Method and system for purifying aluminum electrolysis waste lithium extraction solution

Abstract

A method and system for purifying an aluminum electrolysis waste lithium extraction solution. The method comprises: adding to a lithium extraction solution an alkaline mixture until the pH of the lithium extraction solution reaches a first target pH, performing a first reaction in the lithium extraction solution, then filtering the lithium extraction solution to obtain a first filtrate, wherein the first target pH is between 11 and 11.5; and adding into the first filtrate a calcium removal agent and a catalyst until the pH of the first filtrate reaches a second target pH, performing a second reaction in the first filtrate, and filtering the first filtrate to obtain a purified solution, wherein the second target pH is between 11.5 and 12.

Description

Purification method and system for lithium extraction solution from aluminum electrolysis waste

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to Chinese patent application No. 202310546111.1, filed on May 12, 2023, the entire contents of which are incorporated herein by reference. Technical Field

[0003] The present disclosure relates to the field of aluminum electrolysis waste recycling, and in particular to a method and system for purifying lithium-extracted eluate from aluminum electrolysis waste. Background Art

[0004] Aluminum electrolysis scrap is waste generated during the electrolytic aluminum production process. Since most of the current alumina raw materials contain lithium, during the operation of the electrolytic cell, lithium is continuously enriched in the electrolyte and penetrates into the cathode and lining of the electrolytic cell, resulting in a continuous increase in the lithium content in the electrolyte and the electrolytic cell lining. When the electrolytic cell is damaged, the cathode and lining need to be completely replaced, and the large amount of waste generated is called overhaul slag. The overhaul slag contains a high level of lithium, and the remaining electrolyte also contains a high level of lithium. At the same time, due to the current high price of lithium carbonate, there is an increasing amount of research on extracting lithium from aluminum electrolysis scrap and preparing lithium carbonate products.

[0005] Existing technologies for extracting lithium from aluminum electrolysis waste and producing lithium carbonate products primarily focus on the lithium salt dissolution process, while the crucial purification process of the lithium extraction solution is insufficiently detailed and often oversimplified. Furthermore, the impurity types removed are limited and incomplete, while the lithium loss rate is excessive, resulting in a low lithium carbonate product recovery rate, making practical application difficult. Therefore, how to comprehensively remove impurities from the lithium extraction solution while minimizing lithium loss is a pressing technical challenge.

[0006] Summary of the Invention

[0007] The present disclosure provides a purification method and system for lithium extraction solution from aluminum electrolysis waste, so as to solve the technical problem in the prior art that it is difficult to comprehensively remove impurities in the lithium extraction solution under the premise of low lithium loss rate.

[0008] In a first aspect, the present disclosure provides a method for purifying a lithium-extracted leachate from aluminum electrolysis waste, the method comprising: adding an alkaline mixture to the lithium-extracted leachate to a first target pH, and after performing a first reaction in the lithium-extracted leachate, filtering the lithium-extracted leachate to obtain a first filtrate, wherein the alkaline mixture comprises a regulator and a stabilizer; the regulator is added to the lithium-extracted leachate after the stabilizer; the stabilizer comprises calcium sulfate, and the regulator comprises calcium oxide and / or calcium hydroxide; the first target pH is 11 to 11.5; and adding a decalcifying agent and a catalyst to the first filtrate to a second target pH, and after performing a second reaction in the first filtrate, filtering the first filtrate to obtain a purified leachate, the second target pH being 11.5 to 12.

[0009] In a second aspect, the present disclosure also provides a method for purifying a lithium-extracted eluate from aluminum electrolysis waste, the method comprising: adding an alkaline mixture to the lithium-extracted eluate until the pH of the lithium-extracted eluate reaches a first target pH, and after performing a first reaction in the lithium-extracted eluate, filtering the lithium-extracted eluate to obtain a first filtrate and a first filter residue, respectively, wherein the alkaline mixture comprises a regulator and a stabilizer; the regulator is added to the lithium-extracted eluate after the stabilizer; the stabilizer comprises calcium sulfate, and the regulator comprises calcium oxide and / or calcium hydroxide; the first target pH is 11 to 11.5; and adding a decalcifying agent and a catalyst to the first filtrate until the pH of the first filtrate reaches a second target pH, and after performing a second reaction in the first filtrate, filtering the first filtrate to obtain a purified eluate and a second filter residue, respectively; and adding a washing liquid to the first filter residue and the second filter residue to wash the first filter residue and the second filter residue, then filtering to obtain a washing filtrate, and returning the washing filtrate to the lithium-extracted eluate for treatment.

[0010] In the third aspect, the present disclosure provides a purification system for lithium-extracted leaching liquid of aluminum electrolysis waste, the system being adapted to the above-mentioned method, the system comprising at least two purification devices, the purification device comprising: a filtration unit, the filtration unit comprising a liquid receiving pan, a stirring motor, a scraper and a filter; the bottom surface of the liquid receiving pan is provided with the filter, the output end of the stirring motor is connected to the scraper, and the scraper is provided above the filter; and a liquid receiving unit, the liquid receiving unit comprising a liquid receiving tank body, a vacuum interface, a feeding port, a discharging port and a stirring paddle, the liquid receiving tank body being provided directly below the filter, the feeding port and the discharging port being respectively distributed on both sides of the liquid receiving tank body, the vacuum interface and the discharging port being provided on the same side of the liquid receiving tank body; the stirring paddle is provided in the liquid receiving tank, and the stirring paddle is fixedly connected to the extended end of the stirring motor. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate some embodiments consistent with the present disclosure and, together with the description, serve to explain the principles of the present disclosure.

[0012] In order to more clearly illustrate the embodiments of the present disclosure or the technical solutions in the prior art, the following briefly introduces the drawings required for the embodiments or the description of the prior art. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without inventive work.

[0013] FIG1 is a schematic flow diagram of a method for purifying a lithium extraction solution from aluminum electrolysis waste according to some embodiments of the present disclosure;

[0014] FIG2 is a schematic diagram of a detailed process of a method for purifying a lithium extraction solution from aluminum electrolysis waste according to some embodiments of the present disclosure;

[0015] FIG3 is a schematic flow chart of a method for purifying a lithium extraction solution from aluminum electrolysis waste according to other embodiments of the present disclosure; and

[0016] FIG4 is a schematic structural diagram of a device for purifying lithium-extracting eluate from aluminum electrolysis waste according to some embodiments of the present disclosure.

[0017] In the accompanying drawings, 1-filter unit, 11-liquid receiving tray, 12-stirring motor, 13-scraper, 14-filter screen; 2-liquid receiving unit, 21-liquid receiving tank, 22-vacuum interface, 23-feeding port, 24-discharge port, 25-stirring paddle; 3-slag discharge unit, 31-forklift, 32-forklift lane, 33-filter residue trough, 34-forklift baffle. DETAILED DESCRIPTION

[0018] To make the objectives, technical solutions, and advantages of the embodiments of the present disclosure more clear, the technical solutions in the embodiments of the present disclosure will be clearly and completely described below in conjunction with the accompanying drawings. Obviously, the described embodiments are part of the embodiments of the present disclosure, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present disclosure without making any creative efforts shall fall within the scope of protection of the present disclosure.

[0019] Unless otherwise specified, various raw materials, reagents, instruments and equipment used in the present disclosure can be purchased from the market or prepared by existing methods.

[0020] Existing technologies for extracting lithium from aluminum electrolysis waste and preparing lithium carbonate products mainly focus on the dissolution process of lithium salts, including:

[0021] (1) After the electrolyte is heat-treated, a water-soluble inorganic salt is added to the electrolyte to leach the lithium salt. After the lithium salt leaching is completed, the electrolyte is filtered to obtain filtrate B, and then an alkali (sodium hydroxide or potassium hydroxide) or an aqueous solution thereof is added to filtrate B to remove aluminum ions in filtrate B. Filtrate B is then filtered to obtain filtrate C, and carbonate is added to filtrate C to obtain lithium carbonate precipitation.

[0022] (2) subjecting the electrolyte to an acidification reaction with nitric acid, filtering the electrolyte after the acidification reaction to obtain a filtrate, and subjecting the filtrate to multiple treatments to obtain sodium nitrate, calcium fluoride, and lithium salt products, and "adding a soluble calcium salt or calcium hydroxide to the tertiary filtrate to remove fluoride ions in the filtrate, and then filtering the tertiary filtrate to obtain a quaternary filtrate and a calcium fluoride precipitate, and then adding oxalic acid to the quaternary filtrate to precipitate excess calcium ions."

[0023] (3) The lithium-containing waste is crushed, and then an inorganic acid solution is added to the crushed lithium-containing waste to react lithium fluoride and the like in the lithium-containing waste with the inorganic acid solution, and the reaction product is filtered to obtain filtrate D. Sodium bicarbonate is added to filtrate D to remove iron in filtrate D, and then filtrate D is filtered to obtain filtrate E. Sodium hydroxide is added to filtrate E to remove aluminum in filtrate E, and then filtrate E is filtered to obtain filtrate F. Sodium oxalate is added to filtrate F to remove cobalt in filtrate F, and then filtrate F is filtered to obtain filtrate G, and then sodium carbonate is added to filtrate G to precipitate lithium carbonate.

[0024] Aluminum electrolysis waste mainly consists of electrolyte, carbon slag, and overhaul slag. The main components of the electrolyte are Na3AlF6, calcium fluoride, aluminum oxide, K2NaAlF6, LiNa2AlF6, and LiF. The composition of overhaul slag is more complex, mainly including carbon, aluminum silicate, sodium fluoride, calcium fluoride, lithium fluoride, cryolite, and iron. The main components of carbon slag are carbon and electrolyte.

[0025] Currently, there are three main industrial technologies for extracting lithium from aluminum electrolysis waste: direct acid leaching, acid leaching or salt leaching after roasting, and salt leaching. Regardless of the method used, the lithium extraction solution inevitably contains impurities besides lithium. These impurities primarily include fluorine, calcium, magnesium, iron, aluminum, boron, silicon, manganese, nickel, and copper. These must be removed to ensure the purity of the resulting lithium carbonate product.

[0026] As shown in FIG1 , in a first aspect, an embodiment of the present disclosure provides a method for purifying a lithium-extracting solution from aluminum electrolysis waste, the method comprising:

[0027] S11. adding an alkaline mixture to the lithium extraction solution until the pH of the lithium extraction solution reaches a first target pH, and after performing a first reaction in the lithium extraction solution, filtering the lithium extraction solution to obtain a first filtrate;

[0028] S12. Adding a decalcifying agent and a catalyst to the first filtrate until the pH of the first filtrate reaches a second target pH, and after performing a second reaction in the first filtrate, filtering the first filtrate to obtain a purified eluate.

[0029] In one or more embodiments, the first target pH is 11-11.5, and the second target pH is 11.5-12.

[0030] By adding an alkaline mixture (such as a stabilizer and a regulator), the first target pH is controlled to be 11 to 11.5. On the one hand, the lithium ions in the lithium extraction solution can be stabilized so that they exist in a stable and highly soluble form. On the other hand, adjusting the pH of the lithium extraction solution to 11 to 11.5 can effectively remove fluoride ions, iron ions, aluminum ions, boron ions, silicon ions, manganese ions, nickel ions, copper ions, and some magnesium ions in the lithium extraction solution, thereby ensuring that the concentration of fluoride ions in the lithium extraction solution is below 10 mg / L and the concentration of other impurity ions is close to or equal to 0.

[0031] By adding a decalcifying agent and a catalyst, the second target pH is controlled to be 11.5-12, which can effectively remove calcium ions and magnesium ions in the first filtrate.

[0032] In some embodiments, the alkaline mixture includes a regulator and a stabilizer, and the regulator is added to the lithium extraction solution after the stabilizer.

[0033] In some embodiments, the stabilizer comprises calcium sulfate, and the regulator comprises calcium oxide and / or calcium hydroxide.

[0034] In addition to lithium, the lithium extraction solution also contains impurities such as fluoride ions, iron ions, aluminum ions, boron ions, silicon ions, manganese ions, nickel ions, copper ions, and some magnesium ions. In the first reaction of the lithium extraction solution, on the one hand, adding calcium sulfate to the lithium extraction solution can stabilize the lithium ions in the lithium extraction solution, so that they exist in the form of lithium sulfate with a stable and high solubility, thereby avoiding lithium loss. On the other hand, by adding calcium oxide and / or calcium hydroxide to the lithium extraction solution and adjusting the pH of the lithium extraction solution to 11-11.5, fluoride ions, iron ions, aluminum ions, boron ions, silicon ions, manganese ions, nickel ions, copper ions, and some magnesium ions in the lithium extraction solution can be effectively removed to ensure that the concentration of fluoride ions in the lithium extraction solution is below 10 mg / L and the concentration of other impurity ions is close to or equal to 0.

[0035] In some embodiments, the mass volume ratio of the amount of the stabilizer added to the lithium extraction solution is 6 kg / m 3 ~10kg / m 3 ; and / or, the amount of the regulator added is such that the pH of the lithium extraction solution reaches the first target pH.

[0036] Controlling the amount of stabilizer and regulator added can, on the one hand, stabilize the lithium ions in the lithium extraction solution so that they exist in the form of stable and highly soluble lithium sulfate. On the other hand, it can effectively remove fluoride ions, iron ions, aluminum ions, boron ions, silicon ions, manganese ions, nickel ions, copper ions and some magnesium ions in the lithium extraction solution to ensure that the concentration of fluoride ions in the lithium extraction solution is below 10 mg / L and the concentration of other impurity ions is close to or equal to 0.

[0037] In some embodiments, the decalcifying agent includes sodium carbonate, and the actual amount of sodium carbonate added is 1.5 to 3.0 times the theoretical amount of sodium carbonate added, and the theoretical amount of sodium carbonate added is determined by the calcium ion concentration in the first filtrate; and / or

[0038] The catalyst includes sodium hydroxide, and the mass volume ratio of the added amount of sodium hydroxide to the first filtrate is 0.2 kg / m 3 ~0.5kg / m 3 .

[0039] By controlling the amounts of decalcifying agent and catalyst added, lithium ions in the first filtrate are prevented from binding with carbonate ions after the addition of sodium carbonate, thus preventing lithium loss. Even if a small amount of lithium ions bind to carbonate ions, they will separate from the carbonate ions after the addition of the sodium hydroxide catalyst, and the carbonate ions will bind with calcium, further removing the calcium ions. Lithium ions remain free in the first filtrate, preventing lithium loss.

[0040] The specific principles of calcium removal and catalysis are as follows: Based on solution dynamics, sodium tends to bind more readily to carbonate ions than lithium does to carbonate ions. After the addition of the decalcifier, calcium ions in the first filtrate preferentially bind to carbonate ions in the first filtrate to undergo a calcium removal reaction. If lithium ions combine with carbonate ions in the first filtrate after the addition of the decalcifier to form lithium carbonate, sodium hydroxide catalyst is added to raise the pH of the first filtrate to the second target pH. This separates the lithium ions from the carbonate ions, and the carbonate ions combine with calcium ions to further remove the calcium ions and form sodium carbonate.

[0041] In some embodiments, the first reaction time is 30 to 60 minutes after the pH of the lithium extraction solution reaches the first target pH; and / or

[0042] The second reaction time includes a calcium removal reaction and a catalytic reaction, wherein the calcium removal reaction is carried out for 20 to 30 minutes, and then the catalytic reaction is carried out for 20 to 30 minutes. The catalytic reaction is a catalytic calcium removal reaction.

[0043] By controlling the time of the first reaction, fluoride ions, magnesium ions, iron ions, aluminum ions, boron ions, silicon ions, manganese ions, nickel ions and copper ions in the lithium extraction solution can be effectively removed.

[0044] By controlling the time of the second reaction, calcium ions, magnesium ions, etc. in the first filtrate can be effectively removed.

[0045] In some embodiments, the method further comprises:

[0046] determining whether secondary purification of the purified eluate is required according to the calcium ion concentration in the purified eluate;

[0047] If the calcium ion concentration in the purified eluate is less than 10 mg / L, it is determined that the purified eluate does not need to be subjected to secondary purification;

[0048] If the calcium ion concentration in the purified eluate is greater than 50 mg / L, adding sodium carbonate to perform secondary purification on the purified eluate; and

[0049] If the calcium ion concentration in the purified eluate is 10 mg / L to 50 mg / L, the purified eluate is subjected to secondary purification using resin.

[0050] The determination of whether the calcium ion concentration in the purified solution is completely purified is based on the fact that, in addition to a small amount of calcium ions contained in the lithium extraction solution itself, the majority of calcium ions are introduced by the calcium oxide and / or calcium hydroxide added during the first reaction process. Therefore, by determining the calcium ion concentration, it is possible to indirectly determine whether other impurities in the lithium extraction solution have been completely removed, thereby ensuring the purification effect and ensuring that the fluoride ion concentration and calcium ion concentration in the purified lithium extraction solution are below 10 mg / L, and the concentrations of other impurity ions are close to or equal to 0.

[0051] In a second aspect, an embodiment of the present disclosure further provides a method for purifying a lithium-extracting solution from aluminum electrolysis waste, the method comprising:

[0052] S21. adding an alkaline mixture to the lithium extraction solution until the pH of the lithium extraction solution reaches a first target pH, and after performing a first reaction in the lithium extraction solution, filtering the lithium extraction solution to obtain a first filtrate and a first filter residue;

[0053] S22. adding a decalcifying agent and a catalyst to the first filtrate until the pH of the first filtrate reaches a second target pH, and after performing a second reaction in the first filtrate, filtering the first filtrate to obtain a purified eluate and a second filter residue, respectively; and

[0054] S23. Add washing liquid to the first filter residue and the second filter residue to wash the first filter residue and the second filter residue, filter to obtain a washing filtrate, and return the washing filtrate to the lithium extraction solution for treatment.

[0055] The filter residues obtained from the first reaction and the second reaction are washed with a washing liquid and then filtered to obtain a washing filtrate, and the washing filtrate is returned to the lithium extraction solution for treatment, thereby effectively recovering the lithium element in the first filter residue and the second filter residue, so that there is basically no loss of lithium during the purification process.

[0056] In some embodiments, the liquid-to-solid ratio of the washing liquid to the first filter residue and / or the second filter residue in the washing is 3:1 to 4:1; and / or the number of washing times is 1 to 2 times.

[0057] The washing effect can be ensured by controlling the liquid-to-solid ratio and the number of washes; the lithium ions in the first filter residue and the second filter residue are washed away to obtain pure first filter residue and second filter residue, and the washing filtrate is returned for treatment, thereby ensuring that there is basically no loss of lithium during the purification process.

[0058] In some embodiments, the method further comprises:

[0059] S24. Determine whether secondary purification of the purified eluate is required based on the calcium ion concentration in the purified eluate.

[0060] The difference between the method of the second aspect of the present disclosure and the method of the first aspect mentioned above is that the first filter residue and the second filter residue are obtained and the first filter residue and the second filter residue are treated. The treatment of the first filtrate and the second filtrate in this method is the same as the treatment of the method described in the first aspect, so it will not be repeated here. Since the purification method of the lithium extraction dissolution liquid of the aluminum electrolysis waste adopts part of the technical solutions of the above-mentioned embodiments, it has at least all the beneficial effects brought by the technical solutions of the above-mentioned embodiments, which will not be repeated here one by one.

[0061] As shown in FIG4 , in a third aspect, based on a general inventive concept, an embodiment of the present disclosure further provides a purification system for extracting lithium from aluminum electrolysis waste, the system being adapted to the above method and comprising at least two purification devices, the purification devices comprising:

[0062] The filter unit 1 includes a liquid receiving tray 11, a stirring motor 12, a scraper 13, and a filter screen 14; the filter screen 14 is provided on the bottom surface of the liquid receiving tray 11, the output end of the stirring motor 12 is connected to the scraper 13, and the scraper 13 is provided above the filter screen 14;

[0063] The liquid receiving unit 2 includes a liquid receiving tank body 21, a vacuum interface 22, a feeding port 23, a discharging port 24 and a stirring paddle 25. The liquid receiving tank body 21 is arranged directly below the filter screen 14, and the feeding port 23 and the discharging port 24 are respectively distributed on both sides of the liquid receiving tank body 21. The vacuum interface 22 and the discharging port 24 are arranged on the same side of the liquid receiving tank body 21; the stirring paddle 25 is provided in the liquid receiving tank, and the stirring paddle 25 is fixedly connected to the extended end of the stirring motor 12.

[0064] The purification device includes a filtration unit 1 including a liquid receiving tray 11, a stirring motor 12, a scraper 13 and a filter screen 14, and a liquid receiving unit 2 including a liquid receiving tank body 21, a vacuum interface 22, a feeding port 23, a discharge port 24 and a stirring paddle 25, so that two-step filtration can be achieved through the filtration unit 1, and the filtrate after each filtration is stored through the liquid receiving unit 2 to facilitate subsequent processing, thereby obtaining a pure lithium extraction dissolution solution.

[0065] The system is implemented based on the above method, and the steps of the method can refer to the above embodiments. Since the purification system for extracting lithium from aluminum electrolysis waste adopts part or all of the technical solutions of the above embodiments, it has at least all the beneficial effects brought by the technical solutions of the above embodiments, which will not be described one by one here.

[0066] In some embodiments, the purification system further comprises:

[0067] The slag discharge unit 3 includes a forklift 31, a forklift track 32, and a residue trough 33. The forklift track 32 is located above the liquid receiving tank 21 and below the filter screen 14, surrounding the open end of the liquid receiving tank. The forklift 31 slides within the forklift track 32 to remove the residue from the filter screen 14. The residue trough 33 is located on the side of the liquid receiving tank 21.

[0068] In the embodiment of the present disclosure, by introducing a slag discharge unit 3 including a shovel 31, a shovel lane 32, a filter residue trough 33 and a shovel baffle 34, the slag discharge unit 3 can be cooperated with the scraper 13, and the first filter residue and the second filter residue remaining in the filtration stage will be scraped to the edge of the filter mesh 14 by the scraper 13, and the shovel 31 with its own motor slides in the shovel lane 32, so that the shovel 31 acts as a scraping shovel, ensuring that the filter residue falls into the filter residue trough 33 and is discharged.

[0069] In some embodiments, in order to ensure the scraping effect of the shovel 31, a shovel baffle 34 is set in the opposite direction of the rotation of the shovel 31, so that the filter residue gathers on the surface of the shovel 31 as the shovel 31 moves. After rotating to the corresponding position of the filter residue trough 33, the filter residue can easily fall into the filter residue trough 33.

[0070] The technical solutions of the present disclosure are further described below in conjunction with some examples. It should be understood that these examples are intended only to illustrate the present disclosure and are not intended to limit the scope of the present disclosure. Experimental methods in the following examples where conditions are not specified are generally measured in accordance with national standards. If there are no corresponding national standards, the methods are carried out in accordance with commonly used international standards, conventional conditions, or conditions recommended by the manufacturer.

[0071] Example 1

[0072] First, add the stabilizer calcium sulfate to the lithium extraction solution. The amount of calcium sulfate added is 6 kg / m 3 , then add calcium oxide to the lithium extraction solution, adjust the pH of the lithium extraction solution to 11, and remove fluoride ions, iron ions, aluminum ions, boron ions, silicon ions, manganese ions, nickel ions, copper ions and some magnesium ions in the lithium extraction solution. The reaction of adding calcium sulfate and calcium oxide can be carried out in the lithium extraction solution purification device, and the steps are as follows:

[0073] The lithium-extracted solution is added to the liquid receiving tank 21 of the purification device. The vacuum interface 22 and the discharge port 24 are closed, and the stirring motor 12 is turned on to drive the stirring paddle 25 to rotate. After opening the feed port 23 to add calcium sulfate, calcium oxide is added to the lithium-extracted solution to adjust the pH of the lithium-extracted solution to 11. The first reaction is carried out in the lithium-extracted solution for 60 minutes. The reacted slurry is introduced into the liquid receiving pan 11 of another purification device; the discharge port 24 of the liquid receiving tank is closed, the vacuum equipment connected to the vacuum interface 22 is turned on, and the feed port 23 is closed to ensure that the liquid receiving tank is in a negative pressure state. The stirring motor 12 is turned on to drive the scraper 13 to rotate, continuously pushing the filtered residue from the filter screen 14 to the edge of the liquid receiving pan 11; the slag removal unit 3 is started, and the small forklift 31 and the forklift baffle 34 are driven along the forklift path 32 to scoop up the filter residue at the edge of the liquid receiving pan 11. After running one circle, the filter residue is poured into the filter residue tank 33 for discharge. After the filtration is completed, a first filtrate and a first filter residue are obtained. The concentration of ions in the first filtrate is measured. At this time, the concentration of fluoride ions is less than 10 mg / L, and the concentrations of iron ions, aluminum ions, boron ions, silicon ions, manganese ions, nickel ions, copper ions, etc. are all close to or equal to 0.

[0074] Close the vacuum equipment and vacuum interface 22, open the feeding port 23, add 1.5 times the theoretical value of sodium carbonate into the liquid receiving tank, turn on the stirring motor 12, drive the stirring paddle 25 to rotate, react for 30 minutes, add sodium hydroxide, and the amount of sodium hydroxide added is 0.2kg / m 3 The pH of the first filtrate is adjusted to 11.5, and the reaction is carried out for 30 minutes. The discharge port 24 is opened, and the liquid in the receiving tank is introduced into the next purification device. The operation is repeated to obtain a second filtrate and a second filter residue. The ion concentrations in the second filtrate are measured. The calcium ion concentration of the second filtrate is less than 10 mg / L, the fluoride ion concentration is less than 10 mg / L, and the concentrations of iron ions, aluminum ions, boron ions, silicon ions, manganese ions, nickel ions, and copper ions are all close to or equal to 0. There is essentially no loss of lithium ions, thereby obtaining a purified eluate.

[0075] If the calcium ion concentration in the second filtrate is higher than 50 mg / L, sodium carbonate is added to the second filtrate in an amount 1.5 times the theoretical value to remove the calcium ion concentration, so that the calcium ion concentration in the second filtrate is reduced to below 10 mg / L; if the calcium ion concentration in the second filtrate is between 10 mg / L and 50 mg / L, the second filtrate is passed into a resin purification device to further remove the calcium ions in the filtrate through ion exchange, so that the calcium ion concentration in the second filtrate is reduced to below 10 mg / L, thereby obtaining a purified eluate.

[0076] The first filter residue and the second filter residue are washed twice with washing liquid at a liquid-to-solid ratio of 3:1, and the washing filtrate is returned to the lithium extraction solution for cyclic lithium extraction.

[0077] Example 2

[0078] Comparing Example 2 with Example 1, the difference between Example 2 and Example 1 is:

[0079] First, add the stabilizer calcium sulfate to the lithium extraction solution. The amount of calcium sulfate added is 10 kg / m 3 , then add calcium hydroxide to adjust the pH of the lithium extraction solution to 11.5, react for 30 minutes and filter to obtain the first filtrate. Add 3.0 times the theoretical value of sodium carbonate to the first filtrate and react for 20 minutes, then add sodium hydroxide, the amount of sodium hydroxide added is 0.5kg / m 3 The pH of the first filtrate was adjusted to 12, and the reaction was continued for 20 minutes before filtration to obtain a purified eluate.

[0080] The first filter residue and the second filter residue were washed twice with washing liquid at a liquid-to-solid ratio of 4:1, and the washing filtrate was returned to the lithium extraction solution for cyclic lithium extraction.

[0081] Example 3

[0082] Comparing Example 3 with Example 1, the difference between Example 3 and Example 1 is:

[0083] First, add the stabilizer calcium sulfate to the lithium extraction solution, and the amount of calcium sulfate added is 8kg / m 3 , then add calcium hydroxide to adjust the pH of the lithium extraction solution to 11.3, react for 45 minutes and filter to obtain the first filtrate. Add 2.2 times the theoretical value of sodium carbonate to the first filtrate and react for 25 minutes, then add sodium hydroxide, the amount of sodium hydroxide added is 0.35kg / m 3 The pH of the first filtrate was adjusted to 11.8, and the mixture was reacted for 25 minutes before filtering to obtain a purified eluate.

[0084] The first filter residue and the second filter residue are washed once with a washing liquid at a liquid-to-solid ratio of 4:1, and then filtered to obtain a washing filtrate, which is returned to the lithium extraction eluate for cyclic lithium extraction.

[0085] Relevant data and results:

[0086] The purified eluate obtained in Example 1 was tested, and the results are shown in Table 1.

[0087] Table 1 Ion content of purified eluate

[0088] Note: Lithium extraction solution 1 and lithium extraction solution 2 are two groups of random parallel samples; purified solution 1 is the purified solution of lithium extraction solution 1 after being treated according to Example 1, and purified solution 2 is the purified solution of lithium extraction solution 2 after being treated according to Example 1.

[0089] One or more technical solutions according to the embodiments of the present disclosure have at least the following technical effects or advantages:

[0090] (1) The embodiments of the present disclosure provide a method for purifying a lithium-extracted eluate from aluminum electrolysis waste. Under the premise of ensuring that the lithium content in the lithium-extracted eluate is substantially unchanged, the impurity ions in the lithium-extracted eluate can be removed, so that the concentrations of fluoride ions and calcium ions after purification are lower than 10 mg / L, and the concentrations of ions such as iron ions, aluminum ions, boron ions, silicon ions, manganese ions, nickel ions, and copper ions are close to or equal to 0.

[0091] (2) The embodiments of the present disclosure also provide a purification system for lithium-extracted eluate from aluminum electrolysis waste, which can realize continuous filtration and purification reaction of the lithium-extracted eluate, simplify the equipment configuration by more than 50%, and improve the purification efficiency.

[0092] The present invention provides a method for purifying a lithium-extracting solution from aluminum electrolysis waste. Compared with the traditional solution purification process, the method first adds a stabilizer to ensure that the lithium in the lithium-extracting solution exists in the form of stable, highly soluble lithium sulfate (due to the high solubility of lithium sulfate in water, 100g of water at 20°C can dissolve 25.7g of lithium sulfate); then adds a regulator to adjust the pH of the lithium-extracting solution, thereby removing fluoride ions, iron ions, aluminum ions, boron ions, silicon ions, manganese ions, nickel ions, copper ions, and some magnesium ions in the lithium-extracting solution; then adds sodium carbonate and sodium hydroxide to remove calcium ions, magnesium ions, etc. in the lithium-extracting solution, thereby completing the removal of impurity ions in the lithium-extracting solution. Simultaneously controlling the pH and the addition of stabilizers and catalysts at different stages can ensure that there is essentially no loss of lithium in the lithium-extracting solution. The fluoride ion concentration and calcium ion concentration in the purified eluate are below 10 mg / L, and the concentrations of other impurity ions are close to or equal to 0, thereby achieving comprehensive removal of impurities in the lithium extraction eluate with essentially no lithium loss.

[0093] Various embodiments of the present disclosure may be presented in the form of a range. It should be understood that the description in the form of a range is merely for convenience and brevity and should not be construed as a hard limit to the scope of the present disclosure; therefore, the range description should be considered to have disclosed all possible sub-ranges and single numerical values ​​within the range. For example, a range description from 1 to 6 should be considered to have disclosed sub-ranges, such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., as well as single numbers within the range, such as 1, 2, 3, 4, 5 and 6, regardless of the range. In some embodiments, whenever a numerical range is indicated herein, it is meant to include any cited number (fractional or integer) within the indicated range.

[0094] In the present disclosure, unless otherwise specified, the directional words used, such as "upper" and "lower", refer to the directions of the drawings in the accompanying drawings. In some embodiments, in the description of the present disclosure, the terms "including", "comprising", etc. mean "including but not limited to". In this article, relational terms such as "first" and "second" are merely used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply that there is any such actual relationship or order between these entities or operations. In this article, "and / or" describes the association relationship of associated objects, indicating that three relationships may exist. For example, A and / or B can mean: A exists alone, A and B exist at the same time, and B exists alone. Wherein A and B can be singular or plural. In this article, "at least one" refers to one or more, and "plurality" refers to two or more. "At least one", "at least one of the following items" or similar expressions refer to any combination of these items, including any combination of single or plural items. For example, "at least one of a, b, or c", or "at least one of a, b, and c", can all mean: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, c can be single or multiple, respectively.

[0095] The foregoing description is intended to illustrate only some of the embodiments of the present disclosure, which are intended to enable those skilled in the art to understand and implement the present disclosure. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present disclosure. Therefore, the present disclosure is not intended to be limited to the embodiments shown herein, but rather to be construed in the broadest manner consistent with the principles and novel features claimed herein.

Claims

1. A method for purifying a lithium-extracting solution from aluminum electrolysis waste, comprising: An alkaline mixture is added to the lithium extraction solution until the pH of the lithium extraction solution reaches a first target pH, and after a first reaction is performed in the lithium extraction solution, the lithium extraction solution is filtered to obtain a first filtrate, wherein the alkaline mixture comprises a regulator and a stabilizer; the regulator is added to the lithium extraction solution after the stabilizer; the stabilizer comprises calcium sulfate, and the regulator comprises calcium oxide and / or calcium hydroxide; and the first target pH is 11 to 11.5; as well as A decalcifying agent and a catalyst are added to the first filtrate until the pH of the first filtrate reaches a second target pH, and after a second reaction is carried out in the first filtrate, the first filtrate is filtered to obtain a purified eluate, and the second target pH is 11.5-12.

2. The purification method according to claim 1, wherein: The mass volume ratio of the stabilizer added to the lithium extraction solution is 6 kg / m 3 ~10kg / m 3 ; and / or The amount of the regulator added is an amount that allows the pH of the lithium extraction solution to reach the first target pH.

3. The purification method according to claim 1, wherein: The decalcifying agent includes sodium carbonate, and the actual amount of the sodium carbonate added is 1.5 to 3.0 times the theoretical amount of the sodium carbonate added, and the theoretical amount of the sodium carbonate added is determined by the calcium ion concentration in the first filtrate; and / or The catalyst includes sodium hydroxide, and the mass volume ratio of the added amount of sodium hydroxide to the first filtrate is 0.2 kg / m 3 ~0.5kg / m 3 .

4. The purification method according to claim 1, wherein: The time of the first reaction is 30 to 60 minutes after the pH of the lithium extraction solution reaches the first target pH; and / or The second reaction includes a decalcification reaction and a catalytic reaction. The decalcification reaction is performed for 20 to 30 minutes, and then the catalytic reaction is performed for 20 to 30 minutes.

5. The purification method according to claim 1, further comprising: When the calcium ion concentration in the purified eluate is greater than 50 mg / L, adding sodium carbonate to perform secondary purification on the purified eluate; as well as When the calcium ion concentration in the purified eluate is 10 mg / L to 50 mg / L, the purified eluate is secondary purified by using a resin.

6. A method for purifying lithium-extracted leaching solution from aluminum electrolysis waste, comprising: An alkaline mixture is added to the lithium extraction solution until the pH of the lithium extraction solution reaches a first target pH, and after a first reaction is performed in the lithium extraction solution, the lithium extraction solution is filtered to obtain a first filtrate and a first filter residue, respectively, wherein the alkaline mixture comprises a regulator and a stabilizer; the regulator is added to the lithium extraction solution after the stabilizer; the stabilizer comprises calcium sulfate, and the regulator comprises calcium oxide and / or calcium hydroxide; and the first target pH is 11 to 11.5; as well as adding a decalcifying agent and a catalyst to the first filtrate until the pH of the first filtrate reaches a second target pH, and after performing a second reaction in the first filtrate, filtering the first filtrate to obtain a purified eluate and a second filter residue, respectively; A washing liquid is added to the first filter residue and the second filter residue to wash the first filter residue and the second filter residue, and then filtered to obtain a washing filtrate, and the washing filtrate is returned to the lithium extraction solution for treatment.

7. The purification method according to claim 6, wherein: The mass volume ratio of the stabilizer added to the lithium extraction solution is 6 kg / m 3 ~10kg / m 3 ; and / or The amount of the regulator added is an amount that allows the pH of the lithium extraction solution to reach the first target pH.

8. The purification method according to claim 6, wherein: The decalcifying agent includes sodium carbonate, and the actual amount of the sodium carbonate added is 1.5 to 3.0 times the theoretical amount of the sodium carbonate added, and the theoretical amount of the sodium carbonate added is determined by the calcium ion concentration in the first filtrate; and / or The catalyst includes sodium hydroxide, and the mass volume ratio of the added amount of sodium hydroxide to the first filtrate is 0.2 kg / m 3 ~0.5kg / m 3 .

9. The purification method according to claim 6, wherein: The time of the first reaction is 30 to 60 minutes after the pH of the lithium extraction solution reaches the first target pH; and / or The second reaction includes a decalcification reaction and a catalytic reaction. The decalcification reaction is performed for 20 to 30 minutes, and then the catalytic reaction is performed for 20 to 30 minutes.

10. The purification method according to claim 6, further comprising: When the calcium ion concentration in the purified eluate is greater than 50 mg / L, adding sodium carbonate to perform secondary purification on the purified eluate; as well as When the calcium ion concentration in the purified eluate is 10 mg / L to 50 mg / L, the purified eluate is secondary purified by using a resin.

11. The method for purifying lithium-extracting solution of aluminum electrolysis waste according to any one of claims 6 to 10, wherein: In the washing, the liquid-to-solid ratio of the washing liquid to the first filter residue and / or the second filter residue is 3:1 to 4:1; and / or The washing is performed once to twice.

12. A purification system for lithium extraction solution of aluminum electrolysis waste, the system being used in the method according to any one of claims 1 to 10, the system comprising at least two purification devices, the purification devices comprising: A filtering unit (1) comprises a liquid receiving tray (11), a stirring motor (12), a scraper (13) and a filter screen (14); the filter screen (14) is provided on the bottom surface of the liquid receiving tray (11), the output end of the stirring motor (12) is connected to the scraper (13), and the scraper (13) is provided above the filter screen (14); as well as A liquid receiving unit (2), comprising a liquid receiving tank body (21), a vacuum interface (22), a feeding port (23), a discharging port (24) and a stirring paddle (25), wherein the liquid receiving tank body (21) is arranged directly below the filter screen (14), the feeding port (23) and the discharging port (24) are respectively distributed on both sides of the liquid receiving tank body (21), and the vacuum interface (22) and The discharge port (24) is arranged on the same side of the liquid receiving tank body (21); the stirring paddle (25) is arranged in the liquid receiving tank, and the stirring paddle (25) is fixedly connected to the extended end of the stirring motor (12).

13. The purification system according to claim 12, further comprising: A slag discharge unit (3), the slag discharge unit (3) comprising a shovel truck (31), a shovel track (32), and a slag filter tank (33); The shovel path (32) is arranged on the upper part of the liquid receiving tank body (21) and below the filter screen (14), and is arranged around the open end of the liquid receiving tank; the shovel (31) slides in the shovel path (32) to remove the filter residue filtered by the filter screen (14); the filter residue tank (33) is arranged on the side of the liquid receiving tank body (21).

14. The purification system according to claim 13, further comprising: A forklift baffle (34), wherein the forklift baffle (34) is arranged on the forklift (31) and is located in the opposite direction of the rotation of the forklift.

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