Evaluation of CO2 and CH4 adsorption using a novel amine modified MIL-101-derived nanoporous carbon/polysaccharides nanocomposites: Isotherms and thermodynamics

The high efficiency organic-inorganic nanocomposites were fabricated by the simple impregnation of polysaccharides such as alginate, cellulose and chitosan on the MIL-101-derived nanoporous carbon (MDC) for gas adsorption from natural gas. The volumetric method was employed to investigate CO2 and CH4 uptake at the different temperatures and P < 21 bar. The incorporation of polysaccharides can enhance the CO2 binding affinity and lead to improved CO2 adsorption capacity. Structural analyses of the samples were characterized by N-2 isotherms, FT-IR, TEM, TGA, XRD, FESEM and EDS with mapping analysis. Despite promising advances in the synthesis of MIL-101 as an excellent adsorbent in recent decades, this adsorbent has not yet been commercialized due to the toxic and expensive synthesis procedure of MIL-101. In this work, MIL-101 was synthesized from waste Cr source and without using hydrofluoric acid as a mineral agent. The highest uptake was observed for the nanocomposites of chitosan-MDC (MDC@CT). This behavior of MDC@CT can be explained by the presence of surface NH2-groups which act as primary adsorption sites for CO2. This study also assesses the potential effect of amine-based nitrogen-rich surface functional group loads on MDC@CT on gas adsorption properties. Tris(3-aminoethyl)amine was selected as the amine source in the preparation of amine-modified MDC@CT. The CO2 adsorption was best fitted by Langmuir model, while the CH4 adsorption followed the Freundlich models. The respective negative values of Delta G and Delta H revealed that the adsorption of both the gases were spontaneous and exothermic.

Automated summary

In this study, high efficiency organic-inorganic nanocomposites were fabricated by impregnating polysaccharides on nanoporous carbon for gas adsorption from natural gas. The incorporation of polysaccharides enhanced CO2 binding affinity and the nanocomposite of chitosan-MDC showed the highest uptake capacity. The potential effect of amine-based nitrogen-rich surface functional groups on gas adsorption properties was also assessed in this research.