Catalytic performance of alkaline earth metals doped-Co3O4 for azo dye degradation by peroxymonosulfate activation

Metal doping is a promising avenue to improve the catalytic property of Co-based catalysts for organic pollutants degradation via peroxymonosulfate (PMS) activation. Herein, alkaline earth metals doped mesoporous cobalt oxide catalysts (M/Co3O4, M= Ca, Mg, Sr and Ba) were fabricated by combination of sol-gel method and cellulose template and employed to activate PMS for Ponceau 2 R (PR) decomposition. The doped alkaline earth metals induced strong promotion effects on the catalytic performance with the order of Ca > Mg > Sr > Ba. Notably, the rate constant of Ca/Co3O4 (0.3048 min−1), which displayed the optimum catalytic performance, was 7.5 times that of pure Co3O4 (0.0406 min−1) for PR degradation. Additionally, the influence of PMS and catalyst concentration, pH, doping amount, inorganic salts, and reaction temperature on PR degradation rate were investigated in detail. Ca/Co3O4 manifested excellent catalytic activity after five successive runs without noticeable structure change. Electron paramagnetic resonance (EPR) and radicals scavenging experiments testified that O2∙- rather than •OH and SO4∙- was the dominating species for dye degradation. The reasonable catalytic mechanism was proposed.