Science
Related: About this forumRecovery of Trivalent Lanthanides and Transplutonium Actinides with Resin Supported Diglycomides.
The paper I'll discuss in this post is this one: Scaling Trivalent Actinide and Lanthanide Recovery by Diglycolamide Resin from Savannah River Sites Mark-18A Targets (Kevin P. McCann, Mark A. Jones, Edward A. Kyser, Tara E. Smith, and Nicholas J. Bridges Industrial & Engineering Chemistry Research 2021 60 (1), 507-513).
The elements in the two rows below the "main" periodic table are collectively called the "f elements." The row beginning with the chemical symbol Ln (lanthanum) are called "the lanthanides" - and somewhat more commonly in an annoying and misleading term, "rare earths" - and the row beginning with the chemical symbol Ac (actinium) are called the "actinides." They are placed below the main elements of the periodic table only to make the table fit nicely in the width of a sheet of paper. Properly drawn they represent another "step" in the step shapes in the main part of the table, properly the table should have 32 columns, not 18, although the congener relationship in purely chemical terms between, say protactinium and praseodymium is weak and not all that worthy of consideration.
The lanthanides, with some exceptions, generally exhibit the +3 oxidation state, the "trivalent" state, because the "f orbitals" which are being filled across the row do not participate to any appreciable extent in chemical bonding because of shielding effects.
This is not true for the lower actinides before americium, only actinium itself exhibits only the trivalent state. For a very long time, until the 1940's, when interest in actinide chemistry exploded - no pun intended - thorium was thought of as a congener of hafnium and zirconium, because like them, its most common oxidation state is +4, and protactinium was considered a congener niobium and tantalum because its common oxidation state is +5, and uranium, a congener of molybdenum and tungsten because of its common oxidation state of +6.
Actinium, thorium, protactinium, and uranium all occur naturally in weighable amounts, thorium and uranium on a billion ton scale - their decay is largely responsible for the internal heat of the Earth - actinium and protactinium occur in trace amounts, in concentrations so low that they are best accessed not by isolation from the ores in which they occur, but by the use of nuclear reactions, neutron or proton bombardment.
In 1940's, as he worked on the discovery of new synthetic elements in the periodic table, especially neptunium, plutonium, americium and curium, Glenn Seaborg had the insight that the chemistry of these elements could be discerned by recognizing that they were, in fact, "f elements" as opposed to "d elements" like hafnium, tantalum, and tungsten.
The actinides become "lanthanide-like" at americium. Although americium can be oxidized to higher oxidation states, it's major oxidation state is +3; this is also the case with curium, berkelium and californium.
When I was a kid, the first mass spec with which I was used by one of the companies for which I worked had a californium ionization source; I'm an old guy. (Modern mass specs have other types of ionization inductions, notably electrospray ionization (ESI) for which John Fenn won the Nobel Prize.) The californium where I worked (in California) was the 252 isotope, which has a half-life of about 2.64 years, decaying both by spontaneous fission and by alpha decay to curium-248. The spontaneous fission of californium-252 made it a useful source of neutrons, and it was widely used in chemical analysis using neutron activation analysis, which has been mostly displace by high sensitivity ICP/MS instruments that for most elements can record parts per trillion.
Perhaps a current motivation, particularly in the days of antibody payloads is in neutron boron therapy, where small portable Cf-252 sources might displace the need for expensive accelerators, particular in rural or remote regions: Boron neutron capture therapy: Current status and future perspectives (Dymova, M.A., Taskaev, S.Y., Richter, V.A. and Kuligina, E.V. (2020), Cancer Commun., 40: i-i.)
In the 1960s and 1970's an effort was made to produce large (large being milligram quantities) of californium-252 as a neutron source and as an ionization source. (Mass specs in space robots generally use curium sources because of their longer half-lives.)
Another important isotope is plutonium-244, which has a half-life of 80 million years, and which is used as an internal standard in actinide analysis, and as a target for super-heavy element analysis.
The United States is running out of plutonium-244, and the paper listed above is about recovering it, as well as the transplutonium elements therein. The introduction to the paper covers things on which I touched above:
To recover the valuable materials, the Mark-18A material recovery flowsheet separates the targets aluminum cladding by caustic dissolution, leaving most of the fission products and the actinides as a solid material. The undissolved material is filtered and then subsequently dissolved in >7 M HNO3 at elevated temperatures. The resulting high nitrate solution, containing dissolved plutonium, actinides, and most of the fission products, will be sent through an anion exchange column using Reillex HPQ resin, similar to its use in the SRSs HB-Line Facility.(10?13) Reillex HPQ achieves Pu/Am decontamination factors on the order of 14,000.(11,12) The high decontamination factors are a result of Reillex HPQs high selectivity for the Pu(NO3)6 2 anion at >7 M HNO3 and little to no affinity for lanthanides (Ln), americium, curium, and fission products. As a result, in the Mark-18A material recovery flowsheet, the Ln, Am, Cm, and remaining fission products remain in the raffinate and require additional processing to recover heavy Cm from the >7 M HNO3 raffinate...
The Reillex HPQ resin is an anion exchange resin, a polyvinyl-N-methylpyridinium resin, that intereacts with the anionic plutonium (IV) hexanitrate anion (-2). In Reillex 402, the methyl group is replaced by a proton, in other N-pyridinium alkyl primary ammonium groups of various chain lengths to give a dicationic species.
The structure of these complexes are nicely shown in this cartoon:
Molecularly Engineered Resins for Plutonium Recovery
(S. Fredric Marsh, D. Kirk Veirs, Gordon D. Jarvinen, Mary E. Barr, and Eddie W. Moody, Los Alamos Science 26 (2000) 454-463)
The Los Alamos people note that some of the designed resins may also extract transplutonium nitrate complexes, but it would appearl that straight up Reillex HPQ (the methyl pyridinium is selective toward tetravalent plutonium nitrate complexes) and thus can be utilized in the current setting, where the target are trivalent species, specifically transplutonium actinides and lanthanides.
To save the world, the required inventory of plutonium - even in the "breed and burn" scenario where only a critical mass (realistically a little more) is required for start up - is on the order of hundreds of metric tons, and it is unrealistic that Reillex HPQ would be of much use on that scale.
These charged resins thrill, perhaps in the form of ionic liquids, the imagination about the possibility of electroprocessing.
I recall that when I was writing over in the E&E forum a lot, an anti-nuke of the particularly dull sort announced that nuclear energy was "too dangerous" because a tunnel at the Hanford site which had been abandoned collapsed. Pretty typically this person who is happily on my ignore list was far less interested in the 7 million people who died last year from air pollution while dumb guys get wedgies in their underwear about tunnels built in the 1950's which may contain (gasp) radioactivity. On investigation, it turns out that the tunnel contained some old abandoned chemical reactor vessels for plutonium purification ob rail cars, with trace plutonium on their surfaces. The number of lives lost associated with the collapsed rail tunnel was zero.
Reillex HPQ would be good to decontaminate the decontamination wash solutions to clean off the chemical reactors such as may exist from reprocessing efforts, but not for large scale processing. Let's be clear though, on a scale of risk, when compared with the very real and rising catastrophe of dangerous fossil fuels, unless one is a complete idiot - and sadly complete idiots exist - plutonium stains on a 50 year old chemical vessel is a non starter.
But in the case of the Mark-18A targets, these contain curium on a scale of a few hundred grams, and thus the resins have much to recommend them. Since the quantities are relatively small, but extremely valuable, column scale separations are entirely acceptable.
The authors note that during the last campaign to milk the Mark-18A targets for their valuable components, which took place in the early 1970s, a Dowex anion exchange resin was utilized. A difficulty with this resin, although it was clearly workable, was the release of sulfate from the sulfonylphenyl groups on which this relatively primitive anion exchange resin was based. Sulfates tended to contaminate the eluted products and raffinates, requiring additional clean up steps. Moreover, combustion of the used resins was problematic.
The more modern resin under discussion here contains only carbon oxygen and thus can be readily destroyed in an appropriate oxidation setting designed to contain residues.
The historical separation process is described as follows:
To prevent leaks, the authors were looking for a way to avoid the use of pressure, hence the evaluation of a new approach to the separations. All of the fermium and einsteinium in the targets has now decayed to lower actinides, of course, so they are no longer relevant to the case.
They write:
Although I do not have access to the exact structure of the commercial DGA resin, the structure of these resins is probably something along these lines:
(cf Mohapatra et al., RSC Adv., 2014,4, 10412-10419)
The authors conducted two tests, one using non radioactive fission product simulant with neodymium standing in for the actinides, and a second, also loaded with a fission product simulant spiked with the actinide americium.
The flow chart calls for the dissolution of the aluminum clad targets with caustic (which dissolves aluminum), leaving behind a solid residue of oxides which are then dissolved in 7M nitric acid. It is the nitrate complex which is separated as anionic species by the resin.
Some pictures from the text:
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A new wrinkle in this method as opposed to the method utilized in the 1970s also concerns the detection. For the purposes of these experiments, the complexes were monitored by their UV absorption spectra.
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The authors conclude as follows:
...Americium tracer experiments validated that Am breakthrough closely follows Nd breakthrough. An in-line UV/vis spectrophotometer was able to track the ingrowth of Nd in the raffinate solution. In full-scale processes, detection of Nd in the in-line UV/vis system will indicate Am breakthrough and serve as a warning that Cm breakthrough is forthcoming. Future work will focus on column design for the full-scale process in SRNL hot cells. Additionally, research is underway to apply the CHON principle and incinerate the loaded DGA Resin to reduce volume while directly converting the loaded metal to a stable oxide form for shipment.
Cool paper I think, with some application, for cleaning chemical reaction vessels used in the essential - if we are to save the world - separation of the higher actinides.
I trust you are enjoying, as much as I am, the first weekend in the already magnificent Presidency of Joe Biden, and are doing so safely.
flamin lib
(14,559 posts)Eko
(7,170 posts)and keep straw-manning them is a really cowardly thing to do.
NNadir
(33,368 posts)...that I took one of the people on my ignore list off of it because it appears that they clutter the comments sections of my posts, since there are more posts than I can read.
What might I imagine such a person might have to say to me? Anything meaningful? Anything I care about?
I write lots of posts on DU, many of them, most of them probably, about subjects in the scientific literature. These posts take time and study to write, because as I write them, I am learning new things, poking around for references, studying graphics.
In addition, I make clear my moral stance on energy. I find it ethically unforgivable that between 18,000 to 19,000 people die every day - more people than die each day from Covid-19 - from the dangerous fossil fuel waste also known as "air pollution."
Referring to one of the premier medical scientific journals in the world, Lancet, I support this claim by showing that this death toll represents a solid epidemiological estimate:
Global, regional, and national comparative risk assessment of 79 behavioural, environmental and occupational, and metabolic risks or clusters of risks, 19902015: a systematic analysis for the Global Burden of Disease Study 2015 (Lancet 2016; 388: 1659724) One can easily locate in this open sourced document compiled by an international consortium of medical and scientific professionals how many people die from causes related to air pollution, particulates, ozone, etc.
Now.
I often note that many, most, of the evocations by the anti-nukes I encounter represent logical fallacies of one sort of another, but the whiniest bad thinking in which they engage is a claim that there is a "straw man." As I have zero respect for the intellect of these sorts, to be honest, less than zero, I couldn't care less about how they do or do not define this tiresome locution, "straw man."
It is a fact that a poster on this website, called up one of my posts, probably in the E&E forum where I currently seldom write, long after it had vanished into the void of forgotten posts, to point out some dullard nonsense about a collapsed tunnel at the Hanford Weapons plant. It was certainly nothing I'd heard about, and had I heard of it, I almost certainly would have ignored it.
It is not worth any time or effort to locate that post, to prove what's not worth proving, since I am already wasting time discussing weak thinking in writing this post.
I will say though, as the post about the collapsed tunnel was a perfect indication of the trivializing mentality of anti-nukes, their almost paranoid belief that if a single atom of a radionuclide is not permanently contained it will magically tunnel into their tiny brains and kill them, it stuck in my mind as a kind of symbol.
As a result of hearing about this, and somewhat amused by the kind of mentality that could represent this event as even remotely important, I did look into the event of the collapsed tunnel. It appears that some old chemical reactors for actinide separations were loaded on to a flat bed rail car that was parked in the tunnel. Then everyone forgot about it. The tunnel collapsed, end of story.
Now, since I am expert in actinide chemistry, at least in a theoretical sense if not a practical sense, and since the Hanford plant was dedicated to manufacturing nuclear weapons - which I oppose - I suspect that the chemical reactor contains residual plutonium and perhaps some fission products as stains, a thin microlayer that proved difficult to remove. Undoubtedly the plutonium is present as the (IV) oxide, which has polymeric form and is notoriously difficult to dissolve. If it rains like hell on the tunnel site for a million years, it is very unlikely that the plutonium will migrate 10 meters, if that. The data from the Oklo natural nuclear reactors suggests as much.
Hanford, of course, is the big boogeyman in the mind of anti-nukes, even though the death toll from radiation exposure in the nearby town of Richland is vanishingly small. It is perfectly justifiable in their minds that endless sums of money be spent to "clean up" the site to a safety standard that the air in Los Angeles, and thousands of other cities around the world cannot meet, a standard suggesting that no radioactive atom can even be imagined to find its way into the tiny little brains of scientifically illiterate anti-nukes. Meanwhile, on this planet, two billion people lack access to any form improved sanitation. If we spent the money that we spend on Hanford to provide improved sanitation to those who lack it, we might save some significant fraction of the 432,000 lives lost each year from sewage.
Now.
Is it a lack of courage that prevents, say, Nancy Pelosi from sitting down for a nice professional conversation with say, Marjorie Taylor Greene to discuss whether or not there really are lizard people and whether school shootings are false flag events?
Probably not.
I would submit t's probably disgust.
I hope this clarifies how I feel about all of this, although I expect the effort is a waste of valuable time, time I will not spend again, while feeling absolutely free to discuss the mentality that raises a point about a tunnel at Hanford.
Have a nice evening.
Eko
(7,170 posts)I never said anything to imply this.
"I will say though, as the post about the collapsed tunnel was a perfect indication of the trivializing mentality of anti-nukes, their almost paranoid belief that if a single atom of a radionuclide is not permanently contained it will magically tunnel into their tiny brains and kill them, it stuck in my mind as a kind of symbol."
Total straw man.
Thanks,
Eko.
NNadir
(33,368 posts)Lots of whiny people write there.
Now, if someone were to actually know some science, which is apparently not relevant in this case, one could discern that the urgency of a collapse of a tunnel at Hanford, certainly implies a concern about single atoms, certainly fewer radioactive atoms than a 70 kg person experiencing from K-40 in their bodies.
Why? Because, as stated, plutonium oxide is insoluble, very insoluble, which is why it is often modeled using cerium (IV) oxide, which is similarly insoluble.
But what's the point?
I already stated how I feel about whining about "straw men." I lack a shred of intellectual or moral respect for someone quibbling with this whiny trash, because, basically, I don't give a rat's ass about what any hair splitting fool thinks, implies, or knows.
Now, this is the science forum, and the current whining is taking place topic about which I enjoyed writing, actinide chemistry.
Like I said, there's nothing interesting that I could possibly find in addressing whining, nothing at all, no intellectual pleasure, no moral pleasure; as implied, there is only disgust, and predictably, I'm disgusted.
I will probably once again talk about the airhead who called up one of my posts to tell me all about the big, bad, tunnel collapse at Hanford, and carries on mindlessly "straw, straw, straw!"
At least, in The Wizard of Oz, the "strawman" ended up with a brain. There's no risk of any of that here.
Eko
(7,170 posts)Ive told you that multiple times. I think we need them. All I did was say that nukes weren't safer than renewables and you decided to then call me anti nuke and tons of other things, insult me and misconstrue everything I have said since then. You have problems.