Why Does Zeta Potential Change | Zeta Potential And Ph

The most important factor that affects zeta potential is pH
A zeta potential value quoted without a definition of it’s environment (pH, ionic strength, concentration of any additives) is a meaningless number

Why Does Zeta Potential Change?

Imagine a negative zeta potential in suspension

If more alkali is added to this suspension then the particles tend to acquire more negative charge
If acid is added to this suspension then a point will be reached where the charge will be neutralized
Further addition of acid will cause a build up of positive charge
In general, a zeta potential versus pH curve will be positive at low pH and lower or negative at high pH
There may be a point where the curve passes through zero zeta potential
This point is called the isoelectric point and is very important from a practical consideration
It is normally the point where the colloidal system is least stable

Why Does Zeta Potential Change | Zeta Potential and Ph Chart — Why Does Zeta Potential Change – Zeta Potential and Ph Chart

In the above example it can be seen that if the dispersion pH is below 4 or above 8 there is sufficient charge to confer stability. However if the pH of the system is between 4 and 8 the dispersion may be unstable. This is most likely to be the case at around pH 6 (the isoelectric point)

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