Study On The Extraction Of Rare Earth From Waste Rare Earth Fluorescent Powder Iron Powder By Alkali Fusion-acid Leaching

Rare earth phosphors are widely used in the field of fluorescent lamps,rare earth phosphor powder waste quantity grows day by day from the production,has become a important rare earth secondary resources.Extraction of rare earth from waste rare earth phosphors can improve the efficiency of rare earth resource utilization and reduce environmental pollution.At present,the main technology is alkali fusion-acid leaching recovery of rare earth from waste rare earth phosphors.Using the processing,Eu and Y can be easily extracted from waste rare earth phosphors,can reach more than 95%,however,Ce and Tb is difficult,recovery rate about 70%.The reason is that alkali fusion process Ce and Tb was oxidized into four price oxide,and difficult to soluble in acid.According to rare earth phosphor is difficult to extract bottleneck problem in the process of extracting Ce,Tb,this study proposed the method of iron powder alkali fusion-acid leaching recovery rare earths,and study on the mechanism of iron powder alkali fusion.The results are as follows,?1?Ce,Tb oxide acid leaching of thermodynamics were analyzed by calculating the gibbs free energy values of CeO₂,Ce₂O₃,Tb₂O₃,TbO₂ and hydrochloric acid reaction at different temperatures,and build the Ce-H2 O and Tb-H2 O system potential-pH figure.The results show that CeO₂ is almost insoluble in acid,Ce₂O₃ is easy to dissolve in acid.Both TbO₂ and Tb₂O₃ can be dissolved in acid,but Tb₂O₃ is more easily than TbO₂ reaction with acid.Through acid solution experiment of CeO₂ and Tb₄O₇,learned that CeO₂ leaching efficiency is no more than 2%,even in the presence of hydrogen peroxide solution,the leaching rate is not more than 15%,Tb₄O₇ can be hydrochloric acid leaching,but the condition is relatively harsh.?2?Studied the process conditions of waste rare earth phosphor iron powder alkali fusion-acid leaching extracting rare earth.Experimental results show that waste,sodium hydroxide,reduction of iron powder mass ratio is 1:2:0.005,alkali melting temperature is 700?,alkali fusion time is 3h,hydrochloric acid concentration is 3mol·L-1,acid leaching temperature is 70?,acid leaching time is 1h,ratio of solid to liquid is 1:7.5.In this condition,the leaching rate of rare earth is 99.35%,of which the leaching rate of Ce,Eu,Tb,Y is 99.93%,98.12%,99.37%,99.60%,under the process rare earth leaching rate is very high.?3?Using SEM and XRD to phase analysis for waste phosphor before and after iron powder alkali fusion,The proven mechanism of recovery of rare earth from waste rare earth phosphors by alkali fusion-acid leaching process.The results show that waste of rare earth phosphor powder structure into squares and larger particles before iron powder alkali fusion,phase structure was destroyed after iron powder alkali fusion,and indeed Ce and Tb in the form of trivalent Ce₂O₃,Tb₂O₃.This shows that small amount of iron powder suppresses trivalent Ce trivalent Tb be oxidized in the process of alkali fusion,this laid a theoretical foundation for recovery of rare earth from waste rare earth phosphors by iron powder alkali fusion-acid leaching process.