This document discusses different methods for purifying colloidal dispersions, including dialysis, electrodialysis, and ultrafiltration. Dialysis involves diffusing low molecular weight impurities out of a colloidal solution through a semi-permeable membrane. Electrodialysis enhances this diffusion process by applying an electric potential. Ultrafiltration uses an ultrafilter membrane with small pores to retain colloidal particles while filtering out smaller solutes under pressure.

1. PURIFICATION OF COLLOIDAL
DISPERSION
Sruthi Prabha k
Assistant Professor
Karuna College of Pharmacy, Palakkad

2. PURIFICATION OF COLLOIDAL
DISPERSION
• Colloidal dispersion contain impurities like low molecular
weight water soluble substances and electrolytes
• These should be removed to obtain a pure sol
• Methods used for purification of colloids are
1.Dialysis
2.Electrodialysis
3.Ultrafiltration

3. DIALYSIS
PRINCIPLE:-
• Ions or molecules are removed from a colloidal dispersion by
diffusion through a semi permeable membrane

4. DIALYSIS

5. DIALYSIS
• The semi permeable membrane is fixed tightly to one end of
the hollow glass tube
• The colloidal dispersion is placed in the glass tube and which
is suspended in the vessel of water
• Low molecular weight solute or ions diffuse out of the tube in
to water while the colloidal particles remain inside the tube

6. ELECTRODIALYSIS
PRINCIPLE :-
• Similar to dialysis
• Diffusion of ions or molecules are enhanced by applying a
potential difference across the membrane. This method is
called electro dialysis

7. ELECTRODIALYSIS

8. ELECTRODIALYSIS
• An electro dialysis cell consists of three compartments,
two outer and one center compartment
• The center compartment is separated from the outer
compartments by two dialysis membrane supported by screens
• The outer compartments contain water and electrodes

9. ELECTRODIALYSIS
• The center compartment contain colloidal sol
• When an electric potential is applied, the anions from the sol
move towards the anode compartment and cations from the sol
move towards the cathode compartment
• Based on the charge on the colloidal particles they move
towards any of the membrane
• Non electrolyte impurities diffuse in to both the outer
compartments

10. ELECTRODIALYSIS
• As the density of the colloidal particles increases due to its
accumulation, they settled at the bottom of the compartment
• The supernatant liquid can be decanted to get the purified
colloidal sol

11. ULTRA FILTRATION
• Colloidal particles can easily pass through an ordinary filter
paper.
• If this filter paper is impregnated with colloidon or cellophane
or cellulose acetate, the pore size reduces. such modified filter
papers are called ultra filters

12. ULTRA FILTRATION

13. ULTRA FILTRATION
• Colloidal sol is placed in a compartment, that is closed by a
dialysis membrane having pore size 0.003 micron
• Pressure applied on the sol, liquid and low molecular weight
solutes are forced through the membrane
• Colloidal particles are retained within the compartment
• This separation process is called ultra filtration

14. THANK YOU