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

Abstract

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.