Synthesis and Characterization of Ti-Nb 2 O 5 Catalysts for Discoloration Reaction of Bromophenol Blue and Indigo Carmin
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ORIGINAL PAPER
Synthesis and Characterization of Ti‑Nb2O5 Catalysts for Discoloration Reaction of Bromophenol Blue and Indigo Carmine Dyes Raphaela Azevedo Rafael1,2 · Fábio Bellot Noronha1,2 · Alexandre Barros Gaspar2
© Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract This work investigated the photodegradation of bromophenol blue (BPB) and indigo carmine (IC) dye under UV–Visible light using pure oxides of titanium and niobium, as well as T iO2-Nb2O5 oxides containing 0.5, 2.5 and 5 wt% of T iO2, prepared by wet impregnation of Nb2O5 with Ti tert-butoxide under inert atmosphere. The results of XRD and Raman spectroscopy showed the presence of anatase T iO2 phase and T-Nb2O5 phase with orthorhombic structure in the pure T iO2 and N b2O 5 oxides, respectively. The Nb2O5 oxides doped with TiO2 presented a T-Nb2O5 phase, but there was no formation of TiNb2O7. TiO2 anatase was observed in the mixed oxide with higher Ti content (5 wt% TiO2). A zeta potential analysis showed positive surface charge values for titanium oxide and negative for niobium oxide and mixed oxides. The addition of up to 5 wt% of the TiO2 fold the activity of N b2O5 in the discoloration of both dyes. Pure TiO2 exhibits higher initial activity, which could be related to its positive PZC and higher attraction to sulphonic groups present in the dyes. Despite of the lower initial rate, 2.5 and 5% TiNb catalysts achieved full degradation of the dyes after 4 h of reaction. Keywords Photocatalysis · TiO2/nb2O5 mixed oxides · Bromophenol blue · Indigo carmine
1 Introduction In the last years, the environmental pollution has become one of the biggest problems of the modern society with the increase of industrial activities. Currently, the Brazilian textile industry stands out for being the fifth largest industry in the world in this sector. Every year, the textile industry uses large volumes of water in its production process, which results in millions of liters of contaminated water in bodies of water [1, 2]. Due to the extensive use of dyes and others chemicals, the effluents of textile industry are highly colored, toxic and resistant to conventional treatment systems [3, 4]. In addition Electronic supplementary material The online version of this article (https://doi.org/10.1007/s11244-020-01313-z) contains supplementary material, which is available to authorized users. * Alexandre Barros Gaspar [email protected] 1
Instituto Militar de Engenharia, Praça General Tibúrcio, 80, Urca, Rio de Janeiro, RJ 22290‑270, Brazil
Instituto Nacional de Tecnologia, Avenida Venezuela, 82, Sl. 518, Centro, Rio de Janeiro, RJ 20081‑321, Brazil
2
to water contamination affecting the water resources, the compounds present in the textile industry effluents can undergo biotransformation and cause a large number of diseases, including cancer [5]. Thus, in order to control the contamination of rivers and bodies of water, the law sets limits for contaminants, as well as the treatments that must be perf
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