A method for treating aniline wastewater

Abstract

The application discloses a method for treating aniline wastewater, which comprises the following steps: filtering the aniline wastewater through an adsorption filter device provided with carbon fiber membranes, collecting the filtrate, stopping the filtration when the COD of the filtrate is greater than 400 mg / L, and desorbing the carbon fiber membranes by using water vapor; when the carbon fiber membranes are desorbed by using water vapor, the temperature of the water vapor is 130 DEG C-140 DEG C, and high-concentration wastewater is obtained by collecting the water condensed from the water vapor; the pH value of the high-concentration wastewater is adjusted to 9-13, the high-concentration wastewater after the pH value is adjusted and a catalyst are added into a reaction kettle, air is pressurized into the reaction kettle, stirring is started, and reaction is carried out for 20-50 min; after the reaction is completed, pressure is released and temperature is lowered, and the COD value, ammonia nitrogen content and chroma of the wastewater are detected; the filtrate and the reaction liquid after the oxidation treatment are mixed and punched into an adjusting tank, and subsequent biochemical treatment is carried out.

Description

TECHNICAL FIELD

[0001] The present application relates to a wastewater treatment technology, in particular aniline-containing wastewater treatment technology. Mainly by adsorption / desorption to form high-concentration wastewater, and by catalytic wet oxidation to treat high-concentration wastewater, to reduce the COD, ammonia nitrogen content and color of the wastewater, and to improve the biodegradability and color of the wastewater. BACKGROUND

[0002] High-concentration wastewater containing aniline is difficult to be treated by direct biochemical treatment method, and generally needs to be pretreated before biochemical treatment.

[0003] Common wastewater treatment physical methods such as adsorption, extraction, membrane treatment, etc. can only enrich aniline substances to a certain extent, and cannot fundamentally solve the degradation problem of aniline substances; chemical methods mainly use advanced oxidation processes (AOPs) to treat toxic and harmful organic pollutants in water. The advanced oxidation processes represented by ozone and Fenton oxidation have been widely used in advanced treatment and pretreatment of wastewater, but there are still many limiting factors, for example, ozone oxidation requires an electron donor and is required to be used in neutral water; Fenton oxidation is only suitable for acidic systems, and the pH needs to be adjusted, and a large amount of iron sludge and other waste will be generated, which needs to be effectively treated and disposed. Ozone oxidation and Fenton oxidation are usually suitable for the treatment of low-concentration organic pollutants, otherwise the cost of oxidation treatment will be greatly increased: CN102167461A discloses a method for treating o-chloroaniline production wastewater. First, the pH of the weakly acidic production wastewater in the reactor is adjusted to 2.5-3.5, then a certain amount of catalyst ferrous sulfate and hydrogen peroxide are added, the concentration of Fe 2+ is 80-1120mg / L, the amount of hydrogen peroxide is 4-24ml / L, then stirring for 30-60min, the removal rate of COD can reach 50-60%, the removal efficiency of high-concentration COD of this treatment method is not high, and iron ions are introduced, which needs to be flocculated subsequently. CN110835178A introduces adding an oxidant-sodium persulfate, potassium persulfate to simulate aniline (preparing various aniline substances with a concentration of 0.3mmol / L) wastewater, the addition amount is 16-17 times of the aniline organic matter, and the aniline organic matter is directly degraded, among which the degradation rate of o-chloroaniline is 22.4%, the removal rate of p-chloroaniline is 58.1%, and the removal rate of aniline is 45.19%, the removal effect of this method on aniline substances is limited, and the addition amount of oxidant is large.

[0004] For the treatment of high COD wastewater, the research on activated carbon fiber treatment of organic chemical wastewater uses the process of carbon fiber adsorption, superheated steam desorption and regenerated waste gas combustion to treat organic wastewater with CODCr=1.2*105 mg / L. The process can treat high-concentration wastewater, but nitrogen oxides which pollute the atmosphere are generated when the organic matter is burned, and the process cannot fundamentally achieve environmental pollution-free.

[0005] In recent years, with the research on advanced oxidation technology, the application range of catalytic wet oxidation has gradually expanded, and it has unique advantages for high-COD wastewater treatment. It is more suitable for the treatment of wastewater with COD of 10,000-100,000. Organic matter and nitrogen-containing substances can be oxidized and decomposed into harmless substances such as CO2, H2O and N2. It has the advantages of high treatment efficiency, fast oxidation rate, low secondary pollution and small device. SUMMARY

[0006] The purpose of the present application is to provide a method for treating aniline wastewater.

[0007] To achieve the above-mentioned and other related purposes, the technical solution provided by the present application is as follows: a method for treating aniline wastewater, comprising the following steps:

[0008] Step 1: passing the aniline wastewater through an adsorption and filtration device provided with a carbon fiber membrane, vacuum filtration, and collecting the filtrate; when the COD of the filtrate is greater than 400 mg / L, stopping the filtration and desorbing the carbon fiber membrane with water vapor;

[0009] Step 2: when the carbon fiber membrane is desorbed with water vapor, the temperature of the water vapor is 130-140℃, and the high-concentration wastewater is obtained by collecting the water vapor condensate;

[0010] Step 3: adjusting the pH value of the high-concentration wastewater to 9-13, and adding the high-concentration wastewater after adjusting the pH value and a catalyst into a reaction kettle, heating and warming after closing the reaction kettle, pressurizing air into the reaction kettle, and opening the stirring, and reacting for 20-50 min;

[0011] Step 4: after the reaction is completed, the pressure is released and the temperature is lowered, and the COD value, ammonia nitrogen content and colority of the wastewater are detected;

[0012] Step 5, mixing the filtrate obtained in step 1 and the reaction liquid after oxidation treatment obtained in step 3 and punching into an adjusting tank for subsequent biochemical treatment.

[0013] The preferred technical solution is that the aniline wastewater contains at least one of o-chloroaniline and aniline.

[0014] The preferred technical solution is that the COD of the aniline wastewater is 3000-4000 mg / L, the ammonia nitrogen content is 70-90 mg / L, the colority is greater than 500, and the pH value is 5-6.

[0015] The preferred technical solution is that the catalyst is a heterogeneous noble metal catalyst.

[0016] The preferred technical solution is that the catalyst is Pt, Pd, Ru, Ir or oxides thereof supported on TiO2, ZrO2, CeO2 or Al2O3.

[0017] The preferred technical solution is that the vacuum degree is 0.05-0.08 MPa during vacuum filtration.

[0018] The preferred technical solution is that the mass ratio of the filtrate of step 1 to the water vapor for desorption is 10:1-20:1.

[0019] The preferred technical solution is that in step 3, the amount of catalyst is 0.1-0.5% of the mass of the high-concentration wastewater, the heating temperature is 190-220°C, and the reaction time is 30-40 min.

[0020] The application has the following advantages compared with the prior art due to the use of the above technical solutions:

[0021] 1. The application provides a treatment scheme of adsorption-desorption concentration, catalytic wet oxidation and biochemical degradation for the difficult-to-degrade and dark-colored aniline wastewater, so that the chroma of the wastewater is greatly reduced, and the wastewater can meet the discharge standard after biochemical treatment.

[0022] 2. The COD removal rate of the wastewater after catalytic oxidation can reach 90-94%, and the ammonia nitrogen removal rate is 80-85%; finally, the wastewater after oxidation treatment is mixed with the wastewater after adsorption by the carbon fiber membrane (chroma less than 40) and subjected to biochemical treatment. The method can reduce the amount of wastewater subjected to oxidation treatment, and the biodegradability and chroma of the wastewater subjected to oxidation treatment are greatly improved. DETAILED DESCRIPTION

[0023] The embodiments of the application are described below by specific examples, and those skilled in the art can easily understand other advantages and effects of the application from the disclosure.

[0024] Example 1: A treatment method for aniline wastewater

[0025] The COD of the aniline wastewater to be treated is 3048 mg / L, the ammonia nitrogen content is 86 mg / L, the pH value is about 5, and the chroma is greater than 500 (Pt-Co).

[0026] Concentration of wastewater: The carbon fiber membrane was placed in a Buchner funnel and connected to a water circulating vacuum pump, wastewater was added to the funnel and the vacuum pump was turned on, and the filtrate was collected after the adsorption filtration was stable, the vacuum degree was 0.07 MPa. The average COD of the filtrate was 223 mg / L, the ammonia nitrogen content was 25 mg / L, and the colority was 8.6 (Pt-Co). After the adsorption filtration was completed, the carbon fiber membrane was desorbed with water vapor at 130°C, the amount of water vapor was about 1 / 20 of the amount of filtrate, and concentrated wastewater was obtained, the COD of the concentrated wastewater was 56630 mg / L, the ammonia nitrogen content was 1120 mg / L, and the colority was greater than 500 (Pt-Co).

[0027] Catalytic wet oxidation of high-concentration wastewater: The pH value of the wastewater was adjusted to 13 with a sodium hydroxide solution, 500 mL of high-concentration wastewater with pH = 13 was placed in a 2 L high-pressure reaction kettle, and 1.5 g of Pt catalyst supported on TiO2 was added, heated to 210°C, and air was pressurized to 6 MPa with an air compressor, the oxygen partial pressure was 1.2 MPa, the stirring was started for 30 min and then stopped, the pressure was released and the temperature was lowered to room temperature, the reaction liquid was filtered by opening the kettle cover, the catalyst was reused, and the COD value, ammonia nitrogen content, and colority of the reacted wastewater were detected: COD was 3397 mg / L, ammonia nitrogen content was 157 mg / L, colority was 64.3 (Pt-Co), COD removal rate was 94%, and ammonia nitrogen removal rate was 86%. The oxidized wastewater was mixed with the filtrate and discharged into a conditioning tank for biochemical treatment. The mass ratio of the oxidized wastewater to the filtrate was 1:20, and the COD of the mixed wastewater was 374 mg / L, the ammonia nitrogen content was 32 mg / L, and the colority was 17.6 (Pt-Co).

[0028] Example 2: A method for treating aniline wastewater

[0029] High-concentration wastewater using the wastewater prepared in Example 1, the catalytic wet oxidation step is the same as in Example 1, the catalyst used is a composite Pd-Ru catalyst, and the carrier is CeO2, and the results are as follows:

[0030] The COD value and ammonia nitrogen content of the reacted wastewater were detected, the COD was 4530 mg / L, the ammonia nitrogen content was 224 mg / L, the colority was 84.5 (Pt-Co), the COD removal rate was 92%, and the ammonia nitrogen removal rate was 80%. The oxidized wastewater was mixed with the filtrate and discharged into a conditioning tank for biochemical treatment. The mass ratio of the oxidized wastewater to the filtrate was 1:20, and the COD of the mixed wastewater was 428 mg / L, the ammonia nitrogen content was 35 mg / L, and the colority was 25.8 (Pt-Co).

[0031] Example 3: A method for treating aniline wastewater

[0032] High concentration wastewater used the wastewater prepared in Example 1.

[0033] The pH value of the wastewater was adjusted to 11 with sodium hydroxide solution, 500 mL of high concentration wastewater with pH = 11 was placed in a 2 L high pressure reactor, and 1.8 g of Ru catalyst supported on Al2O3 was added, heated to 220°C, and air was pressurized to 6 MPa with an air compressor, the oxygen partial pressure was 1.2 MPa, the stirring reaction was started for 30 min and then stopped, the pressure was released and the temperature was lowered to room temperature, the reaction liquid was filtered by opening the reactor cover, the catalyst was reused, and the COD value and ammonia nitrogen content of the reacted wastewater were detected, the COD was 6795 mg / L, the ammonia nitrogen content was 213 mg / L, the colority was 127.5 (Pt-Co), the removal rate of COD was 88%, and the removal rate of ammonia nitrogen was 81%. The oxidized wastewater was mixed with the filtrate and discharged into the adjusting tank for biochemical treatment. The mass ratio of the mixed wastewater after oxidation to the filtrate was 1:8, the COD of the mixed wastewater was 535 mg / L, the ammonia nitrogen content was 34 mg / L, and the colority was 34.9 (Pt-Co).

[0034] Example 4: A treatment method for aniline wastewater

[0035] High concentration wastewater used the wastewater prepared in Example 1, the catalyst was the Pt catalyst recovered by filtration in Example 1, and the operation of Experiment 1 was repeated, and the results were as follows:

[0036] The COD value and ammonia nitrogen content of the reacted wastewater were detected, the COD was 3964 mg / L, the ammonia nitrogen content was 179 mg / L, the colority was 63.8 (Pt-Co), the removal rate of COD was 93%, and the removal rate of ammonia nitrogen was 84%. The oxidized wastewater was mixed with the filtrate and discharged into the adjusting tank for biochemical treatment. The mass ratio of the mixed wastewater after oxidation to the filtrate was 1:20, the COD of the mixed wastewater was 401 mg / L, the ammonia nitrogen content was 33 mg / L, and the colority was 23.1 (Pt-Co).

[0037] The experimental results are summarized as follows:

[0038] Adsorption / desorption concentration of wastewater

[0039]

[0040] Catalytic wet oxidation treatment of high concentration wastewater

[0041]

[0042] Note: The percentage in parentheses is the removal rate

[0043] Mixing of filtrate after carbon fiber membrane filtration with catalytic oxidation reaction liquid

[0044]

[0045] Note: The mass ratio of the filtrate after carbon fiber membrane adsorption to the oxidation reaction liquid is 18:1-20:1

[0046] From the experimental results, it can be seen that Pt / TiO2 and Pd-Ru / CeO2 have good degradation and decolorization effects under the above catalytic wet oxidation conditions, the removal rate of COD can reach 90%-94%, the removal rate of ammonia nitrogen is 80-85%, and the effect of the catalyst is not obviously reduced when the catalyst is reused.

[0047] The filtrate after carbon fiber adsorption is mixed with the reaction liquid after catalytic wet oxidation, and the colority of the wastewater is obviously improved, which can reach the first emission standard.

[0048] Example 5: A treatment method of aniline wastewater

[0049] A treatment method of aniline wastewater, comprising the following steps:

[0050] Step 1: passing the aniline wastewater through an adsorption filtration device provided with a carbon fiber membrane, vacuum filtration, and collecting the filtrate; when the COD of the filtrate is greater than 400 mg / L, stopping the filtration and desorbing the carbon fiber membrane with water vapor;

[0051] Step 2: when the carbon fiber membrane is desorbed with water vapor, the temperature of the water vapor is 130°C, and the high-concentration wastewater is obtained by collecting the water vapor condensate;

[0052] Step 3: adjusting the pH value of the high-concentration wastewater to 9, and adding the high-concentration wastewater after adjusting the pH value and the catalyst into a reaction kettle, heating and warming after closing the reaction kettle, pressurizing air into the reaction kettle, and opening the stirring, and reacting for 20 min;

[0053] Step 4: after the reaction is completed, the pressure is released and the temperature is lowered, and the COD value, ammonia nitrogen content and colority of the wastewater are detected;

[0054] Step 5, mixing the filtrate obtained in step 1 and the reaction liquid after oxidation treatment obtained in step 3 and punching into an adjusting tank for subsequent biochemical treatment.

[0055] The preferred embodiment is that the aniline wastewater contains at least one of o-chloroaniline and aniline.

[0056] The preferred embodiment is that the COD of the aniline wastewater is 3000 mg / L, the ammonia nitrogen content is 70 mg / L, the colority is greater than 500, and the pH value is 5.

[0057] The preferred embodiment is that the catalyst is a heterogeneous noble metal catalyst.

[0058] The catalyst is preferably Pt, Pd, Ru, Ir or oxides thereof supported on TiO2, ZrO2, CeO2 or Al2O3.

[0059] The preferred embodiment is that the vacuum degree is 0.05 MPa during vacuum filtration.

[0060] The preferred embodiment is that the mass ratio of the filtrate of step 1 to the water vapor for desorption is 10:1.

[0061] The preferred embodiment is that the amount of catalyst used in step 3 is 0.1% of the mass of the high-concentration wastewater, the heating temperature is 190°C, the oxygen partial pressure is 1 MPa, and the reaction time is 30 min.

[0062] The above description is only intended to explain the preferred embodiments of the present application and is not intended to limit the present application in any form. Any modification or change made to the present application in the same inventive spirit shall still be included in the scope intended to be protected by the present application.

Claims

1. A method for treating aniline wastewater, characterized by comprising: The method comprises the following steps: ​ Step 1: the aniline wastewater is filtered by a vacuum filter with a carbon fiber membrane, and the filtrate is collected; Step 2: when the COD of the filtrate is greater than 400 mg / L, the vacuum filtration is stopped, and the carbon fiber membrane is desorbed by water vapor; when the carbon fiber membrane is desorbed by water vapor, the temperature of the water vapor is 130-140 DEG C, the condensed water of the water vapor is collected to obtain high-concentration wastewater, and the mass ratio of the filtrate to the water vapor for desorption is 10:1-20:1; Step 3: the pH value of the high-concentration wastewater is adjusted to 9-13, the high-concentration wastewater after pH adjustment and a catalyst are added into a reaction kettle, the reaction kettle is closed, air is injected into the reaction kettle, stirring is started, and the reaction is carried out for 20-50 min; the catalyst is a heterogeneous noble metal catalyst, the catalyst is Pt, Pd, Ru, Ir or an oxide thereof supported on TiO2, ZrO2, CeO2 or Al2O3, the amount of the catalyst is 0.1-0.5% of the mass of the high-concentration wastewater, the temperature is raised to 190-220 DEG C, and the reaction time is 30-40 min Step 4: after the reaction is completed, the pressure is released and the temperature is lowered, and the COD value, the ammonia nitrogen content and the colority of the wastewater are detected; Step 5: the filtrate obtained in step 1 and the reaction liquid after oxidation treatment obtained in step 3 are mixed and pumped into a regulating tank, and subsequent biochemical treatment is carried out.

2. The method of treating aniline wastewater according to claim 1, characterized by: The aniline wastewater contains at least one of o-chloroaniline and aniline.

3. The method of treating aniline wastewater according to claim 1, characterized by: The COD of the aniline wastewater is 3000-4000 mg / L, the ammonia nitrogen content is 70-90 mg / L, the colority is greater than 500, and the pH value is 5-6.

4. The method of treating aniline wastewater according to claim 1, characterized by: When the vacuum filtration is carried out, the vacuum degree is 0.05-0.08 MPa.

Images