Electrokinetic Properties Research Articles

Effect of Acid Number on the Electrokinetic Properties of Crude Oil during Low-Salinity Waterflooding

Understanding crude oil/brine interface chemistry is essential to elucidating the effect of low-salinity waterflooding (LSWF) on enhanced oil recovery (EOR). The acid and base functional groups in ...

Investigation of structural, electrokinetic and energy state properties of the semiconductive Zr1-xVxNiSn solid solution

Structural, electrokinetic and energy state characteristics of the Zr1-xVxNiSn semiconductive solid solution (х=0–0.10) were investigated in the temperature interval 80–400 К. It was shown that doping of the ZrNiSn compound by V atoms (rV=0.134 nm) due to substitution of Zr (rZr=0.160 nm) results in increase of lattice parameter а(х) of Zr1-xVxNiSn indicating unforecast structural change. Based on analysis of the motion rate of the Fermi level ΔεF/Δх for Zr1-xVxNiSn in direction of the conduction band it was concluded about simultaneous generation of the structural defects of the donor and acceptor nature (donor-acceptor pairs) by unknown mechanism and creation of the corresponding energy levels in the band gap of the semiconductor.

The effect of cellulose nanocrystals and pH value on the flotation process for extraction of minerals

Nowadays, the development of the new flotation reagents is focused on the environmental-friendly technologies and reducing the costs of industrial wastes treatment and re-cultivation as well. Biopolymer particles are anattractive object for designing effective non-toxic processes of enrichment and extraction of valuable mineral raw materials. The effect of cellulose nanocrystals particles on the electrokinetic properties of hybrid and individual dispersions of silica and titania was studied. The obtained data will allow to implement an effective flotation process of titanium-containing or titanium oxide ores on the example of leucoxene ores of the Yaregskoye deposit, Komi Republic (Russia). Calculations of the interaction of the minerals surface (titania and silica) with nanosized cellulose particles based on the theory of DLVO are presented.

Complexes of fluorinated, silicone and hydrocarbon surfactants with carboxymethylcellulose and their influence on properties of the alumina suspension

The aim of this study was to investigate the influence of different types of surfactants on the adsorption, stability, and electrokinetic properties of the carboxymethylcellulose/alumina system as well as the interactions between the surfactants and the polymer. The authors decided to use fluorinated and silicone surfactants besides the conventional hydrocarbon ones. The obtained results showed that carboxymethylcellulose (cmc) adsorption increased in the presence of surfactants due to the formation of polymer-surfactant complexes (the increase of the adsorption from about 0.020 mg m−2 for pure cmc to 0.030 mg m−2 for MTAB/cmc and SJ2/cmc mixtures). The obtained complexes of 0.00336% MTAB/cmc and 0.004% S-106a/cmc reduced the surface tension of water more efficiently than pure surfactants of the same concentration (from 70.06 to 62.39 mN/m and 71.06 to 64.26 mN/m respectively). Stability of the alumina suspension was studied as well. The obtained results indicate that the addition of carboxymethylcellulose, surfactants, and the cmc-surfactant complexes leads to the increase of alumina suspension stability. The mechanism responsible for stabilization was electrosteric one. The largest stability was observed for the systems containing the mixture of cmc and surfactants. The reason for this is the formation of the adsorption layer composed of alternately arranged regions of polymer and surfactant complexes. Electrokinetic measurements of the studied systems allowed to describe the structure of the electrical double layer and to determine the point of zero charge of alumina (pHpzc ≈ 7.5). The addition of the polymer as well as surfactants leads to the charge reversal of alumina.Graphical abstract.

Isolation and identification of Listeria monocytogenes utilizing DC insulator-based dielectrophoresis

Foodborne pathogens pose one of the greatest challenges facing public health in the modern day. One important pathogen, Listeria monocytogenes, is known to be challenging to detect and identify. Three serovars cause most of the Listeria related food-borne illnesses, which the Centers for Disease Control currently utilizes a combination of pulsed-field gel electrophoresis and whole genome sequencing for identification and the determination of clusters and outbreaks. There is a potential method for rapid collection of epidemiological information by exploiting the electrokinetic and dielectrophoretic properties of the L. monocytogenes serovars. Using dielectrophoresis, the three most commonly identified serovars of L. monocytogenes can be distinguished from each other. The electrokinetic and dielectrophoretic mobilities of each serovar was determined through a combination of electrokinetic velocity and dielectrophoretic trapping assessments, in conjunction with finite element multi-physics modeling. A mathematical model of the data, which defines the various factors of dielectrophoretic trapping, is utilized and verified based on the behavior of L. monocytogenes in the microchannel. The trapping condition for the serovars were evaluated as 2.8±0.2×109, 2.2±0.2×109, and 2.2±0.3×109Vm−2 and the electrokinetic mobility was assessed to be 19±0.7, 17±0.7, and 9.2±0.3×10−9m2V−1s−1 for the L. monocytogenes serovars 1/2a, 1/2b, and 4b, respectively.

Unraveling the effect of sub-cooling temperatures on the kinetic performance of biopolymers for methane hydrate

In deep sea plays, where the driving force or sub-cooling temperature for hydrate formation is high, the commercially used kinetic hydrate inhibitors (KHIs) lose their kinetic inhibition performance, additionally they are toxic. Though, biodegradable biopolymers are deliberated as an alternative KHIs. However, the inhibition performance of biopolymers solely for methane hydrate formation at high sub-cooling temperatures has not been evaluated. In current work the kinetic inhibition performance of five biopolymers (Pectin, Sodium- Carboxymethyl cellulose (Na-CMC), Tapioca starch, Dextran and Xanthan gum) on methane hydrate formation is evaluated using isochoric constant cooling method on sapphire hydrate reactor at 95 bar and sub-cooling temperatures of 9 °C and 12 °C. Induction time, hydrate formation rate, amount of methane consumed and percentage relative inhibition power are determined and used as kinetic inhibition indicators. Present data-set reveals that biopolymers efficiently inhibit methane hydrate formation at high sub-cooling temperatures. Among all studied biopolymers Pectin and Na-CMC commendably delayed hydrate nucleation for 78 and 61min respectively. Furthermore, Tapioca starch, Pectin and Na-CMC significantly reduced hydrate formation rate, methane consumption and percentage relative inhibition power. For further analysis on molecular level Conductor like Screening Model for Real Solvents (COSMO-RS) software is used. The interaction energy estimation using COSMO-RS showed that attractive interactions between biopolymers and water molecules are leading to prolonged nucleation. Furthermore, the effect of biopolymer concentrations (0.12 wt% - 1.5 wt%) on kinetic inhibition is elaborated by establishing a relationship between induction time, air-liquid interfacial and electrokinetic properties.

Electrokinetic Properties of 3D-Printed Conductive Lattice Structures

Lattice structures with lattice parameters in the mm range are routinely fabricated by additive manufacturing. Combining light weight and mechanical strength, these structures have plenty of potential applications. When composed of conducting elements, a 3D lattice has interesting electrical and electromagnetic properties. In this work, the electrokinetic properties of a conducting lattice are described by mixing the theory of resistor networks and continuous-medium electrodynamics. Due to the length scale provided by the lattice parameter, the effective continuous medium that mimics the electrokinetic response of a resistor lattice is characterized by a non-local Ohm’s law.

Cation Diffusion in Compacted Clay: A Pore-Scale View.

Cation diffusion through compacted clays is of great interest due to its potential for buffer materials for waste disposal. The importance of the electrokinetic effect on cationic tracer diffusion is investigated by using pore-scale simulations to consider the influence from the electrokinetic properties and topology of clays. It is indicated that the normalized volume charge density has a significant impact on the cationic diffusion. In clays with a large normalized volume charge density, the electrical double layer has the major impact on cationic diffusion. When the ion strength of the pore solution is constant, the flux from the electromigration term can be negligible. However, once an ion strength gradient is added, the electromigration process should be considered carefully due to its non-negligible role to balance the alteration of total flux. The present study could help improve the understanding of the transport mechanism of simple cationic tracers in compacted clays.

Моделирование плазмы короткодугового ксенонового разряда сверхвысокого давления

AbstractWe have studied a high- (ultrahigh-) pressure short-arc discharge in xenon with thoriated tungsten cathodes. A system of equations formulated based on earlier experimental data indicating possible emission of cathode material (thorium) into the discharge gap has made it possible to determine the electric field strength, plasma temperature, and concentration of thorium atoms as well as thorium and xenon ions in the plasma. The problem has been solved for a model discharge between planar electrodes. The results indicate the key role of thorium atoms in the cathode region. Thorium atoms determine the ionization balance and other electrokinetic properties of plasma. Emission of thorium atoms reduces the plasma temperature at the cathode, which turns out to be noticeably lower than the plasma temperature near the anode; this is a new result that agrees with experimental data. Other electrokinetic characteristics of the plasma (in particular, charged particle concentration and electric field strength) are also in good agreement with the experiment.

Gold substrates of controlled roughness and electrokinetic properties formed by nanoparticle deposition.

The kinetics of positively charged gold nanoparticle self-assembly on oxidized silicon substrates (wafers) under diffusion-controlled transport was studied using scanning electron microscopy (SEM) and atomic force microscopy (AFM). The latter technique allowed the roughness parameters of the monolayer (root mean square) to be determined as a function of the particle coverage. These results were adequately interpreted in terms of a theoretical model developed for surfaces covered by features of spherical shape considering the tip convolution effect. The stability and the electrokinetic characteristics (zeta potential) of the monolayers were also acquired using streaming potential measurements. It was shown that the inversion of the negative zeta potential of the bare substrate (overcharging) occurs at the particle coverage equal to 0.15, and for larger coverages positive zeta potential values were asymptotically attained. Additionally, the desorption kinetics of the particles was investigated by the streaming potential method, which confirmed the stability of the monolayers for a broad range of pHs. It was argued that these results enable to develop an efficient method for the preparation of gold sensors exhibiting a well-controlled surface roughness and electrostatic charge comprising both negative and positive values.

Translational studies of electrophoretic mobility and phase picture of erythrocytes with consideration of development of stress response during a pathological process

Rationale:Modern cell diagnostic methods are in high demand during the development of new approaches in personalized medicine. Coherent phase interferometry and cell microelectrophoresis are among such methods that are being actively introduced into the diagnostic process in medical institutions.Aim:To substantiate the potential use of biophysical and morphodensitometrical erythrocytes parameters as criteria of treatment efcacy and course of adaptation process in patients with gastrointestinal tract disorders.Materials and methods:The study included 25 patients aged from 40 to 54 years (11 males and 14 females), among them 9 (36%) with gastric peptic ulcer, 3 (12%) with duodenal ulcer, 8 (32%) with acute gastritis, and 5 (20%) with acute pancreatitis. Biophysical and morphological particulars of peripheral blood erythrocytes were assessed before and after treatment using cell diagnostic techniques, such as microelectrophoresis and laser modulation interference microscopy. Also, we evaluated changes over time in routine clinical laboratory tests, such as red and white blood cell counts, hemoglobin levels, and erythrocyte sedimentation rate (ESR), and differential leukocyte counts. The control group included 10 healthy donors aged from 36 to 52 years.In vitroexperiments were performed to assess the erythrocyte electrophoretic mobility (EEPM) and morphology of erythrocytes treated with epinephrine or cortisol.Results:After the treatment, the patients demonstrated a decrease in their leukocyte counts (by 27%), a 2-fold increase in monocyte counts and an ESR decrease (by 10%), compared to the corresponding baseline values before treatment (p < 0.05 for all comparisons). EEPM increased by 12% (1.37 vs. 1.22 mcm × cm/V × s, p < 0.05). The erythrocyte pool of the patients before treatment, had a decreased proportion of discocytes, compared to that in the control group (85.2 vs. 95.4%, р < 0.05), increased proportions of echinocytes, stomatocytes and degenerative forms (11, 2.8 and 1%, respectively, р < 0.05). After the treatment, the discocytes counts increased virtually up to their physiological normal range (91.3%). However, the surface of the discoid cells remained heterogeneous with multiple microspicules; this resulted in changes of electrokinetic and morphological properties of erythrocyte response to stress reaction occurring in the body. The impact of the stress effectors was confrmed inin vitroexperiments assessing the effects of epinephrine (1 × 10-9 g/mL) and cortisol (5 × 10-7 g/mL) on erythrocytes. At 120 minutes of the experiment, epinephrine decreased EEPM (1.14 vs. 1.24 mcm × cm/V × s at baseline, р < 0.05) and increased cell sphericity. On the contrary, cortisol increased EEPM (1.72 vs. 1.36 mcm × cm/V × s, р < 0.05), with non-signifcant echinocytic transformation.Conclusion:Biophysical and morphodensitometric parameters of red blood cells obtained with the use of current express methods of cell microelectrophoresis and coherent interference microscopy help to objectivize the intensity of stress response during a pathological process and activation of adaptation mechanisms during the treatment.

Relationship between electrokinetic parameters of red blood cells and acute coronary syndrome

Aim. To assess the state of electrokinetic properties of red blood cells in different variants of the course of acute coronary syndrome (ACS).
 Materials and methods. The study deals with the assessment of clinical and laboratory-instrumental data from 201 patients with ACS, the results of electrokinetic parameters of red blood cells, their predictors.
 Results. According to electrokinetic indices of erythrocytes, no reliable differences between the groups were found out. The mean red blood cell oscillation amplitude (MRBCOA) in group 1 was 1.83 ± 0.05, in group 2 – 1.75 ± 0.06 (t = 0.955, p = 0.341). Stationary red blood cell percentage (SRBCP) in patients with NSTE-ACS was 15.6 ± 1.45, in patients with STE-ACS – 13.54 ± 1.64 (t = 0.957, p = 0.339). The methods of multiple disperse and regressive analysis were used. Predictors of SRBCP indices in NSTE-ACS group appeared to be intima-media complex thickness (IMCT), left ventricle diastolic dysfunction, coronary insufficiency index (CII); in STE-ACS group – IMCT, MRBCOA, troponin I and AST levels. In STE-ACS group, predictors of MRBCOA were SRBCP and troponin I level, in NSTE-ACS – no predictors, influencing MRBCOAwere revealed.
 Conclusions. In NSTE-ACS group, the following predictors, influencing SRBCP were detected:IMCT, CII, LV diastolic dysfunction. In patients of STE-ACS group, there were found the predictors, influencing electrokinetic properties of red blood cells: IMCT, AST, troponin I. In acute coronary syndrome, changes in electrokinetic parameters of red blood cells are mainly influenced by atherosclerotic process, however, in NSTE-ACS, structural-functional status of myocardium is of primary significance, and in STE-ACS – the degree of manifestation of resorptive-necrotic syndrome.

Colloidal interaction between vinylacetate ethylene latex stabilized by polyvinyl alcohol and portland cement

Interaction between three Vinylacetate Ethylene (VAE) latices with varied surface properties (charge or PVOH stabilized) and cement were studied, through the combined techniques of adsorption and zeta potential measurement. The results showed that all the VAE latices possessed a negative charge in neutral pH, but a lower charge density at a high pH. The non-adsorbed amount was excluded, based on extrapolation from the linear regression of the total depletion amount. Thereof, the calculated results indicated an analogous Langmuir type adsorption for all the latices. The zeta potential results showed a negligible effect of the non-ionic latices on the electro kinetic properties of the cement. This revealed the significance of PVOH on the adsorption of non-ionic latices.

Numerical Solution of the Electrokinetic Equations for Multi-ionic Electrolytes Including Different Ionic Size Related Effects.

One of the main assumptions of the standard electrokinetic model is that ions behave as point-like entities. In a previous work (López-García, et al., 2015) we removed this assumption and analyzed the influence of finite ionic size on the dielectric and electrokinetic properties of colloidal suspensions using both the Bikerman and the Carnahan–Starling equations for the steric interactions. It was shown that these interactions improved upon the standard model predictions so that the surface potential, electrophoretic mobility, and the conductivity and permittivity increment values were increased. In the present study, we extend our preceding works to systems made of three or more ionic species with different ionic sizes. Under these conditions, the Bikerman and Carnahan–Starling expressions cease to be valid since they were deduced for single-size spheres. Fortunately, the Carnahan–Starling expression has been extended to mixtures of spheres of unequal size, namely the “Boublik–Mansoori–Carnahan–Starling–Leland” (BMCSL) equation of state, making it possible to analyze the most general case. It is shown that the BMCSL expression leads to results that differ qualitatively and quantitatively from the standard electrokinetic model.

Electrokinetic properties of cysteine-stabilized silver nanoparticles dispersed in suspensions and deposited on solid surfaces in the form of monolayers

Cysteine-stabilized silver nanoparticles (AgNPs) of an average size of 20 ± 5 nm were synthesized in a chemical reduction method. Dynamic light scattering (DLS) measurements showed that the nanoparticles were stable for ionic strength range 10−4 M - 3 × 10−2 M and at 8.1 < pH < 4.5. The electrophoretic mobility measurements allowed to determine the isoelectric point of the nanoparticles which occurred at pH 5.1. Below this value, the nanoparticles were positively charged with the zeta potential equal to +44 mV at pH 4.0 and ionic strength 10−2 M. Under the same ionic strength and at pH 9.0, the AgNPs were negatively charged and their zeta potential was equal to −52 mV. The deposition of the AgNPs on bare and poly(diallyldimethylammonium chloride) (PDADMAC)-modified mica was investigated in situ using streaming potential measurements (SP). The structure and coverage of formed monolayers were also determined applying scanning electron microscopy (SEM). The impact of ionic strength and pH on the electrokinetic properties of the monolayers was studied in detail. It was found that at pH 4.0 and ionic strength of 10−2 M the diffusion-controlled deposition of the nanoparticles on bare mica allowed to obtain monolayers of the coverage equal to 0.29. When the deposition process was conducted on PDADMAC-modified mica at pH 9.0 and ionic strength 10−2 M, the coverage of monolayers attained value of 0.24. The zeta potential of monolayers of the highest coverage decreased with pH. It was found that below pH 4.8 the zeta potential of monolayers was positive whereas above this value it was negative. The streaming potential measurements showed that in spite of the inversion of sign of the zeta potential, the monolayers were characterized by a high stability. pH-dependent release of the nanoparticles was negligible. These experimental results were interpreted in terms of the three-dimensional (3D) electrokinetic model and random sequential adsorption model (RSA), which in turn allowed to determine equilibrium adsorption constant and binding energies (energy minima depth) of the AgNPs in the monolayers.

Expansion and shrinkage of the electrical double layer in charge-asymmetric electrolytes: A non-linear Poisson-Boltzmann description

The spatial extension or thickness of the electrical double layer determines many thermodynamic and electrokinetic properties of charged colloids in solution. In the classical Debye-Hückel formalism of point ions, the thickness of the electrical double layer around a spherical macroion or next to an infinite planar electrode can be characterized by the bulk Debye length of the supporting ionic fluid. As a result, that approach neglects, at least, the influence of the colloidal charge on the spatial extension of the ionic cloud. Given that the Debye-Hückel formalism of point ions is valid only in the limit of very weak colloidal charges, in this work we use the non-linear Poisson-Boltzmann equation to study the thickness of the electrical double layer near a positively charged electrode in spherical and planar geometries, in the presence of several binary charge-asymmetric −1:z+ point-ions electrolytes with monovalent counterions and multivalent coions. The properties of counterions are maintained fixed, whereas the properties of coions (such as their valence and concentration) are varied fulfilling the bulk electroneutrality condition. The thickness of the ionic cloud is quantified here via the recently introduced capacitive compactness idea (Phys. Chem. Chem. Phys. 20 (2018) 262). Physically, this length represents essentially the separation distance between two electrodes associated to the corresponding effective electrical double layer capacitor, in both planar and spherical geometries. Our numerical calculations show that the capacitive compactness obtained via the non-linear Poisson-Boltzmann equation reduces to the Debye length of the supporting bulk electrolyte at the point of zero charge. In the presence of a charge symmetric −1:+1 electrolyte, the capacitive compactness always decreases as a function of the colloidal charge. Contrastingly, the electrical double layer may expand or shrink as a function of the surface charge density, in the presence of multivalent coions, which is confirmed here by primitive model Monte Carlo simulations. This last non-monotonic behaviour of the capacitive compactness for multivalent coions, depending on the colloidal charge, is related to the microscopic behaviour of the local electric field, the mean electrostatic potential, and the net ionic charge per unit volume close to the colloidal surface. At very large colloidal charges, the capacitive compactness of all −1:z+ electrolytes collapses onto a single curve illustrating the dominance of counterions in the non-linear Poisson-Boltzmann theory.

Comparison of adsorption affinity of anionic and cationic polyacrylamides for montmorillonite surface in the presence of chromium(VI) ions

Erosion, which is considered to be global problem, is the process of soil environment degradation due to the impact of wind (soil blowing, deflation) and water (soil washing, deep erosion). This leads to destruction of its structure, nutrients removal and finally bedrock exposition and desertification. One of the ways to prevent this phenomenon is the soil conditioners usage. These substances, also called soil flocculants, are macromolecular compounds which contribute to the reinforcement of soil structure as a result of its adsorption on the mineral surface. The soil conditioners commonly used in agriculture is ionic polyacrylamide (PAM)—both anionic and cationic. These macromolecular substances affect soil surface properties and adsorption behaviour of substances present in the environment—nutrients, organic molecules and also hazardous compounds as well as toxic heavy metals (i.e. chromium(VI) ions). The aim of this study was to investigate the impact of solution pH, type of ionic groups in the polyacrylamide macromolecules and chromium(VI) ion concentration on the adsorption mechanism of Cr(VI) and PAM on the montmorillonite surface. The adsorption and electrokinetic properties of the montmorillonite—AN PAM or CT PAM/Cr(VI) systems were examined by means of spectrophotometry, potentiometric titration, SEM, XRD and DRS methods. It was shown that in the adsorbed layer composed of PAM-Cr(VI) complexes reduction of Cr(VI) to Cr(III) takes place.

The Effect of a Cationic Polyelectrolyte on the Electrokinetic Properties of a Nanofiltration Membrane and Retention of Ions by It

Electrokinetic properties of an asymmetric nanofiltration membrane modified with a cationic polyelectrolyte (styrene–dimethylaminopropylmaleimide copolymer) and the selectivity of the membrane with respect to solutions of differently charged electrolytes have been studied. The modification has been carried out by filtering the polyelectrolyte from the side of the selective layer and the opposite side of the membrane. It has been found that the membrane selectivity to sodium sulfate and magnesium chloride solutions increases with polyelectrolyte concentration in the solution used for membrane modification from the side of the selective layer. A decreased selectivity to sodium sulfate and an unchanged selectivity to magnesium chloride have been observed for the membrane modified from the substrate side.

Preparation and co-dispersion of TiO2-Y2O3 suspensions through the study of their rheological and electrokinetic properties

The development of Generation IV sodium-cooled fast reactors (SFR) is currently studied by several countries, France in particular. To manufacture the UO2-PuO2 fuels for these new types of reactors, new innovative wet colloidal processing routes are investigated. Among these wet colloidal processes, some involve at first the preparation of high solid content water-based suspensions. This key step needs to be investigated in order to obtain highly and easily processable suspensions, featuring optimal viscosity and dispersion state. The structures and properties for all intermediate and final products involved in such ceramic manufacturing processes are heavily affected by these suspension characteristics. Therefore, they are critical to ensure a compliant final product (i.e. fuel pellets) with the required density, homogeneity, mechanical strength and absence of defects. In this scope, preparation process of such suspensions was developed by the use of UO2 and PuO2 surrogating (i.e. mimicking) powders, TiO2 and Y2O3 respectively.

Formation of gold nanoparticle bilayers on gold sensors

Formation of bilayers composed from oppositely charged gold nanoparticles and characterized by comparable size distribution was investigated using gravimetric and microscopic techniques. Positively (AuNPsCH(+)) and negatively charged (AuNPsTC(−)) gold nanoparticles were synthesized according to chemical reduction procedure. The transmission electron microscopy (TEM) revealed that the nanoparticle size was equal to 9.0 ± 3 nm and 14 ± 2 nm in the case of AuNPsCH(+) and AuNPsTC(−), respectively. The electrophoretic mobility measurements allowed to determine the electrokinetic properties of the nanoparticles and their stability under various conditions of pH and ionic strengths. Both the deposition kinetics of AuNPsCH(+) on gold sensors and the formation kinetics of second AuNPsTC(−) layer were determined using quartz microbalance (QCM) measurements. Additionally, the maximum coverage and bilayer structure were evaluated using atomic force microscopy (AFM) and scanning electron microscopy (SEM). In these measurements a negligible hydratation of AuNPsCH(+)/AuNPsTC(−) bilayers was confirmed. The significant increase in the maximum coverage of both supporting and external layers with ionic strength was interpreted as a results of decreasing range of repulsive electrostatic interactions among deposited nanoparticles. The experimental results were quantitatively interpreted in terms of the extended random sequential adsorption (eRSA) model.