FeO-enhanced degradation of bisphenol A in visible light/peroxydisulfate system: production of singlet state oxygen.

In this study, ferrous composites (FeO) were prepared by microreactor to activate peroxydisulfate (PDS) for the degradation of bisphenol A (BPA) with visible (Vis) light irradiation. X-ray diffraction (XRD), energy-dispersive spectrometry (EDS), X-ray photoelectron spectroscopy (XPS), and scanning electron microscope (SEM) were used to characterize the morphology and crystal phase of FeO. Photoluminescence (PL) spectroscopy combined with amperometric tests were used to determine the role of PDS on the performance of photocatalytic reaction. The main reactive species and intermediates for BPA removal were determined by electron paramagnetic resonance (EPR) measurement and quenching experiments. The result indicated that singlet state oxygen (O) contributed more to the BPA degradation than that of other reactive radicals (·OH, SO and ·O); these reactive radicals and O formed by the reaction between photo-generated electrons (e) and holes (h) of FeO and PDS. During this process, the consumption of e and h also improved their separation efficiency and thus enhanced the degradation of BPA. In addition, the photocatalytic activity of FeO in Vis/FeO/PDS system was 3.2-fold and 6.6-fold higher than that of single FeO and PDS under Vis light, respectively. The Fe/Fe cycle could effectively drive the photocatalytic activation of PDS through indirect electron transfer and the formation of reactive radicals. This work illustrated that the degradation of BPA was rapidly in Vis/FeO/PDS system mainly through O, which further improve our understanding on the efficient removal of organic contaminants in the environment.