Removal of Carbon Dioxide from Flue Gases by Adsorption on Activated Carbon

Abstract

Activated carbon offers a variety of pore structures and surface chemistry for separation and purification of gas mixtures. Adsorption and desorption of carbon dioxide and nitrogen was studied at different temperature on two commercially available activated carbon WS-480 and AP-360 for removal of carbon dioxide from flue gas (mixture of CO2 and N2). The various treatments including treatment with gaseous ammonia at high temperature, treatment with aqueous ammonia, treatment with aqueous KOH and treatment with diethylene-amine have been tried to increase the basicity of activated carbon for enhancement of carbon dioxide adsorption. The nitrogen content of the treated samples was determined by elemental analysis (CHN analysis). The change in surface functional groups was determined by Solid state FTIR analysis. The thermal stability of pristine and ammonia treated samples was measured using thermo-gravimetric analysis (TGA). The variation in the BET surface area, pore size distribution and total pore volume were determined by measuring N2 adsorption at 77K. The heat of adsorption and pure component selectivity was calculated for all the samples. The experimental results of pure component CO2 and N2 isotherms were fitted into four model equations, namely Langmuir model, Modified- Langmuir model, Virial equation and Dubinin-Astakhov model. The results show that WS-480 activated carbon gives better adsorption on comparison with AP-360. The increment in adsorption capacity on the ammonia treated samples and KOH treated samples for carbon dioxide adsorption as compared to pristine sample was also noticed.