Effect of Sepiolite on Sorption of Cd by Typical Paddy Soils
The adsorption-desorption of cadmium(Cd) by clay minerals or soils have been extensively studied, however, the effect of the application of sepiolite on Cd adsorption-desorption in soils remains poorly understood. The aim of this study was therefore to investigate Cd sorption and desorption by 3 typical paddy soils pretreated with sepiolite through a batch equilibration method. Our results indicated that the sorption amount of Cd on each tested soil increased with the Cd equilibrium concentration, after adding cadmium ion ranged from 0 to 20 mg· L~(-1), but did not reach a maximum. Freundlich equations were fitted well (R~2> 0.962) to all the sorption experimental results. Sepiolite not only enhanced Cd adsorption, but also increased the retention of Cd by the three soils. At the same initial Cd concentrations, sepiolite added at 5 and 10 mg·kg~(-1) increased the adsorption amount by 17%～34% and 25%～60%, and decreased the release percentage by 1.4%～13.6% and 10.3%～25.0%, respectively, as compared with the controls. Solution initial pH was also an important factor affecting the adsorption of Cd in soil. The enhancement of Cd sorption caused by the solution initial pH increase was apparent with the pH ranged from 2 to 4, but the effect was minimal with the pH ranged from 5 to 8. Moreover, addition of sepiolite obviously increased the sorption amount of Cd by the 3 soils with the pH ranged from 2 to 8. These results provide support for the feasibility of sepiolite used as amendment for the immobilization of Cd in paddy soil.
国家科技期刊平台
NSTL
万方数据
维普
