Construction of antifouling lumen surface on a poly(vinylidene fluoride) hollow fiber membrane via a zwitterionic graft copolymerization strategy

[Display omitted] •A demonstration of effectively constructing an antifouling lumen surface on PVDF hollow fibers.•Grafting density and chain length of the grafted polyzwitterion were well optimized.•The antifouling properties in a BSA solution were evaluated using the resistance-in-series model.•The flux recovery ratio (FRR) increased significantly from 47% to 85% after grafting. Construction of PVDF hollow fiber membranes with antifouling lumen surfaces is of great interest and significance for many industrial applications because the inside-out filtration mode allows good control over module hydrodynamics. For the first time, a zwitterionic polymer was immobilized on the lumen surface of a PVDF hollow fiber membrane via thermal-induced graft copolymerization with an objective to render the PVDF membrane antifouling. The graft copolymerization consists of two steps: ozone-assisted surface pre-activation and grafting of sulfobetaine methacrylate (SBMA). The grafting density and chain length were systematically optimized by manipulating the operational parameters, e.g. ozone treatment and grafting duration. The resultant membranes were studied with respect to their structure, morphology, ultrafiltration (UF) performance, while their fouling behaviors were evaluated by flux recovery ratio and the resistance-in-series model. In comparison to the pristine one, the composite membranes exhibited superior fouling resistance for a 2-h filtration of a 2.0wt% bovine serum albumin (BSA) solution. Especially, the irreversible fouling-induced resistance was prominently reduced from 53% to 15% due to the outstanding hydration capacity of the polySBMA polymer. Consequently, the flux recovery ratio (FRR) increased significantly from 47% to 85%, suggesting the promising prospect of the zwitterion-grafted PVDF hollow fiber membranes for their antifouling properties. Most importantly, the improvement in antifouling was achieved without sacrificing flux or rejection efficiency. This work may provide useful insights about lumen surface nano-structuring of the inner-selective hollow fiber membranes.