Ultrasonic Assisted Synthesis of Bimetal Composite Strontium Oxide/Iron(III) Oxide for the Adsorption Isotherm Analysis of CO 2 Capture

Carbon dioxide (CO2) capture by the bimetal composite of strontium oxide impregnated on iron(III) oxide (SrO/Fe2O3) 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), N2 adsorption–desorption isotherm, CO2 adsorption isotherm at 25 °C, 1 atm and temperature programmed desorption for CO2 (CO2-TPD). The SrO/Fe2O3-200 was observed to be the most efficient with adsorption capacity for physisorption and chemisorption of 5.08 and 100.03 mg CO2/g adsorbent respectively. It exhibited a lower maximum desorption temperature of 523 ℃ compared to SrO and Fe2O3 only. The order of best fit linearized adsorption isotherm models for CO2 adsorption isotherm is Freundlich > Dubinin-Radushkevich > Temkin > Langmuir. The Freundlich isotherm possesses Freundlich constant, n = 1.196 corresponded to favorable adsorption, highest R2 value (0.98) and the calculated adsorption quantity closest to the experimental value. Adsorption process governed by CO2 molecules forms a successive multilayer on the SrO/Fe2O3-200 surfaces and mainly exhibits a physisorption process. The heat of adsorption (bT = 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 CO2 adsorption is physical in nature.