Mineralisation of the antibiotic amoxicillin in pure and surface waters by artificial UVA- and sunlight-induced fenton oxidation

Background: The degradation and mineralisation of the antibiotic amoxicillin by photo-Fenton reactions, mediated by artificial UVA or solar irradiation, were investigated. Experiments were conducted with 30 mg L^-1 amoxicillin solutions prepared with deionised or surface water at Fe²⁺ and H₂O₂ concentrations in the range 0.0179-0.0895 and 1-10mmol L^-1, respectively. Black-light irradiation at 365 nm was provided by a 13W m^-2 lamp, while samples were exposed to sunlight at 20W m^-2 for solar experiments. Results: In all cases, quantitative amoxicillin degradation occurred within 5 min and this was accompanied by lower mineralisation rates. Mineralisation followed first-order kinetics with respect to organic carbon content and it was not affected by the water matrix with either type of illumination. Solar-induced reactions were only marginally faster than artificial irradiation. Increasing the H₂O₂ to Fe²⁺ concentration ratio increases the extent of mineralisation up to a point beyond which degradation is impeded due to radical scavenging associated with the high concentrations of the Fenton reagents. Conclusion: Amoxicillin is readily degradable by homogeneous photocatalysis, being converted to more stable intermediates as indicatedby lower mineralisation rates. The process can be driven by solar irradiation, thus providing a sustainable treatment technology.