field of the zeolite surface. We have developed a CO 2 -PSA A Japanese natural mordenite was modified by acid washing as process using Japanese natural zeolites (8). However, the well as cation-exchange. Crystal structure, porosity, and active adsorption sites responsible for CO 2 adsorption are not sufsites of the modified natural mordenites were characterized, and ficiently elucidated. Among various natural zeolites distribtheir CO 2 adsorptivity were examined. Contraction as well as uted in Japan, the Itado natural mordenites have rather good expansion of the mordenitic unit cell in the natural zeolite and and comparatively homogeneous zeolitic structure. It is distortion of zeolite structure by acid washing are plausibly shown hopeful for industrial application or for use in fundamental by XRD. Long-term washing by nitric acid induces enlargement research ( ). In order to obtain a fundamental understanding of micropore volume, increasing the micropore dimension but deof CO 2 adsorption on natural mordenite, Itado natural mordecreasing the large pore dimension over the mesoporous range. The degree of dehydration has an important role in CO 2 adsorption. nite was modified in this study by acid washing and cation-Metal ionic sites affect both the irreversible CO 2 adsorption and exchange. The modified Itado natural mordenites are carethe CO 2 equilibrium adsorption at low concentration. Li / ionfully characterized, and the dominant factors for CO 2 adsorpexchange brings about a great CO 2 adsorption but reduces the tion are examined.
CO 2 -surface interaction due to molecular size effect. Ca 2/ ionexchange has its main effect in the enhancement of CO 2 desorption EXPERIMENTAL energy.