Actinide Separation of High-Level Waste Using Solvent Extractants on Magnetic Microparticles

Abstract

Polymeric-coated ferromagnetic particles with an absorbed layer of octyl(pheny1)-N,N-diisobutylcarbamoylmethylphosphine oxide (CMPO) diluted by tributyl phosphate (TBP) are being evaluated for application in the separation and the recovery of low concentrations of americium and plutonium from nuclear waste solutions. Due t o their chemical nature, these extractants selectively complex americium and plutonium contaminants onto the particles, which can be recovered from the waste solution using a magnet.The effectiveness of the extractant-absorbed particles at removing transuranics (TRU) from simulated solutions and various nitric acid solutions was measured by gamma and liquid scintillation counting of plutonium and americium. The HNOQ concentration range was 0.01M to 6U. The partition coefficients (Kd) for various actinides at 2M HNO3 were determined t o be between 3000 and 30,000. These values are larger than those projected for TRU recovery by traditional liquid/liquid extraction. Results from transmission electron microscopy indicated a large dependence of Kd on relative magnetite location within the polymer and the polymer surface area.Energy disperse spectroscopy demonstrated homogeneous metal complexation on the polymer surface with no metal clustering. The radiolytic stability of the particles was determined by using 6oCo gamma irradiation under various conditions. The results showed that I Q more strongly depends on the nitric acid dissolution rate of the magnetite than the gamma irradiation dose. Results of actinide separation from simulated high-level waste representative of that at various DOE sites are also discussed.

Water purification using magnetic assistance: A review

“…The partition coefficients for various actinides were determined to be between 3000 and 30,000 using recyclable magnetic polymer microparticles adsorbed with solvents. These values are larger than those projected for transuranics removal by traditional liquid/liquid extraction [145]. Dendrimers with terminal amino groups attached to the magnetic particle surface showed a 50-400-fold increase of the distribution coefficients for europium and americium in comparison to the reference particles without the dendrimers [146].…”

Magnetic nano- and microparticles for metal removal and environmental applications: a review

“…But in this case the slow intraparticle diffusion of the species to complex is a limitation as the price, if synthesis of specific polymers has to be made as it was the case for arsenic removal [5]. Nevertheless following the same kind of idea, biopolymers as alginic acids based polymers could be serious candidates for extraction of heavy metals [30].…”

“…For such an application, it is necessary to use a method of purification that does not generate secondary waste, and involves materials that can be recycled and easily used on an industrial scale. The integrated process which couples magnetic separation (not always 'high-gradient' one) together with surface complexation adsorption, ionic exchange and solvent extraction is sometimes called magnetically assisted chemical separation (MACS), and is considered as promising in order to reduce the aqueous stream volume of high activity waste [4,5].…”

Solvent Replacement for Green Processing

“…Another class of solvents that appears to have significant appeal for green processing of metal waste solutions relies on solventcoated magnetic particles dispersed within the feed phase to be treated (159,160). Once the desired solutes have been removed by extraction, these particles can be recovered conveniently using magnetic filtration.…”