CO2 adsorption on binderless activated carbon monoliths

A series of activated carbon monoliths have been prepared by chemical activation of two lignocellulosic precursors, coconut shell (CACM) and African palm stones (PACM). The incorporation of a conforming step between the impregnation with H3PO4 and the activation step allows the successful development of disc-shape monoliths without the use of a binder. Textural characterization results using N-2 adsorption at 77 K show that the effect of the activating agent highly depends on the nature of the carbon precursor used. While chemical activation with phosphoric acid has mainly no effect when using coconut shell, a large development of both micro- and mesoporosity is observed for African palm stones. Large concentrations of the activating agent produce the partial shrinkage of the narrow microporous structure independently of the precursor used. Concerning the adsorption of CO2 at atmospheric pressure and 273 K, both series of activated carbon monoliths exhibit an improved adsorption behaviour with the activation degree up to an optimum value around similar to 164 mg CO2/g, for sample CACM-32, and similar to 162 mg CO2/g, for sample PACM-28, the amount adsorbed decreasing thereafter. Apparently, the total amount of CO2 adsorbed under these experimental conditions is defined by the volume of narrow micropores (V (n) ).