Degradation of bisphenol A by persulfate activation via oxygen vacancy-rich CoFe₂O_4-x

This research describes the function of oxygen vacancy on CoFe₂O_4-x for persulfate (PS) activation. Novel CoFe₂O_4-x with different vacancy degrees that were successfully developed via hydrogen calcination were characterized using X-ray diffraction analyzer (XRD), Fourier transform infrared (FTIR) spectra, Raman spectroscopy, scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), H₂ temperature-programmed reduction (H₂-TPR), cyclic voltammetry (CV), electrochemical impedance spectra (EIS), nitrogen adsorption-desorption isotherms and dynamic light scattering. The activation of catalysts was analyzed using Bisphenol A (BPA) as pollutant, and the main active species generated during the reaction were identified by using N₂ bubbling and scavenger experiments. Possible oxidation degradation pathways of BPA were speculated using gas chromatography-mass spectrophotometry (GC-MS) and total organic carbon (TOC) analysis. Findings indicated that the oxygen vacancies promoted electronic transfer and participated in the redox cycle from Co³⁺/Fe³⁺ to Co²⁺/Fe²⁺ to generate ¹O₂ and O₂^-. O₂^-, OH and SO₄^- generated from oxygen vacancy; moreover, PS activation could further degrade BPA to small molecules, such as benzenes and quinones. Finally, the toxicity of the reaction mixtures was evaluated and found that the acute toxicity to Daphnia magna decreased after 120 min treatment.