Abstract: Provided are a method and molten salt system for recovering rare earth elements from NdFeB waste and use of ferric oxide as a raw material of a manganese-zinc ferrite. The molten salt system comprising the following components in percentage by weight: 40% of K3AlF6 or Na3AlF6, 40% of KBe2F5, and 20% of KAlF4. By adopting the three-component molten salt system of the present invention, recovery rates of rare earth elements extracted from NdFeB waste all can reach 98% or above. By adopting the three-component molten salt system, extraction temperature is 100-400° C. lower than that of all current similar halogenation methods, and extraction time is fold shorted to 1-3 h. The reduction of the extraction temperature and the shortening of the melting time greatly reduce the energy consumption of extracting rare earth elements from NdFeB waste, and the economic benefits are remarkable.

Abstract: Provided is a method for preparing a soft magnetic manganese-zinc ferrite composite by removing impurities from industrial waste step by step. Manganese-containing waste residue is crushed and dried, and then mixed with a flux in a muffle furnace and roasted at a temperature below 1000° C. till solid-liquid stratification; then, multi-step impurity removal is performed to obtain a high-purity quaternary purification solution of manganese sulfate. Similarly, zinc residue is melted to remove impurities, and then multi-step impurity removal is performed to obtain a high-purity quaternary purification solution of zinc sulfate. According to a manganese-zinc-iron ratio required for the manganese-zinc ferrite, the two purification solutions are mixed, and ferrous sulfate is added.

Abstract: Provided are a method and molten salt system for recovering rare earth elements from NdFeB waste and use of ferric oxide as a raw material of a manganese-zinc ferrite. The molten salt system comprising the following components in percentage by weight: 40% of K3AlF6 or Na3AlF6, 40% of KBe2F5, and 20% of KAlF4. By adopting the three-component molten salt system of the present invention, recovery rates of rare earth elements extracted from NdFeB waste all can reach 98% or above. By adopting the three-component molten salt system, extraction temperature is 100-400° C. lower than that of all current similar halogenation methods, and extraction time is fold shorted to 1-3 h. The reduction of the extraction temperature and the shortening of the melting time greatly reduce the energy consumption of extracting rare earth elements from NdFeB waste, and the economic benefits are remarkable.

Abstract: A method for synchronous production of manganese tetraoxide and ferric oxide for a soft magnetic material by using marine polymetallic nodules includes: 1) crushing and grinding marine manganese nodules and baking to a constant weight; thoroughly mixing with a mixed flux and roasting in a muffle furnace; 2) carrying out solid-liquid separation, washing solid-phase precipitates with water, grinding the solid, adding sulfuric acid, controlling the temperature to be below 50° C., and vacuuming a reactor up; 3) adding a reducing agent to react at room temperature for 5-10 min, adding ammonia water to adjust the pH value to 5.5, and carrying out separation and filtering; 4) controlling the temperatures of manganese sulfate and ferric sulfate solutions to be below 50° C., and adding ammonium sulfide; and 5) washing with deionized water, and calcining at 800-900° C. for 1-3 s by a suspension low-temperature instantaneous firing system.