Ionic Mass Transfer Research Articles

Modeling of the capacity loss of a 12 V automotive lead-acid battery due to ageing and comparison with measurement data

One-dimensional modeling was carried-out to predict the capacity loss of a 12 V automotive lead-acid battery due to ageing. The model not only accounted for electrochemical kinetics and ionic mass transfer in a battery cell, but also considered the anodic corrosion of lead in sulfuric acid. In order to validate the modeling, modeling results were compared with the measurement data of the cycling behaviors of the lead-acid batteries having nominal capacity of 68 Ah that are mounted on the automobiles manufactured by Hyundai Motor Company. The cycling was performed under the protocol of the constant-current discharge and the constant-voltage charge. The discharge rate of C/3 was used. The range of state of charge was between 1 and 0.85. The voltage was kept constant at the gassing voltage until the charge current tapered to 10 mA. The retention capacity of the battery was measured with C/3 discharge rate before the beginning of cycling and after every 40 cycles of cycling. The modeling results were in good agreement with the measurement data.

High rate anodic dissolution in chloride solutions of steel after electrothermochemical treatment

High rate (up to 15 A/cm2) anodic dissolution of St3 steel in chloride solutions (1–6 M NaCl) was investigated after its electrothermochemical al treatment (nitriding and thermal treatment). Various potential ranges (or current density ranges) can be emphasized: the region of anodic anion activation (sublimiting currents), the diffusion limitation area (caused by salt passivation), and the transpassive dissolution region. It is shown that the heat treatment influence is the most substantial in the region of salt passivation (or the limiting current region). The double role of the hydrodynamics is revealed during dissolution under these conditions: the influence of the ionic mass transfer rate in the solution and of the removal of the hard carbonaceous products produced as a result of the selective dissolution of the components of the nitrided steel. It is shown that, in sublimiting currents and transpassive dissolution ranges, the specific dissolution rate depends on the nitrogen content of the studied steel.

The Influence of Biofilm on the Effectiveness of Ion Exchange Process

The ion exchange of ammonia in a synthetic zeolite has been investigated in the presence of Biofilm of nitrifying bacteria. The Biofilm has been cultivated on the zeolite carrier under different hydrodynamic conditions in a plug flow reactor and in a fluidized bed reactor. Samples of the carrier covered by Biofilm have been withdrawn from the reactors and packed into a miniature ion exchange column that has been used to analyze the ion exchange characteristics, i.e., to determine ion exchange equilibria and the mass transport kinetics. For this purpose, the breakthrough curves have been registered at different ammonia loadings and different concentrations of sodium bicarbonate in the solution. To analyze the mass transport mechanism and quantify kinetic coefficients, we have exploited a linear driving force model (i.e., the LDF model) and the generalized model. The ion exchange and mass transfer characteristics of the Biofilm-covered carrier have been compared to those of the virgin zeolite. The effect of Biofilm on the mass transfer kinetics and ion exchange capacity was found to be induced by swelling properties of zeolite.

용액 교반이 미세 패턴 내 무전해 구리 도금에 미치는 영향

The effect of solution agitation on the copper electroless deposition process of ULSI (ultra large scale integration) interconnections was investigated by using physical, electrochemical and electrical techniques. It was found that proper solution agitation was effective to obtain superconformal copper configuration within the trenches of <TEX>$130{\sim}80nm$</TEX> width. The transition of open potential during electroless deposition process showed that solution agitation induced compact structure of copper deposits by suppressing mass transfer of cuprous ions toward substrate. Also, the specific resistivity of copper layers was lowered by increasing agitation speed, which made the deposited copper particles smaller. Considering both copper deposit configuration and electric property, around 500 rpm of solution agitation was the most suitable for the homogeneous electroless copper filling within the ultra-fine patterns.

Enzymatic ketone reductions with co-factor recycling: Improved reactions with ionic liquid co-solvents

Ionic liquids have been applied to two pharmaceutically relevant ketone reductions mediated by isolated enzymes. Alcohol dehydrogenase isolated from Rhodococcus erythropolis (ADH RE) was found to mediate the asymmetric reductions of 4′-Br-2,2,2-trifluoroacetophenone to ( R)-4′-Br-2,2,2-trifluoroacetophenyl alcohol and 6-Br-β-tetralone to its corresponding alcohol ( S)-6-Br-β-tetralol. Both of these reactions employed a second enzyme, glucose dehydrogenase 103 (GDH 103) to recycle the co-factor NAD through the oxidation of glucose to gluconic acid. In the case of 4′-Br-2,2,2-trifluoroacetophenone the traditional organic co-solvent approaches were limited to a maximum product concentration of 10 g L −1 due to substrate deactivation of the biocatalyst. Employing 10% (v/v) [BMP][NTf2], a water immiscible ionic liquid, facilitated conversion of 50 g L −1 ketone to the chiral alcohol in less than 24 h. The initial rate of reaction was improved more than four times in the presence of 10% (v/v) ionic liquid compared to no co-solvent and the product could be readily isolated in 85% (w/w) overall yield with an ee of 99%. In the case of 6-Br-β-tetralone the reaction was found to proceed more favorably with both miscible and immiscible ionic liquid co-solvents compared to a number of organic solvents. Again, the product could be readily isolated in 88% (w/w) overall yield with an ee of >99%. For both bioconversions the stability of both the ADH RE and the GDH 103 co-enzyme was found to be enhanced by the presence of certain ionic liquids compared to both organic solvents and aqueous buffer. In the case of the immiscible ionic liquid [BMP][NTf2] present at a volume fraction of 10%, the measured enzyme half lives were 266 and >300 h, respectively. These promising results were obtained after screening only a limited range (11) of representative, commercially available ionic liquids. Critical factors in the screening of ionic liquids for bioconversion applications appear to be the solubility of the substrate, biocatalyst stability in the presence of the ionic liquid co-solvent and mass transfer rates from the ionic liquid into the aqueous phase.

Performance evaluation of electrodeionization process based on ionic equilibrium with plate and frame modules

The paper describes results of experiments carried out in plate and frame electrodeionization (EDI) modules, aiming to elucidate ion mass transfer phenomena between ion-exchange resin and membrane for more effective desalination. The selective separation rate of different ions in process was investigated with conventional theories such as double electric layer and the Donnan theory to check its consistence. Further, as comparing with ordinary electrodialysis (ED) process, no obvious limiting current point was observed in EDI performance, which was usually used as a criterion for process optimization. Behavior of ion migration in the fluids with different configurations under different operating parameters was also examined and the ionic equilibrium analysis of EDI process was found to be beneficial to determine whether it was in the steady state or in the regeneration stage of operation.

Beyond Spike Timing Theory – Thermodynamics of Neuronal Computation

AbstractThis paper highlights ionic fluxes as information carriers in neurons. The theoretical framework regarding information transfer is presented as changes in the thermodynamic entropy that underlie specific computations determined by ionic flow. The removal or accumulation of information is analyzed in terms of ionic mass transfer related with changes in Shannon information entropy. Specifically, information transfer occurs during an action potential (AP) via the voltage gated ion channels in membranes and the same physical mechanism can be extended to various types of synapses. Since sequential APs from a selected neuron are not alike, then every spike may transfer slightly different amounts of information during their occurrence. The average efficiency in information transfer during APs is estimated using mutual information measures and Hodgkin-Huxley model. This general scheme of ions as carriers of information represents the required physical machinery for a dynamic information transfer that is missing in the current spike-timing description.

Magnetic field effects on microstructural variation of electrodeposited cobalt films

The electrodeposition process of Co films in a sulfuric acid solution was examined in a magnetic field (0–5 T). The surface morphology of Co films electrodeposited without a magnetic field was drastically modified with the variation of hydrogen gas evolution rate. Crystalline α-Co was formed in the range of pH = 1.5–6.0, while β-Co was not observed. When the magnetic field was superimposed perpendicular to the electric field in the acidic solution (pH = 1.5), the hydrogen evolution rate was promoted by MHD convection, which enhanced the ionic mass transfer (H+ and Co2+) near the electrode surface. Moreover, crystalline β-Co was formed simultaneously with the appearance of the elongated ridge-shape precipitates under a higher magnetic field (≥3 T).

Electrosorption capacitance of nanostructured carbon-based materials

The fundamental mechanism of electrosorption of ions developing a double layer inside nanopores was studied via a combination of experimental and theoretical studies. A novel graphitized-carbon monolithic material has proven to be a good electrical double-layer capacitor that can be applied in the separation of ions from aqueous solutions. An extended electrical double-layer model indicated that the pore size distribution plays a key role in determining the double-layer capacitance in an electrosorption process. Because of the occurrence of double-layer overlapping in narrow pores, mesopores and micropores make significantly different contributions to the double-layer capacitance. Mesopores show good electrochemical accessibility. Micropores present a slow mass transfer of ions and a considerable loss of double-layer capacitance, associated with a shallow potential distribution inside pores. The formation of the diffuse layer inside the micropores determines the magnitude of the double-layer capacitance at low electrolyte concentrations and at conditions close to the point of zero charge of the material. The effect of the double-layer overlapping on the electrosorption capacitance can be reduced by increasing the pore size, electrolyte concentration, and applied potential. The results are relevant to water deionization.

Simulation of ion mass transfer processes with allowance for the concentration dependence of diffusion coefficients

The system of equations describing ion transport in a binary electrolyte za-zc with allowance for the linear dependence of the diffusion coefficients on the concentration was analyzed in the framework of the phenomenological Nernst-Planck approach. The expressions are obtained that define concentration profiles of ions and conditions favorable for the limiting current caused by the achievement of the concentration of a saturated solution (in the case of the anodic reaction) and depletion of the near-electrode region in electroactive cations (in the case of the cathodic reaction). The revealed theoretical dependence of the limiting current on the volume concentration of the salt agrees with published experimental data. The voltammetric characteristics of the corresponding systems were calculated. The role of the migrational component of the ion flow is discussed.

Ionic Mass Transfer Accompanying Anodic Dissolution of Zinc in Alkaline Solution

Holographic interferometry was applied in situ to measure the ionic mass-transfer rates near upward-facing zinc anodes dissolving at high current densities in aqueous KOH solutions. The time-varying interference fringe patterns were converted to individual concentration profiles of , , and ions. The measured ionic concentration profiles agreed well with those predicted by a transient diffusion model for a multicomponent electrolyte. When a zinc anode was electrochemically dissolved in KOH electrolyte, the anode potential abruptly shifted in the noble direction, immediately followed by gas evolution. The onset time for this potential rise and accompanying gas evolution agreed well with the calculated time interval required to drive the ion concentration to zero at the zinc electrode surface. The present model can be applied to not only optimize zinc cell designs but also develop a control method for trouble-free, safe operation of a zinc battery without gas evolution.

Ionic mass transfer during electrochemical dissolution of Li metal in PC electrolyte solution

A Li metal anode was electrochemically dissolved in propylene carbonate (PC) containing 0.5 M lithium perchlorate (LiClO 4) and the development of the Li + concentration profile measured in situ by holographic interferometry. As the electrochemical cell configurations both a horizontal anode-over-cathode configuration, with the anode facing upward, and a vertical configuration of the parallel planar electrodes were employed. At low current densities (<2 mA cm −2) no shifting of the interference fringes was observed in either configuration during the initial stage of current passage. Such an incubation period has been observed also during cathodic Li electrodeposition from PC solutions, but in anodic Li dissolution the amount of electricity consumed during the incubation period was found to be appreciably less than in electrodeposition. This incubation phenomenon in electrochemical dissolution may be related to the existence of a solid–electrolyte interface layer on the Li metal surface in PC. The Li + ion mass transfer rate measured after the incubation period agreed with that expected assuming one-dimensional diffusion in stagnant LiClO 4 solution, away from the upward facing horizontal anode. In the case of a vertical plane anode, natural convection of the electrolytic solution was induced by the accumulation of LiClO 4 at the anode. The mass transfer rate of Li + ion measured after incubation was in reasonable agreement with natural convection boundary layer theory.

Electrodeposition of monodisperse copper nanoparticles on highly oriented pyrolytic graphite electrode with modulation potential method

Copper nanoparticles with size of 51 nm and R.S.D. dia of 10% can be obtained by modulation potential electrodeposition: first, a −0.8 V × 120 ms potential step was used to nucleate copper particles on highly oriented pyrolytic graphite (HOPG) electrode surface, where nuclei with a supercritical size were formed, secondly, a 0.082 V × 80 ms strip peak potential ( E s) was used to strip smaller metal nuclei partly, at last, a growth potential, −0.28 V was applied to grow the nearly identical size slowly. Mechanism of copper electrodeposition on HOPG electrode from a solution of 1 mM CuSO 4 and 1.0 M H 2SO 4 has been studied using cyclic voltammogram and chronoamperometry. In copper electrodeposition the charge-transfer step is fast and the rate of growth is controlled by the rate of mass transfer of copper ions to the growing centers. Reduction of Cu(II) ions did not undergo underpotential deposition. The initial deposition kinetics of Cu electrocrystallization corresponds to a model including progressive nucleation and diffusion controlled growth.

Measurements of mass transfer rates in a rectangular liquid fluidised bed using LCDT

Ionic mass transfer from electrolyte to a plate cathode in liquid fluidised bed filled with spherical inert particles has been experimentally studied. The mass transfer rates were measured by using the limiting current diffusion technique (LCDT) in ferri- and ferrocyanide electrolyte systems. The effects of bed height and electrode location from the bottom of test chamber in different electrolyte concentrations and flow velocities on mass transfer coefficient were evaluated. Ranges of the variables used in the study are as follows: Reynolds number=78–300, Galileo number=282,000–298,000, density number=0.335–0.370 and Schmidt number=1831–1995. Experimental data are correlated as follows, by non-linear regression using Statistica Package Program: Sh = 0.199 Re p 3 5 Ga 1 10 Mv 7 2 Sc 1 3 ( d eq E L ) 3 10 ( d eq L Y ) − 3 4 . A comparison between the present data and related several literature correlation's has been achieved by calculating absolute ( σ A) and relative ( σ R) deviations. The deviations in present study are less than those in the literature cited.

Electrocrystallization of Monodisperse Nanocrystal Copper on Highly Oriented Pyrolytic Graphite Electrode

Mechanism of copper electrocrystallization on highly oriented pyrolytic graphite electrode from a solution of 1 mmol/L CuSO4 and 1.0 mol/L H2SO4 has been studied using cyclic voltammogram and chronoamperometry. The results show that in copper electrodeposition the charge-transfer step is fast and the rate of growth is controlled by the rate of mass transfer of copper ions to the growing centers. Reduction of Cu(II) ions did not undergo underpotential deposition. The initial deposition kinetics of Cu electrocrystallization corresponds to a model including progressive nucleation and diffusion controlled growth. Copper nanocrystals with size of 75.6 nm and relative standard deviation of 9% can be obtained by modulation potential electrodeposition.

Extraction Kinetics of Gallium with 2-Ethylhexylphosphonic Acid Mono-2-Ethylhexyl Ester

As the second step to clarify the synergistic extraction mechanism of gallium with the mixed extractant of 2-ethylhexylphosphonic acid mono-2-ethylhexyl ester (EHPNA) and 5-chloro-8-hydroxyquinoline, the initial extraction rate of gallium with EHPNA alone was measured using a stirred transfer cell. First, the aggregation state of EHPNA in the organic solvent, toluene, and the adsorption characteristics at the interface between the aqueous and organic phases were examined. EHPNA was found to exist mainly as dimers in the organic solvent and to adsorb the interface. By considering that the interface is a site for metal-complex formation, the extraction mechanism constructed with the three processes, a mass transfer of metal ions to the interface, an extraction reaction at the interface based on the Eigen mechanism, and a mass transfer of the metal-complex to the bulk organic phase, was proposed to analyze the experimental results.

04/03005 Studies on ionic mass transfer in the presence of spiral coil turbulence promoters in batch fluidized beds: Prasad, P. R. et al. Chemical Engineering and Processing, 2004, 43, (8), 1055–1062

04/03005 Studies on ionic mass transfer in the presence of spiral coil turbulence promoters in batch fluidized beds: Prasad, P. R. et al. Chemical Engineering and Processing, 2004, 43, (8), 1055–1062

Chemical Oscillation with Periodic Adsorption and Desorption of Surfactant Ions at a Water/Nitrobenzene Interface

Chemical oscillations with periodic adsorption and desorption of surfactant ions, alkyl sulfate ions, at a water/nitrobenzene interface have been investigated. The interfacial tension was measured with a quasi elastic laser scattering (QELS) method and the interfacial electrical potential was obtained. We found that this oscillation consists of a series of abrupt adsorptions of ions, followed by a gradual desorption. In addition, we observed that each abrupt adsorption was always accompanied by a small waving motion of the liquid interface. From the analysis of the video images of the liquid interface or bulk phase, we could conclude that each abrupt adsorption is caused by nonlinear amplification of mass transfer of ions from the bulk phase to the liquid interface by a Marangoni convection, which was generated due to local adsorption of the surfactant ions at the liquid interface that resulted in the heterogeneity of the interfacial tension. In the present paper, we describe the mechanism of the chemical oscillation in terms of the hydrodynamic effect on the ion adsorption processes, and we also show the interfacial chemical reaction with ion exchange during the ion desorption process.

Transport processes during electrowashing of filter cakes

Applications of electric fields during washing of filter cakes increases the removal rate of ions from the cake mother liquor, and under appropriate conditions the field also increases the wash flow rate by electroosmosis. Experimental data that show the key effects of the fields on the rates of ion mass transfer are presented: with the downstream electrode acting as a cathode, cation removal rates are increased whilst the removal rate of the anions is decreased. The concentration profile of the cations with washing time shows an increase in concentration to a value above that of the mother liquor, before it decreases due to displacement by the fresh wash liquor. A model is formulated that describes the advection, dispersion, ion migration and electroosmosis transport processes in the cake. Numerical solution of the model gives cation concentration profiles at the exit of the cake that are in qualitative agreement with the experimental observations. Experimentally measured wash liquor flow rates tend to be lower than what traditional colloid science principles predict by a factor of 5–10: reasons for this difference, supported by experimental work from other researchers, are discussed.

Studies on ionic mass transfer in the presence of spiral coil turbulence promoters in batch fluidized beds

The enhancements in mass transfer coefficients due to the presence of spiral coil promoters in batch fluidized beds are presented in this paper. The variables studied are the flow rate of the electrolyte, the geometric parameters of the promoter-coil diameter ( d c), pitch of the coil ( p) and diameter of the coil wire ( d w), void fraction, and particle diameter ( d p). It is found that the mass transfer coefficient increased with increased flow rate and particle diameter. The increased pitch of the coil has decreased the mass transfer coefficient. The increase in coil diameter and diameter of the coil wire have increased mass transfer rates.