2种水稻土中Cu(Ⅱ)和Pb(Ⅱ)的解吸动力学

用一次平衡法研究了2种水稻土表面吸附态Cu(Ⅱ)和Pb(Ⅱ)的解吸动力学行为及柠檬酸和酒石酸对2种重金属离子解吸的影响。结果表明,虽然2种土壤对Pb(Ⅱ)的吸附量比Cu(Ⅱ)高得多,但无论在单一重金属体系还是Cu(Ⅱ)和Pb(Ⅱ)共存体系中,Cu(Ⅱ)的解吸量均大于Pb(Ⅱ),湖州水稻土Cu(Ⅱ)的解吸量大于嘉兴水稻土,说明土壤对重金属离子的吸附亲和力越大,吸附的重金属离子越不易解吸。用E lovich方程拟合动力学数据可以获得比较满意的结果。解吸速率与时间的关系曲线表明,Cu(Ⅱ)和Pb(Ⅱ)的解吸速率随时间的增加迅速减小。Cu(Ⅱ)的解吸速率大于Pb(Ⅱ),柠檬酸和酒石酸不仅使重金属的解吸量增加,而且使Cu(Ⅱ)和Pb(Ⅱ)的解吸速率大大提高。2种有机酸对Cu(Ⅱ)解吸的促进作用大于Pb(Ⅱ),柠檬酸的促进作用大于酒石酸。

Desorption Kinetics of Cu(Ⅱ) and Pb(Ⅱ) in Two Paddy Soils

Desorption kinetics of Cu(II) and Pb(II) in two paddy soils and effects of citric and tartaric acids on desorption of Cu(II) and Pb(II) were investigated with a batch method.Results show that although much more Pb(II) than(Cu(II)) was adsorbed by the soils,more Cu(II) than Pb(II) was desorbed in either single metal system or bi-metal system.The findings suggest that the greater the adsorption affinity of a soil for a heavy metal,the more difficult the desorption of the heavy metal from the soil.The Elovich equation (Q_t=a blnt) can be used to fit the kinetics data with fairly satisfactory results,which indicates that the desorption rate of Cu(II) and Pb(II) decreased sharply with the time going on.Constant b in the Elovich equation can be used to compare desorption rates in different systems.The desorption rate of Cu(II) was greater than that of Pb(II).The presence of citric and tartaric acids increased desorption of heavy metals in both quantity and rate,especially Cu(II). The effect of citric acid was greater than that of tartaric acid.