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EP-4741030-A1 - METHOD OF SEPARATING MIXED MAGNESIUM AND LITHIUM SALTS

EP4741030A1EP 4741030 A1EP4741030 A1EP 4741030A1EP-4741030-A1

Abstract

A method of separating lithium and magnesium includes hydrolyzing a hydrolysis composition that includes MgCl 2 and LiCl, the hydrolyzing including treating the hydrolysis composition with heat to form HCl, water, and a hydrolyzed mixture including LiCl and MgO. The method also includes performing dissolution separation including separating a solvent-soluble fraction in the hydrolyzed mixture that includes LiCl from a substantially solvent-insoluble fraction in the hydrolyzed mixture including a magnesium-containing product including Mg(OH) 2 and/or MgO.

Inventors

  • MARTIN, CHRISTOPHER LEE
  • Musich, Mark

Assignees

  • Energy and Environmental Research Center Foundation

Dates

Publication Date
20260513
Application Date
20251105

Claims (15)

  1. A method of separating lithium and magnesium salts, the method comprising: hydrolyzing a hydrolysis composition that comprises MgCl 2 and LiCl, the hydrolyzing comprising treating the hydrolysis composition with heat to form HCl, water, and a hydrolyzed mixture comprising LiCl and MgO; and performing dissolution separation comprising separating a solvent-soluble fraction in the hydrolyzed mixture that comprises LiCl from a substantially solvent-insoluble fraction in the hydrolyzed mixture comprising a magnesium-containing product comprising Mg(OH) 2 and/or MgO.
  2. The method of claim 1, wherein a molar ratio of MgCl 2 to LiCl in the hydrolysis composition is 1:10 to 10:1.
  3. The method of claim 1, wherein the hydrolysis composition is substantially dry and is 0 wt% to 5 wt% water, and wherein the method comprises adding steam during the hydrolysis, or the hydrolysis composition is 5 wt% to 90 wt% water.
  4. The method of claim 1, wherein the hydrolysis comprises maintaining a temperature of 250 °C to 650 °C and a pressure of 0.05 MPa to 10 MPa.
  5. The method of claim 1, wherein Mg in the magnesium-containing product in the solvent-insoluble fraction is 50 wt% to 100 wt% of the Mg in the MgCl 2 present in the hydrolysis composition, and wherein lithium salts are 0 wt% to 5 wt% of a total amount of salts present in the solvent-insoluble fraction.
  6. The method of claim 1, wherein the LiCl in the solvent-soluble fraction is 50 wt% to 100 wt% of the LiCl present in the hydrolysis composition, and wherein magnesium salts are 0 wt% to 5 wt% of a total amount of salts present in the solvent-soluble fraction.
  7. The method of claim 1, wherein the dissolution separation comprises adding a solvent to the hydrolyzed mixture and dissolving the solvent-soluble fraction in the solvent while the solvent-insoluble fraction remains substantially insoluble in the solvent, and wherein the solvent comprises water, an alcohol, or a combination thereof, and wherein the dissolution separation is performed at a temperature of 10 °C to 150 °C.
  8. The method of claim 1, wherein separating the solvent-soluble fraction from the solvent-insoluble fraction comprises filtration, gravity separation and decanting, centrifugation, or a combination thereof.
  9. The method of claim 1, further comprising: softening a brine composition, the brine composition comprising MgCl 2 and LiCl, the softening comprising treating the brine composition with a softening reagent to form a softened brine composition and one or more softening precipitates; and partially evaporating the softened brine composition to form an evaporated softened brine, water, and one or more evaporation precipitates, wherein the evaporated softened brine is the hydrolysis composition.
  10. The method of claim 9, wherein the brine composition comprises produced water from petroleum extraction, produced water from CO 2 sequestration, water produced from an industrial process, a concentrate thereof, or a combination thereof, or the method further comprises concentrating a starting material brine to form the brine composition, wherein the starting material brine comprises produced water from petroleum extraction, produced water from CO 2 sequestration, water produced from an industrial process, or a combination thereof.
  11. The method of claim 9, wherein the brine composition further comprises a chloride salt of beryllium, calcium, strontium, barium, radium, sodium, potassium, rubidium, cesium, francium, a rare-earth element (REE) (e.g., La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, yttrium, or scandium), or any combination thereof.
  12. The method of claim 9, wherein the softening reagent comprises NaHCO 3 , Na 2 CO 3 , K 2 CO 3 , KHCO 3 , or a combination thereof, and wherein the one or more softening precipitates comprise carbonate salts of Ca, Sr, Ba, or a combination thereof.
  13. The method of claim 9, wherein the softening of the brine composition comprises maintaining a temperature of 10 °C to 150 °C and a pressure of 0.1 MPa to 0.5 MPa, and wherein the evaporating of the softened brine composition comprises maintaining a temperature of 100 °C to 300 °C and a pressure of 0.001 MPa to 1 MPa..
  14. The method of claim 9, wherein the one or more evaporation precipitates comprise salts of Na, K, or a combination thereof.
  15. The method of claim 9, wherein the evaporating of the softened brine composition comprises removing sufficient water to precipitate 5 wt% to 100 wt% of salts in the softened brine composition that do not comprise the MgCl 2 and LiCl.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS This application is a continuation-in-part of and claims the benefit of priority under 35 U.S.C. § 120 to U.S. Utility Application 18/522,842 filed November 29, 2023, which is a continuation-in-part of and claims the benefit of priority under 35 U.S.C. § 120 to U.S. Utility Application 18/515,726 filed November 21, 2023, which is a continuation of and claims the benefit of priority under 35 U.S.C. § 120 to U.S. Utility Application 18/170,392 filed February 16, 2023, which is a continuation-in-part of and claims the benefit of priority under 35 U.S.C. § 120 to U.S. Utility Application 17/651,520 filed February 17, 2022, which claims the benefit under 35 U.S.C. § 119(e) to U.S. Provisional Patent Application Serial No. 63/200,390 filed March 4, 2021, the disclosures of which are incorporated herein in their entirety by reference. BACKGROUND The separation of lithium (Li) and magnesium (Mg) is a significant challenge. For example, brines including lithium and magnesium salts are often encountered as the water fraction of produced fluids during oil and gas extraction, or extracted from geologic reservoirs for valuable dissolved minerals, and generally contain a complex mixture of chloride salts. Cations in these brines can include sodium (Na), potassium (K), calcium (Ca), magnesium (Mg), and lithium (Li). While effective methods exist for separating lithium from cations such as Na, K, and Ca, high concentrations of Mg present difficulties due to the similar ionic radii of Li and Mg. This similarity complicates separation using precipitation-based approaches or direct Li extraction techniques. Typically, Mg is precipitated as Mg(OH)2, forming a sludge that can trap a significant portion of the Li-containing brine. The challenges associated with elevated Mg content in brines have historically impeded the economical recovery of lithium. This has left many brine resources undeveloped worldwide. Addressing these challenges is crucial for expanding the range of brine compositions considered viable for lithium recovery and for processing existing waste streams from prior extraction activities. SUMMARY OF THE INVENTION Various aspects of the present invention provide a method of separating lithium and magnesium salts. The method includes hydrolyzing a hydrolysis composition that includes MgCl2 and LiCl, the hydrolyzing including treating the hydrolysis composition with heat and water (which can already be present in the hydrolysis composition, or can be added if the hydrolysis composition is substantially dry) to form HCl, water (e.g., in the form of steam), and a hydrolyzed mixture including LiCl and MgO. The method also includes performing dissolution separation including separating a solvent-soluble fraction in the hydrolyzed mixture that includes LiCl from a substantially solvent-insoluble fraction in the hydrolyzed mixture including a magnesium-containing product including Mg(OH)2 and/or MgO. Various aspects of the present invention provide a method of separating lithium and magnesium salts. The method includes softening the brine composition, the brine composition including MgCl2 and LiCl, the softening including treating the brine composition with a softening reagent to form a softened brine composition and one or more softening precipitates. The method includes partially evaporating the softened brine composition to form an evaporated softened brine, water, and one or more evaporation precipitates. The method includes hydrolyzing the evaporated softened brine, the hydrolyzing including treating the evaporated softened brine with heat to form HCl, water, and hydrolyzed brine including LiCl and MgO. The method also includes performing dissolution separation including separating a solvent-soluble fraction in the hydrolyzed brine that includes LiCl from a substantially water-insoluble fraction in the hydrolyzed brine including a magnesium-containing product including Mg(OH)2 and/or MgO. Various aspects of the present invention have advantages over other methods of separating magnesium and lithium salts. For example, in various aspects, the method of the present invention allows for effective separation of lithium from magnesium in concentrated geologic brines, overcoming challenges posed by their similar ionic radii. In various aspects, the method of the present invention more effectively and/or more efficiently separates lithium from magnesium as compared to other methods. In various aspects, the method of the present invention produces magnesium hydroxide having a higher density than formed in other processes, facilitating easier separation from the lithium-containing fraction and thereby facilitating improved separation efficiency. In various aspects, the hydrochloric acid produced by the method of the present invention is a valuable product that can be used or sold to offset or recover the costs and time expense of performing the method. In various aspects, by addressing