A recovery treatment method for sodium hydrosulfite production wastewater

Abstract

The present application relates to the technical field of industrial wastewater treatment, and specifically discloses a sodium hydrosulfite production wastewater recycling treatment method, comprising the following steps: step 1: introducing sodium hydrosulfite production wastewater into a hydrolysis unit for treatment with a degradation catalyst, so that abundant hydroxyl radicals are generated by the chelation of ferrous ions and water molecules to degrade organic matter; step 2: introducing the hydrolyzed wastewater into an oxidative degradation unit for secondary degradation treatment, so that active oxygen is generated by electrolysis and the degradation effect of hydroxyl radicals is promoted to degrade organic matter; step 3: adding the treated wastewater into a light reaction unit for degradation by microbial reaction materials, so that crude clean water is obtained through the synergistic effect of nitrifying bacteria, flocculating bacteria and modified adsorption resins; and clean water is obtained after the crude clean water is filtered. The present application performs multiple degradation on production wastewater, and the concentration of organic matter is reduced to meet the discharge standard.

Description

Technical Field

[0001] This invention belongs to the technical field of industrial wastewater treatment, specifically relating to a method for recycling and treating wastewater from sodium dithionite production. Background Technology

[0002] Sodium dithionite, commonly known as "sodium hydrosulfite," is an important chemical reagent widely used in pharmaceuticals and other fields. It is a white, granular crystalline or pale yellow powder with a low ignition point, posing a risk of spontaneous combustion. It is unstable in water, reacting violently with flammable gases to produce a violent combustion. Sodium dithionite has strong reducing properties and can be used to treat wastewater containing heavy metal ions. However, its preparation process also generates wastewater. The process typically uses the "sodium formate method," where sodium thiosulfate and sodium sulfite react in a reactor. The resulting reactants are filtered and washed to remove unreacted impurities and residues. The filtered product still needs to be separated by centrifugation or evaporation crystallization to remove the sodium dithionite. This process generates secondary industrial wastewater with high COD concentrations, containing sulfites, methanol, and other substances, making it a highly polluting waste liquid. The weight of the waste liquid generated may be equal to the weight of the sodium dithionite produced. In the context of modern economic development with rising environmental awareness, while products are being mass-produced to meet market demand, high efficiency and environmental friendliness are crucial requirements.

[0003] In 2021, the global market size of sodium dithionite reached nearly 7 billion yuan, and the market demand for sodium dithionite is increasing year by year. The production of sodium dithionite generates a large amount of wastewater annually. Direct discharge would cause environmental pollution, which is inconsistent with green principles, and the wastewater loses its direct usability, resulting in resource waste. Therefore, wastewater recycling and treatment are necessary to recover the chemical waste within it. The treated wastewater can then be directly utilized or discharged. However, common treatment methods for waste liquid typically involve stepwise recycling or incineration followed by biochemical treatment. These methods are difficult to implement, require significant economic support, and involve the use of rare earth metal oxidants, making them unsuitable for widespread application. Currently, the treatment of sodium dithionite production wastewater is hampered by the diverse types of impurities, complex and costly recycling processes, large wastewater discharge volumes, and time-consuming and labor-intensive treatment processes, impacting economic returns. Therefore, simple and efficient wastewater treatment methods hold considerable research potential.

[0004] Patent CN201510892902.5 discloses a method for treating wastewater from sodium dithionite production. The wastewater can meet the Class I standard requirements of the "Integrated Wastewater Discharge Standard" after treatment. However, it involves reagents such as strong oxidants, and the process flow includes at least 10 steps, which is too many process procedures and the treatment cost is too high. Summary of the Invention

[0005] To address the above problems, the present invention aims to provide a method for recycling and treating wastewater from sodium dithionite production.

[0006] The technical content of this invention is as follows:

[0007] This invention provides a method for recycling and treating wastewater from sodium dithionite production, comprising the following steps:

[0008] Step 1: The sodium dithionite production wastewater is fed into the hydrolysis unit for treatment with a degradation catalyst;

[0009] The amount of degradation catalyst added is 0.5 / 10000 to 3 / 10000 of the wastewater mass; it promotes the generation of high concentration of hydroxyl radicals from the ferrous ions in the water and the reactive oxygen species produced by oxidation and degradation, which can degrade organic matter.

[0010] The degradation catalyst is prepared by dissolving disodium ethylenediaminetetraacetate in water at a solid-liquid ratio of 3-6:18-22 g / mL, adding tourmaline at a mass ratio of 3-5:1 to disodium ethylenediaminetetraacetate, heating at 70-90℃ for 30-40 min, and then drying. The heterocyclic structure and coordinating atoms in the catalyst can chelate with ferrous ions, reducing their redox potential and increasing the chelating activity of ferrous ions, thus promoting the reaction.

[0011] Step 2: The hydrolyzed wastewater is passed into the oxidation degradation unit for secondary degradation treatment, and the degradation catalyst is filtered and recovered to the hydrolysis unit.

[0012] The secondary degradation involves electrolyzing the wastewater under oxygen-bearing conditions at a voltage of 0.1-0.4V for 10m³. 3 The oxygen flow rate of the wastewater is 0.1-0.3 L / min; this step decomposes organic matter using electrical energy, and oxygen is converted into reactive oxygen species under the action of electrical energy to decompose organic matter, and can further increase the concentration of hydroxyl radicals to improve the degradation effect.

[0013] Step 3: Add the treated wastewater to the photoreactor unit for degradation by microbial reaction materials to obtain crude purified water;

[0014] The light intensity of the photoreaction unit is 80-100 lux, the temperature is 30-40℃, and the pH is controlled at 7-8. The microbial reaction material is composed of flocculating bacteria, nitrifying bacteria, and modified adsorbent material in a mass ratio of 1-3:0.3-0.6:11-15, and the addition amount is 1 / 10000 to 5 / 10000 of the wastewater. The flocculating bacteria are one or more of yeast, Alcaligenes, Pseudomonas fluorescens, and Enterobacteriaceae. The reaction tank of this microbial reaction material can flocculate and decompose organic matter, and utilize ammonia nitrogen and decompose oxygen-containing organic matter through nitrifying bacteria. The metal ions generated after decomposition are chelated onto the resin by the flocculating bacteria to increase its biomagnetism and adsorption performance. The ester groups, hydroxyl groups, and anionic groups of the modified resin can form ionic bonds or hydrogen bonds with water molecules, promoting flocculation and improving bacterial activity to promote degradation. It can effectively remove nitrogen oxides and metals.

[0015] The preparation of the modified adsorbent material includes the following steps:

[0016] (1) Mix macroporous resin with acrylic monomer and ferric citrate at a mass ratio of 11-13:1:2-4 and heat at 80-90℃ for 20-30 minutes.

[0017] (2) Add a 30-40% ethylene glycol ether aqueous solution with a solid-liquid ratio of 5:11-15 g / mL and perform vacuum distillation at 90-110℃ for 30-40 min.

[0018] (3) Add 8-12 wt% nano-Fe3O4 and perform ultrasonic reaction, then clean and dry to obtain the final product;

[0019] Acrylic acid monomers and ferric citrate can improve the surface biocompatibility and functional group content of the resin. Hydrogen-bonded ethylene glycol ether aqueous solution can be used to connect the hydroxyl ions on the resin surface to increase the pore sites. Its amphoteric properties can enhance the adsorption performance of the resin for organic matter. Grafting reaction with nano-ferric oxide can improve the surface active adsorption sites to obtain magnetic resin. Ultrasonic reaction can improve the modification performance.

[0020] The ultrasonic reaction is carried out at a temperature of 70-80℃ and a frequency of 20-30KHz for 20-30 minutes.

[0021] Step 4: Pass the coarse water through the filtration unit to obtain purified water.

[0022] The filtration process involves passing wastewater through a filter bed with a flow rate of 1-3 m / h. The filter bed is made of activated carbon mixed with 5-10 wt% hydrotalcite and 20-30 wt% activated clay. Through the synergistic adsorption of adsorption materials of different particle sizes, it exhibits multiple adsorption functions and can effectively remove suspended solids and other substances.

[0023] The reaction times for the wastewater in steps 1, 2, and 3 are 2-4 hours, 3-5 hours, and 10-14 hours, respectively.

[0024] The beneficial effects of this invention are as follows: This invention provides a method for recycling and treating wastewater from sodium dithionite production. The wastewater undergoes multiple degradation processes through four units: a hydrolysis unit, an oxidative degradation unit, a photocatalytic reaction unit, and a filtration unit. In the hydrolysis unit, a degradation catalyst chelates ferrous ions, which interact with water molecules to generate abundant hydroxyl radicals that degrade organic matter. In the oxidative degradation unit, oxygen electrolysis generates active oxygen containing hydroxyl radicals with oxidative degradation properties, further degrading organic matter. In the photocatalytic reaction unit, nitrifying bacteria, flocculating bacteria, and modified adsorption resin work synergistically to utilize nitrogen oxides, adsorb and chelate metal ions, and adsorb and degrade organic matter, further purifying the water. Finally, the filtration unit adsorbs some insoluble impurities to obtain purified water. This method reduces the concentration of organic matter to meet emission standards, achieves a high removal rate of various organic substances in the wastewater, and employs a simple process. The reagents and raw materials involved can be reused repeatedly, conforming to economic principles and demonstrating feasibility. Attached Figure Description

[0025] Figure 1 This is a process flow diagram of the present invention;

[0026] Figure 2 The graph shows the change in hydroxyl radical content over time in the hydrolysis unit and oxidative degradation unit of Example 1. Detailed Implementation

[0027] The present invention will be further described in detail below through specific implementation examples and accompanying drawings. It should be understood that these embodiments are only used to illustrate the present invention and are not intended to limit the scope of protection of the present invention. After reading the present invention, any modifications of the present invention in various equivalent forms by those skilled in the art fall within the scope of the appended claims.

[0028] Unless otherwise specified, all raw materials and reagents used in this invention are from the conventional market.

[0029] The process flow diagram of this invention is as follows: Figure 1 As shown.

[0030] Example 1

[0031] A method for recycling and treating wastewater from sodium dithionite production includes the following steps:

[0032] Step 1: The sodium dithionite production wastewater is fed into the hydrolysis unit and treated for 4 hours under the action of the degradation catalyst. The amount of degradation catalyst added is 1.5 / 10000 of the wastewater mass.

[0033] The degradation catalyst was prepared by dissolving disodium ethylenediaminetetraacetate in water at a solid-liquid ratio of 5:20 g / mL, adding tourmaline at a mass ratio of 4:1 to disodium ethylenediaminetetraacetate, heating at 80°C for 35 min, and then drying.

[0034] Step 2: The hydrolyzed wastewater is passed into the oxidation degradation unit for secondary degradation treatment, and the degradation catalyst is filtered and recovered to the hydrolysis unit.

[0035] The secondary degradation involves electrolyzing the wastewater under oxygen-provided conditions for 5 hours at a voltage of 0.3V for 10m. 3 The oxygen flow rate of the wastewater is 0.2 L / min;

[0036] The content of hydroxyl radicals in the wastewater from steps 1 and 2 was detected, and the results are as follows: Figure 2 As shown, the degradation catalyst in the hydrolysis unit of step 1 can react with ferrous ions in water to generate hydroxyl radicals. The concentration of hydroxyl radicals increases and then decreases with the increase of reaction time. Subsequently, under the action of oxygen electrolysis reaction, the concentration of hydroxyl radicals continues to increase until it stabilizes and then decreases.

[0037] Step 3: Add the treated wastewater to the photoreactor unit and degrade it through microbial reaction materials for 12 hours to obtain crude purified water;

[0038] The light intensity of the photoreaction unit is 90 lux, the temperature is 35℃, and the pH is controlled at 7; the microbial reaction material is composed of flocculants, nitrifying bacteria and modified adsorbent material in a mass ratio of 2:0.4:13, and the addition amount is 3 / 10000 of the wastewater; the flocculants are yeast and Alcaligenes spp.

[0039] The preparation of the modified adsorbent material includes the following steps:

[0040] (1) Mix macroporous resin with acrylic monomer and ferric citrate at a mass ratio of 12:1:3 and heat at 85°C for 25 min.

[0041] (2) Add a 35% ethylene glycol ether aqueous solution with a solid-liquid ratio of 5:13 g / mL and perform vacuum distillation at 100℃ for 35 min.

[0042] (3) Add 10wt% nano-Fe3O4 and react with ultrasonic reaction at 75℃ and 25KHz for 25min, then clean and dry to obtain the product;

[0043] Step 4: The coarse purified water is filtered through an activated carbon filter containing 8 wt% hydrotalcite and 25 wt% activated clay to obtain purified water; the flow rate of the filter is 2 m / h.

[0044] Example 2

[0045] A method for recycling and treating wastewater from sodium dithionite production includes the following steps:

[0046] Step 1: The sodium dithionite production wastewater is fed into the hydrolysis unit and treated for 2 hours under the action of the degradation catalyst. The amount of degradation catalyst added is 0.5 / 10000 of the wastewater mass.

[0047] The degradation catalyst was prepared by dissolving disodium ethylenediaminetetraacetate in water at a solid-liquid ratio of 3:18 g / mL, adding tourmaline at a mass ratio of 3:1 to disodium ethylenediaminetetraacetate, heating at 70°C for 30 min, and then drying.

[0048] Step 2: The hydrolyzed wastewater is passed into the oxidation degradation unit for secondary degradation treatment, and the degradation catalyst is filtered and recovered to the hydrolysis unit.

[0049] The secondary degradation involves electrolyzing the wastewater for 3 hours under oxygen-bearing conditions at a voltage of 0.1V and a concentration of 10m. 3 The oxygen flow rate of the wastewater is 0.1 L / min;

[0050] Step 3: Add the treated wastewater to the photoreactor unit and degrade it with microbial reaction materials for 10-14 hours to obtain crude purified water;

[0051] The light intensity of the photoreaction unit is 80 lux, the temperature is 30℃, and the pH is controlled at 7; the microbial reaction material is composed of flocculants, nitrifying bacteria and modified adsorbent material in a mass ratio of 1:0.3:11, and the addition amount is 1 / 10000 of the wastewater; the flocculants are Pseudomonas fluorescens and Enterobacteriaceae.

[0052] The preparation of the modified adsorbent material includes the following steps:

[0053] (1) Mix macroporous resin with acrylic monomer and ferric citrate at a mass ratio of 11:1:2 and heat at 80°C for 20 min.

[0054] (2) Add a 30% ethylene glycol ether aqueous solution with a solid-liquid ratio of 5:11 g / mL and perform vacuum distillation at 90℃ for 30 min.

[0055] (3) Add 8wt% nano-iron oxide and react with ultrasonic reaction at 70℃ and 20KHz for 20min, then clean and dry to obtain the product;

[0056] Step 4: The coarse purified water is filtered through an activated carbon filter containing 5 wt% hydrotalcite and 20 wt% activated clay to obtain purified water; the flow rate of the filter is 1 m / h.

[0057] Example 3

[0058] A method for recycling and treating wastewater from sodium dithionite production includes the following steps:

[0059] Step 1: The sodium dithionite production wastewater is fed into the hydrolysis unit and treated for 4 hours under the action of the degradation catalyst. The amount of degradation catalyst added is 3 / 10000 of the wastewater mass.

[0060] The degradation catalyst was prepared by dissolving disodium ethylenediaminetetraacetate in water at a solid-liquid ratio of 6:22 g / mL, adding tourmaline at a mass ratio of 5:1 to disodium ethylenediaminetetraacetate, heating at 90°C for 40 min, and then drying.

[0061] Step 2: The hydrolyzed wastewater is passed into the oxidation degradation unit for secondary degradation treatment, and the degradation catalyst is filtered and recovered to the hydrolysis unit.

[0062] The secondary degradation involves electrolyzing the wastewater under oxygen-provided conditions for 5 hours at a voltage of 0.4V for 10m. 3 The oxygen flow rate of the wastewater is 0.3 L / min;

[0063] Step 3: Add the treated wastewater to the photoreactor unit and degrade it with microbial reaction materials for 14 hours to obtain crude purified water;

[0064] The light intensity of the photoreaction unit is 100 lux, the temperature is 35℃, and the pH is controlled at 8; the microbial reaction material is composed of flocculants, nitrifying bacteria and modified adsorbent material in a mass ratio of 3:0.6:15, and the addition amount is 5 / 10000 of the wastewater; the flocculants are yeast and Enterobacteriaceae.

[0065] The preparation of the modified adsorbent material includes the following steps:

[0066] (1) Mix macroporous resin with acrylic monomer and ferric citrate at a mass ratio of 13:1:4 and heat at 90°C for 30 min.

[0067] (2) Add a 40% ethylene glycol ether aqueous solution with a solid-liquid ratio of 5:15 g / mL and perform vacuum distillation at 110℃ for 40 min.

[0068] (3) Add 12wt% nano-Fe3O4 and react with ultrasonic reaction at 80℃ and 30KHz for 30min, then clean and dry to obtain the product;

[0069] Step 4: The coarse purified water is filtered through an activated carbon filter containing 10 wt% hydrotalcite and 30 wt% activated clay to obtain purified water; the flow rate of the filter is 3 m / h.

[0070] Example 4

[0071] A method for recycling and treating wastewater from sodium dithionite production includes the following steps:

[0072] Step 1: The sodium dithionite production wastewater is fed into the hydrolysis unit and treated for 2 hours under the action of the degradation catalyst. The amount of degradation catalyst added is 1 / 10000 of the mass of the wastewater.

[0073] The degradation catalyst was prepared by dissolving disodium ethylenediaminetetraacetate in water at a solid-liquid ratio of 4:19 g / mL, adding tourmaline at a mass ratio of 4:1 to disodium ethylenediaminetetraacetate, heating at 75°C for 30 min, and then drying.

[0074] Step 2: The hydrolyzed wastewater is passed into the oxidation degradation unit for secondary degradation treatment, and the degradation catalyst is filtered and recovered to the hydrolysis unit.

[0075] The secondary degradation involves electrolyzing the wastewater for 3 hours under oxygen-bearing conditions at a voltage of 0.2V and a concentration of 10m. 3 The oxygen flow rate of the wastewater is 0.2 L / min;

[0076] Step 3: Add the treated wastewater to the photoreactor unit and degrade it with microbial reaction materials for 11 hours to obtain crude purified water;

[0077] The light intensity of the photoreaction unit is 90 lux, the temperature is 30℃, and the pH is controlled at 7; the microbial reaction material consists of flocculants, nitrifying bacteria, and modified adsorbent material in a mass ratio of 2:0.4:12, and the addition amount is 2 / 10000 of the wastewater; the flocculants are yeast and Pseudomonas fluorescens.

[0078] The preparation of the modified adsorbent material includes the following steps:

[0079] (1) Mix macroporous resin with acrylic monomer and ferric citrate at a mass ratio of 11:1:4 and heat at 90°C for 20 min.

[0080] (2) Add a 38% ethylene glycol ether aqueous solution with a solid-liquid ratio of 5:14 g / mL and perform vacuum distillation at 105℃ for 40 min.

[0081] (3) Add 11wt% nano-Fe3O4 and react with ultrasonic reaction at 75℃ and 25KHz for 20min, then clean and dry to obtain the product;

[0082] Step 4: The coarse purified water is filtered through an activated carbon filter containing 7 wt% hydrotalcite and 22 wt% activated clay to obtain purified water; the flow rate of the filter is 3 m / h.

[0083] Example 5

[0084] A method for recycling and treating wastewater from sodium dithionite production includes the following steps:

[0085] Step 1: The sodium dithionite production wastewater is fed into the hydrolysis unit and treated for 3 hours under the action of the degradation catalyst. The amount of degradation catalyst added is 2.5 / 10000 of the wastewater mass.

[0086] The degradation catalyst was prepared by dissolving disodium ethylenediaminetetraacetate in water at a solid-liquid ratio of 5:21 g / mL, adding tourmaline at a mass ratio of 3:1 to disodium ethylenediaminetetraacetate, heating at 85°C for 40 min, and then drying.

[0087] Step 2: The hydrolyzed wastewater is passed into the oxidation degradation unit for secondary degradation treatment, and the degradation catalyst is filtered and recovered to the hydrolysis unit.

[0088] The secondary degradation involves electrolyzing the wastewater under oxygen-provided conditions for 5 hours at a voltage of 0.3V for 10m. 3 The oxygen flow rate of the wastewater is 0.3 L / min;

[0089] Step 3: Add the treated wastewater to the photoreactor unit and degrade it with microbial reaction materials for 13 hours to obtain crude purified water;

[0090] The light intensity of the photoreaction unit is 95 lux, the temperature is 30℃, and the pH is controlled at 8; the microbial reaction material is composed of flocculants, nitrifying bacteria and modified adsorbent material in a mass ratio of 2:0.6:14, and the addition amount is 4 / 10000 of the wastewater; the flocculants are yeast, fluorescein bacillus, and enterobacteria.

[0091] The preparation of the modified adsorbent material includes the following steps:

[0092] (1) Mix macroporous resin with acrylic monomer and ferric citrate at a mass ratio of 12:1:3 and heat at 90°C for 30 min.

[0093] (2) Add a 32% ethylene glycol ether aqueous solution with a solid-liquid ratio of 5:12 g / mL and perform vacuum distillation at 100℃ for 35 min.

[0094] (3) Add 9wt% nano-Fe3O4 and react with ultrasonic reaction at 75℃ and 30KHz for 28min, then clean and dry to obtain the product;

[0095] Step 4: The coarse purified water is filtered through an activated carbon filter containing 9 wt% hydrotalcite and 28 wt% activated clay to obtain purified water; the flow rate of the filter is 3 m / h.

[0096] Comparative Example 1

[0097] The difference between Comparative Example 1 and Example 1 is that step 1 of the wastewater treatment in Comparative Example 1 does not involve a hydrolysis unit, while the rest remains the same.

[0098] Comparative Example 2

[0099] The difference between Comparative Example 2 and Example 1 is that step 2 of the wastewater treatment in Comparative Example 2 does not involve an oxidative degradation unit, while the rest remains the same.

[0100] Comparative Example 3

[0101] The difference between Comparative Example 3 and Example 1 is that no modified adsorbent material is added to the photoreaction unit of step 3 in the wastewater treatment of Comparative Example 3, while everything else remains the same.

[0102] Comparative Example 4

[0103] The difference between Comparative Example 4 and Example 1 is that step 4 of the wastewater treatment in Comparative Example 4 uses an activated carbon filter tank, while the rest remains the same.

[0104] I. The COD content of sodium dithionite production wastewater with COD content of 900 mg / mL, SS content of 240 mg / mL, sulfide content of 380 mg / mL and nitrogen oxide content of 220 mg / mL, as well as other industrial mixed wastewater, after treatment by the methods of the examples and comparative examples was detected. The method used was spectrophotometry, as shown in Table 1.

[0105] Table 1 SS content of wastewater

[0106]

[0107] As shown in Table 1, the process of the present invention can reduce the content of suspended solids to below 5%. As shown in Comparative Example 4, the synergistic adsorption of activated carbon and hydrotalcite in the filter tank, and the combination of different particle sizes and adsorption effects can remove impurities from the wastewater to a large extent and significantly reduce the SS content.

[0108] Table 2 COD content of wastewater

[0109]

[0110] As shown in Table 2, the DOC content in the wastewater gradually decreases with the processing technology of this invention.

[0111] Table 3 Sulfide content in wastewater

[0112]

[0113] Table 3 shows that the processing technology of the present invention can reduce the sulfide content to below 8%. Tables 2-3 show that, for the degradation of substances such as COD and sulfides, as shown in Comparative Examples 1-2, the hydrolysis unit and the oxidation unit have a synergistic effect. The hydrolysis unit can degrade organic matter by generating hydroxyl radicals through the addition of a degradation catalyst. The oxidation degradation unit further generates hydroxyl radicals and reactive oxygen species for degradation. In the photoreaction unit, the interaction between the decomposition of organic matter by photosynthetic bacteria and the adsorption of organic matter by adsorbent materials can effectively reduce the content of organic matter.

[0114] Table 4 Ammonia Nitrogen Content in Wastewater

[0115]

[0116]

[0117] As shown in Table 4, the treatment method of the present invention can effectively remove nitrogen oxides with a high removal rate. As shown in Comparative Example 3, the photoreaction unit of the present invention can greatly remove ammonia nitrogen compounds. The adsorbent material used in the present invention can concentrate light energy and simultaneously promote the decomposition of nitrifying bacteria by adsorbing substances. The flocculating bacteria flocculate and degrade substances and chelate metals to improve the adsorption performance of the adsorbent material. The photoreaction unit has multiple functions of degrading and removing organic matter.

[0118] As shown in Tables 1-4, the treatment method of the present invention can effectively reduce the DOC and other substance content in the production wastewater of sodium dithionite. As shown in Comparative Example 1, the present invention first hydrolyzes the production wastewater, and uses a degradation catalyst to catalyze the ferrous ions in the wastewater to generate a high concentration of hydroxyl radicals to oxidize and degrade organic matter. As shown in Comparative Example 2, the present invention performs oxygen electrolysis treatment on the hydrolyzed wastewater to provide active oxygen for further oxidation and degradation of organic matter. As shown in Comparative Example 3, the present invention uses adsorption, flocculation, and decomposition to utilize the organic matter after secondary oxidation and degradation, which effectively reduces the DOC content. As shown in Comparative Example 4, the filter unit of the present invention uses a combination of activated carbon and activated clay for adsorption, which has a stronger impurity removal capacity compared to activated carbon alone.

Claims

1. A method for recycling and treating wastewater from sodium dithionite production, characterized in that, Includes the following steps: Step 1: The sodium dithionite production wastewater is fed into the hydrolysis unit for treatment with a degradation catalyst; The degradation catalyst is obtained by dissolving disodium ethylenediaminetetraacetate in water at a solid-liquid ratio of 3-6:18-22 g / mL, adding tourmaline at a mass ratio of 3-5:1 to disodium ethylenediaminetetraacetate, heating at 70-90℃ for 30-40 min, and then drying. Step 2: The hydrolyzed wastewater is passed into the oxidation degradation unit for secondary degradation treatment, and the degradation catalyst is filtered and recovered to the hydrolysis unit. The secondary degradation involves electrolyzing the wastewater under oxygen-bearing conditions at a voltage of 0.1-0.4V for 10m³. 3 The oxygen flow rate of the wastewater is 0.1-0.3 L / min; Step 3: Add the treated wastewater to the photoreactor unit for degradation by microbial reaction materials to obtain crude purified water; Step 4: Pass the coarse water through the filtration unit to obtain purified water.

2. The method for recycling and treating wastewater from sodium dithionite production according to claim 1, characterized in that, The amount of degradation catalyst added in step 1 is 0.5 / 10000 to 3 / 10000 of the wastewater mass.

3. The method for recycling and treating wastewater from sodium dithionite production according to claim 1, characterized in that, The light intensity of the photoreaction unit in step 3 is 80-100 lux, the temperature is 30-40℃, and the pH is controlled at 7-8; the microbial reaction material is composed of flocculants, nitrifying bacteria and modified adsorbent material in a mass ratio of 1-3:0.3-0.6:11-15, and the amount added is 1 / 10000 to 5 / 10000 of the wastewater; the flocculants are one or more of yeast, Alcaligenes spp., Pseudomonas fluorescens, and Enterobacter.

4. The method for recycling and treating wastewater from sodium dithionite production according to claim 3, characterized in that, The preparation of the modified adsorbent material includes the following steps: (1) Mix macroporous resin with acrylic monomer and ferric citrate at a mass ratio of 11-13:1:2-4 and heat at 80-90℃ for 20-30 minutes. (2) Add 30-40% ethylene glycol ether aqueous solution at a solid-liquid ratio of 5:11-15 g / mL, and carry out vacuum distillation at a temperature of 90-110℃ for 30-40 min; (3) Add 8-12wt% of nano-iron oxide and perform ultrasonic reaction, then clean and dry to obtain the final product.

5. The method for recycling and treating sodium dithionite production wastewater according to claim 4, characterized in that, The ultrasonic reaction is carried out at a temperature of 70-80℃ and a frequency of 20-30KHz for 20-30 minutes.

6. The method for recycling and treating wastewater from sodium dithionite production according to claim 1, characterized in that, The filtration described in step 4 involves passing the wastewater through a filter bed at a flow rate of 1-3 m / h.

7. The method for recycling and treating sodium dithionite production wastewater according to claim 6, characterized in that, The filter is an activated carbon filter containing 5-10 wt% hydrotalcite and 20-30 wt% activated clay.

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