Study of microporosity of active carbon spheres using inverse gas chromatographic and static adsorption techniques

Active carbon spheres (ACSs) with different porous structures prepared in the laboratory were characterized by static adsorption studies and inverse gas chromatographic (IGC) technique. Surface properties such as BET surface area, micropore volume and pore size in different regions of porosity were determined using different theoretical approaches. Thermodynamic parameters such as isosteric heat of adsorption, free energy of adsorption and dispersive component of the surface energy were determined using IGC technique from corrected retention volume of normal alkanes and corresponding branched alkanes. Thermodynamic parameters were used to assess the molecular sieving property of ACSs. It is observed that thermodynamic properties strongly depend on microporous character of ACSs. The variations observed in pore size determined by both of the techniques that is by static adsorption measurements and IGC may be attributed to the variation in analysis temperature, i.e. liquid N2 temperature for adsorption studies and elevated temperature for IGC technique.