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

Patent metadata

Field	Value
Publication number	US-2021207241-A1
Application number	US-202017115128-A
Country	US
Kind code	A1
Filing date	Dec 8, 2020
Priority date	Jul 17, 2019
Publication date	Jul 8, 2021
Grant date	—

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.

First claim

1 - 19 . (canceled)

20 . A composition comprising a pregnant leach solution (PLS) made by the method comprising the following steps:
a. contacting a raw material containing REEs with a first base to form waste solids and an aqueous phase and discarding the waste solids; b. contacting the aqueous phase with a second base to form an REE-enriched preconcentrate and an effluent and discharging the effluent; c. contacting the REE-enriched preconcentrate with an acid to form an acidic preconcentrate; d. filtering the acidic preconcentrate to form an acidic filtrate; and e. contacting the acidic filtrate with a third base and filtering to form a pregnant leach solution; wherein the pregnant leach solution is enriched in REEs and essentially free of solids.

21 . The composition of claim 20 , wherein the raw material is raw acid mine drainage (AMD), an AMD precipitate (AMDp), or an enriched AMD precipitate (eAMDp).

22 . The composition of claim 20 , wherein contacting the raw material with the first base changes the pH of the aqueous phase to about 4.0 to about 4.5.

23 . The composition of claim 20 , wherein the first base comprises NaOH, KOH, ammonia, ammonium hydroxide, quicklime, lime slurry, or a combination thereof.

24 . The composition of claim 20 , wherein contacting the aqueous phase with the second base changes the pH of the aqueous phase to about 8.0 to about 8.5.

25 . The composition of claim 20 , wherein the second base comprises NaOH, KOH, ammonia or an ammonium compound, quicklime, lime slurry, or a combination thereof.

26 . The composition of claim 20 , wherein the contacting the REE-enriched preconcentrate with the acid changes the pH of the REE-enriched preconcentrate to about 0.7 to about 3.0.

27 . The composition of claim 20 , wherein the acid comprises hydrochloric acid, nitric acid, sulfuric acid, or a combination thereof.

28 . The composition of claim 20 , wherein contacting the acidic filtrate with the third base changes the pH of the acidic filtrate to about 2.8 to about 3.0.

29 . The composition of claim 20 , wherein the third base comprises MgO, NaOH, KOH, ammonia or ammonium hydroxide, quicklime, lime slurry, or a combination thereof.

30 . The composition of claim 20 , wherein step (e) further comprises oxidizing the acidic filtrate.

31 . The composition of claim 30 , wherein the acidic filtrate is oxidized mechanically, electrochemically, with an oxidizing agent, or a combination thereof.

32 . The composition of claim 31 , wherein the oxidizing agent is hydrogen peroxide.

33 . The composition of claim 20 , further comprising a step for recovering scandium between steps (a) and (b), the step for recovering scandium comprising contacting the aqueous phase with a fourth base, thereby forming a scandium-enriched solid concentrate, and removing the scandium-enriched solid concentrate from the aqueous phase.

34 . The composition of claim 33 , wherein contacting the aqueous phase with a fourth base changes the pH of the aqueous phase to about 4.9 to about 5.1.

35 . The composition of claim 33 , wherein the fourth base comprises NaOH, KOH, ammonia or an ammonium compound, quicklime, lime slurry, or a combination thereof.

36 . The composition of claim 20 , further comprising adding a flocculating agent, a coagulating agent, or both in any of steps (a), (b), or (c).

37 . The composition of claim 20 , wherein following step (e), the method further comprises subjecting the pregnant leach solution to solvent extraction to produce a refined rare earth resource comprising at least 50% REEs.

38 . The composition of claim 20 , wherein the pregnant leach solution comprises one or more of lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium, scandium, or yttrium.

39 . The composition of claim 38 , wherein, when present, the lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium, scandium, or yttrium are present in the following amounts in μg/L:

Element
Minimum
Maximum

Y
7151
111,224

La
1477
32,650

Ce
4906
86,414

Pr
782
10,803

Nd
3688
48,145

Sm
1133
12,001

Eu
302
3,223

Gd
1820
18,229

Tb
339
3,021

Dy
1995
18,229

Ho
354
3639

Er
908
10,032

Tm
112
1291

Yb
638
7380

Lu
91
1100

Th
0.06
322

U
198
1205

40 . The composition of claim 20 , wherein the pregnant leach solution comprises iron present in an amount less than or equal to about 5 mg/L.

41 . The composition of claim 39 , wherein, when present, the lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutet

Assignees

• Univ West Virginia

Inventors

• Ziemkiewicz Paul
• Noble Aaron
• Vass Chris

Classifications

• Y02P10/20

  Recycling · CPC title

• C22B3/20

  Treatment or purification of solutions, e.g. obtained by leaching (C22B3/18 takes precedence) · CPC title

• C22B3/22

  by physical processes, e.g. by filtration, by magnetic means {, or by thermal decomposition} (treatment or purification of solutions by liquid-liquid extraction C22B3/26) · CPC title

• C22B3/065 Primary

  Nitric acids or salts thereof · CPC title

• C22B3/06

  in inorganic acid solutions {, e.g. with acids generated in situ; in inorganic salt solutions other than ammonium salt solutions} · CPC title