Geologic carbon dioxide storage (GCS) in deep saline sedimentary formations is a potential method for mitigating increased levels of atmospheric CO2. One of the potential impacts of GCS, currently under investigation, is the effect of supercritical CO2 on the geochemistry of the storage formation, as a function of mineral dissolution and evolution of brine composition. There is related interest in brine leakage and migration. Deep saline brines contain high concentrations of Na+, Ca2+, and Mg2+. Of particular concern is the effect of these chemical species on the rate of dissolution of metals and metalloids such as lead (Pb) and arsenic (As). In this study, we focus on ionic strength and cation effects on the dissolution of arsenopyrite (FeAsS) and galena (PbS), which are important mineral sources of As and Pb in the subsurface. Dissolution experiments were conducted in a small-scale flow through system capable of simulating GCS conditions. Experiments were conducted with NaCl, CaCl2, and MgCl2 at concentrations ranging from 10mM to 4 M at acidic and circumneutral pH, and ambient temperature and pressure conditions. Preliminary results indicate that the rate of dissolution of arsenopyrite and galena are enhanced by the presence of cationic species, and the increase in dissolution rate is independent of ionic strength.

Effect of brine constituents on the dissolution of arsenopyrite and galena

247th National Meeting (2014)

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