UV-A/TiO2 photocatalytic decomposition of erythromycin in water: Factors affecting mineralization and antibiotic activity

The photocatalytic mineralization of the antibiotic erythromycin (ERM) in aqueous TiO2 suspensions was investigated. UV-A irradiation was provided by a 9 W lamp at a photon flux of 4.69 × 10−6 einstein/s and runs were performed at ERM initial concentrations between 2.5 and 30 mg/L, 10 commercially available TiO2 catalysts at loadings between 100 and 750 mg/L and at acidic or near neutral conditions. The extent to which the aforementioned factors influence ERM mineralization was assessed measuring the total organic carbon (TOC) content of the solution. Of the various catalysts tested, Degussa P25 (75:25, anatase:rutile) was highly active yielding 90% TOC reduction after 90 min of reaction with 10 mg/L ERM and 250 mg/L TiO2; the second best catalyst consisting of pure anatase (Hombikat UV 100) yielded only 65% reduction. TOC removal decreased with decreasing titania loading and increasing ERM concentration and solution pH. For the range of the ERM concentrations studied, mineralization kinetics appears to follow the Langmuir–Hinshelwood model. Short (i.e. 15 min) photocatalytic treatment of 30 mg/L ERM was capable of abolishing completely the antimicrobial properties of ERM to E. coli but this was accompanied by insignificant levels (i.e. 10%) of total oxidation.