Cation Exchange Modification of Clinoptilolite –Temperature Effects on Equilibrium Adsorption and Kinetic Separations Involving Methane, Nitrogen, and Carbon Dioxide

This study details an experimental analysis of the adsorption behaviour with respect to the equilibrium capacity and kinetic adsorption uptake of pure CO2, CH4, and N2 gases at different temperatures on natural and Fe3+,... [ view full abstract ]

This study details an experimental analysis of the adsorption behaviour with respect to the equilibrium capacity and kinetic adsorption uptake of pure CO₂, CH₄, and N₂ gases at different temperatures on natural and Fe³⁺, Ca²⁺, and Cs⁺ cation exchanged clinoptilolite. Raw clinoptilolite was modified through a cation exchange procedure, the presence of the exchanged cations were confirmed with electron dispersive spectroscopy. The crystal structure of the modified samples was compared using powdered x-ray diffraction and the pore size distribution was determined using nitrogen adsorption at 77K. Equilibrium adsorption isotherms and kinetic adsorption uptake data were experimentally determined for pure component CO₂, CH₄, and N₂ gases at three different temperatures ranging from 303K to 363K over a pressure range of 0.2 atm to 8.0 atm using the gravimetric method. Thermodynamic heats of adsorption were calculated for all three gases on the studied clinoptilolite samples using the experimentally determined Henry’s region adsorption K-constants determined using the chromatographic method. Results show substantial deviation in the heat of adsorption between the modified clinoptilolite zeolite and the parent clinoptilolite sample. This suggests that the extra framework cation type, quantity, and distribution within the pores of the zeolite have a great influence on the adsorptive behaviour.