Method for humifying kitchen waste through alkali activation of peroxydisulfate

Abstract

The invention relates to the technical field of organic solid waste recycling, in particular to a method for humifying kitchen waste through alkali activation of peroxydisulfate. The method comprises the following steps: firstly, carrying out crushing treatment on pretreated kitchen waste residues to obtain slurry; and sequentially adding an alkaline raw material and peroxydisulfate into the slurry, and carrying out an activation reaction to complete humification of the kitchen waste. According to the method, the synergistic effect of free radical oxidation and alkaline polymerization generated by alkali activation of peroxydisulfate is creatively utilized, efficient humification of the kitchen waste can be achieved within one hour under the conditions of normal temperature and normal pressure, the treatment efficiency is improved by hundreds of times compared with that of traditional biological aerobic fermentation, and the method is suitable for industrial production. And the initial investment cost and the occupied area of facilities are obviously reduced.

Description

Technical Field

[0001] This invention relates to the field of organic solid waste resource utilization technology, and in particular to a method for alkali-activated persulfate humification of kitchen waste. Background Technology

[0002] Food waste, as a major component of urban solid waste, is characterized by its large volume, high moisture content, rich organic matter content, and susceptibility to putrefaction and foul odors, posing a severe challenge to urban environmental management and resource utilization. Conventional humification involves the decomposition, transformation, and resynthesis of organic matter by microorganisms, forming various humic acid-based high-molecular-weight organic compounds, thus stabilizing the organic matter. Traditional aerobic fermentation is a typical humification technology. Research and practice have proven that aerobic fermentation can effectively reduce the moisture content of food waste, stabilize it, and convert it into organic fertilizer. However, traditional aerobic fermentation methods have significant limitations: high moisture content affects aeration, thus inhibiting microbial activity, requiring the addition of large amounts of auxiliary materials for adjustment; the treatment cycle is too long (usually 30-60 days or more), requiring a large area; a large amount of malodorous gases (such as NH3 and H2S) are generated during the process; frequent turning is required, and leachate is easily generated; humification efficiency is low, and product quality is unstable.

[0003] Therefore, it is crucial to provide a technical solution that can solve the above-mentioned technical problems. Summary of the Invention

[0004] To address the technical limitations of the aforementioned biological humification process, this invention provides a method for alkali-activated persulfate humification of kitchen waste.

[0005] The objective of this invention can be achieved through the following technical solutions: This invention discloses a method for alkali-activated persulfate humification of kitchen waste, comprising the following steps: (S1) The pretreated food waste (FW) residue is crushed to obtain slurry; (S2) Alkaline raw materials and persulfate are added sequentially to the slurry prepared in step (S1) to carry out the activation reaction and complete the humification of kitchen waste.

[0006] In one embodiment of the present invention, the preprocessing in step (S1) specifically includes the following: Remove large bones and plastic impurities from kitchen waste residue, and control the moisture content of kitchen waste residue to 75%~99%.

[0007] In one embodiment of the present invention, in step (S1), the kitchen waste residue is crushed to a particle size ≤120 μm.

[0008] In one embodiment of the present invention, in step (S1), the ratio of alkaline raw material, persulfate (PDS), and slurry is 20~120 g: 20~120 g: 1L; Preferably, the mass ratio of the alkaline raw material persulfate to the slurry dosage is 1 g: 1 g: 10 mL.

[0009] In one embodiment of the present invention, the alkaline raw material is selected from one or more of potassium hydroxide (KOH), sodium hydroxide, lithium hydroxide, potassium carbonate, or calcium hydroxide.

[0010] In one embodiment of the present invention, the alkaline raw material is potassium hydroxide, which is beneficial for resource utilization.

[0011] In one embodiment of the present invention, in step (S2), the slurry is stirred before addition. During the stirring process, the temperature is room temperature and the rotation speed is 300~700 r / min; preferably, the rotation speed is 500 r / min.

[0012] During the addition process, the alkaline raw materials (stirred for 0.5 to 2 min after addition) and persulfate are added at one time, at room temperature, at 300 to 700 r / min; preferably, the rotation speed is 500 r / min.

[0013] In one embodiment of the present invention, in step (S2), during the activation reaction, the temperature is raised to 70°C and stirring is continued for more than 20 minutes; Preferably, during the activation reaction, the temperature is raised to 70°C and stirred continuously for 20 minutes.

[0014] Compared with the prior art, the present invention has the following beneficial effects: (1) The method provided by the present invention creatively utilizes the synergistic effect of free radical oxidation and alkaline polymerization generated by alkali activation of persulfate. Under normal temperature and pressure conditions, it can achieve efficient humification of kitchen waste within 1 hour. The treatment efficiency is hundreds of times higher than that of traditional biological aerobic fermentation, which significantly reduces the initial investment cost and land area of ​​the facility.

[0015] (2) The method of alkaline activation persulfate humification of kitchen waste provided by the present invention can directly treat kitchen waste with a moisture content of up to 75%~99%, without the need to add a large amount of auxiliary materials to adjust the moisture or physical properties, and successfully solves the technical problem that kitchen waste with high moisture content is difficult to be directly and effectively humified through traditional composting.

[0016] (3) Compared with the traditional aerobic fermentation process, which produces a large amount of odorous gases (NH3, H2S) and leachate, the present invention has the advantages of fast reaction process and less odorous gas production. In addition, due to the small size of the reactor, a small amount of odorous gas is easy to collect and treat. At the same time, since the product can be directly used as liquid organic fertilizer or soil conditioner, no leachate is produced during the reaction process, which greatly improves the operating environment and reduces the pollution load on the surrounding environment.

[0017] (4) In the method of alkaline activation of persulfate humification of kitchen waste provided by the present invention, the whole process is carried out at normal temperature and pressure, and the main equipment is a conventional stirred reactor. No complicated equipment or high temperature and high pressure conditions are required. The reaction process does not require cumbersome operations such as turning the pile. It is simple to operate and easy to achieve large-scale application.

[0018] (5) The method of alkaline activation of persulfate humification of kitchen waste provided by the present invention can guide the organic matter of kitchen waste to polymerize into high-value humus. The analysis results show that the product is rich in fulvic acid (FLA) and humic acid (HLA) with higher aroma, larger molecular weight and deeper humification. Its quality (such as functional group diversity and aromatic structure) is significantly better than that of aerobic fermentation products. Therefore, after simple pH adjustment, the humification product slurry can be directly used as a high-quality liquid organic fertilizer or soil conditioner. Attached Figure Description

[0019] Figure 1 This is a graph showing the reaction temperature changes under different reagent dosages in Example 1; Figure 2 Figure a shows the changes in the Fourier transform infrared spectra of the reaction products under different dosage conditions in Example 2; Figure 3 Figure b shows the Fourier transform infrared spectrum of the reaction products under different dosage conditions in Example 2; Figure 4 This is a graph showing the changes in the three-dimensional fluorescence spectrum of the reaction in Example 3; Figure 5 The Fourier transform infrared spectra of different reaction times in Example 3 are shown. Figure 6 This is a graph showing the changes in solid NMR before and after the reaction in Example 3. Detailed Implementation

[0020] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0021] Unless otherwise specified, all reagents used in the following embodiments are commercially available reagents, and all detection methods and techniques used are conventional detection methods and techniques in the art.

[0022] Example 1 This embodiment provides a method for alkali-activated persulfate humification of kitchen waste, as detailed below: (S1) After sorting out the impurities, the kitchen waste is mechanically crushed to a particle size ≤120 μm to obtain a slurry (with a water content of 90%). (S2) Several 500 mL slurries obtained in step (S1) were placed in a 1 L reactor as the liquid to be treated and stirred continuously at a speed of 500 r / min at room temperature. Group 1: First, add 10 g KOH into the reactor at once and stir continuously for 1 min. Then, add 10 g PDS into the reactor at once. Group 2: First, add 20 g KOH into the reactor all at once and stir continuously for 1 min. Then, add 20 g PDS into the reactor all at once. Group 3: First, add 30 g KOH into the reactor all at once and stir continuously for 1 min. Then, add 30 g PDS into the reactor all at once. Group 4: First, add 40 g of KOH to the reactor all at once and stir continuously for 1 min. Then, add 40 g of PDS to the reactor all at once. Group 5: First, add 50 g of KOH to the reactor all at once and stir continuously for 1 min. Then, add 50 g of PDS to the reactor all at once. Group 6: First, add 60 g of KOH to the reactor all at once and stir continuously for 1 min. Then, add 60 g of PDS to the reactor all at once. Group 7: Add 50 g of KOH to the reactor in one go; Group 8: Add 50 g of PDS to the reactor at once; The reaction continued, and the reaction temperature inside the reactor was subsequently measured continuously. The results are as follows: Figure 1 As shown.

[0023] pass Figure 1 It can be observed that PDS treatment alone does not induce a temperature increase in the system, while KOH treatment alone does induce a temperature increase to some extent, but the degree of temperature increase is much smaller than that of the system treated with both KOH and PDS. The results show that in the coupled system (KOH and PDS), the reaction temperature reaches a maximum of 84℃, and this temperature increase is concentrated in the first 20 minutes after the reaction begins, indicating that an exothermic humification process occurs. Taking 50 g KOH + 50 g PDS as an example, the reaction temperature rapidly rises to 70℃ within 10 minutes and then gradually decreases, dropping to 40℃ at approximately 45 minutes.

[0024] Example 2 This embodiment provides a method for alkali-activated persulfate humification of kitchen waste, as detailed below: (S1) After sorting out the impurities, the kitchen waste is mechanically crushed to a particle size ≤120 μm to obtain a slurry (with a water content of 90%). (S2) Several 500 mL slurries obtained in step (S1) were placed in a 1 L reactor as the liquid to be treated and stirred continuously at a speed of 500 r / min at room temperature. Group 1: First, add 10 g KOH into the reactor at once and stir continuously for 1 min. Then, add 10 g PDS into the reactor at once. Group 2: First, add 20 g KOH into the reactor all at once and stir continuously for 1 min. Then, add 20 g PDS into the reactor all at once. Group 3: First, add 30 g KOH into the reactor all at once and stir continuously for 1 min. Then, add 30 g PDS into the reactor all at once. Group 4: First, add 40 g of KOH to the reactor all at once and stir continuously for 1 min. Then, add 40 g of PDS to the reactor all at once. Group 5: First, add 50 g of KOH to the reactor all at once and stir continuously for 1 min. Then, add 50 g of PDS to the reactor all at once. Group 6: First, add 60 g of KOH to the reactor all at once and stir continuously for 1 min. Then, add 60 g of PDS to the reactor all at once. Group 7: Add 50 g of KOH to the reactor in one go; Group 8: Add 50 g of PDS to the reactor at once; The reaction continued, and the reaction temperature inside the reactor was continuously measured. When the reaction temperature reached about 70°C, the color of the slurry inside the reactor was carefully observed. At this time, the color of the slurry changed from light green to yellowish brown. The reaction was continued for 45 minutes with stirring. After the color of the slurry turned dark brown and stopped changing, stirring was stopped and the reaction was terminated.

[0025] After the reaction was complete, the reaction product was collected and dried at 50°C to constant weight. The dried solid product was then subjected to infrared spectroscopy, and the results are as follows: Figures 2-3 As shown.

[0026] pass Figure 2 and Figure 3 It can be observed that the products obtained from treatment with different levels of KOH and PDS exhibit varying degrees of affinity in aromatic CH4 (700 cm⁻¹). -1 ), phenolic CO (1027 cm⁻¹)-1 ), Amide CN (1384 cm) -1 ), Aromatic C=O (1589 cm) -1 ) and carboxyl-OH (2860 and 2937 cm) -1 The characteristic peaks of the α group all showed varying degrees of enhancement. These phenomena indicate that reactions such as carbonyl-amino condensation (i.e., Maillard reaction) and aromatization occurred during this process.

[0027] Example 3 This embodiment provides a method for alkali-activated persulfate humification of kitchen waste, as detailed below: (S1) After sorting out the impurities, the kitchen waste is mechanically crushed to a particle size ≤120 μm to obtain a slurry (with a water content of 90%). (S2) Place 500 mL of the slurry obtained in step (S1) into a 1 L reactor as the liquid to be treated, and stir continuously at 500 r / min at room temperature. (S2) Several 500 mL slurries obtained in step (S1) were placed in a 1 L reactor as the liquid to be treated and stirred continuously at a speed of 500 r / min at room temperature. Group 1: First, add 10 g KOH into the reactor at once and stir continuously for 1 min. Then, add 10 g PDS into the reactor at once. Group 2: First, add 20 g KOH into the reactor all at once and stir continuously for 1 min. Then, add 20 g PDS into the reactor all at once. Group 3: First, add 30 g KOH into the reactor all at once and stir continuously for 1 min. Then, add 30 g PDS into the reactor all at once. Group 4: First, add 40 g of KOH to the reactor all at once and stir continuously for 1 min. Then, add 40 g of PDS to the reactor all at once. Group 5: First, add 50 g of KOH to the reactor all at once and stir continuously for 1 min. Then, add 50 g of PDS to the reactor all at once. Group 6: First, add 60 g of KOH to the reactor all at once and stir continuously for 1 min. Then, add 60 g of PDS to the reactor all at once. Group 7: Add 50 g of KOH to the reactor in one go; Group 8: Add 50 g of PDS to the reactor at once; The reaction was continued, and the reaction temperature inside the reactor was continuously measured. When the reaction temperature reached about 70°C, the color of the slurry inside the reactor was carefully observed. At this time, the color of the slurry changed from light green to yellowish brown. The reaction was stirred for 45 minutes each (for the fifth group, the reaction was stirred for 0, 2, 5, 10, 20 and 45 minutes respectively), and the reaction was stopped.

[0028] After the reaction was complete, 2 mL of the reaction solution was diluted 50 times with pure water, mixed thoroughly, and then filtered through a 25 mm, 45 μm aqueous filter membrane to obtain 5 mL of liquid. The obtained filtrate was analyzed by three-dimensional excitation-emission matrix fluorescence spectroscopy (3D-EEM spectroscopy). Figure 4 (As shown).

[0029] For the fifth group, reaction products were collected at each reaction time point and dried to constant weight at 50°C. The dried solid products were then subjected to infrared spectroscopy (results are shown below). Figure 5 (as shown) and solid-state NMR detection (results as shown) Figure 6 (As shown).

[0030] pass Figure 4 It was observed that KOH treatment alone could not induce polymerization in food waste, but it could promote the hydrolysis of insoluble proteins and other organic components, thereby enhancing the fluorescence intensity of the soluble microbial byproduct region (excitation wavelength > 250 nm, emission wavelength < 380 nm). PDS treatment alone had a weak oxidizing effect on food waste but could not induce polymerization. In the coupled treatment system, food waste underwent significant humification within one hour, specifically reflected in a significant increase in fluorescence intensity in the humic-like region (excitation wavelength > 250 nm, emission wavelength > 380 nm). The optimal humification performance was achieved with 50 g KOH + 50 g PDS. Taking 50 g KOH + 50 g PDS as an example, the degree of humification rapidly increased within the first 10 minutes after the reaction began, and then stabilized.

[0031] pass Figure 5 It can be observed that, as the reaction proceeds, aromatic CH4 (700 cm) -1 ), Amide CN (1384 cm) -1 ), Aromatic C=O (1589 cm) -1 The reaction intensifies within the first 5 minutes and then stabilizes; the -OH peak of the polysaccharide (3268 cm⁻¹) is observed. -1 The effect gradually weakens; while phenolic CO (1027 cm⁻¹) -1 ) and carboxyl-OH (2860 and 2937 cm) -1The reaction showed a trend of first weakening and then strengthening. These results indicate that polysaccharide degradation, carbonyl-amino condensation (Maillard reaction), aromatization, and oxidation of phenols and carboxylic acids occurred during humification. Furthermore, comparison of the freeze-dried reaction products with standard fulvic acid samples revealed that they exhibited lower phenolic CO2 concentrations (1027 cm⁻¹). -1 ), Amide CN (1384 cm) -1 ), Aromatic C=O (1589 cm) -1 ), carboxyl-OH (2860 and 2937 cm) -1 The product exhibits characteristic peaks at the same positions of functional groups such as , and the infrared peak shape of the product is very similar to that of the standard fulvic acid sample (FA), indicating the successful synthesis of FLA.

[0032] pass Figure 6 It can be observed that in the aliphatic carbon region, both the FW and the product exhibit significant peaks around 30 ppm, attributed to the presence of aliphatic -CH groups in the methyl, methylene, and methylene groups. The higher peak intensity of the product compared to the FW indicates a higher abundance of alkyl groups. In the aromatic carbon region, the peak at 103 ppm in the FW disappears, while a peak at 130 ppm appears. This phenomenon may be due to the ring-opening reaction induced by free radical oxidation and subsequent ring fusion. In the carboxyl / carbonyl carbon region, the peak around 175 ppm in the product is much higher than that in the FW, confirming the formation of more carboxyl groups, indicating that carboxylation may have occurred during humification. The typical alkyl (approximately 33 ppm), aromatic (130 ppm), and carboxyl (179 ppm) group peaks in the product can also be found in the spectrum of standard fulvic acid samples, further confirming the formation of fulvic acid-like substances.

[0033] Example 4 This embodiment provides a method for alkali-activated persulfate humification of kitchen waste, as detailed below: (S1) After sorting out the impurities, the kitchen waste is mechanically crushed to a particle size ≤120 μm to obtain a slurry (moisture content 75%). (S2) Place 500 mL of the slurry obtained in step (S1) into a 1 L reactor as the liquid to be treated, and stir continuously at 500 r / min at room temperature. Weigh 50 g of PDS (analytical grade) and 50 g of KOH (analytical grade). First, add 50 g of KOH to the reactor all at once and stir continuously for 1 min. Then, add 50 g of PDS to the reactor all at once and continue the reaction. Continuously measure the reaction temperature in the reactor. When the reaction temperature reaches about 70℃, carefully observe the color of the slurry in the reactor. At this time, the color of the slurry changes from light green to yellowish-brown. Continue stirring and react for 45 min. After the color of the slurry turns dark brown and no longer changes, stop stirring and end the reaction.

[0034] Example 5 This embodiment provides a method for alkali-activated persulfate humification of kitchen waste, as detailed below: (S1) After sorting out the impurities, the kitchen waste is mechanically crushed to a particle size ≤120 μm to obtain a slurry (with a water content of 99%). (S2) Place 500 mL of the slurry obtained in step (S1) into a 1 L reactor as the liquid to be treated, and stir continuously at 500 r / min at room temperature. Weigh 50 g of PDS (analytical grade) and 50 g of KOH (analytical grade). First, add 50 g of KOH to the reactor all at once and stir continuously for 1 min. Then, add 50 g of PDS to the reactor all at once and continue the reaction. Continuously measure the reaction temperature in the reactor. When the reaction temperature reaches about 70℃, carefully observe the color of the slurry in the reactor. At this time, the color of the slurry changes from light green to yellowish-brown. Continue stirring and react for 45 min. After the color of the slurry turns dark brown and no longer changes, stop stirring and end the reaction.

[0035] The methods provided in Examples 4 and 5 have comparable performance to that in Example 1 in terms of the humification of kitchen waste.

[0036] The above description of the embodiments is provided to enable those skilled in the art to understand and use the invention. It will be apparent to those skilled in the art that various modifications can be made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the above embodiments, and any improvements and modifications made by those skilled in the art based on the interpretation of the present invention, without departing from the scope of the invention, should be within the protection scope of the present invention.

Claims

1. A method for alkali-activated persulfate humification of kitchen waste, characterized in that, Includes the following steps: (S1) The pretreated kitchen waste residue is crushed to obtain slurry; (S2) Alkaline raw materials and persulfate are added sequentially to the slurry prepared in step (S1) to carry out the activation reaction and complete the humification of kitchen waste.

2. The method for alkali-activated persulfate humification of kitchen waste according to claim 1, characterized in that, In step (S1), the preprocessing is specifically as follows: Remove large bones and plastic impurities from kitchen waste residue, and control the moisture content of kitchen waste residue to 75%~99%.

3. The method for alkali-activated persulfate humification of kitchen waste according to claim 1, characterized in that, In step (S1), the kitchen waste residue is crushed to a particle size ≤120 μm.

4. The method for alkali-activated persulfate humification of kitchen waste according to claim 1, characterized in that, In step (S1), the ratio of alkaline raw material, persulfate, and slurry is 20~120 g: 20~120 g: 1L.

5. The method for alkali-activated persulfate humification of kitchen waste according to claim 4, characterized in that, The ratio of alkaline raw materials, persulfate, and slurry is 1 g: 1 g: 10 mL.

6. The method for alkali-activated persulfate humification of kitchen waste according to claim 4, characterized in that, The alkaline raw material is selected from one or more of potassium hydroxide, sodium hydroxide, lithium hydroxide, potassium carbonate, or calcium hydroxide.

7. The method for alkali-activated persulfate humification of kitchen waste according to claim 6, characterized in that, The alkaline raw material is potassium hydroxide.

8. The method for alkali-activated persulfate humification of kitchen waste according to claim 1, characterized in that, In step (S2), the temperature is room temperature and the rotation speed is 300~700 r / min during the dosing process.

9. The method for alkali-activated persulfate humification of kitchen waste according to claim 1, characterized in that, In step (S2), during the activation reaction, the temperature is raised to 70°C and stirred continuously for more than 20 minutes.

10. The method for alkali-activated persulfate humification of kitchen waste according to claim 1, characterized in that, During the activation reaction, wait until the temperature rises to 70°C and stir continuously for 20 minutes.

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