Produzione e caratterizzazione di compositi a base geopolimerica per l’assorbimento di anidride carbonica

In this Thesis, new geopolymer composites loaded with mixed oxides obtained by calcination at 500 °C of commercial hydrotalcites (HTs) were studied for the adsorption of CO2 in the temperature range 200 – 400 ° C. The HTs have been already investigated for the CO2 capture at intermediate temperatures, but being in a powdery form, they require the addition of binders to increase the mechanical properties, but worsening the chemical properties and the adsorption capacity. The geopolymeric mixture was chosen as a "green" bonding matrix since the synthesis is water-based and occurs at low temperature. The commercial HTs, the mixed oxides used as filler and the corresponding composites were fully characterized, determining also the CO2 absorption capacity. It has been shown that both HTs and mixed oxides (Mg-Al-O) obtained by calcination differ in term of structure and composition; furthermore, it was highlighted as the HT absorption capacity did not remain unchanged in the composite materials, depending on the mixed oxide - geopolymer matrix interaction, that may cause a deactivation of the sites involved in the adsorption. The most promising composites resulted to be those loaded with 28 wt.% of calcined Pural 50 and Pural 70 (Sasol, D). Depending on the larger sizes, the mixed oxide particles remained unchanged within the geopolymeric matrix giving adsorption capacity values comparable with the calcined HT, furthermore allowing an easy casting of the materials and high compressive strength values (23-25 MPa).