土壤胡敏酸的解离及其与Cu^(2+)的络合特征

Characteristics of soil humic acid dissociation and its complexation with copper

通过电位滴定法及恒定容量模式 (CCM)研究了 2种土壤胡敏酸的解离特性及其与Cu2 + 的络合特征 ,结果证明在pH3— 7范围内胡敏酸表现为 2种一元酸组成的混合酸 ,实验数据适用于静电模式 .胡敏酸的解离常数和Cu2 + 的络合常数应用计算机程序FITEQL32表明 ,优化的解离常数pKHL1在 3.5 0— 4.89之间 ,pKHL2 在 6 .17— 8.38之间 ,2种形态一元胡敏酸解离常数之比小于 10 5,与滴定曲线只有一个突跃区相一致 .2种土壤胡敏酸与Cu2 + 络合常数logKintACu大小分别为土HA1 346 ,黑垆土HA 2 2 41。

Potentiometric titration and CCM were performed the study on humic acid extracted from soils.Results showed that humic acid is a mixture of two monoprotic acids and it fits the electrostatic model in CCM at pH3—7 .The dissociation constants and Cu complexation constants were determined by the optimization procedure in the computer program FITEQL32.The dissociation constants p K HL1 is in the range of 3\^50 to 4.89, p K HL2 6.17 to 8.38, K HL1 / K HL2 is below 10 5, which is consistant with the results of potentiometric titration curve. The Cu 2+ complexation constant,is 1.346 for old manured loessal soil and 2.241 for dark cultivated loessal soil.A good optimization result is given by nonelectrostatic model.