Preparation and morphological characterization of narrow pore size distributed polypropylene hydrophobic membranes for vacuum membrane distillation via thermally induced phase separation

Abstract

Isotactic polypropylene (iPP) hydrophobic microporous flat sheet membranes were developed via thermally induced phase separation for vacuum membrane distillation (VMD). The synthesized membranes were characterized by contact angle measurements, poremeter and scanning electron microscopy. The membranes had an asymmetric cross-sectional structure with cellular pores on the skin layer and dendritic pores on the non-skin layers. Pure water and 0.5 mol L − 1 aqueous NaCl solution VMD performance was developed with the resultant membranes. The factors of iPP concentration, iPP melt index and nucleating agent concentration affect pore morphology and performance of the membranes significantly. The formation of the membrane is not very sensitive to quench bath temperature, although temperature has a small effect on porosity. It was found that the diluent agent has a strong effect on the morphology and performance of the membranes; soybean oil is a good diluent agent for preparation of narrow pore size iPP hydrophobic membranes with pore size distribution of about 0.02–0.2 μm.