Method for recycling and regenerating iron-nickel alloy etching waste liquid

Abstract

The invention belongs to the technical field of etching liquid recovery and regeneration, and particularly relates to an iron-nickel alloy etching waste liquid recovery and regeneration method which comprises the following steps: consuming residual acid in waste liquid through a reducing agent iron; ferric ions are reduced through a reducing agent iron, water is added, the concentration of Fe < 2 + > is made to be lower than 250 g / L, and FeCl2 crystallization is avoided; the total addition amount of the iron powder is 2.1 times of the amount of Fe < 3 + > added before etching, and the reaction temperature is 75 DEG C; solid in the waste liquid is filtered, Ni is reduced through a reducing agent iron, and nickel elementary substance is obtained; the adding amount of the iron powder is 3 times that of the etched iron-nickel alloy, and the reaction temperature is 85 DEG C; solids in the waste liquid are filtered, ferrous ions are oxidized through an oxidizing agent nitric acid, and a FeCl3 solution is generated; according to the method, the temperature and the reducing agent component are optimized and adjusted, the reduction rate of nickel can be increased in a relatively economical manner, the reaction rate is increased, nickel metal is efficiently extracted, and resource waste is reduced. And the etching liquid can be regenerated to continue the etching operation, and meanwhile, the safety is higher.

Description

Technical Field

[0001] The invention belongs to the technical field of etching liquid recovery and regeneration, and in particular relates to a method for recovering and regenerating iron-nickel alloy etching waste liquid. Background Art

[0002] Etching liquid is widely used in industrial processes such as electronic manufacturing and metal processing to remove some metal or non-metal materials on the surface of materials. As the etching liquid is used, metal ions and impurities gradually accumulate, causing the etching liquid to fail and form waste liquid. Harmful substances such as ferric chloride and hydrochloric acid will remain in the waste liquid. If the iron-nickel alloy etching liquid is directly discharged, it will not only cause water pollution, but the heavy metal ions in the waste liquid will also pose a serious threat to the ecological environment. Recycling can significantly reduce environmental risks.

[0003] Etching waste liquid recycling can recover valuable metal materials through ion exchange, electrolysis, precipitation and other processes. The recovered metal materials and chemicals can be sold as secondary resources to bring economic benefits. Through the recycling and reuse of waste liquid, the company can reduce the procurement cost of new materials, extend the service life of etching liquid, and thus reduce production costs. The recycling and regeneration of waste liquid can also avoid pollution to water, soil and air.

[0004] During the use of Fe-Ni alloy etching solution, Ni²⁺ ions gradually accumulate in the solution. The key to waste liquid recycling is to extract nickel from the waste liquid for recycling and restore its good etching performance. Commonly used methods in the industry include the following: 1. Precipitation method: By adding alkaline chemicals (such as sodium hydroxide or calcium hydroxide), iron and nickel ions are precipitated as hydroxides (Fe(OH)3, Ni(OH)2). The precipitate can be separated by filtration and then further processed or recycled.

[0005] 2. Solvent extraction: Using specific organic solvents can selectively extract iron and nickel ions from waste liquid. This method can achieve higher purity metal separation, but usually requires subsequent electrolysis or chemical treatment to recover the metal.

[0006] 3. Ion exchange method: Ion exchange resin can effectively remove and recover iron and nickel ions in waste liquid. This method is suitable for treating waste liquid containing low concentration of metal ions and is relatively simple to operate.

[0007] 4. Electrolysis: Electrolysis is an effective method for recovering metals. Through electrolysis, iron and nickel ions can be deposited as pure metals at the cathode. This method can recover higher purity iron and nickel.

[0008] During the recycling process, the etching solution may contain organic additives or oxidants. These impurities need to be treated by filtration, redox reaction or other chemical methods to ensure that the purity of the waste liquid is suitable for recycling. Chinese invention patent CN1166816C nickel-containing ferric chloride etching waste liquid regeneration and nickel recovery method discloses a method of using iron powder as a pH regulator and H2S as a precipitant to precipitate Ni²⁺ from the solution as NiS, so that Ni²⁺ is separated from Fe³⁺, Fe 2+ Then it is oxidized to Fe³⁺ by chlorine gas.

[0009] For acidic etching solutions, H + ions, reducing agents will make H + Hydrogen is produced. When the volume fraction of hydrogen in chlorine is more than 5%, it may explode when exposed to strong light. Chlorine is toxic and mainly invades the human body through the respiratory tract and dissolves in the moisture contained in the mucous membrane, causing damage to the upper respiratory tract mucosa. At the same time, the generated NiS cannot be used directly as nickel metal. Therefore, it is urgent to design a new method for recycling and regenerating ferric chloride and nickel ion etching waste liquid. Summary of the invention

[0010] In view of the above-mentioned deficiencies in the prior art, the problem to be solved by the present invention is that the existing iron-nickel alloy etching solution needs to be recycled and regenerated to avoid pollution to water, soil and air, and nickel metal is recycled for use. The adopted method requires the use of chlorine gas, which is toxic and dangerous, and the recovered NiS cannot be used directly as nickel metal. The present invention provides a method for recycling and regenerating iron-nickel alloy etching waste liquid, improves the recovery method and recovery effect of Ni²⁺ ions, improves the chemical reaction rate and reduction rate in a more economical way, and the produced solution can be reused as an etching solution.

[0011] The present invention adopts the following technical scheme: a method for recycling and regenerating iron-nickel alloy etching waste liquid, comprising the following steps: 1. Consume the residual acid (H + ), Iron (Fe) and hydrogen ions (H + ) reacts to produce hydrogen (H2) and divalent iron ions (Fe 2+ ), the chemical equation of the reaction is as follows: Fe(s)+2H + (aq)→Fe 2+ (aq)+ H2 (g) In this reaction, iron (Fe) is oxidized to ferrous ions (Fe 2+ ), while hydrogen ions (H⁺) are reduced to generate hydrogen gas (H2); 2. Through the reducing agent iron to trivalent iron ions (Fe3+ ) to reduce, adding water to make Fe 2+ The concentration is lower than 250g / L to avoid the crystallization of FeCl2. Ferric ions (Fe 3+ ) is reduced by iron (Fe) as follows: 2Fe(s)+2Fe 3+ (aq)→3 Fe 2+ (aq) In this reaction, solid metallic iron (Fe) is oxidized to divalent iron ions (Fe 2+ ), while trivalent iron (Fe 3+ ) is reduced to divalent iron ions (Fe 2+ ); 3. Filter the solids in the waste liquid, including the residual iron powder mixed with nickel, and use them as raw materials for nickel smelting after washing and drying; 4. Reduce Ni²⁺ with the reducing agent iron to obtain nickel element, divalent nickel ion (Ni 2+ ) is reduced by iron (Fe) as follows: 2Fe(s)+ Ni²⁺ (aq)→2 Fe 2+ (aq)+ Ni (s) In this reaction, solid metallic iron (Fe) is oxidized to divalent iron ions (Fe 2+ ), while the divalent nickel ions (Ni²⁺) are reduced to nickel element (Ni); 5. Filter the solids in the waste liquid, including nickel and iron powder, and use them as raw materials for nickel smelting after washing and drying; 6. The oxidant nitric acid is used to oxidize the divalent iron ion (Fe 2+ ) for oxidation, and then hydrochloric acid is added to generate FeCl3 solution, which is used again as etching solution. The ferrous iron ions are oxidized to ferric iron ions.

[0012] The chemical equation for the reaction is: 6Fe 2+ (aq)+2HNO3(aq)+6 H + (aq)→6 Fe 3+ (aq)+2NO(g)+4 H2O (l) In this reaction, Fe 2+ Oxidized to Fe 3+ , while the nitrogen in nitric acid is reduced to nitric oxide gas (NO), and water (H2O) is produced at the same time; The total amount of iron powder added in the above-mentioned steps 1 and 2 is Fe added before etching. 3+The reaction temperature is 70-80℃; In the fourth step, the amount of iron powder added is 2.8-3.2 times of the iron-nickel alloy etched away, and the reaction temperature is 80-90°C.

[0013] According to another embodiment of the present invention or any of the above-mentioned embodiments, the recycling method further includes pre-treatment, in which the etching waste liquid is concentrated under a low-pressure environment to crystallize FeCl3 crystals, and the FeCl3 crystals are centrifuged and then placed in the FeCl3 solution in step 6 as etching liquid.

[0014] According to another embodiment of the present invention or any of the above embodiments of the recycling method, wherein the total amount of iron powder added in the first step and the second step is Fe added before etching 3+ The reaction temperature was 75°C.

[0015] According to another embodiment of the present invention or any of the above embodiments of the recycling method, wherein the amount of iron powder added in the fourth step is 3 times of the iron-nickel alloy etched away, and the reaction temperature is 85°C.

[0016] According to another embodiment of the present invention or any of the above embodiments, the FeCl3 solution in step 6 is concentrated and its components are adjusted before being reused as an etching solution.

[0017] According to another embodiment of the present invention or any of the above embodiments, the iron powder has a purity of more than 95% and a particle size of 0.1-1 micrometer. The smaller the particle size, the larger the surface area. 3+ The larger the contact area, the faster the reduction reaction.

[0018] According to another embodiment of the present invention or the recycling and regeneration method of any of the aforementioned embodiments, in step 6, the nitric acid content in the mixed solution is 30 mL / L.

[0019] Beneficial effects of the present invention: The iron-nickel alloy etching waste liquid recovery and regeneration method disclosed by the present invention adopts suitable reducing agent and oxidizing agent, adjusts the regeneration process at the same time, optimizes and adjusts the temperature and reducing agent content, can improve the nickel reduction rate and reaction rate in a relatively economical way, efficiently extract nickel metal, and reduce resource waste. The etching liquid can be regenerated and the etching operation can be continued. Chlorine is avoided as an oxidizing substance, and the safety is higher. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 The figure is a schematic flow chart of the method for recycling and regenerating the iron-nickel alloy etching waste liquid according to the present invention; Figure 2 The amount of iron powder added in the present invention is3+ and Ni 3+ Schematic diagram of the relationship curve between the reduction rates; Figure 3 The reaction temperature and Fe 3+ and Ni 3+ Schematic diagram of the relationship curve between the reduction rates; Figure 4 The amount of iron powder added and N i2+ Schematic diagram of the relationship curve between the reduction rates; Figure 5 The reaction temperature and Ni 2+ Schematic diagram of the relationship curve between the reduction rates; Figure 6 This is a schematic diagram of the relationship curve between nitric acid and Fe²⁺ oxidation rate described in the present invention. DETAILED DESCRIPTION

[0021] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0022] like Figure 1 As shown, a method for recycling iron-nickel alloy etching waste liquid comprises the following steps: Pretreatment: The etching waste liquid is concentrated under low pressure to crystallize FeCl3 crystals. The FeCl3 crystals are centrifuged and then put into the subsequent FeCl3 solution as etching solution.

[0023] In the first step, the residual acid (H + ), the reducing agent iron is iron powder, the purity is above 95%, and the particle size of iron powder is 0.1-1 micron. The smaller the particle, the larger the surface area, and the smaller the particle size, the smaller the particle size. 3+ The larger the contact area, the faster the reduction reaction.

[0024] Iron (Fe) and hydrogen ions (H + ) reacts to produce hydrogen (H2) and divalent iron ions (Fe 2+ ), the chemical equation of the reaction is as follows: Fe(s)+2H + (aq)→Fe 2+ (aq)+ H2 (g) In this reaction, iron (Fe) is oxidized to ferrous ions (Fe 2+ ), while hydrogen ions (H⁺) are reduced to generate hydrogen gas (H2); In the second step, the reducing agent iron is used to reduce the ferric ions (Fe 3+ ) to reduce, adding water to make Fe 2+ The concentration is lower than 250g / L to avoid the crystallization of FeCl2. Ferric ions (Fe 3+ ) is reduced by iron (Fe) as follows: 2Fe(s)+2Fe 3+ (aq)→3 Fe 2+ (aq) In this reaction, solid metallic iron (Fe) is oxidized to divalent iron ions (Fe 2+ ), while the trivalent iron ion (Fe 3+ ) is reduced to divalent iron ions (Fe 2+ ); The third step is to filter the solids in the waste liquid, including the residual iron powder mixed with nickel, and use them as raw materials for nickel smelting after washing and drying; The fourth step is to reduce Ni²⁺ with the reducing agent iron to obtain nickel element and divalent nickel ion (Ni 2+ ) is reduced by iron (Fe) as follows: 2Fe(s)+ Ni²⁺ (aq)→2 Fe 2+ (aq)+ Ni (s) In this reaction, solid metallic iron (Fe) is oxidized to divalent iron ions (Fe 2+ ), while the divalent nickel ions (Ni²⁺) are reduced to nickel element (Ni); The fifth step is to filter the solids in the waste liquid, including nickel and iron powder, and use them as raw materials for nickel smelting after washing and drying; In the sixth step, the oxidant nitric acid is used to oxidize the divalent iron ions (Fe 2+ ) for oxidation, the nitric acid content in the mixed solution is 30mL / L, and then hydrochloric acid is added to generate FeCl3 solution, which is concentrated and adjusted in composition and used again as etching solution.

[0025] The ferrous iron ions are oxidized to ferric iron ions.

[0026] The chemical equation for the reaction is: 6Fe 2+ (aq)+2HNO3(aq)+6 H + (aq)→6 Fe 3+ (aq)+2NO(g)+4 H2O (l) In this reaction, Fe 2+ Oxidized to Fe 3+, while the nitrogen in nitric acid is reduced to nitric oxide gas (NO), and water (H2O) is produced at the same time; The total amount of iron powder added in the above-mentioned steps 1 and 2 is Fe added before etching. 3+ The amount is 1.9-2.3 times, preferably 2.1 times, and the reaction temperature is 70-80°C, preferably 75°C.

[0027] In the fourth step, the amount of iron powder added is 2.8-3.2 times, preferably 3 times, of the iron-nickel alloy etched away, and the reaction temperature is 80-90°C, preferably 85°C.

[0028] Working principle of the present invention: The reduction rate of Ni²⁺ is affected by Fe 3+ Influence, due to Fe 3+ The oxidizing property is strong and will be reduced first. Therefore, it is necessary to first 3+ ) is reduced to divalent iron (Fe 2+ ), and then reduce Ni²⁺ to generate nickel. Finally, Fe 2+ The filtrate is oxidized by adding nitric acid to generate ferric chloride solution, which can realize the reuse of etching waste liquid. In the process of treating etching waste liquid, firstly, Fe 3+ Reduction to Fe 2+ The optimal reduction rate was 96%. Subsequently, by adding about 3 times the iron powder to replace Ni²⁺, the optimal replacement rate was 85%. Finally, the waste liquid after the first two steps was oxidized with nitric acid. When the nitric acid content was about 30mL / L, Fe 2+ The oxidation effect is the best. The oxidized waste liquid can be reused as etching liquid after concentration and composition adjustment.

[0029] Research process of the present invention: Fe in wastewater 3+ Determination of iron powder weight during reduction: In the etching waste liquid, the amount of iron powder added is the amount of Fe added before etching. 3+ The amount was 1 times, 1.3 times, 1.6 times, 1.9 times, 2.1 times, and 2.4 times. After the reaction, the waste liquid was filtered and analyzed for Fe 3+ and Fe 2+ The reduction rate.

[0030] from Figure 2 It can be seen that when less iron powder is added, only 67% of Fe 3+ The Ni²⁺ was almost not reduced. This is because there is still some residual acid in the waste liquid. The added iron powder will first react with the H + The remaining iron powder will react with Fe 3+and Ni²⁺. As the amount of iron powder added increases, due to Fe 3+ The oxidizing property is strong and will be reduced first, reaching 96%. 3+ After most of it is reduced, the reduction rate of Ni²⁺ gradually increases. During the reduction process, part of Ni²⁺ is reduced to form Ni element, which is deposited on the surface of the unreacted iron powder, thus hindering the Fe 3+ Further reaction with Ni²⁺, therefore Fe 3+ The reduction rate could not be further improved, the optimal theoretical amount was 2.1 times, and the maximum reduction rate reached about 96%.

[0031] Fe in wastewater 3+ Determination of reduction temperature: One times of iron powder was added to the waste liquid samples at different temperatures for reaction. The reaction temperatures were 35°C, 45°C, 55°C, 65°C, 75°C, and 85°C. To prevent the concentration from changing due to water evaporation, distilled water was added to maintain the liquid level during the reaction. After the reaction, the solid in the waste liquid was filtered, and the content of Fe and Ni was used to calculate the ion reduction rate.

[0032] according to Figure 3 As shown in the figure, with the increase of waste liquid reaction temperature, Fe 3+ The reduction rate of Fe3+ and Ni2+ also increased significantly. However, when the temperature reaches 75°C, the reduction rate basically stops increasing, and the effect on the reduction rate is not significant. This is mainly due to the increase in temperature, the increase in the chemical activity of ions in the waste liquid, the decrease in the viscosity of the waste liquid, the increase in the exchange rate of ions, and the increase in the chemical reaction rate and the reduction rate. Therefore, in order to ensure that Fe3+ and Ni2+ can be fully reduced, the reaction temperature should be 75°C.

[0033] Determination of iron powder content during Ni²⁺ reduction in wastewater: The Fe 3+ The etching waste liquid is placed in a 75℃ water bath, and iron powder is added to react with Ni²⁺. The amount of iron powder added is 1-5 times the amount of iron-nickel alloy etched away. After the reaction is completed, the filtered solid is analyzed to calculate the reduction rate of Ni²⁺.

[0034] according to Figure 4As shown in , with the increase of iron powder, the reduction rate of Ni²⁺ in the waste liquid gradually increases. After adding 3 times the iron powder, the reduction rate of Ni no longer continues to increase, and is about 83%, and cannot be further improved. This is because, during the reaction, the generated Ni element will be deposited on the surface of the added iron powder, thereby preventing the iron powder from contacting with Ni²⁺ in the waste liquid, making it impossible for the iron powder to further react with Ni²⁺. Therefore, the maximum reduction rate has been reached at this time, and adding more iron powder cannot further increase the reduction rate, but increases the cost. Therefore, adding 3 times the iron powder can basically achieve the reduction of Ni²⁺.

[0035] Determination of temperature for reduction of Ni²⁺ in wastewater: according to Figure 3 As shown in the figure, as the reaction temperature increases, the replacement rate of Ni²⁺ gradually increases. During the replacement reaction between iron powder and Ni²⁺, Ni²⁺ in the waste liquid diffuses to the surface of the iron powder, and Fe 2+ Diffusion into the waste liquid is a key factor affecting the reaction efficiency. The diffusion rate is affected by the viscosity of the etching waste liquid and the thickness of the diffusion layer. The rise in temperature will increase the activity of ions in the solution, thereby increasing the reaction rate. However, when the temperature exceeds 85°C, the effect of temperature change on the Ni²⁺ replacement rate gradually decreases. Therefore, the temperature of the Ni²⁺ reduction reaction is preferably 85°C, and the reduction rate can reach 85%.

[0036] Fe in wastewater 2+ Determination of oxidation parameters: For the reduced waste liquid, the Fe 2+ Oxidized to Fe 3+ Since nitric acid is used as a strong acidic oxidant in the etching solution, in order to ensure that the waste liquid components can be reused, nitric acid is used as an oxidant to treat the waste liquid.

[0037] according to Figure 5 As shown in 2+ The oxidation rate of nitric acid is also gradually increasing. This is because the strong oxidizing property of nitric acid can convert Fe 2+ Oxidized to Fe 3+ However, when the amount of nitric acid added reached 30 mL / L, Fe 2+ The oxidation rate gradually stabilized and reached 92%. This may be due to the high pH of the solution and the weak acidity, which weakened the oxidizing ability of nitric acid and caused Fe 2+ Cannot be completely oxidized to Fe 3+ At the same time, the temperature may be too low and the reaction time may be insufficient, which may also cause some Fe 2+ Not oxidized to Fe 3+ The waste liquid after oxidation mainly contains Fe2+ , Cl - 、NO 3- etc., and a small amount of Fe 3+ With Ni²⁺, after concentration, it can be reused as etching solution after adding hydrochloric acid.

[0038] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the above implementation is only to illustrate the technical concept and features of the present invention, and its purpose is to enable people familiar with this technology to understand the content of the present invention and implement it, and it cannot be used to limit the protection scope of the present invention. All equivalent changes or modifications made according to the spirit of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for recycling iron-nickel alloy etching waste liquid, characterized in that: The following steps are involved: S1, consume the residual acid (H + ), Iron (Fe) and hydrogen ions (H + ) reacts to produce hydrogen (H2) and divalent iron ions (Fe 2+ ), the chemical equation of the reaction is as follows: Fe(s)+2 H + (aq)→Fe 2+ (aq)+ H2 (g); S2, through the reducing agent iron to trivalent iron ions (Fe 3+ ) to reduce, adding water to make Fe 2+ The concentration is lower than 250g / L to avoid the crystallization of FeCl2. Ferric ions (Fe 3+ ) is reduced by iron (Fe) as follows: 2Fe(s)+2Fe 3+ (aq)→3 Fe 2+ (aq); S3, filtering the solid in the waste liquid, the solid including the residual iron powder mixed with nickel element, washing and drying it as a raw material for nickel smelting; S4, using the reducing agent iron to reduce Ni²⁺, to obtain nickel element, divalent nickel ion (Ni 2+ ) is reduced by iron (Fe) as follows: 2Fe(s)+ Ni2+ (aq)→2 Fe 2+ (aq)+ Ni (s); S5, filtering the solids in the waste liquid, the solids including nickel and iron powder, washing and drying them as raw materials for nickel smelting; S6, the oxidant nitric acid is used to oxidize the divalent iron ions (Fe 2+ ) for oxidation, and then hydrochloric acid is added to generate FeCl3 solution, which is used again as etching solution. The divalent iron ions are oxidized to trivalent iron ions. The chemical equation of the reaction is: 6 Fe 2+ (aq)+2HNO3(aq)+6 H + (aq)→6 Fe 3+ (aq)+2NO(g)+4 H2O (l); The total amount of iron powder added in the above steps S1 and S2 is Fe added before etching. 3+ The reaction temperature is 70-80℃; In the above step S4, the amount of iron powder added is 2.8-3.2 times of the iron-nickel alloy etched away, and the reaction temperature is 80-90°C.

2. The method for recycling iron-nickel alloy etching waste liquid according to claim 1, characterized in that: The method also includes pre-treatment, in which the etching waste liquid is concentrated under a low pressure environment to crystallize FeCl3 crystals, and the FeCl3 crystals are centrifugally separated and then put into the FeCl3 solution in step S6 as etching liquid.

3. The method for recycling iron-nickel alloy etching waste liquid according to claim 1, characterized in that: The total amount of iron powder added in step S1 and step S2 is the amount of Fe added before etching. 3+ The reaction temperature was 75°C.

4. The method for recycling iron-nickel alloy etching waste liquid according to claim 1, characterized in that: In the step S4, the amount of iron powder added is 3 times the amount of the iron-nickel alloy etched away, and the reaction temperature is 85°C.

5. The method for recycling waste iron-nickel alloy etching liquid according to claim 1, characterized in that: The FeCl3 solution in step S6 is concentrated and its composition is adjusted before reuse as an etching solution.

6. The method for recycling iron-nickel alloy etching waste liquid according to claim 1, characterized in that: The purity of iron powder is above 95%, and the particle size of iron powder is 0.1-1 micron.

7. The method for recycling iron-nickel alloy etching waste liquid according to claim 1, characterized in that: In step S6, the nitric acid content in the mixed solution is 30 mL / L.

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