title: Structure-dependent interactions between alkali feldspars and organic compounds: implications for reactions in geologic carbon sequestration.
abstract: Organic compounds in deep saline aquifers may change supercritical CO(2) (scCO(2))-induced geochemical processes by attacking specific components in a mineral's crystal structure. Here we investigate effects of acetate and oxalate on alkali feldspar-brine interactions in a simulated geologic carbon sequestration (GCS) environment at 100 atm of CO(2) and 90 °C. We show that both organics enhance the net extent of feldspar's dissolution, with oxalate showing a more prominent effect than acetate. Further, we demonstrate that the increased reactivity of Al-O-Si linkages due to the presence of oxalate 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 h 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.
authors.affiliation: Department of Energy, Environmental and Chemical Engineering, Washington University in St Louis, St Louis, Missouri 63130, United States.
authors.forename: Yi
authors.initials: Y
authors.lastname: Yang
authors.forename: Yujia
authors.initials: Y
authors.lastname: Min
authors.forename: Young-Shin
authors.initials: YS
authors.lastname: Jun
mesh_terms: D000085:Acetates / Q000737:chemistry*; D000538:Aluminum Silicates / Q000737:chemistry*; D057965:Carbon Sequestration; D055593:Geological Phenomena; D015394:Molecular Structure; D010070:Oxalates / Q000737:chemistry*; D017680:Potassium Compounds / Q000737:chemistry*; D012492:Salts / Q000737:chemistry
chemical_list: D000085:Acetates; D000538:Aluminum Silicates; D010070:Oxalates; D017680:Potassium Compounds; D012492:Salts; C017082:brine; C016447:feldspar