模拟酸雨条件下Cd^(2+)在土壤及其矿物表面的解吸动力学特征  

Kinetic Characteristics of Cd^(2+) Desorption in Minerals and Soils under Simulated Acid Rain

作　　者：王代长[1] 蒋新[1] 卞永荣[1] 郜红建[1] 焦文涛[1] 

机构地区：[1]中国科学院南京土壤研究所,南京210008

出　　处：《环境科学》2004年第4期117-122,共6页Environmental Science

基　　金：国家自然科学基金资助项目 ( 4 0 0 710 46;40 2 0 10 2 5 ) ;国家重点基础研究发展规划项目 ( 19990 1180 1 3 )

摘　　要：利用流动搅动法研究在模拟酸雨条件下土壤和矿物表面Cd2 + 的解吸动力学特征 ,结果表明 ,Cd2 + 的解吸动力学能用一级动力学描述 ,红壤和针铁矿上Cd2 + 解吸率为 70 %～ 1 0 0 % ,砖红壤和高岭土上解吸率为 2 5 %～ 5 0 % ;砖红壤上Cd2 + 解吸动力学可用扩散方程描述 ,但该方程并不适合描述红壤、针铁矿和高岭土上Cd2 + 的解吸 ;Elovich方程在描述Cd2 + 解吸时比双常数方程和抛物线扩散方程要好 ,这也说明Cd2 + 的解吸为一非均相扩散过程 .Cd2 + 的解吸过程分为快反应和慢反应 ,快反应过程在 6 0min内完成 (除砖红壤外 ) ,随后达到平衡状态 .Cd2 + 在土壤表面的快反应与交换态Cd2 + 有关 ,边面羟基化的键合点位与Cd2 + 亲和力的不同是导致Cd2 + 解吸速率和解吸量差异的原因 .流出液 pH值的上升反映出土壤表面存在质子的消耗 ,这可能与硫酸根的专性吸附释放羟基和矿物表面的质子化有关 。The kinetic characteristics of Cd 2+ desorption in minerals and soils under simulated acid rain were studied by using the flow-stirred method. It showed that Cd 2+ desorption could be described by first-order kinetics. Percents of desorption amounts of Cd 2+ calculated were 70%～100% in red soil and goethite, and 25%～50% in latosols and kaolinite. Parabolic diffusion could describe Cd 2+ desorption kinetics in latosols and not suitable for red soil and goethite and kaolinite. Cd 2+ desorption, regarded as a heterogeneous diffusion in minerals and soils, could be fitted by Elovich equation more than Parabolic diffusion and two-constant equation. Cd 2+ desorption could be divided into fast reaction and slow reaction. Except for latosols, fast reaction would be over during 60 min and be close to quasi-equilibrium. Adsorption forms of Cd 2+ in soil surface could be exchangeable and specific. Fast reaction was relative to easily desorbed Cd 2+ . The affinity of edge hydroxyl to Cd 2+ would lead to the difference of Cd 2+ desorption rate and amounts. Increase of pH value in effluent indicated H+ consumption in the processes of Cd 2+ desorption.

关 键 词：镉离子 解吸动力学 土壤 矿物 土壤酸化 

分 类 号：X131.3[环境科学与工程—环境科学]