Thèse Mise en Oeuvre Étude et Optimisation de Procédé de Dépollution par Voie Solaire et de Procédé de Séparation pour le Traitement des Pfas dans les Eaux Usées H/F - 66

Établissement : Université de Perpignan Via Domitia
École doctorale : Energie et Environnement
Laboratoire de recherche : PROcédés, Matériaux et Energie Solaire
Direction de la thèse : Gael PLANTARD
Début de la thèse : 2026-07-01
Date limite de candidature : 2026-04-07T23:59:59

Les substances per- et polyfluoroalkylées (PFAS) constituent une famille de polluants émergents particulièrement préoccupants en raison de l'extrême stabilité de la liaison carbone-fluor, qui les rend quasi indégradables dans l'environnement. Utilisés massivement depuis les années 1950, les PFAS sont aujourd'hui détectés dans les eaux superficielles, souterraines et usées, avec des effets avérés sur la santé humaine et les écosystèmes. Les stations d'épuration conventionnelles se révèlent largement inefficaces pour leur élimination, jouant davantage un rôle de redistribution que de traitement. Face aux restrictions réglementaires croissantes et au manque de solutions durables et efficaces, le développement de technologies innovantes capables de traiter ces composés persistants constitue un enjeu scientifique, environnemental et sociétal majeur.
Le projet vise à évaluer et comparer deux grandes familles de technologies pour le traitement des PFAS dans l'eau :
(i) des procédés d'oxydation avancée, en particulier la photocatalyse solaire, des procédés UV, Fenton, photo-Fenton et ozonation, et
(ii) des procédés de séparation, principalement l'adsorption sur charbon actif.
En parallèle, le projet propose le développement de capteurs électrochimiques innovants permettant le suivi en temps réel de la dégradation des PFAS et de leurs sous-produits. Cette approche intégrée permet à la fois de traiter, surveiller et optimiser les procédés étudiés, en tenant compte de la diversité structurale des PFAS, notamment des composés à chaîne courte et des substituts récents.
La démarche repose sur l'étude de cinq PFAS représentatifs (PFOS, PFOA, PFHxA, PFBS et GenX). Les travaux s'articulent autour de trois axes principaux :
(i) le développement de méthodes analytiques robustes (LC-MS/MS, chromatographie ionique) pour le suivi des PFAS et de leurs produits de dégradation ;
(ii) la conception et l'implémentation de capteurs électrochimiques à bas coût, adaptés au suivi in situ et en continu des procédés ;
(iii) l'évaluation expérimentale et la modélisation des performances des procédés d'oxydation et de séparation, d'abord en eau synthétique puis en eaux usées réelles.
Les résultats expérimentaux seront interprétés à l'aide de modèles cinétiques et de transfert de matière afin d'identifier les conditions opératoires optimales et de prédire les performances à plus grande échelle, notamment sous irradiation solaire naturelle.
Le projet devrait aboutir à (i) de nouvelles connaissances sur les mécanismes et l'efficacité des procédés d'oxydation et de séparation appliqués aux PFAS, (ii) le développement d'un capteur électrochimique opérationnel pour le suivi des traitements, et (iii) la démonstration de la faisabilité de procédés durables basés sur l'énergie solaire en conditions réelles. Les résultats attendus incluent des publications scientifiques et le développement de stratégies pour le traitement des eaux contaminées.
Le bon déroulement du projet repose sur une collaboration étroite entre quatre partenaires universitaires (PROMES, Gérone, Udine et le LBBM), aux compétences complémentaires en génie des procédés solaires, chimie analytique, capteurs électrochimiques et sciences de l'environnement. Cette synergie garantit l'accès aux infrastructures, aux savoir-faire et aux outils nécessaires, tout en favorisant la formation du doctorant dans un contexte international et interdisciplinaire.

Per- and polyfluoroalkyl substances (PFAS) are a large family of synthetic chemicals characterized by highly stable carbon-fluorine bonds, which confer exceptional resistance to thermal, chemical, and biological degradation. Since the 1950s, PFAS have been widely applied in fluoropolymer production, water-repellent textiles, food packaging, and firefighting foams. Their extreme persistence has led to their designation as forever chemicals, and exposure to certain PFAS has been linked to immunotoxicity, developmental effects, endocrine disruption, and carcinogenicity (ATSDR, 2021). Long-chain PFAS such as PFOA and PFOS are now restricted under international regulations, including the Stockholm Convention (UNEP, 2019). PFAS have become globally distributed contaminants, detected in rivers, lakes, groundwater, precipitation, and drinking-water sources (Nguyen, M. A., et al., 2020). Typical concentrations in surface waters range from a few ng·L¹ to several hundred ng·L¹, with elevated values near industrial or firefighting sites (Brusseau, 2020). Wastewater treatment plants (WWTPs) represent a major redistribution pathway, as conventional treatment processes are largely ineffective at removing PFAS. Effluent concentrations commonly span low to several hundred ng·L¹, and frequently include PFOA, PFOS, PFHxA, PFBS, PFHxS, and PFNA (Kim et al., 2024). Hydrophilic short-chain PFAS persist in effluents, whereas long-chain PFAS accumulate in sludge at ng·g¹ to µg·g¹ levels. Thus, WWTPs act more as transformation and redistribution points than as sinks (Lenka et al., 2021). Among the thousands of known PFAS, this study focuses on representative compounds of regulatory and environmental concern: PFOA, PFOS, and selected short-chain alternatives such as PFHxA and PFB. Investigating their degradation through photocatalysis contributes to the development of advanced treatment technologies capable of addressing the extreme persistence of these pollutants in aquatic environments.This research project aims to assess the relevance and performance of different technologies for PFAS removal. Five representative PFAS will be selected to reflect the diversity of this chemical family in terms of molecular structure, chemical nature, composition, origin, and resistance to degradation. A panel of advanced oxidation technologies commonly reported in the literature, including photocatalysis, Fenton processes, ozonation, and UV-based treatments, will be investigated. However, while several studies exist on some oxidation processes, the number of publications combining the keywords PFAS and photocatalysis remains very limited, highlighting a clear scientific gap (19 articles in 2019 with the keywords photocatalysis/PFAS). This lack of data underlines the originality and the key contribution of the present study, which seeks to provide new insights into the potential of photocatalytic processes for PFAS degradation. In parallel, separation technologies such as adsorption onto activated carbon will also be evaluated. The approach will consist of testing, assessing, and quantifying the removal efficiencies of these technologies for the selected PFAS. In order to validate the results under realistic conditions, additional experiments will be conducted using wastewater collected from a wastewater treatment plant (WWTP). Finally, the performance of the different processes will be modeled using existing degradation models for each technology, in order to improve understanding and support the optimization of PFAS treatment strategies.

WP1 : Analytical methodology
Degradation mechanisms vary according to functional group, chain length, and molecular structure, making it necessary to evaluate a representative set of PFAS compounds. For this study, five PFAS have been selected based on environmental relevance, structural diversity, and scientific value for elucidating photocatalytic degradation pathways. Long-chain legacy PFAS (PFOA, PFOS) serve as benchmark compounds; short-chain replacements (PFHxA, PFBS) allow assessment of mobility and reactivity differences; and emerging alternatives (GenX or PFHpA) represent modern industrial substitutes with distinct molecular structures.

WP1.1. Selection of 5 candidates. The selection of PFOA, PFOS, PFHxA, PFBS, and GenX provides a representative and scientifically robust set of PFAS for evaluating degradation performance. PFOA and PFOS are legacy long-chain compounds that are highly persistent, widely regulated, and serve as key benchmarks due to extensive existing data. PFHxA and PFBS represent short-chain alternatives increasingly detected in aquatic environments, allowing comparison of chain-length effects and differences between carboxylates and sulfonates. GenX, as a modern PFOA replacement with a complex ether structure, introduces emerging PFAS chemistry that is more challenging to degrade. Together, these compounds cover structural diversity, environmental relevance, and a broad range of degradation behaviors.
WP1.2. Development of analysis methodologies, monitoring and analysis of PFAS. The concentrations of PFAS and their degradation intermediates will be quantified by LC-MS/MS using negative electrospray ionization (ESI) in multiple reaction monitoring (MRM) mode. A dedicated analytical method will be developed for the target compounds, incorporating isotopically labelled analogues as internal standards. Chromatographic separation and mass-spectrometric detection parameters will be optimized to ensure maximum sensitivity and selectivity.
Sorption experiments using different sorbents, as well as kinetic studies to evaluate degradation models, will be conducted in ultrapure water at elevated concentrations of the selected PFAS. During these assays, small aliquots (e.g., 100 µL) will be collected at predefined time intervals and at varying initial PFAS concentrations, filtered, and injected directly into the chromatographic system. For samples containing low PFAS concentrations (i.e., <1 µg/L), a 20 mL aliquot will be collected, filtered, and subjected to solid-phase extraction (SPE) to preconcentrate the analytes prior to LC-MS/MS analysis. In addition, fluoride will be determined by ion chromatography.

WP2 : Sensor developement and implementation
Sensing solutions will be developed jointly by the partners of Perpignan and Udine Universities.
WP2.1. Sensor design and performance optimization. Disposable low-cost electrodes will be fabricated using different technologies. Methylene blue and methylene green will be incorporated in the electrode material either by incorporation in the carbon paste or in the compounds used for 3D printing. Methods of electropolymerization of these dyes could be also considered. The behavior of the designed electrodes will be evaluated by cyclic voltammetry. In a first approach the sensors will be calibrated in batch using the targeted PFAS, allowing the determination of parameters such as limit of detection and dynamic range. The sensors will be also tested using the degradation compounds of selected PFAS, identified by University of Girona partner. Such study will be important for the precise evaluation of PFAS degradation.
WP2.2. Flow cell design and sensor implementation. Flow cells will be designed for the specific incorporation of electrodes. These measurement cells will be installed in derivation on the pilot degradation reservoirs and calibrated using known concentrations of PFAS. Once calibrated the sensor will be operated during a whole process for a real-time monitoring of PFAS degradation. It is anticipated that a measurement will be carried out every 5 minutes.
WP3: Studies of possibilities for removing PFAS from water
This is the key part of this project's activities. The idea is to validate the feasibility of different treatment and separation methods.
WP3.1 Separation process: AC adsorption. This WP will be devoted to experimentally testing and modelling the sorption capacities of activated carbons for the various selected PFAS. Based on the literature, three ACs will be selected. The experiments will consist of establishing the isotherms and transfer rates of the PFAS/AC couples. The two key parameters, sorption capacity and sorption rate, will be studied using the experimental bench developed at PROMES. A period will be devoted to training the doctoral student. These parameters will be determined for PFAS alone with AC, then for mixtures of PFAS. Based on models in the literature, the experimental data obtained will be modelled (1) by solving differential equations to establish the mass transfer rate and (2) by constructing isotherms to determine the storage capacity of PFAS on AC. Based on these models, the performance of each AC will be established and compared to define the optimal conditions for a separation operation for a PFAS treatment application in water.
WP3.2. Photo-oxidation process: photocatalysis (homogeneous/heterogeneous), UV (AB and C), direct oxidation (ozonation, peroxide). This WP will be devoted to testing various oxidation technologies that are commonly used in the literature to treat organic pollutants, with the aim of demonstrating their feasibility. Heterogeneous photocatalysis, based on the activation of a catalyst by radiation, will be studied on an experimental bench equipped with a solar simulator that can apply radiation representative of solar resources in terms of spectral band and flux density. Different conditions (flux density, PFAS concentration, PFAS cocktail or single PFAS) will be applied to define the photo-oxidative capacity on the targets considered. Drawing on the expertise of PROMES, which will train the doctoral student, the experimental results will be processed using kinetic models to define the photo-oxidation capacity, taking into account the irradiation conditions. As this approach can be transposed to solar conditions, the model will make it possible to predict treatment capacities under natural irradiation conditions.
In a second stage, this approach will be applied to various technologies developed at the PROMES laboratory, namely: homogeneous phase photocatalysis (Fenton, persulphate, peroxide), ozonation, and UV irradiation (UV-AB and UV-C photolysis).
The aim will be to establish and compare the capabilities of each process and to define the optimal operating conditions. Based on the standardization of the methods developed at the laboratory, our results will be compared with those found in the literature.
WP3.3 : validation : experimentations under real conditions. The objective of this project is to demonstrate that PFAS can be treated using sustainable technologies based on the use of solar energy. This final phase will focus on conducting experiments under real-world conditions, namely by using natural irradiation to treat PFAS present in treated wastewater from a wastewater treatment plant (WWTP). The wastewater may be spiked if concentration levels are insufficient to ensure accurate quantification of the compounds. The sensor developed in WP2 will be implemented to validate its performance (sensitivity, robustness) in situ on the photoreactor. It will be used to assess the daily treatment capacity of the solar-based process.