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[+Zeta Potential Theory+]<\/h2>\n<\/div>\n<\/div>\n<\/div>\n
Zeta potential is used to determine electrophoretic mobility of colloidial suspensions.<\/em><\/p>\n Surface Charge and Zeta Potential<\/strong><\/span><\/p>\n A ‘colloid’ exists when one state of matter is finely dispersed within another. Within a colloid, Brownian motion refers to the random movement of particles in a suspension (think electric interactions). The particles’ attraction or repulsion from one another, and therefore stability of these particles in solution, can be measured with zeta potential.<\/p>\n A stable solution will tend to not aggregate and so have a large magnitude zeta potential. As the tendency to flocculate (insert link to other part of page) increases, stability decreases, and zeta potential magnitude decreases.<\/p>\n Each particle has an electrical double layer, akin to (but not the same as) the surface potential of the particle (See figure 1)<\/em>. The measure of the electrical double layer is dependent on the particulate bound to the surface since the extra surface bound material slows diffusion.<\/p>\n Figure 1: Electric double layer (in yellow) around a particle (in blue).<\/em><\/p>\n A large part of the mathematical theory upon which this is based was developed by a cunning man named Smoluchowski. In fact, when running tests with zeta potential we use the Smoluchowski setting (which bases calculations on his electrophoresis equation). Mu is the electrophoretic mobility, epsilon_r is the dielectric constant of the medium (solvent), epsilon_o is the permittivity of free space, eta is the dynamic viscosity, and zeta is the zeta potential.<\/p>\n Smoluchowski Electrophoresis Equation<\/p>\n It should be noted that this equation is valid for thin layers.<\/p>\n Interesting information on aggregation terminology<\/strong><\/span><\/p>\n When particles in a colloid\/suspension first aggregate they form a floc<\/strong>. This is called flocculation<\/strong>. If the aggregate becomes more dense it is said to coagulate<\/strong>. Generally, coagulation is irreversible. Flocculation can be reversed by deflocculation<\/strong>.<\/p>\n For more, detailed information see these wonderful references\u2026<\/p>\n References:<\/strong><\/span><\/p>\n “Zeta Potential: An Introduction in 30 Minutes.” Malvern Instruments. Accessed 20 April 2010. http:\/\/www.nbtc.cornell.edu\/facilities\/downloads\/Zeta%20potential%20-%20An%20introduction%20in%2030%20minutes.pdf<\/a>.<\/p>\n![\"\"](\"http:\/\/i.imgur.com\/yhdrtOo.png\" "\\"\\"")
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