Catalytic degradation of Rhodamine B through peroxymonosulfate activation by the Co-doped hydroxyapatite

Supported Co-based catalysts have shown attractive prospects for peroxymonosulfate (PMS) activation. In this work, Co-doped hydroxyapatite (H-Co/HAP) composites were prepared by a simple hydrothermal method. The Co content in H-Co/HAP could reach 71.2 mg/g, while the Co leaching rate remained relatively low. By right of the excellent catalytic performance, the as-prepared H-Co/HAP could achieve 99.02% degradation of Rhodamine B (RhB) within 10 min in the presence of 0.5 mM PMS and a first-order kinetic rate constant of 0.876 min−1. Even after 8 cycles, the RhB degradation efficiency remained at 81.96%. In addition, the effects of vital reaction parameters, including catalyst dosage, PMS dosage, initial pH, humic acid, and coexisting anions, on the catalytic performance in the H-Co/HAP10/PMS system were systematically investigated and discussed. The degradation mechanism of a non-radical (1O2) as the dominant active specie and a radical (•O2− and SO4•−) as the minor active specie was identified through quenching experiments and electron paramagnetic resonance testing. Moreover, possible degradation pathways of RhB were proposed in the H-Co/HAP10/PMS system. Overall, this study offers a meaningful strategy for designing high-content Co-based catalysts to degrade dye molecules in wastewater. [Display omitted] •Co-doped hydroxyapatite (H-Co/HAP) composites were prepared by a simple hydrothermal method.•Biocompatible HAP was chosen as the supporter to anchor toxic Co2+ by replacing Ca2+.•The Co content in H-Co/HAP could reach 71.2 mg/g, while the Co leaching rate remained relatively low.•The synergistic effect between Co ions and HAP for activating PMS to generate 1O2, SO4•−, and •O2− was explored.•The H-Co/HAP10/PMS system exhibited excellent degradation performance and long-term stability.