Surface impregnation of glycine to activated carbon adsorbents for dry capture of carbon dioxide

Abstract

In order to improve the portability of basic absorbentsmonoethanolamine (MEA) and glycine (Gly),both were supported on microporous activated carbon(AC). Chemical modification by alkali-metal ionexchange (of Li, Na, K) was carried out on Gly-basedabsorbents. All supported absorbents were subjectedto CO2 absorption capacity (pure CO2) and selectivity(indoor level) tests. Textural and chemical characterizationswere carried out on test sorbents. Allimpregnation brought about significant reduction ofspecific surface area and microporosity of the adsorbentDepreciation in the textural properties wasfound to result to reduction in pure CO2 sorption.Contrarily, low-level CO2 removal capacity was enhancedas the absorbent dosage increases, resultingin supported 5 molar MEA in methanol solution. Adsorptioncapacities were improved from 0.016 and0.8 in raw ACs to 1.065 mmol/g for MEA's. Surfacechemistry via X-ray photoelectron spectroscopy (XPS)of the supported sorbents showed the presence ofamine, pyrrole and quaternary-N. In reducing sequenceof potency, pyridine, amine and pyrrolic-Nwere noticed to contribute significantly to CO2 selectiveadsorption. Furthermore, the adsorption isothermstudy confirms the presence of various SNGsheterogeneously distributed on AC. The adsorptionmechanism of the present AC adsorbents favoredFreundlich and Langmuir isotherm at lower and higherCO2 concentrations respectively.