NdFeB magnet scrap pretreated by air oxidation and its leaching process

This paper studied the NdFeB pretreatment with hydrochloric acid wetting and air oxidation to reduce the pretreatment cost of NdFeB scrap, and investigated the rare earth leaching process and leaching kinetics from NdFeB scrap by hydrochloric acid. The results show that the oxidation rate of iron in NdFeB scrap is up to 92.37 % after wetting with 4 mol/L HCl and staying for 20 days in the air, which can meet the requirements of iron oxidation in the rare earth recovery and reduce the production cost; in the leaching process, when the reaction temperature is 363 k, the hydrochloric acid concentration is 2 mol/L, the particle size is of 0.055 mm to 0.088 mm, the ratio of V_L/W_S is 8:1, and the stirring speed is 500 r/min, the rare earth leaching rate from NdFeB scrap can reach 89.36 % after leaching for 60 mins. Studies also show that the rare earth leaching process from NdFeB scrap is followed the unreacted shrinking core model controlled by diffusion, and its apparent reaction activation energy is 17.49 kJ/mol.