Adsorption of ionic surfactants on solid particles determined. This layer attracts counter ions from the medium which form. The zeta potential of a particle characterizes its motion in an electric field and is often thought to be negligible at high ionic strength several moles per liter due to thinning of the electrical double layer edl. As the particle moves due to gravity, kinetic energy, andor under an applied. The existence of the stern layer helps to describe both the dependence of electrode.
This second layer screens the surface charge and its net charge is equal to the surface charge, but has the opposite polarity. Cbse sample papers for class 12 chemistry solved 2016 set 1. 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. Electric double layer is the phenomenon playing a fundamental role in the mechanism of the electrostatic stabilization of colloids. This negative charge on the clay surface and positive charge of the balancing cations create an electrical double layer around. Electrophoresis 2004, 25, 187202 zeta potential of microfluidic substrates. Oct 16, 2014 electrical double layer and zeta potential. Zeta potential definition of zeta potential by medical. Zeta potential is an effective tool for coagulation control because changes in zeta potential indicate changes in the repulsive force between colloids. The net charge density on a microfluidicsubstrate incontact with an aqueous solution gives rise to an electrical double layer and, in the pres. In the colloidal chemistry literature, it is usually denoted using the greek letter zeta. Electric double layer an overview sciencedirect topics. Coagulation and flocculation are designed to remove infectious agents. 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.
Ncl method pcc2 measuring zeta potential of nanoparticles. Adsorption of ionic surfactants on solid particles. A potential difference is set up between these two layers and is called electrokinetic potential or zeta potential. Cont zeta potential or electrokinetic potential is defined as the difference in the potential between shear plane and electroneutral region of the solution. The difference in potential between the adsorbed and diffuse layer is called electrokinetic or zeta potential. The socalled zeta potential can be determined through electrokinetic measurements, and indicates the status regarding surface charges along the interface between solids and liquids. Viscoelastic effects on dispersion due to electroosmotic flow. The zeta potential is the electrical potential at the slipping plane. Overview of zeta potential concept, measurement use, and. 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. New method for determination of surface potential of microscopic particles by second harmonic generation elsa c. Besides, the zetapotential characterizes the electrical double layer on the solidmiquid interface, a fact very important in flotation and flocculation. 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 surface of colloidal particles acquires a positive or negative charge by selective adsorption of a layer of positive and negative ions around it. New method for determination of surface potential of. The relationship between zeta potential and surface potential depends on the level of ions in the solution. Surface charge double layer zeta potential electrical double layer electrical characteristic these keywords were added by machine and not by the authors. The formation of the electrical double layer edl then occurs via. The gouychapman model of the electric double layer can be employed to describe the electric potential, 0, of the. The ec revised the sentence to state zeta potential is derived from the electrophoretic mobility using the henry function, which can be approximated by the smoluchowski equation or huckel equation according to the relative thickness of the electrical double layer compared to the hydrodynamic radius of the particle. Debye parameter a particle radius electrical double layer thickness much smaller than particle v velocity. The electric potential into the electrical double layer edl in physical and dimensionless form are. When a colloidal particle moves in the dispersion medium, a layer of the surrounding liquid remains attached to the particle. It can be either a metal under potential or due to ionic groups on the surface of a dielectric. The approach is suitable for concentrations below the threshold of hemimicelle formation. 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. Feb 23, 2016 it is usually denoted using the greek letter zeta.
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. Sep 04, 2012 with decades of practical experience, dr. The thickness of the electrical double layer the debye length. The zeta potential zisassumed as the potential at the. Its a measure of the electrical charge of particles are that are suspended in liquid. 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. Zetapotential measurement using the smoluchowski equation. You may do so in any reasonable manner, but not in. Membrane surface characteristics separation processes. Viscoelastic effects on dispersion due to electroosmotic. Gouychapmanstern model of the electrical double layer showing the distribution of hydrated ions and water molecules, the stern and diffuse layers, anegative surface charge density scd, and the potentialprofile as afunction of distance from the charged surface solid line. 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.
Files are available under licenses specified on their description page. The double layer model is used to visualize the ionic environment in the vicinity of a charged surface. Part 1 189 lies at the distance of closest approach from the surface, dictated by the size of the ion. Effect of electrolyte concentration on the stern layer.
Particle zeta potentials remain finite in saturated salt. Modeling electroosmotic flow and the electrical double layer. Zetapotential measurement using the smoluchowski equation and the slope of the currenttime relationship in electroosmotic. 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. Media in category electrical double layer the following 31 files are in this category, out of 31 total. 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.
As long as there is no reliable information on the values of the permittivity and the viscosity in the electrical double layer close to the interface, the calculation of the electrokinetic potential from electrokinetic experiments remains open to criticism. Thus, it is widely used for quantification of the magnitude of the charge. Within the diffuse layer there is a notional boundary. Double electric layer can be formed by directionally absorbing the polar group of a phase to another phase, which can be carried out by the electrons on the polymer functional groups going through the phase interface. The potential in the helmholtz layer is described by the poissons equation, which relates the potential with the charge distribution. Fairhurst is one of the worlds experts on zeta potential measurement and its application to product and. Zeta potential electrical double layer colloidal charge laser doppler electrophoresis electroacoustics colloid vibration current debye length maxwellwagner relaxation abstract electroacoustics and laser doppler electrophoresis were employed to measure the mobility of surfacemodi. Highconcentration zeta potential measurements using light. However, as this potential cannot be measured directly, the zeta potential is often considered as an adequate substitute. This process is experimental and the keywords may be updated as the learning algorithm improves. Surface charge double layer zeta potential electrical double layer.
This voltage difference is on the order of millivolts and is referred to as the surface 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. The velocity in metresecond for a unit field strength 1 volt per metre is called the electrophoretic mobility, and is given the symbol e. Zeta potential measurement electrophoresis smoluchowski formula 1921 assumed. In this section, a cursory introduction to electrical double layer theory is presented with specific attention to both the zeta potential and the resulting electroosmotic flow observed in an electric field. From a theoretical viewpoint, the zeta potential is the electric potential in the interfacial double layer dl at the location of the. The zeta potential is the potential at the plane of shear, i. Improving our under standing of the edl model is also important to address the question of surface electrical conduction in porous media re vil and glover, 1997. Zeta potential the liquid layer surrounding the particle exists as two parts.
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. The following factors significantly affect the magnitude of electrokinetic potential. Electrical double layer zeta potential dlvo theory disperse system electrical double layer. I will describe the concept of electroosmosis and the electrical double layer edl, and how to model these in comsol, walking you through two example models. When the nps move in the liquid phase due to gravity, kinetic energy, andor under an. Zeta potential mv stability behavior of the colloid from 0 to 5, rapid coagulation or flocculation from 10 to 30 incippyient instability from 30 to 40 moderate stability from 40 to 60 good stability. Electrical double layer theory under surface and colloidal chemistry. Fairhurst is one of the worlds experts on zeta potential measurement and its application to product and process performance. This layer attracts counter ions from the medium which form a second layer of opposite charges. 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. June 2, 1998 a new noninvasive method for determining the surface. In zeta potential measurements, an electrical field is applied across the sample and the.
For these experiments, the dilution protocol is pivotal to ensuring that sample conditions are kept constant. The electrical potential at the surface of shear is defined as the zeta potential. Eisenthal chemistry department, columbia university, new york, new york 10027. Zeta potential is more important than nernst potential because the electrical double layer also. The figure above represents the change in charge density through the diffuse layer. Zeta potential is a scientific term for electrokinetic potential in colloidal dispersions.
These two layers are collectively called the electrical double layer. Interactions between ppp particles dispersed in polar fluids. Adsorption of ionic surfactants on solid particles determined by zetapotential measurements. Zeta potential the electric potential between the shear plane and the bulk solution is. The ratio between zeta potential and surface potential depends on double layer. The electrical potential within the electric double layer has the maximum value on the particle surface stern layer. The potential difference electroosmosis and allied phenomena between the fixed part and freely mobile portions of double layer known as zeta potential i. Electrical double layer diffusion layer electrochemical reactions electrical circuit analogues. 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. The potential drops with the increase of distance from the surface and reaches 0 at the boundary of the electric double layer. Zeta potential is more important than nernst potential because the electrical double layer also moves, when the particle is under motion. The relationship between zeta potential and surface potential depends on the level of ions. The zetapotential is used in colloid chemistry for observing the behaviour of dispersive systems in liquids.
However, zeta potential is not equal to the stern potential or electric surface potential in the double. Zeta potential point of zero charge pzc ph at which surface potential 0 isoelectric point iep ph at which zeta potential 0. Ohp and the region within it the electrical double layer. Hereafter the potential of the stern layer will be approximately identi. Here, we describe zeta potential measurements on polystyrene latex psl particles at monovalent salt concentrations up to saturation. The zeta potential is the electrical potential located at the shear plane 18, 19. Influence of surface conductivity on the apparent zeta. The potential at the stern layer that is the actual potential influencing the behaviour of the charged species. The zeta potential represents the net charge between the primary. Coagulation and flocculation prepared by husam alnajar. Department of mechanical and industrial engineering, university of toronto, 5 kings college road, toronto, ontario, canada m5s 3g8.
Eisenthal chemistry department, columbia university, new york, new york 10027 received. Everything you want to know practical zeta potential. During a zeta potential measurements, an electrical field is applied across the sample, inducing. Review 1 zeta potential of microfluidic substrates. Zeta potential is widely used for quantification of the magnitude of the electrical charge at the double layer.
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