Enhanced heterogeneous activation of peroxymonosulfate by Ruddlesden-Popper-type La2CoO4+delta nanoparticles for bisphenol A degradation

The scalable synthesis of stable catalysts for environmental remediation applications remains challenging. Nonetheless, metal leaching is a serious environmental issue hindering the practical application of transition metal based catalysts including Co-based catalysts. Herein, for the first time, we describe a facile one-step and scalable spray-flame synthesis of high surface area La2CoO4+delta nanoparticles containing excess oxygen interstitials (+delta) and use them as a stable and efficient catalyst for activating peroxymonosulfate (PMS) towards the degradation of bisphenol A. Importantly, the La2CoO4+delta catalyst exhibits higher catalytic degradation of bisphenol A (95% in 20 min) and stability than LaCoO3-x nanoparticles (60%) in the peroxymonosulfate activation system. The high content of Co2+ in the structure showed a strong impact on the catalytic performance of the La2CoO4+delta + PMS system. Despite its high specific surface area, our results showed a very low amount of leached cobalt (less than 0.04 mg/L in 30 min), distinguishing it as a material with high chemical stability. According to the radical quenching experiments and the electron paramagnetic resonance technology, SO4 center dot-, (OH)-O-center dot, and O-1(2) were generated and SO4 center dot- played a dominant role in bisphenol A degradation. Moreover, the La2CoO4+delta + PMS system maintained conspicuous catalytic performance for the degradation of other organic pollutants including methyl orange, rhodamine B, and methylene blue. Overall, our results showed that we developed a new synthesis method for stable La2CoO4+delta nanoparticles that can be used as a highly active heterogeneous catalyst for PMS-assisted oxidation of organic pollutants.