Green Effectively Enhanced Extraction to Produce Yttrium(III) in Slug Flow Microreactor

Process reinforcement research was carried out in Y‐junction slug flow microreactors under variable conditions, using EHEHPA (2‐ethylhexyl phosphonic acid mono‐2‐ethylhexyl) to extract yttrium(III) from hydrochloric acid solution. The influence of pH and flow rate on the extraction‐reaction efficiency, slug size, mass transfer performance was assessed. The experimental results showed that maximum extraction‐reaction efficiency of 91.85% can be achieved in the smallest microreactor (residence time is 11.25 s), which was significantly higher than traditional extraction requiring more than 10 min. The slug length tended to decrease with the increase of pH and flow rate. Volumetric mass transfer coefficients for the slug flow microreactors were found to be in the range of 1.39×10^?1—1.642 s^?1 that is several orders of magnitude higher as compared to traditional extractors, which testified the beneficial effects of Y‐junction slug flow microreactor. Significant mass transfer reinforcement has prompted the use of microreactor as a suitable alternative to traditional extractors, which can advantageously improve the economic and environmental development of mineral processing.     

A study of mass transfer kinetics of alanyl-alanine on a chiral crown ether stationary phase

The mass transfer kinetics of alanyl-alanine enantiomers in a column packed with a chiral stationary phase (CSP) ChiroSil RCA(+) was studied by means of the moment method. Methanol-water solutions acidified with sulphuric acid were used as the mobile phase. It was shown that the spreading of peaks in the column was strongly affected by abnormal eddy diffusion. This effect was well described within the framework of the Giddings coupling theory. The comprehensive four-term Giddings equation for eddy diffusion was applied, considering simultaneous contribution of the trans-column, trans-channel, short-range inter-channel, and long-range inter-channel dispersion factors. Through these calculations, a predominant importance of the trans-column flow velocity bias was revealed. Besides eddy diffusion, the adsorption kinetic resistance to mass transfer plays a noticeable role in band broadening, all the other contributions (from longitudinal molecular diffusion, external and intraparticle mass transfer) being of minor significance. A relative importance of the mass transfer kinetics increases correlatively with a growth of the retention factor. Both the retention and kinetics of the adsorption of alanyl-alanine on the CSP in study are enantioselective. The influence of the column pressure on retention as well as corrections required because of this influence are also discussed.     

Effect of mass transfer on the film drainage between colliding drops

The influence of mass transfer on the drainage behaviour of the thin liquid film between two drops immersed in another liquid colliding at constant approach velocity has been studied experimentally. The liquid-liquid system used is glycerol in silicone oil. The transferred solute is acetone and the volume concentration difference across the interface ranges from 1 to 5%. The film thickness evolution has been measured using a laser interferometry technique. The direction of mass transfer (from the drops towards the film phase and inversely) has been investigated and the results compared to the case with no mass transfer. When the solute transfers from the drops towards the continuous phase, the drainage rate is significantly higher than in the case with no mass transfer. This result is interpreted as a consequence of the mass transfer induced surface mobility in the film region (the so-called Marangoni effect) due to localized surface tension differences. This effect has been demonstrated by the visualization of the flow patterns in the drops and in the film phase (using a particle tracer technique). In this case, the slope of the film height as a function of time seems to be independent of the approach velocity condition imposed on the drop and appears to be controlled by the interfacial tension gradient. In the opposite case, when the solute transfers from the continuous phase towards the drops, the film drainage rate is lowered with respect to the case of no mass transfer, goes to zero or even changes its sign depending on the mass transfer intensity. The results also show that in the range of solute concentration studied, the effect of mass transfer on the film drainage process takes place at large distances compared to the scales at which lubrication theory is valid.     

Estimation of sodium bicarbonate crystal size distributions in a steady-state bubble column reactor

Sodium bicarbonate is a substance which is produced in the middle stages of the soda ash production process. In this precipitation process, carbon dioxide gas is continuously injected into the bubble column reactor, which contains carbonate and bicarbonate solutions. This work deals with the study of the gas?Cliquid mass transfer, coupled with chemical reactions, and the liquid?Csolid mass transfer, coupled with crystallization. In this mathematical model, a mole balance has been instituted on flows and components through the bubble column, which also utilized a nucleation and growth formula for the solid phase and the Danckwerts?? theory for mass transfer between the gas and liquid phases. The mathematical model can predict the effects of several parameters on the sodium bicarbonate crystal size distributions. We computed the mathematical simulation model results with the experimental results of the bubble column reactor of the Shiraz Petrochemical Complex for validating the model and investigated the effects of different parameters on the sodium bicarbonate crystal size distributions.     

Phenomenological study on heat and mass coupling mechanism of waxy crude oil pipeline transport process

Based on the phase equilibrium model of the paraffin wax precipitation in the process of oil pipeline transportation, theory and method of non-equilibrium thermodynamics were applied to obtain the linear phenomenological equations for the cross-interaction of heat and mass transfer during pipeline transport, which were derived from the irreversible entropy production rate equation. Then, the analysis of the irreversible heat flow and the mass flow were carried out, and the mathematical expressions of the phenomenological coefficient of liquid phase, the phenomenological coefficient of solid phase flow, and the heat flow phenomenological coefficient were obtained. Taking a waxy crude oil transportation pipeline in Daqing Oilfield as an example, based on the analysis of liquid–solid phase equilibrium, the irreversible linear phenomenological mechanism of heat and mass coupling in waxy crude oil pipeline transportation was analyzed in detail from three levels: phenomenological coefficients which reflect characteristic of the effect of force on flow in heat and mass transfer; thermodynamic forces which trigger heat and mass transfer; transmitted heat and mass flow density, providing a theoretical basis for the further study of the wax deposition in the process of pipeline transportation.     

Capillary rise of a meniscus with phase change

The Lucas-Washburn equation, describing the motion of a liquid body in a capillary tube, is extended to account for the effect of phase change - evaporation or condensation. The system is found to always possess a stable equilibrium state when the temperature jump across the interface is confined to a certain range. We show that phase change affects the equilibrium height of the meniscus, the transition threshold from monotonic to oscillatory dynamics, and the frequency of oscillations, when present. At higher mass transfer rates and/or large capillary radii, vapor recoil is found to be the dominant factor. Evaporation lowers the equilibrium height, increases the oscillation frequency and lowers the transition threshold to oscillations. For condensation, two regimes are identified: at high mass transfer rates similar trends to those of evaporation are observed, whereas the opposite is found for low mass transfer rates, resulting in an increased equilibrium height, lower oscillation frequencies and a shift of the transition threshold toward monotonic dynamics.     

锂离子电池多孔电极理论的回顾与新思考

本文总结了Newman多孔电极理论的基本内容,提出若干改进思路. 提出基于离子-空穴耦合传输机制描述浓电解质中的离子输运过程,在此基础上引入离子-电子耦合转移反应的思想处理电极材料中的离子传输问题,并通过计算嵌锂材料的离子扩散系数验证其合理性. 总结了描述多孔电极多尺度结构的相关理论和技术,表明均质化方法和基于结构重建的介观模拟方法均能给出比较合理的有效输运参数,从而提高多孔电极理论模拟结果的准确性.     

The intensification of rapid reactions in multiphase systems using slug flow in capillaries

A multiphase microreactor based upon the use of slug flow through a narrow channel has been developed. The internal circulation, which is stimulated within the slugs by their passage along the channel, is responsible for a large enhancement in the interfacial mass transfer and the reaction rate. Mass transfer performance data has been obtained for a glass chip-based reactor in a 380 microm wide channel by monitoring the extraction of acetic acid from kerosene slugs as they moved along the reactor channel. Finally, the data was compared with that provided from other inter-phase contacting techniques.     

Classical study of the influence of induced rotation and anisotropy effects on energy transfer between an atom and a diatomic molecule

The lagrangian equations of motion for a mass 4 atom colliding with a mass 2 diatomic molecule are solved numerically in order to investigate the validity of some approximations often used in energy transfer theory. The results are shown to be very sensitive to the details of the intermolecular potential; the effect of induced rotation can change the vibrational energy transfer by an order of magnitude.     

Surfactant-enhanced liquid-liquid extraction in microfluidic channels with inline electric-field enhanced coalescence

Continuous microfluidic liquid-liquid extraction is realized in a microfluidic device by generating emulsions with large interfacial areas for mass transfer, and subsequently breaking these emulsions using electric fields into easily separated segments of immiscible liquids (plugs). The microfluidic device employs insulated electrodes in a potassium hydroxide-etched channel to create large electric fields (100 kV m(-1)) that drive coalescence of the emulsion phase. The result is a transition from disperse to slug flow that can then readily be separated by gravity. Extractions of phenol and p-nitrophenol from an aqueous to hexane-surfactant solution serve as model systems. In addition to the increased surface area in the emulsion, extraction efficiency is enhanced by reverse micelles resulting from the presence of surfactants. The surfactant concentration is varied approximately 1-10 wt% and a general two-parameter model is developed to quantify the extraction behavior and demonstrate the effectiveness of reverse micelle enhanced extraction.     

Dissolution of polycyclic aromatic hydrocarbons from a non-aqueous phase liquid into a surfactant solution using a rotating disk apparatus

The mass transfer of two polycyclic aromatic hydrocarbons (PAHs), naphthalene and phenanthrene from a multicomponent non-aqueous phase liquid (NAPL) into a nonionic surfactant solution, Brij 35 was investigated using a rotating apparatus. Few experimental methods have been applied to the study of solubilization kinetics in organic liquids because in those systems, the interfacial area during mixing is more difficult to maintain and measure. This challenge was overcome by permeating the NAPL through a membrane. Mass transfer experiments were conducted in the absence and presence of surfactant, and the concentrations of naphthalene and phenanthrene in the bulk aqueous phase were determined in samples collected at different time intervals from the time of initial contact of the NAPL phase with the aqueous solution phase. Experiments in pure water demonstrated that the rotating apparatus behaves as in much the same way as the Levich's rotating disk. The mass transfer coefficients and the dissolution of PAHs into the surfactant solution were measured at different doses of Brij 35. As the surfactant concentration increased, the mass transfer coefficients for both PAHs from the NAPL decreased.     

Computer simulation of non-linear preparative chromatography processes

Summary A theory of non-linear chromatography based on the mass balance equation is presented. The model is a system of partial differential equations and it includes axial dispersion in the mobile phase, flow in the mobile phase and mass transfer between phases. In the case of the injection of a mixture competition between components for places in the stationary or the mobile phase is taken into account. In the paper are discussed: numerical calculations of concentration and volume overloading and the effect of the mutual influence of the components of the injected mixture on the process of mass transfer between phases. Additionally, results of experiments for convex and concave adsorption isotherms are presented. In both cases the results obtained qualitatively confirm the theoretical analyses.     

An analysis of coating-efficiency as a measure for capillary column performance

Summary An expression is proposed for the value of the Coating-Efficiency C. E. starting from the Golay-equation, extended to situations of appreciable pressure drop by Giddings. A comparison is made between the coating-efficiency following this theory and the simplified expression for coating-efficiency as generally used in the literature, that neglects the effects of resistance to mass transfer in the liquid phase and the pressure drop. It is shown that the complete equation from the coating-efficiency explains the observations made in practice. Application of the theory described will lead to a better check on film formation in capillary columns.     

Automated microfluidic platform for studies of carbon dioxide dissolution and solubility in physical solvents

We present an automated microfluidic (MF) approach for the systematic and rapid investigation of carbon dioxide (CO(2)) mass transfer and solubility in physical solvents. Uniformly sized bubbles of CO(2) with lengths exceeding the width of the microchannel (plugs) were isothermally generated in a co-flowing physical solvent within a gas-impermeable, silicon-based MF platform that is compatible with a wide range of solvents, temperatures and pressures. We dynamically determined the volume reduction of the plugs from images that were accommodated within a single field of view, six different downstream locations of the microchannel at any given flow condition. Evaluating plug sizes in real time allowed our automated strategy to suitably select inlet pressures and solvent flow rates such that otherwise dynamically self-selecting parameters (e.g., the plug size, the solvent segment size, and the plug velocity) could be either kept constant or systematically altered. Specifically, if a constant slug length was imposed, the volumetric dissolution rate of CO(2) could be deduced from the measured rate of plug shrinkage. The solubility of CO(2) in the physical solvent was obtained from a comparison between the terminal and the initial plug sizes. Solubility data were acquired every 5 min and were within 2-5% accuracy as compared to literature data. A parameter space consisting of the plug length, solvent slug length and plug velocity at the microchannel inlet was established for different CO(2)-solvent pairs with high and low gas solubilities. In a case study, we selected the gas-liquid pair CO(2)-dimethyl carbonate (DMC) and volumetric mass transfer coefficients 4-30 s(-1) (translating into mass transfer times between 0.25 s and 0.03 s), and Henry's constants, within the range of 6-12 MPa.     

A perturbation solution for batch extraction with double emulsions: role of continuous phase mass transfer resistance

The effect of the continuous phase mass transfer resistance on solute extraction with double emulsions in a batch reactor is investigated. A model presented by Ho et al. (1982) for diffusion controlled mass transfer into the double emulsions is solved by perturbation analysis. In the case of a significant continuous phase mass transfer resistance, the extraction of solute is a function of the inverse Biot modulus, m. For values of m greater than 0.01 the external phase resistance must be taken into account in order to accurately predict extraction rates. Such conditions will exist when double emulsion drops are relatively small or when stirring rates in the batch extractor are low.     

Determination of the mass transfer coefficients in direct immersion solid‐phase microextraction

Diffusion of the analytes across the diffusion boundary layers and subsequently through the fiber coatings determines the extraction kinetics of solid‐phase microextraction in aqueous matrices. Besides, the matrix effects can distort the behaviors of the analytes transferring across the diffusion boundary layers. However, these processes were always studied via certain simplification, which often left the mass transfer through the fiber coatings unconsidered and the matrix effects partially investigated. Herein, a comprehensive study on the mass transfer processes in direct immersion solid‐phase microextraction was presented. Under different agitation speeds, it was determined that the mass transfer coefficients across the diffusion boundary layers were three to six orders larger than those through the fiber coatings. However, the mass transfer across the diffusion boundary layers was generally the major rate‐limiting step. In addition, the shuttle effect and the barrier effect, which were responsible for accelerating and retarding the extraction kinetics, respectively, were found to be the dominant matrix effect alternately under different agitation speeds. This study comprehensively illustrated the major rate‐limiting step and the dominant matrix effects through recording the mass transfer coefficients.     

Interaction of dispersed phase with concentration polarization

The effect of a dispersed phase in reducing the concentration polarization in a membrane tube has been studied. The presence of a dispersed phase seems to have an effect in controlling the size of eddy formation and the rate of energy dissipation in the fluid medium. The role of eddy length and the energy dissipation rate on the mass transfer coefficient is discussed. Theoretical results obtained for the mass transfer coefficient and for the concentration polarization in the case of gelatin ultrafiltration are compared with the existing experimental results. The theoretical predictions seem to be in good agreement with the experimentally observed results.     

Hypercross-linked polystyrene and its potentials for liquid chromatography: a mini-review

A recently introduced method [Biotechnol. Prog. 13 (1997) 429] for determining intraparticle mass transfer parameters in high speed liquid chromatography is considered in the present study for the case where the eluite adsorbs onto the stationary phase. The validity of the method was verified theoretically using simulated elution profiles and then applied to experimental data obtained using columns packed with either a macroporous or a gel-filled gigaporous stationary phase. For this purpose, experimental measurements were made using alpha-lactalbumin and bovine serum albumin as eluites at several retention factors. Apparent intraparticle diffusivities measured for the gel-filled gigaporous stationary phase were seen to increase with the retention factor, which indicates that for this material surface diffusion is a significant mechanism of mass transfer under retained conditions. Data obtained on the macroporous stationary phase revealed that the intraparticle diffusivity was independent of the retention factor, which suggests that pore diffusion remains the principal mass transfer mechanism even under conditions where proteins are adsorbed on the column packing.     

Mass transfer in a membrane tube with turbulent flow of Newtonian and non-Newtonian fluids

Spectral theory of turbulence has been applied to obtain expressions for the mass transfer coefficient in the case of Newtonian and non-Newtonian fluids. Expression of mass transfer coefficient obtained from the spectral theory of turbulence is then compared with that obtained from other hydrodynamic models. Similarities and advantages of these models are discussed. Mass transfer models developed on the basis of hydrodynamic consideration, show their potential in providing mechanistic aspect of transport behavior with respect to mixing and viscous stresses of the fluid on the membrane surface. The effects of flow index and consistency factor of the non-Newtonian fluids, on the mass transfer phenomena in a membrane tube are discussed.     

中空纤维膜萃取分离混合稀土中的钍

通过中空纤维膜逆流萃取，研究了伯胺Ｎ１９２３对Ｔｈ４＋和ＲＥ３＋的萃取分离过程。测定了水相料液硫酸浓度、水相与油相流量对传质系数的影响，并对包头矿硫酸分解浸出液进行中空纤维膜萃取实验。结果表明，Ｔｈ４＋的传质系数受水相流量影响，与酸度及油相流量无关，总传质速率受水相临界层传质步骤控制。ＲＥ３＋的传质系数不受水相流量影响，油相流量影响很小，但受硫酸浓度的影响，总传质速率受萃取反应速率控制。根据传质速率的不同，对包头矿硫酸浸出液进行萃取分离，在８ｈ内Ｔｈ４＋可基本萃取完全，而ＲＥ３＋及Ｆｅ３＋基本不被萃取，故可在密封条件下分离钍。