Abstract
In this work, we present the results of two synthesis approaches for mesoporous magnesium carbonates, that result in mineralization of carbon dioxide, producing carbonate materials without the use of cosolvents, which makes them more environmentally friendly. In one of our synthesis methods, we found that we could obtain nonequilibrium crystal structures, with acicular crystals branching bidirectionally from a denser core. Both Raman spectroscopy and X-ray diffraction showed these crystals to be a mixture of sulfate and hydrated carbonates. We attribute the nonequilibrium morphology to coprecipitation of two salts and short synthesis time (25 min). Other aqueous synthesis conditions produced mixtures of carbonates with different morphologies, which changed depending on drying temperature (40 or 100 °C). In addition to aqueous solution, we used supercritical carbon dioxide for synthesis, producing a hydrated magnesium carbonate, with a nesquehonite structure, according to X-ray diffraction. This second material has smaller pores (1.01 nm) and high surface area. Due to their high surface area, these materials could be used for adsorbents and capillary transport, in addition to their potential use for carbon capture and sequestration.
Highlights
Magnesium carbonates are some of several minerals proposed for “carbon mineralization”, one of several approaches to Carbon Capture and Sequestration (CCS) [1]
The net chemical reaction for the synthesis of magnesium carbonate is shown in Equations (1) and (2): a Mg2+ precursor (MgX, X represents the anion) reacts in an alkaline tos Químicos Monterrey S.A. de C.V., ACS grade] and sodium bicarbonate [NaHCO3, CTR
We presented two synthesis methods for mesoporous magnesium carbonates from
Summary
Magnesium carbonates are some of several minerals proposed for “carbon mineralization”, one of several approaches to Carbon Capture and Sequestration (CCS) [1]. Magnesium carbonates exist in different structures with different thermodynamic stability and different degrees of hydration. All magnesium carbonates are of interest in CCS since they have stable and long-lasting forms [3], the most attractive one for CCS is MgCO3 , which has a 1:1 molar ratio of magnesium to CO2 , but the hydrated forms are favored during precipitation [4]. This makes the study of the precipitation of magnesium carbonates an important field of study. Even if the most desirable forms of anhydrous MgCO3 were not obtained, hydrated magnesium carbonates such as nesquehonite (MgCO3 ·3H2 O) have been reported to be useful for construction materials [5], a potential application that may sequester carbon for long periods of time
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