Degradation of tetracycline hydrochloride by coupling of photocatalysis and peroxymonosulfate oxidation processes using CuO-BiVO4 heterogeneous catalyst

Abstract

In this study, we synthesized CuO modified BiVO4 composite (CuO-BiVO4) and used it to construct a novel coupling system, in which two processes of photocatalysis and peroxymonosulfate (PMS) oxidation processes were integrated together to synergistic remove tetracycline hydrochloride (TC−HCl). XRD, XPS, FESEM, EDS, PL and UV–vis DRS techniques were applied for characterization of the catalyst features. CASTEP procedure of MS software was employed to calculate the electronic structure of the catalyst. The catalytic performance of CuO-BiVO4+ Vis + PMS system was investigated under impact of different variables such as CuO loading amount, pH, PMS dosage, catalyst dosage, temperature and co-existing ions. Compared with the individual photocatalysis or peroxymonosulfate oxidation process, the catalytic performance of the coupling system was significantly improved. Under visible light irradiation, 100 mL of 80 mg/L TC−HCl solution was completely degraded using 2 mM PMS activated by a CuO-BiVO4 composite in 50 min without adjust pH, and the system synergistic index reached 3.04. The improved catalytic activity is due to the effective separation of photogenerated electrons-holes and the availability of more activation PMS sites. After five cycling experiments, the degradation rates of TC−HCl were reduced slightly to 94 %, which indicated the catalysts exhibited excellent reusability and stability for its practical applications. Active species trapping experiments and ESR tests confirmed that SO4·−,·OH, hVB+, O2·− and 1O2 worked together for the TC−HCl degradation. Furthermore, the possible reaction mechanism of the coupling system was proposed, and the degradation intermediates of TC−HCl were identified by LCMS. In conclusion, integration of CuO-BiVO4, Vis and PMS exhibited an excellent performance for TC−HCl degradation within 50 min reaction, which could be introduced as an effective and promising method for the wastewater treatment.