The effects of electrolyte concentration, ion species and pH on the zeta potential and electrokinetic charge density of montmorillonite

Clay Minerals ◽  
2006 ◽  
Vol 41 (4) ◽  
pp. 853-861 ◽  
Author(s):  
E. E. Saka ◽  
C. Güler
Keyword(s):  
Zeta Potential ◽  
Charge Density ◽  
Negative Charge ◽  
Electrolyte Concentration ◽  
Great Influence ◽  
Electrolyte Solutions ◽  
Ionic Species ◽  
Positive Sign ◽  
Ion Species ◽  
Influence Of Ph

AbstractIn this study, the influence of pH, electrolyte concentration and type of ionic species (such as LiCl, NaCl, KCl, RbCl, CsCl, CaCl2, AlCl3) on the electrokinetic properties (zeta potential and electrokinetic charge density) of montmorillonite has been quantified. The zeta potential of montmorillonite particles did not change significantly with change in pH. The valencies of the ions have proven to have a great influence on the electrokinetic behaviour of the suspension. There is a gradual decrease in the zeta potential (from —24 mV to —12 mV) with increase in monovalent electrolyte concentration (from 10-4 M to 10-1 M). At any monovalent electrolyte concentration, the magnitude of the zeta potential increased with the electrolytes in the order Li+ > Na+ > K+ > Rb+ > Cs+. The zeta potential of the montmorillonite minerals in CaCl2 solutions illustrated the same behaviour as the monovalent cations. Less negative values were obtained for the CaCl2 electrolyte (∼–10 mV) due to the greater valence of the ions. A sign reversal was observed at an AlCl3 concentration of 5 x 10-4 M, and, at greater concentrations, zeta potential values had a positive sign (∼20 mV).The electrokinetic charge density of montmorillonite showed similar trends of variation in mono and divalent electrolyte solutions. Up to concentrations of ∼10-3 M, it remained practically constant at ∼0.5 x 10-3Cm-2, while for greater electrolyte concentrations the negative charge produced more negative values (–16 x 10-3Cm-2). The electrokinetic charge density of montmorillonite particles was constant at low AlCl3 concentrations, but at certain concentrations it increased rapidly and changed sign to positive.

scholarly journals Electroosmotic Flow Hysteresis for Fluids with Dissimilar pH and Ionic Species

Micromachines ◽  
2021 ◽  
Vol 12 (9) ◽  
pp. 1031
Author(s):  
An Eng Lim ◽  
Yee Cheong Lam
Keyword(s):  
Zeta Potential ◽  
Electroosmotic Flow ◽  
Flow Direction ◽  
Velocity Model ◽  
Ionic Species ◽  
Dependent Behavior ◽  
Nacl Concentration ◽  
Solution Pair ◽  
Current Monitoring ◽  
Ion Species

Electroosmotic flow (EOF) involving displacement of multiple fluids is employed in micro-/nanofluidic applications. There are existing investigations on EOF hysteresis, i.e., flow direction-dependent behavior. However, none so far have studied the solution pair system of dissimilar ionic species with substantial pH difference. They exhibit complicated hysteretic phenomena. In this study, we investigate the EOF of sodium bicarbonate (NaHCO3, alkaline) and sodium chloride (NaCl, slightly acidic) solution pair via current monitoring technique. A developed slip velocity model with a modified wall condition is implemented with finite element simulations. Quantitative agreements between experimental and simulation results are obtained. Concentration evolutions of NaHCO3–NaCl follow the dissimilar anion species system. When NaCl displaces NaHCO3, EOF reduces due to the displacement of NaHCO3 with high pH (high absolute zeta potential). Consequently, NaCl is not fully displaced into the microchannel. When NaHCO3 displaces NaCl, NaHCO3 cannot displace into the microchannel as NaCl with low pH (low absolute zeta potential) produces slow EOF. These behaviors are independent of the applied electric field. However, complete displacement tends to be achieved by lowering the NaCl concentration, i.e., increasing its zeta potential. In contrast, the NaHCO3 concentration has little impact on the displacement process. These findings enhance the understanding of EOF involving solutions with dissimilar pH and ion species.

scholarly journals On the cataphoresis of gliadin Part II—The effect of strong electrolytes upon the mobility

1934 ◽  
Vol 147 (860) ◽  
pp. 11-24
Keyword(s):  
Ionic Strength ◽  
Colloidal Particle ◽  
Electrolyte Concentration ◽  
Electrolyte Solutions ◽  
Ionic Species ◽  
Colloid Particle ◽  
Wide Range ◽  
Strong Electrolytes ◽  
Set Up ◽  
Good Agreement

Careful analyses of the cataphoretic velocity of a colloid particle suspended in an electrolyte solution have been made by Smoluchowski, by Debye and Hückel, and by Henry. No actual test of their theoretical conclusions over a sufficiently wide range of ionic strength appears yet to have been made, with the exception of some experimental work recorded by Audubert, whose results indicate good agreement for particles of radius 60 - 130 A, but not for particles of radius 2-8 μ. Unfortunately, no details are given of the measurement of the sizes of such small particles. In adopting the hypothesis of Pauli that a colloidal particle behaves like a large polyvalent ion, it is assumed that on altering the electrolyte concentration there is no change in valency of the ion when the theory of Debye-Hückel and of Henry is applied. In practice those colloids whose charge is derived mainly from adsorption of ions do not exhibit constant valency on variation of the ionic strength of the electrolyte. According to Abramson, quartz particles covered with protein behave as ions of constant valency in solutions of the same ionic strength and hydrion activity. This assumption can be valid only over a restricted range of concentrations. Thus, at high ionic strengths, the valency may be altered appreciably by the adsorption of electrolyte ions, whilst it may reasonably be anticipated that at small ionic strengths the effect of the restriction of ions inside the double layer will lead to an alteration in the effective valency of the particle. In general a Donnan equilibrium is set up wherever one ionic species is constrained in any manner from free diffusion; modification of the effective valency of the colloid ion may be expected in very dilute electrolyte solutions on this account.

Surface charging parameters of charged particles in symmetrical electrolyte solutions

2020 ◽  
Vol 22 (35) ◽  
pp. 20123-20142
Author(s):  
Hadi Saboorian-Jooybari ◽  
Zhangxin Chen
Keyword(s):  
Charge Density ◽  
Surface Charge ◽  
Electrolyte Solution ◽  
Surface Charge Density ◽  
Potential Surface ◽  
Research Work ◽  
Charged Particles ◽  
Electrolyte Solutions ◽  
Surface Charging ◽  
Curvature Dependence

This research work is directed at development of accurate physics-based formulas for quantification of curvature-dependence of surface potential, surface charge density, and total surface charge for cylindrical and spherical charged particles immersed in a symmetrical electrolyte solution.

The effect of the negative charge density on switchable properties of pseudoisocyanine dye

2017 ◽  
Vol 144 ◽  
pp. 54-59 ◽  
Author(s):  
Marián Matejdes ◽  
Daisuke Himeno ◽  
Yasutaka Suzuki ◽  
Jun Kawamata
Keyword(s):  
Charge Density ◽  
Negative Charge ◽  
Negative Charge Density

The ζ-Potential of Kaolinite Particles

1956 ◽  
Vol 9 (4) ◽  
pp. 450 ◽  
Author(s):  
N Street ◽  
AS Buchanan
Keyword(s):  
Charge Density ◽  
Surface Charge ◽  
Electrophoretic Mobility ◽  
Surface Charge Density ◽  
Considerable Increase ◽  
Ionic Species ◽  
Ζ Potential ◽  
Potentiometric Titrations ◽  
Kaolinite Suspension

Electrophoretic mobility measurements, and both conductometric and potentiometric titrations, were carried out on a kaolinite suspension throughout its neutralization by various bases. The concentration of the ionic species present was calculated from the conductometric and potentiometric titrations, and the true ζ-potential calculated from the electrophoretic mobility by Stigter and Mysels's (1955) method. The results indicate that a discontinuity exists in the adsorption of ions in the vicinity of pH 6.5-7.0 causing a considerable increase in the surface charge density of the particles.

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