Migration of exchangeable rare earth and aluminum in leaching process of weathered crust elution-deposited rare earth ore

In order to understand what governs the leaching of exchangeable rare earth (RE) and impurities and enhance the RE leaching process, the effects of the concentration of ammonium sulfate, pH and leaching temperature on the migration of RE and aluminum (Al) during the leaching of weathered crust elution-deposited rare earth ore was studied. The elution curves for ammonium ion (NH4+) were also studied to reduce the consumption of the leaching agent. It was found that a high concentration of leaching agent can enhance the leaching process of RE and Al, reduce the breakthrough volume of NH4+ and more rapidly obtain the equilibrium of NH4+. However, excessive leaching agent can both increase the cost and the burden on the environment. There is almost no variation on the elution curves of RE and Al in the pH range of 4-8 and control of the pH of the leaching agent can be omitted. It is better for the leaching work to be done in summer since higher temperatures can enhance the RE leaching process and improve the use ratio of ammonium. Using 0.1 mol/L ammonium sulfate for leaching 250 g RE ore, 95.42% RE extraction can be obtained when the volume of leachate is 102.6 mL. At this moment, only 18.17% of NH4+ is used to exchange RE and 49.22% of NH4+ is left in the leachate that can be reused as leaching agent by replenishing ammonium sulfate. The results of our studies can provide theoretical guidance for high efficiency and low consumption exploitation of RE ores.