从低品位稀土抛光渣中回收CeO_2的试验

Experimental Study on Recovery of CeO_2 from a Low Grade Rare Earth Polishing Slag

抛光渣是抛光粉在使用过程中因混入杂质而失去使用价值的废弃物,传统的丢弃或掩埋处理不仅造成资源的浪费,而且造成环境污染。本研究以某低品位铈基稀土抛光渣(CeO_2含量为0.88%)为试样,采用初步沉降预富集,硫酸+双氧水浸出,氨水、Na2S相继除杂,草酸沉淀,沉淀产物高温煅烧工艺进行了CeO_2回收试验。结果表明:(1)废弃抛光渣在pH=9的情况下沉降8 h,可得到CeO_2品位为1.70%、回收率为84.62%的预富集产物。(2)预富集产物在硫酸浓度为0.5 mol/L,用量为100 m L,双氧水用量15 m L,反应温度为80℃情况下水浴加热、搅拌、浸出3.5 h,稀土浸出率可达94.70%。(3)用氨水、Na2S对浸出液进行了除杂处理,Al^(3+)、Fe^(3+)、Pb^(2+)、Zn^(2+)的去除率分别为94.03%、76.67%、99.89%、99.94%,然后用草酸沉淀稀土,稀土沉淀率为91.82%。(4)稀土草酸盐沉淀产物高温煅烧得到CeO_2含量为93.48%的晶体,纯度较高,扫描电镜观察表明,该CeO_2晶体多呈块状。

The polishing slag is the waste which lost the value during the utilization process of the polishing powder. The traditional discarding or burying treatment not only waste resources,but also results in environmental pollution. Taking a low grade cerium-based rare earth polishing slag （CeO2 content of 0. 88%） for example,the CeO2 recovery experiment was carried out by the process of preliminary sedimentation pre-concentration,leaching of sulfuric acid and hydrogen peroxide,impurity re-moval of NH3 ·H2O and Na2S,oxalic acid precipitation and high temperature calcination process of precipitation product. The results showed as follows：①when the polished slag waste was settled for 8 hours in the condition of pH=9,the pre-concentra-tion product with CeO2 grade of 1. 70% and recovery rate of 84. 62% could be obtained.②The leaching rate of rare earth is 94. 70% when the concentration of sulfuric acid is 0. 5 mol/L,the dosage is 100 mL,the dosage of hydrogen peroxide is 15 mL,and the reaction temperature is 80 ℃,by water heating,stirring and leaching for 3. 5 hours.③The removal rate of Al3＋, Fe3＋,Pb2＋ and Zn2＋ was 94. 03%,76. 67%,99. 89% and 99. 94% respectively by NH3·H2O and Na2S. The precipitation rate of rare earth reached 91. 82% by the precipitation of rare earth with oxalic acid.④The high-purity crystal with CeO2 con-tent of 93. 48% was obtained by calcination of rare earth oxalate precipitate at high temperature. Scanning electron microscopy showed that the CeO2 crystal mostly shows as blocky.