Mass Transfer Data Research Articles

Performance evaluation during extraction technique in modified rotating disc column: Experimental and mathematical modeling

In this survey, the reactive mass transfer data are determined for extraction technique in the modified rotating disc column. Mathematical models are investigated to compute the mass transfer coefficients of the dispersed phase. An increase in the dispersed phase holdup from 0.85 to 0.12 and a decrease in droplet diameter from 2.24 to 0.74 mm are observed with increasing rotation speed from 170 to 410 rpm in the optimized system. The experiments showed that the optimum transport efficiency in rotor speed of 410 rpm in this column is equal to 98.85% and 99.45% for extraction and stripping stages, respectively. The model's achievement is compared with the solvent extraction data and a significant validity is obtained by coupling the forward mixing approach (average absolute relative error lower than 13%). The mathematical modeling expresses that the axial dispersion and backflow coefficients based on the continuous phase increase by an increase in the rotor speed and inlet continuous phase rate. In contrast, these coefficients reduce at a higher inlet dispersed phase rate. High mass transfer coefficients were obtained in the stripping stage compared to the extraction stage. This report's study provides beneficial information to design solvent extraction equipment.

Heat and Mass Transfer at the Wall of a Square Mechanically Stirred Gas‐Liquid‐Solid Catalytic Reactor

AbstractWall mass and heat transfer rates in a square gas‐sparged, mechanically stirred reactor were measured by the electrochemical technique under the effect of various geometrical and hydrodynamic variables. For the 45° impeller, the mass transfer data fit the equation Sh = 0.7Sc0.33Re0.2Reg0.5 with an average deviation of ±6.9 %. For the 90° impeller, the data fit the equation Sh = 0.95Sc0.33Re0.14Reg0.53 with an average deviation of ±7.5 %. Gas sparging enhanced the wall mass transfer rates by factors of up to 2.61 and 3 for the 90° and 45° impellers, respectively, with a significant decrease in the total power consumption. The contribution of the present results to the operation of multiphase mechanically agitated vessels in different aspects is outlined.

Reactive extraction of zinc ions in the Scheibel column; A case study by applying the mathematical modelling of mass transfer with forward mixing

An experimental and modeling study on the feasibility of the Scheibel extraction column is presented for heavy metal separation from chloride solution. In continuous experiments, the chemical reaction systems are considered zinc extraction by D2EHPA and stripping from the loaded organic phase by chloride solutions. The experimental results represent that the best extraction and stripping rates in the agitation speed of 155 rpm and the rate of inlet phases of 28 L/h are equal to 99.56% and 98.11%, respectively. The mass transfer modeling by applying the forward mixing is interpreted for solvent extraction systems in this column with the fitting technique. The calculated results from theoretical models compared with the experimental data, which good agreement was obtained using this model. The mathematical modeling on the reactive mass transfer data expresses that the axial dispersion coefficients based on the dispersed phase improve with increased agitation speed and dispersed phase rate. In contrast, these coefficients have an inverse relation with the continuous phase flow rate. This paper's experimental and numerical study provides beneficial information about the metallurgical industry to design solvent extraction columns.

Sensitivity of the Non-Equilibrium Approach for Mixture Condensation to Heat and Mass Transfer Correlations and Thermophysical Properties

Abstract The prediction of mixture condensation is still complex due to the coupled heat and mass transfer and insufficient data of thermophysical mixture properties. This article analyzes the impact of various heat and mass transfer correlations on the non-equilibrium approach for mixture condensation in a vertical plain tube. Furthermore, the influence of thermophysical properties from different databases is investigated. The results are shown for ethanol-water, but allow conclusions to other fluid mixtures. They indicate that the liquid heat transfer coefficient in the non-equilibrium approach dominates the qualitative behavior of the condensation process, but the vapor mass transfer coefficient can only decrease or increase the quantitative level of the effective heat transfer with minor impact. More importantly, the logarithm in the vapor mass transfer term is central for the prediction of the condensation heat transfer. As this logarithm contains vapor-liquid equilibrium (VLE) data, it proves that there is a strong connection between VLE and overall prediction of mixture condensation. A demonstration of available data for thermophysical mixture properties of ethanol-water shows significant deviations, which affect the calculations as well. Besides, data from our own experiments are presented for mixture viscosity of ethanol-water. It is recommended to focus not only on improved heat and mass transfer correlations but also on thermophysical properties and VLE data for a precise prediction of mixture condensation.

Modeling of Single Droplet Mass Transfer of Acetic Acid with Triisooctylamine‐Based Solvent

AbstractThe design of mass transfer equipment based on single droplet mass transfer data is still a great challenge, although having been subject of intensive discussion for decades already. Extraction with chemical reaction may rather contribute to additional problems when modeling single droplet mass transfer. Single droplet mass transfer of acetic acid from aqueous carrier into triisooctylamine based solvents modified with the Lewis acid modifier isodecanol and the diluent Shellsol T has been investigated. Mass transfer of acetic acid into triisooctylamine‐based solvent droplets is strictly controlled (actually limited) by diffusion of the laden solvent from the interface into the droplet bulk phase.

Kinetic study and modeling of sulphuric acid decomposition using Cr–Fe2O3 catalyst for sulphur based water splitting processes

Sulphuric acid decomposition is the high temperature (850–900 °C) reaction step of sulphur based water splitting processes (Iodine–Sulphur and Hybrid-Sulphur processes) for hydrogen production. In this work, reaction kinetics and mass transfer data are generated experimentally, for sulphuric acid decomposition using chromium doped iron oxide, Cr–Fe2O3, catalyst in a packed bed reactor (PBR). Experiments are performed using catalyst powder, less porous catalyst particle (pellet) and high porous catalyst particle (foam), between 700 and 850 °C and 0.1–10 ml min−1 liquid feed flow rate. Activation energy and frequency factor of Cr–Fe2O3 catalyst obtained from the powder catalyst study are 74 kJ mol−1 and 183 m3 kg−1 s−1. Internal effectiveness factor (η) of pellet and foam, two industry types of Cr–Fe2O3 catalyst (5 mm size) are calculated from the experimental studies performed at external mass transfer resistance free regime. Internal effectiveness factor of pellet and foam obtained are 0.12 and 0.26 respectively, which shows strong pore diffusion resistance in these catalyst types. Overall effectiveness factor (Ω) for both the catalyst types (pellet and foam) are also obtained for the investigated range of temperatures and flow rates. Further, catalyst particle (pellet and foam) is modeled in COMSOL MULTIPHYSICS® simulation software to get an insight into concentration and temperature profiles. Significant concentration drop and smaller temperature drop are seen in less porous pellet. Small concentration drop and significant temperature drop are observed in porous foam, through simulation studies. Focus of future R&D is to optimise the size and porosity of Cr–Fe2O3 catalyst, for maximum effectiveness factor and thereby maximizing the reaction rate and conversion.

(IMCS First Place Best Poster Award) Encapsulation through Photoinitiated Chemical Vapor Phase Deposition (piCVD) for Obtaining Antifouling and Stabilized Biosensing Interface

Biorecognition elements based biosensing devices have been applied in a broad range of clinical applications and are considered of great potential for being transformed into on-site portable techniques due to their high selectivity and sensitivity. Yet, given the success of immobilization methodologies adapted for various sensing platforms, the drive for enhanced surface microenvironments including constant reaction conditions and suppression of nonspecific binding remains. Considering the complexity of the real sensing scenario with various biofoulants (proteins, cells, polysaccharides, etc.), the fast analytes build-up at the interface would cause sensing accuracy to be either false positive or false negative in a short time. While the concern may be alleviated regarding disposable usage, the fragile biocomponent may degrade even on common storage conditions since the temperature, humidity, as well as air quality, keep varying.Great emphasis has been put on encapsulation techniques to create surface barriers that may simultaneously produce a stable inner environment at the proper humidity and temperature zone and less complicated outer surroundings arising from fouling. However, to compensate for deactivation induced by surface pretreatments and organic solvent used in many widely adopted antifouling techniques, such as spin-coating, layer-by-layer assembly (LbL), surface grafting, etc., high biocomponent loadings are always required. Besides, without precise control over obtaining thin and uniform encapsulation layers, such techniques usually fail to ensure quick mass transfer and accurate data acquisition. Chemical vapor deposition (CVD), on the other hand, is a solvent-free process in which vapor-phase precursors chemically react on a substrate surface to generate uniform films with varying thickness. Previous studies have demonstrated that specific protein-resistant hydrogels can be synthesized via photoinitiated chemical vapor deposition (piCVD) on optical sensors without sacrificing sensitivity and accuracy. However, antifouling layers deposited directly on immobilized biomolecules and used for screening more complicated analytes, such as lysate, have not been investigated.Herein, antifouling and stabilized interfaces capable of sensitively assaying cell lysate were constructed by depositing ultrathin encapsulation layers on silicon wafers with immobilized nanobodies via piCVD. Since an antifouling mechanism can be either interpreted as solvation barrier induced by hydrophilic groups or presented as easy foulants removal given by the low surface energy nature of hydrophobic materials, poly(hydroxyethyl acrylate) (pHEA) and poly(1H,1H,2H,2H-perfluorooctyl acrylate) (pTFOA) are selected and studied as the representatives of the two groups due to their biocompatibility and multiple synthetic routes. Interestingly, despite significant fouling reduction and stabilized local environments under harsh conditions were achieved by both materials, the compatibility of pTFOA with piCVD was much better than pHEA, which was observed as being more sensitive to the environmental humidity and thus exhibited poor repeatability. Consequently, the piCVD was successfully applied to form an encapsulation layer on “sensitive” substrates to reject unwanted binding and provide constant storage microenvironments, indicating great promise for enhanced biosensing interface fabrication

Control of temperature dependence of microbial time-temperature integrator (TTI) by microencapsulation of lactic acid bacteria into microbeads with different proportions of alginate.

This study has been conducted to investigate the temperature dependence and mass transfer kinetics of a microbial time-temperature integrator (TTI) developed by using emulsification/internal ionotropic gelation method. We report the effect of the Na-alginate concentrations (0.5%, 2.0%, 4.0% and 6.0% w/v) and temperature (8, 15, 20, 25 and 30°C) on the TTI responses (changes in pH and titratable acidity [TA]). Results revealed that Ca-alginate microbeads (Ca-AMs) prepared from 2.0% Na-alginate were more uniform and smaller, with a narrow size distribution, in comparison with the other Ca-AMs. For microbeads with above 2.0% Na-alginate, the TTI response rates decreased because of the lower diffusion efficiency. Linearity in the TA was greatest for the 2.0% Ca-AMs. Therefore, the mass transfer and TTI response kinetics data demonstrated that 2.0% Na-alginate was optimal for producing Ca-AMs from which an ideal microbial TTI could be developed to monitor food spoilage processes with accuracy and precision.

Enhancement of heavy metals recovery from aqueous solutions by cementation on a rotating cylinder using a stationary wiper

The goal of the present research is to study the impact of a stationary wiper almost touching a revolving zinc solid cylinder on the rate of Cu+2 cementation. Initial Cu+2 ions concentration, speed of rotation, and the effect of the presence and absence of a wiper were investigated. The degree of Cu+2 cementation was stated in relation to the mass transfer coefficient which was valued under diverse circumstances. The present study showed that the mass transfer coefficient accelerates as rotation speed and quantity of Cu+2 increase. The presence of a wiper enhances the degree of Cu+2 cementation by an extent that varies from 1.59 to 64% subject to the operational circumstances. The present mass transfer data have been interrelated by dimensionless equations. The importance of such relationships in the sizing and running of rotating cylinders used for performing diffusion- restricted reactions is underlined.

Physical properties and reaction kinetics of CO2 absorption into unloaded and CO2 loaded viscous monoethanolamine (MEA) solution

In order to comprehensively understand how solvent free concentration and high viscosity affect mass transfer and consequently absorption flux, CO2 absorption kinetics into unloaded and CO2 loaded viscous monoethanolamine (MEA) solution were studied in this work using the string of discs contactor. Moreover, density and viscosity of unloaded and loaded viscous MEA solutions were measured using an Anton Paar DMA 4500 density meter and an Anton Paar Lovis 2000 ME rolling-ball viscometer, respectively, and the results were correlated using Redlich-Kister and modified Vogel-Tamman-Fulcher equations as a function of temperature, concentration and CO2 loading. Overall mass transfer coefficients of CO2 absorption in viscous MEA solution were measured over a wide temperature range of 298.15 to 343.15 K and CO2 loading in the range of 0 to 0.4 (mol CO2/mol MEA). A simplified kinetic model was applied to interpret the mass transfer data and explain reaction kinetics between CO2 and unloaded and loaded viscous MEA solution. The effect of temperature, CO2 loading and viscosity on second order reaction rate constant and overall mass transfer coefficients was also discussed.

Preliminary Mass Transfer Performance of CO2 Absorption into AMP-PZ-MEA Ternary Amines

Ternary 2–Amino–2–methyl–1–propanol (AMP), Piperazine (PZ) and Monoethanolamine (MEA) amines blended solvent showed its effectiveness as an alternative liquid absorbent in terms of absorption capacity and regeneration heat duty. However, its mass transfer data have not yet been investigated. In the present study, the mass transfer performance of CO2 absorption into AMP–PZ–MEA ternary amines solutions was evaluated in laboratory scale absorption column packed with Sulzer DX structural packing. The absorption performance was presented in terms of overall mass transfer coefficient (KGav) and CO2 removal efficiency. The effects of operating parameters (i.e., liquid flow rate, gas flow rate, and lean CO2 loading) were investigated. The results showed that liquid flow rate and CO2 loading had a significant impact on KGav, while gas flow rate slightly affected KGav. It was also found that KGav increased as liquid flow rate increased but decreased as CO2 loading increased. Additionally, CO2 removal efficiency increased as liquid flow rate increased but decreased as gas flow rate and CO2 loading decreased.

Studies on ionic mass transfer in an electrolytic cell in the presence of triangle teethed baffles

Mass Transfer data obtained using diffusion – controlled cathodic reduction of ferricyanide ion at the microelectrodes fixed on the electrode support in an electrolytic cell in the presence of a Triangle teethed baffles fixed on the cell wall. The electrolyte used in this study was eqimolal potassium ferricyanide, potassium ferrocyanide and excess sodium hydroxide. The mass transfer coefficient increased with increase in flow rate of the electrolyte and width of baffle and decreased with increase in spacing between the baffles. The experimental data are correlated as following: J D = 39.81 R e - 0.63 w s 0.271 .

Hydrodynamic and Mass Transfer in the Desorption Process of CO2 Gas in a Packed-Bed Stripper

A lab-scale packed-bed stripper containing Dixon rings was used to explore the effects of the process variables on the hydrodynamics and mass-transfer in a stripper using a mixed solvent loaded CO2. The variables are the liquid flow rate, reboiler temperature, and amine concentration, and the hydrodynamic and mass-transfer data can be determined using different models. In the case of hydrodynamics, the dimensionless pressure drop at the flooding point and the total pressure drop were explored first. In the case of mass-transfer, the correlation of the mass-transfer coefficient and the parameter importance were also observed. In addition, the number of plates per meter can be compared with the Dixon rings manufacturer. Finally, the performances of a mixed solvent and monoethanolamine (MEA) solvent were also discussed.

Kinetic modelling and extraction of Orthosiphon stamineus stems and leaves by SC-CO2

The aims of this study are to determine the effect of parameters on the extraction yield of Orthosiphon stamineus stems and leaves extract and to examine the mass transfer process by kinetic models to obtain the extraction rate of supercritical carbon dioxide. Other objective is to compare the antioxidant activity of Orthosiphon stamineus stems and leaves extract using supercritical carbon dioxide extraction and Soxhlet extraction.Extraction parameters involved were pressure (10 and 30 MPa) and temperature (40 and 80 °C). DPPH method was used to examine the antioxidant activity of extract. A better correlation of kinetic mass transfer data has successfully fitted using Brunner model compared with Esquivel model with 6.09% average AARD and 0.992 coefficient of determination. The extraction rate of Orthosiphon stamineus leaves and stems were found to be in the rage of 0.52 × 10 −3 to 8.84 × 10 −3 g/min and 0.8160.52 × 10 −3 to 8.816 × 10 −3 g/min, respectively. The maximum antioxidant activity of Orthosiphon stamineus stems and leaves extract were 91.58% and 88%. Similarity in the quality for both extract of Orthosiphon stamineus stems and leaves makes the separation to be unnecessary.

Proficiency of tellurium extraction in pulsed disc and doughnut columns

ABSTRACT In this research, the separation of tellurium from selenium was studied from chloride solution by TBP extractant. In the batch experiments, the experimental findings indicated that the feed acidity, TBP concentration, and contact time were optimized to achieve the high separation factor. In continuous mode of pulsed disc and doughnut column, the impacts of operating parameters have been discussed on the distribution coefficients of selenium and tellurium, and mass transfer enhancement. A new model for predicting Koca was proposed in terms of holdup values, Sherwood, Reynolds, and Schmidt numbers, which has an acceptable agreement with the mass transfer data.

Development of an Oxygen Mass Transport Coefficient Measurement and Separation Method for Proton Exchange Membrane Fuel Cells

The cost and durability of proton exchange membrane fuel cells (PEMFCs) still limit their adoption as sustainable power systems [1]. Operation at high current densities, which decreases the inventory of costly materials [2], is still considered an option [3] in addition to concurrent reductions in Pt catalyst loadings. However, these approaches intensify mass transfer losses especially at the cathode because the oxidant stream is more dilute (21 % O2 in air) than the fuel (100 % H2) and the heavier O2 molecule moves more slowly. The improvement of characterization methods able to measure and separate oxygen mass transfer coefficients is desirable for more accurate identification and localization of resistances in membrane/electrode assemblies (MEAs).Average limiting currents iave are first measured with a dilute oxidant stream for different flow rates. Subsequently, data are fitted to a mathematical model [4] to obtain the overall mass transfer coefficient k: iave =ie (1–exp(–nFkpr /RTief)) (1)with ie the inlet reactant flow rate equivalent current density, n the number of electrons exchanged in the electrochemical reaction, F the Faraday constant, pr the dry inlet reactant stream pressure, R the ideal gas constant, T the temperature, and f the inert gas to reactant fraction in the dry inlet reactant stream. The oxidant diluent is also varied (He, N2, CO2) to separate the molecular diffusion mass transfer coefficient km by extrapolating to the origin the linear correlation between the overall mass transfer resistance and the diluent molecular mass M [4]: k –1=km (M)–1+k e+K (c)–1=km (M)–1+ke (c)–1+kK –1 (2)The ionomer permeability mass transfer coefficient contribution ke was separated from 1/k e+K by taking advantage of the constant Knudsen diffusion resistance (equation 2 above and equation 7 in [5]). For that last step, the linear correlation between the lumped ionomer permeability and Knudsen diffusion mass transfer resistance 1/k e+K and the oxygen concentration c (1 to 7 %) was extrapolated to the origin, which yielded the Knudsen diffusion mass transfer coefficient kK . This approach to isolate the Knudsen contribution is novel. Other techniques are used, including temperature variations [5].Experiments were conducted with a 50 cm2 active area cell and General Motors MEAs with a commercially relevant cathode catalyst loading of 0.05 to 0.15 mg Pt cm–2 (Pt catalyst supported on a high surface area carbon). All MEA tests were duplicated and completed for several temperatures (30 to 80 °C) and relative humidities (50 to 100 %). Four diagnostic methods were employed to supplement the analysis of mass transfer data. The use of O2, 21 % O2 in He, and air enabled the derivation of overpotentials from polarization curves [6]. The high frequency cell resistance was measured with a milliohmmeter. The catalyst area was extracted from the hydrogen adsorption region of cyclic voltammograms [7]. The overall cell water balance was also calculated to assess the presence of liquid water [8].The smallest mass transfer resistance was assigned to the ionomer permeability, which supported the need for repetitive measurements and statistics for an accurate quantification. The slope of the linear correlation between the ionomer permeability and Knudsen diffusion mass transfer resistance and the oxygen concentration was dependent on the water balance. A positive slope occurred under sub-saturated streams whereas a negative slope was correlated with the wettest operating conditions, which will require a method modification to extract the Knudsen diffusion resistance. A plot of the ionomer and molecular diffusion mass transfer resistance versus the total mass transfer overpotential showed two regimes that are differentiated by the absence/presence of liquid water (see figure). Catalyst layers, only several microns thick, have a larger mass transfer resistance and overpotential under flooding conditions.[1] Y. Wang, D. F. R. Diaz, K. S. Chen, Z. Wang, X. C. Adroher, Mater. Today, 32 (2020) 178.[2] A. Kongkanand, M. F. Mathias, J. Phys. Chem. Lett., 7 (2016) 1127.[3] N. Ramaswamy, W. Gu, J. M. Ziegelbauer, S. Kumaraguru, J. Electrochem. Soc., 167 (2020) article 064515.[4] T. Reshetenko, J. St-Pierre, J. Electrochem. Soc., 161 (2014) F1089.[5] N. Nonoyama, S. Okazaki, A. Z. Weber, Y. Ikogi, T. Yoshida, J. Electrochem. Soc., 158 (2011) B416.[6] J. St-Pierre, M. Angelo, K. Bethune, J. Huizingh, T. Reshetenko, M. Virji, Y. Zhai, Modern Fuel Cell Testing Laboratory, in Springer Handbook of Electrochemical Energy, Part D, Chapter 19, Edited by C. Breitkopf, K. Swider-Lyons, Springer, 2017, p. 611.[7] R. N. Carter, S. S. Kocha, F. T. Wagner, M. Fay, H. A. Gasteiger, ECS Trans., 11(1) (2007) 403.[8] J. St-Pierre, N. Jia, M. van der Geest, A. Atbi, H. R. Haas, United States patent 7,132,179, November 7, 2006. Figure 1

Commissioning of the LPCE and purification systems as front-end of the experimental pilot plant for D-T separation

Abstract Liquid Phase Catalytic Exchange (LPCE) as front-end process and Cryogenic Distillation (CD) as back-end process are key processes in detritiation of heavy water used in Cernavoda CANDU-type Nuclear Power Plant (NPP) from Romania as neutron moderator and in the primary heat transfer system. Same technology is used in the Water Detritiation System (WDS) of International Thermonuclear Experimental Reactor (ITER) from Cadarache, France, in order to recover tritium from moderately tritiated water. The purpose of this paper is to give a detailed overview of the current status for the front-end of the ICSI pilot plant, LPCE and purification systems, including all process components. Additionally, the paper will present the results of the non-radiological commissioning of the actual LPCE. The tests were made using protium and deuterium in order to have the confirmation of fully availability for all systems, to verify the operability in manual and automate mode for all sequences involved by start-up, normal operation and safe shut-down of the installation. The principal results consist in the safety and operability design confirmation. Secondly we present the mass transfer data of LPCE column equipped with catalytic package COMPACK C–P 001 consisting of the structured B7 stainless steel packing manufactured and patented by ICSI and a Pt/C/PTFE hydrophobic catalyst at the commissioning low concentration heavy water tests.

Mass transfer studies in RDC column by the coupling effects of perforated structure and reactive extraction of Mo(VI) and W(VI) from sulfate solution

Solvent extraction of molybdenum (VI) and tungsten (VI) by synergism of the mixture of D2EHPA and TBP were conducted in the RDC extractor with perforated structure. The initial aqueous pH, extractant concentration, ammonium hydroxide concentration as a stripping agent, and synergistic enhancement factor were optimized in the initial experiments before collecting column data. In the RDC column, the influence of agitation rate and inlet phase velocities were examined on the hydrodynamic velocities, mass transfer data, and distribution coefficients. The finding data indicated that the impact of agitation speed on the distribution coefficients of molybdenum and tungsten is considerable in comparison the inlet phase flow rates. Published empirical models for estimating the slip and characteristic velocities were compared with the solvent extraction data, and the modified models were presented by considering the reactive extraction. Mass transfer performance based on the dispersed phase was studied by applying the axial dispersion model. Column performance enhances the increment of the operational variables such as agitation speed, inlet solvent phase flow rate, and inlet aqueous phase flow rates, but the variations of agitation speed and solute transfer direction have a high impact on this phenomenon. The previous models for estimating the mass transfer coefficients were compared with the present work. The published models failed to acceptable estimate the mass transfer evaluation due to column geometry and reactive extraction systems. Finally, the new models were proposed by using the dimensionless analysis methods for obtaining the enhancement factor in both extraction and stripping stages.

The performance of pulsed scale-up column for permeable of selenium and tellurium ions to organic phase, case study: Disc and doughnut structure

A research investigation of the overall mass transfer coefficients, holdup and mean drops of dispersed phase as well as slip and characteristic velocities were carried out in the pulsed scale-up column with disc and doughnut structure for extraction of tellurium and selenium from a hydrochloric acid medium with TBP extractant. The impact of operating conditions containing the pulse intensity, inlet aqueous and solvent phase velocities have been studied on the mass transfer rates, and the special column characteristic. By considering the reactive extraction situations, modified models were derived for predicting of holdup, d32, and slip velocity in this extractor. The axial diffusion model for extracting the selenium and tellurium using the TBP system was utilized to determine the mass transfer evaluation. Mass transfer data indicated that the column performance enhanced by increasing the pulse intensity and inlet phase velocities. Because of the reactive extraction system, available correlations failed to correctly estimate the mass transfer data. Thus, a novel model based on dispersed phase holdup, Eö, and Re numbers was developed to estimate the enhancement factor. The values calculated by the derived correlation were compared with the experimental results, and a good agreement was obtained between results.

Revealing mass transfer and hydrodynamic effects in a PRDC column by using the integration of extraction and separation for molybdenum and tungsten ions from aqueous solution

The present work is performed to assess the hydrodynamic parameters and mass transfer coefficients in a PRDC column for the chemical reaction systems. By considering the selective extraction of molybdenum from tungsten, the extraction parameters and synergistic enhancement factor were interpreted at the batch experiments. In the column experiments, the impacts of operating conditions such as the agitation rate, inlet solvent phase velocity as well as inlet aqueous phase velocity were studied on the drop behavior, overall mass transfer coefficients, and extraction efficiencies. The modified correlations by using relationship of dimensionless numbers were illustrated to estimate the hydrodynamic factors (holdup value and the Sauter mean drop diameter) under the physical and reactive systems. The mass transfer coefficients for the continuous phase were evaluated by the axial diffusion method in both extraction and stripping stages. It was observed that the column performance was primarily affected by the agitation speed and mass transfer direction, but this phenomenon slightly changes with the inlet phase velocities. The previous empirical models were compared with the obtained mass transfer data, and the available models were failed to precisely anticipate the experimental data due to chemical reaction conditions. Finally, two new models based on the dimensionless numbers were derived for calculating the overall Sherwood number. The value of separation factor in the extractor indicated the column capacity with the excellent separation for molybdenum from tungsten in the sulfate solution.