Metal electrode modified with VB12 / graphene-modified epoxy resin and its application in catalytic dechlorination of trichloroacetic acid

Abstract

The present invention discloses a metal electrode modified with VB12 / graphene modified epoxy resin and its application in catalytic dechlorination of trichloroacetic acid. In the present invention, the metal electrode modified with VB12 / graphene modified epoxy resin is used as the cathode, and the graphite electrode is used as the anode to form an electrolytic cell device for catalytic electrolysis of the chlorinated disinfection by-product trichloroacetic acid. The highest degradation rate reaches 60% within 6 h of electrolysis, and it is expected to improve the electrolysis efficiency by increasing the graphene doping ratio. Targeted dechlorination is achieved, which has the advantages of strong dechlorination target, high dechlorination efficiency, no secondary pollution, simple electrolytic device and low cost, providing an excellent method for dechlorination of the chlorinated disinfection by-product trichloroacetic acid.

Description

(1) Technical Field

[0001] The present invention relates to a metal electrode modified by VB12 / graphene-modified epoxy resin and its application in the catalytic dechlorination of trichloroacetic acid. (2) Background Art

[0002] Chlorine is the most commonly used disinfectant for drinking water disinfection in China. However, chlorine will react with natural organic matter in water to generate various disinfection by-products (DBPs) with "carcinogenic, teratogenic, and mutagenic" effects. Currently, more than 700 kinds of DBPs are known, among which the earlier identified trihalomethanes and haloacetic acids are the most common carbon-containing disinfection by-products listed in the water quality standards. Trichloroacetic acid (TCAA) is a representative haloacetic acid disinfection by-product with strong cytotoxicity and genotoxicity.

[0003] There are mainly three ways for humans to contact disinfection by-products: skin absorption, direct ingestion, and inhalation. As water is an essential substance for the human body every day, the safety of water quality must be ensured. The ways to reduce DBPs mainly include precursor control, alternative disinfectants, and direct removal of DBPs. However, it is difficult to effectively remove organic matter in source water, and chlorine disinfection is still widely used on a large scale. Therefore, the presence of DBPs in tap water is inevitable, and the control of DBPs at the end is an effective way to ensure the safety of drinking water. (3) Summary of the Invention

[0004] The purpose of the present invention is to provide a new type of electrode material, a metal electrode modified by VB12 / graphene-modified epoxy resin, and its application in the electrolytic dechlorination of trichloroacetic acid, which directly catalyzes the electrolysis for the cleavage of C-Cl, improves the electrolysis efficiency, and aims to reduce the difficult-to-volatilize trichloroacetic acid in drinking water, providing new materials and technical support for the removal of chlorinated disinfection by-products.

[0005] The technical solution adopted by the present invention is as follows:

[0006] The present invention provides a VB12 / graphene-modified epoxy resin modified electrode, which is prepared according to the following steps: (1) Add graphene nanosheets to the ethanol dispersion of vitamin B12 (VB12) powder, and after ultrasonic mixing, obtain a VB12 / graphene mixed solution;

[0007] (2) Mix all the VB12 / graphene mixed solution in step (1) with chitosan, and after ultrasonic dispersion, obtain a mixed solution;

[0008] (3) Add epoxy resin to all the mixed solution in step (2), after ultrasonic dispersion, rotary evaporate and concentrate at room temperature until no liquid flows out. After the concentrate cools, add a water-based curing agent and stir for 15 min to obtain VB12 / graphene-modified epoxy resin;

[0009] (4) Use a coating rod to evenly coat the VB12 / graphene modified epoxy resin prepared in step (3) (it is only necessary to evenly coat both sides of the metal) on the surface of the metal electrode to obtain a metal electrode modified with VB12 / graphene modified epoxy resin.

[0010] Preferably, the ethanol dispersion of vitamin B12 powder in step (1) is to disperse VB12 powder in ethanol, and after ultrasonic mixing at 50 Hz for 20 - 30 min, a VB12 dispersion is obtained; the concentration of the VB12 powder dispersed in ethanol is 0.01 - 0.1 mM, preferably 0.02 mM.

[0011] Preferably, the purity of graphene nanosheets in step (1) > 99.5%.

[0012] Preferably, the ultrasonic mixing in step (1) is to perform ultrasonic treatment at 50 Hz for 30 min, and then stir and mix at room temperature for 20 - 30 min.

[0013] Preferably, the addition amount of graphene nanosheets in step (1) is 10 - 30 mg / mL based on the volume of ethanol, preferably 30 mg / mL.

[0014] Preferably, the addition amount of chitosan in step (2) is 5 - 15 mg / mL based on the volume of ethanol in step (1), preferably 15 mg / mL, and the ultrasonic dispersion is performed at 50 Hz for 30 min.

[0015] Preferably, the addition amount of epoxy resin in step (3) is 1 - 3 g / mL based on the volume of ethanol in step (1), preferably 2 g / mL. The addition amount of the water-based curing agent is 0.1 - 3 g / mL based on the volume of ethanol in step (1), preferably 0.2 g / mL. The ultrasonic dispersion is performed at 50 Hz for 30 min.

[0016] Preferably, the metal electrode in step (4) includes a steel electrode. The metal electrode is pretreated before coating. The pretreatment method is as follows: First, use ethanol and sandpaper to polish the metal electrode until there is no obvious dirt, then use 20% mass concentration alumina slurry (the function is to polish) and sandpaper to polish it until it shows a bright mirror surface. After rinsing it clean with distilled water, first place it in absolute ethanol and perform ultrasonic treatment at 50 Hz for 5 min, then place it in distilled water and perform ultrasonic treatment at 50 Hz for 5 min. After taking it out, clean and dry it to obtain the pretreated metal electrode.

[0017] The present invention also provides an application of the metal electrode modified with VB12 / graphene modified epoxy resin in catalyzing the dechlorination of trichloroacetic acid. The application comprises the following steps: using a graphite electrode as an anode, a metal electrode modified with VB12 / graphene modified epoxy resin as a cathode, using a trichloroacetic acid aqueous solution as an electrolyte, and using a 0.5 g / L sodium sulfate aqueous solution as an electrolyte to increase conductivity, with a current density of 20 mA / cm 2 , an electrolytic catalytic dechlorination reaction is carried out under light-proof and stirring conditions (preferably for 6 hours) to achieve the degradation of trichloroacetic acid.

[0018] Preferably, the anode and cathode are spaced 30 mm apart. The concentration of the trichloroacetic acid aqueous solution is 100-500 μg / L, preferably 200 μg / L.

[0019] The basic principle of the present invention is that atomic H· and VB12 transfer electrons to cooperatively dechlorinate trichloroacetic acid (as shown in Formula 1).

[0020] In the electrocatalytic dechlorination of trichloroacetic acid, the modified electrode at the cathode primarily undergoes a reduction reaction: atomic H· is generated at the cathode (equation 2), while electron-deficient C atoms also exist at the cathode. The generated atomic H· reacts with C atoms adjacent to chlorine to form C--H bonds, increasing the electron cloud density on the corresponding C atoms and reducing the energy of nearby C-Cl bonds, making them more susceptible to attack by nucleophilic groups (equations 3-7), which promotes the reaction and accelerates the dechlorination rate.

[0021] CCl3COOH+4H·+2e - →CH3COOH+H + +3Cl - (Formula 1)

[0022] H2O+e - →H·+OH - (Formula 2)

[0023] CCl3COOH→H + +CCl3COO - (Formula 3)

[0024] CCl3COO - +H·→·CCl3COO+e - (Formula 4)

[0025] ·CCl3COO+H + +2e - → CCl2HCOO+Cl - (Formula 5)

[0026] ·CCl2HCOO+H + +2e -→·CClH2COO + Cl - (Formula 6)

[0027] ·CClH2COO + H + + 2e - -→·CH3C00 + Cl - (Formula 7)

[0028] Compared with the prior art, the beneficial effects of the present invention are mainly reflected in:

[0029] The present invention uses a metal electrode modified with VBl2 / graphene-modified epoxy resin as the cathode and a graphite electrode as the anode to form an electrolytic cell device, which catalytically electrolyzes the chlorinated disinfection by-product trichloroacetic acid. The highest degradation rate reaches 60% within 6 hours of electrolysis, and it is expected to improve the electrolysis efficiency by increasing the graphene doping ratio. It realizes targeted dechlorination, has the advantages of strong dechlorination targeting, high dechlorination efficiency, no secondary pollution, simple electrolytic device, and low cost, providing an excellent method for dechlorinating the chlorinated disinfection by-product trichloroacetic acid. (IV) BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a schematic diagram of the electrolytic cell device of the present invention.

[0031] Figure 2 It is the electrolysis effect diagram of the VB12 / graphene-modified epoxy resin modified electrode prepared in Example 1; A represents the change of the degradation rate of trichloroacetic acid by different materials with time; B represents the first-order reaction rate of the electrolysis reaction of different materials.

[0032] Figure 3 It is the electrolysis effect diagram of the VB12 / graphene-modified epoxy resin modified electrode prepared in Example 2; A represents the change of the degradation rate of trichloroacetic acid by different materials with time; B represents the first-order reaction rate of the electrolysis reaction of different materials.

[0033] Figure 4 It is the electrolysis effect diagram of the VB12 / graphene-modified epoxy resin modified electrode prepared in Example 3; A represents the change of the degradation rate of trichloroacetic acid by different materials with time; B represents the first-order reaction rate of the electrolysis reaction of different materials. (V) SPECIFIC EMBODIMENTS

[0034] The present invention will be further described below in conjunction with specific embodiments, but the protection scope of the present invention is not limited thereto:

[0035] The actual cases are only for description and explanation, rather than limiting conditions. The instruments and reagents used in the cases are not indicated by the manufacturer, but can be obtained through normal procurement channels.

[0036] Example 1. VB12 / Graphene-Modified Epoxy Resin Modified Electrode and Catalytic Dechlorination of Trichloroacetic Acid

[0037] 1. Prepare VB12 / graphene modified epoxy resin.

[0038] (1) Disperse 0.1 mM of VB12 powder in 5.0 mL of ethanol to make the VB12 concentration 0.02 mM. After ultrasonic dispersion at 50 Hz for 30 min, a VB12 dispersion is obtained.

[0039] (2) Add 50 mg of graphene nanosheets to all of the VB12 dispersion in step (1). After ultrasonic treatment at 50 Hz for 30 min, stir and mix at room temperature for 30 min to prepare a VB12 / graphene mixture.

[0040] (3) Mix all of the VB12 / graphene mixture in step (2) with 25 mg of chitosan. After ultrasonic treatment at 50 Hz for 30 min, a mixed solution is obtained.

[0041] (4) Add 10 g of epoxy resin to all of the mixed solution in step (3). After ultrasonic treatment at 50 Hz for 30 min, rotary evaporate at room temperature for 45 min until no liquid flows out. After the concentrate cools, add 1 g of waterborne curing agent and stir for 15 min to obtain about 10 g of VB12 / graphene modified epoxy resin.

[0042] 2. Prepare a metal electrode modified with VB12 / graphene modified epoxy resin.

[0043] (1) Pretreatment of the metal electrode

[0044] The steel electrode (40×70×2 mm) is first polished with ethanol and sandpaper until there is no obvious dirt, and then polished with 20% mass concentration alumina slurry and sandpaper until it becomes a bright mirror surface. After rinsing with distilled water, it is first placed in absolute ethanol and ultrasonically treated at 50 Hz for 5 min, and then placed in distilled water and ultrasonically treated at 50 Hz for 5 min. After taking it out, wash and dry it to obtain a pretreated metal electrode.

[0045] (2) Use a coating rod to evenly coat 1 g of the VB12 / graphene modified epoxy resin prepared in step 1 on the surface of the metal electrode to obtain a metal electrode modified with VB12 / graphene modified epoxy resin, denoted as 10 mg graphene / 0.02 mM vb.

[0046] 3. Assemble an electrolytic cell device.

[0047] Refer to Figure 1, the electrolytic cell device includes an electrolytic cell main body, a beaker, a magnetic stirrer and a power supply; the electrolytic cell main body is made of cylindrical glass, with a height of 158 mm and an outer diameter of 105 mm. A fixed card slot is provided 30 mm from the bottom of the cell to stabilize the electrode and fix the electrode plate spacing at 30 mm. The electrolytic cell main body is wrapped with tin foil and placed in a beaker. The beaker is placed on a magnetic stirrer. The beaker mouth is wrapped with plastic wrap, and a sampling port is provided on the plastic wrap at the beaker mouth. The sampling port is sealed with plastic wrap during the reaction. Using a platinum electrode as the anode and the metal electrode modified with VB12 / graphene prepared in step 2 as the cathode, they are respectively connected to the power supply.

[0048] 4. Catalytic electrolysis for dechlorination of chlorinated disinfection by-products.

[0049] Prepare an aqueous solution of trichloroacetic acid with an initial concentration of 200 μg / L as the electrolyte solution, and use an aqueous solution of sodium sulfate at 0.5 g / L as the electrolyte. Both are added to the beaker. The current density is 20 mA / cm 2 , and carry out electrolytic catalytic dechlorination reaction under dark and stirring conditions. Each group is provided with 2 parallel reaction cells. 30 mL of samples are taken at 0, 0.5, 1, 2, 3, 4, and 6 h respectively, and the concentration of trichloroacetic acid in the samples is measured using GC / ECD. The removal rate of trichloroacetic acid is shown in Figure 2 Curve 10 mg graphene / 0.02 mM vb of A in. B keeps the abscissa of A unchanged and takes the logarithm of the ordinate. Linear fitting is carried out using Origin, and the slope of the straight line represents the reaction rate.

[0050] Under the same conditions, using the metal electrode prepared in (1) of step 2 (i.e., Figure 2 the pure steel electrode in) and the electrode prepared without VB12 powder (i.e., Figure 2 10 mg graphene in) as controls, the results are shown in Figure 2 .

[0051] From Figure 2 it can be seen that the degradation rate of trichloroacetic acid by the 10 mg graphene / 0.02 mM VB12 modified epoxy resin electrode is the highest and the reaction rate is the fastest.

[0052] Example 2

[0053] Change the addition amount of graphene nanosheets in Example 1 to 20 mg / mL ethanol, and keep other operations the same. The results are shown in Figure 3 as shown, Figure 3 indicating that the degradation rate of trichloroacetic acid by the 20 mg graphene / 0.02 mM VB12 modified electrode is the highest and is higher than that of the 10 mg graphene / 0.02 mM VB12 modified electrode; the reaction rate is the fastest and is faster than that of 10 mg graphene / 0.02 mM VB12.

[0054] Example 3

[0055] The addition amount of graphene nanosheets in Example 1 was changed to 30 mg / mL ethanol, and other operations were the same. The results are shown in Figure 4 as follows. Figure 4 It shows that the degradation rate of trichloroacetic acid by the 30 mg graphene / 0.02 mM VB12 modified electrode is the highest, and higher than that of the 20 mg graphene / 0.02 mM VB12 modified electrode; the reaction rate is the fastest, and faster than that of the 20 mg graphene / 0.02 mM VB12.

[0056] In summary, using a pure steel electrode plate, 26.23% of trichloroacetic acid was degraded after 6 h of electrolysis; using a 10 mg graphene-modified epoxy resin coating, 35.75% of trichloroacetic acid was degraded after 6 h of electrolysis; using a 0.02 mM VB12 / graphene-modified epoxy resin coating, 48.48% of trichloroacetic acid was degraded after 6 h of electrolysis; using a 20 mg graphene-modified epoxy resin coating, 50.70% of trichloroacetic acid was degraded after 6 h of electrolysis; using a 0.02 mM VB12 / graphene-modified epoxy resin coating, 55.65% of trichloroacetic acid was degraded after 6 h of electrolysis; using a z30 mg graphene-modified epoxy resin coating, 51.15% of trichloroacetic acid was degraded after 6 h of electrolysis; using a 0.02 mM VB12 / graphene-modified epoxy resin coating, 62.00% of trichloroacetic acid was degraded after 6 h of electrolysis. At the same time, the efficiency of electrolyzing trichloroacetic acid using 0.02 mM VB12 / graphene-modified epoxy resin is higher.

[0057] By adopting a steel electrode modified with VB12 / graphene-modified epoxy resin, the present invention effectively realizes the targeted dechlorination of trichloroacetic acid, and has strong targeting, high dechlorination efficiency, no secondary pollution, simple electrolysis device, and low cost, providing a new and efficient treatment method for the dechlorination of chlorinated disinfection by-products.

[0058] The above-described embodiments are only a relatively preferred solution of the present invention, and do not impose any form of limitation on the present invention. There are other variations and modifications without exceeding the technical solutions recorded in the claims.

Claims

1. A VB12 / graphene modified epoxy resin modified electrode, characterized in that, The electrode is prepared according to the following steps: (1) Add graphene nanosheets into an ethanol dispersion of vitamin B12 powder, and after ultrasonic mixing, obtain a VB12 / graphene mixed solution; (2) Mix all of the VB12 / graphene mixed solution obtained in step (1) with chitosan, and after ultrasonic dispersion, obtain a mixed solution; (3) Add epoxy resin to all of the mixed solution obtained in step (2), and after ultrasonic dispersion, rotary evaporate and concentrate at room temperature until no liquid flows out. After the concentrate cools, add an aqueous curing agent and stir for 15 min to obtain VB12 / graphene modified epoxy resin; (4) Use a coating rod to evenly coat the VB12 / graphene modified epoxy resin prepared in step (3) on the surface of a metal electrode to obtain a metal electrode modified with VB12 / graphene modified epoxy resin.

2. The VB12 / graphene modified epoxy resin modified electrode according to claim 1, wherein, In step (1), the ethanol dispersion of vitamin B12 powder is obtained by dispersing VB12 powder in ethanol and ultrasonic mixing at 50 Hz for 20 - 30 min; the concentration of the VB12 powder dispersed in ethanol is 0.01 - 0.1 mg / mL.

3. The VB12 / graphene modified epoxy resin modified electrode according to claim 1, wherein, In step (1), the ultrasonic mixing is carried out by ultrasonic treatment at 50 Hz for 30 min, and then stirring and mixing at room temperature for 20 - 30 min.

4. The VB12 / graphene modified epoxy resin modified electrode according to claim 1, wherein, In step (1), the addition amount of graphene nanosheets is 10 - 30 mg / mL based on the volume of ethanol.

5. The VB12 / graphene modified epoxy resin modified electrode according to claim 1, wherein In step (2), the addition amount of chitosan is 5 - 15 mg / mL based on the volume of ethanol in step (1), and the ultrasonic dispersion is carried out by ultrasonic treatment at 50 Hz for 30 min.

6. The VB12 / graphene modified epoxy resin modified electrode according to claim 1, wherein In step (3), the addition amount of epoxy resin is 1 - 3 g / mL based on the volume of ethanol in step (1); the addition amount of the aqueous curing agent is 0.1 - 3 g / mL based on the volume of ethanol in step (1); the ultrasonic dispersion is carried out by ultrasonic treatment at 50 Hz for 30 min.

7. The VB12 / graphene modified epoxy resin modified electrode according to claim 1, wherein In step (4), the metal electrode includes a steel electrode. The metal electrode is pretreated before coating. The pretreatment method is as follows: The metal electrode is first polished with ethanol and sandpaper until there is no obvious dirt, then polished with a 20% mass concentration alumina slurry and sandpaper until it shows a bright mirror surface. After rinsing with distilled water, it is first placed in absolute ethanol and ultrasonic treated at 50 Hz for 5 min, then placed in distilled water and ultrasonic treated at 50 Hz for 5 min. After taking it out, it is washed and dried to obtain a pretreated metal electrode.

8. Application of the metal electrode modified with the VB12 / graphene modified epoxy resin as described in claim 1 in the catalytic dechlorination of trichloroacetic acid.

9. The application according to claim 8, wherein The application is as follows: using a graphite electrode as the anode, a metal electrode modified with VB12 / graphene-modified epoxy resin as the cathode, an aqueous solution of trichloroacetic acid as the electrolyte, and an aqueous solution of sodium sulfate at 0.5 g / L as the electrolyte to increase conductivity, with a current density of 20 mA / cm 2 , and performing an electrolytic catalytic dechlorination reaction under the conditions of light avoidance and stirring to achieve the degradation of trichloroacetic acid.

10. The application according to claim 9, wherein The anode and the cathode are spaced 30 mm apart; the concentration of the trichloroacetic acid aqueous solution is 100 - 500 μg / L.

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