Method for preparing nano iron oxide red for lithium battery by using titanium dioxide by-product copperas

Abstract

The invention discloses a method for preparing nano iron oxide red for a lithium battery by using a titanium dioxide by-product copperas, and belongs to the technical field of nano iron oxide red preparation. The method comprises the following steps: by taking a titanium dioxide by-product copperas as a raw material, removing impurities by adopting a recrystallization method and an ammonium fluoride precipitation method in sequence, oxidizing and precipitating a ferrous sulfate solution after impurity removal to obtain a nanoscale iron oxide red precipitate, washing, drying, grinding, and calcining at high temperature to obtain the nano iron oxide red for the lithium battery. The method disclosed by the invention is simple and convenient to operate, low in equipment requirement and easy to industrially popularize, not only solves the problem of environmental pollution caused by the byproduct copperas of the titanium dioxide, but also improves the quality of the nano iron oxide red, conforms to the green and environment-friendly concept, provides a high-quality and low-cost nano iron oxide red material for the lithium battery industry, and has a wide application prospect. The method has remarkable economic benefits and social benefits, and resource recycling and sustainable development are promoted.

Description

Technical Field

[0001] The present invention belongs to the technical field of the preparation of nano - iron oxide red, and more specifically, relates to a method for preparing nano - iron oxide red for lithium batteries by using the by - product green vitriol of titanium dioxide. Background Art

[0002] The chemical formula of iron oxide red is α - Fe2O3. When the particle size of iron oxide reaches the nanoscale, its surface atomic number, specific surface area, surface energy, etc. all increase with the decrease of the particle size, showing excellent electrical conductivity, magnetism and catalytic activity, and are widely used in the positive electrode materials of lithium batteries.

[0003] In China, the sulfuric acid method is basically adopted in the industrial production of titanium dioxide. For every ton of titanium dioxide produced, about 3.5 - 4 tons of by - product green vitriol (ferrous sulfate heptahydrate) is generated. The annual by - product of ferrous sulfate heptahydrate is about 3.5 million tons. If it is not properly disposed of, it will not only cause low utilization rate of iron resources and waste of land resources, but also cause environmental problems such as dust, water source and soil pollution.

[0004] The preparation methods of nano - iron oxide red can be divided into two categories: wet method and dry method. At present, the wet method is mainly used in the industrial production of nano - iron oxide red, mainly using industrial - grade ferrous sulfate, ferric chloride, ferrous chloride or ferric nitrate as raw materials, and preparing nano - iron oxide red by methods such as air oxidation method, colloid chemistry method, hydrolysis method, etc. Its high raw material cost limits the production of nano - iron oxide red to a certain extent.

[0005] Therefore, it is necessary to find a method for efficiently using the by - product green vitriol of titanium dioxide to prepare nano - iron oxide red for lithium batteries, so as to meet the requirements of treating industrial pollution of the three wastes, increasing economic benefits and expanding the application of nano - iron oxide red in lithium batteries. Summary of the Invention

[0006] Aiming at the above problems existing in the prior art, the technical problem to be solved by the present invention is to provide a method for preparing nano - iron oxide red for lithium batteries by using the by - product green vitriol of titanium dioxide, which can comprehensively utilize green vitriol resources and reduce environmental pollution.

[0007] To solve the above - mentioned technical problems, the technical solution adopted by the present invention is as follows:

[0008] A method for preparing nano - iron oxide red for lithium batteries by using the by - product green vitriol of titanium dioxide, taking the by - product green vitriol of titanium dioxide as the raw material, successively adopting the recrystallization method and ammonium fluoride precipitation method for impurity removal, oxidizing and precipitating the impurity - removed ferrous sulfate solution to obtain nano - scale iron oxide red precipitate, and then washing, drying, grinding and high - temperature calcining to prepare nano - iron oxide red for lithium batteries.

[0009] Preferably, in the recrystallization method, the recrystallization temperature is 8 - 10°C, and the cooling rate is 4°C / h.

[0010] The method for preparing nano - iron oxide red for lithium batteries by using by - product green vitriol of titanium dioxide pigment specifically includes the following steps:

[0011] 1) Add by - product green vitriol of titanium dioxide pigment into water at 50 °C, fully stir and dissolve it to form a saturated ferrous sulfate solution, then put it into a reaction kettle for cooling and recrystallization. After the crystallization is stable, carry out suction filtration. The number of recrystallization times is 3 times to obtain ferrous sulfate crystals;

[0012] 2) Dissolve the ferrous sulfate crystals obtained in step 1) in water at 25 °C to prepare a ferrous sulfate solution. When the pH of the ferrous sulfate solution is adjusted to 6 by adding dilute ammonia water, add ammonium fluoride for reaction, and filter through a filter membrane with a pore size of 0.45 μm to obtain a pure ferrous sulfate solution;

[0013] 3) Add hydrogen peroxide to the pure ferrous sulfate solution obtained in step 2) for oxidation; after the solution is completely oxidized, add dilute ammonia water to adjust the pH of the ferric sulfate solution to 6.5 to obtain iron hydroxide precipitate. After slurrying and washing 5 times and ultrasonic washing 3 times, carry out solid - liquid separation to obtain a precursor;

[0014] 4) Put the precursor obtained in step 3) into a vacuum drying oven for drying. After drying, put the precursor into a ball - milling cylinder of a material processing device for grinding; put the ground precursor into a tubular furnace for roasting to obtain nano - iron oxide red.

[0015] Preferably, in step 2), a ferrous sulfate solution with a 2+ mass concentration of 60 g / L of Fe is prepared.

[0016] Preferably, in step 2), the mass ratio of ammonium fluoride to ferrous sulfate crystals is 1:20.

[0017] Preferably, in step 2), the reaction temperature is 30 - 50 °C and the reaction time is 1 h.

[0018] Preferably, in step 4), the grinding is carried out until the particle size is not greater than 0.5 µm.

[0019] Preferably, in step 4), it is roasted in air at a temperature of 750 - 800 °C for 2 h.

[0020] The method for preparing nano - iron oxide red for lithium batteries by using by - product green vitriol of titanium dioxide pigment prepares nano - iron oxide red.

[0021] The application of the nano - iron oxide red in the cathode material of lithium batteries.

[0022] Compared with the prior art, the beneficial effects of the present invention are:

[0023] 1) The present invention successively uses recrystallization and ammonium fluoride precipitation on by - product green vitriol of titanium dioxide to purify ferrous sulfate, effectively removing impurities and improving the purity of raw materials. Then, hydrogen peroxide oxidation method and ammonia precipitation method are used to precipitate ferrous sulfate to obtain iron oxyhydroxide. Next, the iron oxyhydroxide is washed by slurry - adjusting method and ultrasonic method to obtain a precursor. Finally, the precursor after roasting and grinding is used to prepare nano - iron oxide red; this method effectively utilizes the by - product green vitriol of titanium dioxide, realizes the efficient recycling of resources, and increases economic benefits;

[0024] 2) The method of the present invention is simple, economical and feasible, with low equipment requirements and easy to be popularized industrially. It not only solves the environmental pollution problem of by - product green vitriol of titanium dioxide, but also improves the quality of nano - iron oxide red, conforms to the concept of green environmental protection, provides high - quality nano - iron oxide red materials for the lithium - battery industry, and promotes sustainable development. Detailed implementation manners

[0025] To make the purpose, technical solutions and advantages of the present invention clearer, the present invention will be further described below in conjunction with specific embodiments. In the following embodiments, unless otherwise specified, the technical means used are all conventional means well - known to those skilled in the art.

[0026] In the following embodiments, the main impurity ions Ca 2+ , Mg 2+ , Mn 2+ , Al 3+ , Si 4 + , Zn 2+ , K + , S 2+ in the selected by - product green vitriol of titanium dioxide have mass concentrations as follows: 169 mg / L, 124 mg / L, 93 mg / L, 112 mg / L, 219 mg / L, 183 mg / L, 102 mg / L, 134 mg / L.

[0027] Example 1

[0028] A method for preparing nano - iron oxide red for lithium batteries using by - product green vitriol of titanium dioxide includes the following steps:

[0029] 1) Add 10 kg of by - product green vitriol of titanium dioxide to 20 L of water at 50 °C, fully stir and dissolve it into a saturated ferrous sulfate solution, then put it into a reaction kettle for cooling recrystallization. The cooling rate is 4 °C / h, and the recrystallization temperature is 10 °C. After the crystallization is stable, carry out suction filtration to obtain ferrous sulfate crystals, and repeat the whole crystallization process 3 times;

[0030] 2) Dissolve 7.2 kg of the ferrous sulfate crystals obtained in step 1) in 120 L of water at 25 °C to obtain a solution containing Fe 2+When the pH of a ferrous sulfate solution with a mass concentration of 60 g / L is adjusted to 6 with dilute ammonia water, 0.36 kg of ammonium fluoride is added. After reacting at 30 °C for 1 h, a pure ferrous sulfate solution is obtained by filtration through a filter membrane with a pore size of 0.45 μm.

[0031] 3) Add hydrogen peroxide with a mass fraction of 10% to the pure ferrous sulfate solution obtained in step 2) to oxidize ferrous sulfate. After the solution is completely oxidized, add dilute ammonia water to adjust the pH of the ferric sulfate solution to 6.5 to obtain iron oxyhydroxide precipitate. Repeat adding deionized water to the obtained iron oxyhydroxide precipitate for pulp washing 5 times, and then perform ultrasonic washing 3 times. After solid-liquid separation, the precursor of the final product is obtained.

[0032] 4) Put the precursor prepared in step 3) into a vacuum drying oven for drying. After drying, put the precursor into the ball mill cylinder of the material processing device for grinding until the particle size reaches 0.2 μm.

[0033] 5) Put the precursor ground in step 4) into a tube furnace for roasting. After roasting in air at a temperature of 800 °C for 2 h and then pulverizing, nano-iron oxide red with a purity of 99.98% is obtained. The morphology of the nano-iron oxide red is spherical particles with an average particle size of 43 nm.

[0034] Example 2

[0035] A method for preparing nano-iron oxide red for lithium batteries using by-product green vitriol of titanium dioxide includes the following steps:

[0036] 1) Add 10 kg of by-product green vitriol of titanium dioxide to 20 L of water at 50 °C, stir well and dissolve it into a saturated ferrous sulfate solution, then put it into a reaction kettle for cooling recrystallization. The cooling rate is 4 °C / h, and the recrystallization temperature is 8 °C. After the crystallization is stable, perform suction filtration to obtain ferrous sulfate crystals. The whole crystallization process is repeated 3 times.

[0037] 2) Dissolve 7.2 kg of the ferrous sulfate crystals prepared in step 1) in 120 L of water at 25 °C to obtain a ferrous sulfate solution containing Fe 2+ When the pH of a ferrous sulfate solution with a mass concentration of 60 g / L is adjusted to 6 with dilute ammonia water, 0.36 kg of ammonium fluoride is added. After reacting at 30 °C for 1 h, a pure ferrous sulfate solution is obtained by filtration through a filter membrane with a pore size of 0.45 μm.

[0038] 3) Add hydrogen peroxide with a mass fraction of 10% to the pure ferrous sulfate solution obtained in step 2) to oxidize ferrous sulfate. After the solution is completely oxidized, add dilute ammonia water to adjust the pH of the ferric sulfate solution to 6.5 to obtain iron oxyhydroxide precipitate. Repeat adding deionized water to the obtained iron oxyhydroxide precipitate for pulp washing 5 times, and then perform ultrasonic washing 3 times. After solid-liquid separation, the precursor of the final product is obtained;

[0039] 4) Put the precursor prepared in step 3) into a vacuum drying oven for drying. After drying, put the precursor into the ball milling cylinder of the material processing device and grind it to a particle size of 0.3 µm;

[0040] 5) Put the precursor ground in step 4) into a tubular furnace for roasting. Roast it in air at a temperature of 800 °C for 2 h and then crush it. The purity of the prepared nano-iron oxide red is 99.94%. The morphology of the nano-iron oxide red is spherical particles with an average particle size of 51 nm.

[0041] Example 3

[0042] A method for preparing nano-iron oxide red for lithium batteries using by-product green vitriol of titanium dioxide, comprising the following steps:

[0043] 1) Add 10 kg of by-product green vitriol of titanium dioxide to 20 L of water at 50 °C, stir well and dissolve it to a saturated ferrous sulfate solution, then put it into a reaction kettle for cooling recrystallization. The cooling rate is 4 °C / h, the recrystallization temperature is 10 °C. After the crystallization is stable, perform suction filtration to obtain ferrous sulfate crystals. The whole crystallization process is repeated 3 times;

[0044] 2) Dissolve 7.2 kg of the ferrous sulfate crystals prepared in step 1) in 120 L of water at 25 °C to obtain a ferrous sulfate solution with a mass concentration of Fe 2+ of 60 g / L. When adding dilute ammonia water to adjust the pH of the ferrous sulfate solution to 4, add 0.36 kg of ammonium fluoride, react at 50 °C for 1 h, and then filter through a filter membrane with a pore size of 0.45 µm to obtain a pure ferrous sulfate solution;

[0045] 3) Add hydrogen peroxide with a mass fraction of 10% to the pure ferrous sulfate solution obtained in step 2) to oxidize ferrous sulfate. After the solution is completely oxidized, add dilute ammonia water to adjust the pH of the ferric sulfate solution to 6.5 to obtain iron oxyhydroxide precipitate. Repeat adding deionized water to the obtained iron oxyhydroxide precipitate for pulp washing 5 times, and then perform ultrasonic washing 3 times. After solid-liquid separation, the precursor of the final product is obtained;

[0046] 4) Put the precursor prepared in step 3) into a vacuum drying oven for drying. After drying, put the precursor into the ball milling cylinder of the material processing device and grind it to a particle size of 0.3 µm;

[0047] 5) Put the precursor ground in step 4) into a tube furnace for calcination. After calcination in air at a temperature of 800 °C for 2 h and then pulverized, the purity of the prepared nano - iron oxide red is 99.92%, the morphology of the nano - iron oxide red is spherical particles, and the average particle size is 57 nm.

[0048] Example 4

[0049] A method for preparing nano - iron oxide red for lithium batteries using by - product green vitriol of titanium dioxide, comprising the following steps:

[0050] 1) Add 10 kg of by - product green vitriol of titanium dioxide to 20 L of water at 50 °C, stir well and dissolve to a saturated ferrous sulfate solution, then put it into a reaction kettle for cooling recrystallization. The cooling rate is 4 °C / h, the recrystallization temperature is 10 °C, and after the crystallization is stable, carry out suction filtration to obtain ferrous sulfate crystals. The whole crystallization process is repeated 3 times;

[0051] 2) Dissolve 7.2 kg of the ferrous sulfate crystals prepared in step 1) in 120 L of water at 25 °C to obtain a ferrous sulfate solution with a Fe 2+ mass concentration of 60 g / L. When the pH of the ferrous sulfate solution is adjusted to 6 with dilute ammonia water, add 0.36 kg of ammonium fluoride, react at 30 °C for 1 h, and then filter through a filter membrane with a pore size of 0.45 μm to obtain a pure ferrous sulfate solution;

[0052] 3) Add hydrogen peroxide with a mass fraction of 10% to the pure ferrous sulfate solution obtained in step 2) to oxidize ferrous sulfate. After the solution is completely oxidized, adjust the pH of the ferric sulfate solution to 6.5 with dilute ammonia water to obtain iron hydroxide precipitate. Repeat adding deionized water to the obtained iron hydroxide precipitate for pulp washing 5 times, and then carry out ultrasonic washing 3 times. After solid - liquid separation, obtain the precursor of the final product;

[0053] 4) Put the precursor prepared in step 3) into a vacuum drying oven for drying. After drying, put the precursor into the ball - milling cylinder of the material processing device and grind it to a particle size of 0.2 µm;

[0054] 5) Put the precursor ground in step 4) into a tube furnace for calcination. After calcination in air at a temperature of 750 °C for 2 h and then pulverized, the purity of the prepared nano - iron oxide red is 99.96%, the morphology of the nano - iron oxide red is spherical particles, and the average particle size is 49 nm.

[0055] Comparative Example 1

[0056] When preparing nano red iron oxide for lithium battery, the recrystallization temperature in step 1) is 15°C, the cooling rate is 8°C / h, and the entire crystallization process is repeated once; the remaining parameters and preparation process are the same as those in Example 1, and nano red iron oxide with a purity of 96.45% and an average particle size of 67nm is obtained.

[0057] Comparative Example 2

[0058] When preparing nano red iron oxide for lithium battery, in step 2), when dilute ammonia water is added to adjust the pH of ferrous sulfate solution to 2, 0.1 kg of ammonium fluoride is added and the reaction is carried out at 30° C. for 1 hour; the other parameters and preparation process are the same as those in Example 1, and nano red iron oxide with a purity of 97.65% and an average particle size of 62 nm is obtained.

[0059] Comparative Example 3

[0060] When preparing nano iron oxide red for lithium battery, the Fe 2+ A ferrous sulfate solution with a mass concentration of 60 g / L was directly added with hydrogen peroxide with a mass fraction of 10% to oxidize the ferrous sulfate; the other parameters and preparation process were the same as those in Example 1, and nano-iron oxide red with a purity of 89.35% and an average particle size of 71 nm was obtained.

[0061] The nano red iron oxide prepared in Examples 1-4 was tested for the content of major impurity ions, and the test results are shown in Table 1.

[0062] Table 1: Results of main impurity contents in the nano iron oxide red products prepared in Examples 1-4

[0063]

[0064] The nano red iron oxide prepared in Examples 1-4 and Comparative Examples 1-3 was subjected to a high temperature resistance test, and the following test data were obtained. The specific data are shown in Table 2. Temperature resistance test: The above samples were tested for the temperature resistance of the pigment powder according to the national standard HG / T 3853-2006 Pigment Dry Powder Heat Resistance Determination Method, and the test temperature was set to 700°C. Specific operation: The oven temperature was raised to 700°C, and after the oven temperature stabilized, a crucible containing 2.5g of the sample powder to be tested was placed in the oven, and the timing was started when the oven temperature rose to 700°C. The sample was taken out after 30 minutes, and the color difference ΔE of the pigment before and after baking was measured after the sample was cooled.

[0065] Table 2: High temperature resistance test data of nano iron oxide red prepared in Examples 1-4 and Comparative Examples 1-3

[0066]

[0067] As can be seen from Table 2, the nano-sized iron oxide red prepared by the present invention can withstand high temperatures up to 700 °C, and the color difference ΔE is significantly lower than that of the sample of the comparative example, showing excellent high-temperature resistance.

[0068] The above is only a preferred specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention, according to the technical solution and inventive concept of the present invention, making equivalent substitutions or changes should be covered within the protection scope of the present invention.

Claims

1. A method for preparing nano - iron oxide red for lithium batteries using by - product green vitriol of titanium dioxide, characterized in that, Using by-product green vitriol of titanium dioxide as raw material, impurity removal is carried out successively by recrystallization method and ammonium fluoride precipitation method. The purified ferrous sulfate solution is oxidized and precipitated to obtain nano-sized iron oxide red precipitate, and then through washing, drying, grinding and high-temperature calcination, nano iron oxide red for lithium batteries is prepared.

2. The method for preparing nano-sized iron oxide red for lithium batteries by using by-product green vitriol of titanium white powder according to claim 1, characterized in that, In the recrystallization method, the recrystallization temperature is 8 - 10 °C and the cooling rate is 4 °C / h.

3. The method for preparing nano - iron oxide red for lithium batteries using by - product green vitriol of titanium white powder according to claim 1, characterized in that, Specifically, it includes the following steps: 1) Add by-product green vitriol of titanium dioxide into water at 50 °C, fully stir and dissolve it into a saturated ferrous sulfate solution, then put it into a reaction kettle for cooling recrystallization. After the crystallization is stable, carry out suction filtration. The number of recrystallization times is 3 times to obtain ferrous sulfate crystals. 2) Dissolve the ferrous sulfate crystals prepared in step 1) in water at 25 °C to obtain a ferrous sulfate solution. When the pH of the ferrous sulfate solution is adjusted to 6 with dilute ammonia water, add ammonium fluoride for reaction, and filter through a filter membrane with a pore size of 0.45 μm to obtain a pure ferrous sulfate solution. 3) Add hydrogen peroxide to the pure ferrous sulfate solution obtained in step 2) for oxidation; after the solution is completely oxidized, adjust the pH of the ferric sulfate solution to 6.5 with dilute ammonia water to obtain iron oxyhydroxide precipitate. After slurrying and washing 5 times and ultrasonic washing 3 times, solid-liquid separation is carried out to obtain a precursor. 4) Put the precursor prepared in step 3) into a vacuum drying oven for drying. After drying, put the precursor into the ball mill cylinder of the material processing device for grinding; put the ground precursor into a tubular furnace for roasting to obtain nano iron oxide red.

4. The method for preparing nano-sized iron oxide red for lithium batteries by using by-product green vitriol of titanium white powder according to claim 3, wherein In step 2), a ferrous sulfate solution with a Fe 2+ mass concentration of 60 g / L is prepared.

5. The method for preparing nano-sized iron oxide red for lithium batteries by using by-product melanterite of titanium dioxide as claimed in claim 3, wherein In step 2), the mass ratio of ammonium fluoride to ferrous sulfate crystals is 1:

20.

6. The method for preparing nano-sized iron oxide red for lithium batteries by using by-product green vitriol of titanium dioxide according to claim 3, characterized in that, In step 2), the reaction temperature is 30 - 50 °C and the reaction time is 1 h.

7. The method for preparing nano-sized iron oxide red for lithium batteries by using by-product green vitriol of titanium white powder according to claim 3, characterized in that, In step 4), grind to a particle size not greater than 0.5 µm.

8. The method for preparing nano-sized iron oxide red for lithium batteries by using by-product green vitriol of titanium white powder according to claim 3, characterized in that, In step 4), roast in air at a temperature of 750 - 800 °C for 2 h.

9. The method for preparing nano iron oxide red for lithium batteries according to any one of claims 1 - 8, and the nano iron oxide red is prepared.

10. Application of the nano iron oxide red according to claim 9 in the positive electrode material of a lithium battery.

Images