Environment-friendly degradable modified soil conditioning material and preparation method thereof

Abstract

The application discloses an environment-friendly degradable modified soil conditioning material and a preparation method thereof, and belongs to the field of soil remediation. The preparation method comprises the following steps: mixing pretreated carbon material and mixed bacterial strains according to a weight ratio of 1:14-20, and adsorbing for 24-30 hours at 20-25 DEG C to obtain bacterial-loaded pretreated carbon material; mixing the bacterial-loaded pretreated carbon material and modified polylactic acid emulsion according to a weight ratio of 1:8-11, and immersing for 5-10 minutes at 30 DEG C; filtering to take out filter cake, and performing reduced-pressure drying treatment to obtain the modified soil conditioning material. The modified soil conditioning material prepared by the application has good water absorption and water retention capacity and the effect of reducing the harm of heavy metal ions in soil, and the material itself is environment-friendly and degradable.

Description

Technical Field

[0001] This invention belongs to the field of soil remediation, specifically relating to an environmentally friendly and biodegradable modified soil conditioning material and its preparation method. Background Technology

[0002] Soil, as a core component of the Earth's surface ecosystem, is a fundamental resource for maintaining agricultural production, ensuring food security, and supporting ecological balance. It not only provides water, nutrients, air, and a supporting medium for plant growth but also undertakes key ecological functions such as pollutant purification, carbon cycle regulation, and hydrological regulation, serving as a crucial material foundation for the sustainable development of human society. However, under the combined influence of multiple factors such as global population growth, accelerated industrialization, and intensive agricultural production, soil degradation has become increasingly prominent, with soil quality continuously declining. This has become a global challenge restricting high-quality agricultural development and threatening ecological security. Against this backdrop, soil conditioning materials, which can improve soil physicochemical properties, restore soil ecological functions, and enhance soil productivity, have gradually become a research hotspot and application focus in the fields of agricultural production and ecological environmental protection. Their development and application have profound contemporary inevitability and practical urgency. The core value of soil conditioning materials lies in precisely intervening in soil physicochemical properties and ecological functions to improve soil quality and restore soil ecosystems, thereby supporting sustainable agricultural development and ecological environmental security. Soil conditioning materials include various types: (1) Soil pH regulating materials, mainly used to adjust soil pH and improve the physical and chemical properties of acidic or alkaline soils, including lime materials (quicklime, slaked lime), gypsum materials (gypsum, phosphogypsum), humic acid materials, wood ash, etc.; (2) Soil structure improving materials, mainly used to improve soil aggregate structure, enhance soil water and fertilizer retention capacity, and reduce soil erosion, including polymer materials (polyacrylamide, polyvinyl alcohol), natural mineral materials (bentonite, zeolite, diatomaceous earth), organic materials (straw, biochar, peat), etc. These materials can promote soil particle aggregation through physical adsorption, chemical bonding, etc., to form stable soil aggregates and improve soil ventilation. (3) Soil fertility enhancement materials, mainly used to supplement soil organic matter and nutrients, and enhance soil fertility, including organic fertilizer, humic acid fertilizer, amino acid fertilizer, microbial agents, etc. These materials can provide comprehensive nutrients for crop growth, improve the soil microbial environment, promote soil nutrient cycling, and enhance soil sustainable productivity; (4) Soil pollution remediation materials, mainly used to remediate soil pollution such as heavy metal pollution and chemical pesticide pollution, including adsorption materials (biochar, activated carbon, clay minerals) and microbial remediation materials, etc. These materials can reduce the bioavailability of pollutants in the soil through adsorption, chelation, degradation, oxidation-reduction and other effects, and reduce the harm of pollutants to the ecological environment and human health.

[0003] Patent CN112552921A discloses a soil remediation material, preparation method, and soil remediation method for heavy metal contaminated soil. This invention uses coal gangue and red mud as raw materials, oxidizing them with hydrogen peroxide and then adding quicklime for grinding to obtain a soil remediation material for heavy metal contamination. Although coal gangue and red mud are industrial wastes containing various pollutants and cannot be directly used for soil remediation, they can be modified to achieve resource utilization and reduce their environmental pollution. Patent CN116376558A discloses a composition and soil remediation agent for soil remediation and their applications. The core components of this invention consist of a composition of organosilicon polymers and nonionic surfactants, along with a stabilizing agent. The composition enhances the diffusion of the stabilizing agent, thereby increasing its reaction with heavy metals and achieving the remediation of heavy metal-contaminated soil. Soil remediation materials composed of a mixture of organic and inorganic materials have better remediation effects than conventional minerals and industrial waste. However, because organic materials often contain non-degradable components, they can easily pollute groundwater over time, causing ecological harm.

[0004] Therefore, developing an environmentally friendly and biodegradable material for soil conditioning and remediation is one of the important goals in many fields such as soil pollution control, ecological protection, and sustainable agricultural development. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention pre-treats carbon materials to adsorb and immobilize mixed bacterial strains, then impregnates them in a modified polylactic acid emulsion, and finally removes and solidifies them. This yields a modified soil conditioner that improves soil water absorption and retention capacity, is environmentally friendly and biodegradable, and reduces the harmful effects of heavy metal ions in the soil, thus solving the technical problems mentioned in the background art. Specifically, the technical solution of this invention includes the following: One objective of this invention is to provide a method for preparing an environmentally friendly and biodegradable modified soil conditioner, the method comprising the following steps: Pretreated carbon material and mixed bacterial strains were mixed at a weight ratio of 1:14~20 and adsorbed at 20℃~25℃ for 24h~30h to obtain bacterial-loaded pretreated carbon material; The pretreated carbon material and modified polylactic acid emulsion were mixed at a weight ratio of 1:8~11 and impregnated at 30°C for 5 min~10 min. The filter cake was then filtered and dried under reduced pressure to obtain the modified soil conditioning material.

[0006] Furthermore, the preparation method of the pretreated carbon material includes the following steps: Carbon material, dopamine hydrochloride, and deionized water are mixed in a weight ratio of 1:4~5:200~300, and the pH is adjusted to 8.5~9.0. The mixture is then heated to 40℃~50℃ and reacted for 6h~7h to obtain a carbon material@polydopamine dispersion. A carbon material@polydopamine dispersion was irradiated and then precipitated by adding organic reagents. The precipitate is kept at 350℃~450℃ for 1h~2h to obtain the pretreated carbon material.

[0007] Furthermore, the carbon material includes graphene oxide.

[0008] Furthermore, the average particle size of the graphene oxide is 20 μm to 30 μm.

[0009] Furthermore, the irradiation treatment conditions include a cobalt-60 radiation source, a radiation dose rate of 50 Gy / min, and a radiation dose of 15,000 Gy to 30,000 Gy.

[0010] Furthermore, the organic reagent includes anhydrous acetone.

[0011] Furthermore, the mixed strain is derived from OD 600 Serratia marcescens bacterial suspension with an OD of 0.7-0.8 600 The Pseudomonas bacterial suspension and OD were 0.7-0.8. 600 The Burkholderia bacterial suspension with a concentration of 0.7-0.8 was composed of a weight ratio of 0.5-0.6:1:0.5-0.7.

[0012] Furthermore, the strain number of Serratia used in the Serratia bacterial solution is CICC 23005, the strain number of Pseudomonas used in the Pseudomonas bacterial solution is CICC 20677, and the strain number of Burkholderia used in the Burkholderia bacterial solution is CICC 24715.

[0013] Furthermore, the preparation method of the modified polylactic acid emulsion includes the following steps: Polylactic acid (PLA) at a discharge power of 400W~500W and an argon flow rate of 60cm³ 3 / min~80cm 3 Pretreated polylactic acid was obtained by processing it in a plasma processor with a flow rate of 3 to 4 minutes per minute for 3 to 4 minutes. The modified polylactic acid emulsion is obtained by mixing pretreated polylactic acid, dichloromethane and phospholipid derivatives and reacting them at 20℃~25℃ for 5h~6h, then adding water and emulsifier and mixing.

[0014] Furthermore, the polylactic acid has a weight-average molecular weight of 40,000 to 60,000.

[0015] Furthermore, the phospholipid derivative includes 1,2-dioleoyl-sn-glycerol-3-phosphate ethanolamine.

[0016] Furthermore, the emulsifier includes Tween 20 or Tween 40.

[0017] Further, the weight ratio of the pretreated polylactic acid, dichloromethane, phospholipid derivative, water and emulsifier is 1:60~80:0.04~0.07:120~160:0.2~0.3.

[0018] Furthermore, the conditions for vacuum drying include a vacuum degree of 0.01 MPa, a temperature of 25°C, and a drying time of 1 hour.

[0019] The second objective of this invention is to provide an environmentally friendly and biodegradable modified soil conditioning material.

[0020] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention uses a mixed bacterial strain composed of *Serratia marcescens*, *Pseudomonas*, and *Burkholderia*, which are known to reduce heavy metal toxicity. The strain is then immobilized using the adsorption properties of carbon materials. Finally, biodegradable polylactic acid (PLA) is used to further encapsulate and protect the strain, mitigating the adverse effects of the strain entering the soil in a free state and thus inhibiting or even destroying its activity, reducing microbial loss, and improving erosion resistance. This results in a modified soil conditioner that enhances soil water absorption and retention capacity, is environmentally friendly and biodegradable, and reduces heavy metal pollution in the soil. However, in practical applications, it was found that the hydrophobic nature of PLA results in poor water absorption and retention capacity in the soil. Therefore, the hydrophilic carbon material graphene oxide is used to adsorb and immobilize the bacterial strain. However, the effect on reducing heavy metal pollution in soil was found to be poor. This may be due to the antibacterial effect of the physical structure of graphene oxide itself, which has a certain degree of inhibitory effect on bacterial strains. Therefore, after surface etching of dispersed graphene oxide, the dispersion carrier was removed by high-temperature calcination to obtain pretreated carbon material. On the one hand, the sharp edge structure of antibacterial effect was achieved by physically cutting the graphene oxide through destruction; on the other hand, the etching increased the porosity and improved the bacterial loading capacity, thereby improving the ability to treat heavy metal ions. However, due to the destruction of the surface structure of the etched pretreated graphene oxide, the hydrophilic groups were partially destroyed, resulting in poor improvement in hydrophilicity. Therefore, a phospholipid derivative with a hydrophobic-hydrophilic structure was grafted onto the polylactic acid structure through carbon-carbon double bonds at the hydrophobic end, exposing the hydrophilic end, to obtain a modified polylactic acid emulsion with good hydrophilicity. When solidified, this emulsion can improve the porosity and facilitate microbial degradation. Through the synergistic effect of graphene oxide and modified polylactic acid, the water absorption and retention capacity in the soil is increased. Pretreated carbon material with adsorption and fixation of mixed bacterial strains was impregnated in modified polylactic acid emulsion, and then removed and solidified to obtain a modified soil conditioner material that improves soil water absorption and retention capacity, is environmentally friendly and biodegradable, and reduces the harm of heavy metal ions in the soil. Detailed Implementation

[0021] The technical solution of the present invention will be clearly and completely described below through embodiments. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0022] Unless otherwise stated, all raw materials and reagents used in this invention are commercially available or can be prepared by known methods.

[0023] Preparation Example 1 The preparation process of pretreated carbon materials is as follows: Ten parts by weight of graphene oxide carbon with an average particle size of 20 μm were added to 2000 parts by weight of deionized water and stirred at 800 rpm to disperse it evenly. Then, 40 parts by weight of dopamine hydrochloride were added and stirred until completely dissolved. The pH was adjusted to 8.5 with ammonia. After pH adjustment, the mixture was transferred to a water bath and heated to 40°C. The reaction was carried out at 100 rpm for 7 hours to obtain a carbon material@polydopamine dispersion. The carbon material@polydopamine dispersion was transferred to a radiation device with a cobalt-60 radiation source, and the radiation dose rate was adjusted to 50 Gy / min, with the radiation dose controlled at 15000 Gy. After the irradiation treatment was completed, the mixture was removed and an equal amount of anhydrous acetone was added and mixed evenly. The mixture was allowed to settle for 30 minutes. The precipitate was then separated by centrifugation at 1000 rpm. The precipitate was washed with deionized water and dried in a vacuum drying oven at 110°C for 12 hours. The dried precipitate was transferred to a muffle furnace and heated to 350°C at a rate of 5°C / min in air atmosphere. It was then held at this temperature for 2 hours to induce the oxidative pyrolysis of polydopamine. After pyrolysis, the surface residue was removed by sequential rinsing with anhydrous ethanol and deionized water. Finally, the material was dried in a vacuum drying oven at 50°C to remove moisture, yielding the pretreated carbon material.

[0024] Preparation Example 2 The preparation process of pretreated carbon materials is as follows: Ten parts by weight of graphene oxide carbon with an average particle size of 20 μm were added to 2000 parts by weight of deionized water and stirred at 800 rpm to disperse it evenly. Then, 45 parts by weight of dopamine hydrochloride were added and stirred until completely dissolved. The pH was adjusted to 8.5 with ammonia. After pH adjustment, the mixture was transferred to a water bath and heated to 45°C. The mixture was stirred at 100 rpm for 7 hours at this temperature to obtain a carbon material@polydopamine dispersion. The carbon material@polydopamine dispersion was transferred to a radiation device with a cobalt-60 radiation source, and the radiation dose rate was adjusted to 50 Gy / min, with the radiation dose controlled at 20000 Gy. After the irradiation treatment was completed, the mixture was removed and an equal amount of anhydrous acetone was added and mixed evenly. The mixture was allowed to settle for 30 minutes. The precipitate was then separated by centrifugation at 1000 rpm. The precipitate was washed with deionized water and dried in a vacuum drying oven at 110°C for 12 hours. The dried precipitate was transferred to a muffle furnace and heated to 400°C at a rate of 5°C / min in air atmosphere. It was then held at this temperature for 2 hours to induce the oxidative pyrolysis of polydopamine. After pyrolysis, the surface residue was removed by sequential rinsing with anhydrous ethanol and deionized water. Finally, the material was dried in a vacuum drying oven at 50°C to remove moisture, yielding the pretreated carbon material.

[0025] Preparation Example 3 The preparation process of pretreated carbon materials is as follows: Ten parts by weight of graphene oxide carbon with an average particle size of 30 μm were added to 2500 parts by weight of deionized water and stirred at 800 rpm to disperse it evenly. Then, 45 parts by weight of dopamine hydrochloride were added and stirred until completely dissolved. The pH was adjusted to 9.0 with ammonia. After pH adjustment, the mixture was transferred to a water bath and heated to 50°C. The reaction was carried out at 100 rpm for 6.5 h to obtain a carbon material@polydopamine dispersion. The carbon material@polydopamine dispersion was transferred to a cobalt-60 radiation device, and the radiation dose rate was adjusted to 50 Gy / min, with the radiation dose controlled at 25000 Gy. After the irradiation treatment was completed, the mixture was removed and an equal amount of anhydrous acetone was added and mixed evenly. The mixture was allowed to settle for 30 min. The precipitate was then separated by centrifugation at 1000 rpm. The precipitate was washed with deionized water and dried in a vacuum drying oven at 110°C for 12 h. The dried precipitate was transferred to a muffle furnace and heated to 400°C at a rate of 5°C / min in air atmosphere. It was then held at this temperature for 1.5 hours to induce the oxidative pyrolysis of polydopamine. After pyrolysis, the surface residue was removed by sequential rinsing with anhydrous ethanol and deionized water. Finally, the material was dried in a vacuum drying oven at 50°C to remove moisture, yielding the pretreated carbon material.

[0026] Preparation Example 4 The preparation process of pretreated carbon materials is as follows: Ten parts by weight of graphene oxide carbon with an average particle size of 30 μm were added to 3000 parts by weight of deionized water and stirred at 800 rpm to disperse it evenly. Then, 50 parts by weight of dopamine hydrochloride were added and stirred until completely dissolved. The pH was adjusted to 9.0 with ammonia. After pH adjustment, the mixture was transferred to a water bath and heated to 50°C. The reaction was carried out at 100 rpm for 6 hours to obtain a carbon material@polydopamine dispersion. The carbon material@polydopamine dispersion was transferred to a radiation device with a cobalt-60 radiation source, and the radiation dose rate was adjusted to 50 Gy / min, with the radiation dose controlled at 30000 Gy. After the irradiation treatment was completed, the mixture was removed and an equal amount of anhydrous acetone was added and mixed evenly. The mixture was allowed to settle for 30 minutes. The precipitate was then separated by centrifugation at 1000 rpm. The precipitate was washed with deionized water and dried in a vacuum drying oven at 110°C for 12 hours. The dried precipitate was transferred to a muffle furnace and heated to 450°C at a rate of 5°C / min in air atmosphere. It was then held at this temperature for 1 hour to induce the oxidative pyrolysis of polydopamine. After pyrolysis, the surface residue was removed by sequential rinsing with anhydrous ethanol and deionized water. Finally, the material was dried in a vacuum drying oven at 50°C to remove moisture, yielding the pretreated carbon material.

[0027] Preparation Example 5 The preparation process of pretreated carbon materials is as follows: Ten parts by weight of graphene oxide carbon with an average particle size of 30 μm were added to 3000 parts by weight of deionized water and dispersed in a 400W ultrasonic disperser for 20 min to obtain a carbon material dispersion. The carbon material dispersion was transferred to a radiation device with a cobalt-60 radiation source, and the radiation dose rate was adjusted to 50 Gy / min, with the radiation dose controlled at 30000 Gy. After the irradiation treatment was completed, the filter cake was collected by vacuum filtration and dried in a vacuum drying oven at 50℃ to remove water, thus obtaining the pretreated carbon material.

[0028] Preparation Example 6 The preparation process of pretreated carbon materials is as follows: The graphene oxide in Preparation Example 4 was replaced with graphene oxide with an average particle size of 100 nm, and the rest of the preparation process was the same as in Preparation Example 4.

[0029] Preparation Example 7 The preparation process of pretreated carbon materials is as follows: The radiation dose in Preparation Example 4 was increased to 40,000, while the rest of the preparation process remained the same as in Preparation Example 4.

[0030] Preparation Example 8 The preparation process of the mixed strain is as follows: Serratia marcescens strain CICC 23005, Pseudomonas aeruginosa strain CICC 20677, and Burkholderia burkholderia strain CICC 24715 were cultured to OD values ​​of [missing information]. 600 The culture solution was brought to a concentration of 0.7-0.8. Then, the cultured Serratia marcescens, Pseudomonas aeruginosa, and Burkholderia burkholderia cultures were mixed at a ratio of 0.5:1:0.5 and stored in a refrigerator at 5°C for later use.

[0031] Preparation Example 9 The preparation process of the mixed strain is as follows: Serratia marcescens strain CICC 23005, Pseudomonas aeruginosa strain CICC 20677, and Burkholderia burkholderia strain CICC 24715 were cultured to OD values ​​of [missing information]. 600 The culture solution was brought to a concentration of 0.7-0.8. Then, the cultured Serratia marcescens, Pseudomonas aeruginosa, and Burkholderia burkholderia cultures were mixed at a ratio of 0.6:1:0.7 and stored in a refrigerator at 5°C for later use.

[0032] Preparation Example 10 The preparation process of the mixed strain is as follows: Serratia marcescens strain CICC 23005, Pseudomonas aeruginosa strain CICC 20677, and Burkholderia burkholderia strain CICC 24715 were cultured to OD values ​​of [missing information]. 600 The culture solution was brought to a concentration of 0.7-0.8. Then, the cultured Serratia marcescens, Pseudomonas aeruginosa, and Burkholderia burkholderia cultures were mixed at a ratio of 0.2:1:0.3 and stored in a refrigerator at 5°C for later use.

[0033] Preparation Example 11 The preparation process of modified polylactic acid emulsion is as follows: Polylactic acid (PLA) with a weight-average molecular weight of 40,000 was immersed in anhydrous acetone and cleaned with ultrasonic power at 200W for 20 minutes. Then, the anhydrous acetone was replaced with deionized water, and the PLA was cleaned with ultrasonic power at 200W for another 20 minutes. After cleaning, the PLA was removed and placed in a vacuum drying oven at 50℃ to remove moisture before use. The cleaned PLA was then placed in the reaction chamber of the plasma processor, and the air in the reaction chamber was purged with argon gas. The argon gas flow rate was adjusted to 60 cm³. 3The process was initiated at 400W / min, and the plasma processor's discharge power was adjusted to 400W. The plasma was then processed at this power for 3 minutes. After processing, the pretreated polylactic acid was stored in an argon atmosphere. The air inside the reactor was replaced with argon, and the reactor temperature was controlled at 20°C using a temperature control system. One part by weight of the pretreated polylactic acid was then transferred to the reactor, followed by the addition of 60 parts by weight of dichloromethane. The mixture was stirred until the pretreated polylactic acid dissolved. Then, 0.04 parts by weight of 1,2-dioleoyl-sn-glycerol-3-phosphate ethanolamine was added and stirred at 200 rpm for 5 hours. After the reaction, the mixture was removed and placed in a high-speed mixer. 120 parts by weight of deionized water and 0.2 parts by weight of Tween 20 were added and mixed at 8000 rpm for 10 minutes to obtain a modified polylactic acid emulsion.

[0034] Preparation Example 12 The preparation process of modified polylactic acid emulsion is as follows: Polylactic acid (PLA) with a weight-average molecular weight of 40,000 was immersed in anhydrous acetone and cleaned with ultrasonic power at 200W for 20 minutes. Then, the anhydrous acetone was replaced with deionized water, and the PLA was cleaned with ultrasonic power at 200W for another 20 minutes. After cleaning, the PLA was removed and placed in a vacuum drying oven at 50℃ to remove moisture before use. The cleaned PLA was then placed in the reaction chamber of the plasma processor, and the air in the reaction chamber was purged with argon gas. The argon gas flow rate was adjusted to 60 cm³. 3 At a speed of 100 rpm, the switch was turned on, and the discharge power of the plasma processor was adjusted to 450 W. The plasma was then processed at this power for 3 minutes. After processing, the pretreated polylactic acid was stored in an argon atmosphere. The air inside the reactor was replaced with argon, and the temperature of the reactor was controlled at 20°C using a temperature control system. One part by weight of the pretreated polylactic acid was then transferred to the reactor, and 70 parts by weight of dichloromethane were added and stirred until the pretreated polylactic acid dissolved. Then, 0.05 parts by weight of 1,2-dioleoyl-sn-glycerol-3-phosphate ethanolamine were added and stirred at 200 rpm for 5 hours. After the reaction, the mixture was removed and placed in a high-speed mixer. 140 parts by weight of deionized water and 0.2 parts by weight of Tween 20 were added and mixed at 8000 rpm for 10 minutes to obtain a modified polylactic acid emulsion.

[0035] Preparation Example 13 The preparation process of modified polylactic acid emulsion is as follows: Polylactic acid (PLA) with a weight-average molecular weight of 60,000 was immersed in anhydrous acetone and cleaned with ultrasonic power at 200W for 20 minutes. Then, the anhydrous acetone was replaced with deionized water, and the PLA was cleaned with ultrasonic power at 200W for another 20 minutes. After cleaning, the PLA was removed and placed in a vacuum drying oven at 50℃ to remove moisture before use. The cleaned PLA was then placed in the reaction chamber of the plasma processor, and the air in the reaction chamber was purged with argon gas. The argon gas flow rate was adjusted to 70 cm³. 3 The plasma processor was turned on at 450W and the discharge power was adjusted to 4min. The plasma was then processed at this power for 4min. After processing, the pretreated polylactic acid was stored in an argon atmosphere. The air inside the reactor was replaced with argon, and the temperature of the reactor was controlled at 25℃ using a temperature control system. One part by weight of the pretreated polylactic acid was then transferred to the reactor, and 70 parts by weight of dichloromethane were added and stirred until the pretreated polylactic acid dissolved. Then, 0.06 parts by weight of 1,2-dioleoyl-sn-glycerol-3-phosphate ethanolamine were added and stirred at 200r / min for 5.5h. After the reaction, the mixture was removed and placed in a high-speed mixer. 160 parts by weight of deionized water and 0.25 parts by weight of Tween 40 were added and mixed at 8000r / min for 10min to obtain a modified polylactic acid emulsion.

[0036] Preparation Example 14 The preparation process of modified polylactic acid emulsion is as follows: Polylactic acid (PLA) with a weight-average molecular weight of 60,000 was immersed in anhydrous acetone and cleaned with ultrasonic power at 200W for 20 minutes. Then, the anhydrous acetone was replaced with deionized water, and the PLA was cleaned with ultrasonic power at 200W for another 20 minutes. After cleaning, the PLA was removed and placed in a vacuum drying oven at 50℃ to remove moisture before use. The cleaned PLA was then placed in the reaction chamber of a plasma processor, and the air in the reaction chamber was purged with argon gas. The argon gas flow rate was adjusted to 80 cm³ / h. 3 The process was initiated at 500W / min, and the plasma processor's discharge power was adjusted to 500W. The plasma was then processed at this power for 4 minutes. After processing, the pretreated polylactic acid was stored in an argon atmosphere. The air inside the reactor was replaced with argon, and the reactor temperature was controlled at 25°C using a temperature control system. One part by weight of the pretreated polylactic acid was then transferred to the reactor, followed by the addition of 80 parts by weight of dichloromethane. The mixture was stirred until the pretreated polylactic acid dissolved. Then, 0.07 parts by weight of 1,2-dioleoyl-sn-glycerol-3-phosphate ethanolamine was added and stirred at 200 rpm for 6 hours. After the reaction, the mixture was removed and placed in a high-speed mixer. 160 parts by weight of deionized water and 0.3 parts by weight of Tween 40 were added and mixed at 8000 rpm for 10 minutes to obtain a modified polylactic acid emulsion.

[0037] Preparation Example 15 The preparation process of modified polylactic acid emulsion is as follows: In Preparation Example 14, polylactic acid was replaced with polylactic acid with a weight average molecular weight of 80,000, while the rest of the preparation process remained the same as in Preparation Example 14.

[0038] Preparation Example 16 The preparation process of modified polylactic acid emulsion is as follows: In Preparation Example 14, 1,2-dioleoyl-sn-glycerol-3-phosphate ethanolamine was replaced with 1,2-distearate-sn-propanetriyl-3-phosphate choline, while the rest of the preparation process remained the same as in Preparation Example 14.

[0039] Preparation Example 17 The preparation process of polylactic acid emulsion is as follows: Polylactic acid (PLA) with a weight-average molecular weight of 60,000 was immersed in anhydrous acetone and cleaned with ultrasonic power at 200W for 20 minutes. Then, the anhydrous acetone was replaced with deionized water, and the mixture was cleaned with ultrasonic power at 200W for 20 minutes. After cleaning, the PLA was removed and placed in a vacuum drying oven at 50°C to remove moisture. One part by weight of dried PLA and 80 parts by weight of dichloromethane were mixed and stirred until completely dissolved. Then, 160 parts by weight of deionized water and 0.3 parts by weight of Tween 40 were added and mixed at 8000 rpm for 10 minutes to obtain a PLA emulsion. Example 1

[0040] The preparation process of an environmentally friendly and biodegradable modified soil conditioner is as follows: One part by weight of the pretreated carbon material obtained in Preparation Example 1 was mixed with 14 parts by weight of the mixed bacterial strain obtained in Preparation Example 8. The mixture was then stirred and adsorbed at 200 rpm for 30 h at 20 °C to obtain the bacterial-loaded pretreated carbon material. One part by weight of the bacterial-loaded pretreated carbon material was then completely immersed in 8 parts by weight of the modified polylactic acid emulsion obtained in Preparation Example 11. The impregnation temperature was controlled at 30 °C and the impregnation time was 5 min. After impregnation, the filter cake was filtered and dried in an environment with a vacuum degree of 0.01 MPa and a temperature of 25 °C for 1 h to evaporate and remove dichloromethane, thereby obtaining the modified soil conditioner material. Example 2

[0041] The preparation process of an environmentally friendly and biodegradable modified soil conditioner is as follows: One part by weight of the pretreated carbon material obtained in Preparation Example 2 was mixed with 16 parts by weight of the mixed bacterial strain obtained in Preparation Example 8. The mixture was then stirred and adsorbed at 200 rpm for 28 h at 20 °C to obtain the bacterial-loaded pretreated carbon material. One part by weight of the bacterial-loaded pretreated carbon material was then completely immersed in 9 parts by weight of the modified polylactic acid emulsion obtained in Preparation Example 12. The impregnation temperature was then controlled at 30 °C and the impregnation time was 7 min. After impregnation, the filter cake was filtered out and dried in an environment with a vacuum degree of 0.01 MPa and a temperature of 25 °C for 1 h to evaporate and remove dichloromethane, thereby obtaining the modified soil conditioner material. Example 3

[0042] The preparation process of an environmentally friendly and biodegradable modified soil conditioner is as follows: One part by weight of the pretreated carbon material obtained in Preparation Example 3 was mixed with 18 parts by weight of the mixed bacterial strain obtained in Preparation Example 9. The mixture was then stirred and adsorbed at 200 r / min for 26 h at 25 °C to obtain the bacterial-loaded pretreated carbon material. One part by weight of the bacterial-loaded pretreated carbon material was then completely immersed in 10 parts by weight of the modified polylactic acid emulsion obtained in Preparation Example 13. The impregnation temperature was then controlled at 30 °C and the impregnation time was 9 min. After impregnation, the filter cake was filtered and dried in an environment with a vacuum degree of 0.01 MPa and a temperature of 25 °C for 1 h to evaporate and remove dichloromethane, thereby obtaining the modified soil conditioner material. Example 4

[0043] The preparation process of an environmentally friendly and biodegradable modified soil conditioner is as follows: One part by weight of the pretreated carbon material obtained in Preparation Example 4 was mixed with 20 parts by weight of the mixed bacterial strain obtained in Preparation Example 9. The mixture was then stirred and adsorbed at 200 r / min for 24 h at 25 °C to obtain the bacterial-loaded pretreated carbon material. One part by weight of the bacterial-loaded pretreated carbon material was then completely immersed in 11 parts by weight of the modified polylactic acid emulsion obtained in Preparation Example 14. The impregnation temperature was then controlled at 30 °C and the impregnation time was 10 min. After impregnation, the filter cake was filtered out and dried in an environment with a vacuum degree of 0.01 MPa and a temperature of 25 °C for 1 h to evaporate and remove dichloromethane, thereby obtaining the modified soil conditioner material.

[0044] Comparative Example 1 The preparation process of an environmentally friendly and biodegradable modified soil conditioner is as follows: The pretreated carbon material in Example 4 was replaced with the pretreated carbon material obtained in Preparation Example 5, and the rest of the preparation process was the same as in Example 4.

[0045] Comparative Example 2 The preparation process of an environmentally friendly and biodegradable modified soil conditioner is as follows: The pretreated carbon material in Example 4 was replaced with the pretreated carbon material obtained in Preparation Example 6, and the rest of the preparation process was the same as in Example 4.

[0046] Comparative Example 3 The preparation process of an environmentally friendly and biodegradable modified soil conditioner is as follows: The pretreated carbon material in Example 4 was replaced with the pretreated carbon material obtained in Preparation Example 7, and the rest of the preparation process was the same as in Example 4.

[0047] Comparative Example 4 The preparation process of an environmentally friendly and biodegradable modified soil conditioner is as follows: The mixed strain in Example 4 was replaced with the mixed strain obtained in Preparation Example 10, and the rest of the preparation process was the same as in Example 4.

[0048] Comparative Example 5 The preparation process of an environmentally friendly and biodegradable modified soil conditioner is as follows: The modified polylactic acid emulsion in Example 4 was replaced with the modified polylactic acid emulsion obtained in Preparation Example 15, and the rest of the preparation process was the same as in Example 4.

[0049] Comparative Example 6 The preparation process of an environmentally friendly and biodegradable modified soil conditioner is as follows: The modified polylactic acid emulsion in Example 4 was replaced with the modified polylactic acid emulsion obtained in Preparation Example 16, and the rest of the preparation process was the same as in Example 4.

[0050] Comparative Example 7 The preparation process of an environmentally friendly and biodegradable modified soil conditioner is as follows: The modified polylactic acid emulsion in Example 4 was replaced with the polylactic acid emulsion obtained in Preparation Example 17, and the rest of the preparation process was the same as in Example 4.

[0051] Comparative Example 8 The preparation process of an environmentally friendly and biodegradable modified soil conditioner is as follows: The pretreated carbon material in Example 4 was replaced with coconut shell activated carbon obtained through an 80-mesh sieve, and the rest of the preparation process remained the same as in Example 4.

[0052] The water contact angle of water droplets on the surface of the modified soil conditioning materials obtained in Examples 1-4 and Comparative Examples 1-8 was measured using a JC2000A contact angle meter. The results are shown in Table 1 below.

[0053] Table 1 Water contact angle

[0054] Weigh 1g of the modified soil conditioner obtained in Examples 1-4 and Comparative Examples 1-8 and immerse it in 100mL of deionized water for 1h. Then take it out and hang it still until the modified soil conditioner no longer drips water after absorbing water. Weigh it to obtain W1. Calculate the water absorption ratio according to the water absorption ratio = (W1-1) / 1×100%. The results are shown in Table 2 below.

[0055] Table 2 Water Absorption Performance

[0056] The modified soil conditioner material that has been suspended statically was placed in a centrifuge with a speed of 400 r / min for 2 min to dehydrate. Then it was taken out and weighed and recorded as W2. The water retention ratio was calculated according to the formula (W1-W2) / 1×100%. The results are shown in Table 3 below.

[0057] Table 3 Water retention performance

[0058] Prepare a solution with a total volume of 100 mL, pH 4.0, and Cr. 6+ A chromium-containing solution with a mass concentration of 100 mg / L was prepared. Then, 2 g of the modified soil conditioner materials obtained in Examples 1-4 and Comparative Examples 1-8 were weighed and added to the chromium-containing solution. The solution was then shaken at 100 r / min for 2 hours at a constant temperature of 30°C. The solution was then centrifuged, the supernatant was retained, and the remaining Cr content was measured. 6+ The concentration of Cr is denoted as ρ. The removal rate is calculated according to the formula: (100-ρ) / 100×100%. 6+ The removal rate is shown in Table 4 below.

[0059] Table 4 Heavy metal removal performance

[0060] The following conclusions can be drawn from Tables 1-4 above: (1) Through Examples 1-4, it can be found that the prepared modified soil conditioning material has good water absorption and retention capacity, and the treatment effect of heavy metals is good.

[0061] (2) Comparative Example 1 shows that the modified soil conditioning material prepared has a poor effect on treating heavy metals. This may be because when the graphene oxide is treated by ultrasonic dispersion, although the aggregation of graphene oxide can be solved, the stability after ultrasonic dispersion is short. When the graphene oxide is irradiated, it is easy to restore its aggregation, which may result in weak irradiation modification of graphene oxide and weak structural destruction of graphene oxide. This may lead to the inhibition of the activity of mixed strains. On the other hand, the weak irradiation modification of graphene oxide may result in fewer pore structures generated by irradiation of graphene oxide, which is not conducive to the adsorption of mixed strains and ultimately affects the treatment effect of heavy metals.

[0062] (3) Comparative Example 2 shows that the modified soil conditioning material prepared has poor performance in treating heavy metals and water absorption and retention. This may be because although the graphene oxide with a small particle size has a good hydrophilic effect, its aggregation effect is stronger. Under the preparation method of this system, it is difficult to achieve uniform dispersion and encapsulation. This is not only not conducive to the adsorption and activity of mixed strains, but the stronger aggregation effect may also cause the graphene oxide to lose its hydrophilic modification effect. Relying solely on the hydrophilic modification effect of polylactic acid, the water absorption and retention effect is poor.

[0063] (4) Comparative Example 3 shows that the modified soil conditioner prepared has poor performance in treating heavy metals and water absorption and retention. This may be because although irradiation treatment can etch the carbon structure through free radicals and form defective pore structures, which is not only beneficial to improving the adsorption of mixed strains, but also can destroy the complete sheet structure of graphene oxide, so that its antibacterial effect through sheet cutting is effectively weakened, which is beneficial to maintaining the activity of the adsorbed mixed strains. However, excessive irradiation treatment may cause the graphene oxide structure to be over-destroyed and collapse, which may not only lead to loss of hydrophilicity, but also the collapse of the structure is not conducive to the adsorption of mixed strains, thus weakening the performance of the modified soil conditioner.

[0064] (5) Comparative Example 4 shows that the modified soil conditioning material prepared has a poor effect on treating heavy metals. This may be because although Serratia, Pseudomonas and Burkholderia have the effect of weakening the harm of heavy metal ions, the different mixing ratios and preparation methods in this system may lead to the mixed strains being unable to work together to effectively degrade heavy metal ions if the amount of a certain strain in the mixed strain is too high due to the competitive inhibition effect of nutrients.

[0065] (6) Comparative Example 5 shows that the prepared modified soil conditioning material has poor water absorption and retention. This may be because as the molecular weight of polylactic acid increases, the molecular crystallinity is high, and the modification effect of this system may be poor.

[0066] (7) Comparative Example 6 shows that the prepared modified soil conditioner has poor water absorption and retention. This may be because 1,2-distearate-sn-propanetriyl-3-phosphocholine lacks the reactive functional structure of carbon-carbon double bonds compared to 1,2-dioleoyl-sn-glycerol-3-phosphoethanolamine, making it difficult to effectively graft onto polylactic acid to achieve hydrophilic modification, which in turn leads to poor water absorption and retention of the modified soil conditioner.

[0067] (8) Comparative Example 7 shows that the prepared modified soil conditioning material has poor water absorption and retention. This may be due to the hydrophobicity of polylactic acid itself, which reduces the water absorption and retention performance after encapsulation. The effect of single hydrophilic modification by graphene oxide is poor.

[0068] (9) Comparative Example 8 shows that the water absorption and retention effect of the prepared modified soil conditioner is poor. This may be because although activated carbon has a good pore structure and can adsorb and fix mixed strains, on the one hand, it is a hydrophobic material, which is not conducive to improving the hydrophilicity of the material. On the other hand, activated carbon adsorbs water mainly through the capillary effect of the pore structure. The water absorption capacity of the pore structure is limited, which is not conducive to improving the hydrophilic effect of the finally prepared modified soil conditioner, thus resulting in poor water absorption and retention effect.

[0069] The embodiments described above provide a detailed explanation of the technical solutions and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the present invention. Various changes and modifications can be made to the present invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed.

Claims

1. A method for preparing an environmentally friendly and biodegradable modified soil conditioner, characterized in that, The preparation method includes the following steps: Pretreated carbon material and mixed bacterial strains were mixed at a weight ratio of 1:14~20 and adsorbed at 20℃~25℃ for 24h~30h to obtain bacterial-loaded pretreated carbon material; The pretreated carbon material and modified polylactic acid emulsion were mixed at a weight ratio of 1:8~11 and impregnated at 30°C for 5 min~10 min. The filter cake was then filtered and dried under reduced pressure to obtain the modified soil conditioning material.

2. The method for preparing an environmentally friendly and biodegradable modified soil conditioner according to claim 1, characterized in that, The method for preparing the pretreated carbon material includes the following steps: Carbon material, dopamine hydrochloride, and deionized water are mixed in a weight ratio of 1:4~5:200~300, and the pH is adjusted to 8.5~9.

0. The mixture is then heated to 40℃~50℃ and reacted for 6h~7h to obtain a carbon material@polydopamine dispersion. A carbon material@polydopamine dispersion was irradiated and then precipitated by adding organic reagents. The precipitate is kept at 350℃~450℃ for 1h~2h to obtain the pretreated carbon material.

3. The method for preparing an environmentally friendly and biodegradable modified soil conditioner according to claim 2, characterized in that, The carbon material includes graphene oxide.

4. The method for preparing an environmentally friendly and biodegradable modified soil conditioner according to claim 2, characterized in that, The irradiation treatment conditions include a cobalt-60 radiation source, a radiation dose rate of 50 Gy / min, and a radiation dose of 15,000 Gy to 30,000 Gy.

5. The method for preparing an environmentally friendly and biodegradable modified soil conditioner according to claim 1, characterized in that, The mixed strain is derived from OD 600 Serratia marcescens bacterial suspension with an OD of 0.7-0.8 600 The Pseudomonas bacterial suspension and OD were 0.7-0.

8. 600 The Burkholderia bacterial suspension with a concentration of 0.7-0.8 was composed of a weight ratio of 0.5-0.6:1:0.5-0.

7.

6. The method for preparing an environmentally friendly and biodegradable modified soil conditioner according to claim 1, characterized in that, The preparation method of the modified polylactic acid emulsion includes the following steps: Polylactic acid (PLA) at a discharge power of 400W~500W and an argon flow rate of 60cm³ 3 / min~80cm 3 Pretreated polylactic acid was obtained by processing it in a plasma processor with a flow rate of 3 to 4 minutes per minute for 3 to 4 minutes. The modified polylactic acid emulsion is obtained by mixing pretreated polylactic acid, dichloromethane and phospholipid derivatives and reacting them at 20℃~25℃ for 5h~6h, then adding water and emulsifier and mixing.

7. The method for preparing an environmentally friendly and biodegradable modified soil conditioner according to claim 6, characterized in that, The polylactic acid has a weight-average molecular weight of 40,000 to 60,000.

8. The method for preparing an environmentally friendly and biodegradable modified soil conditioner according to claim 6, characterized in that, The phospholipid derivatives include 1,2-dioleoyl-sn-glycerol-3-phosphate ethanolamine.

9. The method for preparing an environmentally friendly and biodegradable modified soil conditioner according to claim 6, characterized in that, The weight ratio of the pretreated polylactic acid, dichloromethane, phospholipid derivative, water and emulsifier is 1:60~80:0.04~0.07:120~160:0.2~0.

3.

10. An environmentally friendly and biodegradable modified soil conditioner, characterized in that, The modified soil conditioner is prepared by any one of the preparation methods of the environmentally friendly and biodegradable modified soil conditioner according to claims 1 to 9.

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