Singlet oxygen-dominated non-radical oxidation pathway for 2,4-Dichlorophenol degradation over CeO₂ coated carbon fibers

CeO₂ was uniformly coated onto the surface of carbon fibers (CF) and the resulting CeO₂@CF was employed for the activation of peroxymonosulfate (PMS) to degrade 2,4-Dichlorophenol (2,4-DCP). Under the initial conditions of a PMS concentration of 10 mmol/L, pH range of 3 to 9 and a CeO₂@CF mass concentration of 0.1 g/L, the system achieved complete degradation of 50 mg/L of 2,4-DCP with high mineralization efficiency within 60 min. Additionally, the CeO₂@CF/PMS system showed high efficiency in the presence of coexisted anions (HCO₃⁻, CO₃²⁻, SO₄²⁻, Cl⁻) and exhibited excellent purification capability for actual coking wastewater. Combined with characterization analyses (SEM-EDS, XRD, Raman, XPS, and EPR), degradation experiments and radical quenching experiments, the physicochemical properties of the prepared catalyst and the 2,4-DCP degradation mechanism were explored. Results revealed that CeO₂ was uniformly coated on the CF surface, maintaining a regular framework structure. During this process, Ce⁴⁺ in CeO₂ was reduced to Ce³⁺, resulting in numerous electron-rich oxygen vacancies forming inside CeO₂@CF. Furthermore, the CeO₂ coating increased the amount of oxygen-containing groups (C=O) on the surface of CF and graphite defects. In the CeO₂@CF/PMS system, •O₂⁻ and ¹O₂ were generated at the active sites of the oxygen vacancies (Vo) and C=O with ¹O₂ dominated non-free radical pathway and played a notable role in the 2,4-DCP degradation process.