难处理稀土电解熔盐废渣高效回收利用研究
发布时间：2018-08-22 18:19
【摘要】：工业上低熔点稀土金属(合金)常采用氟化物-氧化物体系熔盐电解法制备,稀土熔盐电解过程产生含稀土的废熔盐渣成分复杂,稀土回收利用困难,对稀土废熔盐渣中稀土进行高效回收利用具有广阔运用前景及重要现实意义。本文首先对稀土熔盐渣进行了物相分析及能谱分析,确定了稀土主要以REO、REF3及REOF三种形式存在,并且含有石墨等杂质。在此基础上本文进行了高压碱转、机械活化碱转、络合分解、硼砂焙烧及碳酸钠焙烧稀土电解熔盐废渣等探索实验,并遴选出硼砂焙烧法及碳酸钠焙烧法。对添加硼砂及碳酸钠焙烧稀土电解熔盐废渣所得产物进行了物相分析,确定其化学反应式分别为:Na2B4O7·10H2O+REF3=Na2O+REBO3+BF3+H2O,3Na2CO3+2REF3=6NaF+RE2O3+3CO2。通过化学反应动力学研究,得到硼砂及碳酸钠分解稀土熔盐渣反应的活化能分别为159.02 kJ/mol,159.00 kJ/mol,指前因子分别为1.15×109min-1,2.58×109min-1,反应速率常数分别为0.26 min-1,0.28min-1,反应限制性环节均为界面化学反应。硼砂焙烧稀土熔盐渣工艺研究结果表明,最佳工艺条件为:焙烧温度为700℃,焙烧时间为1 min,硼砂添加量为原料质量的38%;最佳浸出条件为:浸出温度为70℃,浸出时间为40 min,液固比为5:1,盐酸浓度为3 mol/L。在最佳条件下,稀土浸出率为97.35%,浸出液pH0.5,浸出液中F-浓度为0.28 g/L,稀土离子浓度为16.97 g/L,REO/F=60.18。碳酸钠焙烧稀土熔盐渣工艺研究结果表明,最佳工艺条件为:焙烧温度为700℃,焙烧时间为60 min,碳酸钠添加量为稀土含量的1.5倍,添加5%的硼砂做添加剂,添加5%的硫脲进行盐酸优溶,浸出温度为85℃。所得焙烧产物结构疏松,非Ce稀土浸出率为96.98%,Ce的浸出率为80.78%,浸出液中F浓度为0.12 g/L,pH值为3.8,稀土离子浓度为64.30 g/L,REO/F=559.13,Al2O3/REO=1.6×10-3,浸出液可直接进P507稀土萃取槽进行萃取分离。
[Abstract]:Low melting point rare earth metals (alloys) are often prepared by fluoride oxide system molten salt electrolysis. The waste molten salt slag containing rare earth is complicated in the process of rare earth molten salt electrolysis, so it is difficult to recycle rare earths. The recovery and utilization of rare earths from waste molten salt slag has broad application prospect and important practical significance. In this paper, the phase analysis and energy spectrum analysis of rare earth molten salt slag are carried out. It is determined that rare earth mainly exists in three forms: REONREF3 and REOF, and contains impurities such as graphite. On this basis, the experiments of high-pressure alkali conversion, mechanically activated alkali conversion, complex decomposition, borax roasting and sodium carbonate roasting rare earth electrolytic molten salt waste residue were carried out, and the borax roasting method and sodium carbonate roasting method were selected. The phase analysis of the products obtained by adding borax and sodium carbonate roasting rare earth electrolytic molten salt waste residue was carried out. The chemical reaction formula was determined as: 1 Na 2B 4O 7 10H2O REF3=Na2O REBO3 BF3 H 2O 3 Na 2CO 3 2REF3=6NaF RE2O3 3CO 2 respectively. The activation energy of borax and sodium carbonate in the decomposition of rare earth molten salt residue is 159.02 KJ / mol, the preexponential factor is 1.15 脳 10 ~ 9 min-1N ~ (-1), the reaction rate constant is 0.26 min ~ (-1) ~ (-1) 0.28 min ~ (-1), and the limiting reaction is interfacial chemical reaction. The results show that the optimum technological conditions are as follows: calcination temperature is 700 鈩，
本文编号：2197919
[Abstract]:Low melting point rare earth metals (alloys) are often prepared by fluoride oxide system molten salt electrolysis. The waste molten salt slag containing rare earth is complicated in the process of rare earth molten salt electrolysis, so it is difficult to recycle rare earths. The recovery and utilization of rare earths from waste molten salt slag has broad application prospect and important practical significance. In this paper, the phase analysis and energy spectrum analysis of rare earth molten salt slag are carried out. It is determined that rare earth mainly exists in three forms: REONREF3 and REOF, and contains impurities such as graphite. On this basis, the experiments of high-pressure alkali conversion, mechanically activated alkali conversion, complex decomposition, borax roasting and sodium carbonate roasting rare earth electrolytic molten salt waste residue were carried out, and the borax roasting method and sodium carbonate roasting method were selected. The phase analysis of the products obtained by adding borax and sodium carbonate roasting rare earth electrolytic molten salt waste residue was carried out. The chemical reaction formula was determined as: 1 Na 2B 4O 7 10H2O REF3=Na2O REBO3 BF3 H 2O 3 Na 2CO 3 2REF3=6NaF RE2O3 3CO 2 respectively. The activation energy of borax and sodium carbonate in the decomposition of rare earth molten salt residue is 159.02 KJ / mol, the preexponential factor is 1.15 脳 10 ~ 9 min-1N ~ (-1), the reaction rate constant is 0.26 min ~ (-1) ~ (-1) 0.28 min ~ (-1), and the limiting reaction is interfacial chemical reaction. The results show that the optimum technological conditions are as follows: calcination temperature is 700 鈩，
本文编号：2197919
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