Mechanisms of Concentration Polarization and Cake Formation in Crossflow Membrane Filtration of Aqueous Colloidal Particles

本研究的目的是在微观层面上对横流膜过滤过程中浓度极化和滤饼形成的热力学和微观流体动力学有一个全面的认识。重点将放在从浓度极化层中无序的类液相到有序的类固体饼层的过渡点的识别上。研究将涉及以下任务：1)胶体分散平衡结构的预测，2)渗透压、沉降系数和扩散系数的评价，3)横流膜过滤条件下胶体体系液固过渡点的预测，4)浓度极化和/或滤饼形成的程度以及由此导致的渗透通量下降行为的预测。5)选择模型实验系统对理论进行验证。6)在不同背景电解质浓度、颗粒浓度、pH、横流速度和操作压力下，使用模型胶体分散体对上述理论方法进行实验验证。本研究可望为胶体分散体横流膜过滤渗透通量下降行为的定量研究提供良好的理论基础。随着膜处理技术，特别是纳滤和超滤技术在自然和废水处理中变得越来越可行，这些结果将变得越来越重要，因为这些技术提供了一种全面的方法来满足无数溶解和胶体污染物的多重水质目标。＊＊＊

0114527 Elimelech The objective of this research is to provide a comprehensive microscopic-level understanding of the thermodynamics and micro-hydrodynamics of concentration polarization and cake formation in crossflow membrane filtration. A major emphasis will be placed on the identification of the transition point from a disordered liquid-like phase in the concentration polarization layer to an ordered solid-like cake layer. The research will involve the following tasks: 1) Prediction of the equilibrium structure of a colloidal dispersion, 2) Evaluation of the osmotic pressure, sedimentation coefficient and diffusion coefficient, 3) Prediction of the liquid-solid transition point in colloidal systems under crossflow membrane filtration conditions, 4) Prediction of the extent of concentration polarization and/or cake formation and the resulting permeate flux decline behavior, 5) Selection of a model experimental system for validation of the theory and 6) Experimental validation of the above theoretical approach using model colloidal dispersions at various background electrolyte concentrations, particle concentrations, pH, crossflow velocities and operating pressures. This research is expected to lead to a sound theoretical basis for quantification of permeate flux decline behavior in crossflow membrane filtration of colloidal dispersions. These results will become increasingly important as membrane processes, particularly nanofiltration and ultrafiltration, become more viable for treatment of natural and waste waters because these technologies offer a comprehensive approach to meeting multiple water quality objectives for a myriad of dissolved and colloidal contaminants. ***