Method for efficiently separating magnesium and lithium from salt lake brine and simultaneously preparing high-purity magnesium oxide and battery-grade lithium carbonate

Patent metadata

Field	Value
Publication number	US-11524901-B2
Application number	US-201916640997-A
Country	US
Kind code	B2
Filing date	Mar 8, 2019
Priority date	Mar 22, 2019
Publication date	Dec 13, 2022
Grant date	Dec 13, 2022

Abstract

This invention provides a method for efficiently separating magnesium and lithium from salt lake brine, and simultaneously preparing high-purity magnesium oxide and battery-grade lithium carbonate. The detailed processing steps are as follows: (1) adding urea into the brine to dissolve, (2) placing the solution into the reactor for hydrothermal reaction, the magnesium ion will precipitate and enter the solid phase; (3) filtering and drying the production to get the magnesium carbonate solid, while the lithium ion remains in the liquid phase; (4) after directly concentration and precipitation, the battery-grade lithium carbonate can be obtained, while the calcination of solid-phase product results in the high-purity magnesium oxide. In this method, urea is used as the precipitant to separate magnesium and lithium in salt lake without introducing any new metal ion, and the brine solution is not diluted. The solid product is white and fluffy powder, which is easy to filter and separate. The extraction rate of lithium is high than 94%, and the purity of MgO obtained by calcination is higher than 99.5%.

First claim

The invention claimed is:

1. A method for the efficient separation of magnesium and lithium from salt lake brine, comprising: adding urea into the brine to dissolve to obtain a solution; placing the solution into a reactor for hydrothermal reaction to obtain a product, so that magnesium ions will precipitate and enter a solid phase; filtering and drying the product to get a magnesium carbonate solid, while lithium ions remain in a liquid phase, so that separation of magnesium and lithium is realized.

2. The method according to claim 1 wherein
the step of adding urea into the brine to dissolve to obtain a solution comprises: adding urea into the brine to form a solution, the molar concentration ratio of magnesium ions to urea being,
the step of placing the solution into a reactor for hydrothermal reaction comprises: transferring the solution obtained to the reactor, the reactor made of stainless steel and lined with polytetrafluoroethylene (PTFE), and conducting the hydrothermal reaction under 90-150° C. for 8-24 h, and
the step of filtering and drying the product comprises: at the end of the hydrothermal reaction, cooling down a temperature of the reactor to room temperature, and then conducting decompression filtration to achieve solid-liquid separation to obtain a solid product and a filtrate, and drying the solid product at 40-60° C. for 3-8 hours without washing to obtain a white powdered magnesium carbonate solid, the lithium ions remaining in the filtrate so that separation of magnesium and lithium is achieved.

3. The method according to claim 2 wherein concentrations of cations within the brine are: [Li + ]=1-20 g/L, [Mg 2+ ]=10-100 g/L, [K + ]=2-20 g/L, and [Nal + ]=1−30 g/L.

4. The method according to claim 2 , wherein a filling volume of the solution in the reactor does not exceed ⅔ of a total volume of the reactor.

5. The method according to claim 2 , wherein the white powdered magnesium carbonate solid is Mg 5 (CO 3 ) 4 (OH) 2 ·4H 2 O, MgCO 3 , or a mixture of Mg 5 (CO 3 ) 4 (OH) 2 ·4H 2 O and MgCO 3 .

6. A method for efficiently separating magnesium and lithium from salt lake brine and simultaneously preparing high-purity magnesium oxide, comprising: adding urea into the brine to dissolve to obtain a solution;
placing the solution into a reactor for hydrothermal reaction to obtain a product, so that magnesium ions will precipitate and enter a solid phase; filtering and drying the product to get a magnesium carbonate solid, while lithium ions remain in a liquid phase, so that separation of magnesium and lithium is realized, and calcining the magnesium carbonate solid to obtain high-purity magnesium oxide.

7. The method according to claim 6 wherein the step of calcining the magnesium carbonate solid comprises: raising a calcining temperature to 500-1000° C. for 1-8 h in air atmosphere with a rising rate of 1-10° C./min.

8. A method for efficiently separating magnesium and lithium from salt lake brine and simultaneously preparing a battery-grade lithium carbonate, comprising: adding urea into the brine to dissolve to obtain a solution;
placing the solution into a reactor for hydrothermal reaction to obtain a product, so that magnesium ions will precipitate and enter a solid phase; filtering and drying the product to get a magnesium carbonate solid, while lithium ions remain in a liquid phase; and concentrating and precipitating the liquid phase to obtain the battery-grade lithium carbonate.

9. The method according to claim 8 wherein the step of concentrating and precipitating the liquid phase to obtain the battery-grade lithium carbonate comprises: heating and evaporating the liquid phase to achieve a lithium ion concentration of 20-30 g/L;
adding sodium carbonate according to the Li + /CO 3 2− molar ratio of 0.5-1.5, and stirring continuously for 30-90 min at 50-100° C.; conducting decompression filtration to achieve solid-liquid separation and washing a solid obtained after the solid-liquid separation for 2-5 times by deionized water, and drying the solid at 90-150° C. for 1-5 h to obtain the battery-grade lithium carbonate.

Assignees

• Univ Beijing Chem Tech

Inventors

• Xiang Xu
• Duan Xue

Classifications

• C01F5/24 Primary

  Magnesium carbonates · CPC title

• C02F2101/10

  Inorganic compounds · CPC title

• C02F1/5272

  using specific organic precipitants · CPC title

• C01D15/08 Primary

  Carbonates; Bicarbonates · CPC title

• C01P2004/03

  obtained by SEM · CPC title