Enhanced flux and fouling resistance forward osmosis membrane based on a hydrogel/MOF hybrid selective layer

Although forward osmosis (FO) technology has been widely adopted for water treatment, it still faces great challenges, including low permeability and fouling problem. Herein, a novel forward osmosis membrane was developed with a stable, uniform and defect-free polyvinyl alcohol/polydopamine coated zeolitic imidazolate framework (PVA/PDA@ZIF-8) hybrid selective layer to simultaneously enhance its transport property and fouling resistance. The prepared FO membrane exhibits improved water flux without losing the selectivity, since the PDA@ZIF-8 provide additional preferential passageway for water transporting while hinder the diffusion of salt. The optimized membrane shows a higher water flux than pristine PVA membrane (14.2 vs. 8.7 L m^-2 h^-1 in FO mode, 24.3 vs. 14.8 L m^-2 h^-1 in PRO mode) with a reasonable selectivity considering as J_s/J_w value (0.44 vs. 0.4 g L^-1 in FO mode, 0.38 vs. 0.33 g L^-1). Moreover, the dynamic fouling experiments with organic foulants (protein and polysaccharide) indicate that the prepared membrane exhibits strong antifouling property and excellent permeation recovery ability (>95.0%) due to the optimized surface property. This study opens a new avenue for treatment wastewater by developing a forward osmosis membrane based on a hydrogel/MOF hybrid selective layer.