Comparison of activated carbon prepared from Jatropha hull by conventional heating and microwave heating

An attempt to compare the yield and porous nature of the activated carbon prepared using the conventional and microwave assisted heating, is the focus of the present work. Towards this Jatropha hull (a biomass precursor) is activated using the popular activating agents, steam and CO2 to assess the relative merit of activating agents and the heating methods. The process optimization exercise is carried out with the minimum number of experiments following the standard full factorial statistical design of experiments (RSM). The activated carbon prepared under the optimized conditions is compared based on the yield and porous nature. The yield of activated carbon is not found to vary significantly for the steam activation, irrespective of the heating method, while it is found to double using CO2 activation with microwave heating as compared to conventional heating. The pore volume and the surface area is found to double using the microwave heating with steam, while it is found to be of the same order of magnitude using CO2 activation. Although the porosity of carbon is of the same order of magnitude using CO2 activation, the activation temperature, the activation time, CO2 flow rate are significantly lower than the conventional heating rendering the process more economical than the conventional heating. The steam-carbon reaction rate is significantly higher than the carbon-CO2 reaction rate, rendering the time requiring for activation lesser using steam activation as compared to CO2 activation. (C) 2011 Elsevier Ltd. All rights reserved.