Development of gas diffusion electrodes (GDE) modified with micro and nanostructured metallic oxides for in situ electrogeneration of H2O2 for environmental applications

Abstract

The production processes used in agriculture generate many pesticide residues. Every year, it is produced large quantities of these products, affecting human and animal health. Monitoring of residual pesticides in the environment has been gaining great interest due to the fact that many of these substances are frequently found in effluents natural waters. So many waste products persist to several conventional treatment processes of water. As an alternative to conventional treatment of these pesticides, electrochemical technology can be considered an unconventional technology that offers an efficient means of pollution control by means of redox reactions, either through direct reactions between the species and the electrode surface pollutants, or synergism of these processes with the power of oxidizing species generated in situ. Among non-conventional technologies, the technology of electrochemical treatment of waste and wastewater has great advantage as its environmental compatibility, considering the fact that the main reagent, the electron, is a "clean reagent". In the electrochemical treatment of organic waste, organic molecules are degraded by reactions that occur through the transfer of oxygen atoms of water molecules from the solvent phase for the species to be oxidized. The use of electrochemical reactors with gas diffusion electrodes (GDE) in situ generation of H2O2 allows processing of solutions containing organic substances and can be used as pre-or post-treatment, together with other processes, for example, the advanced oxidation process (OAP). The production of H2O2 in GDE-type electrodes is based on cathodic reduction of oxygen molecules. This type of electrode does not suffer from limitations imposed by the gas concentration in the aqueous solution and not by diffusion of O2 molecules from the bulk of the solution to the electrode surface, as in conventional electrodes. In recent decades is the remarkable use of chemically modified electrodes, whose objective is to change the pre-set and control the physical-chemical nature of the electrode-solution interface as a way to change the reactivity and selectivity of the sensor base, thus favoring the development of electrodes for various purposes and applications, from catalysis of organic reactions and inorganic electron transfer to the molecules of interest. The purpose of this work aims at the modification of electrodes by impregnation of oxides of ruthenium, iridium and osmium micro and nanostructures, are treated as metals are resistant to acid, to improve efficiency in the electrochemical reduction of oxygen from a process electrode involving two electrons, and consequently increase the yield in the synthesis of hydrogen peroxide in situ. The MGDE more efficient will be used in the process of degradation of two pesticides diuron and glicosato using chemical degradation via direct H2O2 (anodic oxidation). In addition, we intend to make the identification of intermediate degradation of pesticides during the application of each of the processes of degradation, using gas chromatography with mass spectrometry and ion chromatography to establish the route of degradation of each compound.