Fabrication of a novel dual-layer (PES/PVDF) hollow fiber ultrafiltration membrane for wastewater treatment

In this study, a dual-layer hollow fiber ultrafiltration (UF) membrane was fabricated by the inner layer of poly(vinylidiene fluoride) (PVDF) via thermally induced phase separation (TIPS) method and the outer layer of poly(ether sulfone) (PES) via non-solvent induced phase separation (NIPS) method, respectively. The dope solution composition of the inner layer and outer layer and the intermediate-treatment agent between the two layers were studied. The mechanical strength of the dual-layer membrane was larger than that of the inner layer. The increased mechanical strength was attributed to two parts: the formation of the interfacial layer resulting from the penetration and dissolution effects of the outer layer dope solution into the inner layer, and the outer layer with high mechanical strength. The structure near the interface was controlled by the intermediate-treatment agents between the two layers. By decreasing the PVDF solubility of the intermediate-treatment agents, the porosity of the inner layer near the interface was increased, the pure water flux of the resultant membrane was improved and the dextran rejection was maintained. In addition to exhibiting a high rejection of bovine serum albumin protein molecules, the newly developed UF membranes have high tensile strengths of 10.1-11.1 MPa with molecular weight cut-offs (MWCO) of 33-292 kDa and pure water fluxes of 43-90 L m−2h−1 bar−1. Such a novel UF dual-layer hollow fiber membrane is an attractive candidate for the effective treatment of municipal wastewater.