Oxidation process for high-concentration and high-salinity chemical wastewater

Abstract

This invention belongs to the field of water pollution control, specifically involving an oxidation process for high-concentration, high-salinity chemical wastewater. The process involves pretreatment of the wastewater, adjusting the pH to 3-4, adding slow-release iron salts, then adding polyacrylamide to produce flocculation, followed by filtration; then adding hydrogen peroxide to react, adjusting the pH to 8-9, adding a coagulant, and filtration; finally, adding hydrogen peroxide again to react, adding a coagulant, and filtration. The coordination complex of ferric iron catalyzes the generation of ·OH from hydrogen peroxide, oxidizing and removing COD. The highly stable complex of ferric iron is utilized to achieve Fenton-like oxidation and complex breaking under alkaline conditions, realizing Fe... 3+ The three-stage utilization of salts weakens the quenching effect of high concentrations of chloride ions and other salts on free radicals, thereby improving the degradation efficiency of target organic matter and making this invention applicable to complex chemical wastewater. A specially formulated slow-release iron salt is used, which can slowly release Fe... 3+ This avoids the defect of excessively rapid initial consumption, thus allowing free radicals to be continuously generated and improving the oxidation effect.

Description

Technical Field

[0001] This invention relates to the field of water pollution control technology, specifically to an oxidation process for high-concentration, high-salt chemical wastewater. Background Technology

[0002] Wastewater generated during chemical industrial production processes is often characterized by high salinity, complex composition, high toxicity, and difficulty in biodegradation. Advanced oxidation (AEO) or membrane treatment is costly, complex to operate and manage, and subject to stringent environmental regulations. Among these challenges, AEO is particularly important for the treatment of chemical wastewater. AEO processes generate highly reactive free radicals (mainly ·OH) or strong oxides, achieving efficient degradation of recalcitrant organic matter, aromatic compounds, phenols, and persistent pollutants.

[0003] Currently applied advanced oxidation methods include ozone oxidation, photocatalytic oxidation, ultrasonic oxidation, wet oxidation, hydrogen peroxide and Fenton's reagent oxidation, and electrochemical oxidation. However, in the research and development of pretreatment processes for chemical wastewater, the Fenton process used in each experiment can only remove 5000-8000 mg / L of COD, resulting in high sludge production and high Fenton costs. There is an urgent need for an oxidation process that can remove more COD at a lower cost. Summary of the Invention

[0004] The purpose of this invention is to provide an oxidation process for high-concentration, high-salt chemical wastewater to solve the above-mentioned problems.

[0005] The technical principle of this invention is as follows:

[0006] First point: Fe 3+ The wastewater will become very dark after being added, usually dark red or dark brown, because of Fe. 3+ It forms a coordination complex with organic matter in the water, causing a color change in the filtered wastewater. Of the 20-30 common organic chemical functional groups, 50-60% have the potential to interact with Fe. 3+ The ability to coordinate. This allows a significant portion of organic matter in the solution to interact with Fe. 3+ It forms a complex. It can combine with Fe. 3+ Among the substances that form complexes, some complexes can precipitate spontaneously. In this case, the COD in the wastewater decreases as the complexes precipitate.

[0007] Second point: Fe 3+ It readily forms a precipitate in water; theoretically, a large amount of iron hydroxide precipitate will form at pH > 2-3. At pH 3-4, almost all precipitate forms; when Fe... 3+At pH values ​​greater than 3-4, the resulting iron hydroxide is not a single crystalline solid, but rather a highly hydrated amorphous iron hydroxide, namely Fe(OH)3xH2O, or iron hydroxide colloid. It is well known that the surface of iron hydroxide colloid has many -OH groups, exhibiting strong adsorption capabilities—electrostatic adsorption, the ability of surface -OH groups to form coordinate bonds with certain ions or molecules, and adsorption of polar organic compounds. When electrolytes (NaCl, CaCl2) are present in the solution, they compress the electron double layer, promoting colloidal precipitation and forming flocculent precipitates. The use of Fe... 3+ These properties allow for the removal of a portion of COD and suspended solids from complex chemical wastewater through the adsorption of colloids formed by ferric iron, i.e., by adding a certain amount of Fe to the wastewater. 3+ Salt, under low pH conditions of 3-4, can remove the coordination complex precipitates mentioned in "point one" through coagulation and sedimentation, while also adsorbing some organic matter and suspended solids.

[0008] Thirdly: After the treatment in "point two," only the complexes that formed complexes with ferric iron without precipitation and the untreated complex wastewater remain in the solution (at this point, there is no Fe in the solution). 3+ The unprecipitated coordination complexes can be simply divided into two parts: one part is the moderately stable ligands, and the other part is the weakly stable ligands (strongly stable ligands account for only a very small part, such as the complexes of EDTA and ferric iron).

[0009] At this point, a certain amount of hydrogen peroxide is added to the solution. The ferric iron complexed with the organic matter catalyzes the hydrogen peroxide to produce ·OH. The ·OH generated at this time is very close to the reaction substrate to be treated and can directly oxidize the reaction substrate. After a certain period of stirring, the complexed iron ions catalyze all the unreacted hydrogen peroxide until all the organic matter in the wastewater that can be oxidized by ·OH is oxidized and decomposed, thereby achieving further removal of COD from the wastewater.

[0010] The ·OH produced by the ferric iron complexed with organic matter and catalyzed by it is different from that produced by Fe. 3+ The catalytic behavior of ions, because Fe 3+ In point two, the precipitate had already formed at a pH of 3-4. During the reaction, the ferric iron in the complex catalyzed the production of ·OH from hydrogen peroxide.

[0011] Perhaps the partial oxidation of substrates such as aromatics, phenols, and azo compounds leads to the formation of quinones, azo fragments, and condensation products, resulting in no significant change in the color of the solution after the reaction. Some weakly liganded complexes decompose under the "attack" of ·OH, causing the ferric iron complex to detach. After adjusting the pH to 8-9, a small amount of ferric hydroxide colloid is produced in the solution, which, after flocculation and precipitation, yields a deep red filtrate.

[0012] Fourthly, under pH conditions of 9-10, the residual ferric ligands in the solution continue to catalyze the generation of ·OH from hydrogen peroxide, or the oxidative complex-breaking process occurs due to the oxidizing property of hydrogen peroxide itself. A small amount of hydrogen peroxide is added to the filtrate and stirred for 0.5-1 hours. At this time, the color of the solution is greatly reduced, and a small amount of ferric hydroxide precipitate is found at the bottom of the solution, and COD is further removed.

[0013] More specifically, the present invention can be implemented through the following technical solutions:

[0014] An oxidation process for high-concentration, high-salt chemical wastewater includes the following steps:

[0015] Step 1: Pre-treat the high-concentration, high-salt chemical wastewater to obtain pre-treated wastewater;

[0016] Step 2: Adjust the pH of the pretreated wastewater to 3-4, add slow-release iron salt, and stir to react;

[0017] Step 3: Add polyacrylamide to the wastewater treated in Step 2, stir to produce flocculation, filter, and remove the sludge obtained from the filter.

[0018] Step 4: Add hydrogen peroxide to the wastewater treated in Step 3 and stir to react;

[0019] Step 5: Adjust the pH of the wastewater treated in Step 4 to 8-9, add coagulant, coagulate and filter, and remove the sludge obtained from filtration.

[0020] Step 6: Add hydrogen peroxide to the wastewater treated in Step 5 and stir to react;

[0021] Step 7: Add coagulant to the wastewater treated in Step 6, coagulate and filter, and remove the sludge obtained from the filtration.

[0022] Furthermore, the method for preparing the slow-release iron salt includes the following steps:

[0023] A wet mud is prepared by mixing trivalent ferric salt, divalent ferric salt, attapulgite clay, hydrogen peroxide, and trifluoromethanesulfonic acid aqueous solution. The wet mud is dried at a temperature of 70-100°C. During the drying process, the wet mud is ground using a grinder to finally obtain the slow-release ferric salt.

[0024] Furthermore, the mass ratio of the trivalent iron salt, divalent iron salt and attapulgite is 3:(2-2.3):(16.5-17).

[0025] Furthermore, the trifluoromethanesulfonic acid aqueous solution has a mass fraction of 0.000001.7%. The hydrogen peroxide has a mass fraction of 30%.

[0026] Furthermore, the moisture content of the wet mud is 65% to 70%.

[0027] Furthermore, the moisture content of the slow-release iron salt is less than or equal to 10%.

[0028] Furthermore, ceramic grinding balls are added to the grinder, and grinding is performed at a grinding frequency of 20-30 Hz.

[0029] Furthermore, the trivalent ferric salt is one or more of ferric chloride, ferric sulfate, polyferric sulfate, and polyferric chloride.

[0030] Furthermore, the ferrous salt is one or more of ferrous sulfate, ferrous chloride, and ferrous nitrate.

[0031] Furthermore, in step 1, the pretreatment step includes using a bar screen for filtration, sedimentation in a grit chamber, and water quality adjustment in a balance tank.

[0032] Water quality equalization is designed to address the problem of large fluctuations in influent water quality (flow rate, concentration, pH, temperature). Uneven water quality can severely interfere with the dosage and reaction effect of flocculants. A large tank volume allows wastewater flowing in at different times to be mixed evenly, resulting in a relatively stable output flow rate and water quality.

[0033] If the wastewater contains grease, it needs to be sent to an oil removal tank for further oil removal. The purpose of the oil removal tank is to remove grease, fat, and light solids floating on the water surface. These substances can coat the flocs, interfere with flocculation, and clog the filter media.

[0034] In the reaction system of this invention, a ferric salt system is used. However, in practice, it has been found that the following aspects require further optimization for the oxidation treatment of high-concentration, high-salt chemical wastewater:

[0035] Fe 3+ If the initial consumption is too rapid, it cannot continuously generate free radicals, resulting in a waste of oxidant. High concentrations of chloride ions and other salts can quench free radicals, generating weaker chlorine free radicals, which reduce the degradation efficiency of the target organic matter.

[0036] Therefore, in this invention, a slow-release iron salt is initially used, which uses attapulgite as a carrier and oxidizes ferrous ions with hydrogen peroxide in a highly diluted superacid system. Attapulgite contains numerous micropores and mesopores, and a portion of the Fe3+... + It can enter the cavity; in addition, Fe 2+ During the extensive oxidation process, the highly diluted trifluoromethanesulfonic acid solution rapidly acidifies the interior of attapulgite, clearing internal cavities and channels and depolymerizing the structure. In this process, Fe is generated through oxidation. 3+It will fill some of the original channels and cavities, eventually constructing a complex channel structure, thereby achieving the slow release of Fe. 3+ The purpose was to achieve this. Experiments revealed that a trifluoromethanesulfonic acid aqueous solution was necessary; even hydrochloric acid, sulfuric acid, and perchloric acid could not rapidly dissolve the internal cavities of attapulgite and depolymerize its structure within a short time, thus failing to regenerate Fe. 3+ Its binding effect with the cavities inside the attapulgite soil is limited, resulting in a poorer slow-release effect.

[0037] In this invention, the slow-release principle of the iron salt is that attapulgite itself is insoluble in water, due to the large amount of Fe... 3+ Located within the pores and cavities of attapulgite soil, Fe... 3+ Dissolution is difficult and cannot be achieved quickly in a short time. It requires prolonged and vigorous stirring to break up the attapulgite particles before the Fe can dissolve. 3+ Rapid release; therefore, at lower speeds, the special internal structure of slow-release iron salts allows for prolonged release of Fe. 3+ .

[0038] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0039] 1. The coordination complex of ferric iron catalyzes the generation of ·OH from hydrogen peroxide, which then oxidizes and removes COD.

[0040] 2. The Fenton-like and complex-breaking processes under alkaline conditions were completed by utilizing the strong stable complexes of ferric iron.

[0041] 3. Fe was realized 3+ The three-stage utilization weakens the effect of high concentrations of chloride ions and other salts on free radical quenching, thereby improving the degradation efficiency of the target organic matter, making this invention applicable to chemical wastewater with complex composition.

[0042] 4. It uses a specially formulated slow-release iron salt, which can slowly release Fe 3+ This avoids the defect of excessively rapid initial consumption, thus allowing free radicals to be continuously generated and improving the oxidation effect. Attached Figure Description

[0043] Figure 1 This is a process flow diagram of the present invention;

[0044] Figure 2 Fe, a slow-release iron salt of Example 1 3+ Dissolution release curve;

[0045] Figure 3 Fe for the slow-release iron salt of Example 2 3+ Dissolution release curve;

[0046] Figure 4 Fe for the slow-release iron salt of Comparative Example 23+ Dissolution release curve;

[0047] Figure 5 Fe for the slow-release iron salt of Comparative Example 3 3+ Dissolution release curve;

[0048] Figure 6 Fe for the slow-release iron salt of Comparative Example 4 3+ Dissolution release curve;

[0049] Figure 7 Fe for the slow-release iron salt of Comparative Example 5 3+ Dissolution release curve;

[0050] Figure 8 Fe for the slow-release iron salt of Comparative Example 6 3+ Dissolution release curve. Detailed Implementation

[0051] The present invention will now be described in further detail with reference to specific embodiments and accompanying drawings.

[0052] The following detailed description of embodiments of this application is not intended to limit the scope of the claimed application, but merely to illustrate selected embodiments of the application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

[0053] Example 1

[0054] Treatment target: High-concentration, high-salt wastewater from a chemical enterprise, with COD = 2500 mg / L, salinity (NaCl) = 15000 mg / L, containing phenol (concentration 500 mg / L), and B / C ratio = 0.15.

[0055] Processing steps:

[0056] like Figure 1 As shown, an oxidation process for high-concentration, high-salt chemical wastewater includes the following steps:

[0057] Step 1: Pre-treat the high-concentration, high-salt wastewater to obtain pre-treated wastewater; the pre-treatment steps include using a bar screen for filtration, sedimentation in a grit chamber, and water quality adjustment in a balance tank.

[0058] Step 2: Adjust the pH of the pretreated wastewater to 3, add slow-release iron salts, and control the Fe content. 3+ The concentration was 1.3 mmol / L; the reaction was stirred for 0.2 h; the solution used to adjust the pH was hydrochloric acid or sodium hydroxide solution.

[0059] The process involves mixing 1.5 kg of ferric chloride, 1 kg of ferrous chloride, and 8.25 kg of attapulgite clay. This mixture is then combined with a 0.000001.7% (w / w) trifluoromethanesulfonic acid aqueous solution and 0.67 kg (w / w) hydrogen peroxide to create a wet mud with a moisture content of 65%. The wet mud is dried at 70–100°C. During the drying process, the wet mud is ground using a grinder with ceramic grinding balls added, and the grinding is performed at a frequency of 30 Hz. The final product is a slow-release iron salt with a moisture content of less than or equal to 10%.

[0060] Step 3: Add polyacrylamide to the wastewater treated in Step 2 at a dosage of 8 mg / L, stir to produce flocculation, filter, and remove the sludge obtained from the filtration.

[0061] Step 4: Add hydrogen peroxide (27.5% hydrogen peroxide solution) to the wastewater treated in Step 3. The dosage of hydrogen peroxide is 9 g / L (based on the volume of wastewater), and stir for 3 hours.

[0062] Step 5: Adjust the pH of the wastewater treated in Step 4 to 8, add coagulant at a dosage of 5 mg / L, coagulate and filter, and remove the sludge obtained from filtration.

[0063] Step 6: Add hydrogen peroxide (27.5% hydrogen peroxide solution) to the wastewater treated in Step 5. The dosage of hydrogen peroxide is 400 mg / L (based on the volume of wastewater), and stir for 1 hour.

[0064] Step 7: Add coagulant to the wastewater treated in Step 6 at a dosage of 3.5 mg / L, coagulate and filter, and remove the sludge obtained from the filtration.

[0065] Treatment results: Supernatant COD = 280 mg / L, COD removal rate = 88.1%; Phenol concentration = 15 mg / L, phenol removal rate = 97.0%; B / C ratio = 0.38; Sediment sludge moisture content = 78%.

[0066] Example 2

[0067] Subject of treatment: High-concentration, high-salt wastewater generated by a pharmaceutical company, COD = 4200 mg / L, salinity (NaCl) = 28000 mg / L, containing pyridine (concentration 350 mg / L), B / C ratio = 0.12.

[0068] Processing steps:

[0069] Step 1: Pre-treat the above-mentioned high-concentration and high-salt wastewater to obtain pre-treated wastewater; wherein, the pre-treatment steps include using a bar screen filter, sedimentation in a grit chamber, and water quality adjustment in an equalization tank.

[0070] Step 2: Adjust the pH of the pretreated wastewater to 4, add slow-release iron salts, and control the Fe content. 3+ The concentration was 1.2 mmol / L; the reaction was stirred for 0.5 h; the solution used to adjust the pH was hydrochloric acid or sodium hydroxide solution.

[0071] The process involves mixing 1.5 kg of ferric chloride, 1.15 kg of ferrous chloride, and 8.5 kg of attapulgite clay. This mixture is then combined with a 0.000001.7% (w / w) trifluoromethanesulfonic acid aqueous solution and 0.5 kg (w / w) hydrogen peroxide to create a wet mud with a moisture content of 70%. The wet mud is dried at 70–100°C. During the drying process, the mud is ground using a grinder with ceramic grinding balls added, and the grinding is performed at a frequency of 20 Hz. The final product is a slow-release iron salt with a moisture content of less than or equal to 10%.

[0072] Step 3: Add polyacrylamide to the wastewater treated in Step 2 at a dosage of 8.6 mg / L, stir to produce flocculation, filter, and remove the sludge obtained from the filtration.

[0073] Step 4: Add hydrogen peroxide (27.5% hydrogen peroxide solution) to the wastewater treated in Step 3. The dosage of hydrogen peroxide is 11 g / L (based on the volume of wastewater), and stir for 2 hours.

[0074] Step 5: Adjust the pH of the wastewater treated in Step 4 to 9, add coagulant at a dosage of 5.5 mg / L, coagulate and filter, and remove the sludge obtained from filtration.

[0075] Step 6: Add hydrogen peroxide (27.5% hydrogen peroxide solution) to the wastewater treated in Step 5. The dosage of hydrogen peroxide is 550 mg / L (based on the volume of wastewater), and stir for 0.5 h.

[0076] Step 7: Add coagulant to the wastewater treated in Step 6 at a dosage of 3.5 mg / L, coagulate and filter, and remove the sludge obtained from the filtration.

[0077] Treatment results: Supernatant COD = 295 mg / L, COD removal rate = 92.9%; Pyridine concentration = 12 mg / L, Pyridine removal rate = 96.6%; B / C ratio = 0.35; Sediment sludge moisture content = 76%.

[0078] Comparative Example 1

[0079] The only difference between this example and Example 2 is that ferric chloride is used instead of slow-release iron salt; everything else remains the same. COD removal rate = 76.2%.

[0080] Comparative Example 2

[0081] The only difference between this example and Example 1 is that 20% hydrochloric acid is used instead of trifluoromethanesulfonic acid aqueous solution, while the rest remains the same.

[0082] Comparative Example 3

[0083] The only difference between this example and Example 2 is that sulfuric acid is used instead of trifluoromethanesulfonic acid aqueous solution, and the pH of the reaction solution is adjusted to 1, while the rest remains unchanged.

[0084] Comparative Example 4

[0085] The only difference between this example and Example 1 is that perchloric acid is used instead of trifluoromethanesulfonic acid aqueous solution, and the pH of the reaction solution is adjusted to 1, while the rest remains unchanged.

[0086] Comparative Example 5

[0087] The only difference between this example and Example 1 is that bentonite is used instead of attapulgite; everything else remains the same.

[0088] Comparative Example 6

[0089] In this example, 26.5g of ferric chloride and 85g of attapulgite were mixed and ground in a mortar, then baked at 200℃ for 1 hour, removed and cooled to room temperature, and ground again to obtain the reference iron salt.

[0090] Sustained-release characterization test

[0091] Take an 8g sample from the sample (e.g., slow-release iron salt), pour the sample into a container, add 1.1L of distilled water, and stir with a paddle at 60r / min. Collect liquid phase samples from the top of the container at 0.2h (12min), 1h, 2h, 3h, 4h, 5h, and 6h. After filtration and settling, measure the Fe content using a spectrophotometric method (e.g., thiocyanate method). 3+ The concentration of Fe was plotted. 3+ Dissolution release curve.

[0092] Fe in Examples 1-2 and Comparative Examples 2-6 3+ Dissolution release curves are shown in Tables 1-7 and 7 respectively. Figures 2-8 .

[0093] Table 1

[0094]

[0095]

[0096] Table 2

[0097]

[0098] Table 3

[0099]

[0100] Table 4

[0101]

[0102] Table 5

[0103]

[0104]

[0105] Table 6

[0106]

[0107] Table 7

[0108]

[0109] Dissolution difference refers to the current Fe concentration. 3+ Concentration of Fe from the previous moment 3+ Difference in concentration.

[0110] Examples 1-2, Comparative Examples 2-4, Tables 1-5 Figures 2-6 As shown, in Examples 1 and 2 of the present invention, the slow-release iron salt can dissolve and release Fe relatively uniformly within 6 hours. 3+ A certain amount of Fe can be maintained in water for a long time. 3+ This is beneficial for the role of Fe in wastewater treatment. 3+ The three-stage utilization effect can effectively avoid the defect of excessive consumption in the early stage, so that free radicals can be continuously generated and the oxidation effect can be improved.

[0111] In the preparation of slow-release iron salts, the most important step is to acidify the carrier (attapulgite) with a diluted trifluoromethanesulfonic acid solution. This process promotes the oxidation of Fe by hydrogen peroxide. 2+ On the one hand, it can oxidize, and on the other hand, it can quickly and effectively clear the cavities and channels inside the attapulgite soil and depolymerize its structure, thereby facilitating the formation of Fe. 3+ After subsequent precipitation, it effectively combines with the cavities within the attapulgite soil, thereby enhancing the slow-release effect. If other acids (such as hydrochloric acid, sulfuric acid, or even perchloric acid) are used, they cannot rapidly dissolve the cavities within the attapulgite soil and depolymerize its structure in a short time, thus regenerating Fe... 3+ Its binding effect with the cavities inside the attapulgite soil is limited, resulting in a poorer slow-release effect.

[0112] Comparative Example 6, used as a reference, involved simply mixing ferric salts with attapulgite clay and then bonding them at a certain high temperature. Because the sintering temperature was not reached, the resulting reference ferric salt contained Fe... 3+It dissolves quickly in water; this can be seen in Table 7 and... Figure 8 evidence.

[0113] By comparing Example 5, Table 6 and Figure 7 It can be seen that, compared with other types of soil, attapulgite, as a carrier, is more sensitive to the acidification reaction of trifluoromethanesulfonic acid aqueous solution.

[0114] Experimental Example 1

[0115] The experiment revealed that the mass fraction of the trifluoromethanesulfonic acid aqueous solution is crucial. Taking Example 2 as an example, if the mass fraction of the trifluoromethanesulfonic acid aqueous solution is too high (e.g., 0.000002%), it will cause the collapse of a large number of porous structures within the attapulgite soil, preventing the effective binding of Fe. 3+ Its effect is not much different from that of the reference iron salt. Tested according to the "slow-release characterization test", Fe... 3+ The concentration is greater than 9 mmol / L, and a large amount will be released in a short period of time.

[0116] If the mass fraction of trifluoromethanesulfonic acid in the aqueous solution is too small (e.g., 0.000001.3%), the cavities and channels within the attapulgite soil will not be completely cleared and the structure will not be completely depolymerized, thus affecting the Fe... 3+ The binding effect is limited, and a large amount of Fe 3+ It combines with attapulgite particles in a simple, mixed manner, which leads to the following in the "slow-release characterization test": Fe 3+ It will release a large amount in a shorter time, within 0.5 hours, Fe 3+ The concentration is greater than 10 mmol / L.

[0117] In the above embodiments, the coagulant is one of aluminum sulfate, polyaluminum chloride, polyferric sulfate, ferrous sulfate, and polyacrylamide, and can be adjusted according to actual needs.

[0118] Although preferred embodiments of the invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including both the preferred embodiments and all changes and modifications falling within the scope of the invention.

[0119] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. An oxidation process for high-concentration, high-salinity chemical wastewater, characterized in that, Includes the following steps: Step 1: Pre-treat the high-concentration, high-salt chemical wastewater to obtain pre-treated wastewater; Step 2: Adjust the pH of the pretreated wastewater to 3-4, add slow-release iron salt, and stir to react; Step 3: Add polyacrylamide to the wastewater treated in Step 2, stir to produce flocculation, filter, and remove the sludge obtained from the filter. Step 4: Add hydrogen peroxide to the wastewater treated in Step 3 and stir to react; Step 5: Adjust the pH of the wastewater treated in Step 4 to 8-9, add coagulant, coagulate and filter, and remove the sludge obtained from filtration. Step 6: Add hydrogen peroxide to the wastewater treated in Step 5 and stir to react; Step 7: Add coagulant to the wastewater treated in Step 6, coagulate and filter, and remove the sludge obtained from the filtration. The method for preparing the slow-release iron salt includes the following steps: A wet mud is prepared by mixing trivalent ferric salt, divalent ferric salt, attapulgite clay, hydrogen peroxide, and trifluoromethanesulfonic acid aqueous solution. The wet mud is dried at a temperature of 70~100℃. During the drying process, the wet mud is ground using a grinder to finally obtain the slow-release ferric salt.

2. The oxidation process for high-concentration, high-salinity chemical wastewater according to claim 1, characterized in that: The mass ratio of the trivalent iron salt, divalent iron salt and attapulgite is 3:(2~2.3):(16.5~17).

3. The oxidation process for high-concentration, high-salinity chemical wastewater according to claim 2, characterized in that: The hydrogen peroxide has a mass fraction of 30%.

4. The oxidation process for high-concentration, high-salinity chemical wastewater according to claim 3, characterized in that: The moisture content of the wet mud is 65% to 70%.

5. The oxidation process for high-concentration, high-salinity chemical wastewater according to claim 1, characterized in that: The moisture content of the slow-release iron salt is less than or equal to 10%.

6. The oxidation process for high-concentration, high-salinity chemical wastewater according to claim 1, characterized in that: Add ceramic grinding balls to the grinder and grind at a grinding frequency of 20~30Hz.

7. The oxidation process for high-concentration, high-salinity chemical wastewater according to claim 1, characterized in that: The ferric salt is one or more of ferric chloride, ferric sulfate, polyferric sulfate, and polyferric chloride.

8. The oxidation process for high-concentration, high-salinity chemical wastewater according to claim 2, characterized in that: The ferrous salt is one or more of ferrous sulfate, ferrous chloride, and ferrous nitrate.

9. The oxidation process for high-concentration, high-salinity chemical wastewater according to claim 1, characterized in that: In step 1, the pretreatment steps include using a bar screen for filtration, sedimentation in a grit chamber, and water quality adjustment in a balance tank.

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