海水中悬浮粒子的微电泳研究 Ⅰ针铁矿、δ-Mno_2的电泳淌度与酸度、重金属离子及有机物浓度的关系

A MICROELECTROPHORETIC STUDY ON THE SUSPENDED PARTICLES IN SEA WATER Ⅰ.THE EFFECT OF PH, TRACE METAL IONS AND ORGANIC MATTERS ON THE ELECTROPHORETIC MOBILITY OF GOETHITE AND δ-MnO_2

本文用微电泳的方法研究了针铁矿及δ-MnO_2悬浮粒子的电泳行为。支持电解质的离子强度影响淌度的大小,但不改变等电点(IEP)。重金属离子在悬浮粒子上的吸附,使pH高于IEP时的表面电荷由负变正,而在pH低于IEP时影响不大。 小分子量的有机物如氨基酸对悬浮粒子的淌度影响不大,而大分子量的有机物如腐殖酸使IEP左移。天然海水,河水等对悬浮粒子表面电荷的影响是其中的有机物使IEP左移的结果,故天然水体中悬浮粒子无例外地均荷负电。

The electrophoretic behavior of goethite and δ-MnO2 suspended particles is studied with a microelectrophoreis apparatus. The ionic strength of the supporting electrolytes affects the value of the electrophoretic mobility, but does not change the IEP(Iso-electric point) of a given kind of particle. The adsorption of trace metals on the suspended particles changes the sign of surface charge of particles in the range of pH with values greater than IEP, and has little effect in low pH range.Organic matters with small molecule weight such as amino acid show little effect on the mobility of hydrated metal oxides but organics with large molecular weight such as humic acid make the IEP shift leftwards. Natural waters, (seawater, river water etc.) show great effect on the surface charge of hydrated metal oxides particles. The organic content in natural water is responsible for the shift of the IEP. therefore, all suspended particles in natural water systems are, without exception, negatively charged.