A method for treating high-concentration printing and dyeing wastewater

Abstract

The application discloses a treatment method of high-concentration printing and dyeing wastewater, which comprises the following steps: uniformly mixing a reaction catalyst with the high-concentration printing and dyeing wastewater, then transferring to a hydrothermal reaction kettle (PTFE lining) to react, and obtaining a transparent aqueous solution and black precipitate at the bottom after the reaction is completed. It is detected that the removal rate of the dye is greater than 99% and the removal rate of the colority is greater than 95% after the hydrothermal reaction. The obtained clear brine solution after the hydrothermal reaction can be returned to preparation of dye liquor or used as a washing solution in a washing process in a textile dyeing and finishing process, and the obtained black solid is a dye-derived carbon material, which can be used in multiple fields such as electrochemical energy storage, catalysis and adsorption. The application essentially provides a method for direct treatment and resource utilization of high-concentration and high-salinity printing and dyeing wastewater, which can realize reuse of brine in wastewater and utilize waste heat of the wastewater, and has important significance for resource utilization of textile printing and dyeing industrial wastewater.

Description

Technical Field

[0001] This invention belongs to the field of water treatment technology and relates to a method for treating high-concentration dyeing and printing wastewater. Specifically, it relates to a method for treating and recycling high-concentration dyeing and printing wastewater based on hydrothermal technology, which utilizes waste heat to achieve targeted resource conversion of organic components in the wastewater and reuse of brine. Background Technology

[0002] In recent years, with the rapid development of industries such as textile printing and dyeing, the use of dyes has increased significantly, leading to a substantial rise in the discharge of printing and dyeing wastewater. This type of wastewater, containing high concentrations of dyes and dyeing auxiliaries such as NaCl and Na2SO4, exhibits poor biodegradability and is difficult to treat. Existing processes typically treat printing and dyeing wastewater in conjunction with wastewater from other processes to reduce biotoxicity and the stress of dyeing auxiliaries on microorganisms. However, the salt recovery rate is insufficient (<10%), resulting in osmotic pressure imbalance in the subsequent biological treatment system and a high biological treatment load. Furthermore, some dyes are only transferred rather than mineralized during treatment, posing a risk of secondary pollution. Dyes, as carbon-rich substances, can be used as carbon sources to convert into other valuable carbon-based compounds. Simultaneously, salt, as an important auxiliary agent in the printing and dyeing process, is used in large quantities. Salt recovery and utilization can not only alleviate the treatment cost of printing and dyeing wastewater but also mitigate resource waste and environmental harm. On the other hand, the effluent temperature of printing and dyeing wastewater is high (80-120℃), and existing processes do not utilize the waste heat, resulting in energy waste. Summary of the Invention

[0003] Purpose of the invention: This invention addresses the problems of high-concentration dyeing and printing wastewater being difficult to degrade and having poor biodegradability by providing a hydrothermal treatment method for high-concentration dyeing and printing wastewater. Through catalytic reactions, the method achieves directional cleavage of dye molecules and reconstruction of the carbon skeleton, enabling the resource utilization of waste dyes and the reuse of salt and water. The resulting dye-derived carbon materials have high electrochemical activity and can be applied to multiple fields such as electrochemical energy storage, catalysis, and adsorption. This method has a simple operation process, high decolorization efficiency, and can effectively utilize the waste heat of dyeing and printing wastewater.

[0004] Technical Solution: To solve the above-mentioned technical problems, the present invention provides a method for treating high-concentration dyeing and printing wastewater. The method includes the following steps: adding a catalyst to the high-concentration dyeing and printing wastewater to carry out a hydrothermal reaction; filtering to obtain a clear and transparent liquid and a dye-derived carbon material solid; and drying the obtained solid in a vacuum drying oven. The high-concentration dyeing and printing wastewater includes dye bath residue, comprehensive dyeing and printing wastewater, concentrated wastewater from the dye-salt membrane separation process, or an aqueous solution containing high-concentration dyes and salts. The dyes include one or more of acid dyes, basic dyes, reactive dyes, vat dyes, direct dyes, and sulfur dyes. The catalyst includes one or two of oxidizing catalysts or thermally stable porous catalysts.

[0005] The dye concentration is 1–20 g / L, and the salt concentration is 0.5–80 g / L.

[0006] The salts mentioned include sodium chloride, sodium sulfate, or other commonly used dyeing aids in the printing and dyeing process.

[0007] The oxidizing catalyst is one or more of sulfuric acid, persulfate, percarbonate or perchlorate.

[0008] The final concentration of the oxidizing catalyst is 0.01–2 mol / L.

[0009] The thermally stable porous catalyst is a metal-organic framework material, and the amount of the thermally stable porous catalyst used is 0.1-5 g / L.

[0010] The temperature of the hydrothermal reaction is 140–300°C.

[0011] The hydrothermal reaction takes 2 to 12 hours.

[0012] The present invention also includes the dye-derived carbon material solid obtained by the aforementioned processing method.

[0013] The present invention also includes the application of the dye-derived carbon material solid in electrochemical energy storage, catalysis or adsorption.

[0014] Beneficial Effects: Compared with existing technologies, this invention has the following significant advantages: First, this invention primarily targets high-concentration, high-salinity dyeing and printing wastewater, achieving both brine reuse and waste heat utilization. Second, the dye-derived carbon materials prepared by this invention have high non-metallic element doping levels and high specific capacitance, making them applicable to multiple fields such as electrochemical energy storage, catalysis, and adsorption. Finally, this method is simple to operate, highly feasible, and yields excellent results, possessing broad industrial application prospects. Attached Figure Description

[0015] Figure 1 The LC-MS spectrum of the simulated wastewater in Example 3 is shown in Figure 3 (a is the methylene blue standard solution, bd are the products of cleavage or condensation).

[0016] Figure 2 The LC-MS spectrum of the actual wastewater from Example 1 is shown below.

[0017] Figure 3 This is a comparison of the three-dimensional fluorescence spectra before and after the hydrothermal reaction in Example 1;

[0018] Figure 4 This is a comparison of the three-dimensional fluorescence spectra before and after the hydrothermal reaction in Example 3;

[0019] Figure 5 Fourier transform infrared spectrum of Example 1 (DK: solid obtained by drying the upper black liquid after high-speed centrifugation of the actual wastewater sample; DKC: hydrothermal carbon of the actual wastewater);

[0020] Figure 6 Fourier transform infrared spectrum of Example 3 (MB: methylene blue standard sample, MBC: methylene blue hydrothermal carbon);

[0021] Figure 7 The cyclic voltammetry curve of the methylene blue-derived carbon material in Example 3 is shown.

[0022] Figure 8 This is a rate performance diagram of the methylene blue-derived carbon material in Example 3; Detailed Implementation

[0023] The technical solution of the present invention will be described in detail below with reference to examples.

[0024] Example 1: Treatment of High-Concentration Actual Dyeing and Printing Wastewater

[0025] Dilute sulfuric acid was added to actual wastewater (composition as shown in Table 1) from a textile dyeing and printing enterprise to a final concentration of 0.2 mol / L, and NaCl to a final concentration of 18.7 g / L. The wastewater temperature was 120℃, and the reaction was carried out for 4 hours at 200℃ in a hydrothermal reactor (PTFE liner). After the reaction was complete, a clear and transparent liquid and dye-derived carbon material solids were obtained by filtration. The obtained solids were dried in a vacuum drying oven at 60℃ for 12 hours. Testing showed that the dye removal rate was 100% (TU-1901, double-beam UV-Vis spectrophotometer), the color removal rate was 99.5% (dilution method, HJ 1182—2021), and the solid yield was 3.32 kg / m³. 3 Wastewater. The organic elemental composition of the obtained black solid (dye-derived carbon material) was determined, and the results are shown in Table 2. As can be seen from Table 2, the main element of this material is carbon, followed by oxygen, sulfur, and nitrogen; the introduction of nitrogen and oxygen elements helps with charge storage, and the introduction of sulfur may enhance the conductivity of the material.

[0026] Table 1. Wastewater from a Textile Printing and Dyeing Enterprise

[0027]

[0028] Table 2 Organic element analysis of dye-derived carbon materials from actual wastewater

[0029]

[0030] Example 2: Simulated Treatment of High-Concentration Dyeing and Printing Wastewater

[0031] Preparation of simulated high-concentration dyeing and printing wastewater 1: Add methylene blue (basic dye, C10) to deionized water. 16 H 18 N3ClS (molecular weight 319.85) and NaCl were used to make the final concentration of methylene blue approximately 5 g / L and the final concentration of NaCl approximately 20 g / L, and then heated to 80 °C.

[0032] K₂S₂O₈ was added to simulated high-concentration dyeing and printing wastewater 1 at 80℃ until the final concentration was 0.02 mol / L. The mixture was reacted for 8 hours at 200℃ in a hydrothermal reactor (PTFE liner). After the reaction was complete, the mixture was filtered to obtain a clear, transparent liquid and dye-derived carbon material solids. The resulting solids were dried in a vacuum drying oven at 60℃ for 12 hours. Testing showed that the dye removal rate was 98.2%, the color removal rate was 97.5% (dilution ratio method), and the solid yield was 3.05 kg / m³. 3 Wastewater.

[0033] Example 3: Simulated Treatment of High-Concentration Dyeing and Printing Wastewater

[0034] Preparation of simulated high-concentration dyeing and printing wastewater 2: Add methylene blue (basic dye, C) to deionized water. 16 H 18 N3ClS (molecular weight 319.85) and NaCl were used to make the final concentration of methylene blue approximately 5 g / L and the final concentration of NaCl approximately 20 g / L, and then heated to 80 °C.

[0035] Sulfuric acid was added to simulated high-concentration dyeing and printing wastewater 2 at 80℃ to a concentration of 0.2 mol / L. The mixture was then hydrothermally reacted at 200℃ in a PTFE-lined hydrothermal reactor for 8 hours. After the reaction was complete, the mixture was filtered to obtain a clear, transparent liquid and dye-derived carbon material solids. The resulting solids were dried in a vacuum drying oven at 60℃ for 12 hours. The dye removal rate was 100%, the color removal rate was 100%, and the solid yield was 3.86 kg / m³. 3 Wastewater.

[0036] Example 4: Simulated Treatment of High-Concentration Dyeing and Printing Wastewater

[0037] K₂S₂O₈ to 0.01 mol / L and sulfuric acid to 2 mol / L were added to simulated high-concentration dyeing and printing wastewater 1 prepared in Example 2 at 80°C. The mixture was then hydrothermally reacted in a hydrothermal reactor (PTFE liner) at 200°C for 8 hours. After the reaction was complete, the mixture was filtered to obtain a clear and transparent liquid and a dye-derived carbon material solid. The resulting solid was dried in a vacuum drying oven at 60°C for 12 hours. The dye removal rate was 100%, the color removal rate was 99.6%, and the solid yield was 3.42 kg / m³. 3 Wastewater.

[0038] Example 5: Simulated Treatment of High-Concentration Dyeing and Printing Wastewater

[0039] Preparation of simulated high-concentration dyeing and printing wastewater 3: Add methylene blue (basic dye, C60000) to deionized water. 16 H 18 N3ClS (molecular weight 319.85) and NaCl were used to make the final concentration of methylene blue approximately 7 g / L and the final concentration of NaCl 30 g / L, and then heated to 80 °C.

[0040] The preparation process of MIL-100(Fe) is as follows: First, pyromellitic acid and sodium ascorbate are mixed under normal temperature and pressure to obtain a clear solution. Then, ferrous sulfate heptahydrate solution is added and stirred. Finally, sodium hydroxide is added. The mass ratio of pyromellitic acid, sodium ascorbate, ferrous sulfate heptahydrate and sodium hydroxide is 1.0:1.0:2.0:1.0. After the reaction at normal temperature and pressure, the product is centrifuged and washed repeatedly with ultrapure water 3-4 times. It is then placed in a refrigerator and frozen at -20-18℃ for 12-15 hours, and dried in a vacuum freeze dryer at -60-70℃ for 12-15 hours to form MIL-100(Fe) material.

[0041] MIL-100 (Fe) was added to simulated high-concentration dyeing and printing wastewater 3 until the final concentration was 0.05 g / L, and sulfuric acid was added until the final concentration was 0.5 mol / L. The mixture was reacted at 200°C in a hydrothermal reactor (PTFE lined) for 6 hours. After the reaction was complete, the mixture was filtered to obtain a clear and transparent liquid and a dye-derived carbon material solid. The obtained solid was dried in a vacuum drying oven at 60°C for 12 hours. The dye removal rate was 92.6%, the color removal rate was 95%, and the solid yield was 4.58 kg / m³. 3 Wastewater.

[0042] Example 6: Simulated Treatment of High-Concentration Dyeing and Printing Wastewater

[0043] Preparation of simulated high-concentration dyeing and printing wastewater 4: Neutral red (basic dye, C) is added to deionized water. 15 H 17 ClN4 (288.78) and NaCl were used to make the final concentration of neutral red approximately 5 g / L and the final concentration of NaCl 20 g / L, and then heated to 90 °C.

[0044] Sulfuric acid was added to simulated high-concentration dyeing and printing wastewater (4) at 90℃ to a final concentration of 0.5 mol / L. The mixture was reacted for 8 hours at 200℃ in a hydrothermal reactor (PTFE-lined). After the reaction was complete, the mixture was filtered to obtain a clear and transparent liquid and a dye-derived carbon material solid. The resulting solid was dried in a vacuum drying oven at 60℃ for 12 hours. The dye removal rate was 100%, the color removal rate was 99.5%, and the solid yield was 4.29 kg / m³. 3 Wastewater.

[0045] Example 7: Simulated Treatment of High-Concentration Dyeing and Printing Wastewater

[0046] Preparation of simulated high-concentration dyeing and printing wastewater 5: Add vat blue (vat dye C) to deionized water 28 H 14 N2O4 (442.42) and NaCl were used to make the final concentration of Reduced Blue approximately 3 g / L and the final concentration of NaCl 20 g / L, and then heated to 70 °C.

[0047] Sulfuric acid was added to simulated high-concentration dyeing and printing wastewater (5) at 70℃ to a final concentration of 0.5 mol / L. The mixture was reacted for 6 hours at 200℃ in a hydrothermal reactor (PTFE-lined). After the reaction was complete, the mixture was filtered to obtain a clear and transparent liquid and dye-derived carbon material solids. The resulting solids were then dried in a vacuum drying oven at 60℃ for 12 hours. The dye removal rate was 100%, the color removal rate was 100%, and the solid yield was 1.04 kg / m³. 3 Wastewater.

[0048] Example 8: Simulated Treatment of High-Concentration Dyeing and Printing Wastewater

[0049] Preparation of simulated high-concentration dyeing and printing wastewater 6: Add Acid Red (acid dye, C) to deionized water. 20 H 12 N2Na2O7S2,502.43) and disperse black (a mixed disperse dye) were mixed in a 1:1 mass ratio to a total concentration of 5 g / L. NaCl was then added to bring the final NaCl concentration to 20 g / L, and the mixture was heated to 100 °C.

[0050] K₂S₂O₈ was added to simulated high-concentration dyeing and printing wastewater (6) at 100℃ to a concentration of 0.05 mol / L. The mixture was reacted in a hydrothermal reactor (PTFE-lined) at 200℃ for 6 hours. After the reaction was complete, the mixture was filtered to obtain a clear and transparent liquid and a dye-derived carbon material solid. The resulting solid was dried in a vacuum drying oven at 60℃ for 12 hours. The dye removal rate was 99.6%, the color removal rate was 98.4%, and the solid yield was 1.97 kg / m³. 3 Wastewater.

[0051] Comparative Example 1

[0052] Preparation of simulated high-concentration dyeing and printing wastewater 9: Add methylene blue (basic dye, C) to deionized water. 16 H 18 N3ClS (molecular weight 319.85) was used to make the final concentration of methylene blue approximately 5 g / L, and the mixture was heated to 80 °C.

[0053] Simulated high-concentration dyeing and printing wastewater 9 was placed in a hydrothermal reactor (PTFE-lined) and reacted at 200℃ for 8 hours. After the reaction was complete, the mixture was filtered to obtain a blue-black liquid and dye-derived carbon material solids. The resulting solids were then dried in a vacuum drying oven at 60℃ for 12 hours. The dye removal rate was only 35.2%, and the solid yield was 1.78 kg / m³. 3 Wastewater.

[0054] Comparative Example 2

[0055] Phosphoric acid was added to simulated high-concentration dyeing and printing wastewater 1 prepared at 80°C in Example 3 until the final concentration was 0.2 mol / L. The mixture was reacted in a hydrothermal reactor at 200°C for 6 hours. After the reaction was complete, the mixture was filtered to obtain a brownish-black liquid and a dye-derived carbon material solid. The obtained solid was placed in a vacuum drying oven and dried at 60°C for 12 hours. The dye removal rate was only 40.2%.

[0056] Comparative Example 3

[0057] Potassium hydroxide was added to simulated high-concentration dyeing wastewater 1 prepared at 80°C in Example 3 until the final concentration was 0.2 mol / L. The mixture was reacted in a hydrothermal reactor at 200°C for 6 hours. After the reaction was complete, the solid and liquid were separated to obtain a blue-violet liquid and a dye-derived carbon material solid. The obtained solid was dried in a vacuum drying oven at 60°C for 12 hours. The dye removal rate was only 23.6%.

[0058] Comparative Example 4

[0059] Sulfuric acid was added to simulated high-concentration dyeing wastewater 1 prepared at 80°C in Example 3 until the final concentration was 0.2 mol / L. The mixture was reacted in a hydrothermal reactor at 160°C for 8 hours. After the reaction was complete, the solid and liquid were separated to obtain a blue-purple liquid. The dye removal rate was only 28%.

[0060] Application of characterization examples:

[0061] To investigate the decomposition and recombination behavior of dye molecules during hydrothermal treatment, the pyrolysis products of the wastewater treated in Examples 1-8 and Comparative Examples 1-4 were analyzed and identified by LC-MS. Examples 1 and 3 are used as examples for illustration. The test range was m / z 0-2000, and the test method was as follows: The pyrolysis products of the dye were identified by LC-MS analysis. 5 ml of the treated liquid sample was collected, centrifuged, and the supernatant was diluted 500 times before injection. 10 μL of the sample was injected into a C18 reversed-phase column (100 nm × 2.1 nm, 1.7 μm). Mobile phase A was 1% formic acid aqueous solution, and mobile phase B was methanol. The column temperature was maintained at 30 °C, and gradient elution was performed. The elution program is shown in Table 3.

[0062] Table 3 LC-MS Elution Procedure

[0063]

[0064] For the simulated wastewater in Example 3, the results are as follows: Figure 1 As shown, Figure 1 (a) shows a methylene blue standard solution with a single high-intensity ion peak at m / z = 284.1, indicating high purity. New material fragments appeared in the hydrothermal sample after hydrothermal treatment at different retention times. Figure 1 In (b), fragments with m / z = 193.1 and 277.0 were mainly detected. Figure 1 Fragments with m / z = 158.2 and 469.1 were detected in (c). Figure 1 (d) A macromolecular fragment with m / z = 636.3 was detected. The results indicate that during the hydrothermal reaction, the methylene blue molecule underwent degradation, condensation, and recombination reactions, forming low-molecular-weight fragments and high-molecular-weight adducts, providing a precursor basis for the subsequent formation of the carbon skeleton structure.

[0065] For the actual dyeing and printing wastewater system in Example 1, the wastewater contains various dyes and auxiliaries, with a complex composition, making it difficult to accurately deduce the specific molecular structure of each component. Therefore, only qualitative analysis was performed. Figure 2 As shown in (a), a major ion peak was detected in the original wastewater sample at m / z = 340.2. This peak has a high signal intensity and low background noise, suggesting it corresponds to the main dye precursor molecules present in the wastewater. After hydrothermal treatment, the organic matter in the wastewater underwent significant changes. Several new characteristic ion peaks were detected at different retention times, with m / z values ​​significantly higher than those in the original wastewater sample. Compared to the single small-molecule organic matter dominated by m / z = 340.2 before the reaction, several high-m / z products appeared in the system after the hydrothermal reaction, indicating that the organic components in the wastewater underwent complex degradation, recombination, and condensation processes. The above trend is consistent with the typical hydrothermal carbonization reaction pathway, where the original small-molecule dye first undergoes a series of reactions such as dehydration, oxidation, and polymerization under high-temperature acidic conditions, gradually generating large-molecule organic matter or water-soluble carbon precursors, providing an important structural basis for the subsequent preparation of carbon-based functional materials.

[0066] To further verify the changes in organic matter in the wastewater before and after the hydrothermal reaction, three-dimensional fluorescence spectroscopy (EEM) characterization was performed on Examples 1 and 3. The results are as follows: Figure 3 Figure 4 As shown.

[0067] For Example 1, from Figure 3 As can be clearly seen in Figure a, the content of highly efficient chromophores that can be excited and emit fluorescence in the wastewater system is extremely low, with virtually no fluorescent activity. After the hydrothermal reaction, as... Figure 3b. A new, distinct emission region appeared in the hydrothermal sample: the excitation wavelength (EX) was approximately 300-350 nm; the emission wavelength (EM) was approximately 400-500 nm. The new emission peak is in a shorter wavelength range, generally corresponding to substances like humic acids, indicating that the hydrothermal reaction promoted the reconstruction of the original organic components. The new fluorescence peak indicates that during the hydrothermal reaction, some small molecules or inorganic components in the wastewater underwent recombination, condensation, or carbonization precursor reactions, generating new organic molecules or carbon-like precursors with certain π-conjugation characteristics. The overall fluorescence intensity remains low, indicating that the content of luminescent active components in the reaction system is limited, but significant material transformation has occurred in the system before and after the reaction.

[0068] For Example 3, the test results are as follows: Figure 4 As shown in Figure a, the methylene blue standard solution exhibits a strong fluorescence emission peak in the excitation wavelength region of approximately 300 nm and the emission wavelength region of 650–700 nm, with a high overall fluorescence intensity, reflecting that the raw material is dominated by highly conjugated organic dye molecules. Simultaneously, auxiliary emission peaks were also observed near the excitation wavelength of 250–300 nm and the emission wavelength of 450–500 nm. In contrast, the hydrothermal fluid treated by the hydrothermal reaction, such as... Figure 4 b. Its three-dimensional fluorescence spectrum underwent significant changes. The main emission peak, originally located in the visible light region, essentially disappeared, replaced by a new fluorescence emission peak appearing in the excitation wavelength region of 270–300 nm and the emission wavelength region of 350–400 nm, with a significant decrease in overall fluorescence intensity. These changes indicate that during the hydrothermal reaction, the conjugated structure of the methylene blue molecule was disrupted, accompanied by the formation of low-molecular-weight, low-luminescent-activity organic fragments.

[0069] The results of the three-dimensional fluorescence spectroscopy analysis show that the method of the present invention can effectively achieve the degradation and recombination of high molecular organic matter in dye wastewater, providing a molecular-level foundation for subsequent carbon core enrichment and carbon material formation.

[0070] To investigate the composition and changes of functional groups in the electrode material, Fourier transform infrared (FTIR) spectroscopy was performed on the actual wastewater (DK) from Example 1 and the hydrothermally treated dye-derived carbon material solid (DKC). The wavenumber range was 4000 cm⁻¹. -1 Up to 500cm -1 The test results are as follows Figure 5 As shown, DK is at 3424.6cm -1 A broad peak appears at 1614.2 cm⁻¹, attributed to O–H or N–H stretching vibrations, indicating the presence of numerous hydroxyl or amino groups in the raw material; -1 A distinct C=N skeletal vibration peak was observed at this location, further confirming the presence of nitrogen. Additionally, at 1109.6 cm⁻¹... -1A CN / CS stretching vibration absorption peak appears nearby at 641.6 cm⁻¹. -1 The presence of a C–S stretching vibration peak at 3431.5 cm⁻¹ confirms the presence of sulfur in the wastewater. The hydrothermally treated DKC sample showed a peak at 3431.5 cm⁻¹. -1 and 3150.7cm -1 A certain O–H / N–H tensile vibration peak is still retained at 2349.3 cm⁻¹. -1 The characteristic absorption peak of the C≡N triple bond was observed, indicating the presence of nitrogen-rich organic groups in the sample. However, the absorption peaks of nitrogen-containing functional groups such as CN and C=N were significantly weakened, indicating that some nitrogen functional groups underwent degradation or structural reorganization during hydrothermal carbonization. Simultaneously, the characteristic CS peak in the low wavenumber region also weakened, but remained identifiable, suggesting that sulfur was partially retained and may have been stably embedded during the hydrothermal carbonization reaction to form a C–S bonded carbon framework structure. Combined with the elemental analysis results, the proportion of sulfur in the DKC material was higher than that of nitrogen, further confirming the formation and stable existence of carbon-sulfur bonds in hydrothermal carbon materials.

[0071] For Example 3, the Fourier transform infrared (FTIR) spectroscopy test results are as follows: Figure 6 As shown. From Figure 6 It can be seen that the MB sample is located at 3400–3160 cm⁻¹ -1 OH and NH tensile vibration peaks appeared within the range, at 2347 cm⁻¹. -1 A characteristic peak of C≡N triple bond appears at 1595.9 cm⁻¹. -1 The observation of C=N skeletal stretching vibrations at 1105 cm⁻¹ indicates that the methylene blue molecule is rich in nitrogen functional groups and hydroxyl structures. Simultaneously, at 1105 cm⁻¹... -1 and 643.8cm -1 The detection of CN and CS stretching vibration peaks nearby indicates the presence of sulfur and nitrogen-related functional groups in the raw material. After hydrothermal carbonization, the MBC sample still retains OH / NH and C≡N characteristic peaks at similar wavenumber positions, but at 1105 cm⁻¹... -1 and 643cm -1 The enhanced intensity and clear contours of the CN / CS and CS characteristic peaks indicate that the hydrothermal reaction promoted the stable doping of sulfur and nitrogen elements and the reconstruction of the carbon framework.

[0072] In summary, the results of FTIR analysis combined with elemental analysis show that the present invention can enrich and introduce sulfur- and nitrogen-containing functional groups such as CS bonds and CN bonds in situ from dyeing and printing wastewater through a simple hydrothermal carbonization process, thereby preparing carbon-rich, sulfur-rich, and nitrogen-rich functionalized carbon materials, providing an important structural basis for their application in electrochemical energy storage, catalysis, and pollutant adsorption.

[0073] The methylene blue-derived carbon material prepared in Example 3 was tested using a three-electrode system. The three-electrode system consisted of a working electrode (glassy carbon electrode), a counter electrode (platinum sheet), and a reference electrode (mercury / mercuric oxide) to analyze and calculate the electrochemical properties of the material. First, the active material (the dye-derived carbon material prepared in Example 3), acetylene black, and PTFE were mixed uniformly in a weight ratio of 8:1:1. Polytetrafluoroethylene (PTFE) was used as a binder, and anhydrous ethanol as a dispersant. The mixture was ground until it formed a viscous paste. 5 μL of this paste was uniformly drop-coated onto the surface of the pretreated glassy carbon electrode. After the paste was completely dry, it was tested in 6 M KOH solution. The results are as follows: Figure 7 As shown, from Figure 7 It can be seen that the electrode material prepared by this invention exhibits good electrochemical reversibility and excellent rate performance in the scan rate range of 10 mV / s to 200 mV / s. With increasing scan rate, the area of ​​the cyclic voltammetry curve expands while the morphology remains intact, indicating that the electrode material prepared by this invention possesses rapid ion migration and electron transport capabilities.

[0074] The specific capacitance value was calculated by integrating the CV curve and a rate performance spectrum was plotted. The results are as follows: Figure 8 As shown, the results indicate that when the scan rate is 10 mV / s, the specific capacitance of the material is 254.04 F / g. Under high scan rate conditions, the electrode material prepared by this invention can still maintain a high specific capacitance, which verifies the broad prospects of the electrode material prepared by this invention in high-power energy storage device applications.

Claims

1. A method for treating high-concentration dyeing and printing wastewater, characterized in that, The method includes the following steps: adding a catalyst to high-concentration dyeing and printing wastewater for hydrothermal reaction, filtering to obtain a clear and transparent liquid and a dye-derived carbon material solid, and drying the obtained solid in a vacuum drying oven. The high-concentration dyeing and printing wastewater includes dye bath residue, comprehensive dyeing and printing wastewater, or concentrated wastewater from the dye-salt membrane separation process. The dyes include one or more of acid dyes, basic dyes, reactive dyes, vat dyes, direct dyes, and sulfur dyes. The catalyst includes one or two of oxidizing catalysts or thermally stable porous catalysts. The oxidizing catalyst includes one or more of sulfuric acid, persulfate, percarbonate, or perchlorate. The thermally stable porous catalyst is a metal-organic framework material MIL-100(Fe). The temperature of the hydrothermal reaction is 200~300℃.

2. The method for treating high-concentration dyeing and printing wastewater according to claim 1, characterized in that, The dye concentration in the wastewater is 1~20 g / L, and the salt concentration is 0.5~80 g / L.

3. The method for treating high-concentration dyeing and printing wastewater according to claim 1, characterized in that, The final concentration of the oxidizing catalyst is 0.01~2 mol / L.

4. The method for treating high-concentration dyeing and printing wastewater according to claim 1, characterized in that, The amount of the thermally stable porous catalyst used is 0.1~5 g / L.

5. The method for treating high-concentration dyeing and printing wastewater according to claim 1, characterized in that, The hydrothermal reaction takes 2 to 12 hours.

6. The dye-derived carbon material solid obtained by the processing method according to any one of claims 1 to 5.

7. The application of the dye-derived carbon material solid of claim 6 in electrochemical energy storage, catalysis or adsorption.

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