CN111977671B - Method for preparing ammonium bifluoride by recycling rare earth fluorine-containing waste acid - Google Patents
Method for preparing ammonium bifluoride by recycling rare earth fluorine-containing waste acid Download PDFInfo
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
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- C01C1/16—Halides of ammonium
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Abstract
The invention relates to the technical field of preparation of ammonium bifluoride, in particular to a method for preparing ammonium bifluoride by recycling rare earth fluorine-containing waste acid. The method comprises the following steps: (1) mixing the rare earth fluorine-containing waste acid with liquid ammonia to prepare a mixture containing white carbon black and ammonium fluoride; (2) carrying out solid-liquid separation on the mixture containing the white carbon black and the ammonium fluoride to obtain crude white carbon black and ammonium fluoride solution; (3) cleaning, centrifuging and filtering the crude white carbon black to obtain a filter cake, and drying the filter cake to obtain the white carbon black; (4) precipitating ammonium fluoride solution, taking supernatant, and distilling under reduced pressure to obtain NH3And NH4HF2Solution, collecting NH3The liquid ammonia used for preparing step (1); (5) reacting NH4HF2Neutralizing, crystallizing, centrifuging the solution, and drying the centrifuged solid to obtain ammonium bifluoride. The invention has the advantages of high resource degree, high yield and purity and difficult caking.
Description
Technical Field
The invention relates to the technical field of preparation of ammonium bifluoride, in particular to a method for preparing ammonium bifluoride by recycling rare earth fluorine-containing waste acid.
Background
Rare earth (Rare earth) is a general name of seventeen metal elements including lanthanide elements, scandium and yttrium in the chemical periodic table. Rare earth is a non-renewable important strategic resource and is widely applied to the fields of military affairs, metallurgical industry, petrochemical industry, glass ceramics, agriculture and the like. With the continuous expansion of the industrial scale of rare earth, the problem of environmental pollution in the rare earth production process is increasingly prominent, the healthy development of the rare earth industry is seriously influenced, the environmental pollution is not effectively solved all the time, and the environmental protection problem gradually rises to the core of the development of the rare earth industry.
At present, the smelting of rare earth concentrate mainly adopts a three-acid-method high-temperature roasting production process, and the advantages of the process are mainly shown in the following aspects: firstly, the process is mature, the large-scale production of the rare earth smelting is realized, and objective conditions are created for the conversion of resource advantages to industrial advantages; secondly, the radioactive substances are solidified in the slag, so that the radioactive substances are prevented from entering products and waste water, and the technical difficulty and economic feasibility of treating the radioactive substances are simplified; thirdly, the process flow is short, the expansibility is strong, and the primary product and the deep processing product can be produced.
However, the biggest disadvantage of the three-acid-method high-temperature roasting process is the problem of environmental pollution, wherein the most prominent and difficult problem is the pollution of a large amount of acidic wastewater generated by roasting tail gas. Because the discharge amount is large, the components are complex, the impurity quality is high, the corrosion is serious, the standard treatment difficulty is high, the cost is high, and particularly after the large-scale industrial production is realized, the influence on the environment is quite large, the environment is damaged, and the development of enterprises is restricted. Therefore, for the stable and healthy development of the rare earth industry, the treatment problem of the tail gas and the acidic wastewater of the three-acid method roasting is not easy to solve.
Ammonium bifluoride is a corrosive chemical substance, which is decomposed into toxic fluoride, nitric oxide and ammonia gas when meeting moisture, and the ammonium bifluoride is dissolved in water to form weak acid which can dissolve glass; slightly soluble in alcohol, very easily soluble in cold water, and its aqueous solution is strongly acidic, can sublime at higher temperature, can corrode glass, and is corrosive to skin. Ammonium bifluoride is useful as a chemical agent, a glass etchant (used in combination with hydrofluoric acid), a disinfectant and a preservative for fermentation industry, a solvent for metallic beryllium made from beryllium oxide, and a surface treatment agent for silicon steel sheets, and also for manufacturing ceramics, magnesium alloys, cleaning and descaling of boiler water supply systems and steam generation systems, and acid treatment of oil field sands, and also as: alkylation and isomerization catalyst components. Is commonly used for beryllium smelting, welding electrode manufacturing, cast steel, wood preservative and the like, and is an indispensable chemical reagent in chemical industry.
Ammonium bifluoride is a chemical material, generally obtained by neutralizing anhydrous hydrofluoric acid and liquid ammonia, and although the process route is short, a large amount of expensive hydrofluoric acid is used, so that the cost cannot be reduced. The cost of fluosilicic acid and fluorine-containing (waste) liquid is relatively low. According to different raw materials, the production of ammonium bifluoride has the following three production technologies: the hydrogen fluoride-liquid ammonia method is divided into a liquid phase method and a gas phase method according to different production processes; the fluorosilicic acid-liquid ammonia process is only a liquid phase process; ③ the fluorine-containing waste liquid-liquid ammonia method, only the liquid phase method.
Regardless of the raw material, the equipment of the liquid phase method synthesis process is simple, the investment is saved, the process conditions are mild, and the production operation is easy to control. However, the product produced by the liquid phase method has the problems of high water content, easy caking, incapability of long-term storage and the like, and needs to be subjected to subsequent drying operation. The gas phase method for preparing the ammonium bifluoride does not contact water in the technical process, and the ammonium bifluoride is melted, so that the product has low water content, high purity and good stability, and can be stored for a long time. However, the gas phase method has high requirements on the process and equipment, strict requirements on the sealing property, heat exchange, melting temperature control, tail gas treatment and the like in the production process, and has large investment and high production cost.
In the process of smelting rare earth concentrate by adopting a three-generation acid method high-temperature roasting production process, the main component of the generated acidic wastewater is mixed acid of hydrofluoric acid and fluosilicic acid, the prior art does not disclose that the acidic wastewater in the rare earth concentrate smelting process is used as a raw material for preparing ammonium bifluoride, and the yield and purity of the ammonium bifluoride prepared by adopting fluorine-containing waste liquid in the prior art are lower, so that the prepared ammonium bifluoride is easy to agglomerate and is not beneficial to long-term storage.
Chinese patent application CN109809431A discloses a method for recovering ammonium bifluoride and white carbon black from wastewater containing silicon, fluorine and ammonium and co-producing cryolite, which comprises the following steps: (1) adding a precipitant into the wastewater to obtain a precipitate S and a solution A; (2) adding a sodium hydroxide solution into the precipitate S obtained in the step (1) to adjust the pH to be 8-12, and filtering to obtain white carbon black and a solution B; (3) adding an aluminum-containing chemical substance into the solution B obtained in the step (2), fully reacting, filtering to obtain cryolite, and recovering the filtrate; (4) and (2) adding hydrofluoric acid into the solution A obtained in the step (1) to adjust the pH value to be 1-6, and concentrating and crystallizing to obtain ammonium bifluoride. The method has simple treatment process, can simultaneously obtain three products of cryolite, ammonium bifluoride and white carbon black with higher values, and has good practical value. The yield and the purity of the ammonium bifluoride and the white carbon black prepared by the method are low, and the prepared ammonium bifluoride is easy to agglomerate and not beneficial to long-term storage.
Therefore, it is necessary to develop a method for recycling rare earth fluorine-containing waste acid to prepare ammonium bifluoride, which can solve the above technical problems.
Disclosure of Invention
The invention aims to overcome the defects of the prior art, provide a method for preparing ammonium bifluoride by recycling rare earth fluorine-containing waste acid, and simultaneously prepare white carbon black, wherein the yield and purity of the white carbon black and ammonium fluoride are high, and the ammonium bifluoride is not easy to agglomerate and is beneficial to long-term storage.
The invention is realized by the following technical scheme:
a method for preparing ammonium bifluoride by recycling rare earth fluorine-containing waste acid comprises the following steps:
(1) mixing rare earth fluorine-containing waste acid with liquid ammonia to prepare a mixture containing white carbon black and ammonium fluoride, wherein the rare earth fluorine-containing waste acid comprises hydrofluoric acid and fluosilicic acid;
(2) carrying out solid-liquid separation on the mixture containing the white carbon black and the ammonium fluoride to obtain crude white carbon black and ammonium fluoride solution;
(3) cleaning, centrifuging and filtering the crude white carbon black to obtain a filter cake, and drying the filter cake to obtain the white carbon black;
(4) precipitating ammonium fluoride solution, taking supernatant, and distilling under reduced pressure to obtain NH3And NH4HF2Solution, collecting NH3The liquid ammonia used for preparing step (1);
(5) reacting NH4HF2And (4) neutralizing, crystallizing and centrifuging the solution, returning filtrate obtained after centrifugation to the step (4), mixing the filtrate with supernatant, distilling the mixture under reduced pressure, and drying solid obtained after centrifugation to obtain the ammonium bifluoride.
Preferably, the rare earth fluorine-containing waste acid obtained in the step (1) comprises the following components in percentage by weight: 6-10% of hydrofluoric acid, 5-9% of fluosilicic acid and the balance of water.
Preferably, the volume mass ratio of the rare earth fluorine-containing waste acid to the liquid ammonia in the step (1) is 0.01-0.02m3/kg。
Preferably, the rare earth fluorine-containing waste acid in the step (1) is mixed with liquid ammonia and then the pH value is adjusted to 7-9.
Preferably, in the step (1), the rare earth fluorine-containing waste acid is mixed with liquid ammonia, and then the mixture is reacted for 0.5 to 1 hour at the temperature of between 30 and 45 ℃ and then the mixture is reacted for 1 to 2 hours at the temperature of between 20 and 30 ℃ to prepare the mixture containing the white carbon black and the ammonium fluoride.
More preferably, in the step (1), after the reaction is carried out for 0.5-1h at 30-45 ℃, the auxiliary agent A is added, and then the mixture is mixed and reacted for 1-2h at 20-30 ℃.
More preferably, the assistant A is a mixture of sodium aminotriacetate and sodium fluoride, and the mass ratio of the two is 1-3: 1.
More preferably, the addition amount of the additive A is 0.5-1.5% of the mass of hydrofluoric acid.
More preferably, step (1) comprises the steps of:
mixing the rare earth fluorine-containing waste acid and liquid ammonia according to the volume mass ratio of 0.01-0.02m3Mixing per kg, adjusting the pH value to 7-9, reacting at 30-45 ℃ for 0.5-1h, adding an auxiliary agent A, and reacting at 20-30 ℃ for 1-2h to prepare a mixture containing white carbon black and ammonium fluoride, wherein the rare earth fluorine-containing waste acid comprises hydrofluoric acid and fluosilicic acid, the auxiliary agent A is a mixture of sodium aminotriacetate and sodium fluoride, the mass ratio of the two is 1-3:1, and the addition amount of the auxiliary agent A is 0.5-1.5% of the mass of the hydrofluoric acid.
Preferably, a plate-and-frame filter is adopted in the step (2) for solid-liquid separation.
Preferably, the cleaning mode in the step (3) is beating cleaning, and the drying mode is spin flash drying.
Preferably, the specific process of the reduced pressure distillation in the step (4) is at the temperature of 65-75 ℃ and the pressure of-0.06-0.08 MPa.
Preferably, NH in step (5)4HF2The solution is added with an auxiliary agent B after neutralization and before crystallization.
More preferably, the auxiliary agent B is a mixture of sodium polystyrene sulfonate and dicyclohexylcarbodiimide, and the mass ratio of the sodium polystyrene sulfonate to the dicyclohexylcarbodiimide is 1-3: 1.
More preferably, the addition amount of the auxiliary agent B is 0.005-0.02% of the mass of hydrofluoric acid.
More preferably, the step (5) comprises the steps of:
reacting NH4HF2Neutralizing the solution, adding an auxiliary agent B, wherein the addition amount of the auxiliary agent B is 0.005-0.02% of the mass of hydrofluoric acid, the auxiliary agent B is a mixture of sodium polystyrene sulfonate and dicyclohexylcarbodiimide, the mass ratio of the sodium polystyrene sulfonate to the dicyclohexylcarbodiimide is 1-3:1, crystallizing, centrifuging, returning filtrate obtained after centrifuging to the step (4), mixing with supernatant, distilling under reduced pressure, drying, centrifuging to obtain a solid, and obtaining ammonium bifluoride.
More preferably, the method comprises the steps of:
(1) mixing the waste acid containing fluorine with liquid ammonia according to volumeThe mass ratio is 0.01-0.02m3Mixing/kg, adjusting the pH value to 7-9, reacting at 30-45 ℃ for 0.5-1h, adding an auxiliary agent A, and reacting at 20-30 ℃ for 1-2h to prepare a mixture containing white carbon black and ammonium fluoride, wherein the rare earth fluorine-containing waste acid comprises hydrofluoric acid and fluosilicic acid, the auxiliary agent A is a mixture of sodium aminotriacetate and sodium fluoride, the mass ratio of the two is 1-3:1, and the addition amount of the auxiliary agent A is 0.5-1.5% of the mass of the hydrofluoric acid;
(2) performing solid-liquid separation on the mixture containing the white carbon black and the ammonium fluoride by adopting a plate-and-frame filter to obtain crude white carbon black and ammonium fluoride solution;
(3) pulping, cleaning, centrifuging and filtering the crude white carbon black to obtain a filter cake, and performing rotary flash evaporation drying to obtain the white carbon black;
(4) precipitating ammonium fluoride solution, taking supernatant, distilling under reduced pressure at 65-75 ℃ and under-0.06-0.08 MPa to obtain NH3And NH4HF2Solution, collecting NH3The liquid ammonia used for preparing step (1);
(5) reacting NH4HF2Neutralizing the solution, adding an auxiliary agent B, wherein the addition amount of the auxiliary agent B is 0.005-0.02% of the mass of hydrofluoric acid, the auxiliary agent B is a mixture of sodium polystyrene sulfonate and dicyclohexylcarbodiimide, the mass ratio of the sodium polystyrene sulfonate to the dicyclohexylcarbodiimide is 1-3:1, crystallizing, centrifuging, returning filtrate obtained after centrifuging to the step (4), mixing with supernatant, distilling under reduced pressure, drying, centrifuging to obtain a solid, and obtaining ammonium bifluoride.
The invention has the beneficial effects that:
the invention realizes the resource utilization of the fluorine-containing waste acid generated in the rare earth preparation process, prepares the white carbon black and the ammonium bifluoride and reduces the generation of three wastes.
The invention optimizes the reaction process of the fluorine-containing waste acid and the liquid ammonia, and the obtained white carbon black and ammonium fluoride have the advantages of obviously improved yield and purity and good performance.
The addition agent A is added in the reaction process of the fluorine-containing waste acid and the liquid ammonia, so that other impurities are avoided, and the yield and the purity of the white carbon black and the ammonium fluoride are further improved.
In the present invention at NH4HF2The addition agent B is added after the solution is neutralized and before the solution is crystallized, so that the agglomeration of ammonium bifluoride is avoided, and the long-term storage is facilitated.
Detailed Description
The invention will be further described with reference to specific embodiments, and the advantages and features of the invention will become apparent as the description proceeds. These examples are illustrative only and do not limit the scope of the present invention in any way. It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention, and that such changes and modifications may be made without departing from the spirit and scope of the invention.
The rare earth fluorine-containing waste acid adopted in each embodiment and comparative example of the invention is fluorine-containing waste acid generated in the process of smelting rare earth concentrate by adopting a three-generation acid method high-temperature roasting production process by Baotou Huamei rare earth high-tech company, and specifically comprises the following components: h2SiF6：6.89％，HF：8.05％，H2O: 85.06%, and the content of other components is small and ignored.
NH in liquid ammonia used in examples and comparative examples of the present invention3The content was 99.6%.
Example 1
A method for preparing ammonium bifluoride by recycling rare earth fluorine-containing waste acid comprises the following steps:
(1) mixing the rare earth fluorine-containing waste acid and liquid ammonia according to the volume mass ratio of 0.01m3Mixing/kg, adjusting the pH value to 7, reacting at 30 ℃ for 0.5h, adding an auxiliary agent A, and mixing and reacting at 20 ℃ for 1h to prepare a mixture containing white carbon black and ammonium fluoride, wherein the auxiliary agent A is a mixture of sodium aminotriacetate and sodium fluoride, the mass ratio of the sodium aminotriacetate to the sodium fluoride is 1:1, and the addition amount of the auxiliary agent A is 0.5 percent of the mass of hydrofluoric acid;
(2) performing solid-liquid separation on the mixture containing the white carbon black and the ammonium fluoride by adopting a plate-and-frame filter to obtain crude white carbon black and ammonium fluoride solution;
(3) pulping, cleaning, centrifuging and filtering the crude white carbon black to obtain a filter cake, and performing rotary flash evaporation drying to obtain the white carbon black;
(4) will fluorinatePrecipitating the ammonium solution, distilling the supernatant under reduced pressure at 65 deg.C under-0.06 MPa to obtain NH3And NH4HF2Solution, collecting NH3The liquid ammonia used for preparing step (1);
(5) reacting NH4HF2Neutralizing the solution, adding an auxiliary agent B, wherein the addition amount of the auxiliary agent B is 0.005% of the mass of hydrofluoric acid, the auxiliary agent B is a mixture of sodium polystyrene sulfonate and dicyclohexylcarbodiimide, the mass ratio of the sodium polystyrene sulfonate to the dicyclohexylcarbodiimide is 1:1, crystallizing, centrifuging, returning filtrate obtained after centrifuging to the step (4), mixing with supernatant, distilling under reduced pressure, drying solid obtained after centrifuging, and obtaining ammonium bifluoride.
Example 2
A method for preparing ammonium bifluoride by recycling rare earth fluorine-containing waste acid comprises the following steps:
(1) mixing the rare earth fluorine-containing waste acid and liquid ammonia according to the volume mass ratio of 0.02m3Mixing/kg, adjusting the pH value to 9, reacting at 45 ℃ for 1 hour, adding an auxiliary agent A, and mixing and reacting at 30 ℃ for 2 hours to prepare a mixture containing white carbon black and ammonium fluoride, wherein the auxiliary agent A is a mixture of sodium aminotriacetate and sodium fluoride, the mass ratio of the auxiliary agent A to the sodium aminotriacetate is 3:1, and the addition amount of the auxiliary agent A is 1.5% of the mass of hydrofluoric acid;
(2) performing solid-liquid separation on the mixture containing the white carbon black and the ammonium fluoride by adopting a plate-and-frame filter to obtain crude white carbon black and ammonium fluoride solution;
(3) pulping, cleaning, centrifuging and filtering the crude white carbon black to obtain a filter cake, and performing rotary flash evaporation drying to obtain the white carbon black;
(4) precipitating ammonium fluoride solution, distilling supernatant under reduced pressure at 75 deg.C under-0.08 MPa to obtain NH3And NH4HF2Solution, collecting NH3The liquid ammonia used for preparing step (1);
(5) reacting NH4HF2Neutralizing the solution, adding an auxiliary agent B, wherein the addition amount of the auxiliary agent B is 0.02 percent of the mass of hydrofluoric acid, the auxiliary agent B is a mixture of sodium polystyrene sulfonate and dicyclohexylcarbodiimide, the mass ratio of the sodium polystyrene sulfonate to the dicyclohexylcarbodiimide is 3:1, crystallizing, centrifuging, and returning filtrate obtained after centrifuging to the next stepAnd (4) mixing the supernatant in the step (4), distilling under reduced pressure, drying and centrifuging to obtain a solid, and thus obtaining the ammonium bifluoride.
Example 3
A method for preparing ammonium bifluoride by recycling rare earth fluorine-containing waste acid comprises the following steps:
(1) mixing the rare earth fluorine-containing waste acid and liquid ammonia according to the volume mass ratio of 0.015m3Mixing/kg, adjusting the pH value to 8, reacting at 40 ℃ for 0.75h, adding an auxiliary agent A, and mixing and reacting at 25 ℃ for 1.5h to prepare a mixture containing white carbon black and ammonium fluoride, wherein the auxiliary agent A is a mixture of sodium aminotriacetate and sodium fluoride, the mass ratio of the sodium aminotriacetate to the sodium fluoride is 2:1, and the addition amount of the auxiliary agent A is 1% of the mass of hydrofluoric acid;
(2) performing solid-liquid separation on the mixture containing the white carbon black and the ammonium fluoride by adopting a plate-and-frame filter to obtain crude white carbon black and ammonium fluoride solution;
(3) pulping, cleaning, centrifuging and filtering the crude white carbon black to obtain a filter cake, and performing rotary flash evaporation drying to obtain the white carbon black;
(4) precipitating ammonium fluoride solution, distilling supernatant under reduced pressure at 70 deg.C under-0.07 MPa to obtain NH3And NH4HF2Solution, collecting NH3The liquid ammonia used for preparing step (1);
(5) reacting NH4HF2Neutralizing the solution, adding an auxiliary agent B, wherein the addition amount of the auxiliary agent B is 0.015% of the mass of hydrofluoric acid, the auxiliary agent B is a mixture of sodium polystyrene sulfonate and dicyclohexylcarbodiimide, the mass ratio of the sodium polystyrene sulfonate to the dicyclohexylcarbodiimide is 2:1, crystallizing, centrifuging, returning filtrate obtained after centrifuging to the step (4), mixing with supernatant, distilling under reduced pressure, drying solid obtained after centrifuging, and obtaining ammonium bifluoride.
Example 4
The only difference from example 3 is that no auxiliary A is added in step (1), and the other conditions are the same.
Comparative example 1
The difference from the example 3 is only that the additive A is sodium aminotriacetate with equal mass, and the rest conditions are the same.
Comparative example 2
The difference from the example 3 is only that the auxiliary A is sodium fluoride with equal mass, and the other conditions are the same.
Comparative example 3
The difference from the example 3 is only that the heating process in the step (1) is different, and the rest conditions are the same, specifically as follows:
(1) mixing the rare earth fluorine-containing waste acid and liquid ammonia according to the volume mass ratio of 0.015m3Mixing the raw materials per kg, adjusting the pH value to 8, mixing and reacting at 25 ℃ for 1.5h, adding an auxiliary agent A, and reacting at 40 ℃ for 0.75h to obtain a mixture containing white carbon black and ammonium fluoride, wherein the auxiliary agent A is a mixture of sodium aminotriacetate and sodium fluoride, the mass ratio of the sodium aminotriacetate to the sodium fluoride is 2:1, and the addition amount of the auxiliary agent A is 1% of the mass of hydrofluoric acid.
Comparative example 4
The difference from the example 3 is only that the heating process in the step (1) is different, and the rest conditions are the same, specifically as follows:
(1) mixing the rare earth fluorine-containing waste acid and liquid ammonia according to the volume mass ratio of 0.015m3Mixing the raw materials per kg, adjusting the pH value to 8, reacting at 40 ℃ for 2.25 hours, and adding an auxiliary agent A to prepare a mixture containing the white carbon black and the ammonium fluoride, wherein the auxiliary agent A is a mixture of sodium aminotriacetate and sodium fluoride, the mass ratio of the sodium aminotriacetate to the sodium fluoride is 2:1, and the addition amount of the auxiliary agent A is 1% of the mass of hydrofluoric acid.
Comparative example 5
The difference from the example 3 is only that the additive B in the step (5) is polystyrene sodium sulfonate with equal mass, and the rest conditions are the same.
Comparative example 6
The difference from example 3 is only that the auxiliary agent B in step (5) is dicyclohexylcarbodiimide of equal mass, and the other conditions are the same.
Comparative example 7
The difference from the example 3 is that the dosage of the auxiliary agent B in the step (5) is unchanged, the dosage ratio of the sodium polystyrene sulfonate to the dicyclohexylcarbodiimide is different and is 1:2, and the other conditions are the same.
Test example 1
The ammonium bifluoride and white carbon black products of examples 1 to 4 and comparative examples 1 to 7 were tested for yield, purity and water content, and the results are shown in table 1.
TABLE 1 test results for the products of examples 1-4 and comparative examples 1-7
The above detailed description is specific to one possible embodiment of the present invention, and the embodiment is not intended to limit the scope of the present invention, and all equivalent implementations or modifications without departing from the scope of the present invention should be included in the technical scope of the present invention.
Claims (4)
1. A method for preparing ammonium bifluoride by recycling rare earth fluorine-containing waste acid is characterized by comprising the following steps:
(1) mixing rare earth fluorine-containing waste acid with liquid ammonia, reacting at 30-45 ℃ for 0.5-1h, adding an auxiliary agent A, and mixing and reacting at 20-30 ℃ for 1-2h to prepare a mixture containing white carbon black and ammonium fluoride;
the auxiliary agent A is a mixture of sodium aminotriacetate and sodium fluoride, and the mass ratio of the sodium aminotriacetate to the sodium fluoride is 1-3: 1; the addition amount of the additive A is 0.5-1.5% of the mass of hydrofluoric acid;
the rare earth fluorine-containing waste acid comprises the following components in percentage by weight: 6-10% of hydrofluoric acid, 5-9% of fluosilicic acid and the balance of water;
the volume mass ratio of the rare earth fluorine-containing waste acid to the liquid ammonia in the step (1) is 0.01-0.02m3/kg；
(2) Carrying out solid-liquid separation on the mixture containing the white carbon black and the ammonium fluoride to obtain crude white carbon black and ammonium fluoride solution;
(3) cleaning, centrifuging and filtering the crude white carbon black to obtain a filter cake, and drying the filter cake to obtain the white carbon black;
(4) precipitating ammonium fluoride solution, taking supernatant, and distilling under reduced pressure to obtain NH3And NH4HF2Solution, collecting NH3The liquid ammonia used for preparing step (1);
(5) reacting NH4HF2Neutralizing, crystallizing and centrifuging the solution, returning filtrate obtained after centrifugation to the step (4), mixing the filtrate with supernatant, distilling the mixture under reduced pressure, and drying solid obtained after centrifugation to obtain ammonium bifluoride;
NH in step (5)4HF2Adding an auxiliary agent B into the solution after neutralization and before crystallization, wherein the auxiliary agent B is a mixture of sodium polystyrene sulfonate and dicyclohexylcarbodiimide, and the mass ratio of the sodium polystyrene sulfonate to the dicyclohexylcarbodiimide is 1-3: 1;
the addition amount of the auxiliary agent B is 0.005-0.02% of the mass of hydrofluoric acid.
2. The method according to claim 1, wherein the rare earth waste acid containing fluorine in step (1) is mixed with liquid ammonia and then the pH value is adjusted to 7-9.
3. The method according to claim 1, wherein solid-liquid separation is carried out in step (2) by using a plate and frame filter; the cleaning mode in the step (3) is pulping cleaning, and the drying mode is rotary flash drying.
4. The method according to claim 1, wherein the specific process of the reduced pressure distillation in the step (4) is 65-75 ℃ and-0.06-0.08 MPa.
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