Mass Transfer Kinetics Research Articles

Enhancing the parboiling of pantanal rice with ultrasound-assisted hydration: Mass transfer kinetics and bioactive properties

We evaluated the effects of ultrasound-assisted hydration (UH) on process time and concentration of phenolic compounds during the parboiling of native Pantanal paddy rice (Oryza latifolia) in comparison to conventional hydration (CH). This rice variety is produced by indigenous and riverside communities in the Pantanal biome. The UH increased water absorption, with a 58% average reduction in process time. Irreversible changes in the physical structure of rice (visible to the naked eye and in electronic microscopy images) confirmed that the grains parboiled faster. The Peleg model satisfactorily predicted the moisture uptake experimental data (R2 > 0.94). The CH significantly reduced the concentration of total phenolic compounds (TPC) (16–19%), total flavonoids (TF) (30–40%), and antioxidant capacity (AA) (20–39%) of paddy rice hydrated at 65–75 °C. In turn, the UH caused minimal loss of TPC (<1%), lower reduction of TF (∼7%) and AA (4–12%). The results indicate that ultrasound enhances parboiling processes by increasing mass transfer rates during hydration, consequently shortening processing time, reducing the energy demand, and preserving the nutritional quality of rice. The preservation of phenolic compounds during parboiling via ultrasound-assisted hydration (UH) is notable because the significant loss of these compounds in conventional hydration (CH). Therefore, parboiled rice falls short of being classified as a functional food. By preserving the phytochemicals during parboiling, the proposed process here may contribute to classifying Pantanal rice as a functional food, enabling income generation for local communities through the commercialization of parboiled native rice.

Experimental and Theoretical Investigation on the Extractive Mass Transfer of Eu3+ Ions Using Novel Amide Ligands in 1-Hexyl-3-methylimidazolium Bis(trifluoromethylsulfonyl)imide.

Novel amide ligands in the ionic liquid (1-hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide) were utilized for the liquid-liquid biphasic mass transfer of Eu3+ ions from aqueous acidic waste solution. The cation exchange mechanism was found to be operative with the formation of [Eu(NO3)2L3]+ species (L = 4-chloro-N-(1-methyl-1H-pyrazol-3-yl)picolinamide). However, the presence of an inner-sphere water molecule was revealed by density functional theory (DFT) calculations. The viscosity-induced slower kinetics was evidenced during mass transfer, which was improved by increasing temperature. The process was exothermic in nature. The improvement in the kinetics of extractive mass transfer at higher temperatures is evinced by a reduction in the distribution ratio value. The spontaneity of the reaction was evidenced through the negative Gibbs free energy value, whereas the process enhances the entropy of the system, probably by releasing water molecules at least partially during complexation. The structures of bare ligands and complexes have been optimized by using DFT calculations. A high value of complexation energy, solvation energy, and associated enthalpy and free energy change reveal the efficacy in binding Eu with O and N donor atoms. In addition, natural population analysis, atoms-in-molecules analysis, and energy decomposition analysis have been employed to explore the nature of bonding existing in Eu-O and Eu-N bonds.

Surface Engineering over Metal-Organic Framework Nanoarray to Realize Boosted and Sustained Urea Oxidation.

Facilitating C─N bond cleavage and promoting *COO desorption are essential yet challenging in urea oxidation reactions (UORs). Herein a novel interfacial coordination assembly protocol is established to modify the Co-phytate coordination complex on the Ni-based metal-organic framework (MOF) nanosheet array (CC/Ni-BDC@Co-PA) toward boosted and sustained UOR electrocatalysis. Comprehensive experimental and theoretical investigations unveil that surface Co-PA modification over Ni-BDC can manipulate the electronic state of Ni sites, and in situ evolved charge-redistributed surface can promote urea adsorption and the subsequent C─N bond cleavage. Impressively, Co-PA functionalization can impart a negatively charged catalyst surface with improved aerophobicity, not only weakening *COO adsorption and promoting CO2 departure, but also repelling CO3 2- approaching to deactivate Ni species, eventually alleviating CO2 poisoning and enhancing operational durability. Beyond that, improved hydrophilic and aerophobic characteristics would also contribute to better mass transfer kinetics. Consequently, CC/Ni-BDC@Co-PA exhibits prominent UOR performance with an ultralow potential of 1.300V versus RHE to attain 10mA cm-2 , a small Tafel slope of 45mV dec-1 , and strong durability, comparable to the best Ni-based electrocatalysts documented thus far. This work affords a novel paradigm to construct MOF-based materials for promoted and sustained UOR catalysis through elegant surface engineering based on a metal-PA complex.

Mask R-CNN based droplet detection in liquid–liquid systems, Part 2: Methodology for determining training and image processing parameter values improving droplet detection accuracy

Multiphase systems occur in many technical processes, e.g., crystallization, gas–liquid reaction, and liquid–liquid extraction. Operating such processes requires knowledge of fluid dynamics, mass transfer, and reaction kinetics that depend on the phase interface. The particle size distribution quantifies the phase interface of multiphase systems. Multiphase systems can contain solid particles, gas bubbles, or liquid droplets. Our previous work presented an automated and publicly accessible image processing method to determine droplet size distributions (DSD) in liquid–liquid systems based on Mask Region-Based Convolutional Neural Networks (MRCNN). In this work, we developed a methodology to determine training and image processing parameter values that improve the droplet detection accuracy of our MRCNN implementation with a low computational effort. Our methodology combines a sensitivity analysis to reduce the dimensions of training parameters of interest with a systematic final model selection approach based on characteristic training and image processing rating metrics. Applying our methodology to a database of four different image qualities results in a highly improved droplet detection accuracy over the entire droplet diameter range of a DSD. In comparison to the MRCNN models trained on the default hyperparameter values, the average relative error in characteristic DSD properties: minimum diameter, maximum diameter, and the number of detected droplets could be reduced from 6% to 3%, from 7% to 2%, and from 7% to 2%, respectively, keeping the relative error in the Sauter mean diameter constant at 3%. The presented methodology can be universally applied to individual image qualities improving the droplet detection accuracy of our MRCNN implementation. Thus, combining our methodology with the MRCNN implementation increases the reliability of process analysis and process control in liquid–liquid systems. Moreover, our MRCNN implementation and methodology can likely be easily transferred to several applications in which particle detection plays a significant role, e.g., crystallization (solid particles) and gas–liquid reaction (bubbles).

The Influence of Solvent Selection upon the Crystallizability and Nucleation Kinetics of Tolfenamic Acid Form II.

The influence of the solution environment on the solution thermodynamics, crystallizability, and nucleation of tolfenamic acid (TFA) in five different solvents (isopropanol, ethanol, methanol, toluene, and acetonitrile) is examined using an integrated workflow encompassing both experimental studies and intermolecular modeling. The solubility of TFA in isopropanol is found to be the highest, consistent with the strongest solvent-solute interactions, and a concomitantly higher than ideal solubility. The crystallizability is found to be highly dependent on the solvent type with the overall order being isopropanol < ethanol < methanol < toluene < acetonitrile with the widest solution metastable zone width in isopropanol (24.49 to 47.41 °C) and the narrowest in acetonitrile (8.23 to 16.17 °C). Nucleation is found to occur via progressive mechanism in all the solvents studied. The calculated nucleation parameters reveal a considerably higher interfacial tension and larger critical nucleus radius in the isopropanol solutions, indicating the higher energy barrier hindering nucleation and hence lowering the nucleation rate. This is supported by diffusion coefficient measurements which are lowest in isopropanol, highlighting the lower molecular diffusion in the bulk of solution compared to the other solutions. The TFA concentration and critical supersaturation at the crystallization onset is found to be directly correlated with TFA/isopropanol solutions having the highest values of solubility and critical supersaturation. Intermolecular modeling of solute-solvent interactions supports the experimental observations of the solubility and crystallizability, highlighting the importance of understanding solvent selection and solution state structure at the molecular level in directing the solubility, solute mass transfer, crystallizability, and nucleation kinetics.

Dynamic parameter estimation of the alkaline electrolysis system combining Bayesian inference and adaptive polynomial surrogate models

Utility-scale hydrogen production via alkaline electrolysis (AEL) is a promising pathway toward the decarbonization of the power, transportation, and chemical industries. The efficiency, load flexibility, and operational safety of the AEL system are subject to electrochemical, thermal, and mass transfer dynamics, and the corresponding parameters, including overvoltage coefficients, heat capacities and resistances of the stack and lye-gas separators, thickness and permeability of the diaphragm, etc. The community has developed many models to depict these dynamic behaviors. However, due to the lack of a comprehensive parameter estimation method, these models are generally tuned manually in industrial applications, which can be inaccurate and cannot fit their time-varying nature. To fill this gap, we present a fast and accurate parameter estimation method for the AEL system. Specifically, to address the difficulties of strong nonlinearity of the dynamic electrolyzer models and correlation between different parameters, a Bayesian inference-based Markov chain Monte Carlo method is proposed. To reduce the computing time for online estimation, data-driven adaptive polynomial surrogate models are established to replace repeated time-domain simulations of the electrolyzer model so that estimation can be finished within a few minutes. Experiments on a 5 Nm3/hr-rated AEL system validate the proposed method. Compared with the existing Kalman filter variants, the estimation error is reduced by at most 71.1% in terms of RMSE and NRMSE. In addition, the proposed method provides approaches to fault diagnosis and global sensitivity analysis for operating and designing AEL systems.

Comprehensive performance of a diethylenetriamine/2-diethylaminoethanol biphasic absorbent for CO2 capture

The CO2 capture process based on amine absorption–regeneration is currently the most widely used technology, and the performance of absorbent is the key to this process. Biphasic absorbents have attracted considerable interest because of their strong potential to reduce the regeneration energy consumption and equipment investment costs. The mixed solution of diethylenetriamine (DETA) and 2-diethylaminoethanol (DEEA) has been proven to be a biphasic absorbent, but there is still a lack of comprehensive performance evaluation data. In this study, the ratio of the DETA/DEEA solution was optimized as 2 M DETA + 3 M DEEA, and its phase separation property, reaction mechanism, mass transfer kinetics, and desorption thermodynamics were investigated under various conditions. The comprehensive performance of the solution was then evaluated by further analyzing its oxidative degradation, thermal degradation, and metal corrosion characteristics. On this basis, the capital cost and operation cost of using DETA/DEEA biphasic absorbent were analyzed. Under typical coal-fired flue gas (CO2 concentration 12%), because of the high CO2 absorption capacity and excellent phase separation property, the minimal desorption energy consumption of the DETA/DEEA absorbent decreased to 2.14 GJ/t CO2, a 43.7% decrease compared with that of 5 M monoethanolamine (MEA). Under the same experimental conditions, DETA/DEEA exhibited an oxidative degradation rate of only 2.71%, which was 20.7% of 5 M MEA. In addition, the metal corrosion rate of DETA/DEEA was one order of magnitude lower than that of 5 M MEA. However, under a high CO2 loading, its thermal degradation resistance needed to be improved, and it was clear that the rates of oxidative degradation, metal corrosion, and thermal degradation of the CO2 rich lower phase were higher than those of the CO2 lean upper phase. The capital cost and operational capture cost of the DETA/DEEA biphasic process were approximately $107.8/t CO2 and $31.6/t CO2, respectively, which were 2.5% and 36.4% lower than those of the MEA process. These findings provide a theoretical basis for the industrial application of DETA/DEEA.

Mass transfer kinetics of chemical oxygen demand removed from palm oil mill effluent in stirred cylinder batch reactor

Understanding the mechanisms and mass transfer kinetics of chemical oxygen demand (COD) removed from palm oil mill effluent (POME) could be one of the most important steps to achieve an effective design process of engineering acetogenic bacteria. The aim of this study was to evaluate the mass transfer kinetics of COD removed from POME in stirred cylinder batch reactor (SCBR) under an anaerobic environment using the modified mass transfer factor models. The performance of SCBR for the removal of COD increased with an electromagnetic field (EMF) exposure reaches 77.6% of its maximum efficiency when the operation of SCBR was set at the hydraulic retention time of 9 days. The variation of [kLa]d value has a trend of almost similar to that of [kLa]g value and is far higher than that of [kLa]f value to conclude that the resistance of mass transfer for the removal of COD from POME by the SCBR process depends on external mass transfer. The analysis of COD removal efficiency pursuant to the [kLa]d value provides a new insight on the performance of SCBR increased with an EMF exposure contributing to advanced treatment of COD from POME for achieving an effective process of engineering acetogenic bacteria.

A comparative study of electrochemical Brayton cycle and thermally regenerative electrochemical cycle

Both the emerging thermally regenerative electrochemical cycle (TREC) and electrochemical Brayton cycle (EBC) harvest low-grade heat by utilizing the temperature effect of electrode potential. Their key difference lies in the cycle configurations, the Stirling cycle and the Brayton cycle, respectively. Determining which cycle configuration performs better could indicate the direction of thermodynamics for further research. However, this remains an open question to be investigated. To address this, a performance comparison of EBC and TREC using KI/KI3 and K3Fe(CN)6/K4Fe(CN)6 solutions as electrolytes is conducted based on an improved system configuration and a two-dimensional model coupling mass transfer and electrode kinetics. Multi-objective optimization results show that there is no significant difference in performance between EBC and TREC. Under a given temperature difference of 50 °C, the power density and exergy efficiency of optimized EBC are respectively 5.28 W m−2 and 16.6%, compared with 5.93 W m−2 and 15.6% of optimized TREC. The corresponding temperature drops of heat sources are 14.49 °C and 12.26 °C, respectively, indicating that EBC is more suitable for heat sources with large temperature variations. The concentration overpotential is found to be the main contributor to entropy generation in both EBC and TREC besides heat transfer. Their power density and exergy efficiency can be further improved by approximately 50% and 40% by eliminating overpotentials, respectively. This study is expected to provide beneficial insights into the performance optimization and electrolyte improvement of EBC and TREC.

Porous 2D Catalyst Covers Improve Photoelectrochemical Water-Oxidation Performance.

Confined catalysis under the cover of 2D materials has emerged as a promising approach for achieving highly effective catalysts in various essential reactions. In this work, a porous cover structure is designed to boost the interfacial charge and mass transfer kinetics of 2D-covered catalysts. The improvement in catalytic performance is confirmed by the photoelectrochemical oxidation evolution reaction (OER) on a photoanode based on an n-Si substrate modified with a NiOx thin-film model electrocatalyst covered with a porous graphene (pGr) monolayer. Experimental results demonstrate that the pGr cover enhances the OER kinetics by balancing the charge and mass transfer at the photoanode and electrolyte interface compared to the intrinsic graphene cover and cover-free control samples. Theoretical investigations further corroborate that the pore edges of the pGr cover boost the intrinsic catalytic activity of active sites on NiOx by reducing the reaction overpotential. Furthermore, the optimized pores, which can be easily controlled by plasma bombardment, allow oxygen molecules produced in the OER to pass through without peeling off the pGr cover, thus ensuring the structural stability of the catalyst. This study highlights the significant role of the porous cover structure in 2D-covered catalysts and provides new insight into the design of high-performance catalysts.

Coupled characteristics and performance of heat pipe cooled reactor with closed Brayton cycle

Heat pipe cooled reactors with closed Brayton cycle (CBC) have the potential of achieving both high efficiency and high safety. However, the coupled characteristics and performance of CBC coupled with heat pipe reactors have not been well studied. Few works consider both the neutron dynamics in heat pipe cooled reactors and the dynamic heat and mass transfer in CBC. In this paper, a novel nuclear power system configuration, heat pipe cooled reactor with CBC, is proposed and comprehensively analyzed. A dynamic model is built based on the modular modeling idea, and verified using a Brayton cycle test bench. The proposed system has load following capability within certain motor speed, and its maximum thermal-electric energy conversion efficiency exceeds 20%. The dynamic charge amount control strategy is further proposed to improve efficiency. The maximum efficiency improvement is about 5% at 2kWe. The self-power-regulation and inherent passive safety of the reactor are verified through dynamic simulation. The power and temperature overshoots of the dynamic responses are selected as quantitative indicators of system dynamic performance. MAPs of the temperature and power overshoots for unit changes in output power are obtained, and can be used to evaluate the system safety during dynamic operations.

Anion chemistry in energy storage devices.

Anions serve as an essential component of electrolytes, whose effects have long been ignored. However, since the 2010s, we have seen a considerable increase of anion chemistry research in a range of energy storage devices, and it is now understood that anions can be well tuned to effectively improve the electrochemical performance of such devices in many aspects. In this Review, we discuss the roles of anion chemistry across various energy storage devices and clarify the correlations between anion properties and their performance indexes. We highlight the effects of anions on surface and interface chemistry, mass transfer kinetics and solvation sheath structure. Finally, we conclude with a perspective on the challenges and opportunities of anion chemistry for enhancing specific capacity, output voltage, cycling stability and anti-self-discharge ability of energy storage devices.

Kinetic Mass Transfer Behavior of Eu(III) in Nitrilotriacetamide-Impregnated Polymer-Coated Silica Particles

Abstract We investigated the distribution mechanism of Eu(III) in a single polymer-coated silica particle including nitrilotriacetamide (NTA) extractants known as HONTA and TOD2EHNTA. We studied the kinetic rate constants of the distribution process at various concentrations of NO3− (CNO3−) that were prepared using HNO3 and NaNO3 solutions. The rate-determining process during the distribution of Eu(III) was identified as the reaction process of Eu(III) for both extractants, that is, the reaction process of Eu(III) and two NTA molecules in the polymer layer of the silica particle. Furthermore, the reaction of Eu(III) with NO3− ions was found not to be involved in the rate-determining process. The forward (k1) and backward (k−1) reaction kinetic constants for the reaction between Eu(III) and two NTA molecules were determined to be k1 = (5.7 ± 2.2) × 102 M−2 s−1 and k−1 = (2.3 ± 4.4) × 10−4 s−1 for HONTA, and k1 = (6.5 ± 3.0) × 102 M−2 s−1 in the NaNO3 system and k−1 = (2.0 ± 1.5) × 10−4 s−1 in both solutions for TOD2EHNTA. The present study provides a valuable approach for the evaluation and enhancement of the functionality of ‘single extractant-impregnated polymer-coated silica particles’.

Fractal recognition and contact characteristics of ionic electroactive polymer interface based on microstructure analysis

Interface research is one of the basic topics in the study of mass transfer dynamics and actuation deformation processes. The main objective of this paper is to conduct in-depth research on the interface characteristics of ionic electroactive polymers, and this problem has not been studied to a large extent until now. The formation of the interface is closely related to the factors such as substrate pretreatment, the electroless plating process and the adsorption of ions. The interface has an irregular and self-similar microstructure, fractal theory can well analyze its intrinsic fractal characteristics. Based on the three-dimensional rough interface, the fractal characteristics of six two-dimensional cross-sections were identified. The fractal dimension, relative error, correlation coefficient and scale-free interval obtained by these six methods were quantitatively compared. The interfacial morphological characteristics of the ion-activated polymer were analyzed experimentally and the optimal fractal dimension calculation method was determined. A fractal contact model of the ionic electroactive polymer was developed and the calculation of the peel strength of the interface was proposed. The results show that RMSM is a feasible and effective method for the fractal characterization of the profiles of ionically electroactive polymers. The interfacial contact model based on fractal features can effectively characterize the peeling strength of the interface, which can provide a reference for later microscopic fractal studies on the theories of mass transfer process, actuation deformation and ion migration.

Mass transfer and color change kinetics of infrared drying of rose petals and its impact on physico‐chemical properties

AbstractThe present study investigated the effects of infrared and forced convective air at different infrared power levels (300, 400, and 500 W) and hot air temperatures (50, 57, and 65°C) on thin layer drying of rose petals. Infrared drying requires 50%–52% less time as compared with forced convective drying. The initial and final moisture content of rose petals were 84% (w.b.) and 4.5% (w.b.) respectively. The Midilli–Kucuk model gives a superior fit for both the drying methods followed by Avhad and Marchetti, and the Page model. The zero‐order, followed by the first‐order color kinetics model gives the best fitting for L*, a*, and b* values. Moisture diffusivity was increased by infrared power (1.7308 × 10−8 to 4.1495 × 10−8 m2/s) and hot air temperature (9.3715 × 10−9 to 1.1709 × 10−8 m2/s). The activation energy obtained for rose petals in hot air dryers and infrared dryers was 51.09 kJ/mol and 6.50 kW/kg, respectively. Samples dried at 500 W infrared drying for 18 min demonstrated higher retention of color, ascorbic acid (61.03 ± 2.6 mg/100 g), and anthocyanin content (295.75 ± 65.70 mg/100 g) in the rose petals.Practical ApplicationsSeveral drying techniques are available, though continuous efforts have been made to improve drying methods in terms of energy efficiency and product quality attributes. The present work has been carried out considering the dearth of information on the influence of infrared power/intensity on drying behavior and product quality of rose petals. Mass and color kinetics has been studied for a better understanding of the process along with rehydration, ascorbic acid and anthocyanin content. Our results showed that the infrared drying has significant industrial importance as it provides an efficient way to dry flowers, preserving their quality and extending their shelf life.

Mercury removal from aqueous media by aminated polyacrylonitrile beads impregnated with nano-urchin bismuth sulfide particles: Experimental and theoretical analysis under batch and continuous mode

The present study encompasses a thorough analysis of aqueous Hg (II) adsorption using aminated polyacrylonitrile beads incorporated with high-capacity surfactant assisted bismuth sulfide nanoparticles. The porous beads provided effective contact between aqueous Hg and the inorganic nano-adsorbent (PBS2) that was encapsulated in the matrix. The macro-sized beads served as suitable packing material for designing a fixed bed adsorption column for continuous mode analysis without significant pressure build up and offered an easy solid–liquid separation after treatment. A marginal negative zeta potential of the adsorbent beads improved the interaction with Hg2+ facilitating the sorption. The incorporation of amine groups into the polymeric bead surface via amination increased the adsorption capacity further from 83.30 mg/g to 130.00 mg/g (∼56.00%) at 303 K. The associated parameters of batch kinetics (effective pore diffusivity and mass transfer coefficient) were determined using a first principle-based model available in literature. Mercury was chemisorbed via synergistic lone pair interactions of S and N atoms with Hg, leading to formation of coordination bonds (Hg-S and Hg-N). An established mass transfer model was utilized to generate simulated breakthrough curves for the continuous analysis using synthetic feed. Additionally, the adsorption column showed comparable performance using both synthetic and real water samples (synthetically spiked) maintaining high selectivity. The optimized values of axial dispersion coefficient (Ez) and fixed bed mass transfer coefficient (kfb) were estimated and subsequently used for the scale up studies to predict column life. The adsorbent beads were regenerated using 0.05 M EDTA aqueous solution and showed good reusability (>95.00%) after 5 cycles of operation. Overall, this work highlights a reusable Hg adsorbent possessing good selectivity and capacity and simultaneously demonstrating real-field applicability.

Numerical study of thermal and concentration transport in Sisko ternary-nanofluid

The study of the behavior of generalized Newtonian fluid flows and heat transfer has practical implications. In this study, attention is paid to examining the dynamics of flow, heat, and mass transfer in a siskofluid containing multi-nanoparticles. The governing partial differential equations can be turned into ordinary differential equations using the transformations. FEM numerical scheme is used for the solutions of problems. A free study is performed, and the validity of the results is given. The solutions, that are convergent and mesh-free, are used to explore the facts regarding heat and mass. Both shear-thinning and shear-thickening fluids experience less skin friction as the material parameter is increased. The wall heat transfer rate in ternary nanofluids has the highest value in comparison with that in hybrid and mono nanofluids. Similarly, the wall mass flux in the case of ternary nanofluid is the highest in comparison with that in hybrid and mono nanofluid.

Characterization of freeze-dried ginger slices with carboxymethyl cellulose as potential coating material prior to osmotic dehydration

Edible coating prior to osmotic dehydration has been studied extensively to enhance the performance of drying in food products. In this study, the effectiveness of carboxymethyl cellulose (CMC) coating before osmotic dehydration of ginger slices on the mass transfer was studied. The samples were then dried using a freeze dryer, and the changes in colour, structural, and chemical components were determined. Coated ginger showed a minimised solute gain without affecting the water loss performance. The mass transfer kinetics were fitted successfully using the Magee model. After the freeze-drying process, the combination of CMC and osmotic dehydration as a pre-treatment influenced the colour properties and the microstructure without altering the functional groups. From these findings, it shows that CMC coated ginger slices and osmotic dehydration prior to freezedrying can be an alternative to meet the demands of current consumers, and thus be a promising route for obtaining dried ginger.

An Engineering Method of Analyzing the Dynamics of Mass Transfer during Concrete Corrosion Processes in Offshore Structures.

The environment of an underground structure is much more complex than the above-ground environment. Erosion processes are underway in soil and groundwater; groundwater seepage and soil pressure are also typical for underground environments. Alternating layers of dry and wet soil have a strong effect on concrete, and they reduce its durability. Corrosion of cement concretes is caused by the diffusion of free calcium hydroxide, located in the pores of concrete, from the volume of the cement stone to its surface, bordering on an aggressive environment, and the further transition of the substance through the phase boundary solid (concrete)-soil-aggressive environment (liquid). Due to the fact that all minerals in cement stone exist only in saturated or close-to-saturated solutions of calcium hydroxide, a decrease in the content of which in the pores of concrete as a result of mass transfer processes causes a change in the phase and thermodynamic equilibrium in the body of concrete and leads to the decomposition of highly basic compounds of cement stone and, consequently, to the deterioration of the mechanical properties of concrete (reduction in strength, modulus of elasticity, etc.). A mathematical model of mass transfer in a two-layer plate imitating the "reinforced concrete structure-layer of the soil-coastal marine area" system is proposed as a system of nonstationary partial derivative differential equations of the parabolic type with Newmann's boundary conditions inside the building and at the interface between the soil and the marine environment and with conjugating boundary conditions at the interface between the concrete and the soil. When the boundary problem of mass conductivity in the "concrete-soil" system is solved, expressions are obtained to determine the dynamics of the concentration profiles of the target component (calcium ions) in the volumes of the concrete and soil. As a result, one can select the optimum composition of concrete, having high anticorrosion properties, to extend the durability of the concrete constructions of offshore marine structures.

Tannic Acid-Mediated Layered Double Hydroxide Hybridizing PVDF Superwetting Catalytic Membranes Constructed via Ion Diffusion-Induced Interfacial Self-Assembly for Boosting Water Purification

It is a great challenge to fabricate superwetting catalytic membranes with intrinsic self-cleaning capacity for highly stable and effective water purification by simple, mild and energy-efficient manufacturing technologies. Herein, diffusion-induced interfacial self-assembly and polyphenol-mediated strengthening strategies were employed to fabricate tannic acid -mediated layered double hydroxide hybridizing PVDF superwetting catalytic membranes (named as TA@CoFe-LDH@PVDF). The simultaneous phase transformation/in-situ synthesis of CoFe-LDH nanosheets and subsequent coordination assembly with tannic acid (TA) was implemented. Superhydrophilic and underwater-superoleophobic properties were achieved through the cooperation effect of the rough microstructures of CoFe-LDH nanosheets and the strong hydration ability of TA molecules. This enabled efficient separation of various oil-in-water emulsions with more than 99 % separation efficiency and permeation flux up to 593.9 L m-2h−1 bar−1 in cross-flow filtration. Furthermore, due to the reducibility of TA molecules that promoted the Mn+1/Mn+ cycle, TA@CoFe-LDH@PVDF membrane exhibited high static degradation efficiency and kinetics (nearly 100 % in 5.0 min) toward methylene blue by PMS activation. The degradation rate constant (1.04 min−1) was 2.67 times compared to that of CoFe-LDH@PVDF. Surprisingly, it was found that the dynamic mass transfer process in the membrane significantly accelerated the catalytic kinetics, resulting in a degradation rate in dead-end filtration was 23.89 times higher than that under static conditions. Additionally, it was proved that assembled TA could inhibit and reduce metal ion leaching during the catalytic and separation process. This simple manufacturing process of multifunctional membranes with superior performances offers a high application potential in wastewater treatment.