Electroosmosis process

The movement ( migration) of the dispersion medium of colloidal solution , under the influence of electrical field, when dispersed particles are prevented from moving is known as ELECTROOSMOSIS.
It is basically a drying technique .
It is used to dewatering a substance or a colloidal solution electrically.

1. ELECTROOSMOSIS Presented By: WISHAL BUTT

2. DEFINITION The movement ( migration) of the dispersion medium of colloidal solution , under the influence of electrical field, when dispersed particles are prevented from moving is known as ELECTROOSMOSIS.

3. HISTORY Electro-osmotic flow was first reported in 1807 by F. Friedrich Reuss. Dewatering of clay.

4. Electro-osmosis was discovered independently in 1814 by the English chemist Robert Porrett Jr

5. PURPOSE It is basically a drying technique . It is used to dewatering a substance or a colloidal solution electrically.

6. INSTRUMENTATION The electro-osmosis is carried out in a specially designed apparatus. The apparatus consists of a bigger tube having two side tubes T and T’ attached to its ends. The bigger tube is divided into three compartments A, B and C by means of two semi-permeable membranes. A tube carrying a stop-cock is attached to the central compartment A. Two platinum electrodes are inserted in the outer compartments B and C.

7. INSTRUMENTATION

8. WORKING A colloidal dispersion is placed in the central compartment A. the outer compartments B and C are filled with water. The water in compartments B and C also extends to the side tube T and T/. The function of membrane is to prevent the movement of colloidal particles. when a potential difference is applied across the electrodes held close to the membranes in the compartment B and C, dispersion medium begins to move.

9. Cont….. If the particles carry positive charge , the dispersion medium would start moving towards the anode and the level of water in the side tube T would be seen to rise. indicating the presence of negative charge on the dispersion medium. If the particles carry negative charge , the dispersion medium would be seen to move towards cathode and water in the side tube T would start rising.

10. Step-1: A long tube , having two side tubes, T & T’

11. STEP- 2: Colloidal dispersion is separated from chamber Y & Z by the semipermeable membrane.

12. STEP-3: H₂O is filled in compartment y & Z

13. STEP-4: Potential difference is applied.

14. IMPORTANT TERMS ZETA POTENTIAL: zeta potential is the potential difference between the dispersion medium and the stationary layer of fluid attached to the dispersed particle.

15. RELATION Zeta potential can b measured by the process of electroosmosis as well

16. SEMIPERMEABLE: A semipermeable membrane is a membrane that only allows certain types of particles to move through it under certain conditions.

17. APPLICATIONS Dewatering of moist clay: soft clay whose moisture content cannot be reduced by conventional dewatering method , can be reduced by electroosmosis. Electrodes are fixed in soil & current supplied & water moves from anode to cathode. An ejector well system is used as cathode which collects & removes water from the ground.

18. 2. Removal of water from peat 3. Drying of dye paste:

19. DIFFERENCE ELECTROOSMOSIS liquid with free charge move. Semipermeable membrane present. Dispersed phase is stationary. ELECTROPHORESIS charged solid particles move Semipermeable membrane absent. Dispersed phase is not stationary.