Significance of B-site cobalt on bisphenol A degradation by MOFs-templated Co_xFe_3−xO₄ catalysts and its severe attenuation by excessive cobalt-rich phase

We report a facile process to fabricate porous Co_xFe_3−xO₄ catalysts by using a metal organic framework (MOFs) sacrificial template for bisphenol A (BPA) degradation through Oxone activation. The results demonstrated a significantly enhanced catalytic performance with increasing content of cobalt in the catalyst, which peaked at x = 1.51. Further increase in the cobalt content of catalysts exhibited negative effects on the catalytic performance due to the increased cobalt-rich phase with insufficient Fe. The effects of various conditions were evaluated, circa 0.13 (0.20) min⁻¹ of the catalytic rate could be attained in deionized water (reaction condition: [BPA] = 60 μM, [Oxone concentration] = 0.6 mM, [catalyst dosage] = 0.1 (0.3) g L⁻¹, [temperature] = 25 °C, and [initial pH] = 10.2 (6.5)). The radical SO₄^[rad]− was demonstrated to be a major contributor to the catalytic process, as well as HO^[rad]. More importantly, the catalysts exhibited desirable BPA degradation efficiencies in various water matrices. Simple thermal treatment at 450 °C in open air significantly regenerated the spent catalyst. B-site cobalt in catalysts was proved to play an important role in activating Oxone in the proposed mechanism.