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Deconvolution of Smectite Hydration Isotherms
Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.ORCID-id: 0000-0003-4954-6461
Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.ORCID-id: 0000-0003-3927-6197
2019 (Engelska)Ingår i: ACS Earth and Space Chemistry, E-ISSN 2472-3452, Vol. 3, nr 11, s. 2490-2498Artikel i tidskrift (Refereegranskat) Published
Abstract [en]

Sorption isotherm models have traditionally served as an invaluable tool to characterize synthesized and natural mineral particles. However, for particles susceptible to substantial hydration, such as the swelling smectite clay minerals and other layered minerals displaying intercalation of discrete water monolayers, traditional isotherm models inadequately describe the total water uptake as a result of the change in available surface sites and area during the hydration process. With the goal of deconvoluting the water uptake behavior of swelling smectite minerals, this research presents a novel composite isotherm model that describes water uptake by surface adsorption, condensation, and stepwise intercalation. A set of eight montmorillonite samples ion-exchanged with different countercations (Li+, Na+, K+, Cs+, Mg2+, Ca2+, Sr2+, and Cu2+) were used to develop this model, which was based on gravimetric uptake measurements and X-ray diffraction data of basal spacings obtained from relative humidity conditions up to 98% relative humidity.

Ort, förlag, år, upplaga, sidor
American Chemical Society (ACS), 2019. Vol. 3, nr 11, s. 2490-2498
Nyckelord [en]
water vapor, clays, montmorillonite, adsorption, ion hydration, XRD
Nationell ämneskategori
Materialkemi
Identifikatorer
URN: urn:nbn:se:umu:diva-166800DOI: 10.1021/acsearthspacechem.9b00178ISI: 000499739500014Scopus ID: 2-s2.0-85073156810OAI: oai:DiVA.org:umu-166800DiVA, id: diva2:1382549
Forskningsfinansiär
KempestiftelsernaVetenskapsrådet, 2016-03808Tillgänglig från: 2020-01-03 Skapad: 2020-01-03 Senast uppdaterad: 2023-03-24Bibliografiskt granskad
Ingår i avhandling
1. Molecular-level controls on water and organics intercalation in layered minerals
Öppna denna publikation i ny flik eller fönster >>Molecular-level controls on water and organics intercalation in layered minerals
2020 (Engelska)Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
Abstract [en]

Layered minerals are naturally abundant and often display a large surface area in relation to their weight. For swelling layered minerals, most of this area is contained between the layers in the interlayer space. Their large surface area makes them interesting in many different fields and applications, such as adsorbents, catalysts or as carriers for other particles that can be intercalated and exchanged. In order for the materials to be used effectively, it is hence necessary to have a fundamental understanding of how these processes occur, and ways to predict them.

To address adsorption of water, an isotherm model was created to describe the hydration process on layered materials. The model decomposed the process of adsorptions into internal and external, adsorption and condensation, and could specifically handle hydration in the expanding interlayer nanopores. Adsorption and desorption isotherms of two different materials, Montmorillonite and Birnessite was successfully modelled, where the former was ion-exchanged with the counter-cations Li+, Na+, K+, Cs+, Mg2+, Ca2+, Sr2+, Cu2+, whereas the latter contained K+. This indicated that this isotherm model is applicable to also other layered materials. The adsorption process was also characterized experimentally with vibrational spectroscopy (FTIR) and multivariate statistical techniques (MCR), in order to generate spectral- and concentration profiles of the involved components.

In order to also investigate adsorption of different organic molecules, the intercalation of alcohols and a cationic surfactant was investigated in separate studies. Clay-water-alcohol systems of eight alcohols were characterized experimentally by XRD as well as by molecular dynamics simulations, using different combinations of classical force fields for the clay (ClayFF, ClayFFMod, INTERFACE) and for the alcohols (CGenFF, GAFF, OPLS). It was found that the optimal force field combination varied with the fitting approach. A brute force sensitivity analysis indicated that the comparison with the experimental XRD data was more dependent on the relative interlayer loading than the positions of the atoms, an important result for future similar benchmarking studies.

By intercalating and adsorbing a cationic surfactant (CTAB) to Montmorillonite at increasing concentrations, the effects of solvent polarity and the CTAB interlayer content on the Montmorillonite interlayer swelling was investigated. It was found that moderately polar solvents such as DMSO, in combination with CTAB in a planar bilayer configuration resulted in the greatest adsorption of the lipophilic solute alizarin.

Ort, förlag, år, upplaga, sidor
Umeå: Umeå University, 2020. s. 49
Nyckelord
Minerals, Dynamic Vapor Sorption, montmorillonite, XRD, adsorption model, intercalation
Nationell ämneskategori
Geokemi
Identifikatorer
urn:nbn:se:umu:diva-174006 (URN)978-91-7855-342-6 (ISBN)978-91-7855-341-9 (ISBN)
Disputation
2020-09-08, Glasburen, KBC 3.05.081, Umeå, 10:00 (Engelska)
Opponent
Handledare
Tillgänglig från: 2020-08-18 Skapad: 2020-08-13 Senast uppdaterad: 2020-08-14Bibliografiskt granskad

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Lindholm, JerryBoily, Jean-FrancoisHolmboe, Michael

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