The calcite/water interface II. Effect of added lattice ions on the charge properties and adsorption of sodium polyacrylate

The origin of the surface potential of calcium carbonate in aqueous dispersions and the dissolution of calcite in systems containing excess Ca²⁺ and CO^2-₃ have been the subjects of this study. In addition, stabilization of calcite particles with an anionic polyelectrolyte (sodium polyacrylate (NaPA)) and the effect on surface potential and dissolution of calcite have been studied. Preferential dissolution of either Ca²⁺ or CO^2-₃ from the surface, which is governed by the partial pressure of CO₂ in solution and the pH of the solution, mainly determines the surface potential. Both lattice ions (Ca²⁺ and CO^2-₃) adsorb onto the surface and thus alter the surface potential. NaPA adsorbs strongly onto the calcite surface regardless of background electrolyte concentration, and reverses the surface potential to negative values. Chelation of the surface due to NaPA can be partly prevented by adding Ca²⁺ to the dispersion.