A method for preparing potassium humate and Fenton-like catalyst using bamboo powder thermal catalysis

Abstract

This invention discloses a method for preparing potassium humate and a Fenton-like catalyst using bamboo powder thermocatalysis. The preparation method is as follows: bamboo powder is pyrolyzed under a low-oxygen atmosphere; under heating conditions, the pyrolyzed product is mixed and stirred with hydrogen peroxide solution; subsequently, the oxidized solid product is washed and dried to obtain a weathered coal precursor; the obtained weathered coal precursor is mixed with an alkali and subjected to hydrothermal treatment to extract liquid potassium humate and residue containing metallic iron; the residue containing metallic iron is mixed with a template agent, ground, and then calcined at high temperature under a nitrogen atmosphere; the calcined product is soaked in hydrochloric acid, washed with water, and dried to obtain an atomically dispersed iron-carbon Fenton-like catalyst with good performance, which can efficiently degrade antibiotic wastewater.

Description

Technical Field

[0001] This invention relates to the field of biomass resource utilization technology, and in particular to a method for preparing potassium humate and Fenton-like catalysts using bamboo powder thermocatalysis. Background Technology

[0002] Currently, global soil degradation is severe, including desertification, soil pH imbalance, and soil erosion, posing significant threats to land, the environment, agricultural production, and human health. This problem stems from unsustainable economic development and production methods, which have damaged soil ecological structures and led to nutrient loss. Humic acid, a highly reactive organic carbon, can improve soil texture, enhance nutrient supply, promote plant growth, and help maintain the health and stability of soil ecosystems. However, the distribution of natural humic acid in lignite, peat, and weathered coal is uneven, and high-grade raw materials are insufficient and non-renewable, failing to meet the needs of agricultural production. Therefore, sufficient humic acid needs to be obtained through artificial synthesis. Biomass contains abundant carbon resources; it has been reported that over 22 billion metric tons of carbon enter plants annually through photosynthesis, with only a small portion returning to the soil. Therefore, converting waste biomass into artificial humic acid is novel and environmentally friendly.

[0003] Chemical oxidation and hydrolysis of biomass can produce artificial humic acid, which is one of the most sustainable methods for treating large quantities of waste biomass. In a recent study, CN113277492A discloses a method for preparing potassium humate and biochar from agricultural and forestry waste. This method involves vacuum roasting of agricultural and forestry waste with potassium ferrate followed by water quenching to obtain potassium humate and biochar. The low-temperature roasting oxidation method has a simple process and low energy consumption, and its application in the production of humic acid organic fertilizer from biomass holds promise for industrial-scale production and fundamental change. In the research on the low-temperature roasting oxidation method, lignin in biomass is oxidized and hydrolyzed into low-molecular-weight monomers, which are then further condensed to form humic acid macromolecules. The lignin oxidation and hydrolysis process requires a catalyst, but currently, there is a lack of economical and efficient catalysts for this catalytic process. Furthermore, the synthesis of catalysts is relatively complex, and their recovery and reuse present certain difficulties. Additionally, metal elements in the catalyst remain in the residue, leading to resource waste if not recovered.

[0004] Therefore, there is an urgent need to obtain a method for efficiently preparing potassium humate by making full use of biomass materials. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings and deficiencies of existing technologies. This invention provides a technology for converting organic carbon into potassium humate based on metallic iron in iron-rich bamboo powder, and converting the extracted residue into a Fe-NC type Fenton catalyst to address the deficiencies of existing technologies. During the pyrolysis process, metallic iron in the biomass acts as an endogenous metal catalyst, promoting the catalytic oxidation reaction of organic matter, achieving the catalytic pyrolysis of iron-rich bamboo powder, and obtaining potassium humate through alkaline extraction. Through analysis of the metallic iron content in the residue, the residue is further subjected to high-temperature calcination to prepare a Fe-NC type Fenton catalyst, which is then applied to the degradation treatment of antibiotic-containing wastewater, thereby improving the economic benefits of biomass and increasing the added value of biomass resource utilization.

[0006] The objective of this invention is achieved through the following technical solution:

[0007] A method for the thermal catalytic preparation of potassium humate and a Fenton-like catalyst from bamboo powder includes the following steps:

[0008] (1) Bamboo powder undergoes pyrolysis in a low-oxygen atmosphere;

[0009] (2) Under heating conditions, the pyrolysis product is mixed and stirred with hydrogen peroxide solution; then, the oxidized solid product is washed and dried to obtain weathered coal precursor.

[0010] (3) After the obtained weathered coal precursor is mixed with alkali, it is subjected to hydrothermal treatment and extracted to obtain liquid potassium humate and residue containing metallic iron.

[0011] (4) The residue containing metallic iron is mixed with the template agent, ground, and then calcined at high temperature under a nitrogen atmosphere; the calcined product is soaked in hydrochloric acid, washed with water, and dried to obtain an iron-carbon Fenton catalyst.

[0012] Preferably, the iron content of the bamboo powder in step (1) is greater than 10%; more preferably, the iron content of the bamboo powder is greater than 15%.

[0013] Preferably, the bamboo powder in step (1) undergoes the following pretreatment: rinsing with water, soaking in water, drying, crushing, and sieving; more preferably, the water is deionized water, the soaking is for 12-24 hours, the drying is for 20-30 hours at an oven temperature of 70-85℃, and the sieving is for passing through a 100-200 mesh sieve; most preferably, the drying is for 24 hours at an oven temperature of 80℃, and the sieving is for passing through a 200 mesh sieve.

[0014] Preferably, the low-oxygen atmosphere described in step (1) has an oxygen volume content of 5-10% and a nitrogen volume content of 90%-95%.

[0015] Preferably, the pyrolysis in step (1) is performed in a tube furnace at 200-350°C for 2-3 hours; more preferably, it is performed in a tube furnace at 220-280°C for 2 hours.

[0016] Preferably, the heating in step (2) is 70-90°C; more preferably, it is 80°C.

[0017] Preferably, the solid-liquid mass-volume ratio of the bamboo powder in step (1) and the hydrogen peroxide solution in step (2) is 1g:5-15mL, and the mass concentration of the hydrogen peroxide solution is 0.5-2%; more preferably, the solid-liquid mass-volume ratio of the bamboo powder in step (1) and the hydrogen peroxide solution in step (2) is 1g:10mL, and the mass concentration of the hydrogen peroxide solution is 1%.

[0018] Preferably, the mass ratio of bamboo powder in step (1) to alkali in step (3) is 100:10-20.

[0019] Preferably, the alkali mentioned in step (3) includes at least one of potassium hydroxide, potassium carbonate and sodium hydroxide.

[0020] Preferably, the hydrothermal treatment in step (3) involves heating at a temperature of 100-150°C for 2-3 hours.

[0021] Preferably, the extraction in step (3) is filtration, and the filter residue is washed with water until the filtrate is neutral. The filtrate is potassium humate, and the filter residue is a residue containing metallic iron.

[0022] Preferably, the mass ratio of the residue containing metallic iron to the template agent in step (4) is 10:2-5; more preferably, it is 10:3.

[0023] Preferably, the template agent in step (4) includes at least one of potassium chloride, potassium sulfate and potassium carbonate.

[0024] Preferably, the high-temperature calcination in step (4) is calcination at a temperature of 600-800℃ for 2-3 hours.

[0025] Preferably, the hydrochloric acid mentioned in step (4) is 1 mol / L hydrochloric acid.

[0026] Preferably, the washing with water in step (4) is washing with deionized water three times.

[0027] Preferably, the drying process in step (4) involves drying at 70-90°C for 8-12 hours; more preferably, drying at 80°C for 10 hours.

[0028] A Fenton-like catalyst was prepared by the method described above.

[0029] The application of the aforementioned Fenton-like catalysts in the degradation of antibiotics in the environment.

[0030] Preferably, the environment is a body of water or soil, more preferably a body of water.

[0031] Preferably, the antibiotic includes tetracycline.

[0032] The objective of this invention is achieved through the following technical solution:

[0033] The present invention has the following advantages and effects compared with the prior art:

[0034] (1) The high content of metallic iron in bamboo powder can act as a catalyst to accelerate the conversion of organic matter in bamboo powder into humic acid / fulvic acid at appropriate temperatures. This catalytic conversion method is highly efficient and can improve the conversion rate of organic matter. The present invention does not require the additional preparation and addition of transition metal catalysts for processing bamboo powder, and the residue can also be used as an iron-carbon Fenton catalyst for the degradation of antibiotic wastewater. The entire process produces no solid waste or waste liquid discharge, realizing the full resource utilization and high-value utilization of bamboo powder biomass.

[0035] (2) By utilizing the catalytic conversion process of metallic iron in bamboo powder, the organic matter in plants can be converted into valuable humic acid / fulvic acid. These products can be used in soil improvement, fertilizer preparation and other fields to realize the reuse of resources.

[0036] (3) Compared with traditional chemical synthesis methods, using metallic iron in bamboo powder for catalytic conversion can reduce environmental pollution and the use of chemical reagents. This method is more environmentally friendly and in line with the concept of sustainable development.

[0037] (4) Through pyrolysis, the residue contains iron and other metals, which makes the prepared catalyst form a catalytic system with single-atom iron as the reaction center. It can replace the traditional single active iron ore Fenton catalyst because the internal metal iron is evenly distributed and has more surface active sites, resulting in better catalytic activity. It can be used for efficient wastewater treatment. Attached Figure Description

[0038] Figure 1 This is a technical roadmap for the present invention.

[0039] Figure 2 This is the FT-IR image of the potassium humate product obtained in this invention.

[0040] Figure 3 The image shows the XRD pattern of the Fenton-like catalyst obtained in this invention.

[0041] Figure 4These are electron microscope images of the Fenton-like catalyst obtained in this invention. Image a is a SEM image, image b is a TEM image, and image c is an EDX image.

[0042] Figure 5 The figure shows a comparison of the catalytic performance of Fenton-like catalysts for the degradation of tetracycline obtained in different embodiments of the present invention. Detailed Implementation

[0043] The present invention will be further described in detail below with reference to embodiments and accompanying drawings, but the embodiments of the present invention are not limited thereto. Where specific techniques or conditions are not specified in the embodiments, they shall be performed in accordance with the techniques or conditions described in the literature in this field or in accordance with the product instructions. Reagents or instruments whose manufacturers are not specified are all conventional products that can be obtained commercially.

[0044] Phytolysis of bamboo powder to extract humic acid

[0045] According to an embodiment of the present invention, bamboo powder (obtained from bamboo from Shaowu, Fujian, after coarse crushing, and the elemental content is shown in Table 1) is selected as raw material. After rinsing and soaking with deionized water, it is dried in an oven at 80°C for 24 hours. After drying, it is crushed and sieved for later use. The dried bamboo powder is crushed and sieved to a particle size of 100-200 mesh, preferably 200 mesh.

[0046] Table 1. Elemental content data of bamboo powder ash

[0047]

[0048] According to an embodiment of the present invention, the crushed bamboo powder is pyrolyzed under a low-oxygen atmosphere, with an oxygen content of 5%-10%, such as 5%, 7%, or 10%; the pyrolysis temperature is 200-350℃, such as 220℃, 240℃, 260℃, or 280℃; and the pyrolysis time is 1-3 hours, such as 2 hours.

[0049] According to an embodiment of the present invention, the pyrolysis product is mixed with an oxidant solution, preferably a 1% hydrogen peroxide solution, and the amount added is 200 mL for every 20 g of bamboo powder; the mixture is heated and stirred in an oil bath at 80°C for 1 hour and then dried to obtain a weathered coal precursor.

[0050] According to an embodiment of the present invention, the pyrolyzed weathered coal precursor is subjected to hydrothermal extraction after the addition of alkali. The alkali added is one of potassium hydroxide, sodium hydroxide, or potassium carbonate, etc. The amount of alkali added is 10-20% of the mass percentage of bamboo powder, for example, 10%, 15%, or 20%. The hydrothermal temperature for alkali extraction is 100-150°C, for example, 100°C, and the preferred extraction time is 120 min.

[0051] Technical routes for preparing potassium humate and Fenton-like catalysts are as follows: Figure 1 As shown.

[0052] Example 1

[0053] (1) Take 20g of bamboo powder that has been washed with deionized water, dried at 80℃ for 24h and passed through a 200-mesh sieve, and calcine it at 280℃ for 120min in a low oxygen atmosphere with an oxygen volume content of 5% to obtain the pyrolysis product.

[0054] (2) The pyrolysis product was mixed with 200 mL of 1% hydrogen peroxide solution, and the mixture was heated and stirred at 80°C for 1 hour and then dried to obtain the weathered coal precursor.

[0055] (3) Add the weathered coal precursor and potassium hydroxide solution to the reactor at a mass ratio of 0.15:1 (potassium hydroxide: bamboo powder) and perform hydrothermal extraction at 100°C for 120 min.

[0056] (4) After the reaction in step (3) is completed, the product is cooled to room temperature, filtered to separate solid and liquid, washed and filtered until the pH of the filtrate is 7, and the filtrate is dried at 60°C to obtain potassium humate. The filter residue is dried and used for later use.

[0057] In this embodiment, 20g of bamboo powder biomass raw material was processed to obtain 9.31g of potassium humate solid product and 4.69g of unconverted residue (containing iron and heavy metals copper and chromium, residue after pyrolysis). The potassium humate yield reached 46.55%, and the biomass conversion rate was 76.55%. (Note: Potassium humate yield = potassium humate solid product / bamboo powder amount; bamboo powder conversion rate = 1 - unconverted residue / bamboo powder amount). The FT-IR spectrum of the prepared potassium humate is shown below. Figure 2 As shown.

[0058] Example 2

[0059] (1) Take 20g of bamboo powder that has been washed with deionized water, dried at 80℃ for 24h and passed through a 200-mesh sieve, and calcine it at 280℃ for 120min in a low oxygen atmosphere with an oxygen volume content of 7% to obtain the pyrolysis product.

[0060] (2) The pyrolysis product was mixed with 200 mL of 1% hydrogen peroxide solution, and the mixture was heated and stirred at 80°C for 1 hour and then dried to obtain the weathered coal precursor.

[0061] (3) Add the weathered coal precursor and potassium hydroxide solution to the reactor at a mass ratio of 0.15:1 (potassium hydroxide: bamboo powder) and perform hydrothermal extraction at 100°C for 120 min.

[0062] (4) After the reaction in step (3) is completed, the product is cooled to room temperature, filtered to separate solid and liquid, washed and filtered until the pH of the filtrate is 7, and the filtrate is dried at 60°C to obtain potassium humate. The filter residue is dried and used for later use.

[0063] In this embodiment, 20g of bamboo powder biomass raw material was processed to obtain 10.48g of potassium humate solid product and 4.25g of unconverted residue (containing iron and heavy metals copper and chromium after pyrolysis). The potassium humate yield reached 52.40%, and the biomass conversion rate was as high as 78.75%. (Note: Potassium humate yield = potassium humate solid product / bamboo powder amount; bamboo powder conversion rate = 1 - unconverted residue / bamboo powder amount).

[0064] Example 3

[0065] (1) Take 20g of bamboo powder that has been washed with deionized water, dried at 80℃ for 24h and passed through a 200-mesh sieve, and calcine it at 280℃ for 120min in a low oxygen atmosphere with an oxygen volume content of 10% to obtain the pyrolysis product.

[0066] (2) The pyrolysis product was mixed with 200 mL of 1% hydrogen peroxide solution, and the mixture was heated and stirred at 80°C for 1 hour and then dried to obtain the weathered coal precursor.

[0067] (3) Add the weathered coal precursor and potassium hydroxide solution to the reactor at a mass ratio of 0.15:1 (potassium hydroxide: bamboo powder) and perform hydrothermal extraction at 100°C for 120 min.

[0068] (4) After the reaction in step (3) is completed, the product is cooled to room temperature, filtered to separate solid and liquid, washed and filtered until the pH of the filtrate is 7, and the filtrate is dried at 60°C to obtain potassium humate. The filter residue is dried and used for later use.

[0069] In this embodiment, 20g of bamboo powder biomass raw material was processed to obtain 11.64g of potassium humate solid product and 2.25g of unconverted residue (containing iron and heavy metals copper and chromium after pyrolysis). The potassium humate yield reached 58.20%, and the biomass conversion rate was 86.25%. (Note: Potassium humate yield = potassium humate solid product / bamboo powder amount; bamboo powder conversion rate = 1 - unconverted residue / bamboo powder amount).

[0070] Comparative Example 1

[0071] (1) Take 100g of bamboo powder that has been washed with deionized water, dried at 80℃ for 24h, and passed through a 200-mesh sieve. Soak it in 0.1M dilute sulfuric acid, heat it to boiling to leach out the metallic iron in the bamboo powder, then rinse it with deionized water until neutral, and dry the solid for later use.

[0072] (2) Weigh 20g of bamboo powder raw material obtained in step (1) after removing metallic iron, and calcine it at 280°C for 120min in a low oxygen atmosphere with an oxygen volume content of 10% to obtain the pyrolysis product.

[0073] (3) The pyrolysis product was mixed with 200 mL of 1% hydrogen peroxide solution, and the mixture was heated and stirred at 80°C for 1 hour and then dried to obtain the weathered coal precursor.

[0074] (4) Add the weathered coal precursor and potassium hydroxide solution to the reactor at a mass ratio of 0.15:1 (potassium hydroxide: bamboo powder) and perform hydrothermal extraction at 100°C for 120 min.

[0075] (5) After the reaction in step (4) is completed, the product is cooled to room temperature, filtered to separate solid and liquid, washed and filtered until the pH of the filtrate is 7, and the filtrate is dried at 60°C to obtain potassium humate. The filter residue is dried and used for later use.

[0076] In this embodiment, 20g of bamboo powder biomass raw material was processed to obtain 2.65g of potassium humate solid product and 10.25g of unconverted residue (containing iron and heavy metals copper and chromium after pyrolysis). The yield of potassium humate was 13.25%, and the biomass conversion rate was 48.75%. (Note: Potassium humate yield = potassium humate solid product / amount of bamboo powder used; bamboo powder conversion rate = 1 - unconverted residue / amount of bamboo powder used).

[0077] The potassium humate yield of Comparative Example 1 was compared with the humic acid yield of Example 3, demonstrating that the iron element contained in bamboo powder can act as an endogenous iron catalyst to promote the conversion of humic acid.

[0078] Example 4

[0079] (1) Take 20g of bamboo powder that has been washed with deionized water, dried at 80℃ for 24h and passed through a 200-mesh sieve, and calcine it at 280℃ for 120min in a low oxygen atmosphere with an oxygen volume content of 15% to obtain the pyrolysis product.

[0080] (2) The pyrolysis product was mixed with 200 mL of 1% hydrogen peroxide solution, and the mixture was heated and stirred at 80°C for 1 hour and then dried to obtain the weathered coal precursor.

[0081] (3) Add the weathered coal precursor and potassium hydroxide solution to the reactor at a mass ratio of 0.15:1 (potassium hydroxide: bamboo powder) and perform hydrothermal extraction at 100°C for 120 min.

[0082] (4) After the reaction in step (3) is completed, the product is cooled to room temperature, filtered to separate solid and liquid, washed and filtered until the pH of the filtrate is 7, and the filtrate is dried at 60°C to obtain potassium humate. The filter residue is dried and used for later use.

[0083] In this embodiment, 20g of bamboo powder biomass raw material was processed to obtain 7.73g of potassium humate solid product and 5.22g of unconverted residue (containing iron and heavy metals copper and chromium after pyrolysis). The potassium humate yield was 38.65%, and the biomass conversion rate was as high as 73.90%. (Note: Potassium humate yield = potassium humate solid product / bamboo powder amount; bamboo powder conversion rate = 1 - unconverted residue / bamboo powder amount).

[0084] Comparative Example 2

[0085] (1) Take 20g of bamboo powder that has been washed with deionized water, dried at 80℃ for 24h and passed through a 200-mesh sieve, and calcine it at 280℃ for 120min in an oxygen-free atmosphere with zero oxygen volume content to obtain the pyrolysis product.

[0086] (2) The pyrolysis product was mixed with 200 mL of 1% hydrogen peroxide solution, and the mixture was heated and stirred at 80°C for 1 hour and then dried to obtain the weathered coal precursor.

[0087] (3) Add the weathered coal precursor and potassium hydroxide solution to the reactor at a mass ratio of 0.15:1 (potassium hydroxide: bamboo powder) and perform hydrothermal extraction at 100°C for 120 min.

[0088] (4) After the reaction in step (3) is completed, the product is cooled to room temperature, filtered to separate solid and liquid, washed and filtered until the pH of the filtrate is 7, and the filtrate is dried at 60°C to obtain potassium humate. The filter residue is dried and used for later use.

[0089] In this embodiment, 20g of bamboo powder biomass raw material was processed to obtain 6.37g of potassium humate solid product and 7.12g of unconverted residue (containing iron and heavy metals copper and chromium after pyrolysis). The potassium humate yield was 31.85%, and the biomass conversion rate was 64.40%. (Note: Potassium humate yield = potassium humate solid product / amount of bamboo powder used; bamboo powder conversion rate = 1 - unconverted residue / amount of bamboo powder used).

[0090] Example 5

[0091] (1) Take 20g of bamboo powder that has been washed with deionized water, dried at 80℃ for 24h and passed through a 200-mesh sieve, and calcine it at 260℃ for 120min in a low oxygen atmosphere with an oxygen volume content of 10% to obtain the pyrolysis product.

[0092] (2) The pyrolysis product was mixed with 200 mL of 1% hydrogen peroxide solution, and the mixture was heated and stirred at 80°C for 1 hour and then dried to obtain the weathered coal precursor.

[0093] (3) Add the weathered coal precursor and potassium hydroxide solution to the reactor at a mass ratio of 0.15:1 (potassium hydroxide: bamboo powder) and perform hydrothermal extraction at 100°C for 120 min.

[0094] (4) After the reaction in step (3) is completed, the product is cooled to room temperature, filtered to separate solid and liquid, washed and filtered until the pH of the filtrate is 7, and the filtrate is dried at 60°C to obtain potassium humate. The filter residue is dried and used for later use.

[0095] In this embodiment, 20g of bamboo powder biomass raw material was processed to obtain 10.61g of potassium humate solid product and 4.33g of unconverted residue (containing iron and heavy metals copper and chromium after pyrolysis). The potassium humate yield was 53.05%, and the plant conversion rate was as high as 68.75%. (Note: Potassium humate yield = potassium humate solid product / amount of bamboo powder used; bamboo powder conversion rate = 1 - unconverted residue / amount of bamboo powder used).

[0096] Example 6

[0097] (1) Take 20g of bamboo powder that has been washed with deionized water, dried at 80℃ for 24h and passed through a 200-mesh sieve, and calcine it at 240℃ for 120min in a low oxygen atmosphere with an oxygen volume content of 10% to obtain the pyrolysis product.

[0098] (2) The pyrolysis product was mixed with 200 mL of 1% hydrogen peroxide solution, and the mixture was heated and stirred at 80°C for 1 hour and then dried to obtain the weathered coal precursor.

[0099] (3) Add the weathered coal precursor and potassium hydroxide solution to the reactor at a mass ratio of 0.15:1 (potassium hydroxide: bamboo powder) and perform hydrothermal extraction at 100°C for 120 min.

[0100] (4) After the reaction in step (3) is completed, the product is cooled to room temperature, filtered to separate solid and liquid, washed and filtered until the pH of the filtrate is 7, and the filtrate is dried at 60°C to obtain potassium humate. The filter residue is dried and used for later use.

[0101] In this embodiment, 20g of bamboo powder biomass raw material was processed to obtain 9.74g of potassium humate solid product and 6.25g of unconverted residue (containing iron and heavy metals copper and chromium after pyrolysis). The potassium humate yield was 48.70%, and the biomass conversion rate was 68.75%. (Note: Potassium humate yield = potassium humate solid product / amount of bamboo powder used; bamboo powder conversion rate = 1 - unconverted residue / amount of bamboo powder used).

[0102] Example 7

[0103] (1) Take 20g of bamboo powder that has been washed with deionized water, dried at 80℃ for 24h and passed through a 200-mesh sieve, and calcine it at 220℃ for 120min in a low oxygen atmosphere with an oxygen volume content of 10% to obtain the pyrolysis product.

[0104] (2) The pyrolysis product was mixed with 200 mL of 1% hydrogen peroxide solution, and the mixture was heated and stirred at 80°C for 1 hour and then dried to obtain the weathered coal precursor.

[0105] (3) Add the weathered coal precursor and potassium hydroxide solution to the reactor at a mass ratio of 0.15:1 (potassium hydroxide: bamboo powder) and perform hydrothermal extraction at 100°C for 120 min.

[0106] (4) After the reaction in step (3) is completed, the product is cooled to room temperature, filtered to separate solid and liquid, washed and filtered until the pH of the filtrate is 7, and the filtrate is dried at 60°C to obtain potassium humate. The filter residue is dried and used for later use.

[0107] In this embodiment, 20g of bamboo powder biomass raw material was processed to obtain 9.14g of potassium humate solid product and 7.15g of unconverted residue (containing iron and heavy metals copper and chromium after pyrolysis). The potassium humate yield was 45.70%, and the biomass conversion rate was 64.25%. (Note: Potassium humate yield = potassium humate solid product / amount of bamboo powder used; bamboo powder conversion rate = 1 - unconverted residue / amount of bamboo powder used).

[0108] Example 8

[0109] (1) Take 20g of bamboo powder that has been washed with deionized water, dried at 80℃ for 24h and passed through a 200-mesh sieve, and calcine it at 280℃ for 120min in a low oxygen atmosphere with an oxygen volume content of 10% to obtain the pyrolysis product.

[0110] (2) The pyrolysis product was mixed with 200 mL of 1% hydrogen peroxide solution, and the mixture was heated and stirred at 80°C for 1 hour and then dried to obtain the weathered coal precursor.

[0111] (3) Add the weathered coal precursor and potassium hydroxide solution to the reactor at a mass ratio of 0.1:1 (potassium hydroxide: bamboo powder) and perform hydrothermal extraction at 100℃ for 120 min.

[0112] (4) After the reaction in step (3) is completed, the product is cooled to room temperature, filtered to separate solid and liquid, washed and filtered until the pH of the filtrate is 7, and the filtrate is dried at 60°C to obtain potassium humate. The filter residue is dried and used for later use.

[0113] In this embodiment, 20g of bamboo powder biomass raw material was processed to obtain 8.44g of potassium humate solid product and 5.25g of unconverted residue (containing iron and heavy metals copper and chromium after pyrolysis). The potassium humate yield reached 42.20%, and the plant conversion rate was as high as 73.75%. (Note: Potassium humate yield = potassium humate solid product / bamboo powder amount; bamboo powder conversion rate = 1 - unconverted residue / bamboo powder amount).

[0114] Example 9

[0115] (1) Take 20g of bamboo powder that has been washed with deionized water, dried at 80℃ for 24h and passed through a 200-mesh sieve, and calcine it at 280℃ for 120min in a low oxygen atmosphere with an oxygen volume content of 10% to obtain the pyrolysis product.

[0116] (2) The pyrolysis product was mixed with 200 mL of 1% hydrogen peroxide solution, and the mixture was heated and stirred at 80°C for 1 hour and then dried to obtain the weathered coal precursor.

[0117] (3) Add the weathered coal precursor and potassium hydroxide solution to the reactor at a mass ratio of 0.2:1 (potassium hydroxide: bamboo powder) and perform hydrothermal extraction at 100°C for 120 min.

[0118] (4) After the reaction in step (3) is completed, the product is cooled to room temperature, filtered to separate solid and liquid, washed and filtered until the pH of the filtrate is 7, and the filtrate is dried at 60°C to obtain potassium humate. The filter residue is dried and used for later use.

[0119] In this embodiment, 20g of bamboo powder biomass raw material was processed to obtain 10.25g of potassium humate solid product and 4.76g of unconverted residue (containing iron and heavy metals copper and chromium residue after pyrolysis). The potassium humate yield reached 51.25%, and the biomass conversion rate was 76.20%. (Note: Potassium humate yield = potassium humate solid product / bamboo powder amount; bamboo powder conversion rate = 1 - unconverted residue / bamboo powder amount).

[0120] According to embodiments of the present invention, Example 3, compared with Comparative Example 1, demonstrates the role of transition metals in bamboo powder. Examples 1-4, compared with Comparative Example 2, demonstrate that oxidative roasting can improve the conversion rate of humic acid. By utilizing the iron-catalyzed conversion process in bamboo powder, organic matter in plants can be converted into valuable humic acid / fulvic acid. These products can be used in soil improvement, preparation, and other fields, realizing the reuse of resources.

[0121] Preparation and application of Fenton-like catalysts

[0122] According to an embodiment of the present invention, the residue obtained by the above treatment is subjected to roasting treatment, wherein the metal elements contained in the residue after humic acid extraction include iron, copper, chromium, etc. (the metal element content in the residue is shown in Table 2), and the iron element accounts for the majority of the element content.

[0123] Table 2. Metal content in the residue of Example 3

[0124]

[0125] According to embodiments of the present invention, the residues obtained in Example 3 and Comparative Example 1 are further calcined, wherein the residues are mixed and ground uniformly with a template agent. The template agent may be one of potassium chloride, potassium sulfate and potassium carbonate. The template agent can change the chemical composition of the solid surface and increase the active sites on the obtained catalyst.

[0126] Example 10

[0127] (1) Weigh 2g of the residue obtained in Example 3 and mix it with 0.6g of potassium chloride and grind it for 30min;

[0128] (2) Place the mixture in a tube furnace and calcine at 800°C for 2 hours under a nitrogen atmosphere;

[0129] (3) The product obtained by calcination was washed with 1 mol / L hydrochloric acid, then washed three times with deionized water, and then dried in an oven at 80°C for 10 h to obtain an iron-carbon Fenton catalyst.

[0130] (4) The obtained Fenton-like catalyst was subjected to tetracycline degradation experiments in a 100 mL Erlenmeyer flask at room temperature. Typically, a certain amount of catalyst (3 mg) was injected into 100 mL of tetracycline (50 mg / L). -1 The aqueous solution was uniformly dispersed, and the mixture was shaken at 30°C and 30 rpm for 300 minutes to reach adsorption and desorption equilibrium. Then, 10% H₂O₂ solution was added to the mixture to initiate Fenton-catalyzed tetracycline degradation. During the degradation process, 3 mL of solution was collected using a syringe at set time intervals, and 100 μL of methanol was added to quench the reaction. The resulting solution was filtered through a 0.22 μm filter membrane, and the tetracycline concentration was measured at 357 nm using a UV-2006 instrument.

[0131] Comparative Example 3

[0132] (1) Weigh 2g of the residue obtained in Example 3 and grind it directly for 30min;

[0133] (2) Place the mixture in a tube furnace and calcine at 800°C for 2 hours under a nitrogen atmosphere;

[0134] (3) The product obtained by calcination was washed with 1 mol / L hydrochloric acid, then washed three times with deionized water, and then dried in an oven at 80°C for 10 h to obtain an iron-carbon catalyst.

[0135] (4) The obtained Fenton-like catalyst was subjected to tetracycline degradation experiments in a 100 mL Erlenmeyer flask at room temperature. Typically, a certain amount of catalyst (3 mg) was injected into 100 mL of tetracycline (50 mg / L). -1 The aqueous solution was uniformly dispersed, and the mixture was shaken at 30°C and 30 rpm for 300 minutes to reach adsorption and desorption equilibrium. Then, 10% H₂O₂ solution was added to the mixture to initiate Fenton-catalyzed tetracycline degradation. During the degradation process, 3 mL of solution was collected using a syringe at set time intervals, and 100 μL of methanol was added to quench the reaction. The resulting solution was filtered through a 0.22 μm filter membrane, and the tetracycline concentration was measured at 357 nm using a UV-2006 instrument.

[0136] Comparative Example 4

[0137] (1) Weigh 2g of the residue obtained in Comparative Example 1 and mix it with 0.6g of potassium chloride and grind it for 30min;

[0138] (2) Place the mixture in a tube furnace and calcine at 800°C for 2 hours under a nitrogen atmosphere;

[0139] (3) The product obtained by calcination was washed with 1 mol / L hydrochloric acid, then washed three times with deionized water, and then dried in an oven at 80°C for 10 h to obtain an iron-carbon catalyst.

[0140] (4) The obtained Fenton-like catalyst was subjected to tetracycline degradation experiments in a 100 mL Erlenmeyer flask at room temperature. Typically, a certain amount of catalyst (3 mg) was injected into 100 mL of tetracycline (50 mg / L). -1 The aqueous solution was uniformly dispersed, and the mixture was shaken at 30°C and 30 rpm for 300 minutes to reach adsorption and desorption equilibrium. Then, 10% H₂O₂ solution was added to the mixture to initiate Fenton-catalyzed tetracycline degradation. During the degradation process, 3 mL of solution was collected using a syringe at set time intervals, and 100 μL of methanol was added to quench the reaction. The resulting solution was filtered through a 0.22 μm filter membrane, and the tetracycline concentration was measured at 357 nm using a UV-2006 instrument.

[0141] The XRD pattern of the iron-carbon catalyst prepared in Example 10 is shown below. Figure 3 As shown. The catalyst obtained according to Example 10 of the present invention has a smaller nanoparticle structure compared with common catalysts, and metallic iron is uniformly distributed in the catalyst material in the form of single atoms (e.g. Figure 4 (As shown).

[0142] According to embodiments of the present invention, the obtained iron-carbon catalyst was applied to wastewater for the degradation of tetracycline, and the results obtained through the above embodiments were analyzed (e.g.) Figure 5 As shown in the figure, heavy metals can be fixed in the solid catalyst by high-temperature calcination, and the iron-carbon catalyst obtained after adding a template agent and calcining has better ability to degrade tetracycline.

[0143] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A method for the thermocatalytic preparation of potassium humate and a Fenton-like catalyst from bamboo powder, characterized in that, Includes the following steps: (1) Bamboo powder undergoes pyrolysis under a low-oxygen atmosphere; (2) Under heating conditions, the pyrolysis product is mixed and stirred with hydrogen peroxide solution; then, the oxidized solid product is washed and dried to obtain weathered coal precursor. (3) After the obtained weathered coal precursor is mixed with alkali, it is hydrothermally treated and extracted to obtain a liquid containing potassium humate and a residue containing metallic iron. (4) The residue containing metallic iron is mixed with the template agent, ground, and then calcined at high temperature under a nitrogen atmosphere; the calcined product is soaked in hydrochloric acid, washed with water, and dried to obtain an iron-carbon Fenton catalyst. The low-oxygen atmosphere mentioned in step (1) is an oxygen volume content of 5-10% and a nitrogen volume content of 90%-95%; The pyrolysis described in step (1) is performed in a tube furnace at 200-350℃ for 2-3 hours; The heating described in step (2) is 70-90℃; The solid-liquid mass-volume ratio of the bamboo powder mentioned in step (1) and the hydrogen peroxide solution mentioned in step (2) is 1g:(5-15)mL, and the mass concentration of the hydrogen peroxide solution is 0.5-2%. The hydrothermal treatment described in step (3) involves heating at a temperature of 100-150℃ for 2-3 hours; The template agent mentioned in step (4) includes at least one of potassium chloride, potassium sulfate and potassium carbonate; The high-temperature roasting mentioned in step (4) is roasting at a temperature of 600-800℃ for 2-3 hours.

2. The method according to claim 1, characterized in that, The bamboo powder in step (1) undergoes the following pretreatment: rinsing with water, soaking in water, drying, crushing, and sieving.

3. The method according to claim 2, characterized in that, In the pretreatment, the water is deionized water; the soaking is soaking for 12-24 hours; the drying is drying in an oven at 70-85℃ for 20-30 hours; and the sieving is passing through a 100-200 mesh sieve.

4. The method according to claim 1, characterized in that, The mass ratio of the bamboo powder mentioned in step (1) to the alkali mentioned in step (3) is 100:(10-20); The alkali mentioned in step (3) includes at least one of potassium hydroxide, potassium carbonate and sodium hydroxide; The extraction described in step (3) is filtration. The filter residue is washed with water until the filtrate is neutral. The filter residue is a residue containing metallic iron.

5. The method according to claim 1, characterized in that, The mass ratio of the residue containing metallic iron to the template agent in step (4) is 10:(2-5).

6. The method according to claim 1, characterized in that, The hydrochloric acid mentioned in step (4) is 1 mol / L hydrochloric acid; The washing with water mentioned in step (4) refers to washing with deionized water three times; Dry in the drying oven at 70-90℃ for 8-12 hours as described in step (4).

7. The application of Fenton-like catalysts in the degradation of antibiotics in the environment is characterized by, The Fenton-like catalyst described herein is prepared by the method described in any one of claims 1-6.

8. The application according to claim 7, characterized in that, The environment described is water or soil; The antibiotics mentioned include tetracycline.

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