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Interactions of surfactants with a water treatment protein from Moringa oleifera seeds in solution studied by zeta-potential and light scattering measurements
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
2012 (English)In: Biopolymers, ISSN 0006-3525, E-ISSN 1097-0282, Vol. 97, no 4, 209-218 p.Article in journal (Refereed) Published
Abstract [en]

Protein extracted from Moringa oleifera (MO) seeds has been advocated as a cheap and environmental friendly alternative to ionic flocculants for water purification. However, the nature and mechanism of its interaction with particles in water, as well as with dissolved surface-active molecules, are not well understood. In this article, we report studies of the protein and its interaction with four surfactants using dynamic light scattering (DLS), zeta-potential and turbidity measurements. Zeta-potential measurements identified points of charge reversal and the turbidity and DLS measurements were used to characterize the microstructure and size of protein-surfactant complexes. From the points of charge reversal, it was estimated that 7 anions are required to neutralize the positive charges of each protein molecule at pH 7. For protein mixtures with sodium dodecyl sulfate and dodecyl di-acid sodium salt, the peak in turbidity corresponds to concentrations with a large change in zeta-potential. No turbidity was observed for protein mixtures with either the nonionic surfactant Triton X-100 or the zwitterionic surfactant N-dodecyl-N,N-dimethyl-3-ammonio-1-propanesulfonate. Changes of pH in the range 410 have little effect on the zeta-potential, turbidity, and the hydrodynamic radius reflecting the high isoelectric point of the protein. Addition of small amounts of salt has little effect on the size of protein in solution. These results are discussed in the context of the use of the MO protein in water treatment.

Place, publisher, year, edition, pages
2012. Vol. 97, no 4, 209-218 p.
Keyword [en]
charge reversal, dynamic light scattering, electrophoretic mobility, hydrodynamic radius, protein-surfactant interaction, turbidity, zeta-potential
National Category
Natural Sciences
URN: urn:nbn:se:uu:diva-169331DOI: 10.1002/bip.22014ISI: 000299208100002OAI: oai:DiVA.org:uu-169331DiVA: diva2:507418
Available from: 2012-03-05 Created: 2012-02-28 Last updated: 2013-01-07Bibliographically approved

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