Ultrasmall Cu₃(PO₄)₂ Nanoparticles Reinforced Hydrogel Membrane for Super-antifouling Oil/Water Emulsion Separation

Membrane fouling is a persistent and crippling challenge for oily wastewater treatment due to the high susceptibility of membranes to contamination. A feasible strategy is to design a robust and stable hydration layer on the membrane surface to prevent contaminates. A hydrogel illustrates a distinct category of materials with outstanding antifouling performance but is limited by its weak mechanical property. In this research, we report a reinforced hydrogel on a membrane by in situ growing ultrasmall hydrophilic Cu₃(PO₄)₂ nanoparticles in a copper alginate (CuAlg) layer via metal-ion-coordination-mediated mineralization. The embeddedness of hydrophilic Cu₃(PO₄)₂ nanoparticle with a size of 3-5 nm endows the CuAlg/Cu₃(PO₄)₂ composite hydrogel with enhanced mechanical property as well as reinforced hydrate ability. The as-prepared CuAlg/Cu₃(PO₄)₂ modified membrane exhibits a superior oil-repulsive property and achieves a nearly zero flux decline for separating surfactant stabilized oil-in-water emulsions with a high permeate flux up to ∼1330 L m^-2 h^-1 bar^-1. Notably, it is capable of keeping similar permeate flux for both pure water and oil-in-water emulsions during filtration, which is superior to the currently reported membranes, indicating its super-antifouling properties.