Method for preparing high-purity nano aluminum fluoride from aluminum electrolysis fluorine-containing waste

Abstract

The invention provides a method for preparing high-purity nano aluminum fluoride through aluminum electrolysis of fluorine-containing waste, and belongs to the field of nano materials. The method comprises the steps that aluminum electrolysis fluorine-containing waste powder is leached, and first mixed slurry is obtained; performing solid-liquid separation on the first mixed slurry to obtain a first fluorine-containing liquid; adjusting the aluminum-fluorine ratio and the pH value of the first fluorine-containing liquid to obtain a second fluorine-containing liquid; preheating the second fluorine-containing liquid to a set temperature, and adding a crystallization aid into the second fluorine-containing liquid to obtain a third fluorine-containing liquid; heating the third fluorine-containing liquid at a set heating rate at a set final heating temperature and a set heat preservation time, and performing ultrasonic irradiation oscillation in the heating process to obtain second mixed slurry; and carrying out solid-liquid separation on the second mixed slurry to obtain the high-purity nano aluminum fluoride. The nano aluminum fluoride with high purity, narrow particle size distribution and large specific surface area can be prepared through the synergistic effect of ultrasonic waves and the crystallization auxiliary agent and the reasonable matching of crystallization process conditions.

Description

Technical Field

[0001] The present application relates to the technical field of nanomaterials, and in particular to a method for preparing high-purity nano aluminum fluoride from fluorine-containing waste materials by aluminum electrolysis. Background Art

[0002] In the gas-phase catalytic synthesis of fluorinated halogenated hydrocarbons, such as the preparation of the third-generation refrigerant hydrofluorocarbons (HFCs) and the fourth-generation refrigerant hydrofluoroolefins (HFOs), highly corrosive HF is either one of the reactants or is generated during the reaction. Therefore, the catalyst used must be a material that can stably exist in a high-temperature HF atmosphere. So far, aluminum fluoride has been proven to be able to exist stably for a long time in the above-mentioned highly corrosive atmosphere and is an important catalytically active component or carrier for the preparation of fluorinated halogenated hydrocarbons. For this reason, the preparation of aluminum fluoride catalysts has received widespread attention. However, to be used as a catalyst or carrier, aluminum fluoride must have a large specific surface area, and the particle size should be uniform and stable in order to obtain considerable catalytic activity.

[0003] In the prior art, there are many methods for preparing aluminum fluoride catalysts, such as carbonization and fluorination method. Although the raw materials are easy to obtain, the process flow is complicated and involves multiple high-temperature carbonization and decarbonization processes, which may lead to the introduction of impurities and increased energy consumption. At the same time, high-temperature treatment may also cause the specific surface area of ​​aluminum fluoride to decrease rapidly; such as coprecipitation method, although nano aluminum fluoride can be prepared, due to the lack of effective particle formation and growth control means, the particle size is uneven and the impurity content is high; such as sol-gel method, although aluminum fluoride with high specific surface area can be obtained, the raw material cost is high (such as aluminum isopropoxide), and the preparation process is complicated. In addition, some raw materials (such as HFC-23) may also have a serious impact on the environment. Therefore, how to simultaneously improve the purity, particle size uniformity and specific surface area of ​​nano aluminum fluoride is a technical problem that needs to be solved urgently. Summary of the invention

[0004] The present application provides a method for preparing high-purity nano aluminum fluoride from fluorine-containing waste by aluminum electrolysis, in order to solve the following technical problem: how to simultaneously improve the purity, particle size uniformity and specific surface area of ​​nano aluminum fluoride.

[0005] The present application provides a method for preparing high-purity nano aluminum fluoride from fluorine-containing waste by aluminum electrolysis, the method comprising:

[0006] Leaching aluminum electrolysis fluorine-containing waste powder with a set particle size to convert fluoride in the aluminum electrolysis fluorine-containing waste powder into soluble salt to obtain a first mixed slurry;

[0007] Performing solid-liquid separation on the first mixed slurry to obtain a first fluorine-containing liquid;

[0008] adjusting the aluminum-fluorine ratio and pH value of the first fluorine-containing liquid to obtain a second fluorine-containing liquid;

[0009] preheating the second fluorine-containing liquid to a set temperature, and adding a crystallization aid to the second fluorine-containing liquid at the set temperature to obtain a third fluorine-containing liquid; the mass of the crystallization aid is 0.001% to 0.006% of the total mass of the third fluorine-containing liquid;

[0010] At a set heating rate, the third fluorine-containing liquid is heated to a set final heating temperature and a set holding time, and ultrasonic irradiation and oscillation are performed during the heating process to obtain a second mixed slurry; the frequency of the ultrasonic irradiation and oscillation is 5kHz to 15kHz; and

[0011] The second mixed slurry is subjected to solid-liquid separation to obtain high-purity nano aluminum fluoride.

[0012] Optionally, the set temperature is 93°C to 97°C.

[0013] Optionally, the set heating rate is 0.5°C / h to 2°C / h.

[0014] Optionally, the final heating temperature is set to 108°C to 112°C.

[0015] Optionally, the set insulation time is 0.5h to 2h.

[0016] Optionally, the crystallization aid includes one or more of oleic acid, lauric acid, sodium dodecyl sulfate, sodium secondary alkyl sulfonate, polycarboxylic acid water reducer and naphthalene water reducer.

[0017] Optionally, the aluminum-fluorine ratio of the second fluorine-containing liquid is 1:(3.0-3.5).

[0018] Optionally, the pH value of the second fluorine-containing liquid is 2.5-6.0.

[0019] Optionally, the set particle size is 200 mesh to 300 mesh.

[0020] Optionally, the high-purity nano aluminum fluoride meets at least one of the following properties: purity ≥ 99.9%, specific surface area ≥ 450m 2 / g, particle size D90 is 1μm~2μm.

[0021] The above technical solution provided by the embodiment of the present application has the following advantages compared with the prior art:

[0022] The embodiment of the present application provides a method for preparing high-purity nano aluminum fluoride from fluorine-containing waste materials by aluminum electrolysis. Firstly, by using relatively low-frequency ultrasound and relatively short-time irradiation oscillation, the induction period can be shortened at low energy consumption, nucleation can be promoted, and the particle size of aluminum fluoride can be reduced, so that high-purity aluminum fluoride with high purity, good crystal form, uniform particle size, and large specific surface area can be obtained at relatively low supersaturation; secondly, by adding a crystallization aid, the surface activity of the crystal can be effectively changed, the aggregation and adhesion between the crystal particles can be prevented and avoided, and the generation of fine particles can be further ensured; thirdly, by fine control of the temperature of the crystallization process, the reverse dissolution of the newly formed crystal nuclei can be prevented and avoided, and the crystallization yield can be guaranteed; finally, by the synergistic effect of ultrasound and crystallization aids, as well as the reasonable matching of crystallization process conditions, the preparation of nano aluminum fluoride with high purity, narrow particle size distribution, and large specific surface area can be achieved. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The accompanying drawings herein are incorporated in and constitute a part of the specification, illustrate embodiments consistent with the present application, and together with the description, are used to explain the principles of the present application.

[0024] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0025] Figure 1 A schematic flow chart of a method for preparing high-purity nano-aluminum fluoride from fluorine-containing waste materials by aluminum electrolysis provided in an embodiment of the present application. DETAILED DESCRIPTION

[0026] In order to make the purpose, technical solution and advantages of the embodiments of the present application clearer, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0027] Various embodiments of the present application may be presented in the form of a range; it should be understood that the description in the form of a range is only for convenience and brevity, and should not be understood as a rigid limitation on the scope of the present application; therefore, the range description should be considered to have specifically disclosed all possible sub-ranges and single numerical values ​​within the range. For example, the range description from 1 to 6 should be considered to have specifically disclosed sub-ranges, such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., as well as single numbers within the range, such as 1, 2, 3, 4, 5 and 6, which apply regardless of the range. In addition, whenever a numerical range is indicated herein, it is meant to include any cited number (fractional or integer) within the indicated range.

[0028] In addition, in the description of the specification of the present application, the terms "including", "comprising", etc. mean "including but not limited to". In this article, relational terms such as "first" and "second", etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. In this article, "and / or" describes the association relationship of associated objects, indicating that three relationships may exist. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. Wherein A and B can be singular or plural. In this article, "at least one" means one or more, and "plurality" means two or more. "At least one", "the following at least one item (items)" or similar expressions refer to any combination of these items, including any combination of single items (items) or plural items (items). For example, "at least one of a, b, or c", or "at least one of a, b, and c", can all represent: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, c can be single or multiple. "Parts" such as parts by weight and parts by mass indicate the proportional relationship between the components. In the proportional relationship involved in this article, the parameters that need to be described by proportion should be understood as the first term of the proportional formula in the order of description, and the proportional numbers should be understood as the second term of the proportional formula. For example, the mass ratio of substance A, substance B, and substance C is 1:2:3, then substance A, substance B, and substance C should correspond one-to-one with the proportional numbers in the proportional formula in the order of description, that is, the mass of substance A: the mass of substance B: the mass of substance C = 1:2:3.

[0029] Unless otherwise specified, various raw materials, reagents, instruments and equipment used in this application can be purchased from the market or prepared by existing methods.

[0030] Figure 1A schematic flow chart of a method for preparing high-purity nano-aluminum fluoride from fluorine-containing waste materials by aluminum electrolysis provided in an embodiment of the present application.

[0031] like Figure 1 As shown, the present application provides a method for preparing high-purity nano aluminum fluoride from fluorine-containing waste by aluminum electrolysis, the method comprising:

[0032] S1, leaching aluminum electrolysis fluorine-containing waste powder with a set particle size to convert fluoride in the aluminum electrolysis fluorine-containing waste powder into soluble salt to obtain a first mixed slurry;

[0033] In some embodiments, the fluorine-containing waste from aluminum electrolysis includes: one or more of carbon slag, overhaul slag, electrolyte after carbon slag flotation, electrolyte after carbon slag pyrometallurgical treatment, electrolyte salvaged from the electrolytic cell, and regenerated electrolyte obtained after treatment of other fluorine-containing waste from aluminum electrolytic cells.

[0034] In some embodiments, the set particle size is 200 mesh to 300 mesh.

[0035] Limiting the particle size of the aluminum electrolysis fluorine-containing waste powder to 200-300 meshes can ensure that the waste powder has sufficient reaction area during the leaching process, thereby improving the leaching efficiency of fluoride. Exemplarily, the particle size of the aluminum electrolysis fluorine-containing waste powder can be 200 mesh, 220 mesh, 240 mesh, 260 mesh, 280 mesh, 300 mesh, etc.

[0036] In some embodiments, the leaching uses dilute hydrochloric acid, dilute sulfuric acid, dilute nitric acid or sodium hydroxide solution.

[0037] S2, performing solid-liquid separation on the first mixed slurry to obtain a first fluorine-containing liquid;

[0038] S3, adjusting the aluminum-fluorine ratio and pH value of the first fluorine-containing liquid to obtain a second fluorine-containing liquid;

[0039] In some embodiments, the aluminum-fluoride ratio is adjusted using a soluble aluminum salt, a soluble fluoride salt, or hydrofluoric acid.

[0040] In some embodiments, the aluminum-fluorine ratio of the second fluorine-containing liquid is 1:(3.0-3.5).

[0041] Limiting the aluminum-fluorine ratio of the second fluorine-containing liquid to 1:(3.0-3.5) can ensure that the ratio of aluminum and fluorine in the solution is moderate, which is conducive to the generation of aluminum fluoride with higher purity. At the same time, the crystallization efficiency of aluminum fluoride is high, which is conducive to obtaining nano aluminum fluoride products with uniform particle size and high purity. If the aluminum-fluorine ratio is less than 1:3.0, there is too much aluminum in the solution, resulting in too low a fluorine content in the generated aluminum fluoride and low purity. If the aluminum-fluorine ratio is greater than 1:3.5, there is too much fluorine in the solution, resulting in too high a fluorine content in the remaining liquid after crystallization, and direct discharge will cause secondary pollution. Exemplarily, the aluminum-fluorine ratio of the second fluorine-containing liquid can be 1:3.0, 1:3.1, 1:3.2, 1:3.3, 1:3.4, 1:3.5, etc.

[0042] In some embodiments, the pH value of the second fluorine-containing liquid is 2.5-6.0.

[0043] Limiting the pH value of the second fluorine-containing liquid to 2.5-6.0 can ensure that the synthesis kinetics of aluminum fluoride are sufficient, which is conducive to the formation and crystallization of aluminum fluoride. At the same time, the co-precipitation of impurity ions can be suppressed, thereby reducing the impact of impurities on product purity. This is conducive to obtaining nano-aluminum fluoride products with higher purity and more stable quality. If the pH value is less than 2.5, the synthesis kinetics of aluminum fluoride are insufficient, the amount of aluminum fluoride generated is small, and the crystallization rate is affected; if the pH value is greater than 6.0, impurities co-precipitate and the product purity is insufficient. Exemplarily, the pH value of the second fluorine-containing liquid can be 2.5, 3.0, 4.0, 4.5, 5.0, 5.5, 6.0, etc.

[0044] S4, preheating the second fluorine-containing liquid to a set temperature, and adding a crystallization aid to the second fluorine-containing liquid at the set temperature to obtain a third fluorine-containing liquid; the mass of the crystallization aid is 0.001% to 0.006% of the total mass of the third fluorine-containing liquid;

[0045] It should be noted that, within the temperature range from room temperature to the set temperature, the second fluorine-containing liquid can be heated quickly without controlling the heating rate, thereby reducing energy consumption.

[0046] In some embodiments, the crystallization aid includes: one or more of oleic acid, lauric acid, sodium dodecyl sulfate, sodium secondary alkyl sulfonate, polycarboxylic acid water reducer and naphthalene water reducer.

[0047] The mass of the crystallization aid is limited to 0.001% to 0.006% of the total mass of the third fluorine-containing liquid, which can effectively change the surface activity of the aluminum fluoride crystals and prevent and avoid aggregation and adhesion between crystal particles. If the amount of the crystallization aid added is less than 0.001% of the total mass of the solution, the surface activity of the seed crystal will not be changed enough, and aggregation and adhesion between crystal particles will easily occur; if the amount of the crystal growth inducing agent added is greater than 0.006% of the total mass of the solution, the quality of the product aluminum fluoride will be affected due to excessive introduction of impurities. Exemplarily, the mass of the crystallization aid can be 0.001%, 0.002%, 0.003%, 0.004%, 0.005%, 0.006%, etc. of the total mass of the third fluorine-containing liquid.

[0048] S5. At a set heating rate, the third fluorine-containing liquid is heated to a set final heating temperature and a set insulation time, and ultrasonic irradiation and oscillation are performed during the heating process to obtain a second mixed slurry; the frequency of the ultrasonic irradiation and oscillation is 5kHz to 15kHz;

[0049] It should be noted that ultrasonic irradiation oscillation refers to the use of ultrasonic high-frequency sound waves to produce oscillation effects in the medium. When ultrasonic waves propagate in the medium, they cause high-speed and subtle vibrations of the medium particles, thereby causing changes in mechanical quantities such as velocity, acceleration, sound pressure, and sound intensity. These changes further lead to mechanical effects inside the medium, such as cavitation effect and microjet effect, which act together on the medium to produce an oscillation effect.

[0050] Ultrasonic waves can cause the solid solute in the supersaturated solution to precipitate rapidly and gently, and can also strengthen the crystal growth. Ultrasonic nucleation requires a lower supersaturation, a faster growth rate, and the resulting crystal nuclei are more uniform, complete, and smooth. The size distribution range of the crystal nuclei and finished crystals is smaller, and the coefficient of variation is lower.

[0051] The embodiments of the present application use relatively low-frequency ultrasound and relatively short-time irradiation oscillation to shorten the induction period, promote nucleation, and reduce the particle size of aluminum fluoride at relatively low energy consumption, thereby obtaining high-purity aluminum fluoride with high purity, good crystal form, uniform particle size, and large specific surface area at relatively low supersaturation.

[0052] The frequency of ultrasonic irradiation oscillation is limited to 5kHz to 15kHz. If the ultrasonic frequency is less than 5kHz, the effect of shortening the induction period and promoting nucleation is insufficient, which is not conducive to crystal formation; if the ultrasonic frequency is greater than 15kHz, the energy consumption is too high, and the tiny crystal nuclei are easily destroyed by ultrasonic waves, which indirectly reduces the nucleation rate. Exemplarily, the frequency of ultrasonic irradiation oscillation can be 5kHz, 7kHz, 9kHz, 10kHz, 12kHz, 15kHz, etc.

[0053] In some embodiments, the set temperature is 93°C to 97°C.

[0054] In some embodiments, the set heating rate is 0.5°C / h to 2°C / h.

[0055] In some embodiments, the set final heating temperature is 108°C to 112°C.

[0056] In some embodiments, the set insulation time is 0.5h to 2h.

[0057] The main crystallization temperature of aluminum fluoride is between the set temperature and the set final heating temperature. The embodiment of the present application prevents and avoids the reverse dissolution of the newly formed crystal nuclei through the fine control of the temperature during the crystallization process, thereby ensuring the crystallization yield.

[0058] When the temperature of the second fluorine-containing liquid reaches the set temperature, the heating rate is adjusted to 0.5°C / h to 2°C / h, which can ensure that the aluminum fluoride crystal nucleus gradually grows in a stable environment. When heated to the set final heating temperature at 0.5°C / h to 2°C / h, it is kept warm for 0.5h to 2h to ensure that the aluminum fluoride crystal has enough time to grow and stabilize. If the set temperature is lower than 93°C, the heating rate is lower than 0.5°C / h, and the insulation time is lower than 0.5h, the generated crystal nucleus is easy to dissolve, which is not conducive to the crystallization of aluminum fluoride; if the set final heating temperature is higher than 112°C, the heating rate is higher than 2°C / h, and the insulation time is higher than 2h, the crystal grows too fast, which is not conducive to the control of specific surface area and particle size. Exemplarily, the set temperature can be 93°C, 94°C, 95°C, 96°C, 97°C, etc. The set heating rate can be 0.5°C / h, 0.8°C / h, 1°C / h, 1.2°C / h, 1.5°C / h, 1.8°C / h, 2°C / h, etc. The set final heating temperature can be 108°C, 1.9°C, 110°C, 111°C, 112°C, etc. The set insulation time can be 0.5h, 0.7h, 0.9h, 1.2h, 1.5h, 1.8h, 2h, etc.

[0059] S6. Perform solid-liquid separation on the second mixed slurry to obtain high-purity nano aluminum fluoride.

[0060] In some embodiments, the high-purity nano-aluminum fluoride meets at least one of the following properties: purity ≥ 99.9%, specific surface area ≥ 450m 2 / g, particle size D90 is 1μm~2μm.

[0061] In the embodiment of the present application, firstly, by using relatively low-frequency ultrasound and relatively short-time irradiation oscillation, the induction period can be shortened at low energy consumption, nucleation can be promoted, and the particle size of aluminum fluoride can be reduced, so that high-purity aluminum fluoride with high purity, good crystal form, uniform particle size, and large specific surface area can be obtained at low supersaturation; secondly, by adding a crystallization aid, the surface activity of the crystal can be effectively changed, the aggregation and adhesion between the crystal particles can be prevented and avoided, and the generation of fine particles can be further ensured; again, by fine control of the temperature of the crystallization process, the reverse dissolution of the newly formed nucleus can be prevented and avoided, and the crystallization yield can be guaranteed; finally, by the synergistic effect of ultrasound and crystallization aids, as well as the reasonable matching of crystallization process conditions, the preparation of nano aluminum fluoride with high purity, narrow particle size distribution, and large specific surface area can be achieved. Exemplarily, the purity of high-purity nano aluminum fluoride can be 99.9%, 99.92%, 99.93%, 99.95%, 99.96%, 99.97%, etc., and the specific surface area can be 450m 2 / g, 460m 2 / g, 470m 2 / g, 480m 2 / g, 490m 2 / g, etc., and the particle size D90 can be 1μm, 1.2μm, 1.4μm, 1.6μm, 1.8μm, 2μm, etc.

[0062] In summary, the method for preparing high-purity nano aluminum fluoride from fluorine-containing waste materials by aluminum electrolysis provided in the embodiment of the present application has the following advantages:

[0063] (1) Efficient utilization of fluorine-containing waste from aluminum electrolysis

[0064] Wide sources of raw materials: Utilizing various fluorine-containing waste materials generated during aluminum electrolysis, such as carbon slag, overhaul slag, electrolyte, etc., resources are recycled and production costs are reduced.

[0065] Precise particle size control: By setting the particle size of the waste powder to 200-300 meshes, it ensures that the waste powder has sufficient reaction area during the leaching process, thereby improving the leaching efficiency of fluoride.

[0066] (2) High purity and high quality products

[0067] Finely adjust the aluminum-fluorine ratio and pH value: By accurately adjusting the aluminum-fluorine ratio and pH value of the first fluorine-containing solution, the ratio of aluminum to fluorine in the solution is ensured to be moderate, which is conducive to the production of aluminum fluoride with higher purity. At the same time, the appropriate pH value also inhibits the co-precipitation of impurity ions, further improving the purity of the product.

[0068] Synergistic effect of ultrasound and crystallization aids: The use of relatively low-frequency ultrasound for irradiation and oscillation promotes the nucleation and crystal growth of aluminum fluoride and reduces the particle size. At the same time, the addition of crystallization aids effectively changes the surface activity of the crystals, prevents the aggregation and adhesion between crystal particles, and ensures the formation of fine particles. The synergistic effect of the two makes the final product have the characteristics of high purity, good crystal form, uniform particle size, and large specific surface area.

[0069] (3) Fine control of the crystallization process

[0070] Fine temperature control: By finely controlling the temperature of the crystallization process, including parameters such as set temperature, heating rate, set final heating temperature and holding time, it is ensured that the aluminum fluoride crystal nucleus gradually grows in a stable environment, preventing the reverse dissolution of the new crystal nucleus and ensuring the crystallization yield.

[0071] Low energy consumption: In the temperature range of the third fluorine-containing liquid from room temperature to the set temperature, the heating rate is not controlled, and the heating can be fast, which reduces energy consumption. At the same time, the relatively low frequency ultrasonic irradiation oscillation also reduces energy consumption.

[0072] (4) Excellent product performance

[0073] High purity: The final high-purity nano aluminum fluoride has a purity of more than 99.9%, meeting the needs of high-end applications.

[0074] High specific surface area: The specific surface area of ​​the product can reach 450m 2 / g or above, which is conducive to its application in catalysis, adsorption and other fields.

[0075] Uniform particle size: The particle size distribution of the product is narrow, with D90 between 1μm and 2μm, ensuring its stability and consistency in different application scenarios.

[0076] (5) Environmental protection and sustainability

[0077] Reduce pollution: This method effectively utilizes fluorine-containing waste from aluminum electrolysis, reducing the pollution of these wastes to the environment. At the same time, by precisely controlling the crystallization process, the problem of excessive fluorine content in the remaining liquid after crystallization is avoided, reducing the risk of secondary pollution.

[0078] Sustainable development: This method realizes the recycling of resources and conforms to the concept of sustainable development. By optimizing process conditions, it improves resource utilization efficiency, reduces production costs, and provides strong support for the green development of the aluminum electrolysis industry.

[0079] The present application will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are intended only to illustrate the present application and are not intended to limit the scope of the present application. The experimental methods for which specific conditions are not specified in the following examples are usually measured according to industry standards. If there is no corresponding industry standard, then the conditions recommended by the manufacturer are followed.

[0080] Example 1

[0081] This embodiment provides a method for preparing high-purity nano aluminum fluoride from fluorine-containing waste by aluminum electrolysis, the method comprising the following steps:

[0082] S11, weighing a certain amount of electrolyte after carbon slag flotation, crushing it, passing it through a 200-mesh sieve, taking the undersize, mixing the undersize after carbon slag flotation with sulfuric acid for leaching, so as to convert the fluoride in the aluminum electrolysis fluorine-containing waste powder into a soluble salt, and obtaining a first mixed slurry;

[0083] S21, performing solid-liquid separation on the first mixed slurry to obtain a first fluorine-containing liquid;

[0084] S31, adjusting the aluminum-fluorine ratio of the first fluorine-containing liquid to 1:3 and the pH value to 5.0 to obtain a second fluorine-containing liquid;

[0085] S41, preheating the second fluorine-containing liquid to 95° C., and adding a crystallization aid to the second fluorine-containing liquid at 95° C. to obtain a third fluorine-containing liquid; the mass of the crystallization aid is 0.002% of the total mass of the third fluorine-containing liquid, and the crystallization aid is a mixture of oleic acid and polycarboxylic acid water reducer in a mass ratio of 1:6;

[0086] S51, heating the third fluorine-containing liquid to 110° C. at a heating rate of 2° C. / h, then keeping the temperature at 110° C. for 1 hour, and performing ultrasonic irradiation and oscillation during the heating process to obtain a second mixed slurry; the frequency of the ultrasonic irradiation and oscillation is 15 kHz;

[0087] S61, separate the second mixed slurry into solid and liquid, wash the filter cake with boiling water, and dry it to obtain high-purity nano aluminum fluoride. The purity of high-purity nano aluminum fluoride is 99.98%, and the specific surface area is 502m 2 / g, and the particle size distribution is narrow, D10 = 0.456 μm, D50 = 0.658 μm, D90 = 1.043 μm.

[0088] At the same time, the chemical composition of the high-purity nano-aluminum fluoride obtained in Example 1 was measured, and the results are shown in Table 1.

[0089] Table 1 Chemical composition of high-purity nano-aluminum fluoride obtained in Example 1 (wt.%)

[0090] project result F 67.8449 Al 32.1371 Na 0.0020 <![CDATA[SiO2]]> 0.0004 <![CDATA[Fe2O3]]> 0.0003 <![CDATA[SO4 2- ]]> 0.0001 <![CDATA[P2O5]]> 0.0002 Loss on burn 0.0150

[0091] Example 2

[0092] This embodiment provides a method for preparing high-purity nano aluminum fluoride from fluorine-containing waste by aluminum electrolysis, the method comprising the following steps:

[0093] S11, weighing a certain amount of carbon slag, crushing it, passing it through a 300-mesh sieve, taking the sieve residue, mixing the sieve residue with hydrochloric acid for leaching, so as to convert the fluoride in the aluminum electrolysis fluorine-containing waste powder into a soluble salt, and obtaining a first mixed slurry;

[0094] S21, performing solid-liquid separation on the first mixed slurry to obtain a first fluorine-containing liquid;

[0095] S31, adjusting the aluminum-fluorine ratio of the first fluorine-containing liquid to 1:3.5 and the pH value to 2.5 to obtain a second fluorine-containing liquid;

[0096] S41, preheating the second fluorine-containing liquid to 93° C., and adding a crystallization aid to the second fluorine-containing liquid at 93° C. to obtain a third fluorine-containing liquid; the mass of the crystallization aid is 0.001% of the total mass of the third fluorine-containing liquid, and the crystallization aid is a mixture of lauric acid and naphthalene-based water reducer in a mass ratio of 5:6;

[0097] S51, heating the third fluorine-containing liquid to 112° C. at a heating rate of 0.5° C. / h, then keeping the temperature at 112° C. for 0.5 h, and performing ultrasonic irradiation and oscillation during the heating process to obtain a second mixed slurry; the frequency of the ultrasonic irradiation and oscillation is 10 kHz;

[0098] S61, separate the second mixed slurry into solid and liquid, wash the filter cake with boiling water, and dry it to obtain high-purity nano aluminum fluoride. The purity of the high-purity nano aluminum fluoride is 99.92%, and the specific surface area is 493m 2 / g, narrow particle size distribution, D10 = 0.590μm, D50 = 0.888μm, D90 = 1.599μm.

[0099] Example 3

[0100] This embodiment provides a method for preparing high-purity nano aluminum fluoride from fluorine-containing waste by aluminum electrolysis, the method comprising the following steps:

[0101] S11, weighing a certain amount of overhaul slag, passing it through a 250-mesh sieve, taking the undersize, mixing the undersize with sodium hydroxide, and leaching at a certain liquid-solid ratio to convert fluoride in the aluminum electrolysis fluoride-containing waste powder into soluble salt, thereby obtaining a first mixed slurry;

[0102] S21, performing solid-liquid separation on the first mixed slurry to obtain a first fluorine-containing liquid;

[0103] S31, adjusting the aluminum-fluorine ratio of the first fluorine-containing liquid to 1:3.3 and the pH value to 4.0 to obtain a second fluorine-containing liquid;

[0104] S41, preheating the second fluorine-containing liquid to 97° C., and adding a crystallization aid to the second fluorine-containing liquid at 97° C. to obtain a third fluorine-containing liquid; the mass of the crystallization aid is 0.006% of the total mass of the third fluorine-containing liquid, and the crystallization aid is a mixture of sodium dodecyl sulfate and naphthalene-based water reducer in a mass ratio of 1:8;

[0105] S51, heating the third fluorine-containing liquid to 108° C. at a heating rate of 1° C. / h, then keeping the temperature at 108° C. for 2 hours, and performing ultrasonic irradiation and oscillation during the heating process to obtain a second mixed slurry; the frequency of the ultrasonic irradiation and oscillation is 8 kHz;

[0106] S61, separate the second mixed slurry into solid and liquid, wash the filter cake with boiling water, and dry it to obtain high-purity nano aluminum fluoride. The purity of the high-purity nano aluminum fluoride is 99.92%, and the specific surface area is 489m 2 / g, narrow particle size distribution, D10 = 0.752μm, D50 = 0.963μm, D90 = 1.722μm.

[0107] Example 4

[0108] This embodiment provides a method for preparing high-purity nano aluminum fluoride from fluorine-containing waste by aluminum electrolysis, the method comprising the following steps:

[0109] S11, weighing a certain amount of electrolyte after pyrolysis of carbon slag, crushing it, passing it through a 200-mesh sieve, taking the sieve under, mixing it with nitric acid for leaching, so as to convert the fluoride in the aluminum electrolysis fluorine-containing waste powder into a soluble salt, and obtaining a first mixed slurry;

[0110] S21, performing solid-liquid separation on the first mixed slurry to obtain a first fluorine-containing liquid;

[0111] S31, adjusting the aluminum-fluorine ratio of the first fluorine-containing liquid to 1:3.4 and the pH value to 6.0 to obtain a second fluorine-containing liquid;

[0112] S41, preheating the second fluorine-containing liquid to 96° C., and adding a crystallization aid to the second fluorine-containing liquid at 96° C. to obtain a third fluorine-containing liquid; the mass of the crystallization aid is 0.005% of the total mass of the third fluorine-containing liquid, and the crystallization aid is a mixture of sodium secondary alkyl sulfonate and polycarboxylate water reducer in a mass ratio of 3:8;

[0113] S51, heating the third fluorine-containing liquid to 109° C. at a heating rate of 1.5° C. / h, then keeping the temperature at 109° C. for 1.8 hours, and performing ultrasonic irradiation and oscillation during the heating process to obtain a second mixed slurry; the frequency of the ultrasonic irradiation and oscillation is 12 kHz;

[0114] S61, separate the second mixed slurry into solid and liquid, wash the filter cake with boiling water, and dry it to obtain high-purity nano aluminum fluoride. The purity of the high-purity nano aluminum fluoride is 99.91%, and the specific surface area is 486m 2 / g, narrow particle size distribution, D10 = 0.776μm, D50 = 0.992μm, D90 = 1.899μm.

[0115] Example 5

[0116] This embodiment provides a method for preparing high-purity nano aluminum fluoride from fluorine-containing waste by aluminum electrolysis, the method comprising the following steps:

[0117] S11, weighing a certain amount of regenerated electrolyte after the aluminum electrolysis fluorine-containing waste is treated, passing it through a 300-mesh sieve, taking the sieve underflow, mixing it with nitric acid for leaching, so that the fluoride in the aluminum electrolysis fluorine-containing waste powder is converted into a soluble salt, and obtaining a first mixed slurry;

[0118] S21, performing solid-liquid separation on the first mixed slurry to obtain a first fluorine-containing liquid;

[0119] S31, adjusting the aluminum-fluorine ratio of the first fluorine-containing liquid to 1:3.1 and the pH value to 4.5 to obtain a second fluorine-containing liquid;

[0120] S41, preheating the second fluorine-containing liquid to 94° C., and adding a crystallization aid to the second fluorine-containing liquid at 94° C. to obtain a third fluorine-containing liquid; the mass of the crystallization aid is 0.004% of the total mass of the third fluorine-containing liquid, and the crystallization aid is a mixture of sodium dodecyl sulfate and polycarboxylate water reducer in a mass ratio of 5:8;

[0121] S51, heating the third fluorine-containing liquid to 111° C. at a heating rate of 1.8° C. / h, then keeping the temperature at 111° C. for 1.3 h, and performing ultrasonic irradiation and oscillation during the heating process to obtain a second mixed slurry; the frequency of the ultrasonic irradiation and oscillation is 13 kHz;

[0122] S61, separate the second mixed slurry into solid and liquid, wash the filter cake with boiling water, and dry it to obtain high-purity nano aluminum fluoride. The purity of the high-purity nano aluminum fluoride is 99.91%, and the specific surface area is 475m 2 / g, narrow particle size distribution, D10 = 0.257μm, D50 = 0.990μm, D90 = 1.791μm.

[0123] Comparative Example 1

[0124] This comparative example is modified as follows based on the disclosure of Example 1:

[0125] The aluminum-fluorine ratio of the first fluorine-containing liquid is adjusted to 1:2.5.

[0126] Comparative Example 2

[0127] This comparative example is modified as follows based on the disclosure of Example 1:

[0128] The aluminum-fluorine ratio of the first fluorine-containing liquid is adjusted to 1:4.0.

[0129] Comparative Example 3

[0130] This comparative example is modified as follows based on the disclosure of Example 1:

[0131] The pH value of the first fluorine-containing liquid is adjusted to 2.0.

[0132] Comparative Example 4

[0133] This comparative example is modified as follows based on the disclosure of Example 1:

[0134] The pH value of the first fluorine-containing liquid is adjusted to 6.5.

[0135] Comparative Example 5

[0136] This comparative example is modified as follows based on the disclosure of Example 1:

[0137] The mass of the crystallization aid is 0.0005% of the total mass of the third fluorine-containing liquid.

[0138] Comparative Example 6

[0139] This comparative example is modified as follows based on the disclosure of Example 1:

[0140] The mass of the crystallization aid is 0.007% of the total mass of the third fluorine-containing liquid.

[0141] Comparative Example 7

[0142] This comparative example is modified as follows based on the disclosure of Example 1:

[0143] The third fluorine-containing liquid was heated to 110° C. at a heating rate of 0.2° C. / h.

[0144] Comparative Example 8

[0145] This comparative example is modified as follows based on the disclosure of Example 1:

[0146] The third fluorine-containing liquid was heated to 110° C. at a heating rate of 3° C. / h.

[0147] Comparative Example 9

[0148] This comparative example is modified as follows based on the disclosure of Example 1:

[0149] The mixture was kept at 110°C for 0.2 h.

[0150] Comparative Example 10

[0151] This comparative example is modified as follows based on the disclosure of Example 1:

[0152] The mixture was kept at 110°C for 2.5 hours.

[0153] Comparative Example 11

[0154] This comparative example is modified as follows based on the disclosure of Example 1:

[0155] The frequency of the ultrasonic irradiation oscillation is 3 kHz.

[0156] Comparative Example 12

[0157] This comparative example is modified as follows based on the disclosure of Example 1:

[0158] The frequency of the ultrasonic irradiation oscillation is 20 kHz.

[0159] Comparative Example 13

[0160] This comparative example is modified as follows based on the disclosure of Example 1:

[0161] No crystallization aid is added during the preparation of high-purity nano aluminum fluoride.

[0162] Comparative Example 14

[0163] This comparative example is modified as follows based on the disclosure of Example 1:

[0164] No ultrasonic irradiation oscillation is performed during the preparation of high-purity nano-aluminum fluoride.

[0165] The reaction conditions in Examples 1 to 5 and Comparative Examples 1 to 14 and the purity, specific surface area and fluoride ion concentration of the final product in the filtrate after crystallization are shown in Table 2.

[0166] Table 2 Reaction conditions and product properties in Examples 1 to 5 and Comparative Examples 1 to 14

[0167]

[0168] From the data in Table 2, we can see that:

[0169] The aluminum-fluorine ratio of the filtrate in Comparative Example 1 is 1:2.5. Since the aluminum-fluorine ratio is greater than 1:3, there is too much aluminum in the solution, resulting in too low a content of aluminum fluoride and low purity.

[0170] In Comparative Example 2, the aluminum-fluorine ratio of the filtrate is 1:4.0. Since the aluminum-fluorine ratio is less than 1:3.5, there is too much fluorine in the solution, resulting in too high a fluorine content in the remaining liquid after crystallization. Direct discharge will cause secondary pollution.

[0171] The pH value of the filtrate in Comparative Example 3 is 2.0. Since the pH is too low, too little aluminum fluoride is generated, the product purity is not high, and the fluorine content in the filtrate after crystallization is too high, which is 31 mg / L.

[0172] The pH value of the filtrate in Comparative Example 4 was 6.5. Due to the high pH, ​​other impurities were precipitated at the same time, resulting in a product purity of only 90.05% and a specific surface area of ​​only 89 m 2 / g.

[0173] The amount of the crystallization aid added in Comparative Example 5 is 0.0005%. Since the amount of the crystallization aid added is too small, the surface activity of the seed crystal is not sufficiently changed, and the crystal particles are prone to aggregation and adhesion, resulting in a product with a small specific surface area and a large amount of impurities.

[0174] In Comparative Example 6, the amount of the seed growth promoter added is 0.007%. Since the amount of the crystal growth inducing agent added is too much, too much impurity is introduced, which affects the quality of the product aluminum fluoride.

[0175] The heating rate in Comparative Example 7 is 0.2°C / h. Since the heating rate is too slow, the generated crystal nuclei are redissolved without growing up in time, resulting in a small number of crystal nuclei, a small amount of aluminum fluoride generated, and a low product purity.

[0176] The heating rate in Comparative Example 8 is 3° C. / h. Since the heating rate is too fast, the crystals grow too fast, which is not conducive to the control of specific surface area and particle size.

[0177] In Comparative Example 9, the holding time at 110° C. is 0.2 h. Since the high-temperature holding time is too short, the crystals are redissolved without growing in time, resulting in less aluminum fluoride being generated and the product purity is not high.

[0178] In Comparative Example 10, the holding time at 110° C. is 2.5 h. Since the high temperature holding time is too long, the crystals grow too large, which is not conducive to the control of specific surface area and particle size.

[0179] The ultrasonic frequency in Comparative Example 11 is 3 kHz. Since the ultrasonic frequency is too low, the ultrasonic wave does not fully play its role in shortening the induction period, promoting nucleation, and uniforming the particle size. Crystals grow on a smaller number of nuclei, resulting in a large product particle size and a small specific surface area.

[0180] The ultrasonic frequency in Comparative Example 12 is 20 kHz. Since the ultrasonic frequency is too high, the energy consumption of the ultrasonic crystallization process is too high, and the tiny crystal nuclei are easily destroyed by ultrasonic waves, which indirectly reduces the nucleation rate and crystallization rate, and the product purity is not high.

[0181] In Comparative Example 13, no crystallization aid is added. Without the effect of the crystallization aid in changing the surface activity of the crystals and avoiding aggregation and adhesion between crystals, aggregation and adhesion between crystal particles are very likely to occur, resulting in a product with too small specific surface area and a large amount of impurities.

[0182] In Comparative Example 14, ultrasonic irradiation oscillation is not performed, and the role of ultrasound in shortening the induction period, promoting nucleation, uniform particle size and improving crystallization yield is lacking. At a lower supersaturation, the difficulty of spontaneous nucleation of crystals increases, resulting in a low crystallization rate, low product purity, small product specific surface area, and excessively high fluorine content in the remaining liquid after crystallization.

[0183] In addition, one or more technical solutions in the embodiments of the present application have at least the following technical effects or advantages:

[0184] In the present embodiment, the purity of the obtained high-purity nano aluminum fluoride is ≥99.9%, and the specific surface area is ≥450m 2 / g, particle size D90 is 1μm~2μm.

[0185] In the embodiments of the present application, by using relatively low-frequency ultrasound and relatively short-time irradiation oscillation, the induction period can be shortened with relatively low energy consumption, nucleation can be promoted, and the particle size of aluminum fluoride can be uniformed, so that high-purity aluminum fluoride with high purity, good crystal form, uniform particle size, and large specific surface area can be obtained at relatively low supersaturation.

[0186] In the embodiments of the present application, the addition of a crystallization aid can effectively change the surface activity of the crystals, prevent and avoid aggregation and adhesion between crystal particles, and further ensure the generation of fine particles.

[0187] In the examples of the present application, the reverse dissolution of the newly formed crystal nuclei is prevented and avoided through the precise control of the temperature during the crystallization process, thereby ensuring the crystallization yield.

[0188] The above description is only a specific implementation of the present application, so that those skilled in the art can understand or implement the present application. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to the embodiments shown herein, but will conform to the widest range consistent with the principles and novel features applied for herein.

Claims

1. A method for preparing high-purity nano aluminum fluoride from fluorine-containing waste materials by aluminum electrolysis, the method comprising: Leaching aluminum electrolysis fluorine-containing waste powder with a set particle size to convert fluoride in the aluminum electrolysis fluorine-containing waste powder into soluble salt to obtain a first mixed slurry; Performing solid-liquid separation on the first mixed slurry to obtain a first fluorine-containing liquid; adjusting the aluminum-fluorine ratio and pH value of the first fluorine-containing liquid to obtain a second fluorine-containing liquid; preheating the second fluorine-containing liquid to a set temperature, and adding a crystallization aid to the second fluorine-containing liquid at the set temperature to obtain a third fluorine-containing liquid; the mass of the crystallization aid is 0.001% to 0.006% of the total mass of the third fluorine-containing liquid; At a set heating rate, the third fluorine-containing liquid is heated to a set final heating temperature and a set holding time, and ultrasonic irradiation and oscillation are performed during the heating process to obtain a second mixed slurry; the frequency of the ultrasonic irradiation and oscillation is 5kHz to 15kHz; and The second mixed slurry is subjected to solid-liquid separation to obtain high-purity nano aluminum fluoride.

2. The method according to claim 1, characterized in that: The set temperature is 93°C to 97°C.

3. The method according to claim 1, characterized in that The set heating rate is 0.5°C / h to 2°C / h.

4. The method according to claim 1, characterized in that: The final heating temperature is set to be 108°C to 112°C.

5. The method according to claim 1, characterized in that The set insulation time is 0.5h to 2h.

6. The method according to claim 1, characterized in that The crystallization aid includes one or more of oleic acid, lauric acid, sodium dodecyl sulfate, sodium secondary alkyl sulfonate, polycarboxylic acid water reducer and naphthalene water reducer.

7. The method according to claim 1, characterized in that The aluminum-fluorine ratio of the second fluorine-containing liquid is 1:(3.0-3.5).

8. The method according to claim 1, characterized in that The pH value of the second fluorine-containing liquid is 2.5-6.

0.

9. The method according to claim 1, characterized in that: The set particle size is 200 mesh to 300 mesh.

10. The method according to claim 1, characterized in that The high-purity nano aluminum fluoride meets at least one of the following properties: purity ≥ 99.9%, specific surface area ≥ 450m 2 / g, particle size D90 is 1μm~2μm.

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