Extraction And Separation Of Neodymium(Ⅲ) From Chloride Medium By Oxygen-Containing Functionalized Ionic Liquids

Rare earth elements possess unique electrical,magnetic,and optical properties,making them indispensable in various industrial fields,such as fuel cells,superconductors,permanent magnets,and catalysts.However,the overexploitation of rare earth ore resources,which are often found in various minerals such as fluorocarbon cerium ore,monazite,and xenotime,has caused serious ecological environmental problems.Furthermore,the increasing gap between global supply and demand of rare earths makes it increasingly important to develop green and efficient processes for recycling rare earth metals from secondary resources.Ionic liquids play an important role in the field of rare earth metal separation due to their excellent physical and chemical properties and environmentally friendly advantages.In response to the problems of soapification,emulsification,high viscosity,and poor extraction efficiency associated with traditional extractants used in industry,this paper designs and synthesizes a series of functionalized ionic liquids and uses them to construct three different novel green liquid-liquid extraction systems for extracting and separating neodymium(Ⅲ)from chloride media,providing a new pathway for recovering neodymium(Ⅲ)from secondary resources.The specific research contents include:(1)The effects of factors such as the amount of ionic liquid and pH of the aqueous phase on the extraction efficiency were studied.The extraction mechanism involving ionic binding was determined using ultraviolet spectrophotometer,infrared spectrometer and nuclear magnetic resonance spectroscopy.Thermodynamic and kinetic studies of the system showed that the extraction reaction proceeded spontaneously with heat release.Potassium oxalate solution was used for back-extraction,and after five cycles,the extraction efficiency remained stable.Finally,the extraction isotherm and its McCabe-Thiele diagram were used to predict the theoretical number of equilibrium stages for the selected phase,achieving an extraction efficiency of 98%for neodymium(Ⅲ).(2)Extraction and separation of neodymium(Ⅲ)from NdFeB waste using a solvent-free extraction system constructed with a novel carboxylic acid-based ionic liquid.Two carboxylic acid-based ionic liquids with different carbon chain lengths,[A336][OTA]and[A336][BTA],were designed and synthesized to construct a solvent-free extraction system.The effects of the amount of ionic liquid and pH value of the aqueous phase on the extraction efficiency were discussed.The extraction mechanism based on ionic association was proposed and supported by theoretical calculations using ultraviolet spectrophotometer,infrared spectrometer and proton nuclear magnetic resonance.Selective separation experiments of neodymium(Ⅲ)from secondary neodymium-iron-boron material showed that[A336][OTA]had efficient extraction and separation ability.Finally,back-extraction and seven-cycle experiments demonstrated the excellent regeneration ability of the ionic liquid,proving that[A336][OTA]is a promising extraction agent for industrial applications.(3)Extraction of neodymium(Ⅲ)in chloride medium by aqueous two-phase system based on ionic liquid[TBA][P507].In this chapter,P507 was improved,and the hydrophilic ionic liquid[TBA][P507]was synthesized with TBA(tetrabutylammonium bromide)as the cation.Based on this,the aqueous two-phase system was constructed and the extraction performance for neodymium(Ⅲ)in chloride medium was studied.The effects of the type of inorganic salt and the pH of the aqueous phase on the phase diagram were discussed,and the extraction amount and pH of the extraction agent were optimized,achieving a high extraction efficiency of 98.5%.The extraction mechanism was proposed by ultraviolet spectrophotometer and infrared spectrometer,which were supported by quantum chemistry calculations.In addition,the selectivity of[TBA][P507]dual aqueous phase system for neodymium(Ⅲ)in secondary resource NdFeB material liquid was studied.The reverse extraction was carried out using potassium oxalate,and the final product was identified as Nd2O3 by SEM and XRD characterization after calcination at 900℃.