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Sedimentation of monodisperse and bidisperse hard‐sphere colloidal suspensions
Author(s) -
AlNaafa M. A.,
Selim M. Sami
Publication year - 1992
Publication title -
aiche journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.958
H-Index - 167
eISSN - 1547-5905
pISSN - 0001-1541
DOI - 10.1002/aic.690381012
Subject(s) - cyclohexane , sedimentation , hard spheres , dispersity , spheres , volume fraction , chemistry , colloid , particle (ecology) , thermodynamics , analytical chemistry (journal) , mineralogy , chromatography , polymer chemistry , physics , organic chemistry , geology , computational chemistry , sediment , paleontology , oceanography , astronomy
The effect of concentration on the sedimentation rate of uncharged rigid spheres was investigated. Three submicron sizes of silica spheres were prepared according to the method of Stöber (1968). The particles were sterically stabilized by chemisorption of stearyl alcohol at their surface by the method developed by van Helden (1981). The sterically stabilized silica particles dispersed in cyclohexane are known to behave as hard spheres. Monodisperse gravity sedimentation experiments were carried out for the various particle species over a wide concentration range of ϕ = 0.003 to ϕ = 0.37, where ϕ is the particle volume fraction in cyclohexane. The data for dilute suspensions (ϕ < 0.03) were found to be well described by Batchelor's equation: U/U 0 = 1–6.55ϕ, where U is the sedimentation velocity and U 0 is the Stokes velocity of a sphere in isolation. The data over the entire concentration range (0<ϕ<0.37) were found to be well described by the equation: U/U 0 = (1–ϕ) 6.55 . Bidisperse sedimentation experiments were also carried out, and the dilute data were found to be well represented by Batchelor's 1982 theory for polydisperse suspensions. The high concentration data were analyzed in terms of a model that does not distinguish between interactions of like and unlike particles.