Study On Enrichment And Recovery Of Heavy Rare Earth Elements By Microemulsion Method

Medium-heavy rare earth is an important strategic resource in China.With the increasing demand for heavy rare earth,it is required to efficiently extract and enrich rare earth from low-grade rare earth ore and low-concentration rare earth solution.At the same time,nanocrystallization of rare earth oxides has become one of the hot areas of nanotechnology research.Microemulsion membrane separation method has the characteristics of high enrichment ratio.The preparation of nanoparticles by microemulsion method has the advantages of controllable particle size and mild operating conditions.Therefore,microemulsion has a wide application prospect in extraction separation and synthesis of nanomaterials.In this paper,microemulsion was used to extract and enrich rare earth elements,and rare earth nanoparticles were also prepared.It provides a theoretical basis for further exploration of the separation and purification of rare earth elements,and has important theoretical significance for the preparation and development of rare earth nanomaterials.（1）The microemulsion system of AOT/n-butanol/n-heptane/HCl was constructed.The structure of microemulsion was characterized by conductivity,and the extraction and enrichment of rare earth ions(Tb³⁺,Ho³⁺,Er³⁺)were studied.The effects of mass ratio of AOT to n-butanol,mass fraction of n-heptane,concentration of hydrochloric acid,p H of feed solution,concentration of feed solution,ratio of water to emulsion,oscillation time and temperature on the extraction rate and enrichment ratio of rare earth were investigated by single factor method,and the optimum reaction conditions were obtained.The results show that when the AOT:n-butanol is in the range of 1:4 to 2:1,the water content is within21%,the W/O type AOT/n-butanol/n-heptane/HCl microemulsion system can be constructed;when w%（n-heptane）=33%,w%（n-butanol）=55%,C_HCl=1mol/L,water-emulsion ratio=1:5,t=15min,T=25°C,C_RE=0.01mol/L,p H=3,the extraction rate can reach more than 90%,and the maximum enrichment ratio is 180.（2）AOT/n-butanol/cyclohexane system,OP-10/n-butanol/cyclohexane system and TX-100/n-butanol/cyclohexane microemulsion systems were constructed and applied to the preparation of nano-Ho₂O₃ powders.The effects of microemulsion components,the order of adding water phase and oil phase,and calcination on the crystal form,structure and morphology of nano-powders were investigated.The XRD and FTIR results show that the calcined products are nano-Ho₂O₃ with cubic crystal structure.The SEM results showed that the surfactant and precipitant had a significant effect on the morphology of the product.The particle size of the product obtained by AOT/n-butanol/cyclohexane system was larger than that of OP-10/n-butanol/cyclohexane system and TX-100/n-butanol/cyclohexane system.The precursor prepared by using NH₄OH and Na OH as precipitants was granular,and the precursor prepared by using（NH₄）₂CO₃ as precipitant was rod-like.The mass ratio of surfactant to cosurfactant,the order of adding water phase and oil phase had no significant effect on the morphology of the product.The product after roasting has the tendency of crystallization.