Revealing Mechanism of Hemihydrate–Dihydrate Phosphogypsum Transformation and Minimizing Phosphorus Loss in Wet Process Phosphoric Acid

In this study, the influence of temperature, sulfuric acid content, and P2O5 content on the hydration kinetics and dihydrate phosphogypsum morphology during the hemihydrate–dihydrate (HH–DH) wet process phosphoric acid hydration process was systematically studied. The morphology of dihydrate phosphogypsum with different aspect ratios was obtained under different hydration conditions. This is due to the different supersaturation degrees owing to the solubility difference between CaSO4·0.5H2O and CaSO4·2H2O. Dihydrate phosphogypsum morphology with a small aspect ratio can be obtained under low supersaturation conditions, and the reduced phosphorus loss as well as the improved filtration strength is achieved. In this study, the mechanism of the HH–DH hydration process is discussed in detail, which has important guiding significance for improving the recovery rate of phosphorus and filtration strength during the HH–DH wet process phosphoric acid production.