Process for treating electrolytic aluminum waste residues by utilizing segmented roasting method

Abstract

The invention relates to the technical field of solid waste resource recycling, and discloses a process for treating electrolytic aluminum waste residues through a staged roasting method.The step-by-step roasting method is adopted, magnesium hydroxide is used in the first step, fluorine can be effectively fixed, emission of harmful fluorine can be inhibited, the structure of electrolytic aluminum can be destroyed, carbon powder in the electrolytic aluminum waste residues can be removed, and the waste residues can be recycled; more lithium is released; in the second step, lithium hydroxide is used for roasting at low temperature, so that the sintering temperature and the energy consumption are reduced, the waste residues can be completely converted into LiF and other oxides by adding the lithium hydroxide, lithium and aluminum can be separated by using water leaching, and the lithium yield is prevented from being influenced due to the fact that lithium and aluminum are in the same system; no hydrogen fluoride is generated in the whole technological process, corrosion to equipment is small, the technological process is simple, a large amount of equipment does not need to be used, and the method is suitable for industrial production.

Description

Technical Field

[0001] The present invention relates to the technical field of solid waste resource recycling, and in particular to a process for treating electrolytic aluminum waste slag by using a staged roasting method. Background Art

[0002] Lithium is a metallic element, known as green energy metal and "white oil", and is widely used in lithium batteries, glass and ceramics, lithium-based grease, metallurgical casting, medicine and atomic energy industries. With the rapid development of new energy vehicles and energy storage industries, the proportion of lithium consumption used in rechargeable lithium batteries has increased year by year in recent years, and has become the largest lithium consumption area.

[0003] Lithium resources exist in nature mainly in the form of liquid ores and solid ores. The process technology solutions for extracting lithium or lithium salts from lithium ore resources are very common, but there are not many raw materials for extracting lithium and its salts that use other lithium-related materials. For example, in aluminum electrolysis production, in addition to adding cryolite to the electrolyte, certain salts such as fluorides or chlorides are also added to improve the properties of the electrolyte to achieve the purpose of improving current efficiency and reducing energy consumption. One of the commonly used additives is lithium fluoride. Lithium-containing anhydrous aluminum fluoride and lithium-containing cryolite are currently used in aluminum electrolytic waste slag enterprises with good results. They can effectively reduce the initial temperature of the electrolyte, reduce fluorine emissions, and promote energy conservation and consumption reduction in aluminum electrolytic waste slag enterprises. With the use of lithium-containing fluoride salts, lithium-containing aluminum electrolytic waste slag is produced, and its lithium content is 1%-3% (in terms of Li + count).

[0004] At present, many production enterprises use concentrated sulfuric acid pressure boiling method to extract lithium, which has a large amount of hydrofluoric acid overflow, pollutes the environment, and has high energy consumption of equipment. For example, patent document CN105293536A discloses a method for extracting lithium from electrolytic aluminum waste residue, reacting lithium-containing electrolytic aluminum waste residue with concentrated sulfuric acid, adding water for leaching and filtering to obtain filtrate A, then adding sodium carbonate to the filtrate A for reaction, filtering to obtain filter residue B, then adding water to the filter residue B to make a slurry and reacting with lime, filtering to obtain filtrate C, then passing CO2 into the filtrate C for carbonization reaction, then filtering, washing, and drying to obtain lithium carbonate. The obtained battery-grade lithium carbonate has low impurity content and excellent product quality, which solves the current problems of low yield, high production cost, and weak market competitiveness in preparing battery-grade lithium carbonate from ore lithium extraction. However, this method has disadvantages. First, a large amount of hydrofluoric acid is produced and overflowed, which has a great impact on environmental pollution and has high requirements for production equipment. Second, there is a large amount of hydrofluoric acid in the leaching solution after extraction, and the content of other metal elements in the solution is high, that is, for lithium or lithium salts, the content of aluminum and copper as impurity elements is higher, which makes subsequent processing more difficult, resulting in high production costs.

[0005] In addition, some enterprises also use mixed salt calcination method to extract lithium. For example, patent document CN115216645 A discloses a mixed salt calcination method to extract lithium from electrolytic aluminum waste slag. It uses electrolytic aluminum waste slag as raw material, potassium and calcium salts as auxiliary materials, and adopts calcification roasting, potassium salt re-burning, alkali leaching, solid-liquid separation, freezing and impurity removal, and purification process to extract and separate industrial lithium hydroxide and lithium carbonate. The content of other impurity ions in the leaching solution of this method is low, and lithium salts are easily separated and extracted, but the process is complicated. Summary of the invention

[0006] In view of the shortcomings of the prior art, the purpose of the present invention is to provide a process for treating electrolytic aluminum waste slag using a staged roasting method. The present invention can reduce the leaching of impurity ions through staged roasting and the use of lithium hydroxide, and can obtain industrial-grade lithium fluoride products without impurity removal, with a yield of more than 97%. The process flow is simple, and lithium, aluminum and sodium can be comprehensively recovered at the same time; magnesium can also be recycled.

[0007] In order to achieve the above object, the present invention adopts the following technical scheme:

[0008] A process for treating electrolytic aluminum waste slag using a staged roasting method comprises the following steps:

[0009] S1. Preparation of roasting material

[0010] The electrolytic aluminum waste slag and magnesium hydroxide are mixed evenly and then pressed into a shape, and then calcined at a high temperature in a muffle furnace. After cooling, the mixture is ground and sieved to obtain a calcined material.

[0011] In this step, the mass ratio of electrolytic aluminum waste slag to magnesium hydroxide is 0.5-1.5:0.5-1, for example, 0.5:0.5, 0.5:0.1, 1:0.5, 1.5:0.5, 1.5:1 can be selected, but it is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0012] In this step, the high temperature roasting temperature is 300-500°C, for example, 300°C, 350°C, 400°C, 450°C, and 500°C can be selected; the high temperature roasting time is 60-200min, for example, 60min, 80min, 100min, 120min, 140min, 150min, 160min, 180min, and 200min can be selected; but it is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0013] In this step, the specific process of grinding and screening is: grinding evenly to a fineness of 60-200 μm and a square hole sieve residue of less than 20%.

[0014] S2. Preparation of roasted clinker

[0015] The calcined material and lithium hydroxide are mixed evenly and then pressed into a shape, and then calcined at a low temperature in a muffle furnace. After cooling, the mixture is ground and sieved to obtain a calcined clinker.

[0016] In this step, the mass ratio of the calcined material to lithium hydroxide is 1-1.5:0.1-0.5, for example, 1:0.1, 1:0.2, 1:0.3, 1:0.4, 1:0.5, 1.2:0.1, 1.2:0.2, 1.2:0.3, 1.5:0.1, 1.5:0.2, 1.5:0.3, 1.5:0.4, 1.5:0.5 can be selected, but it is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0017] In this step, the temperature of low-temperature roasting is 200-300°C, for example, 200°C, 210°C, 220°C, 230°C, 240°C, 250°C, 260°C, 270°C, 280°C, 290°C, and 300°C can be selected; the time of low-temperature roasting is 60-200min, for example, 60min, 80min, 100min, 120min, 140min, 150min, 160min, 180min, and 200min can be selected; but it is not limited to the listed values, and other values ​​not listed in the numerical range are also applicable.

[0018] In this step, the specific process of grinding and screening is: grinding evenly to a fineness of 60-200 μm and a square hole sieve residue of less than 20%.

[0019] S3, water immersion treatment

[0020] The roasted clinker and deionized water are stirred and mixed evenly, subjected to a leaching treatment, and then filtered to obtain a leachate and a filter residue 1. The filter residue 1 is then washed with deionized water to obtain a washing residue and a washing liquid. The leachate and the washing liquid are combined to obtain a filtrate.

[0021] In this step, the usage ratio of roasted clinker and deionized water is 1kg:1-2L, for example, 1kg:1L, 1kg:1.5L, 1kg:2L can be selected, but it is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0022] In this step, the primary leaching temperature is 80-100°C, for example, 80°C, 85°C, 90°C, 95°C, and 100°C can be selected; the primary leaching time is 0.5-4h, for example, 0.5h, 1h, 1.5h, 2h, 2.5h, 3h, 3.5h, and 4h can be selected, but it is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0023] In this step, the main components of the washing residue obtained are lithium fluoride and magnesium oxide.

[0024] In this step, the main component of the obtained filtrate is sodium aluminate.

[0025] S4, Recycling of aluminum and sodium

[0026] The pH of the filtrate in step S3 is adjusted to 6-8, and aluminum hydroxide solid and sodium ion solution are obtained by filtration and separation.

[0027] In this step, the pH of the solution containing sodium aluminate is adjusted by using an acid solution, and then aluminum hydroxide solid and sodium ion solution are obtained by filtration and separation, thereby achieving separation of aluminum and sodium. The aluminum hydroxide can be subsequently used to prepare aluminum fluoride.

[0028] S5. Acid leaching

[0029] The washing residue and the hydrochloric acid solution in step S3 are stirred and mixed evenly, and a secondary leaching treatment is performed, followed by suction filtration to obtain a magnesium chloride solution and a filter residue 2, and the filter residue 2 is then washed with deionized water to obtain an industrial-grade lithium fluoride product.

[0030] In this step, the usage ratio of washing residue and hydrochloric acid solution is 1kg:1-2L, for example, 1kg:1L, 1kg:1.5L, 1kg:2L can be selected; wherein, the mass fraction of hydrochloric acid solution is 5-10%, for example, 5%, 6%, 7%, 8%, 9%, 10% can be selected, but it is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0031] In this step, the secondary leaching temperature is 80-100°C, for example, 80°C, 85°C, 90°C, 95°C, and 100°C can be selected; the secondary leaching time is 0.5-4h, for example, 0.5h, 1h, 1.5h, 2h, 2.5h, 3h, 3.5h, and 4h can be selected, but it is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0032] Compared with the prior art, the present invention has the following beneficial effects:

[0033] (1) The present invention does not produce hydrogen fluoride during the entire process, has low corrosion to equipment, has a simple process flow, does not require the use of a large amount of equipment, and is suitable for industrial production.

[0034] (2) The present invention adopts a step-by-step roasting method. The first step is to use magnesium hydroxide for roasting at a high temperature, which can not only effectively fix fluorine and inhibit the emission of harmful fluorine, but also destroy the structure of electrolytic aluminum, remove carbon powder in the electrolytic aluminum waste slag, and release more lithium; the second step is to use lithium hydroxide for roasting at a low temperature, which can not only reduce the sintering temperature and energy consumption, but also add lithium hydroxide to convert all the lithium in the waste slag into LiF, and then use water immersion to separate lithium and aluminum, avoiding lithium and aluminum in the same system, thereby affecting the lithium yield.

[0035] (3) The applicant found during the experiment that if the electrolytic aluminum waste slag, magnesium hydroxide and lithium hydroxide were roasted together, the yield would be reduced. The reason may be that magnesium hydroxide destroys the structure of the electrolytic aluminum. If lithium hydroxide is also used at this time, it will play a greater role in alkaline hydrolysis, and the exchange effect between lithium ions and other metal ions will be weak, which will reduce the utilization rate of lithium and the yield. However, if they are roasted separately, magnesium hydroxide is first used to completely destroy the structure of the electrolytic aluminum and remove the carbon powder in the waste slag. Then lithium hydroxide is used for roasting to allow lithium to exchange with the metal impurity ions in the electrolytic aluminum. Subsequently, water leaching can be used to separate lithium magnesium and aluminum sodium. Then, hydrochloric acid leaching can be used to separate lithium and magnesium. Adjusting the pH value can achieve separation of aluminum and sodium. Not only comprehensive recovery is achieved, but also the yield is higher and the process is simpler. If lithium hydroxide is not used, lithium and aluminum cannot be separated efficiently. Lithium and aluminum will be removed in the same system. During the aluminum removal process, aluminum is removed in the form of aluminum hydroxide to form an aluminum-based adsorbent, which greatly reduces the lithium yield. In addition, the entire process is complicated, the cost is high, and the yield is low.

[0036] (4) By adopting the process of the present invention, industrial-grade lithium fluoride can be directly obtained without the need for impurity removal steps, with a yield of more than 97%. At the same time, lithium, aluminum and sodium can be comprehensively recovered to achieve the recycling of magnesium. DETAILED DESCRIPTION

[0037] The present invention is further described in detail below through specific preferred embodiments, but the present invention is not limited to the following embodiments.

[0038] It should be noted that, unless otherwise specified, the chemical reagents involved in the present invention were purchased through commercial channels.

[0039] The present invention uses electrolytic aluminum waste slag as raw material, and the main chemical components are shown in Table 1.

[0040] Table 1 Main components of electrolytic aluminum waste slag raw materials

[0041]

[0042] Example 1

[0043] A process for treating electrolytic aluminum waste slag using a staged roasting method comprises the following steps:

[0044] S1. The electrolytic aluminum waste slag and magnesium hydroxide are mixed uniformly in a mixer at a mass ratio of 1:0.8, and pressed into shape, and then calcined in a muffle furnace at a high temperature of 500° C. for 180 min. After cooling, the mixture is ground through a 200 μm square hole sieve, and the sieve residue is less than 20%, to obtain a calcined material;

[0045] S2, the roasting material and lithium hydroxide are mixed uniformly in a mixer at a mass ratio of 1:0.4, and pressed into shape, and then low-temperature roasted in a muffle furnace, the low-temperature roasting temperature is 250 ° C, the low-temperature roasting time is 180min, and after cooling, it is ground through a 200 μm square hole sieve, and the sieve residue is less than 20%, to obtain a roasted clinker;

[0046] S3, 1kg of roasted clinker and 1.5L of deionized water were placed in a stirring device, stirred and mixed evenly, and leached at 95°C for 3h, followed by suction filtration to obtain a leachate and a filter residue 1, and then the filter residue 1 was washed with deionized water to obtain a washing residue and a washing liquid, and the leachate and the washing liquid were combined to obtain a solution containing sodium aluminate;

[0047] S4, adjusting the pH of the solution containing sodium aluminate in step S3 to 7.5 using sulfuric acid, and filtering and separating to obtain aluminum hydroxide solid and sodium ion solution, thereby achieving separation of aluminum and sodium. The aluminum hydroxide can be used to prepare aluminum fluoride later;

[0048] S5, placing 1 kg of the washing residue obtained in step S3 and 1.5 L of 6 wt% hydrochloric acid solution in a stirring device, stirring and mixing them evenly, and performing leaching treatment at a leaching temperature of 95 ° C. for a leaching time of 3 h, followed by suction filtration to obtain a magnesium chloride solution and a filter residue 2, and then washing the filter residue 2 with deionized water to obtain an industrial-grade lithium fluoride product. The magnesium chloride solution can be heated to obtain magnesium hydroxide, thereby realizing the recycling of magnesium.

[0049] The composition analysis of industrial-grade lithium fluoride is shown in Table 2. The product quality meets the GB / T 22666-2008 standard, and the lithium yield is 98.4%.

[0050] The calculation formula for lithium yield is as follows:

[0051]

[0052] Among them, M 工业级氟化锂 is the mass of industrial-grade lithium fluoride product (g), W 工业级氟化锂 is the mass content of lithium element in industrial grade lithium fluoride, M 料 is the mass of electrolytic aluminum waste slag (g), W 料is the mass content of lithium in electrolytic aluminum waste slag (see Table 1), M Li is the mass (g) of lithium in the added lithium hydroxide.

[0053] Example 2

[0054] A process for treating electrolytic aluminum waste slag using a staged roasting method comprises the following steps:

[0055] S1. Electrolytic aluminum waste slag and magnesium hydroxide are mixed evenly in a mixer at a mass ratio of 1:1, and pressed into shape, and then calcined in a muffle furnace at a high temperature of 500° C. for 180 min. After cooling, the mixture is ground through a 200 μm square hole sieve, and the sieve residue is less than 20%, to obtain a calcined material;

[0056] S2, the roasting material and lithium hydroxide are mixed uniformly in a mixer at a mass ratio of 1:0.4, and pressed into shape, and then low-temperature roasted in a muffle furnace, the low-temperature roasting temperature is 250 ° C, the low-temperature roasting time is 180min, and after cooling, it is ground through a 200 μm square hole sieve, and the sieve residue is less than 20%, to obtain a roasted clinker;

[0057] S3, 1kg of roasted clinker and 1.5L of deionized water were placed in a stirring device, stirred and mixed evenly, and leached at 95°C for 3h, followed by suction filtration to obtain a leachate and a filter residue 1, and then the filter residue 1 was washed with deionized water to obtain a washing residue and a washing liquid, and the leachate and the washing liquid were combined to obtain a solution containing sodium aluminate;

[0058] S4, adjusting the pH of the solution containing sodium aluminate in step S3 to 7.5 using sulfuric acid, and filtering and separating to obtain aluminum hydroxide solid and sodium ion solution, thereby achieving separation of aluminum and sodium. The aluminum hydroxide can be used to prepare aluminum fluoride later;

[0059] S5, placing 1 kg of the washing residue obtained in step S3 and 1.5 L of 6 wt% hydrochloric acid solution in a stirring device, stirring and mixing them evenly, and performing leaching treatment at a leaching temperature of 95 ° C. for a leaching time of 3 h, followed by suction filtration to obtain a magnesium chloride solution and a filter residue 2, and then washing the filter residue 2 with deionized water to obtain an industrial-grade lithium fluoride product. The magnesium chloride solution can be heated to obtain magnesium hydroxide, thereby realizing the recycling of magnesium.

[0060] The composition analysis of industrial-grade lithium fluoride is shown in Table 2. The product quality meets the GB / T 22666-2008 standard, and the lithium yield is 99.0%.

[0061] Example 3

[0062] A process for treating electrolytic aluminum waste slag using a staged roasting method comprises the following steps:

[0063] S1. The electrolytic aluminum waste slag and magnesium hydroxide are mixed uniformly in a mixer at a mass ratio of 1:0.8, and pressed into shape, and then calcined in a muffle furnace at a high temperature of 500° C. for 180 min. After cooling, the mixture is ground through a 200 μm square hole sieve, and the sieve residue is less than 20%, to obtain a calcined material;

[0064] S2, the roasting material and lithium hydroxide are mixed uniformly in a mixer at a mass ratio of 1:0.3, and pressed into shape, and then low-temperature roasted in a muffle furnace, the low-temperature roasting temperature is 250 ° C, the low-temperature roasting time is 180min, and after cooling, it is ground through a 200 μm square hole sieve, and the sieve residue is less than 20%, to obtain a roasted clinker;

[0065] S3, 1kg of roasted clinker and 1.5L of deionized water were placed in a stirring device, stirred and mixed evenly, and leached at 95°C for 3h, followed by suction filtration to obtain a leachate and a filter residue 1, and then the filter residue 1 was washed with deionized water to obtain a washing residue and a washing liquid, and the leachate and the washing liquid were combined to obtain a solution containing sodium aluminate;

[0066] S4, adjusting the pH of the solution containing sodium aluminate in step S3 to 7.5 using sulfuric acid, and filtering and separating to obtain aluminum hydroxide solid and sodium ion solution, thereby achieving separation of aluminum and sodium. The aluminum hydroxide can be used to prepare aluminum fluoride later;

[0067] S5, placing 1 kg of the washing residue obtained in step S3 and 1.5 L of 6 wt% hydrochloric acid solution in a stirring device, stirring and mixing them evenly, and performing leaching treatment at a leaching temperature of 95 ° C. for a leaching time of 3 h, followed by suction filtration to obtain a magnesium chloride solution and a filter residue 2, and then washing the filter residue 2 with deionized water to obtain an industrial-grade lithium fluoride product. The magnesium chloride solution can be heated to obtain magnesium hydroxide, thereby realizing the recycling of magnesium.

[0068] The composition analysis of industrial-grade lithium fluoride is shown in Table 2. The product quality meets the GB / T 22666-2008 standard, and the lithium yield is 97.3%.

[0069] Comparative Example 1

[0070] A process for treating electrolytic aluminum waste slag comprises the following steps:

[0071] S1. The electrolytic aluminum waste slag and magnesium hydroxide are mixed uniformly in a mixer at a mass ratio of 1:0.8, and pressed into shape, and then calcined in a muffle furnace at a high temperature of 500° C. for 180 min. After cooling, the mixture is ground through a 200 μm square hole sieve, and the sieve residue is less than 20%, to obtain a calcined material;

[0072] S2, 1kg of roasted clinker and 1.5L of deionized water were placed in a stirring device, stirred and mixed evenly, and leached at 95°C for 3h, followed by suction filtration to obtain a leachate and a filter residue 1, and then the filter residue 1 was washed with deionized water to obtain a washing residue and a washing liquid, and the leachate and the washing liquid were combined to obtain a solution containing sodium aluminate;

[0073] S3, adjusting the pH of the solution containing sodium aluminate in step S2 to 7.5 using sulfuric acid, and filtering and separating to obtain aluminum hydroxide solid and sodium ion solution, thereby separating aluminum and sodium. The aluminum hydroxide can be used to prepare aluminum fluoride later;

[0074] S4, placing 1 kg of the washing residue obtained in step S2 and 1.5 L of 6 wt% hydrochloric acid solution in a stirring device, stirring and mixing them evenly, and performing leaching treatment at a leaching temperature of 95 ° C. for a leaching time of 3 hours, followed by suction filtration to obtain a magnesium chloride solution and a filter residue 2, and then washing the filter residue 2 with deionized water to obtain an industrial-grade lithium fluoride product. The magnesium chloride solution can be heated to obtain magnesium hydroxide, thereby realizing the recycling of magnesium.

[0075] Compared with Example 1, Comparative Example 1 did not add lithium hydroxide for calcination, and other test conditions remained unchanged.

[0076] The composition analysis of industrial-grade lithium fluoride is shown in Table 2. The product quality does not meet the GB / T 22666-2008 standard, and the lithium yield is 56.8%.

[0077] Comparative Example 2

[0078] A process for treating electrolytic aluminum waste slag comprises the following steps:

[0079] S1. The electrolytic aluminum waste slag and lithium hydroxide are mixed evenly in a mixer at a mass ratio of 1:0.4, and pressed into shape, and then calcined in a muffle furnace at a high temperature of 500° C. for 180 min. After cooling, the mixture is ground through a 200 μm square hole sieve, and the sieve residue is less than 20%, to obtain a calcined material;

[0080] S2, the roasting material and magnesium hydroxide are mixed uniformly in a mixer at a mass ratio of 1:0.8, and pressed into shape, and then low-temperature roasted in a muffle furnace, the low-temperature roasting temperature is 250 ° C, the low-temperature roasting time is 180min, and after cooling, it is ground through a 200 μm square hole sieve, and the sieve residue is less than 20%, to obtain a roasted clinker;

[0081] S3, 1kg of roasted clinker and 1.5L of deionized water were placed in a stirring device, stirred and mixed evenly, and leached at 95°C for 3h, followed by suction filtration to obtain a leachate and a filter residue 1, and then the filter residue 1 was washed with deionized water to obtain a washing residue and a washing liquid, and the leachate and the washing liquid were combined to obtain a solution containing sodium aluminate;

[0082] S4, adjusting the pH of the solution containing sodium aluminate in step S3 to 7.5 using sulfuric acid, and filtering and separating to obtain aluminum hydroxide solid and sodium ion solution, thereby achieving separation of aluminum and sodium. The aluminum hydroxide can be used to prepare aluminum fluoride later;

[0083] S5, placing 1 kg of the washing residue obtained in step S3 and 1.5 L of 6 wt% hydrochloric acid solution in a stirring device, stirring and mixing them evenly, and performing leaching treatment at a leaching temperature of 95 ° C. for a leaching time of 3 h, followed by suction filtration to obtain a magnesium chloride solution and a filter residue 2, and then washing the filter residue 2 with deionized water to obtain an industrial-grade lithium fluoride product. The magnesium chloride solution can be heated to obtain magnesium hydroxide, thereby realizing the recycling of magnesium.

[0084] Compared with Example 1, Comparative Example 2 first uses lithium hydroxide for calcination and then uses magnesium hydroxide for calcination.

[0085] The composition analysis of industrial-grade lithium fluoride is shown in Table 2. The product quality does not meet the GB / T 22666-2008 standard, and the lithium yield is only 68.2%.

[0086] Comparative Example 3

[0087] A process for treating electrolytic aluminum waste slag comprises the following steps:

[0088] S1. Mix the electrolytic aluminum waste slag, magnesium hydroxide and lithium hydroxide in a mixer at a mass ratio of 1:0.8:0.4, and press them into shape. Then, calcine them at a high temperature in a muffle furnace at a temperature of 500° C. for 180 min. After cooling, grind them through a 200 μm square hole sieve, and the sieve residue is less than 20%, to obtain a calcined clinker.

[0089] S2, 1kg of roasted clinker and 1.5L of deionized water were placed in a stirring device, stirred and mixed evenly, and leached at 95°C for 3h, followed by suction filtration to obtain a leachate and a filter residue 1, and then the filter residue 1 was washed with deionized water to obtain a washing residue and a washing liquid, and the leachate and the washing liquid were combined to obtain a solution containing sodium aluminate;

[0090] S3, adjusting the pH of the solution containing sodium aluminate in step S2 to 7.5 using sulfuric acid, and filtering and separating to obtain aluminum hydroxide solid and sodium ion solution, thereby separating aluminum and sodium. The aluminum hydroxide can be used to prepare aluminum fluoride later;

[0091] S4, placing 1 kg of the washing residue obtained in step S2 and 1.5 L of 6 wt% hydrochloric acid solution in a stirring device, stirring and mixing them evenly, and performing leaching treatment at a leaching temperature of 95 ° C. for a leaching time of 3 hours, followed by suction filtration to obtain a magnesium chloride solution and a filter residue 2, and then washing the filter residue 2 with deionized water to obtain an industrial-grade lithium fluoride product. The magnesium chloride solution can be heated to obtain magnesium hydroxide, thereby realizing the recycling of magnesium.

[0092] Compared with Example 1, Comparative Example 3 uses lithium hydroxide and magnesium hydroxide for mixed roasting.

[0093] The composition analysis of industrial-grade lithium fluoride is shown in Table 2. The product quality does not meet the GB / T 22666-2008 standard, and the lithium yield is 70.5%.

[0094] The components of the industrial-grade lithium fluoride prepared in Examples 1-3 and Comparative Examples 1-3 were analyzed. The results are shown in Table 2.

[0095] Table 2 Composition analysis of industrial grade lithium fluoride prepared by different groups

[0096]

[0097] Note 1: The method for comparing the measured value or its calculated value with the limit value specified in the table shall be carried out in accordance with the provisions of Section 5.2 of GB / T 1250;

[0098] Note 2: The main content of LiF is calculated based on fluorine.

[0099] Finally, it should be noted that the above embodiments do not limit the present invention in any form. For those skilled in the art, some modifications and improvements can be made to the present invention. Therefore, any modification or improvement made without departing from the spirit of the present invention belongs to the scope of protection claimed in the present invention.

Claims

1. A process for treating electrolytic aluminum waste slag using a staged roasting method, characterized in that: The steps include: S1, mixing the electrolytic aluminum waste slag and magnesium hydroxide evenly and pressing them into a shape, then calcining them at high temperature in a muffle furnace, and grinding and sieving them after cooling to obtain a calcined material; S2, mixing the roasting material and lithium hydroxide evenly and pressing them into a shape, then roasting them at a low temperature in a muffle furnace, and grinding and sieving them after cooling to obtain a roasted clinker; S3, stirring and mixing the roasted clinker and deionized water, performing a leaching treatment, and then filtering to obtain a leachate and a filter residue 1, and then washing the filter residue 1 with deionized water to obtain a washing residue and a washing liquid, and combining the leachate and the washing liquid to obtain a filtrate; S4, stirring and mixing the washing residue and the hydrochloric acid solution in step S3 evenly, performing secondary leaching treatment, and then filtering to obtain a magnesium chloride solution and a filter residue 2, and then washing the filter residue 2 with deionized water to obtain an industrial-grade lithium fluoride product.

2. The process for treating electrolytic aluminum waste slag by staged roasting method according to claim 1, characterized in that: In step S1, the mass ratio of the electrolytic aluminum waste slag to magnesium hydroxide is 0.5-1.5:0.5-1.

3. The process for treating electrolytic aluminum waste slag by staged roasting method according to claim 1, characterized in that: In step S1, the high temperature calcination temperature is 300-500°C, and the high temperature calcination time is 60-200 minutes.

4. The process for treating electrolytic aluminum waste slag by staged roasting method according to claim 1, characterized in that: In step S2, the mass ratio of the calcined material to lithium hydroxide is 1-1.5:0.1-0.

5.

5. The process for treating electrolytic aluminum waste slag by staged roasting method according to claim 1, characterized in that: In step S2, the temperature of the low-temperature roasting is 200-300° C., and the time of the low-temperature roasting is 60-200 min.

6. The process for treating electrolytic aluminum waste slag by staged roasting method according to claim 1, characterized in that: In step S3, the ratio of the roasted clinker to the deionized water is 1kg:1-2L.

7. The process for treating electrolytic aluminum waste slag by staged roasting method according to claim 1, characterized in that: In step S3, the primary leaching temperature is 80-100° C., and the primary leaching time is 0.5-4 h.

8. The process for treating electrolytic aluminum waste slag by staged roasting method according to claim 1, characterized in that: In step S4, the ratio of the washing residue to the hydrochloric acid solution is 1 kg: 1-2 L, and the mass fraction of the hydrochloric acid solution is 5-10%.

9. The process for treating electrolytic aluminum waste slag by staged roasting method according to claim 1, characterized in that: In step S4, the secondary leaching temperature is 80-100° C., and the secondary leaching time is 0.5-4 h.

10. The process for treating electrolytic aluminum waste slag by staged roasting method according to claim 1, characterized in that: The method further comprises adjusting the pH of the filtrate in step S3 to 6-8, and obtaining aluminum hydroxide solid and sodium ion solution by filtering and separating.

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