Mass Transport Model Research Articles

Artificial Neural Networks for Mineral Production Forecasting in the In Situ Leaching Process: Uranium Case Study

This study was conducted to assess the applicability of artificial neural networks (ANN) for forecasting the dynamics of uranium extraction over exploitation time during the process of In Situ Leaching (ISL). Currently, ISL process simulation involves multiple steps, starting with geostatistical interpolation, followed by computational fluid dynamics (CFD) and reactive transport simulation. While extensive research exists detailing each of these steps, machine learning techniques may offer the potential to directly obtain extraction curves (i.e., the concentration of the mineral produced over the exploitation time of the deposit), thereby bypassing these computationally expensive steps. As a basis, both an empirical experimental configuration and reactive transport simulations were used to generate training data for the neural network model. An ANN was constructed, trained, and tested on several test cases with different initial parameters, then the expected outcomes were compared to those derived from conventional modeling techniques. The results indicate that for the employed experimental configuration and a limited number of features, artificial intelligence technologies, specifically regression-based neural networks can model the recovery rate (or extraction degree) of the ISL process for mineral production, achieving a high degree of accuracy compared to traditional CFD and mass transport models.

Physics-based prediction of moisture-capture properties of hydrogels

Moisture-capturing materials can enable potentially game-changing energy-water technologies such as atmospheric water production, heat storage, and passive cooling. Hydrogel composites recently emerged as outstanding moisture-capturing materials due to their low cost, high affinity for humidity, and design versatility. Despite extensive efforts to experimentally explore the large design space of hydrogels for high-performance moisture capture, there is a critical knowledge gap on our understanding behind the moisture-capture properties of these materials. This missing understanding hinders the fast development of novel hydrogels, material performance enhancements, and device-level optimization. In this work, we combine synthesis and characterization of hydrogel-salt composites to develop and validate a theoretical description that bridges this knowledge gap. Starting from a thermodynamic description of hydrogel-salt composites, we develop models that accurately capture experimentally measured moisture uptakes and sorption enthalpies. We also develop mass transport models that precisely reproduce the dynamic absorption and desorption of moisture into hydrogel-salt composites. Altogether, these results demonstrate the main variables that dominate moisture-capturing properties, showing a negligible role of the polymer in the material performance under all considered cases. Our insights guide the synthesis of next-generation humidity-capturing hydrogels and enable their system-level optimization in ways previously unattainable for critical water-energy applications.

Modeling Mass Transport Dynamics in Deformable Hydrogels during Evaporation.

Hydrogels possess exceptional mechanical properties and biocompatibility, making them widely used in contemporary bioengineering. Specifically, in the development of wearable and implantable health monitoring devices as well as drug delivery systems, hydrogels are utilized to enable precise control over the transport of solutes. Nonetheless, predicting the distribution of substances within hydrogels still poses a significant challenge due to the complex interplay between the movement of water content, migration of solutes, and deformability of the hydrogel polymer network, which presents challenges to theoretical modeling. Our work introduces a numerical model that addresses the movement of water and solute within a flexible hydrogel, accounting for evaporation and/or moisture absorption at the boundary. The model solves for water saturation, solute concentration, and hydrogel deformation iteratively at each time step while computing the boundary movement velocity based on the transport process. By comparing the modeled results of geometry deformation and water and solute distributions during evaporation with our experiments, we demonstrate the accuracy and applicability of our proposed model. This capability to precisely analyze water and solute concentrations in deformable and nonuniform hydrogel environments paves the way for advancements in biosensing and drug delivery methods that rely on elastic porous materials.

Multiscale modeling of heat and mass transfer in dry snow: influence of the condensation coefficient and comparison with experiments

Abstract. Temperature gradient metamorphism in dry snow is driven by heat and water vapor transfer through snow, which includes conduction/diffusion processes in both air and ice phases, as well as sublimation and deposition at the ice–air interface. The latter processes are driven by the condensation coefficient α, a poorly constrained parameter in the literature. In the present paper, we use an upscaling method to derive heat and mass transfer models at the snow layer scale for values of α in the range 10−10 to 1. A transition α value arises, of the order of 10−4, for typical snow microstructures (characteristic length ∼ 0.5 mm), such that the vapor transport is limited by sublimation–deposition below that value and by diffusion above it. Accordingly, different macroscopic models with specific domains of validity with respect to α values are derived. A comprehensive evaluation of the models is presented by comparison with three experimental datasets, as well as with pore-scale simulations using a simplified microstructure. The models reproduce the two main features of the experiments: the non-linear temperature profiles, with enhanced values in the center of the snow layer, and the mass transfer, with an abrupt basal mass loss. However, both features are underestimated overall by the models when compared to the experimental data. We investigate possible causes of these discrepancies and suggest potential improvements for the modeling of heat and mass transport in dry snow.

Surface Complexation and Packed Bed Mass Transport Models Enable Adsorbent Design for Arsenate and Vanadate Removal

Surface Complexation and Packed Bed Mass Transport Models Enable Adsorbent Design for Arsenate and Vanadate Removal

Benchmarking Local pH of Electrocatalysts for Water Electrolysis Using the Rotating Ring-Disk Electrode Technique

Water electrolysis is an important route for production of green hydrogen and remains a field of active research in pursuit of improved electrocatalytic activity and durability. Operating with a near-neutral feed is critical for this technology to be more widely adapted, because it allows the direct use of various water sources and imposes less stringent requirements on the components of the electrochemical cell.During water electrolysis, the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) involving protons and hydroxides can experience a significant change in local pH at the surface of the catalyst, especially in near-neutral bulk conditions. This change in local pH is usually dictated by the reaction conditions such as electrolyte composition and mass transport within the system. Notably, there has been an increase in development of catalysts for water electrolysis with the ability to modulate their local pH in recent years. 1–6 However, comparing and quantifying the local pH modulation effects of these catalysts is challenging due to varying experimental techniques and protocols. The rotating ring-disk electrode (RRDE) with a potentiometric pH sensing ring has been presented as a promising and facile tool for in-situ local pH detection. 3,4,7,8 The local pH at the disk is estimated from the ring pH through solving the convective-diffusion equation under the well-defined mass transport conditions of an RRDE system. 8 In this study, we have investigated the local pH of iridium oxide during OER in both unbuffered and buffered electrolytes under near-neutral to alkaline bulk conditions using the RRDE technique. Our results provide benchmarks for future studies on the local pH modulation effects of catalysts and insights into the impact of electrolyte composition on local pH. In combination with mass transport modelling, we further examined the limitations of this technique and provide suggestions for best practices. References X. Liu et al., Appl. Catal. B Environ., 331, 122715 (2023).Z. Li et al., Angew. Chemie Int. Ed., 62, e202217815 (2023).J. Guo et al., Nat. Energy, 8, 264–272 (2023).X. Zheng et al., Nat. Commun. 2023 141, 14, 1–13 (2023).X. Wang, C. Xu, M. Jaroniec, Y. Zheng, and S. Z. Qiao, Nat. Commun. 2019 101, 10, 1–8 (2019).H. Tan et al., Nat. Commun. 2022 131, 13, 1–9 (2022).Y. Yokoyama et al., Chem. Lett., 49, 195–198 (2020).W. J. Albery and E. J. Calvo, J. Chem. SOC., Faraday Trans. 1, 79, 2583–2596 (1983). Figure 1

Microstructure Modeling of Transport and Kinetics in Solid State Batteries with LLZO Solid Electrolyte Fabricated Using the Freeze-Tape-Casting Method

In traditional Li-ion batteries with liquid electrolyte, the transport of lithium ions in the electrolyte and lithium in the active material within a porous electrode are studied extensively. The continuum-scale modeling of these transport phenomena considers a homogenized simulation domain consisting of liquid electrolyte and solid active material with effective transport properties accounting for the heterogeneity [1]. There have been fewer studies that consider digitized versions of the experimentally imaged microstructure in continuum-scale modeling studies, particularly to study mechanics [2]. Despite of the computational challenges, there are inherent advantages in using fully resolved microstructure modeling to improve fundamental understanding of the relevant physical and chemical phenomena in porous electrodes, such as localized degradation and stress concentration. In the case of solid electrolytes, specifically scaffold-type LLZO solid electrolytes, microstructure modeling is of even more relevance, particularly to study anisotropic transport, localized degradation phenomena, stress and deformation leading to loss of contact, and chemo-mechanics. Thus far, microstructure modeling studies on experimentally obtained microstructure consisting of solid electrolyte and active material have been quite limited [3]. The studies that have explored this realm have employed voxel-based mesh to discretize the computation domain [3]. While these methods are sufficient proof of concept, the lack of precision in defining the interface separating active material and electrolyte when using voxel-based mesh provides a source of potentially significant numerical error. Without a highly resolved interface mesh, the total interfacial area increases artificially which leads to inaccuracies in calculations of local reaction rate and overpotential. A highly resolved, smooth interface is also necessary when simulating mechanical deformation and stress field in the microstructure. In the present investigation, we model mass transport and charge transport in the active material/electrolyte microstructure to simulate concentration and potential fields with varying mesh types in order to compare their effectiveness and characterize the error that can be attributed to the mesh type chosen, particularly in the case of voxel-based meshes. Additionally, we study the effect of microstructure domain length chosen in the two directions perpendicular to the shortest length (electrode thickness) as well as boundary condition formulation on the boundaries in these axes on the simulation results. The microstructures studied in this work are derived from the image stacks of the bi/trilayer LLZO solid electrolyte fabricated using freeze-tape-casting method [4]. Overall, the present work aims to develop a better understanding of the best practices in microstructure modeling, particularly when using microstructure image stacks obtained from fabricated samples.

Microelectrode-Based Diffusivity Measurements of Hydrogen in Molten 2LiF-BeF2

Detailed knowledge of the mass transport behavior of hydrogen isotopes in molten 2LiF-BeF2 salt (FLiBe) is essential to the design of new nuclear fusion technologies that make use of this molten salt to breed tritium to fuel the fusion reaction. However, typical studies of hydrogen transport using macroelectrodes are limited to solely measuring the permeability of an analyte—a property defined as the product of concentration squared and diffusivity. This challenge necessitates the development of microelectrodes capable of dynamically measuring diffusion coefficients when concentrations are variable. Unlike macroelectrodes, microelectrodes can measure diffusivity and concentration independently due to a steady-state current proportional to the product of diffusivity and concentration captured in addition to the Cottrellian current response.This steady-state current is established due to a continuously expanding diffusion layer from the electrode that cannot expand indefinitely within finite experimental setups. Therefore, COMSOL Multiphysics simulations mirroring experimental conditions were performed to validate the analytical mass transport model based on the solution of Fick’s Second Law in radial coordinates. These simulations employed a 2D axisymmetric model to examine the conditions under which the infinite bulk solution approximation is valid, confirming that our electrode design would yield true steady-state current responses indicative of radial diffusion.Platinum microelectrodes developed in this study served a dual purpose: they not only addressed previous limitations in high-temperature molten salt experimentation but also enabled dynamic measurements of both the diffusion coefficient and concentration of hydrogen in molten FLiBe introduced by lithium hydride. Square wave voltammetry and chronoamperometry were performed on a three-electrode cell using a platinum working microelectrode, a tungsten counter electrode, and a Ni/Ni2+ thermodynamic reference electrode. The successful measurement of hydrogen diffusivity in these experiments not only offers essential insights into molten FLiBe behavior but also sets the stage for future investigations into the effects of redox conditions, impurities, and equilibration time on tritium within nuclear fusion reactors.

Identification of Local Overpotentials and Their Spatial Distributions in Polymer Electrolyte Water Electrolyzers

Polymer electrolyte water electrolyzers (PEWEs) are pivotal in the transition to a clean energy economy, promising green and efficient hydrogen production. Understanding the complexities of overpotentials within PEWEs is crucial for optimizing their performance and efficiency1. For PEWEs to attain the highest possible system efficiency, considering a specific material set and operating parameters, meticulous design is imperative. The goal is to achieve a high reaction rate that is not only optimal but also uniform across the entire active surface area of the electrodes. This uniformity should ideally be maintained with minimal sensitivity to variations in operating conditions.This study focuses on the contribution of different overpotential categories and reveals their spatial variations through in-situ analysis to understand and overcome the issues caused by non-uniformity in reaction. Employing a segmented cell and printed circuit board (PCB) approach2, current density distribution (CDD) and distributed area-specific resistance (DASR) measurements are obtained, enabling a detailed examination of the mass transport overpotentials (as shown in Figure 1). Typically, in the fuel cell community, modeling mass transport limitations is thought of as diffusion-limited transport3. In the anode porous transport layer (PTL), oxygen accumulation (i.e. product transport limitation) can cause membrane dry-out and an increase in ASR4. The experimental results elucidate the intricate relationship between ohmic and mass transport losses, emphasizing the deep coupling induced by the two-phase nature of the system. Figure 1 shows that, as mass transport limitation grows, the highest increase in overpotential comes from mass transport-coupled ohmic losses. Beyond conventional diffusion limited mass transport losses, bubble dynamics significantly impact local hydration and ASR, highlighting the need for a holistic approach in device optimization5.This research contributes to the understanding of PEWE dynamics, providing a basis for informed engineering decisions. By unraveling the intricate interdependencies between overpotentials, this work empowers the efficient utilization of expensive catalyst materials. Moreover, it offers insights into mitigating the challenges associated with bubble removal, accomplishing this with lower pumping requirements that scale non-linearly. These insights enrich both theoretical understanding and are paramount for enhancing system efficiency and economic viability of PEWEs, thereby advancing the prospect of sustainable hydrogen production. Reference N. Danilovic and I. Zenyuk, Electrochem. Soc. Interface, 30 (2021).F. H. Roenning, A. Roy, D. S. Aaron, and M. M. Mench, J. Power Sources, 542, 231749 (2022) https://linkinghub.elsevier.com/retrieve/pii/S037877532200742X.A. Z. Weber et al., J. Electrochem. Soc., 161, F1254–F1299 (2014) https://iopscience.iop.org/article/10.1149/2.0751412jes.C. Immerz, B. Bensmann, P. Trinke, M. Suermann, and R. Hanke-Rauschenbach, J. Electrochem. Soc., 165, F1292–F1299 (2018).P. Satjaritanun et al., iScience, 23, 101783 (2020) https://doi.org/10.1016/j.isci.2020.101783. Figure 1

Numerical Simulation of Chemical Reactions’ Influence on Convective Heat Transfer in Hydrothermal Circulation Reaction Zones

Chemical reactions, mineral diffusion, and deposition are pivotal in understanding the mechanisms of mineral deposition and the formation of seafloor sulfides in the hydrothermal circulation process. To understand the formation process of anhydrite in submarine hydrothermal systems, a computational model that combined component transport and chemical reactions was established and simulated using the mass transport model. The deposition rate of calcium sulfate was defined, and the effects of factors such as porosity, ion concentration, and inflow velocity on the temperature field in the reaction zone were thoroughly investigated. The distribution of temperature, porosity, and velocity during the reaction process was obtained, allowing for the identification of the chemical reaction patterns of certain ions in the early stages of hydrothermal activity. The simulation revealed the occurrence of biochemical reactions between two types of ions, leading to their deposition on the solid framework of a porous medium. With the increase in inflow velocity and solute concentration, the average porosities of the porous medium decreased by 0.495% and 0.468%, respectively, which consequently altered the structure of the rock. Such findings contribute to the inference of formation and extinction mechanisms of seafloor crusts and hydrothermal chimneys.

Flow modeling and structural characterization in fungal pellets

Fungal pellets are hierarchical systems that can be found in an ample variety of applications. Modeling transport phenomena in this type of systems is a challenging but necessary task to provide knowledge-based processes that improve the outcome of their biotechnological applications. In this work, an upscaled model for total mass and momentum transport in fungal pellets is implemented and analyzed, using elements of the volume averaging and adjoint homogenization methods departing from the governing equations at the microscale in the intracellular and extracellular phases. The biomass is assumed to be composed of a non-Newtonian fluid and the organelles impervious to momentum transport are modeled as a rigid solid phase. The upscaled equations contain effective-medium coefficients, which are predicted from the solution of adjoint closure problems in a three-dimensional periodic domains representative of the microstructure. The construction of these domains was performed for Laccaria trichodermophora based on observations of actual biological structures. The upscaled model was validated with direct numerical simulations in homogeneous portions of the pellets core. It is shown that no significant differences are observed when the dolipores are open or closed to fluid flow. By comparing the predictions of the average velocity in the extracellular phase resulting from the upscaled model with those from the classical Darcy equation (i.e., assuming that the biomass is a solid phase) the contribution of the intracellular fluid phase was evidenced. This work sets the foundations for further studies dedicated to transport phenomena in this type of systems.

Indigo as a Low‐Cost Redox‐Active Sorbent for Electrochemically Mediated Carbon Capture

AbstractClimate change has driven the need for carbon capture to mitigate anthropogenic greenhouse gas emissions, yet current thermochemical methods are hampered by high energy intensities. Electrochemically mediated carbon capture (EMCC) utilizing redox‐active carbon dioxide (CO2) carriers is an attractive alternative for carbon capture. Here, an economical vat dye compound, indigo, is presented, which can reversibly capture and release CO2 upon electrochemical reduction and oxidation, respectively. Electrode and electrolyte engineering strategies are utilized to improve the reversibility and stability of indigo for EMCC. A bench‐scale prototypical fixed‐bed carbon capture device is constructed to demonstrate indigo's EMCC performance under various practically relevant conditions, such as simulated flue gas and extremely dilute sources pertinent to direct air capture. A hybrid sorbent electrode‐gas diffusion layer approach is revealed to alleviate CO2 mass transport limitations, achieving ≈80% CO2 capacity utilization under a 15% CO2 feed stream. Furthermore, a reactive‐diffusive mass transport model is developed to illustrate engineering approaches that can be universally applied to optimize fixed‐bed EMCC systems. This work advances the potential for a class of low‐cost sorbents for EMCC while underscoring the importance of molecular, electrolyte, materials, and device engineering strategies to enable high‐performance carbon capture.

Analysis of discharge performance and thermo-electric conversion efficiency in thermally regenerative ammonia-based flow battery with foam copper electrode

This paper established a numerical model of mass transport and electrochemical reaction coupling in porous media of thermally regenerative ammonia-based flow battery with foam copper electrode (TRAFB-FCE) for the first time. The effects of the structural parameters of the foam copper electrode on the power density, energy density, discharge capacity, and active species distribution of the battery were comprehensively studied based on the coupled numerical model. Special attention was paid to the selection strategy of the initial reactant concentration for the battery under different discharge conditions. The results suggest that increasing the porosity or thickness of the foam copper electrode causes the voltage and power density of the battery to first increase and then decrease, while the discharge capacity and energy density monotonically increase. Moreover, the battery should avoid discharging at current densities exceeding 720 A·m−2. When the discharge current density is less than 200 A·m−2, it is preferable to set the initial concentration of Cu2+ to 0.4 mol/L, while the discharge current density is in the range of 200–720 A·m−2, the initial concentration of Cu2+ is preferable to be 0.3 mol/L. When it discharges at about 5 % of its maximum power density, the Carnot-relative efficiency of this battery is comparable to the highest value currently reported in the field of liquid-based thermo-electric conversion achieved by the Thermal Regenerative Electrochemical Cycle (TREC) technology, and the power density of the former is 8.87 times that of the latter.

Sea and brackish water desalination through a novel PVDF-PTFE composite hydrophobic membrane by vacuum membrane distillation

The present study aims to evaluate the performance of porous hydrophobic Polyvinylidene fluoride − Polytetrafluoroethylene (PVDF-PTFE) composite membranes for desalination by vacuum membrane distillation (VMD) technique. The effect of operating parameters such as feed NaCl concentration (10,000 to 40,000 mg/L), feed temperature (50 °C to 80 °C), and downstream pressure (80 to 120 mmHg) on water permeation rate was studied. The increase in feed temperature enhanced the water permeation rate due to a rise in driving force across the membrane. For a constant downstream pressure of 80 mmHg, feed temperature of 80 °C and feed flow rate of 80 L/h, the membrane exhibited a maximum water flux of 3 kg/m2h with 99.86% salt rejection when aqueous NaCl concentration of 10,000 mg/L was charged as feed. Membrane characterization was performed using various analytical tools to determine physico-chemical properties such as pore size, structural elucidation, thermal stability, crystallinity, and hydrophobicity of the membrane material. Further, a temperature and concentration polarization coefficient-based analysis was performed by solving the mass and heat transport model equations using MATLAB software. The proposed research study promotes the application of VMD for recovering potable water from highly saline sea/brackish water and alleviates brine disposal issues.

Drug Distribution After Intravitreal Injection: A Mathematical Model.

Intravitreal injection of drugs is commonly used for treatment of chorioretinal ocular pathologies, such as age-related macular degeneration. Injection causes a transient increase in the intraocular volume and, consequently, of the intraocular pressure (IOP). The aim of this work is to investigate how intravitreal flow patterns generated during the post-injection eye deflation influence the transport and distribution of the injected drug. We present mathematical and computational models of fluid motion and mass transport in the vitreous chamber during the transient phase after injection, including the previously unexplored effects of globe deflation as ocular volume decreases. During eye globe deflation, significant fluid velocities are generated within the vitreous chamber, which can possibly contribute to drug transport. Pressure variations within the eye globe are small compared to IOP. Even if significant fluid velocities are generated in the vitreous chamber after drug injection, these are found to have negligible overall effect on drug distribution.

Toward sub-second solution exchange dynamics in flow reactors for liquid-phase transmission electron microscopy

Liquid-phase transmission electron microscopy is a burgeoning experimental technique for monitoring nanoscale dynamics in a liquid environment, increasingly employing microfluidic reactors to control the composition of the sample solution. Current challenges comprise fast mass transport dynamics inside the central nanochannel of the liquid cell, typically flow cells, and reliable fixation of the specimen in the limited imaging area. In this work, we present a liquid cell concept – the diffusion cell – that satisfies these seemingly contradictory requirements by providing additional on-chip bypasses to allow high convective transport around the nanochannel in which diffusive transport predominates. Diffusion cell prototypes are developed using numerical mass transport models and fabricated on the basis of existing two-chip setups. Important hydrodynamic parameters, i.e., the total flow resistance, the flow velocity in the imaging area, and the time constants of mixing, are improved by 2-3 orders of magnitude compared to existing setups. The solution replacement dynamics achieved within seconds already match the mixing timescales of many ex-situ scenarios, and further improvements are possible. Diffusion cells can be easily integrated into existing liquid-phase transmission electron microscopy workflows, provide correlation of results with ex-situ experiments, and can create additional research directions addressing fast nanoscale processes.

Phenol as proton shuttle and buffer for lithium-mediated ammonia electrosynthesis

Ammonia is a crucial component in the production of fertilizers and various nitrogen-based compounds. Now, the lithium-mediated nitrogen reduction reaction (Li-NRR) has emerged as a promising approach for ammonia synthesis at ambient conditions. The proton shuttle plays a critical role in the proton transfer process during Li-NRR. However, the structure-activity relationship and design principles for effective proton shuttles have not yet been established in practical Li-NRR systems. Here, we propose a general procedure for verifying a true proton shuttle and established design principles for effective proton shuttles. We systematically evaluate several classes of proton shuttles in a continuous-flow reactor with hydrogen oxidation at the anode. Among the tested proton shuttles, phenol exhibits the highest Faradaic efficiency of 72 ± 3% towards ammonia, surpassing that of ethanol, which has been commonly used so far. Experimental investigations including operando isotope-labelled mass spectrometry proved the proton-shuttling capability of phenol. Further mass transport modeling sheds light on the mechanism.

A steady two‐dimensional cylindrical mass transport model to determine binary gas diffusivities: A proof‐of‐concept theoretical development

AbstractBinary gas diffusivities, DABs, are key parameters in the analysis of many chemical engineering processes. Significant efforts to estimate diffusivities experimentally were made by Josef Stefan in the 19th century, who designed a column with liquid A at the bottom overlaid by a gas phase through which gas A diffused. His studies led to the determination of DABs for many gas pairs (B is commonly air), and to the development of alternate mass transport systems. The present proof‐of‐concept theory describes a steady two‐dimensional (2D) diffusion model consisting of a vertical cylinder thinly coated on its inner surfaces with either a sublimating or evaporating species A. The gas‐phase mass conservation partial differential equation is rendered dimensionless and solved by separation of variables. The theoretical molar flow rate of species A at the top of the cylinder, calculated analytically, can be equated to the experimental rate of mass loss from the coated walls, ultimately leading to DAB. The solution of the steady 2D diffusion model is explored in terms of the cylinder aspect ratio (height/radius), showing that the latter quantity can be tailored to obtain preselected sublimation rates of A. The interplay of the radial and axial diffusion mechanisms is also demonstrated as a function of geometry. Finally, the model's use in analyzing a projected sublimation/evaporation–diffusion experiment is discussed. This is the first time that a steady 2D diffusive transport model has been proposed to estimate DABs from experimental data.

Membrane Design Principles for Ion-Selective Electrodialysis: An Analysis for Li/Mg Separation.

Selective electrodialysis (ED) is a promising membrane-based process to separate Li+ from Mg2+, which is the most critical step for Li extraction from brine lakes. This study theoretically compares the ED-based Li/Mg separation performance of different monovalent selective cation exchange membranes (CEMs) and nanofiltration (NF) membranes at the coupon scale using a unified mass transport model, i.e., a solution-friction model. We demonstrated that monovalent selective CEMs with a dense surface thin film like a polyamide film are more effective in enhancing the Li/Mg separation performance than those with a loose but highly charged thin film. Polyamide film-coated CEMs when used in ED have a performance similar to that of polyamide-based NF membranes when used in NF. NF membranes, when expected to replace monovalent selective CEMs in ED for Li/Mg separation, will require a thin support layer with low tortuosity and high porosity to reduce the internal concentration polarization. The coupon-scale performance analysis and comparison provide new insights into the design of composite membranes used for ED-based selective ion-ion separation.

Experimental and numerical analysis of the effects of thermal degradation on carbon monoxide oxidation characteristics of a three-way catalyst

This work investigates oxygen-storage capacity (OSC) changes during thermal degradation in modern three-way catalysts. Two experiments are performed using catalysts with different degradation degrees to evaluate OSC and reaction rates. The CO2 production test, where CO and O2 are supplied at a constant temperature, shows decreased CO2 production with more degraded catalysts and reduced purification. The CO2 production test is conducted using transient temperature increases, showing that the maximum CO2 production temperature increases with catalyst degradation. The results reveal an increase in activation energy in the oxygen desorption reaction caused by thermal degradation progresses and a decrease in OSC, resulting in temperature increases in the oxygen storage reaction. In the surface reaction and mass transport model considering the 30 elementary reactions, the predicted results are well-validated for CO2 production, enabling good oxygen storage predictions based on actual data. These results can be used to predict OSC by formulating the changes in active site density and activation energy due to degradation.