A method for degrading polyolefin-based plastics and applications thereof

Abstract

The application discloses a method for degrading polyolefin plastics and application thereof. The method for degrading polyolefin plastics comprises the following steps: 1) polyolefin plastic waste is placed in light and an ozone-containing atmosphere for light-ozone synergistic pretreatment to obtain pretreated polyolefin plastic waste; and 2) the pretreated polyolefin plastic waste is added to soil for biodegradation. The light-ozone synergistic pretreatment and biodegradation are combined, polyolefin plastics can be quickly and efficiently degraded, the operation is simple, the method is economic and efficient, and the method is suitable for recycling and regeneration of plastic waste in a natural environment.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of plastic waste recycling, and particularly relates to a method for degrading polyolefin plastics and application thereof. BACKGROUND

[0002] Plastics have the advantages of light weight, good weather resistance, good thermal stability, excellent insulation performance, strong plasticity, and low manufacturing cost, and have been widely used in various fields. Polyolefin plastics (for example: PE, PP) are the most widely used plastics, and about 77% of plastic products in the world are made of polyolefin plastics. However, the disposal of waste polyolefin plastic products has become a big problem. At present, most of the waste plastics are incinerated or directly landfilled, and only 6% to 26% are recycled. Biodegradation is one of the methods for recycling waste plastics, and has good practical application prospect. Recycling biodegradable plastics can effectively reduce energy consumption and carbon dioxide emission from the whole life cycle. However, direct degradation of polyolefin plastics by microorganisms in the natural environment has the problem of very slow degradation rate, which is difficult to meet the actual application requirements.

[0003] Therefore, it is of great significance to develop a method for rapidly and efficiently biodegrading polyolefin plastics for realizing plastic recycling and recycling bioeconomy. SUMMARY

[0004] The present application aims to provide a method for degrading polyolefin plastics and application thereof.

[0005] The technical scheme adopted by the present application is as follows:

[0006] A method for degrading polyolefin plastics comprises the following steps:

[0007] 1) Polyolefin plastic waste is placed in light and ozone-containing atmosphere for light-ozone synergistic pretreatment to obtain pretreated polyolefin plastic waste;

[0008] 2) The pretreated polyolefin plastic waste is added to soil for biodegradation.

[0009] Preferably, the polyolefin plastic waste in step 1) is at least one of polyethylene waste and polypropylene waste.

[0010] Preferably, the light source intensity of the light in step 1) is 30 W / m 2 ~ 60 W / m 2 .

[0011] Preferably, the ozone concentration of the ozone-containing atmosphere in step 1) is 200 ppm to 2000 ppm.

[0012] Preferably, the time of the light-ozone synergistic pretreatment in step 1) is 12-24 hours.

[0013] Preferably, the mass ratio of the pretreated polyolefin-based plastic waste to the soil in step 2) is 0.0002-0.02:1.

[0014] Preferably, the indigenous bacteria in the soil in step 2) include at least one of Nitrosospira, Sphingomonas, Bradyrhizobium, Rhizobium.

[0015] Preferably, the indigenous fungi in the soil in step 2) include at least one of Mycena, Ascomycetes, Mortierella, Debaryomyces, Metarhizium.

[0016] Preferably, the time of the biodegradation in step 2) is 20-45 days.

[0017] The method for degrading polyolefin-based plastics as described above is used for the recycling of plastic waste in the natural environment.

[0018] The method for degrading polyolefin-based plastics of the present application has the advantages that the light-ozone synergistic pretreatment and biodegradation are combined, the polyolefin-based plastics can be quickly and efficiently degraded, the operation is simple, the cost is low, the indigenous microorganisms in the soil are directly used for biodegradation of the plastics, no additional bacterial agents are needed, the operation process is easy to control, no toxic and harmful raw materials are needed, and the method has a good application prospect in the field of plastic waste recycling.

[0019] Specifically:

[0020] 1) The method for degrading polyolefin-based plastics of the present application has the characteristics of simple operation and good degradation effect, greatly shortens the degradation time of plastic waste, is suitable for recycling of plastic waste in the natural environment, and has a very broad application prospect;

[0021] 2) The method for degrading polyolefin-based plastics of the present application has the characteristics of low treatment cost and simple technology, and reduces the recycling cost of plastics;

[0022] 3) The method for degrading polyolefin-based plastics of the present application directly utilizes the indigenous microorganisms in the soil for biodegradation of the plastics, without the need for additional bacterial agents, further reducing the recycling cost of plastics;

[0023] 4) The method for degrading polyolefin-based plastics of the present application has the characteristics of easy control of the operation process and no need for toxic and harmful raw materials, and has a good application prospect in the field of plastic waste recycling. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 SEM image of the PE plastic film biodegraded in Example 1.

[0025] Figure 2SEM image of the biodegraded PE plastic film in Comparative Example 1.

[0026] Figure 3 SEM image of the biodegraded PE plastic film in Comparative Example 2.

[0027] Figure 4 SEM image of the biodegraded PE plastic film in Comparative Example 3.

[0028] Figure 5 FTIR image of the biodegraded PE plastic film in Example 1 and Comparative Examples 1 to 3.

[0029] Figure 6 XPS image of the biodegraded PE plastic film in Example 1 and Comparative Examples 1 to 3.

[0030] Figure 7 SEM image of the biodegraded PP plastic film in Example 2.

[0031] Figure 8 SEM image of the biodegraded PP plastic film in Comparative Example 4.

[0032] Figure 9 SEM image of the biodegraded PP plastic film in Comparative Example 5.

[0033] Figure 10 SEM image of the biodegraded PP plastic film in Comparative Example 6.

[0034] Figure 11 FTIR image of the biodegraded PP plastic film in Example 2 and Comparative Examples 4 to 6.

[0035] Figure 12 XPS image of the biodegraded PP plastic film in Example 2 and Comparative Examples 4 to 6. DETAILED DESCRIPTION

[0036] The present application will be further explained and described with reference to the following specific examples.

[0037] Notes:

[0038] The soil in the examples and comparative examples was collected from Panyu District, Guangzhou City, and the basic parameters of the soil (tested by industry standard method) were as follows: total nitrogen content was 1.9 g / kg, total phosphorus content was 1.8 g / kg, total potassium content was 18.4 g / kg, alkali-hydrolyzable nitrogen content was 157.6 mg / kg, available phosphorus content was 215.8 mg / kg, available potassium content was 254.5 mg / kg, and organic matter content was 33.8 g / kg. The indigenous microbial community structure of the soil was obtained by 16S rRNA sequencing and ITS sequencing as follows: the indigenous bacteria mainly included Nitrosospira, Sphingomonas, Bradyrhizobium, Rhizobium, etc.; and the indigenous fungi mainly included Crustodontia, Ascomycetes, Mortierella, Debaryomyces, Metarhizium, etc.

[0039] The soil in the examples and comparative examples was pre-stabilized, and the operation was as follows: the soil was placed in a flowerpot, and the water content of the soil was adjusted by watering, and the water content of the soil was adjusted according to 60% of the maximum field water holding capacity, and the soil was cultured for one week.

[0040] Example 1:

[0041] A method for degrading polyolefin plastic, comprising the following steps:

[0042] 1) The PE plastic film was placed in a quartz glass tube, and was subjected to 24h of light-ozone combined pretreatment under light irradiation and ozone introduction, the light source intensity of the light irradiation was 60W / m 2 , and the ozone concentration was 2000ppm, to obtain the pretreated PE plastic film.

[0043] 2) The pretreated PE plastic film was added to the soil for 45 days of biodegradation, and the mass ratio of the pretreated PE plastic film to the soil was 0.0002:1.

[0044] Comparative Example 1:

[0045] A method for degrading polyolefin plastic, comprising the following steps:

[0046] The PE plastic film (without pretreatment) was added to the soil for 45 days of biodegradation, and the mass ratio of the PE plastic film to the soil was 0.0002:1.

[0047] Comparative Example 2:

[0048] A method for degrading polyolefin plastic, comprising the following steps:

[0049] 1) The PE plastic film was placed in a quartz glass tube for 24h of light pretreatment, and the light source intensity of the light irradiation was 60W / m 2 , to obtain the pretreated PE plastic film.

[0050] 2) The pretreated PE plastic film is added to the soil for biodegradation for 45 days, and the mass ratio of the pretreated PE plastic film to the soil is 0.0002:1.

[0051] Comparative Example 3

[0052] A method for degrading polyolefin plastic, comprising the following steps:

[0053] 1) The PE plastic film is placed in a quartz glass tube, and ozone is introduced for ozone pretreatment for 24 h, and the ozone concentration is 2000 ppm, to obtain a pretreated PE plastic film.

[0054] 2) The pretreated PE plastic film is added to the soil for biodegradation for 45 days, and the mass ratio of the pretreated PE plastic film to the soil is 0.0002:1.

[0055] Performance test:

[0056] 1) The scanning electron microscope (SEM) images of the PE plastic films biodegraded in Example 1 and Comparative Examples 1-3 are shown in Figures 1-4 .

[0057] It can be seen from Figures 1-4 that the pretreated PE plastic film in Example 1 (which has undergone light-ozone synergistic pretreatment) has dense and deep grooves on the film surface after biodegradation, and the biodegradation effect is obviously better than that of Comparative Examples 1-3, indicating that light-ozone synergistic pretreatment promotes the natural degradation of the plastic film.

[0058] 2) The infrared spectrum (FTIR) images of the PE plastic films biodegraded in Example 1 and Comparative Examples 1-3 are shown in Figure 5 .

[0059] It can be seen from Figure 5 that the pretreated PE plastic film in Example 1 (which has undergone light-ozone synergistic pretreatment) has C=O bonds after biodegradation, indicating that the biological oxidation effect in the natural degradation process is enhanced.

[0060] 3) The degradation rate of the PE plastic films in Example 1 and Comparative Examples 1-3 is tested, and the degradation rate calculation formula is as follows: degradation rate (%) = (initial plastic film mass - plastic film mass after biodegradation treatment) / initial plastic film mass x 100%, and the O / C ratio of the PE plastic films biodegraded in Example 1 and Comparative Examples 1-3 is tested, and the O / C ratio is determined by X-ray photoelectron spectroscopy (XPS), and the degradation rate test results are shown in Table 1, and the O / C ratio test results are shown in Table 2, and the XPS images are shown in Figure 6 .

[0061] Table 1 degradation rate of PE plastic film

[0062]

[0063] Table 2 O / C ratio of PE plastic film after biodegradation

[0064]

[0065] From Table 1, Table 2 and Figure 6 It can be seen that: the degradation of PE plastic film without pretreatment is very slow, the degradation rate is very low, only 0.04%, and the O / C ratio is also low, only 23.81%; after single light pretreatment, the degradation rate is slightly increased, which is 0.12%, and the O / C ratio is 19.35%; after single ozone pretreatment, the degradation rate is obviously increased, the degradation rate reaches 9.40%, and the O / C ratio is increased to 39.69%; after light and ozone synergistic pretreatment, the degradation rate is significantly increased, the degradation rate reaches 41.91%, and the O / C ratio reaches 46.83%.

[0066] From the above, it can be seen that the present application adopts light and ozone synergistic treatment, and then carries out biodegradation treatment, which is simple in operation, low in cost, and significantly improves the natural degradation efficiency of polyolefin plastics. Compared with the pretreatment, the biodegradation rate of polyethylene plastic is increased by several thousand times, which effectively solves the problem of slow degradation of difficult-to-degrade plastics in the natural environment, and has important significance for realizing the cyclic bioeconomy of polyolefin plastics.

[0067] Example 2:

[0068] A method for degrading polyolefin plastics, comprising the following steps:

[0069] 1) Put the PP plastic film into a quartz glass tube, and perform 24h light-ozone synergistic pretreatment by simultaneously lighting and introducing ozone, the light source intensity of the light is 60W / m 2 , and the ozone concentration is 2000ppm, to obtain pretreated PP plastic film;

[0070] 2) Put the pretreated PP plastic film into soil for 45 days of biodegradation, and the mass ratio of the pretreated PP plastic film to the soil is 0.0002:1.

[0071] Comparative Example 4:

[0072] A method for degrading polyolefin plastics, comprising the following steps:

[0073] Put the PP plastic film (without pretreatment) into soil for 45 days of biodegradation, and the mass ratio of the PP plastic film to the soil is 0.0002:1.

[0074] Comparative Example 5:

[0075] A method for degrading polyolefin plastic, comprising the following steps:

[0076] 1) PP plastic film was placed in a quartz glass tube for 24 h of light pretreatment, the light source intensity of the light was 60 W / m 2 , to obtain pretreated PP plastic film;

[0077] 2) The pretreated PP plastic film was added to the soil for 45 days of biodegradation, the mass ratio of pretreated PP plastic film to soil was 0.0002:1.

[0078] Comparative Example 6:

[0079] A method for degrading polyolefin plastic, comprising the following steps:

[0080] 1) PP plastic film was placed in a quartz glass tube for 24 h of ozone pretreatment, the ozone concentration was 2000 ppm, to obtain pretreated PP plastic film;

[0081] 2) The pretreated PP plastic film was added to the soil for 45 days of biodegradation, the mass ratio of pretreated PP plastic film to soil was 0.0002:1.

[0082] Performance test:

[0083] 1) The SEM images of the biodegraded PP plastic film in Example 2 and Comparative Examples 4-6 are shown in Figures 7-10 .

[0084] It can be seen from Figures 7-10 that: the pretreated PP plastic film in Example 2 (which was subjected to light-ozone synergistic pretreatment) had dense and deep gullies on the film surface after biodegradation, and the biodegradation effect was obviously better than that of Comparative Examples 4-6, indicating that light-ozone synergistic pretreatment promoted the natural degradation of the plastic film.

[0085] 2) The FTIR images of the biodegraded PP plastic film in Example 2 and Comparative Examples 4-6 are shown in Figure 11 .

[0086] It can be seen from Figure 11 that: the pretreated PP plastic film in Example 2 (which was subjected to light-ozone synergistic pretreatment) appeared C=O bond after biodegradation, indicating that the biological oxidation in the natural degradation process was enhanced.

[0087] 3) The degradation rate of the PP plastic film in Example 2 and Comparative Examples 4-6 was tested, and the O / C ratio of the biodegraded PP plastic film in Example 2 and Comparative Examples 4-6 was tested, the O / C ratio was determined by XPS, the degradation rate test results are shown in Table 3, the O / C ratio test results are shown in Table 4, and the XPS graph is shown in Figure 12

[0088] Table 3 Degradation rate of PP plastic film

[0089]

[0090] Table 4 O / C ratio of biodegraded PP plastic film

[0091]

[0092] It can be seen from Tables 3, 4 and Figure 12 that the degradation of the PP plastic film without pretreatment is very slow, the degradation rate is very low, only 0.01%, and the O / C ratio is also low, only 29.49%; after the single light pretreatment, the degradation rate is slightly increased, which is 0.16%, and the O / C ratio is 34.33%; after the single ozone pretreatment, the degradation rate is obviously increased, the degradation rate reaches 9.21%, and the O / C ratio is increased to 43.50%; after the light and ozone synergistic pretreatment, the degradation rate is significantly increased, the degradation rate reaches 45.85%, and the O / C ratio reaches 50.19%.

[0093] In summary, the present application adopts light and ozone synergistic treatment, and then biodegradation treatment, which significantly improves the natural degradation efficiency of polyolefin plastics, and the biodegradation rate of polypropylene plastic is increased by several thousand times compared with the non-pretreated one, effectively solves the problem of slow degradation of difficult-to-degrade plastics in the natural environment, and has important significance for realizing the cyclic bioeconomy of polyolefin plastics.

[0094] The above examples are the preferred embodiments of the present application, but the embodiments of the present application are not limited by the above examples, and any changes, modifications, substitutions, combinations and simplifications made without departing from the spirit and principles of the present application should be equivalent replacement methods, and all are included in the protection scope of the present application.​

Claims

1. A method of degrading polyolefin-based plastics, characterized by, The method comprises the following steps: 1) disposing polyolefin plastic waste in an illumination and ozone-containing atmosphere for illumination-ozone synergistic pretreatment to obtain pretreated polyolefin plastic waste; 2) adding the pretreated polyolefin plastic waste into soil for biodegradation; Step 1) the light source intensity of said light exposure is 30 W / m 2 ~ 60 W / m 2 ; In step 1), the ozone concentration of the ozone-containing atmosphere is 200-2000 ppm; In step 1), the illumination-ozone synergistic pretreatment is performed for 12-24 hours; In step 2), the indigenous bacteria in the soil include at least one of Nitrospira, Sphingomonas, Bradyrhizobium, Rhizobium; In step 2), the indigenous fungi in the soil include at least one of Mycena, Ascomycetes, Mortierella, Debaryomyces, Metarhizium.

2. The method of degrading polyolefin-based plastics according to claim 1, characterized in that: In step 1), the polyolefin plastic waste is at least one of polyethylene waste and polypropylene waste.

3. The method of degrading polyolefin-based plastics according to claim 1, wherein: In step 2), the mass ratio of the pretreated polyolefin plastic waste to the soil is 0.0002-0.02:

1.

4. The method of degrading polyolefin-based plastics according to claim 1 or 3, characterized in that: In step 2), the biodegradation is performed for 20-45 days.

5. Application of the method for degrading polyolefin plastic as claimed in any one of claims 1-4 to the recycling and regeneration of plastic waste in a natural environment.

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