The Study For Extracting Rare Earths And Iron In Hydrochloride System By Using Malonamide Extractant And Extraction Dynamics Research

Separation and purification of rare earth have been a research focus and hotspot at home and abroad.Rare earth has been widely used in every field in the society.There are many methods for separation and purification of rare earth,such as chemical precipitation,ion exchange method,organic solvent extraction,extraction chromatography and liquid membrane method.Solvent extraction is widely used in iron removing from rare earth.Amides extractants that are compared with other sulphur phosphorous extraction agent have unique advantages:simple synthetic preparation,synthesis without producing pollution,good extraction effect,recycled etc.This paper synthesized a kind of malonamide extraction agent:2-dodecyl-N,N,N?,N?-tetrabutylmalonamide?TBDMA?.We studied different interfacial properties of TBDMA-aqueous solution,extraction of iron praseodymium thermodynamics and dynamics,and so on.The main contents are as follows:1.2-dodecyl-N,N,N?,N?-tetrabutylmalonamide?TBDMA?was synthesized and the compound was determined by IR,1HNMR,elemental analysis.2.Thermodynamics of TBDMA extracting rare earth and iron?III?in toluene,cyclohexane was mainly studied due to rare earth ion and iron ion coexistence problem in rare earth hydrometallurgy.The oscillation time,water phase acidity,concentration of extractant,extraction temperature,the different kinds of extraction diluents,the influence of sodium chloride and calcium chloride on the extraction rate were investigated.The concentrations of H⁺,Cl^-were also studied whether had influence on extraction percentage,and the detailed discussions were given.Through the suitable acidity,we could get separation of praseodymium and iron,which had the vital significance to the hydrometallurgy of light rare earth.The relationship between extractant concentration and extraction distribution ratio was studied and the slope was 2 by using the slope method,which was proved each extraction compound molecule contained two extraction agent molecules.Through the calculation of related thermodynamic functions,the extraction reaction was endothermic reaction,and raising temperature was bad for extraction.In addition,compared to the difference of before and after extraction by FTIR and ultraviolet spectra,absorption peak of carbonyl was found to change,which demonstrated H⁺coordinated with oxygen in TBDMA molecule and the extraction compound contained FeCl₄^-.In addition,we also studied the structure of extraction solvent on the extraction performance impact and reversed extraction experiments.The reversed extraction experiments contained extracting time and organic-aqueous volume ratio.The study of thermodynamics built a foundation for the choice of extraction kinetics conditions.3.A simple constant interfacial area cell was assembled and the assembled constant interfacial area cell was used for the experiment of the iron?III?extraction kinetics by TBDMA.The agitation speed,concentration of TBDMA and hydrochloric acid,temperature,concentration of Fe³⁺were studied for the extraction rate.In hydrochloric acid system,the extraction process controlled by the phase interface chemical reaction and interfacial activation energy was 8.90 kJ·mol^-1.In 5.0 m ol·dm^-3 hydrochloric acid system,extraction reaction rate increased with TBDMA concentration and Fe³⁺concentration and the reaction series were 0.77 and 2.06,respectively.Extraction reaction rate increased with the increasing concentration of hydrochloric acid,but not linear increasing.So the hydrochloric acid reaction to extraction rate of progression was not certain.In the conditions that constant pool phase interface area was 17.85 cm²,reaction temperature was 2?5 and hydrochloric acid concentration was 5.0 mol·dm^-3,TBDMA extracting Fe³⁺rate of interface reaction kinetics equation could be represented as r₀=0.664×[TBDMA]^0.77×[Fe³⁺]^2.06.4.In paper,the extractant's relationship of liquid drop volume and time was measured by drop volume technique in different diluents?including octane,benzene,toluene,cyclohexane?.Through interfacial tension design formulas,the relationship of interfacial tension and droplet formation time was gotten:interfacial tension would decrease following the increasing time,then would be constant even time was increasing.We also studied this extractant's interfacial tension in different diluents.Additional,interfacial tension of TBDMA was studied with different diluents with different aqueous solution?hydrochloric acid,hydrogen ion solution,sodium chloride,calcium chloride?.The interfacial tension of TBDMA in different diluents with water and the effect of temperature were also studied.And some explanations were listed.5.The effect of different concentrations of hydrochloric acid,calcium chloride,sodium chloride solution,different temperature and different diluents on the interfacial tension which was between the extractant TBDMA and iron?III?solution were measured by drop volume method.The research provided the foundation for the further study of interfacial tension and a certain theoretical support for the research of extraction mechanism.