Diffusiophoresis

Ejfect of Gas Saturation in Scrubbing If hot unsaturated gas is introduced into a wet scrubber, spray particles will evaporate to cool and saturate the gas. The evaporating liquid molecules moving away from the target droplets will repel particles which might collide with them. This results in the forces of diffusiophoresis opposing particle... 

Radiometric forces Weak forces that cause the motion of particulate matter, including diffusiophoresis, thermophoresis, and photophoresis. 

Flux-force-condensation scrubbers combine the effects of flux force (diffusiophoresis and thermophoresis) and water-vapor condensation. These scrubbers contact hot, humid gas with subcooled liquid, and/or they inject steam into saturated gas, and they have demonstrated that a number of these novel devices can remove fine particulates (see Fig. 22-26). Although limited in terms of commercialization, these systems may find application in many industries. 

For a consideration of wet deposition mechanism it is useful to make a distinction between processes transferring material to cloud droplets before they begin their descent as a raindrop, known collectively as rain-out and processes transferring material to falling raindrops known as washout, There are five mechanisms [8] by which particulate and gaseous compounds may be captured by cloud or rain drop diffusiophoresis, brownian diffusion, impact and interception, solution and oxidation of gaseous species (notably SO2 and NO2) and the cloud condensation nuclei (CCN) pathway. 

Waldmann, L., and Schmitt. K. H. (1966) Thermophoresis and Diffusiophoresis of Aerosols. Chapter VI in Davies, C. N. (Ed.) Aerosol Science, Academic, New York. 

To keep the subject matter to manageable proportions. 1 have omitted interesting problems of a specialized nature, such as photophoresis and diffusiophoresis, which are seldom of controlling importance in applied problems. Details of the kinetic theory of aerosols have also been omitted. Although of major importance, they usually enter fully developed, so to. speak, in applications. Besides, their derivation is covered in other books on aerosol science. 

Aerosol particles may also be removed in the clouds by the different phoretic forces, e.g. by diffusiophoresis. This phenomenon involves the motion of particles due to concentration gradient of condensing or evaporating vapour (Goldsmith et al., 1963). In the case of condensation, particles displace towards the drop surface. According to Goldsmith et al. (1963), velocity caused by diffusiophoresis is... 

Solution concentration gradient Diffusiophoresis Particle growth and dissolution Marangoni effect ... 

The gradient in the concentration of substance dissolved in dispersion medium may lead to diffusiophoresis of dispersed colloidal particles. The theory of diffusiophoresis was developed by B.V. Derjaguin and his collaborators [16]. According to the concepts discussed in their studies, there are two major causes for diffusiophoresis. First, the presence of diffusion adsorption layer (containing ions and uncharged molecules) in a vicinity of the surface and the existence of external concentration gradient of solute result is a complex osmotic pressure distribution near the surface, which causes particle motion. In electrolyte solutions the particle velocity due to diffusiophoresis is proportional to the square of -potential. Second, changes... 

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