Mass Diffusion Research Articles

Construction of heterogeneous MOF-on-MOF for highly efficient gaseous iodine sequestration under static conditions

Considering the unexpected nuclear power waste emission and potential nuclear leakage, the exploration of robust materials for the effective capture and storage of radioactive iodine is of great importance but still remains a challenge. In this work, we report the rational synthesis of functionalized NH2-UiO-66-on-ZIF-67 architecture to enhance the static adsorption and retention of volatile iodine. Such MOF-on-MOF heterostructures was fabricated through seeding ZIF-67 core on the surface of NH2-UiO-66 satellite via a facile polyvinylpyrrolidone (PVP) regulated internal extended growth strategies. NH2-UiO-66-on-ZIF-67 exhibited unique core-satellite structure, which significantly promotes the binding interactions with iodine through synergizing of the N-rich imidazole moieties and surface functionalized amino groups within the porosity channels. As a result, the as fabricated NH2-UiO-66-on-ZIF-67 achieves enhanced mass diffusion and high capture capacity of 3600 mg/g for iodine vapor under static sorption conditions. Moreover, water vapor in humid conditions (relative humidity of 18 %) has almost no effect on the static iodine adsorption performance of the material. This study sheds light on a reliable MOF-on-MOF hybrid strategy for effective radioiodine treatment to ensure the safety nuclear waste management.

The Performance of PEFC with Marimo-like Carbon Considering Relative Humidity

A proton exchange membrane fuel cell (PEMFC) is powered by humidified fuel and air gases supplied to the cells. We evaluated the effect of the relative humidity (RH) of the fuel and air gases on the I-V performance of the Marimo-like carbon (MC). MC is a higher order structure of carbon fibers. The RH increased the proton conductivity of the Nafion, while excessive humidification caused flooding. The highest maximum power density was 303 mW cm-2 (80% RH) for the Pt/MC and 165 mW cm-2 (60% RH) for the Pt/CB (carbon black). At all the RHs, the maximum power density of the Pt/MC was higher than that of the Pt/CB. The fiber structure and I/C (0.1) of the MC increase the mass diffusivity of the Pt/MC. The high mass diffusivity of the Pt/MC found to reduce flooding and promote the wetting of the Nafion by the generated water.

Floating graphite felt-cellulose multilayer sandwich evaporator for solar salt-resistant seawater desalination: Mechanistic role of incorporated super water holding layer

Solar-to-steam generation (SSG) for seawater desalination is emerging process which faces several technology challenges for successful scaling up. Floating solar-to-steam generation (SSG) sandwich-based systems using hydrophilic water bridges have been proved to be fascinating technology for seawater desalination. However, the mechanistic pathways of heat dissipation, mass diffusion and convection are still the key bottlenecks for reliable scaling up. To solve the heat loss and surface salt deactivation, we demonstrate herein the performance of novel SSG structure for seawater desalination via the incorporation of cellulosic sponge as water holder to play a role of water transit between hydrophilic bridge and the top surface. Two systems using low-cost materials were compared, namely graphite felt/hydrophilic paper/polystyrene (GF-HP-PS) and Graphite felt/Water receiver/hydrophilic paper/polystyrene (GF-HP-WR-PS). The process of heat generation and localization was maximum in the GF-WR-HP-PS system, reaching 68.2 °C under 0.5 sun. The photothermal conversion efficiency was found to be 92 and 114 % under 0.5 sun for GF-HP-PS and GF-HP-WR-PS, respectively. On top of that, GF-HP-WR-PS shows effective steadily salt rejection during the desalination of seawater. The WR layer plays a crucial role to govern the confined water, which boosts the dissolution of salt and its convection without significant heat downward convection. As a practical consideration, the cost of used components to fabricate this SSG system is very acceptable and without major restrictions.

Unsteady MHD flow past an oscillating vertical plate with periodic temperature variation and exponential mass diffusion embedded in a porous medium with thermal and mass stratification effects

AbstractThe present study investigates the impacts of both mass and thermal stratification on unsteady magnetohydrodynamic flow past a plate swinging vertically on its own axis while entangled in a porous medium with periodic temperature variation and exponential mass diffusion. The technique of Laplace transform for the unitary Prandtl and Schmidt numbers is employed to obtain the closed‐form solution for the nondimensional system of partial differential equations that govern the system for velocity, temperature, and concentration fields. For various physical factors, such as stratification parameters, phase angle, thermal Grashof number, Darcy number, mass Grashof number, and time on velocity, temperature, concentration, skin‐friction, plate heat flux, and mass flux, numerical computations have been performed, and illustrated in graphs. It has been observed that the steady state is attained more swiftly when stratification is applied to the flow. The desire to enhance the knowledge of fluid flow in many technological as well as environmental circumstances, where such conditions are widely used could be the driving force behind this research. Significant results from the thermal and mass stratification are contrasted with the environment where stratification is absent. Understanding flow mechanisms in both naturally occurring and artificially created environments can be enriched by this innovative method.

Synthesis and consequence of three-dimensionally ordered macroporous Beta zeolite supported NiW catalyst for efficient hydrocracking of 1-methylnaphthalene to BTX

The three-dimensionally ordered macroporous Beta (3DOM-Beta) zeolite was prepared and used as support of NiW sulfide catalyst for hydrocracking. The as-prepared NiW/3DOM-Beta catalyst possessed a high specific surface area and external specific surface area up to 499 m2/g and 241 m2/g, respectively, and a small average layer length (3.62 nm), a high highest average stacking number (4.64) and dispersion (fW=0.24) of metal sulfide phase, which are characteristic of high hydrogenation activity. Its high mesopore volume (0.25 cm3/g) and the highly ordered interconnected macro-meso-microporosity hierarchical structure significantly facilitated diffusive mass transfer. Compared to the NiW sulfide supported on conventional Beta (C-Beta), alkali-treated Beta (A-Beta) and nanosized Beta (Nano-Beta) zeolites, NiW/3DOM-Beta catalyst showed the highest BTX selectivity and yield of 40.7 % and 40.2 % (33.2 % and 32.6 % on NiW/C-Beta, 34.8 % and 33.9 % on NiW/A-Beta, 37.2 % and 36.6 % on NiW/Nano-Beta), and the highest hydrocracking activity (TOF=2.11 × 10-2∙s−1) as well as the smallest coking content (6.7 wt%). This work not only reveals the promotion effects of the ordered mesopore structure of supports on metal dispersion, accessibility of acid sites, diffusion of reactants and products for designing hydrocracking catalyst, but also shows the potential practical application of 3DOM zeolites with interconnected macro-meso-microporosity for the efficient catalytic conversion of macro-hydrocarbons via hydroupgrading.

Pure intertubular seminoma (PITS) of the testis: A multi-institutional cohort of a rare growth pattern of seminoma

Pure intertubular seminoma (PITS) of the testis is described as the presence of seminoma cells within the interstitium of testis without any evidence of diffuse growth pattern or mass lesion of classical seminoma. These tumors are clinically and grossly inconspicuous and are diagnosed incidentally or during investigations for testicular pain, infertility or other symptoms. Rarely metastasis is the first presentation. Microscopic identification can be difficult and poses a diagnostic challenge in the absence of a mass lesion. Seminomas with exclusive intertubular growth patterns were gathered in an international cohort. Diagnoses were confirmed by fellowship-trained or specialized urologic pathologists. Cases with the presence of a classical diffuse or nested pattern of seminoma or any other germ cell tumor component were excluded. The patient's age, tumor characteristics and additional clinicopathologic features were recorded and analyzed. 15 patients of pure intertubular seminoma (PITS) were collated. The mean age of presentation was 29 years. Patients presented with variable symptoms, including undescended testis (26%, n = 4/15), testicular heaviness/pain (20%, n = 3/15) infertility (20%, n = 3/15) and metastasis (6%, n = 1/15); presentation was unknown in 4 patients. Of note, none of the patients presented because of testicular mass. Serum markers were within normal limits in most patients (93%, n = 14/15) with available data. No tumors were identified macroscopically; however, an ill-defined, grey-white, firm area was noted in one orchiectomy specimen. Microscopically, tumor cells were seen in intertubular spaces as dispersed individual cells or small clusters. Tumor cells were round to polygonal with large nuclei and prominent nucleoli. Mild to moderate lymphocytic infiltrates were seen admixed with tumor cells in 40% (n = 6/15) of the tumors. GCNIS was present in association with most PITS (73%, n = 11/15). Tubular atrophy with thickening of the basement membrane and Leydig cell hyperplasia was observed in one tumor. Thirty-three percent (n = 5/15) of the tumors showed pagetoid involvement of rete testis, including the tumor with metastasis. All tumors showed the classical immunohistochemical profile of seminoma, with PLAP, c-KIT, OCT3/4, D2-40 and SALL4 positivity. PITS can be clinically & pathologically inconspicuous, difficult to stage and liable to be misdiagnosed especially if presented with metastasis. Despite the inconspicuousness, PITS may represent an aggressive growth pattern of seminoma with the propensity for rete testis invasion.

Facile synthesis of hierarchically porous carbon monolith without templating agent for various applications in energy and catalysis

Monolithic carbon with hierarchically porous structure has a promising prospect for a wide range of applications in the fields of energy, environment, catalysis, etc. Due to the reliance on the utilization of templating agents, conventional preparation approaches often suffer from time-consuming preparation, complex post-processing, and uneconomical cost. Herein, we develop a novel strategy to match the sol-gel transition with the phase separation process for the direct preparation of hierarchically porous carbon monolith (HPCM) without templating agent. Resorcinol and resol are employed as carbon sources to adjust the polymerization for the formation of bi-continuous microstructure. Well-defined hierarchical pores and large specific surface area for fast mass diffusion enable the HPCM to be a prospective kind of electrode material in supercapacitor with an outstanding specific capacitance over 350 F g−1 (1.0 A g−1). After facile sulfonation, the modified HPCM can act as solid acid catalyst to realize a high-performance production of 5-hydroxymethylfurfural (5-HMF) in a 90 % yield with turnover frequency (TOF) value up to 155.9 h−1. Additionally, HPCM also exhibits an excellent Joule heating effect, which can be applied to the thermal management after compounding with phase change materials. The desirable integrated performance enables HPCM to be a valuable material suitable for various applications.

Numerical study of Casson dusty hybrid nanofluid flow with volume fraction over a Darcy–Forchheimer porous medium

AbstractThis study develops a mathematical model for dusty Casson hybrid nanofluid flow over a vertical stretching sheet, considering the influence of volume fractions for the dust particles and nanoparticles, magnetic field and Darcy–Forchheimer penetrating medium. The nanoparticles used are TC4 (Ti‐6Al‐4V) and Nichrome (80% Ni and 20% Cr), suspended in unused engine oil (EO). The governing partial differential equations are transformed into ordinary ones using suitable transforms. Solutions are obtained numerically via the Matlab built‐in program Bvp4c technique and represent graphically the velocity, temperature, and concentration profiles for both the fluid and dust phases. Additionally, tabular forms present wall shear stress and heat transfer rate variations under different parameter values. It is found that the enhancing volume fraction parameter helps to boost the magnitude of shear stress, heat, and mass diffusivity.

Computational work of casson rheology on 3D swirling plate employing yamada-ota and xue models

This article emphasizes the findings of comparative thermal enhancement in Casson fluid using bases fluid as blood and Xue and Yamada-Ota hybrid nano-structures model towards a 3D swirling plate. Nanofluid flow is a widely investigated topic in engineering and industry, particularly in the cooling of electronic devices. Its proven ability to save energy makes it a viable option for improving cooling systems and sustainability initiatives. Thermal energy incorporates solar radiation, Soret and heat sources while transportation of species happens utilizing activation energy and Dufour impact. It was estimated that the system (partial differential equation) is converted into Odes employing finite element methodology. Such a complicated model is resolved efficient method named as finite element method. By enhancing impacts of chemical reaction and Dufour numbers, mass diffusion is enhanced but opposite behavior is noticed in mass diffusion with the change of Schmidt number. By increasing values of Lorentz force and velocity field inclines. Further, thickness (MBLs) increase with variation of Lorentz force and Casson parameter.

Numerical Study of the 3D MHD Radiative Flow of Williamson Nanofluid with Variable Characteristics Over a Double Stretching Sheet

The current study investigates the influence of variable thermal conductivity and mass conductivity on 3D MHD. The significance of this study lies in mass diffusion on a three-dimensional Williamson nanofluid fluid flow over a double stretched sheet. When thermal radiation and Hall current is present, the heat transfer process is explored to see how chemical reactions affect heat and mass transmission. Additional phenomena, such as momentum slip and convective boundary conditions, contribute to the model's uniqueness. The problem formulation becomes ordinary differential equations with application of the Von Karman similarity variable. Use of the bvp4c function in yields a numerical solution for the system of differential equations. Using MATLAB’s bvp4c function, a numerical solution to the differential equation system is obtained. A graphic is used to discuss the overall result of several metrics compared to the involved profiles. It is believed that as temperature-dependent thermal conductivity and viscosity increase, so does the temperature field. When the Williamson fluid and magnetic parameters rise, the velocity field decays in the x- and y-axis directions. To support the identified issue, a comparison between the current inquiry and a previously published work is also included.

In-situ synthesis of 3D TiO2 microspheres on Ti mesh to enhance photoelectrochemical water splitting

Much attention has been focused on the fabrication of TiO2 microspheres due to their excellent properties and attractive potential in many fields. Here, undoped 3D hierarchical TiO2 microspheres (TMS) were synthesized in situ on Ti mesh using a hydrothermal method by varying NaOH concentration, reaction time and temperature. The 3D TMS grown along the surface of the woven wires of the Ti meshes, using the metal Ti meshes as a substrate, which resulted in improved conductivity. Meanwhile, the original Ti mesh with the macroporosity (due to the 15 % open area of the mesh) can act as fast proton mass diffusion. As a result, the flexible TMS-Ti photoelectrodes exhibit an excellent current density of 1.63 mA/cm2 at a potential of 1.23 V (vs Ag/AgCl). Therefore, the in situ synthesis of TiO2 microspheres on Ti mesh is highly desirable for flexible devices.

Electrochemical Investigation of Plasma Channels During Hydraulic‐Electric Pulsed Discharges

ABSTRACTThe hydraulic‐electric pulsed discharge(HEPD) rock‐breaking technology is a new high‐efficiency technology that generates plasma shock waves to rupture rocks. Since the plasma channel formation mechanism involved in HEPD rock‐breaking technology is difficult to describe, there are fewer theoretical models of this technology. This paper establishes a HEPD plasma model, which integrally considers the mutual coupling between five physical fields. The multi‐physical field model realizes the whole process of plasma channels, breakdown channels, plasma shock waves, and plasma shock wave rock‐breaking during the HEPD. The changes in mass fraction, density, and diffusion flux of relevant elements in the electrochemical reaction equation of the plasma channel are comprehensively analyzed. The obtained plasma multiphysics field model shows that the interpenetration of charged ions forms the breakdown channel and plasma channel. The anion number density is related to the H‐ number density, and the decrease in H‐ number density is due to the fact that the energy in the plasma channel is not sufficient to satisfy the relevant chemical equations to continue the collision reaction. The damage to the rock by the plasma shock wave takes the form of a gradual spreading of the plasma shock wave from the center of the rock to the edges, which leads to rock fragmentation. The model has the potential to establish a link between HEPD rock‐breaking parameters and the efficiency of HEPD rock‐breaking, which could provide a practical way for the development and parameter optimization of hydraulic‐electric pulsed discharge rock‐breaking tools.

Flame propagation, explosion hazard, and pollutant emission characterization of typical clean fuels leaks in plateau low-pressure region

To accelerate energy transformation and sustainable development, various countries are rushing to lay hydrogen doped natural gas pipelines. However, the installation of pipelines will pass through plateau low-pressure region, and the impact of low-pressure environments on the flame propagation, explosion hazards, and pollutant emission characteristics of hydrogen doped natural gas is not yet clear. To solve this problem, a combination of constant volume combustion experiment and numerical simulations is used. The characterization parameters of flame, explosion and pollutant concentration of natural gas/H2/air under low-pressure environment are obtained, and their chemical reaction kinetics are analyzed. When the pressure drops, the laminar burning velocity (LBV) of them increases, and the Lewis number (Le) gradually increases by more than 1. Thermal diffusion is stronger than mass diffusion, and the growth rate of flame thickness exceeds 26 %. The effect of hydrodynamic instability enhances, causing an increment in the average size of flame cells, the critical instability radius, and the Markstein length (Lu). At the equivalent ratio (φ) of 1, there is a change from negative to positive in the Lu, and flame stability continuously strengthens. The explosion overpressure is reduced by 78 % to 90 %, the explosion temperature by 16 % to 20 %. As the φ increases, the LBV exhibits an inverted U-shaped relationship, reaching its maximum value near “φ = 1″. The flame stability first weakens and then strengthens. The explosion hazard is strongest in the range of ”φ = 1–1.2″. With a decrease in pressure, the total reaction rate of fuel consumption is reduced by more than 50 %. The continuous reaction distance is extended by 12 %. Changes in pressure have a relatively weak impact on the content of CO and CO2. The increase in the φ results in an increase in CO content of over 7 %. The content of CO2 reaches its maximum value around “φ = 1″. It is an essential reference for the safe delivery of hydrogen energy and the reduction of environmental pollution.

Non-homogeneous anisotropic bulk viscosity for acoustic wave attenuation in weakly compressible methods

A major limitation of the weakly compressible approaches to simulate incompressible flows is the appearance of artificial acoustic waves that introduce mass conservation errors and lead to spurious oscillations in the force coefficients. In this work, we propose a non-homogeneous anisotropic bulk viscosity term to effectively damp the acoustic waves. By implementing this term in a computational framework based on the recently proposed general pressure equation, we demonstrate that the non-homogeneous and anisotropic nature of the term makes it significantly more effective than the isotropic homogeneous version widely used in the literature. Moreover, it is computationally more efficient than the pressure (or mass) diffusion term, which is an alternative mechanism used to suppress acoustic waves. We simulate a range of benchmark problems to comprehensively investigate the performance of the bulk viscosity on the effective suppression of acoustic waves, mass conservation error, order of convergence of the solver, and computational efficiency. The proposed form of the bulk viscosity enables fairly accurate modelling of the initial transients of unsteady simulations, which is highly challenging for weakly compressible approaches, and to the best of our knowledge, existing approaches can't provide an accurate prediction of such transients.

Rayleigh wave propagation in a modified couple stress visco-thermoelastic diffusion medium

The present investigation is devoted to Rayleigh wave propagation in modified couple stress visco-thermoelastic medium with mass diffusion under Lord–Shulman and Green–Lindsay theories of thermoelasticity. After formulating the problem mathematically, the secular equation is derived for stress free, insulated, and impermeable boundary. The wave characteristics like phase velocity and attenuation coefficient have been obtained numerically by developing numerical algorithm. For a particular material, the numerically simulated results are shown graphically to display the physical meaning of the phenomenon. The current inquiry also leads to several specific cases of interest. A comparison has been conducted with the earlier findings that suggested how the additional parameters might affect the phenomena of Rayleigh waves propagating. The results obtained indicate to the strong impact for the diffusivity and viscosity of Rayleigh thermoelastic waves propagation and applicable on the related phenomenon in geology, geophysics, acoustics, astronomy, and geophysics and agreement with the physical meaning of the phenomenon.

Experimental Study for the Sorption and Diffusion of Supercritical Carbon Dioxide into Polyetherimide.

Supercritical carbon dioxide (SCCO2) is a non-toxic and environmentally friendly fluid and has been used in polymerization reactions, processing, foaming, and plasticizing of polymers. Exploring the behavior and data of SCCO2 sorption and dissolution in polymers provides essential information for polymer applications. This study investigated the sorption and diffusion of SCCO2 into polyetherimide (PEI). The sorption and desorption processes of SCCO2 in PEI samples were measured in the temperature range from 40 to 60 °C, the pressure range from 20 to 40 MPa, and the sorption time from 0.25 to 52 h. This study used the ex situ gravimetric method under different operating conditions and applied the Fickian diffusion model to determine the mass diffusivity of SCCO2 during sorption and desorption processes into and out of PEI. The equilibrium mass gain fraction of SCCO2 into PEI was reported from 9.0 wt% (at 60 °C and 20 MPa) to 12.8 wt% (at 40 °C and 40 MPa). The sorption amount increased with the increasing SCCO2 pressure and decreased with the increasing SCCO2 temperature. This study showed the crossover phenomenon of equilibrium mass gain fraction isotherms with respect to SCCO2 density. Changes in the sorption mechanism in PEI were observed when the SCCO2 density was at approximately 840 kg/m3. This study qualitatively performed FTIR analysis during the SCCO2 desorption process. A CO2 antisymmetric stretching mode was observed near a wavenumber of 2340 cm-1. A comparison of loss modulus measurements of pure and SCCO2-treated PEI specimens showed the shifting of loss maxima. This result showed that the plasticization of PEI was achieved through the sorption process of SCCO2.

Copper dual-doping strategy of porous carbon nanofibers and nickel fluoride nanorods as bi-functional oxygen electrocatalysis for effective zinc-air batteries

Designing and developing efficient, low-cost bi-functional oxygen electrocatalysts is essential for effective zinc-air batteries. In this study, we propose a copper dual-doping strategy, which involves doping both porous carbon nanofibers (PCNFs) and nickel fluoride nanoparticles with copper alone, successfully preparing copper-doped nickel fluoride (NiF2) nanorods and copper nanoparticles co-modified PCNFs (Cu@NiF2/Cu-PCNFs) as an efficient bi-functional oxygen electrocatalyst. When copper is doped into the PCNFs in the form of metallic nanoparticles, the doped elemental copper can improve the electronic conductivity of composite materials to accelerate electron conduction. Meanwhile, the copper doping for NiF2 can significantly promote the transformation of nickel fluoride nanoparticles into nanorod structures, thus increasing the electrochemical active surface area and enhancing mass diffusion. The Cu-doped NiF2 nanorods also possess an optimized electronic structure, including a more negative d-band center, smaller bandgap width and lower reaction energy barrier. Under the synergistic effect of these advantages, the obtained Cu@NiF2/Cu-PCNFs exhibit outstanding bi-functional catalytic performances, with a low overpotential of 0.68 V and a peak power density of 222 mW cm−2 in zinc-air batteries (ZABs) and stable cycling for 800 h. This work proposes a one-step way based on the dual-doping strategy, providing important guidance for designing and developing efficient catalysts with well-designed architectures for high-performance ZABs.

CatchyCFDEM: Open-source microkinetic modeling of heterogeneous catalysis in Eulerian-Lagrangian CFD applied to oxidative coupling of methane

This work introduces catchyCFDEM, an OpenFOAM-based open-source CFD-DEM framework designed for simulating reactive gas–solid fluidized beds with both gas-phase chemistry and heterogeneous catalytic chemistry. A convective gas–solid heat transfer model is implemented and validated using experimental data gathered in a non-reactive pseudo-2D fluidized bed. Catalytic chemistry including different levels of complexity are included: pseudo-homogeneous, heterogeneous without mass transfer, and heterogeneous with diffusive mass transfer. Verification studies are performed by simulating a packed bed reactor using catchyCFDEM and comparing mass fraction profiles to a 1D plug flow simulation in Cantera. To enhance the computational efficiency of the resource-intensive reactive CFD-DEM simulations, speed-up algorithms such as Particle Agglomeration (PA) and in-situ adaptive tabulation (ISAT) are integrated in catchyCFDEM. As a case study, a gas–solid vortex reactor (GSVR) is simulated using the validated framework. The applicability of the GSVR for the oxidative coupling of methane (OCM) is evaluated based on an isothermal analysis evaluating the influence of several operational and geometrical parameters on the process. Finally, a proof-of-concept adiabatic simulation of the GSVR is presented. The catchyCFDEM framework is made publicly available on GitHub.

Effect of multi-component gas on removal of trace hydrogen sulfide activity from blast furnace gas using activated carbon adsorbent

Abstract In the steel industry, blast furnace gas (BFG) is huge with complex components. The existence of hydrogen sulfide (H2S) in the BFG can produce sulfur dioxide (SO2) after combustion, which will increase the source of SO2 pollution and make the desulphurization more difficult, to be threat to people health. At present, the removal of H2S by dry adsorption with modified activated carbon adsorbent is a high-precision and low-cost desulphurization method. However, the effect of complex gas components in BFG on the adsorption of H2S by activated carbon adsorbent is not sufficient. Based on the fixed bed adsorbent evaluation system, a new type of highly efficient copper-cerium oxide (Cu–Ce–O) modified activated carbon H2S adsorbent was developed. And the effects of carbon monoxide (CO), carbon dioxide (CO2), hydrogen (H2), oxygen (O2), sulfur dioxide and hydrogen chloride (HCl) in BFG on the desulfurization activity of adsorbents were investigated. The results showed that the performance of H2S removal decreased in the presence of CO, CO2, HCl and SO2, and improved in the presence of H2 and O2. Other parameters were also studied which might influence the process. The application of modified activated carbon adsorbent in simulated BFG is basically stable. According to the fitting results of adsorption kinetics for the five adsorption models, as the atmosphere becomes BFG from N2, pore diffusion becomes the main adsorption form. However, the effects of internal diffusion, chemical adsorption and external mass transfer decreased. The Bangham model is the most suitable model to describe H2S adsorption process.

A Blood Supply Pathophysiological Microcirculatory Mechanism for Long COVID.

The term "Long COVID" is commonly used to describe persisting symptoms after acute COVID-19. Until now, proposed mechanisms for the explanation of Long COVID have not related quantitative measurements to basic laws. In this work, a common framework for the Long COVID pathophysiological mechanism is presented, based on the blood supply deprivation and the flow diffusion equation. Case-control studies with statistically significant differences between cases (post-COVID patients) and controls, from multiple tissues and geographical areas, were gathered and tabulated. Microvascular loss (ML) was quantified by vessel density reduction (VDR), foveal avascular zone enlargement (FAZE), capillary density reduction (CDR), and percentage of perfused vessel reduction (PPVR). Both ML and hemodynamic decrease (HD) were incorporated in the tissue blood supply reduction (SR) estimation. ML data were found from 763 post-COVID patients with an average VDR, FAZE, CDR, and PPVR of 16%, 31%, 14%, and 21%, respectively. The average HD from 72 post-COVID patients was 37%. The estimated SR for multiple tissues with data from 634 post-COVID patients reached a sizeable 47%. This large SR creates conditions of lower mass diffusion rates, hypoxia, and undernutrition, which at a multi-tissue level, for a long time, can explain the wide variety of the Long COVID symptoms. Disruption of peripheral tissue blood supply by the contribution of both ML and HD is proposed here to be the principal cause of the mechanism leading to Long COVID symptoms.