| Summary: | Bimetallic catalysts have significantly contributed to the chemical community, especially in environmental science. In this work, a CoAl<sub>2</sub>O<sub>4</sub> spinel bimetal oxide was synthesized by a facile co-precipitation method and used for the degradation of organic pollutants through peroxymonosulfate (PMS) activation. Compared with Co<sub>3</sub>O<sub>4</sub>, the as-prepared CoAl<sub>2</sub>O<sub>4</sub> possesses a higher specific surface area and a larger pore volume, which contributes to its becoming increasingly conducive to the degradation of organic pollutants. Under optimal conditions (calcination temperature: 500 °C, catalyst: 0.1 g/L, and PMS: 0.1 g/L), the as-prepared CoAl<sub>2</sub>O<sub>4</sub> catalyst could degrade over 99% of rhodamine B (RhB) at a degradation rate of 0.048 min<sup>−1</sup>, which is 2.18 times faster than Co<sub>3</sub>O<sub>4</sub> (0.022 min<sup>−1</sup>). The presence of Cl<sup>−</sup> could enhance RhB degradation in the CoAl<sub>2</sub>O<sub>4</sub>/PMS system, while HCO<sub>3</sub><sup>−</sup> and CO<sub>3</sub><sup>2−</sup> inhibit RhB degradation. Furthermore, the considerable reusability and universality of CoAl<sub>2</sub>O<sub>4</sub> were testified. Through quenching tests, <sup>1</sup>O<sub>2</sub> and SO<sub>4</sub>•<sup>−</sup> were identified as the primary reactive species in RhB degradation. The toxicity evaluation verified that the degraded solution exhibited lower biological toxicity than the initial RhB solution. This study provides new prospects in the design of cost-effective and stable cobalt-based catalysts and promotes the application of PMS-based advanced oxidation processes for refractory wastewater treatment.
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