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

Abstract

Tetracycline (TC) contamination remains difficult to control because conventional wastewater treatment processes often do not fully remove persistent antibiotic residue s. Although Fe doping and BiVO4 /g-C3N4 heterojunction formation have been reported previously, the composition dependent behavior of Fe doped BiVO4 /g-C3N4 photocatalysts under low intensity UVC irradiation remains insufficiently clarified. This study developed 3% Fe doped BiVO4 /g-C3N4 (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 22⁻ related pathways exerted the strongest influence, while •OH and h 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.