Method for purifying benzotriazole wastewater by adopting photocatalysis-ozone synergistic oxidation system

Abstract

The invention discloses a method for purifying benzotriazole wastewater by adopting a photocatalysis-ozone synergistic oxidation system, and belongs to the technical field of wastewater treatment.The method comprises the following steps that a solid catalyst and H2O2 are added into the benzotriazole wastewater in sequence, then O3 is introduced, mechanical stirring is conducted under ultraviolet irradiation, a mixed reaction is conducted, and the benzotriazole wastewater is obtained. The benzotriazole in the wastewater can be effectively removed, and the residual COD of the purified wastewater can meet the discharge standard. Compared with the prior art, the method has the following characteristics that the initial concentration of the benzotriazole capable of being purified can be up to 1000mg / L, and the residual COD (Chemical Oxygen Demand) of a water body after purification can be less than 60mg / L; the reaction system has high acid-base adaptability and is suitable for purifying a wastewater system with the pH value of 3-11; the technological process is simple and efficient, the equipment requirement is low, the investment cost is low, and industrial production is facilitated; reaction products mainly comprise CO2, H2O and a small amount of inorganic salt, and secondary pollution is avoided.

Description

Technical Field

[0001] The invention belongs to the technical field of wastewater treatment, and in particular relates to a method for purifying benzotriazole wastewater by adopting a photocatalytic-ozone synergistic oxidation system. Background Art

[0002] Benzotriazole is an important chemical additive, which is widely used in dozens of fields such as ultraviolet absorbers, antifreeze, corrosion inhibitors and detergents. The global annual output is stable at more than 10,000 tons, which results in a large amount of high-concentration benzotriazole wastewater being generated during production and use. On the one hand, in the production process of benzotriazole, the most widely used o-phenylenediamine method requires the target reaction and product separation in aqueous solution. However, due to the limitation of mass transfer of products at the interface during the separation process, some benzotriazole products remain in the aqueous solution to form high-concentration wastewater. On the other hand, benzotriazole is widely used in many fields. At the same time, it has high water solubility (28g / L), anti-biodegradability and low adsorption, which makes benzotriazole very easy to enrich in production and domestic wastewater. However, traditional sewage treatment plants cannot effectively remove benzotriazole, which eventually leads to the transfer of benzotriazole to natural water bodies. Reports from many regions around the world have confirmed the presence of varying degrees of benzotriazole residues in surface water and groundwater. As a suspected carcinogen, benzotriazole remaining in natural water bodies may cause irreversible damage to human skin, liver and other organs. Therefore, it is of great significance to develop a simple, efficient and secondary pollution-free method for purifying benzotriazole wastewater.

[0003] The methods currently used to purify such wastewater mainly include oxidation and adsorption. Patent CN111573913A discloses a method for electrocatalytic oxidation treatment of benzotriazole wastewater, which realizes the oxidative degradation of benzotriazole in wastewater by direct electrolytic oxidation and indirect electrolytic oxidation. However, it is necessary to add an acid-base regulator to adjust the pH value of the wastewater to neutrality in the early stage, increase the operating cost, and the benzotriazole concentration that can be treated needs to be controlled below 120mg / L. Patent CN114249475A discloses a wastewater resource treatment method containing benzotriazole, sodium nitrate, sodium nitrite, and sodium chloride, and resin adsorption is used to remove benzotriazole in wastewater, but a large amount of acid and alkali is needed in the process of desorption and recovery of benzotriazole, and the resin with reduced adsorption activity in the later stage, if improperly disposed, has the risk of causing secondary pollution. Therefore, the existing purification technology of benzotriazole wastewater cannot realize the simple and efficient operation and the process of no secondary pollution, and there is still room for improvement. Summary of the invention

[0004] In response to the above technical problems, the present invention provides a method for purifying benzotriazole wastewater using a photocatalytic-ozone synergistic oxidation system, which can achieve efficient removal of high-concentration benzotriazole in water and has no risk of secondary pollution.

[0005] The purpose of the present invention can be achieved through the following technical solutions:

[0006] A method for purifying benzotriazole wastewater using a photocatalytic-ozone synergistic oxidation system comprises the following steps:

[0007] (A) Add solid catalyst, H 2 O 2 , then pass into O 3 and applying mechanical stirring under ultraviolet light irradiation to perform a mixing reaction;

[0008] (B) centrifuging the suspension obtained in step (A) to obtain a solid catalyst and purified water;

[0009] (C) regenerating the solid catalyst obtained in step (B) by calcining at high temperature, and adding it back to step (A) for recycling;

[0010] (D) The COD of the purified water body can meet the discharge standards and can be discharged into the sewage treatment system for further treatment.

[0011] Furthermore, the solid catalyst in step (A) is a composite oxide, wherein the metal elements contained therein include one or more of titanium, silver, platinum, and zinc, and the non-metallic elements include one or more of silicon, sulfur, oxygen, and fluorine; wherein the mass proportion of the metal elements in the solid catalyst is 50% to 80%; and the mass proportion of the non-metallic elements in the solid catalyst is 20% to 50%.

[0012] Furthermore, the preparation method of the solid catalyst is as follows: dissolving the metal salt in water, then using an equal volume impregnation method to immerse the substrate powder in the salt solution, stirring evenly, separating, drying and calcining to obtain the solid catalyst.

[0013] In the solid catalyst, the metal element mainly acts as the reaction active site to catalyze H 2 O 2 and O 3 The non-metallic elements mainly play a structural supporting role, increasing the contact opportunity between pollutants and active substances. Under ultraviolet light, the internal electronic structure of the solid catalyst will be passively adjusted, making it compatible with the H 2 O 2 and O 3The ability to react simultaneously to generate more oxidatively active oxygen species such as hydroxyl free radicals and oxygen anion free radicals, thereby enhancing the reaction system's ability to purify benzotriazole in wastewater while making H 2 O 2 and O 3 The utilization efficiency is increased by 5% to 20%.

[0014] Furthermore, the solid catalyst added in step (A) has a concentration of 200 to 500 mg / L.

[0015] Further, in step (A), H 2 O 2 The added concentration is 0.1% to 0.5% of the wastewater mass. 2 O 2 It will undergo a homolytic cleavage reaction under ultraviolet light stimulation, and react with O 3 The peroxidation reaction and the reduction reaction on the surface of the solid catalyst are transformed into hydroxyl radicals, thereby realizing the mineralization of benzotriazole and intermediates in the wastewater.

[0016] Further, the O introduced in step (A) 3 The concentration is 20-100 mg / L. 3 The benzotriazole structure can be destroyed by direct oxidation, and it can also be oxidized by H 2 O 2 The peroxidation reaction between the solid catalyst and the catalytic decomposition of the active sites is transformed into active oxygen species that are more beneficial for purification.

[0017] Furthermore, the peak wavelength of the ultraviolet light in step (A) is 254 nm, and the light intensity is 250-500 mW / m 2 UV light will affect the solid catalyst and H 2 O 2 It produces an exciting effect, expands the generation pathway of reactive oxygen species and increases their concentration.

[0018] Furthermore, in step (A), the speed of mechanical stirring is 500-1000 r / min, and the reaction time is 2-5 h.

[0019] Furthermore, in step (B), the centrifugal speed is 2000-5000 r / min, and the processing time is 10-30 min.

[0020] Furthermore, in step (C), the high temperature calcination temperature is 500-800°C, and the calcination time is 3-5 hours. During the reaction, some intermediate product molecules will remain on the surface of the solid catalyst through strong interactions such as complexation and hydrogen bonding, shielding the active sites, weakening the contact area between the catalyst and the pollutants and active substances, and thus reducing the wastewater purification efficiency. At this time, the recovered catalyst can be calcined to achieve its activity regeneration.

[0021] Beneficial effects of the present invention:

[0022] 1) According to the test, the maximum initial benzotriazole concentration in the wastewater allowed by this process can reach 1000 mg / L, and the maximum total COD can reach 10 4 mg / L, after purification, the residual COD in the water can be less than 60mg / L, meeting the first-level standard of the pollutant discharge standard for urban sewage treatment plants (GB18918-2002);

[0023] 2) The pH value range suitable for the process is 3 to 11, and no additional reagents need to be added to adjust the acidity and alkalinity of the wastewater within this range;

[0024] 3) The process is simple and efficient, with low investment cost and easy industrial production. The degradation product is mainly CO 2 , H 2 O and a small amount of inorganic salts, the added H 2 O 2 and O 3 It can also be decomposed into H 2 O and O 2 The catalyst can be regenerated and recycled, and the risk of secondary pollution is low. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The present invention will be further described below in conjunction with the accompanying drawings.

[0026] Figure 1 It is a process flow chart of the present invention.

[0027] Figure 2 This is a TEM image of the solid catalyst prepared in Example 5.

[0028] Figure 3 This is a comparison chart of the properties of benzotriazole wastewater before and after the process purification in Example 6. DETAILED DESCRIPTION

[0029] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0030] Embodiment 1

[0031] Preparation of solid catalyst:

[0032] Silver nitrate and zinc nitrate were dissolved in water, and then the equal volume impregnation method was used to take TiO 2 0.5 g of each of Ag and ZnO nanopowders were immersed in a salt solution and stirred at 25°C for 1 h. The suspension was then centrifuged to recover the solid component at a speed of 9000 r / min and a centrifugal time of 5 min. The recovered solid component was repeatedly washed three times with methanol and water, and vacuum dried at 80°C for 24 h. Finally, it was placed in a muffle furnace and calcined at 600°C for 4 h to obtain a solid catalyst containing 0.8 wt% Ag and 1.1 wt% Zn.

[0033] Embodiment 2

[0034] Preparation of solid catalyst:

[0035] Dissolve zinc nitrate and ammonium chloroplatinate in water, then use equal volume immersion method to take gC 3 N 4 1 g of nanopowder was immersed in a salt solution and stirred at 25°C for 1 h. The suspension was then centrifuged to recover the solid component at a speed of 9000 r / min and a centrifugal time of 5 min. The recovered solid component was repeatedly washed three times with methanol and water, vacuum dried at 80°C for 24 h, and finally calcined at 600°C in a muffle furnace for 4 h to obtain a solid catalyst containing 0.2 wt% Zn and 0.3 wt% Pt.

[0036] Embodiment 3

[0037] Preparation of solid catalyst:

[0038] Chloroauric acid tetrahydrate and ammonium chloroplatinate were dissolved in water, and then CdS and TiO 2 0.5 g of each nanopowder was immersed in a salt solution and stirred at 25°C for 1 h. The suspension was then centrifuged to recover the solid component at a speed of 9000 r / min and a centrifugal time of 5 min. The recovered solid component was repeatedly washed three times with methanol and water, and vacuum dried at 80°C for 24 h. Finally, it was placed in a muffle furnace and calcined at 600°C for 4 h to obtain a solid catalyst containing 0.8 wt% Au and 1.2 wt% Pt.

[0039] Embodiment 4

[0040] Preparation of solid catalyst:

[0041] Chloroauric acid tetrahydrate and silver nitrate were dissolved in water, and then 0.5 g of CdS and ZnO nanopowders were immersed in the salt solution by equal volume impregnation method, and stirred at 25°C for 1 hour. The suspension was then centrifuged to recover the solid components. The centrifugal speed was 9000 r / min and the centrifugal time was 5 minutes. The recovered solid components were repeatedly washed 3 times with methanol and water, and vacuum dried at 80°C for 24 hours. Finally, they were placed in a muffle furnace and calcined at 600°C for 4 hours to obtain a solid catalyst containing 0.5wt% Au and 1.0wt% Ag.

[0042] Embodiment 5

[0043] Preparation of solid catalyst:

[0044] Dissolve chloroauric acid tetrahydrate in water, then use the equal volume impregnation method to take TiO 2 1 g of nanopowder was immersed in a salt solution and stirred at 25°C for 1 h. The suspension was then centrifuged to recover the solid component at a centrifugal speed of 9000 r / min for 5 min. The recovered solid component was repeatedly washed 3 times with methanol and water, and vacuum dried at 80°C for 24 h. Finally, it was placed in a muffle furnace and calcined at 600°C for 4 h to obtain a solid catalyst containing 1.2 wt% Au. The TEM image of the solid catalyst obtained in this example is shown in FIG. Figure 2 shown.

[0045] like Figure 1 The process flow chart of the present invention is shown in the following examples. Figure 1 The process shown is carried out.

[0046] Embodiment 6

[0047] This embodiment is described by taking the wastewater produced by a manufacturing enterprise in Jiangsu as an example.

[0048] The initial benzotriazole concentration in the wastewater was 1041 mg / L, the total COD was 38532 mg / L, and the water was yellow-brown. The solid catalyst of Example 1, H 2 O 2 , concentrations of 500 mg / L and 0.5%, respectively, followed by 80 mg / L O 3 Mechanical stirring was applied under UV irradiation with an intensity of 500 mW / m 2, mechanical stirring speed is 700r / min, reaction time is 5h. After the mixed reaction is completed, the suspension obtained by the reaction is centrifuged, the centrifugal speed is 4000r / min, the treatment time is 20min, and the purified water and solid catalyst are obtained respectively. The purified water is colorless and transparent, and the residual COD value is measured to be 26mg / L, which meets the first-level standard of the pollutant discharge standard for urban sewage treatment plants (GB18918-2002). The comparison of water properties before and after purification is as follows Figure 3 After the recovered catalyst was calcined at 800℃ for 3h, the residual COD value of the purified water was measured to be 25mg / L under the same conditions, and the regenerated solid catalyst had no obvious activity reduction.

[0049] Embodiment 7

[0050] This embodiment is described by taking the wastewater produced by a manufacturing enterprise in Sichuan as an example.

[0051] The initial benzotriazole concentration in the wastewater was 289 mg / L, the total COD was 1896 mg / L, and the water also contained some inorganic salts, specifically: 51 mg / L NaCl and 24 mg / L NaNO 3 The solid catalyst of Example 2, H 2 O 2 , concentrations of 200 mg / L and 0.1%, respectively, followed by the introduction of 100 mg / L O 3 Mechanical stirring was applied under UV irradiation with an intensity of 300 mW / m 2 , mechanical stirring speed is 500r / min, reaction time is 2h. After the mixed reaction is completed, the suspension obtained by the reaction is centrifuged at a centrifugal speed of 2000r / min and a treatment time of 20min to obtain purified water and solid catalyst respectively. The residual COD value of the purified water is 32mg / L, which meets the first-level standard of the pollutant discharge standard for urban sewage treatment plants (GB18918-2002). After the recovered catalyst was calcined at 600℃ for 3h, the residual COD value of the purified water under the same conditions was measured to be 34mg / L, and the regenerated solid catalyst had no obvious activity reduction.

[0052] Embodiment 8

[0053] This embodiment is described by taking the wastewater produced by a manufacturing enterprise in Zhejiang as an example.

[0054] The initial benzotriazole concentration in the wastewater was 642 mg / L, and the total COD was 23676 mg / L. The solid catalyst of Example 3, H 2 O 2 , concentrations of 350 mg / L and 0.5%, respectively, followed by the introduction of 50 mg / L O3 Mechanical stirring was applied under UV irradiation with an intensity of 400 mW / m 2 , the mechanical stirring speed is 1000r / min, and the reaction time is 3h. After the mixed reaction is completed, the suspension obtained by the reaction is centrifuged at a centrifugal speed of 5000r / min and a treatment time of 10min to obtain purified water and solid catalyst respectively. The residual COD value of the purified water is 58mg / L, which meets the first-level standard of the pollutant discharge standard for urban sewage treatment plants (GB18918-2002). After the recovered catalyst was calcined at 500℃ for 5h, the residual COD value of the purified water under the same conditions was measured to be 57mg / L, and the regenerated solid catalyst had no obvious activity reduction.

[0055] Embodiment 9

[0056] This embodiment is described by taking the wastewater produced by a manufacturing enterprise in Anhui as an example.

[0057] The initial benzotriazole concentration in the wastewater was 465 mg / L, and the total COD was 10501 mg / L. The solid catalyst of Example 4, H 2 O 2 , concentrations of 200 mg / L and 0.5%, respectively, followed by the introduction of 20 mg / L O 3 Mechanical stirring was applied under UV irradiation with an intensity of 500 mW / m 2 , the mechanical stirring speed is 1000r / min, and the reaction time is 5h. After the mixed reaction is completed, the suspension obtained by the reaction is centrifuged at a centrifugal speed of 2000r / min and a treatment time of 30min to obtain purified water and solid catalyst respectively. The residual COD value of the purified water is 49mg / L, which meets the first-level standard of the pollutant discharge standard for urban sewage treatment plants (GB18918-2002). After the recovered catalyst was calcined at 700℃ for 3h, the residual COD value of the purified water under the same conditions was measured to be 52mg / L, and the regenerated solid catalyst had no obvious activity reduction.

[0058] Embodiment 10

[0059] This embodiment is described by taking wastewater from a manufacturing enterprise in Henan as an example.

[0060] The initial benzotriazole concentration in the wastewater was 103 mg / L, and the total COD was 2318 mg / L. The solid catalyst of Example 5, H 2 O 2 , concentrations of 250 mg / L and 0.2%, respectively, followed by the introduction of 50 mg / L O 3 Mechanical stirring was applied under UV irradiation with an intensity of 250 mW / m2 , the mechanical stirring speed is 8000r / min, and the reaction time is 2h. After the mixed reaction is completed, the suspension obtained by the reaction is centrifuged at a centrifugal speed of 3000r / min and a treatment time of 15min to obtain purified water and solid catalyst respectively. The residual COD value of the purified water is 39mg / L, which meets the first-level standard of the pollutant discharge standard for urban sewage treatment plants (GB18918-2002). After the recovered catalyst was calcined at 500℃ for 4h, the residual COD value of the purified water under the same conditions was measured to be 41mg / L, and the regenerated solid catalyst had no obvious activity reduction.

[0061] The above specific implementation method part specifically introduces the analytical method involved in the present invention. It should be noted that the above introduction is only to help those skilled in the art better understand the method and ideas of the present invention, rather than limiting the relevant content. Without departing from the principle of the present invention, those skilled in the art may also make appropriate adjustments or modifications to the present invention, and the above adjustments and modifications shall also fall within the scope of protection of the present invention.

Claims

1. A method for purifying benzotriazole wastewater using a photocatalytic-ozone synergistic oxidation system, characterized in that: The steps include: (A) adding a solid catalyst and H2O2 to benzotriazole wastewater in sequence, then introducing O3 and applying mechanical stirring under ultraviolet light to carry out a mixing reaction; (B) centrifuging the suspension obtained in step (A) to obtain a solid catalyst and purified water; (C) regenerating the solid catalyst obtained in step (B) by calcining at high temperature, and adding it back to step (A) for recycling; (D) The COD of the purified water body can meet the discharge standards and can be discharged into the sewage treatment system for further treatment.

2. The method for purifying benzotriazole wastewater using a photocatalytic-ozone synergistic oxidation system according to claim 1, characterized in that: The solid catalyst in step (A) is a composite oxide, wherein the metal elements contained therein include one or more of titanium, silver, platinum and zinc, and the non-metallic elements include one or more of silicon, sulfur, oxygen and fluorine.

3. The method for purifying benzotriazole wastewater using a photocatalytic-ozone synergistic oxidation system according to claim 2, characterized in that: The mass proportion of the metal element in the solid catalyst is 50% to 80%; the mass proportion of the non-metal element in the solid catalyst is 20% to 50%.

4. The method for purifying benzotriazole wastewater using a photocatalytic-ozone synergistic oxidation system according to claim 1, characterized in that: The solid catalyst added in step (A) has a concentration of 200 to 500 mg / L.

5. The method for purifying benzotriazole wastewater using a photocatalytic-ozone synergistic oxidation system according to claim 1, characterized in that: The H2O2 addition concentration in step (A) is 0.1% to 0.5% of the wastewater mass.

6. The method for purifying benzotriazole wastewater using a photocatalytic-ozone synergistic oxidation system according to claim 1, characterized in that: The concentration of O3 introduced in step (A) is 20-100 mg / L.

7. The method for purifying benzotriazole wastewater using a photocatalytic-ozone synergistic oxidation system according to claim 1, characterized in that: The peak wavelength of the ultraviolet light in step (A) is 254nm, and the illumination intensity is 250-500mW / m 2 .

8. The method for purifying benzotriazole wastewater using a photocatalytic-ozone synergistic oxidation system according to claim 1, characterized in that: The rotation speed of the mechanical stirring in step (A) is 500-1000 r / min, and the reaction time is 2-5 h.

9. The method for purifying benzotriazole wastewater using a photocatalytic-ozone synergistic oxidation system according to claim 1, characterized in that: The centrifugal speed in step (B) is 2000-5000 r / min, and the processing time is 10-30 min.

10. The method for purifying benzotriazole wastewater using a photocatalytic-ozone synergistic oxidation system according to claim 1, characterized in that: In step (C), the high temperature calcination temperature is 500-800° C. and the calcination time is 3-5 hours.

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