道南膜技术测定CaCl_2溶液体系中汞的化学形态

MEASURING MERCURY SPECIATION IN CaCl_2 SOLUTIONS USING DONNAN MEMBRANE TECHNIQUE

尝试并探索道南膜技术(DMT)测定溶液体系中Hg化学形态的方法条件.结果表明,0.01mol.l-1CaCl2作为背景溶液时,跨过阳离子交换膜的Hg主要形态并非阳离子而是HgCl2和HgCl3-.Hg在阳离子交换膜内扩散为限制Hg跨膜传输的主要因素.Hg在阳离子交换膜内的吸附除静电吸附外还存在结合力更强的化学吸附,成为限制道南膜技术用于Hg形态测定的主要因素.采用动力学DMT方法,缩短试验时间至8h以内,可在一定程度上降低Hg的化学吸附,为DMT方法测定土壤溶液体系中Hg的化学形态提供可能.

The optimal method conditions and theoretical basis of Hg species measurement using Donnan Membrane Technique（DMT）were explored.It was found that when 0.01 mol·l-1 CaCl2 was used as background solution,HgCl2、HgCl-3 were the main contributors to the flux of Hg transport through the cation exchange membrane.The rate-limiting step of Hg transport from the donor side to acceptor side is Hg diffusion in the membrane.Besides electrostatic adsorption of Hg,there is strong chemical adsorption of Hg in the membrane,which plays as an important role in restricting the applicability of DMT on Hg species measurement.The chemical adsorption of Hg can be reduced by shortening the sampling time to 8 hours and Hg species in the donor side can be calculated using the dynamic DMT method,which shows the possibility to measure Hg speciation in soil solution by DMT.