酸性条件下可变电荷土壤对铜吸附动力学特征

用自行设计的动力学装置，研究了酸性条件下Cu在可变电荷土壤表面的反应动力学吸附特征。结果表明，在酸性条件下，Cu吸附过程分为快反应和慢反应。从一级动力学方程拟合的参数可知，3种土壤的最大吸附量依次为砖红壤〉赤红壤〉红壤，Cu最大吸附量随酸度增加显著下降；用Elovich方程和抛物线扩散方程常数b值，解释离子的表观扩散速率，3种土壤的b值依次为砖红壤〉赤红壤〉红壤，且随酸度的增大而降低。从相关系数的比较看，Elovich方程在描述Cu的吸附数据比一级动力学方程和抛物线扩散方程要差。在Cu吸附过程中，pH为5．5和4．3时，红壤和赤红壤流出液中有质子释放，质子的释放可能涉及铜离子的水解；而砖红壤在pH为5．5有质子的释放，pH4-3时有质子的消耗。当原液pH为3.3和3．8时，都存在质子的消耗。3种土壤H＋的消耗过程有较大的区别，砖红壤上快速消耗H＋鱼-远远大于红壤和赤红壤。反应初期，H＋质子的消耗是快速反应，主要包括土壤交换阳离子的缓冲作用、土壤表面的质子化及硫酸根专性吸附释放的羟基中和H＋质子；而以后的反应中，H＋质子对矿物的溶解是一缓慢过程。

Kinetics of Cu Adsorption by Selected Variable Charge Soils Under Acidic Conditions

Characteristics of the reaction kinetics of Cu adsorption by three variable charge soils under acidic conditions were investigated by using a home-made dynamic device. Results showed that Cu adsorption could be divided into rapid and slow reactions. The maximal capacity of Cu adsorption calculated from the first order equation was in the order of Latosol 〉 Latosolic red soil 〉 Red soil, and decreased with increasing acidity. The half-time values （t1/2）were 249 min, 244 min and 444 min for the pH5.5 treatment of the influent, and 28 min, 99 min and 167 min for the pH3.3 treatment of the influent in the Red soil, Latosolic red soil and Latosol, respectively. The b values of the rate con- stant of Elovich and parabolic diffusion equation, by explaining the apparent diffusion rate of ions, were in the sequence of Latosol 〉 Latosolic red soil 〉 Red soil, and decreased with increasing acidity. The first order kinetics and parabolic diffusion equation were better described than Elovich equation by the comparison of the correlative coefficients. In the processes of Cu adsorption, the pH values of effluent were lower than that of pH5.5 and pH4.3 of the influent in the Latosolic red soil and Red soil, and higher pH3.3 and pH3.8. It showed that the former released H＋ and the latter consumed H＋. The released H＋ could be involved in the hydrolyzation of the Cu ions. The amounts of H＋ consumption in the Latosol were bigger than that in the Latosolic red soil and Red soil. At the initial stage, H＋ consumption was a rapid reaction, which could in- clude cation exchange, the specific adsorption of SO2-4 to release OH- for neutralizing H＋ in the solution,and surface protonation of soil min- erals, while the dissolution of the minerals was a slow process.