Highly efficient photocatalytic oxidation of antibiotic ciprofloxacin using TiO2@g-C3N4@biochar composite

In this present study, a novel indirect Z-scheme TiO2@g-C3N4@biochar (TiO2@g-C3N4@BC) composite photocatalyst was successfully fabricated and characterized with SEM, TEM, EDS, XRD, FTIR, PL, XPS, and UV-vis DRS. The photocatalytic degradation behavior of ciprofloxacin (CIP) on the TiO2@g-C3N4@BC was evaluated under UV-vis and visible light irradiation, and the possible reaction mechanism of photocatalytic oxidation of CIP on the TiO2@g-C3N4@BC was explained. The TiO2@g-C3N4@BC composite photocatalyst exhibited stronger photocatalytic oxidation activity for CIP in comparison with TiO2, g-C3N4, TiO2@BC, and TiO2@g-C3N4. After 60 min of UV-vis and visible light irradiation, the photocatalytic removal efficiency of CIP by TiO2@g-C3N4@BC was 99.3 and 89.2%, respectively. The photocatalytic removal performance of CIP was affected by the initial concentration of CIP, catalyst dosage, and pH value. The composite photocatalyst presented excellent stability and reusability after five cycles. An indirect Z-scheme principle of the CIP photocatalytic oxidation reaction on TiO2@g-C3N4@BC was clearly proposed, and the whole process of photocatalytic degradation was the results of the interaction between CIP and reactive active species (·O2-, h+, and ·OH), of which ·O2- is the main active substance. Four CIP degradation pathways were proposed. This work may provide an effective strategy to remove antibiotics in wastewater.