Regeneration method of nickel-phosphorus alloy electroplating waste liquid

Abstract

The invention discloses a regeneration method of nickel-phosphorus alloy electroplating waste liquid. The content of phosphite in the waste liquid is greater than 40 g / L; phosphate is greater than 15 g / L; the total phosphorus element content is greater than 25 g / L; the method comprises the following specific steps: diluting the waste liquid, and adding a sulfuric acid solution with the concentration of 15-20wt%, so that the pH value of the waste liquid is less than 2; adding an oxidizing agent to oxidize phosphite radicals into phosphate radicals; adding a precipitant ferrous sulfate solution to form ferric phosphate precipitate; adding a sodium hydroxide solution, and adjusting the pH value of the waste liquid to 3.0-3.5; cooling, standing and filtering to obtain a filtered clear liquid; and adding a main salt, a complexing agent and a phosphorus increasing agent into the filtered clear liquid to obtain a regenerated liquid, and finally adjusting the pH value of the regenerated liquid to 2.7-2.9 by using a sulfuric acid solution, so that the regenerated liquid meets the plating requirements. The regenerated plating solution has the indifferent system effect on a plated workpiece from a new plating solution, and the service life of the electroplating nickel-phosphorus alloy plating solution can be remarkably prolonged.

Description

Technical Field

[0001] The invention relates to the technical field of plating solution maintenance in an electroplating production process, and in particular to a regeneration method for electroplating nickel-phosphorus alloy waste liquid. Background Art

[0002] Nickel-phosphorus alloy coatings are widely used in electronic devices, aerospace, petrochemicals and other fields due to their high hardness, high corrosion resistance and weldability. In the NdFeB electroplating industry, nickel-phosphorus alloy coatings are often used instead of nickel coatings for products with particularly small or thin sizes. This is mainly because nickel-phosphorus alloy coatings are non-magnetic and can avoid the influence of coatings on the magnetic properties of NdFeB materials.

[0003] Currently, the commonly used method for preparing nickel-phosphorus alloy coatings is to use chemical nickel plating. However, the main problem of chemical nickel-phosphorus alloy plating is that the deposition efficiency is relatively slow and the plating solution needs to be frequently maintained.

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

[0005] The traditional treatment method is often to directly replace the plating solution with a new one, which not only causes a huge waste of resources, but also increases the cost of wastewater treatment, bringing considerable pressure to both the enterprise and the environment. Summary of the invention

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

[0007] To achieve the above object, the solution of the present invention is: a method for regenerating nickel-phosphorus alloy electroplating waste liquid, wherein 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 the main salt, the chelating agent and the phosphorus increasing agent to the filtered clear liquid to obtain the regeneration liquid, and finally adjusting the pH value of the regeneration liquid to 2.7-2.9 with a 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.

[0008] Furthermore, in step S2, the amount of sulfuric acid solution added is 10% to 20% of the total volume of the waste liquid after dilution.

[0009] Furthermore, in step S3, the oxidant is selected from hydrogen peroxide, potassium permanganate or sodium hypochlorite.

[0010] Furthermore, in step S4, the amount of ferrous sulfate solution added is 10 g / L.

[0011] Furthermore, in step S5, the concentration of the added sodium hydroxide solution is 20-30wt%.

[0012] Furthermore, 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 to 2 hours, and then the generated ferric phosphate and ferric hydroxide precipitates are filtered out and the filtered clear liquid is retained.

[0013] Furthermore, 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.

[0014] Furthermore, the regenerated liquid obtained above was subjected to electroplating test to verify the waste liquid regeneration effect.

[0015] After adopting the above scheme, the beneficial effects of the present invention are: The present invention provides a method for regenerating waste liquid of nickel-phosphorus alloy electroplating, which effectively removes harmful byproducts 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 standards and has the same plating effect on the plated workpiece as the new plating solution.

[0016] The regeneration method of the nickel-phosphorus alloy electroplating waste liquid of the present invention is aimed at a specific nickel-phosphorus alloy electroplating waste liquid. First, the nickel phosphate, nickel phosphite and the like in the diluted waste liquid are thoroughly dissolved into soluble substances such as nickel sulfate, phosphoric acid and phosphorous acid using a 15-20 wt% sulfuric acid solution, and the nickel sulfate can be reused. Then, the phosphite in the waste liquid is oxidized into phosphate using an oxidant, and then the precipitant ferrous sulfate is used to precipitate ferric phosphate under acidic conditions to remove the phosphorus element. The electrostatic interaction between phosphate ions and other cations is stronger, and the solubility of phosphate is lower than that of phosphite. Under the same conditions, phosphate ions are more likely to react with the precipitant to form a poorly soluble precipitate. In contrast, phosphite ions will compete with other ions, resulting in an increased loss of nickel ions. Therefore, the phosphite is first oxidized into phosphate, and then precipitated under a low pH environment. In this way, not only can the formation of ferric phosphate precipitation be effectively utilized to effectively remove the phosphorus element, but also the loss of nickel ions can be minimized.

[0017] Next, sodium hydroxide is added to make the iron ions and phosphoric acid generate iron phosphate precipitate and iron hydroxide precipitate, and then the precipitate is removed by cooling, standing and filtering to obtain a filtered clear liquid. Finally, the main salt, complexing agent and phosphorus increasing agent are added to the filtered clear liquid to the process allowable range, and then sulfuric acid solution is used to adjust the pH value to the process allowable range to obtain a regenerated liquid.

[0018] The regeneration method of the present invention prolongs 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 the wastewater treatment cost. At the same time, since the discharge of waste liquid is reduced, environmental pollution is also alleviated, and there is obvious ecological benefit. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a state diagram of nickel-phosphorus alloy electroplating waste liquid according to Example 1 of the present invention; Figure 2 This is a Hull cell test surface state diagram of nickel-phosphorus alloy electroplating waste liquid in Example 1 of the present invention; Figure 3 This is a state diagram of the nickel-phosphorus alloy electroplating waste liquid after regeneration treatment in Example 1 of the present invention; Figure 4 This is a surface state diagram of the liquid Hull cell test after the nickel-phosphorus alloy electroplating waste liquid is regenerated in Example 1 of the present invention; Figure 5 a is a schematic diagram of the appearance of a workpiece electroplated in Example 1, b is a schematic diagram of the appearance of a workpiece electroplated in Example 2, and c is a schematic diagram of the appearance of a workpiece electroplated in Example 3; Figure 6 a is a scanning electron microscope image of a workpiece electroplated in Example 1, b is a scanning electron microscope image of a workpiece electroplated in Example 2, and c is a scanning electron microscope image of a workpiece electroplated in Example 3; Figure 7 In the figure a is a neutral salt spray result diagram of the workpiece electroplated in Example 1, b is a neutral salt spray result diagram of the workpiece electroplated in Example 2, and c is a neutral salt spray result diagram of the workpiece electroplated in Example 3. DETAILED DESCRIPTION

[0020] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0021] The invention provides a regeneration method for electroplating nickel-phosphorus alloy waste liquid. The components of the electroplating nickel-phosphorus alloy plating liquid 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; plating requires a temperature of 60 DEG C and a pH value of 2.7-2.9.

[0022] After a period of production, the nickel-phosphorus alloy electroplating solution becomes turbid and black, and produces flocculent suspended matter. This is because phosphite and phosphate continue to accumulate and the total phosphorus content continues to increase. When the phosphite content is greater than 40g / L and the phosphate content is greater than 15g / L, it means that the plating solution does not meet the plating standards and becomes a nickel-phosphorus alloy electroplating waste liquid. The components of the nickel-phosphorus alloy electroplating 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 content: greater than 25 g / L; The specific steps of regeneration are as follows: Step S1, diluting the waste liquid with deionized water to ensure that the phosphorus concentration in the waste liquid after dilution is ≤10 g / L; Step S2, preparing a sulfuric acid solution with a concentration of 15-20% by weight (wt%) using sulfuric acid and deionized water; Under continuous stirring, slowly add the prepared sulfuric acid solution to the waste liquid. The volume of the sulfuric acid solution added is controlled between 10% and 20% of the total volume of the waste liquid after dilution, so that the pH value of the waste liquid is less than 2. Under this acidic condition, continue the reaction for 1 to 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. The nickel sulfate can be reused. The reaction equation is as follows: NI3(PO4)2↓+H2SO4→H3PO4+NISO4 NI3(PO3)2↓+H2SO4→H3PO3+NISO4 Step S3, under the condition of continuous stirring, adding an oxidant to the waste liquid. The oxidant can be selected from 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 excess hydrogen peroxide is also easily decomposed under high temperature conditions. The addition of the oxidant oxidizes the phosphite in the solution into phosphate, which is easier to react with the precipitant in the subsequent steps to generate precipitated substances.

[0023] 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 phosphate is lower than that of phosphite. Under the same conditions, phosphate ions are more likely to react with precipitants to form insoluble precipitates.

[0024] PO3 3- +H2O2→PO4 3- +H2O PO2 3- +H2O2→PO4 3- +H2O (ineffective reaction) Step S4, under the condition of continuous stirring, adding a precipitant to the waste liquid, preferably ferrous sulfate, and the amount of the precipitant added is 10 g / L. Under acidic conditions, ferrous ions are oxidized into ferric ions by hydrogen peroxide, and then the ferric ions react with the phosphate ions in the waste liquid to generate insoluble iron phosphate precipitates (such as iron phosphate, etc.), thereby effectively removing part of the phosphorus element in the waste liquid.

[0025] Fe 2+ +H2O2→Fe 3+ +H2O Step S5, under the condition of continuous stirring, adding sodium hydroxide solution to the waste liquid to adjust the pH value of the waste liquid to 3.0-3.5. Under this acidic condition, the iron ions and phosphoric acid in the solution further react with the sodium hydroxide to generate iron phosphate precipitate and iron hydroxide precipitate.

[0026] H3PO4+ OH - +Fe 3+ →Fe2(HPO4)3↓+Fe(OH)3↓+H2O H3PO4+ OH - +Fe 3+ →FePO4↓+Fe(OH)3↓+H2O At lower pH values, phosphate ions react more easily with the precipitant to form insoluble precipitates. This is because acidic conditions help reduce the solubility of ions in the solution, thereby promoting the formation of precipitates.

[0027] Phosphite ions will compete with other ions, resulting in increased nickel ion loss. Therefore, phosphite is first oxidized to phosphate and then precipitated under a low pH environment. This not only effectively utilizes the formation of iron phosphate precipitation to effectively remove phosphorus, but also minimizes the loss of nickel ions. In this way, phosphorus and iron in the wastewater can be effectively separated and removed, while retaining other valuable metal ions, such as nickel ions, as much as possible.

[0028] Step S6, cool the waste liquid temperature to 20°C ± 2°C to reduce the solubility of ferric phosphate and ferric hydroxide and enhance the precipitation effect. Then let the waste liquid stand for 1 to 2 hours to ensure sufficient precipitation. After that, remove the generated ferric phosphate and ferric hydroxide precipitates by filtering, and retain the filtered clear liquid. After treatment, the phosphite in the solution is less than 40g / L, the phosphate is less than 15g / L; the total phosphorus content is 15~25mg / L; the total iron content is ≤50mg / L.

[0029] Step S7, adjusting the composition of the filtered clear solution obtained in step S6 to prepare a plating solution required for electroplating nickel-phosphorus alloy. First, add the complexing agent sodium citrate to the filtered clear solution, which stabilizes the metal ions in the solution and prevents them from 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.

[0030] Finally, sulfuric acid solution is used to adjust the pH value to 2.7~2.9, which meets the plating requirements, thus completing the regeneration treatment of the electroplating nickel-phosphorus alloy waste liquid.

[0031] Embodiment 1: The initial formula of the newly prepared nickel-phosphorus alloy electroplating solution A in this embodiment is: Nickel sulfate: 360 g / L; Sodium citrate: 80 g / L; Sodium hypophosphite: 40 g / L; Total phosphorus content: 16 g / L; Plating requires a temperature of 60°C and a pH value of 2.7~2.9.

[0032] After a period of production, the newly prepared nickel-phosphorus alloy electroplating solution becomes turbid and is accompanied by flocculent suspended matter, i.e., nickel-phosphorus alloy electroplating waste liquid B. Figure 1The waste liquid was tested in a Hull cell and found serious scar defects in the high current density area of ​​the test piece, as shown in the attached Figure 2 As shown, the content of each component in the waste liquid is: Nickel sulfate: 372 g / L; Sodium citrate: 76 g / L; Sodium hypophosphite: 42 g / L; Sodium phosphite: 52 g / L; Sodium hydrogen phosphate: 18 g / L; Total phosphorus content: 29 g / L; The specific steps for regenerating the electroplating nickel-phosphorus alloy waste liquid are as follows: S1: Take 200 liters of the above waste liquid and dilute it with 400 liters of deionized water. The phosphorus concentration in the diluted solution is about 9.6 g / L.

[0033] S2: Prepare a sulfuric acid solution with a sulfuric acid concentration of 20 wt%. Stir the waste liquid with air and slowly add 80 L of the prepared sulfuric acid solution. The pH value of the solution is measured to be 1.6, and the reaction is continued for 1 to 2 hours.

[0034] S3: Apply air stirring to the waste liquid and add 600 mL of 30% hydrogen peroxide to the waste liquid.

[0035] S4: air stirring is applied to the waste liquid, and 6 kg of ferrous sulfate is added to the waste liquid. The ferrous sulfate is dissolved in deionized water and then added.

[0036] S5: applying air stirring to the waste liquid, adding 30 wt % sodium hydroxide solution to the waste liquid, and adjusting the pH of the waste liquid to 3.4.

[0037] S6: Use the cooling water pipe to reduce the temperature of the waste liquid to 20°C, then stop the air stirring, let the waste liquid stand for 1 hour, and then use the filter to filter it. The filtration accuracy of the filter element of the filter is 5 microns.

[0038] S7: air stirring is applied to the waste liquid, and 30 kg of sodium citrate, 150 kg of nickel sulfate, and 15 kg of sodium hypophosphite are added in sequence. Then, the pH value of the plating solution is adjusted to 2.7 using a 20% sulfuric acid solution to obtain a regenerated solution C.

[0039] After the above treatment, the electroplating waste liquid becomes clear and transparent again. Figure 3 When the Hull cell test was performed, the coating on the entire surface of the test piece from low to high current density area showed uniform color and flat surface state, as shown in Figure 1. Figure 4 As shown, the production requirements are met. At this time, the content of the treated plating solution is analyzed, and the results are as follows: Nickel sulfate: 367 g / L; Sodium citrate: 75 g / L; Sodium hypophosphite: 39 g / L; Sodium phosphite: 9 g / L (compliant with <40 g / L); Sodium hydrogen phosphate: 3 g / L (compliant with <15 g / L); Total phosphorus content: 17 g / L (in compliance with 15-25 g / L); Total iron content: 8 mg / L (compliance ≤50 mg / L).

[0040] Embodiment 2: In order to verify the usability of the electroplating nickel-phosphorus alloy waste liquid treated by the present invention, a NdFeB workpiece is electroplated according to a normal electroplating process, specifically comprising the following steps: (1) Pre-processing of workpieces The electroplating process is carried out in a pilot line with a plating tank volume of 600L. The substrate workpiece is a sintered NdFeB sheet with a size of 12.5×7.9×0.38 (mm). Before the workpiece enters the plating tank, it must be cleaned and properly activated, which is called pre-treatment. The pre-treatment conditions are as follows: The workpiece was cleaned in a 4% nitric acid aqueous solution for 40 seconds, then cleaned in pure water under ultrasonic conditions for 40 seconds, then activated in a 1% sulfuric acid aqueous solution for 20 seconds, and finally cleaned in pure water for 10 seconds.

[0041] (2) Placing the NdFeB workpiece in a first copper plating solution for pre-copper plating to form a pre-copper plating layer on the surface of the NdFeB substrate. The pre-copper plating temperature is 19°C, the pH value is 10.4, and the anode electrode is a phosphor copper anode. Roll plating is adopted, the current density is 0.2A / square decimeter, the electroplating time is 80 minutes, and the coating thickness is 1.0-1.2 microns.

[0042] In the first copper plating solution, the mass concentration of each chemical component is as follows: Copper ion: 1.9 g / L (copper-containing inorganic salt is copper sulfate); HEDP: 105g / L; Potassium carbonate: 50g / L; Potassium hydroxide: 30g / L; (3) Plating the NdFeB workpiece after step (2) in a second copper plating solution to plate thick copper and form a thick copper layer on the surface of the workpiece. The temperature for plating thick copper is 50°C, the pH value is 8.8, and the anode electrode is a phosphor copper anode. Roll plating is adopted, the current density is 0.3A / square decimeter, the electroplating time is 120 minutes, and the coating thickness is 2.5-3 microns.

[0043] In the second copper plating solution, the mass concentration of each chemical component is as follows: Copper ion: 9.5 g / L (copper-containing inorganic salt is copper sulfate); HEDP: 150g / L; Potassium carbonate: 55g / L; Potassium hydroxide: 35g / L; Brightener is selenium dioxide: 8ml / L; (4) Plating the NdFeB workpiece after step (3) in a nickel-phosphorus alloy electroplating solution to electroplate the nickel-phosphorus alloy and forming a nickel-phosphorus alloy coating on the surface of the workpiece. The temperature of the nickel-phosphorus alloy electroplating solution is 60°C, the pH value is 2.7, and the anode electrode is nickel angle. Roll plating is adopted, the current density is 0.5A / dm2, the electroplating time is 100 minutes, and the coating thickness is 2-3 μm.

[0044] The mass concentration of each chemical component in the electroplating nickel-phosphorus alloy plating solution is as follows: Nickel sulfate: 360 g / L; Sodium citrate: 80g / L; Sodium hypophosphite: 40g / L; The nickel-phosphorus alloy electroplating solution used in step (4) in this embodiment respectively uses the newly prepared nickel-phosphorus alloy electroplating solution A in Example 1, the nickel-phosphorus alloy electroplating waste solution B that has reached the end of its service life, and the nickel-phosphorus alloy electroplating regeneration solution C treated by the present invention.

[0045] Comparative Example 1: Electroplating was carried out according to the above steps (1) to (4), wherein step (4) used a newly prepared nickel-phosphorus alloy electroplating solution A.

[0046] Comparative Example 2: Electroplating was carried out according to the above steps (1) to (4), wherein step (4) used electroplating nickel-phosphorus alloy waste liquid B which had reached the end of its service life.

[0047] Example 3: Electroplating is carried out according to the above steps (1) to (4), wherein step (4) uses the electroplating nickel-phosphorus alloy regeneration solution C treated by the present invention.

[0048] After the nickel-phosphorus alloy is electroplated, the appearance of the product is tested, and the crystallization of the coating is observed with an electron microscope. 32 samples are randomly selected from each barrel for neutral salt spray test. 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 .

[0049] Table 1

[0050] Combined with Figures 5 to 7The test results in the table above show that, under the same electroplating process, after the service life of the nickel-phosphorus alloy electroplating solution, the surface of the electroplated workpiece will have white spots (reference Figure 5 Part b), the salt spray resistance of the coating also decreases (reference Figure 7 b). As verified in Example 3, the nickel-phosphorus alloy electroplating solution that has reached the end of its service life, after being treated by the method of the present invention, the surface appearance of the plated workpiece and the salt spray resistance of the coating have reached the same level as the newly prepared solution, Figures 5 to 7 Part c.

[0051] The above description is only a preferred embodiment of the present invention and is not a limitation on the design of this case. Any equivalent changes made based on the design key of this case shall 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 the main salt, the chelating agent and the phosphorus increasing agent to the filtered clear liquid to obtain the regeneration liquid, and finally adjusting the pH value of the regeneration liquid to 2.7-2.9 with a 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.

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. The method for regenerating nickel-phosphorus alloy electroplating waste liquid as claimed in claim 1, characterized in that: 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.

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

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