Method for softening lithium brine using nanofiltration

Patent metadata

Field	Value
Publication number	US-11203542-B2
Application number	US-201716612282-A
Country	US
Kind code	B2
Filing date	May 11, 2017
Priority date	May 11, 2017
Publication date	Dec 21, 2021
Grant date	Dec 21, 2021

Abstract

Lithium brine is treated with a multiple pass nanofiltration (NF) membrane system. Sulfate is added to permeate from an upstream pass before it flows through a downstream pass. Optionally the sulfate may be added to the permeate by dosing it with sulfuric acid or a slat such as sodium sulfate. The softened brine may then be processed further, for example by a combination of solvent extraction, electrolysis, crystallization and drying, to produce a lithium hydroxide product that can be used to make batteries.

First claim

The invention claimed is:

1. A lithium brine treatment system comprising,
a) a upstream nanofiltration membrane unit;
b) a downstream nanofiltration membrane unit;
c) a sulfate dosing system; and
d) a solvent extraction system that includes at least a lithium extraction unit and a stripping unit, where the stripping unit includes a lithium chloride discharge outlet,
wherein a permeate outlet of the upstream nanofiltration system is connected to a feed inlet of the downstream nanofiltration unit and the sulfate dosing system is connected between the upstream and downstream nanofiltration units.

2. A process for softening lithium brine comprising the steps of,
a) flowing the lithium brine to a nanofiltration membrane unit to produce a first permeate;
b) adding sulfate to the first permeate; and,
c) flowing the first permeate to another nanofiltration membrane unit to produce a softened permeate.

3. The process of claim 2 wherein in step b) an amount of sulfate is added to the first permeate such that a molar concentration of sulfate ions in the first permeate is 70% or more of a sum of the molar concentrations of Ca2+ and Mg2+ ions in the first permeate.

4. The process of claim 2 wherein sulfate is added to the first permeate by adding an aqueous solution of sodium sulfate or sulfuric acid to the first permeate.

5. The process of claim 2 wherein the softened permeate is treated by way of solvent extraction to produce lithium chloride.

6. The process of claim 3 wherein the amount of sulfate is added to the first permeate such that a molar concentration of sulfate ions in the first permeate is less than 80% of a sum of the molar concentrations of Ca2+ and Mg2+ ions in the first permeate.

7. The process of claim 2 wherein the lithium brine has a total dissolved solids concentration between 15 and 35%.

Assignees

• Bl Technologies Inc

Inventors

• Liberatore Frederick

Classifications

• C25B1/16

  Hydroxides (by simultaneous production of alkali metal hydroxides and chlorine, oxyacids or salts of chlorine C25B1/34) · CPC title

• C02F1/442 Primary

  by nanofiltration · CPC title

• C01D15/04

  Halides · CPC title

• C02F2101/10

  Inorganic compounds · CPC title

• B01D61/0271

  comprising multiple nanofiltration steps · CPC title