Organic wastewater treatment process for chemical industry park

Abstract

The invention discloses a chemical industrial park organic wastewater treatment process, which belongs to the technical field of wastewater treatment, and comprises the following steps: adjusting the pH value of pretreated wastewater to 3-4, pumping the wastewater into a Fenton reaction tank, adding H2O2 and an iron-based Fenton reagent into the Fenton reaction tank, staying for 0.5-1.2 h under the illumination condition, then introducing the effluent of the Fenton reaction tank into a degassing neutralization tank, stirring to remove oxygen generated by the Fenton reaction, conveying the oxygen to a second regulating tank through a water pump, regulating the pH value to 7-8, adding a precipitator, stirring for 30 minutes, standing and precipitating for 2-4 hours, and separating out supernate; and carrying out ultrafiltration on the supernate. The organic pollutants and heavy metal pollutants in the organic wastewater in the chemical industrial park are effectively removed through the combined process of pretreatment, Fenton oxidation, coagulating sedimentation and ultrafiltration, the effluent meets the pollutant discharge standard of a municipal sewage treatment plant, and the COD removal rate is 96% or above.

Description

Technical Field

[0001] The invention belongs to the technical field of wastewater treatment, and in particular relates to a process for treating organic wastewater in a chemical park. Background Art

[0002] The industrial concentration area is a provincial high-tech industrial park with circular economy as its pillar industries, with basic chemicals, fine chemicals and new chemical materials as its pillar industries. Since most of the enterprises in the park are small and medium-sized, the amount of wastewater generated is not large, the enterprises themselves lack treatment capacity and initiative, and the industrial wastewater pollutants produced have complex components, high concentrations of pollutants, and large fluctuations. Most enterprises fail to effectively treat wastewater, and the drainage often fails to meet the standards for sewage treatment plants, which poses a great threat to the water environment.

[0003] To solve this problem, the combined process of "pretreatment + coagulation sedimentation + biochemical treatment" is currently used. The COD value of wastewater discharged from industrial parks is 500-1200 mg / L. The main pollutants are organic pollutants, and they are mainly complex pollutants with aromatic groups as the parent body and chromogenic groups, as well as some nitro and amino compounds with relatively high toxicity. They are relatively stable in nature and difficult to be oxidized and removed by microorganisms. The effluent COD of the existing process can reach 43.7-62.7 mg / L, which is not up to standard. In addition, the process cannot effectively remove heavy metal ions in the wastewater, resulting in excessive heavy metal ion content in the discharged water. Summary of the invention

[0004] The purpose of the present invention is to provide a chemical park organic wastewater treatment process to solve the problems of high COD content and heavy metal ion content in effluent from existing chemical park organic wastewater treatment processes.

[0005] The purpose of the present invention can be achieved by the following technical solutions: A chemical park organic wastewater treatment process comprises the following steps: The organic wastewater from the chemical park is passed into the grid pool for pretreatment to remove larger suspended or floating impurities to obtain pretreated wastewater; The pretreated wastewater is passed into the first regulating tank, sulfuric acid solution is added to the first regulating tank through the dosing system to adjust the pH value to 3-4 to obtain primary wastewater, the primary wastewater is pumped into the Fenton reaction tank, H2O2 and iron-based Fenton reagent are added to the Fenton reaction tank, and the primary wastewater is allowed to stay in the Fenton reaction tank for 0.5-1.2h under light conditions, and then the effluent of the Fenton reaction tank enters the degassing neutralization tank, and the oxygen generated by the Fenton reaction is removed by stirring to obtain secondary wastewater; The secondary wastewater is transported to the second regulating tank through a water pump, and sodium hydroxide is added to the second regulating tank through a dosing system to adjust the pH value to 7-8, and then a precipitant is added, and the stirring speed is 60-150rpm for 30min, and then the precipitation is allowed to stand for 2-4h, and the supernatant is separated; The supernatant is pumped to the ultrafiltration tank and filtered using a hollow fiber ultrafiltration membrane. The filtrate is recovered to the sludge treatment system and compressed into a filter cake together with the sediment in the first regulating tank for external transportation. The filtrate is discharged directly.

[0006] Furthermore, the iron-based Fenton reagent is biochar-loaded nano-zero-valent iron with surface-loaded modified chitosan.

[0007] Furthermore, the preparation method of the iron-based Fenton reagent comprises the following steps: Step S1, add ethanol aqueous solution and FeSO4·7H2O to a flask at 25°C, stir for 1-1.5 hours, add biochar to the flask under nitrogen protection, continue stirring for 1 hour, drop sodium borohydride solution into the flask while stirring, continue stirring for 30 minutes, filter, wash the filter cake with deionized water and anhydrous ethanol for 3 times, and finally dry it in a vacuum oven at 60°C for 12 hours to obtain biochar-loaded nano zero-valent iron; Step S2, adding modified chitosan to deionized water, stirring evenly to obtain a modified liquid, placing biochar-loaded nano-zero-valent iron in a stirring tank, stirring and spraying the modified liquid at a speed of 300-600 rpm, and after spraying, continuing to stir for 30-60 minutes, and finally drying at 60°C for 12 hours to obtain an iron-based Fenton reagent.

[0008] Firstly, biochar-loaded nano-zero-valent iron was prepared by liquid phase reduction method, and then modified chitosan was coated on the surface of biochar-loaded nano-zero-valent iron to obtain iron-based Fenton reagent.

[0009] Furthermore, in step S1, the dosage ratio of FeSO4·7H2O, ethanol aqueous solution, biochar and sodium borohydride solution is 20mmol:300mL:2g:150mL, the volume fraction of ethanol aqueous solution is 30%, and the concentration of sodium borohydride solution is 0.3mol / L.

[0010] Furthermore, in step S2, the dosage ratio of the modified liquid and the biochar-loaded nano zero-valent iron is 1 g: 0.8-1.2 mL, and the concentration of the modified chitosan in the modified liquid is 3.2-4.2 mg / mL.

[0011] Furthermore, the preparation method of modified chitosan comprises the following steps: Hydroxypropyl chitosan was dissolved in deionized water to obtain a mixture a, EDC and NHS were dissolved in MES buffer to obtain a mixture b, dihydrochlorin Ce6 was dissolved in DMSO to obtain a mixture c, the mixture c was added to the mixture b, stirred at 400 rpm for 4 h at room temperature in the dark, the mixture a was added dropwise, after the addition was completed, stirred at room temperature in the dark for 24 h, and freeze-dried after dialysis to obtain modified chitosan.

[0012] Furthermore, the dosage ratio of hydroxypropyl chitosan, deionized water, EDC (1-ethyl-(3-dimethylaminopropyl) carbodiimide hydrochloride), NHS (N-hydroxysuccinimide), MES buffer, dihydrochlorin 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. Modified chitosan is obtained by amide reaction using water-soluble hydroxypropyl chitosan and dihydrochlorin Ce6 as raw materials.

[0013] Furthermore, the grid pool is provided with a coarse grid and a fine grid, the coarse grid is 5 mm, and the fine grid is 2 mm.

[0014] Furthermore, the mass fraction of the sulfuric acid solution is 30-40%.

[0015] Furthermore, the precipitant is one or more of calcium oxide, polyferric sulfate, polyaluminium chloride and polyacrylamide; the added amount is 5-10wt% of the secondary wastewater.

[0016] Furthermore, 1.134 g of H2O2 solution and 20-30 mg of iron-based Fenton reagent were added to each liter of primary wastewater, and the mass fraction of H2O2 solution was 30%.

[0017] Furthermore, the hollow fiber ultrafiltration membrane is made of polytetrafluoroethylene (PTFE), and the pore size of the ultrafiltration membrane is 0.2 μm.

[0018] Beneficial effects of the present invention: 1. The present invention provides a process for treating organic wastewater in a chemical park. Through a combined process of "pretreatment + Fenton oxidation + coagulation sedimentation + ultrafiltration", the organic pollutants and heavy metal pollutants in the organic wastewater in the chemical park are effectively removed. The effluent meets the pollutant discharge standards of urban sewage treatment plants, and the COD removal rate is above 96%; 2. The iron-based Fenton reagent provided by the present invention is biochar loaded with modified chitosan on the surface, and the nano-zero-valent iron has a high reduction potential and is easy to prepare. It can react with H2O2 to produce ·OH, thereby quickly and efficiently degrading pollutants. Biochar has the characteristics of multiple void structures, rich surface functional groups, large specific surface area, and strong adsorption capacity. Using biochar as a loading matrix can not only improve the dispersion performance of nano-zero-valent iron, but also use the surface C=C and hydroxyl groups to act as electron donors in π-π aromatic interactions, enhance the interaction between pollutants and catalysts, and help improve the efficiency of Fenton reagent catalytic degradation of organic pollutants. Modified chitosan can increase the surface functional groups of biochar, so that it has better affinity for heavy metals, and can also avoid excessive consumption of nano-zero-valent iron. In addition, the modified chitosan molecular chain also carries dihydrochlorin Ce6, which can form a complex with heavy metal ions, thereby reducing the heavy metal ion content in wastewater. Under light conditions, it can also produce active oxygen, further improving the efficiency of Fenton reagent catalytic degradation of organic pollutants. 3. The present invention accurately controls the pH value of the Fenton reaction tank to 3-4, because when the pH value is too low, when the wastewater enters the Fenton reaction tank, H2O2 is converted into relatively stable H3O2 + structure, which is not conducive to the production of ·OH. At the same time, ·OH reacts with a large amount of H + The combined effect leads to a decrease in OH concentration and poor degradation efficiency, while an excessively high pH value is not conducive to Fe 2+ dissolution, inhibiting the Fenton reaction. At the same time, at a 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 making it lose its reaction activity. DETAILED DESCRIPTION

[0019] 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.

[0020] The hydroxypropyl chitosan in the following examples and comparative examples was purchased from Jingmen Dongxin Biotechnology Co., Ltd., with a molecular weight of about 120,000.

[0021] Example 1 This embodiment provides a biochar, which is prepared by the following steps: 10 kg of corn stalks were cut into small pieces of 2 cm, washed with deionized water to remove surface dust, placed in an electric blast drying oven, dried at 60 ° C for 8 h, crushed with a wall breaker and passed through a 100-mesh sieve, then placed in a muffle furnace, heat treated at 500 ° C in a nitrogen atmosphere for 2 h, taken out, washed with deionized water and dried, crushed through a 100-mesh sieve to obtain biochar.

[0022] Example 2 This embodiment provides a method for preparing modified chitosan, comprising the following steps: 100 mg of hydroxypropyl chitosan was dissolved in 100 mL of deionized water to obtain a mixed solution 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 a mixed solution b, 5 mg of dihydrochlorin Ce6 was dissolved in 5 mL of DMSO to obtain a mixed solution c, the mixed solution c was added to the mixed solution b, and the mixture was stirred at 400 rpm for 4 h at room temperature in the dark, and the mixed solution a was added dropwise. After the addition was completed, the mixture was stirred at room temperature in the dark for 24 h, and the obtained product was dialyzed with deionized water for 3 days, the water was changed once every 12 hours, and then freeze-dried after the dialysis to obtain modified chitosan.

[0023] Example 3 This embodiment provides a method for preparing modified chitosan, comprising the following steps: 100 mg of hydroxypropyl chitosan was dissolved in 100 mL of deionized water to obtain a mixed solution 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 a mixed solution b, and 20 mg of dihydrochlorin Ce6 was dissolved in 5 mL of DMSO to obtain a mixed solution c. The mixed solution c was added to the mixed solution b, and the mixture was stirred at 400 rpm for 4 h at room temperature in the dark. The mixed solution a was added dropwise. After the addition was completed, the mixture was stirred at room temperature in the dark for 24 h. The product was then dialyzed with deionized water for 3 days, with the water changed once every 12 hours. After the dialysis was completed, it was freeze-dried to obtain modified chitosan.

[0024] Example 4 This embodiment provides a method for preparing an iron-based Fenton reagent, comprising the following steps: Step S1, add 300 mL of 30% ethanol aqueous solution and 20 mmol FeSO4·7H2O into a flask at 25°C, stir for 1 hour, add 2 g of biochar into the flask under nitrogen protection, continue stirring for 1 hour, add 150 mL of 0.3 mol / L sodium borohydride solution into the flask while stirring, continue stirring for 30 minutes, filter, wash the filter cake with deionized water and anhydrous ethanol for 3 times, and finally dry it in a vacuum oven at 60°C for 12 hours to obtain biochar-loaded nano zero-valent iron; Step S2, adding the modified chitosan of Example 1 to deionized water, stirring evenly to obtain a modified liquid with a modified chitosan concentration of 3.2 mg / mL, placing the biochar-loaded nano zero-valent iron in a stirring tank, stirring and spraying the modified liquid at a speed of 300 rpm, the dosage ratio of the modified liquid to the biochar-loaded nano zero-valent iron is 1 g: 0.8 mL, after spraying, continue stirring for 30 minutes, and finally dry at 60°C for 12 hours to obtain the iron-based Fenton reagent.

[0025] Example 5 This embodiment provides a method for preparing an iron-based Fenton reagent, comprising the following steps: Step S1, add 300 mL of 30% ethanol aqueous solution and 20 mmol FeSO4·7H2O into a flask at 25°C, stir for 1.5 hours, add 2 g of biochar into the flask under nitrogen protection, continue stirring for 1 hour, add 150 mL of 0.3 mol / L sodium borohydride solution into the flask while stirring, continue stirring for 30 minutes, filter, wash the filter cake with deionized water and anhydrous ethanol for 3 times, and finally dry it in a vacuum oven at 60°C for 12 hours to obtain biochar-loaded nano zero-valent iron; Step S2, adding the modified chitosan of Example 2 to deionized water, stirring evenly to obtain a modified liquid with a modified chitosan concentration of 4.2 mg / mL, placing the biochar-loaded nano zero-valent iron in a stirring tank, stirring and spraying the modified liquid at a speed of 600 rpm, the dosage ratio of the modified liquid to the biochar-loaded nano zero-valent iron is 1 g: 1.2 mL, after spraying, continue stirring for 60 minutes, and finally dry at 60°C for 12 hours to obtain the iron-based Fenton reagent.

[0026] Comparative Example 1 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 by hydroxypropyl chitosan, and the remaining raw materials and preparation process are the same as Example 3.

[0027] Comparative Example 2 This comparative example provides a method for preparing an iron-based Fenton reagent. Compared with Example 3, the biochar-loaded nano-zero-valent iron prepared in step S1 of Example 3 is directly used as the iron-based Fenton reagent, and step S2 is not performed.

[0028] Example 6 A chemical park organic wastewater treatment process comprises the following steps: The organic wastewater from the chemical park is passed into the grid pool for pretreatment. The grid pool is provided with a coarse grid and a fine grid, the coarse grid is 5 mm, and the fine grid is 2 mm, to remove larger suspended or floating impurities and obtain pretreated wastewater; The pretreated wastewater is passed into the first regulating tank, 30wt% sulfuric acid solution is added to the first regulating tank through the dosing system to adjust the pH value to 3 to obtain primary wastewater, the primary wastewater is passed into the Fenton reaction tank through a water pump, 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 to each liter of primary wastewater, and the mass fraction of H2O2 solution is 30%. Under light conditions, the primary wastewater is allowed to stay in the Fenton reaction tank for 0.5h, and then the effluent of the Fenton reaction tank enters the degassing neutralization tank, and the oxygen generated by the Fenton reaction is removed by stirring to obtain secondary wastewater; The secondary wastewater is transported to the second regulating tank through a water pump, and sodium hydroxide is added to the second regulating tank through a dosing system to adjust the pH value to 7, and then a precipitant is added, and after stirring at a speed of 60 rpm for 30 minutes, it is allowed to settle for 2 hours, and the supernatant is separated; The supernatant is pumped to the ultrafiltration tank and filtered using a hollow fiber ultrafiltration membrane made of polytetrafluoroethylene with a pore size of 0.2 μm. The filtrate is recovered to the sludge treatment system and compressed into a filter cake together with the precipitate in the first regulating tank for external transportation, and the filtrate is discharged directly.

[0029] The precipitant is polyferric sulfate; the added amount is 5wt% of the secondary wastewater.

[0030] Example 7 A chemical park organic wastewater treatment process comprises the following steps: The organic wastewater from the chemical park is passed into the grid pool for pretreatment. The grid pool is provided with a coarse grid and a fine grid, the coarse grid is 5 mm, and the fine grid is 2 mm, to remove larger suspended or floating impurities and obtain pretreated wastewater; The pretreated wastewater is passed into the first regulating tank, 35wt% sulfuric acid solution is added to the first regulating tank through the dosing system to adjust the pH value to 3, and primary wastewater is obtained. The primary wastewater is passed into the Fenton reaction tank through a water pump, and 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 to each liter of primary wastewater, and the mass fraction of H2O2 solution is 30%. Under light conditions, the primary wastewater is allowed to stay in the Fenton reaction tank for 1h, and then the effluent of the Fenton reaction tank enters the degassing neutralization tank, and the oxygen generated by the Fenton reaction is removed by stirring to obtain secondary wastewater; The secondary wastewater is transported to the second regulating tank through a water pump, and sodium hydroxide is added to the second regulating tank through a dosing system to adjust the pH value to 7, and then a precipitant is added, and after stirring at a speed of 80 rpm for 30 minutes, it is allowed to settle for 3 hours, and the supernatant is separated; The supernatant is pumped to the ultrafiltration tank and filtered using a hollow fiber ultrafiltration membrane made of polytetrafluoroethylene with a pore size of 0.2 μm. The filtrate is recovered to the sludge treatment system and compressed into a filter cake together with the precipitate in the first regulating tank for external transportation, and the filtrate is discharged directly.

[0031] The precipitant is polyaluminium chloride; the amount added is 8wt% of the secondary wastewater.

[0032] Example 8 A chemical park organic wastewater treatment process comprises the following steps: The organic wastewater from the chemical park is passed into the grid pool for pretreatment. The grid pool is provided with a coarse grid and a fine grid, the coarse grid is 5 mm, and the fine grid is 2 mm, to remove larger suspended or floating impurities and obtain pretreated wastewater; The pretreated wastewater is passed into the first regulating tank, 40wt% sulfuric acid solution is added to the first regulating tank through the dosing system to adjust the pH value to 4 to obtain primary wastewater, the primary wastewater is passed into the Fenton reaction tank through a water pump, 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 to each liter of primary wastewater, and the mass fraction of H2O2 solution is 30%. Under light conditions, the primary wastewater is allowed to stay in the Fenton reaction tank for 1.2h, and then the effluent from the Fenton reaction tank enters the degassing neutralization tank, and the oxygen generated by the Fenton reaction is removed by stirring to obtain secondary wastewater; The secondary wastewater is transported to the second regulating tank through a water pump, and sodium hydroxide is added to the second regulating tank through a dosing system to adjust the pH value to 8, and then a precipitant is added, and after stirring at a speed of 150 rpm for 30 minutes, it is allowed to settle for 4 hours, and the supernatant is separated; The supernatant is pumped to the ultrafiltration tank and filtered using a hollow fiber ultrafiltration membrane made of polytetrafluoroethylene with a pore size of 0.2 μm. The filtrate is recovered to the sludge treatment system and compressed into a filter cake together with the precipitate in the first regulating tank for external transportation, and the filtrate is discharged directly.

[0033] The precipitant is one or more of calcium oxide, polyferric sulfate, polyaluminium chloride and polyacrylamide; the added amount is 10wt% of the secondary wastewater.

[0034] Comparative Example 3 A process for treating organic wastewater in a chemical park. Compared with Example 6, the iron-based Fenton reagent in Example 6 is replaced with a product prepared in Comparative Example 1, and the remaining raw materials and steps are the same as Example 6.

[0035] Comparative Example 4 A process for treating organic wastewater in a chemical park, compared with Example 6, wherein the iron-based Fenton reagent in Example 6 is replaced with a product prepared in Comparative Example 2, and the remaining raw materials and steps are the same as in Example 6.

[0036] Comparative Example 5 A process for treating organic wastewater in a chemical park. Compared with Example 6, the phrase "adding 40 wt % sulfuric acid solution to the second regulating tank through a dosing system to adjust the pH value to 3" in Example 6 is modified to "adding 40 wt % sulfuric acid solution to the second regulating tank through a dosing system to adjust the pH value to 2", and the remaining raw materials and steps are the same as in Example 6.

[0037] Comparative Example 6 A process for treating organic wastewater in a chemical park. Compared with Example 8, the phrase "adding 40 wt % sulfuric acid solution to the second regulating tank through a dosing system to adjust the pH value to 4" in Example 8 is modified to "adding 40 wt % sulfuric acid solution to the second regulating tank through a dosing system to adjust the pH value to 5", and the remaining raw materials and steps are the same as Example 8.

[0038] The organic wastewater treatment process of a chemical park in Hunan was used to treat the organic wastewater. The raw water quality was as follows: COD content 1164.08 mg / L, suspended solids content 450 mg / L, ammonia nitrogen content 80.8 mg / L, Ni 2+ Content 57mg / L, Pb 2+ Content 48mg / L and Cd 2+ The content is 32 mg / L, and the discharged water is tested and the test results are recorded in Table 1.

[0039] COD removal rate: Refer to HJ828-2017 "Determination of Chemical Oxygen Demand of Water Quality - Dichromate Method" to detect COD before and after wastewater treatment. COD removal rate = (COD before treatment - COD after treatment) / COD before treatment; Suspended matter: refer to GB11901-1989 "Determination of suspended matter in water by weight method" for testing; Ammonia nitrogen: refer to HJ535-2009 "Determination of ammonia nitrogen in water - Nessler's reagent spectrophotometry" for detection; Heavy metal ion content: UV-visible spectrophotometry; Table 1

[0040] It can be seen from Table 1 that, compared with Comparative Examples 3, 4, 5, and 6, Examples 6-8 have better treatment effects on organic wastewater in chemical parks, wherein the COD removal rate is above 96%, and the heavy metal ion removal effect is excellent.

[0041] 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", "comprise" or any other variants 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.

[0042] 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 process for treating organic wastewater in a chemical park, characterized in that: The following steps are involved: The organic wastewater from the chemical park is passed into the grid pool for pretreatment to obtain pretreated wastewater; The pre-treated wastewater is adjusted to a pH value of 3-4 with sulfuric acid solution and then pumped into the Fenton reaction tank, H2O2 and iron-based Fenton reagent are added to the Fenton reaction tank, and the reaction tank is left for 0.5-1.2 hours under light conditions. The effluent from the Fenton reaction tank enters the degassing and neutralization tank and is stirred to obtain secondary wastewater; The pH value of the secondary wastewater was adjusted to 7-8, and then a precipitant was added. After stirring for 30 minutes, the mixture was allowed to settle for 2-4 hours, and the supernatant was separated. The supernatant is filtered using a hollow fiber ultrafiltration membrane, and the filtrate is recovered to the sludge treatment system and compressed into a filter cake together with the sediment in the first regulating tank before being transported out, and the filtrate is directly discharged; The iron-based Fenton reagent is biochar loaded with nanometer zero-valent iron with modified chitosan loaded on the surface.

2. A chemical park organic wastewater treatment process according to claim 1, characterized in that: The preparation method of the iron-based Fenton reagent comprises the following steps: Add modified chitosan to deionized water and stir evenly to obtain a modified solution. Place biochar loaded with nano zero-valent iron in a stirring tank and spray the modified solution while stirring. After spraying, continue stirring for 30-60 minutes and finally dry at 60°C for 12 hours to obtain an iron-based Fenton reagent.

3. A chemical park organic wastewater treatment process according to claim 2, characterized in that: The dosage ratio of the modified liquid and the biochar loaded 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.

4. A chemical park organic wastewater treatment process according to claim 1, characterized in that: The method for preparing biochar-loaded nano zero-valent iron comprises the following steps: Add ethanol aqueous solution and FeSO4·7H2O to the flask at 25°C, stir for 1-1.5 hours, then add biochar to the flask under nitrogen protection, continue stirring for 1 hour, add sodium borohydride solution dropwise to the flask while stirring, continue stirring for 30 minutes, filter, wash the filter cake with deionized water and anhydrous ethanol for 3 times, and finally dry it in a vacuum oven at 60°C for 12 hours to obtain biochar-loaded nano zero-valent iron.

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

6. A chemical park organic wastewater treatment process according to claim 4, characterized in that: The preparation method of modified chitosan comprises the following steps: Hydroxypropyl chitosan was dissolved in deionized water to obtain a mixture a, EDC and NHS were dissolved in MES buffer to obtain a mixture b, dihydrochlorin Ce6 was dissolved in DMSO to obtain a mixture c, the mixture c was added to the mixture b, stirred at 400 rpm for 4 h at room temperature in the dark, the mixture a was added dropwise, after the addition was completed, stirred at room temperature in the dark for 24 h, dialyzed and freeze-dried to obtain modified chitosan.

7. A chemical park organic wastewater treatment process according to claim 6, characterized in that: The dosage ratio of hydroxypropyl chitosan, deionized water, EDC, NHS, MES buffer, dihydrochlorin 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.

8. A chemical park organic wastewater treatment process according to claim 1, characterized in that: 1.134 g of H2O2 solution and 20-30 mg of iron-based Fenton reagent were added to every liter of primary wastewater, and the mass fraction of H2O2 solution was 30%.

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