Preparation method for rapid humification of garden waste to synthesize artificial humus

Abstract

The present application discloses a preparation method for rapid humification of garden waste to synthesize artificial humus. The method comprises: crushing and sieving garden waste to obtain biomass powder; then mixing the biomass powder with an iron-based auxiliary agent, and carrying out an oxidation pre-reaction under the action of an ultrasonic cleaner; then ultrasonically uniformly mixing the solution obtained after the pre-reaction with an alkali, and carrying out a hydrothermal humification reaction in a reaction kettle to obtain a humus-containing solution; and finally carrying out solid-liquid separation on the humus-containing solution obtained after the hydrothermal humification reaction, and recovering humus. The humus preparation method of the present invention has a high humus yield and consumes short time.

Description

A method for rapidly synthesizing artificial humus from garden waste Technical Field

[0001] This invention belongs to the field of environmental protection technology, specifically relating to a method for rapidly humifying garden waste to synthesize artificial humus. Background Technology

[0002] Garden waste refers to plant remains generated from the natural shedding or artificial pruning of garden plants, including fallen leaves, shrub trimmings, tree trimmings, lawn trimmings, discarded wildflowers, as well as branches fallen due to severe weather and fallen trees. It is an important component of urban organic solid waste. How to properly handle and dispose of garden waste is an urgent problem that urban development needs to solve, and it is also a cutting-edge research direction in the engineering field. Composting garden waste is currently the most widely used technology, but composting is time-consuming, requires a large area, is complex to operate, and the properties of compost products are not stable enough. Therefore, there is an urgent need to develop a rapid and efficient method for processing garden waste. Simulating and enhancing the natural formation conditions and processes of humus through hydrothermal reactions to artificially synthesize humus has attracted researchers' attention in recent years. However, such hydrothermal reaction methods have both low humus yields and long preparation cycles. Therefore, there is an urgent need to develop a rapid and efficient method for the humification synthesis of artificial humus from garden waste. Summary of the Invention -

[0003] One of the objectives of this invention is to provide a production method that enables the rapid humification of garden waste into artificial humus.

[0004] One of the objectives of this invention is to provide a production method that achieves a high humus yield from garden waste.

[0005] The above-mentioned objectives of the present invention are achieved by the following technical means.

[0006] A method for preparing artificial humus from garden waste, comprising the following steps:

[0007] S1. Pre-treatment of garden waste: Garden waste is crushed and sieved to obtain biomass powder;

[0008] S2, Oxidation Pre-reaction: After mixing biomass powder and iron-based additives, a pre-reaction is carried out under ultrasound.

[0009] S3. Hydrothermal humification reaction: The solution after the pre-oxidation reaction is ultrasonically mixed with alkali and then subjected to hydrothermal humification reaction in a reaction vessel to obtain a solution containing humus.

[0010] S4. Humus Recovery: The humus-containing solution after the hydrothermal humification reaction is subjected to solid-liquid separation to recover the solid and liquid humus separately.

[0011] In step S1, the garden waste includes, but is not limited to: garden plant pruning branches, naturally fallen plant material (fallen leaves, debris, bark), weeds, branches damaged by natural disasters such as typhoons, sawdust, wood chips, camellia shells, etc. generated from garden processing.

[0012] In a preferred embodiment, in step S1, the garden waste needs to be pretreated. The specific method is to immerse the garden waste in water, with the water covering the waste by 2 cm or more, rinse it 1-3 times until the solution is no longer turbid, dry it at 80-120℃ for 3-5 hours, then crush it and pass it through a 60-200 mesh sieve to obtain biomass powder.

[0013] In a preferred embodiment, in step S2, the weight ratio of biomass powder to iron powder is 10-60:1.

[0014] In a preferred embodiment, in step S2, the weight ratio of biomass powder to iron powder is 30-40:1.

[0015] In a preferred embodiment, in step S2, the iron-based additive is selected from one or more of iron powder (zero-valent iron), nano-zero-valent iron, magnetite, iron filings, ferrous sulfate, ferric chloride, and ferric nitrate.

[0016] In a more preferred embodiment, in step S2, the iron-based additive is selected from iron powder, and the iron atoms in the iron powder are in a zero-valence state.

[0017] In a preferred embodiment, in step S2, the reaction temperature of the oxidation pre-reaction is room temperature, and the reaction time is 1-4 hours.

[0018] In a preferred embodiment, in step S2, the ultrasonic cleaning frequency is 20-40kHz and the power is 30-120W.

[0019] In a preferred embodiment, the weight ratio of the alkali in step S3 to the biomass powder in step S2 is 1:3-15.

[0020] In a preferred embodiment, in step S3, the alkali is selected from one or more of sodium hydroxide, calcium hydroxide, potassium hydroxide, sodium bicarbonate, and potassium bicarbonate.

[0021] In a preferred embodiment, in step S3, the ultrasonic mixing time is 0.5-1h, 20-40kHz, and 30-120W.

[0022] In a more preferred embodiment, the ultrasonic mixing time in step S3 is 0.5 h.

[0023] In a preferred embodiment, in step S3, the hydrothermal humification reaction is carried out at a temperature of 160-250°C for 1-4 hours.

[0024] In a preferred embodiment, in step S4, the solid humic material obtained by solid-liquid separation is dried and recovered; the separated liquid humic material can be used directly as liquid fertilizer; or solid humic material can be obtained by acidification, filtration and drying. Specifically, the pH value of the liquid can be adjusted to acidity using dilute sulfuric acid, for example, adjusting the pH to 1-5, more preferably 1-2, precipitating solid, collecting the solid after centrifugation, washing and drying to obtain solid humic acid.

[0025] The artificial humus synthesized in this invention can be used in soil improvement fields such as nurseries, woodlands, potted plants, street trees, and farmland.

[0026] One of the above technical solutions has the following advantages and effects:

[0027] 1. This invention enables the large-scale and efficient disposal of urban landscaping waste, with low product cost and readily available raw materials, giving it advantages for widespread application.

[0028] 2. The present invention employs ultrasonic dispersion to promote the uniform dispersion and distribution of biomass powder, iron-based additives, alkali, etc. in the solution, thereby increasing the contact area and efficiency between raw materials and promoting the humic reaction process.

[0029] 3. This invention employs a process combining pre-reaction and humification reactions. Unlike traditional technologies, this invention adds an iron-based additive as a catalyst in the pre-reaction phase. This reaction does not require heating and does not need to be carried out in a reaction vessel, making it simple to operate and highly effective. Moreover, due to the superior pre-reaction effect, the subsequent humification reaction time is reduced (by approximately 50%), significantly lowering production costs and improving the efficiency of artificial humus production while maintaining the artificial humus synthesis rate.

[0030] 4. This invention introduces an oxidation pre-reaction process using a catalyst represented by zero-valent iron. Unlike traditional technologies, this invention advocates the use of granular iron materials such as iron powder (zero-valent iron). Under ultrasonic action, iron ions are continuously generated as a catalyst, creating a local micro-oxidation environment that significantly accelerates the pre-hydrolysis of macromolecular substances in garden waste.

[0031] 5. This invention has advantages such as fast reaction speed (2-8h), high raw material utilization rate, high artificial humus synthesis rate (over 30%), and clean and environmentally friendly production process. It increases the synthesis rate by more than 40% compared with conventional methods, while saving about 50% of the reaction time. Attached Figure Description

[0032] Figure 1 shows the effect of different biomass precursors on the efficiency of artificial humic synthesis.

[0033] Figure 2 shows the effect of different types of iron ions on the efficiency of artificial humic substance synthesis.

[0034] Figure 3 shows the effect of different zero-valent iron particles on the efficiency of artificial humic synthesis.

[0035] Figure 4 shows the effect of different ultrasound treatment times on the efficiency of artificial humic substance synthesis.

[0036] Figure 5 shows the effect of different hydrothermal humification reaction temperatures on the efficiency of artificial humic synthesis.

[0037] Figure 6 shows the effect of different hydrothermal humification reaction times on the efficiency of artificial humic synthesis.

[0038] Figure 7 shows the effect of different types and concentrations of alkaline substances on the efficiency of artificial humic substance synthesis;

[0039] Figure 8 compares the efficiency of artificial humic substance synthesis under different reaction conditions. Detailed Implementation

[0040] The following specific embodiments further illustrate the technical solution of the present invention. These specific embodiments do not represent a limitation on the scope of protection of the present invention. Non-essential modifications and adjustments made by others based on the concept of the present invention still fall within the scope of protection of the present invention.

[0041] It should be noted that the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0042] Unless otherwise specified, the "iron powder" in this invention refers to conventional iron powder, which is zero-valent iron and does not include nanoscale zero-valent iron (nZVI). Nanoscale zero-valent iron is an elemental iron powder with a particle size ranging from 1 to 100 nanometers.

[0043] Example 1: A method for rapidly synthesizing artificial humus from different types of garden waste

[0044] S1. Pretreatment of garden waste: Soak different biomass raw materials (wood chips, leaves and their mixtures) in deionized water, with the water covering the waste by 2cm or more. Rinse 1-3 times until the solution is clear. Dry at 80-120℃ for 3-5 hours, then crush and pass through a 60-200 mesh sieve to obtain biomass powder.

[0045] S2. Oxidation pre-reaction: Biomass powder and iron powder are mixed in a weight ratio of 50:1 and reacted in an ultrasonic cleaner for 2 hours (frequency 20kHz, power 60W) at a reaction temperature of 25℃.

[0046] S3. Hydrothermal humification reaction: The hydrothermal pre-reaction solution and sodium hydroxide are mixed evenly by ultrasonication at a weight ratio of 5:1 (biomass powder: sodium hydroxide) (frequency 20kHz, power 60W, time 0.5h). The hydrothermal humification reaction is carried out in a reactor at a reaction temperature of 200℃ for 2h to obtain a humic solution.

[0047] S4. Humic substance recovery: The humic substance-containing solution after the hydrothermal humification reaction is subjected to solid-liquid separation. The separated solid is placed in an oven and dried at 80°C to obtain solid humic substance (RS). The pH value of the separated liquid is adjusted to 1-2 by passing 1 mol / L dilute sulfuric acid. After centrifugation, the solid is collected, washed, and dried to obtain artificial humic acid solid (A-HS).

[0048] This application selected two characteristic wastes from the landscaping industry—leaves (pruned branches and leaves) and sawdust (after wood processing)—as research objects. The experimental results are shown in Figure 1. The A-HS synthesis rate of the sawdust group was 33.15%, which is 1.16 times that of the leaf group. Simultaneously, the residual solids rate of the sawdust group was 40.88%, which is 88% of that of the leaf group. This indicates that sawdust, as a reaction product, is more readily subjected to hydrothermal humification. In this experiment, leaves and sawdust were mixed in a 50:50 ratio, and the A-HS synthesis rate was found to be between the two, which is consistent with our analysis. Based on these experimental results, landscaping biomass such as sawdust and leaves have good application prospects. In practical work, the choice of materials can be made based on their source. If leaves are used, attention should be paid to the influence of leaf moisture content, bulk density, and other indicators on the A-HS synthesis efficiency.

[0049] Example 2: Preparation method of artificial humus from garden waste through rapid humification using different types of iron-based additives

[0050] S1. Pretreatment of garden waste: Immerse the biomass raw materials (a mixture of wood chips and leaves) in deionized water, with the water covering the waste by 2 cm or more. Rinse 1-3 times until the solution is clear. Dry at 80-120℃ for 3-5 hours, then crush and pass through a 60-200 mesh sieve to obtain biomass powder.

[0051] S2. Pre-reaction: Biomass powder is mixed with different iron-based additives (iron powder, ferrous sulfate, ferric chloride, 50nm zero-valent iron, 100nm zero-valent iron) at a weight ratio of 50:1 and reacted in an ultrasonic cleaner for 2 hours (frequency 20kHz, power 60W) at a reaction temperature of 25℃.

[0052] S3. Hydrothermal humification reaction: The hydrothermal pre-reaction solution and sodium hydroxide are ultrasonically mixed at a weight ratio of 5:1 (biomass powder: sodium hydroxide) (frequency 20kHz, power 60W, time 0.5h). The hydrothermal humification reaction is carried out in a reactor at a reaction temperature of 200℃ for 2h to obtain a humic solution.

[0053] S4. Humic substance recovery: The humic substance-containing solution after the hydrothermal humification reaction is subjected to solid-liquid separation. The separated solid is placed in an oven and dried at 80°C to obtain solid humic substance (RS). The pH value of the separated liquid is adjusted to 1-2 by passing 1 mol / L dilute sulfuric acid. After centrifugation, the solid is collected, washed, and dried to obtain artificial humic acid solid (A-HS).

[0054] In this study, iron-based additives, acting as catalysts in the pre-oxidation reaction, are a crucial factor influencing the synthesis of artificial humic substances. Therefore, this application first investigated the catalytic effects of iron ions with different valence states, selecting iron powder (zero-valent iron), ferrous sulfate (divalent iron), and ferric chloride (trivalent iron) as research subjects, and recording the synthesis of artificial humic substances, as shown in Figure 2. The figure shows that the synthesis rate of A-HS in the experimental group with added iron-based catalysts was significantly higher than that in the control group. 3+ When Fe(III) was used as a catalyst, the A-HS synthesis rate was 17.65%, which was 3.1 times that of the control group. 0 When iron powder (zero-valent iron) was used as a catalyst, the synthesis rate of A-HS was the highest, reaching 28.35%, which was 4.8 times that of the control group. Therefore, it can be concluded that the synthesis rate of A-HS gradually decreases with increasing iron ion valence state. In this study, by introducing iron powder as a catalyst, solid zero-valent iron could continuously generate Fe. 2+ It continuously attacks biomass macromolecules, generating more and smaller biomass micromolecules, thereby promoting the subsequent hydrothermal replication reaction.

[0055] In this study, the effects of zero-valent iron (iron powder, nano-zero-valent iron (50nm, 100nm)) of different particle sizes as catalysts on the synthesis of artificial humic substances were further investigated. As shown in Figure 3, the synthesis rate of A-HS in the experimental group with zero-valent iron as a catalyst was significantly higher than that in the control group. When 50nm zero-valent iron was used as a catalyst, the synthesis rate of A-HS was 22.3%, which was 3.8 times that of the blank group. When 100nm FeO was used as a catalyst, the synthesis rate of A-HS was 19.24%, which was 3.3 times that of the blank group. It can be seen that when nano-sized zero-valent iron is used as a catalyst, the synthesis rate of artificial humic substances is significantly improved compared with the blank group, but the catalytic efficiency is still significantly lower than that of ordinary zero-valent iron (33.15%).

[0056] Example 3: Method for rapid humification of garden waste into artificial humus under different ultrasonic treatment times

[0057] S1. Pretreatment of garden waste: Soak biomass raw materials (mixture of wood chips and leaves) in deionized water, with the water covering the waste by 2 cm or more. Rinse 1-3 times until the solution is clear. Dry at 80-120℃ for 3-5 hours, then crush and pass through a 60-200 mesh sieve to obtain biomass powder.

[0058] S2. Pre-reaction: Biomass powder and iron powder are mixed in a weight ratio of 50:1 and reacted in an ultrasonic cleaner for 1, 2, 3 and 4 hours respectively (frequency 20kHz, power 60W) at a reaction temperature of 25℃.

[0059] S3. Hydrothermal humification reaction: The hydrothermal pre-reaction solution and sodium hydroxide are mixed evenly by ultrasonication at a weight ratio of 5:1 (biomass powder: sodium hydroxide) (frequency 20kHz, power 60W, time 0.5h). The hydrothermal humification reaction is carried out in a reactor at a reaction temperature of 200℃ for 2h to obtain a humic solution.

[0060] S4. Humic substance recovery: The humic substance-containing solution after the hydrothermal humification reaction is subjected to solid-liquid separation. The separated solid is placed in an oven and dried at 80°C to obtain solid humic substance (RS). The pH value of the separated liquid is adjusted to 1-2 by passing 1 mol / L dilute sulfuric acid. After centrifugation, the solid is collected, washed, and dried to obtain artificial humic acid solid (A-HS).

[0061] In this study, ultrasound promoted the pre-oxidation reaction and was a crucial factor influencing the synthesis of artificial humic substances. Therefore, the effects of different ultrasound reaction times were investigated, as shown in Figure 4. The figure shows that the A-HS synthesis rate increased continuously with increasing reaction time, from 28.25% at 1 hour to 36.65% at 4 hours, an increase of 29.7%. However, when the ultrasound treatment time was 3 hours, the A-HS synthesis rate was 35.22%, not significantly different from that at 4 hours. Furthermore, with increasing ultrasound treatment time, the RS residual solids rate decreased from 67.16% to 20.33%, a reduction of 69.7%. Since the residual solids can be recycled, selecting an appropriate ultrasound reaction time to achieve a balance between the A-HS and RS residual solids rates is an important factor to consider in the actual reaction process.

[0062] Example 4: Preparation method of artificial humus from garden waste through rapid humification at different hydrothermal humification reaction temperatures

[0063] S1. Pretreatment of garden waste: Immerse the biomass raw materials (a mixture of wood chips and leaves) in deionized water, with the water covering the waste by 2 cm or more. Rinse 1-3 times until the solution is clear. Dry at 80-120℃ for 3-5 hours, then crush and pass through a 60-200 mesh sieve to obtain biomass powder.

[0064] S2. Pre-reaction: Biomass powder and iron powder are mixed in a weight ratio of 50:1 and reacted in an ultrasonic cleaner for 2 hours at a reaction frequency of 20kHz, a reaction power of 60W, and a reaction temperature of 25℃.

[0065] S3. Hydrothermal humification reaction: The hydrothermal pre-reaction solution and sodium hydroxide are mixed evenly by ultrasonication at a weight ratio of 5:1 (biomass powder: sodium hydroxide) (frequency 20kHz, power 60W, time 0.5h). The hydrothermal humification reaction is carried out in a reactor at temperatures of 160, 180, 200 and 220℃ for 2h to obtain a humic solution.

[0066] S4. Humic substance recovery: The humic substance-containing solution after the hydrothermal humification reaction is subjected to solid-liquid separation. The separated solid is placed in an oven and dried at 80°C to obtain solid humic substance (RS). The pH value of the separated liquid is adjusted to 1-2 by passing 1 mol / L dilute sulfuric acid. After centrifugation, the solid is collected, washed, and dried to obtain artificial humic acid solid (A-HS).

[0067] This section investigated the effect of different reaction temperatures (160, 180, 200, and 220 °C) on the synthesis efficiency of A-HS. The experimental results are shown in Figure 5. When the reaction temperature was 160 °C, the A-HS synthesis rate was only 19.59%, while when the reaction temperature was increased to 220 °C, the A-HS synthesis rate reached 35.33%, an increase of 80.3%. Therefore, increasing the reaction temperature has a significant promoting effect on the synthesis of A-HS. Further research revealed that when the temperature was 200 °C, the A-HS synthesis rate was 33.53%, not significantly different from that at 220 °C (35.33%), indicating that the promoting effect of temperature on A-HS synthesis tends to stabilize when a certain value is reached. Moreover, we found that at 200 °C, the residual solids rate was 57.79%, twice that at 220 °C (28.65%). The increase in the A-HS synthesis rate at 220 °C (1.8%) was based on a solids loss rate of 29.14%. Since both the A-HS and the remaining solids have corresponding uses in the later stages, this study believes that 180-220℃ is a suitable reaction temperature, while 200℃±10℃ is more suitable.

[0068] Example 5: Preparation method of artificial humus from garden waste through rapid humification under different hydrothermal humification reaction times.

[0069] S1. Pretreatment of garden waste: Immerse the biomass raw materials (a mixture of wood chips and leaves) in deionized water, with the water covering the waste by 2 cm or more. Rinse 1-3 times until the solution is clear. Dry at 80-120℃ for 3-5 hours, then crush and pass through a 60-200 mesh sieve to obtain biomass powder.

[0070] S2. Pre-reaction: Biomass powder and iron powder are mixed in a weight ratio of 50:1 and reacted in an ultrasonic cleaner for 2 hours at a reaction frequency of 20kHz, a reaction power of 60W, and a reaction temperature of 25℃.

[0071] S3. Hydrothermal humification reaction: The hydrothermal pre-reaction solution and sodium hydroxide are mixed evenly by ultrasonication at a weight ratio of 5:1 (biomass powder: sodium hydroxide) (frequency 20kHz, power 60W, time 0.5h). The hydrothermal humification reaction is carried out in a reactor at a reaction temperature of 200℃ for 1, 2, 3 and 4h respectively, to obtain a humic solution.

[0072] S4. Humic substance recovery: The humic substance-containing solution after the hydrothermal humification reaction is subjected to solid-liquid separation. The separated solid is placed in an oven and dried at 80°C to obtain solid humic substance (RS). The pH value of the separated liquid is adjusted to 1-2 by passing 1 mol / L dilute sulfuric acid. After centrifugation, the solid is collected, washed, and dried to obtain artificial humic acid solid (A-HS).

[0073] This study investigated the effect of different reaction times (1, 2, 3, and 4 h) on the synthesis efficiency of A-HS, and the results are shown in Figure 6. When the reaction time increased from 1 h to 4 h, the synthesis efficiency of A-HS increased from 26.25% to 36.92%, an increase of 40.6%. Simultaneously, it was clearly observed that the residual solids rate decreased from 69.57% to 13.48%, a decrease of 80.6%. Notably, after 1 h of heating, the total amount of A-HS and residual solids was 95.82%, while after 4 h, the total amount was only 50.40%, indicating a higher loss of solids (45.42%). The longer the reaction time at high temperatures, the more complete the decomposition of substances. Some products are emitted as carbon dioxide and water, while other soluble products enter the solution. Furthermore, the synthesis rates of A-HS after 2 h, 3 h, and 4 h were 33.57%, 34.42%, and 36.92%, respectively, showing relatively small differences. However, the residual solids rates were 57.79%, 28.36%, and 13.48%, respectively, resulting in significant solid loss. Therefore, considering both the A-HS synthesis rate and residual solids rate, this study suggests that a hydrothermal humification reaction time of 1-3 h is more suitable, while 2 h ± 20 min is even more appropriate.

[0074] Example 6: Preparation method of artificial humus from garden waste through rapid humification under different alkali conditions

[0075] S1. Pretreatment of garden waste: Immerse the biomass raw materials (a mixture of wood chips and leaves) in deionized water, with the water covering the waste by 2 cm or more. Rinse 1-3 times until the solution is clear. Dry at 80-120℃ for 3-5 hours, then crush and pass through a 60-200 mesh sieve to obtain biomass powder.

[0076] S2. Pre-reaction: Biomass powder and iron powder are mixed in a weight ratio of 50:1 and reacted in an ultrasonic cleaner for 2 hours at a reaction frequency of 20kHz, a reaction power of 60W, and a reaction temperature of 25℃.

[0077] S3. Hydrothermal Humic Reaction: The hydrothermal pre-reaction solution is mixed with different alkalis (sodium hydroxide, calcium hydroxide, and sodium bicarbonate) at a weight ratio of 5:1 (biomass powder: alkali substances), and ultrasonically mixed evenly (frequency 20kHz, power 60W, time 0.5h). The hydrothermal humification reaction is carried out in a reactor at a reaction temperature of 200℃ for 2h to obtain a humic solution.

[0078] S4. Humic substance recovery: The humic substance-containing solution after the hydrothermal humification reaction is subjected to solid-liquid separation. The separated solid is placed in an oven and dried at 80°C to obtain solid humic substance (RS). The pH value of the separated liquid is adjusted to 1-2 by passing 1 mol / L dilute sulfuric acid. After centrifugation, the solid is collected, washed, and dried to obtain artificial humic acid solid (A-HS).

[0079] In this study, alkaline substances, acting as catalysts for the hydrothermal humification reaction, are a crucial factor influencing the synthesis of artificial humic substances. Therefore, this application first investigated the catalytic effects of different alkaline substances, selecting sodium hydroxide, calcium hydroxide, and sodium bicarbonate as research subjects, and recorded the synthesis of artificial humic substances, as shown in Figure 7 (left figure). The figure shows that when sodium hydroxide, calcium hydroxide, and sodium bicarbonate were used as alkaline substances, the A-HS synthesis rates were 33.5%, 31.5%, and 30.4%, respectively, indicating excellent A-HS synthesis effects. The alkaline substances selected in this application provided a strongly alkaline environment, achieving optimal A-HS synthesis results.

[0080] In this study, the effect of different concentrations of sodium hydroxide as a catalyst (biomass powder to sodium hydroxide weight ratios of 3:1, 5:1, 10:1, and 15:1) on the synthesis of artificial humic substances was further investigated, as shown in Figure 7 (right figure). When the biomass powder:alkali ratio decreased from 15:1 to 3:1, it meant that the concentration of alkali was continuously increasing, and the synthesis rate of A-HS also increased from 26.3% to 36.19%, an increase of 37.6%. This indicates that increasing the concentration of alkali can effectively improve the synthesis efficiency of A-HS. Of course, as shown in the figure, when the biomass powder:alkali ratio was 5:1 and 3:1, the synthesis rates of A-HS were 35.5% and 36.19%, respectively, with a very small difference. This indicates that there is an optimal range of alkali values ​​depending on the quality of the biomass powder.

[0081] Comparative Example 1: Method for rapid humification of garden waste into artificial humus without oxidative pre-reaction step

[0082] S1. Pretreatment of garden waste: Immerse the biomass raw materials (a mixture of wood chips and leaves) in deionized water, with the water covering the waste by 2 cm or more. Rinse 1-3 times until the solution is clear. Dry at 80-120℃ for 3-5 hours, then crush and pass through a 60-200 mesh sieve to obtain biomass powder.

[0083] S2. Hydrothermal humification reaction: The hydrothermal pre-reaction solution and sodium hydroxide are mixed evenly by ultrasonication at a weight ratio of 5:1 (biomass powder: sodium hydroxide) (frequency 20kHz, power 60W, time 0.5h). The hydrothermal humification reaction is carried out in a reactor at a reaction temperature of 200℃ for 2h to obtain a humic solution.

[0084] S3. Humic substance recovery: The humic substance-containing solution after the hydrothermal humification reaction is subjected to solid-liquid separation. The separated solid is placed in an oven and dried at 80°C to obtain solid humic substance (RS). The pH value of the separated liquid is adjusted to 1-2 by passing 1 mol / L dilute sulfuric acid. After centrifugation, the solid is collected, washed, and dried to obtain artificial humic acid solid (A-HS).

[0085] Comparative Example 2: Preparation method of artificial humus from garden waste without ultrasonic treatment via rapid humification

[0086] S1. Pretreatment of garden waste: Immerse the biomass raw materials (a mixture of wood chips and leaves) in deionized water, with the water covering the waste by 2 cm or more. Rinse 1-3 times until the solution is clear. Dry at 80-120℃ for 3-5 hours, then crush and pass through a 60-200 mesh sieve to obtain biomass powder.

[0087] S2. Pre-reaction: Mix biomass powder and iron powder in a weight ratio of 50:1 and let stand for 2 hours. The reaction temperature is 25℃.

[0088] S3. Hydrothermal humification reaction: The hydrothermal pre-reaction solution is mixed with sodium hydroxide at a weight ratio of 5:1, and then a hydrothermal humification reaction is carried out in a reactor. The reaction temperature of the hydrothermal humification reaction is 200℃ and the reaction time is 2h, to obtain a humic solution.

[0089] S4. Humic substance recovery: The humic substance-containing solution after the hydrothermal humification reaction is subjected to solid-liquid separation. The separated solid is placed in an oven and dried at 80°C to obtain solid humic substance (RS). The pH value of the separated liquid is adjusted to 1-2 by passing 1 mol / L dilute sulfuric acid. After centrifugation, the solid is collected, washed, and dried to obtain artificial humic acid solid (A-HS).

[0090] Example 7: Method for preparing artificial humus through rapid humification of garden waste

[0091] S1. Pretreatment of garden waste: Immerse the biomass raw materials (a mixture of wood chips and leaves) in deionized water, with the water covering the waste by 2 cm or more. Rinse 1-3 times until the solution is clear. Dry at 80-120℃ for 3-5 hours, then crush and pass through a 60-200 mesh sieve to obtain biomass powder.

[0092] S2. Pre-reaction: Biomass powder and iron powder are mixed in a weight ratio of 50:1 and reacted in an ultrasonic cleaner for 2 hours at a reaction frequency of 20kHz, a reaction power of 60W, and a reaction temperature of 25℃.

[0093] S3. Hydrothermal humification reaction: The hydrothermal pre-reaction solution and sodium hydroxide are mixed evenly by ultrasonication at a weight ratio of 5:1 (biomass powder: sodium hydroxide) (frequency 20kHz, power 60W, time 0.5h). The hydrothermal humification reaction is carried out in a reactor at a reaction temperature of 200℃ for 2h to obtain a humic solution.

[0094] S4. Humic substance recovery: The humic substance-containing solution after the hydrothermal humification reaction is subjected to solid-liquid separation. The separated solid is placed in an oven and dried at 80°C to obtain solid humic substance (RS). The pH value of the separated liquid is adjusted to 1-2 by passing 1 mol / L dilute sulfuric acid. After centrifugation, the solid is collected, washed, and dried to obtain artificial humic acid solid (A-HS).

[0095] The yields of artificial humic acid after different hydrothermal humification reactions in Comparative Example 1, Comparative Example 2, and Example 7 are shown in Figure 8.

[0096] This paper selects two comparative examples and one example for comparison, and the experimental results are shown in Figure 8. In Example 7, the A-HS synthesis rate was 33.5%, while in Comparative Example 1, the A-HS synthesis rate was only 20.25%, which is 60.4% of that in Example 7. The difference between the two sets of experiments is that Comparative Example 1 did not undergo a pre-reaction and directly carried out a hydrothermal humification reaction. The experimental results show that the pre-reaction process proposed in this study has a significant effect on the synthesis of A-HS. In Comparative Example 2, the A-HS synthesis rate was 23.19%, which is 14.5% higher than that in Comparative Example 1. The difference between the two sets of experiments is that Comparative Example 2 added a pre-reaction (without ultrasonic treatment), which indicates that the pre-reaction is necessary. In Comparative Example 2, the A-HS was only 55.6% of that in Example 7, which shows that ultrasonic treatment plays an important role in the pre-reaction process.

[0097] The elemental composition of artificial humic acids prepared by different hydrothermal humification reactions in Comparative Examples 1, 2 and 7 is shown in Table 1.

[0098] Table 1. Elemental composition of artificial humic acids prepared by different hydrothermal humification reactions.

[0099] As shown in Table 1, after the hydrothermal humification reaction, the carbon mass fraction in the three experimental groups increased from 57.33% to 59.71% and 63.23%, respectively, while the oxygen mass fraction decreased from 33.57% to 31.83% and 28.65%, indicating that the hydrothermal humification process is a carbon accumulation process, and the degree of hydrothermal humification reaction was higher in Example 7. The H / C, O / C, and C / N ratios of humic acid are generally considered important indicators of maturity and directional condensation. Therefore, this study calculated the values ​​of these three indicators under different reaction conditions, as shown in Table 1. The change in the H / C ratio can reflect the dehydration reaction that occurs during the hydrothermal treatment. In the three experimental groups, Example 7 had the highest H / C ratio and the lowest O / C ratio, indicating that the aromaticity of Example 7 was much higher than that of Comparative Examples 1 and 2, and that hydrothermal pretreatment greatly accelerated the hydrothermal humification process. The O / C value is also considered an indicator of the contribution of carbohydrates and carboxylic acids to humic formation. Clearly, among the three products, control group 1 provided the highest O / C value, indicating that the prepared product contained a high proportion of carboxylic acids and furans. The C / N ratio is generally considered an indicator of humus source, reflecting the original proportion of plant-derived substances. The C / N ratios of the A-HS obtained in all three experiments were around 60%, indicating that the humus source of the A-HA obtained in all three experiments was primarily terrestrial vascular plants.

Claims

1. A method for preparing humic substances, characterized in that, Includes the following steps: S1. Pre-treatment of garden waste: Garden waste is crushed and sieved to obtain biomass powder; S2, Oxidation pre-reaction: After mixing biomass powder and iron-based additives, an oxidation pre-reaction is carried out under ultrasound. S3. Hydrothermal humification reaction: After the solution after oxidation pre-reaction is mixed evenly with alkali by ultrasonication, a hydrothermal humification reaction is carried out in a reaction vessel to obtain a solution containing humus. S4. Humus Recovery: The humus-containing solution after the hydrothermal humification reaction is subjected to solid-liquid separation to recover the solid and liquid humus separately.

2. The method according to claim 1, characterized in that, In step S2, the weight ratio of the biomass powder to the iron-based additive is 10-60:

1.

3. The method according to claim 1, characterized in that, In step S2, the iron-based additive is selected from one or more of iron powder, nano-zero-valent iron, magnetite, iron filings, ferrous sulfate, ferric chloride, and ferric nitrate; preferably, the iron-based additive is selected from iron powder.

4. The method according to claim 1, characterized in that, In step S2, the oxidation pre-reaction time is 1-4 hours.

5. The method according to claim 1, characterized in that, In step S2, the frequency of the ultrasound is 20-40kHz and the power is 30-120W.

6. The method according to claim 1, characterized in that, The weight ratio of the alkali in step S3 to the biomass powder in step S2 is 1:3-15.

7. The method according to claim 1, characterized in that, In step S3, the alkali is selected from one or more of sodium hydroxide, calcium hydroxide, potassium hydroxide, sodium bicarbonate, and potassium bicarbonate.

8. The method according to claim 1, characterized in that, In step S3, the ultrasonic mixing time is 0.5-1h, the frequency is 20-40kHz, and the power is 30-120W.

9. The method according to claim 1, characterized in that, In step S3, the hydrothermal humification reaction is carried out at a temperature of 160-250°C for 1-4 hours.

10. The method according to claim 1, characterized in that, In step S4, the solid humic material obtained from the solid-liquid separation is dried and recovered; the separated liquid humic material can be used directly as liquid fertilizer, or it can be acidified, filtered, and dried to obtain solid humic material.

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