A system for removing iron and extracting lithium from salt lake brine

Abstract

The utility model provides a kind of salt lake brine iron removal lithium extraction system, the system includes the filter device, first dilution device, first pH adjusting device, iron removal resin device, second dilution device, nanofiltration device, first reverse osmosis concentration device connected in turn, and the reverse osmosis concentration device is connected lithium-containing reverse osmosis concentrated water storage tank and boron-containing reverse osmosis water production storage tank respectively, the lithium-containing reverse osmosis concentrated water storage tank is connected lithium extraction device, the discharge end of the lithium extraction device is connected high lithium solution storage tank, the boron-containing reverse osmosis water production storage tank is connected boron extraction device, the discharge end of the boron extraction device is connected high boron solution storage tank, and the feed end of the filter device is connected iron-containing old brine feed pipeline;The utility model system effectively avoids each impurity component, removes iron ion in old brine, and then is used for lithium extraction boron extraction.

Description

Technical Field

[0001] This utility model relates to the field of wastewater treatment technology, and in particular to a system for removing iron and extracting lithium from salt lake brine. Background Technology

[0002] In the development of lithium resources in salt lakes, lithium extraction technology from iron-containing acidified brine is a key bottleneck restricting the industry's development. This brine originates from the tiered extraction process of raw brine in salt lakes: after the raw brine is naturally sun-dried to precipitate minerals such as sodium chloride and carnallite (KCl·MgCl2·6H2O), the resulting mother liquor is further concentrated to form high-lithium-concentration brine (Li). + (≥0.4 mol / L). It still contains various different ions, such as iron, lithium, sodium, magnesium, boron, chloride, sulfate, etc. Among them, the iron ion concentration is ≥0.004 mol / L, the lithium ion concentration is ≥0.4 mol / L, and the chloride ion concentration is ≥6 mol / L.

[0003] To further enrich lithium resources, the old brine needs to be further acidified (pH adjusted to 2.5-3) to partially crystallize boric acid (H3BO3). Lithium is then extracted from the brine using a calcination method: the brine is spray-dried and then calcined at high temperature to convert magnesium, lithium, and chlorides into oxides. MgO is then separated by water leaching, and Li2CO3 is enriched. However, this method is energy-intensive, has a complex operation process, and releases toxic gases such as Cl2 during calcination, posing serious environmental problems. Therefore, the calcination method has been phased out by mainstream processes.

[0004] Membrane separation technology is considered an ideal solution for lithium extraction from high-lithium brine due to its low energy consumption, high selectivity, and strong continuous operation. However, the complex composition of acidified iron-containing brine poses a fatal threat to membrane systems: iron accumulates in the membrane channels, causing rapid and severe fouling and permanent damage to membrane performance, rendering the system unable to operate normally.

[0005] Conventional iron removal methods include oxidation, coagulation and sedimentation, and chemical precipitation. For example, CN116924589A discloses a system and method for the resource-based treatment of wastewater using an ion exchange composite membrane device, which employs coagulants to remove heavy metals such as iron, manganese, chromium, and lead from the water. However, acidified old brine, due to its high mineralization and complex composition, is not suitable for conventional methods. For instance, oxidation methods: Fe 2+ →Fe 3+ It is difficult to precipitate later due to the high concentration of Mg. 2+ / Ca 2+ Competition inhibits Fe(OH)3 nucleation; coagulation precipitation method: aluminum salt / iron salt coagulants have limited hydrolysis in acidic environments (pH<3) and introduce new impurities; chemical precipitation method: pH needs to be adjusted to >4, which leads to co-precipitation of Mg(OH)2 / Li2CO3 and causes lithium loss.

[0006] There is a fundamental conflict between the existing iron removal process and the membrane-based lithium extraction system. Therefore, it is urgent to develop a new iron removal and lithium extraction system for salt lake brine to solve the above problems. Utility Model Content

[0007] In view of the shortcomings of the prior art described above, the purpose of this utility model is to provide a salt lake brine iron removal and lithium extraction system to solve the problem of difficult iron ion separation in acidified brine in the prior art.

[0008] To achieve the above and other related objectives, this utility model provides a system for removing iron and extracting lithium from salt lake brine. The system includes a filtration device, a first dilution device, a first pH adjustment device, an iron removal resin device, a second dilution device, a nanofiltration device, and a first reverse osmosis concentration device connected in sequence. The reverse osmosis concentration device is connected to a lithium-containing reverse osmosis concentrate storage tank and a boron-containing reverse osmosis permeate storage tank, respectively. The lithium-containing reverse osmosis concentrate storage tank is connected to a lithium extraction device. The discharge end of the lithium extraction device is connected to a high-lithium solution storage tank. The boron-containing reverse osmosis permeate storage tank is connected to a boron extraction device. The discharge end of the boron extraction device is connected to a high-boron solution storage tank. The feed end of the filtration device is connected to an iron-containing old brine feed pipeline.

[0009] In this invention, the lithium extraction device includes a second pH adjustment unit, an ion exchange resin unit, and a first MVR evaporation unit connected in sequence. The second pH adjustment unit is connected to a lithium-containing reverse osmosis concentrate storage tank, and the MVR evaporation unit is connected to a high-lithium solution storage tank.

[0010] Preferably, the second pH adjustment unit is connected to the alkali input pipeline.

[0011] Preferably, the ion exchange resin unit is provided with softening and boron removal resin filler.

[0012] In this invention, the boron extraction device includes a third pH adjustment unit, a second reverse osmosis unit, and a second MVR evaporation unit connected in sequence. The third pH adjustment unit is connected to a boron-containing reverse osmosis permeate storage tank, and the second MVR evaporation unit is connected to a high-boron solution storage tank.

[0013] Preferably, the third pH adjustment unit is connected to the alkali input pipeline.

[0014] In this invention, the first pH adjustment device is connected to the acid input pipeline.

[0015] In this invention, the first dilution device is connected to a water tank.

[0016] In this invention, the second dilution device is connected to a water tank.

[0017] In this invention, the iron removal resin device is equipped with macroporous hydrochloric acid iron removal resin filler.

[0018] As described above, the iron removal and lithium extraction system for salt lake brine of this invention has the following beneficial effects:

[0019] This invention relates to a brine iron removal and lithium extraction system. The system sequentially filters iron-containing brine, then uses a first dilution device, a first pH adjustment device, and an iron removal resin device. The resulting iron-removed brine is then passed through a second dilution device, a nanofiltration device, and a first reverse osmosis concentration device to obtain lithium-containing reverse osmosis concentrate and boron-containing reverse osmosis permeate. The lithium-containing concentrate is further processed by a lithium extraction device to obtain a high-lithium solution, and the boron-containing permeate is further processed by a boron extraction device to obtain a high-boron solution. The first dilution device prevents boric acid precipitation and loss during subsequent pH adjustment. The first pH adjustment device converts iron ions in the brine to tetrachloroferrate ions, facilitating adsorption by the iron removal resin, thus reducing the concentration of the brine after iron removal for membrane treatment. This system effectively avoids various impurities. By removing iron ions from the brine before lithium and boron extraction, it avoids the problem of iron clogging the membrane system and simultaneously obtains high-lithium and high-boron solutions, improving resource utilization. Attached Figure Description

[0020] Figure 1 This is a schematic diagram (I) of the salt lake brine iron removal and lithium extraction system of this utility model.

[0021] Explanation of icon numbers

[0022] 1. Filtration device

[0023] 2 First dilution apparatus

[0024] 3 First pH Adjustment Device

[0025] 4. Iron removal resin device

[0026] 5 Second dilution device

[0027] 6 Nanofiltration Unit

[0028] 7 First Reverse Osmosis Concentration Unit

[0029] 8 Lithium-containing reverse osmosis concentrate storage tank

[0030] 9 Boron-containing reverse osmosis permeate storage tank

[0031] 10 Lithium Extraction Unit

[0032] 11 High-lithium solution storage tank

[0033] 12 Second pH Adjustment Unit

[0034] 13 Ion exchange resin units

[0035] 14 First MVR Evaporation Unit

[0036] 20 Boron extraction device

[0037] 21 High-boron solution storage tank

[0038] 22 Third pH Adjustment Unit

[0039] 23 Second Reverse Osmosis Unit

[0040] 24 Second MVR Evaporation Unit Detailed Implementation

[0041] The following specific examples illustrate the implementation of this utility model. Those skilled in the art can easily understand other advantages and effects of this utility model from the content disclosed in this specification. This utility model can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of this utility model.

[0042] In this utility model, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection, an electrical connection, or a communication connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this utility model according to the specific circumstances.

[0043] In this invention, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Therefore, a feature defined with "first" and "second" may explicitly or implicitly include one or more of that feature.

[0044] Please refer to the accompanying drawings. It should be noted that the illustrations provided in this embodiment are only schematic representations of the basic concept of this utility model. Therefore, the drawings only show the components related to this utility model and are not drawn according to the actual number, shape and size of the components. In actual implementation, the form, quantity and proportion of each component can be arbitrarily changed, and the layout of the components may also be more complex.

[0045] This utility model provides a system for removing iron and extracting lithium from salt lake brine. The system includes a filtration device 1, a first dilution device 2, a first pH adjustment device 3, an iron removal resin device 4, a second dilution device 5, a nanofiltration device 6, and a first reverse osmosis concentration device 7 connected in sequence. The reverse osmosis concentration device 7 is connected to a lithium-containing reverse osmosis concentrate storage tank 8 and a boron-containing reverse osmosis permeate storage tank 9. The lithium-containing reverse osmosis concentrate storage tank 8 is connected to a lithium extraction device 10. The discharge end of the lithium extraction device 10 is connected to a high-lithium solution storage tank 11. The boron-containing reverse osmosis permeate storage tank 9 is connected to a boron extraction device 20. The discharge end of the boron extraction device 20 is connected to a high-boron solution storage tank 21. The feed end of the filtration device 1 is connected to an iron-containing old brine feed pipeline.

[0046] The inventors found in their experiments that directly adsorbing ferric or ferrous ions with resin is difficult due to the high concentration and variety of impurity ions, which cause significant interference and cannot effectively reduce the ferric ion concentration. This invention's system for extracting lithium and boron from iron-containing brine first filters the brine through a filtration device 1 to remove suspended impurities such as mud and sand. Then, it is diluted with water through a first dilution device 2 by adding 10-20% fresh water. After further acidification through a first pH adjustment device 3, the ferric ions in the brine are converted to tetrachloroferrate, making them easier to adsorb by the iron-removing resin in the iron-removing resin device 4 (ferric ions are mainly present as water and ions [Fe(H₂O)₆] when the pH value is <1). 3+ It exists in the form of . In iron-containing high-chlorine solutions ≥6 mol / L, CL - It will gradually replace H2O to form tetrachloro and ferrate [FeCl4]. - Then, a resin with adsorption capacity for tetrachloro and ferrate (anions, metal cations with many impurities in the brine will not cause interference) is used to remove iron ions from the brine. At the same time, the dilution in the previous step also prevents the loss of boric acid precipitation after the pH adjustment by adding acid. Then, water is added to the second dilution device 5 to further dilute the brine and reduce the salt concentration in the old brine to facilitate membrane treatment. The brine is then filtered by nanofiltration device 6 to remove divalent ions such as magnesium and sulfate. Then, it is concentrated by reverse osmosis device 7 to obtain lithium-containing reverse osmosis concentrate and boron-containing reverse osmosis permeate. The two are then processed by lithium extraction device and boron extraction device to obtain high-lithium solution and high-boron solution, respectively.

[0047] In a preferred embodiment, such as Figure 1 As shown in the embodiment of this utility model, in the salt lake brine iron removal and lithium extraction system, the lithium extraction device 10 includes a second pH adjustment unit 12, an ion exchange resin unit 13, and a first MVR evaporation unit 14 connected in sequence. The second pH adjustment unit 12 is connected to a lithium-containing reverse osmosis concentrate storage tank 8, and the MVR evaporation unit 14 is connected to a high-lithium solution storage tank 11.

[0048] The second pH adjustment unit 12 is connected to the alkali inlet pipeline. The lithium-containing reverse osmosis concentrate is adjusted to a pH of 9-10 by adding alkali to facilitate boron removal by the ion exchange resin unit 13. The alkali solution can be a sodium hydroxide solution.

[0049] The ion exchange resin unit 13 is equipped with softening and boron removal resin fillers, such as LSC-800 type boron removal resin, D870B, and chelating resins such as Chelex 200 and ZGC-90.

[0050] In a preferred embodiment, such as Figure 1 As shown in the embodiment of this utility model, in the salt lake brine iron removal and lithium extraction system, the boron extraction device 20 includes a third pH adjustment unit 22, a second reverse osmosis unit 23, and a second MVR evaporation unit 24 connected in sequence. The third pH adjustment unit 22 is connected to a boron-containing reverse osmosis permeate storage tank 9, and the second MVR evaporation unit 24 is connected to a high boron solution storage tank 21.

[0051] The third pH adjustment unit 22 is connected to the alkali input pipeline. The alkali can be a sodium hydroxide solution. The boron-containing reverse osmosis permeate is adjusted to a pH of 9.5-10.5 by adding alkali, which converts boron in the brine (in its boric acid form) into tetraborate ions, facilitating subsequent reverse osmosis concentration.

[0052] In a preferred embodiment, in the brine iron removal and lithium extraction system of this utility model, the first pH adjustment device 3 is connected to the acid inlet pipeline. The acid can be hydrochloric acid or sulfuric acid, adjusting the hydrogen ion concentration in the brine to 0.1–0.3 mol / L.

[0053] In a preferred embodiment, in the salt lake brine iron removal and lithium extraction system shown in this embodiment of the present invention, the first dilution device 2 is connected to a water tank. This water tank can use pure water or unsaturated brine (containing lithium, sodium, magnesium, etc.) that does not contain iron ions, with the water volume being 10-20% of the brine volume. Ions introduced by the unsaturated brine can be removed later.

[0054] In a preferred embodiment of the brine iron removal and lithium extraction system of this utility model, the second dilution device 5 is connected to a water tank. This water tank uses pure water to dilute the brine, thereby reducing the salt concentration and osmotic pressure.

[0055] In a preferred embodiment, the iron removal and lithium extraction system for salt lake brine shown in this utility model includes a macroporous hydrochloric acid iron removal resin filler in the iron removal resin device 4. Examples include: hydrochloric acid iron removal resin-P375, hydrochloric acid iron removal special resin ZGA351, Jiangsu Suqing Group SQD-74 macroporous hydrochloric acid iron removal special resin, and Sanyi supplied SY-906 iron removal special resin, etc. Using this macroporous hydrochloric acid iron removal resin, iron in the old brine can be removed without creating other complex conditions.

[0056] In one specific embodiment:

[0057] This embodiment provides a system for removing iron and extracting lithium from salt lake brine, such as... Figure 1 As shown:

[0058] In the material conveying direction, the system includes a filtration device 1, a first dilution device 2, a first pH adjustment device 3, an iron removal resin device 4, a second dilution device 5, a nanofiltration device 6, and a first reverse osmosis concentration device 7 connected in sequence. The reverse osmosis concentration device 7 is connected to a lithium-containing reverse osmosis concentrate storage tank 8 and a boron-containing reverse osmosis permeate storage tank 9, respectively. The lithium-containing reverse osmosis concentrate storage tank 8 is connected to a lithium extraction device 10, and the outlet end of the lithium extraction device 10 is connected to a high-lithium solution storage tank 11. The boron-containing reverse osmosis permeate storage tank 9 is connected to a boron extraction device 20, and the outlet end of the boron extraction device 20 is connected to a high-boron solution storage tank 21. The first pH adjustment device 3 is connected to an acid input pipeline. The first dilution device 2 and the second dilution device 5 are both connected to water tanks. The iron removal resin device 4 is equipped with macroporous hydrochloric acid iron removal resin packing.

[0059] The feed end of the filter device 1 is connected to the feed pipeline containing iron-containing old brine;

[0060] The lithium extraction device 10 includes a second pH adjustment unit 12, an ion exchange resin unit 13, and a first MVR evaporation unit 14 connected in sequence. The second pH adjustment unit 12 is connected to a lithium-containing reverse osmosis concentrate storage tank 8, and the MVR evaporation unit 14 is connected to a high-lithium solution storage tank 11. The second pH adjustment unit 12 is connected to an alkaline solution input pipeline, and the ion exchange resin unit 13 is provided with softening and boron removal resin filler.

[0061] The boron extraction device 20 includes a third pH adjustment unit 22, a second reverse osmosis unit 23, and a second MVR evaporation unit 24 connected in sequence. The third pH adjustment unit 22 is connected to a boron-containing reverse osmosis permeate storage tank 9, the second MVR evaporation unit 24 is connected to a high-boron solution storage tank 21, and the third pH adjustment unit 22 is connected to an alkali input pipeline.

[0062] In another specific embodiment:

[0063] This embodiment employs the above-described salt lake brine iron removal and lithium extraction system for lithium and boron extraction and iron removal from iron-containing old brine, including the following steps:

[0064] 1) Filtration: Filter the iron-containing brine (iron ion concentration 0.004 mol / L, lithium ion concentration 0.4 mol / L, sodium ion concentration...)

[0065] (1.5 mol / L, magnesium ion concentration 4 mol / L, boron concentration 0.4 mol / L, sulfate ion concentration 0.5 mol / L, chloride ion concentration 6 mol / L) are filtered by filter device 1 to remove suspended impurities such as silt and sand.

[0066] 2) Dilution: The filtered brine is diluted with water (pure water, the amount of water added is 15% of the old brine volume) through the first dilution device 2;

[0067] 3) Adding acid: After dilution, hydrochloric acid is added to the brine through the first pH adjustment device 3 to adjust the hydrogen ion concentration in the brine to [value missing].

[0068] 0.2 mol / L, converting iron ions in the brine into tetrachloroferrate ions;

[0069] 4) Iron removal: After adding acid, the brine passes through the iron removal resin device 4, where the tetrachloroferrate ions are adsorbed and removed by the filler macroporous hydrochloric acid iron removal resin (SQD-74 macroporous hydrochloric acid iron removal special resin).

[0070] 5) Dilution: After iron removal, the brine is further diluted with water (pure water) in the second dilution device 5 to reduce the salt concentration to 160±10mg / L;

[0071] 6) Nanofiltration: The brine, after being diluted again, is passed through nanofiltration device 6 to obtain nanofiltration permeate with divalent ions such as calcium, magnesium and sulfate removed;

[0072] 7) Reverse osmosis: Nanofiltration permeate is passed through the first reverse osmosis concentration unit 7 to obtain lithium-containing reverse osmosis concentrate and boron-containing reverse osmosis permeate;

[0073] 8) Lithium Extraction: The lithium-containing reverse osmosis concentrate is adjusted to pH 9-10 by the second pH adjustment unit 12, and then passes through the ion exchange resin unit 13 (D870B and Chelex 200) and the first MVR evaporation unit 14 to obtain a high-lithium solution (lithium concentration).

[0074] 21 g / L, lithium yield ≥ 96%;

[0075] 9) Boron extraction: Boron-containing reverse osmosis permeate is adjusted to pH 9-10.5 by the third pH adjustment unit 22, and then passed through the second reverse osmosis unit 23 and the second MVR evaporation unit 24 to obtain a high boron solution (boron concentration ≥100g / L, boron yield ≥95%).

[0076] In summary, the salt lake brine iron removal and lithium extraction system of this invention can effectively avoid various impurities. After removing iron ions from the old brine, it can be used for lithium and boron extraction. This avoids the problems of high energy consumption and environmental pollution in traditional calcination methods, as well as the problem of membrane fouling in membrane separation methods. The lithium recovery rate is over 96%, and the boron recovery rate is over 95%.

[0077] The above embodiments are merely illustrative of the principles and effects of this utility model and are not intended to limit the scope of this utility model. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of this utility model. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in this utility model should still be covered by the claims of this utility model.

Claims

1. A system for removing iron and extracting lithium from salt lake brine, characterized in that, The system includes a filtration device (1), a first dilution device (2), a first pH adjustment device (3), an iron removal resin device (4), a second dilution device (5), a nanofiltration device (6), and a first reverse osmosis concentration device (7) connected in sequence. The reverse osmosis concentration device (7) is connected to a lithium-containing reverse osmosis concentrate storage tank (8) and a boron-containing reverse osmosis permeate storage tank (9), respectively. The lithium-containing reverse osmosis concentrate storage tank (8) is connected to a lithium extraction device (10). The discharge end of the lithium extraction device (10) is connected to a high-lithium solution storage tank (11). The boron-containing reverse osmosis permeate storage tank (9) is connected to a boron extraction device (20). The discharge end of the boron extraction device (20) is connected to a high-boron solution storage tank (21). The feed end of the filtration device (1) is connected to an iron-containing old brine feed pipeline.

2. The salt lake brine iron removal and lithium extraction system according to claim 1, characterized in that, The lithium extraction device (10) includes a second pH adjustment unit (12), an ion exchange resin unit (13), and a first MVR evaporation unit (14) connected in sequence. The second pH adjustment unit (12) is connected to a lithium-containing reverse osmosis concentrate storage tank (8), and the MVR evaporation unit (14) is connected to a high-lithium solution storage tank (11).

3. The salt lake brine iron removal and lithium extraction system according to claim 2, characterized in that, The second pH adjustment unit (12) is connected to the alkaline solution input pipeline.

4. The salt lake brine iron removal and lithium extraction system according to claim 2, characterized in that, The ion exchange resin unit (13) is provided with softening and boron removal resin filler.

5. The salt lake brine iron removal and lithium extraction system according to claim 1, characterized in that, The boron extraction device (20) includes a third pH adjustment unit (22), a second reverse osmosis unit (23), and a second MVR evaporation unit (24) connected in sequence. The third pH adjustment unit (22) is connected to a boron-containing reverse osmosis permeate storage tank (9), and the second MVR evaporation unit (24) is connected to a high-boron solution storage tank (21).

6. The salt lake brine iron removal and lithium extraction system according to claim 5, characterized in that, The third pH adjustment unit (22) is connected to the alkaline solution input pipeline.

7. The salt lake brine iron removal and lithium extraction system according to claim 1, characterized in that, The first pH adjustment device (3) is connected to the acid input pipeline.

8. The salt lake brine iron removal and lithium extraction system according to claim 1, characterized in that, The first dilution device (2) is connected to a water tank.

9. The salt lake brine iron removal and lithium extraction system according to claim 1, characterized in that, The second dilution device (5) is connected to a water tank.

10. The salt lake brine iron removal and lithium extraction system according to claim 1, characterized in that, The iron removal resin device (4) is equipped with macroporous hydrochloric acid iron removal resin packing.

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