Green kaolin-tailored hydrophobic composite membrane for efficient desalination of high-salinity water

This study reports a novel approach to tune the surface and activate ceramic-polymeric based membranes from widely available and naturally occurring kaolin materials for the desalination of highly saline water via membrane distillation. Electrospraying was used to endow the membrane surface with a fine distribution of silica particles to build on roughness and enhance the grafting of long-chain (F21) fluoroalkyl silane (FAS). Interestingly, the adopted approach significantly transformed the surface properties from hydrophilic with water contact angle WCA similar to 40 degrees to superhydrophobic nature with WCA similar to 160 degrees along with significant increase in the liquid entry pressure. In air-gap membrane distillation with 70,000 ppm NaCl feed solution, the developed membranes exhibited a stable salt rejection (similar to 99.99 %) and a high water permeate flux of 9.3 kg/m(2)h. Notably, the membranes developed via the adopted approach outperformed direct FAS-modified kaolin membranes and other reported ceramic-based membranes. Hence, electrosprayed silica and subsequent FAS treatment approach on the membrane surface can effectively activate and make way for actual applications of the ceramic-based membranes for the desalination of highly saline water.