Wastewater treatment process

Abstract

The invention provides a wastewater treatment process which specifically comprises the following steps: firstly, carrying out electrochemical catalytic oxidation and ozone catalytic treatment on aniline wastewater, and then carrying out biochemical treatment through a biological contact oxidation method, so that the aniline wastewater reaches a sewage discharge standard; a mercaptan-rare earth hybrid MnO2 composite material is added in the electrochemical catalytic oxidation stage and the ozone catalytic pretreatment stage. The mercaptan-rare earth hybrid MnO2 composite material is applied to an electrochemical catalytic oxidation process and an ozone catalytic treatment process, more catalytic sites are provided, and degradation of pollutants in aniline wastewater is promoted. The thiol-rare earth hybridized MnO2 composite material has the characteristics of washing resistance and high strength, can reduce the resistance of wastewater, and can not only degrade pollutants, but also regulate the water quality, provide a better reaction environment for subsequent biochemical treatment, reduce the burden of biochemical treatment and improve the degradation effect after the aniline wastewater pretreatment stage. And the aniline wastewater reaches the discharge standard.

Description

Technical Field

[0001] The present invention relates to the technical field of wastewater treatment, in particular to a wastewater treatment process. Background Art

[0002] Aniline is an important chemical raw material and intermediate, widely used in fuel, pharmaceuticals, explosives, pesticides, and military industries. It is internationally recognized as a hazardous chemical. Aniline is a serious environmental pollutant and a health hazard. Discharge of such wastewater into water bodies not only hinders the growth of aquatic life, but also poses a serious threat to human health. Therefore, my country's wastewater discharge standards have strict requirements for aniline-based substances. Aniline wastewater is characterized by high biological toxicity, high pollutant concentrations, high salinity, and high color, making it a typical difficult-to-degrade industrial wastewater.

[0003] Currently, the main treatment methods for aniline wastewater include physical, chemical, biological, and combined treatment methods. Physical methods, including adsorption, extraction, and membrane separation, utilize physical processes such as adsorption, extraction, and osmosis to separate aniline from wastewater without altering its structure and properties. However, physical methods can easily transfer new pollutants and are costly to treat. Chemical methods, including photocatalytic oxidation, electrocatalytic oxidation, supercritical oxidation, and ultrasonic treatment, all utilize strong oxidants or other pathways to oxidize aniline, generating small molecules or inorganic substances to achieve aniline removal. Chemical methods consume relatively high amounts of energy and are less than ideal in terms of economic efficiency. While biological methods are cost-effective purification methods, the high toxicity of the wastewater limits their use. Furthermore, achieving discharge standards for treated wastewater is difficult and unstable.

[0004] Therefore, it is of great significance to study an effective comprehensive method for the treatment of aniline compound wastewater. Summary of the Invention

[0005] In view of this, the present invention proposes a wastewater treatment process.

[0006] The technical solution of the present invention is achieved as follows:

[0007] A wastewater treatment process comprises the following steps: firstly, subjecting aniline wastewater to electrochemical catalytic oxidation and ozone catalytic treatment, and then subjecting the aniline wastewater to biochemical treatment by biological contact oxidation to meet sewage discharge standards;

[0008] The mercaptan-rare earth hybrid MnO2 composite material is added in both the electrochemical catalytic oxidation and ozone catalytic pretreatment stages.

[0009] Furthermore, the preparation method of the thiol-rare earth hybrid MnO2 composite material includes:

[0010] (1) adding potassium permanganate and manganese sulfate into deionized water, adding sulfuric acid dropwise to adjust the pH value to 2.5-3.5, transferring to an autoclave for hydrothermal reaction, washing and drying to obtain MnO2 powder;

[0011] (2) adding rare earth ions into water to prepare a solution, adding MnO2 under stirring, ultrasonic stirring, washing, and vacuum drying to obtain a rare earth-doped MnO2 composite material;

[0012] (3) dispersing the rare earth-doped MnO2 composite material in anhydrous ethanol, adding maleic anhydride and p-toluenesulfonic acid to react to obtain an intermediate product;

[0013] (4) The intermediate product is dispersed in anhydrous ethanol, alkyl mercaptan and azobisisobutyronitrile are added to react, centrifuged and washed, and vacuum dried to obtain a mercaptan-rare earth hybrid MnO2 composite material.

[0014] Furthermore, in step (1), the molar ratio of potassium permanganate to manganese sulfate is 1:1-3; the solid-liquid ratio of potassium permanganate to deionized water is 1:30-40 g / mL; and the hydrothermal reaction is carried out at 120-140° C. for 12 hours.

[0015] Furthermore, in step (2), the rare earth ions are nitrates containing lanthanum ions or cerium ions; the solid-liquid ratio of the rare earth ions to water is 1:60-80 g / mL; the amount of MnO2 added is 3-4 times the molar amount of the rare earth ions; and the ultrasonic stirring is at 20-30 kHz and 25-35° C. for 4-6 hours.

[0016] Furthermore, in step (3), the solid-liquid ratio of the rare earth-doped MnO2 composite material to anhydrous ethanol is 1:20-40 g / mL; the mass ratio of the rare earth-doped MnO2 composite material to maleic anhydride and p-toluenesulfonic acid is 5-7:1:0.5-0.8; and the reaction is carried out at 80-90°C for 4-6 hours.

[0017] Furthermore, in step (4), the solid-liquid ratio of the intermediate product to anhydrous ethanol is 1:20-30 g / mL; the mass ratio of the alkyl mercaptan and azobisisobutyronitrile to the intermediate product is 1:0.1-0.3:3-5; the reaction temperature is 100-120° C., and the reaction time is 1-3 h.

[0018] Furthermore, the electrochemical catalytic oxidation is specifically:

[0019] After the aniline wastewater is added to the pH adjustment tank for homogenization, it enters the electrochemical catalytic device, where the thiol-rare earth hybrid MnO2 composite material is filled between the three-dimensional electrodes for electrochemical catalytic oxidation.

[0020] Electrochemical catalytic oxidation can improve the ring opening and breaking efficiency of refractory and toxic organic matter, and can remove refractory COD in wastewater. cr and most of the ammonia nitrogen in the wastewater, greatly improving the biodegradability of the wastewater. In addition, the treatment facilities occupy a small area, the process flow is short, the operating cost is low, no chemicals are added during the treatment process, the amount of sludge is small, and the system automation program can operate stably.

[0021] Furthermore, the pH regulating cell is adjusted to 3-5; the current of the electrochemical catalytic device is set to 10-30 mA / cm 2 , voltage 3-5V, temperature 25-35℃, time 1-2h.

[0022] Furthermore, the ozone catalysis is specifically:

[0023] The wastewater after electrochemical catalytic oxidation enters the ozone catalytic oxidation device, and the catalytic reactor is filled with a mercaptan-rare earth hybrid MnO2 composite material to react and obtain treated wastewater.

[0024] Furthermore, the ozone catalytic oxidation device is set to have an ozone concentration of 10-20 mg / L, a flow rate of 1-2 L / min, and a reaction time of 20-40 min.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] 1. The present invention applies the thiol-rare earth hybrid MnO2 composite material in the electrochemical catalytic oxidation process, participates in the electron transfer reaction, generates more highly active oxygen species, provides more catalytic sites, and promotes the degradation of pollutants in aniline wastewater.

[0027] 2. The present invention applies the thiol-rare earth hybrid MnO2 composite material in the ozone catalytic treatment process, which not only provides more active sites, promotes the decomposition of ozone to generate more -OH free radicals or other active species, and improves the degradation efficiency of ozone, but also increases the solubility of ozone in wastewater, has a significant effect on reducing COD in wastewater, and has a significant decolorization effect.

[0028] 3. The thiol-rare earth hybrid MnO2 composite material of the present invention has the characteristics of erosion resistance and high strength, can reduce the resistance of wastewater, and after the aniline wastewater pretreatment stage of the present invention, it can not only degrade pollutants but also regulate water quality, provide a better reaction environment for subsequent biochemical treatment, reduce the burden of biochemical treatment, improve the degradation effect, and make the aniline wastewater meet the discharge standards.

[0029] 4. manganese dioxide in the present invention, as a typical transition metal oxide, has stronger redox ability, can catalyze the degradation of pollutants, and in electrochemical catalytic oxidation and ozone catalysis treatment processes, has significant degradation effect on organic pollutants. Rare earth elements can enhance the catalytic performance and stability of manganese dioxide, improve the electron transfer ability of manganese dioxide, and improve the degradation rate of catalyst. Mercaptan groups can adsorb organic pollutants through the forces such as hydrogen bonds and coordination bonds, improve adsorption sites, and are conducive to catalytic degradation. Mercaptan-rare earth hybridized MnO2 composite material of the present invention has good reproducibility and high environmental protection. Under the synergistic effect of multiple forces, mercaptan-rare earth hybridized MnO2 composite material has strong bonding force and excellent selectivity to aniline wastewater, greatly improves removal efficiency. DETAILED DESCRIPTION

[0030] In order to better understand the technical content of the present invention, specific examples are provided below to further illustrate the present invention.

[0031] Unless otherwise specified, the experimental methods used in the examples of the present invention are all conventional methods.

[0032] Unless otherwise specified, the materials, reagents, etc. used in the examples of the present invention can be obtained from commercial sources.

[0033] The alkyl mercaptan of the present invention is selected from any one of n-dodecyl mercaptan, n-tetradecanethiol, n-hexadecyl mercaptan and n-octadecyl mercaptan.

[0034] Example 1

[0035] A wastewater treatment process, the specific treatment steps are:

[0036] (1) Electrochemical catalytic oxidation: Aniline wastewater is added to a pH regulating tank (pH = 3-5) for homogenization, and then enters an electrochemical catalytic device. The thiol-rare earth hybrid MnO2 composite material is filled between the three-dimensional electrodes, and the current is set to 20 mA / cm 2 , voltage 4V, temperature 30℃, electrochemical catalytic oxidation for 1.5h;

[0037] (2) Ozone catalysis: The wastewater after electrochemical catalytic oxidation is fed into an ozone catalytic oxidation device, the ozone concentration is set to 15 mg / L, the flow rate is 1.5 L / min, the catalytic reactor is filled with a thiol-rare earth hybrid MnO2 composite material, and the reaction is carried out for 30 minutes to obtain the treated wastewater;

[0038] (3) The treated wastewater is biochemically treated through biological contact oxidation.

[0039] The preparation method of the thiol-rare earth hybrid MnO2 composite material in (1) and (2) above comprises:

[0040] S1. Potassium permanganate and manganese sulfate in a molar ratio of 1:2 were added to deionized water, and the solid-liquid ratio of potassium permanganate to deionized water was 1:35 g / mL. Sulfuric acid was added dropwise to adjust the pH to 3.0±0.5. The mixture was transferred to an autoclave and hydrothermally reacted at 130°C for 12 hours. The product was washed and dried to obtain MnO2 powder.

[0041] S2. Add nitrate containing lanthanum ions or cerium ions into water to prepare a solution, wherein the solid-liquid ratio of the nitrate containing lanthanum ions or cerium ions to water is 1:70 g / mL; add MnO2 under stirring, wherein the amount of MnO2 added is 3.5 times the molar amount of the lanthanum ions or cerium ions; and stir ultrasonically at 25 kHz and 30° C. for 5 h. Filter, wash, and vacuum dry to obtain a rare earth-doped MnO2 composite material;

[0042] S3. Dispersing the rare earth-doped MnO2 composite material in anhydrous ethanol at a solid-liquid ratio of 1:30 g / mL, adding maleic anhydride and p-toluenesulfonic acid, wherein the mass ratio of the rare earth-doped MnO2 composite material to maleic anhydride and p-toluenesulfonic acid is 6:1:0.7, and reacting at 85°C for 5 h to obtain an intermediate product;

[0043] S4. Disperse the intermediate product in anhydrous ethanol at a solid-liquid ratio of 1:25 g / mL, add alkyl mercaptan and azobisisobutyronitrile, and the mass ratio of alkyl mercaptan and azobisisobutyronitrile to the intermediate product is 1:0.2:4. React at 110°C for 2h, centrifuge and wash, and vacuum dry to obtain a thiol-rare earth hybrid MnO2 composite material.

[0044] Example 2

[0045] A wastewater treatment process, the specific treatment steps are:

[0046] (1) Electrochemical catalytic oxidation: Aniline wastewater was added to a pH regulating tank (pH = 3-5) for homogenization, and then entered into an electrochemical catalytic device. The thiol-rare earth hybrid MnO2 composite material was filled between the three-dimensional electrodes, and the current was set to 10 mA / cm 2 , voltage 3V, temperature 25℃, electrochemical catalytic oxidation for 1h;

[0047] (2) Ozone catalysis: The wastewater after electrochemical catalytic oxidation is fed into an ozone catalytic oxidation device, the ozone concentration is set to 10 mg / L, the flow rate is 1 L / min, the catalytic reactor is filled with a thiol-rare earth hybrid MnO2 composite material, and the reaction is carried out for 20 minutes to obtain the treated wastewater;

[0048] (3) The treated wastewater is biochemically treated through biological contact oxidation.

[0049] The preparation method of the thiol-rare earth hybrid MnO2 composite material in (1) and (2) above comprises:

[0050] S1. Potassium permanganate and manganese sulfate in a molar ratio of 1:1 were added to deionized water, and the solid-liquid ratio of potassium permanganate to deionized water was 1:30 g / mL. Sulfuric acid was added dropwise to adjust the pH to 3.0±0.5. The mixture was transferred to an autoclave and hydrothermally reacted at 120°C for 12 hours. The product was washed and dried to obtain MnO2 powder.

[0051] S2. Add nitrate containing lanthanum ions or cerium ions to water to prepare a solution, wherein the solid-liquid ratio of the nitrate containing lanthanum ions or cerium ions to water is 1:60 g / mL; add MnO2 under stirring, wherein the amount of MnO2 added is 3 times the molar amount of the lanthanum ions or cerium ions; ultrasonically stir at 20 kHz and 25° C. for 4 h; filter, wash, and vacuum dry to obtain a rare earth-doped MnO2 composite material;

[0052] S3. Dispersing the rare earth-doped MnO2 composite material in anhydrous ethanol at a solid-liquid ratio of 1:20 g / mL, adding maleic anhydride and p-toluenesulfonic acid, wherein the mass ratio of the rare earth-doped MnO2 composite material to maleic anhydride and p-toluenesulfonic acid is 5:1:0.5, and reacting at 80°C for 4 h to obtain an intermediate product;

[0053] S4. Disperse the intermediate product in anhydrous ethanol at a solid-liquid ratio of 1:20 g / mL, add alkyl mercaptan and azobisisobutyronitrile, and the mass ratio of alkyl mercaptan and azobisisobutyronitrile to the intermediate product is 1:0.1:3. React at 100°C for 1h, centrifuge and wash, and vacuum dry to obtain a thiol-rare earth hybrid MnO2 composite material.

[0054] Example 3

[0055] A wastewater treatment process, the specific treatment steps are:

[0056] (1) Electrochemical catalytic oxidation: Aniline wastewater is added to a pH regulating tank (pH = 3-5) for homogenization, and then enters an electrochemical catalytic device. The thiol-rare earth hybrid MnO2 composite material is filled between the three-dimensional electrodes, and the current is set to 30 mA / cm 2 , voltage 5V, temperature 35℃, electrochemical catalytic oxidation for 2h;

[0057] (2) Ozone catalysis: The wastewater after electrochemical catalytic oxidation is fed into an ozone catalytic oxidation device, the ozone concentration is set to 20 mg / L, the flow rate is 2 L / min, the catalytic reactor is filled with a thiol-rare earth hybrid MnO2 composite material, and the reaction is carried out for 40 minutes to obtain treated wastewater;

[0058] (3) The treated wastewater is biochemically treated through biological contact oxidation.

[0059] The preparation method of the thiol-rare earth hybrid MnO2 composite material in (1) and (2) above comprises:

[0060] S1. Potassium permanganate and manganese sulfate in a molar ratio of 1:3 were added to deionized water, and the solid-liquid ratio of potassium permanganate to deionized water was 1:40 g / mL. Sulfuric acid was added dropwise to adjust the pH to 3.0±0.5. The mixture was transferred to an autoclave and hydrothermally reacted at 140°C for 12 hours. The product was washed and dried to obtain MnO2 powder.

[0061] S2. Adding nitrate containing lanthanum ions or cerium ions to water to prepare a solution, wherein the solid-liquid ratio of the nitrate containing lanthanum ions or cerium ions to water is 1:80 g / mL, adding MnO2 under stirring, wherein the amount of MnO2 added is 4 times the molar amount of the lanthanum ions or cerium ions, and stirring the mixture ultrasonically at 30 kHz and 35° C. for 6 h, filtering, washing, and vacuum drying to obtain a rare earth-doped MnO2 composite material;

[0062] S3. Dispersing the rare earth-doped MnO2 composite material in anhydrous ethanol at a solid-liquid ratio of 1:40 g / mL, adding maleic anhydride and p-toluenesulfonic acid, wherein the mass ratio of the rare earth-doped MnO2 composite material to maleic anhydride and p-toluenesulfonic acid is 7:1:0.8, and reacting at 90°C for 6 h to obtain an intermediate product;

[0063] S4. Disperse the intermediate product in anhydrous ethanol at a solid-liquid ratio of 1:30 g / mL, add alkyl mercaptan and azobisisobutyronitrile, and the mass ratio of alkyl mercaptan and azobisisobutyronitrile to the intermediate product is 1:0.3:5. React at 120°C for 3h, centrifuge and wash, and vacuum dry to obtain a thiol-rare earth hybrid MnO2 composite material.

[0064] Comparative Example 1

[0065] The difference from Example 1 is that the thiol-rare earth hybrid MnO2 composite material is replaced by a thiol-MnO2 composite material, and the rest is consistent with Example 1.

[0066] Comparative Example 2

[0067] The difference from Example 1 is that the thiol-rare earth hybrid MnO2 composite material is replaced by a rare earth-MnO2 composite material, and the rest is consistent with Example 1.

[0068] Comparative Example 3

[0069] The difference from Example 1 is that no thiol-rare earth hybrid MnO2 composite material is used, and the rest is the same as Example 1.

[0070] Test Case

[0071] Aniline wastewater (pH = 6-9) containing 20,000 mg / L CODcr, 900 mg / L BOD5, and 80 mg / L aniline substances was treated by the wastewater treatment processes of Examples 1-3 and Comparative Examples 1-3, respectively. The concentrations of various pollutants in the effluent were tested, and the removal efficiency was calculated.

[0072] Removal efficiency = (concentration in initial wastewater - concentration in effluent wastewater) / concentration in initial wastewater × 100%

[0073] The test results are shown in Table 1.

[0074] Table 1

[0075]

[0076] It can be seen from Table 1 that the treatment processes of Examples 1-3 of the present invention can degrade pollutants in wastewater and make the aniline wastewater meet the discharge standards.

[0077] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A wastewater treatment process, characterized in that: The following steps are involved: First, the aniline wastewater is subjected to electrochemical catalytic oxidation and ozone catalytic treatment, and then biochemical treatment is carried out through biological contact oxidation to make the aniline wastewater meet the sewage discharge standard; The mercaptan-rare earth hybrid MnO2 composite material is added in both the electrochemical catalytic oxidation and ozone catalytic pretreatment stages.

2. A wastewater treatment process according to claim 1, characterized in that: The preparation method of the thiol-rare earth hybrid MnO2 composite material comprises: (1) adding potassium permanganate and manganese sulfate into deionized water, adding sulfuric acid dropwise to adjust the pH value to 2.5-3.5, transferring to an autoclave for hydrothermal reaction, washing and drying to obtain MnO2 powder; (2) adding rare earth ions into water to prepare a solution, adding MnO2 under stirring, ultrasonic stirring, washing, and vacuum drying to obtain a rare earth-doped MnO2 composite material; (3) dispersing the rare earth-doped MnO2 composite material in anhydrous ethanol, adding maleic anhydride and p-toluenesulfonic acid to react to obtain an intermediate product; (4) The intermediate product is dispersed in anhydrous ethanol, alkyl mercaptan and azobisisobutyronitrile are added to react, centrifuged and washed, and vacuum dried to obtain a mercaptan-rare earth hybrid MnO2 composite material.

3. A wastewater treatment process according to claim 2, characterized in that: In step (1), the molar ratio of potassium permanganate to manganese sulfate is 1:1-3; the solid-liquid ratio of potassium permanganate to deionized water is 1:30-40 g / mL; and the hydrothermal reaction is carried out at 120-140° C. for 12 hours.

4. A wastewater treatment process according to claim 2, characterized in that: In step (2), the rare earth ion is a nitrate containing lanthanum ion or cerium ion; the solid-liquid ratio of the rare earth ion to water is 1:60-80 g / mL; the amount of MnO2 added is 3-4 times the molar amount of the rare earth ion; and the ultrasonic stirring is at 20-30 kHz and 25-35° C. for 4-6 hours.

5. A wastewater treatment process according to claim 2, characterized in that: In step (3), the solid-liquid ratio of the rare earth-doped MnO2 composite material to anhydrous ethanol is 1:20-40 g / mL; the mass ratio of the rare earth-doped MnO2 composite material to maleic anhydride and p-toluenesulfonic acid is 5-7:1:0.5-0.8; and the reaction is carried out at 80-90°C for 4-6 hours.

6. A wastewater treatment process according to claim 2, characterized in that: In step (4), the solid-liquid ratio of the intermediate product to anhydrous ethanol is 1:20-30 g / mL; the mass ratio of the alkyl mercaptan and azobisisobutyronitrile to the intermediate product is 1:0.1-0.3:3-5; the reaction temperature is 100-120° C., and the reaction time is 1-3 h.

7. A wastewater treatment process according to claim 1, characterized in that: The electrochemical catalytic oxidation is specifically: After the aniline wastewater is added to the pH adjustment tank for homogenization, it enters the electrochemical catalytic device, where the thiol-rare earth hybrid MnO2 composite material is filled between the three-dimensional electrodes for electrochemical catalytic oxidation.

8. A wastewater treatment process according to claim 7, characterized in that: The pH regulating pool adjusts the pH to 3-5; the electrochemical catalytic device sets the current to 10-30 mA / cm 2 , voltage 3-5V, temperature 25-35℃, time 1-2h.

9. A wastewater treatment process according to claim 1, characterized in that: The ozone catalysis is specifically: The wastewater after electrochemical catalytic oxidation enters the ozone catalytic oxidation device, and the catalytic reactor is filled with a mercaptan-rare earth hybrid MnO2 composite material to react and obtain treated wastewater.

10. A wastewater treatment process according to claim 9, characterized in that: The ozone catalytic oxidation device is set to an ozone concentration of 10-20 mg / L, a flow rate of 1-2 L / min, and a reaction time of 20-40 min.

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