Effect of radiolysis of TODGA on the extraction of TODGA/n-dodecane toward Eu(III): An experimental and DFT study

Effect of radiolysis of TODGA on the extraction of TODGA/n-dodecane toward Eu(III): An experimental and DFT study 1 2 equal first-author https://orcid.org/0000-0003-0001-6320 3 equal https://orcid.org/0000-0002-0364-216X 2 1 1 2 2 2 2 corresp * jpeng@pku.edu.cn * jpeng@pku.edu.cn jpeng@pku.edu.cn https://orcid.org/0000-0003-2294-9682 1 corresp hb0012@sina.com hb0012@sina.com hb0012@sina.com Department of Radiochemistry, China Institute of Atomic Energy, Beijing 102413, China Department of Radiochemistry, China Institute of Atomic Energy, Beijing 102413, China Beijing National Laboratory for Molecular Sciences, Radiochemistry and Radiation Chemistry Key Laboratory for Fundamental Science, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, China Beijing National Laboratory for Molecular Sciences, Radiochemistry and Radiation Chemistry Key Laboratory for Fundamental Science, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, China Institute of Nuclear Physics and Chemistry, China Academy of Engineering Physics, Mianyang 621900, China Institute of Nuclear Physics and Chemistry, China Academy of Engineering Physics, Mianyang 621900, China N,N,N’,N’-Tetraoctyl diglycolamide (TODGA) is one of the most promising extractants tailored for high-level liquid radioactive waste treatment during nuclear fuel reprocessing. The γ-radiolysis of TODGA (0.2 mol/L) in n- dodecane ( n DD) solution with and without pre-equilibrated 3.0 mol/L HNO 3 was investigated using HPLC and UPLC-QTOF-MS and compared with the γ-radiolysis of neat TODGA in this study. With increased absorbed doses, the concentration of TODGA decreased exponentially for the studied systems. Moreover, pre-equilibration with HNO 3 (3.0 mol/L) slightly influenced the γ-radiolysis of TODGA in n DD. Seven radiolytic products generated from the rupture of the C – C, C – O, and C – N bonds in TODGA were identified in the studied extraction system. The influence of γ-radiation on TODGA/ n DD for the extraction of Eu(III) was evaluated using the first combination of extraction experiments and density functional theory (DFT) calculations, in which the complexations of Eu(III) with TODGA and its radiolytic products were systematically compared. Based on the radiolysis kinetic model of TODGA, the slope curve of the distribution ratio of Eu(III) ( D Eu ) and the absorbed dose, and fluorescence titration analysis, the empirical equation of the absorbed dose and D Eu was obtained successfully. Below 300 kGy, the experimental D Eu agreed well with the obtained empirical equation for TODGA/ n DD. Conversely, at a high absorbed dose, the experimental D Eu was higher than the theoretical D Eu based on the empirical equation because the radiolytic products of TODGA with similar coordination structures still possessed partial complexation toward Eu(III) This was confirmed by DFT calculations. This work provides a method to predict the extraction distribution ratio of an irradiated extractant system and to understand the complex extraction process. TODGA Radiolytic products Extraction Density functional theory Complexation Introduction 1 Spent nuclear fuel (SNF) reprocessing generates high-level liquid radioactive waste (HLLW), which is composed of unextracted U and Pu, long-lived fission products ( 129 I, 99 Tc, 135 Cs, and 93 Zr), short-lived fission products ( 90 Sr and 137 Cs), minor actinides (MAs) (Np, Am, and Cm), and stable lanthanide isotopes (Eu, Nd, La, Tb, Pr, Gd, Sm, Ce, and Pm)[ 1 1 - 10 10 1-10 ]. To reduce the radiotoxicity and volume of HLLW and improve resource utilization, partitioning and transmutation strategies have been explored to shorten the half-life of long-lived radioisotopes. However, the transmutation efficiency of MAs is limited by the high thermal neutron capture cross-sections of several lanthanide isotopes owing to competition for available neutrons[ 11 11 , 12 12 ]. Thus, separating MAs from lanthanides (Lns) before transmutation is crucial. During the liquid–liquid extraction process, N,N,N’,N’-tetraoctyl diglycolamide (TODGA) has proven to be efficient in extracting actinides (Ans) and lanthanides [ 2 2 , 13 13 - 16 16 13-16 ]. Furthermore, TODGA is a tridentate ligand that shows high distribution ratios for Lns(III)/Ans(III) because the hydrophilic groups exhibit stable metal coordination in the aqueous phase and the hydrophobic groups ensure its solubility in the organic phase[ 17 17 , 18 18 ]. It has been used in some processes, such as the innovative Selective ActiNide EXtraction (i-SANEX) process[ 19 19 , 20 20 ] and the EUROpean Grouped Actinide EXtraction (EURO-GANEX) process[ 21 21 , 22 22 ]. The i-SANEX process was first arranged utilizing an organic solution with TODGA (0.2 mol/L) and 1-octanol (5% v/v) to enable co-extraction of trivalent Lns and Ans from simulated HLLW. At the same time, Pd and Zr were masked by cyclohexane diamine tetraacetic acid (CDTA). Second, the co-extracted Mo and Sr were stripped using 3.0 mol/L HNO 3 aqueous solution with CDTA (0.05 mol/L) and oxalic acid (0.2 mol/L) as scrubbing solvents, followed by a back-extraction step using an aqueous solution containing 2,6-bis(5,6-di(sulfophenyl)-1,2,4-triazin-3-yl)pyridine (SO 3 -Ph-BTP) (1.8×10 -2 mol/L) in HNO 3 (0.35 mol/L) for selective stripping of Ans(III). The final step was the stripping of Lns(III) using a citrate buffer solution. The experimental results obtained by Wilden et al.[ 19 19 ] demonstrated the effectiveness of this process. In the Ans product fraction, Cm(III) and Am(III) were efficiently stripped (more than 99.8%) and regained within six stages. The purity of the Cm(III) and Am(III) products was found to be very good, with only Ru (0.4%), Sr (0.3%), and Lns(III) (0.1%) contamination. Lns(III) stripping is efficient (more than 99.5%) within only four stages using a stripping solution containing citric acid with a pH of 3. The EURO-GANEX process consists of two cycles. In the first cycle, hydrogenated tetrapropene (TPH) containing N,N-di (2-ethylhexyl) isobutyramide (DEHiBA) (1.0 mol/L) was applied to extract U(VI) selectively. In the second cycle, the extraction of Cm(III), Am(III), Pu(IV), Np(VI), and Lns(III) from the first cycle raffinate was achieved using N,N’-dimethyl-N,N’-dioctyl-2(2-hexyloxyethyl)-malonamide (DMDOHEMA) (0.5 mol/L) and TODGA (0.2 mol/L) in a kerosene diluent, while CDTA (0.055 mol/L) was applied as a masking agent, to prevent the extraction of Zr(IV) and Pd(Ⅱ). The Sr and Fe were extracted using HNO 3 (0.5 mol/L) from the loaded solvent, and trans-uranium elements (TRU) were back-extracted by applying an aqueous solution containing aceto-hydroxamic acid (AHA) and SO 3 -Ph-BTP, while Lns(III) was retained in the organic solution. The EURO-GANEX process was successfully demonstrated by the hot test performed by Malmbeck et al.[ 23 23 ]. Moreover, Pu(IV), Np(VI), Am(III), and Lns(III) were efficiently co-extracted from the raffinate of the EURO-GANEX process during the first cycle; Mo and Zr were also co-extracted, whereas the other fission products were successfully refused. Within six strip stages, 99.91% Np, 99.85% Pu, 99.90% Am, and co-extracted Mo and Zr were well back-extracted, whereas 99.9% Lns(III) was retained in the organic solution within four strip stages using an aqueous solution containing AHA and SO 3 -Ph-BTP. Previous studies have shown that TODGA provides significantly higher distribution ratios in alkanes such as n- dodecane ( n DD) than in other studied diluents, such as secondary ketones, primary alcohols, and secondary alcohols [ 24 24 , 25 25 ]. The extraction system of TODGA/ n DD can be applied to separate MAs and Lns from other fission products. Once separated, the extraction of individual elements can be simplified with additional processing, culminating in the separation of MAs from Lns [ 26 26 - 28 28 26-28 ]. Because the extraction system is exposed to the radioactive environment formed by the radionuclides, its radiation stability is an important factor to be examined before its practical application [ 29 29 ]. In the solvent extraction process, the γ-radiolysis of TODGA is problematic because of the highly radioactive HLLW. Because the loss of TODGA and the radiolytic products of TODGA formed during γ-radiation can adversely affect the extraction performance in the liquid–liquid extraction process toward metal ions, it is essential to measure the γ-radiolysis yield and radiolytic products of TODGA and to study their effects on the performance of extracting metal ions. Radiolysis of TODGA in n DD under different conditions has been investigated in some studies [ 30 30 , 31 31 ]. It was found that the magnitude of α-radiolysis of TODGA is lower than that of γ-radiolysis, and they have similar radiolytic products [ 32 32 ]. This is attributed to the fact that the linear energy transference of α particles is higher than that of γ particles, and the radical yield of n DD decreases by recombination in α-radiolysis. Although the γ-radiolysis and extraction of TODGA have been investigated, the effect of γ-radiolysis and radiolytic TOGDA products on extraction in the TODGA/ n DD system has rarely been reported. In addition, if we could predict the extraction performance of the irradiated extractant system using equations, it would be very beneficial and important in controlling the partition process. To the best of our knowledge, the mathematical correlation between the radiolysis of the extractant and the distribution ratio has seldom been studied. In this work, because α and γ rays result in similar radiolysis products of TODGA and γ-radiation is easier to carry out in the laboratory, the radiolytic behavior and γ-radiation stability of TODGA in the 0.2 mol/L TODGA/ n DD system (TODGA/ n DD) and the 0.2 mol/L TODGA/ n DD that was pre-equilibrated with 3.0 mol/L HNO 3 system (HNO 3 -TODGA/ n DD) were studied qualitatively and quantitatively. They were also compared with radiolysis of neat TODGA. The content and radiolysis products of TODGA were determined using HPLC and UPLC-QTOF-MS, respectively. Considering the chemical similarity between trivalent lanthanides and minor actinides, and to avoid the dangers of handling radioactive isotopes in standard laboratories, Eu(III) was selected as a model metal ion in our extraction experiment to assess the extraction performance of TODGA/ n DD after γ-radiation. The density functional theory (DFT) calculation, which can estimate the coordination abilities of TODGA and its radiolytic products, was applied to explain the effect of the radiolytic products on our extraction of Eu(III). For the first time, a combination of theoretical calculations and extraction experiments was used to demonstrate that the radiolytic products maintain partial complexation, which capably explains the extraction behavior of irradiated samples. For the TODGA/nDD system, an in-depth understanding of the effects of γ-irradiation on the extraction behavior was obtained from this study. Experimental 1 Materials 2 Sichuan University synthesized TODGA (≥98%); its purity was confirmed by FT-MS (ESI + ) and 1 H NMR (Fig.S1–S2). Moreover, Eu(NO 3 ) 3 ·6H 2 O (99.99%) was obtained from MREDA Technology Co. Ltd. Formic acid, liquid chromatography-mass spectrometry (LC-MS) grade, was purchased from Thermo Fisher Scientific. Methanol (LC-MS grade) was purchased from Honeywell Trading (Shanghai) Co., Ltd. The aqueous dilution was performed using ultrapure water (18.2 MΩ·cm). All other chemicals were of analytical grade, and the chemicals were not further purified. Gamma irradiation 2 TODGA and TODGA/ n DD solutions equilibrated with and without HNO 3 (3.0 mol/L) before γ-radiation were irradiated in the air at room temperature (25 ± 5 °C) using a 60 Co source (Department of Applied Chemistry in the College of Chemistry, Peking University, China) with an absorbed dose rate of 6.6 kGy/h, as determined by a Fricke dosimeter. Quantitative analysis of TODGA after irradiation 2 An HPLC method with UV detection (SPD-16, Shimadzu, Japan) was used to quantitatively analyze the TODGA concentration in the irradiated samples. Additionally, HPLC was carried out at 25 ± 5 °C using an Agilent HC-C18 liquid chromatography column (5 μm, 4.6 mm × 150 mm) to achieve chromatographic separation with a UV wavelength fixed at 210 nm. The aqueous component was ultrapure water with formic acid (1‰ v/v) (A 1 ); the organic component was methanol (B 1 ). The elution program in our liquid chromatography was listed hereafter: 0–10 min, 30–100% B 1 ; 10–20 min, 100% B 1 ; 20–22 min, 100–30% B 1 . The error values in the quantitative analysis experiments were within 5%. The flow rate was 1.0 mL/min, and the injection volume was 20 µL. Identification and semi-quantification of radiolytic products 2 Ultra-high pressure liquid chromatography (UPLC) (ACQUITY I-Class, Waters, USA) was carried out using an Agilent HC-C18 liquid chromatography column (5 μm, 4.6 mm × 150 mm) at 40 °C to achieve chromatographic separation. The aqueous component was ultrapure water with formic acid (1‰ v/v) (A 2 ), and the organic component was methanol with formic acid (1‰ v/v) (B 2 ). The liquid chromatography elution program was listed hereafter: 0–4 min: 30–100% B 2 ; 4–13 min: 100% B 2 ; 13–13.1 min: 100–30% B 2 ; 13.1–15 min: 30% B. The flow rate was 0.8 mL/min with a 1 µL injection volume. The mass-spectrometer conditions of the quadrupole time-of-flight mass spectrometry (QTOF-MS) (Vion IMS QToF, Waters, USA) are listed here: desolvation temperature: 300 °C; source temperature: 120 °C; desolvation gas flow: 800 L/h; capillary voltage: 2.8 kV; cone gas flow: 50 L/h; positive mode. The data were acquired and processed using a Waters UNIFI Scientific Information System with a mass target match tolerance of less than 5 ppm. Extraction experiment 2 The TODGA was dissolved with n DD to obtain a 0.7 ml organic phase with a concentration of 0.2 mol/L. The Eu(NO 3 ) 3· 6H 2 O was dissolved in 3.0 mol/L HNO 3 to obtain a 0.7 ml aqueous phase with a concentration of 1000 mg/L. Pre-equilibration of the organic extraction phase with 3.0 mol/L HNO 3 was performed before extraction. A vortex mixer at a speed of 2500 rpm (LPD2500, Leopard Scientific Instrument Co., Ltd, Beijing) was used to perform the extraction experiments at 298 ± 1 K. To achieve complete separation between the two phases, the mixtures were centrifuged for 1 min at 5000 rpm in a centrifuge (TGL-16M, Cence, Hunan). After dilution with ultrapure water, the aqueous phase was detected using an ICP-MS (ELEMENT XR, Thermo Scientific, USA) to estimate the concentration of Eu(III). The distribution ratio of Eu(III) ( D Eu ) was calculated using Eq. (1). The phase ratio equals 1:1 in the extraction experiment. <math display="block" id="M1"><mrow><msub><mi>D</mi><mrow><mtext>Eu</mtext></mrow></msub><mo>=</mo><mrow><mo>(</mo><mrow><msub><mi>C</mi><mtext>i</mtext></msub><mo>−</mo><msub><mi>C</mi><mtext>f</mtext></msub></mrow><mo>)</mo></mrow><mo>/</mo><msub><mi>C</mi><mtext>f</mtext></msub><mo>,</mo></mrow></math> where <math id="M2"><mrow><msub><mi>C</mi><mtext>f</mtext></msub></mrow></math> and <math id="M3"><mrow><msub><mi>C</mi><mtext>i</mtext></msub></mrow></math> represent the final and initial Eu (III) concentrations in the diluted aqueous phase, respectively. The extraction had an error rate of less than 5%. Fluorescence spectra titration 2 The fluorescence emission spectra of the titration experiments were investigated at 298 ± 1 K in a cuvette cell with a 1 cm path length using a fluorescence spectrophotometer (F7000, Hitachi, Japan). The concentration of TODGA was 0.1 mol/L in acetonitrile and the initial concentration of Eu(III) was 0.001 mol/L in 2.0 mL acetonitrile. Next, 4 µL of TODGA solution was added at a time. The solution was mixed using a vortexer (VORTEX 3, IKA, Germany) for 5 min after the addition of each ligand. The titration experiments used an excitation wavelength of 395 nm; the bandwidth of the excitation and emission was 2.5 nm. The interval was 1 nm and the spectra were recorded between 550 and 700 nm. Single-component spectra of the metal–ligand complexes and metal solvent species were obtained using the HyperSpec program. Theoretical calculations 2 DFT calculations incorporating electron correlation effects were performed at the level of B3LYP using the Gaussian 09 package [ 33 33 - 35 35 33-35 ]. The relativistic effects of Eu atoms were investigated using the quasi-relativistic effective core potentials (RECPs) and associated valence basis sets, which were improved by the Stuttgart and Dresden groups [ 36 36 - 40 40 36-40 ]. The large-core RECPs used in the structural optimization of Eu(III) contained 52 electrons [ 39 39 , 40 40 ]. All other C, N, O, and H atoms utilized the 6-31G (d) basis set. Geometrical optimization and the electronic calculations of all structures were first performed at the level of B3LYP/6-31G(d)/RECP under the gas phase conditions. The Gibbs free energy ( G g ), entropy ( S g ), and enthalpy ( H g ) were obtained under the gas phase conditions at 298.15 K using the same theory level. To obtain the Gibbs free energy ( G aq ), entropy ( S aq ), and enthalpy ( H aq ) of the species in the n DD phase at 298.15 K, all species were optimized at the B3LYP/6-31 G (d)/RECP level in n DD to better predict their solvation energy[ 41 41 ]. This theory is based on the SMD universal continuum solvation model[ 42 42 ]. Results and discussion 1 Quantitative analysis of TODGA under different conditions after γ-ray irradiation 2 TODGA/ n DD, HNO 3 -TODGA/ n DD, and neat TODGA were subjected to γ-irradiation with absorbed doses ranging from 20 to 500 kGy. The irradiated samples were measured quantitatively using HPLC-UV and their radiolytic stability was analyzed. Figure 1 Figure 1 shows that the TODGA concentration decreased exponentially with increasing absorbed doses, suggesting pseudo-first-order degradation kinetics for TODGA/ n DD, HNO 3 -TODGA/ n DD, and neat TODGA. By comparing TODGA/ n DD and HNO 3 -TODGA/ n DD, it was found that HNO 3 had little influence on the radiolysis of TODGA. Moreover, in the n DD solution, the radiolysis rate of TODGA was higher than that of the neat TODGA. A dodecane-induced "sensitization effect" is responsible for the sensitization of TODGA to radiolysis [ 43 43 ] due to the fact that the radiolysis of TODGA is accelerated by n DD solvents because of the efficiency of n DD in transferring positive charges [ 44 44 - 46 46 44-46 ]. Because the radiolysis behavior of TODGA depends on its concentration in pseudo-first-order kinetics, the rate of radiolysis causes an exponential drop in the TODGA concentration. The radiolysis rate equation is defined by Eq. (2): <math display="block" id="M6"><mrow><mo>−</mo><mfrac><mrow><mtext>d</mtext><msub><mi>C</mi><mrow><mtext>TODGA</mtext></mrow></msub></mrow><mrow><mtext>d</mtext><mi>R</mi></mrow></mfrac><mo>=</mo><msub><mi>C</mi><mrow><mtext>TODGA</mtext></mrow></msub><mo>⋅</mo><mi>k</mi><mo>.</mo></mrow></math> The solution to the rate equation is presented as Eq. (3): <math display="block" id="M7"><mrow><mfrac><mrow><msub><mi>C</mi><mrow><mtext>TODGA</mtext></mrow></msub></mrow><mrow><msubsup><mi>C</mi><mrow><mtext>TODGA</mtext></mrow><mn>0</mn></msubsup></mrow></mfrac><mo>=</mo><msup><mi>e</mi><mrow><mo>−</mo><mi>k</mi><mi>R</mi></mrow></msup><mo>,</mo></mrow></math> where <math id="M8"><mrow><msub><mi>C</mi><mrow><mtext>TODGA</mtext></mrow></msub></mrow></math> (mol/L) is the concentration of TODGA, <math id="M9"><mrow><msubsup><mi>C</mi><mrow><mtext>TODGA</mtext></mrow><mn>0</mn></msubsup></mrow></math> (mol/L) is the original concentration of TODGA before γ-radiation, R (kGy) is the absorbed dose, and the dose constant <math id="M10"><mi>k</mi></math> (kGy -1 ) is the coefficient obtained by fitting the exponential curve. The dose constant <math id="M11"><mi>k</mi></math> can be used to scale the absorbed dose when exponential behavior occurs [ 47 47 ]. Using all the information acquired during the irradiation experiment provides more accurate results, and standard statistical methods can be used to assess the accuracy of the results. The application of <math id="M12"><mi>k</mi></math> to characterize an exponential curve in terms of the absorbed dose is very similar to that of traditional time-dependent kinetics. As expressed by exponential Eq. (3), the reciprocal absorbed dose is governed by the first-order rate law instead of the reciprocal time. If the dose constants k of different systems can be obtained, Equation (4) can be used to calculate the <math id="M13"><mi>G</mi></math> value (µmol/J), which is known as the radiation chemical yield: <math display="block" id="M14"><mrow><mi>G</mi><mo>=</mo><msup><mrow><mn>10</mn></mrow><mn>3</mn></msup><msubsup><mi>C</mi><mrow><mtext>TODGA</mtext></mrow><mn>0</mn></msubsup><mi>k</mi><msup><mi>ρ</mi><mrow><mo>−</mo><mn>1</mn></mrow></msup></mrow></math> where <math id="M15"><mi>ρ</mi></math> is the solution density (kg/L) ( <math id="M16"><mrow><msub><mi>ρ</mi><mrow><mtext>TODGA</mtext></mrow></msub></mrow></math> = 0.91 and <math id="M17"><mrow><msub><mi>ρ</mi><mrow><mn>0.2</mn><mo> </mo><mtext>mol</mtext><mo>/</mo><mtext>L TODGA</mtext><mo>/</mo><mi>n</mi><mtext>DD</mtext></mrow></msub></mrow></math> = 0.77 (25 °C). The measurement results are shown in Table S1. Table 1 Table 1 shows the dose constants <math id="M18"><mi>k</mi></math> and radiation chemical yields <math id="M19"><mi>G</mi></math> of irradiated TODGA/ n DD, HNO 3 -TODGA/ n DD, and neat TODGA. The dose constant <math id="M20"><mi>k</mi></math> of TODGA in n DD is higher than that of neat TODGA because of the “sensitization effect”, while the radiation chemical yields <math id="M21"><mi>G</mi></math> of TODGA/ n DD and HNO 3 - TODGA/ n DD are lower than that of neat TODGA because of the different initial concentrations of irradiated TODGA. These results agree with the literature in which Sugo et al. reported that the <math id="M22"><mi>k</mi></math> value of 0.2 mol/L TODGA/ n DD was 2.2×10 -3 kGy -1 [ 43 43 , 48 48 ]. By using the <math id="M23"><mi>k</mi></math> value, we can predict that the absorbed doses for the half-loss of TODGA concentration ( R 0.5 ) in irradiated TODGA/ n DD, HNO 3 -TODGA/ n DD, and neat TODGA will be approximately 330, 315, and 1060 kGy, respectively. 1 1 Samples 1 1 <math id="M24"><mrow><msubsup><mi>C</mi><mrow><mtext>TODGA</mtext></mrow><mn>0</mn></msubsup></mrow></math> (mol/L) 1 1 <math id="M25"><mi>k</mi></math> (kGy -1 ) 1 1 <math id="M26"><mi>G</mi></math> (µmol/J) 1 1 R 0.5 (kGy) 1 1 TODGA/ n DD 1 1 0.20 1 1 (2.08±0.05)×10 -3 1 1 0.54±0.013 1 1 330 1 1 HNO 3 -TODGA/ n DD 1 1 0.20 1 1 (2.20±0.03)×10 -3 1 1 0.57±0.008 1 1 315 1 1 Neat TODGA 1 1 1.57 1 1 (6.54±0.31)×10 -4 1 1 1.13±0.053 1 1 1060 Identification and semi-quantitative analysis of radiolytic products 2 Ultra-high-performance liquid chromatography with quadrupole time-of-flight mass spectrometry (UPLC-QTOF-MS) can be used to identify and quantify complex mixtures of unknown compounds owing to its high resolution and mass accuracy. The major radiolytic products of TODGA were identified using QTOF-MS; these are presented in Table 2 Table 2 , and their UPLC-QTOF-MS spectra are shown in Figures S3–9. Seven mass signals were identified and attributed to the possible radiolytic products of TODGA (P 1 – P 7 , Table 2 Table 2 ). These radiolytic products were formed by the rupture of the C – N, C – O, and C – C bonds of TODGA. Four radiolysis routes after irradiation are shown in Scheme 1 Scheme 1 . 1 1 Radiolytic products 1 1 Chemical formula 1 1 Theoretical neutral mass  1 1 Observed neutral mass  1 1 Structure 1 1 P 1 1 1 C 28 H 56 N 2 O 3 1 1 468.4291 1 1 468.4274 1 1 http://html.publish.founderss.cn/rc-pub/api/common/picture?pictureId=44253781&type= http://html.publish.founderss.cn/rc-pub/api/common/picture?pictureId=44253783&type= http://html.publish.founderss.cn/rc-pub/api/common/picture?pictureId=44253794&type= 1 1 P 2 1 1 C 20 H 39 NO 4 1 1 357.2879 1 1 357.2892 1 1 http://html.publish.founderss.cn/rc-pub/api/common/picture?pictureId=44253798&type= http://html.publish.founderss.cn/rc-pub/api/common/picture?pictureId=44253800&type= http://html.publish.founderss.cn/rc-pub/api/common/picture?pictureId=44253776&type= 1 1 P 3 1 1 C 18 H 37 NO 2 1 1 299.2824 1 1 299.2825 1 1 http://html.publish.founderss.cn/rc-pub/api/common/picture?pictureId=44253810&type= http://html.publish.founderss.cn/rc-pub/api/common/picture?pictureId=44253824&type= http://html.publish.founderss.cn/rc-pub/api/common/picture?pictureId=44253792&type= 1 1 P 4 1 1 C 18 H 37 NO 1 1 283.2875 1 1 283.2867 1 1 http://html.publish.founderss.cn/rc-pub/api/common/picture?pictureId=44253805&type= http://html.publish.founderss.cn/rc-pub/api/common/picture?pictureId=44253821&type= http://html.publish.founderss.cn/rc-pub/api/common/picture?pictureId=44253807&type= 1 1 P 5 1 1 C 17 H 35 NO 1 1 269.2719 1 1 269.2719 1 1 http://html.publish.founderss.cn/rc-pub/api/common/picture?pictureId=44253839&type= http://html.publish.founderss.cn/rc-pub/api/common/picture?pictureId=44253856&type= http://html.publish.founderss.cn/rc-pub/api/common/picture?pictureId=44253853&type= 1 1 P 6 1 1 C 16 H 35 N 1 1 241.2770 1 1 241.2772 1 1 http://html.publish.founderss.cn/rc-pub/api/common/picture?pictureId=44253858&type= http://html.publish.founderss.cn/rc-pub/api/common/picture?pictureId=44253845&type= http://html.publish.founderss.cn/rc-pub/api/common/picture?pictureId=44253835&type= 1 1 P 7 1 1 C 19 H 39 NO 2 1 1 313.2981 1 1 313.2994 1 1 http://html.publish.founderss.cn/rc-pub/api/common/picture?pictureId=44253870&type= http://html.publish.founderss.cn/rc-pub/api/common/picture?pictureId=44253852&type= http://html.publish.founderss.cn/rc-pub/api/common/picture?pictureId=44253851&type= Figure 2 Figure 2 shows the semi-quantitative analysis of the radiolytic products P 1 – P 7 in the irradiated HNO 3 -TODGA/ n DD and neat TODGA. The absorbed doses ranged from 20 to 500 kGy. Seven radiolytic products were found to exist in the two systems. The detector counts of the radiolytic products P 1 – P 7 roughly increased with increasing absorbed dose. However, some radiolytic products, such as P 1 in irradiated neat TODGA, showed a decrease in detector counts with absorbed doses from 400 kGy to 500 kGy. This is probably because the contents of the radiolytic products during irradiation increased from the radiolysis of the TODGA and decreased by self-radiolysis. The concentration's rate of increase was less than the rate of decrease with absorbed doses from 400 to 500 kGy for P 1 in irradiated neat TODGA. The detector counts of all radiolytic products in irradiated TODGA/ n DD were higher than those in neat TODGA (Figure S10), indicating the “sensitization effect” of n DD. This agreed well with the above result of the radiolysis kinetics of the TODGA with or without n DD. However, the relative detector counts of some radiolytic products differed between the two irradiation systems. For example, the detector count of P 6 was less than that of P 4 in irradiated neat TODGA; however, the converse was true for irradiated HNO 3 -TODGA/ n DD. This can be attributed to the different reaction mechanisms, wherein irradiated neat TODGA produces radical cations by direct ionization reaction. Conversely, in irradiated TODGA/ n DD, n DD radical cations may transfer their charge to TODGA molecules, leading to radiolysis of TODGA[ 43 43 , 49 49 ]. Influence of γ-ray irradiation on the extraction of TODGA system toward Eu(III) 2 HNO 3 -TODGA/ n DD and neat TODGA were subjected to γ-ray irradiation at absorbed doses ranging from 50 to 500 kGy. The irradiated neat TODGA was diluted with n DD to 0.2 mol/L. These organic phases were used to extract Eu(III) from the 3.0 mol/L HNO 3 aqueous phase to evaluate the extraction performance. As shown in Fig. 3 Fig. 3 , <math id="M27"><mrow><msub><mi>D</mi><mrow><mtext>Eu</mtext></mrow></msub></mrow></math> decreased as the absorbed dose increased, but it was slower for irradiated TODGA than for irradiated HNO 3 -TODGA/ n DD, indicating that γ-ray irradiation of the ligand significantly affected the extraction of Eu(III). This further proves that the presence of n DD increased the radiolysis of TODGA. However, the HNO 3 -TODGA/ n DD system after γ-ray irradiation still possesses a high <math id="M28"><mrow><msub><mi>D</mi><mrow><mtext>Eu</mtext></mrow></msub></mrow></math> (2.2×10 3 ), even at 500 kGy. The loss of extractants was the main cause of the decline in extractability after irradiation. Owing to the presence of TODGA and its liquid radiolysis products in the irradiated organic extraction phase, the complexation of radiolytic products on Eu(III) was studied using DFT calculations. This determined the effect if any of the radiolytic products of TODGA on the extraction behavior of the irradiated extraction system. Slope analysis and fluorescence titration 2 Before DFT calculations were conducted to investigate the complexation of TODGA and its radiolytic products with Eu(III), we assessed the stoichiometry of Eu ions and TODGA ligands in the extraction reaction, which could be obtained by the slope analysis in the curve of log D M -log[ L ] (org) . The extraction reaction of Eu(III) by TODGA is expressed by Eq. (5): <math display="block" id="M29"><mrow><msubsup><mrow><mtext>Eu</mtext></mrow><mrow><mrow><mo>(</mo><mrow><mtext>aq</mtext><mo>.</mo></mrow><mo>)</mo></mrow></mrow><mrow><mn>3</mn><mo>+</mo></mrow></msubsup><mo>+</mo><mn>3</mn><msubsup><mrow><mtext>NO</mtext></mrow><mrow><msub><mn>3</mn><mrow><mrow><mo>(</mo><mrow><mtext>aq</mtext><mo>.</mo></mrow><mo>)</mo></mrow></mrow></msub></mrow><mo>−</mo></msubsup><mo>+</mo><mi>n</mi><msub><mrow><mtext>TODGA</mtext></mrow><mrow><mrow><mo>(</mo><mrow><mtext>org</mtext><mo>.</mo></mrow><mo>)</mo></mrow></mrow></msub><mo>⇌</mo><mtext>Eu</mtext><msub><mrow><mrow><mo>(</mo><mrow><msub><mrow><mtext>NO</mtext></mrow><mn>3</mn></msub></mrow><mo>)</mo></mrow></mrow><mn>3</mn></msub><msub><mrow><mtext>TODGA</mtext></mrow><mi>n</mi></msub><msub><mrow/><mrow><mrow><mo>(</mo><mrow><mtext>org</mtext><mo>.</mo></mrow><mo>)</mo></mrow></mrow></msub></mrow></math> The extraction equilibrium concentration constant, <math id="M30"><mrow><msub><mi>K</mi><mrow><mtext>ex</mtext></mrow></msub></mrow></math> , is described as Eq. (6): <math display="block" id="M31"><mrow><msub><mi>K</mi><mrow><mtext>ex</mtext></mrow></msub><mo>=</mo><mfrac><mrow><msub><mrow><mo stretchy="false">[</mo><mtext>Eu</mtext><msub><mrow><mrow><mo>(</mo><mrow><msub><mrow><mtext>NO</mtext></mrow><mn>3</mn></msub></mrow><mo>)</mo></mrow></mrow><mn>3</mn></msub><msub><mrow><mtext>TODGA</mtext></mrow><mi>n</mi></msub><mo stretchy="false">]</mo></mrow><mrow><mrow><mo>(</mo><mrow><mtext>org</mtext><mo>.</mo></mrow><mo>)</mo></mrow></mrow></msub></mrow><mrow><msub><mrow><mo stretchy="false">[</mo><msup><mrow><mtext>Eu</mtext></mrow><mrow><mn>3</mn><mo>+</mo></mrow></msup><mo stretchy="false">]</mo></mrow><mrow><mrow><mo>(</mo><mrow><mtext>aq</mtext><mo>,</mo></mrow><mo>)</mo></mrow></mrow></msub><msubsup><mrow><mo stretchy="false">[</mo><msubsup><mrow><mtext>NO</mtext></mrow><mn>3</mn><mo>−</mo></msubsup><mo stretchy="false">]</mo></mrow><mrow><mrow><mo>(</mo><mrow><mtext>aq</mtext><mo>.</mo></mrow><mo>)</mo></mrow></mrow><mn>3</mn></msubsup><msubsup><mrow><mrow><mo>[</mo><mrow><mtext>TODGA</mtext></mrow><mo>]</mo></mrow></mrow><mrow><mrow><mo>(</mo><mrow><mtext>org</mtext><mo>.</mo></mrow><mo>)</mo></mrow></mrow><mi>n</mi></msubsup></mrow></mfrac></mrow></math> The distribution ratio, <math id="M32"><mrow><msub><mi>D</mi><mrow><mtext>Eu</mtext></mrow></msub></mrow></math> , is defined as Eq. (7): <math display="block" id="M33"><mrow><msub><mi>D</mi><mrow><mtext>Eu</mtext></mrow></msub><mo>=</mo><mfrac><mrow><msub><mrow><mo stretchy="false">[</mo><mtext>Eu</mtext><msub><mrow><mrow><mo>(</mo><mrow><msub><mrow><mtext>NO</mtext></mrow><mn>3</mn></msub></mrow><mo>)</mo></mrow></mrow><mn>3</mn></msub><msub><mrow><mtext>TODGA</mtext></mrow><mi>n</mi></msub><mo stretchy="false">]</mo></mrow><mrow><mrow><mo>(</mo><mrow><mtext>org</mtext><mo>.</mo></mrow><mo>)</mo></mrow></mrow></msub></mrow><mrow><msub><mrow><mo stretchy="false">[</mo><msup><mrow><mtext>Eu</mtext></mrow><mrow><mn>3</mn><mo>+</mo></mrow></msup><mo stretchy="false">]</mo></mrow><mrow><mrow><mo>(</mo><mrow><mtext>aq</mtext><mo>.</mo></mrow><mo>)</mo></mrow></mrow></msub></mrow></mfrac></mrow></math> Equation (7) was substituted into Eq. (6), and Eq. (6) was then transformed into a logarithmic form to obtain Eq. (8). <math display="block" id="M34"><mrow><mi>log</mi><msub><mi>D</mi><mrow><mtext>Eu</mtext></mrow></msub><mo>=</mo><mi>log</mi><msub><mi>K</mi><mrow><mtext>ex</mtext></mrow></msub><mo>+</mo><mtext>nlog</mtext><msub><mrow><mrow><mo>[</mo><mrow><mtext>TODGA</mtext></mrow><mo>]</mo></mrow></mrow><mrow><mrow><mo>(</mo><mrow><mtext>org</mtext><mo>.</mo></mrow><mo>)</mo></mrow></mrow></msub><mo>+</mo><mn>3</mn><mi>log</mi><msub><mrow><mrow><mo>[</mo><mrow><msubsup><mrow><mtext>NO</mtext></mrow><mn>3</mn><mo>−</mo></msubsup></mrow><mo>]</mo></mrow></mrow><mrow><mrow><mo>(</mo><mrow><mtext>aq</mtext><mo>.</mo></mrow><mo>)</mo></mrow></mrow></msub></mrow></math> The n value can be calculated from Eq. (8), which represents the average number of TODGA coordinated to one metal ion. The plot in Fig. 4 Fig. 4 of <math id="M35"><mrow><mi>log</mi><msub><mi>D</mi><mrow><mtext>Eu</mtext></mrow></msub></mrow></math> – <math id="M36"><mrow><mi>log</mi><msub><mrow><mrow><mo>[</mo><mrow><mtext>TODGA</mtext></mrow><mo>]</mo></mrow></mrow><mrow><mrow><mo>(</mo><mrow><mtext>org</mtext><mo>.</mo></mrow><mo>)</mo></mrow></mrow></msub></mrow></math> at a constant aqueous solution of 3.0 mol/L HNO 3 shows that the slope is 3.10 ± 0.11, which indicates that Eu(III) would form complexes with three TODGA molecules. Complexation studies were also performed with TODGA and Eu(III) using fluorescence titration. Figure 5 Figure 5 displays the normalized fluorescence emission spectra with different ratios of Eu(III) and TODGA resulting from the transitions of 5D 0 →7F 1 and 5D 0 →7F 2 . The transition of 5D 0 →7F 1 at 593 nm, owing to the magnetic-dipole transition, was considered independent of the ligand field. The transition of 5D 0 →7F 2 at 617 nm owing to the electric–dipole transition is considered to be hypersensitive to the ligand field, and its intensity depends on the coordination symmetry around the metal ions [ 50 50 ]. With the addition of the TODGA ligand, the change in the ligand field led to a gradual transformation of the single peak at 617 nm into a double peak, which was finally formed at M : L = 1:3. This indicated that the inner coordination sphere of Eu(III) was gradually occupied by TODGA with the addition of the ligand, which is similar to some results from the literature [ 51 51 , 52 52 ]. The spectra of each component were obtained from the fluorescence emission spectra ( Fig. 6 Fig. 6 ). The [Eu(TODGA) n ] 3+ ( n = 1 – 3) complexes and Eu(III) solvent species were also discovered. No complexes with TODGA values greater than or equal to 4 were found in the fluorescence emission spectra, proving that the ratio of Eu(III) to TODGA equals 1:3. The slope value was disputable, although many studies showed that the Ln(III): DGA structures are 1:3 complexes. Antonio et al. elucidated the inner coordination sphere of Eu(III) and TODGA using X-ray absorption spectroscopy (XAS)[ 53 53 ]. One ether O atom and two carbonyl O atoms of a TODGA molecule make up each ligand's tridentate to Eu(III). The coordination number is nine, with twelve distant carbon neighbors, six closest ones from carbonyl carbon atoms, and six slightly farther ones from the ether carbon atoms. Turanov et al.[ 54 54 ] found that the calculated slope value of Eu(II I) extracted by TODGA in n-decane containing 0.002 mol/L dinonylnaphtalene sulfonic acid (HDNNS) was 3.28 ± 0.04. This was estimated by the plot of log D Eu – log[TODGA] and the existence of EuL n (NO 3 ) 3 species by the slope of log D Eu – log[HNO 3 ], which was equal to 2.86 ± 0.08. Pathak et al.[ 55 55 ] investigated the influence of solvent type, acidity of extraction, and concentration of TODGA on luminescence lifetime and found that various ratios of TODGA to Eu ions resulted in the formation of Eu(TODGA) 3 3+ species when Eu(III) was complexed with TODGA. According to the findings of Sasaki et al.[ 56 56 ], extracted Eu(III) complexes require three or four TODGA molecules and three nitrate ions to maintain stability in non-polar diluents by slope analysis. Zhu et al.[ 57 57 ] performed a slope analysis of TODGA to extract some Lns(III) and found that the slope was 3.9 for Eu(III), suggesting that the M(TODGA) 4 (NO 3 ) 3 species finally formed. However, in this work, a 1:3 complexation ratio for TODGA with Eu(III) was determined. The theoretical <math id="M41"><mrow><msub><mi>D</mi><mrow><mtext>Eu</mtext></mrow></msub></mrow></math> values at different concentrations of TODGA can also be obtained using Eq. (8). Equation (9) is obtained by linear fitting, as shown in Fig. 4 Fig. 4 . <math display="block" id="M42"><mrow><mtext>log</mtext><msub><mi>D</mi><mrow><mtext>Eu</mtext></mrow></msub><mo>=</mo><mn>3.10</mn><mtext> log</mtext><msub><mrow><mrow><mo>[</mo><mrow><mtext>TODGA</mtext></mrow><mo>]</mo></mrow></mrow><mrow><mrow><mo>(</mo><mrow><mtext>org</mtext><mo>.</mo></mrow><mo>)</mo></mrow></mrow></msub><mo>+</mo><mn>6.75</mn></mrow></math> Equation (10) can be obtained from Fig. 1 Fig. 1 for irradiated HNO 3 -TODGA/ n DD. It is an exponential radiolysis equation for the concentration of TODGA and the absorbed dose. <math display="block" id="M43"><mrow><mfrac><mrow><msub><mi>C</mi><mrow><mtext>TODGA</mtext></mrow></msub></mrow><mrow><msubsup><mi>C</mi><mrow><mtext>TODGA</mtext></mrow><mn>0</mn></msubsup></mrow></mfrac><mo>=</mo><msup><mi>e</mi><mrow><mo>−</mo><mn>2.20</mn><mo>×</mo><msup><mrow><mn>10</mn></mrow><mrow><mo>−</mo><mn>3</mn></mrow></msup><mi>R</mi></mrow></msup></mrow></math> We can obtain Equation (11) for <math id="M44"><mrow><msub><mi>D</mi><mrow><mtext>Eu</mtext></mrow></msub></mrow></math> and the absorbed dose by substituting Eq. (10) into Eq. (9). This empirical equation enables us to construct a mathematical relationship between the <math id="M45"><mrow><msub><mi>D</mi><mrow><mtext>Eu</mtext></mrow></msub></mrow></math> and absorbed dose in this system. <math display="block" id="M46"><mrow><mi>log</mi><msub><mi>D</mi><mrow><mtext>Eu</mtext></mrow></msub><mo>=</mo><mo>−</mo><mn>2.965</mn><mo>×</mo><msup><mrow><mn>10</mn></mrow><mrow><mo>−</mo><mn>3</mn></mrow></msup><mi>R</mi><mo>+</mo><mn>4.583</mn></mrow></math> The theoretical <math id="M47"><mrow><msub><mi>D</mi><mrow><mtext>Eu</mtext></mrow></msub></mrow></math> with absorbed doses ranging from 50 to 500 kGy was obtained using Eq. (11). As shown in Fig. 7 Fig. 7 , the experimental <math id="M48"><mrow><msub><mi>D</mi><mrow><mtext>Eu</mtext></mrow></msub></mrow></math> was higher than the theoretical <math id="M49"><mrow><msub><mi>D</mi><mrow><mtext>Eu</mtext></mrow></msub></mrow></math> after irradiation, particularly at a high absorbed dose above 300 kGy for the HNO 3 -TODGA/ n DD system. The experimental <math id="M50"><mrow><msub><mi>D</mi><mrow><mtext>Eu</mtext></mrow></msub></mrow></math> is close to the theoretical <math id="M51"><mrow><msub><mi>D</mi><mrow><mtext>Eu</mtext></mrow></msub></mrow></math> below 300 kGy, indicating that the decrease in <math id="M52"><mrow><msub><mi>D</mi><mrow><mtext>Eu</mtext></mrow></msub></mrow></math> is mainly related to the loss of TODGA concentration, with a slight influence from radiolytic products. Because some radiolytic products remained in coordination structures similar to those of TODGA, such as P 1 and P 2 , which were identified by UPLC-QTOF, the complexation of radiolytic products on Eu(III) was investigated further using DFT calculations. Theoretical calculations of complexation of TODGA and radiolytic products with Eu(III) 2 According to the slope and fluorescence titration analyses, the Eu(III): TODGA stoichiometry was 1:3. In addition, Kimberlin et al.[ 58 58 ] reported that several radiolytic products with the TODGA skeleton are involved in heteroleptic complexes with TODGA with a stoichiometry of 1:3 from the ESI-MS spectra. The time-resolved laser fluorescence results showed no change in the peak shape of the fluorescence spectra before and after irradiation (Fig. S11). However, the fluorescence lifetime gradually decreased with increasing absorbed dose (Fig. S12), indicating that γ radiation did not change the M : L ratio of 1:3 but caused a slight partial change in the original fluorescent species. DFT calculations were employed to investigate the coordination abilities of TODGA and its radiolytic products with TODGA skeletons (P 1 and P 2 ). Figure 8 Figure 8 shows the optimized structures of the complexes formed by Eu(III) and the ligands. Theoretical calculations were performed for the [Eu(TODGA) 2 (P n )] 3+ ( n = 1 – 2) species and [Eu(TODGA) 3 ] 3+ complexes. It is realistic that one TODGA molecule in the initial complex is replaced by one radiolytic product to form mixed Ln-radiolytic product-TODGA complexes during γ irradiation, which was already found in the ESI-MS spectra by Kimberlin et al. [ 58 58 ]. In addition, we investigated the optimized structures and coordination abilities of [Eu(Pn) 3 ] 3+ ( n = 1 – 2), which were formed using three radiolytic products to represent a more extreme coordination environment of Eu(III) after γ irradiation. The changes in the Gibbs free energy, entropy, and enthalpy for the complexes formed by the ligands (TODGA, P 1 and P 2 ) and Eu(III) are shown in Table 3 Table 3 . It can be seen that the formation of [Eu(TODGA) 3 ] 3+ complex has more negative ΔG in the gas phase (–2527.3 kJ/mol) and in the n DD phase (–1115.0 kJ/mol) than that of the [Eu(TODGA) 2 (P n )] 3+ and [Eu(P n ) 3 ] 3+ ( n = 1– 2) complexes in the two phases. Moreover, the coordination abilities of the radiolytic products of TODGA decreased, as reflected by the changes in the Eu–O bond length ( Table 4 Table 4 ). The average Eu – O bond length of the complexes changed from 2.4911 Å ([Eu(TODGA) 3 ] 3+ ) to 2.5000 Å ([Eu(P 2 ) 3 ] 3+ ), indicating a decline in the coordination ability of the complex. These results indicate that TODGA shows better coordination ability than the radiolytic products of TODGA; the complexation order is TODGA > P 1 > P 2 . However, the formation of the [Eu(TODGA) 2 (P n )] 3+ and [Eu(P n ) 3 ] 3+ complexes ( n = 1 – 2) had a high negative ΔG in the two phases. Theoretical calculations also indicated that the radiolytic products of TODGA, such as P 1 and P 2 , still maintain a good coordination ability with Eu atoms, proving that the radiolytic products retain partial complexation for Eu(III). Consequently, the experimental <math id="M55"><mrow><msub><mi>D</mi><mrow><mtext>Eu</mtext></mrow></msub></mrow></math> of TODGA was higher than the theoretical <math id="M56"><mrow><msub><mi>D</mi><mrow><mi>E</mi><mi>u</mi></mrow></msub></mrow></math> from the loss of TODGA with the increase in radiolytic products at a high absorbed dose. Furthermore, if the contents of P 1 and P 2 are determined exactly, by combining the TODGA contents, we can predict the <math id="M57"><mrow><msub><mi>D</mi><mrow><mtext>Eu</mtext></mrow></msub></mrow></math> of the irradiated TODGA/ n DD system more precisely. This study will be conducted in future works. In our previous experiments, we found that the radiolytic products P 1 and P 2 were difficult to synthesize, and the radiolytic product P 1 was not sufficiently stable. Therefore, we used DFT calculations to evaluate the coordination abilities of these radiolytic products, thereby justifying the experimental result that the experimental <math id="M58"><mrow><msub><mi>D</mi><mrow><mtext>Eu</mtext></mrow></msub></mrow></math> was higher than the theoretical <math id="M59"><mrow><msub><mi>D</mi><mrow><mtext>Eu</mtext></mrow></msub></mrow></math> due to the high dose TODGA losses in this study. 1 1 (a) Complexation in the gas phase 1 1 Δ H g 1 1 Δ G g 1 1 T Δ S g 1 1 Eu 3+ + 3TODGA → [Eu(TODGA) 3 ] 3+ 1 1 –2693.7 1 1 –2527.3 1 1 –166.4 1 1 Eu 3+ + 2TODGA+ P 1 →  [Eu(TODGA) 2 (P 1 )] 3+   1 1 –2681.7 1 1 –2506.1 1 1 –175.6 1 1 Eu 3+ + 2TODGA+ P 2 → [Eu(TODGA) 2 (P 2 )] 3+ 1 1 –2657.8 1 1 –2487.8 1 1 –170.0 1 1 Eu 3+ + 3P 1 → [Eu(P 1 ) 3 ] 3+ 1 1 –2674.4 1 1 –2462.8 1 1 –211.6 1 1 Eu 3+ + 3P 2 → [Eu(P 2 ) 3 ] 3+ 1 1 –2568.0 1 1 –2380.8 1 1 –187.2 1 1 (b) Complexation in the n DD phase 1 1 Δ H sol 1 1 Δ G sol 1 1 T Δ S sol 1 1 Eu 3+ + 3TODGA → [Eu(TODGA) 3 ] 3+ 1 1 –1281.3 1 1 –1115.0 1 1 –166.3 1 1 Eu 3+ + 2TODGA+ P 1 → [Eu(TODGA) 2 (P 1 )] 3+ 1 1 –1276.4 1 1 –1100.9 1 1 –175.5 1 1 Eu 3+ + 2TODGA+ P 2 → [Eu(TODGA) 2 (P 2 )] 3+ 1 1 –1265.4 1 1 –1095.4 1 1 –170.0 1 1 Eu 3+ + 3P 1 → [Eu(P 1 ) 3 ] 3+ 1 1 –1282.1 1 1 –1070.5 1 1 –211.6 1 1 Eu 3+ + 3P 2 → [Eu(P 2 ) 3 ] 3+ 1 1 –1226.4 1 1 –1039.2 1 1 –187.2 1 1 Structure 1 1 Eu-O 1 1 Eu-O 1 1 Eu-O 1 1 Eu-O 1 1 Eu-O 1 1 Eu-O 1 1 Eu-O 1 1 Eu-O 1 1 Eu-O 1 1 Average 1 1 [Eu(TODGA) 3 ] 3+ 1 1 2.4284 1 1 2.4293 1 1 2.4306 1 1 2.4325 1 1 2.436 1 1 2.439 1 1 2.6022 1 1 2.6088 1 1 2.6131 1 1 2.4911 1 1 [Eu(TODGA) 2 (P 1 )] 3+ 1 1 2.4219 1 1 2.4222 1 1 2.4266 1 1 2.4306 1 1 2.4363 1 1 2.4532 1 1 2.6024 1 1 2.6111 1 1 2.6270 1 1 2.4924 1 1 [Eu(TODGA) 2 (P 2 )] 3+ 1 1 2.3868 1 1 2.4142 1 1 2.4147 1 1 2.4215 1 1 2.4237 1 1 2.5415 1 1 2.5813 1 1 2.5957 1 1 2.6879 1 1 2.4964 1 1 [Eu(P 1 ) 3 ] 3+ 1 1 2.4187 1 1 2.4217 1 1 2.4270 1 1 2.4371 1 1 2.4381 1 1 2.4408 1 1 2.6138 1 1 2.6146 1 1 2.6213 1 1 2.4926 1 1 [Eu(P 2 ) 3 ] 3+ 1 1 2.3628 1 1 2.3821 1 1 2.3931 1 1 2.4798 1 1 2.4799 1 1 2.5147 1 1 2.6043 1 1 2.6271 1 1 2.6559 1 1 2.5000 In conclusion, by combining the exponential equation for the radiolysis kinetics of TODGA in n DD and the equation for slope analysis of the concentration of TODGA and D Eu , we can derive a mathematical equation that includes the absorbed dose and D Eu , which could be used to predict the extraction performance at low absorbed doses. This method can be used to study other extractant systems. This work provides in-depth insights into the effect of γ irradiation on the extraction behavior of the TODGA/ n DD system and provides useful information on the use of nuclear fuel reprocessing. Conclusion 1 In summary, γ-radiolysis of TODGA/ n DD and HNO 3 -TODGA/ n DD was investigated and compared with γ-radiolysis of neat TODGA by analyzing the loss of TODGA and liquid radiolytic products. When the absorbed dose was increased, the TODGA concentration decreased exponentially, and the dose constant of TODGA in n DD was higher than that of neat TODGA because of the “sensitization effect” of n DD. However, the radiolysis of TODGA in n DD was only slightly affected by the pre-equilibration with HNO 3 . Seven radiolytic products of TODGA were identified and semi-quantified using UPLC-QTOF-MS, and four radiolysis routes for TODGA were proposed. The <math id="M60"><mrow><msub><mi>D</mi><mrow><mtext>Eu</mtext></mrow></msub></mrow></math> of the irradiated systems decreased after irradiation, but the HNO 3 -TODGA/ n DD system irradiated with an absorbed dose of 500 kGy maintained a high <math id="M61"><mrow><msub><mi>D</mi><mrow><mtext>Eu</mtext></mrow></msub></mrow></math> of 2.2×10 3 . For the irradiated HNO 3 -TODGA/ n DD, we obtained an empirical equation between <math id="M62"><mrow><msub><mi>D</mi><mrow><mtext>Eu</mtext></mrow></msub></mrow></math> and the absorbed dose by combining the radiolysis kinetics of TODGA and the complexation equation of TODGA with Eu(III), which fits well with the experimental results with absorbed doses below 300 kGy. DFT calculations demonstrated that the radiolytic products of TODGA with similar coordination structures possessed good coordination abilities with Eu atoms, which led to the experimental <math id="M63"><mrow><msub><mi>D</mi><mrow><mtext>Eu</mtext></mrow></msub></mrow></math> being higher than the theoretical <math id="M64"><mrow><msub><mi>D</mi><mrow><mtext>Eu</mtext></mrow></msub></mrow></math> based on the ligand content at high absorbed doses. References S.A. Ansari , P.K. Mohapatra , A review on solid phase extraction of actinides and lanthanides with amide based extractants . J. Chromatogr. A. 1499 , 1 - 20 ( 2017 ). doi: 10.1016/j.chroma.2017.03.035 http://doi.org/10.1016/j.chroma.2017.03.035 A review on solid phase extraction of actinides and lanthanides with amide based extractants S.A. Ansari , P. Pathak , P.K. Mohapatra et al. , Chemistry of diglycolamides: Promising extractants for actinide partitioning . Chem. Rev. 112 , 1751 - 1772 ( 2012 ). doi: 10.1021/cr200002f http://doi.org/10.1021/cr200002f Chemistry of diglycolamides: Promising extractants for actinide partitioning M. Salvatores , G. Palmiotti , Radioactive waste partitioning and transmutation within advanced fuel cycles: Achievements and challenges . Prog. Part. Nucl. Phys. 66 , 144 - 166 ( 2011 ). doi: 10.1016/j.ppnp.2010.10.001 http://doi.org/10.1016/j.ppnp.2010.10.001 Radioactive waste partitioning and transmutation within advanced fuel cycles: Achievements and challenges L. Rodríguez-Penalonga , B. Moratilla Soria , A review of the nuclear fuel cycle strategies and the spent nuclear fuel management eechnologies . Energies 10 , 1235 ( 2017 ). doi: 10.3390/en10081235 http://doi.org/10.3390/en10081235 A review of the nuclear fuel cycle strategies and the spent nuclear fuel management eechnologies X.L. Liu , G. Verma , Z.S. Chen et al. , Metal-organic framework nanocrystal-derived hollow porous materials: Synthetic strategies and emerging applications . The Innovation 3 , 100281 ( 2022 ). doi: 10.1016/j.xinn.2022.100281 http://doi.org/10.1016/j.xinn.2022.100281 Metal-organic framework nanocrystal-derived hollow porous materials: Synthetic strategies and emerging applications Y.F. Zhang , H.X. Liu , F.X. Gao et al. , Application of MOFs and COFs for photocatalysis in CO 2 reduction, H 2 generation, and environmental treatment . EnergyChem. 4 , 100078 ( 2022 ). doi: 10.1016/j.enchem.2022.100078 http://doi.org/10.1016/j.enchem.2022.100078 Application of MOFs and COFs for photocatalysis in CO2 reduction, H2 generation, and environmental treatment X. Wang , S.Q. Pan , Q.K. Zhao et al. , The status of ITER radioactive waste management and enlightenment to CFETR radioactive waste management . Nucl. Tech. 45 , 090603 ( 2022 ). doi: 10.11889/j.0253-3219.2022.hjs.45.090603 http://doi.org/10.11889/j.0253-3219.2022.hjs.45.090603 (in Chinese) The status of ITER radioactive waste management and enlightenment to CFETR radioactive waste management L.Y. Zhen , J.J. Zhang , Y.H. Lin et al. , Analysis of the accuracy of 14 C in gaseous effluent of nuclear power plant by direct measurement method . Nucl. Tech. 45 , 090301 ( 2022 ). doi: 10.11889/j.0253-3219.2022.hjs.45.090301 http://doi.org/10.11889/j.0253-3219.2022.hjs.45.090301 (in Chinese) Analysis of the accuracy of 14C in gaseous effluent of nuclear power plant by direct measurement method G. Yang , J.R. Lin , X.Y. Yang et al. , Adsorption properties of surrounding rock for 137 Cs in a cavern-type low and intermediate radioactive waste repository . Nucl. Tech. 45 , 080301 ( 2022 ). doi: 10.11889/j.0253-3219.2022.hjs.45.080301 http://doi.org/10.11889/j.0253-3219.2022.hjs.45.080301 (in Chinese) Adsorption properties of surrounding rock for 137Cs in a cavern-type low and intermediate radioactive waste repository S.Q. Meng , Y.S. Hu , T.M. Ruan , Impact of nickel and iron on PWR zirconium alloy surface CRUD formation and boron precipitation . Nucl. Tech. 45 , 060602 ( 2022 ). doi: 10.11889/j.0253-3219.2022.hjs.45.060602 http://doi.org/10.11889/j.0253-3219.2022.hjs.45.060602 (in Chinese) Impact of nickel and iron on PWR zirconium alloy surface CRUD formation and boron precipitation M. Nilsson , K.L. Nash , Review Article: A review of the development and operational characteristics of the TALSPEAK process . Solvent Extr. Ion Exch. 25 , 665 - 701 ( 2007 ). doi: 10.1080/07366290701634636 http://doi.org/10.1080/07366290701634636 Review Article: A review of the development and operational characteristics of the TALSPEAK process W.H. Duan , T.X. Sun , J.C. Wang , An industrial-scale annular centrifugal extractor for the TRPO process . Nucl. Sci. Tech. 29 , 46 ( 2018 ). doi: 10.1007/s41365-018-0395-z http://doi.org/10.1007/s41365-018-0395-z An industrial-scale annular centrifugal extractor for the TRPO process Y. Sugo , Y. Sasaki , S. Tachimori , Studies on hydrolysis and radiolysis of N, N, N’, N’-tetraoctyl-3-oxapentane-1,5-diamide . Radiochim. Acta. 90 , 161 - 165 ( 2002 ). doi: 10.1524/ract.2002.90.3_2002.161 http://doi.org/10.1524/ract.2002.90.3_2002.161 Studies on hydrolysis and radiolysis of N, N, N’, N’-tetraoctyl-3-oxapentane-1,5-diamide D. Whittaker , A. Geist , G. Modolo et al. , Applications of diglycolamide based solvent extraction processes in spent nuclear fuel reprocessing, Part 1: TODGA . Solvent Extr. Ion Exch. 36 , 223 - 256 ( 2018 ). doi: 10.1080/07366299.2018.1464269 http://doi.org/10.1080/07366299.2018.1464269 Applications of diglycolamide based solvent extraction processes in spent nuclear fuel reprocessing, Part 1: TODGA Z. Dong , W.J. Yuan , C. Liu et al. , Th(IV) and U(VI) removal by TODGA in ionic liquids: extraction behavior and mechanism, and radiation effect . Nucl. Sci. Tech. 28 , 62 ( 2017 ). doi: 10.1007/s41365-017-0214-y http://doi.org/10.1007/s41365-017-0214-y Th(IV) and U(VI) removal by TODGA in ionic liquids: extraction behavior and mechanism, and radiation effect A. Geist , U. Müllich , D. Magnusson et al. , Actinide(III)/Lanthanide(III) separation via selective aqueous complexation of Actinides(III) using a hydrophilic 2,6-bis(1,2,4-Triazin-3-Yl)-pyridine in nitric acid . Solvent Extr. Ion Exch. 30 , 433 - 444 ( 2012 ). doi: 10.1080/07366299.2012.671111 http://doi.org/10.1080/07366299.2012.671111 Actinide(III)/Lanthanide(III) separation via selective aqueous complexation of Actinides(III) using a hydrophilic 2,6-bis(1,2,4-Triazin-3-Yl)-pyridine in nitric acid P.K. Nayak , R. Kumaresan , K.A. Venkatesan et al. , Extraction behavior of Am(III) and Eu(III) from nitric acid medium in tetraoctyldiglycolamide-bis(2-ethylhexyl)phosphoric acid solution . Sep. Sci. Technol. 49 , 1186 - 1191 ( 2014 ). doi: 10.1080/01496395.2013.874357 http://doi.org/10.1080/01496395.2013.874357 Extraction behavior of Am(III) and Eu(III) from nitric acid medium in tetraoctyldiglycolamide-bis(2-ethylhexyl)phosphoric acid solution M.B. Singh , S.R. Patil , A.A. Lohi et al. , Insight into nitric acid extraction and aggregation of N, N, N’, N’-Tetraoctyl diglycolamide (TODGA) in organic solutions by molecular dynamics simulation . Sep. Sci. Technol. 53 , 1361 - 1371 ( 2018 ). doi: 10.1080/01496395.2018.1445107 http://doi.org/10.1080/01496395.2018.1445107 Insight into nitric acid extraction and aggregation of N, N, N’, N’-Tetraoctyl diglycolamide (TODGA) in organic solutions by molecular dynamics simulation A. Wilden , G. Modolo , P. Kaufholz et al. , Laboratory-scale counter-current centrifugal contactor demonstration of an innovative-SANEX process using a water soluble BTP . Solvent Extr. Ion Exch. 33 , 91 - 108 ( 2015 ). doi: 10.1080/07366299.2014.952532 http://doi.org/10.1080/07366299.2014.952532 Laboratory-scale counter-current centrifugal contactor demonstration of an innovative-SANEX process using a water soluble BTP G. Modolo , A. Wilden , P. Kaufholz et al. , Development and demonstration of innovative partitioning processes (i-SANEX and 1-cycle SANEX) for actinide partitioning . Prog. Nucl. Energ. 72 , 107 - 114 ( 2014 ). doi: 10.1016/j.pnucene.2013.07.021 http://doi.org/10.1016/j.pnucene.2013.07.021 Development and demonstration of innovative partitioning processes (i-SANEX and 1-cycle SANEX) for actinide partitioning J. Brown , F. McLachlan , M. Sarsfield et al. , Plutonium loading of prospective grouped actinide extraction (GANEX) solvent systems based on diglycolamide extractants . Solvent Extr. Ion Exch. 30 , 127 - 141 ( 2012 ). doi: 10.1080/07366299.2011.609378 http://doi.org/10.1080/07366299.2011.609378 Plutonium loading of prospective grouped actinide extraction (GANEX) solvent systems based on diglycolamide extractants K. Bell , C. Carpentier , M. Carrott et al. , Progress towards the development of a new GANEX process . Procedia Chemistry. 7 , 392 - 397 ( 2012 ). doi: 10.1016/j.proche.2012.10.061 http://doi.org/10.1016/j.proche.2012.10.061 Progress towards the development of a new GANEX process R. Malmbeck , D. Magnusson , S. Bourg et al. , Homogenous recycling of transuranium elements from irradiated fast reactor fuel by the EURO-GANEX solvent extraction process . Radiochim. Acta. 107 , 917 - 929 ( 2019 ). doi: 10.1515/ract-2018-3089 http://doi.org/10.1515/ract-2018-3089 Homogenous recycling of transuranium elements from irradiated fast reactor fuel by the EURO-GANEX solvent extraction process I. Kajan , M. Florianová , C. Ekberg et al. , Effect of diluent on the extraction of europium(III) and americium(III) with N, N, N’, N’-tetraoctyl diglycolamide (TODGA) . RSC Adv. 11 , 36707 - 36718 ( 2021 ). doi: 10.1039/D1RA07534A http://doi.org/10.1039/D1RA07534A Effect of diluent on the extraction of europium(III) and americium(III) with N, N, N’, N’-tetraoctyl diglycolamide (TODGA) S. Panja , P.K. Mohapatra , S.C. Tripathi et al. , Role of organic diluents on Am(III) extraction and transport behaviour using N, N, N’, N’-tetraoctyl-3-oxapentanediamide as the extractant . J. Membr. Sci. 403–404 , 71 - 77 ( 2012 ). doi: 10.1016/j.memsci.2012.02.022 http://doi.org/10.1016/j.memsci.2012.02.022 Role of organic diluents on Am(III) extraction and transport behaviour using N, N, N’, N’-tetraoctyl-3-oxapentanediamide as the extractant J. Veliscek-Carolan , Separation of actinides from spent nuclear fuel: A review . J. Hazard. Mater. 318 , 266 - 281 ( 2016 ). doi: 10.1016/j.jhazmat.2016.07.027 http://doi.org/10.1016/j.jhazmat.2016.07.027 Separation of actinides from spent nuclear fuel: A review Y. Wang , Y.Y. Ao , W.J. Yuan et al. , Extraction performance of Eu 3+ by using heterocyclic N-donor ligands with different structures in ionic liquids: an experimental and theoretical study . New J. Chem. 42 , 7206 - 7212 ( 2018 ). doi: 10.1039/C8NJ00517F http://doi.org/10.1039/C8NJ00517F Extraction performance of Eu3+ by using heterocyclic N-donor ligands with different structures in ionic liquids: an experimental and theoretical study C. Marie , P. Kaufholz , V. Vanel et al. , Development of a selective americium separation process using H 4 TPAEN as water-soluble stripping agent . Solvent Extr. Ion Exch. 37 , 313 - 327 ( 2019 ). doi: 10.1080/07366299.2019.1643569 http://doi.org/10.1080/07366299.2019.1643569 Development of a selective americium separation process using H4TPAEN as water-soluble stripping agent Y. Wang , J. Peng , W. Huang et al. , A new strategy for identifying the water-insoluble radiolytic products of BPC6/ionic liquids and accessing their influence on the Cs extraction . Radiat. Phys. Chem. 165 , 108408 ( 2019 ). doi: 10.1016/j.radphyschem.2019.108408 http://doi.org/10.1016/j.radphyschem.2019.108408 A new strategy for identifying the water-insoluble radiolytic products of BPC6/ionic liquids and accessing their influence on the Cs extraction C.A. Zarzana , G.S. Groenewold , B.J. Mincher et al. , A comparison of the γ -radiolysis of TODGA and T(EH)DGA using UHPLC-ESI-MS analysis . Solvent Extr. Ion Exch. 33 , 431 - 447 ( 2015 ). doi: 10.1080/07366299.2015.1012885 http://doi.org/10.1080/07366299.2015.1012885 A comparison of the γ -radiolysis of TODGA and T(EH)DGA using UHPLC-ESI-MS analysis P. Zsabka , K. Van Hecke , A. Wilden et al. , Gamma radiolysis of TODGA and CyMe 4 BTPhen in the ionic liquid tri-n-octylmethylammonium nitrate . Solvent Extr. Ion Exch. 38 , 212 - 235 ( 2020 ). doi: 10.1080/07366299.2019.1710918 http://doi.org/10.1080/07366299.2019.1710918 Gamma radiolysis of TODGA and CyMe4BTPhen in the ionic liquid tri-n-octylmethylammonium nitrate Y. Sugo , M. Taguchi , Y. Sasaki et al. , Radiolysis study of actinide complexing agent by irradiation with helium ion beam . Radiat. Phys. Chem. 78 , 1140 - 1144 ( 2009 ). doi: 10.1016/j.radphyschem.2009.06.031 http://doi.org/10.1016/j.radphyschem.2009.06.031 Radiolysis study of actinide complexing agent by irradiation with helium ion beam W.T. Xu , Y.F. Zhou , D.C. Huang et al. , Luminescent sensing profiles based on anion- responsive lanthanide(III) quinolinecarboxylate materials: solid-state structures, photophysical properties, and anionic species recognition . J. Mater. Chem. C. 3 , 2003 - 2015 ( 2015 ). doi: 10.1039/C4TC02369B http://doi.org/10.1039/C4TC02369B Luminescent sensing profiles based on anion- responsive lanthanide(III) quinolinecarboxylate materials: solid-state structures, photophysical properties, and anionic species recognition C. Lee , W. Yang , R.G. Parr , Development of the Colle-Salvetti correlation-energy formula into a functional of the electron density . Phys. Rev. B. 37 , 785 - 789 ( 1988 ). doi: 10.1103/PhysRevB.37.785 http://doi.org/10.1103/PhysRevB.37.785 Development of the Colle-Salvetti correlation-energy formula into a functional of the electron density A.D. Becke , Density‐functional thermochemistry. III. The role of exact exchange . J. Chem. Phys. 98 , 5648 - 5652 ( 1993 ). doi: 10.1063/1.464913 http://doi.org/10.1063/1.464913 Density‐functional thermochemistry. III. The role of exact exchange W. Küchle , M. Dolg , H. Stoll et al. , Energy‐adjusted pseudopotentials for the actinides. Parameter sets and test calculations for thorium and thorium monoxide . J. Chem. Phys. 100 , 7535 - 7542 ( 1994 ). doi: 10.1063/1.466847 http://doi.org/10.1063/1.466847 Energy‐adjusted pseudopotentials for the actinides. Parameter sets and test calculations for thorium and thorium monoxide X. Cao , M. Dolg , Segmented contraction scheme for small-core actinide pseudopotential basis sets . J. Mol. Struct. 673 , 203 - 209 ( 2004 ). doi: 10.1016/j.theochem.2003.12.015 http://doi.org/10.1016/j.theochem.2003.12.015 Segmented contraction scheme for small-core actinide pseudopotential basis sets M. Dolg , H. Stoll , A. Savin et al. , Energy-adjusted pseudopotentials for the rare earth elements . Theoret. Chim. Acta. 75 , 173 - 194 ( 1989 ). doi: 10.1007/BF00528565 http://doi.org/10.1007/BF00528565 Energy-adjusted pseudopotentials for the rare earth elements M. Dolg , H. Stoll , H. Preuss , A combination of quasirelativistic pseudopotential and ligand field calculations for lanthanoid compounds . Theoret. Chim. Acta. 85 , 441 - 450 ( 1993 ). doi: 10.1007/BF01112983 http://doi.org/10.1007/BF01112983 A combination of quasirelativistic pseudopotential and ligand field calculations for lanthanoid compounds M. Dolg , H. Stoll , H. Preuss , Energy‐adjusted ab initio pseudopotentials for the rare earth elements . J. Chem. Phys. 90 , 1730 - 1734 ( 1989 ). doi: 10.1063/1.456066 http://doi.org/10.1063/1.456066 Energy‐adjusted ab initio pseudopotentials for the rare earth elements H. Struebing , Z. Ganase , P.G. Karamertzanis et al. , Computer-aided molecular design of solvents for accelerated reaction kinetics . Nature Chem. 5 , 952 - 957 ( 2013 ). doi: 10.1038/nchem.1755 http://doi.org/10.1038/nchem.1755 Computer-aided molecular design of solvents for accelerated reaction kinetics A.V. Marenich , C.J. Cramer , D.G. Truhlar , Universal solvation model based on solute electron density and on a continuum model of the solvent defined by the bulk dielectric constant and atomic surface tensions . J. Phys. Chem. B. 113 , 6378 - 6396 ( 2009 ). doi: 10.1021/jp810292n http://doi.org/10.1021/jp810292n Universal solvation model based on solute electron density and on a continuum model of the solvent defined by the bulk dielectric constant and atomic surface tensions Y. Sugo , Y. Izumi , Y. Yoshida et al. , Influence of diluent on radiolysis of amides in organic solution . Radiat. Phys. Chem. 76 , 794 - 800 ( 2007 ). doi: 10.1016/j.radphyschem.2006.05.008 http://doi.org/10.1016/j.radphyschem.2006.05.008 Influence of diluent on radiolysis of amides in organic solution H. Galán , A. Núñez , A.G. Espartero et al. , Radiolytic stability of TODGA: Characterization of degraded samples under different experimental conditions . Procedia Chem. 7 , 195 - 201 ( 2012 ). doi: 10.1016/j.proche.2012.10.033 http://doi.org/10.1016/j.proche.2012.10.033 Radiolytic stability of TODGA: Characterization of degraded samples under different experimental conditions H. Galán , C.A. Zarzana , A. Wilden et al. , Gamma-radiolytic stability of new methylated TODGA derivatives for minor actinide recycling . Dalton Trans. 44 , 18049 - 18056 ( 2015 ). doi: 10.1039/C5DT02484F http://doi.org/10.1039/C5DT02484F Gamma-radiolytic stability of new methylated TODGA derivatives for minor actinide recycling W.J. Yuan , C.Z. Wang , Y.Y. Ao et al. , γ-Radiation effect on Th 4+ extraction behaviour of TODGA/[C 2 mim][NTf 2 ]: identification and extractability study of radiolytic products . RSC Adv. 6 , 7626 - 7632 ( 2016 ). doi: 10.1039/C5RA25364K http://doi.org/10.1039/C5RA25364K γ-Radiation effect on Th4+ extraction behaviour of TODGA/[C2mim][NTf2]: identification and extractability study of radiolytic products B.J. Mincher , R.D. Curry , Considerations for choice of a kinetic fig. of merit in process radiation chemistry for waste treatment . Appl. Radiat. Isot. 5 ( 2000 ). doi: 10.1016/S0969-8043(99)00161-X http://doi.org/10.1016/S0969-8043(99)00161-X Considerations for choice of a kinetic fig. of merit in process radiation chemistry for waste treatment R. Malmbeck , N.L. Banik , Radiolytic behaviour of a TODGA based solvent under alpha irradiation . J. Radioanal. Nucl. Chem. 326 , 1609 - 1615 ( 2020 ). doi: 10.1007/s10967-020-07444-7 http://doi.org/10.1007/s10967-020-07444-7 Radiolytic behaviour of a TODGA based solvent under alpha irradiation S.P. Mezyk , B.J. Mincher , S.B. Dhiman et al. , The role of organic solvent radical cations in separations ligand degradation . J. Radioanal. Nucl. Chem. 307 , 2445 - 2449 ( 2016 ). doi: 10.1007/s10967-015-4582-7 http://doi.org/10.1007/s10967-015-4582-7 The role of organic solvent radical cations in separations ligand degradation B. Rajamouli , P. Sood , S. Giri et al. , A dual‐characteristic bidentate ligand for a ternary mononuclear Europium(III) molecular complex – synthesis, photophysical, electrochemical, and theoretical study . Eur. J. Inorg. Chem. 2016 , 3900 - 3911 ( 2016 ). doi: 10.1002/ejic.201600508 http://doi.org/10.1002/ejic.201600508 A dual‐characteristic bidentate ligand for a ternary mononuclear Europium(III) molecular complex – synthesis, photophysical, electrochemical, and theoretical study A. Wilden , G. Modolo , S. Lange et al. , Modified diglycolamides for the An(III) + Ln(III) co-separation: Evaluation by solvent extraction and time-resolved laser fluorescence spectroscopy . Solvent Extr. Ion Exch. 32 , 119 - 137 ( 2014 ). doi: 10.1080/07366299.2013.833791 http://doi.org/10.1080/07366299.2013.833791 Modified diglycolamides for the An(III) + Ln(III) co-separation: Evaluation by solvent extraction and time-resolved laser fluorescence spectroscopy A. Sengupta , P.K. Mohapatra , M. Iqbal et al. , Spectroscopic investigations of Eu 3+ -complexes with ligands containing multiple diglycolamide pendant arms in a room temperature ionic liquid . J. Lumin. 154 , 392 - 401 ( 2014 ). doi: 10.1016/j.jlumin.2014.05.001 http://doi.org/10.1016/j.jlumin.2014.05.001 Spectroscopic investigations of Eu3+-complexes with ligands containing multiple diglycolamide pendant arms in a room temperature ionic liquid M.R. Antonio , D.R. McAlister , E.P. Horwitz , An europium(III) diglycolamide complex: insights into the coordination chemistry of lanthanides in solvent extraction . Dalton Trans. 44 , 515 - 521 ( 2015 ). doi: 10.1039/C4DT01775G http://doi.org/10.1039/C4DT01775G An europium(III) diglycolamide complex: insights into the coordination chemistry of lanthanides in solvent extraction А.N. Turanov , V.К. Karandashev , Synergistic extraction of U(VI), Th(IV), and Lanthanides(III) from nitric acid solutions using mixtures of TODGA and dinonylnaphthalene sulfonic acid . Solvent Extr. Ion Exch. 36 , 257 - 271 ( 2018 ). doi: 10.1080/07366299.2018.1459157 http://doi.org/10.1080/07366299.2018.1459157 Synergistic extraction of U(VI), Th(IV), and Lanthanides(III) from nitric acid solutions using mixtures of TODGA and dinonylnaphthalene sulfonic acid P.N. Pathak , S.A. Ansari , S.V. Godbole et al. , Interaction of Eu 3+ with N, N, N’, N’-tetraoctyl diglycolamide: A time resolved luminescence spectroscopy study . Spectroc. Acta Pt. A-Molec. Biomolec. Spectr. 73 , 348 - 352 ( 2009 ). doi: 10.1016/j.saa.2009.02.040 http://doi.org/10.1016/j.saa.2009.02.040 Interaction of Eu3+ with N, N, N’, N’-tetraoctyl diglycolamide: A time resolved luminescence spectroscopy study Y. Sasaki , P. Rapold , M. Arisaka et al. , An additional insight into the correlation between the distribution ratios and the aqueous acidity of the TODGA system . Solvent Extr. Ion Exch. 25 , 187 - 204 ( 2007 ). doi: 10.1080/07366290601169345 http://doi.org/10.1080/07366290601169345 An additional insight into the correlation between the distribution ratios and the aqueous acidity of the TODGA system Z.X. Zhu , Y. Sasaki , H. Suzuki et al. , Cumulative study on solvent extraction of elements by N, N, N’, N’-tetraoctyl-3-oxapentanediamide (TODGA) from nitric acid into n-dodecane . Anal. Chim. Acta. 527 , 163 - 168 ( 2004 ). doi: 10.1016/j.aca.2004.09.023 http://doi.org/10.1016/j.aca.2004.09.023 Cumulative study on solvent extraction of elements by N, N, N’, N’-tetraoctyl-3-oxapentanediamide (TODGA) from nitric acid into n-dodecane A. Kimberlin , D. Guillaumont , S. Arpigny et al. , An experimental and computational look at the radiolytic degradation of TODGA and the effect on metal complexation . New J. Chem. 45 , 12479 - 12493 ( 2021 ). doi: 10.1039/D1NJ01143J http://doi.org/10.1039/D1NJ01143J An experimental and computational look at the radiolytic degradation of TODGA and the effect on metal complexation All authors contributed to the study conception and design. Material preparation, data collection and analysis were performed by Hang Zhang, Yin-Yong Ao, Hui-Bo Li and Jing Peng. The first draft of the manuscript was written by Hang Zhang and all authors commented on previous versions of the manuscript. All authors read and approved the final manuscript. The measurements of UPLC-QTOF and ICP-MS were performed at the Analytical Instrumentation Center of Peking University. We acknowledge the help from PKUAIC (Dr. Jiang Zhou, Dr. Li Zhang, and Dr. Jia-Hui Liu). The authors also wish to acknowledge Prof. Song-Dong Ding (Sichuan University) for his assistance in providing TODGA. 10.1007/s41365-023-01198-z 2022-12-08 2023-01-09 2023-01-12 2023-04-11 2023-06-07 © China Science Publishing & Media Ltd. (Science Press), Shanghai Institute of Applied Physics, the Chinese Academy of Sciences, ChineseNuclear Society and Springer Nature Singapore Pte Ltd. 2023 This is a post-peer-review, pre-copyedit version of an article published in Nuclear Science and Techniques. The final authenticated version is available online at: http://dx.doi.org/10.1007/s41365-023-01198-z http://dx.doi.org/10.1007/s41365-023-01198-z . Springer Nature or its licensor (e.g. a society or other partner) holds exclusive rights to this article under a publishing agreement with the author(s) or other rightsholder(s); author self-archiving of the accepted manuscript version of this article is solely governed by the terms of such publishing agreement and applicable law. 2023 38407954 The data that support the findings of this study are openly available in Science Data Bank at https://www.doi.org/10.57760/sciencedb.j00186.00037 https://www.doi.org/10.57760/sciencedb.j00186.00037 and http://resolve.pid21.cn/31253.11.sciencedb.j00186.00037 http://resolve.pid21.cn/31253.11.sciencedb.j00186.00037 . Data availability statement Supplementary Information 1 The online version contains supplementary material available at https://doi.org/10.1007/s41365-023-01198-z https://doi.org/10.1007/s41365-023-01198-z . Nuclear Science and Techniques 4 34