Recovery of rare earth from the ion-adsorption type rare earths ore: II. Compound leaching

摘要

In order to coordinate the content and ratio of ion-exchangeable calcium and ion-exchangeable magnesium in the soil and reduce ammonia nitrogen pollution, recovery of rare earth from the ion-adsorption type rare earths ore with magnesium-ammonium, magnesium-calcium and magnesium-ammonium-calcium compound leaching agent was studied in this paper. Results showed that the leaching ability was in the order of (NH4) 2SO4 > NH4Cl > MgSO4 > MgCl2 approximate to CaCl2 under the same total cationic charge. The content of ion-exchangeable magnesium and ion-exchangeable calcium in water washing tailings could be adjusted to be suitable for the plant growth by changing the composition of leaching agent. In the magnesium-ammonium-calcium compound leaching system, when the mole ratio of magnesium-ammonium-calcium was 15:25:60, 628.57 mg.kg(-1) ion exchangeable magnesium and 77.77 mg.kg(-1) ion-exchangeable calcium in water washing tailings were achieved, while the ratio of ion-exchangeable calcium and magnesium was 8.08. Moreover, the aluminum leaching efficiency was only 492% and the rare earth leaching efficiency could be above 94%. Furthermore, the soybeans could grow normally with water washing tailings in magnesium-ammonium-calcium compound leaching system with an average plant height of 25.5 cm. The application of magnesium-ammonium-calcium compound leaching agent could significantly reduce the ammonia nitrogen pollution, maintain the soil nutrient so as to reduce the dosage of calcium-magnesium fertilizer, and may realize the ecological friendly leaching of the ion-adsorption type rare earths ore. (C) 2016 Elsevier B.V. All rights reserved.