Facile preparation of polyvinylidene fluoride substrate supported thin film composite polyamide nanofiltration: Effect of substrate pore size

Abstract

Polyvinylidene fluoride (PVDF) is rarely used as substrate membrane for thin film composite polyamide (PA) nanofiltration (NF) membrane due to its hydrophobic surface pushes water away during interfacial polymerization. According to Jurin's law, the pressure of membrane surface pushed water away is inversely proportional to the radius of membrane pore. In this study, a series of commercial PVDF membranes with pores ranging from 25 to 450 nm were used as substrates in a traditional interfacial polymerization. This preparation process does not need any pre-modification on substrate or specific equipment. It was found that the PVDF substrate pore size greatly influences the morphologies and surface properties of the corresponding TFC PA NF membrane. Only when a PVDF substrate has moderate pore size, such as 50 and 100 nm, could a continuous and defect-free PA layer will be formed, as verified through SEM characterization. The TFC membrane prepared with the PVDF substrate of 100 nm exhibits a 27.0 L m-2 h-1 bar-1 pure water permeance, and a 96.2% Na2SO4 rejection. The facile and effective method demonstrated in this study provides a new thought for the preparation of PVDF substrate supported PA NF membrane.