腐植酸与Cd、Zn的络合特性研究

通过离子交换平衡法测定了胡敏酸的2 个不同分子量分级组分及富里酸与Cd 、Zn 络合反应的稳定常数及配位数,结果表明:随着腐植酸芳构化程度的提高,其与Cd 、Zn 的络合物的配位数及稳定常数也逐渐提高;当胡敏酸的分子量为48339 时,其对Cd 、Zn 的络合物稳定常数log K 值分别为5-20 和4-81 ,配位数分别为1-26 和1-15 ;而当分子量增加为78180 时,logK 值分别为5-68 和5-37 ,配位数分别为1-32和1-26 。富里酸 镉、锌的稳定常数( 分子量为2300) 分别为4-44 和4-42 ,配位数分别为1-29 和1-30 。这些结果表明,就减轻污染土壤中Cd 、Zn 对植物的危害而言,施用厩肥等芳构化程度较高的有机物比芳构化程度低的更为有效。

STUDIES ON CHARACTERISTICS OF COMPLEXATION OF Cd AND Zn WITH HUMIC ACIDS

The mechanism of complexation of Cd,Zn|humic substance by ion|exchange method was studied.The results showed that the stability constans(log?K) and coordination numbers of cadmium,zinc|humic acids complexation increased gradually with the complicated structure of humic acids.The stability constants(log?K HA ) and coordination number of Cd,Zn|humic acid changed with the molecular weight of graduations of humic acid.When the molecular weight was 48339,the stability constants of Cd|humic acid and Zn|humic acid were 5 20 and 4 81,respectively,and their coordination numbers were 1 26 and 1 15,respectively.However,when the molecular weight was 78180,the stability constants were 5 68 and 5 37,respectively,and the coordination number were 1 32 and 1 26,respectively.When the molecular weight was 2300 the stability constants(log K FA ) of Cd|fulvic acid and Zn|fulvic acid were 4 44 and 4 42,respectively,and the coordination numbers were 1 30 and 1 31,respectively.It showed the heavy metal fixation by complexation with the complicated|structure of humic acids,on the contrary,the migration of cadmium and zinc increased by the simplified| struture of humic acids in soil.