Missions

The InnovTech project is a collaborative project involving the French scientific community working in the field of mineral processing. It is part of the PEPR SOUSSOL, BIEN COMMUN (https://www.soussol-bien-commun.fr/fr) programme, and its objective is to overcome scientific obstacles to the sustainable exploitation of mineral resources. The InnovTech project focuses more specifically on the development of cutting-edge experimental and digital tools to provide an in-depth understanding of industrial mineral processing processes in order to improve their performance and reduce their environmental impact.
Among these mineral resources, tungsten (W) is classified as a critical and strategic raw material (CRM) by the European Union (EU), with the highest economic importance of all CRMs selected since 2014. Tungsten and its derivatives are extracted from their commercial raw materials, mainly wolframite [(Fe,Mn)WO4] and scheelite (CaWO4) ores. After mining and concentrating the minerals, the ore undergoes thermal treatment and a hydrometallurgical process under aggressive conditions (high pressure and high temperature), which are generally applied for the extraction of tungsten compounds.
A thermodynamic study has shown that a thermal route for the treatment of scheelite using various selected chemical agents results in a tungsten-based material that can be leached under milder conditions than scheelite.

Activities

The initial objective of this work is to acquire experimental data on the transformation of scheelite CaWO4 into MgWO4 through reaction with MgCl2. This data will focus on the effect of temperature, particularly on the kinetics of the reaction. This study will be conducted using thermal analysis methods such as differential scanning calorimetry. The solids will be characterised by XRD and microscopy before, during and after the reaction to determine the evolution of the different phases during the reaction. In situ XRD measurements will also be performed.
The second part of the study will involve establishing a phenomenological model of the reaction transforming CaWO4 into MgWO4 based on the concepts of heterogeneous kinetics. Taking into account the geometry of the solids and their evolution, as well as the thermodynamic conditions, will enable us to write a reaction mechanism and obtain an analytical rate law.

Skills

-thermal analysis
-material characterisation
-heterogeneous kinetics

Work Context

The Georges Friedel Laboratory is a Joint Research Unit of the CNRS (UMR 5307). It brings together all of Mines Saint-Étienne's expertise in the fields of materials, mechanics and processes. The position will be assigned to the 'Surfaces, Reactivity and Functionalisation' team, where activities focus on the reactivity of surfaces and interfaces in materials in contact with the environment, and on the functionalisation of surfaces with the aim of obtaining specific properties or functions.

The position is located in a sector under the protection of scientific and technical potential (PPST), and therefore requires, in accordance with the regulations, that your arrival is authorized by the competent authority of the MESR.