Characterization and application of Nb2O5/SiO2 composites prepared by sol-gel process

Reference Presenter Authors
(Institution)
Abstract
17-039 Nelcy Della Santina Mohallem Lima, L.d.(UFMG); Gomes, G.H.(Universidade Federal de Minas Gerais); Mohallem, N.D.(Universidade Federal de Minas Gerais); Coelho, C.R.(UFMG); High surface area silica based materials have been attracted industry attention due to their potential applications in a wide range of technology. At this work, we produced silica-niobium composite xerogels, with high specific surface area (SSA), by sol-gel process, using silicon (IV) ethoxide and ammonium niobate (V) oxalate hydrate. Burning the obtained xerogel at different temperatures lead to different niobium pentoxide phases inside the silica matrix. We investigated the influences of the Nb2O5 species on the porosity, adsorption properties and photoactivity of the composites. We used nitrogen gas adsorption for accessing textural properties, TEM for morphology, and DTA/TG, XRD and FTIR to understand the mechanism of Nb2O5 growth inside the xerogel. The photoactivity was evaluated by the methylene blue (MB) degradation under UVC light. Burning at 500 ºC did not change SSA of samples. At 900 º C, the pentoxide was formed (orthorhombic and monoclinic phases present) and prevented reduction of SSA and shrinkage of the silica matrix pores. At 1100 ºC, both the composite and the reference pores collapse. Microscopy images showed that silica has encapsulated the Nb2O5. By XRD, we could determine that silica has crystallized as cristobalite and the Nb2O5 phase is orthorhombic. Pure silica samples did not show evidences of crystallization. The photobleaching of MB was carried for 3 hours, after 2 hours of dark (for equilibrium with adsorption process). We used composites with proportions of 1:20 and 1:10 (Nb:Si), treated at 900 and 1100 ºC. The best result was for the composite with 1:10 at 900 ºC. Materials annealed at 1100 ºC did not show activity when the photoactive specie is encapsulated. We could understand the mechanism of the Nb2O5 formation by combustion of organometallic complexes inside silica xerogel matrix and showed a possible application for this material for water effluents recovering.
<< Back
Copyright © 2019 Metallum. All rights reserved.
Site produced by: SITESP.NET