Surface modification of broom sorghum-based activated carbon via functionalization with triethylenetetramine and urea for CO2 capture enhancement
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A new type of activated carbon (AC) was synthesized using broom sorghum stalk as a low cost carbon source through chemical activation with H3PO4 and KOH. The AC obtained by KOH had the largest BET surface area of 1619 m2·g‒1 and the highest micropore volume of 0.671 cm3·g‒1. CO2 adsorption was enhanced by functionalizing the AC with two different amines: triethylenetetramine (TETA) and urea. The structure of the prepared ACs was characterized by Brunauer-Emmett-Teller method, scanning electron microscopy, Fourier transform infrared spectroscopy, thermogravimetric analysis and acid-base Boehm titration analyses. The adsorption behavior of CO2 onto raw and amine-functionalized ACs was investigated in the temperature range of 288‒308 K and pressures up to 25 bar. The amount of CO2 uptake at 298 K and 1 bar achieved by AC-TETA and AC-urea was 3.22 and 2.33 mmol·g‒1 which shows a 92% and 40% improvement compared to pristine AC (1.66 mmol·g–1), respectively. Among different model isotherms used to describe the adsorption equilibria, Sips isotherm presented a perfect fit in all cases. Gas adsorption kinetic study revealed a fast kinetics of CO2 adsorption onto the ACs. The evaluation of the isosteric heat of adsorption demonstrated the exothermic nature of the CO2 adsorption onto unmodified and modified samples.
Keywordsactivated carbon broom sorghum functionalization CO2 capture
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