Atakan Toprak and Turkan Kopac* Carbon Dioxide Adsorption Using High Surface Area Activated Carbons from Local Coals Modified by KOH, NaOH and ZnCl 2 Agents DOI 10.1515/ijcre-2016-0042 Abstract: 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 ZnCl 2 at different tempera- tures (600–800 °C) and concentrations (1:1–6:1 agent:coal), for their evaluation in CO 2 adsorption studies. BET, DR, t-plot and DFT methods were used for the characterization of carbon samples based on N 2 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 ZnCl 2 . The highest value for the BET surface area was found as 2,599 m 2 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 CO 2 adsorption capacities obtained at atmospheric pressure and 273 K were considerably affected by the micropore volume and surface area. The highest CO 2 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>ZnCl 2 , according to their surface areas, micropore volumes and CO 2 adsorption capacities. The low-cost experimental methods developed by the utilization of local coals in this study enabled an effective capture of CO 2 before its emission to atmosphere. Keywords: activated carbon, coal, chemical activation, CO 2 adsorption 1 Introduction Meeting the needs of humankind depending on the constant increase of world population has led to ever increasing use of fossil fuels as well as gradual increase in industrialization. This also led to an increase in the concentration of gases (such as CO 2 , CH 4 and NO x ) result- ing in global warming in the atmosphere. Methods should be developed in order to capture and sequestra- tion greenhouse gases with the aim of preventing the continuation of this increase in connection with the energy need (Caglayan and Aksoylu 2013). With an annual amount of about 21 tons, CO 2 has the greatest impact on global warming. CO 2 is released to atmosphere with the use of such fossil fuels as coal, oil and natural gas and the destruction of forests. There are four common methods for capturing CO 2 after the combustion of fossil fuels. These are chemical adsorption, separation with membranes, separation by condensing under the control of pressure and temperature, and storage into solids such as zeolite and activated carbon which have high surface area and porosity (Khoo and Tan 2006). Adsorbents attract the attention of researchers as CO 2 adsorption is easy and costly effective and can be carried out in a wide range of temperatures and pressures. Adsorbents should possess properties, such as high selec- tivity and adsorption capacity for carbon dioxide at different temperatures, adequate adsorption/desorption kinetics, stable adsorption capacity after repeated adsorption/desorption cycles, and adequate mechanical strength after cyclic exposure to high pressure streams (Caglayan and Aksoylu 2013; Lozano-Castello, Cazorla- Amoros, and Linares-Solano 2004; Plaza et al. 2007; Yong, Mata, and Rodrigues 2002). Activated carbon is one of the most commonly used adsorbent material in a wide variety of applications. Due to the high surface area and micropore volume, low cost and easiness of production, it is used in many industrial applications including air pollution, waste water treat- ment, purification, gas adsorption and catalyst (Hsu and Teng 2000; Tsai et al. 2001). Production of activated carbon consists of two stages: carbonization of the raw carbonaceous material in an inert environment and the activation of the carbonized product. Impregnation method known as chemical activation is commonly used to increase the porosity, surface area and the adsorption *Corresponding author: Turkan Kopac, Department of Chemistry, Bülent Ecevit University, Zonguldak, Turkey, E-mail: turkan.kopac@beun.edu.tr Atakan Toprak, Department of Chemistry, Bülent Ecevit University, Zonguldak, Turkey Int. J. Chem. React. Eng. 2017; aop Brought to you by | University of South Carolina Libraries Authenticated Download Date | 2/13/17 8:29 AM