Abstract
Mineral carbonation is known to be among the most efficient ways to reduce the anthropogenic emissions of carbon dioxide. Serpentine minerals (Mg3Si2O5(OH)4), have shown great potential for carbonation. A way to improve yield is to thermally activate serpentine minerals prior to the carbonation reaction. This step is of great importance as it controls Mg2+ leaching, one of the carbonation reaction limiting factors. Previous studies have focused on the optimization of the thermal activation by determining the ideal activation temperature. However, to date, none of these studies have considered the impacts of the thermal activation on the efficiency of the aqueous-phase mineral carbonation at ambient temperature and moderate pressure in flue gas conditions. Several residence times and temperatures of activation have been tested to evaluate their impact on serpentine dissolution in conditions similar to mineral carbonation. The mineralogical composition of the treated solids has been studied using X-ray diffraction coupled with a quantification using the Rietveld refinement method. A novel approach in order to quantify the meta-serpentine formed during dehydroxylation is introduced. The most suitable mineral assemblage for carbonation is found to be a mixture of the different amorphous phases identified. This study highlights the importance of the mineralogical assemblage obtained during the dehydroxylation process and its impact on the magnesium availability during dissolution in the carbonation reaction.
Highlights
The increasing greenhouse gas emissions and anthropogenic carbon dioxide (CO2 ) in the atmosphere are known to play a major role in climate change [1]
Carbonation reaction can be divided in three main steps: (i) the CO2 dissolution in water (ii) the material dissolution and (iii) the precipitation of carbonates as final products
Thermal treatment acts on serpentine dissolution by enhancing Mg2+ availability, making it a key step for the process [9]
Summary
The increasing greenhouse gas emissions and anthropogenic carbon dioxide (CO2 ) in the atmosphere are known to play a major role in climate change [1]. Among the methodologies proposed for mitigation, mineral carbonation appears to be one of the most sustainable [2,3]. This natural and spontaneous phenomenon involves the reaction between CO2 (aqueous or gas) and divalent cations bearing minerals in order to form the associate carbonates [3]: Minerals 2019, 9, 680; doi:10.3390/min9110680 www.mdpi.com/journal/minerals. Thermal treatment acts on serpentine dissolution by enhancing Mg2+ availability, making it a key step for the process [9]. Serpentine dissolution first results in a rapid exchange of surfacing Mg2+ with protons (H+ ) before being extracted from the structure into the solution, during a much slower phase [10,11]. The dissociation of CO2 added to the solution will generate protons and HCO3 - ions, enhancing Mg2+ availability (Pasquier et al, 2014b)
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