Implementing Heterogeneous Crystal Surface Reactivity in Reactive Transport Simulations: The Example of Calcite Dissolution

2021 ◽  
Author(s):  
Lotfollah Karimzadeh ◽  
Cornelius Fischer
Keyword(s):  
Reactive Transport ◽  
Crystal Surface ◽  
Surface Reactivity ◽  
Calcite Dissolution

scholarly journals Implementing the Variability of Crystal Surface Reactivity in Reactive Transport Modeling

2021 ◽  
Author(s):  
Torben Prill ◽  
Cornelius Fischer ◽  
Pavel Gavrilenko ◽  
Oleg Iliev
Keyword(s):  
Contaminated Soils ◽  
Reactive Transport ◽  
Transport Model ◽  
Crystal Surface ◽  
Reaction Rates ◽  
Surface Reactivity ◽  
Reservoir Rock ◽  
Intrinsic Variability ◽  
Multiple Systems ◽  
The Difference

AbstractCurrent reactive transport model (RTM) uses transport control as the sole arbiter of differences in reactivity. For the simulation of crystal dissolution, a constant reaction rate is assumed for the entire crystal surface as a function of chemical parameters. However, multiple dissolution experiments confirmed the existence of an intrinsic variability of reaction rates, spanning two to three orders of magnitude. Modeling this variance in the dissolution process is vital for predicting the dissolution of minerals in multiple systems. Novel approaches to solve this problem are currently under discussion. Critical applications include reactions in reservoir rocks, corrosion of materials, or contaminated soils. The goal of this study is to provide an algorithm for multi-rate dissolution of single crystals, to discuss its software implementation, and to present case studies illustrating the difference between the single rate and multi-rate dissolution models. This improved model approach is applied to a set of test cases in order to illustrate the difference between the new model and the standard approach. First, a Kossel crystal is utilized to illustrate the existence of critical rate modes of crystal faces, edges, and corners. A second system exemplifies the effect of multiple rate modes in a reservoir rock system during calcite cement dissolution in a sandstone. The results suggest that reported variations in average dissolution rates can be explained by the multi-rate model, depending on the geometric configurations of the crystal surfaces.

Mineral surface reactivity: mechanisms and concepts

2021 ◽  
Author(s):  
Cornelius Fischer
Keyword(s):  
Reactive Transport ◽  
Large Scale ◽  
Fluid Transport ◽  
Crystal Surface ◽  
Solid Material ◽  
Surface Reactivity ◽  
Small Scale ◽  
Critical Surface ◽  
Mechanistic Understanding ◽  
Diagenetic Reactions

<p>Diagenetic reactions in sediments and sedimentary rocks are controlled by both fluid transport and surface reactivity. In this chapter, the major focus is on the effect of crystal surface reactivity and its variability. The “energetic landscape” of the solid material in contact with the fluid exerts control on reaction type, kinetics, and products. Critical surface processes include sorption, catalysis, dissolution, and precipitation. For diagenetic reactions, the sequence of processes and thus the potential inhibition of subsequent reactions due to surface modifications is of great interest. Consequently, the evolution of porosity and permeability is governed by the chronological sequence of surface reactions during the diagenetic history. This provides feedback to the fluid transport behaviour in the complex porous material. Because of this coupling, numerical approaches address the problem appropriately by the use of reactive transport codes. Pore scale treatment follows mechanisms at the scale of crystal surfaces that form the pore walls of the sedimentary rock. Such surface-chemical exercises require a parametrization that includes mechanistic understanding and connection to first-principles treatment. At larger scales, so-called continuum scale simulation treats fluid transport and fluid-solid reactions in a more generalized quantitative way. While such field-scale treatment is required and applied for multiple challenges, the small-scale mechanistic understanding is still a crucial part of geochemical research. The observed heterogeneity of surface reactivity requires specific upscaling strategies that are not yet reflected in large-scale analysis and predictions.</p>

Pore-scale hydrodynamic evolution within carbonate rock during CO2 injection and sequestration

2021 ◽  
Author(s):  
Chi Zhang ◽  
Siyan Liu ◽  
Reza Barati
Keyword(s):  
High Resolution ◽  
Reactive Transport ◽  
Injection Rate ◽  
Mineral Dissolution ◽  
Co2 Injection ◽  
Pore Scale ◽  
Modeling Framework ◽  
Calcite Dissolution ◽  
Potential Factors ◽  
The Impact

<p><span>The continuously rising threat of global warming caused by human activities related to CO</span><span><sub>2</sub> emission is facilitating the development of greenhouse gas control technologies. Subsurface CO</span><span><sub>2</sub> injection and sequestration is one of the promising techniques to store CO</span><span><sub>2</sub> in the subsurface. </span><span> </span><span>However, during CO<sub>2</sub> injection, the mechanisms of processes like injectant immobilizations and trapping and pore-scale geochemical reactions such as mineral dissolution/precipitation are not well understood. Consequently, the multi-physics modeling approach is essential to elucidate the impact of all potential factors during CO<sub>2</sub> injection, thus to facilitate the optimization of this engineered application.</span> </p><p><span>Here, we propose a coupled framework to fully utilize the capabilities of the geochemical reaction solver PHREEQC while preserving the Lattice-Boltzmann Method (LBM) high-resolution pore-scale fluid flow integrated with diffusion processes. The model can simulate the dynamic fluid-solid interactions with equilibrium, kinetics, and surface reactions under the reactive-transport scheme.  In a simplified 2D spherical pack, we focused on examining the impact of pore sizes, grain size distributions, porosity, and permeability on the calcite dissolution/precipitation rate. Our simulation results show that the higher permeability, injection rate, and more local pore connectivity would significantly increase the reaction rate, then accelerate the pore-scale geometrical evolutions. Meanwhile, model accuracy is not sacrificed by reducing the number of reactants/species within the system.</span></p><p><span>Our modeling framework provides high-resolution details of the pore-scale fluid-solid interaction dynamics. To gain more insights into the mineral-fluid interfacial properties during CO</span><span><sub>2</sub> sequestration, our next step is to combine the electrodynamic forces into the model. Potentially, the proposed framework can be used for model upscaling and adaptive subsurface management in the future. </span><span> </span></p>

scholarly journals Pulsating dissolution of crystalline matter

2018 ◽  
Vol 115 (5) ◽  
pp. 897-902 ◽  
Author(s):  
Cornelius Fischer ◽  
Andreas Luttge
Keyword(s):  
Reactive Transport ◽  
Reaction Rate ◽  
Crystal Surface ◽  
Reaction Rates ◽  
Spatial And Temporal Variability ◽  
Pharmaceutical Sciences ◽  
Material Flux ◽  
Spatially Resolved ◽  
Site Density ◽  
Fluid Saturation

Fluid–solid reactions result in material flux from or to the solid surface. The prediction of the flux, its variations, and changes with time are of interest to a wide array of disciplines, ranging from the material and earth sciences to pharmaceutical sciences. Reaction rate maps that are derived from sequences of topography maps illustrate the spatial distribution of reaction rates across the crystal surface. Here, we present highly spatially resolved rate maps that reveal the existence of rhythmic pulses of the material flux from the crystal surface. This observation leads to a change in our understanding of the way crystalline matter dissolves. Rhythmic fluctuations of the reactive surface site density and potentially concomitant oscillations in the fluid saturation imply spatial and temporal variability in surface reaction rates. Knowledge of such variability could aid attempts to upscale microscopic rates and predict reactive transport through changing porous media.

Impact of Surface Reactivity on the Simulation of Mineral Dissolution Rates

2021 ◽  
Author(s):  
Jonas Schabernack ◽  
Cornelius Fischer
Keyword(s):  
Nuclear Waste ◽  
Safety Assessment ◽  
Large Time ◽  
Crystal Surface ◽  
Surface Reactivity ◽  
Mineral Dissolution ◽  
Dissolution Rates ◽  
Rate Laws ◽  
Rate Calculation ◽  
Waste Repositories

<p>The kinetics of mineral dissolution plays a key role in many environmental and technical fields, e.g., weathering, building materials, as well as host rock characterization for potential nuclear waste repositories. Mineral dissolution rates are controlled by two parameters: (1) transport of dissolved species over and from the interface determined by advective fluid flow and diffusion (transport control) and (2) availability and distribution of reactive sites on the crystal surface (surface reactivity control). Reactive transport models (RTM) simulating species transport commonly calculate mineral dissolution by using rate laws [1]. However, the applied rate laws solely depend on species concentration in the fluid. While the effect of transport-controlled processes is addressed in current RTM approaches, the intrinsic variability of surface reactivity is neglected. Experimental studies under surface-controlled dissolution conditions have shown that surface reactivity is heterogeneously distributed over the surface [e.g., 2]. This heterogeneity in reactivity is largely caused by nanotopographical structures on the crystal surface, such as steps and etch pits. These structures are generated through defects in the crystal lattice. At these structures, the high density of reactive kink sites is leading to a local increase in surface reactivity observable through high dissolution rates.</p><p>In this study, we test whether the current rate calculation approach applied in RTMs is sufficient to reproduce experimentally observed rate heterogeneities. We apply a standard RTM approach combined with the measured surface topography of a calcite single crystal [2]. Calcite is an important mineral component in the sandy facies of the Opalinus clay formation, that is under investigation for nuclear waste storage. The modeled surface dissolution rate maps are compared to experimentally derived rate maps. Results show that the current RTM is not able to reproduce the measured rate heterogeneities on the calcite surface. To improve the predictive capabilities of RTMs over the large time scales required for the safety assessment of nuclear waste repositories, the surface reactivity that is intrinsic to the mineral needs to be implemented into future rate calculations. Investigating calcite surface reactivity in the context of dissolution can also yield information about other kinetic surface processes such as the adsorption of radionuclides during transport. We show the integration of surface reactivity into rate calculation by using a proxy parameter. The slope of the crystal surface at the nm scale is applied. We show that by adding a factor based on the slope to the rate law the RTM is able to approximate experimental rate maps. Other proxy parameters such as surface roughness could yield similar results as well. The implementation of surface reactivity proxy parameters will allow for a more precise prediction of host rock-fluid interaction over large time scales in RTMs, relevant for safety assessment of nuclear waste repositories.</p><p>[1] Agrawal, P., Raoof, A., Iliev, O. and Wolthers, M. (2020), Advances in Water Resources, 136, 103480. [2] Bibi, I., Arvidson, R.S., Fischer, C. and Lüttge, A. (2018), Minerals, 8, 256.</p>

Influence ofBacillus subtilisCell Walls and EDTA on Calcite Dissolution Rates and Crystal Surface Features

2003 ◽  
Vol 37 (11) ◽  
pp. 2376-2382 ◽  
Author(s):  
A. K. Friis ◽  
T. A. Davis ◽  
M. M. Figueira ◽  
J. Paquette ◽  
A. Mucci
Keyword(s):  
Crystal Surface ◽  
Dissolution Rates ◽  
Calcite Dissolution ◽  
Surface Features

Variability of crystal surface reactivity: What do we know?

2014 ◽  
Vol 43 ◽  
pp. 132-157 ◽  
Author(s):  
Cornelius Fischer ◽  
Inna Kurganskaya ◽  
Thorsten Schäfer ◽  
Andreas Lüttge
Keyword(s):  
Crystal Surface ◽  
Surface Reactivity

scholarly journals Crystal Surface Reactivity Analysis Across Scales: Combined Experimental and Numerical Insight

2020 ◽  
Author(s):  
Cornelius Fischer ◽  
Wolf-Achim Kahl ◽  
Tao Yuan ◽  
Till Bollermann ◽  
Wolfgang Bach
Keyword(s):  
Crystal Surface ◽  
Surface Reactivity

scholarly journals Aragonite is calcite’s best friend at the seafloor

2021 ◽  
Author(s):  
Olivier Sulpis ◽  
Priyanka Agrawal ◽  
Mariette Wolthers ◽  
Guy Munhoven ◽  
Matthew Walker ◽  
...  
Keyword(s):  
Calcium Carbonate ◽  
Reactive Transport ◽  
Transport Model ◽  
Deep Ocean ◽  
Diffusive Transport ◽  
Carbonate Production ◽  
Calcium Carbonates ◽  
Calcite Dissolution ◽  
Calcium Carbonate Dissolution

Abstract In the open ocean, calcium carbonates are mainly found in two mineral forms. Calcite, the least soluble, is widespread at the seafloor, while aragonite, the more soluble, is rarely preserved in marine sediments. Despite its greater solubility, research has shown that aragonite, which could contribute between 10 and 90% to pelagic calcium carbonate production, is able to reach the deep-ocean. If large quantities of aragonite settle and dissolve at the seafloor, this represents a large source of alkalinity that buffers the deep ocean and favours the preservation of less soluble calcite, acting as a deep-sea, carbonate version of galvanization. Here, we investigate the role of aragonite dissolution on the early diagenesis of calcite-rich sediments using a novel 3D, micrometric-scale reactive-transport model combined with 3D, X-ray tomography structures of natural aragonite and calcite shells. Results highlight the important role of diffusive transport in benthic calcium carbonate dissolution, in agreement with recent work. We show that, locally, aragonite fluxes to the seafloor could be sufficient to suppress calcite dissolution in the top layer of the seabed, possibly causing calcite recrystallization. As aragonite producers are particularly vulnerable to ocean acidification, the proposed galvanizing effect of aragonite could be weakened in the future, indirectly boosting calcite dissolution further.

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