Construction of Cu-doped α-Fe2O3/γ-Fe2O3 hetero-phase junction composite and its photocatalytic performance

[Display omitted] •Stable Fe2O3 hetero-phase junction prepared via simple hydrothermal and controlled calcination methods.•Hetero-phase junctions with Cu/Fe ‘redox double cycling’ improve photogenerated carrier separation and utilization.•Toxicity of degradation products notably reduced, potential toxic evolution mechanism revealed. Chlortetracycline hydrochloride (CTC), a class of antibiotics, poses a significant environmental hazard, particularly in aquatic ecosystems. The advancement of highly efficient and readily recyclable materials for water treatment remains an important focus of research in environmental remediation. In this study, Cu-doped α-Fe2O3/γ-Fe2O3 hetero-phase junction materials were prepared by a solvothermal method and a controlled calcination process to enhance the photocatalytic degradation of CTC in water by Fe2O3. Experimental results indicate that the composite material has superior magnetic properties, with Cu2-α-Fe2O3/γ-Fe2O3, featuring a high specific surface area and small pores, showing the best CTC adsorption. The α-Fe2O3/γ-Fe2O3′s interlaced energy levels facilitate quick electron transfer, and copper ion addition optimizes electron paths, generating numerous oxygen vacancies. This, combined with the hetero-phase junction, boosts charge separation and migration. Among the samples tested, The Cu2-α-Fe2O3/γ-Fe2O3 composite demonstrated the most efficient photocatalytic performance, with a degradation rate of 90.19 % for CTC achieved under Visible Light Irradiation. The proposed second-order reaction rate constants were approximately 31.99, 10.07, and 4.48 times higher than those for α-Fe2O3, γ-Fe2O3, and α-Fe2O3/γ-Fe2O3, respectively. The material also demonstrates good degradation effects on other antibiotics (such as oxytetracycline, tetracycline hydrochloride, etc.). Moreover, the structural morphology of the sample remains stable after cycling. O2– and h+ are the main active species in the photocatalytic degradation process of CTC, while OH plays a secondary role. The possible degradation pathways were elucidated by calculating predicted free radical attack sites using density-functional theory (DFT) and by analyzing the products of the CTC degradation process. Additionally, the toxicity risk assessment indicates that the intermediate products have low toxicity and pose a minimal potential risk to the aquatic environment.