Time-of-flight secondary ion mass spectrometry study of zinc carbonation in the presence of stable oxygen-18 and deuterium isotopes

Zinc foil was carbonated in supercritical CO₂ in the presence of water containing stable ¹⁸O or deuterium isotopes. The carbonation resulted in precipitation of zinc carbonate crystals with hexagonal and cubic morphologies until the source of hydroxyl groups was depleted. Time-of-flight secondary ion mass spectrometry was utilized to map the isotopes in the precipitates. The isotopes were detected in the precipitated structures, which confirms the formation of carbonic acid as the initial corrosion procedure step, followed by zinc dissolution. This finally leads to the arrangement of zinc ions with carbonate ions, and storage of OH-groups between ZnCO₃ layers as Zn(OH)₂ or molecular water. The results completed chemical composition data obtained with molecular spectroscopy. Mapping of the distribution of hydrogen and oxygen isotopes by ToF-SIMS provided essential information on the reaction routes of carbonation in a humid scCO₂ environment.