Technical Feasibility Study of Char from Fast-Pyrolysis as Adsorbent for Removing Indoor Air Pollutant

Abstract

This research was to characterize physical and chemical properties of char obtained from fast pyrolysis of two biomass types, i.e. sawdust and acacia wood, in order to use char as an adsorbent for removal of indoor air pollutants. Studied chars were tested as follows: adsorption isotherm for gaseous toluene used as a representative of a volatile organic compound, iodine number, specific surface area and pore characteristics, functional groups on the surface, and morphology by scanning electron microscopy (SEM). The Freundlich isotherm indicated that both chars provided favorable adsorption isotherms. The acacia-wood char had specific adsorption capacity and Freundlich isotherm exponent closer to the activated carbon. Iodine numbers of the acacia-wood and sawdust chars were 731 and 802 mg/g, respectively. The specific surface area and mean pore size of the acacia-wood char were twice as large as those of the sawdust char. These results agreed with SEM images that showed capillary-like pores and greater open pores found in the acacia-wood char than in the sawdust char. The similar functional group of aromatic bonds was observed on the surfaces of both chars. According to these properties, the acacia-wood char is capable of directly using as an adsorbent for removing aromatic indoor pollutants. Furthermore, improvement of the char properties by activation and addition of particular functional groups on the surfaces can increase the char ability to adsorb odors and other air pollutants.