Efficient degradation of antibiotics by heterojunction photocatalysts driving peroxydisulfate activation under visible light irradiation

Heterogeneous iron materials show potential for activating peroxydisulfate (PDS). However, these systems may be constrained by low efficiency and secondary pollution. The visible-light-assisted activation has been demonstrated as a feasible and effective approach to enhance PDS activation by iron-based materials. In this study, a visible-light-responsive Bi2WO6/Fe2O3 heterojunction photocatalyst was synthesized to improve the ability of Fe2O3 for PDS activation through an effective Fe(III)/Fe(II) cycle. Rapid tetracycline (TC, a common antibiotic) removal (91.7% within 60 min at a concentration of 20 mg·L-1) was achieved in the constructed Bi2WO6/Fe2O3/PDS/vis system under conditions of 0.3 g·L-1 PDS and 0.3 g·L-1 catalyst. The corresponding pseudo-first-order rate constant reached 4.16 × 10-2 min-1, which was 8.42 and 16.38 times higher than those of Bi2WO6/Fe2O3/vis and Bi2WO6/Fe2O3/PDS systems, respectively. Moreover, the Bi2WO6/Fe2O3 exhibited favorable stability and reusability even after five cycles. Lastly, a catalytic mechanism for TC removal and PDS activation was proposed based on quenching experiments and electron spin resonance (ESR) tests. The SO4•- and •OH played a major role in TC removal, while •O2– and 1O2 contributed as auxiliary factors. This study presents a promising strategy for activating PDS using cost-effective and stable Fe(III)-based heterojunctions, and such an idea can be used to design catalysts for other high-value reactions.