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Mineral Speciation for CO2 Captured by Potassium Hydroxide.
Ehsan Ezzatpour Ghadim1, Stephanie Bachmann2, Rodrigo S Correa3,4
1School of Engineering, University of Warwick, Coventry, CV4 7AL, UK.
Chemistryopen
|October 14, 2025
Summary
Greenhouse gas capture using potassium hydroxide (KOH) produces valuable minerals. Multimodal analysis reveals KHCO3 and K2CO3 mixtures, with high-purity KHCO3 from aqueous-ethanol solutions, advancing CO2 utilization strategies.
Area of Science:
- Materials Science
- Chemistry
- Environmental Science
Background:
- Greenhouse gas capture, particularly CO2, is crucial for mitigating global warming.
- Mineral products from CO2 capture can serve as industrial feedstock.
- Potassium hydroxide (KOH) is explored as a capture agent in various solvent systems.
Purpose of the Study:
- To investigate the mineral products formed by atmospheric CO2 capture using KOH.
- To analyze the composition and speciation of these mineral products across different solvent conditions.
- To apply advanced analytical techniques for detailed characterization.
Main Methods:
- Multimodal analysis combining single-crystal X-ray diffraction (SCXRD) and powder X-ray diffraction (PXRD) with Pawley and Rietveld refinements.
- High-field nuclear magnetic resonance (NMR) spectroscopy (1H, 13C, 39K), including 2D NOESY and ultrahigh-field 39K NMR.
- Study of reactions in aqueous, aqueous-ethanol, and aqueous-acetone solutions, including solid CO2 enrichment.
Main Results:
- Potassium bicarbonate (KHCO3) was identified as a product in all reaction systems via SCXRD.
- PXRD and NMR data indicated mixtures of crystalline and amorphous phases, primarily KHCO3 and potassium carbonate (K2CO3) and its hydrates.
- Aqueous-ethanol solutions yielded high-purity KHCO3, while other systems showed minor KOH presence.
Conclusions:
- The study elucidates the speciation of potassium minerals formed during CO2 capture.
- A multimodal analytical approach provides comprehensive insights into product composition.
- Optimized solvent conditions, like aqueous-ethanol, can enhance the purity of valuable mineral products like KHCO3.
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