Cu、Cd在2种土壤上的吸附特征

研究了ｃｕ２＋、Ｃｄ２＋在法国２种不同土壤上的吸附特征，并讨论了引起这２种元素吸附差异的可能原因·Ｃｕ２＋、Ｃｄ２＋的吸附量和吸附率均随ｐＨ的升高而升高，在近中性时完全被吸附．吸附量和吸附率均表明Ｃｕ２＋的吸附比Ｃｄ２＋高．Ｃｕ２＋和Ｃｄ２＋在水解作用、沉淀作用、与腐殖质的络合强度以及与Ｃａ２＋、Ｈ＋离子吸附点位的竟争能力等方面的差异是导致这２种离子吸附差异的主要原因．低初始浓度时Ｃｕ２＋的吸附量、吸附率随ｐＨ位变化而变化幅度小于高初始浓度．Ｃｄ的吸附也有类似规律．但不如Ｃｕ明显．土壤的ｐＨ值、ＣＥＣ和粘粒含量均影响土壤对这２种离子的吸附．

Adsorption Characteristics of Cu and Cd on Two Kinds of Soil

The adsorption characteristics of Cu2+ and Cd2+ on two different kinds of soil collected from France was studied and the causes for the difference of adsorption characteristics between Cu2+ and Cd2+ were discussed.The adsorbing capacity and rate of adsorption of Cu2+ and Cd2+ were increasing while pH increased, and Cu2+ and Cd2+ were completely adsorbed when the pH was near 7.Cu2+ was more strongly adsorded than Cd2+ as reflected by the adsorbing capacity and the rate of adsorption.The above difference was mainly caused by the difference of hydrolysis,precipitation,the intensity of complexation with humus and the competition for adsorption sites with Ca2+ and H+ ions between Cu2+ and Cd2+.The adsorbing capacity and rate of adsorption of Cu2+ changed with pH more strikingly at low original concentrations than at high ones.Cd2+ showed a similar but less striking tendency of adsorption.This was attributed to the existence of two different kinds of adsorption sites.The Grignon soil adsorbed more Cu2+ and Cd2+ than the Bordeaux soil because the clay content, CEC and pH value of the former were all higher than the later.