Visible light driven ZnFe₂O₄ for the degradation of oxytetracycline in the presence of HSO₅⁻ at semi-pilot scale and additional H₂ production

This study investigated the synthesis of visible light driven ZnFe₂O₄ for photocatalytic degradation of oxytetracycline (OTC) in a continuous flow reactor and production of hydrogen (H₂). OTC is widely used as a medication and found to create severe health and environmental issues. The use of advanced characterization techniques proved successful formation of ZnFe₂O₄ which was found to be reusable, stable, highly crystalline, and nano-sized. The prepared ZnFe₂O₄ caused 60% removal of OTC and removal efficiency of the latter was promoted to 85% by adding HSO₅^– with ZnFe₂O₄ at 240 min employing reactor flow rate of 0.1 L/min and concentrations of ZnFe₂O₄, OTC, and HSO₅^– as 1.0 g/L, 20 mg/L, and 100 mg/L, respectively. The addition of HSO₅^– was found to give hydroxyl radical (^•OH) and sulfate radical (SO₄^•−) and the latter caused degradation of OTC into degradation products. The removal of OTC was promoted by factors facilitating the rate of formation of ^•OH and SO₄^•−. The ZnFe₂O₄ proved effective in photocatalytic H₂ production and showed H₂ production rate of 23.4 μmol h⁻¹ g⁻¹. The results suggest that ZnFe₂O₄ could be used as an economically viable technology for emerging pollutants degradation and green energy production.