Detection and Elimination of Radioelements by Complexation and Magnetic Sorting – DECRET

In this project, the teams play the following roles: two teams (CEA and ENS Cachan) are responsible for the synthesis of complexing organic molecules, one of them (ENS Cachan) will also develop microfluidic systems. The prepared molecules are evaluated as cesium and uranyl cation complexing agents by another team (ITODYS). This team is also responsible for the preparation of magnetic nanoparticles and carbon mesoporous materials. Finally, the fourth team (IRFAQ) develops foams to be spread on contaminated areas and conducts tests of decontamination.

Several pulvinic acid derivatives have been prepared by the CEA team. Other type of chelating agents, amidoximes, which are more easily accessible, have also been prepared (12 compounds). The complexation of cesium and uranyl cation by these compounds was evaluated by the ITODYS team. Several amidoximes were grafted onto magnetic nanoparticles or mesoporous compounds.
Several fluorescent probes for the selective detection of cesium have been prepared by the ENS Cachan. These systems contain as complexing entities calixarenes, which are functionalized by various fluorophores. These compounds have been incorporated into microfluidic circuits and a demonstrator is designed for the detection of traces of cesium in solution. The detection limit is below the micromolar concentration. The synthesis of fluorescent probes for the detection of uranyl ions is underway, as well as the grafting of magnetic nanoparticles by such compounds.
The thermodynamic and kinetic properties of various molecules synthesized by the CEA and ENS Cachan partners were determined by the ITODYS team, to evaluate their properties of complexation (affinity; selectivity) to cesium and uranyl cations.
Magnetic nanoparticles and mesoporous substrates have been previously functionalized, then amidoxime derivatives were grafted onto their surface.
The chelation properties of the materials thus obtained are being evaluated, and will be compared to those of the free molecules in solution.
The IRFAQ team studied the incorporation of magnetic nanoparticles from the ITODYS in foams. Similar foams, containing nanoparticles grafted by chelating entities, will be used for the decontamination of surfaces.

With regard to the detection of cations, the next steps are, on the one hand, the implementation of trials for cesium detection, using the prepared calixarenes, and on the other hand the synthesis of fluorescent probes for the detection of uranyl ions.
With regard to the study of decontamination, testing for extracting cesium and the uranyl cations using magnetic nanoparticles and functionalized mesoporous materials will be implemented. Syntheses on a larger scale of complexing entities should then be carried out
A pilot unit test for the generation of foams will soon be carried out. The formation of foams containing magnetic nanoparticles will be in particular focus.

Publications:
N. Kumar, Q. P. Xuan, A. Depauw, M. Hemadi, N.-T. Ha-Duong, J.-P. Lefevre, M.-H. Ha-Thi and I. Leray, 2016 submitted to Dalton Transactions.
A. Depauw, N. Kumar, M. H. Ha-Thi and I. Leray, The Journal of Physical Chemistry. A, 2015, 119, 6065-6073.
N. Kumar, I. Leray and A. Depauw, Coordination Chemistry Reviews, 2016, 310, 1-15.
Helal S, Decorse P, Perruchot C, Novak S, Lion C, Ammar S, El Hage Chahine JM and Hémadi M. Functionalized magnetic nanoparticles for the decontamination of water polluted with cesium. AIP Advances, 2016, 6, 056601.
Oral Communications:
Colloque WISG-2016, 10-11 février 2016, Troyes « Nanoparticules magnétiques hybrides pour la décontamination des métaux lourds », M. Hémadi, E. Mazario Masip, A. S. Helal, J. Stemper, N. Kumar, S. Ammar, N.T. Ha-Duong, N. Serradji, C. Perruchot, C. Lion, I. Leray, T. Le Gall, J.M. El Hage Chahine
IUPAC of photochemistry, Osaka, 3-8 avril 2016, I. Leray « Selective detection of alkali cations with specific fluorescent molecular sensors »

The objective of the DECRET research program is twofold and aims to:
• provide a novel solution, specific to and with improved sensitivity for the detection of radioactive elements: cesium and uranium,
• ensure effective decontamination of all surfaces contaminated with these radioactive metals,
in particular by applying to contaminated surfaces a foam composition containing magnetic nanoparticles functionalized with highly specific chelating agents and harvesting these nanoparticles by means of an industrial electromagnet.

The aim of this research program is:
1) to build two quick detection systems for cesium and uranium. These systems will be based on microfluidic devices equipped with a specific detector for each of the two metals. These devices will be based on fluorescent calixarenes.
2) to develop new molecules capable of complexing these metals by exploring two possible technologies:
• (a) sequestering agents with a pulvinic acid backbone (norbadione subunits, natural cesium sequestering agent found in certain mushrooms) and
• (b) calixarenes (cyclic complexing agents).
3) to select the most effective cesium and uranium complexing molecules.
4) to graft them on support materials such as magnetic nanoparticles (doubly functionalized materials) or mesoporous materials (sponge and/or lightweight felt).
5) to incorporate these magnetic nanoparticles in the formulation of a foaming surface decontamination base, with high wetting power enhancing contact between nanoparticles and cesium or uranium contaminated sediments; compatibility of the various components with this aqueous foam will be controlled, thereby ensuring the grafted nanoparticles remain well dispersed and kept in suspension. The foam form will be easy to use in the field in case of accidental contamination.
6) to collect the radioactive elements by passing an electromagnet over the foam loaded with magnetic nanoparticles,
7) in parallel to being grafted on magnetic nanoparticles, the molecules developed under (2) will be grafted onto the surface of previously modified substrates, using a methacrylate monomer functionalized with a calixarene group or a pulvinic acid derivative. These structures would in particular allow to make filters or sponges capable of removing efficiently and selectively the cesium and uranium radioelements potentially present in an aqueous medium.

At this stage, the tests will be performed on « cold » metals. Foam generation tests will be conducted on a pilot unit designed by CEA-DEN (Marcoule). Decontamination trials will be carried out on the one hand using the new chelating molecules and on the other hand using the complete and operational formulations derived from these molecules. The formulations will integrate suitable solvents, additives and supports to facilitate the extraction of metal from the contaminated substrate.

In field applications, the two following systems will be combined:
• a system comprising a metal-containing mesoporous material obtained by grafting polymer brushes functionalized with these new chelating agents.
• and a foam generation system loaded with magnetic nanoparticles allowing quick decontamination by "magnetic harvesting".

The former system is more suitable for the decontamination of effluents (by filtering) or of low porosity hard surfaces (by sponging) and the latter one for the operational decontamination of large surfaces (buildings, land).