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The removal of lambda-cyhalothrin (LCT) from an aqueous solution was investigated and evaluated by the emulsion liquid membrane (ELM) technique using Span 80 as the surfactant, n-hexane as the diluent, and HCl as the stripping phase. Crucial parameters influencing the stability of emulsions through breakage and extraction efficiency, such as emulsification time, surfactant concentration, contact time, emulsification speed, internal phase concentration, external phase-to-membrane volume ratio, effect of feed pH, mixing speed, and internal phase-to-membrane volume ratio were investigated. The results indicated that 94.7% of LCT could be extracted at a contact time of 8 min under ideal experimental conditions, with a low membrane breakage of 0.48%. Furthermore, the extraction kinetics were investigated and the mass transfer coefficient was estimated. Based on the obtained results, the ELM technique could be a promising alternative method to minimize environmental pollution caused by pesticides to a large extent. [ABSTRACT FROM AUTHOR]

Hydrogen sulfide (H2S) is a primary cause of odor and corrosion in sewer systems. In drop structures, falling wastewater impinges the surface of bottom water pool as a jet or numerous drops, triggering a high level of turbulence and thus enhancing the emission of H2S and the absorption of oxygen (O2) at the pool surface. In this study, laboratory experiments were conducted to study the mass transfer at the pool surface with falling water drops or a single jet of water. In the test range of falling flow rate of 49–223 mm/h and falling velocity of 3.1–5.2 m/s [kinetic energy flux (KEF)=0.11–0.80 J/(m2·s)] , the mass transfer coefficient KL for the pool surface was found to be 2.6–14.8×10−5 m/s for H2S. In addition, KL was found to be 76% larger when the pool surface was impinged by water drops than by a single jet. KL was 27%−47% larger in the half of the water surface directly receiving the drops or jet than the other half. The increase of water depth in the pool promoted the mass transfer, especially for the scenario of falling jet. Equations were proposed to predict KL under drops or jet. Moreover, KL for H2S and for O2 was found almost the same, indicating O2 can be a safe surrogate gas for H2S. Finally, the research results were applied to estimate H2S emissions at the pool surface of a prototype drop structure with a falling height of up to 10 m, which showed that turbulent wastewater surface can enhance mass transfer over 100 times compared with a quiescent surface. [ABSTRACT FROM AUTHOR]

An ultrasound-negative pressure cavitation fractional precipitation method was developed to efficiently purify (+)-dihydromyricetin. The precipitation efficiency of the developed method was significantly higher than that of the ultrasound- and negative pressure-fractional precipitation methods. In particular, under an ultrasonic power of 180 to 250 W and a negative pressure intensity of −200 mmHg, highly pure (+)-dihydromyricetin could be obtained with a high yield of up to 97.56% in only one minute of precipitation. Kinetic analysis results showed that when both ultrasound and negative pressure were introduced during fractional precipitation, the rate constant increased by 1.4 to 7.1 times compared to the conventional fractional precipitation, and the activation energy decreased by −1,299 to −4,550 J/mol. In addition, the particle size of the precipitate was reduced by 1.9 to 4.0 times, and the diffusion coefficient increased by 2.3 to 5.0 times. [ABSTRACT FROM AUTHOR]

A method based on particle‐resolved CFD is built and validated, to calculate the fluid‐to‐particle mass and heat transfer coefficients in packed beds of spheres with different tube‐to‐particle diameter ratios (N) and of various particle shapes with N = 5.23. This method is characterized by considering axial dispersion. The mass and heat transfer coefficients increase by 5%–57% and 9%–63% after considering axial dispersion, indicating axial dispersion should be included in the method. The mass and heat transfer coefficients are reduced as N decreases. The catalyst particles without inner holes show higher mass and heat transfer coefficients than the ones with inner holes, because of unfavorable fluid flow in inner holes. The bed of trilobes has the highest mass and heat transfer coefficients, being 85% and 95% higher than the one of spheres. This work provides a versatile method and some useful guidance for the design of packed bed reactors. [ABSTRACT FROM AUTHOR]

The challenging task in our ecosystem is to reduce acidic gas emissions to some extent. Many gases are emitted from the industries like H2S, CO, CO2, SO2, NO, and NO2 as exhaust gases. Among these gases, CO2, NO2, and SO2 are acidic, which results in adverse effects on humans, animals, and plants. The increase in the emission of CO2 gases from both anthropogenic and industrial sources resulted in CO2 mitigation studies. CO2 absorption studies were carried out using iron oxide nanofluid with the novel structured packed absorption column. Iron oxide nanoparticles were synthesized and characterized using XRD, SEM, and TEM analysis. Ammonia is used as an absorbent along with iron oxide nanofluid of three different concentrations (0.0001 w/v%, 0.001 w/v%, and 0.0015 w/v%). It was found that the iron oxide nanofluid of 0.0015 w/v% showed an improved % CO2 removal efficiency. This enhanced % CO2 removal efficiency was due to the increased interfacial area of the ameliorated contact between the liquid and gas phases. In addition, the magnetic field was introduced along with the packed column, which increased CO2 removal efficiency by 1.5%. [ABSTRACT FROM AUTHOR]

This article presents the results of hydrodynamics and mass exchange in a stirred tank upon the introduction of gas from an open gas vortex cavity into local liquid regions with reduced pressure. It establishes conditions for the intensive dispersion of gas. Velocity fields and liquid pressure behind the stirrer paddles are determined by numerical simulation in OpenFOAM. The gas content value, gas bubble diameters, and phase surface are determined experimentally. The stirrer power criterion is calculated by taking into account the gas content and power input. The experimental mass transfer data based on the absorption of atmospheric oxygen into water during the dispersion of gas from the open vortex cavity in the local liquid regions behind the rotating stirrer paddles are presented. In this case, the energy dissipation from the rotating stirrer reaches 25 W/kg, with a phase surface of 1000 m−1 and a surface mass transfer coefficient of up to 0.3·10−3 m/s. These parameters are obviously higher than the data obtained in the apparatus for mass exchange through surface vorticity. The advantage of the given method for gas dispersion in a liquid is the functional stability of the apparatus regardless of how deep the stirrer is immersed in the liquid or the temperature or pressure of the gas. Apparatuses based on the intensive gas dispersion method allow for varying the mass transfer coefficient and gas content across a broad range of values. This allows establishing a dependency between the experimentally obtained mass transfer coefficient, energy dissipation, and phase surface values. An equation for calculating the mass transfer coefficient is formulated by taking into account the geometric parameters of the stirrer apparatus based on the stirring power and phase surface values. [ABSTRACT FROM AUTHOR]

Development of energy-efficient and high-performance bioreactors requires progress in methods for assessing the key parameters of the biosynthesis process. With a wide variety of approaches and methods for determining the phase contact area in gas–liquid flows, the question of obtaining its accurate quantitative estimation remains open. Particularly challenging are the issues of getting information about the mass transfer coefficients instantly, as well as the development of predictive capabilities for the implementation of effective flow control in continuous fermentation both on the laboratory and industrial scales. Motivated by the opportunity to explore the possibility of applying classical and non-classical computer vision methods to the results of high-precision video records of bubble flows obtained during the experiment in the bioreactor vessel, we obtained a number of results presented in the paper. Characteristics of the bioreactor's bubble flow were estimated first by classical computer vision (CCV) methods including an elliptic regression approach for single bubble boundaries selection and clustering, image transformation through a set of filters and developing an algorithm for separation of the overlapping bubbles. The application of the developed method for the entire video filming makes it possible to obtain parameter distributions and set dropout thresholds in order to obtain better estimates due to averaging. The developed CCV methodology was also tested and verified on a collected and labeled manual dataset. An onwards deep neural network (NN) approach was also applied, for instance the segmentation task, and has demonstrated certain advantages in terms of high segmentation resolution, while the classical one tends to be more speedy. Thus, in the current manuscript both advantages and disadvantages of the classical computer vision method (CCV) and neural network approach (NN) are discussed based on evaluation of bubbles' number and their area defined. An approach to mass transfer coefficient estimation methodology in virtue of obtained results is also represented. [ABSTRACT FROM AUTHOR]

Packed-bed bioreactors are often used for aerobic solid-state fermentation, since the forced aeration supplies O2 and removes metabolic heat from the bed. Motivated by the potential for applications in biorefineries, we review studies conducted on packed-bed bioreactors over the last decade, evaluating the insights these studies provide into how large-scale packed beds should be designed and operated. Many studies have used low superficial air velocities and suffer from preferential airflow, such that parts of the bed are not properly aerated. Moreover, some studies have proposed ineffective strategies, such as reversing the direction of the airflow or introducing air through perforated pipes within the bed. Additionally, many studies have used narrow water-jacketed packed-bed bioreactors, but these bioreactors do not reflect heat removal in wide large-scale packed beds, in which heat removal through the side walls makes a minor contribution. Finally, we conclude that, although some attention has been given to characterizing the porosities, water sorption isotherms and volumetric heat and mass transfer coefficients of substrate beds, this work needs to be extended to cover a wider range of solid substrates, and work needs to be done to characterize how these bed properties change due to microbial growth. [ABSTRACT FROM AUTHOR]

This study reports the features of the mass transfer kinetics during the extraction of phenolic compounds and flavonoids from the Carlina acaulis roots. The extraction process of target compounds was optimized and the mathematical model was selected, which implies that the mass transfer of target compounds occurs during the extraction of the solid phase (plant cells) into the liquid phase (extractant). The most effective hydrodynamic conditions for the production of phenolic compounds and flavonoids were determined. An experimental verification of the kinetic equation was carried out by extracting the target compounds from the studied object of various sizes in a vessel with a stirrer using 40% and 70% ethanol as an extractant. The results of the experiment indicated that the target compounds extraction process, namely phenolic compounds and flavonoids from the Carlina acaulis roots, proceeds more efficiently under stirring conditions when using particles with a diameter of 2 mm and 70% ethanol as an extractant. The experimental data are in good agreement with the theoretically calculated results, which confirms the appropriateness of using the selected mathematical model. Studies of the kinetics of Carlina acaulis roots extraction process will allow minimizing the losses of target compounds, and improving the extraction process and the quality of final product. [ABSTRACT FROM AUTHOR]

The two major scale-up criteria in continuously stirred bioreactors are 1) constant aerated power input per volume (Pg/Vl), and 2) the volumetric O2 mass transfer coefficient (kla). However, Pg/Vl is only influenced by the stirrer geometry, stirrer speed, aeration and working volume, while the kla is additionally affected by physiochemical properties of the medium (temperature, pH, salt content, etc.), sparging of gas and also by the bioreactor design. The extremophilic archaeon Sulfolobus acidocaldarius, thriving at 75°C and pH 3.0, has the potential for many biotechnological applications. However, previous studies imply that the family Sulfolobaceae might be affected by higher oxygen concentration in the headspace (>26%). Hence, adequate oxygen supply without being toxic has to be ensured throughout the different scales. In this study, the scale-up criteria Pg/Vl and kla were analyzed and compared in a 2 L chemostat cultivation of S. acidocaldarius on a defined growth medium at 75°C and a pH value of 3.0, using two different types of spargers at the same aerated power input. The scale-up criterion kLa, ensuring a high specific growth rate as well as viability, was then used for scaleup to 20 L and 200 L. By maintaining a constant kla comparable dry cell weight, specific growth rate, specific substrate uptake rates and viability were observed between all investigated scales. This procedure harbors the potential for further scale-up to industrial size bioreactors.

Processes of sucrose diffusion inside plant fruits and their generalization require special attention, namely theoretical generalization of experimental data and organization of energy-saving production of candied fruits while preserving the quality of the finished product. This work deals with the experimental and theoretical studies of the kinetics, hydrodynamics and mass transfer of the process of zucchini fruits saturation with sucrose from an aqueous solution. Experimental studies were conducted in static and dynamic modes. In static mode, fruit saturation occurs from an aqueous solution of sucrose in a stationary state of the solution. Dynamic mode occurs under conditions of air bubbling of an aqueous sucrose solution. Specific heat consumption of the studied modes of saturation of zucchini fruits in sugar syrup was theoretically calculated. The kinetic process of changes in the sucrose concentration in zucchini fruits at different rates of air supply for bubbling was studied in detail. It was found that the process kinetics occur in the regions of external and internal diffusion. Based on Fick's law, a generalization of the saturation processes of the particles of zucchini fruits with sucrose in the external diffusion region was carried out using the similarity theory. The existence of three hydrodynamic regimes during fruit saturation in dynamic mode was proved. Criterion equations were derived allowing us to theoretically calculate the mass transfer coefficient under the conditions of three hydrodynamic regimes. From technological and economic points of view, the most expedient process of zucchini fruit particles saturation with sucrose occurs at a syrup temperature of 70°С and a rate of air flow for bubbling from 6 to 8 m/s. The derived criterion equation allows to establish the numerical value of the air pressure for bubbling depending on the air supply rate.

This study was conducted to investigate the drying kinetics and internal and external mass transfer characteristics of walnuts for an understanding of the drying mechanism. The drying characteristics, mass transfer characteristics, and color of walnut during hot air drying (HAD) were investigated under different initial moisture content (IMC) (0.35, 0.39, and 0.43 g water/g wet mass) and drying temperatures (50, 60, 70, and 80 °C). The results indicated that the IMC and drying temperature both have significant effects on the drying process of walnut, showing the higher the IMC, the longer the preheating time, the smaller the effective moisture diffusivity (Deff) and mass transfer coefficient (hm), and the longer the drying time, but reverse results for drying temperature. The values of Deff and hm for walnut ranged from 4.94 × 10−10 to 1.44 × 10−9 m2/s and 1.24 × 10−7 to 3.90 × 10−7 m/s, respectively. The values of activation energy for moisture diffusion and mass transfer ranged from 21.56 to 23.35 kJ/mol and 28.92 to 33.43 kJ/mol, respectively. Multivariate linear prediction models were also established for estimating the Deff and hm as a function of the HAD process parameters. The drying temperature has a greater effect on the walnut kernel lightness than the IMC. The Verma et al model could be used to describe the HAD process of the walnut. The findings contribute to the understanding of moisture transfer mechanisms in walnuts and have practical value for the evaluation and improvement of drying systems.

In this paper, the results of the study on aluminium evaporation from the Al-Zn alloys (4.2% weight) during remelting in a vacuum induction furnace (VIM) are presented. The evaporation of components of liquid metal alloys is complex due to its heterogeneous nature. Apart from chemical affinity, its speed is determined by the phenomena of mass transport, both in the liquid and gas phase. The experiments were performed at 10-1000 Pa for 953 K - 1103 K. A significant degree of zinc loss has been demonstrated during the analysed process. The relative values of zinc loss ranged from 4 to 92%. Lowering the pressure in the melting system from 1000 Pa to 10 Pa caused an increase in the value of density of the zinc evaporating stream from 3.82⋅10-5 to 0.000564 g⋅cm-2⋅s-1 at 953 K and 3.32⋅10-5 to 0.000421 g⋅cm-2⋅s-1 for 1103 K. Based on the results of the conducted experiments. it was found that evaporation of zinc was largely controlled by mass transfer in the gas phase and only for pressure 10 Pa this process was controlled by combination of both liquid and gas phase mass transfer.

Hydrogen sulphide (H2S) emissions in sewer systems lead to several problems such as corrosion, odour nuisances, and health damage to sewer workers. Although the gas is formed in the liquid phase, its effects are noticeable when released into the sewer atmosphere. Until recently, the lack of analytical procedures for continuous monitoring of H2S in the liquid phase, as well as its toxicity, have challenged the quantification of the mass transfer coefficient under real conditions. Because of this, most studies have mainly focused on batch experiments with artificial wastewater and/or oxygen. The aim of this study was to experimentally determine the overall mass transfer coefficient for H2S during intermittent pumping events common in actual sewer systems, using the two-film theory approach and employing online sensors for liquid and gas phase measurements. The mass transfer coefficient was quantified by carrying out 21 experiments with actual wastewater in a 25 m long gravity pipe of a sewer pilot plant located in Berlin (Germany). Results show that the corrected mass transfer coefficient (KLa20) during a pumping event ranged between 0.1 and 8 h−1 with a median value of 4.2 h−1, within the range of the results obtained by the most common empirical models. HIGHLIGHTS Online sensors enable data acquisition for determining the H2S mass transfer coefficients across the liquid–gas interface.; Experiments were carried out in a sewer pilot plant with actual wastewater.; During pumping the KLa20 coefficient for H2S had a median value of 4.2 h−1.;

The current paper focuses on assessing key parameters affecting the extraction of Chlorpyrifos as well as emulsion stability using the emulsion liquid membrane technology. Five parameters affecting the extraction have been studied: homogenizer speed, emulsification time, agitating time, surfactant concentration, and stripping phase concentration taking into consideration the emulsion breaking. Experiments proved that using the resulting optimum values will maximize both extraction and stripping efficiencies (93.8% and 94.7% respectively), while minimizing the emulsion breakage (increasing the stability of emulsion) to 0.73% with no need to employ a carrier agent. A 10 min agitating time, 3% (v/v) Span 80 as a surfactant, 12700-rpm homogenizer speed, 0.25 M HCl as an internal phase concentration, and 5 min emulsification time are chosen to be the optimum parameters' values. A study of extraction kinetics and estimation of mass transfer coefficient was also accomplished (3.89×10-9 m/s). The conclusions of this work can be extended to the removal of other types of pesticides from water. [ABSTRACT FROM AUTHOR]

Emulsion Liquid Membrane (ELM) is an emerging technology that removes contaminants from water and industrial wastewater. This study investigated the stability and extraction efficiency of ELM for the removal of Chlorpyrifos Pesticide (CP) from wastewater. The stability was studied in terms of emulsion breakage. The proposed ELM included n-hexane as a diluent, span-80 as a surfactant, and hydrochloric acid (HCl) as a stripping agent. Parameters such as mixing speed, aqueous feed solution pH, internal-toorganic membrane volume ratio, and external-to-emulsion volume ratio were investigated. A minimum emulsion breakage of 0.66% coupled with a maximum chlorpyrifos extraction and stripping efficiency were achieved at 96.1% and 95.7% at best-operating conditions of 250/50 external-to-emulsion volume ratio, external feed solution pH 6, 250rpm mixing speed, and 1:1 internal-to-membrane volume ratio at 10min contact time without utilizing a carrier agent. A study of extraction kinetics and estimation of mass transfer coefficient was also conducted (3.89×10-9m/s). The results of this work can be extended to the removal of other types of pesticides from wastewater. [ABSTRACT FROM AUTHOR]

A compact static mixer for gas–liquid dispersion in pipelines is studied in this paper with a Reynolds averaged two fluid model approach. A procedure based on the lumped parameter solution of a population balance model is applied to obtain the bubble Sauter mean diameter needed to model the interphase forces. The gas distribution in the pipe is analyzed in two different operative conditions and the efficiency of the static mixer is assessed in terms of the gas homogeneity in the pipe section, with low coefficients of variations being obtained. A computational model to obtain the volumetric mass transfer coefficient, kLa, developed for partially segregated systems is applied finding kLa values comparable to those typically obtained with other static mixers. The proposed computational model allows us to locally analyze the oxygen transfer rate by observing the limitations due to gas accumulation behind the body of the static mixer, which leads to the local depletion of the driving force. Geometrical optimization of the static element is proposed, based on the analysis of gas–liquid fluid dynamics and of the interphase mass transfer phenomena. [ABSTRACT FROM AUTHOR]

This research work deals with the performance of high-density polyethylene sheets arranged in splash used as a fill for a cooling tower. “A forced-draught counterflow cooling tower” of 400 mm × 400 mm cross-sectional area and 1.7m in height was built. The fill has been studied theoretically and experimentally. Air rates of 0.6, 1.2, and 1.8 kg/s.m2 were utilized with water flow rates within the range of 1 to 1.6 kg/s.m² . The overall volumetric heat transfer coefficient, volumetric mass transfer coefficient (Mt), and the tower characteristics (Mt/L) are shown to be functions of the air and water flow rates concurrently. Four available input parameters were inlet water temperature, airflow rate, water flow rate, and full height. A computer program was prepared to perform numerical analysis for reducing data sets obtained from the plant. In addition, analysis was carried out for evaluating the volumetric heat and mass transfer coefficients along with the performance coefficient. [ABSTRACT FROM AUTHOR]

The development of energy-efficient solutions for large-scale fermenters demands a deep and comprehensive understanding of hydrodynamic and heat and mass transfer processes. Despite a wide variety of research dedicated to measurements of mass transfer intensity in bubble flows, this research subject faces new challenges due to the topical development of new innovative bioreactor designs. In order to understand the fluid dynamics of the gas–liquid medium, researchers need to develop verified CFD models describing flows in the bioreactor loop using a progressive physical and mathematical apparatus. In the current paper, we represent the results of evaluating the key performance indicator of the bioreactor, namely the volumetric mass transfer coefficient ( k L a ) known as a parameter of dominant importance for the design, operation, scale-up, and optimization of bioreactors, using the developed thermometry method. The thermometry method under consideration was examined within a series of experiments, and a comparative analysis was provided for a number of various regimes also being matched with the classical approaches. The methodology, experiment results, and data verification are given, which allow the evaluation of the effectiveness and prediction of the fluid flows dynamics in bioreactors circuits and ultimately the operational capabilities of the fermenter line. [ABSTRACT FROM AUTHOR]

The desulfurization behavior of 316L stainless steel (STS316L) melt with the CaO-SiO2-CaF2-Al2O3-MgO slag was investigated with different CaO/SiO2 (=C/S) ratio and CaF2 content at 1873 K. As the C/S ratio increased, the sulfide capacity increased, whereas the sulfide capacity of the high C/S (=1.7) slag was not affected by CaF2 content. The overall mass transfer coefficient (kO) increased with C/S ratio, but was constant above a critical C/S value, and it was also constant across varied CaF2 content at relatively high C/S (=1.7) condition. Since the metal condition of the present study was constant, the change in kO was caused by slag phase mass transfer coefficient (ks) and sulfur distribution ratio (LS), which were affected by the physicochemical properties of the slag. Since desulfurization reaction requires consideration of both kinetic and thermodynamic factors, the ‘logCS2−−logη’ (where CS2− is sulfide capacity and η is viscosity), was proposed as a meaningful physicochemical parameter. If the slag basicity is relatively high, at which the kO is equivalent regardless of slag compositions, the desulfurization reaction is controlled by metal phase mass transfer. However, if the slag basicity becomes lower, at which the kO significantly decreases, the desulfurization reaction is assumed to be controlled by slag phase mass transfer and/or mixed controlled process.

The current experimental study looks at how the limiting current density is approached on using rotating 2-stage 4- blade flat turbine promoters to improve mass transfer coefficient in an open electrolytic cell. The mass transfer data are obtained at microelectrodes fixed on the cell wall and electrode support using an electrochemical method. The electrolyte was equimolal in potassium ferricyanide, potassium ferrocyanide and excess sodium hydroxide. The mass transfer coefficients were calculated using limiting current data from a diffusion-mediated electrode reduction reaction at the microelectrodes attached to the electrode supports. The limiting current technique has been particularly chosen in view of its accuracy, simplicity, negligible chemical polarization, and absence of any physical change to the reacting surface even after long exposure. The effects of geometric parameters such as turbine diameter (0.05-0.09 m), blade width (0.005-0.015m), turbine rotational speeds (250-1250 rpm) and electrolyte velocity (0.567x10-3 to 7.93x10-3 m/s) were investigated. The mass transfer coefficients were increased by the turbulence created by rotation of the promoter turbines. The mass transfer correlation was formed in terms of dimensionless numbers: Schmidt number (Sc), Sherwood number (She), rotational Reynolds number (Rer), and flow Reynolds number (Ref).

The dissolution of Ti–N solids in liquid titanium was investigated using experimental and numerical methods. To characterize the dissolution rate and the transport phenomena associated with the dissolution process, cylindrical Ti–N rods were immersed into a molten pool of commercially pure titanium produced using an electron beam button furnace. Tests were conducted for various immersion times to observe the evolution in the rod tip profile and measure the volume loss. Generally, the volume fraction of dissolved solid increases with increasing immersion time. A numerical model has been developed to describe the experimental process and aid in understanding the dissolution process. Overall, the predicted volume loss for different immersion times agrees well with the experimental measurements. An effective mass transfer coefficient, in the range of 4.2 × 10−5 to 4.9 × 10−5 m/s, has been derived based on the model results for the experimental conditions examined (e.g. interface velocities and temperatures in the range of 0.09 – 0.11 m/s, and 1766 – 1778 °C, respectively).

Post combustion Carbon capture based on chemical absorption is the best-known technology to reduce CO 2. Recently, attention has been paid to biphasic solvents due to their excellent potential in reducing energy consumption. This study investigated carbon dioxide absorption by biphasic non-aqueous triethylenetetramine (TETA)-ethanol solvent in a T-shaped microchannel. Effect of four parameters including: concentration of TETA (4–8 wt%), liquid flow (2–5 ml/min), inlet CO 2 concentration (5–20 vol%) and gas flow (100–175 ml/min) have been examined. Mass transfer characteristics has been assessed by investigation of absorption percentage, molar flux and overall mass transfer coefficient. The results show that increasing the concentration of amine diminishes all three responses by increasing the solution viscosity. As a result, it decreases the penetration of CO 2 in the solution and the rate of absorption. Furthermore, the TETA-ethanol phase change solvent has been compared with aqueous monoethanolamine (MEA). The results of this comparison indicated that the efficiency of CO 2 absorption and mass transfer coefficient, for TETA-ethanol biphasic solvent are higher than MEA solvent, respectively. Finally, the dimensionless Damköhler number (Da) was utilized in the new correlation to predict K L a for CO 2 absorption into TETA-Ethanol solution with acceptable accuracy. • CO 2 absorption by biphasic TETA-ethanol solvent was investigated in a microchannel. • The mass transfer coefficient for biphasic solvent was 14.38 % higher than MEA solvent. • Damköhler number was utilized in the new correlation to predict K L a. [ABSTRACT FROM AUTHOR]

[Display omitted] The electrodeposition process confronts significant challenges arising from mass transfer limitation and residual stress. To address these issues, an innovative method, combining megasonic agitation with coaxial jet electrodeposition, is introduced. This approach aims to enhance mass transfer and mitigate residual stress. First, an electrodeposition nozzle device was designed, and the liquid-phase mass transfer during electrodeposition was analyzed through finite element simulation. Simulation results indicate that the mass transfer coefficient increases with rising megasonic power density. Notably, when the megasonic power density reached 20 W/cm2, the mass transfer coefficient increased from 0.45 × 10−7 m/s to 18.63 × 10−7 m/s, compared to electrodeposition without megasonic agitation. Secondly, electrodeposition experiments were conducted both with and without megasonic assistance. X-ray diffraction (XRD) was employed to measure the residual stress values of the electrodeposited layers. The results reveal that samples processed with megasonic assistance exhibit lower residual stress values compared to those without. Specifically, at a megasonic power density of 10 W/cm2, the residual stress was 94.3 MPa, representing a 37.7 % reduction compared to the residual stress of 151.5 MPa observed in samples without megasonic agitation. Overall, the findings demonstrate that coaxial megasonic agitation can effectively enhance the liquid-phase mass transfer capability during electrodeposition and reduce the residual stress of the electroplated layer. This innovative method presents a promising avenue for improving electrodeposition processes and achieving superior material properties. [ABSTRACT FROM AUTHOR]

To comprehensively utilize Fe and P in oolitic hematite ore, an innovative method was proposed to enhance P enrichment in the reduced iron during the reduction process. The reduced iron was then converted to low-P-containing molten iron and high-P-containing slag in the presence of CaO–SiO2–FeO–Al2O3 slag. In this study, the P content of the final iron after 0–1,800 s dephosphorization was investigated at different slag composition conditions, and the dephosphorization kinetics of the reduced iron was analyzed. The results showed that the P content of the final iron sample decreased rapidly within 600 s of dephosphorization and became almost constant with increasing dephosphorization time to 1,800 s. The basicity, FeO content, and Al2O3 content also affected the dephosphorization rate of the reduced iron. The apparent dephosphorization rate constant ranged from 1.141 × 10−3 to 2.363 × 10−3 g·(cm2·s)−1, and the overall mass transfer coefficient ranged from 2.47 × 10−3 to 3.38 × 10−3 cm·s−1. The rate-controlling step of the dephosphorization process was the mass transfer of P in both the slag and iron phases. The findings of this study provide a theoretical basis for the utilization of refractory oolitic hematite ore.

The desulfurization in metallurgical process is electrochemical reaction in nature. Desulfurization using the electrochemical method was proposed with the CaO-MgO-Al2O3 molten slag covering molten steel. Effect of an applied external DC voltage, which varied from 0 to 8V, was discussed. The results indicated that sulfur in molten steel could be removed effectively with applied external voltage. According to the mechanism analyses of the desulfurization under the applied external voltage, kinetics formulae were developed, and the model calculated results that were in agreement with the experimental values. The transfer coefficient of sulfur in molten slag under electromigration conditions was approximately 2.09×10-5 m·s-1·V-1. The desulfurization of molten steel with molten slag can be promoted by increasing the applied voltage, reducing the partial pressure of atmospheric oxygen, strengthening the stirring intensity of the reaction system, and optimizing the composition and properties of the slag.

The relative importance of the physical resistances to mass transfer have been explored by using halved 13 mm diameter apple-pectin tablets containing caffeine, in different external stirring environments within a beaker containing simulated gastric fluid. The effects of different external (outside of the tablets) mass-transfer resistances to the tablets created through two different stirrer types and stirrer speeds, and different internal (inside of the tablets) mass-transfer resistances created through different tablet concentrations and thicknesses, have been studied. These studies enable internal diffusion coefficients of caffeine through the apple pectin matrix to be estimated, as well as estimating the external mass-transfer coefficients from benzoic acid dissolution, which are in the range of 6.5 × 10-6 m/s – 2.4 × 10-5 m/s for the 0.6 mm thick tablets and 4.0 × 10-6 m/s – 1.6 × 10-5 m/s for the 7 mm thick tablets. The diffusion coefficients for different caffeine concentrations in the apple pectin half-tablets have also been calculated in this study. The diffusivity of caffeine in the 7 mm half-tablets with 1% caffeine through 99% pectin was around (1.8 ± 0.5) × 10-10 m2/s. This study points towards the development of multifilm mass-transfer theory for food digestion to create a more fundamentally based understanding of in-vitro digestion systems as an addition to the use of realistic in-vitro food digestion apparatus and give a better correlation between in-vitro and in-vivo digestion tests.

Flow-Accelerated Corrosion (FAC) is a pipe wall thinning phenomenon to be monitored and managed in the power plants with high priority. Its management has been conducted with conservative evaluation of thinning rate and residual lifetime of piping based on wall thickness measurements. However, in the actual plants, noticeable case of the wall thinning occurred in branch and junction piping (T tube). There is a problem to manage the wall thickness of the part covered by reinforcing plate of the T tube, because measurement of this area is difficult to be conducted with ordinary ultrasonic testing devices due to the presence of the reinforcing plate. In this study, numerical flow analysis for the T tube was conducted, and the wall thinning profile due to the FAC was evaluated by calculating the mass transfer coefficient. It was found that a localized wall thinning distribution occurs in the area where the reinforcement plate of the T tube exists. And this tendency is affected by pipe geometry and Reynolds number. In previous studies, a model that functionalized by pipe geometry and Reynolds number was introduced to predict this wall thinning trend. In this paper, the effectiveness of the proposed decay function was confirmed by comparing it with measurements taken in actual plants. It was shown that the maximum wall thinning rate at the T tube junction, including below the reinforcing plate, can be evaluated conservatively within an appropriate range by making corrections to the proposed decay function that take into account the causes of variation in the actual data.

The spray of water over a basin using a perforated disk accelerates oxygen transfer. The laboratory model, employed in the current work, consists of a vertical riser that discharges water by free fall into a basin. Four fall heights of water of 2.4, 1.8, 1.2, and 0.6 m were investigated to evaluate the performance of this system. This system was also tested at flow rates of 46.8, 93.7, 140.6, and 187.5 mL/s. This study showed that the oxygen mass transfer coefficient was directly proportional to both the fall height and flow rate of water. The maximum standard aeration efficiency (SAE) value was recorded at the maximum fall height of 2.4 m and flow rate of 187.5 mL/s, at which a maximum KLa20 = 1.82 h–1 was recorded. The multilinear regression-based model developed in this study successfully predicted mass transfer coefficient (KLa20) and standard aeration efficiency (SAE values that agree well with actual measurements under given conditions, with a scattering within ±5%. The optimum flow rate and fall height that achieve the minimum operating cost were obtained at certain KLa20 values. The cost of aeration of 1 m3 of water was calculated, ranging from 0.0076 to 0.008 USD/m3. [ABSTRACT FROM AUTHOR]

Processes of sucrose diffusion inside plant fruits and their generalization require special attention, namely theoretical generalization of experimental data and organization of energy-saving production of candied fruits while preserving the quality of the finished product. This work deals with the experimental and theoretical studies of the kinetics, hydrodynamics and mass transfer of the process of zucchini fruits saturation with sucrose from an aqueous solution. Experimental studies were conducted in static and dynamic modes. In static mode, fruit saturation occurs from an aqueous solution of sucrose in a stationary state of the solution. Dynamic mode occurs under conditions of air bubbling of an aqueous sucrose solution. Specific heat consumption of the studied modes of saturation of zucchini fruits in sugar syrup was theoretically calculated. The kinetic process of changes in the sucrose concentration in zucchini fruits at different rates of air supply for bubbling was studied in detail. It was found that the process kinetics occur in the regions of external and internal diffusion. Based on Fick's law, a generalization of the saturation processes of the particles of zucchini fruits with sucrose in the external diffusion region was carried out using the similarity theory. The existence of three hydrodynamic regimes during fruit saturation in dynamic mode was proved. Criterion equations were derived allowing us to theoretically calculate the mass transfer coefficient under the conditions of three hydrodynamic regimes. From technological and economic points of view, the most expedient process of zucchini fruit particles saturation with sucrose occurs at a syrup temperature of 70°С and a rate of air flow for bubbling from 6 to 8 m/s. The derived criterion equation allows to establish the numerical value of the air pressure for bubbling depending on the air supply rate. [ABSTRACT FROM AUTHOR]

Reaeration is a primary path of reoxygenation in streams, fundamental to environmental and ecological integrity. Previous laboratory studies of reaeration rates in subcritical flows showed large scatter in results, with differences in mass transfer coefficients of more than one order of magnitude between comparable flow conditions. Although supercritical flow is commonly observed in natural streams and engineered channels, systematic measurements of supercritical flow reaeration rates have been unavailable. Experiments in a laboratory open channel flume encompassing sub- and supercritical flows have been undertaken. The subcritical data were consistent with a large body of previous studies. Supercritical flows showed 6–10 times stronger reaeration rates than comparable subcritical conditions, while local rates at hydraulic jumps systematically exceed those in the supercritical flows upstream by a factor up to three. A close relationship between reaeration rates and turbulent dissipation rate is observed, and a systematic Froude number dependency is demonstrated for both sub- and supercritical flows. Observed mass transfer coefficients do not correlate as well with flow Reynolds number and shear Reynolds number. The higher reaeration rates associated with supercritical flows indicates that a change in open channel flow regime for the same Reynolds number may be used to improve water quality. [ABSTRACT FROM AUTHOR]

Distributions of the pressure and mass transfer coefficient on rotating blades under low-pressure (low-Reynolds-number) conditions were visualized, whereas the latter is closely related to the skin-friction distribution. Two types of optical measurement techniques, lifetime-based pressure-sensitive paint (PSP) measurements and sublimation visualization, were implemented for the experiment inside a low-pressure chamber. For the lifetime-based PSP measurement, different types of PSP were compared, and the one most suitable in low-pressure applications was selected. In addition, the gate time setting for the low-pressure condition was determined. For the sublimation method, naphthalene was selected as the sublimation surface based on previous studies. The rotating blade test model was a 0.3-m-diam rotor system with two rectangular blades with an aspect ratio of two. The experiments were carried out at a rotational speed of 2400 rpm and at an ambient pressure of 10 kPa. The three-fourth-span Reynolds number was 9000. The pitch angle of the blades was set to 0-20 deg. Both methods successfully illustrated clear images of the distribution of pressure and mass transfer coefficients on the upper surface of the blade, and the measurement in the low-pressure environment was successful. [ABSTRACT FROM AUTHOR]

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The spinning cone columns (SCC) are one of the distillation columns with increasing applications in food industries. The geometrical complexity and different flow regimes, besides the presence of moving parts, make the design and analysis of these columns challenging. Computational fluid dynamics analysis of SCC columns has shown promising results in analyzing the performance of these towers. The majority of previous works were pertinent to the air/water systems. Therefore, the application of these results to real systems is not very clear. In this study, the liquid film thickness, mass transfer coefficients, HETP, and Murphree vapor efficiency for the water/ethanol system have been predicted in a pilot-scale column. The results show that by increasing the radial distance from the axis, the thickness of the liquid film gradually decreases. This finding is also in consistent with the experimental results. The maximum thickness of the liquid film is <1 mm and is near the axis. Mass transfer coefficients in the liquid phase and in the gas phase increase slightly with increasing flow velocity and remain almost unchanged. The average values of these coefficients in the liquid and gas phases are 0.023 (s−1) and 1.21 (s−1), respectively. HETP increased with increasing gas velocity, the range of which varies between 0.092 and 0.375 m. Also, Murphree vapor efficiency at three rotational speeds of 550, 750, and 1000 rpm are predicted and compared with the experimental data. The results show that the efficiency has been decreased by increasing the strip ratio and increased by increasing the rotational speed. Minimum and maximum efficiencies obtained are 3.48 and 24.56% corresponding to strip ratio = 27.1% and RPM = 550 plus strip ratio = 9.15% and RPM = 1000, respectively. The predicted efficiencies are in a reasonable agreement (within 10.3%) with experimental data. [ABSTRACT FROM AUTHOR]

Phthalates and emerging alternative plasticizers have garnered significant attention due to their ubiquitous presence indoors and potential adverse health effects. However, the occurrences and key transport parameters of indoor alternative plasticizers have not been sufficiently summarized and analyzed, complicating exposure evaluation and pollution control efforts. This study addresses the gap by providing a comprehensive overview of the occurrence and key transport parameters of the most reported plasticizers, including 10 phthalates and 14 alternative plasticizers. The plasticizer content in source materials was found to range up to 27.6 wt%. An empirical formula was developed to predict the surface-adjacent gaseous plasticizer concentration (y 0 ) of source materials, with values ranging from 0.015 to 64.7 μg/m 3 . Variations in plasticizer concentrations across source, gas, particle, and dust phases were thoroughly analyzed over both temporal and spatial dimensions from a global perspective, indicating significant differences between continents over time. A detailed investigation of phthalate regulations across continents suggests that the earlier enactment of phthalate bans in Europe is likely a key factor contributing to the most significant decrease in indoor phthalate concentrations. Furthermore, after systematically reviewing mass-transfer and partitioning theories, we developed empirical formulas to predict mass-transfer coefficients (h m ) and partition coefficients (K) for both phthalates and alternative plasticizers. Notably, the h m and K parameters of the plasticizers were thoroughly calculated for typical indoor interfaces, including airborne particles, settled dust, and impermeable and permeable materials. Overall, this study advances the understanding of indoor plasticizers, facilitating health-risk assessment and the development of suitable control and monitoring technologies., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

This study evaluated the effects of different operating conditions and the air-to-water ratio (G/L) on the kinetics and the mass transfer coefficient of ammonia (KL) in the air stripping method for removing ammonium ions (NH4+) from wastewater with low concentrations in municipal wastewater treatment plants (WWTPs). The impact of operating conditions including the temperature, initial ammonium ion concentration, pH, and air-to-water ratio (G/L) of

A number of industrial operations are linked to mass transfer. The mass transfer coefficient value is necessary to know when designing the industrial equipment in which mass transfer occurs. There are various mass transfer coefficients, as well as equations for their calculation. However, the value of these coefficients determined according to these equations often has to be corrected for the given conditions. The aim of the article is to state the conversion relations - the correction factors enabling the calculation of the mass transfer coefficients values corresponding to the given conditions.

Using nanoparticles can lead to an increase in mass transfer rate in liquid–liquid extraction systems. Increasing the concentration of nanoparticles in liquids results in the deposition of nanoparticles and thus limits its use in extraction systems. In this paper, the effect of adding a surfactant to nanoparticle in liquid-liquid extraction systems on extraction efficiency is investigated. The effect of surfactant concentration on the extraction efficiency has been investigated both separately and in the presence of nanoparticles. In this research, the effect of continuous and dispersed phase velocity, and pulsation intensity on the hydrodynamic characteristics of the system has been investigated for the first time with the simultaneous use of silica nanoparticles and SDS surfactant in the vertical pulsed packed column.Using hydrodynamic system and in the presence of nanoparticles and surfactant, this research article provides optimum conditions to obtain maximum efficiency with minimum additives and pulsation intensity. ANOVA analysis (three-level Box–Behnken experimental design) has been used to investigate the effective parameters and sensitivity analysis. The results showed that pulsation intensity is the most effective factor on response. With increasing pulsation intensity from 1 to 2.5, the droplet size decreases and hold-up is increased from 0.02 to 0.05 (at Qd=Qc= 2 lit/s) in the system. Also, the effects of adding SiO2 nanoparticles and Sodium dodecyl sulfate (SDS) surfactant into a chemical system on the hydrodynamic characteristics were studied. The results showed that by adding nanoparticles the droplet size decreases while hold-up increases. Finally, a semi-empirical correlation has been proposed to predict the droplet size in terms of operational parameters, the system chemical properties and the nanoparticle volume fraction. It was found that when pulsation intensity, nanoparticle concentration and surfactant concentration were 1.75, 0.1, and 0.05 respectively, extraction efficiency increased to 0.98.

Dissolution of gas into flowing water inside a porous medium is important in various hydrogeology processes, such as geological carbon sequestration (GCS). The dissolution rate of CO2 controls the amount of CO2 injection and the safety of the GCS process. In this report, we investigated the dissolution behavior of four gas species, i.e., CO2, O2, N2, and Ar, into flowing water inside a porous medium by using micro-tomography. The trapped gas characteristics can be observed, and thus interfacial area and mass transfer coefficient can be calculated. Compared with the other gases, we found that the dissolution behavior of CO2 gas is unique, and the mass transfer coefficient is one order of magnitude lower than other gases. We believe that the high dissolution ratio of CO2 gas could have generated a layer of the high solute region around the trapped CO2 gas, disrupting the mass transfer process.

The fate of dense non-aqueous phase liquids (DNAPLs) in the environment and the consequential remediation problems have been intensively studied over the last 50 years. However, a scarce literature is present about the mass transfer at the DNAPL/water interface. In this paper, we present a fast method for the evaluation of the mass transfer performance of a surfactant that can easily be employed to support an effective choice for the so-called enhanced remediation strategies. We developed a lab-scale experimental system modelled by means of simple ordinary differential equations to calculate the mass transfer coefficient (K) of trichloroethylene, chosen as representative DNAPL, in the presence and in the absence of two ethoxylated alcohols belonging to the general class of Synperonic surfactants. Our findings revealed that it exists an optimal surfactant concentration range, where K increases up to 40% with respect to pure water.

The coal hydrogen production process requires high-temperature steam as a reactant. Coal-fired boilers are usually used to provide high-temperature steam. The ammonia-based desulphurization process is an effective technology to remove SO2 in the coal-fired flue gas. However, the mass transfer coefficient of SO2 in such an engineered process is not readily available in the literature. In this paper, experiments were carried out to investigate the mass transfer process of SO2 absorption. Combing calculating the air and liquid contact area of the droplet and liquid membrane on the tower wall, the mass transfer coefficient contain parameters pH, gas flue rate and liquid to gas ratio was proposed. The comparison results show that the calculated SO2 mass transfer rate agrees well with the measured data. The relative error of the calculated and experimental values was less than ±20%. This proposed mass transfer coefficient appears to be beneficial for the design and operation of ammonia-based desulfurization FGD system.

A novel aerofoil embedded fiber mesh disk-based rotor has been proposed as an alternative to currently available rotating biological contactors. Specially designed aerofoil structures were incorporated into the rotor to increase its mass transfer performance and liquid hold capacity. The volumetric mass transfer coefficient and liquid hold-up for the novel rotor were determined at the rotational speeds of around 10, 15, 20, 25, 30, and 35 rpm under various submergence levels of 17.4, 21.7, 26.1, 27.8, 30.4, 34.8, 39.1, 43.5, and 50%. A dimensionless correlation for the dynamic liquid hold-up was proposed in terms of the Reynolds number, Froude number, and the submergence ratio. Another dimensionless term Oxygen transfer number (OT number) was proposed to characterize the mass transfer behavior of the reactor. The dependency of OT number was expressed in terms of Peclet number, Froude number, and dimensionless geometrical factor. The volumetric mass transfer coefficient and liquid hold-up were found to be strongly dependent on the rotation speed and submergence level.

Studies of phase transition kinetics are important for such supercritical processes as supercritical drying, adsorption, micronization, etc. In supercritical technologies, “organic solvent—CO2” systems are often formed, the properties of which strongly depend on the system parameters. In this article, the kinetic curves of phase transitions in the “2-propanol—CO2” system were investigated experimentally and theoretically. Experimental studies were carried out in a 250 mL high-pressure apparatus at temperatures of 313 and 333 K and pressures of 6.3 and 7.8 MPa with and without the addition of alginate porous gel. Theoretical studies were carried out using the mass transfer equation, the Peng-Robinson equation of state, and the Van der Waals mixing rules, with Python being used for the calculations. The mass transfer coefficients and equilibrium concentrations of CO2 in the liquid phase were determined using the BFGS optimization method.

The aim of this study was to investigate the long-term effect of magnesium and iron nanoparticles on solute transport and its parameters, which has not been investigated to date. Different concentrations of two types of nanoparticle metal oxides, MgO and Fe3O4, were mixed with a loamy soil and their effects on solute transport and its parameters after three years were investigated. Nanoparticles improved soil structure through increased macro pores compared to the control, by 2.3% in the 3% concentration of MgO to 15.3% in the 3% concentration of Fe3O4. Immobile water content of the soil decreased from 0.42 in the control to 0.05–0.24 cm3 cm−3 in the treatments. The mass transfer coefficient was decreased from 0.48 in the control to 0.005–0.37 in the nanoparticle treatments. Moreover, nanoparticles increased the breakthrough curve peak concentration and decreased discharge time of chloride in the extract from 0.41 and 88.8 min in the control to 0.62–0.76 and 24.7–87.9 min in the treatments, respectively. The results of this study showed that the nanoparticles affected the solute transport and its parameters in the soil. Therefore, nanoparticles could be used to simplify the nutrients transport and leaching of salt and contaminants. [ABSTRACT FROM AUTHOR]

The paper presents the results of experimental investigations of mass transfer processes with the use of the limiting current technique. This experimental work analyzed the not fully developed entrance laminar region. The tested case refers to the convective fluid flow through a system of nine long, square mini-channels that are 2 mm wide and 100 mm long. The method used in the measurements allows one to determine mass transfer coefficients during the electrolyte flow by utilizing electrochemical processes. The received mass transfer coefficients were applied to the analogous heat transfer case. The Chilton–Colburn analogy between mass and heat transfer was applied. The obtained results, in the form of the dependence of Nusselt number within the function of Reynolds and Prandtl numbers, can be a useful formula in the design and analysis of heat transfer processes in mini heat exchangers. [ABSTRACT FROM AUTHOR]

In this paper, the results of the study on aluminium evaporation from the Al-Zn alloys (4.2% weight) during remelting in a vacuum induction furnace (VIM) are presented. The evaporation of components of liquid metal alloys is complex due to its heterogeneous nature. Apart from chemical affinity, its speed is determined by the phenomena of mass transport, both in the liquid and gas phase. The experiments were performed at 10-1000 Pa for 953 K - 1103 K. A significant degree of zinc loss has been demonstrated during the analysed process. The relative values of zinc loss ranged from 4 to 92%. Lowering the pressure in the melting system from 1000 Pa to 10 Pa caused an increase in the value of density of the zinc evaporating stream from 3.82.10-5 to 0.000564 g.cm-2 . s -1 at 953 K and 3.32.10-5 to 0.000421 g.cm-2.s -1 for 1103 K. Based on the results of the conducted experiments. it was found that evaporation of zinc was largely controlled by mass transfer in the gas phase and only for pressure 10 Pa this process was controlled by combination of both liquid and gas phase mass transfer. [ABSTRACT FROM AUTHOR]

The spouted bed provides efficient gas-solid contact, favoring heat and mass transfer. Thus, it has been applied to various physical and chemical processes. In this work, the effects of six cone angles (28°, 30°, 45°, 60°, 75°, and 90°) on the fluid dynamics of a spouted bed with sorghum grains were analyzed by CFD-DEM. Based on fluid dynamics principles, the objective was to identify better configurations for the drying process performance. Smaller cone angles provided better solids circulation, with a higher mass transfer coefficient (kc), granular temperature (gt), and solids mass flow rate (Ws), together with a shorter cycle time (tc). For the range of cone angles analyzed, increase of the cone angle reduced Ws by about 75% and increased tc 4-fold. [ABSTRACT FROM AUTHOR]