Avaliação da degradação simultânea de fipronil, oxibenzona e propilparabeno por UV-C/persulfato em efluente sanitário terciário

Abstract

A wide variety of organic contaminants, such as the contaminants of emerging interest, have been detected in concentrations of the order of ng to µg L-1 in aqueous matrices all over the planet, raising a concern regarding the treatment of water and sewage, since the classic treatment plants are neither designed nor designed to eliminate or degrade these compounds. In order to alleviate this problem, it emerges as a complementary alternative the advancement processes. The present work evaluated the simultaneous degradation of the compounds fipronil, oxybenzone and propylparaben, in tertiary sanitary effluent through the UV process alone or combined with solid persulfate. The initial concentration of target compounds used was 100 µg L-1. The efficiency of the process was monitored by the decay of the mean concentration of the target compounds and the consumption of persulfate oxidant. During the direct photolysis of the compounds, it was possible to reach an average of 47% degradation after 20 minutes of irradiation. On the other hand, when combining UV-C radiation with persulfate, there was a synergism in the percentage of degradation of the mixture, and it improved when increasing the persulfate concentration from 100 to 400 µmol L-1, reaching 74% degradation. The influence of pH (3.0, 7.0 (natural from the matrix) and 11.0) was also evaluated on the degradation of target compounds, in the presence of the best persulfate concentration (400 µmol L-1). The highest degradation efficiency was achieved at pH 3 (94%) while at pH 7.0 and 11.0, 74% and 53% degradation were achieved, respectively. The major species responsible for the degradation of the target compounds varies according to the pH of the medium, being at pH 3.0 the sulfate radical, at pH 7.0 the hydroxyl radical, and at pH 11.0 none of them, with the majority degradation being carried out by the photolysis process. Based on the results, the UV-C/persulfate process can be a complementary alternative to the classic treatments in teaching treatment plants following the interruption of the studied organic micropollutants.