Geopolymers can be regarded as the amorphous counterpart or precursor of crystalline zeolites. Moreover geopolymers have a quite good CO2 adsorption capacity and an excellent CO2/N2 and CO2/CH4 capacity selectivity. The addition of zeolites or hydrotalcites as fillers can further improve the adsorption capacity and composites can be designed and produced in forms of monoliths to be used as solid adsorbents for low and intermediate temperature CO2 capture applications. Concerning geopolymer-zeolite composites, Na-based geopolymer composite revealed a synergistic effect, as the CO2 capacity at low temperature was approximately 20% larger that the value expected. This effect is attributed to the large interaction among the phases obtained by the effective chemical mixing achieved during the geopolymerization reaction. As well different types of hydrotalcites with different Mg/Al ratio can be used as fillers in geopolymer matrices. Upon calcination, the structure of hydrotalcite changes, with loss of interlayered anions and water. The final structure is a mixed oxide metaphase, which presents a large surface area and great affinity for CO2. At the end of each cycle of calcination/CO2 adsorption /desorption the composite regains the initial structure thanks to the memory effect.
Geopolymers composites for CO2 adsorption
V Medri;E Papa;E Landi;P Benito;A Vaccari;
2019
Abstract
Geopolymers can be regarded as the amorphous counterpart or precursor of crystalline zeolites. Moreover geopolymers have a quite good CO2 adsorption capacity and an excellent CO2/N2 and CO2/CH4 capacity selectivity. The addition of zeolites or hydrotalcites as fillers can further improve the adsorption capacity and composites can be designed and produced in forms of monoliths to be used as solid adsorbents for low and intermediate temperature CO2 capture applications. Concerning geopolymer-zeolite composites, Na-based geopolymer composite revealed a synergistic effect, as the CO2 capacity at low temperature was approximately 20% larger that the value expected. This effect is attributed to the large interaction among the phases obtained by the effective chemical mixing achieved during the geopolymerization reaction. As well different types of hydrotalcites with different Mg/Al ratio can be used as fillers in geopolymer matrices. Upon calcination, the structure of hydrotalcite changes, with loss of interlayered anions and water. The final structure is a mixed oxide metaphase, which presents a large surface area and great affinity for CO2. At the end of each cycle of calcination/CO2 adsorption /desorption the composite regains the initial structure thanks to the memory effect.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
