Resourceful treatment system and treatment method for high-salt organic wastewater

Abstract

The invention discloses a resourceful treatment system and a resourceful treatment method for high-salt organic wastewater. The treatment method comprises the following steps: sequentially carrying out membrane catalytic ozonation reaction, nanofiltration membrane filtration, catalytic wet oxidation reaction and chelate resin adsorption treatment on the high-salt organic wastewater. According to the method, macromolecular organic matters in the wastewater are reduced through membrane catalytic ozonation, then residual organic matters are concentrated and separated through a nanofiltration membrane device, and the organic matters in the wastewater are further thoroughly decomposed into carbon dioxide and water through catalytic wet oxidation. Compared with a single oxidation process, the treatment efficiency and the treatment effect of the wastewater are improved through coupling and cooperation of membrane catalytic ozone oxidation and catalytic wet oxidation. The catalytic wet oxidation device is adopted to further treat concentrated water concentrated and separated after membrane catalytic ozonation, so that the treatment load of catalytic wet oxidation equipment is reduced, and meanwhile, the volume of a catalytic wet oxidation reactor can be reduced, so that the equipment investment cost is reduced.

Description

Technical Field

[0001] The present invention belongs to the technical field of wastewater treatment, and relates to a resource treatment system and method for high-salt organic wastewater. Background Art

[0002] High-salt organic wastewater mainly comes from industrial production processes such as chemical, pharmaceutical, coal chemical, petroleum, papermaking, printing and dyeing. High-salt organic wastewater contains a large amount of inorganic salts (more than 1wt%, mainly including sodium chloride (NaCl), sodium sulfate (Na2SO4), etc.). At the same time, the wastewater contains a variety of organic substances (such as organic acids (such as acetates, organic amine salts), esters, ketones, phenols, benzene ring compounds, hydrocarbons, etc.), which are usually difficult to biodegrade. High-salt organic wastewater has the characteristics of high salinity, high COD, and difficulty in degradation, so it is difficult to treat. In addition, the high chloride ion content in the wastewater will also corrode metal equipment or cause the loss of catalyst metal ions. Therefore, the treatment of high-salt organic wastewater has high requirements for equipment materials and catalysts. More importantly, if the high-salt wastewater generated by industries such as chemical, pharmaceutical, and petroleum is discharged into surface water or groundwater without effective treatment, it may eventually enter the marine environment through rivers or seepage. Ultra-high concentrations of chlorides, sulfates, and other salts in wastewater (>1wt%) are difficult to degrade in water, potentially disrupting the osmotic pressure regulation system of marine organisms and damaging aquatic ecosystems. This, in turn, affects the growth and reproduction of aquatic organisms, leading to ecological disasters such as coral bleaching and electrolyte imbalances in fish. Furthermore, recalcitrant organic compounds such as phenols and benzene ring compounds in wastewater are bioaccumulative, potentially posing a threat to marine mammals and human health through the food chain. Therefore, to ensure environmental safety, high-salinity organic wastewater must be fully treated and meet discharge standards before it can be discharged.

[0003] Currently, commonly used methods for treating high-salinity organic wastewater include evaporation and crystallization, membrane separation, advanced oxidation processes, electrolysis, and biological methods. Evaporation and crystallization involve heating to evaporate water, causing salt crystallization and precipitation, achieving solid-liquid separation. Common evaporation and crystallization methods include multiple-effect evaporation (MED) and mechanical vapor recompression (MVR). However, traditional multiple-effect evaporation requires large amounts of steam. While MVR saves steam, it still relies on electricity, resulting in high costs. Furthermore, the crystallized salts may contain organic impurities, making them unusable directly and requiring further purification or treatment. Membrane separation utilizes the selective permeability of membranes such as reverse osmosis (RO) and nanofiltration (NF) to separate salts and organics. This method has high requirements for influent water quality. Excessive influent hardness or organic content can significantly shorten membrane life, and the high-salinity concentrate after membrane concentration still requires evaporation or biological treatment. Advanced oxidation processes, such as Fenton, ozone, electrochemical catalytic oxidation, and wet oxidation, generate hydroxyl radicals (·OH) to degrade recalcitrant organics. However, advanced oxidation processes are expensive, require large amounts of oxidants or catalysts, and may produce secondary pollution such as sludge and ozone. Among them, wet oxidation can effectively decompose high-concentration, highly toxic, and difficult-to-degrade organic pollutants. This technology can effectively and almost non-selectively oxidize various types of high-concentration organic wastewater (including wastewater that is highly toxic and difficult to degrade by conventional methods) without generating secondary pollution. However, wet oxidation processes must be carried out at high temperatures (120-374°C) and high pressures (0.5-20 MPa), placing extremely high demands on the materials used in wet oxidation equipment. Corrosive components such as chloride ions and sulfides in high-salt wastewater can also exacerbate the corrosion of wet oxidation equipment, necessitating the use of corrosion-resistant materials such as titanium alloys and Hastelloy, which significantly increases the cost of wet oxidation equipment. Furthermore, high-salt conditions can lead to poisoning of heterogeneous catalysts and leaching and loss of metal components, which in turn increases costs. Homogeneous catalysts also face difficulties in catalyst recovery and loss of catalyst metal ions, which can cause secondary pollution. Catalytic ozone oxidation technology uses a catalyst to accelerate the ozone chain reaction, producing highly oxidizing hydroxyl radicals, thereby enhancing ozone oxidation capacity. Catalytic ozone oxidation can react almost indiscriminately with any pollutant in wastewater, directly oxidizing it into carbon dioxide, water, or salt without causing secondary pollution. Furthermore, the reaction conditions are mild. However, catalytic ozone oxidation technology suffers from low ozone utilization, incomplete decomposition of organic matter, and is unsuitable for wastewater with excessively high TOC concentrations. Electrolysis, which uses electrochemical reactions to directly oxidize organic matter in high-salinity organic wastewater, consumes significant amounts of electricity and typically requires the use of precious metal electrode materials, resulting in high operating costs. Biological treatment of high-salinity organic wastewater involves acclimating salt-tolerant bacteria (with a salinity tolerance of 1% to 8%) to metabolize and degrade organic matter. However, strain selection and acclimation are lengthy, and the bacteria are sensitive to salinity fluctuations (sudden changes in concentration can lead to bacterial colony death). High salt content also inhibits microbial activity. Summary of the Invention

[0004] In order to improve the above technical problems, the present invention provides a waste salt treatment method, which comprises subjecting high-salt organic wastewater to membrane catalytic ozone oxidation reaction, nanofiltration membrane filtration, catalytic wet oxidation reaction and chelating resin adsorption treatment in sequence, and the treated wastewater is directly used in an ion membrane caustic soda device.

[0005] According to an embodiment of the present invention, the waste salt treatment method comprises the following steps:

[0006] (1) High-salt organic wastewater enters the membrane catalytic ozone oxidation unit for membrane catalytic ozone oxidation reaction, and the catalyst is recovered after the reaction to obtain membrane catalytic ozone oxidation brine;

[0007] (2) using a nanofiltration membrane unit to filter the membrane catalytic ozone oxidized brine to obtain concentrated water and clear water; the clear water enters a chelating resin adsorption unit for purification to obtain refined brine;

[0008] (3) The concentrated water obtained in step (2) enters a catalytic wet oxidation unit for catalytic wet oxidation reaction, and after the reaction, the catalyst is recovered to obtain catalytic wet oxidation refined brine, which enters a chelating resin adsorption unit for refining to obtain refined brine.

[0009] In some embodiments, the high-salt organic wastewater comes from the production wastewater of epichlorohydrin or the production wastewater of epoxy resin.

[0010] In some embodiments, in step (1), the membrane in the membrane catalytic reactor used in the membrane catalytic ozone oxidation unit is a ceramic membrane, for example, a tubular ceramic membrane loaded with TiO2. Preferably, the pore size of the ceramic membrane is 0.05 to 0.15 μm, exemplified by 0.05 μm, 0.1 μm, or 0.15 μm.

[0011] In some embodiments, in step (1), the catalyst used in the membrane-catalyzed ozone oxidation reaction is, for example, activated carbon. For example, the amount of the catalyst used is 2 g / L to 10 g / L, exemplified by 2 g / L, 5 g / L, 8 g / L, or 10 g / L.

[0012] In some embodiments, in step (1), the amount of ozone gas used in the membrane-catalyzed ozone oxidation reaction is 2 g / L to 15 g / L, exemplified by 2 g / L, 3 g / L, 5 g / L, 8 g / L, 10 g / L or 15 g / L.

[0013] In some embodiments, in step (1), the temperature of the membrane-catalyzed ozone oxidation reaction does not exceed 40°C, such as 30°C; the time of the membrane-catalyzed ozone oxidation reaction does not exceed 2 hours, preferably 0.5 to 2 hours, such as 1 hour.

[0014] In some embodiments, in step (1), during the membrane catalytic ozone oxidation reaction, the high-salt organic wastewater undergoes a cyclic reaction between the ozone reactor and the membrane catalytic reactor. For example, the circulation speed is 200 to 300 m / s. 3 / h, for example 240m 3 / h.

[0015] In some embodiments, in step (1), the catalyst recovery is to filter the wastewater after the membrane-catalyzed ozone oxidation reaction through a ceramic ultrafiltration membrane.

[0016] In some embodiments, the pore size of the ceramic ultrafiltration membrane is 0.05 to 0.2 μm, exemplified by 0.05 μm, 0.1 μm, or 0.2 μm.

[0017] In some embodiments, the nanofiltration membrane unit uses a polyamide spiral nanofiltration membrane, for example, the polyamide spiral nanofiltration membrane has a pore size of 1 to 2 nm, exemplified by 1 nm.

[0018] In some embodiments, in step (3), the catalyst used in the catalytic wet oxidation reaction is, for example, copper chloride. For example, the amount of the catalyst used is 1200 to 2000 ppm, exemplified by 1200 ppm, 1300 ppm, 1400 ppm, 1500 ppm, 1600 ppm, 1700 ppm, 1800 ppm, 1900 ppm, or 2000 ppm, based on the copper ion content.

[0019] In some embodiments, in step (3), the temperature of the catalytic wet oxidation reaction is 210°C to 290°C, exemplified by 210°C, 220°C, 230°C, 240°C, 250°C, 260°C, 270°C, 280°C or 290°C; the time of the catalytic wet oxidation reaction does not exceed 4 hours, preferably 2 to 4 hours, for example 3 hours.

[0020] In some embodiments, in step (3), the catalyst is recovered by adjusting the brine after catalytic wet oxidation to alkaline, separating the solid and liquid through a filter membrane assembly to obtain a first solid; mixing the first solid with an acid to regenerate the catalyst, and returning the regenerated catalyst to the catalytic wet oxidation.

[0021] The filter membrane component used in the present invention is selected from a filter membrane component in a membrane filtration catalyst recovery device in a wet oxidation process disclosed in publication number CN219441259U.

[0022] The present invention also provides a waste salt treatment system, comprising a membrane catalytic ozone oxidation unit, a nanofiltration membrane unit, a catalytic wet oxidation unit and a chelate resin adsorption unit connected in sequence, wherein the liquid phase outlet of the nanofiltration membrane unit is connected to the chelate resin adsorption unit.

[0023] According to an embodiment of the present invention, the membrane catalytic ozone oxidation unit includes an ozone reactor and a membrane catalytic reactor.

[0024] In some embodiments, the membrane catalytic reactor used in the membrane catalytic reactor is a ceramic membrane, such as a tubular ceramic membrane loaded with TiO2. Preferably, the pore size of the ceramic membrane is 0.05 to 0.15 μm, exemplified by 0.05 μm, 0.1 μm, or 0.15 μm.

[0025] According to an embodiment of the present invention, the catalytic wet oxidation unit includes a preheater, a heater, and a reactor.

[0026] According to an embodiment of the present invention, the treatment system further comprises a first catalyst recovery unit connected to the liquid phase outlet of the membrane catalytic ozone oxidation unit. For example, the first catalyst recovery unit is selected from a ceramic ultrafiltration membrane.

[0027] In some embodiments, the pore size of the ceramic ultrafiltration membrane is 0.05 to 0.2 μm, exemplified by 0.05 μm, 0.1 μm, or 0.2 μm.

[0028] According to an embodiment of the present invention, the nanofiltration membrane unit uses a polyamide spiral nanofiltration membrane. For example, the pore size of the polyamide spiral nanofiltration membrane is 1 to 2 nm, exemplified by 1 nm.

[0029] According to an embodiment of the present invention, the treatment system further comprises a second catalyst recovery unit connected to the liquid phase outlet of the catalytic wet oxidation unit. For example, the second catalyst recovery unit is selected from a membrane filter assembly.

[0030] In the present invention, the chelate resin adsorption unit can be a conventional chelate resin adsorption tower in the art.

[0031] Beneficial effects of the present invention:

[0032] (1) The present invention couples membrane catalytic ozone oxidation with catalytic wet oxidation processes. The membrane catalytic ozone oxidation is first used to reduce the macromolecular organic matter in the wastewater. The remaining organic matter is then concentrated and separated using a nanofiltration membrane device. The organic matter in the wastewater is then completely decomposed into carbon dioxide and water using catalytic wet oxidation. Compared with a single oxidation process, the present invention uses membrane catalytic ozone oxidation coupled with catalytic wet oxidation to synergistically improve wastewater treatment efficiency and treatment effects, effectively improving the transmission of pollutants to the ocean and groundwater, providing key technical support for environmental protection, and further promoting the coordinated management of industrial wastewater treatment, water environment protection, and marine ecological protection.

[0033] (2) The present invention uses a catalytic wet oxidation device to further treat the concentrated water separated after membrane catalytic ozone oxidation, which not only reduces the processing load of the catalytic wet oxidation equipment, but also can reduce the volume of the catalytic wet oxidation reactor or reduce the number of catalytic wet oxidation reactors to reduce equipment investment costs.

[0034] (3) The membrane catalytic ozone oxidation unit of the present invention includes an ozone reactor and a catalytic membrane. When ozone and brine flow through the catalytic membrane, on the one hand, the catalyst loaded in the pores of the catalytic membrane can catalyze the hydroxyl radicals generated by ozone. On the other hand, the catalytic membrane can also confine the hydroxyl radicals and organic pollutants in the pore reaction channels of the catalytic membrane, thereby increasing the contact frequency between the hydroxyl radicals and the organic pollutants, and thus greatly improving the removal efficiency of organic matter. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 This is a flow chart of the resource treatment system for high-salt organic wastewater of the present invention. DETAILED DESCRIPTION

[0036] The technical solutions of the present invention will be described in further detail below with reference to specific embodiments. It should be understood that the following embodiments are merely illustrative and explanations of the present invention and should not be construed as limiting the scope of protection of the present invention. All technologies implemented based on the above content of the present invention are encompassed within the scope of protection that the present invention is intended to protect.

[0037] Unless otherwise specified, the raw materials and reagents used in the following examples are commercially available or can be prepared by known methods.

[0038] Example 1

[0039] The wastewater from the production of epichlorohydrin has a sodium chloride content of 21wt% and a TOC concentration of 2800mg / L. It is filtered through a precision filter (filtration accuracy of 5μm) and then enters the ozone reactor. The water flow rate is 10.8m 3 / h, the ozone dosage concentration was 300mg / L, the activated carbon (particle size was 45μm, model JPWT-325) catalyst dosage concentration was 2g / L, and a pump was used to make the wastewater and ozone circulate between the ozone reactor and the membrane catalytic reactor (the membrane used in the membrane catalytic reactor was a tubular ceramic membrane (DQCM40-12) loaded with TiO2, with a membrane pore size of 0.1μm) for reaction (reaction time was 1h, reaction temperature was 30℃, and circulation speed was 240m 3 / h).

[0040] After the reaction, the activated carbon catalyst was recovered using a plate-type ceramic ultrafiltration membrane (model FK-B250-1000, with a filtration accuracy of 0.1 μm) to obtain membrane-catalyzed ozone-oxidized brine (TOC concentration of 848 mg / L).

[0041] The membrane catalytic ozone oxidized brine enters the nanofiltration membrane unit (polyamide spiral nanofiltration membrane NF-8040, pore size 1nm) for filtration. The nanofiltration water yield is 70%, and most of the organic matter is intercepted and enters the concentrated water side (concentrated water yield 3.2m 3 / h, TOC concentration is 2799mg / L, clean water enters the water production side (clean water output 7.6m 3 / h, TOC concentration is 6.9 mg / L). The nanofiltration clear water enters the chelating resin tower for purification to obtain refined brine (TOC concentration is 6.9 mg / L).

[0042] Copper chloride solution was added as a catalyst to the nanofiltration concentrated water to make the copper ion concentration in the nanofiltration concentrated water 1500 mg / L, and concentrated hydrochloric acid was added to adjust the pH of the nanofiltration concentrated water to 1. 3 / h of flow rate enters the preheater of the catalytic wet oxidation unit, exchanges heat with the oxidizing brine discharged from the catalytic wet oxidation reactor (the temperature of the nanofiltration concentrated water after heat exchange reaches 201°C), enters the heater to be heated to a temperature of 230°C, and enters the catalytic wet oxidation reactor for oxidation reaction with a reaction temperature of 260°C, a residence time of 3h, a reaction pressure of 4.9MPa, and an oxygen dosage of 9g / L to obtain catalytic wet oxidation brine.

[0043] A 20% sodium hydroxide solution was added to the catalytic wet oxidation brine to adjust the pH of the brine to 11, causing the copper ion catalyst to form a flocculent copper hydroxide precipitate. The catalyst precipitate was recovered using a membrane filter assembly (the filter membrane used was an ePTFE membrane with a pore size of 0.2 μm), dissolved with hydrochloric acid, and then returned to the catalytic wet oxidation reactor for reuse to obtain catalytic wet oxidation refined brine. After refining in a chelating resin tower, the refined brine (TOC concentration of 7.6 mg / L) was obtained.

[0044] The refined brine obtained after membrane catalytic ozone oxidation and catalytic wet oxidation enters the ion membrane caustic soda unit.

[0045] Example 2

[0046] The wastewater from epoxy resin production has a sodium chloride content of 23wt% and a TOC concentration of 3700mg / L. It is filtered through a precision filter (filtration accuracy of 5μm) and then enters the ozone reactor. The water flow rate is 16.2m 3 / h, the ozone dosage concentration was 300mg / L, the activated carbon (particle size was 45μm, model JPWT-325) catalyst dosage concentration was 2g / L, and a pump was used to make the wastewater and ozone circulate between the ozone reactor and the membrane catalytic reactor (the membrane used in the membrane catalytic reactor was a tubular ceramic membrane (DQCM40-12) loaded with TiO2, with a membrane pore size of 0.1μm) for reaction (reaction time was 1h, reaction temperature was 30℃, and circulation speed was 240m 3 / h).

[0047] After the reaction, the activated carbon catalyst was recovered using a plate-type ceramic ultrafiltration membrane (model FK-B250-1000, with a filtration accuracy of 0.1 μm) to obtain membrane-catalyzed ozone-oxidized brine (TOC concentration of 965 mg / L).

[0048] The ozone-oxidized brine enters the nanofiltration membrane unit (polyamide spiral nanofiltration membrane NF-8040, pore size 1nm) for filtration. The nanofiltration water yield is 70%, and most of the organic matter is intercepted and enters the concentrated water side (concentrated water yield 4.9m 3 / h, TOC concentration is 3190mg / L, clean water enters the water production side (clean water output 11.3m 3 / h, TOC concentration is 7.8mg / L). The nanofiltration clear water enters the chelating resin tower for purification to obtain refined brine (TOC concentration is 7.8mg / L).

[0049] Copper chloride solution was added as a catalyst to the nanofiltration concentrated water to make the copper ion concentration in the nanofiltration concentrated water 1500 mg / L, and concentrated hydrochloric acid was added to adjust the pH of the nanofiltration concentrated water to 1. 3 / h of flow rate enters the preheater of the catalytic wet oxidation unit, exchanges heat with the oxidizing brine discharged from the catalytic wet oxidation reactor (the temperature of the nanofiltration concentrated water after heat exchange reaches 200°C), enters the heater to be heated to a temperature of 230°C, and enters the catalytic wet oxidation reactor for oxidation reaction with a reaction temperature of 260°C, a residence time of 3h, a reaction pressure of 4.9MPa, and an oxygen dosage of 9g / L to obtain catalytic wet oxidation brine.

[0050] A 20% sodium hydroxide solution was added to the catalytic wet oxidation brine to adjust the pH of the brine to 11, causing the copper ion catalyst to form a flocculent copper hydroxide precipitate. The catalyst precipitate was recovered using a membrane filter assembly (the filter membrane used was an ePTFE membrane with a pore size of 0.2 μm), dissolved with hydrochloric acid, and then returned to the catalytic wet oxidation reactor for reuse to obtain catalytic wet oxidation refined brine. After refining in a chelating resin tower, the refined brine (TOC concentration of 7.7 mg / L) was obtained.

[0051] The refined brine obtained after membrane catalytic ozone oxidation and catalytic wet oxidation enters the ion membrane caustic soda unit.

[0052] Comparative Example 1

[0053] The wastewater from the production of epichlorohydrin has a sodium chloride content of 21wt% and a TOC concentration of 2800mg / L. It enters the ozone reactor after passing through a precision filter (filtration accuracy of 5μm) with an inlet flow rate of 10.8m 3 / h, the ozone dosage concentration was 300mg / L, the activated carbon (particle size was 45μm, model JPWT-325) catalyst dosage concentration was 2g / L, and a pump was used to make the wastewater and ozone circulate between the ozone reactor and the membrane catalytic reactor (the membrane used in the membrane catalytic reactor was a tubular ceramic membrane (DQCM40-12) loaded with TiO2, with a membrane pore size of 0.1μm) for reaction (reaction time was 4h, reaction temperature was 30℃, and circulation speed was 240m 3 / h).

[0054] After the reaction, the activated carbon catalyst was recovered using a plate-type ceramic ultrafiltration membrane (model FK-B250-1000, filtration accuracy of 0.1 μm) to obtain membrane-catalyzed ozone-oxidized brine (TOC concentration of 107.5 mg / L), which was then purified in a chelating resin tower to obtain refined brine (TOC concentration of 107.5 mg / L).

[0055] Comparative Example 2

[0056] The wastewater from the production of epichlorohydrin has a sodium chloride content of 21wt% and a TOC concentration of 2800mg / L. It enters the ozone reactor after passing through a precision filter (filtration accuracy of 5μm) with an inlet flow rate of 10.8m 3 / h, the ozone dosage concentration was 300mg / L, the activated carbon (particle size was 45μm, model JPWT-325) catalyst dosage concentration was 2g / L, and a pump was used to make the wastewater and ozone circulate between the ozone reactor and the membrane catalytic reactor (the membrane used in the membrane catalytic reactor was a tubular ceramic membrane (DQCM40-12) loaded with TiO2, with a membrane pore size of 0.1μm) for reaction (reaction time was 4h, reaction temperature was 30℃, and circulation speed was 240m 3 / h).

[0057] After the reaction, the activated carbon catalyst was recovered using a plate-type ceramic ultrafiltration membrane (model FK-B250-1000, with a filtration accuracy of 0.1 μm) to obtain membrane-catalyzed ozone-oxidized brine (TOC concentration of 107.5 mg / L).

[0058] The ozone-oxidized brine enters the nanofiltration membrane unit (polyamide spiral nanofiltration membrane NF-8040, pore size 1nm) for filtration. The nanofiltration water yield is 80%, and most of the organic matter is intercepted and enters the concentrated water side (concentrated water yield 2.2m 3 / h, TOC concentration is 511mg / L, clean water enters the water production side (clean water output 8.6m 3 / h, TOC concentration is 6.5mg / L). The nanofiltration clear water enters the chelating resin tower for purification to obtain refined brine (TOC concentration is 6.5mg / L).

[0059] The results showed that even if the membrane-catalyzed ozone oxidation reaction time was extended and the brine after the oxidation reaction was subjected to ultrafiltration and nanofiltration, although the TOC concentration in the nanofiltration clear water was qualified, the TOC concentration in the concentrated water was still as high as 511 mg / L.

[0060] Comparative Example 3

[0061] The wastewater from the production of epichlorohydrin has a sodium chloride content of 21wt% and a TOC concentration of 2800mg / L. It is filtered using a precision filter (filtration accuracy of 5μm). Copper chloride solution is added to the filtered wastewater as a catalyst to adjust the copper ion concentration in the wastewater to 1500mg / L. Concentrated hydrochloric acid is added to adjust the pH of the wastewater to 1. 3 / h flow rate enters the preheater, exchanges heat with the oxidized brine discharged from the catalytic wet oxidation reactor (the wastewater temperature after heat exchange reaches 200°C), enters the heater to be heated to a temperature of 230°C, and enters the catalytic wet oxidation reactor for oxidation reaction at a reaction temperature of 260°C, a residence time of 4 hours, a reaction pressure of 4.9 MPa, and an oxygen dosage of 9 g / L. Catalytic wet oxidation brine is obtained.

[0062] A 20% sodium hydroxide solution was added to the catalytic wet oxidation brine to adjust the pH to 11, causing the copper ion catalyst to form a flocculent copper hydroxide precipitate. The catalyst precipitate was recovered using a membrane filter assembly (the filter membrane used was an ePTFE membrane with a pore size of 0.2 μm), dissolved with hydrochloric acid, and then returned to the reactor for reuse to obtain catalytic wet oxidation refined brine. After refining in a chelating resin tower, the refined brine (TOC concentration of 19.8 mg / L) was obtained.

[0063] Compared with Example 1, the catalytic wet oxidation water load in this comparative example is increased from 3.2m 3 / h increased to 10.8m 3 / h. When the membrane catalytic ozone oxidation unit is not used for pre-treatment of high-salt organic wastewater, the treatment load of the catalytic wet oxidation unit increases and the treatment efficiency decreases. Therefore, it is necessary to increase the total treatment time of the catalytic wet oxidation unit or increase the volume or number of oxidation reactors. In Comparative Example 2, only the catalytic wet oxidation unit is used to treat the high-salt organic wastewater. Although the catalytic wet oxidation reaction time is extended to 4h, the effluent effect is still not as good as that of Example 1. This shows that the pre-membrane catalytic ozone oxidation unit is beneficial to improving the oxidizability of wastewater.

[0064] Comparative Example 4

[0065] The wastewater from the production of epichlorohydrin has a sodium chloride content of 21wt% and a TOC concentration of 2800mg / L. It is filtered through a precision filter (filtration accuracy of 5μm) and then enters the ozone reactor. The water flow rate is 10.8m 3 / h, the ozone dosage concentration was 300mg / L, the activated carbon (particle size was 45μm, model JPWT-325) catalyst dosage concentration was 2g / L, and a pump was used to make the wastewater and ozone circulate between the ozone reactor and the membrane catalytic reactor (the membrane used in the membrane catalytic reactor was a tubular ceramic membrane (DQCM40-12) loaded with TiO2, with a membrane pore size of 0.1μm) for reaction (reaction time was 1h, reaction temperature was 30℃, and circulation speed was 240m 3 / h).

[0066] After the reaction, the activated carbon catalyst was recovered using a plate-type ceramic ultrafiltration membrane (model FK-B250-1000, with a filtration accuracy of 0.1 μm) to obtain membrane-catalyzed ozone-oxidized brine (TOC concentration of 853 mg / L).

[0067] Copper chloride solution was added as catalyst to membrane catalytic ozone oxidation brine to make the copper ion concentration 1500 mg / L, and concentrated hydrochloric acid was added to adjust the pH of membrane catalytic ozone oxidation brine to 1. 3 / h of flow rate enters the preheater of the catalytic wet oxidation unit, exchanges heat with the oxidized brine discharged from the catalytic wet oxidation reactor (the temperature of the membrane catalytic ozone oxidized brine after heat exchange reaches 201°C), enters the heater to be heated to a temperature of 255°C, and enters the catalytic wet oxidation reactor for oxidation reaction with a reaction temperature of 260°C, a residence time of 3h, a reaction pressure of 4.9MPa, and an oxygen dosage of 9g / L to obtain catalytic wet oxidation brine (TOC concentration of 8.6mg / L).

[0068] A 20% sodium hydroxide solution is added to the catalytic wet oxidation brine to adjust the pH of the brine to 11 so that the copper ion catalyst forms a flocculent copper hydroxide precipitate. The catalyst precipitate is recovered using a filter membrane assembly (the filter membrane used is an ePTFE membrane with a pore size of 0.2 μm), dissolved with hydrochloric acid, and then returned to the catalytic wet oxidation reactor for reuse to obtain catalytic wet oxidation refined brine.

[0069] The catalytic wet oxidation brine enters the nanofiltration membrane unit (polyamide rolled nanofiltration membrane NF-8040, pore size 1nm) for filtration, with a nanofiltration water yield of 90% and a concentrated water yield of 1.1m 3 / h, TOC concentration is 21.1mg / L, and clean water output is 9.7m 3 / h, TOC concentration is 7.2mg / L. The concentrated water from the nanofiltration is returned to the catalytic wet oxidation reactor for treatment, and the clear water from the nanofiltration is purified by the chelating resin tower to obtain refined brine (TOC concentration is 7.2mg / L).

[0070] Compared with Example 1, the catalytic wet oxidation water load in this comparative example is increased from 3.2m 3 / h increased to 10.8m 3 / h. When a nanofiltration membrane unit is not used to separate organic matter from the high-salt organic wastewater after membrane catalytic ozone oxidation, the treatment load of the catalytic wet oxidation unit increases and the treatment efficiency decreases. Therefore, it is necessary to increase the total treatment time of the catalytic wet oxidation unit or increase the volume or number of catalytic wet oxidation reactors. In Comparative Example 4, the TOC concentration of the wastewater entering the catalytic wet oxidation unit was 853 mg / L. The temperature rise was small during the reaction, so more heat was required to heat the high-salt organic wastewater before entering the catalytic wet oxidation reactor, thereby increasing the energy consumption of wastewater treatment.

[0071] Comparative Example 5

[0072] The wastewater from the production of epichlorohydrin has a sodium chloride content of 21wt% and a TOC concentration of 2800mg / L. After being filtered through a precision filter (filtration accuracy of 5μm), it enters a nanofiltration membrane unit (polyamide wound nanofiltration membrane NF-8040, pore size of 1nm) for filtration. The water inlet flow rate is 10.8m 3 / h, the nanofiltration water production rate is 60%, of which: the concentrated water production is 4.3m 3 / h, TOC concentration is 6934mg / L; clean water output is 6.5m 3 / h, TOC concentration is 60.2mg / L.

[0073] The nanofiltration concentrated water enters the ozone reactor with an inlet flow rate of 4.3m 3 / h, the ozone dosage concentration was 300mg / L, the activated carbon (particle size was 45μm, model JPWT-325) catalyst dosage concentration was 2g / L, and a pump was used to make the wastewater and ozone circulate between the ozone reactor and the membrane catalytic reactor (the membrane used in the membrane catalytic reactor was a tubular ceramic membrane (DQCM40-12) loaded with TiO2, with a membrane pore size of 0.1μm) for reaction (reaction time was 1h, reaction temperature was 30℃, and circulation speed was 240m 3 / h).

[0074] After the reaction, the activated carbon catalyst was recovered using a plate-type ceramic ultrafiltration membrane (model FK-B250-1000, with a filtration accuracy of 0.1 μm) to obtain membrane-catalyzed ozone-oxidized brine (TOC concentration of 4532 mg / L).

[0075] Copper chloride solution was added as catalyst to membrane catalytic ozone oxidation brine to make the copper ion concentration in membrane catalytic ozone oxidation brine 1500 mg / L, and concentrated hydrochloric acid was added to adjust the pH of membrane catalytic ozone oxidation brine to 1. 3 / h of flow rate enters the preheater of the catalytic wet oxidation unit, exchanges heat with the oxidized brine discharged from the catalytic wet oxidation reactor (the temperature of the membrane catalytic ozone oxidized brine after heat exchange reaches 201°C), enters the heater to be heated to a temperature of 235°C, and enters the catalytic wet oxidation reactor for oxidation reaction with a reaction temperature of 260°C, a residence time of 3h, a reaction pressure of 4.9MPa, and an oxygen dosage of 9g / L to obtain catalytic wet oxidation brine.

[0076] A 20% sodium hydroxide solution was added to a catalytic wet oxidation reactor to adjust the pH of the brine to 11, causing the copper ion catalyst to form a flocculent copper hydroxide precipitate. The catalyst precipitate was recovered using a membrane filter assembly (the filter membrane used was an ePTFE membrane with a pore size of 0.2 μm), dissolved with hydrochloric acid, and then returned to the catalytic wet oxidation reactor for reuse to obtain catalytic wet oxidation refined brine. After refining in a chelating resin tower, the refined brine (TOC concentration of 23.5 mg / L) was obtained.

[0077] These results indicate that if high-salinity organic wastewater is initially treated by nanofiltration, the TOC concentration of the nanofiltration clear water is high, necessitating secondary treatment. Furthermore, the TOC concentration of the nanofiltration concentrate, reaching 6934 mg / L, increases the load on subsequent membrane catalytic ozone oxidation and catalytic wet oxidation processes, thereby impacting treatment effectiveness. Furthermore, low nanofiltration water yields result in more nanofiltration concentrate entering the catalytic wet oxidation unit, further increasing the unit's treatment load. Furthermore, due to the high TOC concentration of the high-salinity organic wastewater entering the nanofiltration membrane unit, the membrane requires frequent backwashing, shortening its service life.

[0078] The above describes the embodiments of the present invention. However, the present invention is not limited to the above embodiments. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included in the scope of protection of the present invention.

Claims

1. A method for treating waste salt, characterized in that: The method includes sequentially subjecting high-salt organic wastewater to membrane catalytic ozone oxidation reaction, nanofiltration membrane filtration, catalytic wet oxidation reaction and chelating resin adsorption treatment; The nanofiltration membrane filtration adopts a polyamide rolled nanofiltration membrane; The temperature of the membrane-catalyzed ozone oxidation reaction does not exceed 40° C.; the time of the membrane-catalyzed ozone oxidation reaction does not exceed 2 hours; The temperature of the catalytic wet oxidation reaction is 210° C. to 290° C.; and the time of the catalytic wet oxidation reaction does not exceed 4 hours.

2. The processing method according to claim 1, characterized in that The steps include: (1) High-salt organic wastewater enters the membrane catalytic ozone oxidation unit for membrane catalytic ozone oxidation reaction, and the catalyst is recovered after the reaction to obtain membrane catalytic ozone oxidation brine; (2) using a nanofiltration membrane unit to filter the membrane catalyzed ozone oxidized brine to obtain concentrated water and clear water; the clear water enters a chelating resin adsorption unit for purification to obtain refined brine; (3) The concentrated water obtained in step (2) enters a catalytic wet oxidation unit for catalytic wet oxidation reaction, and after the reaction, the catalyst is recovered to obtain catalytic wet oxidation refined brine, which enters a chelating resin adsorption unit for refining to obtain refined brine.

3. The processing method according to claim 2, characterized in that In step (1), the membrane in the membrane catalytic reactor used in the membrane catalytic ozone oxidation unit is a tubular ceramic membrane loaded with TiO2; the pore size of the ceramic membrane is 0.05 to 0.15 μm; And / or, in step (1), the catalyst used in the membrane-catalyzed ozone oxidation reaction is activated carbon; the amount of the catalyst used is 2g / L to 10g / L.

4. The processing method according to claim 2, characterized in that In step (1), the amount of ozone gas used in the membrane-catalyzed ozone oxidation reaction is 2 g / L to 15 g / L.

5. The processing method according to claim 2, characterized in that In step (1), during the membrane catalytic ozone oxidation reaction, the high-salt organic wastewater undergoes a circulation reaction between the ozone reactor and the membrane catalytic reactor at a circulation speed of 200 to 300 m / s. 3 / h; And / or, in step (1), the catalyst recovery is to filter the wastewater after the membrane catalytic ozone oxidation reaction through a ceramic ultrafiltration membrane; The pore size of the ceramic ultrafiltration membrane is 0.05-0.2 μm.

6. The processing method according to claim 1, wherein The pore size of the polyamide rolled nanofiltration membrane is 1-2 nm.

7. The processing method according to any one of claims 2 to 6, characterized in that: In step (3), the catalyst used in the catalytic wet oxidation reaction is copper chloride; the amount of the catalyst used is 1200 to 2000 ppm based on the copper ion content; And / or, in step (3), the catalyst is recovered by adjusting the brine after catalytic wet oxidation to alkaline, separating the solid and liquid through a filter membrane assembly to obtain a first solid; mixing the first solid with an acid to regenerate the catalyst, and returning the regenerated catalyst to the catalytic wet oxidation.

8. A waste salt treatment system, characterized in that: The invention comprises a membrane catalytic ozone oxidation unit, a nanofiltration membrane unit, a catalytic wet oxidation unit and a chelate resin adsorption unit which are connected in sequence. The liquid phase outlet of the nanofiltration membrane unit is connected to the chelate resin adsorption unit.

9. The processing system according to claim 8, wherein The treatment system further comprises a first catalyst recovery unit, the first catalyst recovery unit being connected to the liquid phase outlet of the membrane catalytic ozone oxidation unit, the first catalyst recovery unit being selected from a ceramic ultrafiltration membrane; The pore size of the ceramic ultrafiltration membrane is 0.05-0.2 μm.

10. The processing system according to claim 8, wherein The nanofiltration membrane unit adopts a polyamide rolled nanofiltration membrane; the pore size of the polyamide rolled nanofiltration membrane is 1 to 2 nm; And / or, the treatment system further comprises a second catalyst recovery unit, the second catalyst recovery unit is connected to the liquid phase outlet of the catalytic wet oxidation unit, and the second catalyst recovery unit is selected from a membrane filter assembly.

Images