Method for treating ballast water by electrochemical synthesis of hydrogen peroxide

Abstract

The invention belongs to the technical field of electrochemistry, and discloses a method for treating ballast water by electrochemical synthesis of hydrogen peroxide. According to the method, a working electrode and a counter electrode are placed in an electrolytic tank containing ballast water or saline water, constant potential or constant current is applied to the electrolytic tank, oxygen or air is subjected to electrochemical reduction at the working electrode to synthesize hydrogen peroxide, and the hydrogen peroxide is used for ballast water treatment. The hydrophobic carbon material or the fluorine-doped carbon material is selected as the working electrode, the activity and the selectivity of electro-synthesis of hydrogen peroxide in seawater or a conventional electrolyte solution are good, industrial-grade current density efficient synthesis of hydrogen peroxide can be realized in a wide salt concentration and pH range, and the device and the method are suitable for various ballast water treatment environments, high in treatment speed, good in effect and suitable for popularization and application. The method is a pollution-reduction and carbon-reduction-oriented green and economic sustainable scheme, and has important significance in protecting the marine ecological environment and promoting the sustainable development of the shipping industry.

Description

Technical Field

[0001] The invention relates to the field of electrochemical technology, and in particular to a method for treating ballast water by electrochemically synthesizing hydrogen peroxide. Background Art

[0002] In commercial shipping, the transfer of ballast water is the main way for foreign aquatic species to invade. Biological invasion problems caused by off-site discharge will cause serious damage to the local marine ecological environment, and then have adverse effects on human health and economic activities. The International Convention for the Control and Management of Ships' Ballast Water and Sediments promulgated by the International Maritime Organization (IMO) clearly stipulates the relevant standards for ballast water treatment, including that the discharged ballast water must meet specific biological survival limits to prevent the invasion of foreign organisms. Therefore, efficiently treating and disinfecting ballast water to meet the standards of the convention is of great practical significance to the protection of marine ecology.

[0003] At present, the mainstream solutions for treating and disinfecting ballast water in commercial shipping include ultraviolet disinfection, chlorine treatment, and electrolytic chlorine to produce active species oxidation treatment methods (reference publication numbers are CN116729549A, CN104817214A, and CN111018044A Chinese patent applications). However, the above solutions are all limited for different reasons. The effectiveness of ultraviolet disinfection will be affected by the turbidity of the water, and ultraviolet rays will be blocked by suspended particulate matter, reducing the inactivation efficiency, and it is mainly suitable for ships with less ballast water. When the concentration of chlorine is high during chlorine treatment, carcinogens such as trihalomethanes will be produced, and studies have shown that chlorine treatment fails to significantly reduce the colonization pressure of zooplankton (J Appl Ecol. 2020, 57: 331-343.), and the treatment effect will be affected by salinity and temperature, which is not easy to control and maintain. Therefore, it is crucial to develop a ballast water treatment method that is efficient in sterilization and algae removal, environmentally friendly, and widely applicable.

[0004] Hydrogen peroxide has been proven to be an efficient disinfectant that can kill bacteria, viruses and floating plants and animals. The hydrogen peroxide residue after disinfection can be decomposed into water and oxygen. It is an efficient, non-toxic, odorless and environmentally friendly disinfectant. The production process of hydrogen peroxide includes many methods (anthraquinone method, electro-reduction of oxygen method, etc.). However, the traditional anthraquinone process has high energy consumption for producing high-concentration hydrogen peroxide, and is accompanied by the production of a large number of toxic organic byproducts, which poses safety risks during transportation and storage. Electro-reduction of oxygen is a green and economical alternative method for in-situ synthesis of hydrogen peroxide. In recent years, research in this field at home and abroad has focused on the development of efficient catalysts. For example, Chinese patent application CN115747835A uses organic frameworks (ZIFs) as templates to prepare nitrogen-doped carbon materials of different nitrogen types, and electro-catalyzes oxygen reduction to prepare hydrogen peroxide in 0.5 mol / L NaCl simulated seawater. Although some progress has been made, the current density of this scheme is low and insufficient to meet industrial-level applications. The selectivity and stability of synthesizing hydrogen peroxide under high current, neutral and especially high-salt conditions are poor, which limits the application of existing high-efficiency catalysts in ballast water treatment. Summary of the invention

[0005] The object of the present invention is to provide a method for treating ballast water by electrochemically synthesizing hydrogen peroxide, so as to solve the problem that the existing electrocatalytic oxygen reduction catalyst is difficult to synthesize hydrogen peroxide under high current, neutral or high salt conditions.

[0006] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0007] The present invention provides a method for treating ballast water by electrochemically synthesizing hydrogen peroxide. A working electrode and a counter electrode are placed in an electrolytic cell containing ballast water or salt water. A constant potential or a constant current is applied to the electrolytic cell. Oxygen or air is electrochemically reduced at the working electrode to synthesize hydrogen peroxide for ballast water treatment.

[0008] Preferably, in the method, the electrolysis cell containing ballast water or brine comprises a static electrolysis cell or a flow electrolysis cell.

[0009] Preferably, in the method, the working electrode comprises a hydrophobic carbon material or a fluorine-doped carbon material.

[0010] Preferably, in the method, the hydrophobic carbon material comprises hydrophobic carbon nanotubes, hydrophobic activated carbon, hydrophobic carbon black or hydrophobic porous carbon;

[0011] The fluorine-doped carbon material includes fluorine-doped carbon nanotubes, fluorine-doped activated carbon, fluorine-doped carbon black or fluorine-doped porous carbon.

[0012] Preferably, in the method, the working electrode is provided as a single electrode or two or more electrodes;

[0013] When the number of the working electrodes is two or more, the working electrodes are operated in series or in parallel.

[0014] Preferably, in the method, the electrochemical reduction of oxygen or air to synthesize hydrogen peroxide is used to directly treat the ballast water; or, the electrochemical reduction of oxygen or air to synthesize hydrogen peroxide is used in conjunction with chlorination, ultrasonication, ultraviolet light or ozone to treat the ballast water.

[0015] It can be seen from the above technical solution that compared with the prior art, the present invention has the following beneficial effects:

[0016] (1) The working electrode of the present invention is a hydrophobic carbon material or a fluorine-doped carbon material. Based on the high electronegativity of fluorine, the electronic structure of the carbon material is regulated, thereby changing the binding energy and local reaction microenvironment of the key intermediates in the production of hydrogen peroxide, so as to enhance the selectivity of its preparation of hydrogen peroxide. The high hydrophobicity of the material is conducive to enhancing oxygen mass transfer, overcoming the problem of electrode flooding, thereby enhancing the performance of electrosynthesizing hydrogen peroxide under industrial-grade current, and efficiently synthesizing hydrogen peroxide, solving the problem of low efficiency of existing electrocatalytic oxidation materials for ballast water treatment. At the same time, the hydrophobic carbon material or hydrophobic fluorine-doped carbon material of the present invention has good activity and selectivity in electrosynthesizing hydrogen peroxide in seawater or conventional electrolyte solution, and can achieve efficient synthesis of hydrogen peroxide at industrial-grade current density in a wide salt concentration (concentration 0.01-0.8 mol / L) and pH range (pH 1-13), and is suitable for a variety of ballast water treatment environments.

[0017] (2) The present invention uses hydrophobic carbon materials or fluorine-doped carbon materials as working electrodes to electrochemically synthesize hydrogen peroxide to treat ballast water. The method is simple, clean, low-cost, fast, and effective. It is a sustainable solution for a green economy aimed at reducing pollution and carbon emissions, and is of great significance for protecting the marine ecological environment and promoting the sustainable development of the shipping industry.

[0018] (3) The hydrophobic carbon material or fluorine-doped carbon material working electrode of the present invention is mainly composed of carbon elements that are abundant in the earth's crust. The preparation method is simple, the electrode stability is good, and it is easy to achieve large-scale application. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required to be used in the description of the embodiments or the prior art are briefly introduced below.

[0020] Figure 1 The performance of the fluorine-doped carbon nanotube material in preparing Example 2 for electrosynthesis of hydrogen peroxide;

[0021] Figure 2 This is the performance of the fluorine-doped carbon nanotube material of Preparation Example 3 in electrosynthesizing hydrogen peroxide to treat diatoms in seawater. DETAILED DESCRIPTION

[0022] The present invention provides a method for treating ballast water by electrochemically synthesizing hydrogen peroxide. A working electrode and a counter electrode are placed in an electrolytic cell containing ballast water or salt water. A constant potential or a constant current is applied to the electrolytic cell. Oxygen or air is electrochemically reduced at the working electrode to synthesize hydrogen peroxide for ballast water treatment.

[0023] In the present invention, the electrolytic cell containing ballast water or brine preferably includes a static electrolytic cell or a flowing electrolytic cell, and further preferably includes a flowing electrolytic cell.

[0024] In the present invention, the working electrode preferably comprises a hydrophobic carbon material or a fluorine-doped carbon material, and further preferably comprises a fluorine-doped carbon material.

[0025] In the present invention, the hydrophobic carbon material preferably includes hydrophobic carbon nanotubes, hydrophobic activated carbon, hydrophobic carbon black or hydrophobic porous carbon, further preferably includes hydrophobic carbon nanotubes, hydrophobic carbon black or hydrophobic porous carbon, and more preferably includes hydrophobic carbon nanotubes.

[0026] In the present invention, the fluorine-doped carbon material preferably includes fluorine-doped carbon nanotubes, fluorine-doped activated carbon, fluorine-doped carbon black or fluorine-doped porous carbon, further preferably includes fluorine-doped carbon nanotubes, fluorine-doped carbon black or fluorine-doped porous carbon, and more preferably includes fluorine-doped carbon nanotubes.

[0027] In the present invention, the counter electrode is preferably graphite, stainless steel, titanium or Pt, more preferably graphite or Pt, and more preferably Pt.

[0028] In the present invention, the method for preparing the fluorine-doped carbon material comprises the following steps:

[0029] (1) mixing a carbon material with an acid and reacting the mixture to obtain an acidified carbon material;

[0030] (2) The acidified carbon material is mixed with a fluorine-containing precursor and carbonized under a protective atmosphere to obtain a fluorine-doped carbon material.

[0031] In the present invention, in step (1), the carbon material preferably includes carbon nanotubes, activated carbon, carbon black or porous carbon, further preferably includes carbon nanotubes, carbon black or porous carbon, and more preferably includes carbon nanotubes.

[0032] In the present invention, the source of the carbon material in step (1) is not limited, and commercially available products or non-commercially available products known to those skilled in the art may be used.

[0033] In the present invention, in step (1), the acid preferably comprises nitric acid or a mixture of nitric acid and sulfuric acid, and more preferably a mixture of nitric acid and sulfuric acid.

[0034] In the present invention, the volume ratio of the nitric acid to the sulfuric acid is preferably 1:0 to 1:4, more preferably 1:2 to 1:4, and more preferably 1:3.

[0035] In the present invention, the mass concentration of the nitric acid before mixing is preferably 50 to 98%, more preferably 60 to 70%, and more preferably 65%.

[0036] In the present invention, the mass concentration of the sulfuric acid before mixing is preferably 50 to 98%, more preferably 80 to 98%, and even more preferably 98%.

[0037] In the present invention, in step (1), the ratio of the mass of the carbon material to the volume of the acid is preferably 0.1-2 g:40 mL, more preferably 0.5-1.5 g:40 mL, and more preferably 1 g:40 mL.

[0038] In the present invention, in step (1), the reaction temperature is preferably 60-120°C, more preferably 70-90°C, and more preferably 80°C; the reaction time is preferably 0.5-6h, more preferably 2-4h, and more preferably 3h.

[0039] In the present invention, in step (1), the reaction is preferably carried out in a water bath.

[0040] In the present invention, in step (1), after the reaction, the process preferably further comprises: washing, filtering and drying in sequence.

[0041] In the present invention, the washing agent is preferably water. The washing conditions are not limited, and washing until neutral is sufficient.

[0042] In the present invention, the conditions for the filtering and the drying are not limited, and any method known in the art may be used.

[0043] In the present invention, in step (2), the method of mixing the acidified carbon material and the fluorine-containing precursor is preferably: ultrasonically mixing the solution of the acidified carbon material and the fluorine-containing precursor with water, and then drying the resulting mixed solution.

[0044] In the present invention, in step (2), the fluorine-containing precursor preferably includes one or more of polytetrafluoroethylene, polyvinylidene fluoride, perfluorocarboxylic acid, perfluorosulfonic acid, ammonium fluoride, sodium fluoride, hydrogen fluoride, and calcium fluoride, and is further preferably polytetrafluoroethylene, polyvinylidene fluoride, perfluorocarboxylic acid, ammonium fluoride, sodium fluoride, and more preferably polytetrafluoroethylene.

[0045] In the present invention, the concentration of the fluorine-containing precursor solution is preferably 40 to 80 wt %, more preferably 55 to 65 wt %, and even more preferably 60 wt %.

[0046] In the present invention, the ratio of the mass of the acidified carbon material, the volume of the solution of the fluorine-containing precursor and the volume of the water is preferably 100-300 mg: 1600-2500 μL: 10 mL, further preferably 150-250 mg: 1980-2220 μL: 10 mL, and more preferably 200 mg: 2220 μL: 10 mL.

[0047] In the present invention, the mixed ultrasound condition is preferably 10 to 30 min, more preferably 15 to 25 min, and more preferably 20 min.

[0048] In the present invention, the conditions for drying the obtained mixed solution are not limited, and any method known in the art can be used.

[0049] In the present invention, in step (2), the mass ratio of the acidified carbon material to the fluorine-containing precursor is preferably 1:2-12, more preferably 1:8-10, and more preferably 1:10.

[0050] In the present invention, in step (2), the protective atmosphere preferably includes argon, nitrogen or helium.

[0051] In the present invention, in step (2), the carbonization device is preferably a tubular furnace.

[0052] In the present invention, in step (2), the carbonization temperature is preferably 500-1000°C, more preferably 600-700°C, and more preferably 600°C; the carbonization time is preferably 0.5-5h, more preferably 1.5-3h, and more preferably 2h; the heating rate to the desired carbonization temperature is preferably 2-10°C / min, more preferably 4-6°C / min, and more preferably 5°C / min.

[0053] In the present invention, in step (2), after the carbonization, the temperature preferably further comprises: cooling to room temperature.

[0054] In the present invention, the working electrode is preferably provided as a single electrode or two or more electrodes, and is further preferably provided as a single electrode.

[0055] In the present invention, when the working electrodes are provided in two or more forms, the working electrodes are preferably operated in series or in parallel.

[0056] In the present invention, the electrochemical reduction of oxygen or air synthesis of hydrogen peroxide is preferably used to directly treat ballast water; or, the electrochemical reduction of oxygen or air synthesis of hydrogen peroxide is used in conjunction with chlorination, ultrasonication, ultraviolet light or ozone to treat ballast water.

[0057] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0058] Preparation Example 1

[0059] This preparation example provides a method for preparing a fluorine-doped carbon nanotube material, comprising the following steps:

[0060] (1) Weigh 1 g of carbon nanotubes (outer diameter 20-30 nm, length 10-30 μm) in a beaker, add 10 mL of nitric acid (65 wt%) and 30 mL of sulfuric acid (98 wt%), place in a water bath at 80° C. and stir for 3 h, then rinse the product with water until the pH is neutral, filter and dry to obtain acidified carbon nanotubes;

[0061] (2) Weigh 200 mg of acidified carbon nanotubes into a beaker, take 1776 μL of 60 wt% PTFE solution according to the mass ratio of acidified carbon nanotubes to polytetrafluoroethylene (PTFE) of 1:8, add 10 mL of water, stir evenly by ultrasonication for 20 min, and dry the resulting mixed solution; place the dried sample in a tubular furnace, and heat the temperature to 600 °C at a heating rate of 5 °C / min under an argon atmosphere, carbonize at this temperature for 2 h, and then cool to room temperature to obtain a fluorine-doped carbon nanotube material.

[0062] Preparation Example 2

[0063] This preparation example provides a preparation method of fluorine-doped carbon nanotube material. The difference from Preparation Example 1 is that the mass ratio of acidified carbon nanotubes:PTFE in step (2) is changed to 1:9, the volume of PTFE solution is changed to 1998 μL, and the other parameter conditions are the same as those in Preparation Example 1.

[0064] Preparation Example 3

[0065] This preparation example provides a preparation method of fluorine-doped carbon nanotube material. The difference from Preparation Example 1 is that the mass ratio of acidified carbon nanotubes:PTFE in step (2) is changed to 1:10, the volume of PTFE solution is changed to 2220 μL, and the other parameter conditions are the same as those in Preparation Example 1.

[0066] Preparation Example 4

[0067] This preparation example provides a preparation method of fluorine-doped carbon nanotube material. The difference from Preparation Example 1 is that the mass ratio of acidified carbon nanotubes:PTFE in step (2) is changed to 1:11, the volume of PTFE solution is changed to 2442 μL, and the other parameter conditions are the same as those in Preparation Example 1.

[0068] Example 1

[0069] The fluorine-doped carbon nanotube material obtained in Preparation Example 2 was used as the working electrode, Pt as the counter electrode, and Ag / AgCl as the reference electrode to electro-reduce oxygen to synthesize hydrogen peroxide in a double-cell flow reactor. The experimental parameters were: working electrode area 4 cm 2 The cathode electrolyte is 50 mL of seawater (Dalian Bohai Sea, salt concentration 35‰, pH = 7.9), at 0.6-0.9 A / cm 2 The electrochemical reaction was carried out at an industrial current density of Figure 1 shown.

[0070] Depend on Figure 1 It can be seen that the fluorine-doped carbon nanotube material prepared in Preparation Example 2 has an efficiency of electrosynthesizing hydrogen peroxide of >92% at industrial-grade current density, and the hydrogen peroxide concentration reaches 891 mM (3.03 wt%) within half an hour, which can meet the needs of industrial-grade high-current water treatment applications.

[0071] Example 2

[0072] The seawater (Dalian Bohai Sea area, salt concentration 35‰, pH = 7.9) was boiled for disinfection and then cooled to room temperature; the glass bottle, kraft paper, gas diffusion electrode, and beaker were disinfected, and then added to the glass bottle with a volume ratio of seawater to algae solution of 3:1 (the algae solution manufacturer is Binzhou Fengyun Biotechnology Co., Ltd.) and nutrient solution (nutrient solution stock solution manufacturer is Shanghai Guangyu Biotechnology Co., Ltd., and the nutrient solution stock solution is diluted 1000 times to be the nutrient solution), and the volume ratio of algae solution to nutrient solution is 1:2. The bottle was sealed with kraft paper and placed in a biochemical incubator for culture to obtain a diatom solution. The diatoms were counted using the hemocytometer method, and the diatom density was 7.5×10 6 Pieces / mL.

[0073] The dual-cell flow reactor of Example 1 was used, and the fluorine-doped carbon nanotube material obtained in Preparation Example 3 was used as the working electrode. 50 mL of the diatom solution was placed in the sterilized reactor and heated at 0.6 A / cm 2 Hydrogen peroxide was electrosynthesized at a current density of 20 min. 24 mL of the electrosynthesized hydrogen peroxide solution was added to 50 mL of the diatom solution. Samples were taken and measured after 0.5, 1, 3, 5, and 10 min of reaction. The results are as follows: Figure 2 As shown. Figure 2It can be seen that the diatom removal rate is as high as 99.2% within 10 minutes.

[0074] The yield and efficiency of the electrosynthesis of hydrogen peroxide in this embodiment are significantly improved compared with the performance of reported nitrogen-doped carbon materials (Adv. Sci. 2023, 10: 2302446), cobalt-based catalysts (Energy. Environ. Sci. 2021, 14: 5444-5456, Nat. Commun. 2024, 15, 4079), zinc oxide (Energy Environ. Sci., 2023, 16, 3526-3533) and other materials.

[0075] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for treating ballast water by electrochemically synthesizing hydrogen peroxide, characterized in that: The working electrode and the counter electrode are placed in an electrolytic cell containing ballast water or salt water. A constant potential or constant current is applied to the electrolytic cell. Oxygen or air is electrochemically reduced at the working electrode to synthesize hydrogen peroxide for ballast water treatment.

2. The method according to claim 1, characterized in that The electrolytic cell containing ballast water or brine includes a static electrolytic cell or a flow electrolytic cell.

3. The method according to claim 1, characterized in that The working electrode includes a hydrophobic carbon material or a fluorine-doped carbon material.

4. The method according to claim 3, characterized in that The hydrophobic carbon material includes hydrophobic carbon nanotubes, hydrophobic activated carbon, hydrophobic carbon black or hydrophobic porous carbon; The fluorine-doped carbon material includes fluorine-doped carbon nanotubes, fluorine-doped activated carbon, fluorine-doped carbon black or fluorine-doped porous carbon.

5. The method according to claim 1 or 3, characterized in that: The working electrode is provided as a single electrode or two or more electrodes; When the number of the working electrodes is two or more, the working electrodes are operated in series or in parallel.

6. The method according to claim 1, characterized in that The electrochemical reduction of oxygen or air to synthesize hydrogen peroxide is used to directly treat the ballast water; or, the electrochemical reduction of oxygen or air to synthesize hydrogen peroxide is used in conjunction with a chlorination method, an ultrasonic method, an ultraviolet method or an ozone method to treat the ballast water.

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