Probing interfacial reactions with X-ray reflectivity and X-ray reflection interface microscopy: Influence of NaCl on the dissolution of orthoclase at pOH 2 and 85°C

Fenter, Paul; Lee, S.S.; Park, Changyong; Catalano, Jeffrey G.; Zhang, Z.; Sturchio, Neil C.

doi:10.1016/j.gca.2010.03.027

Cited by 15 publications

(8 citation statements)

References 53 publications

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“…The calcite-water interface, however, is highly dynamic (Stipp and Hochella, 1991;Paquette and Reeder, 1995). Actual surface densities of growth sites could conceivably be lower, for example, when sites are blocked by impurities or step edges interact destructively, or higher, for example, when surface nucleation creates additional growth edges on the crystal surface (Kowacz et al, 2007) or when electrolyte ions interact with the mineral surface (Fenter et al, 2010) or with dissolved constituent ions (Di Tommaso and de Leeuw, 2010).…”

Section: Bulk Calcite Growth Ratesmentioning

confidence: 99%

Calcite growth kinetics: Modeling the effect of solution stoichiometry

Wolthers

Nehrke

Gustafsson

et al. 2012

Geochimica et Cosmochimica Acta

132

160

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Until recently the influence of solution stoichiometry on calcite crystal growth kinetics has attracted little attention, despite the fact that in most aqueous environments calcite precipitates from non-stoichiometric solution. In order to account for the dependence of the calcite crystal growth rate on the cation to anion ratio in solution, we extend the growth model for binary symmetrical electrolyte crystals of Zhang and Nancollas (1998) by combining it with the surface complexation model for the chemical structure of the calcite-aqueous solution interface of Wolthers et al. (2008). To maintain crystal stoichiometry, the rate of attachment of calcium ions to step edges is assumed to equal the rate of attachment of carbonate plus bicarbonate ions. The model parameters are optimized by fitting the model to the step velocities obtained previously by atomic force microscopy (AFM, Teng et al., 2000;Stack and Grantham, 2010). A variable surface roughness factor is introduced in order to reconcile the new process-based growth model with bulk precipitation rates measured in seeded calcite growth experiments. For practical applications, we further present empirical parabolic rate equations fitted to bulk growth rates of calcite in common background electrolytes and in artificial seawater-type solutions. Both the process-based and empirical growth rate equations agree with measured calcite growth rates over broad ranges of ionic strength, pH, solution stoichiometry and degree of supersaturation.

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Section: Bulk Calcite Growth Ratesmentioning

confidence: 99%

Calcite growth kinetics: Modeling the effect of solution stoichiometry

Wolthers

Nehrke

Gustafsson

et al. 2012

Geochimica et Cosmochimica Acta

132

160

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“…As expected from the above discussion, the images are of a poorer quality than that reported previously for the same substrate in air. [30][31][32] The poorer quality of the off-specular image also may be related to the beaminduced perturbations upon long (20 min) x-ray exposure, as detailed below. The images nevertheless show the characteristic change in contrast that has been reported previously for elementary steps, with the specular image showing dark lines on a bright background, and the off-specular image showing bright lines on a dark background.…”

Section: A Imaging Elementary Topography At the Orthoclase-(001)-watmentioning

confidence: 99%

“…16 XRIM can therefore image the development of spatial heterogeneity at an interface associated with processes that modify the local interfacial structure, and changes to the interfacial topography (e.g., steps and terraces) and structure (e.g., ion adsorption and surface hydration) are encoded in the spatial variation of the reflectivity signal. [30][31][32] Anticipated applications of XRIM include observations of realtime processes, in situ, at evolving interfaces, such as growth, dissolution, and the nucleation of these processes at defect sites. Although the in-plane spatial resolution of this XRIM instrument (170 nm) (Ref.…”

mentioning

confidence: 99%

“…We have also demonstrated the ability to probe interfacial reactions through ex situ XRIM imaging of reacted samples. 32 In this article, we demonstrate the ability to image interfacial topography in aqueous solutions, define the additional challenges associated with in situ imaging, and reveal the presence of x-ray-induced beam damage during the imaging. We also characterize the nature of this damage and demonstrate the ability to substantially reduce the rate of beam damage by controlling the solution ionic FIG.…”

mentioning

confidence: 99%

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In situ imaging of orthoclase–aqueous solution interfaces with x-ray reflection interface microscopy

Fenter

Lee

Zhang

et al. 2011

Journal of Applied Physics

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The use of x-ray reflection interface microscopy (XRIM) to image molecular-scale topography at the aqueous–solid interface, in situ, is described. Specifically, we image interfacial topography of the orthoclase-(001)–aqueous solution interface at room temperature and describe the challenges associated with in situ XRIM imaging. The measurements show that the reflectivity signal for in situ XRIM measurements is substantially smaller than that for ex situ measurements, because of both intrinsic and extrinsic factors. There is also a systematic temporal reduction in the image intensity with increasing x-ray dose, revealing that interaction of the focused x-ray beam with the orthoclase interfaces leads to interfacial perturbations, presumably in the form of surface roughening. This image fading is localized to the x-ray beam footprint, suggesting that the primary damage mechanism is initiated by photoelectrons produced by x-ray beam absorption near the substrate–electrolyte interface. Finally, the role of aqueous solution composition in controlling the sensitivity of the orthoclase surface to x-ray beam-induced effects is explored. A substantial increase in the orthoclase (001) surface stability was observed in solutions having elevated ionic strength, apparently as a result of the reduced lifetime of radiation chemistry products at these conditions.

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“…Other surface-sensitive techniques, such as X-ray photoelectron spectroscopy (XPS) (Hellmann et al, 1990;Chen et al, 2000) and secondary ion mass spectrometry (SIMS) (Schweda et al, 1997;Nesbitt and Muir, 1988;Nugent et al, 1998) were also used to study cation depletion in reacted feldspars as a function of pH and temperature. Other lesser known techniques, such as high-resolution in-situ X-ray reflectivity (XR) and ex-situ X-ray reflection interface microscopy (XRIM), were used by Fenter and colleagues to probe near-surface orthoclase chemistry after reaction at 25 and 50 °C in solutions at acid, neutral, and very basic pH (Fenter et al, 2000(Fenter et al, , 2010Teng et al, 2001).…”

Section: Previous Workmentioning

confidence: 99%

The hydrothermal alkaline alteration of potassium feldspar: A nanometer-scale investigation of the orthoclase interface

et al. 2021

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Potassium feldspars (KAlSi3O8) are ubiquitous minerals in the Earth's upper crust. This family of minerals has been the subject of numerous experimental and theoretical investigations concerning their dissolution kinetics and the mechanisms controlling chemical alteration at acid and neutral pH, and at temperatures ranging from ambient to hydrothermal conditions. On the other hand, considerably less research on the dissolution behavior of K-feldspars has been carried out at alkaline conditions, in particular at pH > 9 and elevated temperatures. Filling in this gap in knowledge is the major motivation for this study. More specifically, we wanted to document and understand how the K-feldspar interface structurally and chemically evolves during alteration in order to determine the mechanism of dissolution.In this study we examined interfaces of orthoclase samples that were altered in separate experiments in a Ca(OH)2-H2O solution (pH25°C 12.4) at 190 °C for 24 hours. We used a combination of focused ion beam (FIB) milling and advanced analytical transmission electron microscopy (TEM) techniques to investigate the structure and chemistry of the near surface region of post-reaction grains, with particular attention being given to the fluid-solid interface. Even though each grain diminishes in volume due to dissolution, high-resolution TEM imaging indicates that the feldspar structure itself remains completely intact and crystalline, as evidenced by lattice fringes that abruptly terminate at the grain edge.Nanometer-scale chemical composition measurements and mapping by TEM-EDXS (energy dispersive X-ray spectroscopy) and EFTEM (energy filtered TEM) show that the chemistry of the parent feldspar also remains unchanged at the interface. In particular, there is no evidence for the incursion of Ca from the fluid solvent into the structure, either by interdiffusion or by a replacement process. Taken together, the TEM observations point to a sharp chemical reaction front characterized by the congruent (i.e. stoichiometric) release of all elements from the feldspar structure.Nanometer-scale measurements by high resolution analytical TEM also reveal that a surface alteration layer (SAL) of amorphous material forms in situ at the expense of the feldspar structure. The interface demarcates a spatially coincident and nm-sharp chemical and structural discontinuity between the parent feldspar and the amorphous phase. The amorphous SAL has a variable thickness, from under 10 nm up to ~200 nm. This is likely one of the first observed occurrences of a significant surface amorphous layer on feldspar due to alteration in an alkaline solvent. The lack of a gap between the two phases points to an interfacial dissolution-reprecipitation process that continuously operates during hydrothermal alteration, and mostly likely right from the onset of contact with the fluid. After the initial formation of the amorphous layer, a 1-2 µm-thick porous amalgam of secondary crystalline phases comprised of calcite, tobermorite, and hydrogrossular, as wel...

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Probing interfacial reactions with X-ray reflectivity and X-ray reflection interface microscopy: Influence of NaCl on the dissolution of orthoclase at pOH 2 and 85°C

Cited by 15 publications

References 53 publications

Calcite growth kinetics: Modeling the effect of solution stoichiometry

Calcite growth kinetics: Modeling the effect of solution stoichiometry

In situ imaging of orthoclase–aqueous solution interfaces with x-ray reflection interface microscopy

The hydrothermal alkaline alteration of potassium feldspar: A nanometer-scale investigation of the orthoclase interface

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