Method for mineralizing and cracking perfluorinated compound by using molten alkali

Abstract

The invention belongs to the technical field of environmental protection, and relates to a method for mineralizing and cracking a perfluorinated compound by using molten alkali, and the method comprises the following steps: S1, heating a mixture of NaOH and KOH to a molten state; s2, adding a certain amount of perfluorinated compound into the molten alkali, and keeping the temperature of a reaction system unchanged; and S3, after reacting for a certain period of time, mineralizing and cracking all perfluorinated compounds, and converting organic fluorine into NaF or KF. Compared with the prior art, the method disclosed by the invention has the advantages of mild reaction conditions, no need of pressure-bearing equipment, good perfluorinated compound non-selective mineralization cracking effect and the like.

Description

Technical Field

[0001] The invention belongs to the technical field of environmental protection, and in particular relates to a method for mineralizing and cracking perfluorinated compounds using molten alkali. Background Art

[0002] Due to their unique surface activity and thermal stability, perfluorinated compounds are widely used in textiles, tableware coatings, logistics packaging, fire fighting and other fields. However, they also have multiple biological toxicities such as carcinogenicity and teratogenicity, as well as difficulty in degradation. If not properly controlled, they will cause long-term environmental pollution risks. The migration and transformation laws of perfluorinated compounds in environmental media and mineralization degradation technology have gradually become a frontier hot issue in the field of environmental remediation.

[0003] Existing technologies for mineralization and degradation of perfluorinated compounds include: photocatalytic reduction, electrochemical method, ultrasound method, mechanical force method and plasma incineration heat treatment method. However, photocatalytic reduction method is only applicable to light-transmitting water phase system, and the coexisting oxygen-containing anions or oxidizing ions (such as NO3 - 、NO2 - and SO4 2- The degradation efficiency of perfluorinated compounds is limited by the competition of reducing hydrated electrons. The application of electrochemical, sonochemical and mechanochemical methods usually requires complex equipment, which makes it difficult to achieve large-scale engineering applications. Thermal technologies such as plasma incineration can effectively achieve the complete mineralization of various perfluorinated compounds, but the required temperature is usually as high as 1100°C. The complex and harsh application conditions are the main challenges for their large-scale application.

[0004] In summary, the existing perfluorinated compound degradation technology has low treatment efficiency and harsh reaction conditions. Therefore, it is urgent to develop a new technology method for non-selective cracking of perfluorinated compounds with mild reaction conditions, simple operating conditions and high treatment efficiency. Summary of the invention

[0005] The purpose of the present invention is to overcome the defects of the above-mentioned prior art and provide a method for mineralizing and cracking perfluorinated compounds using molten alkali. The method has a good defluorination effect on perfluorinated compounds and the organic fluorine conversion rate is nearly 100%.

[0006] The purpose of the present invention can be achieved by the following technical solutions:

[0007] The invention provides a method for mineralizing and cracking a perfluoro compound by using molten alkali, comprising the following steps: adding the perfluoro compound into the molten alkali and keeping the temperature of the reaction system unchanged, so that the perfluoro compound is mineralized and cracked.

[0008] Furthermore, the molten alkali is KOH or a mixture of KOH and NAOH.

[0009] Furthermore, the mass fraction of NaOH in the molten alkali is 0%-90%.

[0010] Furthermore, the mass fraction of NaOH in the molten alkali is 10%-90%.

[0011] Furthermore, the perfluorinated compound is selected from at least one of perfluorooctane sulfonic acid (PFOS), perfluorohexane sulfonic acid (PFHxS), perfluorobutane sulfonic acid (PFBS), perfluorooctane carboxylic acid (PFOA), perfluorohexane carboxylic acid (PFHxA) or perfluorobutane carboxylic acid (PFBA).

[0012] Furthermore, the mass of the perfluorinated compound is 1%-10% of the mass of the molten alkali.

[0013] Furthermore, the mass of the perfluorinated compound is 1%-5% of the mass of the molten alkali.

[0014] Furthermore, the heating melting temperature of the molten alkali is 150-300° C., and the reaction time is 15-60 min.

[0015] Furthermore, after mineralization and cracking of perfluorinated compounds, organic fluorine is converted into NaF or KF.

[0016] Furthermore, after all perfluorinated compounds are mineralized and cracked, the solid residues are completely dissolved in water, and the F - The total amount is consistent with the total amount of fluorine in the perfluorinated compound before the reaction.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] (1) The present invention provides a method for mineralizing and cracking perfluorinated compounds using molten alkali, which induces homolytic defluorination of sulfonic acid functional groups in perfluorinated compounds, destabilizes carbon-fluorine bonds, and mineralizes organic fluorine into inorganic fluorine. The defluorination treatment effect on perfluorinated compounds is good, and the organic fluorine conversion rate is nearly 100%, thereby effectively achieving pollution control of perfluorinated compounds.

[0019] (2) The present invention provides a method for mineralizing and pyrolyzing perfluorinated compounds using molten alkali. The method has a wide range of applications and can achieve the mineralization degradation of both perfluorosulfonic acid and perfluorocarboxylic acid. The method is applicable to solid wastes contaminated by perfluoro compounds and also to dried water-containing materials.

[0020] (3) The present invention provides a method for cracking perfluorinated compounds by molten alkali mineralization. The method has mild reaction conditions and significantly reduces the reaction temperature to 150-300°C compared to conventional perfluorinated compound treatment technologies represented by plasma incineration, and does not require pressurized reaction equipment. DETAILED DESCRIPTION

[0021] The following is a detailed description of an embodiment of the present invention. This embodiment is implemented on the premise of the technical solution of the present invention, and a detailed implementation method and a specific operation process are given, but the protection scope of the present invention is not limited to the following embodiment.

[0022] The present invention provides a method for mineralizing and cracking perfluorinated compounds using molten alkali, comprising the following steps:

[0023] S1: mixing NaOH and KOH, wherein the mass fraction of NaOH is controlled to be 0%-90%, preferably 10%-90%, and heating the mixed alkali to 150-300° C. to make it in a molten state to obtain molten alkali;

[0024] S2: adding at least one of perfluorooctane sulfonic acid (PFOS), perfluorohexane sulfonic acid (PFHxS), perfluorobutane sulfonic acid (PFBS), perfluorooctane carboxylic acid (PFOA), perfluorohexane carboxylic acid (PFHxA) or perfluorobutane carboxylic acid (PFBA) to the molten alkali in step S1, wherein the mass of the perfluoro compound is 1%-10%, preferably 1%-5% of the mass of the molten alkali, and the temperature of the molten reaction system is kept unchanged;

[0025] S3: After 15-60 minutes of reaction, all perfluorinated compounds are mineralized and cracked, and organic fluorine is converted into NaF or KF.

[0026] In some specific embodiments, after all perfluorinated compounds are mineralized and cracked, the solid residue is completely dissolved in water, and the F - The total amount is consistent with the total amount of fluorine in the perfluorinated compound before the reaction.

[0027] The raw materials and equipment used in the present invention are all conventional raw materials and equipment in the art. In the following embodiments, raw materials or processing techniques, unless otherwise specified, are all conventional commercially available raw materials or conventional processing techniques in the art.

[0028] Example 1

[0029] This embodiment provides a method for mineralizing and cracking perfluorinated compounds using molten alkali, comprising the following steps:

[0030] (1) mixing NaOH and KOH, wherein the mass fraction of NaOH is controlled to be 30% and the mass fraction of KOH is controlled to be 70%, and heating the mixed alkali to 150° C. to make it in a molten state;

[0031] (2) adding 1 wt.% of perfluorooctane sulfonic acid (PFOS) to the molten alkali in step (1), and maintaining the temperature of the molten reaction system at 150°C;

[0032] (3) After reacting for 60 min, the reaction system was cooled to room temperature, and the residue was completely dissolved in 50 mL of water. - Determination of F by ion selective electrode - concentration, found F - The total amount accounts for 99.3% of the total amount of organic fluorine added in step (2), that is, 99.3% of the perfluorinated compounds are mineralized and cracked.

[0033] Example 2

[0034] This embodiment provides a method for mineralizing and cracking perfluorinated compounds using molten alkali, comprising the following steps:

[0035] (1) mixing NaOH and KOH, wherein the mass fraction of NaOH is controlled to be 50% and the mass fraction of KOH is controlled to be 50%, and heating the mixed alkali to 250° C. to make it in a molten state;

[0036] (2) adding 1 wt.% of perfluorooctane sulfonic acid (PFOS), 2 wt.% of perfluorohexanesulfonic acid (PFHxS), and 2 wt.% of perfluorobutanesulfonic acid (PFBS) to the molten alkali in step (1), wherein the total mass fraction of perfluoro compounds is 5 wt.%, and maintaining the temperature of the molten reaction system at 250°C;

[0037] (3) After reacting for 20 min, the reaction system was cooled to room temperature, and the residue was completely dissolved in 50 mL of water. - Determination of F by ion selective electrode - concentration, found F - The total amount accounts for 98.2% of the total amount of organic fluorine added in step (2), that is, 98.2% of the perfluorinated compounds are mineralized and cracked.

[0038] Example 3

[0039] This embodiment provides a method for mineralizing and cracking perfluorinated compounds using molten alkali, comprising the following steps:

[0040] (1) mixing NaOH and KOH, wherein the mass fraction of NaOH is controlled to be 70% and the mass fraction of KOH is controlled to be 30%, and heating the mixed alkali to 300° C. to make it in a molten state;

[0041] (2) adding 1 wt.% of perfluorobutanesulfonic acid (PFBS) to the molten alkali in step (1), and maintaining the temperature of the molten reaction system at 300°C;

[0042] (3) After reacting for 60 min, the reaction system was cooled to room temperature, and the residue was completely dissolved in 50 mL of water. - Determination of F by ion selective electrode- concentration, found F - The total amount accounts for 93.5% of the total amount of organic fluorine added in step (2), that is, 93.5% of the perfluorinated compounds are mineralized and cracked.

[0043] Example 4

[0044] This embodiment provides a method for mineralizing and cracking perfluorinated compounds using molten alkali, comprising the following steps:

[0045] (1) mixing NaOH and KOH, wherein the mass fraction of NaOH is controlled to be 20% and the mass fraction of KOH is controlled to be 80%, and heating the mixed alkali to 150° C. to make it in a molten state;

[0046] (2) adding 1 wt.% of perfluorooctanecarboxylic acid (PFOA), 1 wt.% of perfluorohexanecarboxylic acid (PFHxA), and 1 wt.% of perfluorobutanecarboxylic acid (PFBA) to the molten alkali in step (1), wherein the total mass fraction of the perfluoro compounds is 3 wt.%, and maintaining the temperature of the molten reaction system at 150°C;

[0047] (3) After reacting for 15 min, the reaction system was cooled to room temperature, and the residue was dissolved in 50 mL of water. - Determination of F by ion selective electrode - concentration, found F - The total amount accounts for 99.7% of the total amount of organic fluorine added in step (2), that is, 99.7% of the perfluorinated compounds are mineralized and cracked.

[0048] Example 5

[0049] This embodiment provides a method for mineralizing and cracking perfluorinated compounds using molten alkali, comprising the following steps:

[0050] (1) mixing NaOH and KOH, wherein the mass fraction of NaOH is controlled to be 90% and the mass fraction of KOH is controlled to be 10%, and heating the mixed alkali to 300° C. to make it in a molten state;

[0051] (2) adding 1 wt.% of perfluorooctane sulfonic acid (PFOS) and 1 wt.% of perfluorooctane carboxylic acid (PFOA) to the molten alkali in step (1), wherein the total mass fraction of perfluoro compounds is 2 wt.%, and maintaining the temperature of the molten reaction system at 300°C;

[0052] (3) After reacting for 15 min, the reaction system was cooled to room temperature, and the residue was dissolved in 50 mL of water. - Determination of F by ion selective electrode - concentration, found F -The total amount accounts for 97.4% of the total amount of organic fluorine added in step (2), that is, 97.4% of the perfluorinated compounds are mineralized and cracked.

[0053] Example 6

[0054] This embodiment provides a method for mineralizing and cracking perfluorinated compounds using molten alkali, comprising the following steps:

[0055] (1) mixing NaOH and KOH, wherein the mass fraction of NaOH is controlled to be 30% and the mass fraction of KOH is controlled to be 70%, and heating the mixed alkali to 150° C. to make it in a molten state;

[0056] (2) adding 1 wt.% of perfluorooctane sulfonic acid (PFOS) to the molten alkali in step (1), and maintaining the temperature of the molten reaction system at 150°C;

[0057] (3) After reacting for 45 min, the reaction system was cooled to room temperature, and the residue was completely dissolved in 50 mL of water. - Determination of F by ion selective electrode - concentration, found F - The total amount accounts for 68.1% of the total amount of organic fluorine added in step (2), that is, 68.1% of the perfluorinated compounds are mineralized and cracked.

[0058] The reactants, reaction conditions and reaction results of Examples 1-6 are shown in Table 1.

[0059] Table 1 Reactants, reaction conditions and reaction results of Examples 1-6

[0060]

[0061]

[0062] The results of the above Examples 1-6 show that molten alkali heat treatment can effectively achieve mineralization and cracking of perfluorinated compounds, and perfluorinated carboxylic acids are easier to degrade than perfluorinated sulfonic acids; at the same time, the higher the reaction temperature and the faster the reaction rate, the higher the degradation rate of perfluorinated compounds in the same time (Examples 1, 5, 6).

[0063] The above embodiments are only used to help understand the method and core idea of ​​the present invention. It should be noted that, for those skilled in the art, several improvements and modifications can be made to the present invention without departing from the principles of the present invention, and these improvements and modifications also fall within the scope of protection of the claims of the present invention.

Claims

1. A method for mineralizing and cracking perfluorinated compounds using molten alkali, characterized in that: The method comprises the following steps: adding a perfluorinated compound into molten alkali and maintaining the temperature of the reaction system unchanged, so that the perfluorinated compound is mineralized and cracked.

2. A method for mineralizing and cracking perfluorinated compounds using molten alkali according to claim 1, characterized in that: The molten alkali is KOH or a mixture of KOH and NAOH.

3. A method for mineralizing and cracking perfluorinated compounds using molten alkali according to claim 2, characterized in that: The mass fraction of NaOH in the molten alkali is 0%-90%.

4. A method for mineralizing and cracking perfluorinated compounds using molten alkali according to claim 3, characterized in that: The mass fraction of NaOH in the molten alkali is 10%-90%.

5. The method for mineralizing and cracking perfluorinated compounds using molten alkali according to claim 1, characterized in that: The perfluorinated compound is selected from at least one of perfluorooctane sulfonic acid (PFOS), perfluorohexane sulfonic acid (PFHxS), perfluorobutane sulfonic acid (PFBS), perfluorooctane carboxylic acid (PFOA), perfluorohexane carboxylic acid (PFHxA) or perfluorobutane carboxylic acid (PFBA).

6. The method of using molten alkali mineralization to crack perfluorinated compounds according to claim 1, characterized in that: The mass of the perfluorinated compound is 1%-10% of the mass of the molten alkali.

7. A method for mineralizing and cracking perfluorinated compounds using molten alkali according to claim 6, characterized in that: The mass of the perfluorinated compound is 1%-5% of the mass of the molten alkali.

8. The method for mineralizing and cracking perfluorinated compounds using molten alkali according to claim 1, characterized in that: The heating melting temperature of the molten alkali is 150-300°C, and the reaction time is 15-60min.

9. The method for mineralizing and cracking perfluorinated compounds using molten alkali according to claim 1, characterized in that: After the mineralization and cracking of perfluorinated compounds, organic fluorine is converted into NaF or KF.

10. The method for mineralizing and cracking perfluorinated compounds using molten alkali according to claim 1, characterized in that: After all perfluorinated compounds are mineralized and cracked, the solid residues are completely dissolved in water, and the F - The total amount is consistent with the total amount of fluorine in the perfluorinated compound before the reaction.

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