Method for preparing biological fertilizer by using high-purity threonine preparation process

Abstract

The invention discloses a method for preparing a biological fertilizer by using a high-purity threonine preparation process, and relates to the technical field of biological fertilizer preparation, and the method has the advantages that a specific adsorption slow-release agent is prepared, the specific adsorption slow-release agent is prepared from nano-scale hydroxyapatite and polyglutamic acid, and the specific adsorption slow-release agent is prepared from the nano-scale hydroxyapatite and the polyglutamic acid; the nano-scale hydroxyapatite strongly adsorbs threonine, nutrient components such as nitrogen, phosphorus and potassium and trace elements such as iron, zinc and copper in the fermentation waste liquid by virtue of high specific surface area and good adsorption performance, and is gradually degraded along with the action of microorganisms in soil and the change of the surrounding environment of a plant root system in the use process of the biological fertilizer; nutrients are continuously provided for different growth stages of plants, so that resource waste is effectively reduced, long-acting and stable supply of nutritional ingredients is realized, and rapid loss of the nutrients is avoided, so that the utilization rate of the fertilizer is remarkably improved, fermentation waste liquid which is possibly abandoned originally is successfully converted into valuable biological fertilizer resources, and environmental pollution is reduced. And continuous power and solid guarantee are provided for healthy growth of plants.

Description

Technical Field

[0001] The invention relates to the technical field of biofertilizer preparation, and in particular to a method for preparing biofertilizer by utilizing a high-purity threonine preparation process. Background Art

[0002] At a time when agricultural production is constantly developing and environmental protection is increasingly valued, finding efficient and sustainable fertilizer production methods has become a key issue. High-purity threonine is usually prepared by microbial fermentation, which produces a large amount of fermentation waste liquid. These waste liquids contain nutrients such as threonine, nitrogen, phosphorus, potassium, and trace elements such as iron, zinc, and copper, as well as microbial metabolites and other organic substances. However, most of the current biofertilizer preparation methods have limited utilization of the fermentation waste liquid generated in the preparation of high-purity threonine, and a large amount of waste liquid is directly discharged, which not only wastes resources but also increases sewage treatment costs and environmental pressures. The existing technology has certain defects. First, the existing technology often directly discharges the fermentation waste liquid, resulting in a waste of resources and failing to achieve a long-term supply of nutrients. Second, the additives in the existing technology cannot be well combined with the soil, and have poor water retention and air permeability, which is not conducive to the absorption of nutrients by plant roots. Furthermore, the fermentation process of the existing technology has low fermentation efficiency and poor quality of bio-fertilizer. Therefore, we propose a preparation method for preparing bio-fertilizer using a high-purity threonine preparation process. Summary of the invention

[0003] The object of the present invention is to provide a method for preparing bio-fertilizer by utilizing a high-purity threonine preparation process.

[0004] In order to solve the problems raised in the above background technology, the present invention provides the following technical solution: a method for preparing bio-fertilizer using a high-purity threonine preparation process, wherein the method for preparing bio-fertilizer specifically comprises the following steps: Step 1: pretreatment of fermentation waste liquid, collecting fermentation waste liquid generated in the process of preparing high-purity threonine, introducing the waste liquid into a sedimentation tank for natural precipitation, filtering the precipitated waste liquid using a plate and frame filter press after precipitation to obtain clarified waste liquid, and then adding potassium hydroxide to the waste liquid to adjust the pH value; Step 2: preparing a specific adsorption slow-release agent, selecting nano-hydroxyapatite and polyglutamic acid as preparation materials, performing surface activation treatment on the nano-hydroxyapatite, and then stirring and mixing with the polyglutamic acid solution to react, and generating a specific adsorption slow-release agent after the reaction is completed. The material can specifically adsorb threonine, nitrogen, phosphorus, potassium nutrients and trace elements such as iron, zinc, and copper in the waste liquid. During the subsequent use of the bio-fertilizer, the polyglutamic acid in the specific adsorption slow-release agent will gradually degrade, thereby slowly releasing the adsorbed threonine and other nutrients. With the action of microorganisms in the soil and the absorption of plant roots, the release process is continuous and stable, providing a continuous nutrient supply for different stages of plant growth; Step 3, preparing an additive, selecting graphene quantum dots and chitosan as raw materials, functionalizing and modifying the graphene quantum dots to prepare functionalized graphene quantum dots, wherein after the functionalization and modification, the graphene quantum dots have amino active groups on their surfaces, then dissolving chitosan in an acetic acid solution to prepare a chitosan solution, mixing the functionalized graphene quantum dots with the chitosan solution, and reacting them under ultrasound assistance to obtain an additive; Step 4: adding the specific adsorption slow-release agent into a stirring container, then adding the pretreated fermentation waste liquid thereto, and then adding additives to control mixing; Step 5: placing the mixed raw materials in a fermentation device for fermentation treatment. The inner wall of the fermentation device is made of nano-ceramic material to ensure uniform temperature distribution during the fermentation process. During the fermentation process, a mixed gas containing carbon dioxide, oxygen and inert gas is regularly introduced into the fermentation device for fermentation treatment to promote the activity and metabolism of microorganisms. Step 6: After the fermentation is completed, the fermentation liquid is filtered to remove the remaining small solid particles, and filtered using a microporous filter membrane to complete the preparation of the bio-fertilizer.

[0005] As a further solution of the present invention: in the step 1, the natural sedimentation time of the waste liquid in the sedimentation tank is controlled to be 2h-4h, the filtration accuracy of the plate and frame filter press is 20nm-30nm, and potassium hydroxide is added after filtration to adjust the pH value to 8.0-8.5.

[0006] As a further scheme of the present invention: In the step 2, the specific process of surface activation treatment of nano-hydroxyapatite is as follows: the nano-hydroxyapatite is placed in a dilute hydrochloric acid solution with a concentration of 5%-10%, stirred and soaked at 30℃-40℃ for 2h-3h, then repeatedly rinsed with deionized water until neutral, and then dried in an oven at 80℃-100℃ for 3h-4h to complete the surface activation treatment.

[0007] As a further solution of the present invention: in the step 2, the surface activated nano-hydroxyapatite is mixed with the polyglutamic acid solution in a mass ratio of 2.0-2.5:1.0-1.2, and stirred at a temperature of 45°C-55°C for 2.5h-3.5h to generate a specific adsorption sustained-release agent.

[0008] As a further scheme of the present invention: In the step three, the specific process of functionalizing the graphene quantum dots is as follows: dispersing the graphene quantum dots in an ethanol solution, adding 3-aminopropyltriethoxysilane coupling agent, stirring the reaction at 40°C-50°C for 4h-5h, the mass ratio of the silane coupling agent to the graphene quantum dots is 1:5-8, and after the reaction is completed, centrifugation is performed to obtain the functionalized graphene quantum dots, and the unreacted silane coupling agent is removed by washing with ethanol, and then dried in a vacuum drying oven at 60°C-80°C for 2h-3h.

[0009] As a further scheme of the present invention: in the step three, chitosan is dissolved in an acetic acid solution, the mass fraction of the prepared chitosan solution is controlled to be 10%-15%, and the functionalized graphene quantum dots are mixed with the chitosan solution in a mass ratio of 1:3.0-3.6, the ultrasonic frequency is 40kHz-60kHz, the power is 800W-1200W, and the reaction time is 1h-2h.

[0010] As a further solution of the present invention: in the step 4, after adding the additive, the stirring speed is controlled to be 45r / min-55r / min, and the stirring time is 25min-35min.

[0011] As a further scheme of the present invention: in the step five, the fermentation treatment in the fermentation device is controlled at a temperature of 38°C-48°C and a humidity of 60%-70%. During the fermentation process, a mixed gas is introduced into the fermentation device every 6h-8h. The mixed gas contains carbon dioxide, oxygen and nitrogen. The volume fraction of carbon dioxide in the mixed gas is 10%-15%, the volume fraction of oxygen is 20%-25%, and the rest is nitrogen. The fermentation time is 7 days to 9 days.

[0012] As a further solution of the present invention: in step six, the filtration accuracy of the microporous filtration membrane is 0.1 μm-0.2 μm.

[0013] By adopting the above technical solution, compared with the prior art, the beneficial effects of the present invention are: 1. The present invention prepares a specific adsorption sustained-release agent, which is composed of nano-hydroxyapatite and polyglutamic acid. The nano-hydroxyapatite strongly adsorbs threonine, nitrogen, phosphorus, potassium and other nutrients and trace elements such as iron, zinc and copper in the fermentation waste liquid by virtue of its high specific surface area and good adsorption performance. During the use of the bio-fertilizer, it gradually degrades with the action of microorganisms in the soil and changes in the environment around the plant root system, and continuously provides nutrients for the different growth stages of the plant. This method not only effectively reduces the waste of resources, but also realizes the long-term and stable supply of nutrients, avoids the rapid loss of nutrients, and thus significantly improves the utilization rate of the fertilizer, successfully converts the fermentation waste liquid that may have been discarded into a valuable bio-fertilizer resource, and provides a continuous driving force and a solid guarantee for the healthy growth of plants; 2. The present invention selects graphene quantum dots and chitosan as raw materials for preparing additives. First, after the graphene quantum dots are functionalized, they have amino active groups on their surface, which enables them to be tightly combined with substances in the soil, greatly enhancing the stability of the soil structure. Chitosan is dissolved in an acetic acid solution and reacts with the functionalized graphene quantum dots under the assistance of ultrasound. The ultrasonic treatment can promote full contact and rapid reaction between molecules, making the two more closely combined. This additive can significantly enhance the water retention and air permeability of the soil, creating an extremely suitable growth environment for plant roots. The functionalized graphene quantum dots can efficiently promote the absorption of nutrients by plant roots, while stimulating the activity of microorganisms in the soil. It synergizes with the specific adsorption slow-release agent to provide rich nutrition for plants, effectively promoting the growth and development of plants. 3. The present invention adopts a mixed gas containing carbon dioxide, oxygen and nitrogen in the fermentation process. Carbon dioxide provides a carbon source for the microorganisms in the fermentation process, promotes their growth and metabolic activities, and accelerates the decomposition and conversion of raw materials. The presence of oxygen maintains the respiration of the microorganisms, ensures their activity, enables them to better participate in the fermentation reaction, and promotes the generation and conversion of nutrients. Nitrogen, as an inert gas, stabilizes the fermentation environment and prevents adverse reactions such as excessive oxidation. The nano-ceramic material on the inner wall of the fermentation device ensures uniform temperature distribution, and works together with the mixed gas to promote the activity and metabolism of microorganisms, improve fermentation efficiency and bio-fertilizer quality, and provide a better nutrient source for plant growth. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 A schematic diagram of the method steps in an embodiment of the present invention; Figure 2 This is a schematic diagram of plant growth indicator data in an embodiment of the present invention; Figure 3 This is a schematic diagram of soil improvement index data in an embodiment of the present invention; Figure 4Schematic diagram of the sustained-release index (nitrogen content) of nutrients in the embodiments of the present invention. DETAILED DESCRIPTION

[0015] The specific embodiments of the present invention will be further described below in conjunction with the accompanying drawings. It should be noted that the description of these embodiments is used to help understand the present invention, but does not constitute a limitation of the present invention.

[0016] In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0017] Please see attached Figure 1 -Attached Figure 4 The present invention provides a method for preparing bio-fertilizer by using a high-purity threonine preparation process. The method for preparing bio-fertilizer specifically comprises the following steps: Step 1: pretreatment of fermentation waste liquid, collecting fermentation waste liquid generated in the process of preparing high-purity threonine, introducing the waste liquid into a sedimentation tank for natural precipitation, filtering the precipitated waste liquid using a plate and frame filter press after precipitation to obtain clarified waste liquid, and then adding potassium hydroxide to the waste liquid to adjust the pH value; Step 2: preparing a specific adsorption slow-release agent, selecting nano-hydroxyapatite and polyglutamic acid as preparation materials, performing surface activation treatment on the nano-hydroxyapatite, and then stirring and mixing with the polyglutamic acid solution to react, and generating a specific adsorption slow-release agent after the reaction is completed. The material can specifically adsorb threonine, nitrogen, phosphorus, potassium nutrients and trace elements such as iron, zinc, and copper in the waste liquid. During the subsequent use of the bio-fertilizer, the polyglutamic acid in the specific adsorption slow-release agent will gradually degrade, thereby slowly releasing the adsorbed threonine and other nutrients. With the action of microorganisms in the soil and the absorption of plant roots, the release process is continuous and stable, providing a continuous nutrient supply for different stages of plant growth; Step 3, preparing an additive, selecting graphene quantum dots and chitosan as raw materials, functionalizing and modifying the graphene quantum dots to prepare functionalized graphene quantum dots, wherein after the functionalization and modification, the graphene quantum dots have amino active groups on their surfaces, then dissolving chitosan in an acetic acid solution to prepare a chitosan solution, mixing the functionalized graphene quantum dots with the chitosan solution, and reacting them under ultrasound assistance to obtain an additive; Step 4: adding the specific adsorption slow-release agent into a stirring container, then adding the pretreated fermentation waste liquid thereto, and then adding additives to control mixing; Step 5: placing the mixed raw materials in a fermentation device for fermentation treatment. The inner wall of the fermentation device is made of nano-ceramic material to ensure uniform temperature distribution during the fermentation process. During the fermentation process, a mixed gas containing carbon dioxide, oxygen and inert gas is regularly introduced into the fermentation device for fermentation treatment to promote the activity and metabolism of microorganisms. Step 6: After the fermentation is completed, the fermentation liquid is filtered to remove the remaining small solid particles, and filtered using a microporous filter membrane to complete the preparation of the bio-fertilizer.

[0018] In one embodiment of the present invention: in step 1, the natural sedimentation time of the waste liquid in the sedimentation tank is controlled to be 2h-4h, the filtration accuracy of the plate and frame filter press is 20nm-30nm, and potassium hydroxide is added after filtration to adjust the pH value to 8.0-8.5.

[0019] In one embodiment of the present invention: In step 2, the specific process of surface activation treatment of nano-hydroxyapatite is as follows: the nano-hydroxyapatite is placed in a dilute hydrochloric acid solution with a concentration of 5%-10%, stirred and soaked at 30℃-40℃ for 2h-3h, then repeatedly rinsed with deionized water until neutral, and then dried in an oven at 80℃-100℃ for 3h-4h to complete the surface activation treatment.

[0020] In one embodiment of the present invention: in step 2, the surface activated nano-hydroxyapatite is mixed with the polyglutamic acid solution in a mass ratio of 2.0-2.5:1.0-1.2, and stirred at a temperature of 45°C-55°C for 2.5h-3.5h to generate a specific adsorption sustained-release agent.

[0021] In one embodiment of the present invention: in step three, the specific process of functional modification of graphene quantum dots is: disperse the graphene quantum dots in an ethanol solution, add 3-aminopropyltriethoxysilane coupling agent, stir the reaction at 40°C-50°C for 4h-5h, the mass ratio of silane coupling agent to graphene quantum dots is 1:5-8, after the reaction is completed, centrifuge to obtain functionalized graphene quantum dots, wash with ethanol to remove unreacted silane coupling agent, and then dry in a vacuum drying oven at 60°C-80°C for 2h-3h.

[0022] In one embodiment of the present invention: in step three, chitosan is dissolved in acetic acid solution, the mass fraction of the prepared chitosan solution is controlled to be 10%-15%, and the functionalized graphene quantum dots are mixed with the chitosan solution in a mass ratio of 1:3.0-3.6, the ultrasonic frequency is 40kHz-60kHz, the power is 800W-1200W, and the reaction time is 1h-2h.

[0023] In one embodiment of the present invention: in step 4, after adding the additive, the stirring speed is controlled to be 45r / min-55r / min, and the stirring time is 25min-35min.

[0024] In one embodiment of the present invention: in step five, the fermentation treatment in the fermentation device is controlled at a temperature of 38°C-48°C and a humidity of 60%-70%. During the fermentation process, a mixed gas is introduced into the fermentation device every 6h-8h. The mixed gas contains carbon dioxide, oxygen and nitrogen. The volume fraction of carbon dioxide in the mixed gas is 10%-15%, the volume fraction of oxygen is 20%-25%, and the rest is nitrogen. The fermentation time is 7 days to 9 days.

[0025] In one embodiment of the present invention: in step six, the filtration accuracy of the microporous filtration membrane is 0.1 μm-0.2 μm.

[0026] Example 1, please refer to the attached Figure 1 -Attached Figure 4, collect the fermentation waste liquid generated during the preparation of high-purity threonine, introduce it into the sedimentation tank for natural precipitation for 4 hours, filter it with a plate and frame filter press after precipitation, the filtration accuracy is 20nm, and potassium hydroxide is added after filtration to adjust the pH value to 8.0 to complete the preliminary waste liquid pretreatment, and then prepare to prepare the specific adsorption sustained-release agent, select nano-hydroxyapatite, place it in a 10% dilute hydrochloric acid solution, and then stir and soak it at a temperature of 40°C for 3 hours, then rinse it with deionized water until neutral, and then place it in a 100°C oven to dry for 4 hours, and then stir it with polyglutamic acid solution at a mass ratio of 2.5:1.0 at a temperature of 55°C for 3.5 hours to complete the preparation of the specific adsorption sustained-release agent, and then prepare to prepare the additive, firstly modify the function of graphene quantum dots, select graphene quantum dots and disperse them in an ethanol solution, and then add 3-aminopropyltriethoxysilane as a coupling agent, stir and react at a temperature of 50°C for 5 hours, the mass ratio of silane coupling agent to graphene quantum dots is 1:5, and then centrifuge and wash with ethanol The unreacted silane coupling agent was removed, and the mixture was placed in a vacuum drying oven at 80°C for 3 hours to obtain functionalized graphene quantum dots. Chitosan was then dissolved in an acetic acid solution to prepare a 15% chitosan solution, which was then reacted with the functionalized graphene quantum dots at a mass ratio of 1:3 under ultrasound for 2 hours to obtain an additive. The ultrasonic frequency was 60kHz and the power was 1000W. Subsequently, the specific adsorption sustained-release agent was added to the stirring container, and the collected pretreated waste liquid was added thereto, and the additive was slowly added. The mixture was stirred at a speed of 55r / min for 35 minutes. The mixed raw materials were then placed in a fermentation device with an inner wall of nano-ceramic material, and fermented at a temperature of 45°C and a humidity of 70%. A mixed gas containing 15% carbon dioxide, 25% oxygen, and the rest nitrogen was introduced every 8 hours. The fermentation time was 9 days. After the fermentation was completed, it was filtered with a microporous filter membrane with a pore size of 0.2μm to remove residual small solid particles and complete the preparation of bio-fertilizer.

[0027] Example 2, please refer to the attached Figure 1 -Attached Figure 4, collect the fermentation waste liquid generated during the preparation of high-purity threonine, introduce it into the sedimentation tank for natural precipitation for 4 hours, filter it with a plate and frame filter press after precipitation, the filtration accuracy is 20nm, and potassium hydroxide is added after filtration to adjust the pH value to 8.0 to complete the preliminary waste liquid pretreatment, and then prepare to prepare the specific adsorption sustained-release agent, select activated alumina, place it in a 10% sulfuric acid solution, and then stir and soak it at a temperature of 40°C for 3 hours, then rinse it with deionized water until neutral, and then place it in a 100°C oven to dry for 4 hours, and then stir it with polyglutamic acid solution at a mass ratio of 2.5:1.0 at a temperature of 55°C for 3.5 hours to complete the preparation of the specific adsorption sustained-release agent, and then prepare to prepare the additive, firstly modify the function of graphene quantum dots, select graphene quantum dots and disperse them in an ethanol solution, and then add dimethyldiethoxysilane as a coupling agent, stir and react at a temperature of 50°C for 5 hours, the mass ratio of silane coupling agent to graphene quantum dots is 1:5, and then centrifuge and wash with ethanol to remove unreacted silane coupling agent. agent, and then placed it in a vacuum drying oven at 80°C for 3h to obtain functionalized graphene quantum dots, and then chitosan was dissolved in acetic acid solution to prepare a 15% chitosan solution, and then it was reacted under ultrasound for 2h to obtain an additive, the ultrasonic frequency was 60kHz, the power was 1000W, and then the functionalized graphene quantum dots and the chitosan solution were mixed in a mass ratio of 1:3, and then the specific adsorption sustained-release agent was added to the stirring container, and then the collected pretreated waste liquid was added thereto, and then the additive was slowly added, and stirred at a speed of 55r / min for 35min, and then the mixed raw materials were placed in a fermentation device with an inner wall of nanoceramic material, and fermented at a temperature of 45°C and a humidity of 70%. A mixed gas containing 15% carbon dioxide, 25% oxygen, and the rest nitrogen was introduced every 8h, and the fermentation time was 9 days. After the fermentation was completed, it was filtered with a microporous filter membrane with a pore size of 0.2μm to remove residual small solid particles and complete the preparation of biofertilizer.

[0028] Example 3, please refer to the attached Figure 1 -Attached Figure 4, the fermentation waste liquid generated during the preparation of high-purity threonine was collected, introduced into a sedimentation tank for natural precipitation for 4 hours, and filtered with a plate and frame filter press after precipitation. The filtration accuracy was 20nm. After filtration, potassium hydroxide was added to adjust the pH value to 8.0 to complete the preliminary waste liquid pretreatment. Then, nano-hydroxyapatite was selected and placed in a 10% dilute hydrochloric acid solution. It was stirred and soaked at 40°C for 3 hours, rinsed with deionized water until neutral, and then placed in a 100°C oven to dry for 4 hours. Then, it was stirred with a polyglutamic acid solution at a mass ratio of 2.5:1.0 at 55°C for 3.5 hours to prepare a specific adsorption sustained-release agent. Graphene quantum dots were selected and dispersed in an ethanol solution, and 3-aminopropyltriethoxysilane was added as a coupling agent. The reaction was stirred at 50°C for 5 hours. The mass ratio of silane coupling agent to graphene quantum dots was 1:5 , centrifugal separation, ethanol washing, and drying in a vacuum drying oven at 80°C for 3 hours to obtain functionalized graphene quantum dots, dissolve chitosan in acetic acid solution to prepare a 15% solution, and react with functionalized graphene quantum dots at a mass ratio of 1:3 under ultrasound for 2 hours (ultrasonic frequency 60kHz, power 1000W) to obtain an additive, add the specific adsorption sustained-release agent into a stirring container, add the pretreated waste liquid, add the additive, and stir at a speed of 55r / min for 35 minutes, place the mixed raw materials in an ordinary stainless steel fermentation tank, ferment at 45°C and 70% humidity, and pass a mixed gas containing 15% carbon dioxide, 25% oxygen, and the rest nitrogen every 8 hours. Ferment for 9 days, and finally use a microporous filter membrane (pore size 0.2μm) to filter out residual small solid particles to complete the preparation of biofertilizer.

[0029] Design of the experiment: Experimental Materials Plant seeds: Select corn seeds to ensure uniform seed quality and no pests or diseases; Soil: Select soil of the same type and uniform fertility, pre-treat it, remove impurities and measure its basic physical and chemical properties; Biofertilizer samples: Biofertilizers were prepared according to the methods of Example 1, Example 2 and Example 3, respectively, with 10 portions of biofertilizer prepared for each example; Planting and management The soil is evenly distributed into each planting pot, and corresponding biofertilizers (Example 1, Example 2, Example 3) are applied respectively, and the amount of fertilizer applied is kept consistent; Sow 5 plant seeds in each planting pot, keep the same environmental conditions such as planting depth and watering frequency, and place them in suitable light and temperature conditions for cultivation; Experimental indicators and measurement methods Plant growth indicators Plant height: During the growth of the plant, measure the plant height regularly (e.g. weekly), the vertical distance from the soil surface to the highest point of the plant, and record the average value.

[0030] Number of leaves: Record the number of leaves of the plants at the same time and take the average value.

[0031] Biomass: After the plants grow to maturity, harvest the plants, dry the aboveground and underground parts separately to constant weight, weigh and record the biomass, and calculate the sum of the aboveground and underground biomass as the total biomass.

[0032] Soil improvement index Soil water retention: The soil water content was measured before planting and after plant harvest. A certain amount of soil sample was taken and dried to constant weight at 105°C using the drying method. The water content was calculated based on the weight difference before and after, and the changes in soil water content in different treatment groups were compared. Soil air permeability: The air porosity of the soil is measured using a soil air porosity meter to reflect the air permeability of the soil and compare the numerical differences of different embodiments; Nutrients sustained release index During the growth of plants, soil samples were collected every two weeks, and the contents of major nutrients such as nitrogen, phosphorus, and potassium in the soil were determined by chemical analysis methods. The changing trends of nutrients in the soil of different treatment groups were analyzed to determine the nutrient slow-release capacity of the bio-fertilizer.

[0033] As attached Figure 2 -Attached Figure 4 As shown, it is intuitively proved that the biological fertilizer of Example 1 has the best effect on promoting plant growth. The improvement effect of Example 1 in soil water retention and air permeability is significantly better than that of other groups. The nitrogen content in the soil of Example 1 is maintained at a high level throughout the plant growth cycle, which strongly illustrates that it has better nutrient slow-release ability, and fully proves that Example 1 is better in the preparation and application of biological fertilizer, can more effectively promote plant growth, improve soil and achieve long-term supply of nutrients.

[0034] Although the present invention is disclosed as above in terms of preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art may make possible changes and modifications without departing from the spirit and scope of the present invention. Therefore, any modification, equivalent change and modification made to the above embodiments according to the technical essence of the present invention without departing from the content of the technical solution of the present invention shall fall within the scope of protection defined by the claims of the present invention.

Claims

1. A method for preparing bio-fertilizer using a high-purity threonine preparation process, characterized in that: The method for preparing the bio-fertilizer specifically comprises the following steps: Step 1: pretreatment of fermentation waste liquid: collecting fermentation waste liquid generated in the process of preparing high-purity threonine, introducing the waste liquid into a sedimentation tank for natural precipitation, filtering the precipitated waste liquid using a plate and frame filter press after precipitation, and then adding potassium hydroxide to the waste liquid to adjust the pH value; Step 2: preparing a specific adsorption sustained-release agent, selecting nano-hydroxyapatite and polyglutamic acid as preparation materials, performing surface activation treatment on the nano-hydroxyapatite, and then stirring and mixing with a polyglutamic acid solution to react, and generating a specific adsorption sustained-release agent after the reaction is completed; Step 3, preparing an additive, selecting graphene quantum dots and chitosan as raw materials, functionalizing and modifying the graphene quantum dots to prepare functionalized graphene quantum dots, wherein the graphene quantum dots have amino active groups on their surfaces after functionalization, then dissolving chitosan in an acetic acid solution to prepare a chitosan solution, mixing the functionalized graphene quantum dots with the chitosan solution, and reacting them under ultrasound assistance to obtain an additive; Step 4: adding the specific adsorption slow-release agent into a stirring container, then adding the pretreated fermentation waste liquid thereto, and then adding additives to control mixing; Step 5: placing the mixed raw materials in a fermentation device for fermentation treatment. The inner wall of the fermentation device is made of nano-ceramic material. During the fermentation process, a mixed gas containing carbon dioxide, oxygen and inert gas is regularly introduced into the fermentation device for fermentation treatment; Step 6: After the fermentation is completed, the fermentation liquid is filtered to remove the remaining small solid particles, and filtered using a microporous filter membrane to complete the preparation of the bio-fertilizer.

2. A method for preparing bio-fertilizer using a high-purity threonine preparation process according to claim 1, characterized in that: In the step 1, the natural sedimentation time of the waste liquid in the sedimentation tank is controlled to be 2h-4h, the filtration accuracy of the plate and frame filter press is 20nm-30nm, and potassium hydroxide is added after filtration to adjust the pH value to 8.0-8.

5.

3. A method for preparing bio-fertilizer using a high-purity threonine preparation process according to claim 1, characterized in that: In the step 2, the specific process of surface activation treatment of nano-hydroxyapatite is as follows: the nano-hydroxyapatite is placed in a dilute hydrochloric acid solution with a concentration of 5%-10%, stirred and soaked at 30°C-40°C for 2h-3h, then repeatedly rinsed with deionized water until neutral, and then dried in an oven at 80°C-100°C for 3h-4h to complete the surface activation treatment.

4. A method for preparing bio-fertilizer using a high-purity threonine preparation process according to claim 1, characterized in that: In the step 2, the surface activated nano-hydroxyapatite is mixed with the polyglutamic acid solution in a mass ratio of 2.0-2.5:1.0-1.2, and stirred at a temperature of 45° C.-55° C. for 2.5 h-3.5 h to generate a specific adsorption sustained-release agent.

5. A method for preparing bio-fertilizer using a high-purity threonine preparation process according to claim 1, characterized in that: In the step three, the specific process of functionalizing the graphene quantum dots is as follows: dispersing the graphene quantum dots in an ethanol solution, adding 3-aminopropyltriethoxysilane coupling agent, stirring the reaction at 40°C-50°C for 4h-5h, the mass ratio of the silane coupling agent to the graphene quantum dots is 1:5-8, and after the reaction is completed, centrifugation is performed to obtain functionalized graphene quantum dots, and the unreacted silane coupling agent is removed by washing with ethanol, and then dried in a vacuum drying oven at 60°C-80°C for 2h-3h.

6. A method for preparing bio-fertilizer using a high-purity threonine preparation process according to claim 1, characterized in that: In the step three, chitosan is dissolved in an acetic acid solution, the mass fraction of the prepared chitosan solution is controlled to be 10%-15%, and the functionalized graphene quantum dots and the chitosan solution are mixed at a mass ratio of 1:3.0-3.6, the ultrasonic frequency is 40kHz-60kHz, the power is 800W-1200W, and the reaction time is 1h-2h.

7. A method for preparing bio-fertilizer using a high-purity threonine preparation process according to claim 1, characterized in that: In the step 4, after adding the additive, the stirring speed is controlled to be 45r / min-55r / min, and the stirring time is 25min-35min.

8. A method for preparing bio-fertilizer using a high-purity threonine preparation process according to claim 1, characterized in that: In the step 5, the fermentation treatment in the fermentation device is controlled at a temperature of 38°C-48°C and a humidity of 60%-70%. During the fermentation process, a mixed gas is introduced into the fermentation device every 6h-8h. The mixed gas contains carbon dioxide, oxygen and nitrogen. The volume fraction of carbon dioxide in the mixed gas is 10%-15%, the volume fraction of oxygen is 20%-25%, and the rest is nitrogen. The fermentation time is 7 days to 9 days.

9. The method for preparing bio-fertilizer using a high-purity threonine preparation process according to claim 1, characterized in that: In step six, the filtration accuracy of the microporous filtration membrane is 0.1 μm-0.2 μm.

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