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BACKGROUND: There is increasing concern regarding the rising issue of Cr(VI) pollution in aqueous solutions. It is crucial to find an effective technology for the removal of Cr(VI) in aqueous solutions. In this work, a novel TiO2/BC/g‐C3N4 heterostructure photocatalyst was successfully prepared by a simple hydrothermal method and characterized by scanning electron microscopy, transmission electron microscopy, X‐ray diffraction, Brunauer–Emmett–Teller analysis, Fourier transform infrared spectroscopy, photoluminescence, ultraviolet–visible diffuse reflectance spectroscopy and X‐ray photoelectron spectroscopy. The photocatalytic reduction behavior of Cr(VI) on the TiO2/BC/g‐C3N4 heterostructure was investigated under visible light irradiation, and the possible mechanism of photocatalytic reduction of Cr(VI) was elucidated. RESULTS: The TiO2/BC/g‐C3N4 heterostructure photocatalyst exhibited better photoreduction activity for Cr(VI) under visible light irradiation. After 100 min irradiation with visible light, the TiO2/BC/g‐C3N4 photocatalyst achieved a removal efficiency of 89% for Cr(VI). Compared with TiO2, TiO2/BC and TiO2/g‐C3N4, the photocatalytic removal efficiency of Cr(VI) on the TiO2/BC/g‐C3N4 increased by 40%, 20% and 10% respectively. The photocatalytic reduction of Cr(VI) was dependent on the initial concentration of Cr(VI), catalyst dosage, pH value and atmosphere. Moreover, TiO2/BC/g‐C3N4 presented excellent stability and reusability after five cycles. CONCLUSION: The TiO2/BC/g‐C3N4 heterojunction enables highly efficient photocatalytic reduction of Cr(VI) under visible light irradiation. This enhancement is primarily attributed to the construction of an indirect Z‐scheme TiO2/BC/g‐C3N4 heterojunction, which significantly improves the separation efficiency of photo‐ generated charge carriers during the photochemical process. Furthermore, the presence of BC enhances the adsorption performance of Cr(VI) on TiO2/BC/g‐C3N4, thereby facilitating its photocatalytic reduction. © 2023 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]