Micheline Draye

Cloud point extraction : An alternative to traditional liquid-liquid extraction for lanthanides(III) separation

Cloud point extraction (CPE) was used to extract and separate lanthanum(III) and gadolinium(III) nitrate from an aqueous solution. The methodology used is based on the formation of lanthanide(III)-8-hydroxyquinoline (8-HQ) complexes soluble in a micellar phase of non-ionic surfactant. The lanthanide(III) complexes are then extracted into the surfactant-rich phase at a temperature above the cloud point temperature (CPT). The structure of the non-ionic surfactant, and the chelating agent-metal molar ratio are identified as factors determining the extraction efficiency and selectivity. In an aqueous solution containing equimolar concentrations of La(III) and Gd(III), extraction efficiency for Gd(III) can reach 96% with a Gd(III)/La(III) selectivity higher than 30 using Triton X-114. Under those conditions, a Gd(III) decontamination factor of 50 is obtained.

Cloud-point extraction for selective removal of Gd(III) and La(III) with 8-hydroxyquinoline

Abstract: A less-common extraction procedure, cloud-point extraction, is used with a lipophilic chelating agent (8-hydroxyquinoline) to extract and separate lanthanum(III) and gadolinium(lll) ions from an aqueous solution. Surfactant solutions are used in conjunction with 8-hydroxyquinoline to form a lanthanide complex that is extracted into the micellar phase at a temperature above the cloud-point temperature. The structure of the lipophilic part of the nonionic surfactant, the chelating agent-metal molar ratio, and the cloud-point temperature are identified as factors determining the extraction efficiency and selectivity. With Triton X-114, a selectivity higher than 30 and a decontamination factor of 50 for Gd(IlI) indicate that micelle-mediated cloud-point extraction is promising for the specific separation of actinide ions from nuclear waste. Finally, a microwave procedure is proposed to decrease the duration of the experiment to less than 6 min.

Selective Rejection of Dissolved Uranium Carbonate from Seawater Using Cross‐Flow Filtration Technology

Abstract: Cross-flow membrane filtration equipment was operated to evaluate the selective uranium carbonate rejection from seawater of different flat sheet membranes. The membranes were discriminating by the rejection of uranium, calcium, and sodium under geochemical conditions that mimic uranium in seawater. Then, operating parameters were optimized, and the selective rejection of dissolved uranium was checked on prefiltrated seawater. Concentration factors of 1.1 and 8.5 for sodium and uranium(Vl), respectively, were obtained for a nanofiltration volume ratio of 0.96.

Use of a cross-linked poly(4-vinylpyridine) for nuclear waste treatment

Abstract The nuclear fuel reprocessing currently used generates liquid wastes with a significant level of radioactivity that requires expensive and specific treatments. Therefore, in this study, an attempt has been made to develop another process that is more effective and produces less-active wastes by using a poly(4-vinylpyridine) resin as selective material for fixation of metal ions present at trace level, in particular of nonactive ruthenium and, 106Ru, 95Nb, 125Sb, 144(Ce + Pr), 241Am, Pu, 244Cm.

Synthesis and Utilization of New Extractants for Nuclear Hydrometallurgy

Abstract Recent progress in organic chemistry increases the possibility of controlling metal ions/organic molecules interaction. The use of macrocycles or polypodands (1) makes possible the creation of specific extractants for each metal ion. According to the actual needs in pollution elimination and precious metal recovery, this approach can lead to important renewals of extractants used in hydrometallurgy. In the present work, selective extraction of plutonium by dicyclohexano-18-crown-6 (DCHI8C6) and paladium by thiapolypodands from high-level nuclear waste solutions is investigated, and the results are modeled and discussed.

REMOVAL OF 243Am WITH PHENOL BASED RESINS

Long-term radiotoxicity of nuclear waste produced during spent nuclear fuel reprocessing could be reduced if the minor actinides (neptunium, americium and curium) contained within the waste are separated into short-lived radionuclides for their subsequent transmutation or for separate storage. Cross-linked phenolic resins based on different substituted phenol were shown to be very efficient for selective uptake of Eu3+ from aqueous solutions containing equal amounts of La3+. In this work, we have prepared and characterized cross-linked phenol based resins to investigate the uptake of 243Am. According to the results obtained for Eu selective extraction and to enhance 243Am sorption, the resins are transformed into their Na+–forms before extraction. The ion selectivities of the cross-linked phenol based resins are then compared as a function of the identity of the ion-exchange phenolic matrix. Radiation stability of the resins was studied and each resin was measured for the effect of ionizing radiations with FTIR spectroscopy, moisture regain and ion exchange capacity.

Hafnium hydroxide complexation and solubility: The impact of hydrolysis reactions on the disposition of weapons-grade plutonium

The stability constants for the complexation of hafnium by hydroxide ions is investigated by potentiometric titration over a range of ionic strengths (I{sub m} = 0.1 to 6.6 molal). The stability constants are determined from the titration data using the HYPERQUAD suite of programs. The stability constants at infinite dilution are determined using the Specific Ion Interaction Theory from the stability constants determined by titration. The solubility product of Hf(OH){sub 4} (s) is determined in 0.1 M NaClO{sub 4} by measuring the total hafnium in solution that is in equilibrium with an excess of hafnium hydroxide solid under an argon atmosphere. The total Hf concentration is determined by ICP-AES. The solubility product is determined using the stability constants measured for the Hf hydrolysis products in 0.1 M NaClO{sub 4}. The precipitate examined is confirmed to be a hydroxide by IR spectroscopy. For Hf(OH){sub 4} (s) in 0.1 M NaClO{sub 4}, the solubility product is log K{sub sp} (Hf(OH){sub 4} (s)) = {minus}51.8 {+-} 0.5. The solubility and stability constants determined are used, along with literature values for plutonium solubility and complexation constants, to examine the behavior of hafnium and plutonium under the conditions expected at Yucca Mountain.