Effect of stretching on continuous oil/water separation performance of polypropylene hollow fiber membrane

Abstract

In this work, polypropylene (PP) hollow fiber membranes were fabricated by thermal-induced phase separation method. The influence of cold-stretched and hot-stretched treatment on the morphology and permeability of the PP hollow fiber membranes was investigated. The results showed that there were cracks and crystalline particulate structures on the outer and inner surfaces of the stretched PP hollow fiber membranes, which were not isolated but linked together through fiber-like connections. Compared to the original PP hollow fiber membrane, the mean pore sizes, the porosities, the hydrophobicity and water entry pressure of the stretched PP hollow fiber membranes improved significantly. When applied in conjunction with a vacuum system, the PP hollow fiber membranes could continuously remove oils from water surface, and separate surfactant-free and surfactant-stabilized water-in-oil emulsions, as well. The initial kerosene fluxes of the hot-stretched PP hollow fiber membrane were higher than that of the membranes prepared from original PP hollow fibers or cold-stretched PP hollow fibers. The permeate fluxes of the hot-stretched PP hollow fiber membrane for all different emulsion separations were higher than those of the original PP hollow fiber membrane. There could be seen no emulsion droplet in the optical micrographs after separation, indicating that the water-in-oil emulsions were effectively separated in one-step method.