Antibacterial inactivation of spiramycin after titanium dioxide photocatalytic treatment.

The photocatalytic degradation of an antibiotic (spiramycin) has been studied using immobilized titanium dioxide (TiO 2 ) as a photocatalyst in a laboratory reactor under ultraviolet illumination (365 nm). The degradation of the antibiotic was monitored by ultraviolet spectrophotometry and high-pressure liquid chromatography and confirmed by an antibacterial activity evaluation. Two types of TiO 2 (P25 and PC500) immobilized on glass plates were compared. For TiO 2 PC500 immobilization on glass and paper was also studied. A slightly better degradation was obtained with TiO 2 P25 for which the degradation kinetics were investigated. The Langmuir–Hinshelwood kinetic model is satisfactorily obeyed at initial time and in the course of the reaction. Adsorption and apparent rate constants were determined. These results show a complete degradation of spiramycin, which was confirmed by the inhibition of the antibacterial activity of Staphylococcus xylosus , when exposed to spiramycin solutions treated with photocatalyst for a short time. In addition, the codegradation of spiramycin and tylosin was investigated and showed that tylosin had a higher affinity to the catalyst TiO 2 P25 than spiramycin. The complete degradation of spiramycin confirms the feasibility of such a photocatalytic treatment process for spiramycin elimination from contaminated water. [ABSTRACT FROM AUTHOR]