Ion-Exchange Model for the Leaching Process of Ion-Adsorption-Type Rare-Earth Ores Considering the Influence of Anions.

Clay minerals have a specific adsorption capability for anions, which increases the amount of net negative charge on the surface, leading to the increased adsorption of rare-earth ions in clay minerals and some change from exchangeable to non-exchangeable. Further, anions show a shielding effect on rare-earth ions. The shielding capacity of anions in the leaching agents for rare-earth ions was measured in this study. The relationship between the solid-phase concentration of rare-earth ions shielded and the anion concentration was consistent with the Langmuir model. Based on the Kerr model describing the exchange of rare-earth ions by ammonium ions, an ion-exchange model considering the shielding influence of anions was proposed. The accuracy of the proposed model was higher than that of the Kerr model. When the leaching agent was ammonium sulfate, the calculation accuracy of XW and AY samples was increased by 1.15% and 5.75%, respectively. The improvement in accuracy positively correlated with the proportion of iron oxides, aluminium oxides, and Kaolin. The established ion-exchange model can provide accurate source and sink terms for the numerical simulation of the leaching process of ion-adsorption-type rare-earth ores. [ABSTRACT FROM AUTHOR]