Method for recycling iodine from fluorine-containing iodo-hydrocarbon waste liquid

Abstract

The invention relates to a method for recycling iodine from fluorine-containing iodo-hydrocarbon waste liquid. The method comprises the following steps: stirring fluorine-containing iodo-hydrocarbon waste liquid and a sodium hydroxide solution for hydrolysis reaction to generate a mixed aqueous solution of fluorine-containing alcohol and iodide ions, and extracting and separating by using a perfluorinated solvent to obtain an enriched iodide water phase; oxidizing the iodide ions into elemental iodine through strong acid and an oxidizing agent, extracting the elemental iodine with an organic extractant, and recovering the extractant and separating out the elemental iodine through rectification and evaporation separation; the iodine ion-containing liquid is added into an organic extraction agent, and the iodine ion-containing liquid is prepared through a reaction of a tetrahydrofuran solution of 1-iodopropane, tributylphosphine, 2-methyl-4-chloromethylthiazole-tributylphosphine and tri-n-butylphosphorus tetrafluoroborate; the method can effectively improve the purity and recovery rate of iodine, reduces the moisture content in the iodine-dichloromethane mixed solution, and has high economic value.

Description

Technical Field

[0001] The invention relates to the technical field of resource recovery, in particular to a method for recovering iodine from fluorine-containing iodinated hydrocarbon waste liquid. Background Art

[0002] Fluorinated iodocarbons are widely used in numerous fields, including chemical engineering, pharmaceuticals, and materials. However, their production process generates a large amount of waste liquid, which contains abundant iodine resources. Iodine is a scarce and strategically important resource. Directly discharging fluorinated iodocarbon waste liquids would not only result in a significant waste of iodine resources, but also cause serious environmental pollution due to fluorine-containing substances and other components.

[0003] Currently, existing technologies for recovering iodine from iodinated fluorinated hydrocarbon wastewater present numerous challenges. Some methods suffer from low recovery efficiency and fail to fully extract the iodine from the wastewater; some require complex processes and high equipment requirements, resulting in high production costs; and some methods are prone to introducing new impurities during the recovery process, affecting the purity of the recovered iodine and making it difficult to directly reuse the recovered iodine, limiting its industrial application. Therefore, the development of an efficient, low-cost, high-purity recovery method that can recycle iodine is urgent. Summary of the Invention

[0004] In order to solve the above problems, the present invention provides a method for recovering iodine from iodinated fluorine-containing hydrocarbon waste liquid, the operating steps of which are as follows:

[0005] S1 Hydrolysis Reaction: Place the fluorinated iodinated hydrocarbon waste liquid in a reaction vessel, add a 5-10% sodium hydroxide solution, wherein the molar ratio of sodium hydroxide to the fluorinated iodinated hydrocarbon is (1.05-1.5):1, and stir the reaction at a temperature of 40-60° C. for 30-60 minutes; during this process, the fluorinated iodinated hydrocarbon and the sodium hydroxide undergo a hydrolysis reaction to generate a mixed aqueous solution of fluorinated alcohol and iodide ions;

[0006] S2 solvent extraction separation: add a perfluorinated solvent to the mixed aqueous solution obtained in S1, mix thoroughly and allow to stand for separation. After separation, the upper layer is an aqueous phase containing iodide ions, and the lower layer is an organic phase containing fluorinated alcohol and perfluorinated solvent;

[0007] S3 organic phase removal: separating and removing the lower organic phase containing fluorinated alcohol and perfluorinated solvent, thereby obtaining an aqueous phase enriched with iodide ions;

[0008] S4 oxidation reaction: slowly add a strong acid and an oxidant to the iodide ion-enriched aqueous phase obtained in S3, control the pH of the reaction system to be 1-3, the molar ratio of the oxidant to the iodide ion to be 1:(1-1.5), maintain the reaction temperature at 20-40°C, and the reaction time for 30-60 minutes to oxidize the iodide ion to elemental iodine;

[0009] S5 Extraction and separation of elemental iodine: Add an organic extractant of equal volume to the solution after the oxidation reaction, and stir at 20-30°C for 10-20 minutes to promote the transfer of elemental iodine to the organic phase; after the stirring is completed, stand for 15-30 minutes to separate the layers, at which time the system will be separated into an upper aqueous phase and a lower iodine-containing organic solvent phase; dehydrate by decantation to separate the organic phase and the aqueous phase, remove the upper aqueous phase, and obtain the lower iodine-containing organic solvent phase;

[0010] S6 Extractant Recovery and Mixed Liquid Treatment: The iodine-containing organic solvent phase is subjected to distillation to remove excess extractant and a small amount of water. During the distillation process, the organic extractant-water binary azeotrope is distilled from the top of the tower and can be used in the next batch of extraction processes. The iodine-extractant mixed liquid is obtained at the bottom of the tower and can be used in the next batch of synthesis processes. The extractant in the iodine-extractant mixed liquid is a poor solvent for water and a good solvent for elemental iodine.

[0011] S7 Iodine elemental separation and recovery: The iodine-extractant mixture is further evaporated and separated. After the extractant at the top of the evaporation tower is condensed, it is returned to the set for use in the next batch of extraction process; iodine precipitates and crystallizes at the bottom of the tower. After collection and treatment, the obtained elemental iodine can be used in the next batch of synthesis process.

[0012] The perfluoro solvent is one of perfluorohexane, perfluorocyclohexane and perfluoroheptane.

[0013] The strong acid is one of sulfuric acid, nitric acid and hydrochloric acid.

[0014] The oxidant is one of hydrogen peroxide, nitric acid, nitrous acid, perchloric acid and chlorine.

[0015] The organic extractant is one of n-pentane, chloroform, carbon tetrachloride, ether, petroleum ether and dichloromethane.

[0016] The organic extractant is added with an iodine ion liquid accounting for 0.5-3% by mass of the extractant, and the preparation method thereof is as follows:

[0017] In a reaction vessel equipped with a stirrer and a reflux condenser, 100-120 parts of a 20-30% by mass 1-iodopropane solution in tetrahydrofuran is added, the temperature is raised to 50-60° C. with stirring, and 25-35 parts of tributylphosphine, 0.05-0.35 parts of 2-methyl-4-chloromethylthiazole-tributylphosphine, and 0.5-0.9 parts of tri-n-butylphosphonium tetrafluoroborate are slowly added dropwise; after the dropwise addition is completed, the temperature is maintained under reflux for 12-15 hours to prevent decomposition of the iodide; after the reaction is completed, the reaction solution is transferred to a separatory funnel, anhydrous ether is added, shaken, and the layers are separated, and the upper layer is discarded; the lower layer solution is distilled under reduced pressure at 40-50° C. to remove the tetrahydrofuran solvent to obtain an iodide ion-containing liquid.

[0018] Reaction mechanism

[0019] Iodide ion stabilization mechanism: The generated quaternary phosphonium iodide salt exists in the form of ion pairs, and the iodide ion forms I3 with I2 in the waste liquid - / I5 - Polyiodide anions and quaternary phosphonium cations anchor the organic phase through hydrophobic interaction, and fluoroborate enhances stability through weak coordination and reduces desorption losses.

[0020] Technical Effects

[0021] The present invention provides a method for recovering and utilizing iodine from iodinated fluorine-containing hydrocarbon waste liquid. Compared with the prior art, the present invention has the following significant effects:

[0022] 1. Efficient separation: The iodine in the fluorinated iodinated hydrocarbon is converted into an ionic state through hydrolysis reaction. Combined with perfluorinated solvent extraction and separation, it can effectively separate the fluorinated alcohol and iodide ions, improve the enrichment of iodide ions, and lay a good foundation for subsequent iodine recovery.

[0023] 2. Precise oxidation: During the oxidation reaction, the reaction conditions are strictly controlled to ensure the efficient conversion of iodine ions into elemental iodine, reduce the occurrence of side reactions, and improve the recovery rate and purity of iodine.

[0024] 3. Recycling: The present invention realizes the dual recycling of the extractant and iodine; the extractant is recovered through distillation and evaporation condensation and can be reused in the extraction process; the recovered elemental iodine can be directly applied to the next batch of synthesis process, reducing production costs and improving resource utilization.

[0025] 4. Environmental protection and economy: It avoids the waste of iodine resources and environmental pollution in fluorinated iodine hydrocarbon waste liquid. At the same time, it reduces the company's dependence on external iodine resources through recycling, which has significant economic and environmental benefits.

[0026] 5. Optimized extraction performance: It can effectively improve the extraction rate of iodine, enhance compatibility with fluorine-containing waste liquid, and can tolerate HF below 500ppm. There is no need to remove the catalyst in post-processing, and it can be directly dissolved in the extraction agent to simplify the process. DETAILED DESCRIPTION

[0027] In order to further illustrate the technical means and effects adopted by the present invention to achieve the predetermined invention object, the following is a detailed description in conjunction with examples and comparative examples:

[0028] 1. Iodine content test: refer to GB / T13025.7-1999 General test method for salt production industry - Determination of iodine ion;

[0029] 2. Moisture content test: The water content is determined by Karl Fischer method using iodine-extractant.

[0030] Example 1

[0031] A method for recovering iodine from iodinated fluorine-containing hydrocarbon waste liquid, comprising the following steps:

[0032] S1 Hydrolysis Reaction: Place the fluorinated iodinated hydrocarbon waste liquid in a reaction vessel, add a 5% sodium hydroxide solution, wherein the molar ratio of sodium hydroxide to the fluorinated iodinated hydrocarbon is 1.05:1, and stir the reaction at 40°C for 30 minutes; during this process, the fluorinated iodinated hydrocarbon and the sodium hydroxide undergo a hydrolysis reaction to generate a mixed aqueous solution of fluorinated alcohol and iodide ions;

[0033] S2 solvent extraction separation: add a perfluorinated solvent to the mixed aqueous solution obtained in S1, mix thoroughly and allow to stand for separation. After separation, the upper layer is an aqueous phase containing iodide ions, and the lower layer is an organic phase containing fluorinated alcohol and perfluorinated solvent;

[0034] S3 organic phase removal: separating and removing the lower organic phase containing fluorinated alcohol and perfluorinated solvent, thereby obtaining an aqueous phase enriched with iodide ions;

[0035] S4 oxidation reaction: Slowly add a strong acid and an oxidant to the iodide ion-enriched aqueous phase obtained in S3, control the pH of the reaction system to be 1, the molar ratio of the oxidant to the iodide ion to be 1:1, maintain the reaction temperature at 20°C, and react for 30 minutes to oxidize the iodide ion to elemental iodine;

[0036] S5 Extraction and separation of elemental iodine: Add an organic extractant of equal volume to the solution after the oxidation reaction, and stir at 20°C for 10 minutes to promote the transfer of elemental iodine to the organic phase; after the stirring is completed, stand for 15 minutes to separate the layers, at which time the system will be separated into an upper aqueous phase and a lower organic solvent phase containing iodine; dehydrate by decantation to separate the organic phase and the aqueous phase, remove the upper aqueous phase, and obtain the lower organic solvent phase containing iodine;

[0037] S6 Extractant Recovery and Mixed Liquid Treatment: The iodine-containing organic solvent phase is subjected to distillation to remove excess extractant and a small amount of water. During the distillation process, the organic extractant-water binary azeotrope is distilled from the top of the tower and can be used in the next batch of extraction processes. The iodine-extractant mixed liquid is obtained at the bottom of the tower and can be used in the next batch of synthesis processes. The extractant in the iodine-extractant mixed liquid is a poor solvent for water and a good solvent for elemental iodine.

[0038] S7 Iodine elemental separation and recovery: The iodine-extractant mixture is further evaporated and separated. After the extractant at the top of the evaporation tower is condensed, it is returned to the set for use in the next batch of extraction process; iodine precipitates and crystallizes at the bottom of the tower. After collection and treatment, the obtained elemental iodine can be used in the next batch of synthesis process.

[0039] The perfluorinated solvent is perfluorohexane.

[0040] The strong acid is sulfuric acid.

[0041] The oxidant is hydrogen peroxide.

[0042] The organic extractant is n-pentane.

[0043] The organic extractant is added with an iodine ion liquid accounting for 0.5% by mass of the extractant, and the preparation method thereof is as follows:

[0044] To a reaction vessel equipped with a stirrer and a reflux condenser, 100 g of a 20% solution of 1-iodopropane in tetrahydrofuran was added, and the mixture was stirred and heated to 50° C. Then, 25 g of tributylphosphine, 0.05 g of 2-methyl-4-chloromethylthiazole-tributylphosphine (CAS: 211919-65-2), and 0.5 g of tri-n-butylphosphonium tetrafluoroborate (CAS: 113978-91-9) were slowly added dropwise. After the addition was complete, the reaction was refluxed at this temperature for 12 hours to prevent decomposition of the iodide. After the reaction was completed, the reaction solution was transferred to a separatory funnel, shaken with anhydrous ether, and the layers were separated, after which the upper layer was discarded. The lower layer was distilled under reduced pressure at 40° C. to remove the tetrahydrofuran solvent to obtain an iodide-containing liquid.

[0045] Example 2

[0046] A method for recovering iodine from iodinated fluorine-containing hydrocarbon waste liquid, comprising the following steps:

[0047] S1 Hydrolysis Reaction: Place the fluorinated iodinated hydrocarbon waste liquid in a reaction vessel, add a 6% sodium hydroxide solution, wherein the molar ratio of sodium hydroxide to the fluorinated iodinated hydrocarbon is 1.2:1, and stir the reaction at 45°C for 40 minutes; during this process, the fluorinated iodinated hydrocarbon and the sodium hydroxide undergo a hydrolysis reaction to generate a mixed aqueous solution of fluorinated alcohol and iodide ions;

[0048] S2 solvent extraction separation: add a perfluorinated solvent to the mixed aqueous solution obtained in S1, mix thoroughly and allow to stand for separation. After separation, the upper layer is an aqueous phase containing iodide ions, and the lower layer is an organic phase containing fluorinated alcohol and perfluorinated solvent;

[0049] S3 organic phase removal: separating and removing the lower organic phase containing fluorinated alcohol and perfluorinated solvent, thereby obtaining an aqueous phase enriched with iodide ions;

[0050] S4 oxidation reaction: Slowly add a strong acid and an oxidant to the iodide ion-enriched aqueous phase obtained in S3, control the pH of the reaction system to 2, the molar ratio of the oxidant to the iodide ion to be 1:1.2, maintain the reaction temperature at 25°C, and react for 40 minutes to oxidize the iodide ion to elemental iodine;

[0051] S5 Extraction and separation of elemental iodine: Add an organic extractant of equal volume to the solution after the oxidation reaction, and stir at 25°C for 15 minutes to promote the transfer of elemental iodine to the organic phase; after the stirring is completed, stand for 20 minutes to separate the layers, at which time the system will be separated into an upper aqueous phase and a lower organic solvent phase containing iodine; dehydrate by decantation to separate the organic phase and the aqueous phase, remove the upper aqueous phase, and obtain the lower organic solvent phase containing iodine;

[0052] S6 Extractant Recovery and Mixed Liquid Treatment: The iodine-containing organic solvent phase is subjected to distillation to remove excess extractant and a small amount of water. During the distillation process, the organic extractant-water binary azeotrope is distilled from the top of the tower and can be used in the next batch of extraction processes. The iodine-extractant mixed liquid is obtained at the bottom of the tower and can be used in the next batch of synthesis processes. The extractant in the iodine-extractant mixed liquid is a poor solvent for water and a good solvent for elemental iodine.

[0053] S7 Iodine elemental separation and recovery: The iodine-extractant mixture is further evaporated and separated. After the extractant at the top of the evaporation tower is condensed, it is returned to the set for use in the next batch of extraction process; iodine precipitates and crystallizes at the bottom of the tower. After collection and treatment, the obtained elemental iodine can be used in the next batch of synthesis process.

[0054] The perfluorinated solvent is perfluorocyclohexane.

[0055] The strong acid is nitric acid.

[0056] The oxidant is nitric acid.

[0057] The organic extractant is chloroform.

[0058] The organic extractant is added with an iodine ion-containing liquid accounting for 1% by mass of the extractant, and the preparation method thereof is as follows:

[0059] To a reaction vessel equipped with a stirrer and a reflux condenser, 105 g of a 25% solution of 1-iodopropane in tetrahydrofuran was added, and the mixture was stirred and heated to 55° C. 28 g of tributylphosphine, 0.15 g of 2-methyl-4-chloromethylthiazole-tributylphosphine (CAS: 211919-65-2), and 0.6 g of tri-n-butylphosphonium tetrafluoroborate (CAS: 113978-91-9) were slowly added dropwise. After the addition was complete, the reaction was maintained at this temperature under reflux for 13 hours to prevent decomposition of the iodide. After the reaction was completed, the reaction solution was transferred to a separatory funnel, anhydrous ether was added, and the layers were shaken and separated, and the upper layer was discarded. The lower layer was distilled under reduced pressure at 45° C. to remove the tetrahydrofuran solvent to obtain an iodide-containing liquid.

[0060] Example 3

[0061] A method for recovering iodine from iodinated fluorine-containing hydrocarbon waste liquid, comprising the following steps:

[0062] S1 Hydrolysis Reaction: Place the fluorinated iodinated hydrocarbon waste liquid in a reaction vessel, add an 8% sodium hydroxide solution, wherein the molar ratio of sodium hydroxide to the fluorinated iodinated hydrocarbon is 1.4:1, and stir the reaction at 55°C for 50 minutes; during this process, the fluorinated iodinated hydrocarbon and the sodium hydroxide undergo a hydrolysis reaction to generate a mixed aqueous solution of fluorinated alcohol and iodide ions;

[0063] S2 solvent extraction separation: add a perfluorinated solvent to the mixed aqueous solution obtained in S1, mix thoroughly and allow to stand for separation. After separation, the upper layer is an aqueous phase containing iodide ions, and the lower layer is an organic phase containing fluorinated alcohol and perfluorinated solvent;

[0064] S3 organic phase removal: separating and removing the lower organic phase containing fluorinated alcohol and perfluorinated solvent, thereby obtaining an aqueous phase enriched with iodide ions;

[0065] S4 oxidation reaction: Slowly add a strong acid and an oxidant to the iodide ion-enriched aqueous phase obtained in S3, control the pH of the reaction system to 2, the molar ratio of the oxidant to the iodide ion to be 1:1.4, maintain the reaction temperature at 35°C, and react for 50 minutes to oxidize the iodide ion to elemental iodine;

[0066] S5 Extraction and separation of elemental iodine: Add an organic extractant of equal volume to the solution after the oxidation reaction, and stir at 25°C for 15 minutes to promote the transfer of elemental iodine to the organic phase; after the stirring is completed, stand for 25 minutes to separate the layers, at which time the system will be separated into an upper aqueous phase and a lower iodine-containing organic solvent phase; dehydrate by decantation to separate the organic phase and the aqueous phase, remove the upper aqueous phase, and obtain the lower iodine-containing organic solvent phase;

[0067] S6 Extractant Recovery and Mixed Liquid Treatment: The iodine-containing organic solvent phase is subjected to distillation to remove excess extractant and a small amount of water. During the distillation process, the organic extractant-water binary azeotrope is distilled from the top of the tower and can be used in the next batch of extraction processes. The iodine-extractant mixed liquid is obtained at the bottom of the tower and can be used in the next batch of synthesis processes. The extractant in the iodine-extractant mixed liquid is a poor solvent for water and a good solvent for elemental iodine.

[0068] S7 Iodine elemental separation and recovery: The iodine-extractant mixture is further evaporated and separated. After the extractant at the top of the evaporation tower is condensed, it is returned to the set for use in the next batch of extraction process; iodine precipitates and crystallizes at the bottom of the tower. After collection and treatment, the obtained elemental iodine can be used in the next batch of synthesis process.

[0069] The perfluorinated solvent is perfluorocyclohexane.

[0070] The strong acid is nitric acid.

[0071] The oxidant is nitrous acid.

[0072] The organic extractant is carbon tetrachloride.

[0073] The organic extractant is added with an iodine ion liquid accounting for 2.5% by mass of the extractant, and the preparation method thereof is as follows:

[0074] To a reaction vessel equipped with a stirrer and a reflux condenser, 115 g of a 25% solution of 1-iodopropane in tetrahydrofuran was added, and the mixture was stirred and heated to 55° C. Then, 33 g of tributylphosphine, 0.25 g of 2-methyl-4-chloromethylthiazole-tributylphosphine (CAS: 211919-65-2), and 0.8 g of tri-n-butylphosphonium tetrafluoroborate (CAS: 113978-91-9) were slowly added dropwise. After the addition was complete, the reaction was refluxed at this temperature for 14 hours to prevent decomposition of the iodide. After the reaction was completed, the reaction solution was transferred to a separatory funnel, shaken with anhydrous ether, and the layers were separated, after which the upper layer was discarded. The lower layer was distilled under reduced pressure at 45° C. to remove the tetrahydrofuran solvent to obtain an iodide-containing liquid.

[0075] Example 4

[0076] A method for recovering iodine from iodinated fluorine-containing hydrocarbon waste liquid, comprising the following steps:

[0077] S1 Hydrolysis Reaction: Place the fluorinated iodinated hydrocarbon waste liquid in a reaction vessel, add a 10% sodium hydroxide solution, wherein the molar ratio of sodium hydroxide to the fluorinated iodinated hydrocarbon is 1.5:1, and stir the reaction at 60°C for 60 minutes; during this process, the fluorinated iodinated hydrocarbon and the sodium hydroxide undergo a hydrolysis reaction to generate a mixed aqueous solution of fluorinated alcohol and iodide ions;

[0078] S2 solvent extraction separation: add a perfluorinated solvent to the mixed aqueous solution obtained in S1, mix thoroughly and allow to stand for separation. After separation, the upper layer is an aqueous phase containing iodide ions, and the lower layer is an organic phase containing fluorinated alcohol and perfluorinated solvent;

[0079] S3 organic phase removal: separating and removing the lower organic phase containing fluorinated alcohol and perfluorinated solvent, thereby obtaining an aqueous phase enriched with iodide ions;

[0080] S4 oxidation reaction: Slowly add a strong acid and an oxidant to the iodide ion-enriched aqueous phase obtained in S3, control the pH of the reaction system to 3, the molar ratio of the oxidant to the iodide ion to be 1:1.5, maintain the reaction temperature at 40°C, and react for 60 minutes to oxidize the iodide ion to elemental iodine;

[0081] S5 Extraction and separation of elemental iodine: Add an organic extractant of equal volume to the solution after the oxidation reaction, and stir at 30°C for 20 minutes to promote the transfer of elemental iodine to the organic phase; after the stirring is completed, stand for 30 minutes to separate the layers, at which time the system will be separated into an upper aqueous phase and a lower organic solvent phase containing iodine; dehydrate by decantation to separate the organic phase and the aqueous phase, remove the upper aqueous phase, and obtain the lower organic solvent phase containing iodine;

[0082] S6 Extractant Recovery and Mixed Liquid Treatment: The iodine-containing organic solvent phase is subjected to distillation to remove excess extractant and a small amount of water. During the distillation process, the organic extractant-water binary azeotrope is distilled from the top of the tower and can be used in the next batch of extraction processes. The iodine-extractant mixed liquid is obtained at the bottom of the tower and can be used in the next batch of synthesis processes. The extractant in the iodine-extractant mixed liquid is a poor solvent for water and a good solvent for elemental iodine.

[0083] S7 Iodine elemental separation and recovery: The iodine-extractant mixture is further evaporated and separated. After the extractant at the top of the evaporation tower is condensed, it is returned to the set for use in the next batch of extraction process; iodine precipitates and crystallizes at the bottom of the tower. After collection and treatment, the obtained elemental iodine can be used in the next batch of synthesis process.

[0084] The perfluorinated solvent is perfluoroheptane.

[0085] The strong acid is hydrochloric acid.

[0086] The oxidant is perchloric acid.

[0087] The organic extractant is dichloromethane.

[0088] The organic extractant is added with an iodine ion liquid accounting for 3% by mass of the extractant, and the preparation method thereof is as follows:

[0089] To a reaction vessel equipped with a stirrer and a reflux condenser, 120 g of a 30% solution of 1-iodopropane in tetrahydrofuran was added, and the mixture was stirred and heated to 60° C. Then, 35 g of tributylphosphine, 0.35 g of 2-methyl-4-chloromethylthiazole-tributylphosphine (CAS: 211919-65-2), and 0.9 g of tri-n-butylphosphonium tetrafluoroborate (CAS: 113978-91-9) were slowly added dropwise. After the addition was complete, the reaction was refluxed at this temperature for 15 hours to prevent decomposition of the iodide. After the reaction was completed, the reaction solution was transferred to a separatory funnel, anhydrous ether was added, and the layers were shaken and separated, and the upper layer was discarded. The lower layer was distilled under reduced pressure at 50° C. to remove the tetrahydrofuran solvent to obtain an iodide-containing liquid.

[0090] Comparative Example 1

[0091] No iodine ion liquid was added, and the other steps were the same as in Example 1.

[0092] Comparative Example 2

[0093] The other steps were the same as in Example 1 except that 2-methyl-4-chloromethylthiazole-tributylphosphine was not added.

[0094] Comparative Example 3

[0095] Tri-n-butylphosphonium tetrafluoroborate was not added, and the other procedures were the same as in Example 1.

[0096]

[0097]

[0098] Through the data analysis of the above examples and comparative examples, the present invention can effectively improve the purity and recovery rate of iodine, reduce the water content in the iodine-dichloromethane mixture, and has high economic value.

[0099] The above description is merely a preferred embodiment of the present invention and does not constitute any form of limitation to the present invention. Although the present invention has been disclosed as above in terms of a preferred embodiment, it is not intended to limit the present invention. Any person skilled in the art can, without departing from the scope of the technical solution of the present invention, make some changes or modifications to equivalent embodiments using the technical contents disclosed above. However, any brief modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. A method for recovering iodine from iodinated fluorine-containing hydrocarbon waste liquid, comprising the following steps: S1 Hydrolysis Reaction: Place the fluorinated iodinated hydrocarbon waste liquid in a reaction vessel, add a 5-10% sodium hydroxide solution, wherein the molar ratio of sodium hydroxide to the fluorinated iodinated hydrocarbon is (1.05-1.5):1, and stir the reaction at a temperature of 40-60° C. for 30-60 minutes; during this process, the fluorinated iodinated hydrocarbon and the sodium hydroxide undergo a hydrolysis reaction to generate a mixed aqueous solution of fluorinated alcohol and iodide ions; S2 solvent extraction separation: add a perfluorinated solvent to the mixed aqueous solution obtained in S1, mix thoroughly and allow to stand for separation. After separation, the upper layer is an aqueous phase containing iodide ions, and the lower layer is an organic phase containing fluorinated alcohol and perfluorinated solvent; S3 organic phase removal: separating and removing the lower organic phase containing fluorinated alcohol and perfluorinated solvent, thereby obtaining an aqueous phase enriched with iodide ions; S4 oxidation reaction: slowly add a strong acid and an oxidant to the iodide ion-enriched aqueous phase obtained in S3, control the pH of the reaction system to be 1-3, the molar ratio of the oxidant to the iodide ion to be 1:(1-1.5), maintain the reaction temperature at 20-40°C, and the reaction time for 30-60 minutes to oxidize the iodide ion to elemental iodine; S5 Extraction and separation of elemental iodine: Add an organic extractant of equal volume to the solution after the oxidation reaction, and stir at 20-30°C for 10-20 minutes to promote the transfer of elemental iodine to the organic phase; after the stirring is completed, stand for 15-30 minutes to separate the layers, at which time the system will be separated into an upper aqueous phase and a lower iodine-containing organic solvent phase; dehydrate by decantation to separate the organic phase and the aqueous phase, remove the upper aqueous phase, and obtain the lower iodine-containing organic solvent phase; S6 Extractant Recovery and Mixed Liquid Treatment: The iodine-containing organic solvent phase is subjected to distillation to remove excess extractant and a small amount of water. During the distillation process, the organic extractant-water binary azeotrope is distilled from the top of the tower and can be used in the next batch of extraction processes. The iodine-extractant mixed liquid is obtained at the bottom of the tower and can be used in the next batch of synthesis processes. The extractant in the iodine-extractant mixed liquid is a poor solvent for water and a good solvent for elemental iodine. S7 Iodine elemental separation and recovery: The iodine-extractant mixture is further evaporated and separated. After the extractant at the top of the evaporation tower is condensed, it is returned to the set for use in the next batch of extraction process; iodine precipitates and crystallizes at the bottom of the tower. After collection and treatment, the obtained elemental iodine can be used in the next batch of synthesis process.

2. The method for recovering iodine from iodinated fluorine-containing hydrocarbon waste liquid according to claim 1, wherein: The perfluoro solvent is one of perfluorohexane, perfluorocyclohexane and perfluoroheptane.

3. The method for recovering iodine from iodinated fluorine-containing hydrocarbon waste liquid according to claim 1, wherein: The strong acid is one of sulfuric acid, nitric acid and hydrochloric acid.

4. The method for recovering iodine from iodinated fluorine-containing hydrocarbon waste liquid according to claim 1, wherein: The oxidant is one of hydrogen peroxide, nitric acid, nitrous acid, perchloric acid and chlorine.

5. The method for recovering iodine from iodinated fluorine-containing hydrocarbon waste liquid according to claim 1, wherein: The organic extractant is one of n-pentane, chloroform, carbon tetrachloride, ether, petroleum ether and dichloromethane.

6. The method for recovering iodine from iodinated fluorine-containing hydrocarbon waste liquid according to claim 5, wherein: The organic extractant is added with an iodine ion liquid accounting for 0.5-3% by mass of the extractant, and the preparation method thereof is as follows: In a reaction vessel equipped with a stirrer and a reflux condenser, 100-120 parts of a 20-30% by mass 1-iodopropane solution in tetrahydrofuran is added, the temperature is raised to 50-60° C. with stirring, and 25-35 parts of tributylphosphine, 0.05-0.35 parts of 2-methyl-4-chloromethylthiazole-tributylphosphine, and 0.5-0.9 parts of tri-n-butylphosphonium tetrafluoroborate are slowly added dropwise; after the dropwise addition is completed, the temperature is maintained under reflux for 12-15 hours to prevent decomposition of the iodide; after the reaction is completed, the reaction solution is transferred to a separatory funnel, anhydrous ether is added, shaken, and the layers are separated, and the upper layer is discarded; the lower layer solution is distilled under reduced pressure at 40-50° C. to remove the tetrahydrofuran solvent to obtain an iodide ion-containing liquid.

Images