Sorption and precipitation of iron on koalinitie. V. Comparison between kaolinite and ion exchange materials

Soil Research ◽  
1973 ◽  
Vol 11 (2) ◽  
pp. 197 ◽  
Author(s):  
AW Fordham
Keyword(s):  
Ionic Strength ◽  
Ion Exchange ◽  
Electrolyte Concentration ◽  
Supporting Electrolyte ◽  
Electrolyte Solutions ◽  
Low Concentrations ◽  
Polystyrene Resin ◽  
Sorption Mechanisms ◽  
Preceding Study ◽  
Competing Ions

The uptake of low concentrations of iron(III) by ion exchange materials was measured in the presence of relatively concentrated supporting electrolyte solutions. The results were compared with those obtained under the same conditions in the preceding study of kaolinite suspensions. Distinctive differences between kaolinite and strongly acidic polystyrene resin systems at 0.15M ionic strength were found in (a) the nature of the sorption-pH relationships, (b) the reversibility of the reaction with respect to both concentration and temperature, (c) the effects of competing ions, and (d) the extraction of iron after sorption. Such observations confirmed that the iron-kaolinite bond formed under these conditions was stronger than that normally produced by electrostatic attraction at ion exchange sites. When the electrolyte concentration was lowered to 0.01M , some of the above characteristics of ion exchange uptake appeared in kaolinite systems. A comparison of the effects of time, temperature, and ionic strength between iron sorption by kaolinite and by cellulosic ion exchange materials suggested that both ion exchange and specific sorption mechanisms were operating at the lower ionic strength.

scholarly journals Effect of ionic strength on the ion exchange equilibrium between AMX membrane and electrolyte solutions

2015 ◽  
Vol 51 (1) ◽  
pp. 60-68 ◽  
Author(s):  
Islem Louati ◽  
Fatma Guesmi ◽  
Akram Chaabouni ◽  
Chiraz Hannachi ◽  
Béchir Hamrouni
Keyword(s):  
Ionic Strength ◽  
Ion Exchange ◽  
Anion Exchange ◽  
Natural Waters ◽  
Electrolyte Solutions ◽  
Anion Exchange Membrane ◽  
Exchange Equilibrium ◽  
Thermodynamic Constants ◽  
Separation Factors ◽  
Exchange Membrane

The effect of ionic strength variation on the ion exchange equilibrium between AMX anion exchange membrane and electrolyte solutions containing the most dominant anions on natural waters (Cl−, NO3−, and SO42−) was studied. All experiments were carried out at a constant temperature of 25 °C. Ion exchange isotherms were established, at different ionic strengths from 0.1 to 0.5 M, for the systems (Cl−/NO3−), (Cl−/SO42−) and (NO3−/SO42−). Obtained results showed that for I = 0.1 M the affinity order is SO42 −>NO3−>Cl−. For I = 0.2 M this order is NO3−>SO42−>Cl−. For 0.3 and 0.5 M the AMX membrane becomes more selective for chloride than for nitrate or sulfate. Selectivity coefficients KNO3−Cl−, K2Cl−SO42− and K2NO3−SO42−, thermodynamic constants, and separation factors were calculated and decreased with the increase of ionic strength.

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.

Microstructure determines water and salt permeation in commercial ion exchange membranes

2018 ◽  
Author(s):  
Ryan Kingsbury ◽  
Shan Zhu ◽  
Sophie Flotron ◽  
Orlando Coronell
Keyword(s):  
Energy Efficiency ◽  
Ion Exchange ◽  
Electrolyte Solutions ◽  
Polymer Chains ◽  
Salt Transport ◽  
Mixing Energy ◽  
Electrochemical Processes ◽  
Highly Correlated ◽  
Salt Diffusion ◽  
Exchange Membrane

Ion exchange membrane (IEM) performance in electrochemical processes such as fuel cells, redox flow batteries, or reverse electrodialysis (RED) is typically quantified through membrane selectivity and conductivity, which together determine the energy efficiency. However, water and co-ion transport (i.e., osmosis and salt diffusion / fuel crossover) also impact energy efficiency by allowing uncontrolled mixing of the electrolyte solutions to occur. For example, in RED with hypersaline water sources, uncontrolled mixing consumes 20-50% of the available mixing energy. Thus, in addition to high selectivity and high conductivity, it is desirable for IEMs to have low permeability to water and salt in order to minimize energy losses. Unfortunately, there is very little quantitative water and salt permeability information available for commercial IEMs, making it difficult to select the best membrane for a particular application. Accordingly, we measured the water and salt transport properties of 20 commercial IEMs and analyzed the relationships between permeability, diffusion and partitioning according to the solution-diffusion model. We found that water and salt permeance vary over several orders of magnitude among commercial IEMs, making some membranes better-suited than others to electrochemical processes that involve high salt concentrations and/or concentration gradients. Water and salt diffusion coefficients were found to be the principal factors contributing to the differences in permeance among commercial IEMs. We also observed that water and salt permeability were highly correlated to one another for all IEMs studied, regardless of polymer type or reinforcement. This finding suggests that transport of mobile salt in IEMs is governed by the microstructure of the membrane, and provides clear evidence that mobile salt does not interact strongly with polymer chains in highly-swollen IEMs. <br>

Donnan Equilibria in Polymeric Micellar Systems with Weak Polyelectrolyte Shells: The Lowering of the pH Value

1997 ◽  
Vol 62 (11) ◽  
pp. 1730-1736 ◽  
Author(s):  
Petr Munk ◽  
Zdeněk Tuzar ◽  
Karel Procházka
Keyword(s):  
Ionic Strength ◽  
Block Copolymer ◽  
Ph Value ◽  
Electrolyte Solutions ◽  
Hydrogen Ions ◽  
Micellar Systems ◽  
Weak Electrolytes ◽  
Block Copolymer Micelles ◽  
Copolymer Micelles ◽  
Polyelectrolyte Solutions

When two electrolyte solutions are separated and only some of the ions can cross the boundary, the concentrations of these ions are different on both sides of the boundary. This is the well-known Donnan effect. When weak electrolytes are involved, the imbalance includes also hydrogen ions: there is a difference of pH across the boundary and the dissociation of nondiffusible weak electrolytes is suppressed. The effect is very pronounced when the concentration of the weak electrolyte is high and ionic strength is low. The significance of this phenomenon is discussed for polyelectrolyte solutions, and particularly for block copolymer micelles with weak polyelectrolyte shells. The effect is quite dramatic in the latter case.

scholarly journals Electroreduction of Bi(III) ions in the aspect of expanding the “cap-pair” effect: the role of the nanosized active complexes

2021 ◽  
Author(s):  
Agnieszka Nosal-Wiercińska ◽  
Marlena Martyna ◽  
Sławomira Skrzypek ◽  
Anna Szabelska ◽  
Małgorzata Wiśniewska
Keyword(s):  
Electrolyte Concentration ◽  
Supporting Electrolyte ◽  
Acceleration Process ◽  
Organic Substances ◽  
Effect Mechanism ◽  
Solution Interface

AbstractThe paper discusses the electroreduction of Bi(III) ions in the aspect of expanding the “cap-pair” effect.The “cap-pair” rule is associated with the acceleration of the electrode’s processes by organic substances. The interpretation of the “cap-pair” effect mechanism was expanded to include the effect of supporting electrolyte concentration on the acceleration process and the type of electrochemical active as well as used protonated organic substances. It has also been shown that the phenomena occurring at the electrode/solution interface can influence a change in the dynamics of the electrode’s process according to the “cap-pair” rule.

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.

Polarography of nickel in concentrated chloride media

1966 ◽  
Vol 19 (8) ◽  
pp. 1343 ◽  
Author(s):  
TM Florence
Keyword(s):  
Ionic Strength ◽  
Graphite Electrode ◽  
Supporting Electrolyte ◽  
Anhydrous Methanol ◽  
Pyrolytic Graphite ◽  
Hydration Number ◽  
Mercury Electrode ◽  
Specific Adsorption ◽  
Dropping Mercury Electrode ◽  
Pyrolytic Graphite Electrode

In concentrated chloride media, nickel is reduced at far more positive potentials than in dilute solutions. The positive shift in half-wave potential increases as the ionic strength is raised, and is also greater when the cation of the supporting electrolyte has a high hydration number. Evidence is presented to show that the reduction in overpotential is due to the formation of a nickel chloride complex, [Ni(H2O)5Cl]+, which has a stoicheiometric stability constant of 0.094 � 0.009 at an ionic strength of 10.0. Spectrophotometric results show that this nickel species is not formed in low ionic strength solutions. In anhydrous methanol saturated with lithium chloride, nickel is present as the tetrachloro complex, [NiCl,]2-, which has similar polarographic behaviour to the monochloro complex. Current-potential curves recorded at a rotated pyrolytic graphite electrode enabled the behaviour of nickel to be studied in the absence of specific adsorption of the chloride ion. Nickel is reduced at more positive potentials at a dropping mercury electrode than at the pyrolytic graphite electrode, and the results indicate that this difference is due to specific adsorption of chloride on the mercury electrode.

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