Increased Sustainability of Carbon Dioxide Mineral Sequestration by a Technology Involving Fly Ash Stabilization

Mineral carbonation, involving reactions of alkaline earth oxides with CO_2, has received great attention, as a potential carbon dioxide sequestration technology. Indeed, once converted into mineral carbonate, CO₂ can be permanently stored in an inert phase. Several studies have been focalized to the utilization of industrial waste as a feedstock and the reuse of some by-products as possible materials for the carbonation reactions. In this work municipal solid waste incineration fly ash and other ashes, as bottom ash, coal fly ash, flue gas desulphurization residues, and silica fume, are stabilized by low-cost technologies. In this context, the CO₂ is used as a raw material to favor the chemical stabilization of the wastes, by taking advantage of the pH reduction. Four different stabilization treatments at room temperature are performed and the carbonation reaction evaluated for three months. The crystalline calcium carbonate phase was quantified by the Rietveld analysis of X-ray diffraction (XRD) patterns. Results highlight that the proposed stabilization strategy promotes CO₂ sequestration, with the formation of different calcium carbonate phases, depending on the wastes. This new sustainable and promising technology can be an alternative to more onerous mineral carbonation processes for the carbon dioxide sequestration.