Sviluppo di tecniche meccanochimiche per la valorizzazione di materiali di scarto tramite produzione di idrogeno verde e confinamento dell’anidride carbonica - Development of Mechanochemical Techniques for the Valorisation of Waste Materials through Green Hydrogen Production and Carbon Dioxide Sequestration

Given the growing need to reduce CO₂ emissions and promote sustainable production models, the international scientific community is increasingly focusing on the development of innovative technologies capable of integrating carbon capture, waste valorization, and clean energy production. In this context, the present thesis explores the application of mechanochemical techniques for the valorization of waste materials through CO₂ capture and H₂ production. The study investigated the reactivity of commercial olivine, granite scraps (GS), and Bayer process red mud (RM) subjected to High-Energy Ball Milling (HEBM) treatments in the presence of CO₂ and water. The experimental work focused on CO₂ conversion and the generation of value-added products such as H₂ and CH₄. The results demonstrated that mechanochemical activation can effectively promote CO₂ conversion reactions, significantly enhancing the reactivity of the investigated materials. In the case of olivine, it was possible to monitor and interpret the structural transformations associated with carbonation processes and H₂ production. Granite scraps (GS) exhibited a strong dependence of performance on the chemical conditions of the system, showing high CO₂ conversion and the formation of H₂ and CH₄, particularly under alkaline pre-treatment conditions. Red mud (RM), owing to its natural alkalinity, showed a significant capacity for CO₂ sequestration through the formation of carbonate products. Overall, the results confirm the potential of mechanochemical technologies as a tool for waste valorization and for the development of innovative strategies in carbon capture, utilization and storage (CCUS), contributing to the objectives of the energy transition and the circular economy