Separation of calcium and magnesium from phosphorus tailings by the integrated CO2 absorption-mineralization process

In the processing and utilization of low and medium-grade phosphorus ore, a large amount of phosphorus tailings (PTs) are produced, which results in resource waste and ecological pollution. Phosphorus tailings contain large amounts of calcium, magnesium and phosphorus elements, which is of great significance to recover them. Herein, a route is proposed to prepare light calcium carbonate and enrich P2O5 in phosphorus tailings by integrated CO2 absorption-mineralization process. The dolomite in the phosphorus tailings is activated by calcination, and the leaching effects of inorganic ammonium salts and organic amine leaching agents on calcium and magnesium ions are compared. Then, the effects of different CO2 mineralization conditions on the characteristics of calcium carbonate crystal shape, particle size and morphology are investigated. The results show that using monoethanolamine (MEA) as a leaching agent can selectively leach calcium components, and the calcium carbonate product obtained from CO2 mineralization has the advantages of high purity, uniform crystal shape and small particle size. The regeneration efficiency of MEA after five leaching-mineralization cycles is stable. It is revealed that 265.93 kg of light calcium carbonate product and 9.55 $ could be obtained from each ton of phosphorus tailings during this process, indicating good economic benefits.