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Separation of hydrogen isotopes (D2/H2) attracts wide interest due to its important applications, such as nuclear fusion. Kinetic quantum sieving‐induced separation over tailored nanoporous solids is a promising method; however, the dynamic separation often shows a transient feature, thus a low D2/H2 selectivity even at temperature below 50 K. Herein, we selectively enriched the accessible quantum sieving (AQS) sites in two‐dimensional carbons by chemically growing a pore‐narrowing layer. The spatial density of such AQS sites is 8.5 times higher than that of commercial carbon molecular sieves. The kinetic selectivity of D2/H2 reached 4.6 at 77 K. Column breakthrough experiments revealed that the dynamic D2/H2 separation was enhanced by such a nanopore design. Aspen simulation indicated that D2 was enriched to 93.1% within 11 pressure swing adsorption cycles with a 1% D2/99% H2 mixture as feed. [ABSTRACT FROM AUTHOR]

Hydrogen isotopes, such as protium(H), deuterium(D), and tritium(T), are widely used in medical treatment, nuclear energy, national defense, and other fields. Under the background of the "double carbon" target with carbon peak and carbon neutralization, deuterium-tritium fusion energy is considered to be an important energy strategy in China. However, the relative abundance of deuterium and tritium in nature is extremely low, and it is of great significance to separate hydrogen isotopes economically and effectively. This paper presents the research on water hydrogen isotope separation technology. Firstly, the methods and the principles of hydrogen isotope separation in water are summarized. Then, two perspectives of separation methods were reviewed. From the perspective of engineering application, the electrolysis, distillation and chemical exchange method are focused. From the perspective of laboratory research and development, the membrane separation method and porous material adsorption method are focused. Finally, the separation factors and energy consumption of typical separation technologies are compared. Moreover, to provide a certain reference for the water hydrogen isotope separation technology, several future research directions are prospected.

Liquid phase catalytic exchange (LPCE) appears a highly promising technology for separating hydrogen isotopes due to being less energy-intensive and having a high separation factor. This paper provides an overview of the current development of the hydrophobic catalysts used in the LPCE process, including the LPCE fundamentals, factors influencing its effectiveness, and proposals for future research areas. This paper specifically reviews the active metal catalysts, catalyst supports, operating temperatures, and molar feed ratio(gas-to-liquid,G/L). The addition of a second metal such as Ir, Fe, Ru, Ni, or Cr and modified catalyst supports showed enhancement of LPCE performance. Additionally, the validated optimized temperature of 60–80 °C and G/L of 1.5–2.5 provide an important basis for designing LPCE systems to improve separation efficiency. This paper concludes by highlighting potential research areas and challenges for future advancements in the sustainability of LPCE for hydrogen isotope separation, which include the optimization, scalability, techno-economic analysis, and life-cycle analysis of modified catalyst materials. [ABSTRACT FROM AUTHOR]

The hydrogen isotopes are vital due to their significant applications in scientific research, biomedicine and potential application in fusion energy. D-T fusion, in particular, holds the promise solving human fossil energy reliance and the resulting environmental pollution. Methods including cryogenic distillation and Girdler Sulfide process etc. have been developed to satisfy the demand towards pure D 2 and T 2 but generally suffer high energy consumption and low separation efficiency. Furthermore, emerging methods such as laser catalysis and quantum sieving have been demonstrated but suffers harsh separation conditions, low separation volumes and material life etc. Thermal cycling absorption process (TCAP) delivers seductive aspects regarding hydrogen isotope separation for efficiency and throughput, small footprint and high automation level. Herein, firstly, the advantages and disadvantages of various separation methods are briefly elucidated and provides the necessities for developing new separation methods. Then the preferred TCAP strategy is outlined in detail, containing working mechanisms and optimization process. Finally, the history and outlook of TCAP are listed. We hope this paper would spark some inspirations for further TCAP development towards hydrogen isotope separation. [Display omitted] • The necessity of hydrogen isotope separation was explained. • The pros and cons of the current separation methods were summarized. • The principles, working modes, and optimization of TCAP were summarized. • The future prospects of TCAP were proposed. [ABSTRACT FROM AUTHOR]

The separation of hydrogen isotopes is a vital step in preparing tritium and deuterium fuels for future fusion power plants. This represents a fundamental challenge to fusion energy since the separation process must be able to handle high throughputs of hydrogen isotopes whilst maintaining a low tritium inventory, because tritium is highly radioactive. There are many possible isotope separation techniques, however none that are currently deployable can meet the demands required. To address this gap, recent developments have improved existing processes and created new high-performance processes including Thermal Cycling Absorption Process (TCAP), electrochemical graphene sieving and absorbative separation based on quantum sieving. In this article, ten of the most promising future hydrogen isotope separation technologies are reviewed, to understand the development route to a process that addresses this key challenge of fusion energy. [Display omitted] • Comprehensive review of new and established isotope separation technology. • Cryogenic distillation, TCAP, PSA, membrane, gas chromatography. • Plasma chemical, thermal diffusion, and laser isotope separation. • Tritium inventory, separation factor and scalability are considered. • Effect of quantum sieving in porous solids and palladium absorption. [ABSTRACT FROM AUTHOR]

The quantum sieving is a promising approach for the separation of hydrogen isotopes under cryogenic conditions (< 100 K) in microporous solids. To evaluate the role of pore size and guest–cation interaction strength in this process, the adsorption properties of Li-exchanged LTA zeolites (Li8Na4A and LiA) for D2 and H2 were studied. The single gas adsorption isotherms were measured at different temperatures (39–92 K) and the equilibrium D2/H2 selectivities were determined using a coadsorption manometric technique. The isosteric heat of adsorption (Qiso) as a function of loading was determined from the single gas isotherms. It was found that in the partially exchanged material Li8Na4A the variation of Qiso is smaller than in NaA zeolite. In contrast, in LiA at low loading (< 2 molec/uc) extremely high values were observed (15.0 kJ/mol for D2 and 13.8 kJ/mol for H2) indicating the presence of strongly adsorbing sites. After the filling of these sites the Qiso decreases and remains almost constant reflecting weaker interactions between the guest molecules and Li+ cations located inside the cages (6MR sites). The D2/H2 selectivity at 40 K and high loading (~ 11 mmol/g) increases in the order: Li8Na4A < LiA < NaA. This finding shows that the presence of strongly adsorbing sites in LiA does not allow to increase D2/H2 selectivity. The smaller aperture size in NaA than in LiA (due to a larger size of Na+ cations) appears thus to be more important factor for quantum sieving in LTA zeolites than the strong guest–cation interactions. [ABSTRACT FROM AUTHOR]

Palladium is often used as the preferred material for hydrogen isotope separation, but pure palladium tends to be pulverized due to internal stress after repeated hydrogen absorption and desorption cycles. The pulverized palladium particles will increase hydrogen flow resistance, and even block the whole separation system in serious cases, thus affecting the separation efficiency and stability. In order to find suitable materials for hydrogen isotope separation, Pd/Al2O3 composite with 40.1% (mass fraction) palladium content was prepared by impregnation-reduction method using porous alumina as carrier and PdCl2 solution as palladium precursor. X-ray diffraction (XRD), BET surface area measurement, transmission electron microscope (TEM), and energy dispersive X-ray spectroscopy (EDS) techniques were used to study the phase, specific surface area and pore size distribution, morphology and composition of the material. The kinetics and thermodynamic properties of hydrogen absorption and desorption, hydrogen absorption and desorption cycling properties and anti-pulverization properties were tested by the volumetric absorption/desorption apparatus. Phase analysis results show that the alumina carrier exists in amorphous structure, the supported palladium particles have good crystallinity, and the precursor palladium is fully reduced without introducing other impurities. The results of specific surface area and pore size analysis show that most of the pores in the alumina carrier are mesoporous, the supported palladium exists in the pores of the Al2O3 carrier, and the Al2O3 carrier can bear a higher amount of palladium. The morphology analysis show that the palladium particles are well dispersed and the size range is from 8 nm to 50 nm. The hydrogen storage performance tests show that compared with the pure palladium, the maximum hydrogen capacity of Pd/Al2O3 composites is about 95% of the pure palladium, the plateau pressures of absorption and desorption increase by 21% and 12% separately, and the slope of absorption/desorption plateau increases. The hydrogen absorption rate is 5 times higher than that of pure palladium. It is speculated that the large specific surface area of nanocrystalline palladium particles increases the contact area with hydrogen, and the grain boundaries of nanocrystalline palladium particles provide more diffusion channels and reduce diffusion distance for hydrogen atoms. After 2 000 cycles of thermo induced hydrogen absorption and desorption, the hydrogen uptake capacity and plateau pressure of Pd/Al2O3 composite remain unchanged, and the hydrogen absorption rate increases slightly. No palladium particle pulverization or alumina ball rupture is observed. Pd/Al2O3 composite exhibits excellent anti-pulverization performance and has the potential of application in hydrogen isotope separation.

Graphene has been shown to act as an efficient sieve for hydrogen isotope separation since the perfect monolayer graphene is impermeable to almost all atoms and molecules but permeable to protons. Large-area graphene films can be produced by chemical vapor deposition (CVD) and exhibit a considerably high proton–deuteron separation factor of ∼8. However, the performance of the graphene-based membrane is often limited by the presence of cracks and imperfections introduced mainly during the transfer process. Here, we report a simple but effective method to transfer large-area CVD graphene onto commercial Nafion membranes with the aid of palladium thin films and thus fabricate the Pd/Graphene/Nafion composite membranes, which allow a proton–deuteron separation factor up to ∼10. This transfer method avoids the mechanical damage of graphene caused by deformation of the Nafion membrane. There is no need to remove the palladium thin film, and it will act as a catalyst for the reduction of hydrons during electrochemical pumping. The large-area transfer of graphene and fabrication of composite membranes for efficient separation of hydrogen isotopes will promote the development of graphene-based separation technologies. [ABSTRACT FROM AUTHOR]

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High selectivity of protons over deuterons transport through one-atom-thick graphene membrane has been demonstrated experimentally, but its fundamental mechanism has been controversially discussed. Proposed hypotheses involve local hydrogenation, but the detailed penetration process has not been rigorously explained. In the present study, based on electron cloud density, transition path selection and corresponding barrier calculations, perfect graphene is quasi-impermeable to protons, yet lateral ring chemically bonded protons adjacent hydrogenated hexa-cyclohydride shows the lowest barrier for the penetration of proton. The bridge-flip as a link provides the site for the penetration of the proton through the graphene. The chemically bonded protons slip into C–C to forms a C–H–C bridge bonds, and then flip over the graphene membrane to complete the penetration process. [Display omitted] • Electron cloud distribution is the main factor driving protons to have different penetration paths and barriers. • Protons exhibit lateral ring penetration under the combined action of spatial effects and interatomic forces. • A slight difference in vibrational zero point energies is sufficient to exhibit a higher separation effect. [ABSTRACT FROM AUTHOR]

Porous materials that contain ultrafine pore apertures can separate hydrogen isotopes via kinetic quantum sieving (KQS). However, it is challenging to design materials with suitably narrow pores for KQS that also show good adsorption capacities and operate at practical temperatures. Here, we investigate a metal–organic cage (MOC) assembled from organic macrocycles and ZnII ions that exhibits narrow windows (<3.0 Å). Two polymorphs, referred to as 2α and 2β, were observed. Both polymorphs exhibit D2/H2 selectivity in the temperature range 30–100 K. At higher temperature (77 K), the D2 adsorption capacity of 2β increases to about 2.7 times that of 2α, along with a reasonable D2/H2 selectivity. Gas sorption analysis and thermal desorption spectroscopy suggest a gate‐opening effect of the MOCs pore aperture. This promotes KQS at temperatures above liquid nitrogen temperature, indicating that MOCs hold promise for hydrogen isotope separation in real industrial environments. [ABSTRACT FROM AUTHOR]

The development of proton exchange membrane water electrolysis (PEMWE) offers an updating potential for electrolytic hydrogen isotope separation. However, it has a significantly lower separation factor than the traditional alkaline water electrolysis. In this study, we propose gold as a promising cathodic catalyst for efficient hydrogen isotope separation in PEMWE. Au/C has a protium-to-deuterium (H/D) separation factor of 7.47 in PEMWE, about twice that of Pt/C. In addition, the full cell's electrochemical performance is comparable to that of its Pt/C counterpart. The separation mechanism in PEMWE is explained by the transitional hydrogen evolution reaction mechanism from Heyrovsky to Tafel for Pt and the unchangeable Volmer mechanism for Au. The high separation factor for Au is also calculated by the H/D zero-point vibrational energy difference between transition state and reaction state through a simple density functional theory calculation. This work offers an effective strategy to improve hydrogen isotope separation efficiency in PEMWE. Au/C has a high hydrogen isotope separation factor of 7.5 in the PEMWE cell through the Volmer mechanism, about twice that of Pt/C which follows the Tafel mechanism. [Display omitted] • The electrolytic hydrogen isotope separation factor of Au/C was nearly twice that of Pt/C. • Au/C was employed as a cathodic catalyst in a PEM water electrolyzer for the first time. • The hydrogen isotope separation mechanism for Pt was elucidated by the HER mechanism transition. • The high separation factor for Au was confirmed by the ZPE difference between H and D. [ABSTRACT FROM AUTHOR]

Large volumes of water containing tritium are generated during the operation, decommissioning, and incident-management of nuclear installations and related facilities, and are expected to increase with the ongoing expansion of nuclear power generation. If released into the environment, this water could pose a substantial environmental threat to living organisms. However, conventional isotope separation techniques, such as cryogenic distillation and catalytic exchange, are inadequate for efficiently isolating significant quantities of low-level tritiated water because of the complex machinery and excessive energy required, and the potential for hydrogen-gas detonation. In contrast, water distillation (WD), as a traditional technology, has the unique advantages of simple operation, no corrosive and toxic substances, and no hydrogen explosion risk, but problems of small separation coefficient and low efficiency always exist in this technique. However, the separation effect of WD can be effectively improved by improving the process variables in the process of WD, such as temperature, distillation column diameter, and packing dimensions, so as to adapt WD to the separation of industrial tritiated water. This study provides a thorough exposition of the basic principles and distinctive features of water distillation and examines the effect of various operational parameters on separation efficiency to adapt the process for the industrial separation of tritiated water. The impact of various process variables on the separation efficiency of tritiated water via distillation was investigated, and results show that optimizing these variables can markedly improve the separation efficiency of water distillation. In particular, decreasing the dimensions of the packing material or altering its properties can lead to higher separation factors and lower residual tritiated water concentration. These findings suggest that water distillation can be used for the separation of tritiated water. By optimizing its operational parameters, water distillation can become a viable method for the industrial separation of tritiated water and is expected to play a significant role in this field in the future.

Owing to the large hydrogen isotope effect, palladium and palladium based alloy are of great technological importance for their application in separation of hydrogen isotopes. The present study deals with the investigation of isotope effect on hydrogen desorption kinetics of Pd, Pd 0.77 Ag 0.23 and Pd 0.77 Ag 0.10 Cu 0.13 alloys, using non-isothermal method by employing Differential Scanning Calorimetry (DSC). Pd 0.77 Ag 0.23 and Pd 0.77 Ag 0.10 Cu 0.13 alloys were prepared by arc melting method and characterised by XRD, TXRF and EDS. Both the alloys are found to have FCC phase similar to Pd lattice. Prior to kinetic measurements, samples were activated by hydriding-dehydriding method. Hydrogen/deuterium desorption kinetic measurements were carried out at four different heating rates (8, 12, 16 and 20 K/min) and Kissinger plots were constructed from peak temperature of DSC curves. Activation energies for hydrogen/deuterium desorption from the corresponding hydride/deuteride were calculated from the slope of Kissinger plot which follows the order; Pd > Pd 0.77 Ag 0.23 > Pd 0.77 Ag 0.10 Cu 0.13. Activation energy for deuterium desorption was found to be lower than that of hydrogen desorption and significant isotope effect was observed for the Pd 0.77 Ag 0.10 Cu 0.13 alloy which makes it a favorable candidate material for its application in hydrogen isotope separation, employing self-displacement gas chromatography. • Pd 0.77 Ag 0.23 and Pd 0.77 Ag 0.10 Cu 0.13 alloys prepared and characterised. • Desorption kinetics of hydrides and deuterides were studied employing DSC. • Activation energy of desorption process was calculated using Kissinger plot. • Large isotope effect makes Pd–Ag–Cu alloy suitable for hydrogen isotope separation. [ABSTRACT FROM AUTHOR]

Electrolysis of water is widely used for hydrogen isotope separation and the development of hydrogen evolution reaction (HER) catalysts with high selectivity and activity is of key importance. Herein, we propose single atom catalysts (SACs) as promising catalysts for efficient hydrogen isotope separation. Pt SACs and Pt nanoparticles (NPs) have been fabricated on nanoarray-structured nitrogen-doped graphite foil (NGF) substrate by a polyol reduction method. The as prepared Pt1/NGF electrode exhibits high activity and selectivity toward HER with a low overpotential of 0.022 V at 10 mA·cm−2 and a high separation factor of 6.83 for hydrogen and deuterium separation, much better than Pt NPs counterpart. Density functional theory (DFT) calculations ascribe the high activity and selectivity to the constructed Pt-N2C2 structure. This work develops a new opportunity for the design and application of high-efficiency and stable SACs toward hydrogen isotope separation by electrolysis of water. [ABSTRACT FROM AUTHOR]

This research adopted column porous ceramics (φ=5 mm) as the carriers, the hydrophobic carriers with three different kinds of nanostructured cerium oxide (CeO2) coating were fabricated and then catalysts which were used in hydrogen isotope separation were manufactured by convenient impregnation method, and the catalytic activity were tested through catalytic exchange reaction between hydrogen and saturated water vapor. The samples were characterized by XRD, SEM, EDX, XPS and CO adsorption to verify the influence of hydrophobic structure on the properties of catalyst. The results showed that the hydrophobic nanostructure made no influence on the pore structure of carriers and the metallic Pt content, while the influence of that on the Pt particle dispersion and the enrichment of Pt on surface layer were remarkable. Fluff hydrophobic structure with uniform distribution and serried coverage were more effective to improve the activity of catalyst. Although that structure lead to the decrease of Pt particle dispersion, it could make the Pt particles mostly deposit on the surface layer of the catalysts, which would make more Pt particle participate in the reaction in the same time and the increased catalytic activity could be obtained.

ZIF-67@NH 2 –SiO 2 composites were prepared by loading the metal-organic frameworks ZIF-67 on amino modified SiO 2 gel particles (NH 2 –SiO 2 , 80–100 mesh) through layer-by-layer self-assembly method. Systematic investigation on the effects of ZIF-67 loading amounts on NH 2 –SiO 2 packed stainless steel chromatographic column (specification 1.0 m×2.0 mm I.D.), the flow rate of He as carrier gas and the injection amount of mixed gas (H 2 /D 2) on the hydrogen isotope H 2 /D 2 separation performance at liquid nitrogen temperature, unraveled the optimal conditions for H 2 /D 2 isotope separation. The results showed that the optimal stationary phase materials under the optimized conditions can effectively separate H 2 and D 2 with separation resolution R = 1.52 and the separation time t = 10.15 min. The superior performance of the ZIF-67 is tentatively thought to be due to kinetic quantum sieving (pore size 3.3 Å) effect and chemical affinity sieving effect of Co ion in ZIF-67. [Display omitted] • ZIF-67 is grown on amino modified SiO 2 using layer-by-layer self-assembly method. • The obtained optimal ZIF-67@NH 2 –SiO 2 composite is used as stationary phase material. • The composite is loaded into a 1-m chromatographic column (2.0 mm I.D.). • H 2 /D 2 can be effectively/efficiently separated under liquid N 2 temperature. [ABSTRACT FROM AUTHOR]

[Display omitted] • Nitrogen-doping enhances the H+ and D+ permeability of graphene. • D+ permeates across pyridinic-N defects faster than H+, showing an inverse KIE (0.75). • A normal KIE (1.56) is observed in pyrrolic-N defects. • KIE is influenced by the chemisorption and effective size imparted by defects. 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 k H / k D of 0.75. Conversely, pyrrolic N-containing defects exhibit a normal KIE (k H / k D = 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. [ABSTRACT FROM AUTHOR]

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 H 2 and D 2 at practical operational temperatures. In this study, our investigations into H 2 and D 2 sorption on POC samples revealed a higher uptake of D 2 compared to that of H 2 under identical conditions. We employed quasi-elastic neutron scattering to study the diffusion processes of D 2 and H 2 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 D 2 and H 2. The results indicate that the diffusion coefficient of D 2 is approximately one-sixth that of H 2 in the POC due to the nuclear quantum effect. Furthermore, the results reveal that at 77 K, D 2 has longer residence times compared to H 2 when moving from pore to pore. Consequently, using the kinetic difference of H 2 and D 2 in a porous POC system enables hydrogen isotope separation using a temperature or pressure swing system at around liquid nitrogen temperatures.

Deuterium has numerous applications in industry and scientific research. However, the conventional methods for separation hydrogen isotopes face the problems of low selectivity and high energy consumption. Recently, microporous material adsorption separation technology provides an efficient way for the separation of hydrogen isotopes. Herein, we prepared the metal bistriazolate framework Ni 2 Cl 2 BBTA, featuring a high density of coordinatively unsaturated Ni2+ sites. Interactions between the open metal sites and hydrogen render this material excellent separation ability for the capture of D 2 from the hydrogen isotopes mixture, with the D 2 over H 2 selectivity up to 4.5 at 77 K and 4.0 at 87 K respectively. Notably, recycle experiments show that this material has great potential in the application of hydrogen isotope separation, owing to its good structural stability and reusability. Image 1 • Metal bistriazolate framework was prepared for hydrogen isotope separation. • Ni 2 Cl 2 BBTA has excellent thermal and chemical stability. • D 2 over H 2 selectivity up to 4.5 at 77 K and 4.0 at 87 K respectively was obtained. • There was no loss in the selectivity and adsorption amount after 20 cycles. [ABSTRACT FROM AUTHOR]

Electrolysis of water offers an efficient and eco-friendly route to separate hydrogen isotopes and cathode electrocatalysts featuring high separation factors coupled with high activity and stability are increasingly in demand. In this work, we propose MoS 2 rich in edge sites (MoS 2 -RS) as a promising hydrogen isotope separation electrocatalyst for the first time. MoS 2 -RS cathode exhibits high activity and hydrogen isotope selectivity with a low overpotential of 182.4 mV at 10 mA cm−2, a small Tafel slope of 61 mV dec−1 and a high hydrogen-deuterium separation factor (S H/D) of 10.22 in contrast to 6.33 for the commercial Pt/C catalyst. Density functional theory calculations ascribe the high selectivity of MoS 2 -RS to the H/D zero-point energy difference. Moreover, MoS 2 -RS demonstrates much higher values of S H/D compared with Pt/C catalyst under all test conditions and good long-term stability under acidic conditions. This work not only provides a promising catalytic material for efficient electrolytic separation of hydrogen isotopes but also indicates the direction of rational design of it. [Display omitted] [ABSTRACT FROM AUTHOR]

Abstract The displacement chromatography technique with a tri-column system was used to reduce the protium (H) in the deuterium-tritium (D-T) mixture, and the separation performance was studied numerically by ANSYS FLUENT. The experimental results showed that the isotopic abundance of H in the D-T mixture dropped from 2.7% to an acceptable level of 0.88%. The simulation results showed that a lower porosity (θ) of the filling material made a higher separation factor, but a lower separation efficiency. The velocity of the product gas at the outlet of the separation column approximately had a linear relationship with θ 5/3/(1- θ)2, which partly indicated the pore diffusion resistance. The mixed gas could contact the filling materials more sufficiently under a lower flow rate resulting in a lower protium concentration in the product gas. The separation column with a thin and long shape had a better separation performance and a lower product gas loss. Highlights • Hydrogen isotope separation experiments with tritium are conducted. • ANSYS FLUENT is used to predict isotopic abundances of H, D, and T after separation. • Lower filling material porosity and gas flow rate make a higher separation factor. • Separation of H-D is much easier than separation of D-T. • Thin and long column has better separation performance and lower product gas loss. [ABSTRACT FROM AUTHOR]

Highlights • A commercial alumina PLOT column was used for separation of hydrogen isomers. • HD and o-H 2 was baseline separated by the column initially deactivated by Na 2 SO 4. • The column secondly deactivated by MnSO 4 was prepared for pure HD analysis. • Isotopic purity of commercial HD was determined within 3 min. Abstract To determine residual H 2 and D 2 concentrations in high purity HD, gas chromatography was used to separate the hydrogen isotopes in a 5 A molecular sieve porous layer open tubular (PLOT) column cooled in a slowly warmed dewar. It took more than 15 min to produce one chromatogram in which a platform existed between o-H 2 and p-H 2 , and resolution between o-D 2 and p-D 2 was hardly investigated. In this study, to improve thermal stability of the column oven, the column is designed to be immersed in pure liquid nitrogen instead of a mixture of liquid nitrogen and isopentane. Several alumina PLOT columns under different deactivation conditions are used to separate the hydrogen isotopes at 78 K. Results show that the sulfate deactivated column performs higher elution resolution than the chloride deactivated column. The platform was decreased in a 15 m sodium sulfate deactivated column; o-H 2 and p-H 2 was baseline separated within 1 min; o-H 2 : p-H 2 = 72:28 according to peak areas. o-D 2 and p-D 2 was separated in less than 2 min in the same column, the ratio o-D 2 :p-D 2 = 67:33. Relative short analysis time would help reduce the platform. Residual concentrations of high purity HD (HD = 96%) were determined within 3 min in a 15 m sulfate deactivated column modified by magnesium sulfate. [ABSTRACT FROM AUTHOR]

In this work, metal-organic framework compound CPL-1 of a formula {[Cu 2 (pzdc) 2 (pyz)]⋅2H 2 O} n (pzdc = pyrazine-2,3-dicarboxylate, pyz = pyrazine) possessing kinetic quantum sieving effect on H 2 /D 2 separation was selected to prepare two new chromatography stationary phase materials CPL-1@γ-Al 2 O 3 and MnCl 2 @CPL-1@γ-Al 2 O 3 by loading CPL-1 on γ-Al 2 O 3 particles with size 80–100 mesh through repeating in situ crystallization process, and afterwards by loading MnCl 2 on CPL-1@γ-Al 2 O 3 via impregnation approach. The two optimized materials were thoroughly characterized by IR, XRD, SEM, EDS and TG/DTA method. The experimental results showed that, under liquid nitrogen temperature by using just 1-m chromatographic column and cheap He gas as carrier gas, the MnCl 2 @CPL-1@γ-Al 2 O 3 can solve the problem of long separation time and trailing phenomenon existing in the CPL-1@γ-Al 2 O 3 column, can realize highly effective hydrogen isotope H 2 /D 2 separation with good separation resolution (R = 1.62) and approximate Gauss distribution of chromatographic peak, can be used for both qualitative and quantitative analysis of hydrogen isotope H 2 /D 2 with short separation time of 6.5 min. [ABSTRACT FROM AUTHOR]

The application of platinum supported on polytetrafluoroethylene (Pt/PTFE) as a composite catalyst for the separation of hydrogen isotopes holds much promise but warrants further refinement for improved performance. The objective of the present study was to examine the performance of a new hydrophobic Pt/PTFE catalyst during hydrogen-water exchange-based deuterium separation. The influence of diverse factors such as flow rate, column height, temperature, the volume ratio of filler to catalyst, and flow mode (co-current or counter-current), and so on, on catalytic performance was investigated. The deuterium conversion rate from co-current exchange was superior to that from counter-current exchange. Decreasing the hydrogen flow rate, increasing the feed water flow rate, and decreasing the molar flow ratio of hydrogen to water improved the deuterium conversion rate. In terms of layered filling of the catalyst column, adding more hydrophilic fillers improved the deuterium conversion rate. The characterization results highlight the high catalytic activity of the Pt/PTFE catalyst for hydrogen-water exchange, as well as its high stability in water. [ABSTRACT FROM AUTHOR]

The influences of various critical operation factors on the hydrogen isotope separation performance as well as long-term stability at high current density for practical use are systematically investigated based on the PEM electrolyzer, and a calculation model is proposed to clearly exhibit the deuterium enrichment process in liquid phase. [Display omitted] • Current density and temperature significantly influence the separation performance. • D content less than 2500 ppm in feeding water influences on the separation factor. • High current densities significantly promote the isotope enrichment process. • High durability and stable separation factor are achieved with high current density. • A calculation model was proposed to elucidate the deuterium enrichment process. The separation of heavy hydrogen isotopes is very important for nuclear energy, medical, research and environmental safety. Water electrolysis with proton exchange membrane (PEM) electrolyzer is a promising way for hydrogen isotope separation due to its high efficiency, compact structure, and easy operation. Although some works have investigated the hydrogen isotope separation performance based on PEM electrolysis, few studies involve the high operation current density and long-term stability for practical use, and the influences of various critical operation factors on the separation performance are not systematically elucidated. In this study, a large-current density and high-durability PEM electrolyzer was constructed for hydrogen isotope separation. The influences of the deuterium content in feeding water, operation temperature, and current density on the hydrogen isotope separation performance including the separation factors in hydrogen gas and water at both anode and cathode sides during the PEM electrolysis were systematically investigated. Besides, a long-term deuterated water electrolysis at a high current density of 1 A/cm2 for more than 700 h shows a very stable isotope separation performance, demonstrating the practicability for large-scale hydrogen isotope separation. In addition, a calculation model proposed in this work elucidates the influences of the current density and temperature on the deuterium enrichment performance, which lays a solid foundation for the application of the PEM electrolysis in practical hydrogen isotope separation. [ABSTRACT FROM AUTHOR]

The use of a polymer electrolyte fuel cell (PEFC) with a Nafion membrane for isotopic separation of deuterium (D) was investigated. Mass analysis at the cathode side indicated that D diffused through the membrane and participated in an isotope exchange reaction. The exchange of D with protium (H) in H2O was facilitated by a Pt catalyst. The anodic data showed that the separation efficiency was dependent on the D concentration in the source gas, whereby the water produced during the operation of the PEFC was more enriched in D as the D concentration of the source gas was increased. [ABSTRACT FROM AUTHOR]

Samples NaAlH x D 4−x (0 ≤ x ≥ 4) have been synthesized through a direct hydrogen isotope absorption/desorption cycles using Ti-doped NaAlH 4 as source material, and then the interaction between hydrogen/deuterium and obtained NaAlH x D 4−x and its hydrogen isotope effect were investigated. The results show that hydrogen isotope desorption/absorption kinetics of NaAlH x D 4−x is enhanced with increasing the hydrogen concentration. In addition, NaAlH x D 4−x exhibits kinetics isotope effect during both hydrogen isotope desorption and absorption processes, and the isotope effect keeps stable during cycling. Our study may enable NaAlH 4 to be used as hydrogen isotope separation material in future based on its kinetics isotope effect. [ABSTRACT FROM AUTHOR]

The effect of hydrogen isotopes on the thermodynamic parameters of desorption reaction in the Pd 0.9 X 0.1 -H 2 /D 2 systems (X = Cu, Ag and Au) were investigated using Sieverts' apparatus. The hydrogen/deuterium desorption pressure-composition-temperature profiles generated in this study revealed substantial hydrogen isotope effect on the equilibrium plateau pressures with P eq (D 2 ) > P eq (H 2 ). A correlation was observed for the trend in equilibrium plateau pressures with the unit cell sizes of the Pd 0.9 X 0.1 alloys. Hydrogen isotope separation factor was determined for all these alloys and Pd 0.9 Cu 0.1 alloy was found to have highest separation factor. The results of equilibrium plateau pressure and the separation factor for Pd 0.9 Cu 0.1 alloys merits its candidature for its applicability in gas chromatographic separation of hydrogen isotopes. [ABSTRACT FROM AUTHOR]

By a solution impregnation method, three modified stationary phases were prepared by contacting activated alumina with MnCl at different MnCl:AlO molar ratios = 1:10, 1:5, 1:2.5, respectively. N sorption isotherms at 78 K were examined for the unmodified and modified samples, from which pore size distributions (PSD) of textural properties were derived with density function theory. Elution chromatographic tests of hydrogen isotopes were carried out at 78 K. The results indicated that both the microporous specific surface area (SSA) and the mesoporous SSA decline after modification, while the microporous SSA remains nearly unvaried among the modified ones. The chromatographic retention times as well as the bandwidths decline as the Mn content rises. The resolution of chromatographic peaks increases after modification, it remains unvaried and then decreases as the Mn content increases. The PSD of alumina SSA changed by the modification significantly influences the hydrogen isotopic elution chromatography. [ABSTRACT FROM AUTHOR]

Palladium/kieselguhr (Pd/K) composites with 57 wt.% of Pd were prepared by an improved dipping and thermal decomposition method and heated at elevated temperature to reduce breakdown during hydrogenation-dehydrogenation cycles. The hydrogen absorption kinetic properties of the samples heated at different temperatures were tested under the condition of 20 °C with 100 kPa hydrogen pressure. The 1300 °C heated Pd/K composites were repeated up to 4010 absorption and desorption cycles at temperature ranges between −40 °C and 200 °C. The results show that the phase structure, hydrogen absorption capacity and hydrogen saturation time of the Pd/K were not affected by the change of heat-treated temperatures. And after heat treatment at 1300 °C, the Pd/K particles were strengthened and fraction of larger than 80 mesh were as high as 93.4%. [ABSTRACT FROM AUTHOR]

The University of Rochester’s Laboratory for Laser Energetics has commissioned a hydrogen Isotope Separation System (ISS). The ISS uses two columns—palladium on kieselguhr and molecular sieve—that act in a complementary manner to separate the hydrogen species by mass. The 4-sL per day throughput system is compact and has no moving parts. The columns and the attendant gas storage and handling subsystems are housed in a 0.8 -m 3 glovebox. The glovebox uses a helium cover gas that is continuously processed to extract oxygen and water vapor that permeates through the glovebox gloves and any tritium that is released while attaching or detaching vessels to add feedstock to or drawing product from the system. The isotopic separation process is automated and does not require manual intervention. A total of 315 TBq of tritium was extracted from 23.6 sL of hydrogen with tritium purities reaching 99.5%. Deuterium was the sole residual component in the processed gas. Raffinate contained 0.2 TBq of activity was captured for reprocessing. The total emission from the system to the environment was 0.4 GBq over three weeks. [ABSTRACT FROM AUTHOR]

Realizing ideal deuterium separation from isotopic mixtures remains a daunting challenge because of their almost identical sizes, shapes, and physicochemical properties. Using the quantum sieving effect in porous materials with suitable pore size and open metal sites (OMSs) enables efficient hydrogen isotope separation. Herein, synthetic HKUST-1-derived microporous mixed-valence Cu(I)Cu(II)-BTC (BTC = benzene-1,3,5-tricarboxylate), featuring a unique network of distinct Cu(I) and Cu(II) coordination sites, can remarkably boost the D 2 /H 2 isotope separation, which has a high selectivity ( S D 2 /H 2 ) of 37.9 at 30 K, in comparison with HKUST-1 and other porous materials. Density functional theory (DFT) calculations indicate that the introduction of Cu(I) macrocycles in the framework decreases the pore size and further leads to relatively enhanced interaction of H 2 /D 2 molecules on Cu(II) sites. The significantly enhanced selectivity of Cu(I)Cu(II)-BTC at 30 K can be mainly attributed to the synergistic effect of kinetic quantum sieving (KQS) and chemical affinity quantum sieving (CAQS). The results reveal that Cu(I) OMSs exhibit counterintuitive behaviors and play a crucial role in tuning quantum sieving without a complex structural design, which provides a deeper insight into quantum sieving mechanisms and a new strategy for the intelligent design of highly efficient isotope systems.

The use of catalysed exchange of deuterium (D) between hydrogen (H) gas and liquid water using the bithermal hydrogen water (BHW) process is a promising and environment-friendly approach for the production of heavy water. However, the use of this approach is limited by the lack of a suitable catalyst that has good activity at high operating pressures required for practical applications. We report the development of hydrophobic platinum-doped carbon aerogel (PtCA) catalyst which shows good catalytic activity for H/D isotope exchange reactions at operating pressures up to 20 bar. [ABSTRACT FROM AUTHOR]

Recently we reported hydrogen isotope separation by quantum sieving in metal-organic framework MFU-4, a framework exhibiting gates of about the same size as the molecular radii of D 2 and H 2 . Due to its smaller effective particle size, D 2 penetrates preferentially through the framework, resulting in remarkable selectivity. Surprisingly, MFU-4l, a material of very similar composition, but with substantially larger gate openings, shows appreciable hydrogen isotopologue selectivity. This selectivity occurs at low temperature and is smaller compared to earlier reported CPO-27, a framework exhibiting open metal sites. We show that this is caused by different adsorption enthalpies which are the result of quantum effects. It turns out that two independent hydrogen isotope separation mechanisms have been reported for MOFs: while kinetic quantum sieving works at cryogenic temperatures for materials with small pores, different adsorption energies allow chemical affinity quantum sieving. This effect is maximized by strong adsorption centers, which allow high selectivity at high temperatures (100 K and above), and is more appropriate for the rational design of isotope separation membranes. [ABSTRACT FROM AUTHOR]

Hydrogen isotope catalytic exchange between hydrogen and liquid water is a very effective process for deuterium-depleted potable water production and heavy water detritiation. To improve the characteristics of hydrophobic catalysts for this type of reaction, foamed and cellular structures of hydrophobic carbon-supported platinum catalysts were successfully prepared. Separation of deuterium or tritium from liquid water was carried out by liquid-phase catalytic exchange. At a gas–liquid ratio of 1.53 and exchange temperature of 70 °C, the theoretical plate height of the hydrophobic catalyst (HETP = 34.2 cm) was slightly lower than previously reported values. Changing the concentration of the exchange column outlet water yielded nonlinear changes in the height of the packing layer. Configurations of deuterium-depleted potable water and detritiation of heavy water provide references for practical applications. [ABSTRACT FROM AUTHOR]

In order to support the tritium production and recycling in the fuel cycle system of fusion reactors, the thermal cycling absorption process (TCAP), which is a semi-continuous chromatographic process for hydrogen isotope separation, has been developed for years. The hydrogen isotopes separation capacity mostly depends on the efficiency of the separation columns, therefore, evaluating different column structure designs and packing materials for their separation efficiency is significative. In this work, a unique design of separation column apparatus with the hot/cold cycling system has been developed. Its unique feature is the different separation columns can be changed for testing several factors such as particle size of packing material, fill density and uniformity, column structure on the influence of the column efficiency. Moreover, the methods to measure efficiency of the separation column have been introduced. The experimental results show that the displacement chromatographic method is more suitable for this apparatus to analyze the column efficiency. [ABSTRACT FROM AUTHOR]

A pair of separation column packed with different hydrogen absorption materials (Pd/k and 4A molecular sieves) respectively, whose hydrogen isotopic effect is opposite, is used in Thermal Cycling Absorption Process (TCAP), and its result of hydrogen isotopes separation is better than the traditional TCAP. A dynamic simulation method for the pair of column TCAP system is developed. For a certain percentage of binary gas mixtures of hydrogen isotopes (H 2 and D 2 ) injected into the twin columns system, from simulation results, it can be obtained the binary gas concentration distribution in the two columns after a different number of cycles. Furthermore, the separation process can be optimized. Moreover, it can be seen that the hydrogen isotopes separation effect of twin columns TCAP is almost twice that of the traditional TCAP. [ABSTRACT FROM AUTHOR]

Highlights: [•] Synthetic mordenite whose cation was exchanged with Ca (Ca-MOR) has larger adsorption capacity of hydrogen isotopes than raw material (Na-MOR). [•] Adsorption rate of hydrogen isotopes on Ca-MOR was estimated experimentally at 175 and 194K. [•] Effective diffusivity of hydrogen isotopes in Ca-MOR particle and isotopic difference of it became larger than Na-MOR. [Copyright &y& Elsevier]

Highlights: [•] Breakthrough curves of non-trace H2–D2 replacement adsorption on zeolite are shown. [•] Mass balances are modeled for describing non-trace H2–D2 binary adsorption in a packed-bed. [•] Experimental and analytical breakthrough curves exhibit concentration dependency. [•] The mass transfer rate in replacement adsorption is controlled by desorption process. [•] Isotope effect on mass transfer rates in H2–D2 replacement adsorption is clarified. [Copyright &y& Elsevier]

On the basis of impregnation method, several stationary phases were prepared using γ-AlO with the solution of transition metal salts and the breakthrough curves of gas chromatograph for H isotopes were analyzed under the temperature of liquid nitrogen. The effects of carrier gas, flow rate and doping concentration on the separation performance for H and D were systematically investigated. The overall results showed that the surface areas and adsorptive capacities of modified γ-AlO were slightly lower than unmodified one while the separation performance and symmetry of chromatographic peaks of the former were more excellent. In addition, the chromatographic peaks of ortho- and para-H were no longer separated and the retention time shortened to half on columns of modified γ-AlO. All the magnetic transition metal ions modified γ-AlO did very well for the separation of H/D under the conditions of neon as carrier gas with a flow rate of 60 mL/min and column lengths of 1.0 m and injection amounts of 0.1 mL. Especially, the MnCl modified γ-AlO exhibited the best performance for separating H/D with an optimum doping concentration of 20 wt%. [ABSTRACT FROM AUTHOR]

Single-layer graphene has been demonstrated to be a high-efficiency hydrogen isotope sieving membrane in the electrochemical hydrogen pumping system. In this work, we transferred this membrane to proton exchange membrane water electrolysis (PEMWE), which has wide industrial applications. Two membrane electrode assemblies with decorated Pt and ink-coated Pt were investigated. The graphene with the decorated Pt scheme acquired the reported highest proton-to-tritium separation factor of 19.50 in PEMWE. However, rather than graphene, the decorated catalyst was demonstrated to be responsible for this remarkable separation efficiency. Previous studies from Geim's group underestimated the enhanced separation efficiency of decorated Pt over ink-coated Pt, resulting in an exaggerated separation efficiency for graphene. The behavior of proton transfer with hydrogen isotope separation through graphene was interpreted by a serial-parallel circuit model, which suggested that hydrogen isotope separation occurs at defect sites. The limited separation efficiency for graphene was also well understood by a density functional theory (DFT) calculation using an SW 55-77 model and the transition state theory for the kinetic isotope effect. This research provides a thorough understanding of proton transfer with hydrogen isotope separation through graphene.

Abstract: Water plays a fundamental role in affecting geochemical transport and physical properties of magmas. Here we show the previously undocumented behavior of water within partially molten silicate resting in a temperature gradient, producing O, Li and H isotope redistribution by thermal diffusion leading to enrichment of light isotopes at the hot end of the gradient. After weeks to months, fully molten as well as mostly crystalline portions of water-bearing experiments develop remarkably large isotope and chemical redistributions: up to 28‰ for δ 18O, 144‰ for δD, and 18‰ for δ 7Li. In contrast, long-term dry experiments develop smaller (∼5‰ δ 18O) isotopic fractionations only in the hotter end where it is molten or partially molten. Isotope fractionation of oxygen is linearly related to temperature, and the magnitude of isotopic separation per °C is ∼2× larger for wet experiments than dry ones. We explain this by water de-polymerizing the silicate structure leading to a smaller size of diffusing SiOx fragments. The magnitude of isotope separation between the hot and cold ends for Li, Mg, Fe, O, and H isotopes increases linearly with ΔM heavy–light/M light. These relationships provide predictive tests for natural rocks and highlight the role of water in isotope and compositional redistribution during temperature gradient mediated processes. We discuss the implications to natural environments in which the lightest stable isotopes (H, Li, O) with the greatest ΔM heavy–light/M light and fastest diffusion coefficients are capable of achieving mass-dependent redistribution in a transient temperature gradient. These experiments underscore the importance of solution–reprecipitation in wet subsolidus systems and demonstrate that isotopic redistribution can be established ∼6 orders of magnitude quicker than by diffusion through a traditional silicate melt at higher temperature. This has important implications for timescales of natural isotope and chemical redistribution by thermal diffusion. [Copyright &y& Elsevier]