Effects of residence time and mixing regimes on the precipitation characteristics of CaF2 and MgF2 from high ionic strength sulphate solutions

Eksteen, Jacques; Pelser, Max; Lorenzen, L.; Aldrich, Chris; Georgalli, G.A.

doi:10.1016/j.hydromet.2007.12.002

Cited by 10 publications

(7 citation statements)

References 12 publications

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“…41,42 Their growth process in an aqueous environment is important not only for the fabrication of industrial devices but also for understanding the mechanism of bio-mineralisation, formation of the tooth enamel, 43,44 desalination for oil recovery [45][46][47] and water purification. [48][49][50] Hydration structures formed at the fluorite-water interface strongly influence ion adsorption and desorption in these processes.…”

Section: Afm Simulationmentioning

confidence: 99%

A relationship between three-dimensional surface hydration structures and force distribution measured by atomic force microscopy

et al. 2016

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Hydration plays important roles in various solid-liquid interfacial phenomena. Very recently, three-dimensional scanning force microscopy (3D-SFM) has been proposed as a tool to visualise solvated surfaces and their hydration structures with lateral and vertical (sub) molecular resolution. However, the relationship between the 3D force map obtained and the equilibrium water density, ρ(r), distribution above the surface remains an open question. Here, we investigate this relationship at an interface of an inorganic mineral, fluorite, and water. The force maps measured in pure water are directly compared to force maps generated using the solvent tip approximation (STA) model and from explicit molecular dynamics simulations. The results show that the simulated STA force map describes the major features of the experimentally obtained force image. The agreement between the STA data and the experiment establishes the correspondence between the water density used as an input to the STA model and the experimental hydration structure and thus provides a tool to bridge the experimental force data and atomistic solvation structures. Further applications of this method should improve the accuracy and reliability of both interpretation of 3D-SFM force maps and atomistic simulations in a wide range of solid-liquid interfacial phenomena.

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Section: Afm Simulationmentioning

confidence: 99%

A relationship between three-dimensional surface hydration structures and force distribution measured by atomic force microscopy

et al. 2016

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“…In addition, the growth mechanism of a fluorite crystal in aqueous solution was extensively studied in relation to the fabrication of optical components [35][36][37][38], formation of tooth enamel [39,40] and biomineralization [41][42][43][44][45][46]. Thus, the theoretical basis for atomistic molecular dynamics (MD) simulation of the fluorite-water interface was relatively well-established.…”

Section: Introductionmentioning

confidence: 99%

Influence of ions on two-dimensional and three-dimensional atomic force microscopy at fluorite–water interfaces

et al. 2017

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Abstract. Recent advancement in liquid-environment atomic force microscopy (AFM) has enabled us to visualize three-dimensional (3D) hydration structures as well as two-dimensional (2D) surface structures with subnanometer-scale resolution at solid-water interfaces. However, the influence of ions present in solution on the 2D-and 3D-AFM measurements has not been well understood. In this study, we perform atomic-scale 2D-and 3D-AFM measurements at fluorite-water interfaces in pure water and supersaturated solution of fluorite. The images obtained in these two environments are compared to understand the influence of the ions in solution on these measurements. In the 2D images, we found clear difference in the nanoscale structures but no significant difference in the atomic-scale contrasts. However, the 3D force images show clear difference in the subnanometer-scale contrasts. The force contrasts measured in pure water largely agree with those expected from the molecular dynamics simulation and the solvent tip approximation model. In the supersaturated solution, an additional force peak is observed over the negatively charged fluorine ion site. This location suggests that the observed force peak may originate from cations adsorbed on the fluorite surface. These results demonstrate that the ions can significantly alter the subnanometer-scale force contrasts in the 3D-AFM images.

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“…Fluorite (CaF 2 ) crystals are widely used for various industrial applications. Examples include optical components for semiconductor lithography and other laser technologies , and scintillators for radioactivity investigations. , Thus, the crystal growth and dissolution processes of fluorite have intensively been studied to improve the crystal quality. , In addition, these processes play important roles in the formation of tooth enamel and pathogenesis of dental caries, , as well as in the desalination for oil and gas recovery − and water purification. − Therefore, the physicochemical processes taking place at the fluorite–water interface are important in industrial, environmental, and medical research fields.…”

Section: Introductionmentioning

confidence: 99%

Atomic-Scale Processes at the Fluorite–Water Interface Visualized by Frequency Modulation Atomic Force Microscopy

et al. 2013

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The crystal growth and dissolution processes of a fluorite (CaF2) crystal have attracted much attention due to the importance in the industrial, environmental, and medical applications. While previous studies clarified nanoscale processes at the fluorite–water interface, atomic-scale origins of the processes have yet to be understood. In this study, we have investigated atomic-scale processes at the fluorite–water interface by frequency modulation atomic force microscopy (FM-AFM). We performed atomic-resolution imaging of a fluorite(111) surface in water (pH = 2 and 6.5), saturated solution (pH = 2 and 6), and supersaturated solution (pH = 6, σ = 10 and 100). Based on the results, we present three major findings. First, atomic-scale roughening of the crystal surface takes place at low pH due to the proton adsorption. Second, surface adsorbates with a subnanometer-scale height are formed on the crystal surface at high pH. They are most likely to be calcium hydroxo complexes physisorbed on the crystal surface. Finally, the formation of these complexes can be suppressed by increasing fluorite concentration owing to the increased proportion of Ca2+ and F– in the electric double layer. These findings mark an important step toward the full understanding of the physicochemical processes at the fluorite–water interface.

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Effects of residence time and mixing regimes on the precipitation characteristics of CaF2 and MgF2 from high ionic strength sulphate solutions

Cited by 10 publications

References 12 publications

A relationship between three-dimensional surface hydration structures and force distribution measured by atomic force microscopy

A relationship between three-dimensional surface hydration structures and force distribution measured by atomic force microscopy

Influence of ions on two-dimensional and three-dimensional atomic force microscopy at fluorite–water interfaces

Atomic-Scale Processes at the Fluorite–Water Interface Visualized by Frequency Modulation Atomic Force Microscopy

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