| Scandium is one of the typical scattered metals. It rarely has individual minerals, usually it often associates in the metal minerals of titanium, tungsten, aluminum and so on. The titanium materials used in the process of titanium industry generally are in rich of scandium. Especially in the process of fluidizing chlorination yielding raw titanium tetrachloride, scadium are gathered into the collecting dust of chlorination flue gas. For decades, as the range of application of scandium and its chemical compounds had been continuously extending in the areas of aerospace, war industry and household appliance industry, the study on recycling and extracting scandium has been one of the hotspots on the research with economic and practical value.This article aims to work out an effective process of extracting scandium from the collecting dust of chlorination flue gas after taking the past and present problems of recycling scandium into consideration sufficiently. The research carries out experiments using an applicable extraction agent to eliminate the Fe3+ in the leaching liquor firstly, and extracting Sc3+secondly. At last, the research prepares the farinose solid of scandium oxide by a proper method. The preparing process not only makes the best of water, acid and other valuable metals but also selects preferentially the technological parameters according to the final utilization rate of Scandium.The research of this article includes three aspects:1. The properties and leaching conditions of the collecting dust of chlorination flue gas.2. Extracting scandium by solvent extraction after eliminating Fe3+ from the lixivium of the collecting dust of chlorination flue gas and preparing scandium oxide.3. The comprehensive utilization of materials in the process of solvent extraction. The conclusions of this article include the following items.The moisture content of the collecting dust of chlorination flue gas used in this experiment is about 7.5%. The percentages composition of different range of particle sizes 65-80?m,80-104?m,104-150?m,150-250?m are 9.6%,17.3%,27.7% and 45.4% respectively. The dust comprises mainly chloride contents. It contains 590g scandium oxide in each ton of the dust. The once leaching rate of scandium is 82.7% which is the highest can be gotten by using lmol/L HCl solution to leach the dust directly at 70?, while the liquid-solid ratio is 1:1 and the gross leaching time is 1 hour. And the leaching residue is 43.8%. Besides, the leached Cl" and Sc3+can get into the washing liquor totally after the leached residue being washed three times with pure water at the liquid-solid ratie of 1:2 so that it can be solidified with cement. The gross leaching rate of scandium can reach to 85.26% and its concentration in the lixivium is about 328.07mg/L if when all the washing liquor is used to prepare the new HCl solution and leaching the new collecting dust of chlorination flue gas.The experiment eliminate Fe3+ of the lixivium gotten in leaching process with organic phase which comprised 20% N235 and 10% glycerol and 70% sulfonated kerosene and the removing rate of Fe3+ is up to 99% by single class extraction and the O/A is 1:1, that is to say the concentration of Fe3+ is reduced to 2.46mg/L from 2.50g/L.The results of the extraction of scandium show that the extraction rate of scandium of the TBP organic phase (less than 74%) on scandium is relatively lower than both of P204 and P507 which are 99.66% and 99.25% respectively. However, the system of extraction agent which is composed of P204 is hard for the process of reextraction. At last, the experiment selected the organic phase comprised of 5% P507 and 10% blended alcohol and 85% sulfonated kerosene as the final organic phase of the extraction process to extract scandium. The extracting process parameters are as follows:room temperature extracting, O/A is 1:5, three classes extraction, the vibrating and phase separation time are 2minutes and 10 minutes respectively. On this condition, the extraction rate of scandium can be up to 99.25% which is the highest.The reextraction is operated at 60? with 4.5mol/L HCl solution when the O/A is 1:1 and the classes of reextracting are three. The concentration of scandium ion of the strip liquor yielded in the reextraction is 1.475g/L. And the the stripping rate is 90.6%. The raffinate can be used to leach new the collecting dust of chlorination flue gas after being eliminated Mn2+ and Fe2+.99% of the Sc3+ of the strip liquor can be translated into scandium oxzlic at pH=3.5 and the dosage of oxalic acid content is 1.35 times of that of the scandium ion. And the powder of scandium oxide can be produced by calcinating scandium oxalic for two hours at 600??... |
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