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Papers by Gonzalo R . Quezada

Research paper thumbnail of Molecular simulation of the adsorption of seawater salts on a negatively charged quartz surface

Research paper thumbnail of Describing the adsorption of sodium tripolyphosphate on kaolinite surfaces in a saline medium by molecular dynamics

Research paper thumbnail of Polyacrylic Acid to Improve Flotation Tailings Management: Understanding the Chemical Interactions through Molecular Dynamics

Metals

Molecular dynamic simulations of polyacrylic acid polyelectrolyte (PAA) analyzed its interaction ... more 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 ex...

Research paper thumbnail of Molecular Dynamics Study of the Conformation, Ion Adsorption, Diffusion and Water Structure of Soluble Polymers in Saline Solutions

Polymers

Polymers have interesting physicochemical characteristics such as charge density, functionalities... more Polymers have interesting physicochemical characteristics such as charge density, functionalities, and molecular weight. Such attributes are of great importance for use in industrial purposes. Understanding how these characteristics are affected is still complex, but with the help of molecular dynamics (MD) and quantum calculations (QM), it is possible to understand the behavior of polymers at the molecular level with great consistency. This study was applied to polymers derived from polyacrylamide (PAM) due to its great use in various industries. The polymers studied include hydrolyzed polyacrylamide (HPAM), poly (2-acrylamido-2-methylpropanesulfonate) (PAMPS), polyacrylic acid (PAA), polyethylene oxide polymer (PEO), and guar gum polysaccharide (GUAR). Each one has different attributes, which help in understanding the effects on the polymer and the medium in which it is applied along a broad spectrum. The results include the conformation, diffusion, ion condensation, the structure...

Research paper thumbnail of Adsorption of Phosphate Ions on the Basal and Edge Surfaces of Kaolinite in Low Salt Aqueous Solutions Using Molecular Dynamics Simulations

Research paper thumbnail of Polyacrylamide adsorption on (1 0 1) quartz surfaces in saltwater for a range of pH values by molecular dynamics simulations

Research paper thumbnail of Improving the Flocculation Performance of Clay-Based Tailings in Seawater: A Population Balance Modelling Approach

Minerals

A population balance model described the flocculation of clay-based mining tailings in treated se... more A population balance model described the flocculation of clay-based mining tailings in treated seawater with reduced magnesium content. For the treatment, 0.06 M of lime was added to the liquor, generating solid magnesium complexes that were subsequently removed by vacuum filtration. Magnesium content varied between 10–1440 ppm when mixing raw seawater with treated seawater. The aggregate size was analysed by the Focused Beam Reflectance Measurement (FBRM) technology. The model follows the dynamics of the aggregation-rupture and it provides a good approximation to the temporal evolution. A decrease in collision efficiency was implemented as an indicator of the polymer depletion, describing the size reduction. Lower magnesium content makes larger aggregates with a higher fractal dimension, but an increase in the concentration of clays reduces both the size of aggregates and the fractal dimension, indicating more open and porous structures, with higher permeability to the passage of f...

Research paper thumbnail of Complexation of Alkali and Alkaline-Earth Metal Cations at Spodumene-Saltwater Interfaces by Molecular Simulation: Impact on Oleate Adsorption

Minerals

Spodumene, a lithium aluminum inosilicate, is recovered by froth flotation using surfactants, so-... more Spodumene, a lithium aluminum inosilicate, is recovered by froth flotation using surfactants, so-called collectors. Therefore, the behavior and properties of the water-mineral interface in saline solutions are central. Here, molecular dynamics simulations are used to study the adsorption of alkali and alkaline-earth metal cations from concentrated solutions on the weakest (110) surface plane of negatively-charged spodumene. Results include the envelope density function of inner-sphere complexes for each cation and the density of complexes according to their adsorption contacts. Visualization of complexes for each cation is also included. Once the structure of the cation layers adsorbed on the surface of spodumene is defined, its role as a catalyst or barrier for adsorption of the spodumene collector in flotation is evaluated. The collector studied is the typical sodium oleate. The results show that oleate adsorption is poor and that the few adsorption contacts are mainly via cation ...

Research paper thumbnail of Understanding the flocculation mechanism of quartz and kaolinite with polyacrylamide in seawater: A molecular dynamics approach

Colloids and Surfaces A: Physicochemical and Engineering Aspects

Research paper thumbnail of Enhancing the sedimentation of clay-based tailings in seawater by magnesium removal treatment

Separation and Purification Technology

Research paper thumbnail of Reducing the Magnesium Content from Seawater to Improve Tailing Flocculation: Description by Population Balance Models

Metals

Experimental assays and mathematical models, through population balance models (PBM), were used t... more Experimental assays and mathematical models, through population balance models (PBM), were used to characterize the particle aggregation of mining tailings flocculated in seawater. Three systems were considered for preparation of the slurries: i) Seawater at natural pH (pH 7.4), ii) seawater at pH 11, and iii) treated seawater at pH 11. The treated seawater had a reduced magnesium content in order to avoid the formation of solid complexes, which damage the concentration operations. For this, the pH of seawater was raised with lime before being used in the process—generating solid precipitates of magnesium that were removed by vacuum filtration. The mean size of the aggregates were represented by the mean chord length obtained with the Focused beam reflectance measurement (FBRM) technique, and their descriptions, obtained by the PBM, showed an aggregation and a breakage kernel had evolved. The fractal dimension and permeability were included in the model in order to improve the repre...

Research paper thumbnail of Describing Mining Tailing Flocculation in Seawater by Population Balance Models: Effect of Mixing Intensity

Metals

A population balance model (PBM) is used to describe flocculation of particle tailings in seawate... more A population balance model (PBM) is used to describe flocculation of particle tailings in seawater at pH 8 for a range of mixing intensities. The size of the aggregates is represented by the mean chord length, determined by the focused beam reflectance measurement (FBRM) technique. The PBM follows the dynamics of aggregation and breakage processes underlying flocculation and provides a good approximation to the temporal evolution of aggregate size. The structure of the aggregates during flocculation is described by a constant or time-dependent fractal dimension. The results revealed that the compensations between the aggregation and breakage rates lead to a correct representation of the flocculation kinetics of the tailings of particles in seawater and, in addition, that the representation of the flocculation kinetics in optimal conditions is equally good with a constant or variable fractal dimension. The aggregation and breakage functions and their corresponding parameters are sens...

Research paper thumbnail of Structure of the Interface between Lithium-Rich Spodumene and Saltwater by Density Functional Theory Calculations and Molecular Dynamics Simulations

The Journal of Physical Chemistry C

The surface chemical properties of spodumene, a pyroxene mineral typically found in lithium-rich ... more The surface chemical properties of spodumene, a pyroxene mineral typically found in lithium-rich pegmatites, are key to improve its recovery by means of flotation. Without this information, it is v...

Research paper thumbnail of Molecular dynamics simulations of the conformation and diffusion of partially hydrolyzed polyacrylamide in highly saline solutions

Chemical Engineering Science

Research paper thumbnail of Analysis of the flocculation process of fine tailings particles in saltwater through a population balance model

Separation and Purification Technology

Abstract A population balance model is used to describe the flocculation of tailings particles in... more Abstract A population balance model is used to describe the flocculation of tailings particles in aqueous salt solutions. The synthetic tailings, composed of quartz and kaolin particles, are flocculated in a jar at a constant shear rate where in-situ FBRM determines the size of the aggregates. The model follows the dynamics of aggregation and breakage processes and provides a good approximation to the temporal evolution of aggregate size. The fractal and permeable nature of the aggregates are considered, while the depletion of the collision efficiency allows describing the initial growth of aggregates and subsequent size reduction. The numerical solution requires five parameters, which are obtained by minimizing the difference between experimental size data and model predictions. A specific aim is to study the effect of magnesium hydroxide that is formed at pH ca. 10, and its interaction with flocculant, on the flocculation kinetics parameters. At pH ≥ 10 the aggregates grow less due to the presence of the magnesium hydroxide gel that surrounds quartz, kaolin and flocculant. The fractal dimension is quite stable at pH

Research paper thumbnail of Use of molecular dynamics to study the conformation of an anionic polyelectrolyte in saline medium and its adsorption on a quartz surface

Minerals Engineering

Abstract In seeking to gain insights on the performance of long chain water-soluble polymer flocc... more Abstract In seeking to gain insights on the performance of long chain water-soluble polymer flocculants when conducting mineral processing in highly saline liquors, molecular dynamic simulation was used to study the effect of NaCl concentration on the conformation of an anionic polyelectrolyte and its adsorption on a quartz surface at pH values above its isoelectric point. Increased salinity led to two competing effects on the overall flocculation process: (i) increased polyelectrolyte adsorption on the quartz surface favours the initial aggregate-forming collisions, but (ii) the radius-of-gyration of the polyelectrolyte is reduced, which then may limit the aggregate size achieved. Such results support reported experimental trends and show the advantages of computational methodologies to describe complex systems.

Research paper thumbnail of Ab Initio Calculations of Partial Charges at Kaolinite Edge Sites and Molecular Dynamics Simulations of Cation Adsorption in Saline Solutions at and above the pH of Zero Charge

The Journal of Physical Chemistry C

Research paper thumbnail of Molecular Dynamics Simulations of Quartz (101)–Water and Corundum (001)–Water Interfaces: Effect of Surface Charge and Ions on Cation Adsorption, Water Orientation, and Surface Charge Reversal

The Journal of Physical Chemistry C

Research paper thumbnail of Zeta potential and viscosity of colloidal silica suspensions: Effect of seawater salts, pH, flocculant, and shear rate

Colloids and Surfaces A: Physicochemical and Engineering Aspects

Research paper thumbnail of Generation of Spatially Correlated Network Models of Porous Media

Transport in Porous Media, 2015

A Monte Carlo (MC) algorithm to generate pore networks with spatial correlation of pore sizes is ... more A Monte Carlo (MC) algorithm to generate pore networks with spatial correlation of pore sizes is developed. The algorithm is illustrated for model porous media described as a two-dimensional square lattices of nodes and bonds which represent pore bodies and pore throats, respectively. We seek a spatial rearrangement of pore throats that minimizes the difference between the semivariogram of the network and a given model semivariogram. The spatial correlation of the initially uncorrelated network increases by means of MC moves where the diameters of a pair of randomly chosen pores are interchanged. The algorithm preserves the initial pore size distribution. Finally, the correlated pore throat networks are used to derive correlated pore body networks once a given body-to-throat size ratio is set. A simple parallel implementation of the algorithm is presented.

Research paper thumbnail of Molecular simulation of the adsorption of seawater salts on a negatively charged quartz surface

Research paper thumbnail of Describing the adsorption of sodium tripolyphosphate on kaolinite surfaces in a saline medium by molecular dynamics

Research paper thumbnail of Polyacrylic Acid to Improve Flotation Tailings Management: Understanding the Chemical Interactions through Molecular Dynamics

Metals

Molecular dynamic simulations of polyacrylic acid polyelectrolyte (PAA) analyzed its interaction ... more 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 ex...

Research paper thumbnail of Molecular Dynamics Study of the Conformation, Ion Adsorption, Diffusion and Water Structure of Soluble Polymers in Saline Solutions

Polymers

Polymers have interesting physicochemical characteristics such as charge density, functionalities... more Polymers have interesting physicochemical characteristics such as charge density, functionalities, and molecular weight. Such attributes are of great importance for use in industrial purposes. Understanding how these characteristics are affected is still complex, but with the help of molecular dynamics (MD) and quantum calculations (QM), it is possible to understand the behavior of polymers at the molecular level with great consistency. This study was applied to polymers derived from polyacrylamide (PAM) due to its great use in various industries. The polymers studied include hydrolyzed polyacrylamide (HPAM), poly (2-acrylamido-2-methylpropanesulfonate) (PAMPS), polyacrylic acid (PAA), polyethylene oxide polymer (PEO), and guar gum polysaccharide (GUAR). Each one has different attributes, which help in understanding the effects on the polymer and the medium in which it is applied along a broad spectrum. The results include the conformation, diffusion, ion condensation, the structure...

Research paper thumbnail of Adsorption of Phosphate Ions on the Basal and Edge Surfaces of Kaolinite in Low Salt Aqueous Solutions Using Molecular Dynamics Simulations

Research paper thumbnail of Polyacrylamide adsorption on (1 0 1) quartz surfaces in saltwater for a range of pH values by molecular dynamics simulations

Research paper thumbnail of Improving the Flocculation Performance of Clay-Based Tailings in Seawater: A Population Balance Modelling Approach

Minerals

A population balance model described the flocculation of clay-based mining tailings in treated se... more A population balance model described the flocculation of clay-based mining tailings in treated seawater with reduced magnesium content. For the treatment, 0.06 M of lime was added to the liquor, generating solid magnesium complexes that were subsequently removed by vacuum filtration. Magnesium content varied between 10–1440 ppm when mixing raw seawater with treated seawater. The aggregate size was analysed by the Focused Beam Reflectance Measurement (FBRM) technology. The model follows the dynamics of the aggregation-rupture and it provides a good approximation to the temporal evolution. A decrease in collision efficiency was implemented as an indicator of the polymer depletion, describing the size reduction. Lower magnesium content makes larger aggregates with a higher fractal dimension, but an increase in the concentration of clays reduces both the size of aggregates and the fractal dimension, indicating more open and porous structures, with higher permeability to the passage of f...

Research paper thumbnail of Complexation of Alkali and Alkaline-Earth Metal Cations at Spodumene-Saltwater Interfaces by Molecular Simulation: Impact on Oleate Adsorption

Minerals

Spodumene, a lithium aluminum inosilicate, is recovered by froth flotation using surfactants, so-... more Spodumene, a lithium aluminum inosilicate, is recovered by froth flotation using surfactants, so-called collectors. Therefore, the behavior and properties of the water-mineral interface in saline solutions are central. Here, molecular dynamics simulations are used to study the adsorption of alkali and alkaline-earth metal cations from concentrated solutions on the weakest (110) surface plane of negatively-charged spodumene. Results include the envelope density function of inner-sphere complexes for each cation and the density of complexes according to their adsorption contacts. Visualization of complexes for each cation is also included. Once the structure of the cation layers adsorbed on the surface of spodumene is defined, its role as a catalyst or barrier for adsorption of the spodumene collector in flotation is evaluated. The collector studied is the typical sodium oleate. The results show that oleate adsorption is poor and that the few adsorption contacts are mainly via cation ...

Research paper thumbnail of Understanding the flocculation mechanism of quartz and kaolinite with polyacrylamide in seawater: A molecular dynamics approach

Colloids and Surfaces A: Physicochemical and Engineering Aspects

Research paper thumbnail of Enhancing the sedimentation of clay-based tailings in seawater by magnesium removal treatment

Separation and Purification Technology

Research paper thumbnail of Reducing the Magnesium Content from Seawater to Improve Tailing Flocculation: Description by Population Balance Models

Metals

Experimental assays and mathematical models, through population balance models (PBM), were used t... more Experimental assays and mathematical models, through population balance models (PBM), were used to characterize the particle aggregation of mining tailings flocculated in seawater. Three systems were considered for preparation of the slurries: i) Seawater at natural pH (pH 7.4), ii) seawater at pH 11, and iii) treated seawater at pH 11. The treated seawater had a reduced magnesium content in order to avoid the formation of solid complexes, which damage the concentration operations. For this, the pH of seawater was raised with lime before being used in the process—generating solid precipitates of magnesium that were removed by vacuum filtration. The mean size of the aggregates were represented by the mean chord length obtained with the Focused beam reflectance measurement (FBRM) technique, and their descriptions, obtained by the PBM, showed an aggregation and a breakage kernel had evolved. The fractal dimension and permeability were included in the model in order to improve the repre...

Research paper thumbnail of Describing Mining Tailing Flocculation in Seawater by Population Balance Models: Effect of Mixing Intensity

Metals

A population balance model (PBM) is used to describe flocculation of particle tailings in seawate... more A population balance model (PBM) is used to describe flocculation of particle tailings in seawater at pH 8 for a range of mixing intensities. The size of the aggregates is represented by the mean chord length, determined by the focused beam reflectance measurement (FBRM) technique. The PBM follows the dynamics of aggregation and breakage processes underlying flocculation and provides a good approximation to the temporal evolution of aggregate size. The structure of the aggregates during flocculation is described by a constant or time-dependent fractal dimension. The results revealed that the compensations between the aggregation and breakage rates lead to a correct representation of the flocculation kinetics of the tailings of particles in seawater and, in addition, that the representation of the flocculation kinetics in optimal conditions is equally good with a constant or variable fractal dimension. The aggregation and breakage functions and their corresponding parameters are sens...

Research paper thumbnail of Structure of the Interface between Lithium-Rich Spodumene and Saltwater by Density Functional Theory Calculations and Molecular Dynamics Simulations

The Journal of Physical Chemistry C

The surface chemical properties of spodumene, a pyroxene mineral typically found in lithium-rich ... more The surface chemical properties of spodumene, a pyroxene mineral typically found in lithium-rich pegmatites, are key to improve its recovery by means of flotation. Without this information, it is v...

Research paper thumbnail of Molecular dynamics simulations of the conformation and diffusion of partially hydrolyzed polyacrylamide in highly saline solutions

Chemical Engineering Science

Research paper thumbnail of Analysis of the flocculation process of fine tailings particles in saltwater through a population balance model

Separation and Purification Technology

Abstract A population balance model is used to describe the flocculation of tailings particles in... more Abstract A population balance model is used to describe the flocculation of tailings particles in aqueous salt solutions. The synthetic tailings, composed of quartz and kaolin particles, are flocculated in a jar at a constant shear rate where in-situ FBRM determines the size of the aggregates. The model follows the dynamics of aggregation and breakage processes and provides a good approximation to the temporal evolution of aggregate size. The fractal and permeable nature of the aggregates are considered, while the depletion of the collision efficiency allows describing the initial growth of aggregates and subsequent size reduction. The numerical solution requires five parameters, which are obtained by minimizing the difference between experimental size data and model predictions. A specific aim is to study the effect of magnesium hydroxide that is formed at pH ca. 10, and its interaction with flocculant, on the flocculation kinetics parameters. At pH ≥ 10 the aggregates grow less due to the presence of the magnesium hydroxide gel that surrounds quartz, kaolin and flocculant. The fractal dimension is quite stable at pH

Research paper thumbnail of Use of molecular dynamics to study the conformation of an anionic polyelectrolyte in saline medium and its adsorption on a quartz surface

Minerals Engineering

Abstract In seeking to gain insights on the performance of long chain water-soluble polymer flocc... more Abstract In seeking to gain insights on the performance of long chain water-soluble polymer flocculants when conducting mineral processing in highly saline liquors, molecular dynamic simulation was used to study the effect of NaCl concentration on the conformation of an anionic polyelectrolyte and its adsorption on a quartz surface at pH values above its isoelectric point. Increased salinity led to two competing effects on the overall flocculation process: (i) increased polyelectrolyte adsorption on the quartz surface favours the initial aggregate-forming collisions, but (ii) the radius-of-gyration of the polyelectrolyte is reduced, which then may limit the aggregate size achieved. Such results support reported experimental trends and show the advantages of computational methodologies to describe complex systems.

Research paper thumbnail of Ab Initio Calculations of Partial Charges at Kaolinite Edge Sites and Molecular Dynamics Simulations of Cation Adsorption in Saline Solutions at and above the pH of Zero Charge

The Journal of Physical Chemistry C

Research paper thumbnail of Molecular Dynamics Simulations of Quartz (101)–Water and Corundum (001)–Water Interfaces: Effect of Surface Charge and Ions on Cation Adsorption, Water Orientation, and Surface Charge Reversal

The Journal of Physical Chemistry C

Research paper thumbnail of Zeta potential and viscosity of colloidal silica suspensions: Effect of seawater salts, pH, flocculant, and shear rate

Colloids and Surfaces A: Physicochemical and Engineering Aspects

Research paper thumbnail of Generation of Spatially Correlated Network Models of Porous Media

Transport in Porous Media, 2015

A Monte Carlo (MC) algorithm to generate pore networks with spatial correlation of pore sizes is ... more A Monte Carlo (MC) algorithm to generate pore networks with spatial correlation of pore sizes is developed. The algorithm is illustrated for model porous media described as a two-dimensional square lattices of nodes and bonds which represent pore bodies and pore throats, respectively. We seek a spatial rearrangement of pore throats that minimizes the difference between the semivariogram of the network and a given model semivariogram. The spatial correlation of the initially uncorrelated network increases by means of MC moves where the diameters of a pair of randomly chosen pores are interchanged. The algorithm preserves the initial pore size distribution. Finally, the correlated pore throat networks are used to derive correlated pore body networks once a given body-to-throat size ratio is set. A simple parallel implementation of the algorithm is presented.