Spectroscopic Determination of Optimal Hydration Time of Zircon Surface

Abstract

When a mineral surface is immersed in an aqueous solution, it develops an electric charge produced by the amphoteric dissociation of hydroxyl groups created by the hydration of the solid surface. This is one influential surface property. The complete hydration process takes a time which is specific for each mineral species. The knowledge of the aqueous solution contact time for complete surface hydration is mandatory for further surface phenomena studies. This study deals with the optimal hydration time of the raw zircon (ZrSiO4) surface comparing the classical potentiometric titrations with a fluorescence spectroscopy technique. The latter is easy and reliable as it demands only one sample batch to determine the optimal time to ensure a total hydration of the zircon surface. The analytical results of neutron activation analysis (NAA) showed the presence of trace quantities of Dy3+, Eu3+ and Er3 in the bulk of zircon. The Dy3+ is structured in the zircon crystalline lattice and undergoes the same chemical reactions as zircon. Furthermore, the Dy3+ has a good fluorescent response whose intensity is enhanced by hydration molecules. The results show that, according to the potentiometric analysis, the hydration process for each batch (at least 8 sample batches) takes around 2 h, while the spectrometric method indicates only 5 min from only one batch. Both methods showed that the zircon surface have a 16h optimal hydration time.