Development Of Highly Selective Recovery System Of Rare Earth Elements From Ce-containing NdFeB

At present,the recycling of rare earth permanent magnet secondary resources has a strong urgency.Only in the production process of Nd Fe B,about 30 % of the waste will be produced,which contains about 30 % of the rare earth elements.Moreover,these products have service life,and they will also produce waste containing a large amount of rare earth when they are expired.China accounts for more than 60 %,and the amount of scrap is increasing year by year.A large number of permanent magnet waste is in urgent need of reasonable disposal.In addition,in China's market,the supply of rare earth oxides is in short supply,and the supply gap is expanding year by year.Although recycling can not completely narrow the huge gap between demand and supply,in the long run,the secondary supply of recycling can meet the demand of nearly 50% Nd.Therefore,from the point of view of reducing supply risk and balancing resources,the secondary utilization of rare earth resources in CE rich magnets is also very important.In view of the problems of low rare earth recovery rate,high energy consumption,extensive production process,large amount of chemical raw materials,low added value of products and prominent environmental problems in the current rare earth recovery process,this paper mainly makes the following researches(1)Based on hydrochloric acid optimal solution method,a high temperature and high pressure leaching system was developed for cerium rich magnets.The effects of roasting temperature,roasting time,leaching temperature,leaching time,leaching agent concentration and liquid-solid ratio on leaching rate were systematically studied.The optimal recovery process parameters were obtained,and the leaching mechanism was explained by kinetic analysis.(2)With the goal of high efficiency and high value recovery of permanent magnet,a new efficient leaching agent for recovering water-soluble ammonia salt is developed,so that praseodymium and neodymium in permanent magnet can be selectively recovered with high efficiency and low cost,and solid waste can be reduced,which is of great significance for the full utilization of rare earth resources.(3)Using the newly developed water-soluble ammonia salt leaching agent,the primary and secondary order of leaching conditions on leaching results was systematically explored by orthogonal method,the optimal leaching conditions were determined,and the influence rules were summarized.Finally,the rare earth products with high purity and high added value were obtained.The results show that the complete oxidation of metal elements and the removal of organic matter in CE rich magnets can be achieved by calcining at 800 ? for 2 h.When the liquid-solid ratio is 150(ml / g),leaching time is 8 h,leaching temperature is 200 ?,hydrochloric acid concentration is 0.1 M,99 % PR,95.56 % nd and 93.77 % GD are selectively leached,and only 0.23% Fe is leached.The kinetic principle of leaching process proves that the leaching process of rare earth oxides is controlled by internal diffusion.Because of the difference of solubility of metal oxides in hydrochloric acid,it has high selectivity and avoids the complete dissolution of metal oxides.The results show that the simplified recovery process with low acid consumption and high selectivity is feasible.Subsequently,a new method of extracting and recovering permanent magnet waste with[hbet] Cl aqueous solution was proposed.The optimum leaching conditions are 200 ?,8 h,0.2 m [hbet] Cl,1:150 g/ ml.the optimum leaching effect is pr 99.81 %,nd 97.05 %,Gd95.51 %,CE 56.24 %,Fe 0.2 %.Compared with the common leaching agent,this method has better leaching rate and selectivity,and the leaching sequence conforms to the established chemical properties.The leaching mechanism was analyzed,the lattice energy u and U/x values of ionic crystal decomposition were calculated,and the dissolution order and solubility difference of metal oxides were explained,which laid a foundation for the recovery process.It is an important technical means to realize the high value comprehensive utilization and green,large-scale disposal of rare earth solid waste.