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Salinity and Thermal Effects on CO2 Hydrate Formation and Distribution Probed by Raman and Optical Microscopy in
Sadain Zafar1,2, Claire Pirim1,2, Bertrand Chazallon1,2
1Univ. Lille, CNRS, UMR 8523PhLAMLaboratoire de Physique des Lasers Atomes et Molécules, F-59000 Lille, France.
ACS Omega
|March 9, 2026
Summary
This study reveals how salt concentration affects carbon dioxide (CO2) hydrate formation and stability using advanced microscopy. Salinity influences hydrate growth patterns and dissociation temperatures, crucial for CO2 capture and water desalination technologies.
Area of Science:
- Geochemistry and Materials Science
- Focuses on the formation and behavior of clathrate hydrates, specifically carbon dioxide (CO2) hydrates, under varying conditions.
Background:
- Clathrate hydrates are ice-like structures that can trap gases, with potential applications in desalination and CO2 sequestration.
- Understanding hydrate formation in saline environments is critical for these applications, but microscale processes are not fully understood.
Purpose of the Study:
- To investigate the nucleation, growth, and phase distribution of CO2 hydrates in NaCl solutions using advanced techniques.
- To elucidate the influence of salinity and thermal conditions on hydrate formation and dissociation.
Main Methods:
- Synthesis of CO2 hydrates in NaCl solutions (0-15 wt %) within novel high-pressure microcapillaries.
- Analysis using micro-Raman spectroscopy and optical microscopy for spatially resolved insights.
- Examination of thermal sequences including heating to dissociation and cooling under subcooling.
Main Results:
- Dissociation temperatures of CO2 hydrates decrease with increasing salinity.
- Saline systems exhibit heterogeneous hydrate-brine coexistence and interfacial crystallization, unlike pure water systems.
- Spectral markers effectively distinguish between dissolved CO2, liquid CO2, and enclathrated CO2.
- Subcooling conditions influence hydrate coverage and heterogeneity, modulated by salinity and seed availability.
Conclusions:
- Salinity significantly impacts CO2 hydrate formation kinetics, spatial distribution, and thermodynamic stability.
- Microscale observations provide mechanistic links to macroscopic hydrate formation processes.
- Findings are directly relevant for optimizing hydrate-based CO2 capture and water desalination.
