Removal of the CO2 from flue gas utilizing hybrid composite adsorbent MIL-53(Al)/GNP metal-organic framework

• MIL-53(Al)/GNP composite was successfully synthesized by solvothermal reaction.
• A two-step process was used to activate the hybrid composite sorbents.
• The incorporation of GNP caused improvement of the microporosity of the framework.
• Breathing due to CO2 adsorption on composites was affected by the presence of GNP.
• Sorption capacity of CO2 enhanced 35% by GNP incorporation into MIL-53(Al) at 298 K

In this study, adsorption of the CO2 and N2 gases on the MIL-53(Al) and its hybrid composite with the graphene nano-plates (GNP), MIL-53(Al)/GNP, adsorbents were investigated. These materials were synthesized using the solvothermal reaction method. The prepared samples were characterized by means of the powder X-ray diffraction (PXRD), field emission scanning electron microscopy (FESEM), N2 adsorption–desorption isotherms (BET-BJH surface area measurement) and Fourier transfer infrared (FT-IR) spectroscopy methods as well as; thermogravimetric analysis (TGA). Adsorption equilibrium of the CO2 and N2 on the sorbents were determined through a volumetric adsorption apparatus at 298, 323 and 348 K and pressures of up to 40 bars. It was found that, the adsorption capacities of the CO2 on the MIL-53(Al)/GNP containing 5 wt% GNP increased about 35% (from 9.61 to 12.95 mmol gr−1) in comparison with that of the GNP free sample at 298 K and 40 bars. This enhancement in the adsorption capacity was attributed to the incorporation effect of the GNP displayed in terms of the increase of the specific surface area (SBET), internal pore volume (Vp) and micropore volume (Vmicro) of the MIL-53(Al). Finally, several dual sites isotherm models including the; Langmuir, Sips and Toth were utilized to fit the obtained adsorption experimental data trying to describe the observed breathing effect. In this venue, the ΔHads was calculated in order to predict the thermodynamic behaviors of this MIL sorbent due to adsorption of the CO2.

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