Efeito da temperatura de calcinação do tio2 e influência nas propriedades fotocatalíticas

Abstract

The growing world development has increased the demand for chemical inputs for industries and markets. As well as, the need to invest in processes that optimize the degradation of potential organic pollutants has grown similarly. In this context, photocatalytic processes have been investigated as a promising way to degrade industrial waste and also to obtain high-value chemicals. The most used material for photocatalysis applications is titanium dioxide (TiO2) due to its low cost, non-toxicity and high chemical stability, many studies have invested in improving the physical and chemical properties of this material in order to know its photocatalytic activity. Therefore, the objective of the work was to synthesize TiO2 using the precipitation method and calcinate the material at temperatures 350, 550, 750 and 950ºC and subsequently evaluate the photocatalytic properties in model reaction using Rhodamine B (RhB), as well as, analyze the activity of the TiO2 as a function of conversion and yield for reaction of chemical transformation of glycerol in high value products. The obtained samples were characterized by X-Ray Diffraction (XRD), Diffuse Reflectance Spectroscopy (DRS), Infrared Absorption Spectroscopy (FTIR), N2 physisection analysis using the method developed by Brunauer, Emmett and Teller (BET) to calculate the surface area. In the model reactions using RhB it was possible to visualize the behavior of the materials, the phototacalizers calcined at 350 and 550ºC showed better performance reaching 60.7 and 62.8% of degradation of the dye in 70 min, while the materials calcined at 750 and 950ºC obtained 23.7 and 32.6% RhB degradation, respectively. In reactions using 350 and 550ºC it was possible to observe the formation of de-methylated analogues of Rhodamine B, while in the photocatalytic tests using materials calcined at 750 and 950ºC it was observed the predominance of the chromophore group breaking reactions evidenced by the reduction of the main dye signal in the molecular absorption spectra, with the model reactions it was noticed that the balance between surface area and bandgap energy controls the photocatalytic reactions. In the reactions of glycerol conversion, the formation of three products was observed, namely: glyceraldehyde, tartronic acid and glycolic acid, the materials calcined at 350 and 550ºC presented higher glycerol conversion, in contrast, the results of yield and selectivity showed that the materials calcined at 750 and 950ºC were more selective for glycolic acid, with the glycerol conversion tests it was possible to visualize the influence of structural properties in the direction of photocatalytic reactions.