Project

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Dissolution, growth and toxic ion uptake at phyllosilicate surfaces: Coupling atomistic interactions at the mineral-water interface with Kinetic Monte Carlo model.

Applicant Churakov Sergey
Number 165548
Funding scheme Project funding (Div. I-III)
Research institution Institut für Geologie Universität Bern
Institution of higher education University of Berne - BE
Main discipline Mineralogy
Start/End 01.01.2017 - 30.06.2020
Approved amount 209'236.00
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All Disciplines (3)

Discipline
Mineralogy
Geochemistry
Other disciplines of Environmental Sciences

Keywords (4)

Mineral dissolution and growth; Atomistic simulations; Phyllosilicates; Retention of Heavy metals and radionuclides

Lay Summary (German)

Lead
Tonmineralien sind ein Hauptbestandteil des Bodens. Dank einer schichtartigen Kristallstruktur weisen die Tonmineralien eine grosse spezifische Oberfläche auf, die je nach chemischer Bindung mehr oder weniger stark negativ geladen ist und die Kationen aus dem Porenwasser adsorbiert. Diese Sorptionseigenschaften der Tonmineralien können genutzt werden um die Umwelt vor Chemo- und Radio-toxischen Kontaminationen zu schützen. In diesem Projekt werden die Ausfällungs bzw. Auflösungs Prozesse auf Mineraloberflächen untersucht die zu eine strukturelle Einbau bzw. Freisetzung toxische Elemente in der Umwelt beschreiben.
Lay summary

Nur wenige Mineralien bestimmen das Aufnahmeverhalten verschiedener chemischer Elemente auf Erdoberfläche. Aufgrund seiner hoch spezifischen Oberfläche gelten Schichtsilicaten als wichtigstes Abfangbecken für Umweltverschmutzungen. Deren Fähigkeit die Verunreinigungen an der Oberfläche zu binden, bestimmt im Wesentlichen zahlreiche daran anknüpfende Reaktionen, die Reaktivität und letztendlich die Toxizität der kontaminierenden Elemente. Damit die Umweltverschmutzung durch Schwermetalle und radioaktive Elemente verringert werden kann, ist eine modellbasierte Beschreibung dieser Vorgänge vonnöten. Diese hilft außerdem bei der Sanierung von Altlasten.

Das Projekt an der Universität Bern nutzt verschiedene Methoden der Computersimulation um die Mechanismen der verschiedenen auf der Mineraloberfläche auftretenden Reaktionen zu untersuchen. Die Prozesse werden auf einer atomistischen Skala simuliert und die dabei erhaltenen Daten zur Erklärung der makroskopischen Vorgänge unter verschiedenen Umgebungsbedingungen verwendet. Ein so erhaltenes Modell ist essentiell zur Wiederherstellung kontaminierter Bereiche und dem Schutz vor Schwermetallschadstoffen.

Direct link to Lay Summary Last update: 25.08.2016

Responsible applicant and co-applicants

Employees

Name Institute

Publications

Publication
Review of the current status and challenges for a holistic process-based description of mass transport and mineral reactivity in porous media
Churakov Sergey V., Prasianakis Nikolaos I. (2018), Review of the current status and challenges for a holistic process-based description of mass transport and mineral reactivity in porous media, in American Journal of Science, 318(9), 921-948.

Collaboration

Group / person Country
Types of collaboration
Laboratory of Waste Management, Paul Scherrer institute Switzerland (Europe)
- in-depth/constructive exchanges on approaches, methods or results
- Publication
- Research Infrastructure
- Exchange of personnel
ICB UMR 6303 CNRS Univ. Bourgogne Franche-Comté France (Europe)
- in-depth/constructive exchanges on approaches, methods or results
- Publication
University of Bremen Germany (Europe)
- in-depth/constructive exchanges on approaches, methods or results
- Publication
- Exchange of personnel

Scientific events

Active participation

Title Type of contribution Title of article or contribution Date Place Persons involved
Nuklearchemie Individual talk Churakov S.V. Multiscale mechanistic modelling of reactive transport phenomena in nuclear waste disposal systems, , 25.09.2019 Dresden, Germany Churakov Sergey;
29th Goldschmidt Conference Talk given at a conference Molecular mechanism of dissolution, growth and ion uptake at the clay mineral/water interface 18.08.2019 Barcelona, Spain Schliemann René;
EuroClay 2019 Talk given at a conference Molecular mechanism of dissolution, growth and ion uptake of clay minerals at the mineral/water interface 01.07.2019 Paris, France Schliemann René;
Mid-European Clay Conference Talk given at a conference Molecular mechanism of dissolution, growth and ion incorporation of clay minerals at the mineral/water interface. 17.09.2018 Zagreb, Croatia Schliemann René;
7th International Conference on Clays in natural and engineered barriers for radioactive waste confinement Talk given at a conference Molecular mechanism of dissolution, growth and ion uptake of clay minerals at the mineral/water interface. 24.09.2017 Davos, Switzerland Schliemann René;
16th International Clay Conference Talk given at a conference Molecular mechanism of dissolution and growth of clay minerals at the mineral/water interface 17.07.2017 Granada, Spain Schliemann René;
AIPEA School for Young Scientist: Computational modeling in clay mineralogy Individual talk Ab initio molecular dynamics and metadynamics 15.07.2017 Granada, Spain Churakov Sergey;


Self-organised

Title Date Place

Associated projects

Number Title Start Funding scheme
156412 Detailed understanding of metal adsorption on clay minerals obtained by combining atomistic simulations and X-ray absorption spectroscopy 01.01.2015 Project funding (Div. I-III)
164017 Environmental Atomic Force Microscope 01.03.2016 R'EQUIP
130419 Stable phase composition in novel cementitious systems: C-A-S-H 01.11.2010 Sinergia
177033 A dual wavelength X-ray single crystal diffractometer for accurate investigations at extreme conditions 01.08.2018 R'EQUIP

Abstract

It is the matter of fact that just a few minerals control the uptake behavior of a large number of chemical elements in the subsurface environment. Due to high specific surface area and large pH buffering capacity, phyllosilicate minerals are one of the most important sinks for pollutants in soils and subsurface sediments. The entrapment of contaminants onto the mineral surfaces is the primary factor determining their transport, deposition, reactivity and eventually their effective toxicity. A model based description of ion adsorption and incorporation by minerals is needed to understand and describe the transport of heavy and radioactive elements in order to take environmental pollution under control and to develop cost effective remediation strategies.Current modelling approaches applied for cation uptake by phyllosilicates have well-recognized limitations. By far the most widely used mechanistic sorption model for phyllosilicates minerals e.g. 2 site protolysis non electrostatic surface complexation and cation exchange (2SPNE SC/CE) do not include effects of diffuse double layer formation at the interface of the mineral surface and aqueous solution. On the other hand numerous attempts to include the electrostatic term on the basis of linearized Poisson-Boltzmann equation in the sorption model failed to describe the whole range of experimental data. The difficulties are probably related to the omission of the site specific ion surface interaction parameters, irreversible ion uptake and the limited applicability of linearized Poisson-Boltzmann equation (e.g. ion-ion correlation effects are neglected) at ionic strength above 0.2 M, or in presence of divalent ions. Furthermore, the adsorption of divalent and trivalent cations compatible with the octahedral structure of phyllosilicates have shown to be a precursor of the mineral growth. 2SPNE SC/CE does therefore not count for any kind of newly formed phases, such as neo-formed phyllosilicates. Thus, the commonly used models for adsorption do not describe the irreversible metal uptake due to mineral growth as observed in nature. Therefore, such models can’t produce quantitatively correct results for the long term prediction of the heavy metal mobility in the environment.This PhD project is aimed at combining the molecular based description of surface ion adsorption and protolysis at edge sites of phyllosilicate minerals with a Kinetic Monte Carlo (KMC) model of dissolution and growth. The sorption will be modelled by the titration Grand Canonical Monte Carlo (GCMC) method that was previously applied in house to simulate the ion equilibria in cement systems. This approach allows us to calculate equilibrium ion distribution at the surface for the given chemical potential of ions and pH. The use of crystallographic surface geometry, site specific ion surface interaction parameters, obtained in previous quantum mechanical simulations, together with unrestricted primitive model of electrolytes will allow to capture simultaneously the site specific interaction of ions with the surface and electrostatic effects (e.g. DDL, ion exclusion, electrostatic screening) successfully. The data on the interface structure obtained from the GCMC modelling will be incorporated into the KMC model of crystal growth. The scientific novelty of this project is that the effects of molecular solvent on the kinetics of dissolution and precipitation processes will be considered explicitly. To our best knowledge such an approach has not been applied before and offers a great opportunity for the realistic kinetics modelling of dissolution and growth. The combination of classical atomistic sorption with KMC approach will make possible the formulation of the unified modelling approach for adsorption, dissolution and growth. The development of GCMC and KMC models can be substantially advanced by the use experimental data for model verification. A representative experimental database of sorption and titration data is available in house. Similar, the high resolution images of surface topology of dissolving and growing phyllosilicates exist from our previous work and the studies of other groups published in literature. To implement the new modelling approach, the student will use and further extend the existing in house codes for GCMC and KMC simulations, respectively. Since these codes have been developed in house by the project applicants the necessary expertise and support is available. The coupled model for growth/dissolution and sorption is indispensable for the understanding of the long term behavior of toxic elements in the Earth environment. The most direct application of the model will be related to the geological disposal of radioactive waste where clay rich materials are considered as most efficient barrier slowing down the migration of radionuclides and landfill sites contaminated with heavy metals. The basic concept for coupling the sorption with mineral growth will have a general application to mineral surface reactivity (e.g. impurity entrapment and kinetically controlled element partitioning).
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