Method for preparing ammonium bifluoride from fluorine-containing waste acid in environment-friendly manner

Abstract

The invention discloses a method for preparing ammonium bifluoride from fluorine-containing waste acid in an environment-friendly manner, and belongs to the technical field of ammonium bifluoride preparation. The method for preparing ammonium bifluoride from the fluorine-containing waste acid in an environment-friendly manner comprises the following steps: (1) filtering the fluorine-containing waste acid to remove large-particle impurities, and then adding a precipitator to remove heavy metal ions so as to obtain pretreated fluorine-containing waste acid; (2) adding the pretreated fluorine-containing waste acid into an ion exchange system, and collecting fluorine ion enrichment liquid; and (3) slowly adding liquid ammonia into the fluorine ion-enriched liquid, carrying out a heating reaction to obtain a mixed solution after the reaction is finished, adding an auxiliary agent into the mixed solution, and carrying out a stirring reaction, cooling crystallization, filtration, washing and drying to obtain ammonium bifluoride. The ammonium bifluoride prepared by the method has excellent yield and purity.

Description

Technical Field

[0001] The invention belongs to the technical field of ammonium bifluoride preparation, and particularly relates to an environmentally friendly method for preparing ammonium bifluoride by utilizing fluorine-containing waste acid. Background Art

[0002] In modern industrial production, especially in the chemical fields of phosphate fertilizers and rare earths, the amount of fluorine-containing waste acids is increasing, becoming an environmental problem that needs to be solved urgently. These waste acids not only contain fluoride, but are often accompanied by other heavy metals and toxic and hazardous substances. If they are directly discharged, they will cause serious pollution to the ecological environment, including water pollution, soil pollution and even air pollution, posing a potential threat to the balance of the ecosystem and human health. Therefore, how to effectively treat and utilize these fluorine-containing waste acids and realize their resource utilization and harmlessness has become a research hotspot in the field of environmental protection.

[0003] As an important inorganic compound, ammonium bifluoride is widely used in industrial production, such as glass etcher, disinfectant, preservative, metal solvent and fluorinating agent in organic synthesis. However, the traditional production process of ammonium bifluoride is often accompanied by problems such as high energy consumption and high pollution, which makes it difficult to meet the current requirements of green and sustainable development. Therefore, exploring a method for preparing ammonium bifluoride using fluorine-containing waste acid in an environmentally friendly way not only helps to solve the problem of treating fluorine-containing waste acid, but also realizes the efficient utilization of resources, which has important environmental significance and economic value.

[0004] Patent CN 111977671 B discloses a method for preparing ammonium bifluoride by recycling rare earth fluorine-containing waste acid. The method 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; (2) performing solid-liquid separation on the mixture containing white carbon black and ammonium fluoride to obtain crude white carbon black and ammonium fluoride solution; (3) washing, centrifuging and filtering the crude white carbon black, and drying the obtained filter cake to obtain white carbon black; (4) precipitating the ammonium fluoride solution, taking the supernatant and performing reduced pressure distillation to obtain NH 3 and NH 4 HF 2 The solution is neutralized, crystallized, and centrifuged, and the solid obtained after drying and centrifugation is obtained to obtain ammonium bifluoride. The invention has the advantages of high resource utilization, high yield and purity, and not easy to agglomerate, but its yield and purity still have room for improvement. Summary of the invention

[0005] The object of the present invention is to provide an environmentally friendly method for preparing ammonium bifluoride by utilizing fluorine-containing waste acid, so as to solve the technical problems of poor yield and purity of ammonium bifluoride in the prior art.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] The present invention provides an environmentally friendly method for preparing ammonium bifluoride by utilizing fluorine-containing waste acid, comprising the following steps:

[0008] Step (1): filtering the fluorine-containing waste acid to remove large particle impurities, and then adding a precipitant to remove heavy metal ions to obtain pretreated fluorine-containing waste acid;

[0009] Step (2): adding the pretreated fluorine-containing waste acid into an ion exchange system and collecting a fluoride ion-enriched solution;

[0010] Step (3): slowly adding liquid ammonia to the fluoride ion-enriched solution, heating for reaction, obtaining a mixed solution after the reaction is completed, adding an auxiliary agent to the mixed solution, stirring for reaction, cooling for crystallization, filtering, washing, and drying to obtain ammonium bifluoride.

[0011] Preferably, in step (1), the precipitant is composed of one or more combinations of sodium sulfide, calcium hydroxide, sodium hydroxide, sodium bicarbonate, sodium carbonate and ferrous sulfate.

[0012] Preferably, in step (2), the ion exchange system is composed of a composite ion exchange membrane, an exchange column, an inlet and outlet water system, a regeneration system, a control system, a drainage system and a backwash system, wherein the preparation method of the composite ion exchange membrane comprises the following steps:

[0013] Q1: Add carbazole to a container containing tetrahydrofuran, stir until completely dissolved, add potassium hydroxide, then add 1,10-dibromodecane, heat and stir to react, then add deionized water to quench the reaction, extract, concentrate by rotary evaporation, separate and purify, continue to concentrate by rotary evaporation, and cool to obtain compound 1;

[0014] Q2: Add N,N,N',N'-tetrabutyl-1,6-hexanediamine to a container, then add ethyl acetate, stir to react, then add iodomethane, continue stirring to react, obtain a precipitate, filter, and wash to obtain compound 2;

[0015] Q3: Compound 1 is added to a container containing N-methylpyrrolidone and stirred. Compound 2 is then dissolved in N-methylpyrrolidone and added to the container. The mixture is heated for reaction. After the reaction is completed, the mixture is poured into ethyl acetate for precipitation. The precipitate is filtered, washed, and dried to obtain compound 3.

[0016] Q4: Compound 3 is added to dimethyl sulfoxide to obtain a membrane liquid, and the membrane liquid is filtered and poured into a film-forming surface dish, dried, and soaked to obtain a composite ion exchange membrane.

[0017] In the above process, the synthetic reaction formula of compound 3 is as follows:

[0018]

[0019] After mass spectrometry analysis, the mass spectrum results of compound 1 were: m / z: 385.14 (100.0%), 387.14 (97.4%), 386.14 (24.2%), 388.14 (23.8%), 387.15 (2.8%), 389.15 (2.7%); the mass spectrum results of compound 2 were: m / z: 355.41 (100.0%), 356.41 (25.5%), 357.41 (3.3%); the mass spectrum results of compound 3 were: m / z: 330.81 (100.0%), 331.31 (49.6%), 331.81 (12.1%), 332.32 (1.9%), 331.31 (1.1%).

[0020] Preferably, in Q1, the molar ratio of carbazole to 1,10-dibromodecane is (0.8-1.2):(0.9-1.1), the heating and stirring temperature is 40-50°C, the reaction time is 10-12h, extraction is performed with dichloromethane, and the eluent in the separation and purification process is a mixed solution of dichloromethane and n-hexane, and the volume ratio of dichloromethane to n-hexane is (1-2):(5-10); in Q2, the molar ratio of N,N,N',N'-tetrabutyl-1,6-hexanediamine to iodomethane is (0.9-1.2):(1-1.2), the stirring time is continued for 24-36h, and washing is performed with n-hexane.

[0021] Preferably, in Q3, the molar ratio of compound 1 to compound 2 is (0.9-1.2):(0.8-1.2), the heating reaction temperature is 80-90°C, the reaction time is 72-96h, and the mixture is washed with ethyl acetate and deionized water respectively, and the drying temperature is 60-70°C; in Q4, the amount ratio of compound 3 to dimethyl sulfoxide is (0.25-0.5)g:(7-14)mL, the membrane liquid is filtered using a pinhole organic filter, the drying temperature is 80-90°C, the time is 8-10h, and the mixture is immersed in 1mol / L sodium hydroxide solution for 48-52h.

[0022] Preferably, in step (3), the volume ratio of liquid ammonia to fluoride ion-enriched liquid is (1-2): (0.01-0.02), the heating reaction temperature is 30-45°C, the reaction time is 2-3h, the amount ratio of the mixed solution to the auxiliary agent is (100-120)mL: (8-12)g, and the stirring time is 1-3h.

[0023] Preferably, the preparation method of the auxiliary agent comprises the following steps:

[0024] S1: Add diethylaminoethyl methacrylate and 1,3-propane sultone into a container containing ethyl acetate, heat and stir to react, and after the reaction is completed, filter and dry to obtain a white powder;

[0025] S2: Add polyvinyl alcohol to distilled water, heat and stir, cool and defoam, add N-vinyl pyrrolidone, white powder, azobisisobutyronitrile and N,N'-methylenebisacrylamide in sequence, stir evenly and introduce nitrogen, heat to react, after the reaction is completed, mold, vacuum dry, and crush to obtain an additive.

[0026] In the above process, the synthetic reaction formula of the auxiliary agent is as follows:

[0027]

[0028] Preferably, in S1, the molar ratio of diethylaminoethyl methacrylate to 1,3-propane sultone is (1-2):(1.1-2.1), the heating and stirring reaction temperature is 50-60°C, the time is 10-12h, and the drying temperature is 40-50°C, and the time is 12-14h.

[0029] Preferably, in S2, the dosage ratio of polyvinyl alcohol, distilled water, N-vinyl pyrrolidone, white powder, azobisisobutyronitrile and N,N'-methylenebisacrylamide is (10-12) g: (20-25) mL: (2-3) g: (1-2) g: (0.02-0.024) g: (0.05-0.06) g, the heating reaction temperature is 60-70°C, the reaction time is 15-30 min, the vacuum drying temperature is 80-90°C, and the time is 8-10 h.

[0030] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0031] 1. The present invention first uses carbazole, 1,10-dibromosilane, N,N,N',N'-tetrabutyl-1,6-hexanediamine and methyl iodide as raw materials to prepare a composite ion exchange membrane, then uses diethylaminoethyl methacrylate, 1,3-propane sultone, polyvinyl alcohol and N-vinyl pyrrolidone as raw materials to prepare an auxiliary agent, uses the composite ion exchange membrane to treat pretreated fluorine-containing waste acid to obtain a fluorine ion-enriched liquid, then adds liquid ammonia to the fluorine ion-enriched liquid, reacts, adds the auxiliary agent, and obtains ammonium bifluoride. The method can improve the yield and purity of ammonium bifluoride, thereby realizing the environmental protection and resource utilization of fluorine-containing waste acid.

[0032] 2. The present invention uses carbazole, 1,10-dibromodecane, N,N,N',N'-tetrabutyl-1,6-hexanediamine and iodomethane as raw materials to prepare a composite ion exchange membrane, which is applied to an ion exchange system to treat pretreated fluorine-containing waste acid to reduce impurities in the waste acid. The functional groups in the composite ion exchange membrane can exchange or adsorb specific ions (such as fluoride ions and hydrogen ions) in the fluorine-containing waste acid. Under the selective permeability of the membrane, specific types of ions can be exchanged or transferred through the membrane layer, and impurity ions are retained on one side of the membrane, thereby achieving effective separation and purification of specific ions in the fluorine-containing waste acid. The prepared composite ion exchange membrane has excellent stability and durability, and can be used repeatedly without affecting its separation effect. The use of the composite ion exchange membrane provides higher purity raw materials for the subsequent preparation of ammonium bifluoride, thereby improving the yield and purity of the product.

[0033] 3. The present invention uses diethylaminoethyl methacrylate, 1,3-propane sultone, polyvinyl alcohol and N-vinylpyrrolidone as raw materials to prepare an auxiliary agent, which is added to the crystal forming process of ammonium bifluoride to effectively improve the crystallization speed of ammonium bifluoride and the purity of the crystal. The components in the auxiliary agent can be used as a template or a guiding agent in the ammonium bifluoride solution, and the arrangement and stacking mode of the ammonium bifluoride molecules are affected by their molecular structure or charge distribution, so as to guide the crystal to grow according to a specific crystal form, so as to obtain a crystal with a uniform structure; and the components in the auxiliary agent can be The supersaturation threshold of the ammonium bifluoride solution is reduced to promote the formation of crystal nuclei. When the crystal nuclei are formed, the dispersed components in the additive can be adsorbed on the surface of the crystal nuclei to prevent the crystal nuclei from agglomerating and growing too fast, thereby improving the crystallization efficiency. At the same time, the components in the additive can form hydrogen bonds, ionic bonds, coordination bonds and other interactions with the ammonium bifluoride molecules, which can not only enhance the cohesion of the crystal, but also affect the charge distribution and polarity on the crystal surface, change the interaction between the crystal and the solvent and impurities, help optimize the growth environment and conditions of the crystal, and improve the purity and quality of the crystal. DETAILED DESCRIPTION

[0034] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0035] Example 1

[0036] This embodiment discloses a method for preparing a composite ion exchange membrane, comprising the following steps:

[0037] Q1: Add 25g of carbazole to a container containing 300mL of tetrahydrofuran, stir until completely dissolved, add 33.1g of potassium hydroxide, then add 44.91g of 1,10-dibromodecane, heat and stir at 40°C for 10h, then add 200mL of deionized water to quench the reaction, extract with dichloromethane, concentrate by rotary evaporation, separate and purify (the eluent is a mixed solution of dichloromethane and n-hexane, and V 二氯甲烷 :V 正己烷 =1:5), continue rotary evaporation and concentration, cool to obtain compound 1;

[0038] Q2: Add 3.07 mL of N,N,N',N'-tetrabutyl-1,6-hexanediamine to a container, then add 25 mL of ethyl acetate, stir to react, then add 1.1 g of iodomethane, continue stirring to react for 24 hours, obtain a precipitate, filter, and wash with n-hexane to obtain compound 2;

[0039] Q3: 1.16 g of compound 1 was added to a container containing 20 mL of N-methylpyrrolidone and stirred. Subsequently, 0.98 g of compound 2 was dissolved in 5 mL of N-methylpyrrolidone and added to the container. The mixture was heated at 80°C for 72 h. After the reaction, the mixture was poured into ethyl acetate for precipitation. The mixture was filtered and the precipitate was washed with ethyl acetate and deionized water respectively. The precipitate was dried at 60°C to obtain compound 3.

[0040] Q4: Add 0.33 g of compound 3 to 10.5 mL of dimethyl sulfoxide to obtain a membrane solution. Filter the membrane solution using a pinhole organic filter and pour it into a film-forming surface dish. Dry it at 80°C for 10 h and soak it in 1 mol / L sodium hydroxide solution for 48 h to obtain a composite ion exchange membrane.

[0041] This embodiment discloses a method for preparing an auxiliary agent, comprising the following steps:

[0042] S1: Add 24.08 mL of diethylaminoethyl methacrylate and 15.62 g of 1,3-propane sultone into a container containing 90 mL of ethyl acetate, heat and stir at 60°C for 12 h, and after the reaction, filter and dry at 40°C for 12 h to obtain a white powder;

[0043] S2: Add 11g polyvinyl alcohol to 22.5mL distilled water, heat and stir at 90℃ for 120min, cool and defoam, add 2.5g N-vinyl pyrrolidone, 1.5g white powder, 0.022g azobisisobutyronitrile and 0.055g N,N'-methylenebisacrylamide in sequence, stir evenly and introduce nitrogen, heat at 70℃ for 15min, after the reaction is completed, pour into a mold, vacuum dry at 80℃ for 10h, and crush to obtain an auxiliary agent.

[0044] This embodiment discloses a method for preparing ammonium bifluoride in an environmentally friendly manner using fluorine-containing waste acid, comprising the following steps:

[0045] Step (1): filtering the fluorine-containing waste acid to remove large particle impurities, and then adding calcium hydroxide to remove heavy metal ions to obtain pretreated fluorine-containing waste acid;

[0046] Step (2): adding the pretreated fluorine-containing waste acid into an ion exchange system, which is composed of a composite ion exchange membrane, an exchange column, an inlet and outlet water system, a regeneration system, a control system, a drainage system and a backwash system, and collecting a fluoride ion-enriched liquid;

[0047] Step (3): 1.5 L of liquid ammonia is slowly added to 0.015 L of fluoride ion-enriched solution, and the mixture is heated at 45° C. for 3 h. After the reaction is completed, a mixed solution is obtained. 10 g of an auxiliary agent is added to 110 mL of the mixed solution, and the mixture is stirred for 3 h. The mixture is cooled for crystallization, filtered, washed, and dried to obtain ammonium bifluoride.

[0048] Example 2

[0049] This embodiment discloses a method for preparing a composite ion exchange membrane, comprising the following steps:

[0050] Q1: Add 20g of carbazole to a container containing 300mL of tetrahydrofuran, stir until completely dissolved, add 33.1g of potassium hydroxide, then add 40.42g of 1,10-dibromodecane, heat and stir at 40℃ for 10h, then add 200mL of deionized water to quench the reaction, extract with dichloromethane, concentrate by rotary evaporation, separate and purify (the eluent is a mixed solution of dichloromethane and n-hexane, and V 二氯甲烷 :V 正己烷 =1:5), continue rotary evaporation and concentration, cool to obtain compound 1;

[0051] Q2: Add 2.63 mL of N,N,N',N'-tetrabutyl-1,6-hexanediamine to a container, then add 25 mL of ethyl acetate, stir to react, then add 1 g of iodomethane, continue stirring to react for 24 hours, obtain a precipitate, filter, and wash with n-hexane to obtain compound 2;

[0052] Q3: 1 g of compound 1 was added to a container containing 20 mL of N-methylpyrrolidone and stirred. Subsequently, 0.78 g of compound 2 was dissolved in 5 mL of N-methylpyrrolidone and added to the container. The mixture was heated at 80°C for 72 h. After the reaction, the mixture was poured into ethyl acetate for precipitation. The mixture was filtered and the precipitate was washed with ethyl acetate and deionized water respectively. The precipitate was dried at 60°C to obtain compound 3.

[0053] Q4: Add 0.25 g of compound 3 to 7 mL of dimethyl sulfoxide to obtain a membrane solution. Filter the membrane solution using a pinhole organic filter and pour it into a film-forming surface dish. Dry it at 80°C for 10 h and soak it in 1 mol / L sodium hydroxide solution for 48 h to obtain a composite ion exchange membrane.

[0054] This embodiment discloses a method for preparing an auxiliary agent, comprising the following steps:

[0055] S1: Add 16.05 mL of diethylaminoethyl methacrylate and 10.74 g of 1,3-propane sultone into a container containing 90 mL of ethyl acetate, heat and stir at 60°C for 12 h, and after the reaction is completed, filter and dry at 40°C for 12 h to obtain a white powder;

[0056] S2: Add 10g of polyvinyl alcohol to 20mL of distilled water, heat and stir at 90℃ for 120min, cool and defoam, add 2g of N-vinyl pyrrolidone, 1g of white powder, 0.02g of azobisisobutyronitrile and 0.05g of N,N'-methylenebisacrylamide in sequence, stir evenly and introduce nitrogen, heat at 70℃ for reaction for 15min, after the reaction is completed, pour into a mold, vacuum dry at 80℃ for 10h, and crush to obtain an additive.

[0057] This embodiment discloses a method for preparing ammonium bifluoride in an environmentally friendly manner using fluorine-containing waste acid, comprising the following steps:

[0058] Step (1): filtering the fluorine-containing waste acid to remove large particle impurities, and then adding calcium hydroxide to remove heavy metal ions to obtain pretreated fluorine-containing waste acid;

[0059] Step (2): adding the pretreated fluorine-containing waste acid into an ion exchange system, which is composed of a composite ion exchange membrane, an exchange column, an inlet and outlet water system, a regeneration system, a control system, a drainage system and a backwash system, and collecting a fluoride ion-enriched liquid;

[0060] Step (3): slowly add 1L of liquid ammonia to 0.01L of fluoride ion-enriched solution, heat at 45°C for 3h, and after the reaction is completed, obtain a mixed solution. Add 8g of an auxiliary agent to 100mL of the mixed solution, stir and react for 3h, cool and crystallize, filter, wash, and dry to obtain ammonium bifluoride.

[0061] Example 3

[0062] This embodiment discloses a method for preparing a composite ion exchange membrane, comprising the following steps:

[0063] Q1: Add 30 g of carbazole to a container containing 300 mL of tetrahydrofuran, stir until completely dissolved, add 33.1 g of potassium hydroxide, then add 49.4 g of 1,10-dibromodecane, heat and stir at 40 °C for 10 h, then add 200 mL of deionized water to quench the reaction, extract with dichloromethane, concentrate by rotary evaporation, separate and purify (the eluent is a mixed solution of dichloromethane and n-hexane, and V 二氯甲烷 :V 正己烷 =1:5), continue rotary evaporation and concentration, cool to obtain compound 1;

[0064] Q2: Add 3.51 mL of N,N,N',N'-tetrabutyl-1,6-hexanediamine to a container, then add 25 mL of ethyl acetate, stir to react, then add 1.2 g of iodomethane, continue stirring to react for 24 hours, obtain a precipitate, filter, and wash with n-hexane to obtain compound 2;

[0065] Q3: 1.33 g of compound 1 was added to a container containing 20 mL of N-methylpyrrolidone and stirred. Subsequently, 1.18 g of compound 2 was dissolved in 5 mL of N-methylpyrrolidone and added to the container. The mixture was heated at 80°C for 72 h. After the reaction, the mixture was poured into ethyl acetate for precipitation. The mixture was filtered and the precipitate was washed with ethyl acetate and deionized water respectively. The precipitate was dried at 60°C to obtain compound 3.

[0066] Q4: Add 0.5 g of compound 3 to 14 mL of dimethyl sulfoxide to obtain a membrane solution. Filter the membrane solution using a pinhole organic filter and pour it into a film-forming surface dish. Dry it at 80°C for 10 h and soak it in 1 mol / L sodium hydroxide solution for 48 h to obtain a composite ion exchange membrane.

[0067] This embodiment discloses a method for preparing an auxiliary agent, comprising the following steps:

[0068] S1: Add 32.1 mL of diethylaminoethyl methacrylate and 20.5 g of 1,3-propane sultone into a container containing 90 mL of ethyl acetate, heat and stir at 60°C for 12 h, and after the reaction, filter and dry at 40°C for 12 h to obtain a white powder;

[0069] S2: Add 12g of polyvinyl alcohol to 25mL of distilled water, heat and stir at 90℃ for 120min, cool and defoam, add 3g of N-vinyl pyrrolidone, 2g of white powder, 0.024g of azobisisobutyronitrile and 0.06g of N,N'-methylenebisacrylamide in sequence, stir evenly and introduce nitrogen, heat at 70℃ for reaction for 15min, after the reaction is completed, pour into a mold, vacuum dry at 80℃ for 10h, and crush to obtain an auxiliary agent.

[0070] This embodiment discloses a method for preparing ammonium bifluoride in an environmentally friendly manner using fluorine-containing waste acid, comprising the following steps:

[0071] Step (1): filtering the fluorine-containing waste acid to remove large particle impurities, and then adding calcium hydroxide to remove heavy metal ions to obtain pretreated fluorine-containing waste acid;

[0072] Step (2): adding the pretreated fluorine-containing waste acid into an ion exchange system, which is composed of a composite ion exchange membrane, an exchange column, an inlet and outlet water system, a regeneration system, a control system, a drainage system and a backwash system, and collecting a fluoride ion-enriched liquid;

[0073] Step (3): slowly add 2L of liquid ammonia to 0.02L of fluoride ion-enriched solution, heat at 45°C for 3h, and after the reaction is completed, obtain a mixed solution. Add 12g of an auxiliary agent to 120mL of the mixed solution, stir and react for 3h, cool and crystallize, filter, wash, and dry to obtain ammonium bifluoride.

[0074] Example 4

[0075] This embodiment discloses a method for preparing a composite ion exchange membrane, comprising the following steps:

[0076] Q1: Add 22g of carbazole to a container containing 300mL of tetrahydrofuran, stir until completely dissolved, add 33.1g of potassium hydroxide, then add 42.67g of 1,10-dibromodecane, heat and stir at 40°C for 10h, then add 200mL of deionized water to quench the reaction, extract with dichloromethane, concentrate by rotary evaporation, separate and purify (the eluent is a mixed solution of dichloromethane and n-hexane, and V 二氯甲烷 :V 正己烷 =1:5), continue rotary evaporation and concentration, cool to obtain compound 1;

[0077] Q2: Add 2.85 mL of N,N,N',N'-tetrabutyl-1,6-hexanediamine to a container, then add 25 mL of ethyl acetate, stir to react, then add 1.05 g of iodomethane, continue stirring to react for 24 hours, obtain a precipitate, filter, and wash with n-hexane to obtain compound 2;

[0078] Q3: 1.08 g of compound 1 was added to a container containing 20 mL of N-methylpyrrolidone and stirred. Subsequently, 0.88 g of compound 2 was dissolved in 5 mL of N-methylpyrrolidone and added to the container. The mixture was heated at 80°C for 72 h. After the reaction, the mixture was poured into ethyl acetate for precipitation. The mixture was filtered and the precipitate was washed with ethyl acetate and deionized water respectively. The precipitate was dried at 60°C to obtain compound 3.

[0079] Q4: Add 0.4 g of compound 3 to 9 mL of dimethyl sulfoxide to obtain a membrane solution. Filter the membrane solution using a pinhole organic filter and pour it into a film-forming surface dish. Dry it at 80°C for 10 h and soak it in 1 mol / L sodium hydroxide solution for 48 h to obtain a composite ion exchange membrane.

[0080] This embodiment discloses a method for preparing an auxiliary agent, comprising the following steps:

[0081] S1: Add 20.07 mL of diethylaminoethyl methacrylate and 13.18 g of 1,3-propane sultone into a container containing 90 mL of ethyl acetate, heat and stir at 60°C for 12 h, and after the reaction, filter and dry at 40°C for 12 h to obtain a white powder;

[0082] S2: Add 10.5g polyvinyl alcohol to 23mL distilled water, heat and stir at 90℃ for 120min, cool and defoam, add 2.2g N-vinyl pyrrolidone, 1.2g white powder, 0.021g azobisisobutyronitrile and 0.051g N,N'-methylenebisacrylamide in sequence, stir evenly and introduce nitrogen, heat at 70℃ for 15min, after the reaction is completed, pour into a mold, vacuum dry at 80℃ for 10h, and crush to obtain an auxiliary agent.

[0083] This embodiment discloses a method for preparing ammonium bifluoride in an environmentally friendly manner using fluorine-containing waste acid, comprising the following steps:

[0084] Step (1): filtering the fluorine-containing waste acid to remove large particle impurities, and then adding calcium hydroxide to remove heavy metal ions to obtain pretreated fluorine-containing waste acid;

[0085] Step (2): adding the pretreated fluorine-containing waste acid into an ion exchange system, which is composed of a composite ion exchange membrane, an exchange column, an inlet and outlet water system, a regeneration system, a control system, a drainage system and a backwash system, and collecting a fluoride ion-enriched liquid;

[0086] Step (3): 1.1 L of liquid ammonia is slowly added to 0.012 L of fluoride ion-enriched solution, and the mixture is heated at 45° C. for 3 h. After the reaction is completed, a mixed solution is obtained. 11 g of an auxiliary agent is added to 105 mL of the mixed solution, and the mixture is stirred for 3 h. The mixture is cooled for crystallization, filtered, washed, and dried to obtain ammonium bifluoride.

[0087] Example 5

[0088] This embodiment discloses a method for preparing a composite ion exchange membrane, comprising the following steps:

[0089] Q1: Add 27g of carbazole to a container containing 300mL of tetrahydrofuran, stir until completely dissolved, add 33.1g of potassium hydroxide, then add 47.16g of 1,10-dibromodecane, heat and stir at 40°C for 10h, then add 200mL of deionized water to quench the reaction, extract with dichloromethane, concentrate by rotary evaporation, separate and purify (the eluent is a mixed solution of dichloromethane and n-hexane, and V 二氯甲烷 :V 正己烷 =1:5), continue rotary evaporation and concentration, cool to obtain compound 1;

[0090] Q2: Add 3.29 mL of N,N,N',N'-tetrabutyl-1,6-hexanediamine to a container, then add 25 mL of ethyl acetate, stir to react, then add 1.15 g of iodomethane, continue stirring to react for 24 hours, obtain a precipitate, filter, and wash with n-hexane to obtain compound 2;

[0091] Q3: 1.25 g of compound 1 was added to a container containing 20 mL of N-methylpyrrolidone and stirred. Subsequently, 1.08 g of compound 2 was dissolved in 5 mL of N-methylpyrrolidone and added to the container. The mixture was heated at 80°C for 72 h. After the reaction, the mixture was poured into ethyl acetate for precipitation. The mixture was filtered and the precipitate was washed with ethyl acetate and deionized water respectively. The precipitate was dried at 60°C to obtain compound 3.

[0092] Q4: Add 0.28 g of compound 3 to 12 mL of dimethyl sulfoxide to obtain a membrane solution. Filter the membrane solution using a pinhole organic filter and pour it into a film-forming surface dish. Dry it at 80°C for 10 h and soak it in 1 mol / L sodium hydroxide solution for 48 h to obtain a composite ion exchange membrane.

[0093] This embodiment discloses a method for preparing an auxiliary agent, comprising the following steps:

[0094] S1: Add 28.1 mL of diethylaminoethyl methacrylate and 18.06 g of 1,3-propane sultone into a container containing 90 mL of ethyl acetate, heat and stir at 60°C for 12 h, and after the reaction, filter and dry at 40°C for 12 h to obtain a white powder;

[0095] S2: Add 11.5g of polyvinyl alcohol to 21mL of distilled water, heat and stir at 90℃ for 120min, cool and defoam, add 2.7g of N-vinyl pyrrolidone, 1.8g of white powder, 0.023g of azobisisobutyronitrile and 0.057g of N,N'-methylenebisacrylamide in sequence, stir evenly and introduce nitrogen, heat at 70℃ for reaction for 15min, after the reaction is completed, pour into a mold, vacuum dry at 80℃ for 10h, and crush to obtain an auxiliary agent.

[0096] This embodiment discloses a method for preparing ammonium bifluoride in an environmentally friendly manner using fluorine-containing waste acid, comprising the following steps:

[0097] Step (1): filtering the fluorine-containing waste acid to remove large particle impurities, and then adding calcium hydroxide to remove heavy metal ions to obtain pretreated fluorine-containing waste acid;

[0098] Step (2): adding the pretreated fluorine-containing waste acid into an ion exchange system, which is composed of a composite ion exchange membrane, an exchange column, an inlet and outlet water system, a regeneration system, a control system, a drainage system and a backwash system, and collecting a fluoride ion-enriched liquid;

[0099] Step (3): 1.7 L of liquid ammonia was slowly added to 0.016 L of fluoride ion-enriched solution, and the mixture was heated at 45° C. for 3 h. After the reaction was completed, a mixed solution was obtained. 9 g of an auxiliary agent was added to 115 mL of the mixed solution, and the mixture was stirred for 3 h. The mixture was cooled and crystallized, filtered, washed, and dried to obtain ammonium bifluoride.

[0100] Comparative Example 1

[0101] Comparative Example 1 Compared with Example 1, in the preparation process of the composite ion exchange membrane in Comparative Example 1, no carbazole was added, and other conditions remained unchanged.

[0102] Comparative Example 2

[0103] Comparative Example 2 Compared with Example 1, in the preparation process of the composite ion exchange membrane in Comparative Example 2, N,N,N',N'-tetrabutyl-1,6-hexanediamine was not added, and other conditions remained unchanged.

[0104] Comparative Example 3

[0105] Comparative Example 3 Compared with Example 1, in the preparation process of the auxiliary agent in Comparative Example 3, diethylaminoethyl methacrylate was not added, and other conditions remained unchanged.

[0106] Comparative Example 4

[0107] Comparative Example 4 Compared with Example 1, in the preparation process of ammonium bifluoride in Comparative Example 4, no composite ion exchange membrane is used, and other conditions remain unchanged.

[0108] Comparative Example 5

[0109] Comparative Example 5 Compared with Example 1, in the preparation process of ammonium bifluoride in Comparative Example 5, no auxiliary agent is added, and other conditions remain unchanged.

[0110] According to the method of Examples 1-5 and Comparative Examples 1-4, ammonium bifluoride was prepared, and the yield of ammonium bifluoride was calculated as follows: (actual mass of ammonium bifluoride / theoretical mass of ammonium bifluoride) × 100%, and the purity of ammonium bifluoride was tested according to GB 28655-2012. The water content of ammonium bifluoride was measured according to the loss on drying method, and the water content was calculated as follows: water content = [(m 前 -m 后 ) / m 前 ]×100%, the test results are shown in Table 1:

[0111] Table 1

[0112] project Ammonium bifluoride yield / % Purity of ammonium bifluoride / % Ammonium bifluoride water content / % Example 1 99.98 99.11 0.07 Example 2 99.95 99.04 0.09 Example 3 99.93 99.01 0.10 Example 4 99.91 99.07 0.11 Example 5 99.90 99.03 0.10 Comparative Example 1 96.48 98.04 0.16 Comparative Example 2 96.12 98.01 0.17 Comparative Example 3 98.87 98.03 0.15 Comparative Example 4 95.98 97.92 0.23 Comparative Example 5 98.80 97.89 0.22

[0113] It can be seen from the test results in Table 1 that the ammonium bifluoride prepared according to Examples 1-5 has excellent yield and purity. Comparison between Comparative Example 1 and Examples 1-5 shows that the addition of carbazole can improve the yield and purity of ammonium bifluoride; comparison between Comparative Example 2 and Examples 1-5 shows that the addition of N,N,N',N'-tetrabutyl-1,6-hexanediamine can improve the yield and purity of ammonium bifluoride; comparison between Comparative Example 3 and Examples 1-5 shows that the addition of diethylaminoethyl methacrylate can improve the purity of ammonium bifluoride; comparison between Comparative Example 4 and Examples 1-5 shows that the use of a composite ion exchange membrane can improve the yield and purity of ammonium bifluoride; comparison between Comparative Example 5 and Examples 1-5 shows that the addition of an auxiliary agent can improve the purity of ammonium bifluoride.

[0114] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

[0115] The preferred embodiments of the present invention disclosed above are only used to help explain the present invention. The preferred embodiments do not describe all the details in detail, nor do they limit the invention to only specific implementation methods. Obviously, many modifications and changes can be made according to the content of this specification. This specification selects and specifically describes these embodiments in order to better explain the principles and practical applications of the present invention, so that those skilled in the art can understand and use the present invention well. The present invention is limited only by the claims and their full scope and equivalents.

Claims

1. A method for preparing ammonium bifluoride in an environmentally friendly manner using fluorine-containing waste acid, characterized in that: The following steps are involved: Step (1): filtering the fluorine-containing waste acid to remove large particle impurities, and then adding a precipitant to remove heavy metal ions to obtain pretreated fluorine-containing waste acid; Step (2): adding the pretreated fluorine-containing waste acid into an ion exchange system and collecting a fluoride ion-enriched solution; Step (3): slowly adding liquid ammonia to the fluoride ion-enriched solution, heating for reaction, obtaining a mixed solution after the reaction is completed, adding an auxiliary agent to the mixed solution, stirring for reaction, cooling for crystallization, filtering, washing, and drying to obtain ammonium bifluoride.

2. The method for preparing ammonium bifluoride by utilizing fluorine-containing waste acid in an environmentally friendly manner according to claim 1, characterized in that: In the step (1), the precipitant is composed of one or more combinations of sodium sulfide, calcium hydroxide, sodium hydroxide, sodium bicarbonate, sodium carbonate and ferrous sulfate.

3. The method for preparing ammonium bifluoride by utilizing fluorine-containing waste acid in an environmentally friendly manner according to claim 1, characterized in that: In the step (2), the ion exchange system is composed of a composite ion exchange membrane, an exchange column, an inlet and outlet water system, a regeneration system, a control system, a drainage system and a backwash system, wherein the preparation method of the composite ion exchange membrane comprises the following steps: Q1: Add carbazole to a container containing tetrahydrofuran, stir until completely dissolved, add potassium hydroxide, then add 1,10-dibromodecane, heat and stir to react, then add deionized water to quench the reaction, extract, concentrate by rotary evaporation, separate and purify, continue to concentrate by rotary evaporation, and cool to obtain compound 1; Q2: Add N,N,N',N'-tetrabutyl-1,6-hexanediamine to a container, then add ethyl acetate, stir to react, then add iodomethane, continue stirring to react, obtain a precipitate, filter, and wash to obtain compound 2; Q3: Compound 1 is added to a container containing N-methylpyrrolidone and stirred. Compound 2 is then dissolved in N-methylpyrrolidone and added to the container. The mixture is heated for reaction. After the reaction is completed, the mixture is poured into ethyl acetate for precipitation. The precipitate is filtered, washed, and dried to obtain compound 3. Q4: Compound 3 is added to dimethyl sulfoxide to obtain a membrane liquid, and the membrane liquid is filtered and poured into a film-forming surface dish, dried, and soaked to obtain a composite ion exchange membrane.

4. The method for preparing ammonium bifluoride by utilizing fluorine-containing waste acid in an environmentally friendly manner according to claim 3, characterized in that: In the Q1, the molar ratio of carbazole to 1,10-dibromodecane is (0.8-1.2): (0.9-1.1), the heating and stirring temperature is 40-50°C, the reaction time is 10-12h, and dichloromethane is used for extraction. The eluent in the separation and purification process is a mixed solution of dichloromethane and n-hexane, and the volume ratio of dichloromethane to n-hexane is (1-2): (5-10). In the Q2, the molar ratio of N,N,N',N'-tetrabutyl-1,6-hexanediamine to iodomethane is (0.9-1.2): (1-1.2), the stirring time is continued for 24-36h, and the product is washed with n-hexane.

5. The method for preparing ammonium bifluoride by utilizing fluorine-containing waste acid in an environmentally friendly manner according to claim 3, characterized in that: In the Q3, the molar ratio of compound 1 to compound 2 is (0.9-1.2): (0.8-1.2), the heating reaction temperature is 80-90°C, the reaction time is 72-96h, and it is washed with ethyl acetate and deionized water respectively, and the drying temperature is 60-70°C; in the Q4, the amount ratio of compound 3 to dimethyl sulfoxide is (0.25-0.5)g: (7-14)mL, the membrane liquid is filtered using a pinhole organic filter, the drying temperature is 80-90°C, the time is 8-10h, and it is immersed in 1mol / L sodium hydroxide solution for 48-52h.

6. The method for preparing ammonium bifluoride by utilizing fluorine-containing waste acid in an environmentally friendly manner according to claim 1, characterized in that: In the step (3), the volume ratio of liquid ammonia to fluoride ion-enriched liquid is (1-2): (0.01-0.02), the heating reaction temperature is 30-45° C., the reaction time is 2-3 h, the amount ratio of the mixed solution to the auxiliary agent is (100-120) mL: (8-12) g, and the stirring time is 1-3 h.

7. The method for preparing ammonium bifluoride by utilizing fluorine-containing waste acid in an environmentally friendly manner according to claim 1, characterized in that: The preparation method of the auxiliary agent comprises the following steps: S1: Add diethylaminoethyl methacrylate and 1,3-propane sultone into a container containing ethyl acetate, heat and stir to react, and after the reaction is completed, filter and dry to obtain a white powder; S2: Add polyvinyl alcohol to distilled water, heat and stir, cool and defoam, add N-vinyl pyrrolidone, white powder, azobisisobutyronitrile and N,N'-methylenebisacrylamide in sequence, stir evenly and introduce nitrogen, heat to react, after the reaction is completed, mold, vacuum dry, and crush to obtain an additive.

8. The method for preparing ammonium bifluoride in an environmentally friendly manner using fluorine-containing waste acid according to claim 7, characterized in that: In the S1, the molar ratio of diethylaminoethyl methacrylate to 1,3-propane sultone is (1-2): (1.1-2.1), the heating and stirring reaction temperature is 50-60°C, the time is 10-12h, and the drying temperature is 40-50°C, and the time is 12-14h.

9. The method for preparing ammonium bifluoride by utilizing fluorine-containing waste acid in an environmentally friendly manner according to claim 7, characterized in that: In S2, the dosage ratio of polyvinyl alcohol, distilled water, N-vinyl pyrrolidone, white powder, azobisisobutyronitrile and N,N'-methylenebisacrylamide is (10-12) g: (20-25) mL: (2-3) g: (1-2) g: (0.02-0.024) g: (0.05-0.06) g, the heating reaction temperature is 60-70°C, the reaction time is 15-30 min, and the vacuum drying temperature is 80-90°C, and the time is 8-10 h.

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