THERMODYNAMICS OF ADSORPTION OF METHANOL ON METAL DOPANT ACTIVE-CARBON SYSTEMS

Adsorption of methanol on active carbon and metal doped carbons (Ni, Cu, Zn and Cd) has been studied as a function of temperature. From adsorption data, differential heats and molar entropies of adsorption were calculated as a function of coverages. The values of isosteric heats of adsorption are found to be higher for metal doped carbons which may be due to the chemisorption of methanol molecules on metal sites present on the surface of active carbon. Thermodynamic parameters such as DELTA-G-degrees, DELTA-H-degrees and DELTA-S-degrees were calculated from virial isotherm expression and interpreted thereform. It is observed that metal dopant/active carbon systems are synergic, exhibiting more adsorption affinity for methanol than the sum of its constituents. Results show that an increase in adsorption affinity for metal doped carbons is not due to configurational factors affecting the entropy of adsorption but because of large exothermicity in the enthalpy of adsorption.