Preparation of activated carbons from chestnut wood by phosphoric acid-chemical activation. Study of microporosity and fractal dimension

Lignocellulosic materials are good precursors for the production of activated carbon. In this work, chestnut wood has been used in the preparation of activated carbon by the method of phosphoric acid-chemical activation. The influence of heat treatment temperature (i.e., 300, 400, 500 and 600 °C) and concentration of the solution of phosphoric acid (i.e., 1:1, 1:2 and 1:3 water/H3PO4 proportions) used in the impregnation of chestnut wood on textural properties and fractal dimension has been studied. The products obtained have been characterized by N2 adsorption at −196 °C. The activated carbons are mainly microporous products, both the micropore volume (Vmi) and the specific surface area (SBET) as a rule increasing with increasing temperature and acid concentration. However, Vmi and SBET decrease at 600 °C with regard to 500 °C. The micropore size distribution is similar in the products prepared at 400 and 500 °C, regardless of the acid concentration. For the carbons obtained at the other temperatures, the microporous structure is more heterogeneous for the 1:3 concentration at 300 °C and for the 1:1 and 1:2 concentrations at 600 °C. Similar trends to those shown by Vmi and SBET are usually observed for the fractal dimension.