Potassium-rich straw-based biochar potassium slow-release fertilizer, preparation method and application thereof

Abstract

The application provides a method for preparing biochar potassium slow-release fertilizer by using potassium-rich straw, and the method comprises the following steps: preparing canna indica powder; mixing the canna indica powder with minerals in a proportion to obtain granular composite raw materials; pyrolyzing the granular composite raw materials, naturally cooling to room temperature after the pyrolysis is completed, taking out the solid product, and obtaining granular composite biochar, namely the biochar potassium slow-release fertilizer; and the method can greatly get rid of the dependence on traditional potassium fertilizer by mixing the canna indica plants with minerals to prepare the composite potassium-rich biochar, and effectively solves the problem of treatment and disposal of waste wetland biomass.

Description

Technical Field

[0001] This invention relates to the fields of solid waste resource utilization and sustainable agricultural development, and particularly to a potassium slow-release fertilizer based on potassium-rich straw, its preparation method, and its application. Background Technology

[0002] Potassium deficiency in soil is a significant factor hindering the sustainable development of agriculture in my country. However, the increasing cost of imported potash fertilizers in recent years necessitates a broader search for alternative and effective sources. Constructed wetlands are widely used for treating eutrophic water bodies and wastewater effluent, effectively purifying water quality. However, the operation of constructed wetlands generates a large amount of wetland plant residues, which require regular harvesting to maintain water purification efficiency. The proper disposal of these residues is crucial for the industrialization of ecological wetlands. Constructed wetland plants are a type of potassium-rich biomass waste, with canna lilies being particularly rich in potassium. Recycling and utilizing this potassium is of great significance for realizing the resource utilization of waste and alleviating potassium deficiency in arable land.

[0003] Biochar, prepared from wetland plant residues through pyrolysis, enables efficient potassium recovery and utilization. Simultaneously, applying biochar to the soil can also improve soil structure and reduce carbon emissions to some extent. However, the potassium in biochar exists primarily in inorganic form, which dissolves rapidly upon application to the soil. Potassium not absorbed by plants in the short term is lost through surface runoff, resulting in a waste of potassium resources. Therefore, it is necessary to develop a compound potassium-rich biochar slow-release fertilizer with potassium-slow-release properties by co-pyrolyzing and granulating potassium-rich canna lily raw materials, thereby improving potassium utilization efficiency. Summary of the Invention

[0004] This invention provides a potassium slow-release biochar fertilizer based on potassium-rich straw, its preparation method, and its application. The preparation method recovers and utilizes potassium from wetland plant residues, which can realize the resource utilization of waste and alleviate the lack of potassium resources in arable land. It can also play a role in soil improvement and carbon sequestration and emission reduction to a certain extent.

[0005] The specific technical solution is as follows:

[0006] A method for preparing potassium biochar slow-release fertilizer using potassium-rich straw includes the following steps:

[0007] (1) Preparation of canna powder;

[0008] (2) Mix canna powder with minerals in a certain proportion to obtain powdered composite raw material. Control the moisture content of the powdered composite raw material, granulate it, and dry it to obtain granular composite raw material.

[0009] (3) Pyrolyze the granular composite raw material. After pyrolysis, cool it naturally to room temperature and take out the solid product to obtain granular composite biochar, which is biochar potassium slow-release fertilizer.

[0010] Canna biochar refers to the process of decomposing potassium-rich canna biomass into pyrolytic char under high-temperature conditions. The particle size of the crushed canna is related to the degree of pyrolytic carbonization; excessively large particle size may result in incomplete hydrothermal carbonization of the canna. Canna biochar slow-release fertilizer is a potassium slow-release fertilizer prepared by pyrolyzing modified canna biomass raw materials. It has a certain slow-release effect. The mineral content affects the slow-release effect of potassium in biochar, the moisture content affects the granulation effect during granulation, and the particle size affects the slow-release effect of potassium in biochar. The appropriate temperature and time during the drying process of canna are important factors in determining its good mechanical strength. The heating rate, target temperature, and holding time are important factors in determining the biochar yield.

[0011] Further, in step (1), the method for preparing the canna powder is as follows: take the harvested canna plants, remove impurities, wash and air dry them, and then dry, crush and sieve them in sequence to obtain canna powder.

[0012] Preferably, in step (1), the canna plant is dried at a temperature of 65-105°C for 23-24 hours.

[0013] Preferably, in step (1), the moisture content of the canna lily after air-drying should be less than 20%.

[0014] Preferably, in step (1), the crushed canna lilies are passed through a 40-mesh sieve.

[0015] Preferably, in step (2), the mixing ratio of the canna powder to the minerals is 20:1 to 5:1.

[0016] Preferably, in step (2), the mineral is bentonite. Bentonite has a special interlayer structure that can retain potassium, slow down the release rate of potassium, and improve the utilization efficiency of potassium.

[0017] Preferably, in step (2), the moisture content of the powdered composite material is 18% to 23% to achieve the best molding effect.

[0018] Preferably, in step (2), the length of the granular composite material is 2.5 to 3.5 cm and the diameter is 3.9 to 4.0 mm.

[0019] Preferably, in step (2), the granular composite raw material is dried at 85°C for 23-24 hours.

[0020] Further, in step (3), a certain amount of granular composite raw material is weighed into a crucible, placed in a muffle furnace, the furnace door is closed and the furnace is sealed, the nitrogen valve and the air vent valve are opened, and nitrogen is introduced into the muffle furnace to vent the air inside the furnace. After about 6 minutes, the air vent valve and the nitrogen valve are closed, the pyrolysis program is set, the heating rate is 5℃ / min, and it is kept at 500℃ for 2 hours, and then naturally cooled to room temperature.

[0021] Preferably, in step (3), the muffle furnace is heated at a rate of 5°C / min, and pyrolysis is performed under the condition of heating to 500°C and holding for 2 hours.

[0022] Furthermore, in step (3), the biochar potassium slow-release fertilizer prepared by the preparation method described above.

[0023] Furthermore, in step (3), the biochar potassium slow-release fertilizer is used in the preparation of potassium slow-release fertilizer.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] (1) In this invention, canna powder is mixed with minerals to form a granular composite raw material, which is then pyrolyzed to obtain biochar potassium slow-release fertilizer. This biochar potassium slow-release fertilizer can realize the resource utilization of waste and alleviate the lack of potassium resources in arable land. It can also play a role in soil improvement and carbon sequestration and emission reduction to a certain extent.

[0026] (2) The potassium in the biochar slow-release fertilizer of the present invention comes from the biomass waste canna, which greatly reduces the dependence on traditional potassium fertilizer.

[0027] (3) The canna raw material of the present invention comes from plant residues of artificial wetlands, which effectively solves the problem of treatment and disposal of waste wetland biomass. Detailed Implementation

[0028] The present invention will be further described below with reference to specific embodiments. The following are only specific embodiments of the present invention, but the scope of protection of the present invention is not limited thereto.

[0029] The following examples and comparative examples illustrate the potassium release capacity of biochar and the calculation methods involved:

[0030] Weigh 0.1 g of the prepared powdered biochar and place it in a 15 mL centrifuge tube. Add 10 mL of deionized water and shake the mixture at 25 °C and 180 rpm. After 1 h and 24 h, remove the mixture, filter it through a 0.45 μm filter membrane, and collect the filtered solution. Then, determine the potassium content in the solution using a flame photometer and calculate the potassium release rate from the powdered biochar. The calculation formula is: Release rate = Potassium concentration * Release solution volume * 100% / (Biochar sample mass * Total potassium content). For granular biochar, weigh approximately 0.1 g of sample and add deionized water at a solid-liquid ratio of 1:100. The potassium release test and calculation are consistent with those for powdered biochar.

[0031] The following examples illustrate the method for calculating the yield of composite biochar:

[0032] The yield of all prepared composite biochar was calculated using the formula: Yield = (Weight of composite biochar prepared after pyrolysis / Weight of composite raw material).

[0033] Example 1

[0034] 1. Preparation of 5:1 mixed granular bentonite composite potassium-rich biochar

[0035] (1) Take the harvested canna plants, remove impurities, wash and air dry them, and then process them at 85°C, crush and sieve them to obtain canna powder.

[0036] (2) Mix the canna biomass powder and bentonite in a mass ratio of 5:1;

[0037] (3) The moisture content of the mixture of canna biomass powder and bentonite was controlled at 20%, and the mixture was granulated under a certain pressure to obtain granular composite raw material.

[0038] (3) Weigh the granular composite raw material into a crucible, place it in a muffle furnace, close the furnace door and ensure that the furnace is sealed, open the nitrogen valve and the air vent valve, introduce nitrogen into the muffle furnace to vent the air in the furnace, after about 6 minutes, close the air vent valve and the nitrogen valve, set the pyrolysis program, the heating rate is 5℃ / min, keep at 500℃ for 2 hours, and then cool naturally to room temperature, take out the pyrolysis solid product to obtain granular bentonite composite potassium-rich biochar.

[0039] 2. Determination of the potassium slow-release capacity of a 5:1 mixture of bentonite and potassium-rich biochar

[0040] Using the above-mentioned steps and calculation methods for determining the total potassium content of composite biochar, the total potassium content in composite biochar was determined; using the above-mentioned methods for determining the slow-release capacity of potassium in biochar, the potassium release rate in water from composite biochar was determined.

[0041] In this embodiment, the potassium release rates of bentonite composite potassium-rich biochar prepared by mixing canna lilies and bentonite in a 5:1 ratio, granulating, and co-pyrolyzing were 20.4% and 63.7% at 1 h and 24 h, respectively.

[0042] Comparative Example 1

[0043] 1. Preparation of 5:1 mixed powdered bentonite composite potassium-rich biochar

[0044] (1) Take the harvested canna plants, remove impurities, wash and air dry them, and then dry them at 85℃, crush and sieve them to obtain canna powder.

[0045] (2) Mix the canna biomass powder and bentonite in a mass ratio of 5:1;

[0046] (3) Weigh a certain amount of canna and bentonite mixture into a crucible, place it in a muffle furnace, close the furnace door and ensure that the furnace is sealed, open the nitrogen valve and the air vent valve, introduce nitrogen into the muffle furnace to vent the air in the furnace, after about 6 minutes, close the air vent valve and the nitrogen valve, set the pyrolysis program, the heating rate is 5℃ / min, keep at 500℃ for 2 hours, and then cool naturally to room temperature, take out the pyrolysis solid product to obtain 5:1 mixed powdered bentonite composite potassium-rich biochar.

[0047] The moisture content is 18%–23%; the particle length of the granular composite raw material is 2.5–3.5 cm, and the diameter is 3.9–4.0 mm. The granular composite raw material is dried at 65–105℃ for 12–24 hours.

[0048] 2. Determination of the potassium slow-release capacity of a 5:1 mixed powdered bentonite composite potassium-rich biochar

[0049] Using the above-mentioned steps and calculation methods for determining the total potassium content of composite biochar, the total potassium content in composite biochar was determined; using the above-mentioned methods for determining the slow-release capacity of potassium in biochar, the potassium release rate in water from composite biochar was determined.

[0050] In this embodiment, the potassium release rates of bentonite composite potassium-rich biochar prepared by co-pyrolysis of canna lily and bentonite in a 5:1 ratio were 62.1% and 66.2% at 1 h and 24 h, respectively.

[0051] Comparative Example 2

[0052] 1. Preparation of 10:1 mixed powdered bentonite composite potassium-rich biochar

[0053] (1) Take the harvested canna plants, remove impurities, wash and air dry them, and then process them at 85°C, crush and sieve them to obtain canna powder.

[0054] (2) Mix the canna biomass powder and bentonite in a mass ratio of 10:1;

[0055] (3) Weigh a certain amount of canna and bentonite mixture into a crucible, place it in a muffle furnace, close the furnace door and ensure that the furnace is sealed, open the nitrogen valve and the air vent valve, and introduce nitrogen into the muffle furnace to vent the air in the furnace. After about 6 minutes, close the air vent valve and the nitrogen valve, set the pyrolysis program, the heating rate is 5℃ / min, keep at 500℃ for 2 hours, and then cool naturally to room temperature. Take out the pyrolysis solid product to obtain a 10:1 mixed powdered bentonite composite potassium-rich biochar sample.

[0056] 2. Determination of the potassium slow-release capacity of 10:1 mixed powdered bentonite composite potassium-rich biochar

[0057] Using the above-mentioned steps and calculation methods for determining the total potassium content of composite biochar, the total potassium content in composite biochar was determined; using the above-mentioned methods for determining the slow-release capacity of potassium in biochar, the potassium release rate in water from composite biochar was determined.

[0058] In this embodiment, the potassium release rates of the bentonite composite potassium-rich biochar prepared by co-pyrolysis of canna lily and bentonite in a 10:1 ratio were 73.3% and 78.6% at 1 h and 24 h, respectively.

[0059] Comparative Example 3

[0060] 1. Preparation of 20:1 mixed powdered bentonite composite potassium-rich biochar

[0061] (1) Take the harvested canna plants, remove impurities, wash and air dry them, and then process them at 85°C, crush and sieve them to obtain canna powder.

[0062] (2) Mix the canna biomass powder and bentonite in a mass ratio of 20:1;

[0063] (3) Weigh a certain amount of canna and bentonite mixture into a crucible, place it in a muffle furnace, close the furnace door and ensure that the furnace is sealed, open the nitrogen valve and the air vent valve, introduce nitrogen into the muffle furnace to vent the air in the furnace, after about 6 minutes, close the air vent valve and the nitrogen valve, set the pyrolysis program, the heating rate is 5℃ / min, keep at 500℃ for 2 hours, and then cool naturally to room temperature, take out the pyrolysis solid product to obtain 20:1 mixed powdered bentonite composite potassium-rich biochar.

[0064] 2. Determination of the potassium slow-release capacity of 20:1 mixed powdered bentonite composite potassium-rich biochar

[0065] Using the above-mentioned steps and calculation methods for determining the total potassium content of composite biochar, the total potassium content in composite biochar was determined; using the above-mentioned methods for determining the slow-release capacity of potassium in biochar, the potassium release rate in water from composite biochar was determined.

[0066] In this embodiment, the potassium release rates of the bentonite composite potassium-rich biochar prepared by co-pyrolysis of canna lily and bentonite in a 20:1 ratio were 82.6% and 86.4% at 1 h and 24 h, respectively.

[0067] Comparative Example 4

[0068] 1. Preparation of 20:1 mixed powdered kaolin composite potassium-rich biochar

[0069] (1) Take the harvested canna plants, remove impurities, wash and air dry them, and then dry them at 65-105℃, crush them and sieve them to obtain canna powder.

[0070] (2) Mix the canna biomass powder and kaolin in a mass ratio of 20:1;

[0071] (3) Weigh a certain amount of canna and kaolin mixture into a crucible, place it in a muffle furnace, close the furnace door and ensure that the furnace is sealed, open the nitrogen valve and the air vent valve, introduce nitrogen into the muffle furnace to vent the air in the furnace, after about 6 minutes, close the air vent valve and the nitrogen valve, set the pyrolysis program, the heating rate is 5℃ / min, keep at 500℃ for 2 hours, and then cool naturally to room temperature, take out the pyrolysis solid product to obtain kaolin composite potassium-rich biochar.

[0072] 2. Determination of the potassium slow-release capacity of 20:1 mixed powdered kaolin composite potassium-rich biochar

[0073] Using the above-mentioned steps and calculation methods for determining the total potassium content of composite biochar, the total potassium content in composite biochar was determined; using the above-mentioned methods for determining the slow-release capacity of potassium in biochar, the potassium release rate in water from composite biochar was determined.

[0074] In this embodiment, the potassium release rates of the kaolin composite potassium-rich biochar prepared by co-pyrolysis of canna lily and kaolin in a 20:1 ratio were 81.0% and 85.8% at 1 h and 24 h, respectively.

[0075] Comparative Example 5

[0076] 1. Preparation of 10:1 mixed powdered kaolin composite potassium-rich biochar

[0077] (1) Take the harvested canna plants, remove impurities, wash and air dry them, and then dry them at 65-105℃, crush them and sieve them to obtain canna powder.

[0078] (2) Mix the canna biomass powder and kaolin in a mass ratio of 10:1 until uniform;

[0079] (3) Weigh a certain amount of canna and kaolin mixture into a crucible, place it in a muffle furnace, close the furnace door and ensure that the furnace is sealed, open the nitrogen valve and the air vent valve, introduce nitrogen into the muffle furnace to vent the air in the furnace, after about 6 minutes, close the air vent valve and the nitrogen valve, set the pyrolysis program, the heating rate is 5℃ / min, keep at 500℃ for 2 hours, and then cool naturally to room temperature, take out the pyrolysis solid product to obtain kaolin composite potassium-rich biochar.

[0080] 2. Determination of the potassium slow-release capacity of 10:1 mixed powdered kaolin composite potassium-rich biochar

[0081] Using the above-mentioned steps and calculation methods for determining the total potassium content of composite biochar, the total potassium content in composite biochar was determined; using the above-mentioned methods for determining the slow-release capacity of potassium in biochar, the potassium release rate in water from composite biochar was determined.

[0082] In this embodiment, the potassium release rates of the kaolin composite potassium-rich biochar prepared by co-pyrolysis of canna lily and kaolin in a 10:1 ratio were 75.5% and 85.1% at 1 h and 24 h, respectively.

[0083] Comparative Example 6

[0084] 1. Preparation of 10:1 mixed powdered zeolite composite potassium-rich biochar

[0085] (1) Take the harvested canna plants, remove impurities, wash and air dry them, and then dry them at 65-105℃, crush them and sieve them to obtain canna powder.

[0086] (2) Mix the canna biomass powder and zeolite in a mass ratio of 10:1;

[0087] (3) Weigh a certain amount of canna and zeolite mixture into a crucible, place it in a muffle furnace, close the furnace door and ensure that the furnace is sealed, open the nitrogen valve and the air vent valve, introduce nitrogen into the muffle furnace to vent the air in the furnace, after about 6 minutes, close the air vent valve and the nitrogen valve, set the pyrolysis program, the heating rate is 5℃ / min, keep at 500℃ for 2 hours, and then cool naturally to room temperature, take out the pyrolysis solid product to obtain zeolite composite potassium-rich biochar.

[0088] 2. Determination of the potassium slow-release capacity of 10:1 mixed powdered zeolite composite potassium-rich biochar

[0089] Using the above-mentioned steps and calculation methods for determining the total potassium content of composite biochar, the total potassium content in composite biochar was determined; using the above-mentioned methods for determining the slow-release capacity of potassium in biochar, the potassium release rate in water from composite biochar was determined.

[0090] In this embodiment, the potassium release rates of the zeolite composite potassium-rich biochar prepared by co-pyrolysis of canna lily and zeolite in a 10:1 ratio were 80.5% and 87.7% at 1 h and 24 h, respectively.

[0091] Comparative Example 7

[0092] 1. Preparation of 10:1 mixed powdered SiO2 composite potassium-rich biochar

[0093] (1) Take the harvested canna plants, remove impurities, wash and air dry them, and then dry them at 65-105℃, crush them and sieve them to obtain canna powder.

[0094] (2) Mix the canna biomass powder and SiO2 evenly at a mass ratio of 10:1;

[0095] (3) Weigh a certain amount of canna and SiO2 mixture into a crucible, place it in a muffle furnace, close the furnace door and ensure that the furnace is sealed, open the nitrogen valve and the air vent valve, and introduce nitrogen into the muffle furnace to vent the air in the furnace. After about 6 minutes, close the air vent valve and the nitrogen valve, set the pyrolysis program, the heating rate is 5℃ / min, keep at 500℃ for 2 hours, and then cool naturally to room temperature. Take out the pyrolysis solid product to obtain SiO2 composite potassium-rich biochar.

[0096] 2. Determination of potassium slow-release capacity of 10:1 mixed powdered SiO2 composite potassium-rich biochar

[0097] Using the above-mentioned steps and calculation methods for determining the total potassium content of composite biochar, the total potassium content in composite biochar was determined; using the above-mentioned methods for determining the slow-release capacity of potassium in biochar, the potassium release rate in water from composite biochar was determined.

[0098] In this embodiment, the potassium release rates of the zeolite composite potassium-rich biochar prepared by co-pyrolysis of canna lily and SiO2 in a 10:1 ratio were 97.4% and 99.0% at 1 h and 24 h, respectively.

Claims

1. A method for preparing potassium slow-release biochar fertilizer using potassium-rich straw, characterized in that, Includes the following steps: (1) Take the harvested canna plants, remove impurities, wash and air dry them, and then process them at 85 °C, crush and sieve them to obtain canna powder; (2) Mix the canna biomass powder and bentonite in a mass ratio of 5:1 until homogeneous; (3) The moisture content of the mixture of canna biomass powder and bentonite is controlled to be 20%, and it is granulated under a certain pressure to obtain granular composite raw material; The granular composite raw material has a particle length of 2.5~3.5 cm and a diameter of 3.9~4.0 mm; the granular composite raw material is dried at 65~105 °C for 12~24 h. (4) Weigh the granular composite raw material into a crucible, place it in a muffle furnace, close the furnace door and ensure that the furnace is sealed, open the nitrogen valve and the air vent valve, introduce nitrogen into the muffle furnace to vent the air in the furnace, after about 6 minutes, close the air vent valve and the nitrogen valve, set the pyrolysis program, the heating rate is 5 ℃ / min, keep at 500 ℃ for 2 h, and then cool naturally to room temperature, take out the pyrolysis solid product to obtain granular bentonite composite potassium-rich biochar.