Method for treating carbon fiber production wastewater based on mechanical force and chemical reaction cooperation

Abstract

The application discloses a method for treating carbon fiber production wastewater based on mechanical force and chemical reaction cooperation. The application utilizes a material containing a force-sensitive group, which, under the action of fluid mechanical force, breaks the internal weak covalent bond to generate high-activity free radicals, directly oxidizes and degrades organic pollutants or activates persulfate to generate stronger oxidizing free radicals to oxidize and degrade organic pollutants, so that the efficient and low-consumption removal of refractory organic matters in carbon fiber production wastewater is realized, and the method has a wide application prospect in the field of wastewater treatment in the carbon fiber industry.

Description

Technical Field

[0001] This invention belongs to the field of carbon fiber production wastewater treatment, specifically relating to a method for treating carbon fiber production wastewater based on the synergistic effect of mechanical force and chemical reaction. Background Technology

[0002] The production of acrylonitrile-based carbon fiber generates a large amount of high-concentration organic wastewater during the precursor fiber preparation stage. The main pollutants include residual acrylonitrile monomer, organic solvents such as dimethyl sulfoxide (DMSO) and dimethylacetamide (DMAC), as well as oligomers. This type of wastewater is characterized by high chemical oxygen demand (COD), strong biotoxicity, and low biodegradability (B / C ratio), making it a typical example of recalcitrant industrial wastewater.

[0003] Currently, the treatment of this type of wastewater mainly employs a combined process of "pretreatment + biological treatment." Pretreatment methods include coagulation sedimentation and advanced oxidation (such as the Fenton process and ozone oxidation). However, these methods have significant limitations: coagulation sedimentation has limited efficiency in removing dissolved organic matter; traditional advanced oxidation processes require continuous addition of large amounts of chemical reagents (such as hydrogen peroxide and ferrous sulfate), resulting in high operating costs and the potential generation of chemical sludge that causes secondary pollution; ozone oxidation equipment requires large investments, consumes a lot of energy, and is not sufficiently effective at oxidizing certain organic compounds (such as DMAC).

[0004] In recent years, advanced oxidation technologies based on persulfate activation have attracted attention, with the key being how to efficiently and economically generate sulfate radicals. Existing technologies mostly employ methods such as heat, light, and transition metal ions to activate persulfate, but these still suffer from problems such as high energy input and secondary pollution caused by metal ion dissolution. Therefore, developing a novel catalytic oxidation technology that requires no large amounts of external chemicals, consumes less energy, and is highly efficient is of great significance for the green and sustainable development of the carbon fiber industry. Summary of the Invention

[0005] The purpose of this invention is to provide a method for synergistic treatment of carbon fiber production wastewater based on mechanical force and chemical reaction. This invention utilizes materials containing force-sensitive groups, which, under the action of fluid mechanical forces (such as hydraulic shearing and ultrasonic cavitation), cause the internal weak covalent bonds to break, generating highly reactive free radicals. These free radicals directly oxidize and degrade organic pollutants or activate persulfates to generate even more potent oxidizing free radicals that oxidize and degrade organic pollutants, thereby achieving efficient and low-consumption removal of recalcitrant organic matter from carbon fiber production wastewater.

[0006] The technical solution for achieving the objective of this invention is as follows:

[0007] A method for synergistically treating carbon fiber production wastewater using mechanical force and chemical reaction includes the following steps:

[0008] (1) Introduce the carbon fiber production wastewater into the equalization tank to homogenize the water quality and quantity;

[0009] (2) The homogenized wastewater is pumped into a mechanical and chemical reaction synergistic catalytic reactor. The reactor is filled with catalytic packing material containing mechanosensitive groups. Under the action of pumping, stirring or ultrasound, the wastewater generates fluid shear force or cavitation effect, which causes the weak covalent bonds in the mechanosensitive groups to undergo mechanolytic cleavage. The generated free radicals directly attack the organic molecules in the wastewater and degrade them, thereby achieving the mineralization of organic pollutants. The mechanical and chemical reaction synergistic catalytic reactor is a device that can apply shear force or cavitation effect to the internal fluid.

[0010] (3) The treated effluent enters the subsequent treatment unit for final treatment, and is discharged or reused after meeting the standards.

[0011] Furthermore, in step (2), persulfate is added to the reactor. The weak covalent bonds in the tactic group undergo tactic homolytic cleavage, and the resulting free radicals react with the persulfate to further generate highly active oxide species, thereby achieving the mineralization of organic pollutants. The persulfate is permonosulfate (PMS) or perdisulfate (PDS).

[0012] Furthermore, in step (2), the material containing the serotonin (STP) or its derivatives, such as 8-carboxyspirotonin, organic polysulfide compounds, organic peroxides, etc., and the weak covalent bonds include, but are not limited to, CS bonds, SS bonds, peroxy bonds (-OO-), low bond energy organometallic bonds, etc.

[0013] Furthermore, in step (2), the catalytic filler is prepared by loading a material containing a force-sensitive group onto a porous support through chemical bonding or physical embedding. The porous support includes, but is not limited to, activated carbon, diatomaceous earth, porous ceramics, and polymer microspheres.

[0014] Furthermore, in step (2), the mechanical force and chemical reaction synergistic catalytic reactor is a hydraulic cavitation reactor, a high-speed stirred reactor, a vortex reactor, or a packed bed reactor coupled with an ultrasonic generator.

[0015] Furthermore, in step (2), the hydraulic residence time is 10 to 60 minutes and the reaction temperature range is 20 to 60°C.

[0016] Furthermore, in step (3), the subsequent treatment unit is a neutralization sedimentation tank or a biological treatment unit.

[0017] Compared with the prior art, the present invention has the following advantages:

[0018] (1) This invention is the first to apply the mechanochemical mechanism of generating free radicals by force-induced homolytic cleavage of weak bonds to advanced oxidation treatment of wastewater. It achieves efficient degradation of organic pollutants through the synergistic catalytic oxidation pathway of mechanical force and chemical reaction, avoiding the dependence of traditional processes on large amounts of chemical oxidants or external energy.

[0019] (2) This invention utilizes the hydraulic mechanical energy during the wastewater transportation and mixing process as the driving energy, resulting in high energy utilization. The free radicals generated by the material containing the mechanosensitive group under mechanical force are highly active and non-selective, which can rapidly degrade various characteristic pollutants such as acrylonitrile and DMAC in carbon fiber production wastewater, thereby improving the biodegradability of the wastewater.

[0020] (3) This invention significantly reduces the amount of chemical reagents (such as iron salts and hydrogen peroxide) added, thereby reducing the generation of chemical sludge and the risk of secondary pollution at the source. In addition, the catalytic packing is stable, with no problem of metal ion leaching, making it green and environmentally friendly, and the overall operating cost is significantly lower than that of traditional advanced oxidation processes. Detailed Implementation

[0021] The technical solution of the present invention will be further described in detail below with reference to specific embodiments.

[0022] The present invention discloses a method for synergistic treatment of carbon fiber production wastewater based on mechanical force and chemical reaction. The homogenized carbon fiber production wastewater is fed into a synergistic catalytic reactor containing a material with mechanosensitive groups. Persulfate may also be added if necessary. The reactor generates fluid shear force or cavitation effect by applying shear force (e.g., pumping, stirring) or cavitation (e.g., ultrasound) to the wastewater. This causes the weak covalent bonds in the mechanosensitive groups of the catalytic material to undergo mechanolytic cleavage, generating highly reactive primary free radicals such as sulfur-containing free radicals, carbon-centered free radicals, or peroxy free radicals in situ. These in-situ generated primary free radicals mainly achieve efficient mineralization of organic pollutants through the following two synergistic pathways: (1) Direct oxidation: Carbon-center free radicals and peroxide free radicals directly attack organic molecules such as acrylonitrile and organic solvents in wastewater through hydrogen abstraction, addition and other reactions, destroying their molecular structure and achieving preliminary degradation; (2) Catalytic oxidation: The above-mentioned primary free radicals (especially reducing carbon-center free radicals and sulfur-containing free radicals) provide electrons or transfer energy to the persulfate added to the wastewater, efficiently activating the persulfate and continuously generating sulfate free radicals (SO4•) with extremely strong oxidizing power. - The invention utilizes the above pathway to achieve the efficient conversion and utilization of mechanical energy into chemical energy without the need for large amounts of external chemical agents and energy. This includes secondary free radicals (•OH) that non-selectively attack organic pollutants, deeply mineralizing them into carbon dioxide and water.

[0023] Example 1

[0024] 1. Preparation of catalytic filler: A porous ceramic support is impregnated in a toluene solution of spirothiran, heated under reflux to allow for full adsorption, then the solvent is evaporated and cured at low temperature under an inert atmosphere to obtain a catalytic filler with spirothiran loaded on its surface.

[0025] 2. System Construction: The treatment system is constructed sequentially from an equalization tank, a booster pump, a hydraulic cavitation reactor, and a neutralization sedimentation tank. The hydraulic cavitation reactor is filled with the aforementioned catalytic packing material. The hydraulic cavitation reactor generates cavitation through a venturi tube structure.

[0026] 3. Wastewater Treatment: Wastewater generated during the precursor stage of a carbon fiber production company was taken. Its initial chemical oxygen demand (COD) was 8500 mg / L, and its pH value was 6.5~7.5. The specific treatment method was as follows:

[0027] (1) Introduce the carbon fiber production wastewater into the equalization tank to homogenize the water quality and quantity;

[0028] (2) The homogenized wastewater is pumped into a hydraulic cavitation reactor. The reactor is filled with catalytic packing material, and potassium persulfate composite salt is added at a mass ratio of 0.2:COD=0.2. The reactor is turned on, and the cavitation effect is generated through the Venturi tube structure. When the wastewater flows through the catalytic packing layer, strong fluid shear force and cavitation effect are generated, causing the weak CS bonds of the force-sensitive groups to break, generating free radicals and activating PMS, producing a large number of sulfate free radicals and hydroxyl free radicals, thus achieving deep mineralization of organic pollutants. The hydraulic residence time is 30 minutes. During the reaction, the temperature change of the system is monitored, and the system temperature is maintained at 25℃ through a heat exchange device.

[0029] (3) The treated effluent enters a neutralization sedimentation tank, where the pH is adjusted to neutral and the effluent is allowed to settle. The supernatant is taken to determine its COD and BOD5, and the B / C ratio (BOD5 / COD) is calculated to evaluate the improvement effect on the biodegradability of the wastewater.

[0030] The results showed that the COD of the treated effluent decreased to 1950 mg / L, the removal rate reached 77.1%, and the B / C ratio increased from 0.12 in the influent to 0.35.

[0031] Example 2

[0032] The same treatment system and catalytic packing as in Example 1 were used to treat the same batch of wastewater, with the hydraulic retention time controlled at 10 minutes and all other conditions remaining unchanged.

[0033] The results showed that the COD of the treated effluent decreased to 4200 mg / L, with a removal rate of 50.6%. Although the removal rate was lower than that of Example 1, it still showed a significant pretreatment effect under extremely short residence time, with the B / C ratio increasing to 0.25, indicating that the method of the present invention still has practical value in rapid treatment scenarios.

[0034] Example 3

[0035] Using the same system and catalytic packing as in Example 1, the same batch of wastewater was treated, with the hydraulic retention time controlled at 90 minutes and no PMS added.

[0036] The results showed that the COD of the treated effluent decreased to 2100 mg / L, with a removal rate of 75.3%, and the B / C ratio increased to 0.38. These results indicate that deep degradation can still be achieved by extending the reaction time, without the addition of external oxidants and relying solely on catalytic packing and mechanical force.

[0037] Example 4

[0038] Using the same treatment system and catalytic packing as in Example 1, the same batch of wastewater was treated, with the system temperature maintained at 20°C while other conditions remained unchanged.

[0039] The results showed that the COD of the effluent decreased to 2200 mg / L, with a removal rate of 74.1%. These results indicate that the treatment system can still operate effectively at normal and low temperatures.

[0040] Example 5

[0041] The same treatment system and catalytic packing as in Example 1 were used to treat the same batch of wastewater. The system temperature was maintained at 60°C during wastewater treatment, and PMS was not added. All other conditions remained unchanged.

[0042] The results showed that the COD of the effluent decreased to 1800 mg / L, with a removal rate of 78.8%. These results indicate that heating promotes the generation and mass transfer of free radicals, further improving the treatment efficiency. However, the system can already meet the needs of most scenarios under non-heating conditions (such as in Example 1).

[0043] Comparative Example 1

[0044] The same batch of wastewater was treated using the traditional Fenton method: the pH of the wastewater was adjusted to 3, FeSO4 and H2O2 (molar ratio 1:2) were added, and after reacting for 60 minutes, the pH was adjusted to 9 to precipitate.

[0045] The results showed that the final COD removal rate was 75%, but a large amount of iron sludge was generated (the amount of sludge was about 8% of the volume of the treated water), and the cost of the reagents was significantly higher than that of the example.

[0046] Comparative Example 2

[0047] The same system as in Example 1 was used, but the reactor was not filled with catalytic packing material. Wastewater was treated solely by hydraulic cavitation, with a hydraulic retention time of 30 minutes.

[0048] The results showed that the effluent COD was 6500 mg / L, the removal rate was only 23.5%, and the B / C ratio did not improve significantly. These results indicate that the effect of mechanical force alone is limited.

[0049] Comparative Example 3

[0050] Two types of catalytic packing materials were prepared using non-porous glass beads and ordinary quartz sand as carriers, respectively: (A) a catalytic packing material prepared by loading spirothiazane onto non-porous glass beads; and (B) a catalytic packing material prepared by loading spirothiazane onto ordinary quartz sand. Wastewater was treated under the same conditions as in Example 1.

[0051] The results showed that the COD of the effluent from group A was 5100 mg / L, with a removal rate of 40%; while the COD of the effluent from group B was 7200 mg / L, with a removal rate of 15.3%. These results indicate that porous supports are crucial for the dispersion, immobilization, and mass transfer of materials containing mechanosensitive groups, directly affecting catalytic efficiency.

[0052] Comparative Example 4

[0053] Take the same batch of carbon fiber production wastewater as in Example 1, place it in a beaker, add the same catalytic packing as in Example 1, and stir at low speed of 100 rpm on a magnetic stirrer. Continue the reaction at 25°C for 30 minutes, while simultaneously adding potassium persulfate composite salt at a mass ratio of:COD=0.2. After the reaction is complete, let it stand, take the supernatant to determine the COD, and calculate the B / C ratio.

[0054] The results showed that the COD of the treated effluent was approximately 7800 mg / L, with a COD removal rate of only 8.2%. The B / C ratio increased slightly from 0.12 in the influent to 0.14, showing almost no change. These results indicate that low-speed stirring can only maintain a solid-liquid mixture state and does not generate significant hydraulic cavitation or high shear forces. Under the condition of adding only catalytic packing and persulfate but without applying mechanical activation, the mechanolytic cracking reaction of the CS bond in spirothiran cannot be triggered. Therefore, it is impossible to effectively generate carbon center free radicals or sulfate free radicals. Relying solely on the limited surface adsorption of the material itself and the natural decomposition of persulfate, the degradation effect on organic matter in wastewater is negligible.

Claims

1. A method for synergistic treatment of carbon fiber production wastewater based on mechanical force and chemical reaction, characterized in that, Includes the following steps: (1) Introduce the carbon fiber production wastewater into the equalization tank to homogenize the water quality and quantity; (2) The homogenized wastewater is pumped into a mechanical and chemical reaction synergistic catalytic reactor. The reactor is filled with catalytic packing material containing mechanosensitive groups. Under the action of pumping, stirring or ultrasound, the wastewater generates fluid shear force or cavitation effect, which causes the weak covalent bonds in the mechanosensitive groups to undergo mechanolytic cleavage. The generated free radicals directly attack the organic molecules in the wastewater and degrade them, thereby achieving the mineralization of organic pollutants. The mechanical and chemical reaction synergistic catalytic reactor is a device that can apply shear force or cavitation effect to the internal fluid. (3) The treated effluent enters the subsequent treatment unit for final treatment, and is discharged or reused after meeting the standards.

2. The method according to claim 1, characterized in that, In step (2), persulfate is also added to the reactor. The weak covalent bonds in the mechanosensitive group undergo mechanolytic cleavage, and the resulting free radicals react with the persulfate to further generate highly active oxide species, thereby achieving the mineralization of organic pollutants.

3. The method according to claim 2, characterized in that, Persulfate is either permonosulfate or perdisulfate.

4. The method according to claim 1, characterized in that, In step (2), the material containing the sensitizing group is spirothian or its derivatives, organic polysulfide compounds or organic peroxides.

5. The method according to claim 1, characterized in that, In step (2), the weak covalent bond is a CS bond, an SS bond, a peroxy bond, or a low-energy organometallic bond.

6. The method according to claim 1, characterized in that, In step (2), the catalytic packing is prepared by loading a material containing a mechanosensitive group onto a porous support through chemical bonding or physical embedding.

7. The method according to claim 6, characterized in that, The porous carrier is activated carbon, diatomaceous earth, porous ceramics, or polymer microspheres.

8. The method according to claim 1, characterized in that, In step (2), the synergistic catalytic reactor of mechanical force and chemical reaction is a hydraulic cavitation reactor, a high-speed stirred reactor, a vortex reactor, or a packed bed reactor coupled with an ultrasonic generator.

9. The method according to claim 1, characterized in that, In step (2), the hydraulic residence time is 10 to 60 minutes and the reaction temperature range is 20 to 60°C.

10. The method according to claim 1, characterized in that, In step (3), the subsequent treatment unit is a neutralization sedimentation tank or a biological treatment unit.