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This study investigated catalytic decomposition and mass transfer of aqueous ozone promoted by Fe-Mn-Cu/γ-Al2O3 (Cat) in a rotating packed bed (RPB) for the first time. The results showed that the value of the overall decomposition rate constant of ozone (Kc) and overall volumetric mass transfer coefficient (KLa) are 4.28×10−3 s−1 and 11.60×10−3 s−1 respectively at an initial pH of 6, β of 40, C O 3 ( g ) of 60 mg·L−1 and QL of 85 L·h−1 in deionized water, respectively. Meanwhile, the Kc and KLa values of Fenhe water are 0.88×10−3 s−1 and 2.51×10−3 s−1 lower than deionized water, respectively. In addition, the Kc and KLa values in deionized water for the Cat/O3-RPB system are 44.86% and 47.41% higher than that for the Cat/O3-BR (bubbling reactor) system, respectively, indicating that the high gravity technology can facilitate the decomposition and mass transfer of ozone in heterogeneous catalytic ozonation and provide some insights into the industrial wastewater.

In the titanium dioxide industry, there is a lack of a low-cost and high-efficiency treatment method for chloride containing tail gas. In this paper, the removal of HCl from the titanium dioxide industry by gas cyclone-liquid jet separator was studied, while Ca(OH)2, Na2CO3, NaOH solution, and water were used as absorbents. This paper investigated the influence of gas cyclone-liquid jet separator’s various process parameters on the removal rate of hydrogen chloride gas. The mechanism of mass transfer in the process of removing hydrogen chloride was discussed, and the effect and feasibility of HCl gas removal in the gas cyclone-liquid jet absorption separator were studied. The results showd that the removal efficiency of hydrogen chloride maintained above 95%, up to 99.9%, and the total mass transfer coefficient reached 0.28 mol·m-3·s-1·kPa-1. Under the same conditions, the absorption effect and total mass transfer coefficient of weak basic absorption liquid can be greatly improved by increasing the flow rate of absorption liquid, but the absorption effect and total mass transfer coefficient of strong alkaline absorption liquid can’t be improved obviously. The larger the inlet gas volume, the higher the gas concentration, the lower the absorption efficiency and the lower the total volumetric mass transfer coefficient.

Extraction reactor is a major research area of interest within the field of rare earths extraction and separation. SiC foam offers excellent material characteristics as well as three-dimensional (3-D) reticulated structure; however, very little research has been carried out on its application in extraction reactor so far. In this work, a static mixer reactor based on SiC foam was designed and demonstrated to extract and separate Ce(III) and Pr(III) from nitric acid media by using 2-ethylhexyl phosphoric acid mono-2-ethylhexyl ester (P507) as extractant. The structure–performance relationship between SiC foam and extraction performance was studied by experiment combined with computational fluid dynamics (CFD) simulation. The experiment data are in good agreement with the simulation results. Contrast experiment by using a Kenics mixer was carried out, and SiC foam shows better extraction and mass transfer performance. Using the optimal structural SiC foam (pore size D = 2.3 mm, open porosity e = 85%, foam length L = 80 mm), high extraction efficiency η (Pr(III): 94.6%, Ce(III): 88.5%) and separation factor β (2.27) between Ce(III) and Pr(III) is achieved at a high total throughput of 200 mL/min. Besides, overall volumetric mass transfer coefficient KLa of Pr(III) and Ce(III) are 0.519 and 0.378 s−1 at the residence time τ of 3.6 s, respectively, which reach the high level of microchannel reactors and are better than conventional extractors and other static mixers. SiC foam is found to be applicable as a static mixer for efficient and high-throughput extraction and separation of rare earths.

A microfluidic platform to extract uranium from HNO3 (nitric acid) medium using tri-isoamyl phosphate (TiAP) dissolved (30% v/v) in ionic liquid ([BMIM]PF6) is reported. PTFE microbore tubes serve as the microchannels. The quality of dispersion inside the translucent tubes was observed using a camera. The images obtained are used to understand the observed experimental trends. Overall volumetric mass transfer coefficient was determined considering the microchannel as a differential contactor with co-currently flowing phases. The effects of contact time, flow velocity, organic to aqueous (O/A) ratio and microchannel diameter on mass transfer performance are studied. Effect of different coiling configurations on mass transfer performance was compared. Under optimum conditions, 95.3% of uranium present in the feed (corresponding stage efficiency being 99.2%) could be extracted within a contact time of about 200 s in a single contact. Corresponding (KLa) was 0.024 s−1. Coiling was found to have a significant effect on values of KLa especially at low residence times.

In this study, Mass transfer coefficient was improved using a plurality of pentagonal plates as turbulent promoters in a circular tube. Multi- fluidized beds have a wide range of applications in the processing industry. It is used as a pentagonal plate as a solid, nitrogen as a gas and an electrolyte as a liquid. An apparatus formed by a pentagonal plate promoter arranged concentrically used as an amplification device. The installation of the pentagonal unit has been used to calculate the maximum coefficient of mass transfer. NaOH is used as an electrolytic neutral solution to prepare an equimolar solution of Ferricyanide of potassium and ferrocyanide. The concentration of ions based on volume electrolyte was analyzed using standard permanence solutions and ferri-ferro ions in the iodometric method. The data from substance transfer coefficients are obtained using the diffusion control electrode reaction (Ferricanuro ion reduction). The data transfer coefficients are obtained using current limitation techniques. Compared to single pentagonal plate et al. [17], the maximum enlargement achieved in this study is approximately 30 times. The current research indicates that the variation of the mass axial transfer coefficient is within ± 10%. The mass transfer coefficients increase with the growing speed of the gas surface and the particle size of the promoter. The mass transfer coefficients decrease as the height increases and the characteristic length of the promoter. The liquid apparent speed and the diameter of the accelerator rod significantly affect the mass transfer coefficient.

Simultaneous heat and mass transfer experiments with air–water system were performed in a baffled rotating contactor and volumetric mass transfer coefficient determined towards exploring an alternate strategy for the concentration of fruit juice. The proposed concentration technology is based on the stripping of water from fruit juice by an unsaturated gaseous stream. In the contactor, the phases flowed counter-currently between two rotating circular disks zigzagging across concentric circular baffles fitted in the inner surface of the disks. The volumetric mass transfer coefficient varied between 7 kg/m3s to 20 kg/m3s for the range of operating conditions studied. The evaporation rate of water per unit volume was higher than in falling film type evaporators used conventionally for the concentration of fruit juice. The maximum concentration of orange juice attained in the rotating contactor within two hours with continuous recirculation of the solution was 32.6 °Brix for the operating conditions studied. This was significantly higher than that obtained in a rotating packed bed contactor of similar volume (2.0 L).

In this research gasoil desalting was investigated from mass transfer point of view in an eductor liquid–liquid extraction column (eductor-LLE device). Mass transfer characteristics of the eductor-LLE device were evaluated and an empirical correlation was obtained by dimensional analysis of the dispersed phase Sherwood number. The Results showed that the overall mass transfer coefficient of the dispersed phase and extraction efficiency have been increased by increasing Sauter mean diameter (SMD) and decreasing the nozzle diameter from 2 to 1 mm, respectively. The effects of Reynolds number (Re), projection ratio (ratio of the distance between venturi throat and nozzle tip to venturi throat diameter, Rpr), venturi throat area to nozzle area ratio (Rth-n) and two phases flow rates ratio (RQ) on the mass transfer coefficient (K) were determined. According to the results, K increase with increasing Re and RQ and also with decreasing Rpr and Rth-n. Semi-empirical models of drop formation, rising and coalescence were compared with our proposed empirical model. It was revealed that the present model provided a relatively good fitting for the mass transfer model of drop coalescence. Moreover, experimental data were in better agreement with calculated data with AARE value of 0.085.

Sulfate mass transfer coefficient (MTC) is a sensitive parameter to evaluate the kinetic leakage of anion exchange resin used in condensate polishing system of thermal and nuclear power plant. However, a sufficiently precise determination method has not been well established. In this paper, the final expression of sulfate MTC derived based on plug flow reactor model is the same as Harries’ model, which is widely acknowledged in this field. In the determining system we constructed, in-situ calibration of the concentration of sulfate and its cation conductivity was conducted and sulfate MTC of four typical strongly basic anion exchange resin samples were determined. The systematic error is 8.26 % and the calibrated curve used for quantifying sulfate is obtained. The repeatability and reproducibility standard deviation are 0.05×10-4 m·s-1 and 0.07×10-4 m·s-1 respectively, which are lower than previous works. By controlling test condition accurately, this study has developed a more precise sulfate MTC determining method. This method provides a basis for further research.

In this paper, we proposed a microextraction approach for the extraction and separation of Mn(II) and Co(II) from sulfate solution simulating leachate of spent lithium-ion battery cathode materials using saponified di-(2-ethylhexyl)phosphoric acid system. The effects of the following operational variables were investigated: equilibrium pH, tri-n-butyl phosphate concentration, saponification rate, two-phase ratio and residence time. The results showcased that the microextractor can reach the extraction equilibrium within 20 s, thereby greatly reducing necessary extraction time comparing to that of conventional processes. The volumetric mass transfer coefficient showed 8–21 times larger than that of batch device. With the help of microextractor, 95% of Mn(II) was extracted with a single theoretical stage at a chosen two-phase ratio of 3:1, and the separation factor βMn/Co was as large as 65.5. In the subsequent stripping step, more than 99% of manganese from loaded phase was easily stripped under optimal conditions. The microextraction approach greatly enhances the mass transfer while enabling a continuous and controllable extraction process within a simple structure design. When extracting spent electrode material with microextractors, the comprehensive recovery of mangenese can reach 96%. The microextraction approach has a good applicability in the spent lithium-ion battery cathode materials recycling at both bench and industrial scales.

In this study, a drying process with ethanol pretreatment was developed for effective removal of residual moisture from the plant cell Taxus chinensis. Drying efficiency was improved remarkably by a simple rotary evaporation with ethanol pretreatment. At the optimal amount of ethanol for pretreatment (biomass/ethanol = 3:1, w/v), the drying time was shortened by 1.9 times (40°C), 1.5 times (50°C), and 1.3 times (60°C), respectively, compared to drying without ethanol pretreatment. The experimental data was applied to the representative kinetic drying models, and the modified Page model was shown to be the most suitable. Thermodynamic parameters represented the spontaneous and endothermic characteristics of the drying process by the ethanol pretreatment, and randomness during the drying process was also increased. The highest effective diffusion coefficient (6.216 × 10−14–7.940 × 10−14 m2/s at 40–60°C), Biot number (4.40 × 10−2–6.60 × 10−2 at 40–60°C), and mass transfer coefficient (64.34 × 10−12–123.39 × 10−12 m/s at 40–60°C) were observed when the biomass was pre-treated with an optimal amount of ethanol. In addition, as the drying temperature was increased with the same ethanol amount, these values were also increased.

In this study circulating fluidized bed was adopted to remove of Congo Red from wastewater using Eichhornia crassipes as a adsorbent. Solution flow rate(6,12 and 18)l/hr, bed height(2,4 and 6) cm and Congo Red initaial concentration (10,25 and 50)mg/l were examined in experiments to show their effects on breakthrough curves and time required to reach the adsorbent to fully saturated curve. The mass transfer coefficient "KL"decreased with decreasing the liquid flow rate. The minimum fluidization velocities of bed found equal to 1.6, 2, 2.5 mm/s for heights of 2, 4,6 cm respectively. The increasing of the bed height will increase the contact time of the solute in the bed, and these improve the solute removal efficiency. the increasing in flow rate and initial concentration will increase the mass transfer rate.

The hydrodynamics and mass transfer characteristics of a lab-scale jet bubbling reactor (JBR) including the gas holdup, volumetric mass transfer coefficient and specific interfacial area were assessed experimentally investigating the influence of temperature, pH and superficial gas velocity. The reactor diameter and height were 11 and 30 cm, respectively. It was equipped with a single sparger, operating at atmospheric pressure, 20 and 40 °C, and two pH values of 3 and 6. The height of the liquid was 23 cm, while the superficial gas velocity changed within 0.010–0.040 m·s−1 range. Experiments were conducted with pure oxygen as the gas phase and saturated lime solution as the liquid phase. The liquid-side volumetric mass transfer coefficient was determined under unsteady-state oxygen absorption in a saturated lime solution. The gas holdup was calculated based on the liquid height change, while the specific interfacial area was obtained by a physical method based on the bubble size distribution (BSD) in different superficial gas velocities. The results indicated that at the same temperature but different pH, the gas holdup variation was negligible, while the liquid-side volumetric mass transfer coefficient at the pH value of 6 was higher than that at the pH = 3. At a constant pH but different temperatures, the gas holdup and the liquid-side volumetric mass transfer coefficients at 40 °C were higher than that of the same at 20 °C. A reasonable and appropriate estimation of the liquid-side volumetric mass transfer coefficient (kla) in a pilot-scale JBR was provided which can be applied to the design and scale-up of JBRs.

Studies attempting to optimise photosynthetic biogas upgrading by simultaneous investigation of the bubble column-photobioreactor setup have experienced considerable variability in results and conclusions. To identify the sources of such variation, this work quantitatively compared seven design factors (superficial gas velocity; liquid to gas flow rate (L/G) ratio; empty bed residence time; liquid inlet pH; liquid inlet alkalinity; temperature; and algal concentration) using the L16 Taguchi orthogonal array as a screening design of experiment. Assessments were performed using the signal to noise (S/N) ratio on the performance of CO2 removal (CO­2 removal efficiency, CO2 absorption rate, and overall CO2 mass transfer coefficient) and O2 stripping (O2 concentration in biomethane and O2 flow rate in biomethane). Results showed that pH and L/G ratio were the most critical design factors. Temperature and gas residence times had minimal impact on the biomethane composition. The interactive effect between pH and L/G ratio was the most impactful, followed by the interactive effects between superficial gas velocity and L/G ratio and pH on CO2 removal efficiency. The impact of L/G ratio, algal concentration, and pH (in that order of impact) caused up to a 90% variation in oxygen content in biomethane. However, algal concentration had a diminishing role as the L/G ratio increased. Using only the statistically significant main effects and interactions, the biomethane composition (CO2% and O2%) was predicted with over 95% confidence through regression equations for superficial gas velocity up to 0.2 cm/s.

In this work, the kinetics of decarburization and demanganization of Fe–15Mn–1C alloy by bubbling mixtures of Ar–O2 into the melt at 1823 K was studied. Experiments were conducted at total gas flow rates of 200 and 300 Nml/min and gas mixtures of Ar containing 6.7 to 20 pct O2. Increasing the gas flow rate and oxygen in the gas mixture resulted in higher overall rates of decarburization and demanganization. However, the experiments with the lowest oxygen concentration were the most efficient in terms of oxygen utilization for decarburization. The ratio of manganese loss to decarburization was found to be controlled by the relative mass transport of manganese and carbon in the metal. Based on the estimated mass transfer coefficient for either carbon or manganese, the reaction time for each bubble was estimated to be 0.001 seconds which is about 1 pct of the residence time of the bubble in the liquid. Although the initial competition for oxygen between manganese and carbon was controlled by relative mass transport rates, this work found no evidence that manganese and carbon repartitioned towards the equilibrium over the remaining lifetime of the bubble.

Microchemical technology shows prospect in the process intensification field of carbon capture and storage, however, there remain great challenges in microchemical technology for gas-liquid mass transfer with counter-current flow. In this work, we proposed a micro-apparatus with confined structure for gas-liquid counter-current flow mass transfer. The flow patterns on the confined structure, steady flow and bead flow, were observed, furthermore, the critical flow rate between them was measured. The influences of confined structure geometry, surface tension and viscosity of liquid on the meniscus at the gas-liquid interface were studied. The operation window of micro-apparatus with different types of confined structures was examined. The liquid loading and gas loading of micro-apparatus with S1005 were tested to be 230 μL/min and 500 mL/min, respectively. The system of absorption of pure CO2 in a 1 M NaOH solution was used to study the mass transfer. The average liquid side mass transfer coefficient of 25.1 × 10−5 m/s was measured at liquid flow rate of 30 μL/min and gas flow rate of 300 μL/min, which proves that the micro-apparatus achieves the process intensification of CO2 absorption.

Experiments of hydrodynamic and gas liquid mass transfer were carried out in a bubble column of 19.4 cm internal diameter and of 4 m height. The liquid phase can be either tap water or a coalescence inhibitor system, using aqueous solutions of three alcohols (ethanol, 2-propanol and 1-butanol) with a volumetric concentration of 0.05% v/v and sodium dodecyl sulfate: SDS (10−3 mol/L) as an anionic surfactant. The hydrodynamic study involved placing wall pressure sensors in different axial positions of a bubble column to determine the gas hold-up in different regions and the influence of non-coalescing system on its evolution. The overall liquid movement induced by bubbles and the residence time distribution analysis of liquid phase was performed by using inductivity sensors. Gas hold-up results showed that the presence of the gas is more important in the zone far enough to the gas distributor (zone II). The results of the volumetric mass transfer coefficient (KLa) revealed that KLa decreased with the addition of alcohol, especially when the number of carbons in alcohol increased. KLa decreased more with the addition of anionic surfactant. It was also proven that a decrease in KLa was due to a decrease in KL, which was due to a decrease of bubble rise velocity as well as of the diffusivity when alcohol or ionic surfactant was added. Correlations were developed linking gas holdup and gas-liquid mass transfer coefficient to superficial gas velocity and surface tension gradient.

Liquid desiccant dehumidification is promising as it could be driven by renewable energy. In the present study, it newly investigated the dehumidification characteristics of KCOOH solution in an internally cooled dehumidifier. To select suitable concentration range, the vapor pressure of KCOOH solution with different solution concentration and temperature was measured with static method firstly. Then comparative experimental study was conducted to identify the dehumidification performance of KCOOH and LiCl solution under different solution and air flow rate, temperature and air humidity. Experimental results indicated that 70.3% KCOOH solution had almost the same vapor pressure as 35% LiCl solution. Under the same experimental conditions, the absolute moisture removal of 70.3% KCOOH solution was slightly higher than that of 35% LiCl solution as a result of the increased wetting area. It was found that the mass transfer coefficients of the two liquid desiccants were almost the same. An empirical correlation of S h number was obtained to predict the mass transfer coefficient of KCOOH solution for dehumidification with a mean absolute relative deviation of 7.81%.

In this study, microwave-assisted extraction (MAE) was applied to extract bioactive materials from leaves of Moringa oleifera. The current study was performed in order to clarify and understand the effects of extraction time, temperature, and power on the kinetics and thermodynamics of extraction, diffusion, and mass transfer coefficients and Biot number for the present system. One gram of Moringa oleifera particles with 80 mL solvent (60% ethanol) was extracted under different extraction temperature values (304, 305, 308, and 309 K) and microwave power values (200, 300, 400, and 500 W) for several time periods (30–400 s). According to the kinetic study, activation energy for the present MAE was calculated as 243.367 kj mol−1, where the extraction rate increased with temperature (0.0077, 0.0121, 0.022, and 0.0448 mL mg−1 s−1). Thermodynamic study produced the changes of enthalpy (31.572 kj mol−1), entropy (0.12817 kj mol−1), and Gibbs free energy (− 7.3917, − 7.5199, − 7.90434, and − 8.0325 kj mol−1), respectively. An empirical diffusion model was used for the estimation of diffusion coefficients, mass transfer coefficients, and Biot numbers depending on temperature. The diffusion coefficient (3.058 × 10-10, 3.114 × 10-10, 5.912 × 10-10, and 10.38 × 10-10 m2 s−1), mass transfer coefficient (0.2683, 0.4217, 0.7667, and 1.5613 m s−1), and Biot number (375 × 103, 578.9 × 103, 554.4 × 103, and 624.48 × 103) increased with increase in temperature.

Environmental concerns caused by chemical solvents need be managed through the advantages of hybrid bio-sourced solvents for CO2 capture. On the other side, to accurately predict the height of a CO2 absorption packed column, it is essential to estimate the mass transfer coefficients. This paper provides the experimental results of mass transfer performance of the aqueous mixture of MEA + Glycerol, as an industrially eco-friendly hybrid solvent, instead of a typical commercial alkanolamine solvent for CO2 capture in a laboratory-scale absorption packed column. For the first time, a predictive statistical model was built to investigate the influence of process variables, involving absorption temperature (30−45 °C), inlet gas flow rate (4−6 L/min), the initial solvent concentration of glycerol (5−15 wt %), and MEA (10−30 wt %) on the CO2 removal efficiency (ef), and the volumetric overall gas-phase mass transfer coefficient (KGaV) in the CO2+MEA + Glycerol system. The results of CO2-absorption showed that rising the glycerol concentration from 5 % to 15 % enhances the values of ef and KGaV by 4.5 % and 24.62 %, respectively, when the other three variables are considered fixed at their midpoints. Therefore, the presence of glycerol, as the promoter in a hybrid mixture of MEA-Gly, significantly gives rise to the mass transfer coefficient and CO2 removal efficiency.

The effects of bubble size, solids particle (impurities) and the respective physical mechanisms on gas–liquid columns have received little attention. Therefore, the objective of this work is to study the effect of solid concentration and the ratio of the bubble diameter to the solid diameter on the mass transfer characteristics. Experiments were conducted in a three phase electroflotation column for the systems gas/water/olive stone. Volumetric mass transfer coefficient, kLa, was measured under different solid concentrations values (1–3 g/l) and ratio of the bubble diameter to the solid diameter values. It was found that the kLa rises when the ratio of the bubble diameter to the solid diameter increase. The presence of solid particle has a negative effect on mass transfer coefficients (kLa,kL and a). The liquid side mass transfer coefficient has the same behavior as the volumetric mass transfer coefficient. The capacity of oxygenation CO was also studied. Models relating the mass transfer coefficients kLa, kL and CO were elaborated in each case using linear regression method.

Studies on enhancement of mass transfer coefficient by using single pentagonal plate as promoter inserted at the bottom of the rectangular electrolytic cell have been conducted. The present study contains the assessment of mass transfer rates increases by using single pentagonal plate as turbulent promoter in forced convection flow of electrolyte and it was evaluated from measured limiting current technique. The electrolyte was equimolar ferri- ferrocynide couple in alkaline solution. The mass transfer rates obtained due to diffuse control mechanism. The present study covers effects of height (h) and radius (r) of the promoters, space between the promoters and flow rate of electrolyte on mass transfer. The results have revealed that the velocity (v) increases then mass transfer coefficient increases, if radius of the plate (r) increases then also mass transfer coefficient increases and transfer coefficient increases when decreases in height (h) of the plate from entrance of the rectangular electrolytic cell (h). From the results maximum augmentation is 3.96 times more than the smooth tube and the minimum augmentation is 2.20 times more than the smooth tube. Present study was analysed with mass transfer function and Reynolds’s number. The correlation achieved is JD = 674.26 (Re)−0.96496 (Φ1)0.56634 (Φ2)0.13874 (Φ3)−0.53239 (Sc)−0.088446.

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 .

Gas-liquid volumetric liquid-phase mass transfer coefficient (k L a) was studied in a slurry bubble column at the conditions mimicking Fischer–Tropsch synthesis. To avoid the hydrodynamic disturbances due to the gas switching, oxygen enriched air dynamic absorption method was used. Influence of reactor models (CSTR, ADM and RCFD) on the volumetric mass transfer coefficient was investigated. Effect of operating pressure, superficial gas velocity and solids loading were investigated. From the reactor models investigated, it is recommended to use ADM model for k L a study. If the CSTR model is used, applicability of the model should be checked. With increase in the superficial gas velocity and operating pressure, volumetric liquid-phase mass transfer coefficient increases, while it decreases with the solids loading corroborating with the literature.

In the previous study, greenhouse gas CO2 was successfully used as the precipitator to realize its carbonation by calcium ions in seawater with the help of magnesium oxide. In this study, the reaction process was firstly analyzed by a proposed reaction mechanism, and then the dynamic simulation of the gas–liquid–solid system was carried out via kinetic Monte Carlo simulation. Based on the reaction mechanism, the continuous experimental study was realized in a bubble column. The effects of air flow rate, carbon dioxide flow rate and temperature on the effectiveness evaluation indexes of decalcification efficiency, total mass transfer coefficient and carbon sequestration rate were studied. Finally, a bonnet tower with a diameter of 1 m and a height of 8 m was built to carry out the pilot test. In the laboratory experiments, the calcium removal rate reached 94%, the carbon sequestration rate reached 63.6%, and pure micron calcium carbonate products were obtained. The decalcification rate reached 95% in the pilot test, which is consistent with the results of the laboratory experiment.

Arsenic contamination in drinking water is recognized as major health hazard worldwide. As reported in literature, more than 19% Indians are consuming lethal levels of arsenic for drinking purposes. In this work, arsenic (III) removal was studied using HFN300 polyethersulfone nanofiltration membrane in spiral wound configuration. Various membrane parameters such as hydraulic permeability (4.87 L m−2 h−1 bar−1), mass transfer coefficient (0.957*10−6 m s−1), reflection coefficient (0.9), and solute permeability (2*10−9 m s−1) were estimated using film theory combined Spiegler-Kedem (FTCSK) model. The higher value of reflection coefficient suggested the impervious nature of nanofiltration (NF) membrane used for arsenic (III) solute rejection. The influence of various operating parameters such as transmembrane pressure, initial feed concentration, and feed flowrate on membrane performance was also examined. It was found that arsenic (III) rejection was dependent on pressure and feed concentration. Result showed that more than 96.4% arsenic (III) rejection was achieved for 50 mg L−1 of feed at optimized conditions. As HFN300 membrane was negatively charged at pH 8 and arsenic (III) was available in neutral solute form, electro-migration was not considered for solute rejection mechanism. Solution diffusion with significant coupling between solute and solvent, steric hindrance effect, convection, and solute-membrane affinity interactions were considered dominant factors for the possible solute rejection mechanism. Rejection efficiency (% R) and permeate flowrate (Q2) were simulated and compared with experimental results. It was found that simulated results were in excellent agreement with the experimental results. The maximum error obtained was within 10% for both % R and Q2. This confirms the efficacy of FTCSK model in predicting arsenic (III) removal using NF membrane. The annualized cost per cubic metre of treated water was estimated as 3.32 $/m3. This further confirms the feasibility of using NF process in removing arsenic from contaminated water.

The ionic liquid, 1-butyl-3-methylimidazolium acetate ([bmim][Ac]), was used to remove carbon dioxide (CO2) from a simulated spacecraft cabin atmosphere (2 mm Hg (267 Pa)) partial pressure of CO2 w...

The gas-phase mass transfer coefficient is one of the significant parameter for the determination of mass transfer in absorption columns. A novel correlation was obtained for the calculation of the gas phase mass transfer coefficient in the current research study based on the theoretical investigation and experimental data. Buckingham pi-theorem was utilized to develop an overall dimensionless correlation. The correlation was derived based on the experimental data conducted at the operating conditions’ range of temperature 40–100 °C, CO2 partial pressure of 18-66 kPa, and piperazine (PZ) concentration of 2-8 M. The correlation was validated using the experimental data with an acceptable error of 7.47%. The results showed that the gas-phase mass transfer coefficient was increased by enhancing the amount of holdup and Schmidt number (Sc) at different temperatures and PZ concentrations. Furthermore, by comparing the Sc number with holdup, it was observed that a higher temperature resulted in a higher hold-up amount in the gas-phase of the absorption column.

Mixtures of different types of amine solution Monoethanolamine, Diethanolamine, and Triethanolamine were experimentally used to investigate the overall mass transfer coefficient (KGa) at different operating parameters. The experiments were made in a packed bed reactor (PBR) with 75 cm in high and10 cm inside diameter as a gas-liquid contactor at 25℃ and atmospheric pressure, using a simulation gaseous mixture (air, carbon dioxide) with recycle stream (semi-continuous process). Experimental design process Taguchi was employed. Four factors and three levels were chosen and exploded using L9 (3 ^4) orthogonal array design. These parameters for semi-continuous process were namely: gas flow rate 5,10,and 15 L/min ,airflow rate80,90,and 100 L/h, liquid flow rate 400,450,and 500 mL/min and time absorption time 30,45,and 60min . A Shimadzu GC-8A Gas Chromatograph with a thermal conductivity detector was used to measure the CO2 concentration absorbed in aqueous blended solution. The maximum value for CO2 loading was 8.622 (mol CO2/mol amine) at 15 L/min gas flow and 450 mL/min liquid flow and 100 L/h airflow for 60 min from absorption time. The results showed that the max value of KGa is 0.048 S-1.

Packed beds of spherical particles in a cylindrical vessel have a high porosity region next to the vessel wall that allows preferential fluid flow. Consequently, there are radial variations in porosity (e) and superficial fluid velocity (U) that depend on the vessel-to-particle diameter ratio (D/dp) and the flow regime of the fluid. This work ascertained if these radial variations affected SuperCritical (SC) CO2 extraction curves of oil from pre-pressed seeds at 40 °C and 28 MPa, as compared with the commonly adopted plug flow condition. It focused specifically on comparing extraction curves as a function of the controlling mass transfer mechanism (characterized by the dimensionless Biot number, Bi) and D/dp ratio. A predictive model was adopted to describe the SC-CO2 extraction of oil from sheared seeds comparing plug flow with radial variations in superficial CO2 velocity, U(r), from literature correlations. Selected independent variables included the initial oil content of the substrate (132.7 ≤ Co ≤ 397.2 g/kg), dp (1 or 2 mm), U (1–4 mm/s), and vessel volume (0.038–495 L). Co markedly affected the effective diffusivity of the oil (0.780 ≤ De ≤ 6.24 × 10−10 m2/s), whereas dp and U moderately affected the film mass transfer coefficient (2.44 ≤ kf ≤ 7.40 × 10−5 m/s). Radial variations in superficial CO2 velocity decreased extraction rates, with differences between extraction curves when considering plug flow or adopting U(r) diminishing as Bi increased for D/dp = 20, or as D/dp increased for Bi = 18. Bi increased by increasing U and kf, or decreasing Co and De, whereas D/dp increased by increasing vessel volume. The radial variations in porosity in a packed bed and associated changes in superficial CO2 velocity may have a more pronounced negative impact in laboratory or pilot plant extraction vessels (small D) than industrial vessels (large D), mainly when extracting small particles and applying large superficial CO2 velocities. A proxy for the SC-CO2 extraction of oil from pre-pressed seeds in an industrial extraction vessel (495-L capacity, D/dp = 270) would be plug flow using the porosity, and superficial CO2 velocity predicted for the axis of the extraction vessel (eo and Uo, respectively). Literature correlations predict a value of eo slightly less than e, and value of Uo slightly less than U. The remainder of the CO2 bypassing the vessel along a high porosity region near the vessel wall, containing a small fraction of the loaded substrate.

Mass transfer between the phases is a cornerstone of many technological processes and presents a topic whose understanding and modelling is of high importance. For instance, absorption of gases in liquid droplets is an underlying phenomenon for the desulfurization of flue gases in wet scrubbers. Wet scrubbing is an efficient cleaning method where the liquid is sprayed in a stream of rising gases, removing pollutants due to the concentration difference between the gas phase and droplets. A model for absorption in water droplets has been developed to describe the complex physical and chemical interactions during the exposure to flue gases. The main factors affecting the absorption are the mass transfer of pollutants through the gas–droplet interface and the aqueous phase chemistry in a droplet. The mass transfer coefficient, which has been modeled with several approaches, is the most significant parameter regulating the absorption dynamic into the droplet, while the in-droplet chemistry controls the maximum quantity of dissolved pollutants. Dissociation of sulfur dioxide and the chemical reactions in seawater have been described by the equilibrium reactions. Afterward, the influence of the mass transfer coefficient has been investigated, and the model has been validated against the literature data on a single droplet scale. Obtained results are comparable with the experimental measurements and indicate the applicability of the model for the design and development of industrial scrubbers.

In this work, an absorption technology was used actually to investigation the mass transfer coefficient of carbon dioxide from a gaseous mixture (air, carbon dioxide) in blended solution Monoethanolamine (MEA) and Diethanolamine (DEA) in a bubble column reactor (BCR) . The bubble column reactor(BCR) was made of Plexiglas with 1.5 m high and 0.1 m inside diameter. The overall mass transfer coefficient ( was evaluated at different operating conditions , gas flow rate, air Flow rate ,liquid flow rate .Where the gas flow rates were 10, 15 and 20 L /min , air flow rate 100,150 and 200 L/h ,and liquid flow rate 5 ,10,15 L /min . This experiment by using continuous process with helping centrifugal pump . High-performance gas chromatographic (GC) was performed to evaluate loading during absorption experiment . The experimental results have shown that the loading in range of 0.581-1.367 (mol /mole amine),and the maximum value of overall mass transfer coefficient ( KG) was 0.04 S-1 .

The micro-bubble generator (MBG) is a novel aeration technology utilizing the concept of fluid flow through an orifice, where air is sucked into the internal chamber of the MBG by the pressure difference created by the orifice and immediately pushed by the high-velocity flow of the fluid. This mechanism creates micro-size bubbles with a high dissolution rate. This study focused on studying the effect on the oxygen dissolution rate of the two most important operating parameters, i.e. the volumetric flow rate of the liquid (Q L ) and the volumetric flow rate of the air (Q G ). Various combinations of values for Q L and Q G were systematically compared by means of the oxygen mass transfer coefficient (k L a). The experiment was carried out in a transparent container of 2.8 m x 0.6 m x 0.4 m filled with tap water that was aerated using an orifice/porous-pipe type MBG. The dissolved oxygen (DO) values were measured at distances of 60 cm, 120 cm, and 180 cm from the MBG outlet. The experiment was designed with five different values for Q L and Q G respectively. The results showed that the value of k L a, which is proportional to the oxygen dissolution rate, increased asymptotically with increasing Q L value, while the Q G values did not significantly affect the k L a value.

A pore-array intensified tube-in-tube microchannel (PA-TMC), which is characterized by high throughput and low pressure drop, was developed as a gas–liquid contactor. The sulfite oxidation method was used to determine the oxygen efficiency (φ) and volumetric mass transfer coefficient (kLa) of PA-TMC, and the mass transfer amount per unit energy (e) was calculated by using the pressure drop. The effects of structural and operating parameters were investigated systematically, and the two-phase flow behavior was monitored by using a charge-coupled device imaging system. The results indicated that the gas absorption efficiency and mass transfer performance of the PA-TMC were improved with increasing pore number, flow rate, and number of helical coil turns and decreasing pore size, row number, annular size, annular length, and surface tension. The φ, e and kLa of PA-TMC could reach 31.3%, 1.73 × 10−4 mol/J, and 7.0 s−1, respectively. The Sherwood number was correlated with the investigated parameters to guide the design of PA-TMC in gas absorption and mass transfer processes.

The leaching kinetics of aluminum from peat clay using 4 M HCl at dissimilar leaching temperatures (30–90 °C) was investigated. The maximum of aluminum recovery was 91.27% after 60 min of leaching in agitated Pyrex reactor at 90 °C. The model involved the concept of shrinking core in order to describe aluminum that is located inside the core solid particle of peat clay that shrinks as the extracted solute, and it assumed the unchanged particle structure, a first-order leaching kinetics mechanism and a linear equilibrium at the interface of solid-liquid. The proposed model was corresponding to fit experimental data and to simulate the aluminum leaching from peat clay with four fitting parameters of temperature, which was confirmed with the mass transfer coefficient ( k c , cm/s), diffusion coefficient ( D e , cm 2 /s), and reaction rate constants ( k , cm/s) by following an increasing trend with increasing temperature. Moreover, it was validated by the correlation coefficient ( c coef ≥ 0.9794), the root means square error ( RMSE ≤ 0.485), the mean relative deviation modulus ( E ≤ 3.290%), and the activation energy value (E a = 19.15 kJmol -1 ). This model could describe the aluminum leaching kinetics from peat clay that suitable with experiment parameters and statistical criteria, by giving useful information for optimization, scaling-up, and design.

Представлены результаты экспериментальных исследований гидродинамики и массообмена на вихревых ступенях в режиме барботажа, а также данные численного моделирования методом конечных элементов с использованием моделей k-ε турбулентности и пузырькового течения. Это позволило установить наличие циркуляционного движения жидкости на ступени, определить профили скоростей фаз, получить величину начальной скорости движения газовой фазы, при которой наблюдается согласование экспериментальных и расчетных значений скорости жидкости. Расчетным путем показано влияние цилиндрической перегородки, установленной между завихрителем и стенкой ступени на профиль скорости жидкости и ее распределение в рабочем объеме. Предложено использовать полученные результаты численного моделирования при конструировании многоэлементных ступеней для обеспечения на ней требуемой гидродинамики. Исследованы новые вихревые контактные устройства с кольцевыми каналами, обладающие меньшим гидравлическим сопротивлением в сравнении с тангенциальными устройствами и обеспечивающие развитую межфазную поверхность, стабильную, без флуктуаций, работу ступени при высоких расходах газа и жидкости. Представлены данные для определения гидравлического сопротивления вихревой ступени, величины межфазной поверхности, коэффициентов массоотдачи и эффективности в исследуемом диапазоне нагрузок жидкости и газа L/G = 10–150. Разработаны конструкции вихревых контактных ступеней для промышленной бражной колонны. Контактные устройства с кольцевыми каналами позволяют довести диссипацию энергии в газовой фазе в барботажно-кольцевом режиме до 5 Вт/кг, увеличить межфазную поверхность до 2000 м-1 и достигнуть величины поверхностного коэффициента массотдачи порядка (0.5–0.8)×10-3 м/с., The results of experimental studies of hydrodynamics and mass exchange at vortex stages in bubbling mode are presented, as well as data of numerical simulation by finite element method using models of k-ε This made it possible to establish the presence of circulation movement of liquid at the stage, to determine profiles of phase speeds, to obtain the value of initial speed of gas phase movement, at which coordination of experimental and design values of liquid speed is observed. The design method shows the effect of the cylindrical partition installed between the swirler and the stage wall on the fluid velocity profile and its distribution in the working volume. It is proposed to use the obtained results of numerical modeling when designing multi-element stages to provide the required hydrodynamics on it. New vortex contact devices with annular channels, having lower hydraulic resistance compared to tangential devices and providing a developed interfacial surface, stable without fluctuations, operation of the stage at high gas and liquid flow rates, have been investigated. Data are presented for determination of hydraulic resistance of vortex stage, value of interfacial surface, coefficients of mass output and efficiency in investigated range of loads of liquid and gas L/G = 10-150. Designs of vortex contact stages for industrial brew column have been developed. Contact devices with ring channels allow to bring dissipation of energy in a gas phase in the bubbling and ring mode to 5 W/kg, to increase an interphase surface to 2000 m-1 and to reach the size of superficial coefficient of a massotdacha about (0.5-0.8)·10-3 of m/s.

Sodium chloride salt is used in the cheese salting because it promotes sensorial changes besides preserving the food, but in excess can cause hypertension. Therefore, it has been partially replaced by potassium chloride to not affect the sensory characteristics. In this work the mozzarella cheese was subjected to the diffusion of Na+ and K+ in brine by static and stirred immersion. The diffusion was modeled using the second law of Fick and simulated by the finite element method through the software COMSOL Multiphysics® version 5.2. The main, cross coefficients and the relation between mass transfer coefficient and the mass conductivity were determined through simplex optimization, minimizing the percentage errors between the experimental and simulated concentrations, obtaining 3.79%(w/v) for NaCl and 5.66%(w/v) of KCl in static brine. In stirring brine, the errors obtained were 5.40%(w/v) for NaCl and 6.01%(w/v) for KCl. The resulting main diffusion coefficients were 1.12 × 10−9 (m2/s) for NaCl and 0.91 × 10−9 (m2/s) for KCl.

Natural and waste waters pollution by nitrates is considered a major environmental problem due to the possible consequences on human health and on water bodies through eutrophication phenomenon. Hazelnut shell were employed as packing material in a large lab-scale column for the removal of nitrate from wastewaters, comparing the process performances with those obtained in batch system. A nitrate removal efficiency up to about 67% was observed in batch mode at low pH and with a sorbent mass concentration of 8 g/L with 0.5 mm size. A lower (62%) nitrate removal efficiency was observed at large lab-scale column, though notable volumes of effluents (60–200 L, depending on the inlet flow-rate) were successfully treated with a bed height of 30 cm and a sorbent mass of 590 g. Non-linear regression of batch equilibrium data using Langmuir, Freundlich and SIPS models allowed to estimate the isotherm parameters, subsequently used in a mass transfer dynamic model to fit the experimental data. The regressed film mass transfer coefficient kf, at six different inlet flowrate values were elaborated for the estimation of the characteristic parameters of the empirical correlation between Sherwood, Reynolds and Schmidt numbers. Furthermore, the pressure drop along the column was calculated and the Ergun and Carman equations were employed for the estimation of the empirical friction parameters.

The size of particulate matter (PM) generated by combustion has decreased with the improvement of combustion technology. While small PM has a significant negative impact on the human body, it is difficult for a conventional PM removal device to collect small PM. We developed a fluidized bed type PM removal device with a focusing adhesion force. This device collects small PM effectively and can be operated as a continuous regeneration device at low temperature. To further develop this device, it is important to investigate the PM combustion characteristics in this device. The kinetic model constructed in conventional thermogravimetry could not accurately represent the combustion rates of the solid fuel in the fluidized bed. Therefore, a new thermogravimetric apparatus was constructed in this study that generates the direct collision of air with carbon to reproduce the fluidized bed combustion. The influence of the relative velocity between PM and gas on the combustion rate was investigated. The effect of relative velocity was represented as the mass transfer coefficient of kinetic model. It is observed that the combustion rate shows Arrhenius behavior, and kinetic parameters were determined by fitting. The kinetic model was applied to the numerical simulations of the PM removal device. The numerical collection efficiency was in good agreement with the experimental data. PM adhesion and combustion characteristics were investigated in numerical simulations. It is observed that the adhesion rate is high at a low void fraction and that the combustion rate is high at a high relative velocity. The PM combustion amount is high for the high adhesion and combustion rates. The total combustion amount is determined to be 55% of the total amount of PM deposition after 180 min at each set of conditions.

Membrane contactor is a technology that intensifies conventional absorption column. However, liquid-to-gas ratios (L/G) of membrane contactor in existing reports are much higher compared to CO2 absorption column, which results in higher solvent circulation rate and higher consumption in heating energy. This makes the technology less attractive for deep CO2 removal. Direct reduction of liquid flow rate was not effective in lowering down L/G. Experimental results showed that 50% reduction in liquid flow rate could reduce L/G by 25%, but the reduction in CO2 flux (33%) was higher due to decrease in liquid phase mass transfer coefficient which was dependent on liquid velocity. An alternative method to reduce L/G through membrane module length increase was proven, where L/G was reduced 70% with only 16% flux reduction. The flux reduction was only observed when L/G dropped below 0.80 L/mol and it was due to depletion of unreacted amine for CO2 absorption. The lowest L/G value obtained in this study was 36% lower than the conventional absorption column in liquefied natural gas (LNG) process, showing that membrane contactor technology is not only energy-viable and more compact for deep CO2 removal, but it also offers energy saving advantage.

Gas–liquid mass transfer of rotating disk reactor was studied in CO2 absorption using 1,8-diazabicyclo-[5.4.0]-undec-7-ene (DBU)-glycerol solution as solvent. Effects of the rotating disk structure and various operation parameters on the CO2 absorption rate and CO2 removal efficiency were investigated. The rotating disk with optimal holes is conducive to mass transfer of CO2 and the formation of thin liquid film at the opening increases the gas–liquid contact area. With the increase of rotating speed, the liquid flow pattern on the rotating disk surface changes from thin film flow to separated streams and creates extra liquid lines attached to the rim of the disk, which leads to a very complicated change on the CO2 absorption rate and CO2 removal efficiency. The overall gas-phase mass transfer coefficient increases 138% as the rotating speed increasing from 250 to 1400 r·min−1. Increasing temperature from 298 to 338 K can enhance the CO2 absorption rate due to lowering the viscosity of the solvent. The rate-determined step for the absorption is focused on the gas side. The rotating disk reactor can effectively enhance the absorption of CO2 with viscous DBU-glycerol solvents.

International audience; This work is an experimental investigation of the effect of the nature of surfactants on oxygen mass transfer. The study focuses on three cationic surfactants with different hydrophobic chain lengths, and four nonionic surfactants with different hydrophilic chain lengths. Equilibrium adsorption isotherms are calculated for each surfactant from experimental values of surface tension in static conditions. Surfactant solutions at concentrations between 2.5×10-8 and 5×10-3 mol/L were prepared and oxygen transfer from millimetric air bubbles (between 0.82 and 1.08 mm) was measured by Planar Laser Induced Fluorescence with Inhibition (PLIF-I). When the bulk concentration of surfactant was increased, results showed a sharp decrease of bubble velocity, in the range of 283-75 mm/s, and of liquid-side mass transfer coefficient, in the range of 5.6 ×10-4-0.4 ×10-4 m/s. This effect was observed for all surfactants studied. However, the length of the hydrophilic chain did not appear to affect the hydrodynamics of the rising bubble or the oxygen transfer at the same bulk concentration. Furthermore, for the same bulk concentration, increasing the hydrophobic chain length had an impact on the velocity and the mass transfer coefficient of oxygen. Finally, the Sherwood number was calculated in each medium and compared with classical correlations for gas-liquid mass transfer prediction. Those correlations seemed to reach a limit for a very concentrated medium.

This study presents a method for the experimental determination of the local volumetric mass transfer coefficient k L a L in a high-pressure two-phase flow of water ( H 2 O ) and carbon dioxide ( CO 2 ) in a micro-capillary using a colorimetric method. H 2 O and CO 2 are fed continuously and co-axially injected at high-pressure (10 MPa) and moderate temperature (303 K) into a microcapillary. Under the flow conditions studied, a segmented flow of CO2 in H 2 O is formed. The CO2 dissolves into the H2O-rich phase, thereby reducing the pH to about 3.3, depending on the pressure and temperature. The pH of the H2O-rich phase is determined over the entire length of the capillary using a pH sensitive indicator coupled with high-speed imaging and analysis. The concentration of CO 2 in the water-rich phase is deduced from this pH value using literature experimental data. The CO 2 concentration data and the unit-cell model, which has been modified to account for high pressure conditions, have then been used to determine the volumetric mass transfer coefficient, k L a L , of CO2 into the liquid phase along the entire length of the microreactor. The experimentally derived k L a L ​​ranges between 1 and 13 s−1.

Silica is widely applied in industrial fields due to its good properties, while preparation of high-quality SiO2 by carbonization is an important way to utilize CO2. The experiment was carried out in a microbubble/bubbling experimental device, with its mass transfer kinetics of carbonization analyzed according to the pH-t curves. Under microbubble conditions, with the increasing temperature of 20∼60°C, the specific surface area, oil absorption value and particle size of silica varies at 336.80∼231.29 m2/g, 1.12∼1.81 ml/g and 16.49∼14.60 μm, respectively, which is similar as that with bubble. Aging at 20∼90 °C, they involve in the range of 35.82∼128.76 m2/g, 1.59∼2.44 ml/g and 23.15∼14.46 μm. With total concentration of solution >0.5 M, the concentration increases, the specific surface area and particle size of microbubbles are larger than those of the bubbling silica, and oil absorption value increases at 1.81∼2.44 ml/g. The kinetic analysis shows that it is more consistent with theoretical value, which can be judged as the secondary-reaction process. The microbubbles increase the CO2 utilization rate and volumetric mass transfer coefficient of carbonization by 2-4 times, while the liquid-phase mass transfer coefficient decreases. It indicates that microbubble mass transfer is achieved by significantly increasing the specific surface area.

International audience; Correlation of the mass transfer characteristics of microfluidic parallel-plate electrochemical reactors is proposed for the first time. Firstly, the variation in the mass transfer coefficient (k m) (1.61-3.94 × 10 − 5 m s − 1) over a wide range of interelectrode distances (d elec) from millimetric (3 mm) to micrometric values (100 µm) is reported. Secondly, a drastic slope change in the curve makes it possible to identify the onset of microfluidic behavior in a quantitative way for the first time, i.e. below a 1000 µm gap. Thirdly, a mathematical model is proposed which predicts k m for any d elec of interest. Fourthly, under laminar flow (7 < Reynolds (Re) < 623) and for temperatures in the range of 10-50 • C (532 < Schmidt (Sc) < 3315), new Sherwood (Sh) correlations are obtained for both microfluidic and millimetric configurations. It is thus feasible to extrapolate k m for microfluidic electrochemical reactor scale-up.

Hypothesis Nanobubbles (NBs) in water elicit unique physicochemical and colloidal properties (e.g., high stability and longevity). Aeration kinetics and dissolution behavior of oxygen (O2) NBs are assumed to be bubble size dependent. Experiments As an indicator for aeration efficiency, volumetric mass transfer coefficient (KL·a) was assessed by measuring the dissolved oxygen (DO) levels during aeration using O2 NBs with different sizes. Mass transfer coefficient (KL) was estimated by correlation analysis. Moreover, a modified Epstein-Plesset (EP) model was developed to predict the dissolution behavior by monitoring the DO and size changes during the dissolution of O2 NBs in water. Findings A higher rate of DO increase and a higher equilibrium DO level were both observed after aeration with NBs that present higher surface areas for the mass transfer of O2 and a higher vapor pressure of O2 to drive the partitioning equilibrium. Dissolution kinetics of O2 NBs were highly dependent on the initial bubble size as indicated by the changes of bubble size and DO. Smaller NBs raised up DO faster, whereas larger NBs could lead to higher equilibrium DO levels. Moreover, the rate of DO decline and the quasi-steady DO levels both decreased when the dilution ratio increased, confirming that O2 NBs dictates the DO level in water. Finally, the dissolving NBs may either swell or shrink according to the model prediction.

Oxygen is a harmful substance in many processes because it can bring out corrosion and oxidation of food. This study aimed to enhance the removal of dissolved oxygen (DO) from water by employing a novel rotor–stator reactor (RSR). The effectiveness of the nitrogen stripping coupled with vacuum degassing technique for the removal of DO from water in the RSR was investigated. The deoxygenation efficiency (η) and the mass transfer coefficient (KLa) were determined under various operating conditions for the rotational speed, liquid volumetric flow rate, gas volumetric flow rate, and vacuum degree. The nitrogen stripping coupled with vacuum degassing technique achieved values for η and KLa of 97.34% and 0.0882 s−1, respectively, which are much higher than those achieved with the vacuum degassing technique alone (η = 89.95% and KLa = 0.0585 s−1). A correlation to predict the KLa was established and the predicted KLa values were in agreement with the experimental values, with deviations generally within 20%. The results indicate that RSR is a promising deaerator thanks to its intensification of gas–liquid contact.

In this work, the mass transfer characteristics of two immiscible fluids were investigated in a rotating helical microchannel with hydraulic diameter of 932 μm. Aqueous phosphoric acid solution and 80% tri-n-butyl phosphate (TBP) in kerosene were selected for the investigation of mass transfer performance in quartz glass/high density polyethylene (HDPE) microchannel. High dispersion between the two immiscible fluids can be obtained in the microchannel due to the intensifying action of centrifugal force, and the majority of the droplets with average diameter of 20–100 μm were produced in the microchannel. The flow rate and rotation speed were found to have great effects on the extraction efficiency and average residence time. The empirical correlation of average residence time based on experimental data was developed by theoretical analysis and data fitting method, and a mathematical model of the mass transfer coefficient in dispersed phase was proposed.

Continuous countercurrent fluidized column is fabricated to study the hydrodynamics and mass transfer of chromium(VI) ion from chromium aqueous solution to activated carbon. Hydrodynamics studies including pressure drop, holdup, and the flow pattern are studied. Batch adsorption studies are conducted to find the equilibrium time and effect of mass of adsorbent. Maximum percentage removal is obtained at maximum flow rates of water (1.42 cm/s) and solid particles (24.6 g/s) from the range of parameters studied in this work. For a given water velocity, the total pressure drop linearly increases along the length of the column because of the increase in frictional loss. Also, with an increase in water velocity, the solid holdup increases in the column. The percentage removal of chromium(VI) increased up to 60% along the length of the column because of the increased contact time between the adsorbent and the adsorbate. An empirical correlation is proposed to predict the solid holdup and mass transfer coefficient.

In this study, chemical absorption of carbon dioxide (CO2) was performed by using MDEA + PZ (aMDEA) solvent. A T-shaped microreactor mixer was used as the mass transfer device to improve the absorption rate. Operating conditions used in this study were operating temperature (15–55 °C), input solvent flow rate (0–0.4 l min−1), inlet gas flow rate (1-9 l min−1), and amine concentration in the solvent (0–40 weight percent). All the experiments were carried out at atmospheric pressure and CO2 concentration of 10% in the feed gas. The central composite design method was used to set an experimental design. The results of optimization showed that the use of a microreactor for CO2 adsorption using aMDEA solvent significantly increased the total coefficient of mass transfer in the gas phase, as compared with other mass transfer devices. The maximum value obtained through the model within the range of operating variables for the response (total mass transfer coefficient in the gas phase) was 1769 kmol m−3 h−1 kPa−1.

In this investigation, the concentration profiles in both phases were determined for the uranium extraction from a sulfate solution by Alamine 336 in a horizontal pulsed column. The leach liquor solution contained uranium, iron, magnesium, manganese, aluminum, calcium and other minor elements. The optimum operating parameters for uranium extraction have been carried out at the bench scale. An organic phase with 6% (v/v) Alamine 336 and 5% (v/v) isodecanol in kerosene was chosen to examine the mass transfer performance of the extraction column. The volumetric overall mass transfer of the continuous phase, backmixing parameters and axial dispersion coefficients of two phases were calculated by using plug flow, backflow and axial dispersion models. The influence of operating parameters such as pulsation intensity and phase flow rates on these parameters was studied. The values of volumetric overall mass transfer coefficient calculated by axial dispersion are greater than those models. Because the axial mixing improves the mass transfer performance of this column. The obtained results of the pilot plant experiments showed that the mass transfer performance of this column is high for the uranium extraction from sulfate leach liquors. Furthermore, the practical and novel correlations have been determined for prediction of mass transfer parameters (such as Koca, Ec, Ed, α, β), which are closely matched with the experimental results in the horizontal pulsed column.