Dispersion and depression mechanism of sodium silicate on quartz: Combined molecular dynamics simulations and density functional theory calculations

Highlights: • The distribution of sodium silicate at the solid–liquid surface were displayed. • Sodium silicate formed a dense layer on quartz. • SiO(OH)₃⁻ and Si(OH)₄ were the main species adsorbed on quartz. • Hydrogen bond and the covalent bond were the main driving forces. To investigate the dispersion and depression mechanism of sodium silicate on quartz, the distribution of sodium silicate at the solid–liquid surface and the detailed adsorption configurations of silicate species on quartz surface were studied by combined molecular dynamics simulations and density functional theory calculations. The results demonstrated that sodium silicate formed a dense adsorption layer on quartz. The stable adsorption layer prevented Ca²⁺, Mg²⁺, and collector from contacting quartz. The solution chemistry showed that SiO(OH)₃⁻ and Si(OH)₄ were the main species for the adsorption of sodium silicate on the quartz surface. Both the strong hydrogen bond and the covalent bond were the main driving forces. Meanwhile, the adsorption of electronegative species increased the electronegativity of quartz and enhanced the dispersion of quartz. The dispersion and depression of the quartz in sodium silicate solution were realized.