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

Abstract A study of the influence of two successive thermal treatments, at low (3–4°C min −1 ) and high (ca. 3000°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°C at the low heating rate, followed by a second stage at the high rate, up to 850°C. All the samples obtained under these conditions (except the sample obtained at an intermediate temperature of 400°C) yielded a density much lower than that corresponding to a single thermal treatment up to 850°C at both heating rates. The sample obtained at 400°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 rate, 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.