不同电解质体系中土壤胶体凝聚动力学的动态光散射研究

利用动态光散射技术研究在不同浓度的KNO3和Mg(NO3)2中土壤胶体颗粒的凝聚过程动力学. 通过分析凝聚过程中光强和有效粒径随时间的变化得到: (1)根据凝聚过程中光强的稳定与否, 可以判断土壤胶体凝聚过程中碰撞的发生是由布朗运动支配还是由重力作用支配; (2)在不同的电解质体系下土壤胶体凝聚表现为快速凝聚特征或不同的慢速凝聚特征, 并且在慢速凝聚中存在一个对重力敏感的电解质浓度; (3)两种电解质作用下的土壤胶体凝聚特征相似, 但对Mg(NO3)2体系浓度变化的敏感性远远大于KNO3体系. 此外, 通过分析凝聚平均速率随电解质浓度的变化, 找到慢速凝聚与快速凝聚的电解质浓度转折点, 即临界絮凝浓度(CFC), 提供了一个实验测定CFC的可能方法.

Dynamic Light Scattering Study on the Aggregation Kinetics of Soil Colloidal Particles in Different Electrolyte Systems

Soil colloidal aggregation kinetics was studied at different concentrations of KNO3 and Mg(NO3)2 by dynamic light scattering. By analyzing the change in light intensity and effective diameter of aggregates with time, we conclude that: (1) The stability of the light intensity in an aggregation process is a basis for judging if the collision is dominated either by Brownforce or gravity; (2) With different electrolyte systems, soil colloidal aggregation exhibits a fast diffusion-limited cluster aggregation (DLCA) character or various slowreaction limited cluster aggregation (RLCA) characters and a gravity sensing electrolyte concentration exists in RLCA; (3) The aggregation characters induced by two electrolytes are essentially similar but the aggregating process is more sensitive to the Mg(NO3)2 electrolyte concentration change than to KNO3. By analyzing the change of average aggregation velocity with electrolyte concentration, the turning point where electrolyte concentration changes from slow to fast aggregation is designated as the critical flocculation concentration (CFC). A new method for measuring the CFC experimentally is thus provided.