Belik, Yu. A.

Kharlamova, Tamara S.

Vodyankin, Andrei A.

Vodyankina, Olga V.

English

Tomsk State University Repository

 CATALYSIS: from Science to Industry 2018 Section 1: Oral presentations  31  Bismuth silicates prepared via mechanochemical activation for photocatalytic applications Yu. A. Belik, A.A. Vodyankin, T.S. Kharlamova, O.V. Vodyankina Tomsk State University, Tomsk, Russia belik99q@gmail.com  Bismuth silicates are a family of compounds which is classified as complex oxide systems. Bismuth metasilicate Bi2SiO5 is a substance of Aurivillius family with perovskite-type structure. At the same time, the structure of bismuth orthosilicate Bi4Si3O12 is transitional from perovskite-type to framework, while the one of sillenite Bi12SiO20 is purely a framework similar to γ-Bi2O3. These structural differences provide a sufficiently broad range of peculiar physical and chemical properties. For example, Bi4Si3O12 can be used as potential scintillator material [1] due to lower production cost than that of bismuth orthogermanate Bi4Ge3O12, while having otherwise similar parameters. Up to the current date, there are several new reports, which also indicate on high potential of different bismuth silicate compositions in photocatalytic applications [2, 3]. In this work, environmentally friendly mechanochemical activation was applied, available to carry out the process with great speed in the absence of any solvent. With this method of synthesis, the influence of molar ratio of initial reagents on phase composition and properties of prepared samples was investigated. For the first time, bismuth silicates were obtained via mechanochemical activation followed by calcination. Bismuth oxide Bi2O3 and hydrous silica SiO2·nH2O were used as precursors. The stoichiometric mixtures with different composition were activated in a high-power planetary ball mill AGO-2 for 10 min [4]. The mixtures activated for 10 min were calcined at different temperatures for 2 h, with calcination temperatures being chosen with accordance to the data of TG-DSC. Combined analysis of XRD and TG-DSC data shows that the initial molar ratio of Bi2O3:SiO2 = 6:1 ultimately leads to the formation of γ-Bi12SiO20, which decomposes at 875 °C. The formation of Bi2SiO5 phase (primary) and γ-Bi12SiO20 (impurity) is indicated in the sample with the molar ratio of Bi2O3:SiO2 = 1:1 in the course of calcination of mixtures activated at 500°C. At 600°C metastable Bi2SiO5 phase is partially transformed to Bi4Si3O12. With the molar ratio of Bi2O3:SiO2 = 2:3, at 500 °C two modifications of Bi2SiO5 phase are formed at the same time as Bi4Si3O12.  At 600 °C bismuth metasilicate phase completely transforms to Bi4Si3O12 phase with the formation of γ-Bi12SiO20 phase as impurity. Photoluminescence effect was detected for all samples containing Bi4Si3O12 phase, with the excitation peak at 250 nm. Other materials do not possess photoluminescence effect at all. UV-VIS diffuse reflectance spectroscopy data shows that prepared bismuth silicates absorb visible light and with accordance to XRD data possess different phase composition. As shown above, mechanochemical activation for 10 min does not allow to synthesize single phase samples with molar ratio of Bi2O3:SiO2 = 1:1 and 2:3. Apart from expected stoichiometric phases, other phases of bismuth silicates are also detected. Multiphase composition can possibly be attributed to complex mechanisms of nuclei formation in the course of solid state reactions. A photocatalytic study of all prepared materials in the reaction of Rhodamine B photodecolorization is expected. Additionally, a series of bismuth silicates prepared via conventional hydrothermal method will be discussed in the study, investigated with the methods described above to provide comparison.  This research was supported by “The Tomsk State University competitiveness improvement programme”.  References 1. Kaewkhao, J.; Udomkan, N.; Chewpraditkul, W.; Limsuwan, P. International Journal of Modern Physics B. 2009, 23, 2093–2099. 2. Liu, D.; Wang, J.; Zhang, M. et al. 2014, 6, 15222–15227. 3. Han, Q.; Zhang, J.; Wang, X.; Zhu, J. J. Mater. Chem. A. 2015, 3, 7413–7421. 4. Kharlamova, T.; Pavlova, S.; Sadykov, V. et al. Eur. J. Inorg. Chem. 2008, 939–947. 

Bismuth silicates prepared via mechanochemical activation for photocatalytic applications

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Bismuth silicates prepared via mechanochemical activation for photocatalytic applications

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