# US 10,246,341 B2 · Method for producing lithium carbonate from low-lithium brine by separating magnesium and enriching lithium

> Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt

- Number: US 10,246,341 B2
- Document ID: US10246341B2
- Status: Granted
- Kind: B2
- Application number: 15/789,997
- Filed: 2017-10-21
- Published: 2018-02-15
- Granted: 2019-04-02
- Earliest claimed: 2015-09-18
- Assignees: Xiangtan University
- Applicants: Xiangtan University
- Inventors: Lixin Yang; Mi Fu; Yi Wang; Hongyu Qi; Yu Xu; Yali Liu; Yalin Gui; Jing He
- Web page: https://patentgrep.com/patent/US10246341B2

## CPC

- C01D 15/08: Carbonates; Bicarbonates
- B01D 11/04: of solutions which are liquid
- B01D 12/00: Displacing liquid, e.g. from wet solids or from dispersions of liquids or from solids in liquids, by means of another liquid
- C01F 5/22: from magnesium compounds with alkali hydroxides or alkaline- earth oxides or hydroxides
- C01F 5/24: Magnesium carbonates
- C07F 9/11: with hydroxyalkyl compounds without further substituents on alkyl
- C07B 63/00: Purification; Separation (separation of optically-active compounds C07B57/00); Stabilisation; Use of additives
- C01D: COMPOUNDS OF ALKALI METALS, i.e. LITHIUM, SODIUM, POTASSIUM, RUBIDIUM, CAESIUM, OR FRANCIUM (metal hydrides {monoborane, diborane or addition complexes thereof} C01B6/00; salts of oxyacids of halogens C01B11/00; peroxides, salts of peroxyacids C01B15/00; sulfides C01B17/22; thiosulfates, dithionites, polythionates C01B17/64; compounds containing selenium or tellurium C01B19/00; binary compounds of nitrogen with metals C01B21/06; azides C01B21/08; {compounds other than ammonia and cyanogen, containing nitrogen and other non-metals C01B21/082}; metal amides C01B21/092; nitrites C01B21/50; phosphides C01B21/50; {compounds of noble gases C01B23/0005}; phosphides C01B25/08; salts of oxyacids of phosphorus C01B25/16; carbides C01B32/90; compounds containing silicon C01B33/00; compounds containing boron C01B35/00; cyanides C01C3/08; salts of cyanic acid C01C3/14; salts of cyanamide C01C3/16; thiocyanates C01C3/20)
- B01D: SEPARATION (separating solids from solids by wet methods B03B, B03D; by pneumatic jigs or tables B03B; by other dry methods B07; magnetic or electrostatic separation of solid materials from solid materials or fluids, separation by high-voltage electric fields B03C; centrifuges, vortex apparatus B04; presses per se for squeezing-out liquid from liquid-containing material B30B9/02; treatment of water C02F, e.g. softening by ion-exchange C02F1/42; {arrangements of air intake cleaners in gas turbine plants F02C7/05} ; arrangements or mounting of filters in air-conditioning, air-humidification or ventilation F24F13/28)
- C01F: COMPOUNDS OF THE METALS BERYLLIUM, MAGNESIUM, ALUMINIUM, CALCIUM, STRONTIUM, BARIUM, RADIUM, THORIUM, OR OF THE RARE-EARTH METALS (metal hydrides {monoborane, diborane or addition complexes thereof} C01B6/00; salts of oxyacids of halogens C01B11/00; peroxides, salts of peroxyacids C01B15/00; sulfides or polysulfides of magnesium, calcium, strontium, or barium C01B17/42; thiosulfates, dithionites, polythionates C01B17/64; compounds containing selenium or tellurium C01B19/00; binary compounds of nitrogen with metals C01B21/06; azides C01B21/08; {compounds other than ammonia or cyanogen containing nitrogen and non-metals and optionally metals C01B21/082; amides or imides of silicon C01B21/087}; metal {imides or} amides C01B21/092, {C01B21/0923}; nitrites C01B21/50; {compounds of noble gases C01B23/0005}; phosphides C01B25/08; salts of oxyacids of phosphorus C01B25/16; carbides C01B32/90; compounds containing silicon C01B33/00; compounds containing boron C01B35/00; compounds having molecular sieve properties but not having base-exchange properties C01B37/00; compounds having molecular sieve and base-exchange properties, e.g. crystalline zeolites, C01B39/00; cyanides C01C3/08; salts of cyanic acid C01C3/14; salts of cyanamide C01C3/16; thiocyanates C01C3/20; {double sulfates of magnesium with sodium or potassium C01D5/12; with other alkali metals C01D15/00, C01D17/00})
- C07F: ACYCLIC, CARBOCYCLIC OR HETEROCYCLIC COMPOUNDS CONTAINING ELEMENTS OTHER THAN CARBON, HYDROGEN, HALOGEN, OXYGEN, NITROGEN, SULFUR, SELENIUM OR TELLURIUM (metal-containing porphyrins C07D487/22)
- C07B: GENERAL METHODS OF ORGANIC CHEMISTRY; APPARATUS THEREFOR (preparation of carboxylic acid esters by telomerisation C07C67/47; telomerisation C08F)

## Abstract

The present invention discloses a method for producing lithium carbonate from a low-lithium brine by separating magnesium and enriching lithium. A salt-lake brine is used as a raw material and is converted into halide salts through dehydration by evaporation and separation by crystallization; the halide salts are directly extracted using trialkyl phosphate or a mixture of trialkyl phosphate and monohydric alcohol, and an organic extraction phase as well as remaining halide salts are obtained after solid-liquid separation; reverse extraction is performed on the organic extraction phase to obtain a lithium-rich solution with a low magnesium-to-lithium ratio, and lithium carbonate is obtained after concentration and removal of magnesium by alkalization. The used solid-liquid extraction method is simple with no co-extraction agent used, and a solute distribution driving force is strong, unaffected by phase equilibrium of the brine extraction agent. The mass ratio of magnesium-to-lithium significantly decreases in the extraction phase.

## Claims

### Claim 1

A method for producing lithium carbonate from low-lithium brine by separating magnesium and enriching lithium, comprising:
a. heating, evaporating and condensing a salt-lake brine to separate halide salts;
b. extracting the separated halide salts with trialkyl phosphate or a mixture of trialkyl phosphate and monohydric alcohol as an organic phase;
wherein a ratio of weight (kg) of the separated halide salts to a volume (L) of the organic phase is 1.0:0.5˜5.0;
c. filtering a mixture from step b to produce an organic phase and remaining halide salts after a two-phase separation;
d. reverse extracting the organic phase from step c with water as a reverse extraction agent at a volume ratio of water to organic phase of 1.0:0.5˜10.0 in 1-5 stages of reverse extraction;
e. separating the organic phase from the water of step d after liquid layers are formed and then evaporating and concentrating the separated water to obtain a concentrated water phase;
f. adding sodium carbonate or sodium hydroxide into the concentrated water phase from step e to precipitate magnesium carbonate or magnesium hydroxide, and then filtering the precipitated magnesium carbonate or magnesium hydroxide to remove Mg2+, wherein the water phase has a pH of more than 10 to completely precipitate Mg2+; and
g. adding sodium carbonate into the water phase with Mg2+ removed from step f to precipitate lithium carbonate, and then filtering and drying the precipitated lithium carbonate to produce a final product.

### Claim 2 (depends on 1)

The method of claim 1, wherein step b comprises: first extracting the halide salts, and then heating and melting the remaining halide salts, wherein the water content of the remaining halide salts is controlled such that the halide salts containing crystal water are separated out; adding trialkyl phosphate or a mixture of trialkyl phosphate and monohydric alcohol to the halide salts containing crystal water at a volume-mass ratio of 1.0:0.5˜5.0 to perform a second stage extraction.

### Claim 3 (depends on 1)

The method of claim 1, wherein step b is multi-stage cross flow extraction or multi-stage counter flow extraction.

### Claim 4 (depends on 1)

The method of claim 1, wherein trialkyl phosphate in step b is selected from the group consisting of: tributyl phosphate, tripentyl phosphate, trihexyl phosphate, tri-n-heptyl phosphate, trioctyl phosphate and isomerides thereof; the monohydric alcohol is selected from one or more of saturated monohydric alcohols having 6-20 carbon atoms; and a volume ratio of trialkyl phosphate to monohydric alcohol is 1.0:0.2˜4.0.

### Claim 5 (depends on 1)

The method of claim 1, wherein, when a mass ratio of magnesium to lithium is larger than 1.0 in the reverse extracted water phase from step e, steps a to e are repeated on the reverse extracted water phase from step e to further reduce a magnesium to lithium ratio.