Metal trace elements (MTE) are among the most harmful micropollutants of natural waters. Eliminating them helps improve the quality and safety of drinking water and protect human health. In this work, we used mango ke...Metal trace elements (MTE) are among the most harmful micropollutants of natural waters. Eliminating them helps improve the quality and safety of drinking water and protect human health. In this work, we used mango kernel powder (MKP) as bioadsorbent material for removal of Cr (VI) from water. Uv-visible spectroscopy was used to monitor and quantify Cr (VI) during processing using the Beer-Lambert formula. Some parameters such as pH, mango powder, mass and contact time were optimized to determine adsorption capacity and chromium removal rate. Adsorption kinetics, equilibrium, isotherms and thermodynamic parameters such as ΔG˚, ΔH˚, and ΔS˚, as well as FTIR were studied to better understand the Cr (VI) removal process by MKP. The adsorption capacity reached 94.87 mg/g, for an optimal contact time of 30 min at 298 K. The obtained results are in accordance with a pseudo-second order Freundlich adsorption isotherm model. Finally FTIR was used to monitor the evolution of absorption bands, while Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray Spectroscopy (EDS) were used to evaluate surface properties and morphology of the adsorbent.展开更多
AbstFeS has an excellent performance in removing heavy metal chromium(Ⅵ)in wastewater due to its good adsorption and reduction.The properties of easy aggregation and oxidization of nano-FeS,however,limit the applicat...AbstFeS has an excellent performance in removing heavy metal chromium(Ⅵ)in wastewater due to its good adsorption and reduction.The properties of easy aggregation and oxidization of nano-FeS,however,limit the applications of FeS in engineering.In this study,one FeS adsorbent supported by Al_(2)O_(3) was prepared using high-gravity technology in IS-RPB(Impinging Stream Rotating Packed Bed)to overcome polymerization and oxidation of nano-FeS.Experimental results showed that FeS was uniformly loaded on the surface and pores of Al_(2)O_(3).The specific surface area of FeS/Al_(2)O_(3) is 125 m2·g^(-1) which is nearly 1.6 times that of pure FeS.The adsorption capacity of FeS/Al_(2)O_(3) for chromium(Ⅵ)is 200 mg·g^(-1),1.4 times that of pure FeS.pH value and ionic strength are strongly correlated with the chromium removal performance of FeS/Al_(2)O_(3).Over 98%of chromium can be removed when pH values of FeS/Al_(2)O_(3) ranged from 4 to 6.Higher adsorption capacity is achieved with higher ionic strength in FeS/Al_(2)O_(3).The FeS/Al_(2)O_(3) maintained more than 95%of the adsorption capacity after being preserved for one month,but only 70%for pure FeS.The removal processes of chromium(Ⅵ)conformes to a pseudo-second-order kinetic model(R2≥0.9986),indicating that the rate-limiting step is a chemical sorption process instead of a mass transfer.展开更多
In order to investigate chromium contamination of coal mine water, to analyze chromium leaching mechanism and to evaluate environment pollution potential of coal mine water, we perform site investigations, physical an...In order to investigate chromium contamination of coal mine water, to analyze chromium leaching mechanism and to evaluate environment pollution potential of coal mine water, we perform site investigations, physical and computer modeling in the Xuzhou-Datun coal mine district. The result of our test samples shows that chromium concentration was 9 μg/L in roof leachate and 3 μg/L in coal leachate. The host rock has a higher pollution potential than that of coal seams. Leaching experiments and XRD test results indicate that chromium is released from the process of transforming illite to kaolinite. The pH, pe and temperature of coal mine water affect the chromium leaching behavior. Modeling results suggest that the adsorption of adsorbents controls chromium concentration in coal mine water. The chromium adsorption ratio is quite low in both an acid and in an alkaline environment. Therefore, coal mine water has a high pollution potential. Under other conditions, chromium adsorption is stronger in a neutral water environment, so that chromium concentrations may be very low.展开更多
A certified clay mineral from Iraq, montmorillonite, is used for the adsorption of chromium and lead ions from water. Experimental design is utilized here to plan for the practical work and analysis of the results. Ba...A certified clay mineral from Iraq, montmorillonite, is used for the adsorption of chromium and lead ions from water. Experimental design is utilized here to plan for the practical work and analysis of the results. Batch wise experiments are carried out to equilibrate Cr and Pb solutions (250 mg/L) individually and simultaneously with montmorillonite (5 - 20 g/L) at various pH ranges (2 - 7.5) for 10 - 60 minutes. The results indicate perfect fit with the model used. Chromium adsorption is sensitive to pH changes being high at neutral medium. Lead is almost independent of the pH of the solution. In nearly neutral medium, the sorption capacity of Cr is 21.4 and that of lead is 24.3 mg/g. The optimum conditions for >96% Cr removal are 12 - 15 g clay/L, 40 - 50 minutes and a pH of 5 - 7. For lead, almost 100% removal can be attained using 12 - 15 g clay/L, 40 - 50 min. at a pH of 4 - 6. The effects of various operating parameters are discussed. Simultaneously, the lead shows a greater tendency to sorption than chromium and a ratio of 5:4 can best represent the occupation of the active surface of the clay. The most favorable conditions for simultaneous removing of Cr, 86% and Pb, 100% may be 12.5 g/L clay content and a pH of 7.5 within 30 minutes. The kinetic study of the results indicates the adsorption follow pseudo-second order kinetics in which chemical interaction is also involved. The kinetic study confirms the dependence of chromium adsorption on the pH of the medium being favoured at high pH values.展开更多
Cr(Ⅵ)-amended soil was inoculated with Cr(Ⅵ)-reducing strain,Bacillus sp.XW-4 and incubated at 28 ℃in an incubator. Cr(Ⅵ)reduction,available Cr and Cr fractionin soils were studied.The results show that addition o...Cr(Ⅵ)-amended soil was inoculated with Cr(Ⅵ)-reducing strain,Bacillus sp.XW-4 and incubated at 28 ℃in an incubator. Cr(Ⅵ)reduction,available Cr and Cr fractionin soils were studied.The results show that addition of Bacillus sp.XW-4 can promote Cr(Ⅵ)reduction,but inoculation of this strain has a negative effect on the decrease of available Cr content in soil.In controls (without this strain)amended with 100 and 200 mg/kg of Cr(Ⅵ),Cr(Ⅵ)contents decrease to about 41 and 92 mg/kg respectively after incubation of 4 d,while in soil inoculated with XW-4,Cr(Ⅵ)contents decrease to about 18 and 60 mg/kg,respectively.The content of available Cr in soils with inoculation of XW-4 is higher than that in controls.Chromium is partitioned into water soluble Cr,exchangeable Cr,precipitated Cr,Cr bound to organics and residual Cr.The highest content of Cr is observed in residual form and water soluble Cr is not detected for all treatments after 42 d,but the soils inoculated with Bacillus sp.XW-4 contain higher content of exchangeable Cr and lower content of precipitated Cr than the soil without the inoculum.Inoculation of Bacillus sp.XW-4 can increase chromium activity in soils.展开更多
Kinetic studies of the extraction of chromium（Ⅵ）[Cr（Ⅵ）] from the hydrochloric acid solution with tri-n-octylamine（N235） have been made by a Lewis cell. The influences of various kinetic parameters, such as sti...Kinetic studies of the extraction of chromium（Ⅵ）[Cr（Ⅵ）] from the hydrochloric acid solution with tri-n-octylamine（N235） have been made by a Lewis cell. The influences of various kinetic parameters, such as stirring rate, interfacial area, temperature, N235 and initial Cr（Ⅵ） concentrations were evaluated. The rate equations for the extraction of Cr（Ⅵ） by N235 were obtained on the basis of the slope analysis data. The results indicated that the reaction rate of Cr（Ⅵ） increased with increasing of the stirring rate and interfacial area until that a "plateau" was observed with increasing stirring rate. The activation energies of Cr（Ⅵ） extraction by N235 dissolved in diluents were calculated. Kinetics analysis proved that the mass transfer was controlled mainly by diffusion and the chemical reaction between Cr（Ⅵ） anions and N235 could be achieved at the liquid-liquid interface. On the basis of the relation between ln[Cr（Ⅵ）] and ln R0 or ln[N235] and ln R0, the rate equations can be obtained. This research provides a proof-in-concept analysis for kinetic mechanism.展开更多
The adsorption of Cu(Ⅱ)and Cr(Ⅵ)on diaspore was studied with the help of X-ray diffraction analysis,BET measurement,zeta potential measurement and atomic adsorption spectrometry.The adsorption equilibrium almost rea...The adsorption of Cu(Ⅱ)and Cr(Ⅵ)on diaspore was studied with the help of X-ray diffraction analysis,BET measurement,zeta potential measurement and atomic adsorption spectrometry.The adsorption equilibrium almost reaches within 60 min.The adsorption isotherms of Cu(Ⅱ)and Cr(Ⅵ)could be well described by the Langmuir equation.The adsorption capacities of Cu(Ⅱ)and Cr(Ⅵ)are 1.944 and 1.292 mg/g,respectively.The adsorption percentage of Cr(Ⅱ)increases with the increment of solution pH,but the adsorption percentage of Cr(Ⅵ)decreases.This could be explained by zeta potential theoretical and electrostatic attraction between metal ions and diaspore surface.展开更多
Chromium is a toxic heavy metal that is widely used in industries such as metallurgical industries, and tannery industries. This study investigates the use of an alternative adsorption technology, biosorption, using d...Chromium is a toxic heavy metal that is widely used in industries such as metallurgical industries, and tannery industries. This study investigates the use of an alternative adsorption technology, biosorption, using dried biomass of water spinach （Ipomoea aquatica） in removing chromium from aqueous solutions. Dried biomass was prepared through washing, drying, cutting and alkali treatment. K,Cr207 solutions at an initial concentration of 200~ 14.72 mg/L were added to biomass weight of 200.0~ 1.1 mg at varying pH values of 1.00, 2.00, 3.00~0.02, 4.00~0.58 and 5.00~0.44. The maximum total chromium ion uptake was at pH=2, wherein the biomass adsorbed was 9.56~0.64 ppm Cr/mg biomass. K2Cr207 solutions at concentrations of 10.00~0.32, 50.00~0.95, 100.00~0.76, 200.00~4.82 and 300.00~4.69 mg/L were added to flasks with a biomass weight of 200.00~0.75 mg and pH of 2.00~0.25. The behavior of chromium ion biosorption unto the dried water spinach best fits the Langmuir isotherm with a coefficient of determination （R2） value of 0.9993. The calculated maximum adsorption （%） is 0.13889 kg/kg. The adsorption equilibrium constant （K） is 1705.83 mg/L. The continuous experiment showed that the kinetic behavior of the biomass in a packed bed column followed the following equation with a coefficient of determination （R2） value of 0.7039： C/C0=0.266e^-0.004t展开更多
Through continuous flow experimentation, the reactivity characteristics of zero-valent iron （Fe0）-PRB with ground watercontaminated by nitrate, chromium and the combination of nitrate and chromium were investigated....Through continuous flow experimentation, the reactivity characteristics of zero-valent iron （Fe0）-PRB with ground watercontaminated by nitrate, chromium and the combination of nitrate and chromium were investigated. The results showed thatnitrate could be effectively deoxidized by zero-valent iron. NO^2- -N was the transitional deoxidization product, while NH4＋-Nwas the main final product in the effluent. Chromium could be deoxidized by zero-valent iron more effectively for the chromiumcontaminated ground water which was treated by PRB. The redox products such as Fe3＋ and Cr（III） precipitated on the packingmedia during the process. For the treatment of ground water contaminated by both nitrate and chromium, the results showed thatthe Cr（VI） removal efficiency by the zero-valent iron was not affected by the co-existence of NO^3- -N, while the NO^3- -N removalefficiency decreased with the existence of Cr（VI）.展开更多
文摘Metal trace elements (MTE) are among the most harmful micropollutants of natural waters. Eliminating them helps improve the quality and safety of drinking water and protect human health. In this work, we used mango kernel powder (MKP) as bioadsorbent material for removal of Cr (VI) from water. Uv-visible spectroscopy was used to monitor and quantify Cr (VI) during processing using the Beer-Lambert formula. Some parameters such as pH, mango powder, mass and contact time were optimized to determine adsorption capacity and chromium removal rate. Adsorption kinetics, equilibrium, isotherms and thermodynamic parameters such as ΔG˚, ΔH˚, and ΔS˚, as well as FTIR were studied to better understand the Cr (VI) removal process by MKP. The adsorption capacity reached 94.87 mg/g, for an optimal contact time of 30 min at 298 K. The obtained results are in accordance with a pseudo-second order Freundlich adsorption isotherm model. Finally FTIR was used to monitor the evolution of absorption bands, while Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray Spectroscopy (EDS) were used to evaluate surface properties and morphology of the adsorbent.
基金The present research was under the financial support of Shanxi Provincial Natural Fund(201901D111136).
文摘AbstFeS has an excellent performance in removing heavy metal chromium(Ⅵ)in wastewater due to its good adsorption and reduction.The properties of easy aggregation and oxidization of nano-FeS,however,limit the applications of FeS in engineering.In this study,one FeS adsorbent supported by Al_(2)O_(3) was prepared using high-gravity technology in IS-RPB(Impinging Stream Rotating Packed Bed)to overcome polymerization and oxidation of nano-FeS.Experimental results showed that FeS was uniformly loaded on the surface and pores of Al_(2)O_(3).The specific surface area of FeS/Al_(2)O_(3) is 125 m2·g^(-1) which is nearly 1.6 times that of pure FeS.The adsorption capacity of FeS/Al_(2)O_(3) for chromium(Ⅵ)is 200 mg·g^(-1),1.4 times that of pure FeS.pH value and ionic strength are strongly correlated with the chromium removal performance of FeS/Al_(2)O_(3).Over 98%of chromium can be removed when pH values of FeS/Al_(2)O_(3) ranged from 4 to 6.Higher adsorption capacity is achieved with higher ionic strength in FeS/Al_(2)O_(3).The FeS/Al_(2)O_(3) maintained more than 95%of the adsorption capacity after being preserved for one month,but only 70%for pure FeS.The removal processes of chromium(Ⅵ)conformes to a pseudo-second-order kinetic model(R2≥0.9986),indicating that the rate-limiting step is a chemical sorption process instead of a mass transfer.
基金Our study was funded by the National Natural Science Foundation of China (Nos.40572095, 40730422 and 40772102)the Six Projects Sponsoring Talent Summits of Jiangsu Province and the Jiangsu Province Plan of Post-Graduate Student Inno-vation (No.CX07B-050z)
文摘In order to investigate chromium contamination of coal mine water, to analyze chromium leaching mechanism and to evaluate environment pollution potential of coal mine water, we perform site investigations, physical and computer modeling in the Xuzhou-Datun coal mine district. The result of our test samples shows that chromium concentration was 9 μg/L in roof leachate and 3 μg/L in coal leachate. The host rock has a higher pollution potential than that of coal seams. Leaching experiments and XRD test results indicate that chromium is released from the process of transforming illite to kaolinite. The pH, pe and temperature of coal mine water affect the chromium leaching behavior. Modeling results suggest that the adsorption of adsorbents controls chromium concentration in coal mine water. The chromium adsorption ratio is quite low in both an acid and in an alkaline environment. Therefore, coal mine water has a high pollution potential. Under other conditions, chromium adsorption is stronger in a neutral water environment, so that chromium concentrations may be very low.
文摘A certified clay mineral from Iraq, montmorillonite, is used for the adsorption of chromium and lead ions from water. Experimental design is utilized here to plan for the practical work and analysis of the results. Batch wise experiments are carried out to equilibrate Cr and Pb solutions (250 mg/L) individually and simultaneously with montmorillonite (5 - 20 g/L) at various pH ranges (2 - 7.5) for 10 - 60 minutes. The results indicate perfect fit with the model used. Chromium adsorption is sensitive to pH changes being high at neutral medium. Lead is almost independent of the pH of the solution. In nearly neutral medium, the sorption capacity of Cr is 21.4 and that of lead is 24.3 mg/g. The optimum conditions for >96% Cr removal are 12 - 15 g clay/L, 40 - 50 minutes and a pH of 5 - 7. For lead, almost 100% removal can be attained using 12 - 15 g clay/L, 40 - 50 min. at a pH of 4 - 6. The effects of various operating parameters are discussed. Simultaneously, the lead shows a greater tendency to sorption than chromium and a ratio of 5:4 can best represent the occupation of the active surface of the clay. The most favorable conditions for simultaneous removing of Cr, 86% and Pb, 100% may be 12.5 g/L clay content and a pH of 7.5 within 30 minutes. The kinetic study of the results indicates the adsorption follow pseudo-second order kinetics in which chemical interaction is also involved. The kinetic study confirms the dependence of chromium adsorption on the pH of the medium being favoured at high pH values.
基金Project(20050532009)supported by the Doctoral Foundation of Ministry of Education of ChinaProject supported by Program for Changjiang Scholars and Innovative Research Team in University
文摘Cr(Ⅵ)-amended soil was inoculated with Cr(Ⅵ)-reducing strain,Bacillus sp.XW-4 and incubated at 28 ℃in an incubator. Cr(Ⅵ)reduction,available Cr and Cr fractionin soils were studied.The results show that addition of Bacillus sp.XW-4 can promote Cr(Ⅵ)reduction,but inoculation of this strain has a negative effect on the decrease of available Cr content in soil.In controls (without this strain)amended with 100 and 200 mg/kg of Cr(Ⅵ),Cr(Ⅵ)contents decrease to about 41 and 92 mg/kg respectively after incubation of 4 d,while in soil inoculated with XW-4,Cr(Ⅵ)contents decrease to about 18 and 60 mg/kg,respectively.The content of available Cr in soils with inoculation of XW-4 is higher than that in controls.Chromium is partitioned into water soluble Cr,exchangeable Cr,precipitated Cr,Cr bound to organics and residual Cr.The highest content of Cr is observed in residual form and water soluble Cr is not detected for all treatments after 42 d,but the soils inoculated with Bacillus sp.XW-4 contain higher content of exchangeable Cr and lower content of precipitated Cr than the soil without the inoculum.Inoculation of Bacillus sp.XW-4 can increase chromium activity in soils.
基金Natural Science Foundation of the Jiangsu Higher Education Institutions of China(No.18KJD610001)Doctor of Philosophy(PhD)Start-up Foundation of Changzhou Vocational Institute of Engineering(No.11130900117002)+1 种基金Jiangsu Students’Platform for Innovation and Entrepreneurship Training Program,China(No.201813102026H)Qing-Lan Project of Jiangsu Province,China(No.2018-12)
文摘Kinetic studies of the extraction of chromium（Ⅵ）[Cr（Ⅵ）] from the hydrochloric acid solution with tri-n-octylamine（N235） have been made by a Lewis cell. The influences of various kinetic parameters, such as stirring rate, interfacial area, temperature, N235 and initial Cr（Ⅵ） concentrations were evaluated. The rate equations for the extraction of Cr（Ⅵ） by N235 were obtained on the basis of the slope analysis data. The results indicated that the reaction rate of Cr（Ⅵ） increased with increasing of the stirring rate and interfacial area until that a "plateau" was observed with increasing stirring rate. The activation energies of Cr（Ⅵ） extraction by N235 dissolved in diluents were calculated. Kinetics analysis proved that the mass transfer was controlled mainly by diffusion and the chemical reaction between Cr（Ⅵ） anions and N235 could be achieved at the liquid-liquid interface. On the basis of the relation between ln[Cr（Ⅵ）] and ln R0 or ln[N235] and ln R0, the rate equations can be obtained. This research provides a proof-in-concept analysis for kinetic mechanism.
基金Project(2005CB623701)supported by the Major State Basic Research Development Program of China
文摘The adsorption of Cu(Ⅱ)and Cr(Ⅵ)on diaspore was studied with the help of X-ray diffraction analysis,BET measurement,zeta potential measurement and atomic adsorption spectrometry.The adsorption equilibrium almost reaches within 60 min.The adsorption isotherms of Cu(Ⅱ)and Cr(Ⅵ)could be well described by the Langmuir equation.The adsorption capacities of Cu(Ⅱ)and Cr(Ⅵ)are 1.944 and 1.292 mg/g,respectively.The adsorption percentage of Cr(Ⅱ)increases with the increment of solution pH,but the adsorption percentage of Cr(Ⅵ)decreases.This could be explained by zeta potential theoretical and electrostatic attraction between metal ions and diaspore surface.
文摘Chromium is a toxic heavy metal that is widely used in industries such as metallurgical industries, and tannery industries. This study investigates the use of an alternative adsorption technology, biosorption, using dried biomass of water spinach （Ipomoea aquatica） in removing chromium from aqueous solutions. Dried biomass was prepared through washing, drying, cutting and alkali treatment. K,Cr207 solutions at an initial concentration of 200~ 14.72 mg/L were added to biomass weight of 200.0~ 1.1 mg at varying pH values of 1.00, 2.00, 3.00~0.02, 4.00~0.58 and 5.00~0.44. The maximum total chromium ion uptake was at pH=2, wherein the biomass adsorbed was 9.56~0.64 ppm Cr/mg biomass. K2Cr207 solutions at concentrations of 10.00~0.32, 50.00~0.95, 100.00~0.76, 200.00~4.82 and 300.00~4.69 mg/L were added to flasks with a biomass weight of 200.00~0.75 mg and pH of 2.00~0.25. The behavior of chromium ion biosorption unto the dried water spinach best fits the Langmuir isotherm with a coefficient of determination （R2） value of 0.9993. The calculated maximum adsorption （%） is 0.13889 kg/kg. The adsorption equilibrium constant （K） is 1705.83 mg/L. The continuous experiment showed that the kinetic behavior of the biomass in a packed bed column followed the following equation with a coefficient of determination （R2） value of 0.7039： C/C0=0.266e^-0.004t
文摘Through continuous flow experimentation, the reactivity characteristics of zero-valent iron （Fe0）-PRB with ground watercontaminated by nitrate, chromium and the combination of nitrate and chromium were investigated. The results showed thatnitrate could be effectively deoxidized by zero-valent iron. NO^2- -N was the transitional deoxidization product, while NH4＋-Nwas the main final product in the effluent. Chromium could be deoxidized by zero-valent iron more effectively for the chromiumcontaminated ground water which was treated by PRB. The redox products such as Fe3＋ and Cr（III） precipitated on the packingmedia during the process. For the treatment of ground water contaminated by both nitrate and chromium, the results showed thatthe Cr（VI） removal efficiency by the zero-valent iron was not affected by the co-existence of NO^3- -N, while the NO^3- -N removalefficiency decreased with the existence of Cr（VI）.
