Surface properties and water vapor adsorption–desorption characteristics of bamboo-based activated carbon

Abstract

In this study, the bamboo charcoals and the bamboo-based activated carbons were prepared from Moso bamboo (Phyllostachys pubescens) by N2 carbonization, CO2 activation and NH3 ammonization at 500–900°C and HNO3 oxidation at room temperature followed by air oxidation at 350°C. The structural and surface chemical characteristics of prepared activated carbons were determined by N2 adsorption–desorption isotherms and Boehm titration, respectively. The water vapor adsorption capacity of each prepared activated carbon was examined with varying the pore structure, surface acidic functional groups and nitrogen contents of samples. Water vapor adsorption–desorption of the bamboo charcoals showed that very small micropores which could adsorb water vapor but be impossible for nitrogen molecule to be accessed would be formed when the carbonization was performed above 700°C. The water vapor adsorption capacity at low humidity region was found to be obviously improved by the oxidation with HNO3. The elemental analysis demonstrated that nitrogen was abundantly introduced into the activated carbon through ammonization at 700–900°C. Also, thermogravimetric analysis for NH3-treated activated carbons which were saturated in relative humidity (RH) of 90% indicated that the interaction between water vapor and activated carbon could be strengthened by surface nitrogen. Ammonization at 900°C significantly developed the specific surface area and pore volume and showed the highest capacity of water vapor adsorption.