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

Quezada, Gonzalo R.; Jeldres, Matías; Toro, Norman; Robles, Pedro; Toledo, Pedro G.; Jeldres, Ricardo I.

doi:10.1016/j.colsurfa.2020.125576

Cited by 40 publications

(33 citation statements)

References 52 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…While the height of the unweighted distribution peak decreases (from 400 s −1 to 300 s −1 ), the square-weighted peak increases (from 150 s −1 to 160 s −1 ), indicating that as the number of small aggregates decreases, the number of large massive aggregates increases. These results are expected, because cations promote the flocculant chains' adsorption through cationic bridge bonds with the mineral surface, thus enhancing flocculation [26]. On the other hand, the results show that an increase in salinity (>0.001 M NaCl) severely inhibits flocculation.…”

Section: Aggregation Of Flocculated Particlesmentioning

confidence: 78%

A Criterion for Estimating the Strength of Flocculated Aggregates in Salt Solutions

et al. 2021

Self Cite

View full text Add to dashboard Cite

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.

show abstract

Section: Aggregation Of Flocculated Particlesmentioning

confidence: 78%

A Criterion for Estimating the Strength of Flocculated Aggregates in Salt Solutions

et al. 2021

Self Cite

View full text Add to dashboard Cite

show abstract

“…The colloidal magnesium hydroxide precipitates that appears at pH > 9.5 [20] block the anionic sites on the mica particles, deactivating them. Molecular simulation was recently used to understand the interaction of precipitates of magnesium hydroxide complexes with quartz, kaolinite, and also polymer flocculants [21]. The effect of calcium is less pronounced than the effect of magnesium because the concentration of solid precipitates of calcium is significant at pH values higher than 11.…”

Section: Electrophoretic Mobilitymentioning

confidence: 99%

Chalcopyrite and Molybdenite Flotation in Seawater: The Use of Inorganic Dispersants to Reduce the Depressing Effects of Micas

et al. 2021

Self Cite

View full text Add to dashboard Cite

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.

show abstract

“…For example, Quezada et al [ 18 ] directly observed how a saline medium altered the conformation of an hydrolyzed polyacrylamide (HPAM) in solution and its adsorption on the quartz surface. Even the authors later studied the types of bonds generated by the interaction of HPAM on quartz, kaolin, and brucite surfaces [ 19 ]. The latter is one of the main seawater precipitates that are generated by bringing the pH to highly alkaline conditions than impair flocculation.…”

Section: Introductionmentioning

confidence: 99%

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

et al. 2021

Self Cite

View full text Add to dashboard Cite

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 of the water around the polymer, and interatomic polymer interactions. Such characteristics are important to selecting a polymer depending on the environment in which it is found and its purpose. The effect caused by salinity is particular to each polymer, where polymers with an explicit charge or polyelectrolytes are more susceptible to changes due to salinity, increasing their coiling and reducing their mobility in solution. This naturally reduces its ability to form polymeric bridges due to having a polymer with a smaller gyration radius. In contrast, neutral polymers are less affected in their structure, making them favorable in media with high ionic charges.

show abstract

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

Cited by 40 publications

References 52 publications

A Criterion for Estimating the Strength of Flocculated Aggregates in Salt Solutions

A Criterion for Estimating the Strength of Flocculated Aggregates in Salt Solutions

Chalcopyrite and Molybdenite Flotation in Seawater: The Use of Inorganic Dispersants to Reduce the Depressing Effects of Micas

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

Contact Info

Product

Resources

About