An oxygen self-sufficient fluid bipolar electrochemical filtration system and its application

Abstract

The present invention provides an oxygen self-sufficient fluid bipolar electrochemical filtration system and its application, which relate to the technical field of sewage treatment. The oxygen self-sufficient fluid bipolar electrochemical filtration system comprises a shell, a reference electrode, and a titanium ring, an anode, a polytetrafluoroethylene membrane, a cathode and a titanium sheet arranged in sequence inside the shell; wherein the anode is an iridium oxide-loaded titanium mesh electrode, the cathode is a carbon nanotube confined iron oxide electrode, and the reference electrode is an Ag / AgCl electrode. After the organic micro-pollutant wastewater and silicate are mixed, they are passed into the oxygen self-sufficient fluid bipolar electrochemical filtration system, and after being connected to a three-electrode system, they are energized to remove the organic micro-pollutants. The filtration system can efficiently degrade typical organic micro-pollutants in water, and can achieve a higher current density at a lower voltage, thereby reducing the energy consumption required for treatment.

Description

Technical Field

[0001] The invention relates to the technical field of sewage treatment, and in particular to an oxygen self-supplied fluid bipolar electrochemical filtration system and application thereof. Background Art

[0002] In recent years, the selective removal of organic micropollutants in aquatic environments has attracted worldwide attention. Due to the high toxicity, low concentration and difficulty in degradation of organic micropollutants, current wastewater treatment technologies are usually difficult to remove micropollutants. Advanced oxidation technologies (such as Fenton and photocatalytic technologies) can produce highly active hydroxyl radicals (HO·), but the wastewater composition is complex and the coexisting substances may ineffectively consume active substances such as HO·, making it difficult to achieve selective removal of organic micropollutants.

[0003] In water treatment, singlet oxygen ( 1 O 2 )-mediated non-radical oxidation has become a hot topic of research. Compared with HO·, it has high activity triggered by empty π* orbitals, relatively longer lifetime (microseconds and nanoseconds) and migration distance, wider pH applicable range, and less interference from the background matrix of water. Studies have shown that singlet oxygen exhibits stronger selective degradation ability for electron-rich organic matter (such as antibiotic pollutants such as sulfadiazine, sulfamethoxazole and tetracycline). At present, singlet oxygen is mainly synthesized by photosensitization and enzymatic methods in biological systems, but it is still necessary to overcome the dark toxicity caused by photosensitizers and the stringent requirements of cells on factors such as pH and temperature.

[0004] The electrocatalytic method has unique advantages such as no need for reagents, easy operation and high degree of automation. It can synthesize key precursors (such as hydrogen peroxide and hypochlorite, etc.) in a flexible way, and then synthesize singlet oxygen in situ; in addition, it can also achieve efficient activation of precursors with the assistance of electric fields to generate singlet oxygen (such as cathode activation of permonosulfate and anode excitation of ferrocene). However, the current electrocatalytic method generally has problems such as many by-products, long reaction time, and high energy consumption, making it difficult to achieve engineering application of wastewater treatment technology.

[0005] Therefore, how to develop an oxygen-self-sufficient fluid bipolar electrochemical filtration system and use it to treat wastewater containing organic micropollutants has important academic value and environmental significance for the research and development of new technologies for efficient and low-energy electrocatalytic industrial wastewater treatment and the realization of selective removal of organic micropollutants. Summary of the invention

[0006] The purpose of the present invention is to provide an oxygen self-sufficient fluid bipolar electrochemical filtration system and its application to solve the problems of long reaction time, large number of by-products and high energy consumption in the existing electrocatalytic method for treating wastewater containing organic micropollutants.

[0007] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0008] The invention provides an oxygen self-supplied fluid bipolar electrochemical filtering system, comprising a shell, a reference electrode, and a titanium ring, an anode, a polytetrafluoroethylene membrane, a cathode and a titanium sheet which are sequentially arranged inside the shell.

[0009] Preferably, the anode is an iridium oxide-loaded titanium mesh electrode, the cathode is a carbon nanotube-confined iron oxide electrode, and the reference electrode is an Ag / AgCl electrode.

[0010] Preferably, the method for preparing the iridium oxide loaded titanium mesh electrode is to load iridium oxide on the surface of the titanium mesh by electrodeposition.

[0011] Preferably, the preparation method of the iridium oxide loaded titanium mesh electrode comprises the following steps: using the titanium mesh as a working electrode, a platinum sheet as a counter electrode, Ag / AgCl as a reference electrode, and a solution containing iridium chloride, oxalic acid, and potassium carbonate as an electrolyte solution, and electrodepositing the loaded iridium oxide on the surface of the titanium mesh;

[0012] The concentration of iridium chloride in the electrolyte solution is 3.7-5.6 mmol / L, the concentration of oxalic acid is 47-70 mmol / L, and the concentration of potassium carbonate is 14.5-28.9 mmol / L;

[0013] The current density of electrodeposition is 0.10~0.20mA / cm 2 The electrodeposition time is 10 to 30 minutes.

[0014] Preferably, the method for preparing the carbon nanotube confined iron oxide electrode comprises the following steps:

[0015] 1) mixing the modified carbon nanotubes and an iron salt solution, drying and calcining to obtain carbon nanotube confined iron oxide powder;

[0016] 2) The carbon nanotube-confined iron oxide powder is loaded on a polytetrafluoroethylene membrane to obtain a carbon nanotube-confined iron oxide electrode.

[0017] Preferably, in the method for preparing the carbon nanotube confined iron oxide electrode, the iron salt solution comprises an iron nitrate solution, the solvent of the iron salt solution comprises ethanol and / or acetone, and the concentration of the iron salt solution is 0.9 to 3.6 mmol / L;

[0018] The modified carbon nanotubes and the iron salt solution are added in a ratio of 50-150 mg: 10-30 mL;

[0019] The calcination temperature is 120-160° C., and the calcination time is 8-14 hours.

[0020] Preferably, a water inlet is provided at one end of the shell close to the titanium ring, a water outlet is provided at one end of the shell close to the titanium sheet, and a reference electrode is placed on the water outlet side to contact the outflowing liquid.

[0021] The present invention also provides an application of the above oxygen self-sufficient fluid bipolar electrochemical filtration system in treating organic micro-pollutant wastewater, and the specific application method is as follows:

[0022] The organic micro-pollutant wastewater and silicate are mixed to obtain mixed wastewater, and the mixed wastewater is passed into the above-mentioned oxygen self-sufficient fluid bipolar electrochemical filtration system for electrical treatment in a circulating flow mode to remove the organic micro-pollutants.

[0023] Preferably, the organic micropollutants include one or more of bisphenol A, tetracycline, sulfamethoxazole and norfloxacin, and the concentration of the organic micropollutants in the mixed wastewater is 5 to 30 mg / L; the concentration of silicate in the mixed wastewater is 5 to 15 mmol / L.

[0024] Preferably, the current density of the energization treatment is 1.5 to 3.0 mA / cm 2 , the power-on treatment time is 2.0~4.0h;

[0025] The flow rate of the mixed wastewater passing into the oxygen self-sufficient fluid bipolar electrochemical filtration system is 2.0-6.0 mL / min.

[0026] The present invention has at least the following beneficial effects:

[0027] 1) The oxygen self-sufficient fluid bipolar electrochemical filtration system provided by the present invention can target and induce the generation of singlet oxygen. Oxygen is continuously generated at the anode and supplied to the cathode, hydrogen peroxide is generated on the cathode surface, and then singlet oxygen generation is induced under confined conditions, which can efficiently degrade typical organic micropollutants in water. When it is used to treat wastewater containing organic micropollutants, the additional addition of external reagents is effectively avoided, saving treatment costs.

[0028] 2) Singlet oxygen is the only active oxidizing species in the system of the present invention, which can selectively oxidize electron-rich aromatic organic pollutants in aqueous solutions and on electrode surfaces; the present invention helps to reveal the functional coordination laws and coupling mechanisms of bipolar electrodes, and clarifies the related mechanisms of targeted induction of singlet oxygen by non-iron-based catalysts under confined conditions, and has important scientific and academic value.

[0029] 3) The present invention adopts a method that combines membrane separation with electrochemical technology and operates in a flow-through operation mode. In this system, convection-enhanced mass transfer can significantly enhance the transfer process of target pollutant molecules to the active sites on the membrane surface. It has the advantages of being easy to control and scalable, and is easy to promote engineering applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 The degradation efficiency diagram of tetracycline in aqueous solution of Example 1 and Comparative Examples 1-2 is shown;

[0031] Figure 2 The linear voltammetric curves of different anode materials in the oxygen self-sufficient fluid bipolar electrochemical filtration system in Example 1 and Comparative Example 3;

[0032] Figure 3 The degradation efficiency diagram of tetracycline in aqueous solution of different matrices according to Examples 1 to 3 is shown;

[0033] Figure 4 The electron paramagnetic resonance spectrum of the intensity change of the active species during the reaction process in Example 1;

[0034] Figure 5 It is a schematic structural diagram of the oxygen self-sufficient fluid bipolar electrochemical filtration system of the present invention. DETAILED DESCRIPTION

[0035] The invention provides an oxygen self-supplied fluid bipolar electrochemical filtering system, comprising a shell, a reference electrode, and a titanium ring, an anode, a polytetrafluoroethylene membrane, a cathode and a titanium sheet which are sequentially arranged inside the shell.

[0036] In the present invention, the anode is an iridium oxide-loaded titanium mesh electrode, the cathode is a carbon nanotube-confined iron oxide electrode, and the reference electrode is an Ag / AgCl electrode.

[0037] In the present invention, the polytetrafluoroethylene film between the anode and the cathode plays an insulating role.

[0038] In the present invention, the oxygen self-sufficient fluid bipolar electrochemical filtration system is a flow-through three-electrode electrocatalytic filtration system, and the operation mode is a circulation flow mode.

[0039] In the present invention, the preparation method of the iridium oxide loaded titanium mesh electrode is to load iridium oxide on the surface of the titanium mesh by electrodeposition.

[0040] In the present invention, the preparation method of the iridium oxide loaded titanium mesh electrode comprises the following steps: using the titanium mesh as the working electrode, the platinum sheet as the counter electrode, and Ag / AgCl as the reference electrode, and using a solution containing iridium chloride, oxalic acid, and potassium carbonate as the electrolyte solution, and electrodepositing the loaded iridium oxide on the surface of the titanium mesh.

[0041] In the present invention, the concentration of iridium chloride in the electrolyte solution is 3.7 to 5.6 mmol / L, preferably 4.0 to 5.3 mmol / L, more preferably 4.2 to 5.0 mmol / L, more preferably 4.4 to 4.6 mmol / L, and even more preferably 4.5 mmol / L; the concentration of oxalic acid is 47 to 70 mmol / L, preferably 50 to 65 mmol / L, more preferably 52 to 62 mmol / L, more preferably 54 to 60 mmol / L, and even more preferably 56 mmol / L; the concentration of potassium carbonate is 14.5 to 28.9 mmol / L, preferably 16.6 to 26.8 mmol / L, more preferably 18.8 to 24.6 mmol / L, more preferably 21.0 to 22.4 mmol / L, and even more preferably 21.7 mmol / L.

[0042] In the present invention, the current density of the electrodeposition is 0.10 to 0.20 mA / cm 2 , preferably 0.11 to 0.19 mA / cm 2 , more preferably 0.12 to 0.18 mA / cm 2 , more preferably 0.13 to 0.17 mA / cm 2 , and preferably 0.16 mA / cm 2 The electrodeposition time is 10 to 30 min, preferably 12 to 28 min, more preferably 15 to 25 min, more preferably 18 to 22 min, and even more preferably 20 min.

[0043] In the present invention, the area of ​​the titanium mesh is preferably 7.1 cm 2 The electrodeposition method preferably uses a three-electrode system of CHI660E to electrodeposit iridium oxide on the titanium mesh.

[0044] In the present invention, after the electrodeposition is completed, the step of drying the iridium oxide-loaded titanium mesh electrode is also included. The drying temperature is 100-140°C, preferably 105-135°C, more preferably 110-130°C, more preferably 115-125°C, and even more preferably 120°C; the drying time is 5-15min, preferably 7-13min, more preferably 9-11min, and more preferably 10min.

[0045] In the present invention, the method for preparing the carbon nanotube confined iron oxide electrode comprises the following steps:

[0046] 1) mixing the modified carbon nanotubes and an iron salt solution, drying and calcining to obtain carbon nanotube confined iron oxide powder;

[0047] 2) The carbon nanotube-confined iron oxide powder is loaded on a polytetrafluoroethylene membrane to obtain a carbon nanotube-confined iron oxide electrode.

[0048] In the present invention, the iron salt solution in the preparation method of the carbon nanotube confined iron oxide electrode includes a ferric nitrate solution, the solvent of the iron salt solution includes ethanol and / or acetone, and the concentration of the iron salt solution is 0.9 to 3.6 mmol / L, preferably 1.4 to 3.1 mmol / L, further preferably 1.8 to 2.9 mmol / L, more preferably 2.4 to 2.8 mmol / L, and even more preferably 2.7 mmol / L.

[0049] In the present invention, the addition ratio of the modified carbon nanotubes to the iron salt solution is 50-150 mg:10-30 mL, preferably 65-135 mg:12-28 mL, further preferably 80-120 mg:15-25 mL, more preferably 95-105 mg:18-22 mL, and even more preferably 100 mg:20 mL.

[0050] In the present invention, the modified carbon nanotubes and the iron salt solution are mixed and then ultrasonically dispersed for 0.5 to 2.0 h, preferably 0.8 to 1.8 h, more preferably 1.0 to 1.5 h, and even more preferably 1.2 to 1.4 h.

[0051] In the present invention, the calcination temperature is 120-160°C, preferably 125-155°C, more preferably 130-150°C, more preferably 135-145°C, and even more preferably 140°C; the calcination time is 8-14h, preferably 9-13h, more preferably 10-12h, and more preferably 11h.

[0052] In the present invention, in the preparation method of the carbon nanotube confined iron oxide electrode, after calcination is completed, the solid is washed with a hydrochloric acid solution and then washed with water until neutral. The concentration of the hydrochloric acid solution is 1 to 2 mol / L, preferably 1.2 to 1.8 mol / L, further preferably 1.4 to 1.6 mol / L, and more preferably 1.5 mol / L.

[0053] In the present invention, the preparation method of the modified carbon nanotubes is as follows: carbon nanotubes are mixed with concentrated nitric acid, and heated under reflux to obtain modified carbon nanotubes with open ends.

[0054] In the present invention, the mass volume ratio of the carbon nanotubes to concentrated nitric acid is 100-400 mg:300-700 mL, preferably 150-350 mg:350-650 mL, further preferably 200-300 mg:400-600 mL, more preferably 240-260 mg:450-550 mL, and even more preferably 250 mg:500 mL; the concentration of the concentrated nitric acid is 60-75%, preferably 62-73%, further preferably 65-70%, and even more preferably 68%; the heating reflux time is 8-14 h, preferably 9-13 h, further preferably 10-12 h, and even more preferably 10-11 h.

[0055] In the present invention, after the heating and reflux is completed, the steps of washing with water to neutrality and freeze-drying are also included.

[0056] In the present invention, the method for loading carbon nanotube confined iron oxide powder on a polytetrafluoroethylene membrane is as follows: the carbon nanotube confined iron oxide powder is mixed with 1-methyl-2-pyrrolidone, and ultrasonically dispersed to obtain a carbon nanotube confined iron oxide powder dispersion, and then the carbon nanotube confined iron oxide powder is loaded on the polytetrafluoroethylene membrane by vacuum filtration to obtain a carbon nanotube confined iron oxide electrode.

[0057] In the present invention, the mass volume ratio of the carbon nanotube confined iron oxide powder to 1-methyl-2-pyrrolidone is 30 mg: 10-40 mL, preferably 30 mg: 15-35 mL, more preferably 30 mg: 20-30 mL, and more preferably 30 mg: 25 mL.

[0058] In the present invention, a water inlet is arranged at one end of the shell close to the titanium ring, a water outlet is arranged at one end of the shell close to the titanium sheet, and a reference electrode is placed on the water outlet side to contact the outflowing liquid.

[0059] In the present invention, titanium rods are arranged at both ends of the water outlet and the water inlet of the shell; the titanium rod at the water inlet end is connected to the working electrode clamp of the three-electrode system and is in contact with the titanium ring; the titanium rod at the water outlet end is connected to the auxiliary electrode clamp of the three-electrode system and is in contact with the titanium sheet; one end of the reference electrode is connected to the reference electrode clamp of the three-electrode system, and the other end is placed in the outflow liquid of the water outlet.

[0060] In the present invention, the structure of the oxygen self-sufficient fluid bipolar electrochemical filtration system is as follows: Figure 5 shown.

[0061] In the present invention, the titanium sheet is preferably a titanium sheet having holes on its surface.

[0062] The present invention also provides an application of the above oxygen self-sufficient fluid bipolar electrochemical filtration system in treating organic micro-pollutant wastewater, and the specific application method is as follows:

[0063] The organic micro-pollutant wastewater and silicate are mixed to obtain mixed wastewater, and the mixed wastewater is passed into an oxygen self-supplied fluid bipolar electrochemical filtration system for electrical treatment in a circulating flow mode to remove the organic micro-pollutants.

[0064] In the present invention, the organic micropollutants include one or more of bisphenol A, tetracycline, sulfamethoxazole and norfloxacin, and the concentration of the organic micropollutants in the mixed wastewater is 5 to 30 mg / L, preferably 10 to 25 mg / L, further preferably 18 to 22 mg / L, and more preferably 20 mg / L.

[0065] In the present invention, the concentration of silicate in the mixed wastewater is 5 to 15 mmol / L, preferably 7 to 13 mmol / L, more preferably 9 to 11 mmol / L, and even more preferably 10 mmol / L.

[0066] In the present invention, the pH value of the mixed wastewater is preferably adjusted to 3-9, which may be 3, 4, 5, 6.5, 7, 8, or 9, before it is introduced into the oxygen self-sufficient fluid bipolar electrochemical filtration system.

[0067] In the present invention, the current density of the energization treatment is 1.5 to 3.0 mA / cm 2 , preferably 1.8 to 2.8 mA / cm 2 , more preferably 2.0 to 2.5 mA / cm 2 , more preferably 2.3 to 2.5 mA / cm 2 The time of the electrical treatment is 2.0 to 4.0 h, preferably 2.2 to 3.8 h, more preferably 2.5 to 3.5 h, more preferably 2.8 to 3.2 h, and even more preferably 3 h.

[0068] In the present invention, the flow rate of the mixed wastewater into the oxygen self-sufficient fluid bipolar electrochemical filtration system is 2.0-6.0 mL / min, preferably 2.2-5.0 mL / min, further preferably 2.5-4.0 mL / min, more preferably 2.8-3.5 mL / min, and even more preferably 3.0 mL / min.

[0069] The technical solutions provided by the present invention are described in detail below in conjunction with the embodiments, but they should not be construed as limiting the protection scope of the present invention.

[0070] Example 1

[0071] 1) Preparation of iridium oxide-loaded titanium mesh electrode: 7.1 cm 2The titanium mesh was used as the working electrode, the platinum sheet was used as the counter electrode, and the Ag / AgCl was used as the reference electrode. In a mixed solution containing iridium chloride, oxalic acid, and potassium carbonate, iridium oxide was loaded on the titanium mesh surface by electrodeposition using a three-electrode system of CHI660E. The current density was set to 0.16 mA / cm 2 The electrodeposition time was set to 20 min, the concentration of iridium chloride was 4.5 mmol / L, the concentration of oxalic acid was 56 mmol / L, and the concentration of potassium carbonate was 21.7 mmol / L. After the electrodeposition was completed, the iridium oxide-loaded titanium mesh electrode was placed in a drying oven at 100°C for 15 min.

[0072] 2) Preparation of carbon nanotube confined iron oxide electrode: 250 mg of carbon nanotubes were immersed in 500 mL of 68% concentrated nitric acid solution and heated to reflux for 10 h, then washed with deionized water until neutral, and freeze-dried to obtain modified carbon nanotubes with open ends; 100 mg of modified carbon nanotubes were mixed with 20 mL of 2.7 mmol / L ethanol solution of ferric nitrate nonahydrate, ultrasonically dispersed for 2 h and then dried, the dried solid powder was placed in a magnetic boat and placed in a tubular furnace, heated to 140°C in an air atmosphere and calcined for 10 h, the calcined solid powder was washed once with 1 mol / L hydrochloric acid, and then washed with ultrapure water until the washing liquid was neutral to obtain carbon nanotube confined iron oxide powder. 30 mg of carbon nanotube confined iron oxide powder was mixed with 25 mL of 1-methyl 2-pyrrolidone and ultrasonically dispersed for 0.5 h to obtain a carbon nanotube confined iron oxide powder dispersion; the carbon nanotube confined iron oxide powder was loaded onto a polytetrafluoroethylene membrane by vacuum filtration to prepare a carbon nanotube confined iron oxide electrode.

[0073] 3) Assembly of oxygen self-sufficient fluid bipolar electrochemical filtration system: The iridium oxide loaded titanium mesh electrode prepared in step 1) is used as the anode, the carbon nanotube confined iron oxide electrode prepared in step 2) is used as the cathode, and Ag / AgCl is used as the reference electrode to assemble into an oxygen self-sufficient fluid bipolar electrochemical filtration system. The specific assembly method is to sequentially arrange a titanium ring, an anode, a polytetrafluoroethylene membrane, a cathode and a titanium sheet in the shell, and a water inlet is arranged at one end of the shell close to the titanium ring, and a water outlet is arranged at one end of the shell close to the titanium sheet, and the reference electrode is placed on the water outlet side to contact the effluent. The electrochemical filtration system is powered by the three-electrode system of CHI660E, and the titanium rods arranged at both ends of the water inlet and the water outlet are respectively connected to the working electrode clamp and the auxiliary electrode clamp of the three-electrode system, and then connected to the iridium oxide loaded titanium mesh electrode and the carbon nanotube confined iron oxide electrode inside the shell through the titanium ring and the titanium sheet, and the reference electrode is connected to the reference electrode clamp of the three-electrode system.

[0074] 4) Treatment of simulated wastewater containing organic micropollutants: Take 50 mL of ultrapure water and prepare a mixed solution containing 20 mg / L of tetracycline and 10 mmol / L of sodium silicate. Use 1 mol / L hydrochloric acid solution to adjust the pH value of the mixed solution to 6.5. Pass the mixed solution into the oxygen self-sufficient fluid bipolar electrochemical filtration system at a flow rate of 3 mL / min. The simulated wastewater is treated in a circulating flow operation mode. The mixed solution is passed through the water inlet of the oxygen self-sufficient fluid bipolar electrochemical filtration system, first flows through the anode, then flows through the cathode, and after the effluent flows into the beaker, the mixed solution in the beaker is continuously returned to the anode through a peristaltic pump. Using an electrochemical workstation, apply 2.5 mA / cm 2 The working current density was 3 hours after the experiment, and the degradation efficiency of pollutants was evaluated. Figure 1 It can be seen that the treatment efficiency of the oxygen self-sufficient fluid bipolar electrochemical filtration system for tetracycline can reach 96.60%.

[0075] Example 2

[0076] Tap water was used to replace the ultrapure water in Example 1, and other conditions were the same as in Example 1.

[0077] Example 3

[0078] The ultrapure water in Example 1 was replaced with water from Jingyue Lake of Donghua University, and other conditions were the same as those in Example 1.

[0079] Example 4

[0080] 1) Preparation of iridium oxide-loaded titanium mesh electrode: 7.1 cm 2 The titanium mesh was used as the working electrode, the platinum sheet was used as the counter electrode, and the Ag / AgCl was used as the reference electrode. In a mixed solution containing iridium chloride, oxalic acid, and potassium carbonate, iridium oxide was loaded on the titanium mesh surface by electrodeposition using a three-electrode system of CHI660E. The current density was set to 0.20 mA / cm 2 The electrodeposition time was set to 15 min, the concentration of iridium chloride was 5.0 mmol / L, the concentration of oxalic acid was 60 mmol / L, and the concentration of potassium carbonate was 22.4 mmol / L. After the electrodeposition was completed, the iridium oxide-loaded titanium mesh electrode was placed in a drying oven at 120°C for 10 min.

[0081] 2) Preparation of carbon nanotube confined iron oxide electrode: 250 mg of carbon nanotubes were immersed in 450 mL of 68% concentrated nitric acid solution and heated to reflux for 12 h, then washed with deionized water until neutral, and freeze-dried to obtain modified carbon nanotubes with open ends; 100 mg of modified carbon nanotubes were mixed with 25 mL of 2.5 mmol / L ethanol solution of ferric nitrate nonahydrate, ultrasonically dispersed for 2 h and then dried, the dried solid powder was placed in a magnetic boat and placed in a tubular furnace, heated to 130°C in an air atmosphere and calcined for 11 h, the calcined solid powder was washed once with 2 mol / L hydrochloric acid, and then washed with ultrapure water until the washing liquid was neutral to obtain carbon nanotube confined iron oxide powder. 30 mg of carbon nanotube confined iron oxide powder was mixed with 25 mL of 1-methyl 2-pyrrolidone and ultrasonically dispersed for 1 hour to obtain a carbon nanotube confined iron oxide powder dispersion; the carbon nanotube confined iron oxide powder was loaded onto a polytetrafluoroethylene membrane by vacuum filtration to prepare a carbon nanotube confined iron oxide electrode.

[0082] 3) Assembly of oxygen self-sufficient fluid bipolar electrochemical filtration system: The iridium oxide loaded titanium mesh electrode prepared in step 1) is used as the anode, the carbon nanotube confined iron oxide electrode prepared in step 2) is used as the cathode, and Ag / AgCl is used as the reference electrode to assemble into an oxygen self-sufficient fluid bipolar electrochemical filtration system. The specific assembly method is to sequentially arrange a titanium ring, an anode, a polytetrafluoroethylene membrane, a cathode and a titanium sheet in the shell, and a water inlet is arranged at one end of the shell close to the titanium ring, and a water outlet is arranged at one end of the shell close to the titanium sheet, and the reference electrode is placed on the water outlet side to contact the effluent. The electrochemical filtration system is powered by the three-electrode system of CHI660E, and the titanium rods arranged at both ends of the water inlet and the water outlet are respectively connected to the working electrode clamp and the auxiliary electrode clamp of the three-electrode system, and then connected to the iridium oxide loaded titanium mesh electrode and the carbon nanotube confined iron oxide electrode inside the shell through the titanium ring and the titanium sheet, and the reference electrode is connected to the reference electrode clamp of the three-electrode system.

[0083] 4) Treatment of simulated wastewater containing organic micropollutants: Take 50 mL of ultrapure water and prepare a mixed solution containing 30 mg / L of norfloxacin and 10 mmol / L of sodium silicate. Use 1 mol / L hydrochloric acid solution to adjust the pH value of the mixed solution to 7.0. Pass the mixed solution into the oxygen self-sufficient fluid bipolar electrochemical filtration system at a flow rate of 4 mL / min. The simulated wastewater is treated in a circulating flow operation mode. The mixed solution is passed through the water inlet of the oxygen self-sufficient fluid bipolar electrochemical filtration system, first flows through the anode, then flows through the cathode, and after the effluent flows into the beaker, the mixed solution in the beaker is continuously returned to the anode through a peristaltic pump. Using an electrochemical workstation, apply 3.0 mA / cm 2 The working current density was set at 4h and the experiment was ended after 4h. The degradation efficiency of pollutants was calculated to be 93.45%.

[0084] Example 5

[0085] 1) Preparation of iridium oxide-loaded titanium mesh electrode: 7.1 cm 2 The titanium mesh was used as the working electrode, the platinum sheet was used as the counter electrode, and the Ag / AgCl was used as the reference electrode. In a mixed solution containing iridium chloride, oxalic acid, and potassium carbonate, iridium oxide was loaded on the titanium mesh surface by electrodeposition using a three-electrode system of CHI660E. The current density was set to 0.15 mA / cm 2 The electrodeposition time was set to 22 min, the concentration of iridium chloride was 4.5 mmol / L, the concentration of oxalic acid was 70 mmol / L, and the concentration of potassium carbonate was 21.0 mmol / L. After the electrodeposition was completed, the iridium oxide-loaded titanium mesh electrode was placed in a drying oven at 140°C for 10 min.

[0086] 2) Preparation of carbon nanotube confined iron oxide electrode: 250 mg of carbon nanotubes were immersed in 550 mL of 68% concentrated nitric acid solution and heated to reflux for 12 h, then washed with deionized water until neutral, and freeze-dried to obtain modified carbon nanotubes with open ends; 100 mg of modified carbon nanotubes were mixed with 30 mL of 2.5 mmol / L ethanol solution of ferric nitrate nonahydrate, ultrasonically dispersed for 2 h and then dried, the dried solid powder was placed in a magnetic boat and placed in a tubular furnace, heated to 130°C in an air atmosphere and calcined for 11 h, the calcined solid powder was washed once with 2 mol / L hydrochloric acid, and then washed with ultrapure water until the washing liquid was neutral to obtain carbon nanotube confined iron oxide powder. 30 mg of carbon nanotube confined iron oxide powder was mixed with 25 mL of 1-methyl 2-pyrrolidone and ultrasonically dispersed for 1 hour to obtain a carbon nanotube confined iron oxide powder dispersion; the carbon nanotube confined iron oxide powder was loaded onto a polytetrafluoroethylene membrane by vacuum filtration to prepare a carbon nanotube confined iron oxide electrode.

[0087] 3) Assembly of oxygen self-sufficient fluid bipolar electrochemical filtration system: The iridium oxide loaded titanium mesh electrode prepared in step 1) is used as the anode, the carbon nanotube confined iron oxide electrode prepared in step 2) is used as the cathode, and Ag / AgCl is used as the reference electrode to assemble into an oxygen self-sufficient fluid bipolar electrochemical filtration system. The specific assembly method is to sequentially arrange a titanium ring, an anode, a polytetrafluoroethylene membrane, a cathode and a titanium sheet in the shell, and a water inlet is arranged at one end of the shell close to the titanium ring, and a water outlet is arranged at one end of the shell close to the titanium sheet, and the reference electrode is placed on the water outlet side to contact the effluent. The electrochemical filtration system is powered by the three-electrode system of CHI660E, and the titanium rods arranged at both ends of the water inlet and the water outlet are respectively connected to the working electrode clamp and the auxiliary electrode clamp of the three-electrode system, and then connected to the iridium oxide loaded titanium mesh electrode and the carbon nanotube confined iron oxide electrode inside the shell through the titanium ring and the titanium sheet, and the reference electrode is connected to the reference electrode clamp of the three-electrode system.

[0088] 4) Treatment of simulated wastewater containing organic micropollutants: Take 50 mL of ultrapure water and prepare a mixed solution containing 10 mg / L sulfamethoxazole and 15 mmol / L sodium silicate. Use 1 mol / L hydrochloric acid solution to adjust the pH value of the mixed solution to 4.0. Pass the mixed solution into the oxygen self-sufficient fluid bipolar electrochemical filtration system at a flow rate of 2 mL / min. The simulated wastewater is treated in a circulating flow operation mode. The mixed solution is passed through the water inlet of the oxygen self-sufficient fluid bipolar electrochemical filtration system, first flows through the anode, then flows through the cathode, and after the effluent flows into the beaker, the mixed solution in the beaker is continuously returned to the anode through a peristaltic pump. Using an electrochemical workstation, apply 3.0 mA / cm 2 The working current density was set at 4h and the experiment was ended after 4h. The degradation efficiency of pollutants was calculated to be 92.68%.

[0089] Example 6

[0090] 1) Preparation of iridium oxide-loaded titanium mesh electrode: 7.1 cm 2 The titanium mesh was used as the working electrode, the platinum sheet was used as the counter electrode, and the Ag / AgCl was used as the reference electrode. In a mixed solution containing iridium chloride, oxalic acid, and potassium carbonate, iridium oxide was loaded on the titanium mesh surface by electrodeposition using a three-electrode system of CHI660E. The current density was set to 0.15 mA / cm 2 The electrodeposition time was set to 22 min, the concentration of iridium chloride was 4.5 mmol / L, the concentration of oxalic acid was 70 mmol / L, and the concentration of potassium carbonate was 20.0 mmol / L. After the electrodeposition was completed, the iridium oxide-loaded titanium mesh electrode was placed in a drying oven at 140°C for 10 min.

[0091] 2) Preparation of carbon nanotube confined iron oxide electrode: 250 mg of carbon nanotubes were immersed in 600 mL of 68% concentrated nitric acid solution and heated to reflux for 12 h, then washed with deionized water until neutral, and freeze-dried to obtain modified carbon nanotubes with open ends; 100 mg of modified carbon nanotubes were mixed with 28 mL of 2.5 mmol / L ethanol solution of ferric nitrate nonahydrate, ultrasonically dispersed for 2 h and then dried, the dried solid powder was placed in a magnetic boat and placed in a tubular furnace, heated to 130°C in an air atmosphere and calcined for 11 h, the calcined solid powder was washed once with 2 mol / L hydrochloric acid, and then washed with ultrapure water until the washing liquid was neutral to obtain carbon nanotube confined iron oxide powder. 30 mg of carbon nanotube confined iron oxide powder was mixed with 22 mL of 1-methyl 2-pyrrolidone and ultrasonically dispersed for 1 hour to obtain a carbon nanotube confined iron oxide powder dispersion; the carbon nanotube confined iron oxide powder was loaded onto a polytetrafluoroethylene membrane by vacuum filtration to prepare a carbon nanotube confined iron oxide electrode.

[0092] 3) Assembly of oxygen self-sufficient fluid bipolar electrochemical filtration system: The iridium oxide loaded titanium mesh electrode prepared in step 1) is used as the anode, the carbon nanotube confined iron oxide electrode prepared in step 2) is used as the cathode, and Ag / AgCl is used as the reference electrode to assemble into an oxygen self-sufficient fluid bipolar electrochemical filtration system. The specific assembly method is to sequentially arrange a titanium ring, an anode, a polytetrafluoroethylene membrane, a cathode and a titanium sheet in the shell, and a water inlet is arranged at one end of the shell close to the titanium ring, and a water outlet is arranged at one end of the shell close to the titanium sheet, and the reference electrode is placed on the water outlet side to contact the effluent. The electrochemical filtration system is powered by the three-electrode system of CHI660E, and the titanium rods arranged at both ends of the water inlet and the water outlet are respectively connected to the working electrode clamp and the auxiliary electrode clamp of the three-electrode system, and then connected to the iridium oxide loaded titanium mesh electrode and the carbon nanotube confined iron oxide electrode inside the shell through the titanium ring and the titanium sheet, and the reference electrode is connected to the reference electrode clamp of the three-electrode system.

[0093] 4) Treatment of simulated wastewater containing organic micropollutants: Take 50 mL of ultrapure water and prepare a mixed solution containing 25 mg / L of bisphenol A and 12 mmol / L of sodium silicate. Use 1 mol / L of sodium hydroxide solution to adjust the pH value of the mixed solution to 9.0. Pass the mixed solution into the oxygen self-sufficient fluid bipolar electrochemical filtration system at a flow rate of 6 mL / min. The simulated wastewater is treated in a circulating flow operation mode. The mixed solution is passed through the water inlet of the oxygen self-sufficient fluid bipolar electrochemical filtration system, first flows through the anode, then flows through the cathode, and after the effluent flows into the beaker, the mixed solution in the beaker is continuously returned to the anode through a peristaltic pump. Using an electrochemical workstation, apply 2.0 mA / cm 2 The working current density was set at 4h and the experiment was ended after 4h of treatment. The degradation efficiency of pollutants was calculated to be 94.88%.

[0094] Comparative Example 1

[0095] The sodium silicate in Example 1 was replaced by sodium sulfate of the same concentration, and other conditions were the same as those in Example 1.

[0096] Comparative Example 2

[0097] The sodium silicate in Example 1 was replaced by sodium chloride of equal concentration, and other conditions were the same as those in Example 1.

[0098] Comparative Example 3

[0099] The iridium oxide-loaded titanium mesh in Example 1 was replaced by a titanium mesh with the same parameters, and other conditions were the same as those in Example 1.

[0100] The degradation performance of tetracycline in Example 1 and Comparative Examples 1-2 under different electrolyte conditions is as follows Figure 1 As shown. Figure 1It can be seen that compared with sodium chloride and sodium sulfate, the oxygen self-sufficient fluid bipolar electrochemical filtration system in the presence of sodium silicate has a higher degradation efficiency for tetracycline (sodium silicate: 96.6%, sodium chloride: 65.1%, sodium sulfate: 63.7%). The main reason is that compared with silicate ions, chloride ions and sulfate ions have higher polarity and are more likely to form stable intermediates during the reaction process, thereby inhibiting the generation of hydrogen peroxide; and the presence of silicate ions can effectively prevent the dissociation of intermediates, thereby increasing the generation of hydrogen peroxide, and then improving the degradation efficiency and degradation rate.

[0101] The oxygen evolution performance of different anode materials in Example 1 and Comparative Example 3 was investigated using linear voltammetric scanning curves. Figure 3 As shown, at a current density of 10 mA / cm 2 When , the overpotential of the titanium mesh electrode is 1106mV; while the overpotential of the iridium oxide loaded titanium mesh is reduced by about 90%, and only an overpotential of 116mV is required to achieve the same current density, indicating that the iridium oxide loaded titanium mesh electrode in the present invention has a high-efficiency oxygen evolution performance.

[0102] The degradation performance of tetracycline under different water matrix conditions in Examples 1 to 3 is as follows: Figure 3 As shown. Figure 3 It can be seen that the system can achieve efficient degradation of organic micropollutants in various water matrices, indicating that the method of the present invention has strong anti-interference ability.

[0103] The electron paramagnetic resonance spectrum of the intensity change of the active species during the reaction process in Example 1 is as follows: Figure 4 As shown. Figure 4 It can be seen that when 2,2,6,6-tetramethylpiperidine is used as the capture agent, an obvious triplet peak appears, and the amount of singlet oxygen generated increases with time. Therefore, it is confirmed that the method of the present invention can effectively generate singlet oxygen.

[0104] It can be seen from the above embodiments that the present invention provides a filtration system for removing organic micropollutants based on the bipolar electrochemical generation of singlet oxygen by an oxygen self-supplied fluid. The method of the present invention can efficiently degrade a variety of organic micropollutants in water, which not only effectively avoids the addition of external reagents and saves costs, but also does not cause secondary pollution. It is conducive to the development of sustainable and green water purification methods and has good application prospects.

[0105] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. An oxygen self-sufficient fluid bipolar electrochemical filtration system, characterized in that: It includes a shell, a reference electrode, and a titanium ring, an anode, a polytetrafluoroethylene membrane, a cathode and a titanium sheet arranged in sequence inside the shell; The anode is an iridium oxide-loaded titanium mesh electrode, the cathode is a carbon nanotube-confined iron oxide electrode, and the reference electrode is an Ag / AgCl electrode; The method for preparing the carbon nanotube confined iron oxide electrode comprises the following steps: 1) Mixing the modified carbon nanotubes and the iron salt solution, drying and calcining to obtain carbon nanotube confined iron oxide powder; 2) Carbon nanotube-confined iron oxide powder is loaded on a polytetrafluoroethylene membrane to obtain a carbon nanotube-confined iron oxide electrode.

2. The oxygen self-sufficient fluid bipolar electrochemical filtration system according to claim 1, characterized in that: The method for preparing the iridium oxide loaded titanium mesh electrode is to load iridium oxide on the surface of the titanium mesh by using an electrodeposition method.

3. An oxygen self-sufficient fluid bipolar electrochemical filtration system according to claim 1 or 2, characterized in that: The preparation method of the iridium oxide loaded titanium mesh electrode comprises the following steps: using the titanium mesh as a working electrode, a platinum sheet as a counter electrode, Ag / AgCl as a reference electrode, and a solution containing iridium chloride, oxalic acid, and potassium carbonate as an electrolyte solution, and electrodepositing the loaded iridium oxide on the surface of the titanium mesh; The concentration of iridium chloride in the electrolyte solution is 3.7-5.6 mmol / L, the concentration of oxalic acid is 47-70 mmol / L, and the concentration of potassium carbonate is 14.5-28.9 mmol / L. The current density of electrodeposition is 0.10~0.20mA / cm 2 The electrodeposition time is 10~30min.

4. The oxygen self-sufficient fluid bipolar electrochemical filtration system according to claim 1, characterized in that: In the method for preparing the carbon nanotube confined iron oxide electrode, the iron salt solution comprises an iron nitrate solution, the solvent of the iron salt solution comprises ethanol and / or acetone, and the concentration of the iron salt solution is 0.9-3.6 mmol / L; The modified carbon nanotubes and the iron salt solution are added in a ratio of 50-150 mg: 10-30 mL; The calcination temperature is 120-160° C., and the calcination time is 8-14 hours.

5. An oxygen self-sufficient fluid bipolar electrochemical filtration system according to claim 1 or 4, characterized in that: The shell has a water inlet at one end close to the titanium ring, a water outlet at one end close to the titanium sheet, and a reference electrode is placed on the water outlet side to contact the outflowing liquid.

6. Application of the oxygen self-sufficient fluid bipolar electrochemical filtration system according to any one of claims 1 to 5 in treating organic micro-pollutant wastewater, characterized in that: The application method is as follows: The organic micro-pollutant wastewater and silicate are mixed to obtain mixed wastewater, and the mixed wastewater is passed into an oxygen self-supplied fluid bipolar electrochemical filtration system for energization treatment in a circulating flow mode to remove the organic micro-pollutants.

7. Application of the oxygen self-sufficient fluid bipolar electrochemical filtration system according to claim 6 in treating organic micro-pollutant wastewater, characterized in that: The organic micropollutants include one or more of bisphenol A, tetracycline, sulfamethoxazole and norfloxacin. The concentration of the organic micropollutants in the mixed wastewater is 5-30 mg / L; the concentration of silicate in the mixed wastewater is 5-15 mmol / L.

8. The use of the oxygen self-sufficient fluid bipolar electrochemical filtration system according to claim 7 in treating organic micro-pollutant wastewater, characterized in that: The current density of the energization treatment is 1.5-3.0 mA / cm 2 , the power-on treatment time is 2.0~4.0h; The flow rate of the mixed wastewater passing into the oxygen self-sufficient fluid bipolar electrochemical filtration system is 2.0-6.0 mL / min.

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