Removal of Cr(VI) by nanoscale zero-valent iron (nZVI) from soil contaminated with tannery wastes.

Science.gov (United States)

Singh, Ritu; Misra, Virendra; Singh, Rana Pratap

2012-02-01

The illegal disposal of tannery wastes at Rania, Kanpur has resulted in accumulation of hexavalent chromium [Cr(VI)], a toxic heavy metal in soil posing risk to human health and environment. 27 soil samples were collected at various depths from Rania for the assessment of Cr(VI) level in soil. Out of 27 samples, five samples had shown significant level of Cr(VI) with an average concentration of 15.84 mg Kg(-1). Varied doses of nanoscale zero-valent iron (nZVI) were applied on Cr(VI) containing soil samples for remediation of Cr(VI). Results showed that 0.10 g L(-1) nZVI completely reduces Cr(VI) within 120 min following pseudo first order kinetics. Further, to test the efficacy of nZVI in field, soil windrow experiments were performed at the contaminated site. nZVI showed significant Cr(VI) reduction at field also, indicating it an effective tool for managing sites contaminated with Cr(VI).

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.

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 D.

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.

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.

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

Diverse anaerobic Cr(VI) tolerant bacteria from Cr(VI)-contaminated 100H site at Hanford

Science.gov (United States)

Chakraborty, R.; Phan, R.; Lam, S.; Leung, C.; Brodie, E. L.; Hazen, T. C.

2007-12-01

Hexavalent Chromium [Cr(VI)] is a widespread contaminant found in soil, sediment, and ground water. Cr(VI) is more soluble, toxic, carcinogenic, and mutagenic compared to its reduced form Cr(III). In order to stimulate microbially mediated reduction of Cr(VI), a poly-lactate compound HRC was injected into the chromium contaminated aquifers at site 100H at Hanford. Based on the results of the bacterial community composition using high-density DNA microarray analysis of 16S rRNA gene products, we recently investigated the diversity of the dominant anaerobic culturable microbial population present at this site and their role in Cr(VI) reduction. Positive enrichments set up at 30°C using specific defined anaerobic media resulted in the isolation of an iron reducing isolate strain HAF, a sulfate reducing isolate strain HBLS and a nitrate reducing isolate, strain HLN among several others. Preliminary 16S rDNA sequence analysis identifies strain HAF as Geobacter metallireducens, strain HLN as Pseudomonas stutzeri and strain HBLS as a member of Desulfovibrio species. Strain HAF isolated with acetate as the electron donor utilized propionate, glycerol and pyruvate as alternative carbon sources, and reduced metals like Mn(IV) and Cr(VI). Growth was optimal at 37°C, pH of 6.5 and 0% salinity. Strain HLN isolated with lactate as electron donor utilized acetate, glycerol and pyruvate as alternative carbon sources, and reduced metals like Mn(IV) and Cr(VI). Optimal growth was observed at 37°C, at a pH of 7.5 and 0.3% salinity. Anaerobic active washed cell suspension of strain HLN reduced almost 95 micromolar Cr(VI) within 4 hours relative to controls. Further, with 100 micromolar Cr(VI) as the sole electron acceptor, cells of strain HLN grew to cell numbers of 4.05X 107/ml over a period of 24hrs after an initial lag, demonstrating direct enzymatic Cr(VI) reduction by this species. 10mM lactate served as the sole electron donor. These results demonstrate that Cr(VI

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

International Nuclear Information System (INIS)

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

2009-01-01

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.

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.

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

International Nuclear Information System (INIS)

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

2009-01-01

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 2 CO 3 and filtered through hydrophilic PDVF 0.45 μm 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 μg g -1 (cyclone dust), 2710 μg g -1 (fine dust), and 7800 μg g -1 (slimes dust) which exceeded the maximum acceptable risk concentration (20 μg 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.

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

International Nuclear Information System (INIS)

He, Lulu; Wang, Min; Zhang, Guilong; Qiu, Guannan; Cai, Dongqing; Wu, Zhengyan; Zhang, Xin

2015-01-01

Highlights: • This work aims to develop a long-duration remediation agent (LRA). • LRA was obtained using Na 2 S 2 O 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

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.

The removal of Cr(VI from aqueous solution by almond green hull waste material: kinetic and equilibrium studies

Directory of Open Access Journals (Sweden)

Negin Nasseh

2017-12-01

Full Text Available The discharge of industrial effluents containing hexavalent chromium into the environment can be very harmful to living things. Therefore, prior to effluent discharge into the environment, hexavalent chromium should be removed from contaminated water and especially from wastewaters. In the present work, almond green hull powder (AGHP was investigated for the removal of hexavalent chromium from wastewater. The effects of pH (2–10, adsorbent dose (2–24 g L−1, Cr(VI concentration (10–100 mg L−1, contact time (1–60 min, and temperature (5–50 °C were studied. All the experiments were performed in triplicate and average results were reported. The surface morphology, pore volume and size, pH of zero point charge (pHZPC and surface functional groups of AGHP were characterized. Isotherm and kinetic evaluations were also conducted in the present study. The results revealed that the adsorption of Cr(VI by AGHP was an adsorbate, adsorbent, and temperature dependent process that was favorable under acidic conditions. Furthermore, AGHP absorbed over 99% of chromium from the solutions containing 10–100 mg L−1 of Cr(VI based on the Freundlich model. In summary, hexavalent chromium was not found in almond kernel. Biosorption onto AGHP is an affordable and economical adsorption process for treating Cr(VI-laden industrial wastewater.

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.

Cr(VI) and Cr(III) removal from aqueous solution by raw and modified lignocellulosic materials: a review.

Science.gov (United States)

Miretzky, P; Cirelli, A Fernandez

2010-08-15

In aqueous systems, chromium usually exists in both trivalent and hexavalent oxidation states, being Cr(VI) of particular importance and concern due to its great toxicity. Industrial sources of Cr(VI) are leather tanning, mining of chrome ore, production of steel and alloys, etc. The most common conventional method for Cr(VI) removal is reduction to Cr(III) at pH 2.0 and precipitation of Cr (OH)(3) with lime at pH 9-10. The disadvantage of precipitation is the disposal of the solid waste. Adsorption of Cr by different low cost materials seems to be a suitable choice for wastewater treatment. Many by-products of agriculture have proved to be suitable low cost adsorbents for Cr(VI) and Cr(III) removal from water. Lignocellulosic residues, which include both wood residues and agricultural residues, have adsorption capacity comparable to other natural sorbents, but they have the advantage of very low or no cost, great availability and simple operational process. This study is a review of the recent literature on the use of natural and modified lignocellulosic residues for Cr adsorption. The Cr maximum adsorption capacity and the adsorption mechanism under different experimental conditions are reported when possibly. Copyright 2010 Elsevier B.V. All rights reserved.

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

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.

Hexavalent Chromium reduction by Trichoderma inhamatum

Energy Technology Data Exchange (ETDEWEB)

Morales-Battera, L.; Cristiani-Urbina, E.

2009-07-01

Reduction of hexavalent chromium [Cr(VI)] to trivalent chromium [Cr(III)] is a useful and attractive process for remediation of ecosystems and industrial effluents contaminated with Cr(VI). Cr(VI) reduction to Cr(II) can be achieved by both chemical and biological methods; however, the biological reduction is more convenient than the chemical one since costs are lower, and sludge is generated in smaller amounts. (Author)

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

International Nuclear Information System (INIS)

Ferro Orozco, A.M.; Contreras, E.M.; Zaritzky, N.E.

2010-01-01

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 Cr ) was attained with cheese whey or lactose as electron donors decreasing in the following order: cheese whey ∼ 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.

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

International Nuclear Information System (INIS)

Rodriguez R, Miriam G.; Mendoza, Victor; Puebla, Hector; Martinez D, Sergio A.

2009-01-01

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

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.

A highly sensitive and selective detection of Cr(VI) and ascorbic acid based on nitrogen-doped carbon dots.

Science.gov (United States)

Zhang, Yuhua; Fang, Xian; Zhao, Hong; Li, Zengxi

2018-05-01

A highly sensitive and selective detection of hexavalent chromium (Cr(VI)) and ascorbic acid (AA) was proposed using nitrogen-doped carbon dots (N-CDs). In the absence of AA, the quantitative detection of Cr(VI) was realized through Cr(VI) acting as a quencher to quench the fluorescence of N-CDs by inner filter effect (IFE) and static quenching effect. Under the optimal conditions, the linear range for Cr(VI) detection was from 0.01 to 250μM with a detection limit of 5nM (S/N = 3). In the presence of AA, the fluorescence intensity could be rapidly enhanced compared with the fluorescence of N-CDs/Cr(VI) system since Cr(VI) can be reduced into trivalent chromium (Cr(III)) by AA. And a wide linear range for AA detection was obtained from 1 to 750μM. The detection limit was 0.3μM (S/N = 3). More importantly, this method can be successfully applied to the detection of Cr(VI) in real water samples, and AA in vitamins C tablets and human serum sample. Copyright © 2018 Elsevier B.V. All rights reserved.

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.

Soil humic acids may favour the persistence of hexavalent chromium in soil

International Nuclear Information System (INIS)

Leita, Liviana; Margon, Alja; Pastrello, Arnold; Arcon, Iztok; Contin, Marco; Mosetti, Davide

2009-01-01

The interaction between hexavalent chromium Cr(VI), as K 2 CrO 4 , and standard humic acids (HAs) in bulk solution was studied using three complementary analytical methods: UV-Visible spectroscopy, X-ray absorption spectroscopy and differential pulse stripping voltammetry. The observed UV-Vis and X-ray absorption spectra showed that, under our experimental conditions, HAs did not induce reduction of Cr(VI) to its trivalent chemical form. The interaction between Cr(VI) and HAs has rather led to the formation of Cr(VI)-HAs micelles via supramolecular chemical processes. The reported results could contribute towards explaining the relative persistence of ecotoxic hexavalent chromium in soils. - Humic acids (HAs) did not induce reduction of Cr(VI) to its trivalent chemical form, as the interaction between Cr(VI) and HAs rather led to the formation of Cr(VI)-HAs micelles via supramolecular chemical processes.

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 CrO 4 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.

Adsorption studies for Cr(VI) onto magnetic particles covered with chitosan

International Nuclear Information System (INIS)

Yamaura, Mitiko; Yamamura, Amanda P. Gualberto; Costa, Caroline Hastenreiter

2007-01-01

The magnetic carrier, called magnetic biosorbent, was prepared using magnetite nanoparticles and a biopolymer from the chitin of exoskeletons of marine invertebrates, the chitosan. Experiments of adsorption in batch systems were carried out to investigate the removal of Cr(VI) ions from pH 3 solution using this magnetic biosorbent. Radioisotope Cr-51 was used as the radioactive tracer to mark the Cr in solution, so the concentrations of Cr(VI) ions were determined by gamma spectrometry with a NaI(Tl) detector. Dosage of magnetic biosorbent was studied in the adsorption of chromium ions from dilute metal ion solutions. The removal efficiency obtained was 97% at a dosage of 50 g L -1 . Freundlich and Langmuir isotherm models were used to evaluate the data of equilibrium isotherm in the range of Cr(VI) concentration from 50 mg L -1 to 1200 mg L -1 . The Langmuir model was found to best represent the equilibrium isotherm. Recovery of the Cr(VI) ions from loaded magnetic biosorbent was possible by desorption process using a NaOH solution of pH 10. The results demonstrated that the magnetic biosorbent is effective for the removal of hexavalent Cr ion from solutions by sorption process and the recovery by desorption process is possible. The suspended particles of the magnetic biosorbent exhibited a strong magnetization in the presence of a magnetic field, and being easily attracted and removed from aqueous solutions using a magnet, so indicating the application viability in magnetic separation process. (author)

Cr(VI) reduction from contaminated soils by Aspergillus sp. N2 and Penicillium sp. N3 isolated from chromium deposits.

Science.gov (United States)

Fukuda, Tsubasa; Ishino, Yasuhiro; Ogawa, Akane; Tsutsumi, Kadzuyo; Morita, Hiroshi

2008-10-01

Aspergillus sp. N2 and Penicillium sp. N3 are chromate-resistant filamentous fungi that were isolated from Cr(VI) contaminated soil based on their ability to decrease hexavalent chromium levels in the growth medium. After 120 h of growth in a medium containing 50 ppm Cr(VI) at near neutral pH, Aspergillus sp. N2 reduced the Cr(VI) concentration by about 75%. Penicillium sp. N3 was able to reduce the Cr(VI) concentration by only 35%. However, Penicillium sp. N3 reduced the Cr(VI) concentration in the medium by 93% under acidic conditions. Interestingly, the presence of Cu(II) enhanced the Cr(VI) reducing ability of Aspergillus sp. N2 and Penicillium sp. N3 at near neutral pH. Aspergillus sp. N2 and Penicillium sp. N3 reduced the Cr(VI) concentration in the growth medium to a virtually undetectable level within 120 h. For both Aspergillus sp. N2 and Penicillium sp. N3, mycelial seed cultures were more efficient at Cr(VI) reduction than conidium seed cultures. The mechanisms of Cr(VI) reduction in Aspergillus sp. N2 and Penicillium sp. N3 were enzymatic reduction and sorption to mycelia. Enzymatic activity contributed significantly to Cr(VI) reduction. Aspergillus sp. N2 and Penicillium sp. N3 reduced the levels of Cr(VI) in polluted soil samples, suggesting that these strains might be useful for cleaning up chromium-contaminated sites.

Sampling and analysis considerations for the determination of hexavalent chromium in workplace air; Reflexions sur le prelevement et l'analyse du chrome hexavalent dans l'air des lieux de travail

Energy Technology Data Exchange (ETDEWEB)

Ashley, K.E. [CDC/NIOSH, Cincinnati, Ohio (United States); Howe, A.M. [HSL, Sheffield (United Kingdom); Demange, M. [INRS - Centre de Lorraine, Departement Metrologie des polluants, 54 - Vandoeuvre-les-Nancy (France); Nygren, O. [NIWL, Umea (Sweden)

2004-07-01

Airborne hexavalent chromium Cr(VI) is a known human respiratory carcinogen and allergen. Workers in a variety of industries may be exposed to airborne hexavalent chromium, with exposures frequently occurring via inhalation and/or dermal contact. Analytical methods for the measurement of Cr(VI) compounds in workplace samples, rather than for the determination of total elemental chromium in workplace air, are often desired because exposure limit values for Cr(VI) compounds are much lower than for total Cr. For years, sampling and analytical test methods for airborne Cr(VI) have been investigated so as to provide means for occupational exposure assessment to this highly toxic species. Inter-conversion of trivalent chromium Cr(III) and Cr(VI) can sometimes occur during sampling and sample preparation, and efforts to minimize unwanted redox reactions involving these chromium valences have been sought. Because of differences in toxicity, there is also interest in the ability to differentiate between water soluble and insoluble forms of Cr(VI), and procedures that provide solubility information concerning Cr(VI) compounds have been developed. This paper reviews the state of the art concerning the measurement of airborne Cr(VI) compounds in workplace aerosols and related samples. (authors)

Development and validation of a model of bio-barriers for remediation of Cr(VI) contaminated aquifers using laboratory column experiments.

Science.gov (United States)

Shashidhar, T; Bhallamudi, S Murty; Philip, Ligy

2007-07-16

Bench scale transport and biotransformation experiments and mathematical model simulations were carried out to study the effectiveness of bio-barriers for the containment of hexavalent chromium in contaminated confined aquifers. Experimental results showed that a 10cm thick bio-barrier with an initial biomass concentration of 0.205mg/g of soil was able to completely contain a Cr(VI) plume of 25mg/L concentration. It was also observed that pore water velocity and initial biomass concentration are the most significant parameters in the containment of Cr(VI). The mathematical model developed is based on one-dimensional advection-dispersion reaction equations for Cr(VI) and molasses in saturated, homogeneous porous medium. The transport of Cr(VI) and molasses is coupled with adsorption and Monod's inhibition kinetics for immobile bacteria. It was found that, in general, the model was able to simulate the experimental results satisfactorily. However, there was disparity between the numerically simulated and experimental breakthrough curves for Cr(VI) and molasses in cases where there was high clay content and high microbial activity. The mathematical model could contribute towards improved designs of future bio-barriers for the remediation of Cr(VI) contaminated aquifers.

Hexavalent chromium induces chromosome instability in human urothelial cells

Energy Technology Data Exchange (ETDEWEB)

Wise, Sandra S. [Wise Laboratory of Environmental and Genetic Toxicology, Maine Center for Toxicology and Environmental Health, Department of Applied Medical Science, University of Southern Maine, Science Building, 96 Falmouth Street, Portland, ME 04103 (United States); Holmes, Amie L. [Wise Laboratory of Environmental and Genetic Toxicology, Maine Center for Toxicology and Environmental Health, Department of Applied Medical Science, University of Southern Maine, Science Building, 96 Falmouth Street, Portland, ME 04103 (United States); Department of Radiation Oncology, Dana Farber Cancer Institute, 450 Brookline Ave., Boston, MA 02215 (United States); Liou, Louis [Department of Pathology, Boston University School of Medicine, 670 Albany St., Boston, MA 02118 (United States); Adam, Rosalyn M. [Department of Surgery, Harvard Medical School, Boston, MA 02115 (United States); Wise, John Pierce Sr., E-mail: john.wise@louisville.edu [Wise Laboratory of Environmental and Genetic Toxicology, Maine Center for Toxicology and Environmental Health, Department of Applied Medical Science, University of Southern Maine, Science Building, 96 Falmouth Street, Portland, ME 04103 (United States)

2016-04-01

Numerous metals are well-known human bladder carcinogens. Despite the significant occupational and public health concern of metals and bladder cancer, the carcinogenic mechanisms remain largely unknown. Chromium, in particular, is a metal of concern as incidences of bladder cancer have been found elevated in chromate workers, and there is an increasing concern for patients with metal hip implants. However, the impact of hexavalent chromium (Cr(VI)) on bladder cells has not been studied. We compared chromate toxicity in two bladder cell lines; primary human urothelial cells and hTERT-immortalized human urothelial cells. Cr(VI) induced a concentration- and time-dependent increase in chromosome damage in both cell lines, with the hTERT-immortalized cells exhibiting more chromosome damage than the primary cells. Chronic exposure to Cr(VI) also induced a concentration-dependent increase in aneuploid metaphases in both cell lines which was not observed after a 24 h exposure. Aneuploidy induction was higher in the hTERT-immortalized cells. When we correct for uptake, Cr(VI) induces a similar amount of chromosome damage and aneuploidy suggesting that the differences in Cr(VI) sensitivity between the two cells lines were due to differences in uptake. The increase in chromosome instability after chronic chromate treatment suggests this may be a mechanism for chromate-induced bladder cancer, specifically, and may be a mechanism for metal-induced bladder cancer, in general. - Highlights: • Hexavalent chromium is genotoxic to human urothelial cells. • Hexavalent chromium induces aneuploidy in human urothelial cells. • hTERT-immortalized human urothelial cells model the effects seen in primary urothelial cells. • Hexavalent chromium has a strong likelihood of being carcinogenic for bladder tissue.

Genotoxicity of Tri- and Hexavalent Chromium Compounds In Vivo and Their Modes of Action on DNA Damage In Vitro

Science.gov (United States)

Fang, Zhijia; Zhao, Min; Zhen, Hong; Chen, Lifeng; Shi, Ping; Huang, Zhiwei

2014-01-01

Chromium occurs mostly in tri- and hexavalent states in the environment. Hexavalent chromium [Cr(VI)] compounds are extensively used in diverse industries, and trivalent chromium [Cr(III)] salts are used as micronutrients and dietary supplements. In the present work, we report that they both induce genetic mutations in yeast cells. They both also cause DNA damage in both yeast and Jurkat cells and the effect of Cr(III) is greater than that of Cr(VI). We further show that Cr(III) and Cr(VI) cause DNA damage through different mechanisms. Cr(VI) intercalates DNA and Cr(III) interferes base pair stacking. Based on our results, we conclude that Cr(III) can directly cause genotoxicity in vivo. PMID:25111056

Cr(III) reactivity and foot dermatitis in Cr(VI) positive patients

DEFF Research Database (Denmark)

Hansen, Malene Barré; Menné, Torkil; Johansen, Jeanne Duus

2006-01-01

Chromium allergy has become synonymous with Cr(VI) allergy. However, real exposure to chromium from leather products may include both Cr(III) and Cr(VI). In this study, we investigate the reactivity to both Cr(VI) and Cr(III) in consecutive patients to analyse the relation between foot eczema/leather...... to Cr(III). The increased risk was not due to a higher degree of sensitivity to Cr(VI). Leather was reported most frequently as the suspected cause of chromium dermatitis (54%). However, Cr(VI) allergics having foot eczema and positive or doubtful Cr(III) reactions often had positive reactions to other...

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.

Biosorption of Cr(VI) by coconut coir: Spectroscopic investigation on the reaction mechanism of Cr(VI) with lignocellulosic material

International Nuclear Information System (INIS)

Shen, Ying-Shuian; Wang, Shan-Li; Huang, Shiuh-Tsuen; Tzou, Yu-Min; Huang, Jang-Hung

2010-01-01

In this study, the removal mechanism of Cr(VI) from water by coconut coir (CC) was investigated using X-ray photoelectron spectroscopy (XPS), Cr K-edge X-ray absorption near edge structure (XANES) and FTIR spectroscopy. The results showed that, upon reaction with CC at pH 3, Cr(VI) was reduced to Cr(III), which was either bound to CC or released back into solution. As revealed by the FTIR spectra of CC before and after reacting with Cr(VI), the phenolic methoxyl and hydroxyl groups of lignin in CC are the dominant drivers of Cr(VI) reduction, giving rise to carbonyl and carboxyl groups on CC. These functional groups can subsequently provide binding sites for Cr(III) resulting from Cr(VI) reduction. In conjunction with forming complexes with carbonyl and carboxyl groups, the formation of Cr(III) hydroxide precipitate could also readily occur as revealed by the linear combination fitting of the Cr K-edge XANES spectrum using a set of reference compounds. The phenolic groups in lignin are responsible for initiating Cr(VI) reduction, so lignocellulosic materials containing a higher amount of phenolic groups are expected to be more effective scavengers for removal of Cr(VI) from the environment.

Biosorption of Cr(VI) by coconut coir: Spectroscopic investigation on the reaction mechanism of Cr(VI) with lignocellulosic material

Energy Technology Data Exchange (ETDEWEB)

Shen, Ying-Shuian [Department of Soil and Environmental Sciences, National Chung Hsing University, 250 Kuo Kuang Road, Taichung 40227, Taiwan (China); Wang, Shan-Li, E-mail: slwang@nchu.edu.tw [Department of Soil and Environmental Sciences, National Chung Hsing University, 250 Kuo Kuang Road, Taichung 40227, Taiwan (China); Huang, Shiuh-Tsuen [Department of Soil and Environmental Sciences, National Chung Hsing University, 250 Kuo Kuang Road, Taichung 40227, Taiwan (China); Department of Science Application and Dissemination, National Taichung University, Taichung, Taiwan (China); Tzou, Yu-Min; Huang, Jang-Hung [Department of Soil and Environmental Sciences, National Chung Hsing University, 250 Kuo Kuang Road, Taichung 40227, Taiwan (China)

2010-07-15

In this study, the removal mechanism of Cr(VI) from water by coconut coir (CC) was investigated using X-ray photoelectron spectroscopy (XPS), Cr K-edge X-ray absorption near edge structure (XANES) and FTIR spectroscopy. The results showed that, upon reaction with CC at pH 3, Cr(VI) was reduced to Cr(III), which was either bound to CC or released back into solution. As revealed by the FTIR spectra of CC before and after reacting with Cr(VI), the phenolic methoxyl and hydroxyl groups of lignin in CC are the dominant drivers of Cr(VI) reduction, giving rise to carbonyl and carboxyl groups on CC. These functional groups can subsequently provide binding sites for Cr(III) resulting from Cr(VI) reduction. In conjunction with forming complexes with carbonyl and carboxyl groups, the formation of Cr(III) hydroxide precipitate could also readily occur as revealed by the linear combination fitting of the Cr K-edge XANES spectrum using a set of reference compounds. The phenolic groups in lignin are responsible for initiating Cr(VI) reduction, so lignocellulosic materials containing a higher amount of phenolic groups are expected to be more effective scavengers for removal of Cr(VI) from the environment.

Biosorption of Cr(VI) by coconut coir: spectroscopic investigation on the reaction mechanism of Cr(VI) with lignocellulosic material.

Science.gov (United States)

Shen, Ying-Shuian; Wang, Shan-Li; Huang, Shiuh-Tsuen; Tzou, Yu-Min; Huang, Jang-Hung

2010-07-15

In this study, the removal mechanism of Cr(VI) from water by coconut coir (CC) was investigated using X-ray photoelectron spectroscopy (XPS), Cr K-edge X-ray absorption near edge structure (XANES) and FTIR spectroscopy. The results showed that, upon reaction with CC at pH 3, Cr(VI) was reduced to Cr(III), which was either bound to CC or released back into solution. As revealed by the FTIR spectra of CC before and after reacting with Cr(VI), the phenolic methoxyl and hydroxyl groups of lignin in CC are the dominant drivers of Cr(VI) reduction, giving rise to carbonyl and carboxyl groups on CC. These functional groups can subsequently provide binding sites for Cr(III) resulting from Cr(VI) reduction. In conjunction with forming complexes with carbonyl and carboxyl groups, the formation of Cr(III) hydroxide precipitate could also readily occur as revealed by the linear combination fitting of the Cr K-edge XANES spectrum using a set of reference compounds. The phenolic groups in lignin are responsible for initiating Cr(VI) reduction, so lignocellulosic materials containing a higher amount of phenolic groups are expected to be more effective scavengers for removal of Cr(VI) from the environment. 2010 Elsevier B.V. All rights reserved.

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.

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

International Nuclear Information System (INIS)

Sisman, S. Lara

2015-01-01

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.

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.

Error analysis of equilibrium studies for the almond shell activated carbon adsorption of Cr(VI) from aqueous solutions

International Nuclear Information System (INIS)

Demirbas, E.; Kobya, M.; Konukman, A.E.S.

2008-01-01

In this study, the preparation of activated carbon from almond shell with H 2 SO 4 activation and its ability to remove toxic hexavalent chromium from aqueous solutions are reported. The influences of several operating parameters such as pH, particle size and temperature on the adsorption capacity were investigated. Adsorption of Cr(VI) is found to be highly pH, particle size and temperature dependent. Four adsorption isotherm models namely, Langmuir, Freundlich, Tempkin and Dubinin-Radushkevich were used to analyze the equilibrium data. The Langmuir isotherm provided the best correlation for Cr(VI) onto the almond shell activated carbon (ASC). Adsorption capacity was calculated from the Langmuir isotherm as 190.3 mg/g at 323 K. Thermodynamic parameters were evaluated and the adsorption was endothermic showing monolayer adsorption of Cr(VI). Five error functions were used to treat the equilibrium data using non-linear optimization techniques for evaluating the fit of the isotherm equations. The highest correlation for the isotherm equations in this system was obtained for the Freundlich isotherm. ASC is found to be inexpensive and effective adsorbent for removal of Cr(VI) from aqueous solutions

[New perspectives in biomonitoring of metallic elements: the example of hexavalent chromium].

Science.gov (United States)

Mutti, A; De Palma, G; Goldoni, M

2012-01-01

Plating industry is an important productive sector in all the national territory, because of its contribution to a high number of industrial products and crafts. In the chrome plating sector there is a specific chemical risk due to the exposure to compounds containing hexavalent Chromium [Cr(VI)]. Exhaled breath condensate (EBC) has been used to study both acute and long term exposure to Cr(VI) in chrome plating workers. Cr-EBC correlates with specific oxidative stress biomarkers. Moreover, both total Cr and its hexavalent fraction can be measured in EBC, which therefore is a promising biological fluid to assess the absorbed dose at the target organ level, the pulmonary reduction kinetics of Cr(VI) and in general its local pneumotoxic effects. EBC collection and analysis could give additional information to the traditional measures performed during biomonitoring.

Photocatalytic Reduction of Hexavalent Chromium Induced by Photolysis of Ferric/tartrate Complex

Energy Technology Data Exchange (ETDEWEB)

Feng, Xianghua; Ding, Shimin; Zhang, Lixian [Yangtze Normal Univ., Fuling (China)

2012-11-15

Photocatalytic reduction of hexavalent chromium (Cr(VI)) in ferric-tartrate system under irradiation of visible light was investigated. Effects of light resources, initial pH value and initial concentration of various reactants on Cr(VI) photocatalytic reduction were studied. Photoreaction kinetics was discussed and a possible photochemical pathway was proposed. The results indicate that Fe(III)-tartrate system is able to rapidly and effectively photocatalytically reduce Cr(VI) utilizing visible light. Initial pH variations results in the concentration changes of Fe(III)-tartrate complex in this system, and pH at 3.0 is optimal for Cr(VI) photocatalytic reduction. Efficiency of Cr(VI) photocatalytic reduction increases with increasing initial concentrations of Cr(VI), Fe(III) and tartrate. Kinetics analysis indicates that initial Fe(III) concentration affects Cr(VI) photoreduction most significantly.

Photocatalytic Reduction of Hexavalent Chromium Induced by Photolysis of Ferric/tartrate Complex

International Nuclear Information System (INIS)

Feng, Xianghua; Ding, Shimin; Zhang, Lixian

2012-01-01

Photocatalytic reduction of hexavalent chromium (Cr(VI)) in ferric-tartrate system under irradiation of visible light was investigated. Effects of light resources, initial pH value and initial concentration of various reactants on Cr(VI) photocatalytic reduction were studied. Photoreaction kinetics was discussed and a possible photochemical pathway was proposed. The results indicate that Fe(III)-tartrate system is able to rapidly and effectively photocatalytically reduce Cr(VI) utilizing visible light. Initial pH variations results in the concentration changes of Fe(III)-tartrate complex in this system, and pH at 3.0 is optimal for Cr(VI) photocatalytic reduction. Efficiency of Cr(VI) photocatalytic reduction increases with increasing initial concentrations of Cr(VI), Fe(III) and tartrate. Kinetics analysis indicates that initial Fe(III) concentration affects Cr(VI) photoreduction most significantly

Sandwich-like nano-system for simultaneous removal of Cr(VI) and Cd(II) from water and soil.

Science.gov (United States)

Wang, Dongfang; Zhang, Guilong; Dai, Zhangyu; Zhou, Linglin; Bian, Po; Zheng, Kang; Wu, Zhengyan; Cai, Dongqing

2018-05-07

In this work, a novel nano-system with sandwich-like structure was synthesized via face-to-face combination of two pieces of waste cotton fabrics (CFs) carrying ferrous sulfide (FeS) and carboxyl-functionalized ferroferric oxide (CFFM) respectively, and the obtained nano system was named as FeS/CFFM/CF. Therein, FeS has high reduction and adsorption capabilities for hexavalent chromium (Cr(VI)), CFFM possesses a high adsorption ability on cadmium ion (Cd(II)) through electrostatics attraction and chelation, and CF displays high immobilization ability for FeS and CFFM and adsorption performance on Cd(II). FeS/CFFM/CF could simultaneously remove Cr(VI) and Cd(II) from water, inhibit the uptake of Cr and Cd by fish and water spinach, ensuring the food safety. Besides, this technology could efficiently control migration of Cr(VI) and Cd(II) in sand-soil mixture, which was favorable to prevent their wide diffusion. Importantly, FeS/CFFM/CF possessed a high flexibility and could be conveniently produced with needed scale and shape, and easily separated from water and soil, displaying a promising approach to remediate Cr(VI)/Cd(II)-contaminated water and soil and a huge application potential.

Removal and transformation of hexavalent chromium in sequencing ...

African Journals Online (AJOL)

The objectives of this study are to evaluate the efficiency of removal of hexavalent chromium (Cr(VI)) in a sequencing batch reactor (SBR) and to ascertain the fate of Cr(VI) in the treatment process. An SBR was operated with the FILL, REACT, SETTLE, DRAW and IDLE periods in the time ratio of 2:12:2:1.5:6.5 for a cycle ...

Adsorption of hexavalent chromium by graphite–chitosan binary ...

Indian Academy of Sciences (India)

Hexavalent chromium; graphite–chitosan composite; adsorption kinetics. 1. Introduction ... [2], while Cr(III) is less toxicity and relatively innocuous. Cr(VI) generates in ..... Human Environments (New York: Wiley Inter-Science) p 3. [4] U.S. EPA ...

Influence of pH on Cr(VI) ions removal from aqueous solutions using carboxymethyl cellulose-based hydrogel as adsorbent

Science.gov (United States)

Anah, L.; Astrini, N.

2017-03-01

The major problem in heavy metal pollution is that these metals are not biodegradable and accordingly accumulate in the bodies of living organisms, causing dangerous diseases and serious cell disorder. According to World Health Organization (WHO), the long term exposure of Cr(VI) levels of over 0.1 ppm causes respiratory problems, liver and kidney damage, and carcinogenicity.Due to its easy operation and of various cheap adsorbents development, adsorption has been proved to be efficient and most economically attractive technique and feasible to the removal of toxic heavy metal from wastewater. The study aimed to report the removal of Cr(VI) ions from aqueous solutions through adsorption process using carboxymethyl cellulose-graft-poly(acrylic acid) (CMC-g-PAA) hydrogel as adsorbent.Effect of pH was studied to remove hexavalent chromium.Graft copolymerization of poly(acrylic acid) onto carboxymethyl cellulose was carried out in the presence of benzoyl peroxide redox initiator and methylenbisacrylamide as crosslinker agent. Batch experiments were carried out to investigate the effects ofinitial pH.The adsorption of Cr(VI) ions as a function of pH was conducted in the initial pH range of 1 to 8. The results indicated that acidic pH strongly favored the adsorption. The optimum pH for adsorption of Cr(VI) ranged from 1 to 3, and the maximum uptake of Cr(VI) from the solution was 6.53 mg/g at pH 1 and 30°C. FTIR spectroscopy, SEM analyses were performed on the adsorbent before and after Cr(VI) binding. All analyses confirmed the complexation of Cr(VI) ions on the adsorbent.

The determination of hexavalent chromium (Cr6+) in electronic and electrical components and products to comply with RoHS regulations

International Nuclear Information System (INIS)

Hua, L.; Chan, Y.C.; Wu, Y.P.; Wu, B.Y.

2009-01-01

Toxicity of hexavalent chromium (Cr 6+ ) was focused on with a publication of EU RoHS directive, a novel method to determine hexavalent chromium is developed. It is a combination of energy dispersion X-ray fluorescence spectrometry (EDXRF), spot test, alkali digestion and UV-vis spectrophotometric analysis. First, by EDXRF screening, the presence or absence of element Cr was established. Spot test was followed to identify the valent state of chromium because Cr 6+ and Cr 3+ normally coexist. After alkali digestion, Cr(VI) was separated without an undersired Cr(VI)-Cr(III) interconversions. With a color reagent (DPC) to chelated with Cr(VI), the solution was finally detected by a UV-vis spectrophotometer at a wavelength of 540 nm which is the basis of analyzing Cr(VI) quantitatively. Some parameters affecting analyses were studied. It was found that when pH in the final solution was 2.0, the extraction time was 60 min, the extraction temperature was 90 deg. C, pH during the extraction process was 7.5-8.5, and a mixed buffer solution (0.5 M K 2 HPO 4 /0.5 M KH 2 PO 4 ) was added up to 1 ml, colorimetric reagent was added to 2 ml, it is optimal for extraction. Under this condition, interferences from Fe 3+ , Pb 2+ , Ag + , etc., were overcome. It was also found that the curves are rectilinear in the range of 0-500 μg l -1 , the correlation coefficient is up to 0.999924, and the recovery rates are more than 85%, the Cr(III)-DPCO complex can be kept stable for 24 h with a relative humidity (RH) range of 60-90%, and a temperature range of 5-40 deg. C. So it can be concluded that the proposed method has a good sensitivity and high precision. It is a more convincing and reliable method due to its relative standard deviation (R.S.D.) <1% after six replicate determinations of Cr(VI) in an Fe-Ni alloy sample

In-situ porous reactive wall for treatment of Cr(VI) and trichloroethylene in groundwater

International Nuclear Information System (INIS)

Blowes, D.W.; Bennett, T.A.; Gillham, R.W.

1997-01-01

A permeable reactive wall for treating groundwater contaminated with hexavalent chromium (Cr(VI)) and trichloroethylene (TCE) was installed at the U.S. Coast Guard Support Center in Elizabeth City, NC in June, 1996. The porous reactive wall is 46 m long, 0.6 m wide, and 7.3 m deep. The reactive wall was installed in less then six hours using a continuous trenching technique which simultaneously removed the aquifer material and replaced it with reactive material. The wall is composed of 100% elemental iron in the form of iron filings. Preliminary laboratory experiments, with site groundwater and reactive materials similar to the full-scale wall components, were successful in decreasing 11 mg/L Cr(VI) to < 0.01 mg/L and 1700 μg/L TCE to < 1 μg/L. Detailed field monitoring commenced in November, 1996. The monitoring program includes groundwater sampling upgradient, downgradient and within the reactive wall, and collection of core samples for mineralogical and microbiological study. Preliminary results from the monitoring program indicate that the wall successfully removes Cr(VI) from influent concentrations of 6 mg/L to < 0.01 mg/L, and TCE from 5600 μg/L to 5.3 μg/L within the wall

Cr(VI) removal from aqueous solution by dried activated sludge biomass

International Nuclear Information System (INIS)

Wu Jun; Zhang Hua; He Pinjing; Yao Qian; Shao Liming

2010-01-01

Batch experiments were conducted to remove Cr(VI) from aqueous solution using activated sludge biomass. The effects of acid pretreatment of the biomass, initial pH, biomass and Cr(VI) concentrations on Cr(VI) removal efficiency were investigated. Proton consumption during the removal process and the reducing capacity of sludge biomass were studied. The results show that acid pretreatment could significantly improve Cr(VI) removal efficiency and increase Cr(VI) reducing capacity by 20.4%. Cr(VI) removal was remarkably pH-dependent; lower pH (pH = 1, 2) facilitated Cr(VI) reduction while higher pH (pH = 3, 4) favored sorption of the converted Cr(III). Lower Cr(VI) concentration as well as higher biomass concentration could accelerate Cr(VI) removal. Cr(VI) reduction was not the only reason for proton consumption in the removal process. Pseudo-second-order adsorption kinetic model could successfully simulate Cr(VI) removal except under higher pH conditions (pH = 3, 4).

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.

Oxidation of Cr(III)-Fe(III) Mixed-phase Hydroxides by Chlorine: Implications on the Control of Hexavalent Chromium in Drinking Water.

Science.gov (United States)

Chebeir, Michelle; Liu, Haizhou

2018-05-17

The occurrence of chromium (Cr) as an inorganic contaminant in drinking water is widely reported. One source of Cr is its accumulation in iron-containing corrosion scales of drinking water distribution systems as Cr(III)-Fe(III) hydroxide, i.e., FexCr(1-x)(OH)3(s), where x represents the Fe(III) molar content and typically varies between 0.25 and 0.75. This study investigated the kinetics of inadvertent hexavalent chromium Cr(VI) formation via the oxidation of FexCr(1-x)(OH)3(s) by chlorine as a residual disinfectant in drinking water, and examined the impacts of Fe(III) content and drinking water chemical parameters including pH, bromide and bicarbonate on the rate of Cr(VI) formation. Data showed that an increase in Fe(III) molar content resulted in a significant decrease in the stoichiometric Cr(VI) yield and the rate of Cr(VI) formation, mainly due to chlorine decay induced by Fe(III) surface sites. An increase in bicarbonate enhanced the rate of Cr(VI) formation, likely due to the formation of Fe(III)-carbonato surface complexes that slowed down the scavenging reaction with chlorine. The presence of bromide significantly accelerated the oxidation of FexCr(1-x)(OH)3(s) by chlorine, resulting from the catalytic effect of bromide acting as an electron shuttle. A higher solution pH between 6 and 8.5 slowed down the oxidation of Cr(III) by chlorine. These findings suggested that the oxidative conversion of chromium-containing iron corrosion products in drinking water distribution systems can lead to the occurrence of Cr(VI) at the tap, and the abundance of iron, and a careful control of pH, bicarbonate and bromide levels can assist the control of Cr(VI) formation.

Effet des polyamines sur la réduction du chrome hexavalent par des souches bactériennes et leur résistance

Directory of Open Access Journals (Sweden)

Tahri Joutey, N.

2014-01-01

Full Text Available Effect of polyamines on the reduction of hexavalent chromium by bacterial strains and their resistance. Polyamines are involved in several functions in bacteria. In this study, we examined the role of polyamines in hexavalent chromium (Cr[VI] reduction by three bacterial strains isolated from sites contaminated by tannery effluents. The strains were identified as Serratia proteamaculans, Leucobacter chromiireducens and Brevibacterium frigoritolerans. The inhibition of polyamine synthesis by α-difluoromethylornithine (DFMO caused a decrease in Cr(VI tolerance in the bacterial isolates, indicating the role of endogenous polyamines in resistance to Cr(VI. The exogenous application of polyamines (putrescine, spermidine, cadaverine was found to stimulate growth and Cr(VI reduction by the bacterial strains in Luria-Bertani medium. The results show the importance of polyamines in response to heavy metal stresses, especially Cr(VI toxicity.

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.

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

International Nuclear Information System (INIS)

Wang, Qiang; Huang, Liping; Pan, Yuzhen; Quan, Xie; Li Puma, Gianluca

2017-01-01

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_4"−) and dichromate (Cr_2O_7"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.

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

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. Copyright © 2013 Elsevier B.V. All rights reserved.

Hexavalent chromium reduction by a hypocrea tawa fungal strain

International Nuclear Information System (INIS)

Morales-Battera, L.; Guillen-Jimenez, F. M.; Cristiani-Urbina, E.

2009-01-01

Microbial transformation of the highly toxic, water-soluble and mobile hexavalent chromium [Cr(VI)], to the less toxic, insoluble and immobile trivalent chromium [Cr(III)], is an economically feasible alternative for the treatment of wastewaters contaminated with Cr(VI). The main purpose of this work was to isolate, identify and characterize a microbial strain water by batch enrichment culture techniques, and further identified as Hypocrea tawa by its D1/D2 domain sequence of the 26S rRNA gene with 99,44% similarity. (Author)

Adsorption of Cr(VI and Speciation of Cr(VI and Cr(III in Aqueous Solutions Using Chemically Modified Chitosan

Directory of Open Access Journals (Sweden)

ChunYuan Tao

2012-05-01

Full Text Available A new type of grafting chitosan (CTS was synthesized using 2-hydroxyethyl- trimethyl ammonium chloride (HGCTS. The adsorption of Cr(VI on HGCTS was studied. The effect factors on adsorption and the adsorption mechanism were considered. The results indicated that the HGCTS could concentrate and separate Cr(VI at pH 4.0; the adsorption equilibrium time was 80 min; the maximum adsorption capacity was 205 mg/g. The adsorption isotherm and kinetics were investigated, equilibrium data agreed very well with the Langmuir model and the pseudo second-order model could describe the adsorption process better than the pseudo first-order model. A novel method for speciation of Cr(VI and Cr(III in environmental water samples has been developed using HGCTS as adsorbent and FAAS as determination means. The detection limit of this method was 20 ng/L, the relatively standard deviation was 1.2% and the recovery was 99%~105%.

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.

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.

Reduction of Hexavalent Chromium and Detection of Chromate Reductase (ChrR in Stenotrophomonas maltophilia

Directory of Open Access Journals (Sweden)

Rosa Baldiris

2018-02-01

Full Text Available An Gram negative strain of S. maltophilia, indigenous to environments contaminated by Cr(VI and identified by biochemical methods and 16S rRNA gene analysis, reduced chromate by 100%, 98–99% and 92% at concentrations in the 10–70, 80–300, and 500 mg/L range, respectively at pH 7 and temperature 37 °C. Increasing concentrations of Cr(VI in the medium lowered the growth rate but could not be directly correlated with the amount of Cr(VI reduced. The strain also exhibited multiple resistance to antibiotics and tolerance and resistance to various heavy metals (Ni, Zn and Cu, with the exception of Hg. Hexavalent chromium reduction was mainly associated with the soluble fraction of the cell evaluated with crude cell-free extracts. A protein of molecular weight around 25 kDa was detected on SDS-PAGE gel depending on the concentration of hexavalent chromium in the medium (0, 100 and 500 mg/L. In silico analysis in this contribution, revealed the presence of the chromate reductase gene ChrR in S. maltophilia, evidenced through a fragment of around 468 bp obtained experimentally. High Cr(VI concentration resistance and high Cr(VI reducing ability of the strain make it a suitable candidate for bioremediation.

Cr(III) and Cr(VI) in leather and elicitation of eczema

DEFF Research Database (Denmark)

Hansen, Malene Barré; Menne, Torkil; Johansen, Jeanne Duus

2006-01-01

The aim of the present study was to investigate the relation between the content of Cr(VI) and soluble Cr(III) in leather and the ability of the leather to elicit eczema in chromium allergic patients. An array of chromium-tanned leather samples was analysed for the content of total Cr(VI) and sol...

Column study of enhanced Cr(VI) removal and longevity by coupled abiotic and biotic processes using Fe⁰ and mixed anaerobic culture

DEFF Research Database (Denmark)

Zhong, Jiawei; Yin, Weizhao; Li, Yongtao

2017-01-01

In this study, Fe(0) and mixed anaerobic culture were integrated in one column to investigate the coupled abiotic and biotic effects on hexa-valent chromium (Cr(VI)) removal and column longevity with an abiotic Fe(0) column in the control experiments. According to the breakthrough study, a slower...

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)

Reduction of hexavalent chromium in water samples acidified for preservation

Science.gov (United States)

Stollenwerk, K.G.; Grove, D.B.

1985-01-01

Reduction of hexavalent chromium, Cr(VI), in water samples, preserved by standard techniques, was investigated. The standard preservation technique for water samples that are to be analyzed for Cr(VI) consists of filtration through a 0.45-??m membrane, acidification to a pH plastic bottles. Batch experiments were conducted to evaluate the effect of H+ concentration, NO2, temperature, and dissolved organic carbon (DOC) on the reduction of Cr(VI) to Cr(III). The rate of reduction of Cr(VI) to Cr(III) increased with increasing NO2, DOC, H+, and temperature. Reduction of Cr(VI) by organic matter occurred in some samples even though the samples were unacidified. Reduction of Cr(VI) is inhibited to an extent by storing the sample at 4??C. Stability of Cr(VI) in water is variable and depends on the other constituents present in the sample. Water samples collected for the determination of Cr(VI) should be filtered (0.45-??m membrane), refrigerated, and analyzed as quickly as possible. Water samples should not be acidified. Measurement of total Cr in addition to Cr(VI) can serve as a check for Cr(VI) reduction. If total Cr is greater than Cr(VI), the possibility that Cr(VI) reduction has occurred needs to be considered.The rate of reduction of Cr(VI) to Cr(III) increased with increasing NO//2, DOC, H** plus , and temperature. Reduction of Cr(VI) by organic matter occurred in some samples even though the samples were unacidified. Reduction of Cr(VI) is inhibited to an extent by storing the sample at 4 degree C. Stability of Cr(VI) in water is variable and depends on the other constituents present in the sample. Water samples collected for the determination of Cr(VI) should be filtered (0. 45- mu m membrane), refrigerated, and analyzed as quickly as possible. Water samples should not be acidified. Measurement of total Cr in addition to Cr(VI) can serve as a check for Cr(VI) reduction. If total Cr is greater than Cr(VI), the possibility that Cr(VI) reduction has occurred needs

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.

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. Ca-Al precursor (C3A) was agitated in a hexavalent chromium (Cr(VI)) solution to form Al-Ca-CrO4 LDH product. Ca-Al-CrO4 LDH phase occurred preferentially to Ca-Al-MCl2 LDH phases in the solutions of calcium and magnesium chlorides, it incorporates Cr(VI) preferentially to the chloride salts when they coexist.

Application of double-spike isotope dilution for the accurate determination of Cr(III), Cr(VI) and total Cr in yeast.

Science.gov (United States)

Yang, Lu; Ciceri, Elena; Mester, Zoltán; Sturgeon, Ralph E

2006-11-01

A method is presented for the simultaneous determination of Cr(III) and Cr(VI) in yeast using species-specific double-spike isotope dilution (SSDSID) with anion-exchange liquid chromatography (LC) separation and sector field inductively coupled plasma mass spectrometric (SF-ICP-MS) detection. Total Cr is quantitated using ID SF-ICP-MS. Samples were digested on a hot plate at 95+/-2 degrees C for 6 h in an alkaline solution of 0.5 M NaOH and 0.28 M Na2CO3 for the determination of Cr(III) and Cr(VI), whereas microwave-assisted decomposition with HNO3 and H2O2 was used for the determination of total Cr. Concentrations of 2,014+/-16, 1,952+/-103 and 76+/-48 mg kg-1 (one standard deviation, n=4, 3, 3), respectively were obtained for total Cr, Cr(III) and Cr(VI) in the yeast sample. Significant oxidation of Cr(III) to Cr(VI) (24.2+/-7.6% Cr(III) oxidized, n=3) and reduction of Cr(VI) to Cr(III) (37.6+/-6.5% Cr(VI) reduced, n=3) occurred during alkaline extraction and subsequent chromatographic separation at pH 7. Despite this significant bidirectional redox transformation, quantitative recoveries for both Cr(III) and Cr(VI) were achieved using the SSDSID method. In addition, mass balance between total Cr and the sum of Cr(III) and Cr(VI) concentrations was achieved. Method detection limits of 0.3, 2 and 30 mg kg-1 were obtained for total Cr, Cr(VI) and Cr(III), respectively, based on a 0.2-g sub-sample.

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.

New generation ion-imprinted nanocarrier for removal of Cr(VI) from wastewater

International Nuclear Information System (INIS)

Uygun, Murat; Feyzioğlu, Esra; Özçalışkan, Emir; Caka, Müşerref; Ergen, Aygen; Akgöl, Sinan; Denizli, Adil

2013-01-01

The purpose of this study was to prepare a novel ion-imprinted nanoparticle to remove Cr(VI) ions from waste water. For this, Cr(VI) ions were complexed with 2-methacryloylamido histidine (MAH) and then Cr(VI)-imprinted poly(HEMAH) nanoparticles were synthesized by surfactant-free emulsion polymerization technique. The templates, Cr(VI) ions, were removed from the nanoparticles using 0.1 M of HNO 3 solution. The specific surface area of the Cr(VI)-imprinted poly(HEMAH) nanoparticles was found to be 1,397.85 m 2 /g, and the particle size was calculated as 155.3 nm. These Cr(VI)-imprinted nanoparticles were used for the adsorption/desorption of Cr(VI) ions from its aqueous solutions. The effects of initial Cr(VI) concentration and medium pH on the Cr(VI) adsorption capacity were also studied. The maximum adsorbed amount of Cr(VI) on the imprinted nanoparticles was found to be 3,830.58 mg/g nanoparticle in pH 4.0. In order to investigate the selectivity of the imprinted nanoparticle, adsorption studies were repeated using Cr(III) ions. The selectivity results demonstrated that Cr(VI)-imprinted poly(HEMAH) nanoparticles showed high affinity for the Cr(VI) ions than Cr(III). The Cr(VI)-imprinted nanoparticles were used several times without decreasing their Cr(VI) adsorption capacities

New generation ion-imprinted nanocarrier for removal of Cr(VI) from wastewater

Science.gov (United States)

Uygun, Murat; Feyzioğlu, Esra; Özçalışkan, Emir; Caka, Müşerref; Ergen, Aygen; Akgöl, Sinan; Denizli, Adil

2013-08-01

The purpose of this study was to prepare a novel ion-imprinted nanoparticle to remove Cr(VI) ions from waste water. For this, Cr(VI) ions were complexed with 2-methacryloylamido histidine (MAH) and then Cr(VI)-imprinted poly(HEMAH) nanoparticles were synthesized by surfactant-free emulsion polymerization technique. The templates, Cr(VI) ions, were removed from the nanoparticles using 0.1 M of HNO3 solution. The specific surface area of the Cr(VI)-imprinted poly(HEMAH) nanoparticles was found to be 1,397.85 m2/g, and the particle size was calculated as 155.3 nm. These Cr(VI)-imprinted nanoparticles were used for the adsorption/desorption of Cr(VI) ions from its aqueous solutions. The effects of initial Cr(VI) concentration and medium pH on the Cr(VI) adsorption capacity were also studied. The maximum adsorbed amount of Cr(VI) on the imprinted nanoparticles was found to be 3,830.58 mg/g nanoparticle in pH 4.0. In order to investigate the selectivity of the imprinted nanoparticle, adsorption studies were repeated using Cr(III) ions. The selectivity results demonstrated that Cr(VI)-imprinted poly(HEMAH) nanoparticles showed high affinity for the Cr(VI) ions than Cr(III). The Cr(VI)-imprinted nanoparticles were used several times without decreasing their Cr(VI) adsorption capacities.

New generation ion-imprinted nanocarrier for removal of Cr(VI) from wastewater

Energy Technology Data Exchange (ETDEWEB)

Uygun, Murat, E-mail: muygun@adu.edu.tr [Adnan Menderes University, Kocarl Latin-Small-Letter-Dotless-I Vocational and Training School (Turkey); Feyzioglu, Esra; Oezcal Latin-Small-Letter-Dotless-I skan, Emir; Caka, Mueserref; Ergen, Aygen; Akgoel, Sinan [Ege University, Department of Biochemistry, Faculty of Science (Turkey); Denizli, Adil [Hacettepe University, Department of Chemistry, Faculty of Science (Turkey)

2013-08-15

The purpose of this study was to prepare a novel ion-imprinted nanoparticle to remove Cr(VI) ions from waste water. For this, Cr(VI) ions were complexed with 2-methacryloylamido histidine (MAH) and then Cr(VI)-imprinted poly(HEMAH) nanoparticles were synthesized by surfactant-free emulsion polymerization technique. The templates, Cr(VI) ions, were removed from the nanoparticles using 0.1 M of HNO{sub 3} solution. The specific surface area of the Cr(VI)-imprinted poly(HEMAH) nanoparticles was found to be 1,397.85 m{sup 2}/g, and the particle size was calculated as 155.3 nm. These Cr(VI)-imprinted nanoparticles were used for the adsorption/desorption of Cr(VI) ions from its aqueous solutions. The effects of initial Cr(VI) concentration and medium pH on the Cr(VI) adsorption capacity were also studied. The maximum adsorbed amount of Cr(VI) on the imprinted nanoparticles was found to be 3,830.58 mg/g nanoparticle in pH 4.0. In order to investigate the selectivity of the imprinted nanoparticle, adsorption studies were repeated using Cr(III) ions. The selectivity results demonstrated that Cr(VI)-imprinted poly(HEMAH) nanoparticles showed high affinity for the Cr(VI) ions than Cr(III). The Cr(VI)-imprinted nanoparticles were used several times without decreasing their Cr(VI) adsorption capacities.

The adsorption ability of Cr(VI) on sawdust–polyaniline nanocomposite

International Nuclear Information System (INIS)

Binh Phan, Thi; Que Do, Ngoc; Thanh Thuy Mai, Thi

2010-01-01

The results of this study of sawdust–polyaniline nanocomposite synthesized by a chemical method for Cr(VI) treatment in the environment are presented. Cr(VI) adsorption on a composite was determined by colorimetry. The results showed that sawdust–polyaniline composite synthesized with an aniline:sawdust ratio equal to 0.5 had an adsorption degree of 21.4 mg g −1 and adsorbed nearly 99% of the Cr(VI) after 2 h. The composite could be used for the adsorption of Cr(VI) from waste water. The Cr(VI) adsorption ability of the composite slightly depends on the pH value of the medium. The adsorption is fast during the first half hour and then the rate decreases

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.

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. Copyright © 2015 Elsevier B.V. All rights reserved.

Column study of enhanced Cr(VI) removal and longevity by coupled abiotic and biotic processes using Fe0 and mixed anaerobic culture.

Science.gov (United States)

Zhong, Jiawei; Yin, Weizhao; Li, Yongtao; Li, Ping; Wu, Jinhua; Jiang, Gangbiao; Gu, Jingjing; Liang, Hao

2017-10-01

In this study, Fe 0 and mixed anaerobic culture were integrated in one column to investigate the coupled abiotic and biotic effects on hexa-valent chromium (Cr(VI)) removal and column longevity with an abiotic Fe 0 column in the control experiments. According to the breakthrough study, a slower Cr(VI) breakthrough rate of 0.19 cm/PV was observed in the biotic Fe 0 column whereas the value in the abiotic Fe 0 column was 0.30 cm/PV, resulting in 64% longer life-span and 62% higher Cr(VI) removal capacity in the biotic Fe 0 column than the abiotic one. The solid phase characterization by scanning electron microscopy (SEM), energy dispersive X-ray (EDX) and X-ray diffraction (XRD) confirmed that this enhancement was attributed to the higher consumption of iron and greater production of diverse reactive minerals (e.g., green rust, magnetite and lepidocrocite) induced by the synergistic interaction of Fe 0 and anaerobic culture, providing more reactive sites for Cr(VI) adsorption, reduction and co-precipitation. Furthermore, the decreasing breakthrough rates and growing iron corrosion along the biotic Fe 0 column demonstrated an inhomogeneous distribution of reactive zones in the column and its latter 3/5 section was considered to be the most reactive area for Cr(VI) removal. These results indicate that the inoculation of microorganisms in Fe 0 -based permeable reactive barriers will enable this technology a higher removal capacity and longer life-span for the remediation of Cr(VI)-contaminated groundwater. Copyright © 2017 Elsevier Ltd. All rights reserved.

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.

Superb adsorption capacity of hierarchical calcined Ni/Mg/Al layered double hydroxides for Congo red and Cr(VI) ions

Energy Technology Data Exchange (ETDEWEB)

Lei, Chunsheng [State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology, Wuhan 430070 (China); College of Environmental & Safety Engineering, Changzhou University, Changzhou 213164 (China); Zhu, Xiaofeng [College of Environmental & Safety Engineering, Changzhou University, Changzhou 213164 (China); Zhu, Bicheng; Jiang, Chuanjia; Le, Yao [State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology, Wuhan 430070 (China); Yu, Jiaguo, E-mail: jiaguoyu@yahoo.com [State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology, Wuhan 430070 (China); Department of Physics, Faculty of Science, King Abdulaziz University, Jeddah 21589 (Saudi Arabia)

2017-01-05

Highlights: • Ni/Mg/Al layered double hydroxides (NMA-LDHs) synthesized. • NMA-LDHs with hierarchically hollow microsphere structure. • Calcined NMA-LDHs have large adsorption capacities for CR and Cr(VI) ions. - Abstract: The preparation of hierarchical porous materials as catalysts and sorbents has attracted much attention in the field of environmental pollution control. Herein, Ni/Mg/Al layered double hydroxides (NMA-LDHs) hierarchical flower-like hollow microspheres were synthesized by a hydrothermal method. After the NMA-LDHs was calcined at 600 °C, NMA-LDHs transformed into Ni/Mg/Al layered double oxides (NMA-LDOs), which maintained the hierarchical flower-like hollow structure. The crystal phase, morphology, and microstructure of the as-prepared samples were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, energy-dispersive X-ray spectroscopy elemental mapping, Fourier transform infrared spectroscopy, and nitrogen adsorption−desorption methods. Both the calcined and non-calcined NMA-LDHs were examined for their performance to remove Congo red (CR) and hexavalent chromium (Cr(VI)) ions in aqueous solution. The maximum monolayer adsorption capacities of CR and Cr(VI) ions over the NMA-LDOs sample were 1250 and 103.4 mg/g at 30 °C, respectively. Thermodynamic studies indicated that the adsorption process was endothermic in nature. In addition, the addition of coexisting anions negatively influenced the adsorption capacity of Cr(VI) ions, in the following order: CO{sub 3}{sup 2−} > SO{sub 4}{sup 2−} > H{sub 2}PO{sub 4}{sup −} > Cl{sup −}. This work will provide new insight into the design and fabrication of advanced adsorption materials for water pollutant removal.

Biliary excretion and distribution of 51Cr(III) and 51Cr(VI) in rats

International Nuclear Information System (INIS)

Cikrt, M.; Bencko, V.

1979-01-01

The biliary excretion and distribution of 51 Cr after intravenous administration of 51 Cr(III) ( 51 CrCl 3 ) or 51 Cr(VI) (Na 2 51 CrO 4 .4H 2 O) were studied in rats. The cumulative biliary excretion of 51 Cr 24 hrs after the injection was significantly higher after administration of 51 Cr(VI) than of 51 Cr(III) (3.51+-0.7% and 0.51+-0.05% of administered dose, respectively). This difference was especially due to a higher rate of biliary excretion of 51 Cr in the first hours after 51 Cr(VI) administration. The excretion of 51 Cr via feces was also higher after administration of 51 Cr(VI) (7.35+-0.45%) of administered dose, as against 4.23+-0.23% after 51 Cr(III). On the other hand, no significant difference in urinary excretion of 51 Cr was found. Statistically significant differences were also observed in the distribution of 51 Cr in the organism after administration of both valence states of the metal. (author)

Species dependent radiotracer study of Cr(VI) and Cr(III) using an aqueous biphasic system

Energy Technology Data Exchange (ETDEWEB)

Roy, K.; Lahiri, S. [Chemical Sciences Div., Saha Inst. of Nuclear Physics, Kolkata (India)

2008-07-01

The speciation study of Cr(III) and Cr(VI) was carried out using a polyethylene glycol (PEG) based aqueous biphasic extraction system (ABS). Neutron activated Cr(III) and Cr(VI) salts were assayed in a HPGe detector before and after employing aqueous biphasic extraction. Different salts of various salting out abilities were taken as the salt rich phase. The best condition for extraction of Cr(VI) and the maximum differential attitude of ABS to Cr(VI) and Cr(III) was observed when 2 M Na{sub 2}SO{sub 4} and PEG 4000 (50% w/w) solutions were used. Cr(III) can also be extracted by the PEG with prior complexation with diphenylthiocarbazone (dithizone). The chromium dithizonate complex is quantitatively extracted by the PEG rich phase. (orig.)

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). Copyright © 2014 The Authors. Published by Elsevier B.V. All rights reserved.

Precursor preparation for Ca-Al layered double hydroxide to remove hexavalent chromium coexisting with calcium and magnesium chlorides

Energy Technology Data Exchange (ETDEWEB)

Zhong, Lihua; He, Xiaoman; Qu, Jun; Li, Xuewei; Lei, Zhiwu; Zhang, Qiwu [School of Resources and Environment Engineering, Wuhan University of Technology, Wuhan 430070 (China); Liu, Xinzhong [College of Ecological Environment and Urban Construction, Fujian University of Technology, Fuzhou 350118 (China)

2017-01-15

Al(OH){sub 3} and Ca(OH){sub 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. - Graphical abstract: Activated Ca-Al hydroxides (C{sub 3}A) transformed into Ca-Al-OH compound when agitated in water. Ca-Al precursor (C{sub 3}A) was agitated in a hexavalent chromium (Cr(VI)) solution to form Al-Ca-CrO{sub 4} LDH product. Ca-Al-CrO{sub 4} LDH phase occurred preferentially to Ca-Al-MCl{sub 2} LDH phases in the solutions of calcium and magnesium chlorides, it incorporates Cr(VI) preferentially to the chloride salts when they coexist. - Highlights: • Activated Ca-Al hydroxides transformed into LDH when agitated in water with some inorganic substances. • Hexavalent Cr was incorporated in the LDH structure at high adsorption capacity. • Ca-Al-Cr LDH phase occurred preferentially to Ca-Al-MCl{sub 2} LDH phases with coexistence. • The prepared Ca-Al hydroxides had high performance as adsorbent even with high salinity of the solution.

Precursor preparation for Ca-Al layered double hydroxide to remove hexavalent chromium coexisting with calcium and magnesium chlorides

International Nuclear Information System (INIS)

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. - Graphical abstract: Activated Ca-Al hydroxides (C 3 A) transformed into Ca-Al-OH compound when agitated in water. Ca-Al precursor (C 3 A) was agitated in a hexavalent chromium (Cr(VI)) solution to form Al-Ca-CrO 4 LDH product. Ca-Al-CrO 4 LDH phase occurred preferentially to Ca-Al-MCl 2 LDH phases in the solutions of calcium and magnesium chlorides, it incorporates Cr(VI) preferentially to the chloride salts when they coexist. - Highlights: • Activated Ca-Al hydroxides transformed into LDH when agitated in water with some inorganic substances. • Hexavalent Cr was incorporated in the LDH structure at high adsorption capacity. • Ca-Al-Cr LDH phase occurred preferentially to Ca-Al-MCl 2 LDH phases with coexistence. • The prepared Ca-Al hydroxides had high performance as adsorbent even with high salinity of the solution.

Exposure to particulate hexavalent chromium exacerbates allergic asthma pathology

International Nuclear Information System (INIS)

Schneider, Brent C.; Constant, Stephanie L.; Patierno, Steven R.; Jurjus, Rosalyn A.; Ceryak, Susan M.

2012-01-01

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

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

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.

Comparative Cytotoxicity and Genotoxicity of Particulate and Soluble Hexavalent Chromium in Human and Sperm Whale (Physeter macrocephalus) Skin Cells

Science.gov (United States)

Li Chen, Tânia; LaCerte, Carolyne; Wise, Sandra S.; Holmes, Amie; Martino, Julieta; Wise, John Pierce; Thompson, W. Douglas; Wise, John Pierce

2014-01-01

Chromium (Cr) is a global marine pollutant, present in marine mammal tissues. Hexavalent chromium [Cr(VI)] is a known human carcinogen. In this study we compare the cytotoxic and clastogenic effects of Cr(VI) in human (Homo sapiens) and sperm whale (Physeter macrocephalus) skin fibroblasts. Our data show that increasing concentrations of both particulate and soluble Cr(VI) induce increasing amounts of cytotoxicity and clastogenicity in human and sperm whale skin cells. Furthermore, the data show that sperm whale cells are resistant to these effects exhibiting less cytotoxicity and genotoxicity than the human cells. Differences in Cr uptake accounted for some but not all of the differences in particulate and soluble Cr(VI) genotoxicity, although it did explain the differences in particulate Cr(VI) cytotoxicity. Altogether the data indicate that Cr(VI) is a genotoxic threat to whales, but also suggest that whales have evolved cellular mechanisms to protect them against the genotoxicity of environmental agents such as Cr(VI). PMID:21466859

Mechanisms of hexavalent chromium resistance and removal by microorganisms.

Science.gov (United States)

Joutey, Nezha Tahri; Sayel, Hanane; Bahafid, Wifak; El Ghachtouli, Naïma

2015-01-01

Chromium has been and is extensively used worldwide in multiple industrial processes and is routinely discharged to the environment from such processes. Therefore, this heavy metal is a potential threat to the environment and to public health, primarily because it is non-biodegradable and environmentally persistent. Chromium exists in several oxidation states, the most stable of which are trivalent Cr(Ill) and hexavalent Cr(VI) species. Each species possesses its own individual chemical characteristics and produces its own biological effects. For example, Cr (Ill) is an essential oligoelement for humans, whereas Cr(VI) is carcinogenic and mutagenic. Several chemical methods are used to remove Cr(VI) from contaminated sites. Each of these methods has advantages and disadvantages. Currently, bioremediation is often the preferred method to deal with Cr contaminated sites, because it is eco-friendly, cost-effective and is a "natural" technology. Many yeast, bacterial and fungal species have been assessed for their suitability to reduce or remove Cr(VI) contamination. The mechanisms by which these microorganisms resist and reduce Cr(VI) are variable and are species dependent. There are several Cr-resistance mechanisms that are displayed by microorganisms. These include active efflux of Cr compounds, metabolic reduction of Cr(VI) to Cr (ill), and either intercellular or extracellular prec1p1tation. Microbial Cr (VI) removal typically involves three stages: binding of chromium to the cell surface, translocation of chromium into the cell, and reduction of Cr(VI) to Cr (ill). Cr(VI) reduction by microorganisms may proceed on the cell surface, outside the cell, or intracellularly, either directly via chromate reductase enzymes, or indirectly via metabolite reduction of Cr(VI). The uptake of chromium ions is a biphasic process. The primary step is known as biosorption, a metabolic energyindependent process. Thereafter, bioaccumulation occurs, but is much slower, and is

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 (FeSO 4 ). 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 FeSO 4 , 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.

Exposure to Particulate Hexavalent Chromium Exacerbates Allergic Asthma Pathology

Science.gov (United States)

Schneider, Brent C.; Constant, Stephanie L.; Patierno, Steven R.; Jurjus, Rosalyn A.; Ceryak, Susan M.

2011-01-01

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. PMID:22178736

Reduction of Hexavalent Chromium Using L-Cysteine Capped Nickel Nanocatalysts

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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.

Sulfur-Doped Carbon Nitride Polymers for Photocatalytic Degradation of Organic Pollutant and Reduction of Cr(VI).

Science.gov (United States)

Zheng, Yun; Yu, Zihao; Lin, Feng; Guo, Fangsong; Alamry, Khalid A; Taib, Layla A; Asiri, Abdullah M; Wang, Xinchen

2017-04-01

As a promising conjugated polymer, binary carbon nitride has attracted extensive attention as a metal-free and visible-light-responsive photocatalyst in the area of photon-involving purification of water and air. Herein, we report sulfur-doped polymeric carbon nitride microrods that are synthesized through thermal polymerization based on trithiocyanuric acid and melamine (TM) supramolecular aggregates. By tuning the polymerization temperature, a series of sulfur-doped carbon nitride microrods are prepared. The degradation of Rhodamine B (RhB) and the reduction of hexavalent chromium Cr(VI) are selected as probe reactions to evaluate the photocatalytic activities. Results show that increasing pyrolysis temperature leads to a large specific surface area, strong visible-light absorption, and accelerated electron-hole separation. Compared to bulk carbon nitride, the highly porous sulfur-doped carbon nitride microrods fabricated at 650 °C exhibit remarkably higher photocatalytic activity for degradation of RhB and reduction of Cr(VI). This work highlights the importance of self-assembly approach and temperature-control strategy in the synthesis of photoactive materials for environmental remediation.

Hexavalent chromium is cytotoxic and genotoxic to American alligator cells.

Science.gov (United States)

Wise, Sandra S; Wise, Catherine; Xie, Hong; Guillette, Louis J; Zhu, Cairong; Wise, John Pierce; Wise, John Pierce

2016-02-01

Metals are a common pollutant in the aquatic ecosystem. With global climate change, these levels are anticipated to rise as lower pH levels allow sediment bound metals to be released. The American alligator (Alligator mississippiensis) is an apex predator in the aquatic ecosystem and is considered a keystone species; as such it serves as a suitable monitor for localized pollution. One metal of increasing concern is hexavalent chromium (Cr(VI)). It is present in the aquatic environment and is a known human carcinogen and reproductive toxicant. We measured the cytotoxicity and genotoxicity of Cr(VI) in American alligator cells derived from scute tissue. We found that particulate and soluble Cr(VI) are both cytotoxic and genotoxic to alligator cells in a concentration-dependent manner. These data suggest that alligators may be used as a model for assessing the effects of environmental Cr(VI) contamination as well as for other metals of concern. Copyright © 2015 Elsevier B.V. All rights reserved.

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

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

Effects of citrate on hexavalent chromium reduction by structural Fe(II) in nontronite

Energy Technology Data Exchange (ETDEWEB)

Liu, Xiaolei; Dong, Hailiang; Yang, Xuewei; Kovarik, Libor; Chen, Yu; Zeng, Qiang

2018-02-01

Iron-bearing clay minerals and organic matter are two important components in natural environments that influence hexavalent chromium (Cr(VI)) reduction. Previous studies have shown that organic ligands could influence Cr(VI) reduction by aqueous Fe2+ and pyrite. However, the effects of organic ligands on Cr(VI) reduction by structural Fe(II) in clays are not well understood. In this study, the effects of citrate on Cr(VI) reduction by nontronite (NAu-2) were investigated under near neutral pH condition (pH=6). Our results showed that the presence of citrate decreased the rate but increased the amount of Cr(VI) reduction by structural Fe(II) in NAu-2. The decreased reaction rate was likely due to competitive sorption of citrate and polyanionic dichromate (Cr2O7- ), because sorption of dichromate appeared to be the first step for subsequent Cr(VI) reduction. The increased amount of Cr(VI) reduction in the presence of citrate was likely because citrate provided additional reducing power through ligand-metal electron transfer in the presence of soluble Fe 3+ derived from dissolution of reduced NAu-2. Soluble Cr(III)-citrate complex was the possible form of reduced chromium when citrate was present. In contrast, nanometer-sized Cr2O3 particles were the product of Cr(VI) reduction by reduced NAu-2 without citrate. Our study highlights the importance of organic ligands on Cr(VI) reduction and immobilization when iron-bearing clay minerals are applied to treat Cr(VI) contaminant in organic matter rich environments.

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

Energy Technology Data Exchange (ETDEWEB)

Du, Gaoxiang [School of Materials Science and Technology, China University of Geosciences, Beijing 100083 (China); Li, Zhaohui, E-mail: li@uwp.edu [School of Materials Science and Technology, China University of Geosciences, Beijing 100083 (China); Geosciences Department, University of Wisconsin-Parkside, Kenosha, WI 53144 (United States); Department of Earth Sciences, National Cheng Kung University, 1 University Road, Tainan 70101, Taiwan (China); Liao, Libing [School of Materials Science and Technology, China University of Geosciences, Beijing 100083 (China); Hanson, Renee; Leick, Samantha; Hoeppner, Nicole [Geosciences Department, University of Wisconsin-Parkside, Kenosha, WI 53144 (United States); Jiang, Wei-Teh [Department of Earth Sciences, National Cheng Kung University, 1 University Road, Tainan 70101, Taiwan (China)

2012-06-30

Graphical abstract: Breakthrough curves of Cr(VI) from columns packed with raw zeolite (a) and Fe(III)-zeolite (b). The solid line in (b) is the HYDRUS-1D fit to the observed data with adsorption term only, while the dashed line in (b) includes a reduction term in the HYDRUS-1D fit. Highlights: Black-Right-Pointing-Pointer Zeolite modified with Fe(III) could be used for adsorption and retention of Cr(VI). Black-Right-Pointing-Pointer The Fe present on zeolite was in an amorphous Fe(OH){sub 3} form. Black-Right-Pointing-Pointer A Cr(VI) adsorption capacity of 82 mg/kg was found on Fe(III)-zeolite. Black-Right-Pointing-Pointer A Cr(VI) retardation factor of 3 or 5 was determined from column and batch studies. - Abstract: 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 1.4-2.4 mm 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 82 mg/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 3 mg/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.

Biomarkers of oxidative stress in electroplating workers exposed to hexavalent chromium.

Science.gov (United States)

Pan, Chih-Hong; Jeng, Hueiwang Anna; Lai, Ching-Huang

2018-01-01

This study evaluates levels of biomarkers of oxidative DNA damage and lipid peroxidation in 105 male workers at 16 electroplating companies who had been exposed to hexavalent chromium (Cr(VI)). The study participants were 230 non-smoking male workers, comprising 105 electroplating workers who had been exposed to chromium and 125 control subjects who performed office tasks. Personal air samples, spot urine samples, hair samples, fingernail samples and questionnaires were used to quantify exposure to Cr(VI), oxidative DNA damage, lipid peroxidation, and environmental pollutants. Both the geometric mean personal concentrations of Cr(VI) of the Cr-exposed workers and the total Cr concentrations in the air to which they were exposed significantly exceeded those for the control subjects. The geometric mean concentrations of Cr in urine, hair and fingernails, and the urinary 8-hydroxy-2'-deoxyguanosine (8-OHdG), and malondialdehyde (MDA) levels in the Cr(VI) exposed workers exceeded those in the control subjects. Daily cumulative Cr(VI) exposure and urinary Cr were significantly correlated with urinary 8-OHdG levels following adjustments for covariates. A ten-fold increase in urinary Cr level was associated with a 1.73-fold increase in urinary 8-OHdG level. Daily cumulative Cr(VI) exposure and urinary Cr level were significantly correlated with urinary MDA level following adjustments for covariates. A ten-fold increase in urinary Cr was associated with a 1.45-fold increase in urinary MDA. Exposure to Cr(VI) increased oxidative DNA injury and the oxidative deterioration of lipids in electroplating workers.

Determination of Cr(VI) in wood specimen: A XANES study at the Cr K edge

International Nuclear Information System (INIS)

Strub, E.; Plarre, R.; Radtke, M.; Reinholz, U.; Riesemeier, H.; Schoknecht, U.; Urban, K.; Juengel, P.

2008-01-01

The content of chromium in different oxidation states in chromium-treated wood was studied with XANES (X-ray absorption near-edge structure) measurements at the Cr K absorption edge. It could be shown that wood samples treated with Cr(VI) (pine and beech) did still contain a measurable content of Cr(VI) after four weeks conditioning. If such wood samples were heat exposed for 2 h with 135 deg. C prior conditioning, Cr(VI) was no longer detected by XANES, indicating a complete reduction to chromium (III)

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.

Bioaccumulation and subcellular partitioning of Cr(III) and Cr(VI) in the freshwater green alga Chlamydomonas reinhardtii

Energy Technology Data Exchange (ETDEWEB)

Aharchaou, Imad [Laboratoire Interdisciplinaire des Environnements Continentaux, UMR 7360, Université de Lorraine and CNRS, 8 rue du Général Delestraint, 57070 Metz (France); Rosabal, Maikel; Liu, Fengjie [Institut National de la Recherche Scientifique, Centre Eau Terre Environnement (INRS-ETE), 490 rue de la Couronne, Québec (Québec) G1K 9A9 (Canada); Battaglia, Eric; Vignati, Davide A.L. [Laboratoire Interdisciplinaire des Environnements Continentaux, UMR 7360, Université de Lorraine and CNRS, 8 rue du Général Delestraint, 57070 Metz (France); Fortin, Claude, E-mail: claude.fortin@ete.inrs.ca [Institut National de la Recherche Scientifique, Centre Eau Terre Environnement (INRS-ETE), 490 rue de la Couronne, Québec (Québec) G1K 9A9 (Canada)

2017-01-15

Highlights: • C. reinhardtii accumulated similar levels of Cr(III) and Cr(VI). • The subcellular partitioning of Cr(III) and Cr(VI) was similar. • Cr(III) and Cr(VI) associated mainly with organelles and heat-stable proteins. • Metallomic analysis showed two main Cr-binding biomolecules after 72 h of exposure. - Abstract: Chromium occurs in aquatic environments under two main redox forms, namely Cr(III) and Cr(VI), with different geochemical and biochemical properties. Cr(VI) readily crosses biological membranes of living organisms and once inside the cells it undergoes a rapid reduction to Cr(III). The route of entry for the latter form is, however, poorly known. Using the radioactive tracer {sup 51}Cr we compared the accumulation (absorption and adsorption) of the two Cr forms by the green unicellular alga Chlamydomonas reinhardii after 1 h and 72 h of exposure to 100 nM of either Cr(III) or Cr(VI) at pH 7. Both Cr forms had similar accumulation, with a major part in the extracellular (adsorbed) fraction after 1 h and a major part of total accumulated Cr in the intracellular (absorbed) fraction after 72 h. We also investigated the intracellular partitioning of Cr using an operational fractionation scheme and found that both Cr forms had similar distributions among fractions: Cr was mostly associated with organelles (23 ± 12% after 1 h and 37 ± 7% after 72 h) and cytosolic heat-stable proteins and peptides (39 ± 18% after 1 h and 35 ± 3% after 72 h) fractions. Further investigations using a metallomic approach (SEC-ICP-MS) were performed with the heat-stable proteins and peptides fraction to compare the distribution of the two Cr forms among various biomolecules of this fraction. One Cr-binding biomolecule (∼28 kDa) appeared after 1 h of exposure for both Cr species. After 72 h another biomolecule of lower molecular weight (∼0.7 kDa) was involved in binding Cr and higher signal intensities were observed for Cr(VI) than for Cr(III). We show, for the

Bioaccumulation and subcellular partitioning of Cr(III) and Cr(VI) in the freshwater green alga Chlamydomonas reinhardtii

International Nuclear Information System (INIS)

Aharchaou, Imad; Rosabal, Maikel; Liu, Fengjie; Battaglia, Eric; Vignati, Davide A.L.; Fortin, Claude

2017-01-01

Highlights: • C. reinhardtii accumulated similar levels of Cr(III) and Cr(VI). • The subcellular partitioning of Cr(III) and Cr(VI) was similar. • Cr(III) and Cr(VI) associated mainly with organelles and heat-stable proteins. • Metallomic analysis showed two main Cr-binding biomolecules after 72 h of exposure. - Abstract: Chromium occurs in aquatic environments under two main redox forms, namely Cr(III) and Cr(VI), with different geochemical and biochemical properties. Cr(VI) readily crosses biological membranes of living organisms and once inside the cells it undergoes a rapid reduction to Cr(III). The route of entry for the latter form is, however, poorly known. Using the radioactive tracer "5"1Cr we compared the accumulation (absorption and adsorption) of the two Cr forms by the green unicellular alga Chlamydomonas reinhardii after 1 h and 72 h of exposure to 100 nM of either Cr(III) or Cr(VI) at pH 7. Both Cr forms had similar accumulation, with a major part in the extracellular (adsorbed) fraction after 1 h and a major part of total accumulated Cr in the intracellular (absorbed) fraction after 72 h. We also investigated the intracellular partitioning of Cr using an operational fractionation scheme and found that both Cr forms had similar distributions among fractions: Cr was mostly associated with organelles (23 ± 12% after 1 h and 37 ± 7% after 72 h) and cytosolic heat-stable proteins and peptides (39 ± 18% after 1 h and 35 ± 3% after 72 h) fractions. Further investigations using a metallomic approach (SEC-ICP-MS) were performed with the heat-stable proteins and peptides fraction to compare the distribution of the two Cr forms among various biomolecules of this fraction. One Cr-binding biomolecule (∼28 kDa) appeared after 1 h of exposure for both Cr species. After 72 h another biomolecule of lower molecular weight (∼0.7 kDa) was involved in binding Cr and higher signal intensities were observed for Cr(VI) than for Cr(III). We show, for the

Enhanced Cr(VI) removal by polyethylenimine- and phosphorus-codoped hierarchical porous carbons.

Science.gov (United States)

Chen, Shixia; Wang, Jun; Wu, Zeliang; Deng, Qiang; Tu, Wenfeng; Dai, Guiping; Zeng, Zheling; Deng, Shuguang

2018-08-01

The amino- and phosphorus-codoped (N,P-codoped) porous carbons derived from oil-tea shells were facilely fabricated through a combination of phosphoric acid (H 3 PO 4 ) activation and amino (polyethylenimine, PEI) modification method. The as-synthesized carbon adsorbents were systematically characterized and evaluated for Cr(VI) removal in aqueous solutions. The relationship between adsorbent properties and adsorption behaviors was illustrated. Moreover, the influences of contact time, initial Cr(VI) concentration, pH, coexisting anions and temperature were also investigated. The adsorption behavior of Cr(VI) could be perfectly described by the pseudo-second-order kinetic model and Sips adsorption model. The maximum adsorption capacity of Cr(VI) on the carbon adsorbents synthesized in this work was 355.0 mg/g, and this excellent Cr(VI) capacity could be sustained with other coexisting anions. In addition to high surface area and suitable pore size distribution, the high Cr(VI) removal capacity is induced by rich heteroatoms incorporation and the Cr(VI) removal mechanism was clearly illustrated. Furthermore, the continuous column breakthrough experiment on obtained N,P-codoped carbon was conducted and well fitted by the Thomas model. This work revealed that PEI modification and P-containing groups could significantly enhance Cr(VI) adsorption capacity and make these N,P-codoped biomass-derived carbons potent adsorbents in practical water treatment applications. Copyright © 2018 Elsevier Inc. All rights reserved.

Reduction of Cr(VI) in aqueous solution with DC diaphragm glow discharge

International Nuclear Information System (INIS)

Wang, Xiaoyan; Jin, Xinglong; Zhou, Minghua; Chen, Zhenhai; Deng, Kai

2013-01-01

This paper investigated the reduction of Cr(VI) in aqueous solution with direct current diaphragm glow discharge (DGD). The glow discharge sustained around the hole on a quartz tube which divided the electrolyte cell into two parts. The reduction efficiencies of Cr(VI) under different applied voltages, initial conductivities, hole diameters, hole numbers, initial pH values and initial concentrations were systematically studied. The results showed that the reduction efficiency of Cr(VI) increased with the increase of applied voltage, initial conductivity, hole diameter and hole number. The different initial pH values showed less effects on the reduction of Cr(VI). The reduction efficiency decreased with the increasing initial concentration. In addition, the simultaneous reduction of Cr(VI) and decolorization of acid orange (AO) with DGD were also fulfilled. Furthermore, the energy efficiency for Cr(VI) reduction with DGD was calculated and compared with those in photocatalysis and other glow discharge reactor

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

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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.

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 (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.

Preparation of Silk Sericin/Lignin Blend Beads for the Removal of Hexavalent Chromium Ions

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Kwak, Hyo Won; Shin, Munju; Yun, Haesung; Lee, Ki Hoon

2016-01-01

In the present study, novel adsorbents having high adsorption capability and reusability were prepared using agricultural by-products: silk sericin and lignin. Silk sericin and lignin blend beads were successfully prepared using simple coagulation methods for the removal of hexavalent chromium (Cr(VI)) from aqueous solution. A 1 M lithium chloride (LiCl)/dimethyl sulfoxide (DMSO) solvent system successfully dissolved both sericin and lignin and had sufficient viscosity for bead preparation. Compared to the conventional sericin bead adsorbent, sericin/lignin blend beads showed higher Cr(VI) adsorption capacity. The amount of lignin added to the adsorbent greatly affected the adsorption capacity of the beads, and a 50:50 sericin/lignin blend ratio was optimal. Adsorption behavior followed the Freundlich isotherm, which means the adsorption of Cr(VI) occurred on the heterogeneous surface. Cr(VI) adsorption capability increased with temperature because of thermodynamic-kinetic effects. In addition, over 90% of Cr(VI) ions were recovered from the Cr(VI) adsorbed sericin/lignin beads in a 1 M NaOH solution. The adsorption-desorption recycling process was stable for more than seven cycles, and the recycling efficiency was 82%. It is expected that the sericin/lignin beads could be successfully applied in wastewater remediation especially for hazardous Cr(VI) ions in industrial wastewater. PMID:27598142

Preparation of Silk Sericin/Lignin Blend Beads for the Removal of Hexavalent Chromium Ions

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Hyo Won Kwak

2016-09-01

Full Text Available In the present study, novel adsorbents having high adsorption capability and reusability were prepared using agricultural by-products: silk sericin and lignin. Silk sericin and lignin blend beads were successfully prepared using simple coagulation methods for the removal of hexavalent chromium (Cr(VI from aqueous solution. A 1 M lithium chloride (LiCl/dimethyl sulfoxide (DMSO solvent system successfully dissolved both sericin and lignin and had sufficient viscosity for bead preparation. Compared to the conventional sericin bead adsorbent, sericin/lignin blend beads showed higher Cr(VI adsorption capacity. The amount of lignin added to the adsorbent greatly affected the adsorption capacity of the beads, and a 50:50 sericin/lignin blend ratio was optimal. Adsorption behavior followed the Freundlich isotherm, which means the adsorption of Cr(VI occurred on the heterogeneous surface. Cr(VI adsorption capability increased with temperature because of thermodynamic-kinetic effects. In addition, over 90% of Cr(VI ions were recovered from the Cr(VI adsorbed sericin/lignin beads in a 1 M NaOH solution. The adsorption-desorption recycling process was stable for more than seven cycles, and the recycling efficiency was 82%. It is expected that the sericin/lignin beads could be successfully applied in wastewater remediation especially for hazardous Cr(VI ions in industrial wastewater.

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

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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.

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

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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.

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.

The cytotoxicity and genotoxicity of particulate and soluble hexavalent chromium in leatherback sea turtle lung cells.

Science.gov (United States)

Speer, Rachel M; Wise, Catherine F; Young, Jamie L; Aboueissa, AbouEl-Makarim; Martin Bras, Mark; Barandiaran, Mike; Bermúdez, Erick; Márquez-D'Acunti, Lirio; Wise, John Pierce

2018-05-01

Hexavalent chromium [Cr(VI)] is a marine pollution of concern as recent studies show it has a global distribution, with some regions showing high Cr concentrations in marine animal tissue, and it is extensively used. Leatherback sea turtles (Dermochelys coriacea) are an endangered marine species that may experience prolonged exposures to environmental contaminants including Cr(VI). Human activities have led to global Cr(VI) contamination of the marine environment. While Cr(VI) has been identified as a known human carcinogen, the health effects in marine species are poorly understood. In this study, we assessed the cytotoxic and genotoxic effects of particulate and soluble Cr(VI) in leatherback sea turtle lung cells. Both particulate and soluble Cr(VI) induced a concentration-dependent increase in cytotoxicity. Next, using a chromosome aberration assay, we assessed the genotoxic effects of Cr(VI) in leatherback sea turtle lung cells. Particulate and soluble Cr(VI) induced a concentration-dependent increase in clastogenicity in leatherback sea turtle lung cells. These data indicate that Cr(VI) may be a health concern for leatherback sea turtles and other long-lived marine species. Additionally, these data provide foundational support to use leatherback sea turtles as a valuable model species for monitoring the health effects of Cr(VI) in the environment and possibly as an indicator species to assess environmental human exposures and effects. Copyright © 2018 Elsevier B.V. All rights reserved.

Hexavalent chromium adsorption from aqueous solution using carbon nano-onions (CNOs).

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Sakulthaew, Chainarong; Chokejaroenrat, Chanat; Poapolathep, Amnart; Satapanajaru, Tunlawit; Poapolathep, Saranya

2017-10-01

The capacity of carbon nano-onions (CNOs) to remove hexavalent chromium (Cr(VI)) from aqueous solution was investigated. Batch experiments were performed to quantify the effects of the dosage rate, pH, counter ions, and temperature. The adsorption of Cr(VI) onto CNOs was best described by a pseudo-second order rate expression. The adsorption efficiency increased with increasing adsorbent dosage and contact time and reached equilibrium in 24 h. The equilibrium data showed better compliance with a Langmuir isotherm than a Freundlich isotherm. Effective removal of Cr(VI) was demonstrated at pH values ranging from 2 to 10. The adsorption capacity of Cr(VI) was found to be highest (82%) at pH 3.4 and greatly depended on the solution pH. We found that Cr(VI) adsorption decreased with increasing pH over the pH range of 3.4-10. The adsorption capacity increased dramatically when the temperature increased from 10 °C to 50 °C regardless of the amount of CNOs used. Cr(VI) removal decreased by ∼13% when Zn(II), Cu(II), and Pb(II) were present, while there were no significant changes observed when NO 3 - or SO 4 2- was present. The overall results support that CNOs can be used as an alternative adsorbent material to remove Cr(VI) in the water treatment industry. Copyright © 2017 Elsevier Ltd. All rights reserved.

Enhancement strategies for Cu(II), Cr(III) and Cr(VI) remediation by a variety of seaweed species.

Science.gov (United States)

Murphy, V; Hughes, H; McLoughlin, P

2009-07-15

Various chemical treatments have been applied to six brown, red and green seaweed species with a view to enhancing their metal removal for Cu(II), Cr(III) and Cr(VI). Treatment with acetone resulted in the greatest enhancement for both cationic and anionic species with relatively low mass losses (15-35%), indicating its low risk to biomass operational stability. Cation binding was increased by 69%, while the total Cr removal was augmented by 15%. Cr(VI) binding was shown to be an adsorption-coupled reduction, whereby Cr(VI) was bound to the biomass surface at pH 2 and subsequently reduced to Cr(III). Acetone treatment also resulted in biomasses that were capable of converting up to 83% of Cr(VI) in solution to Cr(III). Blocking of carboxyl and amino functionalities had significant negative effects both on total Cr removal as well as percentage conversion of Cr(VI) to Cr(III). Results therefore indicated the significant role played by these moieties in metal binding to these seaweeds. Potentiometric titrations displayed agreement between the degree of esterification and the decrease in Cu(II) removal for Ulva spp. and Polysiphonia lanosa. FTIR analysis identified changes in biomass functionality and availability after chemical modification, the results of which were in agreement with metal removal studies. In conclusion, these biosorbents represent suitable candidates to replace conventional removal technologies for metal bearing wastewaters, in particular for the detoxification of hazardous Cr(VI) waste streams.

Alkaline hydrothermal stabilization of Cr(VI) in soil using glass and aluminum from recycled municipal solid wastes.

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Gattullo, Concetta Eliana; D'Alessandro, Caterina; Allegretta, Ignazio; Porfido, Carlo; Spagnuolo, Matteo; Terzano, Roberto

2018-02-15

Hexavalent chromium was stabilized in soil by using a mixture of glass and aluminum recovered from municipal solid wastes under alkaline hydrothermal conditions. Cr(VI) concentration was reduced by 94-98% already after 7days of treatment. After the same period, more than 90% of total Cr was stabilized in highly recalcitrant and scarcely mobile chemical forms, with 50% in the residual fraction (when the samples were treated at 1/10w/w mixture/soil ratio). Longer treatments increased Cr stabilization. X-ray microanalyses revealed that Cr was stabilized in geopolymeric structures within large aluminosilicate mineral aggregates (containing both amorphous and crystalline phases). 3D microstructural analyses showed a limited compaction of the soil with still a 20% internal porosity in the neoformed aggregates. Increased pH and salinity after the treatment can be restored by simple soil amendments and washing. Copyright © 2017. Published by Elsevier B.V.

Removal of Cr(VI from Water Using a New Reactive Material: Magnesium Oxide Supported Nanoscale Zero-Valent Iron

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Alessio Siciliano

2016-08-01

Full Text Available The chromium pollution of water is an important environmental and health issue. Cr(VI removal by means of metallic iron is an attractive method. Specifically, nanoscopic zero valent iron (NZVI shows great reactivity, however, its applicability needs to be further investigated. In the present paper, NZVI was supported on MgO grains to facilitate the treatments for remediation of chromium-contaminated waters. The performances and mechanisms of the developed composite, in the removal of hexavalent chromium, were investigated by means of batch and continuous tests. Kinetic studies, under different operating conditions, showed that reduction of Cr(VI could be expressed by a pseudo second-order reaction kinetic. The reaction rate increased with the square of Fe(0 amount, while it was inversely proportional to the initial chromium concentration. The process performance was satisfactory also under uncontrolled pH, and a limited influence of temperature was observed. The reactive material was efficiently reusable for many cycles without any regeneration treatment. The performances in continuous tests were close to 97% for about 80 pore volume of reactive material.

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

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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.

Molasses as an efficient low-cost carbon source for biological Cr(VI) removal

Energy Technology Data Exchange (ETDEWEB)

Michailides, Michail K. [Department of Environmental and Natural Resources Management, University of Patras, 2 G. Seferi Str., GR-30100 Agrinio (Greece); Tekerlekopoulou, Athanasia G., E-mail: atekerle@upatras.gr [Department of Environmental and Natural Resources Management, University of Patras, 2 G. Seferi Str., GR-30100 Agrinio (Greece); Akratos, Christos S.; Coles, Sandra [Department of Environmental and Natural Resources Management, University of Patras, 2 G. Seferi Str., GR-30100 Agrinio (Greece); Pavlou, Stavros [Institute of Chemical Engineering Sciences (FORTH/ICE-HT), Stadiou Str., Platani, P.O. Box 1414, GR-26504 Patras (Greece); Department of Chemical Engineering, University of Patras, GR-26504 Patras (Greece); Vayenas, Dimitrios V. [Department of Environmental and Natural Resources Management, University of Patras, 2 G. Seferi Str., GR-30100 Agrinio (Greece); Institute of Chemical Engineering Sciences (FORTH/ICE-HT), Stadiou Str., Platani, P.O. Box 1414, GR-26504 Patras (Greece)

2015-01-08

Highlights: • Suspended and attached growth reactors were examined for Cr(VI) bio-reduction. • Molasses was proved an efficient and very low cost carbon source. • Molasses was more efficient than sugar in enhancing Cr(VI) reduction. • SBR with recirculation was the most proper operating mode. - Abstract: In the present study, indigenous microorganisms from industrial sludge were used to reduce the activity of Cr(VI). Molasses, a by-product of sugar processing, was selected as the carbon source (instead of sugar used in a previous work) as it is a low-cost energy source for bioprocesses. Initially, experiments were carried out in suspended growth batch reactors for Cr(VI) concentrations of 1.5–110 mg/L. The time required for complete Cr(VI) reduction increased with initial Cr(VI) concentration. Initial molasses concentration was also found to influence the Cr(VI) reduction rate. The optimal concentration for all initial Cr(VI) concentrations tested was 0.8 gC/L. Experiments were also carried out in packed-bed reactors. Three different operating modes were used to investigate the optimal performance and efficiency of the filter, i.e. batch, continuous and SBR with recirculation. The latter mode with a recirculation rate of 0.5 L/min lead to significantly high Cr(VI) reduction rates (up to 135 g/m{sup 2} d). The results of this work were compared with those of a similar work using sugar as the carbon source and indicate that molasses could prove a feasible technological solution to a serious environmental problem.

The Reduction of Cr(VI) to Cr(III) by Natural Fe-Bearing Minerals: A Synchrotron XAS Study

Science.gov (United States)

Xu, H.; Guo, X.; Ding, M.; Migdissov, A. A.; Boukhalfa, H.; Sun, C.; Roback, R. C.; Reimus, P. W.; Katzman, D.

2017-12-01

Cr(VI) in the form of CrO42- is a pollutant species in groundwater and soils that can pose health and environmental problems. Cr(VI) associated with use as a corrosion inhibitor at a power plant from 1956-1972 is present in a deep groundwater aquifer at Los Alamos National Laboratory. A potential remediation strategy for the Cr contamination is reduction of Cr(VI) to Cr(III) via the acceptance of electrons from naturally occurring or induced Fe(II) occurring in Fe-bearing minerals. In this work, using synchrotron-based X-ray techniques, we investigated the Cr reduction behavior by Fe-bearing minerals from outcrop and core samples representative of the contaminated portion of the aquifer. Samples were exposed to solutions with a range of known Cr (VI) concentrations. XANES and EXAFS spectra showed that all the Cr(VI) had been reduced to Cr(III), and micro XRF mapping revealed close correlation of Cr and Fe distribution, implying that Fe(II) in minerals reduced Cr(VI) in the solution. Similar behavior was observed from in-situ XANES measurements on Cr reduction and adsorption by mineral separates from the rock samples in Cr(VI)-bearing solutions. In addition, to obtain reference parameters for interpreting the data of natural samples, we collected Cr and Fe EXAFS spectra of Cr(III)-Fe(III) hydroxide solid solutions, which show progressive changes in the local structure around Cr and Fe over the whole series.

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)

Hexavalent and total chromium at low reporting concentrations in source-water aquifers and surface waters used for public supply in Illinois, 2013

Science.gov (United States)

Mills, Patrick C.; Cobb, Richard P.

2015-01-01

On the basis of their recent review of the human health effects of hexavalent chromium [Cr(VI)] in public drinking water, the U.S. Environmental Protection Agency is considering the need for Federal regulation of Cr(VI). Presently, only total chromium is regulated, at a Maximum Contaminant Level (MCL) of 100 micrograms per liter (µg/L). The occurrence of Cr(VI) in groundwater and surface waters generally is attributed to industrial sources, but can be of natural origin. California’s recently established MCL for Cr(VI) of 10 µg/L illustrates the drinking-water concerns associated with Cr(VI). To improve understanding of the possible impact of a Cr(VI)-specific standard that approximates the California level on the management of Illinois’ public drinking water, the U.S. Geological Survey, in cooperation with the Illinois Environmental Protection Agency, assessed the occurrence and distribution of Cr(VI) in the State’s public-water supplies.

Punica granatum L. protects mice against hexavalent chromium-induced genotoxicity

Directory of Open Access Journals (Sweden)

Renato Ivan de Ávila

2013-12-01

Full Text Available This study investigated the chemoprotective effects of Punica granatum L. (Punicaceae fruits alcoholic extract (PGE on mice exposed to hexavalent chromium [Cr(VI]. Animals were pretreated with PGE (25, 50 or 75 mg/kg/day for 10 days and subsequently exposed to a sub-lethal dose of Cr(VI (30 mg/kg. The frequency of micronucleated polychromatic erythrocytes in the bone marrow was investigated and the Cr(VI levels were measured in the kidneys, liver and plasm. For the survival analysis, mice were previously treated with PGE for 10 days and exposed to a single lethal dose of Cr(VI (50 mg/kg. Exposure to a sub-lethal dose of Cr(VI induced a significant increase in the frequency of micronucleated cells. However, the prophylactic treatment with PGE led to a reduction of 44.5% (25 mg/kg, 86.3% (50 mg/kg and 64.2% (75 mg/kg in the incidence of micronuclei. In addition, the 50 mg/kg dose of PGE produced a higher chemoprotective effect, since the survival rate was 90%, when compared to that of the non-treated group. In these animals, reduced amounts of chromium were detected in the biological materials, in comparison with the other groups. Taken together, the results demonstrated that PGE exerts a protective effect against Cr(VI-induced genotoxicity.

A Novel Early Warning System Based on a Sediment Microbial Fuel Cell for In Situ and Real Time Hexavalent Chromium Detection in Industrial Wastewater.

Science.gov (United States)

Zhao, Shuai; Liu, Pu; Niu, Yongyan; Chen, Zhengjun; Khan, Aman; Zhang, Pengyun; Li, Xiangkai

2018-02-22

Hexavalent chromium (Cr(VI)) is a well-known toxic heavy metal in industrial wastewater, but in situ and real time monitoring cannot be achieved by current methods used during industrial wastewater treatment processes. In this study, a Sediment Microbial Fuel Cell (SMFC) was used as a biosensor for in situ real-time monitoring of Cr(VI), which was the organic substrate is oxidized in the anode and Cr(VI) is reduced at the cathode simultaneously. The pH 6.4 and temperature 25 °C were optimal conditions for the operation. Under the optimal conditions, linearity (R² = 0.9935) of the generated voltage was observed in the Cr(VI) concentration range from 0.2 to 0.7 mg/L. The system showed high specificity for Cr(VI), as other co-existing ions such as Cu 2+ , Zn 2+ , and Pb 2+ did not interfere with Cr(VI) detection. In addition, when the sediment MFC-based biosensor was applied for measuring Cr(VI) in actual wastewater samples, a low deviation (real time in situ detection of Cr(VI) in industrial wastewaters.

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

Science.gov (United States)

Qurie, Mohannad; Khamis, Mustafa; Manassra, Adnan; Ayyad, Ibrahim; Nir, Shlomo; Scrano, Laura; Bufo, Sabino A.; Karaman, Rafik

2013-01-01

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. PMID:24222757

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

International Nuclear Information System (INIS)

Zakaria, Zainul Akmar; Zakaria, Zainoha; Surif, Salmijah; Ahmad, Wan Azlina

2007-01-01

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 -1 of Cr(VI) was reduced at a flow rate of 8.0 mL min -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

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.

Removal of hexavalent Cr by coconut coir and derived chars--the effect of surface functionality.

Science.gov (United States)

Shen, Ying-Shuian; Wang, Shan-Li; Tzou, Yu-Min; Yan, Ya-Yi; Kuan, Wen-Hui

2012-01-01

The Cr(VI) removal by coconut coir (CC) and chars obtained at various pyrolysis temperatures were evaluated. Increasing the pyrolysis temperature resulted in an increased surface area of the chars, while the corresponding content of oxygen-containing functional groups of the chars decreased. The Cr(VI) removal by CC and CC-derived chars was primarily attributed to the reduction of Cr(VI) to Cr(III) by the materials and the extent and rate of the Cr(VI) reduction were determined by the oxygen-containing functional groups in the materials. The contribution of pure Cr(VI) adsorption to the overall Cr(VI) removal became relatively significant for the chars obtained at higher temperatures. Accordingly, to develop a cost-effective method for removing Cr(VI) from water, the original CC is more advantageous than the carbonaceous counterparts because no pyrolysis is required for the application and CC has a higher content of functional groups for reducing Cr(VI) to less toxic Cr(III). Copyright © 2011 Elsevier Ltd. All rights reserved.

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

Characterization of Cr(VI) removal from aqueous solutions by a surplus agricultural waste-Rice straw

International Nuclear Information System (INIS)

Gao Hui; Liu Yunguo; Zeng Guangming; Xu Weihua; Li Ting; Xia Wenbin

2008-01-01

The removal of Cr(VI) from aqueous solution by rice straw, a surplus agricultural byproduct was investigated. The optimal pH was 2.0 and Cr(VI) removal rate increased with decreased Cr(VI) concentration and with increased temperature. Decrease in straw particle size led to an increase in Cr(VI) removal. Equilibrium was achieved in about 48 h under standard conditions, and Cr(III), which appeared in the solution and remained stable thereafter, indicating that both reduction and adsorption played a part in the Cr(VI) removal. The increase of the solution pH suggested that protons were needed for the Cr(VI) removal. A relatively high level of NO 3 - notably restrained the reduction of Cr(VI) to Cr(III), while high level of SO 4 2- supported it. The promotion of the tartaric acid modified rice straw (TARS) and the slight inhibition of the esterified rice straw (ERS) on Cr(VI) removal indicated that carboxyl groups present on the biomass played an important role in chromium remediation even though were not fully responsible for it. Isotherm tests showed that equilibrium sorption data were better represented by Langmuir model and the sorption capacity of rice straw was found to be 3.15 mg/g

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

Study of Cr(VI) adsorption onto magnetite nanoparticles using synchrotron-based X-ray absorption spectroscopy

Science.gov (United States)

Chen, Yen-Hua; Liu, Dian-Yu; Lee, Jyh-Fu

2018-04-01

In this study, the efficiency of Cr(VI) adsorption onto nano-magnetite was examined by batch experiments, and the Cr(VI) adsorption mechanism was investigated using synchrotron-based X-ray absorption spectroscopy. Magnetite nanoparticles with a mean diameter of 10 nm were synthesized using an inexpensive and simple co-precipitation method. It shows a saturation magnetization of 54.3 emu/g, which can be recovered with an external magnetic field. The adsorption data fitted the Langmuir adsorption isotherm well, implying a monolayer adsorption behavior of Cr(VI) onto nano-magnetite. X-ray absorption spectroscopy results indicate that the adsorption mechanism involves electron transfer between Fe(II) in nano-magnetite (Fe2+OFe3+ 2O3) and Cr(VI) to transform into Cr(III), which may exist as an Fe(III)-Cr(III) mixed solid phase. Moreover, the Cr(III)/Cr(VI) ratio in the final products can be determined by the characteristic pre-edge peak area of Cr(VI) in the Cr K-edge spectrum. These findings suggest that nano-magnetite is effective for Cr(VI) removal from wastewater because it can transform highly poisonous Cr(VI) species into nontoxic Cr(III) compounds, which are highly insoluble and immobile under environmental conditions.

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.

Influence of chemical compositions and molecular weights of humic acids on Cr(VI) photo-reduction

International Nuclear Information System (INIS)

Chen, S.Y.; Huang, S.W.; Chiang, P.N.; Liu, J.C.; Kuan, W.H.; Huang, J.H.; Hung, J.T.; Tzou, Y.M.; Chen, C.C.; Wang, M.K.

2011-01-01

Highlights: ► Low molecular weights (M w ) of HA bear more polar and aromatic C in its structure. ► The polar sites of HA dominate the photo-reduction of Cr(VI). ► Low M w of HA exhibits greater photochemical efficiency for Cr(VI) reduction. ► Cr(VI) adsorption on HA is indiscernible, particularly on the small M w of HA. ► Upon Cr(VI) reduction by HA, most of Cr(III) are released into the solution. - Abstract: Humic acids (HA) strongly affect the fate of trace metals in soils and aquatic environments. One of the remarkable properties of HA is its ability to reduce Cr(VI), an extremely toxic anion. However, it is unclear which HA components are involved in Cr(VI) reduction and possess the photo-induced properties. In this study, an ultrafiltration technique was used to fractionate HAs into four fractions of different nominal molecular weights (M w ): >100, 50–100, 10–50 and w HA was enriched with polar and aromatic domains. These polar, including polar C in aliphatic region, and aromatic groups were the major sites for Cr(VI) reduction because they disappeared rapidly upon interaction with Cr(VI). As a result, low M w of HA exhibited greater efficiency of Cr(VI) reduction. Light induced the rapid transfer of electrons between chromate-phenol/carboxyl ester, or the formation of peroxide radicals or H 2 O 2 through the ready decay of peroxy radicals associated with polar substituents, explained the rapid scavenging of Cr(VI) on polar and aromatic groups of HAs under illumination.

Elemental sulfur amendment decreases bio-available Cr-VI in soils impacted by leather tanneries.

Science.gov (United States)

Shi, Jingjing; Chen, Hualin; Arocena, Joselito M; Whitcombe, Todd; Thring, Ronald W; Memiaghe, Jeff Nze

2016-05-01

This study investigated the potential use of elemental S (S(0)) to convert Cr-VI to Cr-III which should decrease the bio-availability hence, toxicity of Cr-VI in soils. The bio-available fraction of Cr in soil was measured by phosphate buffer extraction (PBE) and the results showed that the fraction is about 10% of the total Cr-VI and varied from 12.8 to 42.5 mg kg(-1). The addition of 4.0 mg g(-1) S(0) decreased PBE Cr-VI to soils. Synchrotron-based X-ray absorption near-edge structure (XANES), X-ray fluorescence (XRF) and micro-XRD revealed that Cr-III was the dominant species (99% of total Cr) and Cr was retained by hematite and goethite in soil. Fe-containing minerals may have provided sufficient protection to render the dominant Cr-III species biochemically inert to redox processes in soils. It is concluded that S(0)amendment is a promising approach to remediate Cr-VI contaminated soils. Copyright © 2016 Elsevier Ltd. All rights reserved.

combined effect of polyaniline emeraldine salt for removal of Cr(VI)

Indian Academy of Sciences (India)

Cr(VI) ion is one of the major industrial wastes as dichromate and chromate ions are ... more [9–12]. For the toxic nature of Cr(VI) in aqueous medium, it becomes a ... techniques such as adsorption [13–15], chemical reduction. [16], reverse ...

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.

Hexavalent chromium reduction by bacterial consortia and pure strains from an alkaline industrial effluent.

Science.gov (United States)

Piñón-Castillo, H A; Brito, E M S; Goñi-Urriza, M; Guyoneaud, R; Duran, R; Nevarez-Moorillon, G V; Gutiérrez-Corona, J F; Caretta, C A; Reyna-López, G E

2010-12-01

To characterize the bacterial consortia and isolates selected for their role in hexavalent chromium removal by adsorption and reduction. Bacterial consortia from industrial wastes revealed significant Cr(VI) removal after 15 days when incubated in medium M9 at pH 6·5 and 8·0. The results suggested chromium reduction. The bacterial consortia diversity (T-RFLP based on 16S rRNA gene) indicated a highest number of operational taxonomic units in an alkaline carbonate medium mimicking in situ conditions. However, incubations under such conditions revealed low Cr(VI) removal. Genomic libraries were obtained for the consortia exhibiting optimal Cr(VI) removal (M9 medium at pH 6·5 and 8·0). They revealed the dominance of 16S rRNA gene sequences related to the genera Pseudomonas/Stenotrophomonas or Enterobacter/Halomonas, respectively. Isolates related to Pseudomonas fluorescens and Enterobacter aerogenes were efficient in Cr(VI) reduction and adsorption to the biomass. Cr(VI) reduction was better at neutral pH rather than under in situ conditions (alkaline pH with carbonate). Isolated strains exhibited significant capacity for Cr(VI) reduction and adsorption. Bacterial communities from chromium-contaminated industrial wastes as well as isolates were able to remove Cr(VI). The results suggest a good potential for bioremediation of industrial wastes when optimal conditions are applied. Journal of Applied Microbiology © 2010 The Society for Applied Microbiology. No claim to Mexican Government works.

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

An electrochemical study of U(VI) and Cr(VI) in molten borates

International Nuclear Information System (INIS)

Brigaudeau, M.; Gregori de Pinochet, I. de

1977-01-01

The electrochemical reduction of U(VI) and Cr(VI), in molten Na 2 B 4 O 7 at 800 deg C was studied by means of linear sweep voltammetry, and chronopotentiometry. The reduction of U(VI) to U(V) proceeded reversibly at a platinum electrode. The diffusion coefficient for the U(VI) species at 800 deg C was 4.10 -7 cm 2 .s -1 . The activation energy of diffusion was (34,8 +- 0,8) kcal. mole -1 . Electrochemical studies of Cr(VI) at 800 0 C reveal a two-step reduction process at a platinum electrode. Only the voltammogram for the first step charge transfer process was studied. Analysis indicated that Cr(VI) is reversibly reduced to Cr(III) at a platinum electrode. The diffusion coefficient for Cr(VI) at 800 0 C is 1,9.10 -7 cm 2 .s -1 [fr

Influence of chemical compositions and molecular weights of humic acids on Cr(VI) photo-reduction

Energy Technology Data Exchange (ETDEWEB)

Chen, S.Y.; Huang, S.W. [Department of Soil and Environmental Sciences, National Chung Hsing University, Taichung, 40227 Taiwan, ROC (China); Chiang, P.N. [The Experimental Forest, National Taiwan University, Nantou, 55743 Taiwan, ROC (China); Liu, J.C. [Agricultural Research Institute No. 189, Jhongjheng Rd., Wufong, Taichung County, 41301 Taiwan, ROC (China); Kuan, W.H. [Department of Safety, Health, and Environmental Engineering, Ming Chi University of Technology, Taishan, Taipei, 24301 Taiwan, ROC (China); Huang, J.H. [Department of Soil and Environmental Sciences, National Chung Hsing University, Taichung, 40227 Taiwan, ROC (China); Hung, J.T. [Department of Horticulture, National Taitung Junior College, Taitung, 95045 Taiwan, ROC (China); Tzou, Y.M., E-mail: ymtzou@dragon.nchu.edu.tw [Department of Soil and Environmental Sciences, National Chung Hsing University, Taichung, 40227 Taiwan, ROC (China); Chen, C.C. [Department of Life Science, National Taiwan Normal University, Taipei, 116 Taiwan, ROC (China); Wang, M.K. [Department of Agricultural Chemistry, National Taiwan University, Taipei, 10617 Taiwan, ROC (China)

2011-12-15

Highlights: Black-Right-Pointing-Pointer Low molecular weights (M{sub w}) of HA bear more polar and aromatic C in its structure. Black-Right-Pointing-Pointer The polar sites of HA dominate the photo-reduction of Cr(VI). Black-Right-Pointing-Pointer Low M{sub w} of HA exhibits greater photochemical efficiency for Cr(VI) reduction. Black-Right-Pointing-Pointer Cr(VI) adsorption on HA is indiscernible, particularly on the small M{sub w} of HA. Black-Right-Pointing-Pointer Upon Cr(VI) reduction by HA, most of Cr(III) are released into the solution. - Abstract: Humic acids (HA) strongly affect the fate of trace metals in soils and aquatic environments. One of the remarkable properties of HA is its ability to reduce Cr(VI), an extremely toxic anion. However, it is unclear which HA components are involved in Cr(VI) reduction and possess the photo-induced properties. In this study, an ultrafiltration technique was used to fractionate HAs into four fractions of different nominal molecular weights (M{sub w}): >100, 50-100, 10-50 and <10 kDa. Each HA fraction was characterized by spectroscopic analyses followed by examining Cr(VI) removal on each fraction of HA at pH 1-5. Spectroscopic results indicated that low-M{sub w} HA was enriched with polar and aromatic domains. These polar, including polar C in aliphatic region, and aromatic groups were the major sites for Cr(VI) reduction because they disappeared rapidly upon interaction with Cr(VI). As a result, low M{sub w} of HA exhibited greater efficiency of Cr(VI) reduction. Light induced the rapid transfer of electrons between chromate-phenol/carboxyl ester, or the formation of peroxide radicals or H{sub 2}O{sub 2} through the ready decay of peroxy radicals associated with polar substituents, explained the rapid scavenging of Cr(VI) on polar and aromatic groups of HAs under illumination.

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

KAUST Repository

Tang, Samuel C N; Wang, Peng; Yin, Ke; Lo., Irene Man Chi

2010-01-01

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.

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.

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

International Nuclear Information System (INIS)

Qi, Wenfang; Zhao, Yingxin; Zheng, Xinyi; Ji, Min; Zhang, Zhenya

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"−"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"−"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_4"3"− > SO_4"2"− > Cl"−. - 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"−"1 at pH 1.0. The presence of Cl"−, SO_4"2"− and PO_4"3"− would lead to an obvious negative effect on Cr(VI) adsorption, and their influence order follows PO_4"3"− > SO_4"2"− > Cl"−. The study developed a new way to reutilize wastes and showed a great potential for resource recycling.

Prolonged Particulate Hexavalent Chromium Exposure Suppresses Homologous Recombination Repair in Human Lung Cells.

Science.gov (United States)

Browning, Cynthia L; Qin, Qin; Kelly, Deborah F; Prakash, Rohit; Vanoli, Fabio; Jasin, Maria; Wise, John Pierce

2016-09-01

Genomic instability is one of the primary models of carcinogenesis and a feature of almost all cancers. Homologous recombination (HR) repair protects against genomic instability by maintaining high genomic fidelity during the repair of DNA double strand breaks. The defining step of HR repair is the formation of the Rad51 nucleofilament, which facilitates the search for a homologous sequence and invasion of the template DNA strand. Particulate hexavalent chromium (Cr(VI)), a human lung carcinogen, induces DNA double strand breaks and chromosome instability. Since the loss of HR repair increases Cr(VI)-induced chromosome instability, we investigated the effect of extended Cr(VI) exposure on HR repair. We show acute (24 h) Cr(VI) exposure induces a normal HR repair response. In contrast, prolonged (120 h) exposure to particulate Cr(VI) inhibited HR repair and Rad51 nucleofilament formation. Prolonged Cr(VI) exposure had a profound effect on Rad51, evidenced by reduced protein levels and Rad51 mislocalization to the cytoplasm. The response of proteins involved in Rad51 nuclear import and nucleofilament formation displayed varying responses to prolonged Cr(VI) exposure. BRCA2 formed nuclear foci after prolonged Cr(VI) exposure, while Rad51C foci formation was suppressed. These results suggest that particulate Cr(VI), a major chemical carcinogen, inhibits HR repair by targeting Rad51, causing DNA double strand breaks to be repaired by a low fidelity, Rad51-independent repair pathway. These results further enhance our understanding of the underlying mechanism of Cr(VI)-induced chromosome instability and thus, carcinogenesis. © The Author 2016. Published by Oxford University Press on behalf of the Society of Toxicology. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com.

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. Copyright © 2016 Elsevier Ltd. All rights reserved.

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.

Hexavalent chromium is cytotoxic and genotoxic to hawksbill sea turtle cells

International Nuclear Information System (INIS)

Wise, Sandra S.; Xie, Hong; Fukuda, Tomokazu; Douglas Thompson, W.

2014-01-01

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 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 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

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

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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.

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

Science.gov (United States)

2011-05-12

RDT&E Progress and Plans for Hexavalent Chromium (Cr6+) Bruce Sartwell Weapons Systems and Platforms Program Manager E2S2 Conference May 12, 2011...2011 2. REPORT TYPE 3. DATES COVERED 00-00-2011 to 00-00-2011 4. TITLE AND SUBTITLE RDT&E Progress and Plansfor Hexavalent Chromium (Cr6+) 5a...Development of Accelerated Corrosion Test Protocols Alternatives to Hex Chrome and Cadmium Plating Alternatives to Hex Chrome Pretreatments

Hexavalent chromium causes the oxidation of thioredoxin in human bronchial epithelial cells

International Nuclear Information System (INIS)

Myers, Judith M.; Antholine, William E.; Myers, Charles R.

2008-01-01

Hexavalent chromium [Cr(VI)] species such as chromates are cytotoxic. Inhalational exposure is a primary concern in many Cr-related industries and their immediate environments, and bronchial epithelial cells are directly exposed to inhaled Cr(VI). Chromates are readily taken up by cells and are reduced to reactive Cr species which may also result in the generation of reactive oxygen species (ROS). The thioredoxin (Trx) system has a key role in the maintenance of cellular thiol redox balance and is essential for cell survival. Cells normally maintain the cytosolic (Trx1) and mitochondrial (Trx2) thioredoxins largely in the reduced state. Redox Western blots were used to assess the redox status of the thioredoxins in normal human bronchial epithelial cells (BEAS-2B) incubated with soluble Na 2 CrO 4 or insoluble ZnCrO 4 for different periods of time. Both chromates caused a dose- and time-dependent oxidation of Trx2 and Trx1. Trx2 was more susceptible in that it could all be converted to the oxidized form, whereas a small amount of reduced Trx1 remained even after prolonged treatment with higher Cr concentrations. Only one of the dithiols, presumably the active site, of Trx1 was oxidized by Cr(VI). Cr(VI) did not cause significant GSH depletion or oxidation indicating that Trx oxidation does not result from a general oxidation of cellular thiols. With purified Trx and thioredoxin reductase (TrxR) in vitro, Cr(VI) also resulted in Trx oxidation. It was determined that purified TrxR has pronounced Cr(VI) reducing activity, so competition for electron flow from TrxR might impair its ability to reduce Trx. The in vitro data also suggested some direct redox interaction between Cr(VI) and Trx. The ability of Cr(VI) to cause Trx oxidation in cells could contribute to its cytotoxic effects, and could have important implications for cell survival, redox-sensitive cell signaling, and the cells' tolerance of other oxidant insults

The use of stable isotopes for Cr(VI) determination in silty-clay soil solution.

Science.gov (United States)

Zuliani, Tea; Sčančar, Janez; Milačič, Radmila

2013-09-01

In assessing the environmental hazard of Cr(VI) present in soil, exchangeable Cr(VI) is important, since it can be easily washed out from the upper part of the soil into subsurface soil, surface and ground water, and taken up by plants. The aim of this study was to evaluate the degree of species interconversion that may occur during the extraction of exchangeable Cr(VI) from silty-clay soil with phosphate buffer in order to establish an extraction method that would be effective, accurate and with minimal or no species interconversions. The Cr(VI) concentration in soil extracts was determined by speciated isotope dilution inductively coupled plasma mass spectrometry (SID-ICP-MS). The study was performed on soil samples from a field treated with tannery waste for 17 years. Samples were spiked by enriched stable isotopic solutions of (50)Cr(VI) and (53)Cr(III) that were added to phosphate buffers (0.1 M KH2PO4-K2HPO4 (pH 7.2) and/or 0.1 M K2HPO4 (pH 8)). To optimize extraction, mechanical shaking and/or ultrasound-assisted extraction were compared. The separation and detection of Cr species was performed by high-performance liquid chromatography (HPLC) ICP-MS. When mechanical shaking was applied, 90 % reduction of Cr(VI) was induced by extraction with 0.1 M KH2PO4-K2HPO4, while with 0.1 M K2HPO4 reduction was around 40 %. To shorten the extraction time and the possibility of species interconversions, ultrasound-assisted extraction was further applied only with 0.1 M K2HPO4. For total extraction of exchangeable Cr(VI) with a maximum 10 % reduction of Cr(VI), five consecutive ultrasound-assisted extractions were needed.

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

Karakterisasi Adsorben dari Kulit Manggis dan Kinerjanya pada Adsorpsi Logam Pb(II dan Cr(VI - (Adsorbent Characterization from Mangosteen Peel and Its Adsorption Performance on Pb(II and Cr(VI

Directory of Open Access Journals (Sweden)

Ulfa Haura

2017-06-01

Full Text Available The usage of biomass waste-based adsorbent for the adsorption of hazardous metal in wastewater is not only reducing waste but also lowering adsorbent price. This research aims to study the characteristics of adsorbent from mangosteen peel (Garcinia Mangostana L. and activated charcoal from mangosteen peel, also to compare the adsorption performance on metal ion Pb(II and Cr(VI. Synthetic wastewater used from a solution of Pb(NO32 and K2Cr2O7 with variations in initial concentration of 20, 40, 80, 100 and 200 mg/L. Adsorption performed at pH 5, ratio of adsorbent and waste solution 1/200 (w/v, 60 rpm, 0.5 gs nano-sized adsorbent. Characterization using SEM, FTIR and SEM-EDS showed that both adsorbents characteristics met the requirements of SNI 06-3730-1995. The highest adsorption capacity of activated carbon to adsorb Pb(II and Cr(VI were 38.543 mg/g and 36.838 mg/g while biosorbent adsorb Pb(II and Cr(VI respectively 3.98 mg/g and 36.12 mg/g.Keywords: adsorption, biosorbent, Cr(VI, mangosteen peel, Pb(IIABSTRAKPenggunaan adsorben berbasis limbah biomassa untuk adsorpsi kandungan logam berbahaya dari limbah cair industri selain dapat mengurangi limbah juga dapat menekan harga jual adsorben. Penelitian ini bertujuan untuk mempelajari karakteristik adsorben yang terbuat dari limbah kulit manggis (Garcinia mangostana L. dan arang aktif dari limbah kulit manggis serta membandingkan kinerja kedua jenis adsorben tersebut pada proses adsorpsi ion logam Pb(II dan Cr(VI. Limbah sintetis yang digunakan berupa ion dari Pb(II dan Cr(VI dari larutan Pb(NO32 dan K2Cr2O7 dengan variasi konsentrasi awal 20, 40, 80, 100 dan 200 mg/L. Proses adsorpsi dilakukan pada pH 5, rasio perbandingan berat adsorben dan volume larutan limbah 1:200, kecepatan pengadukan 60 rpm, adsorben berukuran nano dengan berat adsorben 0,5 g. Masing-masing adsorben dikarakterisasi menggunakan SEM untuk mengetahui sturktur morfologi, FTIR untuk mengetahui gugus fungsi dan SEM-EDS untuk

REMOVAL OF Cr(VI FROM AQUEOUS SOLUTION BY ACTIVATED COAL FROM LIGNITE COAL

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Mehmet MAHRAMANLIOĞLU

2001-03-01

Full Text Available Activated coal produced from Ağaçlı Lignite coal was used to remove Cr(VI from aqueous solutions. The adsorption of Cr(VI was studied as a function of initial concentration, time, pH, adsorbent concentration and temperature. The adsorption data were found to fit to Langmuir and Freundlich isotherms. Lagergren equation was used to calculate the adsorption rate. The amount of Cr(VI adsorbed was increased with decreasing pH and decreased with increasing temperature.

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.

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.

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.

A kinetic study of biological Cr(VI) reduction in trickling filters with different filter media types

International Nuclear Information System (INIS)

Dermou, E.; Vayenas, D.V.

2007-01-01

Two pilot-scale trickling filters were used in order to estimate Cr(VI) reduction through biological mechanisms in biofilm reactors operated in SBR mode with recirculation using different filter media types, i.e. plastic media and calcitic gravel. The feed concentrations of Cr(VI) examined were about 5, 10, 20, 30, 50 and 100 mg/l, while the concentration of the organic carbon was constant at 400 mg/l, in order to avoid carbon limitations in the bulk liquid. Maximum reduction rates of 4.8 and 4.7 g Cr(VI)/d were observed for feed Cr(VI) concentration of about 5 mg Cr(VI)/l, for the filters with the plastic support material and the gravel media, respectively. The reduction rates were significantly affected by the feed Cr(VI) concentration in both bioreactors. A dual-enzyme kinetic model was used in order to describe Cr(VI) reduction by aerobically grown mixed cultures. Model predictions were found to correspond very closely to experimental quantitative observations of Cr(VI) reduction at both pilot-scale trickling filters used

Investigation of equilibrium and kinetics of Cr(VI) adsorption by dried Bacillus cereus using response surface methodology.

Science.gov (United States)

Yang, Kai; Zhang, Jing; Yang, Tao; Wang, Hongyu

2016-01-01

In this study, response surface methodology (RSM) based on three-variable-five-level central composite rotatable design was used to analyze the effects of combined and individual operating parameters (biomass dose, initial concentration of Cr(VI) and pH) on the Cr(VI) adsorption capacity of dried Bacillus cereus. A quadratic polynomial equation was obtained to predict the adsorbed Cr(VI) amount. Analysis of variance showed that the effect of biomass dose was the key factor in the removal of Cr(VI). The maximum adsorbed Cr(VI) amount (30.93 mg g(-1)) was found at 165.30 mg L(-1), 2.96, and 3.01 g L(-1) for initial Cr(VI) concentration, pH, and biosorbent dosage, respectively. The surface chemical functional groups and microstructure of unloaded and Cr(VI)-loaded dried Bacillus cereus were identified by Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM), respectively. Besides, the results gained from these studies indicated that Langmuir isotherm and the second-order rate expression were suitable for the removal of Cr(VI) from wastewater. The results revealed RSM was an effective method for optimizing biosorption process, and dried Bacillus cereus had a remarkable performance on the removal of Cr(VI) from wastewater.

Evaluation of the genetic alterations in direct and indirect exposures of hexavalent chromium [Cr(VI)] in leather tanning industry workers North Arcot District, South India.

Science.gov (United States)

Balachandar, Vellingiri; Arun, Meyyazhagan; Mohana Devi, Subramaniam; Velmurugan, Palanivel; Manikantan, Pappusamy; Karthick Kumar, Alagamuthu; Sasikala, Keshavarao; Venkatesan, Chinnakulandai

2010-10-01

The focal aim of the present study was to identify the genetic alterations occurring in the tannery workers and surrounding inhabitants chronically exposed to hexavalent chromium [Cr(VI)]. A total of 108 samples which includes 72 exposed subjects [36 directly exposed (DE) subjects and 36 indirectly exposed (IE) subjects] and 36 controls were recruited for this study. The exposed subjects and controls were selected based on the Cr level present in air and their urine. Directly exposed subjects were categorized based on their work duration in the tannery industries, whereas the indirectly exposed subjects were categorized based on their year of residence in the place adjacent to tannery industries for more than 3 decades. Controls were normal and healthy. Age was matched for the exposed subjects and controls. The exposed subjects as well as the controls were categorized based on their age (group I, 41 years). Cell cultures were established from blood samples (5 ml from each subject) collected from the subjects (exposed subjects and controls) after obtaining informed consent. G-banding (Giemsa staining) of the cultures, micronucleus (MN) assay and comet assay were used to identify the genetic alterations of individuals exposed to Cr(VI) in comparison with the controls. A higher degree of total CA [12 ± 8.49 (21-25 years)] and MN [18.69 ± 7.39 (11-15 years)] was found in DE subjects compared to other groups. In IE subjects, elevated levels of CA [5.67 ± 1.15 (51-60 years)] and MN [25 ± 9.89 (71-80 years)] were observed. As expected, controls exhibited minimal number of alterations. The overall CA frequency due to Cr exposure was significantly different from that of the controls for both chromatid and chromosome type aberrations (P < 0.05 by ANOVA). The MN/1,000 binucleated cells were significantly increased (P < 0.05) in the peripheral lymphocytes of DE and IE subjects in comparison with controls. The mean tail length of comet assay for DE, IE and controls were

Adsorption of Cr(VI) using silica-based adsorbent prepared by radiation-induced grafting

International Nuclear Information System (INIS)

Qiu Jingyi; Wang Ziyue; Li Huibo; Xu Ling; Peng Jing; Zhai Maolin; Yang Chao; Li Jiuqiang; Wei Genshuan

2009-01-01

Silica-based adsorbent was prepared by radiation-induced grafting of dimethylaminoethyl methacrylate (DMAEMA) onto the silanized silica followed by a protonation process. The FTIR spectra and XPS analysis proved that DMAEMA was grafted successfully onto the silica surface. The resultant adsorbent manifested a high ion exchange capacity (IEC) of ca. 1.30 mmol/g and the Cr(VI) adsorption behavior of the adsorbent was further investigated, revealing the recovery of Cr(VI) increased with the adsorbent feed and the equilibrium adsorption could be achieved within 40 min. The adsorption capacity, strongly depended on the pH of the solution, reached a maximum Cr(VI) uptake (ca. 68 mg/g) as the pH was in the range of 2.5-5.0. Furthermore, even in strong acidic (4.0 mol/L HNO 3 ) or alkaline media (pH 11.0), the adsorbent had a sound Cr(VI) uptake capacity (ca. 22 and 30 mg/g, respectively), and the adsorption followed Langmuir mode. The results indicated that this adsorbent, prepared via a convenient approach, is applicable for removing heavy-metal-ion pollutants (e.g. Cr(VI)) from waste waters.

Coconut coir as biosorbent for Cr(VI) removal from laboratory wastewater.

Science.gov (United States)

Gonzalez, Mário H; Araújo, Geórgia C L; Pelizaro, Claudia B; Menezes, Eveline A; Lemos, Sherlan G; de Sousa, Gilberto Batista; Nogueira, Ana Rita A

2008-11-30

A high cost-effective treatment of sulphochromic waste is proposed employing a raw coconut coir as biosorbent for Cr(VI) removal. The ideal pH and sorption kinetic, sorption capacities, and sorption sites were the studied biosorbent parameters. After testing five different isotherm models with standard solutions, Redlich-Peterson and Toth best fitted the experimental data, obtaining a theoretical Cr(VI) sorption capacity (SC) of 6.3 mg g(-1). Acid-base potentiometric titration indicated around of 73% of sorption sites were from phenolic compounds, probably lignin. Differences between sorption sites in the coconut coir before and after Cr adsorption identified from Fourier transform infrared spectra suggested a modification of sorption sites after sulphochromic waste treatment, indicating that the sorption mechanism involves organic matter oxidation and chromium uptake. For sulphocromic waste treatment, the SC was improved to 26.8+/-0.2 mg g(-1), and no adsorbed Cr(VI) was reduced, remaining only Cr(III) in the final solution. The adsorbed material was calcinated to obtain Cr(2)O(3,) with a reduction of more than 60% of the original mass.

NASA and ESA Collaboration on Hexavalent Chrome Alternatives: Pretreatments Only Final Test Report

Science.gov (United States)

Kessel, Kurt R.

2015-01-01

Hexavalent chromium (hex chrome or CR(VI)) is a widely used element within applied coating systems because of its self-healing and corrosion-resistant properties. The replacement of hex chrome in the processing of aluminum for aviation and aerospace applications remains a goal of great significance. Aluminum is the major manufacturing material of structures and components in the space flight arena. The National Aeronautics and Space Administration (NASA) and the European Space Agency (ESA) are engaged in a collaborative effort to test and evaluate alternatives to hexavalent chromium containing corrosion coating systems. NASA and ESA share common risks related to material obsolescence associated with hexavalent chromium used in corrosion-resistant coatings.

Adsorption behavior of carboxylated cellulose nanocrystal—polyethyleneimine composite for removal of Cr(VI) ions

Energy Technology Data Exchange (ETDEWEB)

Liu, Chao; Jin, Ru-Na; Ouyang, Xiao-kun, E-mail: xkouyang@zjou.edu.cn; Wang, Yang-Guang

2017-06-30

Highlights: • A carboxylated cellulose nanocrystal-polyethyleneimine composite (CCN-PEI) was prepared. • The as-prepared CCN-PEI was characterized by SEM, TEM, FT-IR, and XPS. • Results suggested that the reusable CCN-PEI could remove Cr(VI) from aqueous solutions with a high adsorption capacity. • The adsorption isotherm, thermodynamics, and kinetics of the adsorption process are also discussed. - Abstract: 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{sup −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{sup −1}), enthalpy change (ΔH = −5.69 kJ × mol{sup −1}), and entropy change (ΔS = −9.14 kJ × mol{sup −1}), indicate that the adsorption of Cr(VI) ions onto CCN

Modacrylic anion-exchange fibers for Cr(VI) removal from chromium-plating rinse water in batch and flow-through column experiments.

Science.gov (United States)

Lee, Seung-Chan; Kang, Jin-Kyu; Sim, Eun-Hye; Choi, Nag-Choul; Kim, Song-Bae

2017-11-10

The aim of this study was to investigate Cr(VI) removal from chromium-plating rinse water using modacrylic anion-exchange fibers (KaracaronTM KC31). Batch experiments were performed with synthetic Cr(VI) solutions to characterize the KC31 fibers in Cr(VI) removal. Cr(VI) removal by the fibers was affected by solution pH; the Cr(VI) removal capacity was the highest at pH 2 and decreased gradually with a pH increase from 2 to 12. In regeneration and reuse experiments, the Cr(VI) removal capacity remained above 37.0 mg g -1 over five adsorption-desorption cycles, demonstrating that the fibers could be successfully regenerated with NaCl solution and reused. The maximum Cr(VI) removal capacity was determined to be 250.3 mg g -1 from the Langmuir model. In Fourier-transform infrared spectra, a Cr = O peak newly appeared at 897 cm -1 after Cr(VI) removal, whereas a Cr-O peak was detected at 772 cm -1 due to the association of Cr(VI) ions with ion-exchange sites. X-ray photoelectron spectroscopy analyses demonstrated that Cr(VI) was partially reduced to Cr(III) after the ion exchange on the surfaces of the fibers. Batch experiments with chromium-plating rinse water (Cr(VI) concentration = 1178.8 mg L -1 ) showed that the fibers had a Cr(VI) removal capacity of 28.1-186.4 mg g -1 under the given conditions (fiber dose = 1-10 g L -1 ). Column experiments (column length = 10 cm, inner diameter = 2.5 cm) were conducted to examine Cr(VI) removal from chromium-plating rinse water by the fibers under flow-through column conditions. The Cr(VI) removal capacities for the fibers at flow rates of 0.5 and 1.0 mL min -1 were 214.8 and 171.5 mg g -1 , respectively. This study demonstrates that KC31 fibers are effective in the removal of Cr(VI) ions from chromium-plating rinse water.

Removal of Cr(VI) from aqueous solution by flocculant with the capacity of reduction and chelation

International Nuclear Information System (INIS)

Wang, Gang; Chang, Qing; Han, Xiaoting; Zhang, Mingyue

2013-01-01

Highlights: ► We report a novel flocculant with the properties of reduction and chelation for Cr. ► The removal of Cr(VI) by the flocculant depends highly on pH value. ► Some coexisting ions inhibit Cr (VI) removal, but promote total Cr removal. ► Cr and turbidity can be removed simultaneously in the treated wastewater. ► The interaction mechanism is investigated by FTIR and SEM. -- Abstract: A novel agent polyethyleneimine-sodium xanthogenate (PEX) with the multifunction of reduction, chelation, flocculation and precipitation was synthesized by using polyethyleneimine (PEI), carbon disulfide (CS 2 ), and sodium hydroxide (NaOH). The effects of different important parameters, such as pH value, initial Cr(VI) concentration, coexisting ions and turbidity etc., on the removal of chromium from aqueous solution by PEX were investigated in flocculation experiments. The experiments results demonstrated that PEX could efficiently remove Cr(VI) and total Cr (Cr(VI) + Cr(III)) in strongly acidic media. It was proved that the presence of coexisting ions (Na + , Ca 2+ , F − , Cl − , and SO 4 2− ) in the solution had a little influence on the removal of chromium. Furthermore, it was conformed that Cr(VI) ions and turbidity could be simultaneously removed when water samples contained both Cr(VI) ions and turbidity. Finally, the mechanism of interaction between chromium and PEX was further confirmed by Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). The results reveal that dithiocarboxylic acid groups on PEX macromolecule play a major role in Cr(VI) reduction and Cr(III) chelation, and the flocs formation is attributed to the interparticle bridging mechanism of PEX

Reduction of hexavalent chromium by fasted and fed human gastric fluid. II. Ex vivo gastric reduction modeling

Energy Technology Data Exchange (ETDEWEB)

Kirman, Christopher R., E-mail: ckirman@summittoxicology.com [Summit Toxicology, Orange Village, OH, 44022 (United States); Suh, Mina, E-mail: msuh@toxstrategies.com [ToxStrategies, Inc., Mission Viejo, CA, 92692 (United States); Hays, Sean M., E-mail: shays@summittoxicology.com [Summit Toxicology, Allenspark, CO, 8040 (United States); Gürleyük, Hakan, E-mail: hakan@brooksrand.com [Brooks Applied Labs, Bothell, WA, 98011 (United States); Gerads, Russ, E-mail: russ@brooksrand.com [Brooks Applied Labs, Bothell, WA, 98011 (United States); De Flora, Silvio, E-mail: sdf@unige.it [Department of Health Sciences, University of Genoa, 16132 Genoa (Italy); Parker, William, E-mail: william.parker@duke.edu [Duke University Medical Center, Department of Surgery, Durham, NC, 27710 (United States); Lin, Shu, E-mail: shu.lin@duke.edu [Duke University Medical Center, Department of Surgery, Durham, NC, 27710 (United States); Haws, Laurie C., E-mail: lhaws@toxstrategies.com [ToxStrategies, Inc., Katy, TX, 77494 (United States); Harris, Mark A., E-mail: mharris@toxstrategies.com [ToxStrategies, Inc., Austin, TX, 78751 (United States); Proctor, Deborah M., E-mail: dproctor@toxstrategies.com [ToxStrategies, Inc., Mission Viejo, CA, 92692 (United States)

2016-09-01

To extend previous models of hexavalent chromium [Cr(VI)] reduction by gastric fluid (GF), ex vivo experiments were conducted to address data gaps and limitations identified with respect to (1) GF dilution in the model; (2) reduction of Cr(VI) in fed human GF samples; (3) the number of Cr(VI) reduction pools present in human GF under fed, fasted, and proton pump inhibitor (PPI)-use conditions; and (4) an appropriate form for the pH-dependence of Cr(VI) reduction rate constants. Rates and capacities of Cr(VI) reduction were characterized in gastric contents from fed and fasted volunteers, and from fasted pre-operative patients treated with PPIs. Reduction capacities were first estimated over a 4-h reduction period. Once reduction capacity was established, a dual-spike approach was used in speciated isotope dilution mass spectrometry analyses to characterize the concentration-dependence of the 2nd order reduction rate constants. These data, when combined with previously collected data, were well described by a three-pool model (pool 1 = fast reaction with low capacity; pool 2 = slow reaction with higher capacity; pool 3 = very slow reaction with higher capacity) using pH-dependent rate constants characterized by a piecewise, log-linear relationship. These data indicate that human gastric samples, like those collected from rats and mice, contain multiple pools of reducing agents, and low concentrations of Cr(VI) (< 0.7 mg/L) are reduced more rapidly than high concentrations. The data and revised modeling results herein provide improved characterization of Cr(VI) gastric reduction kinetics, critical for Cr(VI) pharmacokinetic modeling and human health risk assessment. - Highlights: • SIDMS allows for measurement of Cr(VI) reduction rate in gastric fluid ex vivo • Human gastric fluid has three reducing pools • Cr(VI) in drinking water at < 0.7 mg/L is rapidly reduced in human gastric fluid • Reduction rate is concentration- and pH-dependent • A refined PK

The Effect of the Concentration of Oxidant, Cr(VI), on the Iron Oxidation in Saline Water

Science.gov (United States)

Ahn, H.; Jo, H. Y.; Ryu, J. H.; Koh, Y. K.

2014-12-01

Deep geological disposal is currently considered as the most appropriate method to isolate high level radioactive wastes (HLRWs) from the ecosystem. If groundwater seeps into underground disposal facilities, water molecules can be dissociated to radicals or peroxides, which can oxidize metal canisters and HLRWs. The oxidized radionuclides with a high solubility can be dissolved in the groundwater. Some dissolved radionuclides can act as oxidants. The continuous radiolysis of water molecules, which results from continuous seepage of groundwater, can enable the continuous production of the radioactive oxidants, resulting in an increase in concentration of oxidants. In this study, the effect of oxidant concentration on iron oxidation in the presence of salt was evaluated. Zero valent iron (ZVI) particles were reacted with Cr(VI) solutions with initial Cr(VI) concentrations ranged from 50 to 300 mg/L in reactors. The initial pH and NaCl concentration were fixed at 3 and 0.5 M, respectively. An increase in the initial Cr(VI) concentration caused an increase in the rate and extend of H2 gas production. The decrement of Cr(VI) was increased as the initial Cr(VI) concentration was increased. The penetration of H+ ions in the presence Cl- ions through the passive film on the ZVI particles caused the reaction between H+ ions and ZVI particles, producing H2 gas and Fe2+ ions. The passive film was damaged during the reaction due to the eruption of H2 gas or peptization by Cl- ions. The Fe2+ ions were reacted with Cr(VI) ions in the solution, producing Fe(III)-Cr(III) (oxy)hydroxides on the passive film of ZVI particles or in the solution as colloidal particles. The Fe(III)-Cr(III) (oxy)hydroxides tends to be precipitated as colloidal particles at a high Cr(VI) concentration and precipitated on the passive film at a low Cr(VI) concentration. The passive film was repaired or thickened by additional formation of Fe(III)-Cr(III) (oxy)hydroxides at a lower Cr(VI) concentration.

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

International Nuclear Information System (INIS)

Pagnanelli, F.; Cruz Viggi, C.; Cibati, A.; Uccelletti, D.; Toro, L.; Palleschi, C.

2012-01-01

Highlights: ► Use of ethanol as electron donor for sulphate-reducing bacteria for the treatment of Cr(VI). ► Isolation of contribution in Cr removal (adsorption vs. bioprecipitation). ► 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 −1 ), ethanol (1.5 g L −1 ) and Cr(VI) (50 mg L −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.

Negative impact of oxygen molecular activation on Cr(VI) removal with core–shell Fe@Fe2O3 nanowires

International Nuclear Information System (INIS)

Mu, Yi; Wu, Hao; Ai, Zhihui

2015-01-01

Highlights: • The presence of oxygen inhibited Cr(VI) removal efficiency with nZVI by near 3 times. • Cr(VI) removal with nZVI was related to adsorption, reduction, co-precipitation, and adsorption reactions. • Molecular oxygen activation competed donor electrons from Fe 0 core and surface bound Fe(II) of nZVI. • Thicker Cr(III)/Fe(III)/Cr(VI) oxyhydroxides shell of nZVI leaded to the electron transfer inhibition. - Abstract: In this study, we demonstrate that the presence of oxygen molecule can inhibit Cr(VI) removal with core–shell Fe@Fe 2 O 3 nanowires at neutral pH of 6.1. 100% of Cr(VI) removal was achieved by the Fe@Fe 2 O 3 nanowires within 60 min in the anoxic condition, in contrast, only 81.2% of Cr(VI) was sequestrated in the oxic condition. Removal kinetics analysis indicated that the presence of oxygen could inhibit the Cr(VI) removal efficiency by near 3 times. XRD, SEM, and XPS analysis revealed that either the anoxic or oxic Cr(VI) removal was involved with adsorption, reduction, co-precipitation, and re-adsorption processes. More Cr(VI) was bound in a reduced state of Cr(III) in the anoxic process, while a thicker Cr(III)/Fe(III)/Cr(VI) oxyhydroxides shell, leading to inhibiting the electron transfer, was found under the oxic process. The negative impact of oxygen molecule was attributed to the oxygen molecular activation which competed with Cr(VI) adsorbed for the consumption of donor electrons from Fe 0 core and ferrous ions bound on the iron oxides surface under the oxic condition. This study sheds light on the understanding of the fate and transport of Cr(VI) in oxic and anoxic environment, as well provides helpful guide for optimizing Cr(VI) removal conditions in real applications

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.

Magnetic solid-phase extraction combined with graphite furnace atomic absorption spectrometry for speciation of Cr(III) and Cr(VI) in environmental waters.

Science.gov (United States)

Jiang, Hong-mei; Yang, Ting; Wang, Yan-hong; Lian, Hong-zhen; Hu, Xin

2013-11-15

A new approach of magnetic solid phase extraction (MSPE) coupled with graphite furnace atomic absorption spectrometry (GFAAS) has been developed for the speciation of Cr(III) and Cr(VI) using zincon-immobilized silica-coated magnetic Fe3O4 nanoparticles (Zincon-Si-MNPs) as the MSPE absorbent. Cr(III) was quantitatively reserved on the absorbent at pH 9.1 while total Cr was reserved at pH 6.5. The absorbed Cr species were eluted by using 2 mol/L HCl and detected by GFAAS. The concentration of Cr(VI) could be calculated by subtracting Cr(III) from total Cr. All the parameters affecting the separation and extraction efficiency of Cr species such as pH, extraction time, concentration and volume of eluent, sample volume and influence of co-existing ions were systematically examined and the optimized conditions were established accordingly. The detection limit (LOD) of the method was 0.016 and 0.011 ng mL(-1) for Cr(III) and Cr(VI), respectively, with the enrichment factor of 100 and 150. The precisions of this method (Relative standard deviation, RSD, n=7) for Cr(III) and Cr(VI) at 0.1 ng mL(-1) were 6.0% and 6.2%, respectively. In order to validate the proposed method, a certified reference material of environmental water was analyzed, and the result of Cr speciation was in good agreement with the certified value. This MSPE-GFAAS method has been successfully applied for the speciation of Cr(III) and Cr(VI) in lake and tap waters with the recoveries of 88-109% for the spiked samples. Moreover, the MSPE separation mechanism of Cr(III) and Cr(VI) based on their adsorption-desorption on Zincon-Si-MNPs has been explained through various spectroscopic characterization. © 2013 Elsevier B.V. All rights reserved.

The potential of compost-based biobarriers for Cr(VI) removal from contaminated groundwater: Column test

International Nuclear Information System (INIS)

Boni, Maria Rosaria; Sbaffoni, Silvia

2009-01-01

This paper presents the results of a column reactor test, aiming at evaluating the performance of a biological permeable barrier made of low-cost waste materials, for Cr(VI) removal from contaminated groundwater. A 1:1 by volume mixture of green compost and siliceous gravel was tested as reactive medium in the experimental activity. A 10 mg/l Cr(VI) contaminated solution was used and the residual Cr(VI) concentration along the column height and in the outlet was determined in the water samples collected daily. Also pH, redox potential and COD were analyzed. At the end of the test, the reactive medium was characterized in terms of Cr(VI) and total chromium. The Cr(VI) removal efficiency was higher than 99% during the entire experimental activity. The influence of the biological activity on Cr(VI) removal efficiency was evaluated by varying the organic carbon and nitrogen dosages in the contaminated solution fed to the system; a removal decrease was observed when the organic carbon was not enough to sustain the microbial metabolism. The Cr(VI) removal was strictly linked to the biological activity of the native biomass of compost. No Cr(III) was detected in the outlet: the Cr(III) produced was entrapped in the solid matrix. Two main processes involved were: adsorption on the organic-based matrix and reduction into Cr(III) mediated by the anaerobic microbial metabolism of the bacteria residing in green compost. Siliceous gravel was used as the structure matrix, since its contribution to the removal was almost negligible. Thanks to the proven efficiency and to the low-cost, the reactive medium used can represent a valid alternative to conventional approaches to chromium remediation.

Magnitude and directional measures of water and Cr(VI) fluxes by passive flux meter.

Science.gov (United States)

Campbell, Timothy J; Hatfield, Kirk; Klammler, Harald; Annable, Michael D; Rao, P S C

2006-10-15

A new configuration of the passive fluxmeter (PFM) is presented that provides for simultaneous measurements of both the magnitude and the direction of ambient groundwater specific discharge qo and Cr(VI) mass flux J(Cr). The PFM is configured as a cylindrical unit with an interior divided into a center section and three outer sectors, each packed with a granular anion exchange resin having high sorption capacity for the Cr(VI) oxyanions CrO4(2-) and HCrO4-. The sorbent in the center section is preloaded with benzoate as the "resident" tracer. Laboratory experiments were conducted in which PFMs were placed in porous packed bed columns, through which was passed a measured volume of synthetic groundwater containing Cr(VI). During the deployment period, some of the resident tracer is depleted while the Cr(VI) is sorbed. The resin was then removed from the four sectors separately and extracted to determine the "captured" mass of Cr(VI) and the residual mass of the resident tracer in each. Cumulative specific discharge, q0t, values were assessed using the residual mass of benzoate retained in the center section. The direction of this discharge theta was ascertained from the mass distribution of benzoate intercepted and retained in the outer three sections of the PFM. Cumulative chromium fluxes, J(Cr)t, were quantified using the total Cr(VI) mass intercepted and retained on the PFM. Experiments produced an average measurement error for direction theta of 3 degrees +/- 14 degrees, while the average measurement errors for q0 and J(Cr) were, respectively, -8% +/- 15% and -12% +/- 23%. Results demonstrate the potential utility of the new PFM configuration for characterizing groundwater and contaminant fluxes.

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 (simulations indicated that biomass growth completely depleted influent ammonium, and called for an additional source of N to account for the measured reduction rates. Iron columns were the least active with undetectable consumption of the injected lactate, slowest 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

Reduction of hexavalent chromium by fasted and fed human gastric fluid. I. Chemical reduction and mitigation of mutagenicity

Energy Technology Data Exchange (ETDEWEB)

De Flora, Silvio, E-mail: sdf@unige.it [Department of Health Sciences, University of Genoa, 16132 Genoa (Italy); Camoirano, Anna, E-mail: Anna.Fiorenza.Camoirano@unige.it [Department of Health Sciences, University of Genoa, 16132 Genoa (Italy); Micale, Rosanna T., E-mail: rosannamicale@yahoo.it [Department of Health Sciences, University of Genoa, 16132 Genoa (Italy); La Maestra, Sebastiano, E-mail: lamaestra78@yahoo.it [Department of Health Sciences, University of Genoa, 16132 Genoa (Italy); Savarino, Vincenzo, E-mail: vsavarin@unige.it [Gastroenterology Unit, Department of Internal Medicine, University of Genoa, 16132 Genoa (Italy); Zentilin, Patrizia, E-mail: Patrizia.Zentilin@unige.it [Gastroenterology Unit, Department of Internal Medicine, University of Genoa, 16132 Genoa (Italy); Marabotto, Elisa, E-mail: emarabotto@libero.it [Gastroenterology Unit, Department of Internal Medicine, University of Genoa, 16132 Genoa (Italy); Suh, Mina, E-mail: msuh@toxstrategies.com [ToxStrategies, Mission Viejo, CA 92692 (United States); Proctor, Deborah M., E-mail: dproctor@toxstrategies.com [ToxStrategies, Mission Viejo, CA 92692 (United States)

2016-09-01

Evaluation of the reducing capacity of human gastric fluid from healthy individuals, under fasted and fed conditions, is critical for assessing the cancer hazard posed by ingested hexavalent chromium [Cr(VI)] and for developing quantitative physiologically-based pharmacokinetic models used in risk assessment. In the present study, the patterns of Cr(VI) reduction were evaluated in 16 paired pre- and post-meal gastric fluid samples collected from 8 healthy volunteers. Human gastric fluid was effective both in reducing Cr(VI), as measured by using the s-diphenylcarbazide colorimetric method, and in attenuating mutagenicity in the Ames test. The mean (± SE) Cr(VI)-reducing ability of post-meal samples (20.4 ± 2.6 μg Cr(VI)/mL gastric fluid) was significantly higher than that of pre-meal samples (10.2 ± 2.3 μg Cr(VI)/mL gastric fluid). When using the mutagenicity assay, the decrease of mutagenicity produced by pre-meal and post-meal samples corresponded to reduction of 13.3 ± 1.9 and 25.6 ± 2.8 μg Cr(VI)/mL gastric fluid, respectively. These data are comparable to parallel results conducted by using speciated isotope dilution mass spectrometry. Cr(VI) reduction was rapid, with > 70% of total reduction occurring within 1 min and 98% of reduction is achieved within 30 min with post-meal gastric fluid at pH 2.0. pH dependence was observed with decreasing Cr(VI) reducing capacity at higher pH. Attenuation of the mutagenic response is consistent with the lack of DNA damage observed in the gastrointestinal tract of rodents following administration of ≤ 180 ppm Cr(VI) for up to 90 days in drinking water. Quantifying Cr(VI) reduction kinetics in the human gastrointestinal tract is necessary for assessing the potential hazards posed by Cr(VI) in drinking water. - Highlights: • Cr(VI) reduction capacity was greater in post-meal than paired pre-meal samples. • Cr(VI) reduction was rapid, pH dependent, and due to heat stable components. • Gastric fluid attenuates

Homologous Recombination Repair Signaling in Chemical Carcinogenesis: Prolonged Particulate Hexavalent Chromium Exposure Suppresses the Rad51 Response in Human Lung Cells

Science.gov (United States)

Qin, Qin; Xie, Hong; Wise, Sandra S.; Browning, Cynthia L.; Thompson, Kelsey N.; Holmes, Amie L.; Wise, John Pierce

2014-01-01

The aim of this study was to focus on hexavalent chromium, [Cr(VI)], a chemical carcinogen and major public health concern, and consider its ability to impact DNA double strand break repair. We further focused on particulate Cr(VI), because it is the more potent carcinogenic form of Cr(VI). DNA double strand break repair serves to protect cells against the detrimental effects of DNA double strand breaks. For particulate Cr(VI), data show DNA double strand break repair must be overcome for neoplastic transformation to occur. Acute Cr(VI) exposures reveal a robust DNA double strand break repair response, however, longer exposures have not been considered. Using the comet assay, we found longer exposures to particulate zinc chromate induced concentration-dependent increases in DNA double strand breaks indicating breaks were occurring throughout the exposure time. Acute (24 h) exposure induced DNA double strand break repair signaling by inducing Mre11 foci formation, ATM phosphorylation and phosphorylated ATM foci formation, Rad51 protein levels and Rad51 foci formation. However, longer exposures reduced the Rad51 response. These data indicate a major chemical carcinogen can simultaneously induce DNA double strand breaks and alter their repair and describe a new and important aspect of the carcinogenic mechanism for Cr(VI). PMID:25173789

Detoxification of hexavalent chromium by Leucobacter sp. uses a reductase with specificity for dihydrolipoamide.

Science.gov (United States)

Sarangi, Abhipsa; Krishnan, Chandraraj

2016-02-01

Leucobacter sp. belongs to the metal stressed community and possesses higher tolerance to metals including chromium and can detoxify toxic hexavalent chromium by reduction to less toxic trivalent chromium. But, the mechanism of reduction of hexavalent chromium by Leucobacter sp. has not been studied. Understanding the enzyme catalyzing reduction of chromium is important to improve the species for application in bioremediation. Hence, a soluble reductase catalyzing the reduction of hexavalent chromium was purified from a Leucobacter sp. and characterized. The pure chromate reductase was obtained from the cell-free extract through hydrophobic interaction and gel filtration column chromatographic methods. It was a monomeric enzyme and showed similar molecular weights in both gel filtration (∼68 KDa) and SDS-PAGE (64 KDa). It reduced Cr(VI) using both NADH and NADPH as the electron donor, but exhibited higher activity with NADH. The optimal activity was found at pH 5.5 and 30 °C. The K(m) and V(max) for Cr(VI) reduction with NADH were 46.57 μM and 0.37 μmol min(-1) (mg protein) (-1), respectively. The activity was inhibited by p-hydroxy mercury benzoate, Ag(2+) and Hg(2+) indicating the role of thiol groups in the catalysis. The spectrophotometric analysis of the purified enzyme showed the absence of bound flavin in the enzyme. The N-terminal amino acid sequence and LC/MS analysis of trypsin digested purified enzyme showed similarity to dihydrolipoyl dehydrogenase. The purified enzyme had dihydrolipoyl dehydrogenase activity with dihydrolipoamide as the substrate, which suggested that Leucobacter sp. uses reductase with multiple substrate specificity for reduction of Cr(VI) detoxification. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

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.

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

International Nuclear Information System (INIS)

Zeng, Chujie; Lin, Yao; Zhou, Neng; Zheng, Jiaoting; Zhang, Wei

2012-01-01

Highlights: ► First reported enhancement effect of RTILs in HF-LPME for the speciation of chromium. ► The addition of RTILs led to 3.5 times improvement of the sensitivity of Cr(VI). ► 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 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 −1 and an enrichment factor of 175 were achieved. The relative standard deviation (RSD) was 4.9% for Cr(VI) (40 ng mL −1 , n = 5). The proposed method was successfully applied to the speciation of chromium in natural water samples with satisfactory results.

Immediate remediation of heavy metal (Cr(VI)) contaminated soil by high energy electron beam irradiation

International Nuclear Information System (INIS)

Zhang, Jing; Zhang, Guilong; Cai, Dongqing; Wu, Zhengyan

2015-01-01

Highlights: • An immediate remediation method for Cr(VI) contaminated soil (CCS) was developed. • High energy electron beam (HEEB) irradiation could reduce Cr(VI) in CCS to Cr(III). • This effect was attributed to electrons, hydrated electrons, and reductive radicals. • This remediation method was effective, environmentally friendly, and low-cost. - Abstract: This work developed an immediate and high-performance remediation method for Cr(VI) contaminated soil (CCS) using high energy electron beam (HEEB) irradiation. The result indicated that, compared with γ-ray irradiation, HEEB irradiation displayed a significant reduction efficiency on Cr(VI) in CCS to Cr(III) with substantially lower toxicity, which was mainly attributed to the reduction effects of electrons, hydrated electrons, and reductive radicals generated in the irradiation process of HEEB. This work could provide a one-step and effective method for the remediation of heavy metal contaminated soil (HMCS)

Immediate remediation of heavy metal (Cr(VI)) contaminated soil by high energy electron beam irradiation

Energy Technology Data Exchange (ETDEWEB)

Zhang, Jing; Zhang, Guilong [Key Laboratory of Ion Beam Bioengineering, Hefei Institutes of Physical Science, Chinese Academy of Sciences and Anhui Province, Hefei 230031 (China); Bioenergy Forest Research Center of State Forestry Administration, Hefei 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 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 230031 (China); Bioenergy Forest Research Center of State Forestry Administration, Hefei 230031 (China)

2015-03-21

Highlights: • An immediate remediation method for Cr(VI) contaminated soil (CCS) was developed. • High energy electron beam (HEEB) irradiation could reduce Cr(VI) in CCS to Cr(III). • This effect was attributed to electrons, hydrated electrons, and reductive radicals. • This remediation method was effective, environmentally friendly, and low-cost. - Abstract: This work developed an immediate and high-performance remediation method for Cr(VI) contaminated soil (CCS) using high energy electron beam (HEEB) irradiation. The result indicated that, compared with γ-ray irradiation, HEEB irradiation displayed a significant reduction efficiency on Cr(VI) in CCS to Cr(III) with substantially lower toxicity, which was mainly attributed to the reduction effects of electrons, hydrated electrons, and reductive radicals generated in the irradiation process of HEEB. This work could provide a one-step and effective method for the remediation of heavy metal contaminated soil (HMCS)

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.

Hydration study of limestone blended cement in the presence of hazardous wastes containing Cr(VI)

International Nuclear Information System (INIS)

Trezza, M.A.; Ferraiuelo, M.F.

2003-01-01

Considering the increasing use of limestone cement manufacture, the present paper tends to characterize limestone behavior in the presence of Cr(VI). The research reported herein provides information regarding the effect of Cr(VI) from industrial wastes in the limestone cement hydration. The cementitious materials were ordinary Portland cement, as reference, and limestone blended cement. The hydration and physicomechanical properties of cementitious materials and the influence of chromium at an early age were studied with X-ray diffraction (XRD), infrared spectroscopy (FTIR), conductimetric and mechanical tests. Portland cement pastes with the addition of Cr(VI) were examined and leaching behavior with respect to water and acid solution were investigated. This study indicates that Cr(VI) modifies the rate and the components obtained during the cement hydration

Transient gestational exposure to drinking water containing excess hexavalent chromium modifies insulin signaling in liver and skeletal muscle of rat progeny.

Science.gov (United States)

Shobana, Navaneethabalakrishnan; Aruldhas, Mariajoseph Michael; Tochhawng, Lalmuankimi; Loganathan, Ayyalu; Balaji, Sadhasivam; Kumar, Mani Kathiresh; Banu, Liaquat Alikhan Sheerin; Navin, Ajit Kumar; Mayilvanan, Chinnaiyan; Ilangovan, Ramachandran; Balasubramanian, Karundevi

2017-11-01

Chromium (Cr), an essential micronutrient potentiates insulin action, whereas excess hexavalent Cr (CrVI) acts as an endocrine disruptor. Pregnant mothers living in areas abutting industries using the metal and chromite ore dumps are exposed to ground water contaminated with Cr. Nevertheless, the impact of prenatal exposure to excess CrVI on insulin signaling in the progeny remains obscure. We tested the hypothesis "transient gestational exposure to drinking water containing excess CrVI may modify insulin signaling during postnatal life". Pregnant Wistar rats were given drinking water containing 50, 100 and 200 ppm CrVI (K 2 Cr 2 O 7 ) from gestational day 9-14 encompassing the period of organogenesis; the male progenies were tested at postnatal day 60. Neither fasting blood glucose nor oral glucose tolerance was altered in CrVI treated progeny. Nevertheless, western blot detection pointed out attenuated expression level of insulin receptor (IR), its downstream signaling molecules (IRS-1, pIRS-1 Tyr632 , Akt and pAkt Ser473 ) and organ specific glucose transporters (GLUT2 in liver and GLUT4 in gastrocnemius muscle), along with a significant increase in serum insulin level in male progenies exposed to CrVI. While 14 C-2-deoxy glucose uptake increased in the liver, the same decreased in the skeletal muscle whereas, 14 C-glucose oxidation recorded a consistent decrease in both tissues of CrVI exposed rats. These findings support our hypothesis and suggest that transient gestational exposure to excess CrVI may affect insulin signaling and glucose oxidation in the progeny, predictably rendering them vulnerable to insulin resistance. Copyright © 2017 Elsevier B.V. All rights reserved.

Hexavalent chromium, a lung carcinogen, confers resistance to thermal stress and interferes with heat shock protein expression in human bronchial epithelial cells.

Science.gov (United States)

Abreu, Patrícia L; Cunha-Oliveira, Teresa; Ferreira, Leonardo M R; Urbano, Ana M

2018-03-16

Exposure to hexavalent chromium [Cr(VI)], a lung carcinogen, triggers several types of cellular stresses, namely oxidative, genotoxic and proteotoxic stresses. Given the evolutionary character of carcinogenesis, it is tempting to speculate that cells that survive the stresses produced by this carcinogen become more resistant to subsequent stresses, namely those encountered during neoplastic transformation. To test this hypothesis, we determined whether pre-incubation with Cr(VI) increased the resistance of human bronchial epithelial cells (BEAS-2B cells) to the antiproliferative action of acute thermal shock, used here as a model for stress. In line with the proposed hypothesis, it was observed that, at mildly cytotoxic concentrations, Cr(VI) attenuated the antiproliferative effects of both cold and heat shock. Mechanistically, Cr(VI) interfered with the expression of two components of the stress response pathway: heat shock proteins Hsp72 and Hsp90α. Specifically, Cr(VI) significantly depleted the mRNA levels of the former and the protein levels of the latter. Significantly, these two proteins are members of heat shock protein (Hsp) families (Hsp70 and Hsp90, respectively) that have been implicated in carcinogenesis. Thus, our results confirm and extend previous studies showing the capacity of Cr(VI) to interfere with the expression of stress response components.

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.

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

International Nuclear Information System (INIS)

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

2015-01-01

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 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

Investigations on the nephrotoxicity and hepatotoxicity of trivalent and hexavalent chromium compounds.

Science.gov (United States)

Dartsch, P C; Hildenbrand, S; Kimmel, R; Schmahl, F W

1998-09-01

In contrast to trivalent chromium (Cr(III)) compounds, hexavalent chromium ((Cr(VI)) compounds are oxidizing agents capable of directly inducing tissue damage and possessing carcinogenic, mutagenic and teratogenic potency. After oral or dermal absorption of Cr(VI), the kidney is the main target organ for chromium accumulation, which might result in acute tubular necrosis in humans. In contrast, an acute toxic effect of Cr(VI) on the liver has not yet been described. Therefore, we used two established epithelial cell lines from the kidney (Opossum kidney cells) and the liver (Hep G2 cells) to design an in vitro-assay which is able to examine acute toxic effects of chromium compounds. Cells of both cell lines were treated with various concentrations of Cr(III) and Cr(VI) ranging from 0.01 micromol/l to 1 mmol/l for 24 h. Thereafter, cell morphology, organization of the intracellular cytoskeleton, number of viable cells and mean cell volume were examined. The results show that Cr(VI), but not Cr(III), has an acute cytotoxic effect and causes a dose-dependent loss in cell viability. The effective dose that caused 50% of cell death was 5 micromol/l for kidney epithelial cells and 50 micromol/l for liver epithelial cells. This means that kidney epithelial cells are 10 times more sensitive towards Cr(VI) treatment than liver epithelial cells and this might explain the known nephrotoxicity in vivo. The loss in cell viability was accompanied by a rounding and detachment of the cells and a marked reduction of intracellular F-actin-containing stress fibers. Microtubules and intermediate-sized filaments were observed to be unaffected. Only in the case of kidney epithelial cells, a dose-dependent cell volume increase was observed after Cr(VI) treatment at concentrations up to 50 micromol/l. At higher concentrations, the cell volume decreased due to the high number of cells undergoing lysis and the appearance of cellular fragments. Various chloride channel blockers with

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. Copyright �

Lactational exposure to hexavalent chromium delays puberty by impairing ovarian development, steroidogenesis and pituitary hormone synthesis in developing Wistar rats

International Nuclear Information System (INIS)

Banu, Sakhila K.; Samuel, Jawahar B.; Arosh, Joe A.; Burghardt, Robert C.; Aruldhas, Michael M.

2008-01-01

Hexavalent chromium (Cr-VI) is used in a wide range of industries. Cr-VI from chromate industries and atmospheric emissions contribute to the Cr contamination in the environment. Cr is a reproductive metal toxicant that can traverse the placental barrier and cause a wide range of fetal effects including ovotoxicity. Therefore, the goal of this study was to investigate the basic mechanisms involved in Cr(VI)-induced ovotoxicity, and the protective role of vitamin C on ovarian follicular development and function in Cr(VI)-induced reproductive toxicity using both in vivo and in vitro approaches. Lactating rats received potassium dichromate (200 mg/L) with or without vitamin C (500 mg/L), through drinking water from postpartum days 1-21. During postnatal days (PND) 1-21 the pups received Cr(VI) via the mother's milk. Pups from both control and treatment groups were continued on regular diet and water from PND-21 onwards, and euthanized on PND-21, -45 and -65. Cr(VI) decreased steroidogenesis, GH and PRL, increased FSH and did not alter LH. Cr(VI) delayed puberty, decreased follicle number, and extended estrous cycle. Spontaneously immortalized rat granulosa cells were treated with 12.5 μM (IC 50 ) potassium dichromate for 12 and 24 h, with or without vitamin C pre-treatment. Cr(VI) decreased the mRNA expressions of StAR, SF-1, 17β-HSD-1, 17β-HSD-2, FSHR, LHR, ERα and ERβ. Vitamin C pre-treatment protected ovary and granulosa cells from the deleterious effects of Cr(VI) toxicity, both in vivo and in vitro. Therefore, Cr(VI) toxicity could be a potential risk to the reproductive system in developing females, and vitamin C plays a protective role against Cr(VI)-induced ovotoxicity

Synthesis of Poly(Ortho-Phenylenediamine Fluffy Microspheres and Application for the Removal of Cr(VI

Directory of Open Access Journals (Sweden)

Zhoufeng Wang

2012-01-01

Full Text Available We reported the synthesis of fluffy poly(o-phenylenediamine (PoPD microspheres via chemical polymerization of oPD monomers by ammonium persulfate (APS at room temperature. The SEM images showed that PoPD microspheres with an average diameter of 1.5 μm and their surfaces consist of highly oriented nanofibers. Furthermore, PoPD microspheres were used as adsorbent materials for the removal of Cr(VI from aqueous solutions. The Cr(VI adsorption behavior on the prepared PoPD microspheres was studied at different adsorption contact times, solution pH values, and amount of the adsorbent. Experimental isotherms of Cr(VI ions were successfully fit to the Langmuir isotherm model. The results indicate that the PoPD fluffy microspheres are an effective adsorbent for the removal of Cr(VI ions from aqueous solutions, and they could be useful in treatment of Cr(VI-polluted wastewaters.

Synthesis of Poly(Ortho-Phenylenediamine) Fluffy Microspheres and Application for the Removal of Cr(VI)

International Nuclear Information System (INIS)

Wang, Z.; Liao, F.

2012-01-01

We reported the synthesis of fluffy poly(o-phenylenediamine) (PoPD) microspheres via chemical polymerization of PoPD monomers by ammonium persulfate (APS) at room temperature. The SEM images showed that PoPD microspheres with an average diameter of 1.5 μm and their surfaces consist of highly oriented nano fibers. Furthermore, PoPD microspheres were used as adsorbent materials for the removal of Cr(VI) from aqueous solutions. The Cr(VI) adsorption behavior on the prepared PoPD microspheres was studied at different adsorption contact times, solution ph values, and amount of the adsorbent. Experimental isotherms of Cr(VI) ions were successfully fit to the Langmuir isotherm model. The results indicate that the PoPD fluffy microspheres are an effective adsorbent for the removal of Cr(VI) ions from aqueous solutions, and they could be useful in treatment of Cr(VI)-polluted wastewaters.

[Occupational exposure to hexavalent chromium during aircraft painting].

Science.gov (United States)

Gherardi, M; Gatto, M P; Gordiani, A; Paci, E; Proietto, A

2007-01-01

Hygienists are interested in hexavalent chromium due to its genotoxic and carcinogenic effect on humans. The use of products containing hexavalent chromium is decreasing in many industrial fields because of the substitution with less-toxic compounds. In the aeronautical industry, however, the chromate are added to primer paint as a corrosion inhibitor of aircrafts surfaces: so hexavalent chromium compounds are available in many primers with a composition ranging from 10% to 13%. The application of these primers by using electrostatic guns potentially exposes painting and coating workers at high concentrations of aerosols containing Cr(VI). The aim of the present study is the evaluation of professional exposure to hexavalent chromium during aircraft painting, by adopting both environmental personal sampling and biological monitoring. To valuate workers exposure levels the personal measurements results have been compared with the exposure limit values (TLV-TWA) and the urinary chromium contents with the biological exposure indices (IBE). Moreover the strategy of coupling environmental sampling with biological monitoring seems to be a useful instrument to measure the validity of the individual protection devices.

Hexavalent chromium-induced apoptosis of granulosa cells involves selective sub-cellular translocation of Bcl-2 members, ERK1/2 and p53

International Nuclear Information System (INIS)

Banu, Sakhila K.; Stanley, Jone A.; Lee, JeHoon; Stephen, Sam D.; Arosh, Joe A.; Hoyer, Patricia B.; Burghardt, Robert C.

2011-01-01

Hexavalent chromium (CrVI) has been widely used in industries throughout the world. Increased usage of CrVI and atmospheric emission of CrVI from catalytic converters of automobiles, and its improper disposal causes various health hazards including female infertility. Recently we have reported that lactational exposure to CrVI induced a delay/arrest in follicular development at the secondary follicular stage. In order to investigate the underlying mechanism, primary cultures of rat granulosa cells were treated with 10 μM potassium dichromate (CrVI) for 12 and 24 h, with or without vitamin C pre-treatment for 24 h. The effects of CrVI on intrinsic apoptotic pathway(s) were investigated. Our data indicated that CrVI: (i) induced DNA fragmentation and increased apoptosis, (ii) increased cytochrome c release from the mitochondria to cytosol, (iii) downregulated anti-apoptotic Bcl-2, Bcl-XL, HSP70 and HSP90; upregulated pro-apoptotic BAX and BAD, (iv) altered translocation of Bcl-2, Bcl-XL, BAX, BAD, HSP70 and HSP90 to the mitochondria, (v) upregulated p-ERK and p-JNK, and selectively translocated p-ERK to the mitochondria and nucleus, (vi) activated caspase-3 and PARP, and (vii) increased phosphorylation of p53 at ser-6, ser-9, ser-15, ser-20, ser-37, ser-46 and ser-392, increased p53 transcriptional activation, and downregulated MDM-2. Vitamin C pre-treatment mitigated CrVI effects on apoptosis and related pathways. Our study, for the first time provides a clear insight into the effect of CrVI on multiple pathways that lead to apoptosis of granulosa cells which could be mitigated by vitamin C.

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 potential application in wastewater treatment plants. The ASSA retained its original Cr(VI) sorption capacity up to three consecutive adsorption–desorption cycles. Finally, from XPS analysis, electrostatic attraction of Cr(VI) species to the adsorbent...

Molecular and cellular mechanisms of hexavalent chromium-induced lung cancer: an updated perspective.

Science.gov (United States)

Urbano, A M; Ferreira, L M R; Alpoim, M C

2012-03-01

For over a century, chromium (Cr) has found widespread industrial and commercial use, namely as a pigment, in the production of stainless steel and in chrome plating. The adverse health effects to the skin and respiratory tract of prolonged exposure to Cr have been known or suspected for a long time, but it was much more recently that the toxicity of this element was unequivocally attributed to its hexavalent state. Based on the combined results of extensive epidemiological studies, animal carcinogenicity studies and several types of other relevant data, authoritative regulatory agencies have found sufficient evidence to classify hexavalent chromium [Cr(VI)] compounds as encountered in the chromate production, chromate pigment production and chromium plating industries as carcinogenic to humans. Crucial for the development of novel strategies to prevent, detect and/or treat Cr(VI)-induced cancers is a detailed knowledge of the molecular and cellular mechanisms underlying these pathologies. Unfortunately, in spite of a considerable research effort, crucial facets of these mechanisms remain essentially unknown. This review is intended to provide a concise, integrated and critical perspective of the current state of knowledge concerning multiple aspects of Cr(VI) carcinogenesis. It will present recent theories of Cr(VI)-induced carcinogenesis and will include aspects not traditionally covered in other reviews, such as the possible involvement of the energy metabolism in this process. A brief discussion on the models that have been used in the studies of Cr(VI)-induced carcinogenicity will also be included, due to the impact of this parameter on the relevance of the results obtained.

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

International Nuclear Information System (INIS)

Rao, Rifaqat A.K.; Rehman, Fouzia

2010-01-01

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 (ΔG 0 ), enthalpy (ΔH 0 ) and entropy (ΔS 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 -1 respectively. The applicability of the adsorbent has been demonstrated by removing Cr(VI) from electroplating wastewater.

BIOSORPTION OF Cr(VI FROM SYNTHETIC WASTEWATER USING THE FRUIT SHELL OF GULMOHAR (Delonix regia: APPLICATION TO ELECTROPLATING WASTEWATER

Directory of Open Access Journals (Sweden)

Attimodde Girirajanna Devi Prasad

2010-05-01

Full Text Available The biosorption of Cr(VI from synthetic solutions and electroplating wastewater using the fruit shell of gulmohar has been investigated in a batch system. The effects of various parameters such as pH, contact time, adsorbent dosage, and initial concentration of Cr(VI on the biosorption process were studied. The complete removal of Cr(VI was observed at pH < 3.0. Studies indicated that both biosorption and bioreduction were involved in the removal of Cr(VI. The sorption equilibrium exhibited a better fit to the Langmuir isotherm than the Freundlich isotherm. The maximum biosorption capacity of fruit shell of gulmohar to remove Cr(VI was 12.28 mg/g. A kinetic model of pseudo-second order provided a good description of the experimental data as compared to a pseudo-first order kinetic model. The sorption rate was found to be dependent on the initial concentration of Cr(VI and biomaterials dosage. The study showed that the abundant and inexpensive fruit shell of gulmohar biosorbent has a potential application in the removal of Cr(VI from electroplating wastewater and its conversion into less or non-toxic Cr (III.

Effect of Organic Substrates on the Photocatalytic Reduction of Cr(VI by Porous Hollow Ga2O3 Nanoparticles

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Jin Liu

2018-04-01

Full Text Available Porous hollow Ga2O3 nanoparticles were successfully synthesized by a hydrolysis method followed by calcination. The prepared samples were characterized by field emission scanning electron microscope, transmission electron microscope, thermogravimetry and differential scanning calorimetry, UV-vis diffuse reflectance spectra and Raman spectrum. The porous structure of Ga2O3 nanoparticles can enhance the light harvesting efficiency, and provide lots of channels for the diffusion of Cr(VI and Cr(III. Photocatalytic reduction of Cr(VI, with different initial pH and degradation of several organic substrates by porous hollow Ga2O3 nanoparticles in single system and binary system, were investigated in detail. The reduction rate of Cr(VI in the binary pollutant system is markedly faster than that in the single Cr(VI system, because Cr(VI mainly acts as photogenerated electron acceptor. In addition, the type and concentration of organic substrates have an important role in the photocatalytic reduction of Cr(VI.

Effect of Organic Substrates on the Photocatalytic Reduction of Cr(VI) by Porous Hollow Ga2O3 Nanoparticles

Science.gov (United States)

Liu, Jin; Gan, Huihui; Wu, Hongzhang; Zhang, Xinlei; Zhang, Jun; Li, Lili; Wang, Zhenling

2018-01-01

Porous hollow Ga2O3 nanoparticles were successfully synthesized by a hydrolysis method followed by calcination. The prepared samples were characterized by field emission scanning electron microscope, transmission electron microscope, thermogravimetry and differential scanning calorimetry, UV-vis diffuse reflectance spectra and Raman spectrum. The porous structure of Ga2O3 nanoparticles can enhance the light harvesting efficiency, and provide lots of channels for the diffusion of Cr(VI) and Cr(III). Photocatalytic reduction of Cr(VI), with different initial pH and degradation of several organic substrates by porous hollow Ga2O3 nanoparticles in single system and binary system, were investigated in detail. The reduction rate of Cr(VI) in the binary pollutant system is markedly faster than that in the single Cr(VI) system, because Cr(VI) mainly acts as photogenerated electron acceptor. In addition, the type and concentration of organic substrates have an important role in the photocatalytic reduction of Cr(VI). PMID:29690548

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, H 2 SO 4 , HNO 3 , and H 3 PO 4 . 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 HNO 3 , H 2 SO 4 , and H 3 PO 4 , 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%-H 3 PO 4 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.

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.

Groundwater remediation of hexavalent chromium along the Columbia River at the Hanford site in Washington state, USA - 59030

International Nuclear Information System (INIS)

Foss, Dyan L.; Charboneau, Briant L.

2012-01-01

The U.S. Department of Energy Hanford Site, formerly used for nuclear weapons production, encompasses 1500 square kilometers in southeast Washington State along the Columbia River. A principle threat to the river are the groundwater plumes of hexavalent chromium (Cr(VI)), which affect approximately 9.8 square kilometers, and 4.1 kilometers of shoreline. Cleanup goals are to stop Cr(VI) from entering the river by the end of 2012 and remediate the groundwater plumes to the drinking water standards by the end of 2020. Five groundwater pump-and-treat systems are currently in operation for the remediation of Cr(VI). Since the 1990's, over 13.6 billion L of groundwater have been treated; over 1, 435 kg of Cr(VI) have been removed. This paper describes the unique aspects of the site, its environmental setting, hydrogeology, groundwater-river interface, riverine hydraulic effects, remediation activities completed to date, a summary of the current and proposed pump-and-treat operations, the in situ redox manipulation barrier, and the effectiveness of passive barriers, resins, and treatability testing results of calcium polysulfide, bio-stimulation, and electrocoagulation, currently under evaluation. (authors)

Polyethylenimine functionalized Fe3O4/steam-exploded rice straw composite as an efficient adsorbent for Cr(VI) removal

Science.gov (United States)

Zhang, Shengli; Wang, Zhikai; Chen, Haoyu; Kai, Chengcheng; Jiang, Man; Wang, Qun; Zhou, Zuowan

2018-05-01

Polyethyleneimine functionalized Fe3O4/steam-exploded rice straw composite (Fe3O4-PEI-SERS), which combines magnetic separation with adsorption of PEI functionalized biosorbent, was successfully prepared via a simple glutaraldehyde crosslinking method. Its adsorption potential for the removal of Cr(VI) was systematically studied in batch mode. Results showed that Cr(VI) adsorption on Fe3O4-PEI-SESERS was highly pH-dependent, and the optimum pH was 2.0. The time to reach equilibrium was related to initial Cr(VI) concentration and was 1 and 6 h for 200 and 300 mg/L of Cr(VI), respectively. The adsorption system followed pseudo-second-order kinetic model and Langmuir isotherm. Its maximum adsorption capacity was 280.11, 317.46 and 338.98 mg/g at 25, 35 and 45 °C, respectively. The competitive uptake from coexisting ions (K+, Na+, Cu2+, Cl- and NO3-) was insignificant except SO42-. After six adsorption/desorption cycles, the adsorbent retained good adsorption capacity. The Cr(VI) removal involved its partial reduction into Cr(III). Due to the properties of high adsorption capacity, strong magnetic responsiveness, good reusability and Cr(VI) detoxification, the Fe3O4-PEI-SESERS has a potential application in Cr(VI) removal from wastewater.

Development of phosphate rock integrated with iron amendment for simultaneous immobilization of Zn and Cr(VI) in an electroplating contaminated soil.

Science.gov (United States)

Zhao, Ling; Ding, Zhenliang; Sima, Jingke; Xu, Xiaoyun; Cao, Xinde

2017-09-01

This study aims to develop an amendment for simultaneous immobilization of Zn and Cr(VI) in an abandoned electroplating contaminated soil. Nature phosphate rock was first activated with oxalic acid (O-PR) and then combined with FeSO 4 or zero-valent iron (ZVI) for immobilization of Zn and Cr(VI) from aqueous solutions. Finally, the optimized approach showing the highest immobilization ability in solution was applied in an electroplating contaminated soil. The O-PR combined with FeSO 4 was more effective in simultaneously removing Zn and Cr(VI) than the O-PR integrated with ZVI within the tested solution pH range of 5.5-8.5. Both O-PR with FeSO 4 and with ZVI removed over 95% of Zn from the solution; however, only 42-46% of Cr(VI) was immobilized by O-PR with ZVI, while O-PR with FeSO 4 almost precipitated all Cr(VI). Moreover, there were 75-95% Zn and 95-100% Cr(VI) remaining in the exhausted O-PR with FeSO 4 solid after toxicity characteristic leaching test (TCLP) while the exhausted O-PR with ZVI solid only retained 44-83% Zn and 32-72% Cr(VI). Zinc was immobilized mainly via formation of insoluble Fe-Zn phosphate co-precipitates, while iron-induced reduction of Cr(VI) into stable Cr(OH) 3 or Cr x Fe (1-x) (OH) 3 was responsible for Cr(VI) immobilization. Application of the O-PR integrated with FeSO 4 in the electroplating contaminated soil rapidly reduced the TCLP extractable Zn and Cr(VI) to below the standard limits, with decrease by 50% and 94%, respectively. This study revealed that combination of oxalic acid activated phosphate rock with FeSO 4 could be an effective amendment for remediation of Zn and Cr(VI) contaminated soil. Copyright © 2017 Elsevier Ltd. All rights reserved.

Antidotal impact of extra virgin olive oil against genotoxicity, cytotoxicity and immunotoxicity induced by hexavalent chromium in rat

Directory of Open Access Journals (Sweden)

Samah Khalil

2013-12-01

Full Text Available An in vivo study was carried out to verify whether extra-virgin olive oil (EVOO has the potential to modulate alterations resulted from exposure to hexavalent chromium (CrVI as potassium dichromate in rats. For this purpose, CrVI was injected intraperitoneally (i.p. at a dose of 0.4 mg/kg bw/day, EVOO was given orally at a dose of 300 μl daily either a lone or co-treated with CrVI at the same doses, routes and duration (26 days. At the end of the experiment, blood and spleen samples were collected. Genotoxicity, cytotoxicity and immunotoxicity biomarkers induced by CrVI were evaluated. Also, histopathological and immunohistochemical investigations of spleen tissue were conducted. A significant increase in genotoxicity and cytotoxicity biomarkers (micronucleus frequency, 8-hydroxy-2-deoxyguanosine level and lactate dehydrogenase activity were recorded in CrVI treated rats. In addition, the immunotoxicity biomarkers showed a significant decrease in phagocytic%, stimulated nitric oxide production and decrease in the serum lysozyme activity. Histopathological and immunohistochemical studies support the cytotoxicity study. Oral administration of EVOO can ameliorate those effects but not restored to control level. Thus, authors recommend that regular consumption of this oil in the diet provides a constant supply of potential antioxidants that could reduce these alterations.

The application of tree bark as bio-indicator for the assessment of Cr(VI) in air pollution

International Nuclear Information System (INIS)

Mandiwana, Khakhathi L.; Resane, Tabby; Panichev, Nikolay; Ngobeni, Prince

2006-01-01

The impact of a chromium smelter on pollution was evaluated by determining Cr(VI) in topsoil, grass and tree bark by electhrothermal atomic absorption spectrometry (ETAAS). It was found that bark reflected the levels of air pollution better than soil and grass due to its high accumulative ability of Cr(VI). The tree bark was contaminated with Cr(VI) by a factor of 9 than in soil. It is therefore suggested that the bark be used as an indicator of air pollution for long-term exposure. The concentration of Cr(VI) in the bark was always a fraction of the total concentration of Cr and ranges between 1.6 and 3%. The method used in the preparation of samples was validated by the analysis of certified reference materials

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 ...

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.

Enhanced Cr(VI) removal from groundwater by Fe0-H2O system with bio-amended iron corrosion

DEFF Research Database (Denmark)

Yin, Weizhao; Li, Yongtao; Wu, Jinhua

2017-01-01

Abstract A one-pot bio-iron system was established to investigate synergetic abiotic and biotic effects between iron and microorganisms on Cr(VI) removal. More diverse iron corrosion and reactive solids, such as green rusts, lepidocrocite and magnetite were found in the bio-iron system than...... transfer on the solid phase. The results also showed that the reduction of Cr(VI) by microorganisms was insignificant, indicating the adsorption/co-precipitation of Cr by iron oxides on iron surface was responsible for the overall Cr(VI) removal. Our study demonstrated that the bio-amended iron corrosion...... in the Fe0-H2O system, leading to 4.3 times higher Cr(VI) removal efficiency in the bio-iron system than in the Fe0-H2O system. The cycling experiment also showed that the Cr(VI) removal capacity of Fe0 in the bio-iron system was 12.4 times higher than that in the Fe0-H2O system. A 62 days of life...

Effect of NaX zeolite-modified graphite felts on hexavalent chromium removal in biocathode microbial fuel cells.

Science.gov (United States)

Wu, Xiayuan; Tong, Fei; Yong, Xiaoyu; Zhou, Jun; Zhang, Lixiong; Jia, Honghua; Wei, Ping

2016-05-05

Two kinds of NaX zeolite-modified graphite felts were used as biocathode electrodes in hexavalent chromium (Cr(VI))-reducing microbial fuel cells (MFCs). The one was fabricated through direct modification, and the other one processed by HNO3 pretreatment of graphite felt before modification. The results showed that two NaX zeolite-modified graphite felts are excellent bio-electrode materials for MFCs, and that a large NaX loading mass, obtained by HNO3 pretreatment (the HNO3-NaX electrode), leads to a superior performance. The HNO3-NaX electrode significantly improved the electricity generation and Cr(VI) removal of the MFC. The maximum Cr(VI) removal rate increased to 10.39±0.28 mg/L h, which was 8.2 times higher than that of the unmodified control. The improvement was ascribed to the strong affinity that NaX zeolite particles, present in large number on the graphite felt, have for microorganisms and Cr(VI) ions. Copyright © 2016 Elsevier B.V. All rights reserved.

Hexavalent chromium exposures and exposure-control technologies in American enterprise: results of a NIOSH field research study.

Science.gov (United States)

Blade, L M; Yencken, M Story; Wallace, M E; Catalano, J D; Khan, A; Topmiller, J L; Shulman, S A; Martinez, A; Crouch, K G; Bennett, J S

2007-08-01

The National Institute for Occupational Safety and Health (NIOSH) conducted 21 field surveys in selected industries to characterize workers' exposures to hexavalent chromium-containing airborne particulate and to evaluate existing technologies for controlling these exposures. Hexavalent chromium Cr(VI) is a respiratory irritant and chronic inhalation may cause lung cancer. Primary evaluation methods included collection of full work shift, personal breathing-zone (PBZ) air samples for Cr(VI), measurement of ventilation system parameters, and documentation of processes and work practices. This study emphasized evaluation of engineering exposure control measures, so PBZ exposures were measured on the outside of personal protective equipment, for example, respirators. Field surveys were conducted in two chromium electroplating facilities, including one where full-shift PBZ exposures to Cr(VI) ranged from 3.0 to 16 times the 1 micro g/m(3)NIOSH recommended exposure limit (REL) despite several engineering controls on the plating tanks. At a painting and coating facility that used Cr(VI)-containing products, full-shift exposures of painters and helpers (2.4 to 55 micro g/m(3)) exceeded the REL, but LEV effectiveness was limited. Other operations evaluated included welding in construction; metal cutting operations on chromium-containing materials in ship breaking; chromate-paint removal with abrasive blasting; atomized alloy-spray coating; foundry operations; printing; and the manufacture of refractory brick, colored glass, prefabricated concrete products, and treated wood products. NIOSH researchers concluded that, in many of the evaluated processes, Cr(VI) exposures at or below the current NIOSH REL are achievable. However, for some processes, it is unclear whether controlling exposures to this range is consistently achievable without respirator use. Some operations involving the application of coatings and finishes may be among those most difficult to control to this

The intracellular redox stress caused by hexavalent chromium is selective for proteins that have key roles in cell survival and thiol redox control

International Nuclear Information System (INIS)

Myers, Judith M.; Antholine, William E.; Myers, Charles R.

2011-01-01

Hexavalent chromium [Cr(VI)] compounds (e.g. chromates) are strong oxidants that readily enter cells where they are reduced to reactive Cr intermediates that can directly oxidize some cell components and can promote the generation of reactive oxygen and nitrogen species. Inhalation is a major route of exposure which directly exposes the bronchial epithelium. Previous studies with non-cancerous human bronchial epithelial cells (BEAS-2B) demonstrated that Cr(VI) treatment results in the irreversible inhibition of thioredoxin reductase (TrxR) and the oxidation of thioredoxins (Trx) and peroxiredoxins (Prx). The mitochondrial Trx/Prx system is somewhat more sensitive to Cr(VI) than the cytosolic Trx/Prx system, and other redox-sensitive mitochondrial functions are subsequently affected including electron transport complexes I and II. Studies reported here show that Cr(VI) does not cause indiscriminant thiol oxidation, and that the Trx/Prx system is among the most sensitive of cellular protein thiols. Trx/Prx oxidation is not unique to BEAS-2B cells, as it was also observed in primary human bronchial epithelial cells. Increasing the intracellular levels of ascorbate, an endogenous Cr(VI) reductant, did not alter the effects on TrxR, Trx, or Prx. The peroxynitrite scavenger MnTBAP did not protect TrxR, Trx, Prx, or the electron transport chain from the effects of Cr(VI), implying that peroxynitrite is not required for these effects. Nitration of tyrosine residues of TrxR was not observed following Cr(VI) treatment, further ruling out peroxynitrite as a significant contributor to the irreversible inhibition of TrxR. Cr(VI) treatments that disrupt the TrxR/Trx/Prx system did not cause detectable mitochondrial DNA damage. Overall, the redox stress that results from Cr(VI) exposure shows selectivity for key proteins which are known to be important for redox signaling, antioxidant defense, and cell survival.

Leachability of Cr(VI) and other metals from asphalt composites with addition of filter dust.

Science.gov (United States)

Vahcic, Mitja; Milacic, Radmila; Mladenovic, Ana; Murko, Simona; Zuliani, Tea; Zupancic, Marija; Scancar, Janez

2008-12-01

The potential use of filter dust in asphalt composites for road construction was investigated. Filter dust contains high concentrations of metals, of which Cr(VI) and Pb are leached with water. Compact and ground asphalt composites with addition of 2% of filter dust by mass were studied. In order to evaluate their environmental impact, leachability tests were performed using water and salt water as leaching agents. The concentrations of Cr(VI) and Pb were determined in leachates over a time period of 182 days. The results indicated that Pb was not leached with leaching agents from asphalt composites. Cr(VI) was also not leached with leaching agents from compact asphalt composites. However, in ground asphalt composites, Cr(VI) was leached with water in concentrations up to 220 microg L(-1) and in salt water up to 150 microg L(-1). From the physico-mechanical and environmental aspects, filter dust can be used as a component in asphalt mixtures.

Hexavalent Chromium Removal from Model Water and Car Shock Absorber Factory Effluent by Nanofiltration and Reverse Osmosis Membrane

Directory of Open Access Journals (Sweden)

Amine Mnif

2017-01-01

Full Text Available Nanofiltration and reverse osmosis are investigated as a possible alternative to the conventional methods of Cr(VI removal from model water and industrial effluent. The influences of feed concentration, water recovery, pH, and the coexisting anions were studied. The results have shown that retention rates of hexavalent chromium can reach 99.7% using nanofiltration membrane (NF-HL and vary from 85 to 99.9% using reverse osmosis membrane (RO-SG depending upon the composition of the solution and operating conditions. This work was also extended to investigate the separation of Cr(VI from car shock absorber factory effluent. The use of these membranes is very promising for Cr(VI water treatment and desalting industry effluent. Spiegler-Kedem model was applied to experimental results in the aim to determine phenomenological parameters, the reflection coefficient of the membrane (σ, and the solute permeability coefficient (Ps. The convective and diffusive parts of the mass transfer were quantified with predominance of the diffusive contribution.

Assessment of the mode of action underlying development of rodent small intestinal tumors following oral exposure to hexavalent chromium and relevance to humans

Science.gov (United States)

Proctor, Deborah M.; Suh, Mina; Haws, Laurie C.; Kirman, Christopher R.; Harris, Mark A.

2013-01-01

Chronic exposure to high concentrations of hexavalent chromium (Cr(VI)) in drinking water causes intestinal adenomas and carcinomas in mice, but not in rats. Cr(VI) causes damage to intestinal villi and crypt hyperplasia in mice after only one week of exposure. After two years of exposure, intestinal damage and crypt hyperplasia are evident in mice (but not rats), as are intestinal tumors. Although Cr(VI) has genotoxic properties, these findings suggest that intestinal tumors in mice arise as a result of chronic mucosal injury. To better understand the mode of action (MOA) of Cr(VI) in the intestine, a 90-day drinking water study was conducted to collect histological, biochemical, toxicogenomic and pharmacokinetic data in intestinal tissues. Using MOA analyses and human relevance frameworks proposed by national and international regulatory agencies, the weight of evidence supports a cytotoxic MOA with the following key events: (a) absorption of Cr(VI) from the intestinal lumen, (b) toxicity to intestinal villi, (c) crypt regenerative hyperplasia and (d) clonal expansion of mutations within the crypt stem cells, resulting in late onset tumorigenesis. This article summarizes the data supporting each key event in the MOA, as well as data that argue against a mutagenic MOA for Cr(VI)-induced intestinal tumors. PMID:23445218

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.

Microbial Precipitation of Cr(III)-Hydroxide and Se(0) Nanoparticles During Anoxic Bioreduction of Cr(VI)- and Se(VI)-Contaminated Water.

Science.gov (United States)

Kim, Yumi; Oh, Jong-Min; Roh, Yul

2017-04-01

This study examined the microbial precipitations of Cr(III)-hydroxide and Se(0) nanoparticles during anoxic bioreductions of Cr(VI) and Se(VI) using metal-reducing bacteria enriched from groundwater. Metal-reducing bacteria enriched from groundwater at the Korea Atomic Energy Research Institute (KAERI) Underground Research Tunnel (KURT), Daejeon, S. Korea were used. Metal reduction and precipitation experiments with the metal-reducing bacteria were conducted using Cr(VI)- and Se(VI)-contaminated water and glucose as a carbon source under an anaerobic environment at room temperature. XRD, SEM-EDX, and TEM-EDX analyses were used to characterize the mineralogy, crystal structure, chemistry, shape, and size distribution of the precipitates. The metal-reducing bacteria reduced Cr(VI) of potassium chromate (K₂CrO₄) to Cr(III) of chromium hydroxide [Cr(OH)3], and Se(VI) of sodium selenate (Na₂SeO₄) to selenium Se(0), with changes of color and turbidity. XRD, SEM-EDX, and TEM-EDX analyses revealed that the chromium hydroxide [Cr(OH)₃] was formed extracellularly with nanoparticles of 20–30 nm in size, and elemental selenium Se(0) nanoparticles had a sphere shape of 50–250 nm in size. These results show that metal-reducing bacteria in groundwater can aid or accelerate precipitation of heavy metals such as Cr(VI) and Se(VI) via bioreduction processes under anoxic environments. These results may also be useful for the recovery of Cr and Se nanoparticles in natural environments.

Origin of hexavalent chromium in groundwater: The example of Sarigkiol Basin, Northern Greece.

Science.gov (United States)

Kazakis, N; Kantiranis, N; Kalaitzidou, K; Kaprara, E; Mitrakas, M; Frei, R; Vargemezis, G; Tsourlos, P; Zouboulis, A; Filippidis, A

2017-09-01

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 was paid to this particular study area due to the co-existence here of two important factors both expected to contribute to Cr(VI) presence and groundwater pollution; namely the area's exposed ophiolitic rocks and its substantial fly ash deposits originating from the local lignite burning power plant. 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 120μgL -1 ) recorded in the groundwater of the unconfined porous aquifer situated near the temporary fly ash disposal site. Recharge of the porous aquifer is related mainly to precipitation infiltration and occasional surface run-off. Nevertheless, a hydraulic connection between the porous and neighboring karst aquifers could not be delineated. Therefore, the presence of Cr(VI) in the groundwater of this area is thought to originate from both the ophiolitic rock weathering products in the soils, and the local leaching of Cr(VI) from the diffused fly ash located in the area surrounding the lignite power plant. This conclusion was corroborated by factor analysis, and the strongly positively fractionated Cr isotopes (δ 53 Cr up to 0.83‰) recorded in groundwater, an ash leachate, and the bulk fly ash. An anthropogenic source of Cr(VI) that possibly influences groundwater quality is especially apparent in the eastern part of the Sarigkiol basin. Copyright © 2017 Elsevier B.V. All rights reserved.

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.

Assessment of the mode of action for hexavalent chromium-induced lung cancer following inhalation exposures

International Nuclear Information System (INIS)

Proctor, Deborah M.; Suh, Mina; Campleman, Sharan L.; Thompson, Chad M.

2014-01-01

Highlights: • No published or well recognized MOA for Cr(VI)-induced lung tumors exists. • MOA analysis for Cr(VI)-induced lung cancer was conducted to inform risk assessment. • Cr(VI) epidemiologic, toxicokinetic, toxicological, mechanistic data were evaluated. • Weight of evidence does not support a mutagenic MOA for Cr(VI)-induced lung cancer. • Non-linear approaches should be considered for evaluating Cr(VI) lung cancer risk. - Abstract: Inhalation of hexavalent chromium [Cr(VI)] is associated with increased lung cancer risk among workers in several industries, most notably chromate production workers exposed to high concentrations of Cr(VI) (≥100 μg/m 3 ), for which clear exposure–response relationships and respiratory irritation and tissue damage have been reported. Data from this industry are used to assess lung cancer risk associated with environmental and current occupational exposures, occurring at concentrations that are significantly lower. There is considerable uncertainty in the low dose extrapolation of historical occupational epidemiology data to assess risk at current exposures because no published or well recognized mode of action (MOA) for Cr(VI)-induced lung tumors exists. We conducted a MOA analysis for Cr(VI)-induced lung cancer evaluating toxicokinetic and toxicological data in humans and rodents and mechanistic data to assess plausibility, dose–response, and temporal concordance for potential MOAs. Toxicokinetic data support that extracellular reduction of Cr(VI), which limits intracellular absorption of Cr(VI) and Cr(VI)-induced toxicity, can be overwhelmed at high exposure levels. In vivo genotoxicity and mutagenicity data are mostly negative and do not support a mutagenic MOA. Further, both chronic bioassays and the epidemiologic literature support that lung cancer occurs at exposures that cause tissue damage. Based on this MOA analysis, the overall weight of evidence supports a MOA involving deposition and accumulation

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.

Hexavalent Chromium Is Cytotoxic and Genotoxic to American Alligator Cells

OpenAIRE

Wise, Sandra S.; Wise, Catherine; Xie, Hong; Guillette, Louis J.; Zhu, Cairong; Wise, John Pierce; Wise, John Pierce

2015-01-01

Metals are a common pollutant in the aquatic ecosystem. With global climate change, these levels are anticipated to rise as lower pH levels allow sediment bound metals to be released. The American alligator (Alligator mississippiensis) is an apex predator in the aquatic ecosystem and is considered a keystone species; as such it serves as a suitable monitor for localized pollution. One metal of increasing concern is hexavalent chromium (Cr(VI)). It is present in the aquatic environment and is ...

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 Δ G° (-8.59 and -11.16 kJ mol-1) and Δ H° (66.46 × 10-1 and 17.84 × 10-1 kJ mol-1), and positive value of Δ 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.

Separation of Cr(III) from Cr(VI) by Triton X-100 cerium(IV) phosphate as a surface active ion exchanger

International Nuclear Information System (INIS)

El-Azony, K.M.; Ismail Aydia, M.; El-Mohty, A.A.

2011-01-01

Triton X-100 cerium(IV) phosphate (TX-100CeP) was synthesized and characterized by using IR, X-ray, TGA/DT and the elemental analysis. The chemical stability of TX-100CeP versus the different concentrations of HCl acid was studied before and after its exposure to the radiation dose (30 K Gray). The effect of HCl concentration on separation of Cr(III) from Cr(VI) by using TX-100CeP as surface active ion exchanger was also studied. A novel method was achieved for the quantifying of Cr(III) and Cr(VI) ions by using the high-performance liquid chromatography (HPLC) at wavelength 650 nm, a stationary phase consists of reversed phase column (Nucleosil phenyl column; 250 x 4.6 mm, 5 μm), and a mobile phase consists of 0.001 M di-(2-ethylhexyl) phosphoric acid (DEHPA) in methanol:water (70:30 v/v). The retention times were 7.0 and 8.5 min, for the Cr(III) and Cr(VI), respectively. The exchange capacity of Cr(III) was quantified (2.1 meq/g) onto the TX-100CeP. (author)

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 ...

Hexavalent Chromium Is Cytotoxic and Genotoxic to Hawksbill Sea Turtle Cells

Science.gov (United States)

Wise, Sandra S.; Xie, Hong; Fukuda, Tomokazu; Thompson, W. Douglas; Wise, John Pierce

2014-01-01

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/cm2 lead chromate induced 108, 79, 54, and 7 percent relative survival, respectively. Additionally, concentrations of 0, 0.1, 0.5, 1, and 5 μg/cm2 lead chromate induced damage in 4, 10, 15, 26, and 36 percent 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 percent relative survival, respectively. Sodium chromate induced 3, 9, 9, 14, 21, and 29 percent 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. PMID:24952338

Effect of Organic Matter on Cr(VI Removal from Groundwaters by Fe(II Reductive Precipitation for Groundwater Treatment

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Anna Gröhlich

2017-06-01

Full Text Available Due to its toxicity, Cr(VI is undesirable in groundwater. Its chemical reduction to Cr(III species, followed by precipitation is the most widely practiced treatment technique for the removal of Cr(VI from polluted waters. The resulting Cr(III species present low solubility, is much less toxic, and can be subsequently removed either by precipitation, or by adsorption onto iron oxy-hydroxides and co-precipitation. The effects of several parameters, such as the pH value of water to be treated, the applied Fe(II dose, and the presence of appropriate mineral surfaces, are well investigated and understood. However, the impact of the presence of humic acids (HAs in this process has only been considered by rather few studies. The main aim of this study was to determine the effect of humic substances on Fe(II reductive precipitation of Cr(VI within a pH range relevant for drinking water treatment. Jar test experiments were performed, using artificial groundwater of defined composition and initial Cr(VI concentration 100 μg/L, ferrous sulphate dosages 0.25–2 mg Fe(II/L, and pH values 6.5–8. It was found that Cr(VI and total chromium (Cr(total can be reliably removed in the absence of HAs in the tested pH range with the addition of Fe(II dosage of 1 mg Fe(II/L. Further on, the results indicated that the reduction of Cr(VI is only slightly affected by the presence of HAs. However, increased residual total Cr concentrations were found at lower Fe(II dosages and/or higher pH values. Additionally, the removal of the Cr(III species formed during Cr(VI reduction was strongly inhibited by the presence of HAs under the examined experimental conditions, since residual concentrations higher than 60 μg/L were determined. The results of this study will have implications to the ongoing discussion of a new, stricter, European Union regulation limit, regarding the presence of total chromium in drinking water.

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)

Banana peel: a green and economical sorbent for the selective removal of Cr(VI) from industrial wastewater.

Science.gov (United States)

Memon, Jamil R; Memon, Saima Q; Bhanger, Muhammad I; El-Turki, Adel; Hallam, Keith R; Allen, Geoffrey C

2009-05-01

This study describes the use of banana peel, a commonly produced fruit waste, for the removal of Cr(VI) from industrial wastewater. The parameters pH, contact time, initial metal ion concentration, and temperature were investigated and the conditions resulting in rapid and efficient adsorption (95% within 10 min) were determined. The binding of metal ions was found to be pH dependent with the optimal sorption occurring at pH 2. The retained species were eluted with 5 mL of 2M H(2)SO(4). To elucidate the mechanism of the process, total amounts of chromium and Cr(VI) were analyzed using flame atomic absorption and ultraviolet-visible (UV-vis) spectroscopic techniques, respectively. The Langmuir and Dubinin-Radushkevich (D-R) isotherms were used to describe the partitioning behavior for the system at different temperatures. Kinetics and thermodynamics of Cr(VI) removal by banana peel were also studied. The influence of diverse ions on the sorption behavior revealed that only Fe(II) ions (of those tested) suppressed the sorption of Cr(VI) ions to some extent. The method was applied for the removal of Cr(VI) from industrial wastewater.

Nano-sized Fe2O3/Fe3O4 facilitate anaerobic transformation of hexavalent chromium in soil-water systems.

Science.gov (United States)

Zhang, Yaxian; Li, Hua; Gong, Libo; Dong, Guowen; Shen, Liang; Wang, Yuanpeng; Li, Qingbiao

2017-07-01

The purpose of this study is to investigate the effects of nano-sized or submicro Fe 2 O 3 /Fe 3 O 4 on the bioreduction of hexavalent chromium (Cr(VI)) and to evaluate the effects of nano-sized Fe 2 O 3 /Fe 3 O 4 on the microbial communities from the anaerobic flooding soil. The results indicated that the net decreases upon Cr(VI) concentration from biotic soil samples amended with nano-sized Fe 2 O 3 (317.1±2.1mg/L) and Fe 3 O 4 (324.0±22.2mg/L) within 21days, which were approximately 2-fold of Cr(VI) concentration released from blank control assays (117.1±5.6mg/L). Furthermore, the results of denaturing gradient gel electrophoresis (DGGE) and high-throughput sequencing indicated a greater variety of microbes within the microbial community in amendments with nano-sized Fe 2 O 3 /Fe 3 O 4 than the control assays. Especially, Proteobacteria occupied a predominant status on the phylum level within the indigenous microbial communities from chromium-contaminated soils. Besides, some partial decrease of soluble Cr(VI) in abiotic nano-sized Fe 2 O 3 /Fe 3 O 4 amendments was responsible for the adsorption of nano-sized Fe 2 O 3 /Fe 3 O 4 to soluble Cr(VI). Hence, the presence of nano-sized Fe 2 O 3 /Fe 3 O 4 could largely facilitate the mobilization and biotransformation of Cr(VI) from flooding soils by adsorption and bio-mediated processes. Copyright © 2017. Published by Elsevier B.V.

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. Copyright © 2015 Elsevier Ltd. All rights reserved.

Redox transformation and reductive immobilization of Cr(VI) in the Columbia River hyporheic zone sediments

Energy Technology Data Exchange (ETDEWEB)

Xu, Fen; Liu, Yuanyuan; Zachara, John M.; Bowden, Mark E.; Kennedy, David W.; Plymale, Andrew E.; Liu, Chongxuan,

2017-12-01

An experimental and modeling study was conducted to investigate the redox transformation and reductive immobilization of groundwater contaminant Cr in hyporheic zone (HZ) sediments from U.S. Department of Energy’s Hanford site, where groundwater Cr(VI) is migrating and discharging to the nearby Columbia River. Experimental results revealed that Cr(VI) can be reduced to immobile reduced Cr by the HZ sediments in the presence/absence of O2. Anaerobic pre-incubation of the sediments increased the effective rate of Cr reduction that was correlated with the increase in HCl-extractable Fe(II) content in the sediments. The reduced Cr was stable in exposure to O2 under field-relevant pH (~7.5) and Mn-containing (~0.02% w/w) conditions. The Cr(VI) reduction rate showed a multi-rate behavior, apparently reflecting the presence of reductants with different reactivity in the sediments. The results from this study indicated that the HZ sediments can reductively immobilize Cr and the sediment redox capacity can be recharged through microbial activities. The results implied that HZ can play a role as a natural permeable redox barrier for removing groundwater Cr before it discharges into a river system.

Isolation and characterization of a chromium-resistant bacterium Serratia sp. Cr-10 from a chromate-contaminated site.

Science.gov (United States)

Zhang, Kundi; Li, Fuli

2011-05-01

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(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(-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(-1) h(-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.

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.)

Experimental data on adsorption of Cr(VI from aqueous solution using nanosized cellulose fibers obtained from rice husk

Directory of Open Access Journals (Sweden)

Sudabeh Pourfadakari

2017-12-01

Full Text Available The aim of this study was to evaluate the efficiency of nano-sized cellulose obtained from rice husk for Cr(VI adsorption. The effect of operational parameters including initial pH (3–10, contact time (0–120 min, adsorbent dosage (0.2–1.5 g/L, and initial Cr(VI concentration (5–50 mg/L were investigated according to one factor at time method. The results showed, in pH=6, contact time=100 min, adsorbent dose=1.5 g/L and 30 mg/L initial chromium concentration, the adsorption efficiency reached to 92.99%. Also Langmuir isotherm with (R2=0.998 at 303 °K and pseudo-first-order kinetic model (R2=0.993 were the best models for describing the Cr(VI adsorption reactions. The negative values of ΔG∘ and positive value of ΔH∘ showed that, the Cr(VI adsorption on NCFs was endothermic and spontaneously process. Therefore, it can be concluded that the application this method is recommended for removing Cr(VI from aqueous solutions. Keywords: Rice husk, Nano-sized cellulose, Cr(VI, Adsorption, Water pollution

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.

Cr(VI) and Conductivity as Indicators of Surface Water Pollution from Ferrochrome Production in South Africa: Four Case Studies

Science.gov (United States)

Loock-Hattingh, M. M.; Beukes, J. P.; van Zyl, P. G.; Tiedt, L. R.

2015-10-01

South Africa is one of the largest ferrochromium (FeCr) producers. Most FeCr is exported to developed countries. Therefore the impact of this industry is of national and international importance. Cr(VI) and conductivity of surface water in four case study areas, near five FeCr smelters were monitored for approximately 1 year. Results indicated that FeCr production in three case study areas had a negative influence on the Cr(VI) concentration and/or the conductivity of surface waters. In the remaining case study areas, drinking water, originating from groundwater, was severely polluted with Cr(VI). The main factors causing pollution were surface run-off and/or seepage, while atmospheric deposition did not seem to contribute significantly. The extinction of diatoms during a severe Cr(VI) surface water pollution event (concentrations up to 216 µg/L) in one of the case study areas was also observed, which clearly indicates the ecological impact of such surface water pollution events.

Simultaneous Treatment of Agro-Industrial and Industrial Wastewaters: Case Studies of Cr(VI/Second Cheese Whey and Cr(VI/Winery Effluents

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Triantafyllos I. Tatoulis

2018-03-01

Full Text Available Hexavalent chromium (Cr(VI was co-treated either with second cheese whey (SCW or winery effluents (WE using pilot-scale biological trickling filters in series under different operating conditions. Two pilot-scale filters in series using plastic support media were used in each case. The first filter (i.e., Cr-SCW-filter or Cr-WE-filter aimed at Cr(VI reduction and the partial removal of dissolved chemical oxygen demand (d-COD from SCW or WE and was inoculated with indigenous microorganisms originating from industrial sludge. The second filter in series (i.e., SCW-filter or WE-filter aimed at further d-COD removal and was inoculated with indigenous microorganisms that were isolated from SCW or WE. Various Cr(VI (5–100 mg L−1 and SCW or WE (d-COD, 1000–25,000 mg L−1 feed concentrations were tested. Based on the experimental results, the sequencing batch reactor operating mode with recirculation of 0.5 L min−1 proved very efficient since it led to complete Cr(VI reduction in the first filter in series and achieved high Cr(VI reduction rates (up to 36 and 43 mg L−1 d−1, for SCW and WW, respectively. Percentage d-COD removal for SCW and WE in the first filter was rather low, ranging from 14 to 42.5% and from 4 to 29% in the Cr-SCW-filter and Cr-WE-filter, respectively. However, the addition of the second filter in series enhanced total d-COD removal to above 97% and 90.5% for SCW and WE, respectively. The above results indicate that agro-industrial wastewater could be used as a carbon source for Cr(VI reduction, while the use of two trickling filters in series could effectively treat both industrial and agro-industrial wastewaters with very low installation and operational costs.

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 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...

Removal of Cr(VI and Toxic Ions from Aqueous Solutions and Tannery Wastewater Using Polymer-Clay Composites

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Abd El-Azeem Sallam

2017-10-01

Full Text Available Polymer-clay composites were prepared by natural zeolite (clinoptilolite or naturally local clay deposits in an N,N-methylene-bis-acrylamide as cross-linked. The resultant composites were used for the removal of Cr(VI from an aqueous solution. Additionally, their effects on soluble ions of tannery wastewater were investigated. The produced composites were characterized using X-ray diffraction (XRD, Fourier transform infrared spectroscopy (FT-IR, and scanning electron microscopy (SEM. The results showed that Cr(VI removal is dependent upon initial concentrations and pH. The adsorption quantity of Cr(VI onto the polymerized clay deposit followed by polymerized zeolite exhibited higher values than their original samples. The polymer-clay composite of clay deposit showed the highest removal of 76.3–100% overall initial concentrations of 10–50 mg L−1 and at initial pH of 2. Kinetics of Cr(VI removal by various sorbents was predicted using a pseudo–second order model. Our findings showed that the levels of salinity and various soluble ions (Cr2+, Na+, Cl− and SO42− in tannery wastewater are very high, and their levels were reduced after treatment, especially by polymerized sorbents. It could be concluded that the polymer-clay composites may be employed as a highly efficient sorbent for the removal of Cr(VI and toxic ions from the wastewater.

Acetate biostimulation as an effective treatment for cleaning up alkaline soil highly contaminated with Cr(VI).

Science.gov (United States)

Lara, Paloma; Morett, Enrique; Juárez, Katy

2017-11-01

Stimulation of microbial reduction of Cr(VI) to the less toxic and less soluble Cr(III) through electron donor addition has been regarded as a promising approach for the remediation of chromium-contaminated soil and groundwater sites. However, each site presents different challenges; local physicochemical characteristics and indigenous microbial communities influence the effectiveness of the biostimulation processes. Here, we show microcosm assays stimulation of microbial reduction of Cr(VI) in highly alkaline and saline soil samples from a long-term contaminated site in Guanajuato, Mexico. Acetate was effective promoting anaerobic microbial reduction of 15 mM of Cr(VI) in 25 days accompanied by an increase in pH from 9 to 10. Our analyses showed the presence of Halomonas, Herbaspirillum, Nesterenkonia/Arthrobacter, and Bacillus species in the soil sample collected. Moreover, from biostimulated soil samples, it was possible to isolate Halomonas spp. strains able to grow at 32 mM of Cr(VI). Additionally, we found that polluted groundwater has bacterial species different to those found in soil samples with the ability to resist and reduce chromate using acetate and yeast extract as electron donors.

Selective and sensitive speciation analysis of Cr(VI) and Cr(III), at sub-μgL-1 levels in water samples by electrothermal atomic absorption spectrometry after electromembrane extraction.

Science.gov (United States)

Tahmasebi, Zeinab; Davarani, Saied Saeed Hosseiny

2016-12-01

In this work, electromembrane extraction in combination with electrothermal atomic absorption spectrometry (ET-AAS) was investigated for speciation, preconcentration and quantification of Cr(VI) and Cr(III) in water samples through the selective complexation of Cr(VI) with 1,5-diphenylcarbazide (DPC) as a complexing agent. DPC reduces Cr(VI) to Cr(III) ions and then Cr(III) species are extracted based on electrokinetic migration of their cationic complex (Cr(III)-DPC) toward the negative electrode placed in the hollow fiber. Also, once oxidized to Cr(VI), Cr(III) ions in initial sample were determined by this procedure. The influence of extraction parameters such as pH, type of organic solvent, chelating agent concentration, stirring rate, extraction time and applied voltage were evaluated following a one-at-a-time optimization approach. Under optimized conditions, the extracted analyte was quantified by ETAAS, with an acceptable linearity in the range of 0.05-5ngmL -1 (R 2 value=0.996), and a repeatability (%RSD) between 3.7% and 12.2% (n=4) for 5.0 and 1.0ngmL -1 of Cr(VI), respectively. Also, we obtained an enrichment factor of 110 that corresponded to the recovery of 66%. The detection limit (S/N ratio of 3:1) was 0.02ngmL -1 . Finally, this new method was successfully employed to determine Cr(III) and Cr(VI) species in real water samples. Copyright © 2016. Published by Elsevier B.V.

Enhanced biotic and abiotic transformation of Cr(vi) by quinone-reducing bacteria/dissolved organic matter/Fe(iii) in anaerobic environment.

Science.gov (United States)

Huang, Bin; Gu, Lipeng; He, Huan; Xu, Zhixiang; Pan, Xuejun

2016-09-14

This study investigated the simultaneous transformation of Cr(vi) via a closely coupled biotic and abiotic pathway in an anaerobic system of quinone-reducing bacteria/dissolved organic matters (DOM)/Fe(iii). Batch studies were conducted with quinone-reducing bacteria to assess the influences of sodium formate (NaFc), electron shuttling compounds (DOM) and the Fe(iii) on Cr(vi) reduction rates as these chemical species are likely to be present in the environment during in situ bioremediation. Results indicated that the concentration of sodium formate and anthraquinone-2-sodium sulfonate (AQS) had apparently an effect on Cr(vi) reduction. The fastest decrease in rate for incubation supplemented with 5 mM sodium formate and 0.8 mM AQS showed that Fe(iii)/DOM significantly promoted the reduction of Cr(vi). Presumably due to the presence of more easily utilizable sodium formate, DOM and Fe(iii) have indirect Cr(vi) reduction capability. The coexisting cycles of Fe(ii)/Fe(iii) and DOM(ox)/DOM(red) exhibited a higher redox function than the individual cycle, and their abiotic coupling action can significantly enhance Cr(vi) reduction by quinone-reducing bacteria.

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

2017-12-01

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.

Redox transformation and reductive immobilization of Cr(VI) in the Columbia River hyporheic zone sediments

Science.gov (United States)

Xu, Fen; Liu, Yuanyuan; Zachara, John; Bowden, Mark; Kennedy, David; Plymale, Andrew E.; Liu, Chongxuan

2017-12-01

An experimental and modeling study was conducted to investigate the redox transformation and reductive immobilization of groundwater contaminant Cr in hyporheic zone (HZ) sediments from U.S. DOE's Hanford Site, where groundwater Cr(VI) is migrating and discharging to the nearby Columbia River. Experimental results revealed that Cr(VI) can be reduced and immobilized by the HZ sediments in the presence/absence of O2. Anaerobic pre-incubation of the sediments increased the effective rate of Cr reduction that was correlated with the increase in HCl-extractable Fe(II) content in the sediments. The reduced Cr was stable when exposed to O2 under field-relevant pH (7.5) with and without dissolved Mn(II), which might be oxidized to form Mn(III/IV) oxides that may oxidize reduced Cr. The Cr(VI) reduction rate showed a multi-rate behavior, apparently reflecting the presence of reductants with different reactivity in the sediments. The results from this study indicated that the HZ sediments can reductively immobilize Cr and the sediment redox capacity can be recharged through microbial activities. The results implied that HZ can play a role as a natural permeable redox barrier for removing groundwater Cr before it discharges into a river system.

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.

Towards Cr(VI)-free anodization of aluminum alloys for aerospace adhesive bonding applications : A review

NARCIS (Netherlands)

Abrahami, S.T.; de Kok, John M.M.; Terryn, H.A.; Mol, J.M.C.

2017-01-01

For more than six decades, chromic acid anodizing (CAA) has been the central process in the surface pre-treatment of aluminum for adhesively bonded aircraft structures. Unfortunately, this electrolyte contains hexavalent chromium (Cr(VI)), a compound known for its toxicity and carcinogenic

Cr(VI) reduction and immobilization by novel carbonaceous modified magnetic Fe_3O_4/halloysite nanohybrid

International Nuclear Information System (INIS)

Tian, Xike; Wang, Weiwei; Tian, Na; Zhou, Chaoxin; Yang, Chao; Komarneni, Sridhar

2016-01-01

Highlights: • A novel magnetic nonohybrids (Fe_3O_4/HNTs@C) were synthesized for Cr(VI) removal. • Cr(VI) was reduced to Cr(III) by Fe_3O_4 nanoparticles and hydroxyl groups. • Cr ions were attached on Fe_3O_4/HNTs@C by ion exchange and coordination interaction. - Abstract: In this work, a novel “Dumbbell-like” magnetic Fe_3O_4/Halloysite nanohybrid (Fe_3O_4/HNTs@C) with oxygen-containing organic group grafting on the surface of natural halloysite nanotubes (HNTs) and homogeneous Fe_3O_4 nanospheres selectively aggregating at the tips of modified halloysite nanotubes was successfully synthesized. XRD, TEM, IR spectroscopy, XPS and VSM were used to characterize this newly halloysite nanohybrid and its formation mechanism was discussed. Cr(VI) ions adsorption experiments showed that the Fe_3O_4/halloysite nanohybrid exhibited higher adsorption ability with a maximum adsorption capacity of 132 mg/L at 303 K, which is about 100 times higher than that of unmodified halloysite nanotubes. More importantly, with the reduction of Fe_3O_4 and electron–donor effect of oxygen-containing organic groups, Cr(VI) ions were easily reduced into low toxicity Cr(III) and then adsorbed onto the surface of halloysite nanohybrid. In addition, appreciable magnetization was observed due to the aggregation of magnetite nanoparticles, which make adsorbent facility separated from aqueous solutions after Cr pollution adsorption.

Evaluating the Impact of the U.S. National Toxicology Program: A Case Study on Hexavalent Chromium.

Science.gov (United States)

Xie, Yun; Holmgren, Stephanie; Andrews, Danica M K; Wolfe, Mary S

2017-02-01

Evaluating the impact of federally funded research with a broad, methodical, and objective approach is important to ensure that public funds advance the mission of federal agencies. We aimed to develop a methodical approach that would yield a broad assessment of National Toxicology Program's (NTP's) effectiveness across multiple sectors and demonstrate the utility of the approach through a case study. A conceptual model was developed with defined activities, outputs (products), and outcomes (proximal, intermediate, distal) and applied retrospectively to NTP's research on hexavalent chromium (CrVI). Proximal outcomes were measured by counting views of and requests for NTP's products by external stakeholders. Intermediate outcomes were measured by bibliometric analysis. Distal outcomes were assessed through Web and LexisNexis searches for documents related to legislation or regulation changes. The approach identified awareness of NTP's work on CrVI by external stakeholders (proximal outcome) and citations of NTP's research in scientific publications, reports, congressional testimonies, and legal and policy documents (intermediate outcome). NTP's research was key to the nation's first-ever drinking water standard for CrVI adopted by California in 2014 (distal outcome). By applying this approach to a case study, the utility and limitations of the approach were identified, including challenges to evaluating the outcomes of a research program. This study identified a broad and objective approach for assessing NTP's effectiveness, including methodological needs for more thorough and efficient impact assessments in the future. Citation: Xie Y, Holmgren S, Andrews DMK, Wolfe MS. 2017. Evaluating the impact of the U.S. National Toxicology Program: a case study on hexavalent chromium. Environ Health Perspect 125:181-188; http://dx.doi.org/10.1289/EHP21.

Higher adsorption capacity of Spirulina platensis alga for Cr(VI) ions removal: parameter optimisation, equilibrium, kinetic and thermodynamic predictions.

Science.gov (United States)

Gunasundari, Elumalai; Senthil Kumar, Ponnusamy

2017-04-01

This study discusses about the biosorption of Cr(VI) ion from aqueous solution using ultrasonic assisted Spirulina platensis (UASP). The prepared UASP biosorbent was characterised by Fourier transform infrared spectroscopy, X-ray diffraction, Brunauer-Emmet-Teller, scanning electron spectroscopy and energy dispersive X-ray and thermogravimetric analyses. The optimum condition for the maximum removal of Cr(VI) ions for an initial concentration of 50 mg/l by UASP was measured as: adsorbent dose of 1 g/l, pH of 3.0, contact time of 30 min and temperature of 303 K. Adsorption isotherm, kinetics and thermodynamic parameters were calculated. Freundlich model provided the best results for the removal of Cr(VI) ions by UASP. The adsorption kinetics of Cr(VI) ions onto UASP showed that the pseudo-first-order model was well in line with the experimental data. In the thermodynamic study, the parameters like Gibb's free energy, enthalpy and entropy changes were evaluated. This result explains that the adsorption of Cr(VI) ions onto the UASP was exothermic and spontaneous in nature. Desorption of the biosorbent was done using different desorbing agents in which NaOH gave the best result. The prepared material showed higher affinity for the removal of Cr(VI) ions and this may be an alternative material to the existing commercial adsorbents.

Biosorption of Cr(VI) in Aqueous Solution using Microorganisms: Comparison of the Use of Rhizopus oryzae, Bacillus firmus, and Trichoderma viride

Science.gov (United States)

Safitri, Anna; Mahardini, Putri; Prasetyawan, Sasangka; Roosdiana, Anna

2018-01-01

In this work, the study of biosorption of Cr(VI) from aqueous solution was conducted using Rhizopus oryzae, Bacillus firmus, and Trichoderma viride as microorganisms that can absorb Cr(VI). The research is focused on determination of optimum conditions including pH, the number of R. oryzae, B. firmus, and T. viride (inoculums), and initial concentrations of Cr(VI) used. Optimum pH was obtained at pH 5, 4.5 and 6, for biosorption of Cr(VI) with R. oryzae, B. firmus, and T. viride, respectively, in the capacity of 45.3%, 24.5%, and 90.3%. The highest amount of Cr(VI) adsorbed for biosorption with R. oryzae, B. firmus, and T. viride, were 55.4%, 18.5%, and 74.5%, respectively, using 6-mL inoculums. The equilibrium concentrations achieved for R. oryzae, B. firmus, and T. viride were 60 mg/mL, 40 mg/mL, and 40 mg/mL, with the amount of Cr(VI) adsorbed were 32.4%, 28.2%, and 89.3%, respectively. The adsorption capacity for R. oryzae, B. firmus, and T. viride were 45.3 mg/1×106 colonies, 36.2 mg/1×106 cells, and 77.8 mg/1×106 colonies, respectively. Overall, the biosorbents effectivity order in the biosorption process of Cr(VI) are T. viride > R. oryzae > B. firmus.

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

International Nuclear Information System (INIS)

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.

2009-01-01

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 3 O 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 (∼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 γ-camera to obtain real time images of a 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 (∼20%) 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 substrate supplied to Fe

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

Signal transduction of p53-independent apoptotic pathway induced by hexavalent chromium in U937 cells

International Nuclear Information System (INIS)

Hayashi, Yoko; Kondo, Takashi; Zhao Qingli; Ogawa Ryohei; Cui Zhengguo; Feril, Loreto B.; Teranishi, Hidetoyo; Kasuya, Minoru

2004-01-01

It has been reported that the hexavalent chromium compound (Cr(VI)) can induce both p53-dependent and p53-independent apoptosis. While a considerable amount of information is available on the p53-dependent pathway, only little is known about the p53-independent pathway. To elucidate the p53-independent mechanism, the roles of the Ca 2+ -calpain- and mitochondria-caspase-dependent pathways in apoptosis induced by Cr(VI) were investigated. When human lymphoma U937 cells, p53 mutated cells, were treated with 20 μM Cr(VI) for 24 h, nuclear morphological changes and DNA fragmentation were observed. Production of hydroxyl radicals revealed by electron paramagnetic resonance (EPR)-spin trapping, and increase of intracellular calcium ion concentration monitored by digital imaging were also observed in Cr(VI)-treated cells. An intracellular Ca 2+ chelator, BAPTA-AM, and calpain inhibitors suppressed the Cr(VI)-induced DNA fragmentation. The number of cells showing low mitochondrial membrane potential (MMP), high level of superoxide anion radicals (O 2 - ), and high activity of caspase-3, which are indicators of mitochondria-caspase-dependent pathway, increased significantly in Cr(VI)-treated cells. An antioxidant, N-acetyl-L-cysteine (NAC), decreased DNA fragmentation and inhibited the changes in MMP, O 2 - formation, and activation of caspase-3 induced by Cr(VI). No increase of the expressions of Fas and phosphorylated JNK was observed after Cr(VI) treatment. Cell cycle analysis revealed that the fraction of G2/M phase tended to increase after 24 h of treatment, suggesting that Cr(VI)-induced apoptosis is related to the G2 block. These results indicate that Ca 2+ -calpain- and mitochondria-caspase-dependent pathways play significant roles in the Cr(VI)-induced apoptosis via the G2 block, which are independent of JNK and Fas activation. The inhibition of apoptosis and all its signal transductions by NAC suggests that intracellular reactive oxygen species (ROS) are

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.

Aberration of mitosis by hexavalent chromium in some Fabaceae members is mediated by species-specific microtubule disruption.

Science.gov (United States)

Eleftheriou, Eleftherios P; Michalopoulou, Vasiliki A; Adamakis, Ioannis-Dimosthenis S

2015-05-01

Because the detrimental effects of chromium (Cr) to higher plants have been poorly investigated, the present study was undertaken to verify the toxic attributes of hexavalent chromium [Cr(VI)] to plant mitotic microtubules (MTs), to determine any differential disruption of MTs during mitosis of taxonomically related species and to clarify the relationship between the visualized chromosomal aberrations and the Cr(VI)-induced MT disturbance. For this purpose, 5-day-old uniform seedlings of Vicia faba, Pisum sativum, Vigna sinensis and Vigna angularis, all belonging to the Fabaceae family, were exposed to 250 μM Cr(VI) supplied as potassium dichromate (K₂Cr₂O₇) for 24, 72 and 120 h and others in distilled water serving as controls. Root tip samples were processed for tubulin immunolabelling (for MT visualization) and DNA fluorescent staining (for chromosomal visualization). Microscopic preparations of cell squashes were then examined and photographed by confocal laser scanning microscopy (CLSM). Cr(VI) halted seedling growth turning roots brown and necrotic. Severe chromosomal abnormalities and differential disturbance of the corresponding MT arrays were found in all mitotic phases. In particular, in V. faba MTs were primarily depolymerized and replaced by atypical tubulin conformations, whereas in P. sativum, V. sinensis and V. angularis they became bundled in a time-dependent manner. In P. sativum, the effects were milder compared to those of the other species, but in all cases MT disturbance adversely affected the proper aggregation of chromosomes on the metaphase plate, their segregation at anaphase and organization of the new nuclei at telophase. Cr(VI) is very toxic to seedling growth. The particular effect depends on the exact stage the cell is found at the time of Cr(VI) entrance and is species-specific. Mitotic MT arrays are differentially deranged by Cr(VI) in the different species examined, even if they are taxonomically related, while their

Chromium(VI) generation in vadose zone soils and alluvial sediments of the southwestern Sacramento Valley, California: A potential source of geogenic Cr(VI) to groundwater

International Nuclear Information System (INIS)

Mills, Christopher T.; Morrison, Jean M.; Goldhaber, Martin B.; Ellefsen, Karl J.

2011-01-01

Highlights: → Southern Sacramento Valley soil and sediment has abundant naturally-occurring Cr(III). → Cr(III) resides mainly in chromite but some is associated with clays and Fe oxides. → Cr(VI) is mostly absent in surface soil but ubiquitous in deeper soil and sediment. → Cr(VI) increased linearly with time during lab soil incubations with no additions. → Cation exchange processes resulted in greater Cr(VI) generation rates. - Abstract: Concentrations of geogenic Cr(VI) in groundwater that exceed the World Health Organization's maximum contaminant level for drinking water (50 μg L -1 ) occur in several locations globally. The major mechanism for mobilization of this Cr(VI) at these sites is the weathering of Cr(III) from ultramafic rocks and its subsequent oxidation on Mn oxides. This process may be occurring in the southern Sacramento Valley of California where Cr(VI) concentrations in groundwater can approach or exceed 50 μg L -1 . To characterize Cr geochemistry in the area, samples from several soil auger cores (approximately 4 m deep) and drill cores (approximately 25 m deep) were analyzed for total concentrations of 44 major, minor and trace elements, Cr associated with labile Mn and Fe oxides, and Cr(VI). Total concentrations of Cr in these samples ranged from 140 to 2220 mg per kg soil. Between 9 and 70 mg per kg soil was released by selective extractions that target Fe oxides, but essentially no Cr was associated with the abundant reactive Mn oxides (up to ∼1000 mg hydroxylamine-reducible Mn per kg soil was present). Both borehole magnetic susceptibility surveys performed at some of the drill core sites and relative differences between Cr released in a 4-acid digestion versus total Cr (lithium metaborate fusion digestion) suggest that the majority of total Cr in the samples is present in refractory chromite minerals transported from ultramafic exposures in the Coast Range Mountains. Chromium(VI) in the samples studied ranged from 0 to 42 �

Chromium(VI) generation in vadose zone soils and alluvial sediments of the southwestern Sacramento Valley, California: A potential source of geogenic Cr(VI) to groundwater

Energy Technology Data Exchange (ETDEWEB)

Mills, Christopher T., E-mail: cmills@usgs.gov [United States Geological Survey, Crustal Geophysics and Geochemistry Science Center, Denver Federal Center, MS 964D, Denver, CO 80225 (United States); Morrison, Jean M.; Goldhaber, Martin B.; Ellefsen, Karl J. [United States Geological Survey, Crustal Geophysics and Geochemistry Science Center, Denver Federal Center, MS 964D, Denver, CO 80225 (United States)

2011-08-15

Highlights: > Southern Sacramento Valley soil and sediment has abundant naturally-occurring Cr(III). > Cr(III) resides mainly in chromite but some is associated with clays and Fe oxides. > Cr(VI) is mostly absent in surface soil but ubiquitous in deeper soil and sediment. > Cr(VI) increased linearly with time during lab soil incubations with no additions. > Cation exchange processes resulted in greater Cr(VI) generation rates. - Abstract: Concentrations of geogenic Cr(VI) in groundwater that exceed the World Health Organization's maximum contaminant level for drinking water (50 {mu}g L{sup -1}) occur in several locations globally. The major mechanism for mobilization of this Cr(VI) at these sites is the weathering of Cr(III) from ultramafic rocks and its subsequent oxidation on Mn oxides. This process may be occurring in the southern Sacramento Valley of California where Cr(VI) concentrations in groundwater can approach or exceed 50 {mu}g L{sup -1}. To characterize Cr geochemistry in the area, samples from several soil auger cores (approximately 4 m deep) and drill cores (approximately 25 m deep) were analyzed for total concentrations of 44 major, minor and trace elements, Cr associated with labile Mn and Fe oxides, and Cr(VI). Total concentrations of Cr in these samples ranged from 140 to 2220 mg per kg soil. Between 9 and 70 mg per kg soil was released by selective extractions that target Fe oxides, but essentially no Cr was associated with the abundant reactive Mn oxides (up to {approx}1000 mg hydroxylamine-reducible Mn per kg soil was present). Both borehole magnetic susceptibility surveys performed at some of the drill core sites and relative differences between Cr released in a 4-acid digestion versus total Cr (lithium metaborate fusion digestion) suggest that the majority of total Cr in the samples is present in refractory chromite minerals transported from ultramafic exposures in the Coast Range Mountains. Chromium(VI) in the samples studied ranged

Cr(VI) induces mitochondrial-mediated and caspase-dependent apoptosis through reactive oxygen species-mediated p53 activation in JB6 Cl41 cells

International Nuclear Information System (INIS)

Son, Young-Ok; Hitron, J. Andrew; Wang Xin; Chang Qingshan; Pan Jingju; Zhang Zhuo; Liu Jiankang; Wang Shuxia; Lee, Jeong-Chae; Shi Xianglin

2010-01-01

Cr(VI) compounds are known to cause serious toxic and carcinogenic effects. Cr(VI) exposure can lead to a severe damage to the skin, but the mechanisms involved in the Cr(VI)-mediated toxicity in the skin are unclear. The present study examined whether Cr(VI) induces cell death by apoptosis or necrosis using mouse skin epidermal cell line, JB6 Cl41 cells. We also investigated the cellular mechanisms of Cr(VI)-induced cell death. This study showed that Cr(VI) induced apoptotic cell death in a dose-dependent manner, as demonstrated by the appearance of cell shrinkage, the migration of cells into the sub-G1 phase, the increase of Annexin V positively stained cells, and the formation of nuclear DNA ladders. Cr(VI) treatment resulted in the increases of mitochondrial membrane depolarization and caspases activation. Electron spin resonance (ESR) and fluorescence analysis revealed that Cr(VI) increased intracellular levels of reactive oxygen species (ROS) such as hydrogen peroxide and superoxide anion radical in dose-dependent manner. Blockage of p53 by si-RNA transfection suppressed mitochondrial changes of Bcl-2 family composition, mitochondrial membrane depolarization, caspase activation and PARP cleavage, leading to the inhibition of Cr(VI)-induced apoptosis. Further, catalase treatment prevented p53 phosphorylation stimulated by Cr(VI) with the concomitant inhibition of caspase activation. These results suggest that Cr(VI) induced a mitochondrial-mediated and caspase-dependent apoptosis in skin epidermal cells through activation of p53, which are mainly mediated by reactive oxidants generated by the chemical.

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

Laser-induced efficient reduction of Cr(VI) catalyzed by ZnO nanoparticles

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Qamar, M. [Center of Excellence in Nanotechnology, King Fahd University of Petroleum and Minerals, KFUPM Box 741, Dhahran 31261 (Saudi Arabia); Gondal, M.A., E-mail: magondal@kfupm.edu.sa [Center of Excellence in Nanotechnology, King Fahd University of Petroleum and Minerals, KFUPM Box 741, Dhahran 31261 (Saudi Arabia); Laser Research Group, Physics Department, King Fahd University of Petroleum and Minerals, Dhahran 31261 (Saudi Arabia); Yamani, Z.H. [Center of Excellence in Nanotechnology, King Fahd University of Petroleum and Minerals, KFUPM Box 741, Dhahran 31261 (Saudi Arabia); Laser Research Group, Physics Department, King Fahd University of Petroleum and Minerals, Dhahran 31261 (Saudi Arabia)

2011-03-15

The present study demonstrates the complete removal of Cr(VI) in aqueous suspensions of zinc oxide nanoparticles using a novel laser-induced photocatalytic process without the use of any additive. The study showed that {approx}95% Cr(VI) was removed within short time (60 min) of laser exposure in the presence of ZnO. However, the removal of chromium using conventional setup under identical conditions was found to be negligible. Effect of critical parameters, such as laser energy, catalyst concentration, chromium concentration, and added electron donor and acceptor on the photocatalytic reduction process was also investigated. The data regarding temporal behavior of metal removal was fitted to first-order kinetic and reaction rate was computed.

Unraveling the Long-Term Effects of Cr(VI on the Performance and Microbial Community of Nitrifying Activated Sludge System

Directory of Open Access Journals (Sweden)

Xingang Wang

2017-11-01

Full Text Available The long-term effects of different influent Cr(VI concentrations (0–0.5 mg L−1 on the nitrification activities and microbial community structures of nitrifying activated sludge system were investigated in this study. Results showed that the performance of ammonia oxidation was significantly inhibited, and the effluent concentration of ammonia nitrogen (NH4+-N increased markedly when the influent Cr(VI loading was equal or greater than 0.2 mg L−1. The specific oxygen utilization rate (SOUR, specific ammonium oxidation rate (SAOR, and specific nitrite oxidation rate (SNOR of the system decreased from 53.24, 6.31, and 7.33 mg N g−1 VSS h−1 to 18.17, 1.68, and 2.88 mg N g−1 VSS h−1, respectively, with an increase of Cr(VI concentration from 0 to 0.5 mg L−1. The protein/polysaccharide (PN/PS ratio increased with the increasing Cr(VI concentration, indicating that excessive PN secreted by microorganisms was conducive to resisting the toxicity of Cr(VI. High-throughput sequencing revealed that the relative abundance of ammonia-oxidizing bacteria (Nitrospira and nitrite-oxidizing bacteria (Nitrosomonas and Nitrosospira all decreased with the increasing Cr(VI concentration, and ammonia-oxidizing bacteria were more sensitive to heavy metal toxicity than nitrite-oxidizing bacteria. The activities of nitrifying activated sludge system could not be completely recovered after a 30-d recovery process.

Different roles of ROS and Nrf2 in Cr(VI)-induced inflammatory responses in normal and Cr(VI)-transformed cells

Energy Technology Data Exchange (ETDEWEB)

Roy, Ram Vinod; Pratheeshkumar, Poyil; Son, Yong-Ok; Wang, Lei [Center for Research on Environmental Disease, University of Kentucky, 1095 VA Drive, Lexington, KY 40536 (United States); Department of Toxicology and Cancer Biology, College of Medicine, University of Kentucky, 1095 VA Drive, Lexington, KY 40536 (United States); Hitron, John Andrew [Center for Research on Environmental Disease, University of Kentucky, 1095 VA Drive, Lexington, KY 40536 (United States); Divya, Sasidharan Padmaja; Zhang, Zhuo [Department of Toxicology and Cancer Biology, College of Medicine, University of Kentucky, 1095 VA Drive, Lexington, KY 40536 (United States); Shi, Xianglin, E-mail: xshi5@email.uky.edu [Center for Research on Environmental Disease, University of Kentucky, 1095 VA Drive, Lexington, KY 40536 (United States)

2016-09-15

Hexavalent chromium (Cr(VI)) is classified as a human carcinogen. Cr(VI) has been associated with adenocarcinomas and squamous cell carcinoma of the lung. The present study shows that acute Cr(VI) treatment in human bronchial epithelial cells (BEAS-2B) increased inflammatory responses (TNF-α, COX-2, and NF-кB/p65) and expression of Nrf2. Cr(VI)-induced generation of reactive oxygen species (ROS) are responsible for increased inflammation. Despite the fact that Nrf2 is a master regulator of response to oxidative stress, silencing of Nrf2 in the acute Cr(VI) treatment had no effect on Cr(VI)-induced inflammation. In contrast, in Cr(VI)-transformed (CrT) cells, Nrf2 is constitutively activated. Knock-down of this protein resulted in decreased inflammation, while silencing of SOD2 and CAT had no effect in the expression of these inflammatory proteins. Results obtained from the knock-down of Nrf2 in CrT cells are very different from the results obtained in the acute Cr(VI) treatment. In BEAS-2B cells, knock-down of Nrf2 had no effect in the inflammation levels, while in CrT cells a decrease in the expression of inflammation markers was observed. These results indicate that before transformation, ROS plays a critical role while Nrf2 not in Cr(VI)-induced inflammation, whereas after transformation (CrT cells), Nrf2 is constitutively activated and this protein maintains inflammation while ROS not. Constitutively high levels of Nrf2 in CrT binds to the promoter regions of COX-2 and TNF-α, leading to increased inflammation. Collectively, our results demonstrate that before cell transformation ROS are important in Cr(VI)-induced inflammation and after transformation a constitutively high level of Nrf2 is important. - Highlights: • Cr(VI)-induced ROS increased inflammation, while Nrf2 had no effect. • In the CrT cells knock-down of Nrf2 resulted in decreased inflammation. • Mechanistic differences in regulating Cr(VI)-induced inflammation.

On the passivation mechanism of Fe{sub 3}O{sub 4} nanoparticles during Cr(VI) removal from water: A XAFS study

Energy Technology Data Exchange (ETDEWEB)

Pinakidou, F., E-mail: fpina@physics.auth.gr [Aristotle University of Thessaloniki, Department of Chemical Engineering, Analytical Chemistry Laboratory, 54124 Thessaloniki (Greece); Katsikini, M. [Aristotle University of Thessaloniki, School of Physics, Section of Solid State Physics, 54124 Thessaloniki (Greece); Simeonidis, K.; Kaprara, E. [Aristotle University of Thessaloniki, Department of Chemical Engineering, Analytical Chemistry Laboratory, 54124 Thessaloniki (Greece); Paloura, E.C. [Aristotle University of Thessaloniki, School of Physics, Section of Solid State Physics, 54124 Thessaloniki (Greece); Mitrakas, M. [Aristotle University of Thessaloniki, Department of Chemical Engineering, Analytical Chemistry Laboratory, 54124 Thessaloniki (Greece)

2016-01-01

Graphical abstract: - Highlights: • Presence of Fe(II) even after high Cr-loading. • The vacancies in the γ-Fe{sub 2}O{sub 3} layer formed offer sites for Cr(III) sorption. • Cr(III) sorbs into the vacancies and Cr(VI) forms outer sphere complexes. • Increasing surface Cr(III) loading changes the polymerization of the Fe–O–Fe chains. • Cr(III) sorption modifies Fe{sub 3}O{sub 4} structure obstructing further Cr(VI) removal. - Abstract: X-Ray Absorption Spectroscopies (XAFS) are employed in order to gather a thorough insight on the uptake mechanism of Cr(VI) by Fe{sub 3}O{sub 4} nanoparticles under water treatment conditions. The XANES measurements identify that the reducing potential of Fe{sub 3}O{sub 4} 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 ({sup 2}E) geometry with Fe-octahedra while it also forms monodentate ({sup 1}V) complexes with the Fe(III)O{sub 4} 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.

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.

Chromium(VI) generation in vadose zone soils and alluvial sediments of the southwestern Sacramento Valley, California: a potential source of geogenic Cr(VI) to groundwater

Science.gov (United States)

Mills, Christopher T.; Morrison, Jean M.; Goldhaber, Martin B.; Ellefsen, Karl J.

2011-01-01

Concentrations of geogenic Cr(VI) in groundwater that exceed the World Health Organization’s maximum contaminant level for drinking water (50 μg L−1) occur in several locations globally. The major mechanism for mobilization of this Cr(VI) at these sites is the weathering of Cr(III) from ultramafic rocks and its subsequent oxidation on Mn oxides. This process may be occurring in the southern Sacramento Valley of California where Cr(VI) concentrations in groundwater can approach or exceed 50 μg L−1. To characterize Cr geochemistry in the area, samples from several soil auger cores (approximately 4 m deep) and drill cores (approximately 25 m deep) were analyzed for total concentrations of 44 major, minor and trace elements, Cr associated with labile Mn and Fe oxides, and Cr(VI). Total concentrations of Cr in these samples ranged from 140 to 2220 mg per kg soil. Between 9 and 70 mg per kg soil was released by selective extractions that target Fe oxides, but essentially no Cr was associated with the abundant reactive Mn oxides (up to ~1000 mg hydroxylamine-reducible Mn per kg soil was present). Both borehole magnetic susceptibility surveys performed at some of the drill core sites and relative differences between Cr released in a 4-acid digestion versus total Cr (lithium metaborate fusion digestion) suggest that the majority of total Cr in the samples is present in refractory chromite minerals transported from ultramafic exposures in the Coast Range Mountains. Chromium(VI) in the samples studied ranged from 0 to 42 μg kg−1, representing a minute fraction of total Cr. Chromium(VI) content was typically below detection in surface soils (top 10 cm) where soil organic matter was high, and increased with increasing depth in the soil auger cores as organic matter decreased. Maximum concentrations of Cr(VI) were up to 3 times greater in the deeper drill core samples than the shallow auger cores. Although Cr(VI) in these vadose zone soils and sediments was only a

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.

Determination of Cr(VI) and Cr(III) in urine and dextrose by inductively coupled plasma emission spectroscopy

Science.gov (United States)

Mianzhi, Zhuang; Barnes, Ramon M.

The determination of Cr(VI) and Cr(III) in human urine and in commercial dextrose solution is performed by induclively coupled plasma-atomic emission spectroscopy after selective preconcentration of the chromium species at different pH values by poly(dithiocarbamate) and poly(acrylamidoxime) chelating resins. The chelating properties of these resins with chromium, including the kinetics of uptake and removal of Cr(III), and the influence of matrix concentrations were evaluated. Chromium in human urine was found to exist exclusively as Cr(III).

KAJIAN ADSORPSI ION LOGAM Cr(VI OLEH ADSORBEN KOMBINASI ARANG AKTIF SEKAM PADI DAN ZEOLIT MENGGUNAKAN METODE SOLID-PHASE SPECTROPHOTOMETRY (SPS

Directory of Open Access Journals (Sweden)

Sulistyo Saputro

2016-10-01

  This study aims to study the use of activated rice husk charcoal and zeolite as combination adsorbents to adsorb Cr(VI metal ions; the effect of the combination adsorbents of activated rice husk charcoal and zeolite’s compositions to adsorb Cr(VI metal ions; and the sensitivity of solid-phase spectrophotometry (SPS as a method to determine the reduced levels of Cr(VI metal ions in the level of 15μ"> g/L. The activated rice husk charcoal used were obtained through the activation process by soaking in a solution of ZnCl2 10% while the zeolite with a solution of H2SO4 10%. The contacting process of the adsorbents with Cr(VI metal ions was done by varying the compositions of the activated rice husk charcoal and zeolite adsorbent, 1:1, 1:2, 1:3, and 2:1. The data analysis of the Cr(VI level used solid-phase spectrophotometry (SPS method. Characterization of activated rice husk charcoal and zeolite used FTIR. The results showed that: (1 a combination of activated rice husk charcoal and zeolite can be used as adsorbent to adsorb Cr(VI metal ions with the adsorption capacity was 0,28 15μ"> g/g; (2 the optimum composition of adsorbents was 1:2 with the percentage of absorption was 40,99%; (3 solid-phase spectrophotometry (SPS is a sensitive method to determine the reduced levels of Cr(VI in the level of 15μ"> g/L with the limit of detection (LOD was 0,021 15μ"> g/L.   Keywords: adsorption, Cr(VI,  activated  rice husk charcoal,  zeolite, solid-phase spectrophotometry

Effect of Cr-Vi on skeletal muscles of albino mice

International Nuclear Information System (INIS)

Nabeel, H.

2006-01-01

Chromium plays an important role in normal carbohydrate and lipid metabolism, as it's an essential trace element in human nutrition. It was found that patients receiving long-term total parenteral nutrition (TPN) without chromium developed glucose intolerance, weight loss and peripheral neuropathy Chromium is present in a normal diet at trace (but essential) levels. Occupational exposure is related to the industrial uses of chrome compounds in production and use of steels, pigments, leather tanning and wood preservation solutions, plating chemicals, and cement. Toxicity is predominantly associated with industrial exposures. Its trivalent form is the most stable form and can't cross the cell membrane. Hexavalent chromium crosses the cell membrane and is reduced to Cr- V, Cr-IV and Cr-111. Once in trivalent form it can combine with nuclear proteins and nucleic acids causing adverse effects and derangements. Hexavalent chromium compounds appear to have severe toxicity and almost all tissues of body are affected. To evaluate the effects on skeletal muscles, present study was carried out. The mice of experimental group (2wks, 4wks, 6wks and 8wks) were injected Potassium dichromate (K/sub 2/ Cr/sub 2/0/sub 7/) intraperitoneally according to experimental design. The drug caused slight to marked inflammation of skeletal muscle fibers and vaculations of nuclei was also observed indicating degenerative changes. (author)

Equilibrium and kinetics study on hexavalent chromium adsorption onto diethylene triamine grafted glycidyl methacrylate based copolymers

International Nuclear Information System (INIS)

Maksin, Danijela D.; Nastasović, Aleksandra B.; Milutinović-Nikolić, Aleksandra D.; Suručić, Ljiljana T.; Sandić, Zvjezdana P.; Hercigonja, Radmila V.; Onjia, Antonije E.

2012-01-01

Highlights: ► Methacrylate based copolymers grafted with diethylene triamine as Cr(VI) sorbents. ► Chemisorption and pore diffusion are characteristics of this sorption system. ► Langmuir isotherm provided best fit and maximum adsorption capacity was 143 mg g −1 . ► Cr(VI) sorption onto amino-functionalized copolymer was endothermic and spontaneous. ► A simple, efficient and cost-effective hexavalent chromium removal method. - Abstract: Two porous and one non-porous crosslinked poly(glycidyl methacrylate-co-ethylene glycol dimethacrylate) [abbreviated PGME] were prepared by suspension copolymerization and functionalized with diethylene triamine [abbreviated PGME-deta]. Samples were characterized by elemental analysis, mercury porosimetry, scanning electron microscopy with energy-dispersive X-ray spectroscopy, and transmission electron microscopy. Kinetics of Cr(VI) sorption by PGME-deta were investigated in batch static experiments, in the temperature range 25–70 °C. Sorption was rapid, with the uptake capacity higher than 80% after 30 min. Sorption behavior and rate-controlling mechanisms were analyzed using five kinetic models (pseudo-first order, pseudo-second order, Elovich, intraparticle diffusion and Bangham model). Kinetic studies showed that Cr(VI) adsorption adhered to the pseudo-second-order model, with definite influence of pore diffusion. Equilibrium data was tested with Langmuir, Freundlich and Tempkin adsorption isotherm models. Langmuir model was the most suitable indicating homogeneous distribution of active sites on PGME-deta and monolayer sorption. The maximum adsorption capacity from the Langmuir model, Q max , at pH 1.8 and 25 °C was 143 mg g −1 for PGME2-deta (sample with the highest amino group concentration) while at 70 °C Q max reached the high value of 198 mg g −1 . Thermodynamic parameters revealed spontaneous and endothermic nature of Cr(VI) adsorption onto PGME-deta.

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...

An attempt to prepare and characterize a soil reference material for Cr(VI) and Cr(III)

International Nuclear Information System (INIS)

Solano, G.; Katz, S.A.; Holzbecher, J.; Chatt, A.

1994-01-01

Reference materials for the speciation and quantification of chromium in contaminated soils were prepared by impregnating diatomaceous earth with BaCrO 4 and Cr 2 O 3 . The chromium concentrations of these materials were confirmed to be 200 mg/kg both by atomic absorption spectrometry and by instrumental neutron activation analysis, but monthly assays over two calendar quarters of the reference material impregnated with BaCrO 4 revealed the hexavalent chromium was not stable in this matrix. (author) 6 refs,; 2 tabs

Nb2O5 nanowires in-situ grown on carbon fiber: A high-efficiency material for the photocatalytic reduction of Cr(VI).

Science.gov (United States)

Du, Yucheng; Zhang, Shihao; Wang, Jinshu; Wu, Junshu; Dai, Hongxing

2018-04-01

Niobium oxide nanowire-deposited carbon fiber (CF) samples were prepared using a hydrothermal method with amorphous Nb 2 O 5 ·nH 2 O as precursor. The physical properties of the samples were characterized by means of numerous techniques, including X-ray diffraction (XRD), energy-dispersive spectroscopy (EDS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), selected-area electron diffraction (SAED), UV-visible spectroscopy (UV-vis), N 2 adsorption-desorption, Fourier transform infrared spectroscopy (FT-IR), and X-ray photoelectron spectroscopy. The efficiency for the removal of Cr(VI) was determined. Parameters such as pH value and initial Cr(VI) concentration could influence the Cr(VI) removal efficiency or adsorption capacity of the Nb 2 O 5 /carbon fiber sample obtained after hydrothermal treatment at 160°C for 14hr. The maximal Cr(VI) adsorption capacity of the Nb 2 O 5 nanowire/CF sample was 115mg/g. This Nb 2 O 5 /CF sample also showed excellent photocatalytic activity and stability for the reduction of Cr(VI) under UV-light irradiation: the Cr(VI) removal efficiency reached 99.9% after UV-light irradiation for 1hr and there was no significant decrease in photocatalytic performance after the use of the sample for 10 repeated cycles. Such excellent Cr(VI) adsorption capacity and photocatalytic performance was related to its high surface area, abundant surface hydroxyl groups, and good UV-light absorption ability. Copyright © 2017. Published by Elsevier B.V.

Self-assembly modified-mushroom nanocomposite for rapid removal of hexavalent chromium from aqueous solution with bubbling fluidized bed.

Science.gov (United States)

Xu, Fei; Liu, Xu; Chen, Yijiao; Zhang, Ke; Xu, Heng

2016-05-18

A self-assembled modified Pleurotus Cornucopiae material (SMPM) combined with improved Intermittent Bubbling Fluidized Bed (IBFB) was investigated to remove the hexavalent chromium ions in aqueous solution. After the modification, the powder-like raw material gradually self-assembled together to SMPM, which had crinkly porous structure, improved the Cr-accommodation ability in a sound manner. Optimized by Taguchi method, Cr(VI) removal efficiency was up to 75.91% and 48.01% for 100 mg/L and 500 mg/L initial concentration of Cr(VI), respectively. Results indicated that the metal removal was dependent on dosage of adsorbent, particle diameter and treatment time. The experimental data obtained from the biosorption process was successfully correlated with Freundlich isotherm model. Thermodynamic study indicated the endothermic nature of the process. The results confirmed that self-assembly modified Pleurotus Cornucopiae material could be applied for the removal of heavy metal from wastewater in continuous fluidized bed process.

EXTRACTION DU Cr(VI PAR MEMBRANE POLYMERE A INCLUSION

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O KEBICHE SENHADJI

2008-06-01

Le pH de la solution aqueuse constituant la phase source est un paramètre clé dans l’opération de transport du Cr(VI à travers les MPIs étudiées. Un pH de 1,2 est recommandé pour la réalisation de l’extraction dans les conditions optimales déterminées.

Application of ICP-MS and HPLC-ICP-MS for diagnosis and therapy of a severe intoxication with hexavalent chromium and inorganic arsenic.

Science.gov (United States)

Heitland, Peter; Blohm, Martin; Breuer, Christian; Brinkert, Florian; Achilles, Eike Gert; Pukite, Ieva; Köster, Helmut Dietrich

2017-05-01

ICP-MS and HPLC-ICP-MS were applied for diagnosis and therapeutic monitoring in a severe intoxication with a liquid containing hexavalent chromium (Cr(VI)) and inorganic arsenic (iAs). In this rare case a liver transplantation of was considered as the only chance of survival. We developed and applied methods for the determination of Cr(VI) in erythrocytes and total chromium (Cr) and arsenic (As) in blood, plasma, urine and liver tissue by ICP-MS. Exposure to iAs was diagnosed by determination of iAs species and their metabolites in urine by anion exchange HPLC-ICP-MS. Three days after ingestion of the liquid the total Cr concentrations were 2180 and 1070μg/L in whole blood and plasma, respectively, and 4540μg/L Cr(VI) in erythrocytes. The arsenic concentration in blood was 206μg/L. The urinary As species concentrations were <0.5, 109, 115, 154 and 126μg/L for arsenobetaine, As(III), As(V), methylarsonate (V) and dimethylarsinate (V), respectively. Total Cr and As concentrations in the explanted liver were 11.7 and 0.9mg/kg, respectively. Further analytical results of this case study are tabulated and provide valuable data for physicians and toxicologists. Copyright © 2017. Published by Elsevier GmbH.

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

African Journals Online (AJOL)

Cr(VI) generation during sample preparation of solid samples – A chromite ore case study. R.I Glastonbury, W van der Merwe, J.P Beukes, P.G van Zyl, G Lachmann, C.J.H Steenkamp, N.F Dawson, M.H Stewart ...

Salt-assisted liquid-liquid microextraction of Cr(VI) ion using an ionic liquid for preconcentration prior to its determination by flame atomic absorption spectrometry

International Nuclear Information System (INIS)

Majidi, B.; Shemirani, F.

2012-01-01

We report on the salt-assisted liquid-liquid microextraction of cationic complexes of Cr(VI) ion using the hydrophilic ionic liquid (IL) 1-butyl-3-methylimidazolium tetrafluoraborate and potassium hydrogen phosphate. This is a novel, simple, non-toxic and effective technique for sample pretreatment technique that displays large extraction efficiency and represents a new platform where Cr(VI) is complexed with 1,5-diphenylcarbazide (DPC) in sulfuric acid medium. It was applied to the extraction of Cr(VI) in the form of the Cr(VI)-DPC complex prior to its determination by flame atomic absorption spectrometry. Cr(III) ion also can be determined by this procedure after oxidation to Cr(VI). Extraction is mainly affected by the amount of water-soluble IL, the kind and quantity of inorganic salts, by pH and the concentration of DPC. Calibration plots are linear in the range from 3 to 150 μg L -1 of Cr(VI), and the limit of detection is 1. 25 μg L -1 . The method was successfully applied to the speciation and determination of trace levels of Cr(III) and Cr(VI) in environmental water samples containing high levels of dissolved salts or food grade salts. (author)

Removal of Cr(VI from Aqueous Solutions Using mino-fuctionalized Nanoporous MCM-41

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Farshid Ghorbani

2016-09-01

Full Text Available An amino-functionalized nanoporous material was prepared by grafting 3-aminopropyl trimethoxysilane (APTMS group onto MCM-41. The as-synthesized material was characterized by X-ray diffraction (XRD analysis, nitrogen adsorption-desorption measurements (BET, thermogravimetric analysis (TGA, and Fourier transform infrared spectrometry (FTIR to confirm the ordered mesoporous structure and the functionalization of the amino group. The NH2-MCM-41 thus obtained was employed as the sorbent to remove Cr(VI ions from aqueous solutions. The batch adsorption process was carried out to evaluate the effects of solution pH, adsorbent dosage, metal ion concentration, and temperature. Results revealed that removal efficiency increased to a maximum of 124 mg.g‒1 and metal uptake decreased (0.1 g.l‒1 with increasing sorbent dosage from 0.1 to 3.5 g.l‒1. A reverse trend was, however, observed with increasing Cr(VI concentration. It was also found that a pH equal to 3 was the optimum level for the removal of Cr(VI ions from aqueous solutions. Thermodynamic examinations revealed the strong dependence of the adsorption process on temperature such that adsorption capacity increased with increasing temperature, indicating the endothermic and spontaneous nature of the adsorption process.

Modulation of histone methylation and MLH1 gene silencing by hexavalent chromium

International Nuclear Information System (INIS)

Sun Hong; Zhou Xue; Chen Haobin; Li Qin; Costa, Max

2009-01-01

Hexavalent chromium [Cr(VI)] is a mutagen and carcinogen, and occupational exposure can lead to lung cancers and other adverse health effects. Genetic changes resulting from DNA damage have been proposed as an important mechanism that mediates chromate's carcinogenicity. Here we show that chromate exposure of human lung A549 cells increased global levels of di- and tri-methylated histone H3 lysine 9 (H3K9) and lysine 4 (H3K4) but decreased the levels of tri-methylated histone H3 lysine 27 (H3K27) and di-methylated histone H3 arginine 2 (H3R2). Most interestingly, H3K9 dimethylation was enriched in the human MLH1 gene promoter following chromate exposure and this was correlated with decreased MLH1 mRNA expression. Chromate exposure increased the protein as well as mRNA levels of G9a a histone methyltransferase that specifically methylates H3K9. This Cr(VI)-induced increase in G9a may account for the global elevation of H3K9 dimethylation. Furthermore, supplementation with ascorbate, the primary reductant of Cr(VI) and also an essential cofactor for the histone demethylase activity, partially reversed the H3K9 dimethylation induced by chromate. Thus our studies suggest that Cr(VI) may target histone methyltransferases and demethylases, which in turn affect both global and gene promoter specific histone methylation, leading to the silencing of specific tumor suppressor genes such as MLH1.

Adsorption of toxic metal ion Cr(VI) from aqueous state by TiO2-MCM-41: equilibrium and kinetic studies.

Science.gov (United States)

Parida, Kulamani; Mishra, Krushna Gopal; Dash, Suresh Kumar

2012-11-30

This paper deals with the immobilization of various weight percentage of TiO(2) on mesoporous MCM-41, characterization of the materials by X-ray diffraction (XRD), nitrogen adsorption-desorption, Fourier Transform Infrared (FTIR) analysis, UV-vis diffuse reflectance spectroscopy (DRS) and evaluation of the adsorption capacity toward Cr(VI) removal. It is found that the MCM-41 structure retained after loading of TiO(2) but the surface area and pore diameter decreased due to pore blockage. Adsorption of Cr(VI) from aqueous state was investigated on TiO(2)-MCM-41 by changing various parameters such as pH, metal ion concentration, and the temperature. When TiO(2) loading was more than 20 wt.%, the adsorption activity (25)TiO(2)-MCM-41 reduced significantly due to considerable decrease in the surface area. It is also observed that TiO(2) and neat MCM-41 exhibits very less Cr(VI) adsorption compared to TiO(2)-MCM-41. The adsorption of Cr(VI) onto (20)TiO(2)-MCM-41 at pH~5.5 and temperature 323 K was 91% at 100mg/L Cr(VI) metal ion concentration in 80 min. The experimental data fitted well to Langmuir and Freundlich isotherms. The adsorption of Cr(VI) on TiO(2)-MCM-41 followed a second order kinetics with higher values of intra-particle diffusion rate. Thermodynamic parameters suggested that the adsorption process is endothermic in nature and desorption studies indicated a chemisorption mode. Copyright © 2012 Elsevier B.V. All rights reserved.

Hexavalent chromium at low concentration alters Sertoli cell barrier and connexin 43 gap junction but not claudin-11 and N-cadherin in the rat seminiferous tubule culture model

Energy Technology Data Exchange (ETDEWEB)

Carette, Diane [INSERM U 1065, Team 5 “Physiopathology of Germ Cell Control: Genomic and Non Genomic Mechanisms” C3M, University of Nice Sophia Antipolis, Nice (France); UMR S775, University Paris Descartes, 45 rue des Saints Pères, 75006, Paris (France); Perrard, Marie-Hélène, E-mail: marie-helene.durand@ens-lyon.fr [Institut de Génomique Fonctionnelle de Lyon, Université de Lyon, Université Lyon I, CNRS, INRA, Ecole Normale Supérieure de Lyon, Lyon (France); Prisant, Nadia [University of Versailles/St Quentin-en-Yvelines (France); UMR S775, University Paris Descartes, 45 rue des Saints Pères, 75006, Paris (France); Gilleron, Jérome; Pointis, Georges [INSERM U 1065, Team 5 “Physiopathology of Germ Cell Control: Genomic and Non Genomic Mechanisms” C3M, University of Nice Sophia Antipolis, Nice (France); Segretain, Dominique [University of Versailles/St Quentin-en-Yvelines (France); UMR S775, University Paris Descartes, 45 rue des Saints Pères, 75006, Paris (France); Durand, Philippe [Institut de Génomique Fonctionnelle de Lyon, Université de Lyon, Université Lyon I, CNRS, INRA, Ecole Normale Supérieure de Lyon, Lyon (France); Kallistem SAS Ecole Normale Supérieure de Lyon, Lyon (France)

2013-04-01

Exposure to toxic metals, specifically those belonging to the nonessential group leads to human health defects and among them reprotoxic effects. The mechanisms by which these metals produce their negative effects on spermatogenesis have not been fully elucidated. By using the Durand's validated seminiferous tubule culture model, which mimics the in vivo situation, we recently reported that concentrations of hexavalent chromium, reported in the literature to be closed to that found in the blood circulation of men, increase the number of germ cell cytogenetic abnormalities. Since this metal is also known to affect cellular junctions, we investigated, in the present study, its potential influence on the Sertoli cell barrier and on junctional proteins present at this level such as connexin 43, claudin-11 and N-cadherin. Cultured seminiferous tubules in bicameral chambers expressed the three junctional proteins and ZO-1 for at least 12 days. Exposure to low concentrations of chromium (10 μg/l) increased the trans-epithelial resistance without major changes of claudin-11 and N-cadherin expressions but strongly delocalized the gap junction protein connexin 43 from the membrane to the cytoplasm of Sertoli cells. The possibility that the hexavalent chromium-induced alteration of connexin 43 indirectly mediates the effect of the toxic metal on the blood–testis barrier dynamic is postulated. - Highlights: ► Influence of Cr(VI) on the Sertoli cell barrier and on junctional proteins ► Use of cultured seminiferous tubules in bicameral chambers ► Low concentrations of Cr(VI) (10 μg/l) altered the trans-epithelial resistance. ► Cr(VI) did not alter claudin-11 and N-cadherin. ► Cr(VI) delocalized connexin 43 from the membrane to the cytoplasm of Sertoli cells.

Estudio de materiales adsorbentes de bajo costo para remover Cr(VI de efluentes acuosos

Directory of Open Access Journals (Sweden)

Claudia Vargas-Niño

2011-01-01

Full Text Available El presente estudio muestra el enorme potencial de dos tipos de sólidos diferentes, una alúmina comercial y un material producto del compostaje, en la adsorción/eliminación de Cr(VI en medio acuoso, en concentraciones de metal equivalentes a las halladas en aguas residuales provenientes de industrias en Colombia. Ambos materiales mostraron propiedades importantes para la eliminación de Cr(VI, considerándose de mayor relevancia el compost por ser un material de bajo costo. Se establecieron las condiciones óptimas para la adsorción de cromo sobre alúmina y sobre compost. Para la alúmina: concentración inicial de Cr(VI = 10 mgL-1, volumen de solución por masa de adsorbente = 100 mL/g, pH = 2,0, tiempo de equilibrio = 1 hora, y agitación = 150 rpm. Para el compost: concentración inicial de Cr(VI = 3 mg L-1, volumen de solución por masa de adsorbente = 50 mL/g, pH = 2.5, tiempo de equilibrio = 3 horas, y agitación = 150 rpm. Además, los resultados mostraron que las propiedades de adsorción del compost se pueden mejorar mediante la adición de pequeñas cantidades de alúmina. El estudio permitió seleccionar al compost como un material promisorio para procedimientos de remediación de aguas residuales que contienen cromo (VI dentro de una política de manejo y uso de residuos sólidos con el objeto de minimizar el impacto ambiental de éstos.

Lung injury, inflammation and Akt signaling following inhalation of particulate hexavalent chromium

International Nuclear Information System (INIS)

Beaver, Laura M.; Stemmy, Erik J.; Constant, Stephanie L.; Schwartz, Arnold; Little, Laura G.; Gigley, Jason P.; Chun, Gina; Sugden, Kent D.

2009-01-01

Certain particulate hexavalent chromium [Cr(VI)] compounds are human respiratory carcinogens that release genotoxic soluble chromate, and are associated with fibrosis, fibrosarcomas, adenocarcinomas and squamous cell carcinomas of the lung. We postulate that inflammatory processes and mediators may contribute to the etiology of Cr(VI) carcinogenesis, however the immediate (0-24 h) pathologic injury and immune responses after exposure to particulate chromates have not been adequately investigated. Our aim was to determine the nature of the lung injury, inflammatory response, and survival signaling responses following intranasal exposure of BALB/c mice to particulate basic zinc chromate. Factors associated with lung injury, inflammation and survival signaling were measured in airway lavage fluid and in lung tissue. A single chromate exposure induced an acute immune response in the lung, characterized by a rapid and significant increase in IL-6 and GRO-α levels, an influx of neutrophils, and a decline in macrophages in lung airways. Histological examination of lung tissue in animals challenged with a single chromate exposure revealed an increase in bronchiolar cell apoptosis and mucosal injury. Furthermore, chromate exposure induced injury and inflammation that progressed to alveolar and interstitial pneumonitis. Finally, a single Cr(VI) challenge resulted in a rapid and persistent increase in the number of airways immunoreactive for phosphorylation of the survival signaling protein Akt, on serine 473. These data illustrate that chromate induces both survival signaling and an inflammatory response in the lung, which we postulate may contribute to early oncogenesis

Titanium dioxide–gold nanocomposite materials embedded in silicate sol–gel film catalyst for simultaneous photodegradation of hexavalent chromium and methylene blue

International Nuclear Information System (INIS)

Pandikumar, Alagarsamy; Ramaraj, Ramasamy

2012-01-01

Graphical abstract: Aminosilicate sol–gel supported TiO 2 –Au nanocomposite material photocatalyst was prepared by deposition–precipitation method and used for the simultaneous oxidation and reduction of methyelene blue dye and Cr(VI) ions. Highlights: ► The EDAS/(TiO 2 –Au) nps is used to design the solid-phase thin film photocatalyst. ► Au promotes the interfacial electron transfer from TiO 2 to Cr(VI) to form Cr(III). ► The holes produced at the TiO 2 oxidize the MB dye. ► The EDAS/(TiO 2 –Au) nps film was used for the simultaneous oxidation and reduction of toxic molecules. ► The photoinduced simultaneous redox process provides dual benefit for the environment remediation. - Abstract: Aminosilicate sol–gel supported titanium dioxide–gold (EDAS/(TiO 2 –Au) nps ) nanocomposite materials were synthesized by simple deposition–precipitation method and characterized. The photocatalytic oxidation and reduction activity of the EDAS/(TiO 2 –Au) nps film was evaluated using hexavalent chromium (Cr(VI)) and methylene blue (MB) dye under irradiation. The photocatalytic reduction of Cr(VI) to Cr(III) was studied in the presence of hole scavengers such as oxalic acid (OA) and methylene blue (MB). The photocatalytic degradation of MB was investigated in the presence and absence of Cr(VI). Presence of Au nps on the (TiO 2 ) nps surface and its dispersion in the silicate sol-gel film (EDAS/(TiO 2 –Au) nps ) improved the photocatalytic reduction of Cr(VI) and oxidation of MB due to the effective interfacial electron transfer from the conduction band of the TiO 2 to Au nps by minimizing the charge recombination process when compared to the TiO 2 and (TiO 2 –Au) nps in the absence of EDAS. The EDAS/(TiO 2 –Au) nps nanocomposite materials provided beneficial role in the environmental remediation and purification process through synergistic photocatalytic activity by an advanced oxidation–reduction processes.

Cr(VI) adsorption on functionalized amorphous and mesoporous silica from aqueous and non-aqueous media

International Nuclear Information System (INIS)

Perez-Quintanilla, Damian; Hierro, Isabel del; Fajardo, Mariano; Sierra, Isabel

2007-01-01

A mesoporous silica (SBA-15) and amorphous silica (SG) have been chemically modified with 2-mercaptopyridine using the homogeneous route. This synthetic route involved the reaction of 2-mercaptopyridine with 3-chloropropyltriethoxysilane prior to immobilization on the support. The resulting material has been characterized by powder X-ray diffraction, nitrogen gas sorption, FT-IR and MAS NMR spectroscopy, thermogravimetry and elemental analysis. The solid was employed as a Cr(VI) adsorbent from aqueous and non-aqueous solutions at room temperature. The effect of several variables (stirring time, pH, metal concentration and solvent polarity) has been studied using the batch technique. The results indicate that under the optimum conditions, the maximum adsorption value for Cr(VI) was 1.83 ± 0.03 mmol/g for MP-SBA-15, whereas the adsorption capacity of the MP-SG was 0.86 ± 0.02 mmol/g. On the basis of these results, it can be concluded that it is possible to modify chemically SBA-15 and SG with 2-mercaptopyridine and to use the resulting modified silicas as effective adsorbents for Cr(VI)

Toxic effect of Cr(VI) in presence of n-TiO2 and n-Al2O3 particles towards freshwater microalgae.

Science.gov (United States)

Dalai, Swayamprava; Pakrashi, Sunandan; Bhuvaneshwari, M; Iswarya, V; Chandrasekaran, N; Mukherjee, Amitava

2014-01-01

The reactivity and toxicity of the soluble toxicants in the presence of the engineered nanomaterials is not well explored. In this study, the probable effects of TiO2 and Al2O3 nanoparticles (n-TiO2, n-Al2O3) on the toxicity of Cr(VI) were assessed with the dominant freshwater algae, Scenedesmus obliquus, in a low range of exposure concentrations (0.05, 0.5 and 1μg/mL). In the presence of 0.05μg/mL n-TiO2, the toxicity of Cr(VI) decreased considerably, which was presumably due to the Cr(VI) adsorption on the nanoparticle surface leading to its aggregation and precipitation. The elevated n-TiO2 concentrations (0.5 and 1μg/mL) did not significantly influence Cr(VI) bio-availability, and a dose dependent toxicity of Cr(VI) was observed. On the other hand, n-Al2O3 did not have any significant effect on the Cr(VI) toxicity. The microscopic observations presented additional information on the morphological changes of the algal cells in the presence of the binary toxicants. The generation of reactive oxygen species (ROS) suggested contribution of oxidative stress on toxicity and LDH release confirmed membrane permeability of algal cells upon stress. Copyright © 2013 Elsevier B.V. All rights reserved.

Cr(VI) reduction and immobilization by novel carbonaceous modified magnetic Fe{sub 3}O{sub 4}/halloysite nanohybrid

Energy Technology Data Exchange (ETDEWEB)

Tian, Xike, E-mail: xktian@cug.edu.cn [Faculty of Material Science and Chemistry, China University of Geosciences, Wuhan 430074 (China); Wang, Weiwei; Tian, Na; Zhou, Chaoxin; Yang, Chao [Faculty of Material Science and Chemistry, China University of Geosciences, Wuhan 430074 (China); Komarneni, Sridhar [Materials Research Laboratory, Materials Research Institute and Department of Ecosystem Science and Management, The Pennsylvania State University, University Park, PA 16802 (United States)

2016-05-15

Highlights: • A novel magnetic nonohybrids (Fe{sub 3}O{sub 4}/HNTs@C) were synthesized for Cr(VI) removal. • Cr(VI) was reduced to Cr(III) by Fe{sub 3}O{sub 4} nanoparticles and hydroxyl groups. • Cr ions were attached on Fe{sub 3}O{sub 4}/HNTs@C by ion exchange and coordination interaction. - Abstract: In this work, a novel “Dumbbell-like” magnetic Fe{sub 3}O{sub 4}/Halloysite nanohybrid (Fe{sub 3}O{sub 4}/HNTs@C) with oxygen-containing organic group grafting on the surface of natural halloysite nanotubes (HNTs) and homogeneous Fe{sub 3}O{sub 4} nanospheres selectively aggregating at the tips of modified halloysite nanotubes was successfully synthesized. XRD, TEM, IR spectroscopy, XPS and VSM were used to characterize this newly halloysite nanohybrid and its formation mechanism was discussed. Cr(VI) ions adsorption experiments showed that the Fe{sub 3}O{sub 4}/halloysite nanohybrid exhibited higher adsorption ability with a maximum adsorption capacity of 132 mg/L at 303 K, which is about 100 times higher than that of unmodified halloysite nanotubes. More importantly, with the reduction of Fe{sub 3}O{sub 4} and electron–donor effect of oxygen-containing organic groups, Cr(VI) ions were easily reduced into low toxicity Cr(III) and then adsorbed onto the surface of halloysite nanohybrid. In addition, appreciable magnetization was observed due to the aggregation of magnetite nanoparticles, which make adsorbent facility separated from aqueous solutions after Cr pollution adsorption.

Two fold modified chitosan for enhanced adsorption of hexavalent chromium from simulated wastewater and industrial effluents.

Science.gov (United States)

Kahu, S S; Shekhawat, A; Saravanan, D; Jugade, R M

2016-08-01

Ionic solid (Ethylhexadecyldimethylammoniumbromide) impregnated phosphated chitosan (ISPC) was synthesized and applied for enhanced adsorption of hexavalent chromium from industrial effluent. The compound obtained was extensively characterized using instrumental techniques like FT-IR, TGA-DTA, XRD, SEM, BET and EDX. ISPC showed high adsorption capacity of 266.67mg/g in accordance with Langmuir isotherm model at pH 3.0 due to the presence of multiple sites which contribute for ion pair and electrostatic interactions with Cr(VI) species. The sorption kinetics and thermodynamic studies revealed that adsorption of Cr(VI) followed pseudo-second-order kinetics with exothermic and spontaneous behaviour. Applicability of ISPC for higher sample volumes was discerned through column studies. The real chrome plating industry effluent was effectively treated with total chromium recovery of 94%. The used ISPC was regenerated simply by dilute ammonium hydroxide treatment and tested for ten adsorption-desorption cycles with marginal decrease in adsorption efficiency. Copyright © 2016 Elsevier Ltd. All rights reserved.

Recyclable magnetic photocatalysts of Fe2+/TiO2 hierarchical architecture with effective removal of Cr(VI) under UV light from water

International Nuclear Information System (INIS)

Xu, S.C.; Zhang, Y.X.; Pan, S.S.; Ding, H.L.; Li, G.H.

2011-01-01

Highlights: ► Fe 2+ /TiO 2 catalyst has a three-level hierarchical architecture. ► With a removal effectiveness of 99.3% at Cr(VI) concentration of 10 mg L −1 . ► Two-step reduction: TiO 2 photoreduces Fe 2+ to Fe and Fe reduces Cr(VI) to Cr(III). ► Hierarchical architecture serves as both photocatalytic reactor and absorbent. ► Fe 2+ /TiO 2 catalyst can be magnetically separated from wastewater and recycled. - Abstract: We report the synthesis and photocatalytic removal of Cr(VI) from water of hierarchical micro/nanostructured Fe 2+ /TiO 2 tubes. The TiO 2 tubes fabricated by a facile solvothermal approach show a three-level hierarchical architecture assembled from dense nanosheets nearly vertically standing on the surface of TiO 2 microtube. The nanosheets with a thickness of about 20 nm are composed of numerous TiO 2 nanocrystals with size in the range of 15–20 nm. Ferrous ions are doped into the hierarchical architecture by a reduction route. The Fe 2+ /TiO 2 catalyst demonstrates an effective removal of Cr(VI) from water under UV light and the removal effectiveness reaches 99.3% at the initial Cr(VI) concentration of 10 mg L −1 . The ferrous ion in the catalyst serves not as the photo-electron trap but as an intermedium of a two-step reduction. The TiO 2 photoreduces the Fe 2+ ions to Fe atoms firstly, then the Fe atoms reduce the Cr(VI) to Cr(III), and the later is removed by adsorption. The hierarchical architecture of the catalyst serves as a reactor for the photocatalytic reaction of Cr(VI) ions and an effective absorbent for the removal of Cr(III) ions. The catalyst can be easily magnetically separated from the wastewater after photocatalytic reaction and recycled after acid treatment.

Well-Dispersed Nanoscale Zero-Valent Iron Supported in Macroporous Silica Foams: Synthesis, Characterization, and Performance in Cr(VI Removal

Directory of Open Access Journals (Sweden)

Chaoxia Zhao

2017-01-01

Full Text Available Well-dispersed nanoscale zero-valent iron (NZVI supported inside the pores of macroporous silica foams (MOSF composites (Mx-NZVI has been prepared as the Cr(VI adsorbent by simply impregnating the MOSF matrix with ferric chloride, followed by the chemical reduction with NaHB4 in aqueous solution at ambient atmosphere. Through the support of MOSF, the reactivity and stability of NZVI are greatly improved. Transmission electron microscopy (TEM results show that NZVI particles are spatially well-dispersed with a typical core-shell structure and supported inside MOSF matrix. The N2 adsorption-desorption isotherms demonstrate that the Mx-NZVI composites can maintain the macroporous structure of MOSF and exhibit a considerable high surface area (503 m2·g−1. X-ray photoelectron spectroscopy (XPS and powder X-ray diffraction (XRD measurements confirm the core-shell structure of iron nanoparticles composed of a metallic Fe0 core and an Fe(II/Fe(III species shell. Batch experiments reveal that the removal efficiency of Cr(VI can reach 100% when the solution contains 15.0 mg·L−1 of Cr(VI at room temperature. In addition, the solution pH and the composites dosage can affect the removal efficiency of Cr(VI. The Langmuir isotherm is applicable to describe the removal process. The kinetic studies demonstrate that the removal of Cr(VI is consistent with pseudo-second-order kinetic model.

Simultaneous removal of Cr(VI) and 4-chlorophenol through photocatalysis by a novel anatase/titanate nanosheet composite: Synergetic promotion effect and autosynchronous doping

International Nuclear Information System (INIS)

Liu, Wen; Sun, Weiling; Borthwick, Alistair G.L.; Wang, Ting; Li, Fan; Guan, Yidong

2016-01-01

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_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.

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.

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

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

Energy Technology Data Exchange (ETDEWEB)

Lin, Hai, E-mail: linhai@ces.ustb.edu.cn [School of Energy and Environmental Engineering, University of Science and Technology Beijing, Beijing 100083 (China); Beijing Key Laboratory on Resource-oriented Treatment of Industrial Pollutants, Beijing 100083 (China); Han, Shaoke; Dong, Yingbo; He, Yinhai [School of Energy and Environmental Engineering, University of Science and Technology Beijing, Beijing 100083 (China); Beijing Key Laboratory on Resource-oriented Treatment of Industrial Pollutants, Beijing 100083 (China)

2017-08-01

Highlights: • An anion adsorbent was synthesized by hyperbranched polyamide modified corncob (HPMC). • The surface characteristics of samples (RCC, HPMC, HPMC-Cr) were studied. • Langmuir isotherm provided more fit and maximum adsorption capacity was 131.6 mg/g. • The adsorption process was chemisorption, controlled by intra-particle diffusion and film diffusion. • Adsorption is fast, stable, spontaneous and endothermic. - Abstract: 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, q{sub max}, 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.

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

International Nuclear Information System (INIS)

Narin, Ibrahim; Kars, Ayse; Soylak, Mustafa

2008-01-01

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 μg/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

A fetal whole ovarian culture model for the evaluation of CrVI-induced developmental toxicity during germ cell nest breakdown

Energy Technology Data Exchange (ETDEWEB)

Stanley, Jone A.; Arosh, Joe A.; Burghardt, Robert C.; Banu, Sakhila K., E-mail: skbanu@cvm.tamu.edu

2015-11-15

Prenatal exposure to endocrine disrupting chemicals (EDCs), including bisphenol A, dioxin, pesticides, and cigarette smoke, has been linked to several ovarian diseases such as premature ovarian failure (POF) and early menopause in women. Hexavalent chromium (CrVI), one of the more toxic heavy metals, is widely used in more than 50 industries. As one of the world's leading producers of Cr compounds, the U.S. is facing growing challenges in protecting human health against adverse effects of CrVI. Our recent findings demonstrated that in vivo CrVI exposure during gestational period caused POF in F1 offspring. Our current research focus is three-fold: (i) to identify the effect of CrVI on critical windows of great vulnerability of fetal ovarian development; (ii) to understand the molecular mechanism of CrVI-induced POF; (iii) to identify potential intervention strategies to mitigate or inhibit CrVI effects. In order to accomplish these goals we used a fetal whole ovarian culture system. Fetuses were removed from the normal pregnant rats on gestational day 13.5. Fetal ovaries were cultured in vitro for 12 days, and treated with or without 0.1 ppm potassium dichromate (CrVI) from culture day 2–8, which recapitulated embryonic day 14.5–20.5, in vivo. Results showed that CrVI increased germ cell/oocyte apoptosis by increasing caspase 3, BAX, p53 and PUMA; decreasing BCL2, BMP15, GDF9 and cKIT; and altering cell cycle regulatory genes and proteins. This model system may serve as a potential tool for high throughput testing of various drugs and/or EDCs in particular to assess developmental toxicity of the ovary. - Highlights: • CrVI (0.1 ppm, a regulatory dose) increased germ cell apoptosis of fetal ovaries. • CrVI (0.1 ppm) increased pro-apoptotic proteins. • CrVI (0.1 ppm) decreased cyclins and CDK1 and cell survival proteins. • CrVI (0.1 ppm) increased oxidative stress during fetal ovarian development. • We propose fetal ovarian culture model for high

A fetal whole ovarian culture model for the evaluation of CrVI-induced developmental toxicity during germ cell nest breakdown

International Nuclear Information System (INIS)

Stanley, Jone A.; Arosh, Joe A.; Burghardt, Robert C.; Banu, Sakhila K.

2015-01-01

Prenatal exposure to endocrine disrupting chemicals (EDCs), including bisphenol A, dioxin, pesticides, and cigarette smoke, has been linked to several ovarian diseases such as premature ovarian failure (POF) and early menopause in women. Hexavalent chromium (CrVI), one of the more toxic heavy metals, is widely used in more than 50 industries. As one of the world's leading producers of Cr compounds, the U.S. is facing growing challenges in protecting human health against adverse effects of CrVI. Our recent findings demonstrated that in vivo CrVI exposure during gestational period caused POF in F1 offspring. Our current research focus is three-fold: (i) to identify the effect of CrVI on critical windows of great vulnerability of fetal ovarian development; (ii) to understand the molecular mechanism of CrVI-induced POF; (iii) to identify potential intervention strategies to mitigate or inhibit CrVI effects. In order to accomplish these goals we used a fetal whole ovarian culture system. Fetuses were removed from the normal pregnant rats on gestational day 13.5. Fetal ovaries were cultured in vitro for 12 days, and treated with or without 0.1 ppm potassium dichromate (CrVI) from culture day 2–8, which recapitulated embryonic day 14.5–20.5, in vivo. Results showed that CrVI increased germ cell/oocyte apoptosis by increasing caspase 3, BAX, p53 and PUMA; decreasing BCL2, BMP15, GDF9 and cKIT; and altering cell cycle regulatory genes and proteins. This model system may serve as a potential tool for high throughput testing of various drugs and/or EDCs in particular to assess developmental toxicity of the ovary. - Highlights: • CrVI (0.1 ppm, a regulatory dose) increased germ cell apoptosis of fetal ovaries. • CrVI (0.1 ppm) increased pro-apoptotic proteins. • CrVI (0.1 ppm) decreased cyclins and CDK1 and cell survival proteins. • CrVI (0.1 ppm) increased oxidative stress during fetal ovarian development. • We propose fetal ovarian culture model for high

Chromium Stable Isotope Fractionation - An Indicator of Hexavalent Chromium Reduction.

Science.gov (United States)

Ellis, A.; Johnson, T. M.; Bullen, T. D.

2001-12-01

Chromium is a common anthropogenic contaminant in surface water and ground water, and is also of interest in oceanography. It is redox-active; the two common valences in natural waters are Cr(VI), which is highly soluble and toxic, and Cr(III), which is relatively insoluble. Redox reactions thus control Cr mobility in aqueous solutions, and reduction of Cr(VI) to Cr(III) is the most important reaction controlling attenuation of Cr in groundwater. Our results show that Cr(VI) reduction favors the lighter isotopes and leads to enrichment of heavier isotopes in the remaining Cr(VI). Cr isotope measurements thus show great promise as indicators of Cr(VI) reduction. We report here the first measurements of the magnitude of Cr isotope fractionation during Cr(VI) reduction and variations in δ 53Cr values obtained from three contaminated sites. Experiments were conducted to measure Cr isotope fractionation during Cr(VI) reduction by suspensions of magnetite and unamended sediments from a local pond, Urbana, IL and San Francisco Estuary near Martinez, CA. Suspensions were incubated anaerobically with constant shaking, and complete Cr(VI) reduction occurred within a few days. Cr(VI) from intermediate time points in the experiments was purified via ion exchange and 53Cr/52Cr ratios were measured via TIMS with a double isotope spike. The instantaneous per mil fractionation, ɛ , was calculated assuming a Rayleigh fractionation model. The ɛ for Cr(VI) reduction on magnetite surfaces yielded a fractionation of -3.5 ‰ . The ɛ values for the pond and estuary sediments were -3.5 ‰ and -3.3 ‰ respectively. The size of this Cr isotope fractionation is encouraging, as current precision is 0.2 \\permil. δ 53Cr values in dissolved Cr(VI) from three contaminated sites range from 1.1 ‰ to 5.8 ‰ , suggesting that Cr(VI) reduction has occurred and has induced isotopic fractionation in these settings. δ 53Cr values measured from Cr(VI) in plating baths show little or no

Facile synthesis of amino-functionalized titanium metal-organic frameworks and their superior visible-light photocatalytic activity for Cr(VI) reduction

International Nuclear Information System (INIS)

Wang, Hou; Yuan, Xingzhong; Wu, Yan; Zeng, Guangming; Chen, Xiaohong; Leng, Lijian; Wu, Zhibin; Jiang, Longbo; Li, Hui

2015-01-01

Highlights: • NH 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 3+ –Ti 4+ intervalence electron transfer is important for Cr(VI) reduction. • Used NH 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 2 -MIL-125(Ti)) were successfully synthesized via a facile solvothermal method. The MIL-125(Ti) and NH 2 -MIL-125(Ti) were well characterized by XRD, SEM, XPS, N 2 adsorption–desorption measurements, thermogravimetric analysis and UV–vis diffuse reflectance spectra (DRS). It is revealed that the NH 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 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 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

Polyethylenimine-modified fungal biomass as a high-capacity biosorbent for Cr(VI) anions: sorption capacity and uptake mechanisms.

Science.gov (United States)

Deng, Shubo; Ting, Yen Peng

2005-11-01

Heavy metal pollution in the aqueous environment is a problem of global concern. Biosorption has been considered as a promising technology for the removal of low levels of toxic metals from industrial effluents and natural waters. A modified fungal biomass of Penicillium chrysogenum with positive surface charges was prepared by grafting polyethylenimine (PEI) onto the biomass surface in a two-step reaction. The presence of PEI on the biomass surface was verified by FTIR and X-ray photoelectron spectroscopy (XPS) analyses. Due to the high density of amine groups in the long chains of PEI molecules on the surface, the modified biomass was found to possess positive zeta potential at pH below 10.4 as well as high sorption capacity for anionic Cr(VI). Using the Langmuir adsorption isotherm, the maximum sorption capacity for Cr(VI) at a pH range of 4.3-5.5 was 5.37 mmol/g of biomass dry weight, the highest sorption capacity for Cr(VI) compared to other sorbents reported in the literature. Scanning electronic microscopy (SEM) provided evidence of chromium aggregates formed on the biomass surface. XPS results verified the presence of Cr(III) on the biomass surface in the pH range 2.5-10.5, suggesting that some Cr(VI) anions were reduced to Cr(III) during the sorption. The sorption kinetics indicated that redox reaction occurred on the biomass surface, and whether the converted Cr(III) ions were released to solution or adsorbed on the biomass depended on the solution pH. Sorption mechanisms including electrostatic interaction, chelation, and precipitation were found to be involved in the complex sorption of chromium on the PEI-modified biomass.

Luteolin inhibits Cr(VI)-induced malignant cell transformation of human lung epithelial cells by targeting ROS mediated multiple cell signaling pathways

Energy Technology Data Exchange (ETDEWEB)

Pratheeshkumar, Poyil; Son, Young-Ok; Divya, Sasidharan Padmaja; Roy, Ram Vinod; Hitron, John Andrew; Wang, Lei [Center for Research on Environmental Disease, University of Kentucky, 1095 VA Drive, Lexington, KY 40536 (United States); Graduate Center for Toxicology, University of Kentucky, 1095 VA Drive, Lexington, KY 40536 (United States); Kim, Donghern; Dai, Jin [Graduate Center for Toxicology, University of Kentucky, 1095 VA Drive, Lexington, KY 40536 (United States); Asha, Padmaja [National Centre for Aquatic Animal Health, Cochin University of Science and Technology, Cochin (India); Zhang, Zhuo [Graduate Center for Toxicology, University of Kentucky, 1095 VA Drive, Lexington, KY 40536 (United States); Wang, Yitao [State Key Laboratory of Quality Research in Chinese Medicine, Institute of Chinese Medical Sciences, University of Macau, Macau (China); Shi, Xianglin, E-mail: xshi5@email.uky.edu [Center for Research on Environmental Disease, University of Kentucky, 1095 VA Drive, Lexington, KY 40536 (United States); Graduate Center for Toxicology, University of Kentucky, 1095 VA Drive, Lexington, KY 40536 (United States)

2014-12-01

Hexavalent chromium [Cr(VI)] is a well-known human carcinogen associated with the incidence of lung cancer. Inhibition of metal induced carcinogenesis by a dietary antioxidant is a novel approach. Luteolin, a natural dietary flavonoid found in fruits and vegetables, possesses potent antioxidant and anti-inflammatory activity. We found that short term exposure of human bronchial epithelial cells (BEAS-2B) to Cr(VI) (5 μM) showed a drastic increase in ROS generation, NADPH oxidase (NOX) activation, lipid peroxidation, and glutathione depletion, which were significantly inhibited by the treatment with luteolin in a dose dependent manner. Treatment with luteolin decreased AP-1, HIF-1α, COX-2, and iNOS promoter activity induced by Cr(VI) in BEAS-2B cells. In addition, luteolin protected BEAS-2B cells from malignant transformation induced by chronic Cr(VI) exposure. Moreover, luteolin also inhibited the production of pro-inflammatory cytokines (IL-1β, IL-6, IL-8, TNF-α) and VEGF in chronic Cr(VI) exposed BEAS-2B cells. Western blot analysis showed that luteolin inhibited multiple gene products linked to survival (Akt, Fak, Bcl-2, Bcl-xL), inflammation (MAPK, NF-κB, COX-2, STAT-3, iNOS, TNF-α) and angiogenesis (HIF-1α, VEGF, MMP-9) in chronic Cr(VI) exposed BEAS-2B cells. Nude mice injected with BEAS-2B cells chronically exposed to Cr(VI) in the presence of luteolin showed reduced tumor incidence compared to Cr(VI) alone treated group. Overexpression of catalase (CAT) or SOD2, eliminated Cr(VI)-induced malignant transformation. Overall, our results indicate that luteolin protects BEAS-2B cells from Cr(VI)-induced carcinogenesis by scavenging ROS and modulating multiple cell signaling mechanisms that are linked to ROS. Luteolin, therefore, serves as a potential chemopreventive agent against Cr(VI)-induced carcinogenesis. - Highlights: • Luteolin inhibited Cr(VI)-induced oxidative stress. • Luteolin inhibited chronic Cr(VI)-induced malignant transformation. �

Luteolin inhibits Cr(VI)-induced malignant cell transformation of human lung epithelial cells by targeting ROS mediated multiple cell signaling pathways

International Nuclear Information System (INIS)

Pratheeshkumar, Poyil; Son, Young-Ok; Divya, Sasidharan Padmaja; Roy, Ram Vinod; Hitron, John Andrew; Wang, Lei; Kim, Donghern; Dai, Jin; Asha, Padmaja; Zhang, Zhuo; Wang, Yitao; Shi, Xianglin

2014-01-01

Hexavalent chromium [Cr(VI)] is a well-known human carcinogen associated with the incidence of lung cancer. Inhibition of metal induced carcinogenesis by a dietary antioxidant is a novel approach. Luteolin, a natural dietary flavonoid found in fruits and vegetables, possesses potent antioxidant and anti-inflammatory activity. We found that short term exposure of human bronchial epithelial cells (BEAS-2B) to Cr(VI) (5 μM) showed a drastic increase in ROS generation, NADPH oxidase (NOX) activation, lipid peroxidation, and glutathione depletion, which were significantly inhibited by the treatment with luteolin in a dose dependent manner. Treatment with luteolin decreased AP-1, HIF-1α, COX-2, and iNOS promoter activity induced by Cr(VI) in BEAS-2B cells. In addition, luteolin protected BEAS-2B cells from malignant transformation induced by chronic Cr(VI) exposure. Moreover, luteolin also inhibited the production of pro-inflammatory cytokines (IL-1β, IL-6, IL-8, TNF-α) and VEGF in chronic Cr(VI) exposed BEAS-2B cells. Western blot analysis showed that luteolin inhibited multiple gene products linked to survival (Akt, Fak, Bcl-2, Bcl-xL), inflammation (MAPK, NF-κB, COX-2, STAT-3, iNOS, TNF-α) and angiogenesis (HIF-1α, VEGF, MMP-9) in chronic Cr(VI) exposed BEAS-2B cells. Nude mice injected with BEAS-2B cells chronically exposed to Cr(VI) in the presence of luteolin showed reduced tumor incidence compared to Cr(VI) alone treated group. Overexpression of catalase (CAT) or SOD2, eliminated Cr(VI)-induced malignant transformation. Overall, our results indicate that luteolin protects BEAS-2B cells from Cr(VI)-induced carcinogenesis by scavenging ROS and modulating multiple cell signaling mechanisms that are linked to ROS. Luteolin, therefore, serves as a potential chemopreventive agent against Cr(VI)-induced carcinogenesis. - Highlights: • Luteolin inhibited Cr(VI)-induced oxidative stress. • Luteolin inhibited chronic Cr(VI)-induced malignant transformation. �

A survey of Cr(VI) contamination of surface water in the proximity of ...

African Journals Online (AJOL)

2013-07-30

Jul 30, 2013 ... In this study, Cr(VI) levels present in surface water within the vicinity of ferrochrome smelters located in .... flict in literature pertaining to the toxicity or carcinogenicity ..... Due to the potential human health risks associated with.

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.

Simulated solarlight catalytic reduction of Cr(VI) on microwave–ultrasonication synthesized flower-like CuO in the presence of tartaric acid

International Nuclear Information System (INIS)

Xu, Zhihui; Yu, Yaqun; Fang, Di; Liang, Jianru; Zhou, Lixiang

2016-01-01

In this study, flower-like CuO was successfully synthesized by a microwave–ultrasound assisted method and well characterized by X-ray diffractions, Fourier transform infrared spectrum, scanning electron microscopy, transmission electron microscopy, specific surface area, UV–vis diffused reflection spectra, X-ray photoelectron spectroscopy and point of zero charge. The photocatalytic performance of the as-prepared CuO was examined on the Cr(VI) reduction in the presence of tartaric acid under simulated solarlight irradiation. The results show that the developed CuO catalyst exhibited good photocatalytic activity with 100% reduction of Cr(VI) after irradiation of 30 min under the test condition of c(Cr(VI)) = 100 μM, catalyst loading = 400 mg/L, c(tartaric acid) = 4 mM and initial pH = 3. The reaction mechanism was proposed. The effects of test parameters, such as catalyst loading, tartaric acid concentration and initial pH, on Cr(VI) reduction efficiency were also investigated. It is worth mentioning that the developed catalyst can work at a relatively wide range of pH with quite high catalytic performance. - Highlights: • Flower-like CuO microstructure was prepared by MW-US assisted method. • The prepared CuO can catalyze the reduction Cr(VI) by tartaric acid under simulated solarlight. • The formation of ≡Cu(II)-tartaric acid complex play a key role in the reduction of Cr(VI). • The catalyst can operate effectively at a relatively wide range of pH.

Hexavalent Chromium: Analysis of the Mechanism of Groundwater Contamination in a Former Industrial Site in the Province of Vicenza (Northern Italy)

OpenAIRE

Valentina Accoto; Pierluigi Bullo; Ruben Faccio; Leonardo Mason; Andrea Sottani

2017-01-01

The study consisted in the analysis of the mobilization mechanisms of hexavalent chromium (Cr(VI)) into groundwater from a decommissioned contaminated factory. The site is located in the Province of Vicenza and formerly was a chrome-plating plant. The subsoil consists predominantly of gravelly deposits with a thickness of at least one hundred meters. An unconfined aquifer is present with water table at about 23 m depth bgl. During the seven years of monitoring (2008-2014), the fluctuation of ...

The effects of welding parameters on ultra-violet light emissions, ozone and CrVI formation in MIG welding.

Science.gov (United States)

Dennis, J H; Mortazavi, S B; French, M J; Hewitt, P J; Redding, C R

1997-01-01

This paper describes the relationships between ultra-violet emission, ozone generation and CrVI production in MIG welding which were measured as a function of shield gas flow rate, welding voltage, electrode stick-out and shield gas composition using an automatic welding rig that permitted MIG welding under reproducible conditions. The experimental results are interpreted in terms of the physico-chemical processes occurring in the micro- and macro-environments of the arc as part of research into process modification to reduce occupational exposure to ozone and CrVI production rates in MIG welding. We believe the techniques described here, and in particular the use of what we have termed u.v.-ozone measurements, will prove useful in further study of ozone generation and CrVI formation and may be applied in the investigation of engineering control of occupational exposure in MIG and other welding process such as Manual Metal Arc (MMA) and Tungsten Inert Gas (TIG).

THE ATM-SMC1 PATHWAY IS ESSENTIAL FOR ACTIVATION OF THE CHROMIUM[VI]-INDUCED S-PHASE CHECKPOINT

Science.gov (United States)

Hexavalent chromium (Cr[VI] is a common industrial waste product, an environmental pollutant, and a recognized human carcinogen. Following cellular uptake, Cr[VI] can cause DNA damage, however, the mechanisims by which mammalian cells respond to Cr-induced DNA damage remain to b...

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 A polypyrrole-coated halloysite nanotube nanocomposite (PPy-HNTs NC) was prepared via in situ polymerization of pyrrole (Py) in the dispersion of HNTs and assessed for the removal of toxic Cr(VI) from aqueous solutions. ATR-FTIR and XRD results...

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.

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

Application of PolyHIPE Membrane with Tricaprylmethylammonium Chloride for Cr(VI) Ion Separation: Parameters and Mechanism of Transport Relating to the Pore Structure.

Science.gov (United States)

Chen, Jyh-Herng; Le, Thi Tuyet Mai; Hsu, Kai-Chung

2018-03-02

The structural characteristics of membrane support directly affect the performance of carrier facilitated transport membrane. A highly porous PolyHIPE impregnated with Aliquat 336 is proposed for Cr(VI) separation. PolyHIPE consisting of poly(styrene- co -2-ethylhexyl acrylate) copolymer crosslinked with divinylbenzene has the pore structure characteristic of large pore spaces interconnected with small window throats. The unique pore structure provides the membrane with high flux and stability. The experimental results indicate that the effective diffusion coefficient D* of Cr(VI) through Aliquat 336/PolyHIPE membrane is as high as 1.75 × 10 -11 m² s -1 . Transport study shows that the diffusion of Cr(VI) through Aliquat 336/PolyHIPE membrane can be attributed to the jumping transport mechanism. The hydraulic stability experiment shows that the membrane is quite stable, with recovery rates remaining at 95%, even after 10 consecutive cycles of operation. The separation study demonstrates the potential application of this new type of membrane for Cr(VI) recovery.

Application of dolochar in the removal of cadmium and hexavalent chromium ions from aqueous solutions

Energy Technology Data Exchange (ETDEWEB)

Panda, L. [Council of Scientific and Industrial Research, Institute of Minerals and Materials Technology, Bhubaneswar 751013 (India); Das, B., E-mail: bdas@immt.res.in [Council of Scientific and Industrial Research, Institute of Minerals and Materials Technology, Bhubaneswar 751013 (India); Rao, D.S.; Mishra, B.K. [Council of Scientific and Industrial Research, Institute of Minerals and Materials Technology, Bhubaneswar 751013 (India)

2011-08-30

Graphical abstract: Dolochar - a waste material from sponge iron industry, is put to test as an adsorbent for removal of cadmium and hexavalent chromium ions from aqueous solutions. The sample consists of lots of voids and pores. Batch adsorption experiments have indicated that, higher pH and temperature enhances sorption for cadmium ions. The adsorption for chromium is found better at acidic pH in comparison to alkaline pH. The adsorption is well fitted to Langmuir isotherm model compared to the Freundlich model indicating monolayer adsorption. The kinetics of adsorption better fit to pseudo second order model.. Display Omitted Highlights: {yields} Dolochar, a waste material is generated during the production of sponge iron. {yields} Dolochar consists of metallic iron, carbon, and lime bearing phases along with lots of voids and pores. {yields} It was found to be an good adsorbent for the removal of cadmium and hexavalent chromium ions from aqueous solutions. {yields} The adsorption follows Langmuir isotherm and kinetics of adsorption better fit of pseudo second order model. - Abstract: Dolochar, a waste material generated in sponge iron industry, is processed and put to test as an adsorbent for removal of Cd(II) and Cr(VI) ions from aqueous solutions. The dolochar samples were characterised to determine the different phases and their distribution by reflection microscopy. The analysis indicated that the sample consists of metallic iron, fused carbon, and Ca-Mg bearing phases (Ca-Mg-silicate-oxide) along with lots of voids and pores. The fixed carbon (FC) content of the material is 13.8% with a Langmuir surface area of 81.6 m{sup 2}/g and micropore area of 34.1 m{sup 2}/g. Batch adsorption experiments have been conducted to study the sorption behaviour of Cd(II) and Cr(VI) ions on dolochar as a function of particle size, contact time, adsorbent dosages, pH and temperature. It is observed that higher pH and temperature enhances sorption of Cd(II) ions. In contrast

Application of dolochar in the removal of cadmium and hexavalent chromium ions from aqueous solutions

International Nuclear Information System (INIS)

Panda, L.; Das, B.; Rao, D.S.; Mishra, B.K.

2011-01-01

Graphical abstract: Dolochar - a waste material from sponge iron industry, is put to test as an adsorbent for removal of cadmium and hexavalent chromium ions from aqueous solutions. The sample consists of lots of voids and pores. Batch adsorption experiments have indicated that, higher pH and temperature enhances sorption for cadmium ions. The adsorption for chromium is found better at acidic pH in comparison to alkaline pH. The adsorption is well fitted to Langmuir isotherm model compared to the Freundlich model indicating monolayer adsorption. The kinetics of adsorption better fit to pseudo second order model.. Display Omitted Highlights: → Dolochar, a waste material is generated during the production of sponge iron. → Dolochar consists of metallic iron, carbon, and lime bearing phases along with lots of voids and pores. → It was found to be an good adsorbent for the removal of cadmium and hexavalent chromium ions from aqueous solutions. → The adsorption follows Langmuir isotherm and kinetics of adsorption better fit of pseudo second order model. - Abstract: Dolochar, a waste material generated in sponge iron industry, is processed and put to test as an adsorbent for removal of Cd(II) and Cr(VI) ions from aqueous solutions. The dolochar samples were characterised to determine the different phases and their distribution by reflection microscopy. The analysis indicated that the sample consists of metallic iron, fused carbon, and Ca-Mg bearing phases (Ca-Mg-silicate-oxide) along with lots of voids and pores. The fixed carbon (FC) content of the material is 13.8% with a Langmuir surface area of 81.6 m 2 /g and micropore area of 34.1 m 2 /g. Batch adsorption experiments have been conducted to study the sorption behaviour of Cd(II) and Cr(VI) ions on dolochar as a function of particle size, contact time, adsorbent dosages, pH and temperature. It is observed that higher pH and temperature enhances sorption of Cd(II) ions. In contrast, the adsorption for Cr(VI

Hexavalent chromium-induced differential disruption of cortical microtubules in some Fabaceae species is correlated with acetylation of α-tubulin.

Science.gov (United States)

Eleftheriou, Eleftherios P; Adamakis, Ioannis-Dimosthenis S; Michalopoulou, Vasiliki A

2016-03-01

The effects of hexavalent chromium [Cr(VI)] on the cortical microtubules (MTs) of five species of the Fabaceae family (Vicia faba, Pisum sativum, Vigna sinensis, Vigna angularis, and Medicago sativa) were investigated by confocal laser scanning microscopy after immunolocalization of total tubulin with conventional immunofluorescence techniques and of acetylated α-tubulin with the specific 6-11B-1 monoclonal antibody. Moreover, total α-tubulin and acetylated α-tubulin were quantified by Western immunoblotting and scanning densitometry. Results showed the universality of Cr(VI) detrimental effects to cortical MTs, which proved to be a sensitive and reliable subcellular marker for monitoring Cr(VI) toxicity in plant cells. However, a species-specific response was recorded, and a correlation of MT disturbance with the acetylation status of α-tubulin was demonstrated. In V. faba, MTs were depolymerized at the gain of cytoplasmic tubulin background and displayed low α-tubulin acetylation, while in P. sativum, V. sinensis, V. angularis, and M. sativa, MTs became bundled and changed orientation from perpendicular to oblique or longitudinal. Bundled MTs were highly acetylated as determined by both immunofluorescence and Western immunoblotting. Tubulin acetylation in P. sativum and M. sativa preceded MT bundling; in V. sinensis it followed MT derangement, while in V. angularis the two phenomena coincided. Total α-tubulin remained constant in all treatments. Should acetylation be an indicator of MT stabilization, it is deduced that bundled MTs became stabilized, lost their dynamic properties, and were rendered inactive. Results of this report allow the conclusion that Cr(VI) toxicity disrupts MTs and deranges the MT-mediated functions either by depolymerizing or stabilizing them.

Removal of Cr(VI) and Ni(II) from aqueous solution by fused yeast: Study of cations release and biosorption mechanism

International Nuclear Information System (INIS)

Yin Hua; He Baoyan; Peng Hui; Ye Jinshao; Yang Feng; Zhang Na

2008-01-01

Biosorption of Cr(VI) and Ni(II) by a fused yeast from Candida tropicalis and Candida lipolytica under varying range of pH, initial metal concentration and reaction time was investigated. Net cation release and Cr removal reached 2.000 mmol/l and 81.37% when treating 20 mg/l Cr(VI) at pH 2 with 25 mg/l biomass for 30 min, while for Ni were 0.351 mmol/l and 64.60%, respectively. Trace metal elements such as Co, Cu, Mn, Mo, Se and Zn played active role in biosorption as important ingredients of functional enzymes. Cr(VI) was reduced to less toxic Cr(III) and chelated with extracellular secretions, and further accumulated inside the cells. For Ni biosorption, however, largely a passive uptake process influenced by ion gradient led to lower adsorption capacity and cations release. Fourier transform infrared (FTIR) spectrum analysis indicated that amide and pyridine on cells were involved in binding with Cr, but for Ni, bound-OH and nitro-compounds were the main related functional groups. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) analysis confirmed that considerable amounts of metals precipitated on cell surface when dealing with high concentration metals

Assessment of the mutagenic potential of hexavalent chromium in the duodenum of big blue® rats.

Science.gov (United States)

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

2017-09-01

A cancer bioassay on hexavalent chromium Cr(VI) in drinking water reported increased incidences of duodenal tumors in B6C3F1 mice at exposures of 30-180ppm, and oral cavity tumors in F344 rats at 180ppm. A subsequent transgenic rodent (TGR) in vivo mutation assay in Big Blue® TgF344 rats found that exposure to 180ppm Cr(VI) in drinking water for 28days did not increase cII transgene mutant frequency (MF) in the oral cavity (Thompson et al., 2015). Herein, we extend our analysis to the duodenum of these same TgF344 rats. At study termination, duodenum chromium levels were below either the limit of detection or quantification in control rats, but were 24.6±3.8μg/g in Cr(VI)-treated rats. The MF in control (23.2×10 -6 ) and Cr(VI)-treated rats (22.7×10 -6 ) were nearly identical. In contrast, the MF in the duodenum of rats exposed to 1-ethyl-1-nitrosourea for six days (study days 1, 2, 3, 12, 19, 26) increased 24-fold to 557×10 -6 . These findings indicate that mutagenicity is unlikely an early initiating event in Cr(VI)-induced intestinal carcinogenesis. Copyright © 2017 Elsevier Inc. All rights reserved.

The behavior of dissolution/passivation and the transformation of passive films during electrocoagulation: Influences of initial pH, Cr(VI) concentration, and alternating pulsed current

International Nuclear Information System (INIS)

Yang, Zhao-hui; Xu, Hai-yin; Zeng, Guang-ming; Luo, Yuan-ling; Yang, Xia; Huang, Jing; Wang, Li-ke; Song, Pei-pei

2015-01-01

Highlights: • Initial pH, Cr(VI) and APC could affect the behavior of dissolution/passivation in Fe-EC. • A dissolution/passivation region was constructed with different initial pH-Cr(VI). • The film was rich in Fe and Cr at high Cr(VI), whereas with lots of Fe but negligible of Cr at low Cr(VI). • The film was non-protective at long T APC , but became more stable and protective at short T APC . • Behavior of dissolution/passivation and passive film transformation in Fe-EC was elucidated. - Abstract: The passivation behavior of an iron anode for electrocoagulation (EC) was first investigated using response surface methodology (RSM). Tested initial pH range, Cr(VI) concentration and alternating pulsed current (APC) were 4.0 to 8.0, 52 to 520 mg L −1 and 10 to 590 s, respectively. The distance between electrodes was 25 mm, and K 2 SO 4 (1 g L −1 ) was used as the supporting electrolyte in a 2.5 L EC reactor. Results confirmed that initial pH, Cr(VI) concentration, and APC significantly influence the extent of passivation. Then, based on the interaction effect on passivation behavior between initial pH and Cr(VI) in RSM, a pH-Cr(VI)-dissolution/passivation diagram was constructed with galvanostatic measurements. The diagram showed an optimal dissolution region for EC operation. This optimum was characterized by a reasonable final pH for extended precipitation and little passivation. Results of the cyclic voltammetry and X-ray photoelectron spectroscopy revealed a significant difference in the composition and stability of oxide films in the region with more pronounced passivation. Interestingly, the APC had both positive and negative effect on the passivation behavior. Long period of APC (T APC = 590 s) produced a non-protective film, which favored the Fe 0 dissolution. However, a more stable and protective passive film with a uniform structure of Fe and Cr oxides was formed by short T APC (10 s). Based on the above results, this study elucidated the

Preparation, characterization and enhanced adsorption performance for Cr(VI) of mesoporous NiFe2O4 by twice pore-forming method

International Nuclear Information System (INIS)

Jia, Zhigang; Peng, Kuankuan; Xu, Lixin

2012-01-01

Magnetic mesoporous NiFe 2 O 4 with higher surface area has been prepared by the twice pore-forming method, including the calcination of the oxalate precursor and leaching of ZnO pore-forming agent. The X-ray diffraction (XRD), Scanning electron microscopy (SEM), Energy dispersive spectroscopy (EDS) and BET surface area measurement are used to evaluate the pore structural parameters and surface chemistry of the adsorbent respectively. The pore-forming mechanism is proposed based on the experimental results. The adsorption behavior of mesoporous NiFe 2 O 4 for Cr(VI) is investigated in detail. The results show that kinetic data follow a pseudo-second-order model and equilibrium data are well fitted by the Langmuir model. The maximum adsorption capacity is 43.68 mg g −1 at pH 2. The removal for Cr(VI) is mainly physisorption process derived from coulombic interaction. The as-prepared TPF-NiFe 2 O 4 is promising as sorbent for Cr(VI) removal because of its higher adsorption capacity, separation convenience and highly efficient reusability. -- Highlights: ► The increase of BET area was realized by leaching of ZnO from mesoporous ZnO/NiFe 2 O 4 . ► TPF-NiFe 2 O 4 demenstrates higher adsorption capacity for Cr(VI) in aqueous solution. ► TPF-NiFe 2 O 4 with magnetic sensitivity is promosing for Cr(VI) removal. ► The used TPF-NiFe 2 O 4 adsorbent can be recycled.

Hexavalent chromium reduction in a sulfur reducing packed-bed bioreactor

Energy Technology Data Exchange (ETDEWEB)

Sahinkaya, Erkan, E-mail: erkansahinkaya@yahoo.com [Department of Bioengineering, Istanbul Medeniyet University, Goeztepe, Istanbul (Turkey); Kilic, Adem [Department of Environmental Engineering, Harran University, Osmanbey Campus, 63000 Sanliurfa (Turkey); Altun, Muslum [Department of Chemistry, Hacettepe University, Beytepe, Ankara (Turkey); Komnitsas, Kostas [Department of Mineral Resources Engineering, Technical University of Crete, 73100 Chania (Greece); Lens, Piet N.L. [Unesco-IHE Institute for Water Education, Westvest 7, Delft 2611 AX (Netherlands)

2012-06-15

Highlights: Black-Right-Pointing-Pointer Elemental sulfur can be used as electron acceptor for sulfide production. Black-Right-Pointing-Pointer Biogenically produced sulfide reduces Cr(VI) to the much less toxic and immobile form of Cr(III). Black-Right-Pointing-Pointer Sulfur packed bioreactor is efficient for Cr(VI) containing wastewater treatment. Black-Right-Pointing-Pointer Reduced form of chromium precipitates in the bioreactor. - Abstract: The most commonly used approach for the detoxification of hazardous industrial effluents and wastewaters containing Cr(VI) is its reduction to the much less toxic and immobile form of Cr(III). This study investigates the cleanup of Cr(VI) containing wastewaters using elemental sulfur as electron acceptor, for the production of hydrogen sulfide that induces Cr(VI) reduction. An elemental sulfur reducing packed-bed bioreactor was operated at 28-30 Degree-Sign C for more than 250 days under varying influent Cr(VI) concentrations (5.0-50.0 mg/L) and hydraulic retention times (HRTs, 0.36-1.0 day). Ethanol or acetate (1000 mg/L COD) was used as carbon source and electron donor. The degree of COD oxidation varied between 30% and 85%, depending on the operating conditions and the type of organic carbon source. The oxidation of organic matter was coupled with the production of hydrogen sulfide, which reached a maximum concentration of 750 mg/L. The biologically produced hydrogen sulfide reduced Cr(VI) chemically to Cr(III) that precipitated in the reactor. Reduction of Cr(VI) and removal efficiency of total chromium always exceeded 97% and 85%, respectively, implying that the reduced chromium was retained in the bioreactor. This study showed that sulfur can be used as an electron acceptor to produce hydrogen sulfide that induces efficient reduction and immobilization of Cr(VI), thus enabling decontamination of Cr(VI) polluted wastewaters.

K4Nb6O17·4.5H2O: A novel dual functional material with quick photoreduction of Cr(VI) and high adsorptive capacity of Cr(III)

International Nuclear Information System (INIS)

Ma, Yuli; Liu, Xiaoqing; Li, Yang; Su, Yiguo; Chai, Zhanli; Wang, Xiaojing

2014-01-01

Graphical abstract: A well crystalline K 4 Nb 6 O 17 ·4.5H 2 O with a wide layer spacing possesses an excellent disposal performance for chromium species of Cr(VI) and Cr(III) as well as the superior recyclability due to its high stability and convenient regeneration process. - Highlights: • A nano-sheet K 4 Nb 6 O 17 ·4.5H 2 O with a large layer spacing was synthesized. • K 4 Nb 6 O 17 ·4.5H 2 O showed a superior photoreduction of Cr(VI) in an acidic solution. • The sample showed a high adsorption capacity of Cr(III) in a near neutral solution. • K 4 Nb 6 O 17 ·4.5H 2 O regenerated conveniently by immersing in a KOH solution. • A complete removal of chromium species was retained after recycling five times. - Abstract: A series of orthorhombic phase K 4 Nb 6 O 17 ·4.5H 2 O was synthesized via a hydrothermal approach. When presented in an acidic pH range, K 4 Nb 6 O 17 ·4.5H 2 O showed a strong ability in quick reduction from Cr(VI) to Cr(III). The resulted Cr(III) ions were removed by an effective adsorption through simply adjusting the solution pH from strong acidity to near neutrality, owing to the sample's unique nano-sheet structure with a wide layer spacing. The Cr(III) ions adsorbed onto samples were released again for reusing by eluting with 1 mol L −1 HCl solution, and K 4 Nb 6 O 17 ·4.5H 2 O regenerated by immersing in a KOH solution. The reduction efficiency of Cr(VI) was still up to 98% after irradiation for 60 min, and the removal efficiency of Cr(III) ions was as high as 83% even after five cycles. Therefore, K 4 Nb 6 O 17 ·4.5H 2 O is clearly demonstrated to be an excellent dual functional material with quick photoreduction of Cr(VI) and high adsorptive capacity of Cr(III). The relevant materials reported herein might be found various environment-related applications

Characteristics and mechanisms of hexavalent chromium removal by biochar from sugar beet tailing

International Nuclear Information System (INIS)

Dong Xiaoling; Ma, Lena Q.; Li Yuncong

2011-01-01

Highlights: → Biochar from sugar beet tailing effectively removed Cr(VI) from solution. → Most of the Cr on the biochar was Cr(III). → Cr(VI) removal was via electrostatic attraction to biochar. → Reduction of Cr(VI) to Cr(III) ion and complexation between Cr(III) ion and biochar function groups were also important. → The maximum sorption capacity of biochar for Cr(VI) was123 mg/g. - Abstract: Removal of Cr(VI) from aqueous solutions using biochar from sugar beet tailing (SBT) was investigated as a function of pH, contact time, and biochar mass via batch experiments. The surface characteristics of SBT biochar before and after Cr(VI) sorption was investigated with scanning electron microscopy equipped with energy dispersive X-ray spectroscopy and Fourier transform infrared spectroscopy. Desorption and X-ray photoelectron spectroscopy studies showed that most of the Cr bound to SBT biochar was Cr(III). These results indicated that the electrostatic attraction of Cr(VI) to positively charged biochar surface, reduction of Cr(VI) to Cr(III) ion, and complexation between Cr(III) ion and SBT's function groups were probably responsible for Cr(VI) removal by SBT biochar. An initial solution with a pH of 2.0 was most favorable for Cr(VI) removal. The sorption process can be described by the pseudo-second order equation and Langmuir isotherm. The maximum sorption capacity for Cr(VI) was 123 mg/g under an acidic medium, which was comparable to other low-cost sorbents.

Treatment of hexavalent chromium Cr (VI) in tanning effluent

International Nuclear Information System (INIS)

Ahmed, I.; Ali, S.

1999-01-01

Most common chemical used in chrome tanning is basic chromium sulphate (BCS). Manufacturing of BCS involves many steps producing liquid waste. Waste generated at every stage contains Cr (VI), which must be reduced to Cr (III) before being disposed to the environment. Different methods were studied for the reduction of toxic Cr (III). Pickle liquor (waste of electroplating industry) can also be used for the reduction of hexavalent chromium Cr (vi) along with other reducing materials / chemicals. In an electroplating process metal is treated with HCl or H/sub 2/SO/sub 4/ to remove scales and rust, the pickled items are then washed with water, washing contains FeCl/sub 2/ or fees/sub 4/ respectively called pickle liquor. During waste treatment pH adjustment to 6.0 - 9.0 and settling the sludge, is discharged to the lagoon. The sludge obtained is dried and disposed off in landfills. Other reducing agents like sodium bisulphite and sulfur dioxide were also studied, but pickle liquor was found to be more effective and economical. (author)

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...

Mode of action of Cr(VI) in immunocytes of earthworms: Implications for animal health.

Science.gov (United States)

Sforzini, Susanna; Moore, Michael N; Mou, Zhuofan; Boeri, Marta; Banni, Mohamed; Viarengo, Aldo

2017-04-01

Chromium (Cr) is one of the major and most detrimental pollutant, widely present in the environment as a result of several anthropogenic activities. In mammalian cells, Cr(VI) is known to enhance reactive oxygen species (ROS) production and to cause toxic and genotoxic effects. Less commonly investigated are the effects and mode of action of this contaminant in invertebrates, particularly in soil organisms. In this work, earthworms of the species Eisenia andrei were exposed for 1 and 3 days to various sublethal concentrations of Cr(VI) (2, 15, 30µgmL -1 ) using the paper contact toxicity test. In amoeboid leukocytes we investigated intracellular ROS and lipoperoxide production, oxidative DNA damage, and the effects on different cell functions. The analysis of the results shows that Cr(VI) triggered severe adverse reactions; the first events were an increase of intracellular ROS levels, generating in the cells oxidative stress conditions leading to membrane lipid peroxidation and oxidative DNA damage. Lysosomes showed relevant changes such as a strong membrane destabilization, which was accompanied by an increased catabolism of cytoplasmic proteins and accumulation of lipofuscin. With an increase in the dose and/or time of exposure, the physiological status of intracellular organelles (such as lysosomes, nucleus and mitochondria) showed further impairment and amoebocyte immune functions were adversely affected, as shown by the decrease of the phagocytic activity. By mapping the responses of the different parameters evaluated, diagnostic of (oxidative) stress events, against lysosomal membrane stability, a "health status" indicator (able to describe the stress syndrome from its early phase to pathology), we have shown that this biomarker is suitable as a prognostic test for health of earthworms. This is viewed as a crucial step toward the derivation of explanatory frameworks for prediction of pollutant impact on animal health. Copyright © 2017. Published by

Hexavalent Chromium Substitution Projects

Science.gov (United States)

2011-05-12

Hexavalent Chromium Substitution Projects Date (12 May 2011) Gene McKinley ASC/WNV (937) 255-3596 Gene.McKinley@wpafb.af.mil Aeronautical Systems...valid OMB control number. 1. REPORT DATE 12 MAY 2011 2. REPORT TYPE 3. DATES COVERED 00-00-2011 to 00-00-2011 4. TITLE AND SUBTITLE Hexavalent ...A-10) – AETC (T-6, T-38 and T1A) • Both Cr Primers & Non-Cr primers as well as Cr Surface Treatment – F-22 8 Non- Chrome Tie-coat & touch-up

Influence of Carbon Sources and Electron Shuttles on Ferric Iron Reduction by Cellulomonas sp. Strain ES6

Energy Technology Data Exchange (ETDEWEB)

Erin K. Field; Robin Gerlach; Sridhar Viamajala; Laura K. Jennings; Alfred B. Cunningham; Brent M. Peyton; William A. Apel

2011-09-01

The reduction of hexavalent chromium, Cr(VI), to trivalent chromium, Cr(III), can be an important aspect of remediation processes at Department of Energy (DOE) and other contaminated sites. Cellulomonas species are found at several Cr(VI) contaminated and uncontaminated locations at the DOE site in Hanford, Washington. Members of this genus have demonstrated the ability to effectively reduce Cr(VI) to Cr(III) fermentatively and therefore play a potential role in hexavalent chromium remediation at this site. Batch studies were conducted with Cellulomonas sp. strain ES6 to assess the influence of various carbon sources, iron minerals, and electron shuttling compounds on Cr(VI) reduction. These chemical species are likely to be present in these terrestrial environments during in situ bioremediation. Results indicated that there were a number of interactions between these compounds that influenced Cr(VI) reduction rates. The type of carbon source as well as the type of electron shuttle present influenced Cr(VI) reduction rates. When an electron shuttle, such as anthraquinone-2,6-disulfonate (AQDS), was present in the system, reduction rates increased significantly. Biologically reduced AQDS (AHDS) reduced Cr(VI) almost instantaneously. The presence of iron minerals and their concentrations did not significantly influence Cr(VI) reduction rates. However, strain ES6 or AQDS could directly reduce surface-associated Fe(III) to Fe(II) which was capable of reducing Cr(VI) at a near instantaneous rate. These results suggest the rate limiting step in these systems is the transfer of electrons from strain ES6 to the intermediate or terminal electron acceptor whether that is Cr(VI), Fe(III), or AQDS.

Influence of hexavalent chromium on lactate-enriched Hanford groundwater microbial communities.

Energy Technology Data Exchange (ETDEWEB)

Somenahally, Anil C [ORNL; Mosher, Jennifer J [ORNL; Yuan, Tong [University of Oklahoma; Podar, Mircea [ORNL; 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; Zhou, Jizhong [University of Oklahoma; Elias, Dwayne A [ORNL

2013-01-01

Microbial reduction and immobilization of chromate (Cr(VI)) is a plausible bioremediation strategy. However, higher Cr(VI) concentrations may impose stress on native Cr-reducing communities. We sought to determine if Cr(VI) would influence the lactate enriched native microbial community structure and function in groundwater from the Cr contaminated site at Hanford, WA. Steady state continuous flow bioreactors were amended with lactate and Cr(VI) (0.0, 0.1 and 3.0 mg/L). Microbial growth, metabolites, Cr(VI) concentrations, 16S rRNA gene sequences and GeoChip based functional gene composition in bioreactors were monitored for 15 weeks. Temporal trends and some 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) was reduced in the bioreactors. With lactate enrichment, the native communities did not significantly differ between Cr concentrations. Native bacterial communities were diverse, whereas after lactate enrichment, Pelosinus spp., and Sporotalea spp., were the most predominant groups in all bioreactors. Similarly, the Archaea diversity significantly decreased from Methanosaeta (35%), Methanosarcina (17%), Halobacteriales (12%), Methanoregula (8%) and others, to mostly Methanosarcina spp. (95%) after lactate enrichment. Composition of several key functional genes was distinct in Low-Cr bioreactors compared to High-Cr. Among the Cr resistant probes (chrA), Burkholderia vietnamiensis, Comamonas testosterone and Ralstonia pickettii proliferated in Cr amended bioreactors. In-situ fermentative conditions facilitated Cr(VI) reduction, and as a result the 3.0 mg/L Cr(VI) did not appear to give chromate reducing strains a competitive advantage for proliferation or for increasing Cr-reduction.

Influence of plants on the reduction of hexavalent chromium in wetland sediments

Energy Technology Data Exchange (ETDEWEB)

Zazo, Juan A. [Department of Chemical Engineering, Universidad Autonoma de Madrid, Madrid, 28049 (Spain)], E-mail: juan.zazo@uam.es; Paull, Jeffery S.; Jaffe, Peter R. [Department of Civil and Environmental Engineering, Princeton University, Princeton, NJ 08544 (United States)

2008-11-15

This work addresses the effect that plants (Typha latifolia and Carex lurida) have on the reduction of Cr(VI) in wetland sediments. Experiments were carried out using tubular microcosms, where chemical species were monitored along the longitudinal flow axis. Cr(VI) removal was enhanced by the presence of plants. This is explained by a decrease in the redox potential promoted by organic root exudates released by plants. Under these conditions sulfate reduction is enhanced, increasing the concentration of sulfide species in the sediment pore water, which reduce Cr(VI). Evapotranspiration induced by plants also contributed to enhance the reduction of Cr(VI) by concentrating all chemical species in the sediment pore water. Both exudates release and evapotranspiration have a diurnal component that affects Cr(VI) reduction. Concentration profiles were fitted to a kinetic model linking sulfide and Cr(VI) concentrations corrected for evapotranspiration. This expression captures both the longitudinal as well as the diurnal Cr(VI) concentration profiles. - The presence of plants enhances the reduction of Cr(VI) in wetland sediments by modifying the governing biogeochemical cycle.

Synthesis, characterization and optimization of poly(p-phenylenediamine)-based organoclay composite for Cr(VI) remediation

CSIR Research Space (South Africa)

Mdlalose, L

2017-04-01

Full Text Available of these materials for environmental remediation. We report here the synthesis, characterization and application of a poly(para-phenylenediamine) (poly-pPD) organoclay-based composite for removal of Cr(VI) complexes from wastewater. Adsorption capacity...

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

2017-01-01

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...

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

International Nuclear Information System (INIS)

Barot, N.S.; Bagla, H.K.

2012-01-01

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 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 2 value of 0.997 and adsorption capacity of 10.20 mg/g. The thermodynamic parameters for biosorption were evaluated as ΔG = -2.837 kJ/mol, ΔH = -4.757 kJ/mol and ΔS = 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.)

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.)

Pengembangan Adsorben dari Limbah Lumpur Industri Crumb Rubber Yang Diaktivasi dengan H3PO4 Untuk Menyerap Ion Cr(VI

Directory of Open Access Journals (Sweden)

Salmariza Salmariza

2014-12-01

Full Text Available Developing an adsorbent from activated sludge waste of crumb rubber industry which was activated by H3PO4 for Adsorption of Cr(VI had been done. The research was carried out by characterization of activated carbon in accordance with Indonesia National Standard (SNI 06-3730-1995, involved determination of iodine absorption, water content, and bounded carbon content. The research was conducted in batch system for activated carbon and adsorbent without activation, by observed pH sollution, contact time, and initial concentration of the treatment solution. Determination of maximum absorption capacity of activated carbon on Cr(VI used the Langmuir isotherm equation. From the characterization study of activated carbon was obtained that adsorption of iodine 482.6 mg/g, water content 0.14%, and bonded carbon content 24.925%. The results revealed that H3PO4 activator affected the adsorption of Cr(VI. Research with batch systems were obtained the optimum pH 2, contact time 120 minutes, and the optimum concentration 50 mg/L for adsorbent without activation and optimum pH 3, contact time 60 minutes, and the optimum concentration 50 mg/L for activated carbon. The maximum adsorption capacity was obtained 1.16 mg/g for adsorbent without activation and 1.99 mg/g for activated carbon.ABSTRAK Pengembangan adsorben dari limbah lumpur aktif Industri Crumb Rubber yang diaktivasi dengan H3PO4 untuk menyerap ion Cr(VI telah dilakukan. Pada penelitian dilakukan karakterisasi karbon aktif sesuai dengan Standar Nasional Indonesia (SNI 06-3730-1995, meliputi penentuan daya serap terhadap iodin, kadar air, dan kadar karbon terikat. Penelitian dilakukan dengan sistem batch terhadap karbon aktif dan adsorben tanpa aktivasi, dengan mengamati pH larutan, waktu kontak, dan konsentrasi awal larutan. Penentuan kapasitas serapan maksimum karbon aktif terhadap Cr(VI menggunakan persamaan Isoterm Langmuir. Hasil penelitian karakterisasi karbon aktif didapatkan daya serap terhadap

Ecotoxicology of Hexavalent Chromium in Freshwater Fish: A Critical Review

Science.gov (United States)

Velma, Venkatramreddy; Vutukuru, S.S.; Tchounwou, Paul B.

2010-01-01

Chromium (Cr) is a naturally occurring element found in rocks, animals, plants, and soil, predominantly in its insoluble trivalent form [Cr(III)]. Intense industrialization and other anthropogenic activities have led to the global occurrence of soluble Cr(VI), which is readily leached from soil to groundwater or surface water, in concentrations above permissible levels. The ecotoxicology of Cr(VI) is linked to its environmental persistence and the ability to induce a variety of adverse effects in biologic systems, including fish. In aquatic ecosystems, Cr(VI) exposure poses a significant threat to aquatic life. This paper reviews the fate and transport of Cr(VI) in the environment and its acute and chronic effects on fish. We also discuss Cr(VI) toxicity at the cellular, biochemical, and genetic levels. An attempt is made in this review to comprehend the staggered data on the toxic effects of Cr(VI) to various species of fish. Such data are extremely useful to the scientific community and public officials involved in health risk assessment and management of environmental contaminants as a guide to the best course of action to restore ecosystems and, in turn, to preserve human health. PMID:19658319

Assessment of immunotoxicity in female Fischer 344/N and Sprague Dawley rats and female B6C3F1 mice exposed to hexavalent chromium via the drinking water.

Science.gov (United States)

Shipkowski, Kelly A; Sheth, Christopher M; Smith, Matthew J; Hooth, Michelle J; White, Kimber L; Germolec, Dori R

2017-12-01

Sodium dichromate dihydrate (SDD), an inorganic compound containing hexavalent chromium (Cr(VI)), is a common environmental contaminant of groundwater sources due to widespread industrial use. There are indications in the literature that Cr(VI) may induce immunotoxic effects following dermal exposure, including acting as both an irritant and a sensitizer; however, the potential immunomodulatory effects of Cr(VI) following oral exposure are relatively unknown. Following the detection of Cr(VI) in drinking water sources, the National Toxicology Program (NTP) conducted extensive evaluations of the toxicity and carcinogenicity of SDD following drinking water exposure, including studies to assess the potential for Cr(VI) to modulate immune function. For the immunotoxicity assessments, female Fischer 344/N (F344/N) and Sprague Dawley (SD) rats and female B 6 C 3 F 1 mice were exposed to SDD in drinking water for 28 consecutive days and evaluated for alterations in cellular and humoral immune function as well as innate immunity. Rats were exposed to concentrations of 0, 14.3, 57.3, 172, or 516 ppm SDD while mice were exposed to concentrations of 0, 15.6, 31.3, 62.5, 125, or 250 ppm SDD. Final mean body weight and body weight gain were decreased relative to controls in 250 ppm B 6 C 3 F 1 mice and 516 ppm SD rats. Water consumption was significantly decreased in F344/N and SD rats exposed to 172 and 516 ppm SDD; this was attributed to poor palatability of the SDD drinking water solutions. Several red blood cell-specific parameters were significantly (5-7%) decreased in 250 ppm mice; however, these parameters were unaffected in rats. Sporadic increases in the spleen IgM antibody response to sheep red blood cells (SRBC) were observed, however, these increases were not dose-dependent and were not reproducible. No significant effects were observed in the other immunological parameters evaluated. Overall, exposure to Cr(VI) in drinking water had limited effects on

DNA damaging bystander signalling from stem cells, cancer cells and fibroblasts after Cr(VI) exposure and its dependence on telomerase

International Nuclear Information System (INIS)

Cogan, Nicola; Baird, Duncan M.; Phillips, Ryan; Crompton, Lucy A.; Caldwell, Maeve A.; Rubio, Miguel A.; Newson, Roger; Lyng, Fiona; Case, C. Patrick

2010-01-01

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.

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.

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 ...

Determination of hexavalent chromium in exhaled breath condensate and environmental air among chrome plating workers.

Science.gov (United States)

Goldoni, Matteo; Caglieri, Andrea; Poli, Diana; Vettori, Maria Vittoria; Corradi, Massimo; Apostoli, Pietro; Mutti, Antonio

2006-03-15

Chromium speciation has attracted attention because of the different toxicity of Cr(III), which is considered relatively non-toxic, and Cr(VI), which can cross cell membranes mainly as a chromate anion and has been classified as a class I human carcinogen. The aims of the present study were to measure soluble Cr(VI) levels in environmental samples, to develop a simple method of quantifying Cr(VI) in exhaled breath condensate (EBC), and to follow the kinetics of EBC Cr(VI) in chrome plating workers.Personal air samples were collected from 10 chrome platers; EBC was collected from the same workers immediately after the work shift on Tuesday and before the work shift on the following Wednesday. Environmental and EBC Cr(VI) levels were determined by means of colorimetry and electrothermal absorption atomic spectrometry, respectively.The method of detecting Cr(VI) in environmental air was based on the extraction of the Cr(VI)-diphenylcarbazide (Cr(VI)-DPC) complex in 1-butanol, whereas EBC Cr(VI) was determined using a solvent extraction of Cr(VI) as an ion pair with tetrabutylammonium ion, and subsequent direct determination of the complex (Cr(VI)-DPC) in EBC.Kinetic data showed that airborne Cr(VI) was reduced by 50% in airway lining fluid sampled at the end of exposure and that there was a further 50% reduction after about 15 h. The persistence of Cr(VI) in EBC supports the use of EBC in assessing target tissue levels of Cr(VI).

Determination of hexavalent chromium in exhaled breath condensate and environmental air among chrome plating workers

International Nuclear Information System (INIS)

Goldoni, Matteo; Caglieri, Andrea; Poli, Diana; Vettori, Maria Vittoria; Corradi, Massimo; Apostoli, Pietro; Mutti, Antonio

2006-01-01

Chromium speciation has attracted attention because of the different toxicity of Cr(III), which is considered relatively non-toxic, and Cr(VI), which can cross cell membranes mainly as a chromate anion and has been classified as a class I human carcinogen. The aims of the present study were to measure soluble Cr(VI) levels in environmental samples, to develop a simple method of quantifying Cr(VI) in exhaled breath condensate (EBC), and to follow the kinetics of EBC Cr(VI) in chrome plating workers. Personal air samples were collected from 10 chrome platers; EBC was collected from the same workers immediately after the work shift on Tuesday and before the work shift on the following Wednesday. Environmental and EBC Cr(VI) levels were determined by means of colorimetry and electrothermal absorption atomic spectrometry, respectively. The method of detecting Cr(VI) in environmental air was based on the extraction of the Cr(VI)-diphenylcarbazide (Cr(VI)-DPC) complex in 1-butanol, whereas EBC Cr(VI) was determined using a solvent extraction of Cr(VI) as an ion pair with tetrabutylammonium ion, and subsequent direct determination of the complex (Cr(VI)-DPC) in EBC. Kinetic data showed that airborne Cr(VI) was reduced by 50% in airway lining fluid sampled at the end of exposure and that there was a further 50% reduction after about 15 h. The persistence of Cr(VI) in EBC supports the use of EBC in assessing target tissue levels of Cr(VI)

Determination of hexavalent chromium in exhaled breath condensate and environmental air among chrome plating workers

Energy Technology Data Exchange (ETDEWEB)

Goldoni, Matteo [Laboratory of Industrial Toxicology, Department of Clinical Medicine, Nephrology and Health Sciences, University of Parma, Via Gramsci 14, 43100 Parma (Italy); National Institute of Occupational Safety and Prevention, Research Centre at University of Parma, Parma (Italy); Caglieri, Andrea [Laboratory of Industrial Toxicology, Department of Clinical Medicine, Nephrology and Health Sciences, University of Parma, Via Gramsci 14, 43100 Parma (Italy); Poli, Diana [Laboratory of Industrial Toxicology, Department of Clinical Medicine, Nephrology and Health Sciences, University of Parma, Via Gramsci 14, 43100 Parma (Italy); National Institute of Occupational Safety and Prevention, Research Centre at University of Parma, Parma (Italy); Vettori, Maria Vittoria [Laboratory of Industrial Toxicology, Department of Clinical Medicine, Nephrology and Health Sciences, University of Parma, Via Gramsci 14, 43100 Parma (Italy); National Institute of Occupational Safety and Prevention, Research Centre at University of Parma, Parma (Italy); Corradi, Massimo [Laboratory of Industrial Toxicology, Department of Clinical Medicine, Nephrology and Health Sciences, University of Parma, Via Gramsci 14, 43100 Parma (Italy); National Institute of Occupational Safety and Prevention, Research Centre at University of Parma, Parma (Italy); Apostoli, Pietro [Laboratory of Industrial Hygiene, Department of Experimental and Applied Medicine, University of Brescia (Italy); Mutti, Antonio [Laboratory of Industrial Toxicology, Department of Clinical Medicine, Nephrology and Health Sciences, University of Parma, Via Gramsci 14, 43100 Parma (Italy)]. E-mail: antonio.mutti@unipr.it

2006-03-15

Chromium speciation has attracted attention because of the different toxicity of Cr(III), which is considered relatively non-toxic, and Cr(VI), which can cross cell membranes mainly as a chromate anion and has been classified as a class I human carcinogen. The aims of the present study were to measure soluble Cr(VI) levels in environmental samples, to develop a simple method of quantifying Cr(VI) in exhaled breath condensate (EBC), and to follow the kinetics of EBC Cr(VI) in chrome plating workers. Personal air samples were collected from 10 chrome platers; EBC was collected from the same workers immediately after the work shift on Tuesday and before the work shift on the following Wednesday. Environmental and EBC Cr(VI) levels were determined by means of colorimetry and electrothermal absorption atomic spectrometry, respectively. The method of detecting Cr(VI) in environmental air was based on the extraction of the Cr(VI)-diphenylcarbazide (Cr(VI)-DPC) complex in 1-butanol, whereas EBC Cr(VI) was determined using a solvent extraction of Cr(VI) as an ion pair with tetrabutylammonium ion, and subsequent direct determination of the complex (Cr(VI)-DPC) in EBC. Kinetic data showed that airborne Cr(VI) was reduced by 50% in airway lining fluid sampled at the end of exposure and that there was a further 50% reduction after about 15 h. The persistence of Cr(VI) in EBC supports the use of EBC in assessing target tissue levels of Cr(VI)

Cr(VI) reduction and immobilization by novel carbonaceous modified magnetic Fe3O4/halloysite nanohybrid.

Science.gov (United States)

Tian, Xike; Wang, Weiwei; Tian, Na; Zhou, Chaoxin; Yang, Chao; Komarneni, Sridhar

2016-05-15

In this work, a novel "Dumbbell-like" magnetic Fe3O4/Halloysite nanohybrid (Fe3O4/HNTs@C) with oxygen-containing organic group grafting on the surface of natural halloysite nanotubes (HNTs) and homogeneous Fe3O4 nanospheres selectively aggregating at the tips of modified halloysite nanotubes was successfully synthesized. XRD, TEM, IR spectroscopy, XPS and VSM were used to characterize this newly halloysite nanohybrid and its formation mechanism was discussed. Cr(VI) ions adsorption experiments showed that the Fe3O4/halloysite nanohybrid exhibited higher adsorption ability with a maximum adsorption capacity of 132 mg/L at 303K, which is about 100 times higher than that of unmodified halloysite nanotubes. More importantly, with the reduction of Fe3O4 and electron-donor effect of oxygen-containing organic groups, Cr(VI) ions were easily reduced into low toxicity Cr(III) and then adsorbed onto the surface of halloysite nanohybrid. In addition, appreciable magnetization was observed due to the aggregation of magnetite nanoparticles, which make adsorbent facility separated from aqueous solutions after Cr pollution adsorption. Copyright © 2016 Elsevier B.V. All rights reserved.

Fixed-bed column study for hexavalent chromium removal and recovery by short-chain polyaniline synthesized on jute fiber

Energy Technology Data Exchange (ETDEWEB)

Kumar, Potsangbam Albino [Department of Civil Engineering, Indian Institute of Technology Guwahati, Assam 781039 (India); Chakraborty, Saswati [Department of Civil Engineering, Indian Institute of Technology Guwahati, Assam 781039 (India)], E-mail: saswati@iitg.ernet.in

2009-03-15

Fixed-bed column studies were conducted to evaluate performance of a short-chain polymer, polyaniline, synthesized on the surface of jute fiber (PANI-jute) for the removal of hexavalent chromium [Cr(VI)] in aqueous environment. Influent pH, column bed depth, influent Cr(VI) concentrations and influent flow rate were variable parameters for the present study. Optimum pH for total chromium removal was observed as 3 by electrostatic attraction of acid chromate ion (HCrO{sub 4}{sup -}) with protonated amine group (NH{sub 3}{sup +}) of PANI-jute. With increase in column bed depth from 40 to 60 cm, total chromium uptake by PANI-jute increased from 4.14 to 4.66 mg/g with subsequent increase in throughput volume from 9.84 to 12.6 L at exhaustion point. The data obtained for total chromium removal were well described by BDST equation till 10% breakthrough. Adsorption rate constant and dynamic bed capacity at 10% breakthrough were observed as 0.01 L/mg h and 1069.46 mg/L, respectively. Adsorbed total chromium was recovered back from PANI-jute as non-toxic Cr(III) after ignition with more than 97% reduction in weight, minimizing the problem of solid waste disposal.

Method for in situ or ex situ bioremediation of hexavalent chromium contaminated soils and/or groundwater

Science.gov (United States)

Turick, Charles E.; Apel, William W.

1997-10-28

A method of reducing the concentration of Cr(VI) in a liquid aqueous residue comprises the steps of providing anaerobic Cr(VI) reducing bacteria, mixing the liquid aqueous residue with a nutrient medium to form a mixture, and contacting the mixture with the anaerobic Cr(VI) reducing bacteria such that Cr(VI) is reduced to Cr(III). The anaerobic Cr(VI) reducing bacteria appear to be ubiquitous in soil and can be selected by collecting a soil sample, diluting the soil sample with a sterile diluent to form a diluted sample, mixing the diluted sample with an effective amount of a nutrient medium and an effective amount of Cr(VI) to form a mixture, and incubating the mixture in the substantial absence of oxygen such that growth of Cr(VI) sensitive microorganisms is inhibited and growth of the anaerobic Cr(VI) reducing bacteria is stimulated. A method of in situ bioremediation of Cr(VI) contaminated soil and/or groundwater is also disclosed.

Removal of Cr(VI Ions from Aqueous Solutions Using Nickel Ferrite Nanoparticles: Kinetic and Equilibrium Study

Directory of Open Access Journals (Sweden)

Raziyeh Zandi Pak

2017-01-01

Full Text Available Background & Aims of the Study: Heavy metals are the most important and main pollutants because of their accumulation and high toxicity even at very low dose and cause serious hazards to ecological system as well as human health. Thus, their removal has been challenged from drinking water and industrial waters with different technologies. The purpose of this work is to investigate the removal of Cr(VI from aqueous solutions. Materials & Methods: NiFe2O4 nanoparticles was prepared by the co-precipitation method and then applied for adsorption of Cr(VI ions from water. Characterization of nanoparticles was carried out via TEM, EDX, XRD and BET analysis. Various physico-chemical parameters like the effect of contact time, pH and adsorbent dose were studied, using batch process to optimize conditions for maximum adsorption. Results: The results demonstrated that the size of the NiFe2O4 nanoparticles was about 12 nm and had selectivity for Cr(VI adsorption. Also, adsorption process was found to be fast with equilibrium time of 55 min. Optimum pH was found to be 3. Maximum adsorption capacity (qm as calculated from Langmuir isotherm was found to be 294.1 mg g-1. Analysis of adsorption kinetics indicated better applicability of pseudo-second-order kinetic model. Conclusions: The results of this study represented that the synthesized NiFe2O4 nanoparticles could be useful for the simultaneous removal of anionic ions from wastewaters.

Use of Cork Waste as Biosorbent for Hexavalent Chromium

International Nuclear Information System (INIS)

Sfaksi, Z.; Azzouz, N.; Abdelwahab, A.

2011-01-01

The biosorption by cork powder is considered as a new method for heavy metal removal from industrial waste waters such as chromium tanning factories. The aim of this study is to evaluate the efficiency extent of this method using a cork powder as biosorbent for hexavalent chromium Cr(VI). The Fourier Transform Infrared spectroscopy (FTIR) analysis permits to distinguish the type of functional groups likely to participate in metal binding. A linear form of BET isotherms for all the three used temperatures (25, 35 and 45 0 C) and a pseudo-second-order Lagergren equation of adsorption kinetics are obtained. Other experimental results highlight the meaningful influence of parameters such as contact time, pH and concentrations of the solution, on chromium adsorption rate that reach a 97% value under definite conditions particularly a pH of 2-3 values. (author)

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

Biosorption of Cr(VI) from aqueous solution using A. hydrophila in up-flow column. Optimization of process variables

Energy Technology Data Exchange (ETDEWEB)

Hasan, S.H.; Srivastava, P.; Ranjan, D. [Banaras Hindu Univ., Varanasi (India). Water Pollution Research Lab.; Talat, M. [Banaras Hindu Univ., Varanasi (India). Dept. of Biochemistry

2009-06-15

In the present study, continuous up-flow fixed-bed column study was carried out using immobilized dead biomass of Aeromonas hydrophila for the removal of Cr(VI) from aqueous solution. Different polymeric matrices were used to immobilized biomass and polysulfone-immobilized biomass has shown to give maximum removal. The sorption capacity of immobilized biomass for the removal of Cr(VI) evaluating the breakthrough curves obtained at different flow rate and bed height. A maximum of 78.58% Cr(VI) removal was obtained at bed height of 19 cm and flow rate of 2 mL/min. Bed depth service time model provides a good description of experimental results with high correlation coefficient (>0.996). An attempt has been made to investigate the individual as well as cumulative effect of the process variables and to optimize the process conditions for the maximum removal of chromium from water by two-level two-factor full-factorial central composite design with the help of Minitab {sup registered} version 15 statistical software. The predicted results are having a good agreement (R{sup 2}=98.19%) with the result obtained. Sorption-desorption studies revealed that polysulfone-immobilized biomass could be reused up to 11 cycles and bed was completely exhausted after 28 cycles. (orig.)

Kinetic study on adsorption of Cr(VI), Ni(II), Cd(II) and Pb(II) ions from aqueous solutions using activated carbon prepared from Cucumis melo peel

Science.gov (United States)

Manjuladevi, M.; Anitha, R.; Manonmani, S.

2018-03-01

The adsorption of Cr(VI), Ni(II), Cd(II) and Pb(II), ions from aqueous solutions by Cucumis melo peel-activated carbon was investigated under laboratory conditions to assess its potential in removing metal ions. The adsorption behavior of metal ions onto CMAC was analyzed with Elovich, intra-particle diffusion rate equations and pseudo-first-order model. The rate constant of Elovich and intra-particle diffusion on CMAC increased in the sequence of Cr(VI) > Ni(II) > Cd(II) > Pb(II). According to the regression coefficients, it was observed that the kinetic adsorption data can fit better by the pseudo-first-order model compared to the second-order Lagergren's model with R 2 > 0.957. The maximum adsorption of metal ions onto the CMAC was found to be 97.95% for Chromium(VI), 98.78% for Ni(II), 98.55% for Pb(II) and 97.96% for Cd(II) at CMAC dose of 250 mg. The adsorption capacities followed the sequence Ni(II) ≈ Pb(II) > Cr(VI) ≈ Cd(II) and Ni(II) > Pb(II) > Cd(II) > Cr(VI). The optimum adsorption conditions selected were adsorbent dosage of 250 mg, pH of 3.0 for Cr(VI) and 6.0 for Ni(II), Cd(II) and Pb(II), adsorption concentration of 250 mg/L and contact time of 180.

Column Adsorption Studies for the Removal of Cr(VI Ions by Ethylamine Modified Chitosan Carbonized Rice Husk Composite Beads with Modelling and Optimization

Directory of Open Access Journals (Sweden)

S. Sugashini

2013-01-01

Full Text Available The objective of this present study is the optimization of process parameters in adsorption of Cr(VI ions by ethylamine modified chitosan carbonized rice husk composite beads (EAM-CCRCBs using response surface methodology (RSM and continuous adsorption studies of Cr(VI ions by ethylamine modified chitosan carbonized rice husk composite beads (EAM-CCRCBs. The effect of process variables such as initial metal ion concentration, adsorbent dosage and pH were optimized using RSM in order to ensure high adsorption capacity at low adsorbent dosage and high initial metal ion concentration of Cr(VI in batch process. The optimum condition suggested by the model for the process variable such as adsorbent dosage, pH and initial metal ion concentration was 0.14 g, 300 mg/L and pH2 with maximum removal of 99.8% and adsorption capacity of 52.7 mg/g respectively. Continuous adsorption studies were conducted under optimized initial metal ion concentration and pH for the removal of Cr(VI ions using EAM-CCRCBs. The breakthrough curve analysis was determined using the experimental data obtained from the continuous adsorption. Continuous adsorption modelling such as bed depth service model and Thomson model were established by fitting it with experimental data.

Spectral and Mechanistic Investigation of Oxidative Decarboxylation of Phenylsulfinylacetic Acid by Cr(VI)

International Nuclear Information System (INIS)

Subramaniam, Perumal; Selvi, Natesan Thamil; Devi, Soundarapandian Sugirtha

2014-01-01

The oxidative decarboxylation of phenylsulfinylacetic acid (PSAA) by Cr(VI) in 20% acetonitrile . 80% water (v/v) medium follows overall second order kinetics, first order each with respect to [PSAA] and [Cr(VI)] at constant [H + ] and ionic strength. The reaction is acid catalysed, the order with respect to [H + ] is unity and the active oxidizing species is found to be HCrO 3 + . The reaction mechanism involves the rate determining nucleophilic attack of sulfur atom of PSAA on chromium of HCrO 3 + forming a sulfonium ion intermediate. The intermediate then undergoes α,β-cleavage leading to the liberation of CO 2 . The product of the reaction is found to be methyl phenyl sulfone. The operation of substituent effect shows that PSAA containing electron-releasing groups in the meta- and para-positions accelerate the reaction rate while electron withdrawing groups retard the rate. An excellent correlation is found to exist between log k 2 and Hammett σ constants with a negative value of reaction constant. The ρ value decreases with increase in temperature evidencing the high reactivity and low selectivity in the case of substituted PSAAs

Effects of common groundwater ions on chromate removal by magnetite: importance of chromate adsorption.

Science.gov (United States)

Meena, Amanda H; Arai, Yuji

2016-01-01

Reductive precipitation of hexavalent chromium (Cr(VI)) with magnetite is a well-known Cr(VI) remediation method to improve water quality. The rapid (important as the reductive precipitation of Cr(III) in describing the removal of Cr(VI) by magnetite, and these interfacial adsorption processes could be impacted by common groundwater ions like sulfate and nitrate. The results of this study highlight new information about the large quantity of adsorbed Cr(VI) surface complexes at the magnetite-water interface. It has implications for predicting the long-term stability of Cr at the magnetite-water interface.Graphical abstractEffects of background anions (sulfate and nitrate) on the Cr(VI) surface coverage at the magnetite-water interface at pH 4 and 9.

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

In Situ Synthesis of γ-AlOOH and Synchronous Adsorption Separation of V(V) from Highly Concentrated Cr(VI) Multiplex Complex solutions

Energy Technology Data Exchange (ETDEWEB)

Zhang, Hailin [National; University of Chinese Academy of Sciences, No. 19A Yuquan Road, Shijingshan District,; Li, Ping [National; Wang, Zheming [Physcial; Zhang, Xin [Physcial; Zheng, Shili [National; Zhang, Yi [National

2017-07-13

Boehmite (γ-AlOOH) was synthesized to selectively adsorb V(V) from K₂CrO₄-KVO₃-H₂O solutions with highly concentrated Cr(VI) and low concentration V(V). The synthesized γ-AlOOH has a BET surface area of 433.2 m²/g and an average pore size of 3.5 nm. It possesses a maximum adsorption capacity of V(V) of 1.53 mmol/g from K₂CrO₄-KVO₃-H₂O solutions. The adsorption of V(V) onto γ-AlOOH follows the Langmuir isotherm model and pseudo-second-order kinetics equation by forming innersphere complexes while the Cr(VI) adsorption forms both inner-sphere and outer-sphere chromate complexes depending on solution pH. The γ-AlOOH was further synthesized in situ by adding HNO₃ into the K₂CrO₄-KAlO₂- KVO₃-H₂O solutions and then used for synchronous adsorption of V(V) and Cr(VI), resulting in increased adsorption capacity of V(V) of 2.88 mmol/g and decreased adsorption capacity of Cr(VI) to 0.073 mmol/g, respectively. In the latter process, adsorption pH values were adjustable, and adsorption reached equilibrium instantaneously, supporting a novel in situ synthesis and adsorption integration strategy with adjustable surface charge of adsorbent and disappearance of diffusion effect.

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)

Mechanism of the reduction of hexavalent chromium by organo-montmorillonite supported iron nanoparticles

International Nuclear Information System (INIS)

Wu, Pingxiao; Li, Shuzhen; Ju, Liting; Zhu, Nengwu; Wu, Jinhua; Li, Ping; Dang, Zhi

2012-01-01

Highlights: ► Organo-montmorillonite supported iron nanoparticles were found to be more efficient in the removal of Cr(VI) than unsupported iron nanoparticles. ► The iron nanoparticles were accommodated by the sectional structure of the clay minerals which were helpful to protect the nanoparticles from aggregating. ► XPS and XANES provided some direct information about the reduction mechanisms. ► The structure of the supported iron nanoparticles was stable in the reaction with Cr(VI). - Abstract: Iron nanoparticles exhibit greater reactivity than micro-sized Fe 0 , and they impart advantages for groundwater remediation. In this paper, supported iron nanoparticles were synthesized to further enhance the speed and efficiency of remediation. Natural montmorillonite and organo-montmorillonite were chosen as supporting materials. The capacity of supported iron nanoparticles was evaluated, compared to unsupported iron nanoparticles, for the reduction of aqueous Cr(VI). The reduction of Cr(VI) was much greater with organo-montmorillonite supported iron nanoparticles and fitted the pseudo-second order equation better. With a dose at 0.47 g/L, a total removal capacity of 106 mg Cr/g Fe 0 was obtained. Other factors that affect the efficiency of Cr(VI) removal, such as pH values, the initial Cr(VI) concentration and storage time of nanoparticles were investigated. X-ray photoelectron spectrometry (XPS) and X-ray absorption near edge structure (XANES) were used to figure out the mechanism of the removal of Cr(VI). XPS indicated that the Cr(VI) bound to the particle surface was completely reduced to Cr(III) under a range of conditions. XANES confirmed that the Cr(VI) reacted with iron nanoparticles was completely reduced to Cr(III).

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.

One step bioconversion of waste precious metals into Serratia biofilm-immobilized catalyst for Cr(VI) reduction.

Science.gov (United States)

Yong, P; Liu, W; Zhang, Z; Beauregard, D; Johns, M L; Macaskie, L E

2015-11-01

For reduction of Cr(VI) the Pd-catalyst is excellent but costly. The objectives were to prove the robustness of a Serratia biofilm as a support for biogenic Pd-nanoparticles and to fabricate effective catalyst from precious metal waste. Nanoparticles (NPs) of palladium were immobilized on polyurethane reticulated foam and polypropylene supports via adhesive biofilm of a Serratia sp. The biofilm adhesion and cohesion strength were unaffected by palladization and catalytic biofilm integrity was also shown by magnetic resonance imaging. Biofilm-Pd and mixed precious metals on biofilm (biofilm-PM) reduced 5 mM Cr(VI) to Cr(III) when immobilized in a flow-through column reactor, at respective flow rates of 9 and 6 ml/h. The lower activity of the latter was attributed to fewer, larger, metal deposits on the bacteria. Activity was lost in each case at pH 7 but was restored by washing with 5 mM citrate solution or by exposure of columns to solution at pH 2, suggesting fouling by Cr(III) hydroxide product at neutral pH. A 'one pot' conversion of precious metal waste into new catalyst for waste decontamination was shown in a continuous flow system based on the use of Serratia biofilm to manufacture and support catalytic Pd-nanoparticles.

Hexavalent chromium removal by chitosan modified-bioreduced nontronite

Science.gov (United States)

Singh, Rajesh; Dong, Hailiang; Zeng, Qiang; Zhang, Li; Rengasamy, Karthikeyan

2017-08-01

Recent efforts have focused on structural Fe(II) in chemically or biologically reduced clay minerals to immobilize Cr(VI) from aqueous solution, but the coulombic repulsion between the negatively charged clay surface and the polyanionic form of Cr(VI), e.g., dichromate, can hinder the effectiveness of this process. The purpose of this study was to investigate the efficiency and mechanism of Cr(VI) removal by a charge-reversed nontronite (NAu-2), an Fe-rich smectite. Chitosan, a linear polysaccharide derived from chitin found in soil and groundwater, was used to reverse the charge of NAu-2. Intercalation of chitosan into NAu-2 interlayer increased the basal d-spacing of NAu-2 from 1.23 nm to 1.83 nm and zeta potential from -27.17 to +34.13 mV, with the amount of increase depending on chitosan/NAu-2 ratio. Structural Fe(III) in chitosan-exchanged NAu-2 was then biologically reduced by an iron-reducing bacterium Shewanella putrefaciens CN32 in bicarbonate buffer with lactate as the sole electron donor, with and without electron shuttle, AQDS. Without AQDS, the extent of Fe(III) reduction increased from the lowest (∼9%) for the chitosan-free NAu-2 to the highest (∼12%) for the highest chitosan loaded NAu-2 (3:1 ratio). This enhancement of Fe(III) reduction was likely due to the attachment of negatively charged bacterial cells to charge-reversed (e.g., positively charged) NAu-2 surfaces, facilitating the electron transfer between cells and structural Fe(III). With AQDS, Fe(III) reduction extent doubled relative to those without AQDS, but the enhancement effect was similar across all chitosan loadings, suggesting that AQDS was more important than chitosan in enhancing Fe(III) bioreduction. Chitosan-exchanged, biologically reduced NAu-2 was then utilized for removing Cr(VI) in batch experiments with three consecutive spikes of 50 μM Cr. With the first Cr spike, the rate of Cr(VI) removal by charged-reversed NAu-2 that was bioreduced without and with AQDS was ∼1

Adsorción de cr(vi) por cocos nucífera l. en residuales de fibrocemento en santiago de cuba

OpenAIRE

Pérez Silva, Rosa María; Calzado Lamela, Orlindes; Cascaret Carmenaty, Dannis Adrián; Tur Naranjo, Enieyis

2014-01-01

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 tal...

A highly selective sorbent for removal of Cr(VI) from aqueous solutions based on Fe3O4/poly(methyl methacrylate) grafted Tragacanth gum nanocomposite: Optimization by experimental design

International Nuclear Information System (INIS)

Sadeghi, Susan; Rad, Fatemeh Alavi; Moghaddam, Ali Zeraatkar

2014-01-01

In this work, poly(methyl methacrylate) grafted Tragacanth gum modified Fe 3 O 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 −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

Immersed single-drop microextraction interfaced with sequential injection analysis for determination of Cr(VI) in natural waters by electrothermal-atomic absorption spectrometry

International Nuclear Information System (INIS)

Pena, Francisco; Lavilla, Isela; Bendicho, Carlos

2008-01-01

Single-drop microextraction (SDME) and sequential injection analysis have been hyphenated for ultratrace metal determination by Electrothermal-Atomic Absorption Spectrometry (ETAAS). The novel method was targeted on extraction of the Cr(VI)-APDC chelate and encompasses the potential of SDME as a miniaturized and virtually solvent-free preconcentration technique, the ability of sequential injection analysis to handle samples and the versatility of furnace autosamplers for introducing microliter samples in ETAAS. The variables influencing the microextraction of Cr(VI) onto an organic solvent drop, i.e., type of organic solvent, microextraction time, stirring rate of the sample solution, drop volume, immersion depth of the drop, salting-out effect, temperature of the sample, concentration of the complexing agent and pH of the sample solution were fully investigated. For a 5 and 20 min microextraction time, the preconcentration factors were 20 and 70, respectively. The detection limit was 0.02 μg/L of Cr(VI) and the repeatability expressed as relative standard deviation was 7%. The SDME-SIA-ETAAS technique was validated against BCR CRM 544 (lyophilized solution) and applied to ultrasensitive determination of Cr(VI) in natural waters