Influence of different radial distribution zones of Douglas fir trunk as precursors on the properties of prepared activated carbons
2022
Ruan, Wei | Wang, Yuan | Luo, Weiyan | Lei, Shengwen | Ye, Yueyuan | Zheng, Zhifeng | Li, Shuirong | Wang, Dechao | Wang, Duo
In this study, four zones including the innermost (IM), the middle inner (MI), the middle outer (MO) and the outermost (OM) zone, evenly distributed from inside to outside along the radial direction of Douglas firs, is used as the precursors for the preparation of activated carbons. The elemental and chemical composition, the cell wall microstructure, the thermal weight loss and the surface crystallinity of Douglas fir trunk are characterized to analyze the differences among four zones. The higher cell wall thickness, lignin and hemicellulose content are observed in the heartwood (IM and MI) of Douglas fir trunk, while higher cellulose content and more oxygen-containing functional groups are found in the sapwood (MO and OM). Using these four zones as the precursors, activated carbons prepared from heartwood of Douglas fir exhibit desired qualities including higher specific surface area and better adsorption performance. BET specific surface area of activated carbons fluctuate between 1595 and 1734 m²/g when the raw material of Douglas fir is not carefully classified, but directly used as a whole. In the heartwood, MI zone rather than IM zone, is confirmed to be a better raw material for the preparation of activated carbon using H₃PO₄ or KOH as the activating agent. Furthermore, when the activated carbon prepared from MI zone is used to be the electrode material of supercapacitors, its specific capacitance reaches 71 F/g at a current density of 1 A/g, which is higher than other activated carbons prepared from IM, MO and OM. This work shows that the preparation of wood-based activated carbon needs careful classification of raw material.
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