A method for rapid degradation and recycling of fluorine-containing organic solid waste

Abstract

This invention relates to the field of waste polymer material recycling and resource utilization, specifically disclosing a method for ultra-fast recycling of fluorinated organic waste through a self-propagating reaction. The method uses liquid sodium-potassium alloy (NaK) as the reaction medium. Under an inert atmosphere, fluorinated organic solid waste is contacted with NaK, and electron transfer is induced by mechanical friction. This catalytically induces the breaking of C–F bonds, triggering a defluorination reaction and releasing heat of reaction, which initiates a self-propagating combustion reaction, ultimately achieving the recovery of carbon materials and metal fluoride products. This method is rapid, requires no external heating, and can efficiently recycle fluorinated waste and prepare high-value-added materials. It is suitable for the green, large-scale treatment of waste fluoropolymers and the preparation of functional materials.

Description

Technical Field

[0001] This invention belongs to the field of solid waste recycling, specifically relating to a method for the rapid degradation and recycling of fluorine-containing organic solid waste. Background Technology

[0002] Fluorinated organic compounds, especially polytetrafluoroethylene (PTFE), are widely used in sealing materials, insulation layers, and anti-corrosion linings due to their excellent heat resistance, chemical corrosion resistance, and low coefficient of friction. While these applications enhance product performance, they also present challenges in waste disposal. Because PTFE's molecular structure contains highly stable carbon-fluorine bonds (C–F bonds), its thermal stability and chemical inertness make it virtually impossible to decompose in the natural environment, leading to long-term accumulation of solid waste and making it a "difficult-to-manage" type of waste.

[0003] Traditional PTFE waste treatment methods mainly include physical treatment, pyrolysis, and incineration, but these methods have many limitations. Physical treatment usually only changes the form of PTFE waste, such as crushing and pulverizing. The performance of the products obtained through physical recycling is far inferior to that of the original PTFE, making resource reuse impossible. For example, CN104175421A discloses a method for recycling polytetrafluoroethylene (PTFE) waste, which uses a three-stage temperature-controlled molding process (washing → drying → crushing) to recover PTFE particles. However, the quality of the PTFE recovered by this method is low, limiting its application scenarios. Although pyrolysis and incineration can partially degrade PTFE, they produce harmful fluorides and highly toxic gases (such as carbon difluoride and carbon tetrafluoride), posing safety hazards and causing serious environmental pollution. Therefore, there is an urgent need to develop a method that can decompose PTFE molecular chains under mild conditions to achieve the green recycling of carbon and fluorine sources in the polymer.

[0004] Besides PTFE, other types of fluorinated organic solid waste, such as perfluoroethylene propylene (FEP) and perfluorooctanoic acid (PFOA, PFOS), also face treatment challenges. FEP, as a copolymer of PTFE, retains strong C–F bonds, and while its thermal decomposition temperature is slightly lower than PTFE, it still exhibits strong chemical inertness. Meanwhile, small-molecule fluorinated organic compounds such as PFOA and PFOS are widely used in surfactants, antifouling coatings, and other fields. They are biodegradable, environmentally mobile, and bioaccumulative, and have been classified as persistent organic pollutants (POPs). Current mainstream treatment methods include high-temperature incineration, plasma decomposition, and supercritical water oxidation, but these generally suffer from high treatment costs, low efficiency, and difficulties in controlling byproducts. Therefore, developing a versatile and mild degradation method applicable to various types of fluorinated solid waste is of great significance not only for PTFE but also for the treatment of FEP and PFOA pollutants.

[0005] In recent years, the molecular-level degradation and component recovery of plastic waste based on chemical reactions to break down the molecular structure of plastics has gradually attracted the attention of researchers. Compared with physical and pyrolysis methods, chemical recycling not only has the advantages of high processing efficiency and high resource recovery rate, but also enables the targeted recovery of specific components, thus providing a new approach to the resource utilization of waste plastics. For fluorinated organic compounds, due to the extremely high bond energy of the C–F bond, traditional chemical recycling methods cannot achieve atomic-level recovery of the structure of fluorinated organic compounds, and still suffer from problems such as harsh reaction conditions, long processing time, and numerous by-products. For example, patent CN114058074A discloses a method for recycling waste polytetrafluoroethylene (PTFE), which uses microwave radiation technology to regenerate waste PTFE. The main principle is to destroy the stable crystalline state of PTFE, transforming it into an amorphous colloid, and then preparing PTFE products of various forms. Although this technology uses a high-energy radiation source to destroy the crystalline state of PTFE, it can only partially destroy the C–F bond, resulting in poor selectivity. In addition, the method is cumbersome and costly, making it unsuitable for large-scale application. Summary of the Invention

[0006] To address the aforementioned problems, this invention proposes an ultrafast chemical recovery method for fluorinated organic compound waste through a contact electrocatalytically induced self-propagating reaction. The technical solution of this invention is as follows:

[0007] A method for rapid degradation and recycling of fluorinated organic solid waste is characterized by using liquid sodium-potassium alloy as the reaction medium, stimulating the C–F bonds in the fluorinated compound molecules in the fluorinated organic solid waste through friction-induced electron transfer, triggering a Waltz-type defluorination reaction, releasing reaction heat and forming a self-sustaining combustion wave, achieving complete breakage and transformation of the polymer interior, and finally generating porous carbon and metal fluoride products.

[0008] Furthermore, the method includes the following steps:

[0009] (1) Material preparation: Dry the fluorine-containing organic solid waste to remove moisture and crush it into powder;

[0010] (2) Under an inert atmosphere, the powder obtained in step (1) is spread in a reaction vessel and liquid sodium-potassium alloy is added dropwise.

[0011] (3) By mechanically perturbing to induce electron transfer, the carbon-fluorine bonds in the fluorine-containing waste powder molecules are activated, triggering the defluorination self-propagating combustion reaction, promoting the internal structural breakage and transformation of fluorine-containing compounds, and generating porous carbon materials and metal fluorides.

[0012] (4) Cool, filter, centrifuge, and collect the product.

[0013] The method of removing moisture in step (1) includes one or more of baking, drying or other methods that can reduce the moisture content of the sample, with a processing temperature range of 60°C to 300°C.

[0014] The pulverization method described in step (1) includes one or more of ball milling, shearing, grinding, or other methods to reduce the particle size of the sample.

[0015] The inert atmosphere mentioned in step (2) is one or more of argon and nitrogen.

[0016] The fluorinated organic solid waste refers to polytetrafluoroethylene, perfluoroethylene propylene, perfluorooctanoic acid, perfluorooctane sulfonate, perfluorooctane, perfluoronaphthane, perfluorodecanoic acid, octafluoronaphthalene, perfluorocarboxylic acid, tetrafluoroethylene, perfluorobutane sulfonic acid, hexafluoropropylene, hexafluoroethane, octafluoropropane, octafluorocyclobutane, perfluorohexylsulfonic acid and their salts and isomers.

[0017] The composition of the liquid sodium-potassium alloy in step (2) meets the requirement of maintaining a liquid state under room temperature reaction conditions, and the mass ratio of sodium to potassium is 60:40 to 10:90, preferably 22:78.

[0018] The amount of liquid sodium-potassium alloy added in step (2) is calculated according to the chemical composition of the fluorine-containing organic solid waste to be degraded and the molar ratio of the selected sodium-potassium alloy, in order to ensure complete reaction.

[0019] The mechanical disturbance method described in step (3) includes one or more of the following: slight scraping, vibration, stirring, or other physical disturbance methods that can trigger the electron transfer process.

[0020] Compared with traditional methods, this invention has advantages such as low energy consumption, high reaction efficiency, and environmental friendliness. It not only improves the treatment efficiency of fluorinated organic compound solid waste but also effectively reduces the risk of hazardous substance generation in traditional treatment methods. Therefore, this invention achieves the harmless treatment of fluorinated organic compound solid waste while also possessing the advantages of resource utilization and environmental friendliness, providing a new technical approach for the resource utilization of fluorinated organic compound waste. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 This is a schematic diagram of the reaction process and reaction apparatus of the present invention;

[0023] Figure 2 Optical images of carbon materials and metal fluorides generated by the reaction of sodium-potassium alloy with fluorine-containing organic compounds according to this invention;

[0024] Figure 3 This is a structural characterization diagram of the carbon material generated by the reaction of sodium-potassium alloy with polytetrafluoroethylene (PTFE) according to the present invention;

[0025] Figure 4 This is a structural characterization diagram of the carbon material generated by the reaction of sodium-potassium alloy with poly(fluoroethylene propylene) (FEP) according to the present invention;

[0026] Figure 5 This is a structural characterization diagram of the carbon material generated by the reaction of sodium-potassium alloy with perfluorooctanoic acid (PFOA) according to the present invention; Detailed Implementation

[0027] To facilitate understanding of the present invention, the present invention will be described more fully and in detail below with reference to the accompanying drawings and preferred embodiments, but the scope of protection of the present invention is not limited to the following specific embodiments.

[0028] Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the scope of the invention. The preferred embodiments and materials described herein are for illustrative purposes only, and various modifications and refinements can be made without departing from the principles of the embodiments of the invention; such modifications and refinements are also considered to be within the scope of the invention.

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

[0030] In this embodiment, a self-propagating reaction between a liquid sodium-potassium alloy and fluorine-containing organic compound powder is used to completely break the C–F bonds in PTFE, thereby obtaining high-value carbon materials and metal fluorides. Specifically, the following steps are included:

[0031] (1) Material preparation: Take waste fluorine-containing organic compound powder, dry it to remove surface moisture; prepare liquid sodium-potassium alloy (liquid at room temperature, with a sodium to potassium molar ratio of 22:78).

[0032] (2) Reaction apparatus: Under the protection of an inert atmosphere (such as argon), the fluorine-containing organic compound powder is evenly spread in a stainless steel reaction vessel.

[0033] (3) Reaction initiation: A small amount of liquid sodium-potassium alloy is added to the surface of the fluorine-containing organic compound. Mechanical stirring and friction induce the transfer of delocalized electrons from the liquid alloy to the fluorine-containing organic compound material, thereby activating the breakage of C–F bonds on the surface of the fluorine-containing compound material.

[0034] (4) Self-propagating reaction: C–F bond breaking is an exothermic reaction that releases heat and forms a combustion center. The heat released by the combustion center spreads rapidly, triggering the breaking and transformation of the entire fluorinated compound sample. The whole process is completed within seconds.

[0035] (5) Product collection and processing: After cooling, the reaction products are collected. The main product is a porous carbon material with a high specific surface area, and the by-product is a stable metal fluoride (such as NaF, KF). They can be separated and purified by simple filtration.

[0036] Example 1: Ultra-fast recycling of PTFE waste

[0037] Waste PTFE powder was dried in an 80°C oven for 6 hours to remove moisture. The dried PTFE was then evenly spread in a stainless steel reactor under argon purging. Approximately stoichiometric amounts of liquid sodium-potassium alloy were added to the PTFE powder surface using a dropper, and the defluorination reaction was initiated by magnetic stirring. PTFE ignited rapidly and underwent fracture transformation in a self-propagating mode, a process lasting several seconds. After cooling, the product was collected and characterized by XRD, Raman, BET, and SEM. The main product was identified as a porous carbon material with a spherical structure. Figure 3 The separation products are NaF and KF. This method achieves efficient and green recycling of PTFE waste.

[0038] Example 2: Ultra-fast recycling of FEP waste

[0039] Waste perfluoroethylene propylene (FEP) film was taken, cut into small pieces (side length <5mm), and treated in a vacuum drying oven at 80℃ for 6 hours to remove residual moisture. The treated FEP sample was weighed and placed in a stainless steel reactor under an argon atmosphere. Liquid sodium-potassium alloy was added dropwise to the FEP surface using a dropper, and the defluorination reaction was initiated by magnetic stirring, rapidly activating the self-propagating reaction. Localized ignition occurred on the FEP surface, and the combustion wave spread along the film, completing the reaction within seconds. XRD and Raman characterization of the reaction product showed it to be a typical multi-level carbon material. Figure 4 ).

[0040] Example 3: Ultra-fast recycling of PFOA waste

[0041] Standard grade perfluorooctanoic acid (PFOA) solid powder was placed in a stainless steel reactor. Liquid sodium-potassium alloy was added dropwise to cover the PFOA surface using a dropper, and the reaction was initiated by magnetic stirring. PFOA was observed to react rapidly with NaK, generating localized exothermic reactions and producing small flashes; the conversion was completed within 3 seconds. The product was cooled and recovered. XRD and Raman analysis showed that porous carbon materials were formed. Figure 5 The results indicate that the method of the present invention can be effectively applied to the rapid degradation and harmless treatment of small molecule fluorinated organic compounds (such as PFOA).

[0042] In summary, the recycling method invented in this invention does not require continuous external energy input, has relatively mild initial reaction conditions, and can be carried out at lower temperatures, thereby reducing energy consumption and production costs. Secondly, the reaction of this invention has a high reaction rate and efficiency, capable of breaking down and degrading the molecular structure of fluorinated organic compounds (such as PTFE, FEP, PFOA, etc.) within seconds, improving the recycling efficiency of waste fluorinated organic compounds. In conclusion, compared with traditional methods, the chemical recycling of fluorinated organic compound waste using self-propagating reactions has lower energy consumption, higher reaction efficiency, and better applicability, making it a more promising technical solution.

[0043] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention in any way. Therefore, any simple modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention should fall within the protection scope of the present invention.

Claims

1. A method for rapid degradation and recycling of fluorine-containing organic solid waste, characterized in that, Using liquid sodium-potassium alloy as the reaction medium, the C–F bonds in fluorine-containing compound molecules are excited by friction-induced electron transfer, triggering a Waltz-type defluorination reaction, releasing reaction heat and forming a self-sustaining combustion wave, achieving complete polymer cleavage and transformation, and ultimately generating porous carbon and metal fluoride products. The specific steps include the following: (1) Material preparation: Dry the fluorine-containing organic solid waste to remove moisture and crush it into powder; (2) Under an inert atmosphere, the powder obtained in step (1) is spread in a reaction vessel and liquid sodium-potassium alloy is added dropwise; (3) By inducing electron transfer through mechanical disturbance, the carbon-fluorine bond in the fluorine-containing waste powder molecules is activated, triggering the defluorination self-propagating combustion reaction, promoting the internal structural breakage and transformation of fluorine-containing compounds, and generating porous carbon materials and metal fluorides; (4) Cool, filter, centrifuge, and collect the product.

2. The method for rapid degradation and recycling of fluorine-containing organic solid waste according to claim 1, characterized in that, The method of removing moisture in step (1) includes one or more of baking, drying or other methods that can reduce the moisture content of the sample, with a processing temperature range of 60°C to 300°C.

3. A method for rapid degradation and recycling of fluorine-containing organic solid waste according to claim 1 or 2, characterized in that, The pulverization method described in step (1) includes one or more of ball milling, shearing, grinding, or other methods to reduce the particle size of the sample.

4. A method for rapid degradation and recycling of fluorine-containing organic solid waste according to claim 1 or 2, characterized in that, The inert atmosphere mentioned in step (2) is either argon or nitrogen.

5. A method for rapid degradation and recycling of fluorine-containing organic solid waste according to claim 1 or 2, characterized in that, The fluorinated organic solid waste refers to polytetrafluoroethylene, perfluoroethylene propylene, perfluorooctanoic acid, perfluorooctane sulfonate, perfluorooctane, perfluoronaphthane, perfluorodecanoic acid, octafluoronaphthalene, perfluorocarboxylic acid, tetrafluoroethylene, perfluorobutane sulfonic acid, hexafluoropropylene, hexafluoroethane, octafluoropropane, octafluorocyclobutane, perfluorohexylsulfonic acid and their salts and isomers.

6. A method for rapid degradation and recycling of fluorine-containing organic solid waste according to claim 1 or 2, characterized in that, The composition of the liquid sodium-potassium alloy in step (2) meets the requirement of maintaining a liquid state under room temperature reaction conditions, and the mass ratio of sodium to potassium is 60:40 to 10:

90.

7. A method for rapid degradation and recycling of fluorine-containing organic solid waste according to claim 1 or 2, characterized in that, In step (2), the mass ratio of sodium to potassium in the liquid sodium-potassium alloy is 22:

78.

8. A method for rapid degradation and recycling of fluorine-containing organic solid waste according to claim 1 or 2, characterized in that, The amount of liquid sodium-potassium alloy added in step (2) is calculated according to the chemical composition of the fluorine-containing organic solid waste to be degraded and the molar ratio of the selected sodium-potassium alloy, based on the stoichiometric ratio, to ensure complete reaction.

9. A method for rapid degradation and recycling of fluorine-containing organic solid waste according to claim 1 or 2, characterized in that, The mechanical disturbance method described in step (3) includes one or more of the following: slight scraping, vibration, stirring, or other physical disturbance methods that can trigger the electron transfer process.

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