Synergistic catalytic activation of persulfate by CuMnO2–CoPc heterostructures on Ti foam: kinetics and mechanism of antibiotic oxidation

Abstract

This study presents a novel heterogeneous catalyst system – CuMnO₂@cobalt phthalocyanine immobilized on titanium foam (CuMnO₂@CoPc/Ti foam) – that is highly effective in treating three common antibiotics, ofloxacin (OFL), levofloxacin (LEVO) and sulfanilamide (SFA), through UV-persulfate-based advanced oxidation (UV/PS). Comprehensive characterization (XRD, SEM-EDS, FTIR, BET, XPS, and UV-vis DRS) confirms a stable mesoporous architecture and uniform coating; the specific surface area increases from 55.3 to 60.8 m² g⁻¹ after CoPc deposition, and the apparent optical band gap narrows from ≈1.41 to ≈1.31 eV, indicating improved visible-light response. Antibiotic decay follows pseudo-first-order kinetics with k_app of 0.0426 ± 0.0015, 0.0410 ± 0.0017, and 0.0393 ± 0.0013 min⁻¹ for OFL, LEVO, and SFA, respectively, delivering >90% removal in 60 min. TOC mineralization reaches ≈69–72%, evidencing deep oxidation beyond parent-compound loss. Mechanistically, XPS verifies persistent Cu²⁺/Cu⁺ and Mn⁴⁺/Mn³⁺ surface couples (Co states stable), while EPR with DMPO detects SO₄˙⁻ and ˙OH, with sulfate radicals dominating. The monolithic catalyst is reusable over 5 cycles with negligible activity loss and ultra-low metal leaching (Cu/Mn/Co ≪ 0.1 mg L⁻¹ by ICP-OES), underscoring chemical robustness. These results highlight CuMnO₂@CoPc/Ti foam as a durable, separable platform for UV/PS treatment of antibiotic-bearing waters and provide a mechanistic blueprint—combining photosensitization and multi-center redox—to guide future reactor-scale implementations.