硅酸盐稀土渣硫酸铵焙烧浸出研究

Roasting and Leaching Process of Mixture of Rare Earth Silicates Slag and Ammonium Sulfate

采用高温直接还原-磁选-(NH4)2SO4焙烧-水浴浸出的工艺流程,从低品位含稀土尾矿中提取稀土。主要考察了(NH4)2SO4配量,焙烧温度和焙烧时间等实验参数对La,Ce,Nd浸出率的影响。通过SEM-EDS,XRD和TG-DSC表征了尾矿经高温直接还原后稀土的赋存状态、不同温度(NH4)2SO4焙烧富稀土渣过程中的物相变化和浸出渣及浸出液烘干后析出晶的物相成分。结果表明:稀土尾矿经高温处理后分别得到了高品位铁精粉和富稀土渣。稀土元素主要以Ca2RE8(Si O4)6O2,CaRE2(Si O4)2硅酸盐形式存在。优化实验条件下,(NH4)2SO4与富稀土按8∶1混匀,400℃焙烧45 min,80℃热水浴浸出时间1 h,浸出液液固比10∶1,La,Ce,Nd浸出率分别为96.13%,98.88%,97.10%。经(NH4)2SO4焙烧处理后,稀土元素的最终产物变为可溶性的(NH4)RE(SO4)2和RE2(SO4)3,萤石部分转变为Ca SO4。

The rare earth was extracted from low-grade rare earth tailings by the technological process of high temperature direct reduction magnetic separation roasting with（ NH4）2SO4water bath leaching in this work. The main influence factors on the leaching rates of rare elements in roasted products were investigated including amount of ammonium sulfate,roasting temperature and roasting time. The existing state of rare earth after direct reduction at high temperatures,the phase of rare earth after roasting with（ NH4）2SO4at different temperatures,and the chemical composition of leaching solution and residue were characterized by SEM-EDS,XRD and TG-DSC. The results showed that the high-grade rare earth slag and powdered iron were obtained by high-temperature roasting and magnetic separation. Rare elements existed mainly in the form of Ca2RE8（ Si O4）6O2and CaRE2（ Si O4）2. The leaching rate of La,Ce and Nd could reach 96. 13%,98. 88% and 97. 1% respectively,under the following optimized experimental conditions： 8∶ 1 of（ NH4）2SO4to slag mass ratio,400 ℃ of roasting temperature for 45 min,80 ℃ of water bath leaching temperature for 1 h and 10∶ 1 of leaching liquid-solid ratio. By roasting with（ NH4）2SO4,the rare earth were transformed into their corresponding sulfate（ NH4） RE（ SO4）2and RE2（ SO4）3. Simultaneously,Ca F2 partially turned into Ca SO4.