【摘要】：工業(yè)上低熔點稀土金屬(合金)常采用氟化物-氧化物體系熔鹽電解法制備,稀土熔鹽電解過程產(chǎn)生含稀土的廢熔鹽渣成分復雜,稀土回收利用困難,對稀土廢熔鹽渣中稀土進行高效回收利用具有廣闊運用前景及重要現(xiàn)實意義。本文首先對稀土熔鹽渣進行了物相分析及能譜分析,確定了稀土主要以REO、REF3及REOF三種形式存在,并且含有石墨等雜質。在此基礎上本文進行了高壓堿轉、機械活化堿轉、絡合分解、硼砂焙燒及碳酸鈉焙燒稀土電解熔鹽廢渣等探索實驗,并遴選出硼砂焙燒法及碳酸鈉焙燒法。對添加硼砂及碳酸鈉焙燒稀土電解熔鹽廢渣所得產(chǎn)物進行了物相分析,確定其化學反應式分別為:Na2B4O7·10H2O+REF3=Na2O+REBO3+BF3+H2O,3Na2CO3+2REF3=6NaF+RE2O3+3CO2。通過化學反應動力學研究,得到硼砂及碳酸鈉分解稀土熔鹽渣反應的活化能分別為159.02 kJ/mol,159.00 kJ/mol,指前因子分別為1.15×109min-1,2.58×109min-1,反應速率常數(shù)分別為0.26 min-1,0.28min-1,反應限制性環(huán)節(jié)均為界面化學反應。硼砂焙燒稀土熔鹽渣工藝研究結果表明,最佳工藝條件為:焙燒溫度為700℃,焙燒時間為1 min,硼砂添加量為原料質量的38%;最佳浸出條件為:浸出溫度為70℃,浸出時間為40 min,液固比為5:1,鹽酸濃度為3 mol/L。在最佳條件下,稀土浸出率為97.35%,浸出液pH0.5,浸出液中F-濃度為0.28 g/L,稀土離子濃度為16.97 g/L,REO/F=60.18。碳酸鈉焙燒稀土熔鹽渣工藝研究結果表明,最佳工藝條件為:焙燒溫度為700℃,焙燒時間為60 min,碳酸鈉添加量為稀土含量的1.5倍,添加5%的硼砂做添加劑,添加5%的硫脲進行鹽酸優(yōu)溶,浸出溫度為85℃。所得焙燒產(chǎn)物結構疏松,非Ce稀土浸出率為96.98%,Ce的浸出率為80.78%,浸出液中F濃度為0.12 g/L,pH值為3.8,稀土離子濃度為64.30 g/L,REO/F=559.13,Al2O3/REO=1.6×10-3,浸出液可直接進P507稀土萃取槽進行萃取分離。
[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，

本文編號：2197919