Raphaël Turgis

Uranium Extraction from Phosphoric Acid Using Bifunctional Amido-Phosphonic Acid Ligands

Ligand systems containing amido-phosphonic acid moieties were synthesized for subsequent U(VI) extraction from phosphoric acid solutions. Studies have shown that the efficiency of extraction (distribution ratios and selectivity of U(VI) over Fe(III)) is influenced by the nature of the N-dialkyl substituents and the length and nature of the spacer. A structure-activity approach resulted in the identification of a specific ligand called DEHCBPA that exhibited larger D-values than the corresponding URPHOS reference system. The distribution ratios for U(VI) extraction increased considerably with a branched N-dialkyl chain when a steric hindrance was introduced into the methylene bridge of the amido-phosphonic acid ligands.

From phosphate rocks to uranium raw materials: hybrid materials designed for selective separation of uranium from phosphoric acid

Innovative hybrid materials with high capacities to selectively extract uranium ions from phosphoric acid media were developed by grafting phosphorous-based ligands within the pores of mesoporous silica (SBA15) or mesoporous carbon (CMK3).

Carbamoylalkylphosphonates for Dramatic Enhancement of Uranium Extraction from Phosphates Ores

We describe here the full synthesis of a novel family of bifunctional ligands and present a complete study of their extraction properties in regards to an aqueous phosphoric acid solution containing uranium. We developed a high yielding synthesis of amido phosphonate ligands and focused our investigation on the effect of steric hindrance on the methylene bridge between the two functions. These new bifunctional ligands were found to extract selectively hexavalent uranium U(VI) with high distribution coefficient (D) and selectivity towards iron Fe (III) in 5 M phosphoric acid solution. From a structure-activity approach a specific ligand called DEHCNPB has been put forward in regard to the outstanding results obtained for the selective extraction, and quantitative recovery of uranium compared to the URPHOS reference system.

Development of a new solvent extraction process based on butyl-1-[N,N-bis(2-ethylhexyl)carbamoyl]nonyl phosphonic acid for the selective recovery of uranium(VI) from phosphoric acid

ABSTRACT The promising new extractant molecule butyl-1-[N,N-bis(2-ethylhexyl)carbamoyl]nonyl phosphonic acid (DEHCNPB) was designed and used to develop a new solvent extraction process for the selective recovery of uranium from phosphoric acid. This bifunctional extracting molecule shows high affinity and selectivity for uranium(VI) versus iron(III) and the other elements present in phosphoric acid (Al, Ti, V, etc.). Batch equilibrium experiments were first carried out to determine the stoichiometries of the different complexes formed with uranium(VI) and iron(III) in organic phase and to optimize the different steps of the process at laboratory scale. These experimental data were then used to develop a chemical model to simulate uranium(VI) and iron(III) extraction from phosphoric acid, which was implemented in the PAREX simulation code. A flowsheet was calculated and tested in laboratory-scale mixer-settlers on a genuine phosphoric acid industrial solution. The continuous counter-current test was very successful and showed the possibility to recover more than 95% of uranium decontaminated from the main impurities. A Fe/U ratio of 0.03% was measured in the uranium product, which confirms the high potential of this new solvent for the further production of nuclear-grade uranium from phosphate ores.

Uranium Extraction by a Bifunctional Amido-Phosphonic Acid: Coordination Structure and Aggregation

ABSTRACT Butyl-N,N-di(2-ethylhexyl)carbamoyl-nonylphosphonate (DEHCNPB) is a new amido-phosphonic acid bifunctional ligand with a high uranium extraction efficiency from wet phosphoric acid. In the present work, the DEHCNPB coordination structure toward uranium and its aggregation properties have been fully characterized using experimental and theoretical approaches. DEHCNPB forms associated species, and its aggregation properties such as aggregation number or CAC have been determined from SAXS and SANS measurements. The preferred site for bonding of DEHCNPB toward U(VI) has been determined from IR, EXAFS, and DFT calculations.

Design and Evaluation of Chelating Resins through EDTA- and DTPA-Modified Ligands

Ion-exchange resins through EDTA or DTPA moieties are synthesized and evaluated for the co-extraction of Cs+ and Sr2+ radionuclides for wastewater treatment. EDTA-bis(amide) and DTPA-bis(amide) derivatives bearing phenol or catechol moieties obtained from tyramine or dopamine, respectively, were used as building blocks to prepare ion-exchange resins. Their synthesis involved the condensation of formaldehyde with various phenolic rings, catechol (C), resorcinol (R), or calixresorcinarene (CR) under alkaline conditions. The resulting formo-phenolic-like resins have both ion-exchange and chelating groups in their structure and are indeed efficient in the remediation of Cs+ and Sr2+, even in salted aqueous solutions.