Device and process for treating high-salt organic wastewater through fixed bed catalysis based on persulfate oxidation

Abstract

The invention discloses a persulfate oxidation-based fixed bed catalysis high-salt organic wastewater treatment device and a persulfate oxidation-based fixed bed catalysis high-salt organic wastewater treatment process. The fixed bed catalysis high-salt organic wastewater treatment device comprises a pretreatment system, a liquid-solid catalytic reaction system, a reverse osmosis system and a catalyst regeneration and treatment system, and the liquid-solid catalytic reaction system comprises a primary filtration and adsorption unit, a primary catalytic oxidation unit, a secondary catalytic oxidation unit and a secondary adsorption and filtration unit. A baffle plate is arranged between every two units, so that the turbulence of wastewater is enhanced, and the liquid-solid mass transfer efficiency is improved. The treatment device disclosed by the invention has the advantages of continuous operation, salt interference resistance, low operation cost and the like, can realize efficient removal of the high-salt organic wastewater, and is suitable for treatment and recycling of the high-salt organic wastewater in the industries of coal chemical industry, pharmacy, printing and dyeing and the like.

Description

Technical Field

[0001] This invention belongs to the field of industrial wastewater treatment and resource utilization technology, specifically relating to a fixed-bed catalytic high-salt organic wastewater treatment device and process based on persulfate oxidation. Background Technology

[0002] High-salinity organic wastewater refers to wastewater with a total salt content greater than 1% and containing a large amount of organic pollutants (COD ≥ 2000 mg / L). Currently, high-salinity organic wastewater accounts for 5% of the total wastewater discharge, originating from a wide range of industries, including coal chemical, pharmaceutical, food, and dyeing industries. High-salinity organic wastewater is often accompanied by large amounts of metal ions and recalcitrant organic pollutants, characterized by high COD, high color, difficulty in biodegradation, and complex composition, posing a significant challenge to industrial water treatment. Improper treatment of high-salinity organic wastewater can lead to soil salinization, groundwater pollution, and severe environmental damage. Furthermore, high-salinity wastewater contains large amounts of industrial salt; improper treatment not only generates large quantities of difficult-to-treat waste salt but also wastes salt resources. Therefore, exploring efficient and feasible high-salinity organic wastewater treatment technologies is of significant practical importance. Currently, removing organic pollutants from high-salinity organic wastewater and recovering salt resources from it to achieve harmlessness and resource utilization is a reasonable approach for the treatment and resource recovery of this type of wastewater. However, due to the impact of high salinity on microorganisms, traditional biological methods are difficult to efficiently treat high-salinity organic wastewater. Furthermore, adsorption and membrane separation methods suffer from drawbacks such as incomplete removal of organic pollutants and the potential for secondary pollution. Traditional advanced oxidation technologies are more effective at removing organic pollutants from wastewater, but they are also susceptible to the influence of water matrix and salt ions, thus hindering their effectiveness in removing organic pollutants.

[0003] To overcome the aforementioned challenges, the development of heterogeneous catalytic oxidation technologies centered on solid catalysts has become a research hotspot. This type of technology aims to efficiently and selectively degrade organic matter under mild conditions through active sites on the catalyst surface. Currently, fixed-bed reactors are commonly used in engineering as the carrier devices for this technology. However, traditional fixed-bed reactors exhibit low liquid-solid mass transfer efficiency when treating high-salt organic wastewater. High salinity often leads to increased wastewater viscosity and a thicker liquid film boundary layer formed on the outer surface of the catalyst particles by organic pollutants, significantly increasing mass transfer resistance. Simultaneously, existing heterogeneous catalysts mostly focus on generating free radicals through the valence state cycle of transition metals, still struggling to completely overcome the interference of high-salt environments. Therefore, there is an urgent need to develop novel catalytic systems with salt resistance and high selective oxidation capabilities to address the characteristics of high-salt wastewater. In recent years, catalytic mechanisms based on Lewis acid sites have attracted attention. Lewis acid sites can specifically adsorb and polarize water and organic molecules through strong electron accepting capabilities, potentially inducing higher-order oxidation pathways independent of free radicals (such as direct electron transfer and singlet oxygen generation). However, how to precisely control and stably maintain the activity and quantity of Lewis acids on the catalyst surface, and how to achieve efficient and sustained contact between the catalyst and wastewater in industrial reactors, remain unsolved problems. Furthermore, how to achieve in-situ, low-cost regeneration of the catalyst after it becomes deactivated due to surface passivation or carbon buildup during long-term operation is also a key factor affecting techno-economic viability. Summary of the Invention

[0004] The purpose of this invention is to provide a fixed-bed catalytic device and process for treating high-salt organic wastewater based on persulfate oxidation. This invention improves the mass transfer efficiency between the catalyst and wastewater by adjusting Lewis acid sites and bimetallic synergistic loading, enabling simple catalyst preparation and recovery as well as efficient treatment of high-salt organic wastewater. This solves the problems of low degradation efficiency and short membrane life faced by traditional advanced oxidation technologies and membrane separation resource recovery technologies for high-salt organic wastewater.

[0005] The technical solution for achieving the objective of this invention is as follows:

[0006] The fixed-bed catalytic high-salt organic wastewater treatment device based on persulfate oxidation consists of a pretreatment system, a liquid-solid catalytic reaction system, a reverse osmosis system, and a catalyst regeneration and treatment system. The pretreatment system comprises a flocculation sedimentation tank, a persulfate (PMS) solution storage tank, a mixing tank, and a pH adjustment tank. The liquid-solid catalytic reaction system consists of a primary filtration adsorption unit, a primary catalytic oxidation unit, a secondary catalytic oxidation unit, and a secondary adsorption filtration unit connected in sequence. The reverse osmosis system includes a reverse osmosis membrane, and the catalyst regeneration and treatment system includes a catalyst recovery device. The flocculation sedimentation tank and the PMS solution storage tank are both connected to the mixing tank, which is connected to the pH adjustment tank. The pH adjustment tank is connected to the primary filtration adsorption unit, the secondary adsorption filtration unit is connected to the reverse osmosis membrane, and the primary and secondary catalytic oxidation units are connected to the catalyst recovery device.

[0007] Furthermore, the mixing tank is equipped with an online pH monitor and a metering pump.

[0008] Furthermore, the pH adjustment tank contains an acidic pH adjuster or an alkaline pH adjuster. The acidic pH adjuster is preferably hydrochloric acid, sulfuric acid, or nitric acid, and the alkaline pH adjuster is preferably sodium hydroxide, potassium hydroxide, or ammonia.

[0009] Furthermore, the PMS solution storage tank contains PMS solution, preferably at a concentration of 0.1 to 2 mmol / L.

[0010] Furthermore, the liquid-solid catalytic reaction system incorporates baffles to force wastewater to flow along the flow channel, overcoming the limitations of horizontal wastewater flow, increasing the turbulence of the wastewater within the bed, and improving the solid-liquid mass transfer time. The shell of the liquid-solid catalytic reaction system is a closed cylindrical structure, with the main body made of carbon steel lined with polytetrafluoroethylene (PTFE) to adapt to high-salt and highly oxidizing reaction environments. The baffles are preferably made of PTFE or stainless steel, with a thickness of 2-5 mm.

[0011] Furthermore, the primary filtration and adsorption unit is equipped with a water distribution system, a perforated partition plate, and a sand core support layer, which, while ensuring that the wastewater flows upward evenly, initially intercepts and filters suspended particles with a diameter greater than 50 μm in the wastewater.

[0012] Furthermore, the bed packing material of the primary filtration adsorption unit is one or both of quartz sand and zeolite spherical particles.

[0013] Furthermore, the primary catalytic oxidation unit bed has a uniform porous structure with a pore size of 0.5~0.8 mm. The primary catalytic oxidation unit bed is filled with modified alumina spheres loaded with transition metals and alkali metals with a particle size of 1~2 mm. The high specific surface area of ​​the small-particle catalyst enhances the initial contact mass transfer between wastewater and the catalyst, thereby rapidly removing most of the organic pollutants from the wastewater.

[0014] Furthermore, the secondary catalytic oxidation unit bed has a uniformly porous structure with a pore size of 1.5~1.8 mm. The secondary catalytic oxidation unit bed is filled with large-particle-size modified alumina spheres loaded with transition metals and alkali metals with a particle size of 2~3 mm. The close gaps formed by the large-particle catalysts increase the catalytic oxidation time and make full use of the remaining oxidant to achieve deep treatment of residual organic pollutants in wastewater.

[0015] Furthermore, the modified alumina spheres loaded with transition metals and alkali metals are prepared through the following steps:

[0016] (1) The activated alumina balls were pretreated by ultrasonic cleaning;

[0017] (2) The pretreated alumina balls were immersed in an aqueous solution of ethylenediaminetetraacetic acid (EDTA) for surface modification;

[0018] (3) Immerse the surface-modified alumina balls in a solution containing transition metal salts and alkali metal salts;

[0019] (4) After the impregnation, the alumina balls are cleaned and dried, and then calcined in air atmosphere to obtain modified alumina balls loaded with transition metals and alkali metals.

[0020] Furthermore, in step (3), the transition metal salt is selected from one or more of copper nitrate, manganese nitrate, cobalt nitrate, and iron nitrate, and the alkali metal salt is selected from one or more of magnesium nitrate and calcium nitrate.

[0021] Furthermore, the secondary adsorption filtration unit is equipped with a sand core stone support bed, and the bed packing is one or a combination of two of graphite-coated sand and activated carbon balls, which further removes particulate matter from the water and decolorizes and deodorizes the wastewater.

[0022] Furthermore, the reverse osmosis membrane is a seawater desalination reverse osmosis membrane, with an operating pressure of 5.0–8.0 MPa and a desalination rate of ≥98%.

[0023] Furthermore, the catalyst recovery unit includes an ultrasonic scrubbing tank, a drying system, and a high-temperature furnace, which can regenerate deactivated catalysts.

[0024] The fixed-bed catalytic oxidation process for treating high-salt organic wastewater based on persulfate oxidation utilizes the aforementioned apparatus. First, the high-salt organic wastewater undergoes flocculation and sedimentation. Then, the wastewater is mixed with a PMS solution and the pH is adjusted. Next, it enters a liquid-solid catalytic reaction system for multi-stage catalytic oxidation. The effluent enters a reverse osmosis system for desalination. The deactivated catalyst in the liquid-solid catalytic reaction system is recovered and regenerated. The specific steps include:

[0025] S1. High-salt organic wastewater is continuously fed into a flocculation sedimentation tank to remove suspended particulate matter from the wastewater. Then, the homogenized wastewater is transported to a mixing tank, and the PMS solution in the PMS solution storage tank is transported to the mixing tank to mix with the homogenized wastewater. The mixture then enters a pH adjustment tank, where acidic or alkaline pH adjusters are automatically added via online pH monitoring and metering pumps to adjust the pH to 3.0~4.0.

[0026] S2. The pH-adjusted mixture is transported to the primary filtration and adsorption unit of the liquid-solid catalytic reaction system. While achieving uniform upward flow of wastewater, it initially intercepts and filters suspended particulate matter with a particle size greater than 50 μm in the wastewater.

[0027] S3. After primary filtration and adsorption, the wastewater flows by gravity into the primary catalytic oxidation unit and the secondary catalytic oxidation unit connected in series, completing the efficient liquid-solid mass transfer and deep series catalytic oxidation of pollutants.

[0028] S4. After deep series catalytic oxidation, the effluent enters the secondary adsorption filtration unit to achieve deep adsorption of residual trace organic matter and potentially harmful gases. Finally, the effluent is discharged through the top overflow outlet in compliance with standards.

[0029] S5. The partially saturated catalyst in the primary catalytic oxidation unit and the secondary catalytic oxidation unit is transported to the catalyst recovery device of the catalyst regeneration and treatment system to restore the catalyst activity. The regenerated catalyst is then reloaded into the liquid-solid catalytic reaction system to achieve recycling.

[0030] Furthermore, the residence time of wastewater in each stage of the liquid-solid catalytic reaction system is 15-30 minutes, and it flows through the primary catalytic oxidation unit and the secondary catalytic oxidation unit bed at room temperature to 50 ℃.

[0031] Compared with the prior art, the present invention has the following advantages:

[0032] (1) By precisely controlling the Lewis acid sites on the catalyst surface and using bimetallic synergistic loading, the activation efficiency and stability of the catalyst for persulfate in a high-salt, high-organic complex pollution environment are significantly improved, achieving efficient degradation of recalcitrant organic pollutants and overcoming the problem of low oxidation efficiency caused by salt interference in traditional homogeneous oxidation technology.

[0033] (2) By setting baffles inside the liquid-solid catalytic reaction system, the flow direction of wastewater is forcibly changed to form turbulence, which greatly improves the liquid-solid mass transfer efficiency between the catalyst surface and the wastewater, effectively avoids channeling and short circuit, ensures full contact between oxidant and pollutants, and improves the reaction rate and oxidant utilization rate.

[0034] (3) Modified alumina balls loaded with transition metals and alkali metals have excellent thermal regeneration performance. They can be effectively restored to Lewis acidity and catalytic activity through high-temperature calcination, realizing the recycling of catalysts and significantly reducing operating costs.

[0035] (4) By using a gradient layering of modified alumina balls with small and large particle sizes loaded with transition metals and alkali metals, the contact area between the catalyst and the wastewater is increased. At the same time, a reasonable bed porosity is maintained to avoid salt precipitation and blockage by high-salt wastewater, which greatly improves the liquid-solid mass transfer efficiency. Meanwhile, through efficient series catalytic oxidation, most of the organic matter that is easy to foul the membrane system is removed, providing ideal feed water for the subsequent reverse osmosis membrane. This fundamentally alleviates the membrane fouling and scaling problems and significantly extends the service life and operational stability of the membrane system.

[0036] (5) The treatment device of the present invention has the ability to remove 0.1~0.5 kg COD per hour for high-salt organic wastewater, the wastewater decolorization rate is over 95%, it can operate continuously and stably for more than 1 week, and the purity of the recovered salt is over 70%, thus realizing the resource recycling of salt. Attached Figure Description

[0037] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used in conjunction with the embodiments of the invention to explain the invention, but do not constitute a limitation thereof. In the drawings:

[0038] Figure 1 This is a fixed-bed catalytic high-salt organic wastewater treatment device and process flow diagram based on persulfate oxidation;

[0039] Figure 2 This is a schematic diagram of a liquid-solid catalytic reaction system;

[0040] In the diagram, 1: Pretreatment system 1, 2: Liquid-solid catalytic reaction system, 3: Reverse osmosis system, 4: Catalyst regeneration and treatment system, 11: Flocculation sedimentation tank, 12: PMS solution storage tank, 13: Mixing tank, 14: pH adjustment tank, 20: Inlet, 21: Primary filtration and adsorption unit, 22: Primary catalytic oxidation unit, 23: Secondary catalytic oxidation unit, 24: Secondary adsorption and filtration unit, 25: Outlet, 26: Perforated partition plate, 27: First packing port, 28: Second packing port, 29: Third packing port, 30: Baffle plate, 31: Reverse osmosis membrane, 41: Catalyst recovery device.

[0041] The technical solution and embodiments of the present invention can be clearly understood from the above accompanying drawings. Those skilled in the art, based on these drawings and the description in the specification, can implement the technical solution of the present invention and understand its innovative points and beneficial effects. Detailed Implementation

[0042] The technical solution of the present invention will be clearly and completely described below with reference to specific embodiments and accompanying drawings. 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.

[0043] The modified alumina spheres loaded with transition metals and alkali metals described in this invention are synthesized using existing methods and can be prepared through a stepwise modification strategy, including the following steps:

[0044] (1) The activated alumina balls were pretreated by ultrasonic cleaning;

[0045] (2) The pretreated alumina balls were immersed in an EDTA aqueous solution for surface modification;

[0046] (3) The surface-modified alumina balls are immersed in a solution containing transition metal salts and alkali metal salts. The transition metal salts are commonly used transition metal salts in the art, including but not limited to copper nitrate, manganese nitrate, cobalt nitrate, and iron nitrate. The alkali metal salts are commonly used alkali metal salts in the art, including but not limited to magnesium nitrate and calcium nitrate.

[0047] (4) After the impregnation, the alumina balls are cleaned and dried, and then calcined in air atmosphere to obtain modified alumina balls loaded with transition metals and alkali metals.

[0048] The specific steps can be as follows:

[0049] (1) First, the spherical activated alumina carrier with a diameter of 1-3 mm was pretreated. The activated alumina balls were subjected to intermittent ultrasonic cleaning in deionized water at a solid-liquid volume ratio of 1:2. The ultrasonic conditions were set to a frequency of 45 kHz, 30 minutes of ultrasonic cleaning each time, and a 10-minute standing interval, and the cycle was repeated 3 times to remove the powder on the carrier surface and to introduce micro-defects on the alumina surface by utilizing the ultrasonic cavitation effect, providing highly active anchoring points and initially controlling the Lewis acidity of the carrier surface.

[0050] (2) Add the pretreated activated alumina balls to an EDTA aqueous solution with a concentration of 30 mM and pH 5.0, mix at 60 rpm for 12 hours, wash with water and filter to obtain surface-modified activated alumina balls, and collect the mother liquor for later use.

[0051] (3) Using the above mother liquor, add the corresponding metal salts according to the molar ratio of transition metal, alkali metal and EDTA of 1:1:3, stir to dissolve and obtain metal treatment solution, immerse the surface-modified activated alumina balls in the metal treatment solution, and mix at 60 rpm for 12 hours.

[0052] (4) The impregnated activated alumina balls are ultrasonically cleaned at a frequency of 45 kHz, with each ultrasonic cleaning lasting 20 minutes and an interval of 10 minutes, and repeated 3 times to remove excess ligands and uncomplexed metal ions. After that, they are filtered and dried, and finally placed in a muffle furnace and heated to 500 ℃ at 5 ℃ / min in an air atmosphere for 2 hours for thermal activation to obtain modified alumina balls loaded with transition metals and alkali metals.

[0053] like Figure 1 As shown, the fixed-bed catalytic high-salt organic wastewater treatment device based on persulfate oxidation of the present invention consists of a pretreatment system 1, a liquid-solid catalytic reaction system 2, a reverse osmosis system 3, and a catalyst regeneration and treatment system 4. The pretreatment system 1 consists of a flocculation sedimentation tank 11, a PMS solution storage tank 12, a mixing tank 13, and a pH adjustment tank 14. The liquid-solid catalytic reaction system 2 consists of a primary filtration adsorption unit 21, a primary catalytic oxidation unit 22, a secondary catalytic oxidation unit 23, and a secondary adsorption filtration unit 24 connected in sequence. The reverse osmosis system 3 includes a reverse osmosis membrane 31. The catalyst regeneration and treatment system 4 includes a catalyst recovery device 41. The flocculation sedimentation tank 11 and the PMS solution storage tank 12 are both connected to the mixing tank 13. The mixing tank 13 is connected to the pH adjustment tank 14. The pH adjustment tank 14 is connected to the primary filtration adsorption unit 21. The secondary adsorption filtration unit 24 is connected to the reverse osmosis membrane 31. The primary catalytic oxidation unit 22 and the secondary catalytic oxidation unit 23 are connected to the catalyst recovery device 41.

[0054] like Figure 1As shown, the fixed-bed catalytic high-salt organic wastewater treatment process based on persulfate oxidation of the present invention is as follows: High-salt organic wastewater flows into a flocculation sedimentation tank for flocculation and sedimentation to remove suspended particulate matter from the wastewater. The wastewater after flocculation and sedimentation is pumped to a mixing tank. PMS solution stored in a PMS solution storage tank is pumped to the mixing tank. The mixing tank is equipped with an online pH monitor and a metering pump to mix the wastewater and PMS solution. After the mixed solution enters a pH adjustment tank to adjust the pH, it is pumped to a liquid-solid catalytic reaction system. The liquid-solid catalytic reaction system is equipped with baffles to force the wastewater to flow along the flow channel, breaking the limitations of horizontal plug flow of wastewater, increasing the turbulence of wastewater in the bed, and improving the solid-liquid mass transfer time. Wastewater first passes through a primary filtration and adsorption unit, which initially traps and filters suspended particles larger than 50 μm, ensuring uniform upward flow. The filtered wastewater is then pumped to a primary catalytic oxidation unit. This unit's bed is packed with small-diameter modified alumina spheres loaded with transition and alkali metals (1-2 mm). The high specific surface area of ​​the small-diameter catalyst enhances initial mass transfer between the wastewater and the catalyst, rapidly removing most organic pollutants. Next, the wastewater passes through a secondary catalytic oxidation unit. This unit's bed is packed with large-diameter modified alumina spheres loaded with transition and alkali metals (2-3 mm). The tight interstices created by the large-diameter catalysts extend the catalytic oxidation time, fully utilizing the remaining oxidant to achieve deep treatment of residual organic pollutants. By using modified alumina spheres of different sizes loaded with transition and alkali metals as the catalytic-adsorption medium, a fixed bed is formed, achieving efficient solid-liquid mass transfer and completing deep tandem catalytic oxidation. The wastewater from the deep catalytic oxidation process flows through a secondary adsorption filtration unit to further remove particulate matter and decolorize and deodorize the wastewater. The effluent from the secondary adsorption filtration unit enters the reverse osmosis membrane of the reverse osmosis system. The membrane's pore size and charge effect facilitate deep desalination and further concentrate dissolved organic matter to meet discharge standards. Deactivated catalysts from the primary and secondary catalytic oxidation units are transported through the material outlet to the catalyst recovery unit of the catalyst regeneration and treatment system for catalyst recovery and regeneration.

[0055] Furthermore, the pH adjustment tank contains an acidic pH adjuster or an alkaline pH adjuster. The acidic pH adjuster is preferably hydrochloric acid, sulfuric acid, or nitric acid, and the alkaline pH adjuster is preferably sodium hydroxide, potassium hydroxide, or ammonia.

[0056] Furthermore, the concentration of the PMS solution was 0.1–2 mmol / L.

[0057] Furthermore, the primary filtration adsorption unit is equipped with a water distribution system, perforated partition plates, and sand core stones at its bottom. The bed packing material of the primary filtration adsorption unit is one or both of quartz sand and zeolite spherical particles.

[0058] Furthermore, the shell of the liquid-solid catalytic reaction system is a closed cylindrical structure, with the main body made of carbon steel lined with polytetrafluoroethylene (PTFE) to withstand high-salt and highly oxidizing reaction environments. The baffles are made of PTFE or stainless steel with a thickness of 2-5 mm.

[0059] Furthermore, the primary catalytic oxidation unit bed has a uniform porous structure with a pore size of 0.5~0.8 mm; the secondary catalytic oxidation unit bed has a uniform porous structure with a pore size of 1.5~1.8 mm.

[0060] Furthermore, the secondary adsorption filtration unit is equipped with a sand core stone support bed, and the bed filler is one or a combination of two of graphite-coated sand and activated carbon balls.

[0061] Furthermore, the reverse osmosis membrane is a seawater desalination reverse osmosis membrane, with an operating pressure of 5.0–8.0 MPa and a desalination rate of ≥98%.

[0062] Furthermore, the catalyst recovery unit includes an ultrasonic scrubbing tank, a drying system, and a high-temperature furnace.

[0063] like Figure 2 As shown, the liquid-solid catalytic reaction system of the present invention includes: a water inlet 20, a primary filtration and adsorption unit 21, a primary catalytic oxidation unit 22, a secondary catalytic oxidation unit 23, a secondary adsorption and filtration unit 24, a water outlet 25, a perforated partition plate 26, a first packing port 27, a second packing port 28, a third packing port 29, and a baffle plate 30.

[0064] Example 1

[0065] To demonstrate the effectiveness of the fixed-bed catalytic high-salt organic wastewater treatment process based on persulfate oxidation of the present invention, experiments were conducted using the aforementioned apparatus and simulated high-salt organic wastewater, including the following steps:

[0066] S1. Water homogenization, online mixing of oxidants and pH adjustment:

[0067] Simulated high-salt organic wastewater is continuously fed into a flocculation sedimentation tank to remove suspended particulate matter. Then, the homogenized wastewater is transported to a mixing tank by a booster pump. PMS solution in the PMS solution storage tank is pumped into the mixing tank and mixed with the homogenized wastewater online and quantitatively according to a set ratio. Dilute sulfuric acid or sodium hydroxide solution is automatically added by online pH monitoring and metering pump to precisely adjust the pH to the optimal range of 3.0~4.0 for the catalytic reaction.

[0068] S2, Primary Processing:

[0069] The pH-adjusted mixture is pumped to the primary filtration and adsorption unit of the liquid-solid catalytic reaction system, which initially intercepts and filters suspended particles with a diameter greater than 50 μm in the wastewater while achieving uniform upward flow of wastewater.

[0070] S3, Deep Tandem Catalytic Oxidation:

[0071] After primary filtration and adsorption, the wastewater flows by gravity into a series of primary and secondary catalytic oxidation units. Each unit is filled with modified alumina spheres loaded with transition and alkali metals of different particle sizes as the catalytic-adsorption medium. The catalyst loading is 1 m³ per treatment unit. 3 The wastewater is packed with 180 kg of catalyst. The primary catalytic oxidation unit is filled with 80 kg of modified alumina spheres loaded with transition metals and alkali metals with a particle size of 1-2 mm, and the secondary catalytic oxidation unit is filled with 100 kg of modified alumina spheres loaded with transition metals and alkali metals with a particle size of 2-3 mm. The empty bed residence time of the wastewater in each unit is controlled to be 20-30 minutes. The wastewater flows through the two-stage bed at room temperature to 50 ℃, completing the efficient liquid-solid mass transfer and deep tandem catalytic oxidation of pollutants.

[0072] S4. Deep adsorption and effluent:

[0073] After deep catalytic oxidation, the effluent enters the secondary adsorption and filtration unit, which is filled with a granular activated carbon adsorption layer. The wastewater flows through this layer at room temperature to achieve deep adsorption of residual trace organic matter and potentially harmful gases. Finally, the effluent is discharged through the top overflow outlet in compliance with standards.

[0074] S5. Catalyst online regeneration and recycling:

[0075] Periodically, partially saturated catalyst from the primary and secondary catalytic oxidation units is unloaded via a pneumatic conveying system and transported to the catalyst recovery unit of the catalyst regeneration and treatment system to restore catalyst activity. The regenerated catalyst, after cooling, is reloaded into the liquid-solid catalytic reaction system via a closed conveying system for recycling. The COD removal rate, color removal rate, and continuous operating time of the unit are shown in Table 2.

[0076] Table 1 shows the water quality parameters of the simulated high-salt organic wastewater.

[0077] Table 1 Water quality parameters of simulated high-salt organic wastewater

[0078] Chloride concentration COD chromaticity 10 g / L 2000 mg / L 200 times

[0079] Comparative Example 1

[0080] This comparative example is largely the same as Example 1, except that in the liquid-solid catalytic reaction system, both the primary and secondary catalytic oxidation units are filled with large-particle-size modified alumina spheres loaded with transition and alkali metals, with a particle size of 2-3 mm. The COD removal rate, color removal rate, and continuous operating time of the device are shown in Table 2.

[0081] Comparative Example 2

[0082] This comparative example is largely the same as Example 1, except that in the liquid-solid catalytic reaction system, both the primary and secondary catalytic oxidation units are filled with small-diameter modified alumina spheres loaded with transition and alkali metals, with a particle size of 1-2 mm. The COD removal rate, color removal rate, and continuous operating time of the device are shown in Table 2.

[0083] Comparative Example 3

[0084] This comparative example is largely the same as Example 1, except that in the liquid-solid catalytic reaction system, both the primary and secondary catalytic oxidation units are filled with modified alumina spheres loaded with transition metals and alkali metals, with mixed particle sizes of 1-2 mm and 2-3 mm. The COD removal rate, color removal rate, and continuous operating time of the device are shown in Table 2.

[0085] Comparative Example 4

[0086] This comparative example is largely the same as Example 1, except that the primary filtration and adsorption unit is missing from the liquid-solid catalytic reaction system. The wastewater, after pH adjustment, directly enters the primary catalytic oxidation unit. The COD removal rate, color removal rate, and continuous operating time of the device are shown in Table 2.

[0087] Comparative Example 5

[0088] This comparative example is largely the same as Example 1, except that the liquid-solid catalytic reaction system lacks a secondary adsorption filtration unit, and the effluent from the secondary catalytic oxidation unit directly enters the reverse osmosis system. The COD removal rate, color removal rate, and continuous operating time of the device are shown in Table 2.

[0089] Table 2. Water treatment effects and operational stability results of Example 1 and Comparative Examples 1-5

[0090] Comparison items Example 1 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Comparative Example 5 COD removal rate ≥99% ≤80% ≤85% ≤85% ≤75% ≤90% Color removal rate ≥98% ≤90% ≤90% ≥88% ≤75% ≤68% Continuous running time >720 hours <360 hours <400 hours <400 hours <200 hours <480 hours

[0091] The comparison of the effects of Example 1 and Comparative Examples 1-5 in Table 2 shows that this invention, by combining a pretreatment system, a liquid-solid catalytic reaction system, a reverse osmosis system, and a catalyst regeneration and treatment system, has developed a water treatment process and device that integrates gradient catalyst loading in the catalytic oxidation unit and filtration anti-clogging and deep adsorption in the filtration and adsorption unit. This not only improves the mineralization rate of recalcitrant organic matter in high-salt organic wastewater but also meets the requirements for precise control of reaction conditions, long-term operation throughout the entire process, and catalyst recycling during wastewater treatment. It solves the technical pain points of traditional fixed-bed reactors in treating high-salt organic wastewater, such as low liquid-solid mass transfer efficiency, frequent shutdowns due to catalyst clogging, incomplete removal of small molecule organic matter leading to membrane fouling, and poor system stability. In terms of COD removal rate, color removal rate, and continuous operating time, it is significantly superior to the comparative examples that changed the catalyst filling method and omitted the filtration unit, fully demonstrating the technical innovation and practicality of this invention.

[0092] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0093] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A fixed bed catalytic high-salinity organic wastewater treatment device based on persulfate oxidation, characterized in that, The device comprises a pretreatment system, a liquid-solid catalytic reaction system, a reverse osmosis system, and a catalyst regeneration and treatment system; the pretreatment system comprises a flocculation sedimentation tank, a PMS solution storage tank, a mixed reagent tank, and a pH adjusting tank; the liquid-solid catalytic reaction system comprises a primary filtration and adsorption unit, a primary catalytic oxidation unit, a secondary catalytic oxidation unit, and a secondary adsorption and filtration unit connected in sequence; the reverse osmosis system comprises a reverse osmosis membrane; and the catalyst regeneration and treatment system comprises a catalyst recovery device; wherein the flocculation sedimentation tank and the PMS solution storage tank are connected to the mixed reagent tank, the mixed reagent tank is connected to the pH adjusting tank, the pH adjusting tank is connected to the primary filtration and adsorption unit, the secondary adsorption and filtration unit is connected to the reverse osmosis membrane, and the primary catalytic oxidation unit and the secondary catalytic oxidation unit are connected to the catalyst recovery device.

2. The fixed bed catalytic high-salinity organic wastewater treatment device according to claim 1, characterized in that, The mixed reagent tank is internally provided with an on-line pH monitor and a metering pump; the pH adjusting tank is provided with an acidic pH adjusting agent or an alkaline pH adjusting agent, the acidic pH adjusting agent is hydrochloric acid, sulfuric acid, or nitric acid, and the alkaline pH adjusting agent is sodium hydroxide, potassium hydroxide, or ammonia water; and the PMS solution storage tank is provided with a PMS solution with a concentration of 0.1-2 mmol / L.

3. The fixed bed catalytic high-salinity organic wastewater treatment device according to claim 1, characterized in that, The liquid-solid catalytic reaction system is internally provided with a baffle, and the shell of the liquid-solid catalytic reaction system is a closed cylindrical structure, the main body of which is made of carbon steel lined with polytetrafluoroethylene, and the baffle is made of polytetrafluoroethylene or stainless steel with a thickness of 2-5 mm.

4. The fixed bed catalytic high-salinity organic wastewater treatment device according to claim 1, characterized in that, The primary filtration and adsorption unit is provided with a water distribution system, a perforated partition plate, and a sand core stone support layer, and the bed layer filler of the primary filtration and adsorption unit is one or both of quartz sand and zeolite spherical particles.

5. The fixed bed catalytic high-salinity organic wastewater treatment device according to claim 1, characterized in that, The bed layer of the primary catalytic oxidation unit is a uniform pore structure with a pore size of 0.5-0.8 mm, and the primary catalytic oxidation unit bed layer is filled with small-diameter modified alumina balls loaded with transition metals and alkali metals with a particle size of 1-2 mm; the bed layer of the secondary catalytic oxidation unit is a uniform pore structure with a pore size of 1.5-1.8 mm, and the secondary catalytic oxidation unit bed layer is filled with large-diameter modified alumina balls loaded with transition metals and alkali metals with a particle size of 2-3 mm.

6. The fixed bed catalytic high-salinity organic wastewater treatment device according to claim 5, characterized in that, The modified alumina balls loaded with transition metals and alkali metals are prepared by the following steps: (1) ultrasonic cleaning pretreatment of active alumina balls; (2) immersing the pretreated alumina balls in an EDTA aqueous solution for surface modification; (3) immersing the surface-modified alumina balls in a solution containing transition metal salts and alkali metal salts; (4) after cleaning and drying, the immersed alumina balls are calcined in an air atmosphere to obtain the modified alumina balls loaded with transition metals and alkali metals.

7. The fixed bed catalytic high salinity organic wastewater treatment device according to claim 6, characterized in that, In step (3), the transition metal salt is selected from one or more of copper nitrate, manganese nitrate, cobalt nitrate, and iron nitrate, and the alkali metal salt is selected from one or more of magnesium nitrate and calcium nitrate.

8. The fixed bed catalytic high salinity organic wastewater treatment device according to claim 1, characterized in that, The secondary adsorption and filtration unit is provided with a sand core stone support bed layer, and the bed layer filler is one or a combination of both of graphite coated sand and activated carbon balls; the reverse osmosis membrane is a seawater desalination reverse osmosis membrane with a working pressure of 5.0-8.0 Mpa and a desalination rate of ≥98%; and the catalyst recovery device comprises an ultrasonic elution tank, a drying system, and a high-temperature furnace.

9. A process for the treatment of high salinity organic wastewater based on the oxidation by persulfate in a fixed bed catalysis, characterized in that, The device is used in the steps of: S1, continuously send high-salt organic wastewater into a flocculation and sedimentation tank to remove suspended particulate matters in the wastewater, then transport the homogenized wastewater to a medicine mixing tank, and transport PMS solution in a PMS solution storage tank to the medicine mixing tank to mix with the homogenized wastewater, then the mixed solution enters a pH adjusting tank, and an acidic or alkaline pH adjusting agent is automatically added by an online pH monitoring and metering pump to adjust the pH to 3.0-4.0; S2, transport the mixed solution after pH adjustment to a primary filtration and adsorption unit of a liquid-solid catalytic reaction system, while realizing uniform upward flow of the wastewater, preliminarily intercept and filter suspended particulate matters with a particle size greater than 50 μm in the wastewater; S3, the wastewater after primary filtration and adsorption flows into a primary catalytic oxidation unit and a secondary catalytic oxidation unit in series by gravity, and high-efficiency liquid-solid mass transfer and deep series catalytic oxidation of pollutants are completed; S4, the effluent after deep series catalytic oxidation enters a secondary adsorption and filtration unit to realize deep adsorption of residual trace organic matters and harmful gases that may be generated, and the final effluent is discharged through a top overflow port to meet the discharge standard; S5, part of the saturated catalysts in the primary catalytic oxidation unit and the secondary catalytic oxidation unit are transported to a catalyst recovery device of a catalyst regeneration and treatment system to restore the activity of the catalysts, and the regenerated catalysts are reloaded into the liquid-solid catalytic reaction system to realize recycling.

10. The fixed bed catalytic high salinity organic wastewater treatment process as claimed in claim 9, wherein, The residence time of the wastewater in each unit of the liquid-solid catalytic reaction system is 15-30 minutes, and the wastewater flows through the bed layers of the primary catalytic oxidation unit and the secondary catalytic oxidation unit at room temperature-50 ℃.

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