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Adsorption, desorption, and surface-promoted hydrolysis of Glucose-1-phosphate in Aqueous Goethite (α-FeOOH) Suspensions
Umeå University, Faculty of Science and Technology, Department of Chemistry.
Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. (Climate Impacts Research Centre, Department of Ecology and Environmental Science, Umeå University, Umeå)
Umeå University, Faculty of Science and Technology, Department of Chemistry. (Pacific Northwest National Laboratory, Richland, Washington, USA)
Umeå University, Faculty of Science and Technology, Department of Chemistry.
2010 (English)In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 26, no 24, 18760-18770 p.Article in journal (Refereed) Published
Abstract [en]

Adsorption, desorption, and precipitation reactions at environmental interfaces govern the fate of phosphorus in terrestrial and aquatic environments. Typically, a substantial part of the total pool of phosphorus consists of organophosphate, and in this study we have focused on the interactions between glucose-1-phosphate (G1P) and goethite (α-FeOOH) particles. The adsorption and surface-promoted hydrolysis reactions have been studied at room temperature as a function of pH, time, and total concentration of G1P by means of quantitative batch experiments in combination with infrared spectroscopy. A novel simultaneous infrared and potentiometric titration (SIPT) technique has also been used to study the rates and mechanisms of desorption of the surface complexes. The results have shown that G1P adsorption occurs over a wide pH interval and at pH values above the isoelectric point of goethite (IEP(goethite) = 9.4), indicating a comparatively strong interaction with the particle surfaces. As evidenced by IR spectroscopy, G1P formed pH-dependent surface complexes on goethite, and investigations of both adsorption and desorption processes were consistent with a model including three types of surface complexes. These complexes interact monodentately with surface Fe but differ in hydrogen bonding interactions via the auxiliary oxygens of the phosphate group. The apparent desorption rates were shown to be influenced by reaction pathways that include interconversion of surface species, which highlights the difficulty in determining the intrinsic desorption rates of individual surface complexes. Desorption results have also indicated that the molecular structures of surface complexes and the surface charge are two important determinants of G1P desorption rates. Finally, this study has shown that surface-promoted hydrolysis of G1P by goethite is base-catalyzed but that the extent of hydrolysis was small.

Place, publisher, year, edition, pages
Americal Chemical Society , 2010. Vol. 26, no 24, 18760-18770 p.
National Category
Earth and Related Environmental Sciences
URN: urn:nbn:se:umu:diva-46540DOI: 10.1021/la1026152ISI: 000285217700029PubMedID: 21087005OAI: diva2:438791
Available from: 2011-09-06 Created: 2011-09-05 Last updated: 2012-03-08Bibliographically approved
In thesis
1. Surface reactions on mineral particles controlling the hydrolysis of glucose phosphates
Open this publication in new window or tab >>Surface reactions on mineral particles controlling the hydrolysis of glucose phosphates
2011 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Phosphorus (P) is an essential nutrient. A significant amount of soil P may be in the form of organophosphates. Due to the size of these compounds, hydrolysis is often required before P can be assimilated by organisms. Hydrolysis may be mediated by mineral surfaces, or catalyzed by extra cellular enzymes. Since both organophosphates and enzymes have a strong affinity for environmental particles, a study of the hydrolysis of organophosphates must focus on reactions at the water/particle interface. This thesis is a summary of four papers, discussing the adsorption, desorption, and abiotic and enzymatic hydrolysis of glucose-1-phosphate (G1P) and glucose-6-phosphate (G6P) in aqueous goethite suspensions. A new technique for simultaneous infrared and potentiometric titrations (SIPT) allowed in-situ measurements of the interfacial reactions. It was found that glucose phosphates form pH-dependent inner sphere complexes on goethite, which coordinate in a monodentate fashion, and are stabilized by hydrogen bonding. Desorption involves a change in speciation of the surface complexes, illustrating the difficulty in determining desorption rates for individual complexes. The surface mediated hydrolysis is primarily base catalyzed for G1P, and acid catalyzed for G6P. The difference is partly due to electronic factors, and partly to differences in glucose group/goethite interactions. Considerably more extensive is the hydrolysis catalyzed by an acid phosphatase (AcPase). The rate of the enzymatic hydrolysis are strongly dependent on the glucose phosphate surface coverage, showing that surface properties affect the adsorption mode of enzymes, and thus their catalytic activity. In solution, AcPase showed a greater specificity towards G6P, but this specificity was partly lost after adsorption onto goethite.

Place, publisher, year, edition, pages
Umeå: Kemiska institutionen, Umeå universitet, 2011
National Category
Other Basic Medicine
urn:nbn:se:umu:diva-46578 (URN)978-91-7459-270-2 (ISBN)
Public defence
2011-09-30, KBC-huset, KB3A9, Umeå universitet, Umeå, 10:00 (English)
Available from: 2011-09-09 Created: 2011-09-06 Last updated: 2011-09-06Bibliographically approved

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