A biochar-based sustained-release embedded microcapsule and preparation method thereof

Abstract

The present invention relates to a biochar-based sustained-release embedded microcapsule and a preparation method thereof, a biochar-based sustained-release embedded microcapsule, comprising biochar powder, a polylactic acid layer arranged outside the biochar powder, an embedding layer arranged outside the polylactic acid layer, and an immersion coating layer arranged outside the embedding layer, and the preparation method thereof is to prepare biochar powder, prepare core layer particles, coat the core layer particles in a gel immobilization solution to prepare embedding fixed layer particles, and wrap the immersion coating layer on the embedding fixed layer particles to form a biochar multi-stage embedded sustained-release capsule. The preparation method of the present application is relatively simple, with appropriate hardness, and after multi-layer embedding, it has a stable biological sustained-release effect, can be used as a carrier of various organisms, is in a solid state, and is convenient for storage and transportation.

Description

Technical Field

[0001] The present invention relates to the technical field of microbial compositions, and in particular to a microcapsule for preparing multi-layered biochar-embedded microorganisms using biomass resources and a preparation method thereof. Background Art

[0002] Biochar is a solid product produced by thermal cracking of biological organic materials in anoxic and hypoxic environments. Its main component is carbon molecules, mostly in the form of powdered particles. Biochar is one of the raw materials for the production of activated carbon. It can be made into a material with adsorption properties and can be used to prepare a slow-release carrier for fertilizers, delay the release of fertilizer nutrients in the soil, reduce fertilizer losses, and improve fertilizer utilization. Biochar can also be used as a soil conditioner to increase soil fertility, increase soil organic carbon content, increase soil organic matter or humic acid content, thereby increasing the soil's nutrient absorption capacity and water holding capacity, thereby achieving the effect of promoting crop growth; biochar is mostly alkaline and can be used as a lime substitute to improve soil pH by increasing soil base saturation, reducing the level of exchangeable aluminum, and consuming soil protons to increase acidic soil pH.

[0003] In the mid-1990s, it was discovered that biochar can be used as a carbon dioxide capture and carbon sequestration agent, which can reduce atmospheric carbon dioxide concentrations and have a regulating effect on the global climate. Biochar can adsorb heavy metals, pesticides, herbicides, and pollutants, etc., reducing the probability of plants absorbing the above components to achieve the purpose of purifying soil or water. In the process of thermal cracking of waste biomass to produce biochar, mixed gas and bio-oil can also be obtained to make hydrogen by-products, which can be used as hydrogen energy, refined bio-oil dyes, synthetic ammonia, etc. In view of the importance of biochar, more and more uses of biochar are being discovered and applied.

[0004] Traditional biochar is produced in earth kilns, brick kilns or steel kilns. It is a slow pyrolysis process that is isolated from oxygen and suffocates. It is characterized by high yield and long time. Modern industrial production of biochar is mainly carried out by high-temperature rapid pyrolysis in equipment such as muffle furnaces. It is characterized by low yield and short time. Different application scenarios have different requirements for the microstructure of biochar. For example, adsorbents require biochar to have a rich porous microstructure. In order to overcome the problems that arise in the above-mentioned biochar production process and meet the actual application needs, the preparation method of biochar is constantly being improved.

[0005] Since the main component of biochar is carbon molecules, straw, feces, food processing waste, domestic garbage, sludge, etc., which are rich in organic matter, have the potential to produce biochar. At present, straw and food processing waste are mostly used to prepare animal feed, but some biological resources are rich in carbon and may also contain a large amount of oil, such as food processing waste. If a large amount of it is added to the feed, it is easy to produce high-fat feed, which is not conducive to the growth of animals. Therefore, it is necessary to seek new ways to utilize biological resources.

[0006] The immobilized microbial technology is not only conducive to the fixation of dominant strains and the improvement of the degradation efficiency of refractory organic matter, but also can maintain a high concentration of biomass in the microbial device, and is easy to separate solids and liquids, which has certain advantages. There are many methods for preparing immobilized microorganisms, mainly adsorption, covalent bonding, gel bonding, embedding, etc. To complete the immobilization of microorganisms, the key is to select a suitable biological carrier, which should have the following characteristics:

[0007] (1) It has a stable network structure and is not easily destroyed at a certain pH value and temperature;

[0008] (2) Ability to control the size and porosity of immobilized microbial particles;

[0009] (3) The immobilization method is simple and easy to perform, and the immobilization conditions are as mild as possible;

[0010] (4) The materials used in the carrier are cheap and readily available, and the immobilization cost is low;

[0011] (5) During long-term operation in the biochemical reactor, the immobilization system has good mechanical and chemical stability;

[0012] (6) The carrier is inert to microorganisms and will not damage cells;

[0013] (7) Immobilization systems allow substrates, products, and other metabolites to diffuse freely;

[0014] (8) The immobilized system should have as many microorganisms as possible per unit volume in order to better play the role of biocatalysis.

[0015] Although there are many scientific research results on carriers, these results have certain problems while having relatively good industrial application effects. For example, the cost of the carriers that have been calcined and granulated is too high and it is difficult to achieve industrial application. At the same time, because the carriers are calcined, their hardness is relatively large and they are not easy to dissolve, making it difficult to achieve a stable microbial sustained release effect. For example, the PVA carrier, which is currently widely used, has good plasticity and excellent microbial embedding effect and sustained release effect, but the material itself is easy to pollute the environment. Another example is the carrier made of materials such as attapulgite and sodium alginate, which is also widely used at present. The water content itself is too high and can only be stored in a liquid storage mode. The storage and transportation costs are too high, and it is also difficult to achieve industrialization. Summary of the invention

[0016] To overcome the above-mentioned shortcomings, the purpose of the present invention is to provide a biochar-based slow-release embedded microcapsule, which utilizes biomass resources such as waste straw and mushroom bags in wheat fields to prepare biochar, thereby expanding the material source of biochar and being able to produce multi-stage embedded slow-release biochar capsules.

[0017] The technical solution adopted by the present invention to solve its technical problem is: a biochar-based sustained-release embedded microcapsule, including core layer particles, the core layer particles contain biochar powder, an embedding fixing layer is arranged outside the core layer particles, and an immersion coating layer is arranged outside the embedding fixing layer.

[0018] Specifically, the core layer particles are made of polylactic acid.

[0019] Specifically, the core layer particles contain microbial powder, and the microbial powder is one or more of freeze-dried powders of Rhodococcus erythropolis, Bifidobacterium, and Bacillus.

[0020] A method for preparing biochar-based sustained-release embedded microcapsules comprises the following steps:

[0021] Step 1: Preparation of biochar powder:

[0022] The plant raw materials are dried and crushed, soaked in alkali solution for 12 hours, filtered, the filter residue is dried, placed in a muffle furnace in an inert gas for thermal cracking at a temperature of 300° C., cooled to room temperature, the material is taken out, washed to neutrality, dried, and crushed to 100-300 mesh particles to obtain biochar powder, wherein the plant raw materials include one or more of Ganoderma lucidum mushroom bag bulk materials, bamboo joints, and straw;

[0023] Step 2: Prepare core layer particles:

[0024] Weigh the following materials separately: 95 parts by weight of polylactic acid and 5 parts by weight of the biochar powder prepared in the above step 1. Place the polylactic acid in a container and heat it on a heater until it dissolves into a liquid state. Add the biochar powder to the polylactic acid solution and stir it continuously. After cooling, add the microbial powder to make the microbial powder and the biochar powder evenly distributed in the polylactic acid solution. When there are no bubbles in the solution, input the solution into a capsule machine to prepare capsule particles with a diameter of 1-2 mm. Wash with water until neutral, and dry at room temperature to obtain core layer particles.

[0025] Step 3: Prepare the embedded fixed layer particles:

[0026] The core layer particles are coated in a gel immobilization solution to prepare embedded fixed layer particles. The preparation method comprises the following steps: preparing a chitin solution, dissolving chitosan powder with a mass fraction of 2.5% in a 0.1 mol / L acetic acid solution to obtain a chitin solution, adding the core layer particles obtained in step 2 to the prepared chitin solution at a mass volume ratio of 1:3, heating and stirring to mix evenly to obtain a chitin solution containing core layer particles, dripping a 1 mol / L sodium hydroxide solution into the chitin solution containing the core layer particles, and obtaining embedded fixed layer particles by an ion exchange gel method;

[0027] Step 4: Preparation of biochar multi-stage embedded sustained-release capsules:

[0028] The dip coating is wrapped on the embedding fixed layer particles to form a multi-stage embedding capsule. The preparation method is as follows: prepare water agar with a mass fraction of 3%, add the embedding fixed layer particles obtained in step three into the water agar, stir well, wait for the water agar to solidify, wash the capsule particles with water, and dry them to obtain the biochar multi-stage embedded sustained-release capsule.

[0029] Specifically, the microbial powder added in step 2 includes Rhodococcus erythropolis, Bifidobacterium, Bacillus, etc., and can also be freeze-dried powder of various fungi. In this step, the microbial powder to be carried is embedded therein.

[0030] The beneficial effects of the present invention are: the preparation method of the present application is relatively simple, the hardness is appropriate, and after multi-layer embedding, it has a stable biological sustained-release effect, can be used as a carrier of various organisms, is in a solid state, and is convenient for storage and transportation. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 It is a schematic diagram of the structure of the sustained-release capsule body of the present invention.

[0032] In the figure, 1 is core layer particles, 2 is embedded fixing layer, and 3 is dip coating layer. DETAILED DESCRIPTION

[0033] The present invention will now be described in further detail with reference to the accompanying drawings.

[0034] Example 1

[0035] A method for preparing biochar-based sustained-release embedded microcapsules, comprising:

[0036] Step 1: Preparation of biochar powder:

[0037] Take 50kg of bulk material from discarded Ganoderma lucidum mushroom bags, remove impurities such as stones, dry and crush, add to a lime water pool and soak for 12 hours, the mass fraction of lime water is 2%, that is, the mass fraction of calcium hydroxide in the lime water is 2%, filter, dry the filter residue, place it in a muffle furnace in an inert gas for thermal cracking at a temperature of 300°C, cool to room temperature, take out the material, wash it to neutrality, dry it, and crush it into 130 mesh particles to obtain biochar powder;

[0038] Step 2: Prepare core layer particles:

[0039] Weigh the following materials respectively: 950g polylactic acid (PLA), 50g biochar powder prepared in the above step 1, place the polylactic acid in a container, heat it on a heater until it melts into a liquid state, add the biochar powder to the polylactic acid solution, and stir it continuously. After cooling, add Rhodococcus erythropolis to make the Rhodococcus erythropolis and biochar powder evenly distributed in the polylactic acid solution. When there are no bubbles in the solution, input the solution into a capsule machine to prepare capsule particles with a diameter of 1-2mm, wash with water until neutral, and dry at room temperature to obtain core layer particles containing Rhodococcus erythropolis.

[0040] Step 3: Prepare the embedded fixed layer particles:

[0041] Prepare chitin solution, weigh 25.0g chitosan powder and dissolve it in 1L acetic acid solution, the concentration of acetic acid solution is 0.1mol / L, prepare chitin solution, take 300g core particles obtained in step 2, add them to 900ml chitin solution, heat and stir to mix evenly, obtain core layer chitin solution, add 2L sodium hydroxide solution with a concentration of 1mol / L dropwise into the core layer chitin solution, and obtain embedded fixed layer particles by ion exchange gel method;

[0042] Step 4: Preparation of biochar multi-stage embedded sustained-release capsules:

[0043] The surface of the embedded fixed layer particles is dip-coated, and the dip coating layer is wrapped around the embedded fixed layer particles to form a biochar multi-stage embedded sustained-release capsule. The method is as follows: 30g of agar powder is weighed and dissolved in 1L of distilled water, and water agar with a mass fraction of 3% is prepared. The embedded fixed layer particles obtained in step three are added to the water agar, and stirred sufficiently. After the water agar solidifies, the biochar multi-stage embedded sustained-release capsule containing Rhodococcus erythropolis is obtained after washing and drying.

[0044] Experimental verification:

[0045] 1. Degradation half-life verification of core layer particles containing Rhodococcus erythropolis:

[0046] Take 5kg of soil contaminated by petroleum hydrocarbons, evenly spread the core layer particles containing Rhodococcus erythropolis prepared in step 2 into the soil, and spray water on the soil every 24 hours to maintain its moist environment to ensure the life activity of Rhodococcus erythropolis, keep its environment at a pH of 8.0 and a temperature of 30°C, and after Rhodococcus erythropolis biochar-embedded polylactic acid treatment, it was found that at a unit of 261 mg / kg, the degradation half-life was about 9 days;

[0047] 2. Half-life verification of biochar multi-stage embedded sustained-release capsules containing Rhodococcus erythropolis:

[0048] Take 5 kg of soil contaminated by polychlorinated biphenyls, evenly spread the biochar multi-stage embedded sustained-release capsules containing Rhodococcus erythropolis prepared in step 4 into the soil, and spray water on the soil every 24 hours to maintain its moist environment to ensure the life activity of Bacillus, maintain its environment at a pH of 8.0 and a temperature of 30°C. After treatment with Rhodococcus erythropolis biochar embedded capsules, it was found that at 261 mg / kg, the optimal degradation half-life was 3 days. This is because after multi-stage embedding, the survival of Rhodococcus erythropolis is guaranteed, the survival rate of Rhodococcus erythropolis is improved, and then the degradation rate is improved.

[0049] Example 2

[0050] A method for preparing a biochar-based sustained-release embedded microcapsule, the specific implementation steps are as follows:

[0051] Step 1: Preparation of biochar powder:

[0052] Take 50kg of discarded bamboo joints from the bamboo garden, dry and crush them, add them into a lime water pool and soak them for 12 hours. The mass fraction of lime water is 2%, that is, the mass fraction of calcium hydroxide in lime water is 2%. Filter, dry the filter residue, place it in a muffle furnace in an inert gas for thermal cracking at a temperature of 300°C, cool it to room temperature, take out the material, wash it to neutrality, dry it, and crush it into 230 mesh particles to obtain biochar powder;

[0053] Step 2: Prepare core layer particles:

[0054] Weigh the following materials respectively: 950g polylactic acid (PLA), 50g 230-mesh biochar powder prepared in the above step 1, place the polylactic acid in a container, heat it on a heater until it melts into a liquid state, add the biochar powder to the polylactic acid solution, add bifidobacterium after cooling, and stir continuously to make the biochar powder and bifidobacterium evenly distributed in the polylactic acid solution. When there are no bubbles in the solution, input the solution into a capsule machine to prepare capsule particles with a diameter of 1-2mm, wash with water until neutral, and dry at room temperature to obtain core layer particles;

[0055] Step 3: Prepare the embedded fixed layer particles:

[0056] The core layer particles are coated in a gel immobilization solution to prepare embedded fixed layer particles, a chitin solution is prepared, 25.0 g of chitosan powder is weighed and dissolved in 1 L of acetic acid solution, the concentration of the acetic acid solution is 0.1 mol / L, to obtain a chitin solution, 300 g of the core layer particles obtained in step 2 are added to the prepared 900 ml chitin solution, heated and stirred to mix evenly, to obtain a core layer chitin solution, 2 L of a sodium hydroxide solution with a concentration of 1 mol / L is dripped into the core layer chitin solution, and embedded fixed layer particles are obtained by an ion exchange gel method;

[0057] Step 4: Preparation of biochar multi-stage embedded sustained-release capsules:

[0058] The surface of the embedded fixed layer particles is dip-coated, and the dip coating layer is wrapped around the embedded fixed layer particles to form a biochar multi-stage embedded sustained-release capsule. The method is as follows: 30g of agar powder is weighed and dissolved in 1L of distilled water, and water agar with a mass fraction of 3% is prepared. The embedded fixed layer particles obtained in step three are added to the water agar, and stirred sufficiently. After the water agar solidifies, the biochar multi-stage embedded sustained-release capsule is obtained after washing and drying.

[0059] Specifically, for experimental observation, when preparing the core layer particles in step 2, 50 ml of crystal violet mixture is added at the same time as the bifidobacteria. The crystal violet mixture is used as a color indicator during the experimental verification of the sustained release rate to observe the experimental changes. In actual production, no crystal violet solution is added.

[0060] Experimental verification:

[0061] 1. Verification of sustained release rate of core layer particles in acidic environment:

[0062] 1L of dilute hydrochloric acid solution was prepared with a pH of 2 to simulate the pH environment of gastric acid in the stomach. The core layer particles prepared in step 2 of this embodiment were added and the indicated color was observed. After 1 minute, the solution turned purple. The sustained release rate was detected to be 0.058ug / min.

[0063] 2. Verification of sustained release rate of embedded fixed layer particles in acidic environment:

[0064] 1L of dilute hydrochloric acid solution was prepared with a pH of 2 to simulate the pH environment of gastric acid in the stomach. The multi-stage embedded sustained-release capsules prepared in step 4 of this embodiment were added and the indicated color was observed. After 4 minutes, the solution turned purple. The sustained-release rate was found to be 0.011ug / min, which was delayed by nearly five times.

[0065] 3. Verification of sustained release rate of core layer particles in alkaline environment:

[0066] 1L of sodium bicarbonate solution was prepared with a pH of 8 to simulate the pH environment in the human oral cavity, and the core layer particles prepared in step 2 of this embodiment were added. The indicated color was observed. After 2 minutes, the solution turned purple. After testing, the sustained release rate was 0.041ug / min.

[0067] 4. Verification of sustained release rate of embedded fixed layer particles in alkaline environment:

[0068] 1L of sodium bicarbonate solution was prepared with a pH of 8 to simulate the pH environment in the human oral cavity, and the multi-stage embedded sustained-release capsules prepared in step 4 of this embodiment were added. The indicated color was observed. After 5 minutes, the solution turned purple. The sustained-release rate was tested to be 0.0082ug / min, and the sustained-release rate was delayed by nearly five times.

[0069] Example 3

[0070] Step 1: Preparation of biochar powder:

[0071] Take 50kg of straw from the rice field, dry it, crush it, add it to a lime water pool and soak it for 12 hours. The mass fraction of lime water is 2%. Filter it, dry the filter residue, place it in a muffle furnace in an inert gas for thermal cracking at a temperature of 300°C, cool it to room temperature, take out the material, wash it to neutrality, dry it, and crush it into 200 mesh particles to obtain biochar powder;

[0072] Step 2: Prepare core layer particles:

[0073] Weigh the following materials respectively: 950g polylactic acid (PLA), 50g 200-mesh biochar powder prepared in the above step 1, place the polylactic acid in a container, heat it on a heater until it melts into a liquid state, add the biochar powder into the polylactic acid solution, and stir it continuously, add Bacillus lyophilized powder, so that the Bacillus biochar powder is evenly distributed in the polylactic acid solution, and when there are no bubbles in the solution, input the solution into a capsule machine to prepare capsule particles with a diameter of 1-2mm, wash with water until neutral, and dry at room temperature to obtain core layer particles containing Bacillus;

[0074] Step 3: Prepare the embedded fixed layer particles:

[0075] Prepare chitin solution, weigh 25.0g chitosan powder and dissolve it in 1L acetic acid solution, the concentration of acetic acid solution is 0.1mol / L, prepare chitin solution, take 300g core particles obtained in step 2, add them to 900ml chitin solution, heat and stir to mix evenly, obtain core layer chitin solution, drop 2L sodium hydroxide solution with a concentration of 1mol / L into the core layer chitin solution, and obtain embedded fixed layer particles by ion exchange gel method;

[0076] Step 4: Preparation of biochar multi-stage embedded sustained-release capsules:

[0077] The surface of the embedded fixed layer particles is dip-coated, and the dip coating layer is wrapped around the embedded fixed layer particles to form a biochar multi-stage embedded sustained-release capsule. The method is as follows: 30g of agar powder is weighed and dissolved in 1L of distilled water, and water agar with a mass fraction of 3% is prepared. The embedded fixed layer particles obtained in step three are added to the water agar, and stirred sufficiently. After the water agar solidifies, the biochar multi-stage embedded sustained-release capsule containing Bacillus is obtained after washing and drying.

[0078] Experimental verification:

[0079] 1. Degradation half-life verification of core layer particles containing Bacillus:

[0080] Take 5kg of soil contaminated by PCBs, evenly spread the core layer particles containing Bacillus prepared in step 2 into the soil, and spray water on the soil every 24 hours to keep it moist to ensure the life activity of Bacillus, keep its environment at pH 7 and temperature at 30°C, and after Bacillus biochar encapsulated polylactic acid treatment, it was found that at 10ppm, the degradation half-life was about ten days;

[0081] 2. Half-life verification of biochar multi-stage embedded sustained-release capsules containing Bacillus:

[0082] Take 5 kg of soil contaminated by polychlorinated biphenyls, and evenly spread the biochar multi-stage embedded sustained-release capsules containing Bacillus prepared in step 4 into the soil, and spray water on the soil every 24 hours to maintain its moist environment to ensure the life activity of Bacillus, and keep its environment at a pH of 7 and a temperature of 30°C. After treatment with Bacillus biochar embedded capsules, it was found that at a unit of 10 ppm, the optimal degradation half-life was 2 days. This is because after multi-stage embedding, the survival of Bacillus is guaranteed, the survival rate of Bacillus is improved, and then the degradation rate is improved.

[0083] The present invention is not limited to the described implementation modes, and anyone should be aware of the structural changes made under the enlightenment of the present invention. Any technical solutions that are the same or similar to the present invention fall within the protection scope of the present invention.

[0084] The techniques, shapes, and structural parts not described in detail in the present invention are all well-known techniques.

Claims

1. A biochar-based sustained-release embedded microcapsule, characterized in that: The core layer particles include biochar powder, an embedding and fixing layer is arranged outside the core layer particles, and an immersion coating layer is arranged outside the embedding and fixing layer. The core layer particles are made of polylactic acid, and the core layer particles include microbial powder, which is one of Rhodococcus erythropolis and Bacillus freeze-dried powder; The preparation method comprises the following steps: Step 1: Preparation of biochar powder: The plant raw materials were dried and crushed, soaked in alkali solution for 12 hours, filtered, the filter residue was dried, and thermally cracked in a muffle furnace in an inert gas at a temperature of 300°C, cooled to room temperature, the material was taken out, washed to neutrality, dried, and crushed to obtain biochar powder; Step 2: Prepare core layer particles: Weigh the following materials separately: 95 parts by weight of polylactic acid and 5 parts by weight of the biochar powder prepared in the above step 1. Place the polylactic acid in a container and heat it on a heater until it dissolves into a liquid state. Add the biochar powder to the polylactic acid solution and stir it continuously. After cooling, add the microbial powder to make the microbial powder and the biochar powder evenly distributed in the polylactic acid solution. When there are no bubbles in the solution, input the solution into a capsule machine to prepare capsule particles with a diameter of 1-2 mm. Wash with water until neutral, and dry at room temperature to obtain core layer particles. Step 3: Prepare the embedded fixed layer particles: The core layer particles are coated in a gel immobilization solution to prepare embedded fixed layer particles. The preparation method comprises the following steps: preparing a chitin solution, dissolving chitosan powder with a mass fraction of 2.5% in a 0.1 mol / L acetic acid solution to obtain a chitin solution, adding the core layer particles obtained in step 2 to the prepared chitin solution at a mass volume ratio of 1:3, heating and stirring to mix evenly to obtain a chitin solution containing core layer particles, dripping a 1 mol / L sodium hydroxide solution into the chitin solution containing the core layer particles, and obtaining embedded fixed layer particles by an ion exchange gel method; Step 4: Preparation of biochar multi-stage embedded sustained-release capsules: The impregnation coating layer is wrapped on the embedding fixed layer particles to form a biochar multi-stage embedded sustained-release capsule. The preparation method is as follows: the embedding fixed layer particles obtained in step three are added into water agar, fully stirred, and after the water agar solidifies, the capsule particles are washed with water and dried to obtain the biochar multi-stage embedded sustained-release capsule.

2. The biochar-based sustained-release embedded microcapsule according to claim 1, characterized in that: The particle size of the biochar powder is 100-300 meshes.

3. The biochar-based sustained-release embedded microcapsule according to claim 1, characterized in that: In the step 4, the dipping coating is water agar with a mass fraction of 3%.

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