The present study attempts to investigate the effects of different chemical agents and chemical ratios on pore structure of coal-based activated carbons. The adsorption isotherm data of two series of activated carbons prepared from bituminous coal by chemical activation with potassium hydroxide and zinc chloride were used. Four well-known models of Dubinin-Stoeckli, Stoeckli, Horvath-Kawazoe, and improved Horvath-Kawazoe were applied for the characterization of these porous solids. Although the results showed some differences among the models that arise from their fundamental assumptions, in general they are found to be comparable. Results showed that samples activated by ZnCl2 provide higher-adsorption capacity than those from KOH. In each series, it was shown that the pore volume increases with increasing impregnation ratio, ranging from 50% to 200%. Activated carbons obtained at low chemical ratio in ZnCl2 series (up to 100%) showed microporous structure, while those with higher ratios became predominantly mesoporous. In the KOH series, increasing KOH created more micropores in the carbon structure in the whole range of studied chemical ratio. 1. Introduction Activated carbon (AC) is among the important carbon based materials that find widespread use in almost every industrial field. They are employed in different applications such as purification, recovery, decolorization, deodorization, separation, catalyst, catalytic support, and gas storage due to the large internal surface area and specific pore structure. On this basis, activated carbon adsorption is of interest to many economic sectors and areas such as chemical, food, pharmaceutical, automobile, petroleum, petrochemical, and gas industries [1–4]. Coals have become the main precursor for the production of activated carbons because of their inherent microstructure and surface chemical properties [5]. Low cost of production and unlimited resources as well as specific beneficial properties, such as well-developed internal pore structure and high surface area, high mechanical and chemical resistance, ease of degradation, and good ion-exchange properties are main reasons for increasing interest in the use of activated carbons obtained from coals [6–8]. Furthermore, coal products are in greater demand since they have greater density and corrosion endurance than other carbons [9, 10]. Important parameters that greatly affect the adsorption performance of a porous carbonaceous adsorbent are porosity and pore structure. Consequently, the determination of pore size distribution (PSD) of coal-based
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