Strongly enhanced Fenton-like oxidation (Fe/peroxydisulfate) by BiOI under visible light irradiation: A novel and green strategy for Fe(III) reduction

In order to accelerate the photo-Fenton reaction process of Fe(III) under visible light irradiation, BiOI was introduced into the Fe(III)/peroxydisulfate (PDS) system. The catalytic oxidation performance of vis-light/BiOI/Fe(III)/PDS system was evaluated using bisphenol AF (BPAF) as a representative organic contaminant. Within 30 min, nearly 100% of BPAF was degraded, proving that the system had an excellent ability to degrade organic pollutants in water. Free radical quenching experiments, electron spin resonance (ESR), and molecular probing experiments determined that the main reactive species in the system were hydroxyl radicals (•OH) and sulfate radicals (SO4•−). The comparative experiments showed that the degradation rates were closely related to the PDS consumption, while the Fe(II) absorbed on the surface of BiOI was responsible for the PDS consumption. The production pathway of Fe(II) was analyzed by XRD, FTIR and XPS characterization, the Fe(III) on the surface of BiOI was reduced by photogenerated electrons to generate Fe(II). The result confirmed that the reduction of Fe(III) by photogenerated electrons could effectively inhibit the recombination of electron-hole pairs, and accelerate the reduction progress of Fe(III)/Fe(II) cycle that was the rate-limiting step in PDS activation. Afterwards, a reliable mechanism for degradation of BPAF in visible light/BiOI/Fe(III)/PDS system was proposed. Finally, the influence of reactant dosages, visible light intensity, initial pH, humic acid (HA) and anions in the solution on the degradation of BPAF were discussed.