Abstract Combining the environmental advantage of magnesium salt compound leaching agent, calcium oxide was used as a precipitant to enrich rare earth elements from rare earth leaching liquor in a magnesium salt system. The use of magnesium salt compound leaching agent and calcium oxide precipitant can achieve the effective circulation of Ca and Mg, and finally solve the ammonia-nitrogen pollution problem in the whole extraction process of the weathered crust elution-deposited rare earth ore. The study suggested that alkaline rare earth sulfates and rare earth hydroxides could generate in the precipitation process, which was proved by the Hazen model calculation and the calcium oxide addition experiments. What's more, it was showed that, under the optimum precipitation conditions, the precipitation efficiency of rare earth was 99.72% and the purity of rare earth concentrate is 82.21%, and the SO3 content in the rare earth concentrate was as high as 13.44% because of the formation of alkaline rare earth sulfates during the precipitation process. In order to reduce the SO3 content, the stirring washing of the precipitation enrichment with an sulfate removal agent was proposed in this paper. The anion of the sulfate removal agent could compete with sulfate ions in the stirring washing process. As a result, sodium hydroxide could be the first choice for further detailed study. When the precipitation enrichment was washed with sodium hydroxide, the purity of the rare earth concentrate was 88.03% and the SO3 content was 7.51% respectively. Hence, a feasible operation would be provided for the non-ammonia enrichment of rare earth from leaching liquor in a magnesium salt system. The research in this paper could have great significance for environmentally-friendly extraction of the weathered crust elution-deposited rare earth ore and the improvement of resource utilization.

中文翻译：

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镁盐体系中稀土浸出液中稀土元素的非氨富集Ⅰ：氧化钙沉淀

摘要 结合镁盐复合浸出剂的环保优势，以氧化钙为沉淀剂，在镁盐体系中从稀土浸出液中富集稀土元素。采用镁盐复合浸出剂和氧化钙沉淀剂，可以实现Ca、Mg的有效循环，最终解决风化壳溶出沉积稀土矿整个提取过程中的氨氮污染问题。研究表明，在沉淀过程中会生成碱性稀土硫酸盐和稀土氢氧化物，这一点得到了Hazen模型计算和氧化钙添加实验的证明。研究表明，在最佳沉淀条件下，稀土的沉淀效率为99。72%，稀土精矿纯度为82.21%，由于沉淀过程中形成碱性稀土硫酸盐，稀土精矿中SO3含量高达13.44%。为了降低SO3含量，本文提出用硫酸盐去除剂对沉淀富集进行搅拌洗涤。硫酸盐去除剂的阴离子在搅拌洗涤过程中会与硫酸根离子竞争。因此，氢氧化钠可能是进一步详细研究的首选。沉淀浓缩物经氢氧化钠洗涤后，稀土精矿纯度分别为88.03%，SO3含量为7.51%。因此，为镁盐系统浸出液中稀土非富氨提供了一种可行的操作方法。