Effects of activation method on the pore structure of activated carbons from apricot stones

Two series of activated carbons were prepared from apricot stones by using carbonization followed by steam activation and one-step pyrolysis/activation in steam. The pore structure of the activated carbons was characterized by CO₂ adsorption at 273 K and by N₂ adsorption at 77 K. The macro-and mesoporosity were determined by mercury porosimetry. Optical microscopy, scanning electron microscopy (SEM) and environmental scanning electron microscopy (ESEM) were used to examine the microstructure of activated carbons. A considerable difference observed between the measured CO₂ and N₂ surface areas indicates a narrow microporosity in all the carbons. The two-step method produced better developed meso-and especially macroporosity. The SEM and optical micrographs show that one-step pyrolysis/steam activation preserves the original cell structure of the raw apricot stones. In general, the apparent surface areas of the two-step carbons are slightly higher than those of the one-step carbons. However, the one-step method would provide lower production costs because it would eliminate the separate carbonization stage.