Abstract
Terrestrial and aquatic ecosystems are highly threatened, mostly by anthropogenic activities.The exploitation of mineral resources is representative of the impacts directly caused by human activities on the environment: soils degradation, damages to landscape environment, destruction of biodiversity, contamination of aquatic ecosystems, discarding of mining effluents… Dissemination of trace elements (TEs) throughout the environment is also one of the most worrying consequences, in terms of environmental, health and economical concerns. The growing demand for mineral resources, associated with the poorly developed recycling technologies have triggered a gradual depletion of some strategic elements, such as manganese, tough essential in many industrial processes, and mostly in chemistry.Uncontrolled proliferation of invasive species is also among the major threats upon the aquatic ecosystems. The control of their development remains a real problem to manage, without any concrete solution so far. Stimulated by the raised of temperatures resulting from climate change, this is a typical example of the indirect consequences of anthropogenic activities.In view of the aforementioned problems, ChimEco laboratory leads large-scale programs of ecological rehabilitation based on adapted phytotechnologies: phytoextraction, rhizofiltration and biosorption. High interest is led on plant species that have the capacity to assimilate metallic elements present in soils or water and to concentrate them in their leaves or roots respectively. The biomass rich in TEs is then considered as a true source of metallic elements to valorize. Among others, manganese from leaves of (hyper)accumulating species is recycled and turned to unusual polymetallic catalysts. These manganese-based ecocatalysts, Eco-Mn, are used in many revisited mechanisms of chemistry by an innovative and original approach named Ecocatalysis.The research carried out during this thesis follows on from the studies already led on Eco-Mn. It provides answers to the global objective set for this thesis: prove how an approach bio-inspired from Nature allows the preparation of new green catalysts with remarkable oxidative properties. To this end, new generations of manganese-based ecocatalysts are synthesized in order to not only valorized terrestrial (hyper)accumulating plant species but also mining effluents rich in manganese and invasive aquatic plant species having accumulated manganese trough rhizofiltration. The results obtained showed that the new Eco-Mn have unusual structures and excellent oxidative capacities that prove they represent potential substitutes to oxidative reagents inconsistent with the requirements of REACH regulation. They allow the synthesis of a wide range of high value-added molecules for many industrial processes. A study of the physiology of (hyper)accumulating species highlights further understanding of what we call the peculiar vegetal footprint of ecocatalysts.This overall work falls within the current ecological and economical challenges which are: the rehabilitation of natural environment impacted by anthropogenic activities, the preservation of terrestrial and aquatic ecosystems, the development of innovative techniques of valorization and recycling as well as the design of new catalytic processes respecting sustainable chemistry principles. It aims at demonstrating that the unusual combination between Nature, Chemistry and Ecology can be a vector of sustainable development and a source of sustainable innovation to solve many current environmental issues.