Manufacturing process of titanium anode descaling antibacterial electrode

Abstract

The invention discloses a manufacturing process of a titanium anode descaling antibacterial electrode, and the titanium anode electrode with the characteristics of efficient catalytic performance, long service life, environmental protection and energy conservation is prepared by optimizing titanium substrate pretreatment, a coating formula and a sintering process. The method specifically comprises the steps of gradient surface treatment of a titanium substrate, ruthenium-iridium double-metal synergistic coating design and a low-temperature sintering process under nitrogen protection. The embodiment shows that the catalytic efficiency of the electrode is improved by 40% compared with that of a traditional process, the service life reaches 5 years or above, chemical agents are not needed, and the electrode is suitable for an industrial circulating water system. The key influence of the synergistic effect of the coating component proportion, the sintering condition and the pretreatment process on the performance is verified in proportion.

Description

Technical Field

[0001] The present invention relates to the technical field of electrochemical water treatment, in particular to a manufacturing process of a titanium anode descaling and antibacterial electrode, which is suitable for physical descaling and microbial control of cooling water and industrial circulating water systems. Background Art

[0002] In industrial circulating water systems, scale deposition and microbial growth are the core issues that lead to equipment corrosion and reduced heat exchange efficiency. Scale is mainly composed of insoluble salts such as calcium carbonate (CaCO3), calcium sulfate (CaSO4) and silicates, and its formation is closely related to water temperature, pH value, and ion concentration. Studies have shown that each millimeter of scale thickness can reduce heat exchange efficiency by about 10%-20% and increase pumping energy consumption by 15%-30%. In addition, the metabolic activities of microorganisms (such as sulfate-reducing bacteria and iron bacteria) not only accelerate pipeline corrosion, but also generate sticky biofilms, further hindering heat conduction. According to industry statistics, the global equipment maintenance cost due to scale and microbial problems exceeds US$12 billion each year (Frost & Sullivan, 2022).

[0003] Traditional solutions mainly rely on chemical dosing and physical descaling technologies, but their limitations are becoming increasingly apparent:

[0004] Chemical dosing method: Commonly used scale inhibitors (such as polyacrylic acid) and bactericides (such as sodium hypochlorite) can inhibit scale and microorganisms in the short term, but long-term use will lead to residual agents, causing eutrophication and biological toxicity of water bodies (Reference 2: Environ. Sci. Technol., 2020). For example, the EU Water Framework Directive has strictly restricted the emission concentration of phosphorus-based scale inhibitors (≤0.1 mg / L). Physical method: Ultrasonic descaling is limited by sound wave attenuation and is only suitable for small-diameter equipment (<50 mm); although electromagnetic descaling is pollution-free, its energy consumption is as high as 0.5-1.0 kWh / m 3 , with poor economic efficiency (Document 3: Desalination, 2021).

[0005] Titanium anode electrochemical technology generates reactive oxygen species such as hydroxyl radicals (·OH) and ozone (O3) through water electrolysis, which can simultaneously decompose scale and inactivate microorganisms. It is considered an important direction for green water treatment. Its core principles are as follows:

[0006] Descaling mechanism: Active oxygen oxidizes CaCO3 into soluble HCO3 - and CO3 2- , Antibacterial mechanism: OH destroys the lipid bilayer of microbial cell membranes, causing leakage of intracellular substances. However, existing titanium anode technology faces three major technical bottlenecks:

[0007] Poor coating adhesion: Traditional IrO2-Ta2O5 coatings are prone to peeling during long-term electrolysis due to mismatched thermal expansion coefficients. Experiments have shown that their bonding strength is only 8-10MPa and their service life is less than 2 years (patent CN102345234A). Low catalytic efficiency: The oxygen evolution reaction (OER) overpotential of a single metal oxide (such as RuO2) is as high as 450mV, resulting in a 30%-40% increase in electrolysis energy consumption. Insufficient process compatibility: High-temperature sintering (>600°C) causes the titanium substrate grains to coarsen (the average grain size increases from 20μm to 50μm), and the tensile strength decreases by 25%-30%.

[0008] To improve the performance of titanium anodes, recent research has focused on process optimization and material innovation, but both have significant drawbacks: Gradient sintering process (CN110272468B): thermal stress is reduced by increasing the temperature in stages (300°C → 600°C), but the coating composition is not optimized, and the catalytic current density is still less than 30mA / cm 2 Nanocarbon composite coating (CN113502018A): Adding carbon nanotubes (CNTs) can increase conductivity to 2000 S / cm, but CNTs are easily oxidized to produce CO2 during electrolysis, causing secondary water pollution. Precious metal alloy coating: While Ir-Ru alloy (mass ratio 1:1) can reduce the overpotential to 350 mV, its cost of $8000 / kg makes it difficult to apply on a large scale.

[0009] With the tightening of environmental regulations and the advancement of the "dual carbon" goals, the market demand for efficient and durable titanium anodes has surged. According to Global Market Insights, the global electrochemical water treatment equipment market will reach US$4.8 billion in 2025, with a compound annual growth rate of 12.3%. The core demands of the industry include higher catalytic activity, longer life, and lower cost. In addition, the following technical gaps still exist in this field: Co-optimization of coating composition and process: Existing solutions either focus on composition improvement (such as adding nanomaterials) or only optimize sintering parameters, and lack systematic design. Balance between environmental protection and performance: High activity often relies on precious metals, while low-cost solutions often sacrifice life and efficiency. Feasibility of industrial production: Laboratory processes are difficult to meet the uniformity requirements of large-scale coating. Summary of the Invention

[0010] To solve the above problems, the present invention is characterized by using gradient pretreatment, ruthenium-iridium synergistic coating design and low-temperature nitrogen sintering process to solve the technical problems of easy peeling of existing electrode coatings and low catalytic efficiency. The specific solution is as follows:

[0011] A manufacturing process for a titanium anode descaling and antibacterial electrode comprises the following steps:

[0012] (1) Pretreatment of titanium substrate;

[0013] (2) Preparation of coating solution;

[0014] (3) coating application;

[0015] (4) High temperature sintering;

[0016] (5) Post-processing.

[0017] Preferably, the titanium substrate pretreatment in step (1) includes:

[0018] (a) Mechanical grinding to remove the surface oxide layer;

[0019] (b) Chemical cleaning: Immerse the titanium substrate in 8-12% oxalic acid solution, heated to 75-85°C, and soak for 1.5-2.5 hours;

[0020] (c) Washing and drying: Rinse with deionized water until neutral, and dry at 80-100℃.

[0021] Preferably, the coating solution in step (2) comprises the following components and mass percentages:

[0022] Titanium tetrachloride (TiCl4): 50-70%;

[0023] Ruthenium salt (RuCl3): 10-20%;

[0024] Iridium salt (IrCl3): 5-10%;

[0025] Organic solvent: 10-20%;

[0026] Dispersant: 1-2%.

[0027] Preferably, the mass ratio of the ruthenium salt to the iridium salt is (2-3):1.

[0028] Preferably, the coating in step (3) is applied by dipping, and after each coating, the coating is dried at 75-85° C. for 8-12 minutes, and the coating is repeated 3-5 times, with a total coating thickness of 5-10 μm.

[0029] Preferably, the conditions for high temperature sintering in step (4) are:

[0030] Sintering temperature: 450-500℃;

[0031] Sintering time: 1-2 hours;

[0032] Protective gas: Nitrogen flow rate is 5-10L / min.

[0033] Preferably, the post-processing in step (5) includes:

[0034] (a) Cool naturally to room temperature;

[0035] (b) Mechanical polishing to remove surface burrs;

[0036] (c) Ultrasonic cleaning to remove residual impurities.

[0037] Preferably, the organic solvent is isopropyl alcohol or n-butanol, and the dispersant is polyvinyl pyrrolidone (PVP).

[0038] The titanium anode electrode prepared by the above method has a surface coating bonding strength of ≥15MPa and a catalytic current density of ≥50mA / cm 2 .

[0039] The application of the titanium anode electrode in the industrial circulating water system has a descaling rate of ≥90% and an antibacterial rate of ≥95%.

[0040] The core technologies of the present invention include:

[0041] Gradient pretreatment process: deep etching with oxalic acid solution combined with mechanical polishing to form a micron-level rough surface (Ra = 1-2μm) to improve coating adhesion;

[0042] Ruthenium-iridium bimetallic synergistic coating: RuCl3 and IrCl3 are mixed in a mass ratio of 2:1 to enhance catalytic activity and stability;

[0043] Low temperature nitrogen sintering: Nitrogen protection at 450-500℃ can inhibit excessive oxidation of metal oxides and reduce grain boundary defects.

[0044] Beneficial effects

[0045] High bonding strength: The bonding strength between the coating and the substrate reaches 15-20MPa (traditional process ≤10MPa);

[0046] Long service life: Accelerated life test (1A / cm 2 , 0.5M H2SO4) for more than 5000 hours;

[0047] Low energy consumption: catalytic current density increased to 50-60mA / cm 2 (Traditional process≤30mA / cm 2 ). DETAILED DESCRIPTION

[0048] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0049] Unless otherwise defined, all technical and scientific terms used herein have the same meanings as those familiar to those skilled in the art. Furthermore, any methods and materials similar or equivalent to those described herein can be applied to the present invention. The preferred embodiments and materials described herein are for illustrative purposes only and are not intended to limit the scope of this application.

[0050] The experimental methods in the following examples, unless otherwise specified, are all conventional methods, and the experimental materials used in the following examples, unless otherwise specified, are all purchased from commercial channels.

[0051] Example 1 Preparation of titanium anode descaling and antibacterial electrode:

[0052] (1) Pretreatment of titanium substrate:

[0053] Titanium plate (TA2, 100 mm × 50 mm × 2 mm) sandblasted (120 mesh sand), Ra = 1.5 μm;

[0054] Immerse in 10% oxalic acid solution and heat at 80°C for 2 hours;

[0055] Rinse with deionized water and dry at 100°C.

[0056] (2) Preparation of coating solution:

[0057] TiCl4 (60%), RuCl3 (15%), IrCl3 (7.5%), n-butanol (15%), PVP (2.5%), stirred for 24 hours.

[0058] (3), (4) Coating and sintering:

[0059] Dip coating 4 times, drying at 85℃ for 10 minutes each time;

[0060] Sintered at 480°C for 1.5 hours under nitrogen protection, with a flow rate of 8 L / min.

[0061] (5) Post-processing:

[0062] Mechanical polishing to surface roughness Ra = 0.2 μm;

[0063] Ultrasonic cleaning (40 kHz, 30 minutes).

[0064] Example 2 Preparation of titanium anode descaling and antibacterial electrode:

[0065] (1) Pretreatment of titanium substrate:

[0066] Titanium plate (TA2, 150 mm × 80 mm × 3 mm) sandblasted (150 mesh sand), Ra = 1.8 μm;

[0067] Immerse in 12% oxalic acid solution and heat at 85°C for 2 hours;

[0068] Rinse with deionized water and dry at 100°C.

[0069] (2) Preparation of coating solution:

[0070] TiCl4 (65%), RuCl3 (18%), IrCl3 (9%), isopropyl alcohol (15%), PVP (2%), stirred for 24 hours.

[0071] (3), (4) Coating and sintering:

[0072] Dip coating 4 times, drying at 85℃ for 10 minutes each time;

[0073] Sintered at 500°C for 2 hours under nitrogen protection, flow rate 10L / min.

[0074] (5) Post-processing:

[0075] Mechanical polishing to surface roughness Ra = 0.2 μm;

[0076] Ultrasonic cleaning (40 kHz, 30 minutes).

[0077] Example 3 Preparation of titanium anode descaling and antibacterial electrode:

[0078] (1) Pretreatment of titanium substrate:

[0079] Titanium plate (TA2, 120 mm × 60 mm × 2.5 mm) sandblasted (100 mesh sand), Ra = 1.2 μm;

[0080] Immerse in 8% oxalic acid solution and heat at 75°C for 2 hours;

[0081] Rinse with deionized water and dry at 100°C.

[0082] (2) Preparation of coating solution:

[0083] TiCl4 (55%), RuCl3 (12%), IrCl3 (6%), n-butanol (20%), PVP (2%), stirred for 24 hours.

[0084] (3), (4) Coating and sintering:

[0085] Dip coating 4 times, drying at 85℃ for 10 minutes each time;

[0086] Sintered at 450°C for 2 hours under nitrogen protection, with a flow rate of 8 L / min.

[0087] (5) Post-processing:

[0088] Mechanical polishing to surface roughness Ra = 0.2 μm;

[0089] Ultrasonic cleaning (40 kHz, 30 minutes).

[0090] Comparative Example 1 (the difference from Example 1 is that there is no nitrogen protection):

[0091] When sintered at 500°C in air, the coating oxidizes to generate RuO2 and IrO3, and the loose structure causes the bonding strength to drop sharply to 6MPa, resulting in the loss of catalytic activity.

[0092] Comparative Example 2 (the difference from Example 1 is that the ratio of ruthenium to iridium is 1:1):

[0093] RuCl3 (12.5%), IrCl3 (12.5%), the bimetallic synergistic effect is weakened, and the catalytic current density is reduced to 35 mA / cm 2 .

[0094] Comparative Example 3 (the difference from Example 1 is that the substrate is cleaned with nitric acid):

[0095] When 5% nitric acid was used for cleaning, the surface was over-etched (Ra=3.5μm) and the coating adhesion dropped to 8MPa.

[0096] The product was tested using the method described in Table 1, and the test results are shown in Table 2.

[0097] Table 1 Detection methods

[0098]

[0099] Table 2 Product test results

[0100]

[0101] According to the above test results, the catalytic current density of the ruthenium-iridium ratio of 2:1 (Example 1) is increased by 57% (55 vs 35 mA / cm 2 ), proving that the bimetallic synergistic effect is significant. Under nitrogen protection, the coating bonding strength is increased by 200% (18 vs 6MPa), and the life is extended by 5.5 times (5200 vs 800 hours). The bonding strength of oxalic acid cleaning (Example 1) is increased by 125% (18 vs 8MPa) compared with nitric acid cleaning (Comparative Example 3), because oxalic acid selectively etches the surface of the titanium substrate to form a more stable microporous structure. Through a systematic comparison of the embodiments and the comparative examples, the core technology of the present invention (gradient pretreatment, ruthenium-iridium synergistic ratio, and nitrogen-protected low-temperature sintering) significantly improves the comprehensive performance of the titanium anode, meeting the needs of industrial circulating water systems for high-efficiency and long-life electrodes. The technical effect exceeds conventional expectations (such as a 100%-200% increase in bonding strength).

[0102] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

[0103] The above description of the present invention and its embodiments is non-limiting and is only one embodiment of the present invention. The actual application is not limited to this. In short, if a person skilled in the art is inspired by this description and, without departing from the purpose of the present invention, designs methods and embodiments similar to this technical solution without creatively designing, they shall fall within the scope of protection of the present invention.

Claims

1. A manufacturing process for a titanium anode descaling and antibacterial electrode, characterized in that: The following steps are involved: (1) Pretreatment of titanium substrate; (2) Preparation of coating solution; (3) coating application; (4) High temperature sintering; (5) Post-processing.

2. The manufacturing process according to claim 1, characterized in that: The titanium substrate pretreatment in step (1) includes: (a) Mechanical grinding to remove the surface oxide layer; (b) Chemical cleaning: Immerse the titanium substrate in 8-12% oxalic acid solution, heated to 75-85°C, and soak for 1.5-2.5 hours; (c) Washing and drying: Rinse with deionized water until neutral, and dry at 80-100℃.

3. The manufacturing process according to claim 1, characterized in that: The coating solution in step (2) includes the following components and mass percentages: Titanium tetrachloride (TiCl4): 50-70%; Ruthenium salt (RuCl3): 10-20%; Iridium salt (IrCl3): 5-10%; Organic solvent: 10-20%; Dispersant: 1-2%.

4. The manufacturing process according to claim 3, characterized in that: The mass ratio of the ruthenium salt to the iridium salt is (2-3):

1.

5. The manufacturing process according to claim 1, characterized in that: The coating in step (3) is applied by dipping, and after each application, the coating is dried at 75-85° C. for 8-12 minutes. The coating is repeated 3-5 times, and the total coating thickness is 5-10 μm.

6. The manufacturing process according to claim 1, characterized in that: The conditions for high temperature sintering in step (4) are: Sintering temperature: 450-500℃; Sintering time: 1-2 hours; Protective gas: Nitrogen flow rate is 5-10L / min.

7. The manufacturing process according to claim 1, characterized in that: The post-processing in step (5) includes: (a) Cool naturally to room temperature; (b) Mechanical polishing to remove surface burrs; (c) Ultrasonic cleaning to remove residual impurities.

8. The manufacturing process according to claim 1, characterized in that: The organic solvent is isopropyl alcohol or n-butanol, and the dispersant is polyvinyl pyrrolidone (PVP).

9. A titanium anode electrode prepared according to any one of claims 1 to 8, characterized in that: Its surface coating bonding strength is ≥15MPa, and the catalytic current density is ≥50mA / cm 2 .

10. Use of the titanium anode electrode according to claim 9 in an industrial circulating water system, characterized in that: Its descaling rate is ≥90% and its antibacterial rate is ≥95%.

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