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Surface chemistry of Al and Si (hydr)oxides, with emphasis on nano-sized gibbsite (α-Al(OH)3)
Umeå University, Faculty of Science and Technology, Chemistry.
2002 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis contains an introduction to the surface chemistry of minerals in aqueous environment, and a summary of five manuscripts concerning adsorption reactions at the surfaces of nano-sized gibbsite (α-Al(OH)3), amorphous silica and kaolinite.

Nano-sized gibbsite was synthesized and thoroughly characterized using X-ray diffraction, high-resolution transmission electron microscopy, atomic force microscopy and Fourier transform infrared spectroscopy. The adsorption of protons and the development of charge at the surfaces were studied using high precision potentiometry and zeta potential measurements. The results showed that singly coordinated surface sites at the particle edges protonate/deprotonate, while ion pairs with the medium ions are formed at doubly coordinated surface sites at the basal planes. This ion pair formation is a slow reaction, requiring long equilibrium times.

The adsorption of o-phthalate, maleate, fumarate, malonate and oxalate onto gibbsite surfaces was studied using Fourier transform infrared spectroscopy, zeta potential measurements, adsorption measurements and theoretical frequency calculations. All ligands were found to form outer-sphere complexes at the basal planes. Significant amounts of inner-sphere complexes at the particle edges were found for malonate and oxalate only. The observed adsorption was described using surface complexation models.

The proton reactions at the surface of amorphous silica were described using a two-site model. XPS indicated that Na+ is accumulated in the vicinity of the surface. Proton reactions at kaolinite surfaces were explained using a nonelectrostatic model, assuming that only the aluminol and silanol sites at the particle edges are reactive. Extensive modeling provided support for this assumption.

Place, publisher, year, edition, pages
2002. , 66 p.
Keyword [en]
Gibbsite, silica, kaolinite, surface complexation, protonation, adsorption, carboxylates, modeling, AFM, IR, XPS
Identifiers
URN: urn:nbn:se:umu:diva-6ISBN: 91-7305-245-0 (print)OAI: oai:DiVA.org:umu-6DiVA: diva2:143930
Public defence
2002-05-31
Available from: 2002-05-31 Created: 2002-05-31Bibliographically approved
List of papers
1. Protonation and charging of nanosized gibbsite (α-Al(OH)3) particles in aqueous suspension
Open this publication in new window or tab >>Protonation and charging of nanosized gibbsite (α-Al(OH)3) particles in aqueous suspension
2002 (English)In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 18, no 12, 4598-4604 p.Article in journal (Refereed) Published
National Category
Physical Chemistry Materials Chemistry
Identifiers
urn:nbn:se:umu:diva-4710 (URN)10.1021/la015753t (DOI)000176091900012 ()
Available from: 2002-05-31 Created: 2002-05-31 Last updated: 2014-09-01Bibliographically approved
2. Proton reactions at kaolinite surfaces – comparison with silica and gibbsite
Open this publication in new window or tab >>Proton reactions at kaolinite surfaces – comparison with silica and gibbsite
In: Soil Science Society of America JournalArticle in journal (Refereed) Submitted
Identifiers
urn:nbn:se:umu:diva-4711 (URN)
Available from: 2002-05-31 Created: 2002-05-31Bibliographically approved
3. Bonding of dicarboxylates to gibbsite surfaces: effects of ligand structure and particle morphology
Open this publication in new window or tab >>Bonding of dicarboxylates to gibbsite surfaces: effects of ligand structure and particle morphology
(English)Manuscript (preprint) (Other academic)
National Category
Chemical Sciences
Identifiers
urn:nbn:se:umu:diva-4712 (URN)
Available from: 2002-05-31 Created: 2002-05-31 Last updated: 2017-01-31Bibliographically approved
4. Surface complexation modeling of dicarboxylate adsorption in nano-sized gibbsite systems: A mechanistic description
Open this publication in new window or tab >>Surface complexation modeling of dicarboxylate adsorption in nano-sized gibbsite systems: A mechanistic description
(English)Manuscript (preprint) (Other academic)
National Category
Chemical Sciences
Identifiers
urn:nbn:se:umu:diva-4713 (URN)
Available from: 2002-05-31 Created: 2002-05-31 Last updated: 2012-08-08Bibliographically approved
5. Comparison of the adsorption of o-phthalate on boehmite (γ-AlOOH), aged γ-Al2O3, and goethite (α-FeOOH)
Open this publication in new window or tab >>Comparison of the adsorption of o-phthalate on boehmite (γ-AlOOH), aged γ-Al2O3, and goethite (α-FeOOH)
Show others...
1988 (English)In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 206, no 1, 252-266 p.Article in journal (Refereed) Published
Abstract [en]

This work is concerned with the adsorption of o-phthalate (1,2-benzenedicarboxylate) at the water-metal (hydr)oxide interface. Previously published infrared spectroscopic, potentiometric, and adsorption data characterizing the boehmite (gamma-AlOOH) system are compared with new data collected for o-phthalate adsorption on aged gamma-Al2O3 and goethite (alpha-FeOOH). The study focuses on identifying bonding mechanisms, stoichiometries, and stabilities of the formed complexes, and comparing these among the three systems. Furthermore, the effects of ionic strength and composition of the ionic medium are investigated. The infrared spectroscopic data provided direct, molecular-level evidence for the existence of two dominating surface complexes on all three solids. One was shown to be a deprotonated outer-sphere species and the other was an inner-sphere surface complex. The inner-sphere complexes on the three solids were structurally related, and they were tentatively assigned to a mononuclear, chelating structure involving both carboxylate groups. The outer-sphere complexes were shown to increase in relative importance at high pH and low ionic strengths, while low pH and high ionic strengths favored the inner-sphere complexes. The information gained from the infrared spectroscopic investigations was used as qualitative input in the formulation of the surface complexation models. New models, based on the extended constant capacitance approach, were presented for the o-phthalate/aged gamma-Al2O3 and o-phthalate/goethite systems.

Keyword
adsorption, infrared spectroscopy, o-phthalate, y-Al2O3, boehmite, goethite, surface complexation
National Category
Physical Chemistry
Identifiers
urn:nbn:se:umu:diva-4714 (URN)10.1006/jcis.1998.5668 (DOI)000076375400031 ()
Available from: 2002-05-31 Created: 2002-05-31 Last updated: 2014-09-01Bibliographically approved

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