High Yield Activated Carbon from Biomass by Air Activation

INTRODUCTION With its large internal surface area, activated carbon has extraordinary adsorptive capabilities. It is employed in a wide range of applications, mostly as a purifying agent to remove trace quantities of undesirable species from gas or liquid phase as well as an economical medium to recover precious materials. The demand for activated carbon has been continuously increasing in the past decade. In 1988, the consumption of activated carbon in industrialized countries was 300,000 tons (Roskill, 1990). The United States accounts for 43% of this amount around 130,000 tons. Since then, the demand in the U.S. market is estimated to have increased at a rate of 5% per year to around 230,000 tons by the year 2000. Because of worldwide increasing environmental problems and stricter regulations set by governments in both industrialized and developing countries, the demand for activated carbon will continue to increase. Commercial production of activated carbon employs high temperatures of above 800°C using steam or carbon dioxide as an activating agent from coal and limited amount of biomass by thermal activation process. On the other hand, yield of activated carbon from biomass is low, e.g., 5 8 % from coconut shell. Consequently, activated carbon produced by conventional method is expensive. The retail price of activated carbon ranges from $2 $6 per kg depending on the type. In this article, a novel thermal process of producing high-yield aitivated carbon from Macadamia shells by air or a mixture of air and inert gas at low temperature is discussed. Characteristics of the carbon are presented.