The Two-Stage Air–CO2 Activation in the Preparation of Activated Carbons. I. Characterization by Gas Adsorption

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Abstract
Three different methods for the preparation of activated carbons from almond shells and olive stones have been carried out in the temperature range 1073–1123 K: (a) carbonization in N2 followed by activation in CO2; (b) direct activation in CO2 and (c) treatment of the raw material in air at 573 K followed by activation in CO2. The characterization of the samples by gas adsorption and mercury porosimetry has shown that methods (a) and (b) yield similar results (and consequently it is preferable to use the direct activation) and that method (c) gives the best results, both in an adsorptive capacity and in the overall yield. On the other hand, the carbons from almond shells are more micro- and mesoporous whereas those from olive stones are more macroporous; in any case, the adsorptive capacity for gas adsorption of activated carbons prepared from both raw materials is very large.