Ultrafiltration membranes prepared via mixed solvent phase separation with enhanced performance for produced water treatment

Ultrafiltration (UF) is a promising membrane process to remove surfactant-stabilized oil emulsions from produced water (PW). However, UF membranes prepared by conventional methods have suffered from low permeate flux and are susceptible to fouling due to the sparsity of pores on the surface. In this study, we used our recently developed mixed solvent phase separation (MSPS) method to fabricate a highly porous poly (vinylidene fluoride) (PVDF) ultrafiltration membrane for the treatment of produced water. The prepared MSPS PVDF membrane showed an asymmetric high-porous structure with a surface porosity of 23.66% and a narrow pore size distribution of 40 ± 19 nm. The MSPS PVDF membrane showed almost complete oil removal and high oily water permeance above 300 L m−2 h−1·bar−1 even after 72 h of continuous testing, which is an order of magnitude higher than the commercial PVDF membranes. In addition, the MSPS PVDF membrane showed excellent regeneration and recovery capabilities with a flux recovery ratio of 97% without any chemical cleaning, making the process economically and environmentally more viable. Moreover, we achieved optimal membrane performance without any further surface modification processes.