海水中重金属离子络合形态的研究(Ⅰ)——二阶导数卷积悬汞电极溶出伏安法

Studies on the Complex States of Heavy Metal Ions in Seawater (Ⅰ)——2nd Order Derivative Convolution Stripping Voltammetry at HMDE

本文推导了络合体系中悬汞电极二阶导数卷积阳极溶出峰电势与络合物累积稳定常数的关系式,在模拟海水离子强度溶液中,测定了一系列简单金属离子及其络合物的溶出峰电势差,用电子计算机进行数学回归分析作曲线拟合,求得了Cd(Ⅱ)-SO_4~2络合体系的各级累积稳定常数,并对海水中镉(Ⅱ)的存在形态作了综合估算。

The relationship between the complex stability constants and peak potential of 2nd order derivative convolution anodic stripping voltammetry at HMDE has been established. The expression is as follows:where the metal ions exist as free state and therefore The shift of peak potential varies with the concentration of the ligand, the differences between the peak potential of free metal ions and that of the complex ions are measured at constant ionic strength and various concentrations of the ligand. Therefore can be calculated and mathematically regressed with computer, from the curve fit, the cumulative stability constants can be obtained. This method is highly sensitive, convenient and rapid.The cumulative stability constants for Cd(Ⅱ)-SO2-4 complex determined by this method at the analog ionic strength of seawater (I=0. 70) are lgβ1 = l. 56, lgβ2=1. 99 and lgβ3=2. 25. The concentration of cadmiun was 8×10-8 mol/L with NaClO4 as supporting electrolyte at pH 2. 50. The species of Cd(Ⅱ ) in sea water are as follows; CdCl2-n(97. 7%); Cd(SO4)2-n4(l. 2%); Cd(H2O).2+n (1. 01%);Cd(OH) + (0. 005%), CdBr.2-n4(0. 077%).