Dissolved Ca2+ ions adsorption and speciation at calcite-water interfaces: Dissolution and zeta potential studies

•Speciation and surface charging of calcite in water are important.•Transfer of dissolved Ca2+ ions from EDL to the interface is a key step.•Water molecules at the interface restricts the dissolved Ca2+ ions transfer.•Ca2+ ions should attain a saturation level in the EDL to transfer through.•Estimated level of Ca2+ ions in EDL’/‘interfacial area, is ~5 × 10-4 M/m2. Aspects related to speciation at the calcite-water interface and surface charging behavior of calcite are of fundamental importance in calcite specific applications such as in paper and pharmaceutical applications. The surface charge of calcite depends mainly on how the speciation process happens at calcite interfaces. Transfer of dissolved Ca2+ ions from the electrical double layer (EDL) to the interface is a key step in the speciation process. The ice-like layer of the water molecules at the interface acts as a barrier and restricts the dissolved Ca2+ ions transfer unless they attain a saturation level in the EDL - where the electric field could be stronger enough for their transfer through the ice-like layer. The acoustophoresis technique that allows measuring the surface charge at wide range of particle concentrations was used. This level was estimated as dissolved Ca2+ ions content in EDL’/‘interfacial area, αCaEDL2+, is ~5 × 10-4 M/m2.