Method for extracting and separating zirconium and hafnium in nitric acid medium

Abstract

A method for extracting and separating zirconium and hafnium in nitric acid medium mainly includes extraction of acidic raw liquid containing zirconium compounds with a synergistic extraction system consisting of DIBK and a phosphonic acids extraction agent, so that the zirconium goes to the aqueous phase and the hafnium goes to the organic phase, thus achieving separation. There is no need of use of toxic substance throughout the process.

1 . A method for extracting and separating zirconium and hafnium in a nitric acid medium, comprising following steps of:
 performing extraction by mixing an extraction agent with an acidic raw liquid formed by mixing a zirconium-containing chemical and nitric acid, mixing a raffinate, which is obtained after phase separation caused by the extraction, with a base to give zirconium hydroxide precipitate, stripping hafnium-containing loaded organic phase with a carbonate solution, mixing a liquid obtained after the stripping with a base solution to give hafnium hydroxide precipitate, and roasting the zirconium hydroxide precipitate and the hafnium hydroxide precipitate, wherein the extraction agent comprises a mixture consisting of diisobutyl ketone (DIBK) and phosphonic acids extraction agent.   
     
     
         2 . The method for extracting and separating zirconium and hafnium in a nitric acid medium according to  claim 1 , wherein free acids are present in the acidic raw liquid at a total acidity of 2.0˜4.0 mol/L; and/or
 zirconium ions and hafnium ions are present in the acidic raw liquid at a total concentration of 0.05˜2.0 mol/L. 
 
     
     
         3 . The method for extracting and separating zirconium and hafnium in a nitric acid medium according to  claim 2 , wherein nitrate ions are present in the acidic raw liquid at a concentration of 2.0˜4.0 mol/L; and/or
 sulfate ions are present at a concentration of 0˜1.0 mol/L. 
 
     
     
         4 . The method for extracting and separating zirconium and hafnium in a nitric acid medium according to  claim 1 , wherein the inorganic salt is at least one selected from the group consisting of ammonium chloride, sodium chloride, magnesium chloride, ammonium sulfate and sodium sulfate. 
     
     
         5 . The method for extracting and separating zirconium and hafnium in a nitric acid medium according to  claim 1 , wherein the phosphonic acids extraction agent accounts for 2˜40% (v/v) by volume; and/or
 m Hf /m (Hf+Zr)  weight ratio is 10˜40% in the liquid after the stripping. 
 
     
     
         6 . The method for extracting and separating zirconium and hafnium in a nitric acid medium according to  claim 5 , wherein the extraction agent is mixed with a diluent before the extraction. 
     
     
         7 . The method for extracting and separating zirconium and hafnium in a nitric acid medium according to  claim 1 , wherein the extraction is performed in a single-stage or multi-stage co-current manner and/or a single-stage or multi-stage counter-current manner. 
     
     
         8 . The method for extracting and separating zirconium and hafnium in a nitric acid medium according to  claim 1 , wherein the carbonate is at least one selected from the group consisting of sodium carbonate, sodium bicarbonate, potassium carbonate, potassium bicarbonate, ammonium carbonate, magnesium carbonate and aluminum carbonate. 
     
     
         9 . The method for extracting and separating zirconium and hafnium in a nitric acid medium according to  claim 1 , wherein the roasting is performed under a condition of 600˜2300° C., and/or the zirconium hydroxide precipitate and the hafnium hydroxide precipitate are washed before roasting. 
     
     
         10 . A method for extracting and separating zirconium and hafnium in a nitric acid medium, comprising mixing a zirconium-containing chemical and nitric acid to form an acidic raw liquid, and
 performing extraction on the acidic raw liquid with an extraction agent to give a raffinate and a hafnium-containing loaded organic phase after phase separation of the extraction, mixing the raffinate with a base solution to give a zirconium hydroxide precipitate, stripping the hafnium-containing loaded organic phase with a carbonate solution, mixing a liquid obtained after stripping with a base solution to give a hafnium hydroxide precipitate, and roasting the zirconium hydroxide precipitate and the hafnium hydroxide precipitate, wherein the extraction agent comprises a mixture consisting of DIBK and phosphonic acids extraction agent.   
     
     
         11 . The method for extracting and separating zirconium and hafnium in a nitric acid medium according to  claim 1 , wherein the phosphonic acids extraction agent is at least one selected from the group consisting of Cyanex 921, Cyanex 923, Cyanex 925 and Cyanex 572. 
     
     
         12 . The method for extracting and separating zirconium and hafnium in a nitric acid medium according to  claim 1 , wherein the extraction agent is pre-extracted with nitric acid before the extraction. 
     
     
         13 . The method for extracting and separating zirconium and hafnium in a nitric acid medium according to  claim 1 , wherein the nitric acid has a concentration of 2.0˜6.0 mol/L in the pre-extraction, and/or the extraction agent has a volume equal to that of the nitric acid in the pre-extraction. 
     
     
         14 . The method for extracting and separating zirconium and hafnium in a nitric acid medium according to  claim 1 , wherein the acidic raw liquid further comprises an inorganic salt. 
     
     
         15 . The method for extracting and separating zirconium and hafnium in a nitric acid medium according to  claim 2 , wherein free acids are present in the acidic raw liquid at a total acidity of 2.5˜3.6 mol/L. 
     
     
         16 . The method for extracting and separating zirconium and hafnium in a nitric acid medium according to  claim 2 , wherein zirconium ions and hafnium ions are present in the acidic raw liquid at a total concentration of 0.5˜1.5 mol/L. 
     
     
         17 . The method for extracting and separating zirconium and hafnium in a nitric acid medium according to  claim 3 , wherein nitrate ions are present in the acidic raw liquid at a concentration of 2.5˜3.5 mol/L. 
     
     
         18 . The method for extracting and separating zirconium and hafnium in a nitric acid medium according to  claim 5 , wherein the phosphonic acid-like extraction agent accounts for 2˜20% (v/v) by volume in the extraction agent. 
     
     
         19 . The method for extracting and separating zirconium and hafnium in a nitric acid medium according to  claim 6 , wherein the diluent is at least one selected from the group consisting of sulfonated kerosene, hexane, isooctane and 200# solvent oil. 
     
     
         20 . The method for extracting and separating zirconium and hafnium in a nitric acid medium according to  claim 7 , wherein two phases are mixed for 2˜30 min.