Synthesis of novel LaCoO3/graphene catalysts as highly efficient peroxymonosulfate activator for the degradation of organic pollutants

Metal leaching in perovskite-based catalysts during peroxymonosulfate activation processes can severely restrict their application in wastewater treatment. Therefore, enhancing the stability of perovskite nanostructures is crucial to improve catalytic performance and broaden applications but has been rarely achieved so far. We developed a scalable method to synthesize novel stable and environmentally-friendly nanocomposites of LaCoO3 and few-layer graphene (consisting of roughly-nine layers) for the removal of organic pollutants from wastewater. With abundant oxygen vacancies and synergistic effects between LaCoO3 and few-layer graphene, the novel LaCoO3/graphene catalyst exhibits outstanding catalytic degradation (>99 %) of diclofenac, metoprolol, carbamazepine, and bisphenol A at a high concentration (40 mg/1) in less than 10 min in the peroxymonosulfate activation system, with mineralization of 57, 55, 61, and 62 %, respectively. The LaCoO3/graphene catalyst exhibited excellent reusability and high catalytic performance within a wide pH range (3-11). The formation of LaCoO3/graphene composites prevents cobalt leaching (0.004 mg/l), stabilizes sub-stoichiometric LaCoO3 and thus increases the content of Co2+ in the structure, leading to much higher catalytic activity than that of pure LaCoO3. Electron paramagnetic resonance and radical quenching experiments revealed that both radical pathways (SO4 center dot-, (OH)-O-center dot, and O-2(center dot-)) and non-radical pathways (O-1(2)) contribute to bisphenol A degradation and the relative contributions of (OH)-O-center dot, SO4 center dot-, and O-1(2)/O-2(center dot-) were determined to 13.4, 32.6, and 54 % for bisphenol A removal, respectively. Overall, our results indicate that LaCoO3/graphene is a promising material towards peroxymonosulfate activation for environmental remediation.