The objective of this work was to determine the adsorption capacity of activated carbons from almond shells in a fixed bed at low concentration of two solvents, n-hexane and toluene, as well as to study the desorption process in order to (examine) n-hexane and toluene recovery. Activated carbons with different physicochemical characteristics were obtained by chemical activation of almond shells varying activation temperature, impregnation ratio and activation time. Although operation conditions affect adsorption uptake under dynamic mode, under the same operating conditions activated carbons exhibit quite different adsorption uptakes. High adsorption uptakes at low n-hexane and toluene concentration have been obtained: 253 mg toluene/g and 122 mg n-hexane/g. However, the reduction of adsorption uptake comparing that obtained in static mode and dynamic mode at the same relative pressure does not follow a trend. This reduction it is not proportional either among the activated carbons for a single solvent or for one activated carbon with both solvents. The deviation of linearity of the Dubinin-Radushkevich model applied to solvent isotherms gives an appropriate idea of heterogeneity of the activated carbon, giving a range of deviation that maximizes n-hexane and toluene adsorption uptake

The financial support from the Spanish Ministry of Environment (contracts 439/2006/3-11.2 and B030/2007/2-11.2) is duly recognized.

Peer reviewed