Multi-physical field simulation calculation and analysis of simulated high-level waste liquid spray calcination.

Aiming at the independent research and development of a simulated high-level waste liquid spray calcination transformation treatment test device, a three-dimensional multi-physical field model of spray calcination was established by means of finite element analysis method. In this paper, the simulated high-level waste liquid is a mixed solution of nitrate solution and sucrose. The main chemical components of nitrate dissolution are HNO3 and NaNO3. The process of evaporation and calcination of high-level waste liquid to form oxides is also called the pretreatment of high-level waste liquid or the conversion of high-level waste liquid. In this experiment, the atomized droplets sprayed at high speed are evaporated, dried and calcined in turn in the calciner to obtain the calcined product. The distribution law of temperature flow field and chemical reaction state and results inside the test device were revealed by simulation calculation. The results show that under the condition of multi-physical field coupling, the chemical reaction temperature has an effect on the yield of the product. The temperature is positively correlated with the product concentration, and the effect of temperature on the yield of NO2 is greater than that of Na2O. At the same time, in this chemical reaction, the concentration of reactants (NaNO3 and HNO3) had a positive correlation with the concentration of main products (NO2 and Na2O). However, the rate of increase in the concentration of the main products (NO2 and Na2O) decreased with the increase of the concentration of the reactants (NaNO3 and HNO3).

Complexation and extraction of trivalent actinides over lanthanides using highly soluble phenanthroline diamide ligands with different side chains.

Although phenanthroline diamide ligands have been widely reported, their limited solubility in organic solvents and poor performance in the separation of trivalent actinides (An(III)) and lanthanides (Ln(III)) at high acidity are still clear demerits. In this study, we designed and synthesized three highly soluble phenanthroline diamide ligands with different side chains. By introducing alkyl chains and ester groups, the ligands solubility in 3-nitrotrifluorotoluene is increased to over 600 mmol/L, significantly higher than the previous reported phenanthroline diamide ligands. Based on anomalous aryl strengthening, benzene ring was incorporated to enhance ligand selectivity toward Am(III). Extraction experiments demonstrated favorable selectivity of all the three ligands towards Am(III). The optimal separation factor (SFAm/Eu) reaches 53 at 4 mol/L HNO3, representing one of the most effective separation of An(III) over Ln(III) under high acidity. Slope analysis, single crystal structure analysis, as well as titration of ultraviolet visible spectroscopy, mass spectrometry, and nuclear magnetic resonanc confirmed the formation of 1:1 and 1:2 complex species between the metal ions and the ligands depending on the molar ratio of metal ions in the reaction mixture. The findings of this study offer valuable insights for developing phenanthroline diamide ligands for An(III)/Ln(III) separation.

Efficient and selective capture of thorium ions by a covalent organic framework.

The selective separation of thorium from rare earth elements and uranium is a critical part of the development and application of thorium nuclear energy in the future. To better understand the role of different N sites on the selective capture of Th(IV), we design an ionic COF named Py-TFImI-25 COF and its deionization analog named Py-TFIm-25 COF, both of which exhibit record-high separation factors ranging from 102 to 105. Py-TFIm-25 COF exhibits a significantly higher Th(IV) uptake capacity and adsorption rate than Py-TFImI-25 COF, which also outperforms the majority of previously reported adsorbents. The selective capture of Py-TFImI-25 COF and Py-TFIm-25 COF on thorium is via Th-N coordination interaction. The prioritization of Th(IV) binding at different N sites and the mechanism of selective coordination are then investigated. This work provides an in-depth insight into the relationship between structure and performance, which can provide positive feedback on the design of novel adsorbents for this field.

Differences in the catalytic properties of Fe isotopes.

The significant differences in the catalytic properties caused by different 'isotopic catalysts' were discovered for the first time. The commonly purchased Fe2O3 is a 'mixture' of different Fe isotopic oxides which means the catalytic effect of Fe2O3 is theoretically a synthetical result of all isotopic compounds. In this work, the differences in catalytic properties of α-Fe2O3 with natural abundance ratio and separated isotopic α-Fe2O3 (α-54Fe2O3, α-56Fe2O3, and α-58Fe2O3) catalyzing thermal decomposition of ammonium perchlorate (AP) were investigated, and are mainly attributed to the difference in the charge distribution of the nuclei of different iron isotopes. The result suggests that isotope effects in different isotopes when utilized as catalysts are caused by nuclear morphology and the nuclear charge distribution. This study will serve as a base as well as an initiation for future studies of the isotopic catalyst.

Synthesis and structure of metal-TCPE (metal = Th, Ce) metal-organic frameworks based on 1,2,4,5-tetrakis(4-carboxyphenyl) ethylene.

Two new metal-organic frameworks (MOFs) (Th/ Ce -TCPE) based on 1,2,4,5-tetrakis(4-carboxyphenyl)ethylene were obtained using a straightforward reaction under moderate conditions. Th and Ce formed the central units of this MOF in the mononuclear and in the unusual trinuclear cluster configurations, respectively. The resulting MOFs were analysed by fluorescence spectroscopy to understand their luminescence. The obtained data revealed that benzene's electron cloud density and torsion angle on the ligand were affected by the acetic acid molecule and Th(IV), which caused Th-TCPE to irradiate stronger blue emission, but Ce-TCPE showed no fluorescence due to the self-quenching. Such a unique luminescence property could be used for fluorescence or radiopharmaceutical sensing.

Influence of Electronic Modulation of Phenanthroline-Derived Ligands on Separation of Lanthanides and Actinides.

The solvent extraction, complexing ability, and basicity of tetradentate N-donor 2,9-bis(5,5,8,8-tetramethyl-5,6,7,8-tetrahydro-1,2,4-benzotriazin-3-yl)-1,10-phenanthroline (CyMe4-BT- Phen) and its derivatives functionalized by Br, hydroxyphenyl, nitryl were discussed and compared. It was demonstrated that four BTPhen ligands are able to selectively extract Am(lll) over Eu(lll). It was notable that the distribution ratio of 5-nitryl-CyMe4-BTPhen for Eu(lll) was suppressed under 0.02, which was much lower compared to DEu(lll) = 1 by CyMe4-BTPhen. The analysis of the effect of the substituent on the affinity to lanthanides was conducted by UV/vis and fluorescence spectroscopic titration. The stability constants of various ligands with Eu(lll) were obtained by fitting titration curve. Additionally, the basicity of various ligands was determined to be 3.1 ± 0.1, 2.3 ± 0.2, 0.9 ± 0.2, 0.5 ± 0.1 by NMR in the media of CD3OD with the addition of DClO4. The basicity of ligands follows the order of L1 > L2 > L3 > L4, indicating the tendency of protonation decreases with the electron-withdrawing ability increase.

Synthesis of luminescent thorium-based metal-organic frameworks with 1,2,4,5-tetrakis(4-carboxyphenyl)benzene.

Three new thorium-based MOFs based on 1,2,4,5-tetrakis(4-carboxyphenyl)benzene (H4TCPB) were obtained under a similar reaction system (metal salt, ligand, solvent, and acid are the same). Th(iv) forms the central unit of the MOFs in mononuclear and binuclear clusters, respectively. All the MOFs show blue ligand-based luminescence under an ultraviolet environment. This is the first time that multiple thorium-based MOFs with luminescence have been found with the same ligand.