Isotope Separation Research Articles

Hydrothermal Methane Venting and Its Microbial Oxidation Along the Eastern Southwest Indian Ridge, 63.5°–68°E

AbstractMethane concentration and its stable carbon isotope ratio studies were carried out in deep waters of ultraslow‐spreading eastern Southwest Indian Ridge (eSWIR), 63.5°–68°E, to identify hydrothermal plumes and associated biogeochemical processes. High methane concentrations (1.0–37.8 nmol/kg) confirm the presence of 11 hydrothermal plumes along the ∼500 km long section of eSWIR. Among these 11 plumes, eight are reporting for the first time. Detailed investigations near 67.67°E; 26.61°S show the presence of three plumes at various depths and their dispersion >100 km along the ridge in east‐west directions. Stable carbon isotope ratios of these plumes show lighter and heavier isotope enrichment (−40‰ to −3‰). Lighter isotope enrichment may indicate that methane could be derived from a combination of abiotic and thermogenic sources and, heavier isotope enrichment is mainly because of microbial methane oxidation. We report strong evidence for the presence of an active hydrothermal field at 67.67°E; 26.61°S in the eSWIR for the first time.

A Gate-Opening Control Strategy via Nitrate-Chloride Anion Exchange for Enhanced Hydrogen Isotope Separation in Metal-Organic Frameworks.

Efficient separation of hydrogen isotopes, especially deuterium (D2), is pivotal for advancing industries such as nuclear fusion, semiconductor processing, and metabolic imaging. Current technologies, including cryogenic distillation and Girdler sulfide processes, suffer from significant limitations in selectivity and cost-effectiveness. Herein, we introduce a novel approach utilizing an imidazolium-based Metal-Organic Framework (MOF), JCM-1, designed to enhance D2/H2 separation through temperature-dependent gate-opening controlled by ion exchange. By substituting NO3⁻ ions in JCM-1(NO3⁻) with Cl⁻ ions to form JCM-1(Cl⁻), we precisely modulate the gate-opening threshold, achieving a significant enhancement in isotope selectivity. JCM-1(NO3⁻) exhibited a D2/H2 selectivity (SD2/H2) of 14.4 at 30 K and 1 bar, while JCM-1(Cl⁻) achieved an exceptional selectivity of 27.7 at 50 K and 1 mbar. This heightened performance is attributed to the reduced pore aperture and higher gate-opening temperature resulting from the Cl⁻ exchange, which optimizes the selective adsorption of D2. Our findings reveal that JCM-1 frameworks, with their tunable gate-opening properties, offer a highly efficient and adaptable platform for hydrogen isotope separation. This work not only advances the understanding of ion-exchanged MOFs but also opens new pathways for targeted applications in isotope separation and other gas separation processes.

A Gate‐Opening Control Strategy via Nitrate–Chloride Anion Exchange for Enhanced Hydrogen Isotope Separation in Metal‐Organic Frameworks

Efficient separation of hydrogen isotopes, especially deuterium (D2), is pivotal for advancing industries such as nuclear fusion, semiconductor processing, and metabolic imaging. Current technologies, including cryogenic distillation and Girdler sulfide processes, suffer from significant limitations in selectivity and cost‐effectiveness. Herein, we introduce a novel approach utilizing an imidazolium‐based Metal‐Organic Framework (MOF), JCM‐1, designed to enhance D2/H2 separation through temperature‐dependent gate‐opening controlled by ion exchange. By substituting NO3⁻ ions in JCM‐1(NO3⁻) with Cl⁻ ions to form JCM‐1(Cl⁻), we precisely modulate the gate‐opening threshold, achieving a significant enhancement in isotope selectivity. JCM‐1(NO3⁻) exhibited a D2/H2 selectivity (SD2/H2) of 14.4 at 30 K and 1 bar, while JCM‐1(Cl⁻) achieved an exceptional selectivity of 27.7 at 50 K and 1 mbar. This heightened performance is attributed to the reduced pore aperture and higher gate‐opening temperature resulting from the Cl⁻ exchange, which optimizes the selective adsorption of D2. Our findings reveal that JCM‐1 frameworks, with their tunable gate‐opening properties, offer a highly efficient and adaptable platform for hydrogen isotope separation. This work not only advances the understanding of ion‐exchanged MOFs but also opens new pathways for targeted applications in isotope separation and other gas separation processes.

Metal-Organic Framework with Open Metal Sites for D2/H2 Separation.

The separation of hydrogen isotopes remains a significant challenge due to their nearly identical physicochemical properties. Recently, metal-organic frameworks employing the chemical affinity quantum sieving effect have garnered increasing attention for hydrogen isotope separation. In this study, Cu-BTT with open metal sites was synthesized and demonstrated high hydrogen isotope adsorption capacities of 266 cm3/g for H2 and 288 cm3/g for D2. Dynamic breakthrough experiments revealed a selectivity of 1.58 at 77 K, highlighting the potential of Cu-BTT as a promising candidate for hydrogen isotope separation.

Apatite Geochemical Perspectives on the Maturation of Continental Arc Crust via Mush‐Facilitated Processes During Magmatic Flare‐Up

AbstractIn volcanic arcs, magma evolves from basaltic to intermediate and felsic composition, resulting in arc crust maturation. It remains unclear whether processes involving mush during magmatic flare‐ups would enhance this evolution. This study revealed a temporal‐compositional evolution of plutonic rocks from mafic (∼94 Ma) to intermediate (∼92–88 Ma) to felsic (∼88 Ma) during a magmatic flare‐up event in the Gangdese arc, Tibet, with increasing radiogenic Sr–Nd isotope enrichment. Apatites in mafic and felsic rocks have εNd(t) values similar to their hosts, while intermediate rocks show higher values. The elemental composition of apatites in mafic and intermediate rocks is similar but differs from those in felsic rocks. Textural and compositional features indicate varying degrees of influence of mafic rock compositions by accumulation. Triangular and linear covariation relationships between apatite‐compatible (e.g., La) and ‐incompatible (e.g., Rb) elements with SiO2, respectively, for all plutonic rocks as a whole, confirm the incorporation of apatite‐rich mushes into the mixing process. These findings suggest that mafic magma crystallized into apatite‐rich mush, which was later remobilized and mixed with felsic magma to form intermediate magma. Felsic rocks represent end‐member magmas resulting from crustal anatexis and/or mafic magma differentiation. Thus, the Gangdese arc's maturation during the magmatic flare‐up progressed sequentially through mafic magma crystallization and mush formation, mush remobilization and mixing with felsic magma, and the eventual accumulation and segregation of felsic magma. This sequence of events during flare‐ups illustrates a common crustal maturation process in volcanic arcs, as also seen in the Andean Cordillera.

Copper and zinc isotope fractionation during phototrophic biofilm growth.

Copper (Cu) and zinc (Zn) are two trace metals that exhibit both limiting and toxic effects on aquatic microorganisms. However, in contrast to good knowledge of these metal interactions with individual microbial cultures, the biofilm, complex natural consortium of microorganisms, remains poorly understood with respect to its control on Cu and Zn in the aquatic environments. Towards constraining the magnitude and mechanisms of Cu and Zn isotope fractionation in the presence of phototrophic biofilms composed of different proportion of diatoms, green algae and cyanobacteria, we studied long-term growth in a rotating annular bioreactor and quantified the uptake of metals and their isotope fractionation at environmentally-relevant Cu and Zn concentrations. An enrichment of the biofilm in heavy Cu isotope at the beginning of growth suggests the dominance of adsorption processes, followed by intracellular uptake leading to progressive enrichment in light isotope and an excretion of heavy isotope, likely linked to Cu(II) reduction. In the case of Zn, we evidenced only weak isotope fractionation which implies the presence of heavier isotope adsorption (notably in the case of cyanobacteria-dominated biofilm) followed by intracellular incorporation of lighter isotopes. The microbial community plays important role in overall magnitude and even direction of fractionation, suggesting sizable complexity of the processes controlling metal isotope fractionation during phototrophic biofilm growth. However, Cu and Zn isotopes during long-term metal accumulation in riverine biofilm can be used for monitoring the source of environmental pollution in aquatic systems, provided that variations within different sources exceed the natural isotopic fractionation between the biofilm and aqueous solution.

Dietary Shifts Among the Developmental Stages of the Ectoparasite, Argulus japonicus (Crustacea; Branchiura), Mirror Ontogeny as Shown Through Differences in Stable Isotope Ratios of Carbon (δ13C) and Nitrogen (δ15N).

Food web architecture and trophic interactions between organisms can be studied using ratios of naturally occurring stable isotopes of carbon (13C/12C) and nitrogen (15N/14N). Most studies, however, focused on free-living organisms, but recently, there has been growing interest in understanding trophic interactions of parasites. The crustacean ectoparasite Argulus japonicus is a well-studied parasite of freshwater teleost fish, which has low host specificity and a cosmopolitan distribution. Little is known about the trophic interactions between various developmental stages of this parasite and its host. This study compares stable isotope ratios of carbon (δ13C) and nitrogen (δ15N) among developmental stages of A. japonicus. It was hypothesised firstly that stable isotopes would vary among the developmental stages of the parasite with differences matching ontogenetic development of the parasite. Secondly, fractionation patterns among developmental stages would relate to different fish tissues and particles, such as algae, ingested by the parasite. Goldfish, Carassius auratus, were infected with A. japonicus, and different developmental stages of the parasite were isolated and prepared for stable isotope analysis. Differences in stable isotope enrichment correlated with the ontogenetic development of the parasite. In adult parasites, δ15N was higher than in the host's tissues, whereas stage two larvae showed the lowest δ15N values. Infection by A. japonicus alters δ13C ratios between infected and uninfected hosts, where the latter group showed lower δ13C compared to uninfected hosts. Source contribution comparison showed that algae was not incorporated into the diet of A. japonicus and tissues of the host served as the only dietary source of nourishment. These results further suggest that the diet of the parasite is mixed and correlates to the ontogenetic development of A. japonicus.

Exploration of functional group effects on D2/H2 separation selectivity within the UiO-66 framework

The incorporation of functional groups into UiO-66 enables effective modulation of the material's pore size and polarity, thus facilitating precise control over its performance in hydrogen isotope separation.

Hydrogen isotope separation at exceptionally high temperature using an unsaturated organometallic complex.

A new approach for hydrogen isotope separation using an unsaturated organometallic complex was proposed. Adsorption measurements of [Mn(dppe)2(CO)(N2)](BArF24) (Mn-dppe) (dppe = 1,2-bis(diphenylphosphino)ethane, BArF24 = B[C6H3(3,5-CF3)2]4) using H2 and D2 revealed a significant difference in the adsorption enthalpy of H2/D2 at much higher room temperatures than in previous studies, with D2 molecules being more strongly adsorbed on unsaturated metal sites. Mixed gas adsorption isotherms were calculated at each temperature using IAST, and it was predicted that D2 uptake was much larger than H2 uptake. Column chromatographic separation using the difference in adsorption enthalpy indicated that deuterium could be concentrated, and DFT calculations suggest that this difference in adsorption force is due to the difference in vibrational potentials involved in metal-dihydrogen bonding. This study introduces a new separation approach that could enable hydrogen isotope separation in the ambient temperature range.

Selenium Biofortification of Vegetables Grown in Calcareous Soil: A Pot Experiment Using 77Se as a Tracer.

Dietary selenium (Se) is vital for human health and can be provided through consumption of Se-rich vegetables. Soil Se is often poorly available and so biofortification using Se-enriched fertilizers is used to enhance dietary intake. This study aimed to (a) evaluate the feasibility of biofortifying vegetables, commonly grown in the calcareous soils of Kurdistan, with a single application of Se (10 g ha-1) as selenate and, (b) trace the fate of applied Se using an enriched stable isotope, ⁷⁷Se. A randomized block pot experiment was conducted with five vegetable species: celery, chard, lettuce, radish, and spring onion. Soils were spiked with 2 µg ⁷⁷Se per pot, simulating 10 g ha-1. Plants were harvested after 8 weeks, and both plant tissues and soils underwent sequential extraction and isotopic analysis to determine Se fractionation and source apportionment. Across all species, plant uptake of native soil Se (Ses) exceeded that of fertilizer-derived Se (Sef). Shoot concentrations of Ses ranged from 58.2 to 115 µg kg-1, while ⁷⁷Sef concentrations varied between 10.5 and 46.9 µg kg-1. Post-harvest soil analyses indicated immobilization of applied ⁷⁷Se: 55% transitioned to organically bound forms, 40% became recalcitrant, and only 5% remained in plant-available fractions. The study underscores the challenges of Se biofortification in calcareous soils, where interaction with CaCO3 may reduce Se availability. Variations in Se uptake among vegetable species highlight the importance of application timing. To enhance biofortification efficacy for fast-growing leafy vegetables, mid-season or foliar Se applications are recommended to counteract rapid soil immobilization.

Verification of uranium composite materials using active interrogation techniques for safeguards purposes

Abstract The uranium isotope characterization for nuclear safeguards and security purposes was conducted using both passive and active non-destructive techniques. The interrogated samples were natural uranium (NU), low-enriched uranium (LEU), and depleted uranium (DU) all in the form of uranium dioxide. The obtained spectra using both techniques were accumulated using a high-efficiency HPGe detector. Improving detector efficiency was developed using the neural network (NN) method based on the obtained intrinsic calibration data. The obtained enrichment results of passive measurements showed good agreement with certified samples to within 1.12% in the case of LEU, 1.03% in the case of NU, and 1.04% in the case of DU.
Active interrogation of the samples was done using the neutron spectrum of a 5 Ci 241Am-Be neutron source. Seven short-lived fission products (FPs) (101Tc, 97Nb, 105Ru, 92Y, 91Sr, 92Sr, and 88Kr) were chosen as indicators to provide a complete characterization of isotopic mass determination, uranium content, and enrichment. Isotopic masses of the samples were calculated using thermal and fast interrogations. A comparison of the obtained results of 238U mass was found to agree within 0.2% with certified value based on fast interrogation, and within 0.3% of 235U mass based on thermal interrogation.

Preparation of Low-Oxygen Ti–Si Alloys by Electromagnetic Separation

Preparation of Low-Oxygen Ti–Si Alloys by Electromagnetic Separation

High-Entropy Zeolitic Imidazolate Frameworks for Dynamic Hydrogen Isotope Separation.

Entropy-driven strategy enables the systematic design of complex systems by using entropy as a quantifiable design parameter for the degree of mixing. In this study, we present mixed-linker zeolitic imidazolate frameworks (ZIFs), sod-ZIF-1 series, that features two types of six-membered rings (6MRs) with aperture sizes of 3.4 Å and 1.7 Å. By adjusting the configurational entropy, the ratio of these 6MRs can be systematically controlled, which significantly influences adsorptive properties, particularly improving the H2 affinity about 3 times throughout the series. This results in the significant enhancement of retention times in dynamic separation of hydrogen isotopes (D2/H2), even over LNG liquefaction temperature. This approach to entropy-driven pore engineering provides new opportunities for enhancing gas adsorption and separation processes.

High‐Entropy Zeolitic Imidazolate Frameworks for Dynamic Hydrogen Isotope Separation

Entropy‐driven strategy enables the systematic design of complex systems by using entropy as a quantifiable design parameter for the degree of mixing. In this study, we present mixed‐linker zeolitic imidazolate frameworks (ZIFs), sod‐ZIF‐1 series, that features two types of six‐membered rings (6MRs) with aperture sizes of 3.4 Å and 1.7 Å. By adjusting the configurational entropy, the ratio of these 6MRs can be systematically controlled, which significantly influences adsorptive properties, particularly improving the H2 affinity about 3 times throughout the series. This results in the significant enhancement of retention times in dynamic separation of hydrogen isotopes (D2/H2), even over LNG liquefaction temperature. This approach to entropy‐driven pore engineering provides new opportunities for enhancing gas adsorption and separation processes.

Coupling molecular and continuum numerical methods for evaluation of thermal and mechanical drives on high rotating isotopic gas flow

The main objective of this study is to develop a hybrid molecular–continuum method to model a gas flow within a centrifuge machine. By implementation of this coupled approach, the effects of mechanical and thermal drives on gas flow and separation process inside a high rotating cylinder are evaluated. In simulating the gas flow inside the high rotating cylinder, there are certain situations where the particle density experiences significant fluctuations. To accurately simulate these events, the direct simulation Monte Carlo (DSMC) approach can be employed as the most effective particle method. However, obtaining a high level of accuracy with this method necessitates a significant amount of computation time. Alternatively, the less time-consuming computational approach, known as fluid technique or computational fluid dynamics (CFD), can be utilized when the flow is in the state of continuum. The goal of coupled DSMC–CFD solution is to integrate particle and fluid simulations to speed up calculation for transitional flows that involve both fields in a unified domain. The DSMC–CFD method is implemented in the OpenFOAM framework to simulate the flow of UF6 gas throughout the regions of a centrifuge machine. This open-source software offers the capability to solve the molecular region and code the coupling between the continuum and molecular regions. This work introduces a modified code based on OpenFOAM to simulate the gas flow in the supersonic rotating cylinder, which provides both molecular and fluid areas. This simulation is conducted under axisymmetric and steady-state to analyze the impact of thermal and mechanical drivers on flow regimes. Also, the isotopic separation and separative work are evaluated.

Mechanistic insights into lithium-ion adsorption and isotope separation on ligand-tuned aluminum-based metal–organic frameworks

Mechanistic insights into lithium-ion adsorption and isotope separation on ligand-tuned aluminum-based metal–organic frameworks

Deciphering the mineral code of urinary stones: A first look at zinc isotopes.

Zinc (Zn) is an essential element for all living organisms, and Zn isotopes play a key role in studying the formation of disease. Despite extensive studies on Zn isotopes in healthy and diseased human tissues, the role of Zn isotopes in urinary stones remains unexplored. This study investigates Zn isotopes in 37 urinary stones using multi-collector inductively coupled plasma mass spectrometry. The δ66Zn values of urinary stones range from -0.15‰ to 0.47‰, with a mean value of 0.11‰. Carbonate apatite (CA) stones exhibit lighter Zn isotopic compositions (δ66Zn=-0.15‰∼-0.03‰) compared to calcium oxalate (CO) stones (δ66Zn=-0.11‰ ∼ 0.47‰). The variation in Zn isotopic compositions between CO and CA stones may result from urinary pH differences during stone formation. At higher urinary pH, CA stones are enriched in lighter Zn isotopes compared to CO stones. Urinary stones are enriched in lighter Zn isotopes compared to blood and urine. This study identifies two steps influencing Zn isotope variations during kidney transport. The first step involves kidney filtration and reabsorption, enriching heavy Zn isotope in the urine. The second step is the deposition process of urinary stones, where light isotopes, due to their lower bond energy, are more prone to breaking. This kinetic fractionation effect leads to an enrichment of light Zn isotope in urinary stones. Overall, this study offers preliminary insights into the geochemical mechanisms that influence the Zn isotopic composition in urinary stones.

Constructing O doped g-C3N4 nanosheets as photocatalysts for photocatalytic water splitting derived hydrogen isotopic water separation

The disposal of tritium-containing wastewater has been an enormous challenge because of its severe hazards to ecological environment. Due to the nearly identical physicochemical properties of hydrogen isotopes, the present disposal methods usually deliver low separation efficiency and high energy-intensive. Herein, photocatalytic water splitting has been firstly carried out to separate hydrogen isotopic water through the hydrogen evolution processes. The O doped graphitic carbon nitride (OGCN) as photocatalyst delivers a competitive separation factor of 4.69 with a gas evolution rate of 6.511 mmol g−1 h−1. The OGCN samples show lager surface area and abundant O dopants after the thermal oxidative etching, thus boosting the diffusion of photogenerated charge carries and delaying the recombination of photogenerated hole-electrons. The separation of hydrogen isotopes is mainly attributed to the kinetic isotope effect and the difference of bond energy between H2O and D2O. The electrochemical impedance spectra imply a lower electrical resistance of H2O than that of D2O, leading to a faster migration rate of charge carriers in H2O solution.

Remnants of a Jurassic marginal sea plate in the Meso-Tethyan Ocean revealed by multi-stage magmatism in the Lagkorco ophiolite, Central Tibet

The formation of marginal sea plate, through multi-stage arc rupture and back-arc spreading, is a fundamental process in mature intra-ocean convergent plate margins. Identifying remnants of ancient marginal sea microplates within suture zones is crucial for unraveling the evolution of ancient ocean basins, although it presents significant challenges. In this study, we present new zircon and titanite UPb ages, along with Sr-Nd-Fe isotopic compositions, for a suite of well-characterized cumulates from the Lagkorco ophiolite which represents remnants of the Bangong-Nujiang Meso-Tethyan oceanic lithosphere. Our integrated dataset, combined with previous findings, reveals three distinct magmatic phases within the Lagkorco ophiolite: i) Unit A: early Jurassic (~184 Ma) amphibolite-facies mafic-felsic complex, ii) Unit B1: early Jurassic (187–192 Ma) oceanic lithosphere, and iii) Unit B2: middle Jurassic (160–170 Ma) oceanic lithosphere. Geochemical data from Unit B1 cumulates indicate a damp (~1 % H2O) but arc-like parental magma. These cumulates exhibit more enriched SrNd isotopes compared to mid-ocean ridge basalts and typical island arc basalts. Unit B1 cumulates exhibit clinopyroxene Fe isotopes (δ56Fe = −0.06 − +0.01) lighter than mid-ocean ridge cumulate clinopyroxene (δ56Fe = +0.02 − +0.05). These data indicate that the Unit B1 cumulates originated from a subduction-modified depleted mantle mixed with minor sediments. Combining our results with previously published data, we propose that the parental magmas for both Unit B1 and Unit B2 were damp but arc-like, which aligns with the repeated re-melting of previously depleted sub-arc mantle during episodic back-arc spreading. Our interpretation suggests two-stage back-arc spreading (Unit B1 and Unit B2) and at least one episode of arc magmatism (Unit A) between 192 and 160 Ma. These results imply the existence of a Jurassic marginal sea plate, akin to the present-day Philippine Sea plate, within the Meso-Tethyan Ocean, which was likely later subducted beneath the Qiangtang continent.

Biosynthesis-Encoded Lipogenic Acetyl-CoA Measurement Using NMR Reveals Glucose-Driven Lipogenesis and Glutamine's Alternative Roles in Kidney Cancer.

Fatty acid de novo synthesis (FADNS) is a critical process in lipogenesis that is characteristically altered in clear cell renal cell carcinoma (ccRCC), which is the major type of kidney cancer. An important challenge in studying the FADNS process has been the accurate measurement of cytosolic lipogenic acetyl-CoA (AcCoA), the precursor in FADNS, due to its compartmentalization within cells. Here, we describe a novel NMR-based method to decode the isotopic enrichment of lipogenic AcCoA, which, as we demonstrated, is encoded in the simple signal ratios of the geminal methyl groups of lanosterol during its biosynthesis. The approach was validated based on the independence of the tracer enrichment and species along with the expected FADNS modulation using differentially enriched tracers and a well-studied drug. Application of this technique to 786-O ccRCC cells showed that glucose may serve as a major carbon source for lipogenic AcCoA in FADNS at physiological nutrient concentrations, at odds with previous studies that indicated glutamine's dominant role through reductive carboxylation under higher nutrient conditions. Further investigation into glutamine's alternative roles in ccRCC cells suggested its major involvement in the bioenergetic TCA cycle, pyrimidine synthesis, and glutathione synthesis, which is also critical in ccRCC growth. The glutamine-dependent glutathione synthesis was also suggested as a possible metabolic vulnerability compared to normal kidney cells using a glutathione synthesis inhibitor. The current study provides a simple tool for studying an important aspect of lipid metabolism and suggests translational implications for targeting glucose-driven lipogenesis and glutamine-supported glutathione synthesis in ccRCC.