Ionic Mass Transfer Research Articles

Electrokinetic transport through the nanopores in cell membrane during electroporation

In electroporation, applied electric field creates hydrophilic nanopores in a cell membrane that can serve as a pathway for inserting biological samples to the cell. It is highly desirable to understand the ionic transfer and fluid flow through the nanopores in order to control and improve the cell transfection. Because of submicron dimensions, conventional theories of electrokinetics may lose their applicability in such nanopores. In the current study, the Poisson–Nernst–Planck equations along with modified Navier–Stokes equations and the continuity equation are solved in order to find electric potential, fluid flow, and ionic concentration through the nanopores. The results show that the electric potential, velocity field, and ionic concentration vary with the size of the nanopores and are different through the nanopores located at the front and backside of the cell membrane. However, on a given side of the cell membrane, angular position of nanopores has fewer influences on liquid flow and ionic transfer. By increasing the radius of the nanopores, the averaged velocity and ionic concentration through the nanopores are increased. It is also shown that, in the presence of electric pulse, electrokinetic effects (electroosmosis and electrophoresis) have significant influences on ionic mass transfer through the nanopores, while the effect of diffusion on ionic mass flux is negligible in comparison with electrokinetics. Increasing the radius of the nanopores intensifies the effect of convection (electroosmosis) in comparison with electrophoresis on ionic flux.

(Invited) Zinc Surface Morphological Variations and Ionic Mass Transfer Rates in Alkaline Solution

The present simplified electrochemical model of a horizontal upward-facing Zn anode combined with a Ni(OH)2/NiOOH cathode thus reasonably simulates the time-dependent coupling phenomena between the electrode surface morphological variations and the ionic mass transfer rate inside the model-pore mesoporous microstructure that extends across the width of a Zn battery cell.

Li dendrite growth and Li+ ionic mass transfer phenomenon

Li metal dendrite growth in LiPF6–propylene carbonate (PC) electrolyte was observed in situ by a laser scanning confocal microscope (LSCM) with a metallographic microscope. The development of the electrodeposited Li dendrite length was analyzed, and compared with dendrites grown in LiClO4–PC electrolyte solution. Different anions make different Solid Electrolyte Interphase (SEI) layers on the electrodeposited Li metal. This difference is one factor which causes the morphological variation and the different dendrite growth behavior of Li metal in these electrolytes. The relationship between the Li dendrite growth and Li+ ionic mass transfer rate associated with the electrodeposition of Li metal is examined, and dendrite initiation and growth rate are discussed. The authors find that ionic mass transfer plays an important role in dendrite growth behavior.

Block copolymer micellization induced microphase mass transfer: Partition of Pd(II), Pt(IV) and Rh(III) in three-liquid-phase systems of S201–EOPO–Na2SO4–H2O

Three-liquid-phase partitioning of Pd(II), Pt(IV) and Rh(III) in systems of S201(diisoamyl sulfide)/nonane–EOPO(polyethylene oxide–polypropylene oxide random block copolymer)–Na2SO4–H2O was investigated. Experimental results indicated that the selective enrichment of Pd(II), Pt(IV) and Rh(III) respectively into the S201 organic top phase, EOPO-based middle phase and Na2SO4 bottom phase was achieved by control over the phase behavior of the three-liquid-phase systems (TLPS). The microphase mass transfer behavior of Pt(IV), Pd(II) and Rh(III) was closely related to the micellization of EOPO molecules. A suggested micro-mechanism model and a mass transfer model describe the micellization of EOPO molecules and the effect on mass transfer of platinum ions across the microphase interfaces. The salting-out induced continuous dehydration and ordered arrangement of the hydrophilic PEO segments in amphiphilic EOPO micelle, and these are the main driving forces for mass transfer of platinum metal ions onto the exposed activity sites of the dehydrated PEO segments. The differences in microphase interfacial structure of EOPO micelles are crucial for the efficient separation between Pt(IV), Pd(II) and Rh(III).

Salting-out induced three-liquid-phase separation of Pt(IV), Pd(II) and Rh(III) in system of S201−acetonitrile−NaCl−water

Salting-out induced three-liquid-phase system (TLPS) of diisopentyl sulfide (S201)−acetonitrile−NaCl−water was explored to extract and separate platinum, palladium and rhodium with one-step method. The influences of phase-forming behaviors of TLPS on partition of platinum-group metal (PGM) ions were investigated by changing the phase-forming salt and its concentration, HCl concentration in equilibrating salt aqueous phases and the initial volume ratio of acetonitrile to aqueous NaCl solution. Experimental results indicated Pd(II), Pt(IV) and Rh(III) were selectively concentrated into the S201 organic top phase, acetonitrile-rich middle phase and NaCl aqueous bottom phase respectively. The three-liquid-phase partition of platinum metal ions occurred with the salting-out induced two-phase splitting of acetonitrile–water mixtures. A micro-mechanism model is proposed to explain the influence of salting-out induced phase splitting behavior of three-liquid-phase system on mass transfer of PGM ions. Appearance of microscopic molecular aggregates accounts for the micro-phase enrichment of platinum metal ions. The competition of two opposite processes, salting-out induced dehydration of acetonitrile molecules in aqueous solutions while strong re-hydration of salting-out acetonitrile molecules in separated acetonitrile-rich phase, plays an important role in affecting the phase-forming behaviors and three-liquid-phase mass transfer of different platinum metal ions.

IONIC MASS TRANSFER IN THREE-PHASE FLUIDIZED BEDS IN THE PRESENCE OF DISC PROMOTERS

Three-phase fluidized beds have wide applications in process industries. The present investigation is carried out to identify the enhancement of ionic mass transfer coefficients due to the presence of a disc promoter in a three-phase fluidized bed. A diffusion-controlled electrode reaction—reduction of ferricyanide ion—was employed to obtain mass transfer coefficient data. The mass transfer coefficient data were obtained by varying the geometric variables of the disc promoter (disc diameter, disc spacing) and dynamic variables (superficial liquid velocity, superficial gas velocity). The effect of particle diameter was also investigated. The investigations revealed that the mass transfer coefficients were enhanced with decreased disc spacing, increased disc diameter, increased superficial gas velocity, increased superficial liquid velocity, and increased particle diameter.

Zinc Surface Morphological Variations and Ionic Mass Transfer Rates in Alkaline Solution

not Available.

In Situ Observation of Dendrite Growth of Electrodeposited Li Metal

The dendrite growth behavior of Li metal galvanostatically electrodeposited on Ni substrate in a –propylene carbonate electrolyte solution was in situ observed by a laser scanning confocal microscope with a metallographic microscope. A Li dendrite precursor is stochastically evolved on Ni substrate probably through a solid electrolyte interphase layer produced by the surface chemical reaction between a reduced Li metal and an organic electrolyte. The measured length of randomly growing Li dendrite arms was statistically analyzed. The initiation period of the dendrite precursor becomes shorter with increasing current density and decreasing concentration. Once it has been initiated, the ionic mass transfer rate starts to govern the growth process of the dendrite arm length, exceeding over the surface chemistry controlling step. The dendrite arm length averaged over the substrate surface grows linearly proportional to the square root of time. The lower the concentration of , the steeper the inclination of the line at , whereas the concentration dependence of inclination is not evident at .

Effect of vibrating disc electrode on ionic mass transfer in an electrolytic cell

In the present investigation, a vertical disc electrode was vibrated in a rectangular electrolytic cell. The cell consisted of equimolal potassium ferricyanide and ferrocyanide electrolyte with excess indifferent electrolyte, sodium hydroxide. The mass transfer data were obtained on the disc electrode by varying the amplitude of vibration (0.033 to 0.089 m), frequency of vibration (2.93 to 16.16 Hz) and diameter (0.0125 to 0.0315 m) of the disc electrode. The mass transfer coefficient was increased with the decrease in the diameter of the disc electrode. The mass transfer coefficient was enhanced from 12 to 52 fold due to vibration.

Onset of buoyancy-driven motion with laminar forced convection flows in a horizontal porous channel

Buoyancy-driven motion in the laminar forced convection flow has been investigated in a horizontal porous channel. The stability equations including the inertia and the dispersion effects have been solved analytically under the linear theory and also the principle of exchanges of stabilities. The resulting critical position x c for the onset of convection becomes larger with increasing the Reynolds number, Re K considering the permeability. This means that the more inertia and dispersion make the system more stable. The ionic mass transfer experiments using the limiting current technique have been conducted to obtain the critical position for the manifest convection, i.e. the undershoot distance x u with comparison of the forced convective mass flux with the mixed-convective one. Based on the experimental results, the inertia and dispersion effects are explained reasonably for the stabilization of the present system.

Experimental investigation of cell design for the electrolysis of iron oxide suspensions in alkaline electrolyte

Following feasibility studies of iron production by electrolytic reduction of hematite particles suspended in a strong alkaline medium, this article concerns the use of engineering methods to investigate the performance of various cell configurations, in view to designing larger processes: a horizontal flow cell with parallel electrodes and two rotating cylindrical electrodes were used for this purpose. The performance was analyzed in terms of current efficiency at 0.1 A cm−2 and deposit morphology. The results reveal a negligible role of the mass transfer of Fe (+III) ions from the bulk electrolyte on the process efficiency, as formerly suggested in reaction mechanism studies. Conventional ion-mass transfer theory is therefore not applicable and another approach is proposed. Dispersed phase transport processes, more precisely the mechanical forces acting on both the 10 μm ore particles and the evolved oxygen bubbles, can quantitatively and qualitatively explain the cells performance. The configuration with the external rotating cathode allows both efficient contacts of the particles with the cathode and rapid removal of the produced gas phase; however the two rotating electrode devices are subject to appreciable ohmic losses due to the current lead system. The parallel plate configuration, with the cathode at the bottom appears as the best configuration for the deposition which can be achieved with low energy consumption.

Potential‐driven peptide extractions across supported liquid membranes: Investigation of principal operational parameters

Fundamental experiments on electromembrane extraction were performed to increase the basic knowledge about the current and the mass transfer of target peptides and background electrolyte ions. Three peptides (angiotensin 2, bradykinin, and enkephalin) were extracted from 500 microL aqueous donor solution (1 mM HCl, positive electrode), through a 200 microm supported liquid membrane (SLM) of 1-octanol/di-isobutylketon/di-(2-ethylhexyl) phosphate (55:35:10 w/w/w) sustained in the pores of a porous hollow fiber, and into 25 microL aqueous acceptor solution (50 mM HCl, negative electrode) present inside the lumen of the fiber by the application of an electrical potential (50 V) and agitation (1050 rpm). Recoveries were typically in the range of 55-65% after 5 min of extraction and were principally determined by the chemical composition of the SLM and by the applied voltage. The electrical current in the system was measured during the extraction and was close to 350 microA. The current arose to some extent from mass transfer of the target peptides, but the major contribution was due to a background current from di-(2-ethylhexyl) phosphate in the SLM and from mass transfer of background electrolytes. Operation at relatively low background current was important to maintain a stable system.

Modeling of Parasitic Hydrogen Evolution Effects in an Aluminum−Air Cell

The aluminum−air battery has potential to serve as a near-term power source for electric vehicles. Parasitic hydrogen evolution caused by anode corrosion during the discharge process, however, has long been recognized as an obstacle to further commercialization of the aluminum−air battery. This paper focuses on the parasitic reaction impacts, with an aim of better understanding and managing the parasitic reaction. On the basis of a mathematical model, effects of the parasitic hydrogen evolution on cell flow field, ionic mass transfer, and current density are investigated. Besides, the possibility of using the parasitically evolved hydrogen to increase the total power output is evaluated.

Modelling of mass transfer coupling with crystallization kinetics in microscale

Microstructure technologies have attracted interests in chemistry, chemical engineering, and biotechnology. To investigate the mass transfer of ions and crystallization of crystals in microscale and then to explain the formation mechanism of the porous structure materials, a microscale mathematical model for mass transfer processes coupling with local reactions is proposed in which the chemical potential gradient Δ μ is used as the driving force to avoid the discontinuity of the kinetics equations in the micro-channels. Meanwhile, the dissolution kinetics of KCl at 298.15 K is measured to determine the dissolution rate constant k d and the average area of crystals Ac. The investigation for the fractional crystallization process of carnallite shows that the calculated mixing time versus channel width agree with the Einstein diffusion equation, which validates that the model can be used to describe the ion diffusion very well. Meanwhile, to have an accurate Δ μ of KCl, in the channel width of or narrower than 2.0×10 −6 m, it is enough to consider the diffusion only, while in the channel width of or wider than 2.0×10 −5 m, diffusion should be coupled with reaction. The investigation also shows the vital of the consideration of the ionic activity coefficient for the investigated systems in micron scales. Moreover, the new formation mechanism of the porous structures in the inorganic material fabrication will be proposed from the process simulation for the synthesis of porous KCl, which will provide a reference for the porous structure formation in the advanced inorganic material synthesis.

Ionic Mass Transfer Rate Accompanying Pulsed Current Electrodeposition of Silver

Ionic Mass Transfer Rate Accompanying Pulsed Current Electrodeposition of Silver

Numerical Simulation of Ionic Mass-Transfer Rates with Natural Convection in CuSO4 – H2SO4 Solution: II. Comparisons Between Numerical Calculations and Optical Measurements

A mathematical model is developed in Part I of this study for the ionic mass-transfer rates associated with natural convection developing along both electrodes immersed in a aqueous electrolyte. The additional effect of an excess amount of is discussed through the comparisons with the optical measurements. The concentration profiles of both and ions and the natural convective velocity profile have been measured by a two-wavelength holographic interferometer and the tracer method. The present calculation quantitatively agrees with the measured ionic mass-transfer rates toward the electrode surface except for copper electrolysis in an unsupported electrolyte above one-half of the limiting current density. The optical observation suggests that a substantially steady state is attained within 180 s after starting the electrolysis in every case. The numerical calculation predicts a further development of ionic mass-transfer phenomena over 600 s. It is closely related to both secondary flow and electrolyte stratification phenomena.

On limiting rate of dimensional electrodeposition at meso- and nanomaterial manufacturing by template synthesis

The following is shown: the interrelation between the ionic mass transfer rates limiting the rate of electrodeposition of silver from a thiocyanate electrolyte and of copper from a pyrophosphate one and the limiting rate of the dimensional electrodeposition of these metals from the studied of complex electrolytes into nanopores with a size of 100–200 nm under the conditions of template synthesis. It is determined that the layer thicknesses at the passed fixed values of the charge can be increased using pulse current electrodeposition in an atmosphere of inert gas (argon). It is shown that the limitations of the possibility to control the electrodeposition rate using pulse electrolysis are due to the material corrosion during a pause at the pulse electrodeposition.

A new developed method assisting mass transfer of Ni ions in via

This paper proposes an idea to assist the mass transfer of Ni ions in via during the electroplating process, which is considered difficult and still unsolved for a via with a high aspect ratio condition. In addition, a new and easier method is proposed to enable observation and analysis of the in situ phenomenon that arises in via plating. The function of selected important operational parameters influencing the electroplating process can be immediately evaluated. Studies show that the added surfactant FS can not only effectively decrease the surface tension of produced H2 bubbles, but also increase the disturbance within the via; therefore it can enable us to enhance the mass transfer of ions even within the via. This phenomenon confirms that the role of surfactant FS is advantageous in assisting the mass transfer of ions in via, and enables electroplating through the polymeric masks process to be effectively carried out without disruption occurring even at a high height-to-width aspect ratio 30 (AR = 30) condition.

Continuous adsorption of Pt ions in a batch reactor and packed-bed column

Continuous adsorption of platinum (Pt) was performed by using a batch reactor and a packed-bed column system in which amine-treated activated carbon (AC) pellets (Norit RO 0.8) were used as adsorbents. The feed solution (pH 2.0) contained a mixture of Pt and base metal ions (Fe 2+, Cr 3+) in chloride media. The central focus of the study was directed at comparing selectivity and mass transfer characteristics of Pt ions in a batch reactor and packed-bed column. In a batch reactor, the AC particles were agitated mildly (500 rpm) within the bulk solution (810 mL) while fresh feed was fed (6 mL/min) to the reactor continuously in up flow mode. The ratio of AC mass to solution volume in the stirred batch reactor was kept constant (1 g: 810 mL) at ambient conditions. The mass transfer of Pt ions in the packed-bed column was evaluated by correlating the ratio of Sherwood and Schmidt numbers with Reynolds numbers. In the case of a batch reactor, the rate equation was integrated and then fitted to the adsorption data in order to determine the rate constants and mass transfer coefficients. Separation factors ( β Pt/Fe, β Pt/Cr), in the order of 10 2 were achieved in a packed-bed column. However, separation factors in a batch reactor were hundred-fold higher than packed-bed column values indicative of superior mass transfer of Pt in an agitated-carbon-in-liquid (ACIL) process.

Numerical Analysis of Ionic Mass Transfer Phenomena Accompanying Electrochemical Reactions in PC and Ionic Liquid

The transient mass transfer rate of Li+ ion caused by the electrochemical deposition and dissolution of Li metal in propylene carbonate (PC) and ionic liquid (IL) containing a lithium salt is numerically analyzed. The previous mesurements of transport properties such as diffusion coefficient of a lithium salt and electrolyte viscosity are used in the present calculation. The concentration profile of Li+ ion developed along electrode surface has been in-situ measured by holographic interferometry. The measurement values are reasonably compared with the calculations except for the apparent incubation period observed in the initial stage of electrochemical deposition and dissolution.