Method for preparing carbon-based phosphorus-potassium fertilizer by using silicon-rich biomass

Abstract

The invention discloses a method for preparing a carbon-based phosphorus-potassium fertilizer by using silicon-rich biomass, and relates to a preparation method of the carbon-based phosphorus-potassium fertilizer. The invention aims to solve the technical problems that the reversal effect of existing biochar on phosphorus fixation in saline-alkali soil is poor, and especially the improvement effect on soil with low phosphorus content is not obvious. The agricultural straw waste is used as a raw material, phosphoric acid microwave co-pyrolysis and atmosphere regulation co-pyrolysis technologies are combined, the process is simple and convenient, the cost is low, the large-scale production potential is achieved, in the preparation process, original components such as KCl and K2CO3 in the straw can react with phosphoric acid to generate compounds such as potassium metaphosphate with fertilizer efficiency, the effectiveness of phosphorus and potassium is further improved, and the production cost is reduced. Absorption of crops to phosphorus, potassium, silicon and other elements is promoted, the physical structure of saline-alkali soil can be effectively improved, the volume weight is reduced, the stability of aggregates is improved, alkalinity is neutralized, and soil fertility, water holding capacity and carbon sequestration potential are synergistically enhanced.

Description

TECHNICAL FIELD

[0001] The present application relates to a preparation method of carbon-based potassium phosphate fertilizer. BACKGROUND

[0002] The global area of saline-alkali soil is more than 1 billion hectares, and the total area of saline soil in China is about 3.69 x 10 7 hm², accounting for about 25% of the cultivated land area. Saline-alkali soil is generally characterized by high pH (8.5-10), high sodium ion (Na + ) and high carbonate content, which leads to the combination of phosphate (PO4 3- ) in soil with calcium (Ca 2+ ), aluminum (Al 3+ ) and other cations to form insoluble phosphate precipitates (such as hydroxyapatite, Ca 10 (PO4)6(OH)2), resulting in a significant decrease in the content of available phosphorus in soil, which can be up to 50%-80%. At the same time, the saline stress environment also inhibits the activity of soil phosphatase, further hindering the mineralization process of organic phosphorus, resulting in a significant decrease in the absorption efficiency of phosphorus by plants, which is less than 30% of that in traditional farmland. Similarly, potassium ions (K + ) are also easily adsorbed by soil colloids or combined with chloride and sulfate, resulting in a decrease in their availability and exacerbating the potassium deficiency of crops.

[0003] Biochar is widely used as an environmental adsorbent material and gradually applied to the improvement of saline-alkali soil due to its high carbon content, large specific surface area, excellent cation exchange capacity, strong adsorption and high stability. The selection of raw materials and modification methods of biochar show significant diversity for different application targets. In the improvement of saline-alkali soil, some targeted strategies have been developed: for example, silicon-rich biochar can use the silicon-phosphorus competitive adsorption mechanism to replace the adsorbed phosphorus on the surface of soil colloids with silicate, thereby improving the availability of phosphorus; and potassium-rich biochar (such as straw or fruit shell) can not only provide a slow-release potassium source, but also reduce the fixation and leaching of potassium through surface functional groups. However, the reversal effect of ordinary biochar on phosphorus fixation in saline-alkali soil is still limited, especially for the soil with low phosphorus content. In addition, traditional water-soluble phosphorus and potassium fertilizers are easily fixed or leached in saline-alkali soil, and their seasonal utilization rate is low, which makes it difficult to continuously meet the nutritional needs of crops.

[0004] Therefore, it is an urgent need for the resource utilization of saline-alkali soil and the green development of agriculture to develop a new type of biochar-based soil improvement material that can simultaneously achieve slow release of phosphorus and potassium, soil structure improvement, and neutralization of alkalinity, and can synergistically enhance the effect of conventional phosphorus and potassium fertilizers. SUMMARY

[0005] The present invention aims to solve the technical problem that existing biochar has poor reversal effect on phosphorus fixation in saline-alkali land, especially its insignificant effect on soil improvement in soil with low phosphorus content, and provides a method for preparing carbon-based phosphorus and potassium fertilizer using silicon-rich biomass.

[0006] The method for preparing carbon-based phosphorus and potassium fertilizer using silicon-rich biomass according to the present invention is carried out according to the following steps:

[0007] 1. The straw powder is ground and sieved in sequence, then dispersed in phosphoric acid solution, left to stand and soak at room temperature for 6 to 8 hours, and then dried to obtain phosphorus-modified biomass powder.

[0008] 2. The phosphoric acid modified biomass powder is kept at 200℃~300℃ for 0.5h~1.5h under inert gas protection, then heated to 350℃~750℃ and kept at that temperature for 0.5h~1.5h, then cooled to room temperature and sieved to obtain phosphorus-modified carbon-based phosphorus and potassium fertilizer.

[0009] The beneficial effects of this invention are as follows:

[0010] This invention, through phosphorus modification, enables biochar to form slow-release phosphorus and potassium compounds such as potassium metaphosphate and potassium pyrophosphate. While enhancing phosphorus availability, it also introduces potassium (from straw), making it a phosphorus and potassium fertilizer source with slow-release properties. This material achieves slow release of phosphorus and potassium nutrients through strong bonding between phosphate and the carbon matrix and optimized pore structure (potassium phosphate crystals filling micropores), which better aligns with crop absorption patterns. Phosphorus modification provides the phosphorus source and acidic environment, while straw ash provides the potassium source. High-temperature pyrolysis drives dehydration and condensation, ultimately forming potassium metaphosphate in the biochar pores. This process significantly enhances the slow-release capacity of biochar for phosphorus and potassium, which is crucial for agricultural applications.

[0011] This invention uses agricultural straw and other solid waste as raw materials, combining microwave co-pyrolysis and atmosphere-controlled co-pyrolysis technologies for phosphoric acid. The process is simple, low-cost, and has the potential for large-scale production. During the preparation process, the original KCl and K2CO3 components in the straw can react with phosphoric acid to generate compounds such as potassium metaphosphate, which have fertilizer efficacy, further enhancing the availability of phosphorus and potassium and promoting the absorption of phosphorus, potassium, silicon, and other elements by crops.

[0012] Furthermore, the phosphorus-modified carbon-based phosphorus and potassium fertilizer prepared by this invention can effectively improve the physical structure of saline-alkali soils, reduce bulk density, improve aggregate stability, and neutralize alkalinity, synergistically enhancing soil fertility, water retention capacity, and carbon sequestration potential. It not only provides organic nutrients but also improves soil aggregate structure, enhances aeration and water retention, making it suitable for various low-quality soils such as saline-alkali land, desertified land, and mining subsidence areas. It offers comprehensive benefits including improved fertility, increased yield, and assistance in pest and disease control. Attached Figure Description

[0013] Figure 1 These are SEM images of the products obtained in Experiment 1 at 550℃ (the temperature of Step 2) and the comparative experiment at 550℃ (the temperature of Step 2) at different magnifications.

[0014] Figure 2 yes Figure 1 b and Figure 1 The EDS plot within the red box in e;

[0015] Figure 3 XRD patterns of phosphorus-modified carbon-based phosphorus and potassium fertilizers obtained at different temperatures (350℃, 550℃ and 750℃ in step two) in Experiment 1;

[0016] Figure 4 To compare the XRD patterns of the products obtained at different temperatures (350℃, 550℃ and 750℃ in step two) in the experiment;

[0017] Figure 5 A graph showing the effective phosphorus OP in the products of Experiment 1 and the comparative experiment;

[0018] Figure 6 A graph showing the total phosphorus (TP) data in the products of Experiment 1 and the comparative experiment;

[0019] Figure 7 This is a graph showing the effect of biochar application on the electrical conductivity of saline-alkali soil in Experiment 3.

[0020] Figure 8 This is a graph showing the effect of biochar application on the pH of saline-alkali soil in Experiment 3.

[0021] Figure 9 A graph showing the effect of biochar application on sodium ions in saline-alkali soil 28 days after the application of biochar in Experiment 3.

[0022] Figure 10 A graph showing the effect of biochar application on potassium ions in saline-alkali soil 28 days after the application of biochar in Experiment 3.

[0023] Figure 11 A graph showing the effect of biochar 28 on magnesium ions in saline-alkali soil in Experiment 3.

[0024] Figure 12 A graph showing the effect of biochar 28 on calcium ions in saline-alkali soil in Experiment 3.

[0025] Figure 13 This is a graph showing the effect of biochar application on the content of various forms of phosphorus in saline-alkali soil 28 days after application in Experiment 3. Detailed Implementation

[0026] Specific Implementation Method 1: This implementation method is a method for preparing carbon-based phosphorus and potassium fertilizer using silicon-rich biomass, specifically carried out according to the following steps:

[0027] 1. The straw powder is ground and sieved in sequence, then dispersed in phosphoric acid solution, left to stand and soak at room temperature for 6 to 8 hours, and then dried to obtain phosphorus-modified biomass powder (pH around 6).

[0028] 2. The phosphoric acid modified biomass powder is kept at 200℃~300℃ for 0.5h~1.5h under inert gas protection, then heated to 350℃~750℃ and kept at that temperature for 0.5h~1.5h, then cooled to room temperature and sieved to obtain phosphorus-modified carbon-based phosphorus and potassium fertilizer.

[0029] Specific Implementation Method Two: This implementation method differs from Specific Implementation Method One in that the straw powder mentioned in step one is rice straw powder. Everything else is the same as in Specific Implementation Method One.

[0030] Specific Implementation Method Three: This implementation method differs from Specific Implementation Method One or Two in that the particle size of the straw powder mentioned in step one is 40 mesh to 60 mesh. Everything else is the same as in Specific Implementation Method One or Two.

[0031] Specific Implementation Method Four: This implementation method differs from Specific Implementation Methods One to Three in that the drying temperature in step one is 60℃~80℃, and the drying time is 8h~12h. Everything else is the same as in Specific Implementation Methods One to Three.

[0032] Specific Implementation Method Five: This implementation method differs from Specific Implementation Method Four in that the sieve mesh used in step one is 40-60 mesh. Everything else is the same as in Specific Implementation Method Four.

[0033] Specific Implementation Method Six: This implementation method differs from Specific Implementation Method Five in that the mass concentration of the phosphoric acid solution mentioned in step one is 7%~9%. Everything else is the same as in Specific Implementation Method Five.

[0034] Specific Implementation Method Seven: This implementation method differs from Specific Implementation Method Six in that the mass ratio of straw powder to phosphoric acid solution in step one is (1~2):(1~2). Everything else is the same as in Specific Implementation Method Six.

[0035] Specific Implementation Method Eight: This implementation method differs from Specific Implementation Method Seven in that the reaction in step two is carried out in a microwave pyrolysis apparatus. Everything else is the same as in Specific Implementation Method Seven.

[0036] Specific Implementation Method Nine: This implementation method differs from Specific Implementation Method Eight in that the inert gas mentioned in step two is nitrogen, and the flow rate of the nitrogen is 50 mL / min to 200 mL / min. Everything else is the same as in Specific Implementation Method Eight.

[0037] Specific Implementation Method Ten: This implementation method differs from Specific Implementation Method Nine in that the sieve mesh used in step two is 40-60 mesh. Everything else is the same as in Specific Implementation Method Nine.

[0038] The invention was verified using the following experiments:

[0039] Experiment 1: This experiment demonstrates a method for preparing carbon-based phosphorus and potassium fertilizer using silicon-rich biomass, specifically carried out according to the following steps:

[0040] 1. The straw powder is ground and sieved in sequence, then dispersed in phosphoric acid solution, left to stand and soak at room temperature for 6 to 8 hours, and then dried to obtain phosphorus-modified biomass powder (pH around 6).

[0041] The straw powder mentioned is rice straw powder;

[0042] The straw powder mentioned in step one has a particle size of 50 mesh;

[0043] The drying temperature is 70℃, and the drying time is 10 hours.

[0044] The sieve used for sieving is 50 mesh.

[0045] The phosphoric acid solution has a mass concentration of 8%.

[0046] The mass ratio of the straw powder to the phosphoric acid solution is 1:1;

[0047] 2. The phosphoric acid modified biomass powder was kept at 250℃ for 1 hour under inert gas protection (heating rate of 15℃ / min). Then, it was heated to 350℃, 550℃ and 750℃ respectively for comparison and kept at 1 hour (heating rate of 15℃ / min). After cooling to room temperature, it was sieved to obtain phosphorus-modified carbon-based phosphorus and potassium fertilizer, which was named PRS350, PRS550 and PRS750 according to the calcination temperature.

[0048] The reaction in step two is carried out in a microwave pyrolysis apparatus;

[0049] The inert gas mentioned in step two is nitrogen, and the flow rate of nitrogen is 100 mL / min;

[0050] The sieve used in step two is 50 mesh.

[0051] Comparative experiment: This experiment is for the preparation of unmodified biochar. The difference from Experiment 1 is that phosphate modification is not involved in step 1. Step 2 is carried out directly to obtain unmodified biochar, which is recorded as RS350, RS550 and RS750 according to the calcination temperature.

[0052] Figure 1 These are SEM images of the products obtained in Experiment 1 at 550℃ (the temperature of Step 2) and the control experiment at 550℃ (the temperature of Step 2) at different magnifications. d, e, and f are from Experiment 1, and a, b, and c are from the control experiment.

[0053] Figure 2 yes Figure 1 b and Figure 1 The EDS plot within the red box in section e. (Through...) Figure 1 and Figure 2 It can be seen that phosphoric acid crystals exist on the surface of the phosphorus-modified biochar. These crystalline complexes are embedded in the rich porous structure of the biochar, which allows for a certain slow-release effect of phosphorus and potassium. Furthermore, the EDS spectrum shows that the enriched locations of phosphorus and potassium are basically the same, indicating that a phosphorus-potassium complex is formed on its surface.

[0054] Figure 3 The image shows the XRD patterns of the phosphorus-modified carbon-based phosphorus and potassium fertilizers obtained at different temperatures (350℃, 550℃ and 750℃ in step two) in Experiment 1. Figure 4 XRD patterns of the products obtained at different temperatures (350℃, 550℃, and 750℃ in step two) were compared in the experiment. Peaks of KCl and SiO2 can be seen in the XRD pattern of the unmodified biochar. In the modified XRD pattern, the original KCl peak disappears, and the broadened peak at approximately θ=22° is considered to be an amorphous carbon peak. Furthermore, SiP2O7 and KPO3 are generated in the modified biochar with increasing temperature. Phosphoric acid modification provides a phosphorus source and an acidic environment, while straw ash provides a potassium source. High-temperature pyrolysis drives dehydration and condensation, ultimately forming potassium metaphosphate in the biochar pores. This process significantly enhances the slow-release capacity of phosphorus and potassium in the biochar, which is crucial for agricultural applications.

[0055] Table 1 presents XRF data, specifically the mass percentage of each element in the products of Experiment 1 and the comparative experiment. The XRF data clearly demonstrates the key advantages of phosphate-modified biochar (PRS series) in elemental composition compared to unmodified biochar (RS series): the phosphorus (P) content of PRS material is significantly increased (15%~16%), successfully achieving phosphorus loading, while retaining the abundant potassium (K) element (26%) in the raw material, making it an improved material that can simultaneously provide phosphorus and potassium nutrition; in addition, the content of harmful chlorine (Cl) and sulfur (S) in the PRS series is extremely low, indicating that it is more environmentally friendly. This perfectly aligns with the goal of developing novel biochar-based materials to simultaneously achieve the slow release and synergistic effect of phosphorus and potassium in saline-alkali land.

[0056] Table 1

[0057]

[0058] Figure 5 The graph shows the available phosphorus (OP) data in the products of Experiment 1 and the comparative experiment. Figure 6 The graph shows the total phosphorus (TP) data in the products of Experiment 1 and the comparative experiment. It can be seen that the total phosphorus content is significantly increased after modification, and also increases with increasing temperature. This is due to the phosphorus enrichment effect of biochar. A similar phenomenon is observed in available phosphorus (OP), but the available phosphorus content decreases at high temperatures. This is because phosphorus typically volatilizes at relatively high temperatures; therefore, within the intermediate temperature range, phosphorus can be stably retained in biochar. However, beyond the intermediate temperature limit, some phosphorus may volatilize or form insoluble compounds (such as Fe₂P), leading to a decrease in the available phosphorus content.

[0059] Experiment 3: The products of Experiment 1 and the control experiment were applied to saline-alkali soil at a dosage of 5%. The soil was required to maintain a field water holding capacity of 60% to 70%. Data were collected over 28 days. CK was the blank saline-alkali soil control group, i.e., no substance was added; RS was the unmodified biochar, i.e., the control experiment; PRS was the modified biochar, i.e., Experiment 1; HRS was the biochar ash content; CRS was the biochar carbon skeleton.

[0060] Figure 7 The graph shows the effect of biochar application on the electrical conductivity of saline-alkali soil in Experiment 3. The effect of phosphorus-modified biochar (PRS) on electrical conductivity: reduces soluble sodium (Na₂O₃). + ).

[0061] PRS can significantly reduce water-soluble Na+ + The content of Na. + It is one of the most common cations in soil and contributes the most to electrical conductivity. Its primary reason for inhibiting the increase of EC values ​​is by promoting the formation of less soluble phosphates or by fixing sodium through other mechanisms.

[0062] Regulating potassium (K) + Release rate of )

[0063] Common biochar (RS) is rich in soluble potassium and rapidly releases large amounts of K. + This leads to a surge in EC values. The phosphorus modification process may convert some potassium into a slower-release form or slow down potassium release through physical encapsulation, thereby avoiding a sharp increase in EC values.

[0064] Formation of insoluble or low-migratory substances (chemical fixation):

[0065] Phosphate (PO4) introduced by phosphorus-modified biochar 3- It can react with Ca in the soil 2+ Mg 2+ Fe3+ Al 3+ They will form precipitates or stable complexes.

[0066] This process transforms highly soluble free ions into less soluble solid substances, "removing" these ions from the soil solution and thus reducing the ionic strength and conductivity of the solution.

[0067] Compared with other treatments:

[0068] HRS (Biochar Ash): Has the highest EC value because ash is a concentrated form of all the salts in biochar and is rich in potassium. + Na + CO3 2- When dissolved in large quantities, the EC value surges, posing a significant risk of salinization.

[0069] RS (common biochar): The EC value is significantly increased because it contains a certain amount of soluble salts, which brings the risk of salt accumulation while improving the soil.

[0070] CRS (Carbon Framework): The EC value increased moderately. Its porous structure may have adsorbed and concentrated some ions, resulting in an EC value that is slightly higher than CK and PRS.

[0071] Figure 8 This is a graph showing the effect of biochar application on the pH of saline-alkali soil in Experiment 3. It can be seen that after the addition of ash (HRS) to the soil, the soil pH value increased significantly from 7.7 to 8.8. This indicates that the accumulation of alkaline functional groups and the enrichment of alkaline cations in the ash powder led to a substantial increase in pH. The pH value was 8.8 after seven days, gradually decreasing to 8.75 after 28 days. This suggests that as the soil cultivation experiment progressed, after 28 days, the alkaline functional groups were leached by water, resulting in a decrease in pH. Similarly, after applying unmodified biochar (RS) to the soil, the pH increased to 8.2, also due to the accumulation of alkaline functional groups, leading to increased soil alkalinity. After applying carbon skeleton (CRS), the soil pH decreased slightly after about 7 days, and dropped from 7.7 to 7.2 after 28 days. This may be because acidic functional groups contained in the carbon skeleton (CRS) began to detach and enter the soil, causing the pH to decrease. After applying phosphoric acid modified biochar (PRS), the pH decreased significantly after 7 days, indicating that its acidic functional groups began to enter the soil at that time. After 28 days, the pH continued to decrease, indicating that its acidic functional groups continued to detach from the biochar. After 28 days, the pH dropped to about 6.99. Therefore, we can see that applying phosphorus-modified silicon-rich biomass-based phosphorus-potassium fertilizer composites is beneficial for improving the basic physicochemical properties of saline-alkali soils.

[0072] Figure 9 This is a graph showing the effect of biochar application on sodium ions in saline-alkali soil 28 days after the application of biochar in Experiment 3. Figure 10This is a graph showing the effect of biochar application on potassium ions in saline-alkali soil 28 days after experiment 3. Figure 11 This is a graph showing the effect of biochar 28 on magnesium ions in saline-alkali soil in Experiment 3. Figure 12 The graph shows the effect of biochar 28 on calcium ions in saline-alkali soil in Experiment 3. The conclusions are as follows:

[0073] 1. Phosphorus-modified biochar PRS for sodium salt (Na) + The effect of ) is most significant, with PRS's Na + The content was much lower than that of RS and CK, which indicates that PRS greatly inhibited the solubility of sodium salt or promoted sodium fixation.

[0074] 2. For potassium salts (K + The impact of ) on: K of PRS + The content is between CK and RS. Ordinary biochar (RS) itself is rich in potassium, which will greatly increase the content of water-soluble potassium in the soil. However, the generation of potassium phosphate in biochar during the phosphorus modification process and the influence of biochar pore formation on potassium phosphate slow down its release rate, but it is still higher than that of the blank soil.

[0075] 3. For magnesium salts (Mg 2+ The effect of ) on the opposite trend

[0076] Mg of PRS 2+ The content was significantly higher than that of CK and RS, indicating that phosphorus modification treatment increased the solubility of magnesium.

[0077] 4. For calcium salts (Ca 2+ The impact of )

[0078] PRS's Ca 2+ The content was slightly lower than that of RS and CK, but the change was not significant. Phosphorus and calcium readily form insoluble precipitates, which may inhibit calcium dissolution to some extent.

[0079] In conclusion, PRS can significantly improve saline-alkali soils, enhance the soil environment, and greatly inhibit sodium salt (Na+). + It can dissolve or promote its fixation, effectively reduce the salt concentration in the soil, reduce the toxicity of sodium ions to crops, and help improve the soil compaction problem caused by excessive sodium. It is very suitable for the treatment and restoration of saline-alkali land.

[0080] PRS provides a slow-release potassium source with a slower release rate than ordinary biochar, reducing potassium loss and extending the fertilizer's effective period. Simultaneously, it significantly increases magnesium salt (Mg) levels. 2+ The effectiveness of this technology allows crops to be supplemented with essential medium-level elements, synergistically promoting crop growth.

[0081] Based on the ease with which plants absorb and utilize different forms of phosphorus compounds, Hedley categorized them into active phosphorus (H2O-Pi, NaHCO3-Pi, and NaHCO3-Po), moderately active phosphorus (NaOH-Pi and NaOH-Po), stable phosphorus (HCl-P), and residual phosphorus (Rs-P). Figure 13 The graph shows the effect of biochar application on the content of various forms of phosphorus in saline-alkali soil 28 days after the application in Experiment 3. The following conclusions can be drawn:

[0082] 1. Impact on plant availability (active phosphorus + moderately active phosphorus): PRS (phosphorus-modified biochar) showed an absolute advantage. PRS significantly increased the pool of active phosphorus most easily absorbed by plants, while also substantially increasing the content of moderately active phosphorus. This indicates that PRS not only directly provides available phosphorus but also increases the phosphorus reserves in the soil that can be activated in the short term, making it the best strategy for improving soil phosphorus availability. HRS (biochar ash) also had a very significant effect on improving active phosphorus, second only to PRS. This is because the ash contains soluble potassium, calcium phosphates, and other minerals, directly providing an effective phosphorus source. RS (original biochar) and CRS (carbon skeleton) had very limited effects on improving soil phosphorus availability.

[0083] 2. Effect on stable phosphorus (HCl-P): PRS also significantly increased the content of stable phosphorus (HCl-P, mainly Ca-P), indicating that some of the added phosphorus was fixed in a more stable form. However, considering the significant increase in available phosphorus, the net effect is a substantial improvement in the total availability and total capacity of phosphorus. The HCl-P content under CRS treatment was actually lower than that under control (CK), possibly because the carbon skeleton adsorbs calcium and other metal ions, slightly affecting the determination or form of HCl-P.

[0084] 3. Impact on Residual Phosphorus (Residual-P): All treatments increased the content of residual phosphorus to varying degrees, indicating an increase in the total phosphorus pool in the soil. PRS showed the largest increase, suggesting that phosphorus-modified biochar is the primary source of phosphorus input into the soil system.

Claims

1. A method for preparing carbon-based phosphorus and potassium fertilizer using silicon-rich biomass, characterized in that... The method is performed according to the following steps:

1. The straw powder is ground and sieved in sequence, then dispersed in phosphoric acid solution, left to stand and soak at room temperature for 6 to 8 hours, and then dried to obtain phosphorus-modified biomass powder.

2. The phosphoric acid modified biomass powder is kept at 200℃~300℃ for 0.5h~1.5h under inert gas protection, then heated to 350℃~750℃ and kept at that temperature for 0.5h~1.5h, then cooled to room temperature and sieved to obtain phosphorus-modified carbon-based phosphorus and potassium fertilizer.

2. The method for preparing carbon-based phosphorus and potassium fertilizer using silicon-rich biomass according to claim 1, characterized in that... The straw powder mentioned in step one is rice straw powder.

3. The method for preparing carbon-based phosphorus and potassium fertilizer using silicon-rich biomass according to claim 1, characterized in that... The straw powder mentioned in step one has a particle size of 40-60 mesh.

4. The method for preparing carbon-based phosphorus and potassium fertilizer using silicon-rich biomass according to claim 1, characterized in that... The drying temperature in step one is 60℃~80℃, and the drying time is 8h~12h.

5. The method for preparing carbon-based phosphorus and potassium fertilizer using silicon-rich biomass according to claim 1, characterized in that... The sieve used in step one is 40-60 mesh.

6. The method for preparing carbon-based phosphorus and potassium fertilizer using silicon-rich biomass according to claim 1, characterized in that... The mass concentration of the phosphoric acid solution mentioned in step one is 7% to 9%.

7. The method for preparing carbon-based phosphorus and potassium fertilizer using silicon-rich biomass according to claim 1, characterized in that... The mass ratio of straw powder to phosphoric acid solution in step one is (1~2):(1~2).

8. The method for preparing carbon-based phosphorus and potassium fertilizer using silicon-rich biomass according to claim 1, characterized in that... The reaction in step two is carried out in a microwave pyrolysis apparatus.

9. A method for preparing carbon-based phosphorus and potassium fertilizer using silicon-rich biomass according to claim 1, characterized in that... The inert gas mentioned in step two is nitrogen, and the flow rate of nitrogen is 50 mL / min to 200 mL / min.

10. A method for preparing carbon-based phosphorus and potassium fertilizer using silicon-rich biomass according to claim 1, characterized in that... The sieve used in step two is 40-60 mesh.

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