Dunite carbonation in batch-tubular reactor

Area of Science:

• Geochemistry
• Environmental Science
• Materials Science

Background:

• Geological carbon sequestration offers permanent storage by reacting CO2 with silicate rocks.
• Fractures in silicate rocks enhance surface area for carbonate precipitation.
• Understanding mineral precipitation is crucial for optimizing sequestration efficiency.

Purpose of the Study:

• To investigate the potential of magnesite precipitation in silicate rocks for carbon sequestration.
• To analyze the conditions favoring carbonate formation within rock fractures.
• To evaluate the impact of precipitation on rock porosity and dissolution rates.

Main Methods:

• Experiments conducted in a batch tubular reactor with a dunite slurry under diffusion-limited conditions.
• Utilized a CO2-rich bulk solution at 1 barg and temperatures from 25-75°C for 7-30 days.
• Characterized magnesite precipitation using micro-Raman spectroscopy, X-ray diffraction, and scanning electron microscopy.

Main Results:

• Magnesite precipitation was observed within the silicate rock tube after 7 days, continuing up to 30 days.
• Silica (SiO2) formation was detected near the magnesite precipitation sites.
• Precipitation within fractures may potentially reduce the long-term dissolution rate of silicate rock.

Conclusions:

• Magnesite precipitation in silicate rocks is a viable pathway for geological carbon sequestration.
• The observed precipitation suggests a mechanism for long-term CO2 storage.
• Further research is needed to assess the impact of mineral precipitation on the long-term stability and efficiency of sequestration.