Polyvinyl alcohol hydrogel-supported forward osmosis membranes with high performance and excellent pH stability

A new class of a polyvinyl alcohol (PVA) hydrogel support was used to fabricate a forward osmosis (FO) membrane with high performance and excellent pH resistance. The intrinsically hydrophilic PVA support formed by non-solvent-induced phase separation and subsequent crosslinking exhibited a thin (∼40 μm) and highly porous scaffold-like structure with high pore interconnectivity, achieving a considerably low structural parameter (∼184 μm). Toluene-assisted interfacial polymerization was also employed to fabricate a polyamide (PA) selective layer with high water permeance and salt selectivity on the prepared hydrophilic PVA support. The fabricated PVA supported-thin film composite (PVA-TFC) membrane exhibited 2.7–3.7 times higher FO mode water flux and 70–78% lower specific salt flux than commercial FO membranes with a draw solution of 1.0 M NaCl and a feed solution of DI water. The PVA-TFC membrane also outperformed other previously reported FO membranes. In addition, the PVA-TFC membrane had superior pH resistance when compared with commercial FO membranes, which is imparted by the excellent pH stability of both its PA selective layer and PVA support. Our strategy paves the way for the fabrication of high-performance and pH-resistant FO membranes that can be employed in harsh water environments.