Influence of intermolecular interactions of concentration polarization during crossflow membrane filtration

摘要

Intermolecular interactions between colloidal or maacromolecular solutes influence their solution properties significantly, thus affecting the flux decline and solute retention behaviors during membrane filtration. Here we present a theoretical approach for incorporating these inteeractions directly in a model of conentration polarization during crossflow membrane filtratioin. Modeling of conentration polarization usually involves solution of the convective - diffusion equation coupled with the osmotic pressure governed permeate transport relatioship. Two parameters in this model, namely, the diffusion coefficient and the osmotic pressure, are influenced by the inter-particle interactions. The methodology presented here considers a DLVO-type interaction in a statistical mechanical theory (Ornstein-Zernicke integral equation with the hypermentted chain closure) to determine the pair correlation function. Using the pair correlation function in the equation of state yields the osmotic compressibility. A second property of the solution, the sedimentation coefficient, is obtained by considering the phydoynamic and intermolecular interactions. The concentration dependent diffusion coefficient of the system is then derived from the osmotic compressibility and the sedimentation coefficient. Finally, the permeate flux is predicted by introducing the concentration dependent diffusivity and the osmotic compressibility in the concentration polarization model.