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 (SBET) and micropore volume (Vmic), and could produce activated carbons with well-developed microporous structure. With 3.0 wt.% H3PO4 impregnation, SBET and Vmic of the activated carbon reached as high as 1281.6 m2/g and 0.535 mL/g, the ratio of Vmic/Vtot (total pore volume) was higher than 80 %.