THE PRODUCTION OF ACTIVATED CARBON FOR WATER-TREATMENT IN MALAWI FROMTHE 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 a s a waste, but research has shown that they can be converted into acti vated carbon by carbonisation at 485 degrees C under N-2 for 30 minute s, followed by activation in steam at 850 degrees C for 5 minutes. Her e we report an improved method of carbon production, using a single-st age steam pyrolysis activation that is more appropriate for the intend ed use. Steam pyrolysis at 750 degrees C for between 30 and 120 minute s produced a high quality microporous activated carbon at a yield of b etween 11% and 17%, with increases in soak time giving improved pore d evelopment and more mesoporosity. The apparent N-2 BET surface area of the M. oleifera carbon produced by soaking at 750 degrees C for 120 m inutes was 730.0 m(2) g(-1) similar to that of the carbon produced pre viously by the two-stage process, 734.3 m(2) g(-1). The phenol adsorpt ive capacities of the carbons pyrolysed at 750 degrees C were similar to a commercial carbon. These results show that it is possible to prod uce high quality activated carbon from the waste seed husks of M. olei fera using a simple one-stage 750 degrees C steam pyrolysis. This prov ides a low-cost method of producing activated carbon locally in develo ping countries for use in water treatment. Copyright (C) 1996 IAWQ. Pu blished by Elsevier Science Ltd.