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Supervisors : Mélanie Davranche et Julien Gigault

Research objectives

Characterize and model REE interactions with organo-mineral colloids, which partially control REE dissemination in the environment.

Rare earth elements (REE) are crucial to a wide range of modern technologies such as catalytic additives, hybrid vehicles, wind turbines, oil refining and lighting technologies; all of them rely on the chemical, optical and electro-optic, and paramagnetic properties of REE.The industrial use of REE and all the strategies developed to increase the REE supply by either mining or recycling also increase the REE fluxes resulting in environmental and occupational exposures. Potential concerns about the environmental safety of their use is raisen, since concentrations already 100 times above background in some areas have been reported. Disruption of biogeochemical cycles by some REE is already apparent notably in aquatic and terrestrial environments. However, many uncertainties in our current understanding and modelling are related to the lack of studies on the REE anthropogenic sources (e.g. mining and mining waste, recycling wastes, gasoil, oil sands, etc.) and transfer. Moreover, no studies were dedicated to the understanding of the mechanisms that control their transport in between soils, waters and sediments. A major reason is that REE are particle-reactive, having high affinity for colloids that subsequently control both their mobility and transport.

The pH.D. project aims at providing both speciation datasets and innovative analytical and modelling tools required to fully understand the intimate bonds linking REE to heterogeneous colloids. Such knowledge is crucial to understand, quantify and predict the REE mobility, bioavailability and toxicity in the environment. Investigate the REE speciation onto heterogeneous surfaces is still unexplored and requires advanced spectrometry and spectroscopic techniques (XAS, WAXS, SAXS, GC-MS, etc.) but also the development of innovative analytical and colloids-characterization methodologies adapted to field studies (e.g. REE selective electrodes, field DLS). Indeed, the “nano-speciation” of REE is still unexplored. By developing multi-dimensional analytical approach, such as field flow fractionation coupled to high resolved mass spectrometry, a one-step further approach will be achieved on the REE distribution to colloidal phase. New development using MSⁿ will allow to characterize trace REE and related mechanisms to colloids and other nanoscale materials. The use of multi angle light scattering associated to these methods will bring new data on the implication of the colloid aggregation mechanisms on the REE distribution.

The ESR will benefit from advanced expertise on REE-surface modelling from UR1, spectroscopy from SOLEIL and huge technical expertise of Cordouan Technology. More precisely, the pH.D. project will consist on a coupling between experimental laboratory work, field campaign and modelling calculations to investigate the distribution of REE on heterogeneous nanoparticules in order to evaluate the ability of such nanoparticules to control the REE bioavailabilty and dissemination in the environment. For this, nanoparticules will not only synthetize in the laboratory but also collected in contrasted REE contaminated sites. The targeted field sites (Portugal, Spain, France) were selected according to both their low (wetlands) and high REE contamination (mine) level.

Presentation of the research project (cooperative aspect)

This PhD position is within the framework of a European ITN project named PANORAMAM: EuroPean trAining NetwOrk on Rare eArth elements environMental trAnsfer: from rock to human involving 15 PhD positions.

Under the supervision of Mélanie Davranche and Julien Gigault, the PhD student will investigate the binding between REE and heterogeneous synthetic and natural nanoparticles under various physico-chemical parameters. The nanoparticles were characterized following advanced characterization techniques (DLS, Zeta potential, SAXS, WAXS, SANS, A4F-UV-SLS-ICPMS, XAS spectroscopy, CryoMET, etc….) as well as the REE-nanoparticles physico-chemical interactions (A4F-UV-ICPMS, XAS spectroscopy, etc). All the produced dataset, will secondly be modelled to test various binding scenaris and determined the most relevant REE-nanoparticles complexation mecanisms in order to estimate REE bioavailabilty and potential dissemination in the environment.

The project involves a strong collaboration with several institution and private company, including required research stays (secondment) with SOLEIL (2 months) on REE-colloids interaction characterization by spectroscopy, CORDouan technology (3 months) colloids characterization, characterization tools development, EDM for field sampling and superior Institut of Technology of Lisboa ( 1 month) for support to field

The PhD student will be also involved in scientific/soft-skills meetings and in research activities conducted in other laboratories/companies from Europe and associated countries.

An important component of the training will be the participation to 3 main major training events:

WS1-(December 2020) REE as emerging contaminants: Properties, uses and dissemination –Germany-fundamental REE biogeochemistry and currently known anthropogenic REE inputs into the environment

SS1 (May 2021) - AMD and REE contamination mitigation - Portugal-Management and remediation solutions of AMD in old mining areas and Management of WEEE, recycling areas

WS2 - Colloids and nanoparticles as REE vectors -France- Structural characterization of colloids and nanoparticles by innovative and fine spectroscopic and scattering techniques: X-Ray absorption fluorescence and scattering, light scattering. REE interactions with bearing phases.

SS2 - (Eco)toxicology of REE –Germany- Eco)toxicological concepts and approaches, Physico-chemical properties of REE for bioavailability, ecotoxicity and environmental risk

In addition to these major milestones of the program, the PhD students will 1) continuously develop their core research skills via their own research project locally and within the network while at secondments and conferences, 2) receive a mandatory amount of hard and soft-skills training specific to their own doctoral school, along with mentoring by joint supervising bodies, 3) use conferences both as dissemination events for ESRs results and network events for progress reports and evaluations, and 4) collaborate into practical activities aimed at network-structuring legacy deliverables.

PANORAMA's research objective is to elucidate the man-induced environmental dissemination of REE and the associated effects on the environmental health. For that purpose, interdisciplinary approaches are required combining geochemistry, ecotoxicology, hydrology, chemical analysis and coupling field monitoring, original in and ex situ experimental set-up and modelling from the element speciation to the environmental impact. PANORAMA’s key aim is to set-up an optimal scientific and non-scientific training to the understanding and forecasting of the environmental impacts of new emerging pollutants such as REE.

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