Degradação do antibiótico Cloranfenicol por fotólise e pelo processo foto-fenton: avaliação química e toxicológica

Abstract

In this work the photodegradation of the antibiotic chloramphenicol (CFC) in different aqueous media (deionized water, surface water and effluent of sewage treatment plant STP), by photolysis and photo-Fenton process using artificial and solar radiation was evaluated. The concentration of H2O2 influenced strongly the degradation of CFC by photo-Fenton at lab scale, being the concentration of 400 mg L-1 of H2O2 chosen experimentally as the best. In addition, it was observed that the concentration of Fe2+ influenced the rate removal of CFC and dissolved organic carbon (DOC). An increase on the Fe2+ concentration from 5 to 10 mg L-1 increases in 1,3 times the rate removal of CFC, keeping constant in the presence of 15 mg L-1 Fe2+. On the other hand, no influence in the rate removal of CFC and DOC was observed in relation to the mode addition of H2O2 (single or multiple), choosing the single mode. Defining the best parameters (10 mg L-1 Fe2+ and 400 mg L-1 H2O2 with replacement after 80% consumption), the degradation of CFC in different matrices for lab scale (artificial source) and pilot plant (solar source) by photo-Fenton process was assessed. In general, removals of 92, 90, 78, 86, 57 and 40% DOC, respectively to deionized water (solar and artificial), surface water (solar and artificial) and effluent of STP (solar and artificial) after 60 min of irradiation exposure were obtained. With relation to the photolysis, it was observed that the photodegradation of CFC is strongly influenced in effluent of STP when compared to matrices of deionized and surface water, due to the presence of contaminants that absorb in the same wavelength than CFC. The byproducts of photolysis in deionized water using solar radiation showed high toxicity in comparison to CFC, indicating the formation of toxic intermediates. On the other hand, applying the photo-Fenton process and artificial radiation at lab-scale, intermediates of lower toxicity, more oxidized and without antimicrobial activity were formed. Based in these results, it was observed that the photo-Fenton process can be used to the treatment of water containing this type of pollutant. In addition, the solar light can be used as radiation source, which is extremely advantageous, once the energetic costs are reduced.