Method and device for treating wastewater containing high concentrations of chlorobenzene, acetone

Abstract

The present application belongs to the technical field of wastewater treatment, and particularly relates to a wastewater treatment method and device containing high-concentration chlorobenzene and acetone. The wastewater first enters a homogenizing tank for buffering and homogenizing, and then enters a first-stage oxidation tank from the bottom, an oxidizing agent is added in the first-stage oxidation tank, and an ultraviolet reactor is used for oxidation cycle treatment, so that chlorobenzene is rapidly degraded into non-volatile intermediate products through oxidation reaction. Acetone and water form azeotrope in the first-stage oxidation tank, and are discharged to a condensing tank through an upper pipeline of the first-stage oxidation tank, and acetone gas is condensed into liquid in the condensing tank. On the basis of the existing photocatalytic oxidation process, only the oxidizing agent is added in the first-stage oxidation tank, chlorobenzene is rapidly photolyzed into non-volatile intermediate products, and at the same time, by controlling the reaction temperature, acetone and water azeotrope is formed in the first-stage oxidation tank, so that chlorobenzene and acetone in the wastewater are separated.

Description

Technical Field

[0001] This invention belongs to the field of wastewater treatment technology, specifically relating to a method and apparatus for treating wastewater containing high concentrations of chlorobenzene and acetone. Background Technology

[0002] Chlorobenzene and acetone are widely used as organic solvents in the rubber industry, which in turn produces wastewater containing high concentrations of chlorobenzene and acetone. This wastewater is one of the most difficult to treat industrial wastewaters, characterized by high biotoxicity. Conventional biological treatment processes are insufficient to treat it to the required standards, necessitating additional oxidation pretreatment measures.

[0003] Photocatalytic oxidation is an advanced oxidation technology that is highly effective in treating chlorobenzene and acetone. Under the action of ultraviolet light and a catalyst, characteristic pollutants in wastewater absorb photon energy to form high-energy excited-state molecules. The oxidant hydrogen peroxide is decomposed into highly reactive hydroxyl radicals, and the two undergo an oxidative decomposition reaction, thereby completely degrading the organic pollutants in the wastewater.

[0004] Compared to chlorobenzene, which is insoluble in water, acetone is a readily soluble organic compound. In existing photocatalytic oxidation processes, the oxidation reaction time is longer due to the varying solubility of the acetone, requiring larger dosages of oxidant and catalyst, resulting in higher operating costs. Separating chlorobenzene and acetone from wastewater for separate treatment can effectively improve oxidation efficiency. Furthermore, acetone is an excellent carbon source for biological nitrogen removal, and the separated acetone can be recycled.

[0005] Patent CN 105819588 A discloses a method for reducing pollutant emissions during phenol-acetone production, comprising at least one of the following steps: (A) collecting phenol-containing wastewater from the phenol-acetone production unit, adjusting the pH to acidic, and extracting and recovering phenols from the wastewater using cumene as an extractant; (B) optimizing the acetone refining tower process to reduce the acetone content in the bottom wastewater; (C) treating the bottom wastewater from the acetone refining tower using a selective permeation membrane to recover alkali; (D) after neutralizing the bottom wastewater from the acetone refining tower following alkali recovery in step (C), mixing it with the condensate from the top of the cumene oxidation tower for detoxification treatment; (E) performing oil separation treatment on the total wastewater from the phenol-acetone unit to recover organic matter including hydrocarbons; (F) performing biological treatment, coagulation sedimentation treatment, and enhanced degradation treatment on the wastewater after oil separation treatment. This method has the function of recovering acetone, but it adds an acetone refining unit, increases the production process and energy consumption, and is not suitable for situations where the wastewater also contains volatile substances such as chlorobenzene.

[0006] Patent CN 115536187 A discloses a method and apparatus for treating chlorobenzene-containing wastewater. The wastewater first enters a homogenizing tank for buffering, then mixes with the effluent from the bottom of an oxidation tank and the chlorobenzene exhaust gas from the top of the homogenizing tank before entering a UV generator for oxidation and recycling. The effluent from the top of the oxidation tank, after pH adjustment, enters a disc filter where solid catalyst particles are trapped. The filter effluent is then pH-adjusted again to a monitoring tank before being discharged. The backwash water from the disc filter contains catalyst, which is collected in a catalyst tank for catalyst recovery. The recovered catalyst is then injected into the oxidation tank via a reagent pump. The exhaust gas is discharged from the top of the oxidation tank after meeting emission standards. This invention achieves the oxidative degradation of chlorobenzene in wastewater using a UV generator. However, when using this method to simultaneously treat acetone contained in the wastewater, not only does the dosage of oxidant and catalyst increase, but the acetone is also not recovered.

[0007] In summary, the following technical problems exist in using existing photocatalytic oxidation technology to treat wastewater containing high concentrations of chlorobenzene and acetone:

[0008] 1. Chlorobenzene and acetone in the wastewater were not separated, the dosage of oxidant and catalyst was large, the oxidation reaction time was long due to different solubilities, and the operating cost was high.

[0009] 2. Acetone was not effectively recycled and utilized. Summary of the Invention

[0010] To address the shortcomings of existing technologies, the present invention aims to provide a wastewater treatment method containing high concentrations of chlorobenzene and acetone. Based on existing photocatalytic oxidation processes, only an oxidant is added to the primary oxidation tank, where chlorobenzene is rapidly photolyzed into non-volatile intermediate products. Simultaneously, by controlling the reaction temperature, an acetone-water azeotrope is formed in the primary oxidation tank, thereby achieving the separation of chlorobenzene and acetone from the wastewater.

[0011] Another objective of this invention is to provide a wastewater treatment device containing high concentrations of chlorobenzene and acetone. The effluent from the primary oxidation tank enters the secondary catalytic oxidation tank, where oxidants and catalysts are added for deep oxidation of chlorobenzene, effectively improving the efficiency of photocatalytic oxidation and ensuring the effect of ultraviolet oxidation.

[0012] The technical solution adopted in this invention is:

[0013] The wastewater treatment method containing high concentrations of chlorobenzene and acetone includes the following steps:

[0014] (1) Homogenization: Wastewater enters the homogenizing tank, and an outlet is set at the bottom of the homogenizing tank;

[0015] (2) Primary oxidation: Water from the bottom of the homogenizing tank enters the primary oxidation tank. An oxidant is added to the primary oxidation tank to carry out an ultraviolet oxidation reaction. Acetone and water form an azeotrope. Chlorobenzene is decomposed into non-volatile intermediate products through an ultraviolet reactor, creating conditions for deep oxidation treatment in the secondary photocatalytic oxidation tank.

[0016] (3) Acetone recovery: The gas phase generated in the primary oxidation tank is sent to the condenser by the induced draft fan. The non-condensable gas in the upper part of the condenser is discharged to the tail gas treatment device for treatment, and the acetone condensate in the lower part is recovered and reused.

[0017] (4) Secondary oxidation: The effluent from the middle of the primary oxidation tank enters the secondary catalytic oxidation tank. Acid is added to the secondary catalytic oxidation tank to adjust the pH, followed by the addition of catalyst and oxidant. The effluent from the bottom of the secondary catalytic oxidation tank enters the ultraviolet reactor, is irradiated by ultraviolet light, and then returns to the secondary catalytic oxidation tank for circulation, thus deeply oxidizing and decomposing chlorobenzene and its oxidation intermediates. One-fifth of the effluent from the secondary oxidation tank is returned to the primary oxidation tank to dilute the concentration of benzoquinone pollutants, an oxidation intermediate, and to ensure the photocatalytic oxidation effect of the primary oxidation tank.

[0018] (5) Sedimentation: Add liquid alkali to 4 / 5 of the effluent from the secondary catalytic oxidation tank to adjust the pH value to neutral, and then enter the sedimentation tank. The catalyst produces a flocculation effect to settle the suspended organic matter here.

[0019] (6) Drainage: The effluent from the sedimentation tank enters the monitoring tank, and the effluent that meets the test standards is discharged.

[0020] The hydraulic residence time in step (1) is 2 to 6 hours.

[0021] The material of the primary oxidation tank in step (2) is an anti-corrosion lining material; the hydraulic retention time is 1 to 2 hours based on the influent; the oxidant is a hydrogen peroxide solution, and the mass ratio of the oxidant dosage (calculated as pure hydrogen peroxide) to the influent COD is (0.5:1) to (1:1).

[0022] The reaction temperature of the primary oxidation tank in step (2) is 55-60℃.

[0023] The ultraviolet reactor in step (2) contains a reaction tube, which is a medium-pressure ultraviolet light reaction tube. The ultraviolet reactor includes a quartz sleeve area (containing a medium-pressure ultraviolet lamp) and a wastewater area, wherein the residence time of the primary oxidation wastewater is 5-40 seconds. The ultraviolet reactor generates high heat during operation, and a cooler is used to control the temperature in the primary oxidation tank to prevent excessive temperature and decomposition of hydrogen peroxide. Controlling the temperature in the primary oxidation tank also helps to reach the boiling point of acetone.

[0024] In step (4), the hydraulic retention time of the secondary catalytic oxidation tank is 1-2 h; the oxidant is hydrogen peroxide solution, and the mass ratio of the oxidant dosage (calculated as pure hydrogen peroxide) to the COD of the influent is (1-2):1; the acid solution is either sulfuric acid solution or hydrochloric acid solution, and the amount added is controlled to control the pH value to 2.3-3.0; the reaction temperature is 45-55℃; the catalyst is ferric chloride, and the amount of catalyst added (calculated as total iron) is 50-125 mg / L, and the amount added is calculated as total iron; the water retention time in the reaction tube of the ultraviolet reactor is 5-20 s.

[0025] In step (5), the hydraulic residence time is 0.5 to 1.5 hours; the alkaline solution is either sodium hydroxide solution or potassium hydroxide solution, and the pH value of the regulating tank is controlled to be 7.0 to 8.5; in step (6), the hydraulic residence time is 1 to 3 hours.

[0026] The wastewater treatment device containing high concentrations of chlorobenzene and acetone includes a homogenizing tank, which is connected to a secondary catalytic oxidation tank via a primary oxidation tank. The secondary catalytic oxidation tank is connected to a monitoring tank via a sedimentation tank. An inlet pipe connects the homogenizing tank to the primary oxidation tank. An outlet pipe connects the secondary catalytic oxidation tank to the sedimentation tank. The outlet pipe is connected to the inlet pipe via a reflux pump. A secondary effluent reflux pipe is provided between the outlet pipe and the reflux pump. An outlet reflux pump pipe is provided between the reflux pump and the inlet pipe.

[0027] The primary oxidation tank is connected to a condenser tank via an induced draft fan. The condenser tank is equipped with a condenser coil. A primary ultraviolet reactor is connected to the primary oxidation tank, and a secondary ultraviolet reactor is connected to the secondary catalytic oxidation tank.

[0028] The primary oxidation tank is connected to a primary oxidation tank feed pipe, the secondary catalytic oxidation tank is connected to a secondary catalytic oxidation tank feed pipe, the sedimentation tank is connected to a sedimentation tank feed pipe, the sedimentation tank is connected to a sedimentation tank slag discharge pipe, the monitoring tank is connected to a drainage pipe, and a cooler is installed inside the primary oxidation tank.

[0029] Wastewater first enters a homogenizing tank for buffering and homogenization, then flows from the bottom into the primary oxidation tank. In the primary oxidation tank, an oxidant is added, and an ultraviolet reactor performs oxidation and circulation treatment. Chlorobenzene undergoes an oxidation reaction here, rapidly degrading into non-volatile intermediate products. Acetone and water form an azeotrope in the primary oxidation tank, which is discharged to a condenser tank via an upper pipeline. Acetone gas condenses into liquid in the condenser tank. Non-condensable gases from the upper part of the condenser tank are discharged to the tail gas treatment unit, while the condensate from the lower part is discharged to the biological treatment process as a supplementary carbon source. The effluent from the primary oxidation tank enters the secondary catalytic oxidation tank from the bottom, where the pH is adjusted. Oxidant and catalyst are added here, and an ultraviolet reactor performs oxidation and circulation treatment, achieving deep degradation of chlorobenzene. The effluent from the secondary catalytic oxidation tank, after pH adjustment, enters the secondary sedimentation tank. The effluent from the secondary sedimentation tank is then discharged after meeting standards through a monitoring tank.

[0030] The principle of this invention is as follows:

[0031] Traditional photocatalytic oxidation is divided into two parts. The first part involves the functional photolysis of chlorobenzene, where the secondary photolysis products of chlorobenzene are oxidized and preliminarily decomposed, and acetone is separated for recovery. The second part involves the deep decomposition of chlorobenzene to achieve compliant discharge, while a portion is recycled to dilute the concentration of the brown intermediate oxidation products in the wastewater from the first part, ensuring the effectiveness of the ultraviolet oxidation in the first part.

[0032] Part 1: Hydrogen peroxide is added as an oxidant to the primary photocatalytic oxidation tank. Upon irradiation with ultraviolet light, the hydrogen peroxide generates hydroxyl radicals. Chlorobenzene in the wastewater, under the combined action of ultraviolet light and hydroxyl radicals, forms non-volatile intermediate products, such as various chlorophenol isomers and benzoquinone mixtures. By controlling the reaction temperature in the primary oxidation tank to 55–60°C, acetone and water form an azeotrope, and hydrogen peroxide decomposes to produce a large amount of gas, carrying acetone at its boiling point to a condenser. This achieves the separation of chlorobenzene and acetone from the wastewater. The acetone is then condensed and recovered in the condenser, achieving acetone recycling.

[0033] Part Two: Oxidant and catalyst are added to the secondary oxidation tank. Since acetone has already been separated in the primary oxidation tank, the secondary oxidation tank is only used for the deep degradation of various chlorophenol isomers and intermediate products of benzoquinone mixtures. This effectively improves the efficiency of photocatalytic oxidation and saves on the amount of oxidant and catalyst used. Benzoquinone products are yellow-brown in wastewater, causing the wastewater to darken and affecting the photocatalytic reaction effect. Part of the effluent from the secondary oxidation tank is recycled back to the primary oxidation tank to dilute the concentration of benzoquinone pollutants and ensure the photocatalytic oxidation effect of the primary oxidation tank.

[0034] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0035] (1) Based on the existing photocatalytic oxidation process, the present invention only adds oxidant to the primary oxidation tank, where chlorobenzene is rapidly photolyzed into non-volatile intermediate products. At the same time, by controlling the reaction temperature, acetone and water azeotrope is formed in the primary oxidation tank, thereby achieving the separation of chlorobenzene and acetone in wastewater.

[0036] (2) After chlorobenzene is oxidized by light in the primary oxidation tank, it forms an excited intermediate product, which creates conditions for deep oxidation treatment in the secondary photocatalytic oxidation tank.

[0037] (3) The effluent from the primary oxidation tank enters the secondary catalytic oxidation tank, where oxidants and catalysts are added. This is used only for the deep oxidation of chlorobenzene, which effectively improves the efficiency of photocatalytic oxidation and ensures the oxidation effect of ultraviolet light.

[0038] (4) Acetone in the wastewater forms an azeotrope with water in the primary oxidation tank, and is then condensed and recovered in the condenser, thus realizing the recycling of acetone.

[0039] (5) Part of the effluent from the secondary oxidation tank is recycled back to the primary oxidation tank to dilute the concentration of benzoquinone pollutants, thereby ensuring the photocatalytic oxidation effect of the primary oxidation tank; thus achieving the purpose of waste reuse. Attached Figure Description

[0040] Figure 1 This is a schematic diagram of the wastewater treatment device containing high concentrations of chlorobenzene and acetone according to the present invention.

[0041] In the diagram: 1. Homogenizing tank; 2. Primary oxidation tank; 3. Secondary catalytic oxidation tank; 4. Sedimentation tank; 5. Monitoring tank; 6. Condensation tank; 7. Condensation coil; 8. Primary UV reactor; 9. Secondary UV reactor; 10. Cooler; 11. Pipeline inlet to primary oxidation tank; 12. Pipeline outlet to secondary catalytic oxidation tank; 13. Secondary effluent return pipeline; 14. Return pump; 15. Pipeline outlet from return pump; 16. Drainage pipeline; 17. Feeding pipeline for primary oxidation tank; 18. Feeding pipeline for secondary catalytic oxidation tank; 19. Feeding pipeline for sedimentation tank; 20. Slag discharge pipeline for sedimentation tank. Detailed Implementation

[0042] The present invention will be further described below with reference to the embodiments, but these embodiments do not limit the implementation of the present invention.

[0043] The analytical testing methods and standards are shown in Table 1:

[0044] Table 1 Analysis and Testing Methods and Standards

[0045]

[0046] Note: B / C is the ratio of BOD to COD.

[0047] A wastewater treatment device containing high concentrations of chlorobenzene and acetone includes a homogenizing tank 1. The homogenizing tank 1 is connected to a primary oxidation tank 2 and a secondary catalytic oxidation tank 3 via a primary oxidation tank 2. The secondary catalytic oxidation tank 3 is connected to a monitoring tank 5 via a sedimentation tank 4. An inlet pipe 11 connects the homogenizing tank 1 to the primary oxidation tank 2. An outlet pipe 12 connects the secondary catalytic oxidation tank 3 to the sedimentation tank 4. The outlet pipe 12 is connected to the inlet pipe 11 via a reflux pump 14. A secondary effluent reflux pipe 13 connects the outlet pipe 12 to the reflux pump 14. An outlet reflux pump pipe 15 connects the reflux pump 14 to the inlet pipe 11. The primary oxidation tank 2 is connected to a condenser tank 6 via an induced draft fan. The condenser tank 6 contains condenser coils 7. A primary ultraviolet reactor 8 is connected to the primary oxidation tank 2, and a secondary ultraviolet reactor 9 is connected to the secondary catalytic oxidation tank 3. The primary oxidation tank 2 is connected to a primary oxidation tank feed pipe 17, the secondary catalytic oxidation tank 3 is connected to a secondary catalytic oxidation tank feed pipe 18, the sedimentation tank 4 is connected to a sedimentation tank feed pipe 19, the sedimentation tank 4 is connected to a sedimentation tank slag discharge pipe 20 below the sedimentation tank 4, the monitoring tank 5 is connected to a drainage pipe 16, and the primary oxidation tank 2 is equipped with a cooler 10.

[0048] The following examples all use the wastewater treatment device containing high concentrations of chlorobenzene and acetone described above to treat the wastewater.

[0049] Example 1

[0050] Special rubber wastewater contains chlorobenzene at a concentration of 500–700 mg / L, acetone at a concentration of 200–300 mg / L, and COD at a concentration of 1300 mg / L.

[0051] The above wastewater treatment methods include the following steps:

[0052] (1) Homogenization: Wastewater enters a homogenizing tank with an outlet at the bottom. The hydraulic retention time is 6.0 h to homogenize the mixed wastewater.

[0053] (2) Primary oxidation: Water from the bottom of the homogenizing tank enters the primary oxidation tank. An oxidant is added to the primary oxidation tank to initiate an ultraviolet (UV) oxidation reaction. Acetone and water form an azeotrope. Chlorobenzene is decomposed into non-volatile intermediate products in the UV reactor, creating conditions for deep oxidation treatment in the secondary photocatalytic oxidation tank. The preferred ratio of hydrogen peroxide solution dosage (based on pure hydrogen peroxide) to influent COD is 1:1, the hydraulic retention time is 1.0 h, and the reaction temperature is 60℃. The UV reactor has a UV power of 500 W / m². 3 The wastewater area in the reaction tube has a hydraulic retention time of 40 seconds;

[0054] (3) Acetone recovery: The gas phase generated in the primary oxidation tank is sent to the condenser by the induced draft fan. The non-condensable gas in the upper part of the condenser is discharged to the tail gas treatment device for treatment, and the acetone condensate in the lower part is recovered and reused; the hydraulic retention time is 3.0h.

[0055] (4) Secondary oxidation: The effluent from the middle of the primary oxidation tank enters the secondary catalytic oxidation tank. Dilute hydrochloric acid solution is added to the secondary catalytic oxidation tank to adjust the pH to 2.3, followed by the addition of ferric chloride solution and hydrogen peroxide solution. The preferred ratio of hydrogen peroxide solution dosage (based on pure hydrogen peroxide) to influent COD is 2:1. The hydraulic retention time is 1.0 h, the reaction temperature is 55℃, and the total iron concentration in the oxidation tank is 125 mg / L. The effluent from the lower part of the secondary catalytic oxidation tank enters the ultraviolet reactor for ultraviolet irradiation, and then returns to the secondary catalytic oxidation tank for circulation, deeply oxidizing and decomposing chlorobenzene and its oxidation intermediates. The power of the ultraviolet reactor is 1000 W / m². 3 The wastewater area in the reaction tube has a hydraulic retention time of 20 seconds. One-fifth of the effluent from the secondary oxidation tank is returned to the primary oxidation tank.

[0056] (5) Sedimentation: 4 / 5 of the effluent from the secondary catalytic oxidation tank is added with sodium hydroxide solution to adjust the pH value to 8.5 and then enters the sedimentation tank. The catalyst produces a flocculation effect, which settles the suspended organic matter here; the hydraulic retention time is 1.5h.

[0057] (6) Drainage: The effluent from the sedimentation tank enters the monitoring tank, with a hydraulic retention time of 3.0h and a pH value of 9.

[0058] Test results: The chlorobenzene content in the effluent from the monitoring tank was <0.2 mg / L, the acetone content was 3-8 mg / L, and the COD was 26.9 mg / L. The chlorobenzene and COD contents both met the enterprise's emission requirements. The acetone recovered from condensation was used to prepare a 50 mg / L solution, and the B / C ratio was measured to be 0.41, which can be used as a high-quality carbon source for the biological denitrification process.

[0059] Example 2

[0060] Special rubber wastewater contains chlorobenzene at a concentration of 90–140 mg / L, acetone at a concentration of 50–80 mg / L, and COD at 320 mg / L.

[0061] The above wastewater treatment methods include the following steps:

[0062] (1) Homogenization: Wastewater enters a homogenizing tank with an outlet at the bottom. The hydraulic retention time is 2.0h, and the wastewater is homogenized.

[0063] (2) Primary oxidation: Water from the bottom of the homogenizing tank enters the primary oxidation tank. An oxidant is added to the primary oxidation tank to initiate an ultraviolet (UV) oxidation reaction. Acetone and water form an azeotrope. Chlorobenzene is decomposed into non-volatile intermediate products in the UV reactor, creating conditions for deep oxidation treatment in the secondary photocatalytic oxidation tank. The preferred ratio of hydrogen peroxide solution dosage (based on pure hydrogen peroxide) to influent COD is 0.5:1, the hydraulic retention time is 2.0 h, and the reaction temperature is 55℃. The UV reactor has a UV power of 500 W / m². 3 The sewage area in the reaction tube has a hydraulic retention time of 5 seconds;

[0064] (3) Acetone recovery: The gas phase generated in the primary oxidation tank is sent to the condenser by the induced draft fan. The non-condensable gas in the upper part of the condenser is discharged to the tail gas treatment device for treatment, and the acetone condensate in the lower part is recovered and reused; the hydraulic retention time is 1.0h.

[0065] (4) Secondary oxidation: The effluent from the middle of the primary oxidation tank enters the secondary catalytic oxidation tank. Dilute hydrochloric acid solution is added to the secondary catalytic oxidation tank to adjust the pH to 3.0, followed by the addition of ferric chloride solution and hydrogen peroxide solution. The preferred ratio of hydrogen peroxide solution dosage (based on pure hydrogen peroxide) to influent COD is 1:1. The hydraulic retention time is 2.0 h, the reaction temperature is 45℃, and the total iron concentration in the oxidation tank is 50 mg / L. The effluent from the lower part of the secondary catalytic oxidation tank enters the ultraviolet reactor for ultraviolet irradiation, and then returns to the secondary catalytic oxidation tank for circulation, deeply oxidizing and decomposing chlorobenzene and its oxidation intermediates. Ultraviolet reactor: Ultraviolet light power is 1000 W / m². 3 The wastewater area in the reaction tube has a hydraulic retention time of 5 seconds. One-fifth of the effluent from the secondary oxidation tank is returned to the primary oxidation tank.

[0066] (5) Sedimentation: 4 / 5 of the effluent from the secondary catalytic oxidation tank is added with sodium hydroxide solution to adjust the pH value to 7 and then enters the sedimentation tank. The catalyst produces a flocculation effect, which settles the suspended organic matter here; the hydraulic retention time is 0.5h.

[0067] (6) Drainage: The effluent from the sedimentation tank enters the monitoring tank, with a hydraulic retention time of 1.0 h and a pH value of 6.

[0068] Test results: The chlorobenzene content in the effluent from the monitoring tank was <0.2 mg / L, the acetone content was 2-6 mg / L, and the COD was 27.6 mg / L. The chlorobenzene and COD contents both met the company's emission requirements. The acetone recovered from condensation was used to prepare a 50 mg / L solution, and the B / C ratio was measured to be 0.40, which can be used as a high-quality carbon source for the biological denitrification process.

[0069] Example 3

[0070] Special rubber wastewater contains 260–330 mg / L chlorobenzene, 160–210 mg / L acetone, and 320 mg / L COD.

[0071] The above wastewater treatment methods include the following steps:

[0072] (1) Homogenization: Wastewater enters a homogenizing tank with an outlet at the bottom. The hydraulic retention time is 4.0 h to homogenize the mixed wastewater.

[0073] (2) Primary oxidation: Water from the bottom of the homogenizing tank enters the primary oxidation tank. An oxidant is added to the primary oxidation tank to initiate an ultraviolet (UV) oxidation reaction. Acetone and water form an azeotrope. Chlorobenzene is decomposed into non-volatile intermediate products in the UV reactor, creating conditions for deep oxidation treatment in the secondary photocatalytic oxidation tank. The preferred ratio of hydrogen peroxide solution dosage (based on pure hydrogen peroxide) to influent COD is 0.8:1, the hydraulic retention time is 1.5 h, and the reaction temperature is 58 °C. The UV reactor has a UV power of 500 W / m². 3 The wastewater area in the reaction tube has a hydraulic retention time of 30 seconds;

[0074] (3) Acetone recovery: The gas phase generated in the primary oxidation tank is sent to the condenser by the induced draft fan. The non-condensable gas in the upper part of the condenser is discharged to the tail gas treatment device for treatment, and the acetone condensate in the lower part is recovered and reused; the hydraulic retention time is 2.5h.

[0075] (4) Secondary oxidation: The effluent from the middle of the primary oxidation tank enters the secondary catalytic oxidation tank. Dilute hydrochloric acid solution is added to the secondary catalytic oxidation tank to adjust the pH to 2.6, followed by the addition of ferric chloride solution and hydrogen peroxide solution. The preferred ratio of hydrogen peroxide solution dosage (based on pure hydrogen peroxide) to influent COD is 1.5:1. The hydraulic retention time is 1.5 h, the reaction temperature is 50℃, and the total iron concentration in the oxidation tank is 90 mg / L. The effluent from the lower part of the secondary catalytic oxidation tank enters the ultraviolet reactor for ultraviolet irradiation, and then returns to the secondary catalytic oxidation tank for circulation, deeply oxidizing and decomposing chlorobenzene and its oxidation intermediates. Ultraviolet reactor: Ultraviolet light power is 1000 W / m². 3 The wastewater area in the reaction tube has a hydraulic retention time of 15 seconds. One-fifth of the effluent from the secondary oxidation tank is returned to the primary oxidation tank.

[0076] (5) Sedimentation: 4 / 5 of the effluent from the secondary catalytic oxidation tank is added with sodium hydroxide solution to adjust the pH value to 8.5 and then enters the sedimentation tank. The catalyst produces a flocculation effect, which settles the suspended organic matter here; the hydraulic retention time is 1 hour.

[0077] (6) Drainage: The effluent from the sedimentation tank enters the monitoring tank, with a hydraulic retention time of 2.0h and a pH value of 7.

[0078] Test results: The chlorobenzene content in the effluent from the monitoring tank was <0.2 mg / L, the acetone content was 4-8 mg / L, and the COD was 33.5 mg / L. The chlorobenzene and COD contents both met the enterprise's emission requirements. The acetone recovered from condensation was used to prepare a 50 mg / L solution, and the B / C ratio was measured to be 0.45, which can be used as a high-quality carbon source for the biological denitrification process.

[0079] Comparative Example 1

[0080] Special rubber wastewater contains chlorobenzene at a concentration of 500–700 mg / L, acetone at a concentration of 200–300 mg / L, and COD at a concentration of 1300 mg / L.

[0081] The above wastewater treatment methods include the following steps:

[0082] (1) Homogenization: Wastewater enters a homogenizing tank with an outlet at the bottom. The hydraulic retention time is 6.0 h to homogenize the mixed wastewater.

[0083] (2) Photocatalytic oxidation: The effluent from the bottom of the homogenizing tank enters the oxidation tank. Dilute hydrochloric acid solution is added to the oxidation tank to adjust the pH to 2.3, followed by the addition of ferric chloride solution and hydrogen peroxide solution. The preferred ratio of hydrogen peroxide solution dosage (based on pure hydrogen peroxide) to influent COD is 3:1. The hydraulic retention time is 3.0 h, the reaction temperature is 50 °C, and the total iron concentration in the oxidation tank is 150 mg / L. The effluent from the bottom of the oxidation tank enters the ultraviolet reactor for ultraviolet irradiation, and then returns to the photocatalytic oxidation tank for circulation, deeply oxidizing and decomposing chlorobenzene and acetone. The power of the ultraviolet reactor is 1000 W / m². 3 The sewage area in the reaction tube has a hydraulic retention time of 40 seconds.

[0084] (3) Sedimentation: Sodium hydroxide solution is added to the effluent from the oxidation tank to adjust the pH value to 8.5, and then it enters the sedimentation tank. The catalyst produces a flocculation effect, which settles the suspended organic matter here; the hydraulic retention time is 1.5h;

[0085] (4) Drainage: The effluent from the sedimentation tank enters the monitoring tank, with a hydraulic retention time of 3.0h and a pH value of 9. The effluent from the monitoring tank meets the discharge standards.

[0086] Test results: The chlorobenzene content in the effluent from the monitoring tank was <0.2 mg / L, the acetone content was 15-20 mg / L, and the COD was 38.9 mg / L. The chlorobenzene and COD contents both met the company's emission requirements.

[0087] The comparison results of process parameters between Comparative Example 1 and Example 1 are shown in Table 1.

[0088] Table 1 Comparison of process parameters between Comparative Example 1 and Example 1

[0089]

[0090] Existing photocatalytic oxidation processes fail to separate chlorobenzene and acetone in wastewater, resulting in high dosages of oxidant and catalyst, long reaction times, and significant degradation of acetone without effective recovery, leading to high operating costs. The present invention, however, requires less oxidant and catalyst, shortens oxidation time, and produces a separated acetone solution with better biodegradability. Its oxidation efficiency and economic benefits are superior to comparative processes.

Claims

1. A method for treating wastewater containing high concentrations of chlorobenzene and acetone, characterized in that, Includes the following steps: (1) Homogenization: Wastewater enters the homogenizing tank, and an outlet is set at the bottom of the homogenizing tank; (2) Primary oxidation: Water from the bottom of the homogenizing tank enters the primary oxidation tank. An oxidant is added to the primary oxidation tank to carry out an ultraviolet oxidation reaction. Acetone and water form an azeotrope. Chlorobenzene is decomposed into non-volatile intermediate products through an ultraviolet reactor, creating conditions for deep oxidation treatment in the secondary photocatalytic oxidation tank. (3) Acetone recovery: The gas phase generated in the primary oxidation tank is sent to the condenser by the induced draft fan. The non-condensable gas in the upper part of the condenser is discharged to the tail gas treatment device for treatment, and the acetone condensate in the lower part is recovered and reused. (4) Secondary oxidation: The effluent from the middle of the primary oxidation tank enters the secondary catalytic oxidation tank. Acid is added to the secondary catalytic oxidation tank to adjust the pH, followed by the addition of catalyst and oxidant. The effluent from the bottom of the secondary catalytic oxidation tank enters the ultraviolet reactor, is irradiated by ultraviolet light, and then returns to the secondary catalytic oxidation tank for circulation, thus deeply oxidizing and decomposing chlorobenzene and its oxidation intermediates. One-fifth of the effluent from the secondary oxidation tank is returned to the primary oxidation tank to dilute the concentration of benzoquinone pollutants, an oxidation intermediate, and to ensure the photocatalytic oxidation effect of the primary oxidation tank. (5) Sedimentation: Add liquid alkali to the effluent from the secondary catalytic oxidation tank to adjust the pH value to neutral, and then enter the sedimentation tank. The catalyst produces a flocculation effect to precipitate suspended organic matter here. (6) Drainage: The effluent from the sedimentation tank enters the monitoring tank, and the effluent that meets the standards is discharged. The reaction temperature of the primary oxidation tank in step (2) is 55-60℃; The ultraviolet reactor in step (2) contains a reaction tube, which is a medium-pressure ultraviolet light reaction tube. The ultraviolet reactor includes a quartz sleeve area and a sewage area, wherein the residence time of the primary oxidation sewage is 5 to 40 seconds.

2. The wastewater treatment method containing high concentrations of chlorobenzene and acetone according to claim 1, characterized in that, The hydraulic residence time in step (1) is 2 to 6 hours.

3. The wastewater treatment method containing high concentrations of chlorobenzene and acetone according to claim 1, characterized in that, The material of the primary oxidation tank in step (2) is an anti-corrosion lining material; the hydraulic retention time is 1 to 2 hours based on the influent; the oxidant is a hydrogen peroxide solution, and the mass ratio of the oxidant dosage to the influent COD is (0.5:1) to (1:1).

4. The wastewater treatment method containing high concentrations of chlorobenzene and acetone according to claim 1, characterized in that, In step (4), the hydraulic retention time of the secondary catalytic oxidation tank is 1-2 h; the oxidant is hydrogen peroxide solution, and the mass ratio of the oxidant dosage to the COD of the influent is (1-2):1; the acid solution is either sulfuric acid solution or hydrochloric acid solution, and the amount added is controlled to control the pH value to 2.3-3.0; the reaction temperature is 45-55℃; the catalyst is ferric chloride, and the amount of catalyst added is 50-125 mg / L, calculated as total iron; the water retention time in the reaction tube of the ultraviolet reactor is 5-20 s.

5. The wastewater treatment method containing high concentrations of chlorobenzene and acetone according to claim 1, characterized in that, In step (5), the hydraulic residence time is 0.5 to 1.5 hours; the alkaline solution is either sodium hydroxide solution or potassium hydroxide solution, and the pH value of the regulating tank is controlled to be 7.0 to 8.5; in step (6), the hydraulic residence time is 1 to 3 hours.

Images