Method for photocatalytic treatment of wastewater containing benzene series

Abstract

The invention relates to a method for photocatalytic treatment of wastewater containing benzene series, and the method comprises the following steps: mixing the wastewater containing benzene series with a concentrated solution of ammoximation process wastewater, and adjusting the pH value of the solution to be less than 7.0 to obtain mixed wastewater; under the irradiation of ultraviolet light, carrying out photocatalytic treatment on the mixed wastewater; the content ratio of the detected substance calculated by H2O2 to the COD in the mixed wastewater is (1-10): 1. According to the method disclosed by the invention, the content of the benzene series in the benzene series-containing wastewater can be effectively reduced, the biodegradability is improved, and the effluent quality of the treated wastewater has a relatively low COD value and a relatively high B / C value.

Description

Technical Field

[0001] The present disclosure relates to a wastewater treatment method, and in particular, to a method for photocatalytically treating wastewater containing benzene series. Background Art

[0002] Wastewater containing benzene series refers to wastewater mixed with benzene organic pollutants. Benzene organic pollutants such as benzene, toluene, chlorobenzene, nitrobenzene, etc. are relatively common pollutants. Benzene series pollutants are stable in nature and are not easily degraded in the environment. Conventional treatment processes such as adsorption and flocculation are difficult to effectively treat. The current treatment methods mainly include adsorption, chemical oxidation, microbial methods, etc.

[0003] The adsorption method often has the problem of adsorbent regeneration, and the adsorbent that cannot be regenerated is treated as hazardous waste, which increases the cost of wastewater treatment. Wet oxidation is the most commonly used chemical oxidation method for benzene wastewater treatment. This method has wide applicability and good treatment effect, but this method usually operates under high temperature and high pressure, with high equipment investment and complex operation. The microbial method usually needs to be used in conjunction with the advanced oxidation method. The advanced oxidation method is used to oxidize benzene substances, improve the biodegradability of the wastewater, and then use the microbial method for treatment. This method has a long treatment process and a long cycle.

[0004] On the other hand, in the production of caprolactam, the COD of wastewater produced by the ammoximation process is as high as 2000-12000 mg / L. The wastewater contains trace amounts of organic impurities such as toluene, cyclohexanone oxime, cyclohexanol, and cyclohexanone. After the wastewater is distilled and organic matter is recovered by the stripping tower, if it is directly discharged into the sewage treatment system, the refractory organic matter in it will impact the biochemical treatment device. Therefore, the wastewater at the bottom of the wastewater stripping tower needs to be pretreated before biochemical treatment to reduce the refractory organic matter in it. Studies have found that organic peroxides in ammoximation wastewater are the main reason affecting the biodegradability of wastewater. However, the properties of this type of organic peroxide in wastewater are relatively stable, and it is difficult to remove it by conventional methods of decomposing hydrogen peroxide. At present, the pretreatment of ammoximation wastewater mainly focuses on catalytic oxidation. For example, CN110540336A discloses a method for treating ammoximation wastewater and its application, which is to add a flocculant to the ammoximation wastewater, adjust the wastewater to acidity after pre-sedimentation, perform enhanced sedimentation, adjust the wastewater to alkalinity after filtration, perform catalytic oxidation reaction, and then enter biochemical treatment. This method produces a large amount of precipitation, and the sedimentation tank occupies a large area. Summary of the invention

[0005] The purpose of the present disclosure is to provide a method for photocatalytic treatment of wastewater containing benzene series, which can effectively reduce the content of benzene series in the wastewater containing benzene series, improve biodegradability, and make the treated wastewater have a lower COD value and a higher B / C value.

[0006] In order to achieve the above-mentioned object, the present invention discloses a method for photocatalytic treatment of wastewater containing benzene series, the method comprising: mixing the wastewater containing benzene series with a concentrated solution of ammoximation process wastewater, adjusting the solution pH to less than 7.0, to obtain mixed wastewater; performing photocatalytic treatment on the mixed wastewater under ultraviolet light irradiation; 2 O 2 The ratio of the detected substances to COD content is (1~10):1.

[0007] Optionally, the mixed wastewater contains H 2 O 2 The ratio of the detected substances to COD content is (5~9):1.

[0008] Optionally, the COD of the wastewater containing benzene series is 50-300 mg / L, preferably 50-200 mg / L; the turbidity of the wastewater containing benzene series is not more than 10NUT; the benzene series in the wastewater containing benzene series is selected from one or more of nitrobenzene, phenol, aniline, nitrochlorobenzene, toluene and xylene.

[0009] Optionally, the COD of the ammoximation industrial wastewater is 300 to 30,000 mg / L, preferably 500 to 15,000 mg / L; 2 O 2 The content of the detected object is 200 to 30,000 mg / L, preferably 500 to 15,000 mg / L.

[0010] Optionally, the preparation method of the concentrated solution includes: concentrating the ammoximation process wastewater by a reduced pressure distillation method or a membrane concentration method to obtain the concentrated solution and fresh water; the temperature of the reduced pressure distillation is 50 to 100°C, preferably 60 to 90°C; the time is 0.2 to 10h, preferably 0.5 to 5h; the vacuum degree is 0.01 to 0.1KPa, preferably 0.02 to 0.08KPa.

[0011] Optionally, the volume of the concentrated liquid is 3-20%, preferably 5-15%, of the volume of the ammoximation process wastewater.

[0012] Optionally, the wavelength of the ultraviolet light is 150-200nm and / or 210-260nm. Preferably, the ultraviolet light is dual-wavelength ultraviolet light, and the dual-wavelength ultraviolet light is selected from vacuum ultraviolet light with a wavelength of 185nm and short-wave ultraviolet light with a wavelength of 254nm. More preferably, the ratio of vacuum ultraviolet light with a wavelength of 185nm to short-wave ultraviolet light with a wavelength of 254nm is 1:(4-19), preferably 1:(4-9).

[0013] Optionally, the method further comprises: before the irradiation, adding a photocatalyst to the mixed wastewater; the photocatalyst comprises titanium dioxide and an active component supported on the titanium dioxide, and the active component is selected from one or more of platinum, rhodium and palladium.

[0014] Optionally, based on the total weight of the titanium dioxide, the content of the active component in terms of metal elements is 1 to 5% by weight, preferably 2 to 4% by weight; the content of the photocatalyst in the mixed wastewater is 500 to 2000 mg / L, preferably 800 to 1500 mg / L.

[0015] Optionally, relative to 1L of the mixed wastewater, the irradiation power is 1 to 10W, preferably 2 to 8W; the irradiation time is 30 to 120min, preferably 45 to 90min.

[0016] Through the above technical scheme, the present disclosure provides a method for photocatalytic treatment of wastewater containing benzene series, wherein the method uses a photocatalyst and a concentrated solution of ammoximation process wastewater to photocatalytically treat benzene series in wastewater containing benzene series, and the photocatalyst and the concentrated solution have H 2 O 2 The detected substances with different properties have a synergistic effect, which can promote the degradation of benzene series in wastewater containing benzene series, reduce the content of benzene organic pollutants in mixed wastewater, improve biodegradability, and make the effluent quality have a lower COD value and a higher B / C value. It can be directly discharged into the sewage treatment plant to achieve the purpose of treating waste with waste.

[0017] Other features and advantages of the present disclosure will be described in detail in the following detailed description. DETAILED DESCRIPTION

[0018] The specific embodiments of the present disclosure are described in detail below. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present disclosure, and are not used to limit the present disclosure.

[0019] The present invention provides a method for photocatalytically treating wastewater containing benzene series, the method comprising: mixing the wastewater containing benzene series with a concentrated solution of ammoximation process wastewater, adjusting the pH of the solution to less than 7.0, to obtain mixed wastewater; performing photocatalytic treatment on the mixed wastewater under ultraviolet light irradiation; 2 O 2 The ratio of the detected substances to COD content is (1~10):1.

[0020] In one embodiment, the pH of the solution is adjusted to 2.0 to 5.0. 2 O 2 The detected objects are those with H 2 O 2The content of this substance is determined by the method of GB1616-2003.

[0021] The inventors of the present disclosure have found in their in-depth research that when the concentrated solution of wastewater from the ammoximation process is used for photocatalytic treatment of benzene-containing wastewater, the light and the concentrated solution containing H 2 O 2 The detected substances of different properties have a synergistic effect, which can promote the degradation of benzene series in wastewater containing benzene series, reduce the content of benzene organic pollutants in mixed wastewater, improve biodegradability, and make the effluent water quality of the treated wastewater have a lower COD value and a higher B / C value, so as to achieve the purpose of treating waste with waste. Among them, B / C is the abbreviation of the ratio of BOD to COD, which indicates the biodegradability of wastewater. When B / C>0.3, the wastewater can be biodegraded.

[0022] In one embodiment of the present disclosure, the mixed wastewater contains H 2 O 2 The ratio of the detected substance to COD is (5-9):1. In the above embodiment, the mixed wastewater has H 2 O 2 The detected objects with properties are excited to produce a variety of free radicals under ultraviolet light irradiation. The free radicals can destroy the structure of benzene series in the wastewater containing benzene series, open the benzene ring, and further degrade it into small molecular organic matter or carbon dioxide, thereby improving the effect of photocatalytic treatment.

[0023] In one embodiment of the present disclosure, the COD of the wastewater containing benzene series is 50-300 mg / L, preferably 50-200 mg / L; the turbidity of the wastewater containing benzene series is not more than 10NUT; the benzene series in the wastewater containing benzene series is selected from one or more of nitrobenzene, phenol, aniline, nitrochlorobenzene, toluene and xylene. In one embodiment, the wastewater containing benzene series is selected from one or more of dye wastewater, petrochemical wastewater, coal chemical wastewater, pesticide wastewater and municipal wastewater, and the content of benzene series in the wastewater containing benzene series is 30-300 mg / L. The COD value of the wastewater containing benzene series disclosed in the present disclosure is above 50, and the B / C is close to 0, which has the characteristics of high toxicity and poor biodegradability.

[0024] In one embodiment of the present disclosure, the COD of the ammoximation industrial wastewater is 300 to 30,000 mg / L, preferably 500 to 15,000 mg / L; 2 O 2 The content of the detected substance is 200 to 30,000 mg / L, preferably 500 to 15,000 mg / L. The ammoximation industrial wastewater disclosed in the present invention contains a large amount of H 2 O 2It is an organic peroxide-like substance with a B / C ratio close to 0. The wastewater cannot be discharged directly into the wastewater treatment system to avoid causing massive death of microorganisms.

[0025] In one embodiment of the present disclosure, the preparation method of the concentrated solution comprises: using a vacuum distillation method or a membrane concentration method to concentrate the ammoximation process wastewater to obtain the concentrated solution and fresh water; the vacuum distillation temperature is 50-100°C, preferably 60-90°C; the time is 0.2-10h, preferably 0.5-5h; the vacuum degree is 0.01-0.1KPa, preferably 0.02-0.08KPa. In the above embodiment, the selected concentration method is conducive to the removal of H in the ammoximation industrial wastewater. 2 O 2 The detected substances of various properties are concentrated in the concentrate, which increases the B / C value of the fresh water after concentration treatment, so that it can be directly fed into the company's existing sewage treatment plant for treatment.

[0026] In one embodiment, the volume of the concentrated solution is 3-20%, preferably 5-15% of the volume of the ammoximation process wastewater.

[0027] In one embodiment of the present disclosure, the wavelength of the ultraviolet light is 150-200nm and / or 210-260nm. In a preferred embodiment, the ultraviolet light is dual-wavelength ultraviolet light, and the dual-wavelength ultraviolet light is selected from vacuum ultraviolet light with a wavelength of 185nm and short-wave ultraviolet light with a wavelength of 254nm. In a preferred embodiment, the ratio of vacuum ultraviolet light with a wavelength of 185nm to short-wave ultraviolet light with a wavelength of 254nm is 1:(4-19), preferably 1:(4-9). In the above embodiment, the selected ultraviolet light is conducive to the photocatalytic ring-opening degradation of benzene series in wastewater containing benzene series.

[0028] In one embodiment of the present disclosure, the method further comprises: before the irradiation, adding a photocatalyst to the mixed wastewater; the photocatalyst comprises titanium dioxide and an active component supported on the titanium dioxide, and the active component is selected from one or more of platinum, rhodium and palladium. In the above embodiment, the selection of titanium dioxide loaded with active metals at a preferred content as the photocatalyst is conducive to further improving the catalytic effect of the photocatalyst.

[0029] In one embodiment of the present disclosure, based on the total weight of the titanium dioxide, the content of the active component in terms of metal elements is 1 to 5 weight %, preferably 2 to 4 weight %; the content of the photocatalyst in the mixed wastewater is 500 to 2000 mg / L, preferably 800 to 1500 mg / L.

[0030] In one embodiment of the present disclosure, relative to 1L of the mixed wastewater, the irradiation power is 1 to 10W, preferably 2 to 8W; the time is 30 to 120min, preferably 45 to 90min.

[0031] The present disclosure is further described in detail by way of examples. The carrier materials used in the examples can be obtained through commercial sources. Among them, titanium dioxide was purchased from Xi'an Qiyue Biotechnology Co., Ltd.

[0032] The determination method of BOD is the five-day biochemical method (HJ 505-2009), the determination method of COD is the potassium dichromate method (GB11914-89), and B / C is the ratio of BOD to COD. The content of active components loaded on the carrier is tested by XRF analyzer, and the instrument model is Rigaku 3271E.

[0033] Example 1

[0034] (1) The COD of ammonia oxime industrial wastewater from a petrochemical plant is 3970 mg / L. 2 O 2 The mass concentration of the detected substance is 6120 mg / L, and B / C is 0.01; the ammoximation industrial wastewater is concentrated by vacuum distillation, the vacuum distillation temperature is 80°C, the time is 2 hours, and the vacuum degree is 0.08 KPa, to obtain a concentrated solution with a volume of 5% of the volume of the ammoximation process wastewater and a fresh water with a volume of 95% of the volume of the ammoximation process wastewater;

[0035] (2) Using a ceramic membrane to filter nitrobenzene wastewater from a chemical plant, a wastewater containing benzene series having a turbidity of 2NUT, a COD of 110 mg / L, and a B / C of 0.05 is obtained; the wastewater containing benzene series is mixed with the concentrated solution obtained in step (1), and the pH of the solution is adjusted to 3.5 to obtain a mixed wastewater, wherein the mixed wastewater is composed of H 2 O 2 The ratio of the detected substances to COD is 8:1;

[0036] (3) The mixed wastewater was irradiated with dual-wavelength ultraviolet light for photocatalytic treatment; the dual-wavelength ultraviolet light was: 15% of vacuum ultraviolet light with a wavelength of 185 nm and 85% of short-wave ultraviolet light with a wavelength of 254 nm (i.e., the ratio of vacuum ultraviolet light with a wavelength of 185 nm to short-wave ultraviolet light with a wavelength of 254 nm was 1:5.7). Relative to 1 L of mixed wastewater, the irradiation power was 6 W and the irradiation time was 60 min. The effluent water quality of the treated wastewater was tested, and the results are shown in Table 1.

[0037] Example 2

[0038] The same as Example 1, except that: in step (2), the mixed wastewater is H2 O 2 The ratio of the detected substances to COD content is 2:1. The effluent quality of the treated wastewater is shown in Table 1.

[0039] Example 3

[0040] The same as Example 1, the only difference is that in step (3), the irradiation power is 8W relative to 1L of mixed wastewater, and the effluent water quality of the treated wastewater is shown in Table 1.

[0041] Example 4

[0042] The same as Example 1, the only difference is that the dual-wavelength ultraviolet light used in step (3) is: 5% of vacuum ultraviolet light with a wavelength of 185nm and 95% of short-wave ultraviolet light with a wavelength of 254nm (that is, the ratio of vacuum ultraviolet light with a wavelength of 185nm to short-wave ultraviolet light with a wavelength of 254nm is 1:19). The effluent water quality of the treated wastewater is shown in Table 1.

[0043] Example 5

[0044] The same as Example 1, the only difference is that: in step (3), a single wavelength ultraviolet light with a wavelength of 254nm is used, and the effluent water quality of the treated wastewater is shown in Table 1.

[0045] Example 6

[0046] As in Example 1, in step (2), the wastewater containing benzene series is wastewater containing phenol discharged from a chemical plant, and the influent water quality is: COD is 152 mg / L, phenol content is 47 mg / L, B / C is 0.22; H 2 O 2 The ratio of the detected substances to COD is 8:1;

[0047] In step (3), a photocatalyst is added, the photocatalyst is titanium dioxide loaded with platinum, the content of platinum in terms of metal element is 3.1% by weight based on the total weight of titanium dioxide, and the content of the photocatalyst in the mixed wastewater is 800 mg / L. The effluent water quality of the treated wastewater is shown in Table 1.

[0048] Comparative Example 1

[0049] The method is the same as Example 1, except that step (1) is not performed, and the concentrated solution of ammonia oximation process wastewater is not added to the wastewater containing benzene series in step (2). The effluent water quality of the treated wastewater is shown in Table 1.

[0050] Comparative Example 2

[0051] The same as Example 1, the only difference is that in step (3), no ultraviolet light is used for irradiation. The effluent water quality of the treated wastewater is shown in Table 1.

[0052] Comparative Example 3

[0053] The same as Example 1, the only difference is that step (1) is not performed, the concentrated solution in step (2) is replaced by the same amount of hydrogen peroxide with a mass fraction of 27%, and the effluent water quality of the treated wastewater is shown in Table 1.

[0054] Comparative Example 4

[0055] The same as Example 1, the only difference is that the pH of the solution is adjusted to 8.0, and the effluent water quality of the treated wastewater is shown in Table 1.

[0056] Wherein, COD removal rate % = 100% × (COD content of the influent water quality of the wastewater containing benzene series - COD content of the effluent water quality of the treated wastewater) / COD content of the influent water quality of the wastewater containing benzene series;

[0057] Table 1

[0058]

[0059]

[0060] From the results in Table 1 above, it can be seen that compared with Comparative Examples 1 to 4, when Examples 1 to 6 use the concentrated solution of the ammoximation process wastewater for photocatalytic treatment of wastewater containing benzene series, the content of benzene series in the wastewater containing benzene series can be effectively reduced, the biodegradability can be improved, and the effluent water quality of the treated wastewater has a lower COD value and a higher B / C value, thereby achieving the purpose of treating waste with waste. However, Comparative Examples 1 to 4 do not use the technical solution disclosed in the present invention, and the effluent water quality of the treated wastewater is poor.

[0061] The preferred embodiments of the present disclosure are described in detail above; however, the present disclosure is not limited to the specific details in the above embodiments. Within the technical concept of the present disclosure, a variety of simple modifications can be made to the technical solution of the present disclosure, and these simple modifications all fall within the protection scope of the present disclosure.

[0062] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present disclosure will not further describe various possible combinations.

[0063] In addition, various embodiments of the present disclosure may be arbitrarily combined, and as long as they do not violate the concept of the present disclosure, they should also be regarded as the contents disclosed by the present disclosure.

Claims

1. A method for photocatalytic treatment of wastewater containing benzene series, characterized in that: The method comprises: mixing the wastewater containing benzene series with the concentrated solution of the ammoximation process wastewater, adjusting the pH of the solution to be less than 7.0, to obtain mixed wastewater; and performing photocatalytic treatment on the mixed wastewater under the irradiation of ultraviolet light; The ratio of the content of the detected substance in terms of H2O2 to COD in the mixed wastewater is (1-10):

1.

2. The method according to claim 1, characterized in that The ratio of the content of the detected substance in terms of H2O2 to COD in the mixed wastewater is (5-9):

1.

3. The method according to claim 1, characterized in that The COD of the wastewater containing benzene series is 50 to 300 mg / L, preferably 50 to 200 mg / L; the turbidity of the wastewater containing benzene series is not more than 10 NUT; The benzene series in the benzene series wastewater is selected from one or more of nitrobenzene, phenol, aniline, nitrochlorobenzene, toluene and xylene.

4. The method according to claim 1, characterized in that: The COD of the ammoximation industrial wastewater is 300 to 30,000 mg / L, preferably 500 to 15,000 mg / L; the content of the detected substance in terms of H2O2 is 200 to 30,000 mg / L, preferably 500 to 15,000 mg / L.

5. The method according to claim 1, characterized in that The preparation method of the concentrated solution comprises: concentrating the ammoximation process wastewater by a reduced pressure distillation method or a membrane concentration method to obtain the concentrated solution and fresh water; the temperature of the reduced pressure distillation is 50 to 100° C., preferably 60 to 90° C.; the time is 0.2 to 10 hours, preferably 0.5 to 5 hours; the vacuum degree is 0.01 to 0.1 KPa, preferably 0.02 to 0.08 KPa.

6. The method according to claim 5, characterized in that The volume of the concentrated liquid is 3-20%, preferably 5-15%, of the volume of the ammoximation process wastewater.

7. The method according to claim 1, characterized in that The wavelength of the ultraviolet light is 150-200nm and / or 210-260nm. Preferably, the ultraviolet light is dual-wavelength ultraviolet light, and the dual-wavelength ultraviolet light is selected from vacuum ultraviolet light with a wavelength of 185nm and short-wave ultraviolet light with a wavelength of 254nm. More preferably, the ratio of vacuum ultraviolet light with a wavelength of 185nm to short-wave ultraviolet light with a wavelength of 254nm is 1:(4-19), preferably 1:(4-9).

8. The method according to claim 1, characterized in that The method further comprises: before the irradiation, adding a photocatalyst to the mixed wastewater; the photocatalyst comprises titanium dioxide and an active component supported on the titanium dioxide, and the active component is selected from one or more of platinum, rhodium and palladium.

9. The method according to claim 8, characterized in that Based on the total weight of the titanium dioxide, the content of the active component in terms of metal elements is 1 to 5% by weight, preferably 2 to 4% by weight; the content of the photocatalyst in the mixed wastewater is 500 to 2000 mg / L, preferably 800 to 1500 mg / L.

10. The method according to claim 1, characterized in that Relative to 1L of the mixed wastewater, the irradiation power is 1 to 10W, preferably 2 to 8W; the irradiation time is 30 to 120min, preferably 45 to 90min.

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