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A green composite adsorbent based on mesoporous silica-gel (SG) and deep eutectic solvent (DES) mixture of choline chloride-urea (ChCl:U) was synthesized as an alternative for carbon dioxide (CO 2) adsorption. The composite adsorbent was prepared by wet impregnation technique with various ChCl:U (mole ratio 1:2) content in SG at 5-15% (w/w). Fourier transform infrared attenuated total reflectance (ATR-FTIR) results showed successful impregnation of ChCl:U into SG with the presence of C=O carbonyl amide group stretching, N-H scissoring bending, CH 2 bending and C-N stretching peaks. Thermal degradation of the adsorbent started with urea at 130°C followed by ChCl at 300°C. Meanwhile, nitrogen physisorption demonstrated a decrease in specific surface areas of the sorbents with increasing ChCl:U weight percentage due to the blockage of micropores by ChCl:U. The optimum CO 2 adsorption capacity of 22.3 mg/g was achieved by 10%ChCl:U/SG200, which was higher than the immobilised SG200, hence making it relevant to become a green and economical adsorbent for CO 2 capture.

Porous surface of silica gel (SG) have been modified with alkyl fatty amine compounds (octadecylamine, ODA) via wet impregnation process. The ODA-based adsorbents were physically characterized by XRD. The presence of crystalline peaks on ODA/SG diffractograms were ascertained the well-dispersion of ODA on the SG surface. XRD analysis displayed the increasing intensity of crystalline ODA with higher percent amine loaded and shifting of the several crystalline peaks of ODA verified the interaction of SG600-ODA. Capacity of CO2 capture by prepared solid adsorbents were evaluated using CO2 adsorption-desorption isotherms. This study shows that increasing percentage of ODA were improved the amount of CO2 uptake by following this trend: 35ODA/SG > 25ODA/SG > 15ODA/SG > SG > 5ODA/SG. However, promotion of 5 wt.% ODA unabled to enhance the capacity of CO2 captured due to pore blockage and reduction in SG pore surface, thus hindered the physisorption between CO2 and SG.