO. The optimized composite contained 75 wt.% SiO2 and possessed hierarchical micro-mesoporous structure with surface area of 676 m2/g. The adsorption performance of synthesized SiO2/RGO samples was investigated by removal efficiency of Cr(VI ions in wastewater. The Cr(VI adsorption reached equilibrium in 30 min and 98.8% Cr(VI adsorption efficiency was achieved at pH = 2 at 35°C. Stability tests showed that SiO2 nanoparticles effectively prevented RGO from the restacking. The mechanisms of composite formation and for Cr(VI adsorption were suggested.

  20. Amino-functionalized alkaline clay with cationic star-shaped polymer as adsorbents for removal of Cr(VI) in aqueous solution

    Science.gov (United States)

    Pan, Yuanfeng; Cai, Pingxiong; Farmahini-Farahani, Madjid; Li, Yiduo; Hou, Xiaobang; Xiao, Huining

    2016-11-01

    Pentaerythritol (PER) was esterified with 2-bromoisobutyryl bromide to synthesize a four-arm initiator 4Br-PER for atom transfer radical polymerization (ATRP). Star-shaped copolymers (P(AM-co-DMAEMA)4, CSP) were prepared via ATRP using dimethyl aminoethyl methacrylate (DMAEMA) and acrylamide (AM) as comonomers, while Br-PER and CuBr/2,2‧-bipyridine (BPY) as the initiator and the catalyst, respectively. The resulting four-arm initiator and star-shaped polymer (CSP) were characterized with FT-IR, 1H NMR and Ubbelohde viscometry. Alkaline clay (AC) was immobilized with CSPs to yield amino groups, and the cationic star polymer-immobilized alkaline clay (CSP-AC) was applied to remove Cr(VI) from the aqueous solution in batch experiments. Various influencing factors, including pH, contact time and immobilization amount of CSP on adsorption capacity of CSP-AC for Cr(VI) were also investigated. The results demonstrated that Cr(VI) adsorption was highly pH dependent. The optimized pH value was 4.0. The adsorption isotherms of the adsorbent fit the Langmuir model well, with the maximum adsorption capacity of 137.9 mg/g at 30 °C. The material should be a promising adsorbent for Cr(VI) removal, with the advantages of high adsorption capacity.

  1. Adsorption behavior of Cr(VI) on modified natural zeolite by a new bolaform N,N,N,N',N',N'-hexamethyl-1,9-nonanediammonium dibromide reagent.

    Science.gov (United States)

    Noroozifar, M; Khorasani-Motlagh, M; Gorgij, M N; Naderpour, H R

    2008-07-15

    The demand for effective adsorbents is to increase in response to the widespread recognition of the deleterious health effects of Cr(VI)-oxyanions exposure through drinking water. In this study, Cr(VI)-oxyanions uptake from aqueous solutions by a new bolaform N,N,N,N',N',N'-hexamethyl-1,9-nonanediammonium dibromide reagent-modified natural zeolitic materials from Zahedan, Iran, was investigated using batch technique. Spectrophotometry method was used for Cr determination. The Cr(VI)-solution concentration varied between 2 and 104 mg L(-1). It was shown that the Cr(VI) uptake strongly depended on pH. The maximum removal of Cr(VI) occurred in acidic media at pH<1.5. The amounts of Cr(VI) adsorbed increased with increase in dose of both adsorbents and their contact time. Based on results an adsorption mechanism has been suggested. The adsorption data for modified zeolite using the amine was consistent with Langmuir isotherm equation and the equilibrium data was analyzed using the Langmuir isotherm.

  2. Chi-square analysis of the reduction of ATP levels in L-02 hepatocytes by hexavalent chromium.

    Science.gov (United States)

    Yuan, Yang; Peng, Li; Gong-Hua, Hu; Lu, Dai; Xia-Li, Zhong; Yu, Zhou; Cai-Gao, Zhong

    2012-06-01

    This study explored the reduction of adenosine triphosphate (ATP) levels in L-02 hepatocytes by hexavalent chromium (Cr(VI)) using chi-square analysis. Cells were treated with 2, 4, 8, 16, or 32 μM Cr(VI) for 12, 24, or 36 h. Methyl thiazolyl tetrazolium (MTT) experiments and measurements of intracellular ATP levels were performed by spectrophotometry or bioluminescence assays following Cr(VI) treatment. The chi-square test was used to determine the difference between cell survival rate and ATP levels. For the chi-square analysis, the results of the MTT or ATP experiments were transformed into a relative ratio with respect to the control (%). The relative ATP levels increased at 12 h, decreased at 24 h, and increased slightly again at 36 h following 4, 8, 16, 32 μM Cr(VI) treatment, corresponding to a "V-shaped" curve. Furthermore, the results of the chi-square analysis demonstrated a significant difference of the ATP level in the 32-μM Cr(VI) group (P ATP levels in L-02 hepatocytes. The decreased ATP levels at 24 h indicated disruption of mitochondrial energy metabolism and the slight increase of ATP levels at 36 h indicated partial recovery of mitochondrial function or activated glycolysis in L-02 hepatocytes.

  3. Hexavalent chromium reduction with scrap iron in continuous-flow system Part 1: effect of feed solution pH.

    Science.gov (United States)

    Gheju, M; Iovi, A; Balcu, I

    2008-05-01

    The reduction of hexavalent chromium by scrap iron was investigated in continuous system, using long-term column experiments, for aqueous Cr(VI) solutions having low buffering capacities, over the pH range of 2.00-7.30. The results showed that the initial pH of Cr(VI) solution significantly affects the reduction capacity of scrap iron. The highest reduction capacity was determined to be 19.2 mg Cr(VI)/g scrap iron, at pH 2.50, and decreased with increasing the initial pH of Cr(VI) solution. A considerable decrease in scrap iron reduction capacity (25%) was also observed at pH 2.00, as compared to pH 2.50, due to the increased contribution of H(+) ions to the corrosion of scrap iron, which leads to a rapid decrease in time of the scrap iron volume. Over the pH range of 2.50-7.30, hexavalent chromium concentration increases slowly in time after its breakthrough in column effluent, until a steady-state concentration was observed; similarly, over the same pH range, the amount of solubilized Cr(III) in treated column effluent decreases in time, until a steady-state concentration was observed. The steady-state concentration in column effluent decreased for Cr(VI) and increased for Cr(III) with decreasing the initial pH of Cr(VI) solution. No steady-state Cr(VI) or Cr(III) concentrations in column effluent were observed at pH 2.00. Over the entire studied pH range, the amount of Fe(total) in treated solution increases as the initial pH of column influent is decreased; the results show also a continuously decrease in time of Fe(total) concentration, for a constant initial pH, due to a decrease in time of iron corrosion rate. Cr(III) concentration in column effluent also continuously decreased in time, for a constant initial pH, over the pH range of 2.50-7.30. This represents an advantage, because the amount of precipitant agent used to remove Fe(total) and Cr(III) from the column effluent will also decrease in time. The optimum pH for Cr(VI) reduction with scrap iron in

  4. Application of modified bentonite using sulfuric acid for the removal of hexavalent chromium from aqueous solutions

    Directory of Open Access Journals (Sweden)

    Masoud Moradi

    2015-09-01

    Full Text Available Background: Environmental contamination by chromium (Cr has become an important issue due to its adverse effects on human health and environment. This study was done to evaluate the application of modified bentonite using sulfuric acid as an adsorbent in the removal of hexavalent Cr from aqueous solution. Methods: Adsorbent features were determined using x-ray diffraction (XRD, fourier transformed infrared spectroscopy (FTIR and scanning electron microscope (SEM techniques. Thereafter, the effect of pH, contact time, adsorbent dosage and different concentrations of Cr was investigated. The experimental data was fitness in terms of kinetic and equilibrium adsorption processes. Results: The maximum capacity (Qm of Cr(VI according to Langmuir model was obtained at 4.21 mg/g. The experimental data properly obeyed the Longmuir and pseudo-second-order models. The highest percentage of Cr(VI adsorption was observed at pH = 3 and the process after 60 minutes reached the equilibrium state. Conclusion: In Langmuir expression, the dimensionless constant separation term (RL values for the adsorption of Cr onto the modified bentonite was in the range of 0-1, indicating that the adsorption is a favorable process and the modified bentonite has good potential in removing hexavalent Cr using sulfuric acid.

  5. Amino-functionalized alkaline clay with cationic star-shaped polymer as adsorbents for removal of Cr(VI) in aqueous solution

    Energy Technology Data Exchange (ETDEWEB)

    Pan, Yuanfeng, E-mail: panyf@gxu.edu.cn [Guangxi Key Laboratory of Petrochemical Resource Processing and Process Intensification Technology, School of Chemistry and Chemical Engineering, Guangxi University, Nanning 530004 (China); Cai, Pingxiong [Guangxi Key Laboratory of Petrochemical Resource Processing and Process Intensification Technology, School of Chemistry and Chemical Engineering, Guangxi University, Nanning 530004 (China); Farmahini-Farahani, Madjid [Department of Chemical Engineering, University of New Brunswick, Fredericton, NB, E3B 5A3 (Canada); Li, Yiduo [Guangxi Key Laboratory of Petrochemical Resource Processing and Process Intensification Technology, School of Chemistry and Chemical Engineering, Guangxi University, Nanning 530004 (China); Hou, Xiaobang [School of Environmental Sci & Eng., North China Electric Power University, Baoding 071003 (China); Xiao, Huining, E-mail: hxiao@unb.ca [Department of Chemical Engineering, University of New Brunswick, Fredericton, NB, E3B 5A3 (Canada)

    2016-11-01

    Highlights: • Four-arm cationic star-shaped copolymers were prepared via Atom Transfer Radical Polymerization (ATRP) with pentaerythritol. • Alkaline clay (AC) was immobilized with cationic star polymer (CSP). • CSP-immobilized AC was first used for Cr(VI) removal. • The adsorbent has a higher adsorption capacity than those reported elsewhere. - Abstract: Pentaerythritol (PER) was esterified with 2-bromoisobutyryl bromide to synthesize a four-arm initiator 4Br-PER for atom transfer radical polymerization (ATRP). Star-shaped copolymers (P(AM-co-DMAEMA){sub 4}, CSP) were prepared via ATRP using dimethyl aminoethyl methacrylate (DMAEMA) and acrylamide (AM) as comonomers, while Br-PER and CuBr/2,2′-bipyridine (BPY) as the initiator and the catalyst, respectively. The resulting four-arm initiator and star-shaped polymer (CSP) were characterized with FT-IR, {sup 1}H NMR and Ubbelohde viscometry. Alkaline clay (AC) was immobilized with CSPs to yield amino groups, and the cationic star polymer-immobilized alkaline clay (CSP-AC) was applied to remove Cr(VI) from the aqueous solution in batch experiments. Various influencing factors, including pH, contact time and immobilization amount of CSP on adsorption capacity of CSP-AC for Cr(VI) were also investigated. The results demonstrated that Cr(VI) adsorption was highly pH dependent. The optimized pH value was 4.0. The adsorption isotherms of the adsorbent fit the Langmuir model well, with the maximum adsorption capacity of 137.9 mg/g at 30 °C. The material should be a promising adsorbent for Cr(VI) removal, with the advantages of high adsorption capacity.

  6. Potential application of highly reactive Fe(0)/Fe3O4 composites for the reduction of Cr(VI) environmental contaminants.

    Science.gov (United States)

    Dos Santos Coelho, Flávia; Ardisson, José Domingos; Moura, Flávia C C; Lago, Rochel M; Murad, Enver; Fabris, José Domingos

    2008-03-01

    We describe the use of highly reactive Fe(0)/Fe3O4 composites for the reduction of Cr(VI) species in aqueous medium. The composites were prepared by simple mechanical alloying of metallic iron and magnetite in different proportions, i.e. Fe(0) 25, 50, 75 and 90wt%. While after 3h of reaction pure Fe(0) and pure Fe3O4 showed only a low reduction efficiency of 15% and 25% Cr(VI) conversion, respectively, the composites, in particular Fe(0)(25wt%)/Fe3O4, showed a remarkable activity with ca. 65% Cr(VI) conversion. Kinetic experiments showed a high reaction rate during the first 3h, which subsequently decreased strongly, probably due to a pH increase from 6 to 8. Experiments with composites based on Fe(0)/alpha-Fe2O3, Fe(0)/gamma-Fe2O3 and Fe(0)/FeOOH showed very low activities, suggesting that Fe(oct)2+ in the magnetite structure plays an important role in the reaction. Scanning and high resolution electron microscopies and Mössbauer spectra (transmission and conversion electron Mössbauer spectroscopy) indicated that the mechanical alloying process promotes a strong interaction and interface between the metallic and oxide phases, with the Fe(0) particles completely covered by Fe3O4 particles. The high efficiency of the composite Fe(0)/Fe3O4 for Cr(VI) reduction is discussed in terms of a special mechanism where an electron is transferred from Fe(0) to magnetite to reduce Fe(oct)3+ to Fe(oct)2+, which is active for Cr(VI) reduction.

  7. Combination of cathodic reduction with adsorption for accelerated removal of Cr(VI) through reticulated vitreous carbon electrodes modified with sulfuric acid-glycine co-doped polyaniline.

    Science.gov (United States)

    Mo, Xi; Yang, Zhao-hui; Xu, Hai-yin; Zeng, Guang-ming; Huang, Jing; Yang, Xia; Song, Pei-pei; Wang, Li-ke

    2015-04-09

    Improving the reduction kinetics is crucial in the electroreduction process of Cr(VI). In this study, we developed a novel adsorption-electroreduction system for accelerated removal of Cr(VI) by employing reticulated vitreous carbon electrode modified with sulfuric acid-glycine co-doped polyaniline (RVC/PANI-SA-GLY). Firstly, response surface methodology confirmed the optimum polymerization condition of co-doped polyaniline for modifying electrodes (Aniline, sulfuric acid and glycine, respectively, of 0.2 mol/L, 0.85 mol/L, 0.93 mol/L) when untraditional dopant glycine was added. Subsequently, RVC/PANI-SA-GLY showed higher Cr(VI) removal percentages in electroreduction experiments over RVC electrode modified with sulfuric acid doped polyaniline (RVC/PANI-SA) and bare RVC electrode. In contrast to RVC/PANI-SA, the improvement by RVC/PANI-SA-GLY was more significant and especially obvious at more negative potential, lower initial Cr(VI) concentration, relatively less acidic solution and higher current densities, best achieving 7.84% higher removal efficiency with entire Cr(VI) eliminated after 900 s. Current efficiencies were likewise enhanced by RVC/PANI-SA-GLY under quite negative potentials. Fourier transform infrared (FTIR) and energy dispersive spectrometer (EDS) analysis revealed a possible adsorption-reduction mechanism of RVC/PANI-SA-GLY, which greatly contributed to the faster reduction kinetics and was probably relative to the absorption between protonated amine groups of glycine and HCrO4(-). Eventually, the stability of RVC/PANI-SA-GLY was proven relatively satisfactory. Copyright © 2015 Elsevier B.V. All rights reserved.

  8. Photo-Catalytic Activity of ZnO Supported on H-ZSM-5 Zeolite to Reduce Cr(VI from Aqueous Solutions

    Directory of Open Access Journals (Sweden)

    Haghighi M. MSc,

    2015-12-01

    Full Text Available Aims The application of photocatalytic processes to remove heavy metals in aqueous solutions and industrial wastewater are regarded as extremely effective, clean and without producing waste methods. The goal of the present study was to investigate the photocatalytic activity of ZnO based on H-ZSM-5 zeolite support. Materials & Methods ZnO/H-ZSM-5 composite synthesized by impregnation method successfully, and photo-reduction of Cr(VI was investigated via this composite in present of UV light irradiation. The prepared composite was characterized by X-ray Diffraction (XRD and Field Emission Scanning Electron Microscopy (FESEM. Data was analyzed by repeated measurement statistical test. Findings ZnO/H-ZSM-5 (79.5% had better removal photo-reduction activity than pure H-ZSM-5 (8.7%; p=0.003 zeolite and ZnO (58.8%; p=0.003. The initial concentration of Cr(VI was a highly influential factor in photo-reduction of Cr(VI; In the way that when the initial concentration increased from 10 to 40mg/l, the photo-reduction percentage decreased from 92.5 to 57.7% in constant operational conditions (p=0.001. Conclusion ZnO/H-ZSM-5 composite has higher removal photo-catalytic activity than pure ZnO and HZSM-5 zeolite. Photo-reduction of Cr(VI by ZnO/H-ZSM-5 composite is an efficient technology for the treatment of water and wastewater containing high concentration of Cr(VI.

  9. Synergistic photocatalysis of Cr(VI) reduction and 4-Chlorophenol degradation over hydroxylated α-Fe{sub 2}O{sub 3} under visible light irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Ji-Chao; Ren, Juan [College of Chemistry and Molecular Engineering, Zhengzhou University, Zhengzhou 450002 (China); Yao, Hong-Chang, E-mail: yaohongchang@zzu.edu.cn [College of Chemistry and Molecular Engineering, Zhengzhou University, Zhengzhou 450002 (China); Zhang, Lin; Wang, Jian-She; Zang, Shuang-Quan [College of Chemistry and Molecular Engineering, Zhengzhou University, Zhengzhou 450002 (China); Han, Li-Feng [Henan Provincial Key Laboratory of Surface & Interface Science, Zhengzhou University of Light Industry, Zhengzhou 450002 (China); Li, Zhong-Jun, E-mail: lizhongjun@zzu.edu.cn [College of Chemistry and Molecular Engineering, Zhengzhou University, Zhengzhou 450002 (China)

    2016-07-05

    Highlights: • The surface hydroxyl of Fe{sub 2}O{sub 3} influences on the Cr(VI) reduction activity. • The synergistic photocatalysis enhances degradation activity of Cr(VI) and 4-CP. • The Fe{sub 2}O{sub 3} catalyst exhibits good stability and degradation activity after 9 runs. - Abstract: A series of Fe{sub 2}O{sub 3} materials with hydroxyl are synthesized in different monohydric alcohol (C{sub 2} – C{sub 5}) solvents by solvothermal method and characterized by XRD, BET, XPS, TG and EA. The amount of hydroxyl is demonstrated to be emerged on the surface of the as-synthesized Fe{sub 2}O{sub 3} particles and their contents are determined to be from 7.99 to 3.74 wt%. The Cr(VI) reduction experiments show that the hydroxyl content of Fe{sub 2}O{sub 3} samples exacts great influence on the photocatalytic activity under visible light irradiation (λ > 400 nm) and that the Fe{sub 2}O{sub 3} sample synthesized in n-butyl alcohol exhibits the optimal photocatalytic activity. The synergistic photocatalysis for 4-Chlorophenol (4-CP) degradation and Cr(VI) reduction over above Fe{sub 2}O{sub 3} sample is further investigated. The photocatalytic ratio of Cr(VI) reduction are enhanced from 24.8% to 70.2% while that of 4-CP oxidation are increased from 13.5% to 47.8% after 1 h visible light irradiation. The Fe{sub 2}O{sub 3} sample keeps good degradation rates of mixed pollutants after 9 runs. The active oxygen intermediates O{sub 2}{sup −}·, ·OH and H{sub 2}O{sub 2} formed in the photoreaction process are discovered by ESR measurement and UV–vis test. The photocatalytic degradation mechanism is proposed accordingly.

  10. Porous structure and Cr(VI) removal abilities of Fe{sub 3}O{sub 4} prepared from Fe-urea complex

    Energy Technology Data Exchange (ETDEWEB)

    Asuha, S., E-mail: asuha42@yahoo.com.cn [Chemistry and Environment Science College, Inner Mongolia Normal University, and Key Laboratory of Physics and Chemistry of Function Materials, Inner Mongolia, 81 Zhaowudalu, Huhhot 010022 (China); Suyala, B.; Zhao, S. [Chemistry and Environment Science College, Inner Mongolia Normal University, and Key Laboratory of Physics and Chemistry of Function Materials, Inner Mongolia, 81 Zhaowudalu, Huhhot 010022 (China)

    2011-09-15

    Highlights: {yields} Solvothermal reaction of [Fe(CON{sub 2}H{sub 4}){sub 6}](NO{sub 3}){sub 3} can produce mesoporous Fe{sub 3}O{sub 4}. {yields} The mesoporous Fe{sub 3}O{sub 4} shows high removal ability for Cr(VI). {yields} The adsorption of Cr(VI) on the Fe{sub 3}O{sub 4} can be well described by Langmuir model. - Abstract: In this work, the porous structure and the Cr(VI) removal abilities of the magnetite (Fe{sub 3}O{sub 4}) nanopowder prepared by one-pot solvothermal reaction of Fe-urea complex ([Fe(CON{sub 2}H{sub 4}){sub 6}](NO{sub 3}){sub 3}) were investigated. Low-angle X-ray diffraction (XRD), nitrogen adsorption-desorption measurements, and transmission electron micrograph (TEM) observations show that the Fe{sub 3}O{sub 4} has a mesoporous structure with an average pore size of 5.3 nm and BET surface area of 120 m{sup 2}/g. The removal of gaseous species including CON{sub 2}H{sub 4}, NO, NO{sub 2} and O{sub 2} during the formation of the Fe{sub 3}O{sub 4} are considered to be the most probable reason for the formation of mesoporous structure. The adsorption behavior of Cr(VI) on the mesoporous Fe{sub 3}O{sub 4} can be well described by Langmuir adsorption model, and the maximum adsorption capacity for Cr(VI) is estimated to be 15.4 mg/g.

  11. Optimization and Modeling of Hexavalent Chromium Removal from Aqueous Solution Via Adsorption on Multiwalled Carbon Nanotubes

    Directory of Open Access Journals (Sweden)

    Mina Gholipour

    2011-09-01

    Full Text Available Hexavalent chromium and its derivatives are potential pollutant due to their mortal affects. Therefore, It is essential to remove these components from wastewaters before disposal. Adsorption can be effective and versatile method for removing of hexavalent chromium. In this article, removal of hexavalent chromium via adsorption on multiwalled carbon nanotubes was investigated as a function of adsorbent dosage, initial solution pH, initial Cr(VI concentrations, contact time and temperature. The batch experiments were conducted at 3 different temperatures (17, 27 and 37ºC and shows that Cr (VI removal obeys pseudo-second order rate equation. Rate constant (K values in 3 temperatures, pre-exponential factor and adsorption activation energy (E was also obtained. The sorption data fitted well with Freundlich isotherm adsorption model. Thermodynamic parameters such as Gibbs free energy (ΔGº, enthalpy (ΔHº and entropy (ΔSº for Cr(VI adsorption were estimated and Results suggest that the adsorption process is a spontaneous and endothermic.

  12. Green synthesis and characterization of alginate nanoparticles and its role as a biosorbent for Cr(VI) ions

    Science.gov (United States)

    Geetha, P.; Latha, M. S.; Pillai, Saumya S.; Deepa, B.; Santhosh Kumar, K.; Koshy, Mathew

    2016-02-01

    Green synthesis of nanoparticles has attained considerable attention in recent years because of its myriad of applications including drug delivery, tissue engineering and water purification. In the present study, alginate nanoparticles stabilized by honey were prepared by cross-linking aqueous solution of alginate with calcium ions. Honey mediated synthesis has been reported earlier for the production of metal nanoparticles. However no literature is available on the use of this technique for polymeric nanoparticles. Highly stable nanoparticles of 10-100 nm size were generated by this technique. The synthesised nanoparticles were characterized by transmission electron microscopy, scanning electron microscopy, atomic force microscopy, dynamic light scattering and Fourier transform infrared spectroscopic techniques. Potential of using these nanoparticles for heavy metal removal was studied by using Cr(VI) from aqueous solution, where a maximum removal efficiency of 93.5% was obtained. This method was also successfully employed for the production of other polymeric nanoparticles like casein, chitosan and albumin.

  13. Removal of Cr(VI) from aqueous solutions by a bacterial biofilm supported on zeolite: optimisation of the operational conditions and Scale-Up of the bioreactor

    Energy Technology Data Exchange (ETDEWEB)

    Pazos, M. [IBB - Instituto de Biotecnologia e Bioengenharia, Centro de Engenharia Biologica, Universidade do Minho, Braga (Portugal); Departamento de Ingenieria Quimica, Universidade de Vigo, Vigo (Spain); Branco, M.; Tavares, T. [IBB - Instituto de Biotecnologia e Bioengenharia, Centro de Engenharia Biologica, Universidade do Minho, Braga (Portugal); Neves, I.C. [Departamento de Quimica, Centro de Quimica, Universidade do Minho, Braga (Portugal); Sanroman, M.A. [Departamento de Ingenieria Quimica, Universidade de Vigo, Vigo (Spain)

    2010-12-15

    The aim of this study was to investigate the feasibility of a bioreactor system and its scale-up to remove Cr(VI) from solution. The bioreactor is based on an innovative process that combines bioreduction of Cr(VI) to Cr(III) by the bacterium Arthrobacter viscosus and Cr(III) sorption by a specific zeolite. Batch studies were conducted in a laboratory-scale bioreactor, taking into account different operating conditions. Several variables, such as biomass concentration, pH and zeolite pre-treatment, were evaluated to increase removal efficiency. The obtained results suggest that the Cr removal efficiency is improved when the initial biomass concentration is approximately 5 g L{sup -1} and the pH in the system is maintained at an acidic level. Under the optimised conditions, approximately 100 % of the Cr(VI) was removed. The scale-up of the developed biofilm process operating under the optimised conditions was satisfactorily tested in a 150-L bioreactor. (Copyright copyright 2010 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  14. Cr(VI) and azo dye removal using a hollow-fibre membrane system functionalized with a biogenic Pd-magnetite catalyst.

    Science.gov (United States)

    Coker, V S; Garrity, A; Wennekes, W B; Roesink, H D W; Cutting, R S; Lloyd, J R

    2014-01-01

    This study investigates the application of a hybrid system combining hollow-fibre membrane technology with the reductive abilities of magnetic nanoparticles for the remediation of toxic Cr(VI) and the azo dye, Remazol Black B. Nano-scale biogenic magnetite (Fe3O4), formed by microbial reduction of the mineral ferrihydrite, has a high reductive capacity due to the presence of Fe(II) in the mineral structure. The magnetic nanoparticles (approximately 20 nm) can be arrayed with Pd0 nanoparticles (approximately 5 nm) making a catalytically active nanomaterial. Membrane units, with and without nanoparticles, were challenged with either Cr(VI) or azo dye and some were supplemented with sodium formate, as an electron donor for contaminant reduction promoted by the Pd. The combination of Pd-magnetite with formate resulted in the most effective remediation strategy for both contaminants and the lifetime of the membrane unit was also increased, with 55% (19 days) and 70% (23 days) removal of the azo dye and Cr(VI), respectively. Low flow rates of 0.1 ml/min resulted in improved efficiencies due to increased contact time with the membrane/nanoparticle unit, with 70-75% removal of each contaminant. Chemical analyses of the nanoparticles post-exposure to Cr(VI) in the membrane modules indicated Pd to be more oxidized when Cr removal was maximized, and that the Cr was partially reduced to Cr(III) at the surface of the magnetite. These results have demonstrated that hollow-fibre membrane units can be enhanced for the removal of soluble, redox sensitive contaminants by incorporation of a layer of palladized biogenic nanoparticulate magnetite.

  15. Adsorción de Cr(VI por Cocos nucífera L. en residuales de Fibrocemento en Santiago de Cuba

    Directory of Open Access Journals (Sweden)

    Rosa María Pérez Silva

    2014-06-01

    Full Text Available Título en ingles: Cr(VI adsorption by Cocos nucífera L. in wastewater of fibrocement from Santiago de CubaTítulo corto: Adsorción de Cr(VI  por Cocos nucífera L.Resumen:  La adsorción y/o formación de complejos de metales pesados basados en la actividad química de la biomasa, es el proceso conocido como biosorción y es la base de una nueva tecnología para su remoción en efluentes industriales y su posterior recuperación. En esta tecnología se pueden utilizar diferentes tipos de biomasas tales como: algas, microorganismos y sub-productos agrícolas. Este trabajo estudió la adsorción de Cr(VI utilizando la cáscara del fruto de la planta Cocos nucífera L. como biomasa orgánica. Los valores óptimos de adsorción de Cr(VI son: pH de 3 unidades; tamaño de partícula menor que 0,074 mm; dosis de adsorbente de 5 g.dm-3 y tiempo contacto de 1 hora. A valores bajos de concentración del metal (1,0; 1,5 y 1,84 mg.dm-3 se obtuvo porcentaje de remoción superiores a 90, sin embargo a altos valores de concentración (2,5 y 3 mg.dm-3, se obtienen valores inferiores al 90 %. El proceso pudo ser estudiado a través de los modelos de Langmuir y de Freundlich, ya que el coeficiente de correlación para ambos modelos fue de 0,994 y 0,991 respectivamente.  Se logra remover los iones Cr(VI a valores de pH de 3 y 7 unidades en una matriz real, alcanzando valores de remoción de 96,85 % y 93,71 % respectivamente.Palabras clave: biosorción, Cr6+, biomasa vegetal, Langmuir, Freundlich.Abstract: Adsorption and/or formation of complexes of heavy metals based on the chemical activity of biomass, is the process known as biosorption and is the base of a new technology for its removal in industrials effluent and its posterior recovery. In this technology, different kinds of biomasses can be utilized such as: algae, microorganisms and agricultural subproducts. In this work, the adsorption of Cr(VI was studied, utilizing the nutshell of Cocos nucífera L

  16. Atrazine immobilization on sludge derived biochar and the interactive influence of coexisting Pb(II) or Cr(VI) ions.

    Science.gov (United States)

    Zhang, Weihua; Zheng, Juan; Zheng, Pingping; Qiu, Rongliang

    2015-09-01

    Sludge derived biochars (SDBCs) may have the potential to simultaneously remove heavy metals and organic contaminants in relation to their various active sorption sites for both metal ions and organic compounds. SDBCs have been proven to provide a considerable capacity for immobilizing Pb(II) and Cr(VI) ions in solution, and in this study their ability to sorb atrazine, in addition to their corresponding interactive influences with coexisting metal ions, is extensively investigated. The results indicate that all atrazine adsorption isotherms fit well with the Freundlich equation, and the greatest value of 16.8 mg g(-1) sorption capacity occurred with SDBCs pyrolyzed at 400°C for 2h. The slow sorption kinetics fit well with the Lagergren's 2nd order reaction, and depend upon the initial atrazine concentration, indicating the significance of a site-specific process. The ionic strength-dependence of the atrazine adsorption behavior further consolidates the involvement of the mechanism of the H-bond with hydroxyl groups on SDBC. However, when Pb(II)/Cr(VI) metal ions coexist in solution, they substantially suppress atrazine adsorption, probably because the inner complex between the hydroxyl groups on SDBCs and Pb(II)/Cr(III) ions intrude the weak H-bond with atrazine. As a result, metal adsorption was found to be unaffected by the coexisting atrazine. Therefore, although SDBC is applicable for atrazine removal/immobilization in most of environmentally relevant conditions, a two-step process may be required if heavy metal ions coexist.

  17. DANGER OF HEXAVALENT CHROMIUM AND STRATEGY FOR THE REMEDITATION

    Directory of Open Access Journals (Sweden)

    Aniruddha Roy

    2013-02-01

    Full Text Available Some metals as micronutrients have a major role in the life and growth process of plants and animals. However, certain forms of some metals may also act as toxic material even in relatively small quantities. Chromium is such a metal, whose concentration above a certain limit may cause a serious problem to the health of living organisms. Chromium (Cr may occur in several chemical forms in organic and inorganic systems. In biological systems only Cr (III and Cr (VI are significant. Among these two states, trivalent chromium (Cr-III is considered as an essential component, while hexavalent Chromium (Cr-VI in biological system has been detected as responsible for so many diseases, even some specific forms of cancer. This paper intends to present the adverse effect of Cr(VI on environment as well as on human beings and also try to find a way out to dissolve the problem by a newly developed efficient and cost effective technique.

  18. Incorporation of zero valent iron nanoparticles in the matrix of cationic resin beads for the remediation of Cr(VI) contaminated waters.

    Science.gov (United States)

    Toli, Aikaterini; Chalastara, Konstantina; Mystrioti, Christiana; Xenidis, Anthimos; Papassiopi, Nymphodora

    2016-07-01

    The objective of present study was to obtain the fixation of nano zero valent iron (nZVI) particles on a permeable matrix and evaluate the performance of this composite material for the removal of Cr(VI) from contaminated waters. The experiments were carried out using the cationic resin Dowex 50WX2 as porous support of the iron nanoparticles. The work was carried out in two phases. The first phase involved the fixation of nZVI on the resin matrix. The resin granules were initially mixed with a FeCl3 solution to obtain the adsorption of Fe(III). Then the Fe(III) loaded resin (RFe) was treated with polyphenol solutions to obtain the reduction of Fe(III) to the elemental state. Two polyphenol solutions were tested as reductants, i.e. green tea extract and gallic acid. Green tea was found to be inefficient, probably due to the relatively big size of the contained polyphenol molecules, but gallic acid molecules were able to reach adsorbed Fe(III) and reduce the cations to the elemental state. The second phase was focused on the investigation of Cr(VI) reduction kinetics using the nanoiron loaded resins (R-nFe). It was found that the reduction follows a kinetic law of first order with respect to Cr(VI) and to the embedded nanoiron. Compared to other similar products, this composite material was found to have comparable performance regarding reaction rates and higher degree of iron utilization. Namely the rate constant for the reduction of Cr(VI), in the presence of 1 mM nZVI, was equivalent to 1.4 h of half-life time at pH 3.2 and increased to 24 h at pH 8.5. The degree of iron utilization was as high as 0.8 mol of reduced Cr(VI) per mole of iron. It was also found that this composite material can be easily regenerated and reused for Cr(VI) reduction without significant loss of efficiency.

  19. Large scale groundwater flow and hexavalent chromium transport modeling under current and future climatic conditions: the case of Asopos River Basin.

    Science.gov (United States)

    Dokou, Zoi; Karagiorgi, Vasiliki; Karatzas, George P; Nikolaidis, Nikolaos P; Kalogerakis, Nicolas

    2016-03-01

    In recent years, high concentrations of hexavalent chromium, Cr(VI), have been observed in the groundwater system of the Asopos River Basin, raising public concern regarding the quality of drinking and irrigation water. The work described herein focuses on the development of a groundwater flow and Cr(VI) transport model using hydrologic, geologic, and water quality data collected from various sources. An important dataset for this goal comprised an extensive time series of Cr(VI) concentrations at various locations that provided an indication of areas of high concentration and also served as model calibration locations. Two main sources of Cr(VI) contamination were considered in the area: anthropogenic contamination originating from Cr-rich industrial wastes buried or injected into the aquifer and geogenic contamination from the leaching process of ophiolitic rocks. The aquifer's response under climatic change scenario A2 was also investigated for the next two decades. Under this scenario, it is expected that rainfall, and thus infiltration, will decrease by 7.7 % during the winter and 15 % during the summer periods. The results for two sub-scenarios (linear and variable precipitation reduction) that were implemented based on A2 show that the impact on the study aquifer is moderate, resulting in a mean level decrease less than 1 m in both cases. The drier climatic conditions resulted in higher Cr(VI) concentrations, especially around the industrial areas.

  20. Tracer Tests and Field Monitoring of In situ Bioreduction of Cr(VI) Bioreduction at the Hanford 100H Site

    Science.gov (United States)

    Long, P. E.; Newcomer, D. R.; Resch, C. T.; Cantrell, K.; Faybishenko, B.; Hazen, T. C.; Brodie, E.; Joyner, D.; Borglin, S.; Conrad, M.; Tokunaga, T.; Wan, J.; Hubbard, S.; Williams, K. H.; Peterson, J. E.; Firestone, M.; Andersen, G.; Desantis, T.; Hanlon, J.; Willett, A.; Koenigsberg, S.

    2006-05-01

    Tracer tests and field monitoring before, during, and after bio-immobilization of Cr(VI) in groundwater at the Hanford 100H field site have provided key data constraining the geohydrology and biogeochemistry of field- scale bioreduction. A slow release polylactate, Hydrogen Release Compound (HRC), was used to stimulate the in situ bioreduction and removal of Cr(VI) from groundwater. Monitoring included an extensive suite of field and laboratory techniques, as well as five Br-tracer injection tests and four pumping tests. To minimize drilling costs, a three-well system (injection well and upgradient and downgradient monitoring wells) was used for conducting the in situ biostimulation and monitoring. Pre-biostimulation Br-tracer tests demonstrated that low-flow pumping (1.2 to 2.5 l/min) on the down-gradient well was required to ensure capture of groundwater flow lines passing through the injection well (5 m from the downgradient pumping well). Detailed Br breakthrough curves were obtained using field-deployed Br ion-selective electrodes (Instrumentation Northwest, Inc.). We also used a multi-parameter flow cell (Hydrolab H2O Multiprobe) to collect hourly data on temperature, pH, redox potential, electrical conductivity, and dissolved oxygen (DO). Field measurements were used to enable repeat groundwater sampling by pumping through specially designed borehole water samplers. Following the HRC injection, the data demonstrated the temporal relationship between the Br arrival and onset of reducing conditions induced by the injection. For example, redox potential decreased from +240 to -130 mV while conductivity changed from ~510 μS/cm to ~850 μS/cm along with a complete removal of DO and a drop in pH. These changes occurred concomitantly with more than a 2- order of magnitude increase in microbial cell numbers. The pore-water conductivity changes were used to constrain interpretation of the results of cross-borehole radar tomography conducted prior to and after the

  1. The speciation of products from the reaction of {sup 51} Cr(VI) with mineral acids by high efficiency liquid chromatography; Especiacao dos produtos da reacao entre {sup 51} Cr(VI) e acidos minerais por cromatografia liquida de alta eficiencia

    Energy Technology Data Exchange (ETDEWEB)

    Pezzin, Sergio H.; Collins, Carol H.; Collins, Kenneth E. [Universidade Estadual de Campinas, SP (Brazil). Inst. de Quimica; Archundia, Cielita [Universidad Nacional Autonoma de Mexico, Mexico DF (Mexico). Inst. de Ciencias Nucleares

    1996-07-01

    The speciation of the products from the reaction of {sup 51} Cr(VI) with concentrated acids (HClO{sub 4}, HCl e HF) was carried out by ion chromatography. The separation was made on a Partisil SCX (10 {mu}m) column, using HClO{sub 4} and Ca(ClO{sub 4}){sub 2} solutions as eluents. The eluates were measured by {gamma}-counting. The results for the reaction (1h) of carrier-free {sup 51} Cr(VI) with HCl show that 96.4% from the {sup 51} Cr is not retained on the column (anionic and/or neutral species). A similar result (92.7% not retained) is observed in a Cr(VI)-HF system. However, for the reaction with HClO{sub 4}, 82% of the {sup 51} Cr was observed as a +3 species and only 5.9% as anionic and/or neutral species. (author)

  2. A study of nanostructured gold modified glassy carbon electrode for the determination of trace Cr(VI)

    Indian Academy of Sciences (India)

    Benzhi Liu; Liyuan Lu; Min Wang; Yanqin Zi

    2008-09-01

    A nanostructured gold modified glassy carbon electrode (Aunano/GCE) was employed for the determination of trace chromium(VI). To prepare Aunano/GCE, the GCE was immersed into KAuCl4 solution and electrodeposition was conducted at the potential of -0.4 V (vs Ag/AgCl) for 600 s. Scanning electron microscopy measurements show that the electrochemically synthesized gold nanoparticles were deposited in aggregated form. Any undue effects caused by the presence of foreign ions in the solution were also analysed to ensure that common interference in the determination of chromium(VI) by square wave voltammetry, do not influence the electrochemical response of the latter element. The results show that this method allows for Cr(VI) determinations with a much lower detection limit (0.01 g L-1) in the presence of excess of Cr(III) than the commonly used diethylenetriammine pentaacetic acid (DTPA) method. The method was applied to determine levels of chromium(VI) in tap water and sewage water.

  3. Facile synthesis of amino-functionalized titanium metal-organic frameworks and their superior visible-light photocatalytic activity for Cr(VI) reduction.

    Science.gov (United States)

    Wang, Hou; Yuan, Xingzhong; Wu, Yan; Zeng, Guangming; Chen, Xiaohong; Leng, Lijian; Wu, Zhibin; Jiang, Longbo; Li, Hui

    2015-04-09

    Porous metal-organic frameworks (MOFs) have been arousing a great interest in exploring the application of MOFs as photocatalyst in environment remediation. In this work, two different MOFs, Ti-benzenedicarboxylate (MIL-125(Ti)) and amino-functionalized Ti-benzenedicarboxylate (NH2-MIL-125(Ti)) were successfully synthesized via a facile solvothermal method. The MIL-125(Ti) and NH2-MIL-125(Ti) were well characterized by XRD, SEM, XPS, N2 adsorption-desorption measurements, thermogravimetric analysis and UV-vis diffuse reflectance spectra (DRS). It is revealed that the NH2-MIL-125(Ti) has well crystalline lattice, large surface area and mesoporous structure, chemical and thermal stability, and enhanced visible-light absorption up to 520 nm, which was associated with the chromophore (amino group) in the organic linker. Compared with MIL-125(Ti), NH2-MIL-125(Ti) exhibited more efficient photocatalytic activity for Cr(VI) reduction from aqueous solution under visible-light irradiation. The addition of hole scavenger, the hole scavenger concentration and the pH value of the reaction solution played important roles in the photo-catalytic reduction of Cr(VI). The presence of Ti(3+)-Ti(4+) intervalence electron transfer was the main reason for photo-excited electrons transportation from titanium-oxo clusters to Cr(VI), facilitating the Cr(VI) reduction under the acid condition. It was demonstrated that amino-functionalized Ti(IV)-based MOFs could be promising visible-light photocatalysts for the treatment of Cr(VI)-contained wastewater.

  4. Photoreduction of Cr(VI) in water using Bi{sub 2}O{sub 3}-ZrO{sub 2} nanocomposite under visible light irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Vignesh, Kumaravel [Post Graduate and Research Department of Chemistry, Thiagarajar College, Madurai 625009, Tamilnadu (India); Priyanka, Rajarajan [Department of Electrical and Electronics Engineering, Thiagarajar College of Engineering, Madurai 625015, Tamilnadu (India); Rajarajan, Muthuramalingam, E-mail: rajarajan_1962@yahoo.com [Department of Chemistry, Cardamom Planters' Association College, Bodinayakanur 626513, Tamilnadu (India); Suganthi, Ayyadurai, E-mail: suganthitcarts@gmail.com [Post Graduate and Research Department of Chemistry, Thiagarajar College, Madurai 625009, Tamilnadu (India)

    2013-02-01

    Highlights: Black-Right-Pointing-Pointer Bi{sub 2}O{sub 3}-ZrO{sub 2} nanocomposite was prepared by simple co-precipitation method. Black-Right-Pointing-Pointer PL measurements confirm the high suppression of electron-hole recombination. Black-Right-Pointing-Pointer The photocatalytic activity was measured by the reduction of Cr(VI). Black-Right-Pointing-Pointer The reaction conditions are optimized. Black-Right-Pointing-Pointer Bi{sub 2}O{sub 3}-ZrO{sub 2} was stable without loss of its activity up to 4 cyclic experiments. - Abstract: Chromium(VI) is a common heavy metal pollutant and extensively used in variety of industrial processes. In the present study, bismuth oxide-zirconium oxide nanocomposite (Bi{sub 2}O{sub 3}-ZrO{sub 2}) was synthesized to improve photoreduction of Cr(VI) under visible light irradiation. The synthesized photocatalyst was characterized by UV-visible-diffuse reflectance spectroscopy (UV-vis-DRS), X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDX), Brunauer-Emmett-Teller (B.E.T) surface area analysis and photoluminescence spectroscopy (PL). Bi{sub 2}O{sub 3}-ZrO{sub 2} was found to be more photoactive than Bi{sub 2}O{sub 3}, ZrO{sub 2}, TiO{sub 2} and ZnO for the reduction of Cr (VI). The influences of various reaction parameters like the effect of catalyst concentration, initial Cr(VI) concentration and addition of inorganic salts on the photocatalytic activity have been investigated in detail. Meanwhile, the stability of Bi{sub 2}O{sub 3}-ZrO{sub 2} was investigated by repeatedly performing Cr(VI) photoreducing experiments.

  5. Accurate quantification of total chromium and its speciation form Cr(VI) in water by ICP-DRC-IDMS and HPLC/ICP-DRC-IDMS.

    Science.gov (United States)

    Markiewicz, Barbara; Komorowicz, Izabela; Barałkiewicz, Danuta

    2016-05-15

    Two analytical procedures have been developed for the determination of total chromium (TCr) and its highly toxic species, i.e. Cr(VI) in water samples using the following methods: inductively coupled plasma dynamic reaction cell isotope dilution mass spectrometry (ICP-DRC-IDMS) and high performance liquid chromatography inductively coupled plasma dynamic reaction cell isotope dilution mass spectrometry (HPLC/ICP-DRC-IDMS). Spectral interferences, predominantly occurring in chromium determination, were removed using a dynamic reaction cell (DRC). The presented procedures facilitate the quantification of trace amounts - below 1 µg L(-1) of TCr and individual Cr species - in various water matrices including drinking water and still bottled water with different mineral composition. Special attention has been paid to the adequate preparation of isotopically enriched (53)Cr(VI) standard solution in order to avoid artifacts in chromium speciation. Both procedures were fully validated as well as establishing the traceability and estimation of the uncertainty of measurement were carried out. Application of all of the above mentioned elements and of the isotope dilution technique, which provides the highest quality of metrological traceability, allowed to obtain reliable and high quality results of chromium determination in water samples. Additionally, the comparison of two methods: HPLC/ICP-DRC-MS and HPLC/ICP-DRC-IDMS for Cr(VI) determination, was submitted basing on the validation parameters. As a result, the lower values for these parameters were obtained using the second method.

  6. DNA damaging bystander signalling from stem cells, cancer cells and fibroblasts after Cr(VI) exposure and its dependence on telomerase

    Energy Technology Data Exchange (ETDEWEB)

    Cogan, Nicola [Bristol Implant Research Centre, University of Bristol, Bristol, BS10 5NB (United Kingdom); Baird, Duncan M. [Department of Pathology School of Medicine, Cardiff University, Henry Wellcome Building for Biomedical Research in Wales, Heath Park, Cardiff, CF14 4XN (United Kingdom); Phillips, Ryan [Bristol Implant Research Centre, University of Bristol, Bristol, BS10 5NB (United Kingdom); Crompton, Lucy A.; Caldwell, Maeve A. [Henry Wellcome Laboratories for Integrative Neuroscience and Endocrinology, University of Bristol, Bristol, BS1 3NY (United Kingdom); Rubio, Miguel A. [Center of Regenerative Medicine in Barcelona, CMRB Dr. Aiguader, 88, 7th Floor, 08003 Barcelona (Spain); Newson, Roger [Radiation and Environmental Science Centre, Focas Institute, Dublin Institute of Technology, Dublin 2 (Ireland); Lyng, Fiona [National Heart and Lung Institute, Imperial College London, London, SW7 2AZ (United Kingdom); Case, C. Patrick, E-mail: c.p.case@bristol.ac.uk [Bristol Implant Research Centre, University of Bristol, Bristol, BS10 5NB (United Kingdom)

    2010-01-05

    The bystander effect is a feature of low dose radiation exposure and is characterized by a signaling process from irradiated cells to non irradiated cells, which causes DNA and chromosome damage in these 'nearest neighbour' cells. Here we show that a low and short dose of Cr(VI) can induce stem cells, cancer cells and fibroblasts to chronically secrete bystander signals, which cause DNA damage in neighboring cells. The Cr(VI) induced bystander signaling depended on the telomerase status of either cell. Telomerase negative fibroblasts were able to receive DNA damaging signals from telomerase positive or negative fibroblasts or telomerase positive cancer cells. However telomerase positive fibroblasts were resistant to signals from Cr(VI) exposed telomerase positive fibroblasts or cancer cells. Human embryonic stem cells, with positive Oct4 staining as a marker of pluripotency, showed no significant increase of DNA damage from adjacent Cr and mitomycin C exposed fibroblasts whilst those cells that were negatively stained did. This selectivity of DNA damaging bystander signaling could be an important consideration in developing therapies against cancer and in the safety and effectiveness of tissue engineering and transplantation using stem cells.

  7. Facile synthesis of amino-functionalized titanium metal-organic frameworks and their superior visible-light photocatalytic activity for Cr(VI) reduction

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Hou [College of Environmental Science and Engineering, Hunan University, Changsha 410082 (China); Key Laboratory of Environment Biology and Pollution Control, Hunan University, Ministry of Education, Changsha 410082 (China); Yuan, Xingzhong, E-mail: yxz@hnu.edu.cn [College of Environmental Science and Engineering, Hunan University, Changsha 410082 (China); Key Laboratory of Environment Biology and Pollution Control, Hunan University, Ministry of Education, Changsha 410082 (China); Wu, Yan [College of Environment and Energy, South China University of Technology, Guangzhou 510006 (China); Zeng, Guangming [College of Environmental Science and Engineering, Hunan University, Changsha 410082 (China); Key Laboratory of Environment Biology and Pollution Control, Hunan University, Ministry of Education, Changsha 410082 (China); Chen, Xiaohong [School of Business, Central South University, Changsha 410083 (China); Leng, Lijian; Wu, Zhibin; Jiang, Longbo [College of Environmental Science and Engineering, Hunan University, Changsha 410082 (China); Key Laboratory of Environment Biology and Pollution Control, Hunan University, Ministry of Education, Changsha 410082 (China); Li, Hui [Institute of Bio-energy, Hunan Academy of Forestry, Changsha 410004 (China)

    2015-04-09

    Highlights: • NH{sub 2} functionalized MIL-125(Ti) was fabricated by a facile solvothermal method. • The photocatalyst could reduce Cr(VI)–Cr(III) under visible light irradiation. • The Ti{sup 3+}–Ti{sup 4+} intervalence electron transfer is important for Cr(VI) reduction. • Used NH{sub 2}-MIL-125(Ti) can be recycled for the photocatalytic reduction. - Abstract: Porous metal-organic frameworks (MOFs) have been arousing a great interest in exploring the application of MOFs as photocatalyst in environment remediation. In this work, two different MOFs, Ti-benzenedicarboxylate (MIL-125(Ti)) and amino-functionalized Ti-benzenedicarboxylate (NH{sub 2}-MIL-125(Ti)) were successfully synthesized via a facile solvothermal method. The MIL-125(Ti) and NH{sub 2}-MIL-125(Ti) were well characterized by XRD, SEM, XPS, N{sub 2} adsorption–desorption measurements, thermogravimetric analysis and UV–vis diffuse reflectance spectra (DRS). It is revealed that the NH{sub 2}-MIL-125(Ti) has well crystalline lattice, large surface area and mesoporous structure, chemical and thermal stability, and enhanced visible-light absorption up to 520 nm, which was associated with the chromophore (amino group) in the organic linker. Compared with MIL-125(Ti), NH{sub 2}-MIL-125(Ti) exhibited more efficient photocatalytic activity for Cr(VI) reduction from aqueous solution under visible-light irradiation. The addition of hole scavenger, the hole scavenger concentration and the pH value of the reaction solution played important roles in the photo-catalytic reduction of Cr(VI). The presence of Ti{sup 3+}–Ti{sup 4+} intervalence electron transfer was the main reason for photo-excited electrons transportation from titanium-oxo clusters to Cr(VI), facilitating the Cr(VI) reduction under the acid condition. It was demonstrated that amino-functionalized Ti(IV)-based MOFs could be promising visible-light photocatalysts for the treatment of Cr(VI)-contained wastewater.

  8. Preparation, characterization and application of CuCrO2/ZnO photocatalysts for the reduction of Cr(VI).

    Science.gov (United States)

    Ketir, Wahiba; Rekhila, Gharib; Trari, Mohamed; Amrane, Abdelatif

    2012-01-01

    The delafossite CuCrO2 elaborated by sol-gel from 40 nm diameter colloid is optically active in the visible region. It is characterized physically and photoelectrochemically. The microstructure is fairly homogenous with a mean crystallite size of ca. 2 microm. The optical gap (1.30 eV), determined from the diffuse reflectance, is well suited to the sunlight spectrum. The Mott Schottky plot is characteristic of P-type conductivity with a flat band potential of -0.26 V(SCE). As application, the photoreduction of chromate is successfully achieved in air-equilibrated suspension CuCrO2/ZnO (1/1). CuCrO2 is photoactivated by visible light and the electrons in the conduction band (-1.34 V(SCE)) are injected to ZnO. In the presence of salicylic acid, a conversion of Cr(VI) to Cr(III) of 57% is obtained under optimal conditions (pH 3 at 25 degrees C, 5 x 10(-4) mol/L) because of the HCrO4- dark adsorption onto ZnO (4HCrO4- + 3C7H6O3 + 18O2 + 16H+ --> 4Cr3+ + 21CO2 + 19H2O, deltaG0 = -557 kcal/mol). Prolonged illumination is accompanied by a deceleration in the photoactivity owing to the competitive water reduction, an issue of energetic concern. The hetero-system exhibits self sensitization for hydrogen production with an evolution rate of 149 micromol/(hr x g).

  9. Toxic hexavalent chromium reduction by Bacillus pumilis, Cellulosimicrobium cellulans and Exiguobacterium

    Science.gov (United States)

    Rehman, Fatima; Faisal, Muhammad

    2015-05-01

    Three bacterial strains Bacillus pumilis, Cellulosimicrobium cellulans and Exiguobacterium were investigated when grown in Luria-Bertani (LB) medium at 500 μg/mL Cr(VI). The hexavalent chromium reduction was measured by growing the strains in DeLeo and Ehrlich (1994) medium at 200 and 400 μg/mL K2CrO4. The optimal Cr (VI) reduction by strains B. pumilis, Exigubacterium and C. cellulans was 51%, 39%, and 41%, respectively, at an initial K2CrO4 concentration of 200 μg/mL at pH 3 and temperature 37°C. At an initial chromate concentration of 400 μg/mL, the Cr(VI) reduction by strains B. pumilis, Exigubacterium and C. cellulans was 24%, 19%, and 18%, respectively at pH 3 at 37°C after 24 h. These strains have ability to reduce toxic hexavalent chromium to the less mobile trivalent chromium at a wide range of different environmental conditions and can be useful for the treatment of contaminated wastewater and soils.

  10. Assessment of Hexavalent Chromium Natural Attenuation for the Hanford Site 100 Area

    Energy Technology Data Exchange (ETDEWEB)

    Truex, Michael J. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Szecsody, James E. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Qafoku, Nikolla P. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Sahajpal, Rahul [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Zhong, Lirong [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Lawter, Amanda R. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Lee, Brady D. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States)

    2015-09-01

    Hexavalent chromium (Cr(VI)) plumes are present in the 100 Area at the Hanford Site. Remediation efforts are under way with objectives of restoring the groundwater to meet the drinking-water standard (48 µg/L) and protecting the Columbia River by ensuring that discharge of groundwater to the river is below the surface-water quality standard (10 µg/L). Current remedies include application of Pump-and-Treat (P&T) at the 100-D, 100-H, and 100-K Areas and Monitored Natural Attenuation (MNA) at the 100-F/IU Area. Remedy selection is still under way at the other 100 Areas. Additional information about the natural attenuation processes for Cr(VI) is important in all of these cases. In this study, laboratory experiments were conducted to demonstrate and quantify natural attenuation mechanisms using 100 Area sediments and groundwater conditions.

  11. Escherichia coli NemA is an efficient chromate reductase that can be biologically immobilized to provide a cell free system for remediation of hexavalent chromium.

    Directory of Open Access Journals (Sweden)

    Katherine J Robins

    Full Text Available Hexavalent chromium is a serious and widespread environmental pollutant. Although many bacteria have been identified that can transform highly water-soluble and toxic Cr(VI to insoluble and relatively non-toxic Cr(III, bacterial bioremediation of Cr(VI pollution is limited by a number of issues, in particular chromium toxicity to the remediating cells. To address this we sought to develop an immobilized enzymatic system for Cr(VI remediation. To identify novel Cr(VI reductase enzymes we first screened cell extracts from an Escherichia coli library of soluble oxidoreductases derived from a range of bacteria, but found that a number of these enzymes can reduce Cr(VI indirectly, via redox intermediates present in the crude extracts. Instead, activity assays for 15 candidate enzymes purified as His6-tagged proteins identified E. coli NemA as a highly efficient Cr(VI reductase (k(cat/K(M= 1.1×10(5 M(-1 s(-1 with NADH as cofactor. Fusion of nemA to the polyhydroxyalkanoate synthase gene phaC from Ralstonia eutropha enabled high-level biosynthesis of functionalized polyhydroxyalkanoate granules displaying stable and active NemA on their surface. When these granules were combined with either Bacillus subtilis glucose dehydrogenase or Candida boidinii formate dehydrogenase as a cofactor regenerating partner, high levels of chromate transformation were observed with only low initial concentrations of expensive NADH cofactor being required, the overall reaction being powered by consumption of the cheap sacrificial substrates glucose or formic acid, respectively. This system therefore offers promise as an economic solution for ex situ Cr(VI remediation.

  12. The reactivity of Fe(II) associated with goethite formed during short redox cycles toward Cr(VI) reduction under oxic conditions

    Energy Technology Data Exchange (ETDEWEB)

    Tomaszewski, Elizabeth J.; Lee, Seungyeol; Rudolph, Jared; Xu, Huifang; Ginder-Vogel, Matthew (UW)

    2017-08-01

    Chromium (Cr) is a toxic metal that causes a myriad of health problems and enters the environment as a result of anthropogenic activities and/or natural processes. The toxicity and solubility of chromium is linked to its oxidation state; Cr(III) is poorly soluble and relatively nontoxic, while Cr(VI) is soluble and a known carcinogen. Solid Fe(II) in iron-bearing minerals, such as pyrite, magnetite, and green rusts, reduce the oxidation state of chromium, reducing its toxicity and mobility. However, these minerals are not the only potential sources of solid-associated Fe(II) available for Cr(VI) reduction. For example, ferric (Fe(III)) (hydr)oxides, such as goethite or hematite, can have Fe(II) in the solid without phase transformation; however, the reactivity of Fe(II) within Fe(III) (hydr)oxides with contaminants, has not been previously investigated. Here, we cyclically react goethite with dissolved Fe(II) followed by dissolved O2, leading to the formation of reactive Fe(II) associated with goethite. In separate reactors, the reactivity of this Fe(II) is probed under oxic conditions, by exposure to chromate (CrO42 -) after either one, two, three or four redox cycles. Cr is not present during redox cycling; rather, it is introduced to a subset of the solid after each oxidation half-cycle. Analysis of X-ray absorption near edge structure (XANES) spectra reveals that the extent of Cr(VI) reduction to Cr(III) depends not only on solid Fe(II) content but also surface area and mean size of ordered crystalline domains, determined by BET surface area analysis and X-ray diffraction (XRD), respectively. Shell-by-shell fitting of the extended X-ray absorption fine structure (EXAFS) spectra demonstrates chromium forms both single and double corner sharing complexes on the surface of goethite, in addition to sorbed Cr(III) species. Finally, transmission electron microscope (TEM) imaging and X-ray energy-dispersive spectroscopy (EDS) illustrate that Cr preferentially

  13. Fabrication of core-shell Fe3O4@MIL-100(Fe) magnetic microspheres for the removal of Cr(VI) in aqueous solution

    Science.gov (United States)

    Yang, Qingxiang; Zhao, Qianqian; Ren, ShuangShuang; Lu, Qiongqiong; Guo, Xinmeng; Chen, Zhijun

    2016-12-01

    Facile regeneration of an adsorbent is very important for commercial feasibility. One typical highly porous metal-organic framework (MOF) materials based on MIL-100(Fe) and magnetic iron oxide particles (denoted as MMCs) with diameter about of 350 nm were successfully synthesized. The growth of MIL-100(Fe) shell on the surface of Fe3O4 was utilized precursor as crystal seed via in-situ step hydrothermal reaction. It is a simple way to obtain well organized core-shell MOF composites, compared to the step-by-step method. MMCs were firstly used to uptake of Cr(VI) anions in aqueous solution. Adsorption experiments were carried out in batch sorption mode investigating with the factors of contact time (0-1000 min), pH (from 2 to 12), dose of adsorbent (4-25 mg), and initial Cr(VI) concentration (range from 10 to 100 ppm).

  14. The usage of activated carbon from teak sawdust (tectona grandis l.f.) and zeolite for the adsorption of Cr(VI) and its analysis using solid-phase spectrophotometry (sps)

    Science.gov (United States)

    Saputro, S.; Masykuri, M.; Mahardiani, L.; Mulyani, B.; Qorina, I.; Yoshimura, K.; Takehara, K.; Matsuoka, S.

    2017-02-01

    This study aims to evaluate the usage of teak sawdust and zeolite as an adsorbent of Cr(VI) ion; optimal composition ratio of the composite adsorbent; and the sensitivity of solid-phase spectrophotometry (SPS) as a method to determine the levels of Cr(VI) ion as an adsorption results of adsorbents. The adsorbent used were teak sawdust activated carbon and zeolite as a single and composite adsorbents. The teak sawdust carbonization using muffle furnace and then activated with H3PO4 10% while the zeolite with H2SO4 10%. The contacting process of the adsorbents with Cr(VI) was done by varying the compositions. Analysis of Cr(VI) level was done using SPS method. Characterization of adsorbent before and after being activated is done using a FTIR. The results showed that teak sawdust and zeolite can be used as adsorbents to adsorb Cr(VI) in the simulated liquid waste with the adsorption capacity 1.19 µg/g the optimum composition ratio of teak sawdust activated carbon and zeolite was 75%:25% with the percentage of adsorption was 62.72%. Solid-phase spectrophotometry is a sensitive method to analyze the decreased levels of Cr(VI) as an adsorption results in µg/L level with the limit of detection (LOD) was 0.03 µg/L.

  15. Terrestrial and aquatic ecotoxicity assessment of Cr(VI) by the ReCiPe method calculation (LCIA): application on an old industrial contaminated site.

    Science.gov (United States)

    Adam, Véronique; Quaranta, Gaétana; Loyaux-Lawniczak, Stéphanie

    2013-05-01

    The most stable forms of chromium in the environment are chromium (III) and chromium (VI), the former being relatively immobile and necessary for organisms, and the latter being highly soluble and toxic. It is thus important to characterise ecotoxicological impacts of Cr(VI). However, there are still some important uncertainties in the calculation of ecotoxicological impacts of heavy metals in the LCIA global approach. The aim of this paper is to understand how the spatial and dynamic characterization of life cycle inventory (LCI) data can be exploited in life cycle impact assessment and particularly for the evaluation of the aquatic and terrestrial ecotoxicity of Cr(VI). To quantify these impacts, we studied an industrial waste landfill in the North of France that was contaminated with chromium. On the polluted area, the aquatic contamination is due to the slag heap as well as to chromium spots in soil. The soil contamination is mainly due to infiltration of chromium from the infill. The concentration of Cr(VI) in soil and water varies according to seasonal climatic variations and groundwater level. These variations have an effect on the Cr(VI) fate factor, in particular on transfer and residence time of the substance. This study underlines the spatial distribution of aquatic ecotoxicity and the temporal variation of freshwater ecotoxicity. We analysed the correlation between precipitation, temperature, concentration and ecotoxicity impact. With regards to the terrestrial ecotoxicity, the study focused on the vertical variation of the ecotoxicity and the major role of the soil layer composition into terrestrial pollution.

  16. Adsorption characteristics of hexavalent chromium on HCB/TiO{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Li; Zhang, Yonggang, E-mail: 13502182420@163.com

    2014-10-15

    Graphical abstract: - Highlights: • Sol–gel method was adopted to prepare HCB/TiO{sub 2}. • Its adsorption performance of Cr(VI) was investigated. • The maximum adsorption capacity for Cr(VI) was at 27.33 mg g{sup −1} in an acidic medium. • The value is worth comparable with other low-cost adsorbents. - Abstract: Sol–gel method was adopted to prepare HCB/TiO{sub 2} and its adsorption ability of hexavalent chromium, Cr(VI), and removal from aqueous solution were investigated. The samples were characterized by Power X-ray diffraction (XRD) and a transmission electron microscope (TEM) which showed that the TiO{sub 2} was deposited on the surface of HCB. FTIR was used to identify the changes of the surface functional groups before and after adsorption. Potentiometric titration method was used to characterize the zero charge (pH{sub pzc}) characteristics of the surface of HCB/TiO{sub 2} which showed more acidic functional groups containing. Batch experiments showed that initial pH, absorbent dosage, contact time and initial concentration of Cr(VI) were important parameters for the Cr(VI) adsorption studies. The Freundlich isotherm model better reflected the experimental data better. Cr(VI) adsorption process followed the pseudo-second order kinetic model, which illustrated chemical adsorption. The thermodynamic parameters, such as Gibbs free energy (ΔG), changes in enthalpy change (ΔH) and changes in entropy change (ΔS) were also evaluated. Negative value of free energy occurred at temperature range of 25–45 °C, so Cr(VI) adsorption by HCB/TiO{sub 2} is spontaneous. Desorption results showed that the adsorption capacity could maintain 80% after five cycles. The maximum adsorption capacity for Cr(VI) was at 27.33 mg g{sup −1} in an acidic medium, of which the value is worth comparable with other low-cost adsorbents.

  17. Controlled reduction of red mud waste to produce active systems for environmental applications: heterogeneous Fenton reaction and reduction of Cr(VI).

    Science.gov (United States)

    Costa, Regina C C; Moura, Flávia C C; Oliveira, Patrícia E F; Magalhães, Fabiano; Ardisson, José D; Lago, Rochel M

    2010-02-01

    In this work, controlled reduction of red mud with H(2) was used to produce active systems for two different environmental applications, i.e. the heterogeneous Fenton reaction and the reduction of Cr(VI). Mössbauer, powder X-ray diffraction, thermal analyses and scanning electron microscopy analyses showed that at different temperatures, i.e. 300, 400, 500 and 600 degrees C, H(2) reduces red mud to different phases, mainly Fe(3)O(4), Fe(0)/Fe(3)O(4) and Fe(0). These Fe phases are dispersed on Al, Si and Ti oxides present in the red mud and show high reactivity towards two environmental applications, i.e. the heterogeneous Fenton reaction and the reduction of Cr(VI). Reduction with H(2) at 400 degrees C showed the best results for the oxidation of the model dye methylene blue with H(2)O(2) at neutral pH due to the presence of the composite Fe(0)/Fe(3)O(4). The reduced red mud at 500-600 degrees C produced Fe(0) highly active for the reduction of Cr(VI) in aqueous medium. Another feature of these red mud based system is that after deactivation due to extensive use they can be completely regenerated by simple treatment with H(2).

  18. Synthesis of 2-Mercaptonicotinic Acid-Capped CdSe Quantum Dots and its Application to Spectrofluorometric Determination of Cr(VI) in Water Samples.

    Science.gov (United States)

    Hosseini, Mohammad Saeid; Khorashahi, Somayeh; Hosseini, Navid

    2016-05-01

    The CdSe quantum dots (QDs) capped with 2-mercaptonicotinic acid (H2MN) were prepared through a controllable process at 80 °C. The prepared QDs were characterized by XRD, TEM, IR, UV-Vis and fluorescence (FL) techniques. It was found that the QDs were nearly mono-disperse with the diameters in the range of 8-10 nm. These QDs are capable to exhibit strong FL even in concentrated acidic media. They exhibit an enhanced fluorescence in the presence of Cr(VI), which was used for the determination of Cr(VI) in water samples. The linear range was found to be 1 × 10(-7)-6.0 × 10(-6) M with the RSD and DL of 0.92 % and 5 × 10(-8) M, respectively. Except that Ca(2+) and Fe(3+) which can be eliminated through a simple precipitation process, the other co-existent ions present in natural water were not interfered. The recoveries obtained for the added amounts of Cr(VI) were in the range of 96.9-103.2 %, which denote on application of the method, satisfactorily.

  19. Cr(VI) transport via a supported ionic liquid membrane containing CYPHOS IL101 as carrier: system analysis and optimization through experimental design strategies.

    Science.gov (United States)

    Rodríguez de San Miguel, Eduardo; Vital, Xóchitl; de Gyves, Josefina

    2014-05-30

    Chromium(VI) transport through a supported liquid membrane (SLM) system containing the commercial ionic liquid CYPHOS IL101 as carrier was studied. A reducing stripping phase was used as a mean to increase recovery and to simultaneously transform Cr(VI) into a less toxic residue for disposal or reuse. General functions which describe the time-depending evolution of the metal fractions in the cell compartments were defined and used in data evaluation. An experimental design strategy, using factorial and central-composite design matrices, was applied to assess the influence of the extractant, NaOH and citrate concentrations in the different phases, while a desirability function scheme allowed the synchronized optimization of depletion and recovery of the analyte. The mechanism for chromium permeation was analyzed and discussed to contribute to the understanding of the transfer process. The influence of metal concentration was evaluated as well. The presence of different interfering ions (Ca(2+), Al(3+), NO3(-), SO4(2-), and Cl(-)) at several Cr(VI): interfering ion ratios was studied through the use of a Plackett and Burman experimental design matrix. Under optimized conditions 90% of recovery was obtained from a feed solution containing 7mgL(-1) of Cr(VI) in 0.01moldm(-3) HCl medium after 5h of pertraction.

  20. Removal of Cr(VI) from low-temperature micro-polluted surface water by tannic acid immobilized powdered activated carbon.

    Science.gov (United States)

    Li, Weiguang; Gong, Xujin; Li, Xin; Zhang, Duoying; Gong, Hainan

    2012-06-01

    In this study, food-grade tannic acid-immobilized powdered activated carbon (TA-PAC) was prepared, and adsorption of Cr(VI) (0.500 mg/L) onto TA-PAC as a function of pH, contact time, adsorption capacities and adsorption isotherms at 280 K was investigated. The results indicated that the immobilization process introduced abundant acid functional groups. The adsorption capacity of TA-PAC was found to be pH-dependent, and the optimal pH value was found to be 4.0. The equilibrium time was 240 min for TA-PAC. Adsorption data for total chromium were modeled using both two-parameter and three-parameter isotherm models. Freundlich and linear forms of three-parameter models yielded the best results for all of the data. Desorption studies of immobilized material suggested that the immobilization of food-grade tannic acid is steady. The adsorption mechanism of Cr(VI) on TA-PAC was assumed to be a comprehensive process consisting of surface reduction of Cr(VI), esterification between catechol and chromate, and ion exchange.

  1. Evaluation of extraction methods for hexavalent chromium determination in dusts, ashes, and soils

    Science.gov (United States)

    Wolf, Ruth E.; Wilson, Stephen A.

    2010-01-01

    One of the difficulties in performing speciation analyses on solid samples is finding a suitable extraction method. Traditional methods for extraction of hexavalent chromium, Cr(VI), in soils, such as SW846 Method 3060A, can be tedious and are not always compatible with some determination methods. For example, the phosphate and high levels of carbonate and magnesium present in the U.S. Environmental Protection Agency (USEPA) Method 3060A digestion for Cr(VI) were found to be incompatible with the High Performance Liquid Chromatography-Inductively Coupled Plasma-Mass Spectrometry (HPLC-ICP-MS) detection method used by our laboratory. Modification of Method 3060A by eliminating the use of the phosphate buffer provided improved performance with the detection method, however dilutions are still necessary to achieve good chromatographic separation and detection of Cr(VI). An ultrasonic extraction method using a 1 mM Na2CO3 - 9 mM NaHCO3 buffer solution, adapted from Occupational Safety and Health Administration (OSHA) Method ID215, has been used with good results for the determination of Cr(VI) in air filters. The average recovery obtained for BCR-545 - Welding Dust Loaded on Filter (IRMM, Belgium) using this method was 99 percent (1.2 percent relative standard deviation) with no conversion of Cr(VI) to Cr(III) during the extraction process. This ultrasonic method has the potential for use with other sample matrices, such as ashes and soils. Preliminary investigations using NIST 2701 (Hexavalent Chromium in Contaminated Soil) loaded onto quartz filters showed promising results with approximately 90 percent recovery of the certified Cr(VI) value. Additional testing has been done using NIST 2701 and NIST 2700 using different presentation methods. Extraction efficiency of bulk presentation, where small portions of the sample are added to the bottom of the extraction vessel, will be compared with supported presentation, where small portions of the sample are loaded onto a

  2. Facile synthesis of AgI/BiOI-Bi{sub 2}O{sub 3} multi-heterojunctions with high visible light activity for Cr(VI) reduction

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Qi [School of Environmental Science and Engineering, Zhejiang Gongshang University, Hangzhou 310018 (China); The Brook Byer Institute for Sustainable Systems and School of Civil and Environmental Engineering, Georgia Institute of Technology, Atlanta 30332 (United States); Shi, Xiaodong; Liu, Enqin [School of Environmental Science and Engineering, Zhejiang Gongshang University, Hangzhou 310018 (China); Crittenden, John C. [The Brook Byer Institute for Sustainable Systems and School of Civil and Environmental Engineering, Georgia Institute of Technology, Atlanta 30332 (United States); Ma, Xiangjuan; Zhang, Yi [School of Environmental Science and Engineering, Zhejiang Gongshang University, Hangzhou 310018 (China); Cong, Yanqing, E-mail: yqcong@hotmail.com [School of Environmental Science and Engineering, Zhejiang Gongshang University, Hangzhou 310018 (China)

    2016-11-05

    Graphical abstract: Highly visible-light-active AgI/BiOI-Bi{sub 2}O{sub 3} with multi-heterojunctions was developed. - Highlights: • Visible-light-active AgI/BiOI-Bi{sub 2}O{sub 3} with multi-heterojunctions was prepared. • Highly enhanced photocatalytic reduction of Cr(VI) was observed. • k{sub Cr(VI)} on AgI/BiOI-Bi{sub 2}O{sub 3} increased by ca.16 times relative to Bi{sub 2}O{sub 3}. • Decreased E{sub g}, shifted E{sub fb} and reduced charge transfer resistance were observed. • Simultaneous reduction of Cr(VI) and degradation of organics were achieved. - Abstract: AgI sensitized BiOI-Bi{sub 2}O{sub 3} composite (AgI/BiOI-Bi{sub 2}O{sub 3}) with multi-heterojunctions was prepared using simple etching-deposition process. Different characterization techniques were performed to investigate the structural, optical and electrical properties of the as-prepared photocatalysts. It was found that the ternary AgI/BiOI-Bi{sub 2}O{sub 3} composite exhibited: (1) improved photocurrent response, (2) smaller band gap, (3) greatly reduced charge transfer resistance and (4) negative shift of flat band potential, which finally led to easier generation and more efficient separation of photo-generated electron-hole pairs at the hetero-interfaces. Thus, for the reduction of Cr(VI), AgI/BiOI-Bi{sub 2}O{sub 3} exhibited excellent photocatalytic activity under visible light irradiation at near neutral pH. AgI/BiOI-Bi{sub 2}O{sub 3} was optimized when the initial molar ratio of KI to Bi{sub 2}O{sub 3} and AgNO{sub 3} to Bi{sub 2}O{sub 3} was 1:1 and 10%, respectively. The estimated k{sub Cr(VI)} on optimized AgI/BiOI-Bi{sub 2}O{sub 3} was about 16 times that on pure Bi{sub 2}O{sub 3}. Good stability was also observed in cyclic runs, indicating that the current multi-heterostructured photocatalyst is highly desirable for the remediation of Cr(VI)-containing wastewater.

  3. Assessment of Cr(VI-induced cytotoxicity and genotoxicity using high content analysis.

    Directory of Open Access Journals (Sweden)

    Chad M Thompson

    Full Text Available Oral exposure to high concentrations of hexavalent chromium [Cr(VI] induces intestinal redox changes, villus cytotoxicity, crypt hyperplasia, and intestinal tumors in mice. To assess the effects of Cr(VI in a cell model relevant to the intestine, undifferentiated (proliferating and differentiated (confluent Caco-2 cells were treated with Cr(VI, hydrogen peroxide or rotenone for 2-24 hours. DNA damage was then assessed by nuclear staining intensity of 8-hydroxydeoxyguanosine (8-OHdG and phosphorylated histone variant H2AX (γ-H2AX measured by high content analysis methods. In undifferentiated Caco-2, all three chemicals increased 8-OHdG and γ-H2AX staining at cytotoxic concentrations, whereas only 8-OHdG was elevated at non-cytotoxic concentrations at 24 hr. Differentiated Caco-2 were more resistant to cytotoxicity and DNA damage than undifferentiated cells, and there were no changes in apoptotic markers p53 or annexin-V. However, Cr(VI induced a dose-dependent translocation of the unfolded protein response transcription factor ATF6 into the nucleus. Micronucleus (MN formation was assessed in CHO-K1 and A549 cell lines. Cr(VI increased MN frequency in CHO-K1 only at highly cytotoxic concentrations. Relative to the positive control Mitomycin-C, Cr(VI only slightly increased MN frequency in A549 at mildly cytotoxic concentrations. The results demonstrate that Cr(VI genotoxicity correlates with cytotoxic concentrations, and that H2AX phosphorylation occurs at higher concentrations than oxidative DNA damage in proliferating Caco-2 cells. The findings suggest that in vitro genotoxicity of Cr(VI is primarily oxidative in nature at low concentrations. Implications for in vivo intestinal toxicity of Cr(VI will be discussed.

  4. Assessment of Cr(VI)-Induced Cytotoxicity and Genotoxicity Using High Content Analysis

    Science.gov (United States)

    Thompson, Chad M.; Fedorov, Yuriy; Brown, Daniel D.; Suh, Mina; Proctor, Deborah M.; Kuriakose, Liz; Haws, Laurie C.; Harris, Mark A.

    2012-01-01

    Oral exposure to high concentrations of hexavalent chromium [Cr(VI)] induces intestinal redox changes, villus cytotoxicity, crypt hyperplasia, and intestinal tumors in mice. To assess the effects of Cr(VI) in a cell model relevant to the intestine, undifferentiated (proliferating) and differentiated (confluent) Caco-2 cells were treated with Cr(VI), hydrogen peroxide or rotenone for 2–24 hours. DNA damage was then assessed by nuclear staining intensity of 8-hydroxydeoxyguanosine (8-OHdG) and phosphorylated histone variant H2AX (γ-H2AX) measured by high content analysis methods. In undifferentiated Caco-2, all three chemicals increased 8-OHdG and γ-H2AX staining at cytotoxic concentrations, whereas only 8-OHdG was elevated at non-cytotoxic concentrations at 24 hr. Differentiated Caco-2 were more resistant to cytotoxicity and DNA damage than undifferentiated cells, and there were no changes in apoptotic markers p53 or annexin-V. However, Cr(VI) induced a dose-dependent translocation of the unfolded protein response transcription factor ATF6 into the nucleus. Micronucleus (MN) formation was assessed in CHO-K1 and A549 cell lines. Cr(VI) increased MN frequency in CHO-K1 only at highly cytotoxic concentrations. Relative to the positive control Mitomycin-C, Cr(VI) only slightly increased MN frequency in A549 at mildly cytotoxic concentrations. The results demonstrate that Cr(VI) genotoxicity correlates with cytotoxic concentrations, and that H2AX phosphorylation occurs at higher concentrations than oxidative DNA damage in proliferating Caco-2 cells. The findings suggest that in vitro genotoxicity of Cr(VI) is primarily oxidative in nature at low concentrations. Implications for in vivo intestinal toxicity of Cr(VI) will be discussed. PMID:22905163

  5. Flow injection solid phase extraction electrothermal atomic absorption spectrometry for the determination of Cr(VI) by selective separation and preconcentration on a lab-made hybrid mesoporous solid microcolumn

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Manuela; Stripeikis, Jorge [Laboratorio de Analisis de Trazas, Departamento de Quimica Inorganica, Analitica y Quimica Fisica, INQUIMAE, Universidad de Buenos Aires, Pabellon 2, Ciudad Universitaria, (1428) Buenos Aires (Argentina); Tudino, Mabel [Laboratorio de Analisis de Trazas, Departamento de Quimica Inorganica, Analitica y Quimica Fisica, INQUIMAE, Universidad de Buenos Aires, Pabellon 2, Ciudad Universitaria, (1428) Buenos Aires (Argentina)], E-mail: tudino@qi.fcen.uba.ar

    2009-06-15

    A lab-made hybrid mesoporous solid was employed in a flow injection solid phase extraction electrothermal atomic absorption spectrometric (FI-SPE-ETAAS) system for the selective retention of Cr(VI). The solid was prepared by co-condensation of sodium tetraethylortosilicate and 3-aminopropyltriethoxysilane by sol-gel methodology and one-pot synthesis and characterized by Fourier transform infrared spectroscopy, X ray diffraction spectroscopy, and scanning electronic microscopy. Adsorption capacities at different pH values of both, Cr(VI) and Cr(III), were also measured in order to obtain the optimum retention for Cr(VI) with no interference of Cr(III). The maximum capacity of adsorption (4.35 mmol g{sup -} {sup 1}) was observed for pH values between 2-3, whilst Cr(III) was found to remain in solution (adsorption capacity = 0.007 mmol g{sup -} {sup 1}). Then, a microcolumn (bed volume: 7.9 {mu}L) was filled with the solid and inserted in the FI-ETAAS system for analytical purposes. Since the analyte was strongly retained by the filling in the anionic form, 0.1 mol L{sup -} {sup 1} hydroxylammonium chloride in 1 mol L{sup -} {sup 1} hydrochloric acid was selected as eluent due to its redox characteristics. In this way, the sorbed Cr(VI) was easily released in the cationic form. The enrichment factor (EF) was found as a compromise between sensitivity and sample throughput and a value of 27 was obtained under optimized conditions: pH 2, sample loading 2 mL min{sup -} {sup 1} (60 s), elution flow rate 0.5 ml min{sup -} {sup 1} (eluent volume: 75 {mu}L). Under optimized conditions the limit of detection for Cr(VI) was 1.2 ng L{sup -} {sup 1}, the precision, expressed as RSD was 2.5%, the sample throughput 21/h, and the microcolumn lifetime was over 300 adsorption/desorption cycles. Cr(III) determination was also performed by simply measuring its concentration at the end of the column and after Cr(VI) retention by the mesoporous solid. Applications of the methodology to

  6. Synergistic photoelectrochemical reduction of Cr(VI) and oxidation of organic pollutants by g-C3N4/TiO2-NTs electrodes.

    Science.gov (United States)

    Zhang, Yi; Wang, Qiang; Lu, Jiani; Wang, Qi; Cong, Yanqing

    2016-11-01

    The g-C3N4/TiO2-NTs electrodes were synthesized by a dip-coating procedure followed by high-temperature annealing used in photoelectrochemical process. From the results, a simultaneous and rapid reduction of Cr(VI) and degradation of phenol in Cr(VI)/phenol system was observed with photoelectrocatalytic activity under UV-visible light irradiation than photocatalytic and electrocatalytic activities. The different kinds of Cr(VI)/organic pollutants systems were also investigated systematically. In addition, different scavengers were also added in Cr(VI)/phenol and Cr(VI)/benzyl alcohol systems to indicate that the hydroxyl radicals and superoxide radicals were the most major active species for the denomination of Cr(VI) and organic pollutants. The intermediates of phenol and benzyl alcohol were also detected during the reaction in order to deduce the photoelectrocatalysis mechanism underg-C3N4/TiO2-NTs electrodes that the charge separation was improved and subsequently electron-transfer efficiency was higher.

  7. Quantification of total and hexavalent chromium in lager beers: variability between styles and estimation of daily intake of chromium from beer.

    Science.gov (United States)

    Vieira, Elsa; Soares, M Elisa; Kozior, Marta; Krejpcio, Zbigniew; Ferreira, Isabel M P L V O; Bastos, M Lourdes

    2014-09-17

    A survey of the presence of total and hexavalent chromium in lager beers was conducted to understand the variability between different styles of lager beer packaged in glass or cans and to estimate daily intake of total Cr and hexavalent chromium from beer. Graphite-furnace atomic absorption spectroscopy using validated methodologies was applied. Selective extraction of hexavalent chromium was performed using a Chromabond NH2/500 mg column and elution with nitric acid. The detection limits were 0.26 and 0.68 μg L(-1) for total Cr and Cr(VI), respectively. The mean content of total Cr ranged between 1.13 μg L(-1) in canned pale lager and 4.32 μg L(-1) in low-alcohol beers, whereas the mean content of Cr(VI) was beer, beer consumption can contribute approximately 2.28-8.64 and 1.6-6.17% of the recommended daily intake of chromium for women and men, respectively.

  8. Fabrication of Polypyrrole/Graphene Oxide Composite Nanosheets and Their Applications for Cr(VI) Removal in Aqueous Solution

    Science.gov (United States)

    Li, Shangkun; Lu, Xiaofeng; Xue, Yanpeng; Lei, Junyu; Zheng, Tian; Wang, Ce

    2012-01-01

    In this paper, we report on the simple, reliable synthesis of polypyrrole (PPy)/graphene oxide (GO) composite nanosheets by using sacrificial-template polymerization method. Herein, MnO2 nanoslices were chosen as a sacrificial-template to deposit PPy, which served as the oxidant as well. During the polymerization of pyrrole on surface of GO nanosheets, MnO2 component was consumed incessantly. As a result, the PPy growing on the surface of GO nanosheets has the morphology just like the MnO2 nanoslices. This method can provide the fabrication of PPy nanostructures more easily than conventional route due to its independence of removing template, which usually is a complex and tedious experimental process. The as-prepared PPy/GO composite nanosheets exhibited an enhanced properties for Cr(VI) ions removal in aqueous solution based on the synergy effect. The adsorption capacity of the PPy/GO composite nanosheets is about two times as large as that of conventional PPy nanoparticles. We believe that our findings can open a new and effective avenue to improve the adsorption performance in removing heavy metal ions from waste water. PMID:22927957

  9. Dynamics of cetyltrimethylammonium bromide mediated reaction of phenylsulfinylacetic acid with Cr(VI: Treatment of pseudo-phase models

    Directory of Open Access Journals (Sweden)

    Subramaniam Perumal

    2015-01-01

    The influence of cetyltrimethylammonium bromide, CTon the oxidative decarboxylation of phenylsulfinylacetic acid, PSAA and several meta- and para-substituted PSAAs by Cr(VI was investigated in 95 % H2O-5 % CH3CN medium. The rate profile displayed a peculiar trend with an initial rate increase at low [CTAB] followed by sharp rate inhibition at higher [CTAB]. The initial rate acceleration can be explained by strong binding of SO42- on the positively charged micellar surface. The specific partitioning of PSAA in micellar phase by hydrophobic interaction and the oxidizing species, HCrO3+ in aqueous phase by electrostatic repulsion accounted the rate retardation at higher [CTAB]. The Hammett plot with different substituted PSAAs showed an excellent correlation affording negative ρ value which supports the proposed mechanism involving a sulfonium cation intermediate formation. The obtained ρ value in CTmedium is found to be slightly lower than that in aqueous medium. The quantitative analysis of rate data for the inhibition shown by CTwas performed using Menger-Portnoy and Piszkiewicz pseudo-phase models. The binding constant for PSAA with micelle was evaluated from Piszkiewicz cooperative model.

  10. Fabrication of polypyrrole/graphene oxide composite nanosheets and their applications for Cr(VI) removal in aqueous solution.

    Science.gov (United States)

    Li, Shangkun; Lu, Xiaofeng; Xue, Yanpeng; Lei, Junyu; Zheng, Tian; Wang, Ce

    2012-01-01

    In this paper, we report on the simple, reliable synthesis of polypyrrole (PPy)/graphene oxide (GO) composite nanosheets by using sacrificial-template polymerization method. Herein, MnO(2) nanoslices were chosen as a sacrificial-template to deposit PPy, which served as the oxidant as well. During the polymerization of pyrrole on surface of GO nanosheets, MnO(2) component was consumed incessantly. As a result, the PPy growing on the surface of GO nanosheets has the morphology just like the MnO(2) nanoslices. This method can provide the fabrication of PPy nanostructures more easily than conventional route due to its independence of removing template, which usually is a complex and tedious experimental process. The as-prepared PPy/GO composite nanosheets exhibited an enhanced properties for Cr(VI) ions removal in aqueous solution based on the synergy effect. The adsorption capacity of the PPy/GO composite nanosheets is about two times as large as that of conventional PPy nanoparticles. We believe that our findings can open a new and effective avenue to improve the adsorption performance in removing heavy metal ions from waste water.

  11. Fabrication of polypyrrole/graphene oxide composite nanosheets and their applications for Cr(VI removal in aqueous solution.

    Directory of Open Access Journals (Sweden)

    Shangkun Li

    Full Text Available In this paper, we report on the simple, reliable synthesis of polypyrrole (PPy/graphene oxide (GO composite nanosheets by using sacrificial-template polymerization method. Herein, MnO(2 nanoslices were chosen as a sacrificial-template to deposit PPy, which served as the oxidant as well. During the polymerization of pyrrole on surface of GO nanosheets, MnO(2 component was consumed incessantly. As a result, the PPy growing on the surface of GO nanosheets has the morphology just like the MnO(2 nanoslices. This method can provide the fabrication of PPy nanostructures more easily than conventional route due to its independence of removing template, which usually is a complex and tedious experimental process. The as-prepared PPy/GO composite nanosheets exhibited an enhanced properties for Cr(VI ions removal in aqueous solution based on the synergy effect. The adsorption capacity of the PPy/GO composite nanosheets is about two times as large as that of conventional PPy nanoparticles. We believe that our findings can open a new and effective avenue to improve the adsorption performance in removing heavy metal ions from waste water.

  12. Airborne exposure to inhalable hexavalent chromium in welders and other occupations: Estimates from the German MEGA database.

    Science.gov (United States)

    Pesch, Beate; Kendzia, Benjamin; Hauptmann, Kristin; Van Gelder, Rainer; Stamm, Roger; Hahn, Jens-Uwe; Zschiesche, Wolfgang; Behrens, Thomas; Weiss, Tobias; Siemiatycki, Jack; Lavoué, Jerome; Jöckel, Karl-Heinz; Brüning, Thomas

    2015-07-01

    This study aimed to estimate occupational exposure to inhalable hexavalent chromium (Cr(VI)) using the exposure database MEGA. The database has been compiling Cr(VI) concentrations and ancillary data about measurements at German workplaces. We analysed 3659 personal measurements of inhalable Cr(VI) collected between 1994 and 2009. Cr(VI) was determined spectrophotometrically at 540 nm after reaction with diphenylcarbazide. We assigned the measurements to pre-defined at-risk occupations using the information provided about the workplaces. Two-thirds of the measurements were below the limit of quantification (LOQ) and multiply imputed according to the distribution above LOQ. The 75th percentile value was 5.2 μg/m(3) and the 95th percentile was 57.2 μg/m(3). We predicted the geometric mean for 2h sampling in the year 2000, and the time trend of Cr(VI) exposure in these settings with and without adjustment for the duration of measurements. The largest dataset was available for welding (N = 1898), which could be further detailed according to technique. The geometric means were above 5 μg/m(3) in the following situations: spray painting, shielded metal arc welding, and flux-cored arc welding if applied to stainless steel. The geometric means were between 1 μg/m(3) and 5 μg/m(3) for gas metal arc welding of stainless steel, cutting, hard-chromium plating, metal spraying and in the chemical chromium industry. The exposure profiles described here are useful for epidemiologic and industrial health purposes. Exposure to Cr(VI) varies not only between occupations, but also within occupations as shown for welders. In epidemiologic studies, it would be desirable to collect exposure-specific information in addition to the job title.

  13. Selective and sensitive speciation analysis of Cr(VI) and Cr(III) in water samples by fiber optic-linear array detection spectrophotometry after ion pair based-surfactant assisted dispersive liquid-liquid microextraction.

    Science.gov (United States)

    Yousefi, Seyedeh Mahboobeh; Shemirani, Farzaneh

    2013-06-15

    A simple ion pair based-surfactant assisted dispersive liquid-liquid microextraction (IP-SA-DLLME) was evaluated for extraction and preconcentration of Cr(VI) and Cr(III) in aqueous samples. In this method, which was used for the first time for chromium speciation analysis, sodium dodecyl sulfate (SDS) was used as both ion-pairing and disperser agent. Cr(VI) ions were converted into their cationic complex with 1,5-diphenylcarbazide (DPC) and then extracted into 1-octanol dispersed in aqueous solution. Cr(III) ion also can be determined by this procedure after oxidation to Cr(VI). After extraction and phase separation, upper organic phase was transferred to a micro cell of a fiber optic-linear array detection spectrophotometry (FO-LADS). The effects of various parameters on the extraction recovery were investigated. Under the optimized conditions and preconcentration of 10 mL of sample, the enrichment factor of 159 and the detection limit of 0.05 μgL(-1) were obtained. Validation of the method was performed by spiking-recovery method and comparison of results with those obtained by ET-AAS method.

  14. Synthesis Technology of PEI Modified Brewer's Grains for the Adsorption of Cr(VI

    Directory of Open Access Journals (Sweden)

    Yihua Jiang

    2015-05-01

    Full Text Available With beer production waste brewer's grains (BSG as the raw material, through polyethylenimine (PEI modified and glutaraldehyde (GA cross-linking process for preparing the modified brewer's grains biosorbents. The simulation of Cr (VI wastewater as treatment object, through the optimization of synthesis conditions of Cr (VI, the optimal synthesis process was obtained. The results showed, 4 g BSG and 100 mL 4% PEI methanol solution were placed in 250 mL conical flask at room temperature, shaking for 24 h. After the mixture,shifted to 200 mL l.5% GA solution directly, magnetic stirring for half an hour, the modified results of brewer’s grain was best. Under the optimal conditions, the average of adsorption rate was 98.82% and adsorption capacity was 45.31 mg/g. The modified brewer's grains of amine surfactant modified is a promising treatment of chromium wastewater biological materials.

  15. Cytogenomics of hexavalent chromium (Cr6+ exposed cells: A comprehensive review

    Directory of Open Access Journals (Sweden)

    Akanksha Nigam

    2014-01-01

    Full Text Available The altered cellular gene expression profile is being hypothesized as the possible molecular basis navigating the onset or progress of various morbidities. This hypothesis has been evaluated here in respect of Cr 6+ induced toxicity. Several studies using gene microarray show selective and strategic dysregulations of cellular genes and pathways induced by Cr 6+ . Relevant literature has been reviewed to unravel these changes in different test systems after exposure to Cr 6+ and also to elucidate association if any, of the altered cytogenomics with Cr 6+ induced toxicity or carcinogenicity. The aim was to verify the hypothesis for critical role of altered cytogenomics in onset of Cr 6+ induced biological / clinical effects by identifying genes modulated commonly by the toxicant irrespective of test system or test concentrations / doses, and by scrutinizing their importance in regulation of the flow of mechanistically linked events crucial for resultant morbidities. Their probability as biomarkers to monitor the toxicant induced biological changes is speculative. The modulated genes have been found to cluster under the pathways that manage onset of oxidative stress, DNA damage, apoptosis, cell-cycle regulation, cytoskeleton, morphological changes, energy metabolism, biosynthesis, oncogenes, bioenergetics, and immune system critical for toxicity. In these studies, the identity of genes has been found to differ remarkably; albeit the trend of pathways′ dysregulation has been found to remain similar. We conclude that the intensity of dysregulation of genes or pathways involved in mechanistic events forms a sub-threshold or threshold level depending upon the dose and type (including speciation of the toxicant, duration of exposure, type of target cells, and niche microenvironment of cells, and the intensity of sub-threshold or threshold level of the altered cytogenomics paves way in toxicant exposed cells eventually either to opt for reversal to

  16. Precursor preparation for Ca-Al layered double hydroxide to remove hexavalent chromium coexisting with calcium and magnesium chlorides

    Science.gov (United States)

    Zhong, Lihua; He, Xiaoman; Qu, Jun; Li, Xuewei; Lei, Zhiwu; Zhang, Qiwu; Liu, Xinzhong

    2017-01-01

    Al(OH)3 and Ca(OH)2 powders are co-ground to prepare a precursor which hydrates into a layered double hydroxide (LDH) phase by agitation in aqueous solution with target hexavalent chromium (Cr(VI)) at room temperature, to achieve an obvious improvement in removal efficiency of Cr(VI) through an easy incorporation into the structure. Although the prepared precursor transforms into LDH phases also when agitated in the solutions of calcium and magnesium chlorides, it incorporates Cr(VI) preferentially to the chloride salts when they coexist. The adsorption isotherm and kinetic studies show that the phenomena occurring on the Al-Ca precursor fit a pseudo-second-order kinetics with a Langmuir adsorption capacity of 59.45 mg/g. Besides, characterizations of the prepared precursor and the samples after adsorption are also performed by X-ray diffraction (XRD), Fourier transform infrared (FT-IR), Transmission electron microscope (TEM) to understand the reason of the preferential incorporation of Cr(VI) to the coexisting chloride salts during the LDH phase formation.

  17. Groundwater contaminant by hexavalent chromium

    Energy Technology Data Exchange (ETDEWEB)

    Parsons, C. [Univ. of Texas, Austin, TX (United States)

    1995-11-01

    Oxidation of trivalent chromium to hexavalent chromium has been investigated as a function of total manganese in soils as well as various incubation conditions. Chromium and manganese contents were analyzed by atomic absorption (graphite furnace and flame emission respectively) following acid digestion. Total hexavalent chromium generation capacity was determined by addition of 0.001 M CrCL3, incubation, and analysis by s-diphenyl carbazide. Samples were then leached with CaSO{sub 4} and MgSO{sub 4} and incubated in various environments (oven, freeze-drier, field moist, ultrafreeze) to test for geogenic generation of Cr(IV). The degree of geogenic generation of hexavalent chromium was compared with total Mn and Cr content as well as hexavalent generational capacity.

  18. Stabilizing Cr species in incinerator fly ashes with/without kaolin addition through a firing process: a molecular study on heated Cr.

    Science.gov (United States)

    Wei, Yu-Ling; Wang, Hsi-Chih; Peng, Yen-Shiun

    2017-07-01

    Cr speciation in Cr-sorbing washed incinerator fly ash (IFA) after heating up to 1100°C is temperature dependent. Higher temperature leads to a greater level of chemical reduction of Cr(VI) that is considerably more toxic than Cr(III). Most Cr(VI) sorbed washed IFA is effectively transformed into Cr(III) after heating to 1100°C for 2 h, as indicated by the disappearance of hexavalent pre-edge peak of Cr K-edge X-ray absorption near edge structure (XANES) spectrum. After heating the Cr-sorbing IFA to 100°C and 500°C for 2 h, water-soluble CaCrO4 is determined to be the principal Cr species due to the chemical reaction between the sorbed Cr(VI) and CaO components of washed fly ash, based on the comparison between sample and reference XANES spectra. Replacing half of the washed fly ash with kaolin could effectively reduce all Cr(VI) after heating to ≧ 900°C for 2 h.

  19. Removal of hexavalent chromium from aqueous solutions using micro zero-valent iron supported by bentonite layer.

    Science.gov (United States)

    Daoud, Waseem; Ebadi, Taghi; Fahimifar, Ahmad

    2015-01-01

    Hexavalent chromium Cr(VI) is of particular environmental concern due to its toxicity, mobility, and challenging removal from industrial wastewater. It is a strong oxidizing agent that is carcinogenic and mutagenic and diffuses quickly through soil and aquatic environments. Moreover, it does not form insoluble compounds in aqueous solutions; therefore, separation by precipitation is not feasible. While Cr(VI) oxyanions are very mobile and toxic in the environment, trivalent Cr(III) cations are the opposite and, like many metal cations, Cr(III) forms insoluble precipitates. Thus, reducing Cr(VI)-Cr(III) simplifies its removal from effluent and also reduces its toxicity and mobility. Permeable reactive barriers (PRBs) with zero-valent iron (ZVI) have been used to remediate contaminated groundwater with metals, but using ZVI in remediation of contaminated groundwater or wastewater is limited due to its lack of stability, easy aggregation, and difficulty in separation of iron from the treated solution. Thus, the technology used in the present study is developed to address these problems by placing a layer of bentonite after the PRB layer to remove iron from the treated water. The removal rates of Cr(VI) under different values of pH were investigated, and the results indicated the highest adsorption capacity at low pH.

  20. Analysis of the bioavailability of Cr(III and Cr(VI based on the determination of chromium in Mentha piperita by graphite furnace atomic absorption spectrometry

    Directory of Open Access Journals (Sweden)

    SVETLANA ĐOGO

    2011-01-01

    Full Text Available Mentha piperita L. (Lamiaceae was cultivated under the controlled laboratory conditions in the presence of varying levels of trivalent and hexavalent chromium in order to determine its capacity to control chromium uptake and its tolerance limit. The plants were grown in pots at 25 °C with controlled soil moisture (about 80 % of the water retention capacity. The soil was treated with increasing concentrations of Cr(NO33 (40, 80, 120, and 200 mg kg-1 and K2Cr2O7 (2.5, 5, 10, and 15 mg kg-1. A control group of plants was grown without the addition of chromium to the soil. For each concentration, three acidity levels were tested: natural, one pH unit below and one above the natural acidity of the soil (pH2 6, pH1 5 and pH3 7. The plant samples were digested according to the standard procedure and chromium content was determined by GFAAS. For all plants, the transportation index was calculated and the results (expressed in mg kg-1 at pH1, pH2 and pH3, respectively, were: 0.21–0.80, 0.06–1.06 and 0.04–0.52. The recoveries were good (72.73–115.3 % as evidenced by the analysis of certified reference materials (NIST SRM 8433 – Corn Bran and NIST SRM 1547 – Peach Leaves. The mobility of chromium through the plants tissues is discussed in regard to its competition with iron and manganese for transport binding sites; hence Mn and Fe were also determined.

  1. One-pot synthesis of Mn-doped TiO{sub 2} grown on graphene and the mechanism for removal of Cr(VI) and Cr(III)

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Zengping; Li, Yaru; Guo, Meng; Xu, Fengyun; Wang, Peng [School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072 (China); Du, Yu [China Tobacco Yunnan Industrial Co., Ltd., Yunnan 651600 (China); Na, Ping, E-mail: naping@tju.edu.cn [School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072 (China)

    2016-06-05

    Highlights: • rGO-Mn-TiO{sub 2} is synthesized through one-pot hydrothermal method. • Cr(total) removal effectiveness reaches to 97.32% in 30 min under visible light, as the initial concentration of Cr(VI) is 20 mg/L. • Mn-TiO{sub 2} and rGO synergistically contribute to the adsorption and photocatalytic reduction of Cr. • Cr(III) being adsorbed by rGO helps to the release of abundant photocatalytic sites of Mn-TiO{sub 2}. - Abstract: Mn-doped TiO{sub 2} grown on reduced graphene oxide(rGO) was synthesized by one-pot hydrothermal method and the photocatalytic removal of Cr by the material was investigated under sunlight. The materials were characterized by a combination of scanning electron microscopy, transmission electron microscopy, X-ray diffraction, thermogravimetric analysis, Brunauer-Emmett-Teller method, UV–vis diffuse reflectance spectra, photoluminescence spectra, electrochemical impedance spectroscopy and X-ray photoelectron spectroscopy. Cr(total) removal efficiency of the material is 97.32% in 30 min and 99.02% in 60 min under sunlight irradiation, as the initial concentration of Cr(VI) is 20 mg/L. The high photocatalytic activity under visible light is considered mainly due to the Mn-doping, and rGO plays an important role in the synergetic effect of adsorption and photocatalysis to sustain the high efficient removal of Cr(VI) and Cr(III). Cr(VI) adsorbed on the surface of rGO is reduced to Cr(III) by photo electrons which are transported through rGO, and the reaction product Cr(III) continues to be adsorbed. The process contributes to the release of abundant photocatalytic sites of Mn-TiO{sub 2} and improves photocatalytic efficiency. The excellent adsorption and photocatalytic effect with the explanation of the synergetic mechanism are very useful not only for fundamental research but also for the potential practical applications.

  2. Chromate Reductase YieF from Escherichia coli Enhances Hexavalent Chromium Resistance of Human HepG2 Cells

    Directory of Open Access Journals (Sweden)

    Xuan Liu

    2015-05-01

    Full Text Available Hexavalent chromium (Cr(VI is a serious environmental pollutant and human toxicant. Mammalian cells are very sensitive to chromate as they lack efficient chromate detoxifying strategy, e.g., chromate-reducing genes that are widely present in prokaryotes. To test whether introduction of prokaryotic chromate-reducing gene into mammalian cells could render higher chromate resistance, an Escherichia coli chromate-reducing gene yieF was transfected into human HepG2 cells. The expression of yieF was measured in stably transfected cells HepG2-YieF by quantitative RT-PCR and found up-regulated by 3.89-fold upon Cr(VI induction. In chromate-reducing ability test, HepG2-YieF cells that harbored the reductase showed significantly higher reducing ability of Cr(VI than HepG2 control cells. This result was further supported by the evidence of increased Cr(VI-removing ability of crude cell extract of HepG2-YieF. Moreover, HepG2-YieF demonstrated 10% higher viability and decreased expression of GSH synthesizing enzymes under Cr(VI stress. Subcellular localization of YieF was determined by tracing GFP-YieF fusion protein that was detected in both nucleus and cytoplasm by laser confocal microscopy. Altogether, this study successfully demonstrated that the expression of a prokaryotic Cr(VI-reducing gene yieF endowed mammalian cell HepG2 with enhanced chromate resistance, which brought new insight of Cr(VI detoxification in mammalian cells.

  3. Chromate Reductase YieF from Escherichia coli Enhances Hexavalent Chromium Resistance of Human HepG2 Cells.

    Science.gov (United States)

    Liu, Xuan; Wu, Gaofeng; Zhang, Yanli; Wu, Dan; Li, Xiangkai; Liu, Pu

    2015-05-26

    Hexavalent chromium (Cr(VI)) is a serious environmental pollutant and human toxicant. Mammalian cells are very sensitive to chromate as they lack efficient chromate detoxifying strategy, e.g., chromate-reducing genes that are widely present in prokaryotes. To test whether introduction of prokaryotic chromate-reducing gene into mammalian cells could render higher chromate resistance, an Escherichia coli chromate-reducing gene yieF was transfected into human HepG2 cells. The expression of yieF was measured in stably transfected cells HepG2-YieF by quantitative RT-PCR and found up-regulated by 3.89-fold upon Cr(VI) induction. In chromate-reducing ability test, HepG2-YieF cells that harbored the reductase showed significantly higher reducing ability of Cr(VI) than HepG2 control cells. This result was further supported by the evidence of increased Cr(VI)-removing ability of crude cell extract of HepG2-YieF. Moreover, HepG2-YieF demonstrated 10% higher viability and decreased expression of GSH synthesizing enzymes under Cr(VI) stress. Subcellular localization of YieF was determined by tracing GFP-YieF fusion protein that was detected in both nucleus and cytoplasm by laser confocal microscopy. Altogether, this study successfully demonstrated that the expression of a prokaryotic Cr(VI)-reducing gene yieF endowed mammalian cell HepG2 with enhanced chromate resistance, which brought new insight of Cr(VI) detoxification in mammalian cells.

  4. Biosorption of hexavalent chromium from aqueous solutions by Macadamia nutshell powder

    Science.gov (United States)

    Pakade, Vusumzi Emmanuel; Ntuli, Themba Dominic; Ofomaja, Augustine Enakpodia

    2016-04-01

    Macadamia nutshell biosorbents treated in three different activating agents [raw Macadamia nutshell powder (RMN), acid-treated Macadamia nutshell (ATMN) and base-treated Macadamia nutshell (BTMN)] were investigated for the adsorption of hexavalent chromium [Cr(VI)] from aqueous solutions. Fourier transform infrared spectroscopy spectra of free and Cr(VI)-loaded sorbents as well as thermogravimetric analysis revealed that the acid and base treatments modified the surface properties of the sorbent. Surface characteristics were also evaluated by the scanning electron microscopy and surface area analyzer. The optimum conditions for the adsorption of Cr(VI) by sorbents were pH 2, contact time 10 h, adsorbent mass 0.2 g and concentration 100 mg L-1. The equilibrium data were fitted into the Langmuir, Freundlich, Redlich-Peterson and Sips isotherms, and no single model could clearly explain the sorption mechanism. Maximum binding capacities of 45.23, 44.83 and 42.44 mg g-1 for RMN, ATMN and BTMN, respectively, were obtained. The kinetic data were analyzed using the pseudo-first, pseudo-second and Elovich kinetic models, and it was observed that the pseudo-second-order model produced the best fit for the experimental data. Macadamia nutshell sorbents showed potential as low-cost adsorbent for the removal of Cr(VI) from aqueous solution.

  5. A highly selective sorbent for removal of Cr(VI) from aqueous solutions based on Fe{sub 3}O{sub 4}/poly(methyl methacrylate) grafted Tragacanth gum nanocomposite: Optimization by experimental design

    Energy Technology Data Exchange (ETDEWEB)

    Sadeghi, Susan, E-mail: ssadeghi@birjand.ac.ir; Rad, Fatemeh Alavi; Moghaddam, Ali Zeraatkar

    2014-12-01

    In this work, poly(methyl methacrylate) grafted Tragacanth gum modified Fe{sub 3}O{sub 4} magnetic nanoparticles (P(MMA)-g-TG-MNs) were developed for the selective removal of Cr(VI) species from aqueous solutions in the presence of Cr(III). The sorbent was characterized by Fourier transform infrared (FTIR) spectroscopy, transmission electron microscopy (TEM), a vibrating sample magnetometer (VSM), and thermo-gravimetric analysis (TGA). A screening study on operational variables was performed using a two-level full factorial design. Based on the analysis of variance (ANOVA) with 95% confidence limit, the significant variables were found. The central composite design (CCD) has also been employed for statistical modeling and analysis of the effects and interactions of significant variables dealing with the Cr(VI) uptake process by the developed sorbent. The predicted optimal conditions were situated at a pH of 5.5, contact time of 3.4 h, and 3.0 g L{sup −1} dose. The Langmuir, Freundlich, and Temkin isotherm models were used to describe the equilibrium sorption of Cr(VI) by the absorbent, and the Langmuir isotherm showed the best concordance as an equilibrium model. The adsorption process was followed by a pseudo-second-order kinetic model. Thermodynamic investigations showed that the biosorption process was spontaneous and exothermic. - Highlights: • Fe3O4 nanoparticles were modified with Poly(methyl methacrylate) grafted Tragacanth gum • P(MMA)-g-TG -MNPs can preferentially adsorb Cr(VI) in the presence of Cr(III) • The effects of operational parameters on Cr(VI) removal were evaluated by RSM • Adsorption mechanism, kinetics, and isotherm have been explored • The sorbent was successfully used to remove Cr(VI) from different water samples.

  6. Effect of the gamma irradiation on the bio-sorption of Cr (Vi) by orange peel;Efecto de la irradiacion gamma en la biosorcion de Cr(VI) por cascara de naranja

    Energy Technology Data Exchange (ETDEWEB)

    Lugo L, V.; Barrera D, C. E.; Sanchez M, V. [Universidad Autonoma del Estado de Mexico, Centro de Investigacion en Quimica Sustentable, Paseo Tollocan esquina Paseo Colon s/n, 50180 Toluca, Estado de Mexico (Mexico); Urena N, F., E-mail: violelugol@yahoo.e [ININ, Carretera Mexico-Toluca s/n, 52750 Ocoyoacac, Estado de Mexico (Mexico)

    2009-07-01

    The orange peel (Citrus sp.) is a bioadsorbent that contains functional groups able to remove Cr (Vi). To study the effect of gamma irradiation in the sorption capacity, the Nn materials were irradiated with gamma rays using a Co{sup 60} source to dose from 10 to 3500 KGy (Nlgamma). The biomass irradiation with gamma rays was successful since it increased the hexavalent chromium removal obtaining a maximum removal percentage of 100%. Sorption isotherms were realized to determine the concentration effect of initial Cr (Vi), the ph effect of the solution and the relationship m/v. (Author)

  7. Methylation levels of P16 and TP53 that are involved in DNA strand breakage of 16HBE cells treated by hexavalent chromium.

    Science.gov (United States)

    Hu, Guiping; Li, Ping; Li, Yang; Wang, Tiancheng; Gao, Xin; Zhang, Wenxiao; Jia, Guang

    2016-05-13

    The correlations between methylation levels of p16 and TP53 with DNA strand breakage treated by hexavalent chromium [Cr(VI)] remain unknown. In this research, Human bronchial epithelial cells (16HBE cells) in vitro and bioinformatics analysis were used to analyze the epigenetic role in DNA damage and potential biomarkers. CCK-8 and single cell gel electrophoresis assay were chosen to detect the cellular biological damage. MALDI-TOF-MS was used to detect the methylation levels of p16 and TP53. qRT-PCR was used to measure their expression levels in different Cr(VI) treatment groups. The transcription factors with target sequences of p16 and TP53 were predicted using various bioinformatics software. The findings showed that the cellular toxicity and DNA strand damage were Cr(VI) concentration dependent. The hypermethylation of CpG1, CpG31 and CpG32 of p16 was observed in Cr(VI) treated groups. There was significant positive correlation between the CpG1 methylation level of p16 and cell damage. In Cr(VI) treated groups, the expression level of p16 was lower than that in control group. The expression level of TP53 increased when the Cr(VI)concentration above 5μM. About p16, there was significant negative correlation between the CpG1 methylation levels with its expression level. A lot of binding sites for transcription factors existed in our focused CpG islands of p16. All the results suggested that the CpG1 methylation level of p16 could be used as a biomarker of epigenetic effect caused by Cr(VI) treatment, which can enhance cell damage by regulating its expression or affecting some transcription factors to combine with their DNA strand sites.

  8. PENGOLAHAN LIMBAH Cr(VI DAN FENOL DENGAN FOTOKATALIS SERBUK TiO2 DAN CuO/TiO2

    Directory of Open Access Journals (Sweden)

    Slamet Slamet

    2011-07-01

    Full Text Available Studi tentang pengolahan limbah Cr(VI dan fenol secara fotokatalisis telah dilakukan dengan fotokatalis TiO2 dan CuO/TiO2. Katalis CuO/TiO2 dipreparasi dengan cara impregnasi terhadap TiO2 Degussa P25 menggunakan larutan garam tembaga yang berasal dari berbagai jenis prekursor. Komposisi Cu dalam katalis divariaskani dari 0,2% hingga 5%. Fotokatalis tersebut kemudian dikarakterisasi DRS (Diffuse Reflectance Spectroscopy dan XRD (X-Ray Diffraction. Aktivitas fotokatalis diuji dengan menggunakan sistem reaktor slurry yang bekerja secara batch dan dilengkapi dengan 6 lampu UV black light selama 5 jam, kemudian hasilnya dianalisis dengan UV-VIS Spectrophotometer. Hasil karakterisasi DRS menunjukan bahwa penambahan CuO dari 1% hingga 5% ke dalam TiO2 dapat meningkatkan pita absorbansi katalis dari 398 hingga 413 nm dan menurunkan band gap dari 3,2 hingga 2,58 eV. Hasil karakterisasi XRD menunjukan adanya struktur kristal anatase dan rutil dalam katalis TiO2 dan CuO/TiO2, sementara struktur kristal CuO muncul pada katalis CuO/TiO2 yang dipreparasi dengan prekursor Cu-Asetat dan Cu-Nitrat. Fotokatalis 0,2% CuO/TiO2 dari prekursor Cu-Asetat memiliki aktivitas optimal yang mereduksi Cr(VI 99,67% dan mendegradasi fenol 97,16%. Sementara jika kedua limbah tersebut diolah secara simultan, katalis TiO2 Degussa P25 memiliki aktivitas yang paling tinggi dengan meningkatkan konversi reduksi Cr(VI menjadi 100% dan menurunkan konversi degradasi fenol menjadi 93,81% dengan waktu reaksi 5 jam.

  9. Effect of fulvic acid on adsorptive removal of Cr(VI) and As(V) from groundwater by iron oxide-based adsorbents

    KAUST Repository

    Uwamariya, V.

    2015-05-15

    Abstract Natural contamination has become a challenging problem in drinking water production due to metal contamination of groundwater throughout the world, and arsenic and chromium are well-known toxic elements. In this study, iron oxide-coated sand (IOCS) and granular ferric hydroxide (GFH) were used to study the effects of fulvic acid (FA) on the adsorptive removal of Cr(VI) and As(V) from synthetic groundwater. IOCS and GFH were characterized by SEM/EDS, and experiments were performed at different pH levels (6, 7, and 8). The surface of IOCS and GFH showed a high content of Fe and O (75 and 60 % of the atomic composition, respectively), suggesting that they can highly effectively adsorb Cr(VI) and As(V). Adsorption tests with the simultaneous presence of As(V) and FA, on the one hand, and Cr(VI) with FA, on the other hand, revealed that the role of FA on chromate and arsenate adsorption was insignificant at almost all pH values investigated with both adsorbents. A small influence as a result of FA was only observed for the removal of As(V) by IOCS at pH 6 with a decrease of 13 and 23 % when 2 and 5 mg/l were added to the synthetic water, respectively. It was also found that organic matter (OM) was leached from the IOCS during batch adsorption experiments. The use of FEEM revealed that humic-like, fulvic-like, and protein-like organic matter fractions are present on the IOCS surface. © 2015 Springer International Publishing Switzerland.

  10. Adsorption of hexavalent chromium by graphite–chitosan binary composite

    Indian Academy of Sciences (India)

    RAJENDRA S DONGRE

    2016-06-01

    Graphite chitosan binary (GCB) composite was prepared for hexavalent chromium adsorption from studied water. GCB was characterized by TGA, FTIR, SEM and X-ray diffraction techniques.Wide porous sorptive surface of 3.89 m$^2$ g$^{−1}$ and absorptive functionalities of GCB was due to 20% (w/w) graphite support on chitosan evidenced from FTIR and SEM that impart maximum adsorption at pH 4, agitation with 200 rpm for 180 min. Adsorption studies revealed intraparticle diffusion models and best-fitted kinetics was pseudo 2nd order one. A wellfitted Langmuir isotherm model suggested monolayer adsorption with an adsorption capacity ($q_m$) of 105.6 mg g$^{−1}$ and $R^2 = 0.945$. Sorption mechanisms based on metal ionic interactions, intrusion/diffusion and chemisorptions onto composite. This graphite chitosan binary composite improve sorbent capacity for Cr(VI).

  11. Fabrication of a novel NiFe2O4/Zn-Al layered double hydroxide intercalated with EDTA composite and its adsorption behavior for Cr(VI) from aqueous solution

    Science.gov (United States)

    Deng, Lin; Shi, Zhou; Wang, Li; Zhou, Shiqing

    2017-05-01

    A novel magnetic NiFe2O4/Zn-Al layered double hydroxide intercalated with EDTA composite (NiFe2O4/ZnAl-EDTA LDH) was prepared through modified coprecipitation method and employed for adsorptive removal of Cr(VI) from aqueous solution. The adsorbents were characterized using Brunauer-Emmett-Teller (BET), scanning electron microscopy (SEM), transmission electron microscope (TEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), vibrating sample magnetometer (VSM), and X-ray photoelectron spectroscopy (XPS). Factors affecting the Cr(VI) adsorption, such as initial solution pH, adsorbent dosage, contact time, initial Cr(VI) concentration, temperature and coexisting ions, were studied systematically. Experiments results show that the magnetic NiFe2O4/ZnAl-EDTA LDH exhibits high adsorption efficiency within a wide pH range of 3.0-7.0 (R>80% at Cr(VI) concentration 50 mg L-1, contact time 360 min, and adsorbent dosage 2 g/L) and quick separation property. The adsorption process is fitted well with the Langmuir isotherm and pseudo-second-order kinetic model. The maximum theoretical adsorption capacity is found to be 77.22 mg g-1 at pH 6.0 and 318 K. The positive ΔH value (2.907 kJ mol-1) and negative ΔG value (-4.722 kJ mol-1) at 298-318 K reveals that the adsorption process is feasible, spontaneous and endothermic. Coexisting anions (PO43-, SO42-, CO32-, HCO3-, Cl-, and NO3-) have no significant effect on Cr(VI) removal. The mechanism study indicates that the adsorption of Cr(VI) onto NiFe2O4/ZnAl-EDTA LDH mainly involves electrostatic attraction and ion exchange interaction. It is interesting to note that a proportion of Cr(VI) adsorbed on the adsorbent surface are reduced to Cr(III) during the adsorption process. Results from this study demonstrate the potential utility of the magnetic NiFe2O4/ZnAl-EDTA LDH that could be developed into a viable technology for efficient removal of Cr(VI) from aqueous solution.

  12. An automatic micro-sequential injection bead injection lab-on-valve (muSI-BI-LOV) assembly for speciation analysis of ultra trace levels of Cr(III) and Cr(VI) incorporating on-line chemical reduction and employing detection by electrothermal atomic absorption spectrometry (ETAAS)

    DEFF Research Database (Denmark)

    Long, Xiangbao; Miró, Manuel; Hansen, Elo Harald

    2005-01-01

    A novel, miniaturized micro-sequential injection Lab-on-Valve (muSI-LOV) system hyphenated with electrothermal atomic absorption spectrometry (ETAAS) is proposed for the automatic preconcentration and speciation analysis of Cr(III) and Cr(VI) utilizing solid-phase extraction on hydrophilic...... and physical conditions, the flow system, by using a total sample loading volume of 3.6 mL, featured retention efficiencies for Cr(III) as high as 86%, and preconcentration factors of 62 and 42 and detection limits (3s) of 0.010 and 0.020 mug L-1 for Cr(III) and Cr(VI), respectively, The relative standard...

  13. Photoredox degradation of different water pollutants (MO, RhB, MB, and Cr(VI)) using Fe–N–S-tri-doped TiO{sub 2} nanophotocatalyst prepared by novel chemical method

    Energy Technology Data Exchange (ETDEWEB)

    Xu, Xuyao; Zhou, Xiaosong, E-mail: zxs801213@163.com; Zhang, Lingling; Xu, Limei; Ma, Lin; Luo, Jin; Li, Mengjia; Zeng, Lihua

    2015-10-15

    Highlights: • TiO{sub 2} was synthesized through simple one-step hydrothermal method. • Photocatalytic activity for degradation of organic dyes and Cr(VI) are investigated. • The synergistic effect is shown in coexistence of MB and Cr(VI). - Abstract: Fe–N–S-tri-doped TiO{sub 2} (FeNS-TiO{sub 2}) was synthesized by a simple one-step hydrothermal method. The as-synthesized samples were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR), and X-ray photoelectron spectroscopy (XPS). The photocatalytic activities of as-synthesized samples were tested by the oxidation of methyl orange (MO), rhodamine B (RhB), methylene blue (MB) and the reduction of aqueous Cr(VI) under visible-light (λ > 420 nm) irradiation, and compared with N-dope P25 (N-P25) and the undoped TiO{sub 2}. Besides, the effects of the coexistence of MO, RhB, and MB on FeNS-TiO{sub 2}-mediated photocatalytic reduction of aqueous Cr(VI) were also studied. The results indicated FeNS-TiO{sub 2} displayed higher visible-light-activated photocatalytic activity than N-P25 and the undoped TiO{sub 2}. Otherwise, FeNS-TiO{sub 2} showed the coexistence of MB enhanced the photocatalytic reduction of Cr(VI), whereas the coexistence of MO and RhB retarded the photocatalytic reduction of Cr(VI) over FeNS-TiO{sub 2}. Moreover, a possible photocatalytic mechanism is discussed.

  14. Isolation and characterization of a chromium-resistant bacterium Serratia sp. Cr-10 from a chromate-contaminated site

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Kundi; Li, Fuli [Chinese Academy of Sciences, Qingdao (China). Qingdao Inst. of Bioenergy and Bioprocess Technology

    2011-05-15

    A novel bacterium, Cr-10, was isolated from a chromium-contaminated site and capable of removing toxic chromium species from solution by reducing hexavalent chromium to an insoluble precipitate. Sequence analysis of 16S rRNA gene of strain Cr-10 showed that it was most closely related to Serratia rubidaea JCM 1240{sup T} (97.68%). Physiological and chemotaxonomic data also supported that strain Cr-10 was identified as Serratia sp., a genus which was never specially reported chromate-resistant before. Serratia sp., Cr-10 was tolerant to a concentration of 1,500 mg Cr(VI) L{sup -1}, which was the highest level reported until now. The optimum pH and temperature for reduction of Cr(VI) by Serratia sp. Cr-10 were found to be 7.0 and 37 C, respectively. The Cr(VI) reduction was significantly influenced by additional carbon sources, and among them fructose and lactose offered maximum reduction, with a rate of 0.28 and 0.25 mg Cr(VI) L{sup -1} h{sup -1}, respectively. The cell-free extracts and filtrate of the culture were able to reduce Cr(VI) while concentration of total chromium remained stable in the process, indicating that the enzyme-catalyzed mechanism was applied in Cr(VI) reduction by the isolate. Additionally, it was found that there was hardly any chromium on the cell surface of the strain, further supporting that reduction, rather than bioadsorption, plays a major role in the Cr(VI) removal. (orig.)

  15. Reversible Second Order Kinetics of Sorption-Desorption of Cr(VI Ion on Activated Carbon from Palm Empty Fruit Bunches

    Directory of Open Access Journals (Sweden)

    Iip Izul Falah

    2015-11-01

    Full Text Available Activated carbon (AC from palm empty fruit bunches has been prepared, and this material was then used to adsorb Cr(VI from a solution. Characterization of the AC was conducted by detection of its functional groups, determination of total volatile compounds (VC content and its iodine number. Study on sorption-desorption kinetics was conducted by comparing results of evaluations of several models with proposed reversible second order model using the data produced in this work. Results of the works showed that the AC had similar characters compared with the AC produced by previous researchers. Application of the kinetics models on sorption Cr(VI onto the AC showed that nearly all of the models gave a good linearity. However, only the proposed model had a good relation with Langmuir isotherm, with respectively sorption (ks and desorption (kd constants were 5.75 x 10-4 L.mg‑1.min-1 and 2.20 x 10-3 min-1; maximum sorption capacity, qm = 20.00 mg.g-1; and equilibrium constant, K from kinetics experiment (0.261 L.mg-1 was comparable with the result from the isotherm experiment (0.269 L.mg-1. Hence, using this model, kinetics and Langmuir parameters can probably be determined from a single kinetics data experiment.

  16. Cr(VI) sorption behavior from aqueous solutions onto polymeric microcapsules containing a long-chain quaternary ammonium salt: Kinetics and thermodynamics analysis

    Energy Technology Data Exchange (ETDEWEB)

    Barassi, Giancarlo; Valdes, Andrea; Araneda, Claudio; Basualto, Carlos; Sapag, Jaime; Tapia, Cristian [Laboratorio de Operaciones Unitarias, Facultad de Ciencias Quimicas y Farmaceuticas, Universidad de Chile, Av. Vicuna Mackenna 20, Santiago (Chile); Valenzuela, Fernando, E-mail: fvalenzu@uchile.cl [Laboratorio de Operaciones Unitarias, Facultad de Ciencias Quimicas y Farmaceuticas, Universidad de Chile, Av. Vicuna Mackenna 20, Santiago (Chile)

    2009-12-15

    This work studies the adsorption of Cr(VI) ions from an aqueous acid solution on hydrophobic polymeric microcapsules containing a long-chain quaternary ammonium salt-type extractant immobilized in their pore structure. The microcapsules were synthesized by adding the extractant Aliquat 336 during the in situ radical copolymerization of the monomers styrene (ST) and ethylene glycol dimethacrylate (EGDMA). The microcapsules, which had a spherical shape with a rough surface, behaved as efficient adsorbents for Cr(VI) at the tested temperatures. The results of kinetics experiments carried out at different temperatures showed that the adsorption process fits well to a pseudo-second-order with an activation energy of 82.7 kJ mol{sup -1}, confirming that the sorption process is controlled by a chemisorption mechanism. Langmuir's isotherms were found to represent well the experimentally observed sorption data. Thermodynamics parameters, namely, changes in standard free energy ({Delta}G{sup 0}), enthalpy ({Delta}H{sup 0}), and entropy ({Delta}S{sup 0}), are also calculated. The results indicate that the chemisorption process is spontaneous and exothermic. The entropy change value measured in this study shows that metal adsorbed on microcapsules leads to a less chaotic system than a liquid-liquid extraction system.

  17. Hexavalent chromium is cytotoxic and genotoxic to hawksbill sea turtle cells.

    Science.gov (United States)

    Wise, Sandra S; Xie, Hong; Fukuda, Tomokazu; Douglas Thompson, W; Wise, John Pierce

    2014-09-01

    Sea turtles are a charismatic and ancient ocean species and can serve as key indicators for ocean ecosystems, including coral reefs and sea grass beds as well as coastal beaches. Genotoxicity studies in the species are absent, limiting our understanding of the impact of environmental toxicants on sea turtles. Hexavalent chromium (Cr(VI)) is a ubiquitous environmental problem worldwide, and recent studies show it is a global marine pollutant of concern. Thus, we evaluated the cytotoxicity and genotoxicity of soluble and particulate Cr(VI) in hawksbill sea turtle cells. Particulate Cr(VI) was both cytotoxic and genotoxic to sea turtle cells. Concentrations of 0.1, 0.5, 1, and 5μg/cm(2) lead chromate induced 108, 79, 54, and 7% relative survival, respectively. Additionally, concentrations of 0, 0.1, 0.5, 1, and 5μg/cm(2) lead chromate induced damage in 4, 10, 15, 26, and 36% of cells and caused 4, 11, 17, 30, and 56 chromosome aberrations in 100 metaphases, respectively. For soluble Cr, concentrations of 0.25, 0.5, 1, 2.5, and 5μM sodium chromate induced 84, 69, 46, 25, and 3% relative survival, respectively. Sodium chromate induced 3, 9, 9, 14, 21, and 29% of metaphases with damage, and caused 3, 10, 10, 16, 26, and 39 damaged chromosomes in 100 metaphases at concentrations of 0, 0.25, 0.5, 1, 2.5, and 5μM sodium chromate, respectively. These data suggest that Cr(VI) may be a concern for hawksbill sea turtles and sea turtles in general.

  18. Chromium Isotopic Fractionation During Biogeochemical Cr (IV) Reduction in Hanford Sediment Column Experiments with Native Aquifer Microbial Communities

    Science.gov (United States)

    Qin, L.; Christensen, J. N.; Brown, S. T.; Yang, L.; Conrad, M. E.; Sonnenthal, E. L.; Beller, H. R.

    2010-12-01

    Hexavalent Chromium contamination in groundwater within the DOE complex, including the Hanford 100D and 100H sites has been a long-standing issue. It has been established that certain bacteria (including denitrifying and sulfate-reducing bacteria) harbor enzymes that catalyze Cr(VI) reduction to relatively nontoxic Cr(III). Microbial reduction of Cr(VI) also occurs indirectly by products of microbial respiration, such as sulfide and Fe(II). Chromium isotopes can be fractionated during Cr(VI) reduction and provides a potential basis for characterizing and discriminating between different microbial metabolic and geochemical pathways associated with Cr(VI) reductive immobilization. Addition of electron donor to contaminated groundwater systems to create conditions favorable for reductive metal immobilization has become a widely utilized remediation practice. We conducted a series of small-scale column experiments with homogenized material from the Hanford 100H aquifer to examine the effects of differing el