Application of Mg(OH)2 nanoplatelets as pore former to prepare PVDF ultrafiltration membranes

Abstract

Porous polymeric membranes have been widely applied to various water treatment processes. Water flux and retention ratio, which usually counterbalance each other, are two critical factors to evaluate the separating performance of a porous membrane for filtration. In this study, Mg(OH)2 nanoplatelets, which cannot be dissolved in both the casting solution and coagulation bath, were employed as additive to prepare PVDF ultrafiltration membrane via phase inversion method induced by immersion precipitation. After the nanoplatelets (≤4wt%) were completely removed from the Mg(OH)2/PVDF hybrid membrane by the dilute hydrochloric acid, it is exciting to find that both the water flux and retention ratio of final production membranes greatly increased, with a little decrease of mechanical strength. Compared with those membranes prepared with soluble LiCl, the membranes using Mg(OH)2 had a reduced possibility to the formation of cracks on membrane surface. This work suggests that nonsolvent-insoluble but hydrophilic nanoparticles have greatly potential application as additive in the filtration membrane preparation.