Layered double oxide (CoAl-LDO) catalysis for enhanced ozonation of methyl orange: Performance assessment and mechanistic insights

Abstract

In this study, we report the successful synthesis of a novel layered double oxide (CoAl-LDO) ozone catalyst through co-precipitation and high-temperature calcination method, utilizing layered double hydroxide (CoAl-LDH) as an uncalcined intermediate product. The synthesized CoAl-LDO exhibits a thinner and more curved plate-like morphology with well-developed porous structures, demonstrating richer content of active oxygen species and enhanced oxygen migration ability. Notably, the CoAl-LDO catalyst demonstrates superior catalytic performance compared to conventional catalysts and ozone alone systems. Utilizing methyl orange (MO) as the target pollutant, CoAl-LDO catalyzed ozonation achieved an impressive removal rate of 88.27 % within 10 min, surpassing the performance of CoAl-LDH (61.84 %), Co3O4 (57.71 %), and O3 alone systems (47.71 %). Moreover, the CoAl-LDO catalyst exhibited excellent stability and reusability, maintaining a removal rate above 72.13 % over four consecutive cycles. In addition, we propose a novel reaction mechanism for the catalytic ozonation based on the interconversion of Co2+ and Co3+ during the reaction process to generate oxygen vacancies (OV), which in turn react with water molecules and ozone molecules to produce ROS (especially O2−). These findings provide unique perspectives for the precise design and rational application of ozone catalysts.