Synthesis of substrates for reverse osmosis membranes

Abstract

Polysulfone (PS) flat sheet ultrafiltration (UF) membranes were synthesized by phase inversion method, using a mixture of n,n-dimethylacetamide (DMAc) & n-methyl-2-pyrrolidinone (NMP) as solvent and water as precipitation medium. Four batches of experiments were conducted, with the addition of different additives to the base casting solutions and comparisons were made between blend membranes and membranes without additives. The influence of additives, nano-sized TiO2 particles both with and without modification, and polyvinyl pyrrolidone (PVP), to the base casting solutions as well as prepared membrane thickness on the morphologies, physical properties as well as membrane performance were investigated. The prepared UF membranes were characterized through several analytical methods, namely, viscosity measurements, scanning electron microscope (SEM) observations, contact angle measurements and permeability tests. Results suggested that UF membrane properties were improved by the additives. Particularly, due to PVP’s hydrophilic nature, the surface of blend membranes were much more hydrophilic than membranes with only pure PS contents. The PS membranes blend with 2 wt.% modified TiO2 and 3 wt.% PVP showed the largest porosity and the highest flux among four batches.