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| Studies on Cr(Ⅵ) and Cd2+ adsorption onto bentonite modified by a BS-12+DTAB complex |
| Received:March 06, 2017 |
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| KeyWord:bentonite;complex modification;adsorption;Cr(Ⅵ);Cd2+ |
| Author Name | Affiliation | E-mail | | XIE Ting | College of Natural Resources and Environment, Northwest A & F University, Yangling 712100, China | | | LI Wen-bin | College of Environmental Science and engineering, China West Normal University, Nanchong 637009, China | | | MENG Zhao-fu | College of Natural Resources and Environment, Northwest A & F University, Yangling 712100, China
Key Lab of Plant Nutrition and Agro-environment in Northwest China, Ministry of Agriculture, Yangling 712100, China | zfmeng1996@263.net | | LU Hao-yuan | College of Natural Resources and Environment, Northwest A & F University, Yangling 712100, China | | | REN Shuang | College of Natural Resources and Environment, Northwest A & F University, Yangling 712100, China | | | YEK Sambath | College of Natural Resources and Environment, Northwest A & F University, Yangling 712100, China | |
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| Abstract: |
| In order to compare the discrepancies between Cr(Ⅵ) and Cd2+ adsorption on bentonite modified by a mixture of amphoteric modifier, dodecyldimethyl betaine(BS-12), and cationic modifier, Dodecyltrimethyl ammonium Bromide(DTAB), batch method was used to study the influence of temperature, ionic strength, pH on discrepancies of adsorption of Cr(Ⅵ) and Cd2+ on different modified bentonites, and the thermodynamic properties were studied also. The results showed that:The Langmuir model was suited for adsorption isotherms of Cr(Ⅵ) and Cd2+ on different samples. The equilibrium adsorption capacity of Cr(Ⅵ) was ordered by BS+150DT(BS-12+150% CEC DTAB)> BS+100DT > BS+50DT > BS+25DT > BS > CK(unmodified bentonite) and BS+150DT treatment had the maximum adsorption capacity(qm) 205.67 mmol·kg-1. On the contrary, the sequence of equilibrium adsorption capacity of Cd2+ was BS > CK > BS+25DT > BS+50DT > BS+100DT > BS+150DT, and 100BS(100% CEC BS-12) had maximum Cd2+ adsorption 232.38 mmol·kg-1. In the range of 10℃ to 40℃, the adsorption capacity of Cr(Ⅵ) on CK and BS modified bentonites were increased with increased temperature, while Cr(Ⅵ) adsorption on BS-DT bentonites was a spontaneous process with a decrease in enthalpy and an increase in entropy. The Cd2+ adsorption on different samples was a spontaneous process with an increase in enthalpy and an increase in entropy. With an increase of pH, the adsorption capacity of Cr(Ⅵ) decreased gradually, while the adsorption capacity of Cd2+ increased gradually. High ionic strength was not conducive to adsorption of Cr(Ⅵ) and Cd2+. Charge type of BS-DT complex modified bentonite was the crucial factor to difference between Cr(Ⅵ) and Cd2+ adsorption. |
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