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Membrane distillation (MD) is a promising desalination technology as it is less sensitive to feed's salinity and can handle high-salinity water. However, the industrial application of MD is restricted by the limited availability of cost-effective hydrophobic membranes. This study developed a simple method to fabricate hydrophobic MD membranes through the coating of a fluoroethylene vinyl ether polymer called LUMIFLON™ LF-200. The fluoropolymer was effectively coated on porous nitrocellulose (NC) and nylon membrane through dip-coating followed by a thermal crosslinking. The coating layer was thin and uniform, covering the surface of the whole membrane matrix, while the high porosity and the microstructure of the membranes were still mostly preserved. After modification, the originally hydrophilic NC and nylon membranes were transformed into hydrophobic, with water contact angles of ∼130°. The 12LF-NC membrane showed a high flux of 10.1 kg m−2 h−1 with salt rejection >99.99% over 120 h in the direct contact MD fed with 10 wt% NaCl solution, which outperformed the commercial PVDF membrane. This coating method has the potential to modify various substrates to produce MD membranes with good performance, which broadens the availability of appropriate membranes for MD application. [Display omitted] • Fluorinated copolymer, LUMIFLON LF-200 is used to prepare hydrophobic MD membranes. • LF-200 was simply dip-coated on hydrophilic substrates and crosslinked under mild heating. • The WCAs of modified nitrocellulose and nylon membranes increased to ∼130° from 0°. • The 12LF-NC membrane had excellent flux >10 kg m−2 h−1 treating 10 wt% salt water. • This method has high efficiency, wide versatility and the potential to scale up. [ABSTRACT FROM AUTHOR]

Solvent resistant membrane distillation (SR-MD) is a novel technology to effectively separate water from waste streams containing solvents with high boiling points, avoiding the high chemical costs and release of harmful gas in conventional treatments. Ceramic membranes are promising for this process as they are highly stable chemically but they require modification to tune the hydrophilicity to hydrophobicity. However, the widely used silanization for hydrophobic modification often involves expensive chemicals and may produce toxic substances. Here, we present a new hydrophobic modification method with the use of fatty acid chloride (FAC), as a greener and cheaper alternative to silanes. In the grafting reaction, the acyl chloride groups react with the –OH groups on the ceramic membranes to form strong ester bonds. We successfully grafted stearoyl chloride (SC) and palmitoyl chloride (PC) on the ceramic tubular membranes. With long carbon chains grafted, the modified membranes exhibited high hydrophobicity with a water contact angle >141° and a liquid entry pressure >3 bar. When tested in SR-MD with a feed solution containing 50 wt% dimethyl sulfoxide, the PC-modified membrane demonstrated a flux of 3.2 kg m−2 h−1, with rejection >98% and separation factor >110 at 60 °C, and a high flux of 4.5 kg m−2 h−1 with rejection >96% at 70 °C. The FAC-modified membranes allow a cost-effective treatment of challenging wastewater containing organic solvents through SR-MD. [Display omitted] • Hydrophobic ceramic membranes for solvent resistant MD were synthesized through fatty acid chloride grafting. • The acyl chloride groups formed strong ester bonds on ceramic surface and the modified membranes had high hydrophobicity. • Flux of 3.2 kg m−2 h−1, rejection >98% and separation factor >110 can be achieved when treating 50 wt% DMSO in SR-MD. • The hydrophobicity and separation performance are comparable to ceramic membrane grafted with silanes. • This study presents a greener and cheaper surface modification chemistry to synthesize hydrophobic ceramic membranes. [ABSTRACT FROM AUTHOR]