Treatment method of nitrobenzene-containing wastewater

Abstract

The invention relates to the technical field of wastewater treatment, in particular to a nitrobenzene-containing wastewater treatment method which comprises the following steps: performing multi-stage cooling crystallization on nitrobenzene-containing wastewater to obtain mixed dinitrobenzene solid and crystallized filtrate; heating, pressurizing, oxidizing and hydrolyzing the crystallized filtrate to obtain treated water; the nitrobenzene-containing wastewater is prepared from the following components in percentage by mass: 0.5 to 1.5 percent of o-dinitrobenzene, 0.3 to 1.0 percent of m-dinitrobenzene, 0.3 to 1.0 percent of p-dinitrobenzene and 3 to 10 percent of nitrobenzene. According to the treatment method, efficient purification and resource utilization of the nitrobenzene wastewater can be achieved, meanwhile, the treatment cost and the environmental risk are reduced, and the treatment method for the nitrobenzene-containing wastewater is efficient, economical and environmentally friendly. The treated wastewater can directly enter a conventional microbiological treatment system, and the problem that microbiological degradation is difficult does not exist.

Description

Technical Field

[0001] The present invention relates to a method for treating wastewater containing nitrobenzene, belonging to the technical field of wastewater treatment. Background Art

[0002] In the chemical industry, nitrobenzene (usually including mononitrobenzene and dinitrobenzene) is an important raw material widely used in fields such as dyes, pesticides, explosives, and rubber auxiliaries. However, during the production and use of mixed dinitrobenzene, wastewater containing these harmful substances will inevitably be generated. In the industrial production of mixed dinitrobenzene, the wastewater (raw water) is mainly generated in the post-treatment water washing process of the nitration reaction products: after benzene undergoes nitration reaction to form a mixture of mononitrobenzene and dinitrobenzene, it is necessary to remove residual acidic catalysts, unreacted nitrating agents, and some organic impurities through cold water washing. The wastewater containing nitrobenzene contains o-dinitrobenzene (mass content 0.5% - 1.5%), m-dinitrobenzene (mass content 0.3% - 1.0%), p-dinitrobenzene (mass content 0.3% - 1.0%), mononitrobenzene (mass content 3% - 10%), and other pollutants (such as phenol, etc.). Among them, the suspended solids in the wastewater containing nitrobenzene are ≤ 100 mg / L, the COD is 2000 - 10000 mg / L, the pH value is 6.0 - 7.0, and the temperature of the wastewater containing nitrobenzene generated during the production process is 80 - 100 °C.

[0003] In the prior art, the patent with the publication number CN102417249B provides a method for treating nitrobenzene wastewater, which uses nitrobenzene wastewater to prepare a water coal slurry additive. It mainly converts the organic substances in the wastewater into a water coal slurry additive through a series of chemical reactions (such as sulfonation reaction, acetone sulfonation, polycondensation reaction, etc.). This method has a complex process, high cost, and is difficult to control. Some by-products (such as water, alcohols, aldehydes, etc.) may be generated during the reaction process, and these by-products may require additional treatment, increasing the complexity and cost of waste treatment.

[0004] Among other conventional wastewater treatment methods, the most common is to use microorganisms to treat nitrobenzene wastewater. However, the degradation of nitrobenzene is difficult, the degradation efficiency of microorganisms is low, and toxic intermediate products may be generated, affecting the activity of microorganisms. Secondly, microorganisms are more sensitive to environmental conditions such as temperature and pH value, and are easily affected by external environmental fluctuations during the treatment process. In addition, the treatment cycle is long, and it takes a long time to achieve the ideal effect. Moreover, when the wastewater composition is complex, microorganisms may be difficult to effectively degrade all pollutants, resulting in unstable treatment effects.

[0005] From the above analysis, it can be seen that traditional wastewater treatment methods have problems such as low treatment efficiency, high cost, and secondary pollution, and are not very suitable for the industrial treatment of wastewater containing nitrobenzene. Summary of the Invention

[0006] In view of the deficiencies existing in the prior art, the present invention provides a method for treating wastewater containing nitrobenzene. The treatment method can achieve the efficient purification and resource utilization of nitrobenzene wastewater, while reducing the treatment cost and environmental risk. It is an efficient, economical and environmentally friendly method for treating wastewater containing nitrobenzene. The treated wastewater can directly enter a conventional microbial treatment system without the problem of difficult microbial degradation, providing a new solution for the treatment of wastewater containing nitrobenzene.

[0007] The technical solution of the present invention to solve the above technical problems is as follows: A method for treating wastewater containing nitrobenzene, and the treatment method is: S1. Perform multi-stage cooling crystallization on the wastewater containing nitrobenzene, and perform solid-liquid separation to obtain solid dinitrobenzene mixture and crystallization filtrate; S2. Perform heat and pressure oxidation hydrolysis treatment on the crystallization filtrate to obtain treated water; The wastewater containing nitrobenzene includes 0.5%-1.5% by mass of o-dinitrobenzene, 0.3%-1.0% by mass of m-dinitrobenzene, 0.3%-1.0% by mass of p-dinitrobenzene, and 3%-10% by mass of mononitrobenzene. The suspended matter in the wastewater containing nitrobenzene is ≤100 mg / L, the COD is 2000-10000 mg / L, the pH value is 6.0-7.0, and the temperature is 80-100°C.

[0008] Further, in step S1, two-stage cooling crystallization is adopted, wherein the final crystallization temperature of the first-stage cooling crystallization is 40-45°C; the final crystallization temperature of the second-stage cooling crystallization is 20-25°C.

[0009] Further, the cooling rate of the first-stage cooling crystallization is 10°C / min - 15°C / min, the stirring speed is 100-200 rpm, and the constant temperature retention time at the final crystallization temperature is 0.5-1.0 h; The cooling rate of the second-stage cooling crystallization is 5°C / min - 8°C / min, the stirring speed is 50-100 rpm, and the constant temperature retention time at the final crystallization temperature is 1.0-1.5 h.

[0010] Further, the specific operation of step S2 is: Add the crystallization filtrate into an autoclave, control the pressure and temperature of the autoclave, and add a catalyst and hydrogen peroxide oxidant for pressure oxidation hydrolysis treatment, and finally remove the catalyst to obtain treated water.

[0011] Further, in step S2, the temperature of the oxidation hydrolysis treatment is 130-180°C, the pressure is 0.1-1.0 Mpa, and the oxidation hydrolysis treatment time is 2-12 h.

[0012] Further, the catalyst is at least one of transition metal salts and metal oxides.

[0013] Further, the transition metal salt is at least one of nickel salt, chromium salt, cobalt salt, manganese salt, copper salt, iron salt, and rhodium salt; The metal oxide is at least one of copper oxide, iron oxide, cerium oxide, and zirconium oxide.

[0014] Further, in step S2, the addition amount of hydrogen peroxide is 1.5% - 4.5% of the mass of the crystallization filtrate; the addition amount of the catalyst is 0.1% - 3.0% of the mass of the crystallization filtrate.

[0015] Further, when the mass content of mononitrobenzene in the crystallization filtrate is not higher than 5%, the addition amount of hydrogen peroxide is at least 2% of the mass of the crystallization filtrate; Based on the mass content of mononitrobenzene in the crystallization filtrate being 5%, for every 1% increase, the addition amount of hydrogen peroxide increases by at least 0.5% of the mass of the crystallization filtrate on the basis of 2% of the mass of the crystallization filtrate.

[0016] Further, the mass content of dinitrobenzene in the treated water is ≤0.01%, and the mass content of mononitrobenzene is ≤0.1%.

[0017] The beneficial effects of the present invention are: A method for treating nitrobenzene-containing wastewater provided in the present invention can address the deficiencies in the existing treatment process of nitrobenzene-containing wastewater. The cost is lower than that of the direct oxidation method (the energy consumption is significantly reduced. Compared with the direct oxidation method for the treatment method of the present invention, the energy consumption is reduced by at least 25%), and the oxidation and hydrolysis treatment cycle is shortened (compared with directly using the oxidation method for the oxidation and hydrolysis treatment cycle of the present invention, the treatment cycle is shortened by at least 1 / 2); moreover, the treatment method of the present invention can also avoid the problems that physical and biological methods are not suitable for industrialization, is simple to operate, and is more suitable for industrial application.

[0018] The method for treating nitrobenzene-containing wastewater of the present invention uses a combination of multi-stage cooling crystallization and high-pressure oxidation treatment processes, which not only effectively treats nitrobenzene-containing wastewater but also enables continuous treatment of nitrobenzene-containing wastewater, reducing equipment and labor costs.

[0019] The method for treating nitrobenzene-containing wastewater according to the present invention can significantly reduce the content of mixed dinitrobenzene in the wastewater through multi-stage cooling crystallization. Further, in a high-temperature and high-pressure environment, refractory organic substances such as mononitrobenzene are decomposed by strongly oxidizing hydroxyl radicals (-OH). It can achieve overall integrated continuous operation. The content of mixed dinitrobenzene in the treated water is ≤0.01%, and the content of mononitrobenzene is ≤0.1%. The final treatment can be directly achieved by using conventional microbial treatment methods, and finally the up-to-standard discharge of the wastewater is realized. Moreover, the purity of the mixed dinitrobenzene (including o-dinitrobenzene, m-dinitrobenzene, and p-dinitrobenzene) obtained by multi-stage cooling crystallization meets the industrial-grade standard (purity ≥99%), and the recycling of resources can be realized.

[0020] Further, in the method for treating nitrobenzene-containing wastewater according to the present invention, by reasonably controlling the two-stage cooling crystallization temperature, cooling rate, and stirring speed, while accelerating the precipitation of mixed dinitrobenzene, it is possible to avoid problems such as equipment blockage caused by crystal agglomeration and the decrease in the purity of mixed dinitrobenzene due to the inclusion of filtrate caused by agglomeration. Moreover, the crystal particles of the precipitated mixed dinitrobenzene are more uniform, effectively improving the quality of mixed dinitrobenzene and realizing recycling. In addition, using two-stage cooling crystallization can save energy while maximizing the recovery of mixed dinitrobenzene, improving the efficiency of subsequent oxidation and hydrolysis treatment, reducing the dosage of catalysts and oxidants, and lowering the usage cost.

[0021] In the method for treating nitrobenzene-containing wastewater according to the present invention, through the mutual cooperation of cooling crystallization and oxidation hydrolysis treatment, the overall process flow is simple to operate, has low energy consumption, realizes the efficient treatment of wastewater, and can realize the recycling of mixed dinitrobenzene. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a schematic diagram of a nitrobenzene-containing wastewater treatment system; In the figure, 1 is a primary crystallization tank; 2 is a cold and heat integrated machine; 3 is a solid-liquid separation device; 4 is a peristaltic pump; 5 is a secondary crystallization tank; 6 is a storage tank; 7 is an oxidation and hydrolysis treatment device. DETAILED DESCRIPTION OF THE INVENTION

[0023] The following provides a detailed description of the specific embodiments of the present invention. The present invention can be implemented in many other ways different from those described herein. Those skilled in the art can make similar improvements without departing from the connotation of the present invention. Therefore, the present invention is not limited by the specific embodiments disclosed.

[0024] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which the present invention belongs. The terms used are only for describing specific embodiments and do not limit the present invention.

[0025] A treatment method for wastewater containing nitrobenzene, the treatment method is as follows: S1. Perform multi-stage cooling crystallization on the wastewater containing nitrobenzene, and perform solid-liquid separation to obtain solid mixed dinitrobenzene and crystallization filtrate; S2. Perform heat and pressure oxidation hydrolysis treatment on the crystallization filtrate to obtain treated water; The wastewater containing nitrobenzene includes 0.5%-1.5% by mass of o-dinitrobenzene, 0.3%-1.0% by mass of m-dinitrobenzene, 0.3%-1.0% by mass of p-dinitrobenzene, and 3%-10% by mass of mononitrobenzene. The suspended matter in the wastewater containing nitrobenzene is ≤100 mg / L, the COD is 2000-10000 mg / L, the pH value is 6.0-7.0, and the temperature is 80-100°C.

[0026] Specifically, in step S1, two-stage cooling crystallization is adopted, wherein the final crystallization temperature of the first-stage cooling crystallization is 40-45°C; the final crystallization temperature of the second-stage cooling crystallization is 20-25°C.

[0027] Specifically, the cooling rate of the first-stage cooling crystallization is 10°C / min - 15°C / min, the stirring speed is 100-200 rpm, and the constant temperature retention time at the final crystallization temperature is 0.5-1.0 h; The cooling rate of the second-stage cooling crystallization is 5°C / min - 8°C / min, the stirring speed is 50-100 rpm, and the constant temperature retention time at the final crystallization temperature is 1.0-1.5 h.

[0028] During the first-stage cooling crystallization, a relatively fast cooling rate and a relatively fast stirring speed are adopted, which can accelerate the precipitation of mixed dinitrobenzene, avoid crystal agglomeration, and improve the crystallization separation efficiency; During the second-stage cooling crystallization, a relatively slow cooling rate and a relatively slow stirring speed are adopted, which can promote the complete growth of crystals, reduce the entrainment of fine particles, and finally the purity of the obtained mixed dinitrobenzene is ≥99%; and the two-stage cooling crystallization makes the removal rate of mixed dinitrobenzene in the wastewater ≥95%, reduces the subsequent oxidation hydrolysis treatment load, and is beneficial to improving the recovery rate of mixed dinitrobenzene.

[0029] More specifically, during the cooling crystallization process, a stirring paddle made of tetrafluoroethylene material is used for stirring, and the stirring paddle of this material is corrosion-resistant and can reduce the introduction of impurities.

[0030] More specifically, after the first-stage cold air crystallization in step S1, constant temperature solid-liquid separation is performed to obtain part of the mixed dinitrobenzene and the first-stage filtrate; the first-stage filtrate is then subjected to the second-stage cooling crystallization, and after the second-stage cooling crystallization, constant temperature solid-liquid separation is performed again to obtain the second part of the mixed dinitrobenzene and the crystallization filtrate.

[0031] More specifically, the solid-liquid separation operation can be any one of filtration or centrifugation.

[0032] Specifically, the specific operation of step S2 is as follows: Add the crystallization filtrate into an autoclave, control the pressure and temperature of the autoclave, add a catalyst and a hydrogen peroxide oxidant for pressure oxidation hydrolysis treatment, and finally remove the catalyst to obtain the treated water.

[0033] More specifically, the mass concentration of hydrogen peroxide used in the embodiment of the present invention is 27.5%.

[0034] Specifically, in step S2, the temperature of the oxidation hydrolysis treatment is 130 - 180 °C, the pressure is 0.1 - 1.0 Mpa, and the oxidation hydrolysis treatment time is 2 - 12 h.

[0035] Preferably, the oxidation hydrolysis treatment time is 2 - 6 h.

[0036] Specifically, the catalyst is at least one of transition metal salts and metal oxides.

[0037] Specifically, the transition metal salt is at least one of nickel salt, chromium salt, cobalt salt, manganese salt, copper salt, iron salt, and rhodium salt; The metal oxide is at least one of copper oxide, iron oxide, cerium oxide, and zirconium oxide.

[0038] The pH of the wastewater containing nitrobenzene is 6 - 7, which cooperates with transition metal salts (such as Fe²⁺ / Cu²⁺). Under this pH condition, the catalytic activity of the transition metal salts is relatively high, which is conducive to maintaining a high catalytic efficiency. Moreover, it can ensure thorough oxidation hydrolysis treatment, avoid the generation of intermediate products (such as aniline-like toxic substances), and reduce the toxicity of the effluent by 90%. In the treatment of wastewater containing nitrobenzene, the toxicity of the effluent is mainly measured by chemical analysis methods. Chemical analysis methods directly detect the concentration changes of toxic substances such as aniline-like substances (where the toxic substances include incompletely oxidized products such as nitrobenzene, phenylenediamine, aniline, and azoaniline, as well as mononitrobenzene and dinitrobenzene) through HPLC and GC-MS. The concentration of aniline-like substances before treatment is C 前 and the concentration of aniline-like substances after treatment is C 后 , and the formula for calculating the toxicity reduction ratio is (1 - C 后 / C 前)× 100%; "The toxicity is reduced by 90%" refers to the result of comparing the treatment method of the present invention with a control group that does not use transition metal salts (Fe²⁺ / Cu²⁺) for catalysis and does not optimize the pH conditions. For example, in the conventional oxidation process, due to low catalytic efficiency, there are more residues of aniline intermediate products. After optimization, the system can completely degrade pollutants through highly efficient catalytic oxidation, reducing the concentration of toxic substances (such as aniline) to 10% of the original level, thus achieving a significant reduction in toxicity.

[0039] Specifically, in step S2, the addition amount of hydrogen peroxide is 1.5% - 4.5% of the mass of the crystallization filtrate; the addition amount of the catalyst is 0.1% - 3.0% of the mass of the crystallization filtrate.

[0040] Specifically, when the mass content of mononitrobenzene in the crystallization filtrate is not higher than 5%, the addition amount of hydrogen peroxide is at least 2% of the mass of the crystallization filtrate; Based on the mass content of mononitrobenzene in the crystallization filtrate being 5%, for every 1% increase, the addition amount of hydrogen peroxide increases by at least 0.5% of the mass of the crystallization filtrate on the basis of 2% of the mass of the crystallization filtrate.

[0041] The above dynamic ratio design can avoid waste of excessive oxidant, prevent the generation of by-products in the system due to insufficient oxidation, and reduce the treatment cost.

[0042] Specifically, the mass content of mixed dinitro in the treated water ≤ 0.01%, and the mass content of mononitrobenzene ≤ 0.1%.

[0043] More specifically, the treatment of the nitrobenzene-containing wastewater can be carried out continuously using a nitrobenzene-containing wastewater treatment system such as Figure 1 . The specific process is as follows: The nitrobenzene-containing wastewater to be treated is discharged into the first-stage crystallization tank 1. The cooling and heating integrated machine 2 controls the temperature of the first-stage crystallization tank 1. After the first-stage cooling crystallization is completed in the first-stage crystallization tank 1, the first-stage filtrate after being treated by the solid-liquid separation device 3 enters the second-stage crystallization tank 5 through the peristaltic pump 4. After the second-stage cooling crystallization is completed in the second-stage crystallization tank 5, the crystallization filtrate after solid-liquid separation enters the storage tank 6. The storage tank 6 is connected to the oxidation and hydrolysis treatment device 7 through the peristaltic pump 4. The oxidation and hydrolysis treatment device 7 is equipped with a thermometer and a pressure gauge. The crystallization filtrate undergoes oxidation and hydrolysis treatment in the oxidation and hydrolysis treatment device 7 to obtain the treated water. After the catalyst is filtered out from the treated water, it can directly enter the microbial treatment system for microbial decomposition, and finally obtain water that can meet the discharge standards.

[0044] Example 1 The nitrobenzene-containing wastewater includes 1.0% by mass of o-dinitrobenzene, 0.5% by mass of m-dinitrobenzene, 0.8% by mass of p-dinitrobenzene, and 5% by mass of mononitrobenzene. The suspended solids in the nitrobenzene-containing wastewater are ≤ 100 mg / L, the COD is 5000 mg / L, the pH value is 6.0 - 7.0, and the temperature is 80 - 100 °C. A method for treating nitrobenzene-containing wastewater, the treatment method is as follows: S1. Perform two-stage cooling crystallization on the nitrobenzene-containing wastewater: The cooling rate of the first-stage cooling crystallization is 10 °C / min, the stirring speed is 100 rpm, the final crystallization temperature is 40 °C, and the constant-temperature retention time at the final crystallization temperature is 1.0 h; The cooling rate of the second-stage cooling crystallization is 5 °C / min, the stirring speed is 80 rpm, the final crystallization temperature is 25 °C, and the constant-temperature retention time at the final crystallization temperature is 1.0 h.

[0045] After two-stage cooling crystallization, a solid mixture of dinitrobenzenes and a crystallization filtrate are obtained; S2. Perform heat-pressurized oxidative hydrolysis treatment on the crystallization filtrate to obtain treated water; Among them, the catalyst is copper oxide, the oxidant is hydrogen peroxide, the addition amount of hydrogen peroxide is 2% of the mass of the crystallization filtrate, and the addition amount of the catalyst is 1% of the mass of the crystallization filtrate; The temperature of the oxidative hydrolysis treatment is 180 °C, the pressure is 1.0 Mpa, and the time of the oxidative hydrolysis treatment is 6 h.

[0046] Example 2 The nitrobenzene-containing wastewater includes 0.5% by mass of o-dinitrobenzene, 1.0% by mass of m-dinitrobenzene, 0.3% by mass of p-dinitrobenzene, and 3% by mass of mononitrobenzene. The suspended solids in the nitrobenzene-containing wastewater are ≤ 100 mg / L, the COD is 3000 mg / L, the pH value is 6.0 - 7.0, and the temperature is 80 - 100 °C. A method for treating nitrobenzene-containing wastewater, the treatment method is as follows: S1. Perform two-stage cooling crystallization on the nitrobenzene-containing wastewater: The cooling rate of the first-stage cooling crystallization is 15 °C / min, the stirring speed is 200 rpm, the final crystallization temperature is 45 °C, and the constant-temperature retention time at the final crystallization temperature is 0.5 h; The cooling rate of the second-stage cooling crystallization is 8 °C / min, the stirring speed is 50 rpm, the final crystallization temperature is 20 °C, and the constant-temperature retention time at the final crystallization temperature is 1.5 h.

[0047] After two-stage cooling crystallization, a solid mixture of dinitrobenzenes and a crystallization filtrate are obtained; S2. Heat and pressurize the crystallization filtrate for oxidative hydrolysis treatment to obtain treated water; Among them, the catalyst is copper oxide, the oxidant is hydrogen peroxide, the addition amount of hydrogen peroxide is 1.5% of the mass of the crystallization filtrate, and the addition amount of the catalyst is 0.1% of the mass of the crystallization filtrate; The temperature for oxidative hydrolysis treatment is 130 °C, the pressure is 1.0 Mpa, and the time for oxidative hydrolysis treatment is 12 h.

[0048] Example 3 The nitrobenzene-containing wastewater contains 1.5% o-dinitrobenzene, 0.3% m-dinitrobenzene, 1.0% p-dinitrobenzene, and 8% mononitrobenzene by mass. The suspended solids in the nitrobenzene-containing wastewater are ≤ 100 mg / L, the COD is 6000 mg / L, the pH value is 6.0 - 7.0, and the temperature is 80 - 100 °C A treatment method for nitrobenzene-containing wastewater, and the treatment method is as follows: S1. Perform two-stage cooling crystallization on the nitrobenzene-containing wastewater: The cooling rate in the first-stage cooling crystallization is 15 °C / min, the stirring speed is 150 rpm, the final crystallization temperature is 40 °C, and the constant-temperature retention time at the final crystallization temperature is 1.0 h; The cooling rate in the second-stage cooling crystallization is 5 °C / min, the stirring speed is 100 rpm, the final crystallization temperature is 25 °C, and the constant-temperature retention time at the final crystallization temperature is 1.0 h.

[0049] After two-stage cooling crystallization, solid dinitrobenzene mixture and crystallization filtrate are obtained; S2. Heat and pressurize the crystallization filtrate for oxidative hydrolysis treatment to obtain treated water; Among them, the catalyst is iron oxide, the oxidant is hydrogen peroxide, the addition amount of hydrogen peroxide is 3.5% of the mass of the crystallization filtrate, and the addition amount of the catalyst is 3% of the mass of the crystallization filtrate; The temperature for oxidative hydrolysis treatment is 160 °C, the pressure is 0.6 Mpa, and the time for oxidative hydrolysis treatment is 4 h.

[0050] Example 4 The nitrobenzene-containing wastewater contains 1.0% o-dinitrobenzene, 0.5% m-dinitrobenzene, 0.5% p-dinitrobenzene, and 10% mononitrobenzene by mass. The suspended solids in the nitrobenzene-containing wastewater are ≤ 100 mg / L, the COD is 10000 mg / L, the pH value is 6.0 - 7.0, and the temperature is 80 - 100 °C A treatment method for nitrobenzene-containing wastewater, and the treatment method is as follows: S1. Perform two-stage cooling crystallization on the nitrobenzene-containing wastewater: The cooling rate of the first-stage cooling crystallization is 12 °C / min, the stirring speed is 150 rpm, the final crystallization temperature is 40 °C, and the constant-temperature retention time at the final crystallization temperature is 1.0 h; The cooling rate of the second-stage cooling crystallization is 5 °C / min, the stirring speed is 80 rpm, the final crystallization temperature is 20 °C, and the constant-temperature retention time at the final crystallization temperature is 1.5 h.

[0051] After two-stage cooling crystallization, dinitrobenzene solid and crystallization filtrate are obtained; S2. Heat and pressurize the crystallization filtrate for oxidative hydrolysis treatment to obtain treated water; Among them, the catalyst is iron oxide, the oxidant is hydrogen peroxide, the addition amount of hydrogen peroxide is 4.5% of the mass of the crystallization filtrate, and the addition amount of the catalyst is 2% of the mass of the crystallization filtrate; The temperature of the oxidative hydrolysis treatment is 150 °C, the pressure is 0.5 Mpa, and the oxidative hydrolysis treatment time is 4 h.

[0052] Example 5 The nitrobenzene-containing wastewater contains 1.0% o-dinitrobenzene, 0.5% m-dinitrobenzene, 0.5% p-dinitrobenzene, and 5% mononitrobenzene by mass. The suspended solids in the nitrobenzene-containing wastewater are ≤100 mg / L, the COD is 10,000 mg / L, the pH value is 6.0 - 7.0, and the temperature is 80 - 100 °C A treatment method for nitrobenzene-containing wastewater, the treatment method is: S1. Perform two-stage cooling crystallization on the nitrobenzene-containing wastewater: The cooling rate of the first-stage cooling crystallization is 10 °C / min, the stirring speed is 100 rpm, the final crystallization temperature is 40 °C, and the constant-temperature retention time at the final crystallization temperature is 1.0 h; The cooling rate of the second-stage cooling crystallization is 5 °C / min, the stirring speed is 50 rpm, the final crystallization temperature is 25 °C, and the constant-temperature retention time at the final crystallization temperature is 1.5 h.

[0053] After two-stage cooling crystallization, dinitrobenzene solid and crystallization filtrate are obtained; S2. Heat and pressurize the crystallization filtrate for oxidative hydrolysis treatment to obtain treated water; Among them, the catalyst is iron oxide, the oxidant is hydrogen peroxide, the addition amount of hydrogen peroxide is 2% of the mass of the crystallization filtrate, and the addition amount of the catalyst is 1% of the mass of the crystallization filtrate; The temperature of the oxidative hydrolysis treatment is 130 °C, the pressure is 0.3 Mpa, and the oxidative hydrolysis treatment time is 2 h.

[0054] Example 6 The nitrobenzene-containing wastewater contains 1.0% o-dinitrobenzene, 0.5% m-dinitrobenzene, 0.3% p-dinitrobenzene, and 5% mononitrobenzene by mass. The suspended solids in the nitrobenzene-containing wastewater are ≤ 100 mg / L, the COD is 10,000 mg / L, the pH value is 6.0 - 7.0, and the temperature is 80 - 100 °C. A treatment method for nitrobenzene-containing wastewater, the treatment method is as follows: S1. Perform two-stage cooling crystallization on the nitrobenzene-containing wastewater: The cooling rate of the first-stage cooling crystallization is 10 °C / min, the stirring speed is 100 rpm, the final crystallization temperature is 40 °C, and the constant-temperature retention time at the final crystallization temperature is 1.0 h; The cooling rate of the second-stage cooling crystallization is 5 °C / min, the stirring speed is 50 rpm, the final crystallization temperature is 25 °C, and the constant-temperature retention time at the final crystallization temperature is 1.5 h.

[0055] After two-stage cooling crystallization, solid mixed dinitrobenzene and crystallization filtrate are obtained; S2. Perform heat and pressure oxidation hydrolysis treatment on the crystallization filtrate to obtain treated water; Among them, the catalyst is iron oxide, the oxidant is hydrogen peroxide, the addition amount of hydrogen peroxide is 2% of the mass of the crystallization filtrate, and the addition amount of the catalyst is 1% of the mass of the crystallization filtrate; The temperature of the oxidation hydrolysis treatment is 130 °C, the pressure is 0.5 Mpa, and the oxidation hydrolysis treatment time is 2 h.

[0056] Example 7 The nitrobenzene-containing wastewater contains 0.5% o-dinitrobenzene, 1.0% m-dinitrobenzene, 0.3% p-dinitrobenzene, and 5% mononitrobenzene by mass. The suspended solids in the nitrobenzene-containing wastewater are ≤ 100 mg / L, the COD is 10,000 mg / L, the pH value is 6.0 - 7.0, and the temperature is 80 - 100 °C. A treatment method for nitrobenzene-containing wastewater, the treatment method is as follows: S1. Perform two-stage cooling crystallization on the nitrobenzene-containing wastewater: The cooling rate of the first-stage cooling crystallization is 10 °C / min, the stirring speed is 100 rpm, the final crystallization temperature is 40 °C, and the constant-temperature retention time at the final crystallization temperature is 1.0 h; The cooling rate of the second-stage cooling crystallization is 5 °C / min, the stirring speed is 50 rpm, the final crystallization temperature is 25 °C, and the constant-temperature retention time at the final crystallization temperature is 1.5 h.

[0057] After two-stage cooling crystallization, solid mixed dinitrobenzene and crystallization filtrate are obtained; S2. Heat and pressurize the crystallization filtrate for oxidative hydrolysis treatment to obtain treated water; Among them, the catalyst is iron oxide, the oxidant is hydrogen peroxide, the addition amount of hydrogen peroxide is 2% of the mass of the crystallization filtrate, and the addition amount of the catalyst is 1% of the mass of the crystallization filtrate; The temperature for oxidative hydrolysis treatment is 130 °C, the pressure is 0.1 Mpa, and the time for oxidative hydrolysis treatment is 2 h.

[0058] Comparative Example 1 The same wastewater as in Example 1 and the same method are used for the treatment of nitrobenzene-containing wastewater. The difference is that in step S1, only primary cooling crystallization is used (the crystallization conditions are the same as those of the primary cooling crystallization in Example 1). The specific treatment method is as follows: S1. Perform primary cooling crystallization on the nitrobenzene-containing wastewater: The cooling rate for cooling crystallization is 10 °C / min, the stirring speed is 100 rpm, the final crystallization temperature is 25 °C, and the constant temperature retention time at the final crystallization temperature is 2.0 h.

[0059] After primary cooling crystallization, solid dinitrobenzene mixture and crystallization filtrate are obtained; S2. Heat and pressurize the crystallization filtrate for oxidative hydrolysis treatment to obtain treated water; Among them, the catalyst is copper oxide, the oxidant is hydrogen peroxide, the addition amount of hydrogen peroxide is 2% of the mass of the crystallization filtrate, and the addition amount of the catalyst is 1% of the mass of the crystallization filtrate; The temperature for oxidative hydrolysis treatment is 180 °C, the pressure is 1.0 Mpa, and the time for oxidative hydrolysis treatment is 6 h.

[0060] Comparative Example 2 The same wastewater as in Example 1 and the same method are used for the treatment of nitrobenzene-containing wastewater. The difference is that in step S1, only primary cooling crystallization is used (the crystallization conditions are the same as those of the secondary cooling crystallization in Example 1). The specific treatment method is as follows: S1. Perform primary cooling crystallization on the nitrobenzene-containing wastewater: The cooling rate for cooling crystallization is 5 °C / min, the stirring speed is 80 rpm, the final crystallization temperature is 25 °C, and the constant temperature retention time at the final crystallization temperature is 2.0 h.

[0061] After primary cooling crystallization, solid dinitrobenzene mixture and crystallization filtrate are obtained; S2. Heat and pressurize the crystallization filtrate for oxidative hydrolysis treatment to obtain treated water; Among them, the catalyst is copper oxide, the oxidant is hydrogen peroxide, the addition amount of hydrogen peroxide is 2% of the mass of the crystallization filtrate, and the addition amount of the catalyst is 1% of the mass of the crystallization filtrate; The oxidation hydrolysis treatment temperature is 180 °C, the pressure is 1.0 Mpa, and the oxidation hydrolysis treatment time is 6 h.

[0062] Comparative Example 3 The same wastewater as in Example 1 and the same method were used for the treatment of nitrobenzene-containing wastewater. The difference is that: the final crystallization temperature of the second-stage cooling crystallization in Step S1 was decreased. The final crystallization temperature of the second-stage cooling crystallization in this Comparative Example 3 was 10 °C. The specific treatment method is as follows: S1. Perform two-stage cooling crystallization on the nitrobenzene-containing wastewater: The cooling rate of the first-stage cooling crystallization is 10 °C / min, the stirring speed is 100 rpm, the final crystallization temperature is 40 °C, and the holding time at the final crystallization temperature is 1.0 h; The cooling rate of the second-stage cooling crystallization is 5 °C / min, the stirring speed is 80 rpm, the final crystallization temperature is 10 °C, and the holding time at the final crystallization temperature is 1.0 h.

[0063] After two-stage cooling crystallization, solid dinitrobenzene mixture and crystallization filtrate are obtained; S2. Perform heat and pressure oxidation hydrolysis treatment on the crystallization filtrate to obtain treated water; Among them, the catalyst is copper oxide, the oxidant is hydrogen peroxide, the addition amount of hydrogen peroxide is 2% of the mass of the crystallization filtrate, and the addition amount of the catalyst is 1% of the mass of the crystallization filtrate; The oxidation hydrolysis treatment temperature is 180 °C, the pressure is 1.0 Mpa, and the oxidation hydrolysis treatment time is 6 h.

[0064] Comparative Example 4 The same wastewater as in Example 1 and the same method were used for the treatment of nitrobenzene-containing wastewater. The difference is that: the cooling rate and stirring speed of the second-stage cooling crystallization in Step S1 are the same as the conditions of the first-stage cooling crystallization. The specific treatment method is as follows: S1. Perform two-stage cooling crystallization on the nitrobenzene-containing wastewater: The cooling rate of the first-stage cooling crystallization is 10 °C / min, the stirring speed is 100 rpm, the final crystallization temperature is 40 °C, and the holding time at the final crystallization temperature is 1.0 h; The cooling rate of the second-stage cooling crystallization is 10 °C / min, the stirring speed is 100 rpm, the final crystallization temperature is 25 °C, and the holding time at the final crystallization temperature is 1.0 h.

[0065] After two-stage cooling crystallization, solid dinitrobenzene mixture and crystallization filtrate are obtained; S2. Perform heat and pressure oxidation hydrolysis treatment on the crystallization filtrate to obtain treated water; Among them, the catalyst is copper oxide, the oxidant is hydrogen peroxide, the addition amount of hydrogen peroxide is 2% of the mass of the crystallization filtrate, and the addition amount of the catalyst is 1% of the mass of the crystallization filtrate; The oxidation hydrolysis treatment temperature is 180 °C, the pressure is 1.0 Mpa, and the oxidation hydrolysis treatment time is 6 h.

[0066] Comparative Example 5 The same wastewater as in Example 1 and the same method were used for the treatment of nitrobenzene-containing wastewater. The difference is that in this Comparative Example 5, only primary cooling crystallization was carried out, that is: after the first-stage cooling crystallization was completed, solid-liquid separation was not carried out, but in the same system, cooling crystallization was continued under the conditions of the second-stage cooling crystallization. The specific treatment method is as follows: S1. Cool and crystallize the nitrobenzene-containing wastewater: Control the cooling rate to 10 °C / min, the stirring speed to 100 rpm. After the temperature in the system drops to 40 °C, keep it at a constant temperature for 1.0 h; then control the cooling rate to 5 °C / min, the stirring speed to 80 rpm, the final crystallization temperature to 25 °C, and the holding time at the final crystallization temperature is 1.0 h.

[0067] Finally, solid-liquid separation is carried out to obtain mixed dinitrobenzene solid and crystallization filtrate; S2. Carry out heat and pressure oxidation hydrolysis treatment on the crystallization filtrate to obtain treated water; Among them, the catalyst is copper oxide, the oxidant is hydrogen peroxide, the addition amount of hydrogen peroxide is 2% of the mass of the crystallization filtrate, and the addition amount of the catalyst is 1% of the mass of the crystallization filtrate; The oxidation hydrolysis treatment temperature is 180 °C, the pressure is 1.0 Mpa, and the oxidation hydrolysis treatment time is 6 h.

[0068] Comparative Example 6 The same wastewater as in Example 1 and the same method were used for the treatment of nitrobenzene-containing wastewater. The difference is that in this Comparative Example 6, the addition amount of hydrogen peroxide was reduced. The specific treatment method is as follows: S1. Carry out two-stage cooling crystallization on the nitrobenzene-containing wastewater: The cooling rate of the first-stage cooling crystallization is 10 °C / min, the stirring speed is 100 rpm, the final crystallization temperature is 40 °C, and the holding time at the final crystallization temperature is 1.0 h; The cooling rate of the second-stage cooling crystallization is 5 °C / min, the stirring speed is 80 rpm, the final crystallization temperature is 25 °C, and the holding time at the final crystallization temperature is 1.0 h.

[0069] After two-stage cooling crystallization, mixed dinitrobenzene solid and crystallization filtrate are obtained; S2. Carry out heat and pressure oxidation hydrolysis treatment on the crystallization filtrate to obtain treated water; Among them, the catalyst is copper oxide, the oxidant is hydrogen peroxide, the addition amount of hydrogen peroxide is 1.5% of the mass of the crystallization filtrate, and the addition amount of the catalyst is 1% of the mass of the crystallization filtrate; The oxidation hydrolysis treatment temperature is 180 °C, the pressure is 1.0 Mpa, and the oxidation hydrolysis treatment time is 6 h.

[0070] Comparative Example 7 The same wastewater as in Example 1 was used to treat the nitrobenzene-containing wastewater. The difference is that in this Comparative Example 7, no cooling crystallization treatment was carried out, and direct oxidation hydrolysis treatment was carried out (increasing the amount of oxidant and raising the treatment temperature and treatment pressure). The specific treatment method is as follows: The nitrobenzene-containing wastewater was subjected to heating and pressurized oxidation hydrolysis treatment to obtain the treated water; Among them, the catalyst is copper oxide, the oxidant is hydrogen peroxide, the addition amount of hydrogen peroxide is 10% of the mass of the crystallization filtrate, and the addition amount of the catalyst is 3% of the mass of the crystallization filtrate; The oxidation hydrolysis treatment temperature is 200 °C, the pressure is 2.0 Mpa, and the oxidation hydrolysis treatment time is 24 h.

[0071] Comparative Example 8 The same wastewater and the same method as in Example 1 were used to treat the nitrobenzene-containing wastewater. The difference is that in this Comparative Example 8, only the first-stage cooling crystallization was carried out in step S1. The specific treatment method is as follows: S1. Cool and crystallize the nitrobenzene-containing wastewater: The cooling rate of the cooling crystallization is 10 °C / min, the stirring speed is 100 rpm, the final crystallization temperature is 40 °C, and the constant temperature retention time at the final crystallization temperature is 1.0 h; After cooling crystallization, solid dinitrobenzene mixture and crystallization filtrate are obtained; S2. Heat and pressurize the crystallization filtrate for oxidation hydrolysis treatment to obtain the treated water; Among them, the catalyst is copper oxide, the oxidant is hydrogen peroxide, the addition amount of hydrogen peroxide is 2% of the mass of the crystallization filtrate, and the addition amount of the catalyst is 1% of the mass of the crystallization filtrate; The oxidation hydrolysis treatment temperature is 180 °C, the pressure is 1.0 Mpa, and the oxidation hydrolysis treatment time is 6 h.

[0072] 1. Detect the water treated in the above examples and comparative examples. The contents of mixed dinitrobenzene (ortho, meta, and para isomers) and mononitrobenzene in the treated water are determined by gas chromatography - mass spectrometry (GC - MS, referring to the HJ 716 - 2014 standard). After enriching the target substances by liquid - liquid extraction, the isomers are separated by a chromatographic column and quantified by mass spectrometry; the purity of the recovered mixed dinitrobenzene is evaluated by gas chromatography - flame ionization detection (GC - FID, according to the GB / T 9335 - 2009 standard). Based on the peak area normalization method, the proportions of various isomers and the total purity are calculated. The specific test results are shown in Table 1 below.

[0073] Table 1 Detection Results

[0074] It can be seen from the above table data that: In Examples 1 - 7, the treatment method described in the present invention is used to treat the nitrobenzene - containing wastewater. The mass content of mixed dinitrobenzene in the treated water ≤ 0.01%, and the mass content of mononitrobenzene ≤ 0.1%; the recovered mixed dinitrobenzene (purity ≥ 94.5%) can be directly used to prepare high - value - added chemical products such as dye intermediates (such as phenylenediamine), pesticide raw materials (such as nitrophenol - based herbicides), rubber auxiliaries (antioxidants and vulcanization accelerators), and energetic material precursors. Its purity meets the quality requirements of raw materials in the fine chemical industry, realizing resource - based recycling. Moreover, the recovery rate of mixed dinitrobenzene is relatively high, all reaching more than 75%. In the treatment method described in the present invention, a step - by - step cooling crystallization operation mode is adopted. During the first - stage cooling crystallization, the high - melting - point ortho - dinitrobenzene (melting point 89°C) can be preferentially precipitated, reducing the coprecipitation of impurities; during the second - stage cooling crystallization process, the temperature is slowly decreased to control the crystal growth rate, obtaining crystal products with large particle size (D50 > 50 μm) and high purity (≥ 98.5%).

[0075] It can be seen from the comparison of the experimental results of Comparative Example 1, Comparative Example 2 and Example 1 that: If only single - stage cooling crystallization is adopted, it will lead to rapid nucleation and growth of crystals, forming irregular crystal lattices, which are prone to encapsulating unreacted raw materials (such as phenol, nitrating agent residues) and by - products (such as nitrophenols). Moreover, when there is no step - by - step crystallization, small crystals redissolve due to their high surface energy and deposit on the surface of large crystals, and impurities are embedded, resulting in a decrease in the purity of mixed dinitrobenzene (the purity of mixed dinitrobenzene in Comparative Examples 1 - 2 is 85% - 88.3%, while the purity of mixed dinitrobenzene in Example 1 is 98.5%). In addition, instantaneous massive crystallization will also cause a sudden increase in the suspended solid concentration, leading to hydrodynamic blockage, an increase in equipment pressure drop, and a decrease in separation efficiency. The recovered mixed dinitrobenzene cannot meet the industrial product standard, and during the treatment process, the equipment is prone to blockage problems, bringing great inconvenience to production.

[0076] From the comparison of the experimental results between Comparative Example 3 and Example 1, it can be seen that when the final crystallization temperature drops to 10 °C, other impurities in the wastewater will precipitate accordingly (such as dinitrophenol, nitrophenol, etc.), resulting in a decrease in the purity of mixed dinitrobenzene. At the same time, the crystal growth rate slows down at low temperatures, and it is easy to form fine crystals (<10 μm). The specific surface area increases, adsorbing more impurities and mixing in the mixed dinitrobenzene, ultimately causing the mixed dinitrobenzene to fail to meet the product standard.

[0077] From the comparison of the experimental results between Comparative Example 4 and Example 1, it can be seen that when the same cooling rate (10 °C / min) and stirring speed (100 rpm) are used in the second stage as in the first stage, it leads to an imbalance in crystal growth kinetics. The specific reasons are as follows: Rapid cooling: When the final temperature of the second stage is 25 °C, the supersaturation increases instantaneously (ΔC / Δt is too large), triggering explosive nucleation and forming crystal clusters (agglomerates); High-shear stirring: The crystal clusters are broken to produce microcrystals (<5 μm). The surface of the microcrystals adsorbs soluble organic substances (such as mononitrobenzene), and it penetrates the filter membrane during solid-liquid separation, resulting in a decrease in the recovery rate of mixed dinitrobenzene (the recovery rate of Comparative Example 4 is 63%, and the recovery rate of Example 1 is 95%). Therefore, adopting the first-stage cooling crystallization and second-stage cooling crystallization conditions defined in the present invention is more conducive to achieving good treatment of wastewater and ensuring high-quality mixed dinitrobenzene.

[0078] From the comparison of the experimental results between Comparative Example 5 and Example 1, it can be seen that if the two-stage crystallization is continuously carried out in the same system without timely removing the primary crystals, the following problems will occur: Crystal redissolution-recrystallization: Part of the primary crystals dissolve during the second-stage cooling process, and new impurities are introduced during recrystallization, resulting in a purity drop to 83.6%.

[0079] From the comparison of the experimental results between Comparative Example 6 and Example 1, it can be seen that when the amount of hydrogen peroxide added decreases from 2% to 1.5%, the generation amount of hydroxyl radicals (·OH) is insufficient (Fenton reaction kinetics), and the degradation path of mononitrobenzene is blocked. The toxicity of aniline substances (LC50≈1 mg / L) is much higher than that of nitrobenzene, resulting in an increase in the toxicity of the effluent (in Comparative Example 6, the residual amount of mononitrobenzene is 0.33%, and aniline is not measured but actually exists). The dynamic ratio design (increasing 0.5% H2O2 for every 1% mononitrobenzene) ensures sufficient ·OH through stoichiometric ratio control (C∶H2O2≈1∶3), and completely mineralizes it into CO2 and H2O.

[0080] From the comparison of the experimental results between Comparative Example 7 and Example 1, it can be seen that: if the crystallization pretreatment is not carried out (Comparative Example 7), the residual content of mixed dinitrobenzene is 0.0667%, and that of mononitrobenzene is 0.667%, far exceeding the experimental results of Example 1. Because the solubility of mixed dinitrobenzene (logKow = 1.98) in high-temperature water is low (≈0.1 g / L), the solid-liquid mass transfer resistance is large during direct oxidation, resulting in low reaction efficiency. In addition, multiple components (mixed dinitrobenzene, mononitrobenzene, phenol) compete to consume ·OH, and the difference in degradation priority leads to an increase in the residual amount.

[0081] From the comparison of the experimental results between Comparative Example 8 and Example 1, it can be seen that: if only the first-stage cooling crystallization is carried out in Step S1, the yield of mixed dinitrobenzene will decrease significantly, and the wastewater entering Step S2 contains more mixed dinitrobenzene, ultimately resulting in a relatively high content of mixed dinitrobenzene and mononitrobenzene in the treated wastewater.

[0082] II. Analysis of the adaptability of microbial treatment (1) Feasibility of Examples 1-7 Data support: The COD content in the wastewater after treatment in Examples 1-7 is 400-600 mg / L, the content of mixed dinitrobenzene is ≤0.01%, and the content of mononitrobenzene is ≤0.1%, meeting the requirements for the influent of microbial treatment (COD < 1000 mg / L, the content of nitrobenzene is < 2 mg / L).

[0083] Biochemical mechanism: In the aerobic biological treatment of wastewater containing nitrobenzene, Pseudomonas putida achieves the complete degradation of pollutants through a specific enzyme system. The specific process is as follows: 1. Hydroxylation and denitration of nitrobenzene: The key reaction is catalyzed by a two-component oxygenase system (including reductase RedA2, ferredoxin Fdx1, and oxidase OxB) secreted by Pseudomonas putida. Under the conditions of dissolved oxygen ≥ 4 mg / L and 30 °C, this enzyme system activates oxygen molecules and inserts them into the benzene ring of nitrobenzene, first generating an unstable cis-dihydroxy intermediate, and then removing the nitro group (-NO2) to be converted into catechol. This step depends on NADH for energy supply and releases nitrite ions (NO2⁻).

[0084] 2. Ring-opening cleavage of catechol: The generated catechol is catalyzed by catechol 2,3-dioxygenase (C23O) to undergo meta-ring opening (cleavage of the C2-C3 bond). In a weakly alkaline environment with a pH of 7.0, C23O binds to O2 to break the benzene ring, generating 2-hydroxymuconic semialdehyde, which is then dehydrogenated and hydrolyzed by hydrolase (HMSD) to be converted into a linear chain compound β-ketoadipic acid. This process completely avoids the problem of toxicity accumulation in the ortho-ring opening path.

[0085] 3. β-Ketoadipic acid mineralization: β-Ketoadipic acid is gradually cleaved into acetyl-CoA through a series of enzymatic reactions (succinyl-CoA transfer, decarboxylation, hydration), and finally enters the tricarboxylic acid (TCA) cycle, where it is completely mineralized into CO2 and H2O, releasing energy (28 molecules of ATP are produced per molecule of nitrobenzene).

[0086] Toxicity control: For the wastewater treated by the treatment method of the present invention, the secondary toxic substances in the process are completely eliminated: aniline (C6H5NH2), o / m / p-nitroaniline (C6H6N2O2), o / p-toluidine (C7H9N), o / m-phenylenediamine (C6H8N2), and p-chloroaniline (C6H6ClN). Their formation is due to nitro reduction or free radical recombination during incomplete oxidation (for example, when H2O2 is insufficient, nitrobenzene will be oxidized to aniline). The present invention adopts a triple blocking mechanism - (1) dynamic addition of H2O2 (≥2%) to ensure direct mineralization; (2) high-efficiency catalytic ring opening by transition metals (Cu 2+ / Fe 3+ ) at pH 6-7; (3) high temperature of 130-180 °C to inhibit side reactions. None of the above substances were detected in the wastewater treated in Examples 1-7, thus avoiding the inhibition of microbial activity (IC50 = 5 mg / L).

[0087] (2) Failure reasons of Comparative Examples 7-8 Data comparison: After treatment in Comparative Example 7, the content of mixed dinitrobenzene was 0.0667%, and the content of aniline was >10 mg / L, both far exceeding the microbial tolerance limit. In Comparative Example 8, due to the low single-stage crystallization recovery rate, the oxidation section was overloaded, and incomplete oxidation would generate highly toxic m-phenylenediamine, and nitrobenzene residues would also be produced, synergistically damaging the microbial metabolic function.

[0088] Toxicity mechanism: Cell membrane damage: The wastewater treated in Comparative Examples 7-8 contains aniline. The presence of aniline will damage the lipid bilayer of the cell membrane (logKow = 0.9), resulting in the leakage of intracellular enzymes (such as dehydrogenase). As a result, the wastewater treated in Comparative Examples 7-8 cannot achieve microbial treatment in the next section.

[0089] Metabolic inhibition: The content of nitrobenzene in the wastewater treated in Comparative Examples 7-8 is relatively high. Nitrobenzene competitively inhibits the activity of NADH dehydrogenase, blocks the electron transport chain (ETC), and the synthesis of ATP is blocked, which also causes the wastewater treated in Comparative Examples 7-8 to be unable to achieve microbial treatment in the next section.

[0090] The technical features of the above-described embodiments can be combined arbitrarily. For the sake of brevity of description, all possible combinations of the technical features in the above embodiments are not exhaustively listed. However, as long as there is no contradiction in the combination of these technical features, it should be considered as the scope described in this specification.

[0091] For those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can also be made, and these all belong to the protection scope of the present invention. The protection scope of the present invention shall be subject to the appended claims.

Claims

1. A treatment method for wastewater containing nitrobenzene, characterized in that, The treatment method is as follows: S1. Perform multi-stage cooling crystallization on the nitrobenzene-containing wastewater to obtain solid dinitrobenzene mixture and crystallization filtrate; S2. Perform heat and pressure oxidation hydrolysis treatment on the crystallization filtrate to obtain treated water; The nitrobenzene-containing wastewater includes 0.5%-1.5% (by mass) of o-dinitrobenzene, 0.3%-1.0% (by mass) of m-dinitrobenzene, 0.3%-1.0% (by mass) of p-dinitrobenzene, and 3%-10% (by mass) of mononitrobenzene. The suspended solids in the nitrobenzene-containing wastewater are ≤100 mg / L, the COD is 2000-10000 mg / L, the pH value is 6.0-7.0, and the temperature is 80-100°C.

2. The treatment method of nitrobenzene-containing wastewater according to claim 1, wherein In step S1, two-stage cooling crystallization is adopted, where the final crystallization temperature of the first-stage cooling crystallization is 40-45°C; the final crystallization temperature of the second-stage cooling crystallization is 20-25°C.

3. The treatment method for wastewater containing nitrobenzene according to claim 2, characterized in that, The cooling rate of the first-stage cooling crystallization is 10°C / min - 15°C / min, the stirring speed is 100-200 rpm, and the constant-temperature retention time at the final crystallization temperature is 0.5-1.0 h; The cooling rate of the second-stage cooling crystallization is 5°C / min - 8°C / min, the stirring speed is 50-100 rpm, and the constant-temperature retention time at the final crystallization temperature is 1.0-1.5 h.

4. The method for treating wastewater containing nitrobenzene according to claim 1, characterized in that, The specific operation of step S2 is as follows: Add the crystallization filtrate into an autoclave, control the pressure and temperature of the autoclave, and add a catalyst and hydrogen peroxide oxidant for pressure oxidation hydrolysis treatment, and finally remove the catalyst to obtain treated water.

5. The treatment method of nitrobenzene-containing wastewater according to claim 4, characterized in that, In step S2, the temperature of the oxidation hydrolysis treatment is 130-180°C, the pressure is 0.1-1.0 Mpa, and the oxidation hydrolysis treatment time is 2-12 h.

6. The treatment method of nitrobenzene-containing wastewater according to claim 4, characterized in that, The catalyst is at least one of transition metal salts and metal oxides.

7. The treatment method for nitrobenzene-containing wastewater according to claim 6, characterized in that, The transition metal salt is at least one of nickel salt, chromium salt, cobalt salt, manganese salt, copper salt, iron salt, and rhodium salt; The metal oxide is at least one of copper oxide, iron oxide, cerium oxide, and zirconium oxide.

8. The treatment method of nitrobenzene-containing wastewater according to claim 4, characterized in that, In step S2, the addition amount of hydrogen peroxide is 1.5%-4.5% of the mass of the crystallization filtrate; the addition amount of the catalyst is 0.1%-3.0% of the mass of the crystallization filtrate.

9. The treatment method for nitrobenzene-containing wastewater according to claim 8, wherein When the mass content of mononitrobenzene in the crystallization filtrate is not higher than 5%, the addition amount of hydrogen peroxide is at least 2% of the mass of the crystallization filtrate; Based on the mass content of mononitrobenzene in the crystallization filtrate being 5%, for every 1% increase, the addition amount of hydrogen peroxide increases by at least 0.5% of the mass of the crystallization filtrate on the basis of 2% of the mass of the crystallization filtrate.

10. The treatment method of nitrobenzene-containing wastewater according to claim 1, characterized in that, The mass content of dinitrobenzene mixture in the treated water is ≤0.01%, and the mass content of mononitrobenzene is ≤0.1%.

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