What is diffuse double layer in clay?
Diffuse double layer (DDL) is an ionic structure that describes the variation of electric potential near a charged surface, such as clay, and behaves as a capacitor. When suspended in an electrolyte, clay particles are surrounded by a hydrosphere of adsorbed water that contains a thin layer of adsorbed cations.
In which model diffuse double layer is present?
Detailed Solution The ionic conditions on the outside surface of a clay particle or a pocket of clay particles dispersed in water or an electrolyte solution are controlled by the proportion of the exchangeable cations that disperse into the solution. Hence, Diffused double-layer is present in the case of clay.
What is Gouy-Chapman theory?
Gouy-Chapman theory (Gouy 1910; Chapman 1913) is an electrostatic model of the spatial distribution of ions adsorbed, but not immobilized, by a charged particle surface reacting with an aqueous electrolyte solution.
What is the Helmholtz double layer?
Helmholtz double layer (HDL) refers to the structural representation of the accumulation of electrical charges present at the boundary of an electrode and electrolyte when they are in contact with each other. HDL is most readily identifiable in fluid-based mixture systems, such as paints used for corrosion prevention.
What are the factors affecting the diffused double layer thickness?
Factors Affecting Diffuse Double Layer:
- (i) Concentration of Total Electrolyte: With an increase in total electrolyte concentration, the thickness of the diffuse double layer decreases.
- (ii) Valence of the Counter Ion:
- (iii) Dielectric Constant:
What is electrode double layer?
An electrical double layer exists at the interface between an electrode and its surrounding electrolyte. This double layer is formed as ions from the solution “stick to” the surface of the electrode. Charges in the electrode are separated from the charges of these ions.
What does the electric diffuse double layer entail?
Diffuse layer contains free ions with a higher concentration of the counterions. The ions of the diffuse layer are affected by the electrostatic force of the charged particle. The electrical potential within the electric double layer has a maximum value on the particle surface (Stern layer).
What is Gouy Chapman diffuse layer?
The Gouy-Chapman theory describes a rigid charged surface, with a cloud of oppositely charged ions in the solution, the concentration of the oppositely charged ions decreasing with distance from the surface. This is the so-called diffuse double layer.
What is double layer colloid?
An electric double layer is a phenomenon that plays a fundamental role in the mechanism of the electrostatic stabilization of colloids. Colloidal particles gain negative electric charge when negatively charged ions of the dispersion medium are adsorbed on the particle surface.
What is Gouy-Chapman diffuse layer?
What is the essence of the concept of diffuse double layer?
The surface of a clay particle, being negatively charged, attracts positive ions. This region of attracted positive ions in solution and the negatively charged surface of the clay is termed the ‘diffuse double layer’.
How is the Gouy-Chapman diffuse double layer modified?
Stern, therefore, modified the Gouy-Chapman diffuse double layer. His theory states that ions do have finite size, so cannot approach the surface closer than a few nm. The first ions of the Gouy-Chapman Diffuse Double Layer are not at the surface, but at some distance d away from the surface.
Where are the ions in the Gouy-Chapman double layer?
The first ions of the Gouy-Chapman Diffuse Double Layer are not at the surface, but at some distance d away from the surface. This distance will usually be taken as the radius of the ion. As a result, the potential and concentration of the diffuse part of the layer is low enough to justify treating the ions as point charges.
How is the Stern model different from the Gouy-Chapman model?
The Gouy-Chapman model fails for highly charged DLs. In 1924 Otto Stern suggested combining the Helmholtz model with the Gouy-Chapman model: In Stern’s model, some ions adhere to the electrode as suggested by Helmholtz, giving an internal Stern layer, while some form a Gouy-Chapman diffuse layer.
Where are counterions located in the Gouy Chapman model?
The plane at distance δ from the surface is usually known as the Stern plane, and the region between this plane and the surface is known as the Stern layer. Outside the Stern layer there is a diffuse layer of counterions, just as in the Gouy–Chapman model. In the simplest Stern model, counterions are entirely mobile and not adsorbed on the surface.