Influence of alkaline (pH 8.3-12.0) and saline solutions on chemical, mineralogical and physical properties of two different bentonites

Tiina Heikola (Corresponding Author), S. Kumpulainen, Ulla Vuorinen, L. Kiviranta, P. Korkeakoski

Research output: Contribution to journalArticleScientificpeer-review

6 Citations (Scopus)

Abstract

The interaction of two different bulk bentonites (Na- and Ca-types) with three types of simulated cement waters (pH 9.7, 11.3 and 12.0) and one saline groundwater simulate (pH 8.3) as a reference, was studied in batch reactors at 25°C. The solution pH was monitored in order to keep the pH as steady as possible by replacing the leaching solution with fresh one when needed. After 554 days, one set of parallel samples was removed from the experiment in order to investigate the possible changes in the bentonite materials.

The buffering capacity of bentonite was clearly observed, especially at the beginning of the high-pH experiments, as the pH of the leaching solutions decreased quite dramatically due to interaction with bentonite. The solution chemistry results showed a decrease of Ca content in all leachate samples, but especially in pH 12.0 experiments. Small amounts of silica were released throughout the experiment. Both bentonites in pH 12.0 experiments also released detectable amounts of Al, while in the lower pH experiments the levels were below detection limit. These observations were also supported by chemical analyses of the bentonite materials. Only minor changes were detected in the mineralogy, and they were mainly concentrated on experiments at pH 11.3 and pH 12.0. The measured swelling pressure showed an increase in pH 12.0 experiments. The results obtained in this research may facilitate modelling of bentonite interaction with high-pH solutions.
Original languageEnglish
Pages (from-to)309-329
Number of pages20
JournalClay Minerals
Volume48
Issue number2
DOIs
Publication statusPublished - 2013
MoE publication typeA1 Journal article-refereed

Fingerprint

Sodium Chloride
Chemical properties
chemical property
Bentonite
Physical properties
physical property
bentonite
experiment
Experiments
Leaching
leaching
Mineralogy
Batch reactors
buffering
Silicon Dioxide
swelling
leachate
Swelling
Groundwater
Cements

Keywords

  • alkaline
  • alteration
  • batch
  • bentonite
  • bentonite buffer
  • saline spent nuclear fuel
  • underground repository

Cite this

Heikola, Tiina ; Kumpulainen, S. ; Vuorinen, Ulla ; Kiviranta, L. ; Korkeakoski, P. / Influence of alkaline (pH 8.3-12.0) and saline solutions on chemical, mineralogical and physical properties of two different bentonites. In: Clay Minerals. 2013 ; Vol. 48, No. 2. pp. 309-329.
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Influence of alkaline (pH 8.3-12.0) and saline solutions on chemical, mineralogical and physical properties of two different bentonites. / Heikola, Tiina (Corresponding Author); Kumpulainen, S.; Vuorinen, Ulla; Kiviranta, L.; Korkeakoski, P.

In: Clay Minerals, Vol. 48, No. 2, 2013, p. 309-329.

Research output: Contribution to journalArticleScientificpeer-review

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T1 - Influence of alkaline (pH 8.3-12.0) and saline solutions on chemical, mineralogical and physical properties of two different bentonites

AU - Heikola, Tiina

AU - Kumpulainen, S.

AU - Vuorinen, Ulla

AU - Kiviranta, L.

AU - Korkeakoski, P.

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N2 - The interaction of two different bulk bentonites (Na- and Ca-types) with three types of simulated cement waters (pH 9.7, 11.3 and 12.0) and one saline groundwater simulate (pH 8.3) as a reference, was studied in batch reactors at 25°C. The solution pH was monitored in order to keep the pH as steady as possible by replacing the leaching solution with fresh one when needed. After 554 days, one set of parallel samples was removed from the experiment in order to investigate the possible changes in the bentonite materials.The buffering capacity of bentonite was clearly observed, especially at the beginning of the high-pH experiments, as the pH of the leaching solutions decreased quite dramatically due to interaction with bentonite. The solution chemistry results showed a decrease of Ca content in all leachate samples, but especially in pH 12.0 experiments. Small amounts of silica were released throughout the experiment. Both bentonites in pH 12.0 experiments also released detectable amounts of Al, while in the lower pH experiments the levels were below detection limit. These observations were also supported by chemical analyses of the bentonite materials. Only minor changes were detected in the mineralogy, and they were mainly concentrated on experiments at pH 11.3 and pH 12.0. The measured swelling pressure showed an increase in pH 12.0 experiments. The results obtained in this research may facilitate modelling of bentonite interaction with high-pH solutions.

AB - The interaction of two different bulk bentonites (Na- and Ca-types) with three types of simulated cement waters (pH 9.7, 11.3 and 12.0) and one saline groundwater simulate (pH 8.3) as a reference, was studied in batch reactors at 25°C. The solution pH was monitored in order to keep the pH as steady as possible by replacing the leaching solution with fresh one when needed. After 554 days, one set of parallel samples was removed from the experiment in order to investigate the possible changes in the bentonite materials.The buffering capacity of bentonite was clearly observed, especially at the beginning of the high-pH experiments, as the pH of the leaching solutions decreased quite dramatically due to interaction with bentonite. The solution chemistry results showed a decrease of Ca content in all leachate samples, but especially in pH 12.0 experiments. Small amounts of silica were released throughout the experiment. Both bentonites in pH 12.0 experiments also released detectable amounts of Al, while in the lower pH experiments the levels were below detection limit. These observations were also supported by chemical analyses of the bentonite materials. Only minor changes were detected in the mineralogy, and they were mainly concentrated on experiments at pH 11.3 and pH 12.0. The measured swelling pressure showed an increase in pH 12.0 experiments. The results obtained in this research may facilitate modelling of bentonite interaction with high-pH solutions.

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KW - batch

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KW - bentonite buffer

KW - saline spent nuclear fuel

KW - underground repository

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