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What are the end products of plastic waste degradation? (H/F)

This offer is available in the following languages:
Français - Anglais

Date Limite Candidature : jeudi 11 août 2022

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General information

Reference : UMR6118-MELDAV-003
Workplace : RENNES
Date of publication : Thursday, July 21, 2022
Scientific Responsible name : Mélanie Davranche
Type of Contract : PhD Student contract / Thesis offer
Contract Period : 36 months
Start date of the thesis : 1 October 2022
Proportion of work : Full time
Remuneration : 2 135,00 € gross monthly

Description of the thesis topic

The contamination of the environment by plastic waste is now proven, but the risks it poses to its functioning and its future are still poorly known and very poorly constrained. There are, in fact, many gray areas on the future of plastic waste and the toxic additives that accompany it. Although it has recently been shown that plastic waste deteriorates into nanoplastics, we still do not know what the ultimate products of this degradation are, polymers? monomers? CO2? Little information also exists on the fate of associated additives and their role in degradation processes. The ULTIMATEPLAST project aims to fill this lack of data and provide the first elements of a treatment method for drinking water. To do this, a number of experiments coupled with innovative analytical and modeling methods will be carried out in order to determine the mechanisms and key parameters of the photooxidation (radical degradation)/abrasion processes of plastics under environmental conditions.

Work Context

Program: The project is divided into 4 tasks
Task 1 Mechanisms of radical degradation: Nanoplastics will be generated in the laboratory from polymers. A polymer degradation protocol will be developed by combining an oxidizing reagent and microwaves capable of generating accelerated radical degradation, the impact of which is similar to that of UV degradation. This protocol will be inspired by an original methodology for the degradation of industrial polymers implemented for membrane filtration studies (Rabiller-Baudry et al., 2020, 2021).
Kinetic task of degradation and by-products formed: In this task, kinetic studies of degradation in UV reactors will be carried out to quantify the flows of nanoplastics and additives released during degradation and to estimate the risks for the environment and the solutions to be put in place. in place. The objective is to understand whether there are different release kinetics depending on the polymers considered and the amount of additive present (eg antioxidants, TiO2) and whether associations/interactions can be set up. The by-products formed will be characterized in terms of composition, size, colloidal stability and release of additives by different couplings. The results will make it possible to propose a kinetic model of photo-chemical and mechanical degradation.
Task 3 Kinetics of mechanical fragmentation and by-products: The methodology developed by Wiesner et al. (Sipe et al., 2022) will be used to study the fragmentation kinetics of plastics (new/aged, with/without additives) and the release of associated additives as a function of the applied mechanical power (in J/s). The modeling of the results will make it possible to propose extrapolations to other abrasion scenarios in connection with the kinetic expressions.
Task 4 Removal of degradation products by membrane processes. In order to suggest eco-efficient elimination routes, the retention by membrane processes of model nanoplastics (Task 1) will be studied according to their size and physico-chemical properties: ultrafiltration (> 5 nm), nanofiltration (≈ 1 nm), reverse osmosis (< 1 nm).

Additional Information

The candidate must hold a master's degree or an engineering degree in geochemistry/geosciences and/or Chemistry

He/she will:
- integrate into several research teams (NanoScale, CIP) as part of daily work
- have a certain taste for bibliography
- be able to develop and manage experiments
- Possess writing and oral skills in both French and English (stay in the USA, Duke University as part of task 3, international conferences)

Skills and an interest or a first experience in the field of elemental analysis, FTIR and/or Py-GCMS, in the physicochemistry of nanoparticles, in the chemistry of polymers would be assets for the application.
Your application must be submitted via this CNRS Portal (cover letter and CV) and via the 3M Doctoral School website. https://theses.doctorat-bretagneloire.fr/3m/theses_2022_3m

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