Characteristics of microporous/mesoporous carbons prepared from rice husk under base- and acid-treated conditions

The study reports the preparation of activated carbon with a high surface area from rice husk using chemical activation with H3PO4 and ZnCl2. Activated carbon prepared from rice husk usually exhibits low specific surface areas due to its high ash content. However, experimental results show that base-leaching and acid-washing processes can effectively enhance the adsorption capacity of rice-husk carbon. The study also investigates the effects of preparation parameters on the surface characteristics of the carbon. These parameters include the kind of activating agent, before and after treatment procedures, impregnation ratio and activation temperature. The chemical and physical properties of samples were examined by EA, ICP-MS, XRD, FTIR, SEM and a N2-adsorption meter. The surface areas obtained from ZnCl2 and H3PO4 activation are as high as 2434 and 1741 m2/g, respectively. These values are higher than that of activated carbon treated with neither base nor acid (1262 and 508 m2/g for ZnCl2 and H3PO4 activation). Thermogravimetric analysis shows that the activation process can be divided into three parts based on temperature zones. The results of this study will be useful in developing resource recovery systems for agricultural biomass.