Photocatalytic removal of Cr(Ⅵ) and efficient degradation of tetracycline by oxygen-enriched vacancy pie-like NH2-MIL-125(Ti)

Abstract

The heavy metals hexavalent chromium and tetracycline hydrochloride have caused considerable harm to the ecological environment of water. This has led to unprecedented requirements for the treatment and protection of the water environment. To address this problem, a cake—NH2-MIL-125(Ti)—was synthesised using a straightforward hydrothermal process, and NH2-MIL-125(Ti) catalysts with different oxygen vacancy concentrations (NMTi-OVs-X catalysts) were prepared through heat treatment. Cr(Ⅵ) and tetracycline hydrochloride (TCH) present in water were used as targets to analyse the samples’ ability to remove catalysis under sunlight. The experimental results indicate that the sample calcined at 300 °C for 300 min (NMTi-OVs-300) exhibits the highest catalytic activity. The effectiveness of TCH and Cr(VI) removal are 80 % and 100 % under simulated sunlight, respectively. Additionally, the reaction kinetic constant is 7.8 and 18.9 times higher than that of NH2-MIL-125(Ti). Proper defect sites contribute to the separation of photogenerated charges, enabling NMTi-OVs-300 to display satisfactory stability and excellent photocatalytic performance. The active substances were determined via electron spin resonance, and a photocatalytic reaction mechanism was suggested. This work provides a novel approach for the photocatalytic degradation of organic pollutants and Cr(VI) using a single semiconductor.