Removal of antibiotics from black water by a membrane filtration-visible light photocatalytic system

To address the problem of pollution caused by antibiotics in black water, we synthesized membranes containing the g-C₃N₄/TiO₂ photocatalysts and tested them for the removal of sulfamethoxazole (SMZ) and tetracycline (TC) in pure water conditions and black water. We compared the basic membrane filtration and photocatalytic performance of the g-C₃N₄/TiO₂ and the PVDF membranes, and investigated the influencing factors and application aspects of membrane filtration-photocatalytic systems for antibiotic removal. The anti-fouling performance and re-usability of g-C₃N₄/TiO₂ membranes were investigated by evaluating the fouling reversibility of photocatalytic membranes. The results showed that g-C₃N₄/TiO₂ improved the porosity, hydrophilicity and permeability of the membranes significantly. PgT-3 (PVDF/g-C₃N₄/TiO₂) membrane with 0.03 wt% of g-C₃N₄/TiO₂ has the best overall performance with 72.8 % and 63.9 % removal efficiency for SMZ and TC respectively. Neutral or weakly acidic solution (pH = 5.0–7.0) is favorable for the removal of both study antibiotics. The complex composition of black water increased the adsorption load on the membrane and caused the inhibition of the photocatalysis of the g-C₃N₄/TiO₂ membrane. The absorption of visible light by g-C₃N₄ accelerates the electron transfer rate and promotes the separation of electrons from holes. The oxidation-active substance h⁺ produced in the system plays an important role in the removal of SMZ and TC.