Preparação de silicatos de cálcio: avaliação do potencial fotocatalítico

• Ano de defesa: 2017
• Autor(a) principal: Alves, Erica Silva dos Santos
• Orientador(a): Alves, Mary Cristina Ferreira
• Banca de defesa: Ribeiro, Danniely de Melo , Nascimento, Marcelo Rodrigues do
• Tipo de documento: Dissertação
• Tipo de acesso: Acesso aberto
• Idioma: por
• Instituição de defesa: Universidade Estadual da Paraíba
• Programa de Pós-Graduação: Programa de Pós-Graduação em Química - PPGQ
• Departamento: Pró-Reitoria de Pós-Graduação e Pesquisa - PRPGP
• País: Brasil
• Palavras-chave em Português: Silicato de cálcio; Fotocatálise heterogênea; Azo corantes
• Área do conhecimento CNPq: CIENCIAS EXATAS E DA TERRA::QUIMICA
• Link de acesso: http://tede.bc.uepb.edu.br/jspui/handle/tede/3307

Calcium silicates are ceramic materials that have been increasingly investigated for having excellent properties such as: biocompatibility, bioactivity, optimum strength, permeability. Being widely used in technological applications, biomedical among other purposes. Despite being found in great abundance in nature, it is associated with other constituents, and therefore, its production without contaminants is necessary. In this context, the present work had the objective of the synthesis of calcium silicates by the method of the polymeric precursors, aiming application in heterogeneous photocatalysis. The preparation of the silicates (Ca2SiO4 and CaSiO3) was carried out in three optimization stages, in which the thermal treatment time, concentration of the silicon solution, as well as the temperature variation during the crystallization process were evaluated. The decomposition of precursor powders was evaluated by thermogravimetric analysis (TG / DTG), and after calcination the material was characterized by X-ray diffraction, infrared and UV-visible spectroscopy. We can observe from the XRD patterns that the increase of the crystallization temperature and the calcination time, favors the obtaining of calcium silicate heterostructures in the phases (Ca2 SiO4 and CaSiO3) with excellent crystalline quality, with the sample treated at 800 ° C for 8h tends to form calcium silicate with the Ca2SiO4 phase (larnite) in the majority in relation to the CaSiO3 phase (wolastonite), while the sample treated at 900 ° C for 8 hours showed an inverse behavior, that is, the CaSiO3 phase the composition of the heterostructure. The infrared spectra of the silicate samples treated at different temperatures and varying calcination times presented spectra with profiles and vibrational modes characteristic of the Ca2SiO4 and CaSiO3 systems, corroborating with the results of XRD. Additionally, a gradual increase in crystallite size was observed as a function of the elevation of the heat treatment temperature and the calcination time. The photocatalytic tests were performed with Remazol Amarelo Ouro dye, monitoring the regions of degradation (238 and 292 nm) and discoloration (412 nm) by spectroscopy in the UV-Visible region. The results presented were very promising with a mean of 78% discoloration and 44 and 21% for degradation of the aromatic groups and π-π * bonds for the sample Ca2SiO4 / CaSiO3 with Ca2SiO4 major phase and 82% discoloration and 44 and 21 % for degradation of the aromatic groups and π-π * bonds for the CaSiO3 / Ca2SiO4 sample with the CaSiO3 major phase. However, the primary results presented for these materials indicated that they have potentials for application in a heterogeneous photocatalysis process, and further studies are needed to optimize the obtained results.