Produção de hidrogênio verde ambientalmente sustentável

Abstract

In the coming years, a very significant worldwide growth (approximately 50% by 2050) in energy and water consumption is expected. The increasingly search for renewable energy sources is one of the pillars to achieve the decarbonization process. Given this scenario, hydrogen gas has been attracting great interest in the industrial and academic environment, as it is considered a clean fuel that has the ability to play an important role in the energy transition, achieving a future with zero emissions of polluting gases, due to its wide industrial application and for being used as an instrument for energy storage. Hydrogen gas can be produced by the electrolysis of water (breaking down of the water molecule under an electric current), forming products (O2(g)) that do not harm the environment, unlike processes that are based on fossil fuels. Contamination of water bodies by gas station accidents and inappropriate releases of effluents from the petrochemical industry is a widely known problem. The presence of aromatic hydrocarbons such as benzene, toluene and xylene (BTXs) in the environment requires close attention due to their toxic character and carcinogenic potential of these compounds. In order to solve these problems, numerous effluent treatments have been carried out, as a large number of aromatic compounds have high stability and resistance to conventional treatments. Thus, advanced electrochemical oxidative processes (POAE) have been studied in order to become an alternative way of treating wastewater, being characterized by the in situ production of hydroxyl radicals (•OH) as the main oxidant, but not the main oxidant exclusive. Among the advantages of this technology, there is the possibility of recovering energy during the process by capturing H2(g), which is produced at the cathode during the oxidation of pollutants at the anode. Therefore, the present work aimed to apply the POAE technology, for the degradation of recalcitrant compounds such as BTX, with simultaneous production of H2(g) integrated into solar panels. The experiments were carried out in a flow reactor with a mass transfer coefficient of 5.11*10-5 (m/s), under three electric current densities (15, 45 and 60 mA/cm²) for 180min, so that pollutant degradation and simultaneously the production of H2(g) were observed. The degradation of aromatic compounds via electrochemical oxidation was monitored by means of absorbance analysis, gas chromatography, COD and TOC. The results showed that all aromatic compounds reached zero concentration under the three electric current densities. At 60 mA/cm², the highest degradation rate was achieved, mainly for the o-xylene compound (being completely removed in less than 60min) and to a lesser extent for benzene (in less than 90min). It was also observed that at high current density, higher is the production of H2(g), with a rate of 6.45, 5.10 and 0.57 ml/min, for benzene under current density of 60, 45 and 15mA/cm², respectively.