A New Treatment of Rare Earth Ores in Molten Sodium Hydroxide

研究了用熔融碱处理稀土矿的新方法。根据实验结果。确定了最佳反应条件：反应温度；350 ^大气下：矿石尺寸。100目<；矿石/NaOH重量比*0.2。反应时间。0.5 h后对得到的反应产物进行洗涤，在最佳条件下加水除碱。在5 M以下0.5 M的HCl浸出条件下，镧和其他稀土金属的氧化物比CeO_2的选择性更强，HCl浸出渣中CeO_2的含量达到60%以上。说明该渣具有足够的铈精矿品位。CeO_2的含量会增加。但铈（IV）的溶解会降低铈精矿的收率。由于铈精矿是由相当均匀的约0.1微米的微颗粒组成。可用于玻璃磨料。等。另一方面。以氯化镧为主要成分的粗稀土氯化物，通过HCl浸出溶液的浓缩得到。动力学研究表明，氧在熔融碱中的溶解过程是反应速率的决定步骤。因此。回转窑连续式反应器比混合槽式反应器更适用。根据结果。我们开发了一种浸出稀土矿的新方法。该方法可方便地应用于中国混合稀土矿丰富的矿区制备铈精矿和氯化稀土混合物。

New treatment method for rare earth ores has been studied by using molten alkali. Basing on the experimental results. the optimum conditions were found as follows : reaction temperature. 350 ^ﾟC : under atmosphere : ore size. 100 mesh< ; ore/NaOH weight ratio*0.2. reaction time. 0.5 h. After washing of the reaction products obtained under the optimum conditions to remove alkali with water. oxides of lanthanum and other rare earth metals were extracted more selectively than CeO_2 in a 0.5 M HCl leaching below 5 M. The content of CeO_2 in the HCl leaching residue reached to 60 % or higher. This shows that the residue has enough grade as cerium concentrate. The content of CeO_2 would be able to increase. but the yield of cerium concentrate will decrease because of cerium (IV) dissolution. Since the cerium concentrate is composed of fairly homogeneous micro particles of ca. 0.1 mum. It can be used for the abrasives of glass. Etc. On the other hand. Crude rare earth chloride in which lanthanum chloride was the principal constituent as obtained by concentration of the HCl leaching solution.Additionally. The kinetic study on the reaction indicated that the dissolution process of oxygen into molten alkali was the rate determining step. Therefore. A continuous reactor of rotary kiln is more suitable than a mixing tank reactor.Based on the results. We have developed a new procedure for leaching rare earth ores. This method can be applied easily for preparation of cerium concentrate and the rare earth chloride mixture at mine sites in China where mixed rare earth ores are abundant.