A preparation method and system of a composite three-dimensional electrode without increasing the salinity of low-salinity water electrolysis effluent

Abstract

This invention provides a composite three-dimensional electrode system that does not increase the salinity of the effluent from low-salinity electrolysis, belonging to the field of wastewater treatment technology. It includes a low-salinity electrochemical oxidation device body, an anode plate, a polymer membrane module, and a cathode plate. The low-salinity electrochemical oxidation device body is respectively provided with an inlet and an effluent system. A main reaction zone is located in the middle of the low-salinity electrochemical oxidation device body, and the polymer membrane module is located within the main reaction zone. The anode plate and cathode plate are respectively located at opposite ends of the low-salinity electrochemical oxidation device body, with the anode plate positioned near the inlet and the cathode plate positioned near the effluent system. The polymer membrane module is positioned between the anode plate and the cathode plate. This invention reduces effluent salinity and microbial toxicity by using a conductive reverse osmosis membrane bag to intercept electrolyte salts and oxidizing free radicals.

Description

Technical Field

[0001] This invention relates to the field of wastewater treatment technology, and in particular to a method and system for preparing a composite three-dimensional electrode that does not increase the salinity of the effluent from low-salinity electrolysis. Background Technology

[0002] Electrochemical oxidation has advantages such as high efficiency, no secondary pollution, simple operation, low susceptibility to external environmental influences, and wide applicability. As a result, it is widely used in the treatment of various wastewaters, especially wastewaters with poor biodegradability, difficult degradation, and that cannot be treated by traditional treatment processes.

[0003] However, single electrochemical processes are often costly, especially for wastewater with high concentrations or poor conductivity. To reduce operating costs, electrocatalysis is often combined with traditional technologies such as biological methods. The mechanism involves first using electrocatalysis to convert high-molecular-weight, recalcitrant organic matter into low-molecular-weight, biodegradable organic matter; then, biological methods remove the small-molecule organic matter, thus achieving wastewater discharge compliance. This technology is feasible only if the microbial toxicity of the effluent from electrocatalysis is within acceptable limits. Some wastewaters have low salinity and poor conductivity, resulting in unsatisfactory electrolysis effects and significantly increased electrolysis costs. Therefore, to improve the electrochemical oxidation treatment effect and reduce its cost, salts need to be added to the wastewater to increase conductivity. However, on the one hand, the added salts lead to increased effluent salinity, which does not meet the requirements of relevant industry emission standards; on the other hand, salts will transform into ·OH, ClO·, and ·SO4 during electrolysis. - Oxidants with microbial toxicity can inhibit the effectiveness of biological treatment methods.

[0004] Developing an electrode and system that can improve the conductivity of wastewater without increasing effluent salinity and microbial toxicity is of great significance for achieving efficient, low-cost wastewater treatment that can be effectively combined with biological methods. Summary of the Invention

[0005] The purpose of this invention is to provide a method and system for preparing a composite three-dimensional electrode that does not increase the salinity of the effluent from low-salinity wastewater electrolysis, thereby solving the technical problems of poor conductivity of existing low-salinity wastewater and the fact that conventional salt addition increases the salinity and microbial toxicity of the effluent, resulting in substandard salinity and the inability to combine electrocatalysis technology with biological methods due to high microbial toxicity.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] A composite three-dimensional electrode system that does not increase the salinity of the effluent from low-salinity electrolysis includes a low-salinity electrochemical oxidation device body, an anode plate, a polymer membrane assembly, and a cathode plate. The low-salinity electrochemical oxidation device body is provided with an inlet and an outlet system. A main reaction zone is provided in the middle of the low-salinity electrochemical oxidation device body. The polymer membrane assembly is located in the main reaction zone. The anode plate and the cathode plate are respectively located at both ends of the low-salinity electrochemical oxidation device body. The anode plate is located near the inlet end of the low-salinity electrochemical oxidation device body, and the cathode plate is located near the outlet system end of the low-salinity electrochemical oxidation device body. The polymer membrane assembly is located between the anode plate and the cathode plate.

[0008] Furthermore, the polymer membrane module includes a plurality of conductive reverse osmosis membrane bags arranged in an array. The bottom clips of each conductive reverse osmosis membrane bag are connected to the body of the low-salinity electrochemical oxidation device. The conductive reverse osmosis membrane bags are fixed to the body of the low-salinity electrochemical oxidation device via the bottom clips to ensure that the opening of the conductive reverse osmosis membrane bag faces the direction of the incoming water.

[0009] Furthermore, the microcosm electrode wire is connected to a conductive reverse osmosis membrane bag, and the conductive reverse osmosis membrane bag contains electrolyte salts.

[0010] Furthermore, the microcosm electrode wire includes a microcosm positive electrode and a microcosm negative electrode. The microcosm positive electrode is connected to the opening of the conductive reverse osmosis membrane bag, and the microcosm negative electrode is connected to the bottom of the conductive reverse osmosis membrane bag. The buckle is set at the bottom of the conductive reverse osmosis membrane bag, and the opening of the conductive reverse osmosis membrane bag is set facing the water inflow direction of the anode plate.

[0011] Furthermore, a first main reaction zone mesh plate is provided between the anode plate and the polymer membrane assembly, and the first main reaction zone mesh plate is provided with a plurality of first main reaction zone mesh holes. A second main reaction zone mesh plate is provided between the cathode plate and the polymer membrane assembly, and the second main reaction zone mesh plate is provided with a plurality of second main reaction zone mesh holes.

[0012] A method for preparing a composite three-dimensional electrode that does not increase the salinity of water electrolyzed from low-salinity water includes the following steps:

[0013] (1) Preparation of microcosm electrode wire

[0014] 1) Preparation of microcosm negative electrode: 200 mesh nickel powder, copper powder, bismuth powder and urea are mixed evenly in a molar ratio of 3:5:2:2, extruded into shape using a mold, and sintered in hydrogen at 950℃ for 1 hour to obtain microcosm negative electrode;

[0015] 2) Preparation of the microcosm cathode: An anode coating containing lead dioxide, iridium dioxide, tantalum pentoxide, and ethylene glycol is uniformly sprayed onto the surface of a pretreated Ti wire substrate. The coating thickness is 0.8±0.1μm. After drying in a tube furnace, the microcosm cathode is obtained. The molar ratio of lead dioxide, iridium dioxide, tantalum pentoxide, and ethylene glycol in the anode coating is 2:6:1:2.

[0016] (2) Preparation of conductive reverse osmosis membrane bags

[0017] 1) Preparation of conductive matrix for conductive reverse osmosis membrane bags: Using a mixture of PEDOT:PSS, PEG 400, PAN and DMF in a molar ratio of 10:5:30:55 and ultrasonically dispersed for 2 hours as a spinning agent, and polyester yarn as the yarn core, electrospinning was carried out under the conditions of 8 kV voltage, 10 cm receiving distance and 0.5 mL / h flow rate. After drying in an oven, the conductive matrix for conductive reverse osmosis membrane bags was obtained.

[0018] 2) Growth of PA separation layer and oxide layer: After plasma treatment of the conductive substrate of the conductive reverse osmosis membrane bag with argon for 5 min, it is soaked in 1 mol / L liquid alkali for 30 min. After removing excess droplets with nitrogen, it is soaked in 3 wt% MPD solution for 3 min. Then, it is soaked in a mixture of TMC, lead dioxide, iridium dioxide and n-hexane in a molar ratio of 1:10:20:90 and ultrasonically dispersed for 2 h for 10 min. Finally, it is heat-treated to obtain the conductive reverse osmosis membrane bag.

[0019] (3) Fabrication of composite three-dimensional electrodes

[0020] The arc-shaped microcosm positive electrode is fixed to the opening of the conductive reverse osmosis membrane bag using conductive adhesive to ensure the shape of the opening. The microcosm negative electrode is fixed to the bottom of the tail of the conductive reverse osmosis membrane bag using conductive adhesive to ensure that the tail sinks and prevents the electrolyte salt from being washed away by water. A certain amount of electrolyte salt is loaded into the conductive reverse osmosis membrane bag to obtain a composite three-dimensional electrode.

[0021] Further, in step (1) 2), the spraying pressure is 0.45 MPa.

[0022] Further, in step (1) 2), the drying temperature is 120°C and the drying time is 30 min.

[0023] Further, in step (2) 1), the drying temperature is 60-80℃ and the drying time is 45min.

[0024] Further, in step (2)2), the temperature of the heat treatment is 80°C and the time of the heat treatment is 10 min.

[0025] The present invention, by adopting the above-described technical solution, has the following beneficial effects:

[0026] 1. The coupling effect between the three-dimensional electrode and the galvanic cell set in this invention significantly improves the electrocatalytic effect and increases energy utilization efficiency.

[0027] 2. The numerous conductive reverse osmosis membrane bags in this invention form numerous streams of high-salinity concentrate, improving the conductivity of the wastewater; at the same time, the conductive reverse osmosis membrane bags reduce the salinity and microbial toxicity of the effluent by intercepting electrolyte salts and oxidative free radicals.

[0028] 3. The polymer membrane bag set in this invention degrades the polymer organic matter into small molecule organic matter, and the total effluent of the system is low-salt, low-microbial-toxicity, biodegradable organic wastewater. It can be combined with biological methods to achieve effluent discharge that meets standards, shorten the electrocatalytic time, and reduce the overall operating cost of the system. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of the composite three-dimensional electrode system of the present invention;

[0030] Figure 2 This is a schematic diagram of the polymer membrane bag of the present invention in a dry state;

[0031] Figure 3 This is a schematic diagram of the polymer membrane bag of the present invention in a water-saturated state.

[0032] In the attached diagram, 0-the main body of the low-salinity electrochemical oxidation device, 1-water inlet, 2-anode plate, 3-first main reaction zone mesh plate, 4-first main reaction zone mesh, 5-main reaction zone, 6-polymer membrane module, 7-second main reaction zone mesh plate, 8-second main reaction zone mesh, 9-cathode plate, 10-water outlet system, 11-electrolyte salt, 12-microcosm positive electrode, 13-conductive reverse osmosis membrane bag, 14-microcosm negative electrode, and 15-clamp. Detailed Implementation

[0033] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and preferred embodiments. However, it should be noted that many details listed in the specification are merely to provide the reader with a thorough understanding of one or more aspects of the invention, and these aspects of the invention can be implemented even without these specific details.

[0034] like Figure 1As shown, a composite three-dimensional electrode system that does not increase the salinity of the effluent from low-salinity electrolysis includes a low-salinity electrochemical oxidation device body 0, an anode plate 2, a polymer membrane module 6, and a cathode plate 9. The low-salinity electrochemical oxidation device body 0 is respectively provided with an inlet 1 and an outlet system 10. A main reaction zone 5 is located in the middle of the interior of the low-salinity electrochemical oxidation device body 0. The polymer membrane module 6 is located within the main reaction zone 5. The anode plate 2 and the cathode plate 9 are respectively located at opposite ends of the interior of the low-salinity electrochemical oxidation device body 0, with the anode plate 2 positioned near the inlet 1 and the cathode plate 9 positioned near the outlet system 10. The polymer membrane module 6 is located between the anode plate 2 and the cathode plate 9. Wastewater enters the low-salinity electrochemical oxidation device body 0 through the inlet 1, enters through the anode plate, and flows with the water flow into the polymer membrane module 6 through the bag opening. After the pollutants in the wastewater are removed, the clean water flows out from the outlet system 10.

[0035] In an embodiment of the present invention, a first main reaction zone mesh plate 3 is disposed between the anode plate 2 and the polymer membrane assembly 6, and the first main reaction zone mesh plate 3 is provided with a plurality of first main reaction zone mesh holes 4. A second main reaction zone mesh plate 7 is disposed between the cathode plate 9 and the polymer membrane assembly 6, and the second main reaction zone mesh plate 7 is provided with a plurality of second main reaction zone mesh holes 8. The main reaction zone mesh plate can intercept impurities, and wastewater enters the polymer membrane assembly 6 through the main reaction zone mesh holes.

[0036] like Figure 2-3As shown, the polymer membrane module 6 includes several conductive reverse osmosis membrane bags 13, which are arranged in an array. The bottom clips 15 of each conductive reverse osmosis membrane bag 13 are connected to the body 0 of the low-salinity electrochemical oxidation device. The conductive reverse osmosis membrane bags 13 are fixed to the body 0 of the low-salinity electrochemical oxidation device via the bottom clips 15 to ensure that the opening of the conductive reverse osmosis membrane bag 13 faces the incoming water direction. The microcosm electrode wire is connected to the conductive reverse osmosis membrane bag 13, and electrolyte salt 11 is placed inside the conductive reverse osmosis membrane bag 13. The microcosm electrode wire includes a microcosm positive electrode 12 and a microcosm negative electrode 14. The microcosm positive electrode 12 is fixed to the opening of the conductive reverse osmosis membrane bag 13 to ensure the shape of the opening. The microcosm negative electrode 14 is fixed to the bottom of the conductive reverse osmosis membrane bag 13 to ensure that the bottom of the bag sinks and prevents the electrolyte salt from being washed away by water. The buckle 15 is set at the bottom of the conductive reverse osmosis membrane bag 13. The opening of the conductive reverse osmosis membrane bag 13 faces the incoming water direction of the anode plate 2. The conductive reverse osmosis membrane bag 13 is conductive and has lead dioxide and iridium dioxide oxidizing substances evenly distributed on its surface. Each conductive reverse osmosis membrane bag 13 can be regarded as a three-dimensional electrode particle, which together with the anode plate 2 and the cathode plate 9 constitutes a three-dimensional electrode, increasing the contact area between the electrode and the pollutants. The microcosm positive electrode 12, the microcosm negative electrode 14, and the conductive reverse osmosis membrane bag 13 constitute a galvanic cell. Countless conductive reverse osmosis membrane bags 13 form countless galvanic cell microcosms in the system. Wastewater enters through anode plate 2 and flows into conductive reverse osmosis membrane bag 13 through the bag opening. The dissolved electrolyte salts 11 react with electrons provided by the external circuit in the wastewater to generate ·OH, ClO·, and ·SO4. - Oxidizing free radicals oxidize and remove pollutants such as organic matter, and are then reduced to their original state. Pollutants are oxidized and removed through the action of a three-dimensional electrode and a galvanic cell. Clean water flows out of the system from the tail of the conductive reverse osmosis membrane bag 13 through the cathode plate 9, while electrolyte salts and residual oxidizing free radicals are intercepted in the conductive reverse osmosis membrane bag 13. The coupling of the three-dimensional electrode and the galvanic cell significantly improves the electrocatalytic effect; numerous membrane bags form numerous streams of concentrate, increasing the conductivity of the wastewater; the membrane bag interception effect reduces the salinity and microbial toxicity of the effluent; the total effluent from the system is low-salt, low-microbial-toxicity, biodegradable wastewater, which can be combined with biological methods to achieve effluent discharge compliance.

[0037] A method for preparing a composite three-dimensional electrode that does not increase the salinity of water electrolyzed from low-salinity water includes the following steps:

[0038] (1) Preparation of microcosm electrode wire

[0039] 1) Preparation of microcosm negative electrode: 200 mesh nickel powder, copper powder, bismuth powder and urea are mixed evenly in a molar ratio of 3:5:2:2, extruded into shape using a mold, and sintered in hydrogen at 950℃ for 1 hour to obtain microcosm negative electrode;

[0040] 2) Preparation of the microcosm cathode: An anode coating comprising lead dioxide, iridium dioxide, tantalum pentoxide, and ethylene glycol was uniformly sprayed onto the surface of a pretreated Ti wire substrate. The coating thickness was 0.8 ± 0.1 μm. After drying in a tube furnace, the microcosm cathode was obtained. The spraying pressure was 0.45 MPa; the drying temperature was 120 °C; and the drying time was 30 min. The molar ratio of lead dioxide, iridium dioxide, tantalum pentoxide, and ethylene glycol in the anode coating was 2:6:1:2.

[0041] (2) Preparation of conductive reverse osmosis membrane bags

[0042] 1) Preparation of conductive substrate for conductive reverse osmosis membrane bags: Using a mixture of PEDOT:PSS, PEG 400, PAN and DMF in a molar ratio of 10:5:30:55 and ultrasonically dispersed for 2 hours as a spinning agent, and polyester yarn as the yarn core, electrospinning was performed under the conditions of 8 kV voltage, 10 cm receiving distance, and 0.5 mL / h flow rate. After drying in an oven, the conductive substrate for conductive reverse osmosis membrane bags was obtained; the drying temperature was 60-80℃, and the drying time was 45 min.

[0043] 2) Growth of PA separation layer and oxide layer: After plasma treatment of the conductive substrate of the conductive reverse osmosis membrane bag with argon for 5 min, it is soaked in 1 mol / L liquid alkali for 30 min. After removing excess droplets with nitrogen, it is soaked in 3 wt% MPD solution for 3 min. Then, it is soaked in a mixture of TMC, lead dioxide, iridium dioxide and n-hexane in a molar ratio of 1:10:20:90 and ultrasonically dispersed for 2 h for 10 min. Finally, it is heat-treated to obtain the conductive reverse osmosis membrane bag. The heat treatment temperature is 80℃ and the heat treatment time is 10 min.

[0044] (3) Fabrication of composite three-dimensional electrodes

[0045] The arc-shaped microcosm positive electrode is fixed to the opening of the conductive reverse osmosis membrane bag using conductive adhesive to ensure the shape of the opening. The microcosm negative electrode is fixed to the bottom of the tail of the conductive reverse osmosis membrane bag using conductive adhesive to ensure that the tail sinks and prevents the electrolyte salt from being washed away by water. A certain amount of electrolyte salt is loaded into the conductive reverse osmosis membrane bag to obtain a composite three-dimensional electrode.

[0046] Example 1: Biochemical wastewater from a pulp and paper mill

[0047] The effluent from the biochemical treatment section of an operating pulp and paper mill was used as the influent for this experiment. Specific water quality details are shown in Table 1.1. The COD concentration was 1436 mg / L, and the Cl... - SO4 2-The concentrations of salt and total dissolved solids (TDS) were 505.23, 245.45, and 1457.99 mg / L, respectively. The salt content was low and the conductivity was poor. The total residual chlorine in the influent was 0 mg / L.

[0048] In this experiment, the Ti / RuO2-IrO2 electrode was used as the control group, and the composite three-dimensional electrode of this invention was used as the experimental group. Electrocatalytic experiments were conducted using the aforementioned pulp and paper biochemical wastewater as the test water body, with samples taken and analyzed at regular intervals. The experimental operating parameters are shown in Table 1.2. The current density was 250 mA / cm², and the water treatment capacity per unit anode plate area was 0.1 m³. 3 / m 2 The running time is 4.5 hours.

[0049] The effluent quality after electrocatalysis is shown in Table 1.1. After 4.5 hours of electrocatalysis, the COD concentrations in the control and experimental groups were 242 and 5 mg / L, respectively, with removal rates of 97.08% and 99.65%. The COD concentration in the experimental group was 237 mg / L lower than that in the control group, and the average COD removal per ton of water was 1.88 mg·L⁻¹ / (KW·ht) higher than that in the control group. This indicates that the composite three-dimensional electrode of this invention is more effective and has higher energy utilization efficiency than the commercially available Ti / RuO₂-IrO₂ electrode. The Cl₂ in the effluent of the experimental group... - SO4 2- Both the TDS concentration and the total residual chlorine concentration were significantly lower than those of the influent, and the total residual chlorine concentration was also 3 mg / L lower. This indicates that the wastewater salinity decreased and the microbial toxicity was lower after the composite three-dimensional electrode electrocatalytic treatment of the present invention. It can shorten the electrocatalytic time and achieve wastewater discharge in compliance with standards and reduce the total operating cost through secondary biological treatment.

[0050] Table 1.1 Influent and Effluent Water Quality

[0051]

[0052] Table 1.2 Operating Parameters

[0053]

[0054] Example 2: Wastewater from a typical cotton spinning mill

[0055] The effluent from a conventional cotton mill in operation was used as the influent for this experiment. Specific water quality details are shown in Table 2.1. The COD concentration was 3547 mg / L, and the Cl... - SO4 2- The concentrations of salt and total dissolved solids (TDS) were 1426.54, 254.36, and 3297.86 mg / L, respectively. The salt content was low and the conductivity was poor. The total residual chlorine in the influent was 0 mg / L.

[0056] This experiment used a Ti / RuO2-IrO2 electrode as the control group and the composite three-dimensional electrode of this invention as the experimental group. Electrocatalytic experiments were conducted using the effluent from a typical cotton mill as the test water body, with samples taken and analyzed at regular intervals. The experimental operating parameters are shown in Table 2.2. The current density was 250 mA / cm², and the water treatment capacity per unit anode plate area was 0.1 m³. 3 / m 2 The running time is 5 hours.

[0057] The effluent quality after electrocatalysis is shown in Table 2.1. After 5 hours of electrocatalysis, the COD concentrations in the control group and the experimental group were 657 and 242 mg / L, respectively, with removal rates of 81.45% and 93.18%. The COD concentration in the experimental group was 415 mg / L lower than that in the control group, and the average COD removal per ton of water was 7.00 mg / L higher than that in the control group. -1 / (KW.ht), indicating that the composite three-dimensional electrode of the present invention performs better than the commercially available Ti / RuO2-IrO2 electrode and has higher energy utilization efficiency. The Cl in the effluent of the experimental group... - SO4 2- Both the TDS concentration and the total residual chlorine concentration were significantly lower than those of the influent, and the total residual chlorine concentration was also 12 mg / L lower. This indicates that the wastewater salinity decreased and the microbial toxicity was lower after the composite three-dimensional electrode electrocatalytic treatment of the present invention. It can shorten the electrocatalytic time and achieve the standard discharge of wastewater and reduce the total operating cost through secondary biological treatment.

[0058] Table 2.1 Influent and Effluent Water Quality

[0059]

[0060] Table 2.2 Operating Parameters

[0061]

[0062] Example 3 Wastewater from a Petrochemical Product

[0063] The effluent from a currently operating petrochemical plant was used as the influent for this experiment. Specific water quality details are shown in Table 3.1. The COD concentration was 2547 mg / L, and the Cl... - SO4 2- The concentrations of salt and total dissolved solids (TDS) were 425.68, 358.66, and 1514.25 mg / L, respectively. The salt content was low and the conductivity was poor. The total residual chlorine in the influent was 0 mg / L.

[0064] In this experiment, the Ti / RuO2-IrO2 electrode was used as the control group, and the composite three-dimensional electrode of this invention was used as the experimental group. Electrocatalytic experiments were conducted using the aforementioned petrochemical wastewater as the test water, with samples taken and analyzed at regular intervals. The experimental operating parameters are shown in Table 3.2. The current density was 250 mA / cm², and the water treatment capacity per unit anode plate area was 0.1 m³.3 / m 2 The running time is 5 hours.

[0065] The effluent quality after electrocatalysis is shown in Table 3.1. After 5 hours of electrocatalysis, the COD concentrations in the control group and the experimental group were 314 and 105 mg / L, respectively, with removal rates of 81.45% and 93.18%. The COD concentration in the experimental group was 209 mg / L lower than that in the control group, and the average COD removal per ton of water was 11.23 mg / L higher than that in the control group. -1 / (KW.ht), indicating that the composite three-dimensional electrode of the present invention performs better than the commercially available Ti / RuO2-IrO2 electrode and has higher energy utilization efficiency. The Cl in the effluent of the experimental group... - SO4 2- Both the TDS concentration and the total residual chlorine concentration were significantly lower than those of the influent, and the total residual chlorine concentration was also 61 mg / L lower. This indicates that the wastewater salinity decreased and the microbial toxicity was lower after the composite three-dimensional electrode electrocatalytic treatment of the present invention. It can shorten the electrocatalytic time and achieve wastewater discharge in compliance with standards and reduce the total operating cost through secondary biological treatment.

[0066] Table 3.1 Influent and Effluent Water Quality

[0067]

[0068] Table 3.2 Operating Parameters

[0069]

[0070] Example 4: Chemical Synthesis Wastewater

[0071] Wastewater from a currently operating chemical synthesis plant was used as the influent for this experiment. Specific water quality details are shown in Table 4.1. The COD concentration was 5214 mg / L, and the Cl... - SO4 2- The concentrations of salt and total dissolved solids (TDS) were 1069.47, 988.22, and 44.25 mg / L, respectively. The salt content was low and the conductivity was poor. The total residual chlorine in the influent was 0 mg / L.

[0072] This experiment used a Ti / RuO2-IrO2 electrode as the control group and the composite three-dimensional electrode of this invention as the experimental group. Electrocatalytic experiments were conducted using the aforementioned chemical synthesis wastewater as the test water body, with samples taken and analyzed at regular intervals. The experimental operating parameters are shown in Table 4.2. The current density was 250 mA / cm², and the water treatment capacity per unit anode plate area was 0.1 m³. 3 / m 2 The runtime is 6 hours.

[0073] The effluent quality after electrocatalysis is shown in Table 4.1. After 6 hours of electrocatalysis, the COD concentrations in the control group and the experimental group were 3715 and 2243 mg / L, respectively, with removal rates of 28.75% and 56.98%. The COD concentration in the experimental group was 1472 mg / L lower than that in the control group, and the average COD removal per ton of water was 20.51 mg / L higher than that in the control group. -1 / (KW.ht), indicating that the composite three-dimensional electrode of the present invention performs better than the commercially available Ti / RuO2-IrO2 electrode and has higher energy utilization efficiency. The Cl in the effluent of the experimental group... - SO4 2- Both the TDS concentration and the total residual chlorine concentration were significantly lower than those of the influent, and the total residual chlorine concentration was also 233 mg / L lower. This indicates that the wastewater salinity decreased and the microbial toxicity was lower after the composite three-dimensional electrode electrocatalytic treatment of the present invention. It can shorten the electrocatalytic time and achieve the standard discharge of wastewater and reduce the total operating cost through secondary biological treatment.

[0074] Table 4.1 Influent and Effluent Water Quality

[0075]

[0076] Table 4.2 Operating Parameters

[0077]

[0078] Example 5: Wastewater from a chemical or pharmaceutical company

[0079] Wastewater from a currently operating chemical or pharmaceutical plant was used as the influent for this experiment. Specific water quality details are shown in Table 5.1. The COD concentration was 15465 mg / L, and the Cl... - SO4 2- The concentrations of salt and total dissolved solids (TDS) were 655.22, 249.85, and 1764.14 mg / L, respectively. The salt content was low and the conductivity was poor. The total residual chlorine in the influent was 0 mg / L.

[0080] This experiment used a Ti / RuO2-IrO2 electrode as the control group and the composite three-dimensional electrode of this invention as the experimental group. Electrocatalytic experiments were conducted using the aforementioned chemical and pharmaceutical wastewater as the test water body, with samples taken and analyzed at regular intervals. The experimental operating parameters are shown in Table 5.2. The current density was 250 mA / cm², and the water treatment capacity per unit anode plate area was 0.1 m³. 3 / m 2 The running time is 5 hours.

[0081] The effluent quality after electrocatalysis is shown in Table 5.1. After 5 hours of electrocatalysis, the COD concentrations in the control group and the experimental group were 13024 and 8264 mg / L, respectively, with removal rates of 15.78% and 46.56%. The COD concentration in the experimental group was 4760 mg / L lower than that in the control group, and the average COD removal per ton of water was 60.64 mg / L higher than that in the control group. -1 / (KW.ht), indicating that the composite three-dimensional electrode of the present invention performs better than the commercially available Ti / RuO2-IrO2 electrode and has higher energy utilization efficiency. The Cl in the effluent of the experimental group... - SO4 2- Both the TDS concentration and the total residual chlorine concentration were significantly lower than those of the influent, and the total residual chlorine concentration was also 68 mg / L lower. This indicates that the wastewater salinity decreased and the microbial toxicity was lower after the composite three-dimensional electrode electrocatalytic treatment of the present invention. It can shorten the electrocatalytic time, achieve wastewater discharge compliance and reduce the total operating cost through secondary biological treatment.

[0082] Table 5.1 Influent and Effluent Water Quality

[0083]

[0084] Table 5.2 Operating Parameters

[0085]

[0086] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A composite three-dimensional electrode system that does not increase the salinity of water electrolyzed from low-salinity water, characterized in that: The device includes a low-salinity electrochemical oxidation unit body, an anode plate, a polymer membrane module, and a cathode plate. The low-salinity electrochemical oxidation unit body is provided with an inlet and an outlet system. A main reaction zone is provided in the middle of the low-salinity electrochemical oxidation unit body. The polymer membrane module is located in the main reaction zone. The anode plate and the cathode plate are respectively located at both ends of the low-salinity electrochemical oxidation unit body. The anode plate is located near the inlet end of the low-salinity electrochemical oxidation unit body, and the cathode plate is located near the outlet system end of the low-salinity electrochemical oxidation unit body. The polymer membrane module is located between the anode plate and the cathode plate. The polymer membrane module includes several conductive reverse osmosis membrane bags, which are arranged in an array. The buckles at the bottom of the conductive reverse osmosis membrane bags are connected to the body of the low-salinity electrochemical oxidation device. Microcosm electrode wires are connected to a conductive reverse osmosis membrane bag, which contains electrolyte salts. The microcosm electrode wire includes a microcosm positive electrode and a microcosm negative electrode. The microcosm positive electrode is connected to the opening of the conductive reverse osmosis membrane bag, and the microcosm negative electrode is connected to the bottom of the conductive reverse osmosis membrane bag. The buckle is set at the bottom of the conductive reverse osmosis membrane bag, and the opening of the conductive reverse osmosis membrane bag is set facing the water inflow direction of the anode plate.

2. The composite three-dimensional electrode system according to claim 1 that does not increase the salinity of water electrolyzed from low-salinity water, characterized in that: A first main reaction zone mesh plate is provided between the anode plate and the polymer membrane assembly, and the first main reaction zone mesh plate is provided with a plurality of first main reaction zone mesh holes. A second main reaction zone mesh plate is provided between the cathode plate and the polymer membrane assembly, and the second main reaction zone mesh plate is provided with a plurality of second main reaction zone mesh holes.

3. A method for preparing a composite three-dimensional electrode that does not increase the salinity of the water electrolyzed from low-salinity water, according to any one of claims 1-2, characterized in that: Includes the following steps: (1) Preparation of microcosm electrode wire 1) Preparation of microcosm negative electrode: 200 mesh nickel powder, copper powder, bismuth powder and urea are mixed evenly in a molar ratio of 3:5:2:2, extruded and sintered in hydrogen at 950℃ for 1 hour to obtain microcosm negative electrode; 2) Preparation of the microcosm cathode: An anode coating containing lead dioxide, iridium dioxide, tantalum pentoxide, and ethylene glycol is uniformly sprayed onto the surface of a pretreated Ti wire substrate. The coating thickness is 0.8 ± 0.1 μm. After drying, the microcosm cathode is obtained. The molar ratio of lead dioxide, iridium dioxide, tantalum pentoxide, and ethylene glycol in the anode coating is 2:6:1:

2. (2) Preparation of conductive reverse osmosis membrane bags 1) Preparation of conductive matrix for conductive reverse osmosis membrane bags: Using a mixture of PEDOT:PSS, PEG 400, PAN and DMF in a molar ratio of 10:5:30:55 and ultrasonically dispersed for 2 hours as a spinning agent, and polyester yarn as the yarn core, electrospinning was carried out under the conditions of 8 kV voltage, 10 cm receiving distance and 0.5 mL / h flow rate. After drying, the conductive matrix for conductive reverse osmosis membrane bags was obtained. 2) Growth of PA separation layer and oxide layer: After plasma treatment of the conductive substrate of the conductive reverse osmosis membrane bag with argon for 5 min, it is soaked in 1 mol / L liquid alkali for 30 min. After removing excess droplets with nitrogen, it is soaked in 3 wt% MPD solution for 3 min. Then, it is soaked in a mixture of TMC, lead dioxide, iridium dioxide and n-hexane in a molar ratio of 1:10:20:90 and ultrasonically dispersed for 2 h for 10 min. Finally, it is heat-treated to obtain the conductive reverse osmosis membrane bag. (3) Fabrication of composite three-dimensional electrodes The positive electrode of the microcosm is fixed to the opening of the conductive reverse osmosis membrane bag using conductive adhesive, and the negative electrode of the microcosm is fixed to the bottom of the conductive reverse osmosis membrane bag using conductive adhesive. A certain amount of electrolyte salt is then loaded into the conductive reverse osmosis membrane bag to obtain a composite three-dimensional electrode.

4. The method for preparing a composite three-dimensional electrode that does not increase the salinity of the water electrolyzed from low-salinity water according to claim 3, characterized in that: In steps (1) and (2), the spraying pressure is 0.45 MPa.

5. The method for preparing a composite three-dimensional electrode that does not increase the salinity of the water electrolyzed from low-salinity water according to claim 3, characterized in that: In steps (1) and (2), the drying temperature is 120°C and the drying time is 30 minutes.

6. The method for preparing a composite three-dimensional electrode that does not increase the salinity of the water electrolyzed from low-salinity water according to claim 3, characterized in that: In step (2)1), the drying temperature is 60-80℃ and the drying time is 45min.

7. The method for preparing a composite three-dimensional electrode that does not increase the salinity of water electrolyzed from low-salinity water according to claim 3, characterized in that: In step (2)2), the temperature of the heat treatment is 80°C and the time of the heat treatment is 10 min.

Images