Systems and processes for recovery of high-grade rare earth concentrate from acid mine drainage

Abstract

In one aspect, the disclosure relates to a continuous process for treating acid mine drainage while simultaneously recovering a high-grade rare earth preconcentrate suitable for extraction of commercially valuable rare earth oxides. In a further aspect, the preconcentrate is from about 0.1% to 5% rare earth elements on a dry weight basis. In another aspect, the disclosure relates to a method for processing the preconcentrate to generate a pregnant leach solution that does not form gels or emulsions and is suitable for processing via solvent extraction. In another aspect, the disclosure relates to a system and plant for carrying out the disclosed process. In still another aspect, the disclosure relates to a composition containing rare earth elements produced by the process disclosed herein. This abstract is intended as a scanning tool for purposes of searching in the particular art and is not intended to be limiting of the present disclosure.

1 . A pregnant leach solution composition comprising:
 lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium, scandium, and yttrium;   wherein a total rare earth element concentration is a sum of each concentrations of lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium, scandium, and yttrium;   wherein thorium and uranium are present in an aggregate concentration of less than 1 mg/L;   wherein cobalt is present in an amount less than about 20 mg/L; and   wherein the total rare earth concentration is about 5 mg/L to about 50 mg/L.   
     
     
         2 . The pregnant leach solution composition of  claim 1 , wherein scandium is present at a concentration of from about 0.05 mg/L to about 1 mg/L; yttrium is present at a concentration of from about 0.5 mg/L to about 10 mg/L; lanthanum is present at a concentration of from about 0.05 mg/L to about 5 mg/L; cerium is present at a concentration of from about 0.5 mg/L to about 7.5 mg/L; praseodymium is present at a concentration of from about 0.05 mg/L to about 2.5 mg/L; neodymium is present at a concentration of from about 0.5 mg/L to about 10 mg/L; samarium is present at a concentration of from about 0.1 mg/L to about 2.5 mg/L; europium present at a concentration of from about 0.05 mg/L to about 1.5 mg/L; gadolinium is present at a concentration of from about 0.1 mg/L to about 5 mg/L; terbium is present at a concentration of from about 0.05 mg/L to about 1.5 mg/L; dysprosium present at a concentration of from about 0.1 mg/L to about 5 mg/L; holmium is present at a concentration of from about 0.05 mg/L to about 2 mg/L; erbium is present at a concentration of from about 0.1 mg/L to about 5 mg/L; thulium is present at a concentration of from about 0.05 mg/L to about 2 mg/L; ytterbium is present at a concentration of from about 0.05 mg/L to about 5 mg/L; and lutetium is present at a concentration of from about 0.01 mg/L to about 1 mg/L. 
     
     
         3 . The pregnant leach solution composition of  claim 1 , wherein iron is present at a concentration less than or equal to about 25 mg/L. 
     
     
         4 .- 5 . (canceled) 
     
     
         6 . The pregnant leach solution composition of  claim 1 , wherein the pregnant leach solution has a pH of from about 2.8 to about 3.0. 
     
     
         7 .- 28 . (canceled) 
     
     
         29 . The pregnant leach solution composition of  claim 1 , wherein scandium is present at a concentration of from about 0.05 mg/L to about 1 mg/L. 
     
     
         30 . The pregnant leach solution composition of  claim 1 , wherein yttrium is present at a concentration of from about 0.5 mg/L to about 10 mg/L 
     
     
         31 . The pregnant leach solution composition of  claim 1 , wherein lanthanum is present at a concentration of from about 0.05 mg/L to about 5 mg/L. 
     
     
         32 . The pregnant leach solution composition of  claim 1 , wherein cerium is present at a concentration of from about 0.5 mg/L to about 7.5 mg/L. 
     
     
         33 . The pregnant leach solution composition of  claim 1 , wherein praseodymium is present at a concentration of from about 0.05 mg/L to about 2.5 mg/L 
     
     
         34 . The pregnant leach solution composition of  claim 1 , wherein neodymium is present at a concentration of from about 0.5 mg/L to about 10 mg/L. 
     
     
         35 . The pregnant leach solution composition of  claim 1 , wherein samarium is present at a concentration of from about 0.1 mg/L to about 2.5 mg/L. 
     
     
         36 . The pregnant leach solution composition of  claim 1 , wherein europium present at a concentration of from about 0.05 mg/L to about 1.5 mg/L. 
     
     
         37 . The pregnant leach solution composition of  claim 1 , wherein gadolinium is present at a concentration of from about 0.1 mg/L to about 5 mg/L 
     
     
         38 . The pregnant leach solution composition of  claim 1 , wherein terbium is present at a concentration of from about 0.05 mg/L to about 1.5 mg/L 
     
     
         39 . The pregnant leach solution composition of  claim 1 , wherein dysprosium present at a concentration of from about 0.1 mg/L to about 5 mg/L 
     
     
         40 . The pregnant leach solution composition of  claim 1 , wherein holmium is present at a concentration of from about 0.05 mg/L to about 2 mg/L 
     
     
         41 . The pregnant leach solution composition of  claim 1 , wherein erbium is present at a concentration of from about 0.1 mg/L to about 5 mg/L 
     
     
         42 . The pregnant leach solution composition of  claim 1 , wherein thulium is present at a concentration of from about 0.05 mg/L to about 2 mg/L 
     
     
         43 . The pregnant leach solution composition of  claim 1 , wherein ytterbium is present at a concentration of from about 0.05 mg/L to about 5 mg/L 
     
     
         44 . The pregnant leach solution composition of  claim 1 , wherein lutetium is present at a concentration of from about 0.01 mg/L to about 1 mg/L.