Enhanced photocatalytic degradation of organic contaminants over CaFe2O4 under visible LED light irradiation mediated by peroxymonosulfate

A simple sol-gel approach is proposed herein to fabricate CaFe 2 O 4 for the degradation of various organic pollutants (rhodamine B (RhB), tetracycline hydrochloride, humic acid, and methylene orange) under LED light irradiation mediated by peroxymonosulfate (PMS). The results indicate that the calcination temperature can significantly influence the performance of CaFe 2 O 4 for PMS activation, and the CaFe 2 O 4 sample obtained at 800 °C (CaFe 2 O 4 -800) exhibits the best efficiency in degrading RhB, which is much higher than that of Fe 2 O 3 -800. This can be attributed to the efficient separation of photogenerated electrons (e − ) and holes (h + ) by PMS, which is validated by transient photocurrent response and photoluminescence measurements. Results from density functional theory calculations indicate that the valence band of CaFe 2 O 4 -800 exhibits a high concentration of carriers and weak localization of electrons, which are favorable for PMS activation. Radical scavenging results confirm that h + and O 2 • − are the dominant reactive species. Moreover, CaFe 2 O 4 -800 not only demonstrated a stable performance during eight cycling runs with negligible iron leaching but also exhibited excellent degradation efficiency under natural water and sunlight. Finally, the mechanism and pathway of RhB degradation by the CaFe 2 O 4 -800/PMS/LED system are also proposed. This work presents the enormous prospect of CaFe 2 O 4 as an environmentally benign photocatalyst for PMS activation.