Method for removing active layer of iridium-tantalum-titanium anode and regeneration of titanium substrate

Abstract

The application discloses a method for removing an iridium-tantalum-titanium anode active layer, comprising the following steps: pretreating a failed iridium-tantalum-titanium anode by using an alkaline descaling agent to remove a scale layer on the surface of the anode; configuring a composite removal solution with ammonium citrate as a main body, wherein the mass concentration of the ammonium citrate is 5-30%, and the pH of the composite removal solution is 6-9; immersing the pretreated titanium anode into the composite removal solution, and treating the titanium anode under the conditions of 60-95 DEG C and stirring for 1-4 hours; after the reaction is completed, taking out the titanium base body, and obtaining a regenerated titanium base body after washing and drying; and recovering iridium from the removal solution. The method for removing the iridium-tantalum-titanium anode active layer has the characteristics of high efficiency, economy and environmental protection, and can realize efficient recovery of the noble metal iridium and perfect regeneration of the titanium base body. The application further provides a regenerated titanium base body recovered by the method.

Description

Technical Field

[0001] This invention relates to the field of precious metal recycling and electrode regeneration technology, specifically to a method for removing the active layer of an iridium-tantalum-titanium anode and a regenerated titanium substrate, and particularly to a method for efficiently removing the active layer of an iridium-tantalum-titanium anode based on ammonium citrate and a regenerated titanium substrate. Background Technology

[0002] Iridium-tantalum-titanium anodes, as excellent shape-stable anodes (DSA), are widely used in industrial fields such as copper foil electrolysis, PCB electroplating, water electrolysis for hydrogen production, and organic electrosynthesis due to their high electrocatalytic activity and excellent stability. Their core structure consists of an active catalytic layer coated on a titanium substrate, composed of iridium oxide (IrO2) and tantalum oxide (Ta2O5), with iridium, as a precious metal, being the main component of the electrode's cost.

[0003] However, iridium-tantalum-titanium anodes will fail during long-term use due to loss of active components, coating passivation, or substrate passivation. The titanium substrate of the failed anode remains intact and accounts for approximately 40% of the total electrode cost, while the surface iridium-tantalum coating accounts for 30-40%. Significant economic benefits would arise from the efficient removal of the failed coating and the recovery of the precious metal iridium, while simultaneously regenerating the titanium substrate.

[0004] Currently, the main industrial methods for treating failed iridium-tantalum-titanium anodes are: (1) Molten salt method: The failed anode is immersed in a mixed molten salt of alkaline and oxidizing substances to remove the coating. This method has a short processing time, but consumes a lot of raw materials, is troublesome to dissolve molten salt blocks, and has high costs. (2) Sulfuric acid electrolysis method: The failed anode is placed in sulfuric acid and electrolyzed alternately as the anode and cathode. This method has low titanium-based corrosion and low acid consumption, but requires rectifier equipment and has high power consumption. (3) Acid boiling method: The failed anode is treated in high-temperature concentrated hydrochloric acid or sulfuric acid. This method is simple and easy to implement, but consumes a lot of acid medium, has a large amount of titanium-based corrosion, serious acid mist, and causes great environmental pollution. (4) Mechanical method: Physical methods such as sandblasting are used to remove the coating. This method is simple to operate and has low titanium-based corrosion, but has low processing capacity and is difficult to completely remove the coating. Although some related methods have emerged since then, these methods still have problems such as high equipment requirements, potential titanium substrate corrosion, or environmental hazards.

[0005] Therefore, it is necessary to provide an efficient, economical, and environmentally friendly method for removing the active layer of an iridium-tantalum-titanium anode, so as to achieve efficient recovery of the precious metal iridium and complete regeneration of the titanium matrix. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide a method for removing the active layer of iridium-tantalum-titanium anodes, which is characterized by high efficiency, economy and environmental protection, and can realize the efficient recovery of the precious metal iridium and the complete regeneration of the titanium matrix.

[0007] The first aspect of this invention is to provide a method for removing the active layer of an iridium-tantalum-titanium anode, the technical solution of which is: A method for removing the active layer of an iridium-tantalum-titanium anode includes the following steps: Step S1: Pre-treat the failed iridium-tantalum-titanium anode with an alkaline descaling agent to remove the scale layer on its surface; Step S2: Prepare a composite removal solution with ammonium citrate as the main component, wherein the mass concentration of ammonium citrate is 5-30% and the pH of the composite removal solution is 6-9. Step S3: Immerse the pretreated titanium anode in the composite removal solution and treat it at 60-95℃ with stirring for 1-4 hours. Step S4: After the reaction is complete, the titanium matrix is ​​removed, rinsed and dried to obtain a regenerated titanium matrix; Step S5: Recover iridium from the removal solution.

[0008] Further, in step S1, the mass concentration of the alkaline descaling agent is 5-20%, and the alkaline descaling agent is sodium hydroxide, sodium carbonate, or sodium acetate; The pretreatment method involves immersing the failed iridium-tantalum-titanium anode in an alkaline descaling agent and soaking or ultrasonically vibrating it at room temperature for 5-60 minutes.

[0009] Further, in step S2, the composite removal solution includes ammonium citrate and an auxiliary coordinating agent, wherein the mass concentration of the auxiliary coordinating agent is 0.5-5%, and the auxiliary coordinating agent is one or more of ethylenediaminetetraacetic acid, sodium citrate, and ammonium oxalate.

[0010] Furthermore, the composite removal solution also includes an oxidant with a mass concentration of 0.1-3%, wherein the oxidant is hydrogen peroxide, ammonium persulfate, or sodium hypochlorite.

[0011] Furthermore, in step S3, the stirring method is mechanical stirring or ultrasonic vibration.

[0012] Further, in step S5, the pH of the removal solution is adjusted to 2-4 to precipitate iridium as iridium hydroxide, thereby recovering iridium.

[0013] Furthermore, in step S5, metallic iridium is extracted using an electrolytic method.

[0014] Furthermore, the failed iridium-tantalum-titanium anodes originate from electrolytic copper foil, PCB electroplating, water electrolysis for hydrogen production, or electrochemical wastewater treatment processes.

[0015] A second aspect of the present invention is to provide a recycled titanium matrix obtained by the method of the first aspect.

[0016] Compared with the prior art, the method for removing the iridium-tantalum-titanium anode active layer provided by the present invention has the following advantages: I. The method for removing the active layer of iridium-tantalum-titanium anodes provided by the present invention uses ammonium citrate as the main component of the composite removal liquid, and through the synergistic effect of auxiliary coordinating agents and oxidants, it has a high efficiency in removing iridium-tantalum oxide coatings, with an iridium stripping rate of over 98%.

[0017] II. The method for removing the active layer of iridium-tantalum-titanium anodes provided by this invention yields a recycled titanium substrate with a corrosion rate of less than 2%, which can be directly reused in the preparation of new electrodes, saving about 40% of the electrode cost; at the same time, it can efficiently recover the precious metal iridium.

[0018] Third, the method for removing the active layer of iridium-tantalum-titanium anodes provided by this invention avoids the use of strong acids, strong alkalis or fluorine-containing reagents, the process conditions are mild, no harmful gases are generated, and it is environmentally friendly.

[0019] IV. The method for removing the active layer of iridium-tantalum-titanium anodes provided by this invention has low equipment requirements, a simple process flow, and is easy to industrialize and promote. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 These are scanning electron microscope (SEM) morphology comparison images of the titanium matrix before and after regeneration in Example 1 of this invention; Figure 2 This is a comparison of the X-ray diffraction (XRD) patterns of the titanium matrix before and after regeneration in Example 1 of this invention. Specific Implementation

[0022] To enable those skilled in the art to better understand the technical solutions in the embodiments of the present invention, and 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 further described below.

[0023] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0024] Example 1

[0025] A method for removing the active layer of an iridium-tantalum-titanium anode includes the following steps: Step S1, Pretreatment of failed iridium-tantalum-titanium anode: Take a failed iridium-tantalum-titanium anode with a size of 6×8 cm, immerse it in a 10% sodium hydroxide solution, and ultrasonically vibrate it for 30 minutes to remove the surface scale layer; Step S2, prepare the composite removal solution: take ammonium citrate to prepare an aqueous solution with a concentration of 15%, add a certain amount of EDTA as an auxiliary complexing agent, and add a certain amount of hydrogen peroxide as an oxidant, wherein the concentration of EDTA is 2% and the concentration of hydrogen peroxide is 1%; and adjust the pH to 7.5 with ammonia water. Step S3: Immerse the pretreated titanium anode in the composite removal solution of step S2, heat it in a constant temperature water bath at 80°C, and add mechanical stirring for 4 hours. Step S4: After the reaction is complete, the titanium substrate is removed, rinsed with deionized water, and dried to obtain a regenerated titanium substrate. The corrosion rate of the regenerated titanium substrate is calculated to be 1.2% by weighing it.

[0026] Step S5: Collect the stripping liquid, adjust the pH to 3 with hydrochloric acid, let it stand and a brown precipitate will precipitate. After filtration and drying, iridium hydroxide is obtained. The iridium recovery rate is calculated to be 98.5%.

[0027] Figure 1 These are scanning electron microscope (SEM) morphology comparison images of the titanium substrate before and after regeneration in Example 1 of this invention. Figure 1 (a) Shows that the surface before regeneration is covered with a dense granular iridium tantalum oxide coating; Figure 1 (b) The coating was completely removed after regeneration, and the titanium substrate structure was clearly and intact exposed with no obvious corrosion damage. Figure 2 This is a comparison of the X-ray diffraction (XRD) patterns of the titanium substrate before and after regeneration in Example 1 of this invention. Before regeneration, the pattern shows obvious characteristic diffraction peaks of IrO2, Ta2O5, and TiO2; after regeneration, all characteristic peaks of the coating oxides completely disappeared, with only the Ti diffraction peak remaining, indicating that the coating has been completely removed and there are no crystal residues.

[0028] The handheld spectral data of the titanium matrix before and after regeneration in this embodiment are shown in Table 1: Table 1: Handheld spectral data of the titanium matrix before and after regeneration in this embodiment

[0029] As shown in Table 1, the effect of titanium substrate regeneration is extremely significant. The active coating is efficiently removed, and the surface of the titanium substrate has high cleanliness, allowing it to be directly reused in the preparation of new electrodes. Combined with the elemental analysis data in Table 1, Figure 1 and Figure 2 Together, it was confirmed that the method of the present invention achieves efficient recovery of precious metals while ensuring the complete regeneration of the titanium matrix.

[0030] Example 2

[0031] A method for removing the active layer of an iridium-tantalum-titanium anode includes the following steps: Step S1, Pretreatment of failed iridium-tantalum-titanium anode: Take a failed iridium-tantalum-titanium anode with a size of 6×8 cm, immerse it in a 15% sodium carbonate solution, and ultrasonically vibrate it for 45 minutes to remove the surface scale layer. Step S2, prepare the composite removal solution: take ammonium citrate to prepare an aqueous solution with a concentration of 25%, add a certain amount of sodium citrate and ammonium oxalate as auxiliary complexing agents, and add a certain amount of ammonium persulfate as an oxidant, wherein the concentration of sodium citrate is 3%, the concentration of ammonium oxalate is 1.5%, and the concentration of ammonium persulfate is 2%; and adjust the pH to 8.0 with ammonia water. Step S3: Immerse the pretreated titanium anode in the composite removal solution of step S2, heat it in a 90°C constant temperature water bath, and supplement it with ultrasonic vibration for 2 hours. Step S4: After the reaction is complete, the titanium substrate is removed, rinsed with deionized water, and dried to obtain a regenerated titanium substrate. The corrosion rate of the regenerated titanium substrate is calculated to be 1.8% by weighing it.

[0032] Step S5: Collect the stripping liquid and recover iridium from it by electrolysis. Using a platinum mesh as the cathode, electrolysis is performed for 2 hours at a current density of 100 A / m², and the iridium recovery rate reaches 99.2%.

[0033] Comparative Example 1 A method for removing the active layer of an iridium-tantalum-titanium anode includes the following steps: Step S1: Take the failed iridium-tantalum-titanium anodes from the same batch (same as Example 1 / Example 2), immerse them directly in a 25% hydrochloric acid solution, and reflux at 100°C for 2 hours; In step S2, after the reaction was completed, the titanium substrate was removed, rinsed, and dried. The corrosion rate of the titanium substrate was calculated to be 15.3%, and there were obvious traces of erosion on the surface.

[0034] In step S3, the iridium recovery method of Example 1 was used, but the iridium recovery rate was only 85.7%, and a large amount of acid mist was generated during the operation.

[0035] Comparative Example 2 Based on Example 1, only the composition of the composite removal solution was changed: 15% sodium citrate was used to completely replace ammonium citrate and EDTA, the oxidant remained 1% hydrogen peroxide, and other process parameters remained unchanged.

[0036] Comparative Example 3 Based on Example 1, the composite removal solution consists only of ammonium citrate and oxidant, with the same concentrations as in Example 1, and other parameters remain unchanged.

[0037] Table 2 shows the statistical results of the recycling methods in each embodiment: Table 2: Statistical analysis of the recycling methods in each embodiment

[0038] The results above show that Example 1 (containing ammonium citrate, EDTA, and H2O2) achieved excellent results with an iridium recovery rate of 98.5% and a titanium matrix corrosion rate of 1.2%. In contrast, Comparative Example 2 (using only sodium citrate and H2O2) lacked the activation effect of ammonium ions, resulting in poor stripping effect and a significantly reduced recovery rate; Comparative Example 3 (using only ammonium citrate and H2O2) lacked the strong coordination of EDTA, so iridium ions could not be completely captured, leading to a decreased recovery rate and difficult separation; while the traditional method using strong acids (Comparative Example 1) caused severe corrosion to the titanium matrix.

[0039] This invention provides a method for removing the active layer of an iridium-tantalum-titanium anode. The core of this method lies in the use of a composite removal liquid system consisting of a main coordinating agent, an auxiliary coordinating agent, and an oxidant. Through synergistic effects, these components achieve efficient, economical, and environmentally friendly resource recovery of the failed anode. Specifically: Ammonium citrate, acting as the main ligand, has carboxyl and hydroxyl groups that can form stable water-soluble complexes with iridium and tantalum ions, promoting the peeling of the oxide coating from the titanium substrate. The ammonium ions (NH4+) in its molecule... + It can preferentially penetrate and relax the dense oxide coating structure, playing a key "swelling activation" role.

[0040] Coordinating agents, such as EDTA, have stronger coordination ability and can form a complementary relationship with ammonium citrate, which can efficiently capture and stabilize dissolved metal ions, preventing their redeposition or loss.

[0041] Oxidizing agents, such as hydrogen peroxide, disrupt the oxide crystal structure of the coating, transforming insoluble iridium (III) oxides into more readily coordinating and soluble iridium (IV) species, thus powering the dissolution process.

[0042] In summary, this invention, through its unique component design, achieves a balance between high recovery rate, low matrix damage, and environmental friendliness under mild conditions (without the need for strong acids, high temperatures, or electrolysis), providing an innovative and highly valuable technical solution for the regeneration of iridium-tantalum-titanium anodes and the recovery of precious metals.

[0043] The embodiments of the present invention have been described in detail above, but the present invention is not limited to the described embodiments. For those skilled in the art, various changes, modifications, substitutions, and variations made to these embodiments without departing from the principles and spirit of the present invention still fall within the protection scope of the present invention.

Claims

1. A method for removing the active layer of an iridium-tantalum-titanium anode, characterized in that, Includes the following steps: Step S1: Pre-treat the failed iridium-tantalum-titanium anode with an alkaline descaling agent to remove the scale layer on its surface; Step S2: Prepare a composite removal solution with ammonium citrate as the main component, wherein the mass concentration of ammonium citrate is 5-30% and the pH of the composite removal solution is 6-9. Step S3: Immerse the pretreated titanium anode in the composite removal solution and treat it at 60-95℃ with stirring for 1-4 hours. Step S4: After the reaction is complete, the titanium matrix is ​​removed, rinsed and dried to obtain a regenerated titanium matrix; Step S5: Recover iridium from the removal solution.

2. The method for removing the iridium-tantalum-titanium anode active layer according to claim 1, characterized in that, In step S1, the mass concentration of the alkaline descaling agent is 5-20%, and the alkaline descaling agent is sodium hydroxide, sodium carbonate, or sodium acetate. The pretreatment method involves immersing the failed iridium-tantalum-titanium anode in an alkaline descaling agent and soaking or ultrasonically vibrating it at room temperature for 5-60 minutes.

3. The method for removing the iridium-tantalum-titanium anode active layer according to claim 1, characterized in that, In step S2, the composite removal solution includes ammonium citrate and an auxiliary coordinating agent, wherein the mass concentration of the auxiliary coordinating agent is 0.5-5%, and the auxiliary coordinating agent is one or more of ethylenediaminetetraacetic acid, sodium citrate, and ammonium oxalate.

4. The method for removing the iridium-tantalum-titanium anode active layer according to claim 3, characterized in that, The composite removal solution also includes an oxidant with a mass concentration of 0.1-3%, wherein the oxidant is hydrogen peroxide, ammonium persulfate, or sodium hypochlorite.

5. The method for removing the iridium-tantalum-titanium anode active layer according to claim 1, characterized in that, In step S3, the stirring method is mechanical stirring or ultrasonic vibration.

6. The method for removing the iridium-tantalum-titanium anode active layer according to claim 1, characterized in that, In step S5, the pH of the removal solution is adjusted to 2-4 to precipitate iridium as iridium hydroxide, thereby recovering iridium.

7. The method for removing the iridium-tantalum-titanium anode active layer according to claim 1, characterized in that, In step S5, metallic iridium is extracted using electrolysis.

8. The method for removing the iridium-tantalum-titanium anode active layer according to claims 1-7, characterized in that, Failed iridium-tantalum-titanium anodes originate from electrolytic copper foil, PCB electroplating, water electrolysis for hydrogen production, or electrochemical wastewater treatment processes.

9. A recycled titanium matrix, characterized in that, It is recovered by the method described in claim 1.

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