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Settling of a charged hydrophobic rigid colloid in aqueous media under generalized gravitational field
Author(s) -
Kundu Dipankar,
Bhattacharyya Somnath,
Gopmandal Partha P.,
Ohshima Hiroyuki
Publication year - 2021
Publication title -
electrophoresis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.666
H-Index - 158
eISSN - 1522-2683
pISSN - 0173-0835
DOI - 10.1002/elps.202000240
Subject(s) - electrokinetic phenomena , colloid , sedimentation , stokes' law , electric field , chemistry , gravitational field , mechanics , slip (aerodynamics) , centrifuge , settling , classical mechanics , materials science , physics , stokes flow , thermodynamics , nanotechnology , geology , paleontology , flow (mathematics) , quantum mechanics , sediment , nuclear physics
The hindrance created by the induced electric filed on the sedimentation of a charged colloid in an aqueous media is studied through numerical modeling. The colloid is considered to be hydrophobic, sedimenting under gravity or a centrifugal force (generalized gravity). The deformation of the charge cloud around the colloid induces an electric field, which generates electrical dipole force on the colloid. The sedimentation velocity is governed by the balance of an electric force, hydrodynamic drag, and gravitational force. Governing equations based on the first principle of electrokinetics is solved numerically through a control volume approach. The dependence of the sedimentation velocity on the electrical properties and slip length of the colloid is investigated. The sedimentation velocity of the charged colloid is slower than the corresponding uncharged particle and this deviation magnifies as the charge density as well as particle slip length is increased. An enhanced g ‐factor creates a size dependency of the charged colloids. The induced sedimentation field is obtained to analyze the electrokinetics. Surface hydrophobicity enhances the sedimentation velocity, which in turn manifests the induced sedimentation field. However, the sedimentation velocity of a charged hydrophobic colloid is lower than the corresponding uncharged hydrophobic particle and this deviation manifests as slip length is increased.