Preparation and characteristics of agricultural waste activated carbon by physical activation having micro- and mesopores

Micro–mesoporous activated carbons were prepared from various agricultural wastes by physical activation. Agricultural wastes such as macadamia nut-shell, corncob, bagasse bottom ash, sawdust fly ash and rice husk fly ash, were optimized and processed to obtain the highest surface area. The effects of the amount of volatile matter in char, the activating agent, the activating temperature and kind of raw materials were investigated in terms of porosity development. It was found that the amount of volatile matter, 17–25% or 300–500 °C suitable for pore development depended on the type of raw material. In addition, the activating agents (CO2 and steam) can differentially improve the porosity of the materials. Corncob and sawdust fly ash activated by CO2 and macadamia nut-shell and bagasse bottom ash activated by steam obtained the same high surface area. Among these materials, bagasse bottom ash and sawdust fly ash had a mesopore volume than other materials including commercial activated carbon. Therefore, both of these materials can be alternative adsorbents to adsorb large molecule of organic compounds.