丙二酸钠搅洗去除稀土富集物中硫酸根

Sulfate removal from alkaline precipitate of rare earth by stirring washing with malonate

在离子型稀土浸出液氧化钙沉淀过程中,硫酸根会参与反应产生碱式硫酸稀土,使所得混合稀土氧化物中硫酸根含量过高。针对这一问题,本文基于竞争配位除硫的思路提出采用丙二酸钠对氧化钙沉淀富集物进行搅洗以除去其中的硫酸根,在搅洗反应温度45℃,搅洗时间10 min,丙二酸钠溶液浓度0.10 mol/L、体积30 mL的条件下,获得了稀土纯度为91.36%、硫酸根含量为3.02%(质量分数)的混合稀土氧化物。通过对反应过程的质量衡算和TG-DSC、XRD、FI-IR等测试表征,确定了在搅洗过程中丙二酸根与碱式硫酸稀土中的硫酸根以摩尔比1:1竞争配位。丙二酸根的引入可有效降低硫酸根含量,但是其搅洗循环效果有待进一步提高。

The process of calcium oxide precipitation enrichment can be linked to the magnesium salt composite leaching technology to realize the circulation of calcium and magnesium,in turn,solve the ammonia nitrogen problem in the ionic rare earth ore processing,including leaching and enriching.However,sulfate will participate to form basic rare earth sulfate in the precipitation process,resulting in a high content of sulfate radical in the roasted product.As continuation of the idea of desulfurization by competitive coordination,this paper proposes to remove sulfate radical from the calcium oxide precipitation enrichment in the stirring washing process using malonate as exchanged ligand.Mixed rare earth oxides with rare earth purity of 91.36%and sulfate content of 3.02%(mass fraction)are obtained at 45℃and the washing time of 10 min,sodium malonate concentration of 0.10 mol/L and sodium malonate volume of 30 mL.1:1 coordination of the malonate and the sulfate in the basic rare earth sulfate during the stirring washing process is determined by the mass balance calculation of the reaction process and the characterization of TG-DSC,XRD,FI-IR,etc.The content of sulfate radical can be effectively reduced by exchanging with malonate,but its cycle stability needs to be further improved.