Solvent Optimization Studies for a New EURO-GANEX Process with 2,2’-Oxybis( N,N -di- n -decylpropanamide) (mTDDGA) and Its Radiolysis Products

The diglycolamide 2,2’-oxybis(N,N-di-n-decylpropanamide) (mTDDGA) is being studied as an extractant for actinides and lanthanides in the European Grouped Actinide Extraction (EURO-GANEX) process. The aim is the development of a more simplified process using a single extractant instead of a mixture of extractants used in the current EURO-GANEX process. This work presents solvent optimization studies of mTDDGA, with regards to the extraction characteristics of the different diastereomers of mTDGA and of mixed diastereomer solutions. Also radiolysis behavior has been studied by irradiation of solvent extraction systems in a gamma irradiation facility using $^{60}$Co. The availability of irradiated organic solutions made it possible to gain valuable insights into the plutonium loading capacity after gamma-irradiation of the solvent up to 445 kGy and to quantify degradation compounds. Solvent extraction characteristic of the major degradation compounds themselves were determined. Like other methylated diglycolamides, we found a remarkable difference in extraction of up to two orders of magnitude between the two diastereomers. High plutonium loading (36 g L$^{−1}$) is feasible using this single extractant, even after absorbing a dose of 445 kGy. This remarkable observation is possibly promoted by the presence of the main degradation compound which extracts plutonium verywell

Stability of different BTBP and BTPhen extracting or masking compounds against γ radiation

The radiolytic stability of hydrophobic extracting compounds CyMe4-BTBP and CyMe4-BTPhen and a hydrophilic masking agent (PhSO3H)2-BTPhen, widely employed for trivalent minor actinoid and lanthanoid separation, against γ radiation was tested. Even though the solvent with a promising fluorinated diluent BK-1 provides better extraction properties compared to octan-1-ol, its radiation stability is much lower, and no extraction was observed already after an absorbed dose of 150 kGy (CyMe4-BTBP) or 200 kGy (CyMe4-BTPhen). For the (PhSO3H)2-BTPhen hydrophilic masking agent, the results showed that the rate of radiolytic degradation was significantly higher in 0.25 M HNO3 than in 0.5 M HNO3. For both the hydrophobic and hydrophilic agents, degradation was slower in the presence of both organic and aqueous phases during irradiation

A capillary micro-reactor as a tool to study pressurized reactions; The influence of pressure on the stereoselectivity of the diels-alder reaction of 2- and 3-furylmethanol with maleimides

The influence of a pressure of 60 MPa on theconversion and the stereoselectivity of the Diels-Alderreaction of 2- and 3-furylmethanol with methyl-, benzyl-, andphenylmaleimide was studied in a capillary micro-reactor. Inthe case of 2-furylmethanol, a 1.7-fold higher conversion wasobtained at 60 MPa with respect to 0.1 MPa experiments.Pressure positively affects the formation of the exo isomer,whereas in the case of 3-furylmethanol pressure does notaffect the reaction

Sequestration of Am3+ and Eu3+ into ionic liquid containing Aza-macrocycle based multiple-diglycolamide ligands: Extraction, complexation, luminescence and DFT studies

Extraction of Am3+ and Eu3+ was carried out into a room temperature ionic liquid, C8mim⋅Tf2N, using two multiple-diglycolamide extractants with three or four diglycolamide arms tethered to either a triaza- or tetraazamacrocyclic ligand termed as TAM-3-DGA and TAM-4-DGA, respectively. The metal ion extraction was highly efficient as only 5 × 10-4 M solutions of TAM-3-DGA resulted in D values of 680 and 845 for Am3+ and Eu3+, respectively, at pH 2.0, while the respective values with a five times lower concentration of TAM-4-DGA were 142 and 296, which is probably the best reported thus far. Though Eu3+ ion was preferentially extracted over Am3+, the selectivity was not as good as reported in molecular diluent-based extraction systems. The extracted species contained two units of the extractant and did not contain any nitrate ion suggesting a cation-exchange mechanism. Studies on the temperature effect on metal ion extraction were carried out to determine the thermodynamic parameters. Luminescence studies of the extracts were also performed which suggested strong complex formation with no inner-sphere water molecules. To understand the ligand coordination to Eu3+ and Am3+ and other bonding parameters, DFT studies were carried out

Highly efficient and selective extraction of Pu(IV) using two alkyl-substituted amides of nitrilo triacetic acid from nitric acid solutions

Liquid-liquid extraction of the actinide ions UO22+, Pu4+, Am3+ was carried out from nitric acid feed solutions using two tripodal amide extractants, viz., N,N,N’,N’,N”,N”-hexa-n-octylnitrilotriacetamide (HONTA) and N,N,N’,N’,N”,N”-hexa-n-dodecylnitrilotriacetamide (HDDNTA) in 10% isodecanol + 90% n-dodecane diluent. The metal ion extraction trend was: Pu(IV) ≫ U(VI) > Am(III) at 3 M HNO3, HONTA being a superior extractant than HDDNTA. Slope analysis indicated ML2 type species for both Pu(IV) and Am(III) at 3 M HNO3 and pH 2.0, respectively, whereas, only in case of HONTA, a ML type species was obtained with U(VI) at 3 M HNO3. Back extraction data suggested that a mixture of 0.5 M HNO3 + 0.5 M oxalic acid was efficient for quantitative stripping (∼90%) of Pu(IV), whereas 1 M Na2CO3 and 1 M α-HIBA gave satisfactory back extraction for U(VI) and Am(III), respectively. The ligand solutions showed reasonably good radiation stability up to an absorbed total gamma ray dose of 274 kGy. Distribution data were also obtained under U(VI) loading conditions for possible nuclear fuel cycle applications

A capillary micro-reactor as a tool to study pressurised reactions: The influence of pressure on the stereoselectivity of the Diels-Alder reaction of 2- and 3-Furylmethanol with maleimides

The influence of a pressure of 60 MPa on theconversion and the stereoselectivity of the Diels-Alderreaction of 2- and 3-furylmethanol with methyl-, benzyl-, andphenylmaleimide was studied in a capillary micro-reactor. Inthe case of 2-furylmethanol, a 1.7-fold higher conversion wasobtained at 60 MPa with respect to 0.1 MPa experiments.Pressure positively affects the formation of the exo isomer,whereas in the case of 3-furylmethanol pressure does notaffect the reaction

Highly Efficient Extraction Chromatography Resin Containing Hexa‑<i>n</i>‑Octyl Nitrilotriacetamide (HONTA) for Selective Recovery of Plutonium from Acidic Feeds

An extraction chromatography resin was prepared by impregnating hexa-n-octyl nitrilotriacetamide (HONTA) on chromosorb-W. This resin shows very efficient performance for selective separation of Pu4+ over other actinides like uranium and americium. The distribution coefficient for Pu4+ (at 3 M HNO3) was on the order of 104 mL/g, with separation factors of >103 for other actinides. The extraction kinetics for Pu4+ was slow and took 20 min of shaking for reaching the equilibrium conditions and followed both the film diffusion and the intraparticle diffusion kinetic models. The Pu4+ sorption on the resin followed the Langmuir monolayer model with a sorption energy of 11.2 kJ/mol. The maximum Pu4+ loading capacity on the resin was 58.2 mg/g resin, which corresponds to 1:1 Pu/ligand complex formation. Excellent column performance was observed for selective separation of Pu4+ from a mixture of Pu, Am, and U in a 3 M HNO3 solution

Gamma-radiolytic stability of new methylated TODGA derivatives for minor actinide recycling

The stability against gamma radiation of MeTODGA (methyl tetraoctyldiglycolamide) and Me2TODGA (dimethyl tetraoctyldiglycolamide), derivatives from the well-known extractant TODGA (N,N,N′,N′-tetraoctyldiglycolamide), were studied and compared. Solutions of MeTODGA and Me2TODGA in alkane diluents were subjected to 60Co γ-irradiation in the presence and absence of nitric acid and analyzed using LC-MS to determine their rates of radiolytic concentration decrease, as well as to identify radiolysis products. The results of product identification from three different laboratories are compared and found to be in good agreement. The diglycolamide (DGA) concentrations decreased exponentially with increasing absorbed dose. The MeTODGA degradation rate constants (dose constants) were uninfluenced by the presence of nitric acid, but the acid increased the rate of degradation for Me2TODGA. The degradation products formed by irradiation are also initially produced in greater amounts in acid-contacted solution, but products may also be degraded by continued radiolysis. The identified radiolysis products suggest that the weakest bonds are those in the diglycolamide center of these molecules