When washing laundry, fibers (mainly polyester and cotton) are inevitably torn from the washed fabrics and end up in the wastewater. Among them, polymer fibers account for a large part of microplastic pollution (e.g. 60% in Lake Geneva). It is thus crucial to extract them for waste water depollution, and to separate natural and synthetic fibers for plastic recycling. To achieve this, we consider the flotation process: gas bubbles are injected in the liquid, to which the fibers will attach and be captured. The objective of the internship is thus to develop a model experiment to study the flotation of polymer fibers in surfactant solutions (laundry detergents).