Adsorption of N₂, No₂ and Co₂ on epistilbite natural zeolite from Jalisco, Mexico after acid treatment

Emissions of carbon dioxide (CO₂) and nitrogen dioxide (NO₂) in recent years has been increased considerably. One way to reduce the concentration of these greenhouse gases in the atmosphere is adsorptive capture. This paper describes the main results of adsorption of N₂, NO₂, and CO₂ on epistilbite, both natural and on samples that were chemically treated at various concentrations of HCl. Data on the adsorption of CO₂ and NO₂ were evaluated by the Freundlich and Langmuir equations. Additionally, the thermodynamic parameters of adsorption were calculated, including the degree of interaction of the zeolite samples with gases by gradually changing the isosteric heat capacities of adsorption. The acid treatment improves the adsorption capacity of epistilbite with respect to NO₂ and CO₂, due the replacement of large extra-framework cation by small H+ ions. The improvement in the distribution of pore sizes in epistilbite samples was calculated by the method of Barrett-Joyner-Halenda. The sample H1 that was prepared in a moderately concentrated acid showed the best behavior in the CO₂ adsorption processes, while the natural EPIN material preferably adsorbs NO₂.