Modification of carbon surfcae by oxidation and ammonia treatment for CO2 adsorption

Abstract

Solid adsorption process is now considered as a potential technique to adsorb CO2 from the flue gas emitted via large industrial plants. Activated carbon was commonly studied as an adsorbent for CO2 capture since it provides potential properties such as high surface area, large pore volume, and low cost. The ability to adsorb CO2 onto the carbon sorbent depends on two main properties; that are, pore structure and surface chemistry. In this work, commercial coconut-based activated carbon (AC), benzene-derived carbon nano spheres (CB), and pyridine-derived carbon nano spheres (CP) were applied as the CO2 adsorbents. The CB and CP carbons were carbonized and then activated with CO2 to obtain activated CB (ACB) and activated CP (ACP), respectively. To modify the surface chemistry, activated carbons (AC, ACB and ACP) were treated by various surface treatment approaches including HNO3 oxidation, amination without HNO3 pre-oxidation, and amination with HNO3 pre-oxidation. The amount of CO2 uptake achieved by the modified carbons was more than the amount obtained by the raw activated carbons. The treatment caused change in the surface chemistry of activated carbon, while there was no significant change in porous property. These results indicated that surface functional groups were successfully incorporated onto the carbon surface and helped increase the CO2 adsorption capacity. The amination with pre-oxidized method gave the highest CO2 capacity of 1.76, 1.39, and 1.28 mmol/g (at 1 atm and 40 °C) for AC, ACB, and ACP, respectively.