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South African Journal of Chemistry
versão On-line ISSN 1996-840X
versão impressa ISSN 0379-4350
S.Afr.j.chem. (Online) vol.65 Durban 2012
RESEARCH ARTICLE
Functionalization of a natural biopolymer with aliphatic polyamines and its sorption properties for vanadium removal from aqueous solutions
Robert L. Mnisi*; Peter P. Ndibewu; Ntebogeng S. Mokgalaka
Tshwane University of Technology, Private Bag X680, Pretoria, 0001, South Africa
ABSTRACT
A low-cost natural adsorbent, Moringa oleifera, was investigated as a potential alternative for currently costly methods of removing vanadium from contaminated aqueous solutions. The unmodified bark was characterized using techniques such as N2-BET, SEM, XRD and FTIR spectroscopy, CHNS elemental determination and AA spectroscopy. Results showed a relatively small surface area, motivating surface functionalization to enhance adsorption capacity. Chemical modification was performed using four aliphatic polyamines: ethylenediamine (EDA), diethylenetriamine (DETA), triethylenetetramine (TETA) and tetraethylenepentamine (TEPA). The modified bark was characterized and then investigated to determine its efficiency in removing VO2+ from aqueous solutions. The bark had a mesoporous amorphous structure and was enriched with N and S groups. FTIR absorption frequencies also revealed that polyamines were indeed immobilized on the adsorbent surface. The polyamine density was calculated and was in the order of EDA>DETA>TETA>TEPA, whereas the adsorption efficiency with VO2+ was in the order DETA>EDA>TETA>TEPA. Adsorbent amination was enhanced by up to 26 % and adsorption performance improved by up to 155 %. It was, therefore, concluded that chemical modification of M. oleifera using polyamines enhances adsorption of VO2+ from aqueous solutions. This can, thus, preconcentrate VO2+ in the bark leading to its use as a good water purifier.
Keywords: Adsorption, functionalization, Moringa oleifera, polyamine, vanadium
Full text available only in PDF format.
Acknowledgements
The financial support from the Tshwane University of Technology is greatly appreciated.
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Received 14 November 2011
Revised 27 February 2012
Accepted 27 February 2012
Submitted by invitation to celebrate 2011 the 'International Year of Chemistry'.
* To whom correspondence should be addressed. E-mail: mnisirl@tut.ac.za