CO2 adsorption at intermediate and low temperature by geopolymer-hydrotalcite composites

Geopolymer-hydrotalcites composites have been prepared and compared to explore their use in the field of CO2 adsorption for a wide range of working temperatures and relative applications. Two commercial hydrotalcites, with different Mg:Al ratio, were tested as fillers for a geopolymer matrix up to the maximum of 37 wt%. A high compressive strength (25-27 MPa) was retained in composites at 500 °C, which is the temperature of hydrotalcites transformation into amorphous mixed solid oxides able to adsorb CO2. Composites were characterized in term of working capacity by testing the CO2 adsorption at low (35 °C) and intermediate (200 °C) temperature, with cycles of adsorption/desorption and regeneration at 500 °C. At 35 °C, CO2 physisorption capacity was between 0.079 and 0.154 mmol g-1, while at 200 °C, the total CO2 capacity value was between 0.114 and 0.141 mmol g-1.