Ab initio molecular dynamics study of the interlayer and micropore structure of aqueous montmorillonite clays

Suter, James L.; Kabalan, Lara; Khader, Mahmoud M.; Coveney, Peter V.

doi:10.1016/j.gca.2015.07.013

Cited by 38 publications

(26 citation statements)

References 41 publications

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“…It has been determined that, in contrast to the chemically-inert basal plane, the edges of particles are extremely reactive [6][7][8][9], containing both Brönsted acid and base groups. Other authors [9][10][11] have reported that the reactive nature of clay layer edges has been implicated in catalysis reactions, such as polymerization.…”

Section: Introductionmentioning

confidence: 99%

Diatoms and Their Capability for Heavy Metal Removal by Cationic Exchange

Hernández-Ávila

Salinas‐Rodríguez

Cerecedo‐Sáenz

et al. 2017

Metals

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This work shows the physicochemical behavior of two different diatoms from the country of Mexico (State of Jalisco and Hidalgo) with similar compositions. These were used to eliminate toxic cations from a synthetic solution containing 5.270 mg As 3+ /L; 4.280 mg Ag + /L; 3.950 mgNi 2+ /L; 4.090 mg Cr 6+ /L; and 4.081 mg Pb 2+ /L. These diatoms were used as filters, and the quantity of cations remaining in the solution after filtering was measured. According to the most important results found, for the recovery of metals, both minerals achieved arsenic, silver, lead, and nickel recoveries up to 95%, and lower than 10% for chromium. This could be due to the absence of an environment to reduce Cr 6+ to Cr 3+ . On the other hand, it was observed that there was no selectivity during the recovery of the other cations present in the solution. According to efficiency of interchange, the mineral from Hidalgo is slightly better than the mineral from Jalisco for the removal of arsenic, lead, and silver. For nickel, and particularly Cr 6+ , the efficiency is higher for the sample from Jalisco.

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Section: Introductionmentioning

confidence: 99%

Diatoms and Their Capability for Heavy Metal Removal by Cationic Exchange

Hernández-Ávila

Salinas‐Rodríguez

Cerecedo‐Sáenz

et al. 2017

Metals

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“…The layer charge of 2:1 phyllosilicates can be considerably greater if the isomorphic substitutions originate from or occur in combination with the tetrahedral sheets [62]. Previous DFT simulations of the 2:1 phyllosilicate edge have considered the effects of isolated isomorphic substitutions in the tetrahedral sheets on properties of the edge [24,34]. The effects of tetrahedral substitutions on the edge structure of high-layer charge minerals (e.g., vermiculite, illite, mica, etc.)…”

Section: Discussionmentioning

confidence: 99%

“…The unsaturated octahedron of each TOT unit is healed with one physisorbed water molecule. Unlike the DFT-based molecular dynamics (DFT-MD), wherein energetically unfavorable initial distributions of physi-and chemi-sorbed water molecules may result in a re-distribution of protons amongst the surface oxygen [20,24,34], classical mechanical simulations must proceed from surface structures chosen a priori; the initial surface configuration was created based on our DFT geometry optimization results. The force fields used in classical mechanical simulation assign an atom type to each atom in the molecular structure based on the chemical element of the atom and its coordination environment.…”

Section: Molecular Dynamics Simulationsmentioning

confidence: 99%

“…When the surface octahedra include isomorphic substitutions, however, this homogeneous assignment is perhaps insufficient. The observed spontaneous transfer of protons on the pyrophyllite B edge surface during DFT-MD simulations [20,24,34]; the effects of isomorphic substitution on the pK a of edge surfaces groups [25]; and the considerable difference between the first hydrolysis constants of Mg and Al in solution (pK a1 = 11.4 v. 5.0, respectively [55]) all suggest that the investigation of alternative initial surface proton distributions is prudent. Liu, et al [24] used constrained DFT-MD to calculate the free-energy profile for H 2 O dissociation from the phyllosilicate edges and identified variations in the surface functional groups when Mg is substituted for solvent accessible Al sites.…”

Section: Density Functional Theory (Dft) Geometry Optimizationsmentioning

confidence: 99%

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Na-Montmorillonite Edge Structure and Surface Complexes: An Atomistic Perspective

Newton

Lee

2017

Minerals

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Abstract:The edges of montmorillonite (MMT) react strongly with metals and organic matter, but the atomic structure of the edge and its surface complexes are not unambiguous since the experimental isolation of the edge is challenging. In this study, we introduce an atomistic model of a Na MMT edge that is suitable for classical molecular dynamics (MD) simulations, in particular for the B edge, a representative edge surface of 2:1 phyllosilicates. Our model possesses the surface groups identified through density functional theory (DFT) geometry optimizations performed with variation in the structural charge deficit and Mg substitution sites. The edge structure of the classical MD simulations agreed well with previous DFT-based MD simulation results. Our MD simulations revealed an extensive H-bond network stabilizing the Na-MMT edge surface, which required an extensive simulation trajectory. Some Na counter ions formed inner-sphere complexes at two edge sites. The stronger edge site coincided with the exposed vacancy in the dioctahedral sheet; a weaker site was associated with the cleaved hexagonal cavity of the tetrahedral sheet. The six-coordinate Na complexes were not directly associated with the Mg edge site. Our simulations have demonstrated the heterogeneous surface structures, the distribution of edge surface groups, and the reactivity of the MMT edge.

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“…Se ha determinado que, en contraste con el plano basal químicamente inerte, los bordes de las partículas son extremadamente reactivos (Bickmore et al, 2003;Churakov, 2006;Churakov, 2007), que contienen ambos grupos de compuestos de base bruta y ácido. Otros autores (Stackhouse et al, 2001;Suter et al, 2015) han informado de que la acción de las demarcaciones de los iones ha sido una reacción de catálisis simple, como la polimerización. Las propiedades de cambio iónico en arcillas han sido más extensamente investigadas en el grupo de montmorillonita que en cualquier otro.…”

Section: Introductionunclassified

Recuperación de Tierras Raras Mediante Intercambio Catiónico, Usando Bentonita Natural: Estudio Preliminar

Salinas‐Rodríguez

Hernández-Ávila

Amador-Ortega

et al. 2019

ICBI

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ResumenEl uso de tierras raras en las innovaciones actuales, que han permitido el desarrollo tecnológico de industrias tales como la de la computación, electrónica, robótica, automotriz, etc., pone de manifiesto la necesidad de encontrar nuevas formas de obtener dichos elementos a partir de fuentes primarias y secundarias. Es por ello, que el presente trabajo muestra los resultados preliminares más importantes, relacionados a la adsorción de algunos elementos de tierras raras y metales preciosos, usando un mineral natural, tal como la bentonita. De este modo, se llevaron a cabo experimentos para recuperar los elementos mencionados (Ce, La, Nd, Yb, Pd y Au) contenidos en soluciones sintéticas, y en soluciones procedentes de la lixiviación de un mineral tipo Sedimentario Exhalativo (SEDEX) del estado de Hidalgo, en México. En todos los casos, se evaluó la Capacidad de Intercambio Catiónico (CIC) de la bentonita natural en función del pH, encontrándose que este parámetro no tiene efecto significativo en la CIC de la bentonita, lográndose recuperaciones del 100% para el caso de Ce y La, y arriba del 99% para el resto de los elementos en ambos tipos de soluciones (sintética y procedente de lixiviación), y con ello, preliminarmente se concluye que la bentonita natural (sin activar), es un material que puede ser usado, además de apoyo en la perforación de pozos petroleros y en la fabricación de moldes y corazones en la industria metalúrgica y del acero, para recuperar valores de metales preciosos y elementos de tierras raras, mediante intercambio iónico. AbstractThe use of rare earths in current innovations, which have allowed the technological development of industries such as computing, electronics, robotics, automotive, etc., highlights the need to find new ways to obtain these elements from primary and secondary sources. That is why, the present work shows the most important preliminary results, related to the adsorption of some rare earth elements and precious metals, using a natural mineral, such as bentonite. Thus, experiments were carried out to recover the aforementioned elements (Ce, La, Nd, Yb, Pd and Au) contained in synthetic solutions, and in solutions from the leaching of a Sedimentary Exhalative (SEDEX) type mineral from the state of Hidalgo, in Mexico. In all cases, the Cation Exchange Capacity (CEC) of natural bentonite was evaluated as a function of pH, finding that this parameter has no significant effect on the CEC of bentonite, achieving 100% recoveries in the case of Ce and La, and above 99% for the rest of the elements in both types of solutions (synthetic and from leaching), and with this, it is preliminary concluded that natural bentonite (without activating), is a material that can be used, in addition to support in the drilling of oil wells and in the manufacture of molds and cores in the metallurgical and steel industry, to recover values of precious metals and rare earth elements.

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Ab initio molecular dynamics study of the interlayer and micropore structure of aqueous montmorillonite clays

Cited by 38 publications

References 41 publications

Diatoms and Their Capability for Heavy Metal Removal by Cationic Exchange

Diatoms and Their Capability for Heavy Metal Removal by Cationic Exchange

Na-Montmorillonite Edge Structure and Surface Complexes: An Atomistic Perspective

Recuperación de Tierras Raras Mediante Intercambio Catiónico, Usando Bentonita Natural: Estudio Preliminar

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