| Rare earth is composed of 15 lanthanide elements with atomic numbers from 57 to 71 and scandium and yttrium elements with atomic numbers of 21 and 39.Because rare earth has excellent characteristics in optics,magnetism,electricity and so on,it has the reputation of "industrial vitamin".Coal gangue is a waste discharged from coal mining and processing.In addition to common metals such as iron,aluminum,calcium and magnesium,coal gangue contains rare earth metals such as lanthanum,cerium,praseodymium and neodymium.In the process of coal gangue extraction,it can be get huge commercial value and environmental benefits if we can separate rare earth and no rare earthIn this study,the acid solute of coal gangue was taken as the research object Because the existence of iron and aluminum had a great influence on the extraction of rare earth,so the method of pure substance simulation was used at first,and the influence of Fe3+,Fe2+,and Al3+on the extraction of mixed rare earth was explored On this basis,the extraction of coal gangue acid with different single extractant was explored.The extraction process and reaction mechanism of miscible rare earth Then,the extraction of mixed rare earth in the acid solution of coal gangue by synergistic extraction system was further studied.P507-P204,Cyanex272-P507 and cyanex272-P204 were determined.Finally,on the basis of the extraction of mixed rare earth by Cyanex272-P204 system,the extraction process and reaction mechanism of mixed rare earth by Cyanex272-P204-LA-H3cit system were studied by adding common complexing extractants such as lactic acid and citric acid with obvious extraction effect.Combined with the production practice,and through the single factor experiment,the extraction process and the reverse extraction process of the mixed rare earth in the acid solution of coal gangue were determined.This paper showed the following conclusions(1)Reducing Fe3+in the solution to Fe2+could effectively improve the extraction rate of mixed rare earth,reduce the extraction rate of iron and aluminum,and the emulsification phenomenon in the process,and it was very beneficial to the whole extraction process(2)In the study of the process and mechanism of extraction and RE3+with a single extractant,the order of the influence of a single extractant on the extraction rate of RE3+was P204>Cyanex272>P507.The expression of its general reaction formula was:RE(a)3++3(HC)2(o)(?)RE(HC2)3(o)+3H+(a).(3)In the study of the process and mechanism of extraction and RE3+with complex extractant,the best reaction conditions of P204-P507 were as follows:the initial pH was 2.2,the concentration of P204 was 12%,the concentration of P507 is 8%,the ratio is 1:1,the oscillation time is 10 min.The best reaction conditions by Cyanex272-P507 were that the initial pH was 2.2,the concentration of P204 was 12%,the concentration of P507 was 8%,the ratio is 1?1,the oscillation time is 10 min;The best reaction conditions by Cyanex272-P204 were that the initial pH wer 2.2,the concentration of Cyanex272 were 6%,the concentration of P204 was 8%,the ratio was 1?1,and the oscillation time was 6 min.By comparing the extraction rates of RE3+,Fe2+and A13+under the best experimental conditions,it is found that Cyanex272-P204 has the highest extraction rate for RE3+,the lowest extraction rate of Fe2+,and it was not easy to cause emulsification.(4)When P204-P507 is used to extract RE3+,the best coextraction coefficient was 1.40,and the coextraction reaction equation was RE(a)3++(HA)2(o)+2(HB)2(o)(?)REHA2(HB2)2(o)+3H+(a).When by Cyanex272-P507,the best coextraction coefficient was 1.26,and its coextraction reaction equation was RE(a)3++2(HA)2(o)+(HC)2(o)(?)REHC2(HA)2(o)+3H+(a)When by Cyanex272-P204 the best coextraction coefficient could reached 1.86,and its coextraction reaction equation was RE(a)3++(HB)(o)+2(HC)2(o)(?)REHB2(HC2)2(o)+3H+(a).(5)In the study of the process and mechanism of the extraction of RE3-by complexation extractant,when the initial pH was 2.2 and the concentration of lactic acid was 0.6 mol/L,the extraction rate of RE3+by Cyanex272-P204-LA system was 92.15%.When the initial pH was 2.2,the ratio of lactic acid concentration to citric acid concentration was 10:1,that is,when the concentration of citric acid was 0.06 mol/1,the extraction of RE3+by Cyanex272-P204-LA-H3cit system was 96.8%,the separation factor?[RE3+/Fe2+]was 204.17,?[Re3+/Al3+]was 93.32.(6)In the study of real system,the best extraction process of RE3-by Cyanex272-P204-LA-H3cit was that the initial pH was 2.2,the concentration of lactic acid was 0.6 mol/L,the concentration of citric acid was 0.06 mol/L,the oscillation time was 6 min,and the extraction temperature was 25?.In the stripping experiment,sulfuric acid solution was used for stripping,the ratio was 1?1.5,the concentration of sulfuric acid was 4 mol/L,the time was 12 min,the stripping temperature was 25?,and the stripping rate of mixed rare earth was 91.49%(7)According to the infrared spectrum analysis,there were no new characteristic peaks in the spectral lines of P507 and P204,Cyanex272 and P507,Cyanex272 and P204,which indicated that no chemical bond recombination and no new group formation occurred in the three synergistic extractants.The extraction and mixing rare earth are all iron exchange reactions.The complexing agent lactate and citric acid did not enter the organic phase of Cyanex272-P204(8)The technology route of "step precipitation/crystallization?extraction separation " was optimized as "direct extraction separation ",which alleviated the serious emulsification in the extraction process and solved the problems of low rare earth extraction rate and complicated process steps.The technical route solved the problem of separation of rare earth and non rare earth materials in the acid solution of coal gangue in theory,and the utilization of multi metals in coal gangue was realized. |
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