Method for recovering rare earth elements from ndfeb waste and use of ferric oxide as raw material of manganese-zinc ferrite

A method for recovering rare earth elements from NdFeB waste, comprising the following steps:

• 1) crushing NdFeB waste into fine particles with a particle size of 3-5 mm, thoroughly mixing the fine particles with a molten salt system, the molten salt system comprising the following components in percentage by weight:
• 40% of K3AlF6 or Na3AlF6, 40% of KBe2F5, and 20% of KAlF4;
• heating the mixture in an electric furnace to 330° C. until the three-component molten salt system begins to melt, wherein as the temperature rises, a liquid phase gradually increases, and the fluidity of the material is improved;
• and
• 2) then, rapidly heating the material to 800-850° C. or 900-950° C. within 10 min, holding the temperature for 1-3 h so that rare earth elements in the NdFeB waste are fluorinated into rare earth fluorides which are dissolved in the molten salt and Fe element in the NdFeB waste deposits in a lower layer of the molten salt in the form of oxides;
• and carrying out solid-liquid separation to separate the rare earth fluorides from the precipitate to obtain a solid precipitate ferric oxide, thereby realizing the separation of Fe from rare earth elements;
• cooling the liquid molten salt after solid-liquid separation to room temperature and then crushing and ball-milling the molten salt to more than 200 meshes;
• adding sodium hydroxide according to a mass ratio of molten salt to sodium hydroxide being 1:1 and roasting the material for conversion at 300-450° C. for 2-4 h and then cooling the material to room temperature;
• adding water to wash away water-soluble salts of fluorine, aluminum, beryllium, potassium, sodium and the like;
• filtering the material, adding 2-6 mol/L hydrochloric acid to the residue to leach rare earth elements, and carrying out filtering to obtain pure rare earth element solutions.