复合镁盐浸取风化壳淋积型稀土矿过程强化研究

Enhancement of the Leaching Process of Weathered Crust Elution-deposited Rare Earth Ore with Composite Magnesium Salt

风化壳淋积型稀土矿是世界中重稀土的主要来源,其中稀土以水合或羟基水合离子吸附在黏土矿物上,可采用离子交换的方式浸出稀土矿。为提高以复合镁盐为浸取剂时稀土的浸出效果,采用柱浸的方式模拟原地浸出过程,研究了复合镁盐浸取风化壳淋积型稀土矿稀土及铝的浸出传质过程,并结合色谱塔板理论进行了分析。结果表明,采用氯化镁和硝酸镁摩尔比为4∶6的复合镁盐浸取剂浸出稀土的效果最佳;在一定范围内较高的镁离子浓度可以通过提供驱动力来克服扩散阻力,从而加强稀土(RE)和铝(Al)的传质过程;pH在4~8范围内几乎不影响稀土和铝的传质效率,强酸性环境(pH=2)下浸出稀土矿会显著加强铝的浸出,不利于后续处理;高温有助于稀土及铝的浸出;采用复合镁盐柱浸回收稀土的最佳工艺条件为:MgCl2和Mg(NO3)2摩尔比为4∶6,镁离子浓度为0.2 moL/dm3,pH为溶液初始值,夏季作业有利于提高浸出传质效率。

The main source of medium and heavy rare earth in the world is weathered crust elution-deposited rare earth ore.The rare earth is adsorbed on the clay minerals in hydrated or hydroxyl hydrated ions,which can be leached by ion exchange.In order to improve the leaching effect of rare earth with composite magnesium salt,the method of column leaching was used to imitate the in-situ leaching process,the mass transfer process of leaching the weathered crust elution-deposited rare earth ores with composite magnesium salt was studied and analyzed with chromatography plate theory.The results showed that the composite magnesium salt with a molar ratio of magnesium chloride to magnesium nitrate of 4:6 was the best method to extract rare earth.The higher concentration of Mg2+in a certain range could overcome the diffusional resistance by providing the driving force,thus strengthening the mass transfer process of rare earth and aluminum.The pH in the range of4 to 8 hardly affected the mass transfer efficiency of rare earth and aluminum,and the leaching of rare earth ore in a strongly acidic environment(pH=2)would significantly enhance the leaching of aluminum,which was not beneficial to the following treatment.High temperature facilitated the leaching of rare earth and aluminum.The optimum conditions for the recovery of rare earth with composite magnesium salt by the method of column leaching are as follows:the molar ratio of MgCl2 and Mg(NO3)2 is 4:6,the concentration of Mg2+is 0.2 moL/dm3,and the pH of the leaching agent is the initial value of the solution,leaching in summer is beneficial to improve the mass transfer efficiency of leaching.