Rare Earth Phosphor Waste Alkali Fusion-water Immersion-reduction Acid Leaching Recovery Rare Earth Process Research

In this paper,based on waste rare earth fluorescent powder characteristics,explores a high-efficiency leaching technology of recovering rare earth from waste rare earth fluorescent powder which combines high temperature alkali fusion pretreatment with acid leaching.It provides suggestions for the development of new technology and process of recovery of rare earth from waste rare earth fluorescent powder.The rare earth's leaching rate only reached 47.32% by direct acid leaching process to treat the waste rare earth fluorescent powder;while using additive roasting,water leaching and acid leaching process,the rare earth leaching rate reaches 85.76%,but still dissatisfactory.By reference the potential-pH diagram and analyzing the acid leaching residue of the leaching process,it found the main reason of low leaching rate is high valence cerium oxides.The water leaching residue need to reduced leaching by using reducing agent.It found that calcinations temperature,sodium hydroxide dosage have remarkable influence on roasting reaction,through study the law of dynamic of high temperature alkali fusion process,and the dynamic process of roasting waste rare earth fluorescent powder by sodium hydroxide confirm to “Shrinking Un-reacted Core Model”,the reaction rate by chemical reaction control,and apparent activation energy of roasting reaction is 77.512 kJ·mol^-1 through the Arrhenius equation the kinetic equation can be described as: 1-?1-x?^1/3=0.4181 ×exp[-77512/?RT?] · t.It found that ascorbic acid's oxidation reduction potential is lower than the hydroxylamine hydrochloride,glucose,formaldehyde and hydrogen peroxide,the reduction effectiveness is the best than hydroxylamine hydrochloride,glucose,formaldehyde and hydrogen peroxide,it is conducive to the leaching of tetravalent cerium oxide through electrochemical study of leaching process.It can obviously improve rare earth leaching rate by using additive roasting,water leaching,acid leaching with aid leaching agent,the rare earth leaching rate can reach more than 98%,aluminum washed with water to remove rate can reach more than 97%.Under the experimental conditions: alkali melting temperature at 1050 ? and alkali fusion time for 2 h,sodium hydroxide and waste powder quality ratio 2.5:1,hydrochloric acid concentration 4 mol·L^-1,liquid to solid ratio 10:1,ascorbic acid concentration was 10%,leaching temperature at 65 ?,leaching time for 2 h,stirring speed 650 r·min^-1.