Photoactivation of oxidative degradation and mineralization of ceftriaxone with excilamp radiation

Among organic compounds resistant to biodegradation, antibiotics are of particular interest because their constantly increasing consumption has resulted in their presence in almost all components of aquatic ecosystems. With the use of advanced oxidation processes, it is possible to achieve conversion not only of target compounds but also of their reaction intermediates, which are often more toxic. Close attention is paid to the use of persulfates as precursors of reactive oxygen species, which are activated via combined methods involving ultraviolet radiation. Modern mercury-free sources include KrCl exilamps emitting quasi-monochromatic radiation. This study is the first to examine the kinetics of oxidation of a β-lactam antibiotic (ceftriaxone) and mineralization of total organic carbon by persulfate under the UVC radiation of a KrCl exilamp. Different oxidative systems were comparatively evaluated. The efficiency of target compound degradation was found to increase in the series {S2O8 2-} << {UV} < {Fe2+/ S2O8 2-} < {UV/ S2O8 2-} < {UV/Fe2+/ S2O8 2-}. The total organic carbon was mineralized only in the oxidative systems {UV/Fe2+/ S2O8 2-} > {UV/ S2O8 2--}. The optimal conditions for complete conversion of ceftriaxone and deep mineralization of total organic carbon (43–60%) in the {UV/Fe2+/ S2O8 2-} system were achieved at a molar ratio of [S2O8 2-]:[Fe2+] = 10. Both sulfate radical anions and hydroxyl radicals were shown to participate in ceftriaxone degradation and mineralization of total organic carbon. The obtained results indicate the viability of using the UVC radiation of a KrCl exilamp in the combined oxidative system {UV/Fe2+/ S2O8 2-} for effective degradation of β-lactam antibiotics.