Synergistic redox cycling in Cu-montmorillonite anchored CoTiO3: A dual-functional composite for high-efficiency peroxymonosulfate activation toward tetracycline degradation

Abstract

Efficient interfacial charge transfer plays a crucial role in for enhancing activation of peroxymonosulfate (PMS) and improving pollutant degradation efficiency. In this study, the interlayer confinement effect of montmorillonite (Mt) with high cation-exchange capacity was utilized to anchor Cu²⁺ for constructing Cu-intercalated montmorillonite (Cu-Mt), which was further integrated with CoTiO₃ (CTO) nanorods to form a CTO@Cu-Mt catalyst. Compared with the single CTO/PMS system, the CTO@Cu-Mt/PMS system exhibited significantly enhanced catalytic performance, with the degradation rate of 98 % within 30 min in tetracycline (TC) degradation. Electrochemical tests showed that Cu species acted as electron transfer mediators and effectively promoted the conversion of Co²⁺ to Co³⁺ through its dynamic valence shift, and this synergistic effect significantly enhanced the interfacial charge transfer efficiency. The post-reaction XPS analysis revealed that the Cu⁺ content exhibited merely a slight decrease of 1.5 % (Δ), confirming the anchoring effect of the interlayer confinement in Cu-Mt on active species, thereby effectively optimizing the Co redox process. Additionally, the Inductively coupled plasma emission spectroscopy (ICP-OES) solution test demonstrated an ultralow Cu leaching concentration of 1.23 mg L⁻¹, further confirming the structural stability of the system. As confirmed by quenching experiments and Electron paramagnetic resonance (EPR) characterization, the efficient degradation of pollutants was primarily attributed to the synergistic interaction of •OH and ¹O₂. The “structure-limited, dual-path synergistic” design strategy proposed in this study establishes a novel theoretical framework for developing highly stable multiphase catalytic oxidation systems.