Adsorption of CO2 on KOH activated carbon adsorbents: Effect of different mass ratios

Nitrogen and oxygen enriched carbons were prepared by the cost-effective synthesis route of carbonization of polyacrylonitrile (PAN) and subsequent KOH activation for CO2 capture. The effect of four impregnation mass ratios (KOH: PAN = 1-4) and activation temperatures (600-900 degrees C) on the synthesized carbon adsorbent properties was explored by different analyses. The X-ray photoelectron spectroscopy (XPS) revealed the existence of basic nitrogen and oxygen functionalities on the adsorbent's surface which increases the adsorption rate for CO 2 by providing its basic sites. By increasing mass ratio (KOH:PAN) from 1:1 to 3:1, the surface area increased from 1152.4 to 1884.2 m(2) g(-1) and the dynamic CO2 adsorption capacity also increased from 2.1 to 2.5 mmol g(-1) respectively, at 30 degrees C (approximately ten times the adsorption capacity of untreated PAN, 0.22 mmol g(-1)). Physisorption and exothermic nature of the process were confirmed by the decrease in the adsorption capacity of the adsorbents with the increase in adsorption temperature. Moreover, good cyclic stability and regenerability over 5 adsorption-desorption cycles were obtained for the adsorbents. The fractional order kinetic and Temkin isotherm models fitted best with the adsorption data. A heterogeneous interaction between CO2 and the surface of adsorbents was suggested by the isosteric heat of adsorption values. Combined with the simple method for the preparation of activated carbon adsorbents, efficient CO2 adsorption and excellent regeneration make it appropriate adsorbents for post-combustion CO2 capture.