Pb和Cd在塿土不同剖面土壤中的竞争吸附作用

Competitive Adsorption Behavior and Mechanism toward Pb and Cd at Different Tier Soil Profiles

多种金属离子的共存影响土壤对重金属离子的吸附作用,从而影响其生物有效性和迁移特征。利用等温吸附方法研究了塿土不同发育层次土壤对Pb^(2+)、Cd^(2+)单一离子和两种离子共存的吸附特征。对于单一的离子吸附,Pb^(2+)在塿娄土耕层、黏化层和钙积层的分配系数为8.0、8.1和6.1,Langmuir方程最大吸附量为6.1、5.8和6.0 mmol kg^(-1);而Cd^(2+)的分配系数为4.2、7.1和4.7,最大吸附量为5.5、4.8和2.9 mmol kg^(-1);三种土壤对Pb^(2+)的吸附性能均强于对Cd^(2+)的吸附。当Pb^(2+)、Cd^(2+)共存时,两种离子间存在竞争吸附作用,致使Pb^(2+)、Cd^(2+)的吸附量均降低,Pb^(2+)、Cd^(2+)互为竞争性吸附离子的亲和力效应在0.8~0.9之间,竞争性的Langmuir吸附方程可用于描述Pb^(2+)、Cd^(2+)的竞争吸附。

The coexistence of various metal ions can affect their adsorption by soil, thus will affect the bioavailability and migration of these ions. The adsorption characteristics of single and competitive adsorption of Pb^2＋ and Cd^2＋ by different layers of Tier Soil were studied through batch adsorption experiences. The distribution coefficient of Pb^2＋ were, respectively, 8.0, 8.1 and 6.1, the maximum adsorption capacities of Langrnuir equation were, respectively, 6.1, 5.8 and 6.0 mmol kg^-1, the distribution coefficient of single Cd^2＋ were, respectively, 4.2, 7.1 and 4.7, and the maximum adsorption capacities of Langrnuir equation were, respectively, 5.5, 4.8 and 2.9 mmol kg^-1 at cultivated, claying and calcic layer of Tier Soil. Pb^2＋ had stronger adsorption capacity than Cd^2＋ in three soils. The adsorption capacities of Pb^2＋ and Cd^2＋ decreased due to their competitive adsorption when they coexisted. The affinity effect between Pb^2＋ and Cd^2＋ was 0.8 - 0.9. And the competitive Langrnuir adsorption equation could be employed to describe the competitive adsorption of Pb^2＋ and Cd^2＋ with high determined coefficient.