Theoretical Analysis of Concentration Polarization Effect on VOC Removal by Pervaporation

Abstract

Pervaporation is an innovative membrane-based separation technology for volatile organic compound (VOC) removal from contaminated groundwater. Concentration polarization is a process phenomenon occurring in pervaporation and several other membrane-based separation technologies. Concentration polarization, defined as concentration gradient of permeating solute between the bulk and the region near the membrane surface, becomes a limiting factor in pervaporation separations using high-performance membrane materials in VOC removal operations. Thus, the ability to predict the impact of concentration polarization upon process performance is highly desirable in process design and optimization. A mathemati-cal model was developed to illustrate the interplay between concentration polarization and process performance in pervapora-tion operation of VOC removal in a membrane channel with rectangular cross section. By incorporating pervaporative mass transfer, laminar hydrodynamics, and boundary-layer theory, the model was built to allow theoretical analysis of the sensitiv-ity of flow velocity, feed concentration, and concentration polarization index (CPI) upon the transmembrane flux and longitu-dinal mass flow.