Organic compounds in deep saline aquifers may change supercritical CO2 (scCO2)-induced geochemical processes by attacking specific components in a mineral’s crystal structure. We investigated the effects of acetate and oxalate on feldspar–brine interactions in a simulated geologic carbon sequestration (GCS) environment at 100 atm of CO2 and 90 °C. We found that both organics enhance the net extent of feldspar’s dissolution, with oxalate showing a more prominent effect than acetate. Furthermore, in the presence of oxalate, the reactivity of Al–O–Si linkages was increased due to results in the promotion of both Al and Si release from feldspars. As a consequence, the degree of Al-Si order may affect the effect of oxalate on feldspar dissolution: a promotion of ~500% in terms of cumulative Si concentration was observed after 75 hours of dissolution for sanidine (a highly disordered feldspar) owing to oxalate, while the corresponding increase for albite (a highly ordered feldspar) was ~90%. These results provide new insights into the dependence of feldspar dissolution kinetics on the crystallographic properties of the mineral under GCS conditions.

Structure-dependent interactions between feldspars and organic compounds: Implications for geologic carbon sequestration

249th National Meeting (2015)

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