Efficient and cost-effective fluorine recovery from liquid-phase wet-process phosphoric acid via two-step precipitation method

Fluorine (F) recovery from wet-process phosphoric acid (WPA) is essential for sustainable resource utilization and environmental protection. In this study, we have proposed a two-step precipitation strategy for recovering F from WPA using anhydrous sodium sulfate and activated silica as precipitants. The optimized F recovery yield, product purity, and maximum P2O5 loss were 87.60 %, >98.50 wt%, and 0.030 wt%, respectively. Moreover, the recovery cost was only USD 60.08 per tonne of P2O5. The precipitation reactions followed the second-order reaction model and were controlled by the moving boundary diffusion mechanism. Temperature significantly influenced the reaction process, while temperature, WPA concentration, and Al3+ content significantly influenced the morphology of the precipitated crystal. Under optimized conditions, the sodium fluorosilicate product had a hexagonal cylindrical axis, low solubility in WPA, and high purity. These findings are promising for the utilization of F resources from phosphate rock and other ores, which is of great economic and environmental significance.