Sintese, caracterização e algumas propriedades do oxido de tetanio (IV) enxertado sobre superficie de silica gel

AUTOR(ES)
DATA DE PUBLICAÇÃO

1993

RESUMO

The synthesis of titanium(IV) oxide on silica gel surface was carried out reacting the silanol groups of the silica gel surface with titanium tetrachloride, in organic solvent. The reproducibility of the method was very satisfactory for the different silicas, always resulting in an average quantity of titanium of 1.5 mmol g. The X-ray photoelectron spectroscopy(XPS) study showed that the species on the silica gel surface is the Ti(IV), in a similar form as TiO2 and MTiO3, according to the binding energy value found for Ti2p of 458.7 eV. The dehydration of the material at high temperatures leads to an increase of the OII/Ti ratio (OII = oxigen bonded to the titanium atoms), due to the reticulation of the hydrated titanium oxide, during the thermal treatment. However, the specific surface area of the material doesn t change significantly. The hydrated titanium oxide grafted on silica gel surface was used as sorbent of dichromate ions from acid solutions. The exchange capacity increased as the pH was decreased and the acid used to this purpose, affects the adsorption. The material was also used to pre-concentrate Cr(VI) from acid solutions in an efficient manner, always resulting in 100% recovery. The material was also able to adsorb different species of organic compounds contained in oil. The adsorbed eIectroactive species on the material was characterized by IR spectroscopy and cyclic voltammetry. These electroactive species showed a similar behavior as those found in the bulk phase, except in the case of nickel hexacyanoferrate. In the nickel hexacyanoferrate case, the matrix effect on the formation process of the zeolitic cavities was observed. The material also presented an interesting property to generate free radicaIs by the hydrogen peroxide sorbed on the surface. The free radical was identifyed by electron spin resonance(ESR) as the superoxide radical, O2, which presented a good stability.

ASSUNTO(S)

espectroscopia fotoeletronica silica gel espectroscopia de infravermelho

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