Impact of pilot-scale PSF substrate surface and pore structural properties on tailoring seawater reverse osmosis membrane performance

Abstract

Recent research pays much attention to the correlations between structural properties of porous substrate and the separation performance of polyamide (PA) thin film composite (TFC) membrane prepared by interfacial polymerization (IP). However, there are limited studies focused on seawater reverse osmosis (SWRO) membrane preparation and optimization. This study reveals profound impacts of substrate surface properties on the separation properties of SWRO membranes, by using different substrates including commercial ultrafiltration (UF) membrane, lab-scale casted polysulfone (PSF) substrate and pilot-scale casted PSF substrates. We demonstrate that the membrane substrates casted using pilot-scale machine led to better SWRO performance than hydrophilic UF membrane or lab-scale casted substrate; and very different SWRO membranes could be made from pilot-scale substrates casted using the same polymer dope solution. These results showed that a high-performance SWRO membrane relies on appropriate substrate possessing the surface properties of relatively hydrophobic, small surface pore size (20-35 nm) and high surface porosity, which directly affect the supply and transport rate of amine for the IP reaction. Our best SWRO membrane exhibits an excellent NaCl rejection of 99.5% together with high water permeance of 1.72 L m−2 h−1 bar−1 under seawater desalination conditions. This work helps pave the way for substrate selection for SWRO membrane fabrication, narrowing the gap between lab-made and commercial SWRO membranes.