LED-driven photocatalytic degradation of tetracycline by chromite ore processing residue (COPR): Mechanism, pathway, toxicity assessment

Soda-based chromite ore processing residue (COPR) is a hazardous waste produced from chromium salt plants. In this study, detoxified water-washed chromite ore processing residue (DW-COPR) was investigated as a catalyst to activate peroxymonosulfate (PMS) to degrade tetracycline (TC) in the presence of visible light. Performance, mechanism, pathways of TC degradation process in the DW-COPR/PMS/light catalytic system and the toxicity analysis of the intermediates were systematically analyzed by EPR, LC-MS, and Toxicity Estimation Software Tool (T.E.S.T). The results indicated that the DW-COPR had excellent properties on TC degradation and practical application, with optimal efficiency of 94.37% in the DW-COPR/PMS/light system, due to the combined participation of radical •OH, SO4•-, O2•-, 1O2, h+, and e-. Simultaneously, the study outlined four potential degradation pathways for TC: deamidation, hydroxylation, benzene ring opening, and carbonylation. It was revealed that the naturally formed spinel structure in DW-COPR played a dominant role in the reusability and recyclable performance. The present work provides a new perspective on the high-value-added resourcing of DW-COPR as catalyst.