Ultrasonic Assisted Synthesis of Bimetal Composite Strontium Oxide/Iron(III) Oxide for the Adsorption Isotherm Analysis of CO2 Capture

Carbon dioxide (CO 2) capture by the bimetal composite of strontium oxide impregnated on iron(III) oxide (SrO/Fe 2 O 3) was studied. The adsorbent was calcined at 200-600°C and their adsorption capacities including adsorption and desorption were investigated. The adsorbents were characterized using X-ray diffraction (XRD), N 2 adsorption-desorption isotherm, CO 2 adsorption isotherm at 25°C, 1 atm and temperature programmed desorption for CO 2 (CO 2-TPD). The SrO/Fe 2 O 3-200 was observed to be the most efficient with adsorption capacity for physisorption and chemisorption of 5.08 and 100.03 mg CO 2 /g adsorbent respectively. It exhibited a lower maximum desorption temperature of 523°C compared to SrO and Fe 2 O 3 only. The order of best fit linearized adsorption isotherm models for CO 2 adsorption isotherm is Freundlich > Dubinin-Radushkevich > Temkin > Langmuir. The Freundlich isotherm possesses Freundlich constant, n = 1.196 corresponded to favorable adsorption, highest R 2 value (0.98) and the calculated adsorption quantity closest to the experimental value. Adsorption process governed by CO 2 molecules forms a successive multilayer on the SrO/Fe 2 O 3-200 surfaces and mainly exhibits a physisorption process. The heat of adsorption (b T = 5.238 J/mol) from the Temkin isotherm suggests the adsorption is an exothermic reaction and mean free energy (E = 2886.8 J/mol) from Dubinin-Radushkevich isotherm indicates the CO 2 adsorption is physical in nature.