Adsorption and breakdown of penicillin antibiotic in the presence of titanium oxide nanoparticles in water

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The fate and transport of antibiotics in natural water systems is controlled in part by interactions with nanometer (10(-9) m) metal oxide particles. Experiments were performed by mixing solutions of ampicillin (AMP), a common, penicillin-class human and veterinary antibiotic, with 25 nm-TiO2 (anatase) nanoparticles at different pH conditions. Both sorption and degradation of AMP were observed in the AMP-nanoparticle solutions. For AMP concentrations from similar to 3 mu M to 2.9 mM the overall AMP removal from solution can be described by linear isotherms with removal coefficients (K-r) of 3028 (+/- 267) L kg(-1) at pH 2, 11,533 (+/- 823) L kg(-1) at pH 4, 12,712 (+/- 672) L kg(-1) at pH 6, and 1941 (+/- 342) L kg(-1) at pH 8. Mass spectral analysis of AMP solutions after removal of the solid nanoparticles yielded ions that indicate the presence of peniclloic acid, penilloic acid and related de-ammoniated by-products as possible compounds resulting from the degradation of AMP at the TiO2 surface.