Values Of Mass Transfer Coefficient Research Articles

Kinetics and modelling of the heat and mass transfer during the solar drying of cassava slices under natural convection mode

Abstract The kinetics and modelling of heat and mass transfer during the solar drying of cassava slices integrated with the pebble's sensible thermal storage material (PSTSM) were investigated. Fifteen (15) thin layer drying models were adopted to model the drying curves following standard criteria for fitness. The maximum temperatures were 52.5 °C and 55 °C for plywood drying chamber (PLC) and Perspex glass chamber (PGC) respectively. It took both drying systems with Perspex and plywood chambers 38 hrs to reduce the moisture content of cassava slices from 56% w.b. to 10.62 and 15.20% w.b. respectively. The effective moisture diffusivity (De) for the system with Perspex glass and plywood chambers were 6.28 × 10−10 m2/s and 4.53 × 10−10 m2/s respectively. The activation energy values were 20.56 kJ/mol and 20.82 kJ/mol for the system with Perspex and plywood respectively. The mass transfer coefficient values for the cassava slices dried in Perspex and plywood were 1.70 × 10−6 and 1.67 × 10−6 m/s respectively. At the same time, the heat transfer coefficients were 2.63 and 2.08 W/m2. K. The Midilli et al. and modified Henderson and Pabis models were adjudged the best to describe the solar drying of cassava slices using the Perspex and plywood drying chamber respectively. Therefore, the obtained results would be useful in the design of solar drying equipment for agricultural products under natural convection mode.

Optimization of BOFS high-gravity carbonation technology: Consideration of theoretical guidance for up-scaling applications

This study investigated the high-gravity (higee) carbonation reaction of a basic oxygen furnace slag (BOFS)-water-CO2 three-phase system via a rotating packed bed (RPB). The effect of different carbonation conditions on the higee carbonation process was explored. To achieve enhanced mass transfer, energy savings, and cost-effectiveness, this study aimed to optimize parameters such as BOFS component, acceleration, gas-liquid velocity ratio, and gas flow rate. Comparative analysis revealed that portlandite-rich BOFS exhibited a significantly higher Ca conversion ratio (2.1 times) and mass transfer coefficient values (KGαe) (5.5 times) than calcium silicate-rich BOFS. Systematic graphical presentation identified an acceleration of 430 m/s2, a gas-liquid velocity ratio of 25–30, and a gas velocity to RPB volume range of 4.7–6.6 min−1 as the optimal operating conditions for high KGαe (>0.2 s−1) and low energy consumption (144–151 kWh/t-CO2). Furthermore, prolonged RPB operation led to a 1.5-fold reduction in mass transfer performance, but reducing the liquid-to-solid ratio was a cost-effective measure to compensate for efficiency losses. The estimated cost for the higee carbonation process ranged from 106 to 111 CNY/t-CO2. These findings can provide valuable insights and practical recommendations for the industrial application of the higee carbonation technology in steel-making plants.

Experimental study of interfacial mass transfer from single CO2 bubbles ascending in stagnant water

The study focuses on the interfacial mass transfer from single CO2 bubbles with initial diameter in the range of 0.7−3.0 mm in a vertical column with stagnant deionized water. The objective is to enhance the understanding of the intricate phenomena involved in interfacial mass transfer by examining the individual effects of the liquid-side mass transfer coefficient and the bubble size. The liquid-side mass transfer coefficient is found in this study to be influenced by both the initial bubble diameter and on the bubble age, i.e., the time the bubble is exposed to the liquid influences the obtained liquid-side mass transfer coefficient. Existing literature suggests that bubbles of diameter <2−3 mm behave as rigid spheres with immobile interface and reduced internal gas circulation, which negatively impact the interfacial mass transfer. The results obtained from this study show that the maximum value of the liquid-side mass transfer coefficient is obtained for bubbles of diameter 2.1−2.3 mm. For bubbles with a mean diameter ≤1.4 mm, the mean liquid-side mass transfer coefficient decreases with decreasing mean bubble diameter. A Lagrangian model description is used with various correlations for the liquid-side mass transfer coefficients to perform numerical simulations of the change in bubble volume during the bubble rise. The existing correlations for the liquid-side mass transfer coefficient give very different simulation results and fail to accurately capture the transient evolution of the bubble as it exposes to the mass transfer phenomenon and hydrostatic pressure gradient. The correlation for the liquid-side mass transfer coefficient proposed by Clift et al. (1978) is modified in this work, and the experimentally obtained data are well predicted by the new modified correlation.

Efficiency, Kinetics and Mechanism of 4-Nitroaniline Removal from Aqueous Solutions by Emulsion Liquid Membranes Using Type 1 Facilitated Transport.

4-Nitroaniline (4NA) is a common organic pollutant that is released into the environment during the manufacture and processing of a wide variety of industrial products. This article describes the use of an emulsion liquid membrane process to remove 4NA from aqueous solutions using a type 1 facilitated transport mechanism. Optimization of the removal process was carried out by analyzing the efficiency of 4NA removal from the feed phase and the initial apparent feed/membrane fluxes and permeabilities under different experimental conditions. The kinetics of the removal process was analyzed using a simplified mass transfer model involving an empirical mass transfer coefficient calculated from experimental data, assuming that the concentrations of 4NA in the external aqueous phase and in the internal w/o emulsion are uniform. The results show that there is a very good fit between the experimental and model data and that the variation in the values of the overall mass transfer coefficients with the experimental conditions coincides with that of the removal efficiency mentioned above. The transport mechanism was studied by identifying the rate-controlling step of the removal process, using models described for adsorption processes, due to the strong parallelism between the transport mechanisms in adsorption and emulsion liquid membrane processes.

Koefisien Perpindahan Massa pada Ekstraksi Polisakarida dari Biji Asam Jawa dengan Pelarut NaOH

Asam jawa merupakan tanaman tropis yang mudah sekali tumbuh di Indonesia. Daging buah asam jawa telah banyak dimanfaatkan sebagai bumbu masakan, pemberi rasa asam, dan obat – obatan. Sedangkan, biji dari buah asam jawa belum dimanfaatkan secara optimal. Biji asam jawa mengandung polisakarida 50-60%, sehingga berpotensi untuk dimanfaatkan sebagai sumber sakarida dengan cara melakukan ektraksi kandungan polisakarida dari biji asam jawa. Penelitian ini bertujuan untuk mengetahui koefisien perpindahan massa polisakarida pada proses ekstraksi biji asam jawa dengan pelarut NaOH. Ekstraksi polisakarida pada biji asam jawa dilakukan dengan ekstraksi secara batch. Untuk 50gram biji asam jawa diekstrak menggunakan 300ml larutan NaOH dengan variasi konsentrasi 0,1N; 0,2N; 0,3N; 0,4N; 0,5N dengan variasi waktu ekstraksi 15;30;45;60;75 menit. Filtrat hasil ektraksi dipisahkan menggunakan etanol 96% dengan perbandingan 1:2 dan didiamkan selama 24jam. Padatan yangdihasilkan dipanaskan pada suhu 75oC dan dilakukan analisa kadar polisakarida menggunakan metode gravimetri.Penelitian ini memberikan hasil nilai koefisien perpindahan massa (kLa) tertinggi pada konsentrasi NaOH 0,5N yakni bernilai 0,01734/menit.

Feasibility of nitrate adsorption from aqueous solution by nitrogen and oxygen-modified pine bark biochar: experimental and computational approach

Efficient and economical wastewater treatment has presented itself as a global challenge. In this context, adsorption is one of the most effective methods to remove contaminants from wastewater. The present study evaluated the feasibility of chemically modified pine bark biochar’s nitrate adsorption ability. Pine bark biochar was modified with urea and sulfuric acid to remove nitrate from an aqueous solution. The physicochemical properties of the biochar samples, such as pH, pH at point of zero charges, surface atomic composition, surface morphology, and surface area, were evaluated. The equilibrium adsorption data were fitted to the Langmuir and Freundlich isotherm models. The kinetic data were fitted to different kinetic models (pseudo-first order, pseudo-second order, intraparticle diffusion, and Elovich). The adsorption data fitted well with the Langmuir and pseudo-first order models. The maximum nitrate adsorption capacity was found to be 1.548 mg g−1. Mass transfer studies were conducted to identify the rate-limiting step, values of the external mass transfer coefficient, and diffusion coefficient in the nitrate adsorption process by the modified biochar. The external mass transfer coefficients were in the range of 2.2 × 10–11–2.86 × 10–10 m s−1. The intraparticle diffusion coefficient ranged from 6.53 × 10–10 to 1.78 × 10–9 m2 s−1. The Biot number value less than 100 indicated that the adsorption was controlled by film diffusion. Interaction energies between nitrate ions and model biochar structures were calculated DFT-based quantum chemical software (Gaussian). The positive interaction energy values (2.3485–2.485 eV) suggested nitrate adsorption on model biochar structures was thermodynamically not feasible.Graphical

Zinc Evaporation from Brass Scraps in the Atmosphere of Inert Gas.

A description of the process of metal evaporation from liquid alloys at an atmospheric pressure has a practical value for both the smelting and remelting of their scraps. The quantities of volatile components that are eliminated in these processes depend on many factors of which the type of melting device, the method and conditions of the process performance, the alloy composition and the kind of applied atmosphere are of the greatest importance. In this paper, the results of the research on zinc evaporation from brass scraps containing 10.53 wt% Zn are presented. The experiments were conducted using the thermogravimetric method at 1080 ÷ 1240 °C in a helium atmosphere. In the research, the levels of zinc removal from copper ranged between 82% and 99%. The values of the overall mass transfer coefficient for zinc kZn, determined based on the experimental data, ranged from 4.74 to 8.46 × 10-5 ms-1. The kinetic analysis showed that the rate of the analysed process was determined by mass transfer in the gas phase.

Analysis of Reaction Kinetics of the Ozonation of Phenolic Compounds and Assessment of the Role of Mass Transfer in the Overall Rate

The ozonation technique for biorefractory phenolic wastewater is preferred as a clean technology. However, its effectiveness and successful implementation on the commercial scale is crucial. The understanding of the rate-determining step and reliable reaction kinetics is the essence to the design and scale-up of ozonation reactors. In the case of phenolic wastewater, it is found that both mass transfer and chemical reaction contribute to the overall reaction rates. However, the mass transfer resistance is often significant in studies that determine the ozonation rate constant. This has resulted in discrepancies in the reported values of the intrinsic reaction kinetic parameters, and such apparent rate constants cannot be useful for suitable reactor design. The aim of this work is to analyze past works on the reaction kinetics of the ozonation of phenol, chlorophenols, and nitrophenols and determine the role of mass transfer steps in the overall reaction rate. The value of the volumetric liquid-side mass transfer coefficient (kLa) is estimated from the overall observed rates using the theory of mass transfer with chemical reaction, and these are found to be appropriate for the reactor geometry used in the respective works. In this way, our appraisal of the literature has provided key insights, which are yet unfamiliar, and renders useful the large body of data published in the literature, which otherwise remains unutilized.

Membrane assisted process intensification and optimization for removal and recovery of phenol from industrial effluents

The best method of preserving the environment is not to discharge any contaminant but to recover them as value from the effluent streams thereby adopting circular economy. This calls for developing new strategies including intensification of conventional processes to make the recovery of contaminants cost effective and environmentally friendly. In this context, experimental studies are reported with respect to conventional solvent extraction and membrane assisted solvent extraction for recovering phenol from effluent streams. Initial studies are carried out with aqueous solutions of phenol with concentrations up to 500 mg/L using hydrophobic polyvinylidene fluoride based hollow fiber membrane element in tandem with conventional solvent extraction using 1- hexanol as solvent. The operating parameters for the membrane assisted solvent extraction were optimized in parallel with conventional solvent extraction using the statistical tool, response surface methodology to provide a comparative assessment highlighting the advantages of membrane assisted solvent extraction in terms of energy consumption, operational simplicity and environmental friendliness. The studies were validated using real effluents obtained from a formaldehyde resin manufacturer. The comparative study highlights the specific advantages and demonstrates the superiority of membrane assisted solvent extraction using a real industrial effluent. It was observed that more than 98 % of phenol could be removed from effluent in membrane assisted solvent extraction and recover about 90 %, continuously allowing the recycle of the solvent. Being closed loop operation, no solvent is exposed to the environment making the process environmentally friendly operation. The mechanism of mass transfer in membrane contactors follows resistance in series model and the experimental values of mass transfer coefficient were estimated to be between 1.7 × 10 −7 and 2.2 × 10 −7 m/s, whereas the empirical values were around 1.3 × 10 −7 m/s.

Method for Intensive Gas–Liquid Dispersion in a Stirred Tank

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.

Mass transfer characteristics of chiral pharmaceuticals on membrane used for polar organic chemical integrative sampler

Passive sampling technology has good application prospects for monitoring trace pollutants in aquatic environments. Further research on the sampling mechanism of this technology is essential to improve the measurement accuracy and extend the application scope of this approach. In this study, adsorption and permeation experiments were performed to investigate the sorption and mass transfer properties of five chiral pharmaceuticals at the enantiomeric level on polyethersulfone (PES) and polytetrafluoroethylene (PTFE) membranes used in a polar organic chemical integrative sampler. Batch adsorption experiments showed that the PES membrane had an adsorption phenomenon for most selected pollutants and an insignificant sorption behavior was observed for all selected pharmaceuticals on the PTFE membrane except for R(S)-fluoxetine. The diffusion coefficients of selected pharmaceuticals onto the PTFE membrane were approximately one order of magnitude higher than those onto the PES membrane. The permeation experiment indicated that under different hydraulic conditions, the change of the relative pollutant concentration through the PTFE membrane for the composite pollutant system was more obvious than that for the single pollutant system, and mass transfer hysteresis exists for both contaminant systems through PES membranes. Using the first-order equation or 3-component model to estimate the overall mass transfer coefficients, the results showed that the overall mass transfer coefficient values of pollutants in the composite pollutant system onto both membranes were higher than those in the single pollutant system. This parameter was mainly influenced by the synergistic effects of the multi-analyte interaction and diminished water boundary layers during the mass transfer process.

Determination of mass transfer coefficient of CO2 removal in water-in-oil emulsion

The removal of carbon dioxide is an important process in natural gas purification since its lower down the calorific value of the natural gas. In addition, carbon dioxide also capable of forming corrosion in the pipeline, thus its removal is crucial. Water-in-oil emulsion was proposed in this research since the absorption of carbon dioxide in emulsion would be an effective method to prevent corrosion. However, the absorption capability of the emulsion and the mass transfer coefficient of carbon dioxide during absorption process needs further investigation. The aim of this study is to determine the diffusivity and mass transfer coefficient of carbon dioxide in the emulsion and observed the correlation between mass transfer coefficient and the carbon dioxide absorption values obtained from experiment. In this study, water-in-oil emulsion was prepared by mixing the aqueous phase and organic phase solutions under two different formulation conditions. Firstly, the methyldiethanolamine (MDEA) and 2 amino-2-methyl-1-propanol (AMP) blending was mixed in different alkaline solution; sodium hydroxide (NaOH) solution, potassium hydroxide (KOH) solution and distilled water (H2O) to form aqueous phase solution. Secondly, MDEA was combined with different alkanolamines; dimethylethanolamine (DMEA), diethanolamine (DEA) and triethanolamine (TEA) in KOH solution to form another aqueous phase solution. The synthesized aqueous phase is then mixed with the organic phase consists of kerosene and Span-80 mixtures. Furthermore, viscosity and particle sizes of the emulsions at different emulsion formulations were measured and the diffusivity and mass transfer coefficients of carbon dioxide were calculated. This study showed that, by using suitable emulsion formulation containing MDEA/AMP in KOH solution, the estimated value of diffusivity and mass transfer coefficient of carbon dioxide was 1.0876 × 1010 m2/s and 1.15 × 103 m/s respectively, with viscosity of 261.03 mPa s and particle size of 189.71 nm was achieved. It was found the diffusion coefficient and mass transfer coefficient of carbon dioxide is highly influenced by the characteristics of emulsion such as viscosity and particles sizes.

Local volumetric mass transfer coefficients in sections of multiple-impeller stirred tank reactors: Data analysis

The analysis of local values of volumetric mass transfer coefficient, kLa, was performed to identify the effects of local hydrodynamics on the mass transfer rate in multiple-impeller stirred tank reactors. The database of kLa values measured by Dynamic Pressure Method was analysed. The database provides data for two vessel sizes (laboratory and pilot-scale reactor), a wide range of operational conditions (gas flow rate, impeller speed), various impeller geometries and sizes and four different batches including viscous media. The local kLa values in multiple impeller configurations were measured in several positions corresponding to the individual impeller regions. The overall kLa value averaged through the whole volume is considered as the best representation of the correct kLa value. Different hydrodynamic effects on mass transfer rate were obtained in the two end regions. In the bottom region, the local kLa values increase with impeller speed faster than the overall kLa. The opposite behaviour was obtained in the uppermost region corresponding to the decrease of power consumption and the mass transfer rate with increasing surface aeration under high impeller speeds. The best representation of the overall kLa value was obtained in the middle position of the vessel, where the exchange flows bring the liquid saturated to different measure from the end regions. Even if the local kLa data in individual impellers' regions are shifted to the average values due to the inter-impeller exchange flows, the differences between them are still significant. We show the local kLa values by the combination of the data measured at different liquid level heights. The results can be used in the fermenter design with various impeller combinations.

DRYING OF CENOSPHERES RECOVERED BY THE WET-BASED METHOD FROM COAL FLY ASH FOR THEIR RATIONAL USE

Since slag and coal fly ash (CFA) are major global pollutants produced by thermal power plants (TPPs), special attention should be paid to their rational disposal. Scanning electron microscopy (SEM) was used to study the morphology of CFA and it was suggested that the use potential of CFA is high due to the presence of a large number of cenospheres (CSs), that can be recovered mostly by wet methods for the production of the wide range of products with improved properties. However, such decisions regarding the application of the cenospheres are largely related to the problem of their drying after removal. The article is devoted to the investigation of the filtration method as less energy-consuming for the drying of cenospheres. The effect of the drying agent velocity on the mass transfer intensity has been established. The values of mass transfer coefficients have been calculated based on the thin-layer experimental data and equation . Calculated mass transfer coefficients for cenospheres have been correlated by the dimensionless expression , based on which equation has been proposed to calculate the mass transfer coefficients, which is important at the filtration drying equipment design stage.

Magnetic-field-induced simultaneous charge separation and oxygen transfer in photocatalytic oxygen activation for algae inactivation

Photocatalytic oxygen activation is an excellent strategy for algae control in water. However, the fast recombination of photogenerated charge and slow rate of oxygen transfer limit the reactive oxygen species generation efficiency for algae inactivation. Herein, to solve above issues, magnetic field was introduced to the BiO2−x/Bi3NbO7 system to effectively covert oxygen into reactive radicals. The electrochemical experiment and DFT calculation results indicated the charge separation could be accelerated by the Lorentz force generated by the magnetic field, resulting in increase of electron concentration. Meanwhile, the value of volumetric gas-liquid mass transfer coefficient was increased by 59.79 % with magnetic field, thus more oxygen could be reduced to superoxide radical. Photocatalytic algae inactivation rate by BiO2−x/Bi3NbO7 with magnetic field could be increased by 2.07 times than that without magnet filed. This work further extends the strategy of using magnetic field to simultaneously facilitate the charge separation and oxygen transfer rate.

Environmental Modelling of Ionic Mass Transfer Coefficient in a Unique Electrocoagulation Reactor

Ionic mass transfer in a novel electrocoagulation reactor (ECR) using a rotating impeller anode is studied experimentally using the limiting current density method. The CFD simulation is also conducted for characterizing the novel electrocoagulation reactor (ECR) and validating the experimental study of ionic mass transfer. Variables included rotational speed and anode diameter. The Bland-Altman method was used to verify the accuracy of experimental and simulation results. Data for the condition 11852 &lt; Re &lt; 58550 and 88 &lt; Sc &lt; 285 were found to fit the equation for the largest diameter of 11.2 cm; Sh = 2.1Re0.93Sc0.33. Based on COD removal efficiency, optimal EC performance is realized at the largest anode diameter of 11.2 cm, confirming the enhancement of aluminum mass transfer by increasing the anode diameter. The experimental values of current density and mass transfer coefficient are validated by CFD simulation for all the rotational speeds and anode diameters. The accuracy is up to 95% for the experimental current densities compared with simulation values.

Effect of osmotic dehydration pre‐treatments on physicochemical and energy parameters of Kosia (Nashi) pear slices dried in a convective oven

In this study, the effects of osmotic dehydration pre-treatments in sucrose solutions on dried Kosia pear slices were determined. The effective diffusion, modeling, color, rehydration, specific energy consumption, specific moisture extraction rate (SMER), evaporation latent heat, energy efficiency (EE), convective heat (hc), and mass transfer coefficient (hm) parameters of fruit slices were investigated. The shortest drying time (17 h) was observed in the drying process of the samples subjected to osmotic dehydration in 25% sucrose solution for 1 h. The best thin-layer drying models were identified as Lewis (R2: .9977) and Jane-Das (R2: .9977) models. Effective diffusion values ranged between 2.13–4.94 × 10−5 m2 s−1. Rehydration ratios ranged between 2.09 and 2.71 g g−1 while rehydration capacities ranged between 57.24% and 63.05%. The least color change was observed in control samples. SMER values of the dried samples ranged between 0.0062–0.00011 kg kWh−1. EE values ranged between 4.19% and 0.03%. Mass transfer coefficient values varied between 1.57 × 10−8 and 1.06 × 10−12 m/s. Heat transfer coefficient value was calculated as 5.773 × 10−7 W m−2 K. Uncertainty that stems from measurements and cannot be controlled was calculated as ±2.324%. Novelty impact statement High sucrose solution ratios of drying pre-treatments reduced the drying time of Kosia pear slices. Control samples retained their color values better. Samples subjected to osmotic dehydration in 25% sugar solution for 1 h had is the optimum values drying performance and energy parameters.

Mathematical Modeling of Hydrodynamic Cavitation as Low Energy Extraction Technique for Lipid Removal from Nannochloropsis sp.

Lipid extraction assisted by hydrodynamic cavitation (HCLE) is one of the promising processes with low energy requirements. This study aims to reduce the energy requirement using a discrete flow system and evaluate two models to calculate the volumetric mass transfer coefficient. The variations of the number of repetitions, cavitation number, microalgae concentration, and temperature have affected the energy requirement value. The first model uses total lipid mass transfer approximation (Model 1) and the second uses separated lipid mass transfer approximation (Model 2). Based on Model 1 the value of total volumetric mass transfer coefficient ( ) f were 1.166 x 10-2, 3.113 x 10-3 and 1.285 x 10-3 min-1 with coefficient of determination (R2) is 0.9797. Whereas, based on Model 2 the value of volumetric mass transfer coefficient from disrupted microalgae ( ) were 1.131 x 10-2, 2.925 x 10-3 and 1.260 x 10-3 min-1 and from the intact microalgae ( ) was 0.051, 0.030 and 0.011 1/min with R2 of 0.9766. Both models gave a similar result. It was shown that lipid release from disrupted microalgae was dominant compared to the intact microalgae. Therefore, the discrete flow system of HCLE is a promising technique for extracting lipids from microalgae

Mass Transfer Coefficient Enhancement Using Spiral Wound Rod as Turbulence P romoter in an Electrolytic Cell

Objectives: to improve efficiency of process equipment by increasing the mass transfer coefficient with a spirally wound rod as the turbulence promoter. Methods:The function of facet promoters, whirl generators, and test sections of different congruous shapes increase the mass transfer coefficients at the reaction surface. Diffusion-controlled redox (ferricyanide - ferrocyanide) reaction has been chosen for the study. Limiting current data from the reduction of ferricyanide is used for mass transfer coefficient calculation. A set of three geometric parameters such as pitch(P), height(H), and width(W) of the promoter were investigated in the current study. Findings: An increase in the mass transfer coefficient values with the increment of flow rate of electrolyte from 0.088 m/s to 0.263 m/s was observed. A rise in the promoter height from 0.03 to 0.07m enhanced the mass transfer coefficient by 25.7 fold, while the increase in the width of the promoter from 0.01 to 0.04m resulted in a rise of the mass transfer coefficient by 26.3 fold. On the contrary, the mass transfer coefficient decreased upon increase in the pitch of the promoter from 0.01 to 0.04m, but overall enhancement is 25.7 fold. The increase in the mass transfer coefficient on an average compared to a rectangular turbulence promoter was 5.71 fold. Novelty: The spiral wound rod as a promoter increased the mass transfer coefficient several folds compared to other promoters. The spiral wound rod is quite simple to manufacture, has low cost and ease of maintenance. Therefore, the promoter used in the study could be employed for heat and/or mass transfer enhancement in Industrial applications. Keywords: Limiting current; Promoter; Mass transfer Coefficient; Swirl flow; Redox reaction

Enhancing interfacial interaction of PDMS matrix with ZIF-8 via embedding TiO2@ZIF-8 composites for phenol extraction in aqueous-aqueous membrane extractive process

The presence of phenol as an organic pollutant in industrial effluents is the biggest threat to the aquatic environment and human health. The aqueous-aqueous extraction process is an attractive method to treat saline phenolic wastewater (feed solution) via diffusion through a semi-permeable polydimethylsiloxane (PDMS) to the receiving solution. To improve the value of mass transfer coefficient, thinning the PDMS layer and embedding it with nanoparticles/metal-organic frameworks (MOFs) can lead to membrane defects or weakened mechanical strength, which is not promising for large-scale practical applications. Therefore, herein, an interfacial design strategy is demonstrated to disperse TiO2@ZIF-8 composites as hybrid particles into the top selective layer (PDMS) of TFC (thin-film composite) membrane to enhance polymer-filler compatibility and mass transfer coefficient. The TiO2@ZIF-8 composites enhanced the affinity to the polymer matrix, thereby increasing the mechanical stability and preventing interfacial voids and agglomeration. Moreover, the TiO2@ZIF-8 incorporated TFC membranes exhibited an enhanced mass transfer coefficient (ko) of (25.28 ± 0.5) × 10−7 and a reduced reverse salt flux of 9.5 mg/m2.h. The enhanced mechanical stability and mass transfer coefficient were attributed to the synergistic effect provided by TiO2@ZIF-8 composites, as ZIF-8 particles provided continuous pathways (pore-flow mode) and TiO2 nanoparticles provided compactivity with PDMS. The synergistic effects of hybrid particles could provide a new strategy to develop PDMS for the extraction of various organic compounds.