Photo-assisted ozonation of cefuroxime with solar radiation in a CPC pilot plant. Kinetic parameters determination

Abstract

The combination of ozone and solar radiation can be considered an effective technology as advanced oxidation process, AOP, for addressing the removal of harmful contaminants of emerging concern in water. Cefuroxime is an example of an antibiotic whose presence may result in a problem if not conveniently removed from the water. Cefuroxime oxidation has been performed employing photolytic ozonation in an autonomous pilot plant, consisting of a solar collector photo-reactor with ozone feeding, solar panel cells, and batteries for energy demands. Firstly, the kinetics of cefuroxime ozonation has been deeply studied in an agitation cell reactor. The stoichiometric ozonation ratio was estimated as zO3 = 1.00 ± 0.06 (O3 mol per cefuroxime mol) and the second-order rate constant in the range 1.50 × 106 – 4.69 × 106 M−1 s−1 for the non-dissociated and dissociated, respectively, cefuroxime molecule. The oxidation intermediates identified included hydroxylation of the initial molecule, attack to the secondary amide group and oxidation of the bi-substituted sulfide position. Secondly, the simultaneous application of ozone and solar radiation in the CPC pilot plant enhanced the degradation of cefuroxime. The kinetics in the CPC reactor was simulated and the importance of the hydroxyl radical over ozonation and photolysis was confirmed, 55% of HO• contribution. Also, over 55% of mineralization was observed during photolytic ozonation in wastewater matrix whereas single ozonation only was able to partially oxidize the initial organic content to short organic acids (formic, acetic, and oxalic) that were accumulated in the water.