Avaliação da influência do método e condições de síntese de nanopartículas de Nb2O5 na degradação fotocatalítica do corante têxtil amarelo reativo BF-4G

Abstract

The growth of the textile industry market has been generating huge concern regarding the use of appropriate treatments for the waste generated by it, since dyes can cause several environmental problems, either due to the large volume of effluent discarded, or due to the toxic potential of the substances present in it. In this context, Advanced Oxidative Processes (AOPs) have been shown to be an effective alternative for the mineralization of these substances. The objective of this work, in this context, was to study the degradation of the BF-4G Reactive Yellow dye by means of heterogeneous photocatalysi, using a niobium-based photocatalyst, known as niobium pentoxide (Nb2O5), taking advantage of the low cost of acquisition of starting material since Brazil is the largest holder of metal mines. Another factor that motivated the choice of this photocatalyst was its similarities with titanium dioxide (TiO2), the main photocatalyst used today, with regard to optical properties such as energy absorption in the ultraviolet region and band gap energy. In this work, the oxides were synthesized by two routes: the polymeric precursor method and the thermal decomposition of a metal complex, the ammonium niobium oxalate. Both methods of synthesis produced structurally very similar oxides; calcination temperatures of 700 and 800 °C led to the formation of the orthorhombic phase whereas, when calcined at 900 °C, the oxides presented a mixture of orthorhombic and monoclinic phases. Morphologically, the oxides were not similar, however, aggregates were observed in all samples. From an optical point of view, all oxides showed effective energy absorption in the ultraviolet region, with emphasis on the sample synthesized by thermal decomposition of metallic precursor and calcined at 700 °C (DT700). For the photocatalytic tests, a batch reactor was used, irradiated with a UV lamp and the results showed that the photolysis degraded 47% of the dye in 120 min. The most active sample (DT700) degraded about 53% of the dye after the same time.