THERMODYNAMICS OF ADSORPTION OF ORGANIC VAPORS ON METAL-LOADED ACTIVE-CARBON

The influence of active carbon as support on the reducibility of suppo rted metals (Ni, Cu, Zn, and Cd) has been studied by temperature progr ammed reduction (TPR). TPR profiles indicate that active carbon acts a s a dispersing agent and that it enhances the reduction of the support ed metals. High-temperature reduction peaks are explained on the basis of metal-surface interactions and of the porosity of the active carbo n. DR analysis of nitrogen adsorption isotherms indicates that the mic roporosity of the active carbon decreases due to a progressive closure of micropores as the metals are supported on the surface of the carbo n. The effect of doped metals on the adsorbing behavior of active carb on for different organic vapors has been studied as a function of temp erature. From adsorption data, thermodynamic parameters such as free e nergy, enthalpy, and entropy of adsorption are computed using a virial isotherm expression and are interpreted. The results show that an inc rease in the adsorption affinity of organic vapors active carbon/metal dopant systems is not due to configurational factors affecting the en tropy of adsorption, but to an enhanced enthalpy of adsorption.