A method for regenerating nickel-phosphorus alloy electroplating waste liquid

Abstract

The invention discloses a regeneration method for electroplating nickel-phosphorus alloy waste liquid, wherein the phosphite in the waste liquid is greater than 40 g / L; the phosphate is greater than 15 g / L; and the total phosphorus content is greater than 25 g / L. The specific steps are as follows: after the waste liquid is diluted, a sulfuric acid solution with a concentration of 15-20 wt% is added to make the pH value of the waste liquid less than 2; an oxidant with a concentration of 15-20 wt% is added to oxidize the phosphite to phosphate; a precipitant ferrous sulfate solution is added to form a ferric phosphate precipitate; a sodium hydroxide solution is added to adjust the pH value of the waste liquid to 3.0-3.5; after cooling, standing and filtering, a filtered clear liquid is obtained; a main salt, a complexing agent and a phosphorus-increasing agent are added to the filtered clear liquid to obtain a regenerated liquid, and finally a sulfuric acid solution is used to adjust the pH value of the regenerated liquid to 2.7-2.9, so that it meets the above-mentioned plating requirements. The regenerated plating solution has the same system effect on the plated workpiece as the new plating solution, and can significantly extend the service life of the electroplating nickel-phosphorus alloy plating solution.

Description

Technical Field

[0001] The present invention relates to the technical field of bath maintenance in the electroplating production process, and particularly relates to a method for regenerating waste liquid of electroplated nickel-phosphorus alloy. Background Art

[0002] Nickel-phosphorus alloy coatings are widely used in fields such as electronic devices, aerospace, and petrochemical industries due to their high hardness, high corrosion resistance, and solderability. In the neodymium iron boron electroplating industry, for products with particularly small or thin sizes, nickel-phosphorus alloy coatings are mostly used instead of nickel coatings, mainly because nickel-phosphorus alloy coatings are non-magnetic and can avoid the influence of the coating on the magnetic properties of neodymium iron boron materials.

[0003] Currently, the commonly used method for preparing nickel-phosphorus alloy coatings is electroless nickel plating. However, the main problems of electroless nickel-phosphorus alloy plating are relatively slow deposition efficiency and the need for frequent bath maintenance.

[0004] In contrast, the deposition efficiency of electroplated nickel-phosphorus alloy can be precisely controlled by the current density, achieving high deposition efficiency, and its bath maintenance cycle can also be greatly extended. However, during the electroplating process, in addition to the reduction and deposition of nickel and phosphorus on the electrode surface, various side reactions will also occur, forming various by-products in the bath. These by-products will cause the bath to become turbid and the viscosity to increase significantly, seriously affecting the stability of the composition and microstructure of the coating.

[0005] Traditional treatment methods often directly replace the bath with a new one, which not only causes a great waste of resources but also increases the cost of wastewater treatment, bringing certain pressures to both enterprises and the environment. Summary of the Invention

[0006] The purpose of the present invention is to provide a method for regenerating waste liquid of electroplated nickel-phosphorus alloy. The regenerated bath meets the plating requirements, and has the same plating effect on the plated workpiece as a new bath. It can significantly extend the service life of the electroplated nickel-phosphorus alloy bath, reduce the production material cost and wastewater treatment cost, and at the same time reduce the pressure of pollutants on the environment, thus having obvious economic and ecological benefits.

[0007] To achieve the above object, the solution of the present invention is: A method for regenerating waste liquid of electroplated nickel-phosphorus alloy. The components in the electroplated nickel-phosphorus alloy bath meeting the plating requirements are as follows: nickel sulfate: 320 - 400 g / L; sodium citrate: 60 - 100 g / L; sodium hypophosphite: 35 - 45 g / L; total phosphorus element content: 15 - 25 g / L;

[0008] The electroplating nickel - phosphorus alloy waste liquid formed after using the above - mentioned electroplating nickel - phosphorus alloy plating solution contains: phosphite: greater than 40 g / L; phosphate: greater than 15 g / L; total phosphorus element content: greater than 25 g / L;

[0009] The specific steps of the regeneration treatment are as follows:

[0010] Step S1, dilute the waste liquid with deionized water so that the phosphorus element concentration in the diluted waste liquid ≤ 10 g / L;

[0011] Step S2, under the condition of continuous stirring, add a sulfuric acid solution with a concentration of 15 - 20 wt% to the waste liquid to make the pH value of the waste liquid < 2, and continuously react for 1 - 2 hours;

[0012] Step S3, under the condition of continuous stirring, add an oxidant with a concentration of 25 - 35% to the waste liquid, and the addition amount is 1 - 2 ml / L to oxidize the phosphite to phosphate;

[0013] Step S4, under the condition of continuous stirring, add a precipitant ferrous sulfate solution to the waste liquid to form a ferric phosphate precipitate;

[0014] Step S5, under the condition of continuous stirring, add a sodium hydroxide solution to the waste liquid to adjust the pH value of the waste liquid to 3.0 - 3.5;

[0015] Step S6, cool the waste liquid, let it stand and then filter to obtain a filtered clear liquid;

[0016] Step S7, add a main salt, a complexing agent and a phosphorus - increasing agent to the filtered clear liquid to obtain a regenerated liquid, and finally use a sulfuric acid solution to adjust the pH value of the regenerated liquid to 2.7 - 2.9 to make it meet the above - mentioned plating requirements; the content of sodium phosphite in the regenerated liquid is less than 40 g / L, the content of sodium hydrogen phosphate is less than 15 g / L; the total phosphorus element content is 15 - 25 mg / L; the total iron element content ≤ 50 mg / L.

[0017] Furthermore, in the said step S2, the addition amount of the sulfuric acid solution is 10% - 20% of the total volume of the diluted waste liquid.

[0018] Furthermore, in the said step S3, the oxidant is selected from hydrogen peroxide, potassium permanganate or sodium hypochlorite.

[0019] Furthermore, in the said step S4, the addition amount of the ferrous sulfate solution is 10 g / L.

[0020] Furthermore, in the said step S5, the concentration of the added sodium hydroxide solution is 20 - 30 wt%.

[0021] Further, in the step S6, the temperature of the waste liquid is cooled to 20°C ± 2°C to reduce the solubility of iron phosphate and iron hydroxide. Then, the waste liquid is allowed to stand for 1 - 2 hours, and then the precipitated iron phosphate and iron hydroxide are filtered off, leaving the filtered clear liquid.

[0022] Further, in the step S7, first add the complexing agent sodium citrate, then add the main salt nickel sulfate, and finally add the phosphorus increasing agent, and sodium hypophosphite is selected as the phosphorus increasing agent.

[0023] Further, the regenerated liquid obtained above is subjected to electroplating tests to verify the waste liquid regeneration effect.

[0024] After adopting the above scheme, the beneficial effects of the present invention are as follows:

[0025] The present invention provides a method for regenerating electroplating nickel - phosphorus alloy waste liquid, which effectively removes harmful by - products in the waste liquid, such as phosphite, sodium hydrogen phosphate, etc., while retaining the effective components in the plating solution. The regenerated plating solution fully meets the plating standard, and has the same plating effect on the plated workpiece as the new plating solution.

[0026] For the specific electroplating nickel alloy waste liquid, the regeneration method of the present invention first uses a 15 - 20 wt% sulfuric acid solution to completely dissolve nickel phosphate, nickel phosphite, etc. in the diluted waste liquid into soluble substances such as nickel sulfate, phosphoric acid, and phosphorous acid, and nickel sulfate can be reused. Then, an oxidant is used to oxidize the phosphite ions in the waste liquid into phosphate ions. Next, the precipitant ferrous sulfate is used to precipitate iron phosphate salts under acidic conditions to remove phosphorus elements. The electrostatic interaction between phosphate ions and other cations is stronger, and the solubility of phosphates is lower than that of phosphites. Under the same conditions, phosphate ions are more likely to react with the precipitant to form insoluble precipitates. In contrast, phosphite ions will undergo competitive reactions with other ions, resulting in an increased loss of nickel ions. Therefore, the phosphite ions are first oxidized into phosphate ions, and then precipitation is carried out in an environment with a lower pH value. This can not only effectively utilize the formation of iron phosphate salt precipitates to effectively remove phosphorus elements, but also minimize the loss of nickel ions to the greatest extent.

[0027] Then, sodium hydroxide is added to form iron phosphate salt precipitates and iron hydroxide precipitates with iron ions and phosphoric acid. After cooling, standing, and filtering, the precipitates are removed to obtain a filtered clear liquid. Finally, the main salt, complexing agent, and phosphorus increasing agent are added to the filtered clear liquid to within the process - allowed range, and then the pH value is adjusted to the process - allowed range using sulfuric acid solution to obtain the regenerated liquid.

[0028] The regeneration method of the present invention extends the service life of the electroplating nickel - phosphorus alloy plating solution, reduces the replacement frequency of the new plating solution, thereby reducing the production material cost and waste water treatment cost. At the same time, since the discharge of waste liquid is reduced, environmental pollution is also alleviated, and obvious ecological benefits are achieved. Brief Description of the Drawings

[0029] Figure 1 is the state diagram of the waste liquid of nickel - phosphorus alloy electroplating in Embodiment 1 of the present invention;

[0030] Figure 2 is the surface state diagram of the Hull cell test of the waste liquid of nickel - phosphorus alloy electroplating in Embodiment 1 of the present invention;

[0031] Figure 3 is the state diagram of the waste liquid of nickel - phosphorus alloy electroplating after regeneration treatment in Embodiment 1 of the present invention;

[0032] Figure 4 is the surface state diagram of the Hull cell test of the waste liquid of nickel - phosphorus alloy electroplating after regeneration treatment in Embodiment 1 of the present invention;

[0033] Figure 5 In it, a is the external view schematic diagram of the electroplated workpiece in Comparative Example 1, b is the external view schematic diagram of the electroplated workpiece in Comparative Example 2, and c is the external view schematic diagram of the electroplated workpiece in Embodiment 3;

[0034] Figure 6 In it, a is the scanning electron microscope image of the electroplated workpiece in Comparative Example 1, b is the scanning electron microscope image of the electroplated workpiece in Comparative Example 2, and c is the scanning electron microscope image of the electroplated workpiece in Embodiment 3;

[0035] Figure 7 In it, a is the neutral salt spray result diagram of the electroplated workpiece in Comparative Example 1, b is the neutral salt spray result diagram of the electroplated workpiece in Comparative Example 2, and c is the neutral salt spray result diagram of the electroplated workpiece in Embodiment 3. Detailed Embodiments

[0036] The following will make a detailed description of the present invention in conjunction with the accompanying drawings and specific embodiments.

[0037] The present invention provides a regeneration method for the waste liquid of nickel - phosphorus alloy electroplating. The components in the nickel - phosphorus alloy electroplating solution are as follows: nickel sulfate: 320 - 400 g / L; sodium citrate: 60 - 100 g / L; sodium hypophosphite: 35 - 45 g / L; total phosphorus element content: 15 - 25 g / L; the required temperature for plating is 60 °C, and the pH value is 2.7 - 2.9.

[0038] After a period of production, the electroplating nickel-phosphorus alloy plating solution becomes turbid and black, and flocculent suspended substances are produced. This is because phosphite and phosphate accumulate continuously, and the total phosphorus content increases continuously. When the phosphite content is greater than 40 g / L and the phosphate content is greater than 15 g / L, it indicates that the plating solution does not meet the plating standard and becomes electroplating nickel-phosphorus alloy waste liquid. The components of the electroplating nickel-phosphorus alloy waste liquid are as follows: nickel sulfate: 320 - 400 g / L; sodium citrate: 60 - 100 g / L; sodium hypophosphite: 35 - 45 g / L; sodium phosphite: greater than 40 g / L; sodium hydrogen phosphate: greater than 15 g / L; total phosphorus element content: greater than 25 g / L;

[0039] The specific steps of the regeneration treatment are as follows:

[0040] Step S1, dilute the waste liquid with deionized water to ensure that the phosphorus element concentration in the diluted waste liquid ≤ 10 g / L;

[0041] Step S2, prepare a sulfuric acid solution with a concentration of 15 - 20 % by weight percentage (wt%) using sulfuric acid and deionized water;

[0042] Under the condition of continuous stirring, slowly add the prepared sulfuric acid solution to the waste liquid. The volume of the added sulfuric acid solution is controlled between 10% - 20% of the total volume of the diluted waste liquid, so that the pH value of the waste liquid < 2. Under this acidic condition, react continuously for 1 - 2 hours to completely dissolve the turbid nickel phosphate, nickel phosphite, etc. in the waste liquid into soluble substances, including nickel sulfate, phosphoric acid, and phosphorous acid. Nickel sulfate can be reused. The reaction equations are as follows:

[0043] NI 3 (PO 4 ) 2 ↓+H 2 SO 4 →H 3 PO 4 +NISO 4

[0044] NI 3 (PO 3 ) 2 ↓+H 2 SO 4 →H 3 PO 3 +NISO 4

[0045] Step S3, under the condition of continuous stirring, an oxidant is added to the waste liquid. The oxidant can be potassium permanganate, sodium hypochlorite, etc. In this embodiment, the oxidant is preferably hydrogen peroxide, with a concentration of 25-35% and an addition amount of 1-2 ml / L. Hydrogen peroxide does not pollute the plating solution, and excessive hydrogen peroxide is also easily decomposed under high-temperature conditions. The addition of the oxidant oxidizes the phosphite ions in the solution into phosphate ions, which are more likely to react with the precipitant in the subsequent steps to form precipitated substances.

[0046] This is because the electrostatic interaction between phosphate ions and other cations is stronger, and it is easier to form insoluble precipitates. The solubility of phosphates is lower than that of phosphites. Under the same conditions, phosphate ions are more likely to react with the precipitant to form insoluble precipitates.

[0047] PO 3 3- +H 2 O 2 →PO 4 3- +H 2 O

[0048] PO 2 3- +H 2 O 2 →PO 4 3- +H 2 O (ineffective reaction)

[0049] Step S4, under the condition of continuous stirring, a precipitant is added to the waste liquid. The precipitant is preferably ferrous sulfate, with an addition amount of 10 g / L. Under acidic conditions, ferrous ions are oxidized into ferric ions by hydrogen peroxide. Subsequently, the ferric ions react with the phosphate ions in the waste liquid to form insoluble iron phosphate precipitates (such as iron phosphate), thereby effectively removing part of the phosphorus element in the waste liquid.

[0050] Fe 2+ +H 2 O 2 →Fe 3+ +H 2 O

[0051] Step S5, under the condition of continuous stirring, sodium hydroxide solution is added to the waste liquid to adjust the pH value of the waste liquid to 3.0-3.5. Under this acidic condition, the ferric ions and phosphoric acid in the solution further react with sodium hydroxide to form iron phosphate precipitates and ferric hydroxide precipitates.

[0052] H 3 PO 4 + OH - +Fe 3+ →Fe2 (HPO 4 ) 3 ↓ + Fe(OH) 3 ↓ + H 2 O

[0053] H 3 PO 4 + OH - + Fe 3+ → FePO 4 ↓ + Fe(OH) 3 ↓ + H 2 O

[0054] At a lower pH value, phosphate ions are more likely to react with the precipitant to form insoluble precipitates. This is because acidic conditions help reduce the solubility of ions in the solution, thus promoting the formation of precipitates.

[0055] Phosphite ions will undergo competitive reactions with other ions, resulting in an increased loss of nickel ions. Therefore, the phosphite is first oxidized to phosphate, and then precipitation is carried out in an environment with a lower pH value. This can not only effectively utilize the formation of iron phosphate precipitates to effectively remove phosphorus elements, but also minimize the loss of nickel ions to the greatest extent. In this way, the effective separation and removal of phosphorus and iron elements in the waste liquid can be achieved, while retaining other valuable metal ions, such as nickel ions, as much as possible.

[0056] Step S6: Cool the temperature of the waste liquid to 20°C ± 2°C to reduce the solubility of iron phosphate salts and iron hydroxide and enhance the precipitation effect. Then let the waste liquid stand for 1 - 2 hours to ensure sufficient precipitation. After that, remove the generated iron phosphate salts and iron hydroxide precipitates through filtration, and retain the filtered clear liquid. After treatment, the content of phosphite in the solution is less than 40 g / L, the content of phosphate is less than 15 g / L; the total phosphorus element content is 15 - 25 mg / L; the total iron element content ≤ 50 mg / L.

[0057] Step S7: For the filtered clear liquid obtained in Step S6, adjust the composition to prepare the plating solution required for electroplating nickel - phosphorus alloy. First, add the complexing agent sodium citrate to the filtered clear liquid, which functions to stabilize the metal ions in the solution and prevent their hydrolysis or precipitation. Then add the main salt nickel sulfate, and finally add the phosphorus - increasing agent sodium hypophosphite. Make the nickel sulfate in the solution reach 320 - 400 g / L; sodium citrate: 60 - 100 g / L; sodium hypophosphite: 35 - 45 g / L.

[0058] Finally, use sulfuric acid solution to adjust the pH value to 2.7 - 2.9, which meets the requirements for plating, and thus completes the regeneration treatment of the electroplating nickel - phosphorus alloy waste liquid.

[0059] Example 1:

[0060] The initial formulation of the newly prepared electroplating nickel-phosphorus alloy plating solution A in this embodiment is as follows:

[0061] Nickel sulfate: 360 g / L;

[0062] Sodium citrate: 80 g / L;

[0063] Sodium hypophosphite: 40 g / L;

[0064] Total phosphorus element content: 16 g / L;

[0065] The required plating temperature is 60°C, and the pH value is 2.7 - 2.9.

[0066] After a period of production with the above newly prepared electroplating nickel-phosphorus alloy plating solution, the plating solution became turbid and was accompanied by flocculent suspended matter, namely the electroplating nickel-phosphorus alloy waste liquid B, and its state is as shown in the appendix Figure 1 shown. When performing a Hull cell test on this waste liquid, severe scar defects were found in the high current density area of the test piece, as shown in the appendix Figure 2 shown. At this time, the content of each component in the waste liquid is as follows:

[0067] Nickel sulfate: 372 g / L;

[0068] Sodium citrate: 76 g / L;

[0069] Sodium hypophosphite: 42 g / L;

[0070] Sodium phosphite: 52 g / L;

[0071] Sodium hydrogen phosphate: 18 g / L;

[0072] Total phosphorus element content: 29 g / L;

[0073] The specific steps for the regeneration treatment of this electroplating nickel-phosphorus alloy waste liquid are as follows:

[0074] S1: Take 200 liters of the above waste liquid and dilute it with 400 liters of deionized water. The phosphorus element concentration in the diluted solution is approximately 9.6 g / L.

[0075] S2: Prepare a sulfuric acid solution with a sulfuric acid concentration of 20 wt%. Apply air agitation to the waste liquid, and while slowly add 80 L of the prepared sulfuric acid solution. Measure the pH value of the solution at this time to be 1.6, and continue the reaction for 1 - 2 hours.

[0076] S3: Apply air agitation to the waste liquid and add 600 mL of hydrogen peroxide with a concentration of 30% to the waste liquid.

[0077] S4: Apply air agitation to the waste liquid and add 6 Kg of ferrous sulfate. The ferrous sulfate is dissolved in deionized water and then added.

[0078] S5: Apply air agitation to the waste liquid, add a 30 wt% sodium hydroxide solution to the waste liquid, and adjust the pH of the waste liquid to 3.4.

[0079] S6: Use a cooling water pipe to lower the temperature of the waste liquid to 20 °C, then stop the air agitation, let the waste liquid stand for 1 hour, and then filter it using a filter press. The filtration accuracy of the filter press filter element is 5 microns.

[0080] S7: Apply air agitation to the waste liquid, and sequentially add 30 kg of sodium citrate, 150 kg of nickel sulfate, and 15 kg of sodium hypophosphite. Then use a 20% sulfuric acid solution to adjust the pH value of the plating solution to 2.7 to obtain the regenerated solution C.

[0081] After the above treatment, the electroplating waste liquid becomes clear and transparent again, as shown in the appendix Figure 3 as shown. Conduct a Hull cell test on it. The coating on the entire test piece surface shows a uniform color and a flat surface state from the low to high current density area, as shown in Figure 4 as shown, meeting the production requirements. At this time, analyze the content of the components in the treated plating solution, and the results are as follows:

[0082] Nickel sulfate: 367 g / L;

[0083] Sodium citrate: 75 g / L;

[0084] Sodium hypophosphite: 39 g / L;

[0085] Sodium phosphite: 9 g / L (meeting the requirement of < 40 g / L);

[0086] Sodium hydrogen phosphate: 3 g / L (meeting the requirement of < 15 g / L);

[0087] Total phosphorus element content: 17 g / L (meeting the requirement of 15 - 25 g / L);

[0088] Total iron element content: 8 mg / L (meeting the requirement of ≤ 50 mg / L).

[0089] Example 2:

[0090] In order to verify the usability of the electroplating nickel - phosphorus alloy waste liquid treated by the present invention, electroplate a neodymium - iron - boron workpiece according to the normal electroplating process, which specifically includes the following steps:

[0091] (1) Pretreat the workpiece

[0092] The electroplating implementation process is carried out on a pilot - scale production line with a plating bath volume of 600 L. The substrate workpiece is a sintered neodymium - iron - boron sheet with dimensions of 12.5 × 7.9 × 0.38 (mm). Before the workpiece enters the plating bath, it needs to be cleaned and appropriately activated, which is called pretreatment. The conditions of the pretreatment are as follows:

[0093] After cleaning the workpiece in a 4% nitric acid aqueous solution for 40 seconds, it is cleaned with pure water for 40 seconds under ultrasonic conditions, then activated in a 1% sulfuric acid aqueous solution for 20 seconds, and finally cleaned with pure water for 10 seconds.

[0094] (2) Place the neodymium iron boron workpiece in the first copper plating solution for pre-copper plating to form a pre-copper plating layer on the surface of the neodymium iron boron substrate. The temperature for pre-copper plating is 19 °C, the pH value is 10.4, and the anode electrode is a phosphor copper anode. Barrel plating is used, the current density is 0.2 A / dm², the electroplating time is 80 minutes, and the coating thickness is 1.0 - 1.2 microns.

[0095] In the first copper plating solution, the mass concentrations of each chemical component are as follows:

[0096] Copper ions: 1.9 g / L (the copper-containing inorganic salt is copper sulfate);

[0097] HEDP: 105 g / L;

[0098] Potassium carbonate: 50 g / L;

[0099] Potassium hydroxide: 30 g / L;

[0100] (3) Place the neodymium iron boron workpiece after step (2) in the second copper plating solution for thickening copper plating to form a thickened copper layer on the surface of the workpiece. The temperature for thickening copper plating is 50 °C, the pH value is 8.8, and the anode electrode is a phosphor copper anode. Barrel plating is used, the current density is 0.3 A / dm², the electroplating time is 120 minutes, and the coating thickness is 2.5 - 3 microns.

[0101] In the second copper plating solution, the mass concentrations of each chemical component are as follows:

[0102] Copper ions: 9.5 g / L (the copper-containing inorganic salt is copper sulfate);

[0103] HEDP: 150 g / L;

[0104] Potassium carbonate: 55 g / L;

[0105] Potassium hydroxide: 35 g / L;

[0106] The brightener is selenium dioxide: 8 ml / L;

[0107] (4) Place the neodymium iron boron workpiece after step (3) in the electroplating nickel-phosphorus alloy plating solution for electroplating nickel-phosphorus alloy to form a nickel-phosphorus alloy coating on the surface of the workpiece. The temperature of the electroplating nickel-phosphorus alloy plating solution is 60 °C, the pH value is 2.7, and the anode electrode is a nickel bar. Barrel plating is used, the current density is 0.5 A / dm², the electroplating time is 100 minutes, and the coating thickness is 2 - 3 microns.

[0108] In the electroplating nickel - phosphorus alloy plating solution, the mass concentrations of each chemical component are as follows:

[0109] Nickel sulfate: 360 g / L;

[0110] Sodium citrate: 80 g / L;

[0111] Sodium hypophosphite: 40 g / L;

[0112] For the electroplating nickel - phosphorus alloy plating solution used in step (4), in this embodiment, the newly prepared electroplating nickel - phosphorus alloy plating solution A in Example 1, the electroplating nickel - phosphorus alloy waste liquid B that has reached the service life, and the electroplated nickel - phosphorus alloy regenerated liquid C treated by the present invention are respectively used.

[0113] Comparative example 1: Electroplating is carried out according to the above steps (1) - (4), wherein the newly prepared electroplating nickel - phosphorus alloy plating solution A is used in step (4).

[0114] Comparative example 2: Electroplating is carried out according to the above steps (1) - (4), wherein the electroplating nickel - phosphorus alloy waste liquid B that has reached the service life is used in step (4).

[0115] Example 3: Electroplating is carried out according to the above steps (1) - (4), wherein the electroplated nickel - phosphorus alloy regenerated liquid C treated by the present invention is used in step (4).

[0116] For the products after electroplating nickel - phosphorus alloy, the appearance of the products is detected, the crystallization of the coating is observed by electron microscope, 32 samples are randomly selected from each barrel for neutral salt spray test, and the experimental standard is: GT / T 24.23.17 - 2008 / IEC60068 - 2 - 11:1981. The experimental results are shown in Table 1 and Figures 5 to 7 。

[0117] Table 1

[0118]

[0119] Combined with the attached Figures 5 to 7 and the test results in the above table, it can be shown that on the premise that the electroplating process is completely the same, after the electroplating nickel - phosphorus alloy plating solution reaches the service life, white - dot - like appearance defects will appear on the surface of the electroplated workpiece (refer to part b in Figure 5 ), and the salt spray resistance test ability of the coating also decreases (refer to part b in Figure 7 ). After verification in Example 3, for the electroplating nickel - phosphorus alloy plating solution that has reached the service life, after being treated by the method of the present invention, the surface appearance of the electroplated workpiece and the salt spray resistance test ability of the coating both reach the level equivalent to that of the newly prepared solution, refer to part c in Figures 5 to 7 .

[0120] The above are only the preferred embodiments of the present invention, and do not limit the design of this case. All equivalent changes made according to the key design of this case fall within the protection scope of this case.

Claims

1. A method for regenerating nickel-phosphorus alloy electroplating waste liquid, characterized in that: The components of the nickel-phosphorus alloy electroplating solution that meets the plating requirements are as follows: nickel sulfate: 320~400 g / L; sodium citrate: 60~100 g / L; sodium hypophosphite: 35~45 g / L; total phosphorus content: 15~25 g / L; The nickel-phosphorus alloy electroplating waste liquid formed after the above nickel-phosphorus alloy electroplating solution is used contains: phosphite: greater than 40 g / L; phosphate: greater than 15 g / L; total phosphorus content: greater than 25 g / L; The specific steps of regeneration are as follows: Step S1, diluting the waste liquid with deionized water, wherein the phosphorus concentration in the waste liquid after dilution is ≤10 g / L; Step S2, adding a sulfuric acid solution with a concentration of 15-20 wt% to the waste liquid under continuous stirring to make the pH value of the waste liquid less than 2, and continuing the reaction for 1-2 hours; Step S3, under continuous stirring, adding an oxidant with a concentration of 25-35% and an addition amount of 1-2 ml / L to the waste liquid to oxidize the phosphite into phosphate; Step S4, adding a precipitant ferrous sulfate solution to the waste liquid under continuous stirring to form a ferric phosphate precipitate; Step S5, adding sodium hydroxide solution to the waste liquid under continuous stirring to adjust the pH value of the waste liquid to 3.0-3.5; Step S6, cooling the waste liquid, letting it stand and then filtering it to obtain a filtered clear liquid; Step S7, adding main salt, complexing agent and phosphorus increasing agent to the filtered clear liquid to obtain regeneration liquid, and finally adjusting the pH value of the regeneration liquid to 2.7-2.9 with sulfuric acid solution to meet the above-mentioned plating requirements; the sodium phosphite content in the regeneration liquid is less than 40g / L, the sodium hydrogen phosphate content is less than 15g / L; the total phosphorus content is 15-25mg / L; the total iron content is ≤50mg / L; In step S7, the complexing agent sodium citrate is added first, then the main salt nickel sulfate is added, and finally the phosphorus increasing agent is added, and the phosphorus increasing agent is selected from sodium hypophosphite.

2. The method for regenerating a nickel-phosphorus alloy electroplating waste liquid as claimed in claim 1, characterized in that: In step S2, the amount of sulfuric acid solution added is 10% to 20% of the total volume of the waste liquid after dilution.

3. The method for regenerating a nickel-phosphorus alloy electroplating waste liquid as claimed in claim 1, characterized in that: In step S3, the oxidant is selected from hydrogen peroxide, potassium permanganate or sodium hypochlorite.

4. The method for regenerating a nickel-phosphorus alloy electroplating waste liquid as claimed in claim 1, characterized in that: In step S4, the amount of ferrous sulfate solution added is 10 g / L.

5. The method for regenerating a nickel-phosphorus alloy electroplating waste liquid as claimed in claim 1, characterized in that: In step S5, the concentration of the added sodium hydroxide solution is 20-30wt%.

6. The method for regenerating a nickel-phosphorus alloy electroplating waste liquid as claimed in claim 1, characterized in that: In step S6, the waste liquid temperature is cooled to 20°C±2°C to reduce the solubility of ferric phosphate and ferric hydroxide, and then the waste liquid is allowed to stand for 1-2 hours, and then the generated ferric phosphate and ferric hydroxide precipitates are filtered out and the filtered clear liquid is retained.

7. A method for regenerating nickel-phosphorus alloy electroplating waste liquid according to any one of claims 1 to 6, characterized in that: The obtained regenerated liquid was subjected to electroplating test to verify the waste liquid regeneration effect.

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