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Sedimentation characteristics of two commercial bentonites in aqueous suspensions

Published online by Cambridge University Press:  09 July 2018

S. Akther ,
J. Hwang  and
H. Lee
S. Akther
Affiliation:
Division of Earth and Environmental Science Systems, Pusan National University, Busan 609-735, Korea
J. Hwang
Affiliation:
Division of Earth and Environmental Science Systems, Pusan National University, Busan 609-735, Korea
H. Lee*
Affiliation:
Division of Earth and Environmental Science Systems, Pusan National University, Busan 609-735, Korea
*
*E-mail: hmlee61@hotmail.com
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Abstract

The sedimentation characteristics of two commercial bentonites, Tixoton (organically treated) and Montigel-F (untreated), were investigated using a 3% w/v clay suspension at different concentrations (1, 3.5 and 10%) of NaCl and pH values (2, 7 and 12). Settling rates, floc diameters and sediment volumes were derived from changes in light transmittance using a Turbiscan Ma 2000 instrument.

Both bentonite suspensions were unstable (flocculated) in NaCl solutions. The settling rate increased with increasing concentration of NaCl and was directly related to floc diameter. The sediment volume reduced with increasing NaCl concentrations, a result of greater double layer compression caused by increased ionic strength. At comparable salt concentrations, the organically-treated bentonite (Tixoton) settled at a much slower rate and had a greater sedimentation volume. The suspensions of both organically-treated and untreated bentonites were stable (dispersed) above pH 7 and unstable in acidic conditions. The settling rate for Tixoton under acid conditions was much smaller than that for the Montigel-F. Differences in sedimentation characteristics between the two bentonite samples are probably due to the presence of an anionic polymer (carboxymethyl cellulose: CMC) in Tixoton.

The viscosity of the bentonite suspensions was also studied. The viscosity of the clay suspension is closely related to clay dispersivity in solution. The CMC was highly effective in increasing the viscosity of the bentonite suspensions, but only under neutral and alkaline conditions.

Keywords

bentonitesuspensiondispersionflocculationsettling ratesediment volumeNaClpHdrilling fluidviscosity
Type
Research Article
Information
Clay Minerals , Volume 43 , Issue 3 , September 2008 , pp. 449 - 457
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 2008

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