磷石膏中杂质深度脱除技术

Deep removal of impurities from phosphogypsum

以深度脱除磷石膏中的杂质,提高其品质为目的,采用XRF、XRD、SEM以及白度分析仪等多种分析表征手段,对水洗、硫酸酸洗以及硫酸酸洗耦合溶剂萃取等3种磷石膏净化除杂方法进行了比较分析研究。结果表明,磷石膏表面粘附的少量可溶性磷、镁化合物以及部分可溶性含硅及氟化合物可采用水洗除去,而磷石膏中几乎全部含有可溶性硅、铝、铁、氟、钾等杂质元素的化合物可采用硫酸酸洗除去。在水洗和酸洗过程中,磷石膏中的二水硫酸钙均经历了溶解再结晶成无水硫酸钙的晶型转变过程,并且在硫酸体系中可有效促进其晶型转变速率。此外,在硫酸酸洗过程中添加磷酸三丁酯,不仅可有效脱除磷石膏中的石英、硫化亚铁、无机炭黑等酸不可溶性杂质,还可有效脱除溶解度较小的氟硅酸钾和带结晶水的氟化铝等杂质,由此可以获得纯度大于99%、白度大于92%,并且分散性较好的棒状细小无水硫酸钙颗粒。采用硫酸酸洗耦合有机溶剂磷酸三丁酯萃取深度净化磷石膏,将为磷石膏资源实现高效利用提供了新途径。

To deeply remove the impurities and improve the quality of phosphogypsum （PG）, three PG purification methods, including water washing, acid pickling, and acid pickling coupling solvent extraction, were comparatively analyzed according to the results of characterization by XRF, XRD, SEM and whiteness. Results showed that a small amount of soluble phosphorus, magnesium compounds and part of soluble silicon, fluorine compounds on the surface of PG could be removed by water washing, while almost all of the acid soluble compounds containing Si, AI, Fe, F and K impurity elements in PG could be removed by acid pickling. It was found that the main mineral phase of CaSO4·2H2O in PG underwent the dissolution and recrystallization to form CaSO4 both in water washing and acid pickling process, while the transformation speed was much faster in the latter. Moreover, when the organic solvent tributyl phosphate （TBP） was added to the acid pickling process, all of the impurities in PG involving the acid insoluble impurities, such as quartz, iron sulfide, inorganic carbon black, and the barely soluble impurities, such as KaSiF6 and aluminum fluoride with crystal water, can be effectively removed. The clubbed CaSO4 with the purity and whiteness of more than 99% and 92%, respectively, could be obtained by this acid pickling coupling with solvent extraction technique, which would provide a new way for the comprehensive utilization of PG.