Conversion of CO2 into mineral carbonates using a regenerable buffer to control solution pH

Steel, Karen M., Alizadehhesari, Kimia, Balucan, Reydick D. and Basic, Bruno (Bašić, Bruno) (2013) Conversion of CO2 into mineral carbonates using a regenerable buffer to control solution pH. Fuel, 111 40-47. doi:10.1016/j.fuel.2013.04.033

Author Steel, Karen M.
Alizadehhesari, Kimia
Balucan, Reydick D.
Basic, Bruno (Bašić, Bruno)
Title Conversion of CO2 into mineral carbonates using a regenerable buffer to control solution pH
Formatted title
Conversion of CO2 into mineral carbonates using a regenerable buffer to control solution pH
Journal name Fuel   Check publisher's open access policy
ISSN 0016-2361
Publication date 2013-09
Year available 2013
Sub-type Article (original research)
DOI 10.1016/j.fuel.2013.04.033
Volume 111
Start page 40
End page 47
Total pages 8
Place of publication Oxford, United Kingdom
Publisher Elsevier
Collection year 2014
Language eng
Formatted abstract
• Use of a regenerable buffer (tertiary amine) is studied to enable mineral carbonation.
• Tertiary amines complex protons to give a pH of 8.2 which enables MgCO3 precipitation.
• Increasing temperature from 18 to 85 °C decreases pH by 2.5 pH units.
• Higher temperatures >85 °C might enable low pHs needed for Mg–silicate dissolution.

The barrier that is currently stalling the rapid conversion of magnesium silicate deposits into magnesium carbonate as method for storing CO2 is considered to be the difference in pH needed for magnesium dissolution from the silicate and magnesium precipitation as the carbonate, whereby rapid dissolution requires a low pH of around 1 while rapid precipitation requires a considerably higher pH of around 8. This paper investigates a novel concept which is to use a tertiary amine to bind with protons and raise the pH to around 8 and to then regenerate the amine through the use of heat due to the strength of the amine-proton bond decreasing with increasing temperature. This approach provides the low pH and high temperature that is needed for Mg dissolution and the high pH need for carbonate precipitation. The amine can be thought of as a regenerable buffer.

Dissolution of Mg from serpentine has been found to be favourable with a solids to solution volume of more than 50 g/L to enable a low pH, and with temperatures close to the boiling point of the solution. The pH needed for magnesium carbonate precipitation was found to be approximately 8.2. Both triethylamine and tripropylamine were found to be capable of achieving this at 18 C. Yields of around 20-40 wt.% carbonate were achieved using residence times of approximately 1 h. The pH swing for the tertiary amines was found to be approximately 2.5 pH units between 5 and 85 C, suggesting that an amine capable of achieving a pH of 8.2 at low temperature generates a pH of 5.7 in solution when heated to 85 C. Further work will examine whether the lower pH values needed for serpentine dissolution can be achieved by heating the protonated amine to higher temperatures.
Keyword Mineral carbonation
Regenerable buffer
CO2 sequestration
CO2 mineralisation
Q-Index Code C1
Q-Index Status Confirmed Code
Institutional Status UQ

Document type: Journal Article
Sub-type: Article (original research)
Collections: School of Chemical Engineering Publications
Official 2014 Collection
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Created: Tue, 04 Jun 2013, 13:48:41 EST by Reydick Balucan on behalf of School of Chemical Engineering