Method for resource utilization of electrolytic aluminum impurity-containing electrolyte

Abstract

The present application relates to the technical field of chemical production, in particular to a method for resource utilization of electrolytic aluminum containing impurities electrolyte, steps comprising: (1) adding inorganic acid to the electrolyte containing impurities; (2) adding aluminum-containing inorganic compound; (3) filtering and washing the filter residue, drying the filter residue after washing to obtain regenerated cryolite electrolyte, mixing the washing water with the filtrate; (4) adjusting the pH value and filtering; (5) evaporating and concentrating, filtering, drying the filter residue to obtain industrial sodium salt, and the filtrate is concentrated salt solution; (6) adjusting the pH value of the concentrated salt solution and filtering; (7) adding sodium carbonate to react, filtering at room temperature, drying the filter residue to obtain industrial lithium carbonate, and collecting the filtrate. The present application classifies the electrolyte containing impurities into products that can be used in industrial production, realizes the resource utilization of the electrolyte containing impurities, reduces resource waste, and reduces the output and emission of waste.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of chemical production, in particular to a method for resource utilization of electrolytic aluminum containing impurities. BACKGROUND

[0002] Aluminum oxide is one of the raw materials of the electrolytic aluminum production process, which is processed from bauxite in industrial production. With the sharp increase in demand for bauxite resources, a large amount of bauxite containing alkali metal elements is mined and used, resulting in the production of aluminum oxide containing alkali metal elements such as lithium and potassium to varying degrees. When such aluminum oxide is used as a raw material for electrolytic aluminum production, lithium and potassium will enter the electrolyte but not participate in the reaction, causing continuous accumulation in the electrolyte. At the same time, in the electrolytic aluminum production process, a small amount of lithium fluoride, calcium fluoride and other additives are usually added to improve the current efficiency and the properties of the electrolyte, further causing the continuous enrichment of impurities containing fluorine and lithium elements. With the enrichment of impurities in the electrolytic cell, the high content of fluorine, lithium and sodium elements has an adverse effect on the service life and current efficiency of the electrolytic cell. Therefore, in order to enable the electrolytic cell to operate normally and stably, the impurity content of the electrolyte must be controlled.

[0003] In the prior art, a portion of the electrolyte containing impurities is usually taken out after the electrolytic cell has been operated for a certain period of time, and a portion of new electrolyte is added to control the impurity content within the standard. For the portion of electrolyte containing impurities taken out, the current treatment scheme of the electrolytic aluminum plant is usually to stack, bury or incinerate, which has the problem of difficult discharge and is easy to cause environmental pollution.

[0004] At the same time, direct destruction or discharge of the electrolyte containing impurities will cause serious resource waste problem, especially the lithium element enriched in the electrolyte containing impurities. If this part of lithium resources is reasonably recycled and utilized, it will help to alleviate the lithium pressure brought by the new energy industry. Therefore, how to efficiently, harmlessly and resourcefully treat the electrolytic aluminum containing impurities will be an urgent industry problem to be solved in the electrolytic aluminum production. SUMMARY

[0005] In view of the problems of resource waste, difficult discharge and easy environmental pollution caused by the inadequate resource treatment of the electrolyte containing impurities in the prior art, the present application provides a method for resource utilization of electrolytic aluminum containing impurities, which converts the fluorine, sodium and lithium elements in the electrolyte containing impurities into compounds that can be used in industrial production and are easy to separate, and collects the remaining impurity-removed electrolyte liquid, which can be repeatedly used in electrolytic aluminum production, realizes the resource utilization of the electrolyte containing impurities, reduces resource waste, reduces the output and discharge of waste materials, and reduces environmental pollution.

[0006] The technical scheme of the present application is as follows:

[0007] A method for resource utilization of electrolytic aluminum containing impurities, comprising the following steps:

[0008] (1) adding inorganic acid into the impurity-containing electrolyte, stirring and mixing at 50-90°C for 40-120 min to obtain an acidification product;

[0009] (2) adding aluminum-containing inorganic compound, stirring and reacting at 50-110°C for 60-720 min to obtain a solid-liquid mixture;

[0010] (3) filtering the solid-liquid mixture, washing the filter residue until the pH value of the washing water is 6.5-7.5, drying the filter residue after washing to obtain regenerated cryolite electrolyte, the main components of the regenerated cryolite electrolyte being aluminum fluoride and sodium hexafluoroaluminate, and mixing the washing water and the filtrate to obtain a mixed solution;

[0011] (4) adding at least one of sodium hydroxide, calcium hydroxide and calcium oxide into the mixed solution, adjusting the pH value to 7-9 and filtering to obtain an evaporation stock solution;

[0012] (5) evaporating and concentrating the evaporation stock solution, filtering and drying the filter residue to obtain industrial sodium salt, and the filtrate being a concentrated salt solution;

[0013] (6) adding sodium hydroxide into the concentrated salt solution, adjusting the pH value to 9-12 and filtering to obtain a lithium extraction stock solution;

[0014] (7) adding sodium carbonate into the lithium extraction stock solution, controlling the reaction temperature to be 50-100°C, stirring and reacting for 30-180 min, filtering at room temperature after the reaction is completed, and drying the filter residue to obtain industrial lithium carbonate, and collecting the filtrate.

[0015] Further, the impurity-containing electrolyte includes electrolytic aluminum waste residue, such as one or more of electrolyte blocks replaced in electrolytic cells during electrolytic aluminum production, electrolytic aluminum electrolyte powder after carbon removal by flotation, and waste residue cleaned out of the tank during electrolytic aluminum tank stoppage after harmless treatment.

[0016] Further, in step (1), the impurity-containing electrolyte is an impurity-containing electrolyte after crushing and sieving, and the mesh number is 50-420.

[0017] Further, in step (1), the inorganic acid is at least one of hydrochloric acid, nitric acid, sulfuric acid and phosphoric acid, and the concentration is 5-10 mol / L.

[0018] Further, in step (2), the aluminum-containing inorganic compound includes one or more of aluminum oxide, aluminum hydroxide, aluminum chloride, aluminum chloride hexahydrate, aluminum nitrate, aluminum nitrate nonahydrate, aluminum sulfate and aluminum sulfite.

[0019] Further, in step (4), the temperature is controlled to be 25-60°C, and the stirring is continued for 30-60 min; and in step (6), the temperature is controlled to be 25-60°C, and the stirring is continued for 30-60 min.

[0020] Further, in step (5), the evaporation temperature is 80-100 DEG C, and the volume ratio of the concentrated salt solution to the evaporation stock solution is 1: (3-5).

[0021] Further, after filtration in step (7), the lithium ion concentration in the filtrate is measured, if the lithium ion concentration >1g / L, then the filtrate is used as the reaction liquid to repeat step (7) until the lithium ion concentration in the filtrate is ≤1g / L, and the finally collected filtrate is the impurity-removed electrolyte.

[0022] Further, the liquid for washing the filter residue in step (3) includes the impurity-removed electrolyte and / or deionized water.

[0023] Further, based on the weight of the impure electrolyte used in step (1), the amount of inorganic acid added in step (1) is 1-5kg / kg, the amount of the aluminum-containing inorganic compound added in step (2) is 0.5-5kg / kg, and the amount of sodium carbonate added in step (7) is 0.1-6kg / kg.

[0024] The beneficial effects of the present application are:

[0025] (1) The present application converts all the fluorine impurities in the impure electrolyte into regenerated cryolite electrolyte mainly composed of aluminum fluoride and sodium hexafluoroaluminate by the method of acid pretreatment and then adding an aluminum-containing inorganic compound to replace the combined impurities, the reaction is complete and thorough, the fluorine element is not lost, the regenerated cryolite electrolyte can be recycled in the aluminum electrolysis process, the finally collected impurity-removed electrolyte can also be applied to the aluminum electrolysis process or recycled as the filter residue washing liquid in the present process, thereby reducing waste discharge and environmental safety hazards.

[0026] (2) The present application separates most of the sodium and lithium elements in the impure electrolyte, the sodium and lithium ion content in the finally collected impurity-removed electrolyte is low, which meets the use requirements of the aluminum electrolysis process; at the same time, industrial-grade sodium salt with a wide range of applications and high-purity lithium carbonate products can be obtained, the purity of the lithium carbonate products can reach more than 98.8%, which meets the industrial use requirements without further purification, and can be directly applied to the new energy industry, which is conducive to alleviating the lithium pressure brought by the new energy industry.

[0027] (3) The raw materials used in the present application are conventional and low-cost raw materials in chemical production, the technical process used is simple, the production energy consumption is low, the material and process cost is low, and the economic benefit is high.

[0028] (4) The products in each link of the present application can be fully reacted and utilized, no waste gas, waste water and waste residue are discharged in the whole process, forming a large recycling system, realizing recycling utilization of resources with zero pollution and zero emission, and providing industrialized landing technical support for the new development goal of green, circular and sustainable aluminum electrolysis industry. DETAILED DESCRIPTION

[0029] In order for those skilled in the technical field to better understand the technical solutions in the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below. Obviously, the described embodiments are only some of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative work should belong to the protection scope of the present application.

[0030] Embodiment 1

[0031] A method for resource utilization of impurity-containing electrolyte of electrolytic aluminum, comprising the following steps:

[0032] (1) crushing the electrolyte block replaced from the electrolytic cell, collecting the impurity-containing electrolyte of 200 mesh component, taking 1 kg and putting into a reactor, adding 1.2 kg of 5 mol / L hydrochloric acid, stirring at 60 ℃ for 60 min, and the stirring speed of the stirrer is 350 r / min, to perform acidification pretreatment on the raw material;

[0033] (2) after the acidification treatment is completed, adding 0.55 kg of aluminum hydroxide solid powder into the reactor, heating to 80 ℃ and continuing to stir for 200 min, and the stirring speed of the stirrer is 300 r / min, to obtain a solid-liquid mixture;

[0034] (3) vacuum filtering the solid-liquid mixture to obtain 1.3 kg of filtrate and 1.14 kg of filter residue. Washing the filter residue with 0.8 kg of deionized water for 3 times, and the pH value of the filtrate obtained in the last time is 6.9, drying the filter residue to obtain regenerated cryolite electrolyte, and mixing the filtrate obtained in the four times of washing and the initial filtrate to obtain 2.75 kg of mixed solution;

[0035] (4) adding 55 g of calcium oxide solid into the mixed solution, controlling the temperature to be 45 ℃, setting the stirring speed of the stirrer to be 350 r / min, stirring for 45 min to obtain a solution with a pH value of 8.3, and further vacuum filtering to obtain 3.26 kg of evaporation stock solution;

[0036] (5) evaporating and concentrating the evaporation stock solution at 100 ℃, vacuum filtering the generated sodium salt solid until the mass of the remaining concentrated solution is 0.85 kg, and after the concentration is completed, a concentrated salt solution is obtained, and the content of Li + in the solution is 14 g / L;

[0037] (6) adding 16 g of sodium hydroxide solid into the concentrated salt solution, controlling the temperature to be 35 ℃, stirring, the stirring speed of the stirrer is 350 r / min, and the stirring time is 60 min, to obtain a solution with a pH value of 11.3, further vacuum filtering to remove impurities, and obtaining 0.75 kg of lithium extraction stock solution;

[0038] (7) to the lithium extraction of the original solution, add 150 g of solid sodium carbonate powder, control the reaction temperature to be 95℃, the stirring speed of the stirrer is 350 r / min, and react for 75 min. After the reaction is completed, vacuum filtration is carried out, and the filter residue is washed with deionized water to obtain 73 g of industrial lithium carbonate with a purity of 99.1%. The Li + content in the filtrate is 0.05 g / L.

[0039] Example 2

[0040] A method for resource utilization of impurity-containing electrolyte of electrolytic aluminum, comprising the following steps:

[0041] (1) The carbon-removed electrolyte powder of electrolytic aluminum is crushed, and the impurity-containing electrolyte of 300 mesh component is collected. 1 kg is weighed and placed in a reactor, 2.1 kg of 7 mol / L nitric acid solution is added, and the raw material is acidified and pretreated at 80℃ for 60 min with a stirring speed of 300 r / min;

[0042] (2) After the acidification treatment is completed, 0.62 kg of aluminum nitrate nonahydrate solid is added to the reactor, and the temperature is raised to 90℃ for further stirring reaction for 180 min with a stirring speed of 280 r / min, to obtain a solid-liquid mixture;

[0043] (3) The solid-liquid mixture is vacuum filtered to obtain 2.43 kg of filtrate and 0.92 kg of filter residue. The filter residue is washed with 1.0 kg of deionized water for 4 times, and the pH value of the filtrate obtained in the last time is 7. The filter residue is dried to obtain regenerated cryolite electrolyte, and the four washing filtrates and the initial filtrate are mixed to obtain 3.82 kg of mixed solution;

[0044] (4) 55 g of calcium oxide solid is added to the mixed solution, the temperature is controlled to be 45℃, the stirring speed of the stirrer is set to be 350 r / min, and stirring is carried out for 45 min to obtain a solution with a pH value of 8.3. Further vacuum filtration is carried out to obtain 3.26 kg of evaporation mother liquor;

[0045] (5) The evaporation mother liquor is evaporated and concentrated at 100℃, and the generated sodium salt solid is vacuum filtered until the mass of the remaining concentrated solution is 0.85 kg. After the concentration is completed, a concentrated salt solution is obtained, and the Li + content in the solution is 14 g / L;

[0046] (6) 16 g of sodium hydroxide solid is added to the concentrated salt solution, the temperature is controlled to be 35℃, the stirring speed of the stirrer is 350 r / min, and stirring is carried out for 60 min to obtain a solution with a pH value of 11.3. Further vacuum filtration is carried out to remove impurities, and 0.75 kg of lithium extraction mother liquor is obtained;

[0047] (7) To the lithium extraction mother liquor, 150 g of solid sodium carbonate powder was added, the reaction temperature was controlled at 95°C, the stirring speed was 350 r / min, and the reaction was carried out for 75 min. After the reaction, vacuum filtration was carried out, and the filter residue was washed with deionized water to obtain 73 g of industrial lithium carbonate with a purity of 99.1%. The Li + content in the filtrate was 0.05 g / L.

[0048] Example 3

[0049] A method for resource utilization of impurity-containing electrolyte of electrolytic aluminum, comprising the following steps:

[0050] (1) The waste residue cleaned out of the tank during electrolytic aluminum tank stopping was crushed after harmless treatment, and the impurity-containing electrolyte of 350 mesh component was collected. 1 kg was weighed and placed in a reactor, 2.0 kg of 10 mol / L sulfuric acid solution was added, and the raw material was acidified and pretreated at 85°C for 40 min with a stirring speed of 400 r / min;

[0051] (2) After the acidification treatment was completed, 0.84 kg of aluminum sulfate solid powder was added to the reactor, the temperature was raised to 90°C, and the reaction was continued for 150 min with a stirring speed of 300 r / min, to obtain a solid-liquid mixture;

[0052] (3) The solid-liquid mixture was vacuum filtered to obtain 2.3 kg of filtrate and 1.4 kg of filter residue. The filter residue was washed with 1.0 kg of deionized water for 4 times, and the pH value of the filtrate obtained in the last time was 6.9. The filter residue was dried to obtain regenerated cryolite electrolyte, and the four washing filtrates and the initial filtrate were mixed to obtain 3.75 kg of mixed solution;

[0053] (4) 65 g of calcium oxide solid was added to the mixed solution, the temperature was controlled at 30°C, the stirring speed was set at 300 r / min, and the stirring was carried out for 40 min to obtain a solution with a pH value of 8.6. Further vacuum filtration was carried out to obtain 3.1 kg of evaporation mother liquor;

[0054] (5) The evaporation mother liquor was evaporated and concentrated at 90°C, and the generated sodium salt solid was vacuum filtered until the remaining concentrated solution had a mass of 1.2 kg. After the concentration was completed, a concentrated salt solution was obtained, and the Li + content in the solution was 9 g / L.

[0055] (6) 45 g of 50% sodium hydroxide solution was added to the concentrated salt solution, the temperature was controlled at 30°C, the stirring speed was 300 r / min, the stirring time was 40 min, and a solution with a pH value of 11.1 was obtained. Further vacuum filtration was carried out to remove impurities, and 0.97 kg of lithium extraction mother liquor was obtained;

[0056] (7) To the lithium extraction mother liquor, 180 g of solid sodium carbonate powder was added, the reaction temperature was controlled at 88°C, the stirring speed was 300 r / min, and the reaction was carried out for 80 min. After the reaction was completed, vacuum filtration was carried out, and the filter residue was washed with deionized water to obtain 70 g of industrial lithium carbonate with a purity of 98.9%. The Li + content in the filtrate was 0.15 g / L.

[0057] Example 4

[0058] A method for resource utilization of impure electrolyte of electrolytic aluminum containing impurities, comprising the following steps:

[0059] (1) The electrolyte blocks displaced from the electrolytic cell and the electrolyte powder after carbon flotation were mixed and crushed, and the impure electrolyte of 300 mesh component was collected. 1 kg of the impure electrolyte was placed in a reactor, 1.8 kg of mixed acid of 5 mol / L hydrochloric acid and 5 mol / L nitric acid was added, and the mixture was stirred at 80°C for 100 min. The stirring speed was 350 r / min, and the raw material was acidified and pretreated;

[0060] (2) After the acidification treatment was completed, 0.92 kg of aluminum hydroxide solid powder was added to the reactor, and the temperature was raised to 85°C. The stirring reaction was continued for 240 min, and the stirring speed was 350 r / min. A solid-liquid mixture was obtained;

[0061] (3) The solid-liquid mixture was vacuum filtered to obtain 1.9 kg of filtrate and 1.77 kg of filter residue. The filter residue was washed with 1.2 kg of deionized water for 3 times, and the pH value of the filtrate obtained in the last time was 7. The filter residue was dried to obtain regenerated cryolite electrolyte. The four washing filtrates and the initial filtrate were mixed to obtain 3.45 kg of mixed solution;

[0062] (4) 52 g of calcium oxide solid was added to the mixed solution, the temperature was controlled at 25°C, the stirring speed was set at 350 r / min, and the stirring was carried out for 40 min. A solution with a pH value of 8.1 was obtained, and further vacuum filtration was carried out to obtain 2.71 kg of evaporation mother liquor;

[0063] (5) The evaporation mother liquor was evaporated and concentrated at 85°C, and the generated sodium salt solid was vacuum filtered until the remaining concentrated liquid had a mass of 0.66 kg. After the concentration was completed, a concentrated salt solution was obtained, and the Li + content in the solution was 11 g / L;

[0064] (6) 50 g of 50% sodium hydroxide solution was added to the concentrated salt solution, the temperature was controlled at 25°C, the stirring speed was 300 r / min, the stirring time was 30 min, and a solution with a pH value of 10.8 was obtained. Further vacuum filtration was carried out to remove impurities, and 0.53 kg of lithium extraction mother liquor was obtained;

[0065] (7) To the lithium extraction mother liquor, 110 g of solid sodium carbonate powder was added, the reaction temperature was controlled at 90°C, the stirring speed was 350 r / min, and the reaction was carried out for 150 min. After the reaction, vacuum filtration was carried out, and the filter residue was washed with deionized water to obtain 61 g of industrial lithium carbonate with a purity of 98.8%. The Li + content in the filtrate was 0.12 g / L.

[0066] Example 5

[0067] A method for resource utilization of impurity-containing electrolyte of electrolytic aluminum, comprising the following steps:

[0068] (1) The impurity-containing electrolyte was obtained by crushing the products of the hazardous treatment of the electrolyte blocks displaced from the electrolytic cell, the electrolyte powder after carbon removal by flotation, and the waste residue cleaned out of the cell during the electrolytic aluminum cell stoppage, and collecting the 300-mesh component. 1 kg of the impurity-containing electrolyte was placed in a reactor, 3.5 kg of a mixed acid of 5 mol / L hydrochloric acid and 6 mol / L sulfuric acid was added, and the raw material was acidified and pretreated at 60°C for 60 min with a stirring speed of 350 r / min;

[0069] (2) After the acidification treatment, 0.55 kg of aluminum hydroxide solid powder was added to the reactor, the temperature was raised to 80°C, and the reaction was continued for 200 min with a stirring speed of 300 r / min, to obtain a solid-liquid mixture;

[0070] (3) The solid-liquid mixture was vacuum filtered to obtain 2.3 kg of filtrate and 1.8 kg of filter residue. The filter residue was washed with 0.9 kg of deionized water for 3 times, and the pH value of the filtrate obtained in the last time was 6.8. The filter residue was dried to obtain regenerated cryolite electrolyte, and the filtrate obtained in the four times of washing and the initial filtrate were mixed to obtain 3.5 kg of mixed solution;

[0071] (4) 29 g of calcium oxide solid was added to the mixed solution, the temperature was controlled at 50°C, the stirring speed was set at 350 r / min, and the stirring was carried out for 60 min to obtain a solution with a pH value of 7.4. Further vacuum filtration was carried out to obtain 2.8 kg of evaporation mother liquor;

[0072] (5) The evaporation mother liquor was evaporated and concentrated at 95°C, and the generated sodium salt solid was vacuum filtered until the mass of the remaining concentrated solution was 0.95 kg. After the concentration was completed, a concentrated salt solution was obtained, and the Li + content in the solution was 15 g / L;

[0073] (6) 22 g of sodium hydroxide solid was added to the concentrated salt solution, the temperature was controlled at 50°C, the stirring speed was 300 r / min, and the stirring time was 60 min to obtain a solution with a pH value of 11.8. Further vacuum filtration was carried out to remove impurities, and 0.76 kg of lithium extraction mother liquor was obtained;

[0074] (7) to the lithium extraction of the original solution, add 220 g of 50% sodium carbonate solution, control the reaction temperature to be 95°C, the stirring speed to be 350 r / min, and react for 180 min. After the reaction is completed, vacuum filtration is carried out, the filter residue is washed with deionized water, and 71 g of industrial lithium carbonate with a purity of 99.3% is obtained. The Li + content in the filtrate is 0.09 g / L.

[0075] Example 6

[0076] A method for resource utilization of impure electrolyte of electrolytic aluminum, comprising the following steps:

[0077] (1) The impure electrolyte is collected by mixing and crushing the products after harmless treatment of the electrolyte powder after carbon flotation in the electrolytic cell and the waste residue cleaned out of the tank during the shutdown of the electrolytic aluminum tank, and the 400-mesh component is weighed at 1 kg and placed in a reactor. Add 3.0 kg of mixed acid of 8 mol / L hydrochloric acid and 5 mol / L nitric acid, stir at 60°C for 70 min, and the stirring speed is 300 r / min. The raw material is acidified and pretreated;

[0078] (2) After the acidification treatment is completed, 0.55 kg of aluminum hydroxide solid powder is added to the reactor, the temperature is raised to 80°C, and the stirring reaction is continued for 180 min, and the stirring speed is 350 r / min. A solid-liquid mixture is obtained;

[0079] (3) The solid-liquid mixture is vacuum filtered to obtain 2.6 kg of filtrate and 1.7 kg of filter residue. The filter residue is washed with 0.8 kg of deionized water for 4 times, and the pH value of the filtrate obtained in the last time is 6.9. The filter residue is dried to obtain regenerated cryolite electrolyte. The four washing filtrates and the initial filtrate are mixed to obtain 3.78 kg of mixed solution;

[0080] (4) Add 61 g of calcium oxide solid to the mixed solution, control the temperature to be 30°C, set the stirring speed to be 400 r / min, and stir for 40 min to obtain a solution with a pH value of 8.8. Further vacuum filtration is carried out to obtain 3.18 kg of evaporation original solution;

[0081] (5) The evaporation original solution is evaporated and concentrated at 99°C, and the generated sodium salt solid is vacuum filtered until the remaining concentrated solution has a mass of 0.85 kg. After the concentration is completed, a concentrated salt solution is obtained, and the Li + content in the solution is 9 g / L;

[0082] (6) Add 18 g of sodium hydroxide solid to the concentrated salt solution, control the temperature to be 25°C, and stir at a stirring speed of 400 r / min for 40 min to obtain a solution with a pH value of 10.9. Further vacuum filtration is carried out to remove impurities, and 0.68 kg of lithium extraction original solution is obtained;

[0083] (7) To the lithium extraction mother liquor, 120 g of solid sodium carbonate powder was added, the reaction temperature was controlled at 90°C, the stirring speed was 400 r / min, and the reaction was carried out for 80 min. After the reaction, vacuum filtration was carried out, and the filter residue was washed with deionized water to obtain 59 g of industrial lithium carbonate with a purity of 98.9%. The Li + content in the filtrate was 0.07 g / L.

[0084] Example 7

[0085] A method for resource utilization of impure electrolyte of electrolytic aluminum containing impurities, comprising the following steps:

[0086] (1) The electrolyte block replaced from the electrolytic cell was crushed, and the impure electrolyte of 300 mesh component was collected. 1 kg of the impure electrolyte was weighed and placed in a reactor, 1.2 kg of a mixed solution of 5 mol / L hydrochloric acid, 5 mol / L sulfuric acid and 5 mol / L sulfuric acid was added, and the mixture was stirred at 66°C for 60 min at a stirring speed of 350 r / min, so as to perform acidification pretreatment on the raw material;

[0087] (2) After the acidification treatment was completed, 0.65 kg of aluminum hydroxide solid powder was added to the reactor, the temperature was increased to 80°C, and the reaction was continued for 200 min at a stirring speed of 350 r / min, so as to obtain a solid-liquid mixture;

[0088] (3) The solid-liquid mixture was subjected to vacuum filtration to obtain 1.48 kg of filtrate and 1.23 kg of filter residue. The filter residue was washed with 1.1 kg of deionized water for 4 times, and the pH value of the filtrate obtained in the last time was 6.9. The filter residue was dried to obtain regenerated cryolite electrolyte. The four washing filtrates and the initial filtrate were mixed to obtain 4.75 kg of a mixed solution;

[0089] (4) 30 g of calcium oxide solid was added to the mixed solution, the temperature was controlled at 30°C, the stirring speed was set at 350 r / min, and the mixture was stirred for 30 min to obtain a solution with a pH value of 8.7. The solution was further subjected to vacuum filtration to obtain 3.58 kg of an evaporation mother liquor;

[0090] (5) The evaporation mother liquor was evaporated and concentrated at 90°C. The generated sodium salt solid was subjected to vacuum filtration until the mass of the remaining concentrated solution was 0.75 kg. After the concentration was completed, a concentrated salt solution was obtained, and the Li + content in the solution was 14 g / L.

[0091] (6) 29 g of sodium hydroxide solid was added to the concentrated salt solution, the temperature was controlled at 25°C, the stirring speed was 350 r / min, and the stirring time was 30 min to obtain a solution with a pH value of 11.7. The solution was further subjected to vacuum filtration to remove impurities, and 0.62 kg of a lithium extraction mother liquor was obtained.

[0092] (7) 100 g of solid sodium carbonate powder was added to the lithium extraction raw solution, the reaction temperature was controlled at 90°C, the stirring speed was 350 r / min, and the reaction was carried out for 75 min. After the reaction, vacuum filtration was carried out, and the residue was washed with deionized water to obtain 75 g of industrial lithium carbonate with a purity of 99.1%. The Li + content in the filtrate was 0.08 g / L.

[0093] Through detection, the yield of Li element in examples 1-7 was all above 82%, and the purity of lithium carbonate was all above 98.8%.

[0094] Although the present application has been described in detail by preferred embodiments, the present application is not limited thereto. Any modification or replacement of the embodiments of the present application made by those skilled in the art without departing from the spirit and essence of the present application shall fall within the scope of the present application. Any modification or replacement made by those skilled in the art within the technical range disclosed by the present application shall fall within the protection scope of the present application.

Claims

1. A method for resource utilization of an impure electrolyte of electrolytic aluminum, characterized in that, The method comprises the following steps: (1) adding inorganic acid into the impurity-containing electrolyte, stirring and mixing at 50-90℃ for 40-120min to obtain an acidification product, and the impurity-containing electrolyte is electrolytic aluminum waste residue; (2) adding aluminum-containing inorganic compound, stirring and reacting at 50-110℃ for 60-720min to obtain a solid-liquid mixture, and the aluminum-containing inorganic compound comprises one or more of aluminum oxide, aluminum hydroxide, aluminum chloride, aluminum chloride hexahydrate, aluminum nitrate, aluminum nitrate nonahydrate, aluminum sulfate and aluminum sulfite; (3) filtering the solid-liquid mixture, washing the filter residue until the pH value of the washing water is 6.5-7.5, drying the filter residue after washing to obtain regenerated cryolite electrolyte, and mixing the washing water and the filtrate to obtain a mixed solution; (4) adding at least one of sodium hydroxide, calcium hydroxide and calcium oxide into the mixed solution, adjusting the pH value to 7-9, and filtering to obtain an evaporation stock solution; (5) evaporating and concentrating the evaporation stock solution, filtering, drying the filter residue to obtain industrial sodium salt, and the filtrate is a concentrated salt solution; (6) adding sodium hydroxide into the concentrated salt solution, adjusting the pH value to 9-12, and filtering to obtain a lithium extraction stock solution; (7) adding sodium carbonate into the lithium extraction stock solution, controlling the reaction temperature to be 50-100℃, stirring and reacting for 30-180min, filtering at room temperature after the reaction, and drying the filter residue to obtain industrial lithium carbonate, and collecting the filtrate.

2. The method for resource utilization of aluminum electrolysis impure electrolyte according to claim 1, characterized in that, In step (1), the impurity-containing electrolyte is electrolytic aluminum waste residue after crushing and screening, and the mesh number is 50-420.

3. The method for resource utilization of aluminum electrolysis impure electrolyte according to claim 1, characterized in that, In step (1), the inorganic acid is at least one of hydrochloric acid, nitric acid, sulfuric acid and phosphoric acid, and the concentration is 5-10mol / L.

4. The method for resource utilization of aluminum electrolysis impure electrolyte according to claim 1, characterized in that, In step (4), the temperature is controlled to be 25-60℃, and the stirring is continued for 30-60min; in step (6), the temperature is controlled to be 25-60℃, and the stirring is continued for 30-60min.

5. The method for resource utilization of aluminum electrolysis impure electrolyte according to claim 1, characterized in that, In step (5), the evaporation temperature is 80-100℃, and the volume ratio of the concentrated salt solution to the evaporation stock solution is 1:(3-5).

6. The method for resource utilization of aluminum electrolysis impure electrolyte according to claim 1, characterized in that, After filtering in step (7), the lithium ion concentration in the filtrate is measured, if the lithium ion concentration is >1g / L, the filtrate is used as the reaction liquid to repeat step (7) until the lithium ion concentration in the filtrate is ≤1g / L, and the finally collected filtrate is the impurity-removed electrolyte.

7. The method for resource utilization of aluminum electrolysis impure electrolyte according to claim 6, characterized in that, In step (3), the liquid for washing the filter residue comprises the impurity-removed electrolyte and / or deionized water.

8. The method for resource utilization of aluminum electrolysis impure electrolyte according to claim 1, characterized in that, In step (1), the inorganic acid is added in an amount of 1-5kg / kg based on the weight of the impurity-containing electrolyte in step (1); in step (2), the aluminum-containing inorganic compound is added in an amount of 0.5-5kg / kg; and in step (7), the sodium carbonate is added in an amount of 0.1-6kg / kg.