An electrochemical tubular ceramic membrane for treating high-salt organic wastewater and its preparation method

Abstract

The application provides an electrochemical tubular ceramic membrane for high-salt organic sewage treatment and a preparation method thereof, and belongs to the technical field of water treatment. The method comprises the following steps: (1) ultrasonic cleaning is performed on a tubular ceramic membrane substrate, and the cleaned tubular ceramic membrane substrate is placed in a blast drying oven for drying; (2) the pretreated tubular ceramic membrane substrate is placed in a magnetron sputtering instrument, titanium is deposited in an argon atmosphere, and a titanium substrate tubular ceramic membrane with a titanium conductive layer is obtained; (3) the titanium substrate tubular ceramic membrane is placed in a magnetron sputtering instrument, ruthenium and iridium are deposited in an argon atmosphere, and a ruthenium-iridium active layer is deposited on the surface of the titanium substrate tubular ceramic membrane, namely the electrochemical tubular ceramic membrane is obtained. The application solves the key technical problems of low free radical concentration and low organic matter mineralization rate in electro-oxidation technology.

Description

Technical Field

[0001] This invention relates to the field of water treatment technology, and in particular to an electrochemical tubular ceramic membrane for treating high-salt organic wastewater and its preparation method. Background Technology

[0002] Industrial wastewater from chemical industrial parks causes severe water pollution, characterized by high salinity, high COD, and complex composition. The high salinity of this water affects the activity of microbial communities in biological treatment processes, making it difficult to achieve satisfactory treatment results for high-salt organic wastewater from chemical plants. Electrochemical oxidation technology is a simple, efficient water treatment technology that requires no external chemical reagents. Current electrode materials primarily rely on indirect electron transfer to treat recalcitrant organic matter, i.e., the release of hydroxyl radicals on the electrode surface to oxidize the recalcitrant organic matter.

[0003] However, the hydroxyl radicals released during electrochemical oxidation have short lifespans and low concentrations in water. Furthermore, the high concentration of chloride ions in wastewater quenches these hydroxyl radicals, impacting the efficiency and energy consumption of electrochemical systems treating high-salt organic wastewater. Therefore, the search for highly efficient electrode materials that release high concentrations of active oxides is currently a hot research topic in the field of electrooxidation for treating high-salt organic wastewater from chemical plants.

[0004] High-salt organic wastewater contains high concentrations of chloride ions, which can undergo chlorine evolution at the anode, generating high concentrations of chlorine free radicals (Cl·, ClO·, Cl2). ·- Ruthenium and iridium, among other oxidizing substances such as hypochlorous acid and hypochlorite ions, are suitable for electrochemical oxidation processes. For example, CN113716658A provides a method for preparing a ternary metal mesh electrode containing a nano-tip structure of ruthenium, iridium, and titanium. The mesh electrode, coated with 23.20% ruthenium, 43.08% iridium, and 32.4% titanium, can treat ammonium ions in wastewater with a chloride ion concentration of 3 g / L. However, the high-temperature calcination process in this technology may result in a loose and easily peeled active layer of the prepared metal oxide, becoming a bottleneck restricting the electrode's ability to generate large quantities of chloride free radicals effectively over a long period.

[0005] Furthermore, the current intensity used in existing technologies is generally too high. For example, CN108264134A provides an electrolytic electrode and electrolytic oxidation treatment method for high-salt, high-COD wastewater, with a current intensity of 8-10A applied during treatment. However, high current and cell voltage have disadvantages such as high energy loss, wasted electricity, and high requirements for equipment and materials. Moreover, it will significantly aggravate the occurrence of side reactions such as oxygen evolution reaction in the system, reducing wastewater treatment efficiency. In addition, the electrodes in current technologies are usually plate electrodes, which can only be used for batch experiments, thus greatly limiting their practical application.

[0006] Membrane materials possess well-developed pore structures. If, based on low-pressure membranes and using the membrane separation interface as a carrier, efficient membrane separation can be achieved while simultaneously removing recalcitrant organic matter from high-salt chemical wastewater through technological coupling, this would be of significant practical importance for expanding the application of low-pressure membrane separation technology in wastewater treatment. Therefore, developing a highly efficient and stable electrochemical anodic filter membrane is currently a breakthrough point for realizing electrochemical oxidation water treatment technology. Summary of the Invention

[0007] To address the aforementioned problems in existing technologies, this invention provides an electrochemical tubular ceramic membrane for treating high-salt organic wastewater and its preparation method. This invention solves the key technical problems of low free radical concentration and low organic matter mineralization rate in electro-oxidation technology.

[0008] The technical solution of the present invention is as follows:

[0009] A method for preparing an electrochemical tubular ceramic membrane includes the following steps:

[0010] (1) Pretreatment and cleaning of tubular ceramic membrane substrate: The tubular ceramic membrane substrate is ultrasonically cleaned and then dried in a forced-air drying oven.

[0011] (2) Sputtering of titanium conductive layer: The tubular ceramic film substrate pretreated in step (1) is placed in a magnetron sputtering instrument and titanium is deposited in an argon atmosphere to obtain a titanium substrate tubular ceramic film with titanium conductive layer.

[0012] (3) Preparation of electrochemical tubular ceramic membrane: The titanium-based tubular ceramic membrane obtained in step (2) is placed in a magnetron sputtering instrument and ruthenium and iridium are deposited in an argon atmosphere, thereby depositing a ruthenium-iridium active layer on the surface of the titanium-based tubular ceramic membrane obtained in step (2), thus obtaining the electrochemical tubular ceramic membrane.

[0013] Preferably, the pore size of the tubular ceramic membrane substrate used in step (1) is 1-5 μm.

[0014] Preferably, the ultrasonic cleaning method in step (1) is as follows: the tubular ceramic membrane substrate is sequentially placed into a solution containing acetone, anhydrous ethanol and ultrapure water for ultrasonic cleaning.

[0015] Preferably, the thickness of the titanium conductive layer deposited in step (2) is 500-1000 nm, and the deposition rate is 1-5 nm min. -1 .

[0016] Preferably, the thickness of the ruthenium-iridium active layer deposited in step (3) is 100-300 nm, and the deposition rate is 1-5 nm min. -1 .

[0017] Preferably, the metal atom ratio of the ruthenium-iridium active layer deposited in step (3) is ruthenium:iridium = 50%: 50%.

[0018] The present invention also provides an application of the electrochemical tubular ceramic membrane obtained by the preparation method, wherein the electrochemical tubular ceramic membrane is used for the treatment of high-salt organic wastewater.

[0019] Furthermore, the application includes the following steps:

[0020] a: The electrochemical tubular ceramic membrane is connected to the positive terminal of a DC power supply via titanium wire and used as the anode, while copper mesh, titanium mesh, or stainless steel wire mesh is used as the cathode;

[0021] b: When voltage is applied, an electrochemical tubular ceramic membrane is used to filter high-salt organic wastewater, and an electro-oxidation reaction is carried out to remove organic matter from the water.

[0022] Preferably, the current density applied to the anode in step b is 1-8 mA cm⁻¹. -2 The filtered water flux is 30-150 Lm -2 h -1 .

[0023] Preferably, the high-salt organic wastewater contains tetrabromobisphenol S, with a concentration ranging from 20 to 200 mg / L. -1 The concentration of chloride ions in the high-salt organic wastewater ranges from 500 to 8000 mg / L. -1 .

[0024] The beneficial technical effects of this invention are as follows:

[0025] 1. The electrochemical tubular ceramic membrane prepared in this invention can effectively remove recalcitrant organic matter from high-salt organic wastewater. Utilizing the chlorine evolution reaction of the ruthenium-iridium electrochemical active layer, it generates chlorine free radicals (Cl·), chloroxychloride free radicals (ClO·), and chlorine diradicals (Cl2·). ·- Various free radical species, including HClO and ClO, as well as active chlorine (HClO, ClO) -This electrochemical tubular ceramic membrane effectively removes recalcitrant organic matter from simulated wastewater through oxidation. It addresses the key technical challenges of low free radical concentration and low organic matter mineralization rates in electro-oxidation technology.

[0026] 2. The electrochemical tubular ceramic membrane of the present invention has higher mechanical strength, simpler preparation process and better chemical stability. The large number of tortuous fluid channels distributed in the membrane can increase the contact between pollutants and free radical species, enhance the mass transfer in the system and the removal effect of organic matter, and can be applied to the efficient treatment of high-salt organic wastewater. Attached Figure Description

[0027] Figure 1 The images show the physical specimen and microstructure of the electrochemical tubular ceramic membrane prepared in Example 1.

[0028] Figure 2 The graph shows the removal rates of tetrabromobisphenol S and TOC in Application Examples 1 and 2.

[0029] Figure 3 The effect of continuous operation for 24 hours on the removal of pollutants and total organic carbon in Application Example 2 is shown.

[0030] Figure 4 For the determination of the concentration of free radicals in the system of Test Example 1.

[0031] Figure 5 Example 2 is used to determine the valence state of sputtered metal. Detailed Implementation

[0032] The present invention will now be described in detail with reference to the accompanying drawings and embodiments. Obviously, the described embodiments are merely some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0033] Example 1:

[0034] The preparation method of the electrochemical tubular ceramic membrane for high-salt organic wastewater treatment in this embodiment is carried out according to the following steps:

[0035] 1. Pretreatment and cleaning of tubular ceramic membrane substrate: The tubular ceramic membrane with a pore size of 2 micrometers is placed in solutions containing acetone, anhydrous ethanol and ultrapure water in sequence, and ultrasonically cleaned for 0.5 hours in each solution. After cleaning, the tubular ceramic membrane substrate is placed in a forced-air drying oven and dried at 100°C for 3 hours to remove the moisture from the tubular ceramic membrane substrate.

[0036] 2. Sputtering of the titanium conductive layer: The pretreated tubular ceramic film from step 1 is placed in a magnetron sputtering instrument, and titanium is deposited in an argon atmosphere to obtain a titanium-based tubular ceramic film with a titanium conductive layer. The deposition rate is 4 nm / min. -1 The thickness is 700nm;

[0037] 3. Preparation of electrochemical tubular ceramic film: The titanium-based tubular ceramic film obtained in step 2 was placed in a magnetron sputtering instrument, and ruthenium and iridium were simultaneously sputtered and deposited in an argon atmosphere at a deposition rate of 4 nm / min. -1 The thickness of the ruthenium-iridium mixture is 200 nm. A ruthenium-iridium active layer is deposited on the surface of the titanium-based ceramic membrane obtained in step 2, wherein the metal atomic ratio of the ruthenium-iridium active layer is ruthenium:iridium = 50%:50%, thus obtaining the electrochemical tubular ceramic membrane for high-salt organic wastewater treatment.

[0038] Figure 1 The image shows the morphological characteristics of the obtained electrochemical ceramic membrane. Figure 1 a and b are field emission scanning electron microscope (FET) images of the surface morphology of the electrochemical tubular ceramic membrane. c and d are EDS spectra of ruthenium and iridium on the surface of the electrochemical tubular ceramic membrane. e is a photograph of the electrochemical tubular ceramic membrane. f is a schematic diagram of the pretreatment and processing of the electrochemical tubular ceramic membrane. As can be seen from the figures, ruthenium and iridium active metal atoms are uniformly loaded onto the substrate surface.

[0039] Application Example 1:

[0040] The electrochemical tubular ceramic membrane prepared in Example 1 was used as the anode, and a titanium mesh was used as the cathode. The object being treated was simulated high-salt organic wastewater, with an initial organic matter tetrabromobisphenol S concentration of 100 mg / L. -1 The chloride ion concentration is 5850 mg / L. -1 The current density is 2 mA cm⁻¹ -2 At that time, the processing effect is as follows Figure 2 As shown, the removal rate of tetrabromobisphenol S can reach 98.9%, and the removal rate of TOC can reach 40.9%.

[0041] Application Example 2:

[0042] The electrochemical tubular ceramic membrane prepared in Example 1 was used as the anode, and a titanium mesh was used as the cathode. The object being treated was simulated high-salt organic wastewater, with an initial organic matter tetrabromobisphenol S concentration of 100 mg / L. -1 The chloride ion concentration is 5850 mg / L. -1 The current density is 2 mA cm⁻¹ -2 The flux is 30 L m -2 h -1 Under the conditions, the treatment effect is as follows Figure 2 As shown, the removal rate of tetrabromobisphenol S can reach ~100%, and the removal rate of TOC can reach 60.8%.

[0043] This application example is a continuous flow experiment. Wastewater is pumped into the reactor via a peristaltic pump, and then discharged at a set flow rate (30 L / m³). -2 h -1 Then, a second peristaltic pump draws it out from inside the ceramic membrane. Figure 3 The purpose of this study is to verify the long-term stability of the electrochemical tubular ceramic membrane during continuous operation of the electrode for 24 hours, and to assess its effectiveness in removing pollutants and total organic carbon.

[0044] As shown in the figure, during 24 hours of continuous operation, the electrochemical system maintained a removal rate of approximately 100% for tetrabromobisphenol S and a stable removal rate of approximately 55% for total organic carbon. This indicates that the electrochemical tubular ceramic membrane of this invention can well meet the needs of continuous long-term wastewater treatment in practice, and the electrode can maintain stable performance without significant performance degradation, which is beneficial for the practical application of the electrode.

[0045] Test Example 1:

[0046] Based on Application Example 1, the concentration of free radicals in the system during the treatment of high-salinity wastewater was tested. The test method was as follows: nitrobenzene, benzoic acid, dimethyl terephthalate, and carbamazepine were selected as hydroxyl radicals, Cl·, ClO·, and Cl2, respectively. ·- Chemical probes were used. These probes exhibited significantly different reaction rate constants with several free radicals, all of which are parameters known in the art. The initial concentration of each of the four probe reagents was 50 μM, determined by high-performance liquid chromatography (HPLC). The degradation kinetic constants of the four chemical probes were calculated using peak area-concentration standard curves according to conventional formulas in the art. Finally, the kinetic constants for hydroxyl radicals, Cl·, ClO·, and Cl2 were calculated. ·- The concentration.

[0047] After testing, the Cl2 in this system ·- The steady-state concentration reached 2.2 × 10⁻⁶. -10 M, followed by ClO·(6.7×10 -13 M), ·OH (0.95×10 -13 M) and Cl·(2.39×10 -15 M).

[0048] As a comparative reference, the inventors selected four prior art documents, namely:

[0049] ①Impact of EfOM in the Elimination of PPCPs by UV / Chlorine: RadicalChemistry and Toxicity Bioassays. Wang et al., Water Res. 2021, 204, 117634;

[0050] ②Facile Ammonium Oxidation to Nitrogen Gas in Acid Wastewater by inSitu Photogenerated Chlorine Radicals. Yan et al., Water Res. 2021, 205, 117678;

[0051] ③A Bipolar Membrane-Integrated Electrochlorination Process for Highly Efficient Ammonium Removal in Mature Landfill Leachate: The Importance of ClO·Generation. Kuang et al., Environ.Sci.Technol.2022;

[0052] ④Multiple Roles of Dissolved Organic Matter in Advanced OxidationProcesses. Yang et al., Environ. Sci. Technol. 2022, 56(16), 11111–11131.

[0053] The concentrations of various free radicals given in the above four articles are as follows: Figure 4 As shown in the figure. It can be seen from the graph that at high concentrations of Cl... - In the electrocatalytic process present, the Cl2 of this invention ·- The steady-state concentration was significantly higher than that reported in comparative literature, exceeding it by approximately one to two orders of magnitude. This indicates that the electrode material in this invention can significantly promote the generation of Cl2 in the electrochemical system. ·- This enhances the efficiency of electrochemical systems in removing organic pollutants.

[0054] Test Example 2:

[0055] The valence state of the electrochemical tubular ceramic membrane prepared in Example 1 was determined, and the material was characterized by grazing incidence X-ray diffraction, X-ray photoelectron diffraction, and BET surface area detection.

[0056] Test results are as follows Figure 5 As shown. Figure 5 a is the grazing incidence X-ray diffraction (GI-XRD) result of the electrochemical tubular ceramic membrane, indicating that Ru and Ir were uniformly sputtered on the surface of the tubular ceramic membrane substrate. Figure 5 b and Figure 5 X-ray photoelectron spectroscopy (XPS) results for c indicate that Ru and Ir exist in a zero-valence state. Figure 5 d represents the BET pore size distribution of the tubular ceramic membrane substrate and the electrochemical tubular ceramic membrane. It can be seen that the internal pore size distribution of the electrochemical tubular ceramic membrane is mainly mesoporous, with a large specific surface area, which can provide more contact opportunities for catalytic reactions, thus improving the efficiency and rate of catalytic reactions.

[0057] Although the embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the specification and embodiments. They can be applied to various fields suitable for the present invention. For those skilled in the art, and for those of ordinary skill in the art, various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the present invention. Therefore, the present invention is not limited to the specific details without departing from the general concept defined by the claims and their equivalents.

Claims

1. Use of an electrochemical tubular ceramic membrane, characterized in that, The electrochemical tubular ceramic membrane is used for treating high-salt organic sewage, and the current density applied to the anode of the electrochemical tubular ceramic membrane is 1-2 mA cm -2 ; The high-salinity organic wastewater contains tetrabromobisphenol S, and the concentration range is 20-200 mg / L -1 ; the concentration range of chlorine ions in the high-salinity organic wastewater is 5850-8000 mg / L -1 ; The preparation method of the electrochemical tubular ceramic membrane comprises the following steps: (1) Pretreatment cleaning of the tubular ceramic membrane substrate: ultrasonic cleaning is performed on the tubular ceramic membrane substrate, and the cleaned tubular ceramic membrane substrate is placed in a blast drying oven for drying; (2) Sputtering of the titanium conductive layer: the pretreated tubular ceramic membrane substrate in step (1) is placed in a magnetron sputtering instrument, titanium is deposited in an argon atmosphere, and a titanium substrate tubular ceramic membrane with a titanium conductive layer is obtained; (3) Preparation of the electrochemical tubular ceramic membrane: the titanium substrate tubular ceramic membrane obtained in step (2) is placed in a magnetron sputtering instrument, ruthenium and iridium are deposited in an argon atmosphere, a ruthenium-iridium active layer is deposited on the surface of the titanium substrate tubular ceramic membrane obtained in step (2), the metal atomic ratio of the deposited ruthenium-iridium active layer is ruthenium: iridium = 50%: 50%, and the electrochemical tubular ceramic membrane is obtained.

2. Use according to claim 1, characterized in that, The pore size of the tubular ceramic membrane substrate used in step (1) is 1-5 μm.

3. Use according to claim 1, characterized in that, The ultrasonic cleaning method in step (1) is as follows: the tubular ceramic membrane substrate is sequentially placed in solutions containing acetone, anhydrous ethanol and ultrapure water for ultrasonic cleaning.

4. Use according to claim 1, characterized in that, The thickness of the titanium conductive layer deposited in step (2) is 500-1000 nm, and the deposition rate is 1-5 nm / min -1 .

5. The use according to claim 1, characterized in that, The thickness of the ruthenium iridium active layer deposited in step (3) is 100-300 nm, and the deposition rate is 1-5 nm min -1 .

6. The use according to claim 1, characterized in that, The method comprises the following steps: a: the electrochemical tubular ceramic membrane is connected to the positive electrode of a direct current power supply by titanium wire and used as an anode, and a copper mesh, a titanium mesh or a stainless steel mesh is used as a cathode; b: a voltage is applied, and the electrochemical tubular ceramic membrane performs electro-oxidation reaction when filtering high-salt organic sewage, so as to remove organic matter in water.

7. Use according to claim 6, characterized in that, The water flux of the step b filtration is 30-150 L m -2 h -1 .

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