ABRASIVE STRIPPING VOLTAMMETRY AND ESR SPECTROSCOPY OF MANGANESE IN CARBONATES

A combined approach using solid state electroanalysis (abrasive stripp ing voltammetry) and ESR spectroscopy was made to characterize the dif ferent species of manganese which are present in natural and synthetic calcium carbonates. Abrasive stripping voltammetry permits identifyin g MnO2 and MnCO3, but the method fails when it comes to detecting unam biguously MnCO3 in the presence of MnO2. Neither can this method detec t Mn2+ ions in mixed crystals of Ca1-xMnxCO3 because of their low conc entrations. ESR spectroscopy can show that Mn2+ ions are present in ca lcite on Ca2+ sites. Additionally, information about the state and sym metry of Mn2+ sites and the local dynamics of the lattice can be obtai ned. In aragonite, only extremely small amounts of individual Mn2+ ion s are present and most of the manganese is found in the form of MnO2 a gglomerates. Solid state electroanalysis and ESR spectroscopy allow a rather complete qualitative specification of manganese in calcium carb onates.