Síntese e caracterização de tungstato de prata para aplicação na degradação fotocatalítica de poluentes orgânicos

Abstract

The increase of environmental contamination by organic pollutants has boosted researches focused in the treatment by different processes. Such pollutants can persist in the environment causing problems as the soil, surface waters and groundwater contamination, mainly. Among the most persistent organic pollutants it is possible to list the pesticides, pharmaceutical products and some classes of dyes. The heterogeneous photocatalysis has been widely investigated by the use of different semiconductor materials that work as photocatalysts in the oxidation of these pollutants. Silver tungstate Ag2WO4 is a semiconductor with outstanding photocatalytic properties because when it is irradiated by ultraviolet (UV) or visible (Vis) light it is able of producing hydroxyl radicals, peroxides and/or superoxides that feature high oxidation potential of organic pollutants. In this research, silver tungstate particles were synthesized by hydrothermal method assisted by microwave radiation, this way, being different from other works which didn’t explore this synthesis method using high control condition. The synthesized materials were characterized by XRD, DRS, SEM/FEG and BET surface area techniques. XRD results showed that it was possible to obtain Ag2WO4 with predominance of alpha phase, the most recommended for photocatalysis, at lower temperatures than suggested by previous works found in the literature. Photocatalytic tests were done in the application stage, in order to degrade potential organic pollutants such as Atrazine, Paraoxon, Paracetamol, Fluoxetine and Sertraline, showing that Atrazine was the molecule that best responded to the use of the photocatalyst, increasing removal rates by photocatalytic degradation. As the synthesized material proved to be more promising for application of Atrazine removal, studies of adsorption and photodegradation of Atrazine were done both in synthetic samples and in surface water. The results of the adsorption kinetics study showed that the adsorption equilibrium time of Atrazine by adsorbent was 30 minutes. In photodegradation studies were used two sources of light, Vis and UV. Under UV light, degradation products were generated, what didn’t occur in the studies using visible light. Thus, the application with surface waters was done under this range of light with addition of hydrogen peroxide H2O2. The material showed itself with good prospects to Atrazine removal under the optimized conditions, contributing to the solution of the environmental problem of the contamination and persistence of organic pollutants in the environment.