The surface hydrophobicity of a poly (vinylidene fluoride) membrane was increased through the phase separation of polycarbonate (PC) solution on the membrane surface. A variety of characterization techniques including surface contact angle measurement, scanning electron microscopy, liquid entry pressure measurement, atomic force microscopy, porosity measurement, pore size measurement, and attenuated total reflectance-Fourier transform infrared spectroscopy were performed to investigate the membrane surface modification. According to the results, the formation of PC deposits on the membrane surface provided hierarchical structures consisting of micro and nanoscale roughness which enhanced the surface hydrophobicity. Direct contact membrane distillation (DCMD) experiments, in which an aqueous solution of sodium chloride (3.5 wt%) resembling the seawater was used as feed, were carried out to assess the performance of membranes. This surface modification technique led to the improved pore wetting resistance of the coated membrane in DCMD application. This novel method is believed to have a great potential to apply on a wide variety of membranes for MD application.

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