Diffusive Mass Transfer Research Articles

Membrane role in heat and mass transfer resistance distribution and performance of hollow fiber membrane contactor for SGMD desalination

Hollow fiber membrane contactor (HFMC) is the core device of heat mass exchange between seawater solution and sweeping air in sweeping gas membrane distillation (SGMD) desalination. In order to reveal the distribution of heat and mass transfer resistance on feed solution side, porous membrane side and sweeping air side, a mathematical model considering the simultaneous heat mass transfer and water vapor diffusion mechanism in the membrane pores was established for the cross-flow HFMC. The simulation results of the model were compared with experimental results and literature results. Comparison shows that the deviation of simulation results of the model is less than 13.4 %, which verifies the accuracy and reliability of the simulation results. Influences of the main structural characteristics of porous membrane on the resistance distribution of heat and mass transfer, efficiency and membrane flux were explored. Air side dominates the heat transfer process, while the membrane side accounts for less than 39 % of the total heat transfer resistance for the main range of membrane microstructure parameters investigated. The mass transfer is controlled by the porous membrane except for thin membrane with a thickness of less than 100 μm. Membranes with porosity above 0.8 and as thin as possible can achieve better mass transfer efficiency and freshwater flux. Increasing mean pore diameter has a strong promotion effect on the increase of membrane flux before it reaches 150 nm, and beyond this critical value, the water vapor diffusion mechanism changes from Knudsen collision to molecular collision. Effects of different operating parameters and membrane microstructure parameters on air temperature distribution and humidity distribution were also analyzed.

Mechanistic Understanding of Sieving Lithium Ions Using a Biobased Sorbent Technology for Sustainable Lithium Reclamation and Cleansing Brines.

Low-cost environmentally benign materials that can be produced in a large scale to extract lithium from brine resources could drive the lithium market toward a clean technology with high lithium recovery and production. Herein, we have investigated the utilization of a novel, environmentally benign, and low-cost biobased sorbent for the extraction of lithium from lithium-rich solutions. This biobased molecular sieving sorbent, iron(III)-tannate (Fe(III)-TA), belongs to a novel class of coordination polymer frameworks derived from a natural polyphenol-tannic acid (TA)-coordinated with iron(III) metal cations. Its lithium adsorption and kinetic isotherm studies conducted using lithium-rich aqueous solutions confirm the sorbent's dual function for lithium sieving via physisorption, chemisorption, and mass transfer diffusion processes. The adsorption equilibrium and kinetic isotherm models combined with the external and internal mass transfer diffusion models reveal a mechanistic pathway for lithium-ion adsorption. Aiding by forming a fluid film for external mass transfer diffusion of lithium ions, analytes adsorb onto the sorbent surface via physisorption and chemisorption followed by the internal mass transfer diffusion, occupying lithium ions in the sorbent's pores. The lithium adsorption efficiency studies conducted for brines with different concentrations of interference alkali and alkaline cations evidence that the sorbent's affinity for lithium ions strongly depends on the analyte concentration. The results evidence that the sorbent has the ability to lower the brine's salinity and significantly reduces the ratios of Mg/Li and Ca/Li by 4-fold and 10-fold, respectively, yielding lithium-rich solutions. Thus, implementing this innovative biobased sorbent technology as an add-in step into traditional lithium extraction and refining processes, one can design a cost-effective pathway to yield lithium-rich leachate by reducing the Mg/Li and Ca/Li ratio. Nonetheless, the present work demonstrates that Fe(III)-tannate is an effective multifunctional sorbent for sieving lithium from lithium-rich aqueous solutions as well as for desalinating brine resources to recover usable water. Thus, this biobased sorbent offers the possibility of effective application of lithium reclamation and remediation of brine, mitigating the environmental impact of brine discharge and large volume of freshwater usage for lithium extraction and refining.

A novel multiphase and multicomponent model for simulating molecular diffusion in shale oil reservoirs with complex fracture networks

Molecular diffusion is critical for enhanced oil recovery (EOR) in shale oil reservoirs with complex fracture networks. Understanding the influence of fractures on diffusive mass transfer is crucial for predicting oil recovery and remaining oil distribution. Diffusive mass transfer between fractures and matrix is critical in comprehensively and effectively simulating molecular diffusion. Resolution of matrix cells significantly affects diffusion accuracy at the fracture–matrix interface. Low resolution results in multiple fractures in the same matrix cell, leading to decreased precision in calculating mass transfer by conventional methods. To address this, a novel multiphase and multicomponent model is proposed. The new model integrating the consideration of fracture spacing modifies molecular diffusion transmissibility between fracture and matrix in an embedded discrete fracture model. The discretization employs the two-point flux approximation in the finite-volume method. Validation compares the coarser mesh to the finest grid as a reliable reference. Results show the proposed model accurately captures diffusive mass transfer in a coarser mesh. Modified models study molecular diffusion's effects on EOR in shale oil reservoirs with complex fracture networks by CO2 huff and puff. Results indicate that increasing injection rates cannot improve oil recovery under extremely low porosity and permeability. Molecular diffusion facilitates CO2 penetration into the formation. This expands the swept CO2 volume and increases both volume expansion and formation energy. In addition, the light and heavy components of the crude oil are diffused into the fractures and eventually produced, which reduces gas production in the case of diffusion.

Physics-based modeling of the effective gas transport properties of single jersey knitted fabrics based on images

Physics-based modeling of the effective gas transport properties of single jersey knitted fabrics based on images

Mechanical insights into desulfurization by peroxymonosulfate oxidation via a non-reactive oxygen species pathway

Air pollution by sulfur dioxide (SO2) remains a pressing concern for both the environment and human health. Desulfurization enhanced by persulfate based advanced oxidation processes (PS-AOPs) has been proven to be a feasible method. However, the inherent contradiction between the rapid diffusion mass transfer of SO2 in the “gas-liquid-gas” phase and the limited lifespan of reactive oxygen species (ROS) can not be ignored. Excessive investment in PS is required to sustainably generate ROS to achieve continuous desulfurization performance, which may lead to excessive PS consumption. To address this issue, whether PS can achieve the oxidation absorption of SO2 via a non-reactive oxygen species pathway was investigated. Experimental and computational results demonstrated that peroxymonosulfate (PMS) instead of peroxydisulfate (PDS) had a great SO2 removal performance, the utilization of PS could be effectively achieved by maintaining a 1:1 molar ratio of PMS and removed SO2. The presence of HOO bonds in the PMS introduced a partial positive charge to the oxygen atom, making the PMS polar and more susceptible to be attacked by the nucleophile HSO3-. So SO2 underwent a series of processes including dissolution, dissociation, one-oxygen atom transfer, and ionization before ultimately being converted into SO42- ions, effectively achieving its removal from flue gas. This study may presents a novel approach for achieving high-efficiency flue gas desulfurization.

Equilibrium Volumetric Experiment Apparatus Review for Mixed-Gas Adsorption

This research aim is to identify the additional equipment and system functions required to set up an experimental system for mixed-gas dynamic adsorption using equilibrium volumetric technique. As well as to review the process variables’ effect on adsorption capability, while using an experimental system apparatus consisting of an equipment previously mentioned in selected papers. In this study, the selected experimental research on mixed-gas adsorption is reviewed, which used the equilibrium volumetric method. The relationship between process variables and adsorption capacity, kinetics, and diffusional mass transfer are observed. The correlation between adsorbate concentration, adsorption temperature, pressure during adsorption process, flow rate of adsorbate and adsorption capacity indicates that using additional equipment in the experimental mixed-gas dynamic adsorption is feasible. The correlation between these parameters is in agreement with common understanding of adsorption. The predicted adsorption capacity and analysis of kinetics adsorption are consistent with the model. The diffusional mass transfer could explain a diffusional step of the adsorbate onto the adsorbent.

Effect of Variable Viscosity on Entropy Generation Analysis Due to Graphene Oxide Nanofluid Convective Flow in Concentric Cylinders

Aggregated studies of graphene nanoparticles is important for the effective utilization of their striking thermophysical properties and extensive industrial applications. This investigation is one such computational study to explore the flow of graphene oxide nanofluids with temperature dependant viscosity between two concentric cylinders. Buongiorno model is used to develop the flow of graphene nanofluids including the impacts of Soret and Dufour effects and the effects of nanoparticle characteristics such as thermophoresis and Brownian motion. The modelled equations are transformed and are numerically solved using linearization method together with Chebyshev’s spectral collocation method under convective conditions. The impacts of embedded parameters on temperature, concentration and skin friction profiles of the chosen nanofluid and their consequent impacts on the predominant cause for the generated entropy are studied. From the tabulated values of Nusselt number and Sherwood number, it is observed that convective heat transfer can be enhanced by thermal Biot number whereas Soret number enhances diffusive mass transfer and variable viscosity parameter preferably reduces the skin friction. A comparison table is presented and it shows that the values obtained from the present method are in good agreement with existing literature. Also, the obtained results are depicted and interpreted in detail. Furthermore, entropy generation is analysed and its irreversibilty is calculated.

Surface and mass transfer kinetic and equilibrium modeling of Pb(II) ions adsorption on hydroxyapatite scaffold: Batch and fixed-bed column studies

This paper presents the results of a study on removal of Pb2+ ions by using hydroxyapatite (HAP) scaffold prepared by replication method. To this aim, the effects of suspension solid content and polymeric foam density on the properties of ceramic foam were investigated. The mean total porosity and apparent porosity of the optimized scaffolds were 92.67 % and 92.04 %, respectively. The Taguchi method was performed for designing batch experiments by considering three controllable variables, namely: (1) initial pH of the solution, (2) initial concentration of Pb2+ ions (C0), and (3) circulating rate of the solution (Ǭ), on the removal efficiency of Pb2+ ions as the response. Based on the obtained results from the ANOVA analysis, the removal efficiency of Pb2+ ions was mainly affected by the initial pH of the solution (90.88 %). The highest removal efficiency (99.1 %) of Pb2+ ions was obtained by optimizing the process under operating conditions of pH = 3.5, C0 = 50 mg.L−1, and Ǭ= 0.5 L.min−1. The Langmuir isotherm model with good accuracy was fitted to the equilibrium results, and the maximum adsorption capacity of 106.38 mg.g−1 was predicted for the HAP scaffold adsorbent. Kinetic studies showed that the mass transfer diffusion steps in the external film and inside the pores are fast, being the adsorption on the adsorbent sites the rate-limiting step of the kinetics, what is plausible given the high porosity of the material. Also, the primary mechanism for Pb2+ adsorption using HAP scaffold adsorbents was found to be dissolution-precipitation. The fixed-bed column adsorption experiments performed under the predicted optimum conditions of batch experiments. In comparison to the powder adsorbents tested in fixed-bed column, this adsorbent presents several advantages. These include the elimination of the requirement for mechanical separation of the shaped adsorbent from the solution after adsorption, prevention of bed clogging, and its high surface area derived from interconnected open pores.

Unlocking exceptional diffusion of porous Ni@SiO2 nanocapsule catalysts for enhanced dry reforming of methane

This paper introduces innovative porous Ni@SiO2 nanocapsule catalysts for high-temperature dry reforming of methane, synthesized through a selective etching method in a mild alkaline solution with varying CTAB concentrations. While core-shell catalysts have been proven effective in addressing issues like active metal sintering and coking, their dense inert oxide shells can impede intrinsic kinetics and hinder gas diffusion. The optimized catalyst, M-NSNC-2, showcases exceptional performance, featuring small Ni nanoparticles (5.3 nm) within a porous SiO2 nanocapsule (>900 m2g−1). M-NSNC-2 demonstrates outstanding methane conversion (>82%), stability (50 hours), and resistance to sintering, agglomeration, and higher-ordered carbon deposition. In comparison to dense Ni@SiO2 nanocapsules (NSNC), M-NSNC-2 exhibits superior performance with nearly 13-fold enhanced mass transfer diffusivity. Additionally, the porous Ni@SiO2 nanocapsule catalyst exhibits an apparent CH4 activation energy of 67.9 kJ/mol at a kinetic regime of 1800,000 mL gcat−1h−1, emphasizing its efficacy in catalyzing dry reforming of methane.

Hypercrosslinked waste polycarbonate to remove heavy metal contaminants from wastewater

In this research, the waste polycarbonate was hypercrosslinked during the Friedel–Crafts reaction to eliminate metallic ions from the wastewater solution. The experiments for inspecting the adsorption behavior of lead and cadmium ions were conducted at the initial concentration of 20–100 mg/L, contact time of 10–80 min, temperature of 20–80 °C, and pH of 6–11. The isotherm, kinetic, and thermodynamic models have been used to explain the behavior of the metal ions removal process. The correlation coefficient and adsorption capacity of the kinetic model for cadmium ion have obtained 0.995 and 160.183 mg/g, respectively, and the correlation coefficient and adsorption capacity of the kinetic model for lead ion has obtained 0.998 and 160.53 mg/g, respectively, which declared that the cascade was not monolayer. The correlation coefficient of the Freundlich is calculated at 0.995 and 0.998 for Cd and Pb, respectively, indicating the resin plane was not homogenized. The n constant for cadmium and lead ions has been calculated at 2.060 and 1.836, respectively, confirming that the resin is not homogenized, and the process has performed well. Afterward, the values of enthalpy and Gibbs free energy changes were obtained at − 7.68 kJ/mol and − 0.0231 kJ/mol.K for lead ions, respectively, which implies the exothermic and spontaneous state of the process. The values of enthalpy and Gibbs free energy changes have been obtained at − 6.62 kJ/mol and − 0.0204 kJ/mol.K for cadmium ions, respectively, which implies the exothermic and spontaneous nature of the adsorption. Also, the optimal empirical conditions for lead and cadmium ions have been found at a time of 60 min, temperature of 20 °C, initial concentration of 100 mg/L, and pH of 10. At a time of 45 min, the diffusion coefficient and mass transfer coefficient for lead ions have been calculated at 0.1269 × 1020 m2/s and 0.2028 × 1015 m/s, respectively. In addition, at a time of 45 min, the diffusion coefficient and mass transfer coefficient for cadmium ions have been calculated at 0.1463 × 1020 m2/s and 0.1054 × 1015 m/s, respectively. Moreover, the mechanism study explains that the C–O–C and C–H in the aromatic groups have a crucial aspect in the bond formation among metallic ions and resin.

The aerobic biofilm on naphthalene as the carbon source: Growth, biodegradability, and mass transfer-diffusion kinetics

Stable biofilm formation and substrate loss during mass transfer are key factors affecting the treatment efficiency of biofilm systems. In this research, a comprehensive study was conducted on the growth, biodegradability and mass transfer process of Ochrobactrum anthropi Na-B biofilm. The results showed that the biofilm mass increased at different rates before tending to stabilize under the optimal conditions. The growth process was divided into six phases and the biofilm which in logarithmic phase showed the highest microbial activity and the best degradation performance, the average removal of 30 mg/L naphthalene reached 61% after 24 h under pH= 7.0, T = 30 °C, and r = 100 rpm. With the growth and maturation of biofilm, microcolonies began to form on the membrane carrier surface and finally presented a dense, continuous and three-dimensional reticular biofilm structure. Furthermore, the mass transfer performance of biofilm declined with the growth of biofilm, the increase of initial naphthalene concentration and the decrease of temperature. The Mass Transfer-Diffusion kinetics of biofilm further indicated that in the range of 5–30 mg/L naphthalene concentration, the internal diffusion resistance in the biofilm was negligible and the mass transfer process of biofilm was mainly restricted by the external mass transfer resistance and biological reaction.

Heating-induced release of trapped bubbles from dead-end pore throats filled with nonvolatile liquid

The release of trapped bubbles from dead-end pore throats filled with nonvolatile liquid has widespread applications in gas–liquid reactors, radiators, foam flooding, ceramic sintering, and droplet microcarriers. As conventional pressure-driven flow cannot induce the transport of bubbles in dead-end pores, this paper explores the possibility of using heating to control the release of bubbles from dead-end pore throats. Visualization experiments of the microfluidics within a dead-end pore throat structure are conducted to address the release process of bubbles during heating. An increase in temperature causes dissolved gas in the solution to be transferred to the bubble, which enhances the bubble pressure and enables the bubble to pass through the pore throat. We analyze the effects of the initial bubble radius and initial temperature on the critical temperature Tcr at which the bubble passes through the pore throat. A larger initial radius does not necessarily make it more difficult for the bubble to pass through the throat, but there is a critical radius above which any increase in radius produces a lower value of Tcr. A theoretical model considering diffusion mass transfer, capillary forces, and corner film flows is developed, and this model is found to be in good agreement with the experimental results. Finally, we obtain three dimensionless numbers that can be used to predict Tcr. Our work provides guidance for the effective regulation of diffusive growth and the heating-induced release of bubbles from dead-end pore throats.

Effect of TiO2 on the Microstructure and Flexural Strength of Lunar Regolith Simulant

Lunar regolith is the preferred material for lunar base construction using in situ resource utilization technology. The TiO2 variations in lunar regolith collected from different locations significantly impact its suitability as a construction material. Therefore, it is crucial to investigate the effects of TiO2 on the properties of lunar regolith. This study aims to evaluate the influence of TiO2 content and sintering temperature on phase transformation, microstructure, and macroscopic properties (e.g., the shrinkage rate, mechanical properties, and relative density) of lunar regolith simulant samples (CUG-1A). The flexural strength and relative density of the sample with a TiO2 content of 6 wt% sintered at 1100 °C reached 136.66 ± 4.92 MPa and 91.06%, which were 65% and 12.28% higher than those of the sample not doped with TiO2, respectively. The experiment demonstrated that the doped TiO2 not only reacted with Fe to form pseudobrookite (Fe2TiO5) but also effectively reduced the viscosity of the glass phase during heat treatment. As the sintering temperature increased, the particles underwent a gradual melting process, leading to a higher proportion of the liquid phase. The higher liquid-phase content had a positive impact on the diffusion of mass transfer, causing the voids and gaps between particles to shrink. This shrinkage resulted in greater density and, ultimately, improved the mechanical properties of the material.

Hierarchically Porous Covalent Organic Frameworks: Synthesis Methods and Applications.

Covalent organic frameworks (COFs) with high porosity have garnered considerable interest for various applications owing to their robust and customizable structure. However, conventional COFs are hindered by their narrow pore size, which poses limitations for applications such as heterogeneous catalysis and guest delivery that typically involve large molecules. The development of hierarchically porous COF (HP-COF), featuring a multi-scale aperture distribution, offers a promising solution by significantly enhancing the diffusion capacity and mass transfer for larger molecules. This review focuses on the recent advances in the synthesis strategies of HP-COF materials, including topological structure design, in-situ templating, monolithic COF synthesis, defect engineering, and crystalline self-transformation. The specific operational principles and affecting factors in the synthesis process are summarized and discussed, along with the applications of HP-COFs in heterogeneous catalysis, toxic component treatment, optoelectronics, and the biomedical field. Overall, this review builds a bridge to understand HP-COFs and provides guidance for further development of them on synthesis strategies and applications.

Heat and Mass Transfer on Unsteady MHD Chemically Reacting Rotating Flow of Jeffrey Fluid Past an Inclined Plates under the Impact of Hall Current, Diffusion Thermo and Radiation Absorption

An analytical solution for two dimensional unsteady MHD free convective double diffusive heat and mass transfer rotating flow of viscous incompressible optically thin non Newtonian fluid (jeffrey fluid) past a semi-infinite porous plate in the presence of generation of heat absorption with hall current, radiation absorption and Dufour effects are presented in this paper. Lorentz force is applied perpendicular direction to the plate with a first-order chemical reaction. The governing PDEs transformed into ODEs by applying the perturbation technique. The effects of various physical parameters like Hall current, heat absorption, radiation parameter, radiation absorption parameter, Grashof number, modified Grashof number, Dufour effect, magnetic field parameter, inclined angle, chemical reaction parameter, etc., are studied with graphically. Temperature profile is increased by raising the values of Dufour effect, radiation absorption parameter and reverse effect of the heat absorption parameter and also concentration profile distribution is downfall by raising the values of Schmited number, chemical reaction parameter. Another significant finding of the current study is that the numerical data are displayed with the use of Matlab programmes to investigate the outcomes of the skin friction solution. the rate of heat and mass transfer at the wall rising under the influence of Dufour effect. Tables, graphs, and reports can be used to display the impact of all pertinent parameters.

Modeling the Structure and Diffusion of Porous Layers

The aim of this work is to develop an adsorber with a fixed bed of adsorbent and a mathematical model of the adsorption bed. On the basis of the theory of fractal clusters, an equation for calculating the layer porosity that takes into account the average cluster radius, the fractal dimension of the cluster structure and the anisotropy index of the adsorbent layer is proposed. The adsorption mechanism in the layer was established, and the proportionality coefficients were estimated based on the tetrahedral packing of grains in the layer. Based on the analysis of the movement of the carrier through the adsorption layer and its deformation, an equation that describes the change in the porosity of the granular layer when the water flow moves through it, depending on the proportionality coefficients, is proposed. An equation that made it possible to calculate the change in the porosity of the layer in comparison with the porosity of the stationary stacking was obtained. An effective design for the adsorber that made it possible to increase the efficiency of using the structure of porous adsorption layers was developed. Equations of the heat and mass transfer taking into account the granule shape coefficient, effective diffusion coefficient and mass transfer coefficient were derived. These equations establish the relationship between the average distance between active centers on the adsorption surface and the degree of filling of the adsorption surface with the adsorbed component.

Quantifying Interseismic Volume Strain from Chemical Mass‐Balance Analysis in Tectonic Mélanges

AbstractEstimating interseismic deformation in subduction fault zones can offer insights into the frequency and magnitude of megathrust earthquakes. Diffusive mass transfer is a significant mechanism of strain during interseismic periods along the plate interface, observed through the pervasive scaly fabrics and mineral veins in tectonic mélanges of ancient accretionary prisms. The dissolution of fluid‐mobile elements (e.g., Si and Large‐Ion Lithophile Elements) along scaly folia and subsequent reprecipitation as veins lead to the enrichment of fluid‐immobile elements (e.g., Ti and High Field Strength Elements) in scaly fabrics. The kinetics of dissolution‐precipitation is temperature‐dependent, suggesting depth‐dependent mass transfer along subduction interfaces. Here, we evaluate the magnitudes of volume strain in a suite of mélange samples that span peak metamorphic temperatures of 130–340°C. Micro‐chemical analysis shows that the depletion of fluid‐mobile elements and enrichment of fluid‐immobile elements in scaly fabrics increases with temperature. Assuming the conservation of Ti, we apply mass balance constraints to calculate the volumetric strain in scaly fabrics. Results indicate average volumetric strain of 28% and 95% in the individual scaly fabrics of the Lower Mugi and Makimine mélanges in Japan, which record temperatures near the updip and downdip isotherms bounding the seismogenic zone, respectively. To determine the total volume strain within an area of interest, we integrate the amount of volume loss along individual microstructures across the network using image analyses, which ranges from 3% to 14% for the mélanges. Our approach demonstrates the potential to fully describe the deformation related to mass transfer by connecting characterization in different scales with geochemical analyses.

Dissolution characteristics of TiC0.3N0.7 in low-carbon and safe blast furnace hearth

Investigating the presence of a Ti(C,N) protective layer in molten iron is of great significance for achieving low carbon and safe production in blast furnaces. This study focuses on analyzing the high temperature dissolution experiment of TiC0.3N0.7 in molten iron to elucidate the kinetics and mechanisms involved, as well as strategies for regulating its dissolution. The results reveal that the dissolution reaction of TiC0.3N0.7 is predominantly influenced by the temperature and flow speed of the molten iron. The dissolution process can be categorized into two stages: dissolution reaction and physical penetration. Diffusion mass transfer is the dominant factor controlling the dissolution of TiC0.3N0.7, with an apparent activation energy of 60.15 kJ/mol. Upon contact with molten iron, dendritic penetration of TiC0.3N0.7 particles occurs, starting from the edges. To enhance the stable presence of TiC0.3N0.7, recommendations include reinforcing furnace cylinder cooling, reducing the heat transfer coefficient of the blast furnace hearth's resistant material, increasing the carbon content of the molten iron, and decreasing the sulfur content of the molten iron.

Сферические субмикронные порошки с нано-поликристаллической субструктурой — перспективное сырье для получения мелкозернистой высокоплотной керамики (обзор)

The review reflects the unique properties and possible areas of application of submicron non-agglomerating powders from refractory oxides obtained by aerosol-spray pyrolysis. An analysis of the experimental results obtained by researchers at different times convincingly proves the promise of using aerosol nanostructured submicron spherical powders to obtain ceramic materials with a high-density, uniform fine-grained structure without pores. The uniqueness of aerosol powders is due to the presence in the particles of the nano-polycrystalline substructure of a developed network of inter-grain boundaries, which during sintering has a significant impact on the efficiency of diffusion mass transfer and contributes to an increase in the speed and completeness of pores overgrowth. Aerosol powders acquire these properties through the use of ultrasonic spray pyrolysis, where equilibrium physicochemical processes occur in ultra-small local volumes of aerosol droplets, ensuring a high degree of uniformity of the resulting powder. The formed ultrathin substructure of aerosol powders ensures their full sintering at low temperatures, making it possible to obtain high-density ceramic materials with extreme physical and mechanical characteristics. The practical use of nanostructured aerosol powders does not require the use of preliminary preparation operations (grinding-grinding, classification, purification from impurities, etc.) and, unlike ultrafine powders, they are easily molded using traditional methods of powder technology (uniaxial pressing, hot casting, etc.).

Investigation of interfacial mass transfer phenomena applying non-invasive Raman imaging and density gradient theory

This study presents a novel non-invasive Raman measurement setup for investigating diffusion and mass transfer processes at liquid/liquid interfaces, based on a photometric setup utilizing customized photon multiplier (CPMs). The results highlight the effectiveness, reliability and applicability of this setup in visualizing and analyzing acetone mass transfer across the aqueous-organic interface. The study focuses on the liquid/liquid extraction of acetone from the aqueous phase into the organic phase, using toluene as the organic solvent. The study's key findings indicate that – in the absence of forced convection – mass transfer across the interface is not the limiting factor in the extraction process; instead, diffusion in the bulk phase takes precedence. Acetone's rapid local transport from the aqueous to the organic phase is observed, with a temporary concentration minimum on the aqueous side of the interface. In the organic phase, local equilibrium is reached near the interface first, only after which acetone disperses into the bulk phase. This dual mechanism—fast interfacial mass transfer and slower bulk-phase diffusion—marks a significant feature of the considered extraction process, which were further substantiated by dynamic concentration gradient theory simulations. The research further demonstrates the feasibility of upscaling interfacial mass transfer simulations using adaptive meshing. However, macroscopic effects like induced convection challenge purely diffusive models. The simulations confirm rapid enrichment of acetone at the interface, followed by slower mass transfer through the interface and bulk phase diffusion, consistent with the experimental data. Experimental and modeled results align well with literature data for liquid/liquid extraction, thereby validating the accuracy of the presented novel diffusion measurement setup and demonstrating its potential to investigate mass transfer phenomena near liquid/liquid interfaces.