Research on edl theories have been carried out for almost more than a century. Zetapotential measurement using the smoluchowski equation and the slope of the currenttime relationship in electroosmotic. Highconcentration zeta potential measurements using light. The first layer, the surface charge either positive or negative, consists of ions. The electrical double layer and its structure springerlink. The zeta potential is the electrical potential located at the shear plane 18, 19. But today this area is experiencing intense activity due to several potential applications. 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 double layer properties of a colloidal dispersion. Department of mechanical and industrial engineering, university of toronto, 5 kings college road, toronto, ontario, canada m5s 3g8. Zeta potential is considered to be the electric potential of this inner area including this conceptual sliding surface. Surface charge double layer zeta potential electrical double layer electrical characteristic these keywords were added by machine and not by the authors. An electrical field is applied to the electrodes, and particles or molecules that have a net charge, or more strictly a net zeta potential will migrate towards the oppositely charged electrode with a velocity, known as the mobility, that is related to their zeta potential. This process is experimental and the keywords may be updated as the learning algorithm improves. The electrochemical doublelayer consists of a stationary and a diffuse ion layer around a colloidal particle.
The particle continues to attract more counterions but now these counterions are being repelled by other counterions in the vic. As this electric potential approaches zero, particles tend to aggregate 2. Zeta potential the liquid layer surrounding the particle exists as two parts. Electrical double layer zeta potential dlvo theory disperse system electrical double layer. Original research significance of zeta potential in the. Electrical double layer lets consider infinite flat solid surface in contact with an electrolyte solution. An electric double layer is a phenomenon that plays a fundamental role in the mechanism of the electrostatic stabilization of colloids. Electric double layer an overview sciencedirect topics. The electrical double lay er edl is the result of the v ariation 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. The primary difference between a double layer on an electrode and one on an interface is the. The following factors significantly affect the magnitude of electrokinetic potential. The electrostatic potential on that surface is called the zeta potential and it is that potential which is measured, when one measures the velocity of the particles in a d. Everything you want to know practical zeta potential.
Chapter 4 sludge conditioning marmara universitesi. A double layer is a structure that appears on the surface of an object when it is exposed to a. The velocity in metresecond for a unit field strength 1 volt per metre is called the electrophoretic mobility, and is given the symbol e. The electrical double layer is divided in an inner stern layer, inside the surface of hydrodynamic shear of dna, and a gouy. Zeta potential is a function of the surface charge of a particle, any adsorbed layer at the interface and the nature and composition of the surrounding medium in which the particle is suspended. The double layer comprises a rigid region next to the mineral surface and a diffuse layer joining with the bulk solution. The edl acts as an electrical capacitor with the electrical potential difference.
The electrical double layer the development of a nett 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 particle, close to the surface. Zeta potential, also known as electrokinetic potential, is measured in millivolts mv. Zeta potential is more important than nernst potential because the electrical double layer also moves, when the particle is under motion. The zeta potential is the potential at the plane of shear, i. Debye parameter a particle radius electrical double layer thickness much smaller than particle v velocity. The double layer model is used to visualize the ionic environment in the vicinity of a. Sep 28, 2010 if the true zeta potential value of a sample is required, measurements should be performed at a range of concentrations to identify a region where the zeta potential results obtained are independent of concentration. Electrical double layer, zeta potential, and electrophoretic charge of. The double layer model is used to visualize the ionic environment in the vicinity of a charged surface. The electric potential at the shear plane is called zeta potential. A dispersion is introduced into a cell containing two electrodes. Thus, it is widely used for quantification of the magnitude of the charge. Edl formation during pipetting and its equivalent circuit. This inner layer, largely immobile and either positively or negatively charged, subsequently attracts a second layer of ions of opposite polarity.
Feb 23, 2016 it is usually denoted using the greek letter zeta. The situation changes with brackish or saline waters. For these experiments, the dilution protocol is pivotal to ensuring that sample conditions are kept constant. Information from its description page there is shown below. The main focus of zeta potential analysis is gaining information on the surface charge of a. To obtain a desired potential at the working electrodes, the double layer capacitor must be first appropriately charged, which means that a capacitive current. The surface of colloidal particles acquires a positive or negative charge by selective adsorption of a layer of positive and negative ions around it. Apr 28, 2015 cont zeta potential or electrokinetic potential is defined as the difference in the potential between shear plane and electroneutral region of the solution. The surface charge potential is linearly dissipated from the surface to the contertions.
Thus, physical quantities such as potential, ion distribution, and electric displacement are dependent on only onedimensional coordinate. 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. In 1924 otto stern suggested combining the helmholtz model with the. The socalled zeta potential can be determined through electrokinetic measurements, and indicates the status regarding surface charges along the interface between solids and liquids. The principle of determining zeta potential is very simple. In the electrical double layer surrounding a particle suspended in an electrolyte solution, a layer of ions is attracted to the surface of the particle due to chemical and electrochemical reactions.
The magnitude of the zeta potential is predictive of the colloidal stability of the solution table 3. Zeta potential measurement electrophoresis smoluchowski formula 1921 assumed. This voltage difference is on the order of millivolts and is referred to as the surface potential. As a result, the electrical potential at this junction is related to the mobility of the particle and is called the zeta potential. May 24, 2018 positive counterions first attach to the negatively charged particle, forming a rigid layer called the stern layer. Introduction zeta potential may be defined as the potential difference between the dispersion medium and the stationary layer of fluid attached to the dispersed particle as shown in figure 1. Colloidal particles gain negative electric charge when negatively charged ions of the dispersion medium are adsorbed on the particle surface. Thus an electrical double layer exists round each particle. Jun 04, 2014 moreover, negatively charged polymer functional groups can demonstrate the electrostatic interactions with the cations from the diffusion part of electrical double layer. As it is impossible to measure it, the potential between interfacial double layer electrokinetic potential.
In other words, zeta potential is the potential difference between the dispersion medium and the stationary layer of fluid attached to the dispersed particle. Application of the zeta potential measurements to explanation. Pdf electrical double layer and zeta potential researchgate. Physical interpretation of single and double layer potentials below is a brief description of a physical interpretation for the single and double layer potentials.
The difference in potential between the adsorbed and diffuse layer is called electrokinetic or zeta potential. Physical interpretation of single and double layer potentials. The zeta potential is caused by the net electrical charge contained within the region bounded by the slipping plane, and also depends on the location of that plane. An improved method of determining the zpotential and surface. Simplifying the measurement of zeta potential using m3pals, technical note available from uk join researchgate to find the people and research you need to help your work. It can be either a metal under potential or due to ionic groups on the surface of a dielectric.
Zetapotential measurement using the smoluchowski equation. The potential curve is useful because it indicates the. 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. In 1853 he showed that an electrical double layer dl is essentially a. Within the diffuse layer there is a notional boundary inside which. 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. Zeta potential can be calculated with the following smoluchowskis formula. Now the zeta potential is only a fraction of the surface potential. Determination of the isoelectric point using zeta potential. This layer attracts counter ions from the medium which form a second layer of opposite charges. In this case, zeta potential is a good approximation of surface potential. The ratio between zeta potential and surface potential depends on double layer.
Zeta potential is an effective tool for coagulation control because changes in zeta potential indicate changes in the repulsive force between colloids. Oct 16, 2014 electrical double layer and zeta potential. Influence of surface conductivity on the apparent zeta. The shear plane slipping plane is an imaginary surface separating the thin layer of liquid bound to the solid surface and showing elastic behavior from the rest of liquid showing normal viscous behavior. Within the diffuse layer there is a notional boundary. Electrical double layer an overview sciencedirect topics. Zeta potential the double layer is formed in order to neutralize the charged colloid and, in turn, causes an elec. By studying the isoelectric point, one can determine how ph affects zeta potential and can determine at which ph the zeta potential is zero. Zeta potential determines if particles in liquid will stick.
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