【摘要】 用平衡法研究了有机酸对土壤胶体吸附 解吸Cd2 + 的影响。结果表明 ,黄棕壤、红壤、砖红壤胶体Cd2 + 最大吸附容量 (Qm)分别为 4 3 7、16 8、1 5 8mmolkg-1。在加入Cd2 + 浓度相同的条件下 ,土壤胶体Cd2 + 吸附量随有机酸浓度的升高呈峰形曲线变化。当有机酸与Cd2 + 共存时 (竞争吸附 ) ,低浓度的草酸 (小于0 5～ 2mmolL-1)或柠檬酸 (小于 0 0 2 5～ 0 2mmolL-1)提高Cd2 + 吸附量 ,高浓度的草酸或柠檬酸能降低Cd2 +吸附量。吸附有机酸后的土壤胶体 (次级吸附 )对Cd2 + 次级吸附量的影响与竞争吸附一致 ,但两者的Cd2 + 吸附量变化幅度不一样。这是由于两种吸附体系液相中有机酸残留浓度不同所致。土壤胶体吸附态Cd2 + 的解吸结果表明 ,草酸浓度不仅影响Cd2 + 的总解吸量、总解吸率 ,还影响土壤胶体表面KNO3 解吸态与DTPA解吸态Cd2 + 的分配比例更多还原

【Abstract】 The effects of organic acids on Cd 2+ sorption desorption in testing soil colloids were studied by batch methods. The results showed the maximum amount of Cd 2+ sorption by yellow brown soil, red soil and latosol was 43 7, 16 8 and 1 58 mmol kg -1 respectively. At the same concentration of Cd 2+ added, the amount of Cd 2+ sorption was generally characterized as peak like curves with the increase of organic acids concentration. When organic acids and Cd 2+ simultaneously were introduced in testing systems (competitive sorption), lower concentration of oxalic acid (<0 5 ～2 mmol L -1 ) or citric acid (<0 025 ～0 2 mmol L -1 ) promoted Cd 2+ sorption, and higher concentration of them decreased the Cd 2+ sorption amount. The effect of Cd 2+ sequential sorption on the soil colloids previously adsorbed organic acids (sequential sorption) was almost same as that of competitive sorption, however, the variation of both amount of Cd 2+ competitive sorption and sequential sorption were not same. Its reason was related to content of residual organic acids in both sorption systems. The results of desorption tests demonstrated that the concentration of oxalic acid impacted total amount and total rate of Cd 2+ desorption as well as distribution ratio of Cd 2+ desorbed by KNO 3 and by DTPA on surfaces of testing soil colloids.更多还原