IMK 209 presentation

FORCES BETWEEN ,[object Object],COLLOIDAL PARTICLES,[object Object]

Hye everyone.......Types of electrostatic forcesrepulsive and interactive..,[object Object]

Main forces that affect the colloids system…Van Der Waals attractive forceselectrostatic repulsive forces,[object Object]

[object Object],[object Object]

DLVO THEORY,[object Object],The DLVO theory, named after the two Russian scientists (Derjaguin and Laudau) and the two Dutch scientists (Verwey and Overbeek) who developed it around the 1940’s, is a corner stone of colloid science.,[object Object]

Boris VladimirovichDerjaguin,[object Object],Lev DavidovichLandau,[object Object],Verwey,[object Object],Overbeek,[object Object]

The central concept of the DLVO theory is that the total interaction energy of two surfaces or particles is given by the summation of the attractive and repulsive contributions. ,[object Object]

For small distances, the sum of the two energies is always – ve (i.e. net attractive) ⟹ cause aggregation,[object Object],When the sum of two energies is + ve ⟹ repulsive force,[object Object]

The Electrical Double Layer,[object Object]

Development of a net charge at the particle surface affects the distribution of ions in the surrounding interfacial region, resulting in an increased concentration of counter ions (ions of opposite charge to that of the particle) close to the surface ,[object Object],Thus an electrical double layer exists round each particle ,[object Object],An electrical double layer exists around each particle.,[object Object]

The liquid layer surrounding the particle exists as two parts; an inner region (Stern layer) where the ions are strongly bound and an outer (diffuse) region where they are less firmly associated ,[object Object],Within this diffuse layer is a notional boundary known as the slipping plane, within which the particle acts as a single entity ,[object Object],The potential at this boundary is known as the zeta potential,[object Object]

What is zeta potential???,[object Object],Zeta potential is ~~~ ,[object Object],[object Object]

The potential difference between the dispersion medium and the stationery layer of fluid attached to the dispersed particle.,[object Object]

When the potential is low, attraction exceeds repulsion and the dispersion will break and coagulate. Considered as not stable.,[object Object],When the potential is high, repulsion force is higher than attraction force, the dispersion is considerable stable.,[object Object]

IMK 209 presentation

IMK 209 presentation

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IMK 209 presentation