Preparation of Tetraethylenepentamine (TEPA) and Imidazole (Ims)-Modified Activated Carbon using Response Surface Methodology for Carbon Capture Applications

Introduction: Carbon capture and storage (CCS) is the most mature technology to capture CO2 from flue gas stream through the adsorption process. The commercial adsorbent, though efficient, is cost-inhibitive. An alternative adsorption approach is by utilizing a palm kernel shell (PKS) as adsorbent. To enhance the adsorption capacity of CO2, impregnation with Tetraethylenepentamine (TEPA) and imidazoles (Ims) were introduced to increase the selectivity and capacity of CO2. The response surface methodology (RSM) technique was utilized to optimize the operating conditions for the preparation of modified AC-PKS for carbon capture applications. Method: The main process variables for this study were impregnation ratio (TEPA: Ims) and impregnation temperature. The 2 Factorial 1 model was developed for iodine number which was selected as the investigated response. The optimum conditions for modified AC-PKS had been identified to be an impregnation ratio 0.17 and a temperature of 90°C which gave a maximum of iodine number 1062.95 mg/g. Based on this optimum condition, the experimental value of iodine number is 1027.58 mg/g and is found to agree adequately with that (1062.95 mg/g) predicted from the model. The higher the iodine number, the greater the surface area available for adsorption. With the high surface area of activated carbon allows it to have more adsorption sites, increasing its capacity to remove contaminants from liquids or gases. According to Scanning electron microscope (SEM), TEPA and Ims molecules were attached to the surface of ACs and stimulated the chemisorption process for excellent adsorption process. Result: Two prominent adsorption peaks were also observed at 3100 cm^-1 and 2800 cm^-1, corresponding to the stretching of the N-H functional group and confirmed the successfulness of impregnation between TEPA and Ims. Based on elemental analysis (EA), the addition of TEPA and imidazole resulted in an increase in the number of amine groups on the surface of the adsorbent. Conclusion: Hence, this modified AC-PKS with optimum impregnation ratio and temperature increased the adsorption capacity and selectivity of CO2 adsorption from the simulated flue gas with 4.239 mol/kg AC compared to the previous study reported for unmodified ACPKS only 1.005 mol/kg AC.