Method for preparing humus-like substance from biomass based on electrocatalysis and application thereof

Abstract

This invention discloses a method and application for the directional preparation of humic substances from biomass based on electrocatalysis. The method involves first constructing a two-electrode electrolytic cell; adding biomass substrate and a peroxide-based oxidant, along with deionized water, and adjusting the solid-liquid ratio to 1:2 to 1:5; wherein the concentration of the peroxide-based oxidant is 37 mmol / L to 370 mmol / L; applying a voltage of 15 V to 30 V and continuously electrocatalyzing the reaction for 1 h to 10 h; after the reaction, directly drying and grinding the solid-liquid products to obtain humic substances. This invention, on the one hand, leverages electrocatalysis and the synergistic effect of the peroxide-based oxidant to generate active species, enabling the decomposition and polymerization of biomass precursors; on the other hand, by avoiding excessive oxidation of precursor substances (polyphenols, quinone intermediates), it ensures the orderly progress of subsequent free radical polymerization reactions, achieving highly efficient reaction conversion and demonstrating good practicality.

Description

Technical Field

[0001] This invention belongs to the technical field of biomass resource utilization, specifically relating to a method and application of biomass-based directional preparation of humic substances. Background Technology

[0002] Humus (HS) is the main component of soil organic matter (SOM), accounting for 70% of the total SOM and 80% of the total soil organic carbon. Humus not only improves soil structure and promotes crop yields, but also addresses climate change through carbon sequestration. In the context of the "dual-carbon" strategy and the green transformation of agriculture, humus has irreplaceable value. However, the formation of natural humus has a long cycle, making it difficult to meet current large-scale application needs. Currently, commercially available humus products mainly rely on extraction from non-renewable resources such as peat, lignite, charcoal, and weathered coal. Therefore, using organic waste such as soybean residue, straw, manure, sludge, and food waste as raw materials, and preparing biomass-based humic-like substances (HLS) through artificial synthesis technology has become a key pathway to overcome resource bottlenecks and achieve the resource-based transformation of organic waste.

[0003] Currently, technologies for the artificial synthesis of humic substances (HLS) mainly include biological and non-biological methods. Biological methods primarily rely on composting, which, while low-cost, suffers from long processing cycles (days to months), large land areas, significant carbon and nitrogen nutrient loss, and greenhouse gas emissions. Non-biological methods, primarily hydrothermal methods, while reducing reaction cycles to hours, typically require maintaining a high-temperature, high-pressure reaction environment, resulting in high energy consumption due to continuous heating and pressurization. Furthermore, hydrothermal methods have demanding reaction conditions, and the stability of the product is highly sensitive to temperature, pressure, substrate pH, and reaction time, making targeted HLS preparation difficult and limiting its large-scale application. Recent research indicates that electrochemical technology, due to its strong controllability and efficient degradation capabilities, is a promising emerging technology. Its reaction thermodynamics and kinetics are controlled by electrochemical parameters such as voltage and current. In biomass pretreatment, the apparent rate can be increased by several orders of magnitude compared to traditional biological treatment. More importantly, electrochemistry can activate free radical reactions in situ. Summary of the Invention

[0004] The purpose of this invention is to provide a method and application for the directional preparation of humic substances from biomass based on electrocatalysis, in order to solve the above-mentioned problems.

[0005] This invention is mainly achieved through the following technical solutions: A method for the targeted preparation of humic substances from biomass based on electrocatalysis includes the following steps: Step S1: Construct a dual-electrode electrolytic cell; Step S2: In a dual-electrode electrolytic cell, biomass substrate and peroxide oxidant are added, along with deionized water, and the solid-liquid ratio is adjusted to 1:2 to 1:5; wherein the concentration of the peroxide oxidant is 37 mmol / L to 370 mmol / L. A voltage of 15 V to 30 V is applied and the electrocatalytic reaction is continued for 1 h to 10 h to allow the biomass substrate to be directly electrolyzed and indirectly oxidized in the anodic region to generate polyphenol and quinone intermediates. Then, the polyphenol and quinone intermediates are diffused into the bulk solution to initiate free radical polymerization in the bulk solution and / or react with primary amines in the cathode region to generate Schiff bases. Step S3: After the reaction is complete, the solid-liquid product is dried and ground to prepare a humic substance.

[0006] Preferably, in the anode region, the biomass substrate is oxidized by means of direct electron transfer or / and by active species generated indirectly through electrochemistry.

[0007] After the polyphenol and quinone intermediates diffuse into the bulk solution, the reaction process is as follows: a free radical polymerization chain reaction is initiated by active species generated by electrocatalysis in conjunction with peroxide-type oxidants, and / or a nucleophilic addition reaction is carried out with the primary amine generated by direct electron transfer reduction at the cathode to generate a Schiff base.

[0008] This invention aims to generate active species through electrocatalysis and synergistic peroxide oxidants, thereby decomposing and polymerizing biomass precursors. On the other hand, it aims to avoid excessive oxidation of precursor substances (polyphenols, quinone intermediates) and ensure the orderly progress of subsequent free radical polymerization reactions.

[0009] like Figure 24 As shown, this invention applies a suitable cell voltage via a DC power supply to electrically activate a peroxide-based oxidant. Simultaneously, through direct electron transfer at the electrode surface, the biomass substrate is degraded to generate polyphenols and quinones as small-molecule precursors. These small-molecule precursors undergo free radical polymerization, cyclization, and cyclization reactions under the influence of active species, gradually polymerizing into macromolecules, thus achieving the directional conversion of biomass to HLS. This invention, by controlling the dosage of the peroxide-based advanced oxidant, the reaction time, and the cell voltage, can control the degree of oxidation, the rate of free radical generation, and the reaction process, achieving the directional humification conversion of biomass and preparing humic-like products suitable for supplementing healthy soil fertility and remediating polluted and degraded soils.

[0010] To better realize the present invention, in step S2, the concentration of the peroxide oxidant is 37 mmol / L ~ 60 mmol / L, and the electrocatalytic reaction is carried out for 5 h ~ 10 h. The humic substance prepared under these conditions can be used to supplement the fertility of healthy soil.

[0011] To better realize the present invention, in step S2, the concentration of the peroxide oxidant is 60 mmol / L to 370 mmol / L, and the electrocatalytic reaction is carried out continuously for 1 h to 3 h. The humic substance prepared under these conditions can be used for the remediation of polluted and degraded soils.

[0012] To better realize the present invention, in step S1, the anode of the two-electrode system is any one of boron-doped diamond electrode, sub-titanium oxide electrode, and coated titanium electrode, and the cathode of the two-electrode system is any one of titanium electrode, carbon electrode, and stainless steel electrode.

[0013] To better realize the present invention, the anode of the two-electrode system is a sub-titanium oxide electrode, and the cathode is a titanium electrode.

[0014] To better realize the present invention, in step S2, the peroxide oxidant includes any one or more of persulfate, perdisulfate, peroxycarbonate, and peracetate.

[0015] To better realize the present invention, in step S2, the peroxide oxidant includes potassium persulfate or sodium persulfate.

[0016] To better realize this invention, the biomass substrate further includes any one or more of soybean residue, wheat straw, corn straw, sawdust, bamboo powder, feces, sludge, and kitchen waste. Among these, wheat straw, corn straw, and sawdust require pre-treatment by crushing before the reaction.

[0017] This invention is mainly achieved through the following technical solutions: An application of the humic-like substance prepared by the above-described method of biomass-directed preparation of humic-like substance based on electrocatalysis: the humic-like substance prepared in step S3 is used to improve the fertility of healthy soil, or the humic-like substance prepared in step S3 is used to remediate polluted or degraded soil.

[0018] To better realize the present invention, the amount of the humic substance used is further 0.5~2 wt%.

[0019] The beneficial effects of this invention are as follows: (1) This invention is based on electrocatalytic synergistic peroxide oxidants, through SO4- • Active substances disrupt the glycosidic and ether bonds in biomass, promoting the decomposition and polymerization of recalcitrant components. Subsequently, under the action of peroxide oxidants, free radical polymerization reactions are initiated for recombination, achieving biomass humification. This invention has the advantages of high conversion efficiency, good controllability, small footprint, and diverse functional products. Compared with traditional artificial humification technologies, this invention specifically addresses the problems of long cycles and high energy consumption in existing biological methods and hydrothermal methods. This invention uses electrocatalytic peroxide oxidants to achieve the directional conversion of biomass into humic substances (HLS), providing a new, highly controllable, and simple pathway for biomass resource utilization.

[0020] (2) This invention achieves the resource conversion of biomass through electrocatalytic peroxide oxidants, which differs from traditional microbial composting and humification technology. It is not limited by microbial activity and can shorten the reaction cycle. Compared with hydrothermal humification technology, this invention does not require high temperature and high pressure conditions, and the reaction can be carried out at normal temperature and pressure, reducing the need for temperature and pressure resistant equipment and reducing equipment investment and operational safety risks. This invention can utilize electricity generated by renewable energy sources such as wind power and solar energy, and achieve precise control of the reaction process by adjusting parameters such as voltage and current density, which is conducive to the consumption of clean energy and reduces the environmental burden caused by fossil energy consumption. The process of this invention is simple, does not require complex temperature and pressure control systems, is easy to automate, and has good practicality.

[0021] (3) This invention enables biomass substrates to generate polyphenols and quinones through direct electrolysis and indirect oxidation in the anodic region. After the polyphenols and quinone intermediates diffuse into the bulk solution, they undergo free radical polymerization initiated by peroxide oxidants and react with primary amines generated at the cathode to form Schiff bases. These two reactions occur simultaneously, gradually increasing the molecular weight of the products and realizing the resource conversion of biomass substrates to obtain humic substances in a targeted manner. This invention, on the one hand, is based on electrocatalysis and the synergistic effect of peroxide oxidants to generate active species, causing the biomass substrates to decompose and polymerize; on the other hand, it avoids excessive oxidation of precursor substances (polyphenols and quinone intermediates), ensuring the orderly progress of subsequent free radical polymerization reactions, achieving highly efficient reaction conversion, and has good practicality.

[0022] (4) By adding an excessive amount of peroxide oxidant, the peroxide oxidant is partially retained. Relying on the rich functional group characteristics of HLS, the peroxide oxidant is stably encapsulated and the functional components are fixed, which synergistically promotes the effect of subsequent soil remediation. The prepared humus-like substance is mainly used for the remediation of polluted or degraded soil and has good practicality. Attached Figure Description

[0023] Figure 1This is a schematic diagram of the fluorescence region integration (FRI) partitioning in a three-dimensional excitation-emission matrix fluorescence spectroscopy (3D-EEM). Figure 2 This is a graph showing the evolution of in-situ electron paramagnetic resonance signals of semiquinone-hydroquinone radicals in the anodic region at different reaction times in Example 2; Figure 3 This is a graph showing the evolution of the EPR signal of the DMPO-H adduct in the cathode region at different reaction times in Example 2; Figure 4 This is a graph showing the change in total primary amine concentration in the cathode region with reaction time in Example 2; Figure 5 This is the EPR analysis chromatogram of the bulk solution in Example 2; Figure 6 This is a graph showing the changes in product composition of HLS prepared directionally based on soybean residue substrate in Example 2; Figure 7 This is a graph showing the changes in product composition of HLS prepared directionally based on soybean residue substrate in Example 3; Figure 8 This is a graph showing the changes in product composition of HLS prepared directionally based on soybean residue substrate in Example 4; Figure 9 This is the EPR analysis diagram of HLS prepared directionally based on soybean residue substrate in Example 4; Figure 10 This is a graph showing the changes in product composition of HLS prepared directionally based on soybean residue substrate in Example 6; Figure 11 This is a graph showing the changes in product composition of HLS prepared directionally based on soybean residue substrate in Example 7; Figure 12 This is a graph showing the changes in product composition of HLS prepared directionally based on soybean residue substrate in Example 8; Figure 13 This is a quantitative analysis diagram of the product prepared by directional preparation of HLS based on soybean residue substrate in Example 7; Figure 14 X-ray diffraction analysis pattern of the HLS product prepared in Example 7; Figure 15 The Fourier transform infrared spectrum of the HLS product prepared in Example 7 is shown below. Figure 16 The image shows the in-situ EPR analysis chromatogram of the HLS product prepared in Example 7. Figure 17 The diagram shows the effect of the HLS product prepared in Example 7 on the improvement of the aggregate structure of saline-alkali soil. Figure 18 The image shows the effect of the HLS product prepared in Example 7 on improving the water retention capacity of saline-alkali soil. Figure 19This is a comparison chart of plant growth in the potted *Elymus sibiricum* experiment in Example 7; Figure 20 The image shows the remediation effect of the HLS product prepared in Example 7 on phthalate-contaminated soil. Figure 21 This is a graph showing the changes in product composition of HLS prepared oriented based on a wood chip substrate in Example 9; Figure 22 This is a graph showing the changes in product composition of HLS prepared directionally based on straw substrate in Example 10; Figure 23 This is a graph showing the changes in product composition of HLS prepared oriented based on bamboo powder substrate in Example 11; Figure 24 This is a schematic diagram illustrating the reaction principle of the method for the directional preparation of humic substances from biomass based on electrocatalysis, as described in this invention. Detailed Implementation

[0024] Example 1: A method for the targeted preparation of humic substances from biomass based on electrocatalysis includes the following steps: (1) Construct a dual-electrode electrolytic cell; (2) The biomass to be treated is added to the electrolytic cell, and a peroxide oxidant is added at the same time, with a concentration of 37 mmol / L to 60 mmol / L. Then, deionized water is added to make the solid-liquid ratio 1:2 to 1:5.

[0025] (3) Apply a cell voltage of 15 V to 30 V under the above conditions, react for 5 h to 10 h and keep stirring throughout the process; (4) After the reaction is completed, without solid-liquid separation, the product is directly dried and ground to prepare humic substances, thus completing the directional preparation of humic substances from the biomass to be treated.

[0026] In this embodiment, the peroxide-based oxidant is completely consumed and does not enter the fertilizer. Therefore, the humus-like substance prepared in this embodiment is mainly used to enhance the fertility of healthy soil.

[0027] Example 2: A method for the targeted preparation of humic substances from biomass based on electrocatalysis, optimized from Example 1, with the only difference being: (2) Add soybean residue to the electrolytic cell. The peroxide oxidant is K2S2O8, and the concentration of the peroxide oxidant is 37 mmol / L. Then, add deionized water to make the solid-liquid ratio 1:2.

[0028] (3) Apply a cell voltage of 25 V and react for 8 h.

[0029] Under the synergistic effect of electrochemistry and oxidants, this embodiment achieves directional reconstruction and humification transformation of the organic components of soybean residue. For example... Figure 6 As shown, based on Figure 1 The schematic diagram of fluorescence region integration (FRI) shows that, compared to the unreacted soybean residue substrate at 0 min, the EEM signal of humic acid-like substances increased after electrocatalytic persulfate synergistic humification treatment. The total relative proportion of the EEM characteristic FRI in regions III (fulvic acid-like substances) and V (humic acid-like substances) in the product reached 73%, with region III accounting for 16% of the signal FRI intensity and region V accounting for 57%. This embodiment can achieve effective enrichment of the target humic components and is suitable for the targeted preparation of HLS from soybean residue.

[0030] like Figure 2 As shown, a significant semiquinone-hydroquinone radical signal appeared in the anodic region during the reaction. This signal intensified within the first 10–30 min of the reaction and then gradually decayed. This result indicates that soybean residue undergoes an oxidation reaction in the anodic region, and the generated phenolic compounds form semiquinone intermediates through electron transfer; this process can be directly driven by the anode.

[0031] like Figure 3 As shown, a strong DMPO-H adduct signal was detected in the cathode region, indicating a strongly reducing environment that favors the hydrogenation reaction. Meanwhile, as... Figure 4 As shown, the total primary amine concentration in the cathode region exhibits a trend of first increasing and then decreasing.

[0032] At the same time, such as Figure 5 As shown, a DMPO·-OSO3H signal was detected in the bulk solution, confirming that K2S2O8 was activated to generate sulfate radicals. At 20 min of reaction, a partially overlapping signal (light gray area) was identified as a semiquinone-hydroquinone radical through peak fitting, indicating that the radical migrated from the anodic region to the bulk solution. At 30 min of reaction, a characteristic signal appeared (…). g =2.0025 (dark gray area), belonging to the non-localized π electrons in the gradually formed humic structure, consistent with the humification process.

[0033] In summary, such as Figure 24 As shown, the biomass substrate is anolyzed or indirectly oxidized into polyphenols and quinones. The polyphenols and quinones then diffuse into the bulk solution and initiate a free radical polymerization chain reaction through electrocatalysis and the active species generated by peroxide-like oxidants, or undergo a nucleophilic addition reaction with the primary amines generated by direct electron transfer reduction at the cathode, thereby forming a Schiff base structure.

[0034] Example 3: A method for the targeted preparation of humic substances from biomass based on electrocatalysis, optimized from Example 1, with the only difference being: (2) Add soybean residue to the electrolytic cell. The peroxide oxidant is K2S2O8, and the concentration of the peroxide oxidant is 51.79 mmol / L. Then, add deionized water to make the solid-liquid ratio 1:2.

[0035] (3) Apply a cell voltage of 25 V and react for 6 h.

[0036] After continuous stirring for 360 min, the organic components of soybean residue underwent directional reconstruction and humification transformation under the synergistic effect of electrochemistry and oxidants. Figure 7 As shown, based on Figure 1 The schematic diagram of fluorescence region integration (FRI) shows that, compared with the unreacted soybean residue substrate at 0 min, the EEM signal of humic acid-like substances increased after electrocatalytic persulfate synergistic humification treatment. The total relative proportion of the EEM characteristic FRI in regions III (fulvic acid-like substances) and V (humic acid-like substances) in the product reached 80%, with the signal FRI intensity of region III accounting for 8% and that of region V accounting for 72%, achieving the targeted enrichment of the target component humic substances.

[0037] Example 4: A method for the targeted preparation of humic substances from biomass based on electrocatalysis, optimized from Example 1, with the only difference being: (2) Add soybean residue to the electrolytic cell. The peroxide oxidant is K2S2O8, and the concentration of the peroxide oxidant is 59.19 mmol / L. Then, add deionized water to make the solid-liquid ratio 1:2.

[0038] (3) Apply a tank voltage of 25 V and react for 5 h.

[0039] After continuous stirring for 300 min, the organic components of soybean residue underwent directional reconstruction and humification transformation under the synergistic effect of electrochemistry and oxidants. For example... Figure 8 As shown, based on Figure 1 The schematic diagram of fluorescence region integration (FRI) shows that, compared with the unreacted soybean residue substrate at 0 min, the EEM signal of humic acid-like substances increased after electrocatalytic persulfate synergistic humification treatment. The total relative proportion of the EEM characteristic FRI in regions III (fulvic acid-like substances) and V (humic acid-like substances) in the product reached 84%, with the signal FRI intensity of region III accounting for 7% and that of region V accounting for 77%, achieving the targeted enrichment of the target component humic substances.

[0040] In this embodiment, the peroxide-based oxidant is completely consumed and does not enter the fertilizer. Therefore, the humus-like substance prepared in this embodiment is mainly used to enhance the fertility of healthy soil.

[0041] This embodiment achieves the targeted preparation of HLS from biomass while ensuring that K2S2O8 does not remain in the HLS, so that it can be used to supplement the fertility of healthy soil systems. To this end, the obtained HLS product is subjected to EPR analysis. For example... Figure 9 As shown, no sulfate radical signal was detected in the product, indicating that the added K2S2O8 was completely consumed and did not enter the HLS.

[0042] Example 5: A method for the targeted preparation of humic substances from biomass based on electrocatalysis includes the following steps: (1) Construct a dual-electrode electrolytic cell; (2) The biomass to be treated is added to the electrolytic cell, and a peroxide oxidant is added at the same time, with a concentration of 60 mmol / L to 370 mmol / L. Then, deionized water is added to make the solid-liquid ratio 1:2 to 1:5 (depending on the biomass density).

[0043] (3) Apply a cell voltage of 15 V to 30 V under the above conditions, react for 1 h to 3 h and keep stirring throughout the process; (4) After the reaction is completed, without solid-liquid separation, the product is directly dried and ground to prepare humic substances, thus completing the directional preparation of humic substances from the biomass to be treated.

[0044] In this embodiment, the peroxide-type oxidant portion is retained. Utilizing the abundant functional groups of HLS, the peroxide-type oxidant is stably encapsulated, and the functional components are immobilized. For example, the peroxide-type oxidant is K2S2O8, and the specific reaction principle is as follows: On the one hand, the protonated amine groups encapsulate the excess K2S2O8 in the system through electrostatic adsorption; On the other hand, the primary amine and quinone form a C=N covalent bond through a Schiff base reaction, which together with the aromatic ring CC and the aromatic ring COC to construct a three-dimensional polymer network, providing a stable support for K2S2O8 encapsulation, while simultaneously immobilizing humic acid-like (HLA) and fulvic acid-like (FLA) compounds.

[0045] Therefore, the humic substance prepared in this embodiment is mainly used for the remediation of contaminated or degraded soil.

[0046] Example 6: A method for the targeted preparation of humic substances from biomass based on electrocatalysis, optimized from Example 5, with the only difference being: (2) Add soybean residue to the electrolytic cell. The peroxide oxidant is K2S2O8, and the concentration of the peroxide oxidant is 74 mmol / L. Then, add deionized water to make the solid-liquid ratio 1:2.

[0047] (3) Apply a tank voltage of 25 V and react for 2.5 h.

[0048] After continuous stirring for 150 min, the organic components of the soybean residue underwent directional reconstruction and humification transformation under the synergistic effect of electrochemistry and oxidants. Figure 10 As shown, based on Figure 1 The schematic diagram of fluorescence region integration (FRI) shows that, compared with the unreacted soybean residue substrate at 0 min, the EEM signal of humic acid-like substances increased after electrocatalytic persulfate synergistic humification treatment. The total relative proportion of the EEM characteristic FRI in regions III (fulvic acid-like substances) and V (humic acid-like substances) in the product reached 81%, with the signal FRI intensity of region III accounting for 5% and that of region V accounting for 76%, achieving the targeted enrichment of the target component humic substances.

[0049] Example 7: A method for the targeted preparation of humic substances from biomass based on electrocatalysis, optimized from Example 5, with the only difference being: (2) Add soybean residue to the electrolytic cell. The peroxide oxidant is K2S2O8, and the concentration of the peroxide oxidant is 296 mmol / L. Then, add deionized water to make the solid-liquid ratio 1:2.

[0050] (3) Apply a tank voltage of 25 V and react for 1 h.

[0051] After continuous stirring for 60 minutes, the organic components of the soybean residue underwent directional reconstruction and humification transformation under the synergistic effect of electrochemistry and oxidants. Figure 11 As shown, based on Figure 1 The schematic diagram of fluorescence region integration (FRI) shows that, compared with the unreacted soybean residue substrate at 0 min, the EEM signal of humic acid-like substances increased after electrocatalytic persulfate synergistic humification treatment. The total relative proportion of the EEM characteristic FRI in regions III (fulvic acid-like substances) and V (humic acid-like substances) in the product reached 94%, with the signal FRI intensity of region III accounting for 4% and that of region V accounting for 90%, achieving the targeted enrichment of the target component humic substances.

[0052] like Figure 13As shown, after 60 min in the electrochemically activated K₂S₂O₈ system, 170.19 mg C / g of humic acid carbon and 37.16 mg C / g of fulvic acid carbon were produced. These results indicate that the synergistic effect of electrochemically activated K₂S₂O₈ can achieve efficient conversion of soybean residue to HLS. Compared to a single system (either K₂S₂O₈ oxidation treatment or electrolysis in an electrolytic cell), the organic substrate of soybean residue did not undergo significant conversion, and both humic acid carbon and fulvic acid carbon were below 25 mg C / g.

[0053] To verify the effect of higher K2S2O8 addition on product performance, X-ray diffraction (XRD) analysis was performed on the HLS product prepared in Example 7. Figure 14 As shown, the XRD pattern of the product still retains the characteristic diffraction peaks of K2S2O8 (PDF#00-012-0483), indicating that the excess K2S2O8 in the reaction system is encapsulated in HLS, thus maintaining its crystallinity.

[0054] To clarify the type of functional group that plays a major role in the encapsulation of excess K2S2O8 in HLS, Fourier transform infrared (FTIR) spectroscopy analysis was performed on the HLS product prepared in Example 7. Figure 15 As shown, P1 (3398 cm) -1 The absorption peak of R1 (2929 cm⁻¹) is the stretching vibration of NH and OH in the repair agent; -1 2857 cm -1 The absorption peak of R2 (1746 cm⁻¹) is attributed to the CH bond vibration of aliphatic methyl or methylene groups in the repair agent; -1 1663 cm -1 The absorption peaks of P2 (1549 cm⁻¹) are characteristic signals of C=O in the repair agent, corresponding to the C=O stretching vibrations of the carboxyl and quinone groups, respectively; -1 ) is the C=C skeletal vibration of the aromatic ring or the NH bending vibration of the amide II band; P3 (1211 cm -1 ) is the stretching vibration signal of the aromatic CO bond (aromatic COC); P4 (853 cm -1The peak (CH) is the out-of-plane bending vibration peak of the aromatic ring. These functional groups play a key role in the construction of HLS-encapsulated K2S2O8: the protonated amine encapsulates the excess K2S2O8 in the system through electrostatic adsorption; the primary amine reacts with the quinone group to form C=N bonds via Schiff base reaction, which, together with the aromatic ring CC and aromatic ring COC, construct a three-dimensional polymer network, providing stable structural support for the encapsulation of K2S2O8, ultimately achieving the encapsulation of K2S2O8 by HLS and its autocatalytic activation to produce SO4. - •

[0055] The HLS product prepared in Example 7 was placed in a system containing DMPO paramagnetic scavenger for in-situ EPR testing to determine the sulfate radical anion (SO42-). - •) Slow release to verify whether the product possesses K2S2O8 sustained-release functionality. For example... Figure 16 As shown, a typical DMPO-OSO3H characteristic signal was detected at a g tensor value of approximately 2.0065, proving that SO4 was generated in the system. - • SO4 can still be detected after 36 hours. - • The stable characteristic signal directly verifies that the product can achieve SO4 through HLS autocatalytic slow release of K2S2O8. - • is continuously generated.

[0056] Preferably, the HLS product prepared in Example 7 is applied to the remediation of saline-alkali soil.

[0057] like Figure 17 As shown, adding different proportions (0 wt%, 0.5 wt%, 1 wt%, 2 wt%) of HLS product to saline-alkali soil and incubating for 15 days resulted in an increase in the proportion of large-size aggregates (5-10 mm) from 1% to 11%, even with only 0.5 wt% of the product. The product prepared by this electrochemical method has a significant effect on improving the aggregate structure of saline-alkali soil, and the particle size can be directionally controlled even at low addition levels.

[0058] like Figure 18 As shown, adding 2 wt% of this soil remediation agent to saline-alkali soil significantly improved the soil's water retention capacity. After 15 days of natural placement, the soil water retention rate of the control group approached 0%, while the soil water retention rate of the treatment group with the added remediation agent remained above 7%. This soil remediation agent can effectively improve the water retention capacity of saline-alkali soil, especially its long-term water stability.

[0059] This embodiment uses the planting of crested wheatgrass (… Elymus dahuricus Turcz. further verified the improvement effect on saline-alkali soil. Two control groups were set up: no remediation and remediation with chicken manure humus. Figure 19As shown, crested wheatgrass cannot grow in unremediated soil, and its growth is poor and it cannot grow normally in soil remediated with chicken manure humus. In contrast, saline-alkali soil remediated with HLS products can effectively promote the growth of crested wheatgrass, and all growth indicators are significantly better than those of the chicken manure humus remediation group, with higher germination rate and plant height. Its germination rate and plant height are 10 times and 6 times that of the chicken manure humus remediation group, respectively.

[0060] Preferably, the HLS product prepared in Example 7 is applied to the remediation of phthalate (DBP) contaminated soil.

[0061] like Figure 20 As shown, after adding this HLS product, the concentration of DBP in the soil gradually decreased within 12 hours, from approximately 98.51 mg / kg initially to 13.91 mg / kg, achieving a removal rate of 85.88%. Even after three rounds of repeated DBP addition, the pollutant could still be effectively degraded. The HLS product prepared by this method has a high efficiency in degrading DBP in soil and long-term purification performance, enabling the continuous removal of DBP-like pollutants.

[0062] Example 8: A method for the targeted preparation of humic substances from biomass based on electrocatalysis, optimized from Example 5, with the only difference being: (2) Add soybean residue to the electrolytic cell. The peroxide oxidant is K2S2O8, and the concentration of the peroxide oxidant is 370 mmol / L. Then, add deionized water to make the solid-liquid ratio 1:2.

[0063] (3) Apply a tank voltage of 25 V and react for 1 h.

[0064] After continuous stirring for 60 minutes, the organic components of the soybean residue underwent directional reconstruction and humification transformation under the synergistic effect of electrochemistry and oxidants. Figure 12 As shown, based on Figure 1 The schematic diagram of fluorescence region integration (FRI) shows that, compared with the unreacted soybean residue substrate at 0 min, the EEM signal of humic acid-like substances increased after electrocatalytic persulfate synergistic humification treatment. The total relative proportion of the EEM characteristic FRI in regions III (fulvic acid-like substances) and V (humic acid-like substances) in the product reached 94%, with the signal FRI intensity of region III accounting for 4% and that of region V accounting for 90%, achieving the targeted enrichment of the target component humic substances.

[0065] Example 9: A method for the targeted preparation of humic substances from biomass based on electrocatalysis, optimized from Example 7, with the only difference being: (2) Add sawdust to the electrolytic cell and add deionized water to make the solid-liquid ratio 1:3.

[0066] To verify the applicability of this electrochemical method to different biomass, 296 mmol / L K₂S₂O₈ was added to the sawdust for directional preparation of humic substances (HLS). Figure 21 As shown, based on Figure 1 The schematic diagram of fluorescence region integration (FRI) shows that after 60 min of electrochemically activated K2S2O8 synergistic treatment, the total relative proportion of the EEM characteristic FRI in regions III (fulvic acids) and V (humic acids) of the sawdust substrate product reached 72%, with region III accounting for 12% of the signal FRI intensity and region V accounting for 60%. This method can effectively enrich the target humified components and is also applicable to the directional preparation of HLS from sawdust.

[0067] Example 10: A method for the targeted preparation of humic substances from biomass based on electrocatalysis, optimized from Example 7, with the only difference being: (2) Add straw to the electrolytic cell and add deionized water to make the solid-liquid ratio 1:3.

[0068] To verify the applicability of this electrochemical method to different biomass, 296 mmol / L K2S2O8 was added to straw for the directional preparation of humic substances (HLS). With the continuous operation of the electrochemically activated K2S2O8 system, the components of the straw in the electrolytic cell underwent directional reconstruction. For example... Figure 22 As shown, based on Figure 1 The schematic diagram of fluorescence region integration (FRI) shows that after 60 min of electrochemically activated K2S2O8 synergistic treatment, the total relative proportion of the EEM characteristic FRI in regions III (fulvic acids) and V (humic acids) in the straw substrate product reached 80%, with region III accounting for 13% of the signal FRI intensity and region V accounting for 67%. This method can effectively enrich the target humified components and is also applicable to the targeted preparation of HLS from straw.

[0069] Example 11: A method for the targeted preparation of humic substances from biomass based on electrocatalysis, optimized from Example 7, with the only difference being: (2) Add bamboo powder to the electrolytic cell and add deionized water to make the solid-liquid ratio 1:4.

[0070] To verify the applicability of this electrochemical method to different biomass, 296 mmol / L K2S2O8 was added to bamboo powder for the directional preparation of humic substances (HLS). With the continuous operation of the electrochemically activated K2S2O8 system, the components of the bamboo powder in the electrolytic cell underwent directional reconstruction. For example... Figure 23 As shown, based on Figure 1 The schematic diagram of fluorescence region integration (FRI) shows that after 60 min of electrochemically activated K2S2O8 synergistic treatment, the total relative proportion of the EEM characteristic FRI in regions III (fulvic acids) and V (humic acids) of the bamboo powder substrate product reached 77%, with region III accounting for 11% and region V accounting for 66%. This method can effectively enrich the target humified components and is also applicable to the directional preparation of HLS from bamboo powder. The results of Examples 9-11 show that this electrochemical method has good applicability to different biomass.

[0071] Table 1

[0072] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Any simple modifications or equivalent changes made to the above embodiments based on the technical essence of the present invention shall fall within the protection scope of the present invention.

Claims

1. A method for the targeted preparation of humic substances from biomass based on electrocatalysis, characterized in that, Includes the following steps: Step S1: Construct a dual-electrode electrolytic cell; Step S2: In a dual-electrode electrolytic cell, biomass substrate and peroxide oxidant are added, along with deionized water, and the solid-liquid ratio is adjusted to 1:2 to 1:5; wherein the concentration of the peroxide oxidant is 37 mmol / L to 370 mmol / L. A voltage of 15 V to 30 V is applied and the electrocatalytic reaction is continued for 1 h to 10 h to allow the biomass substrate to be electrolyzed and oxidized in the anodic region to generate polyphenol and quinone intermediates. Then, free radical polymerization is initiated in the bulk solution, or / and reacts with primary amines in the cathode region to generate Schiff bases. Step S3: After the reaction is complete, the solid-liquid product is dried and ground to prepare a humic substance.

2. The method for the targeted preparation of humic substances from biomass based on electrocatalysis according to claim 1, characterized in that, In step S2, the concentration of the peroxide oxidant is 37 mmol / L ~ 60 mmol / L, and the electrocatalytic reaction is carried out for 5 h ~ 10 h.

3. The method for the targeted preparation of humic substances from biomass based on electrocatalysis according to claim 1, characterized in that, In step S2, the concentration of the peroxide oxidant is 60 mmol / L to 370 mmol / L, and the electrocatalytic reaction is carried out for 1 h to 3 h.

4. A method for the targeted preparation of humic substances from biomass based on electrocatalysis according to any one of claims 1 to 3, characterized in that, In step S1, the anode of the two-electrode system is any one of boron-doped diamond electrode, sub-titanium oxide electrode, or coated titanium electrode, and the cathode of the two-electrode system is any one of titanium electrode, carbon electrode, or stainless steel electrode.

5. The method for the targeted preparation of humic substances from biomass based on electrocatalysis according to claim 4, characterized in that, The anode of the two-electrode system is a sub-titanium oxide electrode, and the cathode is a titanium electrode.

6. A method for the targeted preparation of humic substances from biomass based on electrocatalysis according to any one of claims 1-3, characterized in that, In step S2, the peroxide oxidant includes any one or more of persulfate, perdisulfate, peroxycarbonate, and peracetate.

7. The method for the targeted preparation of humic substances from biomass based on electrocatalysis according to claim 6, characterized in that, In step S2, the peroxide-type oxidant includes potassium persulfate or sodium persulfate.

8. The method for the targeted preparation of humic substances from biomass based on electrocatalysis according to claim 1, characterized in that, The biomass substrate includes any one or more of the following: soybean residue, wheat straw, corn straw, sawdust, bamboo powder, feces, sludge, and kitchen waste.

9. The application of a humic-like substance prepared by a method for the directional preparation of humic-like substances from biomass based on electrocatalysis as described in any one of claims 1 to 8, characterized in that, The humic substances prepared in step S3 can be used to improve the fertility of healthy soils, or to remediate polluted or degraded soils.

10. The application of the humic-like substance prepared by the method for the directional preparation of humic-like substance from biomass based on electrocatalysis according to claim 9, characterized in that, The amount of the humic substance used is 0.5~2 wt%.

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