Efeitos da radiação de micro-ondas em minerais micáceos.

Abstract

Vermiculite (Mg, Ca)0.4 (Mg, Fe)3 (Si, Al)4O10 (OH)2 4H2O, is a hydrated silicate of magnesium, aluminum and iron with lamellar micaceous structure , and basal cleavage. The term vermiculite is also commercially used to designate a group of micaceous minerals consisting of about nineteen varieties of hydrated silicates of magnesium, aluminum, iron and other elements. The vermiculite in its exfoliated form is widely used in construction (lightweight concrete, thermal /acoustic insulation), agriculture (humidity soil control), industry (packaging, paints and brake pads) and as an adsorbent agent for industrial wastewater treatment and waterways contaminated by oil. Present techniques used to exfoliate vermiculite make use of furnaces that use the direct flame or indirect flame systems generally working in temperature range from 800° C up to1000° C. The objective of this thesis is to study the expansion of vermiculite by using microwave radiation, the effects that occur in the mineral vermiculite after being subjected to microwave radiation, as well as evaluating the use of expanded material by microwaves in a practical application in the recovery of water contaminated by oil, simulating an oil pollution. In the present study vermiculite samples in their natural state have been expanded by the use of microwave radiation at a power of 700 W. The low thermal conductivity, diffusivity , chemical composition and moisture of vermiculite in its raw state and the power level applied are factors that influence the rate of expansion . From the data obtained in the present study it was found that the use of microwave radiation remained virtually unchanged the original characteristics of the mineral phase of Vermiculite (the oxides), a fact that contributes to the maintenance of acoustic and thermal insulation properties. In experiments to evaluate the capacity of the vermiculite exfoliated by microwave radiation in the asorption of oil, a water recovery rate of 93.55 % was achieved, against 80.32 % obtained with comercial exfoliated vermiculite, this demonstrated the highest adsorption capacity of vermiculite exfoliated by microwave radiation which is a relevant factor in treatment of streams contaminated by oil.