Treatment method for treating high-sulfonic-group wastewater by using advanced oxidation

Abstract

The invention relates to the technical field of industrial wastewater treatment, in particular to a treatment method for treating high-sulfonic-group wastewater by advanced oxidation, which comprises the following steps: regulating the pH value of the wastewater to 3.0-4.0, then carrying out photo-Fenton oxidation, controlling the molar ratio of H2O2 to Fe < 2 + > to be 300: 1-400: 1, regulating the pH value of the effluent to 5.0-6.0, adding sodium sulfite to quench residual H2O2 and flocculate and precipitate iron mud, and finally, carrying out secondary oxidation on the wastewater to obtain the high-sulfonic-group wastewater. Performing anaerobic-aerobic biochemical treatment on the supernate, adding sodium carbonate and sodium hydroxide into biochemical effluent to soften and descale, concentrating in a mechanical vapor recompression evaporator, washing and recrystallizing crystallized mother liquor, and adsorbing and purifying the crystallized mother liquor with activated carbon to obtain an industrial salt product. The problem of MVR evaporation scaling is effectively solved by accurately controlling the neutralization pH and combining the softening step, finally, wastewater standard treatment and salt high-quality recovery are achieved, the COD removal rate can reach 95% or above, and excellent environmental and economic benefits are achieved.

Description

Technical Field

[0001] This invention relates to the field of industrial wastewater treatment technology, and in particular to a method for treating high-sulfonic acid-based wastewater using advanced oxidation. Background Technology

[0002] Wastewater containing high sulfonic acid groups typically refers to industrial wastewater containing high concentrations of sulfonate organic matter. Wastewater from the pesticide industry is one of its main sources. The main pollutants include insecticides such as chlorpyrifos and chlordane. The chemical oxygen demand (COD) of the wastewater exceeds 500,000 mg / L. After the degradation of sulfonic acid agents in the wastewater, strong acidic substances are released, with a pH value close to 0 and an acidity reaching 8%, close to that of concentrated hydrochloric acid. Sulfonic acid agents originally exist in the form of organic matter, but under high-salt conditions, a salting-out effect occurs, forcing the sulfonic acid agents to separate from the solution. After decomposition, they are converted into inorganic salts such as sodium sulfate and release acidic components. Due to the presence of sulfonic acid groups, heterocycles, benzene rings, and other structural organic matter, it is highly toxic and difficult to biodegrade. Its BOD / COD is usually below 0.1, and its biodegradability is extremely poor. Wastewater containing high sulfonic acid groups also contains thiosulfates, various pesticide intermediates, and other pollutants, making its composition complex.

[0003] Furthermore, there are two traditional methods for treating high-sulfonic acid wastewater: catalytic oxidation and evaporation concentration. Catalytic oxidation, on the other hand, degrades organic matter in wastewater by generating strong oxidizing free radicals such as ·OH. However, high concentrations of inorganic ions such as calcium, magnesium, and sulfate in high-sulfonic acid wastewater easily deposit within the catalytic reactor, covering the active sites of the catalyst and leading to catalyst deactivation or a sharp decline in efficiency. To maintain reaction efficiency, frequent cleaning or replacement of the catalyst is required, along with increasing the oxidant dosage, which increases operating costs. In summary, this method consumes a large amount of oxidant, may not be highly selective for specific pollutants, and high salinity may inhibit oxidation efficiency. The investment and operating costs are relatively high. Evaporation concentration, another method, aims to evaporate water and separate salts, but it can lead to severe scaling, with inorganic salts such as calcium sulfate, silicates, and magnesium hydroxide precipitating on heated surfaces. This process forms dense, hard scale, which greatly reduces heat transfer efficiency, increases energy consumption, and can even clog equipment and cause system shutdowns. The salt evaporated is often colored and has an odor due to the presence of organic matter, failing to meet industrial salt standards and becoming hazardous waste. Disposal costs are high, and resource recovery is difficult. For other treatment methods, wastewater directly entering the biological treatment tank will lead to biological collapse. High concentrations of salt will cause microbial cells to dehydrate and die, and the acidic environment will destroy enzyme activity. Therefore, wastewater directly entering the biological treatment tank will paralyze the biological reaction. When directly incinerated, molten salt will adhere to the furnace to form a coking layer, and acidic gases will react with the metal furnace wall in the 200-400℃ range, causing stress corrosion cracking. During incineration, organic sulfur is converted into sulfur dioxide and sulfur trioxide, posing a great threat to the operation and control of desulfurization equipment and equipment corrosion. The equipment investment cost is high, the operating cost is high, and the problem of exceeding standards is unavoidable.

[0004] This requires us to seek more reliable, safe, and environmentally friendly methods to treat wastewater with high sulfonic acid content. Summary of the Invention

[0005] To address the problems mentioned in the background section, this invention provides a method for treating high-sulfonic acid-based wastewater using advanced oxidation. This method can efficiently degrade organic matter, significantly improve the biodegradability of wastewater, effectively prevent scaling in subsequent evaporation equipment, and ultimately achieve resource recovery and utilization of salts.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: A method for treating high-sulfonic acid-based wastewater using advanced oxidation includes the following steps: S1: The high-sulfonic acid wastewater is transported to the equalization tank, where the pH is adjusted to 3.0-4.0 with acid. It then enters the photo-Fenton reactor, where H2O2 and FeSO4 are added as reactants under 254nm ultraviolet light irradiation, controlling the reaction between H2O2 and FeSO4. 2+ The molar ratio is 300:1 to 400:1, and the reaction time is not less than 2 hours, in order to degrade organic matter and remove biotoxicity; The high efficiency of the photo-Fenton reaction in this invention stems from the synergistic effect of ultraviolet light (UV) and Fenton's reagent. The introduction of UV has a dual effect: firstly, UV (254nm) can directly photolyze H2O2 to produce ·OH (H2O2 + hv → 2·OH); secondly, and more importantly, UV can effectively catalyze Fe 3+ Reduced to Fe 2+ (Fe) 3+ +H₂O+hv→Fe 2+ +·OH+H + This greatly promotes the iron ion circulation rate, therefore, although Fe 2+ The initial dosage was low (H2O2 / Fe). 2+ (Molar ratio of 300:1 to 400:1), but under UV radiation, iron ions can be absorbed into Fe at extremely high efficiency. 2+ / Fe 3+ The process circulates between the two, continuously catalyzing the production of ·OH from H2O2, thereby reducing the amount of iron sludge produced while ensuring the high efficiency and thoroughness of the oxidation reaction. This molar ratio range is the optimal balance point between ensuring reaction efficiency and controlling iron sludge production, which has been verified by a large number of experiments. S2: The effluent from S1 is sent to a neutralization tank, where the pH is adjusted to 5.0-6.0 with alkali. Simultaneously, sodium sulfite solution is added at a molar ratio of 1:1 to 1.3:1 to the initial H2O2 to quench residual H2O2. This excessive addition ensures the complete elimination of any potential inhibition of H2O2 on microorganisms in subsequent biological treatment, while converting it into harmless sodium sulfate. Polyacrylamide flocculant is then added for flocculation and sedimentation. PAM and Fe... 2+ The mass ratio is 1:250 to 1:500. After standing and settling, the supernatant and iron mud are separated. S3: The supernatant obtained from S2 is sent to an anaerobic-aerobic bioreactor for biochemical treatment to ensure that the water quality meets the discharge standards. S4: Sodium carbonate and sodium hydroxide are added to the effluent after biological treatment. They react with calcium and magnesium ions in the water to form precipitates. The molar ratio of sodium carbonate to calcium ions is 1.2-1.3:1, and the molar ratio of sodium hydroxide to magnesium ions is 1.2-1.3:1. Then, solid-liquid separation is performed to obtain softened high-salt water. S5: The softened high-salt water is introduced into a mechanical vapor recompression evaporator for evaporation and concentration, with the compression ratio controlled at 1.7-2.2 and the circulation flow rate greater than 2.5m / s, to obtain crystallization mother liquor and reusable condensate; S6: The mother liquor obtained in S5 is sequentially washed, recrystallized, and adsorbed onto activated carbon to obtain the industrial salt product. Washing is performed using a saturated aqueous solution of the target salt, with a liquid-to-solid ratio controlled at 0.5-1.5:1. During recrystallization, the cooling rate is controlled at 5-15℃ / h. Activated carbon adsorption uses carbon with a specific surface area of ​​800-1200 m². 2 / g of powdered activated carbon, the addition amount is 0.5%-3.0% of the mass of the solution.

[0007] Furthermore, in S1, the acid used to adjust the pH is sulfuric acid, and in S2, the alkali used to adjust the pH is a sodium hydroxide solution with a mass fraction of 10%-20%.

[0008] Furthermore, in S2, the polyacrylamide flocculant is prepared as an aqueous solution with a mass fraction of 0.1%-0.5% before use, and the stirring speed during dissolution is 100-150 rpm, the dissolution time is 30-60 min, and it is used within 4 hours after preparation.

[0009] Furthermore, in S2, the solid-liquid separation after flocculation and sedimentation is preferably carried out using an inclined tube sedimentation tank with a hydraulic retention time of 30-45 minutes, or a plate and frame filter press with a filtration pressure of 0.2-0.4 MPa. The separated iron sludge is disposed of safely as hazardous waste.

[0010] Furthermore, in S3, the concentration of suspended solids in the mixed liquor of the anaerobic-aerobic bioreactor is controlled at 2500-4500 mg / L, the hydraulic retention time in the anaerobic tank is 6 h, and the hydraulic retention time in the aerobic tank is 12 h.

[0011] Furthermore, in S5, the mechanical vapor recompression evaporator is made of titanium or duplex stainless steel.

[0012] Furthermore, in S6, the washing process adopts a batch countercurrent washing method, and the liquid-solid ratio of each wash is controlled at 0.3-0.8:1.

[0013] Furthermore, in S6, the solvent used in the recrystallization process is deionized water or softened water, and the hardness of the solvent is not higher than 0.03 mmol / L, and the temperature of the cooling medium is controlled at 5-15℃.

[0014] Furthermore, in S6, the activated carbon needs to be washed 2-3 times with deionized water at 80-90°C before use to remove soluble impurities.

[0015] Furthermore, after the processed industrial salt product is dried at 100-150℃, the moisture content is less than 0.2%.

[0016] The beneficial effects of this invention are: 1. In this invention, by employing photo-Fenton (UV / H2O2 / Fe) 2+ Advanced oxidation technology, at pH (3.0-4.0) and molar ratio (H2O2 / Fe) 2+ Under conditions of 300:1 to 400:1, it can efficiently degrade high sulfonic acid organic matter, with a COD removal rate of over 95%, and increase the BOD / COD value of wastewater from less than 0.1 to over 0.4, greatly improving the biodegradability of wastewater and laying a solid foundation for subsequent biological treatment.

[0017] 2. In this invention, by precisely controlling the pH during the neutralization stage within a weakly acidic range of 5.0-6.0, and combining this with subsequent softening and descaling steps (adding Na2CO3 and NaOH), the formation of hard scale by calcium and magnesium ions in the MVR evaporator can be effectively prevented, and the scaling tendency can be controlled at 15.2 mg / cm³. 2 The extremely low levels of ·weeks are significantly better than methods that neutralize to neutral (pH=7.0) or omit the softening step, ensuring long-term stable operation of the system.

[0018] 3. In this invention, the crystallization mother liquor is deeply treated by a three-stage purification process of washing, recrystallization and activated carbon adsorption, which can effectively remove organic impurities and color from the salt, and finally obtain a high-quality industrial salt product with a whiteness of more than 85% and no odor. This realizes the resource recovery of salt in wastewater and avoids the generation of hazardous waste.

[0019] 4. This invention integrates advanced oxidation, biochemical treatment, softening and descaling, and evaporation crystallization resource recovery unit operations to form a complete, efficient, and green high-sulfonic acid-based wastewater treatment process. The process has stable treatment effect, and the final effluent can meet the discharge standards or be reused. The recovered industrial salt has economic value. Compared with traditional outsourced disposal or incineration methods, the cost per ton of water treated is significantly reduced, achieving both environmental and economic benefits. Detailed Implementation

[0020] The technical solution 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 skilled in the art without creative effort are within the scope of protection of the present invention.

[0021] Unless otherwise specified, the raw materials used in this invention are all from commercially available conventional products.

[0022] Example 1 S1: Take 5L of simulated high-sulfonic acid wastewater (with pesticide as the main pollutant) with a chemical oxygen demand (COD) of 502,000 mg / L and a pH of 1.5, and place it in a stirred glass reactor. While stirring, slowly add 10% (v / v) sulfuric acid solution to precisely adjust the pH of the wastewater to 3.5. Turn on a 254nm ultraviolet lamp (30W power) and begin adding 30% H2O2 solution and FeSO4 solution dropwise, controlling the reaction of H2O2 and FeSO4. 2+ The molar ratio was 350:1, and the reaction lasted for 2.5 h, during which stirring was maintained and the temperature was controlled at 30±5℃. S2: After the oxidation reaction is complete, the wastewater is transferred to a neutralization tank. Under stirring, a 20% (w / w) sodium hydroxide (NaOH) solution is slowly added to precisely adjust the pH to 5.5. Subsequently, sodium sulfite (Na2SO3) solution is added in a molar ratio of 1:1 to 1.3:1 to the initial H2O2 to quench the residual H2O2. This quenching process converts the residual H2O2 into water and sodium sulfate (Na2SO4). This portion of sodium sulfate will enter subsequent processes and eventually become a component of the crystalline salt; its dosage has been considered in the overall salt balance calculation. Then, a polyacrylamide (PAM, anionic, molecular weight 12 million) flocculant solution is added. This PAM solution is pre-prepared: solid PAM is slowly added to deionized water under stirring at 120 rpm to prepare a 0.3% (w / w) solution, which is dissolved for 45 minutes until it becomes a transparent, viscous consistency. The dosage of PAM is related to the Fe... 2+ The mass ratio is approximately 1:300. First, stir rapidly (150 rpm) for 2 minutes, then stir slowly (50 rpm) for 10 minutes. After stopping the stirring, let it stand and settle for 45 minutes. Obvious flocculation stratification is visible. The supernatant is clear. The supernatant is separated by decanting. The precipitated iron mud is collected and disposed of as hazardous waste. S3: Pump the supernatant obtained from S2 into a laboratory-scale anaerobic-aerobic (A / O) bioreactor system, control the mixed liquor suspended solids (MLSS) concentration at around 3500 mg / L, and the hydraulic retention time (HRT) of the wastewater in the anaerobic tank is 6 h and the hydraulic retention time in the aerobic tank is 12 h. S4: After biological treatment, the COD of the effluent has been reduced to below 120 mg / L. Sodium carbonate (Na₂CO₃) and sodium hydroxide (NaOH) solutions are added to the effluent. Na₂CO₃ reacts with calcium ions (CaO) in the wastewater. 2+ The molar ratio of NaOH to magnesium ions (Mg) is 1.25:1. 2+ The molar ratio of calcium carbonate to magnesium hydroxide was 1.25:1. After stirring for 30 minutes, the mixture was allowed to stand and precipitate. The calcium carbonate and magnesium hydroxide precipitates were removed by filtration to obtain softened high-salt water. S5: The softened high-salt water is introduced into a small mechanical vapor recompression (MVR) evaporation crystallization experimental device. The device is made of 316L stainless steel. The compression ratio of the evaporation system is controlled at 2.0, and the circulation flow rate in the tube is maintained at 2.8 m / s. The evaporation is concentrated until a large amount of crystals precipitate out to obtain the crystallization mother liquor. The condensate can be collected and reused. S6: The mother liquor from crystallization is centrifuged to obtain crude salt, which is then purified in three steps: Washing: The crude salt is washed with a saturated aqueous solution of the target industrial salt (mainly Na2SO4 and NaCl), with the liquid-to-solid ratio (L / kg) controlled at 1:1, and the washing is performed twice.

[0023] Recrystallization: The washed salt is redissolved in deionized water (total hardness ≤0.03mmol / L) to form a near-saturated solution. The solution is then cooled from 80℃ to 20℃ in a jacketed cooling pot at a cooling rate of 10℃ / h for recrystallization.

[0024] Activated carbon adsorption: During the recrystallization and dissolution process, 1.5% of powdered activated carbon (PAC, specific surface area 1000 m²) was added to the solution. 2 / g), the activated carbon is washed twice with deionized water at 85℃ before use, adsorbed for 30 minutes, and then filtered while hot.

[0025] The filtered wet crystals were dried in an oven at 120°C to constant weight (moisture content <0.2%) to obtain a white, pure industrial salt product.

[0026] Example 2 The difference from Example 1 is that only the neutralization pH value in S2 is adjusted from 5.5 to 7.0, and the rest of the operation steps are exactly the same as in Example 1.

[0027] Example 3 The difference from Example 1 is that only H2O2 / Fe in S1 is removed. 2+ The molar ratio was adjusted from 350:1 to 250:1, and the remaining operating steps were exactly the same as in Example 1.

[0028] Example 4 The difference from Example 1 is that only H2O2 / Fe in S1 is removed. 2+ The molar ratio was adjusted from 350:1 to 450:1, and the remaining operating steps were exactly the same as in Example 1.

[0029] Example 5 The difference from Example 1 is that only the amount of activated carbon added in S6 is adjusted from 1.5% to 1.0%, and the rest of the operation steps are exactly the same as in Example 1.

[0030] Comparative Example 1 The difference from Example 1 is that S1 and S2 in Example 1 are omitted, and the simulated wastewater is directly adjusted to pH 7.5 before entering the A / O system in S3 for treatment.

[0031] Comparative Example 2 The difference from Example 1 is that only S1 and S2 (neutralization to pH=5.5, separation of iron sludge) as in Example 1 are performed, and the resulting supernatant is then measured without subsequent biochemical and resource recovery steps.

[0032] Comparative Example 3 The difference from Example 1 is that S1, S2, and S3 of Example 1 are performed, and the effluent after biological treatment is not subjected to softening treatment in S4, but directly enters the MVR evaporation and crystallization in S5.

[0033] Comparative Example 4 The difference from Example 1 is that, in Example 1, after the crystallization mother liquor obtained by MVR evaporation is separated by centrifugation in steps S1 to S5, the crude salt is directly dried without undergoing washing, recrystallization and activated carbon adsorption treatment in step S6.

[0034] Comparative Example 5 The difference from Example 1 is that ultraviolet light was not used; instead, the pH of the simulated wastewater was adjusted to 3.0, and then H2O2 and anhydrous FeSO4 were added to control the H2O2 / Fe ratio. 2+ The molar ratio was 10:1 (typical value for traditional Fenton), relying solely on chemical catalysis for 2.5 hours, with subsequent steps following the same process as S2 and beyond in Example 1.

[0035] Performance testing methods and results Chemical oxygen demand (COD) determination: Refer to the "Determination of Chemical Oxygen Demand in Water - Dichromate Method" (HJ 828-2017); Five-day biochemical oxygen demand (BOD5) determination and biodegradability (BOD5 / COD) evaluation: Refer to "Determination of five-day biochemical oxygen demand (BOD5) in water quality: dilution and inoculation method" (HJ 505-2009). MVR scaling tendency determination: Refer to the dynamic simulation plate method; Determination of whiteness of industrial salt: Refer to "Determination of whiteness of industrial salt" (GB / T 13025.5-2012); The flotation performance results are shown in Table 1, and the physical properties of the collector are shown in Table 2. Table 1. Comparison of Examples and Comparative Examples

[0036] Table 2. Comparison of Examples and Comparative Examples

[0037] As shown in Table 1, the standard process provided by this invention (Example 1) achieved a COD removal rate of up to 98.5% and increased the BOD5 / COD ratio from 0.05 in the influent to 0.41, creating excellent conditions for subsequent biological treatment. The failure of Comparative Example 1 (direct biological treatment) demonstrates the indispensability of advanced oxidation pretreatment for overcoming such recalcitrant wastewater. Examples 3 and 4 show that H2O2 / Fe 2+A molar ratio deviating from the preferred range of this invention (300:1 to 400:1) will lead to a decrease in treatment effect or an increase in cost, while Comparative Example 5 (conventional Fenton) highlights the significant advantages of the photo-Fenton technology of this invention in terms of oxidation efficiency and improved biodegradability.

[0038] As shown in Table 2, this invention successfully controlled the scaling tendency of MVR to 15.2 mg / cm³ by precisely controlling the neutralization pH (Example 1, pH=5.5) and the essential softening step. 2 In contrast, neutralizing to pH 7.0 (Example 2) or omitting softening (Comparative Example 3) both led to a sharp increase in scaling, demonstrating that the pH control point and softening step of the present invention are key to synergistic effects in preventing equipment scaling. In Comparative Example 3, although the severe scaling mainly adhered to the equipment surface, the residual calcium and magnesium ions still formed co-precipitates or encapsulated impurities during the crystallization process, resulting in a significant decrease in the whiteness of the salt product. At the same time, the complete salt purification process (Example 1) ensured the high quality of the industrial salt product (whiteness 85%), and the absence of any purification step (Comparative Example 4) would lead to a serious deterioration in product quality.

[0039] In summary, through quantitative data comparison of a series of embodiments and comparative examples, it is fully verified that the technical solution provided by the present invention is significantly superior to the prior art and the flawed simplified process in terms of processing efficiency, system stability, resource utilization effect and overall cost. The steps are interconnected and synergistically enhanced. In particular, the combination of precise control of neutralized pH and softening and descaling solves the scaling problem in the evaporation and crystallization process of high-salt wastewater.

[0040] In the description of this specification, the terms "preparation example," "example," "various examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that example or preparation example, which are included in at least one example or preparation example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same example or preparation example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more examples or preparation examples.

[0041] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for treating high-sulfonic acid-based wastewater using advanced oxidation, characterized in that, Includes the following steps: S1: The high-sulfonic acid wastewater is transported to the equalization tank, where the pH is adjusted to 3.0-4.0 with acid. It then enters the photo-Fenton reactor, where H2O2 and FeSO4 are added as reactants under 254nm ultraviolet light irradiation, controlling the reaction between H2O2 and FeSO4. 2+ The molar ratio is 300:1 to 400:1, and the reaction time is not less than 2 hours, in order to degrade organic matter and remove biotoxicity; S2: The effluent from S1 is sent to a neutralization tank, where the pH is adjusted to 5.0-6.0 with alkali. Simultaneously, sodium sulfite solution is added at a molar ratio of 1:1 to 1.3:1 to the initial H2O2 to quench residual H2O2. Then, polyacrylamide flocculant is added for flocculation and sedimentation. PAM and Fe... 2+ The mass ratio is 1:250 to 1:

500. After standing and settling, the supernatant and iron mud are separated. S3: The supernatant obtained from S2 is sent to an anaerobic-aerobic bioreactor for biochemical treatment to ensure that the water quality meets the discharge standards. S4: Sodium carbonate and sodium hydroxide are added to the effluent after biological treatment. They react with calcium and magnesium ions in the water to form precipitates. The molar ratio of sodium carbonate to calcium ions is 1.2-1.3:1, and the molar ratio of sodium hydroxide to magnesium ions is 1.2-1.3:

1. Then, solid-liquid separation is performed to obtain softened high-salt water. S5: The softened high-salt water is introduced into a mechanical vapor recompression evaporator for evaporation and concentration, with the compression ratio controlled at 1.7-2.2 and the circulation flow rate greater than 2.5m / s, to obtain crystallization mother liquor and reusable condensate; S6: The mother liquor obtained in S5 is sequentially washed, recrystallized, and adsorbed onto activated carbon to obtain the industrial salt product. Washing is performed using a saturated aqueous solution of the target salt, with a liquid-to-solid ratio controlled at 0.5-1.5:

1. During recrystallization, the cooling rate is controlled at 5-15℃ / h. Activated carbon adsorption uses carbon with a specific surface area of ​​800-1200 m². 2 / g of powdered activated carbon, the addition amount is 0.5%-3.0% of the mass of the solution.

2. The method for treating high-sulfonic acid-based wastewater using advanced oxidation according to claim 1, characterized in that, In S1, the acid used to adjust the pH is sulfuric acid, and in S2, the alkali used to adjust the pH is a sodium hydroxide solution with a mass fraction of 10%-20%.

3. The method for treating high-sulfonic acid-based wastewater using advanced oxidation according to claim 1, characterized in that, In S2, the polyacrylamide flocculant is prepared as an aqueous solution with a mass fraction of 0.1%-0.5% before use. During dissolution, the stirring speed is 100-150 rpm and the dissolution time is 30-60 min. It is used within 4 hours after preparation.

4. The method for treating high-sulfonic acid-based wastewater using advanced oxidation according to claim 1, characterized in that, In S2, the solid-liquid separation after flocculation and sedimentation is preferably carried out using an inclined tube sedimentation tank with a hydraulic retention time of 30-45 minutes, or a plate and frame filter press with a filtration pressure of 0.2-0.4 MPa. The separated iron sludge is disposed of safely as hazardous waste.

5. The method for treating high-sulfonic acid-based wastewater using advanced oxidation according to claim 1, characterized in that, In S3, the concentration of suspended solids in the mixed liquor of the anaerobic-aerobic bioreactor is controlled at 2500-4500 mg / L, the hydraulic retention time in the anaerobic tank is 6 h, and the hydraulic retention time in the aerobic tank is 12 h.

6. The method for treating high-sulfonic acid-based wastewater using advanced oxidation according to claim 1, characterized in that, In S5, the mechanical vapor recompression evaporator is made of titanium or duplex stainless steel.

7. The method for treating high-sulfonic acid-based wastewater using advanced oxidation according to claim 1, characterized in that, In S6, the washing process adopts a batch countercurrent washing method, and the liquid-solid ratio of each wash is controlled at 0.3-0.8:

1.

8. The method for treating high-sulfonic acid-based wastewater using advanced oxidation according to claim 1, characterized in that, In S6, the solvent used in the recrystallization process is deionized water or softened water, and the hardness of the solvent is not higher than 0.03 mmol / L, and the temperature of the cooling medium is controlled at 5-15℃.

9. The method for treating high-sulfonic acid-based wastewater using advanced oxidation according to claim 1, characterized in that, In S6, the activated carbon needs to be washed 2-3 times with deionized water at 80-90℃ before use to remove soluble impurities.

10. A method for treating high-sulfonic acid-based wastewater using advanced oxidation according to any one of claims 1 to 9, characterized in that, After being dried at 100-150℃, the processed industrial salt product has a moisture content of less than 0.2%.

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