Nanotube array membrane electrode, preparation method and application thereof, and electro-catalytic reactor

Abstract

The invention provides a nanotube array membrane electrode, a preparation method and application thereof, and an electro-catalytic reactor. The nanotube array membrane electrode comprises: a titanium substrate; the titanium black nanotube array grows on the surface of the titanium substrate; and a cobalt active species supported on the titanium black nanotube array. The nanotube array membrane electrode has high catalytic activity and good stability, and is suitable for degrading and removing organic pollutants in a continuous flow reaction system.

Description

Technical Field

[0001] This invention relates to electrochemical water treatment technology, and in particular to a nanotube array membrane electrode, its preparation method and application, and an electrocatalytic reactor. Background Technology

[0002] With the increasing development of marine resources and offshore engineering activities, domestic sewage and industrial wastewater generated on offshore platforms, ocean-going vessels, and islands and reefs require on-site treatment. Since these areas are typically far from urban infrastructure and difficult to connect to municipal wastewater treatment systems, and due to space constraints, traditional large-scale centralized wastewater treatment processes are difficult to apply directly. Therefore, developing compact, stable, and decentralized water treatment technologies is of great significance for marine environmental protection and offshore engineering operations.

[0003] Currently, commonly used water treatment technologies include membrane filtration, biological treatment, and chemical oxidation. While membrane separation technology offers high-quality effluent, it is costly and prone to membrane fouling. Biological treatment processes have stringent environmental requirements and exhibit poor stability in space-constrained environments such as offshore platforms. Traditional chemical oxidation methods, while capable of removing some pollutants, have limited effectiveness against recalcitrant organic pollutants. Therefore, developing novel water treatment technologies that can efficiently remove recalcitrant organic pollutants has become a crucial research direction.

[0004] In recent years, advanced oxidation techniques based on peroxymonosulfate (PMS) activation have gained popularity due to their ability to generate sulfate free radicals. and hydroxyl radicals Highly reactive oxygen species, such as PMS, have shown great potential for the removal of recalcitrant organic pollutants. Existing research indicates that PMS can be activated by transition metals, photoactivation, or electrochemical activation. Among these, the electrochemically activated PMS system combines the advantages of high controllability and the generation of various active substances in electrochemical technology, enabling highly efficient oxidative degradation of organic pollutants.

[0005] However, existing PMS activation systems still have certain shortcomings in practical applications. First, some catalytic materials have limited active sites or poor conductivity, resulting in low PMS activation efficiency. In addition, traditional homogeneous catalysts are prone to loss in continuous flow systems, easily leading to metal ion leaching, which affects catalytic stability and may pose a risk of secondary pollution. Recovery and reuse are also difficult, which is not conducive to the long-term stable operation of decentralized water treatment devices (such as marine decentralized water treatment scenarios where energy and space are limited).

[0006] Therefore, developing an electrode material with high catalytic activity, high stability and controllable structure, and constructing an electrocatalytic PMS activation system suitable for marine decentralized water treatment scenarios, is of great significance for improving the removal efficiency of organic pollutants and promoting the engineering application of this technology.

[0007] It should be noted that the information disclosed in the background section above is only for understanding the background of this application, and therefore may include information that does not constitute prior art known to those skilled in the art. Summary of the Invention

[0008] This invention provides a nanotube array membrane electrode, its preparation method and application, and an electrocatalytic reactor, which can achieve efficient oxidative degradation of organic pollutants in water.

[0009] The present invention adopts the following technical solution:

[0010] In a first aspect, a nanotube array film electrode is provided, comprising: a titanium substrate; a sub-titanium oxide nanotube array grown on the surface of the titanium substrate; and cobalt active species loaded on the sub-titanium oxide nanotube array.

[0011] Secondly, a method for fabricating a nanotube array film electrode is provided, comprising the following steps:

[0012] (1) Provide a titanium substrate and pretreat it;

[0013] (2) Using the pretreated titanium substrate as the anode, anodizing was performed in a fluorine-containing electrolyte. After anodizing, the sample was removed, rinsed, and dried. The fluorine-containing electrolyte included ethylene glycol, water, and NH4F, with a mass ratio of ethylene glycol to water of 5:1-7:1 and a mass concentration of NH4F of 0.3wt%-0.7wt% in the fluorine-containing electrolyte.

[0014] (3) The sample obtained in step (2) was calcined in air at 600-650°C to obtain a TiO2 nanotube array on a titanium substrate.

[0015] (4) The titanium substrate on which the TiO2 nanotube array is formed is subjected to a reduction reaction at 700-800°C in a reducing atmosphere to obtain a sub-titanium oxide nanotube array on the titanium substrate.

[0016] (5) Dissolve the cobalt salt in anhydrous ethanol at a concentration of 0.01-0.1 g / mL to obtain a cobalt salt precursor solution;

[0017] (6) After the sample obtained in step (4) is completely immersed in the cobalt salt precursor solution for a predetermined time, it is taken out and dried, and then heat-treated at 300°C in a reducing atmosphere so that the cobalt active species are loaded on the titanium suboxide nanotube array.

[0018] Thirdly, an electrocatalytic reactor is provided for degrading organic pollutants in water, comprising: a reactor body; and the nanotube array membrane electrode described in the first aspect, which serves as a working electrode disposed within the reactor body to electrocatalytically activate persulfate to degrade organic pollutants in water.

[0019] Fourthly, the invention provides an application of the nanotube array membrane electrode described in the first aspect for electrocatalytic activation of persulfate to degrade organic pollutants in water.

[0020] The present invention has the following beneficial effects: In the nanotube array membrane electrode of the present invention, the sub-titanium oxide nanotube array structure provides a high specific surface area and abundant catalytic active sites, which is the key to achieving efficient electrocatalytic activation of PMS and realizing the confinement effect. In conjunction with the cobalt active species loaded on it as a catalyst, the nanotube array membrane electrode of the present invention has high catalytic activity, good stability and is suitable for the degradation and removal of organic pollutants in electrocatalytic reaction systems. In particular, it can efficiently activate trace amounts of PMS under micro-electric conditions to achieve rapid oxidative degradation of pollutants.

[0021] This invention is particularly suitable for decentralized marine water treatment scenarios such as islands, offshore platforms, and ocean-going vessels. It solves the technical bottlenecks of traditional electrochemical systems, such as low mass transfer efficiency, poor catalyst stability, and easy corrosion in complex salinity environments, and achieves efficient degradation and deep mineralization of organic pollutants in water. Attached Figure Description

[0022] Figure 1a This is an XPS characterization image of the Co2p of the nanotube array film electrode obtained in Example 1.

[0023] Figure 1b This is an XPS characterization image of Ti2p of the nanotube array film electrode obtained in Example 1.

[0024] Figure 1c This is the XPS characterization image of the O1s of the TiO2 nanotube array obtained in step (3) of Example 1.

[0025] Figure 1d The TiO obtained in step (4) of Example 1 x XPS characterization of O1s in nanotube arrays.

[0026] Figure 1e It is the Co-TiO obtained in Example 1 xXPS characterization of O1s in nanotube arrays.

[0027] Figure 2a and Figure 2b These are SEM images of the nanotube array film electrode obtained in Example 1 at different magnifications.

[0028] Figure 2c This is the elemental distribution diagram of the nanotube array film electrode obtained in Example 1. Figure 2d The TiO2 obtained in step (4) of Example 1 x Pore ​​size distribution of nanotube array.

[0029] Figure 3 This is a TEM characterization image of the nanotube array film electrode obtained in Example 1.

[0030] Figure 4 This is the result of cobalt ion leaching test in Example 2, based on five cycles of the experiment.

[0031] Figure 5a This is a graph showing the degradation effect of nanotube array membrane electrode on 4-chlorophenol (4-CP) obtained in Example 2 under different amounts of Co(NO3)2·6H2O added.

[0032] Figure 5b This is a line graph comparing the degradation of 4-chlorophenol by the nanotube array film electrode of Example 1 and the control electrode in Example 2.

[0033] Figure 5c This is a diagram showing the degradation effect of the nanotube array membrane electrode of Example 1 on 4-chlorophenol in Example 2.

[0034] Figure 6 This is a graph showing the degradation efficiency of the nanotube array membrane electrode of Example 1 for 4-chlorophenol under different PMS dosages in Example 2.

[0035] Figure 7 This is a graph showing the degradation efficiency of the nanotube array membrane electrode of Example 1 on 4-chlorophenol at different pH values ​​in Example 2.

[0036] Figure 8 This is a graph showing the degradation efficiency of the nanotube array membrane electrode of Example 1 on 4-chlorophenol in different water bodies in Example 2.

[0037] Figure 9 This is Example 2, showing the degradation efficiency of the nanotube array membrane electrode of Example 1 on 4-chlorophenol in the presence of coexisting anions and natural organic matter.

[0038] Figure 10a and Figure 10bThese are the acute and chronic toxicity characterization diagrams of 4-CP and its intermediate products in Example 2.

[0039] Figure 11 This is Example 3, showing the degradation efficiency of the nanotube array membrane electrode from Example 1 for five other pollutants.

[0040] Figure 12 This is a structural breakdown diagram of the electrocatalytic reactor used in the continuous flow experiment in Example 4.

[0041] Figure 13 This is a graph showing the degradation performance of 4-CP by the nanotube array membrane electrode under different water flow rates in Example 4.

[0042] Figure 14 This is the pseudo-first-order kinetic fitting curve of the degradation of 4-CP by the nanotube array membrane electrode in Example 4.

[0043] Figure 15 This is a comparison of the degradation rate constants in the batch experiment and the breakthrough experiment in Example 4. Detailed Implementation

[0044] The embodiments of the present invention are described in detail below. It should be emphasized that the following description is merely exemplary and not intended to limit the scope or application of the present invention. Unless otherwise specified, the embodiments and features described in this application can be combined with each other. In this invention, room temperature refers to 20-30°C.

[0045] This invention provides a nanotube array film electrode, comprising: a titanium substrate; a sub-titanium oxide nanotube array grown on the surface of the titanium substrate; and cobalt active species loaded on the sub-titanium oxide nanotube array.

[0046] In some embodiments, divalent cobalt and trivalent cobalt coexist in the cobalt active species.

[0047] In some embodiments, the average pore size of the titanium suboxide nanotube array is 64.4 nm.

[0048] This invention also provides a method for preparing a nanotube array film electrode, comprising the following steps:

[0049] (1) Provide a titanium substrate and pretreat it;

[0050] (2) Using the pretreated titanium substrate as the anode, anodizing was performed in a fluorine-containing electrolyte. After anodizing, the sample was removed, rinsed, and dried. The fluorine-containing electrolyte included ethylene glycol, water, and NH4F, with a mass ratio of ethylene glycol to water of 5:1-7:1 and a mass concentration of NH4F of 0.3wt%-0.7wt% in the fluorine-containing electrolyte.

[0051] (3) The sample obtained in step (2) was calcined in air at 600-650°C to obtain a TiO2 nanotube array on a titanium substrate.

[0052] (4) The titanium substrate on which the TiO2 nanotube array is formed is subjected to a reduction reaction at 700-800°C in a reducing atmosphere to obtain a sub-titanium oxide nanotube array on the titanium substrate.

[0053] (5) Dissolve the cobalt salt in anhydrous ethanol at a concentration of 0.01-0.1 g / mL to obtain a cobalt salt precursor solution;

[0054] (6) After the sample obtained in step (4) is completely immersed in the cobalt salt precursor solution for a predetermined time, it is taken out and dried, and then heat-treated at 300°C in a reducing atmosphere so that the cobalt active species are loaded on the titanium suboxide nanotube array.

[0055] In some embodiments, the titanium substrate in step (1) is a titanium sheet; the pretreatment of the titanium substrate in step (1) includes: immersing the titanium substrate in a hydrochloric acid solution with a concentration of 1-2 mol / L, treating it under ultrasonic conditions for 10-20 min, taking out the sample after treatment and rinsing it with ultrapure water, and then placing the titanium substrate in acetone and anhydrous ethanol for ultrasonic cleaning in sequence, with each cleaning time being 10-15 min, and drying the cleaned titanium substrate at 80-120℃ for later use.

[0056] In some embodiments, the reducing atmosphere in step (4) is a mixture of hydrogen and nitrogen in a volume ratio of 1:3 to 1:5, with a total gas flow rate of 100-120 mL / min.

[0057] In some embodiments, the cobalt salt in step (5) is Co(NO3)2·6H2O; the predetermined time in step (6) is 20-40 min; the reducing atmosphere in step (6) is a H2 / N2 mixed gas with a volume fraction of 5-10% H2, and the heat treatment time is 3 h.

[0058] In a preferred embodiment, the method for fabricating the nanotube array film electrode includes the following steps:

[0059] (1) Immerse the titanium sheet in a hydrochloric acid solution with a concentration of 1-2 mol / L and treat it under ultrasonic conditions for 10-20 min to remove the surface oxide layer and impurities; after treatment, take out the sample and rinse it with ultrapure water; then place the titanium sheet in acetone and anhydrous ethanol for ultrasonic cleaning in sequence, each cleaning time being 10-15 min; after cleaning, place the titanium sheet in an oven at 80-120℃ to dry for later use.

[0060] (2) Using the pretreated titanium substrate as the anode and the platinum sheet as the cathode, an anodizing reaction was carried out in a fluorinated electrolyte at room temperature with a constant voltage of 30-50V for 1-3 hours. After the anodizing reaction was completed, the sample was taken out, rinsed with deionized water, and dried at 50-60℃. The fluorinated electrolyte included ethylene glycol, water, and NH4F, with a mass ratio of ethylene glycol to water of 5:1-7:1 and a mass concentration of NH4F in the fluorinated electrolyte of 0.3wt%-0.7wt%.

[0061] (3) The sample obtained in step (2) is placed in a muffle furnace for annealing. Under an air atmosphere, the temperature is raised to 600-650℃ at a heating rate of 3-10℃ / min and held for 2h. Then it is naturally cooled to room temperature to obtain a TiO2 nanotube array on the titanium sheet.

[0062] (4) The titanium sheet with TiO2 nanotube array is placed in a tube furnace for gas phase reduction treatment: First, the reaction system is evacuated to below 5 Pa, and then a mixture of hydrogen and nitrogen is introduced, wherein the volume ratio of hydrogen to nitrogen is 1:3-1:5 and the total gas flow rate is 100-120 mL / min. Under this reducing atmosphere, the temperature is raised to 700-800℃ (more preferably 750℃) at 3-5℃ / min and maintained for 45 min-1 h for reduction reaction. After the reaction is completed, the furnace is cooled to room temperature to obtain a titanium suboxide nanotube array on the titanium sheet.

[0063] (5) Dissolve Co(NO3)2·6H2O in anhydrous ethanol (the concentration of Co(NO3)2·6H2O is 0.01-0.1 g / mL, preferably, the concentration of Co(NO3)2·6H2O is 0.05 g / mL), and sonicate for 10-15 min to obtain a uniform cobalt salt precursor solution.

[0064] (6) After immersing the sample obtained in step (4) completely in the cobalt salt precursor solution for 20-40 min, take it out and dry it at 50-60℃. Then place the dried sample in a tube furnace and heat it to 300℃ for 3 h at a heating rate of 3-5℃ / min in a hydrogen reducing atmosphere (H2 / N2 mixed gas with a volume fraction of 5-10%). After the heat treatment, let it cool naturally to room temperature to obtain the nanotube array film electrode.

[0065] This invention provides an electrocatalytic reactor for degrading organic pollutants in water, comprising: a reactor body; and a nanotube array membrane electrode, which serves as the working electrode within the reactor body, for electrocatalytically activating persulfate to degrade organic pollutants in water.

[0066] In some embodiments, the electrocatalytic reactor is configured for batch experiments, and the electrocatalytic reactor further includes a counter electrode and a reference electrode, the counter electrode being a platinum sheet, and the potential of the working electrode being controlled to be -0.5V to -1.5V relative to the reference electrode.

[0067] In some embodiments, the electrocatalytic reactor is configured for continuous flow experiments. The reactor body has an inlet and an outlet. The electrocatalytic reactor also includes a ruthenium-iridium-titanium mesh electrode as an anode and a nanotube array membrane electrode as a cathode. The anode and the cathode are arranged in a parallel plate structure at intervals within the reactor body. The electrocatalytic reactor is configured such that the water to be treated enters from the inlet at a flow rate of 0.1-0.4 mL / min, passes through the anode and cathode in sequence, and flows out from the outlet.

[0068] This invention provides an application of the nanotube array membrane electrode described above for electrocatalytic activation of persulfate to degrade organic pollutants in water.

[0069] In some embodiments, the concentration of the persulfate is 0.25-1 mmol / L; 0.1 mol / L Na2SO4 is also added as a supporting electrolyte in the application.

[0070] In some implementations, the concentration of organic pollutants in the water is 5–30 mg / L.

[0071] The following describes specific embodiments of the present invention.

[0072] Example 1

[0073] The fabrication method of the nanotube array film electrode in Example 1 includes the following steps:

[0074] (1) Immerse the titanium sheet in a 2 mol / L hydrochloric acid solution and treat it under ultrasonic conditions for 10-20 min to remove the surface oxide layer and impurities; after treatment, take out the sample and rinse it with ultrapure water; then place the titanium sheet in acetone and anhydrous ethanol for ultrasonic cleaning, each cleaning time being 10-15 min; after cleaning, place the titanium sheet in an oven at 80-120℃ to dry for later use.

[0075] (2) Using the pretreated titanium substrate as the anode and the platinum sheet as the cathode, an anodizing reaction was carried out in a fluorinated electrolyte at room temperature with a constant voltage of 40V for 3 hours. After the anodizing reaction was completed, the sample was taken out, rinsed with deionized water, and dried at 60°C. The fluorinated electrolyte included ethylene glycol, water, and NH4F, with a mass ratio of ethylene glycol to water of 6:1 and a mass concentration of NH4F of 0.5wt% in the fluorinated electrolyte.

[0076] (3) The sample obtained in step (2) was placed in a muffle furnace for annealing. Under an air atmosphere, the temperature was increased to 620°C at a heating rate of 5°C / min and held for 2 hours. Then it was naturally cooled to room temperature to obtain a TiO2 nanotube array on the titanium sheet.

[0077] (4) The titanium sheet with the TiO2 nanotube array was placed in a tube furnace for gas-phase reduction treatment: First, the reaction system was evacuated to below 5 Pa, and then a mixture of hydrogen and nitrogen gas was introduced, wherein the volume ratio of hydrogen to nitrogen was 1:5 and the total gas flow rate was 120 mL / min. Under this reducing atmosphere, the temperature was increased to 750 °C at 5 °C / min and held for 45 min for the reduction reaction. After the reaction was completed, the furnace was cooled to room temperature to obtain titanium suboxide (TiO2) on the titanium sheet. x Nanotube array;

[0078] (5) Dissolve 0.5g of Co(NO3)2·6H2O solid in 10 mL of anhydrous ethanol and sonicate for 15 min to obtain a uniform cobalt salt precursor solution.

[0079] (6) After completely immersing the sample obtained in step (4) in the cobalt salt precursor solution for 30 min, remove it and dry it at 60 °C to allow the solvent to evaporate completely. Then, place the dried sample in a tube furnace and heat it to 300 °C for 3 h at a heating rate of 5 °C / min under a hydrogen reducing atmosphere (H2 / N2 mixed gas with a volume fraction of 5%). After the heat treatment, allow it to cool naturally to room temperature to obtain the nanotube array film electrode (which can be written as Co-TiO2). x Nanotube array film electrode).

[0080] like Figures 1a-1e As shown, Figure 1a This is the XPS characterization image of Co2p of the nanotube array film electrode obtained in Example 1. Figure 1b This is an XPS characterization image of Ti2p of the nanotube array film electrode obtained in Example 1. Figure 1c This is the XPS characterization image of the O1s of the TiO2 nanotube array obtained in step (3) of Example 1. Figure 1d The TiO obtained in step (4) of Example 1 x XPS characterization of O1s nanotube arrays. Figure 1e It is the Co-TiO obtained in Example 1 x XPS characterization of O1s in nanotube arrays, from Figures 1a-1e It can be seen that the oxygen vacancy concentration gradually increases. The increase in oxygen vacancy concentration after cobalt loading may be due to the introduction of a hydrogen-containing reducing atmosphere for heat treatment during the cobalt loading process (i.e., step (6)).

[0081] like Figure 2a and Figure 2b The image shown is a SEM image of the nanotube array film electrode obtained in Example 1 at different magnifications. Figure 2c This is the elemental distribution diagram of the nanotube array film electrode obtained in Example 1. Figure 2d The TiO2 obtained in step (4) of Example 1 x The pore size distribution diagram of the nanotube array shows that the TiO₂... x The average pore size of the nanotube array is 64.4 nm. As shown in the figure, the nanotube array membrane electrode maintains a complete and highly ordered nanotube array framework, without obvious structural collapse or tube blockage. The cobalt active material (cobalt catalyst) particles are not only uniformly dispersed at the tube openings and on the tube wall surface, but some tiny particles are also successfully anchored in the internal pores of the nanotubes.

[0082] like Figure 3 The figures shown are TEM images of the nanotube array film electrode obtained in Example 1. (a) is a low-magnification overall distribution image, (b) is the lattice fringes of the titanium substrate, (c) is the lattice fringes of cobalt tetroxide, and (d) is the elemental distribution map. As can be seen from the figures, compared with before cobalt loading, TiO₂… x The nanotube walls transitioned from a smooth to a distinctly rough state, and numerous fine and uniformly distributed nanoparticles were observed at the tube opening and on both the inner and outer sides of the tube walls. Lattice fringes belonging to the substrate were clearly observed in both the samples before and after loading. The 0.352 nm spacing lattice corresponds to the (101) plane of the anatase phase TiO2. In the HRTEM image after cobalt loading, characteristic lattices belonging to cobalt oxides were observed in addition to the substrate lattice. The 0.243 nm and 0.466 nm lattice fringes indicated correspond to the (311) and (111) planes of Co3O4, respectively, and the electron diffraction pattern results are consistent with the above results.

[0083] Example 2

[0084] Example 2 verifies the performance of the nanotube array film electrode in batch experiments (h-cell experiments).

[0085] The electrocatalytic reactor used in this batch of experiments includes a reactor body, a cathode, a counter electrode (platinum sheet), and a reference electrode. The cathode is a nanotube array membrane electrode used for the electrocatalytic activation of persulfate to degrade organic pollutants in water.

[0086] In the batch experiment, the water to be treated included simulated wastewater containing 10 mg / L of 4-chlorophenol, 0.25-1 mmol / L of persulfate (potassium persulfate in this example) as an oxidant and 0.1 mol / L of Na2SO4 as a supporting electrolyte, and the reaction time was 15 minutes.

[0087] The following different batch experiments were conducted:

[0088] 1. Using the nanotube array membrane electrode of Example 1 as the cathode, the concentration of persulfate in the water to be treated was 0.5 mmol / L, and the reaction potential was -1 V. For example... Figure 4 As shown, after five cycles of the experiment, the concentration of cobalt ions in the effluent was found to be below 10.5 μg / L by inductively coupled plasma mass spectrometry (ICP-MS), which is far below the national standard limit (1 mg / L), indicating that the nanotube array membrane electrode has excellent stability.

[0089] 2. To investigate the effect of cobalt loading on catalytic performance, in different experiments, the concentration of persulfate was 0.5 mmol / L, the reaction potential was -1 V, and the amount of Co(NO3)2·6H2O solid in step (6) of Example 1 was adjusted to 0.1 g, 0.5 g, and 1 g, respectively, thereby adjusting the cobalt catalyst loading in the final nanotube array membrane electrode. Figure 5a As shown, Figure 5a The following figures illustrate the degradation effect of the nanotube array membrane electrode on 4-chlorophenol under different amounts of Co(NO3)2·6H2O added (where (a) is a degradation line graph, (b) is a bar graph of removal rate, and (c) is a kinetic fitting graph). Experimental results show that when the amount of Co(NO3)2·6H2O solid is 0.5 g, the PMS concentration is 0.5 mM, and the potential is -1 V, the nanotube array membrane electrode (Co-TiO2) exhibits the following degradation effects on 4-chlorophenol: x The removal rate of 4-chlorophenol (NT) reached 91%, which is much higher than the removal rates when the amount of Co(NO3)2·6H2O solid was 0.1g and 1g (54% and 72%, respectively).

[0090] Furthermore, under optimal experimental conditions (using the nanotube array film electrode of Example 1 (i.e., the amount of Co(NO3)2·6H2O solid is 0.5 g), PMS concentration is 0.5 mM, potential is -1 V, reaction time is 15 min), the nanotube array film electrode of Example 1 (written as Co-TiO in the figure) x NT) and the comparison electrode (first comparison electrode: the electrode without cobalt loading, i.e. the TiO2 prepared in step (5) of Example 1) x Nanotube array film electrode (written as TiO in the figure) x NT); and the second contrast electrode: a conventional planar titanium suboxide electrode loaded with cobalt (without growing nanotube arrays) (written as Co-TiO in the figure). x A graph comparing the degradation patterns of 4-chlorophenol, as shown below. Figure 5bAs shown in the figure, the experimental results indicate that the removal efficiency of the nanotube array film electrode in Example 1 is significantly higher than that of Co-TiO₂. x Flat electrode and unloaded cobalt TiO x The NT electrode demonstrates that the nanotube array structure combined with an appropriate amount of cobalt loading significantly improves catalytic activity. Furthermore, the nanotube array membrane electrode exhibits excellent degradation performance for 4-chlorophenol. Figure 5c As shown (where (a) is a degradation line graph, (b) is a kinetic fitting graph, and (c) is a kinetic fitting constant graph), in Figure 5c In E-Co-TiO x NT indicates: the experiment was conducted using the nanotube array membrane electrode of Example 1, with a PMS concentration of 0.5 mM, a potential of -1 V, and a reaction time of 15 min; PMS indicates: the experiment was conducted in a reactor without electrodes, with only PMS added, a PMS concentration of 0.5 mM, a potential of -1 V, and a reaction time of 15 min; Co-TiO x NT indicates: The experiment was conducted using the nanotube array film electrode of Example 1, without the addition of PMS, at a potential of -1V, and for 15 minutes. From Figure 5c It can be seen from this that E-Co-TiO x The NT experiment showed the highest degradation efficiency, with a degradation rate of 91% and a kinetic fitting constant of 0.225 min. -1 .

[0091] 3. To investigate the effect of PMS concentration on the degradation performance of the nanotube array membrane electrode of Example 1, the nanotube array membrane electrode of Example 1 was used as the cathode in different experiments, with a reaction potential of -1 V and PMS concentrations adjusted to 0.25 mM, 0.5 mM, 0.75 mM, and 1 mM. Figure 6 The figure shows the degradation efficiency of the nanotube array membrane electrode of Example 1 for 4-chlorophenol under different PMS dosages (where (a) is the degradation curve, (b) is the removal rate comparison, (c) is the pseudo-first-order kinetic fitting curve, and (d) is the degradation rate constant comparison).

[0092] 4. To investigate the effect of different pH conditions on the degradation performance of the nanotube array membrane electrode of Example 1, different experiments were conducted using the nanotube array membrane electrode of Example 1, a PMS concentration of 0.5 mM, a potential of -1 V, and pH values ​​of 3, 5, 7, 9, and 10. Figure 7 The figure shows the degradation efficiency of the nanotube array membrane electrode of Example 1 for 4-chlorophenol at different pH values ​​(where (a) is the degradation curve, (b) is the removal rate comparison, (c) is the pseudo-first-order kinetic fitting curve, and (d) is the degradation rate constant comparison). The results show that the removal rate remains above 87% from pH 3 to 10.

[0093] 5. To investigate the degradation performance of the nanotube array membrane electrode of Example 1 in different water bodies, the nanotube array membrane electrode of Example 1, a PMS concentration of 0.5 mM, and a potential of -1 V were used in different experiments. The prepared water to be treated was added to different water bodies (tap water, river water, and seawater) for the experiments. Figure 8 The figure shows the degradation efficiency of the nanotube array membrane electrode of Example 1 for 4-chlorophenol in different water bodies (where (a) is the degradation curve, (b) is the removal rate comparison, (c) is the pseudo-first-order kinetic fitting curve, and (d) is the degradation rate constant comparison). The results show that the removal rate of 4-chlorophenol by the nanotube array membrane electrode remains above 80% in different water bodies.

[0094] 6. To investigate the degradation performance of the nanotube array membrane electrode of Example 1 on 4-chlorophenol in the presence of coexisting anions and natural organic matter, different experiments were conducted using the nanotube array membrane electrode of Example 1, a PMS concentration of 0.5 mM, and a potential of -1 V. The prepared water samples were tested under conditions of coexisting anions and natural organic matter. Figure 9 The figure shows the degradation efficiency of the nanotube array membrane electrode of Example 1 for 4-chlorophenol in the presence of coexisting anions and natural organic matter (where (a) is the degradation curve, (b) is the removal rate comparison, (c) is the pseudo-first-order kinetic fitting curve, and (d) is the degradation rate constant comparison). The results show that the degradation efficiency decreases only slightly in the presence of coexisting anions and natural organic matter, indicating that the nanotube array membrane electrode of the present invention has strong environmental adaptability and anti-interference ability.

[0095] 7. The degradation of pollutants by the nanotube array membrane electrode mainly involves the combined action of free radical degradation pathway and non-free radical degradation pathway (direct electron transfer pathway (polymerization pathway)). Table 1 below shows the structural formulas of intermediate products that may be generated during the degradation of 4-chlorophenol (4-CP) by the nanotube array membrane electrode of Example 1.

[0096] Table 1: Structural Formulas of 4-CP and Intermediate Products

[0097]

[0098] During the degradation of 4-chlorophenol using the nanotube array membrane electrode of Example 1 (PMS concentration of 0.5 mM, potential of -1 V, reaction time of 15 min), the toxicity of 4-CP and reaction intermediates was characterized using ECOSAR. Figure 10a and Figure 10bThe figures show the acute and chronic toxicity characterization of 4-CP and its intermediates. In the figures, LC50 (Lethal Concentration 50%) represents the concentration that causes 50% mortality and is mainly used for acute toxicity assessment in animals such as fish and water fleas; EC50 (Effective Concentration 50%) represents the concentration that causes 50% of organisms to produce an effect (such as growth inhibition or photosynthetic inhibition) and is typically used for toxicity assessment in primary producers such as green algae; ChV (Chronic Value) represents the chronic toxicity threshold under long-term exposure conditions, reflecting the long-term effects on organism growth and reproduction. All values ​​in the figures are represented using logarithmic form (Log). In this coordinate system, a larger Log value indicates a higher LC50, EC50, or ChV, meaning a higher concentration is required to produce a toxic effect, indicating lower toxicity; conversely, a smaller Log value indicates higher toxicity. The results of acute toxicity (Log(LC50) and Log(EC50)) and chronic toxicity (Log(ChV)) assessments show that the initial pollutant 4-chlorophenol (4-CP) exhibits certain toxicity to fish, daphnia, and algae, with its corresponding Log values ​​mainly distributed in the "toxic" range, indicating a potential ecological risk. During the degradation process, the Log values ​​of the intermediate products all show a decreasing trend.

[0099] The experimental results of Example 2 show that the prepared nanotube array membrane electrode can efficiently activate the effective utilization rate of persulfate (PMS) (the proportion of PMS used to generate free radicals). Although the total organic carbon (TOC) removal rate is about 38% due to the polymerization of some intermediate products during the reaction, the degradation kinetic rate of the target pollutant (4-chlorophenol) is much higher than that of the conventional system, indicating that the present invention preferentially achieves rapid detoxification and transformation of pollutants.

[0100] Example 3

[0101] Batch experiments were conducted using the electrocatalytic reactor of Example 2 (with the nanotube array membrane electrode of Example 1 as the cathode) to degrade different pollutants.

[0102] In the parallel batch experiment of Example 3, the water to be treated included simulated wastewater containing 10 mg / L of different pollutants (SDZ (sulfadiazine), CIP (ciprofloxacin), Phenol, 2,4-DCP (2,4-dichlorophenol), BPA (bisphenol A)), 0.5 mmol / L potassium persulfate and 0.1 mol / L Na2SO4 as supporting electrolytes, -1V potential, and a reaction time of 15 minutes.

[0103] like Figure 11The figure shows the degradation efficiency of the nanotube array membrane electrode of Example 1 for the above five pollutants (where (a) is the degradation curve, (b) is the removal rate comparison, (c) is the pseudo-first-order kinetic fitting curve, and (d) is the degradation rate constant comparison). The results show that, except for 4-CP in Example 2, the nanotube array membrane electrode of Example 1 also has a removal rate of more than 90% for other organic pollutants.

[0104] Example 4

[0105] Example 4 verifies the performance of the nanotube array film electrode in a continuous flow experiment (also known as a through-flow experiment).

[0106] The electrocatalytic reactor used in this continuous flow experiment includes a reactor body, a cathode, and an anode. Both the cathode and anode are located within the reactor body. The cathode is a nanotube array membrane electrode used for the electrocatalytic activation of persulfate to degrade organic pollutants in the water. The anode is a ruthenium-iridium-titanium mesh electrode. Specifically, as... Figure 12 As shown, the electrocatalytic reactor of this embodiment 4 adopts a plate and frame structure. The first shell 1 and the second shell 2 constitute the reactor body. The first shell 1 has a water inlet 11 and the second shell has a water outlet 21. In the accommodating space formed by the first shell 1 and the second shell 2, the first gasket 3, the ruthenium-iridium-titanium mesh anode 4, the anode current collector 5 (titanium plate), the second gasket 6, the anode 7 (in this example, the nanotube array membrane electrode prepared in embodiment 1), the anode current collector 8 (titanium plate) and the third gasket 9 are arranged sequentially along the water flow direction.

[0107] In the continuous flow experiment of Example 4, the water to be treated included simulated wastewater containing 10 mg / L of 4-chlorophenol, 0.5 mmol / L of potassium persulfate, and 0.1 mol / L of Na₂SO₄. A continuous flow degradation experiment was conducted with a voltage of -1.0 V and a reaction time of 15 min. During the reaction, the water to be treated entered through the inlet under pressure, passed through the anode and cathode sequentially, and was collected from the outlet after treatment, achieving through-flow (during the flow of the water to be treated, the fluid flows at high speed along the surface of the nanotube array to thin the boundary layer; the nanotube structure and the active sites loaded on it can confine the reactants and titanium active species catalyst within the tubular structure, thereby achieving the effect of confined catalysis; and the experimental results show that pressurizing the water flow through the reactor also improves the mass transfer efficiency).

[0108] like Figure 13 The figure shows the degradation performance of 4-CP by the nanotube array membrane electrode under different water flow rates (flow rates of 0.1, 0.15, 0.2, 0.3, and 0.4 mL / min, corresponding to fluxes of 76, 115, 153, 229, and 306 LMH, respectively).

[0109] like Figure 14 The figure shows the pseudo-first-order kinetic fitting curve of the degradation of 4-CP by the nanotube array membrane electrode after calculating the residence time at a water flow rate of 76 LMH.

[0110] like Figure 15 The figure shows a comparison of the degradation rate constants for batch experiments and breakthrough experiments.

[0111] The results above show that in this embodiment, pollutants can complete the degradation reaction within a short residence time, and the pollutant removal rate reaches 99% under low flux conditions. Furthermore, the apparent rate constant of the fitted pseudo-first-order kinetic model is about 52.4 times higher than that of the traditional batch system, indicating that the through-process reaction mode can significantly enhance the interfacial reaction rate and improve the efficiency of engineering applications.

[0112] Comparative Example 1

[0113] The difference from Example 1 is that the reduction reaction temperature in step (4) was changed from 750℃ to 850℃. Characterization results show that the excessively high reduction temperature caused severe melting and sintering of the nanotube array, the original ordered pore structure disappeared, resulting in a significant reduction in the effective specific surface area, proving that 750℃ is the preferred process point that balances conductivity and morphological stability.

[0114] In summary, the Co-TiO of the present invention... x In the NT membrane electrode, the diameter of the highly ordered nanotube array structure matches the particle size of the cobalt active species, physically binding the cobalt species within and on the surface of the nanotubes, effectively inhibiting their dissolution and leaching during the electrocatalytic reaction. This nanotube array membrane electrode exhibits strong environmental adaptability in complex aquatic environments, maintaining high degradation efficiency under varying pH levels, coexisting anions, and the presence of natural organic matter, while also demonstrating good cycle stability and low-toxicity byproducts.

[0115] The above description provides a further detailed explanation of the present invention in conjunction with specific / preferred embodiments, and it should not be construed that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art, various substitutions or modifications can be made to these described embodiments without departing from the concept of the present invention, and all such substitutions or modifications should be considered within the scope of protection of the present invention. In the description of this specification, the reference to terms such as "an embodiment," "some embodiments," "preferred embodiment," "example," "specific example," or "some examples," etc., indicates that the specific features, structures, materials, or characteristics described in connection with that embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in any suitable manner in one or more embodiments or examples. Without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification and the features of different embodiments or examples. Although the embodiments of the present invention and their advantages have been described in detail, it should be understood that various changes, substitutions, and modifications can be made herein without departing from the scope of protection of the patent application.

Claims

1. A nanotube array film electrode, characterized in that, include: Titanium substrate; an array of sub-titanium oxide nanotubes grown on the surface of the titanium substrate; And cobalt active species loaded on the sub-titanium oxide nanotube array.

2. The nanotube array film electrode as described in claim 1, characterized in that: The cobalt active species contain both divalent and trivalent cobalt.

3. A method for fabricating a nanotube array film electrode, characterized in that, Includes the following steps: (1) Provide a titanium substrate and pretreat it; (2) Using the pretreated titanium substrate as the anode, anodizing was performed in a fluorine-containing electrolyte. After anodizing, the sample was removed, rinsed, and dried. The fluorine-containing electrolyte included ethylene glycol, water, and NH4F, with a mass ratio of ethylene glycol to water of 5:1-7:1 and a mass concentration of NH4F of 0.3wt%-0.7wt% in the fluorine-containing electrolyte. (3) The sample obtained in step (2) was calcined in air at 600-650°C to obtain a TiO2 nanotube array on a titanium substrate. (4) The titanium substrate on which the TiO2 nanotube array is formed is subjected to a reduction reaction at 700-800°C in a reducing atmosphere to obtain a sub-titanium oxide nanotube array on the titanium substrate. (5) Dissolve the cobalt salt in anhydrous ethanol at a concentration of 0.01-0.1 g / mL to obtain a cobalt salt precursor solution; (6) After the sample obtained in step (4) is completely immersed in the cobalt salt precursor solution for a predetermined time, it is taken out and dried, and then heat-treated at 300°C in a reducing atmosphere so that the cobalt active species are loaded on the titanium suboxide nanotube array.

4. The preparation method according to claim 3, characterized in that, The titanium substrate mentioned in step (1) is a titanium sheet; the pretreatment of the titanium substrate in step (1) includes: immersing the titanium substrate in a hydrochloric acid solution with a concentration of 1-2 mol / L, treating it under ultrasonic conditions for 10-20 min, taking out the sample after treatment and rinsing it with ultrapure water, and then placing the titanium substrate in acetone and anhydrous ethanol for ultrasonic cleaning in sequence, with each cleaning time being 10-15 min, and drying the cleaned titanium substrate at 80-120℃ for later use.

5. The preparation method according to claim 3, characterized in that, The reducing atmosphere in step (4) is a mixture of hydrogen and nitrogen in a volume ratio of 1:3 to 1:5, with a total gas flow rate of 100-120 mL / min.

6. The preparation method according to claim 3, characterized in that, The cobalt salt in step (5) is Co(NO3)2·6H2O; the predetermined time in step (6) is 20-40 min; the reducing atmosphere in step (6) is a H2 / N2 mixed gas with a volume fraction of 5-10% H2, and the heat treatment time is 3 h.

7. An electrocatalytic reactor for degrading organic pollutants in water, characterized in that, include: Reactor body; The nanotube array membrane electrode as described in any one of claims 1-2 is disposed as a working electrode within the reactor body and electrocatalytically activates persulfate to degrade organic pollutants in the water.

8. The electrocatalytic reactor as described in claim 7, characterized in that: The electrocatalytic reactor is configured for batch experiments and further includes a counter electrode and a reference electrode. The counter electrode is a platinum sheet, and the potential of the working electrode is controlled to be -0.5V to -1.5V relative to the reference electrode. Alternatively, the electrocatalytic reactor is configured for continuous flow experiments, with an inlet and an outlet on the reactor body. The electrocatalytic reactor also includes a ruthenium-iridium-titanium mesh electrode as the anode and a nanotube array membrane electrode as the cathode. The anode and the cathode are arranged in a parallel plate structure at intervals within the reactor body. The electrocatalytic reactor is configured such that the water to be treated enters from the inlet at a flow rate of 0.1-0.4 mL / min, passes through the anode and the cathode in sequence, and flows out from the outlet.

9. The application of a nanotube array membrane electrode according to any one of claims 1-2 for electrocatalytic activation of persulfate to degrade organic pollutants in water.

10. The application as described in claim 9, characterized in that, In the application, the concentration of persulfate is 0.25-1 mmol / L; 0.1 mol / L Na2SO4 is also added as a supporting electrolyte.

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