Carbon Dioxide Adsorption Studies on Fly Ash Zeolites

In this study, the potential of fly ash zeolites (FAZ) Linde (LTA) and faujasite (FAU) to adsorb carbon dioxide (CO2) was investigated in view of the results of implementation in postcombustion carbon-capture technologies. Adsorption isotherms of selected samples were measured at 273.15 K by a Micromeritics Tristar II 3020 surface analyzer. The highest adsorption capacity was obtained for FAZ with a FAU structure synthesized by a two-stage fusion hydrothermal process from fly ash (FA) that was composed of 65 wt% amorphous components. The adsorption capacity for this sample reached a value of 136.40 mg CO2/g FAZ at atmospheric pressure, a result comparable to that for commercial FAU. The selectivity coefficients of CO2 adsorption versus N2 for FAZ were evaluated from the experimental adsorption isotherms of corresponding gases at 100 kPa. The obtained results are in the range of 23–36, indicating strong affinity of FAZ for CO2 molecules. The experimental isotherms of CO2 adsorption fit well with Langmuir and Dubinin-Ashtakov mathematical models. The obtained parameters will be used as input data for calculation and design of a pilot plant carbon-capture installation.