Abstract:The leaching behaviors of calcium and magnesium in the rare earth tailings leached with magnesium sulfate using deionized water, CaCl₂ solution and lime water were investigated. Experimental data indicated that magnesium in the tailings was easy to be leached out since most of the magnesium was in the form of water-soluble phase. Most of calcium in the lime water was electrostatically adsorbed on the clay mineral of the tailings, and the water-soluble magnesium was also gradually converted into exchangeable phase because of back-adsorption of Mg²⁺ on the clay mineral with increasing the pH values. When the liquid-to-solid ratio was 0.80, the contents of readily-available magnesium and calcium were 104.4-207.6 and 201.7-1426.3 mg/kg, respectively, which could meet the requirements for plants. These results suggest a promising route for the environmental remediation of ion-adsorption rare earth ore after in-situ leaching.

Key words: ion-adsorption rare earth ore; magnesium sulfate; environmental remediation; leaching behaviors; lime water