Selective Separation of Rare Earth Metals by Integrated Extraction and Crystallization

Abstract

An integrated recovery process for rare earth recovery includes bringing the acid solution containing rare earth elements into contact with an organic phase containing an extraction agent to extract the rare earth elements into the organic phase. The organic phase is separated from the aqueous phase. The rare earth elements are either collected from the aqueous phase of the extraction process or the rare earth elements are stripped from the organic phase to an aqueous solution. Rare earth powders are collected from the aqueous solution by partly removing the aqueous solvent. Alternatively, the aqueous solvent can be completely removed, the collected rare earth powders are dissolved in an acidic solution, and the mixture is equilibrated for crystallization of the target rare earth element. In both cases, the crystals and a mother liquor are separated by solid/liquid separation.

1 . An integrated recovery process for rare earth recovery, the process comprising:
 preparing an acid solution containing rare earth elements;   bringing the acid solution containing rare earth elements into contact with an organic phase containing an extraction agent, thereby extracting the rare earth elements into the organic phase;   separating the organic phase from the aqueous phase;   collecting the rare earth elements from the aqueous phase of the extraction process or stripping the rare earth elements from the organic phase to an aqueous solution;   collecting rare earth powders from the aqueous solution by removing the aqueous solvent, the collected rare earth powders comprising the rare earth elements;   dissolving the collected rare earth powders in an acidic solution;   equilibrating the mixture for crystallization of a target rare earth element; and   separating the crystals and a mother liquor by solid/liquid separation.   
     
     
         2 . The integrated recovery process of  claim 1 , further comprising:
 washing the crystallized solids to remove impurities and drying the washed solids in a vacuum oven.   
     
     
         3 . The integrated recovery process of  claim 1 , further comprising:
 selecting, as the aqueous solution for extraction, a material selected from the group consisting of sulfuric acid (H 2 SO 4 ), hydrochloric acid (HCl), nitric acid HNO 3 , oxalic acid (H 2 C 2 O 4 ) and phosphoric acid (H 3 PO 4 ).   
     
     
         4 . The integrated recovery process according to  claim 1 , wherein the organic phase comprises a hydrocarbon solvent. 
     
     
         5 . The integrated recovery process according to  claim 1 , further comprising:
 selecting, as the organic phase comprises a material, an organic solvent immiscible with the acid solution, and having a predetermined low evaporation rate.   
     
     
         6 . The integrated recovery process according to  claim 1 , further comprising:
 selecting, as the organic phase comprises a material, a material selected from the group consisting of hexane, heptane, cyclohexane, kerosene, benzene and 1,2-dichloroethylene.   
     
     
         7 . The integrated recovery process according to  claim 1 , further comprising:
 selecting, as the extracting agent, a material selected from the group consisting of di(2-ethylhexyl) phosphoric acid (P-204), 2-ethylhexylphosphonic acid mono-2-ethylhexyl ester (P507), di-n-octylphosphinic acid, bis(2,4,4-trimethylpentyl)phosphinic acid, 2,4,4-trimethylpentylcyclohexylphosphinic acid, and dicyclohexylphosphinic acid.   
     
     
         8 . The integrated recovery process according to  claim 1 , further comprising:
 prior to crystallizing the solids, extracting part of the solvent.   
     
     
         9 . The integrated recovery process according to  claim 1 , further comprising:
 selecting, as the aqueous solution for dissolving the collected rare earth powders, a material selected from the group consisting of hydrochloric acid, sulphuric acid, or nitric acid.   
     
     
         10 . An integrated recovery process for rare earth recovery comprising the following steps:
 (a) preparing an acid solution containing rare earth elements;   (b) bringing the acid solution containing rare earth elements into contact with an organic phase containing an extraction agent, and thereby extracting the rare earth elements into the organic phase;   (c) separating the organic phase from the aqueous phase;   (d) collecting the rare earth elements from the aqueous phase of the extraction process or stripping the rare earth elements from the organic phase to an aqueous solution;   (e) collecting rare earth powders from the aqueous solution by removing the aqueous solvent by partly removing the aqueous solvent to concentrate the mixture; and   (f) separating the crystals and mother liquor by solid/liquid separation.   
     
     
         11 . The integrated recovery process of  claim 10 , further comprising:
 washing the crystallized solids to remove impurities and drying the washed solids in a vacuum oven.   
     
     
         12 . The integrated recovery process of  claim 10 , further comprising:
 selecting, as the aqueous solution for extraction, a material selected from the group consisting of sulfuric acid (H 2 SO 4 ), hydrochloric acid (HCl), nitric acid HNO 3 , oxalic acid (H 2 C 2 O 4 ) and phosphoric acid (H 3 PO 4 ).   
     
     
         13 . The integrated recovery process according to  claim 10 , wherein the organic phase comprises a hydrocarbon solvent. 
     
     
         14 . The integrated recovery process according to  claim 10 , further comprising:
 selecting, as the organic phase comprises a material, a material selected from the group consisting of hexane, heptane, cyclohexane, kerosene, benzene and 1,2-dichloroethylene.   
     
     
         15 . The integrated recovery process according to  claim 10 , further comprising:
 selecting, as the extracting agent, a material selected from the group consisting of di(2-ethylhexyl) phosphoric acid (P-204), 2-ethylhexylphosphonic acid mono-2-ethylhexyl ester (P507), di-n-octylphosphinic acid, bis(2,4,4-trimethylpentyl)phosphinic acid, 2,4,4-trimethylpentylcyclohexylphosphinic acid, and dicyclohexylphosphinic acid.   
     
     
         16 . An integrated recovery process for rare earth recovery comprising the following steps:
 (a) preparing an acid solution containing rare earth elements;   (b) bringing the acid solution containing rare earth elements into contact with an organic phase containing an extraction agent, and thereby extracting the rare earth elements into the organic phase;   (c) separating the organic phase from the aqueous phase;   (d) collecting the rare earth elements from the aqueous phase of the extraction process or stripping the rare earth elements from the organic phase to an aqueous solution;   (e) collecting rare earth powders from the aqueous solution by removing the aqueous solvent, the collected rare earth powders comprising the rare earth elements;;   (f) dissolving the collected rare earth powders in an acidic solution;   (g) extracting at least a portion of the solvent;   (h) equilibrating the mixture for crystallization of a target rare earth element; and   (i) separating the crystals and mother liquor by solid/liquid separation.   
     
     
         17 . The integrated recovery process according to  claim 16 , further comprising:
 selecting, as the aqueous solution for dissolving the collected rare earth powders, a material selected from the group consisting of hydrochloric acid, sulphuric acid, or nitric acid.   
     
     
         18 . The integrated recovery process according to  claim 16 , wherein the organic phase comprises a hydrocarbon solvent. 
     
     
         19 . The integrated recovery process according to  claim 16 , further comprising:
 selecting, as the organic phase comprises a material, a material selected from the group consisting of hexane, heptane, cyclohexane, kerosene, benzene and 1,2-dichloroethylene.   
     
     
         20 . The integrated recovery process according to  claim 17 , further comprising:
 selecting, as the extracting agent, a material selected from the group consisting of di(2-ethylhexyl) phosphoric acid (P-204), 2-ethylhexylphosphonic acid mono-2-ethylhexyl ester (P507), di-n-octylphosphinic acid, bis(2,4,4-trimethylpentyl)phosphinic acid, 2,4,4-trimethylpentylcyclohexylphosphinic acid, and dicyclohexylphosphinic acid.