Gilles Bernier

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.

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.

Water Soluble PDCA Derivatives for Selective Ln(III)/An(III) and Am(III)/Cm(III) Separation

The synthesis and solvent extraction behavior of dipicolinic acid (pyridine-2,6-dicarboxylic acid, PDCA) and their derivatives have been studied for possible use in selective back-extraction of actinides, especially americium. The extraction was performed from an organic phase containing a mixture of trivalent actinides and lanthanides pre-extracted with N,N,N’,N’-tetraoctyl diglycolamide (TODGA). The efficiency of the back-extraction was enhanced when the picolinate platform was used in a heterocyclic decadentate ligand called h4tpaen. Beyond selective An/Ln extraction, the aqueous soluble h4tpaen ligand seemed a potential reagent for an intra-group Am(III)/Cm(III) separation with a separation factor SFCm/Am of about 3.5.

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.