Effect of solvents on performance of polyethersulfone ultrafiltration membranes: investigation of metal ion separations

摘要

The new polyethersulfone (PES) based ultrafiltration membranes were formed using a two stage process ofuddry and wet phase inversion in non solvent coagulation bath. The effects of three different solvents such as, N,udN-dimethylformamide (DMF), N-methyl-2-pyrrolidone (NMP) and Dimethyl sulphoxide (DMSO) of 82.5%udand 85% concentrations on the performance of final membranes were extensively investigated. Scanningudelectron microscopy (SEM) image results proved that PES membranes with an asymmetric structure wereudsuccessfully formed. The number of pores formed on the top layer of PES membranes using above-mentionedudthree solvents was the result of the combined effect of the thermodynamic properties of the systemud(composition, concentrations, and phase behaviour) and membrane formation kinetics, whereas, theudformation of the macroporous sub layer of those membranes was controlled by the diffusion rate of solvent–udnonsolvent. The flux of pure water, membrane resistance, mechanical stability, molecular weight cut-offud(MWCO) and separation performance of the PES membranes were studied. Separation of metal ions fromudaqueous solutions was studied for Ni(II), Cu(II) and Cr(III) using two complexing polymer ligands: polyvinyludalcohol (PVA) and poly(diallyldimethylammonium chloride) (PDDA).The separation and permeate rate (flux)udefficiencies of the new membranes are compared using different solvents and different PES/solventudcompositions.