Seed crystal for recycling lithium ions in wastewater, preparation method and nucleation granulation salt separation process

Abstract

The invention relates to the technical field of wastewater treatment, in particular to a seed crystal for recycling lithium ions in wastewater, a preparation method and a nucleation granulation salt separation process. The preparation method comprises the following steps: carrying out surface etching on spinel type lithium manganate and / or spinel type lithium cobalt oxide by adopting an etching agent or calcining the spinel type lithium manganate and / or spinel type lithium cobalt oxide in a nitrogen atmosphere to obtain a seed crystal for recycling lithium ions in wastewater; spinel-type lithium manganate and / or spinel-type lithium cobalt oxide are / is used as a base material of the obtained seed crystal, and the surface roughness and the electrification of the seed crystal are increased through surface treatment, so that when the seed crystal is applied to a nucleation granulation process as the seed crystal, the recovery of lithium ions in wastewater can be effectively enhanced, the removal rate of the lithium ions in the wastewater is increased, and the production cost is reduced. And the obtained granulated body is low in water content, high in metal grade, free of pollution to recycled water and high in economic value.

Description

Technical Field

[0001] The present disclosure relates to the technical field of wastewater treatment, and in particular to a seed crystal, a preparation method and a core crystal granulation and salt separation process for recovering lithium ions in wastewater. Background Art

[0002] Lithium-ion battery is a rechargeable battery that relies on the movement of lithium ions between the positive and negative electrodes to work. It is widely used in portable devices, satellites, reserve power supplies, electric vehicles and other fields, and has the potential to replace various secondary power sources. Lithium battery wastewater mainly comes from production wastewater, cleaning equipment water, cooling water, etc. generated during the production process; this type of wastewater has complex components, poor biodegradability, and certain toxicity. In addition, this type of wastewater contains a large amount of valuable metal ions, such as lithium, manganese, cobalt, nickel, etc. The recycling of the above valuable metals is of great significance for environmental protection and resource recovery. Existing water treatment processes, such as chemical precipitation, have the advantages of large water treatment capacity and low process threshold, but their treatment accuracy is limited. The water produced after the sedimentation tank often needs to be connected to the ion exchange resin process for terminal precision treatment to ensure that the effluent meets the discharge standards; in addition, this method cannot effectively recover lithium ions in wastewater, resulting in a huge waste of valuable resources. Therefore, there is an urgent need for a new process with high treatment efficiency, low operating costs, and the ability to effectively recover lithium resources.

[0003] In recent years, more and more research has been conducted on nuclear crystal granulation and salt separation technology for the recovery of heavy metal ions in wastewater, and certain results have been achieved. Nuclear crystal granulation and salt separation technology can not only avoid the generation of sludge, but also reduce the recovery cost of heavy metal ions. The core of this technology lies in the design and development of special crystal seeds. Conventional commercial crystal seeds such as garnet and quartz sand have limited ability to remove heavy metal ions, and their crystal structure is quite different from the ions to be precipitated. Therefore, when there are multiple valuable metal ions in the wastewater, it is not possible to achieve the effect of salt separation crystallization and resource recovery, which is not conducive to the recovery of lithium ions.

[0004] Therefore, how to provide a lithium ion-specific crystal seed to achieve enhanced recovery and resource utilization of lithium ions in wastewater has become a problem that needs to be solved urgently. Summary of the invention

[0005] In order to solve the above technical problems, the present disclosure provides a seed crystal, a preparation method and a nuclear crystal granulation and salt separation process for recovering lithium ions in wastewater. The present disclosure is directed to the existing nuclear crystal granulation and salt separation technology, and uses surface-treated spinel lithium manganese oxide and / or spinel lithium cobalt oxide as special seed crystals for recovering lithium resources in wastewater, thereby realizing enhanced recovery and resource utilization of lithium ions in wastewater, and improving the lithium ion removal rate and the purity of the granulation body without adding other processes, thereby ensuring that the wastewater is discharged in compliance with the standards.

[0006] In a first aspect, the present disclosure provides a method for preparing seed crystals for recovering lithium ions in wastewater, the preparation method comprising the following steps:

[0007] Surface treatment is performed on spinel lithium manganese oxide and / or spinel lithium cobalt oxide to obtain seed crystals for recovering lithium ions in wastewater;

[0008] The surface treatment includes surface etching with an etchant, or calcining in a nitrogen atmosphere.

[0009] The present invention uses spinel lithium manganese oxide and / or spinel lithium cobalt oxide having octahedral stable structural units as the matrix material, and performs surface treatment, i.e., surface etching or nitrogen calcination, to increase the surface roughness, thereby reducing the lithium-containing precipitation (Li + In addition, the surface of the seed crystal treated by etching or hydrogenation is rich in oxygen vacancies, which will promote the migration of local electron distribution on the surface, enrich more negative charges around the oxygen vacancies, strengthen the enrichment of induced lithium ions, form local supersaturation in the vacancy confinement, promote the nucleation and growth of lithium-containing precipitation on its surface, thereby enhancing the recovery and resource utilization of lithium ions.

[0010] The following are preferred technical solutions of the present disclosure, but are not intended to be limitations of the technical solutions provided by the present disclosure. Through the following technical solutions, the technical objectives and beneficial effects of the present disclosure can be better achieved and realized.

[0011] As a preferred technical solution of the present disclosure, the etchant includes a sodium borohydride solution.

[0012] Preferably, the concentration of the sodium borohydride solution is 1 to 6 mol / L, for example, 1 mol / L, 2 mol / L, 3 mol / L, 4 mol / L, 5 mol / L or 6 mol / L, but is not limited to the listed values, and other values ​​not listed within the range are also applicable.

[0013] In the present disclosure, the appropriate etchant concentration is conducive to enhancing the enrichment effect of the seed crystal on lithium ions. If the etchant solubility is too high, the surface roughness of the base material will be excessively increased, causing the byproducts generated during the etching process to accumulate on the surface, affecting the purity of the granules in later use.

[0014] Preferably, the surface etching time is 45 to 85 min, for example 45 min, 50 min, 55 min, 60 min, 65 min, 70 min, 75 min or 85 min, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0015] Preferably, the surface etching is followed by drying.

[0016] Preferably, the drying temperature is 45-65°C, such as 45°C, 50°C, 55°C, 60°C or 65°C, but is not limited to the listed values, and other values ​​not listed within the range are also applicable.

[0017] Preferably, the drying time is 6 to 12 hours, for example 6 hours, 7 hours, 8 hours, 9 hours, 10 hours or 12 hours, but is not limited to the listed values, and other values ​​not listed within the range are also applicable.

[0018] As a preferred technical solution of the present disclosure, the calcination temperature is 400-700°C, for example, 400°C, 450°C, 500°C, 550°C, 600°C, 650°C or 700°C, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0019] In the present disclosure, if the calcination temperature is too low, it will lead to uneven temperature distribution inside the material, resulting in reduced porosity and fewer active sites in the matrix material; if the calcination temperature is too high, it will lead to incomplete phase change and reduced stability of the matrix material, which will cause secondary pollution of the water body during the subsequent water treatment process.

[0020] Preferably, the calcination time is 3 to 5 hours, such as 3 hours, 3.5 hours, 4 hours, 4.5 hours or 5 hours, but is not limited to the listed values, and other values ​​not listed within the range are also applicable.

[0021] As a preferred technical solution of the present disclosure, the preparation method of the spinel lithium manganese oxide or the spinel lithium cobalt oxide comprises:

[0022] A lithium source, a manganese source or a cobalt source, a complexing agent and a solvent are mixed, and the pH is adjusted, and then aging, hydrothermal reaction and freeze-drying are carried out in sequence to obtain spinel lithium manganate or spinel lithium cobaltate.

[0023] Furthermore, the mixing includes: dissolving the lithium source, the manganese source or the cobalt source, and the complexing agent in a solvent separately to obtain corresponding raw material solutions, and then mixing all the raw material solutions.

[0024] As a preferred technical solution of the present disclosure, the lithium source includes lithium nitrate.

[0025] Preferably, the manganese source comprises manganese nitrate.

[0026] Preferably, the cobalt source comprises cobalt nitrate.

[0027] Preferably, the complexing agent comprises one or more of citric acid, polyphosphoric acids or hydroxycarboxylic acids.

[0028] Preferably, the polyphosphoric acids include dipolyphosphoric acid and / or tetrapolyphosphoric acid.

[0029] Preferably, the hydroxycarboxylic acid comprises one or more of sodium salicylate, sodium hydroxyacetate or sodium lactate, such as a combination of sodium salicylate and sodium hydroxyacetate, a combination of sodium hydroxyacetate and sodium lactate, and the like.

[0030] Preferably, the molar ratio of Li in the lithium source, Mn in the manganese source and the complexing agent is (0.4-1):(0.8-2.5):(1.2-3), for example, 0.4:1:1.8, 0.8:1:2, 1:1.5:3, 0.7:2:2.4 or 1:1:2, etc., but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0031] Preferably, the molar ratio of Li in the lithium source, Co in the cobalt source and the complexing agent is (0.4-1):(0.8-2.5):(1.2-3), for example, 0.4:1:1.8, 0.8:2.5:2, 1:1.5:3, 0.7:2:2.4 or 1:1:2, etc., but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0032] Preferably, the solvent comprises an ethanol aqueous solution.

[0033] Preferably, in the ethanol aqueous solution, the volume ratio of ethanol to water is (15-45):100, for example 15:100, 20:100, 25:100, 30:100, 35:100, 40:100 or 45:100, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0034] In the present disclosure, the appropriate concentration of ethanol aqueous solution is conducive to enhancing the recovery effect of seed crystals on lithium ions in wastewater. Whether its concentration is too high or too low, the effect of seed crystals will be weakened, thereby reducing the recovery rate of lithium ions.

[0035] Preferably, stirring is performed during the mixing process.

[0036] Preferably, the stirring temperature is 30-50°C, such as 30°C, 35°C, 40°C, 45°C or 50°C, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0037] Preferably, the stirring time is 30 to 90 min, for example 30 min, 40 min, 50 min, 60 min, 70 min, 80 min or 90 min, but is not limited to the listed values, and other values ​​not listed within the range are also applicable.

[0038] Preferably, the stirring speed is 400-600 rpm, for example, 400 rpm, 450 rpm, 500 rpm, 550 rpm or 600 rpm, but is not limited to the listed values, and other values ​​not listed within the range are also applicable.

[0039] Preferably, the pH adjusting agent used to adjust the pH includes one or more of sodium carbonate, calcium hydroxide or sodium hydroxide, preferably sodium hydroxide.

[0040] Preferably, the pH is adjusted to 6-8, such as 6, 7 or 8, but is not limited to the listed values, and other values ​​not listed within the range are also applicable.

[0041] In the present disclosure, the pH adjuster is preferably a sodium hydroxide solution, which does not generate CO2 during use.

[0042] As a preferred technical solution of the present disclosure, the aging time is 30 to 80 minutes, for example, 30 minutes, 40 minutes, 50 minutes, 60 minutes, 70 minutes or 80 minutes, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0043] Preferably, the temperature of the hydrothermal reaction is 200-300°C, for example, 200°C, 220°C, 240°C, 260°C, 280°C or 300°C, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0044] Preferably, the hydrothermal reaction time is 12 to 20 h, such as 12 h, 14 h, 16 h, 18 h or 20 h, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0045] Preferably, the freeze-drying temperature is -60 to -45°C, such as -60°C, -55°C, -50°C or -45°C, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0046] Preferably, the freeze-drying time is 3 to 8 hours, for example 3 hours, 4 hours, 5 hours, 6 hours, 7 hours or 8 hours, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0047] In a second aspect, the present disclosure provides a seed crystal for recovering lithium ions in wastewater, which is prepared by the preparation method described in the first aspect.

[0048] In a third aspect, the present disclosure provides a nuclear crystal granulation and salt separation process for recovering lithium ions from wastewater using the seed crystals as described in the second aspect, the nuclear crystal granulation and salt separation process comprising the following steps:

[0049] (1) filling the seed crystals for recovering lithium ions from wastewater into a nuclear crystal granulation reactor;

[0050] (2) introducing the lithium ion-containing wastewater and the precipitant into a nuclear crystal granulation reactor respectively, so that the seed crystals are fluidized and react;

[0051] The regenerated water obtained after the reaction flows out from the upper end of the nuclear crystal granulation reactor, and the granulated body obtained after the reaction is discharged from the lower end of the nuclear crystal granulation reactor.

[0052] The inlet flow rate of the lithium-containing wastewater and the precipitant disclosed in the present invention is determined according to hydraulic conditions and water chemical conditions.

[0053] The nuclear crystal granulation and salt separation process disclosed in the present disclosure is carried out by using a lithium-containing wastewater lithium removal device, and the lithium-containing wastewater lithium removal device exemplarily includes:

[0054] Nucleation granulation reactor, used to remove lithium ions from lithium-containing wastewater;

[0055] A wastewater feeding unit, used for passing lithium-containing wastewater into the nuclear crystal granulation reactor;

[0056] A precipitant feeding unit, used for introducing the precipitant into the nuclear crystal granulation reactor;

[0057] A water outlet unit for storing treated clean water;

[0058] The nuclear crystal granulation reactor is provided with a wastewater feed port and a granulation body discharge port at the bottom, a precipitant feed port at the lower end of the side wall, and a water outlet at the upper end of the side wall;

[0059] The wastewater feeding unit comprises a wastewater storage tank, a wastewater lifting pump, a wastewater flow meter and a wastewater valve connected in sequence, and the wastewater valve is connected to the wastewater feeding port;

[0060] The precipitant feeding unit comprises a precipitant storage tank, a precipitant lifting pump, a precipitant flowmeter and a precipitant valve connected in sequence, and the precipitant valve is connected to the precipitant feeding port;

[0061] The water outlet unit comprises a water outlet storage tank and a water outlet valve which are connected in sequence, and the water outlet valves are connected to the water outlet.

[0062] The above-mentioned lithium removal device is the basic device structure in the nuclear crystal granulation and salt separation process. Under the same application principle, any improvement to the basic device structure will not affect the application of the seed crystal described in the present disclosure.

[0063] As a preferred technical solution of the present invention, the filling height of the seed crystals for recovering lithium ions in wastewater in step (1) is 15 to 35% of the height of the nuclear crystal granulation reactor, for example, 15%, 20%, 25%, 30% or 35%, etc., but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0064] As a preferred technical solution of the present disclosure, the precipitant in step (2) includes a sodium carbonate solution.

[0065] Preferably, the ratio of the concentration of the precipitant to the concentration of lithium ions in the lithium-containing wastewater is (1.8-4):1, for example, 1.8:1, 2:1, 3.3:1 or 4:1, etc., but is not limited to the listed values, and other unlisted values ​​within the range are also applicable, wherein the unit of concentration is mg / L.

[0066] Preferably, the flow rate ratio of the precipitant to the flow rate of the lithium-containing wastewater is 1:(10-40), for example, 1:10, 1:12, 1:20, 1:30, 1:35 or 1:40, etc., but is not limited to the listed values, and other unlisted values ​​within the range are also applicable, wherein the unit of flow rate is L / h.

[0067] Preferably, the reaction time in step (2) is 3 to 10 minutes, for example, 3 minutes, 4 minutes, 5 minutes, 6 minutes, 7 minutes, 8 minutes, 9 minutes or 10 minutes, but is not limited to the listed values, and other values ​​not listed within the range are also applicable.

[0068] In the present disclosure, the inlet flow rate of lithium-containing wastewater, the ratio concentration of the precipitant and the inlet flow rate are calculated by those skilled in the art based on hydraulic and water chemical parameters.

[0069] Compared with the prior art, the technical solution provided by the embodiments of the present disclosure has the following advantages:

[0070] (1) The present invention uses surface-treated spinel lithium manganese oxide and / or spinel lithium cobalt oxide as special crystal seeds for recovering lithium ions in the nuclear crystal granulation and salt separation technology, which effectively enhances the recovery of lithium ions in wastewater, thereby improving the removal rate of lithium ions in wastewater. At the same time, the granules produced by using the crystal seeds described in the present invention have low water content, high metal grade, no pollution to recycled water, and high economic benefits.

[0071] (2) The preparation method of the seed crystal disclosed in the present invention is simple, and the required raw materials are inexpensive, which is conducive to industrial production and application. BRIEF DESCRIPTION OF THE DRAWINGS

[0072] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present disclosure and, together with the description, serve to explain the principles of the present disclosure.

[0073] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0074] Figure 1 A schematic diagram of the structure of a lithium-containing wastewater lithium removal device provided in a specific embodiment of the present disclosure;

[0075] Figure 2 This is an infrared spectrum of the seed crystal for recovering lithium ions from wastewater as described in Example 1 of the present disclosure;

[0076] Figure 3 This is an XRD diagram of the seed crystal for recovering lithium ions from wastewater as described in Example 1 of the present disclosure;

[0077] Figure 4 This is an infrared spectrum of the seed crystal for recovering lithium ions from wastewater as described in Example 5 of the present disclosure;

[0078] Figure 5 This is the XRD diagram of the seed crystals for recovering lithium ions from wastewater as described in Example 5 of the present disclosure.

[0079] Among them, 1. Nuclear crystal granulation reactor; 2. Wastewater storage tank; 3. Wastewater lifting pump; 4. Wastewater flow meter; 5. Wastewater valve; 6. Precipitant storage tank; 7. Precipitant lifting pump; 8. Precipitant flow meter; 9. Precipitant valve; 10. Outlet water storage tank; 11. Outlet water valve. DETAILED DESCRIPTION

[0080] In order to more clearly understand the above-mentioned objectives, features and advantages of the present disclosure, the scheme of the present disclosure will be further described below. It should be noted that the embodiments of the present disclosure and the features in the embodiments can be combined with each other without conflict.

[0081] In the following description, many specific details are set forth to facilitate a full understanding of the present disclosure, but the present disclosure may also be implemented in other ways different from those described herein; it is obvious that the embodiments in the specification are only part of the embodiments of the present disclosure, rather than all of the embodiments.

[0082] In the first aspect, the present disclosure provides a lithium-containing wastewater lithium removal device, the structural schematic diagram of which is as follows Figure 1 As shown, the lithium-containing wastewater lithium removal device comprises:

[0083] The nuclear crystal granulation reactor 1 is used to fill the crystal seeds and remove the lithium ions in the lithium-containing wastewater;

[0084] A wastewater feeding unit, used for passing lithium-containing wastewater into the nuclear crystal granulation reactor;

[0085] A precipitant feeding unit, used for introducing the precipitant into the nuclear crystal granulation reactor;

[0086] A water outlet unit for storing the treated recycled water;

[0087] The nuclear crystal granulation reactor 1 is provided with a wastewater feed port and a granulation body discharge port at the bottom, a precipitant feed port at the lower end of the side wall, and a water outlet at the upper end of the side wall;

[0088] The wastewater feeding unit comprises a wastewater storage tank 2, a wastewater lifting pump 3, a wastewater flow meter 4 and a wastewater valve 5 which are connected in sequence, and the wastewater valve 5 is connected to the wastewater feeding port;

[0089] The precipitant feeding unit comprises a precipitant storage tank 6, a precipitant lifting pump 7, a precipitant flowmeter 8 and a precipitant valve 9 which are connected in sequence, and the precipitant valve 9 is connected to the precipitant feeding port;

[0090] The water outlet unit includes a water outlet storage tank 10 and a water outlet valve 11 which are connected in sequence, and the water outlet valve 11 is connected to the water outlet.

[0091] In a second aspect, the present disclosure provides a method for preparing seed crystals for recovering lithium ions in wastewater, the preparation method comprising the following steps:

[0092] (1) dissolving a lithium source in a first solvent to obtain a first raw material solution; dissolving a manganese source or a cobalt source in a second solvent to obtain a second raw material solution; dissolving a complexing agent in a third solvent to obtain a third raw material solution; the first solvent, the second solvent and the third solvent independently include ethanol aqueous solution, and the volume ratio of ethanol to water is independently (15-45):100;

[0093] The first raw material liquid, the second raw material liquid and the third raw material liquid are mixed, and a pH adjuster is added, and the mixture is stirred at a speed of 400 to 600 rpm for 30 to 90 minutes at a temperature of 30 to 50° C., and the pH is controlled to be 6 to 8 to obtain a mixed solution;

[0094] In the obtained mixed solution, the molar ratio of Li in the lithium source, Mn in the manganese source and the complexing agent is (0.4-1):(0.8-2.5):(1.2-3);

[0095] Or in the obtained mixed solution, the molar ratio of Li in the lithium source, Co in the cobalt source and the complexing agent is (0.4-1):(0.8-2.5):(1.2-3);

[0096] (2) the mixed solution obtained in step (1) is allowed to stand for 30 to 80 minutes for aging, and then poured into a hydrothermal kettle for hydrothermal reaction at 200 to 300° C. for 12 to 20 hours; after the reaction, solid-liquid separation and washing are performed, and then freeze-drying is performed at -60 to -45° C. for 3 to 8 hours to obtain spinel lithium manganese oxide or spinel lithium cobalt oxide;

[0097] (3) placing the spinel lithium manganese oxide or spinel lithium cobalt oxide obtained in step (2) in a sodium borohydride solution with a concentration of 1 to 6 mol / L for surface etching for 45 to 85 min, and then drying at 45 to 65° C. for 6 to 12 h to obtain seed crystals for recovering lithium ions in wastewater;

[0098] Alternatively, the spinel lithium manganate or spinel lithium cobaltate obtained in step (2) is placed in a nitrogen atmosphere for calcination at a temperature of 400 to 700° C. for 3 to 5 hours to obtain seed crystals for recovering lithium ions in wastewater.

[0099] In a third aspect, the present disclosure provides a nuclear crystal granulation and salt separation process using the lithium-containing wastewater removal device as described in the first aspect and the seed crystal for recovering lithium ions in wastewater as described in the second aspect, the nuclear crystal granulation and salt separation process comprising:

[0100] S1: Filling the seed crystals for recovering lithium ions in wastewater into a 2 m high nuclear crystal granulation reactor 1, the filling height being 15-35% of the height of the nuclear crystal granulation reactor 1;

[0101] S2: introducing the lithium-containing wastewater and the precipitant into the nuclear crystal granulation reactor 1 respectively, so that the seed crystals are fluidized and react, and the reaction time is 3 to 10 minutes, wherein the concentration ratio of the precipitant to the lithium ion concentration in the lithium-containing wastewater is ensured to be (1.8 to 4):1, and the flow rate ratio of the precipitant to the flow rate of the lithium-containing wastewater is 1:(10 to 40);

[0102] The regenerated water obtained after the reaction flows out from the water outlet of the nuclear crystal granulation reactor 1 , and the granulated body obtained after the reaction is discharged from the granulated body discharge port of the nuclear crystal granulation reactor 1 .

[0103] Examples 1-5 respectively provide a method for preparing seed crystals for recovering lithium ions from wastewater and a nuclear crystal granulation and salt separation process. The preparation method refers to the preparation method described in the second aspect of the specific implementation manner, and the specific process parameters are shown in Table 1; the nuclear crystal granulation and salt separation process refers to the nuclear crystal granulation and salt separation process described in the third aspect of the specific implementation manner, and the specific process parameters are shown in Table 2.

[0104] Table 1

[0105]

[0106]

[0107] The seed crystals for recovering lithium ions from wastewater obtained in Example 1 were characterized, and their infrared spectra were as follows: Figure 2 Its XRD pattern is shown in Figure 3 As shown. Figure 2 It can be seen that at 516cm -1 and 618.8cm -1 There are two peaks at , corresponding to Li-O and Mn-O bonds respectively; Figure 3 It can be seen that the peaks at 35.06°, 40.64°, 58.92°, 70.44°, and 74.1° correspond to different crystal planes of LiMn2O4, indicating that the material was successfully synthesized.

[0108] The seed crystals for recovering lithium ions from wastewater obtained in Example 5 were characterized, and their infrared spectra were as follows: Figure 4 Its XRD pattern is shown in Figure 5 As shown. Figure 4 It can be seen that at 582cm -1 and 876cm -1 The two peaks at correspond to the Li-O bond and the Co-O bond, respectively, and the remaining peaks are impurity peaks due to the introduction of organic matter during the synthesis process; at the same time, Figure 5 It can be seen that the strong peaks at 19°, 38°, 46° and 49° correspond to different crystal planes of LiCo2O4. Figure 4 and Figure 5 , which can prove the successful synthesis of lithium cobalt oxide.

[0109] Table 2

[0110]

[0111]

[0112] Comparative Example 1

[0113] Comparative Example 1 uses the first commercial seed crystal (quartz sand) and the second commercial seed crystal (dolomite) available in the prior art to remove and recover lithium ions in lithium-containing wastewater. Except for the seed crystals used, other specific application conditions are the same as those in Example 1.

[0114] Comparative Example 2

[0115] Comparative Example 2 uses the first commercial seed crystal (quartz sand) and the second commercial seed crystal (dolomite) available in the prior art to remove and recover lithium ions in lithium-containing wastewater. Except for the seed crystals used, other specific application conditions are the same as those in Example 2.

[0116] Comparative Example 3

[0117] Comparative Example 3 uses the first commercial seed crystal (quartz sand) and the second commercial seed crystal (dolomite) available in the prior art to remove and recover lithium ions in lithium-containing wastewater. Except for the seed crystals used, other specific application conditions are the same as those in Example 3.

[0118] Comparative Example 4

[0119] Comparative Example 4 uses the first commercial seed crystal (quartz sand) and the second commercial seed crystal (dolomite) available in the prior art to remove and recover lithium ions in lithium-containing wastewater. Except for the seed crystals used, other specific application conditions are the same as those of Example 4.

[0120] Comparative Example 5

[0121] Comparative Example 5 uses the first commercial seed crystal (quartz sand) and the second commercial seed crystal (dolomite) available in the prior art to remove and recover lithium ions in lithium-containing wastewater. Except for the seed crystals used, other specific application conditions are the same as those in Example 5.

[0122] Comparative Example 6

[0123] This comparative example provides a method for preparing crystal seeds for recovering lithium ions in wastewater and a nuclear crystal granulation and salt separation process. The preparation method comprises: etching a first commercial crystal seed (quartz sand) and a second commercial crystal seed (dolomite) with a 1 mol / L sodium borohydride solution for 45 min, and then drying at 45°C for 6 h to obtain crystal seeds for recovering lithium ions in wastewater.

[0124] The nuclear crystal granulation and salt separation process comprises: using the crystal seeds obtained in this comparative example to treat the lithium-containing wastewater with reference to the nuclear crystal granulation and salt separation process in Example 1.

[0125] Comparative Example 7

[0126] This comparative example provides a method for preparing crystal seeds for recovering lithium ions in wastewater and a nuclear crystal granulation and salt separation process. The preparation method comprises: calcining a first commercial crystal seed (quartz sand) and a second commercial crystal seed (dolomite) in a nitrogen atmosphere at 550°C for 4 hours to obtain crystal seeds for recovering lithium ions in wastewater.

[0127] The nuclear crystal granulation and salt separation process comprises: using the crystal seeds obtained in this comparative example to treat the lithium-containing wastewater with reference to the nuclear crystal granulation and salt separation process described in Example 5.

[0128] The lithium ion content of the regenerated water obtained in the nuclear crystal granulation and salt separation process described in Examples 1-5 and Comparative Examples 1-7, the purity of the obtained granules and the moisture content of the obtained granules were measured, and the results are shown in Table 3.

[0129] Table 3

[0130]

[0131]

[0132] As can be seen from Table 3, Examples 1-5 using the seed crystals described in the present disclosure can efficiently recover lithium ions in high-concentration lithium-containing wastewater (lithium ion concentration is not less than 120 mg / L), and the lithium ion removal rate can reach more than 99.2%. The obtained granules have high metal grade and purity of more than 94%, and the water content is below 5%, which has certain economic value.

[0133] Comparative Examples 1-5 used existing commercial seed crystals, and their surfaces were not further processed, so the lithium ion removal rate and the purity of the resulting granules were both low; Comparative Examples 6-7 used existing commercial seed crystals, and were further processed using the method disclosed in the present invention, but due to the large difference between the crystal structure of the matrix material and the ions to be precipitated, a good processing and recovery effect could not be achieved.

[0134] It should be noted that, in this article, relational terms such as "first" and "second" are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the sentence "comprise a ..." do not exclude the existence of other identical elements in the process, method, article or device including the elements.

[0135] The above description is only a specific embodiment of the present disclosure, so that those skilled in the art can understand or implement the present disclosure. Various modifications to these embodiments will be 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 will not be limited to the embodiments described herein, but will conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing seed crystals for recovering lithium ions from wastewater, characterized in that: The preparation method comprises the following steps: Surface treatment is performed on spinel lithium manganese oxide and / or spinel lithium cobalt oxide to obtain seed crystals for recovering lithium ions in wastewater; The surface treatment includes surface etching with an etchant, or calcining in a nitrogen atmosphere.

2. The preparation method according to claim 1, characterized in that: The etchant includes a sodium borohydride solution; Preferably, the concentration of the sodium borohydride solution is 1 to 6 mol / L; Preferably, the surface etching time is 45 to 85 minutes; Preferably, drying is performed after the surface etching; Preferably, the drying temperature is 45-65°C; Preferably, the drying time is 6 to 12 hours.

3. The preparation method according to claim 1, characterized in that: The calcination temperature is 400-700°C; Preferably, the calcination time is 3 to 5 hours.

4. The preparation method according to any one of claims 1 to 3, characterized in that: The preparation method of the spinel lithium manganese oxide or the spinel lithium cobalt oxide comprises: A lithium source, a manganese source or a cobalt source, a complexing agent and a solvent are mixed, and the pH is adjusted, and then aging, hydrothermal reaction and freeze-drying are carried out in sequence to obtain spinel lithium manganate or spinel lithium cobaltate.

5. The preparation method according to claim 4, characterized in that: The lithium source includes lithium nitrate; Preferably, the manganese source comprises manganese nitrate; Preferably, the cobalt source comprises cobalt nitrate; Preferably, the complexing agent comprises one or more of citric acid, polyphosphoric acid or hydroxycarboxylic acid, preferably citric acid; Preferably, the polyphosphoric acid comprises dipolyphosphoric acid and / or tetrapolyphosphoric acid; Preferably, the hydroxycarboxylic acid comprises one or more of sodium salicylate, sodium glycolate or sodium lactate; Preferably, the molar ratio of Li in the lithium source, Mn in the manganese source and the complexing agent is (0.4-1):(0.8-2.5):(1.2-3); Preferably, the molar ratio of Li in the lithium source, Co in the cobalt source and the complexing agent is (0.4-1):(0.8-2.5):(1.2-3); Preferably, the solvent comprises an ethanol aqueous solution; Preferably, in the ethanol aqueous solution, the volume ratio of ethanol to water is (15-45):100; Preferably, stirring is performed during the mixing process; Preferably, the stirring temperature is 30 to 50°C; Preferably, the stirring time is 30 to 90 minutes; Preferably, the stirring speed is 400-600 rpm; Preferably, the pH adjusting agent used to adjust the pH includes one or more of sodium carbonate, calcium hydroxide or sodium hydroxide, preferably sodium hydroxide; Preferably, the pH is adjusted to 6-8.

6. The preparation method according to claim 4 or 5, characterized in that: The aging time is 30 to 80 minutes; Preferably, the temperature of the hydrothermal reaction is 200-300°C; Preferably, the hydrothermal reaction time is 12 to 20 hours; Preferably, the freeze-drying temperature is -60 to -45°C; Preferably, the freeze-drying time is 3 to 8 hours.

7. A seed crystal for recovering lithium ions from wastewater, characterized in that: The preparation is obtained by the preparation method according to any one of claims 1 to 6.

8. A nuclear crystal granulation and salt separation process for recovering lithium ions from wastewater using the seed crystal as claimed in claim 7, characterized in that: The nuclear crystal granulation and salt separation process comprises the following steps: (1) filling the seed crystals for recovering lithium ions from wastewater into a nuclear crystal granulation reactor; (2) introducing the lithium ion-containing wastewater and the precipitant into a nuclear crystal granulation reactor respectively, so that the seed crystals are fluidized and react; The regenerated water obtained after the reaction flows out from the upper end of the nuclear crystal granulation reactor, and the granulated body obtained after the reaction is discharged from the lower end of the nuclear crystal granulation reactor.

9. The nuclear crystal granulation and salt separation process according to claim 8, characterized in that: The filling height of the seed crystals for recovering lithium ions from waste water in step (1) is 15 to 35% of the height of the nuclear crystal granulation reactor.

10. The nuclear crystal granulation and salt separation process according to claim 8 or 9, characterized in that: The precipitant in step (2) comprises a sodium carbonate solution; Preferably, the ratio of the concentration of the precipitant to the concentration of lithium ions in the lithium-containing wastewater is (1.8-4):1, wherein the unit of concentration is mg / L; Preferably, the flow rate ratio of the precipitant to the lithium-containing wastewater is 1:(10-40), wherein the unit of flow rate is L / h; Preferably, the reaction time in step (2) is 3 to 10 minutes.

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