Study On The Extraction Of Rare Earth From Waste Rare Earth Phosphor Based On Phase Regulation

Rare earth phosphors contain strategic rare earth elements such as Ce,Tb,Y,and Eu.They are important modern luminescent materials and are widely used in the field of lighting.As the life of the luminescent product expires,the waste rare earth phosphor produced in the application field is increasing day by day,and has become an important secondary resource of rare earth.At the same time,due to long-term predatory mining and excessive use,the proportion of primary rare earth resources in China has dropped significantly,and it is urgent to strengthen the recycling of rare earth secondary resources.In this paper,the main process of alkali roasting-acid leaching treatment of waste rare earth phosphors has the key problem of low total rare earth yield.The important research results based on iron powder alkali fusion treatment of waste rare earth phosphors,namely iron powder in waste rare earth phosphor powder alkali During the roasting process,the oxidation of trivalent cerium and lanthanum can be effectively inhibited,and the calcined product is easily leached by the acid.A new idea of controlling the phase transformation of the waste rare earth phosphor by alkali roasting is proposed,and the alkali roasting atmosphere-acid leaching is controlled.The new method for treating waste rare earth phosphors,the main research contents and results are as follows:By thermodynamic calculation of the oxides of the valence elements Ce,Tb and Eu in the waste rare earth phosphor,the equilibrium diagram of the dissociation-generation reaction of Ce-O,Tb-O and Eu-O oxides is plotted.Gibbs free energy map,and over equilibrium map and Gibbs free energy map to analyze the oxide stable existence of Ce,Tb and Eu variable elements.The results show that as long as the oxygen concentration is kept at a very low level,elements such as Ce³⁺,Tb³⁺and Eu²⁺are not easily oxidized into high-valent rare earth oxides such as CeO₂,Tb₄O₇ and Eu₂O₃,which is a new process for controlling the alkali roasting atmosphere-acid leaching treatment of waste rare earth phosphors.Development laid the theoretical foundation.The process conditions for controlling the extraction of rare earth from waste rare earth phosphor by controlling the alkali roasting atmosphere-acid leaching process were studied.The results showed that the oxygen concentration in the roasting atmosphere was less than0.4%,the calcination temperature was 700°C,the calcination time was 2.5 h,the material ratio was 1:3,the water washing time was 20 min,the hydrochloric acid concentration was 4mol·L^-1,the acid leaching temperature was 60°C,and the acid leaching time was At 1 h and the liquid-solid ratio of 10:1,the total extraction rate of rare earth was as high as 99.19%,and the extraction rates of Ce,Tb,Y and Eu were 99.11%,99.18%,99.21%and 99.20%,respectively.TG-DSC,SEM and XRD were used to study the alkali melting kinetics of single blue powder and green powder under inert atmosphere,as well as structural cracking and phase transformation.The blue powder and green powder were found under inert atmosphere.Alkali melting mechanism.The results showed that the activation energies of blue powder and green powder were 543.18kJ·mol^-1 and 556.37kJ·mol^-1,respectively.The pre-reaction factors were2.85×10⁵⁴min^-1 and 2.45×10⁵⁹min^-1,respectively,indicating blue powder and green powder alkali.The melting reaction belongs to the chemical reaction control;the blue powder and green powder structure cracking and phase transformation process are mainly:when the alkali melting temperature rises to 300?,Na⁺begins to enter the aluminate structure through lattice distortion defects and crack channels.The positional replacement with the rare earth ions,the replaced rare earth ions Eu³⁺,Ce³⁺,Tb³⁺and O^2-in the system combine to form Eu₂O₃,Ce₂O₃,Tb₂O₃.As the alkali melting temperature is further increased to 450°C,the overall structure of blue powder and green powder aluminate collapses,and the dissociated Mg²⁺and Ba²⁺form O₂ and MgO in the system,and Al³⁺and alkali react to NaAlO₂.