A biochemical treatment method for promoting degradation of plastics

Abstract

The application discloses a biochemical treatment method for promoting plastic degradation, and comprises the following steps: after 15-20 cm of soil containing plastic on the surface is dug out, the soil is mixed with a surface plastic promoter, then a bottom plastic degradation agent is scattered in the soil pit after the soil is dug out, water is sprinkled, the soil mixed with the surface plastic promoter is backfilled into the soil pit, water is sprinkled to make the soil humidity reach 20-30%, and the biochemical treatment is completed; the method can promote the crushing and degradation of microplastics on the surface of the soil, and can also promote the degradation of smaller-diameter microplastics after crushing and settling, is simple in implementation, requires less manual labor, does not need special equipment and repeated treatment of the soil, saves treatment time, and is high in applicability.

Description

Technical Field

[0001] This invention belongs to the field of organic solid waste treatment technology, specifically relating to a biochemical treatment method that promotes the degradation of plastics. Background Technology

[0002] Plastic is one of the most commonly used synthetic materials because it is durable, lightweight, and cost-effective. In 2015, global plastic production reached 6.3 billion tons. However, only 21% of plastic is recycled or incinerated; the rest is weathered and decomposes into tiny fragments, forming "microplastics" with a diameter of less than 5 millimeters. Currently, microplastics are ubiquitous globally, polluting rivers, lakes, and farmland. Plastic pollution has become a global problem, and the issue of promoting plastic degradation urgently needs to be addressed.

[0003] Patent CN115889423A discloses a method for enhancing the biodegradability of microplastics through biochar. Biochar increases microbial abundance, providing a suitable habitat for soil microorganisms and increasing the content of microorganisms in the soil, thereby improving the decomposition efficiency of microplastics. However, since microplastics of different diameters are distributed at different depths in the soil, this method is more dependent on the distribution degree and sedimentation capacity of biochar in the soil, and even more dependent on the types and activities of microorganisms in the soil, resulting in poor applicability.

[0004] Patent CN116060435A discloses a method for the rapid degradation of microplastics in soil environments. By preparing a degradation agent containing microbial strains that degrade plastics, the method achieves the goal of rapidly degrading microplastics through continuous high-temperature fermentation of the microbial strains. However, this method requires continuous high-temperature fermentation treatment with a covered film for 1-2 days, which requires a lot of manpower and energy and has low practicality.

[0005] Therefore, there is a need for a biochemical treatment method that can promote the degradation of microplastics in the soil surface and even smaller microplastics below the soil surface, in order to meet the plastic degradation needs of relevant fields. Summary of the Invention

[0006] The purpose of this invention is to solve the problem of how to promote the degradation of microplastics in the soil surface and microplastics with smaller diameters in the deeper soil layers.

[0007] This invention assists in the breaking down and degradation of microplastics in the soil surface by containing a promoter and a biological agent that promotes microplastic breaking down, and applies a microbial agent to the soil below the surface to assist in the degradation of surface-sedimented microplastics and small-diameter microplastics.

[0008] The objective of this invention can be achieved through the following technical solutions:

[0009] A biochemical treatment method to promote the degradation of plastics includes the following steps:

[0010] Step 1: Excavate 15-20cm of the topsoil containing plastic, and apply a surface plastic accelerator at a concentration of 300-400g / m³. 3 The amount of mixture should be mixed with the excavated soil;

[0011] Step 2: Apply the bottom layer of plastic degradation agent at a concentration of 150-200 g / m³. 2 The amount of seeding agent was applied to the pit after the soil was dug out, and water was sprinkled on it to turn the surface of the bottom plastic degrader black.

[0012] Step 3: Backfill the soil mixed with the surface plastic accelerator into the pit, and sprinkle water at 50-60℃ to bring the soil moisture to 20-30%. The biochemical treatment is now complete.

[0013] Surface plastic accelerator is prepared through the following steps:

[0014] Mix starch microspheres and accelerator carrier at a mass ratio of 1-2:20, while sprinkling water and stirring until the surface humidity of the accelerator carrier reaches 10-20%, then vacuum dry at 40-50℃, pulverize, and pass through a 40-mesh sieve to obtain surface plastic accelerator.

[0015] The bottom plastic degrader is prepared through the following steps:

[0016] Mix starch-based inoculants and biochar at a mass ratio of 1-2:20, while sprinkling water and stirring until the surface moisture of the biochar reaches 10-20%. Then, vacuum dry at 40-50℃, pulverize, and pass through a 40-mesh sieve to obtain the bottom layer plastic degradation agent.

[0017] Furthermore, the promoter carrier is prepared through the following steps:

[0018] Zinc chloride was dissolved in dilute hydrochloric acid with a pH of 4-5 in a reactor. Biochar was added and stirred for 12-16 hours. Then sodium carbonate was added and stirred at 100-200 rpm for 15-20 minutes. The mixture was then hydrothermally reacted at 130-140°C for 12-14 hours. The resulting precipitate was washed and dried to obtain the promoter carrier.

[0019] Furthermore, the ratio of zinc chloride, dilute hydrochloric acid, biochar, and sodium carbonate used is: 0.2-0.3g: 60mL-80mL: 25-30g: 15-20g.

[0020] Furthermore, the starch-inoculant microspheres are prepared through the following steps:

[0021] The fermentation broth of the biodegradable plastic bacteria strain after expansion culture was mixed with 10-12 wt% propionylated starch emulsion and shaken for 10-15 min to obtain starch bacteria solution. Then, 2-3% sodium alginate by weight of starch bacteria solution was added, stirred and mixed to dissolve, and then 6-8 wt% calcium chloride solution was added dropwise. After stirring at 200-300 r / min for 1.5-2 h, the mixture was centrifuged, the precipitate was washed, and dried to obtain starch bacteria microspheres.

[0022] Furthermore, the starch-inoculant is prepared through the following steps:

[0023] The fermentation broth of the biodegradable plastic microbial strain was mixed with 10-12 wt% propionylated starch emulsion at a constant temperature of 50-60℃ and shaken for 10-15 min, and then spray-dried to obtain the starch microbial agent.

[0024] Furthermore, biodegradable plastic bacteria include Pseudomonas aeruginosa, Aureobacillus, Bacillus subtilis, and alkyl consuming bacteria.

[0025] Furthermore, the volume ratio of the fermentation broth to 10-12 wt% propionyl starch emulsion is 1-2:100.

[0026] Furthermore, the propionyl starch emulsion is obtained by mixing propionyl starch with deionized water.

[0027] Furthermore, propionyl starch is prepared by the following steps: dry starch and propionic anhydride are mixed in a reaction vessel, p-toluenesulfonic acid is added, the mixture is stirred and reacted, and then washed, dried and ground to obtain propionyl starch.

[0028] The beneficial effects of this invention are:

[0029] (1) The method of the present invention can promote the breaking and degradation of microplastics on the soil surface, as well as the degradation of smaller diameter microplastics after breaking and settling. The implementation method is simple, requires little manual labor, does not require special equipment or repeated treatment of the soil, saves treatment time, and has high applicability.

[0030] (2) The method of the present invention prepares a surface plastic promoter and a bottom plastic degrader and mixes them with soil containing plastic on the surface and soil in the bottom layer, respectively. The surface plastic promoter promotes the degradation and breakage of microplastics, and the bottom plastic degrader promotes the degradation of microplastics in the surface and soil by microorganisms and fungicides, thereby improving the plastic degradation capacity in the soil.

[0031] (3) The method of the present invention prepares an accelerator carrier by compounding zinc oxide on the surface of biochar. While the biochar adsorbs the microplastics, the zinc oxide also attaches to the surface of the microplastics, so that the zinc oxide promotes the degradation and breakage of the microplastics under the conditions of oxygen and light. At the same time, the surface plastic accelerator in the present invention contains starch microspheres. These microspheres can form a film on the plastic surface after being sprayed with water in the method of the present invention. The water in the film is conducive to the formation and transmission of hydroxyl radicals, which is beneficial to the degradation of microplastics.

[0032] (4) The method of the present invention prepares starch bacterial agent by mixing the bacterial agent of degradable plastic with propionyl starch. The propionyl starch protects the bacterial agent while increasing the adsorption capacity of the bacterial strain of degradable plastic. The bacterial agent adsorbs the microplastic along with the propionyl starch and the microplastic, and the bacterial strain of degradable plastic is also adsorbed on the surface of the microplastic, thereby improving the microplastic degradation capacity of the bacterial strain. Detailed Implementation

[0033] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0034] Example 1

[0035] A biochemical treatment method to promote the degradation of plastics includes the following steps:

[0036] Step 1: Dig out 15cm of the top layer of soil containing plastic, and apply a surface plastic accelerator at a rate of 300g / m³. 3 The amount of mixture should be mixed with the excavated soil;

[0037] The mixing process increases soil looseness and oxygen content, and also makes it easier for the surface plastic accelerator to move in the soil under gravity.

[0038] Step 2: Apply the bottom layer plastic degradation agent at a rate of 150g / m³ 2 The amount of seeding agent was applied to the pit after the soil was dug out, and water was sprinkled on it to turn the surface of the bottom plastic degrader black.

[0039] The bottom of the pit contains a high level of microplastics that have been degraded for many years. Furthermore, the surface microplastics will settle into the bottom soil after degradation. When the bottom plastic degrading agent is mixed with the soil at the bottom of the pit, the starch-containing bacteria in the bottom plastic degrading agent flows out from the pores of the biochar under the impact and dissolution of water flow and mixes into the soil at the bottom of the pit. The propionylated starch has enhanced hydrophobicity, making it easier for the starch-containing bacteria to combine with the microplastics in the soil at the bottom of the pit, thus promoting the degradation of microplastics. The starch also provides a carbon source for the bacteria, making the bacteria more quickly activated. The rich porous surface area of ​​the biochar also provides a habitat for microorganisms in the soil, increasing the abundance of microorganisms in the soil and improving the degradation efficiency.

[0040] Step 3: Backfill the soil mixed with the surface plastic accelerator into the pit, and sprinkle 50°C water to bring the soil moisture to 20%. The biochemical treatment is now complete.

[0041] The accelerator carrier of the surface plastic accelerator has a porous surface area, making it easier to adsorb onto the surface of microplastics in the soil. The surface of the accelerator carrier contains zinc oxide. Under high humidity, zinc oxide will generate active oxidizing substances such as hydroxyl and superoxide free radicals under ultraviolet and visible light. These active oxidizing substances will damage the polymer chains of microplastics, generate more free radicals, increase the Young's modulus of microplastics, increase the brittleness of microplastics, promote plastic breakage, increase contact area, and improve degradation ability.

[0042] Preparation of accelerator carrier:

[0043] In a reaction vessel, 0.2 g of zinc chloride was dissolved in 60 mL of dilute hydrochloric acid with a pH of 4. 25 g of biochar was added and stirred for 12 h. Then, 15 g of sodium carbonate was added and stirred at 100 r / min for 15 min. The solution was then subjected to hydrothermal reaction at 130 °C for 12 h. The precipitate obtained at the bottom of the reaction vessel was washed with deionized water and anhydrous ethanol until the washing solution was nearly neutral. The washed product was then placed in a forced-air drying oven and dried at 60 °C for 8 h to obtain the accelerator carrier.

[0044] Biochar is obtained by pyrolyzing straw at high temperature in a muffle furnace and then passing it through a 60-mesh sieve.

[0045] By mixing zinc chloride with biochar and reacting it hydrothermally, zinc chloride is converted into zinc oxide in the pores on the surface of the biochar.

[0046] Preparation of starch bacteria agent

[0047] The biodegradable plastic microbial strain was cultured on a larger scale to obtain a strain number greater than 8 x 10⁻⁶. 8The fermentation broth was prepared by adding the fermentation broth at a volume ratio of 1:100 to a sterilized 10wt% propionylated starch emulsion. The mixture was then mixed in a constant temperature shaker at 50°C for 10 min and dried in a spray dryer at an inlet air temperature of 90°C and an outlet air temperature of 45°C to obtain the starch inoculum.

[0048] Preparation of starch-infused microspheres:

[0049] The biodegradable plastic microbial strain was cultured on a larger scale to obtain a strain number greater than 8 x 10⁻⁶. 8 The fermentation broth was prepared by mixing propionylated starch with deionized water at 50°C and stirring to prepare a 10 wt% propionylated starch emulsion. The fermentation broth was added to the sterilized propionylated starch emulsion at a volume ratio of 1:100 and mixed in a constant temperature shaker at 50°C for 10 min to obtain a starch culture solution. Sodium alginate was then mixed with the starch culture solution to prepare a starch culture solution with a sodium alginate content of 2 wt% and stirred at 200 r / min for 10 min. Then, 6 wt% calcium chloride solution was added dropwise to the starch culture solution containing sodium alginate and stirred continuously for 1.5 h. The mixture was then centrifuged at 3000 r / min for 5 min, and the lower precipitate was washed with isopropanol, petroleum ether, and anhydrous ethanol, respectively. The microspheres were collected, dried at 50°C, and obtained starch culture agent microspheres.

[0050] The microbial strains that can degrade plastics are: Pseudomonas aeruginosa and Aureobacterium chrysogenum.

[0051] The freeze-dried bacterial culture powder was purchased from Beijing Bio-Bio Biotechnology Co., Ltd.

[0052] The microspheres formed by sodium alginate and starch-based microbial agents have excellent water absorption and retention capabilities, as well as good adhesion. When combined with water, they can form a film on the plastic surface. The water in the film facilitates the formation of free hydroxyl radicals, thereby promoting the degradation of microplastics. Furthermore, the film generates adsorption stress on the microplastics. After continuous exposure to sunlight, the film gradually dries and cracks. The resulting desorption stress on the microplastic surface further promotes the breakage of the plastic. The broken microplastics provide a larger contact area, enhancing the degradation ability of the microbial agent and increasing the degradation rate.

[0053] The preparation method of propionyl starch is as follows:

[0054] 10g of dried starch was mixed with 30mL of propionic anhydride in a reaction vessel, and 0.5g of p-toluenesulfonic acid was added. The mixture was stirred and reacted for 4h. After the reaction was completed, the solution was cooled to room temperature and washed thoroughly with ice-cold distilled water at 2°C to remove unreacted propionic anhydride and p-toluenesulfonic acid. The solid product was obtained by vacuum filtration through a Buchner funnel. The solid product was dried in an oven at 45°C for 24h, ground, and passed through a 100-mesh sieve to obtain propionyl starch.

[0055] The propionyl group of starch is attached to the starch molecule by substituting some of the hydrophilic hydroxyl groups, which enhances the hydrophobicity of propionyl starch; and the acylation reaction increases the roughness of the starch surface, thereby enhancing the adsorption of starch.

[0056] Preparation of surface plastic accelerator:

[0057] Starch microbeads and accelerator carriers were mixed at a mass ratio of 1:20. Water was sprinkled while stirring until the surface moisture of the accelerator carrier reached 10%. Then, the mixture was vacuum dried at 40°C, pulverized, and passed through a 40-mesh sieve to obtain the surface plastic accelerator.

[0058] Spraying water on the surface of the accelerator carrier promotes the fixation of starch bacteria agent in the pores of the accelerator carrier surface.

[0059] Preparation of the underlying plastic degrading agent:

[0060] Starch inoculant and biochar were mixed at a mass ratio of 1:20. Water was sprinkled while stirring until the surface moisture of the biochar reached 10%. Then, the mixture was vacuum dried at 40°C, pulverized, and passed through a 40-mesh sieve to obtain the bottom plastic degradation agent.

[0061] Sprinkling water on the surface of biochar promotes the fixation of starch bacteria in the pores of the biochar carrier.

[0062] Example 2

[0063] A biochemical treatment method to promote the degradation of plastics includes the following steps:

[0064] Step 1: Excavate 17.5cm of the topsoil containing plastic, and apply a surface plastic accelerator at a concentration of 350g / m³. 3 The amount of mixture should be mixed with the excavated soil;

[0065] Step 2: Apply the bottom layer plastic degradation agent at a concentration of 175g / m³ 2 The amount of seeding agent was applied to the pit after the soil was dug out, and water was sprinkled on it to turn the surface of the bottom plastic degrader black.

[0066] Step 3: Backfill the soil mixed with the surface plastic accelerator into the pit, and sprinkle water at 55°C to bring the soil moisture to 25%. The biochemical treatment is now complete.

[0067] Preparation of accelerator carrier:

[0068] 0.25 g of zinc chloride was dissolved in 70 mL of dilute hydrochloric acid with a pH of 4.5 in a reactor. 27.5 g of biochar was added and stirred for 14 h. Then 17.5 g of sodium carbonate was added and stirred at 150 r / min for 17 min. The solution was then placed in a reactor and hydrothermally reacted at 135 °C for 13 h. The precipitate obtained at the bottom of the reactor was washed with deionized water and anhydrous ethanol until the washing solution was nearly neutral. The washed product was then placed in a forced-air drying oven and dried at 65 °C for 10 h to obtain the accelerator carrier.

[0069] Biochar is obtained by pyrolyzing agricultural waste such as straw and rice husks at high temperature in a muffle furnace and then passing it through a 60-mesh sieve.

[0070] Preparation of starch-inducing agents:

[0071] The biodegradable plastic microbial strain was cultured on a larger scale to obtain a strain number greater than 8 x 10⁻⁶. 8 The fermentation broth was prepared by adding the fermentation broth to a sterilized 11wt% propionylated starch emulsion at a volume ratio of 1.5:100. The mixture was then mixed in a constant temperature shaker at 55°C for 12.5 min and dried in a spray dryer at an inlet air temperature of 95°C and an outlet air temperature of 47.5°C to obtain the starch inoculant.

[0072] Preparation of starch-infused microspheres:

[0073] The biodegradable plastic microbial strain was cultured on a larger scale to obtain a strain number greater than 8 x 10⁻⁶. 8 The fermentation broth was prepared by mixing propionylated starch with deionized water at 55°C and stirring to prepare an 11 wt% propionylated starch emulsion. The fermentation broth was added to the sterilized propionylated starch emulsion at a volume ratio of 1.5:100, and the mixture was stirred in a constant temperature shaker at 55°C for 12.5 min to obtain a starch culture solution. Sodium alginate was then mixed with the starch culture solution to prepare a starch culture solution with a sodium alginate content of 2.5 wt%, and stirred at 200 r / min for 12 min. Then, 7 wt% calcium chloride solution was added dropwise to the starch culture solution containing sodium alginate and stirred continuously for 1.8 h. The mixture was then centrifuged at 3000 r / min for 6.5 min, and the lower precipitate was washed with isopropanol, petroleum ether, and anhydrous ethanol, respectively. The microspheres were collected, dried at 55°C, and obtained starch culture agent microspheres.

[0074] The microbial strains that can degrade plastics are: Aureobacterium tumefaciens and Bacillus subtilis;

[0075] The freeze-dried bacterial culture powder was purchased from Beijing Bio-Bio Biotechnology Co., Ltd.

[0076] The preparation method of propionyl starch is as follows:

[0077] 12.5 g of dried starch was mixed with 40 mL of propionic anhydride in a reaction vessel, and 0.65 g of p-toluenesulfonic acid was added. The mixture was stirred and reacted for 5 h. After the reaction was completed, the solution was cooled to room temperature and washed thoroughly with ice-cold distilled water at 3 °C to remove unreacted propionic anhydride and p-toluenesulfonic acid. The solid product was obtained by vacuum filtration through a Buchner funnel. The solid product was dried in an oven at 47.5 °C for 26 h, ground, and passed through a 100-mesh sieve to obtain propionyl starch.

[0078] Preparation of surface plastic accelerator:

[0079] Starch microbeads and accelerator carriers were mixed at a mass ratio of 1.5:20. Water was sprinkled while stirring until the surface moisture of the accelerator carrier reached 15%. The mixture was then vacuum dried at 45°C, pulverized, and passed through a 40-mesh sieve to obtain the surface plastic accelerator.

[0080] Preparation of the underlying plastic degrading agent:

[0081] Starch inoculant and biochar were mixed at a mass ratio of 1.5:20. Water was sprinkled while stirring until the surface moisture of the biochar reached 15%. The mixture was then vacuum dried at 45°C, pulverized, and passed through a 40-mesh sieve to obtain the bottom plastic degradation agent.

[0082] Example 3

[0083] A biochemical treatment method to promote the degradation of plastics includes the following steps:

[0084] Step 1: Excavate 20cm of the topsoil containing plastic, and apply a surface plastic accelerator at a rate of 400g / m³. 3 The amount of mixture should be mixed with the excavated soil;

[0085] Step 2: Apply the bottom layer plastic degradation agent at a rate of 200g / m³ 2 The amount of seeding agent was applied to the pit after the soil was dug out, and water was sprinkled on it to turn the surface of the bottom plastic degrader black.

[0086] Step 3: Backfill the soil mixed with the surface plastic accelerator into the pit, and sprinkle 60°C water to bring the soil moisture to 30%. The biochemical treatment is now complete.

[0087] Preparation of accelerator carrier:

[0088] 0.3 g of zinc chloride was dissolved in 80 mL of dilute hydrochloric acid with a pH of 5 in a reactor. 30 g of biochar was added and stirred for 16 h. Then 20 g of sodium carbonate was added and stirred at 200 r / min for 20 min. The solution was then subjected to hydrothermal reaction at 140 °C for 14 h. The precipitate obtained at the bottom of the reactor was washed with deionized water and anhydrous ethanol until the washing solution was nearly neutral. The washed product was then placed in a forced-air drying oven and dried at 70 °C for 12 h to obtain the promoter carrier.

[0089] Biochar is obtained by pyrolyzing agricultural waste such as straw and rice husks at high temperature in a muffle furnace and then passing it through a 60-mesh sieve.

[0090] Preparation of starch bacteria agent

[0091] The biodegradable plastic microbial strain was cultured on a larger scale to obtain a strain number greater than 8 x 10⁻⁶. 8 The fermentation broth was prepared by adding the fermentation broth to a sterilized 12wt% propionylated starch emulsion at a volume ratio of 2:100. The mixture was then mixed in a constant temperature shaker at 60°C for 15 min and dried in a spray dryer at an inlet air temperature of 100°C and an outlet air temperature of 50°C to obtain the starch inoculum.

[0092] Preparation of starch-infused microspheres:

[0093] The biodegradable plastic microbial strain was cultured on a larger scale to obtain a strain number greater than 8 x 10⁻⁶. 8 The fermentation broth was prepared by mixing propionylated starch with deionized water at 60°C and stirring to prepare a 12wt% propionylated starch emulsion. The fermentation broth was added to the sterilized propionylated starch emulsion at a volume ratio of 2:100 and mixed in a constant temperature shaker at 60°C for 15 min to obtain a starch culture solution. Sodium alginate was then mixed with the starch culture solution to prepare a starch culture solution with a sodium alginate content of 3wt% and stirred at 300 r / min for 15 min. Then, 8wt% calcium chloride solution was added dropwise to the starch culture solution containing sodium alginate and stirred continuously for 2 h. The mixture was then centrifuged at 3000 r / min for 8 min, and the lower precipitate was washed with isopropanol, petroleum ether, and anhydrous ethanol, respectively. The microspheres were collected, dried at 60°C, and obtained starch culture agent microspheres.

[0094] The microbial strains that can degrade plastics are: Bacillus subtilis and alkyl-eating bacteria;

[0095] The freeze-dried bacterial culture powder was purchased from Beijing Bio-Bio Biotechnology Co., Ltd.

[0096] The preparation method of propionyl starch is as follows:

[0097] 15g of dried starch was mixed with 45mL of propionic anhydride in a reaction vessel, and 0.75g of p-toluenesulfonic acid was added. The mixture was stirred and reacted for 6 hours. After the reaction was completed, the solution was cooled to room temperature and washed thoroughly with ice-cold distilled water at 4°C to remove unreacted propionic anhydride and p-toluenesulfonic acid. The solid product was obtained by vacuum filtration through a Buchner funnel. The solid product was dried in an oven at 50°C for 28 hours, ground, and passed through a 100-mesh sieve to obtain propionyl starch.

[0098] Preparation of surface plastic accelerator:

[0099] Starch microbeads and accelerator carriers were mixed at a mass ratio of 2:20. Water was sprinkled while stirring until the surface moisture of the accelerator carrier reached 20%. Then, the mixture was vacuum dried and pulverized at 50°C and passed through a 40-mesh sieve to obtain the surface plastic accelerator.

[0100] Preparation of the underlying plastic degrading agent:

[0101] Starch inoculant and biochar were mixed at a mass ratio of 2:20. Water was sprinkled while stirring until the surface moisture of the biochar reached 20%. The mixture was then vacuum dried at 50°C, pulverized, and passed through a 40-mesh sieve to obtain the bottom plastic degradation agent.

[0102] Comparative Example 1

[0103] Step 1: Excavate 15cm of the top layer of soil containing plastic, and mix biochar with the excavated soil at a ratio of 300g / m³. 3 Mix the amount of mixture;

[0104] Step 2: Apply biochar at a concentration of 150g / m³ 2 The application rate is applied to the pit after the soil has been excavated, and water is sprinkled to turn the surface of the bottom plastic degrader black.

[0105] Step 3: Backfill the soil mixed with biochar into the pit, and sprinkle water to bring the soil moisture to 30%. The biochemical treatment is now complete.

[0106] Comparative Example 2

[0107] The difference from Example 1 is that:

[0108] Step 1: Excavate 15cm of the top layer of soil containing plastic, and mix the plastic accelerator with the excavated soil at a ratio of 300g / m³. 3 The mixture;

[0109] Step 2: Backfill the soil mixed with the plastic accelerator into the pit and sprinkle water to bring the soil moisture to 20%.

[0110] Preparation of plastic accelerators:

[0111] The accelerator carrier and starch bacteria agent are mixed at a mass ratio of 1:20. While sprinkling water, the mixture is stirred until the surface moisture of the accelerator carrier reaches 10%. Then, it is vacuum dried at 40°C, pulverized, and passed through a 40-mesh sieve to obtain the plastic accelerator.

[0112] Plastic decomposition capacity tests were conducted on Examples 1-3 and Comparative Examples 1-2. The test method was as follows: 10 kg of soil with the same plastic content was treated with the same plastic mixtures of polyethylene, polypropylene, and polyester, broken into 5 mm × 5 mm plastic flakes. The mass of microplastics in the soil was measured after 18 weeks of treatment under natural conditions. Plastic fragments in the soil were separated and collected by flotation separation, and the mass of plastic after treatment was measured. The degradation rate was calculated, and the results are shown in Table 1.

[0113] Table 1

[0114] Degradation rate 41.4％ 42.1％ 42.8％ 18.2％ 26.8％

[0115] As can be seen from the data in Table 1, the degradation rates of Examples 1-3 are all higher than 50%, which greatly improves the degradation ability of plastics compared with Comparative Example 1, which only uses biochar. The plastic degradation rate of Comparative Example 2 is much lower than that of Examples 1-3, indicating that the bottom plastic degrading agent prepared by the present invention can degrade the microplastics that settle down from the surface soil. However, in Comparative Example 2, since the plastic accelerator is only mixed in the surface soil, the microplastics in the surface soil become smaller and settle downwards after decomposition, and detach from the plastic accelerator, resulting in a low degradation rate. In contrast, the biochemical treatment method of the present invention effectively degrades the microplastics in the soil surface and the microplastics that settle downwards from the surface, resulting in a high degradation rate.

[0116] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0117] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A biochemical treatment method for promoting the degradation of plastics, characterized in that, Includes the following steps: Step 1: Excavate 15-20cm of the topsoil containing plastic, and apply a surface plastic accelerator at a concentration of 300-400g / m³. 3 The amount of mixture should be mixed with the excavated soil; Step 2: Apply the bottom layer of plastic degradation agent at a concentration of 150-200 g / m³. 2 The amount of seeding agent was applied to the pit after the soil was dug out, and water was sprinkled on it to turn the surface of the bottom plastic degrader black. Step 3: Backfill the soil mixed with the surface plastic accelerator into the pit, and sprinkle water at 50-60℃ to bring the soil moisture to 20-30%. The biochemical treatment is now complete. The surface plastic accelerator is prepared through the following steps: Mix starch microspheres and accelerator carrier at a mass ratio of 1-2:20, while sprinkling water and stirring until the surface humidity of the accelerator carrier reaches 10-20%, then vacuum dry at 40-50℃, pulverize, and pass through a 40-mesh sieve to obtain surface plastic accelerator. The underlying plastic degrading agent is prepared through the following steps: Mix starch-based inoculant with biochar at a mass ratio of 1-2:20, while sprinkling water and stirring until the surface moisture of the biochar reaches 10-20%, then vacuum dry at 40-50℃, pulverize, and pass through a 40-mesh sieve to obtain the bottom plastic degradation agent. The promoter carrier is prepared by the following steps: Zinc chloride was dissolved in dilute hydrochloric acid with a pH of 4-5 in a reactor, biochar was added and stirred for 12-16 hours, then sodium carbonate was added, and the mixture was stirred at 100-200 r / min for 15-20 minutes. The mixture was then hydrothermally reacted at 130-140℃ for 12-14 hours. The resulting precipitate was washed and dried to obtain the promoter carrier. The starch-inoculant microspheres are prepared through the following steps: The fermentation broth of the biodegradable plastic bacteria strain after expansion culture was mixed with 10-12 wt% propionylated starch emulsion and shaken for 10-15 min to obtain starch bacteria solution. Then, 2-3% sodium alginate by weight of starch bacteria solution was added, stirred and mixed to dissolve, and then 6-8 wt% calcium chloride solution was added dropwise. After stirring at 200-300 r / min for 1.5-2 h, the mixture was centrifuged, the precipitate was washed, and dried to obtain starch bacteria microspheres.

2. The biochemical treatment method for promoting plastic degradation according to claim 1, characterized in that, The ratio of zinc chloride, dilute hydrochloric acid, biochar, and sodium carbonate used is: 0.2-0.3g: 60mL-80mL: 25-30g: 15-20g.

3. The biochemical treatment method for promoting plastic degradation according to claim 1, characterized in that, The starch-initiating agent is prepared through the following steps: The fermentation broth of the biodegradable plastic microbial strain was mixed with 10-12 wt% propionylated starch emulsion at a constant temperature of 50-60℃ and shaken for 10-15 min, and then spray-dried to obtain the starch microbial agent.

4. The biochemical treatment method for promoting plastic degradation according to claim 3, characterized in that, The biodegradable plastic strains include Pseudomonas aeruginosa, Aureobacillus chrysogenum, Bacillus subtilis, and alkyl consuming bacteria.

5. The biochemical treatment method for promoting plastic degradation according to claim 3, characterized in that, The volume ratio of the fermentation broth to 10-12 wt% propionyl starch emulsion is 1-2:

100.

6. The biochemical treatment method for promoting plastic degradation according to claim 1, characterized in that, The propionyl starch emulsion is obtained by mixing propionyl starch with deionized water.

7. The biochemical treatment method for promoting plastic degradation according to claim 6, characterized in that, The propionyl starch is prepared by the following steps: dry starch and propionic anhydride are mixed in a reaction vessel, p-toluenesulfonic acid is added, the mixture is stirred and reacted, and then washed, dried and ground to obtain propionyl starch.