Path from Reaction Control to Equilibrium Constraint for Dissolution Reactions

Crundwell, Frank K.

doi:10.1021/acsomega.7b00344

Cited by 9 publications

(6 citation statements)

References 34 publications

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“…Instead, a novel electro-chemo-mechanical mechanism is proposed to explain the rate enhancement phenomenon which combines three different theories from three different fields which appear to be different facets of a unifying physics concerning the ability of interfacial electric fields to influence chemical reaction rates at the solid−liquid interface. These are (1) the theory of electrochemical pressure solution, 5,13 (2) the Crundwell electrochemical model of dissolution, 22,24,25 and (3) a newly proposed theory of dynamic "surface resonance" proposed as a means of enhancing catalytic reactions above the stochiometric kinetic equilibrium (i.e., the 'Sabatier's max- imum') by oscillating the surface potential of a catalytic interface. 26 This new understanding of electro-chemo-mechanical enhancement of the dissolution reaction has important implications.…”

Section: ■ Introductionmentioning

confidence: 99%

Frequency Dependent Silica Dissolution Rate Enhancement under Oscillating Pressure via an Electrochemical Pressure Solution-like, Surface Resonance Mechanism

et al. 2022

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From atomic force microscopy (AFM) experiments, we report a new phenomenon in which the dissolution rate of fused silica is enhanced by more than 5 orders of magnitude by simply pressing a second, dissimilar surface against it and oscillating the contact pressure at low kHz frequencies in deionized water. The silica dissolution rate enhancement was found to exhibit a strong dependence on the pressure oscillation frequency consistent with a resonance effect. This harmonic enhancement of the silica dissolution rate was only observed at asymmetric material interfaces (e.g., diamond on silica) with no evidence of dissolution rate enhancement observed at symmetric material interfaces (i.e., silica on silica) within the experimental time scales. The apparent requirement for interface dissimilarity, the results of analogous experiments performed in anhydrous dodecane, and the observation that the silica “dissolution pits” continue to grow in size under contact stresses well below the silica yield stress refute a mechanical deformation or chemo-mechanical origin to the observed phenomenon. Instead, the silica dissolution rate enhancement exhibits characteristics consistent with a previously described ‘electrochemical pressure solution’ mechanism, albeit, with greatly amplified kinetics. Using a framework of electrochemical pressure solution, an electrochemical model of mineral dissolution, and a recently proposed “surface resonance” theory, we present an electro-chemo-mechanical mechanism that explains how oscillating the contact pressure between dissimilar surfaces in water can amplify surface dissolution rates by many orders of magnitude. This reaction rate enhancement mechanism has implications not only for dissolution but also for potentially other reactions occurring at the solid–liquid interface, e.g. catalysis.

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Section: ■ Introductionmentioning

confidence: 99%

Frequency Dependent Silica Dissolution Rate Enhancement under Oscillating Pressure via an Electrochemical Pressure Solution-like, Surface Resonance Mechanism

et al. 2022

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“…[ 32 ] This formulation can be considered as a parametrization to model the dissolution far from equilibrium up to the saturation condition. [ 34 ] The factors and mechanisms of dissolution rate, even for such common salt as NaCl, is still not completely understood and is a subject of recent works [ 35–37 ] :

f ((), Δ \overset{G}{false}) = ([], \exp ((), \frac{λΔ \bar{G}}{italicRT}) - 1)

…”

Section: Methodsmentioning

confidence: 99%

Inferring kinetic dissolution of NaCl in aqueous glycol solution using a low‐cost apparatus and population balance model

et al. 2020

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An experimental methodology for inferring brine dissolution rate in monoethylene glycol (MEG) solutions at different temperatures using a webcam combined with a mathematical model is presented. The measurement system is designed to track the RGB (red, green, and blue) colour variations during the dissolution process. A dynamic model augmented with the population balance equation is applied to describe the dissolution process. Moreover, the dissolution rate is consistently related to the temperature and MEG concentration through the driving force based on the Gibbs energy and chemical affinity. The applied low-cost measurement apparatus proved to be a useful resource for tracking the dissolution dynamics in a wide range of undersaturation.

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“…This expression is clearly in agreement with the experimental results shown in Figure 7. (28) The full reaction path between reaction control and equilibrium is discussed next [72].…”

Section: Testing the Surface-vacancy Model-reverse Reaction 81 Orders Of Reaction For The Reverse Reactionmentioning

confidence: 99%

“…, and the value of m is taken as 1 for the sake of simplicity. Thus, this expression means that the rate decreases as a parabolic function of increasing salt concentration, C, representing the path from rate control to equilibrium [8,72]. The rate of dissolution of NaCl is shown in Figure 8 as a function of the concentration of NaCl in solution, C. This is not a parabolic function-in contrast, it is linear.…”

Section: Dissolution Of Salts Between Reaction Control and Equilibriummentioning

confidence: 99%

“…The surface-vacancy model envisages the chemically independent removal of cations and anions, with the relationship between them governed only by surface charge (or the potential difference across the Helmholtz layer). Equilibrium, therefore, can be achieved in a partial manner [4,72]. A set of conditions can be envisaged in which one of the 'partial reactions' is in equilibrium, while the other is not.…”

Section: Predictions From the Surface-vacancy Modelmentioning

confidence: 99%

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The Surface-Vacancy Model—A General Theory of the Dissolution of Minerals and Salts

Crundwell

2021

Minerals

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The kinetics of the dissolution of salts and minerals remains a field of active research because these reactions are important to many fields, such as geochemistry, extractive metallurgy, corrosion, biomaterials, dentistry, and dietary uptake. A novel model, referred to as the surface-vacancy model, has been proposed by the author as a general mechanism for the primary events in dissolution. This paper expands on the underlying physical model while serving as an update on current progress with the application of the model. This underlying physical model envisages that cations and anions depart separately from the surface leaving a surface vacancy of charge opposite to that of the departing ion on the surface. This results in an excess surface charge, which in turn affects the rate of departing ions. Thus, a feedback mechanism is established in which the departing of ions creates excess surface charge, and this net surface charge, in turn, affects the rate of departure. This model accounts for the orders of reaction, the equilibrium conditions, the acceleration or deceleration of rate in the initial phase and the surface charge. The surface-vacancy model can also account for the effect of impurities in the solution, while it predicts phenomena, such as ‘partial equilibrium’, that are not contemplated by other models. The underlying physical model can be independently verified, for example, by measurements of the surface charge. This underlying physical model has implications for fields beyond dissolution studies.

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Path from Reaction Control to Equilibrium Constraint for Dissolution Reactions

Cited by 9 publications

References 34 publications

Frequency Dependent Silica Dissolution Rate Enhancement under Oscillating Pressure via an Electrochemical Pressure Solution-like, Surface Resonance Mechanism

Frequency Dependent Silica Dissolution Rate Enhancement under Oscillating Pressure via an Electrochemical Pressure Solution-like, Surface Resonance Mechanism

Inferring kinetic dissolution of NaCl in aqueous glycol solution using a low‐cost apparatus and population balance model

The Surface-Vacancy Model—A General Theory of the Dissolution of Minerals and Salts

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