TiO2 photocatalysis applied to the degradation and antimicrobial activity removal of oxacillin: Evaluation of matrix components, experimental parameters, degradation pathways and identification of organics by-products

The TiO2 photocatalytic degradation of oxacillin (OXA) in synthetic and natural waters was studied. The matrix effects, in terms of antibiotic and antimicrobial activity removal, were evaluated in the presence of iron ions, natural mineral water and additives contained in commercial formulations of the antibiotic. A slight improvement in degradation was observed in the presence of iron ions. On the other hand, the presence of excipients in a commercial formulation or inorganic ions in natural mineral water slightly inhibited the efficiency of the system. An experimental design using pH, catalyst load and light intensity as variables was also evaluated. The best performances were achieved at natural pH (similar to 6.0) using 2.0 g L-1 of TiO2 with 150W of applied power. The evaluation of OXA concentration indicated that the photodegradation process showed a Langmiur-Hinshewoold kinetic model. The extent of the process was evaluated following the evolution of chemical oxygen demand (COD) and dissolved organic carbon (DOC). Total removal of both, the antibiotic and its antimicrobial activity, was achieved after 120 min; while 100% of mineralization was observed within 480 min of treatment. Finally, five by-products were identified, the degradation routes were elucidated and a schema of the antibiotic degradation was proposed. (C) 2015 Elsevier B.V. All rights reserved.