Effects of Small Amounts of Phosphoric Acid as Additive in the Preparation of Microporous Activated Carbons

Abstract

The activated carbons with well-developed microporosity were prepared from fir wood (Cunninghamia lanceolata) impregnated with small amounts of phosphoric acid (impregnation ratios, 1.5 – 4.5 wt.%). For comparison purpose, a parallel study of fir wood without impregnation was carried out in the same conditions. The results showed that the addition of small amounts of H₃PO₄ could lower the thermal decomposition temperature of fir wood and significantly promote the adsorption capacity and the yield of activated carbon. The yield without phosphoric acid impregnation was 6.55 wt.%, which rose to 19.82 wt.% in the case of 3.0 wt.% H₃PO₄ impregnation. Using small amounts of phosphoric acid as additive was beneficial to improve specific surface area (S_BET) and micropore volume (V_mic), and could produce activated carbons with well-developed microporous structure. With 3.0 wt.% H₃PO₄ impregnation, S_BET and V_mic of the activated carbon reached as high as 1281.6 m²/g and 0.535 mL/g, the ratio of V_mic/V_tot (total pore volume) was higher than 80 %.

DOI: http://dx.doi.org/10.5755/j01.ms.24.4.18999