Dynamic CO2 adsorption on activated carbon adsorbents synthesized from polyacrylonitrile (PAN): Kinetic and isotherm studies

In this research work, PAN-based activated carbon adsorbents have been synthesized by using the simple and cost-effective route of carbonization and chemical activation. The effect of different activating agents like NaNH2, NaOH, K2CO3, and KOH on the textural properties of PAN and its adsorption potential for CO2 under dynamic conditions was investigated. The KOH activated carbon adsorbent exhibited the surface area of 1890 m(2) g(-1) whereas, NaNH2, NaOH, and K(2)CO3 activated carbons showed the surface area of 833 m(2) g(-1), 1020 m(2) g(-1) and 1250 m(2) g(-1) respectively. The porosity of the adsorbents was affirmed by SEM and HRTEM analysis. Whereas, XPS analysis have been revealed the various types of basic functional groups which contains oxygen and nitrogen on the carbon surface. The adsorbent, PAN-KOH shows the best CO2 uptake of 1.2 mmol g(-1) which is about four times the adsorption capacity of the carbonized PAN (0.32 mmol g(-1)) under 12.5% CO2 concentration flow. Moreover, the adsorbents showed a stable adsorption capacity over multiple sorption cycles. The best information of the adsorption at all adsorption temperatures was given by fractional order kinetic model whereas, the best fit of Freundlich isotherm model with the adsorption data and high Q(st) values confirms the adsorbent's surface heterogeneity. Thus, the present study provides a two-step synthesis process to produce nitrogen and oxygen-containing activated carbons from low-cost and commercially available PAN for its use in CO2 capture practical applications.