• • CO2•− generated via 3CBBP* oxidizing HCOO− achieved 98.2% degradation of 10 μmol·L−1 metronidazole within 30 min under 8 mmol·L−1 HCOO− and 200 μmol·L−1 CBBP, demonstrating a highly efficient reductive degradation route for recalcitrant pollutants.
• • The degradation efficiency increased with HCOO− concentration (up to 8 mmol·L−1) and remained unaffected across pH variations, indicating robustness for applications in diverse water chemistries without pH adjustment.
• • Common anions (Cl−, NO3−, CO3^2−, low HCO3−) inhibited MNZ degradation, whereas high HCO3− (≥? mmol·L−1) slightly enhanced it; humic acid (HA) suppressed degradation proportionally to its concentration, highlighting matrix-specific interference that must be managed in real water treatment.
• • The hν/CBBP/HCOO− system exhibited effective MNZ degradation in real water samples, underscoring its practical viability for treating micropollutants in natural and engineered aquatic systems.