Method for electrocatalytic hydrogenation dehalogenation of haloacetic acid or halomethane in water body

Abstract

The invention discloses a method for electrocatalytic hydrogenation dehalogenation of haloacetic acid or halomethane in a water body, which is characterized in that a conductive material of which the surface is modified with ruthenium or platinum is used as a catalytic cathode, water is used as a hydrogen source, and the haloacetic acid or halomethane in the water body is subjected to electrochemical hydrogenation dehalogenation to form acetic acid or methane. The price of precious metal in the catalytic cathode is lower, and the unit price of ruthenium is far lower than that of palladium and rhodium; and compared with a palladium-modified catalytic cathode, the dechlorination selectivity is higher, and the selectivity of hydrodechlorination of trichloroacetic acid into acetic acid in a water body is improved by 11.7%.

Description

(I) Technical field

[0001] The invention belongs to the field of electrochemical water treatment, and specifically relates to a method for electrochemically hydrogenating and dehalogenating haloacetic acid or methyl halide in water into acetic acid and methane by using a conductive material with surface modified with ruthenium or platinum as a catalytic cathode and water as a hydrogen source. (II) Background technology

[0002] Haloacetic acids and halomethanes are common halogen-containing organic pollutants in drinking water, surface water and groundwater. These two types of pollutants are characterized by low concentration, high toxicity and difficulty in treatment. If they are not controlled or treated, they will cause great harm to the ecological environment and human health. The electrochemical method using surface-modified palladium conductive materials as catalytic cathodes can remove haloacetic acids and trihalomethanes from water at room temperature and pressure, but this method has the problem of incomplete dehalogenation. Taking the electrochemical catalytic hydrogenation dechlorination of trichloroacetic acid in water as an example, the current electrochemical catalytic hydrogenation method using surface-modified palladium conductive materials usually produces a high proportion of monochloroacetic acid as the final product [Electrochimica Acta 232 (2017) 13–21], and the toxicity of monochloroacetic acid is nearly 50 times that of trichloroacetic acid [Fundam.Appl.Toxicol.17,240–253 (1991)].

[0003] The existing method discloses an electrochemical catalytic hydrogenation method using a rhodium-containing material as a catalyst. The hydrogen in this method is generated in situ by electrolysis of water, and various haloacetic acids can be highly selectively hydrogenated and dehalogenated into acetic acid [Nature Water, 2023, 1(1):95-103]. However, the rhodium in the catalyst used in this method is too expensive and requires a large amount of palladium metal (palladium film), which makes it difficult to apply on a large scale. (III) Summary of the invention

[0004] The present invention aims to provide a method for electrocatalytic hydrogenation and dehalogenation of haloacetic acid or methyl halide in water, wherein a conductive material with surface modified with ruthenium or platinum is used as a catalytic electrode and water is used as a hydrogen source to electrochemically hydrogenate and dehalogenate haloacetic acid or methyl halide in water into acetic acid or methane. The method of the present invention adopts the conductive material with surface modified with ruthenium or platinum, which can not only reduce the unit price and the amount of precious metal, but also has the advantage of high dehalogenation selectivity.

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

[0006] The invention provides a method for electrocatalytic hydrogenation and dehalogenation of haloacetic acid or methyl halide in water. The method uses a conductive material with a surface modified with ruthenium or platinum as a catalytic electrode and water as a hydrogen source to electrochemically hydrogenate and dehalogenate the haloacetic acid or methyl halide in water into acetic acid or methane.

[0007] Furthermore, the haloacetic acid includes trichloroacetic acid, dichloroacetic acid, monochloroacetic acid, tribromoacetic acid, dibromoacetic acid, and monobromoacetic acid; the halogenated methane includes chloroform, dichloromethane, chloromethane, bromodichloromethane, bromoform, and dibromochloromethane.

[0008] Furthermore, the conductive material is any conductive solid material with stable chemical properties under the reaction conditions, including metal materials or carbon materials.

[0009] Furthermore, the metal material includes nickel, titanium, copper, silver, stainless steel, etc.; the carbon material includes carbon paper, activated carbon, carbon fiber, graphite felt, foamed glassy carbon, etc.

[0010] Furthermore, the electrode is Ru / Ni, Ru / stainless steel, Ru / graphite felt, Ru / C / carbon paper, Ru / Al2O3 / carbon paper, Pt / Ni, Pt / stainless steel, Pt / graphite felt.

[0011] Furthermore, the temperature range of the electrochemical hydrogenation dehalogenation reaction is 5 to 90° C., and the potential is -0.5 V to -0.8 V vs. silver / silver chloride reference electrode.

[0012] Furthermore, the concentration of the haloacetic acid or methyl halide in the water body is in the range of 10 μg / L to 1 g / L, preferably 3 mg / L.

[0013] Furthermore, the water body includes drinking water, surface water or groundwater.

[0014] The electrocatalytic hydrogenation and dehalogenation of haloacetic acid or methyl halide in water of the present invention is carried out by a diaphragm electrolytic cell according to the following steps: a diaphragm electrolytic cell is used as a reactor, a cationic membrane is used as a diaphragm, a conductive material with surface modification of ruthenium or platinum is used as a cathode, iridium oxide modified titanium is used as an anode, a sodium sulfate aqueous solution is used as an anolyte, a water body (pH=7.2) containing haloacetic acid or methyl halide + sodium sulfate is used as a cathode liquid, the cathode liquid temperature is controlled to be 5-90°C (preferably 25°C), the cathode potential is -0.5V vs. silver / silver chloride reference electrode (saturated potassium chloride aqueous solution), and after 60 minutes of reaction, the haloacetic acid or methyl halide in the water body is electrochemically hydrogenated and dehalogenated to acetic acid or methane. The sodium sulfate aqueous solution concentration of the anolyte is 5mM; the sodium sulfate concentration in the cathode liquid is 1-5mM (preferably 2mM), and the haloacetic acid or methyl halide concentration is 10μg / L-1g / L, preferably 1-5mg / L (more preferably 3mg / L).

[0015] The electrocatalytic hydrogenation and dehalogenation of haloacetic acid or methyl halide in water of the present invention is carried out by a membrane-free electrolytic cell according to the following steps: a membrane-free beaker is used as a reactor, a conductive material with surface modification of ruthenium or platinum is used as a cathode, iridium oxide modified titanium is used as an electrode, a water body (pH=7.2) containing haloacetic acid or methyl halide + sodium sulfate is used as an electrolyte, the electrolyte temperature is controlled to be 5-90°C (preferably 25°C), the electrode potential is -0.8V vs. silver / silver chloride reference electrode (saturated potassium chloride aqueous solution), and after 60 minutes of reaction, the haloacetic acid or methyl halide in the water is electrochemically hydrogenated and dehalogenated to acetic acid or methane. The sodium sulfate concentration in the electrolyte is 1-5mM (preferably 2mM), and the haloacetic acid or methyl halide concentration is 10μg / L-1g / L, preferably 1-5mg / L (more preferably 3mg / L).

[0016] The content of ruthenium or platinum on the surface of the conductive material, the current density or the electrode potential are not critical factors of the present invention and can be varied according to the concentration of the haloacetic acid and the methyl halide. Preferably, the content of ruthenium or platinum is 0.1-3 mg / cm based on the surface area of ​​the conductive material. 2 , more preferably 1 mg / cm 2 .

[0017] The method of modifying ruthenium or platinum on the conductive material is not a key factor of the present invention. The conductive material can be modified by electroplating or chemical plating, or by brush coating with Nafion as an adhesive. When the brush coating method is used for modification, the ruthenium or platinum can be first loaded on a carbon support, or can be first loaded on a metal oxide, such as aluminum oxide, titanium oxide, and cerium oxide.

[0018] The type of electrochemical reactor and anode material are not key factors of the present invention either, and the reaction can be carried out in a diaphragm electrochemical reactor or in a diaphragmless electrochemical reactor. The anode material can be selected from stable materials in any reaction system, such as a titanium anode or a noble metal modified titanium anode (iridium oxide modified titanium anode).

[0019] Compared with the prior art, the beneficial effects of the present invention are mainly reflected in: (1) the present invention uses a conductive material with a surface modified with ruthenium or platinum as a catalytic electrode, the unit price of ruthenium or platinum is much lower than that of rhodium, and no palladium is needed, which effectively reduces the cost of the reaction device; (2) compared with the palladium-modified catalytic cathode, the conductive material with a surface modified with ruthenium or platinum as a catalytic cathode of the present invention has higher dechlorination selectivity, and the selectivity of trichloroacetic acid hydrogenation dechlorination to acetic acid in water is increased by 11.7%. (IV) Description of the drawings

[0020] Figure 1 , ion chromatogram of the reaction solution before and after the reaction.

[0021] Figure 2 , schematic diagram of the electrolytic cell. (V) Specific implementation methods

[0022] The present invention is further described below in conjunction with specific embodiments, but the protection scope of the present invention is not limited thereto:

[0023] In the following examples, the electrochemical reactor and components were provided by Hangzhou Sai'ao Electrochemical Instrument Co., Ltd. Unless otherwise specified, the cathode or anode was purchased from Hangzhou Sai'ao Electrochemical Instrument Co., Ltd. The initial pH of the cathode liquid or electrolyte was adjusted by sulfuric acid or sodium hydroxide.

[0024] Conversion rate Yield Selectivity Where C0 is the initial reactant molar concentration, C1 is the reactant molar concentration at the end of the reaction, and C2 is the target product molar concentration at the end of the reaction.

[0025] Example 1: Electrochemical Hydrogenation Dechlorination of Trichloroacetic Acid in Tap Water

[0026] The H-type electrolytic cell was used as the reactor, Nafion 324 membrane was used as the diaphragm, and Ru-modified nickel foam was used as the cathode (Ru / Ni, 2×4 cm 2 , Ru content 1mg / cm 2 ), iridium oxide modified titanium as anode (2×4cm 2 , iridium oxide content 1.25mg / cm 2 ). 50mL 5mM sodium sulfate aqueous solution was used as the anolyte, 50mL tap water (pH=7.2, temperature=25°C) containing 3mg / L trichloroacetic acid + 2mM sodium sulfate was used as the catholyte, the cathode potential was controlled to be -0.5V vs. silver / silver chloride reference electrode (saturated potassium chloride aqueous solution), the reaction was performed for 60min, and samples were taken before and after the reaction for ion chromatography detection. The results are shown in Figure 1 , the conversion rate of trichloroacetic acid in tap water = 100%, the yield of acetic acid = 97.4%, and the selectivity of acetic acid 97.4%.

[0027] The preparation method of Ru-modified nickel foam is as follows: First, nickel foam (25 mm × 25 mm × 1.2 mm) was ultrasonically treated in acetone for 20 min, and then -1 The nickel foam was immersed in HNO3 aqueous solution for 5 min, and finally washed with a large amount of deionized water. Then, the nickel foam was used as the cathode and the platinum electrode was used as the anode. -1 RuCl3 and 0.1 mol·L -1 The aqueous solution of aminosulfonic acid is the cathode electrolyte, containing 0.5 mol·L -1 The aqueous solution of Na2SO4 was used as the anolyte and 0.1A·cm -2Electrodeposition was carried out at a current density of 100 to obtain ruthenium-loaded nickel foam (Ru / Ni).

[0028] Ion chromatography analysis conditions: Dionex ICS-2100 ion chromatograph, Dionex Ion Pac AG19 anion protection column (50mm×4mm) and Ion Pac AS19 anion separation column (250mm×4mm); ASRS-ULTRA anion suppressor (4mm); eluent: KOH isocratic elution, gradient program is 0-40min, 8mmol / L; flow rate: 1mL / min; injection volume: 25μL; column temperature: 30℃; detection cell temperature: 35℃; suppressor current 20mA; conductivity detection; external standard method quantification.

[0029] Example 2-6: Electrochemical Hydrodehalogenation of Different Halogenated Organic Compounds in Tap Water

[0030] The trichloroacetic acid in Example 1 was replaced by the same amount of reactants shown in Table 1, and other operations were the same. The results are shown in Table 1. It can be seen that various haloacetic acids and methyl halides can be electrochemically hydrogenated and dehalogenated to acetic acid or methane with high selectivity under the experimental conditions of Example 1.

[0031] Table 1 Electrochemical hydrogenation and dehalogenation reaction of different halogenated organic compounds in tap water

[0032]

[0033] Unless otherwise specified, the other reaction conditions are the same as those in Example 1.

[0034] Example 7-13: Electrochemical Hydrogenation Dechlorination of Trichloroacetic Acid in Tap Water - Different Catalytic Cathodes

[0035] The catalytic cathode in Example 1 was changed to the catalytic cathode shown in Table 2, and other operations were the same. The results are shown in Table 2. It can be seen that various catalytic cathodes modified with ruthenium or platinum can electrochemically hydrogenate and dechlorinate trichloroacetic acid to acetic acid with high selectivity.

[0036] Table 2 Electrochemical hydrogenation and dechlorination of trichloroacetic acid at different catalytic cathodes

[0037]

[0038]

[0039] Unless otherwise specified, the other reaction conditions were the same as those in Example 1, and the content of the noble metal on the catalytic cathode was 1 mg / cm 2 .

[0040] aPreparation method of Ru / SS and Ru / GF: Use 3 layers of 304 stainless steel mesh (25mm×25mm×0.2mm) or graphite felt (25mm×25mm×2mm) to replace nickel foam (25mm×25mm×1.2mm), and the other reaction conditions are consistent with the preparation method of Ru-modified nickel foam in Example 1.

[0041] b The preparation methods of Ru / C / CP and Ru / Al2O3 / CP are as follows: first, a Ru content of 1 mg / cm 2 Weigh Ru / C (Sigma-Aldrich, product number 206180) or Ru / Al2O3 (Sigma-Aldrich, product number 439916) according to the standard; then, add isopropanol and ethanol in a ratio of 1:3 to disperse the catalyst evenly; then add Nafion solution according to 5 times the weight of the catalyst and ultrasonically disperse for 20 minutes to obtain a slurry; finally, use a brush to evenly apply the slurry on carbon paper at a temperature range of 80°C to 90°C, and wait for the slurry to solidify to obtain Ru / C / CP and Ru / Al2O3 / CP.

[0042] c Preparation method of Pt / Ni, Pt / SS and Pt / GF: use "H2PtCl6 and HCl" instead of "RuCl3 and aminosulfonic acid", the matrix conductive materials are foamed nickel (25mm×25mm×1.2mm), 3 layers of 304 stainless steel mesh (25mm×25mm×0.2mm) and graphite felt (25mm×25mm×2mm), and the other reaction conditions are the same as the preparation method of Ru-modified foamed nickel in Example 1.

[0043] Examples 14-19. Electrochemical Hydrodechlorination of Trichloroacetic Acid in Water—Different Temperatures, Different Reactant Concentrations, Different Water Bodies, and Different Precious Metal Loadings

[0044] Example 1 was adjusted according to the conditions in Table 3, and other operations were the same. The results are shown in Table 3. It can be seen that in the temperature range of 5 to 40°C and the reactant concentration range of 10 μg / L to 1 g / L, trichloroacetic acid in tap water and well water can be highly selectively hydrogenated and dechlorinated to acetic acid on the Ru-modified nickel foam cathode.

[0045] Table 3 Hydrodechlorination reaction of trichloroacetic acid in water under different conditions

[0046]

[0047] Unless otherwise specified, the other reaction conditions are the same as those in Example 1. a The Ru content in the catalytic cathode is 3 mg / cm 2 , the reaction time is 6 hours; bThe Ru content in the catalytic cathode is 0.5 mg / cm 2 , the reaction time is 40 minutes; c The Ru content in the catalytic cathode is 0.1 mg / cm 2 , the reaction time is 20 minutes.

[0048] Example 20: Electrochemical Hydrogenation Dechlorination of Trichloroacetic Acid in Tap Water

[0049] A beaker without a diaphragm was used as the reactor and Ru-modified nickel foam was used as the cathode (2×4 cm 2 , Ru content 1mg / cm 2 ), iridium oxide modified titanium as anode (2×4cm 2 , iridium oxide content 1.25mg / cm 2 ). 50mL of tap water (pH=7.2, temperature=25°C) containing 3mg / L trichloroacetic acid + 2mM sodium sulfate was used as the electrolyte, and the cathode potential was controlled to be -0.8V vs. silver / silver chloride reference electrode (saturated potassium chloride aqueous solution). After 60min of reaction, the conversion rate of trichloroacetic acid in tap water = 99.7%, the yield of acetic acid = 97.3%, and the selectivity of acetic acid was 97.6%.

[0050] Example 21: Electrochemical Hydrogenation Dechlorination of Trichloroacetic Acid in Tap Water

[0051] As Figure 2 The electrolytic cell shown is a reactor, a Nafion 324 membrane is a diaphragm, and a Ru / C particle layer bonded by Nafion resin is a cathode (2×4 cm 2 , Ru content 1mg / cm 2 ), the iridium oxide particle layer bonded by Nafion resin is the anode (2×4cm 2 , iridium oxide content 1.25mg / cm 2 ). 50mL of tap water (pH=7.2, temperature=25°C) containing 3mg / L trichloroacetic acid was used as the cathode liquid, 50mL of deionized water was used as the anode liquid, and the cathode potential was controlled to be -0.8V vs. silver / silver chloride reference electrode (saturated potassium chloride aqueous solution). After 60min of reaction, the conversion rate of trichloroacetic acid in tap water = 99.5%, the yield of acetic acid = 96.3%, and the selectivity of acetic acid was 96.8%.

[0052] Comparative Example 1: Electrochemical Hydrogenation Dechlorination of Trichloroacetic Acid in Tap Water

[0053] The H-type electrolytic cell was used as the reactor, Nafion 324 membrane was used as the diaphragm, and Pd-modified nickel foam was used as the cathode (3×4 cm 2 , Pd content 1mg / cm 2 ), iridium oxide modified titanium as anode (2×4cm2 , iridium oxide content 1.25mg / cm 2 ). 50mL 5mM sodium sulfate aqueous solution is the anolyte, 50mL tap water (pH=7.2, temperature=25°C) containing 3mg / L trichloroacetic acid + 2mM sodium sulfate is the catholyte, the cathode potential is controlled to be -0.5V vs. silver / silver chloride reference electrode (saturated potassium chloride aqueous solution), after 60min of reaction, the conversion rate of trichloroacetic acid in tap water = 99.8%, the yield of monochloroacetic acid = 16.8%, the yield of acetic acid = 82.5%, and the selectivity of acetic acid is 85.7%. After 120min of reaction, the conversion rate of trichloroacetic acid in tap water = 100%, the yield of monochloroacetic acid = 16.1%, the yield of acetic acid = 83.7%, and the selectivity of acetic acid is 83.7%.

[0054] Compared with Example 1, the selectivity of acetic acid decreased by 11.7% at the same reaction time. The selectivity of acetic acid remained almost unchanged when the reaction time was extended.

[0055] The preparation method of Pd-modified nickel foam is as follows: First, nickel foam (25 mm × 25 mm × 1.2 mm) was ultrasonically treated in acetone for 20 min, and then heated to 40 °C in 0.5 mol·L -1 The nickel foam was immersed in HNO3 aqueous solution for 5 min, and finally washed with a large amount of deionized water. Then, the nickel foam was used as the cathode and the platinum electrode was used as the anode. -1 PdCl2 and 0.1 mol·L -1 The catholyte is an aqueous solution of HCl, containing 0.5 mol·L -1 The aqueous solution of Na2SO4 was used as the anolyte and 0.1A·cm -2 Electrodeposition was carried out at a current density of 1000 nm to obtain palladium-supported nickel foam (Pd / Ni).

[0056] Comparative Example 2: Electrochemical Hydrogenation Dechlorination of Chloroform in Tap Water

[0057] The H-type electrolytic cell was used as the reactor, Nafion 324 membrane was used as the diaphragm, and Pd-modified nickel foam was used as the cathode (3×4 cm 2 , Pd content 1mg / cm 2 ), iridium oxide modified titanium as anode (2×4cm 2 , iridium oxide content 1.25mg / cm 2). 50mL 5mM sodium sulfate aqueous solution is the anolyte, 50mL tap water (pH=7.2, temperature=25°C) containing 3mg / L chloroform + 2mM sodium sulfate is the catholyte, the cathode potential is controlled to be -0.5V vs. silver / silver chloride reference electrode (saturated potassium chloride aqueous solution), after 60min of reaction, the conversion rate of chloroform in tap water = 99.7%, the total yield of dichloromethane and monochloromethane = 13.1%, the yield of methane = 86.6%, and the selectivity of methane 86.9%. After 120min of reaction, the conversion rate of chloroform in tap water = 100%, the total yield of dichloromethane and monochloromethane = 11.1%, the yield of methane = 87.2%, and the selectivity of methane 87.2%.

[0058] Compared with Example 5, the selectivity of methane decreased by 11.1% at the same reaction time. The selectivity of methane remained almost unchanged when the reaction time was extended.

[0059] Comparative Example 3: Electrochemical Hydrogenation Dechlorination of Trichloroacetic Acid in Tap Water

[0060] The H-type electrolytic cell was used as the reactor, Nafion 324 membrane was used as the diaphragm, and iridium-modified nickel foam was used as the cathode (3×4 cm 2 , iridium content 1mg / cm 2 ), iridium oxide modified titanium as anode (2×4cm 2 , iridium oxide content 1.25mg / cm 2 ). 50mL 5mM sodium sulfate aqueous solution is the anolyte, 50mL tap water (pH=7.2, temperature=25°C) containing 3mg / L trichloroacetic acid + 2mM sodium sulfate is the catholyte, the cathode potential is controlled to be -0.5V vs. silver / silver chloride reference electrode (saturated potassium chloride aqueous solution), after 60min of reaction, the conversion rate of trichloroacetic acid in tap water = 99.8%, the yield of monochloroacetic acid = 11.3%, the yield of acetic acid = 88.1%, and the selectivity of acetic acid is 88.3%. After 120min of reaction, the conversion rate of trichloroacetic acid in tap water = 100%, the yield of monochloroacetic acid = 10.5%, the yield of acetic acid = 89.2%, and the selectivity of acetic acid is 89.2%.

[0061] Compared with Example 1, the selectivity of acetic acid decreased by 9.1% at the same reaction time. The selectivity of acetic acid remained almost unchanged when the reaction time was extended.

[0062] The preparation method of iridium-modified nickel foam is as follows: First, nickel foam (25 mm × 25 mm × 1.2 mm) was ultrasonically treated in acetone for 20 min, and then in 0.5 mol·L -1 The nickel foam was immersed in HNO3 aqueous solution for 5 min, and finally washed with a large amount of deionized water. Then, the nickel foam was used as the cathode and the platinum electrode was used as the anode.-1 IrCl3 and 0.1 mol·L -1 The catholyte is an aqueous solution of HCl, containing 0.5 mol·L -1 The aqueous solution of Na2SO4 was used as the anolyte and 0.1A·cm -2 Electrodeposition was carried out at a current density of 1000 nm to obtain palladium-supported nickel foam (Ir / Ni).

[0063] Comparative Example 4: Electrochemical Hydrogenation Dechlorination of Trichloroacetic Acid in Tap Water

[0064] The H-type electrolytic cell was used as the reactor, Nafion 324 membrane was used as the diaphragm, and silver-modified nickel foam was used as the cathode (3×4 cm 2 , silver content 1mg / cm 2 ), iridium oxide modified titanium as anode (2×4cm 2 , iridium oxide content 1.25mg / cm 2 ). 50mL 5mM sodium sulfate aqueous solution is the anolyte, 50mL tap water (pH=7.2, temperature=25°C) containing 3mg / L trichloroacetic acid + 2mM sodium sulfate is the catholyte, the cathode potential is controlled to be -0.5V vs. silver / silver chloride reference electrode (saturated potassium chloride aqueous solution), after 60min of reaction, the conversion rate of trichloroacetic acid in tap water = 95.2%, the yield of dichloroacetic acid = 9.8%, the yield of monochloroacetic acid = 11.5%, the yield of acetic acid = 74.3%, and the selectivity of acetic acid is 78.0%. After 120min of reaction, the conversion rate of trichloroacetic acid in tap water = 100%, the yield of monochloroacetic acid = 15.5%, the yield of acetic acid = 85.2%, and the selectivity of acetic acid is 85.2%.

[0065] Compared with Example 1, the selectivity of acetic acid decreased by 19.4% at the same reaction time.

[0066] The preparation method of silver-modified nickel foam is as follows: First, nickel foam (25 mm × 25 mm × 1.2 mm) was ultrasonically treated in acetone for 20 min, and then in 0.5 mol·L -1 The nickel foam was immersed in HNO3 aqueous solution for 5 min, and finally washed with a large amount of deionized water. Then, the nickel foam was used as the cathode and the platinum electrode was used as the anode. -1 AgNO3 and 0.1 mol·L -1 The aqueous solution of HNO3 is the cathode electrolyte, containing 0.5 mol·L -1 The aqueous solution of Na2SO4 was used as the anolyte and 0.1A·cm -2 Electrodeposition was carried out at a current density of to obtain palladium supported on nickel foam (Ag / Ni).

[0067] Comparative Example 5: Electrochemical Hydrogenation Dechlorination of Tetrachloromethane in Tap Water

[0068] The H-type electrolytic cell was used as the reactor, Nafion 324 membrane was used as the diaphragm, and Ru-modified nickel foam was used as the cathode (3×4 cm 2 , Ru content 1mg / cm 2 ), iridium oxide modified titanium as anode (2×4cm 2 , iridium oxide content 1.25mg / cm 2 ). 50mL 5mM sodium sulfate aqueous solution was used as the anolyte, 50mL tap water (pH=7.2, temperature=25°C) containing 3mg / L tetrachloromethane + 2mM sodium sulfate was used as the catholyte, the cathode potential was controlled to be -0.5V vs. silver / silver chloride reference electrode (saturated potassium chloride aqueous solution), after 60min of reaction, the conversion rate of tetrachloromethane in tap water = 84.5%, the methane yield = 59.3%, and the methane selectivity 70.2%.

[0069] This comparative example shows that the electrochemical hydrogenation dechlorination activity and dehalogenation selectivity of the Ru-modified nickel foam catalytic cathode for tetrachloromethane are far inferior to those of trichloroacetic acid, dichloroacetic acid, monochloroacetic acid, tribromoacetic acid, trichloromethane and monobromodichloromethane.

[0070] Comparative Example 6: Electrochemical Hydrogenation Dechlorination of Tetrachloroethane in Tap Water

[0071] The H-type electrolytic cell was used as the reactor, Nafion 324 membrane was used as the diaphragm, and Pt-modified nickel foam was used as the cathode (3×4 cm 2 , Pt content 1mg / cm 2 ), iridium oxide modified titanium as anode (2×4cm 2 , iridium oxide content 1.25mg / cm 2 ). 50mL 5mM sodium sulfate aqueous solution was used as the anolyte, 50mL tap water (pH=7.2, temperature=25°C) containing 3mg / L tetrachloroethane + 2mM sodium sulfate was used as the catholyte, the cathode potential was controlled to be -0.5V vs. silver / silver chloride reference electrode (saturated potassium chloride aqueous solution), after 60min of reaction, the conversion rate of tetrachloroethane in tap water was 86.7%, the methane yield was 62.2%, and the selectivity of methane was 71.7%.

[0072] This comparative example shows that the electrochemical hydrogenation dechlorination activity and dehalogenation selectivity of the Pt-modified nickel foam catalytic cathode for tetrachloroethane are far inferior to those of trichloroacetic acid, dichloroacetic acid, monochloroacetic acid, tribromoacetic acid, trichloromethane and monobromodichloromethane.

[0073] Comparative Example 7: Electrochemical Hydrogenation Dechlorination of 2,4,6-Trichlorophenol in Tap Water

[0074] The H-type electrolytic cell was used as the reactor, Nafion 324 membrane was used as the diaphragm, and Ru-modified nickel foam was used as the cathode (3×4 cm 2 , Ru content 1mg / cm 2 ), iridium oxide modified titanium as anode (2×4cm 2 , iridium oxide content 1.25mg / cm 2 ). 50mL 5mM sodium sulfate aqueous solution was used as the anolyte, 50mL tap water (pH=7.2, temperature=25°C) containing 3mg / L 2,4,6-trichlorophenol + 2mM sodium sulfate was used as the catholyte, the cathode potential was controlled to be -0.5V vs. silver / silver chloride reference electrode (saturated potassium chloride aqueous solution), after 60min of reaction, the conversion rate of 2,4,6-trichlorophenol in tap water was 86.8%, the phenol yield was 2.1%, and the selectivity of phenol was 2.4%.

[0075] This comparative example shows that the electrochemical hydrogenation dechlorination reaction activity and dehalogenation selectivity of the Ru-modified nickel foam catalytic cathode for 2,4,6-trichlorophenol are far inferior to those of trichloroacetic acid, dichloroacetic acid, monochloroacetic acid, tribromoacetic acid, trichloromethane and monobromodichloromethane.

Claims

1. A method for electrocatalytic hydrogenation and dehalogenation of haloacetic acid or methyl halide in water, characterized in that: The method uses a conductive material with a surface modified with ruthenium or platinum as a catalytic electrode and water as a hydrogen source to electrochemically hydrogenate and dehalogenate haloacetic acid or halomethylethane in water to form acetic acid or methane.

2. The method according to claim 1, characterized in that The haloacetic acids include trichloroacetic acid, dichloroacetic acid, monochloroacetic acid, tribromoacetic acid, dibromoacetic acid, and monobromoacetic acid; the halogenated methane includes chloroform, dichloromethane, monochloromethane, bromodichloromethane, bromoform, and dibromochloromethane.

3. The method according to claim 1, characterized in that The conductive material includes a metal material or a carbon material.

4. The method according to claim 3, characterized in that The metal materials include nickel, titanium, copper, silver, and stainless steel; the carbon materials include carbon paper, activated carbon, carbon fiber, graphite felt, and foamed glassy carbon.

5. The method according to claim 1, characterized in that The electrodes are Ru / Ni, Ru / stainless steel, Ru / graphite felt, Ru / C / carbon paper, Ru / Al2O3 / carbon paper, Pt / Ni, Pt / stainless steel, and Pt / graphite felt.

6. The method according to claim 1, characterized in that The reaction temperature range of the electrochemical hydrogenation dehalogenation is 5 to 90°C.

7. The method according to claim 1, characterized in that The concentration range of the haloacetic acid or methyl halide in the water body is 10 μg / L to 1 g / L.

8. The method according to claim 1, characterized in that The water body includes drinking water, surface water or groundwater.

9. The method according to claim 1, characterized in that The content of ruthenium or platinum is 0.1-3 mg / cm based on the surface area of ​​the conductive material. 2 .

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