Impact of particle size in serpentine thermal treatment: Implications for serpentine dissolution in aqueous-phase using CO2 in flue gas conditions

Abstract

Mineral carbonation represents a promising way of reducing the emission of anthropogenic GHG emissions, particularly in the Province of Québec where large amounts of serpentine mining residues are waiting for remediation. However, when used in reactors, serpentine minerals need to be activated to promote Mg2+ leaching. In this study, ground and unground samples have been thermally activated in a muffle furnace at different temperatures and residence times. Their mineralogical composition have been determined using XRD coupled with Rietveld refinements from which the amorphous phases have been distinguished and quantified. The objectives are to determine the influence of the particle size distribution of the samples on the dehydroxylation process and on the dissolution under aqueous mineral carbonation reaction. Results show that in a muffle furnace, unground particles tend to heat faster than ground particles. This is due to the larger spaces left between the particles, allowing a better heat diffusion through the sample. In ground particles samples, water vapor tends to be entrapped in those space, leading to the formation of a water vapor layer, slowing down the heat process. Carbonation experiments were performed on the different resulting fractions obtained. Regarding Mg dissolution efficiencies, 6 batches experiments show that Mg2+ extraction is higher when performed on sample ground prior to thermal activation. The collected information will advance the knowledge on serpentine heat activation mechanism and help to improve carbonation technologies efficiencies.