The preparation of active carbons from coal by chemical and physical activation

A series of activated carbons was prepared from bituminous coal by chemical activation with potassium hydroxide and zinc chloride and also by physical activation with carbon dioxide. The effect of process variables such as carbonization time, temperature, particle size, chemical agents, method of mixing and impregnation ratio in the chemical activation process was studied in order to optimize those preparation parameters. Partial gasification of the high surface area carbon obtained by zinc chloride activation in CO2 with different exposure times shows some improvement in adsorption. The physical properties of the chemically activated carbon was also compared with those obtained purely by physical activation. The most important parameter in chemical activation of coal with both of the chemical agents was found to be impregnation ratio. Carbonization temperature is another variable which had a high effect on pore volume evolution. While increasing the carbonization temperature enhances surface area and pore volumes of KOH-activated carbon, it destroys carbon structure in the ZnCl2 carbon series. Under the experimental conditions investigated, the optimum conditions for high surface area carbons with KOH and ZnCl2 activation are identified. Copyright (C) 1996 Elsevier Science Ltd