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NNadir

(33,362 posts)
Sat May 1, 2021, 04:46 PM May 2021

Magnetic Separation Method for Isolating Rare-Earth Elements and Zirconium from Molten Salts

The paper to which I'll briefly refer is this one, published by Russian scientists in an English edition: Alekseeva, L.S., Savinykh, D.O., Orlova, A.I. et al. Magnetic Separation Method for Isolating Rare-Earth Elements and Zirconium from Molten Salts. Inorg Mater 56, 583–590 (2020).

Strontium ferrites are magnetic particles that find utility in many electronic storage devices. This paper uses magnetic particles that are also strontium based, particles which apparently have a Curie Point higher than the temperature of molten salts.

From the introduction:

Pyroelectrochemical technology utilizing molten salts, primarily molten alkali chlorides, as solvents is commonly thought to have considerable potential. Pyrochemical processes are characterized by small volumes of waste, its high specific activity, and the near absence of liquid technological high-level waste. This technology has a number of advantages: melts are good solvents, they are stable at high temperatures and under irradiation, and the use of melts allows one to run the process without water, necessary for all living systems. Work with chloride melts, with application in pyroelectrochemical technology, has been and is being carried out in many countries all over the world: in Russia [1–7], the United States, Japan [8], Korea [9], and the United Kingdom [3, 10] (zeolite sorption). The behavior of U, Np, Pu, and Am in LiCl–KCl melts has been the subject of extensive studies [1, 11–25]. The diversity of studies, in particular, in recent years [20–23], indicates that this is a topical issue.

Extraction of actinides (Am and Cm), rare-earth elements (REEs), and zirconium from melts is one of the key issues in this technology, in particular in Russia [5, 6, 24, 25].

Extraction, preconcentration, and consolidation methods under development for subsequent isolation of actinide fission products from the biosphere include precipitation, ion exchange, zone crystallization, and sorption.

In this work, we propose using a magnetic field for extracting components dissolved in a LiCl–KCl melt.

Actinide- and rare-earth-containing strontium hexaferrite with the magnetoplumbite structure and zirconium-containing spinel ferrites are of interest as magnetic carriers capable of absorbing melt components to be extracted.


The authors synthesized spinel magnetic ferrite particles isomorphous with a magnetic mineral containing lead, magnetoplumbite. They noted that many of the compounds in this class of isomorphs can incorporate lanthanide elements (aka "rare earths.&quot

However their spinel structure was a compound, again isomorphous, of strontium, copper, iron and oxygen.

They heated a molten salt composed of potassium and lithium chloride at 450C and were able to extract neodymium and zirconium.

It was hardly quantitative according to a table in the paper:



There are lots of people who are molten salt reactor kind of guys and gals; I used to be one myself, but I changed my mind. However, in recent years I have begun to rethink molten salts in all kinds of chemical separations processes, and redox processes, including but not limited to separation and recovery of valuable materials in used nuclear fuels. (It should be noted that there are an infinite number of molten salts, given the existence and wide study of "ionic liquids" some of which are partially or wholly organic molecules.

I'm not sure this work has much practical import, although one can imagine these things in certain kinds of molecular filters, but any magnetic material with a curie point high enough to be stable in a molten alkali metal salt is interesting. For the record, I do not favor the use of potassium salts in nuclear fuel settings since the separation from cesium is problematic. Rubidium, which is present mostly in a form (Rb-87) that occurs naturally all over the planet as a fission product is a better choice.

I trust you're having a nice Saturday.
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