Preparation of tubular electro-catalytic membrane with catalytic oxidation function

Abstract

The invention discloses a preparation method of a novel tubular Ti-NATA / SnO2-Sb electro-catalytic membrane added with a titanium dioxide nanotube array (TiO2-NATA) as a middle layer. The preparation method comprises the following steps: taking SnCl4H2O and SbCl3 as raw materials, carrying out alkali washing oil removal and oxalic acid etching, putting into an ethylene glycol solution containing 0.25 wt.% of NH4F and 2wt.% of H2O for positive polarization, then carrying out cathodization in a NaClO4 solution, carrying out high-temperature calcination to obtain an intermediate layer, then preparing an ethylene glycol, citric acid, SnCl4H2O and SbCl3 composite sol-gel solution, brushing the sol-gel solution loaded metal oxide catalyst layer by using a brush according to a certain weight, and finally preparing the SnCl4H2O / SbCl3 composite sol-gel catalyst layer. And drying in a drying oven, calcining in a muffle furnace, circulating to a certain weight, and calcining for 2 hours in the muffle furnace at the temperature of 500 DEG C to obtain the tubular Ti-NATA / SnO2-Sb electro-catalytic membrane. The TiO2 nanotube array intermediate layer has good conductivity, catalytic activity and large specific surface area, and can provide more active sites and improve the electrode activity when being used for modifying the electrode; and meanwhile, the service life of the electrode can be prolonged by introducing the TiO2 nanotube array intermediate layer.

Description

Technical Field

[0001] This invention relates to the field of water treatment materials, and in particular to the preparation of a tubular electrocatalytic membrane with catalytic oxidation function. Background Technology

[0002] In recent years, the chemical industry has developed rapidly, but the accompanying environmental problems have followed one after another. The discharge of industrial wastewater is increasing daily, and the impact of dissolved organic matter in it is even more serious. Electrocatalytic oxidation technology is widely used due to its high efficiency and lack of secondary pollution, but traditional electrocatalytic oxidation technology also has its drawbacks, such as high operating costs, especially for the treatment of recalcitrant wastewater, where energy consumption and equipment costs are also high. Therefore, in recent years, the direction of electrocatalytic oxidation has been towards using electrocatalytic membranes as electrodes. Electrocatalytic membranes combine electrochemical oxidation with membrane filtration. Compared with the original flat electrode, electrocatalytic membranes have through-pores inside, and water flows perpendicularly through the electrode during the reaction. The porous structure of electrocatalytic membranes can increase the electroactive area and increase the mass transfer rate, thereby improving degradation efficiency while reducing energy consumption.

[0003] Electrocatalytic membrane materials can be mainly classified into three types: titanium-based membranes, carbon-based membranes, and titanium suboxide membranes. Among them, titanium is widely used due to its corrosion resistance, chemical stability, and good electrical conductivity. Electrocatalytic membranes can be classified into two types: plate-type and tubular-type. The two types of electrocatalytic membranes differ in reactor design. Plate-type membrane reactors require the electrocatalytic membrane to be adhered and sealed to the reactor wall to separate the inlet and outlet water chambers. In contrast, tubular electrocatalytic membranes have their own chambers, naturally separating the inlet and outlet water chambers. This results in a simpler reactor design and easier scale-up. Summary of the Invention

[0004] In view of this, the present invention aims to propose a tubular Ti-NATA / SnO2-Sb electrocatalytic membrane with catalytic oxidation function. By utilizing the advantages of the large area and self-contained cavity of the tubular electrocatalytic membrane, a high-efficiency electrofiltration system can be formed, which can effectively treat organic matter in wastewater.

[0005] To achieve the above objectives, the technical solution of the present invention is implemented as follows:

[0006] The tubular Ti-NATA / SnO2-Sb electrocatalytic membrane was prepared by the following steps:

[0007] 1) Pretreatment of porous titanium tubes:

[0008] The porous titanium tube was polished to a bright finish using sandpaper. After rinsing with ultrapure water, the surface grease was removed with NaOH solution. After cleaning, oxalic acid was used for etching to increase the specific surface area. After treatment, the surface of the titanium tube had an uneven, textured layer, resulting in a clean surface free of oil and oxide scale.

[0009] 2) Titanium dioxide nanotube array:

[0010] The pretreated porous titanium tubes were immersed in an ethylene glycol solution containing NH4F and H2O for anodic oxidation to form a nanotube array (NTA). After cleaning, the cleaned porous titanium tubes were used as cathodes and placed in a NaClO4 solution for cathodication. Finally, the porous titanium tubes were calcined in a high-temperature muffle furnace to obtain the intermediate layer of titanium dioxide nanotube array (TiO2-NATA).

[0011] 3) Supported SnO2-Sb catalyst layer:

[0012] A metal oxide catalyst layer was loaded onto the intermediate layer of a titanium dioxide nanotube array (TiO2-NATA) using a sol-gel method. A mixed sol consisting of ethylene glycol, citric acid, SnCl4·5H2O, and SbCl3 was brushed onto the titanium tubes after the intermediate layer was loaded, and then dried in an oven to remove the intersolvent, resulting in a porous dry gel or aerogel. This dry gel was then calcined at high temperature in a muffle furnace to eliminate pores and achieve gel densification and sintering. This process was repeated, with a final long-term calcination in a muffle furnace for fixation. After calcination, the tubes were cooled to room temperature and ultrasonically cleaned with ultrapure water until the washing solution was clear to ensure thorough removal of loosely bound ash from the substrate and avoid affecting the electrolysis process.

[0013] Further: In step 1), the mass fraction of the NaOH solution is 40%, the reaction time is 40-80 minutes, and the reaction requires heating in a water bath at 80-90°C.

[0014] Furthermore, in step 1), the oxalic acid solution has a mass fraction of 10%, the reaction time is 100-120 min, and the reaction needs to be boiled.

[0015] Furthermore, in step 2), the ethylene glycol solution is an ethylene glycol solution of 0.25 wt.% NH4F and 2 wt.% H2O, the reaction voltage is 20 V, the oxidation time is 6-8 h, and the cathode electrode material is graphite.

[0016] Furthermore, in step 2), the concentration of the NaClO4 solution is 1 mol / L, and the reaction current density is 5-10 mA / cm². 2 The cathodic treatment time is 10-20 min, and the anode electrode material is graphite.

[0017] Furthermore, in step 2), the temperature of the muffle furnace is 500-600℃, and the calcination time is 1 hour.

[0018] Furthermore, in step 3), the mixed sol composed of ethylene glycol, citric acid, SnCl4·5H2O, and SbCl3 is prepared by first dissolving citric acid in a dilute ethylene glycol solution at 60°C and continuously stirring for 30 minutes to induce a hydrolysis reaction to generate citrate ester. Then, the temperature of the above solution is raised to 90°C, and SnCl4·5H2O and SbCl3 are added to make the molar ratio of ethylene glycol:citric acid:SnCl4·5H2O:SbCl3 140:30:9:1. After boiling for 2 hours, the temperature is cooled to room temperature, and the gel solution is aged for 3-6 months to prepare a uniformly dispersed catalyst layer with suitable crystal particle size.

[0019] Furthermore, in step 3), the gel coating weight is 20-60 mg / g; the oven temperature is 130-150℃, and the drying time is 10-20 min; the muffle furnace temperature is 500-600℃, and the calcination time is 10-20 min, with the final calcination time being 2 h.

[0020] Compared with existing technologies, the tubular Ti-NATA / SnO2-Sb electrocatalytic membrane of the present invention has the following advantages:

[0021] (1) The tubular Ti-NATA / SnO2-Sb electrocatalytic membrane system of this invention has high degradation efficiency, no secondary pollution, and the material pores are not easily blocked. The electrocatalytic anode material has a nanostructured intermediate layer, which enhances the bonding between the substrate and the supported active catalyst layer, slows down the loss of the active layer, and effectively improves the operational stability and applicability of the system. The tubular Ti-NATA / SnO2-Sb electrocatalytic membrane generates active oxide species such as hydroxyl radicals, which promote the degradation of organic matter.

[0022] (2) The tubular Ti-NATA / SnO2-Sb electrocatalytic membrane of the present invention is convenient for designing reactors. The tubular electrocatalytic membrane can form its own cavity, which makes it easy to separate the inlet cavity from the outlet cavity. Attached Figure Description

[0023] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0024] Figure 1 This is a schematic diagram of the anodizing and cathodicization apparatus of the present invention.

[0025] Figure 2 This is a scanning electron microscope image of the surface of the electrocatalytic membrane described in Example 1 of the present invention.

[0026] Figure 3 The changes in organic matter in the reverse osmosis concentrate of dyeing and printing wastewater treated by the electrocatalytic membrane reactor in Example 2 under different treatment volumes over time. Detailed Implementation

[0027] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other.

[0028] The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0029] Example 1

[0030] A tubular electrocatalytic membrane with catalytic oxidation function is prepared by the following steps:

[0031] (1) Pretreatment of porous titanium tubes: The porous titanium tubes were polished alternately with 200-grit and 2000-grit sandpaper until they were shiny. After rinsing with ultrapure water for 10 min, they were placed in a 40% NaOH solution and reacted in an 85℃ water bath for 60 min. Then, they were ultrasonically cleaned with ultrapure water for 30 min. The cleaned porous titanium tubes were then placed in 10% oxalic acid and boiled for 120 min for etching. Finally, they were rinsed with ultrapure water for 30 min until they were colorless.

[0032] (2) Titanium dioxide nanotube array: The treated porous titanium tubes were immersed in an ethylene glycol solution containing 0.25 wt.% NH4F and 2 wt.% H2O, and anodized at 20 V for 6 h to form a nanotube array (NTA). After rinsing the porous titanium tubes with ultrapure water for 15 min, the rinsed porous titanium tubes were used as the cathode and graphite as the anode, and placed in a 1 mol / L NaClO4 solution at a current density of 5 mA / cm². 2 The titanium nanotubes were subjected to cathodic treatment for 15 minutes. Then they were washed with ultrapure water for 10 minutes, dried at room temperature, and finally calcined in air at 500°C for 1 hour to obtain the intermediate layer of titanium dioxide nanotube array (TiO2NATA).

[0033] (3) Supported SnO2-Sb catalyst layer:

[0034] ① Preparation of sol-gel: 630.42g of citric acid was dissolved in 868.98g of dilute ethylene glycol solution at 60℃, and stirred continuously for 30min to allow hydrolysis to occur, generating citrate ester. Then, the temperature of the solution was raised to 90℃, and 315.54g of SnCl4·5H2O and 22.812g of SbCl3 were added to form a mixed solution of ethylene glycol, citric acid, SnCl4·5H2O, and SbCl3 (molar ratio 140:30:9:1). After boiling the solution for 2h, the temperature was cooled to room temperature to form a pale yellow sol-gel solution. Before coating, the gel solution was aged for 3 months to prepare a uniformly dispersed catalyst layer with suitable crystal particle size.

[0035] ② Coating with SnO2-Sb layer: A porous titanium tube with grown TiO2-NATA was coated with gel using a brush at a gel weight of 40 mg / g. The tube was then dried in an oven at 140℃ for 10 min, followed by annealing in a muffle furnace at 500℃ for 10 min. This process was repeated 15 times until the desired weight was achieved. Finally, the tube was annealed in a muffle furnace at 500℃ for 2 h. After cooling to room temperature, the electrocatalytic membrane was ultrasonically cleaned with ultrapure water until the washing solution became clear, thus preparing the tubular Ti-NATA / SnO2-Sb electrocatalytic membrane.

[0036] Example 2

[0037] A diagram of an anodizing and cathodicization device, the structure of which is as follows: Figure 1 As shown, during anodizing, the anode is the tubular Ti-NATA / SnO2-Sb electrocatalytic membrane prepared in Example 1, and the cathode is a graphite electrode; during cathodicization, the anode is a graphite electrode, and the cathode is a tubular Ti-NATA / SnO2-Sb electrocatalytic membrane.

[0038] A cyclic experimental setup was used, with a tubular Ti-NATA / SnO2-Sb electrocatalytic membrane as the anode and a stainless steel mesh as the cathode, and a current density of 20 mA / cm² was set. 2 A peristaltic pump at a speed of 150 rpm was used to remove reverse osmosis concentrate from dyeing and printing wastewater. Experimental results are as follows: Figure 3 As shown, the tubular Ti-NATA / SnO2-Sb electrocatalytic membrane of the present invention can effectively degrade organic pollutants in the reverse osmosis concentrate of dyeing and printing wastewater under different treatment volumes.

[0039] The above detailed description is a specific description of one of the feasible embodiments of the present invention. This embodiment is not intended to limit the patent scope of the present invention. All equivalent implementations or modifications that do not depart from the present invention should be included in the scope of the technical solution of the present invention.

Claims

1. A tubular Ti-NATA / SnO2-Sb electrocatalytic membrane with catalytic oxidation function, characterized in that: It is prepared by the following steps: 1) Pretreatment of porous titanium tubes: This includes two steps: alkaline degreasing with NaOH solution and etching with oxalic acid. After treatment, the surface of the porous titanium tube has an uneven, textured layer, resulting in a clean surface free of oil and oxide scale. 2) Titanium dioxide nanotube array: The pretreated porous titanium tubes were immersed in an ethylene glycol solution containing NH4F and H2O and anodized in an anodizing and cathodic device to form a nanotube array (NTA); after cleaning, the cleaned porous titanium tubes were used as cathodes and cathodilated in NaClO4 solution; finally, the porous titanium tubes were calcined in a high-temperature muffle furnace to obtain the intermediate layer of titanium dioxide nanotube array (TiO2-NATA). 3) Loaded SnO2-Sb catalyst layer: A metal oxide catalyst layer was loaded onto the intermediate layer of a titanium dioxide nanotube array (TiO2-NATA) using the sol-gel method. A mixed sol composed of ethylene glycol, citric acid, SnCl4·5H2O, and SbCl3 was brushed onto the titanium tube after the intermediate layer was loaded. The tube was dried in an oven and then calcined at high temperature in a muffle furnace to eliminate the pores of the dry gel and achieve gel densification and sintering. This process was repeated until the weight was reached, and then the tube was calcined in a muffle furnace for a long time to fix it. After calcination, the tube was cooled to room temperature and ultrasonically cleaned with ultrapure water until the washing solution was clear.

2. The tubular NATA / SnO2-Sb electrocatalytic membrane with catalytic oxidation function according to claim 1, characterized in that... In step 1), the porous titanium tube is a non-uniform cylinder with an open top and closed bottom, and a pore diameter of 20 μm. The topmost part is a smooth cylindrical rod 3 cm long with a wall thickness of 2.5 mm and an outer diameter of 1.2 cm. Below it is a 10 cm cylinder with an outer diameter of 3 cm and a wall thickness of 2.5 mm. The bottommost part is a hemisphere with a height of 1 cm, an outer diameter of 3 cm, and a wall thickness of 2.5 mm.

3. The tubular Ti-NATA / SnO2-Sb electrocatalytic membrane with catalytic oxidation function according to claim 1, characterized in that... In step 1), the NaOH solution has a mass fraction of 40%, the reaction time is 40-80 minutes, and the reaction requires heating in a water bath at 80-90°C.

4. The tubular Ti-NATA / SnO2-Sb electrocatalytic membrane with catalytic oxidation function according to claim 1, characterized in that... In step 1), the oxalic acid solution has a mass fraction of 10%, the reaction time is 100-120 min, and the reaction needs to be boiled.

5. The tubular Ti-NATA / SnO2-Sb electrocatalytic membrane with catalytic oxidation function according to claim 1, characterized in that... The device for anodizing and cathodic treatment in step 2) is a cylindrical glass vessel with an outer diameter of 10 cm and a height of 20 cm, which is open at the top and closed at the bottom.

6. The tubular Ti-NATA / SnO2-Sb electrocatalytic membrane with catalytic oxidation function according to claim 1, characterized in that... In step 2), the ethylene glycol solution is a 0.25 wt.% NH4F and 2 wt.% H2O ethylene glycol solution, the anodizing voltage is 20V, the anodizing time is 6-8h, and the cathode electrode material is graphite.

7. The tubular Ti-NATA / SnO2-Sb electrocatalytic membrane with catalytic oxidation function according to claim 1, characterized in that... In step 2), the concentration of the NaClO4 solution is 1 mol / L, and the cathodic current density is 5-10 mA / cm². 2 The cathodic treatment time is 10-20 min, and the anode electrode material is graphite.

8. The tubular Ti-NATA / SnO2-Sb electrocatalytic membrane with catalytic oxidation function according to claim 1, characterized in that... In step 2), the temperature of the muffle furnace is 500-600℃, and the calcination time is 1 hour.

9. The tubular Ti-NATA / SnO2-Sb electrocatalytic membrane with catalytic oxidation function according to claim 1, characterized in that... In step 3), the mixed sol composed of ethylene glycol, citric acid, SnCl4·5H2O, and SbCl3 is prepared by first dissolving citric acid in a dilute ethylene glycol solution at 60°C and stirring continuously for 30 minutes to allow it to undergo a hydrolysis reaction to generate citrate ester. Then, the temperature of the above solution is raised to 90°C, and SnCl4·5H2O and SbCl3 are added to it, so that the molar ratio of ethylene glycol:citric acid:SnCl4·5H2O:SbCl3 is 140:30:9:

1. After boiling for 2 hours, the temperature is cooled to room temperature, and the gel solution is aged for 3-6 months to prepare a uniformly dispersed catalyst layer with suitable crystal particle size.

10. A tubular Ti-NATA / SnO2-Sb electrocatalytic membrane with catalytic oxidation function according to claim 1, characterized in that... In step 3), the gel coating weight is 20-60 mg / g, the oven temperature is 130-150℃, the drying time is 10-20 min, the muffle furnace temperature is 500-600℃, the calcination time is 10-20 min, and the final calcination time is 2 h.

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