engleski

The electrokinetic properties of carbonates in aqueous media revisited

The electrokinetic properties of model carbonate particles in aqueous media have been investigated with respect to their dependence on pH (ranging from 6-11) at 25oC as a function of their structural and chemical diversities and of their biomimetical or inorganic precipitation modes. The model carbonates used were the calcium carbonate polymorphs – calcite, aragonite, and vaterite (CaCO3) - and the alkali-earth metal carbonate isomorphs – strontianite (SrCO3), and witherite (BaCO3). The results obtained in this study show that the most important potential-determining ions (pdi) are the alkali-earth cations (Me2+), and confirm the previous findings which showed that H+ and OH- are of secondary influence for the electrical surface properties. The differences in the electrophoretic mobility (EPM) and, consequently, the electrokinetic potential (the zeta-potential) of the investigated carbonate solids are governed by dissolution-precipitation processes at the mineral/solution interfaces, depending on the solubility product and on the concentration of Me2+ that dominates in solution. The biomimetical precipitation route yielded solids that were, in terms of their electrokinetic properties, similar to those obtained by the inorganic process route.

carbonates; carbonate isomorphs; calcium carbonate polymorphs; electrokinetics

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