Carbon Dioxide Adsorption Using High Surface Area Activated Carbons from Local Coals Modified by KOH, NaOH and ZnCl2 Agents

Activated carbons of various features were produced by the impregnation of local coal samples that were taken from Kilimli region of Zonguldak (Turkey) with chemical agents KOH, NaOH and ZnCl₂ at different temperatures (600–800 °C) and concentrations (1:1–6:1 agent:coal), for their evaluation in CO₂ adsorption studies. BET, DR, t-plot and DFT methods were used for the characterization of carbon samples based on N₂ adsorption data obtained at 77 K. The pore sizes of activated carbons produced were generally observed to be in between 13–25 Å, containing highly micropores. Mesopore formations were higher in samples treated with ZnCl₂. The highest value for the BET surface area was found as 2,599 m² g⁻¹ for the samples treated with KOH at 800 °C with a KOH to coal ratio of 4:1. It was observed that the CO₂ adsorption capacities obtained at atmospheric pressure and 273 K were considerably affected by the micropore volume and surface area. The highest CO₂ adsorption capacities were found as 9.09 mmol/g (28.57 % wt) and 8.25 mmol g⁻¹ (26.65 % wt) for the samples obtained with KOH and NaOH treatments, respectively, at ratio of 4:1. The activated carbons produced were ordered as KOH>NaOH>ZnCl₂, according to their surface areas, micropore volumes and CO₂ adsorption capacities. The low-cost experimental methods developed by the utilization of local coals in this study enabled an effective capture of CO₂ before its emission to atmosphere.