The production of activated carbon for water treatment in Malawi from the waste seed husks of Moringa oleifera

Moringa oleifera is a multi-purpose tree whose seeds can be used as a coagulant in water treatment. The seed husks are currently discarded as a waste, but research has shown that they can be converted into activated carbon by carbonisation at 485 degrees C under N-2 for 30 minutes, followed by activation in steam at 850 degrees C for 5 minutes. Here we report an improved method of carbon production, using a single-stage steam pyrolysis activation that is more appropriate for the intended use. Steam pyrolysis at 750 degrees C for between 30 and 120 minutes produced a high quality microporous activated carbon at a yield of between 11% and 17%, with increases in soak time giving improved pore development and more mesoporosity. The apparent N-2 BET surface area of the M. oleifera carbon produced by soaking at 750 degrees C for 120 minutes was 730.0 m(2) g(-1) similar to that of the carbon produced previously by the two-stage process, 734.3 m(2) g(-1). The phenol adsorptive capacities of the carbons pyrolysed at 750 degrees C were similar to a commercial carbon. These results show that it is possible to produce high quality activated carbon from the waste seed husks of M. oleifera using a simple one-stage 750 degrees C steam pyrolysis. This provides a low-cost method of producing activated carbon locally in developing countries for use in water treatment. Copyright (C) 1996 IAWQ. Published by Elsevier Science Ltd.