Solvent-assisted amine modification of graphite oxide for CO₂ adsorption

Amine-modified graphite oxides (GAs) for CO₂ adsorption were prepared using 3-aminopropyltriethoxysilane. Graphite was first oxidized using highly concentrated acid, and then modified with the amine using a solvent-assisted method. Ethanol and water were used as the solvents, and the solvent effects were investigated. The morphological changes, functionalities, and compositions of the GAs were characterized by scanning electron microscopy, Fourier-transform infrared and X-ray photoelectron spectroscopies, and elemental analysis. The CO₂ adsorption behavior was evaluated by thermogravimetric analysis at 30°C under atmospheric pressure. The GA prepared in water (GA-W) had a higher CO₂ adsorption uptake (1.64 mol kg^-1) than did the GA prepared in ethanol (1.31 mol kg^-1). The amine loading was predominantly influenced by the solvent, and water was an effective solvent for amine modification. GA-W also showed good regenerability in repeated adsorption-desorption cycles with high adsorption/desorption rates.