Photodegradation of Ciprofloxacin antibiotic over TiO 2 grown by PEO: ecotoxicity response in Lactuca sativa L . and Lemna minor

TiO2 is one of the most used materials in the photocatalysis of organic pollutants. It can be prepared by different techniques including electrochemical methods. The influence of the structure of TiO2 films grown electrochemically using plasma electrolytic oxidation (PEO) was investigated in terms of the photocatalytic activity. The film microstructure and morphology were analyzed and its influence in photocatalytic response was evaluated by photodegradation of ciprofloxacin (CIP). A strong influence of the synthesis temperature on the structural properties (pore diameter and crystallite size) was observed, which could be correlated with the photocatalytic activity change of the synthesized materials. To correlate the structural to the photocatalytic activity, besides Pareto graphs and analysis, a variable called microstructure ratio-SR (pore diameter/crystallite size) was evaluated. Results have shown  the F2020005 film (20 mA cm−2, 20 °C and 0.05 mol L−1) presented the highest photocatalytic activity. As a complementary study, ecotoxicity tests were realized using Lactuca sativa L. seeds and the macrophyte Lemna minor. In these experiments, it was observed that the effluents of the photocatalysis carried out with the materials synthesized by PEO presented lower toxicity, compared to the CIP solution without any treatment. The best results for the degradation of CIP were obtained using films synthesized at higher temperatures. CIP photocatalytic degradation using TiO2 films grown by PEO was effective, generating byproducts of low toxicity.