Surface reactions of galena in the presence of leakages from geologic sequestration: CO₂-H₂O-PbS interactions

Geologic sequestration (GS), particularly deep saline aquifers, can store vast amounts of CO₂, curtailing climate change. This work aims to understand the consequences of potential leakage from GS sites, specifically the effect of dissolved CO₂ and salts on groundwater quality when PbS (galena) is ubiquitous. High concentrations of CO₂ and salts induce the dissolution and precipitation of galena. Saturated (P_CO2=1 atm) and unsaturated CO₂ solutions were prepared with varying ionic strengths. Simulated systems for a continuous CO₂ leakage and one-time leakage are investigated by monitoring dissolution rates of galena using inductively coupled plasma mass spectrometry. In-situ and ex-situ AFM experiments were run on (111) and (100) surfaces of galena. XRD analysis was used to identify secondary mineral phases. Different planes of galena indicated a clear difference in dissolution rates. These results provide fundamental information on the reactivities of galena with CO₂ and help to understand potential effects of CO₂ leakage.