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 Bi 2 WO 6 /Fe 2 O 3 heterojunction photocatalyst was synthesized to improve the ability of Fe 2 O 3 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 Bi 2 WO 6 /Fe 2 O 3 /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 Bi 2 WO 6 /Fe 2 O 3 / vis and Bi 2 WO 6 /Fe 2 O 3 /PDS systems, respectively. Moreover, the Bi 2 WO 6 /Fe 2 O 3 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 SO 4 • - and • OH played a major role in TC removal, while • O 2 – and 1 O 2 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.