About the foundations of direct aqueous carbonation with dissolution enhancing organic salts

Abstract

Direct aqueous carbonation is a promising mineral carbonation route. Under mildly acidic conditions, this single-step carbonation process aims to simultaneously dissolve Ca/Mg-bearing silicates or wastes and precipitate Ca/Mg carbonates. By and large, since mineral dissolution is rate limiting due to the lack of protons at near-neutral pH, research has mainly been concerned with the issue of enhancing dissolution. By analysing the liquid phase, it has been established that polyacid organic salts can significantly enhance silicate dissolution under such unfavourable conditions. Comparatively little attention has been paid to the investigation of the very basis of the whole process, i.e. the concomitance of silicate dissolution and carbonate precipitation. By taking a close look at the solid phases in lizardite and olivine slurries, this work confirms the co-occurrence of magnesium silicate dissolution and magnesite precipitation inside a stirred reactor operating at 120°C, 20 bar of CO2 and 0.1M disodium oxalate, thereby bringing indisputable evidence that supports the foundation of direct aqueous carbonation with organic salts

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