Ndfeb magnet, because of their excellent magnetic, known as 'magnetic king', is widely applied to many fields.
In the production of ndfeb magnet produces about 20% of the raw material weight ndfeb waste, including cutting blocks and waste oil etc.
Ndfeb waste contains about 30% of the rare earth elements [
Which contains about 90% of neodymium, the rest of terbium and dysprosium, etc. )
China is the ndfeb magnet production power, accounting for 80% of global production.
In 2005, production of ndfeb 3 in our country.
520000 tons, ndfeb waste caused by the more than 7000 tons, has a current production capacity of ndfeb with greater than 20% speed growth, predicts 2010 summary of output in China will exceed 100000 tons, will produce about 20000 tons of ndfeb waste.
In order to save resources, reduce industrial waste at the same time, environmental protection, comprehensive utilization of waste recycling of ndfeb magnet is necessary.
And will have a significant social benefit and considerable economic benefits.
1 ndfeb waste recycling process.
Optimal solution method [1 hydrochloric acid
Hydrochloric acid principle of optimal solution method is strictly control acid decomposition process conditions, let the waste in the rare earth first dissolved in hydrochloric acid solution.
Optimal solution method by oxidizing roasting, decomposition in removing impurity, extraction, separation and precipitation of burning and so on four parts.
Oxidizing roasting, the key step for the optimal solution method, will into rare earth oxide, iron into Fe2O3, to facilitate the next step acid decomposition;
Decomposition in removing impurity: add a small amount of water in the reactor, many times to join the hydrochloric acid and materials, control of rare earth concentration and pH, let solvent extraction separation of rare earths priority: after removing impurity of the rare earth chloride solution using P50 separation of rare earth elements, get a single rare earth chloride;
Lake burning: separate the extraction liquid into the sedimentation tank, adding ammonium oxalate precipitation agent, rare earth oxalate or rare earth carbonate precipitation, burn, rare earth oxides.
The process is shown in figure 1.
2 soluble method  the solution method is using hydrochloric acid as solvent, will dissolve waste materials of rare earth elements and iron ion state, then in addition to iron, such as extraction separation process of rare earth oxides.
Soluble method by leaching solution, in addition to iron, extraction separation, precipitation of burning and so on four parts.
Leaching solution: after ndfeb waste screening directly dissolved in concentrated hydrochloric acid at room temperature, the rare earth ions and iron into form, using hydrogen peroxide oxidation of Fe2 + as Fe3 +;
In addition to iron: iron using N503 extraction;
After extraction separation, in addition to iron the solution by P507 extraction separation of rare earth elements, get a single rare earth chloride;
Precipitation burning rare earth oxides.
The process is shown in figure 2.
Figure 2 agent method, process flow diagram 1.
3 acid double salt method [
Sulphuric acid -
Double salt method is to use waste sulfuric acid as solvent to dissolve ndfeb magnet, and then with Na2SO4 solution under a certain temperature reaction and producing ammonium sulphate double salt precipitate out, add sulfuric acid double salt precipitation in oxalic acid solution, the generation of rare earth oxalate precipitation, after burning for rare earth oxide.
The process flow is shown in figure 3.
Figure 3 sulfuric acid double salt method, process flow diagram 2, the development trend at present, ndfeb magnet is mainly a hydrometallurgical recycling.
HCL - extraction process, easy to realize large-scale production, but oxalate precipitation or producyion washing wastewater pollution is larger, and the ammonia as the saponification agent, high concentrations of ammonia nitrogen in the wastewater caused by water pollution.
The sulfate - double salt precipitation process, difficult to realize large-scale production, all into ferrous sulfate and dissolved Fe, waste iron during recovery of rare earth elements, more water pollution.
From the perspective of economic and environmental protection, better than other process by hydrochloric acid optimal solution method.
The method can reduce the use amount of acid, acid slag as iron concentrate can be directly sold to steel or cement plant as a production cement iron correction element;
At the time of extraction separation using caustic soda or whitewash instead of ammonia water as the medium of saponification can effectively reduce the ammonia nitrogen in wastewater.
3, summary ndfeb magnets whether the size of the demand, and demand growth, are quite striking.
Is a rare earth power in China, and its industrial reserves accounted for more than 70% of the world's total reserves, but rare earth is non-renewable resources, and in the process of mining and materials processing produce huge amounts of waste, environmental pollution and resource waste.
Can be obtained from the waste ndfeb magnet neodymium oxide, terbium oxide and dysprosium oxide, cobalt oxide valuable products, etc.
For industrial waste recycling, in line with the national development of circular economy industrial policy.