Synthesis and Morphological Control of Siderite (FeCO<sub>3</sub>) Particles by CO<sub>2</sub> Blowing

Siderite (FeCO3) is a well-known iron carbonate mineral. Recently, efforts have been made to synthesize FeCO3 using an environmentally friendly Carbon dioxide Capture and Utilization (CCU) process and apply it as a filler material. This study investigates the synthesis of FeCO3 particles and the factors that affect their morphology. A rhombohedral FeCO3 powder was produced by suspending Fe powder in water and blowing CO2 gas into the suspension. The effects of Fe2+ and HCO3– supply behavior on the particle size were investigated. Increasing the Fe powder content in the suspension promoted Fe2+ dissolution, leading to larger FeCO3 particles. Furthermore, reducing the particle size of the Fe powder to 3–5 μm and increasing the reaction temperature to 50°C promoted Fe2+ dissolution, resulting in FeCO3 particles with an average size of approximately 0.5 μm. In contrast, increasing the CO2 flow rate did not affect the particle size because the hydration reaction of CO2 was the rate-limiting step. These findings indicate that the supply behavior of Fe2+ is the dominant factor that controls the particle size during FeCO3 synthesis.