Synthesis of new complexing entities based on calix[4]pyrrole for the decontamination of aqueous media from natural radionuclides

Radionuclides are found naturally in air, soil, and water and generate radioactivity in the environment. As a result of recent anthropogenic activities such as uranium mining or the production of oil and natural gas, larger quantities of natural radionuclides have been released and induce a risk to Human health. One of the most important routes for Human contamination with radionuclides, other than inhalation, is water contamination that results from the high hydro-solubility of certain radionuclide salts. In fact, maximum contaminant levels for radionuclides contamination, especially in public water supplies, have been internationally regulated. In order to comply with these requirements, methods for decontaminating water from radionuclides have been developed, among which macrocyclic extractants such as calix-pyrroles. With a preorganized cyclic structure, these macrocycles exhibit chelating properties that are also found in their phenoxy-calix[4]pyrrole (PCP) homologs. However, the latter has an increased potential for chemical functionalization allowing the introduction of additional chelation sites due to the presence of four phenolic entities. In this context, the synthesis of PCP derivatives and the study of their ability to complex and extract stable or radioactive elements have been studied. For this, the functionalization of the PCP was carried out by functional groups such as: carboxylic acid, hydroxamic acid, azide, amine and hetero-aryl-extended derivatives. At the end of these syntheses, the study of the chelation capacities of the derivative 2-pyridino-1,2,3-triazolo-PCP was carried out and the existence of a selective complexation of ferrous and ferric iron in DMSO was demonstrated by molecular fluorescence. As for the chelation capacities for halides, they were studied by ¹H NMR and molecular fluorescence titrations and showed a selectivity for fluoride. A second part of this work was devoted to the synthesis and study of the properties of a new polymer of PCP cross-linked by epichlorohydrin (PCP-EP), in the aim of engaging it into solid/liquid extractions, applied for the decontamination of aqueous effluents containing radionuclides. In this series of polymers, PCP-EP is the first to be reported in literature. Accordingly, its structure was determined by NMR, FTIR and TGA, then its chelation capacities towards halides was tested by ion chromatography after solid/liquid extractions. The results demonstrated that this polymer, unlike its monomeric structure, has a higher affinity for iodide. The solid/liquid extraction capacities of radionuclides by PCP-EP were then studied by a gamma spectrometer coupled to a High Purity Germanium detector, using aqueous solutions containing radionuclides and resulted in an extraction rate of 22 % for Ra-226. The development of a Doehlert experimental design was then carried out in order to optimize the experimental extraction conditions. During this step, the study of Ba²⁺, a stable metal with a chemical behavior similar to Ra²⁺, was prioritized in order to reduce the production of radioactive waste. The results of this experimental design led to optimal extraction conditions of pH, temperature and time, which translated to an aqueous radionuclides-containing solution, showed the ability of PCP-EP to extract 89 % Ra-226. (author)