Kinetic Comparison of Photocatalysis with the Photo-Fenton Process on the Removal of Tetracycline Using Bismuth-Modified Lanthanum Orthoferrite Nanostructures

In this study, we investigate visible-light-driven photocatalytic and photo-Fenton degradation of tetracycline (TC) using bismuth-impregnated lanthanum orthoferrite (Bi_xLa_1–xFeO₃ (x = 0, 0.01, 0.05, 0.07)) nanostructures. Bi doping significantly improves the removal of TC, with Bi_0.05La_0.95FeO₃ (LFO-Bi5) exhibiting optimal degradation. In both photocatalysis (PC) and photo-Fenton catalysis (PFC), the reaction follows pseudo-first-order kinetics, with LFO-Bi5 showing rate constants of 0.0065/min for PC and 0.02716/min for PFC, surpassing LaFeO₃ by 2.76 and 3.43 times, respectively. The long-term presence of photoexcited carriers in LFO-Bi5 is confirmed through transient PL, TRPL, and EIS studies. The superior degradation capabilities are attributed to radicals in photocatalysis and OH^• radicals in photo-Fenton catalysis. The PFC exhibited faster kinetics due to the rapid production of OH^• radicals via the Fe-redox cycle and direct dissociation of H₂O₂ at oxygen vacancies. LFO-Bi5 demonstrates excellent photostability and reusability for up to six consecutive cycles. The degradation pathway and toxicological properties of the intermediates are analyzed, highlighting the potential of LFO-Bi5 catalysts in antibiotic-contaminated water treatment.