Fe-doped BiVO4/g-C3N4 heterojunction for efficient tetracycline degradation under low-intensity UV irradiation

Tetracycline (TC) contamination remains difficult to control because conventional wastewater treatment processes often do not fully remove persistent antibiotic residues. Although Fe doping and BiVO 4 /g-C 3 N 4 heterojunction formation have been reported previously, the composition-dependent behavior of Fe-doped BiVO 4 /g-C 3 N 4 photocatalysts under low-intensity UVC irradiation remains insufficiently clarified. This study developed 3% Fe-doped BiVO 4 /g-C 3 N 4 (FeBVO: CN) heterojunction photocatalysts with different FeBVO: CN mass ratios and evaluated their TC degradation performance, operating conditions, reactive-species involvement, reusability, and preliminary synthesis cost. The composites were synthesized by hydrothermal treatment followed by calcination and characterized using X-ray diffraction, Fourier transform infrared spectroscopy, ultraviolet-visible spectroscopy, and field emission scanning electron microscopy. Among the prepared samples, FeBVO/CN-2:1 showed the highest photocatalytic activity, achieving 83.6% TC degradation within 120 min at 5 mg L −1 TC, 200 mg L − 1 catalyst loading, and pH 10. The degradation followed pseudo-first-order (PFO) kinetics with a rate constant of 0.01509 min − 1 . Scavenger experiments suggested that •O 2 − -related pathways exerted the strongest influence, while •OH and h + also contributed to TC transformation. The catalyst retained 77.1% degradation efficiency after three cycles, indicating preliminary reusability under the tested conditions. This work advances the field by linking FeBVO: CN composition with structural features, optical response, photocatalytic activity, reactive-species behavior, and practical operating constraints under low-intensity UVC irradiation. Mulliken-estimated band-edge positions, together with the scavenger results, supported a proposed Z-scheme-like charge-transfer pathway as the more thermodynamically consistent interpretation of the observed reactive-species behaviour.