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Title: Phyllosilicate mineral dissolution upon alkaline treatment under aerobic and anaerobic conditions

Abstract

The dissolution of phyllosilicate minerals exposed to high-pH environments has been studied to determine the influence of alkaline treatments and variable redox conditions on clay dissolution and the potential formation of new phases via incongruent dissolution phenomena. The present study focused on the dissolution of phyllosilicate minerals (illite, muscovite, and montmorillonite) under anaerobic and aerobic conditions using comparative solutions (sodium hydroxide and ammonium hydroxide) at similar ionic strength in the presence and absence of oxygen. Our batch data show that there is a rapid decrease in aluminum dissolution (< 240 hrs) and slow increase in silica over time (up to 1440 hrs). This trend was particularly evident for montmorillonite which shows the greatest dissolution for ammonium hydroxide, likely due to intercalation of the polyatomic cation ammonium into the mineral’s expandable layers. When comparing alkaline treatments, the strong base, sodium hydroxide, dissolved more of the mica minerals, illite and muscovite, likely due to ion-pairing between the silicate tetrahedra [SiO4]n- and Na+ cations in solution. In addition, redox conditions affect the systems similarly with treatment, although the sodium hydroxide treatment results in greater variability in solution redox conditions. For all investigated phyllosilicates, the calculated aqueous aluminum and silicon ratios over time aremore » significantly different from the minerals’ stoichiometric ratios. As a result, we conclude that incongruent dissolution occurred and suggest formation of secondary precipitates. Understanding the potential for clay mineral alterations from interaction with alkaline solutions has implications for in situ remediation, mining operations, and waste interactions with the subsurface. This research shows that incongruent dissolution is likely and will lead to secondary precipitation which may have long term physical and chemical impacts in the subsurface.« less

Authors:
 [1];  [2];  [1]; ORCiD logo [2];  [2]
  1. Florida International University
  2. BATTELLE (PACIFIC NW LAB)
Publication Date:
Research Org.:
Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
1605414
Report Number(s):
PNNL-SA-149956
DOE Contract Number:  
AC05-76RL01830
Resource Type:
Journal Article
Journal Name:
Applied Clay Science
Additional Journal Information:
Journal Volume: 189
Country of Publication:
United States
Language:
English
Subject:
mineral dissolution, phyllosilicate, alkaline, ammonia

Citation Formats

Di Pietro, Silvina, Emerson, Hilary P., Katsenovich, Yelena, Qafoku, Nikolla, and Szecsody, James E. Phyllosilicate mineral dissolution upon alkaline treatment under aerobic and anaerobic conditions. United States: N. p., 2020. Web. doi:10.1016/j.clay.2020.105520.
Di Pietro, Silvina, Emerson, Hilary P., Katsenovich, Yelena, Qafoku, Nikolla, & Szecsody, James E. Phyllosilicate mineral dissolution upon alkaline treatment under aerobic and anaerobic conditions. United States. doi:10.1016/j.clay.2020.105520.
Di Pietro, Silvina, Emerson, Hilary P., Katsenovich, Yelena, Qafoku, Nikolla, and Szecsody, James E. Fri . "Phyllosilicate mineral dissolution upon alkaline treatment under aerobic and anaerobic conditions". United States. doi:10.1016/j.clay.2020.105520.
@article{osti_1605414,
title = {Phyllosilicate mineral dissolution upon alkaline treatment under aerobic and anaerobic conditions},
author = {Di Pietro, Silvina and Emerson, Hilary P. and Katsenovich, Yelena and Qafoku, Nikolla and Szecsody, James E.},
abstractNote = {The dissolution of phyllosilicate minerals exposed to high-pH environments has been studied to determine the influence of alkaline treatments and variable redox conditions on clay dissolution and the potential formation of new phases via incongruent dissolution phenomena. The present study focused on the dissolution of phyllosilicate minerals (illite, muscovite, and montmorillonite) under anaerobic and aerobic conditions using comparative solutions (sodium hydroxide and ammonium hydroxide) at similar ionic strength in the presence and absence of oxygen. Our batch data show that there is a rapid decrease in aluminum dissolution (< 240 hrs) and slow increase in silica over time (up to 1440 hrs). This trend was particularly evident for montmorillonite which shows the greatest dissolution for ammonium hydroxide, likely due to intercalation of the polyatomic cation ammonium into the mineral’s expandable layers. When comparing alkaline treatments, the strong base, sodium hydroxide, dissolved more of the mica minerals, illite and muscovite, likely due to ion-pairing between the silicate tetrahedra [SiO4]n- and Na+ cations in solution. In addition, redox conditions affect the systems similarly with treatment, although the sodium hydroxide treatment results in greater variability in solution redox conditions. For all investigated phyllosilicates, the calculated aqueous aluminum and silicon ratios over time are significantly different from the minerals’ stoichiometric ratios. As a result, we conclude that incongruent dissolution occurred and suggest formation of secondary precipitates. Understanding the potential for clay mineral alterations from interaction with alkaline solutions has implications for in situ remediation, mining operations, and waste interactions with the subsurface. This research shows that incongruent dissolution is likely and will lead to secondary precipitation which may have long term physical and chemical impacts in the subsurface.},
doi = {10.1016/j.clay.2020.105520},
journal = {Applied Clay Science},
number = ,
volume = 189,
place = {United States},
year = {2020},
month = {5}
}