Waste-derived tuff for CO2 Capture: Enhanced CO2 adsorption performances by Cation-Exchange tailoring

Mitigating greenhouse gas emissions through CO2 capture from industrial flue gases is imperative for addressing climate change. This article delves into the potential of natural tuff, derived from construction and demolition (C&D) waste, as an affordable and sustainable CO2 adsorbent for post-combustion capture. By tailoring the tuff structure and chemical composition through cation-exchange, the crucial role of cation type in enhancing its textural properties, particularly its microporosity and specific surface area, has been highlighted. Notably, Li- and Na-exchanges greatly enhance these properties, indicating a heightened potential for CO2 capture. The work further explores the dynamic CO2 adsorption of both untreated and modified tuff in a fixed-bed reactor under low CO2 partial pressures (< 0.2 atm), particularly examining the effects of extra-framework cation nature (Na+, Li+) and composition, and the influence of NH4+ pre-treatment. Results show that Na- and Li-exchanged tuff exhibit enhanced CO2 uptake (up to 1 mmol g−1) compared to untreated tuff (0.54 mmol g−1), with Li-exchange resulting in the highest capacity due to both superior textural properties and stronger ion-quadrupole interactions with CO2 molecules. The multi-cyclic stability of the synthesized samples has been also assessed; regardless of the specific cation-exchange type, all the samples provide stable performances over 10 consecutive adsorption/desorption cycles.