Search

Nanopore technology is widely used for sequencing DNA, RNA, and peptides with single-molecule resolution, for fingerprinting single proteins, and for detecting metabolites. However, the molecular driving forces controlling the analyte capture, its residence time, and its escape have remained incompletely understood. The recently developed Nanopore Electro-Osmotic trap (NEOtrap) is well fit to study these basic physical processes in nanopore sensing, as it reveals previously missed events. Here, we use the NEOtrap to quantitate the electro-osmotic and electrophoretic forces that act on proteins inside the nanopore. We establish a physical model to describe the capture and escape processes, including the trapping energy potential. We verified the model with experimental data on CRISPR dCas9-RNA-DNA complexes, where we systematically screened crucial modeling parameters such as the size and net charge of the complex. Tuning the balance between electrophoretic and electro-osmotic forces in this way, we compare the trends in the kinetic parameters with our theoretical models. The result is a comprehensive picture of the major physical processes in nanopore trapping, which helps to guide the experiment design and signal interpretation in nanopore experiments.

Nanopore technology is widely used for sequencing DNA, RNA, and peptides with single-molecule resolution, for fingerprinting single proteins, and for detecting metabolites. However, the molecular driving forces controlling the analyte capture, its residence time, and its escape have remained incompletely understood. The recently developed Nanopore Electro-Osmotic trap (NEOtrap) is well fit to study these basic physical processes in nanopore sensing, as it reveals previously missed events. Here, we use the NEOtrap to quantitate the electro-osmotic and electrophoretic forces that act on proteins inside the nanopore. We establish a physical model to describe the capture and escape processes, including the trapping energy potential. We verified the model with experimental data on CRISPR dCas9-RNA-DNA complexes, where we systematically screened crucial modeling parameters such as the size and net charge of the complex. Tuning the balance between electrophoretic and electro-osmotic forces in this way, we compare the trends in the kinetic parameters with our theoretical models. The result is a comprehensive picture of the major physical processes in nanopore trapping, which helps to guide the experiment design and signal interpretation in nanopore experiments.

Electrokinetic treatment of masonry for desalination or electroosmotic dewatering depends on a poultice, in which the electrodes are placed, which fulfills several purposes. Poultice composed of kaolinite and CaCO3 have been shown to have good workability and high pH buffering capacity. In this work, the electroosmotic (EO) permeability is studied in different kaolinite - CaCO3 mixtures. In addition, the effect on EO of using NaCl as a mixing solution is investigated. A special cell is used to test the EO in the specimens. A phenomenological approach, based on the potential gradient and the flux of solution, was used to calculate the EO flow rate and EO permeability coefficient. Results showed that by increasing the concentration of CaCO3 in the poultice mixture, the EO flow rate decreased and the poultice with 80 % CaCO3 and more did not have any EO flow. Furthermore, the ionic strength in the mixing solution decreases the EO flow rate.

Affinity biosensors play a crucial role in clinical diagnosis, pharmaceuticals, immunology, and other areas of human health. Affinity biosensors rely on the specific binding between target analytes and biological ligands such as antibodies, nucleic acids, aptamers, or other receptors to primarily generate electrochemical or optical signals. Considerable effort has been put into improving the performance of the affinity technologies to make them more sensitive, efficient and reproducible, of the many approaches electrokinetic phenomena are a viable option. In this perspective, studies that combine electrokinetic phenomena with affinity biosensor are discussed about their promise for achieving higher sensitivity and lower detection limit.

Fuel cells are a next-generation, clean energy-conversion technology designed to replace existing internal combustion engines. Their implementation is important in reducing carbon emissions and addressing the world climate crisis. However, many system limitations still need to be resolved before fuel cells can enter widespread use, particularly with regard to transport of chemical species within the fuel cell. Fuel cells are composed of several key components, but paramount among them are the fuel-cell catalyst layers, responsible for the fuel-cell reactions that produce electricity, and the fuel-cell membrane, responsible for transporting ions within the system. Transport of chemical species is irrevocably tied to the performance of each component. Improving fuel-cell efficiency by minimizing gas crossover requires understanding gas transport within fuel-cell membranes. Addressing the issue of fuel-cell flooding and the associated reduction in performance requires study of water transport within the membranes, as well as gas transport within the catalyst layers. This dissertation studies these phenomena and provides guidance on proper measurement techniques as well as the transport properties of current state-of-the-art materials.Following an Introduction in Chapter 1, the dissertation begins with a detailed examination of the use of microelectrodes to study the properties of fuel-cell membranes, particularly gas transport. There is an extensive history of using microelectrodes to study fuel-cell membranes ex-situ, but little standardization of cell design and technique. Different designs available in the literature are discussed as are the results of prior studies. Author recommendations are made for proper use of microelectrode systems to ensure consistent experimental results. Then, a new flow-through microelectrode cell design that ameliorates several of the key issues with prior designs, such as equilibration time, is presented. The cell design is evaluated in

This thesis presents the theory and experimental results on two topics: the electroosmotic (EO) pump and the electrorheological effect in microemulsions. In the first section, I gave the theoretical background, the sample fabrication and experimental measurements of the fluid flow for the electroosmotic pump. The electroosmotic pump is basically a simple microchannel in which the channel wall exhibits the charge separation effect. The result of the experiment shows that when an electric field was applied across the microchannel, there can be fluid flow with no moving parts, i.e., the electroosmotic pump operates as a pump with no moving components. My results also show that the efficiency of the electroosmotic pump increases with decreasing channel diameter, thereby verifying the EO to be an interfacial effect. In the second section, the electrorheological effect in water-in-oil microemulsions is presented in both its theoretical and experimental aspects. Based on the theory of the dielectric electrorheological effect and the giant electrorheological effect, a device for observing and recording data of the microemulsions was made. The experimental results show that by applying an electric field to the water-in-oil microemulsions under the constant flow rate condition, one can observe a measurable pressure difference that correlates with the applied field, i.e., the electrorheological effect. This effect is apparently caused by the rearrangement of microemulsion particles into aligned columns along the applied field direction. Also, the experimental results show that the pressure difference increases with decreasing size of the microemulsion particles.

This thesis focuses on two topics involving electric field-fluid interactions. The first is the experimental realization of a coherent, macroscopic state of aligned dipolar filaments of water molecules under an applied electric field. The second is the conception and design of an electroosmotic micropump with gate voltage-induced giant Onsager coefficient. The first topic is relevant to a new kind of electrorheological (ER) fluids, purely composed of water molecules dispersed in silicone oil. This is inspired by the microscopic mechanism of giant ER (GER) effect as well as water’s evident polar characteristic when confined in nanoscale structures. We fabricated a setup including an active region with 60% porosity to permit only vaporized water molecules passing through. The vaporized water molecules from a thermostatic reservoir are shown to form filamentary or columnar structures, penetrating through the porous silicone oil, as a state with minimum energy in response to an external electric field. The formation of such structures is visualized directly by utilizing water-soluble fluorescent probe and captured by inverted confocal microscopy through a transparent electrode. The attendant GER effect, represented by a well-defined yield stress, is measured as a manifestation of such a coherent new molecular state. A phenomenological theory is presented to support the experimental data, with excellent quantitative agreement. The second topic of this thesis is the conception and design of a novel micropump actuated by the electroosmotic (EO) effect. The efficiency for the traditional EO micropumps is limited by the non-slip boundary condition at the liquid/solid interface, typically not surpassing 1%. This ceiling can be broken by our new design of gate voltage-induced EO micropump coupled with slipping effect from superhydrophobic surfaces. The basic idea is first separating the bulk ions by using a pulsed gate voltage, then driving the separated bulk ions with tangent

Dampness in masonries is a major problem in many buildings and monuments worldwide. Techniques based on electro-osmosis have been proposed as conservation methods to dehumidify masonry subjected to capillary suction. Although electroosmotic techniques have been applied for decades, the effect is still debated. This paper reports an experimental investigation on electro-osmosisin single bricks in a laboratory setup originally designed for electro-desalination. Two types of bricks were used. The samples had different lengths and different initial water content. A poultice composition was designed with neglectableelectroosmotic effect and effective buffering of the acid produced from the electrode process at the anode. Four poultices with different concentrations of CaCO3 and kaolinite were examined, and the poultice consisting of calcium carbonate:kaolinite:water with the ratio of 40:10:50 (wt %) fulfilled the requirement. It was seen that more the kaolinite in the mixture, more the electro-osmosis. A constant voltage of 75V was applied to the electrodes in each end of the setup. The zeta potential of the bricks was comparable to the zeta potential in kaolinite, and thus electro-osmosis in the bricks was expected. However, the water content reached saturation all through the brick specimens in every experiment, and there was no difference in water content in the two poultices. Thus, the capillary forces causing water suction into the bricks from the poultices were the strongest and overshadowed the possible electroosmotic effect. Therefore, this work shows that capillary forces need to be taken into account when designing setups for evaluation of electro-osmosis in materials with strong capillarity. The same is valid for in real applications, in case a continuous source of water is present.

Ammonium (NH4+) can be recovered from water for fertiliser production or even energy production purposes. Because NH4+ recovery is more effective at increased concentrations, electrodialysis (ED) can be used to concentrate NH4+ from side streams, such as sludge reject water, and simultaneously achieve high NH4+ removal efficiencies. However, the effect of osmosis and back-diffusion increases when the NH4+ concentration gradient between the diluate and the concentrate stream increases, resulting in a limitation of the concentration factor and an increase in energy consumption for NH4+ removal. In this study, we showed that operation at dynamic current density (DCD) reduced the effect of osmosis and back-diffusion, due to a 75% decrease of the operational run time, compared to operation at a fixed current density (FCD). The concentration factor increased from 4.5 for an FCD to 6.7 for DCD, while the energy consumption of 90% NH4+ removal from synthetic sludge reject water at DCD remained stable at 5.4 MJ·kg-N−1., Sanitary Engineering

BACKGROUND: In this work, a small-scale ceramic microbial fuel cell (MFC) with a novel type of metal-carbon-derived electrocatalyst containing iron and nicarbazin (Fe-NCB) was developed, to enhance electricity generation from neat human urine. Substrate oxidation at the anode provides energy for the separation of ions and recovery from urine without any chemical or external power additions. RESULTS: The catalyst was shown to be effective in clear electrolyte synthesis of high pH, compared with a range of carbon-based metal-free materials. Polarisation curves of tested MFCs showed up to 53% improvement (44.8 W m-3) in performance with the use of Fe-NCB catalyst.Catholyte production rate and pH directly increased with power performance while the conductivity decreased showing visually clear extracted liquid in the best-performing MFCs. CONCLUSIONS: Iron based catalyst Fe-NCB was shown to be a suitable electrocatalyst for the air-breathing cathode, improving power production from urine-fed MFCs. The results suggest electrochemical treatment through electro-osmotic drag while the electricity is produced and not consumed. Electro-osmotic production of clear catholyte is shown to extract water from urine against osmotic pressure. Recovering valuable resources from urine would help to transform energy intensive treatments to resource production, and will create opportunities for new technology development. © 2018 The Authors. Journal of Chemical Technology & Biotechnology published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Ammonium (NH4+) can be recovered from water for fertiliser production or even energy production purposes. Because NH4+ recovery is more effective at increased concentrations, electrodialysis (ED) can be used to concentrate NH4+ from side streams, such as sludge reject water, and simultaneously achieve high NH4+ removal efficiencies. However, the effect of osmosis and back-diffusion increases when the NH4+ concentration gradient between the diluate and the concentrate stream increases, resulting in a limitation of the concentration factor and an increase in energy consumption for NH4+ removal. In this study, we showed that operation at dynamic current density (DCD) reduced the effect of osmosis and back-diffusion, due to a 75% decrease of the operational run time, compared to operation at a fixed current density (FCD). The concentration factor increased from 4.5 for an FCD to 6.7 for DCD, while the energy consumption of 90% NH4+ removal from synthetic sludge reject water at DCD remained stable at 5.4 MJ·kg-N−1., Sanitary Engineering

Power output limitation is one of the main challenges that needs to be addressed for full-scale applications of the Microbial Fuel Cell (MFC) technology. Previous studies have examined electrochemical performance of different cathode electrodes including the development of novel iron based electrocatalysts, however the long-term investigation into continuously operating systems is rare. This work aims to study the application of platinum group metals-free (PGM-free) catalysts integrated into an air-breathing cathode of the microbial fuel cell operating on activated sewage sludge and supplemented with acetate as the carbon energy source. The maximum power density up to 1.3 Wm-2 (54 Wm-3) obtained with iron aminoantipyrine (Fe-AAPyr) catalyst is the highest reported in this type of MFC and shows stability and improvement in long term operation when continuously operated on wastewater. It also investigates the ability of this catalyst to facilitate water extraction from the anode and electroosmotic production of clean catholyte. The electrochemical kinetic extraction of catholyte in the cathode chamber shows correlation with power performance and produces a newly synthesised solution with a high pH > 13, suggesting caustic content. This shows an active electrolytic treatment of wastewater by active ionic and pH splitting in an electricity producing MFC.

Soluble salts are among the most harmful alteration agents affecting the building materials. In recent years, several researches have been devoted to counteract alterations induced by soluble salts using electrokinetic techniques. However, the applicability of these techniques for conservation purposes remains limited due to adverse side effects, such as the extreme pH values occurring near the electrodes, which can affect the stone to be treated. The decrease in efficiency of the treatment caused by the dominant transport of H+ and OH− groups is also an undesired effect. The reduced duration of these treatments due to the drying of the material in contact with the anode also limits their practical use. To overcome these problems, a new electrokinetic design that includes a so called proton pump is presented in this report. This design is based on placing two electrodes in the anodic compartment in order to modulate the net amount of H+ produced. The design was applied to desalinate sandstone samples contaminated with several soluble salts. The application of this new approach allowed us to establish an additional electroosmotic process at the anode, which was able to increase the duration of the treatment. Moreover, the new setup provided improved pH buffer ability due to the generation of OH− in the anodic compartment, which increased the effectiveness of the treatment by hindering the entrance of H+ in the porous structure.

BackgroundCryoelectrolysis is a new minimally invasive tissue ablation surgical technique that combines the ablation techniques of electrolytic ablation with cryosurgery. The goal of this study is to examine the hypothesis that electrolysis can take place in a frozen aqueous saline solution.MethodTo examine the hypothesis we performed a cryoelectrolytic ablation protocol in which electrolysis and cryosurgery are delivered simultaneously in a tissue simulant made of physiological saline gel with a pH dye. We measured current flow, voltage and extents of freezing and pH dye staining.ResultsUsing optical measurements and measurements of currents, we have shown that electrolysis can occur in frozen physiological saline, at high subzero freezing temperatures, above the eutectic temperature of the frozen salt solution. It was observed that electrolysis occurs when the tissue resides at high subzero temperatures during the freezing stage and essentially throughout the entire thawing stage. We also found that during thawing, the frozen lesion temperature raises rapidly to high subfreezing values and remains at those values throughout the thawing stage. Substantial electrolysis occurs during the thawing stage. Another interesting finding is that electro-osmotic flows affect the process of cryoelectrolysis at the anode and cathode, in different ways.DiscussionThe results showing that electrical current flow and electrolysis occur in frozen saline solutions imply a mechanism involving ionic movement in the fluid concentrated saline solution channels between ice crystals, at high subfreezing temperatures. Temperatures higher than the eutectic are required for the brine to be fluid. The particular pattern of temperature and electrical currents during the thawing stage of frozen tissue, can be explained by the large amounts of energy that must be removed at the outer edge of the frozen lesion because of the solid/liquid phase transformation on that interface.ConclusionElectrolysi

BackgroundCryoelectrolysis is a new minimally invasive tissue ablation surgical technique that combines the ablation techniques of electrolytic ablation with cryosurgery. The goal of this study is to examine the hypothesis that electrolysis can take place in a frozen aqueous saline solution.MethodTo examine the hypothesis we performed a cryoelectrolytic ablation protocol in which electrolysis and cryosurgery are delivered simultaneously in a tissue simulant made of physiological saline gel with a pH dye. We measured current flow, voltage and extents of freezing and pH dye staining.ResultsUsing optical measurements and measurements of currents, we have shown that electrolysis can occur in frozen physiological saline, at high subzero freezing temperatures, above the eutectic temperature of the frozen salt solution. It was observed that electrolysis occurs when the tissue resides at high subzero temperatures during the freezing stage and essentially throughout the entire thawing stage. We also found that during thawing, the frozen lesion temperature raises rapidly to high subfreezing values and remains at those values throughout the thawing stage. Substantial electrolysis occurs during the thawing stage. Another interesting finding is that electro-osmotic flows affect the process of cryoelectrolysis at the anode and cathode, in different ways.DiscussionThe results showing that electrical current flow and electrolysis occur in frozen saline solutions imply a mechanism involving ionic movement in the fluid concentrated saline solution channels between ice crystals, at high subfreezing temperatures. Temperatures higher than the eutectic are required for the brine to be fluid. The particular pattern of temperature and electrical currents during the thawing stage of frozen tissue, can be explained by the large amounts of energy that must be removed at the outer edge of the frozen lesion because of the solid/liquid phase transformation on that interface.ConclusionElectrolysi

Reverse osmosis (RO) promises to play an increasingly crucial role in water supply, especially via desalination. One of the major problems faced by RO technology is the decline in membrane performance due to concentration polarisation (CP) and fouling. CP increases the osmotic pressure gradient across the membrane, hence reducing the net driving pressure gradient. Moreover, CP increases the probability of fouling. An electro-osmosis technique is proposed in this thesis which has the potential to reduce CP because it induces the movement of fluid in the vicinity of membrane, thus improving mixing within the boundary layer and enhancing mass transfer. Computational Fluid Dynamics (CFD) is used to simulate steady and unsteady electro-osmotic flow (EOF) in 2D unobstructed and obstructed channels. First, a mathematical simplification of EOF is developed that reduces the required computational load while retaining the model’s accuracy and physical meaning. It is shown that EOF can be mimicked using a slip velocity. The results from CFD are found to be in good agreement both with published data and with more rigorous simulation approaches. For steady EOF in unobstructed channels, the spatial variation in slip velocity is found to be the driver for mass transfer enhancement. For uniform-unsteady EOF in unobstructed channels, a sinusoidal time-varying electro-osmotic slip velocity has negligible effect on the time-averaged hydrodynamics and mass transfer, because the effect is nullified within the time oscillation period. Nevertheless, there are still benefits for using unsteady EOF for fouling reduction/prevention, as increases in slip velocity frequency and amplitude increase the maximum wall stress which is a proxy for fouling reduction. For unsteady EOF in spacer-filled channels, the simulation results show that an oscillating slip velocity has the potential to induce vortex shedding. This occurs when a resonant slip velocity frequency is used for Reynolds numbers near t

Electrophoretic NMR (eNMR) and pulsed-field-gradient NMR (PFG-NMR) methods were used to study transport processes in situ and in a chemically resolved manner in the electrolyte of an experimental direct methanol fuel cell (DMFC) setup, constituted of several layers of Nation 117. The measurements were conducted at room temperature for membranes fully swollen by methanol-water mixtures over a wide concentration interval. The experimental setup and the experimental protocol for the eNMR experiments are discussed in detail. The magnitude of the water and methanol self-diffusion coefficients show a good agreement with previously published data while the ratio of the two self-diffusion coefficients may indicate an imperfect mixing of the two solvent molecules. On the molecular level, the drag of water and methanol molecules by protons is roughly of the same magnitude, with the drag of methanol molecules increasing with increasing methanol content. The electro-osmotic drag defined on mass-flow basis increased for methanol from a low level with increasing methanol concentration while that of water remained roughly constant. (C) 2010 Elsevier Ltd. All rights reserved., QC20100709

Peat is an accumulation of partially decayed vegetation matter with high non-crystalline colloid which is formed in wetland systems. Using electro-osmotic techniques to improve peat entails developing a fundamental understanding of the electro-osmotic environment in peat which is an excellent context for this study. Electro-osmotic properties, electro-osmotic experiments, and the physicochemical effects on the peat due to electro-osmotic treatment were investigated. In addition, chemico-geomechanical sensitivities of peat to pH gradients were examined. The electro-osmotic properties of peat in the presence of different cations were also modeled by means of artificial neural networks. Soil samples were collected to evaluate the correlations between electro-osmotic parameters. Electro-osmotic apparatus were designed and developed specific to provide conditions to get a good quality of undisturbed non-homogeneous samples. Electro-osmotic experiments were then conducted on the peat. To determine the physicochemical effects on the peats due to electro-osmotic treatment, different undisturbed specimens were treated for short and long periods of time in the presence of peat water. Since the foremost effective mechanism during electro-osmotic treatment was electrolysis reactions at the electrodes, chemico-geomechanical sensitivities of peat to pH gradients were also investigated in the process. A backpropogation neural network was applied to model the electro-osmotic properties. The results of the study showed that the zeta potential, specific surface area, water contents, and liquid limit increased as the organic content increased. The negative charge in peat was highly pH-dependent and surface charge dropped to zero at pH 2.3 to 3.5. The zeta potential of the peat was affected by the type of cations, the pH, the valance of cations, the concentration of the cations, degree of humification, and hydrated radius of the cations. The greater degree of humification resulted in t

Peat is an accumulation of partially decayed vegetation matter with high non-crystalline colloid which is formed in wetland systems. Using electro-osmotic techniques to improve peat entails developing a fundamental understanding of the electro-osmotic environment in peat which is an excellent context for this study. Electro-osmotic properties, electro-osmotic experiments, and the physicochemical effects on the peat due to electro-osmotic treatment were investigated. In addition, chemico-geomechanical sensitivities of peat to pH gradients were examined. The electro-osmotic properties of peat in the presence of different cations were also modeled by means of artificial neural networks. Soil samples were collected to evaluate the correlations between electro-osmotic parameters. Electro-osmotic apparatus were designed and developed specific to provide conditions to get a good quality of undisturbed non-homogeneous samples. Electro-osmotic experiments were then conducted on the peat. To determine the physicochemical effects on the peats due to electro-osmotic treatment, different undisturbed specimens were treated for short and long periods of time in the presence of peat water. Since the foremost effective mechanism during electro-osmotic treatment was electrolysis reactions at the electrodes, chemico-geomechanical sensitivities of peat to pH gradients were also investigated in the process. A backpropogation neural network was applied to model the electro-osmotic properties. The results of the study showed that the zeta potential, specific surface area, water contents, and liquid limit increased as the organic content increased. The negative charge in peat was highly pH-dependent and surface charge dropped to zero at pH 2.3 to 3.5. The zeta potential of the peat was affected by the type of cations, the pH, the valance of cations, the concentration of the cations, degree of humification, and hydrated radius of the cations. The greater degree of humification resulted in t

Although simple as a concept, electrophoretic NMR (eNMR) has so far failed to find wider application. Problems encountered are mainly due to disturbing and partly irreproducible convection-like bulk flow effects from both electro-osmosis and thermal convection. Additionally, bubble formation at the electrodes and rf noise pickup has constrained the typical sample geometry to U-tube-like arrangements with a small filling factor and a low resulting NMR sensitivity. Furthermore, the sign of the electrophoretic mobility cancels out in U-tube geometries. We present here a new electrophoretic sample cell based on a vertically placed conventional NMR sample tube with bubble-suppressing palladium metal as electrode material. A suitable radiofrequency filter design prevents noise pickup by the NMR sample coil from the high-voltage leads which extend into the sensitive sample volume. Hence, the obtained signal-to-noise ratio of this cell is one order of magnitude higher than that of our previous U-tube cells. Permitted by the retention of the sign of the displacement-related signal phase in the new cell design, an experimental approach is described where bulk flow effects by electro-osmosis and/or thermal convection are compensated through parallel monitoring of a reference signal from a non-charged species in the sample. This approach, together with a CPMG-like pulse train scheme provides a superior first-order cancellation of non-electrophoretic bulk flow effects., QC20100709

We consider a charged porous material that is saturated by two fluid phases that are immiscible and continuous on the scale of a representative elementary volume. The wetting phase for the grains is water and the nonwetting phase is assumed to be an electrically insulating viscous fluid. We use a volume-averaging approach to derive the linear constitutive equations for the electrical current density as well as the seepage velocities of the wetting and nonwetting phases on the scale of a representative elementary volume. These macroscopic constitutive equations are obtained by volume-averaging Ampere's law together with the Nernst Planck equation and the Stokes equations. The material properties entering the macroscopic constitutive equations are explicitly described as functions of the saturation of the water phase, the electrical formation factor, and parameters that describe the capillary pressure function, the relative permeability function, and the variation of electrical conductivity with saturation. New equations are derived for the streaming potential and electro-osmosis coupling coefficients. A primary drainage and imbibition experiment is simulated numerically to demonstrate that the relative streaming potential coupling coefficient depends not only on the water saturation, but also on the material properties of the sample, as well as the saturation history. We also compare the predicted streaming potential coupling coefficients with experimental data from four dolomite core samples. Measurements on these samples include electrical conductivity, capillary pressure, the streaming potential coupling coefficient at various level of saturation, and the permeability at saturation of the rock samples. We found very good agreement between these experimental data and the model predictions.

We consider a charged porous material that is saturated by two fluid phases that are immiscible and continuous on the scale of a representative elementary volume. The wetting phase for the grains is water and the nonwetting phase is assumed to be an electrically insulating viscous fluid. We use a volume-averaging approach to derive the linear constitutive equations for the electrical current density as well as the seepage velocities of the wetting and nonwetting phases on the scale of a representative elementary volume. These macroscopic constitutive equations are obtained by volume-averaging Ampere's law together with the Nernst Planck equation and the Stokes equations. The material properties entering the macroscopic constitutive equations are explicitly described as functions of the saturation of the water phase, the electrical formation factor, and parameters that describe the capillary pressure function, the relative permeability function, and the variation of electrical conductivity with saturation. New equations are derived for the streaming potential and electro-osmosis coupling coefficients. A primary drainage and imbibition experiment is simulated numerically to demonstrate that the relative streaming potential coupling coefficient depends not only on the water saturation, but also on the material properties of the sample, as well as the saturation history. We also compare the predicted streaming potential coupling coefficients with experimental data from four dolomite core samples. Measurements on these samples include electrical conductivity, capillary pressure, the streaming potential coupling coefficient at various level of saturation, and the permeability at saturation of the rock samples. We found very good agreement between these experimental data and the model predictions.

Recent studies in Southeast Asia on Bangkok and Singapore clays have shown that electro-osmosis induces faster rate of consolidation. Literature on the effectiveness of electro-osmosis technique on peat, however, is scarce. In the Sarawak State of Malaysia, peat covers about 13% of area of the State. Experimental studies were undertaken to assess the effectiveness of electro-osmosis technique on a North Sarawak peat. Peat sample was collected from a location 35 km from Miri City along the Miri to Marudi road and geotechnical characterization experiments were carried out. For electro-osmosis experiments, an experimental set-up was designed and fabricated. A preliminary experiment using a commercially available prefabricated electric vertical drain as electrodes was carried out. Several other lessons learnt during the preliminary experiment led to the modification of the set up and selection of experimental variables. The paper presents the details of the preliminary experiment, observations and results.

Realkalisation is an electrochemical technique for repairing concrete structures damaged by rebar corrosion due to carbonation. The treatment aims at restoring alkalinity of the concrete by application of a continuous current between the rebar, acting as a cathode, and an external auxiliary electrode placed in a carbonate solution and connected to a positive pole of a power supply. Here we report the application of neutron diffraction in the in situ monitoring of a realkalisation treatment, analysing at the same time the development of the electro-osmotic flux and the microstructural variations in the surroundings of the rebar.

A CFD model is created to analyze methanol transport in a flowing electrolyte direct methanol fuel cell (FE-DMFC) by solving the 3D advection-diffusion equation, with consideration of electro-osmosis. The average methanol flux at the anode and cathode surfaces is simulated and compared to equivalent direct methanol fuel cells. Methanol crossover is defined as methanol flux at the cathode surface, and the results reveal that methanol crossover can be drastically reduced by the flowing electrolyte. The performance of the FE-DMFC at peak power current density is evaluated, and diffusion is shown to be the dominant contribution, although electro-osmosis increases with current density. The power consumption of the electrolyte pump is shown to be negligible compared to the cell power output. This indicates that thin electrolyte channels with high flow rates could further improve the efficiency

In problems of groundwater flow and solute transport in clayey soils subject to salt concentration gradients, chemical and electro-osmosis can be too important to disregard, as is commonly done in geohydrology. In this thesis, we consider the quantification of these couple effects to be able to simulate experiments and natural situations involving possible chemically and electrically driven water flow. Because clay can act as a semi-permeable membrane, groundwater flow in clay layers may be driven by osmosis. This can be mathematically accounted for by extending Darcys law with a term related to a salt concentration difference. Also, electrical potential differences may induce water flow, in which case we speak of electro-osmosis. In this work, the incorporation of these processes in existing groundwater models has been thoroughly investigated. The relevant processes and corresponding coefficients have been reviewed and we have suggested some improvements. The equations are used to model lab and field experiments and it is shown how to obtain numerical and analytical solutions for these equations. Some mathematical properties of the model equations are studied and some existing numerical codes for groundwater flow are extended with chemical and electro-osmosis. An important result is derived when membrane potential is coupled to chemical osmosis. It is shown how an experiment that is shorted can be modeled and how measurements of parameters such as permeability should be corrected for electrical effects.

In problems of groundwater flow and solute transport in clayey soils subject to salt concentration gradients, chemical and electro-osmosis can be too important to disregard, as is commonly done in geohydrology. In this thesis, we consider the quantification of these couple effects to be able to simulate experiments and natural situations involving possible chemically and electrically driven water flow. Because clay can act as a semi-permeable membrane, groundwater flow in clay layers may be driven by osmosis. This can be mathematically accounted for by extending Darcys law with a term related to a salt concentration difference. Also, electrical potential differences may induce water flow, in which case we speak of electro-osmosis. In this work, the incorporation of these processes in existing groundwater models has been thoroughly investigated. The relevant processes and corresponding coefficients have been reviewed and we have suggested some improvements. The equations are used to model lab and field experiments and it is shown how to obtain numerical and analytical solutions for these equations. Some mathematical properties of the model equations are studied and some existing numerical codes for groundwater flow are extended with chemical and electro-osmosis. An important result is derived when membrane potential is coupled to chemical osmosis. It is shown how an experiment that is shorted can be modeled and how measurements of parameters such as permeability should be corrected for electrical effects.

(1) Packning; (2) Pelare; (3) Tillsatsmedel; (4) Jordspikning; (5) Termisk behandling; (6) Vakuummetoden; (7) Elektroosmos

(1) Packning; (2) Pelare; (3) Tillsatsmedel; (4) Jordspikning; (5) Termisk behandling; (6) Vakuummetoden; (7) Elektroosmos

The oil sands industry generates large quantities of mineral waste, such as fluid fine tailings, whose disposal is often challenging. The use of planar electrokinetic geocomposites in fluid fine tailings disposal areas could improve in-situ dewatering by allowing water to drain after it is expelled during consolidation and by permitting the use of electro-osmosis to displace a significant portion of the remaining water. Four dewatering experiments involving mature fine tailings are presented here: in three of them, increasing normal stresses are applied on the mature fine tailings followed by electro-osmosis; in the fourth test, electro-osmosis is applied before the normal stress is increased. The results show that planar electrokinetic geocomposites adequately filter mature fine tailings; the particles did not clog or blind the filter. Mature fine tailings were significantly dewatered under an applied normal stress followed by electro-osmosis. Electro-osmosis was very efficient at extracting the more tightly bound water that remained after mechanical dewatering. In one configuration, a significant improvement of the shear strength from nearly 0 kPa to a mean value of 25 kPa was obtained, which is significantly higher than the 10 kPa required by Alberta regulations. The final solids content in that case was about 70%, starting from an initial solids content of 45%. The energy required for that test was 10.6 kW h per dry tonne. (Authors)., The oil sands industry generates large quantities of mineral waste, such as fluid fine tailings, whose disposal is often challenging. The use of planar electrokinetic geocomposites in fluid fine tailings disposal areas could improve in-situ dewatering by allowing water to drain after it is expelled during consolidation and by permitting the use of electro-osmosis to displace a significant portion of the remaining water. Four dewatering experiments involving mature fine tailings are presented here: in three of them, increasing normal stresses are applied on the mature fine tailings followed by electro-osmosis; in the fourth test, electro-osmosis is applied before the normal stress is increased. The results show that planar electrokinetic geocomposites adequately filter mature fine tailings; the particles did not clog or blind the filter. Mature fine tailings were significantly dewatered under an applied normal stress followed by electro-osmosis. Electro-osmosis was very efficient at extracting the more tightly bound water that remained after mechanical dewatering. In one configuration, a significant improvement of the shear strength from nearly 0 kPa to a mean value of 25 kPa was obtained, which is significantly higher than the 10 kPa required by Alberta regulations. The final solids content in that case was about 70%, starting from an initial solids content of 45%. The energy required for that test was 10.6 kW h per dry tonne. (Authors).