Amino-functionalized magnetic nanoparticle （NH2-MNP） were prepared by a sol-gel approach. The adsorption behavior of Cu（II） ions on NH2-MNP was discussed systematically by batch experiments. The effects of initial...Amino-functionalized magnetic nanoparticle （NH2-MNP） were prepared by a sol-gel approach. The adsorption behavior of Cu（II） ions on NH2-MNP was discussed systematically by batch experiments. The effects of initial Cu（II） ions concentration, time, pH and temperature were investigated. In kinetic studies, the pseudo-second-order model was successfully employed, and the pseudo-first-order model substantiated that Cu（II） adsorption on NH2-MNP was a diffusion-based process. Langmuir model and Dubinin-Radushkevich model （R2〉0.99） were more corresponded with the adsorption isotherm data of Cu（II） ions than Freundlich model. The adsorption capacity was increased with the increment of temperature and pH. NH2-MNP remains excellent Cu（II） recoveries after reusing five adsorption and desorption cycles, making NH2-MNP a promising candidate for repetitively removing heavy metal ions from environmental water samples. According to the results obtained from adsorption activation energy and thermodynamic studies, it can be inferred that the main adsorption mechanism between absorbent and Cu（II） ions is ion exchange-surface complexation.展开更多
In the present work, the adsorption of sulfate and fluoride by two oxisols was studied, and during the adsorption OH- released from soils were measured and the change in surface charge carried by one of the soils afte...In the present work, the adsorption of sulfate and fluoride by two oxisols was studied, and during the adsorption OH- released from soils were measured and the change in surface charge carried by one of the soils after the adsorption of fluoride was examined. The results show that the adsorption of sulfate by oxisols and the release of OH- from oxisols both increased with the increase of sulfate added at a constant pH, but decreased when pH became higher gradually. The adsorption and release both decreased markedly after removal of iron oxide. The ratio of OH- to SO42- for Fe-removed soils decreased to 15-34% of the original soils. These results suggest that iron oxide was the chief carrier of hydroxyl groups capable of ligand exchange with sulfate in oxisols.Compared with sulfate, however, the amount of fluoride adsorbed, OH- released during the adsorption of fluoride and the ratio of OH- to F- were much larger. The effect of iron oxide on the adsorption of fluoride by oxisols was smaller than that on the adsorption of sulfate. The ratios of OH- to F- for an oxisol from Brazil were 0.62 and 0.48 respectively before and after removal of free iron oxides. This implied that iron oxide only provided a small amount of exchangeable hydroxyl groups capable of ligand exchange with fluoride in oxisol. The research results indicate that among the factors inducing the changes in some properties of oxisols after adsorption of fluoride, the role became less important in the sequence of the release of OH-> the increase of negative charge > the decrease of positive charge.展开更多
Humic substances （HS） substantially affect heavy metal （M） adsorption on mineral surfaces. However, quantitative descriptions of ternary systems involving M, HS and mineral surfaces remain unclear. This study exam...Humic substances （HS） substantially affect heavy metal （M） adsorption on mineral surfaces. However, quantitative descriptions of ternary systems involving M, HS and mineral surfaces remain unclear. This study examines adsorption in a model ternary system including Eu（III）, fulvic acid （FA） and silica, and describes the adsorption of Eu（III） and FA by combining a double-layer model （DLM） and the Stockholm humic model （SHM）. SHM explains the binding of H＋ and Eu^3＋ to EA and the DLM for FA and Eu（Ill） adsorption on silica. Experimental results showed that the presence of FA promotes Eu（III） adsorp- tion at acidic pH values, but decreases it at basic pH values, which indicates the formation of ternary surface complexes. Modeling calculations have shown that two ternary surface complexes are required to describe the experimental results in which Eu^3＋ acts as a bridge between the surface site and FA. The present study suggests that the discrete-site approach to HS is a promising method for interpreting the adsorption data for M, HS and mineral ternary systems.展开更多
基金Project(CXZZ11-0812)supported by Graduate Students Innovative Projects of Jiangsu Province,ChinaProject(J20122288)supported by Guizhou Provincial Natural Science Foundation of China+1 种基金Project(Y4110235)supported by Zhejiang Provincial Natural Science Foundation of ChinaProject(JKY2011008)supported by Fundamental Research Funds for the Central Universities,China
文摘Amino-functionalized magnetic nanoparticle （NH2-MNP） were prepared by a sol-gel approach. The adsorption behavior of Cu（II） ions on NH2-MNP was discussed systematically by batch experiments. The effects of initial Cu（II） ions concentration, time, pH and temperature were investigated. In kinetic studies, the pseudo-second-order model was successfully employed, and the pseudo-first-order model substantiated that Cu（II） adsorption on NH2-MNP was a diffusion-based process. Langmuir model and Dubinin-Radushkevich model （R2〉0.99） were more corresponded with the adsorption isotherm data of Cu（II） ions than Freundlich model. The adsorption capacity was increased with the increment of temperature and pH. NH2-MNP remains excellent Cu（II） recoveries after reusing five adsorption and desorption cycles, making NH2-MNP a promising candidate for repetitively removing heavy metal ions from environmental water samples. According to the results obtained from adsorption activation energy and thermodynamic studies, it can be inferred that the main adsorption mechanism between absorbent and Cu（II） ions is ion exchange-surface complexation.
文摘In the present work, the adsorption of sulfate and fluoride by two oxisols was studied, and during the adsorption OH- released from soils were measured and the change in surface charge carried by one of the soils after the adsorption of fluoride was examined. The results show that the adsorption of sulfate by oxisols and the release of OH- from oxisols both increased with the increase of sulfate added at a constant pH, but decreased when pH became higher gradually. The adsorption and release both decreased markedly after removal of iron oxide. The ratio of OH- to SO42- for Fe-removed soils decreased to 15-34% of the original soils. These results suggest that iron oxide was the chief carrier of hydroxyl groups capable of ligand exchange with sulfate in oxisols.Compared with sulfate, however, the amount of fluoride adsorbed, OH- released during the adsorption of fluoride and the ratio of OH- to F- were much larger. The effect of iron oxide on the adsorption of fluoride by oxisols was smaller than that on the adsorption of sulfate. The ratios of OH- to F- for an oxisol from Brazil were 0.62 and 0.48 respectively before and after removal of free iron oxides. This implied that iron oxide only provided a small amount of exchangeable hydroxyl groups capable of ligand exchange with fluoride in oxisol. The research results indicate that among the factors inducing the changes in some properties of oxisols after adsorption of fluoride, the role became less important in the sequence of the release of OH-> the increase of negative charge > the decrease of positive charge.
基金supported by the National Natural Science Foundation of China(91226113,J1210001)
文摘Humic substances （HS） substantially affect heavy metal （M） adsorption on mineral surfaces. However, quantitative descriptions of ternary systems involving M, HS and mineral surfaces remain unclear. This study examines adsorption in a model ternary system including Eu（III）, fulvic acid （FA） and silica, and describes the adsorption of Eu（III） and FA by combining a double-layer model （DLM） and the Stockholm humic model （SHM）. SHM explains the binding of H＋ and Eu^3＋ to EA and the DLM for FA and Eu（Ill） adsorption on silica. Experimental results showed that the presence of FA promotes Eu（III） adsorp- tion at acidic pH values, but decreases it at basic pH values, which indicates the formation of ternary surface complexes. Modeling calculations have shown that two ternary surface complexes are required to describe the experimental results in which Eu^3＋ acts as a bridge between the surface site and FA. The present study suggests that the discrete-site approach to HS is a promising method for interpreting the adsorption data for M, HS and mineral ternary systems.
