The experimental characterization and simulation of CO2 adsorption in a packed bed of waste-derived CaO–chitosan composites

Waste-derived calcium oxide (CaO) and chitosan were synthesized from oyster shells and tilapia fish scales, respectively, and combined to form CaO–chitosan composite adsorbents for CO2 capture. The materials were characterized by FTIR, BET, SEM, and TGA/DTG to elucidate their functional groups, textural properties, morphology, and thermal stability, respectively. Equilibrium CO2 adsorption data were fitted with the Langmuir isotherm, and the resulting parameters were implemented in a COMSOL Multiphysics 5.4 model. The simulation employed experimentally derived Langmuir parameters within a 2D-axisymmetric Brinkman–LDF–Langmuir model for a cylindrical packed-bed reactor with 16 cm bed height and 4 cm diameter. Pure CaO exhibited the highest porosity and delayed CO2 breakthrough, while CaO mixed with 10% chitosan showed the highest Langmuir capacity but shorter adsorption time due to reduced bed porosity. Pure chitosan exhibited a low BET surface area of 0.1732 m2/g, and a pore volume of 0.0005 cm3/g, resulting in rapid CO₂ breakthrough and shorter adsorption times compared with CaO-based composites. The combined experimental–numerical approach demonstrates how waste-derived mineral–biopolymer composites can be engineered and evaluated as sustainable low-CO2 adsorbents to moderate-temperature packed-bed applications.