A method for treating circulating cooling water

Abstract

This invention belongs to the field of water treatment technology. It discloses a method for treating circulating cooling water, using a coated titanium sheet as the anode and a titanium sheet as the cathode to electrochemically treat the circulating cooling water. The preparation method of the coated titanium sheet includes the following steps: (1) fixing the titanium sheet substrate onto a magnetron sputtering substrate, and fixing a bismuth metal target and a titanium nitride target respectively, and evacuating the vacuum chamber; (2) introducing argon gas into the magnetron sputtering chamber and raising the temperature; (3) turning on the radio frequency power supply and sputtering a titanium nitride layer onto the titanium sheet substrate; then simultaneously turning on the DC power supply and the radio frequency power supply, sputtering a Bi-TiN composite layer as an intermediate layer on the surface of the titanium nitride layer; finally, using the radio frequency power supply, sputtering a layer of titanium nitride on the composite layer to obtain the coated titanium sheet. The coated titanium anode of this invention has a lower chlorine evolution potential, a larger oxygen-chlorine potential difference, and a longer enhanced lifespan compared to traditional electrodes, thus reducing energy consumption and cost.

Description

Technical Field

[0001] This invention belongs to the field of water treatment technology, and specifically relates to a method for treating circulating cooling water. Background Technology

[0002] Circulating cooling water, as a core component of industrial water systems, plays a vital role in modern industrial sectors such as power generation, textiles, metallurgy, industrial heating equipment, and central air conditioning systems. However, with the repeated recycling of circulating water in production processes, a series of problems have gradually emerged, including scaling and deposition on pipe walls, accelerated corrosion of equipment metal surfaces, and excessive proliferation of microbial communities. Traditionally, treatment technologies for circulating water systems mainly fall into three categories: chemical treatment, physical treatment, and biological treatment. However, these methods generally have limitations. For example, chemical treatment may cause secondary pollution, physical treatment has high energy consumption, and biological treatment faces challenges such as easy equipment aging and unsatisfactory descaling effects. In view of this, electrochemical technology, due to its high efficiency and environmental friendliness, has been widely used in the field of circulating cooling water treatment.

[0003] Electrochemical circulating water treatment technology relies on an external DC power supply to drive the electrolysis of chloride ions (Cl⁻) in the water, generating active chlorine substances with strong oxidizing capabilities (such as ClO⁻ and HClO). These substances have a significant bactericidal effect on microorganisms. Simultaneously, metal cations are reduced to precipitates (such as calcium carbonate CaCO₃ and magnesium carbonate MgCO₃) during electrolysis, facilitating subsequent separation and removal. Furthermore, the electric field can disrupt the cell structure of microorganisms and interfere with their metabolic activities, thus achieving a comprehensive effect of corrosion prevention, sterilization, and scale inhibition. In this process, the selection of the anode material is particularly crucial, as it is not only the main site of sterilization and dechlorination reactions but also directly determines the efficiency of the entire water treatment system. Therefore, the electrocatalytic activity and long-term stability of the anode material are core indicators for evaluating its quality. Currently, the industry widely uses titanium anodes with noble metal oxide coatings (DSA).

[0004] Given the large fluctuations in chloride ion concentration in circulating cooling water (300–20000 mg / L), the anode surface primarily experiences chloride evolution, accompanied by oxygen evolution as a side reaction, especially at lower chloride ion concentrations where the oxygen evolution reaction is more pronounced. This necessitates a high oxygen-chlorine potential difference in the anode material to effectively suppress the oxygen evolution reaction and improve chloride evolution efficiency. Although Ti / RuO2+ IrO2+ TiO2 coated electrodes are favored for their high activity and large oxygen-chlorine potential difference, the high cost of precious metals limits their large-scale application, and the low conductivity of metal oxides also increases energy consumption. Therefore, developing a novel coating material and its preparation process that can improve the electrocatalytic activity and stability of the electrode while reducing cost and energy consumption has become a pressing technical challenge for the circulating cooling water treatment industry. Summary of the Invention

[0005] The purpose of this section is to outline some aspects of embodiments of the present invention and to briefly describe some preferred embodiments.

[0006] As one aspect of the present invention, the present invention provides a method for treating circulating cooling water, which uses a coated titanium sheet as an anode and a titanium sheet as a cathode to perform electrochemical treatment on the circulating cooling water, wherein the method for preparing the coated titanium sheet includes the following steps.

[0007] (1) Fix the titanium sheet substrate onto the magnetron sputtering substrate, and fix the bismuth metal target and the titanium nitride target respectively, and evacuate the vacuum chamber;

[0008] (2) Argon gas is introduced into the magnetron sputtering chamber and the temperature is increased;

[0009] (3) Turn on the radio frequency power supply and sputter a titanium nitride layer on the titanium substrate; then turn on the DC power supply and the radio frequency power supply at the same time, and sputter a Bi-TiN composite layer as an intermediate layer on the surface of the titanium nitride layer. The thickness of the intermediate layer is 90~270nm. Finally, use the radio frequency power supply to sputter a layer of titanium nitride on the Bi-TiN composite layer to obtain the coated titanium sheet.

[0010] As a preferred embodiment of the method for treating circulating cooling water according to the present invention: in step (1), the vacuum chamber is evacuated, which includes first adjusting the vacuum degree to 0.1 Pa, and then adjusting the vacuum degree to ≤1×10 Pa. -5 Pa.

[0011] As a preferred embodiment of the method for treating circulating cooling water according to the present invention: in step (2), argon gas is introduced at a rate of 30~100 mL / min and the atmosphere pressure is maintained at 0.3~3.0 Pa.

[0012] As a preferred embodiment of the method for treating circulating cooling water according to the present invention: in step (2), the temperature for heating is set to 180~220℃.

[0013] As a preferred embodiment of the method for treating circulating cooling water according to the present invention: in step (3), a titanium nitride layer is sputtered on a titanium substrate, and the thickness of the titanium nitride layer is 20~30nm.

[0014] As a preferred embodiment of the method for treating circulating cooling water according to the present invention: in step (3), a Bi-TiN composite layer is sputtered on the surface of the titanium nitride layer as an intermediate layer, and the thickness of the intermediate layer is 180~200nm.

[0015] As a preferred embodiment of the method for treating circulating cooling water according to the present invention: in step (3), the mass ratio of Bi to TiN in the intermediate layer is 1:1.

[0016] As a preferred embodiment of the method for treating circulating cooling water according to the present invention: in step (3), a titanium nitride layer is sputtered on the Bi-TiN composite layer, and the thickness of the titanium nitride layer is 3~7nm.

[0017] As a preferred embodiment of the method for treating circulating cooling water according to the present invention: in step (3), the radio frequency power supply is turned on and the power of the radio frequency power supply is controlled to be 40~60W.

[0018] As a preferred embodiment of the method for treating circulating cooling water according to the present invention: in step (3), the DC power supply and the RF power supply are turned on simultaneously, and the power of both the DC power supply and the RF power supply is set to 40~60W.

[0019] The beneficial effects of this invention are as follows: This invention utilizes a special electrode preparation method to dope a certain amount of base metal elements into the original titanium substrate and prepare a conductive and corrosion-resistant protective layer on the substrate. This ensures the chloride ion removal rate while increasing the reaction potential of the oxygen evolution reaction, suppressing side reactions, increasing the oxygen-chlorine potential difference, and extending the electrode's reaction life. The electrode of this invention not only ensures high catalytic activity and stability but also significantly reduces electrode preparation costs. Simultaneously, the doping of zero-valent metals ensures conductivity and reduces reaction energy consumption.

[0020] Electrochemical performance tests revealed that the coated titanium anode prepared using this invention exhibits a lower chlorine evolution potential, a greater oxygen-chlorine potential difference, and a longer enhanced lifespan compared to traditional electrodes, indicating its advantages in terms of power consumption and service life. Secondly, circulating water treatment tests showed that its chloride and calcium ion removal rates are both higher than those of traditional titanium anodes, and its tank voltage is lower, indicating that it is better than traditional titanium anodes in terms of chlorine removal, sterilization, scale inhibition, and reduced power consumption. Furthermore, the preparation process provided by this invention does not use precious metals, significantly reducing costs. Detailed Implementation

[0021] To make the above-mentioned objectives, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to specific examples.

[0022] Example 1:

[0023] Step 1: Fix the titanium substrate (titanium sheet) onto the magnetron sputtering substrate, and place the metal Bi target and TiN target on two target guns in the same vacuum chamber and fix them (the target gun corresponding to the metal Bi target is designated as target gun A, and the target gun corresponding to the TiN target is designated as target gun B). Target gun A uses DC current, and target gun B uses RF current.

[0024] Step 2: Evacuate the vacuum chamber using a mechanical pump and a molecular pump for pre-sputtering under rough and high vacuum conditions, respectively. The corresponding vacuum levels for rough and high vacuum are 0.1 Pa and 1 × 10⁻⁶ Pa, respectively. -5 Pa;

[0025] Step 3: After reaching high vacuum, argon gas is introduced into the magnetron sputtering chamber at a rate of 60 mL / min. An electric gate valve is used to control the valve angle between the molecular pump and the chamber to maintain the sputtering atmosphere pressure in the chamber at 0.3 ~ 3.0 Pa. The temperature of the magnetron sputtering substrate is set to 200 ℃.

[0026] Step 4: First, turn on the RF power supply and set its power to 50W. Control the TiN target material of the B target gun to sputter a TiN layer on the surface of the titanium substrate for about 10 minutes, with a sputtering thickness of about 25nm. Then, turn on the DC power supply and the RF power supply simultaneously, setting both to 50W. Sputter a Bi-TiN composite layer as an intermediate layer on the TiN layer surface for 15 minutes, with a sputtering thickness of about 90nm and a loading of 100mg, where the mass ratio of Bi to TiN is 1:1. Finally, set the RF power supply to 50W and sputter another TiN layer on the Bi-TiN composite layer surface for about 5 minutes, with a sputtering thickness of about 12.5nm, to obtain the coated titanium anode.

[0027] Example 2:

[0028] Intermediate layer: Bi-TiN composite layer, sputtering time of 30 min, sputtering thickness of approximately 180 nm, loading of 200 mg, wherein the mass ratio of Bi to TiN is 1:1, and other preparation conditions are the same as in Example 1.

[0029] Example 3:

[0030] Intermediate layer: Bi-TiN composite layer, sputtering time of 45 min, sputtering thickness of approximately 270 nm, loading of 300 mg, wherein the mass ratio of Bi to TiN is 1:1, and other preparation conditions are the same as in Example 1.

[0031] Comparative Example 1:

[0032] Step 1: Fix the titanium substrate (titanium sheet) onto the magnetron sputtering substrate, and place the metal Bi target and TiN target on two target guns in the same vacuum chamber and fix them (the target gun corresponding to the metal Bi target is designated as target gun A, and the target gun corresponding to the TiN target is designated as target gun B). Target gun A uses DC current, and target gun B uses RF current.

[0033] Step 2: Evacuate the vacuum chamber using a mechanical pump and a molecular pump for pre-sputtering under rough and high vacuum conditions, respectively. The corresponding vacuum levels for rough and high vacuum are 0.1 Pa and 1 × 10⁻⁶ Pa, respectively. -5 Pa;

[0034] Step 3: After reaching high vacuum, argon gas is introduced into the magnetron sputtering chamber at a rate of 60 mL / min. An electric gate valve is used to control the valve angle between the molecular pump and the chamber to maintain the sputtering atmosphere pressure in the chamber at 0.3 ~ 3.0 Pa. The temperature of the magnetron sputtering substrate is set to 200 ℃.

[0035] Step 4: First, turn on the RF power supply and set its power to 50W. Control the TiN target material of the B target gun to sputter a TiN layer on the surface of the titanium substrate for about 10 minutes, with a sputtering thickness of about 25nm. Then, turn on the DC power supply and set its power to 50W. Sputter an intermediate layer, a Bi metal layer, on the surface of the TiN layer, with a sputtering thickness of about 180nm. Finally, sputter another TiN layer for about 5 minutes, with a sputtering thickness of about 12.5nm, to obtain the coated titanium anode.

[0036] The electrochemical performance of the coated titanium anodes prepared in Examples 1, 2, and 3 and the comparative example of this invention was tested:

[0037] To evaluate the performance of anode samples with different coatings, the following experiments were conducted on four samples, each with an area of ​​1×1 cm².

[0038] First, the first sample was placed in an electrolytic cell containing a 0.5 mol / L sulfuric acid solution along with a titanium cathode and a saturated calomel electrode. Next, the second sample was placed in an electrolytic cell containing a saturated sodium chloride solution along with the titanium cathode and saturated calomel electrode. These two samples were tested using an electrochemical workstation, measuring their oxygen evolution potential and chloride evolution potential, and calculating the oxygen-chlorine potential difference. The electrolyte temperature was maintained at 25°C, and the anolyte current density was 0.02 A / cm². For the third sample, it was placed in an electrolytic cell containing a 1 mol / L sulfuric acid solution along with a titanium cathode, and an enhanced lifespan test was conducted using a DC power supply. Electrode failure was considered to have occurred when the cell voltage increased by 5 V compared to the initial stage. In this experiment, the electrolyte temperature was 40°C, and the anolyte current density was 2 A / cm². Finally, the fourth sample was placed in an electrolytic cell containing a 3.5% sodium chloride solution along with a titanium cathode, and constant current electrolysis was performed using a DC power supply. The electrolyte temperature was maintained at 25°C, and the anolyte current density was 0.15 A / cm². After electrolysis for 1 hour, the effective chlorine content in the electrolyte was determined by chemical analysis, and the chlorine evolution efficiency was calculated. The experimental results are shown in Table 1.

[0039] Table 1. Electrochemical performance test results of coated titanium anodes

[0040]

[0041] As shown in Table 1, the oxygen-chlorine potential difference of the coated titanium anode prepared by this invention is significantly improved, and it is also corrosion resistant with a strengthening life of over 230 h. Compared with the traditional Ti / RuO2 + IrO2 + TiO2 anode (oxygen-chlorine potential difference of about 100~150 mV, strengthening life of about 100 h), the coated titanium anode prepared by this invention has obvious advantages in the application of circulating water treatment systems. Furthermore, since this invention does not use low-conductivity metal oxides, it greatly reduces reaction energy consumption. This invention improves the oxygen-chlorine potential difference, strengthening life, and chlorine evolution efficiency while reducing energy consumption, and has good application prospects.

[0042] The circulating water treatment performance of the coated titanium anodes prepared in Examples 1, 2, 3 and Comparative Example 1 of this invention was tested:

[0043] The prepared coated titanium anode and titanium sheet were used as cathodes and placed together in a simulated circulating cooling water environment (i.e., calcium chloride aqueous solution) for electrolysis experiments. The experiment was powered by a DC power supply and conducted under conditions where the electrolyte temperature was kept constant at 25℃ and the anode current density was set to 0.03 A / cm². The electrolytic cell volume was 60 L, and the effective electrode area was 50 cm². During the experiment, after 6 hours of continuous electrolysis, the cell voltage, Cl⁻ concentration, and Ca²⁺ concentration were measured. Detailed results are shown in Table 2.

[0044] Table 2. Test results of electrolytic circulating water performance of coated titanium anodes.

[0045]

[0046] As can be seen from Table 2, the coated titanium anode prepared in this invention exhibits small changes in tank pressure during the electrolytic treatment of circulating water, and Cl - and Ca 2+ The removal rate is high, significantly better than that of traditional Ti / RuO2 +IrO2 +TiO2 anodes. The coated titanium anode prepared by this invention has excellent electrochemical performance in the process of circulating water treatment.

[0047] This invention employs magnetron sputtering to fabricate a uniform electrode with adjustable thickness via atomic deposition, avoiding the randomness, uneven distribution of active centers, limited sites, and easy detachment during electrolysis inherent in traditional electrode fabrication. Furthermore, the Bi-TiN co-sputtering method ensures uniform doping between the active sites of Bi and TiN, resulting in a synergistic effect. TiN accelerates electron transfer, while Bi provides abundant active sites, enhancing electro-oxidation capabilities and increasing the chlorine-oxygen potential difference, which is beneficial for the precipitation of large amounts of chlorine in water. Simultaneously, the TiN interlayer prevents corrosion caused by prolonged electroreaction processes. This significantly extends the electrode's lifespan.

[0048] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A method for treating circulating cooling water, characterized in that: Electrochemical treatment of circulating cooling water is performed using a coated titanium sheet as the anode and a titanium sheet as the cathode. The method for preparing the coated titanium sheet includes the following steps. (1) Fix the titanium sheet substrate onto the magnetron sputtering substrate, and fix the bismuth metal target and the titanium nitride target respectively, and evacuate the vacuum chamber; (2) Argon gas is introduced into the magnetron sputtering chamber and the temperature is increased; (3) Turn on the radio frequency power supply and sputter a titanium nitride layer on the titanium substrate; then turn on the DC power supply and the radio frequency power supply at the same time, and sputter a Bi-TiN composite layer as an intermediate layer on the surface of the titanium nitride layer. The thickness of the intermediate layer is 90~270nm. Finally, use the radio frequency power supply to sputter a layer of titanium nitride on the Bi-TiN composite layer to obtain the coated titanium sheet.

2. The method for treating circulating cooling water according to claim 1, characterized in that: In step (1), the vacuum chamber is evacuated, which includes first adjusting the vacuum level to 0.1 Pa, and then adjusting the vacuum level to ≤1×10 Pa. -5 Pa.

3. The method for treating circulating cooling water according to claim 1 or 2, characterized in that: In step (2), argon gas is introduced at a rate of 30~100 mL / min, and the atmosphere pressure is maintained at 0.3~3.0 Pa.

4. The method for treating circulating cooling water according to claim 1 or 2, characterized in that: In step (2), the temperature is set to 180~220℃.

5. The method for treating circulating cooling water according to claim 1 or 2, characterized in that: In step (3), a titanium nitride layer is sputtered on the titanium substrate, and the thickness of the titanium nitride layer is 20~30nm.

6. The method for treating circulating cooling water according to claim 1 or 2, characterized in that: In step (3), a Bi-TiN composite layer is sputtered on the surface of the titanium nitride layer as an intermediate layer, and the thickness of the intermediate layer is 180~200nm.

7. The method for treating circulating cooling water according to claim 1 or 2, characterized in that: In step (3), the mass ratio of Bi to TiN in the intermediate layer is 1:

1.

8. The method for treating circulating cooling water according to claim 1 or 2, characterized in that: In step (3), a titanium nitride layer is sputtered on the Bi-TiN composite layer, and the thickness of the titanium nitride layer is 3~7nm.

9. The method for treating circulating cooling water according to claim 1 or 2, characterized in that: In step (3), the radio frequency power supply is turned on and the power of the radio frequency power supply is controlled to be 40~60W.

10. The method for treating circulating cooling water according to claim 1 or 2, characterized in that: In step (3), the DC power supply and the RF power supply are turned on simultaneously, and the power of both the DC power supply and the RF power supply is set to 40~60W.

Images