Study of the adsorption properties of lignocellulosic material activated chemically by gas adsorption and immersion calorimetry

This work refers to the characterization of activated carbon obtained by chemical activation by KOH and ZnCl2 of a lignocellulosic material, by the techniques of adsorption of nitrogen at 77 K and immersion calorimetry in cyclohexane and water. The obtained results show that the enthalpy of immersion in these two liquids is in perfect correlation with the specific surface area. In addition, the oxidizing treatment by the nitric acid of the activated carbon partially transforms the mesoporosity into microporosity; indeed, the isotherms of type IV tend toward isotherms of type I; this shows that the created superficial oxygenated functions reduce the diameter of the pores preventing the accessibility of the nitrogen molecule to a part of porosity; these results are confirmed by the immersion calorimetry since the enthalpies of immersion of oxidized coals, in cyclohexane and water, decrease and increase, respectively.

The objective that we set, relative to the study of the properties of adsorption of a composed local lignocellulosic Algeria (olives stones) activated chemically by the techniques of physical adsorption and immersion calorimetry. Indeed, initially, we prepared carbon activated by thermal treatments to various temperatures of the olives stones impregnated to different rates of agent activating (ZnCl2, KOH). Then, one studied the influence of the oxidation of the activated carbon by aqueous nitric acid solutions of various concentrations, on the development of porous texture and the chemical structure.