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/Co 3 O 4, 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/Co 3 O 4 (0.3048 min −1 ), which displayed the optimum catalytic performance, was 7.5 times that of pure Co 3 O 4 (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/Co 3 O 4 manifested excellent catalytic activity after five successive runs without noticeable structure change. Electron paramagnetic resonance (EPR) and radicals scavenging experiments testified that O 2 ∙ - ${}_2^{\bullet -}$ rather than • $\mathrm{•}$ OH and SO 4 ∙ - ${}_4^{\bullet -}$ was the dominating species for dye degradation . The reasonable catalytic mechanism was proposed.