Effect of Anions on the Degradation of Ceftriaxone by UV/H2O2 Process Using a 222 nm Far-UVC KrCl* Excilamp

Over the last few years, the KrCl* excilamp (222 nm) has emerged as a promising Far-UVC source to drive advanced oxidation processes (AOPs) for degrading organic contaminants in water. In the present study, we explored the effect of common anions (Cl⁻, SO₄²⁻, NO₃⁻, HCO₃⁻) in the concentration range of 1–100 mM on the kinetics of degradation and mineralization of ceftriaxone (CEF) by Far-UVC/H₂O₂ process using excilamp in synthetic (deionized water + anions) and real (tap) water. Nitrate at 1 mM and other anions at all concentrations exhibited a promotion effect by accelerating the degradation rate. It can be attributed to the contribution of secondary radicals generated by anions under Far-UVC exposure. However, the mineralization in terms of total organic carbon (TOC) removal decreased in the presence of HCO₃⁻ and NO₃⁻. When reducing the H₂O₂ dose, chloride ions provided significant process intensification by increasing the rate constant by 3.5 times and reaching 30% TOC removal along with complete CEF degradation. Examining tap water revealed the high performance of the Far-UVC/H₂O₂ process for degrading and mineralizing CEF without the inhibition effect of matrix components. Results demonstrate that anions as radical precursors tend to promote the oxidation processes rather than inhibit them. This opens up good prospects for practical application of KrCl* excilamp in water treatment.