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.

THE END