African Journal of Biotechnology Vol. 5 (23), pp. 2397-2401, 4 December 2006   

ISSN 1684–5315 © 2006 Academic Journals        

Full Length Research Paper

pH dependence of sorption of Cd²⁺, Zn²⁺, Cu²⁺ and Cr³⁺ on crude water and sodium chloride extracts of Moringa stenopetala and Moringa oleifera

Sajidu, S. M. I.¹, Henry, E. M. T.²*, Persson, I.³, Masamba, W. R. L.¹, Kayambazinthu, D.⁴

¹Department of Chemistry, Chancellor College, University of Malawi, P.O. Box 280, Zomba, Malawi.

²Department of Chemistry, School of Science & Technology, University of Fort Hare,  Private Bag X1314, Alice 5700, South Africa.

³Department of Chemistry, Swedish University of Agricultural Sciences, Box 7015, 75007 Uppsala, Sweden.

⁴Forestry Research Institute of Malawi, P.O Box 270, Zomba, Malawi.

*Corresponding author. E-mail: ehenry@ufh.ac.za.  Phone:  040 653 2341. Cell: 084 608 2136. Fax: 040 653 1669.

Accepted 26 September, 2006

The ability of crude water and sodium chloride extracts of partially defatted powder of Moringa stenopetala (MS) and Moringa oleifera (MO) to remove heavy metals (Cd2+, Zn2+, Cu2+ and Cr3+) from single ion solution was investigated. At initial metal concentration of about 4 ppm, the extracts showed complete sorption for Cd2+, Zn2+ and Cr3+ ions at pH above 7.8, 4.0 and 4.0, respectively, at a dose of 1.0 ml of sorbent in 9.50 ml of metal solution. Cu2+ sorption increases slightly with pH to about 60% for MS at pH 6 and then becomes constant up to pH 8 when sorption rises to completion. Preliminary characterization of the actual powder by proton nuclear magnetic resonance showed clear presence of amide (-CO-N-H), benzenoid (Ar-H), saturated alkyl and unsaturated fragments in both MS and MO. The mass spectrum showed the presence of amino (R-NH2) fragments. The remarkable heavy metal sorption ability of M. stenopetala and M. oleifera could thus be attributable to, among other mechanisms, coordination or complex formation between the metal cations and pH dependent oxygen and nitrogen anionic sites of the Moringa proteins.

Key words:     Moringa stenopetala, Moringa oleifera, heavy metals, sorption, water.