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Sample records for seleniumiv vi adsorption

  1. Investigation of uranium (VI) adsorption by polypyrrole

    Energy Technology Data Exchange (ETDEWEB)

    Abdi, S. [Faculty of Chemical, Petroleum and Gas Engineering, Semnan University, Semnan 35195-363 (Iran, Islamic Republic of); Nasiri, M., E-mail: mnasiri@semnan.ac.ir [Faculty of Chemical, Petroleum and Gas Engineering, Semnan University, Semnan 35195-363 (Iran, Islamic Republic of); Mesbahi, A. [Faculty of Chemical, Petroleum and Gas Engineering, Semnan University, Semnan 35195-363 (Iran, Islamic Republic of); Khani, M.H. [Nuclear Fuel Cycle Research School, Nuclear Science and Technology Research Institute, Tehran, 14395-836 (Iran, Islamic Republic of)

    2017-06-15

    Highlights: • The adsorbent (polypyrrole) was synthesized by a chemical method using PEG, DBSNa and CTAB as the surfactant. • The solution pH was one of the most important parameters affecting the adsorption of uranium. • The CTAB provided higher removal percentage compared with the other surfactants. • The maximum adsorption capacity obtained from Langmuir isotherm was 87.72 mg/g. • The pseudo second-order model fitted well with the adsorption kinetic of polypyrrole to uranium. - Abstract: The purpose of this study was to investigate the adsorption of uranium (VI) ions on the polypyrrole adsorbent. Polypyrrole was synthesized by a chemical method using polyethylene glycol, sodium dodecylbenzenesulfonate, and cetyltrimethylammonium bromide as the surfactant and iron (III) chloride as an oxidant in the aqueous solution. The effect of various surfactants on the synthesized polymers and their performance as the uranium adsorbent were investigated. Adsorbent properties were characterized by scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR) techniques. The effect of different parameters such as pH, contact time, initial metal ion concentrations, adsorbent dose, and the temperature was investigated in the batch system for uranium adsorption process. It has been illustrated that the adsorption equilibrium time is 7 min. The results showed that the Freundlich model had the best agreement and the maximum adsorption capacity of polypyrrole for uranium (VI) was determined 87.72 mg/g from Langmuir isotherm. In addition, the mentioned adsorption process was fast and the kinetic data were fitted to the Pseudo first and second order models. The adsorption kinetic data followed the pseudo-second-order kinetic model. Moreover, the thermodynamic parameters ΔG{sup 0}, ΔH{sup 0} and ΔS{sup 0} showed that the uranium adsorption process by polypyrrole was endothermic and spontaneous.

  2. Factors affecting the adsorption of chromium (VI) on activated carbon

    Energy Technology Data Exchange (ETDEWEB)

    Yavuz, R.; Orbak, I.; Karatepe, N. [Istanbul Technical University, Istanbul (Turkey)

    2006-09-15

    The aim of this investigation was to determine the adsorption behavior of chromium (VI) on two different activated carbon samples produced from Tuncbilek lignite. The effects of the initial chromium (VI) concentration (250-1000 mg/L), temperature (297-323 K) and pH (2.0-9.5) on adsorption were investigated systematically. The effectiveness of the parameters on chromium adsorption was found to be in the order of pH, the initial Cr(VI) concentration and the temperature. Increasing the pH from 2.0 to 9.5 caused a decrease in adsorption. However, the adsorption was increased by increasing the initial Cr(VI) concentration and temperature. The multilinear mathematical model was also developed to predict the Cr(VI) adsorption on activated carbon samples within the experimental conditions.

  3. Predicting chromium (VI) adsorption rate in the treatment of liquid ...

    African Journals Online (AJOL)

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    The adsorption rate of chromium (VI) on commercial activated carbon during the ... time and initial chromium (VI) ion concentration. .... model, the separation factor r, according to Calvo et al (2001) cited .... Lead (II) and nickel (II) adsorption kinetics .... heavy metal by Talaromyces helicus: a trained fungus for copper and.

  4. Predicting chromium (VI) adsorption rate in the treatment of liquid ...

    African Journals Online (AJOL)

    The adsorption rate of chromium (VI) on commercial activated carbon during the treatment of the flocculation effluent of liquid-phase oil-based drill-cuttings has been investigated in terms of contact time and initial chromium (VI) ion concentration. Homogenizing 1 g of the activated carbon with 100 ml of the flocculation ...

  5. Langmuir and Freundlich Isotherm Adsorption Equations for Chromium (VI) Waste Adsorption by Zeolite

    International Nuclear Information System (INIS)

    Murni Handayani; Eko Sulistiyono

    2009-01-01

    The research of chromium (VI) waste adsorption by zeolite has done. Wastes which are produced by Industries, both radioactive waste and heavy metal waste need done more processing so that they are not endanger environment and human health. Zeolite has very well-ordered crystal form with cavity each other to way entirely so that cause surface wide of zeolite become very big and very good as adsorbents. This research intends to know appropriate isotherm adsorption method to determine maximum capacity of zeolite to chromium (VI) waste. The equations which used in adsorption process are Langmuir and Freundlich isotherm Adsorption equations. The instrument was used in adsorption process by using Atomic Adsorption Spectroscopy (AAS). The experiment result showed that the biggest mass of chromium (VI) metal ion which was absorb by zeolite in 20 ppm concentration was 7.71 mg/gram zeolite. Adsorption process of Chromium (VI) waste by zeolite followed Langmuir and Freundlich isotherm equations with R 2 >0,9 . Appropriate equation to determine maximum adsorption capacity of zeolite for chromium (VI) waste adsorption is Langmuir equation. The maximum adsorption capacity of zeolite is 52.25 mg/gram. (author)

  6. [Adsorptive Stabilization of Soil Cr (VI) Using HDTMA Modified Montmorillonite].

    Science.gov (United States)

    2016-03-15

    A series of organo-montomorillonites were prepared using Na-montomorillonite and hexadecyl trimethyl ammonium bromide (HDTMA). The organo-montomorillonites were then investigated for the remediation of Cr(VI) contaminated soils. FT-IR, XRD, SEM and N2 -BET, CEC, Zeta potential measurement were conducted to understand the structural changes of montmorillonites as different amounts of HDTMAs were added as modifier. The characterization results indicated that the clay interlayer spacing distance increased from 1. 25 nm to 2. 13 nm, the clay surface roughness decreased, the clay surface area reduced from 38.91 m² · g⁻¹ to 0.42 m² · g⁻¹, the clay exchangeable cation amount reduced from 62 cmol · kg⁻¹ to 9.9 cmol · kg⁻¹ and the clay surface charge changed from -29.1 mV to 5.59 mV as the dosage of HDTMA in montmorillonite was increased. The TCLP (toxicity characteristic leaching procedure) was used to evaluate the leachate toxicity of Cr(VI). The effects of the initial soil Cr(VI) concentration, montmorillonites dosage, reaction time and HDTMA modification amount were investigated, respectively. The results revealed that modification of montmorillonites would manifest an attenuated physical adsorptive effect and an enhanced electrostatic adsorptive effect on Cr(VI), suggesting electrostatic effect was the major force that resulted in improved Cr(VI) adsorption onto HDTMA modified montmorillonites.

  7. Ferric chloride modified zeolite in wastewater on Cr (VI) adsorption characteristics

    Science.gov (United States)

    Wu, Xiaoqing; Zhang, Kang; Chen, Wen; Zhang, Hua

    2018-03-01

    Zeolite was modified by ferric chloride(Fe-Z) removal Cr (VI) ion from wastewater. The results showed that the effect of Cr(VI) adsorption on modified zeolite depended significantly on pH. It is favorable for the adsorption of Cr(VI) in acid condition. The Langmuir isotherm model has high fitting accuracy with experimental data, demonstrated that is monolayer adsorption and chemical adsorption.The pseudo-second-order equation provided the best correlation to the data. The model can describe the adsorption reaction process well.

  8. SPECIATION OF SELENIUM AND ARSENIC COMPOUNDS BY CAPILLARY ELECTROPHORESIS WITH HYDRODYNAMICALLY MODIFIED ELECTROOSMOTIC FLOW AND ON-LINE REDUCTION OF SELENIUM(VI) TO SELENIUM(IV) WITH HYDRIDE GENERATION INDUCTIVELY COUPLED PLASMA MASS SPECTROMETRIC DETECTION

    Science.gov (United States)

    Capillary electrophoresis (CE) with hydride generation inductively coupled plasma mass spectrometry was used to determine four arsenicals and two selenium species. Selenate (SeVI) was reduced on-line to selenite (SeIV') by mixing the CE effluent with concentrated HCl. A microporo...

  9. 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

  10. Study on Adsorption of Chromium (VI) by Activated Carbon from Cassava Sludge

    Science.gov (United States)

    Yang, Jinhui; Li, Chuanshu; Yang, Bin; Kang, Sijun; Zhang, Zhen

    2018-03-01

    In this paper, a new type of adsorbent prepared by waste sludge from alcohol production industry was used to adsorb Cr (VI) in activated carbon from cassava sludge. A series of static adsorption experiments were carried out on the initial concentration of solution Cr (VI), pH value of solution, adsorption time and dosage of adsorbent. The results of single factor experiments show that the removal rate of Cr (VI) increases with the initial concentration of Cr(VI), while the adsorption amount is opposite. When the pH value of the solution is low, the adsorption effect of activated carbon is better.The adsorption time should be controlled within 40-60min. When the activated carbon dosage is increased, the removal rate increases but the adsorption capacity decreases.

  11. Surface complexation modeling of the effects of phosphate on uranium(VI) adsorption

    Energy Technology Data Exchange (ETDEWEB)

    Romero-Gonzalez, M.R.; Cheng, T.; Barnett, M.O. [Auburn Univ., AL (United States). Dept. of Civil Engeneering; Roden, E.E. [Wisconsin Univ., Madison, WI (United States). Dept. of Geology and Geophysics

    2007-07-01

    Previous published data for the adsorption of U(VI) and/or phosphate onto amorphous Fe(III) oxides (hydrous ferric oxide, HFO) and crystalline Fe(III) oxides (goethite) was examined. These data were then used to test the ability of a commonly-used surface complexation model (SCM) to describe the adsorption of U(VI) and phosphate onto pure amorphous and crystalline Fe(III) oxides and synthetic goethite-coated sand, a surrogate for a natural Fe(III)-coated material, using the component additivity (CA) approach. Our modeling results show that this model was able to describe U(VI) adsorption onto both amorphous and crystalline Fe(III) oxides and also goethite-coated sand quite well in the absence of phosphate. However, because phosphate adsorption exhibits a stronger dependence on Fe(III) oxide type than U(VI) adsorption, we could not use this model to consistently describe phosphate adsorption onto both amorphous and crystalline Fe(III) oxides and goethite-coated sand. However, the effects of phosphate on U(VI) adsorption could be incorporated into the model to describe U(VI) adsorption to both amorphous and crystalline Fe(III) oxides and goethite-coated sand, at least for an initial approximation. These results illustrate both the potential and limitations of using surface complexation models developed from pure systems to describe metal/radionuclide adsorption under more complex conditions. (orig.)

  12. Surface complexation modeling of the effects of phosphate on uranium(VI) adsorption

    International Nuclear Information System (INIS)

    Romero-Gonzalez, M.R.; Cheng, T.; Barnett, M.O.; Roden, E.E.

    2007-01-01

    Previous published data for the adsorption of U(VI) and/or phosphate onto amorphous Fe(III) oxides (hydrous ferric oxide, HFO) and crystalline Fe(III) oxides (goethite) was examined. These data were then used to test the ability of a commonly-used surface complexation model (SCM) to describe the adsorption of U(VI) and phosphate onto pure amorphous and crystalline Fe(III) oxides and synthetic goethite-coated sand, a surrogate for a natural Fe(III)-coated material, using the component additivity (CA) approach. Our modeling results show that this model was able to describe U(VI) adsorption onto both amorphous and crystalline Fe(III) oxides and also goethite-coated sand quite well in the absence of phosphate. However, because phosphate adsorption exhibits a stronger dependence on Fe(III) oxide type than U(VI) adsorption, we could not use this model to consistently describe phosphate adsorption onto both amorphous and crystalline Fe(III) oxides and goethite-coated sand. However, the effects of phosphate on U(VI) adsorption could be incorporated into the model to describe U(VI) adsorption to both amorphous and crystalline Fe(III) oxides and goethite-coated sand, at least for an initial approximation. These results illustrate both the potential and limitations of using surface complexation models developed from pure systems to describe metal/radionuclide adsorption under more complex conditions. (orig.)

  13. Uranium(VI) adsorption properties of a chelating resin containing polyamine-substituted methylphosphonic acid moiety

    International Nuclear Information System (INIS)

    Matsuda, Masaaki; Akiyoshi, Yoshirou

    1991-01-01

    Uranium(VI) adsorption and desorption properties of a chelating resin containing polyamine-substituted methylphosphonic acid moiety of 2.29 mmol/g-resin (APA) were examined. Uranium(VI) adsorption properties of several ion exchange resins and extractant agents which were known as excellent adsorbents for uranium(VI), were examined together for a comparison with those of APA. Uranium(VI) adsorption capacity of APA at the concentration of 100 mg·dm -3 -uranium(VI) in 100 g·dm -3 -H 2 SO 4 aq. soln., 190 g·dm -3 -H 3 PO 4 aq. soln. and uranium enriched sea water, was 0.2, 0.05 and 0.05 mmol·g -1 respectively. The adsorption capacity of APA for uranium(VI) in these solutions was larger than that of another adsorbents, except the adsorption of uranium(VI) in enriched sea water on ion exchange resin containing phosphoric acid moiety (adsorption capacity ; 0.2 mmol·g -1 ). Uranium(VI) adsorption rate on APA was high and the relation between treatment time (t : min) and uranium(VI) concentration (y : mg·dm -3 ) in 100 g·dm -3 H 2 SO 4 aq. soln. after treatment, was shown as following equation, y=20 0.048t+1.90 (0≤t≤30). The adsorbed uranium(VI) on APA was able to be eluted with a mixed aq. soln. of hydrogen peroxide and sodium hydroxide and also was able to be eluted with an aq. alkaline soln. dissolved reduction agents such as sodium sulfite and hydrazine. From these results, it was thought that uranium(VI) adsorbed on APA was eluted due to the reduction to uranium(VI) by these eluents. (author)

  14. Adsorption of U(VI) onto kaolin studied by batch method

    International Nuclear Information System (INIS)

    Hongxia Zhang; Zhi Liu; Peizhuo Hu; Tonghuan Liu; Wangsuo Wu

    2013-01-01

    Adsorption of U(VI) on purified kaolin was studied by batch methods under ambient conditions, including contact time, pH, fulvic acid, etc. Three kinetic models were used to model the kinetic adsorption which was very well described by the pseudo-second-order rate equation, and the activation energy of adsorption was 52.20 kJ/mol. The Freundlich and Dubinin-Radushkevich models fitted the experimental data better than the Langmuir model for the adsorption and desorption isotherms. The thermodynamic parameters indicated that the adsorption of U(VI) on kaolin was an endothermic and spontaneous process. (author)

  15. Effect of Salicylic and Picolinic Acids on the Adsorption of U(VI) onto Oxides

    International Nuclear Information System (INIS)

    Park, Kyoung Kyun; Jung, Euo Chang; Cho, Hye Ryun; Song, Kyu Seok

    2009-01-01

    The effect of organic acids on the adsorption of U(VI) onto oxide surfaces (TiO 2 (anatase), SiO 2 (amorphous) and Al 2 O-3(amorphous)) has been investigated. Two different organic acids, salicylic and picolinic acids, were used. Changes of adsorption ratio of U(VI), which depend on the existence of organic acids in a sample, were measured as a function of pH. Quantities of adsorbed organic acids, which depend on the existence of U(VI) in a sample, were also measured as a function of pH. It is confirmed that the soluble complex formation of U(VI) with organic acids can deteriorate the adsorption of U(VI) onto TiO 2 surface. It is noteworthy that salicylic acid does not affect the adsorption of U(VI) onto SiO 2 surface, however, picolinic acid enhances the adsorption of U(VI) onto SiO 2 surface. The latter effect can be understood by considering the formation of a ternary surface complex on SiO 2 surface, which was confirmed by the co-adsorption of picolinic acid with U(VI) and the change in a fluorescence spectra of U(VI) on surface, In the case of Al 2 O-3, organic acids themselves were largely adsorbed onto a surface without deteriorating the adsorption of U(VI). This would support the possibility of a ternary surface complex formation on the Al 2 O-3 surface, and an additional spectroscopic study is required.

  16. Effect of uranium (VI) on the growth of yeast and influence of metabolism of yeast on adsorption of U (VI)

    International Nuclear Information System (INIS)

    Sakamoto, Fuminori; Ohnuki, Toshihiko; Kozai, Naofumi; Wakai, Eiichi; Francis, A.J.

    2005-01-01

    We have carried out the growth experiments of 3 strains of yeast in a medium containing uranium (VI) to elucidate the effect of U (VI) on the growth of microorganisms. Hansenula fabianii J640 grew in the liquid medium containing 0.1 mM U (VI) at lower rate than the control, but Saccharomyces cerevisiae did not grow under this condition. The H. fabianii J640 pre-cultured for 21 h in the liquid medium without U (VI) grew even after the exposure to 1 mM U (VI), but did not grow without pre-cultivation. For the pre-cultured H. fabianii J640, radioactivity of U in the medium was the same as the initial one for 110 h, and then gradually decreased. TEM-EDS analysis of H. fabianii J640 exposed to 1 mM U (VI) for 165 h showed accumulation of U (VI) on the cells. When H. fabianii J640 was not pre-cultured, radioactivity of U in the medium was lower than the initial one. These results indicated that U (VI) inhibits the growth of yeast, and that the adsorption of U (VI) by the cells depends on the metabolism of yeast. (author)

  17. 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

  18. Adsorption equilibrium studies of uranium (VI) onto cross-linked chitosan-citric acid

    International Nuclear Information System (INIS)

    Ho Thi Yeu Ly; Nguyen Van Suc; Vo Quang Mai; Nguyen Mong Sinh

    2011-01-01

    Investigation of U(VI) adsorption by the cross- linked chitosan with citric acid was conduced by bath method. Effect of parameters such as pH, contact time, adsorbent dosage and other metal cations was determined. The maximum adsorption capacity of U(VI) at pH 4 was found to be 71.43 mg U(VI) / g cross-linked chitosan - citric acid after 300 min of contact time. The Langmuir and Freundlich isotherm models were used to describe adsorption equilibrium. The correction values, R 2 of two models were found to be 0.991 and 0.997, respectively. Therefore, it could be concluded that the adsorption equilibrium for U(VI) was followed the Langmuir and the Freundlich isotherm models. (author)

  19. Adsorption of Cu(II) and Cr(VI) ions by chitosan: kinetics and ...

    African Journals Online (AJOL)

    The ability of chitosan as an adsorbent for Cu (II) and Cr (VI) ions in aqueous solution was studied. The experiments were done as batch processes. Equilibrium studies were done on both cross-linked and non-cross-linked chitosan for both metals. Cr (VI) adsorption behaviour could be described using the Langmuir ...

  20. 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.

  1. Kinetic and equilibrium study of uranium(VI) adsorption by Bacillus licheniformis

    International Nuclear Information System (INIS)

    Zheng-ji Yi; University of Science and Technology Beijing, Beijing; Jun Yao

    2012-01-01

    Uranium pollution is a severe problem worldwide. Biosorption has been proposed as one of the most promising technologies for the removal of uranyl cations. Here we report on the adsorption behavior of uranium(VI) [U(VI)] on Bacillus licheniformis biomass to explore the potentiality of its application in uranium contamination control. The adsorption equilibrium, adsorption kinetics, and effects of temperature, pH and initial biosorbent dosage on the adsorption equilibrium were investigated in detail through batch experiments. The adsorption process is pronouncedly affected by the solution pH and the optimum pH range should be 4.5-5.0.Temperature range from 25 to 45 deg C has a certain effect on the rate of biosorption, but little effect on the equilibrium adsorption capacity. The U(VI) percentage removal increased concurrently with increasing biomass dosage, whereas the adsorption capacity decreased. The process follows the Langmuir isotherm model. The adsorption kinetics data were fitted very well by the pseudo-first-order rate model. Finally, the calculation results of thermodynamic constant (ΔG a = 9.98 kJ/mol) reveal that the adsorption process can be identified as a spontaneous chemical process. The present results suggest that B. licheniformis has considerable potential for the removal of uranyl from aqueous solution. (author)

  2. 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.

  3. Adsorption of chromium (Vi) on radiation grafted N,N-dimethylaminoethylmethacrylate onto polypropylene, from aqueous solutions

    International Nuclear Information System (INIS)

    Burillo, G.; Serrano G, J.; Bonifacio M, J.

    2013-01-01

    Polypropylene (Pp) grafted with dimethylaminoethylmethacrylate (DMAEMA), was prepared by irradiation with a 60 Co γ source. The obtained Pp-g-DMAEMA was used to study the Cr(Vi) ion adsorption as a function of contact time, initial ph, initial concentration of metal ion and temperature. Chromium adsorption data on Pp-g-DMAEMA at various initial concentration fit well the Freundlich and Langmuir isotherms. The maximum adsorption capacity (a max ) was found to be 0.3103 x 0 -4 mol g -1 . The thermodynamic parameters ΔH 0 , ΔG 0 and ΔS 0 were estimated showing the adsorption process to be exothermic and spontaneous. (Author)

  4. 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.

  5. 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.

  6. 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.

  7. 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.

  8. Polyethylene imine modified hydrochar adsorption for chromium (VI) and nickel (II) removal from aqueous solution.

    Science.gov (United States)

    Shi, Yuanji; Zhang, Tao; Ren, Hongqiang; Kruse, Andrea; Cui, Ruofan

    2018-01-01

    An adsorbent hydrochar was synthesized from corn cobs and modified with polyethylene imine (PEI). The hydrochars before and after modification were characterized by scanning electron microscopy, Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and thermogravimetric analysis. FTIR and XPS revealed that the PEI was grafted onto the hydrochar via ether and imine bonds formed with glutaraldehyde. The maximum adsorption capacities for Cr(VI) (33.663mg/g) and Ni(II) (29.059mg/g) on the modified hydrochars were 365% and 43.7% higher, respectively, than those on the unmodified hydrochar. A pseudo-second-order model described the adsorption of Ni(II) and Cr(VI) on all the adsorbents. The adsorption of Cr(VI) was endothermic, spontaneous, increased disorder, and obeyed the Langmuir model. By contrast, the adsorption of Ni(II) was exothermic, spontaneous, decreased disorder, and obeyed the Freundlich model. XPS confirmed that the adsorption sites and mechanisms for Ni(II) and Cr(VI) on the modified hydrochars were different. Copyright © 2017 Elsevier Ltd. All rights reserved.

  9. Effective Microporosity for Enhanced Adsorption Capacity of Cr (VI) from Dilute Aqueous Solution: Isotherm and Kinetics

    OpenAIRE

    Lloyd Mukosha; Maurice S. Onyango; Aoyi Ochieng; John Siame

    2017-01-01

    The adsorbent pore structure significant to enhanced adsorption capacity of Cr (VI) from dilute aqueous solution is evaluated. As reference, low-cost micro-mesoporous activated carbon (AC) of high basicity, mesoporosity centred about 2.4 nm, and effective microporosity centred about 0.9 nm was tested for removal of Cr (VI) from dilute aqueous solution in batch mode. At pH 2 the low-cost AC exhibited highly improved Langmuir Cr (VI) capacity of 115 mg/g which was competitive to high performanc...

  10. U(VI) adsorption on natural iron-coated sands: comparison of approaches for modeling adsorption on heterogeneous environmental materials

    International Nuclear Information System (INIS)

    Logue, Brian A.; Smith, Robert W.; Westall, John C.

    2004-01-01

    Adsorption of U(VI) on 6 samples of natural Fe-rich sands from Oyster, VA was studied over a range of U(VI) concentrations (0.1-100 μM), pH values (3-7.6), and dithionite-citrate-bicarbonate (DCB) extractable amounts of Fe (3.1-12.3 μmol/g). Four modeling approaches were applied to represent the U(VI) adsorption data. Model I was a two-site, diffuse double layer, surface complexation model based on data for synthetic ferrihydrite [Geochim. Cosmochim. Acta 58 (1994) 5465-5478]. Considering the magnitude of approximations necessary for application of the laboratory-based model to natural sands, Model I was surprisingly accurate, as determined by the goodness of fit parameter, χ 2 /N of 53.1-22.2. Model II was based on the reactions and diffuse double layer treatment of Model I, but was calibrated to a portion of U(VI) adsorption data for each sand, and then used to predict adsorption data for the same sand under different experimental conditions. Model II did not increase the accuracy of the predictions made with Model I, χ 2 /N of 42.4-27.6. Models III and IV were four-site affinity spectrum models, without an explicit electric double layer model or explicit surface hydrolysis reactions. Model III was based on a discrete log K spectrum approach, and Model IV was obtained from adjusting all surface stability constants and site concentrations for all surface sites. Models III and IV represented the U(VI) adsorption data with the greatest accuracy, χ 2 /N ranged from 13.8 to 4.4. Model I provides evidence supporting the practice of using pure phase thermodynamic reaction constants for describing the adsorption characteristics of environmentally important sorbents in certain simple cases. Yet, affinity spectrum approaches (Models III and IV) become increasingly important as more accurate interpolation of adsorption data is necessary, the sorbent becomes increasingly complex, or the range of experimental conditions expands

  11. 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.

  12. 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

  13. 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

  14. 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.

  15. Effect of porosity and surface chemistry on the adsorption-desorption of uranium(VI) from aqueous solution and groundwater

    International Nuclear Information System (INIS)

    Yakout, S.M.

    2016-01-01

    Rice straw-based biochars modified with different chemical regents were used as an adsorbent for uranium(VI). Effect of pyrolysis temperature and nature of modifying agent's as well as surface chemistry, surface charge, and pore structure on U(VI) removal was investigated. Amount and nature of the surface groups has, in general, more influence than its porosity on U(VI) adsorption. The adsorption was maximum for the initial pH of 5.5. Rice straw derived biochars had comparable U(VI) adsorption as compared to other adsorbents. The U(VI) removal was 90 % from groundwater. NaHCO 3 was found to be the most efficient desorbent eluent for U(VI). (author)

  16. Selective adsorption of molybdenum(VI) from Mo-Re bearing effluent by chemically modified astringent persimmon

    Energy Technology Data Exchange (ETDEWEB)

    Xiong Ying, E-mail: xiongying_1977@hotmail.com [School of Chemistry, Key Laboratory of Rare-scattered Elements of Liaoning Province, Liaoning University, Shenyang 110036 (China); Wang Haitao; Lou Zhenning; Shan Weijun; Xing Zhiqiang; Deng Guichun [School of Chemistry, Key Laboratory of Rare-scattered Elements of Liaoning Province, Liaoning University, Shenyang 110036 (China); Wu Dongbei [Department of Chemistry, Tongji University, 200092 (China); Fang Dawei [School of Chemistry, Key Laboratory of Rare-scattered Elements of Liaoning Province, Liaoning University, Shenyang 110036 (China); Biswas, Biplob Kumar [Department of Applied Chemistry, Saga University, Honjo 1, Saga 840-8502 (Japan); Department of Applied Chemistry and Chemical Engineering, Jessore Science and Technology University, Jessore (Bangladesh)

    2011-02-28

    Graphical abstract: The use of persimmon for the recovery of Mo(VI) from aqueous chloride medium was investigated. The excellent adsorption characteristics for Mo(VI) were confirmed by adsorption and elution tests using a column packed with the APF gel. Research highlights: {yields} Astringent persimmon was chemically cross-linked by formaldehyde to obtain a novel kind of adsorption gel. By comparing with the adsorption of some other metal ions, especially for Re(VII), this new gel exhibited selectivity only for molybdenum with a remarkably high capacity for Mo(VI) (1.05 mol/kg dry gel). {yields} The adsorption mechanisms of molybdenum on the astringent persimmon gel have been determined for deferent molybdenum species. And, the endothermic adsorption process followed pseudo-second order kinetics, and the adsorption behavior obeys the Langmuir mode. {yields} The excellent adsorption characteristics for Mo(VI) were confirmed by adsorption and elution tests using a column packed with the APF gel, especially from an actual industrial waste effluent. - Abstract: Astringent persimmon was chemically cross-linked by formaldehyde to obtain a novel kind of adsorption gel, which was named as APF gel. The adsorption behaviors of Mo(VI) and Re(VII) along with other coexisting metals onto the APF gel were studied in the present paper. The APF gel was found to be effective for the adsorption of Mo(VI) while the gel is almost completely inert toward rhenium and calcium over the whole hydrochloric acid concentration region. The APF gel has a low affinity for iron, copper, lead, nickel, manganese and zinc ions when the concentration of HCl is higher than 1 mol/L. The gel exhibited selectivity only for Mo(VI) with a remarkably high adsorption capacity 1.05 mol/kg, and the adsorption behavior obeys the Langmuir model. According to the thermodynamic and kinetic studies, the endothermic adsorption process followed pseudo-second order kinetics. Also, its excellent adsorption

  17. Adsorption-desorption reactions of selenium (VI) in tropical cultivated and uncultivated soils under Cerrado biome.

    Science.gov (United States)

    Lessa, J H L; Araujo, A M; Silva, G N T; Guilherme, L R G; Lopes, G

    2016-12-01

    Soil management may affect selenium (Se) adsorption capacity. This study investigated adsorption and desorption of Se (VI) in selected Brazilian soils from the Cerrado biome, an area of ever increasing importance for agriculture expansion in Brazil. Soil samples were collected from cultivated and uncultivated soils, comprising clayed and sandy soils. Following chemical and mineralogical characterization, soil samples were subjected to Se adsorption and desorption tests. Adsorption was evaluated after a 72-h reaction with increasing concentrations of Se (0-2000 μg L -1 ) added as Na 2 SeO 4 in a NaCl electrolyte solution (pH 5.5; ionic strength 15 mmol L -1 ). Desorption, as well as distribution coefficients (K d ) for selenate were also assessed. Soil management affected Se adsorption capacity, i.e., Se adsorbed amounts were higher for uncultivated soils, when compared to cultivated ones. Such results were also supported by data of K d and maximum adsorption capacity of Se. This fact was attributed mainly to the presence of greater amounts of competing anions, especially phosphate, in cultivated soils, due to fertilizer application. Phosphate may compete with selenate for adsorption sites, decreasing Se retention. For the same group of soils (cultivated and uncultivated), Se adsorption was greater in the clayed soils compared to sandy ones. Our results support the idea that adding Se (VI) to the soil is a good strategy to increase Se levels in food crops (agronomic biofortification), especially when crops are grown in soils that have been cultivated over the time due to their low Se adsorption capacity (high Se availability). Copyright © 2016 Elsevier Ltd. All rights reserved.

  18. Functionalized Sugarcane Bagasse for U(VI) Adsorption from Acid and Alkaline Conditions.

    Science.gov (United States)

    Su, Shouzheng; Liu, Qi; Liu, Jingyuan; Zhang, Hongsen; Li, Rumin; Jing, Xiaoyan; Wang, Jun

    2018-01-15

    The highly efficient removal of uranium from mine tailings effluent, radioactive wastewater and enrichment from seawater is of great significance for the development of nuclear industry. In this work, we prepared an efficient U(VI) adsorbent by EDTA modified sugarcane bagasse (MESB) with a simple process. The prepared adsorbent preserves high adsorptive capacity for UO 2 2+ (pH 3.0) and uranyl complexes, such as UO 2 (OH) + , (UO 2 ) 2 (OH) 2 2+ and (UO 2 ) 3 (OH) 5 + (pH 4.0 and pH 5.0) and good repeatability in acidic environment. The maximum adsorption capacity for U(VI) at pH 3.0, 4.0 and 5.0 is 578.0, 925.9 and 1394.1 mg/g and the adsorption capacity loss is only 7% after five cycles. With the pH from 3.0 to 5.0, the inhibitive effects of Na + and K + decreased but increased of Mg 2+ and Ca 2+ . MESB also exhibits good adsorption for [UO 2 (CO 3 ) 3 ] 4- at pH 8.3 from 10 mg/L to 3.3 μg/L. Moreover, MESB could effectively extract U(VI) from simulated seawater in the presence of other metals ions. This work provided a general and efficient uranyl enriched material for nuclear industry.

  19. Adsorption Studies of Chromium(VI) on Activated Carbon Derived from Mangifera indica (Mango) Seed Shell

    Science.gov (United States)

    Mise, Shashikant; Patil, Trupti Nagendra

    2015-09-01

    The removal of chromium(VI) from synthetic sample by adsorption on activated carbon prepared from Mangifera indica (mango) seed shell have been carried out at room temperature 32 ± 1 °C. The removal of chromium(VI) from synthetic sample by adsorption on two types of activated carbon, physical activation and chemical activation (Calcium chloride and Sodium chloride), Impregnation Ratio's (IR) 0.25, 0.50, 0.75 for optimum time, optimum dosages and variation of pH were studied. It is observed that contact time differs for different carbons i.e. for physically and chemically activated carbons. The contact time decreases for chemically activated carbon compared to the physically activated carbon. It was observed that as dosage increases the adsorption increased along with the increase in impregnation ratio. It was also noted that as I.R. increases the surface area of Mangifera indica shell carbon increased. These dosage data were considered in the construction of isotherms and it was found that adsorption obeys Freundlich Isotherm and does not obey Langmuir Isotherm. The maximum removal of chromium (VI) was obtained in highly acidic medium at a pH of 1.50.

  20. 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

  1. Adsorption of chromium (Vi) on radiation grafted N,N-dimethylaminoethylmethacrylate onto polypropylene, from aqueous solutions

    Energy Technology Data Exchange (ETDEWEB)

    Burillo, G. [UNAM, Instituto de Ciencias Nucleares, Departamento de Quimica, Ciudad Universitaria, 04510 Mexico D. F. (Mexico); Serrano G, J.; Bonifacio M, J., E-mail: juan.serrano@inin.gob.mx [ININ, Carretera Mexico-Toluca s/n, 52750 Ocoyoacac, Estado de Mexico (Mexico)

    2013-08-01

    Polypropylene (Pp) grafted with dimethylaminoethylmethacrylate (DMAEMA), was prepared by irradiation with a {sup 60}Co {gamma} source. The obtained Pp-g-DMAEMA was used to study the Cr(Vi) ion adsorption as a function of contact time, initial ph, initial concentration of metal ion and temperature. Chromium adsorption data on Pp-g-DMAEMA at various initial concentration fit well the Freundlich and Langmuir isotherms. The maximum adsorption capacity (a{sub max}) was found to be 0.3103 x 0{sup -4} mol g{sup -1}. The thermodynamic parameters {Delta}H{sup 0}, {Delta}G{sup 0} and {Delta}S{sup 0} were estimated showing the adsorption process to be exothermic and spontaneous. (Author)

  2. The adsorption of molybdenum(VI) onto activated carbon from acid solution

    International Nuclear Information System (INIS)

    De Wet, H.F.

    1985-11-01

    The adsorption of molybdenum(VI) onto activated carbon is dependent on which nuclides are present in the solution. In this study the adsorption of Mo(VI) onto activated carbon is examined as a function of two variables, namely: the total molybdenum concentration and the pH. The equilibration time, the influence of ionic strength and the reversibility of the system was also examined. A series of solutions of a specified molybdenum concentration were equilibrated with activated carbon. In these experiments the pH varied from 5,5 to 0,9 while the temperature and ionic strength remained constant. The solutions were analysed colorimetrically and the pH equilibrium of each was measured. The molybdenum concentration for the series of experiments varied from 5x10 -4 M to 2x10 -2 M. 61 refs., 39 figs., 38 tabs

  3. Role of U(VI) adsorption in U(VI) Reduction by Geobacter species

    International Nuclear Information System (INIS)

    Lovely, Derrick

    2008-01-01

    Previous work had suggested that Acholeplasma palmae has a higher capacity for uranium sorption than other bacteria studied. Sorption studies were performed with cells in suspension in various solutions containing uranium, and results were used to generate uranium-biosorption isotherms. Results from this study showed that the U(VI) sorption capacity of G. uraniireducens was relatively similar in simple solutions, such as sodium chloride or bicarbonate. However, this ability to sorb uranium significantly decreased in groundwater. This suggested that certain chemicals present in the groundwater were inhibiting the ability of cell components of Geobacter to adsorb uranium. It was hypothesized that uranium removal would also be diminished in the bicarbonate solution. However, this did not seem to be the case, as uranium was as easily removed in the bicarbonate solution as in the sodium chloride solution.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2001-04-01

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

  5. The Adsorption of Cr(VI Using Chitosan-Alumina Adsorbent

    Directory of Open Access Journals (Sweden)

    Darjito Darjito

    2013-12-01

    Full Text Available Chitosan as adsorbent has been used widely, however it was not effective yet for metal ions adsorption in industrial scale. In acidic condition, chitosan’s active site tends to decrease. This drawback can was solved by coating of chitosan active site on alumina. This paper discloses to overcome that limitation. The charateristic of the active side was analysed by FTIR spectrometry toward vibration N-H group at 1679.15 cm-1, C=O group of oxalate at 1703.30 cm-1, and Al-O group of alumina at 924.07 cm-1. The adsorption capacity of the developed adsorbent was tester to adsorb Cr(VI ions under various of pH value such as 1, 2, 3, 4, 5, 6, and 7. The contact time affect toward the adsorption was also reported in 20, 30, 40 50, 60, 70, and 80 minute. In addition, the concentration effects (100, 200, 300, 400, 500, and 600 ppm was also studied. Chromium (VI was measured using spectronic-20. Adsorption capacity was obtained at 66.90 mg/g under optimum conditions pH 2, and contact time 60 minute, respectively.

  6. 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%.

  7. Spectroscopic Confirmation of Uranium (VI)-Carbonato Adsorption Complexes on Hematite

    International Nuclear Information System (INIS)

    Bargar, John R

    1999-01-01

    Evaluating societal risks posed by uranium contamination from waste management facilities, mining sites, and heavy industry requires knowledge about uranium transport in groundwater, often the most significant pathway of exposure to humans. It has been proposed that uranium mobility in aquifers may be controlled by adsorption of U(VI)-carbonato complexes on oxide minerals. The existence of such complexes has not been demonstrated, and little is known about their compositions and reaction stoichiometries. We have used Attenuated Total Reflectance Fourier Transform Infrared (ATR-FTIR) and Extended X-ray Absorption Fine Structure (EXAFS) spectroscopies to probe the existence, structures, and compositions of FeO surface -U(VI)-carbonato complexes on hematite throughout the pH range of uranyl uptake under conditions relevant to aquifers. U(VI)-carbonato complexes were found to be the predominant adsorbed U(VI) species at all pH values examined, a much wider pH range than previously postulated based on analogy to aqueous U(VI)-carbonato complexes, which are trace constituents at pH < 6. This result indicates the inadequacy of the common modeling assumption that the compositions and predominance of adsorbed species can be inferred from aqueous species. By extension, adsorbed carbonato complexes may be of major importance to the groundwater transport of similar actinide contaminants such as neptunium and plutonium

  8. Spectroscopic confirmation of uranium(VI)-carbonato adsorption complexes on hematite

    Science.gov (United States)

    Bargar, John R.; Reitmeyer, Rebecca; Davis, James A.

    1999-01-01

    Evaluating societal risks posed by uranium contamination from waste management facilities, mining sites, and heavy industry requires knowledge about uranium transport in groundwater, often the most significant pathway of exposure to humans. It has been proposed that uranium mobility in aquifers may be controlled by adsorption of U(VI)−carbonato complexes on oxide minerals. The existence of such complexes has not been demonstrated, and little is known about their compositions and reaction stoichiometries. We have used attenuated total reflectance Fourier transform infrared (ATR-FTIR) and extended X-ray absorption fine structure (EXAFS) spectroscopies to probe the existence, structures, and compositions of ≡FeOsurface−U(VI)−carbonato complexes on hematite throughout the pH range of uranyl uptake under conditions relevant to aquifers. U(VI)−carbonato complexes were found to be the predominant adsorbed U(VI) species at all pH values examined, a much wider pH range than previously postulated based on analogy to aqueous U(VI)−carbonato complexes, which are trace constituents at pH carbonato complexes may be of major importance to the groundwater transport of similar actinide contaminants such as neptunium and plutonium.

  9. Approaches to surface complexation modeling of Uranium(VI) adsorption on aquifer sediments

    Science.gov (United States)

    Davis, J.A.; Meece, D.E.; Kohler, M.; Curtis, G.P.

    2004-01-01

    Uranium(VI) adsorption onto aquifer sediments was studied in batch experiments as a function of pH and U(VI) and dissolved carbonate concentrations in artificial groundwater solutions. The sediments were collected from an alluvial aquifer at a location upgradient of contamination from a former uranium mill operation at Naturita, Colorado (USA). The ranges of aqueous chemical conditions used in the U(VI) adsorption experiments (pH 6.9 to 7.9; U(VI) concentration 2.5 ?? 10-8 to 1 ?? 10-5 M; partial pressure of carbon dioxide gas 0.05 to 6.8%) were based on the spatial variation in chemical conditions observed in 1999-2000 in the Naturita alluvial aquifer. The major minerals in the sediments were quartz, feldspars, and calcite, with minor amounts of magnetite and clay minerals. Quartz grains commonly exhibited coatings that were greater than 10 nm in thickness and composed of an illite-smectite clay with occluded ferrihydrite and goethite nanoparticles. Chemical extractions of quartz grains removed from the sediments were used to estimate the masses of iron and aluminum present in the coatings. Various surface complexation modeling approaches were compared in terms of the ability to describe the U(VI) experimental data and the data requirements for model application to the sediments. Published models for U(VI) adsorption on reference minerals were applied to predict U(VI) adsorption based on assumptions about the sediment surface composition and physical properties (e.g., surface area and electrical double layer). Predictions from these models were highly variable, with results overpredicting or underpredicting the experimental data, depending on the assumptions used to apply the model. Although the models for reference minerals are supported by detailed experimental studies (and in ideal cases, surface spectroscopy), the results suggest that errors are caused in applying the models directly to the sediments by uncertain knowledge of: 1) the proportion and types of

  10. The effect of various cations and pH on the adsorption of U(VI) on Amberlite IR-118H resin

    International Nuclear Information System (INIS)

    Kilislioglu, Ayben

    2003-01-01

    The effects of various metal cations and pH on the adsorption of uranium(VI) on strongly acidic cation exchanger Amberlite IR-118H (AIR-118H) were studied. The metal cations suppress U(VI) adsorption differently depending on their ionic radii. Adsorption of U(VI) on AIR-118H peaks at pH 3.4, which was attributed to the occurrence of different forms of U(VI) at different pH values. The adsorption data were then processed using the Frumkin-Fowler-Guggenheim equation, and the standard free energy of adsorption was calculated

  11. 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.

  12. 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

  13. ADSORPTION OF CHROMIUM (VI FROM AQUEOUS SOLUTIONS BY DIFFERENT ADMIXTURES – A BATCH EQUILIBRIUM TEST STUDY

    Directory of Open Access Journals (Sweden)

    K. SHIVA PRASHANTH KUMAR

    2014-08-01

    Full Text Available Wide variety of inorganic compounds such as nutrients and trace metals, organic chemicals, radioactive contaminants and pathogens are commonly present as contaminants in the groundwater. Migration of contaminants in soil involves important mechanisms such as molecular diffusion, dispersion under physical processes, adsorption, precipitation and oxidation - reduction under chemical processes and biodegradation under biological process. Cr (VI is a major and dangerous contaminant as per the ground water is concerned. There are numerous research work carried out with concentrated efforts by the researchers towards removal of Cr (VI contaminant from aqueous solutions. There are few studies relevant to Cr (VI removal with respect to utilization of low cost admixtures and also soil type. In the present study, different low cost admixtures like rice husk (RH, shredded tyre (ST and fly ash (FA are used to understand the performance in removal of Cr (VI from aqueous solution and also two different soil types are used along with the admixture. The results are discussed in terms of sorption capacity and performance of individual admixture and combination of admixture with soil in removal of contaminant. The fly ash, rice husk and shredded tyre admixtures are used and the results revealed that the shredded tyre showed higher performance in removal of contaminant concentration. Also, the soil which has more fine particle content (size<0.075 mm IS sieve showed reasonable reduction in concentration of contaminant at the lower levels of contaminant initial concentration. The sorption capacity results of Cr (VI contaminant, treated with various admixtures are further validated with the published work of other investigators. The shredded tyre (ST showed more adsorption capacity, i.e., 3.283 mg/g at pH of 4.8. For other admixtures, adsorption capacity value is varying in the range of 0.07 mg/g to 1.7 mg/g. Only in case of activated alumina and modified saw dust

  14. Adsorption isotherm studies of chromium (VI) from aqueous solutions using sol-gel hydrotalcite-like compounds

    Energy Technology Data Exchange (ETDEWEB)

    Ramos-Ramirez, Esthela, E-mail: ramosre@quijote.ugto.mx [Centro de Investigaciones en Quimica Inorganica de la Universidad de Guanajuato, Noria Alta s/n, Col. Noria Alta, C.P. 36050, Guanajuato, Gto. (Mexico); Gutierrez Ortega, Norma L.; Conteras Soto, Cesar A. [Centro de Investigaciones en Quimica Inorganica de la Universidad de Guanajuato, Noria Alta s/n, Col. Noria Alta, C.P. 36050, Guanajuato, Gto. (Mexico); Instituto Nacional de Investigaciones Nucleares, Carretera Mexico-Toluca s/n, km 36.5, La Marquesa, Coyoacan Mexico, C.P. 52750 (Mexico); Olguin Gutierrez, Maria T. [Instituto Nacional de Investigaciones Nucleares, Carretera Mexico-Toluca s/n, km 36.5, La Marquesa, Coyoacan Mexico, C.P. 52750 (Mexico)

    2009-12-30

    In under-developed countries, industries such as paint and pigment manufacturing, leather tanning, chrome plating and textile processing, usually discharge effluents containing Cr(VI) and Cr(III) into municipal sanitary sewers. It has been reported that Cr(VI) acts as a powerful epithelial irritant and as a human carcinogen. In the present work, hydrotalcite-like compounds with a Mg/Al ratio = 2 were synthesized by the sol-gel method. The hydrotalcite-like compounds and their corresponding thermally treated products were characterized by powder X-ray diffraction, infrared spectroscopy and N{sub 2} adsorption. The hydrotalcite-like compounds and the heated solids were used as adsorbents for Cr(VI) in aqueous solutions. Adsorption isotherm studies of Cr(VI) from aqueous solution are described. The adsorbent capacity was determined using the Langmuir, Freundlich and Dubinin-Radushkevich adsorption isotherm models. The Cr(VI) adsorption isotherm data fit best to the Langmuir isotherm model. The maximum Cr(VI) uptake by hydrotalcite and the heated solids was determined using the Langmuir equation and was found to range between 26 and 29 mg Cr(VI)/g adsorbent.

  15. Adsorption isotherm studies of chromium (VI) from aqueous solutions using sol-gel hydrotalcite-like compounds

    International Nuclear Information System (INIS)

    Ramos-Ramirez, Esthela; Gutierrez Ortega, Norma L.; Conteras Soto, Cesar A.; Olguin Gutierrez, Maria T.

    2009-01-01

    In under-developed countries, industries such as paint and pigment manufacturing, leather tanning, chrome plating and textile processing, usually discharge effluents containing Cr(VI) and Cr(III) into municipal sanitary sewers. It has been reported that Cr(VI) acts as a powerful epithelial irritant and as a human carcinogen. In the present work, hydrotalcite-like compounds with a Mg/Al ratio = 2 were synthesized by the sol-gel method. The hydrotalcite-like compounds and their corresponding thermally treated products were characterized by powder X-ray diffraction, infrared spectroscopy and N 2 adsorption. The hydrotalcite-like compounds and the heated solids were used as adsorbents for Cr(VI) in aqueous solutions. Adsorption isotherm studies of Cr(VI) from aqueous solution are described. The adsorbent capacity was determined using the Langmuir, Freundlich and Dubinin-Radushkevich adsorption isotherm models. The Cr(VI) adsorption isotherm data fit best to the Langmuir isotherm model. The maximum Cr(VI) uptake by hydrotalcite and the heated solids was determined using the Langmuir equation and was found to range between 26 and 29 mg Cr(VI)/g adsorbent.

  16. High performance of phosphate-functionalized graphene oxide for the selective adsorption of U(VI) from acidic solution

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Xia [Institute of Plasma Physics, Chinese Academy of Sciences, P.O. Box 1126, Hefei, 230031 (China); University of Science and Technology of China, Hefei, 230026 (China); Li, Jiaxing, E-mail: lijx@ipp.ac.cn [Institute of Plasma Physics, Chinese Academy of Sciences, P.O. Box 1126, Hefei, 230031 (China); Collaborative Innovation Center of Radiation Medicine of Jiangsu Higher Education Institutions (China); School for Radiological and Interdisciplinary Sciences (RAD-X), Soochow University, 215123, Suzhou (China); Wang, Xiangxue; Chen, Changlun [Institute of Plasma Physics, Chinese Academy of Sciences, P.O. Box 1126, Hefei, 230031 (China); Wang, Xiangke [Institute of Plasma Physics, Chinese Academy of Sciences, P.O. Box 1126, Hefei, 230031 (China); Collaborative Innovation Center of Radiation Medicine of Jiangsu Higher Education Institutions (China); School for Radiological and Interdisciplinary Sciences (RAD-X), Soochow University, 215123, Suzhou (China); Faculty of Engineering, King Abdulaziz University, Jeddah 21589 (Saudi Arabia)

    2015-11-15

    In this study, phosphate-functionalized graphene oxide (PGO) was prepared by grafting triethyl phosphite onto the surface of GO using Arbuzov reaction. The as-prepared PGO was characterized by scanning electron microscopy, X-ray photoelectron spectroscopy, Fourier transformed infrared spectroscopy and Zeta potential. The application of the PGO to remove U(VI) from aqueous solution was investigated with a maximum adsorption capacity of 251.7 mg/g at pH = 4.0 ± 0.1 and T = 303 K. The adsorption mechanism was also investigated by X-ray photoelectron spectroscopy analysis, indicating a chemical adsorption of U(VI) on PGO surface. Moreover, experimental results gave a better removal efficiency toward U(VI) on PGO surface than other heavy metal ions at acidic solution, indicating the selective extraction of U(VI) from environmental pollutants. - Highlights: • The successful grafting phosphonate to graphene oxide by the Arbuzov reaction. • Selective adsorption of U(VI) on PGO surface over other heavy metal ions from acidic solution. • Electrostatic interactions of U(VI) with phosphonate and oxygen-containing functional groups on PGO surface. • Higher sorption capacity on PGO surface than GO surface for the U(VI) removal.

  17. Adsorption isotherm studies of chromium (VI) from aqueous solutions using sol-gel hydrotalcite-like compounds.

    Science.gov (United States)

    Ramos-Ramírez, Esthela; Ortega, Norma L Gutiérrez; Soto, Cesar A Contreras; Gutiérrez, Maria T Olguín

    2009-12-30

    In under-developed countries, industries such as paint and pigment manufacturing, leather tanning, chrome plating and textile processing, usually discharge effluents containing Cr(VI) and Cr(III) into municipal sanitary sewers. It has been reported that Cr(VI) acts as a powerful epithelial irritant and as a human carcinogen. In the present work, hydrotalcite-like compounds with a Mg/Al ratio=2 were synthesized by the sol-gel method. The hydrotalcite-like compounds and their corresponding thermally treated products were characterized by powder X-ray diffraction, infrared spectroscopy and N(2) adsorption. The hydrotalcite-like compounds and the heated solids were used as adsorbents for Cr(VI) in aqueous solutions. Adsorption isotherm studies of Cr(VI) from aqueous solution are described. The adsorbent capacity was determined using the Langmuir, Freundlich and Dubinin-Radushkevich adsorption isotherm models. The Cr(VI) adsorption isotherm data fit best to the Langmuir isotherm model. The maximum Cr(VI) uptake by hydrotalcite and the heated solids was determined using the Langmuir equation and was found to range between 26 and 29 mg Cr(VI)/g adsorbent.

  18. Adsorption of uranium(VI) to manganese oxides: X-ray absorption spectroscopy and surface complexation modeling.

    Science.gov (United States)

    Wang, Zimeng; Lee, Sung-Woo; Catalano, Jeffrey G; Lezama-Pacheco, Juan S; Bargar, John R; Tebo, Bradley M; Giammar, Daniel E

    2013-01-15

    The mobility of hexavalent uranium in soil and groundwater is strongly governed by adsorption to mineral surfaces. As strong naturally occurring adsorbents, manganese oxides may significantly influence the fate and transport of uranium. Models for U(VI) adsorption over a broad range of chemical conditions can improve predictive capabilities for uranium transport in the subsurface. This study integrated batch experiments of U(VI) adsorption to synthetic and biogenic MnO(2), surface complexation modeling, ζ-potential analysis, and molecular-scale characterization of adsorbed U(VI) with extended X-ray absorption fine structure (EXAFS) spectroscopy. The surface complexation model included inner-sphere monodentate and bidentate surface complexes and a ternary uranyl-carbonato surface complex, which was consistent with the EXAFS analysis. The model could successfully simulate adsorption results over a broad range of pH and dissolved inorganic carbon concentrations. U(VI) adsorption to synthetic δ-MnO(2) appears to be stronger than to biogenic MnO(2), and the differences in adsorption affinity and capacity are not associated with any substantial difference in U(VI) coordination.

  19. 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)

  20. Column study of chromium(VI) adsorption from electroplating industry by coconut coir pith

    Energy Technology Data Exchange (ETDEWEB)

    Suksabye, Parinda [Joint Graduate School of Energy and Environment, King Mongkut' s University of Technology Thonburi, 91 Pracha-Utit Road, Bangmod, Thungkru, Bangkok 10140 (Thailand); Thiravetyan, Paitip [Division of Biotechnology, School of Bioresources and Technology, King Mongkut' s University of Technology Thonburi, 83 Moo.8 Thakham, Bangkhuntien, Bangkok 10150 (Thailand)], E-mail: paitip.thi@kmutt.ac.th; Nakbanpote, Woranan [Pilot Plant Development and Training Institute, King Mongkut' s University of Technology Thonburi, 83 Moo.8 Thakham, Bangkhuntien, Bangkok 10150 (Thailand)

    2008-12-15

    The removal of Cr(VI) from electroplating wastewater by coir pith was investigated in a fixed-bed column. The experiments were conducted to study the effect of important parameters such as bed depth (40-60 cm) and flow rate (10-30 ml min{sup -1}). At 0.05 C{sub t}/C{sub 0}, the breakthrough volume increased as flow rate decreased or a bed depth increased due to an increase in empty bed contact time (EBCT). The bed depth service time model (BDST) fit well with the experimental data in the initial region of the breakthrough curve, while the simulation of the whole curve using non-linear regression analysis was effective using the Thomas model. The adsorption capacity estimated from the BDST model was reduced with increasing flow rate, which was 16.40 mg cm{sup -3} or 137.91 mg Cr(VI) g{sup -1} coir pith for the flow rates of 10 ml min{sup -1} and 14.05 mg cm{sup -3} or 118.20 mg Cr(VI) g{sup -1} coir pith for the flow rates of 30 ml min{sup -1}. At the highest bed depth (60 cm) and the lowest flow rate (10 ml min{sup -1}), the maximum adsorption reached 201.47 mg Cr(VI) g{sup -1} adsorbent according to the Thomas model. The column was regenerated by eluting chromium using 2 M HNO{sub 3} after adsorption studies. The desorption of Cr(III) in each of three cycles was about 67-70%. The desorption of Cr(III) in each cycle did not reach 100% due to the fact that Cr(V) was present through the reduction of Cr(VI), and was still in coir pith, possibly bound to glucose in the cellulose part of coir pith. Therefore, the Cr(V) complex cannot be desorbed in solution. The evidence of Cr(V) signal was observed in coir pith, {alpha}-cellulose and holocellulose extracted from coir pith using electron spin resonance (ESR)

  1. Column study of chromium(VI) adsorption from electroplating industry by coconut coir pith

    International Nuclear Information System (INIS)

    Suksabye, Parinda; Thiravetyan, Paitip; Nakbanpote, Woranan

    2008-01-01

    The removal of Cr(VI) from electroplating wastewater by coir pith was investigated in a fixed-bed column. The experiments were conducted to study the effect of important parameters such as bed depth (40-60 cm) and flow rate (10-30 ml min -1 ). At 0.05 C t /C 0 , the breakthrough volume increased as flow rate decreased or a bed depth increased due to an increase in empty bed contact time (EBCT). The bed depth service time model (BDST) fit well with the experimental data in the initial region of the breakthrough curve, while the simulation of the whole curve using non-linear regression analysis was effective using the Thomas model. The adsorption capacity estimated from the BDST model was reduced with increasing flow rate, which was 16.40 mg cm -3 or 137.91 mg Cr(VI) g -1 coir pith for the flow rates of 10 ml min -1 and 14.05 mg cm -3 or 118.20 mg Cr(VI) g -1 coir pith for the flow rates of 30 ml min -1 . At the highest bed depth (60 cm) and the lowest flow rate (10 ml min -1 ), the maximum adsorption reached 201.47 mg Cr(VI) g -1 adsorbent according to the Thomas model. The column was regenerated by eluting chromium using 2 M HNO 3 after adsorption studies. The desorption of Cr(III) in each of three cycles was about 67-70%. The desorption of Cr(III) in each cycle did not reach 100% due to the fact that Cr(V) was present through the reduction of Cr(VI), and was still in coir pith, possibly bound to glucose in the cellulose part of coir pith. Therefore, the Cr(V) complex cannot be desorbed in solution. The evidence of Cr(V) signal was observed in coir pith, α-cellulose and holocellulose extracted from coir pith using electron spin resonance (ESR)

  2. Column study of chromium(VI) adsorption from electroplating industry by coconut coir pith.

    Science.gov (United States)

    Suksabye, Parinda; Thiravetyan, Paitip; Nakbanpote, Woranan

    2008-12-15

    The removal of Cr(VI) from electroplating wastewater by coir pith was investigated in a fixed-bed column. The experiments were conducted to study the effect of important parameters such as bed depth (40-60cm) and flow rate (10-30ml min(-1)). At 0.05 C(t)/C(0), the breakthrough volume increased as flow rate decreased or a bed depth increased due to an increase in empty bed contact time (EBCT). The bed depth service time model (BDST) fit well with the experimental data in the initial region of the breakthrough curve, while the simulation of the whole curve using non-linear regression analysis was effective using the Thomas model. The adsorption capacity estimated from the BDST model was reduced with increasing flow rate, which was 16.40mg cm(-3) or 137.91mg Cr(VI)g(-1) coir pith for the flow rates of 10ml min(-1) and 14.05mg cm(-3) or 118.20mg Cr(VI)g(-1) coir pith for the flow rates of 30ml min(-1). At the highest bed depth (60cm) and the lowest flow rate (10mlmin(-1)), the maximum adsorption reached 201.47mg Cr(VI)g(-1) adsorbent according to the Thomas model. The column was regenerated by eluting chromium using 2M HNO(3) after adsorption studies. The desorption of Cr(III) in each of three cycles was about 67-70%. The desorption of Cr(III) in each cycle did not reach 100% due to the fact that Cr(V) was present through the reduction of Cr(VI), and was still in coir pith, possibly bound to glucose in the cellulose part of coir pith. Therefore, the Cr(V) complex cannot be desorbed in solution. The evidence of Cr(V) signal was observed in coir pith, alpha-cellulose and holocellulose extracted from coir pith using electron spin resonance (ESR).

  3. Comparative study of adsorption properties of Turkish fly ashes II. The case of chromium (VI) and cadmium (II)

    International Nuclear Information System (INIS)

    Bayat, Belgin

    2002-01-01

    The purpose of the study described in this paper was to compare the removal of Cr(VI) and Cd(II) from an aqueous solution using two different Turkish fly ashes; Afsin-Elbistan and Seyitomer as adsorbents. The influence of four parameters (contact time, solution pH, initial metal concentration in solution and ash quality) on the removal at 20±2 deg. C was studied. Fly ashes were found to have a higher adsorption capacity for the adsorption of Cd(II) as compared to Cr(VI) and both Cr(VI) and Cd(II) required an equilibrium time of 2 h. The adsorption of Cr(VI) was higher at pH 4.0 for Afsin-Elbistan fly ash (25.46%) and pH 3.0 for Seyitomer fly ash (30.91%) while Cd(II) was adsorbed to a greater extent (98.43% for Afsin-Elbistan fly ash and 65.24% for Seyitomer fly ash) at pH 7.0. The adsorption of Cd(II) increased with an increase in the concentrations of these metals in solution while Cr(VI) adsorption decreased by both fly ashes. The lime (crystalline CaO) content in fly ash seemed to be a significant factor in influencing Cr(VI) and Cd(II) ions removal. The linear forms of the Langmuir and Freundlich equations were utilised for experiments with metal concentrations of 55±2 mg/l for Cr(VI) and 6±0.2 mg/l for Cd(II) as functions of solution pH (3.0-8.0). The adsorption of Cr(VI) on both fly ashes was not described by both the Langmuir and Freundlich isotherms while Cd(II) adsorption on both fly ashes satisfied only the Langmuir isotherm model. The adsorption capacities of both fly ashes were nearly three times less than that of activated carbon for the removal of Cr(VI) while Afsin-Elbistan fly ash with high-calcium content was as effective as activated carbon for the removal of Cd(II). Therefore, there are possibilities for use the adsorption of Cd(II) ions onto fly ash with high-calcium content in practical applications in Turkey

  4. Kinetic study of Chromium VI adsorption onto palm kernel shell activated carbon

    Science.gov (United States)

    Mohammad, Masita; Sadeghi Louyeh, Shiva; Yaakob, Zahira

    2018-04-01

    Heavy metal contamination of industrial effluent is one of the significant environmental problems due to their toxicity and its accumulation throughout the food chain. Adsorption is one of the promising methods for removal of heavy metals from aqua solution because of its simple technique, efficient, reliable and low-cost due to the utilization of residue from the agricultural industry. In this study, activated carbon from palm kernel shells has been produced through chemical activation process using zinc chloride as an activating agent and carbonized at 800 °C. Palm kernel shell activated carbon, PAC was assessed for its efficiency to remove Chromium (VI) ions from aqueous solutions through a batch adsorption process. The kinetic mechanisms have been analysed using Lagergren first-order kinetics model, second-order kinetics model and intra-particle diffusion model. The characterizations such as BET surface area, surface morphology, SEM-EDX have been done. The result shows that the activation process by ZnCl2 was successfully improved the porosity and modified the functional group of palm kernel shell. The result shows that the maximum adsorption capacity of Cr is 11.40mg/g at 30ppm initial metal ion concentration and 0.1g/50mL of adsorbent concentration. The adsorption process followed the pseudo second orders kinetic model.

  5. Adsorption Effectivity Test of Andisols Clay-Zeolite (ACZ) Composite as Chromium Hexavalent (Cr(VI)) Ion Adsorbent

    Science.gov (United States)

    Pranoto; Masykur, A.; Nugroho, Y. A.

    2018-03-01

    Adsorption of chromium hexavalent (Cr(VI)) ion in aqueous solution was investigated. This research was purposed to study the influence of the composition of ACZ, temperature activation, and contact time against adsorption capacity of Cr(VI) ion in aqueous solution. Determination of adsorption effectivity using several parameter such as composition variation of ACZ, contact time, pH, activation temperature, and concentration. In this research, andisol clay and zeolite has been activated with NaOH 3 M and 1 M, respectively. Temperature variation used 100, 200, and 400°C. While composition variation ACZ used 0:100, 25:75, 50:50, 75:25, 100:0. The pH variation was used 2 – 6 and concentration variation using 2, 4, 6, 8, 10, and 12 ppm. Characterization in this research used such as UV-Vis, Surface Area Analyzer (SAA) and Acidity Analysis. Result of this research is known that optimum composition of ACZ was 50:50 with calcination temperature 100°C. Optimum adsorption of Cr(VI) at pH 4 with removal percentage 76.10 % with initial concentration 2 ppm and adsorption capacity is 0.16 mg/g. Adsorption isotherm following freundlich isotherm with value Kf = 0.17 mg/g and value n is 0.963. Based on results, ACZ composite can be used as Cr(VI) ion adsorbents in aqueous solutions.

  6. 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

  7. Cinética e equilíbrio de adsorção dos oxiânions Cr (VI, Mo (VI e Se (VI pelo sal de amônio quaternário de quitosana Kinetics and equilibrium of adsorption of oxyanions Cr (VI, Mo (VI and Se (VI by quaternary ammonium chitosan salt

    Directory of Open Access Journals (Sweden)

    Viviane A. Spinelli

    2005-07-01

    Full Text Available O sal quaternário de quitosana foi sintetizado com cloreto de glicidil trimetil amônio. A modificação química foi caracterizada por espectrometria no IV, RMN de 13C e ¹H, e mmol/g de grupos quaternários presentes na matriz polimérica por condutimetria. A remoção de Cr (VI, Mo (VI e Se (VI, em meio aquoso, foi investigada em processo de batelada. A adsorção mostrou ser dependente do pH para o Cr (VI e Se (VI, com um pH ótimo de adsorção, entre 4,0 a 6,0. Para o Mo (VI a adsorção manteve-se quase constante no intervalo de pH entre 4,0 e 11,5. O modelo de isoterma de Langmuir descreveu melhor os dados de equilíbrio na faixa de concentração investigada. No presente estudo, um grama do sal quaternário de quitosana reticulado com glutaraldeído adsorveu 68,3 mg de Cr, 63,4 mg de Mo e 90,0 mg de Se. A velocidade de adsorção, no processo, segue a equação cinética de pseudo segunda-ordem, sendo que o equilíbrio para os três íons foi alcançado próximo aos 200 minutos. A análise dispersiva de raios-X para o Cr (VI mostrou que o principal mecanismo de adsorção é a troca iônica entre os íons Cl- da superfície do polímero pelos oxiânions. O trocador aniônico apresentou a seguinte ordem de seletividade: Cr (VI > Mo (VI > Se (VI.Quaternary chitosan salt was synthesized in the presence of glycidyl trimetyl ammonium chloride. The polymer was characterized by spectroscopic techniques: infrared, 13C and ¹H NMR, while the amount of quaternary ammonium groups was obtained by condutimetry. The removal of Cr (VI, Mo (VI and Se (VI from aqueous solutions was carried out in batch adsorption processes. The process seemed to be pH dependent for Cr (VI and Se (VI with an optimum pH ranging from 4.0 to 6.0; while for Mo (VI the adsorption remained almost constant within the range between 4.0 and 11.5. The Langmuir isotherm model provided the best fit of the equilibrium data over the whole concentration investigated. In the experiment

  8. Surface complexation modeling of U(VI) adsorption by aquifer sediments from a former mill tailings site at Rifle, Colorado

    Science.gov (United States)

    Hyun, S.P.; Fox, P.M.; Davis, J.A.; Campbell, K.M.; Hayes, K.F.; Long, P.E.

    2009-01-01

    A study of U(VI) adsorption by aquifer sediment samples from a former uranium mill tailings site at Rifle, Colorado, was conducted under oxic conditions as a function of pH, U(VI), Ca, and dissolved carbonate concentration. Batch adsorption experiments were performed using tailings site at Naturita, Colorado, indicated that possible calcite nonequilibrium of dissolved calcium concentration should be evaluated. The modeling results also illustrate the importance of the range of data used in deriving the best fit model parameters. ?? 2009 American Chemical Society.

  9. 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.

  10. Adsorption of chromium(VI) on pomace-An olive oil industry waste: Batch and column studies

    International Nuclear Information System (INIS)

    Malkoc, Emine; Nuhoglu, Yasar; Dundar, Murat

    2006-01-01

    The waste pomace of olive oil factory (WPOOF) was tested for its ability to remove chromium(VI) from aqueous solution by batch and column experiments. Various thermodynamic parameters, such as ΔG o , ΔH o and ΔS o have been calculated. The thermodynamics of chromium(VI) ion onto WPOOF system indicates spontaneous and endothermic nature of the process. The ability of WPOOF to adsorb chromium(VI) in a fixed bed column was investigated, as well. The effect of operating parameters such as flow rate and inlet metal ion concentration on the sorption characteristics of WPOOF was investigated. The longest breakthrough time and maximum of Cr(VI) adsorption is obtained at pH 2.0. The total adsorbed quantities, equilibrium uptakes and total removal percents of chromium(VI) related to the effluent volumes were determined by evaluating the breakthrough curves obtained at different flow rates and different inlet chromium(VI) concentrations for adsorbent. The data confirmed that the total amount of sorbed chromium(VI) and equilibrium chromium(VI) uptake decreased with increasing flow rate and increased with increasing inlet chromium(VI) concentration. The Adams-Bohart model were used to analyze the experimental data and the model parameters were evaluated

  11. 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.

  12. Adsorption of U(VI) ions from aqueous solutions by activated carbon prepared from Antep pistachio (Pistacia vera L.) shells

    International Nuclear Information System (INIS)

    Donat, Ramazan; Erden, Kadriye Esen

    2017-01-01

    Antep pistachio (Pistacia vera L.) shells an abundant and low cost natural resource in Turkey was used to prepare activated carbon by physiochemical activation and carbon dioxide (CO_2) atmosphere as the activating agents at 700 C for 2 h. The adsorption equilibrium of U(VI) from aqueous solutions on such carbon has been studied using a batch system. The parameters that affect the U(VI) adsorption, such as particle size of adsorbent, contact time, of pH of the solution, and temperature, have been investigated and conditions have also been optimized. The equilibrium data for U(VI) ions' adsorption onto activated carbon well fitted to the Langmuir equation, with a maximum monolayer adsorption capacity of 8.68 mg/g, The Freundlich and Dubinin-Radushkevich (D-R) isotherms have been applied and the data correlated well with Freundlich model and that the adsorption is physical in nature (E_a=15.46 kJ/mol). Thermodynamic parameters [ΔH_s=11.33 kJ/mol, ΔS=0.084 kJ/molK, ΔG (293.15 K)=-13.29 kJ/mol] showed the endothermic heat of adsorption and the feasibility of the process.

  13. Adsorption of U(VI) ions from aqueous solutions by activated carbon prepared from Antep pistachio (Pistacia vera L.) shells

    Energy Technology Data Exchange (ETDEWEB)

    Donat, Ramazan [Pamukkale Univ., Denizli (Turkey). Dept. of Chemistry; Erden, Kadriye Esen [Pamukkale Univ., Kinikli-Denizli (Turkey). Denizli Vocational School of Technical Sciences

    2017-08-01

    Antep pistachio (Pistacia vera L.) shells an abundant and low cost natural resource in Turkey was used to prepare activated carbon by physiochemical activation and carbon dioxide (CO{sub 2}) atmosphere as the activating agents at 700 C for 2 h. The adsorption equilibrium of U(VI) from aqueous solutions on such carbon has been studied using a batch system. The parameters that affect the U(VI) adsorption, such as particle size of adsorbent, contact time, of pH of the solution, and temperature, have been investigated and conditions have also been optimized. The equilibrium data for U(VI) ions' adsorption onto activated carbon well fitted to the Langmuir equation, with a maximum monolayer adsorption capacity of 8.68 mg/g, The Freundlich and Dubinin-Radushkevich (D-R) isotherms have been applied and the data correlated well with Freundlich model and that the adsorption is physical in nature (E{sub a}=15.46 kJ/mol). Thermodynamic parameters [ΔH{sub s}=11.33 kJ/mol, ΔS=0.084 kJ/molK, ΔG (293.15 K)=-13.29 kJ/mol] showed the endothermic heat of adsorption and the feasibility of the process.

  14. Comparison of U(VI) adsorption onto nanoscale zero-valent iron and red soil in the presence of U(VI)–CO_3/Ca–U(VI)–CO_3 complexes

    International Nuclear Information System (INIS)

    Zhang, Zhibin; Liu, Jun; Cao, Xiaohong; Luo, Xuanping; Hua, Rong; Liu, Yan; Yu, Xiaofeng; He, Likai

    2015-01-01

    Highlights: • NZVI can be used for adsorbing U(VI)–CO_3 complexes. • Use of NZVI is feasible for remediation of uranium-contaminated soils. • The mechanism of U(VI)–CO_3 complexes adsorbing onto NZVI has been explained. - Abstract: The influence of U(VI)–CO_3 and Ca–U(VI)–CO_3 complexes on U(VI) adsorption onto red soil and nanoscale zero-valent iron (NZVI) was investigated using batch adsorption and fixed-bed column experiments to simulate the feasibility of NZVI as the reactive medium in permeable- reactive barriers (PRB) for in situ remediation of uranium-contaminated red soils. The adsorption capacity (q_e) and distribution constant (K_d) of NZVI and red soil decreased with increasing pH, dissolved carbonate and calcium concentrations, but the q_e and K_d values of NZVI were 5–10 times higher than those of red soil. The breakthrough pore volume (PV) values increased with the decrease of pH, dissolved carbonate and calcium concentration; however, the breakthrough PV values of the PRB column filled with 5% NZVI were 2.0–3.5 times higher than the 100% red soil column. The U(VI)–CO_3 complexes adsorbed onto the surface of red soil/NZVI (≡SOH) to form SO–UO_2CO_3"− or SO–UO_2 (CO_3)_2"3"−. XPS and XRD analysis further confirmed the reduction of U(VI) to U(IV) and the formation of FeOOH on NZVI surfaces. The findings of this study are significant to the remediation of uranium-contaminated red soils and the consideration of practical U(VI) species in the natural environment.

  15. Comparison of U(VI) adsorption onto nanoscale zero-valent iron and red soil in the presence of U(VI)–CO{sub 3}/Ca–U(VI)–CO{sub 3} complexes

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Zhibin [Key Laboratory of Radioactive Geology and Exploration Technology Fundamental Science for National Defense, East China Institute of Technology, Nanchang 330013 (China); State Key Laboratory Breeding Base of Nuclear Resources and Environment (East China Institute of Technology), Ministry of Education, Nanchang 330013 (China); Chemistry, Biological and Materials Sciences Department, East China Institute of Technology, Nanchang 330013 (China); Liu, Jun [State Key Laboratory Breeding Base of Nuclear Resources and Environment (East China Institute of Technology), Ministry of Education, Nanchang 330013 (China); Cao, Xiaohong, E-mail: xhcao@ecit.cn [Key Laboratory of Radioactive Geology and Exploration Technology Fundamental Science for National Defense, East China Institute of Technology, Nanchang 330013 (China); State Key Laboratory Breeding Base of Nuclear Resources and Environment (East China Institute of Technology), Ministry of Education, Nanchang 330013 (China); Chemistry, Biological and Materials Sciences Department, East China Institute of Technology, Nanchang 330013 (China); Luo, Xuanping [Chemistry, Biological and Materials Sciences Department, East China Institute of Technology, Nanchang 330013 (China); Hua, Rong; Liu, Yan [Key Laboratory of Radioactive Geology and Exploration Technology Fundamental Science for National Defense, East China Institute of Technology, Nanchang 330013 (China); State Key Laboratory Breeding Base of Nuclear Resources and Environment (East China Institute of Technology), Ministry of Education, Nanchang 330013 (China); Chemistry, Biological and Materials Sciences Department, East China Institute of Technology, Nanchang 330013 (China); Yu, Xiaofeng; He, Likai [Chemistry, Biological and Materials Sciences Department, East China Institute of Technology, Nanchang 330013 (China); and others

    2015-12-30

    Highlights: • NZVI can be used for adsorbing U(VI)–CO{sub 3} complexes. • Use of NZVI is feasible for remediation of uranium-contaminated soils. • The mechanism of U(VI)–CO{sub 3} complexes adsorbing onto NZVI has been explained. - Abstract: The influence of U(VI)–CO{sub 3} and Ca–U(VI)–CO{sub 3} complexes on U(VI) adsorption onto red soil and nanoscale zero-valent iron (NZVI) was investigated using batch adsorption and fixed-bed column experiments to simulate the feasibility of NZVI as the reactive medium in permeable- reactive barriers (PRB) for in situ remediation of uranium-contaminated red soils. The adsorption capacity (q{sub e}) and distribution constant (K{sub d}) of NZVI and red soil decreased with increasing pH, dissolved carbonate and calcium concentrations, but the q{sub e} and K{sub d} values of NZVI were 5–10 times higher than those of red soil. The breakthrough pore volume (PV) values increased with the decrease of pH, dissolved carbonate and calcium concentration; however, the breakthrough PV values of the PRB column filled with 5% NZVI were 2.0–3.5 times higher than the 100% red soil column. The U(VI)–CO{sub 3} complexes adsorbed onto the surface of red soil/NZVI (≡SOH) to form SO–UO{sub 2}CO{sub 3}{sup −} or SO–UO{sub 2} (CO{sub 3}){sub 2}{sup 3−}. XPS and XRD analysis further confirmed the reduction of U(VI) to U(IV) and the formation of FeOOH on NZVI surfaces. The findings of this study are significant to the remediation of uranium-contaminated red soils and the consideration of practical U(VI) species in the natural environment.

  16. Adsorption of uranium(VI) from sulphate solutions using Amberlite IRA-402 resin: Equilibrium, kinetics and thermodynamics study

    International Nuclear Information System (INIS)

    Solgy, Mostafa; Taghizadeh, Majid; Ghoddocynejad, Davood

    2015-01-01

    Highlights: • Adsorption of uranium from sulphate solutions by an anion exchange resin. • The effects of pH, contact time and adsorbent dosage were investigated. • The adsorption equilibrium is well described by the Freundlich isotherm model. • The adsorption kinetics can be predicted by the pseudo second-order model. • The adsorption is a physical, spontaneous and endothermic process. - Abstract: In the present study, adsorption of uranium from sulphate solutions was evaluated using Amberlite IRA-402 resin. The variation of adsorption process was investigated in batch sorption mode. The parameters studied were pH, contact time and adsorbent dosage. Langmuir and Freundlich isotherm models were used in order to present a mathematical description of the equilibrium data at three different temperatures (25 °C, 35 °C and 45 °C). The final results confirmed that the equilibrium data tend to follow Freundlich isotherm model. The maximum adsorption capacity of Amberlite IRA-402 for uranium(VI) was evaluated to be 213 mg/g for the Langmuir model at 25 °C. The adsorption of uranium on the mentioned anion exchange resin was found to follow the pseudo-second order kinetic model, indicating that chemical adsorption was the rate limiting-step. The values of thermodynamic parameters proved that adsorption process of uranium onto Amberlite IRA-402 resin could be considered endothermic (ΔH > 0) and spontaneous (ΔG < 0)

  17. Preparation of graphene oxide-manganese dioxide for highly efficient adsorption and separation of Th(IV)/U(VI).

    Science.gov (United States)

    Pan, Ning; Li, Long; Ding, Jie; Li, Shengke; Wang, Ruibing; Jin, Yongdong; Wang, Xiangke; Xia, Chuanqin

    2016-05-15

    Manganese dioxide decorated graphene oxide (GOM) was prepared via fixation of crystallographic MnO2 (α, γ) on the surface of graphene oxide (GO) and was explored as an adsorbent material for simultaneous removal of thorium/uranium ions from aqueous solutions. In single component systems (Th(IV) or U(VI)), the α-GOM2 (the weight ratio of GO/α-MnO2 of 2) exhibited higher maximum adsorption capacities toward both Th(IV) (497.5mg/g) and U(VI) (185.2 mg/g) than those of GO. In the binary component system (Th(IV)/U(VI)), the saturated adsorption capacity of Th(IV) (408.8 mg/g)/U(VI) (66.8 mg/g) on α-GOM2 was also higher than those on GO. Based on the analysis of various data, it was proposed that the adsorption process may involve four types of molecular interactions including coordination, electrostatic interaction, cation-pi interaction, and Lewis acid-base interaction between Th(IV)/U(VI) and α-GOM2. Finally, the Th(IV)/U(VI) ions on α-GOM2 can be separated by a two-stage desorption process with Na2CO3/EDTA. Those results displayed that the α-GOM2 may be utilized as an potential adsorbent for removing and separating Th(IV)/U(VI) ions from aqueous solutions. Copyright © 2016 Elsevier B.V. All rights reserved.

  18. The influence of ferric iron in calcined nano-Mg/Al hydrotalcite on adsorption of Cr (VI) from aqueous solution

    Energy Technology Data Exchange (ETDEWEB)

    Xiao Lili [College of Chemistry, Dalian University of Technology, Dalian, Liaoning 116023 (China); Ma Wei, E-mail: chmawv@yahoo.com [College of Chemistry, Dalian University of Technology, Dalian, Liaoning 116023 (China); Han Mei; Cheng Zihong [College of Chemistry, Dalian University of Technology, Dalian, Liaoning 116023 (China)

    2011-02-15

    Research highlights: {yields} The reconstruction processes of CH-Mg/Al and CH-Mg/Al/Fe were fast and efficient, but the adsorption of Cr (VI) on CH-Mg/Al/Fe reached equilibrium faster. {yields} The removal mechanism involved not only intercalation but also adsorption on external surface of the layers and interlayer anion exchange. {yields} The existence of Fe3{sup +} in Mg/Al calcined hydrotalcite led to the interlayer anion exchange more difficult and it is affected equilibrium amount of Cr (VI) adsorption. - Abstract: The influence of ferric iron in calcined nano-Mg/Al hydrotalcite on removal of Cr (VI) from aqueous solution was studied from aspects of structure characteristics, adsorption properties and mechanism discussions. The calcined hydrotalcites (CH-Mg/Al and CH-Mg/Al/Fe) were obtained by thermal decomposition of their corresponding precursors and characterized by XRD, TEM, pH{sub PZC} and FTIR. The adsorption properties were studied as a function of pH, initial Cr (VI) concentration and contact time. The results showed that the nature of adsorption is endothermic and spontaneous for both CH-Mg/Al and CH-Mg/Al/Fe, but the thermodynamic parameter value changes revealed the addition of Fe{sup 3+} is disadvantage to adsorption process and the theoretical saturated adsorption capacity decreased by approximately 10.2 mg/g at tested temperatures. The removal mechanism involved not only intercalation but adsorption on external surface of the layers and interlayer anion exchange for both CH-Mg/Al and CH-Mg/Al/Fe. Furthermore, the results also indicated that intercalation accounts for a large proportion during removal process whatever for CH-Mg/Al, or for CH-Mg/Al/Fe. Additionally, the replacement of Al{sup 3+} by Fe{sup 3+} in CH-Mg/Al led to the interlayer anion exchange more difficult. On the basis of the results, it is concluded that the existence of ferric iron in calcined Mg/Al hydrotalcite is unfavorable to removal of Cr (VI) from aqueous solution.

  19. The new concept of hyphenated analytical system: Simultaneous determination of inorganic arsenic(III), arsenic(V), selenium(IV) and selenium(VI) by high performance liquid chromatography-hydride generation-(fast sequential) atomic absorption spectrometry during single analysis

    International Nuclear Information System (INIS)

    Niedzielski, P.

    2005-01-01

    The paper presents a new conception of determination of inorganic speciation forms of arsenic: As(III) and As(V) as well selenium Se(IV) and Se(VI) by means of the high performance liquid chromatography hyphenated with a detection by the atomic absorption spectrometry with hydride generation (HPLC-HG-AAS). The application of optimization procedure conditions of chromatographic separation of arsenic and selenium speciation forms (using anion-exchange Supelco LC-SAX1 column and phosphate buffer at pH 5.40 as a mobile phase) as well as the use of the atomic absorption spectrometry as a detector, which enables work in fast sequential mode, allowed to develop original detection methodology of simultaneous determination of arsenic As(III), As(V) and selenium Se(IV) and Se(VI) speciation forms within a 220 s single analysis. The obtained detection limits were 7.8 ng mL -1 for As(III); 12.0 ng mL -1 for As(V); 2.4 ng mL -1 for Se(IV) and 18.6 ng mL -1 for Se(VI) and precision 10.5%, 12.1%, 14.2% and 17.3%, respectively, for 100 ng mL -1 . The described method was used for ground water analysis

  20. Factors influencing U(VI adsorption onto soil from a candidate very low level radioactive waste disposal site in China

    Directory of Open Access Journals (Sweden)

    Zuo Rui

    2016-01-01

    Full Text Available The properties of soil at disposal sites are very important for geological disposal of very low level radioactive waste in terms of U(VI. In this study, soil from a candidate very low level radioactive waste disposal site in China was evaluated for its capacity on uranium sorption. Specifically, the equilibrium time, initial concentration, soil particle, pH, temperature, and carbonate were evaluated. The results indicated that after 15-20 days of sorption, the Kd value fluctuated and stabilized at 355-360 mL/g. The adsorptive capacity of uranium was increased as the initial uranium concentration increased, while it decreased as the soil particle size increased. The pH value played an important role in the U(VI sorption onto soil, especially under alkaline conditions, and had a great effect on the sorption capacity of soil for uranium. Moreover, the presence of carbonate decreased the sorption of U(VI onto soil because of the role of the strong complexation of carbonate with U(VI in the groundwater. Overall, this study assessed the behavior of U(VI sorption onto natural soil, which would be an important factor in the geological barrier of the repository, has contribution on mastering the characteristic of the adsorption of uranium in the particular soil media for the process of very low level radioactive waste disposal.

  1. Adsorption Isotherm of Chromium (Vi) into Zncl2 Impregnated Activated Carbon Derived by Jatropha Curcas Seed Hull

    Science.gov (United States)

    Mohammad, M.; Yakub, I.; Yaakob, Z.; Asim, N.; Sopian, K.

    2017-12-01

    Hexavalent chromium is carcinogenic and should be removed from industrial wastewater before discharged into water resources. Adsorption by using activated carbon from biomass is an economic and conventional way on removing the heavy metal ions from wastewater. In this research, activated carbon is synthesized from Jatropha curcas L. seed hull through chemical activation with ZnCl2 and carbonized at 800 °C (JAC/ZnCl2). The activated carbon has been characterized using FTIR, SEM-EDX, BET and CHNS-O analyzer. Adsorption isotherms have been analysed using Langmuir and Freundlich models to determine its removal mechanism. The maximum adsorption capacity of Cr (VI) metal ions onto JAC/ZnCl2 activated carbon is 25.189 mg/g and following Langmuir isotherm model which is monolayer adsorption.

  2. Adsorption of Cu (II), Pb (II) and Cr (VI) from aqueous solutions using black wattle tannin-immobilized nanocellulose.

    Science.gov (United States)

    Xu, Qinghua; Wang, Yulu; Jin, Liqiang; Wang, Yu; Qin, Menghua

    2017-10-05

    A novel nanocomposite based on black wattle (BW) tannin and nanocellulose was prepared and applied in heavy metal ions adsorptive removal from aqueous solutions. Firstly, nanocrystalline cellulose was oxidized by sodium periodate to get dialdehyde nanocellulose (DANC). BW tannin was then covalently immobilized onto DANC, which was used as both the matrix and crosslinker, to obtain tannin-nanocellulose (TNCC) composite. The resulting nanocomposite was characterized using FTIR, AFM, and TG. The successful immobilization was confirmed by the chromogenic reaction between FeCl 3 and TNCC and FT-IR analysis. AFM images revealed that TNCC was ellipsoidal particles with lengths ranging from 100-400nm. Zeta potential measurement showed that TNCC was negative charged at a pH range from 1-12. Compared to the original tannin, the thermal stability of TNCC was slightly increased by the addition of nanocellulose. TNCC demonstrated the maximum adsorption efficiency at pH2 for Cr(VI) and pH 6 for Cu(II) and Pb(II), respectively. The adsorption for these three metal ions followed pseudo second-order kinetics, indicating the chemisorption nature. The adsorption isotherms all fitted well with the Sips model, and the calculated maximum adsorption capacities were 51.846mgg -1 , 53.371mgg -1 and 104.592mgg -1 for Cu(II), Pb(II) and Cr (VI), respectively. Copyright © 2017 Elsevier B.V. All rights reserved.

  3. Kinetic and equilibrium characterization of uranium(VI) adsorption onto carboxylate-functionalized poly(hydroxyethylmethacrylate)-grafted lignocellulosics.

    Science.gov (United States)

    Anirudhan, T S; Divya, L; Suchithra, P S

    2009-01-01

    This study investigated the feasibility of using a new adsorbent prepared from coconut coir pith, CP (a coir industry-based lignocellulosic residue), for the removal of uranium [U(VI)] from aqueous solutions. The adsorbent (PGCP-COOH) having a carboxylate functional group at the chain end was synthesized by grafting poly(hydroxyethylmethacrylate) onto CP using potassium peroxydisulphate-sodium thiosulphite as a redox initiator and in the presence of N,N'-methylenebisacrylamide as a crosslinking agent. IR spectroscopy results confirm the graft copolymer formation and carboxylate functionalization. XRD studies confirm the decrease of crystallinity in PGCP-COOH compared to CP, and it favors the protrusion of the functional group into the aqueous medium. The thermal stability of the samples was studied using thermogravimetry (TG). Surface charge density of the samples as a function of pH was determined using potentiometric titration. The ability of PGCP-COOH to remove U(VI) from aqueous solutions was assessed using a batch adsorption technique. The maximum adsorption capacity was observed at the pH range 4.0-6.0. Maximum removal of 99.2% was observed for an initial concentration of 25mg/L at pH 6.0 and an adsorbent dose of 2g/L. Equilibrium was achieved in approximately 3h. The experimental kinetic data were analyzed using a first-order kinetic model. The temperature dependence indicates an endothermic process. U(VI) adsorption was found to decrease with an increase in ionic strength due to the formation of outer-sphere surface complexes on PGCP-COOH. Equilibrium data were best modeled by the Langmuir isotherm. The thermodynamic parameters such as DeltaG(0), DeltaH(0) and DeltaS(0) were derived to predict the nature of adsorption. Adsorption experiments were also conducted using a commercial cation exchanger, Ceralite IRC-50, with carboxylate functionality for comparison. Utility of the adsorbent was tested by removing U(VI) from simulated nuclear industry wastewater

  4. Study of polyethyleneimine- and amidoxime-functionalized hybrid biomass of Spirulina (Arthrospira) platensis for adsorption of uranium (VI) ion.

    Science.gov (United States)

    Bayramoglu, Gulay; Akbulut, Aydin; Arica, M Yakup

    2015-11-01

    This study investigates the potential application of the polyethyleneimine- (PEI) and amidoxime-modified Spirulina (Arthrospira) platensis biomasses for the removal of uranium ion in batch mode using the native biomass as a control system. The uranium ion adsorption was also characterized by attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectra, zeta potential analysis, and surface area measurement studies. The effects of pH, biomass amount, contact time, initial uranium ion concentration, and ionic strength were evaluated by using native and modified algal biomass preparations. The uranium ion removal was rapid, with more than 70% of total adsorption taking place in 40 min, and equilibrium was established within 60 min. From the experimental data, it was found that the amount of adsorption uranium ion on the algal preparations decreased in the following series: amidoxime-modified algal biomass > PEI-modified algal biomass > native algal biomass. Maximum adsorption capacities of amidoxime- and PEI-modified, and native algal biomasses were found to be 366.8, 279.5, and 194.6 mg/g, respectively, in batchwise studies. The adsorption rate of U(VI) ion by amidoxime-modified algal biomass was higher than those of the native and PEI-modified counterparts. The adsorption processes on all the algal biomass preparations followed by the Dubinin-Radushkevitch (D-R) and Temkin isotherms and pseudo-second-order kinetic models. The thermodynamic parameters were determined at four different temperatures (i.e., 15, 25, 35, and 45 °C) using the thermodynamics constant of the Temkin isotherm model. The ΔH° and ΔG° values of U(VI) ion adsorption on algal preparations show endothermic heat of adsorption; higher temperatures favor the process. The native and modified algal biomass preparations were regenerated using 10 mM HNO3. These results show that amidoxime-modified algal biomass can be a potential candidate for effective removal of U(VI) ion from

  5. Studies on adsorption capacity of clay-Sargassum sp biosorbent for Cr (VI) removal in wastewater from electroplating industry

    Science.gov (United States)

    Aprianti, Tine; Aprilyanti, Selvia; Apriani, Rachmawati; Sisnayati

    2017-11-01

    Various raw biosorbents have been studied for pollutant treatment of heavy metals contained in wastewater. In this study, clay and brown seaweed, Sargassum sp, are used for hexavalent chromium [Cr (VI)] biosorption. The adsorption capacity is adequately improved by combining clay and Sargassum sp as the adsorbent agent. Ion exchange of metal ions has shown strong coordination cross-linkage due to organic functional hydroxyl groups (OH-) contained in brown seaweed that provide sites to capture and bind the metal ions. Clay is known as an inexpensive adsorbent due to its wide availability besides its large specific surface area. Combining clay and Sargassum sp as biosorbent resulting better adsorption, the adsorption capacity reaches most favorable results of 99.39% at Sargassum: clay ratio of 40:60 on contact time 10 h. This study has proven that composit biosorbent used has succeeded in reducing hexavalent chromium pollutant in wastewater.

  6. Impact of uranyl-calcium-carbonato complexes on uranium(VI) adsorption to synthetic and natural sediments.

    Science.gov (United States)

    Stewart, Brandy D; Mayes, Melanie A; Fendorf, Scott

    2010-02-01

    Adsorption on soil and sediment solids may decrease aqueous uranium concentrations and limit its propensity for migration in natural and contaminated settings. Uranium adsorption will be controlled in large part by its aqueous speciation, with a particular dependence on the presence of dissolved calcium and carbonate. Here we quantify the impact of uranyl speciation on adsorption to both goethite and sediments from the Hanford Clastic Dike and Oak Ridge Melton Branch Ridgetop formations. Hanford sediments were preconditioned with sodium acetate and acetic acid to remove carbonate grains, and Ca and carbonate were reintroduced at defined levels to provide a range of aqueous uranyl species. U(VI) adsorption is directly linked to UO(2)(2+) speciation, with the extent of retention decreasing with formation of ternary uranyl-calcium-carbonato species. Adsorption isotherms under the conditions studied are linear, and K(d) values decrease from 48 to 17 L kg(-1) for goethite, from 64 to 29 L kg (-1) for Hanford sediments, and from 95 to 51 L kg(-1) for Melton Branch sediments as the Ca concentration increases from 0 to 1 mM at pH 7. Our observations reveal that, in carbonate-bearing waters, neutral to slightly acidic pH values ( approximately 5) and limited dissolved calcium are optimal for uranium adsorption.

  7. REMOVAL OF U(VI) IN MULTI-COMPONENT SYSTEMS BY ADSORPTION USING ACTIVATED CARBON DERIVED FROM RICE STRAW

    International Nuclear Information System (INIS)

    YAKOUT, S.M.; RIZK, M.A.

    2008-01-01

    The use of low cost activated carbon derived from rice straw has been investigated as a replacement for the current expensive methods for radionuclides removal from wastewater. The adsorption studies were carried out in multi-component systems. The effects of common cations and anions on uranium uptake were investigated. Different cations under investigation showed marginal effect on the adsorption of uranium, except in case of iron ion where the adsorption was significantly depressed by the addition of Fe ion (R % was 20%). Coexistence of iron ions at high levels may compete strongly for the adsorption sites with uranium ions resulting in a substantial reduction of uranium removal. The prepared activated carbon showed good selectivity in uranium extraction even in the presence of large concentrations (100 ppm) of anionic complexing agents and common electrolyte species.The simultaneous presence of both U(VI) / Th(IV) reduced sorption through competition for sorption sites on carbon surface. It is concluded that multi-species adsorption can be significantly affected by adsorbate interactions. Understanding these interactions needs great attention in adsorption study in the future

  8. 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)

  9. Simulating adsorption of U(VI) under transient groundwater flow and hydrochemistry: Physical versus chemical nonequilibrium model

    Science.gov (United States)

    Greskowiak, J.; Hay, M.B.; Prommer, H.; Liu, C.; Post, V.E.A.; Ma, R.; Davis, J.A.; Zheng, C.; Zachara, J.M.

    2011-01-01

    Coupled intragrain diffusional mass transfer and nonlinear surface complexation processes play an important role in the transport behavior of U(VI) in contaminated aquifers. Two alternative model approaches for simulating these coupled processes were analyzed and compared: (1) the physical nonequilibrium approach that explicitly accounts for aqueous speciation and instantaneous surface complexation reactions in the intragrain regions and approximates the diffusive mass exchange between the immobile intragrain pore water and the advective pore water as multirate first-order mass transfer and (2) the chemical nonequilibrium approach that approximates the diffusion-limited intragrain surface complexation reactions by a set of multiple first-order surface complexation reaction kinetics, thereby eliminating the explicit treatment of aqueous speciation in the intragrain pore water. A model comparison has been carried out for column and field scale scenarios, representing the highly transient hydrological and geochemical conditions in the U(VI)-contaminated aquifer at the Hanford 300A site, Washington, USA. It was found that the response of U(VI) mass transfer behavior to hydrogeochemically induced changes in U(VI) adsorption strength was more pronounced in the physical than in the chemical nonequilibrium model. The magnitude of the differences in model behavior depended particularly on the degree of disequilibrium between the advective and immobile phase U(VI) concentrations. While a clear difference in U(VI) transport behavior between the two models was noticeable for the column-scale scenarios, only minor differences were found for the Hanford 300A field scale scenarios, where the model-generated disequilibrium conditions were less pronounced as a result of frequent groundwater flow reversals. Copyright 2011 by the American Geophysical Union.

  10. 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.

  11. 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.

  12. Adsorption of chromium(VI) and Rhodamine B by surface modified tannery waste: Kinetic, mechanistic and thermodynamic studies

    Energy Technology Data Exchange (ETDEWEB)

    Anandkumar, J. [Centre for the Environment, Indian Institute of Technology Guwahati, Guwahati 781039, Assam (India); Mandal, B., E-mail: bpmandal@iitg.ernet.in [Department of Chemical Engineering, Indian Institute of Technology, Guwahati 781039, Assam (India)

    2011-02-28

    In this study, various activation methods have been employed to examine the potential reuse of tannery residual biomass (TRB) obtained from vegetable tanning process for the removal of Cr(VI) and Rhodamine B (RB) from aqueous solution. The maximum BET surface area (10.42 m{sup 2}/g), honey comb pore distribution and uptake of both Cr(VI) and RB were achieved when only 3-fold volume of HCl was used to activate the biomass. The pH and temperature experiment showed that they have considerable impact on the adsorption capacity of the used adsorbent. The presence of other ions (Na{sup +}, Ca{sup 2+} and NH{sub 4}{sup +}) significantly reduces the metal uptake but marginal enhancement in the dye removal was observed when Na{sup +} and NH{sub 4}{sup +} ions were present in the solution. The equilibrium data fitted satisfactorily with the Langmuir model and monolayer sorption capacity obtained as 177-217 and 213-250 mg/g for Cr(VI) and RB at 30-50 deg. C, respectively. The sorption kinetics was found to follow the pseudo-second-order kinetic model. The increase in adsorption capacity for both metal and dye with increase in temperature indicates that the uptake was endothermic in nature. The results indicate that the HCl modified TRB (A-TRB) could be employed as a low cost adsorbent for the removal of both Cr(VI) and RB from the aqueous solution including industrial wastewater.

  13. Facile additive-free synthesis of iron oxide nanoparticles for efficient adsorptive removal of Congo red and Cr(VI)

    Energy Technology Data Exchange (ETDEWEB)

    Hao, Tao; Yang, Chao; Rao, Xuehui; Wang, Jide [Ministry Key Laboratory of Oil and Gas Fine Chemicals, College of Chemistry and Chemical Engineering, Xinjiang University, Urumqi 830046 (China); Niu, Chunge, E-mail: ncg@petrochina.com.cn [Petrochemical Research Institute, Karamay Petrochemical Company, Karamay 834000 (China); Su, Xintai, E-mail: suxintai827@163.com [Ministry Key Laboratory of Oil and Gas Fine Chemicals, College of Chemistry and Chemical Engineering, Xinjiang University, Urumqi 830046 (China)

    2014-02-15

    The iron oxide nanoparticles had been successfully synthesized via an additive-free hydrolysis process at 75 °C for 12 h. The product was characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), and N{sub 2} adsorption–desorption. The results of XRD and N{sub 2} adsorption–desorption demonstrated that the as-prepared product was mainly α-Fe{sub 2}O{sub 3} with a large surface area of 164.1 m{sup 2} g{sup −1}. The TEM images illustrated that the as-prepared product was found to consist of a mixture of irregular spherical nanoparticles (a diameter of ∼50 nm) and nanowhiskers (a diameter of ∼50 nm and uneven length). The as-prepared product was used to investigate its promising applications in water treatment. Due to its small size and large surface area, the maximum adsorption capacities of Congo red and Cr(VI) have been determined using the Langmuir equation and found to reach up to 253.8 and 17.0 mg g{sup −1}, respectively. The facile synthesis method and the superior adsorption performance derived from the iron oxide nanoparticles display the potential applications for the removal of Congo red and Cr(VI) from aqueous solution.

  14. Characterizing particle-scale equilibrium adsorption and kinetics of uranium(VI) desorption from U-contaminated sediments

    Science.gov (United States)

    Stoliker, Deborah L.; Liu, Chongxuan; Kent, Douglas B.; Zachara, John M.

    2013-01-01

    Rates of U(VI) release from individual dry-sieved size fractions of a field-aggregated, field-contaminated composite sediment from the seasonally saturated lower vadose zone of the Hanford 300-Area were examined in flow-through reactors to maintain quasi-constant chemical conditions. The principal source of variability in equilibrium U(VI) adsorption properties of the various size fractions was the impact of variable chemistry on adsorption. This source of variability was represented using surface complexation models (SCMs) with different stoichiometric coefficients with respect to hydrogen ion and carbonate concentrations for the different size fractions. A reactive transport model incorporating equilibrium expressions for cation exchange and calcite dissolution, along with rate expressions for aerobic respiration and silica dissolution, described the temporal evolution of solute concentrations observed during the flow-through reactor experiments. Kinetic U(VI) desorption was well described using a multirate SCM with an assumed lognormal distribution for the mass-transfer rate coefficients. The estimated mean and standard deviation of the rate coefficients were the same for all Micropore volumes, assessed using t-plots to analyze N2 desorption data, were also the same for all dry-sieved micropore volumes and mass-transfer rate properties. Pore volumes for dry-sieved size fractions exceeded values for the corresponding wet-sieved fractions. We hypothesize that repeated field wetting and drying cycles lead to the formation of aggregates and/or coatings containing (micro)pore networks which provided an additional mass-transfer resistance over that associated with individual particles. The 2–8 mm fraction exhibited a larger average and standard deviation in the distribution of mass-transfer rate coefficients, possibly caused by the abundance of microporous basaltic rock fragments.

  15. Chromium (VI) ion adsorption by grafted cross-linked chitosan beads in aqueous solution - a mathematical and statistical modeling study.

    Science.gov (United States)

    Igberase, E; Osifo, P; Ofomaja, A

    2017-12-01

    Chitosan outstanding qualities and efficient way of binding metal ions even to near zero concentration is the major reason for special attention. Modification of chitosan allows the polymer to be applied in numerous field of research. Depending on the modification techniques, chitosan possesses increased adsorption capacity. In this study chitosan beads (CS) were formulated from chitosan flakes, the beads were cross-linked with glutaraldehyde and thereafter grafted with ethyldiaminetetraacetic acid. The stability and amine concentration of the beads were determined. The chemical functionalities of the beads were obtained by Fourier transform infrared spectroscopy, X-ray diffraction and thermogravimetric analysis (TGA). However, in the adsorption studies with Cr(VI), the number of runs in the experiment was obtained by response surface methodology (RSM), and the maximum adsorption capacity (Q m ) from each run was determined from the Langmuir model. The results of the experiment showed that the non-modified beads were soluble at pH 1-4 and insoluble at pH 5, while the modified beads were insoluble at pH 1-6. The amine concentration of CS, CCS and grafted cross-linked chitosan beads (GCCS) were 4.4, 3.8 and 5.0 mmol/g, respectively. The point of zero charge (pH PZC ) of GCCS was found to be 4.4. The quadratic model was significant and adequate in describing the experimental data. The difference between experimental and predicted Q m was negligible. From the design matrix and results, increased Q m was achieved at pH 5, contact time 70 min, temperature 45°C, adsorbent dosage 5 g and initial concentration 70 mg/l. The desorption of the beads loaded with Cr(VI) was successful with 0.5 M HCl eluant and contact time of 180 min, leading to cost minimization.

  16. Phosphorus-modified poly(styrene-co-divinylbenzene)–PAMAM chelating resin for the adsorption of uranium(VI) in aqueous

    Energy Technology Data Exchange (ETDEWEB)

    Cao, Qiong [College of Chemistry and Chemical Engineering, Central South University, Changsha 410083 (China); Liu, Yaochi, E-mail: liuyaochi72@163.com [College of Chemistry and Chemical Engineering, Central South University, Changsha 410083 (China); Wang, Chunzhi [Baling Company, China Petroleum and Chemical Corporation (China); Cheng, Jiashun [College of Chemistry and Chemical Engineering, Central South University, Changsha 410083 (China)

    2013-12-15

    Highlights: • A series of phosphorus-modified poly(styrene-co-divinylbenzene)–PAMAM chelating resins were synthesized. • The materials were commercially available and economic. • The new resins were high effective and selective adsorbents. • U(VI) adsorption is fitted with pseudo-second-order equation and Langmuir model. • The new resins can be regenerated. -- Abstract: Polyamidoamine (PAMAM) modified poly(styrene-co-divinylbenzene) absorbents carrying phosphorus functional groups (PS-PAMAM-PPA) were prepared and used as adsorbents for the adsorption of uranium(VI) from aqueous solution. Different generations of PAMAM were used for obtaining different chelating resins, PS-PPA, PS-1.0G PAMAM-PPA, PS-2.0G PAMAM-PPA, PS-3.0G PAMAM-PPA and PS-4.0G PAMAM-PPA. The synthesized resins were characterized by FTIR and XPS. The effects of many physio-chemical properties on metal ion adsorption to adsorbent phase, such as solution pH, kinetic studies, initial uranium concentration, temperature, were investigated using batch method. The results showed that the maximum adsorption capacity (99.89 mg/g) was observed at the pH 5.0 and 25 °C with initial U(VI) concentration 100 mg/L and adsorbent dose 1 g/L. PS-1.0G PAMAM-PPA had the largest adsorption capacity for U(VI) compared with other prepared adsorbents. The adsorption kinetics of U(VI) onto PS-1.0G PAMAM-PPA followed the mechanism of the pseudo-second-order equation, indicating that the chemical adsorption was a rate-limiting step. The calculated thermodynamic parameters (ΔG, ΔH, ΔS) stated that the adsorption of U(VI) onto PS-1.0G PAMAM-PPA were spontaneous, endothermic and feasible. The adsorption isotherms obeyed the Langmuir isotherm models. The desorption studies showed that PS-1.0G PAMAM-PPA could be used repeatedly and adsorption and desorption percentage did not have any noticeable loss after 27 cycles in a fixed bed.

  17. 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...

  18. Characterizations and Cr (VI) adsorption properties of polyaniline/filter-paper composite

    DEFF Research Database (Denmark)

    Li, Xiaoqiang; Liu, Wanwan; Li, Mengjuan

    2014-01-01

    Polyaniline/filter-paper (PANI/FP) composite was prepared by in situ polymerization of polyaniline onto FP and subsequently evaluated for the removal of Cr (VI) from aqueous solution. Scanning electron microscopy and Fourier-transform infrared were used to investigate the morphology...

  19. Studies on adsorption behaviour of Cr(VI) onto synthetic hydrous ...

    African Journals Online (AJOL)

    Results indicate the following order to fit the isotherms equations: Redlich- ... The results are compared, and indicated that the best fit is obtained with the Lagergren or pseudo first-order and the power-function models. ... the exothermic nature of the adsorption process and the other is the ion-ion type ... HOW TO USE AJOL.

  20. Batch wise removal of chromium (vi) by adsorption on novel synthesized poly aniline composites with various brans and iso thermal modeling of equilibrium data

    International Nuclear Information System (INIS)

    Kanwal, F.; Rehman, R.; Anwar, J.; Saeed, M.

    2012-01-01

    Summary: Several novel adsorbents have been investigated now-a-days for removal of poisonous substances from waste water. In this research work, poly aniline composites with rice bran, maize bran and wheat bran had been synthesized and applied for the adsorption of Cr(Vi) from waste water. Morphological changes occurring in the surface of composites were characterized by recording their FT-IR spectra. Rice bran, maize bran and wheat bran modified the surface morphology of polyaniline by preventing the aggregation of monomers resulting in improved adsorption capacity. Operational conditions were optimized and applied to Langmuir and Freundlich isotherms for investigating the adsorption mechanism and maximum sorption capacity. Thermodynamic studies positively showed the feasibleness of these adsorbents for the removal of Cr(Vi). (author)

  1. Modeling uranium(VI) adsorption onto montmorillonite under varying carbonate concentrations: A surface complexation model accounting for the spillover effect on surface potential

    Science.gov (United States)

    Tournassat, C.; Tinnacher, R. M.; Grangeon, S.; Davis, J. A.

    2018-01-01

    The prediction of U(VI) adsorption onto montmorillonite clay is confounded by the complexities of: (1) the montmorillonite structure in terms of adsorption sites on basal and edge surfaces, and the complex interactions between the electrical double layers at these surfaces, and (2) U(VI) solution speciation, which can include cationic, anionic and neutral species. Previous U(VI)-montmorillonite adsorption and modeling studies have typically expanded classical surface complexation modeling approaches, initially developed for simple oxides, to include both cation exchange and surface complexation reactions. However, previous models have not taken into account the unique characteristics of electrostatic surface potentials that occur at montmorillonite edge sites, where the electrostatic surface potential of basal plane cation exchange sites influences the surface potential of neighboring edge sites ('spillover' effect). A series of U(VI) - Na-montmorillonite batch adsorption experiments was conducted as a function of pH, with variable U(VI), Ca, and dissolved carbonate concentrations. Based on the experimental data, a new type of surface complexation model (SCM) was developed for montmorillonite, that specifically accounts for the spillover effect using the edge surface speciation model by Tournassat et al. (2016a). The SCM allows for a prediction of U(VI) adsorption under varying chemical conditions with a minimum number of fitting parameters, not only for our own experimental results, but also for a number of published data sets. The model agreed well with many of these datasets without introducing a second site type or including the formation of ternary U(VI)-carbonato surface complexes. The model predictions were greatly impacted by utilizing analytical measurements of dissolved inorganic carbon (DIC) concentrations in individual sample solutions rather than assuming solution equilibration with a specific partial pressure of CO2, even when the gas phase was

  2. Covalently bonded ionic liquid onto cellulose for fast adsorption and efficient separation of Cr(VI): Batch, column and mechanism investigation.

    Science.gov (United States)

    Dong, Zhen; Zhao, Long

    2018-06-01

    Combining the advantages of both cellulose and ionic liquid, ionic liquid functionalized cellulose (ILFC) as adsorbent was prepared through radiation grafting glycidyl methacrylate onto cellulose microsphere following by reaction with ionic liquid 1-aminopropyl-3-methyl imidazolium nitrate. Its adsorption properties towards Cr(VI) were investigated in batch and column experiments. In batch experiments, the adsorption kinetics was well fitted with pseudo-second-order mode with equilibrium time of 2 h and the adsorption capacity reached 181.8 mg/g at pH 2 calculated from Langmuir model. In fixed column, both Yoon-Nelson and Thomas models gave satisfactory fit to experimental data and breakthrough curves, and equilibrium adsorption capacity calculated by Thomas model was 161.0 mg/g. Moreover, ILFC exhibited high selectivity towards Cr(VI) even in synthetic chrome-plating wastewater. Besides, adsorption/desorption test revealed ILFC can be regenerated and reused several times without obvious decrease in adsorbed amount. The adsorption process was demonstrated to anion exchange-reduction mechanism via XPS analysis. Copyright © 2018 Elsevier Ltd. All rights reserved.

  3. 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.

  4. 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.

  5. Laser-ignited frontal polymerization of shape-controllable poly(VI-co-AM) hydrogels based on 3D templates toward adsorption of heavy metal ions

    Science.gov (United States)

    Fan, Suzhen; Liu, Sisi; Wang, Xiao-Qiao; Wang, Cai-Feng; Chen, Su

    2016-06-01

    Given the increasing heavy metal pollution issue, fast preparation of polymeric hydrogels with excellent adsorption property toward heavy metal ions is very attractive. In this work, a series of poly( N-vinylimidazole-co-acrylamide) (poly(VI-co-AM)) hydrogels were synthesized via laser-ignited frontal polymerization (LIFP) for the first time. The dependence of frontal velocity and temperature on two factors monomer ratios and initiator concentrations was systematically investigated. Poly(VI-co-AM) hydrogels with any self-supporting shapes can be synthesized by a one-step LIFP in seconds through the application of 3D templates. These shape-persistent hydrogels are pH-responsive and exhibit excellent adsorption/desorption characteristics toward Mn(II), Zn(II), Cd(II), Ni(II), Cu(II) and Co(II) ions, and the adsorption conformed to the pseudo-second-order kinetic model. The reusability of the hydrogels toward mental ions adsorption was further researched, which suggested that the hydrogels can be reused without serious decrease in adsorption capacity. This work might open a promising strategy to facilely prepare shape-controllable hydrogels and expand the application of LIFP.

  6. 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

  7. Lithium adsorption and migration in group IV-VI compounds and GeS/graphene heterostructures: a comparative study.

    Science.gov (United States)

    Hao, Kuan-Rong; Fang, Lincan; Yan, Qing-Bo; Su, Gang

    2018-04-18

    By means of first-principles calculations, the adsorption and transport properties of lithium (Li) in orthorhombic group IV-VI compounds MX (M = Ge, Sn; X = S, Se) and GeS/graphene heterostructures have been systematically investigated. Strong interactions and distinct charge transfer between Li and compounds MX are observed. The Li diffusion barriers along the zigzag direction are found to be much lower than that along the armchair direction in monolayer and bulk MX, showing distinct anisotropic diffusion features. In particular, monolayer GeS has a lowest barrier of 0.173 eV (zigzag) among them and it will transit from a semiconductor to a metallic state after Li intercalation, indicating fast Li and electron transport properties. As a comparison, the addition of graphene in a GeS/graphene heterostructure could enhance its binding with Li, decrease the Li diffusion barrier and inhibit the volume expansion dramatically, suggesting a potential performance improvement. Our study not only reveals the directional transport properties of Li in MX, but also improves the understanding of the role of graphene in the MX/graphene heterostructure, and shows great potential application in the field of electrode materials.

  8. Synthesis of Cross-Linked Chitosan and Application to Adsorption and Speciation of Se (VI and Se (IV in Environmental Water Samples by Inductively Coupled Plasma Optical Emission Spectrometry

    Directory of Open Access Journals (Sweden)

    Yang Bai

    2011-06-01

    Full Text Available A new type of cross-linked chitosan was synthesized with Diethylene Triamine (DCCTS. The adsorption of Se (VI on DCCTS was studied. The effect factors on adsorption and the adsorption mechanism were considered. The results indicated that the DCCTS could concentrate and separate Se (IV at pH = 3.6; the maximum adsorption efficiency was 94%, the adsorption equilibrium time was 30 min; the maximum adsorption capacity was 42.7 mg/g; the adsorption fitted Langmuir equation. A novel method for speciation of Se (VI and Se (IV in environmental water samples has been developed using DCCTS as adsorbent and ICP–OES as determination means. The detection limit of this method was 12 ng/L, the relatively standard deviation was 4.5% and the recovery was 99%~104%.

  9. Effect of fulvic acid on adsorptive removal of Cr(VI) and As(V) from groundwater by iron oxide-based adsorbents

    KAUST Repository

    Uwamariya, V.

    2015-05-15

    Abstract Natural contamination has become a challenging problem in drinking water production due to metal contamination of groundwater throughout the world, and arsenic and chromium are well-known toxic elements. In this study, iron oxide-coated sand (IOCS) and granular ferric hydroxide (GFH) were used to study the effects of fulvic acid (FA) on the adsorptive removal of Cr(VI) and As(V) from synthetic groundwater. IOCS and GFH were characterized by SEM/EDS, and experiments were performed at different pH levels (6, 7, and 8). The surface of IOCS and GFH showed a high content of Fe and O (75 and 60 % of the atomic composition, respectively), suggesting that they can highly effectively adsorb Cr(VI) and As(V). Adsorption tests with the simultaneous presence of As(V) and FA, on the one hand, and Cr(VI) with FA, on the other hand, revealed that the role of FA on chromate and arsenate adsorption was insignificant at almost all pH values investigated with both adsorbents. A small influence as a result of FA was only observed for the removal of As(V) by IOCS at pH 6 with a decrease of 13 and 23 % when 2 and 5 mg/l were added to the synthetic water, respectively. It was also found that organic matter (OM) was leached from the IOCS during batch adsorption experiments. The use of FEEM revealed that humic-like, fulvic-like, and protein-like organic matter fractions are present on the IOCS surface. © 2015 Springer International Publishing Switzerland.

  10. 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

  11. 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.

  12. 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.

  13. Assessment of Cadmium (II) and Chromium (VI) removal from aqueous solution using coconut “Cocosnucifera” Coir as biosorbent in batch and fixed-bed column adsorption

    International Nuclear Information System (INIS)

    Capili, M.L.S.; Escover, J.J.; San Miguel, J.A.N.; Duavis, A.G.; Sucgang, R.J.

    2015-01-01

    Heavy metals from industrial effluents are considered contaminants and pose various health risks. Coconut coir is an agricultural waste material abundantly found in the Philippines and is a potential biosorbent of heavy metals. The adsorption of cadmium (II) and chromium (VI) in aqueous solutions were studied under different parameters using coconut coir as the adsorbent. The properties of coconut coir such as crystalline and morphological structure, along with the functional groups present were determined using XRD, SEM and FTIR respectively. The effect of solution pH, initial metal ion concentration and adsorbent dose were determined and optimized concentration of each solution was carried out using AAS. XRF was done to prove that the decrease of metal concentration in the solution was due to the adsorption of the coir. The data obtained from the optimum parameter of each metal were fitted to the Freundlich and Langmuir isotherm models as well as Elovich, first-order and second-order Lagergren kinetic models. These parameters were also used for the adsorption column experiment to determine and compare the adsorption capacity of the coir when applied to a continuous process. Removal optimum parameters for cadmium were at pH 4, initial metal ion concentration of 0.2 mg/L and 0.6g adsorbent dose with a removal efficiency of 99.62%. Optimum parameters for chromium were obtained at pH 5, initial metal ion concentration of 1.2 mg/L and 1g adsorbent dose with a removal efficiency 10.52%. The study indicated that coconut coir is significantly effective in the adsorption of cadmium ions in aqueous solutions than chromium ions based on the reported removal efficiency.(author)

  14. Simultaneous adsorption and reduction of U(VI) on reduced graphene oxide-supported nanoscale zerovalent iron

    Energy Technology Data Exchange (ETDEWEB)

    Sun, Yubing [School of Environment and Chemical Engineering, North China Electric Power University, Beijing 102206 (China); Institute of Plasma Physics, Chinese Academy of Science, P.O. Box 1126, Hefei, 230031 (China); Ding, Congcong; Cheng, Wencai [Institute of Plasma Physics, Chinese Academy of Science, P.O. Box 1126, Hefei, 230031 (China); Wang, Xiangke, E-mail: xkwang@ipp.ac.cn [School of Environment and Chemical Engineering, North China Electric Power University, Beijing 102206 (China); Faculty of Engineering, King Abdulaziz University, Jeddah 21589 (Saudi Arabia)

    2014-09-15

    Graphical abstract: - Highlights: • Sorption and in-situ reduction of U(VI) is observed. • The composites are more effective for U(VI) removal and solidification. • The inner-sphere surface complexes are observed. - Abstract: The reduced graphene oxide-supported nanoscale zero-valent iron (nZVI/rGO) composites were synthesized by chemical deposition method and were characterized by SEM, high resolution TEM, Raman and potentiometric acid-base titrations. The characteristic results showed that the nZVI nanoparticles can be uniformly dispersed on the surface of rGO. The removal of U(VI) on nZVI/rGO composites as a function of contact time, pH and U(VI) initial concentration was investigated by batch technique. The removal kinetics of U(VI) on nZVI and nZVI/rGO were well simulated by a pseudo-first-order kinetic model and pseudo-second-order kinetic model, respectively. The presence of rGO on nZVI nanoparticles increased the reaction rate and removal capacity of U(VI) significantly, which was attributed to the chemisorbed OH{sup −} groups of rGO and the massive enrichment of Fe{sup 2+} on rGO surface by XPS analysis. The XRD analysis revealed that the presence of rGO retarded the transformation of iron corrosion products from magnetite/maghemite to lepidocrocite. According to the fitting of EXAFS spectra, the U-C (at ∼2.9 Å) and U-Fe (at ∼3.2 Å) shells were observed, indicating the formation of inner-sphere surface complexes on nZVI/rGO composites. Therefore, the nZVI/rGO composites can be suitable as efficient materials for the in-situ remediation of uranium-contaminated groundwater in the environmental pollution management.

  15. Adsorption

    Directory of Open Access Journals (Sweden)

    Sushmita Banerjee

    2017-05-01

    Full Text Available Application of saw dust for the removal of an anionic dye, tartrazine, from aqueous solutions has been investigated. The experiments were carried out in batch mode. Effect of the parameters such as pH, initial dye concentration and temperature on the removal of the dye was studied. Equilibrium was achieved in 70 min. Maximum adsorption of dye was achieved at pH 3. Removal percent was found to be dependent on the initial concentration of dye solution, and maximum removal was found to be 97% at 1 mg/L of tartrazine. The removal increases from 71% to 97% when the initial concentration of dye solution decreases from 15 mg/L to 1 mg/L. The equilibrium adsorption data were analyzed by Langmuir, Freundlich, Temkin and Dubinin–Radushkevich isotherm models. The (Langmuir adsorption capacity of the adsorbent is found to be 4.71 mg/g at 318 K. Kinetic modeling of the process of removal was carried out and the process of removal was found to follow a pseudo second order model and the value of rate constant for adsorption process was calculated as 2.7 × 10−3 g mg−1 min−1 at 318 K. The thermodynamic parameters such as change in free energy (ΔG°, enthalpy (ΔH° and entropy (ΔS° were determined and the negative values of ΔG° indicated that the process of removal was spontaneous at all values of temperatures. Further, the values of ΔH° indicated the endothermic nature of the process of removal.

  16. Quantifying differences in the impact of variable chemistry on equilibrium Uranium(VI) adsorption properties of aquifer sediments.

    Science.gov (United States)

    Stoliker, Deborah L; Kent, Douglas B; Zachara, John M

    2011-10-15

    Uranium adsorption-desorption on sediment samples collected from the Hanford 300-Area, Richland, WA varied extensively over a range of field-relevant chemical conditions, complicating assessment of possible differences in equilibrium adsorption properties. Adsorption equilibrium was achieved in 500-1000 h although dissolved uranium concentrations increased over thousands of hours owing to changes in aqueous chemical composition driven by sediment-water reactions. A nonelectrostatic surface complexation reaction, >SOH + UO₂²⁺ + 2CO₃²⁻ = >SOUO₂(CO₃HCO₃)²⁻, provided the best fit to experimental data for each sediment sample resulting in a range of conditional equilibrium constants (logK(c)) from 21.49 to 21.76. Potential differences in uranium adsorption properties could be assessed in plots based on the generalized mass-action expressions yielding linear trends displaced vertically by differences in logK(c) values. Using this approach, logK(c) values for seven sediment samples were not significantly different. However, a significant difference in adsorption properties between one sediment sample and the fines (< 0.063 mm) of another could be demonstrated despite the fines requiring a different reaction stoichiometry. Estimates of logK(c) uncertainty were improved by capturing all data points within experimental errors. The mass-action expression plots demonstrate that applying models outside the range of conditions used in model calibration greatly increases potential errors.

  17. Chitosan supramolecularly cross linked with trimesic acid - Facile synthesis, characterization and evaluation of adsorption potential for chromium(VI).

    Science.gov (United States)

    Bhatt, Ronak; Sreedhar, B; Padmaja, P

    2017-11-01

    A facile synthesis of Chitosan Supramolecularly cross-linked with Trimesic Acid (CTMA) is reported in this work. The adsorption potential of CTMA for removal of hexavalent chromium was evaluated and the influence of pH, temperature, contact time and adsorbent dose on the adsorption process was investigated. The experimental results showed that CTMA could efficiently adsorb Cr 6+ and partially reduce it to the less toxic Cr 3+ state. The maximum adsorption capacity of CTMA for Cr 6+ was found to be 129.53mg/g at pH 2.0. CTMA and chromium loaded CTMA were characterised by FT-IR, Raman, TGA-DSC, SEM-EDX, XRD, ESR and XPS spectroscopic techniques. Chitosan was observed to be cross- linked with TMA via ionic, hydrogen bonding and pi-pi supramolecular interactions while adsorption of chromium onto CTMA was by electrostatic forces and hydrogen bonding. From the observed results it was evident that CTMA was successfully applied for simultaneous removal of chromium, lead and iron from chrome plating effluent. Copyright © 2017 Elsevier B.V. All rights reserved.

  18. Developments in Synthetic Application of Selenium(IV Oxide and Organoselenium Compounds as Oxygen Donors and Oxygen-Transfer Agents

    Directory of Open Access Journals (Sweden)

    Jacek Młochowski

    2015-06-01

    Full Text Available A variety of selenium compounds were proven to be useful reagents and catalysts for organic synthesis over the past several decades. The most interesting aspect, which emerged in recent years, concerns application of hydroperoxide/selenium(IV oxide and hydroperoxide/organoselenium catalyst systems, as “green reagents” for the oxidation of different organic functional groups. The topic of oxidations catalyzed by organoselenium derivatives has rapidly expanded in the last fifteen years This paper is devoted to the synthetic applications of the oxidation reactions mediated by selenium compounds such as selenium(IV oxide, areneseleninic acids, their anhydrides, selenides, diselenides, benzisoselenazol-3(2H-ones and other less often used other organoselenium compounds. All these compounds have been successfully applied for various oxidations useful in practical organic syntheses such as epoxidation, 1,2-dihydroxylation, and α-oxyfunctionalization of alkenes, as well as for ring contraction of cycloalkanones, conversion of halomethyl, hydroxymethyl or active methylene groups into formyl groups, oxidation of carbonyl compounds into carboxylic acids and/or lactones, sulfides into sulfoxides, and secondary amines into nitrones and regeneration of parent carbonyl compounds from their azomethine derivatives. Other reactions such as dehydrogenation and aromatization, active carbon-carbon bond cleavage, oxidative amidation, bromolactonization and oxidation of bromide for subsequent reactions with alkenes are also successfully mediated by selenium (IV oxide or organoselenium compounds. The oxidation mechanisms of ionic or free radical character depending on the substrate and oxidant are discussed. Coverage of the literature up to early 2015 is provided. Links have been made to reviews that summarize earlier literature and to the methods of preparation of organoselenium reagents and catalysts.

  19. An efficient ultrasound assisted approach for the impregnation of room temperature ionic liquid onto Dowex 1 × 8 resin matrix and its application toward the enhanced adsorption of chromium (VI)

    International Nuclear Information System (INIS)

    Kalidhasan, S.; Santhana Krishna Kumar, A.; Vidya Rajesh; Rajesh, N.

    2012-01-01

    Highlights: ► Ultrasound assisted impregnation of an ionic liquid in a Dowex resin matrix is studied through various physicochemical and spectroscopic techniques. ► Chromium is adsorbed with a high adsorption capacity of 230.9 mg g −1 . ► The adsorbent is regenerated using HCl–ascorbic acid mixture. ► Chromium could be effectively detoxified from an industrial effluent and the developed method was validated with the analysis of a certified reference material. - Abstract: The work discussed in this paper is based on the utilization of ultrasound in conjunction with an ionic liquid (Aliquat 336) impregnated Dowex 1 × 8 resin for the effective adsorption of chromium. Ionic liquids are known for their selectivity toward metal extraction and ultrasonic medium offers efficient energy transfer for impregnating the ionic liquid in the resin matrix. The molecular interaction between the ionic liquid impregnated resin and chromium was studied through various physicochemical and spectroscopic techniques. The influence of various analytical parameters on the adsorption of Cr(VI) such as pH, adsorbent dosage, temperature and interference of foreign ions was studied in detail. Chromium (VI) was quantitatively adsorbed in the pH range of 3.5–4, with a high adsorption capacity of 230.9 mg g −1 in conformity with the Langmuir isotherm model. The study of thermodynamic parameters showed that the adsorption process is exothermic and spontaneous. The adsorbent could be regenerated using 1 mol L −1 HCl–0.28 mol L −1 ascorbic acid mixture. Chromium could be effectively detoxified from an industrial effluent and finally the developed method was validated with the analysis of a certified reference material (BCR-715). The obtained results indicated that the ultrasonic assisted impregnation of the room temperature ionic liquid significantly enhances and improves the removal efficiency of Cr(VI).

  20. 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

  1. 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.

  2. Effect of the humic acids in the adsorption of U (Vi) in a Mexican natural zeolite; Efecto de los acidos humicos en la adsorcion de U (VI) en una zeolita natural mexicana

    Energy Technology Data Exchange (ETDEWEB)

    Sandoval G, H. A.; Lopez del R, H.; Davila R, J. I.; Mireles G, F., E-mail: hlopezdelrio@hotmail.com [Universidad Autonoma de Zacatecas, Unidad Academica de Estudios Nucleares, Cipres No. 10, Fracc. La Penuela, 98068 Zacatecas (Mexico)

    2012-10-15

    The uranium adsorption was studied in a Mexican natural zeolite of the clinoptilolite type in presence and absence of humic acids (Ha). The adsorption kinetics of the binary U-zeolite and ternary U-Ha-zeolite systems were compared, and the effect of the humic matter impregnated in the zeolite in the uranium removal in function of the solution ph was studied. The experiments were made to environmental conditions and lightly acid ph, with fixed concentrations of uranium and Ha of 1 x 10{sup -5} M and 20 ppm, respectively, and a reason m/V of 5 mg/ml. The uranium adsorption in absence of Ha was of 96% and decreased to 45% in the ternary system U-Ha-zeolite. The data of the binary system U-zeolite were analyzed with three kinetic models of adsorption (pseudo-first order, pseudo-second order and Elovich). By means of non lineal regression was found that the uranium adsorption obeys a kinetic of pseudo-second order. It was observed that the uranium adsorption in the zeolite impregnated with Ha is favored to more ph at 5. (Author)

  3. Adsorção de cromo (VI por carvão ativado granular de soluções diluídas utilizando um sistema batelada sob pH controlado Chromium (VI adsorption by GAC from diluted solutions in batch system and controlled ph

    Directory of Open Access Journals (Sweden)

    Renata Santos Souza

    2009-09-01

    Full Text Available Na Amazônia o cromo é empregado principalmente na indústria de couro e de madeira, sendo responsável por vários problemas de saúde porque é tóxico para os seres vivos. A remoção de cromo de efluentes industriais é feita por meio de diversos processos como a adsorção. Este trabalho mostra os resultados da adsorção de Cr(VI por carvão ativado granular comercial (CAG como adsorvente de soluções diluídas empregando um sistema de adsorção batelada com controle de pH. Os grupos funcionais da superfície do CAG foram determinados pelo método de Boehm. Além disso, o efeito do pH na adsorção de Cr(VI, o equilíbrio e a cinética de adsorção foram estudados nas condições experimentais (pH = 6, MA = 6g, tempo de adsorção 90min.. Na superfície do CAG, os grupos carboxílicos foram determinados em maior concentração (MAS=0,43 mmol/gCAG, estes, presentes em concentrações elevadas aumentam a adsorção do metal, principalmente em valores de pH ácidos. A capacidade de adsorção é dependente do pH da solução, devido a sua influência nas propriedades de superfície do CAG e nas diferentes formas iônicas das soluções de Cr(VI. Os dados de equilíbrio da adsorção foram ajustados satisfatoriamente pela isoterma de Langmuir (R²=0,988, tipo favorável. A partir da cinética de adsorção a 5mg/L e 20mg/L, os resultados obtidos foram compatíveis com o valor limite preconizado na legislação nacional (Res. nº 357/05. Portanto, para o sistema experimental utilizando CAG foi eficiente na remoção de Cr(VI a partir de correntes líquidas contendo baixas concentrações do metal.In Amazonia, chromium is mainly used in the leather and wood industries. It is responsible for many health problems, because of its toxicity. These industries remove chromium waste by various processes, such as adsorption. This work shows the results of Cr(VI adsorption by commercial granular activated carbon (GAC as adsorbent from diluted

  4. Irradiated uranium reprocessing, Final report I-VI, Part VI - Separation of uranium, plutonium and fission products from HNO{sub 3} solution on the zirconium phosphate (part I), Adsorption equilibrium and kinetics; Prerada ozracenog urana. Zavrani izvestaj - I-VI, VI Deo - Odvajanje urana, plutonijuma i fisionih produkata iz rastvora HNO{sub 3} na cirkonijum fosfatu (deo I.), Ravnoteza i kinetika adsorpcije

    Energy Technology Data Exchange (ETDEWEB)

    Gal, I; Ruvarac, A [Institute of Nuclear Sciences Boris Kidric, Odeljenje za eksploataciju nuklearnog goriva, Vinca, Beograd (Serbia and Montenegro)

    1961-12-15

    Separation of uranium, plutonium and long-lived fission products was investigated on a inorganic ion exchanger. Zirconium phospate was chosen for this purpose because its ion exchanger properties were well known. This report deals with the study of equilibrium and kinetics of the adsorption.

  5. Irradiated uranium reprocessing, Final report I-VI, Part VI - Separation of uranium, plutonium and fission products from HNO3 solution on the zirconium phosphate (part I), Adsorption equilibrium and kinetics

    International Nuclear Information System (INIS)

    Gal, I.; Ruvarac, A.

    1961-12-01

    Separation of uranium, plutonium and long-lived fission products was investigated on a inorganic ion exchanger. Zirconium phospate was chosen for this purpose because its ion exchanger properties were well known. This report deals with the study of equilibrium and kinetics of the adsorption

  6. Water structure and aqueous uranyl(VI) adsorption equilibria onto external surfaces of beidellite, montmorillonite, and pyrophyllite: results from molecular simulations.

    Science.gov (United States)

    Greathouse, Jeffery A; Cygan, Randall T

    2006-06-15

    Molecular dynamics simulations were performed to provide a systematic study of aqueous uranyl adsorption onto the external surface of 2:1 dioctahedral clays. Our understanding of this key process is critical in predicting the fate of radioactive contaminants in natural groundwaters. These simulations provide atomistic detail to help explain experimental trends in uranyl adsorption onto natural media containing smectite clays. Aqueous uranyl concentrations ranged from 0.027 to 0.162 M. Sodium ions and carbonate ions (0.027-0.243 M) were also present in the aqueous regions to more faithfully model a stream of uranyl-containing groundwater contacting a mineral system comprised of Na-smectite. No adsorption occurred near the pyrophyllite surface, and there was little difference in uranyl adsorption onto the beidellite and montmorillonite, despite the difference in location of clay layer charge between the two. At low uranyl concentration, the pentaaquouranyl complex dominates in solution and readily adsorbs to the clay basal plane. At higher uranyl (and carbonate) concentrations, the mono(carbonato) complex forms in solution, and uranyl adsorption decreases. Sodium adsorption onto beidellite occurred both as inner- and outer-sphere surface complexes, again with little effect on uranyl adsorption. Uranyl surface complexes consisted primarily of the pentaaquo cation (85%) and to a lesser extent the mono(carbonato) species (15%). Speciation diagrams of the aqueous region indicate that the mono(carbonato)uranyl complex is abundant at high ionic strength. Oligomeric uranyl complexes are observed at high ionic strength, particularly near the pyrophyllite and montmorillonite surfaces. Atomic density profiles of water oxygen and hydrogen atoms are nearly identical near the beidellite and montmorillonite surfaces. Water structure therefore appears to be governed by the presence of adsorbed ions and not by the location of layer charge associated with the substrate. The water

  7. Eco-friendly waste water treatment by cow dung powder (adsorption studies of Cr(III), Cr(VI) and Cd(II) using tracer technique)

    International Nuclear Information System (INIS)

    Bagla, Hemlata; Barot, Nisha

    2010-01-01

    A rising quality of life with high rate of resource consumption have an unintended and negative impact on environment, generating waste hulk with far beyond handling capacities of mankind. The threat of water famine looms greatest as our rivers are poisoned due to urbanization and industrialization. To combat against water pollution and to find sustainable solution for the same, globally, we have embraced Green chemistry approach which is one of the Waste Management and Treatment Strategies. In the present investigation we have studied different parameters for the effective adsorption of heavy metal pollutant employing dry cow dung powder as a natural adsorbent. (author)

  8. Adsorption of uranium on halloysite

    International Nuclear Information System (INIS)

    Kilislioglu, A.; Bilgin, B.

    2002-01-01

    Adsorption of uranium (U(VI)) from aqueous solutions on halloysite type clay was studied as a function of amount of adsorbent, initial concentration and pH. The values of adsorption data were fitted to Freundlich, Langmuir and Dubinin-Radushkevich (D-R) adsorption isotherms. The mean energy of adsorption was calculated as 5.91 kJ/mol from D-R adsorption isotherm. Lagergren and Bangham equation has been used for dynamic modelling of process and the rate constants of adsorption of uranium on halloysite type clay were calculated at 293, 313 and 333 K. In order to explain the mechanism of adsorption reaction, the rate constants were calculated at high and low uranium concentrations. Adsorption reaction was studied at 293, 303, 313, 323 and 333 K for halloysite type clay and also thermodynamic constants have been calculated. The results show that the adsorption reaction was endothermic and more spontaneous at high temperature. (orig.)

  9. Adsorption of uranium on halloysite

    Energy Technology Data Exchange (ETDEWEB)

    Kilislioglu, A.; Bilgin, B. [Istanbul Univ. (Turkey). Faculty of Engineering

    2002-07-01

    Adsorption of uranium (U(VI)) from aqueous solutions on halloysite type clay was studied as a function of amount of adsorbent, initial concentration and pH. The values of adsorption data were fitted to Freundlich, Langmuir and Dubinin-Radushkevich (D-R) adsorption isotherms. The mean energy of adsorption was calculated as 5.91 kJ/mol from D-R adsorption isotherm. Lagergren and Bangham equation has been used for dynamic modelling of process and the rate constants of adsorption of uranium on halloysite type clay were calculated at 293, 313 and 333 K. In order to explain the mechanism of adsorption reaction, the rate constants were calculated at high and low uranium concentrations. Adsorption reaction was studied at 293, 303, 313, 323 and 333 K for halloysite type clay and also thermodynamic constants have been calculated. The results show that the adsorption reaction was endothermic and more spontaneous at high temperature. (orig.)

  10. Polyaniline (PANI) modified bentonite by plasma technique for U(VI) removal from aqueous solution

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Xinghao [Institute of Nuclear Physics and Chemistry, China Academy of Engineering Physics, Mianyang 621900 (China); Intelligent Manufacturing Technology Research Institute, Hefei University of Technology, Hefei 230088 (China); Cheng, Cheng [Institute of Plasma Physics, Chinese Academy of Sciences, Hefei 230031 (China); Xiao, Chengjian, E-mail: xiaocj@caep.cn [Institute of Nuclear Physics and Chemistry, China Academy of Engineering Physics, Mianyang 621900 (China); Shao, Dadong, E-mail: shaodadong@126.com [Institute of Plasma Physics, Chinese Academy of Sciences, Hefei 230031 (China); Xu, Zimu, E-mail: xzm@mail.ustc.edu.cn [Intelligent Manufacturing Technology Research Institute, Hefei University of Technology, Hefei 230088 (China); Wang, Jiaquan; Hu, Shuheng [Intelligent Manufacturing Technology Research Institute, Hefei University of Technology, Hefei 230088 (China); Li, Xiaolong; Wang, Weijuan [Institute of Nuclear Physics and Chemistry, China Academy of Engineering Physics, Mianyang 621900 (China)

    2017-07-31

    Highlights: • PANI/bentonie can be synthesized by simple plasma technique. • PANI/bentonie has an excellent adsorption capacity for trace uranium in solution. • U(VI) adsorption on PANI/bentonite is a spontaneous and endothermic process. - Abstract: Polyaniline (PANI) modified bentonite (PANI/bentonie) was synthesized by plasma induced polymerization of aniline on bentonite surface, and applied to uptake of uranium(VI) ions from aqueous solution. The as-synthesized PANI/bentonie was characterized by scanning electron microscopy (SEM), powder X-ray diffraction (XRD), thermal gravimetric analysis (TGA), and X-ray photoelectron spectroscopy (XPS). Batch adsorption technique was utilized to investigate the adsorption of U(VI) on bentonite and PANI/bentonite. The adsorption of U(VI) (10 mg/L) on PANI/bentonite surface is fairly depend on solution pH, ionic strength, and temperature in solution. The modified PANI on PANI/bentonite surface significantly enhances its adsorption capability for U(VI). The presence of humic acid (HA) can sound enhance U(VI) adsorption on PANI/bentonite at pH < 6.5 because of the strong complexation, and inhibits U(VI) adsorption at pH > 6.5. According to the thermodynamic parameters, the adsorption of U(VI) on PANI/bentonite surface is a spontaneous and endothermic process. The results highlight the application of PANI/bentonite composites as candidate material for the uptake of trace U(VI) from aqueous solution.

  11. Sorption mechanism of U(VI) on to natural soil system: a study using intra-particle diffusion model

    International Nuclear Information System (INIS)

    Rout, S.; Kumar, A.; Ravi, P.M.; Tripathi, R.M.

    2015-01-01

    The rate of U(VI) adsorption onto natural soils from different parent materials has been studied experimentally using the batch adsorption method at five different initial U(VI) concentrations. The utility of Weber and Morris Interparticle diffusion model for describing the mechanism and kinetics of sorption is discussed. The study reveals that the mechanism of U(VI) sorption involves three steps such as: external surface adsorption, gradual adsorption stage which is the rate determining step and the last portion refers to the final equilibrium stage. The steps involved in sorption of U(VI) on to soil is same irrespective of soil types and initial U(VI) concentration. (author)

  12. Adsorptive property of rice husk for uranium

    International Nuclear Information System (INIS)

    Feng Yuan; Yi Facheng

    2011-01-01

    The adsorption experiments were researched by using the rice husk powder as the adsorbent to remove the U(VI) from aqueous solution. The affecting factors on the U(VI) removal rate such as rice husk particle size, pH, initial concentration, adsorption time, temperature and dosage of adsorbent were evaluated, kinetics and adsorption isotherm law were analyzed, and mechanisms for U(VI) removal were discussed by SEM, FT-IR and energy spectrum analysis. The results show that U(VI) removal rate increases with the decrease of the size of adsorbent, and with the increase of adsorbent dosage and temperature. The process of adsorption can be described by an equation of pseudo 2nd-order mode, and the relation coefficient is 1. The process of adsorption also fits to Freundlich isotherm (R 2 =0.995 4). The adsorption of uranium on rice husk changes the surface form of rice husk. Hydroxyl, carboxylic, P-O and Si-O are the main functional groups in the reaction with U(VI). The adsorption mechanism is mixture adsorption, including the physical and chemical adsorption. (authors)

  13. 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

  14. 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.

  15. 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.

  16. Mucopolysaccharidosis VI

    Directory of Open Access Journals (Sweden)

    Harmatz Paul

    2010-04-01

    Full Text Available Abstract Mucopolysaccharidosis VI (MPS VI is a lysosomal storage disease with progressive multisystem involvement, associated with a deficiency of arylsulfatase B leading to the accumulation of dermatan sulfate. Birth prevalence is between 1 in 43,261 and 1 in 1,505,160 live births. The disorder shows a wide spectrum of symptoms from slowly to rapidly progressing forms. The characteristic skeletal dysplasia includes short stature, dysostosis multiplex and degenerative joint disease. Rapidly progressing forms may have onset from birth, elevated urinary glycosaminoglycans (generally >100 μg/mg creatinine, severe dysostosis multiplex, short stature, and death before the 2nd or 3rd decades. A more slowly progressing form has been described as having later onset, mildly elevated glycosaminoglycans (generally ARSB gene, located in chromosome 5 (5q13-5q14. Over 130 ARSB mutations have been reported, causing absent or reduced arylsulfatase B (N-acetylgalactosamine 4-sulfatase activity and interrupted dermatan sulfate and chondroitin sulfate degradation. Diagnosis generally requires evidence of clinical phenotype, arylsulfatase B enzyme activity ®, clinical management was limited to supportive care and hematopoietic stem cell transplantation. Galsulfase is now widely available and is a specific therapy providing improved endurance with an acceptable safety profile. Prognosis is variable depending on the age of onset, rate of disease progression, age at initiation of ERT and on the quality of the medical care provided.

  17. Polyaniline (PANI) modified bentonite by plasma technique for U(VI) removal from aqueous solution

    International Nuclear Information System (INIS)

    Liu, Xinghao; Cheng, Cheng; Xiao, Chengjian; Shao, Dadong; Xu, Zimu; Wang, Jiaquan; Hu, Shuheng; Li, Xiaolong; Wang, Weijuan

    2017-01-01

    Highlights: • PANI/bentonie can be synthesized by simple plasma technique. • PANI/bentonie has an excellent adsorption capacity for trace uranium in solution. • U(VI) adsorption on PANI/bentonite is a spontaneous and endothermic process. - Abstract: Polyaniline (PANI) modified bentonite (PANI/bentonie) was synthesized by plasma induced polymerization of aniline on bentonite surface, and applied to uptake of uranium(VI) ions from aqueous solution. The as-synthesized PANI/bentonie was characterized by scanning electron microscopy (SEM), powder X-ray diffraction (XRD), thermal gravimetric analysis (TGA), and X-ray photoelectron spectroscopy (XPS). Batch adsorption technique was utilized to investigate the adsorption of U(VI) on bentonite and PANI/bentonite. The adsorption of U(VI) (10 mg/L) on PANI/bentonite surface is fairly depend on solution pH, ionic strength, and temperature in solution. The modified PANI on PANI/bentonite surface significantly enhances its adsorption capability for U(VI). The presence of humic acid (HA) can sound enhance U(VI) adsorption on PANI/bentonite at pH 6.5. According to the thermodynamic parameters, the adsorption of U(VI) on PANI/bentonite surface is a spontaneous and endothermic process. The results highlight the application of PANI/bentonite composites as candidate material for the uptake of trace U(VI) from aqueous solution.

  18. Extraction of uranium (VI) from sea water using hydrous metalic oxide binded with hydrophilic polymers

    International Nuclear Information System (INIS)

    Shigetomi, Yasumasa; Kojima, Takehiro; Kamba, Hideaki

    1978-01-01

    In the past five years, many researches have been made to extract U(VI) from sea water. This is a report of the extraction of U(VI) from sea water using hydrous titanium oxide binded with hydrophilic polymers, the apparatus for the adsorption and the separation of U(VI) by means of ion exchange. (author)

  19. Synthesis and characterization of polyaniline/zeolite nanocomposite for the removal of chromium(VI from aqueous solution

    Directory of Open Access Journals (Sweden)

    Abdulsalam A. Shyaa

    2015-01-01

    Batch adsorption experiments were used to investigate the effect of various experimental parameters on the equilibrium adsorption of chromium(VI on PANI/zeolite nanocomposite. The adsorption characteristics of the composite toward Cr(VI in dilute aqueous solution were followed spectrophotometrically. The effect of contact time, size of the sorbent and the concentration of Cr(VI in solution on the metal uptake behavior of the composite were studied. It has been observed that the capacity of chromium adsorption on PANI/zeolite increases with initial metal concentration, the metal ion adsorption on surfactant is well represented by the Freundlich isotherm.

  20. Kinetic study of time-dependent fixation of U{sup VI} on biochar

    Energy Technology Data Exchange (ETDEWEB)

    Ashry, A. [Division of Agricultural and Environmental Sciences, School of Biosciences, University of Nottingham, Sutton Bonington, Leicestershire LE12 5RD (United Kingdom); Radiation Protection Department, Nuclear Research Centre, Egyptian Atomic Energy Authority, Cairo (Egypt); Bailey, E.H., E-mail: liz.bailey@nottingham.ac.uk [Division of Agricultural and Environmental Sciences, School of Biosciences, University of Nottingham, Sutton Bonington, Leicestershire LE12 5RD (United Kingdom); Chenery, S.R.N. [British Geological Survey, Nicker Hill, Keyworth, Nottingham NG12 5GG (United Kingdom); Young, S.D. [Division of Agricultural and Environmental Sciences, School of Biosciences, University of Nottingham, Sutton Bonington, Leicestershire LE12 5RD (United Kingdom)

    2016-12-15

    Biochar, a by-product from the production of biofuel and syngas by gasification, was tested as a material for adsorption and fixation of U{sup VI} from aqueous solutions. A batch experiment was conducted to study the factors that influence the adsorption and time-dependent fixation on biochar at 20 °C, including pH, initial concentration of U{sup VI} and contact time. Uranium (U{sup VI}) adsorption was highly dependent on pH but adsorption on biochar was high over a wide range of pH values, from 4.5 to 9.0, and adsorption strength was time-dependent over several days. The experimental data for pH > 7 were most effectively modelled using a Freundlich adsorption isotherm coupled to a reversible first order kinetic equation to describe the time-dependent fixation of U{sup VI} within the biochar structure. Desorption experiments showed that U{sup VI} was only sparingly desorbable from the biochar with time and isotopic dilution with {sup 233}U{sup VI} confirmed the low, or time-dependent, lability of adsorbed {sup 238}U{sup VI}. Below pH 7 the adsorption isotherm trend suggested precipitation, rather than true adsorption, may occur. However, across all pH values (4.5-9) measured saturation indices suggested precipitation was possible: autunite below pH 6.5 and either swartzite, liebigite or bayleyite above pH 6.5.

  1. Uranium(VI) transport modeling: geochemical data and submodels

    International Nuclear Information System (INIS)

    Tripathi, V.S.

    1984-01-01

    Understanding the geochemical mobility of U(VI) and modeling its transport is important in several contexts including ore genesis, uranium exploration, nuclear and mill-tailings waste management, and solution mining of uranium ores. Adsorption is a major control on partitioning of solutes at the mineral/solution interface. The effect of carbonate, fluoride, and phosphate complexing on adsorption of uranium was investigated. A critical compilation of stability constants of inorganic complexes and solid compounds of U(VI) necessary for proper design of experiment and for modeling transport of uranium was prepared. The general features of U(VI) adsorption in ligand-free systems are similar to those characteristic of other hydrolyzable metal ions. The adsorption processes studied were found to be reversible. The adsorption model developed in ligand-free systems, when solution complexing is taken into account, proved remarkably successful in describing adsorption of uranium in the presence of carbonate and fluoride. The presence of phosphate caused a much smaller decrease in the extent of adsorption than expected; however, a critical reassessment of the stability of UO 2 2+ .HPO 4 2- complexes, showed that phosphato complexes, if any, are extremely weak under experimental conditions. Removal of uranium may have occurred due to precipitation of sodium uranyl phosphates in addition to adsorption

  2. Bioprospecting of gum kondagogu (Cochlospermum gossypium) for bioremediation of uranium (VI) from aqueous solution and synthetic nuclear power reactor effluents

    International Nuclear Information System (INIS)

    Sashidhar, R.B.; Selvi, S. Kalaignana; Vinod, V.T.P.; Kosuri, Tanuja; Raju, D.; Karuna, R.

    2015-01-01

    An ecofriendly green chemistry method using a natural biopolymer, Gum Kondagogu (GK) for the removal of U (VI) from aqueous, simulated nuclear effluents was studied. The adsorption characteristic of GK towards U (VI) from aqueous solution was studied at varied pH, contact time, adsorbent dose, initial U (VI) concentration and temperature using UV–Visible spectroscopy and ICP-MS. Maximum adsorption was seen at pH 4, 0.1% GK with 60 min contact time at room temperature. The GK- U (VI) composite was characterized by FT-IR, zeta potential, TEM and SEM-EDAX. The Langmuir isotherm was found to be 487 mg of U (VI) g −1 of GK. The adsorption capacity and (%) of U (VI) was found to be 490 ± 5.4 mg g −1 and 98.5%. Moreover adsorption of U (VI) by GK was not influenced by other cations present in the simulated effluents. The adsorbed U (VI) was efficiently stripped from composite using 1 M HCl. - Highlights: • An eco-friendly method for removal of U (VI) from simulated nuclear effluents by Gum Kondagogu. • The Langmuir and Freundlich isotherm indicated favourable adsorption. • The adsorption (%) of U (VI) by GK was found to be 98.5%. • Desorption studies on biosorbed metal ions showed that HCl was a good eluent

  3. Cranial mononeuropathy VI

    Science.gov (United States)

    ... Abducens palsy; Lateral rectus palsy; VIth nerve palsy; Cranial nerve VI palsy; Sixth nerve palsy; Neuropathy - sixth nerve ... Cranial mononeuropathy VI is damage to the sixth cranial nerve. This nerve is also called the abducens nerve. ...

  4. Towards a consistent geochemical model for prediction of uranium(VI) removal from groundwater by ferrihydrite

    International Nuclear Information System (INIS)

    Gustafsson, Jon Petter; Daessman, Ellinor; Baeckstroem, Mattias

    2009-01-01

    Uranium(VI), which is often elevated in granitoidic groundwaters, is known to adsorb strongly to Fe (hydr)oxides under certain conditions. This process can be used in water treatment to remove U(VI). To develop a consistent geochemical model for U(VI) adsorption to ferrihydrite, batch experiments were performed and previous data sets reviewed to optimize a set of surface complexation constants using the 3-plane CD-MUSIC model. To consider the effect of dissolved organic matter (DOM) on U(VI) speciation, new parameters for the Stockholm Humic Model (SHM) were optimized using previously published data. The model, which was constrained from available X-ray absorption fine structure (EXAFS) spectroscopy evidence, fitted the data well when the surface sites were divided into low- and high-affinity binding sites. Application of the model concept to other published data sets revealed differences in the reactivity of different ferrihydrites towards U(VI). Use of the optimized SHM parameters for U(VI)-DOM complexation showed that this process is important for U(VI) speciation at low pH. However in neutral to alkaline waters with substantial carbonate present, Ca-U-CO 3 complexes predominate. The calibrated geochemical model was used to simulate U(VI) adsorption to ferrihydrite for a hypothetical groundwater in the presence of several competitive ions. The results showed that U(VI) adsorption was strong between pH 5 and 8. Also near the calcite saturation limit, where U(VI) adsorption was weakest according to the model, the adsorption percentage was predicted to be >80%. Hence U(VI) adsorption to ferrihydrite-containing sorbents may be used as a method to bring down U(VI) concentrations to acceptable levels in groundwater

  5. 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...

  6. Removal of chromium (vi) by using eucalyptus bark (biosorption)

    International Nuclear Information System (INIS)

    Khatoon, S.; Anwar, J.; Fatima, H.B.

    2009-01-01

    Adsorption of Chromium (VI) on the Eucalyptus bark has been studied with variation in parameters. Different parameters like particle size of adsorbent, concentration of adsorbate, amount of adsorbent, stirring speed, time, temperature and pH were studied. The adsorption has been carried out in batch process. The adsorption capacity increases with decreasing the particle size of adsorbent. The optimum conditions for the maximum adsorption are attained with 2.0 g of adsorbent, 40 ppm metal ion concentration, at room temperature (10 degree C), with 90 min contact time, with 300 rpm agitation speed and at pH 2. (author)

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

    Directory of Open Access Journals (Sweden)

    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.

  8. Influence of Calcite and Dissolved Calcium on Uranium(VI) Sorption to a Hanford Subsurface Sediment

    International Nuclear Information System (INIS)

    Dong, Wenming; Ball, William P.; Liu, Chongxuan; Wang, Zheming; Stone, Alan T.; Bai, Jing; Zachara, John M.

    2005-01-01

    The influence of calcite and dissolved calcium on U(VI) adsorption was investigated using a calcite-containing sandy silt/clay sediment from the U. S. Department of Energy Hanford site. U(VI) adsorption to sediment, treated sediment, and sediment size fractions was studied in solutions that both had and had not been preequilibrated with calcite, at initial [U(VI)] ) 10-7-10-5 mol/L and final pH ) 6.0- 10.0. Kinetic and reversibility studies (pH 8.4) showed rapid sorption (30 min), with reasonable reversibility in the 3-day reaction time. Sorption from solutions equilibrated with calcite showed maximum U(VI) adsorption at pH 8.4 (0.1. In contrast, calcium-free systems showed the greatest adsorption at pH 6.0-7.2. At pH > 8.4, U(VI) adsorption was identical from calcium-free and calcium-containing solutions. For calcite-presaturated systems, both speciation calculations and laser-induced fluorescence spectroscopic analyses indicated that aqueous U(VI) was increasingly dominated by Ca2UO2(CO3)3 0(aq) at pH<8.4 and that formation of Ca2UO2(CO3)3 0(aq) is what suppresses U(VI) adsorption. Above pH 8.4, aqueous U(VI) speciation was dominated by UO2(CO3)3 4- in all solutions. Finally, results also showed that U(VI) adsorption was additive in regard to size fraction but not in regard to mineral mass: Carbonate minerals may have blocked U(VI) access to surfaces of higher sorption affinity

  9. 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.

  10. Polyaniline (PANI) modified bentonite by plasma technique for U(VI) removal from aqueous solution

    Science.gov (United States)

    Liu, Xinghao; Cheng, Cheng; Xiao, Chengjian; Shao, Dadong; Xu, Zimu; Wang, Jiaquan; Hu, Shuheng; Li, Xiaolong; Wang, Weijuan

    2017-07-01

    Polyaniline (PANI) modified bentonite (PANI/bentonie) was synthesized by plasma induced polymerization of aniline on bentonite surface, and applied to uptake of uranium(VI) ions from aqueous solution. The as-synthesized PANI/bentonie was characterized by scanning electron microscopy (SEM), powder X-ray diffraction (XRD), thermal gravimetric analysis (TGA), and X-ray photoelectron spectroscopy (XPS). Batch adsorption technique was utilized to investigate the adsorption of U(VI) on bentonite and PANI/bentonite. The adsorption of U(VI) (10 mg/L) on PANI/bentonite surface is fairly depend on solution pH, ionic strength, and temperature in solution. The modified PANI on PANI/bentonite surface significantly enhances its adsorption capability for U(VI). The presence of humic acid (HA) can sound enhance U(VI) adsorption on PANI/bentonite at pH 6.5. According to the thermodynamic parameters, the adsorption of U(VI) on PANI/bentonite surface is a spontaneous and endothermic process. The results highlight the application of PANI/bentonite composites as candidate material for the uptake of trace U(VI) from aqueous solution.

  11. Transient groundwater chemistry near a river: Effects on U(VI) transport in laboratory column experiments

    Science.gov (United States)

    Yin, Jun; Haggerty, Roy; Stoliker, Deborah L.; Kent, Douglas B.; Istok, Jonathan D.; Greskowiak, Janek; Zachara, John M.

    2011-01-01

    In the 300 Area of a U(VI)-contaminated aquifer at Hanford, Washington, USA, inorganic carbon and major cations, which have large impacts on U(VI) transport, change on an hourly and seasonal basis near the Columbia River. Batch and column experiments were conducted to investigate the factors controlling U(VI) adsorption/desorption by changing chemical conditions over time. Low alkalinity and low Ca concentrations (Columbia River water) enhanced adsorption and reduced aqueous concentrations. Conversely, high alkalinity and high Ca concentrations (Hanford groundwater) reduced adsorption and increased aqueous concentrations of U(VI). An equilibrium surface complexation model calibrated using laboratory batch experiments accounted for the decrease in U(VI) adsorption observed with increasing (bi)carbonate concentrations and other aqueous chemical conditions. In the column experiment, alternating pulses of river and groundwater caused swings in aqueous U(VI) concentration. A multispecies multirate surface complexation reactive transport model simulated most of the major U(VI) changes in two column experiments. The modeling results also indicated that U(VI) transport in the studied sediment could be simulated by using a single kinetic rate without loss of accuracy in the simulations. Moreover, the capability of the model to predict U(VI) transport in Hanford groundwater under transient chemical conditions depends significantly on the knowledge of real-time change of local groundwater chemistry.

  12. Estudo das propriedades do pseudofruto do cajueiro na adsorção de Cr (VI

    Directory of Open Access Journals (Sweden)

    Thiago C. Medeiros

    2013-11-01

    Full Text Available Study of the cashew properties for Cr (VI adsorptionIn this study, the Cr(VI adsorption properties by cashew (Anacardium occidentale L. were studied in a batch system. The effects of pH (5.0 and 7.0, drying process – S (oven-dried and lyophilized, particle size – P (0.10 – 0.25 and 0.25 – 0.84 mm, mass of adsorbent – m (1.0 and 1.5 g initial chromium concentration – C (500 and 1000 mg L-1 contact time – t (1 and 3 h and stirring rate – v (0 and 150 rpm, on the adsorption process were studied using a fractional factorial design (27-4. Under ideal conditions the efficiency of adsorption of 87.24% for total chromium and 100.00% for Cr (VI were achieved. The maximum adsorption capacity achieved was 11.43 mg/g. The adsorbent was characterized by infrared and X-ray fluorescence spectroscopy. Test reactions performed with Cr(VI in conjunction with the aqueous extract of the adsorbent and pH monitoring during adsorption were carried out to better understand the mechanisms of adsorption. The proposed mechanism consists of two steps: reduction of Cr(VI in solution or at the surface of the adsorbent, and subsequent adsorption of Cr(III by ion exchange or complexation.

  13. Exfoliated polypyrrole-organically modified montmorillonite clay nanocomposite as a potential adsorbent for Cr (VI) removal

    CSIR Research Space (South Africa)

    Setshedi, KZ

    2013-01-01

    Full Text Available Exfoliated polypyrrole-organically modified montmorillonite clay nanocomposite (PPy OMMT NC), was prepared as a potential adsorbent, via in situ polymerization of pyrrole monomer for adsorption of toxic Cr(VI) from aqueous solution. The WAXD...

  14. Mesoporous polymer-coated PAN beads for environmental applications. Fabrication, characterisation and uranium adsorption studies

    International Nuclear Information System (INIS)

    Aly, Z.; Scales, N.; Davis, J.; Lumpkin, G.

    2017-01-01

    Adsorption of U(VI) and other heavy metals on millimetre sized polymer-coated polyacrylinitrile (PAN) beads was investigated. PAN was used as scaffolds for the polymer layer thus producing porous material of high surface area, improved mechanical strength and improved adsorption capabilities. Extensive U(VI) adsorption studies were undertaken and results modelled using different kinetic and equilibrium models. Parameters including thermodynamic parameters were evaluated. Sorbent capacities were assessed as 124, 16, and 33 mg g"-"1 for PCP, SPP and Dowex at 60 deg C respectively. U(VI) adsorption mechanism for these adsorbents was postulated. Recovered uranium may be used for production of cheap electricity. (author)

  15. Study of the removal of mercury(II) and chromium(VI) from aqueous solutions by Moroccan stevensite

    International Nuclear Information System (INIS)

    Benhammou, A.; Yaacoubi, A.; Nibou, L.; Tanouti, B.

    2005-01-01

    The objective of the present study was to investigate the adsorption of the heavy metals mercury(II) and chromium(VI), from aqueous solutions, onto Moroccan stevensite. A mineralogical and physicochemical characterization of natural stevensite was carried out. In order to improve the adsorption capacity of stevensite for Cr(VI), a preparation of stevensite was carried out. It consists in saturating the stevensite by ferrous iron Fe(II) and reducing the total Fe by Na 2 S 2 O 4 . Then, the adsorption experiments were studied in batch reactors at 25 ± 3 deg. C. The influence of the pH solution on the Cr(VI) and Hg(II) adsorption was studied in the pH range of 1.5-7.0. The optimum pH for the Cr(VI) adsorption is in the pH range of 2.0-5.0 while that of Hg(II) is at the pH values above 4.0. The adsorption kinetics were tested by a pseudo-second-order model. The adsorption rate of Hg(II) is 54.35 mmol kg -1 min -1 and that of Cr(VI) is 7.21 mmol kg -1 min -1 . The adsorption equilibrium time for Hg(II) and Cr(VI) was reached within 2 and 12 h, respectively. The adsorption isotherms were described by the Dubinin-Radushkevich model. The maximal adsorption capacity for Cr(VI) increases from 13.7 (raw stevensite) to 48.86 mmol kg -1 (modified stevensite) while that of Hg(II) decreases from 205.8 to 166.9 mmol kg -1 . The mechanism of Hg(II) and Cr(VI) adsorption was discussed

  16. Fixed bed adsorption of hexavalent chromium onto natural zeolite from air stream

    OpenAIRE

    F. Golbabaei; E. Rahmanzadeh; G. R. Moussavi; A. Faghihi zarandi; M. R. Baneshi

    2014-01-01

    Introduction: Chromium (VI) is a known human carcinogenic agent which is used in numerous industrial processes such as electroplating, welding, textile, cement and steel fabrication. The aim of this study was to determine the effectiveness of natural zeolite on the fixed bed adsorption of Cr (VI) from air stream. . Material and Method: In this experimental study, chromium mists were generated by a nebulizer (3A model, Italy). Performance of natural zeolite in the Cr (VI) adsorption and ...

  17. 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 ...

  18. Removal of chromium (VI) from electroplating wastewater using an anion exchanger derived from rice straw.

    Science.gov (United States)

    Cao, Wei; Dang, Zhi; Yia, Xiao-Yun; Yang, Chen; Lu, Gui-Ning; Liu, Yun-Feng; Huang, Se-Yan; Zheng, Liu-Chun

    2013-01-01

    An anion exchanger from rice straw was used to remove Cr (VI) from synthetic wastewater and electroplating effluent. The exchanger was characterized using Fourier transform infrared (FTIR) spectrum and scanning electron microscopy (SEM), and it was found that the quaternary amino group and hydroxyl group are the main functional groups on the fibrous surface of the exchanger. The effect of contact time, initial concentration and pH on the removal of Cr (VI), and adsorption isotherms at different temperature, was investigated. The results showed that the removal of Cr (VI) was very rapid and was significantly affected by the initial pH of the solution. Although acidic conditions (pH = 2-6) facilitated Cr (VI) adsorption, the exchanger was effective in neutral solution and even under weak base conditions. The equilibrium data fitted well with Langmuir adsorption model, and the maximum Cr (VI) adsorption capacities at pH 6.4 were 0.35, 0.36 and 0.38 mmol/g for 15, 25 and 35 degrees C, respectively. The exchanger was finally tested with real electroplating wastewater, and at sorbent dosage of 10 g/L, the removal efficiencies for Cr (VI) and total Cr were 99.4% and 97.8%, respectively. In addition, the positive relationship between adsorbed Cr (VI) and desorbed Cl- suggested that Cr (VI) was mainly removed by ion exchange with chlorine.

  19. Box-Behnken experimental design for chromium(VI) ions removal by bacterial cellulose-magnetite composites.

    Science.gov (United States)

    Stoica-Guzun, Anicuta; Stroescu, Marta; Jinga, Sorin Ion; Mihalache, Nicoleta; Botez, Adriana; Matei, Cristian; Berger, Daniela; Damian, Celina Maria; Ionita, Valentin

    2016-10-01

    In this study bacterial cellulose-magnetite composites were synthesised for the removal of chromium(VI) from aqueous solutions. Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), thermogravimetric analysis and X-ray Photoelectron Spectroscopy (XPS) were used to characterize the bacterial cellulose-magnetite composites and to reveal the uniform dispersion of nanomagnetite in the BC matrix. Magnetic properties were also measured to confirm the magnetite immobilization on bacterial cellulose membrane. The effects of initial Cr(VI) concentration, solution pH and solid/liquid ratio upon chromium removal were examined using the statistical Box-Behnken Design. Because of the possibility of magnetite dissolution during chromium(VI) adsorption, the degree of iron leaching was also analysed in the same conditions as Cr(VI) adsorption. From the factors affecting chromium(VI) adsorption the most important was solution pH. The highest Cr(VI) removal efficiency was observed at pH 4, accompanied by the lowest iron leaching in the solution. The adsorption experiments also indicated that the adsorption process of chromium(VI) is well described by Freundlich adsorption model. Our results proved that the BC-magnetite composites could be used for an efficient removal of chromium(VI) from diluted solutions with a minimum magnetite dissolution during operation. Copyright © 2016 Elsevier B.V. All rights reserved.

  20. Phosphoryl functionalized mesoporous silica for uranium adsorption

    International Nuclear Information System (INIS)

    Xue, Guo; Yurun, Feng; Li, Ma; Dezhi, Gao; Jie, Jing; Jincheng, Yu; Haibin, Sun; Hongyu, Gong; Yujun, Zhang

    2017-01-01

    Highlights: • Phosphoryl functionalized mesoporous silica (TBP-SBA-15) is synthesized. • The amino and phosphoryl groups are successfully grafted on SBA-15. • TBP-SBA-15 has high and rapid uranium adsorption capacity in broad pH range. • The U(VI) adsorption of TBP-SBA-15 is spontaneous and belongs to chemical adsorption. - Abstract: Phosphoryl functionalized mesoporous silica (TBP-SBA-15) was synthesized by modified mesoporous silica with γ-amino propyl triethoxy silane and tributyl phosphate. The obtained samples were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), small angle X-ray diffraction (SAXRD), thermo-gravimetric/differential thermalanalyzer (TG/DTA), N_2 adsorption–desorption (BET) and Fourier transform infrared spectroscopy (FT-IR) techniques. Results showed that TBP-SBA-15 had large surface areas with ordered channel structure. Moreover, the effects of adsorption time, sorbent dose, solution pH, initial uranium concentration and temperature on the uranium adsorption behaviors were investigated. TBP-SBA-15 showed a high uranium adsorption capacity in a broad range of pH values. The U(VI) adsorption rate of TBP-SBA-15 was fast and nearly achieved completion in 10 min with the sorbent dose of 1 g/L. The U(VI) adsorption of TBP-SBA-15 followed the pseudo-second-order kinetic model and Freundlich isotherm model, indicating that the process was belonged to chemical adsorption. Furthermore, the thermodynamic parameters (ΔG"0, ΔH"0 and ΔS"0) confirmed that the adsorption process was endothermic and spontaneous.

  1. Phosphoryl functionalized mesoporous silica for uranium adsorption

    Energy Technology Data Exchange (ETDEWEB)

    Xue, Guo; Yurun, Feng; Li, Ma; Dezhi, Gao; Jie, Jing; Jincheng, Yu; Haibin, Sun [Key Laboratory for Liquid-Solid Structural Evolution & Processing of Materials of Ministry of Education, Shandong University, Jinan 250061 (China); Key Laboratory of Special Functional Aggregated Materials, Ministry of Education, Shandong University, Jinan 250061 (China); Hongyu, Gong, E-mail: gong_hongyu@163.com [Key Laboratory for Liquid-Solid Structural Evolution & Processing of Materials of Ministry of Education, Shandong University, Jinan 250061 (China); Key Laboratory of Special Functional Aggregated Materials, Ministry of Education, Shandong University, Jinan 250061 (China); Yujun, Zhang, E-mail: yujunzhangcn@163.com [Key Laboratory for Liquid-Solid Structural Evolution & Processing of Materials of Ministry of Education, Shandong University, Jinan 250061 (China); Key Laboratory of Special Functional Aggregated Materials, Ministry of Education, Shandong University, Jinan 250061 (China)

    2017-04-30

    Highlights: • Phosphoryl functionalized mesoporous silica (TBP-SBA-15) is synthesized. • The amino and phosphoryl groups are successfully grafted on SBA-15. • TBP-SBA-15 has high and rapid uranium adsorption capacity in broad pH range. • The U(VI) adsorption of TBP-SBA-15 is spontaneous and belongs to chemical adsorption. - Abstract: Phosphoryl functionalized mesoporous silica (TBP-SBA-15) was synthesized by modified mesoporous silica with γ-amino propyl triethoxy silane and tributyl phosphate. The obtained samples were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), small angle X-ray diffraction (SAXRD), thermo-gravimetric/differential thermalanalyzer (TG/DTA), N{sub 2} adsorption–desorption (BET) and Fourier transform infrared spectroscopy (FT-IR) techniques. Results showed that TBP-SBA-15 had large surface areas with ordered channel structure. Moreover, the effects of adsorption time, sorbent dose, solution pH, initial uranium concentration and temperature on the uranium adsorption behaviors were investigated. TBP-SBA-15 showed a high uranium adsorption capacity in a broad range of pH values. The U(VI) adsorption rate of TBP-SBA-15 was fast and nearly achieved completion in 10 min with the sorbent dose of 1 g/L. The U(VI) adsorption of TBP-SBA-15 followed the pseudo-second-order kinetic model and Freundlich isotherm model, indicating that the process was belonged to chemical adsorption. Furthermore, the thermodynamic parameters (ΔG{sup 0}, ΔH{sup 0} and ΔS{sup 0}) confirmed that the adsorption process was endothermic and spontaneous.

  2. Removal U(VI) from artificial seawater using facilely and covalently grafted polyacrylonitrile fibers with lysine

    Energy Technology Data Exchange (ETDEWEB)

    Li, Wenting; Liu, Qi; Liu, Jingyuan; Zhang, Hongsen; Li, Rumin; Li, Zhanshuang; Jing, Xiaoyan [Key Laboratory of Superlight Material and Surface Technology, Ministry of Education, Harbin Engineering University, Harbin 150001 (China); Wang, Jun, E-mail: zhqw1888@sohu.com [Key Laboratory of Superlight Material and Surface Technology, Ministry of Education, Harbin Engineering University, Harbin 150001 (China); Institute of Advanced Marine Materials, Harbin Engineering University, 150001 (China)

    2017-05-01

    Highlights: • Novel lysine modified fibrous adsorbents were prepared using a facile and green method. • PAN-Lys exhibited high adsorption activity and fast adsorption rate. • PAN-Lys significantly remove U(VI) from simulated seawater. - Abstract: Polyacrylonitrile fibers (PANF) covalently modified with lysine (PAN-Lys) was facilely synthesized and carefully characterized. The critical factors affecting U(VI) adsorption from aqueous solution were exploited, such as initial pH, contact time, concentration and temperature. The adsorption process is strongly dependent on solution pH. With excellent adsorption capacity and high affinity toward U(VI), the process for U(VI) is extremely rapid and the equilibrium can be reached within 20 min. The thermodynamics and kinetics were strictly evaluated. In addition, the hypothetical adsorption mechanisms were proposed. Moreover, the adsorption behavior at low concentrations (3–30 μg L{sup −1}) in simulated seawater was also investigated. Therefore, PAN-Lys can be potentially utilized for the efficient removal of U(VI) from seawater.

  3. Development of Surface Complexation Models of Cr(VI) Adsorption on Soils, Sediments and Model Mixtures of Kaolinite, Montmorillonite, γ-Alumina, Hydrous Manganese and Ferric Oxides and Goethite

    Energy Technology Data Exchange (ETDEWEB)

    Koretsky, Carla [Western Michigan University

    2013-11-29

    Hexavalent chromium is a highly toxic contaminant that has been introduced into aquifers and shallow sediments and soils via many anthropogenic activities. Hexavalent chromium contamination is a problem or potential problem in the shallow subsurface at several DOE sites, including Hanford, Idaho National Laboratory, Los Alamos National Laboratory and the Oak Ridge Reservation (DOE, 2008). To accurately quantify the fate and transport of hexavalent chromium at DOE and other contaminated sites, robust geochemical models, capable of correctly predicting changes in chromium chemical form resulting from chemical reactions occurring in subsurface environments are needed. One important chemical reaction that may greatly impact the bioavailability and mobility of hexavalent chromium in the subsurface is chemical binding to the surfaces of particulates, termed adsorption or surface complexation. Quantitative thermodynamic surface complexation models have been derived that can correctly calculate hexavalent chromium adsorption on well-characterized materials over ranges in subsurface conditions, such pH and salinity. However, models have not yet been developed for hexavalent chromium adsorption on many important constituents of natural soils and sediments, such as clay minerals. Furthermore, most of the existing thermodynamic models have been developed for relatively simple, single solid systems and have rarely been tested for the complex mixtures of solids present in real sediments and soils. In this study, the adsorption of hexavalent chromium was measured as a function of pH (3-10), salinity (0.001 to 0.1 M NaNO3), and partial pressure of carbon dioxide(0-5%) on a suite of naturally-occurring solids including goethite (FeOOH), hydrous manganese oxide (MnOOH), hydrous ferric oxide (Fe(OH)3), γ-alumina (Al2O3), kaolinite (Al2Si2O5(OH)4), and montmorillonite (Na3(Al, Mg)2Si4O10(OH)2-nH2O). The results show that all of these materials can bind substantial quantities of

  4. Removal of Cr (VI) from aqueous solutions using peanut shell as adsorbent

    International Nuclear Information System (INIS)

    Ilyas, M.; Ahmad, A.; Saeed, M.

    2013-01-01

    The biosorption of Cr (VI) ions from aqueous solution by peanut shell (PNS) biosorbent was studied in a batch mode system. Factors affecting Cr (VI) biosorption such as pH (2-7), initial chromium ion concentrations (20-60 mg/l), contact time (6 h), adsorbent dosage (0.2-1.0 g) and temperature (293-313 K) were investigated. The adsorption equilibrium was established at 360 minutes. A comparison of the kinetic models has showed that pseudo-second order equation best described adsorption kinetics. Maximum adsorption was achieved at pH 2.0 and 3.0. The adsorption equilibrium data was fitted well to the Langmuir adsorption isotherm as compared to the Freundlich adsorption isotherm. The values of separation factor, R/sub L/ was found between 0.0235 and 0.0633 (0 < R/sub L/ < 1) which pointed out favorable adsorption of Cr (VI) on PNS adsorbent. The adsorption capacity was measured in terms of monolayer adsorption and was found to be 4.32 mg/g at 313 K. The thermodynamic parameters (ΔG, ΔH and ΔS) values indicated the endothermic, non spontaneous and entropy driven system of the adsorption process. (author)

  5. Sorption of U(VI) on natural sepiolite and sepiolite-agar agar composite adsorbent

    International Nuclear Information System (INIS)

    Esen, K.; Donat, R.; Cetisli, H.; Aytas, S.

    2006-01-01

    Adsorption of uranium (VI) ions onto clay minerals is one of the significant reactions affecting the transport of uranium in the environment. The use of composite adsorbents for the removal of metal ions and radionuclide from industrial wastes has attracted great interest to researchers in recent years[1]. In this study, natural sepiolite type clay and an organic compound, agar agar, were chosen as the adsorbent material. Composite adsorbent was prepared from sepiolite and agar agar. Adsorption of uranium (VI) on this composite and on natural sepiolite adsorbent was investigated. Thermodynamic investigations were carried out to get more information about the adsorption of uranium. Adsorption of U (VI) has been studied as a function of solution pH, time, temperature and initial concentration of uranium on natural sepiolite and agar agar composite. The maximum sorption yield of U (VI) on composite and on sepiolite from batch experiments is calculated approximately 89% and 76% respectively in the optimum experimental adsorption condition. The adsorption data were fitted to Freundlich and Dubinin-Radushkevich (D-R) adsorption isotherms. Using the experimental data obtained different temperatures, thermodynamic constants ΔH d egree, ΔS d egree and ΔG d egree were calculated. The results show that the adsorption process on natural sepiolite and sepiolite-agar agar composite are both egzothermic natures. [1] S. M. Hasany, M. M. Saeed, M. Ahmed, J. Radioanal. Nucl. Chem. Vol. 252 (3), 477-484 (2002)

  6. THERMODYNAMICS AND ADSORPTION ISOTHERMS FOR THE ...

    African Journals Online (AJOL)

    BAFFA

    The use of maize (Zea mays) cob for the biosorption of Cr(VI), Ni(II) and Cd(II) is ... Variations in the concentration of the different adsorbates during the adsorption process .... Langmuir isotherm is the dimensionless separation .... The use of Sago waste for the sorption of lead and copper. Water S. Afr., 24 (3), p251-256.

  7. Protein Adsorption in Three Dimensions

    Science.gov (United States)

    Vogler, Erwin A.

    2011-01-01

    Recent experimental and theoretical work clarifying the physical chemistry of blood-protein adsorption from aqueous-buffer solution to various kinds of surfaces is reviewed and interpreted within the context of biomaterial applications, especially toward development of cardiovascular biomaterials. The importance of this subject in biomaterials surface science is emphasized by reducing the “protein-adsorption problem” to three core questions that require quantitative answer. An overview of the protein-adsorption literature identifies some of the sources of inconsistency among many investigators participating in more than five decades of focused research. A tutorial on the fundamental biophysical chemistry of protein adsorption sets the stage for a detailed discussion of the kinetics and thermodynamics of protein adsorption, including adsorption competition between two proteins for the same adsorbent immersed in a binary-protein mixture. Both kinetics and steady-state adsorption can be rationalized using a single interpretive paradigm asserting that protein molecules partition from solution into a three-dimensional (3D) interphase separating bulk solution from the physical-adsorbent surface. Adsorbed protein collects in one-or-more adsorbed layers, depending on protein size, solution concentration, and adsorbent surface energy (water wettability). The adsorption process begins with the hydration of an adsorbent surface brought into contact with an aqueous-protein solution. Surface hydration reactions instantaneously form a thin, pseudo-2D interface between the adsorbent and protein solution. Protein molecules rapidly diffuse into this newly-formed interface, creating a truly 3D interphase that inflates with arriving proteins and fills to capacity within milliseconds at mg/mL bulk-solution concentrations CB. This inflated interphase subsequently undergoes time-dependent (minutes-to-hours) decrease in volume VI by expulsion of either-or-both interphase water and

  8. Vi, de civiliserede

    DEFF Research Database (Denmark)

    Nyemann, Dorthe

    2016-01-01

    Vi har i årtier troet på, at mennesker under de rette omstændigheder kan lykkes med at leve i fred og fordragelighed med hinanden. Skal vi til at erkende, at også vores samfundsstrukturer kun er en tynd fernis ovenpå et utæmmeligt voldspotentiale og egoisme?......Vi har i årtier troet på, at mennesker under de rette omstændigheder kan lykkes med at leve i fred og fordragelighed med hinanden. Skal vi til at erkende, at også vores samfundsstrukturer kun er en tynd fernis ovenpå et utæmmeligt voldspotentiale og egoisme?...

  9. Removal of Cr (VI) for the handling of industrial effluent using the magnetite

    International Nuclear Information System (INIS)

    Yamaura, Mitiko; Camilo, Ruth L.; Cohen, Victor H.; Goncalves, Maria A.

    2000-01-01

    This work deals of Cr (VI) adsorption behaviour on synthetic magnetite. Magnetite was prepared by adding an alkaline solution in an aqueous solution containing both Fe(II) and Fe(III) ions. Characterization by X-ray diffraction analysis was verified. Distribution coefficients and adsorption isotherms of chromium on magnetite were studied and magnetic field influence from 0 to 0.35 Tesla on adsorption capacity is also verified. (author)

  10. 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.

  11. 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.

  12. 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).

  13. Selective removal of U(VI) from low concentration wastewater by functionalized HKUST-1@H3PW12O40

    International Nuclear Information System (INIS)

    Hui Zhang; Jinhua Xue; Nan Hu; Jing Sun; Dexin Ding; Yongdong Wang; Le Li

    2016-01-01

    The adsorption of U(VI) from low concentration solution by HKUST-1@H 3 PW 12 O 40 was studied as a function of various experimental parameters including pH, interfering ions, contact time, initial uranium concentration and temperature by batch experiments. Equilibrium data were found to fit with Langmuir isotherm model better than Freundlich isotherm model. The kinetic adsorption was fitted by the pseudo-second-order model well. Thermodynamic data from the adsorption experiments indicate that adsorption process is spontaneous and endothermic. HKUST-1@H 3 PW 12 O 40 can selectively adsorb U(VI) from multi-metal ion solutions and the adsorption capacity of HKUST-1@H 3 PW 12 O 40 don't decrease significantly after three cycles of desorption-reuse. The results show that HKUST-1@H 3 PW 12 O 40 is suitable for removal of U(VI) from low concentration solutions. (author)

  14. Removal of U(VI) from aqueous solution using TiO{sub 2} modified β-zeolite

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Peng; Yuan, Ni; Xiong, Wei; Wu, Hanyu; Pan, Duoqiang; Wu, Wangsuo [Lanzhou Univ. (China). Radiochemistry and Nuclear Environment Laboratory; Ministry of Education, Lanzhou (China). Key Laboratory of Special Function Materials and Structure Design

    2017-07-01

    β-Zeolite was synthesized and modified with TiO{sub 2}. The synthesized materials were characterized and used for removal of U(VI) from aqueous solutions. The influences of pH, contact time and temperature on U(VI) adsorption onto modified β-zeolite by TiO{sub 2} were studied by batch technique, and XPS was employed to analysed the experimental data. The dynamic process showed that the adsorption of U(VI) onto TiO{sub 2}/β-zeolite matched the pseudo-second-order kinetics model, and the adsorption of U(VI) were significantly dependent on pH values. Through simulating the adsorption isotherms by Langmuir, Freundlich and Dubini-Radushkevich (D-R) models, it could be seen, respectively that the adsorption patterns of U(VI) onto TiO{sub 2}/β-zeolite were mainly controlled by surface complexation, and the adsorption processes were endothermic and spontaneous. The modification of β-zeolite by TiO{sub 2} it shows a novel material for the removing of U(VI) from water environment for industrialized application.

  15. Bioprospecting of gum kondagogu (Cochlospermum gossypium) for bioremediation of uranium (VI) from aqueous solution and synthetic nuclear power reactor effluents.

    Science.gov (United States)

    Sashidhar, R B; Selvi, S Kalaignana; Vinod, V T P; Kosuri, Tanuja; Raju, D; Karuna, R

    2015-10-01

    An ecofriendly green chemistry method using a natural biopolymer, Gum Kondagogu (GK) for the removal of U (VI) from aqueous, simulated nuclear effluents was studied. The adsorption characteristic of GK towards U (VI) from aqueous solution was studied at varied pH, contact time, adsorbent dose, initial U (VI) concentration and temperature using UV-Visible spectroscopy and ICP-MS. Maximum adsorption was seen at pH 4, 0.1% GK with 60 min contact time at room temperature. The GK- U (VI) composite was characterized by FT-IR, zeta potential, TEM and SEM-EDAX. The Langmuir isotherm was found to be 487 mg of U (VI) g(-1) of GK. The adsorption capacity and (%) of U (VI) was found to be 490 ± 5.4 mg g(-1) and 98.5%. Moreover adsorption of U (VI) by GK was not influenced by other cations present in the simulated effluents. The adsorbed U (VI) was efficiently stripped from composite using 1 M HCl. Copyright © 2015 Elsevier Ltd. All rights reserved.

  16. Removing uranium (VI) from aqueous solution with insoluble humic acid derived from leonardite.

    Science.gov (United States)

    Meng, Fande; Yuan, Guodong; Larson, Steven L; Ballard, John H; Waggoner, Charles A; Arslan, Zikri; Han, Fengxiang X

    2017-12-01

    The occurrence of uranium (U) and depleted uranium (DU)-contaminated wastes from anthropogenic activities is an important environmental problem. Insoluble humic acid derived from leonardite (L-HA) was investigated as a potential adsorbent for immobilizing U in the environment. The effect of initial pH, contact time, U concentration, and temperature on U(VI) adsorption onto L-HA was assessed. The U(VI) adsorption was pH-dependent and achieved equilibrium in 2 h. It could be well described with pseudo-second-order model, indicating that U(VI) adsorption onto L-HA involved chemisorption. The U(VI) adsorption mass increased with increasing temperature with maximum adsorption capacities of 91, 112 and 120 mg g -1 at 298, 308 and 318 K, respectively. The adsorption reaction was spontaneous and endothermic. We explored the processes of U(VI) desorption from the L-HA-U complex through batch desorption experiments in 1 mM NaNO 3 and in artificial seawater. The desorption process could be well described by pseudo-first-order model and reached equilibrium in 3 h. L-HA possessed a high propensity to adsorb U(VI). Once adsorbed, the release of U(VI) from L-HA-U complex was minimal in both 1 mM NaNO 3 and artificial seawater (0.06% and 0.40%, respectively). Being abundant, inexpensive, and safe, L-HA has good potential for use as a U adsorbent from aqueous solution or immobilizing U in soils. Copyright © 2017 Elsevier Ltd. All rights reserved.

  17. Investigation of the removal of chromium (VI by Nanocomposites Chitosan-tragacanth solution from aqueous solution

    Directory of Open Access Journals (Sweden)

    Adel Almasi Nahnaji

    2016-03-01

    Full Text Available Background: The aim of this study was to investigate the removal of chromium (VI by Nanocomposites Chitosan-tragacanth solution from aqueous solution. Methods: In this study, chitosan-tragacanth nanocomposites were synthesized and analyzed by electron microscopy (SEM, (TEM and Fourier transform spectroscopy (FT-IR for the size and shape of the surface. The nano-composite of chitosan-tragacanth, for the adsorption of chromium (VI in aqueous solution was used as adsorbent. Results: The optimum conditions with multiple experiments to enhance the absorption were evaluated. The highest absorption of Cr (VI was occurred in the adsorbent dosage of 0.2 g, 8 ppm concentration of chromium ions, the pH=6 and also retention time of 50 min; in 298 ˚K temperature. After determining optimal conditions of adsorption, isotherms equations and study and thermodynamic parameters were applied. Adsorption process of chromium (VI on nano-composite chitosan - Tragacanth was conformed with Temkin isotherm. Conclusion: The thermodynamic parameters such as standard Gibbs free energy changes, changes in enthalpy and entropy changes in the standard showed that the adsorption process of Cr (VI is spontaneous and heating, and kinetics studies of models Lagergren, Ho , Alovich and intraparticle is used, the results show that the adsorption kinetics follows the pseudo-second order.

  18. Adsorption of uranyl ions in nanoparticles of magnetite

    International Nuclear Information System (INIS)

    Holland, Helber; Yamaura, Mitiko

    2009-01-01

    This work studied the uranium (VI) adsorption, in the form of UO 2 2+ ions, of the nitride solution by the syntetic magnetite. This solution was prepared by precipitation adding a solution of NaOH to the solution containing the ions Fe 2+ . The time of contact and the isothermal of equilibrium of ions UO 2 2+ adsorption was verified. The isothermal of equilibrium presented more concordance with the Freundlich model, which characterized a heterogeneous adsorption surface of the magnetite. The great advantage of this technology is the combination of two separation techniques, by adsorption and magnetic, resulting in a highly efficient and reusable system

  19. II-VI semiconductor compounds

    CERN Document Server

    1993-01-01

    For condensed matter physicists and electronic engineers, this volume deals with aspects of II-VI semiconductor compounds. Areas covered include devices and applications of II-VI compounds; Co-based II-IV semi-magnetic semiconductors; and electronic structure of strained II-VI superlattices.

  20. Characterization of U(VI)-carbonato ternary complexes on hematite: EXAFS and electrophoretic mobility measurements

    Science.gov (United States)

    Bargar, John R.; Reitmeyer, Rebecca; Lenhart, John J.; Davis, James A.

    2000-01-01

    We have measured U(VI) adsorption on hematite using EXAFS spectroscopy and electrophoresis under conditions relevant to surface waters and aquifers (0.01 to 10 μM dissolved uranium concentrations, in equilibrium with air, pH 4.5 to 8.5). Both techniques suggest the existence of anionic U(VI)-carbonato ternary complexes. Fits to EXAFS spectra indicate that U(VI) is simultaneously coordinated to surface FeO6 octahedra and carbonate (or bicarbonate) ligands in bidentate fashions, leading to the conclusion that the ternary complexes have an inner-sphere metal bridging (hematite-U(VI)-carbonato) structure. Greater than or equal to 50% of adsorbed U(VI) was comprised of monomeric hematite-U(VI)-carbonato ternary complexes, even at pH 4.5. Multimeric U(VI) species were observed at pH ≥ 6.5 and aqueous U(VI) concentrations approximately an order of magnitude more dilute than the solubility of crystalline β-UO2(OH)2. Based on structural constraints, these complexes were interpreted as dimeric hematite-U(VI)-carbonato ternary complexes. These results suggest that Fe-oxide-U(VI)-carbonato complexes are likely to be important transport-limiting species in oxic aquifers throughout a wide range of pH values.

  1. Application of HDTMA-intercalated bentonites in water waste treatment for U(VI) removal

    International Nuclear Information System (INIS)

    Krajnak, Adrian; Viglasova, Eva; Galambos, Michal; Krivosudsky, Lukas; Universitat Wien, Vienna

    2017-01-01

    Bentonite deposits in Slovakia are systematically investigated as potential adsorbents for wastewater and radioactive waste treatment applications. Herein, adsorption properties (isotherms, kinetics and thermodynamics) of raw and organo-modified bentonites towards uranium species in aqueous solutions were investigated. Organo-modified bentonites was prepared by practical and simple chemical modification method with hexadecyltrimethylammonium bromide (denoted as HDTMA-bentonites). The adsorption processes of U(VI) on HDTMA-bentonites were spontaneous and endothermic, and well simulated by pseudo-second-order model. The maximum adsorption capacity of U(VI) was calculated to be 31.45 mg/g at pH 8.5 and T = 298 K. Slovak bentonites Jelsovy potok and Kopernica, their natural and HDTMA-modified forms might be a promising sorbent for the treatment of U(VI) contaminants in aqueous solutions. (author)

  2. Sorption of Chromium (VI Using Excess Municipal Sludge

    Directory of Open Access Journals (Sweden)

    Farzaneh Mohammadi

    2014-04-01

    Full Text Available Removing or decreasing hexavalent Chromium from wastewater to the permitted levels is important due to its non-biodegradation, bioaccumulation, cancer-causing and toxic effects. In this study, biosorption of Cr(VI from aqueous solutions by Excess Active Municipal Sludge was investigated as a function of initial Chromium (VI concentration (in the range of 5-90 mg/l, initial pH (in the range of 2-8, agitation speed (in the range of 50-200 rpm, adsorbent dosage (in the range of 2-10 g/l and agitation time (in the range of 5-480 min in a batch system. The optimum conditions were found by full factorial design approach. The results showed that the equilibrium time for adsorbent is 120 minutes. Also, sorption data have a good fitness by Freundlich isotherm model and adsorption kinetic is adopted with pseudo-second order model. In batch studies, at optimum condition (90 mg/l initial concentration, pH 2, agitation speed 200 rpm and adsorbent dosage 4 g/l, the adsorption performance was about 96%; the maximum adsorption capacity was calculated about 41.69 mg of Cr/g of adsorbent. Overall, it can be concluded that Excess Active Municipal Sludge, has a good performance as a biological, biodegradable, abundant and low-cost adsorbent for the removal of Cr (VI from aqueous solutions.

  3. Removal and recovery of molybdenum from aqueous solutions by adsorption onto Surfactant-Modified coir pith, a lignocellulosic polymer

    Energy Technology Data Exchange (ETDEWEB)

    Namasivayam, Chinnaiya [Environmental Chemistry Division, Department of Environmental Sciences, Bharathiar University, Coimbatore (India); Sureshkumar, Molagoundanpalayam Venkatachalam [Department of Chemistry, PARK College of Engineering and Technology, Coimbatore (India)

    2009-01-15

    Coconut coir pith, a lignocellulosic polymer, is an unwanted by-product of the coir fiber industry. The pith was used as a biosorbent for the removal of Molybdenum(VI) after modification with a cationic surfactant, hexadecyltrimethylammonium bromide. The optimum pH for maximum adsorption of Mo(VI) was found to be 3.0. Langmuir, Freundlich and Dubinin Radushkevich isotherms were used to model the adsorption equilibrium data and the system was seen to follow all three isotherms. The Langmuir adsorption capacity of the biosorbent was found to be 57.5 mg g{sup -1}. Kinetic studies showed that the adsorption generally obeyed a second-order kinetic model. Desorption studies showed that the recovery of Mo(VI) from the spent adsorbent was feasible. The effect of foreign anions on the adsorption of Mo(VI) was also examined. (Abstract Copyright [2009], Wiley Periodicals, Inc.)

  4. Magnetic biochar combining adsorption and separation recycle for removal of chromium in aqueous solution.

    Science.gov (United States)

    Xin, Ouyang; Yitong, Han; Xi, Cao; Jiawei, Chen

    2017-03-01

    Biochar has been developed in recent years for the removal of contaminants such as Cr (VI) in water. The enhancement of the adsorption capacity of biochar and its recyclable use are still challenges. In this study, magnetic biochar derived from corncobs and peanut hulls was synthesized under different pyrolysis temperatures after pretreating the biomass with a low concentration of 0.5 M FeCl 3 solution. The morphology, specific surface area, saturation magnetization and Fourier transform infrared spectroscopy (FT-IR) spectra were characterized for biochar. The magnetic biochar performed well in combining adsorption and separation recycle for the removal of Cr (VI) in water. The Cr (VI) adsorbance of the biochar was increased with the increase in pyrolysis temperature, and the magnetic biochar derived from corncobs showed better performance for both magnetization and removal of Cr (VI) than that from peanut hulls. The Langmuir model was used for the isothermal adsorption and the maximum Cr (VI) adsorption capacity of corncob magnetic biochar pyrolyzed at 650 °C reached 61.97 mg/g. An alkaline solution (0.1 M NaOH) favored the desorption of Cr (VI) from the magnetic biochar, and the removal of Cr (VI) still remained around 77.6% after four cycles of adsorption-desorption. The results showed that corncob derived magnetic biochar is a potentially efficient and recoverable adsorbent for remediation of heavy metals in water.

  5. 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.

  6. 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.

  7. Selective Adsorption of Uranium (VI) on NaHCO Leached ...

    African Journals Online (AJOL)

    NICO

    with a variety of organic and inorganic ligands to form complex species of different ... approach for the synthesis of magnetic particles for uranium .... equations (1) and (2), respectively. Extraction efficiency. (C. C ). C o e o. = −. × 100. (1).

  8. Heavy metal adsorption by modified oak sawdust: Thermodynamics and kinetics

    International Nuclear Information System (INIS)

    Argun, Mehmet Emin; Dursun, Sukru; Ozdemir, Celalettin; Karatas, Mustafa

    2007-01-01

    This paper describes the adsorption of heavy metal ions from aqueous solutions by oak (Quercus coccifera) sawdust modified by means of HCl treatment. Our study tested the removal of three heavy metals: Cu, Ni, and Cr. The optimum shaking speed, adsorbent mass, contact time, and pH were determined, and adsorption isotherms were obtained using concentrations of the metal ions ranging from 0.1 to 100 mg L -1 . The adsorption process follows pseudo-second-order reaction kinetics, as well as Langmuir and D-R adsorption isotherms. The paper discusses the thermodynamic parameters of the adsorption (the Gibbs free energy, entropy, and enthalpy). Our results demonstrate that the adsorption process was spontaneous and endothermic under natural conditions. The maximum removal efficiencies were 93% for Cu(II) at pH 4, 82% for Ni(II) at pH 8, and 84% for Cr(VI) at pH 3

  9. 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

  10. Extraction chromatography of U(VI) and Pu(IV) adsorbed on amberlite XAD-7/dibutyloctanamide

    International Nuclear Information System (INIS)

    Prabhu, D.R.; Mahajan, G.R.; Nair, G.M.; Subramanian, M.S.

    1992-01-01

    The adsorption of U(VI) and Pu(IV) into the neutral poly acrylic resin Amberlite XAD-7, impregnated with dibutyloctanamide was found to be maximum at around 6M HNO 3 . Both these ions were found to be adsorbed as their monosolvates. The thermodynamic parameters obtained from the data at different temperatures indicated that the adsorption reaction was enthalpy favoured and entropy disfavored. (author). 5 refs., 1 tab

  11. Recovery of U(Vi) with unexpanded perlite

    International Nuclear Information System (INIS)

    Cuevas J, A.K.; Davila R, J. I.; Lopez del R, H.; Mireles G, F.

    2015-09-01

    Perlite is a glass volcanic rock that is hydrated by the addition of water during its formation. Is a natural material widely used in the chemical and construction industries, but recently beginning to be studied their adsorptive properties. In this paper the adsorption capacity of unexpanded perlite to remove U(Vi) in aqueous solution depending on the grain size of the material was investigated, as well as the contact time between the liquid and solid phases, ph of solution and initial concentration of uranium. The adsorption was dependent on the surface area of the material, recovering higher uranium percentage to smaller particle size. Meanwhile kinetics showed that the uranium adsorption is rapid, reaching equilibrium in 1 h. Adsorption to slightly acidic conditions was favored but dropped dramatically to ph highly acidic and basic; at a concentration of 1 x 10 -3 M UO 2 +2 the maximum uranium recovery was 46% at ph 6. In dilute solutions (1 x 10 -5 to 1 x 10 -3 M) the adsorption percentage reached values between 34 and 42%, but was reduced to 1% at a concentration of 1 x 10 -2 M. (Author)

  12. Synthesis of surface Cr (VI)-imprinted magnetic nanoparticles for selective dispersive solid-phase extraction and determination of Cr (VI) in water samples.

    Science.gov (United States)

    Qi, Xue; Gao, Shuang; Ding, Guosheng; Tang, An-Na

    2017-01-01

    A facile, rapid and selective magnetic dispersed solid-phase extraction (dSPE) method for the extraction and enrichment of Cr (VI) prior to flame atomic absorption spectrometry (AAS) was introduced. For highly selective and efficient extraction, magnetic Cr (VI)-imprinted nanoparticles (Fe 3 O 4 @ Cr (VI) IIPs) were prepared by hyphenating surface ion-imprinted with sol-gel techniques. In the preparation process, chromate (Cr(VI)) was used as the template ion; vinylimidazole and 3-aminopropyltriethoxysilane were selected as organic functional monomer and co-monomer respectively. Another reagent, methacryloxypropyltrimethoxysilane was adopted as coupling agent to form the stable covalent bonding between organic and inorganic phases. The effects of various parameters on the extraction efficiency, such as pH of sample solution, the amount of adsorbent, extraction time, the type and concentration of eluent were systematically investigated. Furthermore, the thermodynamic and kinetic properties of the adsorption process were studied to explore the internal adsorption mechanism. Under optimized conditions, the preconcentration factor, limit of detection and linear range of the established dSPE-AAS method for Cr (VI) were found to be 98, 0.29μgL -1 and 4-140μgL -1 , respectively. The developed method was also successfully applied to the analysis of Cr (VI) in different water samples with satisfactory results, proving its reliability and feasibility in real sample analysis. Copyright © 2016 Elsevier B.V. All rights reserved.

  13. Adsorption of uranium ions by crosslinked polyester resin functionalized with acrylic acid from aqueous solutions

    International Nuclear Information System (INIS)

    Cemal Oezeroglu; Niluefer Metin

    2012-01-01

    In this paper, the crosslinked polyester resin containing acrylic acid functional groups was used for the adsorption of uranium ions from aqueous solutions. For this purpose, the crosslinked polyester resin of unsaturated polyester in styrene monomer (Polipol 353, Poliya) and acrylic acid as weight percentage at 80 and 20%, respectively was synthesized by using methyl ethyl ketone peroxide (MEKp, Butanox M60, Azo Nobel)-cobalt octoate initiator system. The adsorption of uranium ions on the sample (0.05 g copolymer and 5 mL of U(VI) solution were mixed) of the crosslinked polyester resin functionalized with acrylic acid was carried out in a batch reactor. The effects of adsorption parameters of the contact time, temperature, pH of solution and initial uranium(VI) concentration for U(VI) adsorption on the crosslinked polyester resin functionalized with acrylic acid were investigated. The adsorption data obtained from experimental results depending on the initial U(VI) concentration were analyzed by the Freundlich, Langmuir and Dubinin-Radushkevich (D-R) adsorption isotherms. The adsorption capacity and free energy change were determined by using D-R isotherm. The obtained experimental adsorption data depending on temperature were evaluated to calculate the thermodynamic parameters of enthalpy (ΔH o ), entropy (ΔS o ) and free energy change (ΔG o ) for the U(VI) adsorption on the crosslinked polyester resin functionalized with acrylic acid from aqueous solutions. The obtained adsorption data depending on contact time were analyzed by using adsorption models such as the modified Freundlich, Elovich, pseudo-first order and pseudo-second-order kinetic models. (author)

  14. Recovery of U(Vi) with unexpanded perlite; Recuperacion de U(VI) con perlita no expandida

    Energy Technology Data Exchange (ETDEWEB)

    Cuevas J, A.K.; Davila R, J. I.; Lopez del R, H.; Mireles G, F., E-mail: cuja2105@hotmail.com [Universidad Autonoma de Zacatecas, Unidad Academica de Estudios Nucleares, Cipres No. 10, Fracc. La Penuela, 98068 Zacatecas, Zac. (Mexico)

    2015-09-15

    Perlite is a glass volcanic rock that is hydrated by the addition of water during its formation. Is a natural material widely used in the chemical and construction industries, but recently beginning to be studied their adsorptive properties. In this paper the adsorption capacity of unexpanded perlite to remove U(Vi) in aqueous solution depending on the grain size of the material was investigated, as well as the contact time between the liquid and solid phases, ph of solution and initial concentration of uranium. The adsorption was dependent on the surface area of the material, recovering higher uranium percentage to smaller particle size. Meanwhile kinetics showed that the uranium adsorption is rapid, reaching equilibrium in 1 h. Adsorption to slightly acidic conditions was favored but dropped dramatically to ph highly acidic and basic; at a concentration of 1 x 10{sup -3} M UO{sub 2}{sup +2} the maximum uranium recovery was 46% at ph 6. In dilute solutions (1 x 10{sup -5} to 1 x 10{sup -3} M) the adsorption percentage reached values between 34 and 42%, but was reduced to 1% at a concentration of 1 x 10{sup -2} M. (Author)

  15. Fixed bed adsorption of hexavalent chromium onto natural zeolite from air stream

    Directory of Open Access Journals (Sweden)

    F. Golbabaei

    2014-07-01

    Conclusion: Due to the extensive use of chromium in various industries and regulatory requirements related to workplace health and safety, Cr emission control in the occupational environment is essential. The adsorption process is one of the controlling measures of chromium emissions. The results indicated that natural zeolite has a high efficiency in Cr (VI adsorption.

  16. Adsorption of hexavalent chromium on modified corn stalk using different cross-linking agents

    Science.gov (United States)

    Chen, Suhong; Zhu, Yi; Han, Zhijun; Feng, Gao; Jia, Yuling; Fu, Kaifang; Yue, Qinyan

    2017-12-01

    In this study, four different types of adsorbents modified from corn stalk were synthesized after the reaction with epichlorohydrin, N,N-dimethylformamide, triethylamine and different cross-linking agents. The surface functional groups and thermal stability of modified corn stalk (MCSs) were characterized using FTIR and TG analysis, respectively. The feasibility of using MCSs to remove Cr(VI) were evaluated. Adsorption isotherms were determined and modeled with Langmuir, Freundlich and Temkin equations. The experimental results showed that MCS modified using diethylenetriamine (DETA) had the best modification effect, and the adsorption capacity of Cr(VI) reached as high as 227.27 mg/g at 323 K. Thermodynamic study showed that the Cr(VI) adsorption onto MCSs was endothermic processes. As a result, MCS by using DETA as cross-linking agent has good potential for the removal of Cr(VI) from aqueous solutions.

  17. Batch versus column modes for the adsorption of radioactive metal onto rice husk waste: conditions optimization through response surface methodology.

    Science.gov (United States)

    Kausar, Abida; Bhatti, Haq Nawaz; Iqbal, Munawar; Ashraf, Aisha

    2017-09-01

    Batch and column adsorption modes were compared for the adsorption of U(VI) ions using rice husk waste biomass (RHWB). Response surface methodology was employed for the optimization of process variables, i.e., (pH (A), adsorbent dose (B), initial ion concentration (C)) in batch mode. The B, C and C 2 affected the U(VI) adsorption significantly in batch mode. The developed quadratic model was found to be validated on the basis of regression coefficient as well as analysis of variance. The predicted and actual values were found to be correlated well, with negligible residual value, and B, C and C 2 were significant terms. The column study was performed considering bed height, flow rate and initial metal ion concentration, and adsorption efficiency was evaluated through breakthrough curves and bed depth service time and Thomas models. Adsorption was found to be dependent on bed height and initial U(VI) ion concentration, and flow rate decreased the adsorption capacity. Thomas models fitted well to the U(VI) adsorption onto RHWB. Results revealed that RHWB has potential to remove U(VI) ions and batch adsorption was found to be efficient versus column mode.

  18. 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 ...

  19. Magnetic chitosan for removal of uranium (VI)

    International Nuclear Information System (INIS)

    Stopa, Luiz Claudio Barbosa

    2007-01-01

    The chitosan, an aminopolysaccharide formed for repeated units of D-glucosamine, is a deacetylation product of chitin. It presents favorable ionic properties acting as chelant, being considered a removing ionic of contaminants from water effluents. It has ample bioactivity, that is, is biocompatible, biodegradable, bioadhesive and biosorbent. The chitosan interacts for crosslinked by means of its active groups with other substances, can still coat superparamagnetic materials as magnetite nanoparticles producing one conjugated polymer-magnetite. Superparamagnetic materials are susceptible for the magnetic field, thus these particles can be attracted and grouped by a magnetic field and as they do not hold back the magnetization, they can be disagrouped and reused in processes for removal of contaminants from industrial effluents and waste water. The present work consisted of preparing coated magnetic magnetite particles with chitosan (PMQ). The PMQ powder has showed a magnetic response of intense attraction in the presence of a magnetic field without however becoming magnetic, a typical behavior of superparamagnetic material. It was characterized by Fourier transform infrared spectrometry and measurements of magnetization. Its performance of Uranium (VI) adsorption as uranyl species, U0 2 2+ , was evaluated with regard to the influence of adsorbent dose, speed of agitation, pH, the contact time and had studied the isotherms of adsorption as well as the behavior of desorption using ions of carbonate and oxalate. The optimal pH to the best removal occurred in pH 5 and that the increase of the dose increases the removal, becoming constant above of 20 g.L -1 . In the kinetic study the equilibrium was achieved after 20 minutes. The results of equilibrium isotherm agreed well with the Langmuir model, being the maximum adsorption capacity equal 41.7 mg.g -1 . In the desorption studies were verified 94% of U0 2 2+ recovered with carbonate ion and 49.9% with oxalate ion

  20. Reduction and Removal of Chromium VI in Water by Powdered Activated Carbon

    Directory of Open Access Journals (Sweden)

    Yanan Chen

    2018-02-01

    Full Text Available Cr adsorption on wood-based powdered activated carbon (WPAC was characterized by scanning electron microscopy coupled with energy dispersive spectroscopy (SEM-EDS, Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS. The highest Cr(VI adsorption (40.04% was obtained under acidic conditions (pH 3, whereas Cr removal at pH 10 was only 0.34%. The mechanism of Cr(VI removal from aqueous solutions by WPAC was based on the reduction of Cr(VI to Cr(III with the concomitant oxidation of C-H and C-OH to C-OH and C=O, respectively, on the surface of WPAC, followed by Cr(III adsorption. Raman spectroscopy revealed a change in the WPAC structure in terms of the D/G band intensity ratio after Cr(VI adsorption. SEM-EDS analysis showed that the oxygen/carbon ratio on the WPAC surface increased from 9.85% to 17.74%. This result was confirmed by XPS measurements, which showed that 78.8% of Cr adsorbed on the WPAC surface was in the trivalent state. The amount of oxygen-containing functional groups on the surface increased due to the oxidation of graphitic carbons to C-OH and C=O groups.

  1. Removal of chromium(VI) from water and wastewater using surfactant modified coconut coir pith as a biosorbent.

    Science.gov (United States)

    Namasivayam, C; Sureshkumar, M V

    2008-05-01

    Coconut coir pith, an agricultural solid waste was used as biosorbent for the removal of chromium(VI) after modification with a cationic surfactant, hexadecyltrimethylammonium bromide. Optimum pH for Cr(VI) adsorption was found to be 2.0. Reduction of Cr(VI) to Cr(III) occurred to a slight extent during the removal. Langmuir, Freundlich and Dubinin Radushkevich (D-R) isotherms were used to model the adsorption equilibrium data and the system followed all the three isotherms. The adsorption capacity of the biosorbent was found to be 76.3 mg g(-1), which is higher or comparable to the adsorption capacity of various adsorbents reported in literature. Kinetic studies showed that the adsorption obeyed second order and Elovich model. Thermodynamic parameters such as delta G0, delta H0 and delta S0 were evaluated, indicating that the overall adsorption process was endothermic and spontaneous. Effects of foreign anions were also examined. The adsorbent was also tested for the removal of Cr(VI) from electroplating effluent.

  2. Removal of chromium (VI from aqueous medium using chemically modified banana peels as efficient low-cost adsorbent

    Directory of Open Access Journals (Sweden)

    Ashraf Ali

    2016-09-01

    Full Text Available The adsorptive removal of hexavalent chromium Cr(VI from aqueous solutions was investigated by acrylonitrile grafted banana peels (GBPs. Banana peels were treated with 10% HCl, followed by alkaline hydrolysis with 10% NaOH, and washed thoroughly. The bleaching of alkali hydrolyzed peels was carried out with sodium chlorate (NaClO3 in the presence of hydrogen peroxide and glacial acetic acid. The grafting co-polymerization of acrylonitrile onto the bleached pulp was initiated by Fenton’s reagent (Fe+2/H2O2. The optimum conditions for adsorption of Cr(VI were found to be the following: pH 3, adsorbent dose 4 g/L, concentration 400 mg/L and contact time of 120 min. The surface morphology of adsorbent was characterized by scanning electron microscopy (SEM before and after the adsorption. The adsorption of Cr(VI onto grafted banana peels (GBPs was recorded to be 96%. The adsorption data were fully fitted with the Freundlich and Langmuir isotherm model and followed a pseudo-second order kinetic model. Thermodynamic study showed that the adsorption is exothermic and spontaneous. Owing to high efficiency and low cost, grafted banana peels (GBPs can be used as effective adsorbent for Cr(VI removal from wastewater.

  3. Biosorption behaviors of uranium (VI) from aqueous solution by sunflower straw and insights of binding mechanism

    International Nuclear Information System (INIS)

    Lian Ai; Xuegang Luo; Xiaoyan Lin; Sizhao Zhang

    2013-01-01

    Uranium (VI)-containing water has been recognized as a potential longer-term radiological health hazard. In this work, the sorptive potential of sunflower straw for U (VI) from aqueous solution was investigated in detail, including the effect of initial solution pH, adsorbent dosage, temperature, contact time and initial U (VI) concentration. A dose of 2.0 g L -1 of sunflower straw in an initial U (VI) concentration of 20 mg L -1 with an initial pH of 5.0 and a contact time of 10 h resulted in the maximum U (VI) uptake (about 6.96 mg g -1 ) at 298 K. The isotherm adsorption data was modeled best by the nonlinear Langmuir-Freundlich equation. The equilibrium sorption capacity of sunflower straw was observed to be approximately seven times higher than that of coconut-shell activated carbon as 251.52 and 32.37 mg g -1 under optimal conditions, respectively. The positive enthalpy and negative free energy suggested the endothermic and spontaneous nature of sorption, respectively. The kinetic data conformed successfully to the pseudo-second-order equation. Furthermore, energy dispersive X-ray, fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy demonstrated that U (VI) adsorption onto sunflower straw was predominantly controlled by ion exchange as well as complexation mechanism. The study revealed that sunflower straw could be exploited for uranium remediation of aqueous streams as a promising adsorbent. (author)

  4. Probing uranyl(VI) speciation in the presence of amidoxime ligands using electrospray ionization mass spectrometry.

    Science.gov (United States)

    Mustapha, Adetayo M; Pasilis, Sofie P

    2013-10-15

    Extraction processes using poly(acrylamidoxime) resins are being developed to extract uranium from seawater. The main complexing agents in these resins are thought to be 2,6-dihydroxyiminopiperidine (DHIP) and N(1),N(5)-dihydroxypentanediimidamide (DHPD), which form strong complexes with uranyl(VI) at the pH of seawater. It is important to understand uranyl(VI) speciation in the presence of these and similar amidoxime ligands to understand factors affecting uranyl(VI) adsorption to the poly(acrylamidoxime) resins. Experiments were carried out in positive ion mode on a quadrupole ion trap mass spectrometer equipped with an electrospray ionization source. The ligands investigated were DHIP, DHPD, and N(1),N(2)-dihydroxyethanediimidamide (DHED). DHED and DHPD differ only in the number of carbons separating the oxime groups. The effects on the mass spectra of changes in uranyl(VI):ligand ratio, pH, and ligand type were examined. DHIP binds uranyl(VI) more effectively than DHPD or DHED in the pH range investigated, forming ions derived from solution-phase species with uranyl(VI):DHIP stoichiometries of 1:1, 1:2, and 2:3. The 2:3 uranyl(VI):DHIP complex appears to be a previously undescribed solution species. Ions related to uranyl(VI):DHPD complexes were detected in very low abundance. DHED is a more effective complexing agent for uranyl(VI) than DHPD, forming ions having uranyl(VI):DHED stoichiometries of 1:1, 1:2, 1:3, and 2:3. This study presents a first look at the solution chemistry of uranyl(VI)-amidoxime complexes using electrospray ionization mass spectrometry. The appearance of previously undescribed solution species suggests that the uranyl-amidoxime system is a rich and relatively complex one, requiring a more in-depth investigation. Copyright © 2013 John Wiley & Sons, Ltd.

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

    Directory of Open Access Journals (Sweden)

    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.

  6. Uranium (Vi) sorption onto zirconium diphosphate chemically modified

    International Nuclear Information System (INIS)

    Garcia G, N.; Ordonez R, E.

    2010-10-01

    This work deals with the uranium (Vi) speciation after sorption onto zirconium diphosphate (ZrP 2 O 7 ) surface, hydrated and in a surface modified with organic acids. Oxalic and citric acids were chosen to modify the ZrP 2 O 7 surface because they have poly carboxylic groups and they mimic the organic matter in nature. Thus the interest of this work is to evaluate the uranium (Vi) sorption edge at different s ph values in natural and modified surfaces. The luminescence technique (fluorescence and phosphorescence, respectively) was used for the quantification and speciation of uranyl sorbed at the zirconium diphosphate interface. The fluorescence experiment, showed that adsorption of uranyl on surface of zirconium diphosphate tends to 100%. The speciation shows that there are different complexes in surface which were formed between zirconium diphosphate and uranyl, since it is produced a displacement of wavelength in fluorescence spectra of each system. (Author)

  7. Kinetics and equilibrium studies for sorption of Cu (II) and Cr (VI) ions onto polymeric composite resins

    International Nuclear Information System (INIS)

    El-Zahhhar, A.A.; Abdel-Aziz, H.M.; Siyam, T.

    2005-01-01

    The sorption behavior of Cu (II) and Cr (VI) ions from aqueous solutions was studied using polymeric composite resins. Batch sorption experiments were performed as a function of hydrogen ion concentration, complexing agent concentration, resin weight and ionic strength. Kinetic parameters as a function of initial ion concentration were determined to predict the sorption behavior of Cu (II) and Cr (VI) onto polymeric composite resins. The equilibrium data could be fitted by the frendlich adsorption isotherm equation

  8. Biosorption of chromium (VI) from aqueous solutions and ANN modelling.

    Science.gov (United States)

    Nag, Soma; Mondal, Abhijit; Bar, Nirjhar; Das, Sudip Kumar

    2017-08-01

    The use of sustainable, green and biodegradable natural wastes for Cr(VI) detoxification from the contaminated wastewater is considered as a challenging issue. The present research is aimed to assess the effectiveness of seven different natural biomaterials, such as jackfruit leaf, mango leaf, onion peel, garlic peel, bamboo leaf, acid treated rubber leaf and coconut shell powder, for Cr(VI) eradication from aqueous solution by biosorption process. Characterizations were conducted using SEM, BET and FTIR spectroscopy. The effects of operating parameters, viz., pH, initial Cr(VI) ion concentration, adsorbent dosages, contact time and temperature on metal removal efficiency, were studied. The biosorption mechanism was described by the pseudo-second-order model and Langmuir isotherm model. The biosorption process was exothermic, spontaneous and chemical (except garlic peel) in nature. The sequence of adsorption capacity was mango leaf > jackfruit leaf > acid treated rubber leaf > onion peel > bamboo leaf > garlic peel > coconut shell with maximum Langmuir adsorption capacity of 35.7 mg g -1 for mango leaf. The treated effluent can be reused. Desorption study suggested effective reuse of the adsorbents up to three cycles, and safe disposal method of the used adsorbents suggested biodegradability and sustainability of the process by reapplication of the spent adsorbent and ultimately leading towards zero wastages. The performances of the adsorbents were verified with wastewater from electroplating industry. The scale-up study reported for industrial applications. ANN modelling using multilayer perception with gradient descent (GD) and Levenberg-Marquart (LM) algorithm had been successfully used for prediction of Cr(VI) removal efficiency. The study explores the undiscovered potential of the natural waste materials for sustainable existence of small and medium sector industries, especially in the third world countries by protecting the environment by eco-innovation.

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

    Directory of Open Access Journals (Sweden)

    T. Burks

    2015-01-01

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

  10. 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.

  11. Chromium (Ⅵ) removal from aqueous solutions through powdered activated carbon countercurrent two-stage adsorption.

    Science.gov (United States)

    Wang, Wenqiang

    2018-01-01

    To exploit the adsorption capacity of commercial powdered activated carbon (PAC) and to improve the efficiency of Cr(VI) removal from aqueous solutions, the adsorption of Cr(VI) by commercial PAC and the countercurrent two-stage adsorption (CTA) process was investigated. Different adsorption kinetics models and isotherms were compared, and the pseudo-second-order model and the Langmuir and Freundlich models fit the experimental data well. The Cr(VI) removal efficiency was >80% and was improved by 37% through the CTA process compared with the conventional single-stage adsorption process when the initial Cr(VI) concentration was 50 mg/L with a PAC dose of 1.250 g/L and a pH of 3. A calculation method for calculating the effluent Cr(VI) concentration and the PAC dose was developed for the CTA process, and the validity of the method was confirmed by a deviation of <5%. Copyright © 2017. Published by Elsevier Ltd.

  12. Chromium(VI Removal from Aqueous Solution by Magnetite Coated by a Polymeric Ionic Liquid-Based Adsorbent

    Directory of Open Access Journals (Sweden)

    Thania Alexandra Ferreira

    2017-05-01

    Full Text Available An evaluation of the chromium(VI adsorption capacity of four magnetite sorbents coated with a polymer phase containing polymethacrylic acid or polyallyl-3-methylimidazolium is presented. Factors that influence the chromium(VI removal such as solution pH and contact time were investigated in batch experiments and in stirred tank reactor mode. Affinity and rate constants increased with the molar ratio of the imidazolium. The highest adsorption was obtained at pH 2.0 due to the contribution of electrostatic interactions.

  13. Chromium(VI) Removal from Aqueous Solution by Magnetite Coated by a Polymeric Ionic Liquid-Based Adsorbent

    Science.gov (United States)

    Ferreira, Thania Alexandra; Rodriguez, Jose Antonio; Paez-Hernandez, María Elena; Guevara-Lara, Alfredo; Barrado, Enrique; Hernandez, Prisciliano

    2017-01-01

    An evaluation of the chromium(VI) adsorption capacity of four magnetite sorbents coated with a polymer phase containing polymethacrylic acid or polyallyl-3-methylimidazolium is presented. Factors that influence the chromium(VI) removal such as solution pH and contact time were investigated in batch experiments and in stirred tank reactor mode. Affinity and rate constants increased with the molar ratio of the imidazolium. The highest adsorption was obtained at pH 2.0 due to the contribution of electrostatic interactions. PMID:28772865

  14. Natural biosorbents (garlic stem and horse chesnut shell) for removal of chromium(VI) from aqueous solutions.

    Science.gov (United States)

    Parlayıcı, Şerife; Pehlivan, Erol

    2015-12-01

    The biosorption of Cr(VI) by the garlic stem (GS)-Allium sativum L. and horse chesnut shell (HCS)-Aesculus hippocastanum plant residues in a batch type reactor was studied in detail for the purpose of wastewater treatment. The influence of initial Cr(VI) concentration, time, and pH was investigated to optimize Cr(VI) removal from aqueous solutions and equilibrium isotherms and kinetic data. This influence was evaluated. The adsorption capacity of the GS and the HCS for Cr(VI) was determined with the Langmuir and Freundlich isotherm models, and the data was fitted to the Langmuir. The adsorption capacity of the GS and the HCS was found to be 103.09 and 142.85 mg/g of adsorbent from a solution containing 3000 ppm of Cr(VI), respectively. The GS's capacity was considerably lower than that of the HCS in its natural form. Gibbs free energy was spontaneous for all interactions, and the adsorption process exhibited exothermic enthalpy values. The HCS was shown to be a promising biosorbent for Cr(VI) removal from aqueous solutions.

  15. 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.

  16. 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.

  17. 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.

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

    Energy Technology Data Exchange (ETDEWEB)

    Yuan Peng, E-mail: yuanpeng@gig.ac.cn [Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640 (China); Liu Dong; Fan Mingde; Yang Dan [Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640 (China); Graduate School of Chinese Academy of Sciences, Beijing 100039 (China); Zhu Runliang; Ge Fei [College of Chemical Engineering, Xiangtan University, Xiangtan 411105 (China); Zhu Jianxi; He Hongping [Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640 (China)

    2010-01-15

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

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

    Science.gov (United States)

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

    2010-01-15

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

  20. Uranium(VI) Reduction by Nanoscale Zerovalent Iron in Anoxic Batch Systems

    International Nuclear Information System (INIS)

    Yan, Sen; Hua, Bin; Bao, Zhengyu; Yang, John; Liu, Chongxuan; Deng, Baolin

    2010-01-01

    This study investigated the influences of pH, bicarbonate, and calcium on U(VI) adsorption and reduction by synthetic nanosize zero valent iron (nano Fe 0 ) particles under an anoxic condition. The results showed that about 87.1%, 82.7% and 78.3% of U(VI) could be reduced within 96 hours in the presence of 10 mM bicarbonate at pHs 6.92, 8.03 and 9.03, respectively. The rates of U(VI) reduction and adsorption by nano Fe 0 , however, varied significantly with increasing pH and concentrations of bicarbonate and/or calcium. Solid phase analysis by X-ray photoelectron spectroscopy confirmed the formation of UO 2 and iron (hydr)oxides as a result of the redox interactions between adsorbed U(VI) and nano Fe 0 . This study highlights the potential important role of groundwater chemical composition in controlling the rates of U(VI) reductive immobilization using nano Fe 0 in subsurface environments.

  1. Sorption and desorption studies of chromium(VI) from nonviable cyanobacterium Nostoc muscorum biomass

    International Nuclear Information System (INIS)

    Gupta, V.K.; Rastogi, A.

    2008-01-01

    This communication presents results pertaining to the sorptive and desorptive studies carried out on chromium(VI) removal onto nonviable freshwater cyanobacterium (Nostoc muscorum) biomass. Influence of varying the conditions for removal of chromium(VI), such as the pH of aqueous solution, the dosage of biosorbent, the contact time with the biosorbent, the temperature for the removal of chromium, the effect of light metal ions and the adsorption-desorption studies were investigated. Sorption interaction of chromium on to cyanobacterial species obeyed both the first and the second-order rate equation and the experimental data showed good fit with both the Langmuir and freundlich adsorption isotherm models. The maximum adsorption capacity was 22.92 mg/g at 25 o C and pH 3.0. The adsorption process was endothermic and the values of thermodynamic parameters of the process were calculated. Various properties of the cyanobacterium, as adsorbent, explored in the characterization part were chemical composition of the adsorbent, surface area calculation by BET method and surface functionality by FTIR. Sorption-desorption of chromium into inorganic solutions and distilled water were observed and this indicated the biosorbent could be regenerated using 0.1 M HNO 3 and EDTA with upto 80% recovery. The biosorbents were reused in five biosorption-desorption cycles without a significant loss in biosorption capacity. Thus, this study demonstrated that the cyanobacterial biomass N. muscorum could be used as an efficient biosorbent for the treatment of chromium(VI) bearing wastewater

  2. 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.

  3. Chromate adsorption on selected soil minerals: Surface complexation modeling coupled with spectroscopic investigation

    Energy Technology Data Exchange (ETDEWEB)

    Veselská, Veronika, E-mail: veselskav@fzp.czu.cz [Department of Environmental Geosciences, Faculty of Environmental Sciences, Czech University of Life Sciences Prague, Kamýcka 129, CZ-16521, Prague (Czech Republic); Fajgar, Radek [Department of Analytical and Material Chemistry, Institute of Chemical Process Fundamentals of the CAS, v.v.i., Rozvojová 135/1, CZ-16502, Prague (Czech Republic); Číhalová, Sylva [Department of Environmental Geosciences, Faculty of Environmental Sciences, Czech University of Life Sciences Prague, Kamýcka 129, CZ-16521, Prague (Czech Republic); Bolanz, Ralph M. [Institute of Geosciences, Friedrich-Schiller-University Jena, Carl-Zeiss-Promenade 10, DE-07745, Jena (Germany); Göttlicher, Jörg; Steininger, Ralph [ANKA Synchrotron Radiation Facility, Karlsruhe Institute of Technology, Hermann-von-Helmholtz-Platz 1, DE-76344, Eggenstein-Leopoldshafen (Germany); Siddique, Jamal A.; Komárek, Michael [Department of Environmental Geosciences, Faculty of Environmental Sciences, Czech University of Life Sciences Prague, Kamýcka 129, CZ-16521, Prague (Czech Republic)

    2016-11-15

    Highlights: • Study of Cr(VI) adsorption on soil minerals over a large range of conditions. • Combined surface complexation modeling and spectroscopic techniques. • Diffuse-layer and triple-layer models used to obtain fits to experimental data. • Speciation of Cr(VI) and Cr(III) was assessed. - Abstract: This study investigates the mechanisms of Cr(VI) adsorption on natural clay (illite and kaolinite) and synthetic (birnessite and ferrihydrite) minerals, including its speciation changes, and combining quantitative thermodynamically based mechanistic surface complexation models (SCMs) with spectroscopic measurements. Series of adsorption experiments have been performed at different pH values (3–10), ionic strengths (0.001–0.1 M KNO{sub 3}), sorbate concentrations (10{sup −4}, 10{sup −5}, and 10{sup −6} M Cr(VI)), and sorbate/sorbent ratios (50–500). Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and X-ray absorption spectroscopy were used to determine the surface complexes, including surface reactions. Adsorption of Cr(VI) is strongly ionic strength dependent. For ferrihydrite at pH <7, a simple diffuse-layer model provides a reasonable prediction of adsorption. For birnessite, bidentate inner-sphere complexes of chromate and dichromate resulted in a better diffuse-layer model fit. For kaolinite, outer-sphere complexation prevails mainly at lower Cr(VI) loadings. Dissolution of solid phases needs to be considered for better SCMs fits. The coupled SCM and spectroscopic approach is thus useful for investigating individual minerals responsible for Cr(VI) retention in soils, and improving the handling and remediation processes.

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

    Science.gov (United States)

    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.

  5. The applications of populus fiber in removal of Cr{sup (VI)} from aqueous solution

    Energy Technology Data Exchange (ETDEWEB)

    Li, Miaomiao; Gong, Yumei, E-mail: ymgong@dlpu.edu.cn; Lyu, Aichao; Liu, Yuanfa, E-mail: morning309@126.com; Zhang, Hong, E-mail: zhang_hong1234@sina.com

    2016-10-15

    Highlights: • A sorbent for heavy metal ions based on populus fibers is prepared by a green way. • The chromium adsorption on the sorbent accords with the pseudo-second-order kinetics. • The proposed adsorption involves static attraction and chelation by the sorbent on chromium. • The sorbent is expected to be applied in universal conditions. - Abstract: The surface modification of natural materials to be applied in removal of Cr{sup (VI)} from aqueous solutions has attracted much attention. A natural sorbent for Cr{sup (VI)} based on natural populus fibers (PF) is prepared by transforming the cyano groups (AN) in polyacrylonitriles (PAN) grafted from PF into amidoxime groups (AO), which has strong ability to attract and chelate heavy metal ions. The prepared sorbent is characterized by Fourier Transform Infrared Spectra (FT-IR), thermogravimetric analysis (TGA), solid-state nuclear magnetic resonance ({sup 13}C NMR) and scanning electron microscope (SEM). As potassium dichromate solution (K{sub 2}Cr{sub 2}O{sub 7}) is used as a target solution for detecting adsorption capacity of the sorbent, the adsorption kinetics of the sorbent for chromiun is consistent with the pseudo-second-order kinetic model by analyzing the adsorption amount as a function of the sorbent dispersed duration in solution at pH = 2. The expected adsorption mechanism is that the Cr{sup (VI)} in anionic ions Cr{sub 2}O{sub 7}{sup 2−} and HCrO{sub 4}{sup −} are adsorbed through electrostatic attraction but when Cr{sup (VI)} is reduced to Cr{sup (III)} by AO, the electronegative nitrogen and oxygen in AO chelate it through coordination bond. The as-prepared PF derivant with high adsorption efficiency of chromium 180.5 mg/g (3.47 mmol/g), low cost, reusability and greenly preparation process suggests that the development of natural PF as a sorbent in removal of Cr{sup (VI)} from aqueous solutions is a destined significant approach.

  6. Preparation and characterization of porous reduced graphene oxide based inverse spinel nickel ferrite nanocomposite for adsorption removal of radionuclides

    Energy Technology Data Exchange (ETDEWEB)

    Lingamdinne, Lakshmi Prasanna; Choi, Yu-Lim [Department of Environmental Engineering, Kwangwoon University, Seoul, 139-701 (Korea, Republic of); Kim, Im-Soon [Graduate School of Environmental Studies, Kwangwoon University, Seoul, 139-701 (Korea, Republic of); Yang, Jae-Kyu [Ingenium College of Liberal Arts, Kwangwoon University, Seoul, 139-701 (Korea, Republic of); Koduru, Janardhan Reddy, E-mail: reddyjchem@gmail.com [Graduate School of Environmental Studies, Kwangwoon University, Seoul, 139-701 (Korea, Republic of); Chang, Yoon-Young, E-mail: yychang@kw.ac.kr [Department of Environmental Engineering, Kwangwoon University, Seoul, 139-701 (Korea, Republic of)

    2017-03-15

    Highlights: • Novel porous Ferromagnetic, GONF and Superparamagnetic, rGONF preparation. • The nanosize particles GONF (41.14 nm) and rGONF (32.16 nm) preparation. • Adsorption mechanism and modeling developments for radionuclides. • Zeta potential and surface site density of nanocomposites for comparison. - Abstract: For the removal of uranium(VI) (U(VI)) and thorium(IV) (Th(IV)), graphene oxide based inverse spinel nickel ferrite (GONF) nanocomposite and reduced graphene oxide based inverse spinel nickel ferrite (rGONF) nanocomposite were prepared by co-precipitation of GO with nickel and iron salts in one pot. The spectral characterization analyses revealed that GONF and rGONF have a porous surface morphology with an average particle size of 41.41 nm and 32.16 nm, respectively. The magnetic property measurement system (MPMS) studies confirmed the formation of ferromagnetic GONF and superparamagnetic rGONF. The adsorption kinetics studies found that the pseudo-second-order kinetics was well tune to the U(VI) and Th(IV) adsorption. The results of adsorption isotherms showed that the adsorption of U(VI) and Th(IV) were due to the monolayer on homogeneous surface of the GONF and rGONF. The adsorptions of both U(VI) and Th(IV) were increased with increasing system temperature from 293 to 333 ± 2 K. The thermodynamic studies reveal that the U(VI) and Th(IV) adsorption onto GONF and rGONF was endothermic. GONF and rGONF, which could be separated by external magnetic field, were recycled and re-used for up to five cycles without any significant loss of adsorption capacity.

  7. Peat and coconut fiber as biofilters for chromium adsorption from contaminated wastewaters.

    Science.gov (United States)

    Henryk, Kołoczek; Jarosław, Chwastowski; Witold, Żukowski

    2016-01-01

    Batch adsorption experiments were performed for the removal of chromium (III) and chromium (VI) ions from aqueous solutions using Canadian peat and coconut fiber. The Langmuir model was used to describe the adsorption isotherm. The maximum adsorption for peat reached 18.75 mg/g for Cr(III) and 8.02 mg/g for Cr(VI), whereas the value for fiber was slightly higher and reached 19.21 mg/g for Cr(III) and 9.54 mg/g for Cr(VI). Both chromium forms could be easily eluted from the materials. The adsorption of chromium forms to organic matter could be explained in terms of formation of donor-acceptor chemical covalent bound with hydroxyl groups as ligands and chromium as the central atom in the formed complex. The chromate-reducing activities were monitored with the use of electron paramagnetic resonance spectroscopy. The results showed that both adsorption and reduction occurred simultaneously and the maximum adsorption capacity of hexavalent chromium being equal to 95% for fiber and 92% for peat was obtained at pH 1.5. The reduction of Cr(VI) in wastewaters began immediately and disappeared after 20 h. Both materials contained yeast and fungi species which can be responsible for reduction of chromium compounds, due to their enzymatic activity (Chwastowski and Koloczek (Acta Biochim Pol 60: 829-834, 2013)). The reduction of Cr(VI) is a two-phase process, the first phase being rapid and based on chemical reaction and the second phase having biological features. After the recovery step, both types of organic materials can be used again for chromium adsorption without any loss in the metal uptake. Both of the materials could be used as biofilters in the wastewater treatment plants.

  8. Zero-valent iron nanoparticles embedded into reduced graphene oxide-alginate beads for efficient chromium (VI) removal.

    Science.gov (United States)

    Lv, Xiaoshu; Zhang, Yuling; Fu, Wenyang; Cao, Jiazhen; Zhang, Jiao; Ma, Hanbo; Jiang, Guangming

    2017-11-15

    Zero-valent iron nanoparticles (Fe 0 NPs) technologies are often challenged by poor dispersibility, chemical instability to oxidation, and mobility during processing, storage and use. This work reports a facile approach to synthesize Fe 0 NPs embedded reduced graphene oxide-alginate beads (Fe@GA beads) via the immobilization of pre-synthesized Fe 0 NPs into graphene oxide modified alginate gel followed by a modelling and in-situ reduction process. The structure/composition characterization of the beads finds that the graphene sheets and the Fe 0 NPs (a shape of ellipsoid and a size of beads. We demonstrate that these Fe@GA beads show a robust performance in aqueous Cr(VI) removal. With a optimized Fe and alginate content, Fe@GA bead can achieve a high Cr(VI) removal efficiency and an excellent mechanical strength. The initial Cr(VI) concentration, ionic strength, temperature and especially solution pH are all critical factors to control the Fe@GA beads performance in Cr(VI) removal. Fitness of the pseudo second-order adsorption model with data suggests adsorption is the rate-controlling step, and both Langmuir and Freundlich adsorption isotherm are suitable to describe the removal behavior. The possible Cr(VI) removal path by Fe@GA beads is put forward, and the synergistic effect in this ternary system implies the potentials of Fe@GA beads in pollutant removal from water body. Copyright © 2017 Elsevier Inc. All rights reserved.

  9. 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.

  10. Chromium(VI) removal from water using fixed bed column of polypyrrole/Fe3O4 nanocomposite

    CSIR Research Space (South Africa)

    Bhaumik, M

    2013-06-07

    Full Text Available on the adsorption characteristics of adsorbent was explored at pH 2. Experimental results confirmed that the breakthrough curves were dependent on bed mass, initial Cr(VI) concentration and flow rate. Three kinetic models; Yoon–Nelson, Thomas, Bohart–Adams were...

  11. 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...

  12. cis-dioxomolybdenum(VI)-(ONO)

    Indian Academy of Sciences (India)

    Various ONO type Schiff base ligands L(H)2 used for the preparation of ... and derivatives.6–33 Depending on the method of prepa- ration .... HCl. Scheme 6. Synthesis of a Mo(VI) Schiff base complexe by selective inversion at C–1 carbon of a ...

  13. VI Tallinna arhitektuuritriennaal / Leonhard Lapin

    Index Scriptorium Estoniae

    Lapin, Leonhard, 1947-

    2005-01-01

    15.-17. IX Tallinnas Niguliste kirikus toimuval VI Tallinna arhitektuuritriennaalil esinevad inglise arhitektuurikriitik Peter Davey, šveitsi arhitekt Peter Zumthor, soome arhitekt Juha Leviskä, eesti arhitekt Vilen Künnapu, eesti kunstiajaloolane Juhan Maiste jt. Külastatakse KUMU, tutvutab autor Pekka Vapaavuori

  14. Effect of selected ligands on the U(VI) immobilization by zerovalent iron

    International Nuclear Information System (INIS)

    Noubactep, C.

    2006-01-01

    The effect of Cl - , CO 3 2- , EDTA, NO 2 - , NO 3 - , PO 4 3- , SO 4 2- , and humic substances (HS) on the U(VI) co-precipitation from aqueous solutions by zerovalent iron (ZVI) was investigated in the neutral pH range.Batch experiments without shaking were conducted for 14 days mostly with five different ZVI materials (15 g/l), selected ligands (10mM) and an U(VI) solution (20 mg/l, 0.084mM). Apart from Cl - , all tested ligands induced a decrease of U(VI) coprecipitation. This decrease is attributed to the surface adsorption and complexation of the ligands at the reactive sites on the surface of ZVI and their corrosion products. The decrease of U(VI) removal was not uniform with the five ZVI materials. Generally, groundwater with elevated EDTA concentration could not be remediated with the ZVI barrier technology. The response of the system on the pre-treating by two ZVI materials in 250mM HCl indicated that in situ generated corrosion products favor an irreversible U(VI) uptake. Thus for the long term performance of ZVI barrier, the iron dissolution should continue in such a way that fresh iron oxide be always available for U(VI) coprecipitation. (author)

  15. 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

  16. 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.

  17. Temperature Dependence of Uranium and Vanadium Adsorption on Amidoxime-Based Adsorbents in Natural Seawater

    Energy Technology Data Exchange (ETDEWEB)

    Kuo, Li-Jung [Marine Sciences Laboratory, Pacific Northwest National Laboratory, Sequim WA 98382 USA; Gill, Gary A. [Marine Sciences Laboratory, Pacific Northwest National Laboratory, Sequim WA 98382 USA; Tsouris, Costas [Oak Ridge National Laboratory, Oak Ridge TN 37831 USA; Rao, Linfeng [Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley CA 94720 USA; Pan, Horng-Bin [Department of Chemistry, University of Idaho, Moscow ID 83844 USA; Wai, Chien M. [Department of Chemistry, University of Idaho, Moscow ID 83844 USA; Janke, Christopher J. [Oak Ridge National Laboratory, Oak Ridge TN 37831 USA; Strivens, Jonathan E. [Marine Sciences Laboratory, Pacific Northwest National Laboratory, Sequim WA 98382 USA; Wood, Jordana R. [Marine Sciences Laboratory, Pacific Northwest National Laboratory, Sequim WA 98382 USA; Schlafer, Nicholas [Marine Sciences Laboratory, Pacific Northwest National Laboratory, Sequim WA 98382 USA; D' Alessandro, Evan K. [Rosensteil School of Marine and Atmospheric Chemistry, University of Miami, Miami FL 33149 USA

    2018-01-16

    The apparent enthalpy and entropy of the complexation of uranium (VI) and vanadium (V) with amidoxime ligands grafted onto polyethylene fiber was determined using time series measurements of adsorption capacities in natural seawater at three different temperatures. The complexation of uranium was highly endothermic, while the complexation of vanadium showed minimal temperature sensitivity. Amidoxime-based polymeric adsorbents exhibit significantly increased uranium adsorption capacities and selectivity in warmer waters.

  18. Synthesis of DNPH/SDS/Fe3O4 Nanoparticles for Removal of Cr (VI Ions From Aqueous Solution

    Directory of Open Access Journals (Sweden)

    Soheil Sobhanardakani

    2016-06-01

    Full Text Available In this study, sodium dodecyl sulfate (SDS coated magnetite modified with 2, 4-Dinitrophenylhydrazine was used to remove Cr (VI ions from aqueous solution. The modified magnetite nanoparticles were characterized by X-ray diffraction (XRD analysis, Fourier transform infrared spectroscopy (FT-IR, scanning electron microscopy (SEM, and SEM–EDXS measurement. The synthesized nanoparticles exhibited a high surface area of 75.5 m2 g−1 and were of 20 - 35 nm in particle size. The effects of parameters, including pH, dose of adsorbent, temperature and contact time were investigated to find the optimum adsorption conditions. Adsorption data fits well with the Langmuir isotherm model with a maximum adsorption capacity (qm and a Langmuir adsorption equilibrium constant (b of 169.5 mg g-1 and 0.168 L mg-1, respectively. The adsorption kinetic agrees well with pseudo-second-order model.

  19. Interfacial adsorption of insulin - Conformational changes and reversibility of adsorption

    NARCIS (Netherlands)

    Mollmann, SH; Jorgensen, L; Bukrinsky, JT; Elofsson, U; Norde, W; Frokjaer, S

    The adsorption of human insulin to Teflon particles was studied with respect to conformational changes and the reversibility of adsorption was examined by total internal reflection fluorescence (TIRF). Adsorption isotherms for the adsorption of human insulin indicated high affinity adsorption, even

  20. Synthesis, Characterization and Hexavalent Chromium Adsorption Characteristics of Aluminum- and Sucrose-Incorporated Tobermorite

    Directory of Open Access Journals (Sweden)

    Zhiguang Zhao

    2017-05-01

    Full Text Available Tobermorites were synthesized from the lime-quartz slurries with incorporations of aluminum and sucrose under hydrothermal conditions, and then used for adsorption of Cr(VI. The chemical components, and structural and morphological properties of tobermorite were characterized by X-ray diffraction (XRD, thermogravimetric-differential scanning calorimetry (TG-DSC, Fourier transform infrared spectroscopy (FT-IR, nuclear magnetic resonance (NMR, scanning electron microscopy (SEM, X-ray photoelectron spectroscopic (XPS and N2 adsorption–desorption measurements. The formation and crystallinity of tobermorite could be largely enhanced by adding 2.3 wt.% aluminum hydroxide or 13.3 wt.% sucrose. Sucrose also played a significantly positive role in increasing the surface area. The adsorption performances for Cr(VI were tested using a batch method taking into account the effects of pH, the adsorption kinetics, and the adsorption isotherms. The adsorption capacities of the aluminum- and sucrose-incorporated tobermorites reached up to 31.65 mg/g and 28.92 mg/g, respectively. Thus, the synthesized tobermorites showed good adsorption properties for removal of Cr(VI, making this material a promising candidate for efficient bulk wastewater treatment.

  1. Formation of stable uranium(VI) colloidal nanoparticles in conditions relevant to radioactive waste disposal.

    Science.gov (United States)

    Bots, Pieter; Morris, Katherine; Hibberd, Rosemary; Law, Gareth T W; Mosselmans, J Frederick W; Brown, Andy P; Doutch, James; Smith, Andrew J; Shaw, Samuel

    2014-12-09

    The favored pathway for disposal of higher activity radioactive wastes is via deep geological disposal. Many geological disposal facility designs include cement in their engineering design. Over the long term, interaction of groundwater with the cement and waste will form a plume of a hyperalkaline leachate (pH 10-13), and the behavior of radionuclides needs to be constrained under these extreme conditions to minimize the environmental hazard from the wastes. For uranium, a key component of many radioactive wastes, thermodynamic modeling predicts that, at high pH, U(VI) solubility will be very low (nM or lower) and controlled by equilibrium with solid phase alkali and alkaline-earth uranates. However, the formation of U(VI) colloids could potentially enhance the mobility of U(VI) under these conditions, and characterizing the potential for formation and medium-term stability of U(VI) colloids is important in underpinning our understanding of U behavior in waste disposal. Reflecting this, we applied conventional geochemical and microscopy techniques combined with synchrotron based in situ and ex situ X-ray techniques (small-angle X-ray scattering and X-ray adsorption spectroscopy (XAS)) to characterize colloidal U(VI) nanoparticles in a synthetic cement leachate (pH > 13) containing 4.2-252 μM U(VI). The results show that in cement leachates with 42 μM U(VI), colloids formed within hours and remained stable for several years. The colloids consisted of 1.5-1.8 nm nanoparticles with a proportion forming 20-60 nm aggregates. Using XAS and electron microscopy, we were able to determine that the colloidal nanoparticles had a clarkeite (sodium-uranate)-type crystallographic structure. The presented results have clear and hitherto unrecognized implications for the mobility of U(VI) in cementitious environments, in particular those associated with the geological disposal of nuclear waste.

  2. Ship-in-a-bottle CMPO in MIL-101(Cr) for selective uranium recovery from aqueous streams through adsorption

    Energy Technology Data Exchange (ETDEWEB)

    De Decker, Jeroen [Department of Inorganic and Physical Chemistry, Center for Ordered Materials, Organometallics, and Catalysis (COMOC), Ghent University, Krijgslaan 281-S3, 9000 Ghent (Belgium); Folens, Karel [Laboratory of Analytical Chemistry and Applied Ecochemistry, Ghent University, Coupure Links 653, 9000 Ghent (Belgium); De Clercq, Jeriffa [Department of Materials, Textiles, and Chemical Engineering, Industrial Catalysis and Adsorption Technology (INCAT), Ghent University, Valentin, Vaerwyckweg 1, 9000 Ghent (Belgium); Meledina, Maria; Van Tendeloo, Gustaaf [EMAT, University of Antwerp, Groenenborgerlaan 171, 2020 Antwerp (Belgium); Du Laing, Gijs [Laboratory of Analytical Chemistry and Applied Ecochemistry, Ghent University, Coupure Links 653, 9000 Ghent (Belgium); Van Der Voort, Pascal, E-mail: pascal.vandervoort@ugent.be [Department of Inorganic and Physical Chemistry, Center for Ordered Materials, Organometallics, and Catalysis (COMOC), Ghent University, Krijgslaan 281-S3, 9000 Ghent (Belgium)

    2017-08-05

    Highlights: • Highly stable metal-organic framework, MIL-101(Cr), for uses in aqueous, acidic adsorption. • Uranium recovery from low concentration acidic solutions. • One-step ship-around-the-bottle synthetic approach to incorporate CMPO in MIL-101(Cr). • Highly selective U(VI) adsorbent in competition with a high variety of metals, incl. rare earths and transition metals. • Regenerable and reusable adsorbent via 0.1 M nitric acid stripping. - Abstract: Mesoporous MIL-101(Cr) is used as host for a ship-in-a-bottle type adsorbent for selective U(VI) recovery from aqueous environments. The acid-resistant cage-type MOF is built in-situ around N,N-Diisobutyl-2-(octylphenylphosphoryl)acetamide (CMPO), a sterically demanding ligand with high U(VI) affinity. This one-step procedure yields an adsorbent which is an ideal compromise between homogeneous and heterogeneous systems, where the ligand can act freely within the pores of MIL-101, without leaching, while the adsorbent is easy separable and reusable. The adsorbent was characterized by XRD, FTIR spectroscopy, nitrogen adsorption, XRF, ADF-STEM and EDX, to confirm and quantify the successful encapsulation of the CMPO in MIL-101, and the preservation of the host. Adsorption experiments with a central focus on U(VI) recovery were performed. Very high selectivity for U(VI) was observed, while competitive metal adsorption (rare earths, transition metals...) was almost negligible. The adsorption capacity was calculated at 5.32 mg U/g (pH 3) and 27.99 mg U/g (pH 4), by fitting equilibrium data to the Langmuir model. Adsorption kinetics correlated to the pseudo-second-order model, where more than 95% of maximum uptake is achieved within 375 min. The adsorbed U(VI) is easily recovered by desorption in 0.1 M HNO{sub 3}. Three adsorption/desorption cycles were performed.

  3. Ship-in-a-bottle CMPO in MIL-101(Cr) for selective uranium recovery from aqueous streams through adsorption

    International Nuclear Information System (INIS)

    De Decker, Jeroen; Folens, Karel; De Clercq, Jeriffa; Meledina, Maria; Van Tendeloo, Gustaaf; Du Laing, Gijs; Van Der Voort, Pascal

    2017-01-01

    Highlights: • Highly stable metal-organic framework, MIL-101(Cr), for uses in aqueous, acidic adsorption. • Uranium recovery from low concentration acidic solutions. • One-step ship-around-the-bottle synthetic approach to incorporate CMPO in MIL-101(Cr). • Highly selective U(VI) adsorbent in competition with a high variety of metals, incl. rare earths and transition metals. • Regenerable and reusable adsorbent via 0.1 M nitric acid stripping. - Abstract: Mesoporous MIL-101(Cr) is used as host for a ship-in-a-bottle type adsorbent for selective U(VI) recovery from aqueous environments. The acid-resistant cage-type MOF is built in-situ around N,N-Diisobutyl-2-(octylphenylphosphoryl)acetamide (CMPO), a sterically demanding ligand with high U(VI) affinity. This one-step procedure yields an adsorbent which is an ideal compromise between homogeneous and heterogeneous systems, where the ligand can act freely within the pores of MIL-101, without leaching, while the adsorbent is easy separable and reusable. The adsorbent was characterized by XRD, FTIR spectroscopy, nitrogen adsorption, XRF, ADF-STEM and EDX, to confirm and quantify the successful encapsulation of the CMPO in MIL-101, and the preservation of the host. Adsorption experiments with a central focus on U(VI) recovery were performed. Very high selectivity for U(VI) was observed, while competitive metal adsorption (rare earths, transition metals...) was almost negligible. The adsorption capacity was calculated at 5.32 mg U/g (pH 3) and 27.99 mg U/g (pH 4), by fitting equilibrium data to the Langmuir model. Adsorption kinetics correlated to the pseudo-second-order model, where more than 95% of maximum uptake is achieved within 375 min. The adsorbed U(VI) is easily recovered by desorption in 0.1 M HNO 3 . Three adsorption/desorption cycles were performed.

  4. 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.

  5. 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.

  6. Energy Transfer between U(VI) and Eu(III) Ions Adsorbed on a Silica Surface

    Energy Technology Data Exchange (ETDEWEB)

    Park, K. K.; Cha, W.; Cho, H. R.; Im, H. J.; Jung, E. C.; Song, K. [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2011-05-15

    Understanding of chemical behavior of actinide in a groundwater flow is important for assessing the possibility of their migration with water flows in a radioactive waste disposal site. Uranium is ubiquitous in the environment and a major actinide in a nuclear fuel cycle. Americium and curium having isotopes of long half life are minor actinides in a spent fuel. If a minor actinide coexists with uranium in a groundwater flow, some interactions between them could be expected such as minor actinide adsorption onto uranium precipitates and competition with each other for an adsorption to a mineral surface site. Eu(III) ion is frequently used as a chemical analogue of Am(III) and Cm(III) ions in a migration chemistry. The luminescent spectra of U(VI) and Eu(III) ions show a dependency on the coordination symmetry around them, and the changes in intensity or bandwidth of spectra can yield valuable information on their local environment. The luminescent lifetime also strongly depends on the coordination environment, and its measurement is valuable in probe studies on micro-heterogeneous systems. The excited U(VI) ion can be quenched through Stern.Volmer process, hydrolysis of excited species, exciplex formation, electron transfer or energy transfer. In case of U(VI)-Eu(III) system, the interaction between two ions can be studied by measuring the effect of Eu(III) ion on the quenching of U(VI) ion luminescence. There are only a few investigations on the interaction between an excited U(VI) ion and a lanthanide(III) ion. In perchlorate solution, the energy transfer to Eu(III) ion occurred only in solutions of pH>3.87. In this study, the quenching of U(VI) luminescence by Eu(III) on a silica surface was measured. The results will be discussed on the basis of a chemical interaction between them

  7. Vi mangler endnu et panel

    DEFF Research Database (Denmark)

    Ritter, Thomas

    2016-01-01

    Vi mangler højtuddannede værdiskabere, som transformerer gode idéer og teknologier til indtjening og velstand. Først i mødet med markedet afgøres fremtiden. Troels Lund Poulsen bør nedsætte et kommercialiseringspanel, der byder ind med løsninger, hvordan Danmark bliver et land ikke kun med gode...

  8. Understanding the role of clay minerals in the chromium(VI) bioremoval by Pseudomonas aeruginosa CCTCC AB93066 under growth condition: microscopic, spectroscopic and kinetic analysis.

    Science.gov (United States)

    Kang, Chunxi; Wu, Pingxiao; Li, Yuewu; Ruan, Bo; Li, Liping; Tran, Lytuong; Zhu, Nengwu; Dang, Zhi

    2015-11-01

    Laboratory batch experiments were conducted to investigate the role of clay minerals, e.g., kaolinite and vermiculite, in microbial Cr(VI) reduction by Pseudomonas aeruginosa under growth condition in glucose-amended mediums as a method for treating Cr(VI)-contaminated subsurface environment such as soil. Our results indicated that glucose could acted as an essential electron donor, and clay minerals significantly enhanced microbial Cr(VI) reduction rates by improving the consumption rate of glucose and stimulating the growth and propagation of P. aeruginosa. Cr(VI) bioreduction by both free cells and clay minerals-amended cells followed the pseudo-first-order kinetic model, with the latter one fitting better. The mass balance analyses and X-ray photoelectron spectroscopy analysis found that Cr(VI) was reduced to Cr(III) and the adsorption of total chromium on clay minerals-bacteria complex was small, implying that Cr(VI) bioremoval was not mainly due to the adsorption of Cr(VI) onto cells or clay minerals or clay minerals-cells complex but mainly due to the Cr(VI) reduction capacity of P. aeruginosa under the experimental conditions studied (e.g., pH 7). Atomic force microscopy revealed that the addition of clay minerals (e.g. vermiculite) decreased the surface roughness of Cr(VI)-laden cells and changed the cell morphology and dimension. Fourier transform infrared spectroscopy revealed that organic matters such as aliphatic species and/or proteins played an important role in the combination of cells and clay minerals. Scanning electron microscopy confirmed the attachment of cells on the surface of clay minerals, indicating that clay minerals could provide a microenvironment to protect cells from Cr(VI) toxicity and serve as growth-supporting materials. These findings manifested the underlying influence of clay minerals on microbial reduction of Cr(VI) and gave an understanding of the interaction between pollutants, the environment and the biota.

  9. Removal of Hexavalent Chromium by Adsorption on Microwave Assisted Activated Carbon Prepared from Stems of Leucas Aspera

    Science.gov (United States)

    Shanmugalingam, A.; Murugesan, A.

    2018-05-01

    This study reports adsorption of Cr(VI) ions from aqueous solution using activated carbon that was prepared from stems of Leucas aspera. Eight hundred and fifty watts power of microwave radiation, 12 min of radiation time, 60% of ZnCl2 solution and 24 h of impregnation time are the optimal parameters to prepare efficient carbon effective activated carbon. It was designated as MWLAC (Microwave assisted Zinc chloride activated Leucas aspera carbon). Various adsorption characteristics such as dose of the adsorbent, agitation time, initial Cr(VI) ion concentration, pH of the solution and temperature on adsorption were studied for removal of Cr(VI) ions from aqueous solution by batch mode. Also the equilibrium adsorption was analyzed by the Langmuir, Freundlich, Tempkin and D-R isotherm models. The order of best describing isotherms was given based on R2 value. The pseudo-second-order kinetic model best fitted with the Cr(VI) adsorption data. Thermodynamic parameters were also determined and results suggest that the adsorption process is a spontaneous, endothermic and proceeded with increased randomness.

  10. Adsorption. What else?

    OpenAIRE

    Rodrigues, Alirio E.

    2012-01-01

    [EN] Chemical Engineering today combines Molecular and Materials Engineerig and Process and Product Engineering (ChE=M2P2). Cyclic adsorptive processes (Simulated Moving Bed –SMB and Pressure Swing Adsorption-PSA) will be discussed for “old” and “new” applications making use of “old” and “new” (MOFs) adsorbent materials. After revisiting my memory as PhD student and the First Brazilian Adsorption meeting I will review the basic concepts involved in adsorption processes and then...

  11. Preparation of Ca-alginate coated nZVI core shell beads for uranium (VI) removal from aqueous solution

    International Nuclear Information System (INIS)

    Shuhong Hu; Xiaoyan Lin; Yahui Zhang; Meiling Shi

    2017-01-01

    In this study, the core-shell nanoscale zero-valent iron (nZVI)@Alg-Ca beads were synthesized by coaxial electronic injection method for removal of U (VI) from aqueous solution, and characterized by SEM, EDX and XPS. The results showed that the pseudo-second-order models and the Langmuir isotherm model fitted well with the data obtained. The removal mechanism may include both physical adsorption of U (VI) on the surface or inside of core-shell nZVI@Alg-Ca beads and subsequent reduction of U (VI) to U (IV). Therefore, the core-shell nZVI@Alg-Ca beads would have an application prospect in effective removal of U (VI) contamination from aqueous solution. (author)

  12. Infrared spectroscopic studies of uranyl(VI) species adsorbed from aqueous [UO2(CO3)3]4- solutions on to a polymer bearing amidoxime groups

    International Nuclear Information System (INIS)

    Hirotsu, Takahiro; Katoh, Shunsaku; Sugasaka, Kazuhiko; Seno, Manabu; Itagaki, Takaharu

    1987-01-01

    Infrared spectra of uranyl(VI) species adsorbed from aqeuous [UO 2 (CO 3 ) 3 ] 4- solutions on to a polymer having amidoxime groups were examined in order to obtain information on the adsorption mechanism. The subtraction spectra in a region of 500-1 500 cm -1 exhibit only a distinct band at 886 cm -1 ascribed to the v 3 mode of the O=U=O moiety and no band assigned to carbonato ligands, suggesting the existence of a carbonato-free uranyl(VI) complex; this is consistent with the adsorption equilibrium reported previously. (author)

  13. Study of the biosorption of chromium (VI) on crosslinked-quaternary chitosan for their application on the bioremediation of waster waters

    International Nuclear Information System (INIS)

    Diaz, Carlos; Jacinto, Cristian; Medina, Rosa; Navarro, Abel; Cuizano, N.; Llanos, Bertha

    2013-01-01

    In this work, the stoichiometric amounts of the amino-quaternaries and cross-linker were studied to produce the most stable cross-linked quaternary Chitosan (QC2). Preliminary assays were carried out to test the improvement in their mechanical and chemical properties (extreme conditions, surface area and thermogravimetry). Then, the adsorption of chromium (VI) on the QC2 was studied at changing experimental conditions like: pH, adsorbent dose, initial chromium concentration and ionic strength. Moreover, the kinetics of the process was also evaluated as well as the optimization, the desorption of chromium (VI) from the adsorbent for metal recovery and adsorbent recycling. Finally, was characterized by using instrumental techniques such as FTIR, SEM. These tools allowed us to investigate the adsorption mechanism. The calculated parameters indicate a high adsorbent/adsorbato affinity for QC2 with a maximum adsorption capacity of 208 mg g -1 for Cr (VI), elucidating its potential use for the removal of chromium from aqueous solutions. Also showed a pseudo-second order adsorption kinetics with a velocity constant of 0.289 g.mg -1 .min -1 . Desorption of chromium was efficiently accomplish with a mixture of 1M of NaCl and NaOH, reaching a recovery up to 99.78% of the initial metal concentration at pH 4.5. Finally, high ionic strength shows an effect on the adsorption of chromium (VI) onto the studied adsorbents. (author)

  14. 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.

  15. Reduction of Cr (VI) into Cr (III) by organelles of Chlorella vulgaris in aqueous solution: An organelle-level attempt.

    Science.gov (United States)

    Chen, Zunwei; Song, Shufang; Wen, Yuezhong

    2016-12-01

    The priority pollutant chromium (Cr) was ubiquitous and great efforts have been made to reduce Cr (VI) into less-toxic Cr (III) by alga for the convenient availability and low expense. However, the functional role of organelle inside the algal cell in Cr (VI) reduction was poorly understood. In this study, organelles in green algae Chlorella vulgaris were extracted and further decorated for Cr (VI) reduction tests. Results showed that the chloroplast exhibited not only adsorption ability of total Cr (21.18% comparing to control) but also reduction potential of Cr (VI) (almost 70% comparing to control), whose most suitable working concentration was at 17μg/mL. Furtherly, the isolated thylakoid membrane (ITM) showed better Cr (VI) reduction potential with the presence of sodium alginate (SA), even though the Hill reaction activity (HRA) was inhibited. As for photosystem II (PSII), the addition of mesoporous silica SBA-15 enhanced the reduction ability through improving the light-harvesting complex (LHC) II efficiency and electron transport rate. On the whole, the reduction ability order of the three kinds of materials based on chloroplast in C. vulgaris was PSII@SBA-15>Chloroplast>ITM@SA. The attempt made in this study to reduce the Cr (VI) with C. vulgaris organelles might not only offer basement to detect the potential action mechanism of Cr (VI) reduction by C. vulgaris but also provide a new sight for the scavenge of heavy metal with biological materials. Copyright © 2016 Elsevier B.V. All rights reserved.

  16. A surface structural model for ferrihydrite II: Adsorption of uranyl and carbonate

    NARCIS (Netherlands)

    Hiemstra, T.; Riemsdijk, van W.H.; Rossberg, A.; Ulrich, K.

    2009-01-01

    The adsorption of uranyl (UO22+) on ferrihydrite has been evaluated with the charge distribution (CD) model for systems covering a very large range of conditions, i.e. pH, ionic strength, CO2 pressure, U(VI) concentration, and loading. Modeling suggests that uranyl forms bidentate inner sphere

  17. A Simple Adsorption Experiment

    Science.gov (United States)

    Guirado, Gonzalo; Ayllon, Jose A.

    2011-01-01

    The study of adsorption phenomenon is one of the most relevant and traditional physical chemistry experiments performed by chemistry undergraduate students in laboratory courses. In this article, we describe an easy, inexpensive, and straightforward way to experimentally determine adsorption isotherms using pieces of filter paper as the adsorbent…

  18. Adsorption of uranium from aqueous solution by PAMAM dendron functionalized styrene divinylbenzene

    Energy Technology Data Exchange (ETDEWEB)

    Ilaiyaraja, P., E-mail: chemila07@gmail.com [Radiological Safety Division, Radiological Safety and Environmental Group, Indira Gandhi Centre for Atomic Research, Kalpakkam 603102, Tamilnadu (India); Singha Deb, Ashish Kumar; Sivasubramanian, K. [Radiological Safety Division, Radiological Safety and Environmental Group, Indira Gandhi Centre for Atomic Research, Kalpakkam 603102, Tamilnadu (India); Ponraju, D. [Safety Engineering Division, Reactor Design Group, Indira Gandhi Centre for Atomic Research, Kalpakkam 603102, Tamilnadu (India); Venkatraman, B. [Radiological Safety Division, Radiological Safety and Environmental Group, Indira Gandhi Centre for Atomic Research, Kalpakkam 603102, Tamilnadu (India)

    2013-04-15

    Highlights: ► A new chelating resin PAMAMG{sub 3} -SDB has been synthesized for uranium adsorption. ► The maximum adsorption capacity was determined to be 130.25 mg g{sup −1} at pH 5.5. ► Adsorption capacity increases linearly with increasing dendron generation. ► The adsorbed uranium shall be easily desorbed by simply adjusting the pH < 3. ► Quantitative adsorption of uranium was observed even at high ionic strength. -- Abstract: A new polymeric chelating resin was prepared by growing third generation poly(amido)amine (PAMAMG{sub 3}) dendron on the surface of styrene divinylbenzene (SDB) and characterized by FTIR, TGA and SEM. The ideal branching of dendron in the chelating resin was determined from potentiometric titration. Adsorption of uranium (VI) from aqueous solution using PAMAMG{sub 3}-SDB chelating resin was studied in a series of batch experiments. Effect of contact time, pH, ionic strength, adsorbent dose, initial U(VI) concentration, dendron generation and temperature on adsorption of U(VI) were investigated. Kinetic experiments showed that U(VI) adsorption on PAMAMG{sub 3}-SDB followed pseudo-second-order kinetics model appropriately and equilibrium data agreed well with the Langmuir isotherm model. Thermodynamic parameters (ΔH°, ΔS°, ΔG°) were evaluated from temperature dependent adsorption data and the uranium adsorption on PAMAMG{sub 3}-SDB was found to be endothermic and spontaneous in nature. The sticking probability value (5.303 × 10{sup −9}), kinetic and isotherm data reveal the chemisorption of uranium on PAMAMG{sub 3}-SDB and adsorption capacity of the chelating resin was estimated to be 130.25 mg g{sup −1} at 298 K. About 99% of adsorbed U(VI) can be desorbed from PAMAMG{sub 3}-SDB by a simple acid treatment suggesting that the chelating resin is reusable.

  19. Radioactive nuclide adsorption

    International Nuclear Information System (INIS)

    Fukushima, Kimichika.

    1982-01-01

    Purpose: To improve the efficiency of a radioactive nuclide adsorption device by applying a nickel plating on a nickel plate to render the surface active. Constitution: A capturing device for radioactive nuclide such as manganese 54, cobalt 60, 58 and the like is disposed to the inside of a pipeway provided on the upper portion of fuel assemblies through which liquid sodium as the coolant for LMFBR type reactor is passed. The device comprises a cylindrical adsorption body and spacers. The adsorption body is made of nickel and applied with a nickel plating on the surface thereof. The surface of the adsorption body is unevened to result in disturbance in the coolant and thereby improve the adsorptive efficiency. (Kawakami, Y.)

  20. Characterization of U(VI) Sorption-Desorption Processes and Model Upscaling

    International Nuclear Information System (INIS)

    Bai, Jing; Dong, Wenming; Ball, William P.

    2006-01-01

    The objectives of the overall collaborative EMSP effort (with which this project is associated) were to characterize sorption and desorption processes of U(VI) on pristine and contaminated Hanford sediments over a range of sediment facies and materials properties and to relate such characterization both to fundamental molecular-scale understanding and field-scale models of geochemistry and mass transfer. The research was intended to provide new insights on the mechanisms of U(VI) retardation at Hanford, and to allow the development of approaches by which laboratory-developed geochemical models could be upscaled for defensible field-scale predictions of uranium transport in the environment. Within this broader context, objectives of the JHU-based project were to test hypotheses regarding the coupled roles of adsorption and impermeable-zone diffusion in controlling the fate and transport of U(VI) species under conditions of comparatively short-term exposure. In particular, this work tested the following hypotheses: (1) the primary adsorption processes in the Hanford sediment over the pH range of 7 to 10 are surface complexation reactions of aqueous U(VI) hydroxycarbonate and carbonate complexes with amphoteric edge sites on detrital phyllosilicates in the silt/clay size fraction; (2) macroscopic adsorption intensity (at given aqueous conditions) is a function of mineral composition and aquatic chemistry; and (3) equilibrium sorption and desorption to apply in short-term, laboratory-spiked pristine sediments; and (4) interparticle diffusion can be fully understood in terms of a model that couples molecular diffusion of uranium species in the porewater with equilibrium sorption under the relevant aqueous conditions. The primary focus of the work was on developing and applying both models and experiments to test the applicability of ''local equilibrium'' assumptions in the modeling interpretation of sorption retarded interparticle diffusion, as relevant to processes of

  1. Microbial reductive transformation of phyllosilicate Fe(III) and U(VI) in fluvial subsurface sediments.

    Science.gov (United States)

    Lee, Ji-Hoon; Fredrickson, James K; Kukkadapu, Ravi K; Boyanov, Maxim I; Kemner, Kenneth M; Lin, Xueju; Kennedy, David W; Bjornstad, Bruce N; Konopka, Allan E; Moore, Dean A; Resch, Charles T; Phillips, Jerry L

    2012-04-03

    The microbial reduction of Fe(III) and U(VI) was investigated in shallow aquifer sediments collected from subsurface flood deposits near the Hanford Reach of the Columbia River in Washington State. Increases in 0.5 N HCl-extractable Fe(II) were observed in incubated sediments and (57)Fe Mössbauer spectroscopy revealed that Fe(III) associated with phyllosilicates and pyroxene was reduced to Fe(II). Aqueous uranium(VI) concentrations decreased in subsurface sediments incubated in sulfate-containing synthetic groundwater with the rate and extent being greater in sediment amended with organic carbon. X-ray absorption spectroscopy of bioreduced sediments indicated that 67-77% of the U signal was U(VI), probably as an adsorbed species associated with a new or modified reactive mineral phase. Phylotypes within the Deltaproteobacteria were more common in Hanford sediments incubated with U(VI) than without, and in U(VI)-free incubations, members of the Clostridiales were dominant with sulfate-reducing phylotypes more common in the sulfate-amended sediments. These results demonstrate the potential for anaerobic reduction of phyllosilicate Fe(III) and sulfate in Hanford unconfined aquifer sediments and biotransformations involving reduction and adsorption leading to decreased aqueous U concentrations.

  2. 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.

  3. 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.

  4. 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

  5. Adsorption of selenium by amorphous iron oxyhydroxide and manganese dioxide

    Science.gov (United States)

    Balistrieri, L.S.; Chao, T.T.

    1990-01-01

    This work compares and models the adsorption of selenium and other anions on a neutral to alkaline surface (amorphous iron oxyhydroxide) and an acidic surface (manganese dioxide). Selenium adsorption on these oxides is examined as a function of pH, particle concentration, oxidation state, and competing anion concentration in order to assess how these factors might influence the mobility of selenium in the environment. The data indicate that 1. 1) amorphous iron oxyhydroxide has a greater affinity for selenium than manganese dioxide, 2. 2) selenite [Se(IV)] adsorption increases with decreasing pH and increasing particle concentration and is stronger than selenate [Se(VI)] adsorption on both oxides, and 3. 3) selenate does not adsorb on manganese dioxide. The relative affinity of selenate and selenite for the oxides and the lack of adsorption of selenate on a strongly acidic surface suggests that selenate forms outer-sphere complexes while selenite forms inner-sphere complexes with the surfaces. The data also indicate that the competition sequence of other anions with respect to selenite adsorption at pH 7.0 is phosphate > silicate > molybdate > fluoride > sulfate on amorphous iron oxyhydroxide and molybdate ??? phosphate > silicate > fluoride > sulfate on manganese dioxide. The adsorption of phosphate, molybdate, and silicate on these oxides as a function of pH indicates that the competition sequences reflect the relative affinities of these anions for the surfaces. The Triple Layer surface complexation model is used to provide a quantitative description of these observations and to assess the importance of surface site heterogeneity on anion adsorption. The modeling results suggest that selenite forms binuclear, innersphere complexes with amorphous iron oxyhydroxide and monodentate, inner-sphere complexes with manganese dioxide and that selenate forms outer-sphere, monodentate complexes with amorphous iron oxyhydroxide. The heterogeneity of the oxide surface sites

  6. Preparation, characterization, uranium (VI) biosorption models, and conditions optimization by response surface methodology (RSM) for amidoxime-functionalized marine fungus materials

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Xuechun; Gao, Yang; Jiang, Min; He, Dianxiong; Liao, Sen; Hou, Dan; Yan, Xueming; Long, Wei; Wu, Yaxin; Tan, Ni [Univ. of South China, Hengyang (China). School of Chemistry and Chemical Engineering

    2017-08-01

    Amidoxime-functionalized marine fungus Fusarium sp. ZZF51 (ZGDA) was synthesized and studied to adsorb uranium (VI) from the aqueous solution. Different instrumental techniques such as FTIR, SEM, and TGA were employed for the characterization of the manufactured materials, and theirs ability of removal uranium (VI) was optimized using RSM. The experimental results showed the maximum adsorption capacity for the synthesized materials was 230.78 mg g{sup -1} at the following optimization conditions: S-L ratio 150 mg L{sup -1}, pH 5.13, uranium (VI) initial concentration 40 mg L{sup -1}, and equilibrium time 122.40 min. More than 85% of the absorbed uranium (VI) could be desorbed by 0.5 or 1.0 mol L{sup -1} HCl, and the modified mycelium could be reused at least five times. The thermodynamic experimental data of adsorption uranium (VI) could fit better with Langmuir and Freundlich isotherms models, and the pseudo-second-order model was better to interpret the kinetics process. The modified fungus materials exhibited the better sorption capacity for uranium (VI) in comparison with raw biomass should be attributed to the strong chelation of amidoxime to uranium (VI) ions.

  7. A comparative study of the adsorption of uranium on commercial and natural (Cypriot) sea sand samples

    International Nuclear Information System (INIS)

    Maria Efstathiou; Ioannis Pashalidis

    2013-01-01

    The adsorption of hexavalent uranium on two different types of sea sand [e.g. a local, Cypriot (N S S) and a commercially available marine sediment (C S S)] has been investigated as a function of pH, initial metal concentration, ionic strength and contact time under normal atmospheric conditions. Before carrying out the adsorption experiments, the sea sand samples have been characterized by XRD, XRF, N 2 -adsorption, acid/base titrations and FTIR spectroscopy. Sample characterization showed clearly that the two sea sand types differ significantly in their composition, particularly in their calcite and FeOOH content. According to experimental data obtained from acid/base titrations and adsorption batch experiments sea sand composition affects the acid/base and the adsorption properties of the adsorbents. The extraordinary high affinity of N S S for hexavalent uranium in the alkaline pH region can be attributed to the formation of mixed U(VI)-carbonato surface species on the FeOOH crystal phases present in N S S, which effectively compete the formation of U(VI)-carbonato complexes in solution. On the other hand, data obtained by adsorption experiments carried out in solution of different ionic strengths don't differ significantly from one another indicating the formation of inner-sphere complexes. Finally, the adsorption on sea sands is a relatively fast two-step process. (author)

  8. 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.

  9. Electrospinning synthesis of porous Al{sub 2}O{sub 3} nanofibers by pluronic P123 triblock copolymer surfactant and properties of uranium (VI)-sorption

    Energy Technology Data Exchange (ETDEWEB)

    Ren, Bo [The Key Laboratory of Superlight Materials and Surface Technology, Ministry of Education, Harbin 150001 (China); Department of Applied Chemistry Engineering, Jilin Vocational College of Industry and Technology, Jilin 132013 (China); Institute of Petrochemistry Heilongjiang Academy of Sciences, Harbin 150001 (China); Fan, Meiqing [The Key Laboratory of Superlight Materials and Surface Technology, Ministry of Education, Harbin 150001 (China); Department of Applied Chemistry Engineering, Jilin Vocational College of Industry and Technology, Jilin 132013 (China); Tan, Lichao [The Key Laboratory of Superlight Materials and Surface Technology, Ministry of Education, Harbin 150001 (China); Li, Rumin, E-mail: lirumin@hrbeu.edu.cn [The Key Laboratory of Superlight Materials and Surface Technology, Ministry of Education, Harbin 150001 (China); Song, Dalei; Liu, Qi [The Key Laboratory of Superlight Materials and Surface Technology, Ministry of Education, Harbin 150001 (China); Wang, Jun, E-mail: zhqw1888@sohu.com [The Key Laboratory of Superlight Materials and Surface Technology, Ministry of Education, Harbin 150001 (China); Institute of Advanced Marine Materials, Harbin Engineering University, Harbin 150001 (China); Zhang, Bin [Institute of Petrochemistry Heilongjiang Academy of Sciences, Harbin 150001 (China); Jing, Xiaoyan [The Key Laboratory of Superlight Materials and Surface Technology, Ministry of Education, Harbin 150001 (China)

    2016-07-01

    Porous Alumina (Al{sub 2}O{sub 3}) nanofibers were prepared by electrospinning process using pluronic P123 triblock copolymer surfactant as template. The characterizations of the adsorbent were investigated by X-ray diffraction (XRD) fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and nitrogen adsorption–desorption. The obtained nanofibers were used as adsorbents for the removal of Uranium (VI). The maximum adsorption occurred at pH 5, the equilibrium adsorption amount was about 87 mg/g, and the equilibrium time was 6.0 h. A pseudo-second order model could best describe adsorption kinetics. The adsorption equilibrium data fit Freundlich adsorption isotherm equation well. Thermodynamic parameters such as standard enthalpy (ΔH{sup 0}), standard entropy (ΔS{sup 0}), standard free energy (ΔG{sup 0}) and activation energy (E{sub a}) were calculated. The results predict an endothermic nature of adsorption and a spontaneous process. - Highlights: • The porous Al{sub 2}O{sub 3} nanofibers were used for U(VI)-sorption for the first time. • The adsorption process was endothermic and spontaneous. • The maximum adsorption capacity was 87 mg g{sup −1} at 25 °C.

  10. Nanospherical inorganic α-Fe core-organic shell necklaces for the removal of arsenic(V) and chromium(VI) from aqueous solution

    Science.gov (United States)

    Azzam, Ahmed M.; Shenashen, Mohamed A.; Selim, Mahmoud M.; Yamaguchi, Hitoshi; El-Sewify, Islam M.; Kawada, Satoshi; Alhamid, Abdulaziz A.; El-Safty, Sherif A.

    2017-10-01

    Mesoporous nanospherical necklaces (NSN) of inorganic α-Fe core-organic shell and ethylenediaminetetraacetic acid (EDTA) were fabricated. The necklaces were 1 μm in length and 50 nm in thickness, with massive nanospherical particles connecting and overlapping in a neat micro-/nano-necklace archery cage for capturing/trapping of As(V) and Cr(VI) species from water sources. The α-Fe core and the dressing shell of EDTA provided numerous active sites for adsorption, which led to 100% adsorption uptake of these toxic ions. The adsorption isotherms revealed that NSN adsorbent with mesoporous caves and organic-decorated surfaces was promising and effective for the spontaneous and endothermic removal of both ions from contaminated water. The NSN structure exhibited long-term stability. The adsorption efficiency and uptake of the deleterious arsenic and chromium species were achieved after multi-particulate processing of reuse cycles. The pH-dependent removal of As(V) and Cr(VI) species is an emerging topic in selective adsorption assays among competitive ions. Furthermore, the ion-selective conditions at pH 5 for As(V) and pH 7 for Cr(VI) significantly affected the adsorption capacity and affinity of 306.7 and 406.5 mg g-1 into NSN cages, respectively. The obtained results could be used as a basis to provide effective and low-cost products for the purification of wastewater resources from toxic metals.

  11. Surface modification of glass beads with glutaraldehyde: Characterization and their adsorption property for metal ions

    Energy Technology Data Exchange (ETDEWEB)

    Ozmen, Mustafa; Can, Keziban; Akin, Ilker; Arslan, Gulsin [Department of Chemistry, Selcuk University, 42031, Konya (Turkey); Tor, Ali, E-mail: ali.alitor@gmail.com [Department of Environmental Engineering, Selcuk University, Engineering Faculty, Campus, 42031, Konya (Turkey); Cengeloglu, Yunus; Ersoz, Mustafa [Department of Chemistry, Selcuk University, 42031, Konya (Turkey)

    2009-11-15

    In this study, a new material that adsorbs the metal ions was prepared by modification of the glass beads surfaces with glutaraldehyde. First, the glass beads were etched with 4 M NaOH solution. Then, they were reacted with 3-aminopropyl-triethoxysilane (APTES). Finally, silanized glass beads were treated with 25% of glutaraldehyde solution. The characterization studies by using Fourier Transform Infrared Spectroscopy (FT-IR), Thermal Gravimetric Analysis (TGA), elemental analysis and Scanning Electron Microscopy (SEM) indicated that modification of the glass bead surfaces was successfully performed. The adsorption studies exhibited that the modified glass beads could be efficiently used for the removal of the metal cations and anion (chromate ion) from aqueous solutions via chelation and ion-exchange mechanisms. For both Pb(II) and Cr(VI), selected as model ions, the adsorption equilibrium was achieved in 60 min and adsorption of both ions followed the second-order kinetic model. It was found that the sorption data was better represented by the Freundlich isotherm in comparison to the Langmuir and Redlich-Peterson isotherm models. The maximum adsorption capacities for Pb(II) and Cr(VI) were 9.947 and 11.571 mg/g, respectively. The regeneration studies also showed that modified glass beads could be re-used for the adsorption of Pb(II) and Cr(VI) from aqueous solutions over three cycles.

  12. Study on Shale Adsorption Equation Based on Monolayer Adsorption, Multilayer Adsorption, and Capillary Condensation

    Directory of Open Access Journals (Sweden)

    Qing Chen

    2017-01-01

    Full Text Available Shale gas is an effective gas resource all over the world. The evaluation of pore structure plays a critical role in exploring shale gas efficiently. Nitrogen adsorption experiment is one of the significant approaches to analyze pore size structure of shale. Shale is extremely heterogeneous due to component diversity and structure complexity. Therefore, adsorption isotherms for homogeneous adsorbents and empirical isotherms may not apply to shale. The shape of adsorption-desorption curve indicates that nitrogen adsorption on shale includes monolayer adsorption, multilayer adsorption, and capillary condensation. Usually, Langmuir isotherm is a monolayer adsorption model for ideal interfaces; BET (Brunauer, Emmett, Teller adsorption isotherm is a multilayer adsorption model based on specific assumptions; Freundlich isotherm is an empirical equation widely applied in liquid phase adsorption. In this study, a new nitrogen adsorption isotherm is applied to simultaneously depict monolayer adsorption, multilayer adsorption, and capillary condensation, which provides more real and accurate representation of nitrogen adsorption on shale. In addition, parameters are discussed in relation to heat of adsorption which is relevant to the shape of the adsorption isotherm curve. The curve fitting results indicate that our new nitrogen adsorption isotherm can appropriately describe the whole process of nitrogen adsorption on shale.

  13. Adsorption of Cs-137 and U-238 in semi-arid soils

    International Nuclear Information System (INIS)

    Hernandez T, U. O.; Monroy G, F.; Anguiano A, J.; Fernandez R, E.

    2013-10-01

    Is of great importance to determine the adsorption properties of the soils where radioactive wastes are stored, fundamentally of the radioisotopes contained in these wastes, with the purpose of knowing like will be their behavior in the event of happening radionuclide migration toward the surrounding means. Therefore, in this work the adsorption properties of 137 Cs + and 238 UO 2 2+ in soils coming from the Storage Center of Radioactive Wastes are studied. Was studied the effect of the soil type and the particle size of the soil in the adsorption properties of Cs (I) and U (Vi). 13 soil samples and six different particle sizes were analyzed. The adsorption studies were carried out by the radiotracers technique in static way. The results indicate an important adsorption affinity toward the Cs-137 and a very vulnerable affinity for the 238 UO 2 2+ . (author)

  14. 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.

  15. 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.

  16. Sorption study of 226Ra(II) et 238U(VI) on to peat organic matter, in mining environment

    International Nuclear Information System (INIS)

    Bordelet, Gabrielle

    2014-01-01

    The environmental footprint of former uranium mining sites is a major concern for society. In order to guarantee the protection of ecosystems and thus a minimal radiological impact on the biosphere, it is important to understand and to be able to model the phenomena controlling the migration of uranium and its decay products, specially radium ( 226 Ra) (AREVA's Envir-at-Mines project). In the environment, among solid phases which can retain 238 U(VI) and 226 Ra(II), peat is known to have relevant affinity for U(VI). Because peat is usually composed at 90% dry weight of organic matter, the aim of this study was to qualify and quantify peat organic matter affinity for 238 U(VI) and 226 Ra(II). Peat samples extracted from Les Sagnes (close to a former uranium mining site in Limousin area, France) was characterised and batch adsorption/desorption experiments were conducted. The results indicate that 226 Ra(II) adsorption onto that peat is higher than 97% for pH ≥ 4-6 (depending on the organic/mineral ratio in dry peat) corresponding to K d values about 4500 ± 500 mL/g and 238 U(VI) adsorption is higher than 80% at pH ≥ 3 with K d maximal values reaching 11000 mL/g around pH 4.5. Only a little desorption was measured after one month. An ion exchange modelling for radium adsorption onto one type of organic matter sorption site was enough to fit the experimental adsorption K d for the peat over the whole range of pH. However, uranium sorption on peat can be modelled on that organic sorption site only from pH 1 to 5. From pH 5 to 10, to explain the experimental uranium adsorption K d values (close to 1500 mL/g), uranium sorption onto mineral phases (such as smectite and iron oxide in this study) has to be considered. An operational data set is given for both 238 U(VI) and 226 Ra(II) sorption onto Les Sagnes peat. Unlike usual peat, peat from Les Sagnes contains more than 10% dry weight of mineral matter. That is why it is necessary to model sorption of those two

  17. Sorption Studies of Chromium(VI and Mercury(II by High Temperature Activated Carbon from Syzygium Jambolanum Nut

    Directory of Open Access Journals (Sweden)

    S. Sophie Beulah

    2010-01-01

    Full Text Available High temperature activated Syzygium Jambolanum nut carbon (HSJC has been effectively used for the removal of Cr(VI and Hg(II from aqueous solution by batch experiments. Effect of pH, carbon dose and equilibration time were determined. Adsorption followed Freundlich and Langmuir isotherms. Kinetic studies indicated that the removal process followed reversible first order equation. Desorption of Cr(VI was done with 1 M NaOH and 10% H2O2 mixture and Hg(II with 2% Na2S in 1% NaOH. The performance of HSJC was compared with a commercial activated carbon (CAC.

  18. adsorption, eosin, humic, peat

    OpenAIRE

    anshar, andi muhammad

    2015-01-01

    Eosin is one of the dyes commonly used in the industry and has the potential to cause pollution of the water environment. The Eosin pollution treatment methods used in this study was the adsorption method using humin fraction obtained from the peat land comes from Kalimantan. From the research data showed that the adsorption of eosin in humin result of washing with HCl / HF optimum at pH 4 and a contact time of 60 minutes with the adsorption-order rate was 8,4 x 10-3 min-1

  19. Competitive Protein Adsorption - Multilayer Adsorption and Surface Induced Protein Aggregation

    DEFF Research Database (Denmark)

    Holmberg, Maria; Hou, Xiaolin

    2009-01-01

    In this study, competitive adsorption of albumin and IgG (immunoglobulin G) from human serum solutions and protein mixtures onto polymer surfaces is studied by means of radioactive labeling. By using two different radiolabels (125I and 131I), albumin and IgG adsorption to polymer surfaces...... is monitored simultaneously and the influence from the presence of other human serum proteins on albumin and IgG adsorption, as well as their mutual influence during adsorption processes, is investigated. Exploring protein adsorption by combining analysis of competitive adsorption from complex solutions...... of high concentration with investigation of single protein adsorption and interdependent adsorption between two specific proteins enables us to map protein adsorption sequences during competitive protein adsorption. Our study shows that proteins can adsorb in a multilayer fashion onto the polymer surfaces...

  20. Sorption and desorption studies of chromium(VI) from nonviable cyanobacterium Nostoc muscorum biomass

    Energy Technology Data Exchange (ETDEWEB)

    Gupta, V.K. [Department of Chemistry, Indian Institute of Technology Roorkee, Roorkee 247667 (India)], E-mail: vinodfcy@iitr.ernet.in; Rastogi, A. [Department of Chemistry, Indian Institute of Technology Roorkee, Roorkee 247667 (India)

    2008-06-15

    This communication presents results pertaining to the sorptive and desorptive studies carried out on chromium(VI) removal onto nonviable freshwater cyanobacterium (Nostoc muscorum) biomass. Influence of varying the conditions for removal of chromium(VI), such as the pH of aqueous solution, the dosage of biosorbent, the contact time with the biosorbent, the temperature for the removal of chromium, the effect of light metal ions and the adsorption-desorption studies were investigated. Sorption interaction of chromium on to cyanobacterial species obeyed both the first and the second-order rate equation and the experimental data showed good fit with both the Langmuir and freundlich adsorption isotherm models. The maximum adsorption capacity was 22.92 mg/g at 25 {sup o}C and pH 3.0. The adsorption process was endothermic and the values of thermodynamic parameters of the process were calculated. Various properties of the cyanobacterium, as adsorbent, explored in the characterization part were chemical composition of the adsorbent, surface area calculation by BET method and surface functionality by FTIR. Sorption-desorption of chromium into inorganic solutions and distilled water were observed and this indicated the biosorbent could be regenerated using 0.1 M HNO{sub 3} and EDTA with upto 80% recovery. The biosorbents were reused in five biosorption-desorption cycles without a significant loss in biosorption capacity. Thus, this study demonstrated that the cyanobacterial biomass N. muscorum could be used as an efficient biosorbent for the treatment of chromium(VI) bearing wastewater.

  1. Bio sorption process for uranium (VI) by using algae-yeast-silica gel composite adsorbent

    International Nuclear Information System (INIS)

    Turkozu, D. A.; Aytas, S.

    2006-01-01

    Many yeast, algae, bacteria and various aquatic flora are known to be capable of concentrating metal species from dilute aqueous solution. Many researcher have found that non-living biomaterials can be used to accumulate metal ions from environment. In recent studies, mainly two process are used in biosorption experiments. These are the use of free cells and the use of immobilized cells on a solid support. A variety of inert supports have been used to immobilize biomaterials either by adsorption or physical entrapment. This uptake is often considerable and frequently selective, and occurs via a variety of mechanisms including active transport, ion exchange or complexation, and adsorption or inorganic precipitation. Biosorbent may be used as an ion exchange material. Adsorption occurs through interaction of the metal ions with functional groups that are found in the cell wall biopolymers of either living or dead organisms. In this study, the algae-yeast-silica gel composite adsorbent was tested for its ability to recover U(VI) from diluted aqueous solutions. Macro marine algae (Jania rubens.), yeast (Saccharomyces cerevisiae) and silica gel were used to prepare composite adsorbent. The ability of the composite biosorbent to adsorb uranium (VI) from aqueous solution has been studied at different optimized conditions of pH, concentration of U(VI), temperature, contact time and matrix ion effect was also investigated. The adsorption patterns of uranium on the composite biosorbent were investigated by the Langmuir, Freundlich and Dubinin-Radushkhevic isotherms. The thermodynamic parameters such as variation of enthalpy ΔH, variation of entropy ΔS and variation of Gibbs free energy ΔG were calculated. The results suggested that the macro algae-yeast-silica gel composite sorbent is suitable as a new biosorbent material for removal of uranium ions from aqueous solutions

  2. Hybrid adsorptive membrane reactor

    Science.gov (United States)

    Tsotsis, Theodore T [Huntington Beach, CA; Sahimi, Muhammad [Altadena, CA; Fayyaz-Najafi, Babak [Richmond, CA; Harale, Aadesh [Los Angeles, CA; Park, Byoung-Gi [Yeosu, KR; Liu, Paul K. T. [Lafayette Hill, PA

    2011-03-01

    A hybrid adsorbent-membrane reactor in which the chemical reaction, membrane separation, and product adsorption are coupled. Also disclosed are a dual-reactor apparatus and a process using the reactor or the apparatus.

  3. Co adsorption in kaolinite

    International Nuclear Information System (INIS)

    Souza, Eliel S.; Silva, Paulo S.C.

    2017-01-01

    Adsorption of metal ions in clay minerals has been used as an alternative to water and effluents treatment. Kaolinite is a clay mineral that presents low specific surface area and exchange ion capacity. Nevertheless, structural modifications can be achieved by means of acid or thermal activation. In this paper, it was studied the surface area of kaolinite/bentonite, kaolinite/activated carbon mixtures, thermal activated kaolinite and thermal activated kaolinite/activated carbon mixture. The mixture of kaolinite/activated carbon was tested for pH, contact time, interfering ions and initial concentration effects in the cobalt adsorption. Results showed that the optimized parameters are pH 6 and contact time of 30 min. Chromium acted as a competitive ion, zinc does not appear to have affected adsorption while iron seems to have favored it. Langmuir and Freundlich isotherms indicated that the adsorption of Co in the mixture of kaolinite/activated carbon is a spontaneous process. (author)

  4. Co adsorption in kaolinite

    Energy Technology Data Exchange (ETDEWEB)

    Souza, Eliel S.; Silva, Paulo S.C., E-mail: eliel201019@hotmail.com, E-mail: pscsilva@ipen.br [Instituto de Pesquisas Energética s e Nucleares (IPEN/CNEN-SP), São Paulo, SP (Brazil)

    2017-07-01

    Adsorption of metal ions in clay minerals has been used as an alternative to water and effluents treatment. Kaolinite is a clay mineral that presents low specific surface area and exchange ion capacity. Nevertheless, structural modifications can be achieved by means of acid or thermal activation. In this paper, it was studied the surface area of kaolinite/bentonite, kaolinite/activated carbon mixtures, thermal activated kaolinite and thermal activated kaolinite/activated carbon mixture. The mixture of kaolinite/activated carbon was tested for pH, contact time, interfering ions and initial concentration effects in the cobalt adsorption. Results showed that the optimized parameters are pH 6 and contact time of 30 min. Chromium acted as a competitive ion, zinc does not appear to have affected adsorption while iron seems to have favored it. Langmuir and Freundlich isotherms indicated that the adsorption of Co in the mixture of kaolinite/activated carbon is a spontaneous process. (author)

  5. Når vi taler om 68

    DEFF Research Database (Denmark)

    Jensen, Henrik; Metz, Georg

    Når vi taler om 68 er en intellektuel samtale mellem to ligeværdige gentlemen og skallesmækkere. En essayistisk dyst om porno, RAF, Pittelkow og livsfilosofi......Når vi taler om 68 er en intellektuel samtale mellem to ligeværdige gentlemen og skallesmækkere. En essayistisk dyst om porno, RAF, Pittelkow og livsfilosofi...

  6. Structure sensitivity in adsorption

    DEFF Research Database (Denmark)

    Hammer, Bjørk; Nielsen, Ole Holm; Nørskov, Jens Kehlet

    1997-01-01

    The structure sensitivity of CO adsorption on different flat, stepped, kinked and reconstructed Pt surfaces is studied using large-scale density-functional calculations. We find an extremely strong structure sensitivity in the adsorption energy with variations up to 1 eV (or 100%) from one...... structure to the next. We propose a model to explain this behavior, and use it to discuss more generally the origin of structure sensitivity in heterogeneous catalysis....

  7. Biosorption of Cr (VI) ions from electroplating industrial effluent using immobilized Aspergillus niger biomass.

    Science.gov (United States)

    Chhikara, S; Dhankhar, R

    2008-09-01

    A fungus, Aspergillus niger was chemically treated with 0.1 M H2SO4 and 0.1 N NaOH to form biosorbent and it was immobilized in calcium alginate beads. The biosorption capacity of immobilized biosorbents for Cr (VI) was found to depend on pH, contact time, biosorbent dose and initial concentration of Cr (VI). The maximum uptake of Cr (VI) was 92.5, 95.9 and 98.4 mg respectively at a pH of 1.5 and with an increase in pH up to 10.5 the metal uptake decreased gradually up to 38.75, 50.19 and 65.28 mg respectively for acid treated, untreated and base treated fungal biosorbents. Increase in biosorbent dose up to 1 g of biomass and contact time up to 60 min resulted in an increase in biosorption from 19.6, 15.6 and 26.1 mg at a biosorbent dose of 0.1 g 100 ml(-1) to 92.45, 95.7 and 98.52 mg at a biosorbent dose of 1.0 g 100 ml(-1) and then further increase in adsorbent dose and contact time did not resulted in more Cr (VI) adsorption by per unit weight of biosorbent. The value of Kad (adsorption rate constant) revealed the pseudo-first order nature of biosorption. The percentage metal uptake by the biosorbent was found to decrease upto 62.33, 52.67 and 83.5 percent respectively for acid treated, untreated and base treated fungal biosorbents at the 300 mgl(-1) Cr (VI) ion concentration. The resulted data was found to fit well in Langmuir model of adsorption isotherm with a high value of correlation coefficient. The value of Qmax, b (Langmuir constants), R(L) (separation factor) and delta G (Gibb's free energy) revealed the favourable nature of adsorption. The biosorbed metal was eluted from the biosorbent by using 0.1 M H2SO4 as elutant. Immobilized biosorbent can be reused for five consecutive biosorption/desorption cycles without apparent loss of efficiency after its reconditioning. The biosorbent was found to perform well in the electroplating industrial effluent.

  8. Econophys-Kolkata VI Conference

    CERN Document Server

    Chakrabarti, Bikas; Chakraborti, Anirban; Ghosh, Asim

    2013-01-01

    The primary goal of the book is to present the ideas and research findings of active researchers such as physicists, economists, mathematicians and financial engineers working in the field of “Econophysics,” who have undertaken the task of modeling and analyzing systemic risk, network dynamics and other topics. Of primary interest in these studies is the aspect of systemic risk, which has long been identified as a potential scenario in which financial institutions trigger a dangerous contagion mechanism, spreading from the financial economy to the real economy. This type of risk, long confined to the monetary market, has spread considerably in the recent past, culminating in the subprime crisis of 2008. As such, understanding and controlling systemic risk has become an extremely important societal and economic challenge. The Econophys-Kolkata VI conference proceedings are dedicated to addressing a number of key issues involved. Several leading researchers in these fields report on their recent work and al...

  9. 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

  10. Removal of Chromium(VI from Aqueous Solutions Using Fe3O4 Magnetic Polymer Microspheres Functionalized with Amino Groups

    Directory of Open Access Journals (Sweden)

    Kai Wang

    2015-12-01

    Full Text Available Magnetic polymer microspheres (MPMs using glycidylmethacrylate (GMA as a functional monomer were synthesized in the presence of Fe3O4 nanoparticles via dispersion polymerization. After polymerization, the magnetic polymer microbeads were modified with ethylenediamine (EDA. The obtained ethylenediamine-functionalized magnetic microspheres (EDA-MPMs were characterized by scanning electron microscope (SEM, X-ray diffraction (XRD, vibrating-sample magnetometer (VSM and Fourier transform infrared (FT-IR spectroscopy. Then the EDA-MPMs were applied as adsorbents for the removal of Cr(VI from aqueous solution. Langmuir equation was appropriate to describe the experimental data. The maximum adsorption capacities obtained from the Langmuir model were 236.9, 242.1 and 253.2 mg/g at 298, 308 and 318 K, respectively. The Cr(VI adsorption equilibrium was established within 120 min and the adsorption kinetics was compatibly described by the pseudo-second order equation. The thermodynamic parameters (ΔG°, ΔH°, ΔS° of the sorption process revealed that the adsorption was spontaneous and was an endothermic process. The regeneration study demonstrated that the EDA-MPMs could be repeatedly utilized with no significant loss of adsorption efficiency.

  11. Sorption performance of activated nkaliki clay in removing chromium (vi) ion from aqueous solution: kinetics, isotherm, and thermodynamic studies

    International Nuclear Information System (INIS)

    Ajemba, R.O.; Ugonabo, V.I.; Okafor, V.N.

    2017-01-01

    Bentonite from Nkaliki was modified by acid activation using different concentrations of sulphuric acid. The physicochemical properties of the raw and modified samples were analyzed. The sorption performance of the modified and raw bentonite was studied in the removal of chromium (VI) ion from aqueous solution. Effect of key process parameters on the adsorption process was studied. Results of the physicochemical analyses showed that the acid activation altered the structural arrangements of the bentonite. The surface area and adsorption capacity increased from 37.6m/sup 2//g to 74m/sup 2//g and 45 to 98%, respectively, after activating with 6mol/l of H/sub 2/SO/sub 4/. The chromium (VI) ion adsorption increased with increase in process parameters studied. The kinetics analysis of the adsorption data follows the pseudo second-order kinetics, while equilibrium analysis conformed to the Langmuir isotherm. The thermodynamic parameters revealed that adsorption process is spontaneous and endothermic. This study shows that modified Nkaliki bentonite could be used for wastewater treatment. (author)

  12. Removal of Cr(VI) ions by sewage sludge compost biomass from aqueous solutions: Reduction to Cr(III) and biosorption

    Science.gov (United States)

    Chen, Huixia; Dou, Junfeng; Xu, Hongbin

    2017-12-01

    Sewage sludge compost biomass was used as a novel biosorbent to remove hexavalent chromium from water. Surface area analysis, scanning electron microscopy, fourier-transform infrared spectroscopy, energy-dispersive X-ray spectroscopy, and point zero charge was applied to study the microstructure, compositions and chemical bonding states of the biomass adsorbent. Effects of contact time, biomass dosage, agitation speed, pH, the initial concentration of Cr(VI) and Cr(Ⅲ) on its adsorption removal were also performed in the batch experiments. A model describing adsorption, desorption and reduction phenomena during the sorption process has been referenced to model Cr(VI) sorption onto sewage sludge compost biomass. The result of characterization test shows that adsorption of Cr(VI) onto sewage sludge compost biomass followed by the partial reduction to Cr(Ⅲ) by biomass groups such as hydroxyl, carboxyl, and amino groups. The absorption kinetics model in the description of adsorption-coupled reduction of Cr(VI) fits successfully the kinetic data obtained at different temperatures and describes the kinetics profile of total, hexavalent and trivalent chromium. The study shows that sewage sludge compost biomass could be used as a potential biosorbent for removal of hexavalent chromium from wastewaters.

  13. A review on adsorption refrigeration technology and adsorption deterioration in physical adsorption systems

    Energy Technology Data Exchange (ETDEWEB)

    Wang, D.C.; Li, Y.H. [College of Electromechanical Engineering, Qingdao University, 308 Ningxia Road, Qingdao 266071 (China); Laboratory of Fiber Materials and Modern Textile, the Growing Base for State Key Laboratory, Qingdao University, 308 Ningxia Road, Qingdao 266071 (China); Li, D.; Zhang, J.P. [College of Electromechanical Engineering, Qingdao University, 308 Ningxia Road, Qingdao 266071 (China); Xia, Y.Z. [Laboratory of Fiber Materials and Modern Textile, the Growing Base for State Key Laboratory, Qingdao University, 308 Ningxia Road, Qingdao 266071 (China)

    2010-01-15

    As one kind of environmentally friendly refrigeration, the adsorption refrigeration has attracted many attentions in resent decades. This paper introduces the researches of adsorption refrigeration systems with the commonly used working pairs, advanced adsorption cycles, heat and mass transfer enhancement and attempts of adsorption refrigeration applications. Poor heat and mass transfer problem is a bottleneck to prevent the improvements of the adsorption refrigeration technique. Two ways to enhance the heat and mass transfer are discussed in this paper. The adsorption deterioration of adsorbent, another obstacle to physical adsorption refrigeration applications, is also pointed out. And the possible reasons and the possible methods are analyzed. (author)

  14. 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.

  15. Treatment of Cr(VI)-containing wastewaters with exopolysaccharide-producing cyanobacteria in pilot flow through and batch systems

    Energy Technology Data Exchange (ETDEWEB)

    Colica, Giovanni; Mecarozzi, Pier Cesare; De Philippis, Roberto [Florence Univ., Firenze (Italy). Dept. of Agricultural Biotechnology

    2010-08-15

    Seven exopolysaccharide-producing cyanobacteria were tested with regard to their capability to remove Cr(VI) from the wastewater of a plating industry. The cyanobacterium which showed, under lab conditions, the most promising features with regard to both Cr(VI) removal (about 12 mg of Cr(VI) removed per gram of dry biomass) and growth characteristics (highest growth rate and simplest culture medium) was Nostoc PCC7936. Furthermore, in lab experiments, it was also found that a HCl pretreatment is essential to abate the concentration of Cr(VI) in solution and that the viability of the biomass is not necessary. Subsequently, three pilot devices were tested, one batch (a dialysis cell) and two flow-through systems (a filter press and a column filled with quartz grain). The best performances were obtained with the filter press, where it was observed a sharp decrease in the concentration of Cr(VI), partly due to the adsorption of the metal by the biomass (about 50%) and partly due to its reduction to Cr(III). The results are discussed in terms of the role played by the different components (biomass and polysaccharide) of the cyanobacterial cultures in the removal of Cr(VI). (orig.)

  16. Characterizations of nano-TiO{sub 2}/diatomite composites and their photocatalytic reduction of aqueous Cr (VI)

    Energy Technology Data Exchange (ETDEWEB)

    Sun, Qing; Li, Hui; Zheng, Shuilin, E-mail: shuilinzh@sina.com; Sun, Zhiming, E-mail: szmcumtb@hotmail.com

    2014-08-30

    Graphical abstract: Nano-TiO{sub 2}/diatomite (DIA) composites were successfully synthesized by a typical hydrolysis precipitation method. The composites show good photocatalytic activity and stability for aqueous Cr (VI) removal. - Highlights: • TiO{sub 2} nanoparticles/diatomite composite was synthesized and characterized. • The composite exhibited a good photocatalytic performance in Cr (VI) reduction. • The photocatalyst showed good photocatalytic stability. • The composite is a promising material for Cr (VI) photocatalytic reduction. - Abstract: In this paper, the TiO{sub 2} nanoparticles were immobilized on diatomite (DIA) via a typical hydrolysis precipitation process using TiCl{sub 4} as precursor. The as-prepared composites were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). TiO{sub 2} nanoparticles with the average grain size of around 7–14 nm were well deposited on the surface of diatomite. The photocatalytic activity toward the reduction of aqueous Cr (VI) was demonstrated under UV light. The influence of initial pH values, catalyst amount, illumination intensity and initial concentration of Cr (VI) on photocatalytic reduction of Cr (VI) were investigated. Compared with the commercial TiO{sub 2} (P25, Degussa), the TiO{sub 2}/DIA composites had better reactive activity because of their relatively higher adsorption capacity. Furthermore, the prepared photocatalyst exhibited relatively good photocatalytic stability depending on the reusability tests.

  17. Flower-, wire-, and sheet-like MnO2-deposited diatomites: Highly efficient absorbents for the removal of Cr(VI).

    Science.gov (United States)

    Du, Yucheng; Wang, Liping; Wang, Jinshu; Zheng, Guangwei; Wu, Junshu; Dai, Hongxing

    2015-03-01

    Flower-, wire-, and sheet-like MnO2-deposited diatomites have been prepared using a hydrothermal method with Mn(Ac)2, KMnO4 and/or MnSO4 as Mn source and diatomite as support. Physical properties of the materials were characterized by means of numerous analytical techniques, and their behaviors in the adsorption of chromium(VI) were evaluated. It is shown that the MnO2-deposited diatomite samples with different morphologies possessed high surface areas and abundant surface hydroxyl groups (especially the wire-like MnO2/diatomite sample). The wire-like MnO2/diatomite sample showed the best performance in the removal of Cr(VI), giving the maximum Cr(VI) adsorption capacity of 101 mg/g. Copyright © 2014. Published by Elsevier B.V.

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

    Science.gov (United States)

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

    2013-04-01

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

  19. Adsorption of uranium from aqueous solution using biochar produced by hydrothermal carbonization

    International Nuclear Information System (INIS)

    Zhi-bin Zhang; East China Institute of Technology, Fuzhou; China University of Geosciences, Wuhan; China University of Geosciences, Wuhan; Xiao-hong Cao; Yun-hai Liu; East China Institute of Technology, Fuzhou; Ping Liang; East China Institute of Technology, Fuzhou; China University of Geosciences, Wuhan

    2013-01-01

    The ability of biochar produced by hydrothermal carbonization (HTC) has been explored for the removal and recovery of uranium from aqueous solutions. The micro-morphology and structure of HTC were characterized by Fourier transform infrared spectroscopy and scanning electron microscopy. The influences of different experimental parameters such as solution pH, initial concentration, contact time, ionic strength and temperature on adsorption were investigated. The HTC showed the highest uranium sorption capacity at initial pH of 6.0 and contact time of 50 min. Adsorption kinetics was better described by the pseudo-second-order model and adsorption process could be well defined by the Langmuir isotherm. The thermodynamic parameters, ΔGdeg(298 K), ΔHdeg and ΔSdeg were determined to be -14.4, 36.1 kJ mol -1 and 169.7 J mol -1 K -1 , respectively, which demonstrated the sorption process of HTC towards U(VI) was feasible, spontaneous and endothermic in nature. The adsorbed HTC could be effectively regenerated by 0.05 mol/L HCl solution for the removal and recovery of U(VI). Complete removal (99.9 %) of U(VI) from 1.0 L industry wastewater containing 15.0 mg U(VI) ions was possible with 2.0 g HTC. (author)

  20. Ship-in-a-bottle CMPO in MIL-101(Cr) for selective uranium recovery from aqueous streams through adsorption.

    Science.gov (United States)

    De Decker, Jeroen; Folens, Karel; De Clercq, Jeriffa; Meledina, Maria; Van Tendeloo, Gustaaf; Du Laing, Gijs; Van Der Voort, Pascal

    2017-08-05

    Mesoporous MIL-101(Cr) is used as host for a ship-in-a-bottle type adsorbent for selective U(VI) recovery from aqueous environments. The acid-resistant cage-type MOF is built in-situ around N,N-Diisobutyl-2-(octylphenylphosphoryl)acetamide (CMPO), a sterically demanding ligand with high U(VI) affinity. This one-step procedure yields an adsorbent which is an ideal compromise between homogeneous and heterogeneous systems, where the ligand can act freely within the pores of MIL-101, without leaching, while the adsorbent is easy separable and reusable. The adsorbent was characterized by XRD, FTIR spectroscopy, nitrogen adsorption, XRF, ADF-STEM and EDX, to confirm and quantify the successful encapsulation of the CMPO in MIL-101, and the preservation of the host. Adsorption experiments with a central focus on U(VI) recovery were performed. Very high selectivity for U(VI) was observed, while competitive metal adsorption (rare earths, transition metals...) was almost negligible. The adsorption capacity was calculated at 5.32mg U/g (pH 3) and 27.99mg U/g (pH 4), by fitting equilibrium data to the Langmuir model. Adsorption kinetics correlated to the pseudo-second-order model, where more than 95% of maximum uptake is achieved within 375min. The adsorbed U(VI) is easily recovered by desorption in 0.1M HNO 3 . Three adsorption/desorption cycles were performed. Copyright © 2017 Elsevier B.V. All rights reserved.

  1. Emissions of chromium (VI) from arc welding.

    Science.gov (United States)

    Heung, William; Yun, Myoung-Jin; Chang, Daniel P Y; Green, Peter G; Halm, Chris

    2007-02-01

    The presence of Cr in the +6 oxidation state (Cr[VI]) is still observed in ambient air samples in California despite steps taken to reduce emissions from plating operations. One known source of emission of Cr(VI) is welding, especially with high Cr-content materials, such as stainless steels. An experimental effort was undertaken to expand and update Cr(VI) emission factors by conducting tests on four types of arc-welding operations: gas-metal arc welding (GMAW), shielded metal arc welding (SMAW), fluxcore arc welding, and pulsed GMAW. Standard American Welding Society hood results were compared with a total enclosure method that permitted isokinetic sampling for particle size-cut measurement, as well as total collection of the aerosol. The fraction of Cr(VI) emitted per unit mass of Cr electrode consumed was determined. Consistent with AP-42 data, initial results indicate that a significant fraction of the total Cr in the aerosol is in the +6 oxidation state. The fraction of Cr(VI) and total aerosol mass produced by the different arc welding methods varies with the type of welding process used. Self-shielded electrodes that do not use a shield gas, for example, SMAW, produce greater amounts of Cr(VI) per unit mass of electrode consumed. The formation of Cr(VI) from standard electrode wires used for welding mild steel was below the method detection limit after eliminating an artifact in the analytical method used.

  2. Anaerobic bio-removal of uranium (VI) and chromium (VI): Comparison of microbial community structure

    Energy Technology Data Exchange (ETDEWEB)

    Martins, Monica [Centro de Ciencias do Mar, Universidade do Algarve, Campus de Gambelas, 8005-139 Faro (Portugal); Faleiro, Maria Leonor [IBB - Centro de Biomedicina Molecular e Estrutural, Universidade do Algarve, Campus de Gambelas, 8005-139 Faro (Portugal); Chaves, Sandra; Tenreiro, Rogerio [Universidade de Lisboa, Faculdade de Ciencias, Centro de Biodiversidade, Genomica Integrativa e Funcional (BioFIG), Campus de FCUL, Campo Grande 1749-016 Lisboa (Portugal); Santos, Erika [Centro de Ciencias do Mar, Universidade do Algarve, Campus de Gambelas, 8005-139 Faro (Portugal); Costa, Maria Clara, E-mail: mcorada@ualg.pt [Centro de Ciencias do Mar, Universidade do Algarve, Campus de Gambelas, 8005-139 Faro (Portugal)

    2010-04-15

    Several microbial communities, obtained from uranium contaminated and non-contaminated samples, were investigated for their ability to remove uranium (VI) and the cultures capable for this removal were further assessed on their efficiency for chromium (VI) removal. The highest efficiency for removal of both metals was observed on a consortium from a non-contaminated soil collected in Monchique thermal place, which was capable to remove 91% of 22 mg L{sup -1} U(VI) and 99% of 13 mg L{sup -1} Cr(VI). This study revealed that uranium (VI) removing communities have also ability to remove chromium (VI), but when uranium (VI) was replaced by chromium (VI) several differences in the structure of all bacterial communities were observed. TGGE and phylogenetic analysis of 16S rRNA gene showed that the uranium (VI) removing bacterial consortia are mainly composed by members of Rhodocyclaceae family and Clostridium genus. On the other hand, bacteria from Enterobacteriaceae family were detected in the community with ability for chromium (VI) removal. The existence of members of Enterobacteriaceae and Rhodocyclaceae families never reported as chromium or uranium removing bacteria, respectively, is also a relevant finding, encouraging the exploitation of microorganisms with new abilities that can be useful for bioremediation.

  3. Anaerobic bio-removal of uranium (VI) and chromium (VI): Comparison of microbial community structure

    International Nuclear Information System (INIS)

    Martins, Monica; Faleiro, Maria Leonor; Chaves, Sandra; Tenreiro, Rogerio; Santos, Erika; Costa, Maria Clara

    2010-01-01

    Several microbial communities, obtained from uranium contaminated and non-contaminated samples, were investigated for their ability to remove uranium (VI) and the cultures capable for this removal were further assessed on their efficiency for chromium (VI) removal. The highest efficiency for removal of both metals was observed on a consortium from a non-contaminated soil collected in Monchique thermal place, which was capable to remove 91% of 22 mg L -1 U(VI) and 99% of 13 mg L -1 Cr(VI). This study revealed that uranium (VI) removing communities have also ability to remove chromium (VI), but when uranium (VI) was replaced by chromium (VI) several differences in the structure of all bacterial communities were observed. TGGE and phylogenetic analysis of 16S rRNA gene showed that the uranium (VI) removing bacterial consortia are mainly composed by members of Rhodocyclaceae family and Clostridium genus. On the other hand, bacteria from Enterobacteriaceae family were detected in the community with ability for chromium (VI) removal. The existence of members of Enterobacteriaceae and Rhodocyclaceae families never reported as chromium or uranium removing bacteria, respectively, is also a relevant finding, encouraging the exploitation of microorganisms with new abilities that can be useful for bioremediation.

  4. Solid phase extraction of uranium(VI) onto benzoylthiourea-anchored activated carbon

    International Nuclear Information System (INIS)

    Zhao Yongsheng; Liu Chunxia; Feng Miao; Chen Zhen; Li Shuqiong; Tian Gan; Wang Li; Huang Jingbo; Li Shoujian

    2010-01-01

    A new solid phase extractant selective for uranium(VI) based on benzoylthiourea anchored to activated carbon was developed via hydroxylation, amidation and reaction with benzoyl isothiocyanate in sequence. Fourier transform infrared spectroscopy and total element analysis proved that benzoylthiourea had been successfully grafted to the surface of the activated carbon, with a loading capacity of 1.2 mmol benzoylthiourea per gram of activated carbon. The parameters that affect the uranium(VI) sorption, such as contact time, solution pH, initial uranium(VI) concentration, adsorbent dose and temperature, have been investigated. Results have been analyzed by Langmuir and Freundlich isotherm; the former was more suitable to describe the sorption process. The maximum sorption capacity (82 mg/g) for uranium(VI) was obtained at experimental conditions. The rate constant for the uranium sorption by the as-synthesized extractant was 0.441 min -1 from the first order rate equation. Thermodynamic parameters (ΔH 0 = -46.2 kJ/mol; ΔS 0 = -98.0 J/mol K; ΔG 0 = -17.5 kJ/mol) showed the adsorption of an exothermic process and spontaneous nature, respectively. Additional studies indicated that the benzoylthiourea-anchored activated carbon (BT-AC) selectively sorbed uranyl ions in the presence of competing ions, Na + , Co 2+ , Sr 2+ , Cs + and La 3+ .

  5. Solid phase extraction of uranium(VI) onto benzoylthiourea-anchored activated carbon

    Energy Technology Data Exchange (ETDEWEB)

    Zhao Yongsheng; Liu Chunxia; Feng Miao; Chen Zhen; Li Shuqiong; Tian Gan; Wang Li; Huang Jingbo [College of Chemistry, Sichuan University, 29 Wangjiang Lu, Chengdu, 610064, Sichuan (China); Li Shoujian, E-mail: sjli000616@scu.edu.cn [College of Chemistry, Sichuan University, 29 Wangjiang Lu, Chengdu, 610064, Sichuan (China)

    2010-04-15

    A new solid phase extractant selective for uranium(VI) based on benzoylthiourea anchored to activated carbon was developed via hydroxylation, amidation and reaction with benzoyl isothiocyanate in sequence. Fourier transform infrared spectroscopy and total element analysis proved that benzoylthiourea had been successfully grafted to the surface of the activated carbon, with a loading capacity of 1.2 mmol benzoylthiourea per gram of activated carbon. The parameters that affect the uranium(VI) sorption, such as contact time, solution pH, initial uranium(VI) concentration, adsorbent dose and temperature, have been investigated. Results have been analyzed by Langmuir and Freundlich isotherm; the former was more suitable to describe the sorption process. The maximum sorption capacity (82 mg/g) for uranium(VI) was obtained at experimental conditions. The rate constant for the uranium sorption by the as-synthesized extractant was 0.441 min{sup -1} from the first order rate equation. Thermodynamic parameters ({Delta}H{sup 0} = -46.2 kJ/mol; {Delta}S{sup 0} = -98.0 J/mol K; {Delta}G{sup 0} = -17.5 kJ/mol) showed the adsorption of an exothermic process and spontaneous nature, respectively. Additional studies indicated that the benzoylthiourea-anchored activated carbon (BT-AC) selectively sorbed uranyl ions in the presence of competing ions, Na{sup +}, Co{sup 2+}, Sr{sup 2+}, Cs{sup +} and La{sup 3+}.

  6. Characterizations of nano-TiO2/diatomite composites and their photocatalytic reduction of aqueous Cr (VI)

    Science.gov (United States)

    Sun, Qing; Li, Hui; Zheng, Shuilin; Sun, Zhiming

    2014-08-01

    In this paper, the TiO2 nanoparticles were immobilized on diatomite (DIA) via a typical hydrolysis precipitation process using TiCl4 as precursor. The as-prepared composites were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). TiO2 nanoparticles with the average grain size of around 7-14 nm were well deposited on the surface of diatomite. The photocatalytic activity toward the reduction of aqueous Cr (VI) was demonstrated under UV light. The influence of initial pH values, catalyst amount, illumination intensity and initial concentration of Cr (VI) on photocatalytic reduction of Cr (VI) were investigated. Compared with the commercial TiO2 (P25, Degussa), the TiO2/DIA composites had better reactive activity because of their relatively higher adsorption capacity. Furthermore, the prepared photocatalyst exhibited relatively good photocatalytic stability depending on the reusability tests.

  7. Learning the vi and Vim Editor

    CERN Document Server

    Robbins, Arnold; Hannah, Elbert

    2008-01-01

    There's nothing that hard-core Unix and Linux users are more fanatical about than their text editor. Editors are the subject of adoration and worship, or of scorn and ridicule, depending upon whether the topic of discussion is your editor or someone else's. vi has been the standard editor for close to 30 years. Popular on Unix and Linux, it has a growing following on Windows systems, too. Most experienced system administrators cite vi as their tool of choice. And since 1986, this book has been the guide for vi. However, Unix systems are not what they were 30 years ago, and neither is this

  8. Adsorptive Removal of Toxic Chromium from Waste-Water Using Wheat Straw and Eupatorium adenophorum.

    Directory of Open Access Journals (Sweden)

    Dagang Song

    Full Text Available Environmental pollution with heavy metals is a serious issue worldwide posing threats to humans, animals and plants and to the stability of overall ecosystem. Chromium (Cr is one of most hazardous heavy metals with a high carcinogenic and recalcitrant nature. Aim of the present study was to select low-cost biosorbent using wheat straw and Eupatorium adenophorum through simple carbonization process, capable of removing Cr (VI efficiently from wastewater. From studied plants a low cost adsorbent was prepared for removing Cr (VI from aqueous solution following very simple carbonization method excluding activation process. Several factors such as pH, contact time, sorbent dosage and temperature were investigated for attaining ideal condition. For analysis of adsorption equilibrium isotherm data, Langmuir, Freundlich and Temkin models were used while pseudo-first-order, pseudo-second-order, external diffusion and intra-particle diffusion models were used for the analysis of kinetic data. The obtained results revealed that 99.9% of Cr (VI removal was observed in the solution with a pH of 1.0. Among all the tested models Langmuir model fitted more closely according to the data obtained. Increase in adsorption capacity was observed with increasing temperature revealing endothermic nature of Cr (VI. The maximum Cr (VI adsorption potential of E. adenophorum and wheat straw was 89.22 mg per 1 gram adsorbent at 308K. Kinetic data of absorption precisely followed pseudo-second-order model. Present study revealed highest potential of E. adenophorum and wheat straw for producing low cost adsorbent and to remove Cr (VI from contaminated water.

  9. Efficient simultaneous removal of U(VI) and Cu(II) from aqueous solution using core-shell nZVI@SA/CMC-Ca beads

    International Nuclear Information System (INIS)

    Shuhong Hu; Xiaoyan Lin; Wenhui Zhao; Ministry of Education, Sichuan; Xuegang Luo

    2018-01-01

    Core-shell nanoscale zero-valent iron@alginate/carboxymethyl cellulose sodium composite loaded with calcium (nZVI@SA/CMC-Ca) beads were synthesized in this study using coaxial electronic injection method. The adsorbent structure was characterized via FT-IR, SEM, EDX and XPS. The adsorption behavior of U(VI) and Cu(II) on core-shell nZVI@SA/CMC-Ca beads was studied under various experimental parameters like pH, contact time and temperature. The isotherm and the kinetic data, pertaining to the adsorption of U(VI) and Cu(II) by core-shell nZVI@SA/CMC-Ca beads obeyed both the Langmuir and Freundlich isotherms model and the pseudo-second-order kinetics model, respectively. The thermodynamic parameters revealed the spontaneous and endothermic nature of the adsorption. The experiment of regeneration and reusability suggested core-shell nZVI@SA/CMC-Ca bead was a regenerated material. (author)

  10. 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.

  11. 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.

  12. Hazelnut shell activated carbon. A potential adsorbent material for the decontamination of uranium(VI) from aqueous solutions

    International Nuclear Information System (INIS)

    Mijia Zhu; Hankui Chai; Jun Yao; China University of Geosciences; Yunpeng Chen; Zhengji Yi

    2016-01-01

    Batch experiments were conducted to study the ability of hazelnut shell activated carbon (HSAC) to remove uranium(VI) ions from aqueous solutions. The effects of various operational parameters, such as contact time (0-200 min), pH (2.0-7.0), initial U(VI) concentration (20-240 mg/L) and adsorbent dosage (4.0-50 g/L) were examined. Results showed that the adsorption process was rapid within the first 100 min and then achieved equilibrium at 140 min. The kinetics followed a pseudo-second-order rate equation, and the adsorption process was well fit with the Langmuir model. HSAC exhibited good uranium adsorption capacity (16.3 mg/g) at pH 6.0, 140 min contact time and 8.0 g/L adsorbent dosage. Furthermore, the regeneration efficiency was 96.3 % over five cycles under the optimum operational conditions. These properties revealed that HSAC can be a suitable adsorbent for the fast and convenient removal of U(VI) from contaminated water. (author)

  13. 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.

  14. Extended analysis of Mo VI

    International Nuclear Information System (INIS)

    Edlen, B.; Rahimullah, K.; Tauheed, A.; Chaghtai, M.S.Z.

    1985-01-01

    The analysis of the RbI-like spectrum Mo VI has been extended to include a total of some 110 classified lines and 44 energy levels belonging to the one-electron configurations 4s 2 4p 6 ( 1 S)nl with n ranging up to 9 and l up to 7. The analysis is based on recordings of vacuum spark spectra made at Lund in the region 230-2350 A, complemented by a list of lines from 2193 to 6336 A observed and identified by Romanov and Striganov in a Penning type arc discharge. The one-electron level system is partly mixed with core-excited configurations, not treated in the present paper. Especially the nf series is strongly perturbed by 4s 2 4p 5 4d 2 , and an anomalous behaviour of the ng series is explained by interaction with the 2 G term of 4s4p 6 4d 2 . The ionization limit, derived from 6h, 7i and 8k by means of the polarization formula, is found to be 555 132+-2 cm -1 . (orig.)

  15. Regenerative adsorption distillation system

    KAUST Repository

    Ng, Kim Choon

    2013-12-26

    There is provided a regenerative adsorption distillation system comprising a train of distillation effects in fluid communication with each other. The train of distillation effects comprises at least one intermediate effect between the first and last distillation effects of the train, each effect comprising a vessel and a condensing tube for flow of a fluid therein. The system further comprises a pair of adsorption-desorption beds in vapour communication with the last effect and at least one intermediate effect, wherein the beds contain an adsorbent that adsorbs vapour from the last effect and transmits desorbed vapour into at least one of the intermediate effect.

  16. Regenerative adsorption distillation system

    KAUST Repository

    Ng, Kim Choon; Thu, Kyaw; Amy, Gary; Chunggaze, Mohammed; Al-Ghasham, Tawfiq

    2013-01-01

    There is provided a regenerative adsorption distillation system comprising a train of distillation effects in fluid communication with each other. The train of distillation effects comprises at least one intermediate effect between the first and last distillation effects of the train, each effect comprising a vessel and a condensing tube for flow of a fluid therein. The system further comprises a pair of adsorption-desorption beds in vapour communication with the last effect and at least one intermediate effect, wherein the beds contain an adsorbent that adsorbs vapour from the last effect and transmits desorbed vapour into at least one of the intermediate effect.

  17. Kiintoainehäviöselvitys

    OpenAIRE

    Ylimys, Jussi

    2014-01-01

    Teoriaosassa käydään läpi yleisesti pyörrepuhdistuslaitoksen toimintaa sekä kiintoainehäviöitä paperi- ja kartonkitehtailla. Tämän opinnäytetyön tarkoituksena oli tutkia Metsä Boardin Kyröskosken tehtaan kiintoainehäviötä. Työssä selvitettiin, minkälaista kiintoainetta jätevesilaitokselle päätyy ja miksi. Selvityksen kohteena oli myös, missä kohteissa kiintoainehäviöt tarkalleen syntyvät ja kuinka paljon häviötä tapahtuu. Kahden edellä mainitun tiedon perusteella selvitettiin, kuinka palj...

  18. 29 CFR 1910.1026 - Chromium (VI).

    Science.gov (United States)

    2010-07-01

    ... allows employees to consume food or beverages at a worksite where chromium (VI) is present, the employer... effect on productivity. 2. Plating Bath Surface Tension Management and Fume Suppression • Lower surface...

  19. Physical adsorption and molecular dynamics

    International Nuclear Information System (INIS)

    Cohan, N.V.

    1981-01-01

    Some aspects of noble gases adsorption (except He) on graphite substracts are reviewed. Experimental results from this adsorption are analyzed and compared with molecular dynamics calculations. (L.C.) [pt

  20. Studies of Cr (VI) uptake by a green resin: dry cow dung

    International Nuclear Information System (INIS)

    Barot, Nisha S.; Bagla, Hemlata

    2009-01-01

    In the present investigation dry cow dung powder has been employed as an indigenous, inexpensive and eco-friendly material for the removal of Cr (VI) from aqueous medium. The effect of various process parameters such as optimum pH, temperature, amount of resin, time of equilibration and concentration of metal ion etc. have been studied. Many naturally available materials are used for the adsorption of heavy metal pollutant, where most of them are modified physically or chemically. Dry cow dung powder has been utilized with simple chemical treatment thus manifesting the principle of Green Chemistry. (author)

  1. 24 CFR 971.11 - HOPE VI developments.

    Science.gov (United States)

    2010-04-01

    ... 24 Housing and Urban Development 4 2010-04-01 2010-04-01 false HOPE VI developments. 971.11... § 971.11 HOPE VI developments. Developments with HOPE VI implementation grants that have approved HOPE... with reasonable revitalization plans. Future HUD actions to approve or deny proposed HOPE VI...

  2. 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.

  3. Uranium(VI) speciation by spectroscopy

    International Nuclear Information System (INIS)

    Meinrath, G.

    1997-01-01

    The application of UV-Vis and time-resolved laser-induced fluorescence (TRLF) spectroscopies to direct of uranium(VI) in environmental samples offers various prospects that have, however, serious limitations. While UV-Vis spectroscopy is probably not sensitive enough to detect uranium(VI) species in the majority of environmental samples, TRLFS is principially able to speciate uranium(VI) at very low concentration levels in the nanomol range. Speciation by TRLFS can be based on three parameters: excitation spectrum, emission spectrum and lifetime of the fluorescence emission process. Due to quenching effects, the lifetime may not be expected to be as characteristics as, e.g., the emission spectrum. Quenching of U(VI) fluorescence by reaction with organic substances, inorganic ions and formation of carbonate radicals is one important limiting factor in the application of U(VI) fluorescence spectroscopy. Fundamental photophysical criteria are illustrated using UV-Vis and fluorescence spectra of U(VI) hydrolysis and carbonato species as examples. (author)

  4. Application of high resolution X-ray emission spectroscopy on the study of Cr ion adsorption by activated carbon

    International Nuclear Information System (INIS)

    Espinoza-Quinones, Fernando R.; Modenes, Aparecido N.; Camera, Adriana S.; Stutz, Guillermo; Tirao, German; Palacio, Soraya M.; Kroumov, Alexander D.; Oliveira, Ana P.; Alflen, Vanessa L.

    2010-01-01

    In this work granular activated carbon has been chosen as an absorbent in order to investigate the Cr(VI) reduced by adsorption experiments. Several batch chromium-sorption experiments were carried out using 0.25 g of granular activated carbon in 50 mL aqueous solution containing approximately 70 and 140 mg L -1 of Cr(VI) and Cr(III), respectively. Cr-Kβ fluorescence spectra of Cr adsorbed in a carbon matrix and Cr reference materials were measured using a high-resolution Johann-type spectrometer. Based on evidence from the Cr-Kb satellite lines, the Cr(VI) reduction process has actually happened during metal adsorption by the activated carbon.

  5. Uranium(VI) retention on quartz and kaolinite. Experiments and modelling

    International Nuclear Information System (INIS)

    Mignot, G.

    2001-01-01

    The behaviour of uranium in the geosphere is an important issue for safety performance assessment of nuclear waste repositories, or in the context of contaminated sites due to mining activity related to nuclear field. Under aerobic conditions, the fate of uranium is mainly governed by the ability of minerals to sorb U(VI) aqueous species. Hence, a thorough understanding of U(VI) sorption processes on minerals is required to provide a valuable prediction of U(VI) migration in the environment. In this study, we performed sorption/desorption experiments of U(VI) on quartz and kaolinite, for systems favouring the formation in solution (i) of UO 2 2+ and monomeric hydrolysis products or (ii) of di-/tri-meric uranyl aqueous species, and / or U(VI)-colloids or UO 2 (OH) 2 precipitates, or (iii) of uranyl-carbonate complexes. Particular attention was paid to determine the surface characteristics of the solids and their modification due to dissolution/precipitation processes during experiments. A double layer surface complexation model was applied to our experimental data in order to derive surface complexation equilibria and intrinsic constants which allow a valuable description of U(VI) retention over a wide range of pH, ionic strength, initial concentration of uranium [0.1-10μM] and solid - solution equilibration time. U(VI) sorption on quartz was successfully modeled by using two sets of adsorption equilibria, assuming (i) the formation of the surface complexes SiOUO 2 + , SiOUO 2 OH and SiO(UO 2 ) 3 (OH) 5 , or (ii) the formation of the mono-dentate complex SiO(UO 2 ) 3 (OH) 5 and of the bidentate complex (SiO) 2 UO 2 . Assumptions on the density of each type of surface sites of kaolinite and on their acid-base properties were made from potentiometric titrations of kaolinite suspensions. We proposed on such a basis a set of surface complexation equilibria which accounts for U(VI) uptake on kaolinite over a wide range of chemical conditions, with aluminol edge sites as

  6. 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

  7. Sulfate adsorption on goethite

    Energy Technology Data Exchange (ETDEWEB)

    Rietra, R P.J.J.; Hiemstra, T; Riemsdijk, W.H. van

    1999-10-15

    Recent spectroscopic work has suggested that only one surface species of sulfate is dominant on hematite. Sulfate is therefore a very suitable anion to test and develop adsorption models for variable charge minerals. The authors have studied sulfate adsorption on goethite covering a large range of sulfate concentrations, surface coverages, pH values, and electrolyte concentrations. Four different techniques were used to cover the entire range of conditions. For characterization at low sulfate concentrations, below the detection limit of sulfate with ICP-AES, the authors used proton-sulfate titrations at constant pH. Adsorption isotherms were studied for the intermediate sulfate concentration range. Acid-base titrations in sodium sulfate and electromobility were used for high sulfate concentrations. All the data can be modeled with one adsorbed species if it is assumed that the charge of adsorbed sulfate is spatially distributed in the interface. The charge distribution of sulfate follows directly from modeling the proton-sulfate adsorption stoichoimemtry sine this stoichiometry is independent of the intrinsic affinity constant of sulfate. The charge distribution can be related to the structure of the surface complex by use of the Pauling bond valence concept and is in accordance with the microscopic structure found by spectroscopy. The intrinsic affinity constant follows from the other measurements. Modeling of the proton-ion stoichoimetry with the commonly used 2-pK models, where adsorbed ions are treated as point charges, is possible only if at least two surface species for sulfate are used.

  8. U(VI) sorption on granite: prediction and experiments

    International Nuclear Information System (INIS)

    Nebelung, C.; Brendler, V.

    2010-01-01

    One widely accepted approach - component additivity (CA) - to describe the sorption of contaminants onto complex materials such as rocks or soils is based on the assumption that the surface of a complex mineral assemblage is composed of a mixture of mineral constituents whose surface properties are known from independent studies. An internally consistent SCM (surface complexation model) database can be developed that describes the adsorption reactions of solutes to each phase. Here, the capability of such a methodology was tested, using the code MINTEQA2 including thermodynamic data of the NEA-TDB, and literature data for SCM, namely the DDL model. The sorption characteristics of U(VI) on granite (from Eibenstock, Saxony, Germany, with the main components quartz, albite, orthoclase, and muscovite) was predicted and then compared to batch experiments. Granite plays an important role in the remediation of former uranium ore mining and milling sites, but is also one of the host rocks considered for final disposal of nuclear materials. Safety assessment requires a detailed understanding of this system and its retention potential with regard to hazardous components. Namely the sorption of uranium in this complex rock is not fully understood yet. The experiments thus also provided a better understanding of the far-field behaviour in granitic geological nuclear repositories. The robustness of the prediction was tested by variation of the granite composition and the variation of the specific surface area (SSA) - first all components were predicted with a uniform granite SSA, second with a distinct SSA for each granite component (determined on pure minerals for the same grain size fractions). Changes in compositions yielded only marginal differences in the prediction. Different approaches to SSA showed somewhat larger deviations. In conclusion, the CA methodology is a valid and robust approach to U(VI) sorption onto complex substrates such as granite, provided sufficient

  9. Uranyl adsorption and surface speciation at the imogolite-water interface: Self-consistent spectroscopic and surface complexation models

    Science.gov (United States)

    Arai, Y.; McBeath, M.; Bargar, J.R.; Joye, J.; Davis, J.A.

    2006-01-01

    Macro- and molecular-scale knowledge of uranyl (U(VI)) partitioning reactions with soil/sediment mineral components is important in predicting U(VI) transport processes in the vadose zone and aquifers. In this study, U(VI) reactivity and surface speciation on a poorly crystalline aluminosilicate mineral, synthetic imogolite, were investigated using batch adsorption experiments, X-ray absorption spectroscopy (XAS), and surface complexation modeling. U(VI) uptake on imogolite surfaces was greatest at pH ???7-8 (I = 0.1 M NaNO3 solution, suspension density = 0.4 g/L [U(VI)]i = 0.01-30 ??M, equilibration with air). Uranyl uptake decreased with increasing sodium nitrate concentration in the range from 0.02 to 0.5 M. XAS analyses show that two U(VI) inner-sphere (bidentate mononuclear coordination on outer-wall aluminol groups) and one outer-sphere surface species are present on the imogolite surface, and the distribution of the surface species is pH dependent. At pH 8.8, bis-carbonato inner-sphere and tris-carbonato outer-sphere surface species are present. At pH 7, bis- and non-carbonato inner-sphere surface species co-exist, and the fraction of bis-carbonato species increases slightly with increasing I (0.1-0.5 M). At pH 5.3, U(VI) non-carbonato bidentate mononuclear surface species predominate (69%). A triple layer surface complexation model was developed with surface species that are consistent with the XAS analyses and macroscopic adsorption data. The proton stoichiometry of surface reactions was determined from both the pH dependence of U(VI) adsorption data in pH regions of surface species predominance and from bond-valence calculations. The bis-carbonato species required a distribution of surface charge between the surface and ?? charge planes in order to be consistent with both the spectroscopic and macroscopic adsorption data. This research indicates that U(VI)-carbonato ternary species on poorly crystalline aluminosilicate mineral surfaces may be important in

  10. 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.

  11. Supercritical CO2 Assisted Synthesis of EDTA-Fe3O4 Nanocomposite with High Adsorption Capacity for Hexavalent Chromium

    Directory of Open Access Journals (Sweden)

    Gunjan Bisht

    2016-01-01

    Full Text Available Efficiency of EDTA functionalized nanoparticles in adsorption of chromium (VI from water was investigated in this study. Magnetic iron oxide nanoparticles (IONPs were synthesized by a simple chemical coprecipitation route and EDTA coating onto IONPs was attained via supercritical carbon dioxide (Sc CO2, a technology with green sustainable properties. The obtained nanoparticles were then characterized by UV-Visible spectroscopy, Fourier transform infrared spectroscopy (FTIR, X-ray powder diffraction (XRD, transmission electron microscopy (TEM, scanning electron microscopy (SEM, and vibrating magnetometric analysis (VSM. The synthesized nanoparticle and its modified variant were evaluated as adsorbent for chromium (VI removal from water through batch adsorption technique and the effect of analytic concentration; contact time and adsorbent concentration were studied at pH 2. The results showed higher removal efficiency for modified magnetic iron oxide nanoparticles (MIONPs (i.e., 99.9% than their nonmodified variant IONPs, that is, 34.06% for the same concentration after 18 hours of incubation. Also maximum adsorption capacity (qe = 452.26 mg/g of MIONPs attained can be related to their preparation in Sc CO2 as qe calculated from IONPs, that is, 170.33 mg/g, is lower than that of MIONPs. The adsorption data fit well with Freundlich isotherm equation while kinetic adsorption studies of chromium (VI were modeled by pseudo-second-order model.

  12. 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.

  13. Comparative EXAFS study of uranium(VI) and neptunium(V) sorption onto kaolinite

    International Nuclear Information System (INIS)

    Reich, T.; Amayri, S.; Reich, Ta.; Jermolajev, J.

    2005-01-01

    Full text of publication follows: We investigated the surface sorption process of U(VI) and Np(V) on kaolinite by extended X-ray absorption fine structure (EXAFS) spectroscopy in the 10 μM concentration range. Batch experiments with kaolinite in CO 2 -equilibrated systems showed that the adsorption edge of U(VI) occurs at pH 5.5, i.e., near the pH PZC of kaolinite. The adsorption edge of Np(V) occurs well above the pH PZC value at pH 8.5. This may indicate that the bonds between Np(V) and the surface functional groups of kaolinite are not as strong as in the case of U(VI). U(VI) and Np(V) have in common that the amount which is adsorbed decreases when the pH is increased beyond the absorption maximum. This behavior can be attributed to the formation of U(VI) and Np(V) carbonato complexes in the aqueous solutions. The aim of this comparative EXAFS study was to investigate the reason for the different affinities of U(VI) and Np(V) for kaolinite by measuring their local environments at the clay surface. Samples were prepared from 4 g/L kaolinite, 0.1 M NaClO 4 , pH 3.0 - 10.5, presence and absence of ambient CO 2 . The U L 3 - and Np L 2 -edge EXAFS spectra of the wet paste samples were measured at room temperature in fluorescence mode at the Rossendorf Beamline (ROBL) at the European Synchrotron Radiation Facility. The measured U-O and U-Al/Si distances indicate inner-sphere sorption of U(VI) on kaolinite. There was no evidence of uranium neighbors in the EXAFS spectra, suggesting that the adsorbed U(VI) complexes were predominantly monomeric. The average distance between uranium and its equatorial oxygen atoms, O eq , increased from 2.32 to 2.38 Angstrom in the presence of atmospheric CO 2 when the pH was increased from 5.0 to 8.5. In the CO 2 -free system, the U-O eq distance was independent from pH and equal to 2.32 Angstrom. The lengthening of the average U-O eq distance in the presence of carbonate (or bicarbonate) suggests the formation of ternary U(VI

  14. Chemical Interaction between U(VI) and Eu(III) ions on a Silica Surface

    International Nuclear Information System (INIS)

    Park, K. K.; Cha, W. S.; Cho, H. R.; Im, H. J.; Jung, E. C.

    2010-01-01

    Understanding the chemical behavior of actinide in groundwater flow is important for assessing the possibility of its migration with water flow in the radioactive waste disposal site. Precipitation/ dissolution in groundwater and adsorption/desorption onto a geological solid surface would determine its migration. The sorption in a geochemical system was expected to be a reaction on a naturally equilibrated surface. However, the construction of a waste disposal facility could disturb this equilibrium state, induce a new reaction environment and affect a nanoscopic surface reaction of actinide. Uranium is ubiquitous in the natural environment and a representative element in a nuclear fuel cycle and in a high level radioactive waste. In oxic environments, it is typically present as uranyl oxocation (UO 2 2+ ), which is easily adsorbed and thereby removed from a solution in the near neutral pH range. This adsorption would form a new surface condition to give an unexpected adsorption behavior for other actinide ions. Eu(III) frequently is used as a chemical analogue of Am(III) and Cm(III) in migration chemistry. The adsorption phenomena has been interpreted with the help of a SCM(surface complexation model). Some spectroscopic techniques such as EPR (Electron Paramagnetic Resonance), IR (InfraRed), EXAFS (Extended X-ray Absorption Fine Structure) and TRLFS (Time Resolved Laser Fluorescence Spectroscopy) have been used for the identification of a modeled adsorbing species. In the case of fluorescence elements, TRLFS has advantages over other techniques for its high sensitivity being proportional to laser source intensity and good selectivity depending on specific transition and lifetime. This technique can be applied to a species on a solid surface not absorbing light such as silica. U(VI) and Eu(III) have fluorescente properties reflecting their coordination structure. In this study, the interaction between U(VI) and Eu(III) on a silica surface was studied by a

  15. 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.

  16. 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.

  17. Removal of Heavy Metals by Adsorption onto Activated Carbon Derived from Pine Cones of Pinus roxburghii.

    Science.gov (United States)

    Saif, Muhammad Jawwad; Zia, Khalid Mahmood; Fazal-ur-Rehman; Usman, Muhammad; Hussain, Abdullah Ijaz; Chatha, Shahzad Ali Shahid

    2015-04-01

    Activated carbon derived from cones of Pinus roxburghii (Himalayan Pine) was used as an adsorbent for the removal of copper, nickel and chromium ions from waste water. Surface analysis was carried out to determine the specific surface area and pore size distribution of the pine cone derived activated carbon. Optimal parameters, effect of adsorbent quantity, pH, equilibrium time, agitation speed and temperature were studied. Equilibrium data were evaluated by Langmuir and Freundlich isotherm models. Langmuir isotherm afforded the best fit to the equilibrium data with a maximum adsorption capacity of 14.2, 31.4 and 29.6 mg/g for Cu(II), Ni(II) and Cr(VI) respectively. Maximum adsorption of Cu(II), Ni(II) was observed in the pH range 4.0 to 4.5, whereas the best adsorption of Cr(VI) was observed at pH 2.5. It was found that 180 minutes was sufficient to gain adsorption equilibrium. The adsorption process follows a pseudo-second-order kinetic model.

  18. 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.

  19. Enhancing the sorption efficiency of polystyrene by immobilizing MgO and its application for uranium (VI) removal from aqueous solutions

    Energy Technology Data Exchange (ETDEWEB)

    Elhefnawy, O.A.; Elabd, A.A. [Nuclear and Radiological Regulatory Authority (NRRA), Cairo (Egypt). Nuclear Safeguards and Physical Protection Dept.

    2016-07-01

    Magnesium oxide immobilized polystyrene (PS/MgO) was prepared by the thermal attachment method for the removal of U(VI) from aqueous solutions. PS/MgO was characterized by different techniques [scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD)]. The effects of pH, adsorbent amount, contact time, initial U(VI) concentration, temperature and co-existing cations on the removal process were investigated by using batch technique. The results showed that the maximum adsorption capacity was 163 (mg g{sup -1}) at pH 6 and 293 K. The adsorption kinetics of U(VI) onto PS/MgO followed pseudo-second order and intra-particle kinetic models. The adsorption isotherms obeyed the Freundlich isotherm model. The thermodynamic parameters show that the process is endothermic and spontaneous. PS/MgO is an attractive adsorbent for U(VI) removal from aqueous solutions due to its accessibility, low preparation cost and high removal capacity.

  20. 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.

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

    Directory of Open Access Journals (Sweden)

    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.

  2. 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...

  3. Plutonium(VI) accumulation and reduction by lichen biomass: correlation with U(VI)

    International Nuclear Information System (INIS)

    Ohnuki, Toshihiko; Aoyagi, Hisao; Kitatsuji, Yoshihiro; Samadfam, Mohammad; Kimura, Yasuhiko; William Purvis, O.

    2004-01-01

    The uptake of plutonium(VI) and uranium(VI) by lichen biomass was studied in the foliose lichen Parmotrema tinctorum to elucidate the migration behavior of Pu and U in the terrestrial environment. Pu and U uptake by P. tinctorum averaged 0.040±0.010 and 0.055±0.015 g g dry -1 , respectively, after 96 h incubation with 4.0x10 -4 mol l -1 Pu solutions of pH 3, 4 and 5. SEM observations showed that the accumulated Pu is evenly distributed on the upper and lower surfaces of P. tinctorum, in contrast to U(VI), which accumulated in both cortical and medullary layers. UV/VIS absorption spectroscopy demonstrates that a fraction of Pu(VI) in the solution is reduced to Pu(V) by the organic substances released from P. tinctorum, and the accumulated Pu on the surface is reduced to Pu(IV), while U(VI) keeps the oxidation state of VI. Since the solubility of Pu(IV) hydroxides is very low, reduced Pu(VI) does not penetrate to the medullary layers, but is probably precipitated as Pu(IV) hydroxides on the cortical lichen surface. It is concluded that the uptake and reduction of Pu(VI) by lichens is important to determine the mobilization and oxidation states of Pu in the terrestrial environment

  4. Fundamentals of high pressure adsorption

    Energy Technology Data Exchange (ETDEWEB)

    Zhou, Y.P.; Zhou, L. [Tianjin University, Tianjin (China). High Pressure Adsorption Laboratory

    2009-12-15

    High-pressure adsorption attracts research interests following the world's attention to alternative fuels, and it exerts essential effect on the study of hydrogen/methane storage and the development of novel materials addressing to the storage. However, theoretical puzzles in high-pressure adsorption hindered the progress of application studies. Therefore, the present paper addresses the major theoretical problems that challenged researchers: i.e., how to model the isotherms with maximum observed in high-pressure adsorption; what is the adsorption mechanism at high pressures; how do we determine the quantity of absolute adsorption based on experimental data. Ideology and methods to tackle these problems are elucidated, which lead to new insights into the nature of high-pressure adsorption and progress in application studies, for example, in modeling multicomponent adsorption, hydrogen storage, natural gas storage, and coalbed methane enrichment, was achieved.

  5. The application of Fe–Mn hydrous oxides based adsorbent for removing selenium species from water

    KAUST Repository

    Szlachta, Małgorzata

    2013-02-01

    In this study, the adsorptive removal of selenium(IV) and selenium(VI) from water by a newly developed ion exchange adsorbent, based on Fe(III) and Mn(III) hydrous oxides, was examined. This study was conducted to determine the influence of various operating parameters, such as initial anion concentration, contact time, adsorbent dose, pH, solution temperature, and the presence of competitive anions, on the treatment performance. The high Se(IV) adsorptive capacity of the adsorbent (up to 41.02. mg/g at pH 4) was due to its high affinity for selenite, as reflected in the fast rate of uptake (batch studies) and an efficient long-term removal (column experiments). Although adsorption of anions traditionally decreases as pH increases, the mixed adsorbent was capable of purifying large volumes of Se(IV)-containing water (at pH 7) to reach concentrations lower than 10 μg/L, which meets the European Commission standards. The presence of sulphate and carbonate did not influence Se(IV) adsorption. However, high phosphate and silicate concentrations may have decreased the removal efficiency of Se(IV). Data from the batch and column adsorption experiments were fitted with a number of approved models, which revealed the adsorption mechanism and allowed for a comparison of the results. © 2012 Elsevier B.V.

  6. 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.

  7. 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.

  8. ViA: a perceptual visualization assistant

    Science.gov (United States)

    Healey, Chris G.; St. Amant, Robert; Elhaddad, Mahmoud S.

    2000-05-01

    This paper describes an automated visualized assistant called ViA. ViA is designed to help users construct perceptually optical visualizations to represent, explore, and analyze large, complex, multidimensional datasets. We have approached this problem by studying what is known about the control of human visual attention. By harnessing the low-level human visual system, we can support our dual goals of rapid and accurate visualization. Perceptual guidelines that we have built using psychophysical experiments form the basis for ViA. ViA uses modified mixed-initiative planning algorithms from artificial intelligence to search of perceptually optical data attribute to visual feature mappings. Our perceptual guidelines are integrated into evaluation engines that provide evaluation weights for a given data-feature mapping, and hints on how that mapping might be improved. ViA begins by asking users a set of simple questions about their dataset and the analysis tasks they want to perform. Answers to these questions are used in combination with the evaluation engines to identify and intelligently pursue promising data-feature mappings. The result is an automatically-generated set of mappings that are perceptually salient, but that also respect the context of the dataset and users' preferences about how they want to visualize their data.

  9. Uranium adsorption by non-treated and chemically modified cactus fibres in aqueous solutions

    International Nuclear Information System (INIS)

    Melpomeni Prodromou; Ioannis Pashalidis

    2013-01-01

    The adsorption efficiency of Opuntia ficus indica fibres regarding the removal of hexavalent uranium [U(VI)] from aqueous solutions has been investigated prior and after the chemical treatment (e.g. phosphorylation and MnO 2 -coating) of the biomass. The separation/removal efficiency has been studied as a function of pH, uranium concentration, adsorbent mass, ionic strength, temperature and contact time. Evaluation of the experimental data shows that biosorption is strongly pH-depended and that the MnO 2 -coated product presents the highest adsorption capacity followed by the phosphorylated and non-treated material. Experiments with varying ionic strength/salinity don't show any significant effect on the adsorption efficiency, indicating the formation of inner-sphere surface complexes. The adsorption reactions are in all cases exothermic and relatively fast, particularly regarding the adsorption on the MnO 2 -coated product. The results of the present study indicate that adsorption of uranium from waters is very effective by cactus fibres and particularly the modified treated fibres. The increased adsorption efficiency of the cactus fibres is attributed to their primary and secondary fibrillar structure, which result in a relative relative high specific surface available for sorption. (author)

  10. Removal of uranium(VI) from aqueous solutions by new phosphorus-containing carbon spheres synthesized via one-step hydrothermal carbonization of glucose in the presence of phosphoric acid

    International Nuclear Information System (INIS)

    Zhi-bin Zhang; East China Institute of Technology, Fuzhou; China University of Geosciences, Wuhan; Zhi-wei Zhou; Xiao-hong Cao; Yun-hai Liu; Guo-xuan Xiong; East China Institute of Technology, Fuzhou; Ping Liang; East China Institute of Technology, Fuzhou; China University of Geosciences, Wuhan

    2014-01-01

    The novel phosphorus-rich hydrothermal carbon spheres (HCSs-PO 4 ) have been synthesized via one-step hydrothermal carbonization of glucose in the presence of phosphoric acid. The textural and surface chemistry properties were characterized using Boehm titrations, scanning electron microscopy and Fourier transform infrared spectrometer. The content of oxygen-containing functional groups on the surface of HCSs increased from 0.053 to 1.009 mmol g -1 by phosphate group modification. The adsorption ability of HCSsPO 4 has been explored for the removal of uranium from aqueous solutions. The adsorption kinetic data were best described by the pseudo-second-order equation. Adsorption process could be well defined by the Langmuir isotherm, the adsorption capacity of HCSs increased from 80.00 to 285.70 mg g -1 after phosphate group modification. And thermodynamic parameters indicated the adsorption process was feasible,endothermic and spontaneous. Selective adsorption studies showed that the HCSs-PO 4 could selectively remove U(VI), and the selectivity coefficients had been improved in the presence of co-existing ions, Na(I), Ni(II), Sr(II), Mn(II), Mg(II) and Zn(II). Complete removal (99.9 %) of U(VI) from 1.0 L industry wastewater containing 15.0 mg U(VI) ions was possible with 12.0 g HCSs-PO 4 . (author)

  11. Traps for phosphorus adsorption

    International Nuclear Information System (INIS)

    Montoya, Nawer D; Villegas, Wilson E; Rodriguez, Lino M; Taborda, Nelson; Montes de C, Consuelo

    2001-01-01

    Several AL 2 O 3 supported oxides such as: NiO, CuO, Co 2 O 3 BaO, CeO 2 and ZnO were investigated for phosphorus adsorption. Zno/y-Al 2 O 3 exhibited the highest phosphorus adsorption capacity. However, since it diminishes the activity of to the reaction mixture it should be located upstream of the NoX catalyst, i.e. 0,3% Pd-H-MOR, in order to protect it against p poisoning. The treatment procedure with citric acid was effective for the removal of more than 70% phosphorus from the adsorbent, ZnO/y-Al 2 O 3

  12. Adsorption of Uranyl Ions at the Nano-hydroxyapatite and Its Modification.

    Science.gov (United States)

    Skwarek, Ewa; Gładysz-Płaska, Agnieszka; Bolbukh, Yuliia

    2017-12-01

    Nano-hydroxyapatite and its modification, hydroxyapatite with the excess of phosphorus (P-HAP) and hydroxyapatite with the carbon ions built into the structure (C-HAP), were prepared by the wet method. They were studied by means of XRD, accelerated surface area and porosimetry (ASAP), and SEM. The size of crystallites computed using the Scherrer method was nano-hydroxyapatite (HAP) = 20 nm; P-HAP-impossible to determine; C-HAP = 22 nm; nano-HAP/U(VI) = 13.7 nm; P-HAP/U(VI)-impossible to determine, C-HAP/U(VI) = 11 nm. There were determined basic parameters characterizing the double electrical layer at the nano-HAP/electrolyte and P-HAP/electrolyte, C-HAP/electrolyte inter faces: density of the surface charge and zeta potential. The adsorption properties of nano-HAP sorbent in relation to U(VI) ions were studied by the batch technique. The adsorption processes were rapid in the first 60 min and reached the equilibrium within approximately 120 min (for P-HAP) and 300 min (for C-HAP and nano-HAP). The adsorption process fitted well with the pseudo-second-order kinetics. The Freundlich, Langmuir-Freundlich, and Dubinin-Radushkevich models of isotherms were examined for their ability to the equilibrium sorption data. The maximum adsorption capabilities (q m ) were 7.75 g/g for P-HAP, 1.77 g/g for C-HAP, and 0.8 g/g for HAP at 293 K.

  13. Diffusion Influenced Adsorption Kinetics.

    Science.gov (United States)

    Miura, Toshiaki; Seki, Kazuhiko

    2015-08-27

    When the kinetics of adsorption is influenced by the diffusive flow of solutes, the solute concentration at the surface is influenced by the surface coverage of solutes, which is given by the Langmuir-Hinshelwood adsorption equation. The diffusion equation with the boundary condition given by the Langmuir-Hinshelwood adsorption equation leads to the nonlinear integro-differential equation for the surface coverage. In this paper, we solved the nonlinear integro-differential equation using the Grünwald-Letnikov formula developed to solve fractional kinetics. Guided by the numerical results, analytical expressions for the upper and lower bounds of the exact numerical results were obtained. The upper and lower bounds were close to the exact numerical results in the diffusion- and reaction-controlled limits, respectively. We examined the validity of the two simple analytical expressions obtained in the diffusion-controlled limit. The results were generalized to include the effect of dispersive diffusion. We also investigated the effect of molecular rearrangement of anisotropic molecules on surface coverage.

  14. Enhancement of uranium(VI) biosorption by chemically modified marine-derived mangrove endophytic fungus Fusarium sp. ZZF51

    International Nuclear Information System (INIS)

    Chen, F.; Tan, N.; Long, W.; Yang, S.K.; She, Z.G.; Lin, Y.C.

    2014-01-01

    Fusarium sp. ZZF51, mangrove endophytic fungus originated from South China Sea coast, was chemically modified by formaldehyde, methanol and acetic acid to enhance its affinity of uranium(VI) from waste water. The influencing factors about uranium(VI) adsorption such as contact time, solution pH, the ratio of solid/liquid (S/L) and initial uranium(VI) concentration were investigated, and the suitable adsorption isotherm and kinetic models were determined. In addition, the biosorption mechanism was also discussed by FTIR analysis. Experimental results show that the maximum biosorption capacity of formaldehyde-treated biomass for uranium(VI) at the optimized condition of pH 6.0, S/L 0.6 and equilibrium time 90 min is 318.04 mg g -1 , and those of methanol-treated and HAc-treated biomass are 311.95 and 351.67 mg g -1 at the same pH and S/L values but different equilibrium time of 60 and 90 min, respectively. Thus the maximum biosorption capacity of the three kind of modified biomass have greatly surpassed that of the raw biomass (21.42 mg g -1 ). The study of kinetic exhibits a high level of compliance with the Lagergren's pseudo-second-order kinetic models. Langumir and Freundlich models have proved to be well able to explain the sorption equilibrium with the satisfactory correlation coefficients higher than 0.96. FTIR analysis reveals that the carboxyl, amino and hydroxyl groups on the cell wall of Fusarium sp. ZZF51 play an important role in uranium(VI) biosorption process. (author)

  15. BIOSORPTION OF CHROMIUM (VI) USING IMMOBILIZED ...

    African Journals Online (AJOL)

    USER

    2016-05-20

    May 20, 2016 ... dangerous for survival of human if adequate steps are not taken for treatment of ..... homogeneous surface by monolayer ... qo , Kf, and KT are adsorption constants of Langmuir, Freundlich and Temkin isotherms, b and BT.

  16. Kinetics of Cation and Oxyanion Adsorption and Desorption on Ferrihydrite: Roles of Ferrihydrite Binding Sites and a Unified Model

    Energy Technology Data Exchange (ETDEWEB)

    Tian, Lei [School of Environment and Energy, South China University of Technology, Guangzhou, Guangdong 510006, People’s Republic of China; The Key Lab of Pollution Control and Ecosystem Restoration in Industry; Shi, Zhenqing [School of Environment and Energy, South China University of Technology, Guangzhou, Guangdong 510006, People’s Republic of China; The Key Lab of Pollution Control and Ecosystem Restoration in Industry; Lu, Yang [School of Environment and Energy, South China University of Technology, Guangzhou, Guangdong 510006, People’s Republic of China; The Key Lab of Pollution Control and Ecosystem Restoration in Industry; Dohnalkova, Alice C. [Environmental; Lin, Zhang [School of Environment and Energy, South China University of Technology, Guangzhou, Guangdong 510006, People’s Republic of China; The Key Lab of Pollution Control and Ecosystem Restoration in Industry; Dang, Zhi [School of Environment and Energy, South China University of Technology, Guangzhou, Guangdong 510006, People’s Republic of China; The Key Lab of Pollution Control and Ecosystem Restoration in Industry

    2017-08-29

    Understanding the kinetics of toxic ion reactions with ferrihydrite is crucial for predicting the dynamic behavior of contaminants in soil environments. In this study, the kinetics of As(V), Cr(VI), Cu, and Pb adsorption and desorption on ferrihydrite were investigated with a combination of laboratory macroscopic experiments, microscopic investigation and mechanistic modeling. The rates of As(V), Cr(VI), Cu, and Pb adsorption and desorption on ferrihydrite, as systematically studied using a stirred-flow method, was highly dependent on the reaction pH and metal concentrations and varied significantly among four metals. Spherical aberration-corrected scanning transmission electron microscopy (Cs-STEM) showed, at sub-nano scales, all four metals were distributed within the ferrihydrite particle aggregates homogeneously after adsorption reactions, with no evidence of surface diffusion-controlled processes. Based on experimental results, we developed a unifying kinetics model for both cation and oxyanion adsorption/desorption on ferrihydrite based on the mechanistic-based equilibrium model CD-MUSIC. Overall, the model described the kinetic results well, and we quantitatively demonstrated how the equilibrium properties of the cation and oxyanion binding to various ferrihydrite sites affected the adsorption and desorption rates. Our results provided a unifying quantitative modeling method for the kinetics of both cation and oxyanion adsorption/desorption on iron minerals.

  17. Examination of Uranium(VI) Leaching During Ligand Promoted Dissolution of Waste Tank Sludge Surrogates

    Energy Technology Data Exchange (ETDEWEB)

    Powell, Brian; Powell, Brian A.; Rao, Linfeng; Nash, Kenneth. L.

    2008-06-10

    The dissolution of synthetic boehmite (?-AlOOH) by 1-hydroxyethane-1,1-diphosphonic acid (HEDPA) was examined in a series of batch adsorption/dissolution experiments. Additionally, the leaching behavior of {sup 233}U(VI) from boehmite was examined as a function of pH and HEDPA concentration. The results are discussed in terms of sludge washing procedures that may be utilized during underground tank waste remediation. In the pH range 4 to 10, complexation of Al(III) by HEDPA significantly enhanced dissolution of boehmite. This phenomenon was especially pronounced in the neutral pH region where the solubility of aluminum, in the absence of complexants, is limited by the formation of sparsely soluble aluminum hydroxides. At pH higher than 10, dissolution of synthetic boehmite was inhibited by HEDPA, likely due to sorption of Al(III):HEDPA complexes. Addition of HEDPA to equilibrated U(VI)-synthetic boehmite suspensions yielded an increase in the aqueous phase uranium concentration. Partitioning of uranium between the solid and aqueous phase is described in terms of U(VI):HEDPA speciation and dissolution of the boehmite solid phase.

  18. Micro-electrolysis of Cr (VI) in the nanoscale zero-valent iron loaded activated carbon.

    Science.gov (United States)

    Wu, Limei; Liao, Libing; Lv, Guocheng; Qin, Faxiang; He, Yujuan; Wang, Xiaoyu

    2013-06-15

    In this paper we prepared a novel material of activated carbon/nanoscale zero-valent iron (C-Fe(0)) composite. The C-Fe(0) was proved to possess large specific surface area and outstanding reducibility that result in the rapid and stable reaction with Cr (VI). The prepared composite has been examined in detail in terms of the influence of solution pH, concentration and reaction time in the Cr (VI) removal experiments. The results showed that the C-Fe(0) formed a micro-electrolysis which dominated the reaction rate. The Micro-electrolysis reaches equilibrium is ten minutes. Its reaction rate is ten times higher than that of traditional adsorption reaction, and the removal rate of Cr reaches up to 99.5%. By analyzing the obtained profiles from the cyclic voltammetry, PXRD and XPS, we demonstrate that the Cr (VI) is reduced to insoluble Cr (III) compound in the reaction. Copyright © 2013 Elsevier B.V. All rights reserved.

  19. 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.

  20. Spectroscopic studies of U(VI) sorption at the kaolinite-water interface. Final report

    International Nuclear Information System (INIS)

    Thompson, H.A.; Parks, G.A.; Brown, G.E. Jr.

    1994-01-01

    Efficient use of U as a resource and safe handling, recycling and disposal of U-containing wastes require an understanding of the factors controlling the fate of U, where fate refers to the destination of U, typically expressed as an environmental medium or a process phase. The sorption process constitutes a change in elemental fate. Partitioning of an element from solution to a solid phase, or sorption, can be divided into three broad categories: adsorption, surface precipitation, and absorption. Extended X-ray absorption fine structure (EXAFS), a type of X-ray absorption spectroscopy (XAS), offers the possibility for distinguishing among different modes of sorption by characterizing the atomic environment of the sorbing element. In this study, the authors use EXAFS to determine the structure of U(VI) sorption complexes at the kaolinite-water interface. In Chapter One, they present an overview of selected aspects of U structural chemistry as a basis for considering the structural environment of U at the solid-water interface. To evaluate the utility of XAS for characterization of the structural environment of U(VI) at the solid-water interface, they have carried out an in-depth analysis of XAS data from U(VI)-containing solid and solution model compounds, which they describe in Chapter Two. In Chapter three, they consider sorption of U by kaolinite as a means of effecting the removal of U from surface collection pond waters on the Rocky Flats Plant site in northern Colorado

  1. Voltammetric study of chromium(VI)-ammonia/ammonium chloride solutions in the presence of dimethylglyoxime

    International Nuclear Information System (INIS)

    Ginzburg, V.G.; Salikhdzhanova, R.M.F.

    1987-01-01

    The authors believed complexation to be possible in the system Cr(VI)-dimethylglyoxime (DMG, H 2 D) by reduction of Cr(VI) to Cr(III) on a mercury electrode. The DMG can be used in chromium voltammetry and is promising for a number of reasons: The Cr(III) has an affinity for donor nitrogen atoms in the DMG molecule. Insertion of the H 2 D into the inner sphere of the complex is expected to weaken the bond between the Cr(III) and the hydroxyl group, slow down formation of the insoluble hydroxide Cr(OH) 3 , and lower the rate of the electrode reaction Cr(III) → Cr(II). Molecules of H 2 D adsorb on a mercury electrode. It is therefore possible to accelerate the electrode process by including adsorptive preconcentration of the chromium and thus lowering its detection limit. This paper reports the voltammetric behavior of the system Cr(VI)-DMG-NH 4 + (proton donor) for the purpose of lowering the chromium detection limit

  2. Copper adsorption in tropical oxisols

    Directory of Open Access Journals (Sweden)

    Silveira Maria Lucia Azevedo

    2003-01-01

    Full Text Available Cu adsorption, at concentrations between 0 to 800 mg L-1, was evaluated in surface and subsurface samples of three Brazilian soils: a heavy clayey-textured Rhodic Hapludalf (RH, a heavy clayey-textured Anionic ''Rhodic'' Acrudox (RA and a medium-textured Anionic ''Xanthic'' Acrudox (XA. After adsorption, two consecutive extractions were performed to the samples which received 100 mg L-1 copper. Surface samples adsorbed higher amounts of Cu than the subsurface, and exhibited lower Cu removed after the extractions, reinforcing the influence of the organic matter in the reactions. Cu adsorption was significant in the subsurface horizons of the Oxisols, despite the positive balance of charge, demonstrating the existence of mechanisms for specific adsorption, mainly related to the predominance of iron and aluminum oxides in the mineral fractions. In these samples, Cu was easily removed from the adsorption sites. RH demonstrated a higher capacity for the Cu adsorption in both horizons.

  3. Effect of pH on the Removal of Chromium (Cr (VI by Sugar Cane Bagasse

    Directory of Open Access Journals (Sweden)

    Nasim Ahmed Khan

    2001-12-01

    Full Text Available The industrial estates in India are dominated by small and medium scale industries, which are posing a serious threat to the environment by virtue of discharging effluents of a polluting nature. The problems become severe due to the presence of heavy metals in the effluents. Chromium is widely used in a number of industries such as electroplating, metal finishing, cooling towers, dyes, paints, anodising and leather tanning industries. The toxicity of chromium (VI is well known and is considered a hazard to the health of humans and animals. The presence of chromium (VI in aquatic environments at high concentrations is also lethal to marine species. The treatment of chromium bearing effluents have been reported through several methods, such as chemical reduction,  precipitation, ion exchange, electrochemical reduction, evaporation, reverse osmosis and adsorption. However among these, adsorption is found to be highly effective, inexpensive and an easy method to operate. India is an agricultural country and generates a considerable amount of agricultural wastes such as sugar cane bagassess, coconut jute, nut shell, rice straw, rice husk, waste tea leaves, ground nut husk, crop wastes, peanut hulls and fertilizer wastes. Successful studies on these materials could be beneficial to developing countries and could be easily applied as adsorbents for the removal of chromium from wastewater. Most of the previous work highlights the use of commercial activated carbon but these adsorbents are relatively expensive and less feasible to be used in developing countries. Keeping these in view batch experiments have been designed to study the feasibility of sugar cane bagasse to remove chromium (VI from the aqueous solutions. While evaluationg the impact of various parameters, such as adsorbent does, contact time, initial concentration and pH on chromium removal efficiency, the results indicate a prominent effect of pH on the chromium reduction by the adsorbent

  4. 76 FR 60593 - Title VI; Proposed Circular

    Science.gov (United States)

    2011-09-29

    ..., several of them related to ambiguous language in the existing Circular. The proposed Circular reorganizes... regional entity, and inclusive of public and private entities. This term is used exclusively in Chapter IV... revisions to the Title VI Circular. The section that addresses the existing requirement for a Language...

  5. Chromium(VI) bioremediation by probiotics.

    Science.gov (United States)

    Younan, Soraia; Sakita, Gabriel Z; Albuquerque, Talita R; Keller, Rogéria; Bremer-Neto, Hermann

    2016-09-01

    Chromium is a common mineral in the earth's crust and can be released into the environment from anthropogenic sources. Intake of hexavalent chromium (Cr(VI)) through drinking water and food causes toxic effects, leading to serious diseases, and is a commonly reported environmental problem. Microorganisms can mitigate or prevent the toxic effects caused by heavy metals in addition to having effective resistance mechanisms to prevent cell damage and bind to these metals, sequestering them from the cell surface and removing them from the body. Species of Lactobacillus, Streptococcus, Bacillus and Bifidobacterium present in the human mouth and gut and in fermented foods have the ability to bind and detoxify some of these substances. This review address the primary topics related to Cr(VI) poisoning in animals and humans and the use of probiotics as a way to mitigate or prevent the toxic effects caused by Cr(VI). Further advances in the genetic knowledge of such microorganisms may lead to discoveries which will clarify the most active microorganisms that act as bioprotectants in bodies exposed to Cr(VI) and are an affordable option for people and animals intoxicated by the oral route. © 2016 Society of Chemical Industry. © 2016 Society of Chemical Industry.

  6. Vi har selv designet naturens love

    DEFF Research Database (Denmark)

    Bentzen, Martin Mose

    2014-01-01

    ForskerZonenNaturlovene er universelt gyldige i de flestes øjne. De gælder altid, uanset hvad vi tænker. Men dette billede står ikke uimodsagt i videnskabsfilosofien, og der er meget, der tyder på, at det ikke er specielt empirisk korrekt...

  7. Energy balance of ENDF/B-VI

    International Nuclear Information System (INIS)

    MacFarlane, R.E.

    1994-01-01

    ENDF/B-VI through Release 2 has been tested for neutron-photon energy balance using the Heater module of the NJOY nuclear data procesing system. The situation is much improved over ENDF/B-V, but there are still a number of maerials that show problems

  8. Adsorption and collective paramagnetism

    CERN Document Server

    Selwood, Pierce W

    1962-01-01

    Adsorption and Collective Paramagnetism describes a novel method for studying chemisorption. The method is based on the change in the number of unpaired electrons in the adsorbent as chemisorption occurs. The method is applicable to almost all adsorbates, but it is restricted to ferromagnetic adsorbents such as nickel, which may be obtained in the form of very small particles, that is to say, to ferromagnetic adsorbents with a high specific surface. While almost all the data used illustratively have been published elsewhere this is the first complete review of the subject. The book is addresse

  9. Enzymatic reduction of U(VI) in groundwaters

    International Nuclear Information System (INIS)

    Addelouas, A.; Gong, W.; Lutze, W.; Nuttall, E.; Fritz, B.; Crovisier, J.L.

    1999-01-01

    The use of enzymatic reduction of U(VI) in remediation of groundwater contaminated with U(VI) is receiving considerable attention. Certain strains of bacteria can combine the oxidation of an organic compound to the reduction of U(VI) to U(IV), which precipitates as uraninite. In the present study, we tested the reduction of U(VI) in groundwaters with various origins and compositions. In all groundwaters u(VI) was reduced by sulfate reducing bacteria that had been activated by ethanol and tri-metaphosphate. The reduction rate of U(VI) depends on sulfate concentration in water and the abundance of bacteria in the system. This work shows that bacteria capable of U(VI) reduction are ubiquitous in nature, and suggests the possibility of a large application of the enzymatic reduction of U(VI) for in situ clean up of groundwaters contaminated with uranium. (authors)

  10. Adsorption study of selenium ions from aqueous solutions using MgO nanosheets synthesized by ultrasonic method

    Energy Technology Data Exchange (ETDEWEB)

    Cui, Wenwen; Li, Ping; Wang, Zheming; Zheng, Shili; Zhang, Yi

    2018-01-01

    tMgO nanosheets with thickness ranges of 3–10 molecule layers and high specific area (166.44 m2g-1)were successfully fabricated by an ultrasound-assisted exfoliation method and used as adsorbent forthe removal of both selenite (Se(IV)) and selenate (Se(VI)) from aqueous solutions. The resulting MgOnanosheets displayed high maximum adsorption capacities of 103.52 and 10.28 mg g-1for Se(IV) andSe(VI), respectively. ATR-FTIR and XPS spectroscopic results suggested that both Se(IV) and Se(VI) formedinner-sphere surface complexes on MgO nanosheets under the present experimental conditions. Fur-thermore, high adsorption capacity for Se(IV/VI) in the presence of coexistent anions (SO42-, PO43-, Cl-,and F-) and efficient regeneratability of adsorbent by NaOH solution were observed in the competitiveadsorption and regeneration steps. The simple one-step synthesis process of MgO nanosheets and highadsorption capacities offer a promising method for Se(IV/VI) removal in water treatment.

  11. 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.

  12. New Synthesis of nZVI/C Composites as an Efficient Adsorbent for the Uptake of U(VI) from Aqueous Solutions.

    Science.gov (United States)

    Liu, Haibo; Li, Mengxue; Chen, Tianhu; Chen, Changlun; Alharbi, Njud S; Hayat, Tasawar; Chen, Dong; Zhang, Qiang; Sun, Yubing

    2017-08-15

    New nanoscale zerovalent iron/carbon (nZVI/C) composites were successfully prepared via heating natural hematite and pine sawdust at 800 °C under nitrogen conditions. Characterization by SEM, XRD, FTIR, and XPS analyses indicated that the as-prepared nZVI/C composites contained a large number of reactive sites. The lack of influence of the ionic strength revealed inner-sphere complexation dominated U(VI) uptake by the nZVI/C composites. Simultaneous adsorption and reduction were involved in the uptake process of U(VI) according to the results of XPS and XANES analyses. The presence of U-C/U-U shells demonstrated that innersphere complexation and surface coprecipitation dominated the U(VI) uptake at low and high pH conditions, respectively. The uptake behaviors of U(VI) by the nZVI/C composites were fitted well by surface complexation modeling with two weak and two strong sites. The maximum uptake capacity of U(VI) by the nZVI/C composites was 186.92 mg/g at pH 4.0 and 328 K. Additionally, the nZVI/C composites presented good recyclability and recoverability for U(VI) uptake in regeneration experiments. These observations indicated that the nZVI/C composites can be considered as potential adsorbents to remove radionuclides for environmental remediation.

  13. 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.

  14. Study on Shale Adsorption Equation Based on Monolayer Adsorption, Multilayer Adsorption, and Capillary Condensation

    OpenAIRE

    Chen, Qing; Tian, Yuanyuan; Li, Peng; Yan, Changhui; Pang, Yu; Zheng, Li; Deng, Hucheng; Zhou, Wen; Meng, Xianghao

    2017-01-01

    Shale gas is an effective gas resource all over the world. The evaluation of pore structure plays a critical role in exploring shale gas efficiently. Nitrogen adsorption experiment is one of the significant approaches to analyze pore size structure of shale. Shale is extremely heterogeneous due to component diversity and structure complexity. Therefore, adsorption isotherms for homogeneous adsorbents and empirical isotherms may not apply to shale. The shape of adsorption-desorption curve indi...

  15. 77 FR 64399 - Order of Succession for HUD Region VI

    Science.gov (United States)

    2012-10-19

    ... Region VI AGENCY: Office of Field Policy and Management, HUD. ACTION: Notice of Order of Succession... its Field Offices (Region VI). This Order of Succession supersedes all previous Orders of Succession for HUD Region VI. DATES: Effective Date: October 9, 2012. FOR FURTHER INFORMATION CONTACT: Lawrence D...

  16. ENDF-201, ENDF/B-VI summary documentation supplement 1, ENDF/HE-VI summary documentation

    International Nuclear Information System (INIS)

    McLane, V.

    1996-12-01

    The National Nuclear Data Center (NNDC) provides coordination for and serves as the secretariat to the Cross Section Evaluation Working Group (CSWEG). CSEWG is responsible for the oversight of the ENDF/B Evaluated Nuclear Data File. All data are checked and reviewed by CSEWG, and the file is maintained at the NNDC. For a description of the ENDF/B-VI file, see the ENDF-102 Data Formats and Procedures for the Evaluated Nuclear Data File ENDF-6. The purpose of this addendum to the ENDF/B-VI Summary Documentation is to provide documentation of Releases 1, 2, 3, and 4 for the ENDF/B-VI and ENDF/HE-VI evaluated nuclear data libraries. These releases contain many new and revised evaluations for the neutron, photo-atomic interaction, radioactive decay data, spontaneous fission product yield, neutron-induced fission product yield, thermal neutron scattering, proton, deuteron, and triton sublibraries. The summaries have been extracted mainly from the ENDF/B-VI File 1 comments (MT = 451), which have been checked, edited, and may also include supplementary information. Some summaries have been provided by the evaluators in electronic format, while others are extracted from reports on the evaluations. All references have been checked and corrected, or updated where appropriate. A list of the laboratories which have contributed evaluations used in ENDF/B-VI is given

  17. ENDF-201, ENDF/B-VI summary documentation supplement 1, ENDF/HE-VI summary documentation

    Energy Technology Data Exchange (ETDEWEB)

    McLane, V.

    1996-12-01

    The National Nuclear Data Center (NNDC) provides coordination for and serves as the secretariat to the Cross Section Evaluation Working Group (CSWEG). CSEWG is responsible for the oversight of the ENDF/B Evaluated Nuclear Data File. All data are checked and reviewed by CSEWG, and the file is maintained at the NNDC. For a description of the ENDF/B-VI file, see the ENDF-102 Data Formats and Procedures for the Evaluated Nuclear Data File ENDF-6. The purpose of this addendum to the ENDF/B-VI Summary Documentation is to provide documentation of Releases 1, 2, 3, and 4 for the ENDF/B-VI and ENDF/HE-VI evaluated nuclear data libraries. These releases contain many new and revised evaluations for the neutron, photo-atomic interaction, radioactive decay data, spontaneous fission product yield, neutron-induced fission product yield, thermal neutron scattering, proton, deuteron, and triton sublibraries. The summaries have been extracted mainly from the ENDF/B-VI File 1 comments (MT = 451), which have been checked, edited, and may also include supplementary information. Some summaries have been provided by the evaluators in electronic format, while others are extracted from reports on the evaluations. All references have been checked and corrected, or updated where appropriate. A list of the laboratories which have contributed evaluations used in ENDF/B-VI is given.

  18. Starch-g-Poly-(N, N-dimethyl acrylamide-co-acrylic acid): an efficient Cr (VI) ion binder.

    Science.gov (United States)

    Kolya, Haradhan; Roy, Anirban; Tripathy, Tridib

    2015-01-01

    Synthesis of Starch-g-(Poly N, N-dimethylacrylamide-co-acrylic acid) was carried out by solution polymerization technique using potassium perdisulfate (K(2)S(2)O(8)) as the initiator. The graft copolymer was characterized by measuring molecular weight, using size exclusion chromatography (SEC), FTIR spectroscopy and X-ray diffraction (XRD) studies. The synthetic graft copolymer was used for removal of hexavalent chromium ion [Cr (VI)] from its aqueous solution. Various operating variables affecting the metal sorption such as, the amount of adsorbent, solution pH, contact time, temperature and the Cr (VI) solution concentration were extensively investigated. FTIR and UV-VIS spectroscopy, cyclic voltammetry (CV) were employed to study the metal complexation. The adsorption data could be well described by the pseudo-second-order and Langmuir isotherm model which indicate a chemisorption process. Calculation of the various thermodynamic parameters for the adsorption was also done. The negative value of free energy change (ΔG°) indicates the spontaneous nature of the adsorption. Copyright © 2014 Elsevier B.V. All rights reserved.

  19. Enzymatic reduction of U(VI) in groundwaters; Reduction enzymatique de U(VI) dans des eaux souterraines

    Energy Technology Data Exchange (ETDEWEB)

    Addelouas, A.; Gong, W. [Center for Radioactive Waste Management, Advanced Materials Laboratory, 1001 University, Albuquerque (United States); Lutze, W.; Nuttall, E. [New Mexico Univ., Albuquerque, NM (United States). Dept. of Chemical and Nuclear Engineering; Fritz, B.; Crovisier, J.L. [Centre National de la Recherche Scientifique (CNRS), 67 - Strasbourg (France). Centre de Sedimentologie et Geochimie de la Surface

    1999-03-01

    The use of enzymatic reduction of U(VI) in remediation of groundwater contaminated with U(VI) is receiving considerable attention. Certain strains of bacteria can combine the oxidation of an organic compound to the reduction of U(VI) to U(IV), which precipitates as uraninite. In the present study, we tested the reduction of U(VI) in groundwaters with various origins and compositions. In all groundwaters u(VI) was reduced by sulfate reducing bacteria that had been activated by ethanol and tri-metaphosphate. The reduction rate of U(VI) depends on sulfate concentration in water and the abundance of bacteria in the system. This work shows that bacteria capable of U(VI) reduction are ubiquitous in nature, and suggests the possibility of a large application of the enzymatic reduction of U(VI) for in situ clean up of groundwaters contaminated with uranium. (authors) 12 refs.

  20. Adsorption of Cu(II) and Cr(VI) ions by chitosan: Kinetics and ...

    African Journals Online (AJOL)

    drinie

    2001-01-01

    Jan 1, 2001 ... dimensional structure of the molecules to chelate and remove ions of a specific ... alginates, carrageenan, lignins, proteins, chitin and chitin derivatives. Another ... formation of a chitosan chelate with Cu ions is shown in Fig.1.

  1. Kinetic and Thermodynamic Studies of the Adsorption of Cr(VI) onto ...

    African Journals Online (AJOL)

    NICO

    processing, paint and pigments, and the textile and steel fabrica- tion industries1. ...... of stainless steel nets coated with single wall carbon nanotubes,. J. Hazard. ... prepared from Algerien sheep hoofs, Europ. J. Sci. Res., 2009 35,. 416–425.

  2. Selective Adsorption of Uranium (VI) on NaHCO 3 Leached ...

    African Journals Online (AJOL)

    Ion imprinted nano-magnetic composite polymers for selective removal of hexavalent uranium were prepared by a precipitation polymerization technique in the presence of γ-methacryloxypropyltrimethoxysilane (γ-MPS) coated magnetite and other pre-polymerization reagents. The synthesized magnetic polymers were then ...

  3. New developments for localized adsorption

    International Nuclear Information System (INIS)

    Boudh-hir, M.E.

    1989-02-01

    Using the diagrammatic expansion, new developments for localized adsorption are found. It is proved that the correlations in the system, in the absence of the attractive site potential, and the periodicity of the sites play a fundamental role in the adsorption phenomena. 14 refs, 2 figs, 2 tabs

  4. 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.

  5. Chemical modification of silica gel with synthesized Schiff base hydrazone derivative and application for preconcentration and separation of U(VI) ions from aqueous solutions

    International Nuclear Information System (INIS)

    Gamze Karayel Incili; Gul Asiye Aycik

    2014-01-01

    Schiff base hydrazone derivative (HL) sorbent was synthesized according to the literature to be used in the adsorption and preconcentration of U(VI) ions from aqueous solution and it was exposed to immobilization, and new solid support material was obtained. For this purpose, Schiff base hydrazone derivative (HL) was chemically bonded to silica gel surface immobilized 3-aminopropyl trimethoxysilane, then analyzed by Fourier transform infrared, Brunauer-Emmett-Teller, scanning electron microscopy and elemental analysis. The influence of the solution pH, amount of sorbent, contact time, temperature, foreign ion effect and initial U(VI) concentration was investigated. The maximum U(VI) uptake capacity was found to be 8.46 mg/g. (author)

  6. Sn(II) oxy-hydroxides as potential adsorbents for Cr(VI)-uptake from drinking water: An X-ray absorption study

    International Nuclear Information System (INIS)

    Pinakidou, Fani; Kaprara, Efthimia; Katsikini, Maria; Paloura, Eleni C.; Simeonidis, Konstantinos; Mitrakas, Manassis

    2016-01-01

    The feasibility of implementing a Sn(II) oxy-hydroxide (Sn_6O_4(OH)_4) for the reduction and adsorption of Cr(VI) in drinking water treatment was investigated using XAFS spectroscopies at the Cr-K-edge. The analysis of the Cr-K-edge XANES and EXAFS spectra verified the effective use of Sn_6O_4(OH)_4 for successful Cr(VI) removal. Adsorption isotherms, as well as dynamic Rapid Small Scale Test (RSSCT) in NSF water matrix showed that Sn_6O_4(OH)_4 can decrease Cr(VI) concentration below the upcoming regulation limit of 10 μg/L for drinking water. Moreover, an uptake capacity of 7.2 μg/mg at breakthrough concentration of 10 μg/L was estimated from the RSSCT, while the residual Cr(VI) concentration ranged at sub-ppb level for a significant period of the experiment. Furthermore, no evidence for the formation of Cr(OH)_3 precipitates was found. On the contrary, Cr(III)-oxyanions were chemisorbed onto SnO_2, which was formed after Sn(II)-oxidation during Cr(VI)-reduction. Nevertheless, changes in the type of Cr(III)-inner sphere complexes were observed after increasing surface coverage: Cr(III)-oxyanions preferentially sorb in a geometry which combines both bidentate binuclear ("2C) and monodentate ("1V) geometries, at the expense of the present bidentate mononuclear ("2E) contributions. On the other hand, the pH during sorption does not affect the adsorption mechanism of Cr(III)-species. The implementation of Sn_6O_4(OH)_4 in water treatment technology combines the advantage of rapidly reducing a large amount of Cr(VI) due to donation of two electrons by Sn(II) and also the strong chemisorption of Cr(III) in a combination of the "2C and "1V configurations, which enhances the safe disposal of spent adsorbents. - Highlights: • Effective Cr(VI) removal from drinking water by Sn_6O_4(OH)_4 • Sn_6O_4(OH)_4 transformation to SnO_2 after Cr(VI) reduction to Cr(III) • Strong Cr(III) sorption onto SnO_2 by formation of inner sphere complexes • Cr(III) sorption

  7. Hvad skal vi med Trump-satire?

    DEFF Research Database (Denmark)

    Møller, Mette

    2017-01-01

    Trump-satire er et stort hit, og særligt en lang række satiriske videohilsner til Trump fra lande verden over får folk til at trække på smilebåndet. Men hvorfor er det så sjovt at gøre grin med Trump, og hvad kan vi bruge den politiske humor til?......Trump-satire er et stort hit, og særligt en lang række satiriske videohilsner til Trump fra lande verden over får folk til at trække på smilebåndet. Men hvorfor er det så sjovt at gøre grin med Trump, og hvad kan vi bruge den politiske humor til?...

  8. 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.

  9. Supercritical CO2 Assisted Synthesis of EDTA-Fe3O4 Nano composite with High Adsorption Capacity for Hexavalent Chromium

    International Nuclear Information System (INIS)

    Bisht, G.; Neupane, S.; Makaju, R.

    2016-01-01

    Efficiency of EDTA functionalized nanoparticles in adsorption of chromium (Vi) from water was investigated in this study. Magnetic iron oxide nanoparticles (IONPs) were synthesized by a simple chemical coprecipitation route and EDTA coating onto IONPs was attained via supercritical carbon dioxide (Sc CO 2 ), a technology with green sustainable properties. The obtained nanoparticles were then characterized by UV-Visible spectroscopy, Fourier transform infrared spectroscopy (FTIR), X-ray powder diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), and vibrating magnetometric analysis (VSM). The synthesized nanoparticle and its modified variant were evaluated as adsorbent for chromium (Vi) removal from water through batch adsorption technique and the effect of analytic concentration; contact time and adsorbent concentration were studied at ph 2. The results showed higher removal efficiency for modified magnetic iron oxide nanoparticles (MIONPs) (i.e., 99.9%) than their non modified variant IONPs, that is, 34.06% for the same concentration after 18 hours of incubation. Also maximum adsorption capacity (q e = 452.26 mg/g) of MIONPs attained can be related to their preparation in Sc CO 2 asq e calculated from IONPs, that is, 170.33 mg/g, is lower than that of MIONPs. The adsorption data fit well with Freundlich isotherm equation while kinetic adsorption studies of chromium (Vi) were modeled by pseudo-second-order model

  10. Nanomaterials application for heavy metals recovery from polluted water: The combination of nano zero-valent iron and carbon nanotubes. Competitive adsorption non-linear modeling.

    Science.gov (United States)

    Vilardi, Giorgio; Mpouras, Thanasis; Dermatas, Dimitris; Verdone, Nicola; Polydera, Angeliki; Di Palma, Luca

    2018-06-01

    Carbon Nanotubes (CNTs) and nano Zero-Valent Iron (nZVI) particles, as well as two nanocomposites based on these novel nanomaterials, were employed as nano-adsorbents for the removal of hexavalent chromium, selenium and cobalt, from aqueous solutions. Nanomaterials characterization included the determination of their point of zero charge and particle size distribution. CNTs were further analyzed using scanning electron microscopy, thermogravimetric analysis and Raman spectroscopy to determine their morphology and structural properties. Batch experiments were carried out to investigate the removal efficiency and the possible competitive interactions among metal ions. Adsorption was found to be the main removal mechanism, except for Cr(VI) treatment by nZVI, where reduction was the predominant mechanism. The removal efficiency was estimated in decreasing order as CNTs-nZVI > nZVI > CNTs > CNTs-nZVI* independently upon the tested heavy metal. In the case of competitive adsorption, Cr(VI) exhibited the highest affinity for every adsorbent. The preferable Cr(VI) removal was also observed using binary systems of the tested metals by means of the CNTs-nZVI nanocomposite. Single species adsorption was better described by the non-linear Sips model, whilst competitive adsorption followed the modified Langmuir model. The CNTs-nZVI nanocomposite was tested for its reusability, and showed high adsorption efficiency (the q max values decreased less than 50% with respect to the first use) even after three cycles of use. Copyright © 2018 Elsevier Ltd. All rights reserved.

  11. The status of ENDF/B-VI

    International Nuclear Information System (INIS)

    Roussin, R.; Dunford, C.; McKnight, R.; Young, P.

    1988-01-01

    A new version of the United States evaluated nuclear data file, ENDF/B-VI, is presently under development. Major emphasis is being placed on correcting some long-standing nuclear data problems that adversely affect applied calculations for both fission and fusion reactors. The paper reviews modifications to the formats and utility codes, outlines the evaluation activities, discusses the data testing programs, and projects a date for the unrestricted release of the new library. 27 refs., 2 tabs

  12. Prospek pengembangan industri perkulitan pada pelita VI

    Directory of Open Access Journals (Sweden)

    D Karyadi

    1995-06-01

    Full Text Available The leather industry is one of the strong competitive industry, as it comes from renewable natural resources. Therefore, the leather industry has good prospect to develop at the Pelita VI to be the industrial products export competitive. To develop leather industry and leather products should be given closed attention and well managed, especially concerning raw material supply, quality and leather waste treatment.

  13. Adsorption of Cs-137 and U-238 in semi-arid soils; Adsorcion de Cs-137 y U-238 en suelos semiaridos

    Energy Technology Data Exchange (ETDEWEB)

    Hernandez T, U. O. [Instituto Tecnologico de Toluca, Av. Tecnologico s/n, 52140 Metepec, Estado de Mexico (Mexico); Monroy G, F.; Anguiano A, J. [ININ, Carretera Mexico-Toluca s/n, 52750 Ocoyoacac, Estado de Mexico (Mexico); Fernandez R, E., E-mail: uohtrejo@gmail.com [Universidad Politecnica del Valle de Toluca, Carretera Toluca-Almoloya de Juarez Km. 5.6, Santiaguito Tlalcilalcali, Estado de Mexico (Mexico)

    2013-10-15

    Is of great importance to determine the adsorption properties of the soils where radioactive wastes are stored, fundamentally of the radioisotopes contained in these wastes, with the purpose of knowing like will be their behavior in the event of happening radionuclide migration toward the surrounding means. Therefore, in this work the adsorption properties of {sup 137}Cs{sup +} and {sup 238}UO{sub 2}{sup 2+} in soils coming from the Storage Center of Radioactive Wastes are studied. Was studied the effect of the soil type and the particle size of the soil in the adsorption properties of Cs (I) and U (Vi). 13 soil samples and six different particle sizes were analyzed. The adsorption studies were carried out by the radiotracers technique in static way. The results indicate an important adsorption affinity toward the Cs-137 and a very vulnerable affinity for the {sup 238}UO{sub 2}{sup 2+}. (author)

  14. Vi behøver innovation

    DEFF Research Database (Denmark)

    McAloone, Tim C.

    2007-01-01

    -Produktion og Maskiner. Innovation og bæredygtighed er to områder som vi i Skandinavien giver meget stor opmærksomhed for at kunne vedligeholde vores globale konkurrencekraft og stærke velfærdssamfund. Gennem årene har mange brancher bidraget til skabelsen af vidensbaserede innovationer, og det faktum, at de......Analyse: Vi behøver innovation En ny miljøbølge ruller, og danske virksomheder bør ride med Af Tim McAloone, fredag 02. feb 2007 kl. 04:50 Tim McAloone Lektor og ph.d. ved Institut for mekanik, energi og konstruktion ved DTU. Tim McAloone skriver fremover jævnligt kommentarer i Ingeniøren...... skandinaviske lande er relativt små, har ledt til en interessant evne til at etablere og derefter samarbejde inden for tætte netværk, som strækker sig over både faglige og geografiske grænser. Samtidig har vi set miljøhensyn vinde og tabe samfundsmæssig og industriel opmærksomhed på en nærmest periodisk basis...

  15. Adsorption Desalination: A Novel Method

    KAUST Repository

    Ng, Kim Choon

    2010-11-15

    The search for potable water for quenching global thirst remains a pressing concern throughout many regions of the world. The demand for new and sustainable sources and the associated technologies for producing fresh water are intrinsically linked to the solving of potable water availability and hitherto, innovative and energy efficient desalination methods seems to be the practical solutions. Quenching global thirst by adsorption desalination is a practical and inexpensive method of desalinating the saline and brackish water to produce fresh water for agriculture irrigation, industrial, and building applications. This chapter provides a general overview of the adsorption fundamentals in terms of adsorption isotherms, kinetics, and heat of adsorption. It is then being more focused on the principles of thermally driven adsorption desalination methods. The recent developments of adsorption desalination plants and the effect of operating conditions on the system performance in terms of specific daily water production and performance ratio are presented. Design of a large commercial adsorption desalination plant is also discussed herein.

  16. Adsorption facility and adsorption vessel for radioactive carbon dioxide

    International Nuclear Information System (INIS)

    Harashina, Heihachi; Miwa, Keiichi; Kobayashi, Takeo.

    1992-01-01

    If 14 CO 2 gas-containing gases to be adsorbed are pressurized and sent to a packaging adsorption means, CO 2 ingredient in the gases to be adsorbed is adsorbed or absorbed, and remaining gases are passed through and sent out to downstream. CO 2 adsorption or absorption of the packaging adsorption means is judged by monitoring the state of the remaining gases, and if it is normal, remaining gases are sent further to downstream and processed. If abnormality is found, a gas feedback system is operated, and CO 2 removing gas is sent again to the packaging adsorption means, in which CO 2 gases are adsorbed or absorbed again repeatingly. With such procedures, in a case where C 14 nuclides having a long half decay time are supplied in the form of 14 CO 2 gas, they are efficiently adsorbed or absorbed in the packaging system to improve removing and storing property of 14 C nuclides. (T.M.)

  17. Carbon nanomaterials for gas adsorption

    CERN Document Server

    Terranova, Maria Letizia

    2012-01-01

    Research in adsorption of gases by carbon nanomaterials has experienced considerable growth in recent years, with increasing interest for practical applications. Many research groups are now producing or using such materials for gas adsorption, storage, purification, and sensing. This book provides a selected overview of some of the most interesting scientific results regarding the outstanding properties of carbon nanomaterials for gas adsorption and of interest both for basic research and technological applications. Topics receiving special attention in this book include storage of H, purific

  18. Hydrogen purification by periodic adsorption

    Energy Technology Data Exchange (ETDEWEB)

    Barg, Christian; Secchi, Argimiro R.; Trierweiler, Jorge O. [Rio Grande do Sul Univ., Porto Alegre, RS (Brazil). Dept. de Engenharia Quimica]. E-mail: cbarg@enq.ufrgs.br; arge@enq.ufrgs.br; jorge@enq.ufrgs.br

    2000-07-01

    The periodic adsorption processes have been widely used for industrial applications, mainly because it spends less energy than the usual gas separation processes, like the cryogenic distillation. The largest commercial application of periodic adsorption processes is the pressure swing adsorption (PSA) applied to hydrogen purification. Although its wide use in the chemical and petrochemical industry, there are no reports in the open literature about complete modeling studies of a complex commercial unit, with multiple adsorbents and multiple beds and several feed components. This study has as objective the modeling, optimization and dynamical analysis of an industrial PSA unit for hydrogen purification. (author)

  19. Strong Selective Adsorption of Polymers.

    Science.gov (United States)

    Ge, Ting; Rubinstein, Michael

    2015-06-09

    A scaling theory is developed for selective adsorption of polymers induced by the strong binding between specific monomers and complementary surface adsorption sites. By "selective" we mean specific attraction between a subset of all monomers, called "sticky", and a subset of surface sites, called "adsorption sites". We demonstrate that, in addition to the expected dependence on the polymer volume fraction ϕ bulk in the bulk solution, selective adsorption strongly depends on the ratio between two characteristic length scales, the root-mean-square distance l between neighboring sticky monomers along the polymer, and the average distance d between neighboring surface adsorption sites. The role of the ratio l / d arises from the fact that a polymer needs to deform to enable the spatial commensurability between its sticky monomers and the surface adsorption sites for selective adsorption. We study strong selective adsorption of both telechelic polymers with two end monomers being sticky and multisticker polymers with many sticky monomers between sticky ends. For telechelic polymers, we identify four adsorption regimes at l / d 1, we expect that the adsorption layer at exponentially low ϕ bulk consists of separated unstretched loops, while as ϕ bulk increases the layer crosses over to a brush of extended loops with a second layer of weakly overlapping tails. For multisticker chains, in the limit of exponentially low ϕ bulk , adsorbed polymers are well separated from each other. As l / d increases, the conformation of an individual polymer changes from a single-end-adsorbed "mushroom" to a random walk of loops. For high ϕ bulk , adsorbed polymers at small l / d are mushrooms that cover all the adsorption sites. At sufficiently large l / d , adsorbed multisticker polymers strongly overlap. We anticipate the formation of a self-similar carpet and with increasing l / d a two-layer structure with a brush of loops covered by a self-similar carpet. As l / d exceeds the

  20. 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

  1. 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

  2. Equilibrium and kinetic study on chromium (VI removal from simulated waste water using gooseberry seeds as a novel biosorbent

    Directory of Open Access Journals (Sweden)

    J. Aravind

    2015-07-01

    Full Text Available Gooseberry seed (Phyllanthus acidus was used as an adsorbent to determine its feasibility for the removal of Cr(VI. Various parameters such as pH, temperature, contact time, initial metal concentration and adsorbent dosage were investigated to determine the biosorption performance. Equilibrium was attained within 60 minutes and maximum removal of 96% was achieved under the optimum conditions at pH 2. The adsorption phenomenon demonstrated here was monolayer represented by Langmuir isotherm with R2 value of 0.992 and the Langmuir constants k and q0 was found to be 0.0061 (L/mg and 19.23 (mg/g. The adsorption system obeyed Pseudo second order kinetics with R2 value of 0.999. The results of the present study indicated that gooseberry seed powder can be employed as adsorbent for the effective removal of hexavalent chromium economically.

  3. Water adsorption on goethite: Application of multilayer adsorption models

    Science.gov (United States)

    Hatch, C. D.; Tumminello, R.; Meredith, R.

    2016-12-01

    Adsorbed water on the surface of atmospheric mineral dust has recently been shown to significantly affect the ability of mineral dust aerosol to act as cloud condensation nuclei. We have studied water adsorption as a function of relative humidity (RH) on goethite (α-FeO(OH)), a common component of atmospheric mineral dust. The goethite surface area and particle size was determined using BET analysis and with N2 as an adsorbate and scanning electron microscopy, respectively. Water adsorption on the sample was monitored using horizontal attenuated total reflectance Fourier transform infrared (HATR-FTIR) spectroscopy equipped with a flow cell. Water content was determined using Beer's law and the optical constants for bulk water. The results were analyzed using Type II adsorption isotherms to model multilayer adsorption, including BET (Brunauer, Emmet and Teller), FHH (Frenkel, Halsey and Hill) and Freundlich. BET fits to experimental data provide parameters of monolayer coverage, while the FHH and Freundlich isotherms provide insights into multilayer adsorption mechanisms. Results indicate that goethite contains 5% H2O by mass at 50% RH, which increases to 12% by mass at 90% RH. Adsorption parameters and experimental results will be presented.

  4. Reactivity enhancement of iron sulfide nanoparticles stabilized by sodium alginate: Taking Cr (VI) removal as an example

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Jun; Wang, Xian-Bin; Zeng, Raymond J., E-mail: rzeng@ustc.edu.cn

    2017-07-05

    Highlights: • Sodium alginate can be used to stabilize FeS nanoparticles. • FeS-SA enhances Cr(VI) removal efficiency from 65% to 100% compared to naked FeS. • Reduction and adsorption respectively account for 82% and 18% of Cr removal by FeS-SA. • Analysis of reaction products reveals the co-existence of α-FeOOH, S{sub 8}, and Cr(OH){sub 3.} - Abstract: The widespread distribution of chromium(VI) in the environment leads to groundwater contamination. The use of iron sulfide (FeS) to remove Cr(VI) has therefore been proposed. However, aggregation is one of the main problems associated with the use of FeS nanoparticles prepared by traditional methods In this study, we used sodium alginate (SA) to stabilize FeS nanoparticles (FeS-SA). SA could prevent aggregation of FeS by the concurrent electrostatic repulsion and steric hindrance. Homogeneously dispersed FeS-SA nanoparticles 100 nm in diameter were observed. FeS-SA showed high efficiency in Cr(VI) removal, corresponding to an enhancement of efficiency from 65% (7.50 mmol Cr(VI) per g FeS) to 100% (11.54 mmol Cr per g FeS) relative to that achieved with naked FeS. Analysis of reaction products by X-ray diffraction and X-ray photoelectron spectroscopy revealed the co-existence of α-FeOOH, S{sub 8}, and Cr(OH){sub 3} that apparently were introduced by Fe(II), S(−II), and Cr(VI), respectively. In-depth analysis of the removal mechanism revealed that reduction and adsorption respectively account for 82% and 18% of the Cr removal. In addition, higher pH and CaCl{sub 2} concentration resulted in lower removal efficiency. This study provides a promising application of SA in enhancing FeS reactivity for the remediation of groundwater pollution.

  5. Prediction of Pure Component Adsorption Equilibria Using an Adsorption Isotherm Equation Based on Vacancy Solution Theory

    DEFF Research Database (Denmark)

    Marcussen, Lis; Aasberg-Petersen, K.; Krøll, Annette Elisabeth

    2000-01-01

    An adsorption isotherm equation for nonideal pure component adsorption based on vacancy solution theory and the Non-Random-Two-Liquid (NRTL) equation is found to be useful for predicting pure component adsorption equilibria at a variety of conditions. The isotherm equation is evaluated successfully...... adsorption systems, spreading pressure and isosteric heat of adsorption are also calculated....

  6. Ultra Low Concentration Adsorption Equilibria

    National Research Council Canada - National Science Library

    Mahle, John J; Buettner, Leonard C; LeVan, M. D; Schindler, Bryan J

    2006-01-01

    .... Specifically this work focuses on novel experimental and modeling methods to characterize and predict at ultra-low chemical vapor concentrations the protection afforded by adsorption-based vapor filtration systems...

  7. Potential Theory of Multicomponent Adsorption

    DEFF Research Database (Denmark)

    Shapiro, Alexander; Stenby, Erling Halfdan

    1998-01-01

    We developed a theory of multicomponent adsorption on the basis of the potential concept originally suggested by Polanyi. The mixture is considered as a heterogeneous substance segregated in the external field emitted by the adsorbent. The same standard equation of state, with no additional fitting...... parameters, is used for the segregated and for the bulk phases. With this approach, few parameters are needed to correlate pure component adsorption isotherms. These parameters may be used to predict adsorption equilibria of multicomponent mixtures without additional adjustment. A connection between...... the potential theory and the spreading pressure concept is established, and problems of the theory consistency are studied. Numerical algorithms are suggested for evaluation of the segregated state of the mixture in the potential field of adsorption forces. Comparison with experimental data shows good agreement...

  8. 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

  9. Adsorption kinetics of surfactants on activated carbon

    Science.gov (United States)

    Arnelli; Aditama, WP; Fikriani, Z.; Astuti, Y.

    2018-04-01

    A study on the adsorption of both cationic and anionic surfactants using activated carbon as well as the investigation of the adsorption isotherms and adsorption kinetics has been conducted. The results showed that the adsorption of sodium lauryl sulfate (SLS) by activated carbon was Langmuir’s adsorption isotherm while its adsorption kinetics showed pseudo-second order with an adsorption rate constant of 2.23 x 103 g mg-1 hour-1. Meanwhile, the adsorption of HDTMA-Br by activated carbon showed that the isotherm adsorption tended to follow Freundlich’s isotherm and was pseudo-second order with an adsorption rate constant of 89.39 g mg-1 hour-1.

  10. Adsorption of amylase enzyme on ultrafiltration membranes

    DEFF Research Database (Denmark)

    Beier, Søren; Enevoldsen, Ann Dorrit; Kontogeorgis, Georgios

    2007-01-01

    A method to measure the static adsorption on membrane surfaces has been developed and described. The static adsorption of an amylase-F has been measured on two different ultrafiltration membranes, both with a cut-off value of 10 kDa (a PES membrane and the ETNA10PP membrane, which is a surface......-modified PVDF membrane). The adsorption follows the Langmuir adsorption theory. Thus, the static adsorption consists of monolayer coverage. The static adsorption is expressed both as a permeability drop and an adsorption resistance. From the adsorption isotherms the maximum static permeability drops...... and the maximum static adsorption resistances are determined. The maximum static permeability drop for the hydrophobic PES membrane is 75 % and the maximum static adsorption resistance is 0.014 m2hbar/L. The maximum static permeability drop for the hydrophilic surface-modified PVDF membrane (ETNA10PP) is 23...

  11. Adsorption of antibiotics on microplastics.

    Science.gov (United States)

    Li, Jia; Zhang, Kaina; Zhang, Hua

    2018-06-01

    Microplastics and antibiotics are two classes of emerging contaminants with proposed negative impacts to aqueous ecosystems. Adsorption of antibiotics on microplastics may result in their long-range transport and may cause compound combination effects. In this study, we investigated the adsorption of 5 antibiotics [sulfadiazine (SDZ), amoxicillin (AMX), tetracycline (TC), ciprofloxacin (CIP), and trimethoprim (TMP)] on 5 types of microplastics [polyethylene (PE), polystyrene (PS), polypropylene (PP), polyamide (PA), and polyvinyl chloride (PVC)] in the freshwater and seawater systems. Scanning Electron Microscope (SEM) and X-ray diffractometer (XRD) analysis revealed that microplastics have different surface characterizes and various degrees of crystalline. Adsorption isotherms demonstrated that PA had the strongest adsorption capacity for antibiotics with distribution coefficient (K d ) values ranged from 7.36 ± 0.257 to 756 ± 48.0 L kg -1 in the freshwater system, which can be attributed to its porous structure and hydrogen bonding. Relatively low adsorption capacity was observed on other four microplastics. The adsorption amounts of 5 antibiotics on PS, PE, PP, and PVC decreased in the order of CIP > AMX > TMP > SDZ > TC with K f correlated positively with octanol-water partition coefficients (Log K ow ). Comparing to freshwater system, adsorption capacity in seawater decreased significantly and no adsorption was observed for CIP and AMX. Our results indicated that commonly observed polyamide particles can serve as a carrier of antibiotics in the aquatic environment. Copyright © 2018 Elsevier Ltd. All rights reserved.

  12. Adsorption of Chromium from Aqueous Solution Using Polyaniline

    Directory of Open Access Journals (Sweden)

    Majid Riahi Samani

    2011-10-01

    Full Text Available New group of polymers have been synthesized that are conductive of electricity so they are called conducting polymers. One of the most conducting polymers is "polyaniline". In the present study, polyaniline was synthesized by oxidizing aniline monomer under strongly acidic conditions using potassium iodate as an initiator of oxidative polymerization. Synthesized polyaniline as a powder used as an adsorbent to remove chromium from aqueous solution. Experiments were conducted in batch mode with variables such as amount of polyaniline, chromium solution pH and adsorbtion isotherms. Due to presence of Cr (III in solution after using polyaniline, removal mechanism is the combination of surface adsorption and reduction. It seems that polyaniline reduces the Cr(VI to Cr(III and adsorbs the Cr(III and a part of remaining  Cr(VI. It is well known that nitrogen atom in compounds of amine derivative makes co-ordinate bond with positive charge of metals due to the presence of electron in sp3 orbital of nitrogen. The majority of total chromium removal  occurred at 30minute for polyaniline  and the optimum  time for  hexavalent chromium  removal was about 5 min. Polyaniline has the maximum total cheomiume removal at pH, 3-9. The maximum hexavalent chromium removal occurred at acidic pH for polyanilines. The equilibrium adsorption data for polyaniline fitted both Freundlich’s and Langmuir’s isotherms. This research shows that polyaniline can be used as an adsorbent  for removal chromium from aqueous solution.

  13. Adsorption refrigeration technology theory and application

    CERN Document Server

    Wang, Ruzhu; Wu, Jingyi

    2014-01-01

    Gives readers a detailed understanding of adsorption refrigeration technology, with a focus on practical applications and environmental concerns Systematically covering the technology of adsorption refrigeration, this book provides readers with a technical understanding of the topic as well as detailed information on the state-of-the-art from leading researchers in the field. Introducing readers to background on the development of adsorption refrigeration, the authors also cover the development of adsorbents, various thermodynamic theories, the design of adsorption systems and adsorption refri

  14. Sorption of uranium (VI) on homoionic sodium smectite experimental study and surface complexation modeling.

    Science.gov (United States)

    Korichi, Smain; Bensmaili, Aicha

    2009-09-30

    This paper is an extension of a previous paper where the natural and purified clay in the homoionic Na form were physico-chemically characterized (doi:10.1016/j.clay.2008.04.014). In this study, the adsorption behavior of U (VI) on a purified Na-smectite suspension is studied using batch adsorption experiments and surface complexation modeling (double layer model). The sorption of uranium was investigated as a function of pH, uranium concentration, solid to liquid ratio, effect of natural organic matter (NOM) and NaNO(3) background electrolyte concentration. Using the MINTEQA2 program, the speciation of uranium was calculated as a function of pH and uranium concentration. Model predicted U (VI) aqueous speciation suggests that important aqueous species in the [U (VI)]=1mg/L and pH range 3-7 including UO(2)(2+), UO(2)OH(+), and (UO(2))(3)(OH)(5)(+). The concentration of UO(2)(2+) decreased and that of (UO(2))(3)(OH)(5)(+) increased with increasing pH. The potentiometric titration values and uptake of uranium in the sodium smectite suspension were simulated by FITEQL 4.0 program using a two sites model, which is composed of silicate and aluminum reaction sites. We compare the acidity constants values obtained by potentiometric titration from the purified sodium smectite with those obtained from single oxides (quartz and alpha-alumina), taking into account the surface heterogeneity and the complex nature of natural colloids. We investigate the uranium sorption onto purified Na-smectite assuming low, intermediate and high edge site surfaces which are estimated from specific surface area percentage. The sorption data is interpreted and modeled as a function of edge site surfaces. A relationship between uranium sorption and total site concentration was confirmed and explained through variation in estimated edge site surface value. The modeling study shows that, the convergence during DLM modeling is related to the best estimation of the edge site surface from the N(2

  15. Study of Mo (VI Removal from Aqueous Solution: Application of Different Mathematical Models to Continuous Biosorption Data

    Directory of Open Access Journals (Sweden)

    Fatemeh Kafshgari

    2013-01-01

    Full Text Available Molybdenum (VI biosorption process was investigated by marine algae Cystoseria indica pretreated with 0.1 M CaCl2 solution in a packed bed column. The biosorbent was characterized by FTIR, BET and SEM analyses. The results showed that Mo (VI ions should be chelated with the hydroxyl, carboxyl and amine groups of the biomass. The effects of inlet metal concentration and flow rate on biosorption process were investigated and the experimental breakthrough curves were obtained. Results showed that the maximum biosorption capacity of Ca-pretreated C. indica for Mo (VI was found to be 18.32 mg/g at optimum flow rate of (1.4 mL/min. The controlled-rate step shifted from external to internal mass transfer limitations, as the flow rate increased. Also, it was observed that the breakthrough and exhaustion time decreased from 17.14 hr to 9.05 hr and from 0.006 h to 0.002 hr respectively, with the increase of flow rate from 0.7 to 2.1 ML/min. The increase in the initial concentration of Mo (VI solution from 30 to 95 ml min-1 increases the adsorption capacity from 18.32 to 30.19 mg/g and decreases the percentage of Mo (VI removal from 61 to 38%. Also, the treated volume was the greatest (1.42 L at the lowest inlet concentration. Column data obtained under different conditions were described using the Thomas, Yoon and Nelson, Yan and Belter models. The breakthrough curve predictions by Belter model were found to be very satisfactory.

  16. Amazon kaolinite functionalized with diethylenetriamine moieties for U(VI) removal: Thermodynamic of cation-basic interactions

    Energy Technology Data Exchange (ETDEWEB)

    Guerra, Denis L., E-mail: denis@cpd.ufmt.br [Universidade Federal de Mato Grosso, UFMT, Centro de Recursos Minerais, Cuiaba, Mato Grosso, 78060 900 (Brazil); Leidens, Victor L.; Viana, Rubia R. [Universidade Federal de Mato Grosso, UFMT, Centro de Recursos Minerais, Cuiaba, Mato Grosso, 78060 900 (Brazil); Airoldi, Claudio [Chemistry Institute, State University of Campinas, P.O. Box 6154, 13084-971 Campinas, Sao Paulo (Brazil)

    2010-08-15

    The compound N-[3-(trimethoxysilyl)propyl]diethylenetriamine (MPDET) was anchored onto Amazon kaolinite surface (KLT) by heterogeneous route. The modified and natural kaolinite clay samples were characterized by transmission electron microscopy (TEM), scanning electron microscopic (SEM), N{sub 2} adsorption, powder X-ray diffraction, thermal analysis, ion exchange capacities, and nuclear magnetic nuclei of {sup 29}Si and {sup 13}C. The well-defined peaks obtained in the {sup 13}C NMR spectrum in the 5.0-62.1 ppm region confirmed the attachment of organic functional groups as pendant chains bonded into the porous clay. The adsorption of uranyl on natural (KLT) and modified (KLT{sub MPDET}) kaolinite clays was investigated as a function of the solution pH, metal concentration, temperature, and ionic strength. The ability of these materials to remove U(VI) from aqueous solution was followed by a series of adsorption isotherms adjusted to a Sips equation at room temperature and pH 4.0. The maximum number of moles adsorbed was determined to be 8.37 x 10{sup -3} and 13.87 x 10{sup -3} mmol g{sup -1} for KLT and KLT{sub MPDET} at 298 K, respectively. The energetic effects ({Delta}{sub int}H, {Delta}{sub int}G, and {Delta}{sub int}S) caused by metal cations adsorption were determined through calorimetric titrations.

  17. Amazon kaolinite functionalized with diethylenetriamine moieties for U(VI) removal: Thermodynamic of cation-basic interactions

    International Nuclear Information System (INIS)

    Guerra, Denis L.; Leidens, Victor L.; Viana, Rubia R.; Airoldi, Claudio

    2010-01-01

    The compound N-[3-(trimethoxysilyl)propyl]diethylenetriamine (MPDET) was anchored onto Amazon kaolinite surface (KLT) by heterogeneous route. The modified and natural kaolinite clay samples were characterized by transmission electron microscopy (TEM), scanning electron microscopic (SEM), N 2 adsorption, powder X-ray diffraction, thermal analysis, ion exchange capacities, and nuclear magnetic nuclei of 29 Si and 13 C. The well-defined peaks obtained in the 13 C NMR spectrum in the 5.0-62.1 ppm region confirmed the attachment of organic functional groups as pendant chains bonded into the porous clay. The adsorption of uranyl on natural (KLT) and modified (KLT MPDET ) kaolinite clays was investigated as a function of the solution pH, metal concentration, temperature, and ionic strength. The ability of these materials to remove U(VI) from aqueous solution was followed by a series of adsorption isotherms adjusted to a Sips equation at room temperature and pH 4.0. The maximum number of moles adsorbed was determined to be 8.37 x 10 -3 and 13.87 x 10 -3 mmol g -1 for KLT and KLT MPDET at 298 K, respectively. The energetic effects (Δ int H, Δ int G, and Δ int S) caused by metal cations adsorption were determined through calorimetric titrations.

  18. ADSORPSI POLUTAN ION DIKROMAT MENGGUNAKAN ZEOLIT ALAM TERMODIFIKASI AMINA (Adsorption of Dichromate Ions Pollutant Using Ammine Modified-Natural Zeolites

    Directory of Open Access Journals (Sweden)

    Eko Sri Kunarti

    2015-11-01

    24,66 kJ/mol. ABSTRACT Chromium (VI is a heavy metal pollutant that is harmful to health and the environment, therefore Cr(VI ions in aqueous solution removal is important to overcome the environmental pollution. Adsorption process is one of simple techniques that can be used to take metal ions. Adsorption study of dichromate ions as a wastewater model of Cr(VI has been conducted in this research by using ammine modified natural zeolite as adsorbents. The research was initiated by preparation of adsorbent of ammine-modified natural zeolites. The preparation was started by washing the natural zeolite (Z using distilled water and refluxing by 3M hydrochloric acid. Refluxed zeolites (ZA were modified by a quaternary ammonium salt, N-cethyl-N,N,N-trimethylammonium bromide (CTAB, and a primary amine, propylamine (PA. The natural zeolite (Z, acid activated zeolite (ZA and amine-modified zeolites were then applied for adsorption of dichromate ions. Characterization of zeolite samples was performed by infrared spectroscopy and X-ray diffraction methods to confirm the crystal structure, and atomic absorption spectroscopy method to analyze the adsorbed dichromate ions. Results showed that all zeolite samples contain clinoptilolite, mordernite and quartz minerals. The zeolite structure was not changed by heat and chemical treatments. Modification of zeolites enhanced the adsorption efficiency of natural zeolites. The dichromate ions were better adsorbed on ammine modified-zeolites compared to that of unmodified-zeolite with adsorption ability of CTAB modified zeolite (CTAB-Z was greater than that of propylammine modified zeolite (PA-Z. The adsorption of dichromate on zeolite samples was achieved in the order of CTAB-Z > PA-Z > ZA > Z, with the adsorption efficiency was about 1.96; 1.74; 0.90 and 0.48 mg/g, respectively. The dichromate ions adsorption by CTAB modified zeolite is chemical adsorption (chemisorption with the adsorption energy of 24.66 kJ/mol.

  19. Adsorption-Desorption Characteristics of Plutonium and Americium with Sediment Particles in the Estuarine Environment

    International Nuclear Information System (INIS)

    Murray, C.N.; Fukai, R.

    1976-01-01

    The particle formation of plutonium and americium, their adsorption onto fresh water sediments and the desorption from the sediments in sea water were studied in the Laboratory under simulated river-estuary conditions, using γ-emitting plutonium-237 and americium-241. The results of the experiments show that the particle formation of plutonium depends on its valence states, on pH and on the salinity of the medium. For river water at pH4, some 25%, 20% and 30% of the added 237 Pu was in particulate form, larger than 0.45pm, for Pu (III), Pu (IV) and Pu (VI), respectively, while 65%, 90% and 50% of the respective valence states was associated with particles at pH 8. In sea water the general pattern remains similar, although Pu (VI) is more soluble in sea water owing to higher ligand concentrations for carbonate and bicarbonate complexes. The pH-dependency of particle formation of Am (III) is more steep than that of plutonium and seems to be influenced by colloidal substances occurring in the experimental media. The adsorption-desorption characteristics of plutonium and americium with the sediment in river water as well as sea water reflect the characteristics of their particle formation, being dependent upon such properties as valence states, the pH and salinity of the medium. A sewage effluent added to the media has small but measurable effects on the adsorption-desorption processes of plutonium. (author)

  20. Voltammetry of Os(VI)-modified polysaccharides

    Czech Academy of Sciences Publication Activity Database

    Trefulka, Mojmír; Paleček, Emil

    2010-01-01

    Roč. 22, č. 16 (2010), s. 1837-1845 ISSN 1040-0397 R&D Projects: GA AV ČR(CZ) GPP301/10/P548; GA MŠk(CZ) LC06035 Grant - others:GA AV ČR(CZ) KAN400310651 Program:KA Institutional research plan: CEZ:AV0Z50040507; CEZ:AV0Z50040702 Keywords : chemical modification of polysaccharides * electroactive labels * osmium(VI) complexes Subject RIV: BO - Biophysics Impact factor: 2.721, year: 2010

  1. Environmental survey of Region VI, Haltenbanken, 2009; Miljoeundersoekelse i Region VI, Haltenbanken, 2009

    Energy Technology Data Exchange (ETDEWEB)

    Holm, May-Helen; Cochrane, Sabine; Mannvik, Hans-Petter; Wasbotten, Ingar Halvorsen

    2010-07-01

    There has been an environmental investigation in Region VI Halten Bank. This report presents the results of the chemical and biological assays performed on samples from a total of 316 stations in 16 fields and 15 regional stations. A status of environmental conditions in the region is given at the end of the report. (AG)

  2. Environmental Survey in Region VI, Haltenbanken, 2009. Summary report; Miljoeundersoekelse i Region VI, Haltenbanken, 2009. Sammendragsrapport

    Energy Technology Data Exchange (ETDEWEB)

    Mannvik, Hans-Petter; Wasbotten, Ingar Halvorsen

    2010-07-01

    An environmental survey of Region VI, Haltenbanken, has been carried out. This report presents the results from the analyses carried out on samples from a total of 316 stations at 16 fields and 15 regional stations. A status of the environmental conditions in the region is given at the end of the report. (Author)

  3. Fremtidens lavenergibyggeri - kan vi gøre som vi plejer?

    DEFF Research Database (Denmark)

    Larsen, Tine Steen

    2011-01-01

    Stramninger af kravene til energiforbruget i vores boliger medfører stor fokus på energiberegningen, men erfaringer fra lavenergiboliger opført i dag viser, at vi, for at sikre succes for fremtidens boliger, også skal inddrage dokumentation af indeklimaet og forbedre samarbejdet mellem arkitekter...

  4. Uranium removal from drinking water by adsorption onto granular ferric hydroxide (GEH)

    International Nuclear Information System (INIS)

    Bahr, Carsten

    2012-01-01

    Uranium contamination of groundwater is encountered in many regions worldwide. Effective and simple removal technologies are required by waterworks faced with this problem, particularly in Germany which set a specification for maximum permissible uranium content in drinking water in November 2011. The present thesis examines the suitability of Granular Ferric Hydroxide (GEH) as a water treatment adsorbent for uranium removal. Adsorption isotherms generated in the studies showed that GEH is capable of adsorbing uranium, in fact achieving highest loading levels as compared to other oxide-based absorbents. Experimental data for uranium adsorption as a function of pH for the model systems U(VI) / H 2 O and U(VI) / H 2 O / CO 2 successfully fits the Surface Complexation Model using the adjusted parameter set for ferrihydrite. Test findings showed that adsorption capacity varies substantially depending on the water matrix processed and is significantly reduced when real ground water or drinking water is processed. The main parameters influencing adsorption capacity were found to be pH and the associated carbonate concentration, as well as the concentrations of calcium and phosphate and to a lesser extent of sulfate and humic substances. The reduced capacity is caused by adsorption competition and changes in chemical speciation of uranium brought about by the water matrix at hand. Both the kinetics and the dynamics of adsorption can be successfully described by the Homogeneous Surface Diffusion Model (HSDM). The characteristic transport coefficients for film diffusion and particle diffusion were determined using empirical correlations and lab testing. The comparatively slow kinetics of adsorption are caused by the rate-determining particle diffusion and lead to a relatively flat breakthrough curve. Experiments on small adsorber columns (RSSCT method) were used to simulate uranium breakthrough in GEH fixed-bed filters on a laboratory scale, permitting accurate prediction

  5. Synthesis, characterization and oxidative behaviour of dioxoruthenium(VI) complexes

    International Nuclear Information System (INIS)

    Agarwal, D.D.; Rastogi, Rachana

    1995-01-01

    Dioxoruthenium(VI) complexes are found to give low yield of epoxide but good yield of cyclohexanone. The complexes are electro active giving metal centered Ru VI /Ru V couple. Cis-stilbene gives trans epoxide and benzaldehyde. Norbornene gives exo epoxy norbornene. The selectivity for allylic oxidation is high. In the present note the synthesis of dioxoruthenium(VI) complexes and their oxidation behaviour is reported. The dioxoruthenium(VI) complexes have been stoichiometrically found to be good oxidants. (author). 21 refs., 1 tab

  6. Enzymatic U(VI) reduction by Desulfosporosinus species

    International Nuclear Information System (INIS)

    Suzuki, Y.; Kelly, S.D.; Kemner, K.M.; Banfield, J.F.

    2004-01-01

    Here we tested U(VI) reduction by a Desulfosporosinus species (sp.) isolate and type strain (DSM 765) in cell suspensions (pH 7) containing 1 mM U(VI) and lactate, under an atmosphere containing N 2 -CO 2 -H 2 (90: 5: 5). Although neither Desulfosporosinus species (spp.) reduced U(VI) in cell suspensions with 0.25% Na-bicarbonate or 0.85% NaCl, U(VI) was reduced in these solutions by a control strain, desulfovibrio desulfuricans (ATCC 642). However, both Desulfosporosinus strains reduced U(VI) in cell suspensions depleted in bicarbonate and NaCl. No U(VI) reduction was observed without lactate and H 2 electron donors or with heat-killed cells, indicating enzymatic U(VI) reduction. Uranium(VI) reduction by both strains was inhibited when 1 mM CuCl 2 was added to the cell suspensions. Because the Desulfosporosinus DSM 765 does not contain cytochrome c 3 used by Desulfovibrio spp. to reduce U(VI), Desulfosporosinus species reduce uranium via a different enzymatic pathway. (orig.)

  7. Evaluation of adsorption of uranium from aqueous solution using biochar materials

    Energy Technology Data Exchange (ETDEWEB)

    Correa, Wagner Clayton; Guilhen, Sabine Neusatz; Ortiz, Nilce; Fungaro, Denise Alves, E-mail: wcorrea@ipen.br, E-mail: snguilhen@ipen.br, E-mail: notriz@ipen.br, E-mail: dfungaro@ipen.br [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil)

    2015-07-01

    Uranium is present in the environment as a result of leaching from natural deposits and activities associated with nuclear fuel, copper mining, uranium mining, milling industry, etc. For the purpose of protecting ecosystem stability and public health, it is crucial to eliminate uranium from aqueous solutions before they are discharged into the environment. Various technologies have been used for removing U(VI) ions from aqueous systems. Among these methods, adsorption has been applied in wastewater because of simple operation procedure and high removal efficiency. Brazil is the largest producer of charcoal in the world, with nearly half of the woody biomass harvested for energy in Brazil being transformed into charcoal. Biochar exhibits a great potential as an adsorbent because of favorable physical/chemical surface characteristics. The objective of this work was to evaluate the adsorption potential of biochar materials prepared from pyrolysis of Bamboo (CBM), Eucalyptus (CEM) and Macauba (CMA) nuts for the removal of uranium from solutions. Adsorption experiments were carried out by a batch technique. Equilibrium adsorption experiments were performed by shaking a known amount of biochar material with 100 mL of U(VI) solution in Erlenmeyer flasks in a shaker at 120 rpm and room temperature (25 deg C) for 24 h. The adsorbent was separated by centrifugation from the solution. The U(VI) concentration remaining in the supernatant solution was determined using inductively coupled plasma optical emission spectrometry (ICP-OES). The influences of different experimental parameters such as solution pH and bioadsorbent dose on adsorption were investigated. The highest uranium adsorption capacity were obtained at pH 3.0 and 16 g/L biomass dosage for CMA, pH 3.0 and 12 g/L biomass dosage for CBM and pH 2.0 and 10 g/L biomass dosage for CEM. The results demonstrated that the biomass derived char can be used as a low-cost adsorbent for removal of uranium from wastewater. (author)

  8. Evaluation of adsorption of uranium from aqueous solution using biochar materials

    International Nuclear Information System (INIS)

    Correa, Wagner Clayton; Guilhen, Sabine Neusatz; Ortiz, Nilce; Fungaro, Denise Alves

    2015-01-01

    Uranium is present in the environment as a result of leaching from natural deposits and activities associated with nuclear fuel, copper mining, uranium mining, milling industry, etc. For the purpose of protecting ecosystem stability and public health, it is crucial to eliminate uranium from aqueous solutions before they are discharged into the environment. Various technologies have been used for removing U(VI) ions from aqueous systems. Among these methods, adsorption has been applied in wastewater because of simple operation procedure and high removal efficiency. Brazil is the largest producer of charcoal in the world, with nearly half of the woody biomass harvested for energy in Brazil being transformed into charcoal. Biochar exhibits a great potential as an adsorbent because of favorable physical/chemical surface characteristics. The objective of this work was to evaluate the adsorption potential of biochar materials prepared from pyrolysis of Bamboo (CBM), Eucalyptus (CEM) and Macauba (CMA) nuts for the removal of uranium from solutions. Adsorption experiments were carried out by a batch technique. Equilibrium adsorption experiments were performed by shaking a known amount of biochar material with 100 mL of U(VI) solution in Erlenmeyer flasks in a shaker at 120 rpm and room temperature (25 deg C) for 24 h. The adsorbent was separated by centrifugation from the solution. The U(VI) concentration remaining in the supernatant solution was determined using inductively coupled plasma optical emission spectrometry (ICP-OES). The influences of different experimental parameters such as solution pH and bioadsorbent dose on adsorption were investigated. The highest uranium adsorption capacity were obtained at pH 3.0 and 16 g/L biomass dosage for CMA, pH 3.0 and 12 g/L biomass dosage for CBM and pH 2.0 and 10 g/L biomass dosage for CEM. The results demonstrated that the biomass derived char can be used as a low-cost adsorbent for removal of uranium from wastewater. (author)

  9. Enhanced adsorption of chromium onto activated carbon by microwave-assisted H{sub 3}PO{sub 4} mixed with Fe/Al/Mn activation

    Energy Technology Data Exchange (ETDEWEB)

    Sun, Yuanyuan [Shandong Provincial Key Laboratory of Water Pollution Control and Resource Reuse, School of Environmental Science and Engineering, Shandong University, Jinan 250100 (China); Yue, Qinyan, E-mail: qyyue58@aliyun.com [Shandong Provincial Key Laboratory of Water Pollution Control and Resource Reuse, School of Environmental Science and Engineering, Shandong University, Jinan 250100 (China); Mao, Yanpeng [School of Energy and Power Engineering, Shandong University, Jinan 250100 (China); Gao, Baoyu; Gao, Yuan; Huang, Lihui [Shandong Provincial Key Laboratory of Water Pollution Control and Resource Reuse, School of Environmental Science and Engineering, Shandong University, Jinan 250100 (China)

    2014-01-30

    Highlights: • FeCl{sub 3}, AlCl{sub 3} and MnCl{sub 2} were used as the assisted activator to produce carbons. • Doping with MnCl{sub 2} was favorable for the enlargement of activated carbon. • The assisted activator had good performance for holding more fixed carbon. • The maximum adsorption capacities followed the order of AC-Fe > AC-Al > AC-Mn > AC. • The XPS analysis was used to confirm the adsorption/transformation mechanism. -- Abstract: FeCl{sub 3}, AlCl{sub 3} and MnCl{sub 2} were used as the assisted activation agent in activated carbon preparation by H{sub 3}PO{sub 4} activation using microwave heating method. The physico-chemical properties of activated carbons were investigated by scanning electron microscope (SEM), N{sub 2} adsorption/desorption, Boehm's titration, X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). To investigate the adsorption performances of chromium onto these newly developed activated carbons, a batch of experiments were performed under different adsorption conditions: solution pH, initial Cr(VI) ion concentration, contact time and co-existing ions. The results suggested that carbon with MnCl{sub 2} as assisted activation agent displayed the highest BET surface area (1332 m{sup 2}/g) and the highest pore volume (1.060 cm{sup 3}/g). FeCl{sub 3}, AlCl{sub 3} and MnCl{sub 2} had successfully improved Cr(VI) adsorption and activated carbon with FeCl{sub 3} as assisted activation agent exhibited the best uptake capacity. To study the transformation of Cr(VI) in adsorption process, total chromium in the aqueous solution was also recorded. The ratio of the amount of Cr(VI) to Cr(III) on each adsorbent was explained by XPS analysis results. Both the co-existing salts (Na{sub 2}SO{sub 4} and NaNO{sub 3}) demonstrated promoted effects on Cr(VI) removal by four carbons. The pseudo-second-order model and Freundlich equation displayed a good correlation with

  10. 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.

  11. Coumarin-modified microporous-mesoporous Zn-MOF-74 showing ultra-high uptake capacity and photo-switched storage/release of U{sup VI} ions

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Le; Wang, Lin Lin; Gong, Le Le; Feng, Xue Feng; Luo, Ming Biao; Luo, Feng, E-mail: ecitluofeng@163.com

    2016-07-05

    Graphical abstract: Table of content Herein, through coordination-based post-synthetic strategy, microporous-mesoporous Zn-MOF-74 was easily functionalized by grafting coumarin on coordinatively unsaturated Zn(II) centers, yielding a series of coumarin-modified Zn-MOF-74 materials. The obtained samples afforded ultra-high adsorption capacity for UVI ions from water with maximum adsorption capacities as high as 360 mg/g (the record value in MOFs) and remarkable photo-switched capability of 50 mg/g. - Highlights: • This work shows the record uptake capability of U{sup VI} (360 mg/g) in MOFs. • This work shows, for the first time, photo-switching behaviour towards U{sup VI} in aqueous solution. • This work demonstrates a simple and effective method to largely enhance uptake capability of U{sup VI}. • This work demonstrates a distinct method to prepare photo-sensitive MOFs for photo-switching behaviour towards guest molecules. - Abstract: Driven by an energy crisis but consequently puzzled by various environmental problems, uranium, as the basic material of nuclear energy, is now receiving extensive attentions. In contrast to numerous sorbents applied in this field, metal-organic framework (MOFs), as a renovated material platform, has only recently been developed. How to improve the adsorption capacity of MOF materials towards U{sup VI} ions, as well as taking advantage of the nature of these MOFs to design photo-switched behaviour for photo-triggered storage/release of U{sup VI} ions are at present urgent problems and great challenges to be solved. Herein, we show a simple and facile method to target the goal. Through coordination-based post-synthetic strategy, microporous- mesoporous Zn-MOF-74 was easily functionalized by grafting coumarin on coordinatively unsaturated Zn(II) centers, yielding a series of coumarin-modified Zn-MOF-74 materials. The obtained samples displayed ultra-high adsorption capacity for U{sup VI} ions from water at pH value of 4 with

  12. Diagnostic and treatment strategies in mucopolysaccharidosis VI

    Directory of Open Access Journals (Sweden)

    Vairo F

    2015-10-01

    Full Text Available Filippo Vairo,1–3 Andressa Federhen,1,3,4 Guilherme Baldo,1,2,5–7 Mariluce Riegel,1,6 Maira Burin,1 Sandra Leistner-Segal,1,8 Roberto Giugliani1,5,6,81Medical Genetics Service, Hospital de Clínicas de Porto Alegre, Porto Alegre, Brazil; 2Department of Genetics, Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil; 3Clinical Research Group on Medical Genetics, Hospital de Clínicas de Porto Alegre, Porto Alegre, Brazil; 4Post-Graduate Program in Child and Adolescent Health, Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil; 5Gene Therapy Center, Hospital de Clínicas de Porto Alegre, Porto Alegre, Brazil; 6Post-Graduate Program in Genetics and Molecular Biology, Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil; 7Department of Physiology, Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil; 8Post-Graduate Program in Medical Sciences, Universidade Federal do Rio Grande do Sul, Porto Alegre, BrazilAbstract: Mucopolysaccharidosis VI (MPS VI is a very rare autosomal recessive disorder caused by mutations in the ARSB gene, which lead to deficient activity of the lysosomal enzyme ASB. This enzyme is important for the breakdown of the glycosaminoglycans (GAGs dermatan sulfate and chondroitin sulfate, which accumulate in body tissues and organs of MPS VI patients. The storage of GAGs (especially dermatan sulfate causes bone dysplasia, joint restriction, organomegaly, heart disease, and corneal clouding, among several other problems, and reduced life span. Despite the fact that most cases are severe, there is a spectrum of severity and some cases are so attenuated that diagnosis is made late in life. Although the analysis of urinary GAGs and/or the measurement of enzyme activity in dried blood spots are useful screening methods, the diagnosis is based in the demonstration of the enzyme deficiency in leucocytes or fibroblasts, and/or in the identification of pathogenic mutations in the ARSB gene

  13. The potential impact of microbial Fe(III) reduction on subsurface U(VI) mobility at a low level radioactive waste storage site

    International Nuclear Information System (INIS)

    Wilkins, M.J.; Livens, F.R.; Vaughan, D.J.; Lloyd, J.R.; Beadle, I.; Small, J.S.

    2005-01-01

    Full text of publication follows: Fe(III) oxy-hydroxides have the potential to be utilised as terminal electron acceptors by indigenous microbial communities in the British Nuclear Fuels (BNFL) low level radioactive waste storage site at Drigg (Cumbria, UK) and these organisms may have a critical control on the biogeochemical cycling of several environmentally important radionuclides. In terms of radiological impact at Drigg, uranium is the most significant contributor to radiological impact and it is strongly influenced by biogeochemical processes. In terms of mass (moles) it is also the most abundant radionuclide in the Drigg inventory. Thus, the potential biotic and abiotic effects of Fe(III) reduction on U(VI) mobility in the Drigg subsurface are of interest. Culture-dependent and molecular techniques showed that the sediments in and around the Drigg site contained a diversity of Fe(III)-reducing bacteria. A series of microcosm experiments were utilised to create environmentally relevant experimental conditions. Microcosms set up using Drigg sediment and synthetic ground water were spiked with 100 μM U(VI) and acetate as an electron donor. U(VI) concentrations in groundwater were measured using a chemical assay while total U levels were determined using ICP-MS. Fe(II) levels were determined using the ferrozine method. Sediment surface areas were measured using BET analysis. The low surface area of the sediments resulted in only a small proportion of the 100 μM U(VI) spike sorbing onto mineral surfaces. The addition of ferri-hydrite to some microcosms resulted in an immediate lowering of soluble U(VI) concentrations, suggesting that the formation of soluble U(VI) complexes were not responsible for the minimal adsorption. The presence of biogenic Fe(II) in the microcosms did not affect the soluble U(VI) concentration. Similarly, soluble U(VI) levels remained unchanged when sediments were spiked with U(VI) post-microbial Fe(III) reduction. However, a lowering in

  14. Fabrication of core-shell Fe{sub 3}O{sub 4}@MIL-100(Fe) magnetic microspheres for the removal of Cr(VI) in aqueous solution

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Qingxiang, E-mail: qxyangzz@163.com; Zhao, Qianqian; Ren, ShuangShuang; Lu, Qiongqiong; Guo, Xinmeng; Chen, Zhijun, E-mail: chenzj@zzuli.edu.cn

    2016-12-15

    Facile regeneration of an adsorbent is very important for commercial feasibility. One typical highly porous metal-organic framework (MOF) materials based on MIL-100(Fe) and magnetic iron oxide particles (denoted as MMCs) with diameter about of 350 nm were successfully synthesized. The growth of MIL-100(Fe) shell on the surface of Fe{sub 3}O{sub 4} was utilized precursor as crystal seed via in-situ step hydrothermal reaction. It is a simple way to obtain well organized core-shell MOF composites, compared to the step-by-step method. MMCs were firstly used to uptake of Cr(VI) anions in aqueous solution. Adsorption experiments were carried out in batch sorption mode investigating with the factors of contact time (0–1000 min), pH (from 2 to 12), dose of adsorbent (4–25 mg), and initial Cr(VI) concentration (range from 10 to 100 ppm). - Graphical abstract: One typical highly porous metal-organic framework (MOF) materials based on MIL-100(Fe) and magnetic iron oxide particles (denoted as MMCs) were successfully synthesized. Utilizing Fe{sub 3}O{sub 4} precursor as crystal seed to grow MIL-100(Fe) shell by in-situ step hydrothermal reaction. It is a simple way to obtain core-shell MOF composites. MMCs could effectively uptake of Cr(VI) anions in aqueous solution. - Highlights: • Fe{sub 3}O{sub 4}@MIL-100(Fe) composites with core-shell structure were successfully prepared through a simple method. • The influence factors on Cr(VI) adsorption by Fe{sub 3}O{sub 4}@MIL-100(Fe) were investigated. • Cr(VI) can efficiently adsorbed by Fe{sub 3}O{sub 4}@MIL-100(Fe) composites from aqueous solution.

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

    Directory of Open Access Journals (Sweden)

    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.

  16. Direct determination of molybdenum in seawater by adsorption voltametry

    International Nuclear Information System (INIS)

    Berg, M.G. van den.

    1985-01-01

    Complex ions of molybdenum(VI) with 8-hydroxyquinoline (oxine) are shown to adsorb onto the hanging mercury drop electrode. This property forms the basis of a sensitive electrochemical technique by which dissolved molybdenum in seawater can be determined directly. The reduction current of adsorbed complex ions is measured by differential pulse adsorption voltametry, preceded by a period of 1 or 2 min of unstirred collection at an adsorption potential of -0.2 V. In the presence of 2 x 10 -3 M oxine and at pH 2.5 the potential of the main reduction peak is located at -0.59 V. The peak current-molybdenum concentration relationship is linear up to 3 x 10 -7 M; the detection limit is 4 nM. Greater sensitivity is obtained after stirred collection at pH 3.0 and with 10 -4 M oxine, but the calibration curve is nonlinear. In these conditions the limit of detection lies at 10 -10 M after 10 min stirred collection. 19 references, 8 figures

  17. Enhanced selective metal adsorption on optimised agroforestry waste mixtures.

    Science.gov (United States)

    Rosales, Emilio; Ferreira, Laura; Sanromán, M Ángeles; Tavares, Teresa; Pazos, Marta

    2015-04-01

    The aim of this work is to ascertain the potentials of different agroforestry wastes to be used as biosorbents in the removal of a mixture of heavy metals. Fern (FE), rice husk (RI) and oak leaves (OA) presented the best removal percentages for Cu(II) and Ni(II), Mn(II) and Zn(II) and Cr(VI), respectively. The performance of a mixture of these three biosorbents was evaluated, and an improvement of 10% in the overall removal was obtained (19.25mg/g). The optimum mixture proportions were determined using simplex-centroid mixture design method (FE:OA:RI=50:13.7:36.3). The adsorption kinetics and isotherms of the optimised mixture were fit by the pseudo-first order kinetic model and Langmuir isotherm. The adsorption mechanism was studied, and the effects of the carboxylic, hydroxyl and phenolic groups on metal-biomass binding were demonstrated. Finally, the recoveries of the metals using biomass were investigated, and cationic metal recoveries of 100% were achieved when acidic solutions were used. Copyright © 2015 Elsevier Ltd. All rights reserved.

  18. Supramolecular structures on silica surfaces and their adsorptive properties.

    Science.gov (United States)

    Belyakov, Vladimir N; Belyakova, Lyudmila A; Varvarin, Anatoly M; Khora, Olexandra V; Vasilyuk, Sergei L; Kazdobin, Konstantin A; Maltseva, Tetyana V; Kotvitskyy, Alexey G; Danil de Namor, Angela F

    2005-05-01

    The study of adsorptive and chemical immobilization of beta-cyclodextrin on a surface of hydroxylated silicas with various porous structure is described. Using IR spectroscopy, thermal gravimetrical analysis with a programmed heating, and chemical analysis of the silica surface, it is shown that the process of adsorption-desorption of beta-cyclodextrin depends on the porous structure of the silica. The reaction of esterification was used for chemical grafting of beta-cyclodextrin on the surface of hydroxylated silicas. Hydrolytic stability of silicas chemically modified by beta-cyclodextrin apparently is explained by simultaneous formation of chemical and hydrogen bonds between surface silanol groups and hydroxyl groups of beta-cyclodextrin. The uptake of the cations Cu(II), Cd(II), and Pb(II) and the anions Cr(VI) and As(V) by silicas modified with beta-cyclodextrin is investigated as a function of equilibrium ion concentrations. The increase of ion uptake and selectivity of ion extraction in comparison with starting silicas is established. It is due to the formation of surface inclusion complexes of the "host-guest" type in which one molecule of beta-cyclodextrin interacts simultaneously with several ions.

  19. A biological oil adsorption filter

    Energy Technology Data Exchange (ETDEWEB)

    Pasila, A [University of Helsinki (Finland). Dept. of Agricultural Engineering and Household Technology

    2005-12-01

    A new oil adsorption method called adsorption filtration (AF) has been developed. It is a technology where by oil residues can be cleaned from water by running it through a simple filter made from freeze treated, dried, milled and then fragmented plant material. By choosing suitable plants and fragmentation sizes it is possible to produce filters, which pass water but adsorb oil. The aim of this study was to investigate the possibilities of manufacturing oil adsorbing filter materials from reed canary grass (Phalaris arundinacea), flax (Linum usitatissimum L.) or hemp fibre (Cannabis sativa L.). The oil (80 ml) was mixed with de-ionised water (200 ml) and this mixture was filtered through 10 or 20 g adsorption filters. Fine spring harvested hemp fibre (diameter less than 1 mm) and reed canary grass fragments adsorb 2-4 g of oil per gram of adsorption material compared to 1-3 g of water. Adsorption filtration is thus a novel way of gathering spilled oil in shallow coastal waters before the oil reaches the shore. (author)

  20. A biological oil adsorption filter

    International Nuclear Information System (INIS)

    Pasila, A.

    2005-01-01

    A new oil adsorption method called adsorption filtration (AF) has been developed. It is a technology where by oil residues can be cleaned from water by running it through a simple filter made from freeze treated, dried, milled and then fragmented plant material. By choosing suitable plants and fragmentation sizes it is possible to produce filters, which pass water but adsorb oil. The aim of this study was to investigate the possibilities of manufacturing oil adsorbing filter materials from reed canary grass (Phalaris arundinacea), flax (Linum usitatissimum L.) or hemp fibre (Cannabis sativa L.). The oil (80 ml) was mixed with de-ionised water (200 ml) and this mixture was filtered through 10 or 20 g adsorption filters. Fine spring harvested hemp fibre (diameter less than 1 mm) and reed canary grass fragments adsorb 2-4 g of oil per gram of adsorption material compared to 1-3 g of water. Adsorption filtration is thus a novel way of gathering spilled oil in shallow coastal waters before the oil reaches the shore. (author)

  1. Kinetic and thermodynamic studies on the adsorption of heavy metals from aqueous solution by melanin nanopigment obtained from marine source: Pseudomonas stutzeri.

    Science.gov (United States)

    Manirethan, Vishnu; Raval, Keyur; Rajan, Reju; Thaira, Harsha; Balakrishnan, Raj Mohan

    2018-05-15

    The difficulty in removal of heavy metals at concentrations below 10 mg/L has led to the exploration of efficient adsorbents for removal of heavy metals. The adsorption capacity of biosynthesized melanin for Mercury (Hg(II)), Chromium (Cr(VI)), Lead (Pb(II)) and Copper (Cu(II)) was investigated at different operating conditions like pH, time, initial concentration and temperature. The heavy metals adsorption process was well illustrated by the Lagergren's pseudo-second-order kinetic model and the equilibrium data fitted excellently to Langmuir isotherm. Maximum adsorption capacity obtained from Langmuir isotherm for Hg(II) was 82.4 mg/g, Cr(VI) was 126.9 mg/g, Pb(II) was 147.5 mg/g and Cu(II) was 167.8 mg/g. The thermodynamic parameters revealed that the adsorption of heavy metals on melanin is favorable, spontaneous and endothermic in nature. Binding of heavy metals on melanin surface was proved by Fourier Transform Infrared Spectroscopy (FT-IR) and X-ray Photoelectron Spectroscopy (XPS). Contemplating the results, biosynthesized melanin can be a potential adsorbent for efficient removal of Hg(II), Cr(VI), Pb(II) and Cu(II) ions from aqueous solution. Copyright © 2018 Elsevier Ltd. All rights reserved.

  2. Enhanced removal of Se(VI) from water via pre-corrosion of zero-valent iron using H2O2/HCl: Effect of solution chemistry and mechanism investigation.

    Science.gov (United States)

    Shan, Chao; Chen, Jiajia; Yang, Zhe; Jia, Huichao; Guan, Xiaohong; Zhang, Weiming; Pan, Bingcai

    2018-04-15

    Although the removal of Se(VI) from water by using zero-valent iron (ZVI) is a promising method, passivation of ZVI severely inhibits its performance. To overcome such issue, we proposed an efficient technique to enhance Se(VI) removal via pre-corrosion of ZVI with H 2 O 2 /HCl in a short time (15 min). The resultant pcZVI suspension was weakly acidic (pH 4.56) and contained abundant aqueous Fe 2+ . 57 Fe Mössbauer spectroscopy showed that pcZVI mainly consisted of Fe 0 (66.2%), hydrated ferric oxide (26.3%), and Fe 3 O 4 (7.5%). Efficient removal of Se(VI) from sulfate-rich solution was achieved by pcZVI compared with ZVI (in the absence and presence of H 2 O 2 ) and acid-pretreated ZVI. Moreover, the efficient removal of Se(VI) by pcZVI sustained over a broad pH range (3-9) due to its strong buffering power. The presence of chloride, carbonate, nitrate, and common cations (Na + , K + , Ca 2+ , and Mg 2+ ) posed negligible influence on the removal of Se(VI) by pcZVI, while the inhibitory effect induced by sulfate, silicate, and phosphate indicated the significance of Se(VI) adsorption as a prerequisite step for its removal. The consumption of aqueous Fe 2+ was associated with Se(VI) removal, and X-ray absorption near edge structure revealed that the main pathway for Se(VI) removal by pcZVI was a stepwise reduction of Se(VI) to Se(IV) and then Se 0 as the dominant final state (78.2%). Moreover, higher electron selectivity of pcZVI was attributed to the enhanced enrichment of Se oxyanions prior to their reduction. Copyright © 2018 Elsevier Ltd. All rights reserved.

  3. Solid-Phase Extraction of Trace Amounts of Uranium(VI in Environmental Water Samples Using an Extractant-Impregnated Resin Followed by Detection with UV-Vis Spectrophotometry

    Directory of Open Access Journals (Sweden)

    Ahmad Hosseini-Bandegharaei

    2013-01-01

    Full Text Available A stable extractant-impregnated resin (EIR containing Chrome Azurol B was prepared using Amberlite XAD-2010 as a porous polymeric support. The new EIR was employed for trace separation and preconcentration of U(VI ion followed by spectrophotometric determination with the arsenazo III procedure. CAB/XAD-2010 exhibited excellent selectivity for U(VI ion over coexisting ions. Experimental parameters including pH, contact time, shaking speed, and ionic strength were investigated by batch extraction methods. Maximum sorption of U(VI ions occurred at pH 4.3–6.9. The capacity of EIR was found to be 0.632 mmol·g−1. Equilibrium was reached in 25 min and the loading half-time, t1/2, was less than 6 min. The equilibrium adsorption isotherm of U(VI was fitted with the Langmuir adsorption model. In addition, a column packed with CAB/XAD-2010 was used for column-mode separation and preconcentration of U(VI ion. For the optimization of the dynamic procedure, effects of sample volume, sample and eluent flow rate, eluent concentration, and its volume were investigated. The preconcentration factors for U(VI were found out to be 160. But, for convenience, a preconcentration factor of 150 was utilized for the column-mode preconcentration. The dynamic procedure gave a detection limit of 5.0×10-10 mol·L−1 (0.12 μg·L−1 for U(VI ion. The proposed dynamic method showed good performance in analyzing environmental water samples.

  4. Rice husk: an alternate and low cost material for treating chromium (VI) containing water

    International Nuclear Information System (INIS)

    Doria Herrera; Gloria Maria; Hormaza Anaguano, Angelina; Gallego Suarez, Dario

    2011-01-01

    This paper shows the ability of the native rice husk to remove ions of Cr (VI) in simulated water from tanneries in laboratory conditions. The influences of the variables pH, metal concentration, dosage and contact time on adsorption process was evaluated. It was found a removal more than 94% at pH value of 1, dosage of 3 g/L, concentration of 3 mg/L, at a speed of 127 rpm and at a time of 720 min. The results were evaluated with a 95% level of significance using the statistical tool ANOVA. The information regarding the balance process was fitted to the models of Freundlich, Langmuir, Dubinin-Raduskevich and Thempkin obtaining a better correlation with the Langmuir isotherm with an adsorption capacity of 1.25 mg/g at a pH value of 1. In order to prove the occurrence of structural changes on the adsorbent material, analysis was performed through the DRIFT technique (diffuse reflectance infrared spectroscopy) before and after the removal process and as well abromatological analyses to determine any variation in its composition.

  5. Adsorption studies on Pt(111)

    International Nuclear Information System (INIS)

    Hopster, H.

    1977-06-01

    The adsorption of O 2 , CO, and C 2 H 2 as well as the CO oxidation on Pt(111) were studied by high-resolution electron spectroscopy. Using a platinum monocrystal sample with a contonuous stage density, the adhesion coefficient for O 2 and the reaction probability for CO were determined as a function of stage density and oxygen cover by measuring the oxygen cover and its time behaviour. The study of vibrations of adsorbed CO showed that CO is bound in linear form on two different adsorption sites. The adsorption of acetylene was studied at 140 K and 300 K. The frequencies of the C-H stretching and flexural vibrations as well as the C-C-H bonding angle were determined. (orig./GSC) [de

  6. 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.)

  7. Zero-valent iron particles embedded on the mesoporous silica–carbon for chromium (VI) removal from aqueous solution

    Energy Technology Data Exchange (ETDEWEB)

    Xiong, Kun, E-mail: kunxiong312@gmail.com; Gao, Yuan [Chongqing Technology and Business University, Engineering Research Center for Waste Oil Recovery Technology and Equipment of Ministry of Education, Chongqing Key Laboratory of Catalysis & Environmental New Materials (China); Zhou, Lin [Chengdu Radio and TV University (China); Zhang, Xianming [Chongqing Technology and Business University, Engineering Research Center for Waste Oil Recovery Technology and Equipment of Ministry of Education, Chongqing Key Laboratory of Catalysis & Environmental New Materials (China)

    2016-09-15

    Nanoscale zero-valent iron (nZVI) particles were embedded on the walls of mesoporous silica–carbon (MSC) under the conditions of high-temperature carbonization and reduction and used to remove chromium (VI) from aqueous solution. The structure and textural properties of nZVI–MSC were characterized by the powder X-ray diffraction, transmission electron microscopy and N{sub 2} adsorption and desorption. The results show that nZVI–MSC has highly ordered mesoporous structure and large surface area, indistinguishable with that of MSC. Compared with the support MSC and iron particles supported on the activated carbon (nZVI/AC), nZVI–MSC exhibited much higher Cr(VI) removal efficiency with about 98 %. The removal process obeys a pseudo first-order model. Such excellent performance of nZVI–MSC could be ascribed to the large surface and iron particles embedded on the walls of the MSC, forming an intimate contact with the MSC. It is proposed that this feature might create certain micro-electrode on the interface of iron particles and MSC, which prevented the formation of metal oxide on the surface and provided fresh Fe surface for Cr(VI) removal.

  8. 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.)

  9. VI School on Cosmic Rays and Astrophysics

    International Nuclear Information System (INIS)

    2017-01-01

    VI School on Cosmic Rays and Astrophysics 17-25 November 2015, Chiapas, Mexico The VI School on Cosmic Rays and Astrophysics was held at the MCTP, at the Autonomous University of Chiapas (UNACH), Tuxtla Gutiérrez, Chiapas, Mexico thanks to the Science for Development ICTP-UNACH-UNESCO Regional Seminar, 17-25 November 2015 (http://mctp.mx/e-VI-School-on-Cosmic-Rays-and-Astrophysics.html). The School series started in La Paz, Bolivia in 2004 and it has been, since then, hosted by several Latin American countires: 1.- La Paz, Bolivia (August, 2004), 2.- Puebla, Mexico (September, 2006), 3.- Arequipa, Peru (September, 2008), 4.- Santo André, Brazil (September, 2010), 5.- La Paz, Bolivia (August, 2012). It aims to promote Cosmic Ray (CR) Physics and Astrophysics in the Latin American community and to provide a general overview of theoretical and experimental issues on these topics. It is directed to undergraduates, postgraduates and active researchers in the field. The lectures introduce fundamental Cosmic Ray Physics and Astrophysics with a review of standards of the field. It is expected the school continues happening during the next years following a tradition. In this edition, the list of seminars included topics such as experimental techniques of CR detection, development of CR showers and hadronic interactions, composition and energy spectrum of primary CR, Gamma-Ray Bursts (GRBs), neutrino Astrophysics, spacecraft detectors, simulations, solar modulation, and the current state of development and results of several astroparticle physics experiments such as The Pierre Auger Observatory in Argentina, HAWC in Mexico, KASCADE and KASCADE Grande, HESS, IceCube, JEM-EUSO, Fermi-LAT, and others. This time the school has been complemented with the ICTP-UNACH-UNESCO Seminar of theory on Particle and Astroparticle Physics. The organization was done by MCTP, the Mesoamerican Centre for Theoretical Physics. The school had 46 participants, 30 students from Honduras, Brazil

  10. Procedure for plutonium determination using Pu(VI) spectra

    International Nuclear Information System (INIS)

    Walker, L.F.; Temer, D.J.; Jackson, D.D.

    1996-01-01

    This document describes a simple spectrophotometric method for determining total plutonium in nitric acid solutions based on the spectrum of Pu(VI). Plutonium samples in nitric acid are oxidized to Pu(VI) with Ce(IV) and the net absorbance at the 830 nm peak is measured

  11. A CMOS rail-to-rail linear VI-converter

    NARCIS (Netherlands)

    Vervoort, P.P.; Vervoort, P.P.; Wassenaar, R.F.

    1995-01-01

    A linear CMOS VI-converter operating in strong inversion with a common-mode input range from the negative to the positive supply rail is presented. The circuit consists of three linear VI-converters based on the difference of squares principle. Two of these perform the actual V to I conversion,

  12. Cloning and expression of a Vi mimotope of Salmonella enterica ...

    African Journals Online (AJOL)

    STORAGESEVER

    2009-09-15

    Sep 15, 2009 ... A recombinant His-Vi protein of Salmonella enterica serovar Typhi was successfully constructed and cloned into ... mainly through consumption of food or water contami- nated with .... and healthy individuals (double arrows) followed by the detection using recombinant His-Vi protein as the primary antibody ...

  13. Research progress in the electrochemical synthesis of ferrate(VI)

    International Nuclear Information System (INIS)

    Macova, Zuzana; Bouzek, Karel; Hives, Jan; Sharma, Virender K.; Terryn, Raymond J.; Baum, J. Clayton

    2009-01-01

    There is renewed interest in the +6 oxidation state of iron, ferrate (VI) (Fe VI O 4 2- ), because of its potential as a benign oxidant for organic synthesis, as a chemical in developing cleaner ('greener') technology for remediation processes, and as an alternative for environment-friendly battery cathodes. This interest has led many researchers to focus their attention on the synthesis of ferrate(VI). Of the three synthesis methods, electrochemical, wet chemical and thermal, electrochemical synthesis has received the most attention due to its ease and the high purity of the product. Moreover, electrochemical processes use an electron as a so-called clean chemical, thus avoiding the use of any harmful chemicals to oxidize iron to the +6 oxidation state. This paper reviews the development of electrochemical methods to synthesize ferrate(VI). The approaches chosen by different laboratories to overcome some of the difficulties associated with the electrochemical synthesis of ferrate(VI) are summarized. Special attention is paid to parameters such as temperature, anolyte, and anode material composition. Spectroscopic work to understand the mechanism of ferrate(VI) synthesis is included. Recent advances in two new approaches, the use of an inert electrode and molten hydroxide salts, in the synthesis of ferrate(VI) are also reviewed. Progress made in the commercialization of ferrate(VI) continuous production is briefly discussed as well

  14. KENO-VI Primer: A Primer for Criticality Calculations with SCALE/KENO-VI Using GeeWiz

    International Nuclear Information System (INIS)

    Bowman, Stephen M.

    2008-01-01

    The SCALE (Standardized Computer Analyses for Licensing Evaluation) computer software system developed at Oak Ridge National Laboratory is widely used and accepted around the world for criticality safety analyses. The well-known KENO-VI three-dimensional Monte Carlo criticality computer code is one of the primary criticality safety analysis tools in SCALE. The KENO-VI primer is designed to help a new user understand and use the SCALE/KENO-VI Monte Carlo code for nuclear criticality safety analyses. It assumes that the user has a college education in a technical field. There is no assumption of familiarity with Monte Carlo codes in general or with SCALE/KENO-VI in particular. The primer is designed to teach by example, with each example illustrating two or three features of SCALE/KENO-VI that are useful in criticality analyses. The primer is based on SCALE 6, which includes the Graphically Enhanced Editing Wizard (GeeWiz) Windows user interface. Each example uses GeeWiz to provide the framework for preparing input data and viewing output results. Starting with a Quickstart section, the primer gives an overview of the basic requirements for SCALE/KENO-VI input and allows the user to quickly run a simple criticality problem with SCALE/KENO-VI. The sections that follow Quickstart include a list of basic objectives at the beginning that identifies the goal of the section and the individual SCALE/KENO-VI features that are covered in detail in the sample problems in that section. Upon completion of the primer, a new user should be comfortable using GeeWiz to set up criticality problems in SCALE/KENO-VI. The primer provides a starting point for the criticality safety analyst who uses SCALE/KENO-VI. Complete descriptions are provided in the SCALE/KENO-VI manual. Although the primer is self-contained, it is intended as a companion volume to the SCALE/KENO-VI documentation. (The SCALE manual is provided on the SCALE installation DVD.) The primer provides specific examples of

  15. Identifying key controls on the behavior of an acidic-U(VI) plume in the Savannah River Site using reactive transport modeling.

    Science.gov (United States)

    Bea, Sergio A; Wainwright, Haruko; Spycher, Nicolas; Faybishenko, Boris; Hubbard, Susan S; Denham, Miles E

    2013-08-01

    Acidic low-level waste radioactive waste solutions were discharged to three unlined seepage basins at the F-Area of the Department of Energy (DOE) Savannah River Site (SRS), South Carolina, USA, from 1955 through 1989. Despite many years of active remediation, the groundwater remains acidic and contaminated with significant levels of U(VI) and other radionuclides. Monitored Natural Attenuation (MNA) is a desired closure strategy for the site, based on the premise that regional flow of clean background groundwater will eventually neutralize the groundwater acidity, immobilizing U(VI) through adsorption. An in situ treatment system is currently in place to accelerate this in the downgradient portion of the plume and similar measures could be taken upgradient if necessary. Understanding the long-term pH and U(VI) adsorption behavior at the site is critical to assess feasibility of MNA along with the in-situ remediation treatments. This paper presents a reactive transport (RT) model and uncertainty quantification (UQ) analyses to explore key controls on the U(VI)-plume evolution and long-term mobility at this site. Two-dimensional numerical RT simulations are run including the saturated and unsaturated (vadose) zones, U(VI) and H(+) adsorption (surface complexation) onto sediments, dissolution and precipitation of Al and Fe minerals, and key hydrodynamic processes are considered. UQ techniques are applied using a new open-source tool that is part of the developing ASCEM reactive transport modeling and analysis framework to: (1) identify the complex physical and geochemical processes that control the U(VI) plume migration in the pH range where the plume is highly mobile, (2) evaluate those physical and geochemical parameters that are most controlling, and (3) predict the future plume evolution constrained by historical, chemical and hydrological data. The RT simulation results show a good agreement with the observed historical pH and concentrations of U(VI), nitrates

  16. Theoretical insight of adsorption cooling

    KAUST Repository

    Chakraborty, Anutosh

    2011-06-03

    This letter proposes and presents a thermodynamic formulation to calculate the energetic performances of an adsorption cooler as a function of pore widths and volumes of solid adsorbents. The simulated results in terms of the coefficient of performance are validated with experimental data. It is found from the present analysis that the performance of an adsorption cooling device is influenced mainly by the physical characteristics of solid adsorbents, and the characteristics energy between the adsorbent-adsorbate systems. The present study confirms that there exists a special type of silicagel having optimal physical characteristics that allows us to obtain the best performance.

  17. Theoretical insight of adsorption cooling

    KAUST Repository

    Chakraborty, Anutosh; Leong, Kai Choong; Thu, Kyaw; Saha, Bidyut Baran; Ng, Kim Choon

    2011-01-01

    This letter proposes and presents a thermodynamic formulation to calculate the energetic performances of an adsorption cooler as a function of pore widths and volumes of solid adsorbents. The simulated results in terms of the coefficient of performance are validated with experimental data. It is found from the present analysis that the performance of an adsorption cooling device is influenced mainly by the physical characteristics of solid adsorbents, and the characteristics energy between the adsorbent-adsorbate systems. The present study confirms that there exists a special type of silicagel having optimal physical characteristics that allows us to obtain the best performance.

  18. Potential Theory of Multicomponent Adsorption

    DEFF Research Database (Denmark)

    Shapiro, Alexander; Stenby, Erling Halfdan

    1998-01-01

    We developed a theory of multicomponent adsorption on the basis of the potential concept originally suggested by Polanyi. The mixture is considered as a heterogeneous substance segregated in the external field emitted by the adsorbent. The same standard equation of state, with no additional fitting...... and high degree of predictability of the theory developed....... the potential theory and the spreading pressure concept is established, and problems of the theory consistency are studied. Numerical algorithms are suggested for evaluation of the segregated state of the mixture in the potential field of adsorption forces. Comparison with experimental data shows good agreement...

  19. Fast gas adsorption measurements for complicated adsorption mechanisms

    NARCIS (Netherlands)

    Robens, E.; Poulis, J.A.; Massen, C.H.

    2000-01-01

    Jäntti introduced a method to reduce the time required for the stepwise measurement of adsorption isotherms. After each pressure change he measured the adsorbed mass three times and calculated its equilibrium value at the new pressure. In the present paper, we discuss the applicability of this

  20. Sn(II) oxy-hydroxides as potential adsorbents for Cr(VI)-uptake from drinking water: An X-ray absorption study.

    Science.gov (United States)

    Pinakidou, Fani; Kaprara, Efthimia; Katsikini, Maria; Paloura, Eleni C; Simeonidis, Konstantinos; Mitrakas, Manassis

    2016-05-01

    The feasibility of implementing a Sn(II) oxy-hydroxide (Sn6O4(OH)4) for the reduction and adsorption of Cr(VI) in drinking water treatment was investigated using XAFS spectroscopies at the Cr-K-edge. The analysis of the Cr-K-edge XANES and EXAFS spectra verified the effective use of Sn6O4(OH)4 for successful Cr(VI) removal. Adsorption isotherms, as well as dynamic Rapid Small Scale Test (RSSCT) in NSF water matrix showed that Sn6O4(OH)4 can decrease Cr(VI) concentration below the upcoming regulation limit of 10μg/L for drinking water. Moreover, an uptake capacity of 7.2μg/mg at breakthrough concentration of 10μg/L was estimated from the RSSCT, while the residual Cr(VI) concentration ranged at sub-ppb level for a significant period of the experiment. Furthermore, no evidence for the formation of Cr(OH)3 precipitates was found. On the contrary, Cr(III)-oxyanions were chemisorbed onto SnO2, which was formed after Sn(II)-oxidation during Cr(VI)-reduction. Nevertheless, changes in the type of Cr(III)-inner sphere complexes were observed after increasing surface coverage: Cr(III)-oxyanions preferentially sorb in a geometry which combines both bidentate binuclear ((2)C) and monodentate ((1)V) geometries, at the expense of the present bidentate mononuclear ((2)E) contributions. On the other hand, the pH during sorption does not affect the adsorption mechanism of Cr(III)-species. The implementation of Sn6O4(OH)4 in water treatment technology combines the advantage of rapidly reducing a large amount of Cr(VI) due to donation of two electrons by Sn(II) and also the strong chemisorption of Cr(III) in a combination of the (2)C and (1)V configurations, which enhances the safe disposal of spent adsorbents. Copyright © 2016 Elsevier B.V. All rights reserved.

  1. Testing of ENDF/B-VI data for shielding applications

    International Nuclear Information System (INIS)

    Ingersoll, D.T.

    1995-01-01

    Version VI of the U.S. Evaluated Nuclear Data File (END/B-VI) was released for open distribution in 1990 after an extensive multiyear, multilaboratory evaluation effort coordinated by the Cross Section Evaluation Working Group (CSEWG). More than 75 of the 320 evaluations contained in the library are new for Version VI, including many relatively important nuclides and many with substantial changes to the cross-section data. Also, several important changes were made to the basic data formats for Version VI to permit better representation of the data and to allow additional types of data. Although these format changes yielded improved evaluations, they hindered processing of the data for use in applications codes and delayed the timely integral testing of the data. It has been only during the past year that significant integral testing of END/B-VI data has been achieved. The results and conclusions from some of these efforts are summarized in the following paragraphs

  2. Spectrophotometry of Comet West 1976 VI

    International Nuclear Information System (INIS)

    Rozenbush, V.K.

    1986-01-01

    Spectra obtained for the coma, nuclear fragments A and D, and tail of Comet West 1976 VI on April 1, 2 and 7, 1976 are noted to encompass coma spectra which differed from those of the nuclear fragments, which exhibited a strong continuum with superimposed emissions that included a stronger CO(+)-band system than that of the coma. A detailed comparison between fragment spectra has revealed great differences in both quasi-simultaneously obtained and five-day-separated cases. The relative intensities of different CO(+) bands are compared to the theoretical ones, and the abundances of CO(+) ions corresponding to different vibrational transitions are determined relative to that of CN. 24 references

  3. Cranial nerves III, IV and VI

    International Nuclear Information System (INIS)

    Laine, I.J.; Smoker, W.R.; Kuta, A.J.; Felton, W.L.

    1991-01-01

    Because of advances in CT and MR imaging, accurate identification and evaluation of cranial nerve lesions is now possible. Cranial nerves III, IV, and VI, providing motor and sensory control of the eye, can be evaluated as a unit. In this paper, the authors present an overview of the anatomy and pathology of these cranial nerves. We first illustrate their normal anatomic pathways from the brain stem to the orbit. This is followed by clinical examples of patients with a variety of isolated and complex palsies of these three cranial nerves. This is accomplished by inclusion of ocular photographs, correlative imaging studies, and the use of diagrams. Knowledge of the gross and imaging anatomy and the ophthalmologic manifestations of pathology affecting these three cranial nerves permits a tailored approach to their evaluation

  4. New energy level identifications in Kr VI

    International Nuclear Information System (INIS)

    Tauheed, A.; Pinnington, E.H.; Ansbacher, W.; Kernahan, J.A.

    1990-01-01

    Beam-foil delayed spectra from 89.0 to 101.0 nm are used to identify the intercombination lines connecting the 4s4p 2 4 P and 4s 2 4p 2 P levels in Kr VI. The existing analysis is extended to include the 4s 2 5s 2 S 1/2 , 4f 2 F 5/2 , 2 F 7/2 , 4p 3 2 D 3/2 , 2 D 5/2 , 2 P 3/2 , 4 S 3/2 and 4s4p 2 4 P 1/2 , 4 P 3/2 , 4 P 5/2 levels. Lifetime measurements for the 4s4p 2 4 P 1/2 , 4 P 5/2 , 4p 3 2 D 3/2 and 2 D 5/2 levels are also discussed in support of these assignments. (orig.)

  5. Spectrum and energy levels of Y VI

    International Nuclear Information System (INIS)

    Persson, W.; Reader, J.

    1986-01-01

    The spectrum of the five-times-ionized yttrium atom (Y VI), excited in a sliding-spark discharge, was studied in the 160--2500 A-circle range. About 900 Y VI lines were classified as transitions between 101 odd and 69 even energy levels.The energy-level system established includes almost all levels of the 4s 2 4p 4 , 4s4p 5 , 4s 2 4p 3 4d, 5d, 5s, 6s, and 5p configurations and a number of levels of the 7s, 4f, and 4s4p 4 4d configurations. The observed level system has been theoretically interpreted by means of Hartree--Fock calculations and least-squares parametric fits. Strong configuration mixings are found between the 4s4p 5 and 4s 2 4p 3 4d configurations, between the 4s 2 4p 3 5p and 4s4p 4 4d configurations, and between the 4s 2 4p 3 4f and 4s4p 4 4d configurations. From the optimized energy-level values, a system of Ritz-type wavelength standards with accuracies varying from 0.0003 to 0.003 A-circle in the range 179--500 A-circle has been determined. The ionization energy as determined from 4s 2 4p 3 ns levels (n = 5-7) is 737 110 +- 200 cm/sup -1/ (91.390 +- 0.025 eV)