Polyacrylic Acid to Improve Flotation Tailings Management: Understanding the Chemical Interactions through Molecular Dynamics

Molecular dynamic simulations of polyacrylic acid polyelectrolyte (PAA) analyzed its interaction with the main minerals that make up characteristic tailings of the mining industry, in this case, quartz, kaolinite, and montmorillonite. The simulations were carried out with the package Gromacs 2020.3. The interaction potentials used were General AMBER Force Field (GAFF) for PAA and CLAYFF-MOH for mineral surfaces. The SPC/E model described water molecules and Lennard-Jones 12-6 parameters adjusted for SPC/E model were used for Na+ and Cl− ions. The studied systems were carried out at pH 7, obtaining stable adsorption between the PAA and the studied surfaces. Interestingly, the strongest adsorptions were for montmorillonite at both low and high salt concentrations. The effect of salinity differs according to the system, finding that it impairs the absorption of the polymer on montmorillonite surfaces. However, a saline medium favors the interaction with quartz and kaolinite. This is explained because montmorillonite has a lower surface charge density and a greater capacity to adsorb ions. This facilitated the adsorption of PAA. It was possible to identify that the main interaction by which the polymer is adsorbed is through the hydroxyl of the mineral surface and the COO−Na+ complexes. Molecular dynamics allows us to advance in the understanding of interactions that define the behavior of this promising reagent as an alternative for sustainable treatment of complex tailings in highly saline environments.

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Computational Investigation Into the Adsorption of Pollutants Onto Mineral Surfaces: Arsenate and Dolomite

MRS Proceedings ◽

10.1557/proc-0930-jj05-04 ◽

2006 ◽

Vol 930 ◽

Author(s):

Kat F. Austen ◽

Kate Wright ◽

Ben Slater ◽

Julian D. Gale

Keyword(s):

Molecular Dynamics ◽

Computational Modeling ◽

Solvation Energy ◽

Water Molecules ◽

Mineral Surfaces ◽

Computational Investigation ◽

Solution Interface ◽

Modeling Techniques ◽

Computationally Expensive ◽

Adsorption Geometry

ABSTRACTComputational modeling techniques have been used to investigate the interaction of arsenate with the dolomite (211) surface. The suitability of a variety of techniques has been assessed in the context of their applicability to the problem, in order to determine the least computationally expensive method of modeling the mineral-solution interface. To this end, various methods of solvating arsenate have been investigated, and a reliable solvation energy has been determined for the molecule. The adsorption geometry of the primary arsenate ion at the dolomite surface has been determined under vacuum conditions. Additionally, solvation of the dolomite surface has studied using molecular dynamics, and results show that there is some layering 2Å above the surface, and that dissociation of the water molecules occurs in this layer.

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All-atom molecular dynamics simulations of weak polyionic brushes: influence of charge density on the properties of polyelectrolyte chains, brush-supported counterions, and water molecules

Soft Matter ◽

10.1039/d0sm01000f ◽

2020 ◽

Vol 16 (33) ◽

pp. 7808-7822

Author(s):

Harnoor Singh Sachar ◽

Turash Haque Pial ◽

Bhargav Sai Chava ◽

Siddhartha Das

Keyword(s):

Molecular Dynamics ◽

Charge Density ◽

Molecular Dynamics Simulations ◽

Polyacrylic Acid ◽

Water Molecules ◽

Dynamics Simulations

All-atom molecular dynamics simulations are used to probe the effects of charge density on the microstructure of polyacrylic acid brushes.

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Gating Mechanism of Hv1 Studied by Molecular Dynamic Simulations

Materials Proceedings ◽

10.3390/iocn2020-07862 ◽

2020 ◽

Vol 4 (1) ◽

pp. 20

Author(s):

Thi Tuong Vy Phan

Keyword(s):

Molecular Dynamics ◽

Cancer Progression ◽

Md Simulations ◽

Proton Channel ◽

Water Molecules ◽

State Structure ◽

Ph Homeostasis ◽

Dynamic Simulations ◽

Closed State ◽

Gating Mechanism

The voltage-gated proton channel (Hv1) plays the important role in proton extrusion, pH homeostasis, sperm motility, and cancer progression. The closed-state structure of Hv1 was recently revealed by X-ray crystallography. However, the opened-state structure has not been captured yet. To investigate the mechanism of proton transfer in Hv1, molecular dynamics (MD) simulations were performed with the closed-state structure of Hv1 under electric field and pH conditions. The residues arrangement on the closed-state structure revealed that the selectivity filter (Asp108) which is located in the hydrophobic layer (consists of two Phe residues 146 and 179) might prevent water penetration. In molecular dynamics simulations, we observed that the channel opened by moving 3 Arg up on the S4 helix and a continuous hydrogen-bonded chain of water molecules (a “water wire”) went through the channel when it opened. During simulations, the open channel allowed water molecules to pass through the channel but excluded other ions. This indicates the Hv1 channel is highly selective for protons. Our results clearly showed the Hv1 channel is voltage-and pH-gradient sensing.

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Acceleration of molecular dynamics simulation of multiphase systems on GPU

Proceedings of the Mavlyutov Institute of Mechanics ◽

10.21662/uim2012.2.053 ◽

2012 ◽

Vol 9 (2) ◽

pp. 76-79

Author(s):

D.F. Marin

Keyword(s):

Molecular Dynamics ◽

Molecular Dynamics Simulation ◽

Molecular Dynamics Simulations ◽

Intermolecular Interaction ◽

Dynamics Simulation ◽

Water Molecules ◽

Lennard Jones ◽

Multiphase Systems ◽

And Performance ◽

Dynamics Simulations

The paper presents results on acceleration of molecular dynamics simulations with the usage of GPUs. A system of water molecules is considered as an example of polar liquid. The intermolecular interaction is modeled with the usage of Coulomb and truncated Lennard-Jones potentials. Results of computational experiments on acceleration and performance of the developed code are presented.

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QM/MM Simulations of Organic Phosphorus Adsorption at the Diaspore-Water Interface

10.26434/chemrxiv.8075204 ◽

2019 ◽

Author(s):

Prasanth Babu Ganta ◽

Oliver Kühn ◽

Ashour Ahmed

Keyword(s):

Interaction Energy ◽

Dynamics Simulation ◽

Water Molecules ◽

Hydroxyl Groups ◽

Water Interface ◽

Mineral Surfaces ◽

Soil Mineral ◽

Phosphorus Adsorption ◽

Covalent Bonds ◽

Binding Mechanisms

The phosphorus (P) immobilization and thus its availability for plants are mainly affected by the strong interaction of phosphates with soil components especially soil mineral surfaces. Related reactions have been studied extensively via sorption experiments especially by carrying out adsorption of ortho-phosphate onto Fe-oxide surfaces. But a molecular-level understanding for the P-binding mechanisms at the mineral-water interface is still lacking, especially for forest eco-systems. Therefore, the current contribution provides an investigation of the molecular binding mechanisms for two abundant phosphates in forest soils, inositol hexaphosphate (IHP) and glycerolphosphate (GP), at the diaspore mineral surface. Here a hybrid electrostatic embedding quantum mechanics/molecular mechanics (QM/MM) based molecular dynamics simulation has been applied to explore the diaspore-IHP/GP-water interactions. The results provide evidence for the formation of different P-diaspore binding motifs involving monodentate (M) and bidentate (B) for GP and two (2M) as well as three (3M) monodentate for IHP. The interaction energy results indicated the abundance of the GP B motif compared to the M one. The IHP 3M motif has a higher total interaction energy compared to its 2M motif, but exhibits a lower interaction energy per bond. Compared to GP, IHP exhibited stronger interaction with the surface as well as with water. Water was found to play an important role in controlling these diaspore-IHP/GP-water interactions. The interfacial water molecules form moderately strong H-bonds (HBs) with GP and IHP as well as with the diaspore surface. For all the diaspore-IHP/GP-water complexes, the interaction of water with diaspore exceeds that with the studied phosphates. Furthermore, some water molecules form covalent bonds with diaspore Al atoms while others dissociate at the surface to protons and hydroxyl groups leading to proton transfer processes. Finally, the current results conﬁrm previous experimental conclusions indicating the importance of the number of phosphate groups, HBs, and proton transfers in controlling the P-binding at soil mineral surfaces.

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Multicanonical Molecular Dynamics Simulation Study of the Liquid-Solid and Solid-Solid Transitions in Lennard-Jones Clusters

ASME/JSME 2011 8th Thermal Engineering Joint Conference ◽

10.1115/ajtec2011-44457 ◽

2011 ◽

Author(s):

Toshihiro Kaneko ◽

Kenji Yasuoka ◽

Ayori Mitsutake ◽

Xiao Cheng Zeng

Keyword(s):

Molecular Dynamics ◽

Heat Capacity ◽

Transition Temperature ◽

Peak Position ◽

Temperature Curve ◽

Dynamics Simulation ◽

Lennard Jones ◽

Dynamics Simulations ◽

First Time ◽

Good Agreement

Multicanonical molecular dynamics simulations are applied, for the first time, to study the liquid-solid and solid-solid transitions in Lennard-Jones (LJ) clusters. The transition temperatures are estimated based on the peak position in the heat capacity versus temperature curve. For LJ31, LJ58 and LJ98, our results on the solid-solid transition temperature are in good agreement with previous ones. For LJ309, the predicted liquid-solid transition temperature is also in agreement with previous result.

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The Impact of the Electric Field on Surface Condensation of Water Vapor: Insight from Molecular Dynamics Simulation

Nanomaterials ◽

10.3390/nano9010064 ◽

2019 ◽

Vol 9 (1) ◽

pp. 64 ◽

Cited By ~ 7

Author(s):

Qin Wang ◽

Hui Xie ◽

Zhiming Hu ◽

Chao Liu

Keyword(s):

Molecular Dynamics ◽

Water Vapor ◽

Electric Field ◽

Intermolecular Forces ◽

Dynamics Simulation ◽

Water Molecules ◽

Attraction Force ◽

Condensation Rate ◽

Shape Transformation ◽

The Impact

In this study, molecular dynamics simulations were carried out to study the coupling effect of electric field strength and surface wettability on the condensation process of water vapor. Our results show that an electric field can rotate water molecules upward and restrict condensation. Formed clusters are stretched to become columns above the threshold strength of the field, causing the condensation rate to drop quickly. The enhancement of surface attraction force boosts the rearrangement of water molecules adjacent to the surface and exaggerates the threshold value for shape transformation. In addition, the contact area between clusters and the surface increases with increasing amounts of surface attraction force, which raises the condensation efficiency. Thus, the condensation rate of water vapor on a surface under an electric field is determined by competition between intermolecular forces from the electric field and the surface.

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Electrical Breakdown Mechanism of Transformer Oil with Water Impurity: Molecular Dynamics Simulations and First-Principles Calculations

Crystals ◽

10.3390/cryst11020123 ◽

2021 ◽

Vol 11 (2) ◽

pp. 123

Author(s):

Bin Cao ◽

Ji-Wei Dong ◽

Ming-He Chi

Keyword(s):

Molecular Dynamics ◽

Thermal Diffusion ◽

First Principles ◽

Electrical Breakdown ◽

Transformer Oil ◽

Water Molecules ◽

Conducting Channel ◽

Breakdown Mechanism ◽

Water Impurity ◽

Dynamics Simulations

Water impurity is the essential factor of reducing the insulation performance of transformer oil, which directly determines the operating safety and life of a transformer. Molecular dynamics simulations and first-principles electronic-structure calculations are employed to study the diffusion behavior of water molecules and the electrical breakdown mechanism of transformer oil containing water impurities. The molecular dynamics of an oil-water micro-system model demonstrates that the increase of aging acid concentration will exponentially expedite thermal diffusion of water molecules. Density of states (DOS) for a local region model of transformer oil containing water molecules indicates that water molecules can introduce unoccupied localized electron-states with energy levels close to the conduction band minimum of transformer oil, which makes water molecules capable of capturing electrons and transforming them into water ions during thermal diffusion. Subsequently, under a high electric field, water ions collide and impact on oil molecules to break the molecular chain of transformer oil, engendering carbonized components that introduce a conduction electronic-band in the band-gap of oil molecules as a manifestation of forming a conductive region in transformer oil. The conduction channel composed of carbonized components will be eventually formed, connecting two electrodes, with the carbonized components developing rapidly under the impact of water ions, based on which a large number of electron carriers will be produced similar to “avalanche” discharge, leading to an electrical breakdown of transformer oil insulation. The water impurity in oil, as the key factor for forming the carbonized conducting channel, initiates the electric breakdown process of transformer oil, which is dominated by thermal diffusion of water molecules. The increase of aging acid concentration will significantly promote the thermal diffusion of water impurities and the formation of an initial conducting channel, accounting for the degradation in dielectric strength of insulating oil containing water impurities after long-term operation of the transformer.

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Origin and control of ionic hydration patterns in nanopores

Communications Materials ◽

10.1038/s43246-021-00162-x ◽

2021 ◽

Vol 2 (1) ◽

Author(s):

Miraslau L. Barabash ◽

William A. T. Gibby ◽

Carlo Guardiani ◽

Alex Smolyanitsky ◽

Dmitry G. Luchinsky ◽

...

Keyword(s):

Molecular Dynamics ◽

Molecular Dynamics Simulations ◽

Distribution Functions ◽

Water Molecules ◽

Surrounding Water ◽

Ionic Hydration ◽

Hydration Shells ◽

Water Layers ◽

Dynamics Simulations ◽

And Control

AbstractIn order to permeate a nanopore, an ion must overcome a dehydration energy barrier caused by the redistribution of surrounding water molecules. The redistribution is inhomogeneous, anisotropic and strongly position-dependent, resulting in complex patterns that are routinely observed in molecular dynamics simulations. Here, we study the physical origin of these patterns and of how they can be predicted and controlled. We introduce an analytic model able to predict the patterns in a graphene nanopore in terms of experimentally accessible radial distribution functions, giving results that agree well with molecular dynamics simulations. The patterns are attributable to a complex interplay of ionic hydration shells with water layers adjacent to the graphene membrane and with the hydration cloud of the nanopore rim atoms, and we discuss ways of controlling them. Our findings pave the way to designing required transport properties into nanoionic devices by optimising the structure of the hydration patterns.

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