Relation between immersion enthalpies of activated carbons in different liquids, textural properties, and phenol adsorption

Abstract

The immersion enthalpies in benzene, cyclohexane, water, and phenol aqueous solution with a concentration of 100 mg L−1 are determined for eight activated carbons obtained from peach seeds (Prunus persica) by thermal activation with CO2 at different temperatures and times of activation. The results obtained for the immersion enthalpy show values between −4.0 and −63.9 J g−1 for benzene, −3.0 and −47.9 J g−1 for cyclohexane, −10.1 and −43.6 J g−1 for water, and −11.1 and −45.8 J g−1 for phenol solution. From nitrogen adsorption isotherms, the surface area, micropore volume, and average pore diameter of the activated carbons were obtained. These parameters are related with the immersion enthalpies, and the obtained trends are directly proportional with two first parameters in the nonpolar solvents, which is a behavior of microporous activated carbons with hydrophobic character. Phenol adsorption from aqueous solution on activated carbons is proportional to their surface area and their immersion enthalpy in the solution.