Effect of dispersed phase on reducing concentration polarization

Abstract

Concentration polarization is an important limitation in the performance of pressure-driven membrane processes, such as hyperfiltration, ultrafiltration and microfiltration. Various methods have been developed to minimize the transient build-up of retained solutes. In this paper, introduction of a dispersed phase to induce turbulence at the membrane surface is proposed as an effective strategy to combat the deleterious effects of concentration polarization. A mathematical model has been developed to explain the formation of concentration polarization in a membrane tube during turbulent flow conditions. The theoretical model is based on the concept of energy spectrum of the turbulent flow field and its modification to account for the presence of dispersed phase. It has been shown that the density ratio of dispersed phase to continuous phase and the ratio of particle diameter to membrane tube diameter have considerable effect on concentration polarization. At moderate Reynolds number, reduction in concentration polarization is greater and effective. The theoretical model for concentration polarization has been validated using experimental data, presented in the literature.