Humic organic fertilizer prepared by mixing waste biomass through ionic liquid pretreatment and preparation method of humic organic fertilizer

Abstract

The invention provides a method for preparing a humified organic fertilizer by pretreating mixed waste biomass with ionic liquid, and belongs to the technical field of solid waste recycling. Comprising the following steps: pre-treating residual sludge of a sewage treatment plant and agricultural straw waste biomass, adding ionic liquid, standing for pre-treatment, adding a catalyst, transferring to a hydrothermal reaction kettle, carrying out closed hydrothermal reaction, carrying out solid-liquid separation and the like. According to the humified organic fertilizer, the sludge and the agricultural straw are pretreated before hydrothermal treatment, hydrolysis of protein, cellulose and lignin can be accelerated, conversion of humus is promoted, and favorable conditions are provided for improving the fertilizer efficiency of a hydrothermal product.

Description

Technical Field

[0001] The invention relates to a humified organic fertilizer prepared by pretreating mixed waste biomass with ionic liquid and a preparation method thereof, belonging to the technical field of solid waste resource utilization. Background Art

[0002] Resource processing of the large amount of waste biomass produced each year has become an important issue of global concern. At present, most of the waste biomass is incinerated, landfilled or left to rot in the field, causing carbon emissions and environmental pollution. In fact, waste biomass contains a large amount of cellulose, hemicellulose, lignin, protein, lipids and various nutrients such as nitrogen and phosphorus, and is a valuable resource. Therefore, it has become a development trend to use different technologies (such as pyrolysis, hydrothermal carbonization, anaerobic digestion, gasification) to increase the value of waste biomass and convert it into other useful products for soil fertilization, environmental pollution control and energy production.

[0003] Humus is a complex organic mixture, accounting for more than 80% of soil organic matter, which can improve soil water holding capacity and soil fertility. A number of technologies have successfully converted waste biomass into humified organic fertilizers. Composting uses microbial reactions to convert biomass into humus, which has the advantages of environmental protection and low cost, but it is time-consuming, usually taking several months, and is prone to nitrogen loss. Chemical oxidation can oxidize biomass to synthesize humus within a few hours by adding reagents such as oxidants and catalysts. It is fast and has a high yield, but the introduction of chemicals leads to high costs and may cause secondary pollution. Hydrothermal reaction is a thermochemical reaction that uses water or other solutions as a medium under sealed, high pressure and mild temperature (150-300°C) conditions. The reaction time is relatively short (2-10 hours). It is similar to the natural formation process of biomass humus and is an artificially enhanced humification reaction. In order to increase the humification degree of hydrothermal reaction, pretreatment can be used to destroy the complex and stubborn structure of lignocellulose. At present, the pretreatment of lignocellulose mainly includes physical and chemical methods. Physical methods have limited destructive effects and require high energy consumption; chemical methods require the addition of additional chemical reagents such as acids, alkalis and oxidants, require corrosion-resistant equipment, and increase the cost of waste liquid treatment. Ionic solutions are organic salts composed of organic cations and organic or inorganic anions, which can form strong hydrogen bonds with cellulose to dissolve these biomacromolecules. Compared with other pretreatments, ionic liquid pretreatment is less toxic to humans and the environment and requires less energy.

[0004] Therefore, there is an urgent need in the art for a method for preparing humified organic fertilizer by pretreating mixed waste biomass with ionic liquid. Summary of the invention

[0005] The purpose of the present invention is to prepare organic fertilizer from excess sludge and agricultural waste biomass by catalytic hydrothermal method and utilize it as a resource, and to increase the humus content of carbon-based organic fertilizer by pretreating excess sludge and agricultural waste biomass with ionic liquid, so as to improve the soil quality of nutrient-poor soil.

[0006] To achieve the purpose, the technical solution adopted by the present invention is to provide a method for preparing humified organic fertilizer by pretreating mixed waste biomass with ionic liquid.

[0007] In a first aspect of the present invention, there is provided a method for preparing humified organic fertilizer by pretreating mixed waste biomass with ionic liquid, comprising the following steps:

[0008] Step 1: Take the waste sludge from the sewage treatment plant and the agricultural straw waste biomass and pre-treat them respectively;

[0009] Step 2: Mix the residual sludge and agricultural straw after pretreatment, add ionic liquid, and let stand for pretreatment;

[0010] Step 3: adding a catalyst to the pretreated mixed waste biomass and transferring it to a hydrothermal reactor for a closed hydrothermal reaction;

[0011] Step 4: Separate the hydrothermal product into solid and liquid, and the solid product is humified organic fertilizer;

[0012] Step 5: Apply the prepared humified organic fertilizer to the soil to improve the soil physical and chemical properties and crop growth performance.

[0013] Preferably, in step 1, the residual sludge mainly includes residual sludge from urban sewage treatment plants and domestic sewage treatment plants, and the agricultural straw includes straw waste biomass rich in lignin and cellulose, such as wheat, rice, and corn.

[0014] Preferably, in step 1, the residual sludge pretreatment comprises the following steps: the residual sludge is concentrated by gravity concentration or flotation concentration, the residual sludge concentration after concentration is 10-30 g / L, and the supernatant is collected for later use; the pretreatment of agricultural straw refers to crushing the biomass into fine fragments with a diameter of 0.1-5 cm by a crusher or the like.

[0015] Preferably, in step 2, the mass ratio of the residual sludge to the agricultural straw is 1:3-5:1, and after the materials are mixed according to the mass ratio, the supernatant produced in the pretreatment process in step 1 is added to make the solid content of the mixture 5-35%.

[0016] Preferably, in step 2, the ionic liquid is a cationic imidazolium ionic liquid, and the dosage is 0.2-2% of the volume of the mixture. After the ionic liquid and the waste biomass are uniformly mixed, they are allowed to stand for 0.5-5 hours at 15-75° C. for pretreatment.

[0017] Preferably, in step 3, the catalyst is an iron salt or manganese salt metal catalyst, and the dosage is 1-50 mg metal / g (dry mixture).

[0018] Preferably, in step 3, the hydrothermal reactor is a closed reactor that is temperature-resistant, pressure-resistant and corrosion-resistant, and is provided with an anti-corrosion lining inside.

[0019] Preferably, in step 3, the hydrothermal reaction conditions refer to that the volume of the mixed liquid accounts for 30-55% of the volume of the reactor, the hydrothermal reaction temperature is 180°C-260°C, the hydrothermal reaction time is 1h-10h, and after the hydrothermal reaction is completed, the internal container is cooled to room temperature.

[0020] Preferably, in step 4, the hydrothermal solid and liquid products are separated by centrifugation or filtration, the liquid phase product is treated as waste liquid, and the solid phase product is washed with tap water and dried to a moisture content of ≤30%. The solid phase product is the humified organic fertilizer.

[0021] The second aspect of the present invention provides a humified organic fertilizer prepared by the above method.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] (1) Sewage sludge and agricultural straw are waste biomass, which are cheap and readily available, have low operating costs, and are easy to promote and apply.

[0024] (2) Pretreatment of sludge and agricultural straw before hydrothermal treatment can accelerate the hydrolysis of protein, cellulose and lignin, promote the transformation of humus, and provide favorable conditions for improving the fertilizer efficiency of hydrothermal products.

[0025] (3) Compared with pretreatment methods such as acid solution and alkaline solution, ionic liquid has the advantages of less harm to the environment and a clean and environmentally friendly production process. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 A schematic diagram of a process for preparing humified organic fertilizer by pretreating mixed waste biomass with ionic liquid;

[0027] Figure 2 Photo of humified organic fertilizer;

[0028] Figure 3 Comparative photos of the growth of lettuce plants grown in red soil with 5% humified organic fertilizer and original red soil within 20 days;

[0029] Figure 4 To study the effect of adding 5% humified organic fertilizer on the total carbon, total phosphorus and total potassium content of red soil;

[0030] Figure 5This study investigates the effect of adding 5% humified organic fertilizer on the dissolved organic matter content in red soil.

[0031] Figure 6 This paper studies the effects of ionic liquid pretreatment and untreatment on the organic matter, humic acid, fulvic acid and nutrient content of humified organic fertilizer prepared from different raw materials.

[0032] Figure 7 The changes in organic matter, humic acid, fulvic acid and nutrient content of humified organic fertilizers prepared under different pretreatment conditions. DETAILED DESCRIPTION

[0033] In order to make the present invention more clearly understood, a preferred embodiment is described in detail with reference to the accompanying drawings as follows:

[0034] like Figure 1-7 As shown, the present invention provides a method for preparing humified organic fertilizer by pretreating mixed waste biomass with ionic liquid.

[0035] Example 1

[0036] A process schematic diagram of a method for preparing humified organic fertilizer by pretreating mixed waste biomass with ionic liquid comprises the following steps:

[0037] like Figure 1 As shown, the excess sludge taken from the sewage treatment plant is gravity concentrated to make the concentrated sludge concentration 20g / L, and the rice straw is mechanically crushed into fine pieces with a diameter of about 2cm. The excess sludge and rice straw after pretreatment are mixed at a mass ratio of 1:1, and the supernatant produced in the sludge concentration process is added to make the solid content of the mixture 20%. 1% of cationic imidazole ionic liquid is added and allowed to stand at room temperature for 2h. MnCl2 catalyst is added to the pretreated mixed waste biomass at an amount of 20mg Mn / g (dry mixture), and it is transferred to a hydrothermal reactor for a closed hydrothermal reaction at a reaction temperature of 220℃ and a reaction time of 4h. After the reaction is completed, it is naturally cooled to room temperature, the hydrothermal mixture is centrifuged, and the solid phase product obtained is dried to a moisture content of less than 30%, and a humified organic fertilizer can be obtained.

[0038] Example 2

[0039] A method for preparing humified organic fertilizer by pretreating mixed waste biomass with ionic liquid comprises the following steps:

[0040] The residual sludge taken from the sewage treatment plant is concentrated by gravity to make the sludge concentration after concentration to be 30g / L, and the rice straw is mechanically crushed into fine pieces with a diameter of about 2cm. The residual sludge and rice straw after pretreatment are mixed in a mass ratio of 1:1, and the supernatant produced in the sludge concentration process is added to make the solid content of the mixture 25%. 1% of the volume of the mixture is added with 1-ethyl-trimethylimidazolium chloride ionic liquid to make the ionic liquid and the waste biomass evenly mixed, and the mixture is allowed to stand for 1h at 25°C for pretreatment. FeCl3 catalyst is added to the pretreated mixed waste biomass in an amount of 30mgFe / g (dry mixture), and it is transferred to a hydrothermal reactor for a closed hydrothermal reaction at a reaction temperature of 220°C and a reaction time of 4h. After the reaction is completed, it is naturally cooled to room temperature, the hydrothermal mixture is centrifuged, and the solid phase product obtained is dried to a moisture content of less than 30%, and a humified organic fertilizer can be obtained, such as Figure 2 The organic matter content, humic acid content, fulvic acid content and total nutrient element content of the prepared humified organic fertilizer are shown in Table 1.

[0041] Table 1 Fertilizer efficiency index of humified organic fertilizer prepared by ionic liquid pretreatment of mixed waste biomass

[0042]

[0043] Example 3

[0044] A method for preparing humified organic fertilizer by pretreating mixed waste biomass with ionic liquid to improve soil physical and chemical properties and crop growth performance comprises the following steps:

[0045] The excess sludge taken from the sewage treatment plant is concentrated by gravity to make the concentration of the concentrated sludge 20g / L, and the rice straw is mechanically crushed into fine pieces with a diameter of about 2cm. The excess sludge and rice straw after pretreatment are mixed at a mass ratio of 1.5:1, and the supernatant produced in the sludge concentration process is added to make the solid content of the mixture 30%. 1% of the volume of the mixture is added with 1-ethyl-trimethylimidazolium chloride ion liquid, so that the ion liquid and the waste biomass are evenly mixed, and the mixture is left to stand for 2h at 25℃ for pretreatment. FeCl3 catalyst is added to the pretreated mixed waste biomass, and the addition amount is 50mg Fe / g (dry mixture), and it is transferred to a hydrothermal reactor for closed hydrothermal reaction, and the reaction temperature is 220℃ and the reaction time is 6h. After the reaction is completed, it is naturally cooled to room temperature, the hydrothermal mixture is centrifuged, and the obtained solid phase product is dried to a moisture content of less than 30%, and humified organic fertilizer can be obtained. The prepared humified organic fertilizer was applied to the red soil at an amount of 5% of the mass of the red soil, stirred until well mixed, and tap water was added to keep the soil moisture content at 70% of the field water holding capacity. The soil was cultivated under natural conditions for 7 days to activate the microorganisms in the soil, and then the same number of lettuce seeds of the same size were planted to observe the germination of the seeds and their growth within 20 days. Figure 3 After 20 days of cultivation, the carbon, nitrogen and phosphorus contents of the red soil were tested. Figure 4 As shown in the figure, adding humic acid organic fertilizer can significantly improve the fertility of the soil. The soil was leached and the leached liquid was measured by three-dimensional fluorescence spectrum. Figure 5 shown. Figure 5 In the graph, region I is a tyrosine-like fluorescent component, region II is a tryptophan-like fluorescent component, region III is a fulvic acid-like fluorescent component, region IV is a soluble microbial metabolite-like fluorescent component, and region V is a humic acid-like fluorescent component, indicating that the content of humus-like substances in the soil increases after the addition of humified organic fertilizer.

[0046] Application Example 1

[0047] The residual sludge from the sewage treatment plant was concentrated by gravity to a concentration of 20 g / L. At the same time, the rice straw was mechanically crushed into fine pieces with a diameter of about 2 cm. Straw, residual sludge and a mixture of straw and residual sludge with a mass ratio of 1:1 were used as raw materials, and the supernatant produced during the sludge concentration process was added to make the solid content of the mixture 20%. One group was added with 2% cationic imidazole ionic liquid and left to stand at 25°C for 1 hour for pretreatment, while the other group was not pretreated.

[0048] The two groups of mixed waste biomass were transferred to a hydrothermal reactor, and FeCl3 catalyst (dosage was 20 mgFe / g (dry mixture)) was added to conduct a closed hydrothermal reaction at a reaction temperature of 240°C for 6 hours. After the reaction was completed, it was naturally cooled to room temperature, the hydrothermal mixture was centrifuged, the solid phase product was washed with deionized water, and dried in an oven at 105°C for 2 hours to obtain humified organic fertilizers with different raw materials.

[0049] from Figure 6 It can be seen that IL pretreatment has a general effect on improving the humic acid content of straw hydrothermal carbon, has no effect on improving the humic acid content of sludge hydrothermal carbon, and has a significant effect on improving the humic acid content of straw / sludge hydrothermal carbon.

[0050] Application Example 2

[0051] The residual sludge from the sewage treatment plant was concentrated by gravity to make the concentrated sludge concentration 30g / L, and the rice straw was mechanically crushed into fine pieces with a diameter of about 2cm. The residual sludge and rice straw after pretreatment were mixed in a mass ratio of 1:1, and a total of five groups of experiments were set up. The supernatant produced in the sludge concentration process was used to adjust the solid content of the hydrothermal mixture to 25%. One group added 1% of the volume of the mixture with 1-ethyl-trimethylimidazolium chloride ion liquid, and the other group added 30% of the volume of the mixture with Fenton's reagent (Fe2+=4g / L, H2O2(30%)=40ml / L). The two groups of experiments were pretreated at 25℃ for 1h. The third group of experiments used physical methods-ultrasound for pretreatment at 25℃ for 1h, and the fourth group of experiments did not perform pretreatment. The 1% volume of the mixture with 1-ethyl-trimethylimidazolium chloride ion liquid was hydrothermally heated with the raw materials, and the control group did not perform any treatment. Transfer each group of mixed waste biomass to a hydrothermal reactor, add FeCl3 catalyst (dosage is 30 mgFe / g (dry mixture)), and conduct a closed hydrothermal reaction at a reaction temperature of 220°C and a reaction time of 4h. After the reaction is completed, cool naturally to room temperature, centrifuge the hydrothermal mixture, wash the solid phase product with deionized water, and dry it in an oven at 105°C for 2h to obtain humified organic fertilizer. The organic matter content, humic acid content, fulvic acid content and total nutrient element content of the prepared humified organic fertilizer are shown in the figure below. Ionic liquid pretreatment is better than physical pretreatment and common chemical pretreatment in improving the content of hydrothermal carbon humic acid, and simple ionic liquid and raw material co-hydrothermal cannot achieve the same effect.

[0052] The humified organic fertilizer prepared by ionic liquid pretreatment meets the requirements of qualified organic fertilizer, bio-organic fertilizer and humic acid bio-organic fertilizer, which greatly improves the value of straw / residual sludge hydrothermal humified organic fertilizer.

[0053] Table 1 Fertilizer indicators and compliance rate of humified organic fertilizer prepared by ionic liquid pretreatment

[0054]

[0055] The above is only a preferred embodiment of the present invention, and is not any formal or substantial limitation of the present invention. It should be pointed out that ordinary technicians in this technical field can make several improvements and supplements without departing from the present invention, and these improvements and supplements should also be regarded as the protection scope of the present invention. Any technician familiar with this profession, without departing from the spirit and scope of the present invention, can make some changes, modifications and equivalent changes made by using the technical content disclosed above, which are equivalent embodiments of the present invention; at the same time, any changes, modifications and evolutions of any equivalent changes made to the above embodiments based on the essential technology of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. A method for preparing humified organic fertilizer by pretreating mixed waste biomass with ionic liquid, characterized in that: The following steps are involved: Step 1: Take the waste sludge from the sewage treatment plant and the agricultural straw waste biomass and pre-treat them respectively; Step 2: Mix the residual sludge and agricultural straw after pretreatment, add ionic liquid, and let stand for pretreatment; Step 3: adding a catalyst to the pretreated mixed waste biomass and transferring it to a hydrothermal reactor for a closed hydrothermal reaction; Step 4: Separate the hydrothermal product into solid and liquid, and the solid product is humified organic fertilizer; Step 5: Apply the prepared humified organic fertilizer to the soil to improve the soil physical and chemical properties and crop growth performance.

2. The method for preparing humified organic fertilizer by pretreating mixed waste biomass with ionic liquid according to claim 1, characterized in that: In step 1, the residual sludge includes residual sludge from urban sewage treatment plants and domestic sewage treatment plants, and the agricultural straw includes straw waste biomass containing lignin and cellulose.

3. The method for preparing humified organic fertilizer by pretreating mixed waste biomass with ionic liquid according to claim 1, characterized in that: In step 1, the residual sludge pretreatment includes: concentrating the residual sludge by gravity concentration or flotation concentration, the residual sludge concentration after concentration is 10-30g / L, and collecting the supernatant for later use; the pretreatment of agricultural straw refers to crushing the biomass into fine fragments with a diameter of 0.1-5cm by a crusher or other method.

4. The method for preparing humified organic fertilizer by pretreating mixed waste biomass with ionic liquid according to claim 1, characterized in that: In the step 2, the mass ratio of the residual sludge to the agricultural straw is 1:3-5:

1. After the materials are mixed according to the mass ratio, the supernatant produced in the pretreatment process in step 1 is added to make the solid content of the mixture 5-35%.

5. The method for preparing humified organic fertilizer by pretreating mixed waste biomass with ionic liquid according to claim 1, characterized in that: In step 2, the ionic liquid is a cationic imidazole ionic liquid, and the dosage is 0.2-2% of the volume of the mixture. After the ionic liquid and the waste biomass are uniformly mixed, they are allowed to stand for 0.5-5 hours at 15-75° C. for pretreatment.

6. The method for preparing humified organic fertilizer by pretreating mixed waste biomass with ionic liquid according to claim 1, characterized in that: In step 3, the catalyst is an iron salt or manganese salt metal catalyst, and the dosage is 1-50 mg metal / g (dry mixture). The hydrothermal reactor is a closed reactor that is temperature-resistant, pressure-resistant and corrosion-resistant, and is provided with an anti-corrosion lining inside.

7. The method for preparing humified organic fertilizer by pretreating mixed waste biomass with ionic liquid according to claim 1, characterized in that: In step 3, the hydrothermal reaction conditions refer to that the volume of the mixed liquid accounts for 30-55% of the volume of the reactor, the hydrothermal reaction temperature is 180°C-260°C, the hydrothermal reaction time is 1h-10h, and after the hydrothermal reaction is completed, the internal container is cooled to room temperature.

8. The method for preparing humified organic fertilizer by pretreating mixed waste biomass with ionic liquid according to claim 1, characterized in that: In step 4, the hydrothermal solid and liquid products are separated by centrifugation or filtration, the liquid phase product is treated as waste liquid, and the solid phase product is washed with tap water and dried to a moisture content of ≤30%. The solid phase product is the humified organic fertilizer.

9. A humified organic fertilizer prepared by the method according to any one of claims 1 to 8.

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