A method for preparing amorphous silicon-aluminum based oxides using lithium slag and the product thereof.

Abstract

This invention discloses a method for preparing amorphous silicon-aluminum based oxides from lithium slag and the resulting product, relating to the field of lithium slag recycling technology. The method employs a pH-controllable acetate buffer system as a precipitation regulator and precisely controls the pumping rate of the precipitation regulator into the lithium slag acid leaching solution. This significantly improves the problem of simultaneous and disordered precipitation of various metal hydroxides and silicon-aluminum compounds due to drastic local pH changes during precipitation, resulting in high impurity content in the amorphous silicon-aluminum based oxide product. Furthermore, it maintains the overall pH of the precipitation system within the optimal precipitation window for silicic acid and aluminum hydroxide, leading to more thorough precipitation of silicon-aluminum compounds in the lithium slag and significantly increasing the yield of silicon-aluminum compounds. This method offers advantages such as high yield, high purity, adjustable silicon-aluminum ratio in the product, and a simple, mild, and controllable preparation process, making it suitable for large-scale preparation of amorphous silicon-aluminum based oxides.

Description

Technical Field

[0001] This invention relates to the field of industrial solid waste treatment technology, mainly to the field of lithium slag recycling technology, and specifically to a method for preparing amorphous silicon-aluminum based oxides using lithium slag and the product thereof. Background Technology

[0002] Lithium slag refers to the solid waste generated during the lithium extraction process from lithium ore. Typically, producing one ton of lithium salt generates approximately 8-10 tons of lithium slag. With the rapid development of global industries such as new energy vehicles and energy storage batteries, the demand for lithium resources has surged, leading to a continuous increase in lithium slag emissions. Statistics show that my country's annual lithium slag emissions exceed 15 million tons, occupying a large amount of land resources and posing a risk of leachate pollution to water and soil.

[0003] Currently, the main applications of lithium slag are concentrated in the building materials sector, such as its use as a concrete admixture or roadbed material. However, these applications limit the amount of lithium slag consumed and have low added value, failing to fully realize the potential value of lithium slag. Furthermore, the composition of lithium slag fluctuates significantly due to the influence of raw materials and production processes, and its comprehensive utilization is often limited by the uncontrollable nature of raw materials, resulting in poor universality of utilization methods.

[0004] The lithium slag produced by existing acid roasting processes contains over 60% silicon-aluminum compounds, demonstrating its potential for producing high-value-added silicon-aluminum materials. Amorphous silicon-aluminum-based oxides can be used in industries such as ceramics, glass, and construction, and can also be used as high-performance materials such as catalysts, adsorbents, and functional fillers. They possess advantages such as high specific surface area, abundant pore structure, and tunable surface acidity. The preparation of traditional silicon-aluminum-based oxides usually relies on chemical raw materials (such as sodium silicate and aluminum salts), which is costly. However, utilizing the silicon-aluminum components in lithium slag for green production can achieve resource utilization of solid waste and reduce production costs, which is conducive to the large-scale promotion and application of silicon-aluminum-based oxides.

[0005] Patent CN115448318A discloses a comprehensive recycling method for extracting silicon and aluminum from lithium slag. The method first involves dilute acid leaching of the lithium slag to extract and enrich fluorine and lithium from it, followed by concentrated acid leaching to obtain a high-purity aluminum-containing solution. The aluminum-containing solution is then further treated with aluminum precipitation to obtain a high-quality aluminum hydroxide product. The filtrate from the aluminum precipitation is evaporated to obtain a rubidium sulfate-containing product. The lithium slag after acid leaching is then treated with alkali to obtain a silicate solution. The silicate solution reacts with CO2 to produce a high-quality precipitated silica product. The slag phase obtained from the alkali treatment mainly contains insoluble minerals such as quartz silicon and spodumene, which can be used as building material raw materials.

[0006] Patent CN111670260A discloses a process for extracting valuable substances from lithium slag, the process comprising: (a) hydrothermally treating the lithium slag with an aqueous solution of an alkaline compound at a selected temperature and duration; (b) performing an ion exchange step on the alkaline-treated lithium slag; and (c) recovering valuable substances selected from the group consisting of aluminum compounds, silicon compounds, and compounds containing silicon and aluminum.

[0007] Patent CN119569077A discloses a method for preparing lithium slag-based molecular sieves from eutectic salt-assisted molten lithium slag. The method involves acid washing pretreatment of lithium slag raw materials to obtain pretreated lithium slag; co-grinding and mixing the pretreated lithium slag with eutectic salt to obtain uniformly, and reacting at 200~350℃ for 2~6 hours to obtain eutectic lithium slag; then, after aging and crystallization treatment of the eutectic lithium slag, solid-liquid separation is performed, the solid is washed until neutral, and dried to obtain lithium slag-based molecular sieves.

[0008] However, while existing technologies can obtain silicon-aluminum compounds from lithium slag, unreasonable process steps and parameter design (e.g., using strong acids and bases to promote the precipitation of reactants, causing drastic local pH changes in the system, leading to the simultaneous and disordered precipitation of various metal hydroxides (such as Fe, Ca, Mg, etc.) with silicon-aluminum compounds, forming a complex mixture) prevent the direct preparation of high-purity, high-yield amorphous silicon-aluminum-based oxides with an adjustable silicon-aluminum ratio. Therefore, developing a process for preparing high-purity, high-yield amorphous silicon-aluminum-based oxides from lithium slag can effectively broaden the utilization pathways of lithium slag, realize the resource-based and high-value utilization of solid waste, and is of great significance for promoting the circular economy and sustainable development. Summary of the Invention

[0009] The purpose of this invention is to overcome the problem that existing technologies cannot directly prepare amorphous silicon-aluminum-based oxides with high purity, high yield, and adjustable silicon-aluminum ratio. This invention proposes a method for preparing amorphous silicon-aluminum-based oxides using lithium slag and the resulting products.

[0010] To achieve the above-mentioned objective, this invention proposes a method for preparing amorphous silicon-aluminum based oxides using lithium slag, comprising the following steps:

[0011] (1) Pretreatment: The lithium slag is dried, crushed and sieved to obtain lithium slag powder;

[0012] (2) Low temperature activation: After mixing and grinding lithium slag powder with strong alkali at a mass ratio of 1:0.5~1.5, the mixture is activated at 100~300℃ for 1~3h to obtain activated lithium slag;

[0013] (3) Acid leaching to remove impurities: The activated lithium slag is mixed with hydrochloric acid solution at a solid-liquid ratio of 1:5~20 (g / ml) and dissolved. After the dissolution reaction is completed, ascorbic acid is added to carry out a reduction reaction. After the reduction reaction is completed, the solid and liquid are separated to obtain the lithium slag acid leaching solution.

[0014] (4) Buffer precipitation: The lithium slag acid leaching solution is slowly injected into a continuously stirred buffer solution to carry out the precipitation reaction. After the precipitation reaction is completed, the solid and liquid are separated, and the solid phase is washed and dried to obtain amorphous silicon aluminum-based oxide.

[0015] This invention discloses a method for preparing amorphous silica-alumina-based oxides using lithium slag. During the precipitation process, a pH-controllable acetate buffer system is used as a precipitation regulator, and the rate at which the precipitation regulator is pumped into the lithium slag acid leaching solution is precisely controlled. This significantly improves the problem of simultaneous and disordered precipitation of various metal hydroxides (such as Fe, Ca, Mg, etc.) and silica-alumina compounds due to drastic local pH changes during precipitation, resulting in high impurity content in the amorphous silica-alumina-based oxide product. Furthermore, it ensures that the overall pH of the precipitation system is maintained within the optimal precipitation window for silicic acid and aluminum hydroxide (through the reduction of iron ions to Fe by ascorbic acid). 2+ This method avoids intersecting precipitation windows between lithium slag and silicon / aluminum, thus ensuring more thorough precipitation of silicon / aluminum compounds in lithium slag and significantly improving the yield and purity of these compounds. Furthermore, by controlling the pH window of the acetate buffer system (where a silicon-rich product is obtained under low pH conditions, and the aluminum content dynamically increases with increasing pH), the silicon-aluminum ratio in the silicon-aluminum based oxide product can be accurately adjusted, meeting market demands for amorphous silicon / aluminum based oxides with varying silicon-aluminum ratios. This method for preparing amorphous silicon / aluminum based oxides using lithium slag offers advantages such as high yield, high purity, adjustable silicon-aluminum ratio in the product, and a simple, mild, and controllable preparation process, making it suitable for large-scale application in the preparation of amorphous silicon / aluminum based oxides.

[0016] In step (1), preferably, the lithium slag contains ≥30wt% silica, ≥10wt% alumina, and ≤5wt% Fe2O3; the preferred lithium slag composition has greater recycling value.

[0017] Preferably, the lithium slag is passed through a 200-mesh sieve; this is beneficial for the rapid and complete reaction between the lithium slag and the strong alkali.

[0018] In step (2), preferably, the strong alkali is sodium hydroxide and / or potassium hydroxide, which can better dissolve the silicon and aluminum elements in the lithium slag.

[0019] In step (3), preferably, the concentration of the hydrochloric acid solution is 1-3 mol / L, which can better dissolve the silicon and aluminum elements in the lithium slag.

[0020] Preferably, the temperature of the dissolution reaction is 50-70℃ and the time is 10-90 min; the energy consumption is low, the reaction efficiency is high, and the reaction is more thorough.

[0021] Preferably, the mass ratio of ascorbic acid to activated lithium slag is 1:15-30; this allows for better reduction of Fe. 3+ Ions, thus avoiding Fe during the precipitation of silicon and aluminum. 3+ Ions also precipitate at the same time, resulting in a large amount of iron ions in the product.

[0022] Preferably, the reduction reaction is carried out at a temperature of 20-70°C for 10-60 minutes; this method results in low energy consumption, high reaction efficiency, and more thorough precipitation of impurities.

[0023] Preferably, solid-liquid separation is performed by filtration or centrifugation; this method offers fast separation speed and good results.

[0024] In step (4), preferably, the buffer solution is an acetate-sodium acetate solution with a pH of 3.5-5.5 and a total concentration of 0.1-2 mol / L. The acetate buffer solution can maintain the stability of the pH of the system. It resists the drastic pH changes caused by the addition of a small amount of acid or base or dilution through the balance of conjugate acid-base pairs. The preferred pH value of the buffer solution can maintain the optimal window for silica-alumina precipitation, resulting in more thorough silica-alumina precipitation and lower impurity content.

[0025] Preferably, the volume ratio of the buffer solution to the lithium slag acid leaching solution is 5-30:1; this results in more thorough silicon-aluminum precipitation.

[0026] Preferably, the injection rate of the lithium slag acid leaching solution to the volume ratio of the buffer solution is 0.06~0.6 / min:1 (i.e., the injection rate of the lithium slag acid leaching solution in 1 unit of buffer solution is 0.06-0.6 units / min); the pH value is more stable during the precipitation process, which is conducive to maintaining the optimal window for silicon-aluminum precipitation, resulting in more thorough silicon-aluminum precipitation and lower impurity content.

[0027] Preferably, the stirring speed is 100-600 r / min; this can avoid excessively high local concentrations in the system, which would affect the purity of the product.

[0028] Preferably, the precipitation reaction is carried out at a temperature of 15-30°C for 5-30 minutes. If the precipitation reaction temperature is too high, the precipitation rate will increase, which will cause local pH changes in the system and affect the purity of the product.

[0029] Preferably, the pH value of the filtrate obtained from solid-liquid separation is adjusted (e.g., by adding NaOH or Na2CO2 to raise the pH to 10-11, at which point Mg will form Mg(OH)2 precipitate and Ca will form Ca(OH)2 / CaCO3 precipitate) to generate a precipitate. After separating the precipitate, the pH is adjusted to recover a buffer solution with almost no loss.

[0030] To further achieve the above-mentioned objectives, the present invention also proposes a product, which is an amorphous silicon-aluminum based oxide prepared by the above method; the amorphous silicon-aluminum based oxide product has high purity and an adjustable silicon-aluminum ratio, which can meet the customized needs of downstream products in industrial applications (such as molecular sieves, catalyst supports, and precursors for ceramic materials).

[0031] The beneficial effects of the technical solution of this invention are as follows:

[0032] 1. The present invention utilizes a method for preparing amorphous silicon-aluminum based oxides from lithium slag, which can significantly improve the problem of high impurity content in amorphous silicon-aluminum based oxide products caused by the simultaneous and disordered precipitation of various metal hydroxides (such as Fe, Ca, Mg, etc.) and silicon-aluminum compounds due to drastic changes in the local pH value of the system during the precipitation process.

[0033] 2. The method of preparing amorphous silicon-aluminum based oxides using lithium slag in this invention can maintain the overall pH value of the precipitation system at the optimal precipitation window of silicic acid and aluminum hydroxide, thereby making the precipitation of silicon-aluminum compounds in lithium slag more thorough and significantly improving the yield of silicon-aluminum compounds.

[0034] 3. The present invention utilizes a method for preparing amorphous silicon-aluminum based oxides from lithium slag. By controlling the pH window value of the acetate buffer system (a silicon-rich product can be obtained under low pH conditions, and the aluminum content in the product dynamically increases with increasing pH), the silicon-aluminum ratio in the silicon-aluminum based oxide product can be accurately adjusted, thereby meeting the market demand for amorphous silicon-aluminum based oxides with different silicon-aluminum ratios.

[0035] 4. The method of preparing amorphous silicon-aluminum based oxides using lithium slag in this invention has the advantages of high yield, high purity, adjustable silicon-aluminum ratio in the product, and simple, mild, and controllable preparation process, making it suitable for large-scale preparation of amorphous silicon-aluminum based oxides.

[0036] 5. The amorphous silicon-aluminum based oxide product of this invention has high purity and the silicon-aluminum ratio in the product is adjustable, which can meet the customized needs of downstream products in industrial applications (such as molecular sieves, catalyst supports, and precursors for ceramic materials). Attached Figure Description

[0037] Figure 1 The image shown is an XRD pattern of the lithium slag raw material in an embodiment of the present invention.

[0038] Figure 2 The image shows the XRD pattern of the amorphous silicon-aluminum based oxide prepared in Example 1 of this invention. Detailed Implementation

[0039] The specific embodiments of the present invention will be further described below with reference to examples, but the present invention is not limited to the scope of the embodiments described herein.

[0040] The specific composition of the lithium slag raw material used in the specific embodiments of the present invention is shown in Table 1 (XRD diagram as shown). Figure 1 (as shown)

[0041] Table 1 Composition of lithium slag raw materials

[0042]

[0043] Example 1

[0044] A method for preparing amorphous silicon-aluminum based oxides using lithium slag includes the following steps:

[0045] (1) Pretreatment: The lithium slag is dried, crushed and sieved (200 mesh) to obtain lithium slag powder;

[0046] (2) Low-temperature activation: Lithium slag powder and strong alkali (sodium hydroxide) are mixed and ground at a mass ratio of 1:1.2, and then activated in a muffle furnace at 200°C for 2 hours to obtain activated lithium slag;

[0047] (3) Acid leaching to remove impurities: The activated lithium slag is mixed with hydrochloric acid (2mol / L) solution at a solid-liquid ratio of 1:20 (g / ml) to dissolve (temperature 60℃, time 40min). After the dissolution reaction is completed, ascorbic acid (mass ratio of 1:20 to activated lithium slag) is added to carry out the reduction reaction (temperature 60℃, time 20min). After the reduction reaction is completed, the solid and liquid are separated (filtered) to obtain the lithium slag acid leaching solution.

[0048] (4) Buffer precipitation: The lithium slag acid leaching solution was slowly (volume ratio of 0.3 / min:1 to the buffer solution) injected into a continuously stirred (300 r / min) buffer solution (pH value 5, total concentration 1M acetate-sodium acetate solution, volume ratio of 10:1 to the lithium slag acid leaching solution) to carry out the precipitation reaction (temperature 25℃, time 15min). After the precipitation reaction was completed, the solid and liquid were separated, and the solid phase was washed and dried to obtain amorphous silicon-aluminum based oxide (XRD pattern as shown). Figure 2 (As shown).

[0049] Example 2

[0050] A method for preparing amorphous silicon-aluminum based oxides using lithium slag includes the following steps:

[0051] (1) Pretreatment: The lithium slag is dried, crushed and sieved (200 mesh) to obtain lithium slag powder;

[0052] (2) Low-temperature activation: Lithium slag powder and strong alkali (sodium hydroxide) are mixed and ground at a mass ratio of 1:1, and then activated at 300℃ for 1 hour to obtain activated lithium slag;

[0053] (3) Acid leaching to remove impurities: The activated lithium slag is mixed with hydrochloric acid (3mol / L) solution at a solid-liquid ratio of 1:5 (g / ml) to dissolve (temperature 50℃, time 90min). After the dissolution reaction is completed, ascorbic acid (mass ratio of 1:15 to activated lithium slag) is added to carry out the reduction reaction (temperature 50℃, time 30min). After the reduction reaction is completed, the solid and liquid are separated (filtered) to obtain the lithium slag acid leaching solution.

[0054] (4) Buffer precipitation: The lithium slag acid leaching solution was slowly injected (volume ratio of 0.06 / min:1 to buffer solution) into a continuously stirred (100r / min) buffer solution (pH value of 4, total concentration of 2M acetic acid-sodium acetate solution, volume ratio of 20:1 to lithium slag acid leaching solution) to carry out precipitation reaction (temperature of 15℃, time of 30min). After the precipitation reaction was completed, the solid and liquid were separated, and the solid phase was washed and dried to obtain amorphous silicon aluminum-based oxide.

[0055] Example 3

[0056] A method for preparing amorphous silicon-aluminum based oxides using lithium slag includes the following steps:

[0057] (1) Pretreatment: The lithium slag is dried, crushed and sieved (200 mesh) to obtain lithium slag powder;

[0058] (2) Low-temperature activation: Lithium slag powder and strong alkali (sodium hydroxide) are mixed and ground at a mass ratio of 1:0.8, and then activated at 300℃ for 1 hour to obtain activated lithium slag;

[0059] (3) Acid leaching to remove impurities: The activated lithium slag is mixed with hydrochloric acid (1mol / L) solution at a solid-liquid ratio of 1:10 (g / ml) to dissolve (temperature is 70℃, time is 10min). After the dissolution reaction is completed, ascorbic acid (mass ratio of activated lithium slag is 1:30) is added to carry out the reduction reaction (temperature is 30℃, time is 10min). After the reduction reaction is completed, the solid and liquid are separated (filtered) to obtain the lithium slag acid leaching solution.

[0060] (4) Buffer precipitation: The lithium slag acid leaching solution was slowly (volume ratio of 0.6 / min to buffer solution was 1) injected into a continuously stirred (600 r / min) buffer solution (pH value of 3.5, total concentration of 0.5M acetic acid-sodium acetate solution, volume ratio of 30:1 to lithium slag acid leaching solution) to carry out precipitation reaction (temperature of 30℃, time of 5min). After the precipitation reaction was completed, the solid and liquid were separated, and the solid phase was washed and dried to obtain amorphous silicon aluminum-based oxide.

[0061] Comparative Example 1

[0062] A method for preparing amorphous silicon-aluminum based oxides using lithium slag is similar to that in Example 1, except that: (3) activated lithium slag is mixed and dissolved with hydrochloric acid (2mol / L) solution at a solid-liquid ratio of 1:20 (g / ml) (temperature is 60℃, time is 40min). After the dissolution reaction is completed, solid and liquid are separated (filtered) to obtain lithium slag acid leaching solution.

[0063] Comparative Example 2

[0064] A method for preparing amorphous silicon-aluminum based oxides using lithium slag is similar to that in Example 1, except that: (4) the lithium slag acid leaching solution is slowly (volume ratio of 0.3 / min:1 with buffer solution) injected into a continuously stirred (300r / min) buffer solution (pH value of 5, total concentration of 1M phosphate buffer solution, volume ratio of 10:1 with lithium slag acid leaching solution) to carry out a precipitation reaction (temperature of 25℃, time of 15min). After the precipitation reaction is completed, the solid and liquid are separated, and the solid phase is washed and dried to obtain amorphous silicon-aluminum based oxides.

[0065] Comparative Example 3

[0066] A method for preparing amorphous silicon-aluminum based oxides using lithium slag is similar to that in Example 1, except that: (4) the lithium slag acid leaching solution is slowly (volume ratio of 0.3 / min:1 to buffer solution) injected into a continuously stirred (300r / min) buffer solution (pH value of 5, chloride ion concentration of 1M hydrochloric acid-sodium chloride solution, volume ratio of 10:1 to lithium slag acid leaching solution) for precipitation reaction (temperature of 25℃, time of 15min). After the precipitation reaction is completed, the solid and liquid are separated, and the solid phase is washed and dried to obtain amorphous silicon-aluminum based oxides.

[0067] Comparative Example 4

[0068] A method for preparing amorphous silicon-aluminum based oxides using lithium slag is similar to that in Example 1, except that: (4) the lithium slag acid leaching solution is directly mixed with a buffer solution (pH value of 5, total concentration of 1M acetic acid-sodium acetate solution, volume ratio of 10:1 to lithium slag acid leaching solution) to carry out a precipitation reaction (temperature of 25℃, time of 15min). After the precipitation reaction is completed, the solid and liquid are separated, and the solid phase is washed and dried to obtain amorphous silicon-aluminum based oxides.

[0069] Comparative Example 5

[0070] A method for preparing amorphous silicon-aluminum based oxides using lithium slag is similar to that in Example 1, except that: (4) a buffer solution (pH value of 5, total concentration of 1M acetic acid-sodium acetate solution, volume ratio of 10:1 to lithium slag acid leaching solution) is slowly (injection rate: 1 unit / min of buffer solution is injected into every 0.3 units of lithium slag acid leaching solution) into the continuously stirred (300r / min) lithium slag acid leaching solution to carry out a precipitation reaction (temperature of 25℃, time of 15min). After the precipitation reaction is completed, the solid and liquid are separated, and the solid phase is washed and dried to obtain amorphous silicon-aluminum based oxides.

[0071] Comparative Example 6

[0072] A method for preparing amorphous silicon-aluminum based oxides using lithium slag is similar to that in Example 1, except that: (4) the lithium slag acid leaching solution is slowly (volume ratio of 0.8 / min:1 with buffer solution) injected into a continuously stirred (300r / min) buffer solution (pH value of 5, total concentration of 1M acetic acid-sodium acetate solution, volume ratio of 10:1 with lithium slag acid leaching solution) to carry out a precipitation reaction (temperature of 25℃, time of 15min). After the precipitation reaction is completed, the solid and liquid are separated, and the solid phase is washed and dried to obtain amorphous silicon-aluminum based oxides.

[0073] Comparative Example 7

[0074] A method for preparing amorphous silicon-aluminum based oxides using lithium slag is similar to that in Example 1, except that: (4) the lithium slag acid leaching solution is slowly (volume ratio of 0.3 / min:1 with buffer solution) injected into a continuously stirred (300r / min) buffer solution (pH value of 3, total concentration of 1M acetic acid-sodium acetate solution, volume ratio of 10:1 with lithium slag acid leaching solution) to carry out a precipitation reaction (temperature of 25℃, time of 15min). After the precipitation reaction is completed, the solid and liquid are separated, and the solid phase is washed and dried to obtain amorphous silicon-aluminum based oxides.

[0075] Comparative Example 8

[0076] A method for preparing amorphous silicon-aluminum based oxides using lithium slag is similar to that in Example 1, except that: (4) the lithium slag acid leaching solution is slowly (volume ratio of 0.3 / min:1 with buffer solution) injected into a continuously stirred (300r / min) buffer solution (pH value of 6, total concentration of 1M acetic acid-sodium acetate solution, volume ratio of 10:1 with lithium slag acid leaching solution) to carry out a precipitation reaction (temperature of 25℃, time of 15min). After the precipitation reaction is completed, the solid and liquid are separated, and the solid phase is washed and dried to obtain amorphous silicon-aluminum based oxides.

[0077] Experimental example:

[0078] Silicon-aluminum based oxides were extracted from lithium slag raw material 1 and lithium slag raw material 2 using the methods in Examples 1-3 and Comparative Examples 1-9, respectively. The dissolution rate of silicon and aluminum elements in lithium slag, the extraction rate of silicon and aluminum elements in lithium slag, and the content of impurities in silicon-aluminum based compound products were detected, respectively. The results are shown in Tables 2 and 3.

[0079] Table 2. Extraction of silicon-aluminum based oxides from lithium slag feedstock 1

[0080]

[0081] Note: Comparative Examples 1-8 are subsequent experiments conducted based on the activated lithium slag obtained in step 2 of Example 1.

[0082] Table 3. Extraction of silicon-aluminum oxides from lithium slag feedstock 2

[0083]

[0084] Note: Comparative Examples 1-8 were conducted using the activated lithium slag obtained in step 2 of Example 1, followed by subsequent experiments.

[0085] Analysis of the data in Tables 2 and 3 shows that this invention can achieve efficient extraction of silicon and aluminum from lithium slag from different sources, obtaining amorphous silicon-aluminum based oxides with high purity and adjustable silicon-aluminum ratio. Compared with Example 1, Comparative Example 1 did not add ascorbic acid reducing agent, and the Fe in the acid leaching solution was lower. 3+Precipitation was significantly affected by pH, resulting in a substantial increase in impurity content. Comparative Example 2, using a phosphate buffer system, caused calcium ions in the acid leaching solution to combine with phosphate ions and precipitate, significantly impacting the purity of the aluminosilicate-based compound. Comparative Example 3, with its strong acid system, lacked buffering capacity and could not maintain pH within the required range (the solution was strongly acidic, failing to reach the precipitation pH, resulting in almost no precipitation). Comparative Examples 4 and 5 caused the buffer solution to fail; when the precipitation pH was reached, almost all ions in the solution began to precipitate simultaneously. Precipitates of different ions easily clump together, increasing co-precipitation, reducing selectivity, and significantly decreasing the extraction rate of aluminosilicate-based compounds. Comparative Examples 6, 7, and 8 demonstrate that only under specific injection rates and pH ranges can amorphous aluminosilicate-based compounds with high yields and high purity be obtained.

[0086] The above description is merely a specific embodiment of the present invention and the technical principles used, and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing amorphous silicon-aluminum based oxides using lithium slag, characterized in that, Includes the following steps: (1) Pretreatment: The lithium slag is dried, crushed and sieved to obtain lithium slag powder; (2) Low temperature activation: After mixing and grinding lithium slag powder with strong alkali at a mass ratio of 1:0.5-1.5, the mixture is activated at 100-300℃ for 1-3 hours to obtain activated lithium slag; (3) Acid leaching to remove impurities: The activated lithium slag is mixed with hydrochloric acid solution at a solid-liquid ratio of 1:5-20 (g / ml) and dissolved. After the dissolution reaction is completed, ascorbic acid is added to carry out a reduction reaction. After the reduction reaction is completed, the solid and liquid are separated to obtain lithium slag acid leaching solution. The mass ratio of ascorbic acid to activated lithium slag is 1:15-30. (4) Buffer precipitation: The lithium slag acid leaching solution is slowly injected into a continuously stirred buffer solution to carry out the precipitation reaction. After the precipitation reaction is completed, the solid and liquid are separated, and the solid phase is washed and dried to obtain amorphous silicon-aluminum based oxide. The volume ratio of the buffer solution to the lithium slag acid leaching solution is 5-30:

1. The buffer solution is an acetic acid-sodium acetate solution with a pH value of 3.5-5.5 and a total concentration of 0.1-2 mol / L. The injection rate of the lithium slag acid leaching solution to the volume ratio of the buffer solution is 0.06~0.6 / min:

1. The temperature of the precipitation reaction is 15-30℃ and the time is 5-30 min.

2. The method for preparing amorphous silicon-aluminum based oxides according to claim 1, characterized in that, In step (1), the lithium slag contains ≥30wt% silica, ≥10wt% alumina, and ≤5wt% Fe2O3.

3. The method for preparing amorphous silicon-aluminum based oxides according to claim 1, characterized in that, In step (2), the strong base is sodium hydroxide and / or potassium hydroxide.

4. The method for preparing amorphous silicon-aluminum based oxides according to claim 1, characterized in that, In step (3), the concentration of the hydrochloric acid solution is 1-3 mol / L.

5. The method for preparing amorphous silicon-aluminum based oxides according to claim 1, characterized in that, In step (3), the temperature of the dissolution reaction is 50-70℃ and the time is 10-90min.

6. The method for preparing amorphous silicon-aluminum based oxides according to claim 1, characterized in that, In step (3), the temperature of the reduction reaction is 20-70℃ and the time is 10-60min.

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