磷石膏基胶结材固结磷尾矿性能及浸出特征

Properties and leaching characteristics of cemented phosphate tailings backfill with phosphogypsum-based cementation material

以磷石膏基材料代替水泥作为磷尾矿充填胶结材,研究了磷尾矿固结浆体和硬化体性能、浸出液污染特性和固结机理。结果表明,在同样条件下,磷石膏基材料固结磷尾矿浆体比水泥泌水量要小、浆体流动性能更优;磷石膏基材料胶结磷尾矿硬化体除3 d抗压强度略低外,其他龄期的强度是水泥的1.21~1.95倍。3 d之后,磷石膏基材料和水泥胶结尾矿硬化体浸出液总磷含量基本相近,但pH明显远低于水泥,总磷也低于污水综合排放标准限值,对环境危害低。硬化体SEM和XRD分析发现,磷石膏基材料水化生成的水化硅酸钙凝胶、针状钙矾石晶体和磷尾矿中白云石、含磷矿物生成的透钙磷石等,是整个磷尾矿固结硬化体具有较高强度、较低总磷含量和pH值主要原因。该研究表明,磷石膏基材料固化磷尾矿比水泥更有应用前景。

Cementation mechanism and properties,which include the cementation slurry and a hardened specimen,along with the contamination properties of liquid leaching of phosphate tailings cementation with a phosphogypsum-based material（ PM）,as opposed to cement,were investigated in this study. The results showed that the bleeding quantity of a phosphate tailing cementation slurry with PM was smaller,and that the slurry fluidity with PM was better than that with cement under the same conditions. The compressive strength of the phosphate tailing hardened specimen with PM with different hydration age was 1. 21 to 1. 95 times higher than that with cement,except for a 3 day hydration. After a 3 day hydration period,the total phosphorus in the liquid leaching of hardened specimens with PM and cement was similar,but the pH with PM was far lower than that with cement. The total phosphorus in liquid leaching with PM was below the integrated wastewater discharge standard of China,which implied that the liquid leaching of hardened specimens with PM was safe to the environment. SEM and XRD analyses revealed that the main compositions of cemented phosphorus tailing included hydrated calcium silicate gels and acicular ettringite crystals,which were generated from the hydration of PM,dolomite,and brushite crystals,all of which contributed to higher compressive strength,lower total phosphorus,and pH. This finding suggests that PM is a more promising material for phosphate tailings cementation than cement.