A simple method for developing mesoporosity in activated carbon

A simple process was proposed based on a combination of chemical and physical activation for the production of activated carbon. The process was expected to improve the mesoporosity in activated carbons. The KOH- or ZnCl2-chemical activation coupled with CO2-physical activation of lignocellulosic materials, such as coconut shells and palm stones, were used as a simultaneously chem-physical activation for increasing the mesoporosity. The porosity of the resultant activated carbons was characterized by nitrogen adsorption isotherms at 77 K. Both chemicals and CO2 had effects on the formation of mesopores. Intensified activation conditions, such as high chemical ratio to the precursors, long soaking time, elevated temperature, increased the mesoporosity in activated carbons. The surface area and the nature of the porosity can be controlled by means of the experimental parameters. By changing the ratio of activating agent to carbon precursor, it is possible to control the pore size from supermicropore (1.5-2.0 nm) to mesopore (2-3.49 nm). The BET-surface area of the carbons can be over 2100 m(2)/g; the mesopore content (ratio of mesopore volume to total pore volume) is 71%. Furthermore, the activated carbon from palm stones possesses mesopore content as high as 94%. (C) 2002 Elsevier Science B.V. All rights reserved.