阅读说明：本技术 一种改进的锂加工方法 (Improved lithium processing method ) 是由 亚当·布伦 斯科特·伊斯特伍德 于 2019-08-17 设计创作，主要内容包括：一种改进的加工锂冶金溶液的方法,其中包括以下步骤：i.含镁的锂浸出溶液经过一个电化学除镁步骤,形成贫镁的锂浸出溶液；ii.步骤i)获得的贫镁的锂浸出溶液经过下游浓缩和回收工艺处理；其中,电化学除镁步骤在一个三腔电渗析构造中进行,产生氢氧化镁沉淀和一个分离的盐酸流,它们是可回收的副产物。(An improved method of processing a lithium metallurgical solution comprising the steps of: i. subjecting the magnesium-containing lithium leach solution to an electrochemical magnesium removal step to form a magnesium-depleted lithium leach solution; subjecting the magnesium depleted lithium leach solution obtained in step i) to a downstream concentration and recovery process; wherein the electrochemical magnesium removal step is carried out in a three-chamber electrodialysis configuration, producing magnesium hydroxide precipitate and a separated hydrochloric acid stream, which are recoverable by-products.)

1. An improved method of processing a lithium metallurgical solution comprising the steps of:

i. subjecting the magnesium-containing lithium leach solution to an electrochemical magnesium removal step to form a magnesium-depleted lithium leach solution;

subjecting the magnesium depleted lithium leach solution obtained in step i) to a downstream concentration and recovery process wherein the electrochemical magnesium removal step is carried out in a three-chamber electrochemical configuration comprising a cathode chamber, a central chamber having an anion exchange membrane forming a boundary between the cathode chamber and the central chamber and a cation exchange membrane forming a boundary between the anode chamber and the central chamber, the step producing magnesium hydroxide precipitate and a separated hydrochloric acid stream, which are recoverable by-products.

2. An improved method of processing a lithium metallurgical solution comprising the steps of:

i. subjecting the magnesium-containing lithium leach solution to an electrochemical magnesium removal step to form a magnesium-depleted lithium leach solution;

subjecting the magnesium depleted lithium leach solution obtained in step i) to a downstream concentration and recovery process wherein the electrochemical magnesium removal step is carried out in a three-compartment electrodialysis configuration comprising a cathode compartment, a central compartment having an anion exchange membrane forming a boundary between the cathode compartment and the central compartment and a cation exchange membrane forming a boundary between the anode compartment and the central compartment, the step producing magnesium hydroxide precipitate and a separated hydrochloric acid stream, which are recoverable by-products.

3. An improved method of processing a lithium metallurgical solution comprising the steps of:

i. subjecting the magnesium-containing lithium leach solution to an electrochemical magnesium removal step to form a magnesium-depleted lithium leach solution;

subjecting the magnesium depleted lithium leach solution obtained in step i) to a downstream concentration and recovery process;

wherein the electrochemical magnesium removal step is carried out in a single stage, three chamber electrodialysis configuration comprising a cathode chamber, a central chamber having an anion exchange membrane forming a boundary between the cathode chamber and the central chamber, and a cation exchange membrane forming a boundary between the anode chamber and the central chamber, which step produces magnesium hydroxide precipitate and a separated hydrochloric acid stream, which are recyclable by-products.

4. An improved method of treating a lithium leach solution, comprising:

i. subjecting the magnesium-containing lithium leach solution to an electrochemical magnesium removal step to form a magnesium-depleted lithium leach solution;

subjecting the magnesium depleted lithium leach solution obtained in step i) to a polishing step to produce a treated leach liquor (PLS); and

subjecting the treated leach liquor to conventional concentration and recovery steps to recover lithium in the form of lithium carbonate;

wherein the step of removing magnesium further comprises:

introducing the lithium leach solution obtained in step i) into a cathode compartment of an electrochemical cell comprising a cathode;

introducing a sulfuric acid electrolyte solution into an anode chamber containing an anode;

the anode chamber and the cathode chamber are separated by a central chamber to form a three-chamber electrolytic cell, an anion exchange membrane is arranged to form a boundary between the cathode chamber and the central chamber, and a cation exchange membrane is arranged to form a boundary between the anode chamber and the central chamber;

introducing a dilute hydrochloric acid solution into the central chamber;

applying an electric current between the anode and the cathode to promote migration of hydrogen ions produced by the anode to the central chamber through the cation exchange membrane and chloride ions produced by the cathode chamber to the central chamber through the anion exchange membrane to form hydrochloric acid;

magnesium is precipitated in the cathode compartment as magnesium hydroxide, producing a magnesium depleted lithium solution.

5. An improved method for recovering lithium from a lithium leach solution, comprising:

i. subjecting the magnesium-containing lithium leach solution to an electrochemical magnesium removal step to form a magnesium-depleted lithium leach solution, a magnesium hydroxide precipitate and a separated hydrochloric acid stream;

separating magnesium hydroxide from the magnesium depleted lithium leach solution via a solid/liquid separation step;

subjecting the separated magnesium depleted lithium leach solution of step ii) to a polishing step to produce a treated leach liquor (PLS);

subjecting the treated leach liquor to conventional concentration and recovery steps to recover lithium in the form of lithium carbonate;

wherein the step of removing magnesium further comprises:

introducing the lithium leach solution obtained in step i) into a three-chamber electrochemical cell comprising a cathode chamber, an anode chamber and a central chamber therebetween, having an anion exchange membrane forming a boundary between the cathode chamber and the center chamber, and having a cation exchange membrane forming a boundary between the anode chamber and the center chamber;

feeding the lithium leach solution obtained in step i) to a cathode compartment comprising a cathode;

introducing a sulfuric acid electrolyte solution into an anode chamber containing an anode;

introducing a hydrochloric acid solution into the central chamber;

applying an electric current between the anode and the cathode to promote migration of hydrogen ions produced by the anode to the central chamber through the cation exchange membrane and chloride ions produced by the cathode chamber to the central chamber through the anion exchange membrane to form hydrochloric acid;

magnesium is precipitated in the cathode compartment as magnesium hydroxide, producing a magnesium depleted lithium solution.

6. A method according to any one of claims 1 to 3, characterized in that the method is adapted for processing lithium metallurgical solutions as a stand-alone electrolytic cell.

7. A method according to any one of claims 1 to 3, characterized in that the method is suitable for processing lithium metallurgical solutions, possibly incorporating a serial continuous flow treatment operation.

8. A method according to claim 4 or 5, characterized in that the method is adapted for recovering lithium from a lithium leach solution, as a separate electrolytic cell.

9. A process according to claim 4 or claim 5, adapted for recovery of lithium from a lithium leach solution, and which may be incorporated into a serial continuous flow process operation.

Technical Field

The present invention relates to an improved method of processing lithium metallurgical solutions. More particularly, the present invention relates to processes for removing impurities from lithium metallurgical solutions.

Background

The following discussion of the background art is intended to facilitate an understanding of the present invention only. The discussion is not an acknowledgement or admission that any of the material referred to was or was part of the common general knowledge as at the priority date of the application.

In all lithium process schemes, a key process step is the removal of magnesium from the lithium brine to recover lithium of satisfactory purity. Typically, soda ash is used to precipitate magnesium and calcium from pegmatite through hard rock treatment, which dissolve with the lithium, in the process minimizing the loss of lithium.

In the brine commonly found in south america, the traditional process relies on evaporation over a long period of time to precipitate calcium and magnesium by saturation. The result of this process is generally a loss of lithium of up to 50%. By using evaporation to obtain crystalline salts of calcium and magnesium, the amount of soda ash used is minimized. In both hard rock and brine, magnesium must be removed prior to lithium recovery.

Brine has a particular feature in common with hard rock treatment that requires the addition of reagents to remove magnesium because both calcium chloride and magnesium chloride are highly soluble. Both lime and sodium carbonate used to precipitate magnesium result in high hard rock treatment costs. Lime is a mixture containing many impurities, so the use of lime to remove magnesium produces a tailings product with no residual value.

The disadvantages of the brine loop are very obvious and can be calculated quantitatively. The use of solar evaporation requires the use of very large evaporation pans, which results in high investment costs. The result of the purification solution is that lithium is lost by crystallization up to 50%, and the purification solution and "polishing" requires the use of other chemicals and also produces solid waste of no appreciable value.

Magnesium is a waste product in the current disposal process and adds significant expense to the process of separation from lithium.

There is currently no satisfactory process for separating magnesium from metallurgical solutions to produce an economical stream of magnesium and metal of sufficient purity.

The present invention is directed to overcoming, or at least ameliorating, one or more of the deficiencies of the prior art described above or providing the consumer with a useful economic choice.

Each document, reference, patent application, or patent cited herein is expressly incorporated by reference in its entirety to the extent that it is intended to be read and considered as part of this document by the reader. The documents, references, patent applications or patents cited herein are not repeated herein, but merely for the sake of brevity of the text.

Throughout this specification, unless the context requires otherwise, the term "brine" is to be understood to include salt, seawater and metallurgical solutions containing salt.

Throughout this specification, reference to a metallurgical solution will be considered to apply to any metal that is desired to be recovered from a metal feedstock, including but not limited to ore, hard rock, brine or slurry.

References to metals are to be considered to include any metal, including but not limited to lithium.

Throughout this specification, unless the context requires otherwise, an understanding of the word "comprise" or "comprises" will imply the inclusion of a stated element or group of elements but not the exclusion of any other element or group of elements.

Disclosure of Invention

According to one aspect of the present invention, there is provided an improved method of processing lithium metallurgical solutions comprising the steps of:

i) subjecting the magnesium-containing lithium leach solution to an electrochemical magnesium removal step to form a magnesium-depleted lithium leach solution;

ii) the magnesium depleted lithium leach solution obtained in step i) is subjected to a downstream concentration and recovery process wherein the electrochemical magnesium removal step is carried out in a three-chamber electrochemical configuration, producing magnesium hydroxide precipitate and a separated hydrochloric acid stream, which are recoverable by-products.

According to one aspect of the present invention, there is provided an improved method of processing a lithium metallurgical solution comprising the steps of:

i) subjecting the magnesium-containing lithium leach solution to an electrochemical magnesium removal step to form a magnesium-depleted lithium leach solution;

ii) subjecting the magnesium depleted lithium leach solution obtained in step i) to a downstream concentration and recovery process;

wherein the electrochemical magnesium removal step is carried out in a three-chamber electrodialysis configuration, producing magnesium hydroxide precipitate and a separated hydrochloric acid stream, which are recoverable by-products.

According to one aspect of the present invention, there is provided an improved method of processing a lithium metallurgical solution comprising the steps of:

i) subjecting the magnesium-containing lithium leach solution to an electrochemical magnesium removal step to form a magnesium-depleted lithium leach solution;

ii) the magnesium depleted lithium leach solution obtained in step i) is subjected to a downstream concentration and recovery process

Wherein the electrochemical magnesium removal step is carried out in a three-chamber electrodialysis configuration, producing magnesium hydroxide precipitate and a separated hydrochloric acid stream, which are recoverable by-products.

According to another aspect of the present invention, there is provided an improved method of treating a lithium leach solution, comprising:

i) subjecting the magnesium-containing lithium leach solution to an electrochemical magnesium removal step to form a magnesium-depleted lithium leach solution;

ii) subjecting the magnesium depleted lithium leach solution obtained in step i) to a polishing step to produce a treated leach liquor (PLS); and

iii) subjecting the treated leach liquor to conventional concentration and recovery steps to recover lithium in the form of lithium carbonate;

wherein the step of removing magnesium further comprises:

introducing the lithium leach solution obtained in step i) into a cathode compartment of an electrochemical cell comprising a cathode;

introducing a sulfuric acid electrolyte solution into an anode chamber containing an anode;

the anode chamber and the cathode chamber are separated by a central chamber to form a three-chamber electrolytic cell, an anion exchange membrane is arranged to form a boundary between the cathode chamber and the central chamber, and a cation exchange membrane is arranged to form a boundary between the anode chamber and the central chamber;

introducing a dilute hydrochloric acid solution into the central chamber;

applying an electric current between the anode and the cathode to promote migration of hydrogen ions produced by the anode to the central chamber through the cation exchange membrane and chloride ions produced by the cathode chamber to the central chamber through the anion exchange membrane to form hydrochloric acid;

magnesium is precipitated in the cathode compartment as magnesium hydroxide, producing a magnesium depleted lithium solution.

According to yet another aspect of the present invention, there is provided an improved method of recovering lithium from a lithium leach solution, comprising:

i) subjecting the magnesium-containing lithium leach solution to an electrochemical magnesium removal step to form a magnesium-depleted lithium leach solution, a magnesium hydroxide precipitate and a separated hydrochloric acid stream;

ii) the magnesium hydroxide is separated from the magnesium depleted lithium leach solution via a solid/liquid separation step;

iii) subjecting the magnesium depleted lithium leach solution obtained in step i) to a polishing step to produce a treated leach liquor (PLS);

iv) subjecting the treated leach liquor to conventional concentration and recovery steps to recover lithium in the form of lithium carbonate;

wherein the step of removing magnesium further comprises:

introducing the lithium leach solution obtained in step i) into a three-chamber electrochemical cell comprising a cathode chamber, an anode chamber and a central chamber therebetween, having an anion exchange membrane forming a boundary between the cathode chamber and the center chamber, and having a cation exchange membrane forming a boundary between the anode chamber and the center chamber;

feeding the lithium leach solution obtained in step i) to a cathode compartment comprising a cathode;

introducing a sulfuric acid electrolyte solution into an anode chamber containing an anode;

introducing a hydrochloric acid solution into the central chamber;

applying an electric current between the anode and the cathode to promote migration of hydrogen ions produced by the anode to the central chamber through the cation exchange membrane and chloride ions produced by the cathode chamber to the central chamber through the anion exchange membrane to form hydrochloric acid;

magnesium is precipitated in the cathode compartment as magnesium hydroxide, producing a magnesium depleted lithium solution.

In a preferred embodiment of the invention, the method is adapted for processing a lithium metallurgical solution or a lithium leach solution as a separate electrolytic cell.

In a preferred embodiment of the invention, the method is suitable for processing lithium metallurgical solutions or lithium leach solutions, incorporated into a serial continuous flow processing operation.

Brief description of the drawings

Other features of the present invention will be more fully described in the following description of several non-limiting embodiments. The description is intended only to illustrate the invention. It is not intended to be interpreted as limiting the broad overview, disclosure or description of the invention described above. Will be described with reference to the accompanying drawings, in which:

fig. 1 depicts a process flow diagram for leaching lithium material using the present invention.

FIG. 2 depicts one embodiment of a magnesium separation step.

Figure 3 shows the results of an experiment applying the method of the present invention to the synthesis of a lithium leach solution.

Fig. 4 shows the experimental results of applying the method of the magnesium separation step to a test lithium solution consisting of seawater.

Detailed Description

The flow chart of the present invention is described with reference to fig. 1 and 2.

Fig. 1 shows a flow diagram 10 for treating a metallurgical solution containing lithium. A lithium-containing metallurgical solution 11, such as a hard rock ore or brine, is subjected to a preparation and leaching step 12 using known methods to produce a lithium leach solution 14 containing chlorine and impurities, such as magnesium. The lithium leach solution 14 is subjected to an electrochemical magnesium removal step 16, such as an electrodialysis step, to produce a hydrochloric acid stream 18, and a separation step 22, either by a separate solid/liquid separation step or by using series filters, to produce a stream 20, to remove magnesium hydroxide precipitate 24 and produce a magnesium depleted lithium leach solution 26. The magnesium-depleted lithium leach solution 26 is then subjected to a concentration step 28 using conventional methods (e.g. membrane distillation, reverse osmosis, electrodialysis or evaporation). Sodium carbonate 30 is then added using known processes and the resulting concentrated lithium solution 29 is subjected to a recovery step to produce lithium carbonate 32.

The electrochemical magnesium removal step 16 is a key step in the overall lithium recovery scheme, which is shown in further detail in fig. 2. Features described as being the same as in fig. 1 are labeled with the same numbers.

The magnesium removal step 16 is in the form of an electrochemical cell, such as an electrodialysis configuration, including a cathode compartment 30, an anode compartment 32 and a central compartment 34. Cathode 36 is located in cathode chamber 30 or forms one boundary of cathode chamber 30 and anion exchange membrane 38 forms the contiguous boundary between cathode chamber 30 and center chamber 34. The anode 40 is located at the anode chamber 32 or forms one boundary of the cathode chamber 32 and the cation exchange membrane 42 forms the contiguous boundary between the anode chamber 32 and the center chamber 34.

The lithium leach solution 14 is fed to the cathode compartment 30. Hydroxide ions are generated at the cathode 36 and react with magnesium present in the lithium leach solution 14 to form a hydroxide precipitate that settles out of solution. The hydrogen gas generated at cathode 36 prevents hydroxide precipitates from depositing at cathode 36.

The hydrochloric acid solution 44 is fed into the central chamber 34. Chloride ions present in the lithium leach solution 14 continue to migrate through the anion exchange membrane 38 into the central chamber 34. The sulfuric acid electrolyte solution 46 is fed into the anode chamber 32 where hydrogen ions are formed and continue to migrate through the cation exchange membrane 42 into the central chamber 34. These hydrogen ions form hydrochloric acid (HCl) with chloride ions that have migrated through the anion exchange membrane 38 into the central chamber 34. This produces a more concentrated hydrochloric acid stream 18 which can be reused or sold. Conventional processes do not produce a useful or valuable HCl stream.

In the case where magnesium is precipitated as a hydroxide in the cathode compartment 30 and has been separated, a magnesium depleted lithium solution 26 is formed, which may then be subjected to further processing operations as described above in fig. 1.

The process of the present invention has several advantages over conventional processes for removing impurities, such as magnesium, from a solution. The three-chamber configuration enables chloride to be removed from the feed solution (lithium leach solution), producing hydrochloric acid (HCl), and precipitating magnesium as magnesium hydroxide, both of which are potentially revenue streams not available from conventional processing techniques. Removal of magnesium sulfate may increase lithium recovery and minimize lithium loss in the waste stream (i.e., possibly higher lithium recovery).

The 3 chamber containing configuration prevents the formation of chlorine gas, which is another advantage compared to prior art electrochemical methods using a single membrane configuration. The application of the method to commerce can have great safety and environmental significance.

The flow diagram proposed by the present invention may result in higher lithium recovery rates and also greatly reduce processing costs, including minimizing or eliminating the need for soda ash addition, eliminating other solution purification costs and the concentration requirement for lithium carbonate recovery.

Examples of the invention

Example 1:

1 l of solution containing 2800 mg of magnesium; 617 mg of lithium; 4190 mg sodium; the chloride was equilibrated after 2 hours of electrolysis at 4.5 amps.

As described in the present invention, the cell has two membranes, receiving chloride from the cathode compartment through an anion exchange membrane and hydrogen ions from the anode compartment through a cation exchange membrane, recovering acid in the central compartment, magnesium is precipitated in the cathode compartment-flows out of the cell and settles in the batch circulation vessel; the sulfuric acid is used as supporting anolyte, and the electrolyzed water generates oxygen and hydrogen ions at the anode and hydrogen ions and hydroxyl ions at the cathode.

The results of this experiment are shown in figure 2. After 2 hours of electrolysis at 4.5 amps, the magnesium was reduced to 0.7 mg; lithium effectively remained the same, sodium remained the same, and 9 grams HCl hydrochloride was produced (73% current efficiency).

Example 2:

the experiment was the same as example 1, but this time using lithium-doped seawater (real impurities instead of synthesis solution) as the feed solution. The results are shown below and in fig. 3.

6.3g of HCl are produced (current efficiency 51.4%).

Example 3:

a 10 liter sample of seawater was fortified with approximately the following components by mass:

Na-96.0g/L

K-5.8g/L

Li-0.5g/L

Mg-1.7g/L

Ca-0.5g/L

SO4-11.6g/L

Cl-155.7g/L

B-0.5g/L

the solution was electrolyzed with 5 amps for 11 hours. As a result 91.5% of the magnesium was removed and the pH of the final solution was > 11; about 45% of the calcium was removed; the settling of magnesium was very satisfactory; 44.48 grams of hydrochloric acid was produced, reflecting an overall current efficiency of about 61%.

Modifications and variations as would be apparent to a skilled addressee are deemed to be within the scope of the present invention.