Modification of Phosphogypsum Morphology and Properties via Deep Purification

Phosphogypsum contains impurities such as fluorine (F), P 2 O 5 , Al, Mg, Fe, and Cu. Because purification technologies remain insufficiently developed, phosphogypsum is poorly utilized and tends to accumulate over the long term, causing serious environmental pollution. In this study, fluorine in phosphogypsum was removed through sulfuric acid pretreatment, while organic matter was eliminated and the whiteness of phosphogypsum was improved by calcination. The optimal process conditions were determined as follows: a sulfuric acid mass fraction of 30%; a solid-to-liquid ratio (phosphogypsum to sulfuric acid solution) of 1:1.9; a leaching temperature of 95 °C; a leaching time of 25 min; a calcination temperature of 550 °C; and a calcination time of approximately 50 min. Under these conditions, the whiteness of phosphogypsum reached 95.2%, and the fluoride ion removal rate achieved 83.1%. The proposed approach provides a feasible route to mitigate phosphogypsum-related pollution and enhance its utilization, offering considerable economic and social benefits.