Skip to Main Content
Skip Nav Destination
GEOREF RECORD

The pH of aqueous bentonite suspensions

Stephan Kaufhold, Reiner Dohrmann, Dietrich Koch and Georg Houben
The pH of aqueous bentonite suspensions
Clays and Clay Minerals (June 2008) 56 (3): 338-343

Abstract

The pH of aqueous bentonite suspensions is known to be influenced by carbonates present even in minor amounts. On the other hand, at high solid:liquid ratios (at standard pH measurement conditions: 2% w/w suspension), the type of exchangeable cation in the smectite is also known to determine pH (particularly Na (super +) or Ca (super 2+) ). By cation-exchange tests we proved that exchanging the Ca (super 2+) for Na (super +) results in an increase in the pH. However, this increase in pH was only found if excess salts were removed from the system (by washing or dialysis, respectively). The effect of the type of exchangeable cation can, at least partially, be explained by hydrolysis of Ca (super 2+) . On the other hand, a pronounced alkalinity of Na bentonites is observed which can, at least partially, be attributed to the hydrolysis of montmorillonite (Na (super +) is exchanged for H (super +) of water). The increase in the volume of the Stern layer, caused by increasing the degree of delamination, is also suggested to play a role. H (super +) and Na (super +) are concentrated in the Stern layer. Hence, increasing the Stern layer volume decreases the amount of H (super +) and Na (super +) in solution and thus increases pH. Unfortunately, both processes, montmorillonite hydrolysis and delamination, depend on the ionic strength. Distinguishing the processes quantitatively, therefore, is an analytical challenge, and impossible based on the data presented here. To model the pore-water chemistry of clays and clay stones, all of the above-mentioned processes have to be considered. It is possible that other reactions, not identified in the present work, contribute toward the pH values of aqueous bentonite suspensions.


ISSN: 0009-8604
EISSN: 1552-8367
Coden: CLCMAB
Serial Title: Clays and Clay Minerals
Serial Volume: 56
Serial Issue: 3
Title: The pH of aqueous bentonite suspensions
Affiliation: BGR Bundesanstalt fuer Geowissenschaften und Rohstoffe, Hannover, Federal Republic of Germany
Pages: 338-343
Published: 200806
Text Language: English
Publisher: Clay Minerals Society, Clarkson, NY, United States
References: 11
Accession Number: 2008-104158
Categories: Sedimentary petrology
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 1 table
Secondary Affiliation: LBEG Landesamt fuer Bergbau, Energie und Geologie Hannover, DEU, Federal Republic of GermanyS&B Industrial Minerals, DEU, Federal Republic of Germany
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Abstract, Copyright, Clay Minerals Society. Reference includes data from GeoScienceWorld, Alexandria, VA, United States
Update Code: 200836
Close Modal

or Create an Account

Close Modal
Close Modal