Solid products characterization in a multi-step mineralization process

• A multi-step pH-swing process makes value-added products from captured CO2.
• High yields of carbonate precipitate are obtained from carbonation of the extracted magnesium.
• Different forms of magnesium carbonate can be obtained depending on reaction temperature.
• Different forms of iron hydroxide can be obtained depending on reaction pH.
• The precipitate has a purity of 99.9% based on MgO content.

In this paper, we describe a carbon dioxide mineralization process and its associated solid products. These solid products include amorphous silica, iron hydroxides and magnesium carbonates. These products were subjected to various characterization tests, and the results are published here. It was found that the iron hydroxides from this process can have different crystalline properties, and their formation depended very much on the pH of the reaction conditions. Different forms of magnesium carbonate were also obtained, and the type of carbonate precipitated was found to be dependent on the carbonation temperature. Hydromagnesite was obtained mainly at low temperatures, while dypingite was obtained at higher temperatures. Near ambient conditions, nesquehonite was the predominant form of magnesium carbonate obtained. The process mass balance shows that 3.1 tonne of hydrated magnesium carbonate with 99.82 wt% purity is obtained for each tonne of CO2 sequestrated. And for each tonne of carbon dioxide sequestrated, about 3.74 tonnes of mineral ore are needed as a source of magnesium.