Highly targeted solidification behavior of hazardous components in phosphogypsum

Abstract

In this study, an effective approach has developed to solidify phosphorus, fluorine and heavy metals in phosphogypsum by using carbide slag(CS) and polymer, and the effect of carbide slag and polymer addition on the pH and the speciations of phosphorus, fluorine in phosphogypsum has discussed in detail. The experimental results showed that in the carbide slag modified phosphogypsum system, soluble phosphorus and fluoride were significant fixed and converted into Ca3(PO4)2, CaF2 and other stable precipitates. The pH-related leaching test results indicated that there was little significant relationship between the total phosphorus leaching concentration and pH under neutral and alkaline conditions. Fluorapatite is the control phase of phosphorus in the phosphogypsum system, and the fluorite and fluorapatite are the main control phases of fluorine leaching. After long-term leaching, the proportion of the control phase of fluorite was reduced. In the polymer modified phosphogypsum system, large amount of soluble phosphorus and fluorine were solidified, which achieve high effective solidification of phosphorus and fluorine. The pH-related leaching test showed that the polymer has a significant effect on phosphorus and fluorine under different pH conditions. Besides, the curing effect has a significant relationship with pH. At the same time, carbide slag and polymer have a certain effect on the conversion between the speciations of heavy metals in the system. The experimental results showed that the pH, phosphorus, fluorine and heavy metals in the carbide slag-phosphogypsum (CS-PG) system meet the requirements of the ''Integrated Wastewater Discharge Standard (GB 8978–1996)'' of China.

Keywords

• Phosphogypsum
• Carbide slag
• Solidification
• Long-term stability
• High targeting