Abstract
The detachment of soil particles from capillary walls of a fabric, the electro-osmotic washing, was found effective in detergency, giving even higher detergent efficiency than that obtained by the standard mechanical washing by the Launder-O-Meter. Moreover, the damage of the cloth was practically absent, as observed by the scanning electron microscope. Thus, it was concluded that the electro-osmotic flow in capillaries acted effectively in producing the force to remove soil particles from walls. A theory was then derived on the basis of the Bernoulli law together with the DLVO theory of colloid stability. The lift force on soil particles due to the deformation of stream-line of electro-osmotic flow is proportional to the square of flow velocity, and hence to the square of zeta potential. On the other hand, the soil particle is attached to the wall by the van der Waals attraction, which is opposed by the electrostatic repulsion, the latter being proportional to the square of zeta potential. Thus, the total force acting on the soil particle in electro-osmotic flow must be a linear function of zeta potential squared. Experimental results obtained were in agreement with the theoretical expectation, when we assume the first order reaction scheme for the change in time of the fraction of particles remaining on the wall.
