Bi₄O₅I₂ nanosheets as a novel nanofiller for fabrication of antifouling polyethersulfone nanocomposite membranes

Bi₄O₅I₂ is one of the bismuth-rich oxyhalides that exhibited impressive activity in the photodegradation of different organic pollutants. In this research, Bi₄O₅I₂ nanosheets were synthesized, characterized, and applied for fabricating a hydrophilic and antifouling polyethersulfone (PES) membrane by blending in the membrane matrix. The prepared nanocomposite membranes exhibited improved antifouling properties especially when UV irradiation was used during the washing of the fouled membranes. Hydrophilicity enhancement and photocatalytic property of the Bi₄O₅I₂ nanosheets have an excellent synergistic effect, which can yield more hydroxyl radicals (•OH) for efficient removal of the foulant from the membrane surface. The pure water flux can achieve 235.4 L/m² h (3 bar) when 0.5 wt% Bi₄O₅I₂ was used. The addition of the nanosheets to the membrane matrix in low amounts decreased the membrane surface roughness and increased membrane porosity. The BSA, Reactive Orange 16, Reactive Black 5, and Pb(II) filtration tests showed that the 1 wt% Bi₄O₅I₂ PES membranes provided a good performance of 98.3, 70.3, 92.6, and 47.2 % rejection ability, respectively. In this research, for the first time, the Bi₄O₅I₂ photocatalyst was blended into the membrane matrix which provided a new idea for the progress of highly effective self-cleaning ultrafiltration membranes.