Inhibitory Effect of MgO, FeO, CaF2, and Al2O3 Additives on the Dissolution Behavior of Ca from Silicate Mineral Phases into Water

The inhibitory effect of MgO, FeO, CaF2, and Al2O3 additive on the dissolution of Ca into water from 10 quasi-ternary silicate mineral phases was studied according to the silicate crystal structure. After adding MgO or FeO, the dissolution ratio of Ca decreased by Ca2+ substitution with Mg2+ or Fe2+. In the CaF2-added silicate phase Ca4Si2O7F2, non-existence of the face-sharing type of linkage between CaOx polyhedrons could be a reason for the low dissolution ratio of Ca. In Al2O3-containing silicates, Al atoms could form [AlO4]5− and [AlO6]9− polyhedrons linked to [SiO4]4− tetrahedrons to form a complicated silicate network structure with a higher polymerization degree, which helps suppress the dissolution of Ca. The dissolution ratio of Ca is also inversely correlated to the overall polymerization degree in the silicate network structure. Using multivariate analysis, the dissolution ratio of Ca was predicted utilizing factors internal to the silicate structure (corrected basicity, polymerization degree of silicate network structure, lattice energy, and average nearest neighbor Ca–O distance). For both quasi-binary and quasi-ternary systems, the overall polymerization degree of silicate network strongly affects the dissolution of Ca, while the other factors only make slight contributions.