Pore structure and adsorption characteristics of steam pyrolysis carbons from Moringa oleifera

Abstract

A series of activated carbons has been prepared from the waste seed husks of the tropical multi-purpose tree Moringa oleifera, using a single-stage steam pyrolysis activation. Carbons were characterised by N 2 adsorption, CHN analysis and scanning electron microscopy. Nitrogen adsorption isotherms were analysed by the BET, t-plot and Horváth and Kawazoe methods. All the carbons were microporous, with those activated at 750 °C for 120 minutes ( 750 120 ) and 800 °C for 30 or 60 minutes having the highest BET surface areas, of 730, 713 and 774 m 2 g −1, respectively. A simple acid rinse of the 800 °C/30 minutes carbon increased the surface area to 932m 2g −1. The 800/60 carbon had the highest mesopore and macropore surface area, 135.7 m 2g −1, compared to 92.7m 2g −1 for the 800 30 carbon. Scanning electron micrographs of the 800 30 carbon showed a lignocellulosic macropore structure, cleaned by the steam pyrolysis. These results show that it is possible to produce a high quality microporous activated carbon from M. oleifera husks using a simple single-stage steam pyrolysis activation.