A process for treating organic wastewater in a chemical park

Abstract

The invention discloses a process for treating organic wastewater in a chemical park, and belongs to the technical field of wastewater treatment. The process comprises the following steps: adjusting the pH value of pretreated wastewater to 3-4, pumping the pretreated wastewater into a Fenton reaction tank, adding H2O2 and an iron-based Fenton reagent into the Fenton reaction tank, and allowing the pretreated wastewater to remain in the Fenton reaction tank for 0.5-1.2 hours under light conditions; then, effluent from the Fenton reaction tank enters a degassing and neutralization tank, is stirred to remove oxygen generated by the Fenton reaction, and is transported to a second regulating tank through a water pump, wherein the pH value is adjusted to 7-8, a precipitant is added, and the pretreatment is stirred for 30 minutes, followed by static precipitation for 2-4 hours, and a supernatant is separated; and the supernatant is subjected to ultrafiltration. The process effectively removes organic pollutants and heavy metal pollutants in the organic wastewater in the chemical park through the combined process of "pretreatment+Fenton oxidation+coagulation precipitation+ultrafiltration", and the effluent meets the pollutant emission standard of a municipal sewage treatment plant, wherein the COD removal rate is above 96%.

Description

Technical Field

[0001] This invention belongs to the field of wastewater treatment technology, specifically relating to a process for treating organic wastewater in a chemical industrial park. Background Art

[0002] The industrial park is a provincial-level high-tech industrial park specializing in circular economy, with basic chemicals, fine chemicals, and new chemical materials as its pillar industries. However, because most of the enterprises in the park are small to medium-sized, their wastewater generation is relatively small, and they lack the capacity and initiative to treat it themselves. Furthermore, the industrial wastewater they generate is characterized by complex composition, high concentration, and large fluctuations in pollutants. Most enterprises fail to effectively treat their wastewater, and the discharged wastewater frequently fails to meet the standards for discharge into sewage treatment plants, posing a significant threat to the water environment.

[0003] To address this challenge, a combined process of "pretreatment + coagulation sedimentation + biochemical treatment" is currently employed. However, the COD values ​​of wastewater discharged from industrial parks range from 500 to 1200 mg / L, with the main pollutants being organic pollutants. These are primarily complex pollutants with aromatic groups as the parent compound and chromogenic groups, as well as some highly toxic nitro and amino compounds. These compounds are relatively stable and difficult to remove through microbial oxidation. Existing processes can achieve effluent CODs of 43.7-62.7 mg / L, which is substandard. Furthermore, this process cannot effectively remove heavy metal ions from the wastewater, resulting in excessive levels of heavy metal ions in the discharged water. Summary of the Invention

[0004] The purpose of this invention is to provide a process for treating organic wastewater in chemical industrial parks, which solves the problems of high COD content and heavy metal ion content in the effluent from existing organic wastewater treatment processes in chemical industrial parks.

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

[0006] A process for treating organic wastewater in a chemical industrial park includes the following steps:

[0007] Organic wastewater from the chemical industrial park is pretreated by passing it through a bar screen to remove larger suspended or floating impurities, resulting in pretreated wastewater.

[0008] The pretreated wastewater is fed into the first equalization tank. Sulfuric acid solution is added to the first equalization tank through a dosing system to adjust the pH value to 3-4, resulting in primary wastewater. The primary wastewater is then pumped into the Fenton reaction tank. H2O2 and iron-based Fenton reagent are added to the Fenton reaction tank. Under light conditions, the primary wastewater is allowed to remain in the Fenton reaction tank for 0.5-1.2 hours. After that, the effluent from the Fenton reaction tank enters the degassing and neutralization tank, where oxygen generated by the Fenton reaction is removed by stirring, resulting in secondary wastewater.

[0009] Secondary wastewater is pumped to the second equalization tank. Sodium hydroxide is added to the second equalization tank through a dosing system to adjust the pH to 7-8. Then, a precipitant is added, and the mixture is stirred at 60-150 rpm for 30 minutes. After settling for 2-4 hours, the supernatant is separated.

[0010] The supernatant is pumped to the ultrafiltration tank and filtered using a hollow fiber ultrafiltration membrane. The filtered material is recovered to the sludge treatment system and, together with the sediment in the first equalization tank, is compressed into a filter cake and transported off-site. The filtrate is discharged directly.

[0011] More specifically, the iron-based Fenton reagent is bio-carbon-supported nano-zero-valent iron with surface-loaded modified chitosan.

[0012] Furthermore, the preparation method of the iron-based Fenton reagent includes the following steps:

[0013] Step S1: Add ethanol aqueous solution and FeSO4·7H2O to the flask at 25℃ and stir for 1-1.5h. Then, under nitrogen protection, add biochar to the flask and stir continuously for 1h. While stirring, add sodium borohydride solution dropwise to the flask and continue stirring for 30min. After filtration, wash the filter cake three times with deionized water and anhydrous ethanol. Finally, dry it in a vacuum oven at 60℃ for 12h to obtain biochar-supported nano-zero valent iron.

[0014] Step S2: Add modified chitosan to deionized water and stir until homogeneous to obtain a modified solution. Place biochar-supported nano-zero valent iron in a mixing tank and spray the modified solution while stirring at 300-600 rpm. After spraying, continue stirring for 30-60 minutes and finally dry at 60°C for 12 hours to obtain iron-based Fenton reagent.

[0015] First, biochar-supported nano-zero valent iron was prepared by liquid-phase reduction. Then, modified chitosan was coated on the surface of the biochar-supported nano-zero valent iron to obtain iron-based Fenton reagent.

[0016] Furthermore, in step S1, the ratio of FeSO4·7H2O, aqueous ethanol solution, biochar, and sodium borohydride solution is 20 mmol: 300 mL: 2 g: 150 mL, the volume fraction of the aqueous ethanol solution is 30%, and the concentration of the sodium borohydride solution is 0.3 mol / L.

[0017] Furthermore, in step S2, the ratio of modified liquid to biochar-supported nano-zero-valent iron is 1g:0.8-1.2mL, and the concentration of modified chitosan in the modified liquid is 3.2-4.2mg / mL.

[0018] Furthermore, the preparation method of modified chitosan includes the following steps:

[0019] Hydroxypropyl chitosan was dissolved in deionized water to obtain mixture a. EDC and NHS were dissolved in MES buffer to obtain mixture b. Dihydroporphyrin Ce6 was dissolved in DMSO to obtain mixture c. Mixture c was added to mixture b. The mixture was stirred at 400 rpm for 4 h in the dark at room temperature. Mixture a was then added dropwise. After the addition was completed, the mixture was stirred for 24 h in the dark at room temperature. After dialysis, the mixture was freeze-dried to obtain modified chitosan.

[0020] Furthermore, the ratio of hydroxypropyl chitosan, deionized water, EDC (1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride), NHS (N-hydroxysuccinimide), MES buffer, dihydroporphyrin Ce6, and DMSO was 100 mg:100 mL:15 mg:30 mg:5 mL:5-20 mg:5 mL. The MES buffer concentration was 50 mmol / L, and the pH was 6.0. Modified chitosan was obtained by amide reaction using water-soluble hydroxypropyl chitosan and dihydroporphyrin Ce6 as raw materials.

[0021] Furthermore, the bar screen pool is equipped with coarse and fine bar screens, with the coarse bar screen being 5mm and the fine bar screen being 2mm.

[0022] Furthermore, the sulfuric acid solution has a mass fraction of 30-40%.

[0023] Furthermore, the precipitant is one or more of calcium oxide, polyferric sulfate, polyaluminum chloride, and polyacrylamide; the amount added is 5-10 wt% of the secondary wastewater.

[0024] Furthermore, 1.134g of H2O2 solution and 20-30mg of iron-based Fenton reagent are added to each L of primary wastewater, with the H2O2 solution having a mass fraction of 30%.

[0025] Furthermore, the hollow fiber ultrafiltration membrane is made of polytetrafluoroethylene (PTFE) with a pore size of 0.2 μm.

[0026] The beneficial effects of this invention are:

[0027] 1. This invention provides a process for treating organic wastewater in chemical industrial parks. Through a combination of "pretreatment + Fenton oxidation + coagulation sedimentation + ultrafiltration", organic pollutants and heavy metal pollutants in organic wastewater in chemical industrial parks are effectively removed. The effluent meets the pollutant discharge standards of urban sewage treatment plants, with a COD removal rate of over 96%.

[0028] 2. The iron-based Fenton reagent provided by this invention is a biochar-supported nano-zero-valent iron with surface-modified chitosan. The nano-zero-valent iron has a high reduction potential and is simple to prepare. It can react with H2O2 to produce ·OH, thereby rapidly and efficiently degrading pollutants. Biochar has the characteristics of multiple pore structures, abundant surface functional groups, large specific surface area, and strong adsorption capacity. Using biochar as a supporting matrix can not only improve the dispersion performance of nano-zero-valent iron, but also utilize the C=C and hydroxyl groups on the surface to act as electron donors in π-π aromatic interactions, enhancing the interaction between pollutants and catalysts, which is beneficial to improving the efficiency of Fenton reagent in catalytic degradation of organic pollutants. Modified chitosan can increase the surface functional groups of biochar, making it more compatible with heavy metals, and can also avoid excessive consumption of nano-zero-valent iron. In addition, the modified chitosan molecular chain also carries dihydroporphyrin Ce6, which can form complexes with heavy metal ions, thereby reducing the content of heavy metal ions in wastewater. Under light conditions, it can also generate active oxygen, further improving the efficiency of Fenton reagent in catalytic degradation of organic pollutants.

[0029] 3. This invention precisely controls the pH of the Fenton reactor to be 3-4, because when the pH is too low, H2O2 is converted into the more stable H3O2 when wastewater enters the Fenton reactor. + The structure is unfavorable for the production of ·OH, and at the same time, ·OH reacts with a large amount of H+ in the wastewater. + The combined effect leads to a decrease in ·OH concentration and poor degradation efficiency, while excessively high pH values ​​are unfavorable for Fe. 2+ Dissolution inhibits the Fenton reaction; simultaneously, at higher pH, Fe... 0 The Fe(OH)2 and Fe(OH)3 precipitates formed on the surface occupy the active sites of the reaction, passivating the surface of the iron-based Fenton reagent and causing it to lose its reactivity. Detailed Implementation

[0030] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0031] In the following examples and comparative examples, hydroxypropyl chitosan was purchased from Jingmen Dongxin Biotechnology Co., Ltd., with a molecular weight of approximately 120,000.

[0032] Example 1

[0033] This embodiment provides a biochar, which is prepared through the following steps:

[0034] 10 kg of corn stalks were cut into 2 cm pieces, washed with deionized water to remove surface dust, placed in an electric heating drying oven, dried at 60°C for 8 hours, then pulverized through a 100-mesh sieve using a high-speed blender, and then placed in a muffle furnace for heat treatment at 500°C under a nitrogen atmosphere for 2 hours. After removal, the stalks were washed with deionized water, dried, and pulverized through a 100-mesh sieve to obtain biochar.

[0035] Example 2

[0036] This embodiment provides a method for preparing modified chitosan, including the following steps:

[0037] 100 mg of hydroxypropyl chitosan was dissolved in 100 mL of deionized water to obtain mixture a. 15 mg of EDC and 30 mg of NHS were dissolved in 5 mL of MES buffer (50 mM, pH 6.0) to obtain mixture b. 5 mg of dihydroporphyrin Ce6 was dissolved in 5 mL of DMSO to obtain mixture c. Mixture c was added to mixture b, and the mixture was stirred at 400 rpm for 4 h in the dark at room temperature. Mixture a was then added dropwise. After the addition was complete, the mixture was stirred in the dark at room temperature for 24 h. The resulting product was then dialyzed with deionized water for 3 days, with the water changed every 12 h. After dialysis, the product was freeze-dried to obtain modified chitosan.

[0038] Example 3

[0039] This embodiment provides a method for preparing modified chitosan, including the following steps:

[0040] 100 mg of hydroxypropyl chitosan was dissolved in 100 mL of deionized water to obtain mixture a. 15 mg of EDC and 30 mg of NHS were dissolved in 5 mL of MES buffer (50 mM, pH 6.0) to obtain mixture b. 20 mg of dihydroporphyrin Ce6 was dissolved in 5 mL of DMSO to obtain mixture c. Mixture c was added to mixture b, and the mixture was stirred at 400 rpm for 4 h in the dark at room temperature. Mixture a was then added dropwise. After the addition was complete, the mixture was stirred for 24 h in the dark at room temperature. The resulting product was then dialyzed with deionized water for 3 days, with the water changed every 12 h. After dialysis, the product was freeze-dried to obtain modified chitosan.

[0041] Example 4

[0042] This embodiment provides a method for preparing an iron-based Fenton reagent, including the following steps:

[0043] Step S1: At 25℃, add 300mL of 30% ethanol aqueous solution and 20mmol FeSO4·7H2O to the flask and stir for 1h. Then, under nitrogen protection, add 2g of biochar to the flask and continue stirring for 1h. While stirring, add 150mL of 0.3mol / L sodium borohydride solution dropwise to the flask and continue stirring for 30min. After filtration, wash the filter cake three times with deionized water and anhydrous ethanol, and finally dry it in a vacuum oven at 60℃ for 12h to obtain biochar-supported nano-zero valent iron.

[0044] Step S2: Add the modified chitosan from Example 1 to deionized water and stir until homogeneous to obtain a modified solution with a concentration of 3.2 mg / mL. Place biochar-supported nano-zero valent iron in a stirring tank and spray the modified solution while stirring at 300 rpm. The ratio of the modified solution to the biochar-supported nano-zero valent iron is 1 g: 0.8 mL. After spraying, continue stirring for 30 min and finally dry at 60 °C for 12 h to obtain iron-based Fenton reagent.

[0045] Example 5

[0046] This embodiment provides a method for preparing an iron-based Fenton reagent, including the following steps:

[0047] Step S1: At 25℃, add 300mL of 30% ethanol aqueous solution and 20mmol FeSO4·7H2O to the flask and stir for 1.5h. Then, under nitrogen protection, add 2g of biochar to the flask and stir continuously for 1h. While stirring, add 150mL of 0.3mol / L sodium borohydride solution dropwise to the flask and continue stirring for 30min. After filtration, wash the filter cake three times with deionized water and anhydrous ethanol, and finally dry it in a vacuum oven at 60℃ for 12h to obtain biochar-supported nano-zero valent iron.

[0048] Step S2: Add the modified chitosan from Example 2 to deionized water and stir until homogeneous to obtain a modified solution with a concentration of 4.2 mg / mL. Place biochar-supported nano-zero valent iron in a stirring tank and spray the modified solution while stirring at 600 rpm. The ratio of the modified solution to biochar-supported nano-zero valent iron is 1 g: 1.2 mL. After spraying, continue stirring for 60 min and finally dry at 60 °C for 12 h to obtain iron-based Fenton reagent.

[0049] Comparative Example 1

[0050] This comparative example provides a method for preparing an iron-based Fenton reagent. Compared with Example 3, the modified chitosan in Example 3 is replaced with hydroxypropyl chitosan, and the other raw materials and preparation process are the same as in Example 3.

[0051] Comparative Example 2

[0052] This comparative example provides a method for preparing an iron-based Fenton reagent. Compared with Example 3, the biochar-supported nano-zero-valent iron prepared in step S1 of Example 3 is directly used as the iron-based Fenton reagent, and the operation in step S2 is not performed.

[0053] Example 6

[0054] A process for treating organic wastewater in a chemical industrial park includes the following steps:

[0055] Organic wastewater from the chemical industrial park is pretreated by passing it into a bar screen. The bar screen is equipped with a coarse screen (5mm) and a fine screen (2mm) to remove larger suspended or floating impurities, thus obtaining pretreated wastewater.

[0056] The pretreated wastewater is fed into the first equalization tank. A 30wt% sulfuric acid solution is added to the first equalization tank through a dosing system to adjust the pH value to 3, resulting in primary wastewater. The primary wastewater is then pumped into the Fenton reaction tank. H2O2 and iron-based Fenton reagent are added to the Fenton reaction tank. 1.134g of H2O2 solution and 20-30mg of iron-based Fenton reagent are added per L of primary wastewater. The mass fraction of the H2O2 solution is 30%. Under light conditions, the primary wastewater is allowed to remain in the Fenton reaction tank for 0.5h. After that, the effluent from the Fenton reaction tank enters the degassing and neutralization tank. The oxygen produced by the Fenton reaction is removed by stirring, resulting in secondary wastewater.

[0057] Secondary wastewater is pumped to the second equalization tank. Sodium hydroxide is added to the second equalization tank through a dosing system to adjust the pH to 7. Then, a precipitant is added, and the mixture is stirred at 60 rpm for 30 minutes. After settling for 2 hours, the supernatant is separated.

[0058] The supernatant is pumped to the ultrafiltration tank and filtered using a hollow fiber ultrafiltration membrane. The hollow fiber ultrafiltration membrane is made of polytetrafluoroethylene and has a pore size of 0.2μm. The filtered material is recovered to the sludge treatment system and, together with the sediment in the first equalization tank, is compressed into a filter cake and transported off-site. The filtrate is discharged directly.

[0059] The precipitant is polyferric sulfate; the amount added is 5 wt% of the secondary wastewater.

[0060] Example 7

[0061] A process for treating organic wastewater in a chemical industrial park includes the following steps:

[0062] Organic wastewater from the chemical industrial park is pretreated by passing it into a bar screen. The bar screen is equipped with a coarse screen (5mm) and a fine screen (2mm) to remove larger suspended or floating impurities, thus obtaining pretreated wastewater.

[0063] The pretreated wastewater is fed into the first equalization tank. A 35wt% sulfuric acid solution is added to the first equalization tank through a dosing system to adjust the pH value to 3, resulting in primary wastewater. The primary wastewater is then pumped into the Fenton reaction tank. H2O2 and iron-based Fenton reagent are added to the Fenton reaction tank. 1.134g of H2O2 solution and 25mg of iron-based Fenton reagent are added per L of primary wastewater. The mass fraction of the H2O2 solution is 30%. Under light conditions, the primary wastewater is allowed to remain in the Fenton reaction tank for 1 hour. After that, the effluent from the Fenton reaction tank enters the degassing and neutralization tank. The oxygen produced by the Fenton reaction is removed by stirring, resulting in secondary wastewater.

[0064] Secondary wastewater is pumped to the second equalization tank. Sodium hydroxide is added to the second equalization tank through a dosing system to adjust the pH to 7. Then, a precipitant is added, and the mixture is stirred at 80 rpm for 30 minutes. After settling for 3 hours, the supernatant is separated.

[0065] The supernatant is pumped to the ultrafiltration tank and filtered using a hollow fiber ultrafiltration membrane. The hollow fiber ultrafiltration membrane is made of polytetrafluoroethylene and has a pore size of 0.2μm. The filtered material is recovered to the sludge treatment system and, together with the sediment in the first equalization tank, is compressed into a filter cake and transported off-site. The filtrate is discharged directly.

[0066] The precipitant is polyaluminum chloride; the amount added is 8 wt% of the secondary wastewater.

[0067] Example 8

[0068] A process for treating organic wastewater in a chemical industrial park includes the following steps:

[0069] Organic wastewater from the chemical industrial park is pretreated by passing it into a bar screen. The bar screen is equipped with a coarse screen (5mm) and a fine screen (2mm) to remove larger suspended or floating impurities, thus obtaining pretreated wastewater.

[0070] The pretreated wastewater is fed into the first equalization tank. A 40wt% sulfuric acid solution is added to the first equalization tank through a dosing system to adjust the pH value to 4, resulting in primary wastewater. The primary wastewater is then pumped into the Fenton reaction tank. H2O2 and iron-based Fenton reagent are added to the Fenton reaction tank. 1.134g of H2O2 solution and 30mg of iron-based Fenton reagent are added per L of primary wastewater. The mass fraction of the H2O2 solution is 30%. Under light conditions, the primary wastewater is allowed to remain in the Fenton reaction tank for 1.2h. After that, the effluent from the Fenton reaction tank enters the degassing and neutralization tank. The oxygen produced by the Fenton reaction is removed by stirring, resulting in secondary wastewater.

[0071] Secondary wastewater is pumped to the second equalization tank. Sodium hydroxide is added to the second equalization tank through a dosing system to adjust the pH to 8. Then, a precipitant is added, and the mixture is stirred at 150 rpm for 30 minutes. After settling for 4 hours, the supernatant is separated.

[0072] The supernatant is pumped to the ultrafiltration tank and filtered using a hollow fiber ultrafiltration membrane. The hollow fiber ultrafiltration membrane is made of polytetrafluoroethylene and has a pore size of 0.2μm. The filtered material is recovered to the sludge treatment system and, together with the sediment in the first equalization tank, is compressed into a filter cake and transported off-site. The filtrate is discharged directly.

[0073] The precipitant is one or more of calcium oxide, polyferric sulfate, polyaluminum chloride, and polyacrylamide; the amount added is 10 wt% of the secondary wastewater.

[0074] Comparative Example 3

[0075] A process for treating organic wastewater in a chemical industrial park, compared with Example 6, replaces the iron-based Fenton reagent in Example 6 with the product prepared in Comparative Example 1, while the other raw materials and steps are the same as in Example 6.

[0076] Comparative Example 4

[0077] A process for treating organic wastewater in a chemical industrial park, compared with Example 6, replaces the iron-based Fenton reagent in Example 6 with the product prepared in Comparative Example 2, while the other raw materials and steps are the same as in Example 6.

[0078] Comparative Example 5

[0079] A process for treating organic wastewater in a chemical industrial park, compared with Example 6, modifies "adding 40wt% sulfuric acid solution to the second equalization tank through a dosing system to adjust the pH value to 3" in Example 6 to "adding 40wt% sulfuric acid solution to the second equalization tank through a dosing system to adjust the pH value to 2", while the remaining raw materials and steps are the same as in Example 6.

[0080] Comparative Example 6

[0081] A process for treating organic wastewater in a chemical industrial park, compared with Example 8, modifies "adding 40wt% sulfuric acid solution to the second equalization tank through a dosing system to adjust the pH value to 4" in Example 8 to "adding 40wt% sulfuric acid solution to the second equalization tank through a dosing system to adjust the pH value to 5", while the remaining raw materials and steps are the same as in Example 8.

[0082] The organic wastewater treatment processes for chemical industrial parks provided in Examples 6-8 and Comparative Examples 3-6 were used to treat organic wastewater from a chemical industrial park in Hunan Province. The raw water quality was as follows: COD 1164.08 mg / L, suspended solids 450 mg / L, ammonia nitrogen 80.8 mg / L, Ni 2+Content 57 mg / L, Pb 2+ Content 48 mg / L and Cd 2+ The concentration was 32 mg / L, and the effluent was tested. The test results are recorded in Table 1.

[0083] COD removal rate: COD of wastewater before and after treatment was tested according to HJ828-2017 "Determination of Chemical Oxygen Demand in Water - Dichromate Method". COD removal rate = (COD before treatment - COD after treatment) / COD before treatment;

[0084] Suspended solids: Tested according to GB11901-1989 "Determination of Suspended Solids in Water - Gravimetric Method";

[0085] Ammonia nitrogen: The determination was performed according to HJ535-2009 "Determination of Ammonia Nitrogen in Water - Nessler's Reagent Spectrophotometric Method";

[0086] Heavy metal ion content: determined by ultraviolet-visible spectrophotometry;

[0087] Table 1

[0088]

[0089] As can be seen from Table 1, compared with Comparative Examples 3, 4, 5 and 6, Examples 6-8 have better treatment effects on organic wastewater from chemical industrial parks, with COD removal rate of over 96% and excellent heavy metal ion removal effect.

[0090] It should be noted that, in this document, relational terms such as first and second, etc., are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "comprises," "comprising," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that includes a list of elements includes not only those elements but also other elements not explicitly listed, or elements inherent to such process, method, article, or apparatus.

[0091] While 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 these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A process for treating organic wastewater in a chemical industrial park, characterized in that, The following steps are involved: (1) The organic wastewater from the chemical industrial park is fed into a grit chamber for pretreatment to obtain pretreated wastewater; (2) After adjusting the pH of the pretreated wastewater to 3-4 with sulfuric acid solution, pump it into the Fenton reaction tank. Add H2O2 and iron-based Fenton reagent to the Fenton reaction tank. Under light conditions, let it stay for 0.5-1.2h. The effluent from the Fenton reaction tank enters the degassing and neutralization tank and is stirred to obtain secondary wastewater. (3) Adjust the pH of the secondary wastewater to 7-8, then add the precipitant, stir for 30 minutes, let it stand for 2-4 hours to settle, and then separate the supernatant. (4) The supernatant is filtered using a hollow fiber ultrafiltration membrane. The filtered material is recovered to the sludge treatment system and compressed into a filter cake together with the sediment in the first equalization tank before being transported off-site. The filtrate is discharged directly. The iron-based Fenton reagent is biochar-supported nano-zero-valent iron with surface-loaded modified chitosan. The method for preparing modified chitosan includes the following steps: dissolving hydroxypropyl chitosan in deionized water to obtain mixture a; dissolving EDC and NHS in MES buffer to obtain mixture b; dissolving dihydroporphyrin Ce6 in DMSO to obtain mixture c; adding mixture c to mixture b; stirring at 400 rpm for 4 hours at room temperature in the dark; adding mixture a dropwise; stirring for 24 hours at room temperature in the dark after the addition is complete; dialysis; and freeze-drying to obtain modified chitosan; wherein the ratio of hydroxypropyl chitosan, deionized water, EDC, NHS, MES buffer, dihydroporphyrin Ce6, and DMSO is 100 mg: 100 mL: 15 mg: 30 mg: 5 mL: 5-20 mg: 5 mL; the concentration of MES buffer is 50 mmol / L; and the pH is 6.

0. The preparation method of iron-based Fenton reagent includes the following steps: Modified chitosan was added to deionized water and stirred until homogeneous to obtain a modified solution. Biochar-supported nano-zero valent iron was placed in a mixing tank and the modified solution was sprayed while stirring. After spraying, stirring was continued for 30-60 minutes. Finally, the solution was dried at 60°C for 12 hours to obtain iron-based Fenton reagent.

2. The process for treating organic wastewater in a chemical industrial park according to claim 1, characterized in that, The ratio of modified solution to biochar-supported nano-zero valent iron is 1g:0.8-1.2mL, and the concentration of modified chitosan in the modified solution is 3.2-4.2mg / mL.

3. The process for treating organic wastewater in a chemical industrial park according to claim 1, characterized in that, A method for preparing nano-zero-valent iron supported on biochar includes the following steps: Ethanol aqueous solution and FeSO4·7H2O were added to a flask at 25℃ and stirred for 1-1.5 h. Biochar was added to the flask under nitrogen protection and stirred continuously for 1 h. Sodium borohydride solution was added dropwise to the flask while stirring. After stirring for another 30 min, the mixture was filtered. The filter cake was washed three times with deionized water and anhydrous ethanol. Finally, it was dried in a vacuum oven at 60℃ for 12 h to obtain biochar-supported nano-zero valent iron.

4. The process for treating organic wastewater in a chemical industrial park according to claim 3, characterized in that, The ratio of FeSO4·7H2O, ethanol aqueous solution, biochar, and sodium borohydride solution was 20 mmol: 300 mL: 2 g: 150 mL, the volume fraction of ethanol aqueous solution was 30%, and the concentration of sodium borohydride solution was 0.3 mol / L.

5. The process for treating organic wastewater in a chemical industrial park according to claim 1, characterized in that, Add 1.134g of H2O2 solution and 20-30mg of iron-based Fenton reagent to each liter of primary wastewater. The mass fraction of the H2O2 solution is 30%.

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