LAUSR

ABSTRACT The goal of this study was to prepare a robust anti‐wetting and anti‐fouling polyethersulfone (PES) membrane for the rejection of a highly saline (NaCl and CaCl2·2H2O) feed solution containing humic acid (HA) in direct contact membrane distillation (DCMD). Response surface methodology (RSM) was used to determine the optimum formulation of the used materials. The variable factors selected were polydimethyl siloxane (PDMS) and silica (SiO2); liquid entry pressure (LEP) and contact angle (CA) were selected as responses. Scanning electron microscopy (SEM) analysis confirmed the SiO2 deposition and Fourier‐transform infrared spectroscopy (FTIR) test evidenced the new functional groups i.e., Si–OH, siloxane, and C–F bond vibrations at 3446, 1099 cm−1, and 1150–1240 cm−1 respectively on the membrane surface. The average roughness (Ra) was increased four times for the coated membranes (0.202–0.242 &mgr;m) as compared to that for pristine PES membrane (0.053 &mgr;m). The optimum PES‐13 membrane exhibited consistent flux of 12 LMH and salt rejection (> 99%) with anti‐fouling characteristic in DCMD using the feed solution of 3.5 wt% NaCl + 10 mM CaCl2·2H2O + 10 mg L−1 HA. The PES‐13 membrane may therefore be a key membrane for application in DCMD against CaCl2·2H2O‐containing salty solutions with HA. HighlightsPES membrane was prepared for application in DCMD using silica nanoparticles.Response surface methodology was employed to optimize the coating formulation.Modified membranes were resistant to fouling against calcium‐humic acid feed.The high fluxes for PES‐13 membrane were recorded with all three feed solutions.