A method for non-destructive recovery of steel wires and coatings
Patent Information
- Application Number
- CN202611027477.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-07-10
- Publication Date
- 2026-09-25
AI Technical Summary
[0004]本发明要解决的技术问题是，克服现有技术缺陷，提供一种无损回收钢丝及镀层的方法，能够解决现有技术中钢丝基体易腐蚀、镀层回收效率低以及资源利用率低等问题
[0023]1、实现钢丝基体无损回收。本发明通过氨基三亚甲基膦酸在钢丝基体表面形成吸附保护膜，可有效抑制过硫酸铵对基体的腐蚀，回收得到的钢丝基体表面光滑、无氧化斑点，力学性能与回收前相比下降率＜2%，可直接重复用于镀层钢丝加工，显著提升了资源利用率。
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Abstract
Description
Technical Field
[0001] This invention relates to a method for non-destructive recycling of steel wire and coating, belonging to the field of metal material recycling technology. Background Technology
[0002] Coated steel wire, possessing both the high strength of the base material and the excellent properties of the coating such as corrosion resistance and conductivity, is widely used in tire frames, communication cables, and mechanical transmission components. With industrial development and product upgrades, a large amount of waste coated steel wire is generated. Directly discarding or incinerating this wire not only wastes metal resources but also causes environmental pollution. Therefore, achieving efficient and non-destructive separation and recycling of the steel wire matrix and the coating metal from waste coated steel wire has significant resource utilization value and environmental protection significance.
[0003] Currently, the main methods for recycling waste coated steel wire include mechanical stripping, high-temperature pyrolysis, and chemical dissolution. Mechanical stripping easily causes mechanical damage to the steel wire substrate; high-temperature pyrolysis consumes a lot of energy and easily produces harmful gases; chemical dissolution is currently the most widely used recycling method, which dissolves the coating metal through acidic or alkaline solutions. However, traditional chemical dissolution methods have many drawbacks: acidic dissolution systems often use strong acids such as hydrochloric acid and sulfuric acid, which, although highly efficient, corrode the steel wire substrate, making it impossible to achieve damage-free recycling of the substrate; alkaline dissolution systems are only applicable to specific coatings (such as zinc plating), have narrow applicability, and have a slow dissolution rate, making the recycling of the coating metal difficult. Summary of the Invention
[0004] The technical problem to be solved by the present invention is to overcome the defects of the prior art and provide a method for non-destructive recycling of steel wire and coating, which can solve the problems of easy corrosion of steel wire substrate, low coating recycling efficiency and low resource utilization rate in the prior art.
[0005] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows:
[0006] A method for non-destructive recycling of steel wire and coating includes the following steps:
[0007] Step a, prepare a composite recovery solution, wherein the composite recovery solution includes ammonium persulfate, aminotrimethylenephosphonic acid and deionized water;
[0008] Step b: After removing oil and dirt from the surface of the waste coated steel wire, rinse it with deionized water and dry it for later use.
[0009] Step c: Immerse the dried coated steel wire in the composite recycling solution and let it flow until the coating is completely dissolved to separate the steel wire from the coating. After the reaction is complete, remove the steel wire from the composite recycling solution to obtain an undamaged steel wire substrate and a recycling solution containing coating metal ions.
[0010] Step d: Wash away the surface recovery liquid from the non-destructive steel wire substrate, clean and dry it, and then recycle it.
[0011] Step e involves fractionally precipitating the recovered solution containing plating metal ions, then electrolytically refining it to obtain pure plating metal, which is then washed, dried, and directly recycled.
[0012] Ammonium persulfate, as a strong oxidant, can oxidize and dissolve metal coatings under certain conditions. However, when used alone, the dissolution rate is uneven, and excessive local oxidation can easily damage the steel wire substrate. Aminotrimethylenephosphonic acid (ATPA) has excellent complexing properties, forming stable complexes with various metal ions and exhibiting some corrosion inhibition. However, when used alone, it cannot achieve efficient dissolution of the coating. Therefore, this invention uses ammonium persulfate as the main oxidant to directionally oxidize the coating metal under specific acidity, converting the coating metal into ionic form. ATA, as a dual-functional component of chelation and corrosion inhibition, rapidly encapsulates the coating metal ions to form stable chelates. Through the synergistic effect of oxidation and dissolution and complexation stability, efficient dissolution and directional recovery of the coating metal are achieved. Simultaneously, an ultra-thin protective film is formed on the surface of the steel wire substrate, ensuring the integrity of the steel wire substrate. Furthermore, the recovery process generates no harmful gases, making it environmentally friendly and easy to handle. This solution requires no complex additives, achieving both efficient coating stripping and protecting the steel wire substrate through natural synergistic effects between components. The preparation and usage process is extremely simple.
[0013] In step a, the preparation process of the composite recovery solution is as follows: first, aminotrimethylenephosphonic acid is added to deionized water and stirred until dissolved. Then, the pH value of the solution is adjusted to 2.0-4.5 with dilute sulfuric acid or dilute ammonia. Next, ammonium persulfate is added, and stirring continues until completely dissolved. The solution is then allowed to stand for 10-20 minutes to obtain a uniform and stable composite recovery solution. This order of addition ensures that aminotrimethylenephosphonic acid is uniformly dispersed in the solvent first, and the subsequently added ammonium persulfate can slowly dissociate under the set pH conditions, avoiding excessively high local oxidation intensity.
[0014] In step a, the proportions of each component in the composite recovery solution are: 50~160 g / L ammonium persulfate, 35~110 g / L aminotrimethylenephosphonic acid, and deionized water as the solvent.
[0015] In step c, during the flow soaking process, you control the liquid temperature to be 30~60℃.
[0016] In step e, the stepwise precipitation involves adding an alkaline precipitant to the recovery solution containing plating metal ions, adjusting the pH to the range where hydroxide precipitates of the plating metal are generated, and then filtering to obtain the hydroxide precipitate product.
[0017] The alkaline precipitant is sodium hydroxide or potassium hydroxide.
[0018] The coating comprises one or more of copper, zinc, cobalt, nickel, tin, manganese, molybdenum, indium, titanium, and bismuth. When the coating contains multiple metal elements, a stepwise precipitation method is used to obtain the precipitates of each metal hydroxide one by one.
[0019] Dilute sulfuric acid or dilute hydrochloric acid was added to the hydroxide precipitate and stirred until dissolved to obtain a transparent and homogeneous electrolyte. An insoluble electrode plate was used as the anode and each pure plating metal electrode plate was used as the cathode to obtain the metals in the plating by electrolysis.
[0020] The method further includes step f, in which ammonium persulfate and aminotrimethylenephosphonic acid are added to the recovered liquid filtered in step e, and the pH value of the recovered liquid is adjusted to 2.0~4.5 by adding a pH adjuster, and then it is reused repeatedly.
[0021] The pH adjuster is dilute sulfuric acid or dilute ammonia.
[0022] The beneficial effects of this invention are:
[0023] 1. Achieve non-destructive recycling of steel wire substrate. This invention utilizes aminotrimethylenephosphonic acid to form an adsorption protective film on the surface of the steel wire substrate, which effectively inhibits the corrosion of the substrate by ammonium persulfate. The recycled steel wire substrate has a smooth surface without oxidation spots, and its mechanical properties decrease by less than 2% compared to before recycling. It can be directly reused for coating steel wire processing, significantly improving resource utilization.
[0024] 2. High coating recovery rate and high purity of recovered metal. The coating metal ions are complexed and stabilized, and high-purity metal can be obtained through simple precipitation, dissolution and electrolysis, with a recovery rate of 98.2%. The recovered metal can be reused in the production of steel wire coatings.
[0025] 3. Excellent environmental performance. The recovered liquid does not contain highly toxic or polluting components such as cyanide, and no harmful gases such as chlorine or nitrogen oxides are generated during the recovery process. Furthermore, the recovered liquid can be recycled.
[0026] 4. Simple process and low cost. The process of this invention is short and easy to operate, requiring no complicated equipment; the components of the composite recovery liquid are widely available and can be recycled, while achieving dual recovery of the steel wire substrate and the coating metal, significantly reducing the recovery cost and making it easy to promote industrialization.
[0027] 5. Wide applicability. This invention is applicable to the recycling of steel wires with various coatings, such as copper, zinc, and nickel, and has a good dissolution effect on coatings of different thicknesses, solving the problem of narrow applicability of traditional methods. Attached Figure Description
[0028] Figure 1 These are photographs of a 1.25 mm steel wire before and after the coating separation of the present invention, wherein (a) is before separation and (b) is after separation;
[0029] Figure 2 This is a photograph of a 1.25 mm steel wire after the coating has separated in the comparative example. Detailed Implementation
[0030] The present invention will be further described below with reference to the accompanying drawings. The following embodiments are only used to illustrate the technical solution of the present invention more clearly, and should not be used to limit the scope of protection of the present invention.
[0031] Example 1
[0032] This invention discloses a method for non-destructive recycling of steel wire and coating, comprising the following steps:
[0033] Step 1: Preparation of the composite recovery solution.
[0034] First, aminotrimethylenephosphonic acid was added to deionized water and stirred until dissolved. Then, the pH of the solution was adjusted to 3.2 with dilute sulfuric acid or dilute ammonia. Next, ammonium persulfate was added, and stirring continued until completely dissolved. The solution was allowed to stand for 15 minutes to obtain a homogeneous and stable composite recovery solution. The concentration of ammonium persulfate in the composite recovery solution was 105 g / L, the concentration of aminotrimethylenephosphonic acid was 73 g / L, and the solvent was deionized water.
[0035] Step 2: Pretreatment of coated steel wire.
[0036] Waste brass-plated steel wire with a diameter of 1.25 mm and a coating thickness of 1.5 μm was selected and subjected to ultrasonic degreasing treatment. The ultrasonic power was 150 W, the ultrasonic frequency was 25 kHz, and the treatment time was 15 min. After degreasing, it was rinsed with deionized water and dried with hot air at 80℃ for 5 min for later use.
[0037] Step 3: Coating dissolution and separation.
[0038] The pretreated 1.25 mm brass-plated steel wire was immersed in the composite recycling solution, and the reaction temperature was controlled at 45℃. The wire was immersed in a flowing solution with a stirring rate of 100 r / min. The pH value was monitored in real time. When the pH value rose to 4.6, a small amount of dilute sulfuric acid was added to finely adjust it to 3.5. The reaction continued until no bubbles were generated in the composite recycling solution, and there were no discolored patches on the surface of the steel wire. The color was uniform, indicating that the coating was completely dissolved. The steel wire was then removed, and the undamaged steel wire substrate was obtained.
[0039] Step four: recycling of the steel wire matrix.
[0040] The steel wire substrate, after being separated from the coating, is washed with deionized water to remove the surface recovery liquid, and then cleaned, dried, and recycled.
[0041] The recycled steel wire substrate underwent mechanical property testing, and the results are shown in Table 1. All testing procedures were conducted in accordance with relevant national or industry standards. Views of the steel wire before and after coating separation are shown in [Table 1]. Figure 1 (a) is a 1.25 mm coated steel wire, and (b) is the 1.25 mm steel wire substrate after the coating is removed.
[0042] Step 5: Recycling of the coating metal.
[0043] Sodium hydroxide was added to the composite recovery solution containing dissolved copper and zinc ions in step three and stirred to adjust the pH to 4.3. The solution was allowed to stand and filtered to obtain copper hydroxide precipitate. Sodium hydroxide was then added to the filtrate to adjust the pH to 6.3, and the solution was allowed to stand and filtered to obtain zinc hydroxide precipitate. Dilute sulfuric acid was added to both copper hydroxide and zinc hydroxide, and stirred until dissolved to obtain 62.5 g / L copper sulfate and 31.8 g / L zinc sulfate electrolytes. For the copper sulfate electrolyte, a titanium plate was used as the anode and pure copper as the cathode, with a current density of 18 A / dm² and a temperature of 32℃ to electrolyze and obtain copper from the coating. For the zinc sulfate electrolyte, graphite was used as the anode and pure zinc as the cathode, with a current density of 23 A / dm² and a temperature of 25℃ to electrolyze and obtain zinc from the coating. The recovered coating metals were then directly recycled after cleaning and drying. The detection indicators of the recovered coating metals are shown in Table 1.
[0044] Step Six: Recycled Solution. After adding ammonium persulfate and aminotrimethylenephosphonic acid to the filtered recycled solution from Step Five, adjust the pH of the recycled solution to 2.0-4.5 by adding a pH adjuster, and then repeat the recycling process. The pH adjuster is dilute sulfuric acid or dilute ammonia.
[0045] Example 2
[0046] This invention discloses a method for non-destructive recycling of steel wire and coating, comprising the following steps:
[0047] Step 1: Preparation of the composite recovery solution.
[0048] First, aminotrimethylenephosphonic acid was added to deionized water and stirred until dissolved. Then, the pH of the solution was adjusted to 2.0 with dilute sulfuric acid or dilute ammonia. Next, ammonium persulfate was added, and stirring continued until completely dissolved. The solution was allowed to stand for 20 minutes to obtain a homogeneous and stable composite recovery solution. The concentration of ammonium persulfate in the composite recovery solution was 50 g / L, the concentration of aminotrimethylenephosphonic acid was 110 g / L, and the solvent was deionized water.
[0049] Step 2: Pretreatment of coated steel wire.
[0050] Waste brass-plated steel wire with a diameter of 1.25 mm and a coating thickness of 1.5 μm was selected and subjected to ultrasonic degreasing treatment. The ultrasonic power was 150 W, the ultrasonic frequency was 25 kHz, and the treatment time was 15 min. After degreasing, it was rinsed with deionized water and dried with hot air at 80℃ for 5 min for later use.
[0051] Step 3: Coating dissolution and separation.
[0052] The pretreated 1.25 mm brass-plated steel wire was immersed in the composite recycling solution, and the reaction temperature was controlled at 60℃. The wire was immersed in a flowing solution with a stirring rate of 100 r / min. The pH value was monitored in real time. When the pH value rose to 4.6, a small amount of dilute sulfuric acid was added to finely adjust it to 3.5. The reaction continued until no bubbles were generated in the composite recycling solution, and there were no discolored patches on the surface of the steel wire. The color was uniform, indicating that the coating was completely dissolved. The steel wire was then removed, and the undamaged steel wire substrate was obtained.
[0053] Step 4: Recycling of the steel wire matrix.
[0054] The steel wire substrate, after being separated from the coating, is washed with deionized water to remove the surface recovery liquid, and then cleaned, dried, and recycled.
[0055] Step 5: Recycling of the coating metal.
[0056] Potassium hydroxide was added to the composite recovery solution containing dissolved copper and zinc ions in step three and stirred. The pH was adjusted to 4.3, and the solution was allowed to stand and filtered to obtain copper hydroxide precipitate. Sodium hydroxide was added to the filtrate to adjust the pH to 6.3, and the solution was allowed to stand and filtered to obtain zinc hydroxide precipitate. Dilute hydrochloric acid was added to the copper hydroxide and zinc hydroxide respectively and stirred until dissolved to obtain 60.4 g / L copper sulfate and 32.3 g / L zinc sulfate electrolytes. The copper sulfate electrolyte was electrolyzed with a titanium plate as the anode and pure copper as the cathode at a current density of 18 A / dm² and a temperature of 32℃ to obtain copper from the coating. The zinc sulfate electrolyte was electrolyzed with a graphite anode and pure zinc as the cathode at a current density of 23 A / dm² and a temperature of 25℃ to obtain zinc from the coating. After cleaning and drying, the solutions were directly recovered. The detection indicators of the recovered coating metals are shown in Table 1.
[0057] Step Six: Recycled Solution. After adding ammonium persulfate and aminotrimethylenephosphonic acid to the filtered recycled solution from Step Five, adjust the pH of the recycled solution to 2.0-4.5 by adding a pH adjuster, and then repeat the recycling process. The pH adjuster is dilute sulfuric acid or dilute ammonia.
[0058] Example 3
[0059] This invention discloses a method for non-destructive recycling of steel wire and coating, comprising the following steps:
[0060] Step 1: Preparation of the composite recovery solution.
[0061] First, aminotrimethylenephosphonic acid was added to deionized water and stirred until dissolved. Then, the pH of the solution was adjusted to 4.5 with dilute sulfuric acid or dilute ammonia. Next, ammonium persulfate was added, and stirring continued until completely dissolved. After standing for 10 minutes, a homogeneous and stable composite recovery solution was obtained. The concentration of ammonium persulfate in the composite recovery solution was 160 g / L, the concentration of aminotrimethylenephosphonic acid was 35 g / L, and the solvent was deionized water.
[0062] Step 2: Pretreatment of coated steel wire.
[0063] Waste brass-plated steel wire with a diameter of 1.25 mm and a coating thickness of 1.5 μm was selected and subjected to ultrasonic degreasing treatment. The ultrasonic power was 150 W, the ultrasonic frequency was 25 kHz, and the treatment time was 15 min. After degreasing, it was rinsed with deionized water and dried with hot air at 80℃ for 5 min for later use.
[0064] Step 3: Coating dissolution and separation.
[0065] The pretreated 1.25 mm brass-plated steel wire was immersed in the composite recycling solution, and the reaction temperature was controlled at 30℃. The wire was immersed in a flowing solution with a stirring rate of 100 r / min. The pH value was monitored in real time. When the pH value rose to 4.6, a small amount of dilute sulfuric acid was added to finely adjust it to 3.5. The reaction continued until no bubbles were generated in the composite recycling solution, and there were no discolored patches on the surface of the steel wire. The color was uniform, indicating that the coating was completely dissolved. The steel wire was then removed, and the undamaged steel wire substrate was obtained.
[0066] Step four: recycling of the steel wire matrix.
[0067] The steel wire substrate, after being separated from the coating, is washed with deionized water to remove the surface recovery liquid, and then cleaned, dried, and recycled.
[0068] Step 5: Recycling of the coating metal.
[0069] Potassium hydroxide was added to the composite recovery solution containing dissolved copper and zinc ions in step three and stirred. The pH was adjusted to 4.3, and the solution was allowed to stand and filtered to obtain copper hydroxide precipitate. Sodium hydroxide was added to the filtrate to adjust the pH to 6.3, and the solution was allowed to stand and filtered to obtain zinc hydroxide precipitate. Dilute hydrochloric acid was added to the copper hydroxide and zinc hydroxide respectively and stirred until dissolved to obtain 64.1 g / L copper sulfate and 31.5 g / L zinc sulfate electrolytes. The copper sulfate electrolyte was electrolyzed with a titanium plate as the anode and pure copper as the cathode at a current density of 18 A / dm² and a temperature of 32℃ to obtain copper from the coating. The zinc sulfate electrolyte was electrolyzed with a graphite anode and pure zinc as the cathode at a current density of 23 A / dm² and a temperature of 25℃ to obtain zinc from the coating. After cleaning and drying, the solutions were directly recovered. The detection indicators of the recovered coating metals are shown in Table 1.
[0070] Step Six: Recycled Solution. After adding ammonium persulfate and aminotrimethylenephosphonic acid to the filtered recycled solution from Step Five, adjust the pH of the recycled solution to 2.0-4.5 by adding a pH adjuster, and then repeat the recycling process. The pH adjuster is dilute sulfuric acid or dilute ammonia.
[0071] Comparative Example 1
[0072] Immerse a clean, dry 1.25 mm wire in a 105 g / L ammonium persulfate aqueous solution under flowing conditions until the coating is completely dissolved. Rinse and dry the wire. The properties of the wire after coating removal are shown in Table 1, and views of the wire after coating removal are shown in [Image of wire after coating removal]. Figure 2 .
[0073] Table 1. Performance tests of 1.25 mm steel wire and coating before and after recycling
[0074]
[0075] Table 1 shows that the original coated steel wire strength was 1255 MPa. In Example 1 of this invention, the steel wire strength after coating separation was 1240 MPa, a strength loss of 15 MPa, and a strength loss rate of <2%. In contrast, the steel wire strength after coating separation in the comparative example was 1152 MPa, a strength loss of 103 MPa, and a strength loss rate of >8%, exceeding six times that of the example. Figure 1 and Figure 2 As can be seen, the surface of the steel wire after separating the coating in the embodiment is smooth and uniform, without corrosion spots or pits. In contrast, the surface of the steel wire after separating the coating in the comparative example shows obvious signs of excessive corrosion, with corrosion spots and pits. The present invention achieves a coating metal recovery rate of 98.2% and a coating metal recovery purity of 99.5%, significantly improving resource utilization.
[0076] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.
Claims
1. A method for non-destructive recycling of steel wire and coating, characterized in that: Includes the following steps: Step a, prepare a composite recovery solution, wherein the composite recovery solution includes ammonium persulfate, aminotrimethylenephosphonic acid and deionized water; Step b: After removing oil and dirt from the surface of the waste coated steel wire, rinse it with deionized water and dry it for later use. Step c: Immerse the dried coated steel wire in the composite recycling solution and let it flow until the coating is completely dissolved to separate the steel wire from the coating. After the reaction is complete, remove the steel wire from the composite recycling solution to obtain an undamaged steel wire substrate and a recycling solution containing coating metal ions. Step d: Wash away the surface recovery liquid from the non-destructive steel wire substrate, clean and dry it, and then recycle it. Step e involves fractionally precipitating the recovered solution containing plating metal ions, then electrolytically refining it to obtain pure plating metal, which is then washed, dried, and directly recycled.
2. The method for non-destructive recycling of steel wire and coating according to claim 1, characterized in that: In step a, the preparation process of the composite recovery solution is as follows: first, add aminotrimethylenephosphonic acid to deionized water, stir to dissolve, then adjust the pH value of the solution to 2.0~4.5 with dilute sulfuric acid or dilute ammonia, then add ammonium persulfate, continue stirring until completely dissolved, and let stand for 10~20 min to obtain a uniform and stable composite recovery solution.
3. The method for non-destructive recycling of steel wire and coating according to claim 1, characterized in that: In step a, the proportions of each component in the composite recovery solution are: 50~160 g / L ammonium persulfate, 35~110 g / L aminotrimethylenephosphonic acid, and deionized water as the solvent.
4. The method for non-destructive recycling of steel wire and coating according to claim 1, characterized in that: In step c, during the flow soaking process, you control the liquid temperature to be 30~60℃.
5. The method for non-destructive recycling of steel wire and coating according to claim 1, characterized in that: In step e, the stepwise precipitation involves adding an alkaline precipitant to the recovery solution containing plating metal ions, adjusting the pH to the range where hydroxide precipitates of the plating metal are generated, and then filtering to obtain the hydroxide precipitate product.
6. The method for non-destructive recycling of steel wire and coating according to claim 5, characterized in that: The alkaline precipitant is sodium hydroxide or potassium hydroxide.
7. The method for non-destructive recycling of steel wire and coating according to claim 5, characterized in that: The coating comprises one or more of copper, zinc, cobalt, nickel, tin, manganese, molybdenum, indium, titanium, and bismuth. When the coating contains multiple metal elements, a stepwise precipitation method is used to obtain the precipitates of each metal hydroxide one by one.
8. The method for non-destructive recycling of steel wire and coating according to claim 5, characterized in that: Dilute sulfuric acid or dilute hydrochloric acid was added to the hydroxide precipitate and stirred until dissolved to obtain a transparent and homogeneous electrolyte. An insoluble electrode plate was used as the anode and each pure plating metal electrode plate was used as the cathode to obtain the metals in the plating by electrolysis.
9. The method for non-destructive recycling of steel wire and coating according to claim 1, characterized in that: The method further includes step f, in which ammonium persulfate and aminotrimethylenephosphonic acid are added to the recovered liquid filtered in step e, and the pH value of the recovered liquid is adjusted to 2.0~4.5 by adding a pH adjuster, and then it is reused repeatedly.
10. The method for non-destructive recycling of steel wire and coating according to claim 9, characterized in that: The pH adjuster is dilute sulfuric acid or dilute ammonia.