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

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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. ***