A method for preparing artificial humus synthesized by rapid humification of garden waste

Abstract

The present application discloses a method for preparing artificial humus by rapid humification of garden waste. The method comprises crushing and sieving garden waste to obtain biomass powder; then mixing the biomass powder with an iron-based additive, and performing an oxidation pre-reaction under the action of an ultrasonic cleaner; then uniformly mixing the solution after the pre-reaction with an alkali ultrasonic, and then performing a hydrothermal humification reaction in a reactor to obtain a humus-containing solution; finally, performing solid-liquid separation on the humus-containing solution after the hydrothermal humification reaction, and recovering the humus. The method for preparing humus of the present invention has a high humus yield and is time-consuming.

Description

Technical Field

[0001] The invention belongs to the technical field of environmental protection, and in particular relates to a method for preparing artificial humus synthesized by rapid humification of garden waste. Background Art

[0002] Garden waste refers to the plant residues produced when garden green plants fall naturally or are pruned artificially, including dead branches and leaves, shrub prunings, tree prunings, lawn prunings, abandoned flowers, etc., as well as branches and fallen trees due to disastrous weather. It is an important part of urban organic solid waste. How to properly handle and dispose of garden waste is a difficult problem that urgently needs to be solved in urban development, and it is also a frontier research direction in the engineering community. Garden waste composting is currently the most widely used technology, but composting takes a long time, occupies a large area, is complicated to operate, and the properties of the compost product are not stable enough. Therefore, it is urgent to develop a method for quickly and efficiently treating garden waste. The use of hydrothermal reaction to simulate and strengthen the natural formation conditions and processes of humus for artificial synthesis of humus has attracted the attention of researchers in recent years. However, this type of hydrothermal reaction method has a low humus yield on the one hand and a long preparation cycle on the other hand. Therefore, it is urgent to develop a method for preparing artificial humus by humification of garden waste quickly and efficiently. Summary of the invention

[0003] One of the purposes of the present invention is to provide a production method capable of realizing rapid humification of garden waste to synthesize artificial humus.

[0004] One of the purposes of the present invention is to provide a production method for achieving high humus yield of garden waste.

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

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

[0007] S1. Pretreatment of garden waste: crushing and sieving the garden waste to obtain biomass powder;

[0008] S2, oxidation pre-reaction: after mixing the biomass powder and the iron-based additive, pre-react under ultrasound;

[0009] S3, hydrothermal humification reaction: the solution after the oxidation pre-reaction is evenly mixed with alkali ultrasonic, and then a hydrothermal humification reaction is carried out in a reactor to obtain a humus-containing solution;

[0010] S4. Recovering humus: performing solid-liquid separation on the humus-containing solution after the hydrothermal humification reaction, and recovering solid and liquid humus respectively.

[0011] Among them, in step S1, the garden waste includes but is not limited to: pruned branches of garden plants, natural fallen plants (fallen leaves, debris, bark), weeds, branches damaged by natural disasters such as typhoons, sawdust, wood chips, tea oil shells, etc. produced by garden processing.

[0012] In a preferred embodiment, in step S1, the garden waste also needs to be pretreated, and the specific scheme is to immerse the garden waste in water, the water covers the waste by 2 cm or more, rinse 1-3 times until the solution is not turbid, dry at 80-120°C for 3-5h, and 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 the biomass powder to the iron powder is 10-60:1.

[0014] In a preferred embodiment, in step S2, the weight ratio of the biomass powder to the 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-valent 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 base 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, 30-120W.

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

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

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

[0025] The artificial humus synthesized by the invention can be used in soil improvement fields such as nurseries, woodlands, potted plants, roadside trees, and farmlands.

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

[0027] 1. The present invention can achieve large-scale and efficient disposal of urban gardening and greening waste, has low product cost, and the raw materials are widely available, which has the advantage of promotion and application.

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

[0029] 3. The present invention adopts a process flow combining pre-reaction and humification reaction. Different from the traditional technology, the present invention adds an iron-based additive as a catalyst in the pre-reaction. The reaction does not need to be heated and does not need to be carried out in a reactor. The operation is simple and the effect is obvious. Moreover, due to the good effect of the pre-reaction, the subsequent humification reaction time is reduced (reduced by about 50%). Under the condition of ensuring the synthesis rate of artificial humus, the production cost is greatly reduced and the production efficiency of artificial humus is improved.

[0030] 4. The present invention introduces an oxidation pre-reaction process of a catalyst represented by zero-valent iron. Different from the traditional technology, the present invention advocates the use of granular iron materials such as iron powder (zero-valent iron). Under the action of ultrasound, iron ions are continuously generated as a catalyst to create a local micro-oxidation environment, which significantly accelerates the early pre-hydrolysis of macromolecular substances in garden waste.

[0031] 5. The present invention has the advantages of fast reaction speed (2-8h), high raw material utilization rate, high artificial humus synthesis rate (more than 30%), clean and environmentally friendly production process, etc., which is more than 40% higher than the conventional synthesis rate and saves about 50% of the reaction time. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1is the effect of different biomass precursors on the efficiency of artificial humus synthesis;

[0033] Figure 2 is the effect of different iron ion types on the efficiency of artificial humus synthesis;

[0034] Figure 3 is the effect of different zero-valent iron particles on the efficiency of artificial humus synthesis;

[0035] Figure 4 The effect of different ultrasound exposure time on the synthesis efficiency of artificial humus;

[0036] Figure 5 The effect of different hydrothermal humification reaction temperatures on the synthesis efficiency of artificial humus;

[0037] Figure 6 The effect of different hydrothermal humification reaction time on the synthesis efficiency of artificial humus;

[0038] Figure 7 The effect of different alkaline substances types and concentrations on the efficiency of artificial humus synthesis;

[0039] Figure 8 It is a comparison of the synthesis efficiency of artificial humus under different reaction conditions. DETAILED DESCRIPTION

[0040] The technical solution of the present invention is further described below by specific embodiments, which do not limit the protection scope of the present invention. Some non-essential modifications and adjustments made by others based on the concept of the present invention still fall within the protection scope of the present invention.

[0041] It should be noted that the terms "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, commodity or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, commodity or device. In the absence of further restrictions, the elements defined by the sentence "comprises a ..." do not exclude the existence of other identical elements in the process, method, commodity or device including the elements.

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

[0043] Example 1 Preparation method of artificial humus synthesized by rapid humification of different types of garden waste

[0044] S1. Pretreatment of garden waste: Immerse different biomass raw materials (wood chips, leaves and their mixture) in deionized water, with the water covering the waste by 2 cm or more, rinse 1-3 times until the solution is not turbid, dry at 80-120°C for 3-5h, then crush and pass through a 60-200 mesh sieve to obtain biomass powder.

[0045] S2. Oxidation pre-reaction: biomass powder and iron powder were mixed in a weight ratio of 50:1, and reacted in an ultrasonic cleaner for 2 hours (frequency 20 kHz, power 60 W), and the reaction temperature was 25°C.

[0046] S3. Hydrothermal humification reaction: The solution after the hydrothermal pre-reaction was mixed with sodium hydroxide in a weight ratio of 5:1 (biomass powder: sodium hydroxide), and ultrasonically mixed evenly (frequency 20 kHz, power 60 W, time 0.5 h), and then hydrothermal humification reaction was carried out in a reactor. The reaction temperature of the hydrothermal humification reaction was 200° C. and the reaction time was 2 h to obtain a humus-containing solution.

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

[0048] This application selected leaves (garden pruning branches and leaves) and sawdust (after wood processing) as two characteristic wastes of the garden industry as research objects. Figure 1 As shown, the A-HS synthesis rate of the sawdust group is 33.15%, which is 1.16 times that of the leaf group. At the same time, the residual solid rate of the sawdust group is 40.88%, which is 88% of that of the leaf group. This shows that when sawdust is used as a reaction product, it is easier to undergo hydrothermal humification reaction. In this experiment, leaves and sawdust were mixed in a ratio of 50:50 and the results showed that the A-HS synthesis rate was between the above two, which is consistent with our analysis. According to the results of this experiment, garden biomass such as sawdust and leaves have good application prospects. In actual work, they can be selected and used according to the different sources of materials. If leaves are used, attention should be paid to the influence of indicators such as leaf moisture content and bulk density on the A-HS synthesis efficiency.

[0049] Example 2: Preparation method of artificial humus synthesized by rapid humification of garden waste with different types of iron-based additives

[0050] S1. Pretreatment of garden waste: immerse the biomass raw material (a mixture of sawdust and leaves) in deionized water, with the water covering the waste by 2 cm or more, rinse 1-3 times until the solution is not turbid, dry at 80-120°C for 3-5h, then crush and pass through a 60-200 mesh sieve to obtain biomass powder.

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

[0052] S3. Hydrothermal humification reaction: The solution after the hydrothermal pre-reaction was evenly mixed with sodium hydroxide by ultrasonic method in a weight ratio of 5:1 (biomass powder: sodium hydroxide) (frequency 20 kHz, power 60 W, time 0.5 h), and then a hydrothermal humification reaction was carried out in a reactor. The reaction temperature of the hydrothermal humification reaction was 200° C. and the reaction time was 2 h to obtain a humus-containing solution.

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

[0054] In this study, iron-based additives, as catalysts for oxidation pre-reaction, are important factors affecting the synthesis of artificial humus. Therefore, this application first studied the catalytic effects of iron ions with different valence states, selected iron powder (zero-valent iron), ferrous sulfate (ferrous iron) and ferric chloride (ferric iron) as research objects, and recorded the synthesis of artificial humus, such as Figure 2 As shown in the figure, it can be seen that the synthesis rate of A-HS in the experimental group with iron substances added as catalyst is much higher than that in the control group. 3+ When Fe(III) was used as the 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 the increase of the valence of iron ions. In this study, the introduction of iron powder as a catalyst, solid zero-valent iron can continuously produce Fe 2+ , continuously attacking biomass macromolecules to generate more and smaller biomass small molecules, thereby promoting the subsequent hydrothermal replication reaction effect.

[0055] In this study, the effects of zero-valent iron with different particle sizes (iron powder, nano zero-valent iron (50nm, 100nm)) as catalysts on the synthesis of artificial humus were further studied. Figure 3 As shown in the figure, the synthesis rate of A-HS in the experimental group with zero-valent iron as a catalyst is much higher than that in the control group. When 50nm zero-valent iron is used as a catalyst, the synthesis rate of A-HS is 22.3%, which is 3.8 times that of the blank group, and when 100nm Fe0 is used as a catalyst, the synthesis rate of A-HS is 19.24%, which is 3.3 times that of the blank group. It can be seen that when nano-scale zero-valent iron is used as a catalyst, the synthesis rate of artificial humus is also significantly improved compared with the blank group, but compared with ordinary zero-valent iron (33.15%), the catalytic efficiency is still far behind.

[0056] Example 3 Preparation method of artificial humus synthesized by rapid humification of garden waste under different ultrasonic action times

[0057] S1. Pretreatment of garden waste: immerse the biomass raw materials (mixture of sawdust and leaves) in deionized water, with the water covering the waste by 2 cm or more, rinse 1-3 times until the solution is not turbid, dry at 80-120°C for 3-5h, then crush and pass through a 60-200 mesh sieve to obtain biomass powder.

[0058] S2. Pre-reaction: biomass powder and iron powder were mixed in a weight ratio of 50:1, and different sample groups were reacted in an ultrasonic cleaner for 1, 2, 3, and 4 h (frequency 20 kHz, power 60 W), and the reaction temperature was 25°C.

[0059] S3. Hydrothermal humification reaction: The solution after the hydrothermal pre-reaction was mixed with sodium hydroxide in a weight ratio of 5:1 (biomass powder: sodium hydroxide), and ultrasonically mixed evenly (frequency 20 kHz, power 60 W, time 0.5 h), and then hydrothermal humification reaction was carried out in a reactor. The reaction temperature of the hydrothermal humification reaction was 200° C. and the reaction time was 2 h to obtain a humus-containing solution.

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

[0061] In this study, ultrasound can promote the oxidation pre-reaction and is an important factor affecting the synthesis of artificial humus. Therefore, this paper studies the effects of different ultrasonic reaction times, such as Figure 4As shown. It can be seen from the figure that with the increase of reaction time, the A-HS synthesis rate continues to increase, from 28.25% at 1h to 36.65% at 4h, with a growth rate of 29.7%. However, when the ultrasonic action time is 3h, the A-HS synthesis rate is 35.22%, which is slightly different from the synthesis rate at 4h. Moreover, with the increase of ultrasonic action time, the RS residual solid rate decreases from 67.16% to 20.33%, a decrease of 69.7%. Since the residual solid can also be recycled and reused, choosing the appropriate ultrasonic reaction time to achieve a balance between the A-HS and RS residual solid rates is an important factor to be considered in the actual reaction process.

[0062] Example 4 Preparation method of artificial humus synthesized by rapid humification of garden waste at different hydrothermal humification reaction temperatures

[0063] S1. Pretreatment of garden waste: immerse the biomass raw material (a mixture of sawdust and leaves) in deionized water, with the water covering the waste by 2 cm or more, rinse 1-3 times until the solution is not turbid, dry at 80-120°C for 3-5h, then crush and pass through a 60-200 mesh sieve to obtain biomass powder.

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

[0065] S3. Hydrothermal humification reaction: The solution after the hydrothermal pre-reaction was mixed with sodium hydroxide in a weight ratio of 5:1 (biomass powder: sodium hydroxide), and ultrasonically mixed evenly (frequency 20 kHz, power 60 W, time 0.5 h), and then a hydrothermal humification reaction was carried out in a reactor. The reaction temperatures of the hydrothermal humification reaction were 160, 180, 200 and 220° C., and the reaction time was 2 h to obtain a humus-containing solution.

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

[0067] This section studies the effect of different reaction temperatures (160, 180, 200, 220°C) on the synthesis efficiency of A-HS. Figure 5As shown. When the reaction temperature is 160°C, the A-HS synthesis rate is only 19.59%, while when the reaction temperature is increased to 220°C, the A-HS synthesis rate is 35.33%, an increase of 80.3%. Therefore, increasing the reaction temperature has a greater promoting effect on the synthesis of A-HS. Further research found that when the temperature is 200°C, the A-HS synthesis rate is 33.53%, which is not much different from 220°C (35.33%), indicating that when the temperature reaches a certain value, the promoting effect on A-HS synthesis will tend to stabilize. Moreover, we found that at 200°C, the residual solid rate was 57.79%, which is twice that at 220°C (28.65%). The increase in the A-HS synthesis rate at 220°C (1.8%) is based on a solid loss rate of 29.14%. Since both A-HS and the remaining solid have corresponding uses in the later stage, this study believes that 180-220℃ is a more appropriate reaction temperature, and 200℃±10℃ is more appropriate.

[0068] Example 5 Preparation method of artificial humus synthesized by rapid humification of garden waste under different hydrothermal humification reaction times

[0069] S1. Pretreatment of garden waste: immerse the biomass raw material (a mixture of sawdust and leaves) in deionized water, with the water covering the waste by 2 cm or more, rinse 1-3 times until the solution is not turbid, dry at 80-120°C for 3-5h, then crush and pass through a 60-200 mesh sieve to obtain biomass powder.

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

[0071] S3. Hydrothermal humification reaction: The solution after the hydrothermal pre-reaction was mixed with sodium hydroxide in a weight ratio of 5:1 (biomass powder: sodium hydroxide), and ultrasonically mixed evenly (frequency 20 kHz, power 60 W, time 0.5 h), and then a hydrothermal humification reaction was carried out in a reactor. The reaction temperature of the hydrothermal humification reaction was 200° C., and the reaction times were 1, 2, 3 and 4 h, respectively, to obtain a humus-containing solution.

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

[0073] This paper studies the effect of different reaction times (1, 2, 3, 4 h) on the synthesis efficiency of A-HS. Figure 6 As shown. When the reaction time increases from 1h to 4h, the A-HS synthesis efficiency increases from 26.25% to 36.92%, with a growth rate of 40.6%; at the same time, it can be clearly seen that the residual solid rate decreases from 69.57% to 13.48%, with a decrease rate of 80.6%. It is worth noting that when heated for 1h, the total amount of A-HS and residual solids is 95.82%, while the total amount is only 50.40% when heated for 4h, which means that the loss of solid matter is high (45.42%). The longer the duration at high temperature, the more thorough the decomposition of the substance, part of the product is discharged as carbon dioxide and water, and the other part of the soluble product will enter the solution. Moreover, when heated for 2h, 3h and 4h, the synthesis rate of A-HS is 33.57%, 34.42% and 36.92% respectively, and the difference in synthesis rate is small. However, the residual solid rate is 57.79%, 28.36% and 13.48% respectively, resulting in a large loss of solids. Therefore, based on comprehensive consideration of the A-HS synthesis rate and residual solid rate, this study believes that the hydrothermal humification reaction time of 1-3h is more appropriate, and 2h±20min is more appropriate.

[0074] Example 6 Preparation method of artificial humus synthesized by rapid humification of garden waste under the action of different alkalis

[0075] S1. Pretreatment of garden waste: immerse the biomass raw material (a mixture of sawdust and leaves) in deionized water, with the water covering the waste by 2 cm or more, rinse 1-3 times until the solution is not turbid, dry at 80-120°C for 3-5h, then crush and pass through a 60-200 mesh sieve to obtain biomass powder.

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

[0077] S3. Hydrothermal humification reaction: The solution after the hydrothermal pre-reaction was mixed with different alkalis (sodium hydroxide, calcium hydroxide and sodium bicarbonate) at a weight ratio of 5:1 (biomass powder: alkali substance), and ultrasonically mixed evenly (frequency 20 kHz, power 60 W, time 0.5 h), and then hydrothermal humification reaction was carried out in a reactor. The reaction temperature of the hydrothermal humification reaction was 200 ° C, and the reaction time was 2 h to obtain a humus-containing solution.

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

[0079] In this study, alkaline substances, as catalysts for hydrothermal humification reactions, are important factors affecting the synthesis of artificial humus. Therefore, this application first studied the catalytic effects of different alkaline substances, selected sodium hydroxide, calcium hydroxide and sodium bicarbonate as research objects, and recorded the synthesis of artificial humus, such as Figure 7 As shown (left figure). It can be seen from the figure that when sodium hydroxide, calcium hydroxide and sodium bicarbonate are used as alkaline substances, the A-HS synthesis rates are 33.5%, 31.5% and 30.4% respectively, and the synthesis effect of A-HS is better. The alkaline substances selected in this application provide a strong alkaline environment and achieve a better A-HS synthesis effect.

[0080] In this study, the effects of different concentrations of sodium hydroxide as a catalyst (the weight ratio of biomass powder to sodium hydroxide was 3:1, 5:1, 10:1, and 15:1, respectively) on the synthesis of artificial humus were further studied. Figure 7 As shown (right figure). When the ratio of biomass powder: alkali substances is reduced from 15:1 to 3:1, it means that the concentration of alkali substances continues to increase, and the synthesis rate of A-HS also increases from 26.3% to 36.19%, with a growth rate of 37.6%. This shows that increasing the concentration of alkali substances can effectively improve the synthesis efficiency of A-HS. Of course, it can be seen from the figure that when the ratio of biomass powder: alkali substances is 5:1 and 3:1, the synthesis rates of A-HS are 35.5% and 36.19% respectively, and the difference is very small. This shows that there is a better range of values ​​for alkali substances according to the quality of different biomass powders.

[0081] Comparative Example 1 Preparation method of artificial humus synthesized by rapid humification of garden waste without oxidation pre-reaction step

[0082] S1. Pretreatment of garden waste: immerse the biomass raw material (a mixture of sawdust and leaves) in deionized water, with the water covering the waste by 2 cm or more, rinse 1-3 times until the solution is not turbid, dry at 80-120°C for 3-5h, then crush and pass through a 60-200 mesh sieve to obtain biomass powder.

[0083] S2. Hydrothermal humification reaction: The solution after the hydrothermal pre-reaction was mixed with sodium hydroxide in a weight ratio of 5:1 (biomass powder: sodium hydroxide), and ultrasonically mixed (frequency 20 kHz, power 60 W, time 0.5 h), and then hydrothermal humification reaction was carried out in a reactor. The reaction temperature of the hydrothermal humification reaction was 200° C. and the reaction time was 2 h to obtain a humus-containing solution.

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

[0085] Comparative Example 2 Preparation method of artificial humus synthesized by rapid humification of garden waste without adding ultrasonic action

[0086] S1. Pretreatment of garden waste: immerse the biomass raw material (a mixture of sawdust and leaves) in deionized water, with the water covering the waste by 2 cm or more, rinse 1-3 times until the solution is not turbid, dry at 80-120°C for 3-5h, then crush and pass through a 60-200 mesh sieve to obtain biomass powder.

[0087] S2. Pre-reaction: biomass powder and iron powder were mixed in a weight ratio of 50:1 and allowed to stand for 2 hours at a reaction temperature of 25°C.

[0088] S3. Hydrothermal humification reaction: The solution after the hydrothermal pre-reaction is mixed with sodium hydroxide in 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° C. and the reaction time is 2 h to obtain a humus-containing solution.

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

[0090] Example 7 Preparation method of artificial humus synthesized by rapid humification of garden waste

[0091] S1. Pretreatment of garden waste: immerse the biomass raw material (a mixture of sawdust and leaves) in deionized water, with the water covering the waste by 2 cm or more, rinse 1-3 times until the solution is not turbid, dry at 80-120°C for 3-5h, then crush and pass through a 60-200 mesh sieve to obtain biomass powder.

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

[0093] S3. Hydrothermal humification reaction: The solution after the hydrothermal pre-reaction was mixed with sodium hydroxide in a weight ratio of 5:1 (biomass powder: sodium hydroxide), and ultrasonically mixed evenly (frequency 20 kHz, power 60 W, time 0.5 h), and then hydrothermal humification reaction was carried out in a reactor. The reaction temperature of the hydrothermal humification reaction was 200° C. and the reaction time was 2 h to obtain a humus-containing solution.

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

[0095] The yields of artificial humic acid after the hydrothermal humification reactions in Comparative Example 1, Comparative Example 2 and Example 7 are as follows: Figure 8 Shown

[0096] This paper selects two comparative examples and one embodiment for comparison. The experimental results are as follows: Figure 8 As shown. The A-HS synthesis rate in Example 7 is 33.5%, while the A-HS synthesis rate in Comparative Example 1 is only 20.25%, which is 60.4% of that in Example 7. The difference between the two groups of experiments is that Comparative Example 1 did not perform a pre-reaction, but directly performed a hydrothermal humification reaction. The experimental results show that the pre-reaction process proposed in this study has a greater effect on the synthesis of A-HS. The A-HS synthesis rate in Comparative Example 2 is 23.19%, which is 14.5% higher than that in Comparative Example 1. The difference between the two groups of experiments is that Comparative Example 2 adds a pre-reaction (without ultrasonic action), which shows that the pre-reaction is necessary. The A-HS in Comparative Example 2 is only 55.6% of that in Example 7, which shows that ultrasonic action plays an important role in the pre-reaction process.

[0097] The elemental compositions of artificial humic acid prepared by different hydrothermal humification reactions in Comparative Example 1, Comparative Example 2 and Example 7 are shown in Table 1;

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

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[0101] As can be seen from Table 1, after the hydrothermal humification reaction, the carbon mass fraction in the three groups of experiments increased from 57.33% to 59.71% and 63.23% respectively, and the oxygen mass fraction decreased from 33.57% to 31.83% and 28.65%, indicating that the hydrothermal humification process is a polycarbon process, and the degree of hydrothermal humification reaction in Example 7 is higher. The H / C, O / C and C / N ratios of humic acid are generally regarded as important indicators of maturity and directional condensation. Therefore, this study calculated the values ​​of the three indicators under different reaction conditions, as shown in Table 1. The change in the H / C ratio can reflect the dehydration reaction occurring during the hydrothermal treatment. Among the three groups of experiments, the H / C value in Example 7 is the largest, and the O / C value is the smallest, which shows that the aromaticity of Example 7 is much higher than that of Comparative Examples 1 and 2, and the hydrothermal pretreatment greatly accelerates the hydrothermal humification process. The O / C value is also regarded as an indicator of the contribution of carbohydrates and carboxylic acids to the formation of humus. Obviously, 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 usually regarded as an indicator of the origin of humus, reflecting the original proportion of plant-derived substances. The C / N ratios of A-HS obtained in the three groups of experiments were all around 60%, indicating that the humus sources of A-HA obtained in the three groups of experiments were more terrestrial vascular plants.

Claims

1. A method for preparing artificial humus by rapid humification of garden waste, characterized in that: The following steps are involved: S1. Pretreatment of garden waste: crushing and sieving the garden waste to obtain biomass powder; S2, oxidation pre-reaction: after mixing the biomass powder and the iron-based additive, an oxidation pre-reaction is carried out under ultrasound; S3, hydrothermal humification reaction: after the solution after the oxidation pre-reaction is uniformly mixed with the alkali ultrasonic, a hydrothermal humification reaction is carried out in a reactor to obtain a humus-containing solution; S4, recovering humus: performing solid-liquid separation on the humus-containing solution after the hydrothermal humification reaction, and recovering solid and liquid humus respectively; In step S2, the iron-based additive is selected from iron powder; In step S2, the frequency of the ultrasound is 20-40 kHz, and the power is 30-120 W.

2. The method for preparing artificial humus by rapid humification of garden waste 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 for preparing artificial humus by rapid humification of garden waste according to claim 1, characterized in that: In step S2, the oxidation pre-reaction time is 1-4 h.

4. The method for preparing artificial humus by rapid humification of garden waste 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.

5. The method for preparing artificial humus by rapid humification of garden waste 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.

6. The method for preparing artificial humus by rapid humification of garden waste according to claim 1, characterized in that: In step S3, the ultrasonic mixing time is 0.5-1 h, the frequency is 20-40 kHz, and the power is 30-120 W.

7. The method for preparing artificial humus by rapid humification of garden waste according to claim 1, characterized in that: In step S3, the reaction temperature of the hydrothermal humification reaction is 160-250° C., and the reaction time is 1-4 h.

8. The method for preparing artificial humus by rapid humification of garden waste according to claim 1, characterized in that: In step S4, the solid humus obtained by the solid-liquid separation is dried and recovered; the liquid humus obtained by separation can be directly used as liquid fertilizer, or solid humus can be obtained by acidification, filtration and drying.

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