Recycling of Industrial Waste Gypsum Using Mineral Carbonation

Direct mineral carbonation (MC) is used to mitigate carbon dioxide (CO₂) emissions. This method has the great advantages of reducing the amount of industrial residues and creating valuable materials by incorporating CO₂. Waste gypsum, industrial waste including flue gas desulfurization (FGD) gypsum (25.27–53.40 wt% of CaO), and phosphogypsum (30.50–39.06 wt% of CaO) can be used for direct MC (conversion rate up to 96%). Mineral carbonation converts waste gypsum into calcium carbonate (CaCO₃), which can be recycled during desulfurization. Furthermore, ammonium sulfate ((NH₄)₂SO₄), which is used as a fertilizer, can be prepared as a by-product when the carbonation reaction is performed using ammonia (NH₃) as a base. In this study, recent progress in the carbonation kinetics and preparation of CaCO₃ using FGD gypsum and phosphogypsum with NH₃ was investigated. Temperature, CO₂ partial pressure, CO₂ flow rate, and NH₃ concentration were reviewed as factors affecting carbonation kinetics and efficiency. The factors influencing the polymorphs of the prepared CaCO₃ were also reviewed and summarized. A state-of-the-art bench-scale plant study was also proposed. In addition, economic feasibility was investigated based on a bench-scale study to analyze the future applicability of this technology.