Leaching Behaviors of Calcium and Aluminum from an Ionic Type Rare Earth Ore Using MgSO₄ as Leaching Agent

• Main Authors: Qiang He, Jiang Qiu, Minglu Rao, Yanfei Xiao
• Format: Article
• Language: English
• Published: MDPI AG 2021-07-01
• Series: Minerals
• Subjects: ionic-type rare earth ore; calcium; aluminum; leaching behavior; MgSO₄
• Online Access: https://www.mdpi.com/2075-163X/11/7/716

During the leaching process of ionic rare earth ore (ICREO), ion-exchangeable phase calcium (IEP-Ca) and ion-exchangeable phase aluminum (IEP-Al) are leached along with rare earth, which causes many problems in the enrichment process, such as increasing the precipitant agent consumption and rare earth loss, etc. The agitation leaching kinetics and the column leaching mass transfer process of IEP-Ca and IEP-Al were studied to understand the leaching behavior of impurity in ICREO, which provides guides for the adjustment of the leaching process and to limit the co-leaching of impurities. IEP-Ca and IEP-Al were leached by ion exchange, with the leaching agent cations and the leaching kinetics described by an internal diffusion-controlled shrinking core model with an apparent activation energy of 8.97 kJ/mol and 10.48 kJ/mol, respectively. In addition, a significant reduction in the leaching efficiency of aluminum was caused by the hydrolysis reaction reinforced by the increase in MgSO₄ concentration and temperature. The leaching kinetic data of IEP-Ca and IEP-Al was verified by the column leaching mass transfer process. There was a synchronous increase in the peak concentration of the outflow curve and leaching efficiency of calcium with the concentration of MgSO₄ since IEP-Ca was easily leached. Therefore, as the leaching efficiency of calcium was already very high in the 0.20 mol/L MgSO₄ leaching process, the leaching rate of calcium was limited by the leaching temperature and injection rate of MgSO₄. For aluminum, the hydrolysis of Al³⁺ was promoted by increasing the MgSO₄ concentration and the leaching temperature, thereby effectively reducing the content of aluminum in the leachate.