The depressing effect of an anionic polyacrylamide on molybdenite flotation and the importance of polymer anionicity

Echeverry-Vargas, Luver; Estrada, Darwin; Toledo, Pedro G.; Gutiérrez, Leopoldo

doi:10.1016/j.colsurfa.2021.127506

Cited by 11 publications

(12 citation statements)

References 29 publications

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“…As was previously mentioned, different polymers of high molecular weight based on PAMs are effectively used as flocculants in the copper processing plants [7]. The main functional group of PAMs is the amide group (R-CHCONH 2 ), and for industrial applications they are modified to produce hydrolyzed PAMs (HPAMs), which contain a series of acrylic units along the main chain such as carboxylic (R-COOH − ), sulfonic (R-SOO − ) and amine (R-NHH + ) groups, which render PAMs weakly to moderately anionic or cationic [7]. These modifications are responsible for the stretching phenomenon of the PAM molecules, which induces the bridging action on the mineral particles.…”

Section: Introductionmentioning

confidence: 97%

“…Polyacrylamide (PAMs) polymers are used as flocculants in copper processing plants to improve the settling rates of tailings in the thickening stages; consequently, residual PAMs dissolved in the process water are recycled to flotation, affecting the efficiency of the process. Previous studies showed that PAMs depress the flotation of different minerals [6,14,15], and their effect on molybdenite was reported [7].…”

Section: Introductionmentioning

confidence: 99%

“…Molybdenum is a strategic metal which is found together with copper sulfides in the porphyry copper deposits, and molybdenite (MoS 2 ) is the main molybdenum-containing mineral [5][6][7][8][9][10]. Molybdenite particles, when dispersed in flotation slurries, occur as anisotropic entities with non-polar hydrophobic surfaces, referred to as faces, and polar hydrophilic surfaces known as edges [11].…”

Section: Introductionmentioning

confidence: 99%

“…The faces are less active than the edges, but defects in the form of nanoedges create hydroxylated metallic sites for the adsorption of all types of molecules [12]. Similar to other naturally hydrophobic materials [13], molybdenite flotation is strongly affected by the presence of polymers in solution [7]. Polyacrylamide (PAMs) polymers are used as flocculants in copper processing plants to improve the settling rates of tailings in the thickening stages; consequently, residual PAMs dissolved in the process water are recycled to flotation, affecting the efficiency of the process.…”

Section: Introductionmentioning

confidence: 99%

“…These modifications are responsible for the stretching phenomenon of the PAM molecules, which induces the bridging action on the mineral particles. The number of hydrolyzed units of the HPAMs establishes the degree of anionicity (DA) of the polymer, which can be calculated by dividing the moles of the acrylates ions m by the total moles of the acrylate ions m plus the moles of the acrylamide units n. The presence of mechanically degraded HPAMs by the action of the pumps used to recirculate process water to flotation can also affect the efficiency of molybdenite flotation [6,7]. Therefore, the interaction of the HPAMs with molybdenite particles in the flotation process is currently of interest.…”

Section: Introductionmentioning

confidence: 99%

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Molecular Dynamics Simulations of the Interactions between a Hydrolyzed Polyacrylamide with the Face and Edge Surfaces of Molybdenite

2022

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Process water used in mineral processing operations corresponds to water recovered from the thickeners and tailings dams, containing residual reagents such as hydrolyzed polyacrylamides (HPAMs). These polymers depress the flotation of different minerals, and their effect on molybdenite has been experimentally demonstrated. The objective of this work was to study the interactions between a segment of a HPAM with the face and edge of molybdenite. The sigma profile, the radial distribution functions of the HPAM, and the orientation and atomic density profiles of water molecules on the face and edge surfaces of molybdenite were calculated. The results obtained from molecular dynamics simulations showed that the interactions between the HPAM and molybdenite are mainly explained by the interactions of the amide group with the faces and edges of the mineral. Molecular dynamics simulations also showed that the HPAM molecule rearranges in such a way that the amide group moves towards the molybdenite face or edge, and the carboxylate group moves away from the mineral surface. The results obtained in the simulations showed that the interactions of the HPAM with the molybdenite edge are slightly stronger than the interaction of this molecule with the mineral face. Simulations demonstrated that the presence of the sodium and hydroxide ions reduces the concentration of HPAM around the face and edge surfaces, which is expected to affect HPAM adsorption on molybdenite. The conclusions obtained through molecular dynamics simulations are in line with the results obtained in previous studies carried out at a macroscopic scale, which reported that HPAMs adsorb onto molybdenite particles and reduce their hydrophobicity.

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Section: Introductionmentioning

confidence: 97%