Probing Anisotropic Surface Properties of Illite by Atomic Force Microscopy

Shao, Hua; Chang, Jing; Lu, Zhenzhen; Luo, Binbin; Grundy, James S.; Xie, Guangyuan; Xu, Zhenghe; Liu, Qingxia

doi:10.1021/acs.langmuir.9b00270

Cited by 25 publications

(14 citation statements)

References 52 publications

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“…Knowing the surface potential of the tip, the interactions with MoS 2 surfaces can be determined, enabling their surface potential to be calculated according to DLVO theory. The nanosized end of the tip permits the surface properties of nano- to microscale sample surfaces, e.g., crystal plane of anisotropic minerals , and domains on heterogeneous surfaces, to be explored by force measurement . The AFM force measurement has significant advantages over other methods for in situ surface characterization.…”

Section: Resultsmentioning

confidence: 99%

Face or Edge? Control of Molybdenite Surface Interactions with Divalent Cations

Ralston

Liu

2019

J. Phys. Chem. C

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Molybdenite, MoS2, a 2-D transition metal dichalcogenide, is a potential substitute for graphene. Molybdenite mineral particles are separated from gangue minerals by flotation, a process often performed in saline waters, where the presence of divalent cations can cause serious selectivity issues. A fundamental question is posed: how do divalent cations, which are subject to hydrolysis as a function of pH, interact with anisotropic molybdenite surfaces? By use of a combination of atomic force microscopy (AFM) surface force measurements with time-of-flight secondary ion mass spectrometry (ToF-SIMS) surface spectroscopy, the surface potentials and surface ion species of MoS2 immersed in aqueous MgCl2 and CaCl2 solutions were distinguished for the face and the edge surfaces, respectively, for the first time. The adsorption mechanisms of MgII and CaII on anisotropic MoS2 surfaces are revealed as a function of pH, ion species in solution, and solid characteristics (dielectric constant and surface chemical groups). As a consequence of these fundamental insights, improved particle flotation pathways are available.

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Section: Resultsmentioning

confidence: 99%

Face or Edge? Control of Molybdenite Surface Interactions with Divalent Cations

Ralston

Liu

2019

J. Phys. Chem. C

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“…The illite basal surfaces were prepared on sapphire substrates using the method described in our previous study . A Dimension Icon AFM (Bruker, Camarillo, CA, USA) was used in this work.…”

Section: Methodsmentioning

confidence: 99%

“…The illite basal surfaces were prepared on sapphire substrates using the method described in our previous study. 37 A Dimension Icon AFM (Bruker, Camarillo, CA, USA) was used in this work. Surface force measurements between AFM tips and the samples were carried out in 10 mM KCl at pH 8.0 and 10.8 with varying concentrations (0, 0.1, 0.5, 1.0, and 5.0 mM) of CaCl 2 or MgCl 2 .…”

Section: ■ Experimentsmentioning

confidence: 99%

Probing Interaction of Divalent Cations with Illite Basal Surfaces by Atomic Force Microscopy

Shao

Chang

et al. 2019

J. Phys. Chem. C

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Smooth basal surfaces of illite were prepared successfully, and the interaction forces between a Si3N4 tip and illite basal surface with various concentrations of divalent cations in 10 mM KCl solution at pH 8.0 and 10.8 were measured using an atomic force microscope (AFM). The influence of divalent cation concentration on the interaction forces was investigated, and the surface potentials of the basal surfaces in varying concentrations of divalent cation solutions were determined by fitting the interaction forces with the classical Derjaguin–Landau–Verwey–Overbeek (DLVO) theory. With an increasing CaII or MgII concentration, the surface potentials became less negative in pH 8.0 solution, while the surface potentials reversed from negative to positive after addition of 1.0 mM or more divalent cations in pH 10.8 solution. Electrostatic interaction and specific adsorption were the major contributors to the interaction between divalent cations and illite basal surface in solutions at pH 8.0 and 10.8, respectively. CaII and MgII cations had a similar effect magnitude on the illite basal surfaces at pH 8.0. In contrast, MgII cations had a more profound effect than CaII on the surface potential of the illite basal surface in pH 10.8 solution, likely due to the low solubility of Mg(OH)2 at this pH. This quantitative description of the illite basal surface charge influenced by divalent cations can provide fundamental insight into the mechanisms of tailings treatment and slime coatings in minerals processing.

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“…Illite layers consist of an octahedral sheet sandwiched by two tetrahedral sheets with a high degree of isomorphic substitution. They possess two basal siloxane surfaces with permanent negative charge, which is predominantly balanced by K + (Nieto et al, 2010;Shao et al, 2019). Illite has been referred to as K-deficient mica (Gualtieri and Ferrari, 2006) with small crystal size, poor crystallinity, and low mineralogical purity (Rieder et al, 1998;Nieto et al, 2010).…”

Section: Introductionmentioning

confidence: 99%

Ice nucleation by smectites: The role of the edges

Kumar

Klumpp

Barak

et al. 2022

Preprint

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Abstract. Smectites, like other clay minerals, have been shown to promote ice nucleation in immersion freezing mode and likely contribute to the population of ice nucleating particles (INPs) in the atmosphere. Smectites are layered aluminosilicates, which form platelets that depending on composition might swell or even delaminate in water by intercalation of water molecules between their layers. They comprise among others montmorillonites, hectorites, beidellites, and nontronites. In this study, we investigate the ice nucleation (IN) activity of a variety of natural and synthetic smectite samples with different exchangeable cations. The montmorillonites STx-1b and SAz-1, the nontronite SWa-1, and the hectorite SHCa-1 are all rich in Ca2+ as the exchangeable cation, the bentonite MX-80 is rich in Na+ with a minor contribution of Ca2+, the synthetic Laponite is a pure Na+ smectite. The bentonite SAu-1 is rich in Mg2+ with a minor contribution of Na+, and the synthetic interstratified mica-montmorillonite Barasym carries NH4+ as the exchangeable cation. In emulsion freezing experiments, all samples except Laponite exhibited one or two heterogeneous freezing peaks with onsets between 239 K and 248 K and a quite large variation in IN activity, yet without clear correlation with the exchangeable cation, with the type of smectite, or with mineralogical impurities in the samples. To further investigate the role of the exchangeable cation, we performed ion exchange experiments. Replacing NH4+ with Ca2+ in Barasym reduced its IN activity to the one of other Ca-rich montmorillonites. In contrast, stepwise exchange of the native cations in STx-1b once with Y3+ and once with Cu2+ showed no influence on IN activity. However, aging of smectite suspensions in pure water up to several months revealed a decrease in IN activity with time, which we attribute to the delamination of smectites in aqueous suspensions, which may proceed over long timescales. The dependence of IN activity on platelet stacking and thickness can be explained if the hydroxylated chains forming at the edges are the location of ice nucleation in smectites, since the edges need to be thick enough to host a critical ice embryo. We hypothesize that at least three smectite layers need to be stacked together to host a critical ice embryo on clay mineral edges and that the larger the surface edge area is the higher the freezing temperature. Comparison with reported platelet thicknesses of the investigated smectite samples suggests that the observed freezing temperatures are indeed limited by the surface area provided by the mostly very thin platelets. Specifically, Laponite, which did not show any IN activity, is known to delaminate into single layers of about 1 nm thickness, which would be too thin to host a critical ice embryo.

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Probing Anisotropic Surface Properties of Illite by Atomic Force Microscopy

Cited by 25 publications

References 52 publications

Face or Edge? Control of Molybdenite Surface Interactions with Divalent Cations

Face or Edge? Control of Molybdenite Surface Interactions with Divalent Cations

Probing Interaction of Divalent Cations with Illite Basal Surfaces by Atomic Force Microscopy

Ice nucleation by smectites: The role of the edges

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