(723r) Fabrication of Polysulfone Membrane for the Treatment of Oil-in-Water Emulsion

This paper focuses on the fabrication of polysulfone (PSf) membrane for the treatment of oily wastewater coming out from the post-treatment unit of petroleum industries where finely divided oil droplets are uniformly dispersed in large volumes of water. Flat sheet asymmetric polymeric membranes were prepared from homogeneous solution of PSf by phase inversion method. N-methyl-2-pyrrolidone (NMP) and Dimethyl Acetamide (DMAc) were used as solvents separately. Different molecular weights of PVP and PEG were used as the polymeric additives in the casting solution. The morphology and structure of the resulting membranes were observed by scanning electron microscope (SEM). The pore number, pore permeability and their distribution and average pore size of the membranes were determined by the liquid displacement method. The permeation performances of the membranes were evaluated in terms of pure water flux (PWF), equilibrium water content (EWC) and hydraulic permeability. Results show that with increase in molecular weight of PVP and PEG, the pore number as well as pore area in membranes increases. With increase in molecular weight of PEG from 400 to 20000, the PWF increases from 15.3 to 2713.4 L.m ^-2.hr ^-1with NMP as solvent while with DMAc as solvent, the PWF increases from 24.5 to 555.6 L.m ^-2.hr ^-1. The performances of different PSf membranes were evaluated by treating with pure water as well as with laboratory made oil-in-water (o/w) emulsion. Experiments were carried out with different membranes in a semi batch filtration cell made of Teflon and the influence of operating conditions such as transmembrane pressure and feed properties such as initial oil concentration and pH of feed solution on membrane performance were investigated. Results show that the membrane properties such as porosity and hydrophilicity are found to have a significant influence on the permeate flow rate and hence subsequent oil removal. The experimental results showed that oil retentions of almost all the membranes were over 90% and oil concentration in the permeate was below 10 mg/L, which met the requirement for discharge. It was concluded that the ultrafiltration (UF) membranes developed in the study were reasonably resistant to fouling and hence the developed PSf membranes may be considered feasible in treating oily wastewater.