Hydrogen Isotope Separation Research Articles

Investigation of the Dynamic Behaviour of H2 and D2 in a Kinetic Quantum Sieving System.

Porous organic cages (POCs) are nanoporous materials composed of discrete molecular units that have uniformly distributed functional pores. The intrinsic porosity of these structures can be tuned accurately at the nanoscale by altering the size of the porous molecules, particularly to an optimal size of 3.6 Å, to harness the kinetic quantum sieving effect. Previous research on POCs for isotope separation has predominantly centered on differences in the quantities of adsorbed isotopes. However, nuclear quantum effects also contribute significantly to the dynamics of the sorption process, offering additional opportunities for separating H2 and D2 at practical operational temperatures. In this study, our investigations into H2 and D2 sorption on POC samples revealed a higher uptake of D2 compared to that of H2 under identical conditions. We employed quasi-elastic neutron scattering to study the diffusion processes of D2 and H2 in the POCs across various temperature and pressure ranges. Additionally, neutron Compton scattering was utilized to measure the values of the nuclear zero-point energy of individual isotopic species in D2 and H2. The results indicate that the diffusion coefficient of D2 is approximately one-sixth that of H2 in the POC due to the nuclear quantum effect. Furthermore, the results reveal that at 77 K, D2 has longer residence times compared to H2 when moving from pore to pore. Consequently, using the kinetic difference of H2 and D2 in a porous POC system enables hydrogen isotope separation using a temperature or pressure swing system at around liquid nitrogen temperatures.

Viability of hydrogen isotopes separation via heterolytic dissociation-driven Chemical Affinity Quantum Sieving on inexpensive alkali-earth oxides

The quest for economically viable strategies to separate hydrogen molecule isotopologues has recently provided clear indications on the design principles that ought to be implemented to satisfy the growing request for deuterium and tritium homodimers. In this respect, we investigate by electronic structure calculations whether easily obtainable, environmentally respectful, and inexpensive alkali-earth oxides may be suitable materials when it comes to separating hydrogen isotopologues. We found that hydrogen dimers heterolytically dissociate upon chemisorption on the most reactive three-coordinated vertex Mg, Ca, Sr and O sites, the formed species remaining in close proximity due to a strong H+/H– interaction. The inclusion of quantum zero point motion in the description of the adsorption energetics, mandatory if one wishes to differentiate the isotopologues behavior, indicated that the chemisorption energy becomes more negative the heavier the isotope involved. Isotopic selectivities estimated via Ideal Adsorbed Solution Theory (IAST) appear orders of magnitude higher than those previously presented. As chemisorbed species may catalyze an exchange reaction with gaseous molecules hinging on their nature as Broensted acid and Lewis base, we searched for possible processes competing with the desorption of vicinal adsorbed species; our results suggest that production of heterodimers (e.g. HD) is unlikely.

An LSC approach for tritium determination in gaseous mixtures optimized with respect to handling, reaction parameters and miniaturization towards microfluidic analysis

Abstract The handling and analysis of gaseous tritium is of interest for hydrogen isotope separation experiments. In this work, we present an easy-to-handle setup for catalytic oxidation to HTO, recovering all of the initially dosed gaseous tritium as determined by LSC, using CuO as a catalyst at a reaction temperature of 900 °C. Aiming to reduce cocktail waste, the LSC determination was downscaled to a microfluidic setup. The performance was evaluated based on the counting efficiency, which was shown to decrease significantly, as the sample volume was reduced to µl amounts, while no changes were observed over a wide range of sample-to-cocktail ratios.

Graphene-based electrochemical system for tritium enrichment

In this study, a tritium enrichment system in the water phase has been developed based on the combination of a proton exchange membrane (PEM) electrolysis cell and a fuel cell. As the PEM, NafionTM and laboratory-synthesized sulfonated poly(ether ether ketone) membranes modified with an additional graphene layer in order to enhance the tritium separation factor were used. Both differences in the kinetics of the hydrogen evolution reaction and transport through the graphene layer of different isotopes are the driving factors expected to affect the separation of hydrogen isotopes. The separation factor was measured both during the electrolysis and fuel cell stage using different membranes. The facilitating effect of the graphene on the separation efficiency was determined during the study. The separation factor obtained by the proposed method was evidently higher than that obtained by other conventional methods.

Efficient hydrogen isotope separation utilizing photocatalytic capability

An N–O–C3N4 catalyst for catalytic hydrogen isotope separation.

Effect of Water Vapor on Hydrogen Isotopes Separation by Polymer Electrolyte Fuel Cell

IntroductionHydrogen isotopes are protium (H), deuterium (D) and tritium (T). D and T are important materials not only for fission and fusion reactors, but also for semiconductors since the strong hydrogen termination improves the durability. Various techniques for hydrogen isotope separation have been known for long time, but they have some drawbacks such as low separation efficiency and poor energy consumption. Therefore, new separation and purification methods are required.In polymer electrolyte fuel cell (PEFC), wettability is optimized well and small amount of Pt catalyst is used. The configuration is also key issue for the conventional method of water-hydrogen chemical exchange. Therefore, we investigated the effect of water in hydrogen isotope separation by PEFC [1].ExperimentalA mixture hydrogen gas of H2 and D2 was supplied to the PFEC. The separation factor for dry and wet gas flow was measured, respectively. Hydrogen gas and water vapor from PEFC were analyzed by quadrupole mass spectrometry (Q-mass) and Fourier infrared spectrometer (FTIR), respectively. The separation factor and mass balance were calculated.Results and discussionWhen no electricity was generated, FTIR results showed that D was enriched in water vapor. This is explained by a gas-phase chemical exchange reaction occurring on a platinum catalyst. When the PEFC was operated, the electrochemical reaction promoted the D separation. A large amount of D (about 45%) was transferred to water vapor during power generation. The separation factor was approximately 1.7, while it was approximately 1.3 for no generation. The present results suggested that gas-phase chemical exchange and the cell reaction had a synergistic effect on D separation.

Deuterium Enrichment by PEM Water Electrolysis Using Water Circulation

Artemis Project, an international space exploration project proposed by the United States and involving Japan, plans a long-term manned lunar exploration in the late 2020s. That project considers the capture of He3, a resource for fusion that does not exist on Earth. On the other hand, He3 is produced by the half-life of tritium (T). Now new hydrogen isotope separation is required for recovering T exhausted from nuclear reactors.The water electrolysis is well known to enrich protium (H) in gas phase and, deuterium (D) and T in the electrolyte [1]. The modern electrolysis is performed by solid polymer membrane water electrolysis (PEMWE). However, there are few reported cases for the isotope separation by PEMWE. In this study for pursing high D separation, the optimization of the electrolysis system was investigated.The initial D concentrations in the electrolyte were 10, 30, and 50 at% IrO2 was used as the anode catalyst and Pt/C as the cathode one. The electrolysis was galvanostatically conducted. Hydrogen gas was analyzed by a quadrupole mass spectrometer (Q-Mass) to determine the ratio of H2, HD, and D2. The electrolyte was analyzed by Fourier transform infrared spectrophotometer (FT-IR) to determine the ratio of H2O, HDO, and D2O.Figure. 1 shows the schematic illustration of gas and water flow chart in experimental setup. Electrolyte was sent to the cell by the electric pump constantly. When the experiment was carried out, evolved gas and drained water was analyzed. The water out from the cell was returned into the electrolyte tank and electrolyzed repeatedly. The gas was introduced to Q-Mass. By using this circulation system, D was concentrated in the electrolyte efficiently . In this experiment, its concentration reached about 95at.%. To quantitatively evaluate the D enrichment by PEMWE, the separation factor α was calculated from the ratio of D concentrations in the electrolyte to the gas. The value of α was approximately 4.0. However, the valueslightly decreased above 90 at.% D. More detailed results will also be presented in our Poster, #176411. Figure 1

Highly effective quantum sieving of hydrogen isotopes on flexible metal-organic frameworks with mobile ligands

The separation of hydrogen isotopes is crucial in nuclear energy and biomedicine, but current techniques have limited separation coefficients. Utilizing flexible metal-organic frameworks (MOFs) with quantum sieving capabilities offers a promising solution. However, achieving high hydrogen isotope adsorption capacity while maintaining a high separation factor remains a challenge. This study presents a novel approach for the quantum sieving of hydrogen isotopes using MOFs with mobile ligands. The stable crystal structure of the microporous MOFs enables large hydrogen isotope adsorption capacity. The presence of mobile ligands acts as the gate in the dynamic adsorption and separation process, enhancing the performance of hydrogen isotope separation. The smaller quantum radius and larger molecular weight of deuterium facilitate its easier entry into the micropores, resulting in a maximum selectivity for D2 over H2 of 36.7 and a D2 uptake of 17.3 mmol g−1. Furthermore, the kinetic quantum sieving of hydrogen isotopes necessitates MOFs with mobile ligands that maintain their flexibility from 20 K to 70 K, as demonstrated by ultralow-frequency Raman spectra.

Machine learning aided computational exploration of metal–organic frameworks with open Cu sites for the effective separation of hydrogen isotopes

Efficient separation of hydrogen isotopes is of vital importance to develop nuclear energy industry, while it remains a significant challenge to separate D2 from H2 due to their identical physicochemical properties. As one of the efficient alternatives to conventional techniques, the thermodynamic quantum sieving technology using metal–organic frameworks (MOFs) featuring open metal sites (OMSs) has shown a great potential. However, the lack of transferable force fields in conventional molecular simulations and high expense of brute-force screening hinder the quick discovery of MOFs targeted for D2/H2 separation. Herein, based on the established force field with high accuracy and transferability, machine learning and feature engineering are applied to address these challenges. Machine learning comprehensively assesses different descriptors that influence the separation performance of 929 experimentally-reported MOFs bearing Cu(II)-OMS. By employing the same metal nodes, new Cu MOF database (6,748 MOFs) is constructed, in which 45 hypothetical MOFs are firstly identified out through feature engineering that exhibiting high performance. Furthermore, grand canonical Monte Carlo simulations are performed on these MOFs, among which the optimal one exhibits comparable selectivity (36.9) and high adsorbent performance score (315.9) that surpasses the state-of-the-art materials do. This work not only presents a cost-effective approach firstly applying in the separation of hydrogen isotopes, but also provides experimental guidance for the design of high-performance adsorbents.

Radiation stability of electron beam irradiated high degree sulfonated poly(ether ether ketone) membranes for the applications in nuclear facilities

Sulfonated poly(ether ether ketones) (SPEEK) have raised interest as a replacement of Nafion® proton exchange membranes (PEM) for the application in harsh environments involving material exposure to ionizing radiation, for example, radioactive hydrogen isotope separation from water. This study is dedicated to evaluate the effects of high dose (500 kGy) electron beam irradiation on the physico-chemical and thermomechanical properties of highly sulfonated (degree of sulfonation 60–90 %) SPEEK membranes irradiated in air and water. Spectrometric and thermogravimetric analysis indicated slight changes in the material properties after irradiation with increase of the degree of sulfonation (DS). Tensile tests and thermomechanical analysis of irradiated samples indicated notable deterioration of properties at higher DS values. Results demonstrate that SPEEK membranes with DS around 70 % could be a replacement of the traditional PEM for the applications where exposure to ionizing radiation occurs.

Inverse kinetic isotope effect of proton and deuteron permeation through pyridinic N-doped graphene

Graphene is becoming an increasingly popular platform for developing high-efficiency hydrogen isotope separation technologies operated at room temperature. However, its performance can be strongly affected by contributions from atomic defects. Understanding the influence of defects on the hydrogen isotope selectivity of graphene is thus imperative but remains elusive. In this work, we investigated the electrically driven proton/deuteron permeation through nitrogen-doped graphene membranes with varying N concentrations and configurations. The results show that N-doping significantly enhances the proton and deuteron permeability of graphene (by one order of magnitude). More importantly, deuterons are found to permeate faster through pyridinic N-containing defects than protons, demonstrating a pronounced inverse kinetic isotope effect (KIE) with kH/kD of 0.75. Conversely, pyrrolic N-containing defects exhibit a normal KIE (kH/kD = 1.56). The exclusive contribution of the pyridinic N to the inverse KIE is confirmed by the reversed KIE factor of the pyridinic N-dominated sample subjected to modification. Theoretical calculations indicate that the explicit dependence of KIE on N configuration originates from the different leading mechanisms of proton/deuteron permeation through these N-containing defects, which is governed by the size and the chemisorption imparted by defects. These findings provide fundamental insights into the correlation between defect characteristics and proton/deuteron transport in graphene, and contribute to developing economical hydrogen isotope separation technologies through the defect engineering of graphene.

Recent Progress in Functional Nanomaterials towards the Storage, Separation, and Removal of Tritium.

Tritium is a sustainable next-generation prime fuel for generating nuclear energy through fusion reactions to fulfill the increasing global energy demand. Owing to the scarcity-high demand tradeoff, tritium must be bred inside a fusion reactor to ensure sustainability and must therefore be separated from its isotopes (protium and deuterium) in pure form, stored safely, and supplied on demand. Existing multistage isotope separation technologies exhibit low separation efficiency and require intensive energy inputs and large capital investments. Furthermore, tritium-contaminated heavy water constitutes a major fraction of nuclear waste, and accidents like the one at Fukushima Daiichi leave behind thousands of tons of diluted tritiated water, whose removal is beneficial from an environmental point of view. In this review, the recent progress and main research trends in hydrogen isotope storage and separation by focusing on the use of metal hydride (e.g., intermetallic, and high-entropy alloys), porous (e.g., zeolites and metal organic frameworks (MOFs)), and 2-D layered (e.g., graphene, hexagonal boron nitride (h-BN), and MXenes) materials to separate and store tritium based on their diverse functionalities are discussed. Finally, the challenges and future directions for implementing tritium storage and separation are summarized in the reviewed materials.

Permeation of low-pressure deuterium through niobium under radio-frequency plasma condition

The behavior of permeation of deuterium through niobium under the condition of radio-frequency plasma has been investigated in this paper. The external solenoid coupled plasma was applied as plasma source. The dependences of stable permeation flux on mode of discharge, membrane temperature, input power, gas pressure, surface oxidation layer and impurity concentration have been studied. The bulk diffusion was one of the controlling steps with 0.5 mm membrane and the substantially increase was due to plasma assisted dissociation. The mixtures with large amount of argon or nitrogen had finite influence on stable permeation flux which was attributed to the ion energy driven dissociation at surface. These results imply the inductively coupled plasma driven permeation is beneficial to rapid separation and purification of hydrogen isotopes for low surface sputtering rate of membrane surface and gases with hydrogen-containing compounds.

Application of membrane electrode assembly for water hydrogen isotope exchange

Hydrogen isotope separation will be important for future hydrogen energy applications. The materials used in polymer electrolyte fuel cells (PEFCs), such as the hydrophobic support and Pt catalyst, are essentially the same to those used in the conventional isotope-separation method of water hydrogen chemical exchange. Hereby, deuterium (D) separation was performed with a PEFC. The separation was improved with increasing the water vapor and temperature. D was enriched into the dew water in the cell. The quantities of D conversion from the gas through the vapor to the dew water was measured. The conversion values were less than the simulated ones. This was attributed to the vapor pressure drop and the wetted catalyst surface by the water condensation.

Molybdenum disulfide nanosheets rich in edge sites for efficient hydrogen isotope separation by water electrolysis

Molybdenum disulfide nanosheets rich in edge sites for efficient hydrogen isotope separation by water electrolysis

Gas Chromatography and Thermal Cycling Absorption Techniques for Hydrogen Isotopes Separation in Water Detritiation Systems

This work introduces state-of-the-art water detritiation processes and discusses the main technologies and materials adopted. Focus is given to the gas chromatography (GC) and the thermal cycling absorption process (TCAP), which are studied as potential back-end technologies for tritium recovery through a water detritiation system designed for a small-scale unit. GC and the TCAP are evaluated critically in order to establish their applicability for the final purification of the DT stream recovered at the bottom of the cryo-distillation column of a water detritiation unit. Both solutions (GC and the TCAP with an inverse column) exhibit safe and feasible operation modes and are characterised by a good technological level; furthermore, both of these processes meet the main design specifications required by the proposed application. However, the use of GC is preferred, since this system can operate with modest temperature cycling and producing streams (D2 and T2) of better purity.

Proton penetration mechanism and selective hydrogen isotope separation through two-dimensional biphenylene.

Hydrogen isotope separation is of prime significance in various scientific and industrial applications. Nevertheless, the existing technologies are often expensive and energy demanding. Two-dimensional carbon materials are regarded as promising candidates for cost-effective separation of different hydrogen isotopes. Herein, based on theoretical calculations, we have systematically investigated the proton penetration mechanism and the associated isotope separation behavior through two-dimensional biphenylene, a novel graphene allotrope. The unique non-uniform rings with different sizes in the biphenylene layer resemble the topological defects of graphene, serving as proton transmission channels. We found that a proton can readily pass through biphenylene with a low energy barrier in some specific patterns. Furthermore, large kinetic isotope effect ratios for proton-deuteron (13.58) and proton-triton (53.10) were observed in an aqueous environment. We thus conclude that biphenylene would be a potential carbon material used for hydrogen isotope separation. This subtle exploitation of the natural structural specificity of biphenylene provides new insight into the search for materials for hydrogen isotope separation.

New Achievements of H2-HD-D2 Isotopic Separation with the Cryogenic Distillation Experimental Stand from ICSI Cryogenic Laboratory

In the design process of a cryogenic distillation plant for the separation of hydrogen isotopes, two main objectives, often impossible to achieve simultaneously, are taken into account: a high separation factor for different mixtures and isotope concentrations and the reduction of design, manufacturing, and operating costs with increased efficiency and safety. All this should result from the use of a method for calculating the separation efficiency, a method that will generate a conceptual design that must form the basis of the final technical design. Unfortunately, most design methods treat these plants as chemical plants, although in the case of cryogenic plants, it is not possible to readjust the new process operating parameters quickly and with great precision so that the separation efficiency and performance are not affected. There are three causes affecting the separation performance of cryogenic distillation plants, namely, nonideality of the cryogenic process, imperfection of heat exchangers, and heat losses. This paper presents our proposed solutions for increasing the efficiency of the cryogenic distillation process and discusses solutions tested in experimental campaigns with the cryogenic distillation stand developed in the Cryogenic Laboratory at ICSI Rm. Vâlcea.

Effect of anode gas circulation on deuterium isotope separation by polymer electrolyte fuel cell

Separation of hydrogen isotopes is an important process in materials science, biomedical research, and nuclear fields. In this study, we used a polymer electrolyte fuel cell to separate protium (H) and deuterium (D). Here a circulation system recycled hydrogen gas at the anode was used. H and D were enriched in the gas and water phases, respectively. The separation efficiency depends on the gas flow rate through the parameter λ, which describes the stoichiometric ratio of circulation gas to feed gas. H and D were simultaneously enriched in their respective phases. The circulation system prolonged the gas circulation time in the system to improve the separation efficiency.

Thermodynamics and kinetics hydrogen isotope effects of hydrogen/deuterium absorption in Pd-5wt.%Pt alloy

Palladium–Platinum (Pd–Pt) alloys have excellent hydrogen isotope separation properties near room temperature compared to pure palladium (Pd), and are expected to be used as filling materials in thermal cyclic absorption (TCAP) columns. However, most studies on the thermodynamic and kinetic hydrogen isotope effects of hydrogen absorption/deuterium in Pd–Pt alloys have been conducted at temperatures of 273 K or above, with few studies involving the performance of TCAP in the cold-cycle operating temperature range (253 K–303 K). In this work, the performance of Pd-5wt.%Pt alloy for the absorption of hydrogen/deuterium at low temperatures (263 K–323 K) was investigated. The results show that the enthalpy and entropy of dissolution of hydrogen and deuterium in the α-phase of Pd-5wt.%Pt alloy are −11.77 kJ/mol (H), 104.00 J mol−1 K−1(H); −5.50 kJ/mol (D), 87.88 J mol−1 K−1 (D), respectively, which are lower than the enthalpy and entropy change values of pure Pd materials. The apparent reaction activation energies of protium and deuterium absorption are −4.14 kJ/mol (H2) and −11.87 kJ/mol (D2), respectively, which are lower than those of pure palladium. The excellent hydrogen isotope separation performance of Pd–Pt alloys may originate from the fast hydrogen absorption and discharge isotope kinetic performance.