A brief review on flue gas desulfurization gypsum recovery toward calcium carbonate preparation

The past several years have witnessed great progress in utilization of industrial waste gypsum. Newly developed carbonation technology toward CaCO₃ preparation also reveals a significant utilization way to recover high-value products from waste gypsum, whereas there is a shortage of systematic reviews reporting the most recent progress in carbonation of flue gas desulfurization gypsum (FGDG). This review provides a timely and comprehensive summary of major achievements regarding FGDG carbonation and calcium carbonate production to address future investigation directions. We start with a brief introduction of FGDG production and utilization approaches in practical use with their advantages and disadvantages. Then we systematically summarize two types of carbonation, including a direct way and an indirect way. The direct way typically involves three steps: CO₂ capture and CO₃²⁻ formation; CaSO₄·2H₂O dissolution; CaCO₃ crystallization. High purity CaCO₃ is prepared and the polymorph of precipitated CaCO₃ is affected by many factors, such as the Ca²⁺/CO₃²⁻ ratio, reaction conditions, impurities, and additives. The indirect way involves gypsum thermal reduction, carbonation, and sulfur recovery. Finally, challenges of current work and perspectives are presented to expedite future industrialization progress and provide a promising research direction for FGDG carbonation.