Method for degrading polypropylene by using heat-resistant pseudomonas

Abstract

A method for degrading polypropylene by using heat-resistant Pseudomonas. The method comprises: injecting a microbial agent containing a heat-resistant Pseudomonas solution into soil containing polypropylene in at least two steps, wherein the temperature of the soil is 35-40°C, and is maintained for 20-24 h; and then raising the temperature of the soil to 60-63°C, and maintaining the temperature for 4-6 h until the next injection of the microbial agent.

Description

A method for degrading polypropylene using thermotolerant Pseudomonas

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to the Chinese patent application filed with the China Patent Office on July 31, 2023, with application number 202310954236.8 and invention name “A method for degrading polypropylene in soil”, the entire contents of which are incorporated herein by reference. Technical Field

[0003] The present application relates to the field of polypropylene degradation, and in particular to a method for degrading polypropylene in soil. Background Art

[0004] Polypropylene is a thermoplastic synthetic resin material with excellent properties, typically synthesized from propylene monomers through a polyaddition reaction. Polypropylene is the world's second-largest plastic polymer after polyethylene. Its lightweight, chemical and heat-resistant properties, electrical insulation, and flexibility make it widely used in plastic parts, consumer packaging, and fiber products. Global demand for polypropylene currently stands at approximately 45 million tons annually, primarily in the packaging industry, which accounts for approximately 30% of total consumption. However, due to the long decomposition cycle of polypropylene plastic, it cannot be effectively and promptly removed from the environment, leading to a series of environmental pollution problems.

[0005] Therefore, the treatment of polypropylene plastics has become an environmental issue that urgently needs to be addressed. During the processing of polypropylene plastics, secondary polypropylene microplastic particles are generated that are small in size and difficult to remove. Methods for degrading secondary polypropylene microplastic particles mainly include chemical degradation, physical degradation, and biological degradation. Among them, the biodegradation method is very effective and has a low degree of environmental pollution, which is in line with the concept of sustainable development and has good research prospects in degrading microplastic pollution. At present, research on the microbial degradation of polypropylene microplastics is still in the stage of isolating metabolic strains, and there is a lack of polypropylene microplastic-degrading strains that can be studied and applied.

[0006] To this end, existing technologies have isolated Pseudomonas aeruginosa LXI681 and Achromobacter denitrificans through enrichment culture, which have the ability to degrade polypropylene microplastics. However, in actual applications, the degradation rate of these bacteria in soil remediation is low because the soil ambient temperature does not meet the optimal degradation conditions for polypropylene microplastics. Even if the soil ambient temperature meets the standard, conventional bacterial strains have difficulty surviving at higher temperatures.

[0007] Summary of the Invention

[0008] Therefore, the technical problem to be solved by the present application is to overcome the low degradation rate of polypropylene in the prior art, thereby providing a method for degrading polypropylene in soil by optimizing the degradation process conditions, which can improve the degradation rate of polypropylene in soil.

[0009] The present application provides a method for degrading polypropylene in soil, comprising the following steps: injecting a bacterial agent containing a thermotolerant Pseudomonas solution into soil containing polypropylene in at least two injections, wherein the temperature of the soil is 35-40°C and maintained at this temperature for 20-24 hours; then raising the temperature of the soil to 60-63°C and maintaining this temperature until 4-6 hours before the next injection of the bacterial agent.

[0010] The preparation method of the thermotolerant Pseudomonas liquid comprises the following steps: S1, taking strain LICME 200610 WGH-6 with a preservation number of CGMCC NO: 20527, culturing it at 35-40°C to a logarithmic growth phase, raising the culture temperature of the strain in the logarithmic growth phase to 60-63°C according to a temperature difference of 1-2°C per acclimation cycle, and obtaining a primary screening strain; S2, culturing the primary screening strain at 60-63°C, rescreening, and purifying the strain to obtain a thermotolerant Pseudomonas strain; and S3, inoculating the thermotolerant Pseudomonas strain into a culture medium and fermenting it at 35-40°C for 24-60 hours.

[0011] The bacterial agent containing the thermotolerant Pseudomonas liquid also includes a degradation liquid, wherein the composition of the degradation liquid includes K2HPO4 0.4g / L-0.6g / L, KH2PO4 3.5g / L-4g / L, (NH4)2HPO4 0.5g / L-1g / L, MgCl2·6H2O 18mg / L-22mg / L, FeCl3 0.1mg / L-0.3mg / L, CaCl2 1mg / L-3mg / L, Na2SO4 180mg / L-220mg / L, and KNO3 1g / L-1.5g / L, and the pH value of the degradation liquid is 7.0-7.2.

[0012] The bacterial activity of the Pseudomonas liquid was 1.0×10 8 ~1.0×10 9 CFU / mL.

[0013] The volume ratio of the thermotolerant Pseudomonas liquid to the degradation liquid in the bacterial agent containing the thermotolerant Pseudomonas liquid is 1:2-5.

[0014] The composition of the culture medium used in steps S1 to S3 includes 4-6 g / L glucose, 9-11 g / L beef extract, 9-11 g / L peptone, and 4-6 g / L NaCl. The pH value of the culture medium is 7.0-7.2.

[0015] Each acclimation period in step S1 is 10-18 hours. The acclimation period is the time the strain is cultured under a certain temperature.

[0016] The culturing time in step S2 is 24-48 hours.

[0017] The degradation method further comprises the step of injecting a degradation liquid into the soil separately. The components and content of each component of the degradation liquid injected separately are the same as those of the degradation liquid in the bacterial agent.

[0018] The injection interval of the bacterial agent containing the heat-resistant Pseudomonas liquid in the early stage of degradation treatment is 4-8 days, and the injection interval of the bacterial agent containing the Pseudomonas liquid in the late stage of degradation treatment is 20-40 days; during degradation treatment, the degradation liquid is injected separately after each injection of the bacterial agent containing the Pseudomonas liquid, and the injection time of the degradation liquid alone and the injection time interval of the bacterial agent containing the heat-resistant Pseudomonas liquid are 5-30 days; wherein, the early stage of degradation treatment is the 1st to 19th day from the start of degradation treatment, and the late stage of degradation treatment is the 20th day and thereafter from the start of degradation treatment.

[0019] The ratio of the single injection volume of the bacterial agent containing the Pseudomonas liquid to the soil volume is 120-150 L / m 3 .

[0020] When the degradation liquid is injected alone, the ratio of the single injection volume of the degradation liquid to the volume of the soil is 28-33 L / m 3 .

[0021] This application uses a microplastic online monitoring system based on Raman spectroscopy to monitor the degradation of polypropylene in the soil in real time.

[0022] The present application adopts a high-efficiency, low-carbon heat stabilization system to achieve the in-situ injection of the bacterial agent containing the heat-resistant Pseudomonas liquid and / or the degradation liquid. When the bacterial agent is injected in situ, the temperature of the soil is maintained at 35-40°C and maintained at this temperature for 20-24 hours. The soil temperature is increased to 60-63°C and maintained at this temperature until 4-6 hours before the next injection of the bacterial agent. The high-efficiency, low-carbon heat stabilization system includes: a heat source generation module, a heat exchanger, a controller and a temperature acquisition device.

[0023] The heat source generation module and the heat exchanger are interconnected through a pipeline to form a loop. A power device is provided on the pipeline to provide power for the circulation of the medium in the heat source generation module and the heat exchanger. The heat exchanger includes a plurality of heating units arranged side by side, and the heating units are arranged vertically. The temperature collection device is located between two adjacent heating units. The temperature collection device is used to collect the temperature of the soil between the heating units. The temperature collection device and the power device are both electrically connected to the controller. When the temperature of the soil between the heating units is lower than a threshold value, the controller controls the power device to accelerate the flow rate of the medium in the heat source generation module and the heat exchanger.

[0024] The heating unit includes several heating groups arranged in parallel, the water inlet of each heating group is connected to the water outlet of the power device, and the water outlet of the heating group is connected to the water inlet of the power device; each heating group includes a horizontally arranged connecting pipe and a vertically arranged capillary tube, the connecting pipe and the capillary tube are connected, and the inner diameter of the connecting pipe is larger than the inner diameter of the capillary tube.

[0025] The capillary comprises an external sleeve and an internal sleeve, wherein the internal sleeve is sleeved inside the external sleeve; the external sleeve is provided with an external liquid outlet, and the internal sleeve is provided with an internal liquid outlet at a position corresponding to the external liquid outlet, and the external liquid outlet and the internal liquid outlet have the same structure; the top cover of the external sleeve is provided with a through hole, and the interior of the internal sleeve is connected with a connecting rod, the connecting rod and the internal sleeve are coaxially arranged, the connecting rod is connected to the inner wall of the internal sleeve through a supporting rod, and the connecting rod passes through the through hole; one end of the connecting rod is located outside the external sleeve, and one end of the connecting rod located outside the external sleeve is provided with a gear, and the gear The wheel is connected to the drive motor through a transmission belt; the medium in the heat source generation module and the heat exchanger is the microbial agent and / or the degradation liquid for soil remediation, and the drive motor is controlled to drive the gear to rotate, so that the inner sleeve and the outer sleeve rotate relative to each other, so that the inner liquid outlet on the inner sleeve and the outer liquid outlet on the outer sleeve coincide with each other, and the microbial agent and / or the degradation liquid are added to the soil through the inner liquid outlet and the outer liquid outlet. After the addition is completed, the drive motor is controlled to stagger the inner liquid outlet and the outer liquid outlet, so that the microbial agent and / or the degradation liquid cannot pass through the inner liquid outlet and the outer liquid outlet.

[0026] A first bearing is mounted at the upper end of the outer sleeve, with the lower end of its outer ring fixed to the outer wall of the outer sleeve, and the connecting rod fixed to the inner ring of the first bearing. A second bearing is mounted at the bottom of the outer sleeve, with its outer ring fixed to the inner wall of the outer sleeve, and the lower end of the connecting rod fixed to the inner ring of the second bearing. The outer sleeve is covered with a non-woven fabric that covers the external liquid outlet. The capillaries are arranged in rows, and the gears in the same row of capillaries are connected to the drive motor via the same transmission belt.

[0027] The distance between adjacent heating units is 0.5m-2m, and the distance between adjacent capillaries is 0.1m-0.5m.

[0028] The heat source generating module is a solar heat collector, the inner diameter of the connecting pipe is 10 to 20 centimeters, the inner diameter of the capillary tube is 1 to 2 centimeters, and the power device is a water pump.

[0029] The technical solution of this application has the following advantages:

[0030] 1. The present application provides a method for degrading polypropylene in soil, comprising injecting a thermotolerant Pseudomonas solution into soil containing polypropylene at least twice, wherein the soil temperature is 35-40°C and maintained at this temperature for 20-24 hours; thereafter, raising the soil temperature to 60-63°C and maintaining this temperature until 4-6 hours before the next injection of the thermotolerant Pseudomonas solution. The thermotolerant Pseudomonas solution is obtained by acclimating Pseudomonas LICME 200610 WGH-6 to high temperature resistance, followed by screening, purification, and fermentation. The present application subjects the strain LICME 200610 WGH-6, which has the ability to degrade polypropylene plastic, to a slow thermotolerant acclimation process, increasing the temperature by 1-2°C per acclimation cycle, to obtain a strain capable of normal growth at 60-63°C. After screening and purification, a thermotolerant Pseudomonas strain with stable performance is obtained, which is fermented to obtain a thermotolerant Pseudomonas solution. The acclimated thermotolerant Pseudomonas solution exhibits high activity in a soil temperature environment of 60-63°C. In this application, a solution containing thermotolerant Pseudomonas is injected into the soil, and the soil temperature is controlled between 35-40°C for 20-24 hours to allow the thermotolerant Pseudomonas strains to multiply in large quantities in the soil at a suitable growth and reproduction temperature. After that, the soil temperature is raised to 60-63°C, so that the thermotolerant Pseudomonas can efficiently degrade polypropylene in the soil.

[0031] 2. The method for degrading polypropylene in soil provided by the present application limits the time for in-situ injection of the bacterial agent containing the heat-resistant Pseudomonas liquid and the degradation liquid in the early stage of degradation and the late stage of degradation, that is, in the early stage of degradation, a high-frequency injection of the bacterial agent is adopted to ensure the number of surviving microorganisms colonized in the soil, and in the late stage of degradation, the injection frequency of the bacterial agent is reduced to achieve the purpose of supplementing the bacterial agent. At the same time, after each injection of the bacterial agent, a period of time is allowed to pass before injecting the degradation liquid that provides the necessary nutrient source for the survival of the heat-resistant Pseudomonas strain in the bacterial agent, so as to avoid insufficient nutrition of the heat-resistant Pseudomonas strain and affect its growth and reproduction in the soil. Based on this, the degradation method of the present application can reduce the amount of bacterial agent used while ensuring the degradation effect of polypropylene microplastics, thereby avoiding secondary pollution of the environment.

[0032] 3. The method for degrading polypropylene in soil provided by the present application comprises the use of an efficient and low-carbon thermal stabilization system to realize the in-situ injection of the bacterial agent and / or the degradation liquid, and to keep the soil temperature within a certain range, specifically, when the bacterial agent is injected in situ, the soil temperature is kept at 35-40°C, and the temperature is maintained for 20-24 hours, the soil temperature is increased to 60-63°C, and the temperature is maintained until 4-6 hours before the next injection of the bacterial agent, and the soil temperature is maintained at 35-40°C 4-6 hours before the next injection of the bacterial agent; the efficient and low-carbon thermal stabilization system comprises: a heat source generation module, a heat exchanger, a controller and a temperature acquisition device, wherein the heat source generation module The heat source module and the heat exchanger are interconnected by a pipeline to form a loop. The pipeline is provided with a power device, which provides power for the circulation of the medium in the heat source generation module and the heat exchanger. The heat exchanger includes a plurality of heating units arranged side by side, and the heating units are arranged vertically. The temperature acquisition device is located between two adjacent heating units and is used to collect the temperature of the soil between the heating units. The temperature acquisition device and the power device are both electrically connected to the controller. When the temperature of the soil between the heating units is lower than a threshold, the controller controls the power device to accelerate the flow rate of the medium in the heat source generation module and the heat exchanger. The present application adopts an efficient and low-carbon thermal stabilization system to maintain the soil temperature at 60-63°C when degrading polypropylene in the soil, thereby ensuring that the heat-resistant Pseudomonas strain can better perform its degradation effect. The efficient and low-carbon thermal stabilization system has two functions: in-situ heating and in-situ injection. The bacterial agent and degradation agent are injected into the soil in situ through the efficient and low-carbon thermal stabilization system, and the soil temperature is maintained through the thermal circulation of the medium, thereby improving the degradation rate of polypropylene in the soil. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In order to more clearly illustrate the specific implementation methods of the present application or the technical solutions in the prior art, the following is a brief introduction to the drawings required for use in the specific implementation methods or the description of the prior art. Obviously, the drawings described below are some implementation methods of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0034] FIG1 is a schematic structural diagram of a high-efficiency, low-carbon thermal stabilization system according to Example 1 of the present application;

[0035] FIG2 is an enlarged view of section A in the structure of the high-efficiency, low-carbon, thermally stable system according to Example 1 of the present application;

[0036] FIG3 is a schematic structural diagram of a capillary tube and a connecting tube in the high-efficiency, low-carbon thermal stabilization system of Example 1 of the present application;

[0037] FIG4 is a schematic structural diagram of an external sleeve in a high-efficiency, low-carbon, thermally stable system according to Example 1 of the present application;

[0038] FIG5 is a schematic structural diagram of an internal sleeve in a high-efficiency, low-carbon, thermally stable system according to Example 1 of the present application;

[0039] FIG6 is a flow chart of the method for preparing the thermotolerant Pseudomonas solution according to Example 2 of the present application;

[0040] Among them, the figure numbers are as follows: 1-temperature acquisition device, 2-heating unit, 3-controller, 4-power device, 5-heat source generation module, 6-heating group, 7-heat exchanger, 8-transmission belt, 9-connecting pipe, 10-capillary tube, 11-first bearing, 12-perforation, 13-top cover, 14-external liquid outlet, 15-gear, 16-connecting rod, 17-support rod, 18-internal sleeve, 19-internal liquid outlet, 20-external sleeve. DETAILED DESCRIPTION

[0041] The following examples are provided to further better understand the present application, but are not limited to the best implementation mode described herein, and do not limit the content and protection scope of the present application. Any product identical or similar to the present application obtained by anyone under the inspiration of the present application or by combining the features of the present application with other prior arts shall fall within the scope of protection of the present application.

[0042] If no specific experimental steps or conditions are specified in the examples, the conventional experimental steps or conditions described in the literature in this field can be used. If the manufacturer of the reagents or instruments is not specified, they are all commercially available conventional reagents.

[0043] The original strain of Pseudomonas used in the examples and comparative examples of the present application was purchased from the General Microbiological Culture Collection Center with a collection number of CGMCC NO: 20527.

[0044] The test site is located in the suburbs of a city in North China. Due to the influence of human activities, industrial and agricultural activities and other factors, the soil in the area is contaminated by polypropylene.

[0045] Example 1

[0046] The present embodiment provides a high-efficiency, low-carbon heat stabilization system, which is used to inject a bacterial agent containing a heat-resistant Pseudomonas liquid in situ into the soil to be remediated. Please refer to Figure 1, the high-efficiency, low-carbon heat stabilization system includes: a heat source generation module 5, a heat exchanger 7, a controller 3 and a temperature acquisition device 1, wherein the heat source generation module 5 and the heat exchanger 7 are interconnected through a pipeline to form a loop, and a power device 4 is provided on the pipeline, and the power device 4 provides power for the circulation of the medium in the heat source generation module 5 and the heat exchanger 7; the heat exchanger 7 includes a plurality of heating units 2 arranged side by side, and the heating units 2 are arranged vertically; the temperature acquisition device 1 is located between two adjacent heating units 2, and the temperature acquisition device 1 is used to collect the temperature of the soil between the heating units 2, and the temperature acquisition device 1 and the power device 4 are both electrically connected to the controller 3; when the temperature of the soil between the heating units 2 is lower than the threshold value, the controller 3 controls the power device 4 to accelerate the flow rate of the medium in the heat source generation module 5 and the heat exchanger 7.

[0047] Specifically, please continue to refer to Figures 1 to 3. The high-efficiency, low-carbon thermal stabilization system of this embodiment also includes the heating unit 2, and the heating unit 2 includes several heating groups 6 arranged in parallel. The water inlet of each heating group 6 is connected to the water outlet of the power device 4, and the water outlet of the heating group 6 is connected to the water inlet of the power device 4; each heating group 6 includes a horizontally arranged connecting pipe 9 and a vertically arranged capillary tube 10, and the connecting pipe 9 is connected to the capillary tube 10, and the inner diameter of the connecting pipe 9 is larger than the inner diameter of the capillary tube 10.

[0048] Please refer to Figures 3 to 5. The capillary tube 10 includes an external sleeve 20 and an internal sleeve 18. The internal sleeve 18 is sleeved inside the external sleeve 20. The external sleeve 20 has an external liquid outlet 14, and the internal sleeve 18 has an internal liquid outlet 19 at a position corresponding to the external liquid outlet 14. The external liquid outlet 14 and the internal liquid outlet 19 have the same structure. The top cover 13 of the external sleeve 20 has a through hole 12. The interior of the internal sleeve 18 is connected to a connecting rod 16. The connecting rod 16 and the internal sleeve 18 are coaxially arranged. The connecting rod 16 is connected to the inner wall of the internal sleeve 18 through a support rod 17. The connecting rod 16 passes through the through hole 12. One end of the connecting rod 16 is located outside the external sleeve 20, and the end located outside the external sleeve 20 is connected to the inner wall of the internal sleeve 18. A gear 15 is provided at one end of the connecting rod 16, and the gear 15 is connected to the drive motor through a transmission belt 8; the medium in the heat source generating module 5 and the heat exchanger 7 is the bacterial liquid and / or the degradation liquid for soil remediation. By controlling the drive motor to drive the gear 15 to rotate, the internal sleeve 18 and the external sleeve 20 are caused to rotate relative to each other, so that the internal liquid outlet 19 on the internal sleeve 18 and the external liquid outlet 14 on the external sleeve 20 coincide with each other, and the bacterial agent and / or the degradation liquid are added to the soil through the internal liquid outlet 19 and the external liquid outlet 14. After the addition is completed, the drive motor is controlled to stagger the internal liquid outlet 19 and the external liquid outlet 14, so that the bacterial agent and / or the degradation liquid cannot pass through the internal liquid outlet 19 and the external liquid outlet 14.

[0049] Specifically, please continue to refer to Figures 3 to 5. A first bearing 11 is provided at the upper end of the external sleeve 20, and the lower end of the outer ring of the first bearing 11 is fixed to the outer wall of the external sleeve 20, and the connecting rod 16 is fixed to the inner ring of the first bearing 11; a second bearing is provided at the bottom of the external sleeve 20, and the outer ring of the second bearing is fixed to the inner wall of the external sleeve 20, and the lower end of the connecting rod 16 is fixed to the inner ring of the second bearing; the external sleeve 20 is covered with non-woven fabric, and the non-woven fabric covers the external liquid outlet 14; the capillaries 10 are arranged in rows, and the gears 15 of the capillaries 10 in the same row are connected to the drive motor through the same transmission belt 8.

[0050] Specifically, the distance between adjacent heating units 2 is 0.5m-2m, and the distance between adjacent capillaries 10 is 0.1m-0.5m; and / or, the heat source generating module 5 is a solar collector, the inner diameter of the connecting pipe 9 is 10 to 20 cm, the inner diameter of the capillary 10 is 1 to 2 cm, and the power device 4 is a water pump.

[0051] Example 2

[0052] This embodiment provides a method for degrading polypropylene in soil. The specific method and steps are as follows:

[0053] Preparation method of thermotolerant Pseudomonas liquid: As shown in Figure 6, the original strain LICME 200610 WGH-6, i.e., the Pseudomonas strain, is cultured at 37°C to the logarithmic growth phase, with an acclimation period of 12 hours and a temperature difference gradient of 1°C, and the culture temperature is gradually increased, i.e., cultured at 38°C for 12 hours, and the Pseudomonas strain that can grow normally at 38°C is transferred to a new culture medium, cultured at 39°C for 12 hours, and the Pseudomonas strain that can grow normally at 39°C is transferred to a new culture medium, and so on, until a strain that can grow normally at 61°C is screened out through acclimation. The thermotolerant Pseudomonas strain obtained by the initial screening is then inoculated at 61°C and cultured for 24 hours, rescreened, and strain purified to finally obtain a thermotolerant Pseudomonas strain that is thermotolerant and can degrade polypropylene. The thermotolerant Pseudomonas strain obtained above is fermented at 37°C for 48 hours to obtain a thermotolerant Pseudomonas liquid, and the activity of the thermotolerant Pseudomonas liquid is 1.0×10 9 CFU / mL, wherein the culture medium formula in each step of the preparation method of the thermotolerant Pseudomonas liquid is the same, specifically, 5 g / L glucose, 10 g / L beef extract, 10 g / L peptone, 5 g / L NaCl, and pH 7.0.

[0054] The degradation solution was prepared according to K2HPO4 0.5g / L, KH2PO4 3.815g / L, (NH4)2HPO4 0.825g / L, MgCl2·6H2O 20mg / L, FeCl3 0.2mg / L, CaCl2 2mg / L, Na2SO4 200mg / L, KNO3 1.2625g / L, and pH 7.0.

[0055] The bacterial agent was prepared according to the volume ratio of the thermotolerant Pseudomonas solution to the degradation solution of 1:2.

[0056] On the soil to be repaired, the high-efficiency, low-carbon thermal stabilization system provided in Example 1 of the present application is buried in the soil to be repaired, so that the upper surface of the high-efficiency, low-carbon thermal stabilization system is located on the surface of the ground. At this time, the liquid outlet position of the capillary tube of each heating unit is within the range of 10 meters between the surface and underground. The high-efficiency, low-carbon thermal stabilization system provided in Example 1 of the present application can be used to keep the soil temperature at 61°C during the degradation of polypropylene microplastics.

[0057] According to a single injection volume of 135L of bacterial agent per cubic meter of soil to be treated, the above-mentioned heat-resistant Pseudomonas agent was injected into the soil to be repaired in situ through the high-efficiency, low-carbon heat stabilization system provided in Example 1 of the present application at the early stage of degradation treatment (the 1st day and 10th day from the start of degradation treatment) and the late stage of degradation treatment (the 20th day, 40th day, 70th day and 110th day from the start of degradation treatment), and according to a single injection volume of 30L of degradation liquid per cubic meter of soil to be treated, the above-mentioned heat-resistant Pseudomonas agent was injected into the soil to be repaired in situ at the early stage of degradation treatment (the 1st day and 10th day from the start of degradation treatment) and the late stage of degradation treatment (the 20th day, 40th day, 70th day and 110th day from the start of degradation treatment). On 0d, 55d, 90d, and 140d, the degradation liquid was separately injected into the soil to be repaired in situ through the high-efficiency, low-carbon thermal stabilization system provided in Example 1 of the present application. The soil temperature was maintained at 37°C each time the bacterial agent was injected. At this temperature, the heat-resistant Pseudomonas strain can grow and reproduce rapidly, thereby increasing the number of the strain in the soil. 20h after the injection of the bacterial agent, the temperature of the soil to be repaired was raised to 61°C, at which temperature the degradation of polypropylene microplastics was achieved, and 5h before the next bacterial agent injection, the temperature of the soil to be repaired was lowered to 37°C. Among them, the early stage of degradation treatment is the 1st to 19th day from the start of degradation treatment, and the late stage of degradation treatment is the 20th day and thereafter from the start of degradation treatment.

[0058] Example 3

[0059] This embodiment provides a method for degrading polypropylene in soil. The specific method and steps are as follows:

[0060] Preparation method of thermotolerant Pseudomonas liquid: The original strain LICME 200610 WGH-6, i.e., the Pseudomonas strain, is cultured at 35°C to the logarithmic growth phase, with an acclimation period of 10 hours and a temperature difference increase gradient of 2°C, and the culture temperature is gradually increased until a strain that can grow normally in a 60°C environment is screened out after acclimation. The thermotolerant Pseudomonas strain obtained by the initial screening is then inoculated and cultured at 60°C for 48 hours, followed by rescreening and strain purification, and finally a thermotolerant Pseudomonas strain that is thermotolerant and can degrade polypropylene is obtained. The thermotolerant Pseudomonas strain obtained above is fermented at 35°C for 60 hours to obtain a thermotolerant Pseudomonas liquid, and the activity of the thermotolerant Pseudomonas liquid is 1.0×10 8 CFU / mL, wherein the culture medium formula in each step of the preparation method of the thermotolerant Pseudomonas liquid is the same, specifically, 4 g / L glucose, 11 g / L beef extract, 9 g / L peptone, 6 g / L NaCl, and a pH value of 7.2.

[0061] The degradation solution was prepared according to K2HPO4 0.4g / L, KH2PO4 3.5g / L, (NH4)2HPO4 1g / L, MgCl2·6H2O 22mg / L, FeCl3 0.1mg / L, CaCl2 3mg / L, Na2SO4 220mg / L, KNO3 1.5g / L, and pH 7.2.

[0062] The bacterial agent was prepared according to the volume ratio of the thermotolerant Pseudomonas solution to the degradation solution of 1:5.

[0063] On the soil to be repaired, the high-efficiency, low-carbon thermal stabilization system provided in Example 1 of the present application is buried in the soil to be repaired, so that the upper surface of the high-efficiency, low-carbon thermal stabilization system is located on the surface of the ground. At this time, the liquid outlet position of the capillary tube of each heating unit is within 10 meters of the surface and underground. The high-efficiency, low-carbon thermal stabilization system provided in Example 1 of the present application is used to maintain the soil temperature at 60°C during the degradation of polypropylene microplastics.

[0064] According to a single injection volume of 120L of bacterial agent per cubic meter of soil to be treated, the above-mentioned heat-resistant Pseudomonas agent was injected into the soil to be repaired in situ through the high-efficiency, low-carbon heat stabilization system provided in Example 1 of the present application at the early stage of degradation treatment (the 1st, 6th, and 16th days from the start of degradation treatment) and the late stage of degradation treatment (the 34th, 60th, and 90th days from the start of degradation treatment). According to a single injection volume of 28L of degradation liquid per cubic meter of soil to be treated, the above-mentioned heat-resistant Pseudomonas agent was injected into the soil to be repaired in situ at the early stage of degradation treatment (the 1st, 6th, and 16th days from the start of degradation treatment) and the late stage of degradation treatment (the 34th, 60th, and 90th days from the start of degradation treatment). At 42d, 80d, and 130d, the degradation liquid was injected into the soil to be repaired in situ through the high-efficiency, low-carbon thermal stabilization system provided in Example 1 of the present application. The soil temperature was maintained at 35°C each time the bacterial agent was injected. At this temperature, the heat-resistant Pseudomonas strain can grow and reproduce rapidly, thereby increasing the number of the strain in the soil. 24h after the injection of the bacterial agent, the temperature of the soil to be repaired was raised to 60°C, at which temperature the degradation of polypropylene microplastics was achieved, and 4h before the next bacterial agent injection, the temperature of the soil to be repaired was lowered to 35°C. Among them, the early stage of degradation treatment is the 1st to 19th day from the start of degradation treatment, and the late stage of degradation treatment is the 20th day and thereafter from the start of degradation treatment.

[0065] Example 4

[0066] This embodiment provides a method for degrading polypropylene in soil. The specific method and steps are as follows:

[0067] Preparation method of thermotolerant Pseudomonas liquid: The original strain LICME 200610WGH-6, i.e., the Pseudomonas strain, is cultured at 40°C to the logarithmic growth phase, with an acclimation period of 18 hours and a temperature gradient of 2°C, and the culture temperature is gradually increased until a strain that can grow normally in a 63°C environment is screened out. The thermotolerant Pseudomonas strain obtained by initial screening is then inoculated and cultured at 63°C for 24 hours, followed by rescreening and strain purification, and finally a thermotolerant Pseudomonas strain that is thermotolerant and can degrade polypropylene is obtained. The thermotolerant Pseudomonas strain obtained above is fermented at 40°C for 24 hours to obtain a thermotolerant Pseudomonas liquid, and the activity of the thermotolerant Pseudomonas liquid is 1.0×10 9CFU / mL, wherein the culture medium formula in each step of the preparation method of the thermotolerant Pseudomonas liquid is the same, specifically, 6 g / L glucose, 9 g / L beef extract, 11 g / L peptone, 4 g / L NaCl, and pH 7.1.

[0068] A degradation solution was prepared according to K2HPO4 0.6 g / L, KH2PO4 4 g / L, (NH4)2HPO4 0.5 g / L, MgCl2·6H2O 18 mg / L, FeCl3 0.3 mg / L, CaCl2 1 mg / L, Na2SO4 180 mg / L, and KNO3 1 g / L, with the pH value of the degradation solution being 7.1.

[0069] The bacterial agent was prepared according to the volume ratio of the heat-resistant Pseudomonas liquid to the degradation liquid of 1:3.

[0070] On the soil to be repaired, the high-efficiency, low-carbon thermal stabilization system provided in Example 1 of the present application is buried in the soil to be repaired, so that the upper surface of the high-efficiency, low-carbon thermal stabilization system is located on the surface of the ground. At this time, the liquid outlet position of the capillary tube of each heating unit is within 10 meters of the surface and underground. The high-efficiency, low-carbon thermal stabilization system provided in Example 1 of the present application is used to maintain the soil temperature at 63°C during the degradation of polypropylene microplastics.

[0071] According to a single injection volume of 150L of bacterial agent per cubic meter of soil to be treated, the above-mentioned thermotolerant Pseudomonas agent was injected into the soil to be repaired in situ through the high-efficiency, low-carbon thermal stabilization system provided in Example 1 of the present application at the early stage of degradation treatment (the 1st day and 10th day from the start of degradation treatment) and the late stage of degradation treatment (the 20th day, 40th day, 70th day and 110th day from the start of degradation treatment), and according to a single injection volume of 33L of degradation liquid per cubic meter of soil to be treated, the above-mentioned thermotolerant Pseudomonas agent was injected into the soil to be repaired in situ at the early stage of degradation treatment (the 1st day and 10th day from the start of degradation treatment) and the late stage of degradation treatment (the 20th day, 40th day, 70th day and 110th day from the start of degradation treatment), and the above-mentioned thermotolerant Pseudomonas agent was injected into the soil to be repaired in situ through the high-efficiency, low-carbon thermal stabilization system provided in Example 1 of the present application at the early stage of degradation treatment (the 1st day and 10th day from the start of degradation treatment), and the above-mentioned thermotolerant Pseudomonas agent was injected into the soil to be repaired in situ at the early stage of degradation treatment (the 20th day, 40th day, 70th day and 110th day from the start of degradation treatment). d, 55d, 90d, and 140d, the degradation agent is injected into the soil to be repaired in situ through the high-efficiency, low-carbon thermal stabilization system provided in Example 1 of the present application. The soil temperature is maintained at 40°C each time the bacterial agent is injected. At this temperature, the heat-resistant Pseudomonas strain can grow and reproduce rapidly, thereby increasing the number of the strain in the soil. 22h after the injection of the bacterial agent, the temperature of the soil to be repaired is increased to 63°C, at which temperature the degradation of polypropylene microplastics is achieved, and 6h before the next bacterial agent injection, the temperature of the soil to be repaired is reduced to 40°C. Among them, the early stage of degradation treatment is the 1st to 19th day from the start of degradation treatment, and the late stage of degradation treatment is the 20th day and thereafter from the start of degradation treatment.

[0072] Comparative Example 1

[0073] This comparative example provides a method for degrading polypropylene in soil. The specific method and steps are the same as those in Example 2, except that the soil temperature is maintained at 50°C during the degradation of polypropylene microplastics.

[0074] Comparative Example 2

[0075] This comparative example provides a method for degrading polypropylene in soil. The specific method and steps are the same as those in Example 2, except that the soil temperature is maintained at 70°C during the degradation of polypropylene microplastics.

[0076] Comparative Example 3

[0077] This comparative example provides a method for degrading polypropylene in soil. The specific method and steps are the same as those in Example 2, except that the active bacteria are not heat-resistant acclimated. That is, the bacterial liquid used is obtained by fermenting the Pseudomonas strain LICME 200610 WGH-6 with a preservation number of CGMCC NO: 20527 at 37°C for 48 hours.

[0078] Comparative Example 4

[0079] This comparative example provides a method for degrading polypropylene in soil. The specific method and steps are the same as those in Example 2, except that the soil temperature is maintained at 37°C during the degradation of polypropylene microplastics.

[0080] Experimental example

[0081] The degradation rates of polypropylene in the soil of Examples 2-4 and Comparative Examples 1-4 were detected on the 10th, 15th, 30th, 75th, 135th, and 180th days at the start of the degradation treatment. The detection method was to use a microplastic online monitoring system based on Raman spectroscopy to monitor the degradation of polypropylene in the soil in real time. The microplastic online monitoring system was arranged between the heat source transmission modules of the high-efficiency and low-carbon thermal stabilization system. The detection results are shown in Table 1.

[0082] Table 1 Degradation rate of polypropylene in soil

[0083] According to Table 1, compared with Comparative Examples 1-4, Examples 2-4 performed well in the degradation of polypropylene in the soil, especially on the 180th day of the degradation treatment, the degradation rate of polypropylene in the soil to be repaired in Example 2 reached 55.7%. Compared with Comparative Example 1, the degradation rate of Example 2 increased by 57.3%, which shows that the degradation method of the present application has the highest degradation rate when the soil temperature is maintained at 61°C. Similarly, on the 180th day of the degradation treatment, the degradation rate of Example 2 was 51.8% higher than that of Comparative Example 2, which shows that when the soil temperature was increased to 70°C, it exceeded the tolerance range of the heat-resistant acclimated strain, resulting in a decrease in the degradation rate; the degradation rate of Example 2 was 206.0% higher than that of Comparative Example 3, indicating that the degradation effect of the acclimated strain on polypropylene in the soil was much higher than that of the unacclimated strain; the degradation rate of Example 2 was 259.4% higher than that of Comparative Example 4, proving that the degradation effect of the acclimated strain at a suitable temperature was much higher than its degradation effect at room temperature.

[0084] Obviously, the above embodiments are merely examples for clarity of explanation and are not intended to limit the implementation methods. Those skilled in the art will readily appreciate that other variations or modifications based on the above descriptions are possible. It is not necessary and impossible to enumerate all implementation methods here. Obvious variations or modifications arising therefrom remain within the scope of protection of the present invention.

Claims

1. A method for degrading polypropylene in soil, characterized in that: The steps include: Injecting the thermotolerant Pseudomonas solution into the soil containing polypropylene at least twice, the temperature of the soil is 35-40°C, and the temperature is maintained for 20-24 hours; then raising the temperature of the soil to 60-63°C, and maintaining the temperature until 4-6 hours before the next injection of the bacterial agent; Wherein, the preparation method of the thermotolerant Pseudomonas liquid comprises: S1, taking the strain LICME 200610 WGH-6 with a deposit number of CGMCC NO: 20527, culturing it at 35-40°C to the logarithmic growth phase, raising the culture temperature of the strain in the logarithmic growth phase to 60-63°C according to a temperature difference of 1-2°C per acclimation cycle, and obtaining a primary screening strain; S2, culturing the initially screened strain at 60-63° C., rescreening, and purifying the strain to obtain a thermotolerant Pseudomonas strain; S3, inoculating the thermotolerant Pseudomonas strain into a culture medium and fermenting at 35-40° C. for 24-60 hours.

2. The degradation method according to claim 1, characterized in that: The bacterial agent containing the thermotolerant Pseudomonas liquid also includes a degradation liquid, wherein the composition of the degradation liquid includes K2HPO4 0.4g / L-0.6g / L, KH2PO4 3.5g / L-4g / L, (NH4)2HPO4 0.5g / L-1g / L, MgCl2·6H2O 18mg / L-22mg / L, FeCl3 0.1mg / L-0.3mg / L, CaCl2 1mg / L-3mg / L, Na2SO4 180mg / L-220mg / L, KNO3 1g / L-1.5g / L, and the pH value of the degradation liquid is 7.0-7.2; and / or, The bacterial activity of the Pseudomonas liquid was 1.0×10 8 ~1.0×10 9 CFU / mL.

3. The degradation method according to claim 2, characterized in that: The composition of the culture medium used in any one of steps S1 to S3 includes 4-6 g / L glucose, 9-11 g / L beef extract, 9-11 g / L peptone, and 4-6 g / L NaCl, and the pH value of the culture medium is 7.0-7.2; and / or, Each acclimatization period in step S1 is 10-18 hours; and / or, The culturing time in step S2 is 24-48 hours; and / or, The volume ratio of the thermotolerant Pseudomonas liquid to the degradation liquid in the bacterial agent containing the thermotolerant Pseudomonas liquid is 1:2-5; and / or, The degradation method further comprises the step of separately injecting a degradation liquid into the soil.

4. The degradation method according to claim 3, characterized in that: The injection interval of the bacterial agent containing the heat-resistant Pseudomonas solution in the early stage of degradation treatment is 4-8 days, and the injection interval of the bacterial agent containing the Pseudomonas solution in the late stage of degradation treatment is 20-40 days. During the degradation treatment, the degradation liquid is injected separately after each injection of the bacterial agent containing the Pseudomonas solution. The time interval between the injection of the degradation liquid separately and the injection of the bacterial agent containing the heat-resistant Pseudomonas solution is 5-30 days, wherein the early stage of degradation treatment is the 1st to 19th day from the start of degradation treatment, and the late stage of degradation treatment is the 20th day and thereafter from the start of degradation treatment; and / or, The ratio of the single injection volume of the bacterial agent containing the Pseudomonas liquid to the soil volume is 120-150 L / m 3 and / or, When the degradation liquid is injected alone, the ratio of the single injection volume of the degradation liquid to the soil volume is 28-33 L / m 3 .

5. The degradation method according to any one of claims 1 to 4, characterized in that: The degradation method also includes using a microplastic online monitoring system based on Raman spectroscopy to monitor the degradation of polypropylene in the soil in real time.

6. The degradation method according to claim 4, characterized in that: The in-situ injection of the bacterial agent containing the thermotolerant Pseudomonas solution and / or the degradation solution is achieved by using a high-efficiency low-carbon heat stabilization system, wherein the high-efficiency low-carbon heat stabilization system comprises: a heat source generation module (5), a heat exchanger (7), a controller (3) and a temperature acquisition device (1), wherein: The heat source generation module (5) and the heat exchanger (7) are interconnected via a pipeline to form a loop, and a power device (4) is provided on the pipeline, and the power device (4) provides power for the circulation of the medium in the heat source generation module (5) and the heat exchanger (7); The heat exchanger (7) comprises a plurality of heating units (2) arranged side by side, wherein the heating units (2) are arranged vertically; The temperature collection device (1) is located between two adjacent heating units (2), and the temperature collection device (1) is used to collect the temperature of the soil between the heating units (2). The temperature collection device (1) and the power device (4) are both electrically connected to the controller (3); When the temperature of the soil between the heating units (2) is lower than a threshold value, the controller (3) controls the power device (4) to increase the flow rate of the medium in the heat source generation module (5) and the heat exchanger (7).

7. The degradation method according to claim 6, characterized in that: The heating unit (2) comprises a plurality of heating groups (6) arranged in parallel, the water inlet of each heating group (6) being connected to the water outlet of the power device (4), and the water outlet of the heating group (6) being connected to the water inlet of the power device (4); each heating group (6) comprises a horizontally arranged connecting pipe (9) and a vertically arranged capillary tube (10), the connecting pipe (9) and the capillary tube (10) being connected, and the inner diameter of the connecting pipe (9) being larger than the inner diameter of the capillary tube (10).

8. The degradation method according to claim 7, characterized in that: The capillary tube (10) comprises an external sleeve (20) and an internal sleeve (18), wherein the internal sleeve (18) is sleeved inside the external sleeve (20); the external sleeve (20) is provided with an external liquid outlet (14), and the internal sleeve (18) is provided with an internal liquid outlet (19) at a position corresponding to the external liquid outlet (14), and the external liquid outlet (14) and the internal liquid outlet (19) have the same structure; the top cover (13) of the external sleeve (20) is provided with a perforation (12), and the internal sleeve (18) is provided with a perforation (19). A connecting rod (16) is connected to the inside of the tube (18), the connecting rod (16) and the internal sleeve (18) are coaxially arranged, the connecting rod (16) is connected to the inner wall of the internal sleeve (18) through a support rod (17), and the connecting rod (16) passes through the through hole (12); one end of the connecting rod (16) is located outside the external sleeve (20), and a gear (15) is provided at one end of the connecting rod (16) located outside the external sleeve (20), and the gear (15) is connected to a driving motor through a transmission belt (8); The medium in the heat source generation module (5) and the heat exchanger (7) is the bacterial agent and / or the degradation liquid used for soil repair. The gear (15) is driven to rotate by controlling the drive motor, so that the internal sleeve (18) and the external sleeve (20) rotate relative to each other, so that the internal liquid outlet (19) on the internal sleeve (18) and the external liquid outlet (14) on the external sleeve (20) overlap, and the bacterial agent and / or the degradation liquid are added to the soil through the internal liquid outlet (19) and the external liquid outlet (14). After the addition is completed, the drive motor is controlled to stagger the internal liquid outlet (19) and the external liquid outlet (14), so that the bacterial agent and / or the degradation liquid cannot pass through the internal liquid outlet (19) and the external liquid outlet (14).

9. The degradation method according to claim 8, characterized in that: A first bearing (11) is arranged at the upper end of the outer sleeve (20), the lower end of the outer ring of the first bearing (11) is fixed to the outer wall of the outer sleeve (20), and the connecting rod (16) is fixed to the inner ring of the first bearing (11); a second bearing is arranged at the bottom of the outer sleeve (20), the outer ring of the second bearing is fixed to the inner wall of the outer sleeve (20), and the lower end of the connecting rod (16) is fixed to the inner ring of the second bearing; and / or, The outer sleeve (20) is coated with non-woven fabric, which covers the outer liquid outlet (14); the capillaries (10) are arranged in rows, and the gears (15) of the capillaries (10) in the same row are connected to a drive motor via the same transmission belt (8).

10. The degradation method according to any one of claims 7 to 9, characterized in that: The distance between adjacent heating units (2) is 0.5m-2m, and the distance between adjacent capillaries (10) is 0.1m-0.5m; and / or, the heat source generating module (5) is a solar collector, the inner diameter of the connecting pipe (9) is 10 to 20 centimeters, the inner diameter of the capillary tube (10) is 1 to 2 centimeters, and the power device (4) is a water pump.

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