DIFFUSIOPHORESIS CAUSED BY GRADIENTS OF STRONGLY ADSORBING SOLUTES

A theory is developed for diffusiophoresis of rigid insulating particles in a gradient of an adsorbing solute for the case of strong adsorption. The range of the interaction between the solute and the particle's surface is assumed small relative to the particle's radius (a), but the adsorption length (K), defined as the thickness of a film of solution having the bulk concentration which would contain the same amount of solute per unit area as adsorbs, is allowed to be arbitrarily large. An expression relating the particle's velocity to the solute concentration gradient is obtained in analytical form. If K >> a, then the particle's velocity is determined by a rather than by K.