Investigating the mineral carbonation of

Aqueous mineral carbonation of industrial waste (e.g. fly ash) is a potentially attractive sequestration technology to reduce CO2 emissions. Therefore, the carbonation capacity of solutions rich in Mg and Ca (similar to those found in suspensions of Victorian brown coal fly ash) was studied in relation to various process variables. This investigation is pivotal to understand the preferred experimental conditions for achieving high CO2 uptake rate as well as the extent of carbonation of Mg and Ca. About 100% of Ca and Mg were carbonated in less than 40 min in the presence of Mg or Ca only or different mixtures of these two ions in the solution. Furthermore, the presence of Mg in the solution was shown to slow the precipitation rate of calcite. A quantitative comparison of X-ray diffraction spectra for solid precipitates showed that carbonation via Mg or Ca only in the solution resulted in formation of unidentified precipitate, calcite and vaterite, respectively. For the mixtures of Mg and Ca, the predominant phases were calcite, magnesian calcite and aragonite. The results showed that the carbonation reaction rate increased with increasing reaction temperature. However, it exhibited a maximum value at 40 °C and a further increase in temperature from 40 °C onwards resulted in insignificant change on the carbonation yield.