Low ultraviolet dose with high efficiency: Synergistic coupling of far-UVC and ferrate(VI) for ultrafast and selective degradation of micropollutants

Enhancing the reactivity and yield of reactive species to reduce the ultraviolet (UV) fluence requirement for activating ferrate (Fe(VI)) is critical for advancing UV-based Fe(VI) processes toward practical wastewater treatment applications, yet it remains challenging. Herein, we developed a far-UVC-driven Fe(VI) activation system for the efficient degradation of micropollutants. The results demonstrated that switching from conventional low-pressure UV lamps (LPUV, UV₂₅₄) and UVA₃₆₅ to 222 nm far-UVC achieved ultrafast degradation of carbamazepine (CBZ) at an extremely low UV dose of 29.76 mJ/cm² under pH 8.0 conditions. The fluence-based degradation rate constants were 15.8 and 142.0 times higher than those achieved by UV₂₅₄ and UVA₃₆₅ photolysis of Fe(VI), respectively. This improved degradation can be attributed to the increased generation of high-valent iron intermediates [(Fe(V)/Fe(IV)] in the system. Notably, the presence of complex matrixes barely influenced CBZ degradation, and the UV₂₂₂/Fe(VI) system maintained significantly enhanced performance in various real waters compared to Fe(VI) alone. Additionally, 10 structurally diverse pollutants were selected for evaluation the selectivity of the UV₂₂₂/Fe(VI) system, finding that their lnk_obs values correlated well with their E_HOMO and vertical IP (R² = 0.86). Overall, this study proposes a promising oxidation technology that was efficient, energy-saving, cost-effective, and selective for the rapid elimination of micropollutants.