(358g) Origins of Concentration Gradients for Diffusiophoresis
Fluid and particle transport that is driven by gradients of pressure, gravity, or electro-magnetic potential is well-known and studied in many fields. A subtler type of transport, called diffusiophoresis, occurs in a gradient of chemical concentration, either electrolyte or non-electrolyte. Although this mechanism of particle transport is well-known, the diffusiophoresis mechanism is often considered to be an esoteric laboratory phenomenon. However, in this talk it is shown that concentration gradients can develop in a surprisingly wide variety of physical phenomena â?? imposed gradients, asymmetric reactions, dissolution, crystallization, evaporation, mixing, sedimentation, and others â?? so that diffusiophoresis is in fact a very common transport mechanism in complex fluids, in both natural and artificial systems. It is anticipated that in georeservoir extractions, physiological systems, drying operations, laboratory and industrial separations, crystallization operations, membrane processes, and many other situations, diffusiophoresis is already occurring â?? often without being recognized â?? and that opportunities exist for designing this transport to great advantage. In this talk methods are shown for identifying when diffusiophoresis might be important, and for analyzing transport in complex fluid systems, from both a modeling and experimental standpoint.