Novel polyamide forward osmosis membrane prepared via synergistically substrate-floating interfacial polymerization and salt regulation for efficient solvent recovery

Abstract

Obtaining an ultrathin and high-quality skin layer on a macro-porous substrate is considered as an obstacle for the desalted membrane fabrication, although macro-porous substrate seems nearly ideal for the forward osmosis (FO) membranes. In this work, a novel substrate-floating interfacial polymerization (SFIP) method was proposed to realize the fabrication of a defect-free polyamide skin layer on a macro-porous substrate. Meanwhile, inorganic salt such as NaCl was added into aqueous phase to cause local differences in interface tension during SFIP process, promoting the MPD transfer from the bulk to surface of aqueous solution via Marangoni convection so as to diffuse more MPD molecules. The resulting FO membrane exhibited an excellent ethanol flux (JV)/reverse LiCl flux (JS) value of 277.17 g L−1, which was 2–10 times higher than the data reported in previous literature. Besides, our SFIP method was also employed to fabricate the polyamide skin layer on the hydrophobic PVDF substrate, and found that the hydrophilicity/hydrophobicity of substrate could control the forming position of polyamide skin layer via SFIP method. This work provides a feasible strategy for fabricating high-quality desalted membranes, and demonstrates their potential in organic solvent recovery for energy conservation and emission reduction.