Carbon dioxide sequestration of iron ore mining waste under low-reaction condition of a direct mineral carbonation process

Mining waste that is rich in iron-, calcium- and magnesium-bearing minerals can be a potential feedstock for sequestering CO2 by mineral carbonation. This study highlights the utilization of iron ore mining waste in sequestering CO2 under low-reaction condition of a mineral carbonation process. Alkaline iron mining waste was used as feedstock for aqueous mineral carbonation and was subjected to mineralogical, chemical, and thermal analyses. A carbonation experiment was performed at ambient CO2 pressure, temperature of 80 degrees C at 1-h exposure time under the influence of pH (8-12) and particle size (< 38-75 mu m). The mine waste contains Fe-oxides of magnetite and hematite, Ca-silicates of anorthite and wollastonite and Ca-Mg-silicates of diopside, which corresponds to 72.62% (Fe2O3), 5.82% (CaO), and 2.74% (MgO). Fe and Ca carbonation efficiencies were increased when particle size was reduced to < 38 mu m and pH increased to 12. Multi-stage mineral transformation was observed from thermogravimetric analysis between temperature of 30 and 1000 degrees C. Derivative mass losses of carbonated products were assigned to four stages between 30-150 degrees C (dehydration), 150-350 degrees C (iron dehydroxylation), 350-700 degrees C (Fe carbonate decomposition), and 700-1000 degrees C (Ca carbonate decomposition). Peaks of mass losses were attributed to ferric iron reduction to magnetite between 662 and 670 degrees C, siderite decarbonization between 485 and 513 degrees C, aragonite decarbonization between 753 and 767 degrees C, and calcite decarbonization between 798 and 943 degrees C. A 48% higher carbonation rate was observed in carbonated products compared to raw sample. Production of carbonates was evidenced from XRD analysis showing the presence of siderite, aragonite, calcite, and traces of Fe carbonates, and about 33.13-49.81 g CO2/kg of waste has been sequestered from the process. Therefore, it has been shown that iron mining waste can be a feasible feedstock for mineral carbonation in view of waste restoration and CO2 emission reduction.

Automated summary

This study explores the utilization of iron ore mining waste as a feedstock for sequestering CO2 through mineral carbonation. The study shows that alkaline iron mining waste can be effectively used in the process, resulting in higher carbonation efficiency and carbonate production. This finding is important for waste restoration and reducing CO2 emissions.