Abstract
Nanoparticles play a major role in industrial processes and natural phenomena in a variety of fields including chemical engineering, chemistry, physics, public health and biology. Nanoparticles are suspended in fluids during production, handling, processing, and by unintentional and/or undesirable release to the environment. In many cases the suspending fluid is a gas, as for example in large scale production, air pollution, clean room applications and many more. The small size of nanoparticles makes it possible to compare their transport properties to the fluid itself. Brownian particle diffusion is one of the most important mechanisms leading to significant transport rates. Diffusion is well known in mass transfer, however, differences arise because of the wide spectrum of nanoparticle sizes and their morphology (aggregate structure) - a concept understood in particle science and technology but needed in many diverse fields of nanoparticle applications. Nanoparticle transport can be controlled by external force fields because these forces may act exclusively on the nanoparticles and have negligible effects on fluid molecules. These include thermophoresis and forces in electrical fields.
Highlights
1.1 Importance of nanoparticles and their transport Nanoparticles play a major role in many industrial processes and natural phenomena in a variety of fields including chemical engineering, chemistry, physics, public health and biology
If the solvent fully penetrates the chain the Rouse theory can be applied (Rouse, 1953). In this case the friction coefficient of the chain can be approximated by the sum of the friction coefficients of the individual “beads”: ς agg = ς p ⋅ N p. If we apply these concepts to agglomerates suspended in gas, we find similar conditions for nanoparticle agglomerates in the free molecular regime
More than one third of all particles traveled at least that distance from their original position during that time interval which can been seen from the Gaussian curve represented by Eq 2
Summary
1.1 Importance of nanoparticles and their transport Nanoparticles play a major role in many industrial processes and natural phenomena in a variety of fields including chemical engineering, chemistry, physics, public health and biology. Examples of man-made ambient nanoparticles are emissions from industrial operations, farming, motor vehicles, ships, jet planes and solid fuel rockets In these processes, nucleation and coagulation are major mechanisms in the formation and dynamics of nanoparticles. Brownian coagulation leads to the formation of larger particles and a decrease in the total particle number concentration These mechanisms result in ambient ultrafine particles (nanoparticles) of different morphological properties and may be present as liquid droplets, compact solid particles, and agglomerates. Agglomerate formation occurs due to particle collisions (coagulation) and the fusion (formation chemical bonds) of particles in contact forming chemical bonds (sintering) Such mechanisms result in agglomerate structures with fractal dimension of about 1.8 (Friedlander, 2000) (Fig. 1b).
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