A method for coupling physicochemical treatment and biodegradable disposal of plastics

Abstract

This invention discloses a method for coupling physicochemical treatment and biodegradation of plastics. The method includes the following steps: S1. Mixing plastics, organic solvents, and a metal catalyst, and reacting to degrade them to obtain organic products. The metal catalyst is cobalt acetate and / or manganese acetate; S2. Biodegrading the organic products from step S1 using a mixed colony, which includes *Pseudomonas*, *Bacillus*, *Flavobacterium*, and *Rhodococcus*. This invention uses cobalt acetate and / or manganese acetate as metal catalysts. The catalytic oxidation of the metal catalyst can efficiently depolymerize traditional plastics, overcoming the bottleneck of C-C bond breaking that is difficult for microorganisms to achieve. It can successfully convert plastics into organic products mainly composed of dicarboxylic acids, benzoic acid, and terephthalic acid, and the mixed colony process completely mineralizes the organic products. This method achieves complete removal of plastics without producing any toxic or harmful substances.

Description

Technical Field

[0001] This invention belongs to the technical field of plastic degradation, and more specifically, relates to a method for coupling physicochemical treatment and biodegradation of plastics. Background Technology

[0002] Plastics are polymers made from monomers through addition or condensation polymerization. Due to their excellent properties and relatively low production costs, a large amount of plastics are produced annually and widely used in production and daily life worldwide. According to surveys, nearly 400 million tons of plastics were produced globally in 2021, with polyethylene (PE), polypropylene (PP), polystyrene (PS), polyvinyl chloride (PVC), and polyethylene terephthalate (PET) accounting for approximately 75% of the production. Unfortunately, due to limitations in recycling and waste disposal, a large amount of traditional plastics end up in terrestrial and aquatic environments, forming microplastics during migration. These plastics and microplastics entering aquatic and other environmental substrates can negatively impact human life and the ecological environment, posing potential risks to human health. In recent years, scientists have detected the presence of microplastics in human lungs and blood. These phenomena have raised concerns about the potential for plastics to cause internalization and translocation of biological damage. Therefore, we urgently need to find and develop methods to decompose and recycle the value of traditional plastic waste.

[0003] Currently, the main methods for disposing of traditional plastics are incineration and landfill. Landfilling is insufficient for treating traditional plastics, while incineration may generate toxic byproducts such as dioxins. Other physicochemical treatment methods, such as photodegradation, chemical degradation, and thermal degradation, are energy-intensive and also have problems such as high energy consumption and the generation of toxic and harmful byproducts. Considering the limitations of physicochemical methods for degrading plastics, in recent years, exploring microorganisms with the potential to degrade plastics and utilizing biological systems for effective and environmentally friendly plastic degradation has become a new hot topic. Patent CN115109717A discloses the isolation of a strain of *Gordonia* spp. from polystyrene foam in mangroves and confirms that this strain can achieve a degradation of 2.66% to 7.73% of polystyrene; patent CN115960782A discloses the isolation of a strain of *Evansella clarkii* SCSIO 43802 from the ocean, which can grow using polyethylene as a single carbon source and can degrade 5.3% of polyethylene plastic. However, the degradation efficiency of existing methods is insufficient to meet practical needs. Therefore, finding a set of efficient and low-consumption microbial degradation technologies to achieve efficient disposal of plastics has become an urgent technical problem to be solved. Summary of the Invention

[0004] To address the aforementioned technical problems, the primary objective of this invention is to provide a method that couples physicochemical treatment with biodegradation for plastic disposal. This method utilizes a physicochemical technique of high-temperature chemical oxidation to depolymerize the main chains of different types of plastics, overcoming the difficulty of microorganisms breaking C-C bonds. Subsequently, the highly bioavailable depolymerized products are transferred to a mixed microbial colony, where the mixed intermediate products are completely mineralized into carbon dioxide and water through microbial metabolism. This process highly couples physicochemical and biotechnological techniques, achieving highly efficient removal of various types of traditional plastics.

[0005] The second objective of this invention is to provide a method for coupling physicochemical treatment and biodegradation of plastics for application in the degradation of plastics.

[0006] To achieve the above objectives, the present invention is implemented through the following technical solution:

[0007] A method for coupling physicochemical treatment and biodegradation of plastics includes the following steps:

[0008] S1. A mixture of plastic, organic solvent, and metal catalyst is reacted and degraded to obtain organic products; the metal catalyst is cobalt acetate and / or manganese acetate.

[0009] S2. The organic products from step S1 are biodegraded using mixed colonies, which include Pseudomonas, Bacillus, Flavobacterium, and Rhodococcus.

[0010] The inventors discovered through research that current microbial processes for treating plastics with a C-bond backbone, such as PP, PE, PVC, and PS, are slow and yield low-level treatment. The main bottleneck lies in the stable C-bond structure, making it difficult for microorganisms to break the C-bonds and thus hindering the further utilization of these plastics. This invention uses cobalt acetate and / or manganese acetate as metal catalysts. The catalytic oxidation of these metal catalysts efficiently depolymerizes traditional plastics such as PE, PP, PVC, PS, and PET, overcoming the bottleneck of microbial C-bond breaking and successfully converting the plastics into organic compounds primarily composed of dicarboxylic acids, benzoic acid, and terephthalic acid. Subsequently, a series of mixed colonies completely mineralize the organic products within 36 hours. This method achieves complete removal of plastics without producing any toxic or harmful substances.

[0011] Preferably, the plastic is selected from one or more of polyethylene, polypropylene, polystyrene, polyvinyl chloride, and polyethylene terephthalate.

[0012] Preferably, in step S1, the reaction temperature is 190–210°C. Specifically, the reaction time can be adjusted according to the type of plastic, such as 2–3 hours for PE, PP, and PVC, and 4–5 hours for PS and PET.

[0013] Preferably, in step S1, the pH of the reaction is 11.5 to 12.

[0014] Preferably, in step S1, the reaction pressure is 75-85 bar.

[0015] Preferably, in step S1, the gaseous atmosphere of the reaction includes oxygen and nitrogen, wherein the partial pressure of oxygen is 8 bar and the partial pressure of nitrogen is 72 bar.

[0016] Preferably, the metal catalyst comprises cobalt acetate and manganese acetate, wherein the molar ratio of cobalt acetate to manganese acetate is 1:1.

[0017] Specifically, the organic products include dicarboxylic acids, benzoic acid, benzaldehyde, terephthalic acid, and mono(2-hydroxyethyl) terephthalic acid, with carbon chain lengths ranging from 4 to 22 carbon atoms. PE and PP primarily produce dicarboxylic acids of varying lengths; the chlorine in PVC decomposes at high temperatures as HCl, and its remaining structure also reacts to produce dicarboxylic acids with varying carbon chain lengths; PS primarily produces benzoic acid and benzaldehyde; and PET primarily produces terephthalic acid and mono(2-hydroxyethyl) terephthalic acid.

[0018] Preferably, in step S1, the organic solvent is N-hydroxyphthalimide.

[0019] Preferably, in step S1, the ratio of the metal catalyst to the plastic is 10-15:300 mM / mg. Specifically, when the plastic is PS, 15 mM cobalt acetate and manganese acetate can be added to the reaction. When the plastic is PE, PP, PVC, or PET, 10 mM cobalt acetate and manganese acetate can be added to the reaction.

[0020] Preferably, the biodegradation temperature is 35–38°C.

[0021] In this invention, a mixed bacterial colony obtained from sludge screening from a wastewater treatment plant is used to utilize and treat organic matter products. Under constant temperature, aerobic, and neutral conditions, the mixed bacterial colony is enriched through multiple subcultures with dicarboxylic acids, benzoic acid, and terephthalic acid added to the culture medium as carbon sources. Additionally, extra carbon sources and nutrients are added to the culture medium. The enriched mixed bacterial colony exhibits excellent organic matter degradation rates, demonstrating the ability to completely mineralize 100 mg of dicarboxylic acids of varying lengths within 24 hours and 100 mg of benzoic acid or terephthalic acid within 36 hours. This method can achieve the removal of the vast majority of organic matter products within 36 hours.

[0022] Preferably, the aerobic, neutral conditions are achieved using a constant-temperature shaker. The optimal conditions are 37°C, a shaker speed of 225 rpm, and pH = 7.5.

[0023] Preferably, the additional carbon source is sodium acetate, added at a concentration of 0.5-1 mM / L. The nutrients include vitamin solutions and trace element / salt solutions.

[0024] Preferably, based on the 16S amplicon high-throughput sequencing results, the relative abundance of Pseudomonas spp. is 34.9%, the relative abundance of Bacillus spp. is 34.3%, the relative abundance of Flavobacterium spp. is 19.0%, and the relative abundance of Rhodococcus spp. is 5.4% in the mixed colonies.

[0025] Furthermore, this invention claims protection for the application of a method that couples physicochemical treatment with biodegradation of plastics in the degradation of plastics.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] This invention provides a method for coupling physicochemical treatment and biodegradation of plastics. It employs cobalt acetate and / or manganese acetate as catalytic oxidants to efficiently depolymerize traditional plastics such as PE, PP, PVC, PS, and PET, overcoming the bottleneck of C / C bond breaking, which is difficult for microorganisms to achieve. The method successfully converts plastics into organic products primarily composed of dicarboxylic acids, benzoic acid, and terephthalic acid. Subsequently, a series of mixed bacterial colonies completely mineralize the organic products within 36 hours. This method achieves complete removal of plastics without generating any toxic or harmful substances. Attached Figure Description

[0028] Figure 1 This is a schematic diagram illustrating the principle of a method for coupling physicochemical treatment and biodegradation of plastics in Embodiment 1 of the present invention.

[0029] Figure 2 This represents the main community composition of the mixed colonies in Example 1 of the present invention.

[0030] Figure 3 This is a graph showing the product proportions after chemical oxidation of PS and PET plastics in Experimental Example 3 and Example 5 of the present invention.

[0031] Figure 4 This is a graph showing the product proportions after chemical oxidation of PE, PP, and PVC plastics in Experimental Example 1, Example 2, and Example 4 of the present invention.

[0032] Figure 5 This is a statistical graph showing the degradation effect of mixed colonies on different types of organic matter produced by chemical oxidation in Experiment Example 6 of the present invention. Detailed Implementation

[0033] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, but the embodiments do not limit the present invention in any way. Unless otherwise specified, the reagents, methods and equipment used in the present invention are conventional reagents, methods and equipment in this technical field.

[0034] Example 1: A method for coupling physicochemical treatment and biodegradable disposal of plastics

[0035] (1) As Figure 1 As shown, 300 mg of polyethylene (PE) was placed in the organic solvent N-hydroxyphthalimide (25 mM). Cobalt acetate and manganese acetate were added as catalysts (molar ratio of cobalt acetate to manganese acetate was 1:1, and the amount of metal catalyst was 10 mM). The pH of the system was adjusted to 11.8–12 using NaOH. The reaction was carried out under an oxygen and nitrogen atmosphere at a partial pressure of 8 bar for oxygen, 72 bar for nitrogen, and a temperature of 200 °C for 2–5 h. Organic products were obtained after the reaction.

[0036] (2) Biodegradation: Mixed bacterial colonies screened from wastewater treatment plant sludge were used to utilize and dispose of organic products. These mixed bacterial colonies were enriched through multiple subculturings in a culture medium under constant temperature, aerobic, and neutral conditions (achieved via a constant temperature shaker, optimal conditions being 37℃, shaker speed 225 rpm, pH = 7.5). The culture medium included: a carbon source, an additional carbon source, and nutrients. The carbon sources were dicarboxylic acid, benzoic acid, and terephthalic acid; the additional carbon source was sodium acetate (concentration 0.75 mM / L); the nutrients included vitamin solutions and trace element / salt solutions. The specific composition of the nutrients is shown in Table 1 below.

[0037] Table 1

[0038] reagents Dosage (g / L) reagents Dosage (g / L) Trace elements / salt solutions Vitamin solution <![CDATA[FeCl2·4H2O]]> 0.002 Vitamin H 0.00002 <![CDATA[MnSO4·H2O]]> 0.001 Vitamin B 0.00002 <![CDATA[ZnSO4·7H2O]]> 0.002 Vitamin B6 0.0001 <![CDATA[CuCl2·2H2O]]> 0.002 Vitamin B1 0.00005 NaCl 1.0 Vitamin B2 0.00005 <![CDATA[MgCl2·6H2O]]> 0.01 Vitamin B3 0.00005 <![CDATA[KH2PO4]]> 0.5 Vitamin B5 0.00005 <![CDATA[K2HPO4]]> 1.5 p-Aminobenzoic acid 0.00005 <![CDATA[NH4NO3]]> 1.0 Alpha-lipoic acid 0.00005 KCl 0.3 Vitamin B12 0.000001 <![CDATA[CaCl2·2H2O]]> 0.015 <![CDATA[NaHCO3]]> 2.52

[0039] The mixed colonies enriched by the above method have the following community composition: Figure 2As shown, the community mainly consisted of *Pseudomonas* (relative abundance 34.9%), *Bacillus* (relative abundance 34.3%), *Flavobacterium* (relative abundance 19.0%), and *Rhodococcus* (relative abundance 5.4%). The mixed colonies were inoculated into aerobic liquid medium supplemented with sodium acetate and vitamin solution. An organic product solution was added, and the culture was carried out at 37°C, 225 rpm, and pH 7.5 for 36 h. After 36 h of incubation, over 90% of the intermediate organic matter in the medium was completely mineralized by the mixed colonies.

[0040] Example 2

[0041] The difference between this embodiment and Embodiment 1 is that polypropylene (PP) is used.

[0042] Example 3

[0043] The difference between this embodiment and Example 1 is that polystyrene (PS) is used and the amount of metal catalyst is 15 mM.

[0044] Example 4

[0045] The difference between this embodiment and Embodiment 1 is that polyvinyl chloride (PVC) is used.

[0046] Example 5

[0047] The difference between this embodiment and Embodiment 1 is that polyethylene terephthalate (PET) is used.

[0048] Example 6

[0049] The difference between this embodiment and Embodiment 1 is that polyethylene (PE), polypropylene (PP), polystyrene (PS), polyvinyl chloride (PVC), and polyethylene terephthalate (PET) are used.

[0050] Test Example 1

[0051] (1) The organic products obtained after the treatment in steps (1) of Examples 1-5 were quantitatively analyzed by liquid chromatography and converted into molar amounts of carbon for comparison. The main products of PS and PET after the reaction accounted for, for example... Figure 3As shown; the main products of PE, PVC, and PP account for, for example... Figure 4 As shown.

[0052] Depend on Figure 3 It is evident that the main products of benzene-ring-containing plastics PS and PET also possess benzene ring structures. These are benzoic acid, benzaldehyde, terephthalic acid, and mono(2-hydroxyethyl) terephthalic acid, respectively. In PS products, benzoic acid accounts for 63.5% of the carbon molar ratio, and benzaldehyde accounts for 0.8%; in PET products, terephthalic acid accounts for 68.3%, and mono(2-hydroxyethyl) terephthalic acid accounts for 1.6%. PE, PP, and PVC plastics mainly produce dicarboxylic acids with varying carbon chain lengths, such as... Figure 4 As shown. The PE product contains 9.8% C4-C6 dicarboxylic acids and 9.8% C7-C6 dicarboxylic acids. 10 Dicarboxylic acids accounted for 12.4%, C 11 -C 22 The proportion of dicarboxylic acids was 14.2%; in the PP product, C4-C6 dicarboxylic acids accounted for 12.4%, and C7-C6 dicarboxylic acids accounted for the remainder. 10 Dicarboxylic acids accounted for 5.9%, C 11 -C 22 Dicarboxylic acids accounted for 7.3%; in PVC products, C4-C6 dicarboxylic acids accounted for 13.7%, and C7-C6 dicarboxylic acids accounted for the remainder. 10 Dicarboxylic acids accounted for 8.3%, C 11 -C 22 Dicarboxylic acids account for 9.1%. It is worth noting that the Cl element in PVC decouples from the carbon chain in the reaction as HCl, ultimately becoming Cl... - It exists in the mixture.

[0053] (2) During the experiment in step (2) of Example 6, a small amount of liquid was taken and the organic matter was detected by liquid chromatography. The results are referenced. Figure 5 As shown in the figure, the mixed colonies of Example 6 of this application achieved a degradation efficiency of over 95% for the three main products—dicarboxylic acid, benzoic acid, and terephthalic acid—within 36 days. The mixed colonies completely degraded dicarboxylic acids of different carbon chain lengths within 24 hours, achieved complete degradation of benzoic acid within 36 hours, and achieved a 97.7% degradation of terephthalic acid. This demonstrates excellent degradation performance.

[0054] This invention provides a method for coupling physicochemical treatment and biodegradation of plastics. It employs cobalt acetate and / or manganese acetate as catalytic oxidants to efficiently depolymerize traditional plastics such as PE, PP, PVC, PS, and PET, overcoming the bottleneck of C / C bond breaking, which is difficult for microorganisms to achieve. The method successfully converts plastics into organic products primarily composed of dicarboxylic acids, benzoic acid, and terephthalic acid. Subsequently, a series of mixed bacterial colonies completely mineralize the organic products within 36 hours. This method achieves complete removal of plastics without generating any toxic or harmful substances.

[0055] The foregoing examples are merely illustrative, used to explain some features of the method described in this invention. The appended claims are intended to claim the broadest possible scope, and the embodiments presented herein are demonstrated by the applicant's actual experimental results. Therefore, the applicant intends that the appended claims are not limited by the selection of examples illustrating the features of the invention. Some numerical ranges used in the claims also include sub-ranges within them, and variations within these ranges should also be interpreted as being covered by the appended claims where possible.

Claims

1. A method of disposing of plastics by coupling a physical-chemical treatment with biodegradation, characterized in that, Includes the following steps: S1. Mixing plastic, organic solvent and metal catalyst, and reacting to obtain organic product; wherein the metal catalyst is cobalt acetate and / or manganese acetate; S2. The organic products from step S1 are biodegraded using mixed colonies, which include Pseudomonas, Bacillus, Flavobacterium, and Rhodococcus.

2. The method of claim 1, wherein, In step S1, the reaction temperature is 190–210°C.

3. The method according to claim 1, characterized in that, In step S1, the pH of the reaction is 11.5 to 12.

4. The method according to claim 1, characterized in that, In step S1, the reaction pressure is 75-85 bar.

5. The method according to claim 1, characterized in that, In step S1, the organic solvent is N-hydroxyphthalimide.

6. The method according to claim 1, characterized in that, The metal catalyst comprises cobalt acetate and manganese acetate, wherein the molar ratio of cobalt acetate to manganese acetate is 1:

1.

7. The method according to claim 1, characterized in that, In the mixed colonies, the relative abundance of Pseudomonas was 34.9%, the relative abundance of Bacillus was 34.3%, the relative abundance of Flavobacterium was 19.0%, and the relative abundance of Rhodococcus was 5.4%.

8. The method according to claim 1, characterized in that, The plastic is selected from one or more of polyethylene, polypropylene, polystyrene, polyvinyl chloride, and polyethylene terephthalate.

9. The application of the method for coupling physicochemical treatment and biodegradation of plastics as described in any one of claims 1 to 8 in the degradation of plastics.

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