The biosorption mechanism of Cr （Ⅳ） ions on Synechococcus sp. biosorbent was studied by analyzing the biosorption kinetics as well as speciation change and bond formation during the biosorption process. The kinetic...The biosorption mechanism of Cr （Ⅳ） ions on Synechococcus sp. biosorbent was studied by analyzing the biosorption kinetics as well as speciation change and bond formation during the biosorption process. The kinetics study shows that the adsorption process of Cr （Ⅳ） consists of a very fast stage in the first several minutes, in which more than half of the saturation adsorption is attained, and a slower stage that approximately follows the first order kinetic model, basically Freundlich isotherm models were observed. Comparative studies of FT-LR spectra of K2Cr2O7, free cells of Synechococcus sp., and Cr-bound cells of Synechococcus sp show that the speciation of chromium that binds to the cells ofSynechococcus sp. is Cr （Ⅲ）, instead of Cr （Ⅳ）, and the carboxylic, alcoholic, amido and amino groups may be involved in the binding of Cr （Ⅲ）. Integrative analyses of the surface electric potential, the effect of pH value on adsorption behavior of Cr （Ⅵ）, and the results of FT-IR show that the biosorption of Cr （Ⅵ） follows two subsequent steps, biosorption of Cr2O7 ^2- by electrostatical force at the protonated active sites and reduction of Cr2O7^2- to Cr^3＋ by the reductive groups on the surface of the biosorbents.展开更多
Protoplasts from Candida tropicalis and Candida lipolytica were fused under an optimized electrofusion （electrical pulse strength 6 kV/cm, pulse duration time 40μs and pulse times 5） and then regenerated on YEPD me...Protoplasts from Candida tropicalis and Candida lipolytica were fused under an optimized electrofusion （electrical pulse strength 6 kV/cm, pulse duration time 40μs and pulse times 5） and then regenerated on YEPD media for achieving new genotypes with higher chromium loading capacity. A target fusant RHJ-004 was screened out by its chromium resistance and chromium-sorbing capacity tests for further research. The comparative study of applicability shows that the fusant has better performance than its parent strains in respect of solution pH, biomass concentration and chromium loading capacity. Especially for treating low concentration Cr（VI） （〈20 mg/L）, above 80% chromium is sequestered from the aqueous phase at pH 1-9. Atomic force microscopy （AFM） visualizes the distribution of chromium on the binding sites of the cells, suggesting that the altered surface structure and intracellular constitutes of the fusant associate with its increased biosorption capacity. The rapid biosorption processes of chromium foUow the Langmuir model well.展开更多
Heavy metal biosorption is an effective process for the removal and recovery of heavy metal ions.Equilibrium isotherms obtained experimentally are usually correlated empirically with commonly used adsorption models, w...Heavy metal biosorption is an effective process for the removal and recovery of heavy metal ions.Equilibrium isotherms obtained experimentally are usually correlated empirically with commonly used adsorption models, without considering the underlying mechanisms of biosorption.Commonly used models for correlating biosorption isotherm data are briefly reviewed and the use of the adsorption models in correlating the desorption processes is analysed.A set of biosorption/desorption experiments for a marine alga derived biosorbent are carried out to test the use of the adsorption models in the desorption process.Experimental data indicate that the amount of the heavy metal ions desorbed from the biomass could not be calculated with the adsorption models.This suggests that the empirical use of adsorption models in the correlation may not be valid when the reversibility of the biosorption equlibrium in the desorption process needs to be considered.Therefore,mechanism based biosorption models are needed for better correlation of equilibrium isotherm data.展开更多
Four types of common seaweeds(Laminaria japonica,Undaria pinnatifida,Porphyra haitanensis,and Gracilaria lemaneiformis) were examined to remove Cr(Ⅵ) ions from aqueous solution.The experimental parameters that affect...Four types of common seaweeds(Laminaria japonica,Undaria pinnatifida,Porphyra haitanensis,and Gracilaria lemaneiformis) were examined to remove Cr(Ⅵ) ions from aqueous solution.The experimental parameters that affected the biosorption process including pH,biomass dosage,contact time and temperature were investigated via batch experiments.The surface characteristics of seaweeds before and after Cr(Ⅵ) adsorption were studied with scanning electron microscopy and Fourier transform infrared spectroscopy.The results show that an initial solution with the pH of 1.0 is most favorable for Cr(Ⅵ) adsorption.Rapid adsorption is observed in the initial stage and adsorption equilibrium state is reached within 1 h.The adsorption efficiency by Porphyra haitanensis is the maximum among four types of seaweed powders,followed by Laminaria japonica and Undaria pinnatifida with biosorption efficiency up to 90%.The removal rate of Gracilaria lemaneiformis is less than 60%.The kinetic data obtained using the seaweeds are found to follow pseudo-second order kinetic model.Experimental sorption data adequately correlate with the Langmuir model.FTIR indicates that amino and carboxyl groups play an important role in the process of Cr(Ⅵ) adsorption and a large percentage of Cr(Ⅵ) ions are reduced by reductive groups on the surface of seaweeds.展开更多
The ability of Stenotrophomonas maltophilia was demonstrated to selectively remove Cu2+from Cu(NO3)2 solution under the circumstance that 1 mg/L benzo[a]pyrene(BaP) was either present or not. The removal ratios of 2 a...The ability of Stenotrophomonas maltophilia was demonstrated to selectively remove Cu2+from Cu(NO3)2 solution under the circumstance that 1 mg/L benzo[a]pyrene(BaP) was either present or not. The removal ratios of 2 and 10 mg/L Cu2+by 0.25 g/L biosorbent are up to 80% and 49% at 10 min, respectively. The biosorption includes ion exchange, NO3 reduction, ion release, and cell oxidation by Cu2+. BaP does not significantly affect Cu2+removal and ion release. Although 2 mg/L Cu2+increases the release of PO4 3, K+, NH4 +and Ca2+, 10 mg/L Cu2+has strong oxidation on cell, and then decreases NO3 reduction and hinders the release of K+, NH4 +and Ca2+. Exogenous cations inhibit the Cu2+biosorption, while additional anions increase the removal ratios of 10 mg/L Cu2+from 52% to 88%.展开更多
A novel technology for lead removal with nonliving Rhizopus oligosporus immobilized in calcium alginate was studied. The results show that the main influencing factors include pH value and interfering cations. pH valu...A novel technology for lead removal with nonliving Rhizopus oligosporus immobilized in calcium alginate was studied. The results show that the main influencing factors include pH value and interfering cations. pH value has different effects on biosorption of various heavy metals and lead adsorption can be proceeded by controlling pH value in a range of 2–5; interfering cations especially Cu(II) can make the adsorption amount of Pb(II) decrease by immobilized Rhizopus oligosporus. Desorption efficiency of different eluants and kinetics were investigated. Citrate acid with concentration of 0.3 mol ? L?1 is the best for the elution of Pb(II) and desorption rate is over 98%when the reaction equilibrium reaches 3 h. Immobilized biomass keeps high lead biosorption capacity after five cycles of regeneration.展开更多
The Microcystis aeruginosa(MA) was immobilized on sodium alginate and used as biosorbent for removal of Cd(Ⅱ) ions from aqueous solution.The biosorption process is pH dependent,and the optimum biosorption was observe...The Microcystis aeruginosa(MA) was immobilized on sodium alginate and used as biosorbent for removal of Cd(Ⅱ) ions from aqueous solution.The biosorption process is pH dependent,and the optimum biosorption was observed at pH 6.0 with the biosorption capacity of 98.38 mg/g.Among Langmuir,Freundlich and Temkin isotherm models,the Freundlich and the Temkin isotherm fit well with the experimental data.Cd(Ⅱ) ions biosorption follows the pseudo-second-order kinetic model.The rate controlling mechanism study reveals that film diffusion is the rate-limiting step and intraparticle diffusion is also involved in biosorption.Thermodynamic parameters,such as Gibbs free energy(ΔG°),the enthalpy(ΔH°) and entropy(ΔS°) were calculated,and revealed that the biosorption process is spontaneous,exothermic and random.Furthermore,the immobilized MA can be regenerated using 0.1 mol/L HCl solutions.展开更多
基金Project(50321402) supported by the National Natural Science Foundation of China
文摘The biosorption mechanism of Cr （Ⅳ） ions on Synechococcus sp. biosorbent was studied by analyzing the biosorption kinetics as well as speciation change and bond formation during the biosorption process. The kinetics study shows that the adsorption process of Cr （Ⅳ） consists of a very fast stage in the first several minutes, in which more than half of the saturation adsorption is attained, and a slower stage that approximately follows the first order kinetic model, basically Freundlich isotherm models were observed. Comparative studies of FT-LR spectra of K2Cr2O7, free cells of Synechococcus sp., and Cr-bound cells of Synechococcus sp show that the speciation of chromium that binds to the cells ofSynechococcus sp. is Cr （Ⅲ）, instead of Cr （Ⅳ）, and the carboxylic, alcoholic, amido and amino groups may be involved in the binding of Cr （Ⅲ）. Integrative analyses of the surface electric potential, the effect of pH value on adsorption behavior of Cr （Ⅵ）, and the results of FT-IR show that the biosorption of Cr （Ⅵ） follows two subsequent steps, biosorption of Cr2O7 ^2- by electrostatical force at the protonated active sites and reduction of Cr2O7^2- to Cr^3＋ by the reductive groups on the surface of the biosorbents.
基金Project(NSFC-GDNSF U0933002) supported by the Joint Funds of the National Natural Science Foundation of China and the Natural Science Foundation of Guangdong Province,ChinaProject(50978122) supported by the National Natural Science Foundation of China
文摘Protoplasts from Candida tropicalis and Candida lipolytica were fused under an optimized electrofusion （electrical pulse strength 6 kV/cm, pulse duration time 40μs and pulse times 5） and then regenerated on YEPD media for achieving new genotypes with higher chromium loading capacity. A target fusant RHJ-004 was screened out by its chromium resistance and chromium-sorbing capacity tests for further research. The comparative study of applicability shows that the fusant has better performance than its parent strains in respect of solution pH, biomass concentration and chromium loading capacity. Especially for treating low concentration Cr（VI） （〈20 mg/L）, above 80% chromium is sequestered from the aqueous phase at pH 1-9. Atomic force microscopy （AFM） visualizes the distribution of chromium on the binding sites of the cells, suggesting that the altered surface structure and intracellular constitutes of the fusant associate with its increased biosorption capacity. The rapid biosorption processes of chromium foUow the Langmuir model well.
文摘Heavy metal biosorption is an effective process for the removal and recovery of heavy metal ions.Equilibrium isotherms obtained experimentally are usually correlated empirically with commonly used adsorption models, without considering the underlying mechanisms of biosorption.Commonly used models for correlating biosorption isotherm data are briefly reviewed and the use of the adsorption models in correlating the desorption processes is analysed.A set of biosorption/desorption experiments for a marine alga derived biosorbent are carried out to test the use of the adsorption models in the desorption process.Experimental data indicate that the amount of the heavy metal ions desorbed from the biomass could not be calculated with the adsorption models.This suggests that the empirical use of adsorption models in the correlation may not be valid when the reversibility of the biosorption equlibrium in the desorption process needs to be considered.Therefore,mechanism based biosorption models are needed for better correlation of equilibrium isotherm data.
基金Project(KLUEH201302) supported by Funded by the Key Laboratory of Urban Environment and Health,Institute of Urban Environment,Chinese Academy of SciencesProject(51004053) supported by the National Natural Science Foundation of China+2 种基金Project(3502Z20116008) supported by the Science and Technology Research Project of Xiamen City,ChinaProject(JA11146) supported by the Program for Fostering Distinguished Young Scholars in University of Fujian Province,ChinaProject(2011B003) supported by the Foundation for Young Professors of Jimei University,China
文摘Four types of common seaweeds(Laminaria japonica,Undaria pinnatifida,Porphyra haitanensis,and Gracilaria lemaneiformis) were examined to remove Cr(Ⅵ) ions from aqueous solution.The experimental parameters that affected the biosorption process including pH,biomass dosage,contact time and temperature were investigated via batch experiments.The surface characteristics of seaweeds before and after Cr(Ⅵ) adsorption were studied with scanning electron microscopy and Fourier transform infrared spectroscopy.The results show that an initial solution with the pH of 1.0 is most favorable for Cr(Ⅵ) adsorption.Rapid adsorption is observed in the initial stage and adsorption equilibrium state is reached within 1 h.The adsorption efficiency by Porphyra haitanensis is the maximum among four types of seaweed powders,followed by Laminaria japonica and Undaria pinnatifida with biosorption efficiency up to 90%.The removal rate of Gracilaria lemaneiformis is less than 60%.The kinetic data obtained using the seaweeds are found to follow pseudo-second order kinetic model.Experimental sorption data adequately correlate with the Langmuir model.FTIR indicates that amino and carboxyl groups play an important role in the process of Cr(Ⅵ) adsorption and a large percentage of Cr(Ⅵ) ions are reduced by reductive groups on the surface of seaweeds.
基金Projects(21007020,U0933002,U0833002) supported by the National Natural Science Foundation of ChinaProject(2009B030500002) supported by the Science and Technology Projects of Guangdong Province,China
文摘The ability of Stenotrophomonas maltophilia was demonstrated to selectively remove Cu2+from Cu(NO3)2 solution under the circumstance that 1 mg/L benzo[a]pyrene(BaP) was either present or not. The removal ratios of 2 and 10 mg/L Cu2+by 0.25 g/L biosorbent are up to 80% and 49% at 10 min, respectively. The biosorption includes ion exchange, NO3 reduction, ion release, and cell oxidation by Cu2+. BaP does not significantly affect Cu2+removal and ion release. Although 2 mg/L Cu2+increases the release of PO4 3, K+, NH4 +and Ca2+, 10 mg/L Cu2+has strong oxidation on cell, and then decreases NO3 reduction and hinders the release of K+, NH4 +and Ca2+. Exogenous cations inhibit the Cu2+biosorption, while additional anions increase the removal ratios of 10 mg/L Cu2+from 52% to 88%.
文摘A novel technology for lead removal with nonliving Rhizopus oligosporus immobilized in calcium alginate was studied. The results show that the main influencing factors include pH value and interfering cations. pH value has different effects on biosorption of various heavy metals and lead adsorption can be proceeded by controlling pH value in a range of 2–5; interfering cations especially Cu(II) can make the adsorption amount of Pb(II) decrease by immobilized Rhizopus oligosporus. Desorption efficiency of different eluants and kinetics were investigated. Citrate acid with concentration of 0.3 mol ? L?1 is the best for the elution of Pb(II) and desorption rate is over 98%when the reaction equilibrium reaches 3 h. Immobilized biomass keeps high lead biosorption capacity after five cycles of regeneration.
基金Project(41271332) supported by the National Natural Science Foundation of ChinaProject(11JJ2031) supported by the Natural Science Foundation of Hunan Province,China+1 种基金Project(2012SK2021) supported by the Science and Technology Planning Program of Hunan Province,ChinaProject(CX2012B138) supported by the Hunan Provincial Innovation Foundation for Postgraduate,China
文摘The Microcystis aeruginosa(MA) was immobilized on sodium alginate and used as biosorbent for removal of Cd(Ⅱ) ions from aqueous solution.The biosorption process is pH dependent,and the optimum biosorption was observed at pH 6.0 with the biosorption capacity of 98.38 mg/g.Among Langmuir,Freundlich and Temkin isotherm models,the Freundlich and the Temkin isotherm fit well with the experimental data.Cd(Ⅱ) ions biosorption follows the pseudo-second-order kinetic model.The rate controlling mechanism study reveals that film diffusion is the rate-limiting step and intraparticle diffusion is also involved in biosorption.Thermodynamic parameters,such as Gibbs free energy(ΔG°),the enthalpy(ΔH°) and entropy(ΔS°) were calculated,and revealed that the biosorption process is spontaneous,exothermic and random.Furthermore,the immobilized MA can be regenerated using 0.1 mol/L HCl solutions.
