Study On The Process And Mechanism Of Extracting Rare Earth From NdFeB Waste

The rapid development of magnetic material industry is promoted by the wide application of Nd-Fe-B magnetic materials.It is predicted that the domestic output will reach 250000 tons in 2020.A lager number of waste will be produced in the process of Nd-Fe-B production,and the waste contains plenty of valuable components such as Pr and Nd.Therefore,it is of great economic significance to recycle and utilize the rare earth from Nd-Fe-B magnet scrap.The process and reaction mechanism of extracting rare earth from Nd-Fe-B magnet scrap was studied systematically.Major research work includes:(1)The rare earth(RE)extraction conditions from Nd-Fe-B magnet scrap were studied by oxidation roasting-hydrochloric acid decomposition.The influence of calcination temperature and time on the iron oxidation rate was discussed in the roasting process.In the leaching process,the effects of hydrochloric acid concentration,reaction time,reaction temperature and liquid to solid ratio on leaching rate of rare earth were investigated too,and the influence of p H and the aging time of the impurity on the leaching liquid were analyzed.The results show that the oxidation rate of iron reaches maximum with calcining at 700℃ for 1.5 hours,and iron is completely oxidated to the trivalent iron.The RE leaching rate reaches 99.33% at the optimum conditions.After change the p H to 3.5 and the aging time to more than 2 hours for neutralization process,little impurities of Cu,Pb,Co and Fe are dissolved in the leaching solution.The Fe content in the leaching solution is only 0.0014g/L,the rare earth leaching solution meets the requirements of RE extraction.(2)To reduce the cost of waste disposal,the mechanism of rare earth leaching in the Nd-Fe-B magnet scrap by using hydrochloric acid wetting and air oxidation method was discussed,and the kinetics of rare earth in the leaching process were analyzed.The results show that the concentration of hydrochloric acid in 4mol/L,the ratio of liquid to solid is 1:5,and the period of 20 days can meet the requirements of rare earth in the early treatment process.It can greatly reduce the production cost.The leaching rate of rare earth was linear with the temperature,acidity and particle size.The activation energy is 17.49 k J/mol.(3)Then,the synthesis of Praseodymium neodymium oxide with regular morphology was studied by the solution of Pr Cl3 and Nd Cl3 as raw material.Through orthogonal experiment,the effects of various technological conditions on the particle size of Praseodymium neodymium oxide were analyzed,and the optimum conditions for preparing a certain morphology of Praseodymium neodymium oxide were found out.The results show that: At the RE2O3 concentration of 0.3mol/L,the H2C2O4 concentration of 0.6mol/L,the precipitation temperature at 60℃ and the stirring rate in 500r/min,RE2O3 powder with the center particle size of D50 in 14.36μm and the specific surface area in 856.21m2/g were prepared,which the particle shape is columnar,with uniform particle size and good dispersion.The results show that the roasting acid decomposition process can be well from Nd-Fe-B scraps extraction of rare earth,reccycling high iron and low taste of Nd-Fe-B waste by hydrochloric acid wet air oxidation method can be greatly reduce the cost of recycling.