Increase in hydrophilicity of polysulfone membrane using polyethylene glycol methyl ether

Abstract

Flat sheet asymmetric polymeric membranes were prepared from homogeneous solution of polysulfone (PSF) by the phase inversion method using N-methyl-2-pyrrolidone (NMP) as solvents. Polyethylene glycol methyl ether (PEGME) of three different molecular weights (550Da, 2000Da and 5000Da) was used as the polymeric additive in the casting solution. The morphology and structure of the resulting membranes were observed by field emission scanning electron microscope (FESEM). The pore number, pore permeability and their distribution and average pore size of the membranes were determined by the liquid–liquid displacement porosimetry (LLDP) method. The permeation performances of the membranes were evaluated in terms of pure water flux (PWF), hydraulic permeability, and solute rejection, while hydrophilicity was evaluated in terms of porosity, equilibrium water content (EWC) and water contact angle. Solution of bovine serum albumin (BSA) of molecular weight 68,000Da was used to study the permeation performance of prepared membranes using a batch membrane cell of 350mL capacity. Results showed that with increase in molecular weight of PEGME, the pore number as well as pore area in membranes increased. Membranes with PEGME of higher molecular weights have higher PWF and higher hydraulic permeability due to high porosity. With increase in molecular weight of PEGME from 550 to 5000, the PWF increased from 17.5 to 227.8Lm−2h−1. Similarly, EWC increased from 59.7% for PEGME 550 to 70.8% for PEGME 5000 membranes. Contact angle was also decreased from 71° for PEGME 550 to 47° for PEGME 5000.