Enthalpies of immersion in benzene, cyclohexane and water of granular activated carbons prepared by chemical activation with solutions of MgCl2 and CaCl2

Granular-type activated carbons were prepared from African palm shells (Elaeis guineensis) by chemical activation with aqueous solutions of MgCl2 and CaCl2 at concentrations of 3, 5 and 7 % w/v, at temperatures between 773 and 1073 K. The textural parameters were obtained from N-2 adsorption isotherms of the prepared activated carbons. The textural parameters included the surface area and pore volume, with values between 10 and 501 m(2) g(-1) and 0.01 and 0.29 cm(3) g(-1), respectively. Enthalpic characterisation of the activated carbons was performed through the immersion calorimetry technique in three different solvents: benzene, cyclohexane and water. The enthalpies of immersion values of the solids in water were between -7.4 and -42.7 J g(-1); for the immersion in benzene, the values were between -13.9 and -38.6 J g(-1) and were between -6.4 and -24.2 J g(-1) for the immersion in cyclohexane. The results show that activation with MgCl2 and CaCl2 salts produces activated carbons with differences in their characteristics of energy and affinity for the calorimetric liquids that are related to the surface properties.