Visible-light photocatalytic membranes based on heterostructured Fe₃O₄-doped g-C₃N₄/TiO₂ catalysts

BACKGROUND: Desalination membranes have been widely in demand for separating dyes and salts. However, dyes are easily adsorbed on/in the membranes, deteriorating membrane performance. Coupling photocatalysis and membrane separation might be a promising strategy for efficiently alleviating membrane fouling. Aiming at the defects of single catalyst, this work constructed photocatalytic membranes based on heterostructured Fe₃O₄-doped g-C₃N₄ (FeCN)/TiO₂ catalysts by successively filtrating FeCN aqueous dispersion and titanium butoxide/isopropanol solution on the hydrolyzed polyacrylonitrile substrate. RESULTS: The H-bonds among TiO₂, FeCN and substrate lead to excellent load stability of the photoresponsive layer. Due to the low-potential conduction band and high conductivity of Fe₃O₄ and the low-potential conduction band of TiO₂ in FeCN/TiO₂, electrons can be more easily transferred to guarantee the high separation efficiency of electrons and holes. Hence the membrane not only exhibited superior permeability (104 L m⁻² h⁻¹ bar⁻¹) and dye desalting performance (Coomassie brilliant blue R250 rejection of >98.80% and NaCl rejection of <7.00%), but also displayed highly efficient and stable dye photodegradation. CONCLUSION: The degradation efficiency surpassed that reported in the literature in comparable circumstances, and the recovery rate of permeability still reached 89.12% after three fouling–photodegradation cycles. This work provides new opportunities for designing high-efficiency self-cleaning membranes to solve membrane fouling based on low-cost materials.