Study of the degradation of tetracycline by visible photo-Fenton catalyzed by ultrasound-assisted LaFeO₃/PS

The powdered LaFeO₃ material had shortcomings such as easy agglomeration and difficult separation, so it was limited in large-scale applications. The deposition of powdered catalysts in polystyrene resin (PS) made up for the above shortcomings of powdered materials. Therefore, in this study, the self-assembled LaFeO₃ gel was deposited on the PS through ultrasound-assisted sol-gel and hydrothermal methods. The dispersion and distribution of LaFeO₃ on PS broadens the forbidden band width of LaFeO₃, improves its redox ability, solves the problem of agglomeration, and consequently improves its photo-Fenton catalytic activity. The LaFeO₃/PS composite prepared under the following experimental conditions shows the highest photocatalytic activity: La∶Fe∶Citric acid(CA) molar ratio=1∶1∶2, ultrasonic time 40 min, hydrothermal temperature 90℃, hydrothermal time 18 h, LaFeO₃ initiator/polystyrene mass ratio=32∶1. The removal rate of tetracycline hydrochloride (TC) is up to 96.51%(rate of degradation k=0.0160 min⁻¹) under visible light irradiation in the Fenton process catalyzed by LaFeO₃/PS. Free radical capture experiments show that •O₂⁻ is the main active species. According to the capture experiment, the degradation mechanism of TC was proposed. Through LC/MS analysis, the degradation path of TC was obtained. The photo-Fenton process catalyzed by LaFeO₃/PS is a promising technology for the degradation of organic pollutants due to the high stability of the catalyst and the efficient use of solar energy.