Crisotilas naturais brasileiras : ativação da superficie e aplicação na imobilização de biocatalizadores

AUTOR(ES)
DATA DE PUBLICAÇÃO

1989

RESUMO

Crysotile asbestos is clay mineral having a lamelar structure coiled in cilindric fibriles of 50 nm in external diameter and showing a positive zeta potencial. Natural chrysotile asbestos is composed by bundles of this fibriles, more or less denselly packed, containing varying quantities of several impurities. Because of its fibrilar nature, this material should have a high surface free energy; however, in the natural state, its activity is low. Brazilian chrysotile asbestos was purified removing the free impurities and the powdered material. Fibrilization was assessed by monolayer adsorption capacity (Vm), through methylene blue adsorption from solution. The fibrilization degree obtained by jet-water and ultrassonification was studied. It is show that in controled conditions, an increase in Vm proportional to the time of treatment is obtained; for instance: after 30 min. ultrassonification at 250 KHz, Vm increased 60% in relation to the original sample. Surface activation was accomplished by ultrassonofication in aquimolar acétic acid/sodium acetate buffer. A dependence of Vm with the buffer concentration was observed, for low concentrations, and saturation at higher values. Tipically, after 30 min. of ultrassonification at 250 KHz in 3,3x10 M buffer, Vm increased 75% in relation to the original material. This value is roughly 25% of the theoretically expected geometrical surface area of the fibriles. The activated chrysotile asbestos was used to support "Saccharomyces cerevisiae". Adsorption isoterms showed and adsorption capacity of 0,9 g per gram of chryssotile, at 25°C, showing that this material has a supporting efficiency comparable withthe bests in the market, qualitative results show that the suported biocatalist activity and life-time are comparable to the free yeast.

ASSUNTO(S)

crisotila

ACESSO AO ARTIGO

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