Continuous process for the aqueous carbonation of serpentinite leachate derived from carbonic acid

We present a modelling approach for the continuous aqueous carbonation of serpentinite leachate derived from carbonic acid, suitable for practical application to large-scale CO₂sequestration. Experiments involved bubbling of gaseous carbon dioxide (CO₂) at a partial pressure of 1 bar into an aqueous suspension of thermally activated serpentinite. Isothermal heating of the ground mineral (-53 μm) at 720 °C for a total period of 30 min resulted in a reactive mineral showing some development of forsterite from the predominantly antigorite basis, with residual hydroxyl content of 53.9 %. An Avrami-Erofe'ev solid state model was fitted to early stage dissolution data (<10 % Mg extraction) and this was used in conjunction with a kinetic formulation of the carbonate system to model continuous mineral dissolution. Dissolution over a contact time of 5 min was sufficient to produce an alkalised solution that was then degassed in a batch operation at 30°C yielding nesquehonite. X-ray powder diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) analyses were used to assess changes to the heat activated serpentinite prior to and following dissolution. ICP-OES analysis, and alkalinity measurements were used to estimate magnesium (Mg) and carbon elemental balances.