Diffusion of particles refers to their movement in liquid or gas. Particles suspended in a liquid or a gas are in continuous interaction with the surrounding liquid or gas molecules. The latter are in constant random motion (Brownian motion), meaning that small suspended particles (especially those of less than approximately 100 nm)  are consequently also in constant random zigzag motion, leading to homogenous diffusion as well as increased frequency of particle coagulation and attachment (see also atmospheric dry deposition).




Occurs in






 Fate descriptors 




D=\frac{k\cdot T\cdot C_{c}}{3\pi \cdot \eta\cdot d_{p} }

C_{c}=1+\frac{2\lambda }{d}\cdot \left [1.165 +0.482\cdot exp\left ( -\frac{0.997}{Kn} \right )\right ]

Particle diffusivity in air

x_{rms}=\sqrt{2\cdot D\cdot t}

Root mean square displacement

            Particle size                                     Temperature

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Read also



W. Hinds (1999), Aerosol Technology – Properties, Behavior, and Measurement of Airborne Particles, John Wiley & Sons.
A. Einstein (1905),  Über die von der molekularkinetischen Theorie der Wärme geforderte Bewegung von in ruhenden Flüssigkeiten suspendierten Teilchen, Ann. Phys. 17: 549-560.



  Christof Asbach

  Institut für Energie- und Umwelttechnik (IUTA)

  Email: asbach@iuta.de