Photocatalytic Destruction of Ceftriaxone in Aqueous Solutions

The kinetic tendencies in the destruction of cephalosporin antibiotics (ceftriaxone (CEF)) in photoinitiated oxidative systems were studied using a xenon lamp as a source of quasisolar radiation (UV–Vis). It was established that the oxidative systems under study can be arranged in the following series according to the efficiency and rate of antibiotic destruction: {UV–Vis/Fe²⁺/S₂O\(_{8}^{{2 - }}\)} > {Fe²⁺/S₂O\(_{8}^{{2 - }}\)} \( \gg \) {UV–Vis/S₂O\(_{8}^{{2 - }}\)} > {UV–Vis}. The optimum conditions for the oxidative destruction of CEF in the {UV–Vis/Fe²⁺/S₂O\(_{8}^{{2 - }}\)} system are reached at [S₂O\(_{8}^{{2 - }}\)] : [CEF] = 30 : 1 and [S₂O\(_{8}^{{2 - }}\)] : [Fe²⁺] = 1 : 0.1. As the temperature increases to 40°C, the initial CEF oxidation rate and efficiency increase. The apparent activation energy of the CEF oxidation in the {UV–Vis/Fe²⁺/S₂O\(_{8}^{{2 - }}\)} system was 45 kJ mol^–1, which is comparable to the values obtained for cephalosporin antibiotics. It was proved, using inhibitors of radical reactions, that the oxidative destruction of CEF in combined {UV–Vis/Fe²⁺/S₂O\(_{8}^{{2 - }}\)} proceeds by a multiradical mechanism involving reactive oxygen species (ROS): hydroxyl radicals and sulfate and superoxide radical anions. The obtained tendencies are in good agreement with the results of open-air studies with natural solar radiation; in the {Solar/Fe²⁺/S₂O\(_{8}^{{2 - }}\)} system, the oxidation of CEF is significantly intensified due to combined activation of persulfate by the iron ions, the UV-C (<300 nm) component of natural solar radiation, and the thermal exposure. The results indicate that using the combined {Solar/Fe²⁺/S₂O\(_{8}^{{2 - }}\)} oxidation system is promising for the destruction of antibiotics in order to reduce their release into the environment.