Enhancing hydrophilicity and comprehensive antifouling properties of microfiltration membrane by novel hyperbranched poly(N-acryoyl morpholine) coating for oil-in-water emulsion separation

Hydrophilic polymers with low affinity for foulants were broadly utilized as functional membrane surface modifiers to mitigate fouling owing to superior hydration capability. Herein, novel hydrophilic hyperbranched poly(N-acryoyl morpholine) (HPA) synthesized through one-step RAFT polymerization was immobilized onto commercial PVDF microfiltration membrane surface using biomimetic adhesion polydopamine as an intermediate reaction platform. The surface composition and morphology of HPA decorated membranes (M-PD/HPA) were examined, demonstrating that the nano-sized HPA was facilely anchored on the membrane surface without obviously changing membrane pore size and distribution. In comparision with hydrophobic pure membrane (M-PVDF), hydrophilic and underwater superoleophobic M-PD/HPA exhibited excellent multiple defense capability toward oil, protein and bacteria due to the presence of a steric repulsive barrier of hydrated HPA layer. For model hexane-in-water emulsion separation at 0.02 MPa, permeation flux of M-PD/HPA up to 149.8 L m(-2) h(-1) was improved by three times and the rejection was up to 99.5%. Importantly, for the separation of complex artificial oily wastewater, relevant flux reduction of M-PD/HPA was decreased from 60.9% of M-PVDF to 36.8% and flux recovery ratio of M-PD/HPA was increased from 34.8% to 82.6%. Therefore, M-PD/HPA has a promising prospect for emulsified oil separation and water purification.