Method for preparing humic-acid-containing water-soluble silicon-potassium fertilizer by means of thermocatalysis of silicon-rich biomass solid waste

Abstract

A method for preparing a humic-acid-containing water-soluble silicon-potassium fertilizer by means of the thermocatalysis of silicon-rich biomass solid waste. The method comprises: taking silicon-rich biomass solid waste as a raw material, reacting same with an activating agent and a catalyst together, and performing catalytic roasting and carbonization by means of atmospheric oxygen control to decompose organic matter and recombine carbon chains, so as to obtain a weathered coal-like precursor; then adding an oxidizing agent for further oxidation, so as to convert the weathered coal-like precursor into potassium humate and enrich the functional groups of potassium humate; subsequently, further adding an extracting agent, and then performing solid-liquid separation to obtain a liquid which is a humic-acid-containing water-soluble silicon-potassium fertilizer; and recovering the catalyst from the residues by means of magnetic separation, and reusing the catalyst. By means of a simple and convenient process, resource utilization of the silicon-rich biomass solid waste is achieved, silicon in the raw material is utilized, and the humic-acid-containing water-soluble silicon-potassium fertilizer is further used again in silicon-requiring crops, such as rice and corn, thereby achieving circulation of silicon in nature. Compared with traditional silicon fertilizers and humic acid fertilizers, the humic-acid-containing water-soluble silicon-potassium fertilizer has the advantages of reducing the amount and increasing the efficiency, and the process has good environmental benefits and economic benefits.

Description

A method for producing water-soluble silicon-potassium fertilizer containing humic acid by thermal catalysis of silicon-rich biomass solid waste Technical Field

[0001] The present invention relates to the field of biomass solid waste resource utilization, and in particular to a method for preparing water-soluble silicon-potassium fertilizer containing humic acid through thermal catalysis of silicon-rich biomass solid waste. Background Art

[0002] Globally, over 100 billion tons of agricultural biomass are generated annually. As one of the world's major agricultural nations, China generates significant amounts of agricultural biomass solid waste, including rice husks, straw, nut shells, and stalks. However, much of this biomass waste is currently disposed of primarily through incineration, which releases significant amounts of greenhouse gases. Therefore, innovative strategies and approaches are urgently needed to maximize the value of biomass solid waste.

[0003] Crops such as bamboo, rice, and reeds require a large amount of silicon during their growth, so the biomass solid waste produced by these crops contains a large amount of silicon. Silicon is one of the important nutrients in plant bodies and is considered to be the fourth most important element after nitrogen, phosphorus, and potassium. Silicon is an important component of plant cell walls. It can enhance crop lodging resistance, disease and pest resistance, increase crop yield, improve quality, and increase the effectiveness of phosphate fertilizers. However, at present, the effective silicon content in compound silicon fertilizers is low, and the method of synthesizing silicon fertilizers is complex and costly. If the recycling of effective silicon in silicon-rich biomass solid waste can be achieved, it will be of great significance.

[0004] Humic acid is an important and relatively expensive organic fertilizer that has been highly recognized by the market for many years. It is traditionally produced using alkaline extraction from weathered coal and lignite. However, sources of weathered coal and lignite with high humic acid content are relatively scarce, resulting in limited production and high market prices. Consequently, the technology for producing biochemical humic acid from biomass solid waste has begun to develop. However, composting to produce biochemical humic acid presents challenges such as unstable fertilizer efficiency and low economic returns; hydrothermal production of biochemical humic acid presents challenges such as harsh conditions and high costs; and rapid pyrolysis to produce humic acid presents challenges such as complex products and high energy consumption. In response to the current problems in biomass production of biochemical humic acid, CN202211344371.2 discloses a method for producing agricultural and forestry biomass solid waste into water-soluble fertilizer containing super-mineral humic acid by low-temperature roasting; CN202211629558.7 discloses a method for converting traditional Chinese medicine residue into Chinese herbal organic fertilizer using a cobalt-iron catalyst, which uses a cobalt-iron catalyst to pyrolyze and activate the residue. Therefore, the use of low-temperature catalytic pyrolysis can effectively achieve the conversion of biomass organic matter into humic acid, and the cost is low, which is expected to achieve industrial production.

[0005] Therefore, in response to the current problems with silicon fertilizers and based on the feasibility of low-temperature catalytic pyrolysis, a method is developed to convert silicon-rich biomass solid waste organic matter into humic acid while achieving effective silicon utilization therein, which has high economic and environmental benefits.

[0006] Summary of the Invention

[0007] The primary purpose of the present invention is to overcome the shortcomings and deficiencies of the prior art and to provide a method for producing water-soluble silicon-potassium fertilizer containing humic acid by thermal catalysis of silicon-rich biomass solid waste.

[0008] Another object of the present invention is to provide an application of an iron nanocatalyst in the preparation of a water-soluble silicon-potassium fertilizer containing humic acid.

[0009] The purpose of the present invention is achieved through the following technical solutions:

[0010] The invention discloses an application of an iron nanocatalyst in the preparation of a water-soluble silicon-potassium fertilizer containing humic acid. The preparation method of the iron nanocatalyst comprises the following steps: mixing an iron salt and a precipitant in water, hydrolyzing the mixture at 60-100° C. for 1-2 hours, adding a ferrous salt and a pH regulator to adjust the pH to neutral, and refluxing the mixture at boiling point for 1-2 hours to obtain the iron nanocatalyst.

[0011] Preferably, the molar ratio of the precipitant to the iron salt is 1:2.

[0012] Preferably, the molar ratio of the ferrous salt to the ferric salt is 1:4.

[0013] Preferably, the molar concentration of the iron salt in water is 0.4 mol / L.

[0014] Preferably, the iron salt includes at least one of ferric chloride, ferric nitrate and ferric sulfate.

[0015] Preferably, the precipitant comprises at least one of NH4OH and NaOH.

[0016] Preferably, the ferrous salt includes at least one of ferrous chloride, ferrous nitrate and ferrous sulfate.

[0017] Preferably, the pH adjuster includes at least one of KOH and NaOH.

[0018] Preferably, all steps of the preparation method are carried out under N2 conditions.

[0019] A method for producing water-soluble silicon-potassium fertilizer containing humic acid by thermal catalysis of silicon-rich biomass solid waste comprises the following steps:

[0020] (1) The iron nanocatalyst is mixed with silicon-rich biomass solid waste and an activator, and the mixture is calcined at 200-400° C. in an atmosphere of nitrogen to oxygen ratio of 9:1-3:1 for 3-5 h to obtain a weathered coal-like precursor;

[0021] (2) The weathered coal precursor obtained in step (1) is mixed with an oxidant aqueous solution, oxidized at 60-100° C. for 8-12 hours, and then an extractant is added to separate the solid and liquid; the obtained liquid is a water-soluble silicon-potassium fertilizer product containing humic acid.

[0022] Preferably, the silicon-rich biomass solid waste in step (1) includes at least one of bamboo, rice husks, reeds and plant straws; and the plant straws include at least one of rice, sugarcane and corn stalks.

[0023] Preferably, the silicon-rich biomass solid waste in step (1) is silicon-rich biomass solid waste powder, more preferably silicon-rich biomass solid waste powder obtained by washing and crushing the silicon-rich biomass solid waste; most preferably, the silicon-rich biomass solid waste powder is silicon-rich biomass solid waste powder passed through a 200-mesh sieve.

[0024] Preferably, the amount of the catalyst in step (1) is 0.5% to 2% of the mass of the silicon-rich biomass solid waste powder; more preferably 1%.

[0025] Preferably, the activator in step (1) includes at least one of K3PO4, K2SO4, KNO3, KNO2 and K2SO3.

[0026] Preferably, the amount of the activator in step (1) is 10% to 50% of the mass of the silicon-rich biomass solid waste powder; more preferably 30%.

[0027] Preferably, the oxidant in step (2) includes at least one of H2O2, HNO3 and CH3COOOH.

[0028] Preferably, the amount of the oxidant in step (2) is 1% to 5% of the mass of the silicon-rich biomass solid waste powder, more preferably 2%.

[0029] Preferably, the mass fraction of the oxidant aqueous solution in step (2) is 1% to 5%; more preferably 1%.

[0030] Preferably, the extraction agent in step (2) includes at least one of KOH, K2CO3 and K4P2O7.

[0031] Preferably, the amount of the extracting agent in step (2) is 5% to 20% of the mass of the silicon-rich biomass solid waste powder; more preferably 10%.

[0032] Preferably, the liquid product of the humic acid-containing water-soluble silicon-potassium fertilizer in step (2) is used as a water-soluble fertilizer after being concentrated or diluted.

[0033] Preferably, the method further comprises the following steps:

[0034] (3) The solid residue obtained by separation in step (2) is subjected to magnetic separation to obtain an iron nanocatalyst.

[0035] The principle of the method of the present invention is as follows:

[0036] In the present invention, silicon-rich biomass solid wastes such as bamboo, rice husks, reeds, and plant straws such as rice, sugarcane, and corn stalks are cleaned and crushed, then mixed with an activator and a catalyst in a certain proportion and subjected to atmosphere-controlled oxygen catalytic roasting and carbonization to obtain a weathered coal precursor and activate the silicon therein. The role of the catalyst is mainly to reduce the activation energy of the decomposition and polymerization of lignin, cellulose, and hemicellulose therein to achieve the recombination of carbon chains and form humic acid and its precursor; the role of the activator is mainly to further enhance the effect of the catalyst, promote the formation of organic functional groups, and convert insoluble silicon into soluble silicon, while providing certain nutrients such as N, P, and K. The obtained weathered coal precursor is mixed with an oxidant in a certain proportion for oxidation. The role of the oxidant is mainly to further oxidize, converting the weathered coal precursor into potassium humate and enriching its functional groups. An extractant is then added to extract the obtained product. The role of the extractant is mainly to further participate in the reaction, extracting humic acid and soluble silicon therein, and further supplementing nutrients such as N, P, and K. The obtained product is subjected to solid-liquid separation, and the obtained liquid is the water-soluble silicon-potassium fertilizer containing humic acid. The solid residue is separated by magnetic separation to recover the added catalyst for reuse.

[0037] The present invention has the following advantages and effects compared to the prior art:

[0038] (1) The present invention adopts an atmosphere-controlled oxygen catalytic roasting-oxidation method to achieve an organic matter conversion rate of 50-70% in silicon-rich biomass solid waste. The process is simple, the cost is low, and large-scale industrial application can be achieved.

[0039] (2) The catalyst used in the present invention is a nano-scale iron catalyst, which has extremely high catalytic activity and is conducive to promoting the stability of the pH value of the reaction environment. It can also be reused by magnetic separation. The catalyst and oxidant are used to promote the decomposition and polymerization of organic matter in silicon-rich biomass, further improve the yield of humic acid, and improve agricultural and economic benefits. At the same time, the activator and extractant used can provide the product with nutrients such as N, P, and K, further improving the agricultural and economic benefits of the water-soluble silicon-potassium fertilizer containing humic acid.

[0040] (3) The present invention realizes the utilization of effective silicon, so that the insoluble silicon in silicon-rich biomass solid waste is converted into soluble silicon, which enters the solution to obtain liquid silicon fertilizer containing humic acid, thereby realizing the soil-crop-soil silicon cycle. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] FIG1 is a flow chart of the present invention;

[0042] FIG2 is an XRD pattern of the special iron nanocatalyst obtained in Example 1;

[0043] FIG3 is a performance cycle stability diagram of the special iron nanocatalyst obtained in Example 1;

[0044] FIG4 is a Fourier transform infrared absorption spectrum of humic acid in the humic acid-containing water-soluble silicon-potassium fertilizer obtained in Example 1;

[0045] FIG5 is a comparison diagram of crop planting of the water-soluble silicon-potassium fertilizer containing humic acid, commercial silicon fertilizer, and humic acid fertilizer in Example 4. DETAILED DESCRIPTION

[0046] The following describes the embodiments of the present invention through specific examples. Those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this description. The present invention can also be applied through other different specific embodiments. The details of this description can be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention.

[0047] Before further describing the specific embodiments of the present invention, it should be understood that the scope of protection of the present invention is not limited to the specific embodiments described below; the terms used in the examples of the present invention are intended to describe specific embodiments rather than to limit the scope of protection of the present invention; and all technical and scientific terms used in the present invention have the same meanings as those commonly understood by those skilled in the art.

[0048] The present invention will be described in further detail below with reference to examples and drawings, but the embodiments of the present invention are not limited thereto.

[0049] If no specific conditions are specified in the examples of the present invention, the experiments were carried out according to conventional conditions or the conditions recommended by the manufacturer; all raw materials, reagents, etc. used without specifying the manufacturer are conventional products that can be purchased commercially.

[0050] The process of the present invention is shown in Figure 1.

[0051] Example 1

[0052] (1) Under N2 conditions, 0.4 mol of iron salt (35.97 g Fe(NO3)3, 32.5 g FeCl3) was dissolved in 1 L of water to prepare a 0.4 mol / L iron salt solution. 8 g of precipitant (NaOH) was then added, mixed and stirred, and hydrolyzed at 60-100°C for 1-2 h. 0.1 mol of ferrous salt (6.34 g FeCl2, 12.09 g Fe(NO3)2) and pH regulator (NaOH) were then added to adjust the pH to neutral. The solution was refluxed at boiling point for 1-2 h to obtain a special iron nanocatalyst. The XRD pattern of the iron nanocatalyst is shown in FIG2 .

[0053] (2) Weighing 10 kg of silicon-rich biomass solid waste (bamboo), washing and crushing it and passing it through a 200-mesh sieve, and mixing it evenly with the catalyst (100 g of special iron nanocatalyst) obtained in step (1) and activators (1 kg of K3PO4, 1 kg of K2SO4 and 1 kg of KNO3), and calcining it at 300 ° C. in an atmosphere with a nitrogen to oxygen ratio of 7:1 for 4 h to obtain a weathered coal precursor;

[0054] (3) The weathered coal precursor obtained in step (2) was mixed with an oxidant (10 L of a 1% H2O2 solution and 10 L of a 1% CH3COOOH solution), and oxidized at 80°C for 10 h to obtain a preliminary product. An extractant (0.5 kg KOH, 0.25 kg K2CO3, and 0.25 kg K4P2O7) was then added, and the solid-liquid separation was performed;

[0055] (4) The catalyst obtained in step (3) and the carbonized residue mixture were magnetically separated to recover a catalyst mass of 98.2 g; the recovered catalyst was subjected to steps (2) to (5) repeatedly and a stability test was performed. The results are shown in FIG3 .

[0056] (5) The liquid obtained in step (3) is a water-soluble silicon-potassium fertilizer product containing humic acid, and 9.6 kg of a solid product of a water-soluble silicon-potassium fertilizer containing humic acid (silicon content reaches 13.5%) is obtained by concentration and granulation, and it meets the Class I quality of the HG / T 5933-2021 "Humic Acid Organic-Inorganic Compound Fertilizer" standard and the NY / T 3829-2021 "Silicon-Containing Water-Soluble Fertilizer" standard. The results are shown in Tables 1 and 2; the Fourier transform infrared absorption spectrum of humic acid in the water-soluble silicon-potassium fertilizer product containing humic acid is shown in Figure 4.

[0057] In this example, 10 kg of silicon-rich biomass solid waste was treated with 100 g of catalyst, 3 kg of activator, approximately 2 kg of oxidant, and 1 kg of extractant. After the reaction, magnetic separation was performed to obtain 98.2 g of a special iron catalyst and 9.6 kg of a solid product of a water-soluble silicon-potassium fertilizer containing humic acid (silicon content of 13.5%). The yield was calculated as 96% based on the formula: yield = mass of the solid product of the water-soluble silicon-potassium fertilizer containing humic acid / mass of the silicon-rich biomass powder.

[0058] Table 1 Technical index test results of HG / T 5933-2021 "Humic acid organic-inorganic compound fertilizer"

[0059] Table 2 NY / T 3829-2021 "Silicon-containing water-soluble fertilizers" technical index test results

[0060] Comparative Example 1

[0061] (1) Under N2 conditions, 0.4 mol of iron salt (35.97 g Fe(NO3)3, 32.5 g FeCl3) was dissolved in 1 L of water to prepare a 0.4 mol / L iron salt solution, and then 8 g of a precipitant (NaOH) was added, mixed and stirred, and hydrolyzed at 60-100°C for 1-2 h. Then, 0.1 mol of ferrous salt (6.34 g FeCl2, 12.09 g Fe(NO3)2) and a pH regulator (NaOH) were added to adjust the pH to neutral, and the solution was refluxed at boiling point for 1-2 h to obtain a special iron nanocatalyst;

[0062] (2) Weighing 10 kg of silicon-rich biomass solid waste (bamboo), washing and crushing it and passing it through a 200-mesh sieve, and mixing it with the catalyst obtained in step (1) (50 g of special iron nanocatalyst and 50 g of commercial iron oxide catalyst) and activator (1 kg K3PO4, 1 kg K2SO4 and 1 kg KNO3), and calcining it at 300 ° C. in an atmosphere with a nitrogen to oxygen ratio of 7:1 for 4 h to obtain a weathered coal precursor;

[0063] (3) The weathered coal precursor obtained in step (2) was mixed with an oxidant (10 L of a 1% H2O2 solution and 10 L of a 1% CH3COOOH solution), and oxidized at 80°C for 10 h to obtain a preliminary product. An extractant (0.5 kg KOH, 0.25 kg K2CO3, and 0.25 kg K4P2O7) was then added, and the solid-liquid separation was performed;

[0064] (4) The catalyst obtained in step (3) and the carbonized residue mixture were separated by magnetic separation to recover 97.4 g of catalyst;

[0065] (5) The liquid obtained in step (3) is a humic acid-containing water-soluble silicon-potassium fertilizer product, and 7.9 kg of a humic acid-containing water-soluble silicon-potassium fertilizer solid product (silicon content is 3.6%) is obtained through concentration and granulation, which meets the Class I quality standard of HG / T 5933-2021 "Humic acid organic-inorganic compound fertilizer", but does not meet the standard of NY / T 3829-2021 "Silicon-containing water-soluble fertilizer".

[0066] In this example, 10 kg of silicon-rich biomass solid waste was treated with 100 g of catalyst, 3 kg of activator, approximately 2 kg of oxidant, and 1 kg of extractant. After the reaction, magnetic separation yielded 97.4 g of iron catalyst and 7.9 kg of a solid product containing humic acid-soluble silicon-potassium fertilizer (silicon content: 3.6%). The yield was calculated as 84% ​​(yield = mass of solid product containing humic acid-soluble silicon-potassium fertilizer / mass of silicon-rich biomass powder). Compared with Example 1, this example replaced a certain amount of the specialized iron nanocatalyst with an equal amount of a commercial iron oxide catalyst. Testing revealed a significant decrease in pH compared to Example 1 (results shown in Table 3), a slight decrease in the amount of iron catalyst obtained through magnetic separation, and a decrease in the yield of the solid product containing humic acid-soluble silicon-potassium fertilizer, as well as its silicon content. This indicates that the self-made iron nanocatalyst is more conducive to the production of humic acid and the utilization of silicon.

[0067] Table 3 pH results before and after the reaction of Example 1 and Comparative Example 1

[0068] Example 2

[0069] (1) Under N2 conditions, 0.4 mol of iron salt (35.97 g Fe(NO3)3, 32.5 g FeCl3) was dissolved in 1 L of water to prepare a 0.4 mol / L iron salt solution, and then 8 g of a precipitant (NaOH) was added, mixed and stirred, and hydrolyzed at 60-100°C for 1-2 h. Then, 0.1 mol of ferrous salt (6.34 g FeCl2, 12.09 g Fe(NO3)2) and a pH regulator (NaOH) were added to adjust the pH to neutral, and the solution was refluxed at boiling point for 1-2 h to obtain a special iron nanocatalyst;

[0070] (2) Weighing 10 kg of silicon-rich biomass solid waste (rice straw), washing and crushing it and passing it through a 200-mesh sieve, and mixing it evenly with the catalyst (100 g of special iron nanocatalyst) obtained in step (1) and activators (1 kg K3PO4, 1 kg K2SO4 and 1 kg KNO3), and calcining it at 300 ° C. in an atmosphere with a nitrogen to oxygen ratio of 7:1 for 4 h to obtain a weathered coal-like precursor;

[0071] (3) The weathered coal precursor obtained in step (2) was mixed with an oxidant (10 L of a 1% H2O2 solution and 10 L of a 1% CH3COOOH solution), and oxidized at 80°C for 10 h to obtain a preliminary product. An extractant (0.5 kg KOH, 0.25 kg K2CO3, and 0.25 kg K4P2O7) was then added, and the solid-liquid separation was performed;

[0072] (4) The catalyst obtained in step (3) and the carbonized residue mixture were magnetically separated and the catalyst mass was recovered to be 98.1 g;

[0073] (5) The liquid obtained in step (3) is a humic acid-containing water-soluble silicon-potassium fertilizer product, and 9.2 kg of a humic acid-containing water-soluble silicon-potassium fertilizer solid product (silicon content is 17.2%) is obtained through concentration and granulation, and the solid product meets the Class I quality requirements of the HG / T 5933-2021 "Humic Acid Organic-Inorganic Compound Fertilizer" standard and the NY / T 3829-2021 "Silicon-Containing Water-Soluble Fertilizer" standard.

[0074] In this example, 10 kg of silicon-rich biomass solid waste was treated with 100 g of catalyst, 3 kg of activator, approximately 2 kg of oxidant, and 1 kg of extractant. After the reaction, magnetic separation yielded 98.1 g of a specialized iron catalyst and 9.2 kg of a solid product containing humic acid-soluble silicon-potassium fertilizer (silicon content: 17.2%). The yield was calculated as 92% (yield = mass of solid product containing humic acid-soluble silicon-potassium fertilizer / mass of silicon-rich biomass powder). Compared to Example 1, the raw material in this example was rice straw, which has a higher silicon content than bamboo. The resulting solid product containing humic acid-soluble silicon-potassium fertilizer also had a higher silicon content, effectively utilizing the material.

[0075] Example 3

[0076] (1) Under N2 conditions, 0.4 mol of iron salt (35.97 g Fe(NO3)3, 32.5 g FeCl3) was dissolved in 1 L of water to prepare a 0.4 mol / L iron salt solution, and then 8 g of a precipitant (NaOH) was added, mixed and stirred, and hydrolyzed at 60-100°C for 1-2 h. Then, 0.1 mol of ferrous salt (6.34 g FeCl2, 12.09 g Fe(NO3)2) and a pH regulator (NaOH) were added to adjust the pH to neutral, and the solution was refluxed at boiling point for 1-2 h to obtain a special iron nanocatalyst;

[0077] (2) Weighing 10 kg of silicon-rich biomass solid waste (rice husk), cleaning and crushing it and passing it through a 200-mesh sieve, and mixing it evenly with the catalyst (100 g of special iron nanocatalyst) obtained in step (1) and activators (1 kg of K3PO4, 1 kg of K2SO4 and 1 kg of KNO3), and calcining it at 300 ° C. in an atmosphere with a nitrogen to oxygen ratio of 7:1 for 4 h to obtain a weathered coal-like precursor;

[0078] (3) The weathered coal precursor obtained in step (2) was mixed with an oxidant (10 L of a 1% H2O2 solution and 10 L of a 1% CH3COOOH solution), and oxidized at 80°C for 10 h to obtain a preliminary product. An extractant (0.5 kg KOH, 0.25 kg K2CO3, and 0.25 kg K4P2O7) was then added, and the solid-liquid separation was performed;

[0079] (4) The catalyst obtained in step (3) and the carbonized residue mixture were magnetically separated and the catalyst mass was recovered to be 98.2 g;

[0080] (5) The liquid obtained in step (3) is a humic acid-containing water-soluble silicon-potassium fertilizer product, and 9.8 kg of a humic acid-containing water-soluble silicon-potassium fertilizer solid product (silicon content is 21.3%) is obtained through concentration and granulation, and the solid product meets the Class I quality standards of HG / T 5933-2021 "Humic Acid Organic-Inorganic Compound Fertilizer" and NY / T 3829-2021 "Silicon-Containing Water-Soluble Fertilizer" standards.

[0081] In this example, 10 kg of silicon-rich biomass solid waste was treated with 100 g of catalyst, 3 kg of activator, approximately 2 kg of oxidant, and 1 kg of extractant. After the reaction, magnetic separation yielded 98.2 g of a special iron catalyst and 9.8 kg of a solid product containing humic acid-soluble silicon-potassium fertilizer (silicon content: 21.3%). The yield was calculated as 98% using the formula (yield = mass of the solid product containing humic acid-soluble silicon-potassium fertilizer / mass of the silicon-rich biomass powder). Compared to Examples 1 and 2, the raw material in this example was rice husk, which has a higher silicon content than bamboo and rice straw. The resulting solid product containing humic acid-soluble silicon-potassium fertilizer also had a higher silicon content. Multiple examples have demonstrated that this technical approach can effectively utilize silicon from silicon-rich biomass solid waste.

[0082] Comparative Example 2

[0083] (1) Under N2 conditions, 0.4 mol of iron salt (35.97 g Fe(NO3)3, 32.5 g FeCl3) was dissolved in 1 L of water to prepare a 0.4 mol / L iron salt solution, and then 8 g of a precipitant (NaOH) was added, mixed and stirred, and hydrolyzed at 60-100°C for 1-2 h. Then, 0.1 mol of ferrous salt (6.34 g FeCl2, 12.09 g Fe(NO3)2) and a pH regulator (NaOH) were added to adjust the pH to neutral, and the solution was refluxed at boiling point for 1-2 h to obtain a special iron nanocatalyst;

[0084] (2) Weighing 10 kg of silicon-rich biomass solid waste (rice husk), cleaning and crushing it and passing it through a 200-mesh sieve, and mixing it evenly with the catalyst (100 g of special iron nanocatalyst) obtained in step (1) and activators (1 kg of K3PO4, 1 kg of K2SO4 and 1 kg of KNO3), and calcining it at 300 ° C in an air atmosphere for 4 h to obtain a weathered coal precursor;

[0085] (3) The weathered coal precursor obtained in step (2) was mixed with an oxidant (10 L of a 1% H2O2 solution and 10 L of a 1% CH3COOOH solution), and oxidized at 80°C for 10 h to obtain a preliminary product. An extractant (0.5 kg KOH, 0.25 kg K2CO3, and 0.25 kg K4P2O7) was then added, and the solid-liquid separation was performed;

[0086] (4) The catalyst obtained in step (3) and the carbonized residue mixture were magnetically separated and the catalyst mass was recovered to be 98.2 g;

[0087] (5) The liquid obtained in step (3) is a humic acid-containing water-soluble silicon-potassium fertilizer product, and 7.4 kg of a humic acid-containing water-soluble silicon-potassium fertilizer solid product (silicon content is 18.9%) is obtained through concentration and granulation, and the solid product meets the Class I quality requirements of the HG / T 5933-2021 "Humic Acid Organic-Inorganic Compound Fertilizer" standard and the NY / T 3829-2021 "Silicon-Containing Water-Soluble Fertilizer" standard.

[0088] In this embodiment, 10 kg of silicon-rich biomass solid waste was treated, with 100 g of catalyst added, 3 kg of activator added, approximately 2 kg of oxidant, and 1 kg of extractant added. After the reaction, magnetic separation was performed to obtain 97.8 g of a special iron catalyst and 7.4 kg of a solid product containing humic acid-soluble silicon-potassium fertilizer (silicon content was 18.9%). The yield was calculated as 74% by yield = mass of the solid product containing humic acid-soluble silicon-potassium fertilizer / mass of the silicon-rich biomass powder. Compared with Example 3, this embodiment used an air atmosphere, and the mass of the product after step 2 was significantly reduced, resulting in a large amount of thermal decomposition, resulting in a decrease in the final product yield and quality.

[0089] Example 4

[0090] (1) Select corn seeds with full grains, no pests, and uniform size and disinfect them for growth experiments. Accurately weigh 1 kg of soil and place it in a flowerpot.

[0091] (2) Each group of 100 seeds was mixed with equal amounts of commercial silicon fertilizer, humic acid fertilizer, and water-soluble silicon-potassium fertilizer containing humic acid prepared in Example 1, and evenly planted in flower pots. After the seeds emerged, they were watered quantitatively and placed in a greenhouse with 16 h of light at a temperature of (26±2)°C, 8 h of darkness at a temperature of (24±2)°C, and a relative humidity of 70%.

[0092] (3) Adjust the soil moisture with deionized water and regularly replenish the soil moisture by weighing to maintain a constant soil moisture level. This was repeated three times, and corn seedlings were harvested and compared four weeks after sowing. The results are shown in Figure 5 and Table 4.

[0093] In this example, corn seedlings cultured for four weeks using the water-soluble silicon-potassium fertilizer containing humic acid prepared in Example 1 had a plant height of 24.37 cm and a root length of 14.01 cm, demonstrating superior fertilizer efficiency compared to commercial silicon fertilizers and humic acid fertilizers alone. This indicates that the water-soluble silicon-potassium fertilizer containing humic acid prepared by this process has a high content of soluble active silicon and a certain amount of humic acid, which has a better growth stimulating effect on silicon-requiring plants such as corn.

[0094] Table 4 Example 4 Corn crop growth experimental results

[0095] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be considered as equivalent replacement methods and are included in the scope of protection of the present invention.

Claims

1. Application of an iron nanocatalyst in the preparation of water-soluble potassium humate silicate fertilizer; characterized in that, The preparation method of the iron nanocatalyst includes the following steps: Mix an iron salt and a precipitant in water, hydrolyze at 60-100 °C for 1-2 h, then add a ferrous salt and a pH regulator to adjust the pH to neutral, and reflux at the boiling point for 1-2 h to obtain the iron nanocatalyst.

2. The application according to claim 1, wherein All steps of the preparation method are carried out under N2 conditions.

3. The application according to claim 1, wherein The molar ratio of the precipitant to the iron salt is: 1:2; The molar ratio of the ferrous salt to the iron salt is: 1:4; The molar concentration of the iron salt in water is: 0.4 mol / L.

4. The application according to claim 1, wherein The iron salt includes at least one of ferric chloride, ferric nitrate, and ferric sulfate; The precipitant includes at least one of NH4OH and NaOH; The ferrous salt includes at least one of ferrous chloride, ferrous nitrate, and ferrous sulfate; The pH regulator includes at least one of KOH and NaOH.

5. A method for thermally catalytically preparing water-soluble silicon potassium fertilizer containing humic acid from silicon-rich biomass solid waste, characterized in that, It includes the following steps: (1) Mix the iron nanocatalyst described in any one of claims 1-4 with silicon-rich biomass solid waste and an activator evenly, and calcine at 200-400 °C in an atmosphere with a nitrogen-to-oxygen ratio of 9:1-3:1 for 3-5 h to obtain a weathered coal-like precursor; (2) Mix the weathered coal-like precursor obtained in step (1) with an aqueous solution of an oxidant, oxidize at 60-100 °C for 8-12 h, and then add an extractant to separate the solid and liquid; the obtained liquid is a water-soluble humic acid silicon potassium fertilizer product.

6. The method according to claim 5, wherein The silicon-rich biomass solid waste in step (1) includes at least one of bamboo, rice husk, reed, and plant straw; The silicon-rich biomass solid waste in step (1) is silicon-rich biomass solid waste powder; The activator in step (1) includes at least one of K3PO4, K2SO4, KNO3, KNO2, and K2SO3.

7. The method according to claim 5, wherein The dosage of the catalyst in step (1) is 0.5%-2% of the mass of the silicon-rich biomass solid waste powder; The dosage of the activator in step (1) is 10%-50% of the mass of the silicon-rich biomass solid waste powder.

8. The method according to claim 5, wherein The oxidant in step (2) includes at least one of H2O2, HNO3, and CH3COOOH; The extractant in step (2) includes at least one of KOH, K2CO3, and K4P2O7.

9. The method according to claim 5, wherein The dosage of the oxidant in step (2) is 1%-5% of the mass of the silicon-rich biomass solid waste powder; more preferably 2%; The mass fraction of the aqueous solution of the oxidant in step (2) is 1%-5%; more preferably 1%; The dosage of the extractant in step (2) is 5%-20% of the mass of the silicon-rich biomass solid waste powder.

10. The method according to claim 5, wherein The method further includes the following steps: (3) Perform magnetic separation on the solid residue separated in step (2) to obtain the iron nanocatalyst.

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