Ornidazole degradation based on peroxymonosulfate activation induced by oxygen vacancies (OV)-enriched Cu-Co-TiO2: Coexistence of free-radical and non-radical pathways

Abstract

Employing transition-metal catalysts in peroxymonosulfate (PMS) activation reactions to facilitate combined free-radical and non-radical interactions is regarded as a proficient approach for decomposing organic contaminants. However, the creation of active catalysts faces significant challenges due to low activation efficiency, inadequate action sites, and instability of current activation materials. Here, we successfully prepared bimetallic Cu and Co co-doped TiO₂ (Cu-Co-TiO₂) catalyst using the sol-gel technique. Excellent ornidazole (ONZ) removal efficiency (0.628 min⁻¹) was demonstrated by the Cu-Co-TiO₂/PMS system, which was applicable across a broad pH range (4−10) and unaffected by different water matrices. Moreover, the coexistence of free-radical (SO₄^•-, •OH and O₂^•−) and non-radical (¹O₂) routes in the Cu-Co-TiO₂/PMS system, where SO₄^•- and ¹O₂ are the predominant active substances, was confirmed by quenching experiments and electron paramagnetic resonance (EPR) study. The synergistic impact of Cu/Co bimetal may hasten the redox cycles of Cu⁺/Cu²⁺ and Co²⁺/Co³⁺, causing plenty of oxygen vacancies (O_V) and improving PMS activation efficiency. The quantitative structure-activity relationship (QSAR) examination of the intermediates showed a decrease in toxicity, and the potential pathways of ONZ degradation were illustrated using Liquid Chromatography Mass Spectrometry (LC-MS) technology. This work not only demonstrated the effectiveness and stability of Cu-Co-TiO₂ as a PMS activator, but it also offered fresh information on how to remove organic pollutants from wastewater by using PMS activation via the radical and non-radical oxidation pathway.