Abstract:

Impurities such as silicon，organic matter，and soluble fluoride in phosphogypsum severely restrict its value⁃added utilization.Currently，the flotation method is the most widely used pretreatment process，but positive flotation has high costs and complex processes，and traditional reverse flotation agents have poor stability and dispersibility.To address these issues，this study focused on phosphogypsum and research on the removal of silicon，organic matter，and soluble fluoride impurities in phosphogypsum was conducted through a one⁃stage co⁃reverse flotation process.The concentrate after new benzyl quaternary ammonium salt co⁃reverse flotation reagent（PG-1） reverse flotation was analyzed by SEM-EDS，XRD and XPS.The results showed that under the optimal process conditions of natural slurry pH of 2.3~2.5，MIBC dosage of 300 g/t，PG-1 dosage of 300 g/t，slurry concentration of 25%，and aeration rate of 0.20 m³/h，the raw phosphogypsum had a CaSO₄·2H₂O content was 86.75%，SiO₂ content was 6.68%，whiteness was 32.59%，organic matter content was 0.72%，and soluble fluoride content was 0.40%.After a one⁃stage co⁃reverse flotation to remove impurities and increase whiteness，the obtained phosphogypsum concentrate had a SiO₂ content of 2.47%，whiteness of 63.74%，organic matter content of 0.03%，soluble fluoride content of 0.039%，a yield of 80.17%，and CaSO₄·2H₂O content of 93.52%，meeting the requirements of the building gypsum first⁃grade product in the national standard GB/T 23456—2018“phosphogypsum”.This research provided a new method for the pretreatment process of value⁃added use of phosphogypsum.

Key words: phosphogypsum, co-reverse flotation, desilication, whitening, purification