Study on the New Mechanism of Ce-F Migration and Separation in Clean Metallurgy of Baotou Rare Earth Ore

Author:Li Kai

Supervisor:chen ji

Database:Doctor

Degree Year:2019

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Pages:123

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The recovery of Ce(Ⅳ)and F(Ⅰ)from nitric acid solution was studied in this dissertation.The research content of this dissertation is mainly comprised of two parts.The first part studied the nitric acid leaching process of cerium for the oxidation roasted Baotou rare earth concentrate,and the kinetic equation of the leaching is calculated.The second part studied the extraction of Ce(Ⅳ)in the nitric acid system by different neutral phosphorus extractant.Depending on the characteristics of the nitric acid system,the structure of the extractant is continuously improved in cooperation with Shanghai Institute of Organic Chemistry in order to obtain the best extraction performance.The details were as follows:1.The oxidation roasting process of Baotou rare earth ore was studied by TG-MS and XRD,and the reaction of oxidation roasting process was obtained.Through the XRD and SEM-EDS analysis of the samples before and after acid leaching,the reaction in the leaching process was obtained.Then the kinetics of nitric acid leaching of oxidation roasted Baotou rare earth concentrate was studied.The effects of leaching temperature,HNO3 concentration,liquid-solid ratio(L/S)and stirring speed on rare earth leaching were studied.The kinetics of nitric acid leaching process was simulated,and the leaching kinetic equation was calculated.2.The traditional commercial extractant Cyanex923 was used to extract Ce(Ⅳ)and Ce(IV)-F(Ⅰ)from the nitric acid solution.The effects HNO3 concentration,the Cyanex923 concentration,the F concentration,the salting-out agent concentration and the temperature of the extraction of Ce(Ⅳ)and F(Ⅰ)were studied.The extraction of HNO3,Ce(Ⅳ)and Ce(Ⅳ)-F have been studied respectively,and the extracted complexes are considered to be HNO3·Cyanex923,Ce(NO3)4·2Cyanex923 and Ce(HF)(NO3)2·Cyanex923 individually.The extraction mechanism was studied by Infrared Spectra which demonstrates that the NO3-ion is a bidentate ligand.CeF3 nanoparticle obtained in this extraction system by reductive stripping was compared with CeF3 acquired in H2SO4 system.The results showed that CeF3 obtained in HNO3 system has low impurity content which could be removed by simply burning.Comparison with the sulfuric acid system,the nitric acid system has stronger extraction ability,higher saturation capacity and higher purity CeF3.The extraction process applied in the HNO3 liquor of bastnaesite indicates a potential approach to recover Ce(Ⅳ)and F in light RE resources.3.The new extractant 2-ethylhexyl bis(2-ethylhexyl)phosphinate(EHBEHP)was synthesized on the basis of the extractant DEHEHP,which was used to improve the low extraction capacity and the low saturation capacity of DEHEHP.The mechanism of EHBEHP extraction of HNO3,Ce(IV)and Ce(IV)-F(I)was obtained by using the slope method and the infrared spectrum respectively.The extraction ability and saturation capacity of EHBEHP and DEHEHP are compared,and it is proved that EHBEHP has stronger extraction ability and higher saturation capacity than DEHEHP.4.A new extractant Tris(2-ethylhexyl)phosphine oxide(TEHPO)was synthesized on the basis of the extractant Cyanex923 to improve the interfacial phenomenon and the low saturation capacity of the Cyanex923 in the nitric acid system.The mechanism of the extraction of HNO3 and Ce(IV)by TEHPO was obtained by using the slope method,the infrared spectrum and the ESI-MS,and it was found that TEHPO can effectively extract of Ce(IV)from HNO3 system in form of quantitive extraction of 2:1.The extraction ability,saturation capacity and interfacial phenomenon of the TEHPO and Cyanex923 in the nitric acid system for Ce(IV)are compared.The results show that the extraction ability of TEHPO is slightly stronger than that of Cyanex923,TEHPO has a higher saturation capacity and a better interface than Cyanex923.The above conclusion suggests that the TEHPO is more suitable for the extraction of Ce(IV)in the HNO3 system.