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Marek Kosmulski - One of the best experts on this subject based on the ideXlab platform.
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simple model of surface induced electrolytic dissociation of weak acids in organic solvents
Adsorption-journal of The International Adsorption Society, 2010Co-Authors: Marek KosmulskiAbstract:The electric conductivity of solutions of oxalic and phosphoric acid (up to 0.025 M) in ethanol and methanol has been studied in the presence of TiO2 (1–10% by mass). TiO2 enhanced the conductivity of solutions of oxalic and phosphoric acid in the both alcohols. The experimentally observed behavior was successfully modeled using a model with two types of surface sites. Sites of the first type bind the acids in molecular form. Sites of the second type bind the acids in form of hydrogen oxalate and dihydrogen phosphate anions, respectively, and protons are released to the solution, and contribute to enhanced conductivity. The adsorption model properly reflects the Electrokinetic Potential of titania particles in alcoholic solutions of oxalic and phosphoric acid.
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surface induced electrolytic dissociation of oxalic acid in polar organic solvents
Langmuir, 2010Co-Authors: Marek Kosmulski, Piotr Prochniak, Jarl B. RosenholmAbstract:The presence of titania powder (chiefly anatase) enhanced electrolytic dissociation of oxalic acid in lower aliphatic alcohols (but not in water). The surface-induced dissociation was manifested in enhanced electric conductance of a dispersion containing solvent, oxalic acid, and titania, which was substantially higher than the conductance of dispersion containing only solvent and titania and of solution of oxalic acid in that solvent. This phenomenon can be applied to control the Electrokinetic Potential of particles in polar organic solvents.
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high ionic strength Electrokinetics of clay minerals
Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2006Co-Authors: Marek Kosmulski, Per DahlstenAbstract:Abstract The Electrokinetic Potential of kaolin and montmorillonite at high ionic strengths (up to 2M of 1-1 electrolyte) was measured as a function of pHby means of three instruments. The present results indicate that the Electrokinetic Potential does not cease at high ionic strengths. Potassium andcesium salts induced a shift in the IEP of kaolin to high pH. Similar shifts were observed for montmorillonite, but only in the presence of cesium.The increase in 1-1 electrolyte concentration resulted in depression of the absolute value of the ζ Potential of kaolin and montmorillonite at neutraland basic pH. However, ζ Potentials at high ionic strengths were surprisingly high in the absolute value. Namely, the negative ζ Potentials up to−20mV were measured in 1M solutions of Li and Na salts.© 2006 Elsevier B.V. All rights reserved. Keywords: Clay minerals; Zeta Potential; Isoelectric point; Ionic strength 1. Introduction When the ionic strength is not too high, addition of 1-1 elec-trolyte (alkali nitrate V, chlorate VII or halide) at otherwise thesame experimental conditions induces a decrease in the abso-lute value of the Electrokinetic Potential [1]. Then addition ofeven more electrolyte would depress the Electrokinetic Potentialto zero. Till very recently direct measurements of the electroki-netic Potential at high ionic strength were not possible, and itwas believed that the Electrokinetic Potential at electrolyte con-centrations of about 1M is about zero. Indeed, popular modelsof the electric double layer (triple layer model, Stern) produce
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electroacoustics and electroosmosis in low temperature ionic liquids
Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2005Co-Authors: Marek Kosmulski, Jarl B. Rosenholm, Czeslaw Saneluta, Krystyna MarczewskaboczkowskaAbstract:Abstract The electroacoustic method made it possible to study Electrokinetic phenomena at high ionic strengths. Interestingly, the ζ Potential does not cease at ionic strengths as high as 3 M in aqueous systems. Here, we show that also in low temperature ionic liquids the Electrokinetic phenomena do exist. Dispersions of anatase in 1-alkyl-3-methylimidazolium (alkyl = butyl, hexyl, octyl or decyl) trifluoromethanesulfonates, hexafluorophosphates, and mixed tetrafluoroborate-chloride ionic liquids were studied. These ionic liquids are molten salts at room temperature, and they can be considered as about 3 M salt solutions in the absence of solvent. The Electrokinetic Potential of anatase determined by means of the electroacoustic method was negative for all ionic liquids studied, although for a few ionic liquids the standard deviation in a series of 20 consecutive measurements was higher than the absolute value. Absorption of moisture by the ionic liquids has rather insignificant effect on the Electrokinetic Potential of anatase. Electroosmosis in specimens of porous alumina saturated with ionic liquids was studied, and the Electrokinetic charge of alumina was also negative.
Ute Pyell - One of the best experts on this subject based on the ideXlab platform.
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quantification of zeta Potential and Electrokinetic surface charge density for colloidal silica nanoparticles dependent on type and concentration of the counterion probing the outer helmholtz plane
Journal of Physical Chemistry C, 2018Co-Authors: Alaa H Jalil, Ute PyellAbstract:Electrokinetic data were measured for dilute aqueous dispersions of amorphous silica nanoparticles of various size via capillary electrophoresis with borate buffers containing either Li+, Na+, K+, or guanidinium as a counterion. Taking the mobility-dependent relaxation effect into account (modified analytic approximation developed by Ohshima), reliable values are obtained for the Electrokinetic Potential and the Electrokinetic charge density dependent on the type of cation and the concentration of buffer. The reliability was confirmed by comparison of the results obtained for the nanoparticles with those values obtained for the planar-limiting case (fused-silica capillary inner wall/electrolyte interface). Regarding the inner part of the electrical double layer as a (mono)layer of unspecifically adsorbed counterions, we calculate (together with data gained by Brown et al. on the same type of nanoparticles via in situ photoelectron spectroscopy and potentiometric titration) the charge density at the outer ...
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quantification of zeta Potential and Electrokinetic surface charge density for colloidal silica nanoparticles dependent on type and concentration of the counterion probing the outer helmholtz plane c
The Journal of Physical Chemistry, 2018Co-Authors: Alaa H Jalil, Ute PyellAbstract:Electrokinetic data were measured for dilute aqueous dispersions of amorphous silica nanoparticles of various size via capillary electrophoresis with borate buffers containing either Li⁺, Na⁺, K⁺, or guanidinium as a counterion. Taking the mobility-dependent relaxation effect into account (modified analytic approximation developed by Ohshima), reliable values are obtained for the Electrokinetic Potential and the Electrokinetic charge density dependent on the type of cation and the concentration of buffer. The reliability was confirmed by comparison of the results obtained for the nanoparticles with those values obtained for the planar-limiting case (fused-silica capillary inner wall/electrolyte interface). Regarding the inner part of the electrical double layer as a (mono)layer of unspecifically adsorbed counterions, we calculate (together with data gained by Brown et al. on the same type of nanoparticles via in situ photoelectron spectroscopy and potentiometric titration) the charge density at the outer Helmholtz plane and the fraction of charge included in the Stern layer for electrolytes containing the alkali ions Li⁺, Na⁺, or K⁺. This approach explains differences in the Electrokinetic charge density as a result of differences in the properties of the Stern layer due to differences in the size of the hydrated cation and the hydration state of the silica surface.
Christophe Labbez - One of the best experts on this subject based on the ideXlab platform.
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C-S-H/solution interface: Experimental and Monte Carlo studies
Cement and Concrete Research, 2010Co-Authors: Christophe Labbez, Isabelle Pochard, Bo Jönsson, André NonatAbstract:The surface charge density of C-S-H particles appears to be one of the key parameters for predicting the cohesion strength, understanding the ion retention, the pollutant leakage, and admixture adsorption in hydrated cement pastes. This paper presents a Monte Carlo simulation of the surface-ions interactions that permits the prediction of surface charge density (σ), Electrokinetic Potential (ζ) and ions adsorption of mineral surfaces in equilibrium with a given electrolyte solution. Simulated results are compared to experimental data obtained by titration, Electrokinetic Potential measurements and ions uptake in the case of C-S-H suspensions. An excellent agreement is found between simulated and experimental results. The wide spread idea that calcium is a Potential determining ion in cement paste systems appears to be incorrect. Instead, the pH controls the charging behaviour of C-S-H nano-particles. This paper also shows to what extent the electrostatic interactions contribute to the measured Ca/Si ratio.
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experimental and theoretical evidence of overcharging of calcium silicate hydrate
Journal of Colloid and Interface Science, 2007Co-Authors: Christophe Labbez, Isabelle Pochard, André Nonat, Bo JönssonAbstract:Electrokinetic measurements such as electrophoresis may show an inversion of the effective surface charge of colloidal particle called overcharging. This phenomenon has been studied by various theoretical approaches but up to now very few attempts of confrontation between theory and experiment have been conducted. In this work we report electrophoretic measurements as well as Monte Carlo simulations of the Electrokinetic Potential for the surface of calcium silicate hydrate (CSH), which is the major constituent of hydrated cement. In the simulations, the surface charge of CSH nanoparticles in equilibrium with the ionic solution is determined by a single site characteristic and electrostatic interactions between all explicit charges at the surface and in the electric double layer. We will show that ordinary electrostatic interactions are enough to describe all experimental observations. Actually, an excellent agreement is found between experimental and simulated results without any fitting parameter, both with respect to surface titration and Electrokinetic behaviour. The agreement extends over a wide range of electrostatic coupling, from a weakly charged surface with mainly monovalent counter-ions to a highly charged one with divalent counter-ions.
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surface charge density and Electrokinetic Potential of highly charged minerals experiments and monte carlo simulations on calcium silicate hydrate
Journal of Physical Chemistry B, 2006Co-Authors: Christophe Labbez, Isabelle Pochard, Bo Jönsson, André Nonat, Bernard CabaneAbstract:In this paper, we are concerned with the charging and Electrokinetic behavior of colloidal particles exhibiting a high surface charge in the alkaline pH range. For such particles, a theoretical approach has been developed in the framework of the primitive model. The charging and Electrokinetic behavior of the particles are determined by the use of a Monte Carlo simulation in a grand canonical ensemble and compared with those obtained through the mean field theory. One of the most common colloidal particles has been chosen to test our theoretical approach. That is calcium silicate hydrate (C-S-H) which is the main component of hydrated cement and is known for being responsible for cement cohesion partly due to its unusually high surface charge density. Various experimental techniques have been used to determine its surface charge and Electrokinetic Potential. The experimental and simulated results are in excellent agreement over a wide range of electrostatic coupling, from a weakly charged surface in contact with a reservoir containing monovalent ions to a highly charged one in contact with a reservoir with divalent ions. The electrophoretic measurements show a charge reversal of the C-S-H particles at high pH and/or high calcium concentration in excellent agreement with simulation predictions. Finally, both simulation and experimental results clearly demonstrate that the mean field theory fails not only quantitatively but also qualitatively to describe a C-S-H dispersion under realistic conditions.
André Nonat - One of the best experts on this subject based on the ideXlab platform.
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C-S-H/solution interface: Experimental and Monte Carlo studies
Cement and Concrete Research, 2010Co-Authors: Christophe Labbez, Isabelle Pochard, Bo Jönsson, André NonatAbstract:The surface charge density of C-S-H particles appears to be one of the key parameters for predicting the cohesion strength, understanding the ion retention, the pollutant leakage, and admixture adsorption in hydrated cement pastes. This paper presents a Monte Carlo simulation of the surface-ions interactions that permits the prediction of surface charge density (σ), Electrokinetic Potential (ζ) and ions adsorption of mineral surfaces in equilibrium with a given electrolyte solution. Simulated results are compared to experimental data obtained by titration, Electrokinetic Potential measurements and ions uptake in the case of C-S-H suspensions. An excellent agreement is found between simulated and experimental results. The wide spread idea that calcium is a Potential determining ion in cement paste systems appears to be incorrect. Instead, the pH controls the charging behaviour of C-S-H nano-particles. This paper also shows to what extent the electrostatic interactions contribute to the measured Ca/Si ratio.
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experimental and theoretical evidence of overcharging of calcium silicate hydrate
Journal of Colloid and Interface Science, 2007Co-Authors: Christophe Labbez, Isabelle Pochard, André Nonat, Bo JönssonAbstract:Electrokinetic measurements such as electrophoresis may show an inversion of the effective surface charge of colloidal particle called overcharging. This phenomenon has been studied by various theoretical approaches but up to now very few attempts of confrontation between theory and experiment have been conducted. In this work we report electrophoretic measurements as well as Monte Carlo simulations of the Electrokinetic Potential for the surface of calcium silicate hydrate (CSH), which is the major constituent of hydrated cement. In the simulations, the surface charge of CSH nanoparticles in equilibrium with the ionic solution is determined by a single site characteristic and electrostatic interactions between all explicit charges at the surface and in the electric double layer. We will show that ordinary electrostatic interactions are enough to describe all experimental observations. Actually, an excellent agreement is found between experimental and simulated results without any fitting parameter, both with respect to surface titration and Electrokinetic behaviour. The agreement extends over a wide range of electrostatic coupling, from a weakly charged surface with mainly monovalent counter-ions to a highly charged one with divalent counter-ions.
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surface charge density and Electrokinetic Potential of highly charged minerals experiments and monte carlo simulations on calcium silicate hydrate
Journal of Physical Chemistry B, 2006Co-Authors: Christophe Labbez, Isabelle Pochard, Bo Jönsson, André Nonat, Bernard CabaneAbstract:In this paper, we are concerned with the charging and Electrokinetic behavior of colloidal particles exhibiting a high surface charge in the alkaline pH range. For such particles, a theoretical approach has been developed in the framework of the primitive model. The charging and Electrokinetic behavior of the particles are determined by the use of a Monte Carlo simulation in a grand canonical ensemble and compared with those obtained through the mean field theory. One of the most common colloidal particles has been chosen to test our theoretical approach. That is calcium silicate hydrate (C-S-H) which is the main component of hydrated cement and is known for being responsible for cement cohesion partly due to its unusually high surface charge density. Various experimental techniques have been used to determine its surface charge and Electrokinetic Potential. The experimental and simulated results are in excellent agreement over a wide range of electrostatic coupling, from a weakly charged surface in contact with a reservoir containing monovalent ions to a highly charged one in contact with a reservoir with divalent ions. The electrophoretic measurements show a charge reversal of the C-S-H particles at high pH and/or high calcium concentration in excellent agreement with simulation predictions. Finally, both simulation and experimental results clearly demonstrate that the mean field theory fails not only quantitatively but also qualitatively to describe a C-S-H dispersion under realistic conditions.
Alaa H Jalil - One of the best experts on this subject based on the ideXlab platform.
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quantification of zeta Potential and Electrokinetic surface charge density for colloidal silica nanoparticles dependent on type and concentration of the counterion probing the outer helmholtz plane
Journal of Physical Chemistry C, 2018Co-Authors: Alaa H Jalil, Ute PyellAbstract:Electrokinetic data were measured for dilute aqueous dispersions of amorphous silica nanoparticles of various size via capillary electrophoresis with borate buffers containing either Li+, Na+, K+, or guanidinium as a counterion. Taking the mobility-dependent relaxation effect into account (modified analytic approximation developed by Ohshima), reliable values are obtained for the Electrokinetic Potential and the Electrokinetic charge density dependent on the type of cation and the concentration of buffer. The reliability was confirmed by comparison of the results obtained for the nanoparticles with those values obtained for the planar-limiting case (fused-silica capillary inner wall/electrolyte interface). Regarding the inner part of the electrical double layer as a (mono)layer of unspecifically adsorbed counterions, we calculate (together with data gained by Brown et al. on the same type of nanoparticles via in situ photoelectron spectroscopy and potentiometric titration) the charge density at the outer ...
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quantification of zeta Potential and Electrokinetic surface charge density for colloidal silica nanoparticles dependent on type and concentration of the counterion probing the outer helmholtz plane c
The Journal of Physical Chemistry, 2018Co-Authors: Alaa H Jalil, Ute PyellAbstract:Electrokinetic data were measured for dilute aqueous dispersions of amorphous silica nanoparticles of various size via capillary electrophoresis with borate buffers containing either Li⁺, Na⁺, K⁺, or guanidinium as a counterion. Taking the mobility-dependent relaxation effect into account (modified analytic approximation developed by Ohshima), reliable values are obtained for the Electrokinetic Potential and the Electrokinetic charge density dependent on the type of cation and the concentration of buffer. The reliability was confirmed by comparison of the results obtained for the nanoparticles with those values obtained for the planar-limiting case (fused-silica capillary inner wall/electrolyte interface). Regarding the inner part of the electrical double layer as a (mono)layer of unspecifically adsorbed counterions, we calculate (together with data gained by Brown et al. on the same type of nanoparticles via in situ photoelectron spectroscopy and potentiometric titration) the charge density at the outer Helmholtz plane and the fraction of charge included in the Stern layer for electrolytes containing the alkali ions Li⁺, Na⁺, or K⁺. This approach explains differences in the Electrokinetic charge density as a result of differences in the properties of the Stern layer due to differences in the size of the hydrated cation and the hydration state of the silica surface.