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

Abstract

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 N2 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 ΔG and ΔH revealed that the adsorption of both the gases were spontaneous and exothermic.