A method for synergistically enhancing the yield and quality of humic acid production from biomass waste.

Abstract

This invention discloses a method for synergistically enhancing the yield and quality of humic acid production from biomass waste: Biomass waste is dried and crushed to obtain dry raw material powder; the dry raw material powder is mixed with deionized water and added to a hydrothermal reactor for the first step of hydrothermal humification, yielding a mixture of hydrothermal char and hydrothermal liquid; the obtained hydrothermal product is recycled back into the hydrothermal reactor for further hydrothermal humification; the obtained hydrothermal product undergoes solid-liquid separation to obtain hydrothermal char and hydrothermal liquid; the obtained hydrothermal char undergoes multiple alkaline dissolution separations to obtain a humic acid-containing solution; the pH of the obtained hydrothermal liquid or humic acid-containing solution is adjusted to acidity to obtain humic acid and acidified waste liquid, with the humic acid separated from the solution in the form of a precipitate. This invention enables simultaneous improvement in the yield and quality of humic acid from the hydrothermal humification of biomass waste, reduces water consumption, and realizes the resource reuse of hydrothermal liquid, providing a new method for enhancing the hydrothermal humification process for humic acid production.

Description

Technical Field

[0001] This invention relates to a method for synergistic enhancement of humic acid yield and quality based on hydrothermal humification, belonging to the technical field of biomass solid waste resource utilization. Background Technology

[0002] Humic acid is a complex macromolecular organic compound with oxygen-containing functional groups such as quinone, carboxyl, and phenolic hydroxyl groups, as well as aromatic structures. It significantly promotes soil aggregate formation, microbial reproduction, plant growth and development, and regulates environmental pH, and is widely distributed in surface soils, oceans, and rivers. The formation of natural humic acid takes decades or even centuries, while current commercial humic acid production relies on non-renewable resources like coal; or it uses aerobic composting methods, which suffer from low yield, unstable quality, long composting cycles, and odor emissions. Therefore, developing a rapid and sustainable method for humic acid production is of great significance. Hydrothermal technology can accelerate the humification process of raw materials, and hydrothermal humification has been proposed as an alternative technology for humic acid production in recent years.

[0003] Existing technologies convert crop straw into humic acid through alkaline hydrothermal humification, but these technologies primarily focus on increasing humic acid yield while paying little attention to its quality. Furthermore, the hydrothermal fluids are not recycled and consume large amounts of water. Therefore, there is an urgent need to find a method that synergistically enhances both humic acid yield and quality. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a method for synergistic enhancement of humic acid yield and quality.

[0005] To address the aforementioned problems, this invention provides a method for synergistically enhancing the yield and quality of humic acid production from biomass waste, comprising the following steps:

[0006] Step 1): Dry and crush the biomass waste to obtain dry raw material powder;

[0007] Step 2): The dry raw material powder is mixed with deionized water and then added to the hydrothermal reactor to carry out the first step of hydrothermal humification. The hydrothermal product obtained is a mixture of hydrothermal carbon and hydrothermal liquid.

[0008] Step 3): The hydrothermal products obtained in Step 2) are recycled back into the hydrothermal reactor for the second step of hydrothermal humification, or only the hydrothermal liquid is extracted. Deionized water and dry raw material powder are added as needed and then recycled back into the hydrothermal reactor for the second step of hydrothermal humification. The hydrothermal products obtained are recycled back into the hydrothermal reactor for further hydrothermal humification as needed.

[0009] Step 4): Separate the hydrothermal products obtained in Step 3) into hydrothermal carbon and hydrothermal liquid; the obtained hydrothermal carbon is subjected to multiple alkaline dissolution separations to obtain a humic acid-containing solution; the pH of the obtained hydrothermal liquid or humic acid-containing solution is adjusted to acidic to obtain humic acid and acidified waste liquid, and the humic acid is separated from the solution in the form of precipitate.

[0010] Preferably, in step 1), the biomass waste is at least one of crop straw, Chinese medicine residue, garden waste, and domestic wet waste.

[0011] Preferably, in step 2), the solid-liquid mass ratio of the dry raw material powder to the deionized water is 1:1 to 1:20, the hydrothermal reaction time of the first step of hydrothermal humification is 0.5 to 8 hours, and the hydrothermal reaction temperature is 140 to 280°C.

[0012] More preferably, the hydrothermal reaction temperature is 200°C.

[0013] Preferably, step 3) is any one of the following methods:

[0014] Method 1: After solid-liquid separation of the hydrothermal products obtained in step 2), hydrothermal carbon and hydrothermal liquid are obtained. Deionized water is added to the hydrothermal liquid and dry raw material powder is added again. The product is directly circulated into the hydrothermal reactor without adjusting the pH to carry out the second step of hydrothermal humification.

[0015] Method 2: After solid-liquid separation of the hydrothermal products obtained in step 2), hydrothermal carbon and hydrothermal liquid are obtained. Deionized water is added to the hydrothermal liquid and the pH is adjusted to alkaline. After adding dry raw material powder again, it is recycled into the hydrothermal reactor for the second step of hydrothermal humification.

[0016] Method 3: The hydrothermal products obtained in step 2), namely the mixture of hydrothermal carbon and hydrothermal liquid, are adjusted to alkaline pH and then circulated into the hydrothermal reactor for the second step of hydrothermal humification.

[0017] Method 4: After solid-liquid separation of the hydrothermal products obtained in step 2), hydrothermal carbon and hydrothermal liquid are obtained. Deionized water is added to the hydrothermal liquid and the pH is adjusted to neutral. After adding dry raw material powder again, it is circulated into the hydrothermal reactor for the second step of hydrothermal humification. After solid-liquid separation of the hydrothermal products obtained in the second step of hydrothermal humification, hydrothermal carbon and hydrothermal liquid are obtained. Deionized water is added to the hydrothermal liquid and the pH is adjusted to alkaline. After adding dry raw material powder again, it is circulated into the hydrothermal reactor for the third step of hydrothermal humification.

[0018] Preferably, in step 3), the added mass of deionized water does not exceed 100% of the original liquid.

[0019] More preferably, the alkaline pH range is 8 to 14; and the neutral pH range is 6.5 to 7.5.

[0020] Preferably, in step 4), the pH range of the acid is 0.5 to 6.

[0021] More preferably, the acidity has a pH range of less than 1.

[0022] This invention addresses the problems of low yield, unstable quality, high water consumption, high reagent consumption, and lack of resource utilization of hydrothermal fluids in the current hydrothermal humification process for humic acid production. It proposes a method that combines hydrothermal fluid circulation with acid-base regulation to synergistically improve humic acid yield and quality. Hydrothermal fluid circulation allows abundant humic acid precursors (such as phenolic compounds, small molecule acids, and furans) in the hydrothermal fluid to participate in humic acid formation again. The alkaline environment facilitates lignin decomposition and the participation of decomposition products in the reaction, thereby improving humic acid quality and providing a new approach to enhance hydrothermal humification for humic acid production.

[0023] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0024] This invention utilizes hydrothermal fluid circulation combined with acid-base regulation hydrothermal humification technology. The yield of humic acid and the three-dimensional fluorescence (3D EEM) spectrum show that this invention can improve both the yield and quality of humic acid from biomass waste through hydrothermal humification, reduce water consumption in the hydrothermal humification process by more than 50%, and realize the resource reuse of hydrothermal fluid. This provides a new method for enhancing hydrothermal humification to produce humic acid. Attached Figure Description

[0025] Figure 1 A schematic diagram illustrating the principle of the method for synergistically enhancing the yield and quality of humic acid production from biomass waste provided by this invention.

[0026] Figure 2 The graph shows the changes in humic acid yield in each embodiment;

[0027] Figure 3 The images show the 3D EEM spectra of humic acid in each embodiment. Detailed Implementation

[0028] To make the present invention more apparent and understandable, preferred embodiments are described in detail below with reference to the accompanying drawings.

[0029] like Figure 1The diagram shows a method for synergistic enhancement of yield and quality in the preparation of humic acid by hydrothermal humification in Examples 1-4. It includes Example 1, in which the hydrothermal liquid obtained from solid-liquid separation is used for circulating hydrothermal humification without pH adjustment; Example 2, in which the hydrothermal liquid obtained from solid-liquid separation is used for circulating hydrothermal humification with pH adjustment; Example 3, in which a mixture of hydrothermal liquid and hydrothermal carbon is used for circulating hydrothermal humification with pH adjustment; and Example 4, in which the hydrothermal liquid obtained from solid-liquid separation is adjusted to neutral pH and circulated, and then the hydrothermal liquid obtained is adjusted to alkaline pH for two cycles of hydrothermal humification.

[0030] Example 1

[0031] Astragalus membranaceus residue was dried, crushed, and sieved through a 100-mesh sieve to obtain astragalus powder. 15g of astragalus powder was weighed and mixed with deionized water at a solid-liquid mass ratio of 1:10 in a 250mL hydrothermal reactor liner. The mixture was thoroughly mixed, and the liner was placed in the reactor. The reactor was then placed in an oven and heated to 200℃ for 4 hours. The obtained hydrothermal product was separated into solid and liquid phases by vacuum filtration. The obtained hydrothermal solution was replenished to 150mL with deionized water, and then astragalus powder was added again, maintaining the solid-liquid mass ratio at 1:10. Under the same hydrothermal conditions, a second step of circulating hydrothermal humification was performed to obtain hydrothermal products again, which were then separated into solid and liquid phases by vacuum filtration. The obtained hydrothermal char was subjected to multiple alkaline dissolution separations to obtain a humic acid-containing solution. The pH of this solution was adjusted to <1 with 6mol / L hydrochloric acid to obtain humic acid and acidified waste liquid. The humic acid was separated from the solution as a precipitate.

[0032] Example 2

[0033] Astragalus membranaceus residue was dried, crushed, and sieved through a 100-mesh sieve to obtain astragalus powder. 15g of astragalus powder was weighed and mixed with deionized water at a solid-liquid mass ratio of 1:10 in a 250mL hydrothermal reactor liner. The mixture was thoroughly mixed, and the liner was placed in the reactor. The reactor was then placed in an oven and heated to 200℃ for 4 hours. The obtained hydrothermal product was separated into solid and liquid phases by vacuum filtration. The obtained hydrothermal solution was replenished with deionized water to 150mL, and then adjusted to alkalinity (pH=13) with sodium hydroxide. Astragalus powder was then added again, maintaining the solid-liquid mass ratio at 1:10. Under the same hydrothermal conditions, a second step of circulating hydrothermal humification was performed to obtain hydrothermal products again. These products were then separated into solid and liquid phases using a centrifuge. The resulting hydrothermal carbon underwent multiple alkaline dissolution separations to obtain a humic acid-containing solution. The pH of the humic acid-containing solution and the hydrothermal solution obtained from solid-liquid separation was adjusted to <1 using 6mol / L hydrochloric acid, yielding humic acid and acidified waste liquid. The humic acid was separated from the solution as a precipitate.

[0034] Example 3

[0035] Astragalus membranaceus residue was dried, crushed, and sieved through a 100-mesh sieve to obtain Astragalus membranaceus powder. 15g of Astragalus membranaceus powder was weighed and mixed with deionized water at a solid-liquid mass ratio of 1:10 in a 250mL hydrothermal reactor liner. The mixture was thoroughly mixed, and the liner was placed in the reactor. The reactor was then placed in an oven and heated to 200℃ for 4 hours. The resulting hydrothermal mixture was adjusted to alkalinity (pH=13) with sodium hydroxide. Under the same hydrothermal conditions, a second-step circulating hydrothermal humification process was performed to obtain hydrothermal products again. Solid-liquid separation was achieved using a centrifuge. The resulting hydrothermal carbon underwent multiple alkaline dissolution separations to obtain a humic acid-containing solution. The pH of the humic acid-containing solution and the hydrothermal liquid obtained from solid-liquid separation was adjusted to <1 using 6mol / L hydrochloric acid, yielding humic acid and acidified waste liquid. The humic acid was separated from the solution as a precipitate.

[0036] Example 4

[0037] Astragalus membranaceus residue was dried, crushed, and sieved through a 100-mesh sieve to obtain astragalus powder. 15g of astragalus powder was weighed and mixed with deionized water at a solid-liquid mass ratio of 1:10 in a 250mL hydrothermal reactor liner. The mixture was thoroughly mixed, and the liner was placed inside the reactor. The reactor was then placed in an oven and heated to 200℃ for 4 hours. The obtained hydrothermal product was subjected to solid-liquid separation via vacuum filtration. The resulting hydrothermal solution was replenished with deionized water to 150mL, and the pH was adjusted to neutral (pH=7) with sodium hydroxide. Astragalus powder was then added again, maintaining the solid-liquid mass ratio at 1:10. Under the same hydrothermal conditions, a second step of circulating hydrothermal humification was performed to obtain the hydrothermal product again. Solid-liquid separation was achieved by vacuum filtration. The obtained hydrothermal fluid was replenished to 150 mL with deionized water and then adjusted to alkalinity (pH = 13) with sodium hydroxide. Astragalus powder was added again, and the solid-liquid mass ratio was maintained at 1:10. Under the same hydrothermal conditions, the third step of circulating hydrothermal humification was carried out. The hydrothermal products were separated into solid and liquid by centrifugation. The obtained hydrothermal carbon was separated by multiple alkaline dissolutions to obtain a humic acid-containing solution. The pH of the humic acid-containing solution and the hydrothermal fluid obtained from solid-liquid separation was adjusted to <1 with 6 mol / L hydrochloric acid to obtain humic acid and acidified waste liquid. The humic acid was separated from the solution in the form of a precipitate.

[0038] The humic acid yield (based on dry raw materials) was obtained through calculation as follows: Figure 2As shown, the humic acid yields obtained in Examples 1-4 were significantly higher than those obtained in the original one-step hydrothermal humification (including only steps 1), 2), and 4) (6.54±0.09 wt.%), specifically 8.34±0.03 wt.%, 18.20±0.25 wt.%, 20.70±1.27 wt.%, and 16.92±0.53 wt.%, respectively. Humic acid precursors exist in the hydrothermal fluid, and continue to participate in humic acid formation after recycling. Subsequently, the humic acid dissolves in the hydrothermal fluid or polymerizes in the hydrothermal carbon, thus increasing the humic acid yield. The extracted humic acid was dissolved in a 0.1 mol / L sodium hydroxide solution, and the quality of the humic acid was observed by 3DEEM analysis. The results are as follows. Figure 3 As shown, the fluorescence regions of the humic acid produced under the original conditions and in Examples 1-4 all fall within the humic acid region, proving that the extracted substance is humic acid. Meanwhile, the fluorescence intensity indicates that, compared to the original process, Example 1 did not show a significant improvement in fluorescence intensity and range. Simple hydrothermal cycling cannot help dissolve substances that improve humic acid quality (such as lignin). Examples 2-4 showed significantly enhanced fluorescence intensity and a larger range, with maximum fluorescence intensities reaching 650, 400, and 500 respectively. Compared to the maximum fluorescence intensity of 110 in the original process, this is a significant improvement. This is because adjusting the hydrothermal liquid to alkalinity promotes the decomposition of lignin, and the decomposed lignin participates in humic acid formation, thus improving the quality of humic acid.

[0039] The results show that the hydrothermal humification method for biomass waste can improve the yield and quality of humic acid by synergistically enhancing the yield and quality of humic acid. In particular, the acid-base adjustment of the circulating hydrothermal fluid can significantly improve both the yield and quality of humic acid, reduce water consumption, and realize the resource reuse of the hydrothermal fluid. This provides a new method for the high-value utilization of biomass waste and the large-scale preparation of humic acid.

Claims

1. A method for synergistically enhancing the yield and quality of humic acid production from biomass waste, characterized in that, Includes the following steps: Step 1): After drying and crushing the biomass waste, dry raw material powder is obtained; the biomass waste is Chinese medicine residue; Step 2): The dry raw material powder is mixed with deionized water and then added to the hydrothermal reactor to carry out the first step of hydrothermal humification. The hydrothermal product obtained is a mixture of hydrothermal carbon and hydrothermal liquid. Step 3): Specifically, it can be any of the following methods: Method 1: After solid-liquid separation of the hydrothermal products obtained in step 2), hydrothermal carbon and hydrothermal liquid are obtained. Deionized water is added to the hydrothermal liquid and the pH is adjusted to alkaline. After adding dry raw material powder again, it is recycled into the hydrothermal reactor for the second step of hydrothermal humification. Method 2: The hydrothermal products obtained in step 2), namely the mixture of hydrothermal carbon and hydrothermal liquid, are adjusted to alkaline pH and then circulated into the hydrothermal reactor for the second step of hydrothermal humification. Method 3: After solid-liquid separation of the hydrothermal products obtained in step 2), hydrothermal carbon and hydrothermal liquid are obtained. Deionized water is added to the hydrothermal liquid and the pH is adjusted to neutral. After adding dry raw material powder again, it is circulated into the hydrothermal reactor for the second step of hydrothermal humification. After solid-liquid separation of the hydrothermal products obtained in the second step of hydrothermal humification, hydrothermal carbon and hydrothermal liquid are obtained. Deionized water is added to the hydrothermal liquid and the pH is adjusted to alkaline. After adding dry raw material powder again, it is circulated into the hydrothermal reactor for the third step of hydrothermal humification. Step 4): Separate the hydrothermal products obtained in Step 3) into hydrothermal carbon and hydrothermal liquid; the obtained hydrothermal carbon is separated by multiple alkaline dissolutions to obtain a solution containing humic acid; the pH of the obtained hydrothermal liquid or the solution containing humic acid is adjusted to acidic to obtain humic acid and acidified waste liquid, and the humic acid is separated from the solution in the form of precipitate.

2. The method for synergistically enhancing the yield and quality of humic acid production from biomass waste as described in claim 1, characterized in that, In step 2), the solid-liquid mass ratio of the dry raw material powder to deionized water is 1:1 to 1:20, the hydrothermal reaction time of the first step of hydrothermal humification is 0.5 to 8 hours, and the hydrothermal reaction temperature is 140 to 280°C.

3. The method for synergistically enhancing the yield and quality of humic acid production from biomass waste as described in claim 2, characterized in that, The hydrothermal reaction temperature is 200℃.

4. The method for synergistically enhancing the yield and quality of humic acid production from biomass waste as described in claim 1, characterized in that, In step 3), the added mass of deionized water does not exceed 100% of the original liquid.

5. The method for synergistically enhancing the yield and quality of humic acid production from biomass waste as described in claim 1, characterized in that, The alkaline pH range is 8 to 14; the neutral pH range is 6.5 to 7.

5.

6. The method for synergistically enhancing the yield and quality of humic acid production from biomass waste as described in claim 1, characterized in that, In step 4), the pH range of the acidity is 0.5 to 6.

7. The method for synergistically enhancing the yield and quality of humic acid production from biomass waste as described in claim 6, characterized in that, The pH range of the acidity is less than 1.

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