Method for recovering o-nitroaniline in wastewater

Abstract

The invention discloses a method for recycling o-nitroaniline in wastewater, and belongs to the technical field of wastewater treatment.The recycling method comprises the following steps that S1, wastewater containing o-nitroaniline is subjected to pH adjustment and cooling; s2, collecting the cooled wastewater, putting the wastewater into an evaporator for evaporation, and putting the wastewater subjected to flash evaporation into a filter press with filter cloth for filtration; s3, putting the filtered wastewater into a reaction tank, carrying out heating reaction, and feeding the wastewater into a water washing tower through a recycled aniline pump for water washing; and S4, transferring washing liquor after washing into an extraction kettle filled with an extraction agent for extraction, transferring an organic phase out for recovery, and enabling a water phase to enter a wastewater treatment section, thereby completing recovery. The method for recovering o-nitroaniline in wastewater provided by the invention has excellent recovery efficiency, the recovered o-nitroaniline has a certain economic value, the economic benefit of an enterprise is favorably improved, meanwhile, the COD index of the treated wastewater is greatly reduced, and the pollution to the environment is reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of wastewater treatment, and particularly relates to a method for recovering o-nitroaniline in wastewater. Background Art

[0002] o-Nitroaniline is an important organic chemical raw material, widely used in the production and preparation of veterinary drugs, medicines, and dyes. It is also an intermediate in the production of o-phenylenediamine.

[0003] At present, the domestic production of o-nitroaniline mainly adopts the ammonolysis method for production and preparation: o-nitrochlorobenzene is added to an autoclave containing a certain concentration of ammonia water, and ammonolysis is carried out at 185-190℃ and 4-4.5MPa to generate o-nitroaniline crude product, which is then flashed, layered and extracted to obtain the finished o-nitroaniline. However, a large amount of wastewater is generated during the production process of o-nitroaniline. The wastewater contains ammonium chloride and o-nitroaniline. As the main product of the workshop, o-nitroaniline, if not fully recycled, will not only cause waste of resources, but also cause great pressure on the subsequent wastewater treatment process, and cause certain damage to the environment. Therefore, the recovery of o-nitroaniline in wastewater is an issue that needs to be addressed and solved urgently. Summary of the invention

[0004] The object of the present invention is to provide a method for recovering o-nitroaniline in wastewater to solve the technical problems mentioned in the background technology.

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

[0006] A method for recovering o-nitroaniline in wastewater comprises the following steps:

[0007] S1. adjusting the pH value of wastewater containing o-nitroaniline and cooling it;

[0008] S2, collecting the cooled wastewater and putting it into an evaporator for evaporation, and putting the wastewater after flash evaporation into a filter press equipped with filter cloth for filtration;

[0009] S3, putting the filtered wastewater into a reaction tank, heating the reaction, and then pumping the aniline into a water washing tower for washing;

[0010] S4, the washing liquid after water washing is transferred into an extraction kettle filled with an extractant for extraction, the organic phase is transferred out for recovery, and the water phase enters the wastewater treatment section, and the recovery is completed.

[0011] As a preferred embodiment of the present invention, the pH in S1 is adjusted to 2-3.

[0012] As a preferred embodiment of the present invention, the evaporation method in S2 is flash evaporation.

[0013] As a preferred embodiment of the present invention, the stirring rate of the evaporator in S2 is 600-800 r / min.

[0014] As a preferred embodiment of the present invention, the mesh size of the filter cloth in S2 is 1000-1500 meshes. By using the filter cloth with a mesh size of 1000-1500 meshes, the solid particles in the wastewater and the crystals of o-nitroaniline can be effectively separated from the liquid.

[0015] As a preferred embodiment of the present invention, the filter cake after filtration in S2 is recovered into a recovery tank, washed, separated, dried, and packaged for storage.

[0016] As a preferred embodiment of the present invention, the temperature in S3 is raised to 175-180°C.

[0017] As a preferred embodiment of the present invention, the extractant used in S4 is one of benzene, chloroform, cyclohexane and ether.

[0018] Beneficial effects of the present invention:

[0019] The method for recovering o-nitroaniline in waste water provided by the present invention recovers o-nitroaniline in waste water before the waste water is treated, flash evaporation is first performed on the waste water after collection, and then the waste water is taken out for filtration, the filtered waste water enters a reaction tank, and then a temperature reaction is performed, the filter cake is taken out for recovery, and finally the waste water enters the washing and stratification process again through an aniline recovery pump, and finally the washing liquid after washing is transferred to an extraction kettle equipped with an extractant for extraction, the organic phase is transferred out for recovery, and the aqueous phase enters the waste water treatment section, that is, the recovery is completed, and the recovery rate of o-nitroaniline can reach 65%-70%, which significantly improves the resource utilization rate, and the COD index of the waste water after treatment is greatly reduced, thereby reducing the pollution to the environment. In addition, the recovered o-nitroaniline has a certain economic value, which is helpful to improve the economic benefits of the enterprise. DETAILED DESCRIPTION

[0020] 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.

[0021] The wastewater used in the embodiments and comparative examples of the present invention was taken from a chemical plant in Anhui Province, and the contents of various components in the wastewater were as follows: COD = 32800 mg / L, pH = 5.5, and o-nitroaniline = 1991.5 mg / L.

[0022] Example 1

[0023] The present embodiment provides a method for recovering o-nitroaniline in wastewater, comprising the following steps:

[0024] S1, adjusting the pH value of the wastewater containing o-nitroaniline to 2, and cooling;

[0025] S2, collecting the cooled wastewater and putting it into an evaporator for flash evaporation, the stirring rate of the evaporator is 600r / min, putting the wastewater after flash evaporation into a filter press equipped with filter cloth (1000 mesh) for filtration, and recovering the filter cake after filtration into a recovery tank, washing, separating, drying, and packaging for storage;

[0026] S3, putting the filtered wastewater into a reaction tank, heating it to 175°C for reaction, and then pumping the aniline back into a water washing tower for washing;

[0027] S4. The washing liquid after water washing is transferred into an extraction kettle filled with benzene for extraction, the organic phase is transferred out for recovery, and the water phase enters the wastewater treatment section, and the recovery is completed.

[0028] Example 2

[0029] The present embodiment provides a method for recovering o-nitroaniline in wastewater, comprising the following steps:

[0030] S1, adjusting the pH value of the wastewater containing o-nitroaniline to 2, and cooling;

[0031] S2, collecting the cooled wastewater and putting it into an evaporator for flash evaporation, the stirring rate of the evaporator is 600r / min, putting the wastewater after flash evaporation into a filter press equipped with a filter cloth (1500 mesh) for filtration, and recovering the filtered filter cake into a recovery tank, washing, separating, drying, and packaging for storage;

[0032] S3, putting the filtered wastewater into a reaction tank, heating it to 175°C for reaction, and then pumping the aniline back into a water washing tower for washing;

[0033] S4. The washing liquid after water washing is transferred into an extraction kettle filled with benzene for extraction, the organic phase is transferred out for recovery, and the water phase enters the wastewater treatment section, and the recovery is completed.

[0034] Example 3

[0035] The present embodiment provides a method for recovering o-nitroaniline in wastewater, comprising the following steps:

[0036] S1, adjusting the pH of the wastewater containing o-nitroaniline to 3 and cooling;

[0037] S2, collecting the cooled wastewater and putting it into an evaporator for flash evaporation, the stirring rate of the evaporator is 600r / min, putting the wastewater after flash evaporation into a filter press equipped with filter cloth (1000 mesh) for filtration, and recovering the filter cake after filtration into a recovery tank, washing, separating, drying, and packaging for storage;

[0038] S3, putting the filtered wastewater into a reaction tank, heating it to 175°C for reaction, and then pumping the aniline back into a water washing tower for washing;

[0039] S4. The washing liquid after water washing is transferred into an extraction kettle filled with benzene for extraction, the organic phase is transferred out for recovery, and the water phase enters the wastewater treatment section, and the recovery is completed.

[0040] Example 4

[0041] The present embodiment provides a method for recovering o-nitroaniline in wastewater, comprising the following steps:

[0042] S1, adjusting the pH value of the wastewater containing o-nitroaniline to 2, and cooling;

[0043] S2, collecting the cooled wastewater and putting it into an evaporator for flash evaporation, the stirring rate of the evaporator is 800r / min, putting the wastewater after flash evaporation into a filter press equipped with filter cloth (1000 mesh) for filtration, and recovering the filter cake after filtration into a recovery tank, washing, separating, drying, and packaging for storage;

[0044] S3, putting the filtered wastewater into a reaction tank, heating it to 180°C for reaction, and then pumping the aniline back into a water washing tower for washing;

[0045] S4. The washing liquid after water washing is transferred into an extraction kettle filled with benzene for extraction, the organic phase is transferred out for recovery, and the water phase enters the wastewater treatment section, and the recovery is completed.

[0046] Example 5

[0047] The present embodiment provides a method for recovering o-nitroaniline in wastewater, comprising the following steps:

[0048] S1, adjusting the pH value of the wastewater containing o-nitroaniline to 2, and cooling;

[0049] S2, collecting the cooled wastewater and putting it into an evaporator for flash evaporation, the stirring rate of the evaporator is 700r / min, putting the wastewater after flash evaporation into a filter press equipped with filter cloth (1000 mesh) for filtration, and recovering the filter cake after filtration into a recovery tank, washing, separating, drying, and packaging for storage;

[0050] S3, putting the filtered wastewater into a reaction tank, heating it to 178°C for reaction, and then pumping the aniline back into a water washing tower for washing;

[0051] S4, the washing liquid after water washing is transferred into an extraction kettle filled with cyclohexane for extraction, the organic phase is transferred out for recovery, and the water phase enters the wastewater treatment section, and the recovery is completed.

[0052] Comparative Example 1

[0053] This comparative example provides a method for recovering o-nitroaniline in wastewater, comprising the following steps:

[0054] S1, adjusting the pH of the wastewater containing o-nitroaniline to 4 and cooling;

[0055] S2, collecting the cooled wastewater and putting it into an evaporator for flash evaporation, the stirring rate of the evaporator is 600r / min, putting the wastewater after flash evaporation into a filter press equipped with filter cloth (1000 mesh) for filtration, and recovering the filter cake after filtration into a recovery tank, washing, separating, drying, and packaging for storage;

[0056] S3, putting the filtered wastewater into a reaction tank, heating it to 175°C for reaction, and then pumping the aniline back into a water washing tower for washing;

[0057] S4. The washing liquid after water washing is transferred into an extraction kettle filled with benzene for extraction, the organic phase is transferred out for recovery, and the water phase enters the wastewater treatment section, and the recovery is completed.

[0058] Comparative Example 2

[0059] This comparative example provides a method for recovering o-nitroaniline in wastewater, comprising the following steps:

[0060] S1, adjusting the pH value of the wastewater containing o-nitroaniline to 2, and cooling;

[0061] S2, collecting the cooled wastewater and putting it into an evaporator for flash evaporation, the stirring rate of the evaporator is 600r / min, putting the wastewater after flash evaporation into a filter press equipped with a filter cloth (800 mesh) for filtration, and recovering the filter cake after filtration into a recovery tank, washing, separating, drying, and packaging for storage;

[0062] S3, putting the filtered wastewater into a reaction tank, heating it to 175°C for reaction, and then pumping the aniline back into a water washing tower for washing;

[0063] S4. The washing liquid after water washing is transferred into an extraction kettle filled with benzene for extraction, the organic phase is transferred out for recovery, and the water phase enters the wastewater treatment section, and the recovery is completed.

[0064] Comparative Example 3

[0065] This comparative example provides a method for recovering o-nitroaniline in wastewater, comprising the following steps:

[0066] S1, adjusting the pH value of the wastewater containing o-nitroaniline to 2, and cooling;

[0067] S2, collecting the cooled wastewater and putting it into an evaporator for flash evaporation, the stirring rate of the evaporator is 500r / min, putting the wastewater after flash evaporation into a filter press equipped with filter cloth (1000 mesh) for filtration, and recovering the filter cake after filtration into a recovery tank, washing, separating, drying, and packaging for storage;

[0068] S3, putting the filtered wastewater into a reaction tank, heating it to 175°C for reaction, and then pumping the aniline back into a water washing tower for washing;

[0069] S4. The washing liquid after water washing is transferred into an extraction kettle filled with benzene for extraction, the organic phase is transferred out for recovery, and the water phase enters the wastewater treatment section, and the recovery is completed.

[0070] Comparative Example 4

[0071] This comparative example provides a method for recovering o-nitroaniline in wastewater, comprising the following steps:

[0072] S1, adjusting the pH value of the wastewater containing o-nitroaniline to 2, and cooling;

[0073] S2, collecting the cooled wastewater and putting it into an evaporator for flash evaporation, the stirring rate of the evaporator is 600r / min, putting the wastewater after flash evaporation into a filter press equipped with filter cloth (1000 mesh) for filtration, and recovering the filter cake after filtration into a recovery tank, washing, separating, drying, and packaging for storage;

[0074] S3, putting the filtered wastewater into a reaction tank, heating it to 165°C for reaction, and then pumping the aniline back into a water washing tower for washing;

[0075] S4. The washing liquid after water washing is transferred into an extraction kettle filled with benzene for extraction, the organic phase is transferred out for recovery, and the water phase enters the wastewater treatment section, and the recovery is completed.

[0076] The organic phase and aqueous phase collected in Examples 1 to 5 and Comparative Examples 1 to 4 were subjected to performance tests, and the recovery rate of o-nitroaniline and the COD removal rate (%) were calculated. The calculation results are shown in Table 1:

[0077] Table 1

[0078] project Recovery rate (%) COD removal rate (%) Example 1 68.3 54.5 Example 2 67.6 55.8 Example 3 65.4 54.7 Example 4 68.7 55.7 Example 5 69.5 55.2 Comparative Example 1 54.7 38.3 Comparative Example 2 55.1 38.6 Comparative Example 3 54.9 40.2 Comparative Example 4 55.2 39.4

[0079] It can be seen from Table 1 that the recovery rate of o-nitroaniline and the COD removal rate in Examples 1-5 are higher than those in Comparative Examples 1-4. It can be seen from the comparison between Examples 1-5 and Comparative Examples 1-4 that the pH value, stirring rate, filter cloth mesh number and reaction temperature in the recovery process of o-nitroaniline in wastewater will affect the effect of recovering o-nitroaniline. It can be seen that the method for recovering o-nitroaniline in wastewater provided by the present invention has excellent recovery efficiency, and the recovered o-nitroaniline has a certain economic value, which helps to improve the economic benefits of the enterprise.

[0080] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device.

[0081] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for recovering o-nitroaniline from wastewater, characterized in that: S1. adjusting the pH value of wastewater containing o-nitroaniline and cooling it; S2, collecting the cooled wastewater and putting it into an evaporator for evaporation, and putting the wastewater after flash evaporation into a filter press equipped with filter cloth for filtration; S3, putting the filtered wastewater into a reaction tank, heating the reaction, and then pumping the aniline into a water washing tower for washing; S4, the washing liquid after water washing is transferred into an extraction kettle filled with an extractant for extraction, the organic phase is transferred out for recovery, and the water phase enters the wastewater treatment section, and the recovery is completed.

2. The method for recovering o-nitroaniline from wastewater according to claim 1, characterized in that: The pH in S1 was adjusted to 2-3.

3. A method for recovering o-nitroaniline in wastewater according to claim 1, characterized in that: The evaporation method in S2 is flash evaporation.

4. The method for recovering o-nitroaniline from waste water according to claim 1, characterized in that: The stirring rate of the evaporator in S2 is 600-800r / min.

5. The method for recovering o-nitroaniline from wastewater according to claim 1, characterized in that: The mesh number of the filter cloth in S2 is 1000-1500 mesh.

6. The method for recovering o-nitroaniline from wastewater according to claim 1, characterized in that: The filter cake after filtration in S2 is recovered into a recovery tank, washed, separated, dried, and packaged for storage.

7. The method for recovering o-nitroaniline from wastewater according to claim 1, characterized in that: In S3, the temperature is raised to 175-180°C.

8. The method for recovering o-nitroaniline from wastewater according to claim 1, characterized in that: The extractant used in S4 is one of benzene, chloroform, cyclohexane and ether.