Modification and characterization of prepared polysulfone ultrafi ltration membranes via photografted polymerization: Effect of different additives

Abstract

The modified ultrafi ltration (UF) membranes were prepared by graft polymerization of acrylic acid (AA) that is a hydrophilic monomer onto the surface of ultrafi ltration membranes. Primary UF membranes were formed by wet phase inversion method by using polysulfone (PSf)/ N-methylene-2-pyrrolidone (NMP)/ poly (ethylene glycol) (PEG) casting solution and water coagulant. PEG acts as a pore-former that in this study is used in a wide range of molecular weights (M.W.) from 600 to 20000 Da. Changing the molecular weight of PEG additive, controls the structure and permeation properties of membranes. It can be observed that an increase in the molecular weight of PEG additive leads to an increase in water permeability. By increasing the irradiation time, rejection of dye and PEG increases, although solution permeability decreases. Increasing PEG rejection by increasing irradiation time shows the developing sieving mechanism by grafting and reduction in pore size. Grafting of AA onto membrane surface is confi rmed by InfraRed spectra (IR). Scanning electron microscopy (SEM) images show a signifi cant increase in membrane pore size than the one prepared from PEG 20000 Da, but its permeability is not too high to attribute to incomplete exit of this additive. Modifi ed membrane prepared from PEG600 (tirr = 30 min and [AA] = 6%) have desirable performance in separation of these dyes but other membranes prepared from higher M.W. PEG are not effective in separation of dyes. It was observed that this membrane showed acceptable performance both in terms of fl ux and rejection and has the characteristics of a NF-type membrane. © 2009, Taylor & Francis Group, LLC.