COMPETITIVE EFFECTS IN THE ADSORPTION OF CH3I ON KI-IMPREGNATED ACTIVATED CARBONS IN THE PRESENCE OF CO2

This paper describes an investigation of the adsorption of CH,I on a K I-impregnated carbon and the influence of competitive adsorption on th e process. A gravimetric method was used to study the equilibrium capa city and kinetics for the adsorption of CO2 and CH3I in the presence o f He, and CH3I in the presence of CO2 on the carbon. The results of th ese experiments were compared with those obtained from measurements ca rried out using a McBain spring apparatus to obtain the equilibrium up take of CH3I vapour on the KI-impregnated carbon at 293 K. The adsorpt ion kinetic results covering the range 275-333 K show that the rates o f adsorption are only weakly dependent on the temperature. The apparen t activation energies for adsorption of CO2 and CH3I in the presence o f He, and CH3I in the presence of CO2 were 20.0 +/- 1.1, 6.5 +/- 0.3 a nd 10.0 +/- 0.5 kJ mol(-1), respectively. The rates of adsorption of C H3I in the presence of CO2 were about half the corresponding rate of t he adsorption of CH3I in the presence of He. However, the equilibrium capacities were very similar in both cases. Adsorption experiments car ried out over a CH3I partial pressure range, 3.08-38.5 kPa in CO2 show ed that the initial adsorption rate constant was linearly dependent on the CH3I concentration. The results are discussed in terms of competi tive adsorption in the CH3I-CO2 system. Copyright (C) 1996 Elsevier Sc ience Ltd