Method for leaching separation of mixed rare earth concentrate

Abstract

A method for leaching separation of a mixed rare earth concentrate includes: completing surface modification on the mixed rare earth concentrate under the action of a plasma gas flow, and obtaining a surface-modified mixed rare earth concentrate; performing mineral phase transformation on the surface-modified mixed rare earth concentrate, transforming a bastnaesite phase in the mixed rare earth concentrate into a cerium oxyfluoride, and obtaining a mineral phase transformation product containing the cerium oxyfluoride; performing acid leaching on the mineral phase transformation product, and obtaining an acid leachate and an acid leaching residue; completing surface modification on the acid leaching residue under the action of a plasma gas flow, and obtaining a surface-modified acid leaching residue; and performing alkaline leaching on the surface-modified acid leaching residue, and obtaining an alkaline leachate and an alkaline leaching residue.

What is claimed is: 
     
         1 . A method for leaching separation of a mixed rare earth concentrate, comprising:
 performing a surface modification on the mixed rare earth concentrate under an action of a plasma gas flow to obtain a surface-modified mixed rare earth concentrate;   performing a mineral phase transformation on the surface-modified mixed rare earth concentrate to transform a bastnaesite phase in the mixed rare earth concentrate into cerium oxyfluoride and obtain a mineral phase transformation product containing the cerium oxyfluoride;   acid leaching the mineral phase transformation product to obtain an acid leachate and an acid leaching residue, wherein the acid leachate comprises a rare earth ion and a fluoride ion, and the acid leaching residue comprises monazite;   performing a surface modification on the acid leaching residue under an action of a plasma gas flow to obtain a surface-modified acid leaching residue; and   alkaline leaching the surface-modified acid leaching residue to obtain an alkaline leachate and an alkaline leaching residue, wherein the alkaline leachate comprises a phosphorus element, and the alkaline leaching residue comprises a rare earth element.   
     
     
         2 . The method for leaching separation of a mixed rare earth concentrate according to  claim 1 , wherein the performing a surface modification on the mixed rare earth concentrate under the action of a plasma gas flow to obtain a surface-modified mixed rare earth concentrate comprises:
 processing the mixed rare earth concentrate in a plasma cleaner that has an atmosphere of a first preset atmosphere and a power of 100 W-300 W for 10 min-60 min to obtain the mixed rare earth concentrate whose surface oxidation performance is changed, wherein the first preset atmosphere is a gas mixture of hydrogen and inert gas.   
     
     
         3 . The method for leaching separation of a mixed rare earth concentrate according to  claim 1 , wherein the performing a mineral phase transformation on the surface-modified mixed rare earth concentrate to transform a bastnaesite phase in the mixed rare earth concentrate into a cerium oxyfluoride and to obtain a mineral phase transformation product containing the cerium oxyfluoride comprises:
 fluidized roasting the surface-modified mixed rare earth concentrate in an inert atmosphere to transform the bastnaesite phase in the mixed rare earth concentrate into the cerium oxyfluoride and obtain a roasted product containing the cerium oxyfluoride, and taking the roasted product as the mineral phase transformation product.   
     
     
         4 . The method for leaching separation of a mixed rare earth concentrate according to  claim 3 , wherein the fluidized roasting the surface-modified mixed rare earth concentrate in an inert atmosphere to transform the bastnaesite phase in the mixed rare earth concentrate into the cerium oxyfluoride and obtain a roasted product containing the cerium oxyfluoride comprises:
 putting the surface-modified mixed rare earth concentrate in a roasting furnace, then continuously introducing inert gas into the bottom of the roasting furnace, and keeping the mixed rare earth concentrate in a fluidized state in the inert atmosphere by using the inert gas as fluidizing gas; and   adjusting a heating temperature of the roasting furnace to heat the mixed rare earth concentrate in the fluidized state at a temperature of 450° C.-750° C. for 20 min-120 min, and completing a reaction of transforming the bastnaesite of the mixed rare earth concentrate into the cerium oxyfluoride to obtain the roasted product.   
     
     
         5 . The method for leaching separation of a mixed rare earth concentrate according to  claim 4 , wherein a gas flow rate of the inert gas continuously introduced into the bottom of the roasting furnace is 300 mL/min-1000 mL/min. 
     
     
         6 . The method for leaching separation of a mixed rare earth concentrate according to  claim 1 , wherein the acid leaching the mineral phase transformation product to obtain an acid leachate and an acid leaching residue comprises:
 adding the mineral phase transformation product to a hydrochloric acid leachate, performing stirring at a temperature of 60° C.-100° C., an ultrasonic power of 300 W-600 W, and a stirring speed of 200 r/min-600 r/min for 20 min-120 min, to obtain the acid leachate and the acid leaching residue.   
     
     
         7 . The method for leaching separation of a mixed rare earth concentrate according to  claim 6 , wherein a liquid-solid ratio between the hydrochloric acid leachate and the mineral phase transformation product is 4-20:1, the hydrochloric acid leachate comprises a hydrochloric acid solution with a concentration of 1 mol/L-10 mol/L and a leaching aid with a concentration of 0.1 mol/L-0.5 mol/L, and the leaching aid is aluminum chloride or boric acid. 
     
     
         8 . The method for leaching separation of a mixed rare earth concentrate according to  claim 1 , wherein the performing a surface modification on the acid leaching residue under the action of a plasma gas flow to obtain a surface-modified acid leaching residue comprises:
 processing the acid leaching residue in a plasma cleaner that has an atmosphere of a second preset atmosphere and a power of 100 W-300 W for 10 min-60 min, to obtain the acid leaching residue whose surface oxidation performance is changed, wherein the second preset atmosphere comprises a gas mixture of hydrogen and inert gas.   
     
     
         9 . The method for leaching separation of a mixed rare earth concentrate according to  claim 1 , wherein the alkaline leaching the surface-modified acid leaching residue to obtain an alkaline leachate and an alkaline leaching residue comprises:
 adding the surface-modified acid leaching residue to a sodium hydroxide solution, performing a reaction at a temperature of 120° C.-200° C., a pressure of 0.1 MPa-5 MPa, and a stirring speed of 200 r/min-600 r/min for 60 min-360 min, to obtain the alkaline leachate and the alkaline leaching residue, wherein an alkali-mineral ratio between the sodium hydroxide solution and the acid leaching residue is 1-7:1, and a liquid-solid ratio is 1-10:1.   
     
     
         10 . The method for leaching separation of a mixed rare earth concentrate according to  claim 1 , further comprising:
 adding a hydrochloric acid solution with a concentration of 1 mol/L-10 mol/L to the alkaline leaching residue to dissolve the alkaline leaching residue and obtain an acid solution comprising the rare earth element.