Influence of thermal treatment regime on the density and reactivity of activated carbons from almond shells

A study of the influence of two successive thermal treatments, at low (3-4 degrees C min(-1)) and (ca. 3000 degrees C min(-1)) heating rate, on the properties and reactivity of chars obtained from almond shells was carried out. The combined thermal treatment consisted of a first stage at intermediate temperatures from 275 to 400 degrees C at the low heating rate, followed by a second stage at the high rate, up to 850 degrees C. All the samples obtained under these conditions (except the sample obtained at an intermediate temperature of 400 degrees C) yielded a density much lower than that corresponding to a single thermal treatment up to 850 degrees C at both heating rates. The sample obtained at 400 degrees C behaved in a very interesting manner since its density was the highest obtained. A correlation has been obtained between the high reactivity of the samples obtained by a single treatment at high heating rare, and the Ca content and dispersion. The adsorption properties of the activated carbons obtained at approximately 50% burn-off were very similar regardless of the reactivity and the porous structure of the precursor chars. (C) 2000 Elsevier Science Ltd. All rights reserved.