General information
Position description
Category
F08 Geochemistry - Engineer / Researcher
Job title
Phd : Redox processes in hydrothermal salt systems
Contract
Thesis
Contractual hours
Full-time
Contract duration
36 months
Context and contributions of the position
Thesis proposal: Redox processes in hydrothermal salt systems for understanding the mechanisms and kinetics of natural hydrogen production.
Among the geochemical processes responsible for the production of natural hydrogen, serpentinization is a chemical reaction resulting from the interaction, in the subsurface, between a peridotite-type mantle rock and a hydrothermal solution. Hydration of the rock's anhydrous minerals increases the salinity of the interstitial solution, accompanied by anoxic oxidation of the rock's ferrous iron by reduction of the water to dihydrogen.
Although redox processes are at the heart of the serpentinization reaction, they remain poorly described in a hydrothermal context, i.e. under conditions of high salinity, of the order of several hundred grams per liter, temperatures approaching 250°C and pressures above 100 bar. Moreover, their experimental characterization is a scientific and technical challenge.
Job description
Joining the Bureau of Geological and Mining Research (BRGM) means joining the benchmark public establishment in Earth sciences bringing together 1,000 expert and passionate people, spread over 29 entities located in mainland France and overseas.
BRGM's activity aims to provide geological knowledge and understanding of phenomena related to the soil and subsoil, with one challenge: responding to the challenges of environmental change through innovative projects with societal challenges.
The main aim of the thesis project is to develop a methodology for characterizing the redox state and dynamics of hot saline systems, such as those found in the western part of the Pyrenean structure. Two main actions are envisaged to achieve this objective:
1) Implementation and modeling of interaction processes involving Fe(III)/Fe(II) and H2O/H2 redox couples in simplified synthetic aqueous brines that mimic hydrothermal brines from the Aquitaine Basin;
2) Application to experiments on H2 generation by serpentinization of natural rock.
The implementation and modeling of interaction processes will be carried out at BRGM, which has :
i) the equipment and expertise required to carry out the experiments and ensure operando kinetic monitoring of redox reactions using electrochemistry
ii) the geochemical modeling tools and expertise to size the tests and interpret the results obtained.
To this end, BRGM has hydrothermal reactors equipped with robust all-solid probes for operando measurement of physico-chemical parameters, and sampling cannulas to sample fluids and, where appropriate, solids for chemical analysis (speciation measurement of redox elements, physico-chemical characterization of balances by XRD and Raman spectroscopy).
BRGM also uses the PhreeSCALE geochemical calculation code, developed in-house, to describe the chemical properties of brines and mineral-brine equilibria up to high salinities of several hundred grams per liter, and temperatures and pressures representative of hydrothermal conditions.
Experiments using natural rock will be carried out at ISTO, which has the expertise required to carry out water-rock interaction tests using a full range of autoclaves, and to characterize the physico-chemical properties of fluids and solids. In particular, ISTO has two sampling autoclaves designed to react high-salinity fluids with powdered rock up to 350°C and 500 bar.
Profile
Requested start date : 01/10/2024
Education : MSc or Equivalent higher education qualification
Experience : Junior
The candidate's profile will include experimental skills in chemistry and electrochemistry, as well as theoretical knowledge of chemical thermodynamics.
Working conditions
This full-time position involves periodic travel in France or abroad.
The doctoral student will be on a CNRS contract.
Director: Mohamed Azaroual (BRGM/ISTO)
Co-director: Arnault Lassin (BRGM/ISTO)
Supervisors: Stéphanie Betelu (BRGM), Florian Osselin (VEMA Hydrogen)
Contact: a.lassin@brgm.fr
The thesis is part of a partnership between ISTO and BRGM, within the framework of the REDISH action of axis 12 "Aquitaine Basin" of the PEPR project "Sous-sol, bien commun".
Thesis work includes laboratory tests and theoretical developments. The breakdown of time spent in each organization will be: 70% BRGM - 30% ISTO, both located in Orléans.
Key words: Natural hydrogen, hydrothermal brines, geochemistry, analytical electrochemistry, experimentation, modeling.
The BRGM guarantees you a transparent recruitment procedure. To apply send us your application (updated CV and cover letter) until 12/05/2024.
Know that all our positions are open to everyone, at BRGM, we are committed to diversity!
Position location
Job location
France, Centre-Val de Loire, Loiret (45)
Location
Orléans