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Tunable Manipulation of Mineral Carbonation Kinetics in Nanoscale Water Films via Citrate Additives
- Miller, Quin R. S., Schaef, Herbert T., Kaszuba, John P., Qiu, Lin, Bowden, Mark E., McGrail, Bernard P.
- Environmental science & technology 2018 v.52 no.12 pp. 7138-7148
- X-ray diffraction, additives, adsorption, carbon dioxide, carbonation, citrates, environmental science, ligands, magnesite, magnesium, magnesium carbonate, mineralization, models
- We explored the influence of a model organic ligand on mineral carbonation in nanoscale interfacial water films by conducting five time-resolved in situ X-ray diffraction (XRD) experiments at 50 °C. Forsterite was exposed to water-saturated supercritical carbon dioxide (90 bar) that had been equilibrated with 0–0.5 m citrate (C₆H₅O₇–³) solutions. The experimental results demonstrated that greater concentrations of citrate in the nanoscale interfacial water film promoted the precipitation of magnesite (MgCO₃) relative to nesquehonite (MgCO₃·3H₂O). At the highest concentrations tested, magnesite nucleation and growth were inhibited, lowering the carbonation rate constant from 9.1 × 10–⁶ to 3.6 × 10–⁶ s–¹. These impacts of citrate were due to partial dehydration of Mg²⁺(aq) and the adsorption of citrate onto nuclei and magnesite surfaces. This type of information may be used to predict and tailor subsurface mineralization rates and pathways.