Fast Evaluation of Differential Capacity and Surface Charge in Electrical Double Layers with A.C. Oscillopolarography

2000 ◽  
Vol 65 (3) ◽  
pp. 371-379 ◽  
Author(s):  
Shuping Bi ◽  
Hong Gao ◽  
Wei Tang ◽  
Zhiguo Yang ◽  
Sidan Du ◽  
...  
Keyword(s):  
Surface Charge ◽  
Analytical Procedure ◽  
Low Cost ◽  
Mercury Electrode ◽  
Double Layers ◽  
Differential Capacity ◽  
Fast Evaluation ◽  
Charge Densities ◽  
Electrical Double Layers ◽  
Simple Manipulation

The application of a.c. oscillopolarography for a fast evaluation of differential capacity and surface charge in electrical double layers on the mercury electrode is described. The Cd = f(E), Q = f(E) and γ = f(E) functions are displayed. The obtained values of differential capacity and surface charge densities are in agreement with those from the a.c. bridge method. The new method has the distinct advantages of a rapid analytical procedure, visual detection, very simple manipulation and low-cost instrumentation. It is very useful in practical analysis where accurate values of differential capacity and surface charge are not required.

Effect of Fe/Al oxides on desorption of Cd2+ from soils and minerals as related to diffuse layer overlapping

Soil Research ◽  
2011 ◽  
Vol 49 (3) ◽  
pp. 231 ◽  
Author(s):  
Yan-ping Wang ◽  
Ren-kou Xu ◽  
Jiu-yu Li
Keyword(s):  
Charge Density ◽  
Surface Charge ◽  
Surface Charge Density ◽  
Charged Particles ◽  
Double Layers ◽  
Mineral Particles ◽  
Variable Charge ◽  
Electrical Double Layers ◽  
Oppositely Charged ◽  
Positively Charged

Cadmium is a toxic metal with high reactivity in acid variable charge soils. Adsorption and desorption of Cd2+ in soil and mineral particles can be affected by the interaction between the electrical double layers on oppositely charged particles, because the interaction can decrease the surface-charge density of the particles. We studied the effect of Fe/Al oxides on desorption of Cd2+ from soils and minerals and proposed the desorption mechanisms based on the overlapping of diffuse layers between negatively charged soils and mineral particles and positively charged Fe/Al oxide particles. Our results indicate that the overlapping of diffuse layers of electrical double layers between positively charged Fe/Al oxides [crystalline and amorphous Al(OH)3 and amorphous Fe(OH)3] and negatively charged Ultisol, Alfisol, kaolinite, and bentonite caused the effective negative surface-charge density on the soils and minerals to become less negative, and thus the adsorption affinity of these negatively charged surfaces for Cd2+ declined as a result of the incorporation of the Fe/Al oxides. Consequently, the release of exchangeable Cd2+ from the surfaces of the soils and minerals increased with the amount of Fe/Al oxides added. The more positive the charge on the surfaces of the Fe/Al oxides, the stronger the interaction of the electrical double layers between the oxides and soils and minerals, and thus the greater the release of Cd2+ from the soils and minerals. A decrease in pH led to an increase in the positive surface charge on the Fe/Al oxides and enhancement of the interaction of the electrical double layers between the oxides and soils and minerals. As a result, more Cd2+ was desorbed from the soils and minerals. This study suggests that the interaction between oppositely charged particles of variable charge soils can enhance the mobility of cadmium in the soils and thus increase its environmental risk.

Theory of films. - I. Single dielectric films

1973 ◽  
Vol 334 (1596) ◽  
pp. 49-58 ◽  
Keyword(s):  
Free Energy ◽  
Charge Density ◽  
Surface Charge ◽  
Dielectric Layer ◽  
Surface Charge Density ◽  
Aqueous Electrolyte ◽  
Van Der Waals ◽  
Double Layers ◽  
Dielectric Films ◽  
Electrical Double Layers

The van der Waals free energy of a system of two half-spaces of aqueous electrolyte separated by a dielectric layer is studied. The coupling of the van der Waals free energy to the structure of the electrical double layers in the system is calculated in two cases: (i) fixed surface charge density; (ii) fluctuating surface charge density due to the ionization of long chain carboxylic acid groups adsorbed on to the surfaces of the dielectric layer.

Electrokinetics of polymeric fluids in narrow rectangular confinements

Soft Matter ◽  
2021 ◽  
Author(s):  
Aditya Natu ◽  
Uddipta Ghosh
Keyword(s):  
Cross Section ◽  
Rectangular Cross Section ◽  
Double Layers ◽  
Polymeric Fluids ◽  
Polymeric Liquids ◽  
Electrical Double Layers

Flow of polymeric liquids in narrow confinements of rectangular cross section, in the presence of electrical double layers is analyzed here. Our analysis is motivated by the fact that many...

The surface charge on manganese dioxides

Soil Research ◽  
1981 ◽  
Vol 19 (1) ◽  
pp. 41 ◽  
Author(s):  
RM McKenzie
Keyword(s):  
Theoretical Model ◽  
Surface Charge ◽  
Charge Densities

Surface charge was measured on four synthetic manganese dioxides. Charge densities on two cryptomelanes followed closely the values predicted by a theoretical model. Charge densities on two birnessites were much higher, and did not fit the model.

Molecular solvent models of electrical double layers

1991 ◽  
Vol 36 (11-12) ◽  
pp. 1677-1684 ◽  
Author(s):  
G.M. Torrie ◽  
G.N. Patey
Keyword(s):  
Double Layers ◽  
Electrical Double Layers ◽  
Solvent Models
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