Influence mechanism of hydrated cations on surface hydration of slime mineral particles
To elucidate the microscopic mechanisms underlying the impact of hydrated cations on the surface hydration of slime mineral particles(specifically,kaolinite and quartz,the primary minerals in slime),this study focused on construct-ing two common hydrated cations in slime water:[Na(H2O)5]+ and[Ca(H2O)8]2+.Using density functional theory,the ad-sorption of these two hydrated cations on the surfaces of kaolinite(001),(00(-1))and α-quartz(001),as well as their compet-itive adsorption with water molecules were simulated.The simulation results revealed that the adsorption energy of hy-drated cations on all three surfaces was over 50%lower than that of water molecules.The adsorption stability on mineral surfaces was as follows:α-quartz(001)surface>kaolinite(001)surface>kaolinite(00(-1))surface.The adsorption energy of the competitively stable configuration was 34%-57%lower than that of a single hydrated cation on kaolinite and quartz.Additionally,the[Ca(H2O)8]2+ configuration exhibited a greater stability than the[Na(H2O)5]+ configuration under both adsorption conditions.When the hydrated cations adsorbed onto three surfaces,strong hydrogen bonds formed with sur-face,surpassing the strength of hydrogen bonds between water molecules and kaolinite/quartz surfaces.The hierarchy of hydrogen bonds between two hydrated cations on mineral surfaces was as follows:kaolinite(001)surface>α-quartz(001)surface>kaolinite(00(-1))surface.Under a competitive adsorption,the hydrogen bond between[Na(H2O)5]+ and mineral surface strengthened,while the bond between[Ca(H2O)8]2+ and mineral surface weakened.Although hydrogen bonding did not entirely correlate with changes in adsorption energy,electrostatic interactions in the adsorption configuration were identified.The electrostatic interaction in the single adsorption configuration of hydrated cations proved stronger than that in water molecular adsorption.Under a competitive adsorption,the electrostatic interactions between hydrated cations and mineral surfaces intensified,with[Ca(H2O)8]2+ demonstrating stronger interaction than[Na(H2O)5]+.Given the robust ad-sorption of hydrated cations on the surfaces of kaolinite and quartz,the dehydration of slime particles becomes more chal-lenging.This could increase hydration repulsion between particles,resulting in a more stable dispersion of particles in slime water.
slime particlessurface hydrationhydrated cationkaolinitequartzdensity functional theory
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