Abstract

The pharmaceutical industry is one of the fastest growing economic sectors in the world. The existence of medicines for the most different diseases has made the use of these products grow vertiginously in recent years. When ingested these compounds are partially absorbed by the body, and part excreted in its original form. Sewage treatment plants (ETS), with processes based on biological degradation, can not remove these drugs from water. When it is returned to the environment, or intended for human consumption, this water contains small amounts of these compounds, which can cause deleterious effects to both humans and the environment. In this situation the use of photocatalytic methods can be an important alternative in the removal of these contaminants from the aquatic environment. This work studied the photodegradation of the antibiotic metronidazole (MNZ) in aqueous solution by photolytic and photocatalytic methods (POA) using ultraviolet light, hydrogen peroxide (H2O2) and titanium dioxide (TiO2). To investigate the photocatalytical process, an experimental design 23 was performed to evaluate the influence of the variables pH, hydrogen peroxide concentration and TiO2 concentration over the photodegradation of drug, which was spectrophotometrycally monitored in the UV-VIS region. The kinetic model of pseudofirst order described quite well the degradation behavior of the drug. The photocatalytical process only in presence of H2O2, the highest rate of degradation obtained was 8.66% at pH 4. In the heterogeneous photocatalysis experiments the highest degradation rate of the MNZ was 72.1% when TiO2 was used in concentration of 100 mg∙L-1, H2O2 at the concentration of 1000 mg∙L-1 at pH 10. The statistical analysis of the results showed that in the heterogeneous photocatalysis experiments with TiO2 only the pH/H2O2 interaction had no significant effect. Cytotoxicity assays employing Artemia salina as bioindicator showed a 90% reduction in sample toxicity after the photocatalytical treatment.

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