Investigation of coal chemical activation compared with physical activation

The usage of activated carbon as an efficient adsorbent is gradually in different separately processes of material and environmental application. Coal is one of the suitable raw material to produce active carbon (AC) with different properties. In this study, sub-bituminous coal extracted from Abnil mine in Zarand region are used to make Ac. It was prepared by chemical activation with zinc chloride and potassium hydroxide and also by physical activation with carbon dioxide and steam. The activation process was carried out in a horizontal reactor at various activation temperatures in the 400–1000°C range, different dwell times and impregnation ratio of 50%, 100% and 150%. According to weight loss percentages and iodine numbers of AC, the effect of preparation parameters such as carbonization and activation temperature, dwell time, chemical agents and their impregnation ratio were evaluated. It appears that in carbonization, chemically and physically activation of coal iodine number and weight loss will be rise by increasing dwell time at constant temperature and by temperature enhancement at constant dwell time. In both cases, after a certain time and temperature it rise constantly and sometimes may be decreased. The results show that steam atmosphere was better than carbon dioxide in physical activation and zinc chloride had well behavior than potassium hydroxide in chemical activation. In compared with physically activation, chemically activation of char had better results on surface area and pore development. At final activation temperature of 600 °C and impregnation ratio of 50% were found to be suitable for producing high surface area chemically activated carbon which iodine number were achieved as high as 813.78. Also the iodine number of AC was 778.32 by physically activation at 1000°C and weight loss of 45.4% on steam atmosphere.