The precipitation of the water-leaching solution of Baotou mixed rare earth (RE) concentrate roasted with sulfuric acid using ammonium bicarbonate for producing RE carbonate produces a mass of ammonia-nitrogen wastewater because of the relatively low solubility of rare earth sulfate. To solve the serious problem of ammonia-nitrogen pollution, new precipitators need to be developed urgently so as to meet the requirements of environmental protection and impurities content of the product (SO₄²⁻<1.8 wt% in RE carbonates products). In this paper, we studied the effects of feeding modes on the behavior of SO₄²⁻ during the preparation of light RE carbonate (RE = La, Ce, Pr, Nd) from their sulfate solutions using Mg(HCO₃)₂ as a precipitant. The results indicate that the contents of SO₄²⁻ in the La and Ce precipitates using positive feeding mode exceed 16 wt% because of the formation of La₂(CO₃)_2.15(SO₄)_0.85·4H₂O and Ce₂(CO₃)_2.15(SO₄)_0.85·3H₂O, while those of the Pr and Nd precipitates are 4 wt%–5 wt% since they exist in the form of n-carbonate. The precipitates prepared using synchronous feeding mode are all RE carbonate with only 4 wt%–5 wt% of SO₄²⁻ enclosed in the precipitation. The content of SO₄²⁻ in the RE carbonate obtained using reverse feeding mode is the lowest. Among them, the content of SO₄²⁻ in La precipitate is only 1.40 wt%. Both synchronous and reverse feeding modes can effectively reduce the content of SO₄²⁻ in RE carbonate, which provides theoretical guidance for the preparation of qualified light RE carbonate products by Mg(HCO₃)₂ precipitation method.

硫酸焙烧包头混合稀土（RE）精矿的水浸液沉淀使用碳酸氢铵生产碳酸稀土，由于硫酸稀土的溶解度较低，产生大量氨氮废水。为解决氨氮污染严重的问题，迫切需要开发新型沉淀器，以满足环保和产品杂质含量（稀土碳酸盐产品中SO ₄ ²⁻ <1.8 wt%）的要求。在本文中，我们研究了在使用 Mg(HCO ₃ ) ₂从硫酸盐溶液制备轻质稀土碳酸盐（RE = La、Ce、Pr、Nd）过程中，进料模式对 SO ₄ ^2-行为的影响作为沉淀剂。该结果表明，SO内容₄ ^2-在La和Ce的沉淀物用正进给模式，因为La中形成的超过16％（重量）₂（CO ₃）_2.15（SO ₄）_0.85 ·4H ₂ O和Ce的₂（ CO ₃ ) _2.15 (SO ₄ ) _0.85 ·3H ₂ O，而Pr和Nd沉淀物的含量为4wt%~5wt%，因为它们以n-碳酸盐的形式存在。使用同步进料模式制备的沉淀物都是稀土碳酸盐，只有 4 wt%–5 wt% SO ₄ ²⁻包裹在沉淀中。采用反向进料方式得到的稀土碳酸盐中SO ₄ ^2-的含量最低。其中，La沉淀物中SO ₄ ^2-的含量仅为1.40 wt%。同步和反向进料方式均能有效降低稀土碳酸盐中SO ₄ ^2-的含量，为Mg(HCO ₃ ) ₂沉淀法制备合格的轻质稀土碳酸盐产品提供了理论指导。