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 kgf-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.
Keywords: 13X zeolite; CO2 capture; adsorption; aerogel; chitosan; freeze-drying.