Direct Sorption Capture of CO2 from Air

The adsorption behaviors of microporous carbon adsorbent ASK-1 with respect to CO2 capture from the CO2/N2 mixtures were investigated at temperatures of 233, 273, and 313 K at pressures up to 1000 kPa. The activated carbon with the micropore pore volume of 0.53 cm3/g and the specific BET surface of 1440 m2/g was prepared from coal-tar raw materials of Kamchatka krai (Russia) by chemical activation using KOH at a temperature of 1173 K. The isotherms of one-component adsorption of gases were calculated using the Dubinin–Radushkevich equation of the theory of volume filling of micropores. The adsorption equilibrium of the СО2/N2 mixtures with the CO2 content ranging from 0.05 to 20 mol % were calculated using the ideal adsorption solution applied to the isotherms of individual gases in order to evaluate the efficiency of the adsorbent for capturing CO2, as well as to identify the optimal conditions for separating the СО2/N2 mixture. The availability of ASK-1 to purify air from technogenic CO2 was determined by analyzing the adsorption behaviors of the components and estimating the potential CO2 selectivity of the adsorbent as a function of the mixture composition, pressure, and temperature.