阅读说明：本技术 改进的电化学电解池装置以及分离杂质的方法 (Improved electrochemical cell apparatus and method for separating impurities ) 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：一种从水溶液中分离杂质的电化学方法,包括以下步骤：使含有杂质离子的进料水溶液循环至含有阴极的电化学电解池的阴极室中；使酸性电解质溶液循环至包含阳极的阳极室中；阳极室与阴极室用中心室分开,形成含三个腔室的电解池,在阴极室和中心室之间有阴离子交换膜,形成一个边界,而在阳极室和中心室之间则有一个阳离子交换膜,形成另一个边界；在中心室内添加氯化物溶液或使其循环至中心室中；在阳极和阴极之间施加电流,促进阳极产生的氢离子通过阳离子交换膜迁移到中心室,促进阴极室产生的氯离子通过阴离子交换膜迁移到中心室,从而形成盐酸；其中,杂质离子以氢氧化物的形式沉淀在阴极室中,使产生的溶液中消耗掉了杂质。(An electrochemical process for separating impurities from an aqueous solution comprising the steps of: recycling the aqueous feed solution containing impurity ions to the cathode compartment of the electrochemical cell containing the cathode; circulating an acidic electrolyte solution into an anode chamber comprising an anode; the anode chamber and the cathode chamber are separated by a central chamber to form an electrolytic cell comprising three chambers, an anion exchange membrane is arranged between the cathode chamber and the central chamber to form a boundary, and a cation exchange membrane is arranged between the anode chamber and the central chamber to form another boundary; adding or recycling a chloride solution to 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; wherein impurity ions are precipitated in the cathode compartment as hydroxides, which result in a solution depleted of impurities.)

1. According to the present invention there is provided an electrochemical process for separating impurities including alkaline earth metals and aluminium from an aqueous solution, the process comprising the steps of:

recycling the aqueous feed solution containing impurity ions to the cathode compartment of the electrochemical cell containing the cathode;

circulating an acidic electrolyte solution into an anode chamber comprising an anode;

the anode chamber and the cathode chamber are separated by a central chamber to form an electrolytic cell having three chambers, 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;

circulating the chloride solution into the central chamber or adding it to 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;

wherein impurity ions are precipitated in the cathode compartment as hydroxides, producing a solution depleted of impurities.

2. The method of claim 1, wherein the feed aqueous solution comprises any one of brine, salt, or seawater.

3. A method according to any of the preceding claims, characterized in that the impurity ions comprise any one or more of magnesium or aluminium.

4. A method according to any of the preceding claims, characterized in that the acidic electrolyte solution in the anode compartment is any of sulphuric acid, hydrochloric acid or phosphoric acid.

5. A method according to any of the preceding claims, characterised in that the chloride solution in the central chamber is an acidic chloride solution.

6. According to the present invention there is provided an electrochemical process for the separation of magnesium and/or aluminium from an aqueous solution comprising the steps of:

recycling an aqueous feed solution comprising magnesium and/or aluminium ions to the cathode compartment of an electrochemical cell comprising a cathode;

circulating an acidic electrolyte solution into an anode chamber comprising an anode;

the anode chamber and the cathode chamber are separated by a central chamber to form an electrolytic cell having three chambers, 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;

circulating the chloride 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 in the central chamber;

wherein magnesium and/or aluminium ions are precipitated as hydroxides in the cathode compartment to produce a solution depleted in magnesium and/or aluminium.

7. The method of claim 6, characterized in that the feed aqueous solution comprises any of brine, salt or seawater.

8. A method according to claim 6 or 7, characterised in that the acidic electrolyte solution in the anode compartment is any one of sulphuric acid, hydrochloric acid or phosphoric acid.

9. A method according to any one of claims 6, 7 or 8, characterised in that the chloride solution in the central chamber is an acidic chloride solution.

10. According to the present invention there is provided an electrochemical process for the separation of magnesium and/or aluminium from a metallurgical solution comprising the steps of:

recycling a feed metallurgical solution comprising magnesium and/or aluminium ions to the cathode compartment of an electrochemical cell comprising a cathode;

circulating an acidic electrolyte solution into an anode chamber comprising an anode;

the anode chamber and the cathode chamber are separated by a central chamber to form an electrolytic cell containing three chambers, an anion exchange membrane forming a boundary of the cathode chamber, and a cation exchange membrane forming a boundary of the anode chamber; recycling the chloride solution to 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 in the central chamber;

in which magnesium and/or aluminium ions are precipitated as hydroxides in the cathode compartment and the resulting metallurgical solution is depleted of magnesium and/or aluminium.

11. The method according to claim 10, characterized in that the metallurgical solution contains lithium.

12. A method according to claim 10 or 11, characterized in that the acidic electrolyte solution in the anode compartment is any one of sulphuric acid, hydrochloric acid or phosphoric acid.

13. A method according to any one of claims 10, 11 or 12, characterized in that the chloride solution in the central chamber is an acidic chloride solution.

14. According to the present invention there is provided a three-chamber electrochemical cell for separating impurity ions including alkaline earth metals and aluminium from aqueous solutions, comprising:

a cathode compartment comprising a cathode and at least one boundary of the cathode compartment being formed by an anion exchange membrane;

an anode compartment comprising an anode and having at least one boundary formed by a cation exchange membrane;

forming a central chamber between said anion and cation exchange membranes;

a power source connected to the anode and the cathode to facilitate application of an electric current therebetween;

wherein an aqueous feed solution containing contaminant ions is fed to the cathode compartment where the contaminant ions are precipitated as hydroxides, chloride ions migrate through the anion exchange membrane to the central compartment, and an acidic electrolyte solution is fed to the anode compartment, hydroxide ions are generated in the anode compartment and migrate through the cation exchange membrane to the central compartment, thereby forming hydrochloric acid in the central compartment, and an aqueous solution depleted of contaminants is formed in the cathode compartment.

15. According to the present invention there is provided a three-chamber electrochemical cell for separating magnesium and/or aluminium ions from an aqueous solution, comprising:

a cathode compartment comprising a cathode and at least one boundary of the cathode compartment being formed by an anion exchange membrane;

an anode compartment comprising an anode and having at least one boundary formed by a cation exchange membrane;

forming a central chamber between said anion and cation exchange membranes;

a power source connected to the anode and the cathode to facilitate application of an electric current therebetween;

wherein an aqueous feed solution containing magnesium and/or aluminium ions is fed to the cathode compartment where impurity ions are precipitated as hydroxides, chloride ions migrate through the anion exchange membrane to the central compartment and an acidic electrolyte solution is fed to the anode compartment, hydroxide ions are generated in the anode compartment and migrate through the cation exchange membrane to the central compartment, thereby forming hydrochloric acid in the central compartment and an aqueous solution depleted in magnesium and/or aluminium is formed in the cathode compartment.

16. According to the present invention there is provided a three-chamber electrochemical cell for separating magnesium and/or aluminium ions from a metallurgical solution, comprising:

a cathode compartment comprising a cathode and at least one boundary of the cathode compartment being formed by an anion exchange membrane;

an anode compartment comprising an anode and having at least one boundary formed by a cation exchange membrane;

forming a central chamber between said anion and cation exchange membranes;

a power source connected to the anode and the cathode to facilitate application of an electric current therebetween;

wherein a feed metallurgical solution containing magnesium and/or aluminium ions is sent to the cathodic compartment where the magnesium and/or aluminium ions are precipitated in the form of hydroxide, chloride ions migrate through the anion exchange membrane to the central compartment and an acidic electrolyte solution is sent to the anodic compartment, hydroxide ions are generated in the anodic compartment and migrate through the cation exchange membrane to the central compartment, thereby forming hydrochloric acid in the central compartment and a metallurgical solution depleted in magnesium and/or aluminium is formed in the cathodic compartment.

17. The electrochemical cell device of any one of claims 14, 15, or 16, characterized in that the electrochemical cell is configured to function as a stand-alone cell.

18. The electrochemical cell device of any one of claims 14, 15, or 16, characterized in that the electrochemical cells are incorporated as part of a serial continuous flow operation.

19. A method for removing impurities according to any one of claims 1 to 13, characterized in that the method utilizes a separate electrolytic cell.

20. The method of removing impurities according to any one of claims 1 to 13, characterized in that the method is incorporated as part of a serial continuous flow operation.

Technical Field

The present invention relates to a process for separating magnesium from an aqueous solution. More particularly, the invention relates to processes for separating magnesium from brine, seawater and 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.

The presence of impurities (e.g., magnesium or aluminum) in aqueous solutions, particularly brine or seawater solutions, can inhibit the separation and recovery of precious salts, metals or other compounds from the solution.

Current processes for recovering magnesium metal from brine or seawater use alternatives to soda ash or caustic precipitation. For example, korean patent KR101663515(B1) discloses a method for obtaining precipitation of mg (oh)2 or MgCO3 by controlling pH.

The reason why the use of the membrane for separating magnesium is limited is that there is a problem of membrane contamination once magnesium is precipitated. PCT/NO99/00343 discloses a process for obtaining magnesium hydroxide precipitate from seawater using electrodialysis techniques (in the form of ion exchange membranes). However, as described in many other literature documents, the precipitation of magnesium (and calcium) from brine must be carried out in a separate step prior to ion exchange membrane processing.

In addition, these processes require the addition and/or regeneration of caustic formulations to promote magnesium precipitation. Mixing the caustic formulation with seawater is a disadvantage because it results in an inability to fine control the precipitation process, which can be achieved by incremental adjustments if the two are not mixed. This, in turn, can result in precipitation occurring only locally and uncontrolled (i.e., all salts, metals, or other compounds are precipitated completely non-selectively from solution).

There is no satisfactory economical process for the isolation or direct precipitation of magnesium hydroxide of sufficient purity.

The present invention seeks to overcome, or at least ameliorate, one or more of the above-identified deficiencies in the prior art, or to provide the consumer with a useful or commercial 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 or slurry.

Throughout the specification, reference to "leach solution" includes, but is not limited to, any metal-containing solution, metallurgical solution, bittern or brine concentrate.

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 the present invention, there is provided an electrochemical process for separating impurities from an aqueous solution comprising the steps of:

recycling the aqueous feed solution containing impurity ions to the cathode compartment of the electrochemical cell containing the cathode;

circulating an acidic electrolyte solution to an anode chamber comprising an anode;

the anode chamber and the cathode chamber are separated by a central chamber to form an electrolytic cell having three chambers, 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;

adding or recycling a chloride solution to 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;

wherein impurity ions are precipitated in the cathode compartment as hydroxides, which result in a solution depleted of impurities.

The aqueous feed solution preferably comprises any of brine, salt or seawater.

The impurity ions preferably include any one or more of magnesium or aluminum.

The acidic electrolyte solution in the anode chamber is preferably any one of sulfuric acid, hydrochloric acid, or phosphoric acid.

The chloride solution in the central chamber is preferably an acidic chloride solution.

According to the present invention there is provided an electrochemical process for the separation of magnesium and/or aluminium from an aqueous solution comprising the steps of:

recycling an aqueous feed solution comprising magnesium and/or aluminium ions to the cathode compartment of an electrochemical cell comprising a cathode;

circulating an acidic electrolyte solution into an anode chamber comprising an anode;

the anode chamber and the cathode chamber are separated by a central chamber to form an electrolytic cell having three chambers, 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;

recycling the chloride solution to 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 in the central chamber;

in which magnesium and/or aluminium ions are precipitated as hydroxides in the cathode compartment, resulting in a solution depleted in magnesium and/or aluminium.

The feed aqueous solution preferably comprises any of brine, salt or seawater.

The acidic electrolyte solution in the anode chamber is preferably any one of sulfuric acid, hydrochloric acid, or phosphoric acid.

The chloride solution in the central chamber is preferably an acidic chloride solution.

According to the present invention there is provided an electrochemical process for the separation of magnesium and/or aluminium from a metallurgical solution comprising the steps of:

recycling a feed metallurgical solution comprising magnesium and/or aluminium ions to the cathode compartment of an electrochemical cell comprising a cathode;

circulating an acidic electrolyte solution into an anode chamber comprising an anode;

the anode chamber and the cathode chamber are separated by a central chamber to form an electrolytic cell having three chambers, 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;

recycling the chloride solution to 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 in the central chamber;

in which magnesium and/or aluminium ions are precipitated as hydroxides in the cathode compartment and the resulting metallurgical solution is depleted of magnesium and/or aluminium.

The metallurgical solution preferably comprises lithium.

The acidic electrolyte solution in the anode chamber is preferably any one of sulfuric acid, hydrochloric acid, or phosphoric acid.

The chloride solution in the central chamber is preferably an acidic chloride solution.

According to the present invention there is provided a three-chamber electrochemical cell for separating impurity ions from an aqueous solution, comprising:

a cathode compartment comprising a cathode and at least one boundary of the cathode compartment being formed by an anion exchange membrane;

an anode compartment comprising an anode and at least one boundary of the anode compartment being formed by a cation exchange membrane;

forming a central cavity between said anion and cation exchange membranes;

a power source connected to the anode and the cathode to facilitate application of an electric current therebetween;

wherein an aqueous feed solution containing contaminant ions is fed to the cathode compartment where the contaminant ions are precipitated as hydroxides, chloride ions migrate through the anion exchange membrane to the central compartment, and an acidic electrolyte solution is fed to the anode compartment, hydroxide ions are generated in the anode compartment and migrate through the cation exchange membrane to the central compartment, thereby forming hydrochloric acid in the central compartment, and an aqueous solution depleted of contaminants is formed in the cathode compartment.

According to the present invention there is provided a three-chamber electrochemical cell for separating magnesium and/or aluminium ions from an aqueous solution, comprising:

a cathode compartment comprising a cathode and at least one boundary of the cathode compartment being formed by an anion exchange membrane;

an anode compartment comprising an anode and having at least one boundary formed by a cation exchange membrane;

forming a central chamber between said anion and cation exchange membranes;

a power source connected to the anode and the cathode to facilitate application of an electric current therebetween;

wherein an aqueous feed solution containing magnesium and/or aluminium ions is fed to the cathode compartment where the magnesium and/or aluminium ions precipitate as hydroxides, chloride ions migrate through the anion exchange membrane to the central compartment and an acidic electrolyte solution is fed to the anode compartment, hydroxide ions are generated in the anode compartment and migrate through the cation exchange membrane to the central compartment, thereby forming hydrochloric acid in the central compartment and an aqueous solution depleted in magnesium and/or aluminium is formed in the cathode compartment.

According to the present invention there is provided a three-chamber electrochemical cell for separating magnesium and/or aluminium ions from a metallurgical solution, comprising:

a cathode compartment comprising a cathode and at least one boundary of the cathode compartment being formed by an anion exchange membrane;

an anode compartment comprising an anode and having at least one boundary formed by a cation exchange membrane;

forming a central chamber between said anion and cation exchange membranes;

a power source connected to the anode and the cathode to facilitate application of an electric current therebetween;

wherein a feed metallurgical solution containing magnesium and/or aluminium ions is sent to the cathodic compartment where the magnesium and/or aluminium ions are precipitated in the form of hydroxide, chloride ions migrate through the anion exchange membrane to the central compartment and an acidic electrolyte solution is sent to the anodic compartment, hydroxide ions are generated in the anodic compartment and migrate through the cation exchange membrane to the central compartment, thereby forming hydrochloric acid in the central compartment and a metallurgical solution depleted in magnesium and/or aluminium is formed in the cathodic compartment.

In a preferred embodiment of the present invention, the electrochemical cell apparatus and method of removing impurities of the present invention are configured to be used as a stand-alone electrolytic cell.

In other preferred embodiments of the invention, the electrochemical cell apparatus and method of removing impurities are configured for use or incorporated as part of a series continuous flow 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 to be illustrative of 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 is a schematic representation of one embodiment of an electrochemical cell structure of the present invention.

Figure 2 shows the results of an experiment applying the electrochemical cell apparatus and method of the present invention to a synthetic lithium leach solution.

Fig. 3 shows the experimental results of applying the electrochemical cell apparatus and method of the present invention to a seawater test lithium solution.

Detailed Description

FIG. 1 depicts an illustration of the method of the present invention.

An electrochemical cell unit 10 in the form of an electrodialysis cell comprises a cathode compartment 12, an anode compartment 14 and a central compartment 16. The cathode 18 is located in the cathode chamber 12 or forms a boundary of the cathode chamber 12 and the anion exchange membrane 19 forms an abutting boundary between the cathode chamber 12 and the central chamber 16. Anode 20 is positioned in anode chamber 14 or forms a boundary of anode chamber 14, while cation exchange membrane 21 forms an adjoining boundary between anode chamber 14 and central chamber 16.

An aqueous feed solution 22 (e.g., brine, salt, seawater or a metallurgical solution) is fed into the cathode chamber 12. Hydroxide ions are generated at the cathode 18 and react with impurities (e.g., magnesium and/or aluminum) to form hydroxide precipitates in the aqueous feed solution 22 that settle out of solution. The hydrogen gas generated at the cathode 18 prevents the hydroxide precipitate from contaminating the cathode.

A chloride solution 24, such as hydrochloric acid, but preferably phosphoric acid, is fed to the central chamber 16. Phosphoric acid and other non-oxidizable, non-oxidizing, strongly dissociating acids are preferred over hydrochloric acid because hydrochloric acid can form chlorine gas at the anode. Chloride ions present in the aqueous feed solution 22 continue to migrate through the anion exchange membrane 19 into the central chamber 16. An acidic electrolyte solution 26 is fed into anode chamber 14 where hydrogen ions are formed and continue to migrate across cation exchange membrane 21 into central chamber 16. These hydrogen ions form hydrochloric acid with chloride ions that have migrated through the anion exchange membrane 19 into the central chamber 16.

As the impurities precipitate in the cathode compartment as hydroxides, a solution is formed which is depleted of the impurities and can be separated from the precipitated impurities for further processing.

The present method has several advantages over conventional methods of removing impurities such as magnesium or aluminum from a solution. One skilled in the art will recognize that other impurities may be removed without departing from the scope of the invention. The configuration of the 3 chambers enables chloride to be removed from the feed solution, thereby producing hydrochloric acid, while magnesium precipitates as magnesium hydroxide, both of which are potentially revenue streams not found in conventional treatment processes. Furthermore, in case the feed stream is a metallurgical stream, impurities are removed, thereby achieving a better metal 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.

Examples of the invention

Example 1:

6 liters of solution containing 1300mg/l magnesium; 10800mg/l sodium; the chloride was equilibrated after 4 hours of electrolysis at 3.0 amps.

The cell of the invention has two membranes, chloride ions being received from the cathode chamber to the central chamber via an anion exchange membrane and hydrogen ions being received from the anode chamber to the central chamber via a cation exchange membrane, thereby becoming an acid in the central chamber. Magnesium precipitates in the cathode compartment-flows out of the cell and settles in a batch recovery vessel; sulfuric acid is a supporting anolyte-water is electrolyzed, thus generating oxygen and hydrogen ions at the anode and hydrogen and hydroxyl ions at the cathode.

The result of this test was that after 4 hours of electrolysis at 3.0 amps, the magnesium content had dropped to 850mg/l, the sodium remained unchanged, and 5.66 g of HCl (36% current efficiency) was produced.

Example 2:

the experiment was similar to example 1, but this time a different ion exchange membrane supplier was used and the feed solution was only 3 litres. The solution was electrolyzed at 3.0 amps for 2 hours. The results are described below. Initial solution: mg-1280 Mg/l; ca-420 mg/l; sodium-10800 mg/l final solution: mg-690 Mg/l; ca-420 mg/l; sodium-10800 mg/l produced 5.43g HCl (current efficiency 72.7%).

Whatever the number of ion exchange membranes, is suitable for use in the present invention and there is no preference for the membrane manufacturer.

The electrochemical cell apparatus and method of removing impurities of the present invention can be used as a stand-alone cell or incorporated as part of a series continuous flow operation, depending on the requirements of the user.

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