Abstract
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 COO−Na+ 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.
Highlights
The large amount of waste generated annually is one of the main problems presented by the mining industry
Such studies have demonstrated the usefulness of molecular dynamics in describing phenomena related to mineral processing, helping to improve knowledge about the phenomena that intervene at the microscale and define the efficiency of operations
Molecular dynamics simulations were used to determine the adsorption of polyacrylic acid (PAA) on electrically charged mineral surfaces in NaCl solutions
Summary
The large amount of waste generated annually is one of the main problems presented by the mining industry. The kaolinite (Al2Si2O5(OH)4) comprises an octahedral sheet of aluminum hydroxide and a tetrahedral sheet of silica This clay has two crystallographically different surfaces: the basal faces that have a negative charge throughout the pH range, and the edges, which vary in charge (negative or positive) with the variation of the pH as a response to the protonation or deprotonation of the groups aluminol (Al-OH) and silanol (Si-OH) in the exposed planes with hydroxyl termination. The affinity of HPAM with minerals present in the copper tailings and with the presence of magnesium precipitate has recently been quantified [27], which demonstrated the detriment of this precipitate in thickening processes using conventional flocculants Such studies have demonstrated the usefulness of molecular dynamics in describing phenomena related to mineral processing, helping to improve knowledge about the phenomena that intervene at the microscale and define the efficiency of operations. Considering the potential uses offered by this reagent in highly saline media, the influence of sodium chloride on the adsorption mechanisms and on the relevant functional groups to generate stable adsorption is analyzed
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