Hierarchically structured activated carbon granules for CO2 sorption via high-shear wet granulation and activation of waste coffee dust

• High-shear co-granulation of coffee waste and polymer microspheres to form granules • Investigated the effect of activation conditions on the textural properties of ACGs • Structured ACGs with a surface area up to 1573 m2 g-1 and pore volume of 0.54 cm3 g-1 • CO₂ adsorption capacities up to 4.3 mmol g-1 at 1 bar and 10 mmol g-1 at 10 bar The processing of composite granules of waste coffee dust and hollow polymer microspheres with sucrose solution as binder with high-shear granulation is demonstrated as a precursor for subsequent conversion to highly porous, hierarchically porous, mechanically stable structured granules for CO 2 capture. The optimization of the granulation parameters, such as binder volume, waste coffee dust to hollow polymer microsphere weight ratio, and the agitator & chopper speed of the granulator, produced near-spherical granules of 4-16 mm in diameter. Subsequent pre-carbonization followed by activation using KOH as a chemical activator yielded activated carbon granules (ACGs) in the 3-5 mm size range. The ACGs exhibited hierarchical porosity with a high specific surface area (350-1573 m 2 g -1 ), total pore volume (0.14-0.54 cm 3 g -1 ), and significant microporosity (0.08-0.50 cm 3 g -1 ). These textural properties enabled high CO₂ adsorption capacities of up to 4.3 mmol g -1 and 10 mmol g -1 at 1 bar and 10 bar, respectively, at 20 °C. The ACGs demonstrated a CO₂/N₂ selectivity in the range of 17.7 to 21.2 and a moderate isosteric heat of adsorption (18-43 kJ mol -1 ), indicating physisorption and efficient regeneration potential. These findings highlight the potential of structured ACGs as a sustainable, high-performance material with ease of processing for practical CO 2 capture and gas separation applications, contributing to circular economy goals through waste valorization. This work demonstrates a scalable shaping route from spent coffee waste to mechanically robust, hierarchically porous granules without a separate palletization step, suitable for practical CO 2 capture applications and also contributing to circular economy goals through waste valorization.