Diffusion Separation Research Articles

Isotopic fractionation of methane on Mars via diffusive separation in the subsurface

Many processes have been identified in the Martian subsurface which may produce or release methane that eventually can be emitted into the atmosphere. Given the wide range of isotopic values for source carbon reported on Mars and the importance of atmospheric methane isotopologues as a tracer for subsurface processes, it is critical to quantify the level of isotopic fractionation that can occur during subsurface transport. On Earth, isotopic fractionation occurs when methane transport is dominated by Knudsen diffusion through small pores. However, unlike the Earth, on Mars the low atmospheric pressure and commensurate longer mean free path suggest that most subsurface transport of methane occurs in the Knudsen regime, amplifying this effect. Here, we report on simulations of diffusion through the martian subsurface and report on the level of fractionation that would be expected under two end-member scenarios. For Interplanetary Dust Particles (IDPs) incorporated in near-surface sediments in which methane is released quickly upon generation, atmospheric emissions of methane are expected to be representative of the reservoir isotopic ratio. However, for deeper sources in which methane accumulates as trapped gas, subsurface transport will result in depletions of 13CH4 compared to reservoir concentrations by approximately −31‰. Over time, both the reservoir and the emitted gas will evolve to become isotopically enriched in 13CH4 compared to a standard of constant isotopic ratio. This necessitates temporal measurements of emitted methane to understand the δ13C of the reservoir and depth of the release, preferably with hourly or better frequency. Finally, a seasonal cycle in δ13C with an amplitude of 5.3‰ is expected with adsorption acting to create small temporary reservoirs that are filled and emptied over the year by the subsurface thermal wave. This effect may provide a way to probe near-surface thermophysical properties.

Wind-Tunnel-in-the-Loop Exploration and Optimization of Active Flow Control Parameters

This paper considers the use of surrogate-based analysis and optimization (SBAO) methods to investigate the performance of pulsed jet actuators for active separation control in a wind tunnel. Two experimental setups are examined: pressure-induced separation on a one-sided diffuser and trailing-edge separation on a NACA 64A-015 airfoil. In both cases the modeling is done using Gaussian process regression (kriging), and the investigated active-flow-control parameters are the amplitude, frequency, and duty cycle of the actuators that are used to mitigate boundary-layer separation. In the diffuser test case, a parameter-space exploration is conducted to examine the effect of the three input parameters on the amount of reverse flow detected by an array of calorimetric shear-stress sensors. In the airfoil test case, an optimization strategy is followed to maximize an objective function constructed with the airfoil sectional lift coefficient and the mass flow consumption of the actuators. Both experiments consistently indicate that lowering the duty cycle of the pulsed-jet actuators below 0.5 may lead to efficiency gains in active separation control by limiting their mass flow consumption for equal performance, but with a concomitant supply pressure increase. Overall, the results presented herein demonstrate that SBAO methods could provide a potential for more efficient wind tunnel investigations involving multiparameter problems.

Secondary Aggregation Induced by Volatile Additive for Improved Exciton Diffusion and Charge Separation in High Efficiency Organic Photovoltaic Devices

Comprehensive SummaryThe morphology of the active layer plays a crucial role in the performance of organic photovoltaics. Although volatile additives are commonly used to manipulate the morphology, their mechanism of action remains poorly understood. In this study, we conducted a systematic exploration of the mechanism of the traditional volatile additive 1‐CN in film formation kinetics of typical PM6:Y6 system. We found that 1‐CN induces a secondary aggregation effect, improving film morphology and promoting face‐on crystalline orientation. Through elucidating its impact on exciton dynamics, we established a link between morphology optimization and increased exciton diffusion length and accelerated charge separation. Our findings unveil the unique mechanism of action of volatile additive, providing a new perspective for improving the morphology and enhancing the performance of organic photovoltaic devices.

Badanie mieszaniny metan-wodór w rurociągach pionowych

The paper presents an assessment of issues regarding the separation phenomena of methane-hydrogen mixtures in vertical pipelines. In the first part of the paper, the explosion risk is underlined. Thus, the widespread use of methane in both the industrial and domestic sectors is well known. In practice, due to recent trends, the injection of hydrogen into dedicated methane installations, the differences in densities can lead to separation phenomena which have an unfavorable effect on the operating regimes of equipment using this mixture and also, on the risk of explosion. The use of hydrogen in the industry is not new, but the increasing impact in terms of the number of users may involve a higher number of accidents due to the increased field of probability of hazardous situations in terms of explosions. The second part presents the used methods. The diffusion and gravitational separation are presented as phenomena having opposite effects. The used methods are theoretical and simulation approaches. The theoretical model is based on a nondynamic model. Therefore, no time parameter was not involved in the model. A linear dependence with the height of the concentration variation was observed for the range of heights considered. The conducted simulation underlined the same conclusion regarding the magnitude of gravitational separations in the methane-hydrogen mixtures. The main conclusion of the approach is that the separation phenomenon effect due to the gas density differences is negligible. The approach also revealed, as expected that the higher level of pipe is exposed to a higher risk of increased hydrogen concentration.

High-Pressure-Field Induced Synthesis of Ultrafine-Sized High-Entropy Compounds with Excellent Sodium-Ion Storage.

Emerging high entropy compounds (HECs) have attracted huge attention in electrochemical energy-related applications. The features of ultrafine size and carbon incorporation show great potential to boost the ion-storage kinetics of HECs. However, they are rarely reported because high-temperature calcination tends to result in larger crystallites, phase separation, and carbon reduction. Herein, using the NaCl self-assembly template method, by introducing a high-pressure field in the calcination process, the atom diffusion and phase separation are inhibited for the general formation of HECs, and the HEC aggregation is inhibited for obtaining ultrafine size. The general preparation of ultrafine-sized (<10 nm) HECs (nitrides, oxides, sulfides, and phosphates) anchored on porous carbon composites is realized. They are demonstrated by combining advanced characterization technologies with theoretical computations. Ultrafine-sized high entropy sulfides-MnFeCoCuSnMo/porous carbon (HES-MnFeCoCuSnMo/PC) as representative anodes exhibit excellent sodium-ion storage kinetics and capacities (a high rating capacity of 278 mAh g-1 at 10 A g-1 for full cell and a high cycling capacity of 281 mAh g-1 at 20 A g-1 after 6000 cycles for half cell) due to the combining advantages of high entropy effect, ultrafine size, and PC incorporation. Our work provides a new opportunity for designing and fabricating ultrafine-sized HECs.

High‐Pressure‐Field Induced Synthesis of Ultrafine‐Sized High‐Entropy Compounds with Excellent Sodium‐Ion Storage

AbstractEmerging high entropy compounds (HECs) have attracted huge attention in electrochemical energy‐related applications. The features of ultrafine size and carbon incorporation show great potential to boost the ion‐storage kinetics of HECs. However, they are rarely reported because high‐temperature calcination tends to result in larger crystallites, phase separation, and carbon reduction. Herein, using the NaCl self‐assembly template method, by introducing a high‐pressure field in the calcination process, the atom diffusion and phase separation are inhibited for the general formation of HECs, and the HEC aggregation is inhibited for obtaining ultrafine size. The general preparation of ultrafine‐sized (&lt;10 nm) HECs (nitrides, oxides, sulfides, and phosphates) anchored on porous carbon composites is realized. They are demonstrated by combining advanced characterization technologies with theoretical computations. Ultrafine‐sized high entropy sulfides‐MnFeCoCuSnMo/porous carbon (HES‐MnFeCoCuSnMo/PC) as representative anodes exhibit excellent sodium‐ion storage kinetics and capacities (a high rating capacity of 278 mAh g−1 at 10 A g−1 for full cell and a high cycling capacity of 281 mAh g−1 at 20 A g−1 after 6000 cycles for half cell) due to the combining advantages of high entropy effect, ultrafine size, and PC incorporation. Our work provides a new opportunity for designing and fabricating ultrafine‐sized HECs.

Day/Night Differences in Molecular Oxygen in the Martian Upper Atmosphere

AbstractWe use the extensive stellar occultation data set of the Imaging Ultraviolet Spectrograph aboard the Mars Atmosphere and Volatile EvolutioN spacecraft to determine the first quantification of vertical variation in O2 mole fraction separately for day and night in the ∼90–130 km altitude range. The upper atmospheric O2 variation is expected to be due to the interplay between diffusion and advection because of its long photochemical lifetime. It is therefore a useful tracer of the state of atmospheric mixing and circulation. The altitude‐averaged mixing ratio is measured to be 2.69(±0.03) × 10−3 for the nightside and 2.05(±0.03) × 10−3 for the dayside. The average O2 mole fraction for day and night are nearly identical below 105 km, consistent with the value of 1.61 × 10−3 derived from the Mars Curiosity Rover/Sample Analysis at Mars near‐surface measurements. At higher altitudes, dominated by molecular diffusive separation, the measured O2 mole fraction demonstrates a vertical gradient with a local time dependence. The nightside mole fraction is a factor of 1.37 ± 0.04 larger than the dayside value at ∼125 km. This nightside enhancement is explained in terms of the relative role of solar‐driven rapid horizontal winds at high altitudes and slower vertical diffusion, resulting in a nightside (dayside) downward (upward) diffusive flux. Using the 1‐D diffusion model, the measured profiles correspond to a vertical eddy diffusion coefficient K = 3.5(±1.5) × 106 cm2/s. The Mars Climate Database predicts comparable but lower day‐night differences in oxygen mole fraction due to an overestimated K = 7.0(±1.0) × 106 cm2/s, which affects atmospheric mixing as well as the rate of atmospheric escape to space.

Quaternized poly(vinyl toluene-co-α-methyl styrene)/poly(vinyl alcohol) interpenetrating anion exchange membrane for efficient acid reclamation

With increasing urbanization and better lifestyle, more industries are being set up worldwide. Eco-friendly treatment of industrial waste is one of the major challenges to be resolved. Membrane can be a better option to treat industrial waste in sustainable manner. Herein, we report synthesis of anion exchange membrane (AEM) via. interpenetrating type crosslinked-network of N-methyl morpholine functionalized poly(vinyl toluene-co-α-methyl styrene) (PVM) and poly(vinyl alcohol) (PVA). The composition of QPVM to PVA varied from 1:1, 1:1.25, and 1:1.50 to optimize for better membrane performance in terms of ionic conductivity, proton diffusion coefficient and selectivity towards metal ions. AEM with composition of 1:1.25 PVA:QPVM (PVM-1.25) exhibits overall better physicochemical and electrochemical traits bearing ∼63% of water uptake and ⁓10.5 mS cm-1 of ionic conductivity (IC) with counter-ion transport number of 0.93. The structural and functional group analysis of prepared membranes were performed by 1H nuclear magnetic resonance (NMR) and Fourier transform infrared (FTIR) spectroscopy. All synthesized AEMs were systematically evaluated for acid reclamation application, and results were corroborated in terms of proton diffusion coefficient (UH+), metal diffusion coefficient (UMn+)and separation factor (Sf) using variable divalent and trivalent metal ions in simulant acidic waste models. PVM-1.25 membrane showed highest proton diffusion coefficient of 39.35 × 10−3 m h−1 with separation factor of 42.57 in presence of Al3+ ions, which is ∼42% and ∼66% higher than Fe2+ (UH+= 27.71 × 10−3 m h−1 and Sf=19.87) and Zn2+ (UH+= 23.62 × 10−3 m h−1 and Sf=12.27), respectively. PVM-1.25 membrane also showed chemical, thermal and mechanical stability. Based on the results, PVM-1.25 can be considered a good candidate for reclamation of acid from industrial waste stream.

Intramolecular Triplet Diffusion Facilitates Triplet Dissociation in a Pentacene Hexamer.

Triplet dynamics in singlet fission depend strongly on the strength of the electronic coupling. Covalent systems in solution offer precise control over such couplings. Nonetheless, efficient free triplet generation remains elusive in most systems, as the intermediate triplet pair 1 (T1 T1 ) is prone to triplet-triplet annihilation due to its spatial confinement. In the solid state, entropically driven triplet diffusion assists in the spatial separation of triplets, resulting in higher yields of free triplets. Control over electronic coupling in the solid state is, however, challenging given its sensitivity to molecular packing. We have thus developed a hexameric system (HexPnc) to enable solid-state-like triplet diffusion at the molecular scale. This system is realized by covalently tethering three pentacene dimers to a central subphthalocyanine scaffold. Transient absorption spectroscopy, complemented by theoretical structural optimizations and steady-state spectroscopy, reveals that triplet diffusion is indeed facilitated due to intramolecular cluster formation. The yield of free triplets in HexPnc is increased by a factor of up to 14 compared to the corresponding dimeric reference (DiPnc). Thus, HexPnc establishes crucial design aspects for achieving efficient triplet dissociation in strongly coupled systems by providing avenues for diffusive separation of 1 (T1 T1 ), while, concomitantly, retaining strong interchromophore coupling which preserves rapid formation of 1 (T1 T1 ).

Intramolekulare Triplett‐Diffusion erleichtert die Triplett‐Dissoziation in einem Pentacen‐Hexamer

AbstractDie Triplett‐Dynamik bei der Singulettspaltung hängt stark von der Stärke der elektronischen Kopplung ab. Kovalente Systeme in Lösung bieten eine präzise Kontrolle über solche Kopplungen. Dennoch bleibt die effiziente Erzeugung freier Triplett‐Zustände in den meisten Systemen schwer fassbar, da das intermediäre Triplett‐Paar 1(T1T1) aufgrund seiner räumlichen Begrenzung anfällig für Triplett‐Triplett‐Annihilation ist. Im Festkörper unterstützt die durch Entropie angetriebene Triplett‐Diffusion die räumliche Trennung der Triplett‐Zustände, was zu vermehrten Bildung freier Triplett‐Zustände führt. Einfluss auf die elektronische Kopplung im Festkörper zu nehmen ist jedoch herausfordernd, da sie sich mit der Anordnung der Moleküle im Festkörper ändert.. Daher haben wir ein hexameres System (HexPnc) entwickelt, um eine festkörperähnliche Triplett‐Diffusion auf molekularer Ebene zu ermöglichen. Dieses System besteht aus drei Pentacen‐Dimeren, die kovalent an ein zentrales Subphthalocyanin gebunden sind. Transiente Absorptionsspektroskopie, ergänzt durch theoretische Strukturoptimierungen und stationäre Spektroskopie, zeigt, dass die Triplett‐Diffusion tatsächlich durch intramolekulare Clusterbildung erleichtert wird. Die Ausbildung freier Triplett‐Zustände in HexPnc ist im Vergleich zum entsprechenden dimeren Referenzsystem (DiPnc) bis zu 14‐mal höher. Somit etabliert HexPnc entscheidende Designaspekte für die effiziente Triplett‐Dissoziation in stark gekoppelten Systemen, indem es Wege für die diffusive Trennung von 1(T1T1) aufzeigt. Gleichzeitig wird jedoch eine starke interchromophore Kopplung beibehalten, die die schnelle Bildung von 1(T1T1) nicht einschränkt.

Molecular dynamics simulation of strained controlled gas diffusion in polyimide membranes

The study of the diffusion and separation performance of small molecules within polyimide membranes under uniaxial stress is crucial for their applications under high-temperature and high-pressure conditions. In this study, we systematically investigated the diffusion behavior and diffusion selectivity of N2, CF4, C2F6, SF6, C2H4, C2H6, CH4, and SO2 gases, as well as their gas mixtures, within polyimide membranes under different tensile temperatures (300 K, 400 K, 500 K, 600 K) and tensile rates (1011 s−1, 1010 s−1, 109 s−1, 108 s−1) using molecular dynamics simulations. Our findings indicate that the diffusion coefficients of gas molecules within the polymer membrane increase with increasing strain or temperature. Excessive or overly rapid tensile rates are not favorable for the most efficient diffusion of molecules within the membrane. The strain has a relatively small impact on the diffusion coefficients of gas molecules that strongly adsorb to the polymer membrane. In contrast, the differences in the kinetic diameters of gas molecules affect diffusion selectivity under varying strain. These results suggest that a combination of molecular kinetic diameter, gas-polymer interactions, internal free volume, and pore distribution influences the effective gas diffusion within polyimide membranes. By controlling strain appropriately, the diffusion separation performance of this membrane material can be effectively improved.

Binary mixture convection in a horizontal channel under the Soret effect action

The mathematical model describing stationary flow of binary liquid mixture is under consideration. The exact solution of the equations of convective heat and mass transfer is constructed for the special form of the functions of temperature and concentration. All possible statements of boundary value problems are studied in order to analyse thermal diffusion separation of binary mixture in a long horizontal channel with rigid walls. It is discovered that only one of the statements (at inhomogeneous heating of both rigid walls) leads to feasible results. With the help of the constructed solution for the mentioned boundary value problem the effect of layer thickness, given flow rate and action of gravity force on the separation process, is analysed.

Mixed matrix membranes incorporating two-dimensional ZIF-8 nanosheets for enhanced CO2/N2 separation

In this report, a few unit-cell thick ZIF-8 nanosheets with (002) basal planes exposed with 4-membered windows were synthesized by using sodium dodecyl sulfate, an anionic surfactant as a structure directing agent, which were used as fillers to fabricate mixed matrix membranes (MMMs) for CO2/N2 separation. The 2D ZIF-8 fillers contributed to not only decreasing transport resistance due to highly porous nature but also strengthening CO2/N2 diffusive separation of the MMMs due to keen molecular sieving through 4-membered windows, smaller than conventional 6-membered windows of ZIF-8. Aligned filler dispersion in out-of-plane direction was maintained up to 10 wt% filler loading and the MMM with 10 wt% filler loading showed optimal performance of CO2 permeability of ∼350 Barrer and CO2/N2 selectivity of ∼94, outperforming most of the reported 2D nanosheet-based MMMs in addition to exceeding the 2019 upper bound. To check commercial viability, thin film nanocomposite (TFN) membranes composed of a skin layer of ∼780 nm including 10 wt% filler loading were prepared. The TFN membranes exhibited CO2 permeance of ∼710 GPU and CO2/N2 selectivity of ∼77, which surpasses most of state-of-the-art polymeric thin film composite (TFC) and TFN membranes especially in terms of selectivity.

Ultra-sensitive detection of tumor necrosis factor alpha based on silver-coated gold core shell and magnetically separated recognition of SERS aptamer sensors.

A highly sensitive tumor necrosis factor α (TNF-α) detection method based on a surface-enhanced Raman scattering (SERS) magnetic patch sensor is reported. Magnetic beads (MNPs) and core shells were used as the capture matrix and signaling probe, respectively. For this purpose, antibodies were immobilized on the surface of magnetic beads, and then Au@4-MBN@Ag core-shell structures coupled with aptamers and TNF-α antigen were added sequentially to form a sandwich immune complex. Quantitative analysis was performed by monitoring changes in the characteristic SERS signal intensity of the Raman reporter molecule 4-MBN. The results showed that the limit of detection (LOD) of the proposed method was 4.37 × 10-15 mg·mL-1 with good linearity (R2 = 0.9918) over the concentration range 10-12 to 10-5 mg·mL-1. Excellent assay accuracy was also demonstrated, with recoveries in the range 102% to 114%. Since all reactions occur in solution and are separated by magnetic adsorption of magnetic beads, this SERS-based immunoassay technique solves the kinetic problems of limited diffusion and difficult separation on solid substrates. The method is therefore expected to be a good clinical tool for the diagnosis of the inflammatory biomarker THF-α and in vivo inflammation screening.

Influence of deposited liquid structures on the separation efficiency of thin oleophilic fiber layers of mist filters

The presence of oil mists constitutes a significant hazard to both, human health and the environment. In industrial applications, the effective separation of these mists typically relies on the utilization of multi-layer nonwoven coalescence filters. The underlying mechanisms governing droplet deposition, liquid transport within the filter matrix, and the evolution of the overall differential pressure have been extensively documented in the existing literature. However, limited and contradictory information is currently available regarding the impact of deposited liquid structures under varying saturation levels on the separation efficiency of coalescence filters.In this study, the influence of an increased liquid saturation at different filtration velocities on the fractional and total separation efficiency of thin porous non-woven fiber layers comparable to the first fiber layers of the first filter layer of commercially utilized coalescence filters are evaluated. As the oil load increases to a saturation of S≤ 0.4, the total separation efficiency (number-based) decreases, for all investigated filtration velocities. In addition, a shift of the most penetrating particle size (MPPS) to smaller droplet sizes and a decrease of the MPPS efficiency is observed. This decrease is attributed to a higher interstitial velocity resulting from the accumulation of liquid within the filter matrix, leading to a lower fractional separation efficiency in the diffusion regime. However, at saturation levels S≥ 0.6, the separation efficiency (meaning both, fractional and total separation efficiency) begins to increase due to the formation of partial oil films, leading to a blockage of void space. These films significantly enhance inertial separation. At the highest investigated saturations (S=0.8), the highest separation efficiencies due to a nearly complete coverage of the filter layers by an oil film are observed. The film formation is confirmed through backlit images of the oil-loaded filter material. Furthermore, an increase of the MPPS efficiency for a saturation of S=0.8 with increasing filtration velocity due to increased diffusional separation is recorded, which cannot yet conclusively answered by the authors. Additionally, the differential pressure across the fiber sheets is presented, revealing a more pronounced influence of the oil film on the differential pressure at increasing filtration velocities.

Harnessing imidazole containing crosslinked AEM for HCl resurrection from industrial spent effluent by integrated diffusion dialysis and electrodialysis: Effect of small and macromolecular crosslinker

Herein, we report the preparation of crosslinked copolymer-based AEMs via a one-pot mechanism. AEMs were prepared by the nucleophilic substitution reaction of polyacrylonitrile-co-polyvinyl imidazole (PAN-co-PVI) copolymer (AN: VI = 63:37 mol/mol) with the small and macromolecular crosslinker. The AEM was then used for the separation and concentration of hydrochloric acid from its simulated waste mixture with ferrous chloride of the electroplating industry using diffusion dialysis (DD) followed by electrodialysis (ED). The separation has also been performed by the integrated approach of DD and ED processes. DD performance was carried out with three different crosslinked membranes namely M-PCMSt, M-XDC, and M-XDB synthesized using poly-chloromethyl styrene (PCMSt), xylene dichloride (XDC), and xylene dibromide (XDB) as crosslinker respectively. The DD performances were compared by measuring the diffusion coefficient and separation factor. M-PCMSt prepared using a macromolecular crosslinker (PCMSt) exhibited the highest crosslinking density and lowest extractable (%) in DMF due to strong network formation and lowest free volume. Due to its lowest water uptake and high mechanical strength in both water and acid swollen states, it was further used to concentrate the acid by ED and integrated the DD-ED process separately. A ∼2.49 and 1.575 times higher recovery was achieved by integrated process from DD and ED separately. Different parameters such as the effect of membrane-stack designing, current density, the effect of feed solution concentration, the effect of the volume ratio, flow rate of the circulating initial solution, and influence of gravity have been optimized. M-PCMSt shows the best separation behaviour with >92% recovered acid purity and ∼94.5 % acid recovery at 4 mAcm-2 current density which is better than polyethylene poly-(4-methyl styrene)-based interpolymer membrane.

Different metal precursor based rapid synthesis of α-Ni(OH)2-type Ni-Co-Mn layered double hydroxides and its use as electrodes for high performance energy storage devices

Improvement in the specific capacity of battery type electrode material is vital for creating hybrid devices with superior electrochemical performance. To accomplish this, mixed metal hydroxides, Ni0.7Co0.2Mn0.1(OH)2, are synthesized via a simple co-precipitation method by rapid pH switching using chloride, nitrate, acetate and sulphate salts of Ni, Co and Mn. P-XRD analysis confirmed the formation of pure and highly crystalline materials stabilized in the α-Ni(OH)2 structure. Finely divided particle type microstructure with sub 100 nm size and homogenous distribution of elements are confirmed by FESEM and EDX analysis, respectively. Among the studied samples, the layered hydroxide synthesized using chloride salts (Ni0.7Co0.2Mn0.1 LDH-Cl) shows the highest specific surface area of 58.8 m2 g−1 and pore volume of 0.083 cc g−1. The compound exhibited a high specific capacity of 978 C g−1 at 1 A g−1. The observed capacity is much higher than all other double hydroxides studied here and those we have come across in the literature reports on similar metal hydroxides. The diffusion dominance (b = 0.55) and quantitative separation of diffusion and capacitive capacity at different scan rates for Ni0.7Co0.2Mn0.1 LDH-Cl is also studied by CV analysis. Nyquist plot equivalent circuit fitting shows low charge transfer resistance (Rct = 17.6 Ω) and Warburg impedance (Zw = 35 Ω) for Ni0.7Co0.2Mn0.1 LDH-Cl. The high-capacity retention of 90 % for 5000 CV cycles at 100 mV sec−1 and 99 % for 1000 GCD cycles at 5 A g−1 for Ni0.7Co0.2Mn0.1 LDH-Cl confirm its potential for use as a battery type electrode material for practical applications.

Triton's photochemical model: Update

Titan, Triton, and Pluto are the Solar System objects with the nitrogen-ethane atmospheres. The progress in Titan's photochemistry, stimulated by the very successful Cassini-Huygens mission, facilitated photochemical interpretation of Pluto's atmosphere that was observed by the New Horizons mission and supporting ground-based measurements. Here is an update of Triton's atmospheric and ionospheric photochemistry that combines the previous photochemical model (Krasnopolsky and Cruikshank 1995, Photochemistry of Triton's atmosphere and ionosphere, J. Geophys. Res. 100, 21,271-21,286) with findings in Titan's and Pluto's photochemistry and progress in chemical kinetics.Our modeling of Triton's photochemistry is restricted to the conditions of the Voyager 2 flyby in 1989, when data on vertical profiles of temperature, haze, and densities of N2, CH4, N, and electrons were obtained using radio- and solar UVS occultations and imaging.Significant differences between the composition and photochemistry of Triton's atmosphere and those of Titan and Pluto are mostly caused by the low CH4 tropospheric abundance of 100 ppm, smaller than those on Titan and Pluto by two orders of magnitude. This methane is strongly depleted photochemically to a ppb level in the upper atmosphere of Triton, while it is enriched by diffusive separation on Titan and Pluto. Therefore atomic species and their chemistry are much more abundant on Triton than on Titan and Pluto. Atomic ions C+ and N+ with slow recombination rates dominate in Triton's ionosphere with electron densities, significantly exceeding those on Titan and Pluto.The proposed model agrees with all observational constraints and presumes thermal escape of H2 + H with a rate of 45 g cm−2 Byr−1, loss of nitrogen of 40 g cm−2 Byr−1 on thermal escape and precipitation of nitriles, and sublimation and loss of methane of 270 g cm−2 Byr−1.C2H6 and HCN are minor species in the photochemical precipitations on Triton, and their detection in Triton's ice may refer to either the primordial composition or ice photochemistry.Seven versions of the model are calculated to study its sensitivity to some basic input parameters. The model can be used for planning future studies of Triton's atmosphere. An analog of the Ion-Neutral Mass Spectrometer onboard Triton's orbiter looks promising.

Design of tropinium-functionalized anion exchange membranes for acid recovery via diffusion dialysis process

Diffusion dialysis (DD) process utilizing anion exchange membranes (AEMs) is an environmentally-friendly and energy-efficient technology. From acidic wastewater, DD is needed for acid recovery. This research reports the development of a series of dense tropinium-functionalized AEMs via solution casting method. Fourier Infrared transform (FTIR) spectroscopy verified the successful preparation of AEMs. The developed AEMs exhibited a dense morphology, featuring 0.98–2.42 mmol/g of ion exchange capacity (IEC), 30–81% of water uptake (WR) and 7–32% of linear swelling ratio (LSR). They displayed exceptional mechanical, thermal and chemical stability and were employed for acid waste treatment from HCl/FeCl2 mixtures via DD process. AEMs possessed 20 to 59 (10−3 m/h) and 166 to 362 of acid diffusion dialysis coefficient (UH+) and separation factor (S) respectively at 25 °C. Compared to DF-120 commercial membrane (UH+ = 0.004 m/h, S = 24.3), their DD efficiency was improved under identical experimental conditions.

Inference of main ion particle transport coefficients with experimentally constrained neutral ionization during edge localized mode recovery on DIII-D

The plasma and neutral density dynamics after an edge localized mode are investigated and utilized to infer the plasma transport coefficients for the density pedestal. The Lyman-Alpha Measurement Apparatus (LLAMA) diagnostic provides sub-millisecond profile measurements of the ionization and neutral density and shows significant poloidal asymmetries in both. Exploiting the absolute calibration of the LLAMA diagnostic allows quantitative comparison to the electron and main ion density profiles determined by charge-exchange recombination, Thomson scattering and interferometry. Separation of diffusion and convection contributions to the density pedestal transport are investigated through flux gradient methods and time-dependent forward modeling with Bayesian inference by adaptation of the Aurora transport code and IMPRAD framework to main ion particle transport. Both methods suggest time-dependent transport coefficients and are consistent with an inward particle pinch on the order of 1 m s−1 and diffusion coefficient of 0.05 m2 s−1 in the steep density gradient region of the pedestal. While it is possible to recreate the experimentally observed phenomena with no pinch in the pedestal, low diffusion in the core and high outward convection in the near scrape-off layer are required without an inward pedestal pinch.