Preparation method of modified additive suitable for low-temperature composting

Abstract

The invention discloses a preparation method of a modified additive suitable for low-temperature composting, and belongs to the technical field of waste recycling, and the preparation method comprises the following steps: (1) pretreatment of natural montmorillonite: crushing natural montmorillonite, screening, and adding screened montmorillonite fine powder into a sulfuric acid solution; filtering and separating out unreacted solid impurities, and washing the filtered montmorillonite with deionized water until the pH value of the washing liquid is close to neutral; drying the washed montmorillonite, and further grinding; and (2) montmorillonite modification: dissolving chitosan in glacial acetic acid, dissolving montmorillonite in water, adding the solution into a chitosan acetic acid solution, adjusting the pH value of the solution to 9-11, stirring and aging, and carrying out suction filtration, washing, drying and grinding to obtain the product. According to the preparation method of the modified additive, the natural montmorillonite is modified to improve the physicochemical properties and functionality of the montmorillonite, the modified additive with good compatibility and smooth surface is prepared, and the composting effect can be greatly enhanced.

Description

Technical Field

[0001] The invention relates to the technical field of waste resource utilization, and in particular to a method for preparing a modified additive suitable for low-temperature composting. Background Art

[0002] For organic solid wastes such as kitchen waste and livestock manure, if these wastes are not effectively treated, they will not only occupy a large amount of landfill space, but may also cause land, water and air pollution, thereby threatening human health and the ecological environment. Composting, as an eco-friendly and sustainable waste treatment method, can convert waste into organic fertilizer through the degradation of microorganisms, effectively reducing the volume of waste and realizing resource recovery. However, temperature changes during the composting process significantly affect the activity of microbial communities and composting efficiency. Especially in the cold and arid areas of the northwest, the low temperature climate inhibits the activity of common spoilage bacteria, resulting in low composting efficiency. At the same time, the emission of odor and greenhouse gases in low temperature environments is particularly prominent.

[0003] Based on this, in the actual composting process, the application of additives is a simple and effective method to promote the humification of compost. Montmorillonite is a common additive. Montmorillonite is a layered mineral composed of hydrated aluminum silicate, which has good adsorption performance and high water absorption and expansion capacity. Montmorillonite has the characteristics of multilayer and high specific surface area. Adding it to the compost as an additive can gather lignin and cellulose in the compost pile to the surface of montmorillonite, which is conducive to its utilization and decomposition by microorganisms.

[0004] Natural montmorillonite has many impurities on its surface, and its overall strength and toughness are poor. In addition, during composting in cold and arid areas, the interlayer cationic hydration may cause the montmorillonite to expand or even partially peel off, resulting in a poor enhanced composting effect. Summary of the invention

[0005] In order to solve the above-mentioned deficiencies in the prior art, the purpose of the present invention is to provide a method for preparing a modified additive suitable for low-temperature composting, to modify natural montmorillonite to improve the physical and chemical properties and functionality of montmorillonite, and to prepare a modified additive with good compatibility and smooth surface, which can greatly enhance the composting effect.

[0006] The technical solution adopted by the present invention to solve the technical problem is:

[0007] A method for preparing a modified additive suitable for low-temperature composting is provided, comprising the following steps:

[0008] (1) Pretreatment of natural montmorillonite: crush the natural montmorillonite and then screen it, slowly add the screened montmorillonite fine powder into the sulfuric acid solution, stir while adding, and stir for 40-60 minutes at room temperature; filter and separate the unreacted solid impurities, and rinse the filtered montmorillonite with deionized water until the pH value of the washing liquid is close to neutral; dry the rinsed montmorillonite at 55-65° C. to ensure that the water is completely evaporated; and further grind the dried montmorillonite;

[0009] (2) Montmorillonite modification: Chitosan was dissolved in glacial acetic acid and stirred for 20-40 min. Montmorillonite was dissolved in water and stirred evenly. Then the mixture was slowly added to the chitosan acetic acid solution. After stirring for 40-60 min, the pH value of the solution was adjusted to between 9 and 11. The solution was stirred and aged continuously. Finally, the product was obtained by filtration, washing, drying and grinding.

[0010] Furthermore, in step (1), the montmorillonite is first crushed to a size of 80 mesh or more, and then crushed to a size of 100 mesh after drying.

[0011] Furthermore, in step (1), the concentration of the sulfuric acid solution is 1 mol / L.

[0012] Furthermore, in step (1), the mass ratio of montmorillonite to sulfuric acid solution is 1:10.

[0013] Furthermore, in step (2), the concentration of glacial acetic acid is 2%.

[0014] Furthermore, in step (2), the mass ratio of chitosan to montmorillonite is 1:18-22.

[0015] Furthermore, in step (2), the ratio of chitosan to glacial acetic acid added is 1 g / 100 ml.

[0016] Furthermore, the addition ratio of montmorillonite to water is 1 g / 2-3 ml.

[0017] Furthermore, the modified montmorillonite was added to the mixed solid garbage and corn stalks in an amount of 7.5% of the mass of the pile, and composting was carried out in a reactor.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] The preparation method of the modified additive exemplified by the present invention is to add chitosan to montmorillonite to modify the additive. Chitosan is a renewable resource with good biocompatibility, which can promote the growth of microorganisms, thereby accelerating the decomposition of organic matter in the composting process and improving the composting efficiency. The hydrophilicity of chitosan and the hygroscopicity of montmorillonite are combined to improve the moisture retention capacity of the compost. The modified montmorillonite of the present invention is used as a compost additive to achieve an ideal composting effect under the cold and drought conditions in the northwest. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Other features, objects and advantages of the present application will become more apparent by reading the detailed description of non-limiting embodiments made with reference to the following drawings:

[0021] Figure 1 The change of carbon-nitrogen ratio of the pile;

[0022] Figure 2 is the change of moisture content of the pile;

[0023] Figure 3 The change of pH value of the pile;

[0024] Figure 4 The change of germination rate of seeds in pile;

[0025] Figure 5 This is the change of humus in the pile. DETAILED DESCRIPTION

[0026] The present application is further described in detail below in conjunction with the accompanying drawings and embodiments. It is to be understood that the specific embodiments described herein are only used to explain the relevant invention, rather than to limit the invention. It is also necessary to explain that, for ease of description, only the parts related to the invention are shown in the accompanying drawings.

[0027] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present application will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0028] This embodiment provides a method for preparing a modified additive suitable for low-temperature composting, and the specific method is:

[0029] (1) Pretreatment of natural montmorillonite: Grind the natural montmorillonite ore with a mortar and pestle to form small particles, use a screen to screen the crushed ore, remove large particles of impurities, and retain fine powder below 80 mesh; slowly add the screened montmorillonite fine powder into 1 mol / L sulfuric acid solution while stirring, the mass ratio of montmorillonite to sulfuric acid solution is 1:10, and stir the mixture at room temperature for 1 hour; filter and separate the unreacted solid impurities, and rinse the filtered montmorillonite with deionized water for several times until the pH value of the washing solution is close to neutral; dry the washed montmorillonite at 60°C overnight for at least 6 hours to ensure that the water is completely evaporated; then grind the washed montmorillonite into a finer powder with a mortar, with a target particle size of about 100 mesh;

[0030] (2) Modification of montmorillonite: Dissolve 2 g of chitosan in 200 ml of 2% glacial acetic acid and stir for 30 min. Dissolve 40 g of montmorillonite in 100 ml of water and stir evenly. Then slowly add the mixture to the chitosan acetic acid solution. After stirring for 1 h, add 1 mol / L NaOH solution to adjust the pH to between 9 and 11. Continue stirring and aging. Finally, filter, wash, dry and grind to obtain the product.

[0031] The modified montmorillonite is added to the mixed solid garbage and corn stalks, and the additive addition amount is 7.5% of the mass of the compost. The composting is carried out in a simple reactor. The solid garbage and corn stalks are mixed so that the moisture content of the mixture is 55-65%, the carbon-nitrogen ratio is 20-30, the aeration volume is set to 0.5L / min, and 15kg of compost is produced in each reactor.

[0032] The pile with additives added in an amount of 7.5% of the pile mass was compared with the blank group for analysis, and the changes in the carbon-nitrogen ratio of the pile, the changes in the moisture content of the pile, the changes in the pH value of the pile, the changes in the germination rate of seeds in the pile, and the changes in the humus in the pile were compared and analyzed. The results are shown in the figure.

[0033] like Figure 1 As shown in the figure, the carbon-nitrogen ratio of the pile body changes. As can be seen from the figure, the carbon-nitrogen ratio of the pile body with additives is lower than that of the blank group, indicating that the nitrogen content of the pile body increases after the addition of additives. Figure 2 As shown in the figure, the moisture content of the pile body changes. It can be seen from the figure that the moisture content of the pile body with additives is significantly lower than that of the blank group. Figure 3 As shown in the figure, the pH value of the pile body changes. It can be seen from the figure that in the 2nd to 10th hour, the pH value of the pile body with additives is higher than that of the blank group, and then it is basically the same. Figure 4 As shown in the figure, the germination rate of seeds in the pile changes. It can be seen from the figure that the germination rate of seeds can be improved after adding additives. Figure 5 As shown in the figure, the humus content in the pile has been significantly increased after the addition of additives.

[0034] Those skilled in the art should understand that the scope of the invention involved in this application is not limited to the technical solutions formed by a specific combination of the above technical features, but should also cover other technical solutions formed by any combination of the above technical features or their equivalent features without departing from the inventive concept. For example, the above features are replaced with (but not limited to) technical features with similar functions disclosed in this application.

Claims

1. A method for preparing a modified additive suitable for low-temperature composting, characterized in that: The following steps are involved: (1) Pretreatment of natural montmorillonite: crush the natural montmorillonite and then screen it, slowly add the screened montmorillonite fine powder into the sulfuric acid solution, stir while adding, and stir for 40-60 minutes at room temperature; filter and separate the unreacted solid impurities, and rinse the filtered montmorillonite with deionized water until the pH value of the washing liquid is close to neutral; dry the rinsed montmorillonite at 55-65° C. to ensure that the water is completely evaporated; and further grind the dried montmorillonite; (2) Montmorillonite modification: Chitosan was dissolved in glacial acetic acid and stirred for 20-40 min. Montmorillonite was dissolved in water and stirred evenly. Then the mixture was slowly added to the chitosan acetic acid solution. After stirring for 40-60 min, the pH value of the solution was adjusted to between 9 and 11. The solution was stirred and aged continuously. Finally, the product was obtained by filtration, washing, drying and grinding.

2. The method for preparing a modified additive suitable for low-temperature composting according to claim 1, characterized in that: In step (1), the montmorillonite is first crushed to a size of 80 mesh or more, and then crushed to a size of 100 mesh after drying.

3. The method for preparing a modified additive suitable for low-temperature composting according to claim 1, characterized in that: In step (1), the concentration of the sulfuric acid solution is 1 mol / L.

4. The method for preparing a modified additive suitable for low-temperature composting according to claim 1, characterized in that: In step (1), the mass ratio of montmorillonite to sulfuric acid solution is 1:

10.

5. The method for preparing a modified additive suitable for low-temperature composting according to claim 1, characterized in that: In step (2), the concentration of glacial acetic acid is 2%.

6. The method for preparing a modified additive suitable for low-temperature composting according to claim 1, characterized in that: In step (2), the mass ratio of chitosan to montmorillonite is 1:18-22.

7. The method for preparing a modified additive suitable for low-temperature composting according to claim 1, characterized in that: In step (2), the ratio of chitosan to glacial acetic acid added is 1 g / 100 ml.

8. The method for preparing a modified additive suitable for low-temperature composting according to claim 1, characterized in that: The ratio of montmorillonite to water added is 1g / 2-3ml.

9. The method for preparing a modified additive suitable for low-temperature composting according to claim 1, characterized in that: The modified montmorillonite is added to mixed solid garbage and corn stalks in an amount of 7.5% of the mass of the pile, and composting is carried out in a reactor.

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