Effect Of Electrical Double Layer Research Articles

Insights into the mechanism involved by electric double layer on phosphate removal of metal-bearing environmental remediation agent: Taking tricalcium aluminate as representative

Metal-bearing materials are known to be desirable environmental captures for phosphate removal, yet few studies focus on understanding the reaction process, especially formed a special phenomenon, i.e., electric double layer (EDL), which might influence the phosphate removal. To fill in this gap, we fabricated metal-bearing tricalcium aluminate (C3A, Ca3Al2O6) as representative, to remove phosphate and unveil the impact by electric double layer (EDL). Specifically, a preeminent removal capacity of 142.2 mg·g−1 was achieved at the initial phosphate concentration below 300 mg·L−1. Following thorough the characterizations, the process was that the released Ca2+ or Al3+ of C3A formed positive charged stern layer attracted phosphate to generate Ca or Al-precipitation. At high phosphate concentration (>300 mg·L−1), C3A exhibited inferior removal capability for phosphate (<45 mg·g−1), due to the aggregation of C3A particles with low water permeability under the EDL effect, obstructing Ca2+ and Al3+ to release for phosphate removal. In addition, the feasibility application of C3A was evaluated based on response surface methodology (RSM), highlighting its prospective phosphate treatment. This work not only provides a theoretical guidance for the application of C3A to remove phosphate, but also deepens the understand of phosphate removal mechanism by metal-bearing materials, shedding light on environmental remediation.

PH Effects in a Model Electrocatalytic Reaction Disentangled.

Varying the solution pH not only changes the reactant concentrations in bulk solution but also the local reaction environment (LRE) that is shaped furthermore by macroscopic mass transport and microscopic electric double layer (EDL) effects. Understanding ubiquitous pH effects in electrocatalysis requires disentangling these interwoven factors, which is a difficult, if not impossible, task without physical modeling. Herein, we demonstrate how a hierarchical model that integrates microkinetics, double-layer charging, and macroscopic mass transport can help understand pH effects of the formic acid oxidation reaction (FAOR). In terms of the relation between the peak activity and the solution pH, intrinsic pH effects without consideration of changes in the LRE would lead to a bell-shaped curve with a peak at pH = 6. Adding only macroscopic mass transport, we can already reproduce qualitatively the experimentally observed trapezoidal shape with a plateau between pH 5 and 10 in perchlorate and sulfate solutions. A quantitative agreement with experimental data requires consideration of EDL effects beyond Frumkin correlations. Specifically, the peculiar nonmonotonic surface charging relation affects the free energies of adsorbed intermediates. We further discuss pH effects of FAOR in phosphate and chloride-containing solutions, for which anion adsorption becomes important. This study underpins the importance of a full consideration of multiple interrelated factors for the interpretation of pH effects in electrocatalysis.

Evaluation of Electrical Impedance Spectra by Long Short-Term Memory to Estimate Nitrate Concentrations in Soil.

Monitoring the nitrate concentration in soil is crucial to guide the use of nitrate-based fertilizers. This study presents the characteristics of an impedance sensor used to estimate the nitrate concentration in soil based on the sensitivity of the soil dielectric constant to ion conductivity and on electrical double layer effects at electrodes. The impedance of synthetic sandy soil samples with nitrate nitrogen concentrations ranging from 0 to 15 mg/L was measured at frequencies between 20 Hz and 5 kHz and noticeable conductance and susceptance effects were observed. Long short-term memory (LSTM), a variant of recurrent artificial neural networks (RNN), was investigated with respect to its suitability to extract nitrate concentrations from the measured impedance spectra and additional physical properties of the soils, such as mass density and water content. Both random forest and LSTM were tested as feature selection methods. Then, numerous LSTMs were trained to estimate the nitrate concentrations in the soils. To increase estimation accuracy, hyperparameters were optimized with Bayesian optimization. The resulting optimal regression model showed coefficients of determination between true and predicted nitrate concentrations as high as 0.95. Thus, it could be demonstrated that the system has the potential to monitor nitrate concentrations in soils in real time and in situ.

Electro osmotically flow of fourth-grade fluid in complex channel with porous medium and lubricated walls: applications in petroleum industry

This article offers a distinct survey of a multiphase flow through a uniform channel. The electro-osmotic phenomenon is the main source of the flow. Fourth-grade fluid model is used as the base liquid which is suspended with metallic particles to form a bi-phase viscous suspension. Skin friction effects are tackled by employing lubrication effects on the opposite walls of the channel. Porous media is governed by the modified Darcy’s law and the Poisson differential equation is considered for electric double-layer effects. An approximate solution is achieved for the nonlinear fluid flow. The obtained findings are also compared with the existing literature for the limiting case. It is inferred that the shear thickness effects cause the momentum of the bi-phase flow to decline, gradually. However, the motion of the metallic particles is supported by the lubrication effects on the walls of the channel.

Accelerated/decelerated dynamics of the electric double layer at hydrogen-terminated diamond/Li+ solid electrolyte interface

The electrical response of the electric double layer (EDL) effect at the interface between a hydrogen-terminated diamond (H-diamond) and a Li+-conducting solid electrolyte [i.e., LiNbO3 and Li3PO4] was investigated by using an all-solid-state H-diamond-based EDL transistor (EDLT). A 5-nm-thick LiNbO3 or Li3PO4 interlayer was inserted between a H-diamond and a Li–Si–Zr–O (700 nm) Li+ solid electrolyte. We performed Hall measurements and pulse response measurements to investigate the EDL charging characteristics exhibited. The Hall measurements evidenced that all EDLTs exhibited EDL-induced hole density modulation, with a large EDL capacitance (CEDL) to 15 μF/cm2 in the Li + -deficient region (negative VG side). On the other hand, in the pulse response measurement, insertion of an LiNbO3 or Li3PO4 interlayer caused significant acceleration/deceleration of the switching response speed, ranging from τ = 61.4 ms to 229 μs? CEDL at the LiNbO3/H-diamond and Li3PO4/H-diamond interface, particularly on the Li+ rich side, was indicated as determining the switching response speed. The results indicate that the very thin EDL (i.e., 5 Å) can be formed at the solid/solid electrolyte interface, even when inorganic solid electrolytes are used instead of liquid electrolytes, and CEDL at the solid/solid electrolyte can be controlled by electrolyte compositions within a thickness of several Å from the interface.

Transient solute dispersion in electro‐osmotic viscoplastic flow in a microchannel

AbstractThe transport of a neutral solute in incompressible electro‐osmotic flow of Bingham plastic non‐Newtonian liquid flowing through a microchannel is studied theoretically. The flow is driven by a constant axially applied electric field. The non‐dimensional conservation equations with associated boundary conditions are solved with Gill's series expansion technique. The whole transport process is analyzed using three transport coefficients, namely, advection coefficient, dispersion coefficient and the apparent asymmetry coefficient, respectively. The mean concentration distribution of the solute is calculated via a third‐order approximation of the series expansion. The study investigates the collective effects of yield stress and electric double layer (EDL) thickness (inverse Debye length) on the transport of solute. The long‐term behaviour of mean concentration distribution is shown to be accurately predicted by second‐order approximations; however, utilizing third or higher order approximations in Gill's series expansion enables a more refined analysis of the small and moderate time behavior of transport coefficients. The present analysis is relevant to emerging applications in bio‐microfluidics exploiting electroviscous fluent media.

Effect of the Electric Double Layer (EDL) in Multicomponent Electrolyte Reduction and Solid Electrolyte Interphase (SEI) Formation in Lithium Batteries.

Electrolytes, consisting of salts, solvents, and additives, must form a stable solid electrolyte interphase (SEI) to ensure the performance and durability of lithium(Li)-ion batteries. However, the electric double layer (EDL) structure near charged surfaces is still unsolved, despite its importance in dictating the species being reduced for SEI formation near a negative electrode. In this work, a newly developed model was used to illustrate the effect of EDL on SEI formation in two essential electrolytes, the carbonate-based electrolyte for Li-ion batteries and the ether-based electrolyte for batteries with Li-metal anodes. Both electrolytes have fluoroethylene carbonate (FEC) as a common additive to form the beneficial F-containing SEI component (e.g., LiF). However, the role of FEC drastically differs in these electrolytes. FEC is an effective SEI modifier for the carbonate-based electrolyte by being the only F-containing species entering the EDL and being reduced, as the anion (PF6-) will not enter the EDL. For the ether-based electrolyte, both the anion (TFSI-) and FEC can enter the EDL and be reduced. The competition of the two species within the EDL due to the surface charge and temperature leads to a unique temperature effect observed in prior experiments: the FEC additive is more effective in modulating SEI components at a low temperature (-40 °C) than at room temperature (20 °C) in the ether-based electrolyte. These collective quantitative agreements with experiments emphasize the importance of incorporating the effect of the EDL in multicomponent electrolyte reduction reactions in simulations/experiments to predict/control the formation of the SEI layer.

Pathways to enhance electrochemical CO2 reduction identified through direct pore-level modeling.

Electrochemical conversion of CO2 to fuels and valuable products is one pathway to reduce CO2 emissions. Electrolyzers using gas diffusion electrodes (GDEs) show much higher current densities than aqueous phase electrolyzers, yet models for multi-physical transport remain relatively undeveloped, often relying on volume-averaged approximations. Many physical phenomena interact inside the GDE, which is a multiphase environment (gaseous reactants and products, liquid electrolyte, and solid catalyst), and a multiscale problem, where "pore-scale" phenomena affect observations at the "macro-scale". We present a direct (not volume-averaged) pore-level transport model featuring a liquid electrolyte domain and a gaseous domain coupled at the liquid-gas interface. Transport is resolved, in 2D, around individual nanoparticles comprising the catalyst layer, including the electric double layer and steric effects. The GDE behavior at the pore-level is studied in detail under various idealized catalyst geometries configurations, showing how the catalyst layer thickness, roughness, and liquid wetting behavior all contribute to (or restrict) the transport necessary for CO2 reduction. The analysis identifies several pathways to enhance GDE performance, opening the possibility for increasing the current density by an order of magnitude or more. The results also suggest that the typical liquid-gas interface in the GDE of experimental demonstrations form a filled front rather than a wetting film, the electrochemical reaction is not taking place at a triple-phase boundary but rather a thicker zone around the triple-phase boundary, the solubility reduction at high electrolyte concentrations is an important contributor to transport limitations, and there is considerable heterogeneity in the use of the catalyst. The model allows unprecedented visualization of the transport dynamics inside the GDE across multiple length scales, making it a key step forward on the path to understanding and enhancing GDEs for electrochemical CO2 reduction.

Streaming Potential in Gas Phase Discrete Unsaturated Pore

The seismoelectric effect of porous media is the main basis for seismoelectric logging. At present, most of the studies on the seismoelectric effect in unsaturated porous media adopt the model of pores with continuous distribution of gas and liquid. There is a lack of theoretical research on the micro mechanism of the seismoelectric effect of unsaturated porous media with discrete gas phase, and the existing studies do not consider the effect of the electric double layer at the gas–liquid interface on the seismoelectric effect. Based on the capillary model, this work adopted the gas phase discrete model, combined the electric double layer theory and the seepage principle, considered the effect of electric double layer at the pore wall and the gas–liquid interface, and studied the micro principle of the seismoelectric effect of unsaturated porous media. Firstly, we studied the variation of gas–water two-phase flow pattern with saturation in unsaturated pores, then proposed the equivalent principle of series circuits, deduced the effective streaming current and conductance of a pore containing multiple bubbles, and then deduced the streaming potential coupling coefficient in the unsaturated pores. We also studied the effect of pore parameters such as saturation, pore size, bubble spacing, pore fluid viscosity, and salinity on the streaming potential coupling coefficient. The results show that the streaming potential coupling coefficient first increases and then decreases with the decrease in saturation, which is the same as the trend measured in Allègre’s experiment, and provide a theoretical explanation for the non-monotonic change in the coupling coefficient with saturation in unsaturated porous media.

Determination of -potential of nanofluids based on electrolyte solutions from the measurements by the methods of electrical spectroscopy and laser correlation spectroscopy

The work discusses the problem of measurement of the -potential for electrolyte-based suspensions of nanoparticle. A theory is presented for the effect of the diffuse electric double layer, including the interphase (stagnant) layer, on the effective conductivity of such suspensions. The theory is based on the method of compact groups of inhomogeneities applied to a model system of hard-core–penetrable-shell particles embedded together with the base liquid in a uniform host of the conductivity . The cores represent the particles. The shells are electrically inhomogeneous in the radial direction, their conductivity profile being a continuous function σ2(r). The overlapping components obey the rule of dominance, according to which the local conductivity value is determined by the distance from the point to the center of to the nearest particle. This model is possible to analyze rigorously in the static limit. The desired conductivity is found from the integral relation which allows us to express the electrical conductivity in the terms of the -potential, thickness of the stagnant layer, matrix molarity, etc. The theory reveals the existence of different scenarios of behavior of the conductivity depending on the geometrical and electrical parameters of the stagnant layer. It is shown that the functional dependence between the thickness and -potential can be obtained from the rate of change of the conductivity with concentration for diluted suspensions; this rate can be measured experimentally. It is pointed out that the hydrodynamic radius of a nanoparticle can be obtained from the Smoluchowski-Einstein diffusion coefficient, which can be measured by the method of laser correlation spectroscopy. We give all necessary estimates and relations to demonstrate the opportunity of measuring the -potential by analyzing together the results obtained by the indicated methods. Namely, in order to find the-potential, it is necessary to simultaneously do a series of independent measurements: find the slope of the conductivity and estimate the thickness of the stagnant layer.

Fabrication of nickel sulfide/hierarchical porous carbon from refining waste for high-performance supercapacitor

The increasingly solid waste with high toxicity and complex composition brought serious environmental and economic problems. Nickel sulfide/hierarchical porous carbon (Ni3S2/HPCs) have been successfully synthesized from the Ni3S2/coke solid waste as raw materials by a co-activation method. KOH was used as the activator and KCl was used as the template to modulate the pore structure, resulting in the high specific surface area of 2738 m2 g−1 and the improved distribution of Ni3S2. The trace amount of Ni3S2 provided a wide range of active sites for charge storage and transfer. The synergistic effect of pseudocapacitance and electric double layer enhanced the energy storage properties and stability of Ni3S2/HPCs. The optimized Ni3S2/HPC-3 exhibited high capacitance of 360 F g−1 at a current density of 1 A g−1, in 6 M KOH electrolyte and high cycle stability of 95.7 % after 10,000 cycles at 10 A g−1. The assembled symmetrical supercapacitor achieved a power density of 19.65 W h kg−1 at 450 W kg−1 in 1 M Na2SO4 electrolyte, outperforming most other carbon-based symmetrical supercapacitors. This work demonstrates the high-value utilization of refining solid waste to fabricate an electric double layer/pseudocapacitor composite material through a facile synthesis strategy, which also provides a new insight of resources recycling.

Capacitive deionization performance of asymmetric nanoengineered CoFe2O4 carbon nanomaterials composite.

Capacitive deionization (CDI) is a relatively new technique that uses electric double layer (EDL) effects, high-affinity chemical groups, redox-active materials, and membrane capacitive electrosorption principle for the desalination. In this paper, hydrothermal synthesis of cobalt ferric oxide (CFO) metal oxide nanoparticles (NPs) coupled with the vacuum filtration method, or the freeze-drying method is used to fabricate high-performance nanocomposites: CFO-graphene, CFO-CNTs, and CFO-3DrGO. Two times of hydrothermal reaction methods were conducted to fabricate the CFO-3DrGO nanoengineered as a pseudocapacitive/EDL electrode. The results have demonstrated that the SAC of CFO-3DrGO/CFO (64.5mgg-1) is greater than that of the CFO-graphene/CFO (55.16mgg-1) and CFO-CNTs/CFO (21.5mgg-1) due to the better surface area of the CFO-3DrGO nanocomposite (330 m2g-1). The higher surface area of the CFO-3DrGO is due to the porous and interconnected 3D structure of the 3DrGO, and it provides a larger surface area to form EDL capacitance. In addition, the added porous 3DrGO entangled with the spinel crystals (CoFe2O4) in the composite allowed for a quick ion diffusion across the interconnected open macroporous structures.

In situ growing Prussian blue nanocrystals on Ti3C2 lamellae as high-performance electrode for potassium-ion storage

Surface modification played an important role in tailoring electrode surface chemistry to improve electrochemical performance. More often than not, electrode materials were coated with conductive assistants (e.g. graphite) to enhance their surface electronic conductivity. However, suchlike conductive enclosure was usually not a good ionic conductor in electrolyte. This not only required a lot of strenuous synthetic efforts in thinning surface coatings and avoiding uneven layer thickness, but also retarded surface ionic kinetics in any case. Here, an attempt was made by in situ growing Prussian blue (PB) nanocrystals on well-conductive Ti3C2 lamellae. When used as an electrode, Ti3C2 functioned as an electron bridge to connect current collector with potassium reservoir (viz. PB). Besides, the open-up Ti3C2 framework could buffer volumetric variation of PB during potassiation/depotassiation and also accommodate K+ through electric double-layer capacitive effect. On the other hand, exposed PB nanocrystals were in full contact with electrolyte, so that it would improve the accessibility of K+ by shortening their diffusion path. More strikingly, PB and Ti3C2 components did not operate on their own; instead, they showed great synergy that significantly enhanced the overall performance of the battery. This composite electrode could deliver high K-storage capacity of 355 mAh g−1 after 1000 cycles at 1 A g−1 and exhibit outstanding rate-capacity of 267 mAh g−1 at 10 A g−1.

Synthesis of nitrogen-doped graphene driven from photothermal decomposition of ammonium bicarbonate and its application in supercapacitors

In this work, nitrogen-doped graphene is achieved in a short time at low temperature by UV light radiation which induces thermal decomposition of ammonium bicarbonate (NH4HCO3) to release NH3 as nitrogen source. XRD and XPS results confirm that the most of oxygen-containing functional groups are removed from graphene oxide after photoreduction and nitrogen doping, and thus graphene oxide was reduced to form N-doped graphene. The N content of the obtained graphene is 2.91 at.%. The SEM images show that the graphene film on Ni foam is composed of spherical graphene nanoparticles, making it easy to adsorb more ions to form electric double-layer capacitance effect and increase the specific capacitance. As expected, the specific capacitance of UV assisted N-doped graphene is as high as 328.85 F g−1 at 0.5 A g−1, which is larger than that of graphene without nitrogen doping (261.13 F g−1 at 0.5 A g−1). Meanwhile, N-doped graphene shows good rate performance and cycle stability (capacitance retention rate: 96.1 % after 10, 000 cycles). This work shows the excellent supercapacitive performance of N-doped graphene, and also provides a simple and environmentally friendly method for rapid reduction and nitrogen doping of graphene oxide to prepare high-performance graphene.

Electroosmotic effect on two immiscible (conducting–non-conducting) fluids flowing in the porous channel under magnetic field

In this article, we investigate the motion of two-phase immiscible fluids in the channel with the porous medium in the presence of a magnetic field. Depending on the different levels of permeability, the channel is classified into two regions. The lower region (region-I) consists of non-conducting modified Casson fluid and the upper region (region-II) consist of conducting Newtonian fluid. The external electric field is applied in the region-II and the electroosmotic effect is produced at the wall and the interface region. Due to the interfacial effect, the non-conducting fluid was driven by conducting fluid. To compute the flow dynamic and electric potential nature, the momentum equation and Poisson–Boltzmann equation have been solved analytically in the state of periodic vibrations. The impact of physiological parameters such as Debye–Hückel parameter, electric field, magnetic field, Darcy numbers, viscosity ratio, Casson parameter and Womersley number has been investigated and the various behaviours were characterised. Based on numerical computations performed on the aforementioned parameters, we found that the Casson parameter, Darcy numbers and electric double layer (EDL) effects are predominant features. In the velocity profiles, we identified the flow of the fluid was enhanced by the augmented values of Darcy numbers, electric field (wall zeta potential), Debye–Hückel parameter and Casson parameter. The retardation flow occurred for the higher values of the magnetic field, viscosity ratio and electric field (interface zeta potential). Based on the conditional cases, the Womersley number possesses inconsistent behaviour. The depletion nature was found in the percentage flow rate of the Casson parameter. By increasing the value of the electric field and Casson parameter, the magnitude of wall shear stress to Darcy number increases and decreases for higher values of the magnetic field, viscosity ratio and pulsatile Reynolds number. It is first noticed that for any value of M1 and M2, Darcy number (Da2) plays a dual role in the upper wall shear stress. The present study leads to the pumping effect of gas pipelines or designing the microfluidic devices which are manipulated in biosensors/biochips.

MoS2-encapsulated nitrogen-doped carbon bowls for highly efficient and selective removal of copper ions from wastewater

Capacitive deionization has been considered as a promising wastewater treatment technology because of its low-cost and highly efficient. Herein, we prepared hollow bowl-type carbon materials loaded with molybdenum sulfide (HBC-MoS2) composites and fabricated it as an innovative electrode material to remove Cu2+ in a multi-ion coexistence system. With the synergistic effect of electric double layer (EDL) and complexation between MoS2 and Cu2+, the HBC-MoS2-0.02 electrode achieved effective removal of copper ions from low concentration wastewater (25 mg/L) and high electrosorption capacity of 28.97 mg g−1 at 1.0 V. Even in the presence of competing ions (Na+/Zn2+/Cu2+), the HBC-MoS2-0.02 electrode still can effectively remove Cu2+ with a final adsorption capacity of 28 mg g−1, showing its superiority. The mechanism of Cu2+ removal by HBC-MoS2 is mainly due to the synergistic effect of EDL and complexation.

Porous macroradical epoxy-based supercapacitors

Intrinsic p -type conductivity was observed in an otherwise aliphatic epoxy backbone through derivatization with stable radicals. The conductive potential of this combined radical-epoxy material was further investigated by prospecting for energy storage systems. This work identifies macroradical epoxy composites with 10% (w/w) conductive carbon as viable devices in supercapacitor application. In cross-linking, the appropriate selection of the diamine spacer has a profound impact on the curing and the resulting conformation of the polymer. The short-chain diamine spacer 1,2-diaminoethane exhibits the best supercapacitor performance yielding a maximum specific capacitance of 195 F g −1 at 1.0 A g −1 . The specific capacitance remains at 99% at 1.0 A g −1 after repeatedly charging and discharging 10,000 times. The observed cycling stability is rare for materials exhibiting pseudocapacitance. This better performance than a reference conventional epoxy composite is attributed to the overall contributions of the electric double layer and pseudocapacitance effect with the effective utilization of the nanoscale porous polymeric structure. Furthermore, the pseudocapacitance is significantly enhanced by using the short-chain diamine spacer due to the closer radical-to-radical interactions and the excellent dispersibility of the added conductive particles. • Macroradical epoxies have promising energy-storage prospects. • Macroradical epoxy composite electrodes are viable supercapacitors. • Superior cycling performance is observed, rare for pseudocapacitors. • Rheology and small-angle x-ray scattering correlate with electrode chemistry. • Magnets used during cross-linking are valuable in distinguishing morphology.

Theoretical analysis of electrical double layer effects on the multiphase flow of Jeffrey fluid through a divergent channel with lubricated walls

A theoretical study of two-phase non-Newtonian fluid with heat transfer is presented in this article. Jeffrey fluid model is used as the base liquid to form a multiphase suspension with the help of gold particles. Heating effects have also been applied on an electro-osmotic two-phase flow through a divergent channel. The lubrication effects have been applied to dampen the skin friction of the opposite walls. An analytical solution is obtained for the nonlinear multiphase fluid flow with heat transfer. Separate expressions for the volumetric flow rate of two-phase flow and pressure gradient are determined via a complex mathematical manipulation. A concise parametric study reveals that slippery walls of the channel have a prominent influence on the momentum of both phases.

Investigating saturated hydraulic conductivity of remolded loess subjected to CaCl2 solution of varying concentrations

• The K sat characteristics of remolded loess under CaCl 2 solutions are presented. • The response of EDL effect to CaCl 2 concentrations is evaluated. • Microstructure evolution of loess induced by CaCl 2 solutions is revealed. • The mechanism of K sat change in seepage process is disclosed. • The findings in this study have broad application value to other soils. Loess has been widely used in site remediation engineering projects in the Chinese Loess Plateau. With the interaction between CaCl 2 solution and cutoff wall, how does its permeability change, is the response pattern consistent for different concentrations, and what is the mechanism? To address this series of problems, the effects of CaCl 2 solutions of varying concentrations on the permeability of remolded loess were investigated by saturated permeability test, and the mechanisms underlying these effects were explored through free swelling ratio, zeta potential, thermogravimetric analysis (TGA), grain-size tests, as well as SEM and MIP tests. The results indicate that K sat values of the samples permeated with both deionized water (DW) and 0.001 mol/L CaCl 2 solution increase with time, with a greater increase observed in the latter. This is mainly due to that the electrical double layer (EDL) effect induced by Ca 2+ , as the dominant factor, controls particle flocculation and pore structure development. Under seepage of a 0.010 mol/L CaCl 2 solution, the EDL effect plays a dominant role during the initial stage. However, chemical weathering causes the disintegration of loess particles, and the dissolution of carbonates is inhibited by Ca 2+ . These are not conducive to pore development; thus, K sat first increases and then decreases significantly. The K sat of samples permeated with a 0.005 mol/L CaCl 2 solution first increases and then stabilizes, which represents the transitional stage of the two aforementioned change trends. This is mainly because the effective pores are increased by leaching and cation exchange, and then the porosity is in dynamic equilibrium under the combined action of the EDL effect, geochemical action, and microstructural evolution. Thus, the saturated hydraulic conductivity ( K sat ) of remolded loess is sensitive to the concentrations of CaCl 2 solutions, with different response modes.

Extending pore network models to include electrical double layer effects in micropores for studying capacitive deionization

Capacitive Deionization (CDI) is an electro-driven water desalination device. It consists of oppositely charged porous electrodes on either side of a dielectric spacer. The electrodes may be either capacitive or pseudocapacitive electrodes. Capacitive electrodes work by storing ions in the Electrical Double Layers (EDLs) of micropores. To model the uptake of ions into EDLs, transport equations are coupled with appropriate EDL structure model. Previous research has shown that pore structure effects CDI performance. A Pore Network Model (PNM) is a unique tool capable of measuring the effects of pore structure. To the best of the author's knowledge, there is no pore network model of CDI or any PNM in general which applies EDL theory. It is in this work that discretized PDEs are derived for modelling the capacitive storage of ions in a pore network using EDL theory. The EDL theories studied were: Helmholtz, Gouy-Chapman-Stern and modified Donnan. Results from the PNM framework were compared to finite element solver results, and it was found that the error in concentration and potential never exceeded 10% or 15% respectively. Lastly, the new pore network framework was used to accurately predict salt content in effluent of a stop flow CDI cell found in literature.