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

- The colloidal sediment phase rare earth was little leached even if the pH reached 1.00.
- Compound leaching with MgSO4/FeSO4 or MgSO4/ascorbic acid was proposed.
- The influence of Mg/Fe proportion and pH values was investigated.
- The leaching performance of the Mg/Fe leaching system was unsatisfactory.
- 85.85% RE leaching efficiency and 5.33% Ce partition were achieved with MgSO4/ascorbic acid compound leaching.

The colloidal sediment phase rare earth was little leached even if the pH of leaching agent reached 1.00, but part of it could be reduction leaching by the ferrous ion. To solve the problems appeared in the FeSO4 leaching process, a magnesium-ferrous compound leaching was put forward in this paper. It was demonstrated that lower proportion of Mg/Fe and higher acidity of leaching agent, could result in a higher rare earth leaching efficiency and relative a bigger cerium partition in the leaching liquor. But the leaching performance of the magnesium-ferrous compound leaching system was unsatisfactory because of some problems. Therefore, another compound leaching method using MgSO4 and ascorbic acid was proposed, taking advantage of the reducibility and the ability to strengthening the leaching process of ascorbic acid. It was shown that about 50% rare earths colloid sediment phase was dissolved into the leaching liquor when with 0.20 mol/L MgSO4 and 0.5 g/L ascorbic acid. 85.85% rare earth leaching efficiency and a low content of Fe and Al were achieved as well. Therefore, compound leaching with MgSO4 and ascorbic acid was proposed to an excellent alternative leaching agent for further studies, which may realize efficiency extraction, low consumption and be environmentally friendly.