Biomass-derived activated carbon was prepared from the agro waste materials, (wild sugarcane (WS) and saw dust (SD)) by chemical activation using phosphoric acid. The crystallinity, morphology, functional groups of the synthesized activated carbon were investigated. The effects of contact time (10-60 min), mass of adsorbent (0.05-0.2 g) and concentrations of CO2 (1 × 10-4 to 10 × 10-4 M) were analysed and the optimum adsorption conditions were found. Freundlich, Langmuir, Temkin, Dubinin-Radushkevich and Sips isotherm were used to analyse the adsorption data. The adsorption process was fitted with the Freundlich model. Adsorption capacity of agro waste-based sorbent was 5.225 × 10-3 mol/g. Thermodynamic parameters, such as ΔH0, ΔG0, ΔS0 , were calculated and it was found that the present system was a spontaneous process. From the kinetic studies, it was inferred that the Pseudo-second-order kinetics describes the kinetics of CO2 on AC-WSSD with an equilibrium point attained at 50 minutes with a high R2 value of 0.9602. The Brunauer Emmett Teller (BET) surface area of 1220 m2/g and an iodine value of 1360 m2/g were better indications for adsorption process. The interaction between CO2 and functional groups on the surface of the activated carbon was confirmed by FTIR. Desorption studies were carried out for three cycles with an efficiency of 93.2%.
Keywords: Biomass-activated carbon; CO2 capture; environmental wastes; isotherm; kinetics.