Enhanced anti-wetting, slippery-surface membranes engineered for long-term operation with hypersaline synthetic and seawater feeds in membrane distillation

Abstract

This study aimed to prepare a membrane by engineering a “slippery” surface on a polyethersulfone (PES) membrane for long-term, direct-contact membrane distillation (DCMD). Membrane surfaces and wettability were analyzed using field-emission scanning electron microscopy, atomic force microscopy, and attenuated total reflection–Fourier-transform infrared spectroscopy. Contact angles and liquid entry pressures also were measured. The wetting and fouling-resistance competence of the modified PES membrane (PES-M) in DCMD was assessed using two hypersaline feed solutions, i.e., multiple salts (2000 mg L−1 [CaSO4 + CaCO3 + CaCl2∙2H2O + NaCl]) + 20 mg L−1 humic acid (MSHA-F) and Busan seawater feed. The effectiveness of the PES-M membrane against the MSHA-F solution was evaluated over multiple cycles. The membrane was cleaned after each 50-h cycle and successfully reused for three consecutive cycles after cleaning with a clean-in-place method. The PES-M membrane displayed robust performance against both feeds, particularly against MSHA-F for 150 h, during which it lost only 20% flux and showed a final conductivity of 68.8 μS/cm. The PES-M membrane is a resilient candidate that can resist fouling and wetting.