Geopolymer and geopolymer-zeolite adsorbents for environmental remediation

Geopolymers and geopolymer composites are promising materials in view of a possible use as adsorbents and membranes for environmental remediation. Indeed, the micro and mesoporous structure, together with the ability to establish electrostatic forces with carbon dioxide molecules and the ion exchange properties, makes them suitable for selective adsorption of CO2 from gaseous streams [1] and wastewater filtration, such as ultrafiltration in the range 0.01–0.1 μm. Furthermore, Cold Sintering Process (CSP) [3] allows to tailor the composition and the porosity in a wide range to maximize the adsorbent performance. Adsorption isotherms reported relevant CO2/N2 separation performances (CO2 capacity up to 1.9 mmol/g and selectivity up to 600), greatly higher than that of most conventional adsorbents. Concerning ultrafiltration, dynamic adsorption tests highlighted a higher affinity for Li+ compared to Ca2+ and Na+ using K-based geopolymer membranes with Si/Al ratio equal 2, making them suitable for recovery and separation of cations from brines or salt water. Research activities are carried in the framework of the MUR PRIN 2022 Project GEA - GEopolymer based Adsorbents for effective adsorption and selective separation of CO2 and eutrophication pollutants, - Prot. 20229THRM2, funded by the European Union – Next Generation EU.