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Model nanoplastics: from the analysis of their physicochemical characteristics to their colloidal behavior in aquatic environments
Original title: Nanoplastiques modèles : de l'analyse de leurs caractéristiques physico-chimique à leur comportement colloïdal en milieu aquatique
Summary
This French-language thesis studied environmentally produced nanoplastics — how to identify them in natural samples, characterise their physical and chemical properties, and understand how they aggregate in water. The work aimed to develop more environmentally realistic nanoplastic models for toxicity and fate studies.
Environmental pollution from plastic waste is a global problem. The impact of nanoplastics in the ocean is greatly influenced by their aggregation properties. This aggregation is generally controlled by the intrinsic properties of nanoplastics as well as those of the surrounding environment. We studied the parameters affecting this property by first setting up a systematic method to characterize nanoplastics (size distribution, shape, functionality, appearance and surface hydrophobicity). Nanoplastic model materials have been then elaborated from two different processes: i) bottom_up approach: soap free and free of additives emulsion polymerization; ii) top-down approach: mechanical degradation of microplastics. The methods allow the control of the nanoplastic properties (composition, morphology, surface condition) and the model materials were characterized using the methods developed and optimized within this work (electronic microscopy, atomic force microscopy, potentiometric titration, dynamic and static light scattering, zetametry). Finally, we studied the homoagregation phenomenon in the marine environment and highlighted the parameters affecting the behavior from intrinsic properties of nanoplastics as well as those of the surrounding medium.