Preparation of coffee-shell activated carbon and its application for water vapor adsorption

Abstract

Coffee-shell activated carbon was prepared by a two-step activation method including carbonization process and potassium hydroxide (KOH) activation process. The influences of activation temperature, activation time and mass ratio of KOH to char on activated carbon water vapor adsorption performance were investigated by single factor design. The optimum preparation conditions of activated carbon with large adsorption capacity were determined. The water vapor adsorption experiments of activated carbon were carried out under 70% relative humidity and adsorption temperature of 298 K. Pore structure characteristics were studied via N2 adsorption-desorption isotherm. The results show that the optimum preparation conditions are activation temperature of 1073 K, activation time of 10 min and mass ratio of KOH to char of 3:1. The Brunauer–Emmett–Teller (BET) specific surface area, total pore volume and water vapor adsorption capacity of the optimum coffee-shell activated carbon are 2349 m2/g, 1.036 cm3/g and 0.7409 g/g, respectively. All isotherms are type I with narrow pore size distributions in micropore region. Moreover, the obtained activated carbon was characterized by pH, elemental analysis and Fourier transform Infrared (FT-IR) spectroscopy. The results show that the obtained activated carbon would be one of the potential adsorbents for dehumidification in solar energy drying system.