Johannes Vind defended his doctoral degree in Athens, Greece

Johannes Vind defended his doctoral degree on the topic of trace element mineralogy and distribution in the Bayer process in National Technical University of Athens (NTUA), Greece.

The dissertation was supervised by prof. Ioannis Paspaliaris (NTUA), prof. Dimitrios Panias (NTUA), prof. Maria Taxiarhou (NTUA) as well as by Dr Vicky Vassiliadou (Aluminium of Greece, Mytilineos). The selection of specific trace elements was inspired by the elevated concentrations of some of the so-called (technology) critical elements found in some bauxite ores. Specifically, attention was given to scandium (Sc), rare earth elements (REE), gallium (Ga) as well as vanadium (V).

It was revealed that during alumina refining, the mass of Sc as well as REEs is transferred almost entirely into bauxite residue, the by-product of the Bayer process. At the same time, the initial REE minerals found in the raw materials undergo specific changes in the caustic leaching process and are found as newly formed REE titanate minerals inside bauxite residue. Scandium, on the other hand, was mainly found in association with iron oxide and oxyhydroxide minerals both in the initial bauxite ore and the resulting bauxite residue, meaning that there are little changes taking place during bauxite processing. The accumulation points of Ga and V are mainly in the composition of processing liquors that circulate in the alumina refining system.

The results of this research contain useful implications in the context of the ongoing efforts of creating a sustainable value chain in the valorisation of bauxite residue. The evolving technologies attempting to extract critical elements from bauxite residue could be adjusted to target the specific REE- or Sc-containing mineral species. Also, modelling and predictions can be made about the extraction of Ga and V from Bayer process liquors.

Published literature:

1. Vind, A. Malfliet, B. Blanpain, P.E. Tsakiridis, A.H. Tkaczyk, V. Vassiliadou, D. Panias, Rare Earth Element Phases in Bauxite Residue. Minerals 8, 77 (2018) https://doi.org/10.3390/min8020077
2. Vind, A. Malfliet, C. Bonomi, P. Paiste, I. Sajó, B. Blanpain, A.H. Tkaczyk, V. Vassiliadou, D. Panias, Modes of Occurrences of Scandium in Greek Bauxite and Bauxite Residue, Minerals Engineering 123, 35-48 (2018), https://doi.org/10.1016/j.mineng.2018.04.025.
3. Vind, A. Alexandri, V. Vassiliadou, D. Panias, Distribution of selected trace elements in the Bayer process, Metals 8(5), 327 (2018), https://doi.org/10.3390/met8050327