Detergency

It is a process by which soil is removed from a surface and undergoes solubilization or dispersion.

Result of several physicochemical phenomenons taking place at the interface of three phases : surface/soil/detergent.

The phenomenons are :

– Wetting of surface

– Removal of soil from surface

 – Avoiding re-deposition of soil on surface.

Basic Principal:

1.Wetting of surface: The detergent must come into contact with the surface so that adherence forces of detergent with subtract of surface should be higher than  adherence forces of soil with subtract of surface

          F_{detergent/surface} > F_{soil /surface}   ( Here F = adherence force )

It lower the superficial tension of the detergent solution and the interfacial tensions between aqueous bath, soil and surface

2.Removal of soil:The detergent solution wets the surface, is absorbed by it and lowers the surface’s attraction to allow the soil to separate itself from the surface.

3.Avoiding re-deposition

Chemical reactions

 – lipids undergo saponification

 – mineral soil undergoes solubilization

 – soil undergoes emulsification

 Liquid soil = hydrophobic ; detergent solution = hydrophilic.