scholarly journals Study of polyacrylic acid adsorption on the interface of hydroxyapatite – electrolyte solutions

2013 ◽  
Vol 12 (3) ◽  
pp. 270-278
Keyword(s):  
Ionic Strength ◽  
Layer Thickness ◽  
Double Layer ◽  
Polyacrylic Acid ◽  
Electrolyte Solutions ◽  
Effect Of Temperature ◽  
Solution Composition ◽  
Ph Values ◽  
Adsorbed Amount ◽  
Double Layer Thickness

The adsorption of polyacrylic acid (PAA) on hydroxyapatite (HAP) from HAP saturated solutions was studied in this work as a function of PAA concentration, temperature, pH and ionic strength. In all experiments, the adsorption was studied under conditions of negatively charged adsorbent and adsorbate, respectively. These conditions ensured that adsorption was not electrostatically favored. The solution composition was found to influence significantly the maximum of the adsorbed amount. In fact, the adsorption of PAA, was found to increase with ionic strength, due to the decrease of double layer thickness of HAP particles. The effect of temperature and ionic strength on the kinetics of adsorption are also reported. Adsorption isotherms obtained at 30oC were found to be Langmuirtype, while at higher temperatures they were of the Brunauer-Emmett-Teller (BET) type. The absorbed amount of PAA was found to decrease with temperature, while it increased with ionic strength. For pH values lower than 6.5, the adsorption increased while for pH between 6.5 and 9 the adsorbed amount remained almost constant.

The primary electroviscous effect in a suspension of spheres with thin double layers

1983 ◽  
Vol 132 ◽  
pp. 337-347 ◽  
Author(s):  
E. J. Hinch ◽  
J. D. Sherwood
Keyword(s):  
Layer Thickness ◽  
Double Layer ◽  
High Surface ◽  
Particle Radius ◽  
Double Layers ◽  
Asymptotic Results ◽  
Electroviscous Effect ◽  
Surface Potentials ◽  
Double Layer Thickness

We study the primary electroviscous effect in a suspension of spheres when the double layer thickness κ−1 is small compared with the particle radius a. The case of a 1–1 symmetric electrolyte is examined using the methods of Dukhin & coworkers (1974), whilst the asymmetric electrolyte is studied along lines similar to those of O'Brien (1983). Sherwood's (1980) asymptotic results for high surface potentials and high Hartmann numbers are extended and complemented.

scholarly journals Insight into Debye Hückel length (κ−1): smart gravimetric and swelling techniques reveals discrepancy of diffuse double layer theory at high ionic concentrations

2021 ◽  
Author(s):  
Talal AL-Bazali
Keyword(s):  
Layer Thickness ◽  
Double Layer ◽  
Critical Concentration ◽  
Ionic Concentration ◽  
Diffuse Double Layer ◽  
Ionic Concentrations ◽  
Osmotic Water ◽  
Ionic Valence ◽  
High Concentrations ◽  
Double Layer Thickness

AbstractSmart gravimetric and swelling techniques were utilized in this work to examine the validity of the Debye Hückel length (κ−1) equation when shale interacts with highly concentrated salt solutions. The swelling and shrinkage behavior of two different shales, when exposed to monovalent and divalent ionic solutions (NaCl, KCl and CaCl2) at concentrations ranging from 2 to 22%w/w was observed and measured. Shale swelling and shrinkage results show that Debye Hückel length (κ−1) equation seems to work adequately at low ionic concentrations where osmotic water flow out of shale plays a major role in decreasing the diffuse double layer thickness by withdrawing water out and thereby shrinking κ−1. At high ionic concentration levels, the flow of associated water into the diffuse double layer negates the withdrawal of osmotic water out of the diffuse double layer which could maintain κ−1 or possibly increase it. Data on measured ionic uptake into shale suggests that excessive ionic diffusion into shale, especially at high concentrations, leads to higher electrical repulsion between alike ions in the diffuse layer which could lead to the expansion of the diffuse double layer thickness. Furthermore, swelling and shrinkage data analysis for shale suggests the existence of a ‘critical concentration’ below which the Debye Hückel length equation works. Above the critical concentration, the validity of the Debye Hückel length equation might be in question. The critical concentration is different for all ions and depends on ionic valence, hydrated ion diameter, and clay type.

Specific adsorption of sulfamate ions at the mercury/solution interface

1982 ◽  
Vol 60 (13) ◽  
pp. 1643-1647 ◽  
Author(s):  
Ernesto R. Gonzalez
Keyword(s):  
Ionic Strength ◽  
Activity Coefficient ◽  
Double Layer ◽  
Adsorbed Water ◽  
Water Molecules ◽  
Electrostatic Model ◽  
Solution Composition ◽  
Solution Interface ◽  
Double Layer Capacity ◽  
Mercury Electrodes

The adsorption of sulfamate ions on mercury electrodes has been studied by measuring the double layer capacity in constant ionic strength solutions of composition xM NH4SO3NH2 + (1−x)M NH4F. It was found that sulfamate ions are weakly adsorbed on mercury, the amount adsorbed being significant only for x > 0.1 at positive charges on the electrode. Because of this, the properties of the inner layer were found to be strongly dependent on the adsorbed water molecules and the structure of the diffuse layer. It was determined that the adsorption of sulfamate ions can be described by an isotherm based on the electrostatic model of the double layer. The possible effects of the activity coefficient variation with solution composition are discussed.

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