可变电荷土壤和恒电荷土壤Cl-吸附特性的研究

对不同浓度KCl和不同pH下，3种可变电荷土壤和4种恒电荷土壤Cl-吸附量进行了测定。结果表明，土壤Cl-吸附量随平衡Cl-浓度C（e）增加而增大，恒电荷土壤呈线性，可变电荷土壤在添加Cl-0.5~5.0mmol/L下，符合Langmuir吸附等温式。同一浓度下的Cl-吸附量及其随浓度增加的速率均为砖红壤>红壤>赤红壤>黄棕壤>棕壤、暗棕壤和黑土，与这些土壤所带正电荷量顺序相一致。Langmuir方程K值较小且几种土壤差异不大。恒电荷土壤对Cl-的吸附量很小，在浓度较低时常出现负吸附，其吸附机理可能更多的是与K+吸附时的同时吸附。7种土壤Cl-吸附量均随pH增加而降低，但降低强度可变电荷土壤远大于恒电荷土壤。

Characteristics of Cl- adsorption by constant charge soils and variable charge soils.

The adsorption of chloride ions by three variable charge soils and four constant charge soils of China were measured under different pH and various concentrations of KCl. The results showed that although the amount of Cl- adsorbed by soils increased with increasing Cl- concentration, the linear relationship was only found in constant charge soils. For variable charge soils, within the range of 0.5 to 5 mmol/L of Cl- added, the adsorption can be described by the Langmuir equation satisfactorily. And the adsorption energy parameter (K) calculated from the equation was similar in magnitude. When equal Cl- added, the amount of Cl- adsorption by different soils decreased in the sequence Latersol > red earth > red latersol > yellow brown earth > brown earth, dark brown earth and black soil, which was agreed with the order of their positive charges. The adsorption of chloride by constant charge soils, which caused by co-adsorption with K+ mainly, was a little and a negative adsorption was usually observed at low concentrations. The adsorption of Cl- decreased with increasing with pH. However, the decreasing speed was higher in variable charge soils than that in constant charge soils.