温度和砷酸根对砖红壤中Cd（II）吸附动力学的影响

土壤中砷和镉同时存在的现象普遍存在,但目前对砷酸根与Cd(II)在可变电荷土壤表面协同作用的机制还了解不多。用一次平衡法研究了288 K和308 K温度条件下Cd(II)在昆明砖红壤表面的吸附动力学,比较了加入砷酸根对Cd(II)吸附动力学的影响。结果显示,加As(V)和升高温度均不仅增加Cd(II)的吸附量,而且提高了吸附反应的速率。Cd(II)在砖红壤表面的吸附反应进行的特别快,几乎在30 min内达到准平衡,假二级动力学方程能很好拟合30 min内的吸附动力学数据(r2>0.999 5)。从反应速率常数计算得到的活化能的结果表明,加As(V)显著降低了Cd(II)吸附反应的活化能,这是As(V)促进可变电荷土壤吸附Cd(II)的根本原因。

Effects of temperature and arsenate on adsorption kinetics of cadmium by an Oxisol

Arsenic and cadmium contamination are a common co-occurrence in soils.However,the mechanisms for co-sorption of arsenate and Cd(II) on variable charge soils were not understood well until now.Effects of temperature and arsenate added on adsorption kinetics of Cd(II) by an Oxisol from Kunming,Yunnan Province were investigated with a batch method in this study.The results obtained indicated that both the rise of temperature and the addition of arsenate increased the quantity of Cd(II) adsorbed by the soil and accelerated the adsorption reaction of Cd(II) to the soil surface.The adsorption of Cd(II) by the soil was very quick at the beginning of the reaction and slowed down after 30 min.Pseudo second order equation fitted the kinetic data of Cd(II) adsorption well in the range of time from 0 to 30 min(r2>0.999 5).The Arrhenius activation energy for the adsorption was calculated based on the rate constants obtained at different temperature and the results showed that the presence of arsenate decreased the activation energy obviously,which was the main reason for Cd(II) adsorption enhanced by arsenate in the variable charge soil.The findings obtained in the present study is of fundamental significance in understanding the mechanisms of co-sorption between cations and anions on soils and can provide references for the remediation of heavy metal contaminated soils.