Phosphorus iron salt adsorbent and application thereof in pre-enrichment of low-concentration lithium-containing solution

Abstract

The invention provides a phosphorus and iron salt adsorbent for pre-enrichment of a low-concentration lithium-containing solution, the phosphorus and iron salt adsorbent is a mixture of iron phosphate and a calcium compound, and the mass ratio of the iron phosphate to the calcium compound in the mixture is 1: (0.1-1). The invention also provides application of the phosphorus iron salt adsorbent in pre-enrichment of a low-concentration lithium-containing solution. The adsorbent disclosed by the invention is low in cost, the preparation method is simple, the low-concentration lithium-containing solution can be primarily enriched without adding organic matters and using a technical means of evaporation and concentration, organic pollution is avoided, and energy consumption is reduced.

Description

Technical Field

[0001] This invention belongs to the field of lithium adsorbents, specifically relating to a phosphorus iron salt adsorbent and its application in the pre-enrichment of low-concentration lithium-containing solutions. Background Technology

[0002] Currently, evaporation is commonly used to concentrate solutions with low lithium concentrations. However, this method is not only extremely energy-intensive, but also concentrates impurities along with the lithium, resulting in low purity of the final lithium precipitation product. Extraction methods have been developed using extractants such as N523 and TBP to separate lithium from the solution, achieving good purification. However, these extractants are all organic, and flammable substances such as sulfonated kerosene are often used as diluents during production, posing stringent safety requirements. Furthermore, the partial dissolution of organic matter in the solution system creates organic wastewater, increasing the difficulty of wastewater treatment. Therefore, current research is more active in the area of ​​inorganic adsorbents, including aluminum-based, manganese-based, and titanium-based adsorbents. Aluminum-based adsorbents have achieved large-scale industrial application, while other adsorbents have not yet been widely adopted due to difficulties in preparation, high prices, and high solubility. However, aluminum-based adsorption has a fatal flaw: it only separates lithium, with very limited enrichment capacity. Further concentration still requires evaporation. How to economically and efficiently enrich low-concentration lithium-containing solutions remains a major challenge for the industry.

[0003] A search revealed the following adsorbents and methods for enriching solutions with low lithium concentrations: CN117999120A discloses a method for preparing particulate lithium adsorbent, comprising the following steps: mixing lithium adsorbent or its precursor powder, various polymers, pore-forming agents and organic solvents under normal pressure and temperature of 10-190℃, stirring for 1-120 min to obtain a homogeneous mixture; dripping the above homogeneous mixture into a solution, or extruding and crushing the above homogeneous mixture, and washing to obtain particulate lithium adsorbent.

[0004] CN117999120A discloses a method for preparing lithium aluminum salt adsorbent, its application, and an apparatus, belonging to the fields of new materials and salt lake chemical technology. The preparation method includes the following steps: washing lithium carbonate with pure water to remove water-soluble impurities, and preparing a lithium carbonate slurry by mixing the filter cake in a certain proportion; passing CO2 gas into the lithium carbonate slurry to carry out a hydrogenation reaction, and filtering the reaction slurry to obtain a hydrogenated liquid; passing the hydrogenated liquid through an ion exchange resin column for purification and impurity removal to obtain a refined hydrogenated liquid; carrying out a precipitation reaction with an aluminum salt solution, and filtering to obtain a powdered lithium aluminum salt adsorbent; mixing the powdered lithium aluminum salt adsorbent, binder, and solvent in a mixing device, and obtaining the final product through an extrusion granulation process. The method and apparatus for preparing battery-grade lithium carbonate based on this lithium aluminum salt adsorbent are also provided.

[0005] The above-mentioned adsorbents are all complex in composition and expensive. Therefore, it is of great significance to develop an adsorbent and method that is simple in technology, low in cost, and can enrich lithium without evaporation. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the present invention aims to provide a phosphorus iron salt adsorbent and its application in the pre-enrichment of low-concentration lithium-containing solutions. This adsorbent is low in cost, simple to prepare, does not require the addition of organic matter, and does not use evaporation and concentration techniques to achieve the preliminary enrichment of low-concentration lithium-containing solutions, thus avoiding organic pollution and saving energy.

[0007] The method of this invention is mainly aimed at lithium-containing solutions with lithium ion concentrations below 1 g / L. Solutions with low lithium concentrations generally come from two sources: one is lithium-containing salt lakes, typically containing 50-600 mg / L of lithium, with high levels of sodium, potassium, and other salts, and some salt lakes also containing high levels of magnesium ions; the other is intermediate liquid generated during the lithium extraction process. For example, some manufacturers use phosphate precipitation after sodium carbonate precipitation, resulting in an intermediate liquid with a lithium concentration of 100-300 mg / L. After separation using aluminum-based adsorbents, these solutions can yield relatively pure low-lithium solutions, but only impurities are removed; they do not achieve good enrichment.

[0008] To achieve the above-mentioned objectives, the technical solution of this invention is as follows: This invention provides a ferric phosphate adsorbent for pre-enrichment of low-concentration lithium-containing solutions. The ferric phosphate adsorbent is a mixture of ferric phosphate and calcium compounds, wherein the mass ratio of the mixture is: ferric phosphate: calcium compound = 1:(0.1-1); the calcium compound includes one or more of calcium chloride, calcium oxide, calcium hydroxide, and calcium nitrate; the ferric phosphate adsorbent is used for pre-enrichment of low-concentration lithium-containing solutions.

[0009] Preferably, the mass ratio of the mixture is: ferric phosphate: calcium compound = 1: (0.1-0.5).

[0010] Preferably, the primary nucleation particle size of the iron phosphate is less than 2000 nm. Controlling it within this range results in good adsorption effect of the adsorbent.

[0011] Preferably, the primary nucleation particle size of the iron phosphate is less than 1000 nm. More preferably, the primary nucleation particle size of the iron phosphate is less than 200 nm.

[0012] The present invention also provides the application of ferric phosphate adsorbent in the pre-enrichment of low-concentration lithium-containing solutions, wherein the ferric phosphate adsorbent is ferric phosphate, or the ferric phosphate adsorbent is the aforementioned ferric phosphate adsorbent.

[0013] Preferably, the application of the phosphorus iron salt adsorbent in the pre-enrichment of low-concentration lithium-containing solutions includes the following steps: (1) 1-200g of adsorbent is required for 1L of low-concentration lithium solution. The adsorbent described in claim 5 is added to the low-concentration lithium solution, the pH is adjusted to 8-13, the adsorbent is an alkaline substance, and the reaction is carried out at 0℃-100℃ for 10min-12h. Liquid-solid separation is then performed to complete the adsorption. The low-concentration lithium solution is a lithium solution with a lithium ion concentration of less than 1g / L. (2) The adsorbent after lithium adsorption is washed with water several times, then acid is added to leach out and the pH is adjusted to 1~5. The reaction is carried out at 0℃~100℃ for 10min~12h, and the liquid and solid are separated to complete the desorption. The lithium-containing pre-enriched liquid and filter cake can be obtained. The filter cake is washed to obtain the regenerated adsorbent.

[0014] Preferably, the lithium-containing low-concentration solution has a lithium ion concentration of less than 1 g / L, and more preferably a lithium ion concentration of 10-600 mg / L.

[0015] Preferably, the alkaline substance includes one or a combination of sodium hydroxide, potassium hydroxide, calcium oxide, calcium hydroxide, and ammonia.

[0016] Preferably, the acid includes one or a combination of sulfuric acid, hydrochloric acid, and nitric acid.

[0017] Preferably, the pH adjustment in step (1) is preferably adjusted to 10-12. The adsorbent of the present invention needs to be used under alkaline conditions. If it is used under acidic conditions, the adsorbent of the present invention cannot play its role in enriching lithium.

[0018] Preferably, step (2) yields a lithium-containing pre-enriched solution with a concentration greater than 1 g / L, and more preferably, a lithium-containing pre-enriched solution with a concentration of 1.5 to 6 g / L.

[0019] Preferably, the washing with water in step (2) involves washing 1-3 times with hot water at 40ºC-100ºC. There are no fixed requirements for the quality of the water; each time, 1-2 times the mass of the filter cake obtained after lithium adsorption and filtration can be used for washing.

[0020] Preferably, the filter cake is washed with an acidic solution of pH 2 to 6 until the lithium content in the filtrate is ≤0.5 mg / L to obtain a regenerated adsorbent; more preferably, it is washed with an acidic solution of pH 2 to 3.

[0021] More preferably, step (1) requires 20-100g of adsorbent per 1L of low-concentration lithium solution.

[0022] More preferably, step (1) involves reacting at 20℃~80℃ for 1~8h.

[0023] Further preferred, step (2) involves reacting at 20℃~80℃ for 1~8h.

[0024] The present invention will be further explained and described below. In an alkaline environment, the surface of ferric phosphate becomes hydroxylated and negatively charged, while lithium ions are positively charged, thus allowing them to be adsorbed onto the ferric phosphate surface through electrostatic interactions. Simultaneously, the ferric phosphate surface has numerous phosphorus-containing groups, which strongly attract lithium ions, which tend to precipitate with phosphate ions. At the microscopic level, the differences in particle structure morphology are key factors determining the arrangement, distribution, and density of surface active sites, thereby affecting the capture of target particles. This study found that adding calcium compounds during adsorption significantly promotes the adsorption effect of lithium by ferric phosphate. Furthermore, this study discovered that the primary nucleation particle size of ferric phosphate particles has a significant impact on its adsorption performance; therefore, by controlling or selecting the primary particle properties of ferric phosphate, ferric phosphate with different adsorption capacities can be obtained. Currently, numerous academic papers and patents have studied the preparation of ferric phosphate, and the related technologies are relatively mature. Its main application is as a precursor for lithium iron phosphate; however, this invention discovers another new application for ferric phosphate.

[0025] The primary nucleation particle size (also called primary particle size, primary grain, or original particle size) described in this invention refers to the particle size of a single fine crystal produced during the chemical crystallization process. The secondary particle size (secondary grain) refers to the particle size after agglomeration. This invention only limits the primary particle size (primary nucleation particle size) and does not limit the secondary particle size, because our experimental research has shown that as long as the primary particle size is within the control range of this invention, even if the secondary particle size is very large (hundreds of micrometers), this invention can still be achieved.

[0026] Due to agglomeration, the particle size obtained by laser particle size analyzer is usually secondary. Only under the observation of analytical equipment such as scanning electron microscope (SEM), transmission electron microscope (TEM), and scanning tunneling microscope (STM) can the morphology and particle size of primary grains (i.e., primary particle size) be observed. For amorphous particles, there are also original particles and agglomerated particles.

[0027] Compared with the prior art, the advantages of the present invention are: 1. The phosphorus iron salt adsorbent described in this invention is low in cost, simple to prepare and use, does not require the addition of organic matter, and does not use evaporation and concentration techniques to achieve the preliminary enrichment of low-concentration lithium-containing solutions, thus avoiding organic pollution and saving energy.

[0028] 2. The phosphorus iron salt adsorbent of the present invention can enrich lithium-containing solutions with a concentration of less than 1 g / L into lithium-containing pre-enriched solutions with a concentration of 1.5~6 g / L, turning waste into treasure, and transforming raw materials or intermediates that are difficult to utilize with existing technologies into raw materials that can be further processed into usable raw materials, with good enrichment effect.

[0029] 3. The phosphorus iron salt adsorbent of the present invention can be regenerated and reused during application.

[0030] The detailed structure of the present invention will be further described below with reference to the accompanying drawings and specific embodiments. Attached Figure Description

[0031] Figure 1 The XRD pattern of the adsorbent prepared in Example 1; Figure 2 SEM image of the adsorbent prepared in Example 1; Figure 3 The XRD pattern of the adsorbent prepared in Example 7; Figure 4 SEM image of the adsorbent prepared in Example 7; Figure 5 SEM image of the adsorbent used in Example 9; Figure 6 The XRD pattern of the adsorbent used in Example 10; Figure 7 SEM image of the adsorbent used in Example 10; Figure 8 The XRD pattern of the adsorbent used in Comparative Example 1 is shown. Figure 9 SEM image of the adsorbent used in Comparative Example 1; Figure 10 The XRD pattern of the adsorbent used in Comparative Example 4 is shown. Figure 11 This is a SEM image of the adsorbent used in Comparative Example 4. Detailed Implementation Example 1:

[0032] Preparation of ferric phosphate: Prepare 5L of solution containing 0.5mol / L phosphorus (sodium phosphate dodecahydrate as phosphorus source), adjust pH to 2 with sulfuric acid, add 2.5mol of ferrous sulfate heptahydrate, and after complete dissolution, add 1.5mol of hydrogen peroxide under stirring, heat to boiling and react for 2 hours, filter, wash thoroughly with water, and dry to obtain ferric phosphate.

[0033] Figure 1 The image shows the XRD characterization of the adsorbent prepared in Example 1. It has no complete peaks and is an amorphous substance. Figure 2 SEM image of the adsorbent prepared in Example 1. Figure 2 As can be seen, the particles are aggregates of primary microparticles with irregular shapes. These primary microparticles have extremely small particle sizes. Ten randomly labeled particle sizes using the Nano Measurer software range from 37 to 63 nm. Most other primary microparticles are similar.

[0034] 20g of the above-mentioned ferric phosphate was added to 1L of a solution containing 505mg / L lithium. The main other component in the solution was sodium sulfate (50.23g / L), and the pH was 6.84. The pH was adjusted to 10 with sodium hydroxide. The reaction was carried out at 30°C for 2 hours with stirring. After filtration, 41.43g of lithium-containing adsorbent (50.64% water content) was obtained, along with the post-adsorption liquid. Measurement showed that the lithium concentration in the post-adsorption liquid decreased to 358.16mg / L, indicating an adsorption capacity of 7.34mg / g (calculated on a dry basis of ferric phosphate). The lithium-containing adsorbent was washed three times with 60°C hot water, 50mL of water was added, and the mixture was stirred thoroughly. The pH was adjusted to 3 with sulfuric acid, and the reaction was carried out at 30°C for 2 hours with stirring. After filtration, a lithium-containing solution and filter cake were obtained. Measurement showed that the lithium content in the solution was 2.02g / L, achieving the pre-enrichment objective.

[0035] The filter cake was washed with a sulfuric acid solution with a pH of 2-3 until the lithium content in the filtrate was ≤0.5 mg / L, thus obtaining the regenerated adsorbent. The regenerated adsorbent was operated according to the steps in Example 1, and the adsorption capacity still reached 7.29 mg / g.

[0036] Example 2: Mixed Adsorbent I 20g of the ferric phosphate prepared in Example 1 and 6g of calcium chloride were mixed and added to 1L of a solution containing 505mg / L lithium. The other main components of the solution were sodium sulfate (50.23g / L) and pH 6.84. The pH was adjusted to 12 with sodium hydroxide. The mixture was reacted at 20°C for 1 hour with stirring. After filtration, 43.18g of lithium-containing adsorbent (49.94% water content) was obtained, along with the post-adsorption liquid. The lithium concentration in the post-adsorption liquid was measured to be reduced to 201.59mg / L, indicating that the lithium adsorption capacity was 15.17mg / g (calculated on a dry basis of ferric phosphate). The lithium-containing adsorbent was washed three times with 95°C hot water, 50mL of water was added, and the mixture was stirred evenly. The pH of the system was adjusted to 2 with hydrochloric acid, and the mixture was reacted at 30°C for 1 hour with stirring. After filtration, a lithium-containing solution was obtained. The lithium content in the solution was measured to be 4.11g / L, achieving the pre-enrichment purpose.

[0037] Example 3 Mixed Adsorbent II 30g of ferric phosphate and 6g of calcium oxide prepared in Example 1 were added to 1L of a solution containing 443.4mg / L lithium (the original solution pH was 5.66). Other major components in the solution were sodium sulfate (10.11g / L) and potassium sulfate (1.58g / L). After adding the adsorbent, the solution pH reached 12.79. The mixture was reacted at 20°C for 5 hours with stirring, and then filtered to obtain 62.78g of lithium-containing adsorbent (48.33% water content). The post-adsorption liquid was also obtained. Measurements showed that the lithium concentration in the post-adsorption liquid decreased to 1.31mg / L, indicating that the lithium adsorption capacity was 14.74mg / g (calculated on a dry basis of ferric phosphate). The lithium-containing adsorbent was washed once with 95°C hot water, 70mL of water was added, and the mixture was stirred thoroughly. The pH of the system was adjusted to 2 with sulfuric acid, and the mixture was reacted at 20°C for 3 hours with stirring. The mixture was then filtered to obtain a lithium-containing solution. Measurements showed that the solution contained 4.25g / L of lithium, achieving the pre-enrichment objective.

[0038] Example 4: High-salt magnesium-containing solution 20g of the ferric phosphate prepared in Example 1 and 4g of calcium oxide were mixed and added to 2L of a solution containing 511.4mg / L of lithium. Other main components in the solution were sodium sulfate (101.3g / L) and magnesium sulfate (52.3g / L). After the calcium oxide was added to the lithium-containing solution, the pH increased to 11.5. The mixture was reacted at 25°C for 1 hour under stirring. After filtration, 40.1g of lithium-containing adsorbent (50.35% water content) was obtained, along with the post-adsorption liquid. Measurements showed that the lithium concentration in the post-adsorption liquid decreased to 439.76mg / L, indicating an adsorption capacity of 7.16mg / g (calculated on a dry basis of ferric phosphate). The lithium-containing adsorbent was washed three times with 95°C hot water, 50mL of water was added, and the mixture was stirred thoroughly. The pH of the system was adjusted to 2 with hydrochloric acid, and the mixture was reacted at 25°C for 1 hour under stirring. After filtration, a lithium-containing solution was obtained. Measurements showed that the solution contained 1.98g / L of lithium, achieving the pre-enrichment objective.

[0039] Example 5: Ultra-low concentration lithium-containing solution 20g of ferric phosphate prepared in Example 1 and 8g of calcium hydroxide were mixed and added to 10L of a lithium solution containing 10.24mg / L. After the calcium hydroxide was added to the lithium-containing solution, the pH rose to 12. The mixture was reacted at 25°C for 1 hour under stirring. After filtration, 41.23g of lithium-containing adsorbent (51.11% water content) was obtained, along with the post-adsorption liquid. The lithium concentration in the post-adsorption liquid was measured to be reduced to 0.053mg / L, indicating that the lithium adsorption capacity was 5.09mg / g (calculated on a dry basis of ferric phosphate). The lithium-containing adsorbent was washed once with 95°C hot water, 50mL of water was added, and the mixture was stirred evenly. The pH of the system was adjusted to 2 with sulfuric acid, and the mixture was reacted at 25°C for 2 hours under stirring. After filtration, a lithium-containing solution was obtained. The lithium content in the solution was measured to be 1.38g / L, achieving the pre-enrichment purpose.

[0040] Example 6: Comparison of the adsorption capacity of mixed adsorbents in high-salt solutions Four portions of the adsorbent prepared in Example 1 (20g each) were taken. One portion was used alone, and the other three portions were mixed with calcium-containing additives (the amount of additives was based on the calcium content, each containing 2.86g of calcium). Specifically, one portion was mixed with 4g of calcium oxide (containing approximately 2.86g of calcium), one portion with 10.52g of calcium chloride dihydrate (containing approximately 2.86g of calcium), and one portion with 16.87g of calcium nitrate tetrahydrate (containing approximately 2.86g of calcium). This mixture was then added to a 2L solution containing 487.12mg / L lithium, with other components mainly consisting of 100g / L sodium sulfate. The pH of the solution was adjusted to 12 with sodium hydroxide (the pH of the calcium oxide adsorbent did not need adjustment; after being added to the lithium-containing solution, it rose to 12.08). The mixture was then reacted at 25°C for 1 hour under stirring. After filtration, the lithium content in the filtrate was measured, and the lithium adsorption capacity was calculated (based on a dry basis of ferric phosphate). Table 1 compares the adsorption effects of Example 6. As can be seen from Table 1, under the same conditions, the adsorption effect of adding calcium salt additives is significantly better than that of using the adsorbent alone. Moreover, the adsorption capacity of using the adsorbent alone is only 2.78 mg / g, which is difficult to desorb to more than 1 g / L.

[0041] Table 1. Comparison of the effects of different additives and the use of ferric phosphate adsorbent alone. additive none Calcium oxide Calcium chloride Calcium nitrate Filtrate concentration 459.34 mg / L 415.12 mg / L 413.5 mg / L 416.22 mg / L Lithium adsorption capacity 2.78 mg / g 7.2 mg / g 7.36 mg / g 7.09 mg / g Example 7 Preparation of ferric phosphate: Prepare 5L of a solution containing 0.2mol / L phosphorus (sodium phosphate dodecahydrate as the phosphorus source), adjust the pH to 2 with sulfuric acid, heat to 80°C, and add 5L of a solution containing 0.2mol / L iron (ferric chloride hexahydrate as the iron source) under stirring. React for 2 hours, filter, wash thoroughly with water, and dry to obtain ferric phosphate.

[0042] Figure 3The image shows the XRD pattern of the adsorbent prepared in Example 7. It has no complete peaks and is also amorphous. Figure 4 The SEM image of the adsorbent prepared in Example 7 shows that the primary particles are spherical with obvious boundaries between adjacent particles. The particle size is much larger than that of Example 1. The particle size marked 10 in the figure is in the range of 510~810 nm. The particle size of other primary particles is also mostly similar.

[0043] 20g of the above-mentioned ferric phosphate was added to 1L of a solution containing 505mg / L lithium. The main other component in the solution was sodium sulfate (50.23g / L), and the pH was 6.84. The pH was adjusted to 12 with sodium hydroxide. The reaction was carried out at 20°C for 1 hour with stirring. After filtration, 41.17g of lithium-containing adsorbent (49.84% water content) was obtained, along with the post-adsorption liquid. Measurement showed that the lithium concentration in the post-adsorption liquid decreased to 393.12mg / L, indicating an adsorption capacity of 5.59mg / g (calculated on a dry basis of ferric phosphate). The lithium-containing adsorbent was washed three times with 90°C hot water, 60mL of water was added, and the mixture was stirred thoroughly. The pH was adjusted to 3 with sulfuric acid, and the reaction was carried out at 80°C for 1 hour with stirring. After filtration, a lithium-containing solution was obtained. Measurement showed that the solution contained 1.27g / L of lithium, achieving the pre-enrichment objective.

[0044] Example 8: In this example, the lithium concentration of the lithium-containing solution is relatively low, and the amount of adsorbent used is relatively large. 50g of ferric phosphate and 10g of calcium oxide prepared in Example 7 were added to 1L of a solution containing 241.9mg / L lithium (the original solution pH was 6.76). The other main component in the solution was sodium sulfate (5.23g / L). After adding the adsorbent, the pH of the solution reached 12.11. The mixture was reacted at 20°C for 1 hour with stirring, and then filtered to obtain 101.86g of lithium-containing adsorbent (49.74% water content). The post-adsorption liquid was also obtained. The lithium concentration in the post-adsorption liquid was measured to be reduced to 0.44mg / L, indicating that the lithium adsorption capacity was 4.83mg / g (calculated on a dry basis of ferric phosphate). The lithium-containing adsorbent was washed once with 95°C hot water, 100mL of water was added, and the mixture was stirred evenly. The pH of the system was adjusted to 2 with sulfuric acid, and the mixture was reacted at 20°C for 1 hour with stirring, and then filtered to obtain a lithium-containing solution. The lithium content in the solution was measured to be 1.54g / L, achieving the pre-enrichment purpose.

[0045] Example 9 Existing ferric phosphate was selected as the adsorbent (purchased from Changsha Shenghua Research Institute). Its XRD characterization was similar to that of Example 1, showing that it was amorphous. Figure 5 The SEM characterization of the iron phosphate used in Example 9 shows that the primary particles are also spherical, with obvious boundaries at the agglomeration points. The particle size is larger than that of Example 6, basically reaching the micrometer level. The particle size marked 10 in the figure is in the range of 1.1~1.9μm. The particle size of other primary particles is also mostly similar to this.

[0046] 20g of the above-mentioned ferric phosphate and 4g of calcium oxide were added to 2L of a solution containing 503.34mg / L of lithium. The other main component of the solution was sodium sulfate (11.88g / L) (pH 7.13). After adding the adsorbent, the pH of the solution reached 11.79. The mixture was reacted at 40°C for 1 hour under stirring. After filtration, 40.54g of lithium-containing adsorbent (49.83% water content) was obtained, along with the post-adsorption liquid. The lithium concentration in the post-adsorption liquid was measured to be reduced to 392.44mg / L, indicating that the lithium adsorption capacity was 11.09mg / g (calculated on a dry basis of ferric phosphate). The lithium-containing adsorbent was washed three times with 95°C hot water, 50mL of water was added, and the mixture was stirred evenly. The pH of the system was adjusted to 2 with sulfuric acid, and the mixture was reacted at 30°C for 6 hours under stirring. After filtration, a lithium-containing solution and a filter cake were obtained. The lithium content in the solution was measured to be 3.11g / L, achieving the pre-enrichment purpose.

[0047] Example 10 Preparation of ferric phosphate: Prepare 5L of a 0.5mol / L phosphorus solution (sodium phosphate dodecahydrate as the phosphorus source), adjust the pH to 2 with sulfuric acid, prepare 5L of a 0.5mol / L iron solution (ferric sulfate as the iron source), heat the phosphorus-containing solution to boiling, add the iron-containing solution, react for 4 hours, filter, wash thoroughly with water, and dry to obtain ferric phosphate.

[0048] Figure 6 The XRD pattern of the adsorbent used in Example 10 shows obvious crystal diffraction peaks, indicating that it is crystalline iron phosphate. Figure 7 The image shows an SEM image of the adsorbent used in Example 10. It reveals fine primary grains with clear boundaries between adjacent grains, eventually forming irregular secondary particles. Using Nano Measurer software, 24 primary grains at different locations were labeled, showing their distribution between 50 and 170 nm.

[0049] 20g of the above-mentioned ferric phosphate was added to 1L of a solution containing 259.6mg / L lithium. The main other component in the solution was sodium sulfate (12.49g / L), and the pH was 5.84. The pH was adjusted to 10 with sodium hydroxide. The reaction was carried out at 20°C for 5 hours with stirring. After filtration, 39.39g of lithium-containing adsorbent (49.13% water content) was obtained, along with the post-adsorption liquid. Measurements showed that the lithium concentration in the post-adsorption liquid decreased to 98.24mg / L, indicating an adsorption capacity of 8.07mg / g (calculated on a dry basis of ferric phosphate). The lithium-containing adsorbent was washed three times with 60°C hot water, 50mL of water was added, and the mixture was stirred thoroughly. The pH was adjusted to 2 with nitric acid, and the reaction was carried out at 30°C for 1 hour with stirring. After filtration, a lithium-containing solution and a filter cake were obtained. Measurements showed that the lithium content in the solution was 2.32g / L, achieving the pre-enrichment objective.

[0050] Example 11 20g of ferric phosphate and 6g of calcium chloride used in Example 10 were mixed and added to 1L of a solution containing 325.61mg / L lithium. The other main components of the solution were sodium sulfate (67.53g / L) and the pH of the solution was 6.22. The pH of the solution was adjusted to 11 with sodium hydroxide, yielding 41.12g of lithium-containing adsorbent (50.11% water content). The concentration of the adsorbent was measured to be 109.24mg / L after adsorption, indicating that the lithium adsorption capacity was 10.82mg / g. The lithium-containing adsorbent was washed three times with 95°C hot water, 50mL of water was added, and the mixture was stirred evenly. The pH of the system was adjusted to 3 with sulfuric acid, and the reaction was carried out at 30°C for 2 hours under stirring. After filtration, a lithium-containing solution and filter cake were obtained. The lithium content in the solution was measured to be 2.99g / L, achieving the pre-enrichment purpose.

[0051] Example 12 Existing ferric phosphate was selected as the adsorbent (purchased from Maclean's reagents), and its characterization was similar to that of the ferric phosphate used in Example 10, with a primary particle size distribution of less than 200 nm.

[0052] 20g of the above-mentioned ferric phosphate and 5g of calcium oxide were added to 2L of a solution containing 503.34mg / L of lithium. The other main component of the solution was sodium sulfate (11.88g / L) (solution pH 7.13). After adding the adsorbent, the pH of the solution reached 12.24. The reaction was carried out at 30°C for 4 hours with stirring. After filtration, 41.33g of lithium-containing adsorbent (water content 49.22%) was obtained, along with the post-adsorption liquid. The lithium concentration in the post-adsorption liquid was measured to be reduced to 351.98mg / L, indicating that the lithium adsorption capacity was 15.14mg / g (calculated on a dry basis of ferric phosphate). The lithium-containing adsorbent was washed once with 95°C hot water, 50mL of water was added, and the mixture was stirred evenly. The pH of the system was adjusted to 2 with hydrochloric acid, and the reaction was carried out at 30°C for 1 hour with stirring. After filtration, a lithium-containing solution and a filter cake were obtained. The lithium content in the solution was measured to be 4.22g / L, achieving the pre-enrichment purpose.

[0053] Example 13 Existing ferric phosphate was selected as the adsorbent (purchased from Ron Reagent), and its characterization was similar to that of the ferric phosphate used in Example 10, with the primary particle size distribution being less than 200 nm.

[0054] 20g of the above-mentioned ferric phosphate was added to 1L of a solution containing 467.24mg / L lithium. The main other component in the solution was sodium sulfate (23.14g / L), and the pH was 8.62. The pH was adjusted to 10 with ammonia. The reaction was carried out at 30°C for 2 hours with stirring. After filtration, 40.04g of lithium-containing adsorbent (49.59% water content) was obtained, along with the post-adsorption liquid. Measurements showed that the lithium concentration in the post-adsorption liquid decreased to 318.88mg / L, indicating an adsorption capacity of 7.42mg / g (calculated on a dry basis of ferric phosphate). The lithium-containing adsorbent was washed twice with 95°C hot water, 50mL of water was added, and the mixture was stirred thoroughly. The pH was adjusted to 2 with sulfuric acid, and the reaction was carried out at 20°C for 1 hour with stirring. After filtration, a lithium-containing solution and a filter cake were obtained. Measurements showed that the lithium content in the solution was 2.08g / L, achieving the pre-enrichment objective.

[0055] Comparative Example 1 (the primary particle size of ferric phosphate is too large): Take the available ferric phosphate (purchased from Aladdin Reagents). Figure 8 The XRD pattern of iron phosphate used in Comparative Example 1 shows obvious crystal diffraction peaks. Figure 9 The SEM images show the iron phosphate used in Comparative Example 1. The SEM images reveal a distinct crystalline structure, with some particles exhibiting a plate-like structure (labeled 1 and 2 in the figure), while others are relatively complete crystals (labeled 3 and 4 in the figure). Both plate-like and blocky crystals have relatively smooth surfaces, indicating they are primary nucleation particles with relatively large primary particle sizes, exceeding 2 micrometers.

[0056] Take 20g of the above-mentioned iron phosphate and operate according to Example 1. The concentration of the liquid after adsorption was measured to be only 477.22mg / L. It can be seen that the lithium adsorption capacity is only 1.39mg / g, that is, the adsorption capacity is very weak and there is basically no enrichment effect.

[0057] Comparative Example 2: 20g of ferric phosphate from Comparative Example 1 was used to replace the ferric phosphate in Example 2. The procedure was followed as in Example 2. The concentration of the adsorbed solution was measured to be only 485.58mg / L, indicating that the lithium adsorption capacity was only 0.97mg / g, with virtually no enrichment effect (calcium chloride had no promoting effect).

[0058] Comparative Example 3: Take 30g of iron phosphate from Comparative Example 1 to replace the iron phosphate in Example 3, and operate according to Example 3. The concentration of the liquid after adsorption was measured to be only 394.56mg / L, indicating that the lithium adsorption capacity was only 1.63mg / g, with basically no enrichment effect (calcium oxide had no promoting effect).

[0059] Comparative Example 4: Replace the ferric phosphate in Example 1 with existing ferric phosphate (purchased from Changsha Fumao Chemical Materials Co., Ltd.). Figure 10The XRD pattern of iron phosphate used in Comparative Example 4 shows obvious crystal diffraction peaks. Figure 11 The image shows the SEM characterization of ferric phosphate used for example 4. The image clearly shows distinct grains, some with relatively regular shapes (labeled 1 and 2 in the image), while others appear disordered (labeled 3 and 4 in the image). However, it can be seen that most primary grains have a relatively large particle size, exceeding 5 micrometers.

[0060] Take 20g of the above-mentioned iron phosphate and operate according to Example 1. The concentration of the liquid after adsorption was measured to be only 487.54mg / L. It can be seen that the lithium adsorption capacity is only 0.873mg / g, that is, the adsorption capacity is very weak and there is basically no enrichment effect.

[0061] The above description is a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any person skilled in the art who makes equivalent substitutions, changes, or combinations based on the technical solution and concept of the present invention within the technical scope disclosed in the present invention (such as performing multi-stage adsorption and desorption to improve the recovery rate, etc., are simple combinations of the methods of the present invention) should be covered within the scope of protection of the claims of the present invention.

Claims

1. A phosphorus iron salt adsorbent for pre-concentration of low concentration lithium containing solutions, characterized in that, The phosphorus iron salt adsorbent is a mixture of iron phosphate and calcium compound, the mass ratio of the mixture is: iron phosphate: calcium compound = 1: (0.1-1); the calcium compound includes one or several of calcium chloride, calcium oxide, calcium hydroxide, calcium nitrate; the phosphorus iron salt adsorbent is a phosphorus iron salt adsorbent for pre-enrichment of low-concentration lithium-containing solution.

2. The ferrophosphorus salt adsorbent according to claim 1, characterized in that The mass ratio of the mixture is: iron phosphate: calcium compound = 1: (0.1-0.5).

3. The ferrophosphorus salt adsorbent according to claim 1 or 2, characterized in that, The primary nucleation particle size of the iron phosphate is less than 2000 nm.

4. The ferrophosphorus salt adsorbent according to claim 3, characterized in that The primary nucleation particle size of the iron phosphate is less than 1000 nm, and further preferably the primary nucleation particle size of the iron phosphate is less than 200 nm.

5. Application of a phosphorus iron salt adsorbent in pre-enrichment of low-concentration lithium-containing solution, the phosphorus iron salt adsorbent is iron phosphate, or the phosphorus iron salt adsorbent is the phosphorus iron salt adsorbent according to any one of claims 1-4.

6. The use of the phosphorus iron salt adsorbent according to claim 5 for pre-concentration of low concentration lithium-containing solutions, characterized in that, The application specifically includes the following steps: (1) 1-200 g of the adsorbent in claim 5 is added to 1 L of low-concentration lithium-containing solution, the pH is adjusted to 8-13 with an alkaline substance, and the mixture is reacted at 0-100 ℃ for 10 min-12 h, then liquid-solid separation is performed to complete adsorption; the low-concentration lithium-containing solution is a lithium-containing solution with a lithium ion concentration of less than 1 g / L; (2) the adsorbent after adsorbing lithium is washed with water several times, then an acid solution is added to adjust the pH to 1-5, and the mixture is reacted at 0-100 ℃ for 10 min-12 h, then liquid-solid separation is performed to complete desorption, and a lithium-containing pre-enrichment solution and a filter cake are obtained, and the filter cake is washed to obtain regenerated adsorbent.

7. Use according to claim 6, characterized in that, The low-concentration lithium-containing solution is a lithium-containing solution with a lithium ion concentration of less than 1 g / L, preferably a lithium ion concentration of 10-600 mg / L.

8. Use according to claim 6, characterized in that, The alkaline substance includes one or a combination of sodium hydroxide, potassium hydroxide, calcium oxide, calcium hydroxide, and ammonia.

9. Use according to claim 6, characterized in that, The acid includes one or a combination of sulfuric acid, hydrochloric acid, and nitric acid.

10. Use according to claim 6, characterized in that, Step (2) obtains a lithium-containing pre-enrichment solution with a concentration of more than 1 g / L, and preferably a lithium-containing pre-enrichment solution with a concentration of 1.5-6 g / L.

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