Mass Transfer Parameters Research Articles

Mass transfer limitations in binderless ZSM‐5 zeolite granules during adsorption of flavour compounds from aqueous streams

AbstractBACKGROUNDRecently, a new process concept has been proposed to selectively adsorb wort off‐flavours, i.e. aldehydes, from alcohol‐free beers with hydrophobic zeolites.RESULTSIn this work, we investigated the uptake of a mixture of wort flavour compounds (2‐methylpropanal, 2‐methylbutanal, 3‐methylbutanal, furfural, and methional), from a model solution onto binderless hydrophobic ZSM‐5 zeolite granules in order to quantify mass transfer parameters and identify bottlenecks. Subsequently, the homogenous solid diffusion model was employed to regress the effective diffusion coefficients for each molecule and experimental condition, which ranged between 10−15 and 10−13 m2 s−1, indicating strong intraparticle mass transfer limitation. Furthermore, it was found that the effective diffusion coefficient is inversely correlated to the molecules' hydrophobicity, expressed as the logD value and its isotherm affinity constant.CONCLUSIONThese results give valuable insight to design and improve the adsorbent material and an off‐flavour removal unit at industrial scale. © 2020 The Authors. Journal of Chemical Technology & Biotechnology published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Multiscale modelling of CO2 reduction to methanol over industrial Cu/ZnO/Al2O3 heterogeneous catalyst: Linking ab initio surface reaction kinetics with reactor fluid dynamics

There has been a growing trend to couple different levels of modelling, such as going from first-principle calculations to the meso (e.g. kinetic Monte Carlo - KMC) and macro scale (e.g. computational fluid dynamics - CFD). In the current investigation, we put forward a CFD study of CO2 hydrogenation to methanol for heterogeneous reacting flows in reactors with complex shape geometries, coupled with first-principle calculations (density functional theory - DFT). KMC operation simulations were also performed to obtain insight into the uppermost layer conditions during the reaction. With computational fluid dynamics, the focus was placed on the non-uniform catalytic reduction of carbon dioxide to formate, which we treated with a detailed mean-field first-principle microkinetic model, analysed, and corroborated with experiments. The results showed a good consistent agreement with experimental data. The formulated methodological approach paves the way towards full virtual multiscale system descriptions of industrial processing units, encompassing all conventional stages, from catalyst design to the optimization of mass transfer parameters. Such a bridging is outlined for carbon capture and utilization.

Migration of antioxidants from polylactic acid films, a parameter estimation approach: Part II – assessment of partition, diffusion and convective mass transfer coefficients

Abstract Migration kinetics of a polymer-food system can be studied using physical parameters such as the diffusion (D), partition (Kp,f), and convective mass transfer (h) coefficients. A mathematical model considering all three important migration parameters was proposed in part I of this paper series. However, there are other existing mass transfer models focus solely on either D and/or Kp,f. With various options available, how would a researcher choose an appropriate mathematical model for investigating the kinetics migration of a food packaging-simulant system? To address this question, this paper analyzes and compares the newly proposed mathematical model with the existing ones using a selected migration case study. Based on the output, a decision tree analysis for determining mass transfer parameters for migration studies is proposed. The decision tree analysis was beneficial as guidance and was able to provide an insight into the kinetic behaviors of a migrant in a polymer-food system by providing a method to select the right model for the aforementioned system.

Mass Transfer Modeling of CO2 Absorption into Blended Aqueous MDEA–PZ Solution

In this research, the rate of CO2 absorption into methyl diethanolamine–piperazine (MDEA–PZ) solution was investigated. To model the mass transfer flux in the reactive absorption processes, the dimensionless parameters of the process were obtained using the Buckingham Pi theorem and considering the effective parameters in mass transfer. The CO2 mass transfer flux in the reactive absorption process depends on the mass transfer parameters of both the liquid and gas phases. Based on the dimensionless parameters obtained, a correlation is proposed to calculate the mass transfer flux of acidic gases in MDEA–PZ solutions. The mass transfer flux in the reactive absorption process is modeled based on the four laws of chemical equilibrium, phase equilibrium, mass balance, and charge balance. Experimental data from the literature were used to determine the constants of the derived correlation as a function of dimensionless parameters. In the provided correlation, the effects of dimensionless parameters including film parameter, CO2 loading, ratio of diffusion coefficients in the gas–liquid phase, CO2 partial to total pressure, and film thickness ratio as well as factors such as temperature, the number of free amines in the solution, the partial pressure of CO2, on the CO2 mass transfer flux were investigated. According to the results, the absorption rate decreases with increasing CO2 loading and film parameter, and the mean absolute deviation is about 3.6%, which indicates the high accuracy of the correlation.

PREDICTION OF MASS TRANSFER COEFFICIENT OF THE CONTINUOUS PHASE IN A STRUCTURED PACKED EXTRACTION COLUMN IN THE PRESENCE OF SIO2 NANOPARTICLES

In this experimental study, mass transfer and hydrodynamic parameters of water/kerosene/acetic acid system in a packed column were investigated, in which the mass transfer direction was set from the continuous phase (saturated water of kerosene and acetic acid) to the dispersed phase (saturated kerosene of water) in all the experiments. To assess the impact of nanoparticles on mass transfer, the experiments were performed in the presence of SiO2 nanoparticles and absence of the nanoparticles. The results showed that the addition of the nanoparticles to the base fluid (saturated kerosene of water) increased the mass transfer efficiency to the critical concentration, 0.05 vol. %, due to the intensified internal circulation of the droplets. Beyond the critical concentration, the mass transfer efficiency declined by the occurrence of an agglomeration phenomenon, i.e., the change of the mass transfer mechanism from turbulence to diffusion due to the accumulation of the nanoparticles. An empirical correlation for the continuous phase Sherwood number was presented. The mean value of the absolute relative error was calculated to 8.04%, indicating that the proposed correlation represented the experimental data very well. (Less)

Relative Effect of Additional Solid Media on Bubble Hydrodynamics in Bubble Column and Airlift Reactors towards Mass Transfer Enhancement

Many researchers have focused on multi-phase reactor development for improving mass transfer performance. However, solid particle addition in gas–liquid contactor for better oxygen mass transfer performance is still limited. Hence, this study aims to analyze the relative effect of different types of local solid media on the bubble hydrodynamic characteristics towards mass transfer enhancement in bubble columns (BCR) and airlift reactors (ALR). This was investigated by varying solid media types (ring, sphere, cylinder, and square), solid loadings (0%–15%), and superficial gas velocities (Vg) (2.6–15.3 × 10−3 m/s) in terms of the bubble hydrodynamic and oxygen mass transfer parameters. The result showed that bubble size distribution in BCR and ALR with additional plastic media was smaller than that without media addition, approximately 22%–27% and 5%–29%, respectively, due to the increase of the bubble breaking rate and the decrease of the bubble rising velocity (UB). Further, adding media in both reactors significantly decreased the UB value. Since media increased flow resistance, resulting in decreased liquid velocity, it can also be the moving bed to capture or block the bubbles from free rising. Therefore, oxygen mass transfer performance was investigated. The oxygen transfer coefficient (KLa) in BCR with solid media addition was enhanced up to 31%–56% compared to a non-addition case, while this enhancement was greater at higher solid loading due to its higher effective surface, resulting in a higher bubble break-up rate compared to the lower loading. In ALR, up to 38.5% enhanced KLa coefficient was archived after adding plastic media over the non-addition case. In conclusion, ring and cylinder media were found to be the most significant for improving KLa value in BCR and ALR, respectively, without extra energy.

Supercritical Extraction of Heracleum persicum Plant and Mathematical Modeling

Background: Supercritical CO2 is the most applicable solvent because of its unique properties such as; high selectivity, non-explosivity, non toxicity, low cost of purchasing and its unique critical points. The solubility of this solvent changed rapidly with only a small change in pressure and temperature especially in pressure. According to literatures, the method of supercritical extraction is the best technology for extracting sensitive constituents. Despite of numerous studies in the literature for extracting essential oil from plants, no studies can be found about this valuable medicinal plant by CO2 supercritical extraction method. Method: In this study, the extraction of main medicinal constituents from Heracleum Persicum and mathematical modeling was done using supercritical carbon dioxide. The experimental data were investigated was analyzed by using gas chromatography (GC) and mass spectrometer chromatography (GC-MS) methods. The model of seed and bed, which includes three parameters of mass transfer, axial dispersion, and effective penetration coefficients, were used for modeling the extraction process. This model was used based on the equilibrium of the fluid phase and solid phase to communicate with the experimental data. Then the obtained yield of supercritical technology was compared with the hydro distillation method. Results: The main extracted constituents of some different varieties of Heracleum by different methods and solvents have been determined. The extracted chemicals by supercritical fluid technology from the seeds of the Heracleum Persicum encompasses hexyl butanoate, octyl 2- methyl butyrate, octylisobutyrate and anethole which are so effective against epilepsy and has the most antibacterial, antiviral and antifungal effects. So supercritical fluid extraction is more selective than the other methods. Conclusion: Extracting of essential oil and mathematical modeling from H. persicum were performed under different operating conditions of temperature, pressure, particle size and solvent flow rate. Experimental and modeling results showed that the operating parameters used in different conditions had a different effect on extraction efficiency and model parameters.

Технологічні особливості капсулювання гранульованих добрив плівкою на основі модифікованого ПЕТФ

Проаналізовано взаємодію твердої дисперсної фази, рідкого плівкоутворювача та повітря під час капсулювання гранульованих мінеральних добрив. Показано, що на поверхні частинки відбувається передача тепла від повітря до розчину плівкоутворювача і видалення розчинника у середовище газової фази. Оцінено вплив гідродинаміки, тепло- та масообміну на процес капсулювання амонійної селітри та нітроамофоски в апараті псевдозрідженого стану плівками, які складаються з модифікованого поліетилентерефталату, гідролізного лігніну та цеоліту. Встановлено, що визначальним технологічним параметром процесу капсулювання є швидкість повітря, за якої шар твердого матеріалу буде перебувати у стані стійкого псевдозрідження. Теоретичним методом розраховано швидкість повітря в апараті для капсулювання аміачної селітри 5,6 м/с та нітроамофоски 6,1 м/с. Проведено аналітично-експериментальні дослідження тепломасообміну під час капсулювання гранульованих добрив у апараті псевдозрідженого стану циліндричного типу періодичної дії за встановлених гідродинамічних режимів. Отримано експериментальні залежності температури повітря від висоти шару досліджуваних мінеральних добрив за витрати плівкоутворювача 1∙10-4 кг/с, 3∙10-4 кг/с і 5∙10-4 кг/с з використанням 7-канального інтелектуального перетворювача, який дав змогу одночасно фіксувати температуру в семи точках з виводом інформації на ПК. Графічним методом за кутом нахилу температурних кривих встановлено значення коефіцієнтів тепловіддачі α під час капсулювання аміачної селітри 135,7 Вт/(м2К) і нітроамофоски 118,3 Вт/(м2К). Для плівкоутворювального розчину, який складався із етилацетату 87 % (мас), модифікованого ПЕТФ 10 % (мас), гідролізного лігніну 3 % (мас) визначено коефіцієнти масовіддачі β під час капсулювання аміачної селітри 0,251 м/с і нітроамофоски 0,198 м/с. На підставі отриманих коефіцієнтів масовіддачі встановлено максимальну витрату плівкоутворювача Pmax (104кг/с∙кг добрив): аміачна селітра – 20,512, нітроамофоски – 22,857. За отриманими технологічними параметрами здійснено капсулювання досліджуваних добрив. За характером кінетичних кривих вивільнення компонентів із капсульованих частинок аміачної селітри і нітроамофоски встановлено, що за визначеними технологічними параметрами отримано мінеральні добрива із прогнозованими властивостями.

Enhanced mass transfer and reduced pressure drop in a compound rotating zigzag bed

A rotating zigzag bed (RZB) had achieved the commercial application of Higee in continuous distillation processes, and then a compound rotating zigzag bed (CRZB) was developed from the RZB. The CRZB rotor was composed of a disk layer including several perforated concentric circular ripple disks fixed on a perforated rotating ring at the inner part of the rotor and several coupled rotational-stationary baffles at the outer part of the rotor. And a stationary four-arm liquid distributor was located at the eye of the CRZB rotor. The effective interfacial area (ae) and local liquid-side mass transfer coefficient (kL) of the CRZB rotor were measured by experiments of a chemical absorption of CO2 in NaOH solution, and the local gas-side mass transfer coefficient (kG) of the CRZB rotor was measured by experiments of a stripping of ethanol from an ethanol-water mixture by air. The gas pressure drop across the CRZB was measured with air-water system. Effects of gas flow rate, liquid flow rate and rotational speed on these mass transfer parameters and gas pressure drop were investigated. The stationary four-arm liquid distributor led to stronger end effect of the CRZB rotor than that of the RZB rotor. The end effect of the CRZB rotor had significant effect on the ae and kL of the rotor. The ae of the CRZB rotor was much higher than that of the RZB rotor because the total space in the disk layer of the CRZB rotor served as mass transfer zones and the CRZB rotor had stronger end effect than the RZB rotor. The local volumetric liquid- and gas-side mass transfer coefficients (kLae and kGae) of the CRZB rotor reached 2.3 times higher than those of the RZB rotor at a higher liquid flow rate and a rotational speed of 1200 rpm. The gas pressure drop across the CRZB was lower than that across the RZB, because the coupled rotational-stationary baffles were abandoned at the inner part of the CRZB rotor, which reduced the gas flow resistance and led to a lower pressure drop compared to the RZB. Thus, mass transfer was enhanced and gas pressure drop was reduced in the CRZB compared to the RZB, which showed the CRZB had excellent potential as a representative of the second-generation RZB for commercial applications.

High bioreactor production and emulsifying activity of an unusual exopolymer by Chromohalobacter canadensis 28.

Unusual composition of an exopolymer (EP) from an obligate halophilic bacterium Chromohalobacter canadensis 28 has triggered an interest in development of an effective bioreactor process for its production. Its synthesis was investigated in 2‐L bioreactor at agitation speeds at interval 600‐1000 rpm, at a constant air flow rate of 0.5 vvm; aeration rates of 0.5, 1.0, and 1.5 vvm were tested at constant agitation rate of 900 rpm. EP production was affected by both, agitation and aeration. As a result twofold increase of EP yield was observed and additionally increased up to 3.08 mg/mL in a presence of surfactants. For effective scale‐up of bioreactors mass transfer parameters were estimated and lowest values of KLa obtained for the highest productivity fermentation was established. Emulsification activity of EP exceeded that of trade hydrocolloids xanthan, guar gum, and cellulose. A good synergism between EP and commercial cellulose proved its potential exploration as an enhancer of emulsifying properties of trade emulsions. A pronounced lipophilic effect of EP was established toward olive oil and liquid paraffin. Cultivation of human keratinocyte cells (HaCaT) with crude EP and purified γ‐polyglutamic acid (PGA) showed higher viability than control group.

Analysis of gradient elution chromatography using the transport model

A transport model is considered to describe gradient elution in liquid chromatography in packed beds with the linear isotherm dependent on the mobile phase modulator. By applying a coordinate transformation, the model is solved analytically using the Laplace transform approach. The moment generating property of the Laplace domain solution is used to derive analytical expressions for the first three moments of the response to rectangular injections. These moments are instructive for analyzing the retention time, band broadening and asymmetry of elution profiles. Compared to isocratic elution, the derivation of analytical solutions and moments for gradient elution is more complicated, because the retention behavior of the solutes depends on the varying mobile phase modulator. Several case studies are evaluated theoretically. To gain confidence on the derived analytical results, a high-resolution finite volume scheme is also applied to solve the same model equations numerically. The analytical solutions and moments provided are utilized to predict the effects of starting and ending times of gradient, magnitude of modulator concentration variation, gradient slopes, and mass transfer coefficient on retention and peak shape. The analytical moment expressions derived can be used to determine retention and mass transfer parameters from experimental peaks and to predict elution behaviors if these parameters are known.

Simulation and multi-objective optimization of heat and mass transfer in direct contact membrane distillation by response surface methodology integrated modeling

Membrane distillation (MD) traditionally utilizes low-grade thermal energy to drive vapor transport through hydrophobic membrane pores for water treatment. The concurrent enhancement of water flux, thermal efficiency and water productivity to achieve the global optimization of MD is still a challenge. In this work, a new simulation and optimization approach is proposed by integrating theoretical heat and mass transfer models with response surface methodology to investigate the complicate interaction effects of various influencing factors on heat and mass transfer parameters, including overall mass transfer coefficient, feed/permeate side heat transfer coefficients, membrane surface temperature and temperature polarization coefficient, in direct contact membrane distillation (DCMD). The operating and module configuration variables show important interaction effects on enhancing the heat and mass transfer in the membrane module. The significantly elevated heat transfer coefficient on account of the combined high feed temperature, short module length and high feed velocity leads to a great improvement of water flux and thermal efficiency. The ultimate global optimum conditions for the high water productivity were determined where the high levels of heat transfer coefficient (5905W/(m2·K)), temperature polarization coefficient (0.66), water flux (63.0kg/(m2·h)) and thermal efficiency (0.83) all synchronously approach to their own pinnacles. The results indicate that it is an effective way to take advantages of the interaction effects of operating conditions with module configuration parameters to achieve the overall enhancement of MD performance.

Effect of magnetic and boundary parameters on flow characteristics analysis of micropolar ferrofluid through the shrinking sheet with effective thermal conductivity

Ferrofluids have many applications in mechanical and electrical engineering. In this paper, characteristics of ferrofluid over a shrinking sheet with effective thermal conductivity model are studied by the homotopy perturbation method (HPM) and Akbari-Ganji's method (AGM). Also, the Finite Element Method (FEM) has been applied for numerical solution. The governing equations formulated by the Tiwari-Das model. It is supposed that base fluid and nanoparticles are water and Fe3O4respectively. Effect of related parameters of micro-rotation velocity and dimensionless velocity have taken for suction and injection of mass transfer parameter. Results show that the magnetic and boundary parameters, in contrast to the micro-rotation parameter, have the same impact on velocity. Moreover, a comparison has been made between the results of this study with other researchers shows the impressive accuracy and efficiency of these methods.

Novel biphasic amino-functionalized ionic liquid solvent for CO2 capture: kinetics and regeneration heat duty.

Amino-functionalized ionic liquid biphasic solvents present excellent absorption capacity, regeneration ability, and energy consumption savings, which make them a possible candidate for CO2 capture. The kinetics and regeneration heat duty of the [TETAH][Lys]-ethanol-water system capturing CO2 were investigated in this work. The mass transfer and kinetic parameters, including the overall reaction rate constant (kov), the reaction rate constant (k2), and the enhancement factor (E), were assessed at diverse concentrations and temperatures. At 303.15K, the k2 of CO2 capture into the [TETAH][Lys]-ethanol-water solution was 58,907.30m3kmol-1s-1. The Arrhenius equation was introduced to evaluate the relations between k2 and the reaction temperature, which can be presented as [Formula: see text] The regeneration heat duty of the novel biphasic solvent was 35.5 and 62.39% lower than those of [TETAH][Lys]-water and the benchmark monoethanolamine solution, respectively. An efficient absorption performance and lower energy requirement indicate the great potential for this application.

Impedance-Resolved Beginning-of-Life Electrochemical Performance and Durability of Treated Carbon Felt Electrodes in Vanadium Redox Flow Batteries

Vanadium redox flow batteries (VRFBs) have been targeted as a potential technology for integration of renewable energy sources onto grids as well as improving grid-level power generation efficiency. The primary reasons VRFBs are well-suited for this role are on account of their modularity, scalability, and relatively high performance [1]. There are still, however, many design parameters that can be more highly optimized to improve and specialize aspects of this technology. The kinetics at the anode of VRFBS utilizing graphite felt electrodes on are generally more limiting than at the cathode [2] as well as showing more rapid signs of performance degradation and are as such an area where sources of losses can be improved significantly.Electrochemical impedance spectroscopy is a commonly used method for characterizing sources of losses in VRFB systems. Impedance spectra are often analyzed in the context of the theory of Randles circuits, where electrochemical phenomena are treated analogously to circuit elements. Data reduction equations can then quantify these circuit elements and subsequently determine the values of physical parameters of interest in the system. The Randles circuit, however, has no geometric framework, nor any term which can capture the physical behavior of electrolyte resistance that is distributed throughout a porous medium. A model which was developed by Paasch and co-workers [3], referred to as the macrohomogeneous porous electrode (MHPE) model, addresses this phenomenon and has been used by others to characterize EIS data in systems with porous electrode where electrolyte resistance is non-negligible. Nguyen [4] et. al furthered this model in the context of inhomogeneous porous electrodes and membranes, Sun and co-workers [5] were the first to demonstrate the single MHPE model in the context of the all vanadium chemistry and Pezeshki and co-workers applied the model to quantify the effects of cell architecture in VRFBs [6].Much work on improving carbon felt-based electrodes in VRFBs does so by attempting to make charge transfer more facile [7]. As the charge transfer becomes smaller the effect of the distributed ohmic (pore) resistance begins to account for a larger portion of the cell losses and neglecting to account for it can misrepresent the series ohmic resistance (primarily membrane) and the charge transfer resistance.This work looks at the impact of using three different EIS models on different electrodes (seven treatments and one control) and the impact on the fitted parameters based on the utilization of a specific model. The first two models are both Randles circuits, which differ in the portions of the frequency spectrum which they are using. The first Randles circuit utilizes the full frequency spectrum referred to as RFS model (Randles Full Spectrum), the second Randles circuit truncates the spectrum, referred to as RTS model (Randles Truncated Spectrum), and excludes the distributed ohmic (pore) resistance, and third model is the aforementioned MHPE model. The electrode treatments include a nitric acid soak, heat treatment in 3 different gaseous environments (Oxygen, Nitrogen and Ammonia), and hydrothermal treatments in a nitric acid | sulfuric acid environment for 3 different durations. Electrodes were tested in-situ and cycled to characterize beginning-of-life stability.The results show that there are non-trivial tradeoffs between utilizing the different models. The serial ohmic resistance cannot be predicted accurately by either of the Randles circuit models (RFS and RTS) for all of the electrode treatments where it is overestimated as seen in Figure 1. Further, if the RFS model is used, it can yield kinetics parameters that differ from the MHPE model by over 50%. However, the RTS model is in relatively high agreement with the MHPE model for kinetics parameters and mass transfer parameters that can be extracted from EIS data. Over the course of cycling the electrodes treated in the ammonia atmosphere demonstrated both the highest stability and the lowest charge transfer resistance of all of the tested electrodes. Figure 1

Comparison of mass transfer parameters inside a USEPA flux hood for two VOCs.

Odorous emissions from area sources at wastewater treatment plants have become an environmental issue due to negative impacts on neighboring communities causing annoyance. Enclosure devices (such as dynamic flux chambers) have been used as direct methods to estimate area source emission rates from liquid-gas surfaces. Previously, model compounds have provided information about the internal mass transfer behavior of these sampling devices and the parameters estimated for certain model compounds that can be adapted for other compounds with similar liquid-gas partitioning properties. Acetic acid and butyric acid (both gas-phase-controlled compounds) were compared in order to assess the validity of adapting results from one compound to another. Mass transfer parameters for acetic acid and butyric acid were determined for a USEPA flux hood using a sweep air flow rate of 5 L/min. Mass transfer rates estimated for butyric acid, using the mass transfer parameters of acetic acid, were of the same order of magnitude as the experimental butyric acid mass transfer rates.

Simulating Scale Dependencies on Dispersive Mass Transfer in Porous Media Under Various Boundary Conditions

Studies on mass transfer and transport of dissolved contaminants through heterogeneous hydrogeology rely on realistic expressions of their functional parameters. Hydrodynamic dispersion is one such parameter inheriting significant ambiguities in its estimation when subjected to heterogeneous flow conditions. In this study, a numerical model has been developed to explicitly evaluate the variability of dispersion coefficient on time-based and space-based scales for simulating contaminant transport mechanism in saturated porous media under nonlinear sorption mass transfer. Four types of inlet (solute source) conditions, viz., constant continuous, pulsating, exponentially decaying and sinusoidal varying were considered, and the resulting concentration profiles were compared. The governing partial differential equations were solved using an implicit finite difference technique. The results from sensitivity analysis suggest that the magnitude of the fluid velocity was influenced by the type of dispersion coefficient for different inlet boundary conditions. However, sorption partition coefficients and porosities were generally insensitive to the nature of dispersion under these boundary conditions. When time-dependent dispersion coefficient was adopted, an asymptotic increase in retained solute mass was observed for increased fluid velocity irrespective of the boundary conditions. The behavior of the concentration profile obtained using distance-dependent dispersion coefficient was unique when sinusoidal decaying solute boundary condition was used. The study rightly emphasizes the need for simultaneously updating mass transfer and transport parameters while accounting for the variation in solute inlet conditions.

Antioxidant and antimicrobial properties of organic fruits subjected to PEF-assisted osmotic dehydration

The effect of PEF pre-treatment prior to osmotic dehydration on mass transfer parameters, colour, antioxidant and antimicrobial properties in organic strawberries and kiwifruits was evaluated. An increase of water loss in both fruits upon the application of combined processes was noticed (up to 21.6%), while a decrease of solid gain was observed only in kiwifruit samples dehydrated in sucrose (about 45%). In general, the combined treatments were beneficial for colour maintenance in both fruit tissues. The antioxidant capacity (DPPH) and activity (ORAC) increased after PEF treatment, however, all the combined treatments reduced significantly these values (of about 20 and 28% for strawberry and of about 56 and 35% for kiwifruit, respectively for DPPH and ORAC methods). In general, PEF treatment alone was also effective with regard to an increase in the antimicrobial activity of the samples against the tested microorganisms (B. subtilis, E.coli, S. cerevisiae). Industrial relevancePEF pre-treatment coupled with osmotic dehydration could be applied at industrial level to obtain semi-dried fruit products. Moreover, both processes could be used as pre-treatments for drying process, in order to develop healthy and microbiologically stable fruit snacks. In fact, in the present work we observed that PEF pre-treatment alone promoted higher antioxidant and antimicrobial activity. The combined process decreased both parameters, suggesting that an accurate study is necessary to evaluate the benefits of these processes in terms of bioactive compounds retention and time and energy consumption in further drying process. The results of the present study could be used as a starting point for the industries to design novel products with intermediate moisture content intended for further processing.

Mass Transfer and Colour Analysis during Vacuum Frying of Colombian Coastal Carimañola.

This study is aimed at analysing the effect of vacuum frying on the kinetic parameters of mass transfer, the CIE L∗a∗b∗ colour parameters of the Carimañola. For the kinetic analysis, the moisture and oil content were measured by means of an experimental design consisting of two factors: frying time with seven levels (60, 120, 180, 240, 300, 420, and 540 s) and frying temperature with three levels (120, 130, and 140°C). The diffusivity coefficient, the moisture transfer rate, and the oil adsorption rate, with their respective activation energies, were calculated. For the colour analysis, the reflectance technique was used to determine the colour coordinates of the CIE L∗a∗b∗ space, and the general colour change was calculated (ΔE). Concerning the kinetics, the increase in temperature and frying time reduced the moisture content, while the oil content decreased with the increase in temperature and increases with frying time. The diffusivity ranged from 1, 238 × 10−6 m2/s at 120°C to 2, 84 × 10−6 m2/s at 140°C. The mass transfer coefficients for moisture ranged from 2 × 10−4 m/s at 120°C to 4 × 10−4 m/s at 140°C. The values of the oil uptake rate were from 0.0022 s−1 at 120°C to 0.0018 s−1 at 140°C. Finally, the luminosity parameter shows a decrease with the increase in temperature, although the first 240 s shows a rise and then begins to decrease. Vacuum frying allowed Carimañolas to be obtained with a lower oil and moisture content, with an appropriate colouring, eye-catching and visually attractive to consumers.

Enhanced performance on simultaneous removal of NOx-SO2-CO2 using a high-gravity rotating packed bed and alkaline wastes towards green process intensification

In order to intensify the gas-liquid absorption processes in the field of energy and environment, high-gravity rotating packed bed (HiGee RPB) has been successfully applied in the multiple air pollutants abatement and CO2 capture by mineralization. Since the mass transfer and chemical reaction through gas-liquid absorption were found to be the key factors affecting acid gas removal, a mass transfer model based on the two-film theory for simultaneous removal of NOx-SO2-CO2 in an RPB was developed in this study. The mass transfer parameters including overall gas-phase mass transfer coefficient (KGa), height of a transfer unit (HTU), liquid mass transfer rate (kL) and enhancement factor (E) were theoretically determined from the experimental data. The effect of key dimensionless operating factors such as high gravity factor (β), gas-to-liquid ratio (GLR), and liquid-to-solid ratio (LSR) on mass transfer parameters were evaluated. Based on the results obtained in this study, the enhancement of high gravity filed on mass transfer and removal efficiencies of NOx and CO2 were significantly higher than that of SO2. It was inferred that the carbonation reaction could compensate the removal efficiency of acid gaseous pollutants at the lower mass transfer rate. The relationship between mass transfer rate and energy consumption for the multiple air pollutant control via a HiGee process was established. The favorable operating factors for NOx-SO2-CO2 simultaneous removal in an RPB were suggested as β of 233.8, GLR of 69.5 and LSR of 40.