Estudos de pré-concentração de platina explorando materiais de sílica organofuncionalizados.

Abstract

The present work aims to develop an organofunctionalized material through a silylation reaction, by a heterogeneous route, using the Stöber method, capable of effectively coordinating platinum íons (Pt4+). The synthesis of modified silica was carried out by the sol-gel process, where functionalization was carried out one pot through the addition of N´-[(trimethoxysilyl)propylethylenetriamine, tetraethylorthosilicate (TEOS) and ammonium hydroxide, the latter being a catalyst for hydrolysis and condensation reactions. The adsorptive/coordinative capacity of the organofunctionalized silica was evaluated through Fourier transform infrared (FTIR) and electronic absorption techniques. Through infrared spectroscopy, it was possible to observe the presence of bands referring to silanol groups (Si-OH) between 3470 and 3090 cm- 1, and an intense broad band related to siloxane groups (Si-O-Si) at 1029 cm-1. In addition, it was possible to identify bands at 2904 and 2829 cm-1 referring to the N-H groups of the amines present in the organofunctionalization of silica, coming from N´-[(trimethoxysilyl)propylethylenetriamide, as expected; and, at 1465 cm-1, the C-N band of amines is observed. Fourier transform Infrared spectroscopy (FITR) was used as a proposal to observe, through the spectra, the possible changes that occurred with the organofunctionalized compound after reacting with a 10-4 mol L-1 potassium hexachloroplatinate solution. It was possible to observe the shift to lower wave numbers of the signals referring to the N-H and C-N bands, suggesting that the interaction between Pt4+ ions and the silica material is predominantly through coordinative bonds between the ion and the amino groups. After the studies in the infrared region, test were performed on the electronic absorption of platinum ions with different concentrations, and then an analytical curve was constructed. However, two analytical curves were performed in order to quantitatively analyze the adsorption of platinum ions on silica materials. The first with concentrations of 10-3, 10-4, 10-5, 10-6 mol L-1 resulted in a good linear regression coefficient of 0,9995. At lower concentrations, at values of 12,2, 48,8, 97,5, and 195 ppm, the linear regression was also satisfactory, but with a value of 0,9801. Thus, the synthesized compound SIL-TMSDT proved to be effective for platinum (Pt4+) adsorption and efficiency pre-concentration.