PhD offer University of Montpellier: Understanding of mechanisms and pathways of PFAS degradation by electro-oxidation in drinking water

7 Mar 2024
Job Information

Organisation/Company

University of Montpellier

Research Field

Chemistry

Researcher Profile

First Stage Researcher (R1)

Country

France

Application Deadline

21 Apr 2024 - 08:00 (Europe/Paris)

Type of Contract

Temporary

Job Status

Full-time

Offer Starting Date

9 Sep 2024

Is the job funded through the EU Research Framework Programme?

Not funded by an EU programme

Is the Job related to staff position within a Research Infrastructure?

No

Offer Description

What is the ExposUM Doctoral Nexus?

The Doctoral Nexus proposed by the ExposUM Institute are networks of 3 to 4 PhD students from different disciplines and affiliated to at least two different research units. Compared with a traditional PhD, taking part in a Doctoral Nexus will encourage the ability to work in a team and to design projects in a transdisciplinary way while deepening one's own field of expertise. A specific teaching programme will be offered and the doctoral students concerned will also have the opportunity to organise a seminar within the Nexus network. Theses are funded from the outset for 4 years, including the PhD student's salary and an environmental allowance.

PhD project: Understanding of mechanisms and pathways of PFAS degradation by electro-oxidation in drinking water

Context

The overall objective of the research project is focused on Per- and Polyfluoroalkyl Substances (PFAS). These environmental molecules are widely used and practically nonbiodegradable. Consequently, they are detected ubiquitously in the environment and received increasing attention as global environmental contaminants. In biology, a recent study suggests that PFAS may activate the PXR nuclear receptor, which senses the presence of foreign toxic substances and in response up regulates the expression of proteins involved in the detoxification and clearance of these substances from the body. Interestingly, PXR is also a regulator of the growth and apoptosis of colon tumors. Numerous studies have demonstrated the degradation of perfluoroalkyl substances (PFAS) in water by advanced oxidation or reduction processes. Nevertheless, there is a lack of comprehensive and comparative overview of the various degradation pathways and mechanisms [1]. In water treatment, toxic degradation byproducts form a substantial obstacle for industrial applications of electrochemical technologies. Concerning PFAS degradation by electro-oxidation, if the total applied energy density is not sufficient and/or if the electroactive material is not well adapted, PFAS are merely degraded to shorter-chain compounds potentially toxic. Additionally, in water containing chloride or bromide at relevant concentrations, the formation of perchlorate, bromate, and toxic organic halides is a concern. It is therefore important to evaluate the toxicity of the electrochemically treated water and to determine mechanisms and pathways of PFAS degradation.

Objective and methods

The global objective is to gain better understanding of the degradation pathways and mechanisms of PFAS degradation by electro-oxidation processes. The methodology of the project is to (i) evaluate the treatment effectiveness using electrochemical methods (ii) identify degradation pathways and characterize byproducts of PFAS model molecules (iii) assess the toxic potency of the water before and after treatment using bioassays using bioluminescent bacterizes commonly developed at IEMM (iv) hence propose a selection of the most relevant water samples at different time treatment to Dr. Cavailles’s team (INSERM Montpellier) to characterize the effects of PFAS and oxidation byproducts as PXR activating- environmental disruptors on colorectal tumorigenesis, on the tumor immune microenvironment and the response to chemotherapies in relation with PhD project 3 of the NEXUS project named PYPHAS. Our objectives for this PhD are then organized around three tasks.

Task 1. Analytical development Liquid chromatography hyphenated to tandem mass spectrometry (LC/MS/MS) represents the state-of-the-art analytical technology to monitor organic compounds in complex matrices with high sensitivity and specificity. The total concentration of PFAS in drinking water should not exceed 0.50 g/L in Europe, and the individual concentration of 20 of them should be less than 0.1 g/L. Thus, an optimized LC/MS/MS workflow associated with an efficient sample treatment, such as a pre-concentration step by solid phase extraction (SPE), will be developed to reach the targeted PFAS quantification limits. Regarding the identification of unknown degradation products issued from electro-oxidation, further investigation will be conducted by high resolution mass spectrometry (HR-MS) for exact mass measurement combined with iterative fragmentation steps (MSn) to ensure unambiguous structural elucidation. Pr Christine Enjalbal (IBMMUMR5247) expert in mass spectrometry will oversee this analytical task. Guillaume Cazals and Eddy Petit, both engineers at the Pôle Chimie analytical facilities (PAC Chimie Balard, newly created UAR 2041) master all available technologies required to identify and quantify PFAS and byproducts by mass spectrometry.

Task 2. Identification of chemical pathways Heterogeneous AOPs use catalysts to activate oxidating agents (e.g., H2O2, O3, persulfate), which contribute to the generation of powerful reactive oxidant species (ROS) such as hydroxyl radicals (•OH) and sulfate radicals (SO4 −•). The defluorination (breaking C−F bonds) and the elimination of head groups (e.g., carboxylate and sulfonate groups) depend on the dominant ROS engaged on the process. The objective of this task is to identify the transformation pathways during oxidation reactions so as to provide insights into PFAS degradation mechanisms, which are fundamental for the design of heterogeneous AOPs. IEM’s group has a long time experience on the development of electrochemical techniques for water remediation focused on emergent micropollutants and pharmaceuticals [2,3]. More recently, the team focused its attention on the degradation of perfluorooctanoic acid (PFOA) by anodic oxidation with the concomitant identification of shorter polyfluoroalkyl substances (from C7 to C3) [4].

Task 3. Evaluation of toxicity via bioassays The generic Aliivibrio fischeri bioluminescence assay will be carried out to give information on the general toxic potency of the water. Herein, exposure of the marine bioluminescent bacterium A. fischeri to toxic components in the extracts results in a decrease in bioluminescence compared to a blank caused by the inhibition of the bacterial metabolism. The main objective will be to make a correlation between degradation pathway and toxicity of PFAS and byproducts according to process and time treatment. This type of bioassay has been used previously to evaluate the effectiveness of water treatment with advanced oxidation in our group [5]. In parallel, the most relevant treated water samples (i.e. non-toxic and/or presenting a toxicity due to the presence of a specific compound or byproduct identified through bioluminescence assay) will be tested by Dr. Cavailles’s group and PhD 3 (INSERM Montpellier).

Expected results

This study lays the groundwork for future research to analyze and elucidate the transformation products and pathways of PFAS in various treatment systems. The completion of this research project will give knowledge on the possible breakthrough and low removal efficiencies which is important since short chain PFAS are known to be formed during degradation of long chain PFAS. Designing and evaluating new removal technologies that will eliminate a wide range of PFAS, particularly the short chain molecules, is a crucial direction for future research to help mitigate the PFAS crisis.

Feasibility

The feasibility of this project is based both on the expertise of the host laboratory and the wide national and international collaborations already in place. In addition, this project benefits from the technical and scientific support of scientists and a technical staff. All the facilities necessary for the implementation of the project are already available within the university and IEM.

[1] Chemical Engineering Journal 450 (2022) 138352 [2] Electrochimica Acta 188 (2016) 378-384. [3] Chemical Engineering Journal 419 (2021) 129467 [4] ChaÏma Gomri, Advanced Water Remediation: Adsorption and Electrooxidation Techniques for Effective PFAS Treatment, Thèse Université de Montpellier, 15 déc. 2023 [5] Chemosphere 172 (2017) 1-9

Application procedure

The application must include the following:

• a CV
• a letter of motivation
• a copy of the degree required for registration
• any additional specific information requested by the doctoral school SCB (https://edscb.umontpellier.fr/ ).

If you would like to apply for this position, please send an e-mail to [email protected]  and [email protected]  , with a CC to [email protected]  to inform them of your interest.

Before Sunday 21 April, 8pm CET

More information availalble here (as of March 11th, 2024):

https://www.umontpellier.fr/articles/appel-a-projet-doctoral-nexus-campagne-2024

Requirements

Research Field

Chemistry

Education Level

Master Degree or equivalent

Languages

ENGLISH

Level

Good

Languages

FRENCH

Level

Good

Internal Application form(s) needed
Sujets Nexus 2024 Cretin.pdf
English
(828.35 KB - PDF)
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Additional Information
Work Location(s)

Number of offers available

1

Company/Institute

IEM Montpellier

Country

France

Geofield

Where to apply

E-mail

[email protected]

Contact

State/Province

FRANCE

City

Montpellier

Website

https://www.umontpellier.fr/

Street

163 rue Auguste Broussonnet

Postal Code

34000

STATUS: EXPIRED