CO2 adsorption by organohydrotalcites at low temperatures and high pressure

In this study, the maximum CO2-capture capacities of two families of organohydrotalcites, with intercalated dodecyl sulphate or tetradecanedioate anions in their uncalcined and calcined states, were studied. Adsorption conditions with high CO2 gas pressures (up to 35 atm) and low temperatures (0 °C and 35 °C) were tested. The calcined Mg-Al hydrotalcite with tetradecanedioate anion had the highest CO2-adsorption capacity (176.66 mg·g−1 at 0 °C), which was 24.4% higher than the best results obtained with the calcined Mg-Al hydrotalcites with carbonate. Approximately, 1.34 g of calcined hydrotalcite was necessary to reduce the amount of CO2 in 1 m3 of air to the preindustrial level. A thorough characterisation of the surfaces and structures of the samples was performed using different techniques. The CO2 adsorption process was modelled using different mathematical equations: Langmuir, Freundlich, Sips, Toth, Dubinin-Radushkevich, and Temkin. The adsorption nature of the hydrotalcites enables us to achieve adsorption–desorption cycles by simply changing the CO2 pressure conditions. These results may contribute to the development of new CO2 capture materials for use in carbon capture and use technologies and for the mitigation of greenhouse gas emissions.