Degradação de diclofenaco por fotólise direta e peroxidação foto-assistida em reator tubular

Abstract

Water is an essential asset for the maintenance of life, for this reason, water quality has been a subject often discussed and studied. In this context, in the last decades, researchers from different parts of the world reported the presence of contaminants in very small concentrations in the effluents of WWTP (Wastewater Treatment Plant), in the range of µg/L and ng/L, which were called emerging micropollutants. Among them, drugs such as diclofenac have been constantly detected. Regarding the degradation of these pollutants, Advanced Oxidative Processes have shown good results. In this sense, the present work aimed to evaluate the degradation of potassium diclofenac in water base through direct photolysis and photo-assisted peroxidation (H2O2/UV) in a tubular reactor operating in batch. The reactor used in the experiments is available in the Chemical Engineering laboratory at UEA – EST and consists of a titanium cylinder that contains a 254 nm UV lamp through which the solution to be treated passes, in addition a pump connected to the reactor provides circulation continuum of the solution. To analyze the degradation, an experimental design 22 was carried out with triplicate at the central point, considering the variables flow and time. For both methods, the maximum degradation was obtained with the lower flow limit (120 L/h) and upper time limit (2 hours). A maximum degradation of 8.1% was reached by the direct photolysis method and 35.2% by H2O2/UV, for which only time was statistically significant at a confidence level of 95%. In addition, it was possible to observe the color change of the solution from colorless to greenish due to the formation of dimers when exposing diclofenac to UV light. Thus, it is concluded that photo-assisted peroxidation is the most promising method for the degradation of potassium diclofenac and, therefore, different concentrations of H2O2 can be studied in future works in order to obtain the complete degradation of the drug.