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A simple criterion is proposed to quantitatively estimate the resistance of aggregates based on incremental mechanical shear disturbances. Aggregate strength can be affected by the hydrodynamic conditions under which flocculation occurs; therefore, an experimental method is standardized to determine the resistance of aggregate structures that are formed under defined conditions of salinity (NaCl 0–0.1 M), mixing time (3 min), and mean shear rate (G = 273 s−1). Kaolin particles were flocculated in saline solutions with an anionic flocculant of high molecular weight. The method involves increasing the mean shear rate (G = 0–1516 s−1). Each increment represents a new experiment that starts from the base of 273 s−1. Target aggregates are increasingly fragmented as mechanical disturbance increases. The monotonic relationship between the mean shear rate increments (ΔG) and the final size of the aggregates is used for a quantitative estimate of the resistance of the target aggregates since this resistance underlies this relationship. The evolution of aggregate size is analyzed by the Focused Beam Reflectance Measurement (FBRM) method, which may capture the chord length distribution on concentrated slurries. To estimate and compare the resistance of the target aggregates in solutions with different salinities, a pseudo-first-order model that describes the rupture degree as a function of shear rate increments obtains the characteristic shear rate. The rupture percentage is reached with considerably lower agitation increments at higher salinity than at low salinity. This criterion is expected to help improve the efficiency of solid–liquid separation processes, especially in plants operating with seawater, be it raw or partially desalinated.
Matías Jeldres; Luis Ayala; Pedro Robles; Edelmira Gálvez; Williams Leiva; Pedro Toledo; Ricardo Jeldres. A Criterion for Estimating the Strength of Flocculated Aggregates in Salt Solutions. Minerals 2021, 11, 713 .
AMA StyleMatías Jeldres, Luis Ayala, Pedro Robles, Edelmira Gálvez, Williams Leiva, Pedro Toledo, Ricardo Jeldres. A Criterion for Estimating the Strength of Flocculated Aggregates in Salt Solutions. Minerals. 2021; 11 (7):713.
Chicago/Turabian StyleMatías Jeldres; Luis Ayala; Pedro Robles; Edelmira Gálvez; Williams Leiva; Pedro Toledo; Ricardo Jeldres. 2021. "A Criterion for Estimating the Strength of Flocculated Aggregates in Salt Solutions." Minerals 11, no. 7: 713.
The objective of this work was to study the effect of muscovite and biotite on the flotation of chalcopyrite and molybdenite in seawater, and the use of sodium hexametaphosphate and sodium silicate to improve copper and molybdenum recoveries. The impact of the inorganic dispersants on the settling properties of the resulting flotation tailings was also studied. It was found that muscovite and biotite depress the flotation of chalcopyrite and molybdenite in seawater, with this depressing effect being stronger at pH 11 than at pH 9. Sodium hexametaphosphate and sodium silicate increased the recoveries of copper and molybdenum in seawater. These dispersants render the mineral particles more negatively charged and remove the hydroxy-complexes of magnesium and calcium from the mineral particles causing dispersion of the slimes. The settling rates of the flotation tailings slightly decrease when sodium hexametaphosphate and sodium silicate were added in the flotation stage. The presence of ultrafine particles dispersed by the action of the inorganic dispersants negatively impacted the flocculation and sedimentation processes leading to high flocculant consumption, low settling rates and high turbidity of the supernatant.
Rodrigo Yepsen; Joaquín Roa; Pedro Toledo; Leopoldo Gutiérrez. Chalcopyrite and Molybdenite Flotation in Seawater: The Use of Inorganic Dispersants to Reduce the Depressing Effects of Micas. Minerals 2021, 11, 539 .
AMA StyleRodrigo Yepsen, Joaquín Roa, Pedro Toledo, Leopoldo Gutiérrez. Chalcopyrite and Molybdenite Flotation in Seawater: The Use of Inorganic Dispersants to Reduce the Depressing Effects of Micas. Minerals. 2021; 11 (5):539.
Chicago/Turabian StyleRodrigo Yepsen; Joaquín Roa; Pedro Toledo; Leopoldo Gutiérrez. 2021. "Chalcopyrite and Molybdenite Flotation in Seawater: The Use of Inorganic Dispersants to Reduce the Depressing Effects of Micas." Minerals 11, no. 5: 539.
The crystal growth kinetics and interfacial properties of titanium (Ti) are studied using molecular dynamics computer simulation. The interactions between the Ti atoms are modeled via an embedded atom method potential. First, the free solidification method (FSM) is used to determine the melting temperature Tm at zero pressure where the transition from liquid to body-centered cubic crystal occurs. From the simulations with the FSM, the kinetic growth coefficients are also determined for different orientations of the crystal, analyzing how the coupling to the thermostat affects the estimates of the growth coefficients. At Tm, anisotropic interfacial stiffnesses and free energies as well as kinetic growth coefficients are determined from capillary wave fluctuations. The so-obtained growth coefficients from equilibrium fluctuations and without the coupling of the system to a thermostat agree well with those extracted from the FSM calculations.
R. E. Rozas; L. G. MacDowell; P. G. Toledo; J. Horbach. Crystal growth of bcc titanium from the melt and interfacial properties: A molecular dynamics simulation study. The Journal of Chemical Physics 2021, 154, 184704 .
AMA StyleR. E. Rozas, L. G. MacDowell, P. G. Toledo, J. Horbach. Crystal growth of bcc titanium from the melt and interfacial properties: A molecular dynamics simulation study. The Journal of Chemical Physics. 2021; 154 (18):184704.
Chicago/Turabian StyleR. E. Rozas; L. G. MacDowell; P. G. Toledo; J. Horbach. 2021. "Crystal growth of bcc titanium from the melt and interfacial properties: A molecular dynamics simulation study." The Journal of Chemical Physics 154, no. 18: 184704.
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.
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 StyleGonzalo 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 StyleGonzalo 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.
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.
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 StyleGonzalo 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 StyleGonzalo 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.
The Finite Particle Method (FPM) and the Decoupled Finite Particle Method (DFPM) are variants of the Smoothed Particle Hydrodynamics (SPH) in which the estimation of a field and its gradient for an arbitrary distribution of particles is performed by imposing first order consistency equations (C1). A modification of the kernel is introduced that involves the inversion of a correction matrix for each interpolation point in the system. In the FPM, the inversion is rigorously performed and therefore the method has first-order consistency (C1). However, in DPFM the vanishingly small non-diagonal terms in the correction matrix are neglected to obtain a more straightforward method, at expense of consistency. Following the idea of DFPM, the Semi-Decoupled Finite Particle Method (SDFPM) and the Corrected Semi Decoupled Finite Particle Method (CSDFPM) are introduced. In the SDFPM, the kernel is normalized by a Shepard factor and the first order consistency equations are solved by neglecting non-diagonal terms in the correction matrix as in the DFPM method. In the corrected version of this method (CSDFPM), the SDFPM estimation is used as the initial guess to get a second corrected estimation in the C1 equations. The precision of FPM, DFPM, SDFPM, and CSDFPM is tested by evaluating the gradient components of a field around a cylindrical obstacle and around a cylindrical hole by using (i) trial field functions with an ordered array of particles and (ii) the pressure field with a distribution of particles taken from a flow simulation. Drag coefficients for flow around a cylinder are obtained by the different methods and compared in a wide range of Reynolds numbers, including the laminar and turbulent regimes. The gradient components and drag coefficients calculated with the proposed methods show a precision comparable to the FPM at a lower computational cost.
Cristian V. Achim; Roberto E. Rozas; Pedro G. Toledo. Semi-decoupled first-order correction for smoothed particle hydrodynamics. Applied Mathematical Modelling 2020, 93, 314 -325.
AMA StyleCristian V. Achim, Roberto E. Rozas, Pedro G. Toledo. Semi-decoupled first-order correction for smoothed particle hydrodynamics. Applied Mathematical Modelling. 2020; 93 ():314-325.
Chicago/Turabian StyleCristian V. Achim; Roberto E. Rozas; Pedro G. Toledo. 2020. "Semi-decoupled first-order correction for smoothed particle hydrodynamics." Applied Mathematical Modelling 93, no. : 314-325.
Stabilization of synthetic clay-rich tailings in seawater with sodium polyacrylate (NaPA) has been studied by measurements of yield stress, viscoelastic moduli, zeta potential, and particle chord length distribution. The tailings are kaolin-quartz and sodium montmorillonite-quartz mixtures in seawater at pH 8 at which all surfaces are anionic. The yield stress of both tailings decays exponentially with the dose of NaPA. Reducing the initial value of yield stress to a preset fraction (1-1/e) requires 52 g/ton NaPA for kaolin-quartz and 31 g/ton NaPA for montmorillonite-quartz tailing. At these dosages, in the linear viscoelastic range, both tailings respond similarly to the presence of NaPA, increasing their liquid-like character and suspension stability. The stabilizing action of NaPA is supported by a slight increase of the negative zeta potential and a clear shift of the particle size distribution to the finer sizes. The underlying stabilizing mechanism involves steric-electrostatic repulsion of the clay particles. These results suggest an alternative to improve the management of clay-rich tailings in processes that use raw seawater at natural pH.
Matías Jeldres; Pedro Robles; Pedro G. Toledo; Manuel Saldaña; Luciano Quezada; Ricardo I. Jeldres. Improved dispersion of clay-rich tailings in seawater using sodium polyacrylate. Colloids and Surfaces A: Physicochemical and Engineering Aspects 2020, 612, 126015 .
AMA StyleMatías Jeldres, Pedro Robles, Pedro G. Toledo, Manuel Saldaña, Luciano Quezada, Ricardo I. Jeldres. Improved dispersion of clay-rich tailings in seawater using sodium polyacrylate. Colloids and Surfaces A: Physicochemical and Engineering Aspects. 2020; 612 ():126015.
Chicago/Turabian StyleMatías Jeldres; Pedro Robles; Pedro G. Toledo; Manuel Saldaña; Luciano Quezada; Ricardo I. Jeldres. 2020. "Improved dispersion of clay-rich tailings in seawater using sodium polyacrylate." Colloids and Surfaces A: Physicochemical and Engineering Aspects 612, no. : 126015.
Chalcocite (Cu2S) has the fastest kinetics of dissolution of Cu in chlorinated media of all copper sulfide minerals. Chalcocite has been identified as having economic interest due to its abundance, although the water necessary for its dissolution is scarce in many regions. In this work, the replacement of fresh water by sea water or by reject brine with high chloride content from desalination plants is analyzed. Additionally, the effect of adding MnO2 from available manganese nodules in vast quantities at the bottom of the sea is studied. Reject brine shows better results than sea water, and the addition of MnO2 to the brine significantly increases the kinetics of chalcocite dissolution in a short time. H2SO4 concentration is found to be irrelevant when working at high concentrations of chloride and MnO2. The best results, 71% Cu extractions in 48 h, are obtained for reject brine, 100 mg of MnO2 per 200 g of mineral and H2SO4 0.5 mol/L. The results are expected to contribute to a sustainable process of dissolution of chalcocite by using the reject brine from desalination plants.
David Torres; Emilio Trigueros; Pedro Robles; Williams Leiva; Ricardo Jeldres; Pedro Toledo; Norman Toro. Leaching of Pure Chalcocite with Reject Brine and MnO2 from Manganese Nodules. Metals 2020, 10, 1426 .
AMA StyleDavid Torres, Emilio Trigueros, Pedro Robles, Williams Leiva, Ricardo Jeldres, Pedro Toledo, Norman Toro. Leaching of Pure Chalcocite with Reject Brine and MnO2 from Manganese Nodules. Metals. 2020; 10 (11):1426.
Chicago/Turabian StyleDavid Torres; Emilio Trigueros; Pedro Robles; Williams Leiva; Ricardo Jeldres; Pedro Toledo; Norman Toro. 2020. "Leaching of Pure Chalcocite with Reject Brine and MnO2 from Manganese Nodules." Metals 10, no. 11: 1426.
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.
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 StyleGonzalo 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 StyleGonzalo 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.
Protein adsorption is influenced by many factors such as temperature, pH, protein size and structure, or surface energy and roughness, among others. Self-assembled monolayers (SAMs) and the Langmuir-Blodgett (LB) technique are two of the techniques more used to produces ultrathin films of proteins on surfaces. In this work, we established protocols for the preparation of nanocoatings of bovine serum albumin (BSA) protein on glass surface using SAMs and LB. Furthermore, we determined how small changes in temperature and pH can affect the covering when SAMs are used. Using a combination of different analyses, such as relative roughness, dynamic contact angles, and atomic force microscopy (AFM), it was possible to establish conditions to obtain a uniform nanocoating using SAMs. The results of the analysis of the nanocoating performed using the LB technique were very similar to those obtained using SAMs. The Derjaguin–Landau–Verwey–Overbeek (DLVO) theory in conjunction with the AFM images showed that electrostatic interactions are very important in the self-assembly process, but a process dominated solely by attraction is not sufficient to achieve a good SAM nanocoating, since it does not allow proper orientation and packaging of BSA molecules on the glass surface.
Sergio-Miguel Acuña-Nelson; José-Miguel Bastías-Montes; Fabiola-Rossana Cerda-Leal; Julio-Enrique Parra-Flores; Juan-Salvador Aguirre-García; Pedro G. Toledo. Nanocoatings of Bovine Serum Albumin on Glass: Effects of pH and Temperature. Journal of Nanomaterials 2020, 2020, 1 -11.
AMA StyleSergio-Miguel Acuña-Nelson, José-Miguel Bastías-Montes, Fabiola-Rossana Cerda-Leal, Julio-Enrique Parra-Flores, Juan-Salvador Aguirre-García, Pedro G. Toledo. Nanocoatings of Bovine Serum Albumin on Glass: Effects of pH and Temperature. Journal of Nanomaterials. 2020; 2020 ():1-11.
Chicago/Turabian StyleSergio-Miguel Acuña-Nelson; José-Miguel Bastías-Montes; Fabiola-Rossana Cerda-Leal; Julio-Enrique Parra-Flores; Juan-Salvador Aguirre-García; Pedro G. Toledo. 2020. "Nanocoatings of Bovine Serum Albumin on Glass: Effects of pH and Temperature." Journal of Nanomaterials 2020, no. : 1-11.
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.
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 StyleGonzalo 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 StyleGonzalo 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.
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.
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 StyleGonzalo 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 StyleGonzalo 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.
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.
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 StyleGonzalo 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 StyleGonzalo 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.
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.
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 StyleGonzalo 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 StyleGonzalo 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.
The effect of seawater ions presents a great challenge to theories about mechanisms of pyrite oxidation, collector adsorption, and surface reactions. As the use of seawater is key to the sustainability of the mining industry in regions without fresh water, there is a need to study the surfaces of minerals and products that are formed in the presence of seawater salts. In this study, atomic force microscopy (AFM) was used to analyze the topography of pyrite surfaces subjected to treatments, including oxidation and exposure to xanthate and solutions of seawater salts and xanthate, at pH 8.5. Topographic details were related to surface products. The results showed that xanthate was adsorbed without hindrance on oxide-free pyrite which validated one well-known model. The results also showed that pyrite oxidized forming a structure of interconnected pillars and that xanthate was adsorbed on the top and skirt of these pillars; the experimental evidence on the increase in the height and width of these pillars validated another well-known model. In the presence of seawater salts, the cations covered the surface of the pyrite, suppressing collector adsorption regardless of the dose. The results are expected to help in decisions about the flotation of sulfide minerals in water with limited metallurgical quality.
Álvaro Paredes; Sergio M. Acuña; Pedro G. Toledo. AFM Study of Pyrite Oxidation and Xanthate Adsorption in the Presence of Seawater Salts. Metals 2019, 9, 1177 .
AMA StyleÁlvaro Paredes, Sergio M. Acuña, Pedro G. Toledo. AFM Study of Pyrite Oxidation and Xanthate Adsorption in the Presence of Seawater Salts. Metals. 2019; 9 (11):1177.
Chicago/Turabian StyleÁlvaro Paredes; Sergio M. Acuña; Pedro G. Toledo. 2019. "AFM Study of Pyrite Oxidation and Xanthate Adsorption in the Presence of Seawater Salts." Metals 9, no. 11: 1177.
Charge screening and adsorption capacity of monovalent ions onto pyrite (Py) in aqueous suspensions and the effect of potassium amyl xanthate (PAX) has been studied by measuring the changes in zeta potential (zp) versus pH with streaming potential. PAX addition in the absence of salts leads to an increase in |zp| suggesting dissolution of the surface ferric hydroxides and recovery of bare Py, corroborating existing theories. In the presence of salt, addition of PAX at pH > 6, for which hydroxides interference in not expected, has little effect over the zp, except when Li is present. The water network around the polar head of PAX is expected to be similar to that of hydrated Li+ facilitating the linkage between them and, thus, the formation of Li-mediated Py–PAX bridges. We speculate that these bridges lead to a xanthate shield around anionic sites on Py, decreasing |zp|. An increased PAX dose amplifies the effect of Li as a Py activator but only at low salt. At high salt concentrations, >0.01 M, PAX molecules do not find room to percolate to the surface of Py. Results for monovalent cations should improve our understanding of copper flotation processes in the presence of Py in saltwater.
Alvaro Paredes; Sergio M. Acuña; Leopoldo Gutiérrez; Pedro G. Toledo. Zeta Potential of Pyrite Particles in Concentrated Solutions of Monovalent Seawater Electrolytes and Amyl Xanthate. Minerals 2019, 9, 584 .
AMA StyleAlvaro Paredes, Sergio M. Acuña, Leopoldo Gutiérrez, Pedro G. Toledo. Zeta Potential of Pyrite Particles in Concentrated Solutions of Monovalent Seawater Electrolytes and Amyl Xanthate. Minerals. 2019; 9 (10):584.
Chicago/Turabian StyleAlvaro Paredes; Sergio M. Acuña; Leopoldo Gutiérrez; Pedro G. Toledo. 2019. "Zeta Potential of Pyrite Particles in Concentrated Solutions of Monovalent Seawater Electrolytes and Amyl Xanthate." Minerals 9, no. 10: 584.
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 StyleGonzalo 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 StyleGonzalo 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.
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.
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 StyleRicardo 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 StyleRicardo 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.
Oscillatory rheological assays are used to determine the viscoelastic properties of flocculated kaolinite sediments over a range of sodium chloride concentration, flocculant dose, and settling time. The plunger method is used to promote efficient mixing between flocculant, particles, and electrolytes, ensuring the least amount of disturbance in the system. The suspensions are prepared at natural pH, varying salt concentration and flocculant dose, and then allowed to settle for a pre-set time. The sediment is then subjected to oscillatory rheological tests under small amplitude oscillatory shear (SAOS) and large amplitude oscillatory shear (LAOS) regimes. It is very remarkable that the viscoelastic moduli respond differently depending on the variable being examined; on the one hand, the salinity changes the internal structure of the floc network conforming the sediment by adopting liquid-like characteristics as salinity increases, on the other hand, different flocculant doses and settling times lead to unaltered floc network architectures.
Ricardo I. Jeldres; Eder C. Piceros; Liey-Si Wong-Pinto; Williams H. Leiva; Nelson Herrera; Pedro G. Toledo. Dynamic moduli of flocculated kaolinite sediments: effect of salinity, flocculant dose, and settling time. Colloid and Polymer Science 2018, 296, 1935 -1943.
AMA StyleRicardo I. Jeldres, Eder C. Piceros, Liey-Si Wong-Pinto, Williams H. Leiva, Nelson Herrera, Pedro G. Toledo. Dynamic moduli of flocculated kaolinite sediments: effect of salinity, flocculant dose, and settling time. Colloid and Polymer Science. 2018; 296 (12):1935-1943.
Chicago/Turabian StyleRicardo I. Jeldres; Eder C. Piceros; Liey-Si Wong-Pinto; Williams H. Leiva; Nelson Herrera; Pedro G. Toledo. 2018. "Dynamic moduli of flocculated kaolinite sediments: effect of salinity, flocculant dose, and settling time." Colloid and Polymer Science 296, no. 12: 1935-1943.
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.
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 StyleGonzalo 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 StyleGonzalo 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.