Preparation of tobacco-stem activated carbon from using response surface methodology and its application for water vapor adsorption in solar drying system

Tobacco-stem activated carbons (TACs) were prepared by ZnCl2 activation and used for water vapor adsorption in solar drying system. The effects of activation temperature, activation time, and ZnCl2 impregnation ratio on water vapor adsorption performance and BET specific surface area of TACs were carried out and the preparation conditions were analyzed by surface response methodology. Pore structure and morphology of the samples were characterized by N-2 adsorption-desorption isotherm and scanning electron microscope. Water vapor adsorption and desorption isotherms of TACs were carried out. A six subsequent adsorption-regeneration cycle of water vapor was investigated. The result shows that BET specific surface area of 1893.6 m(2)/g, water vapor adsorption capacity of 563.4 mg/g are obtained in the optimum preparation conditions of activation temperature 621 degrees C, activation time 73 min and ZnCl2 impregnation ratio of 1.70. Pore structure and surface area analysis shows that TAC21 is prepared as a microporous activated carbon and suitable for water vapor adsorption application. Both TAC18 and TAC21 possess an excellent reversibility of water vapor adsorption under the tested condition. The result confirms that the TAC adsorbents would be the potential candidates for dehumidification and heat recovery in solar drying system.