Separations of Actinides and Lanthanides From Used Nuclear Fuel with Destructible Ligands.

[NNadir]

As the United States commits scientific suicide in the reign of its idiot king installed by the weakest minds with the lowest moral sense, work on saving the world goes on in the rest of the world. The paper I'll discuss in this post is from the nation that now leads in nuclear innovation, China, given the deliberate destruction of American scientific strength by uneducated incompetent fascist fools running our government for the purpose of destroying it.

A key resource for saving the world is used nuclear fuel, which contains many valuable materials, among them the transuranium actinides neptunium, plutonium, americium, and curium, along with some higher actinides. The transuranium actinides are always formed in the presence of their formal congeners the lanthanides (aka "rare earth" elements), particularly the sub-gadolinium lanthanides from lanthanum up to an including gadolinium. The separation of plutonium, neptunium and uranium from the lanthanides has been industrially practiced for decades, but (as I'm working to inform my son) increasingly available transplutonium actinides, americium and curium. I believe these two elements offer some properties that make them important resources for a sustainable world, particularly given their exceptionally valuable neutronics.

The paper to which I'll refer in this post is this one:

Efficient Trivalent Actinide-Lanthanide Separations Using Hydrophilic CHON-Compliant Phenanthroline-Dicarboxamide Ligands Yong Qiang Wan, Huai Xin Hao, Yang Yang Zhang, Yu Xiao Guo, Zhi Jun Ma, Zhi Peng Wang, Jun Li, and Pavle Mocilac Industrial & Engineering Chemistry Research 2025 64 (24), 12185-12199.

From the introduction:

The proposed innovative SANEX (i-SANEX) process for separation of minor actinides offers an effective method for advanced nuclear separation. (1−3) This method is essentially an extension of the DIAMEX process, utilizing diglycolamide ligands (4) to efficiently extract both actinides (An) and lanthanides (Ln) from the raw PUREX raffinate. (5) The subsequent step involves stripping the minor actinides into the aqueous phase using an efficient hydrophilic ligand. Developing such ligands is a challenge, and to date, no ligands have been implemented in industrial applications, while both i-SANEX and DIAMEX are still under development. (6)

There are several classes of hydrophilic ligands developed for the i-SANEX process, which include sulfonated bistriazinyl-pyridines (SO₃–BTP), (7) sulfonated bistriazinyl-bipyridines (TS-BTBP), (8) bistriazinyl-phenanthrolines (TS-BTPhen), (8,9) and bistriazolyl-phenanthrolines (10) (DS-BTrzPhen). Their ability to strip minor actinides from DIAMEX raffinate is satisfactory for most of them, while the disadvantage of sulfonated ligands is not being CHON-compliant. On the other hand, the number of promising CHON-compliant ligands is limited and includes primarily bistriazolyl-pyridines such as PTD. (11,3) In this context, “CHON” refers to ligands composed solely of carbon, hydrogen, oxygen, and nitrogen. This criterion is significant because the subsequent processing of extracts containing americium (Am) and curium (Cm) complexed with these ligands will involve solvent evaporation and thermal oxidation. During this process, C, H, O, and N will combust into gaseous oxides, leaving behind only metal oxides. The presence of other elements would complicate the final stages of reprocessing and result in unnecessary secondary waste. (12)

A crucial category of CHON-compliant ligands is the 1,10-phenanthroline-dicarboxamides, commonly referred to as diamide-phenanthrolines (Figure 1a) or “DAPhens”. (13) These ligands operate on the hard–soft (O/N) donor concept. Initially developed for the SANEX process, DAPhens were designed to be lipophilic, while their development was inspired by dipicolinic acid diamides by adapting the “hard–soft” donor concept from pyridine to phenanthroline. (14) A landmark study published in 2014 by Xiao et al. introduced Et-Tol-DAPhen (Figure 1b), which demonstrated favorable separation factors for actinides compared to europium (Eu) (SF_An/Eu) in acidic media. (15) While DAPhens exhibited moderate SF_An/Ln values in conventional solvents, (16) they demonstrated improved efficiency in 1,2-dichloroethane (17) or nitrobenzene, (18,19) while in 1-(trifluoromethyl)-3-nitrobenzene (F-3) the SF_An/Ln values reached excellent levels, ranging from 600 to 700. (20−22) DAPhens were also tested in ionic liquids, however without significant improvement in selectivity. (23,24) Derivatives of DAPhen with 4,7-dichloro (25,26) and fluoro (27) functional groups on the phenanthroline core moiety were also developed (Figure 1c)...(28)

Structures of ligands:



The caption:

Figure 1. (a) General structures of 1,10-phenanthroline-dicarboxamides, (b) Et-Tol-DAPhen, (15) (c) 4,7-derivatized chloro- and fluoro-DAPhens, (28,27) and (d) DS-Ph-DAPhen. (30)

The caption:

Figure 2. Recently developed hydrophilic DAPhens: (a) 2OH-DAPhen (32) or Phen-2DIC2OH, (31) and (b) 4OH-DAPhen. (32)

The caption:

Figure 3. Structures of (A) AE-DAPhen (ligand 1) and (B) AEE-DAPhen (ligand 2).

The paper goes into the synthetic details of these ligands, and then describes a number of experiments to determine the separation factors (SF) for lanthanide species (focusing on europium in many cases) and the actinides curium and americium. I note that these two actinides, unlike the other actinides in used nuclear fuel, uranium (which dominates the mass), neptunium and plutonium, do not form volatile fluorides, and thus will remain with those fission products which cannot be volatilized, consisting largely of the lanthanides. Thus I see this process as synergetic with the important fluoride volatility residues.

There are a lot of graphics showing separation factors under various conditions, and I will not produce most of them, but offer this sample:



The caption:

Figure 9. DM(III), SF_Eu/Cm, and SF_Cm/Am for AE-DAPhen (Ligand 1) vs TODGA as a function of increasing concentration of nitric acid (acidity test) by the masking method. Aqueous phase: 10 mM ligand 1 in aqueous HNO3. Organic phase: 0.2 M TODGA in kerosene/1-octanol (95:5, v/v).

The separation of curium from americium is relatively modest, but one could argue that it would be OK - even in some cases desirable - to carry some curium - as a source of spontaneous fission neutrons - in an americium based nuclear fuel.

The paper contains some wonderful scientific details, including molecular orbital discussions related to the binding, but they are superfluous to discuss here.

Some additional commentary from the authors:

The primary goal of this study was to develop highly soluble hydrophilic DAPhen ligands, and this goal was successfully achieved. The ligands developed herein demonstrated high solubility and good selectivity in aqueous media, remaining soluble at various concentrations and acidity levels (see Figure 5). It is important to note that ligand 2 (AEE-DAPhen) is, in fact, a viscous sticky hydrophilic liquid. Additionally, compliancy with CHON, along with their ease of synthesis and the relatively low cost of the starting materials, makes these ligands both technically applicable and financially feasible for use in actual industrial nuclear separations.

We thoroughly investigated the ability of the two ligands, 1 and 2, to separate Am(III) ions from Eu(III) ions using two different methods: masking and stripping. Both methods yielded similar excellent results for SF_Eu/Am of 201–210 at 0.5 M acidity. However, increasing the ligand concentration to 30 mM brings the SF_Eu/Am values to 290–325 even at a 0.75 M acidity. The lower separation factors for ligand 2 (AEE-DAPhen) can be considered as evidence that the presence of hydrophilizing ethylene-glycol chains may interfere with the selectivity and extraction characteristics of these ligands. In fact, poly(ethylene-glycol) chains were so far avoided as hydrophilizing groups due to their ability to interfere with the coordination process. Our theoretical study herein suggests that ethylene-glycol chains do engage in coordination with lanthanides, whereas it could be assumed that the interaction in the case of ligand 2 could be more pronounced due to the flexibility of the chains. Yet, there is no crucial evidence that the presence of these chains is detrimental to selectivity toward Am(III) ions since ligand 2 can still be regarded as a selective ligand.

From the paper's conclusion:

We successfully developed and characterized AE-DAPhen and AEE-DAPhen, which exhibit superior solubility and selectivity for Am(III) in acidic solutions. Their solubilities in aqueous nitric acid solutions proved to be better than those of similar, recently reported hydrophilic DAPhen ligands due to the more efficient hydrophilizing groups. Their synthesis is simple and straightforward, based on relatively cheap starting materials, and with good overall yields, making them attractive options in actual industrial nuclear separations. Their selectivity and extractability toward Am(III) ions expressed by _Cm/Am, D_Am, and SF_Eu/Am parameters proved to be very good, reaching 325 (for ligand 1) and 291 (for ligand 2) at 30 mM ligand concentration and the acidities ranging from 0.5 and 0.75 M, which are comparable or better than recently reported similar hydrophilic ligands. The separation tests of Cm(III) from Eu(III) ions showed lower but still feasible SF_Eu/Cm values of 50 to 55 at 0.5 M acidity and 10 mM ligand concentration, bringing the relative SF_Cm/Am value parameter to an unprecedented range of 7.4 to 7.8.

It's a nice paper to see. The key to saving the world is mass efficient use of actinide resources, especially ²³⁸U, so called "depleted uranium" by converting it to plutonium and higher actinides.

Even though the United States is a free fall stemming from its long history of and enthusiasm for racism, the rest of the world can go on to do the necessary tasks we have abrogated.

Have a nice weekend.