Effects of solvent compositions on physicochemical properties and anti-fouling ability of PVDF microfiltration membranes for wastewater treatment

Polyvinylidene fluoride (PVDF)-based microfiltration membranes applied in membrane bioreactor for wastewater treatment were prepared by immersion-precipitation method. The effects of different solvent compositions such as N-N dimethylformamide (DMF). N-N dimethylacetylamide (DMAC), triethyl phosphate (TEP), dimethyl sulphoxide (DMSO) and the mixed solvents on physicochemical characteristics of the final membranes were studied. The membrane permeability and fouling performance were assessed via pure water flux and critical flux experiments, respectively. Experimental results proved that the formation of the top-layer of the PVDF membranes prepared from different solvents was controlled by the equilibrium thermodynamics, whereas the sub-layer of those membranes was dominated by the diffusion rate of solvent-dnonsolvent. Furthermore, the mixture of reagents facilitated the formation of porous top-layer and the finger-like pore except for DMF and TER There was no significant correlation found between the solvent compositions and the hydrophilicity of the membranes. However, the membranes prepared with DMSO as the solvent or part of the solvents exhibited more negative charge and greater permeability than the membranes without DMSO in the casting solution, and these properties were supposed to improve the critical flux value and mitigate the membrane fouling potential. (C) 2012 Elsevier B.V. All rights reserved.