Comparative Study of BiOX (X = Cl, Br, I)/Polyethersulfone Self‐Cleaning Ultrafiltration Membranes Prepared Based on Reverse Thermally Induced Phase Separation Method

ABSTRACT To address the trade‐off effect and membrane fouling in conventional polyethersulfone (PES) ultrafiltration membranes, we developed BiOX/PVP/PES (X = Cl, Br, I) composite membranes via reverse thermally induced phase separation (RTIPS) by incorporating hydrophilic polyvinylpyrrolidone (PVP) with bismuth oxyhalide (BiOX) photocatalysts. The BiOI/PVP/PES membrane exhibited optimal performance, achieving a pure water flux of 3750.89 L/(m 2 ·h) and 96.96% humic acid rejection (HA)—significantly surpassing BiOBr and BiOCl‐modified counterparts. Photocatalytic cycling tests confirmed superior self‐cleaning capability, demonstrating a reversible‐to‐total fouling ratio (Rr/Rt) of 0.9 and exceptional antifouling stability. Structural characterization revealed nanoflower‐like BiOI/PVP architectures with hierarchical 3D porosity, providing abundant active sites and an enhanced surface area, which critically enhanced photocatalytic activity and fouling resistance. This work establishes a rational design strategy for high‐flux, self‐cleaning ultrafiltration membranes with synergistic separation and regeneration properties.