Presentation imk 209
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Transcript of Presentation imk 209
Our Group Members are …….
Tan Pek HoonLam See NgarTan Hui YingLoh Mun LaiTey Jit Xiong
Types of Forces between colloidal particles
Electrostatic Repulsion
Excluded Volume
Repulsion
Van der Waals
force of attraction
Steric Force
Entropic Force
What is DLVO Theory??
Derjaguin
Landau
Verwey
Overbeek
Electrical Double Layer
Ionization of adsorbed surface group
Eg : Gum arabic (ionic emulsifier)
WHAT IS ZETA POTENTIAL???
Zeta potential is the charge that develops at the interface between a solid surface and
its liquid medium.
measured in MilliVolts
its value can be related to the stability of colloidal dispersions
indicates the degree of repulsion between adjacent
How to measure???
not measurable directly
Determined by: electrophoretic mobility dynamic electrophoretic mobility
What is the effect of Ionic Strength
and pH on Colloidal particle?
• The stronger the Ionic strength , the closer the
particles are together ; the mutual repulsion of like electrical charges is lower , therefore the colloidal particle is less stable.
• Higher pH values (usually above seven) are
mandatory to guarantee an efficient surface charge density capable to provide a good stability.