Separation method of nickel in zinc-nickel alloy plating solution

Abstract

The invention provides a method for separating nickel from a zinc-nickel alloy plating solution. The method comprises the following steps: adding a first acid adjusting solution and an aqueous solution of ferricyanate into a zinc-nickel alloy plating solution to obtain a mixed precipitate of zinc hexacyanoferrate and nickel hexacyanoferrate; adding an alkali adjusting solution to obtain a nickel hydroxide precipitate, and adding an aqueous solution of an oxidizing agent to obtain a high nickel hydroxide precipitate; and finally adding a second acid adjusting solution and an aqueous solution of a reducing agent to obtain a nickel salt solution. The high nickel hydroxide which is large in particle and easy to separate is obtained through two-step precipitation and one-step oxidation, the nickel ions can be independently separated through reduction, the nickel ions can be efficiently separated under the background of a high-concentration coordination agent, the method can be simply and rapidly completed, the nickel content can be further measured through a classic method, and the method is suitable for large-scale popularization and application. And the accuracy of the analysis result is ensured, and the separation method not only can remarkably improve the detection efficiency, but also can provide more reliable data support for electroplating quality control.

Description

Technical Field

[0001] The present invention relates to the technical field of electroplating, and in particular, to a method for separating nickel in a zinc-nickel alloy plating solution. Background Art

[0002] The composition of a zinc-nickel alloy plating solution (tank solution, mostly alkaline) is complex and usually contains a large amount of complexing agents (such as polyene polyamines). These complexing agents will interfere with the determination of metal ions, making it difficult to analyze the nickel content.

[0003] Currently, the standard methods for nickel determination include atomic absorption spectrometry and dimethylglyoxime spectrophotometry. The essence of dimethylglyoxime spectrophotometry is the spectrophotometry of the complex of dimethylglyoxime and nickel(III) ions. However, the above methods require the drawing of a standard working curve, which is time-consuming and laborious. The principle of the dimethylglyoxime gravimetric method is precipitation dissolution equilibrium, which can quickly determine the content of nickel ions in the solution. However, in the presence of a large amount of complexing agents, the determination accuracy cannot be guaranteed. The essence of complexometric titration is the EDTA titration method using complexation reactions, which is also a common analytical method for nickel. However, since the coordination properties between zinc and nickel are very close, chemical titration complexing agents cannot distinguish between the two. Chinese application CN201710259374.9 discloses a method for determining the nickel ion content by using triethylenetetramine to form a stable purple-red complex with nickel ions. However, the determination accuracy in the presence of a large amount of complexing agents cannot be guaranteed either.

[0004] Moreover, the above methods are all affected by the complexing agents in the zinc-nickel alloy plating solution, resulting in low determination accuracy and complex operations. To improve the analysis accuracy, it is necessary to separate the nickel ions, and then further accurate determination can be carried out. However, limited by the interference of complexing agents in the system and the similar chemical properties of zinc and nickel, there is currently no reliable method to achieve the full separation of nickel ions in the zinc-nickel alloy plating solution. Summary of the Invention

[0005] The main object of the present invention is to provide a method for separating nickel in a zinc-nickel alloy plating solution to solve the problem in the prior art that it is difficult to separate nickel ions in the zinc-nickel plating solution, resulting in difficulty in accurately determining nickel ions in the presence of a large amount of complexing agents.

[0006] To achieve the above object, according to one aspect of the present invention, a method for separating nickel in a zinc-nickel alloy plating solution is provided. The zinc-nickel alloy plating solution includes zinc ions, nickel ions, and a complexing agent. The separation method includes the following steps: Step S1, adding a first acid adjusting solution to the zinc-nickel alloy plating solution to obtain a first acidic feed solution, and adding an aqueous solution of ferrocyanate to the first acidic feed solution to carry out a first precipitation reaction to obtain a mixed precipitate, which includes zinc ferrocyanide and nickel ferrocyanide; Step S2, adding an alkali adjusting solution to the mixed precipitate to obtain an alkaline feed solution to carry out a second precipitation reaction to obtain nickel hydroxide precipitate; Step S3, adding an aqueous solution of an oxidizing agent to the nickel hydroxide precipitate to carry out an oxidation reaction to obtain nickel hydroxide precipitate; Step S4, adding a second acid adjusting solution to the nickel hydroxide precipitate to obtain a second acidic feed solution, and adding an aqueous solution of a reducing agent to the second acidic feed solution to carry out a reduction reaction to obtain a nickel salt solution.

[0007] Further, in step S1, the first acid adjusting solution includes one or more of sulfuric acid solution, nitric acid solution, and hydrochloric acid solution, with a molar concentration of 0.5 - 3 mol / L; and / or the pH of the first acidic feed solution ≤ 3; and / or the ferrocyanate includes potassium ferrocyanide and / or sodium ferrocyanide; preferably, the molar concentration of the aqueous solution of ferrocyanate is 0.05 - 0.5 mol / L.

[0008] Further, in step S1, the molar ratio of ferrocyanate to zinc ions in the zinc-nickel alloy plating solution is (10 - 2):1; and / or the molar ratio of ferrocyanate to nickel ions in the zinc-nickel alloy plating solution is (10 - 2):1; and / or the temperature of the first precipitation reaction is 20 - 50 °C, and the time is 10 - 30 min.

[0009] Further, in step S2, the alkali adjusting solution includes NaOH solution and / or KOH solution, with a molar concentration of 1 - 3 mol / L; and / or the pH of the alkaline feed solution ≥ 10.

[0010] Further, in step S2, the temperature of the second precipitation reaction is 20 - 50 °C, and the time is 10 - 30 min.

[0011] Further, in step S3, the oxidizing agent includes sodium persulfate and / or potassium persulfate; preferably, the molar concentration of the aqueous solution of the oxidizing agent is 0.05 - 0.5 mol / L.

[0012] Further, in step S3, the molar ratio of the oxidizing agent to the nickel hydroxide precipitate is (10 - 3):1; and / or the temperature of the oxidation reaction is 20 - 50 °C, and the time is 10 - 30 min.

[0013] Further, in step S4, the second acid adjustment solution includes one or more of sulfuric acid solution, nitric acid solution, and hydrochloric acid solution, with a molar concentration of 0.5 - 3 mol / L; and / or the pH of the second acidic feed liquid ≤ 5; and / or the reducing agent includes one or more of potassium iodide, sodium sulfite, and sodium thiosulfate; preferably, the molar concentration of the aqueous solution of the reducing agent is 0.1 - 0.5 mol / L.

[0014] Further, in step S4, the molar ratio of the reducing agent to nickel hydroxide precipitate is (10 - 2):1; and / or the temperature of the reduction reaction is 20 - 40 °C, and the time is 10 - 30 min.

[0015] Further, in the zinc-nickel alloy plating solution, the molar concentration of zinc ions is 0.01 - 0.3 mol / L, the molar concentration of nickel ions is 0.01 - 0.3 mol / L, and the molar concentration of the complexing agent is 0.1 - 3 mol / L.

[0016] Applying the technical solution of the present invention, first, potassium ferricyanide is used to separate zinc and nickel from a large amount of complexing agent system under acidic conditions, then the properties of generating hydroxides are used to distinguish zinc and nickel under alkaline conditions, and then nickel hydroxide is further oxidized. Through two-step precipitation and one-step oxidation, nickel hydroxide with larger particles and easy to separate is obtained. After reduction, nickel ions can be separated separately, and further, the content of nickel can be accurately measured independently. The separation method of the present invention can efficiently separate nickel ions under the background of high-concentration complexing agent (complexing agent), and this method can be completed simply and quickly. The classical method can be further adopted to determine the nickel content, and the accuracy of the analysis result is ensured. This separation method can not only significantly improve the detection efficiency, but also provide more reliable data support for electroplating quality control. Specific Embodiments

[0017] It should be noted that, without conflict, the embodiments in this application and the features in the embodiments can be combined with each other. The present invention will be described in detail below with reference to the embodiments.

[0018] Unless otherwise specified, the "solution" in the present invention refers to an aqueous solution.

[0019] As described in the background art of the present invention, in the prior art, it is difficult to separate nickel ions in the zinc-nickel plating solution, resulting in the problem that it is difficult to accurately measure nickel ions in the presence of a large amount of complexing agents. To solve the above problems, in a typical embodiment of the present invention, a method for separating nickel in a zinc-nickel alloy plating solution is provided. The zinc-nickel alloy plating solution includes zinc ions, nickel ions, and a complexing agent. The separation method includes the following steps: Step S1, adding a first acid adjusting solution to the zinc-nickel alloy plating solution to obtain a first acidic feed solution, and adding an aqueous solution of ferrocyanate to the first acidic feed solution to perform a first precipitation reaction to obtain a mixed precipitate, which includes zinc ferrocyanide and nickel ferrocyanide; Step S2, adding an alkali adjusting solution to the mixed precipitate to obtain an alkaline feed solution to perform a second precipitation reaction to obtain nickel hydroxide precipitate; Step S3, adding an aqueous solution of an oxidizing agent to the nickel hydroxide precipitate to perform an oxidation reaction to obtain nickel hydroxide precipitate; Step S4, adding a second acid adjusting solution to the nickel hydroxide precipitate to obtain a second acidic feed solution, and adding an aqueous solution of a reducing agent to the second acidic feed solution to perform a reduction reaction to obtain a nickel salt solution.

[0020] The zinc-nickel alloy plating solution of the present invention is a zinc-nickel alloy plating solution containing a strong complexing agent (complexing agent). Considering the interference of a large amount of strong complexing agents in the electroplating zinc-nickel bath solution, such as polyene polyamines, a first acid adjusting solution is first added thereto (generally, the zinc-nickel alloy plating solution also contains sodium carbonate, and adding acid will generate carbon dioxide, so it is preferred to stir and exhaust the bubbles), and after obtaining the first acidic feed solution, an aqueous solution of ferrocyanate is added. Under acidic conditions, ferrocyanate is used as a precipitant, and the zinc ions and nickel ions in the zinc-nickel alloy plating solution are precipitated by the ferrocyanate ions therein. After filtration or centrifugal separation, a mixed precipitate of zinc ferrocyanide and nickel ferrocyanide is obtained, so as to separate zinc and nickel from the system with a large amount of complexing agents to exclude the influence of the strong complexing agent in the subsequent separation and analysis process. The inventors unexpectedly found during the research process that when potassium ferrocyanide is used as a precipitant, the precipitated zinc ferrocyanide and nickel ferrocyanide are mostly colloid systems and are difficult to separate solid from liquid. Therefore, potassium ferricyanide is used as a precipitant to achieve the best precipitation and separation effect.

[0021] Subsequently, an alkali adjusting solution is added to the mixed precipitate. In an alkaline system, zinc ions first react to form zinc hydroxide precipitate, and with the continuous addition of the alkali adjusting solution, in the presence of excess OH - it is further converted into soluble tetrahydroxy zinc ions, while nickel ions undergo a second precipitation reaction, and the reaction formula is Ni 2+ +OH - =Ni(OH) 2 ↓, obtaining a light green nickel hydroxide precipitate, thus utilizing the property difference of zinc and nickel to form hydroxides, enabling zinc ions to enter the solution and nickel ions to enter the precipitate, and achieving the separation of zinc and nickel.

[0022] Then, an aqueous solution of an oxidant is added to the nickel hydroxide precipitate, and the nickel hydroxide precipitate is oxidized by the oxidant to nickel oxyhydroxide with larger particles, i.e., nickel hydroxide peroxide. An exemplary reaction formula is The nickel hydroxide peroxide precipitate that is more convenient for separation is filtered or centrifuged to remove the oxidant in the solution, and a black nickel hydroxide peroxide precipitate can be obtained, ensuring that nickel ions are separated out alone, providing a pure nickel sample for subsequent determination of the content. The color of the nickel hydroxide precipitate is light green, and the color of nickel hydroxide peroxide after oxidation is black. During the partial oxidation of nickel hydroxide to nickel hydroxide peroxide, there may be a mixed color of the two substances, i.e., the intermediate color of blue-gray.

[0023] Finally, a second acid is added to the nickel hydroxide peroxide precipitate to adjust the solution, and an aqueous solution of a reducing agent is added under acidic conditions to carry out a reduction reaction to obtain a nickel salt solution containing divalent nickel ions, thereby separating nickel ions alone. Further using classical methods or standard methods can achieve the independent and accurate determination of nickel ions. For example, the weight method using dimethylglyoxime is used for the determination of nickel ion content.

[0024] The present invention is a nickel separation method with two-step precipitation and one-step oxidation. By adjusting different acidic and basic solution systems, zinc and nickel are first separated from a system with a large amount of complexing agents, and then, based on the different properties of zinc and nickel compounds, zinc and nickel are distinguished. Further adding an oxidant can separate nickel alone under simple separation conditions, laying a solid foundation for further realizing the independent and accurate determination of the nickel content. Moreover, in the actual determination of the nickel content in a zinc-nickel alloy plating solution, by pretreating the zinc-nickel alloy plating solution, separating nickel and then separately determining it, the choice of analysis methods becomes larger, and a variety of classical methods can be used for the accurate determination of the nickel content. Furthermore, the precipitation method of the present invention is a heterogeneous transformation, the chemical reaction is complete, and combined with the oxidation method, a precipitate of a nickel compound with larger particles can be obtained, which is easy to separate. It is an efficient separation method for nickel ions (Ni 2+ ) in a zinc-nickel electroplating bath solution.

[0025] In summary, in the present invention, zinc and nickel are first separated from a large amount of complexing agent systems by using potassium ferricyanide under acidic conditions, and then zinc and nickel are distinguished by utilizing the property of forming metal hydroxides under alkaline conditions. Then, nickel hydroxide is further oxidized, and nickel hydroxide of relatively large particle size and easy to separate is obtained through two-step precipitation and one-step oxidation. After reduction, nickel ions can be separated alone, and the content of nickel can be accurately determined independently. The separation method of the present invention can efficiently separate nickel ions under the background of a high-concentration complexing agent, and this method can be easily and quickly completed. The classical method can be further adopted to determine the nickel content, and the accuracy of the analysis result is ensured. This separation method not only significantly improves the detection efficiency, but also provides more reliable data support for the quality control of bath electroplating. Through the separation method of two-step precipitation and one-step oxidation, the present invention effectively eliminates the interference of the complexing agent, can effectively separate nickel ions from the zinc-nickel plating solution, ensures the accuracy and reliability of the subsequent nickel content determination, helps to optimize the composition control of the zinc-nickel alloy plating solution, improves the coating quality and production efficiency, and has significant economic and environmental benefits.

[0026] In a preferred embodiment, in step S1, the first acid adjustment solution includes one or more of sulfuric acid solution, nitric acid solution and hydrochloric acid solution, and the molar concentration is 0.5-3 mol / L; and / or the pH of the first acidic feed liquid ≤ 3; and / or the ferricyanate includes potassium ferricyanide and / or sodium ferricyanide; preferably, the molar concentration of the aqueous solution of the ferricyanate is 0.05-0.5 mol / L. The above ferricyanate can better precipitate and separate zinc and nickel from a large amount of complexing agent systems, provide a good basis for the subsequent separation of zinc and nickel, is beneficial to further improving the accuracy of nickel content determination, and while enabling the metal ions in the plating solution to react fully, the formed precipitate is also easier to separate. At the same time, the above ferricyanate can achieve better precipitation effects in different types of plating solutions. The control of the molar concentration helps to further improve the purity of the precipitate and reduce the interference of impurities in the subsequent treatment steps.

[0027] In a preferred embodiment, in step S1, the molar ratio of the ferricyanate to the zinc ions in the zinc-nickel alloy plating solution is (10-2):1; and / or the molar ratio of the ferricyanate to the nickel ions in the zinc-nickel alloy plating solution is (10-2):1; within the above range, on the basis of making the precipitation of zinc ions and nickel ions in the zinc-nickel alloy plating solution more complete, the precipitation adsorption or encapsulation caused by excessive ferricyanate ions can be further reduced. And / or the temperature of the first precipitation reaction is 20-50 °C, and the time is 10-30 min. The above conditions are more conducive to improving the precipitation reaction rate of zinc ions and nickel ions. By precisely controlling the molar ratio and reaction conditions, zinc ions and nickel ions can be more fully precipitated, and at the same time, an appropriate amount of precipitating agent is used to reduce the treatment cost, which is suitable for large-scale industrial production.

[0028] To provide a more suitable alkaline environment, thereby further promoting the precipitation of nickel and the dissolution of zinc, so as to more fully separate zinc from nickel and improve the accuracy of subsequent nickel content determination. In a preferred embodiment, in step S2, the alkali-adjusted solution includes NaOH solution and / or KOH solution, with a molar concentration of 1-3 mol / L; and / or the pH of the alkaline feed liquid is ≥10. The selection of these aqueous alkali solutions can be flexibly adjusted according to the specific composition of the plating solution to achieve the best separation effect, especially suitable for the separation of nickel ions in zinc-nickel alloy plating solutions.

[0029] In a preferred embodiment, in step S2, the temperature of the second precipitation reaction is 20-50 °C and the time is 10-30 min. The above conditions are more conducive to increasing the dissolution rate of zinc ions and the precipitation reaction rate of nickel ions, achieving a more complete separation of zinc and nickel. The mild reaction conditions can also reduce side reactions that may be caused by high temperatures or the denaturation of other components in the solution, improving the purity and stability of nickel precipitation, and thus enhancing the accuracy of subsequent determination.

[0030] To more effectively oxidize nickel hydroxide precipitate into nickel peroxide hydroxide precipitate and improve the stability and purity of the precipitate. In a preferred embodiment, in step S3, the oxidant includes sodium persulfate and / or potassium persulfate; preferably, the molar concentration of the aqueous solution of the oxidant is 0.05-0.5 mol / L. The persulfate with the above concentration as the oxidant can effectively oxidize nickel hydroxide into nickel peroxide hydroxide that is easier to separate. This oxidation product forms a distinctively colored, relatively large-particle black precipitate in the solution, which is easy to filter or centrifuge, thereby significantly improving the separation efficiency of nickel ions.

[0031] In a preferred embodiment, in step S3, the molar ratio of the oxidant to the nickel hydroxide precipitate is (10-3):1; and / or the temperature of the oxidation reaction is 20-50 °C and the time is 10-30 min. Within the above range, the nickel hydroxide precipitate can be more fully converted into nickel peroxide hydroxide precipitate, improving the completeness of the oxidation reaction, reducing the measurement error of nickel ions caused by incomplete reaction, and reducing unnecessary side reactions caused by excessive oxidant, which may affect the measurement accuracy, thus being beneficial for subsequent separation and determination.

[0032] For the purpose of more fully reducing nickel hydroxide precipitate to divalent nickel ions to facilitate the accurate determination of subsequent content, in a preferred embodiment, in step S4, the second acid adjusting solution includes one or more of sulfuric acid solution, nitric acid solution and hydrochloric acid solution, and the molar concentration is 0.5 - 3 mol / L; and / or the pH of the second acidic feed liquid ≤ 5; and / or the reducing agent includes one or more of potassium iodide, sodium sulfite and sodium thiosulfate; preferably, the molar concentration of the aqueous solution of the reducing agent is 0.1 - 0.5 mol / L. These reducing agents can effectively reduce high-valent nickel ions back to the divalent state under acidic conditions, reduce the interference of high-valent nickel ions in the subsequent analysis process, improve the specificity of the determination, and controlling the reducing agent concentration within the above range also helps to improve the reduction efficiency and reduce the reaction time.

[0033] In a preferred embodiment, in step S4, the molar ratio of the reducing agent to the nickel hydroxide precipitate is (10 - 2):1, preferably (5 - 2):1; and / or the temperature of the reduction reaction is 20 - 40 °C and the time is 10 - 30 min. The molar ratio of the reducing agent within the above range is conducive to the sufficient supply of the reducing agent, reducing the nickel hydroxide precipitate that is not fully reduced to the Ni(II) state, improving the recovery accuracy of nickel ions, and at the same time being able to reduce unnecessary side reactions such as the reduction of zinc. The efficient reduction reaction under mild conditions can not only accelerate the reaction process, but also reduce the precipitation dissolution or the reduction of other metal ions that may be brought about by high temperature or long-time reaction, improve the stability of the nickel hydroxide precipitate and the purity of separation, and can promote the effective dissolution of the nickel hydroxide precipitate and the more sufficient separation of nickel ions, so as to further reduce the precipitation loss and improve the accuracy of the determination.

[0034] To further improve the universality of the separation method, in a preferred embodiment, in the zinc-nickel alloy plating solution, the molar concentration of zinc ions is 0.01 - 0.3 mol / L, the molar concentration of nickel ions is 0.01 - 0.3 mol / L, and the molar concentration of the complexing agent is 0.1 - 3 mol / L. The above zinc-nickel alloy plating solution is more suitable for using the method of the present invention for nickel separation, and the accuracy of subsequent nickel content determination is higher.

[0035] Typically but not limitedly, in step S1, the molar ratio of ferrocyanate to zinc ions in the zinc-nickel alloy plating solution is 10:1, 9:1, 8:1, 7:1, 6:1, 5:1, 4:1, 3:1, 2:1 or a range value composed of any two of these values; the molar ratio of ferrocyanate to nickel ions in the zinc-nickel alloy plating solution is 10:1, 9:1, 8:1, 7:1, 6:1, 5:1, 4:1, 3:1, 2:1 or a range value composed of any two of these values.

[0036] Typically but not limited to, in step S3, the molar ratio of the oxidant to the nickel hydroxide precipitate is 10:1, 9:1, 8:1, 7:1, 6:1, 5:1, 4:1, 3:1, or a range value composed of any two of these values.

[0037] Typically but not limited to, in step S4, the molar ratio of the reducing agent to the nickel hydroxide precipitate is 10:1, 9:1, 8:1, 7:1, 6:1, 5:1, 4:1, 3:1, 2:1, or a range value composed of any two of these values.

[0038] The following further describes the present application in detail with specific embodiments, and these embodiments should not be construed as limiting the scope claimed by the present application.

[0039] Unless otherwise specified, in the following examples and comparative examples:

[0040] The unit "M" refers to mol / L.

[0041] The concentration of the nickel sulfate standard solution is 0.2736 M.

[0042] The zinc-nickel standard solution contains 0.2735 M zinc ions and 0.2736 M nickel ions.

[0043] The zinc-nickel alloy plating solution theoretically contains 0.2735 M zinc ions, 0.2736 M nickel ions, and approximately 2.7 M complexing agent.

[0044] Example 1

[0045]

Verification experiment of nickel standard solution

[0046] In step S1, accurately transfer 0.200 mL of the nickel sulfate standard solution to a beaker, add a first acid adjustment solution (sulfuric acid solution, 2 M) to obtain a first acidic feed solution (pH is 2 - 3), and add an aqueous solution of ferricyanate (potassium ferricyanide solution, 0.1 M, with a molar ratio of 5:1 to the nickel ions in the standard solution) to the first acidic feed solution to perform a first precipitation reaction (temperature is 25 °C, time is 15 min). Use a crucible to filter and separate the solid to obtain nickel ferricyanide precipitate.

[0047] In step S2, add an alkali adjustment solution (NaOH solution, 2 M) to the nickel ferricyanide precipitate to redissolve the precipitate, continue to add dropwise to obtain an alkaline feed solution (pH ≥ 10), and perform a second precipitation reaction (temperature is 25 °C, time is 20 min). Filter and separate to obtain a light green nickel hydroxide precipitate.

[0048] Step S3, an aqueous solution of an oxidizing agent (sodium persulfate solution, 0.1 M, with a molar ratio of 6:1 to the nickel hydroxide precipitate) is added to the nickel hydroxide precipitate to carry out an oxidation reaction (temperature is 25°C, time is 20 min), followed by filtration and separation to obtain a black nickel hydroxide precipitate.

[0049] Step S4, a second acid adjustment solution (sulfuric acid solution, 2 M) is added to the nickel hydroxide precipitate to obtain a second acidic feed solution (pH ≤ 3). An aqueous solution of a reducing agent (potassium iodide solution, 0.2 M, with a molar ratio of 5:1 to the nickel hydroxide precipitate) is added to the second acidic feed solution to carry out a reduction reaction (temperature is 25°C, time is 15 min) to obtain a nickel salt solution.

[0050] Step S5, the nickel content is determined using the dimethylglyoxime gravimetric method: ethanol and 1% dimethylglyoxime are added to the nickel salt solution, the pH is adjusted to 7 - 8, aged for 30 min, filtered by suction and weighed, and the nickel content in the separated solution is measured. The nickel concentration in the nickel sulfate standard solution is measured to be 0.2738 M, with a relative error of 0.1%.

[0051] Among them, the volume can be converted to the original volume of the pipetted solution as needed, and the relative error = |measured value - theoretical value| ÷ theoretical value × 100%.

[0052] Comparative Example 1

[0053] The difference from Example 1 is that the Ni in the nickel sulfate standard solution is directly determined using the dimethylglyoxime gravimetric method: ethanol and 1% dimethylglyoxime are added to the nickel sulfate standard solution, the pH is adjusted to 7 - 8, aged for 30 min, filtered by suction and weighed. The nickel concentration in the nickel sulfate standard solution is measured to be 0.2738 M, with a relative error of 0.1%.

[0054] As can be seen from Example 1 and Comparative Example 1, for the nickel standard solution, the separation method of the present invention does not cause loss of nickel, and the determination result of nickel ions after separating the nickel concentration in a single solution is highly accurate. As can be seen from Example 2 and Comparative Example 2, for the zinc-nickel standard solution, the separation method of the present invention can completely separate nickel, and the determination result of nickel ions after separation is highly accurate.

[0055] Example 2

[0056]

Separation of Zinc-Nickel Standard Solution

[0057] Step S1, accurately pipette 0.200 mL of the zinc-nickel standard solution into a beaker, add a first acid adjustment solution (sulfuric acid solution, 2 M) to obtain a first acidic feed solution (pH is 2 - 3). An aqueous solution of a ferricyanate (potassium ferricyanide solution, 0.1 M, with a molar ratio of 5:1 to the zinc ions in the standard solution and a molar ratio of 5:1 to the nickel ions in the standard solution) is added to the first acidic feed solution to carry out a first precipitation reaction (temperature is 25°C, time is 15 min), and the solid is filtered and separated using a crucible to obtain a mixed precipitate of zinc ferrocyanide and nickel ferrocyanide.

[0058] Step S2, add an alkali to adjust the solution (NaOH solution, 2M) to the mixed precipitate, redissolve the precipitate, continue to add dropwise to obtain an alkaline feed liquid (pH≥10) for the second precipitation reaction (temperature is 25°C, time is 20 min), filter and separate to obtain a light green nickel hydroxide precipitate.

[0059] Step S3, add an aqueous solution of an oxidant (sodium persulfate solution, 0.1M, molar ratio to nickel hydroxide precipitate is 6:1) to the nickel hydroxide precipitate for an oxidation reaction (temperature is 25°C, time is 20 min), filter and separate to obtain a black nickel hydroxide precipitate.

[0060] Step S4, add a second acid to adjust the solution (sulfuric acid solution, 2M) to the nickel hydroxide precipitate to obtain a second acidic feed liquid (pH≤3), add an aqueous solution of a reducing agent (potassium iodide solution, 0.2M, molar ratio to nickel hydroxide precipitate is 5:1) to the second acidic feed liquid for a reduction reaction (temperature is 25°C, time is 15 min) to obtain a nickel salt solution.

[0061] Step S5, use the dimethylglyoxime gravimetric method to determine the nickel content: add ethanol and 1% dimethylglyoxime to the nickel salt solution, adjust the pH to 7 - 8, age for 30 min, filter by suction and weigh to determine the nickel content in the separated solution. The nickel concentration in the zinc-nickel standard solution is measured to be 0.2738M, and the relative error is 0.1%.

[0062] Comparative Example 2

[0063] The difference from Example 2 is that the Ni in the zinc-nickel standard solution is directly determined by the dimethylglyoxime gravimetric method: add ethanol and 1% dimethylglyoxime to the zinc-nickel standard solution, adjust the pH to 7 - 8, age for 30 min, filter by suction and weigh. The nickel concentration in the zinc-nickel standard solution is measured to be 0.2738M, and the relative error is 0.1%.

[0064] As can be seen from Example 3 and Comparative Example 3, for the zinc-nickel alloy plating solution, when the nickel content is directly measured without separating nickel, the determination result of nickel ions is relatively low; using the separation method of the present invention can completely separate nickel in the plating solution, and the determination result of nickel ions after separation is highly accurate. ​ .

[0065] Example 3

[0066]

Zinc-nickel alloy plating solution

[0067] Step S1, accurately transfer 0.200 mL of the zinc-nickel alloy plating solution to a beaker, add a first acid to adjust the solution (sulfuric acid solution, 2M), stir to remove any possible bubbles to obtain a first acidic feed liquid (pH is 2 - 3). Add an aqueous solution of a ferricyanate (potassium ferricyanide solution, 0.1M, molar ratio to zinc ions in the plating solution is 5:1, molar ratio to nickel ions in the plating solution is 5:1) to the first acidic feed liquid for a first precipitation reaction (temperature is 30°C, time is 30 min), filter and separate the solid using a crucible to obtain a mixed precipitate of zinc ferricyanide and nickel ferricyanide.

[0068] Step S2: Add alkali to adjust the solution (NaOH solution, 2M) to the mixed precipitate. The precipitate redissolves. Continue to add dropwise to obtain an alkaline feed liquid (pH ≥ 10) for the second precipitation reaction (temperature: 25°C, time: 20 min). Filter and separate to obtain a light green nickel hydroxide precipitate.

[0069] Step S3: Add an aqueous solution of an oxidant (sodium persulfate solution, 0.1M, molar ratio to nickel hydroxide precipitate is 6:1) to the nickel hydroxide precipitate for an oxidation reaction (temperature: 25°C, time: 20 min). Filter and separate to obtain a black nickel hydroxide precipitate.

[0070] Step S4: Add a second acid to adjust the solution (sulfuric acid solution, 2M) to the nickel hydroxide precipitate to obtain a second acidic feed liquid (pH ≤ 3). Add an aqueous solution of a reducing agent (potassium iodide solution, 0.2M, molar ratio to nickel hydroxide precipitate is 5:1) to the second acidic feed liquid for a reduction reaction (temperature: 25°C, time: 15 min) to obtain a nickel salt solution.

[0071] Step S5: Use the dimethylglyoxime gravimetric method to determine the nickel content: Add ethanol and 1% dimethylglyoxime to the nickel salt solution, adjust the pH to 7 - 8, age for 30 min, filter with suction and weigh to determine the nickel content in the separated solution. The nickel concentration in the zinc - nickel alloy plating solution is measured to be 0.2738M, with a relative error of 0.1%.

[0072] Comparative Example 3

[0073] The difference from Example 3 is that the dimethylglyoxime gravimetric method is used to directly measure Ni in the zinc - nickel alloy plating solution: Add ethanol and 1% dimethylglyoxime to the zinc - nickel alloy plating solution, adjust the pH to 7 - 8, age for 30 min, filter with suction and weigh. The nickel concentration in the zinc - nickel alloy plating solution is measured to be 0.2452M, with a relative error of 10.4%.

[0074] ​ ​ ​ 。

[0075] Example 4

[0076] The difference from Example 3 is that in Step S1, add a first acid to adjust the solution (nitric acid solution, 0.5M) to the zinc - nickel alloy plating solution to obtain a first acidic feed liquid (pH ≤ 3). Add an aqueous solution of a ferricyanate (potassium ferricyanide solution, 0.05M, molar ratio to zinc ions in the plating solution is 10:1, molar ratio to nickel ions in the plating solution is 10:1) to the first acidic feed liquid for a first precipitation reaction (temperature: 20°C, time: 30 min). Use a crucible to filter and separate the solid to obtain a mixed precipitate of zinc ferrocyanide and nickel ferrocyanide.

[0077] Example 5

[0078] The difference from Example 3 is that in step S1, a first acid adjusting solution (hydrochloric acid solution, 3M) is added to the zinc-nickel alloy plating solution to obtain a first acidic stock solution (pH ≤ 3). An aqueous solution of ferricyanate (sodium ferricyanide solution, 0.5M, with a molar ratio of 2:1 to zinc ions in the plating solution and a molar ratio of 2:1 to nickel ions in the plating solution) is added to the first acidic stock solution to carry out a first precipitation reaction (temperature is 50 °C, time is 10 min). The solid is separated by filtration using a crucible to obtain a mixed precipitate of zinc ferrocyanide and nickel ferrocyanide.

[0079] Example 6

[0080] The difference from Example 3 is that in step S2, an alkali adjusting solution (NaOH solution, 1M) is added to the mixed precipitate, and the precipitate redissolves. Continuing to add, a basic stock solution (pH ≥ 10) is obtained to carry out a second precipitation reaction (temperature is 20 °C, time is 30 min). After filtration and separation, a light green nickel hydroxide precipitate is obtained.

[0081] Example 7

[0082] The difference from Example 3 is that in step S2, an alkali adjusting solution (KOH solution, 3M) is added to the mixed precipitate, and the precipitate redissolves. Continuing to add, a basic stock solution (pH ≥ 10) is obtained to carry out a second precipitation reaction (temperature is 50 °C, time is 10 min). After filtration and separation, a light green nickel hydroxide precipitate is obtained.

[0083] Example 8

[0084] The difference from Example 3 is that in step S3, an aqueous solution of an oxidant (sodium persulfate solution, 0.05M, with a molar ratio of 10:1 to the nickel hydroxide precipitate) is added to the nickel hydroxide precipitate to carry out an oxidation reaction (temperature is 20 °C, time is 30 min). After filtration and separation, a black nickel hydroxide precipitate is obtained.

[0085] Example 9

[0086] The difference from Example 3 is that in step S3, an aqueous solution of an oxidant (potassium persulfate solution, 0.5M, with a molar ratio of 3:1 to the nickel hydroxide precipitate) is added to the nickel hydroxide precipitate to carry out an oxidation reaction (temperature is 50 °C, time is 10 min). After filtration and separation, a black nickel hydroxide precipitate is obtained.

[0087] Example 10

[0088] The difference from Example 3 is that in step S4, a second acid adjusting solution (nitric acid solution, 0.5 M) is added to the nickel hydroxide precipitate to obtain a second acidic feed solution (pH ≤ 5). An aqueous solution of a reducing agent (sodium sulfite solution, 0.1 M, with a molar ratio of 10:1 to the nickel hydroxide precipitate) is added to the second acidic feed solution to carry out a reduction reaction (at a temperature of 20°C for 30 min) to obtain a nickel salt solution.

[0089] Example 11

[0090] The difference from Example 3 is that in step S4, a second acid adjusting solution (hydrochloric acid solution, 3 M) is added to the nickel hydroxide precipitate to obtain a second acidic feed solution (pH ≤ 5). An aqueous solution of a reducing agent (sodium thiosulfate solution, 0.5 M, with a molar ratio of 2:1 to the nickel hydroxide precipitate) is added to the second acidic feed solution to carry out a reduction reaction (at a temperature of 40°C for 10 min) to obtain a nickel salt solution.

[0091] The nickel ion concentrations in the corresponding sample solutions measured in the above examples and comparative examples are shown in Table 1.

[0092] Nickel content test method: Dimethylglyoxime gravimetric method, standard number GB / T 223.25-1994 "Methods for chemical analysis of iron, steel and alloys - Dimethylglyoxime gravimetric method for the determination of nickel content".

[0093] Table 1

[0094]

[0095] As can be seen from the above, compared with the comparative examples, in each embodiment of the present invention, zinc and nickel are first separated from a large amount of complexing agent system by potassium ferricyanide under acidic conditions, and then zinc and nickel are distinguished by the property of forming hydroxides under alkaline conditions. Then nickel hydroxide is further oxidized, and large-particle and easily separable nickel hydroxide is obtained through two-step precipitation and one-step oxidation. After reduction, nickel ions can be separately separated, and further the nickel content can be independently and accurately determined. The separation method of the present invention can efficiently separate nickel ions under the background of a high-concentration complexing agent (chelating agent), and this method can be easily and quickly completed. The classical method can be further adopted to determine the nickel content, and the accuracy of the analysis result is ensured. This separation method can not only significantly improve the detection efficiency, but also provide more reliable data support for electroplating quality control.

[0096] In addition, it can be seen that when all process parameters are within the preferred range of the present invention, the comprehensive effect is better.

[0097] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for separating nickel from a zinc-nickel alloy plating solution, wherein the zinc-nickel alloy plating solution comprises zinc ions, nickel ions and a complexing agent, characterized in that: The separation method comprises the following steps: Step S1, adding a first acid regulating solution to the zinc-nickel alloy plating solution to obtain a first acidic feed solution, adding an aqueous solution of ferrocyanate to the first acidic feed solution to perform a first precipitation reaction to obtain a mixed precipitate, wherein the mixed precipitate includes zinc ferrocyanide and nickel ferrocyanide; Step S2, adding an alkali regulating solution to the mixed precipitate to obtain an alkaline feed solution to perform a second precipitation reaction to obtain a nickel hydroxide precipitate; Step S3, adding an aqueous solution of an oxidant to the nickel hydroxide precipitate to perform an oxidation reaction to obtain a nickel hydroxide precipitate; Step S4, adding a second acid regulating solution to the nickel hydroxide precipitate to obtain a second acidic liquid, and adding an aqueous solution of a reducing agent to the second acidic liquid to perform a reduction reaction to obtain a nickel salt solution.

2. The separation method according to claim 1, characterized in that In the step S1, The first acid adjustment solution comprises one or more of a sulfuric acid solution, a nitric acid solution and a hydrochloric acid solution, and the molar concentration is 0.5 to 3 mol / L; and / or the pH of the first acidic feed solution is ≤ 3; and / or The ferrocyanide includes potassium ferrocyanide and / or sodium ferrocyanide; preferably, the molar concentration of the aqueous solution of the ferrocyanide is 0.05-0.5 mol / L.

3. The separation method according to claim 1 or 2, characterized in that In the step S1, The molar ratio of the ferrocyanide to the zinc ions in the zinc-nickel alloy plating solution is (10-2):1; and / or The molar ratio of the ferrocyanide to the nickel ions in the zinc-nickel alloy plating solution is (10-2):1; and / or The temperature of the first precipitation reaction is 20-50° C. and the time is 10-30 min.

4. The separation method according to any one of claims 1 to 3, characterized in that In the step S2, The alkali adjustment solution includes NaOH solution and / or KOH solution with a molar concentration of 1 to 3 mol / L; and / or the pH of the alkaline solution is ≥10.

5. The separation method according to any one of claims 1 to 4, characterized in that In the step S2, the temperature of the second precipitation reaction is 20-50° C. and the time is 10-30 min.

6. The separation method according to any one of claims 1 to 5, characterized in that In the step S3, The oxidant includes sodium persulfate and / or potassium persulfate; preferably, the molar concentration of the aqueous solution of the oxidant is 0.05-0.5 mol / L.

7. The separation method according to any one of claims 1 to 6, characterized in that In the step S3, the molar ratio of the oxidant to the nickel hydroxide precipitate is (10-3):1; and / or The temperature of the oxidation reaction is 20-50° C. and the time is 10-30 minutes.

8. The separation method according to any one of claims 1 to 7, characterized in that In the step S4, The second acid adjustment solution comprises one or more of a sulfuric acid solution, a nitric acid solution and a hydrochloric acid solution, and the molar concentration is 0.5 to 3 mol / L; and / or the pH of the second acidic feed solution is ≤ 5; and / or The reducing agent includes one or more of potassium iodide, sodium sulfite and sodium thiosulfate; preferably, the molar concentration of the aqueous solution of the reducing agent is 0.1-0.5 mol / L.

9. The separation method according to any one of claims 1 to 8, characterized in that In the step S4, The molar ratio of the reducing agent to the nickel hydroxide precipitate is (10-2):1; and / or The temperature of the reduction reaction is 20-40° C. and the time is 10-30 minutes.

10. The separation method according to any one of claims 1 to 9, characterized in that In the zinc-nickel alloy plating solution, the molar concentration of the zinc ions is 0.01-0.3 mol / L, the molar concentration of the nickel ions is 0.01-0.3 mol / L, and the molar concentration of the complexing agent is 0.1-3 mol / L.

Images