Tailings as a Source for Generating Valuable Magnesium and Calcium Carbonates by Leaching and Carbonization

Mining produces a lot of disposable mineral waste after the ore has been removed. This waste with added CO2 can be used as a feedstock for carbonate production. The advantage of this production process is the recycling of a waste product with additional carbon capture. However, the processing challenge is a feed with a fluctuating composition of the mining waste, which makes classical engineering and control with fixed process parameters difficult. For characterization, model particles and tailings are studied for their behavior with fluctuating acid and mass concentrations as a function of the leaching time. The results confirm the possibility of leaching calcium (max 7 g L–1) and magnesium (max 0.7 g L–1) using hydrochloric acid with concentrations lower than the stoichiometry. The amount varies depending on the particle, concentration, and pH. Mathematically, the leaching over time can be described by an exponential expression, which is applied to both investigated cases for the leaching of calcium and magnesium ions. Finally, a pH shift process is used to precipitate solid CaCO3 from the ion-enriched solution obtained, thus demonstrating in one example the successful production of CaCO3 and carbon capture from mine waste.