A scalable dual-layer PAN/SAN nanofibrous membrane for treatment of saline oily water using membrane distillation

Abstract

Single-layer hydrophobic membranes are prone to fouling while subjected to a feed containing hydrophobic contaminants. In this study, using the green solvent Dimethyl sulfoxide (DMSO), dual-layer nanofibrous poly-acrylonitrile (PAN)/styrene-acrylonitrile (SAN) membranes were fabricated using the highly productive electroblowing process. Then through a simple hot-pressing process, the desirable hydrophilicity was achieved for PAN/SAN membrane. The water contact angle (WCA) for the top layer fell from 112.2 ± 1° to 37.5 ± 1° after hot-pressing, while the WCA for the bottom layer decreased slightly from 147.1 ± 1° to 142.3 ± 1°. Moreover, an underwater oil contact angle (UOCA) of 158.1 ± 1° was achieved for the PAN/SAN membrane. Direct contact membrane distillation (DCMD) tests were performed for synthetic saline water and synthetic saline oily water. While the permeate flux dropped for the single-layer SAN membrane, the dual-layer PAN/SAN membrane, due to underwater superoleophobicity, achieved a stable permeate flux for 24 h with a nearly complete salt rejection (>99.9 %). This study addresses the pore wetting and declines in the permeate flux of the membrane distillation (MD) application in the treatment of saline oily water by implementing scalable, cost-efficient, and eco-friendly approaches.