Zeta potential titration

Zeta potential titration is a titration of heterogeneous systems, such as colloids, emulsions, etc. This systems have very large surface area. This titration have been designed for studying the properties of these surfaces.

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• Iso-electric point is one of such properties. It is important because colloids are usually unstable in the vicinity of iso-electric point ± 2 pH units. Acid and base are titration reagents for this titration type. There is a book published by M.Kosmulski that presents values of iso-electric points for hundreds different materials ^[1]. Attached Figure illustrates results of such titrations for concentrated alumina (4%vl) and rutile (7%vl)dispersions. It is seen that iso-electric point of alumina is around pH 9.3, whereas for rutile it is around pH 4. Alumina is unstable in the pH range from 7 to 11. Rutile is unstable within pH range from 2 to 6.

• Another purpose of this titration is determination of the optimum dose of surfactant for achhieving stabilization or flocculation of heterogeneous system. Examples can be found in the book by Dukhin and Goetz ^[2]

Zeta potential plays role of indicator. Measurement of zeta potntial can be performed using microelectrophoresis, or electrophoretic light scattering, or electroacoustic phenomena. The last method makes possible conducting this type of titrations for concentrated systems, with no dilution. There is detail description of such titrations, both pH and surfactant, in the book by Dukhin and Goetz, ref. 2.

References

1. ^ Kosmulski, M. "Chemical properties of Material Surfaces, Surfactant Science Series, Elsevier, 2001
2. ^ Dukhin, A.S. and Goetz, P.J. "ultrasound for chacterizing colloids", Elsevier, 2002

Category

Interface and Colloid Science