The constant increase of CO₂ concentration in the atmosphere is recognized worldwide to severely impact the environment and human health. Zeolites possess a high adsorption capacity for CO₂ removal, but their powdery form prevents their use in many practical applications. When binding agents are used, a partial occlusion of the porosity can severely compromise the adsorption capacity. In this regard, a great challenge is producing compact composite adsorbents while maintaining a high specific surface area to preserve the pristine performance of zeolites. Here, this goal was achieved by preparing beads with a high content of zeolite 13X (up to 90 wt %) using a chitosan aerogel as the binding agent. A facile preparation procedure based on the freeze-drying of hydrogel beads obtained by phase inversion led to a peculiar microstructure in which a very fine polymeric framework firmly embeds the zeolite particles, providing mechanical coherence and strength (compressive strain >40% without bead fragmentation, deformation <20% under 1 kg_f-load) and yet preserving the powder porosity. This allowed us to fully exploit the potential of the constituents, reaching a high specific surface area (561 m² g^–1) and excellent CO₂ uptake capacity (4.23 mmol g^–1) for the sample at 90% zeolite. The beads can also be reused after being fully regenerated by means of a pressure swing protocol at room temperature.

A great challenge of research is the utilization of natural or synthetic zeolites, in place of natural pozzolans, for manufacturing blended cements. The difficulties of interpretation of the pozzolanic behavior of natural zeolite-rich materials and the role played by their nature and composition can be overcome by studying more simple systems, such as pure synthetic zeolites. This study aims at investigating the pozzolanic ability of isostructural zeolites with different framework compositions, such as three sodium zeolites of the faujasite (FAU) framework type: LSX, X, and Y. The pozzolanic activity has been estimated by thermogravimetry and X-ray diffraction analysis. The overall outcome of the investigation is that the zeolite structure affects its pozzolanic activity, as zeolites with similar framework densities exhibit distinct abilities to fix lime. Moreover, the framework composition is effective either from a kinetic point of view or on the total amount of fixed lime. Zeolite X appears to possess the best average features.