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Dr. Gonzalo Quezada
Universidad de Concepción

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0 Minerals
0 Surface Chemistry
0 Viscoelasticity
0 Seawater
0 molecular dynamics simulation

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Journal article
Published: 21 June 2021 in Metals
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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 COONa+ 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.

ACS Style

Gonzalo Quezada; Eder Piceros; Pedro Robles; Carlos Moraga; Edelmira Gálvez; Steven Nieto; Ricardo Jeldres. Polyacrylic Acid to Improve Flotation Tailings Management: Understanding the Chemical Interactions through Molecular Dynamics. Metals 2021, 11, 987 .

AMA Style

Gonzalo Quezada, Eder Piceros, Pedro Robles, Carlos Moraga, Edelmira Gálvez, Steven Nieto, Ricardo Jeldres. Polyacrylic Acid to Improve Flotation Tailings Management: Understanding the Chemical Interactions through Molecular Dynamics. Metals. 2021; 11 (6):987.

Chicago/Turabian Style

Gonzalo Quezada; Eder Piceros; Pedro Robles; Carlos Moraga; Edelmira Gálvez; Steven Nieto; Ricardo Jeldres. 2021. "Polyacrylic Acid to Improve Flotation Tailings Management: Understanding the Chemical Interactions through Molecular Dynamics." Metals 11, no. 6: 987.

Journal article
Published: 29 December 2020 in Minerals Engineering
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The adsorption of partially hydrolyzed polyacrylamide (HPAM) on quartz plays a key role in solid-liquid separation processes that seek to recover water for processing. In this work, computational molecular dynamics is used to study the water-quartz interface in the presence of HPAM under conditions of high salt and wide pH range. The salts used are mostly those of seawater. Small water-structure maker cations are preferentially adsorbed onto the polymer rather than onto the quartz surfaces. In freshwater, the adsorption of HPAM on quartz is reduced to very few contacts, however in saltwater the adsorption contacts of HPAM increase although decrease with surface charge, mainly due to electrostatic repulsion. In the presence of monovalent cations and for any surface charge on the quartz, above the isoelectric point, the adsorption contacts of HPAM decreases as the cation size increases, which is expected considering that smaller cations are more effective in neutralizing both quartz and HPAM. The results show that the adsorption of HPAM occurs exclusively via salt bridges. One way of describing the conformation of an HPAM chain adsorbed onto quartz is to reduce it to the skeleton of carbon atoms of the polymer chain and then determine the fraction of these atoms in loops, trains, and tails. In general, the adsorption contacts of HPAM are few, the carbon fractions in trains and loops are tiny, and therefore most of the carbon atoms in HPAM remain in long tails ready to get entangled with other tails thus favoring the flocculation process. The results are expected to contribute to sustainable water management through the right choice of flocculant based on molecular aspects.

ACS Style

Gonzalo R. Quezada; Roberto E. Rozas; Pedro G. Toledo. Polyacrylamide adsorption on (1 0 1) quartz surfaces in saltwater for a range of pH values by molecular dynamics simulations. Minerals Engineering 2020, 162, 106741 .

AMA Style

Gonzalo R. Quezada, Roberto E. Rozas, Pedro G. Toledo. Polyacrylamide adsorption on (1 0 1) quartz surfaces in saltwater for a range of pH values by molecular dynamics simulations. Minerals Engineering. 2020; 162 ():106741.

Chicago/Turabian Style

Gonzalo R. Quezada; Roberto E. Rozas; Pedro G. Toledo. 2020. "Polyacrylamide adsorption on (1 0 1) quartz surfaces in saltwater for a range of pH values by molecular dynamics simulations." Minerals Engineering 162, no. : 106741.

Journal article
Published: 24 December 2020 in Minerals
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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 bridges. The findings here indicate that molecular simulation can facilitate the search for effective collectors for environmentally sustainable spodumene flotation processes in saltwater.

ACS Style

Gonzalo R. Quezada; Pedro G. Toledo. Complexation of Alkali and Alkaline-Earth Metal Cations at Spodumene-Saltwater Interfaces by Molecular Simulation: Impact on Oleate Adsorption. Minerals 2020, 11, 12 .

AMA Style

Gonzalo R. Quezada, Pedro G. Toledo. Complexation of Alkali and Alkaline-Earth Metal Cations at Spodumene-Saltwater Interfaces by Molecular Simulation: Impact on Oleate Adsorption. Minerals. 2020; 11 (1):12.

Chicago/Turabian Style

Gonzalo R. Quezada; Pedro G. Toledo. 2020. "Complexation of Alkali and Alkaline-Earth Metal Cations at Spodumene-Saltwater Interfaces by Molecular Simulation: Impact on Oleate Adsorption." Minerals 11, no. 1: 12.

Journal article
Published: 20 September 2020 in Colloids and Surfaces A: Physicochemical and Engineering Aspects
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The scarcity of water resources for mining activities drives the search for new low-quality water sources such as well-water and seawater. Seawater was found to be a promising alternative, but it may pose significant operational challenges, for example, when it needs to be recovered from the tailings in thickening stages for subsequent recycling. This is mainly explained by the high saline environment and colloidal magnesium precipitates that are generated at highly alkaline conditions. In this work, we use molecular dynamics (MD) simulations to understand the affinity of the flocculant with colloidal magnesium precipitates and the main minerals that make up a mining tailing such as quartz and kaolinite. The results are contrasted with the in-situ characterization of aggregates through the Focused Beam Reflectance Measurement (FBRM). Through X-ray diffraction, it was found that the magnesium precipitates are mainly composed of brucite crystals. The MD results allowed to explain the experimental results, mainly when solid magnesium precipitates appear at high pH, where the flocculant loses its effectiveness sharply. This is related to the undesired association among the flocculant with brucite. The adsorption is mainly carried out by the interaction between the deprotonated oxygen from the acrylic group of the polymer and the oxygen from the hydroxide of the brucite surface. There is also a significant contribution of hydrogen bonding between nitrogen from the acrylamide group and oxygen from the hydroxide.

ACS Style

Gonzalo R. Quezada; Matías Jeldres; Norman Toro; Pedro Robles; Pedro G. Toledo; Ricardo I. Jeldres. Understanding the flocculation mechanism of quartz and kaolinite with polyacrylamide in seawater: A molecular dynamics approach. Colloids and Surfaces A: Physicochemical and Engineering Aspects 2020, 608, 125576 .

AMA Style

Gonzalo R. Quezada, Matías Jeldres, Norman Toro, Pedro Robles, Pedro G. Toledo, Ricardo I. Jeldres. Understanding the flocculation mechanism of quartz and kaolinite with polyacrylamide in seawater: A molecular dynamics approach. Colloids and Surfaces A: Physicochemical and Engineering Aspects. 2020; 608 ():125576.

Chicago/Turabian Style

Gonzalo R. Quezada; Matías Jeldres; Norman Toro; Pedro Robles; Pedro G. Toledo; Ricardo I. Jeldres. 2020. "Understanding the flocculation mechanism of quartz and kaolinite with polyacrylamide in seawater: A molecular dynamics approach." Colloids and Surfaces A: Physicochemical and Engineering Aspects 608, no. : 125576.

Journal article
Published: 04 September 2020 in Minerals
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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 fluid. The model efficiently illustrates the experimental data, with R-square (R2) greater than 0.9 and Goodness of Fit (GoF) greater than 95% in most cases, wherein the fitting parameters allowed for analysing the impact of magnesium and clays on the collision efficiency, collision frequency, and fragmentation rate. The model is predictive with few parameters, and it is potentially a powerful tool for water management optimisation.

ACS Style

Gonzalo R. Quezada; Matías Jeldres; Pedro Robles; Norman Toro; David Torres; Ricardo I. Jeldres. Improving the Flocculation Performance of Clay-Based Tailings in Seawater: A Population Balance Modelling Approach. Minerals 2020, 10, 782 .

AMA Style

Gonzalo R. Quezada, Matías Jeldres, Pedro Robles, Norman Toro, David Torres, Ricardo I. Jeldres. Improving the Flocculation Performance of Clay-Based Tailings in Seawater: A Population Balance Modelling Approach. Minerals. 2020; 10 (9):782.

Chicago/Turabian Style

Gonzalo R. Quezada; Matías Jeldres; Pedro Robles; Norman Toro; David Torres; Ricardo I. Jeldres. 2020. "Improving the Flocculation Performance of Clay-Based Tailings in Seawater: A Population Balance Modelling Approach." Minerals 10, no. 9: 782.

Journal article
Published: 02 March 2020 in Metals
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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 representation of the irregular structure of the aggregates. Then, five parameters were optimized: Three for the aggregation kernel and two for the breakage kernel. The results show that raising the pH from 8 to 11 was severely detrimental to the flocculation performance. Nevertheless, for pH 11, the aggregates slightly exceeded 100 µm, causing undesirable behaviour during the thickening operations. Interestingly, magnesium removal provided a suitable environment to perform the tailings flocculation at alkaline pH, making aggregates with sizes that exceeded 300 µm. Only the fractal dimension changed between pH 8 and treated seawater at pH 11—as reflected in the permeability outcomes. The PBM fitted well with the experimental data, and the parameters showed that the aggregation kernel was dominant at all-polymer dosages. The descriptive capacity of the model might have been utilized as a support in practical decisions regarding the best-operating requirements in the flocculation of copper tailings and water clarification.

ACS Style

Gonzalo R. Quezada; Matías Jeldres; Norman Toro; Pedro Robles; Ricardo I. Jeldres. Reducing the Magnesium Content from Seawater to Improve Tailing Flocculation: Description by Population Balance Models. Metals 2020, 10, 329 .

AMA Style

Gonzalo R. Quezada, Matías Jeldres, Norman Toro, Pedro Robles, Ricardo I. Jeldres. Reducing the Magnesium Content from Seawater to Improve Tailing Flocculation: Description by Population Balance Models. Metals. 2020; 10 (3):329.

Chicago/Turabian Style

Gonzalo R. Quezada; Matías Jeldres; Norman Toro; Pedro Robles; Ricardo I. Jeldres. 2020. "Reducing the Magnesium Content from Seawater to Improve Tailing Flocculation: Description by Population Balance Models." Metals 10, no. 3: 329.

Journal article
Published: 25 February 2020 in Separation and Purification Technology
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The pH of the seawater was raised with lime before it was used into the process, generating solid precipitates of magnesium that were removed by vacuum filtration. Then this treated seawater was applied to improve the flocculation of clay-based tailings in a highly alkaline environment (pH 11). Tailings settling assays were conducted by using a PTFE 30 mm turbine type stirrer with an in-situ floc size characterisation utilising the Focused Beam Reflectance Measurement (FBRM) and Particle Vision Measurement (PVM) techniques. After mixing the pulp with the flocculant, the sample was settled, registering the evolution of the mudline and turbidity of the supernatant liquid. When operating with direct seawater at pH 11, magnesium complexes arise that impairs the flocculant performance. The polymer loses selectivity for the particles, causing weak aggregation and low settling rates. However, by diminishing the magnesium content before the seawater is incorporated into the process, the flocculant was able to bridge the particles and achieve a promising flocculation response. Microscopic characterisation of aggregates showed that these were larger and denser, improving the sedimentation rates considerably. The proposed research provides a new strategy to advance in tailings management issues for the mining industry, focusing on plants that use seawater in their operations.

ACS Style

Matías Jeldres; Eder C. Piceros; Norman Toro; Pedro Robles; Steven Nieto; Gonzalo R. Quezada; Ricardo I. Jeldres. Enhancing the sedimentation of clay-based tailings in seawater by magnesium removal treatment. Separation and Purification Technology 2020, 242, 116762 .

AMA Style

Matías Jeldres, Eder C. Piceros, Norman Toro, Pedro Robles, Steven Nieto, Gonzalo R. Quezada, Ricardo I. Jeldres. Enhancing the sedimentation of clay-based tailings in seawater by magnesium removal treatment. Separation and Purification Technology. 2020; 242 ():116762.

Chicago/Turabian Style

Matías Jeldres; Eder C. Piceros; Norman Toro; Pedro Robles; Steven Nieto; Gonzalo R. Quezada; Ricardo I. Jeldres. 2020. "Enhancing the sedimentation of clay-based tailings in seawater by magnesium removal treatment." Separation and Purification Technology 242, no. : 116762.

Journal article
Published: 11 February 2020 in Metals
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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 sensitive to the choice of the fractal dimension of the aggregates, whether constant or time dependent, however, under optimal conditions, a constant fractal dimension is sufficient. The model is robust and predictive with a few parameters and can be used to find the optimal flocculation conditions at different mixing intensities, and the optimal flocculation time can be used for a cost-effective evaluation of the quality of the flocculant used.

ACS Style

Gonzalo R. Quezada; Luís Ayala; Williams H. Leiva; Norman Toro; Pedro G. Toledo; Pedro Robles; Ricardo I. Jeldres. Describing Mining Tailing Flocculation in Seawater by Population Balance Models: Effect of Mixing Intensity. Metals 2020, 10, 240 .

AMA Style

Gonzalo R. Quezada, Luís Ayala, Williams H. Leiva, Norman Toro, Pedro G. Toledo, Pedro Robles, Ricardo I. Jeldres. Describing Mining Tailing Flocculation in Seawater by Population Balance Models: Effect of Mixing Intensity. Metals. 2020; 10 (2):240.

Chicago/Turabian Style

Gonzalo R. Quezada; Luís Ayala; Williams H. Leiva; Norman Toro; Pedro G. Toledo; Pedro Robles; Ricardo I. Jeldres. 2020. "Describing Mining Tailing Flocculation in Seawater by Population Balance Models: Effect of Mixing Intensity." Metals 10, no. 2: 240.

Research article
Published: 20 December 2019 in The Journal of Physical Chemistry C
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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 very difficult to find a collector that prefers the spodumene surface over that of associated aluminosilicates. The crystal structure of spodumene includes chains of Si-centered tetrahedra and Al-centered octahedra, with Li occupying cavities between the polyhedra. In this work, DFT calculations are used for a small group of atoms of the mineral crystal to determine the termination of the (110) surface, the weakest plane, and then to determine the most energy-favorable deprotonation reaction. The excess charge generated by the removal of one hydrogen in the deprotonation reaction is distributed over the surface atoms of the spodumene cluster. Then, molecular dynamics simulations are used to study the adsorption of water and alkali and alkaline earth metal cations from concentrated solutions on the surface (110) of a large slab of spodumene, both neutral and negatively charged. Results include density profiles of adsorbed cations, orientation profiles of water molecules close to the mineral surface for different cations, and the distance at which the mineral surface becomes neutral or reverses the charge. The new results on the surface chemistry of spodumene should allow reinterpretation of available data from spodumene flotation.

ACS Style

Gonzalo Renato Quezada; Pedro G. Toledo. 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 2019, 124, 1446 -1457.

AMA Style

Gonzalo Renato Quezada, Pedro G. Toledo. 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. 2019; 124 (2):1446-1457.

Chicago/Turabian Style

Gonzalo Renato Quezada; Pedro G. Toledo. 2019. "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 124, no. 2: 1446-1457.

Journal article
Published: 20 November 2019 in Chemical Engineering Science
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The impact of salts on partially hydrolyzed polyacrylamide (HPAM) is of great interest in mineral processing, considering that the use of seawater seems to be the only sustainable solution in regions with severe aridity. Here the conformation and transport of an HPAM chain in several saline solutions are studied by means of molecular dynamics simulations. Results indicate that the electrostatic repulsion between anionic acrylate units causes the polymer to adopt diverse and complex expanded tertiary conformations, however in the presence of cations this repulsion is shielded causing the polymer to fold into balled-up conformations. The structure assumed by the HPAM chain depends slightly on the type of cation and much on intramolecular crosslinking. Cations influence the ordering of water structure and orientation of water dipoles reducing the mobility of water, ions, and HPAM. These results are expected to contribute to a better understanding of particle flocculation for sustainable water management.

ACS Style

Gonzalo R. Quezada; Jorge H. Saavedra; Roberto E. Rozas; Pedro G. Toledo. Molecular dynamics simulations of the conformation and diffusion of partially hydrolyzed polyacrylamide in highly saline solutions. Chemical Engineering Science 2019, 214, 115366 .

AMA Style

Gonzalo R. Quezada, Jorge H. Saavedra, Roberto E. Rozas, Pedro G. Toledo. Molecular dynamics simulations of the conformation and diffusion of partially hydrolyzed polyacrylamide in highly saline solutions. Chemical Engineering Science. 2019; 214 ():115366.

Chicago/Turabian Style

Gonzalo R. Quezada; Jorge H. Saavedra; Roberto E. Rozas; Pedro G. Toledo. 2019. "Molecular dynamics simulations of the conformation and diffusion of partially hydrolyzed polyacrylamide in highly saline solutions." Chemical Engineering Science 214, no. : 115366.

Journal article
Published: 17 November 2019 in Separation and Purification Technology
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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 < 10 with a representative value of 2.7, typical of a clustered network, although in the presence of magnesium at pH ≥ 10 the fractal dimension of the aggregates is only 2.2, typical of Gaussian chains. Tailings aggregates in the presence of hydroxide are smaller and weakly three-dimensional and therefore contribute little to the settling velocity. The aggregation and breakage parameters are largely constant for a particulate system which composition remains unchanged over a pH range, and if the composition changes, for example by precipitation of magnesium hydroxide, then the aggregation parameters are different but close to constant.

ACS Style

Gonzalo R. Quezada; Jahir Ramos; Ricardo I. Jeldres; Pedro Robles; Pedro G. Toledo. Analysis of the flocculation process of fine tailings particles in saltwater through a population balance model. Separation and Purification Technology 2019, 237, 116319 .

AMA Style

Gonzalo R. Quezada, Jahir Ramos, Ricardo I. Jeldres, Pedro Robles, Pedro G. Toledo. Analysis of the flocculation process of fine tailings particles in saltwater through a population balance model. Separation and Purification Technology. 2019; 237 ():116319.

Chicago/Turabian Style

Gonzalo R. Quezada; Jahir Ramos; Ricardo I. Jeldres; Pedro Robles; Pedro G. Toledo. 2019. "Analysis of the flocculation process of fine tailings particles in saltwater through a population balance model." Separation and Purification Technology 237, no. : 116319.

Journal article
Published: 07 November 2019 in Metals
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Multivariate analytical models are quite successful in explaining one or more response variables, based on one or more independent variables. However, they do not reflect the connections of conditional dependence between the variables that explain the model. Otherwise, due to their qualitative and quantitative nature, Bayesian networks allow us to easily visualize the probabilistic relationships between variables of interest, as well as make inferences as a prediction of specific evidence (partial or impartial), diagnosis and decision-making. The current work develops stochastic modeling of the leaching phase in piles by generating a Bayesian network that describes the ore recovery with independent variables, after analyzing the uncertainty of the response to the sensitization of the input variables. These models allow us to recognize the relations of dependence and causality between the sampled variables and can estimate the output against the lack of evidence. The network setting shows that the variables that have the most significant impact on recovery are the time, the heap height and the superficial velocity of the leaching flow, while the validation is given by the low measurements of the error statistics and the normality test of residuals. Finally, probabilistic networks are unique tools to determine and internalize the risk or uncertainty present in the input variables, due to their ability to generate estimates of recovery based upon partial knowledge of the operational variables.

ACS Style

Manuel Saldaña; Javier González; Ricardo I. Jeldres; Ángelo Villegas; Jonathan Castillo; Gonzalo Quezada; Norman Toro. A Stochastic Model Approach for Copper Heap Leaching through Bayesian Networks. Metals 2019, 9, 1198 .

AMA Style

Manuel Saldaña, Javier González, Ricardo I. Jeldres, Ángelo Villegas, Jonathan Castillo, Gonzalo Quezada, Norman Toro. A Stochastic Model Approach for Copper Heap Leaching through Bayesian Networks. Metals. 2019; 9 (11):1198.

Chicago/Turabian Style

Manuel Saldaña; Javier González; Ricardo I. Jeldres; Ángelo Villegas; Jonathan Castillo; Gonzalo Quezada; Norman Toro. 2019. "A Stochastic Model Approach for Copper Heap Leaching through Bayesian Networks." Metals 9, no. 11: 1198.

Journal article
Published: 26 August 2019 in The Journal of Physical Chemistry C
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ACS Style

Gonzalo R. Quezada; Roberto E. Rozas; Pedro G. Toledo. 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 2019, 123, 22971 -22980.

AMA Style

Gonzalo R. Quezada, Roberto E. Rozas, Pedro G. Toledo. 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. 2019; 123 (37):22971-22980.

Chicago/Turabian Style

Gonzalo R. Quezada; Roberto E. Rozas; Pedro G. Toledo. 2019. "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 123, no. 37: 22971-22980.

Journal article
Published: 04 April 2019 in Minerals
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The effect of alkali metal chlorides on the viscoelastic behavior and yielding properties of silica suspensions was studied through creep-recovery and dynamic oscillatory tests with stress control. Then, the viscoelasticity of the pulps was correlated with the silica zeta potential, aggregate size, and the percentage of cations adsorbed on the surface of the ore. The results indicate that larger cations are more prone to adhere to the silica surface, which increases the number of ionic bonds that bind the particles. This generates stronger particle networks and a greater agglomeration of particles, especially those smaller than 10 µm. As the size of the bare cations increases, the rheological response provides higher values of yield stress, complex viscosity, and viscoelastic moduli, but in turn, pulps undergo minor deformations under the application of stress. Dynamic oscillatory tests suggest structural changes, with the phase angle following the inverse relationship with the bare cation size, indicating that the liquid-like character of the pulps increases as the size of the cations increases.

ACS Style

Ricardo I. Jeldres; Eder C. Piceros; Williams H. Leiva; Pedro G. Toledo; Gonzalo R. Quezada; Pedro A. Robles; Julio Valenzuela. Analysis of Silica Pulp Viscoelasticity in Saline Media: The Effect of Cation Size. Minerals 2019, 9, 216 .

AMA Style

Ricardo I. Jeldres, Eder C. Piceros, Williams H. Leiva, Pedro G. Toledo, Gonzalo R. Quezada, Pedro A. Robles, Julio Valenzuela. Analysis of Silica Pulp Viscoelasticity in Saline Media: The Effect of Cation Size. Minerals. 2019; 9 (4):216.

Chicago/Turabian Style

Ricardo I. Jeldres; Eder C. Piceros; Williams H. Leiva; Pedro G. Toledo; Gonzalo R. Quezada; Pedro A. Robles; Julio Valenzuela. 2019. "Analysis of Silica Pulp Viscoelasticity in Saline Media: The Effect of Cation Size." Minerals 9, no. 4: 216.

Short communication
Published: 03 October 2018 in Minerals Engineering
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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.

ACS Style

Gonzalo R. Quezada; Ricardo I. Jeldres; Phillip D. Fawell; Pedro G. Toledo. Use of molecular dynamics to study the conformation of an anionic polyelectrolyte in saline medium and its adsorption on a quartz surface. Minerals Engineering 2018, 129, 102 -105.

AMA Style

Gonzalo R. Quezada, Ricardo I. Jeldres, Phillip D. Fawell, Pedro G. Toledo. Use of molecular dynamics to study the conformation of an anionic polyelectrolyte in saline medium and its adsorption on a quartz surface. Minerals Engineering. 2018; 129 ():102-105.

Chicago/Turabian Style

Gonzalo R. Quezada; Ricardo I. Jeldres; Phillip D. Fawell; Pedro G. Toledo. 2018. "Use of molecular dynamics to study the conformation of an anionic polyelectrolyte in saline medium and its adsorption on a quartz surface." Minerals Engineering 129, no. : 102-105.

Journal article
Published: 01 February 2018 in Colloids and Surfaces A: Physicochemical and Engineering Aspects
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ACS Style

Cristian P. Romero; Ricardo I. Jeldres; Gonzalo R. Quezada; Fernando Concha; Pedro G. Toledo. 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 2018, 538, 210 -218.

AMA Style

Cristian P. Romero, Ricardo I. Jeldres, Gonzalo R. Quezada, Fernando Concha, Pedro G. Toledo. 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. 2018; 538 ():210-218.

Chicago/Turabian Style

Cristian P. Romero; Ricardo I. Jeldres; Gonzalo R. Quezada; Fernando Concha; Pedro G. Toledo. 2018. "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 538, no. : 210-218.

Research article
Published: 03 November 2017 in The Journal of Physical Chemistry C
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Quartz and corundum surfaces in water are capable of adsorbing and releasing protons, a behavior attributed to the amphoteric character of their silanol and ab initio calculations are used to obtain different charge densities on crystalline (101) quartz and (001) corundum surfaces and the corresponding charge delocalization after deprotonation of the silanol and aluminol groups, respectively. Then, classical molecular dynamics simulations are used to study the interaction of water with the charged quartz and corundum surfaces in the presence of aqueous solutions of monovalent alkali and alkaline-earth metal chlorides. Results include density profiles of adsorbed cations, and the effect of cations on the orientation profiles of water molecules close to the mineral surfaces and the distance at which such surfaces become neutral or reverse their charges. In all cases where there are experimental or simulation data, the results here compare very well. The adsorption density of cations on quartz increases with the size of the cations, either monovalent or divalent. The density of adsorbed monovalent cations on corundum decreases for larger cation sizes, while this behavior on quartz is the opposite. In both cases the adsorption of cations is enhanced by the increase of the surface charge. Adsorption on corundum is much more extensive compared to that on quartz for all surface charges and cations. The sequence of simulations of cation adsorption on silica and alumina provide support to the idea that high isoelectric point materials preferentially adsorb well-hydrated cations and low isoelectric point materials preferentially adsorb poorly hydrated cations. The results of this work are expected to contribute to improving current knowledge on the interaction of mineral oxides with macromolecules, such as polyelectrolytes in solid–liquid separation processes and biomolecules in lung inflammatory processes.

ACS Style

Gonzalo R. Quezada; Roberto E. Rozas; Pedro G. Toledo. 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 2017, 121, 25271 -25282.

AMA Style

Gonzalo R. Quezada, Roberto E. Rozas, Pedro G. Toledo. 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. 2017; 121 (45):25271-25282.

Chicago/Turabian Style

Gonzalo R. Quezada; Roberto E. Rozas; Pedro G. Toledo. 2017. "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 121, no. 45: 25271-25282.

Journal article
Published: 01 August 2017 in Minerals Engineering
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ACS Style

Gonzalo Quezada; Ricardo I. Jeldres; Christian Goñi; Pedro G. Toledo; Anthony D. Stickland; Peter J. Scales. Viscoelastic behaviour of flocculated silica sediments in concentrated monovalent chloride salt solutions. Minerals Engineering 2017, 110, 131 -138.

AMA Style

Gonzalo Quezada, Ricardo I. Jeldres, Christian Goñi, Pedro G. Toledo, Anthony D. Stickland, Peter J. Scales. Viscoelastic behaviour of flocculated silica sediments in concentrated monovalent chloride salt solutions. Minerals Engineering. 2017; 110 ():131-138.

Chicago/Turabian Style

Gonzalo Quezada; Ricardo I. Jeldres; Christian Goñi; Pedro G. Toledo; Anthony D. Stickland; Peter J. Scales. 2017. "Viscoelastic behaviour of flocculated silica sediments in concentrated monovalent chloride salt solutions." Minerals Engineering 110, no. : 131-138.

Journal article
Published: 23 November 2015 in Transport in Porous Media
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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.

ACS Style

Gonzalo R. Quezada; P. G. Toledo; Jorge H Saavedra; R. E. Rozas. Generation of Spatially Correlated Network Models of Porous Media. Transport in Porous Media 2015, 111, 499 -515.

AMA Style

Gonzalo R. Quezada, P. G. Toledo, Jorge H Saavedra, R. E. Rozas. Generation of Spatially Correlated Network Models of Porous Media. Transport in Porous Media. 2015; 111 (2):499-515.

Chicago/Turabian Style

Gonzalo R. Quezada; P. G. Toledo; Jorge H Saavedra; R. E. Rozas. 2015. "Generation of Spatially Correlated Network Models of Porous Media." Transport in Porous Media 111, no. 2: 499-515.