Search Results (9)

The growing energy demand has emphasized the importance of developing nuclear technologies and high-purity lithium isotopes (⁶Li and ⁷Li) as raw materials. This study investigates how voltage and migration time affect two types of low-density polyethylene membranes—one impregnated with ionic liquids and the other non-impregnated—for lithium isotope separation via electromigration from a lithium-loaded organic phase to an aqueous solution. We developed a laboratory-made setup for high-precision lithium isotope measurements (2RSD = ±0.30‰) of natural carbonate samples (LSVEC) and an optimized protocol for isotope ratio measurements using quadrupole ICP-MS with the sample-standard bracketing method (SSB). The results document that both impregnated and non-impregnated membranes can achieve promising ⁶Li enrichment under different environmental conditions, including ionic liquids and organic solutions in the cathode chamber. Lithium-ion mobility is influenced by voltage in an environment assisted by 0.1 mol/L tetrabutylammonium perchlorate and increases quasi-linearly from 5 to 15 V. Between 20 and 25 h, the lithium-ion concentration had the maximum value, after which the trend declined. In the BayesGLM model, we incorporated all data and systematically eliminated those with a low enrichment factor, either individually or in groups. Our findings indicated that the model was not significantly affected by the exclusion of measurements with low α. This suggests that voltage and migration time are crucial, and achieving a better enrichment factor depends on applying the optimal ratio of ionic liquids, crown ethers, and organic solvents. Ionic liquids used for impregnation sustain enrichment in the first hours, particularly for ⁷Li; however, after 25 h, ⁶Li demonstrated a higher enrichment capacity. The maximum single-stage separation factor for ⁶Li/⁷Li was achieved at 24 and 48 h for an impregnated membrane M2 (α = 1.021/1.029) and a non-impregnated membrane M5 (α = 1.031/1.038). Full article

The enrichment of ⁶Li isotopes from a natural stage of 7.6% to above 59% is required for the development of next-generation green technologies capable of sustaining climate change mitigation and energy-mix targets. In this study, we developed two categories of custom laboratory-made organic membranes, membranes that were non-impregnated before electromigration (AI-1) and membranes impregnated with LiNTf₂ (AI-2), to evaluate their performance in lithium isotope separation. Both types of membranes were exposed in synthesis to ionic liquid and crown ether. The objective of the study was to test the performance of membranes in separating lithium isotopes from a lithium-loaded organic phase in an aqueous solution with variable potentials and time intervals. The results show that the impregnated AI-2 membranes increased the enrichment of ⁶Li in the early stages, and the effect decreased after 25 h. The efficiency of lithium isotope enrichment was positively related to the potential profile applied, migration time, and concentration of organic solution in the anode chamber. The 0.5 mol/L Bis-(trifluoromethane) sulfonimide lithium salt (Li[NTf₂]) with 0.1 M tetra butyl ammonium perchlorate (TBAP) in acetonitrile (CH₃CN) ionic solution significantly improved Li isotope separation compared with an aqueous environment with higher salt concentrations. The maximum isotopic separation coefficient (α) for AI-1.2 (15-crown-5 ether and 1 mol/L LiNTf₂ in TBAP solution after 48 h of electromigration) gradually increased to 1.0317. Our results demonstrated that in the laboratory-made setup described, the migration efficiency and Li isotope separation in the catholyte environment needed a minimum of 9 V and a migration time of 6 h, respectively; these values varied with the concentration of the organic solution in the anode chamber. The ability of laboratory-engineered membranes to impart isotope selectivity and enhance permselectivity or selectivity towards singly charged ions was demonstrated through the functionality of single-collector inductively coupled plasma mass spectrometry (ICP-MS). This technology is particularly valuable and commercially feasible for future lithium isotope research in nuclear technology. Full article

Enriched lithium isotopes (⁶Li and ⁷Li) are essential in the nuclear energy industry, where ⁶Li is bombarded with neutrons to produce tritium for fusion reactions, while ⁷Li is used as a core coolant and pH regulator. Separation of ⁶Li and ⁷Li by electromigration is a promising method for producing enriched lithium isotopes that fulfill industrial needs. In this work, based on a previously proposed biphasic system electromigration routine, a three-stage system of ‘LiCl aqueous solution (anolyte)|B12C4-[EMIm][NTf₂] organic solution|NH₄Cl aqueous solution (catholyte)’ was constructed and the rules of lithium isotope separation and lithium-ion migration investigated. It was shown that the isotope enrichment effect of the catholyte was greatly affected by the experimental conditions, while that of the organic solution was less affected. As the B12C4 concentration increased, enhancement of ⁷Li enrichment in the catholyte and ⁶Li enrichment in the organic solution was observed, and α(C/O) and α(O/A) reached 0.975 and 1.018 at B12C4 of 0.5 mol/L. With the increase in current, migration time, and LiCl concentration, the isotope that was enriched in the catholyte trended from ⁷Li to ⁶Li (about 6 mA, 12 h or LiCl of 5 mol/L). Taking lithium-ion transport efficiency and lithium isotope separation effect into consideration together, a current of at least 6 mA, duration of at least 12 h, LiCl concentration of at least 1 mol/L and B12C4 concentration of 0.2 mol/L are suggested for the electromigration process. The work provides an important reference for system construction and experimental design of a biphasic electromigration separation method, which is expected to be an industrial alternative because of its environmental protection and high efficiency. Full article

Nuclear fusion is a phenomenon that is well known within the nuclear physics community as a viable option for alternative energy as many natural gases and fossil fuels are phased out of commercial use. Deuterium and tritium fusion reactions are currently the leading candidates for nuclear fusion, with a major limiting factor being a means to produce tritium on an industrial scale. Lithium-6 is a well-known isotope that can produce tritium and helium following a fission reaction with a neutron. Unfortunately, the lithium-6 enrichment methods are limited to the COLEX process, which leaves behind an alarming amount of mercury waste as a potential environmental contaminant. Deep eutectic solvents are believed to be a potential alternative to lithium isotope separations due to the ease of generation, in addition to the minimum environmental waste generated when these solvents are employed. Previous studies have suggested that deep eutectic solvents are capable of separating lithium isotopes by utilizing a 2-thenoyltrifluoroacetone and trioctylphosphine oxide system that can biphasically react with a buffered solution containing lithium chloride. This system displays a separation factor of 1.068, which when compared to the 1.054 separation within the COLEX process, makes it a potential candidate for lithium-6/7 separation. Within this study, we investigate this system in comparison to two newly synthesized deep eutectic solvents and find that within these acetylacetone-based systems, little isotopic separation is observed. We investigate these systems both experimentally and computationally, showing the different lithium cation affinities, in addition to proposing how the electron-donating or -withdrawing nature can influence these systems. Full article

Previous studies on the Ke’eryin pegmatite-type lithium ore field in the Songpan–Ganzi Orogenic Belt have explored the characteristics of the parent rock but have not precisely determined its magma source area. This uncertainty limits our understanding of the regularity of lithium ore formation in this region. In this study, to address the issue of the precise source area of the parent rock of lithium mineralization, a detailed analysis of the Li isotope composition of the ore-forming parent rock (Ke’eryin two-mica monzogranite) and its potential source rocks (Triassic Xikang Group metamorphic rocks) was conducted. The δ⁷Li values of the Ke’eryin two-mica monzogranite, Xikang Group metasandstone, and Xikang Group mica schist are −3.3–−0.7‰ (average: −1.43‰), +0.1–+6.9‰ (average: +3.83‰), and −9.1–0‰ (average: −5.00‰), respectively. The Li isotopic composition of the Ke’eryin two-mica monzogranite is notably different from the metasandstone and aligns more closely with the mica schist, suggesting that the mica schist is its primary source rock. The heavy Li isotopic composition of the two-mica monzogranite compared to the mica schist may have resulted from the separation of the peritectic garnet into the residual phase during the biotite dehydration melting process. Moreover, the low-temperature weathering of the source rocks may have been the main factor leading to the lighter lithium isotope composition of the Xikang Group mica schist compared to the metasandstone. Further analysis suggests that continental crust weathering and crustal folding and thickening play crucial roles in the enrichment of lithium during multi-cycle orogenies. Full article

In terms of isotopic technologies, it is essential to be able to produce materials with an enriched isotopic abundance (i.e., a compound isotopic labelled with ²H, ¹³C, ⁶Li, ¹⁸O or ³⁷Cl), which is one that differs from natural abundance. The isotopic-labelled compounds can be used to study different natural processes (like compounds labelled with ²H, ¹³C, or ¹⁸O), or they can be used to produce other isotopes as in the case of ⁶Li, which can be used to produce ³H, or to produce LiH that acts like a protection shield against fast neutrons. At the same time, ⁷Li isotope can be used as a pH controller in nuclear reactors. The COLEX process, which is currently the only technology available to produce ⁶Li at industrial scale, has environmental drawbacks due to generation of Hg waste and vapours. Therefore, there is a need for new eco-friendly technologies for separation of ⁶Li. The separation factor of ⁶Li/⁷Li with chemical extraction methods in two liquid phases using crown ethers is comparable to that of COLEX method, but has the disadvantages of low distribution coefficient of Li and the loss of crown ethers during the extraction. Electrochemical separation of lithium isotopes through the difference in migration rates between ⁶Li and ⁷Li is one of the green and promising alternatives for the separation of lithium isotopes, but this methodology requires complicated experimental setup and optimisation. Displacement chromatography methods like ion exchange in different experimental configurations have been also applied to enrich ⁶Li with promising results. Besides separation methods, there is also a need for development of new analysis methods (ICP-MS, MC-ICP-MS, TIMS) for reliable determination of Li isotope ratios upon enrichment. Considering all the above-mentioned facts, this paper will try to emphasize the current trends in separation techniques of lithium isotopes by exposing all the chemical separation and spectrometric analysis methods, and highlighting their advantages and disadvantages. Full article

⁶Li and ⁷Li are strategic resources. Because Li⁺ ions have no outermost electrons and the radii of ⁶Li and ⁷Li differ by only one neutron, the separation of the naturally stable isotopes of Li, especially by solvent extraction, is recognized as a difficult problem worldwide. Therefore, in this paper, an advanced β-diketone-driven deep eutectic solvent (DES) extraction system containing 2-thenoyltrifluoroacetone (HTTA) and tri-n-octyl phosphine oxide (TOPO) is introduced to the extraction and separation of ⁶Li⁺ and ⁷Li⁺ ions. Compared with those of reported HTTA extraction systems and crown ether extraction systems, the separation coefficient (${\beta }_{7_{\mathrm{Li}/}{6}_{\mathrm{Li}}}$) of the β-diketone-driven DES extraction system can reach the best value of 1.068, which is now the highest known β-value reported in the extraction system. From the intramolecular hydrogen bond of HTTA to the intermolecular hydrogen bond of DES, the bond energy increases by 47.8%. Because the active site of the proton in DES provides a higher energy barrier for the separation of ⁷Li, the ${\beta }_{7_{\mathrm{Li}/}{6}_{\mathrm{Li}}}$ is significantly increased. The extractions were characterized by spectrum, using ¹H nuclear magnetic resonance (NMR) spectroscopy, Fourier-transform infrared (FT-IR) spectroscopy, and X-ray photoelectron spectroscopy (XPS). The mechanism was determined on the basis of the reaction kinetics and density functional theory (DFT). The DES extractant shows excellent cycle performance with regard to stripping and reusability. In conclusion, the highly efficient, economical, and stable β-diketone-driven DES extraction system can be used for the separation of naturally stable Li isotopes, which provides good industrial application prospects. Full article

The adsorption of lithium ions(Li⁺) and the separation of lithium isotopes have attracted interests due to their important role in energy storage and nuclear energy, respectively. However, it is still challenging to separate the Li⁺ and its isotopes with high efficiency and selectivity. A novel cellulose-based microsphere containing crown ethers groups (named as MCM-g-AB15C5) was successfully synthesized by pre-irradiation-induced emulsion grafting of glycidyl methacrylate (GMA) and followed by the chemical reaction between the epoxy group of grafted polymer and 4′-aminobenzo-15-crown-5 (AB15C5). By using MCM-g-AB15C5 as adsorbent, the effects of solvent, metal ions, and adsorption temperature on the adsorption uptake of Li⁺ and separation factor of ⁶Li/⁷Li were investigated in detail. Solvent with low polarity, high adsorption temperature in acetonitrile could improve the uptake of Li⁺ and separation factor of lithium isotopes. The MCM-g-AB15C5 exhibited the strongest adsorption affinity to Li⁺ with a separation factor of 1.022 ± 0.002 for ⁶Li/⁷Li in acetonitrile. The adsorption isotherms in acetonitrile is fitted well with the Langmuir model with an ultrahigh adsorption capacity up to 12.9 mg·g⁻¹, indicating the unexpected complexation ratio of 1:2 between MCM-g-AB15C5 and Li⁺. The thermodynamics study confirmed the adsorption process is the endothermic, spontaneous, and chemisorption adsorption. As-prepared novel cellulose-based adsorbents are promising materials for the efficient and selective separation of Li⁺ and its isotopes. Full article