Facile preparation of robust anti-wetting membrane by simple two-step FeOOH and fluorosilane membrane modification

A membrane contactor system using a hydrophobic microporous membrane can effectively harvest valuable gaseous compounds, such as NH3, CH4, H2, and volatile fatty acids, in waste streams. However, widespread implementation of membrane contactor-based resource recovery is still hindered by membrane wetting, which lowers selectivity and decreases mass transfer rate during membrane contactor operation. Herein, for the first time, we present a facile and scalable approach for preparing membrane with superior hydrophobicity and physico-chemical robustness by simple two-step membrane modification using only three chemicals: n-butanol, FeCl3·6H2O, and fluorosilane. Firmly grafted re-entrant FeOOH nanostructure and fluorosilane were confirmed by scanning electron microscopy, energy dispersive X-ray spectrometry, Fourier transform infrared spectroscopy, and X-ray diffractometry. The superior wetting resistance of the modified membrane was confirmed by liquid entry pressure (LEP) and contact angle (CA) analysis (LEP = 2.92 bar & CA = 149.1°). In addition, the modified membrane exhibited excellent resistance to harsh acid–base exposure, and great tensile strength of 5.8 MPa. The modified membrane achieved ammonia recovery flux of 1.02 g/m2h without wetting occurrence from feed solution containing 5.00 g/L of sodium dodecyl sulfate surfactant. We expect that the membrane modification procedure developed in this study will widen the potential of membrane contactor-based recovery of valuable gaseous compounds from various waste streams.