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.