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Adsorption of a Water Treatment Protein from Moringa oleifera Seeds to a Silicon Oxide Surface Studied by Neutron Reflection
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 Physics.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
2010 (English)In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 26, no 6, 3902-3910 p.Article in journal (Refereed) Published
Abstract [en]

An extract from the seeds of the Moringa oleifera tree that is principally a low molecular mass protein is known to be efficient as a coagulating agent for water treatment. The present paper investigates the adsorption of the purified protein to silica interfaces in order to elucidate the mechanism of its function as a flocculent. Neutron reflection permits the determination of the structure and composition of interfacial layers at the solid/solution interface. Dense layers of protein with about 5.5 mg m(-2) were found at concentrations above 0.025% wt. The overall thickness with a dense layer in excess of 60 angstrom at 0.05 wt % suggests strong co-operative binding rather than single isolated molecules. All ionic surfactant, sodium dodecyl sulfate, was also seen to coadsorb. This strong adsorption of protein in combination with the tendency for the protein to associate suggests a mechanism for destabilizing particulate dispersions to provide filterable water. This call occur even for the protein that has previously been identified as being of low mass (about 7 kDaltons) and thus is unlikely to be efficient in bridging or depletion flocculation.

Place, publisher, year, edition, pages
2010. Vol. 26, no 6, 3902-3910 p.
National Category
Biological Sciences Physical Sciences
Identifiers
URN: urn:nbn:se:uu:diva-135431DOI: 10.1021/la9031046ISI: 000275226700025PubMedID: 20163083OAI: oai:DiVA.org:uu-135431DiVA: diva2:374935
Available from: 2010-12-06 Created: 2010-12-06 Last updated: 2017-12-11Bibliographically approved
In thesis
1. Adsorption and Ordering of Surface Active Molecules and Particles at Solid Interfaces and in the Bulk
Open this publication in new window or tab >>Adsorption and Ordering of Surface Active Molecules and Particles at Solid Interfaces and in the Bulk
2012 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Factors that influence the process of adsorption and order of dilute and concentrated systems of molecules and particles are explored in this thesis.  The results are based largely on neutron scattering techniques.  Study of the adsorption from dilute solutions of a common surfactant, AOT (sodium bis (2-ethylhexyl) sulfosuccinate), at a solid/liquid interface showed that AOT molecules adsorbed to the interface in a bilayer structure, with the hydrocarbon tails at maximum packing density even at very low concentrations.  At higher AOT concentrations, a stack of fluctuating layers each separated by large amounts of water next to the dense bilayer was seen.  The driving force for adsorption is dominated by self-assembly of AOT.  It was found that an oriented lamellar phase wets the interface below the bulk concentration for formation of this phase.

Proteins can be viewed as polymeric surfactants.  The adsorption of proteins from seeds of the Moringa oleifera tree to a silicon oxide surface was studied to elucidate the mechanism of the protein as a flocculent in water treatment processes.  The protein was found to adsorb at the interface as dense layers with a thickness suggestive of co-adsorption rather than single isolated molecules.  The strong adsorption and tendency to associate in solution suggest mechanisms for flocculating particulate impurities in water.

As with surfactants, dispersions of colloidal particles can assemble in regular structures by self-assembly.  Polystyrene latex particles were studied and could form large three-dimensional crystals of about 1×1 cm2 in a 2 mm path cell.  The diffraction pattern indicated a close packed structure with the 110 axis perpendicular to the container wall.  The crystal was well-aligned and oriented by the direction of flow.  At the solid interface large two-dimensional domains of about 20 cm2 of highly oriented particles were formed.  The particle-particle separation at the surface and in the bulk was determined by the charge repulsion of the particles.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2012. 56 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 915
National Category
Condensed Matter Physics
Research subject
Physics with spec. in Atomic, Molecular and Condensed Matter Physics
Identifiers
urn:nbn:se:uu:diva-171739 (URN)978-91-554-8327-2 (ISBN)
Public defence
2012-05-16, Häggsalen, Ångströmlaboratoriet, Lägerhyddsvägen 1, Uppsala, 09:15 (English)
Opponent
Supervisors
Available from: 2012-04-24 Created: 2012-03-27 Last updated: 2012-08-01Bibliographically approved

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Hellsing, MajaRennie, Adrian

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