Formation and evolution of channels and voids in gravity sedimentation of kaolin suspensions studied by MRI

Abstract

Magnetic resonance imaging was employed for the first time to visualize the gravity sedimentation of kaolin suspensions, allowing the internal spatial distribution of kaolin during sedimentation to be investigated. This revealed very complex behaviours dependent on the initial kaolin concentration and solution pH, including vertical channelling, curved channelling, layers/voids and voids only. We show that the number of channels formed increases with the solution pH, with the channels distributed in an evenly spaced-out pattern. The discovery of spontaneous and very stable “void” spaces within the suspension is similar to that previously reported in charged gases (plasmas) and in suspensions of charged Latex particles, which have been explained by the presence of many-body attractive forces. The discovery of such spontaneous voids occurring during kaolin sedimentation, may provide a fundamental explanation for the formation of water channels.