Study On Electrochemical Process Of Recovering Rare Earth From Waste Phosphor Powder

Rare earth elements are widely used in the fields of luminescent materials,magnetic materials,catalytic materials and polishing materials due to their special properties,playing an important role in the transformation of the green economy.With the continuous development of the rare earth fluorescent lamp industry and the continuous expansion of its application field,China's production and sales of rare earth phosphors for lamp use have been increasing year by year.The phosphors contain a large amount of rare earth metals,which makes the discarded phosphors become abundant secondary resources for the recycling and utilization of rare earth elements.Its recycling not only saves rare earth resources,but also helps environmental protection,which is of great practical significance to realize the sustainable development of rare earth resources.At present,the methods of recovering rare earth from waste rare earth phosphors include flotation separat ion,hydrometallurgy,autoclave dissolution,high temperature alkali fusion,mechanical activation,direct extraction and supercritical CO₂ extraction.Since the blue and green powders in tricolor phosphors have the structure of aluminum and magnesium spin el and their chemical properties are stable,it is difficult to leach Ce and Tb in blue and green powders by single acid leaching method,which consumes a large amount of acid,and the recovery rate of rare earth is not high.In this paper,two-step acid leaching method is adopted to destroy the structure of aluminum-magnesium spinel,and its kinetic model is studied,and the rare earth elements in the acid leaching solution are recovered by electrochemical deposition.The complete process route of two-step acid leaching-electrochemical deposition is proposed.The research is expected to further improve the rare earth recovery process and provide the relevant theoretical basis for industrial production.The main results are as follows:1.Two-step acid leaching was used in this paper to improve the leaching rates of Ce and Tb in waste phosphors.The effect of different acid leaching parameters on Ce and Tb leaching rate was studied.The results showed that sodium citrate with a mass ratio of 1:0.8 had the best effect on the structure of spinel.Pickling process parameters on the leaching rate of Ce and Tb has important effects,the optimum craft:the concentration of nitric acid for 2 mol/L,leaching temperature 60?,leaching time is 2h and reaction speed is 300 rpm.The Ce and Tb leaching rates reached 98.88%and97.12%respectively under the condition that sodium citrate with the optimal process and mass ratio of 1:0.8 was used as the leaching agent.2.In this paper,the kinetics of acid leaching reaction was studied,the kinetics model of acid leaching reaction and the activation energy of acid leaching reaction were established,and the activation energy of acid leaching reaction was calculated by arronius equation.3.Study on electrochemical deposition process.The results show that rare earth elements in acid leaching solution can be recovered by electrochemical deposition.The deposition conditions were as follows:amino acetic acid was used as complexing agent,pH of acid leaching solution was equal to 3,current density was 0.015a/cm²,and the experimental temperature was room temperature.The purity of rare earth oxides in sediments was 99.13%,and the recovery efficiency of rare earth elements reached98.98%.The electrochemical deposition mechanism is summarized.In summary,this study provides an environmentally friendly and economically viable new process,which will contribute to the rational recovery of rare earth secondary resources.