Method for simultaneously preparing filter aid and aluminum salt from lithium slag

Abstract

The invention discloses a method for simultaneously preparing a filter aid and aluminum salt from lithium slag, and relates to the technical field of waste resource utilization. The method comprises the steps that the lithium slag is pretreated to remove substances with magnetism and / or large specific gravity in the lithium slag, and pretreated slag is obtained; uniformly mixing a mixed solution of ammonium sulfate and sulfuric acid with the pretreatment slag, grinding, carrying out hydrothermal reaction on the mixed slurry, and carrying out solid-liquid separation to obtain silicon slag and an aluminum ammonium sulfate solution; carrying out microwave treatment on the silicon slag to obtain a filter aid; and carrying out cooling crystallization and recrystallization purification on the aluminum ammonium sulfate solution to prepare aluminum ammonium sulfate. According to the method, the spodumene lithium extraction tailings are used as the raw material, valuable components in the lithium slag can be efficiently utilized in an environment-friendly mode, the filter aid and the aluminum salt which are excellent in performance are prepared, cyclic utilization of resources is achieved, and the method has important practical significance and wide application prospects. In addition, valuable metal elements such as rubidium, cesium, titanium and beryllium can be comprehensively recycled, and the resource utilization rate is increased.

Description

Technical Field

[0001] The present invention relates to the technical field of waste resource utilization, and more particularly, to a method for simultaneously preparing a filter aid and an aluminum salt using lithium slag. Background Art

[0002] Lithium slag is a solid waste generated during the extraction of lithium from lithium ore, containing various valuable elements and compounds. With the rapid development of the lithium battery industry, the output of lithium slag is also increasing continuously. If not processed and utilized, these lithium slags will not only occupy a large amount of land resources but also cause environmental pollution. Therefore, how to efficiently and environmentally process and utilize lithium slag has become an urgent problem to be solved.

[0003] Traditional methods for treating lithium slag mainly include landfilling and simple resource recovery, but these methods have problems such as low resource utilization rate and environmental pollution. In recent years, researchers have begun to explore new ways to recycle lithium slag. In the prior art, Patent CN108273826B discloses a method for the comprehensive high-value recycling of lithium slag. This patent reacts and wet magnetic separates the spodumene leaching slag in a dispersed suspension state with soluble carbonate, and finally obtains pyrophyllite raw materials for fiberglass, thereby improving the economic and environmental benefits of spodumene leaching slag. However, this method requires crystallization to recover sulfate products, has disadvantages such as high cost and low alkali conversion efficiency, and is difficult to achieve industrial application. Patent CN108147658A obtains pyrophyllite raw materials for fiberglass through steps such as flotation desulfurization and magnetic separation to remove iron. The pyrophyllite for fiberglass produced by this method has characteristics such as high iron and high sulfur, and its market application is limited to a certain extent. Patent CN113976309B discloses a method for comprehensively recovering lithium, tantalum, niobium, silicon-aluminum micro-powder, iron concentrate, and gypsum from lithium slag. High-purity gypsum concentrate and silicon-aluminum micro-powder are obtained through flotation and weak magnetic and strong magnetic separation, and at the same time, coarse-grained niobium and tantalum-rich materials and coarse-grained iron concentrate are obtained through gravity separation and weak magnetic separation. Although this method realizes the comprehensive high-value utilization of lithium slag, the silicon-aluminum micro-powder prepared by the above process has problems such as low yield, complex process, poor separation effect, and unstable product quality.

[0004] In the preparation of filter aids, traditional filter aid production processes mostly rely on raw materials such as natural diatomite. However, natural diatomite resources are limited, and the mining and processing processes have a certain impact on the environment. At the same time, as an important chemical raw material, aluminum salts have a wide range of applications in many fields such as water treatment, papermaking, and textile. Its traditional production methods mostly use raw materials such as bauxite, but the over-exploitation of bauxite resources also faces problems of resource depletion and environmental damage.

[0005] Therefore, how to efficiently and environmentally utilize the valuable components in lithium slag, prepare filter aids and aluminum salts with excellent performance, and realize the recycling of resources has important practical significance and broad application prospects.

[0006] In view of this, the present invention is hereby proposed. Summary of the Invention

[0007] The object of the present invention is to provide a method for simultaneously preparing a filter aid and an aluminum salt using lithium slag, aiming to solve the problem of lithium slag treatment and provide a new raw material source and production process for the production of filter aids and aluminum salts.

[0008] The present invention is implemented as follows:

[0009] In a first aspect, the present invention provides a method for simultaneously preparing a filter aid and an aluminum salt using lithium slag, which includes:

[0010] S1: Pretreat the lithium slag to remove substances with magnetism and / or high specific gravity in the lithium slag, obtaining pretreated slag and pretreated material;

[0011] S2: Mix and grind a mixed solution of ammonium sulfate and sulfuric acid with the pretreated slag to obtain a mixed slurry;

[0012] S3: Perform a hydrothermal reaction on the mixed slurry and carry out solid-liquid separation to obtain silicon slag and an ammonium aluminum sulfate solution;

[0013] S4: Perform microwave treatment on the silicon slag to obtain a filter aid;

[0014] S5: Cool and crystallize the ammonium aluminum sulfate solution to obtain ammonium aluminum sulfate crystals and a filtrate;

[0015] S6: Recrystallize and purify the ammonium aluminum sulfate crystals to prepare ammonium aluminum sulfate.

[0016] In an optional embodiment, the lithium slag is a weakly acidic slag obtained by subjecting spodumene to conversion calcination, acid roasting, leaching, and stirring and washing; the chemical composition of the lithium slag is: SiO2 60 - 70 wt%, Al2O3 22 - 26 wt%, Fe2O3 0.5 - 1.5 wt%, CaO 0.2 - 0.5 wt%, SO3 0.1 - 0.5 wt%, and the combined content of K2O and Na2O is 0.5 - 1.50 wt%.

[0017] In an optional embodiment, the pretreatment includes one or more of magnetic separation and gravity separation;

[0018] Preferably, the magnetic separation includes one or more of weak magnetic separation and strong magnetic separation, with a magnetic field intensity of 0.2 - 1.8 T;

[0019] Preferably, the gravity separation includes one or more of a spiral chute, a shaking table, and a jig.

[0020] In an alternative embodiment, the yield of the pretreated material is 3% to 15%, and the chemical composition of the pretreated material is: SiO2 55 to 60 wt%, Al2O3 17 to 21 wt%, Fe2O3 3.0 to 8.0 wt%, CaO 1.0 to 3.0 wt%, SO3 0.05 to 0.3 wt%, and the combined content of K2O and Na2O is 0.6 to 1.5 wt%.

[0021] And / or, the yield of the pretreated slag is 85% to 97%, and the chemical composition of the pretreated slag is: SiO2 65 to 75 wt%, Al2O3 22 to 26 wt%, Fe2O3 0.2 to 0.50 wt%, CaO 0.1 to 0.4 wt%, SO3 0.05 to 0.3 wt%, and the combined content of K2O and Na2O is 0.4 to 0.8 wt%.

[0022] In an alternative embodiment, in the mixed solution, the molar concentration of ammonium sulfate is 0.5 to 3 mol / L, and the molar concentration of sulfuric acid is 1.5 to 10 mol / L; and the molar ratio of ammonium sulfate to sulfuric acid is 1:3 to 1:5;

[0023] Preferably, the mass ratio of the pretreated slag to the volume of the mixed solution is 1 g:1 mL to 1 g:5 mL.

[0024] In an alternative embodiment, the grinding equipment is one or more of a porcelain-lined ball mill, a stirred mill, and a nano sand mill; the fineness of the mixed slurry with a particle size below 25 μm accounts for 90% to 98%.

[0025] In an alternative embodiment, the temperature of the hydrothermal reaction is 60 to 200 °C, and the reaction time is 0.5 to 3 h;

[0026] And / or, the solid-liquid separation includes one or more of gravity sedimentation, centrifugation, and pressure filtration;

[0027] And / or, the SiO2 content in the silicon slag is ≥95 wt%, and the concentration of the ammonium aluminum sulfate solution is 0.5 to 1.5 mol / L.

[0028] In an alternative embodiment, the power of the microwave treatment is 400 to 800 W, the microwave treatment time is 0.5 to 4 h, and the treatment temperature is 40 to 80 °C;

[0029] And / or, the temperature of the cooling crystallization is 0 to 20 °C, the stirring speed is 100 to 400 r / min, the cooling rate is 1 °C / min to 10 °C / min, and the crystallization time is 0.5 to 4 h;

[0030] And / or, the purity of the ammonium aluminum sulfate after recrystallization purification is >99%.

[0031] In an alternative embodiment, the method further includes step S7: recovering valuable metal elements from the filtrate step by step by solvent extraction method.

[0032] In an alternative embodiment, the solvent extraction method includes adopting different extraction and separation techniques according to different valuable metal elements in the solution. When rubidium and cesium are contained in the filtrate, BAMBP is used to extract and separate rubidium and cesium. When beryllium is contained in the filtrate, carboxylic acid is used to extract and separate beryllium. When titanium is contained in the filtrate, N1923 is used to extract and separate titanium;

[0033] Preferably, the tail liquid after extraction and separation is a mixed solution containing ammonium sulfate and sulfuric acid, which can be returned to the pretreatment slag system for reuse.

[0034] The present invention has the following beneficial effects:

[0035] The method for simultaneously preparing a filter aid and an aluminum salt from lithium slag provided by the present invention uses the tail slag of spodumene lithium extraction as a raw material. Through pretreatment, substances with magnetism and / or high specific gravity in the lithium slag can be removed to avoid affecting subsequent products. By mixing and grinding the pretreatment slag with a mixed solution of ammonium sulfate and sulfuric acid, the valuable components in the lithium slag can be efficiently and environmentally utilized under hydrothermal reaction to prepare a filter aid and an aluminum salt with excellent performance, realizing the recycling of resources, which has important practical significance and broad application prospects. In addition, the present invention can also comprehensively recover valuable metal elements such as rubidium, cesium, titanium, and beryllium to improve resource utilization rate. The method adopts a process combining mineral processing and chemical engineering, without three wastes discharge, and the process is simple, the conditions are mild and easy to implement. The ammonium aluminum sulfate prepared by this method has high purity, and the filter cake of the filter aid has a large specific resistance, broadening the application range of the product. This method can reduce the stacking and landfill of lithium slag, avoid environmental pollution of its harmful components to soil, water bodies, etc., meet the requirements of sustainable development, and has significant economic and social benefits. Brief Description of the Drawings

[0036] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following will briefly introduce the drawings required for use in the embodiments. It should be understood that the following drawings only show some embodiments of the present invention, and therefore should not be regarded as limiting the scope. For those of ordinary skill in the art, other related drawings can be obtained based on these drawings without creative efforts.

[0037] Figure 1 It is a process flow chart of the method for simultaneously preparing a filter aid and an aluminum salt from lithium slag provided by the present invention. Detailed Embodiments

[0038] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be described clearly and completely below. For those not specified in the embodiments, they are carried out according to conventional conditions or conditions recommended by the manufacturer. For reagents or instruments without indicating the manufacturer, they are all conventional products that can be obtained through commercial purchase.

[0039] Please refer to Figure 1 , the present invention provides a method for simultaneously preparing a filter aid and an aluminum salt using lithium slag, which includes the following steps:

[0040] S1: Pretreat the lithium slag to remove substances with magnetism and / or high specific gravity in the lithium slag, obtaining pretreated slag and pretreated material.

[0041] The lithium slag is a weakly acidic slag obtained after the conversion calcination, acid roasting, leaching, and stirring and washing of spodumene; the chemical composition of the lithium slag is: SiO2 60 - 70 wt%, Al2O3 22 - 26 wt%, Fe2O3 0.5 - 1.5 wt%, CaO 0.2 - 0.5 wt%, SO3 0.1 - 0.5 wt%, and the combined content of K2O and Na2O is 0.5 - 1.50 wt%. In addition, the lithium slag also contains trace amounts of metal elements such as rubidium (608 ppm), cesium (182 ppm), titanium (640 ppm), beryllium (83 ppm), etc.

[0042] This method uses the tailings of spodumene lithium extraction as raw materials, makes full use of components such as aluminum and silicon in the lithium slag to prepare a filter aid and an aluminum salt. In addition, the present invention can also comprehensively recover valuable metal elements such as rubidium, cesium, titanium, and beryllium, improving the resource utilization rate.

[0043] In the present invention, through pretreatment, components that are easy to recover or have an impact on the subsequent filter aid or aluminum salt can be recovered in advance. Among them, the pretreatment includes one or more of magnetic separation and gravity separation; preferably, the magnetic separation includes but is not limited to one or more of weak magnetic separation and strong magnetic separation, with a magnetic field intensity of 0.2 - 1.8 T; the gravity separation includes but is not limited to one or more of a spiral chute, a shaking table, and a jigs.

[0044] Through the above pretreatment, the yield of the pretreated material is 3% - 15%, and the yield of the pretreated slag is 85 - 97%.

[0045] Among them, the chemical composition of the pretreated material is: SiO2 55 - 60wt%, Al2O3 17 - 21wt%, Fe2O3 3.0 - 8.0wt%, CaO 1.0 - 3.0wt%, SO3 0.05 - 0.3wt%, and the combined content of K2O and Na2O is 0.6 - 1.5wt%; the chemical composition of the pretreated slag is: SiO2 65 - 75wt%, Al2O3 22 - 26wt%, Fe2O3 0.2 - 0.50wt%, CaO 0.1 - 0.4wt%, SO3 0.05 - 0.3wt%, and the combined content of K2O and Na2O is 0.4 - 0.8wt%.

[0046] It can be seen that the contents of Fe2O3 and CaO in the pretreated material are significantly higher than those in the lithium slag, fully proving that iron and calcium elements are separated by magnetic separation and gravity separation. From the composition of the pretreated slag, it can be seen that the proportions of silicon and aluminum are slightly larger than those in the lithium slag, while the contents of Fe2O3, CaO, SO3, K2O, and Na2O are significantly reduced, which is beneficial to the subsequent utilization of silicon and aluminum in the pretreated slag.

[0047] S2: Mix and grind the mixed solution of ammonium sulfate and sulfuric acid with the pretreated slag to obtain a mixed slurry.

[0048] In the mixed solution, the molar concentration of ammonium sulfate is 0.5 - 3mol / L, and the molar concentration of sulfuric acid is 1.5 - 10mol / L; in the mixed solution, the molar ratio of ammonium sulfate to sulfuric acid is 1:3 - 1:5; the mass ratio of the pretreated slag to the volume of the mixed solution is 1g:1mL - 1g:5mL.

[0049] In the present invention, by adding ammonium sulfate and sulfuric acid to the pretreated slag, it is used to react with Al2O3 in the pretreated slag to prepare aluminum salts.

[0050] The grinding is to make the pretreated slag be ground under the action of the mixed solution to make its particle size smaller and more uniform. Specifically, the proportion of the fineness of the mixed slurry below 25μm is 90 - 98%.

[0051] The grinding equipment includes but is not limited to one or more of a porcelain-lined ball mill, a stirred mill, and a nano sand mill; it should be understood that other common grinding equipment on the market can also be used as the grinding equipment of this application as long as it can achieve the mixing effect.

[0052] S3: Perform a hydrothermal reaction on the mixed slurry and carry out solid-liquid separation to obtain silicon slag and ammonium aluminum sulfate solution;

[0053] Since Al2O3 in the pre-treated slag does not react with ammonium sulfate and sulfuric acid at room temperature, in the present invention, the mixed slurry is subjected to a hydrothermal reaction at a temperature of 60-200 °C for a reaction time of 0.5-3 h; the whole reaction is carried out in a reaction kettle. During the hydrothermal reaction, water vapor will form a certain high pressure in the reaction kettle, further promoting the reaction of Al2O3 with ammonium sulfate to produce aluminum sulfate.

[0054] After the hydrothermal reaction, the silicon slag and ammonium aluminum sulfate can be separated by solid-liquid separation. Among them, there are various methods of solid-liquid separation, including but not limited to one or more of gravity sedimentation, centrifugation, and pressure filtration.

[0055] The content of SiO2 in the silicon slag after solid-liquid separation is ≥95 wt%, and the concentration of the ammonium aluminum sulfate solution is 0.5-1.5 mol / L.

[0056] S4: Microwave treatment is carried out on the silicon slag to obtain a filter aid;

[0057] In the present invention, microwave treatment of the silicon slag can improve the filtration efficiency of the silicon slag, and at the same time can also improve the filtration accuracy, enhance the mechanical strength and optimize the chemical stability.

[0058] Specifically, microwave treatment can change the physical structure of the silicon slag, increase its porosity and specific surface area, thereby enhancing the permeability and retention capacity of the filter medium and accelerating the filtration speed. Microwave treatment can make the silicon slag particles more uniform, reduce large particles and irregular particles, improve the filtration accuracy, and effectively intercept fine particles and impurities. Microwave treatment can enhance the mechanical strength of the silicon slag, making it more durable during the filtration process, reducing breakage and deformation, and extending the service life. Microwave treatment can improve the chemical stability of the silicon slag, making it more stable in acidic, alkaline and other environments, reducing chemical reactions with the filtered substances, and avoiding contamination.

[0059] Among them, the power of the microwave treatment is 400-800 W, the microwave treatment time is 0.5-4 h, and the treatment temperature is 40-80 °C.

[0060] S5: Cooling crystallization is carried out on the ammonium aluminum sulfate solution to obtain ammonium aluminum sulfate crystals and a filtrate;

[0061] The main purpose of cooling crystallization of the ammonium aluminum sulfate solution is to reduce the solubility of the solute (ammonium aluminum sulfate) by lowering the solution temperature, so that crystals precipitate from the solution, which is beneficial to removing impurities to improve the purity. In addition, by controlling the cooling rate, the size and morphology of the crystals can be adjusted, and the desired crystal characteristics can be obtained by adjusting the cooling process.

[0062] Specifically, the temperature for cooling crystallization is 0 to 20 °C, the stirring speed is 100 to 400 r / min, the cooling rate is 1 °C / min to 10 °C / min, and the crystallization time is 0.5 to 4 h. Among them, the temperature and cooling rate of cooling crystallization are relatively crucial, which can control the size and morphology of the crystals.

[0063] S6: Recrystallize and purify the ammonium aluminum sulfate crystals to prepare ammonium aluminum sulfate.

[0064] The main purpose of recrystallizing and purifying the ammonium aluminum sulfate crystals is to further improve their purity and remove residual impurities. Through dissolution and recrystallization, it is beneficial to remove impurities in the crystals and obtain ammonium aluminum sulfate with higher purity. In addition, recrystallization can optimize the crystal morphology and size, making them more uniform and regular, which is convenient for subsequent use. The purity of ammonium aluminum sulfate after recrystallization and purification is > 99%.

[0065] S7: Use solvent extraction method to recover valuable metal elements step by step from the filtrate.

[0066] The solvent extraction method includes using different extraction and separation techniques according to different valuable metal elements in the solution. When rubidium and cesium are contained in the filtrate, BAMBP is used to extract and separate rubidium and cesium. When beryllium is contained in the filtrate, carboxylic acid is used to extract and separate beryllium. When titanium is contained in the filtrate, N1923 is used to extract and separate titanium; preferably, the tail liquid after extraction and separation is a mixed solution containing ammonium sulfate and sulfuric acid, which can be returned to the pretreatment slag system for reuse.

[0067] The features and properties of the present invention will be further described in detail below in conjunction with embodiments.

[0068] Example 1

[0069] The lithium slag used in this example is the lithium slag produced by a lithium carbonate production enterprise in Jiangsu, and the analysis results of its chemical composition are shown in Table 1.

[0070] Table 1. Analysis results of the chemical composition of lithium slag (wt%)

[0071] Chemical components <![CDATA[Al2O3]]> <![CDATA[SiO2]]> <![CDATA[Fe2O3]]> MgO CaO <![CDATA[TiO2]]> <![CDATA[K2O]]> <![CDATA[Na2O]]> <![CDATA[Li2O]]> LOI Others Content 24.19 68.38 0.83 0.25 0.47 0.08 0.48 0.23 0.18 3.82 1.09

[0072] The specific process flow is as follows:

[0073] Take a certain amount of lithium slag and first perform pretreatment by weak magnetic + strong magnetic. The weak magnetic field intensity is 0.3 T, and the strong magnetic field intensity is 1.2 T. The content of Fe2O3 in the pretreated slag is 0.34%.

[0074] Prepare a mixed solution of sulfuric acid and ammonium sulfate, where the molar concentration of sulfuric acid is 6 mol / L, the molar concentration of ammonium sulfate is 2 mol / L, and the molar ratio of sulfuric acid to ammonium sulfate is 3:1; the solid-liquid ratio of the pretreated slag to the mixed solution (the volume ratio of the pretreated slag to the mixed solution of sulfuric acid and ammonium sulfate) is 1:2 (g:mL) for mixing, and it is ground to 95% of -25 μm using a nano sand mill. The obtained mixed slurry is subjected to hydrothermal reaction at a reaction temperature of 120 °C for 2 h. After the reaction, solid-waste separation is directly carried out to obtain silicon slag and ammonium aluminum sulfate solution. The silicon slag is subjected to microwave treatment with a microwave treatment power of 600 W, a treatment time of 2 h, and a treatment temperature of 60 °C to prepare a filter aid, and the specific resistance of the filter aid cake is measured to be 4.7×10 11 m / kg. Cooling crystallization is carried out on the ammonium aluminum sulfate solution to obtain ammonium aluminum sulfate crystals, where the cooling rate is 5 °C / min, the cooling crystallization temperature is 10 °C, the stirring speed is 200 r / min, and the crystallization time is 2 h. The ammonium aluminum sulfate crystals are recrystallized and purified to obtain ammonium aluminum sulfate products with a product purity of 99.3%.

[0075] The filtrate after aluminum removal is used to form an organic phase with the extractant t-BAMBP and a diluent by extraction method, the organic phase ratio O / A = 1:1, the extractant concentration is 1 mol / L, the extraction time is 5 min. After extraction, the organic phase and the aqueous phase are separated, and a secondary countercurrent stripping is carried out under the condition of pH = 13 to obtain a rubidium- and cesium-rich solution. The extraction rates of cesium and rubidium are 98.68% and 66.37% respectively, the stripping rates of cesium and rubidium are 97.69% and 98.52% respectively, and the comprehensive recovery rates of cesium and rubidium are 96.40% and 65.39% respectively. The tail liquid after extracting valuable elements is all returned to the pretreated slag operation for recycling.

[0076] Example 2

[0077] The lithium slag used in this example is still the lithium slag produced by a certain lithium carbonate production enterprise in Jiangsu used in Example 1.

[0078] The specific process flow is as follows:

[0079] Take a certain amount of lithium slag, first carry out pretreatment by gravity separation + high-intensity magnetic separation. Gravity separation is carried out using a spiral chute, and the high-intensity magnetic separation intensity is 1.5 T. The content of Fe2O3 in the pretreated slag is 0.36%.

[0080] Prepare a mixed solution of sulfuric acid and ammonium sulfate, where the molar concentration of sulfuric acid is 6 mol / L, the molar concentration of ammonium sulfate is 1.5 mol / L, and the molar ratio of sulfuric acid to ammonium sulfate is 4:1; mix the pretreated slag with the mixed solution at a solid-liquid ratio (the volume ratio of the pretreated slag to the mixed solution of sulfuric acid and ammonium sulfate) of 1:3 (g:mL), and grind it with a stirred mill to 96% passing -25 μm. Obtain the mixed slurry for hydrothermal reaction, with the reaction temperature at 150 °C and the reaction time of 1 h. After the reaction, directly conduct solid-waste separation to obtain silicon slag and ammonium aluminum sulfate solution. Microwave-treat the silicon slag with a microwave power of 500 W, a treatment time of 3 h, and a treatment temperature of 80 °C to prepare a filter aid, and measure the specific resistance of the filter aid cake to be 5.1×10 11 m / kg. Cool and crystallize the ammonium aluminum sulfate solution to obtain ammonium aluminum sulfate crystals, where the cooling rate is 3 °C / min, the cooling crystallization temperature is 15 °C, the stirring speed is 300 r / min, and the crystallization time is 1 h. Recrystallize and purify the ammonium aluminum sulfate crystals to obtain ammonium aluminum sulfate products with a product purity of 99.2%.

[0081] For the filtrate after aluminum removal, use an extraction method with an organic phase composed of an extractant t-BAMBP and a diluent, with an organic phase ratio O / A = 1:1, an extractant concentration of 1.2 mol / L, an extraction time of 7 min. After extraction, separate the organic phase and the aqueous phase, and perform a secondary countercurrent stripping under the condition of pH = 13.5 to obtain a rich rubidium and cesium solution. The extraction rates of cesium and rubidium are 98.41% and 65.84% respectively, the stripping rates of cesium and rubidium are 98.13% and 98.65% respectively, and the comprehensive recovery rates of cesium and rubidium are 96.57% and 64.95% respectively. The tail liquid after extracting valuable elements is all returned to the pretreated slag operation for recycling.

[0082] Example 3

[0083] The lithium slag used in this example is the lithium slag produced by a lithium carbonate production enterprise in Sichuan, and the analysis results of its chemical composition are shown in Table 2.

[0084] Table 2 Analysis results of the chemical composition of lithium slag (wt%)

[0085] Chemical components <![CDATA[Al2O3]]> <![CDATA[SiO2]]> <![CDATA[Fe2O3]]> MgO CaO <![CDATA[TiO2]]> <![CDATA[K2O]]> <![CDATA[Na2O]]> <![CDATA[Li2O]]> LOI Others Content 23.67 66.21 0.82 0.27 0.46 0.10 0.68 0.45 0.20 3.69 3.45

[0086] The specific process flow is as follows:

[0087] Take a certain amount of lithium slag, first perform pretreatment by gravity separation + magnetic separation. The gravity separation is carried out with a shaking table, and the magnetic separation intensity is 1.5 T. The content of Fe2O3 in the pretreated slag is 0.33%.

[0088] Prepare a mixed solution of sulfuric acid and ammonium sulfate, where the molar concentration of sulfuric acid is 8 mol / L, the molar concentration of ammonium sulfate is 2 mol / L, and the molar ratio of sulfuric acid to ammonium sulfate is 4:1; the solid-liquid ratio of the pretreatment residue to the mixed solution (the volume ratio of the pretreatment residue to the mixed solution of sulfuric acid and ammonium sulfate) is 1:2 (g:mL) for mixing, and it is ground to 95% passing through -25 μm using a stirred mill. The obtained mixed slurry is subjected to hydrothermal reaction at a reaction temperature of 100 °C for 2 h. After the reaction, solid-waste separation is directly carried out to obtain silicon slag and ammonium alum solution. The silicon slag is subjected to microwave treatment with a microwave treatment power of 700 W, a treatment time of 1 h, and a treatment temperature of 70 °C to prepare a filter aid, and the specific resistance of the filter aid cake is measured to be 4.4×10 11 m / kg. Cooling crystallization is carried out on the ammonium alum solution to obtain ammonium alum crystals, where the cooling rate is 6 °C / min, the cooling crystallization temperature is 5 °C, the stirring speed is 300 r / min, and the crystallization time is 2 h. The ammonium alum crystals are recrystallized and purified to obtain ammonium alum products with a product purity of 99.4%.

[0089] The filtrate after aluminum removal uses an extraction method with an organic phase composed of an extractant t-BAMBP and a diluent, the organic phase ratio O / A = 1:1, the extractant concentration is 1.5 mol / L, the extraction time is 3 min. After the extraction, the organic phase and the aqueous phase are separated, and a secondary countercurrent stripping is carried out under the condition of pH = 13.2 to obtain a rich rubidium and cesium solution. The extraction rates of cesium and rubidium are 98.85% and 66.37% respectively, the stripping rates of cesium and rubidium are 98.31% and 98.92% respectively, and the comprehensive recovery rates of cesium and rubidium are 97.18% and 65.65% respectively. The tail liquid after extracting valuable elements is all returned to the pretreatment residue operation for recycling.

[0090] Example 4

[0091] The lithium slag used in this example is still the lithium slag produced by a certain lithium carbonate production enterprise in Sichuan used in Example 3.

[0092] The specific process flow is as follows:

[0093] Take a certain amount of lithium slag and first perform pretreatment using weak magnetic + strong magnetic. The weak magnetic separation intensity is 0.2 T, and the strong magnetic separation intensity is 1.4 T, and the content of Fe2O3 in the pretreatment residue is 0.38%.

[0094] Prepare a mixed solution of sulfuric acid and ammonium sulfate, where the molar concentration of sulfuric acid is 6 mol / L, the molar concentration of ammonium sulfate is 2 mol / L, and the molar ratio of sulfuric acid to ammonium sulfate is 3:1; the solid-liquid ratio of the pretreatment residue to the mixed solution (the volume ratio of the pretreatment residue to the mixed solution of sulfuric acid and ammonium sulfate) is 1:4 (g:mL) for mixing, and it is ground to 92% passing -25 μm using a stirred mill. The obtained mixed slurry is subjected to hydrothermal reaction at a reaction temperature of 200 °C for 0.5 h. After the reaction, solid-liquid separation is directly carried out to obtain silicon slag and ammonium alum solution. The silicon slag is subjected to microwave treatment with a microwave power of 600 W, a treatment time of 2 h, and a treatment temperature of 60 °C to prepare a filter aid, and the specific resistance of the filter aid cake is measured to be 5.3×10 11 m / kg. Cooling crystallization is carried out on the ammonium alum solution to obtain ammonium alum crystals, where the cooling rate is 5 °C / min, the cooling crystallization temperature is 10 °C, the stirring speed is 200 r / min, and the crystallization time is 2 h. The ammonium alum crystals are recrystallized and purified to obtain ammonium alum products with a product purity of 99.1%.

[0095] The filtrate after aluminum removal is subjected to extraction using an organic phase composed of an extractant t-BAMBP and a diluent, with an organic phase ratio O / A = 1:1, an extractant concentration of 1.0 mol / L, an extraction time of 10 min. After extraction, the organic phase and the aqueous phase are separated, and a secondary countercurrent stripping is carried out under the condition of pH = 13.5 to obtain a rich rubidium and cesium solution. The extraction rates of cesium and rubidium are 99.13% and 68.32% respectively, the stripping rates of cesium and rubidium are 98.46% and 98.71% respectively, and the comprehensive recovery rates of cesium and rubidium are 97.60% and 67.44% respectively. The tail liquid after extracting valuable elements is all returned to the pretreatment residue operation for recycling.

[0096] Comparative Example 1

[0097] Compared with Example 1, the difference is that the silicon slag obtained after solid-liquid separation is not subjected to microwave treatment and is directly used as a filter aid product. The specific resistance of the filter aid cake is measured to be 6.7×10 9 m / kg, and the purity of the ammonium alum product prepared is 99.4%.

[0098] Comparative Example 2

[0099] Compared with Example 1, the difference is that the ammonium alum crystals are not subjected to recrystallization and purification treatment. The indexes of the filter aid and the ammonium alum product are measured. The specific resistance of the filter aid cake is 4.4×10 11 m / kg, and the purity of the ammonium alum product prepared is 96.7%.

[0100] Comparative Example 3

[0101] Compared with Example 1, the difference is that in this comparative example, the lithium slag was not pretreated and was directly mixed and ground with a mixed solution of ammonium sulfate and sulfuric acid. The indexes of the filter aid and ammonium alum products were measured. The specific resistance of the filter aid filter cake was 3.5×10 10 m / kg, and the purity of the ammonium alum product prepared was 97.5%.

[0102] Comparative Example 4

[0103] Compared with Example 1, the difference is that in this comparative example, ammonium chloride was used instead of ammonium sulfate, and the prepared aluminum salt was a mixed aluminum salt of aluminum chloride and ammonium alum. The silicon slag was treated by microwave to prepare a filter aid. The indexes of the filter aid and aluminum salt products were measured. The specific resistance of the filter aid filter cake was 6.7×10 9 m / kg, and the purity of the ammonium alum product prepared was 84.3%.

[0104] Comparative Example 5

[0105] Compared with Example 1, the difference is that in this comparative example, the lithium slag raw material was the lithium slag produced by extracting lithium from lepidolite by a certain lithium carbonate production enterprise in Jiangxi. The chemical composition analysis results are shown in Table 3.

[0106] Table 3 Chemical composition analysis results of lithium slag (wt%)

[0107]

[0108] It can be seen from Table 3 that the contents of SiO2 and Al2O3 are significantly lower than the requirements for lithium slag in the present invention. At the same time, the contents of Fe2O3, CaO, SO3, K2O and Na2O are significantly greater than the requirements for lithium slag in the present invention. By using the above lithium slag to prepare a filter aid and an aluminum salt product, it was detected that the filter aid prepared with this lithium slag had no filter aid effect, a large amount of calcium sulfate with unstable properties was contained in the product, and the purity of the ammonium alum product prepared was only 93.2%. This fully proves that when the chemical composition of the lithium slag is not within the scope of the present invention, it is impossible to prepare qualified filter aid and aluminum salt products by using the above scheme.

[0109] Comparative Example 6

[0110] Compared with Example 1, the difference is that in this comparative example, it was ground to -25μm with 80% by a nano mill. The obtained mixed slurry was subjected to a hydrothermal reaction at a reaction temperature of 50°C and a reaction time of 6h. After the reaction, solid waste separation was directly carried out to obtain silicon slag and ammonium alum solution. The silicon slag was treated by microwave to prepare a filter aid; the ammonium alum solution was cooled and crystallized to obtain ammonium alum crystals, and the ammonium alum crystals were recrystallized to obtain ammonium alum products. The indexes of the filter aid and aluminum salt products were measured. The specific resistance of the filter aid filter cake was 7.8×10 8 m / kg, and the purity of the ammonium alum product prepared was 99.5%.

[0111] By changing the grinding fineness and the hydrothermal reaction temperature, the influence on the purity of ammonium aluminum sulfate product is relatively small. However, due to insufficient hydrothermal reaction temperature, even though the reaction time is increased, there is still a certain amount of undissolved aluminum salt in the silicon slag, resulting in a decline in the quality of the produced filter aid, and the specific resistance of the filter aid filter cake is significantly reduced.

[0112] In summary, the method for simultaneously preparing a filter aid and an aluminum salt using lithium slag provided by the present invention uses the lithium tailings slag from spodumene lithium extraction as a raw material. Through pretreatment, substances with magnetism and / or high specific gravity in the lithium slag can be removed to avoid affecting subsequent products. By mixing and grinding the pretreated slag with a mixed solution of ammonium sulfate and sulfuric acid, the valuable components in the lithium slag can be efficiently and environmentally utilized under hydrothermal reaction to prepare a filter aid and an aluminum salt with excellent performance, realizing the recycling of resources, which has important practical significance and broad application prospects. In addition, the present invention can also comprehensively recover valuable metal elements such as rubidium, cesium, titanium, and beryllium to improve resource utilization rate. This method adopts a process combining mineral processing and chemical engineering, without three-waste emissions, and has a simple process, mild conditions and is easy to implement. The ammonium aluminum sulfate prepared by this method has high purity, and the filter aid filter cake has a large specific resistance, broadening the application range of the product. This method can reduce the stacking and landfill of lithium slag, avoid environmental pollution of its harmful components to soil, water bodies, etc., meets the requirements of sustainable development, and has significant economic and social benefits.

[0113] The above are only the preferred embodiments of the present invention and are not used to limit the present invention. For those skilled in the art, the present invention can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for simultaneously preparing a filter aid and an aluminum salt using lithium slag, characterized in that, It includes: S1: Pretreat the lithium slag to remove substances with magnetism and / or high specific gravity in the lithium slag, obtaining pretreated slag and pretreated material; S2: Mix and grind a mixed solution of ammonium sulfate and sulfuric acid with the pretreated slag to obtain a mixed slurry; S3: Conduct a hydrothermal reaction on the mixed slurry and perform solid-liquid separation to obtain silicon slag and ammonium aluminum sulfate solution; S4: Conduct microwave treatment on the silicon slag to obtain a filter aid; S5: Cool and crystallize the ammonium aluminum sulfate solution to obtain ammonium aluminum sulfate crystals and a filtrate; S6: Recrystallize and purify the ammonium aluminum sulfate crystals to prepare ammonium aluminum sulfate.

2. The method for simultaneously preparing a filter aid and an aluminum salt using lithium slag according to claim 1, wherein, The lithium slag is a weakly acidic slag obtained by subjecting spodumene to crystal transformation calcination, acid roasting, leaching, and stirring and washing; the chemical composition of the lithium slag is: SiO2 60 - 70 wt%, Al2O3 22 - 26 wt%, Fe2O3 0.5 - 1.5 wt%, CaO 0.2 - 0.5 wt%, SO3 0.1 - 0.5 wt%, and the combined content of K2O and Na2O is 0.5 - 1.50 wt%.

3. The method for simultaneously preparing a filter aid and an aluminum salt using lithium slag according to claim 1, wherein The pretreatment includes one or more of magnetic separation and gravity separation; Preferably, the magnetic separation includes one or more of weak magnetic separation and strong magnetic separation, and the magnetic field intensity is 0.2 - 1.8 T; Preferably, the gravity separation includes one or more of a spiral chute, a shaking table, and a jigger.

4. The method for simultaneously preparing a filter aid and an aluminum salt using lithium slag according to claim 1, characterized in that, The yield of the pretreated material is 3% - 15%, and the chemical composition of the pretreated material is: SiO2 55 - 60 wt%, Al2O3 17 - 21 wt%, Fe2O3 3.0 - 8.0 wt%, CaO 1.0 - 3.0 wt%, SO3 0.05 - 0.3 wt%, and the combined content of K2O and Na2O is 0.6 - 1.5 wt%; And / or, the yield of the pretreated slag is 85 - 97%, and the chemical composition of the pretreated slag is: SiO2 65 - 75 wt%, Al2O3 22 - 26 wt%, Fe2O3 0.2 - 0.50 wt%, CaO 0.1 - 0.4 wt%, SO3 0.05 - 0.3 wt%, and the combined content of K2O and Na2O is 0.4 - 0.8 wt%.

5. The method for simultaneously preparing a filter aid and an aluminum salt using lithium slag according to claim 1, characterized in that, In the mixed solution, the molar concentration of ammonium sulfate is 0.5 - 3 mol / L, and the molar concentration of sulfuric acid is 1.5 - 10 mol / L; and the molar ratio of ammonium sulfate to sulfuric acid is 1:3 - 1:5; Preferably, the mass ratio of the pretreated slag to the volume of the mixed solution is 1 g:1 mL - 1 g:5 mL.

6. The method for simultaneously preparing a filter aid and an aluminum salt using lithium slag according to claim 1, characterized in that, The equipment for grinding is one or more of a porcelain-lined ball mill, a stirring mill, and a nano sand mill; the fineness of the mixed slurry with a particle size below 25 μm accounts for 90 - 98%.

7. The method for simultaneously preparing a filter aid and an aluminum salt using lithium slag according to claim 1, wherein The temperature of the hydrothermal reaction is 60 - 200 °C, and the reaction time is 0.5 - 3 h; And / or, the solid-liquid separation includes one or more of gravity sedimentation, centrifugation, and pressure filtration; And / or, the SiO2 content in the silicon slag is ≥95 wt%, and the concentration of the ammonium aluminum sulfate solution is 0.5 - 1.5 mol / L.

8. The method for simultaneously preparing a filter aid and an aluminum salt using lithium slag according to claim 1, wherein The power of the microwave treatment is 400 - 800 W, the microwave treatment time is 0.5 - 4 h, and the treatment temperature is 40 - 80 °C; And / or, the temperature of the cooling crystallization is 0 to 20 °C, the stirring speed is 100 to 400 r / min, the cooling rate is 1 °C / min to 10 °C / min, and the crystallization time is 0.5 to 4 h; And / or, the purity of ammonium aluminum sulfate after recrystallization purification is > 99%.

9. The method for simultaneously preparing a filter aid and an aluminum salt using lithium slag according to claim 1, wherein, The method further includes step S7: recovering valuable metal elements from the filtrate by solvent extraction method in steps.

10. The method for simultaneously preparing a filter aid and an aluminum salt using lithium slag according to claim 9, characterized in that, The solvent extraction method includes adopting different extraction and separation techniques according to different valuable metal elements in the solution. When rubidium and cesium are contained in the filtrate, BAMBP is used to extract and separate rubidium and cesium. When beryllium is contained in the filtrate, carboxylic acid is used to extract and separate beryllium. When titanium is contained in the filtrate, N1923 is used to extract and separate titanium; Preferably, the tail liquid after extraction and separation is a mixed solution containing ammonium sulfate and sulfuric acid, which can be returned to the pretreatment slag system for reuse.

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