Reference : UMR5214-PETNOT-001
Nombre de Postes : 1
Workplace : MONTPELLIER
Date of publication : Monday, January 9, 2023
Scientific Responsible name : Petru NOTINGHER and Philippe COMBETTE
Type of Contract : PhD Student contract / Thesis offer
Contract Period : 36 months
Start date of the thesis : 1 February 2023
Proportion of work : Full time
Remuneration : 2 135,00 € gross monthly
Description of the thesis topic
Context. Microplastics (particles smaller than 5 mm) come from the degradation of waste (bottles, packaging, etc.) and from the abrasion of everyday objects (soles, fishing nets, tires, synthetic pitches, clothing, etc.). They are also dispersed in the environment as microbeads during losses during transport or during the storage of raw materials. About 150,000 tonnes of microplastics are emitted each year in France, the majority transiting towards the sea via rivers and winds. These particles have harmful effects both for the environment and for human health. Thus, microplastics of size < 150 µm can easily penetrate the body and be transported by the blood to most organs (in particular the brain). By their nature, they contain endocrine disruptors, responsible (among other things) for cancer, hormonal disorders and inflammation, for which the cost of medical care exceeds €26 billion at European level. In addition, these microplastics have a great capacity to fix hydrocarbons and heavy metals, the negative effects of which on human health no longer need to be demonstrated. When we know that each human ingests, via food, water and air, approximately 5 grams of microplastics per week (the equivalent of a credit card), the drastic reduction of this pollution appears as an obvious necessity.
State of the art. The solutions currently used to filter plastics are essentially based on mechanical processes, which limit the size of the particles recovered to 200 µm (impossibility for water to pass through finer meshes with reasonable pressures, and very rapid clogging of the filter) . Principles such as centrifugation, extraction, adsorption, sedimentation, degradation by micro-organisms, multimedia filters, or separation by gyratory sieve, are used to separate small particles. The preliminary study of these processes has shown their limits, such as the difficulty of setting up in a natural environment, the size of the equipment, clogging and the difficulties of adapting to microplastics.
Scientific and technological objectives. The objective of the thesis is to develop a technique allowing the recovery of microplastics smaller than 200 µm in aqueous medium. The proposed approach is based on the use of the dielectric properties of the particles and phenomena of an electrostatic , triboelectric , electrophoretic and dielectrophoretic [3-5] nature, which can make it possible to orient these particles towards a unit storage, ideally without mechanical action and without size limit. The complementarity with principles from fluid mechanics will also be studied in order to potentially optimize recovery. The purpose of the research is to develop and validate a solution that is technically viable and adaptable to large-scale deployment through the creation of a start-up.
Method. The scientific obstacles to be overcome during the project are linked in particular to the masses and dimensions of the particles targeted, which determine the forces involved and therefore the intensity and frequency of the electric fields to be used, to the charging technique to be used if necessary and to the dielectric properties of materials and media. Electro-hydrodynamic phenomena will first be addressed in the context of a highly heterogeneous medium composed of an a priori polar aqueous phase and dispersed solid dielectric particles. The work will first focus on the characterization of the materials concerned and on the modeling of their movements under an electric field, in order to study the feasibility of the various processes and to identify avenues for the implementation of the solution to be adopted. In parallel, the geometric structure of the filter will be studied in order to create hydrodynamic blocking effects (like the Tesla system) allowing the control of the circulation of the charged fluid in a set of connected channels. The identified solution(s) will then be studied and optimized, in particular by coupling experiments/simulations.
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The work will take place at the Institute of Electronics and Systems (IES, UMR CNRS 5214), located in Montpellier. The activities of the IES are related to 5 thematic axes (Materials, Energy, Sensors and instrumentation, Reliability and systems in constrained environment, Photonics and waves) associating 9 research teams. Dielectric phenomena in materials and particles (in particular polymers) and their applications, as well as electro-hydrodynamic approaches at micro-scales, are major subjects of the “Electrical Engineering, Materials and Systems” and “Materials, Micro and Nanodevices” teams, for which they enjoy high international recognition. This work, carried out thanks to several doctoral theses, has given rise to numerous scientific publications (including 61 articles and 10 invited conferences since 2016) and 3 technology transfers over the past 5 years. The subject fits naturally into the research fields of these teams, aiming for new developments in a theme of great societal and scientific interest. The doctoral student will be supervised by two professors with skills in the two areas mentioned.
Constraints and risks
No particular risk identified.
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