| Stripping rare earth from organic phase is not only a necessary part of rare earth separation,but also a new method for the preparation of nano/micro materials.With the continuous improvement of environmental requirements,seeking new green stripping technology has become a current research hot spot of rare earth industry.In this paper,stripping performance of two rare earth organic phases were studied,and controllable formation and elimination methods of nano/micro particles in the stripping process were emphasized.At the same time,application in improving the phase separation performance and preparation of nano/micro materials were also emphasized.High purity rare earths precipitation wastewater contains a lot of hydrochloric acid and a small amount of rare earth.In this study,most of oxalic acid was removed by precipitation method,and hydrochloric acid was recovered.In order to realize the recycling of waste water and meet the requirement of green process,it is necessary to study the allowable concentration of residual oxalic acid in stripping acid and the specific method to ensure that precipitation does not occur during stripping process.Therefore,the solubility equilibrium of 15 rare earth oxalates in different concentrations of rare earth and acid solution were studied.It was found that the solubility of rare earth oxalate precipitation increased with the acid concentration increasing.However,with the increase of RE concentration,the solubility decreased greatly first and then increased.When the concentration of rare earth is0.05-0.10mol/L,the solubility of rare earth oxalate is the lowest.These facts indicate that increasing the concentration of both HCl and RE can effectively prevent the formation of rare earth oxalate precipitation and ensure the phase separation performance..Therefore,the excess oxalic acid in the waster water was first removed by the rare earth precipitation method.Then the filtered solution by adding hydrochloric acid to 4-6mol/L can be used for rare earth stripping.With the dependence of solubility on the concentration of acid and rare earth,the suitablerecycle condition of waste water as stripping acid were predicted and proved by stripping test.Rare earth and its composite oxide nano/micro particles can be synthesized by complex sol-gel method and combustion method as well as alkoxide hydrolysis method.But these methods are still difficult to industrialization because of their shortcomings such as large consumption,much exhaust gas,and that alcohol is very sensitive to water.Based on the hydrolysis characteristics of rare earth salicylate complexes,this study proposed the preparation of nano/micro rare earth materials by hydrolysis of weak coordination compounds.Firstly,the salicylate complex was synthesized in ethanol or butyl acetate.The activity of rare earth in water was studied by monitoring the UV spectra of organic phase.The composition and stability constants of methyl salicylate complexes were determined by equimolar series method.The results show that Y3+and methyl salicylate are coordinated at ratio 1:1,and their composition is YMS.Al3+and methyl salicylate are coordinated at ratio 3:2,and their composition is Al3MS2.The dissociation degree of Y-MS is 0.225 and the stability constant is 7.65x104(lg K=4.88),while the dissociation degree of Al-MS is0.258 and the stability constant is 2.72x103(lg K=3.43).The Er-doped YAG up-conversion luminescent material powders were prepared successfully by the hydrolysis of rare earth salicylate complex.Nanosized Er:YAG with pure YAG crystal phase can be obtained at around 1000?,which is 600? lower than that by directly calcining the mixture of their oxides.The resultant powders were spherical particles and well dispersed,with an average particle size of approximately 80 nm.This method can be used as a new effective nano/micro YAG powder preparation method. |
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