Thermodynamic Analysis of Adsorption of H2S on Modified Activated Carbon

Coke oven gas is one of by-products generated in the process of dry distillation of coal to form coke. The coke oven gas is of high value in used as not only energy but also chemical material, but it contains hydrogen sulfide (H₂S) gas which limits its application. Thus, it is necessary to remove H₂S from the coke oven gas in order to use it as energy or chemical material. The thermodynamic analysis is helpful to explain the adsorption of H₂S on modified activated carbon. So this study examined the thermodynamic properties of adsorption of H₂S on the activated carbon impregnated with 7% NaCO₃, which was determined by the early experimental results of modification of activated carbon. The thermodynamic properties including H2S adsorption isotherms and adsorption heat of H₂S on modified activated carbon were separately ascertained at 20~95°C through measuring the adsorption capability of H2S on the modified activated carbon. The results showed the adsorption data were correlated with the Freundlich-type isotherm equation. Thermodynamic calculation and analysis also showed that the adsorption of H₂S on the modified activated carbon was physical adsorption at 20~70°C and chemical adsorption at 70~95°C. In addition, with the improvement of reaction temperature, the adsorption capacity of modified activated carbon was decreasing initially then increasing, because of the transition from physical adsorption to chemical adsorption.