A statistical method to estimate low-energy hadronic cross sections

In this article we propose a model based on the Statistical Bootstrap approach to estimate the cross sections of different hadronic reactions up to a few GeV in c.m.s energy. The method is based on the idea, when two particles collide a so called fireball is formed, which after a short time period decays statistically into a specific final state. To calculate the probabilities we use a phase space description extended with quark combinatorial factors and the possibility of more than one fireball formation. In a few simple cases the probability of a specific final state can be calculated analytically, where we show that the model is able to reproduce the ratios of the considered cross sections. We also show that the model is able to describe proton\,-\,antiproton annihilation at rest. In the latter case we used a numerical method to calculate the more complicated final state probabilities. Additionally, we examined the formation of strange and charmed mesons as well, where we used existing data to fit the relevant model parameters.Comment: 12 pages, 12 figures, submitted to EPJ

Radioactive Barium Ion Trap Based on Metal–Organic Framework for Efficient and Irreversible Removal of Barium from Nuclear Wastewater

Highly efficient and irreversible capture of radioactive barium from aqueous media remains a serious task for nuclear waste disposal and environmental protection. To address this task, here we propose a concept of barium ion trap based on metal–organic framework (MOF) with a strong barium-chelating group (sulfate and sulfonic acid group) in the pore structures of MOFs. The functionalized MOF-based ion traps can remove >90% of the barium within the first 5 min, and the removal efficiency reaches 99% after equilibrium. Remarkably, the sulfate-group-functionalized ion trap demonstrates a high barium uptake capacity of 131.1 mg g^–1, which surpasses most of the reported sorbents and can selectively capture barium from nuclear wastewater, whereas the sulfonic-acid-group-functionalized ion trap exhibits ultrafast kinetics with a kinetic rate constant <i>k</i>₂ of 27.77 g mg^–1 min^–1, which is 1–3 orders of magnitude higher than existing sorbents. Both of the two MOF-based ion traps can capture barium irreversibly. Our work proposes a new strategy to design barium adsorbent materials and provides a new perspective for removing radioactive barium and other radionuclides from nuclear wastewater for environment remediation. Besides, the concrete mechanisms of barium–sorbent interactions are also demonstrated in this contribution

Two-Dimensional Covalent Triazine Framework Membrane for Helium Separation and Hydrogen Purification

Ultrathin membranes with intrinsic pores are highly desirable for gas separation applications, because of their controllable pore sizes and homogeneous pore distribution and their intrinsic capacity for high flux. Two-dimensional (2D) covalent organic frameworks (COFs) with layered structures have periodically distributed uniform pores and can be exfoliated into ultrathin nanosheets. As a representative of 2D COFs, a monolayer triazine-based CTF-0 membrane is proposed in this work for effective separation of helium and purification of hydrogen on the basis of first-principles calculations. With the aid of diffusion barrier calculations, it was found that a monolayer CTF-0 membrane can exhibit exceptionally high He and H₂ selectivities over Ne, CO₂, Ar, N₂, CO, and CH₄, and the He and H₂ permeances are excellent at appropriate temperatures, superior to those of conventional carbon and silica membranes. These observations demonstrate that a monolayer CTF-0 membrane may be potentially useful for helium separation and hydrogen purification

Graphene-like Poly(triazine imide) as N₂‑Selective Ultrathin Membrane for Postcombustion CO₂ Capture

To reduce the emission of greenhouse gases, the separation of CO₂ from flue gases emitted by power plants with combustion of carbon-based fossil fuels is of great importance. Compared with CO₂-selective membranes, N₂-selective membranes are more promising for such systems with low concentrations of CO₂. Using density functional theory (DFT) calculations and molecular dynamic (MD) simulations, we demonstrated in this work that the poly­(triazine imide) (PTI) membrane can be efficiently employed to separate N₂ from CO₂ with a selectivity of 273 and a N₂ permeance of 10⁶ GPU, superior to those of most conventional membranes. Furthermore, it was revealed that the presence of H₂O has a negligible influence on gas separation performance of the PTI membrane. This experimentally available N₂-selective ultrathin membrane may be expected to find practical applications in postcombustion CO₂ capture

Synthesis of Zeolitic Imidazolate Framework Membrane Using Temperature-Switching Synthesis Strategy for Gas Separation

In this work, ZIF-9 membranes were successfully synthesized using temperature-switching synthesis method. Compared with the conventional hydrothermal synthesis at a constant temperature, this method could promote the growth of crystals on the support. Scanning electron microscopy (SEM) demonstrated that the obtained membranes had continuous and well-intergrown layer with a denser surface and better crystal size uniformity. As a result, gas separation performance was enhanced. It is also found that the properties of membrane can remain almost stable at a relatively broad range of operating temperature and transmembrane pressure drop, which is beneficial for the practical operation of membrane in the separation process. More importantly, this synthesis strategy can be conveniently extended to the preparation of other MOF membranes with improved performance

Computation-Ready, Experimental Covalent Organic Framework for Methane Delivery: Screening and Material Design

CH₄ storage associated with adsorbed natural gas technology attracts considerable researches on finding porous materials with remarkable CH₄ delivery performance. In this work, we update the online accessible computation-ready, experimental (CoRE) covalent organic frameworks (COFs) database with 280 COFs in 12 topologies. All framework structures are constructed and compiled from the respective experimental studies and are further evaluated for CH₄ delivery. The highest deliverable capacity (DC) between 65 and 5.8 bar among the CoRE COFs is 190 v­(STP)/v at 298 K achieved by 3D PI-COF-4. Structure–property relationships show that large volumetric surface area generally benefits CH₄ delivery. 2D-COFs can also be top performing materials if constructing their pore channels is passable in three dimensions, as the volumetric surface area will be increased accordingly. This idea can be realized by enlarging the interlayer spacings of 2D-COFs. We also evaluate the DC of CoRE COFs under conditions of 233 K, 65 bar (storage) and 358 K, 5.8 bar (discharge). The highest DC obtained from the CoRE COFs and the designed 2D-COFs are 314 and 337 v­(STP)/v, respectively

Understanding the Effect of Trace Amount of Water on CO₂ Capture in Natural Gas Upgrading in Metal–Organic Frameworks: A Molecular Simulation Study

In this work, molecular simulations were performed to investigate the effect of trace amount of water on CO₂ capture in natural gas upgrading process in a diverse collection of 25 metal–organic frameworks (MOFs). The results show that the interaction between water molecules and MOFs plays a crucial role: at the condition of weak interaction, water molecules move freely in the materials and show a negligible effect on the adsorption selectivity of CO₂/CH₄; while when the interaction is strong enough that water molecules are adsorbed to the preferential adsorption sites in MOFs, the effect can be significant, depending on the strength of water adsorption. In this case, the electrostatic interaction produced by the MOF framework is the dominant factor. This work provides a better understanding of the different behaviors of water effect on CO₂ capture observed previously that may guide the future application of MOFs in industrial separations

Sulfate-Rich Metal–Organic Framework for High Efficiency and Selective Removal of Barium from Nuclear Wastewater

Capture of radioactive barium from nuclear wastewater is of great importance for environmental protection. Here, [Zr₆(OH)_10.8(SO₄)_3.6(BDC-NH₂)₃(H₂O)_7.4]·nH₂O (Zr-BDC-NH₂-SO₄) was selected as an adsorbent for its high content of sulfate group, which is a strong barium-chelating group, and its binding sites are fully exposed. Zr-BDC-NH₂-SO₄ exhibits high adsorption capacity of 181.8 mg g^–1, which is higher than those of most reported adsorbents, and showed excellent high selectivity even when the concentrations of background metal ions are 10 times of Ba²⁺. The breakthrough study showed good adsorption performance with fast kinetics and low outlet concentration. In addition, the great stability of Zr-BDC-NH₂-SO₄ under γ radiation has been confirmed, making it possible to be applied in real nuclear wastewater treatment. Moreover, the adsorption of Ba²⁺ is irreversible and therefore it could avoid secondary pollution. Overall, this work provides a stable, efficiency adsorbent for removing radioactive barium from nuclear wastewater

Ionic Liquid/Metal–Organic Framework Composites for H₂S Removal from Natural Gas: A Computational Exploration

The separation of H₂S/CH₄ mixture was computationally examined in the composites of ionic liquids (ILs) supported on metal–organic frameworks (MOFs) at room temperature. Cu-TDPAT was selected as supporter for four types of ILs combined from identical cation [BMIM]⁺ with different anions ([Cl]⁻, [Tf₂N]⁻, [PF₆]⁻, and [BF₄]⁻). The results show that introducing ILs into Cu-TDPAT can greatly enhance the adsorption affinity toward H₂S compared to the pristine MOF, and the strongest enhancement occurs in the composite containing the anion [Cl]⁻ with the smallest size. The H₂S/CH₄ adsorption selectivities of each composite are significantly higher than those of the pristine Cu-TDPAT within the pressure range examined, and the selectivity generally shows an increasing trend with increasing the loading of the IL. By further taking the H₂S working capacity into account, this work also reveals that the [BMIM]­[Cl]/Cu-TDPAT composite exhibits the best separation performance in both VSA and PSA processes. These findings may provide useful information for the design of new promising IL/MOF composites applied for H₂S capture from natural gas

Adsorption of Nitrogen-Containing Compounds from Model Fuel over Sulfonated Metal–Organic Framework: Contribution of Hydrogen-Bonding and Acid–Base Interactions in Adsorption

Adsorptive denitrogenation (ADN) was carried out by adsorption of indole (IND) and quinoline (QUI) over metal–organic frameworks (MOFs) including acidic UiO-66SO₃H for the first time. The adsorbed amount of IND increased with increasing content of SO₃H in UiO-66. The favorable effect of the SO₃H group on the adsorptive removal of IND could be explained by hydrogen bonding between the O of SO₃H and the H of IND, which was firmly supported by the adsorption of pyrrole and methylpyrrole and by theoretical calculations. The application of an SO₃H group in the adsorptive removal of neutral IND is meaningful since neutral nitrogen-containing compounds are not easy to remove and since UiO-66SO₃H is reusable after simple washing with ethanol. The expected increase in QUI adsorption (due to acid–base interaction) with acidic SO₃H was observed when QUI was present at low concentrations (<∼400 ppmw). This favorable contribution of acidic SO₃H to the adsorption of basic QUI was also supported by calculations for the adsorption of one QUI molecule on the SO₃H group of UiO-66. Interestingly, the adsorbed amount of QUI decreased with increasing content of SO₃H in UiO-66 when the QUI concentration was high (initial concentration of 1000 ppmw). One of the reasons for the negative effect of acidic SO₃H on QUI adsorption might be the presence of only one H atom in SO₃H or steric hindrance (due to decreased pore space), although detailed works are needed to support this