Descontaminação de efluentes contendo Cefalexina por processos (foto)eletroquímicos com filmes de TiO2 e TiO2-X

Abstract

The present work aims the degradation of the drug Cephalexin in aqueous media through different methodologies: photolysis, photocatalysis, photoelectrocatalysis and electrocatalysis using pure and Ti3+ doped TiO2 films to reduce the solution toxicity. The nanostructured films (TiO2NT) were synthesized using the electrochemical anodizing method and self-doped in situ through electrochemical reduction. The semiconductor was analyzed structurally and morphologically and the dopant presence was studied using techniques such as x-ray diffractometry and cyclic voltammetry. The films performance faces the degradation techniques was carried through linear sweep voltammetry with pulsed light so the photo-current response could be investigated. The drug degradation using the different methodologies was analyzed by UV-Vis spectrophotometry and among the studied techniques, the one that obtained a substantial drug degradation and a higher decrease in solution toxicity was the reductive photoelectrocatalysis, applying a potential of -1.5V versus standard hydrogen electrode for self-doped films at -1.4V. Among the synthesized films, all had a good photo-current response, but the self-doped film at -1.4 V showed the highest photocatalytic activity. The study of the electrocatalysis showed interesting results because it promoted the Cephalexin reduction to a molecule that absorbs at the same wavelength, increasing the absorption bands intensity in the scanning spectrum over time, but the decrease in the solution toxicity was not as significant. Tests of chemical oxygen demand were conducted in order to verify the efficiency of COD removal and toxicological tests of minimal inhibitory concentration against Staphylococcus aureus bacteria evaluated if the studied methodologies were able to reduce the original solution toxicity. In COD tests, all effluents from (photo)electrocatalytic tests had a reduction in concentration of COD. In MIC tests, the initial Cephalexin solution did not cause bacterial death/inhibition, but the same result remained for the tests effluents, indicating that the formed products did not have a higher toxicity than the initial solution.