CN112830843A

CN112830843A - Biodegradable biomass charcoal-based compound fertilizer and preparation method thereof

Info

Publication number: CN112830843A
Application number: CN202110225750.9A
Authority: CN
Inventors: 吴佳伟
Original assignee: Individual
Current assignee: Individual
Priority date: 2021-03-01
Filing date: 2021-03-01
Publication date: 2021-05-25

Abstract

The invention discloses a biodegradable biomass charcoal-based compound fertilizer and a preparation method thereof. The compound fertilizer comprises a biochar-based fertilizer and a degradable coating. Has the advantages that: the prepared microalgae alcohol is a chain compound, has no aromatic ring and is easier to biodegrade; the degradable sulfur-based polymer is prepared by the way of microalgae alcohol and sulfur dioxide alternate free radical copolymerization, so that the sulfur nutrient is released, and the plant growth is promoted; the plant-based crosslinking agent is utilized to enable the polyvinyl alcohol gel and the sulfur-based polymer to form an interpenetrating crosslinking structure at an interface, so that the crosslinking degree is increased, the porosity of the coating is reduced, the release rate of phosphorus and nitrogen is reduced, and the utilization rate is increased; the biomass charcoal obtained by the non-directional pyrolysis in the air atmosphere has a rougher surface, and the resistance of the post-stage nutrient release of ammonium dihydrogen phosphate is increased.

Description

Biodegradable biomass charcoal-based compound fertilizer and preparation method thereof

Technical Field

The invention relates to the technical field of compound fertilizers, in particular to a biodegradable biomass charcoal-based compound fertilizer and a preparation method thereof.

Background

The compound fertilizer contains more than two of nitrogen, phosphorus and potassium, while the common fertilizer is ammonium dihydrogen phosphate, also called anfu powder, which is very easy to absorb moisture and decomposes in humid air to generate ammonia, so that the nitrogen element is lost due to volatilization and the fertility is degraded. Therefore, the use of the coating reduces the deliquescence and increases the slow release property, so that the elements in the fertilizer can be effectively utilized. Coatings are typically made using petroleum-based polymers. However, the scarcity of fossil fuels requires the development of renewable environment-friendly polymers to replace the petroleum-based coating of the current slow-release fertilizers. Meanwhile, most of polymer coatings such as polyacrylamide are not degradable and are easy to remain in soil, so that the accumulation causes pollution to the soil and influences the complete release and effective utilization of nutrients. In addition, the sulfur is an important element after nitrogen, phosphorus and potassium, which can promote the growth of plants, but the polymerization of the released sulfur in the coating material is less at present, and a sulfur polymer coating needs to be prepared, so that the diversity of nutrient elements in the compound fertilizer is increased. Therefore, the preparation of a biodegradable biomass charcoal-based compound fertilizer is a problem to be solved urgently.

Disclosure of Invention

The invention aims to provide a biodegradable biomass charcoal-based compound fertilizer and a preparation method thereof, so as to solve the problems in the background technology.

In order to solve the technical problems, the invention provides the following technical scheme:

preferably, the compound fertilizer comprises a biochar-based fertilizer and a degradable coating; the degradable coating comprises a sulfur-based polymer, polyvinyl alcohol gel.

Preferably, the raw materials of the degradable coating comprise the following components: the adhesive comprises, by weight, 25-32 parts of a sulfur-based polymer, 15-22 parts of polyvinyl alcohol and 2-6 parts of a vegetable oil-based crosslinking agent.

Preferably, the sulfur-based polymer is prepared by free radical copolymerization of microalgal alcohol and sulfur dioxide.

Preferably, the raw materials of the biomass charcoal-based fertilizer comprise biomass charcoal and ammonium dihydrogen phosphate saturated solution; the mass ratio of the biomass charcoal to the saturated ammonium dihydrogen phosphate solution is (1:1) - (1: 1.2).

Preferably, the biomass charcoal is obtained by non-directional pyrolysis in an air atmosphere.

Preferably, the mass ratio of the biochar-based fertilizer to the degradable coating is (1:0.1) - (1: 0.2).

Preferably, the preparation method of the biodegradable biomass charcoal-based compound fertilizer comprises the following steps:

s1: preparing a charcoal-based fertilizer: adding the ammonium dihydrogen phosphate saturated solution into the biomass charcoal dispersion solution, and performing rotary evaporation to obtain a biomass charcoal-based fertilizer for later use;

s2: preparing a compound fertilizer:

(1) preparing a sulfur-based polymer; (2) preparing degradable coating paint: A. stirring and dissolving polyvinyl alcohol in deionized water to obtain a solution A for later use; B. stirring and dissolving the sulfur-based polymer in DMF, and adding a vegetable oil-based crosslinking agent to obtain a solution B for later use; (3) preparing a compound fertilizer: adding the prepared biochar-based fertilizer into the solution A, and performing rotary evaporation to dryness to obtain a compound fertilizer A; and transferring the mixture to a pan of a coating machine, and spraying the solution B on the compound fertilizer A to obtain the compound fertilizer.

Preferably, the specific process of step S1 is: adding biomass charcoal into deionized water, and stirring for 40-60 minutes under a magnetic stirrer; transferring the biomass carbon into an ultrasonic device, and carrying out ultrasonic treatment for 40-60 minutes to obtain a biomass carbon dispersion liquid; adding saturated ammonium dihydrogen phosphate solution, and stirring for 10-12 hours under magnetic stirring; and (4) rotary evaporation to dryness at the drying temperature of 55-65 ℃ to obtain the biochar-based fertilizer for later use.

Preferably, the specific process of step S2 is:

(1) preparation of sulfur-based polymers:

A. preparation of microalgal alcohol: adding microalgae oil into a toluene-formic acid solvent, and reacting for 1-1.5 hours at a stirring speed of 200-250 rmp and a reaction temperature of 40 ℃ in a nitrogen atmosphere; adding hydrogen peroxide, setting the temperature to be 70-75 ℃, stirring at the speed of 400-500 rmp, reacting for 3 hours, adding toluene, mixing, washing with warm water, filtering and drying to obtain a product A; placing the product A in an allyl acetic acid solution, setting the temperature at 90 ℃ for reacting for 18 hours, adding allyl vinyl ester, continuing to react for 8 hours, washing the product with a saturated sodium hydroxide solution until the pH value is 7, filtering, washing and drying to obtain microalgae alcohol for later use;

B. sequentially adding microalgae alcohol and tert-butyl peroxide into a high-pressure reaction kettle, introducing sulfur dioxide gas, setting the stirring speed to be 120-140 rpm, the reaction temperature to be 80-85 ℃, and the reaction time to be 24-36 hours; washing with dichloromethane and methanol in sequence, and drying to obtain a sulfur-based polymer for later use;

(2) preparing degradable coating paint: A. stirring and dissolving polyvinyl alcohol in deionized water at the dissolving temperature of 75-80 ℃ to obtain a solution A with the concentration of 2-3% for later use; B. stirring and dissolving a sulfur-based polymer in DMF at the temperature of 45-50 ℃; adding a vegetable oil-based cross-linking agent, and uniformly stirring to obtain a solution B with the concentration of 3-7% for later use;

(3) preparing a compound fertilizer: adding the prepared biochar-based fertilizer into the solution A, stirring for 3-4 hours at a set temperature of 80-85 ℃, and performing rotary evaporation to obtain a compound fertilizer A; transferring the mixture into a pan of a coating machine, setting the temperature of a heater to be 70-75 ℃, the rotating speed to be 15-20 rmp and the pressure of a high-pressure spray gun to be 3-4 kg/cm²And spraying the solution B on the compound fertilizer A to obtain the compound fertilizer.

Preferably, in step S2 (1), the molar ratio of microalgae alcohol to tert-butyl peroxide is (1:1) - (2: 1).

In the technical scheme, ammonium dihydrogen phosphate is adsorbed to form a biochar-based fertilizer by utilizing the porosity of biochar, and polyvinyl alcohol and a sulfur-based polymer form a coating on the surface of the biochar-based fertilizer, so that the ammonium dihydrogen phosphate can be better slowly released; the biodegradable coating is finally and completely degraded to release nutrients, so that the plant can conveniently absorb the phosphorus, and the utilization rate of the phosphorus is increased. The method comprises the following specific steps:

firstly, the biomass charcoal is obtained by non-directional pyrolysis in the air atmosphere, and compared with the directional pyrolysis biomass charcoal obtained in the nitrogen atmosphere or the oxygen atmosphere, the surface of the biomass charcoal has a rougher surface, so that the resistance of the ammonium dihydrogen phosphate released in the later stage is increased; meanwhile, the binding force of the film layer is increased. And the surface of the soil colloid has high soluble salt content, so that the ionic strength is increased, more cations are generated, the soil colloid can generate coupling, the migration and the loss of the soil colloid are reduced, the water retention is increased, and the erosion is reduced. In addition, when the degradable coating of the compound fertilizer is completely degraded, the biomass charcoal can form a thicker sand sheath at the root of the plant, so that the uptake of phosphorus is facilitated, and the utilization rate of phosphorus in the later stage is increased.

Secondly, the polyvinyl alcohol is a water-soluble, non-toxic and biodegradable polymer, which can adsorb the surface of the biochar through electrostatic acting force and can also form intermolecular hydrogen bond force with ammonium dihydrogen phosphate, so that the polyvinyl alcohol is adhered to the surface of the biomass charcoal fertilizer, then polyvinyl alcohol gel is formed, then the sulfur-based polymer is crosslinked on the polyvinyl alcohol gel and covers the surface of the polyvinyl alcohol gel to form a sulfur-based polymer layer, and at the interface of the polyvinyl alcohol gel and the sulfur-based polymer layer, due to the existence of a plant-based crosslinking agent, an interpenetrating crosslinking structure is formed, the porosity of a coating is reduced, the release rate of phosphorus and nitrogen is reduced, and the utilization rate is increased. Wherein, the plant-based crosslinking agent is also a biodegradable substance and has no toxicity.

Thirdly, the microalgae alcohol is obtained by firstly carrying out epoxidation and then ring opening reaction on microalgae oil which is a long-chain unsaturated fatty acid substance to obtain hydroxyl with higher abundance, and then forming a branched chain by utilizing the exchange reaction between the hydroxyl by allyl vinyl ester. The microalgae alcohol structure contains allyl branched chains, chain addition reaction can be generated, and the sulfur-based polymer is prepared by the way of microalgae alcohol and sulfur dioxide alternate free radical copolymerization. Wherein the microalgal alcohol is extracted from renewable microalgae. Sulfur dioxide is one of the polluted gases, the utilization rate of the sulfur dioxide in chemical products is low, sulfur is proved to be an important element after nitrogen, phosphorus and potassium, the growth rate of plants is reduced due to the lack of sulfur, and the sulfur content in the soil is only 0.01-0.05% generally, which cannot meet the growth of the plants. Therefore, the sulfur-based polymer prepared by combining the two can provide the sulfur nutrient for plants, reduce the dependence on fossil-based polymers and reduce environmental pollution. And the molecular structure of the membrane contains ester groups, and the membrane can be degraded by dissolution, enzymolysis and cell phagocytosis in organisms. Meanwhile, the cross-linking is carried out through the cross-linking with the polyvinyl alcohol, so that molecular chains are increased, the porosity of the formed film is reduced, a more compact film is formed, the sulfur-based polymer enables the coating film to be smoother, the moisture is effectively prevented from entering, the deliquescence of the ammonium dihydrogen phosphate is reduced, and the initial slow release rate is increased. In addition, microalgae alcohols are chain-type compounds, and have no aromatic ring in the structure after polymerization with sulfur dioxide, so that the microalgae alcohols are easy to degrade.

The release process of the compound fertilizer comprises the following steps: the composite fertilizer absorbs water slowly in a sudden process, so that the polyvinyl alcohol gel absorbs water and swells, the water enters the biomass charcoal, and the ammonium dihydrogen phosphate in the shallow layer in the gaps of the biomass charcoal is dissolved to generate nutrients which are exuded from the three-dimensional network structure of the matrix; then, ammonium dihydrogen phosphate in deep layers of the gaps of the biomass charcoal is dissolved, and the swelling process is continued, so that cracks-holes are generated on the sulfur-based polymer layer, the release rate of the sulfur is increased, the release resistance is increased due to the roughness of the biomass, and the biomass is still slowly released; after the release of nutrients is finished, the biomass charcoal forms a sand sheath on the root system, and the utilization rate of phosphorus is increased.

And (3) degrading the compound fertilizer: the soil for planting plants is rich in organic compound decomposition enzyme and fungi, while the biomass carbon can increase the fluidity of the fungi and promote the biodegradation of polyvinyl alcohol and sulfur-containing copolymer, and in addition, the hydrolysis of the polyvinyl alcohol is also one of the ways for increasing the degradation. The degradation time of the coating is 165-192 days. And (3) degradation process: cracks occur in about 10 days, holes are generated in about 32 days, polymer frameworks crack in about 50 days, small molecules in the frameworks overflow in about 165-192 days and are completely degraded in about 89 days.

Compared with the prior art, the invention has the following beneficial effects: (1) the prepared microalgae alcohol is a chain compound, has no aromatic ring and is easier to biodegrade; (2) the degradable sulfur-based polymer is prepared by microalgae alternate free radical copolymerization of alcohol and sulfur dioxide, so that sulfur nutrients are released and plant growth is promoted. (3) The plant-based crosslinking agent is utilized to enable the polyvinyl alcohol gel and the sulfur-based polymer to form an interpenetrating crosslinking structure at an interface, so that the crosslinking degree is increased, the porosity of the coating is reduced, the release rate of phosphorus and nitrogen is reduced, and the utilization rate is increased. (4) The sulfur-based polymer enables the coating film to be smoother, and hydroxyl groups are replaced by sulfur, so that the hydrophilicity of the film is effectively reduced, the deliquescence of ammonium dihydrogen phosphate is reduced, and the initial slow release rate is increased. (5) The biomass charcoal obtained by the non-directional pyrolysis in the air atmosphere has a rougher surface, and the resistance of the post-stage nutrient release of ammonium dihydrogen phosphate is increased.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

Example 1:

a preparation method of a biodegradable biomass charcoal-based compound fertilizer comprises the following steps:

s1: preparing a charcoal-based fertilizer: weighing biomass charcoal and ammonium dihydrogen phosphate saturated solution according to the mass ratio of 1: 1; adding biomass charcoal into deionized water, and stirring for 40 minutes under a magnetic stirrer; transferring the biomass carbon into an ultrasonic device, and carrying out ultrasonic treatment for 60 minutes to obtain a biomass carbon dispersion liquid; adding saturated ammonium dihydrogen phosphate solution, and stirring under magnetic stirring for 12 hr; and (5) rotary evaporating to dryness at the drying temperature of 60 ℃ to obtain the biochar-based fertilizer for later use.

S2: preparing a compound fertilizer: (1) preparation of sulfur-based polymers: A. preparation of microalgal alcohol: adding the microalgae oil into a toluene-formic acid solvent, and reacting for 1 hour at the reaction temperature of 40 ℃ and the stirring speed of 250rmp under the nitrogen atmosphere; adding hydrogen peroxide, setting the temperature at 75 ℃, stirring at 500rmp, reacting for 3 hours, adding toluene, mixing, washing with warm water, filtering and drying to obtain a product A; placing the product A in an allyl acetic acid solution, setting the temperature at 90 ℃ for reacting for 18 hours, adding allyl vinyl ester, continuing to react for 8 hours, washing the product with a saturated sodium hydroxide solution until the pH value is 7, filtering, washing and drying to obtain microalgae alcohol for later use; B. weighing microalgae alcohol and tert-butyl peroxide according to a molar ratio of 1:1, sequentially adding the microalgae alcohol and tert-butyl peroxide into a high-pressure reaction kettle, introducing sulfur dioxide gas, setting the stirring speed at 120rpm, the reaction temperature at 85 ℃ and the reaction time at 30 hours; washing with dichloromethane and methanol in sequence, and drying to obtain a sulfur-based polymer for later use; (2) preparing degradable coating paint: A. stirring and dissolving 20 parts of polyvinyl alcohol in deionized water at the dissolving temperature of 75 ℃ to obtain a solution A with the concentration of 2% for later use; B. 29 parts of sulfur-based polymer is stirred and dissolved in DMF, and the dissolving temperature is 45 ℃; adding 6 parts of vegetable oil-based crosslinking agent, and stirringUniformly stirring to obtain a solution B with the concentration of 6% for later use; (3) preparing a compound fertilizer: adding the prepared biochar-based fertilizer into the solution A, stirring for 3 hours at the set temperature of 82 ℃, and performing rotary evaporation to obtain a compound fertilizer A; transferring into a pan of a coating machine, setting the temperature of a heater at 75 ℃, the rotating speed at 18rmp and the pressure of a high-pressure spray gun at 3kg/cm²And spraying the solution B on the compound fertilizer A to obtain the compound fertilizer.

In this example, the mass ratio of the biochar-based fertilizer to the degradable coating was 1: 0.15.

Example 2:

s1: preparing a charcoal-based fertilizer: weighing biomass charcoal and ammonium dihydrogen phosphate saturated solution according to the mass ratio of 1: 1; adding biomass charcoal into deionized water, and stirring for 40 minutes under a magnetic stirrer; transferring the biomass carbon into an ultrasonic device, and performing ultrasonic treatment for 40 minutes to obtain a biomass carbon dispersion liquid; adding saturated ammonium dihydrogen phosphate solution, and stirring for 10 hours under magnetic stirring; and (5) rotary evaporating to dryness at the drying temperature of 55 ℃ to obtain the biochar-based fertilizer for later use.

S2: preparing a compound fertilizer: (1) preparation of sulfur-based polymers: A. preparation of microalgal alcohol: adding the microalgae oil into a toluene-formic acid solvent, and reacting for 1 hour at a stirring speed of 200rmp and a reaction temperature of 40 ℃ in a nitrogen atmosphere; adding hydrogen peroxide, setting the temperature at 70 ℃, stirring at 400rmp, reacting for 3 hours, adding toluene, mixing, washing with warm water, filtering and drying to obtain a product A; placing the product A in an allyl acetic acid solution, setting the temperature at 90 ℃ for reacting for 18 hours, adding allyl vinyl ester, continuing to react for 8 hours, washing the product with a saturated sodium hydroxide solution until the pH value is 7, filtering, washing and drying to obtain microalgae alcohol for later use; B. weighing microalgae alcohol and tert-butyl peroxide according to a molar ratio of 1:1, sequentially adding the microalgae alcohol and tert-butyl peroxide into a high-pressure reaction kettle, introducing sulfur dioxide gas, setting the stirring speed at 120rpm, the reaction temperature at 80 ℃ and the reaction time at 24 hours; washing with dichloromethane and methanol in sequence, and drying to obtain a sulfur-based polymer for later use; (2) degradable coatingPreparing materials: A. stirring and dissolving 15 parts of polyvinyl alcohol in deionized water at the dissolving temperature of 75 ℃ to obtain a solution A with the concentration of 2% for later use; B. 25 parts of sulfur-based polymer is stirred and dissolved in DMF, and the dissolving temperature is 45 ℃; adding 2 parts of vegetable oil-based crosslinking agent, and uniformly stirring to obtain a solution B with the concentration of 3% for later use; (3) preparing a compound fertilizer: adding the prepared biochar-based fertilizer into the solution A, stirring for 3 hours at the set temperature of 80 ℃, and performing rotary evaporation to obtain a compound fertilizer A; transferring into a pan of a coating machine, setting the temperature of a heater at 70 deg.C, the rotation speed at 15rmp, and the pressure of a high-pressure spray gun at 3kg/cm²And spraying the solution B on the compound fertilizer A to obtain the compound fertilizer.

In this example, the mass ratio of the biochar-based fertilizer to the degradable coating was 1: 0.1.

Example 3:

s1: preparing a charcoal-based fertilizer: weighing biomass charcoal and ammonium dihydrogen phosphate saturated solution according to the mass ratio of 1: 1.2; adding biomass charcoal into deionized water, and stirring for 60 minutes under a magnetic stirrer; transferring the biomass carbon into an ultrasonic device, and carrying out ultrasonic treatment for 60 minutes to obtain a biomass carbon dispersion liquid; adding saturated ammonium dihydrogen phosphate solution, and stirring under magnetic stirring for 12 hr; and (5) rotary evaporating to dryness at the drying temperature of 65 ℃ to obtain the biochar-based fertilizer for later use.

S2: preparing a compound fertilizer: (1) preparation of sulfur-based polymers: A. preparation of microalgal alcohol: adding the microalgae oil into a toluene-formic acid solvent, setting the reaction temperature to be 40 ℃ and the stirring speed to be 250rmp to react for 1.5 hours under the nitrogen atmosphere; adding hydrogen peroxide, setting the temperature at 75 ℃, stirring at 500rmp, reacting for 3 hours, adding toluene, mixing, washing with warm water, filtering and drying to obtain a product A; placing the product A in an allyl acetic acid solution, setting the temperature at 90 ℃ for reacting for 18 hours, adding allyl vinyl ester, continuing to react for 8 hours, washing the product with a saturated sodium hydroxide solution until the pH value is 7, filtering, washing and drying to obtain microalgae alcohol for later use; B. weighing microalgae alcohol and tert-butyl peroxide according to the molar ratio of 2:1,sequentially adding the materials into a high-pressure reaction kettle, introducing sulfur dioxide gas, setting the stirring speed to be 140rpm, the reaction temperature to be 85 ℃ and the reaction time to be 36 hours; washing with dichloromethane and methanol in sequence, and drying to obtain a sulfur-based polymer for later use; (2) preparing degradable coating paint: A. stirring and dissolving 22 parts of polyvinyl alcohol in deionized water at the dissolving temperature of 80 ℃ to obtain a solution A with the concentration of 3% for later use; B. 32 parts of sulfur-based polymer is stirred and dissolved in DMF, and the dissolving temperature is 50 ℃; adding 6 parts of vegetable oil-based crosslinking agent, and uniformly stirring to obtain a solution B with the concentration of 7% for later use; (3) preparing a compound fertilizer: adding the prepared biochar-based fertilizer into the solution A, stirring for 4 hours at the set temperature of 85 ℃, and performing rotary evaporation to obtain a compound fertilizer A; transferring into a pan of a coating machine, setting the temperature of a heater at 75 deg.C, the rotation speed at 20rmp, and the pressure of a high-pressure spray gun at 4kg/cm²And spraying the solution B on the compound fertilizer A to obtain the compound fertilizer.

In this example, the mass ratio of the biochar-based fertilizer to the degradable coating was 1: 0.2.

Example 4:

s1: preparing a charcoal-based fertilizer: weighing biomass charcoal and ammonium dihydrogen phosphate saturated solution according to the mass ratio of 1: 1.5; adding biomass charcoal into deionized water, and stirring for 50 minutes under a magnetic stirrer; transferring the biomass carbon into an ultrasonic device, and performing ultrasonic treatment for 50 minutes to obtain a biomass carbon dispersion liquid; adding saturated ammonium dihydrogen phosphate solution, and stirring for 11 hours under magnetic stirring; and (5) rotary evaporating to dryness at the drying temperature of 60 ℃ to obtain the biochar-based fertilizer for later use.

S2: preparing a compound fertilizer: (1) preparation of sulfur-based polymers: A. preparation of microalgal alcohol: adding the microalgae oil into a toluene-formic acid solvent, and reacting for 1.25 hours at a stirring speed of 225rmp and a reaction temperature of 40 ℃ in a nitrogen atmosphere; adding hydrogen peroxide, setting the temperature at 72 ℃, stirring at 450rmp, reacting for 3 hours, adding toluene, mixing, washing with warm water, filtering and drying to obtain a product A; the product a was placed in an allyl acetic acid solution,setting the temperature to 90 ℃ for reacting for 18 hours, adding allyl vinyl ester, continuing to react for 8 hours, washing the mixture by using a saturated sodium hydroxide solution until the pH value is 7, filtering, washing and drying the mixture to obtain microalgae alcohol for later use; B. weighing microalgae alcohol and tert-butyl peroxide according to a molar ratio of 1.5:1, sequentially adding the microalgae alcohol and tert-butyl peroxide into a high-pressure reaction kettle, introducing sulfur dioxide gas, setting the stirring speed at 130rpm, the reaction temperature at 83 ℃ and the reaction time at 30 hours; washing with dichloromethane and methanol in sequence, and drying to obtain a sulfur-based polymer for later use; (2) preparing degradable coating paint: A. stirring and dissolving 18 parts of polyvinyl alcohol in deionized water at the dissolving temperature of 78 ℃ to obtain a solution A with the concentration of 2.5% for later use; B. stirring and dissolving 28 parts of sulfur-based polymer in DMF at the dissolving temperature of 48 ℃; adding 4 parts of vegetable oil-based crosslinking agent, and uniformly stirring to obtain a solution B with the concentration of 3-7% for later use; (3) preparing a compound fertilizer: adding the prepared biochar-based fertilizer into the solution A, stirring for 3.5 hours at the set temperature of 82 ℃, and performing rotary evaporation to dryness to obtain a compound fertilizer A; transferring into a pan of a coating machine, setting the temperature of a heater at 72 ℃, the rotating speed at 18rmp and the pressure of a high-pressure spray gun at 3.5kg/cm²And spraying the solution B on the compound fertilizer A to obtain the compound fertilizer.

Example 5: the rest is the same as the example 1 without adding the coating;

example 6: the same as in example 1 except that the sulfur-based polymer was not added;

example 7: the procedure of example 1 was repeated except that polyvinyl alcohol was not added;

example 8: the biomass charcoal is subjected to directional pyrolysis in a nitrogen atmosphere, and the rest is the same as that in the embodiment 1;

example 9: eugenol containing aromatic rings is used to replace microalgal alcohol, the rest is the same as in example 1;

experiment: taking the biodegradable biomass charcoal-based compound fertilizer prepared in the embodiment 1-9, performing a dissolution experiment on the compound fertilizer according to the national standard GB/T23348-2009 sustained release fertilizer, wherein the experiment condition is that the illumination time is 10 hours per day at room temperature, and measuring the dissolution rate of the sustained release fertilizer in water at the 10 th day and the 30 th day; detecting the plant height; the coatings prepared in examples 1-8 were tested for degradation performance after 150 days; meanwhile, the fertilizers prepared in the example 1 and the example 5 are applied to a test field of corn, and the yield is compared; the results are shown in the following table:

and (4) conclusion: as can be seen from the data of the examples 1 to 4, the prepared sustained-release coating film has better biodegradability, and the degradation rate reaches more than 90% in 150 days. Meanwhile, in a water-soluble experiment, the slow release performance of the coating is better, the slow release speed of the phosphorus nutrient is reduced by about 80%, and the release of the sulfur nutrient is slower because the degradation of the polymer is slower.

From a comparison of the yields of example 5 and example 1, it can be seen that increasing the coated slow release fertilizer increased the yield by 5.1%, indicating that: the utilization rate of the slow-release fertilizer is higher than that of the common fertilizer. Meanwhile, the release rate of phosphorus nutrient is fast, and the sulfur nutrient is released because the sulfur-based polymer is the source of the sulfur nutrient; and which can reduce the release rate, as can be verified by comparing the data of example 6 and example 7, the slow release properties can be produced by using either polyvinyl alcohol or sulfur-based polymers as the coating ingredients; meanwhile, as the plant-based crosslinking agent is utilized to enable the polyvinyl alcohol gel and the sulfur-based polymer to form an interpenetrating crosslinking structure at the interface, the crosslinking degree is increased, the porosity of the coating is reduced, the release rate of phosphorus and nitrogen is reduced, the utilization rate is increased, and the reason why the release rate of example 5 is far greater than that of examples 6 and 7 is also that.

Comparing the data from example 8 with example 1, it can be seen that the release rate was not much different at day 10, but increased at day 30 due to: the biomass charcoal obtained by the non-directional pyrolysis in the air atmosphere has a rougher surface, and the resistance of the post-stage nutrient release of ammonium dihydrogen phosphate is increased.

Comparing the data of example 9 with example 1, it can be seen that the release rate of nutrients is reduced and the biodegradability after 150 days is also reduced slightly, because microalgal alcohol is a chain-type compound, which has no aromatic ring in the structure and is more easily degraded after polymerization with sulfur dioxide, so that the release rate of nutrients is slightly faster.

Finally, it should be noted that: although the present invention has been described in detail with reference to the foregoing embodiments, it will be apparent to those skilled in the art that changes may be made in the embodiments and/or equivalents thereof without departing from the spirit and scope of the invention. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A biodegradable biomass charcoal-based compound fertilizer is characterized in that: the compound fertilizer comprises a charcoal-based fertilizer and a degradable coating; the degradable coating comprises a sulfur-based polymer, polyvinyl alcohol gel.

2. The biodegradable biomass charcoal-based compound fertilizer according to claim 1, characterized in that: the raw materials of the degradable coating comprise the following components: the adhesive comprises, by weight, 25-32 parts of a sulfur-based polymer, 15-22 parts of polyvinyl alcohol and 2-6 parts of a vegetable oil-based crosslinking agent.

3. The biodegradable biomass charcoal-based compound fertilizer according to claim 2, characterized in that: the sulfur-based polymers are prepared by free radical copolymerization of microalgal alcohol and sulfur dioxide.

4. The biodegradable biomass charcoal-based compound fertilizer according to claim 1, characterized in that: the raw materials of the biomass charcoal-based fertilizer comprise biomass charcoal and saturated ammonium dihydrogen phosphate solution; the mass ratio of the biomass charcoal to the saturated ammonium dihydrogen phosphate solution is (1:1) - (1: 1.2).

5. The biodegradable biomass charcoal-based compound fertilizer according to claim 3, characterized in that: the biomass charcoal is obtained by non-directional pyrolysis in an air atmosphere.

6. The biodegradable biomass charcoal-based compound fertilizer according to claim 1, characterized in that: the mass ratio of the biochar-based fertilizer to the degradable coating is (1:0.1) - (1: 0.2).

7. A preparation method of a biodegradable biomass charcoal-based compound fertilizer is characterized by comprising the following steps: the method comprises the following steps:

s2: preparing a compound fertilizer:

8. The preparation method of the biodegradable biomass charcoal-based compound fertilizer according to claim 7, characterized by comprising the following steps: the specific process of step S1 is: adding biomass charcoal into deionized water, and stirring for 40-60 minutes under a magnetic stirrer; transferring the biomass carbon into an ultrasonic device, and carrying out ultrasonic treatment for 40-60 minutes to obtain a biomass carbon dispersion liquid; adding saturated ammonium dihydrogen phosphate solution, and stirring for 10-12 hours under magnetic stirring; and (4) rotary evaporation to dryness at the drying temperature of 55-65 ℃ to obtain the biochar-based fertilizer for later use.

9. The preparation method of the biodegradable biomass charcoal-based compound fertilizer according to claim 7, characterized by comprising the following steps: the specific process of step S2 is:

(1) preparation of sulfur-based polymers:

10. The preparation method of the biodegradable biomass charcoal-based compound fertilizer according to claim 9, characterized by comprising the following steps: in step S2 (1), the molar ratio of microalgal alcohol to t-butyl peroxide is (1:1) to (2: 1).