Degradação de fármacos de interesse ambiental utilizando-se o processo foto-Fenton assistido por lâmpada de LED UV/vis

Abstract

In recent years, the presence of drugs in the environment has been a cause for concern since these compounds are frequently detected in treatment plants even after conventional treatment. Most of these compounds arriving at the treatment plants come from the metabolic excretion of humans and animals. Conventional methods of treatment are not efficient for the complete elimination of these substances since they are designed to be persistent. New treatment techniques have been studied for degradation of these contaminants. The photo-Fenton process has proven to be quite effective in the degradation of several contaminants and with a relatively low operating cost. Moreover, there is possibility of replacing mercury vapor lamps by light (light emitting diode-LED) in the process. Bearing in mind that decreases the cost of energy and they not are contains mercury in its constitution. This studed had as main objective to study the mineralization of antihypertensive drus losartan (LOS) and hydrochlorothiazide (HDTZ) using the photo-Fenton process employing LED lamp of the 50W. The optimization of the system efficiency in the mineralization of LOS and HDTZ was avaluated using the experimental matrix of Doehlert and the desirability function. The optimization allowed to determine the best conditions to achieve maximum efficiency in the mineralization of LOS and HDTZ simultaneously. Under optimized conditions of concentration of Fe2+ (10mg L-1) and H2O2 (100mg L-1), a mineralization percentage of 80% was obtained in 360 minutes of reaction. Effect of photolysis and UV/H2O2 association were avaluated the Dossolved Organic Carbon (DOC) removal was of 10% and 30%, respectively. It was also evaluated the ability to remove DOC in the absence of radiation, Fenton system, the maximum DOC removal of approximately 30% very similar to that observed under conditions of UV/H2O2. The kinetic study has shown that DOC removal using the LED-assisted photo-Fenton system does not follow peseudo-fist order. Another model describe in the literature that the reaction in two steps: one fast and one slow was using obtaining a R2 of 0.9987. The energy cost was evaluated using electrical energy in order of magnitude m3 recommended by IUPAC (Internation Union of Pure and Applied Chemistry). The value obtained to mineralize 80% of the mixture of LOS and HDTZ at concentration of 20 mg L-1 was 130 kWh m-3. The results of this research showed that the optimization is important to search the best performance of a treatment system and highight the use of the desirability function that allows to evaluate similtaneously more than one answer. The LED is a promising technology as it significantly reduces energy costs by promoting the implementation of real wastewater treatment systems. In addition, of photo-Fenton assisted- LED/UV-VIS process has longer durability and is more environmentally friendly, meaning it contains no mercury that is toxic and needs proper disposal.