Electroosmotic Permeability Research Articles

Studies on Nylon-66 membrane using aqueous solutions of potassium and lead nitrate salts as permeants

Abstract Measurements on hydrodynamic and electro-osmotic permeability of water and aqueous solutions of KNO 3 and Pb(NO 3 ) 2 in the concentration (C) range of 10 - 4 $10^{-4}$ M to 10 - 3 $10^{-3}$ M are made across the Nylon-66 membrane. The data obtained are used to ascertain the form of transport equation using the theory of non-equilibrium thermodynamics. Conductance of membrane equilibrated with water and aqueous solutions are measured and the data are used to estimate phenomenological coefficients. These phenomenological coefficients are used to determine the average pore radius, the average number of pores and the membrane constant. Zeta potentials are evaluated using electro-osmotic permeability and membrane-permeant conductance data to understand the electrical nature of the membrane-permeant interface. It is observed that hydrodynamic permeability and electro-osmotic permeability depend linearly on the applied pressure difference and the potential difference, respectively.

A comparative study of the electro-osmotic behavior of cation and anion exchange membranes in alcohol-water media

Fuel flow coupled to the migration of ions is an important aspect of direct alcohol fuel cells, since it strongly affects the fuel cell performance. Solvent uptake and electro-osmotic transport in alcohol-water media have been investigated for different ion selective membranes. Cation and anion exchange membranes, and methanol and ethanol were used to assess the influence of the ion nature of the membrane and the type of alcohol. Current-voltage curves were also measured to determine the values of the limiting current density of each membrane system and analyze the influence of the concentration polarization effects on the measure of the electro-osmotic flow. The obtained results indicated that both the ionic nature and the type of alcohol affect the electro-osmotic transport. The membrane system with the anion exchange membrane and methanol-water solvent presented the lowest electro-osmotic permeability and a lower influence of the concentration polarization effects.

A study on electrokinetic dewatering of oil sands tailings

Oil sands tailings (mature fine tailing (MFT)) are the final product of oil sands processing and are in the form of slurry with a very low solid content. After sedimentation, due to a low hydraulic conductivity of the tailings, dewatering and consolidating the tailings is difficult. Since electrokinetics (EK) has been successfully applied on dewatering and consolidation of low permeability soils, this study is carried out to assess the effectiveness and efficiency of EK dewatering of MFT, a man-made geomaterial. Two series of tests were conducted in this study. In the first series, four EK cell tests were performed on oil sands tailings to measure the electroosmotic permeability, ke, which is the key parameter for assessment of the EK treatment. In the second series, the model tests were designed and carried out to investigate the feasibility of EK dewatering on oil sands tailings. The performance of the EK dewatering was compared under two conditions — under a surcharge load of 5 kPa for consolidation, followed by EK dewatering and under simultaneous treatment of a surcharge load of 5 kPa and EK treatment. The final water content, undrained shear strength and plasticity of MFT were measured after all tests. It was observed that the EK dewatering model tests resulted in significant overall increases in the undrained shear strength and reductions in the water content of tailings samples, along with significant changes of the tailings plasticity.

Effect of concentration polarization on electrodialytic concentrating of dilute NaCl and NH4NO3 solutions

Electrodialytic concentrating of dilute sodium chloride and ammonium nitrate solutions is studied in a wide range of current densities. Using the model of limiting electrodialytic concentrating, based on the experimental data, the transport characteristics of MK-40/MA-40 membrane pair in the above electrolytes and the hydration numbers of these electrolytes were determined. It is found that a degree of concentration polarization has an effect on the main parameters of limiting electrodialytic concentrating: the current efficiency, the water transfer number across the test membrane pair, and the concentration of solution in the concentrating compartment. These parameters determine the effectiveness of concentrating. It is found that the electrodialytic concentrating is most effective at the limiting current due to the lowest electroosmotic permeability of membrane pair and the highest current efficiency.

"Studies on Polarizability and Effective Pressure of Aqua Guard Water, Aqua Fina Water, Pepsi and Thums up Across Urinary Bladder Membranes of Goat"

Water is an integral part of life. Water plays many roles in biological systems. Acid-base balance of the body is primarily maintained by proper urination. Development of pressure, sustenance of pressure and finally release of pressure across urinary bladder membranes is the normal pattern of urination. Passive collection and active expulsion of urine is the primary function of the bladder. Bladder surface should not interact with urine as regards passive collection is concerned. After experiencing certain value of pressure, it begins to interact which finally leads to expulsion of urine with drastic change in polarizability. Use of aquaguard water, aquafina water and cold drinks (Pepsi ,Thums up etc.) are becoming fashion of the modern society. These liquids differ minutely in their physical properties but interactional behavior is quite significant. Hydrodynamic and electro-osmotic permeability measurements of these liquids have been carried out across urinary bladder membranes. Methodology of non equilibrium thermodynamics have been used to explain the data. It has been found that thumsup produces maximum change in polarizability as compared to other permeants.

Electroosmotic transport of water and aprotic solvent in heterogeneous membranes

Electrosmotic water transport in MK-40, MA-40, and MA-41 electrodialysis membranes before and after their treatment by aprotic solvent solution and electroosmotic permeability of a MK-40/MA-40 membrane couple in water and N,N-dimethyl acetamide were studied for the first time. It is found that N,N-dimethyl acetamide produces practically no effect on the properties of the studied ion-exchange materials and its transport number through the MK-40/MA-40 membrane couple is independent both of the initial lithium chloride concentration in a desalting cell of the concentrator electrodyalizer and its volume fraction in the solution. The initial concentration of lithium chloride in the desalting cell does not affect the transport numbers of water in the studied membrane couple either. However, these depend on the volume fraction of the organic component in the solution and this dependence features an extremum. A method for estimation of electroosmotic permeability of the membrane couple in aqueous-organic solutions of electrolytes is suggested.

Regeneration performance of carbon nanotube by binary metallic oxide electrodes electrokinetic system

This study was aimed to investigate the regeneration performance of carbon nanotube saturated with 150mgL−1 of nonylphenol (NP) by binary metallic oxide electrodes-electrokinetic (BMOEEK) system under potential gradient of 2Vcm−1 for 8h of treatment. Twenty experiments were conducted with four processing fluids of de-ionized water (DW), citric acid (CA), NaOH, and NaCl in a Pyrex glass cylindrical cell. An inert electrode of carbon (C) and three binary metallic electrodes of PbO2/Ti (PT), PbO2–Co/Ti (PCT), and PbO2–SnO2+Sb2O3/Ti (PSST) were investigated in this study. Results showed that higher electroosmotic permeability (6.2–26.3×10−6cm2V−1s−1) was found in BMOEEK-CA, -NaOH, and -NaCl systems than in BMOEEK-DW system (0.8–1.4×10−6cm2V−1s−1). A significant detached Pb2+ was found in BMOEEK systems with PT electrode. The best CNT regeneration efficiency of 71.4–80.0% was found in BMOEEK-NaCl system with PSST electrodes, which was 1.4–1.6 times greater than in BMOEEK-DW system. This might be resulted from both hypochlorite (OCl−) generation in anode reservoir by disassociation of NaCl and less Pb2+ detached from electrode with coating of Co and insulated layer of SnO2+Sb2O3. For BMOEEK-NaOH and -NaCl systems, the degradation of NP is much more prominent than the combined removal by electroosmosis and electromigration and for the other two systems, the removal percentage is significant. It is concluded that both binary metallic electrode and processing fluid definitely played key roles in enhancing the regeneration performance of CNT. The electrode characteristics (progressive cyclic voltammogram, and SEM micrograph with EDS), electrokinetic behavior (specimen pH and current density), and regeneration mechanism in investigated systems would also be discussed in this study.

Structure Effects on Electro-Osmosis in Microporous Media

The structure effects on electro-osmosis in microporous media have been studied by modeling the multiphysical transport using our numerical framework. The three-dimensional microstructures of porous media are reproduced by a random generation-growth method, and then the nonlinear governing equations for the electrokinetic transport are solved by a highly efficient lattice Poisson–Boltzmann method. The simulation results indicate that the porous structure type (granular, fibrous, or network) influences the electro-osmotic permeability significantly. At the low porosity regime (<0.4), the network structure exhibits the highest electro-osmotic permeability because of its highest surface–volume ratio among the three types of structure at the same porosity. When the porosity is high (>0.5), the granular structure leads to the highest electro-osmotic permeability due to its lower shape resistance characteristics. The present modeling results improve our understanding of hydrodynamic and electrokinetic transport in geophysical systems, and help guide the design of porous electrodes in micro-energy systems.

A thermodynamic study of 1,4-dioxane across cellulose acetate membrane under different conditions

The cellulose membrane used in the present studies was prepared by impregnating cellulose acetate dissolved in acetone and mixed up with aqueous KBr, which has been added through a sintered G2 (porosity) disc. The flow of water, 1,4-dioxane and their different compositions through this membrane has been measured at different temperatures under different electric and magnetic field strengths. The results are interpreted in terms of a unit rate process. The electro osmotic permeability coefficients, enthalpy of activation (ΔH*), entropy of activation (ΔS*), free energy of activation (ΔG*), number of pores, pore radius and zeta potential have also been calculated. The flow process of various aqueous–dioxane mixtures across the membrane does not seem to be thermodynamically feasible. However, the dipolar nature of the solvent mixture does affect the membrane structure as shown by the variation in pore radius, number of pores and zeta potential.

Measurement of Membrane Characteristics Using the Phenomenological Equation and the Overall Mass Transport Equation in Ion-Exchange Membrane Electrodialysis of Saline Water

The overall membrane pair characteristics included in the overall mass transport equation are understandable using the phenomenological equations expressed in the irreversible thermodynamics. In this investigation, the overall membrane pair characteristics (overall transport number 𝜆, overall solute permeability 𝜇, overall electro-osmotic permeability 𝜙 and overall hydraulic permeability 𝜌) were measured by seawater electrodialysis changing current density, temperature and salt concentration, and it was found that 𝜇 occasionally takes minus value. For understanding the above phenomenon, new concept of the overall concentration reflection coefficient 𝜎∗ is introduced from the phenomenological equation. This is the aim of this investigation. 𝜎∗ is defined for describing the permselectivity between solutes and water molecules in the electrodialysis system just after an electric current interruption. 𝜎∗ is expressed by the function of 𝜇 and 𝜌. 𝜎∗ is generally larger than 1 and 𝜇 is positive, but occasionally 𝜎∗ becomes less than 1 and 𝜇 becomes negative. Negative 𝜇 means that ions are transferred with water molecules (solvent) from desalting cells toward concentrating cells just after an electric current interruption, indicating up-hill transport or coupled transport between water molecules and solutes.

Laboratory assessment of electro-osmotic stabilization of soft clay

The application of electro-osmosis (EO) for stabilizing soft clays is receiving more attention in geotechnical engineering. When the application of traditional ground improvement techniques, such as surcharge, pre-loading, wick drains, and vacuum pre-loading, is not appropriate for a particular situation, innovative techniques such as electro-osmosis need to be considered. Although the effectiveness of electro-osmosis has been widely demonstrated in many field applications, geotechnical engineers are still hesitant to apply electro-osmosis due to unknown effects such as electro-chemical changes, which could not be accounted for in the design. This paper presents a design of an electro-osmotic triaxial testing apparatus suitable for electro-osmotic treatment of soft clays and for measuring electro-osmotic permeability and generated pore-water pressure, as well as a testing procedure that accounts for the contribution of electro-chemical changes in the improvement of soil properties. A series of electro-osmotic triaxial tests with various initial stresses and boundary conditions were conducted and the results are presented in the paper.

Electro-Osmotic Permeability Coefficient of Peat with Different Degree of Humification

Electro-Osmotic Permeability Coefficient of Peat with Different Degree of Humification

Dewatering of a biological industrial sludge by electrokinetics-assisted filter press

The objective of this work was to evaluate the performance of biological industrial sludge dewatering by a pilot-scale filter press assisted by electrokinetics (EK). In all experiments the following conditions were kept constant: (1) dry solids content in the sludge feed: 5.0 wt%; and (2) constant electric-current mode. Application of 1 A and 4 A of electric current for 45 min for dewatering was capable of yielding sludge filter cakes with moisture contents of 65.0% and 53.2%, respectively. However, the former would provide a better compromise between the residual moisture content and the electricity cost. This practice has been shown to be cost-effective. The reduction of sludge moisture content might be ascribed to the mechanisms of mechanical pressure, electroosmosis, and ohmic heating in said dewatering system. The estimated electroosmotic permeability was found to be comparable to that of reported by other researchers.

A Three-Scale Model of pH-Dependent Flows and Ion Transport with Equilibrium Adsorption in Kaolinite Clays: II Effective-Medium Behavior

In part I (Lima et al., Transp Porous Media, 2009), a three-scale model governing the movement of an aqueous saline solution containing four monovalent species (Na+, H+, Cl−, OH−) in kaolinite clays was derived. Unlike purely macroscopic approaches, the novelty of the formulation relied on the double averaging of the nanoscopic electro- chemistry of particle/electrolyte solution interface ruled by the electrical double layer coupled with protonation/deprotonation reactions. The passage from the nano to the micro (pore)-scale gave rise to ion-sorbed concentrations and slip velocity at the solid/fluid interface which are coupled with the microscopic Stokes problem and Nernst–Planck equations governing the hydrodynamics and ion transport in the micropores. Application of a formal homogenization procedure led to macroscopic governing equations with effective electro-chemical parameters, such as retardation coefficients, electro-osmotic permeability, and electric conductivity. In this study, we reconstruct the constitutive laws of the macroscopic coefficients by solving the nano and microscopic closure problems. New generalized isotherms for Na+ and H+ − OH− sorption are build-up based on a perturbation approach and the limitations of classical Freundlich isotherm for modeling ion sorption at the solid/fluid interface are discussed. The macroscopic governing equations are discretized by the finite volume method and numerical simulations of a transient electroosmosis experiment for desalination of a clay sample by electrokinetics are presented.

A computer simulation of continuous ion exchange membrane electrodialysis for desalination of saline water

A computer simulation program including the principle of ① mass transport, ② current density distribution, ③ energy consumption and ④ limiting current density is developed for predicting desalinating performance of a continuous (one-pass flow) electrodialysis process. In this simulation the following parameters are inputted; ① membrane characteristics such as overall transport number, overall solute permeability, overall electro-osmotic permeability, overall hydraulic permeability, direct current electric resistance etc. ② electrodialyzer specifications such as flow-pass thickness, flow-pass width and flow-pass length of a desalting cell etc. and ③ electrodialytic conditions such as current density, electrolyte concentration in a feeding solution, linear velocity in desalting cells, standard deviation of normal distribution of solution velocity ratio etc. In a practical-scale electrodialyzer, electrolyte concentration in a desalting cell is decreased along a flow-pass and it gives rise to electrolyte concentration distribution. It causes electric resistance distribution and current density distribution. Solution velocities in desalting cells vary between the cells, and give rise to solution velocity distribution. In this simulation, these distributions are taken into account assuming that the frequency distribution of solution velocity ratio is equated by the normal distribution. Further, the influences of electrodialyzer specifications and elctrodialysis conditions described above on the performances of an electrodialyzer (desalting ratio, current efficiency, electrolyte concentration at the outlets of desalting cells, cell voltage, energy consumption, electrolyte concentration distribution, current density distribution, and limiting current density) are predicted. The simulation model is developed on the basis of the experiments and its reasonability is supported by the performance of electrodialyzers operating in salt-manufacturing plants.

A computer simulation of batch ion exchange membrane electrodialysis for desalination of saline water

A computer simulation program is developed for predicting desalinating performance of a batch electrodialysis process. The program includes the principle of ① mass transport, ② current density distribution, ③ cell voltage, ④ mass balance/energy consumption and ⑤ limiting current density. In this simulation the following parameters are inputted; ① membrane characteristics such as overall transport number, overall solute permeability, overall electro-osmotic permeability, overall hydraulic permeability, direct current electric resistance etc., ② electrodialyzer specifications such as flow-pass thickness, flow-pass width and flow-pass length in a desalting cell etc. and ③ electrodialytic conditions such as voltage, electrolyte concentration in a feeding solution, linear velocity in desalting cells, standard deviation of normal distribution of solution velocity ratio etc. The following phenomena were computed and discussed; ① Changes of electrolyte concentration and current density with operation time. ② Influence of cell voltage on operation time (batch duration), water recovery and energy consumption. ③ Influence of volume of an electrolyte solution prepared at first on operation time. ④ Influence of cell voltage, electrolyte concentration and standard deviation of solution velocity ratio in desalting cells on limiting current density. ⑤ Energy consumption in a reverse osmosis process. ⑥ Excepting limiting current density, the performance of an electrodialyzer is never influenced by the standard deviation of normal distribution of solution velocity ratio in desalting cells. ⑦ Energy consumption in electrodialysis is less than that in reverse osmosis at feeding saline water concentration less than about 2000 mg/l .

Study of the Internal Morphology of Cation-Exchange Membranes by Means of Electroosmotic Permeability Relaxations

The effect of an ac sinusoidal perturbation of known amplitude and frequency superimposed to the usual dc applied electric voltage difference on the electroosmotic flow through three cation-exchange membranes with different morphology has been studied. A dispersion of the electroosmotic permeability on the frequency of the applied ac signal has been found for the three membranes investigated, observing that the electroosmotic permeability reaches maximum values for some characteristic values of the frequency. These characteristic frequency values, which are related to relaxation processes in heterogeneous media, depend on the membrane system and permit to obtain information about the different structures of the membrane system. Thus, the study of the electroosmotic permeability relaxation can be used as a method to study the internal morphology of a cation-exchange membrane in a given electrolyte medium.

Injection of saline solutions to improve the electro-osmotic pressure and consolidation of foundation soil

Injection of saline solutions can enhance the effect of electro-osmotic pressure. This study considers the consolidation and stability of foundation soil for building construction. Kaolinite (KGa-1) and Taipei silty clay were subjected to zeta potential (ZP), electro-osmosis and laboratory vane shear tests with injection of saline solutions. The ZP values decrease (i.e., less negative potential) with increased cationic valences and concentrations. The increased electro-osmotic permeability from injecting CaCl 2 (1 N, EOC5) solution is about 172% higher than that without injection due to an increase of drained water from the cathode and the resulting increase of undrained shear strength. Average undrained shear strength for injecting CaCl 2 solution over a period of 7 days is about 4 to 5 times greater than that without injection during electro-osmosis tests. Electro-osmosis tests with injection of saline solutions reveal that the increase of undrained soil shear strength (Δ S u) is proportional to the ZP tests.

Perfluorinated nanocomposite membranes modified by polyaniline: Electrotransport phenomena and morphology

This work summarizes results on the modification of perfluorinated sulfocationic membranes MF-4SC by in situ chemical polymerization of aniline. The investigation of transport properties of polyaniline/MF-4SC composite membranes after bulk modification – conductivity, diffusion and electroosmotic permeability, proton permselectivity – as well as porosimetry and polarization behavior is carried out as functions of aniline polymerization parameters and acid concentration. The fibrous-cluster model of a composite membrane is proposed for the estimation of transport and structural parameters, taking into account different mechanism of charge transfer in structural fragments of the composite. The atomic force microscopy images and curves of water distribution on the effective pore radii in the composite membranes testify to a morphological transition from the nano- to the microsize of polyaniline inclusions with increasing the aniline polymerization time. This effect is confirmed by the analysis of two-phase model transport and structural parameters. High values of the “true” proton transport numbers of composites are obtained and discussed. The dynamic hydration numbers of protons and chloride co-ions are estimated using the “true” transport numbers of protons and the electroosmotic coefficients of composites. The current–voltage curves of composite membranes in the “free standing” state after bulk and surface modification by polyaniline are investigated. The effect of stabilization of limiting current density is observed for MF-4SC membrane after bulk modification. The effect of current–voltage curves asymmetry is observed for different orientation of the polyaniline layer towards the current direction for an anisotropic composite membrane after surface modification.

Electro-osmosis in gels: Application to Agar-Agar

Widely used in food- and bio-engineering as a reference material, Agar-Agar gel is the focus of an experimental investigation concerning the electro-osmosis phenomenon. After presenting the experimental methods, one trial is discussed in detail. A fair reproducibility of results is obtained, and the averaged electro-osmotic permeability is provided. This value lies in the range generally measured on various kind of soils, even if Agar-Agar gel does not share any micro-structural characteristics with soils. To cite this article: F. Cherblanc et al., C. R. Mecanique 336 (2008).