When a colloidal particle moves in the dispersion medium, a layer of the surrounding liquid remains attached to the particle. Everything you want to know practical zeta potential. Electrical properties of the red blood cell membrane and. Electrical double layer, zeta potential, and electrophoretic. The potential drops with the increase of distance from the surface and reaches 0 at the boundary of the electric double layer. Zeta potential determination of polymeric materials using. Unfortunately, the fundamental interfacial property. Ep11 electric double layer edl and dlvo forces nano 202 ucsd darren lipomi duration. Zeta potential the liquid layer surrounding the particle exists as two parts. The dl refers to two parallel layers of charge surrounding the object. Thus, physical quantities such as potential, ion distribution, and electric displacement are dependent on only one.
As a result, the electrical potential at this junction is related to the mobility of the particle and is called the zeta potential. Within the diffuse layer there is a notional boundary inside which. The electrical potential within the electric double layer has the maximum value on the particle surface stern layer. Electrical double layer, zeta potential, electrokinetic analyzer, streaming current potential, polymeric materials 1.
Pdf when clay particles are fully hydrated, the negative charge is balanced by the cations in the soil solution attracted by the coulomb forces. However, the magnitude of the coupling coefficient remains greater than zero up to. The object might be a solid particle, a gas bubble, a liquid droplet, or a porous body. Measurement of streaming potential coupling coefficient in sandstones saturated with natural. This does not hold true for saline waters due to double layer compression.
Jan 26, 2018 ep11 electric double layer edl and dlvo forces nano 202 ucsd darren lipomi duration. New method for determination of surface potential of microscopic particles by second harmonic generation elsa c. Zeta potential is therefore a function of the surface charge of the particle, any adsorbed layer at the interface, and the nature and composition of the surrounding suspension medium. Pdf electrical double layer and zeta potential researchgate. When a layer of macromolecules is adsorbed on the particles surface, it shifts the shear plane further from the surface and alters the zeta potential. The magnitude of the zeta potential we interpret from our measurements also decreases with increasing brine salinity in the low. This layer attracts counter ions from the medium which form a second layer of opposite charges. Zeta potential is a scientific term for electrokinetic potential in colloidal dispersions. In this model he assumed that no electron transfer reactions occur at the electrode and the solution is composed only of electrolyte.
Introduction the zeta potential, also known as the electrokinetic potential, originates from the accumulation of electrical charges at a solidliquid interface where an electrical double layer is formed. Within the diffuse layer there is a notional boundary. Such behavior is qualitatively incompatible with standard meanfield theories of the electrical double layer but is consistent with. During a zeta potential measurements, an electrical field is applied across the sample, inducing the movement of charged particles. For details of the theory of electrical doublelayer a. The magnitude of the zeta potential indicates the degree of electrostatic repulsion between adjacent, similarly charged particles in a dispersion. The electrical double layer and the theory of electrocapillarity. The relationship between zeta potential and surface potential depends on the level of ions in the solution. Jan 10, 2020 from the fundamental theorys perspective, zeta potential is the electrical potential in the interfacial double layer dl at the location of the slipping plane shown in figure \\pageindex1\. In the colloidal chemistry literature, it is usually denoted using the greek letter zeta. The figure above represents the change in charge density through the diffuse layer.
This voltage drop, called the zeta potential, varies depending on the properties of the colloid. When a colloidal particle moves in the dispersion medium, a layer of the surrounding liquid remains. Stern layer, the potential profile in the stern layer is. In fresh water, the large double layer makes the zeta potential a good approximation of the surface potential. Potential drop across the mobile part of the double layer, that is responsible for electrokinetic phenomena. The relationship between zeta potential and surface potential depends on the level of ions. Using molecular dynamics simulations with recently developed importance sampling methods, we show that the differential capacitance of a model ionic liquid based doublelayer capacitor exhibits an anomalous dependence on the applied electrical potential.
New method for determination of surface potential of. For example, adding salt to a colloid shrinks the electrical double layer, and reduces the zeta potential. If you continue browsing the site, you agree to the use of cookies on this website. Herein we quantify the average thickness of the stern layer at the silica sio 2 nanoparticleaqueous electrolyte interface as a function of nacl concentration following direct measurement of the nanoparticles surface potential by x. Electrical double layer, zeta potential, and electrophoretic charge of. The electrical double layer department of chemical. What can be derived and measured is an electrokinetic potential termed the zeta potential. Zeta potential vs surface potential the relationship between zeta potential and surface potential depends on the level of ions in solution. Surface charge double layer zeta potential electrical double layer electrical characteristic these keywords were added by machine and not by the authors. This plane is the interface which separates mobile fluid from fluid that remains attached to the surface. Oct 28, 20 the second layer, known as the diffusive layer, is made of free ions attracted to the surface due to the influence of electric attraction and thermal motion. This second layer screens the surface charge and its net charge is equal to the surface charge, but has the opposite polarity. Water flow also drags the excess counterions in the diffuse layer along the pores surface and creates a macroscopic current density, the streaming current and a macroscopic electrical potential difference, the.
Electrical double layer potential distribution in nanoporous. A study of electrical double layer effects in the pretreatment of twoelectrode cells for enzyme electrodes. It is found that most of the electrical potential drop occurs. It is a weil known fa ct that this double layer is generally insufficient to stabilize an emulsion. The difference in potential between the adsorbed and diffuse layer is called electrokinetic or zeta potential. Electrical double layer zeta potential dlvo theory disperse system electrical double layer. The potential curve is useful because it indicates the strength of the electrical force between particles and the distance at which this force. This process is experimental and the keywords may be updated as the learning algorithm improves.
The socalled zeta potential can be determined through electrokinetic measurements, and indicates the status regarding surface charges along the interface between solids and liquids. Influence of surface conductivity on the apparent zeta. The electrical double layer edl is the result of the variation of electric potential near a surface, and has a significant influence on the behaviour of colloids and other surfaces in contact with solutions or solidstate fast ion conductors. Oct 16, 2014 electrical double layer and zeta potential the surface of colloidal particles acquires a positive or negative charge by selective adsorption of a layer of positive and negative ions around it. Theory of the electric double layer of stabilized emulsions. The total electrical potential drop is divided into two parts, one on either side of the interface. The zeta potential serves as an important parameter in characterizing the electrostatic interaction between particles in dispersed systems and the properties of dispersion as affected by this electrical phenomenon.
The model which gave rise to the term electrical double layer was first put forward in the 1850s by helmholtz. Its a measure of the electrical charge of particles are that are suspended in liquid. This voltage difference is on the order of millivolts and is referred to as the surface potential. This video explains zeta potential in suspension formulation.
Electrical double layer potential distribution in nanoporous electrodes from molecular modeling and classical electrodynamics analysis by evan marshall ney a thesis submitted in partial fulfillment of the requirements for the degree of master of science in mechanical engineering supervised by assistant professor dr. Electrical double layer, zeta potential, and electrophoretic charge of double. The zeta potential is the electrical potential located at the shear plane 18, 19. The zeta potential is a key indicator of the stability of colloidal dispersions. Measurement of streaming potential coupling coefficient in. We discuss the assumptions made in applying to dna the charge. Electrical double layer the development of a net charge at the particle surface affects the distribution of ions in the surrounding interfacial region, resulting in an increased concentration of counter ions ions of opposite charge to that of the. Eisenthal chemistry department, columbia university, new york, new york 10027. Water flow also drags the excess counterions in the diffuse layer along the pores surface and creates a macroscopic current density, the streaming current and a macroscopic electrical potential difference, the streaming potential 14, 17. Electrical double layer lets consider infinite flat solid surface in contact with an electrolyte solution.
Electrical double layer an overview sciencedirect topics. The electrical double layer edl is a structure which describes the variation of electric potential near a surface, and has a significant influence on the behaviour of colloids and other surfaces in contact with solutions or solidstate fast ion conductors. Electric double layer an overview sciencedirect topics. The chemistry and physics of charged interfaces is regulated by the structure of the electrical double layer edl. The first layer, the surface charge either positive or negative, consists of ions. Electrical double layer project gutenberg selfpublishing. The electrical double layer is divided in an inner stern layer, inside the surface of hydrodynamic shear of dna, and a gouy. Aug 04, 2015 this video explains zeta potential in suspension formulation. Since zeta potential is not equal to the electric surface potential in a double layer or to the stern potential, it is often the only value that can be used to describe doublelayer properties of. The effect of the electrical double layer on hydrodynamic. Sep 05, 2017 electrical double layer theory under surface and colloidal chemistry slideshare uses cookies to improve functionality and performance, and to provide you with relevant advertising. Effect of electrolyte concentration on the stern layer.
The hydrolyzable metal ions produce two points of zero charge pzcs, one of which is that of the soil. Electrical double layer theory linkedin slideshare. The first layer, the surface charge either positive or negative, comprises ions. The ratio between the np velocity and the external applied field, known as electrophoretic mobility, is then measured and converted to the zeta. Electrical double layer, zeta potential, electrokinetic analyzer, streaming currentpotential, polymeric materials 1. The potential curve is useful because it indicates the strength of the electrical force between particles and the distance at which this force comes into play. A double layer dl, also called an electrical double layer, edl is a structure that appears on the surface of an object when it is exposed to a fluid. As we leave the surface, the potential drops off roughly linearly in the stern layer and then exponentially through the diffuse layer, approaching zero at the imaginary boundary of the double layer.
Although zeta potential is an intermediate value, it is sometimes considered to be more significant than surface potential as far as electrostatic repusion is concerned. Here, it is assumed that the potential at the ohp is the zeta potential. From a theoretical viewpoint, zeta potential is the electric potential in the interfacial double layer of a dispersed particle or droplet versus a point in the continuous phase away from the interface. Zeta potential is the electrical potential at the slipping plane. Modeling electroosmotic flow and the electrical double layer.
The double layer model is used to visualize the ionic environment in the. The second layer, known as the diffusive layer, is made of free ions attracted to the surface due to the influence of electric attraction and thermal motion. From the fundamental theorys perspective, zeta potential is the electrical potential in the interfacial double layer dl at the location of the slipping plane shown in figure \\pageindex1\. Verwey communicated at the meeting of february 25, 1950 i ntrod uction. The electric double layer has a life of its own the. The electrical double layer at the interface of two inmiscible liquids is of the double diffuse type. The following factors significantly affect the magnitude of electrokinetic potential. Understanding zeta potential in suspension youtube. Zeta potential a complete course in 5 minutes as electric double layer edl. Zeta potential of clay minerals and quartz contaminated by. Nevertheless, zeta potential is often the only available path for characterization of double layer properties. The value of the electric potential at the slipping plane is called the zeta potential, which is a very important parameter in the theory of interaction of colloidal. Examples of such approximated complex profiles are. Electrical double layer effect is a phenomenon present both in electrical double layer capacitors more commonly known as supercapacitors and in electrochemical batteries.
235 1025 1411 1344 1390 687 1131 244 808 1322 718 497 469 1201 167 1002 581 567 1312 613 620 1554 941 1461 1287 502 1237 195 1398 317 1220 55 1039