The role of interfacial electrical conditions in detergency

A detergent system is treated as a lyophobic colloid system and the interaction between particulate soil and fibres in an electrolyte solution is represented by the superposition of the potentials due to London—van der Waals' attraction, the Born repulsion and double layer repulsion. The resultant potential-energy curves are used to discuss the influence of electrical forces in soil removal and redeposition. It is shown that the particle size of the soil, and the concentration and valency of electrolyte, are important parameters which determine the influence of interfacial electrical conditions in detergency. It is also shown that ease of soil removal is incompatible with a high degree of stability against redeposition. The relation between the surface potential (ψ0) which is used in the theory to describe interfacial electrical conditions, and the zeta potential, derived from electrokinetic experiments, is discussed, and reasons for the lack of correlation between interfacial electrical conditions (described by zeta potentials) and detergent efficiency are given.