Effects of Heat Pretreatment During Impregnation on the Preparation of Activated Carbon from Chinese Fir Wood by Phosphoric Acid Activation

Activated carbons were prepared from Chinese fir wood by phosphoric acid activation. The effects of heat pretreatment from 80 to 180 °C during impregnation on the properties of fir wood and its activated carbons were discussed. The crystallinity index and surface chemistry of the pretreated fir wood were characterized by X-ray diffraction and Fourier transform infrared spectroscopy (FT-IR). The porous texture of activated carbons was investigated by N₂ adsorption–desorption isotherms. The results showed that with increasing pretreatment temperature, the crystallinity of the pretreated samples decreased, which gave rise to a significant development of pores, especially micropores as high as 97.2 %. FT-IR results revealed that the carbonyl-containing and phosphorus-containing groups of the pretreated samples increased with increasing pretreatment temperature. For a temperature of 140 °C, the specific surface area, the total pore volume, and the micropore volume reached a maximum of 1603.0 m²/g, 0.792 cm³/g, and 0.770 cm³/g, respectively. However, a higher pretreatment temperature was not beneficial for activation. Thus, heat pretreatment during impregnation can be regarded as an excellent method for manufacturing phosphoric acid-activated carbon with a high micropore volume.