CO₂ capture by nanocellulose/silica/polyethyleneimine composites: a Box-Behnken experimental approach

A nanocomposite adsorbent composed of nanocellulose, mesoporous silica, and polyethyleneimine was synthesized. Its CO₂ adsorption performance was evaluated. The structure of CNC/SiO₂/PEI was fully characterized using XRD, FTIR, zeta potential, FE-SEM, and BET analyses, which confirmed the preservation of CNC crystallinity, the successful incorporation of SiO₂, and the effective functionality of PEI groups. The effects of operating conditions on CO₂ adsorption capacity were investigated using response surface methodology. Maximum adsorption was achieved under the optimal conditions of 0.93 wt% PEI, 7 bar pressure, and 25°C temperature, yielding a maximum CO₂ adsorption capacity of 349.63 mg/g. Isotherm data were best fitted by the Langmuir model, indicating monolayer adsorption on the active sites of PEI, while adsorption kinetics followed a pseudo-second-order model, suggesting a chemical mechanism via the amine groups. Reuse experiments showed that after 10 adsorption–desorption cycles, the nanocomposite retained 89.46% of its initial capacity. Only a small change in surface zeta potential was observed, indicating excellent structural stability. Overall, the CNC/SiO₂/PEI nanocomposite demonstrated high adsorption capacity, favorable kinetics, and excellent recyclability, showing great potential as an efficient adsorbent for carbon capture applications.