阅读说明：本技术 焦磷酸盐-柠檬酸盐铜镍合金镀液中铜和镍的滴定分析方法 (Titration analysis method for copper and nickel in pyrophosphate-citrate copper-nickel alloy plating solution ) 是由 黎小阳 郭崇武 陈康 赖奂汶 于 2019-10-12 设计创作，主要内容包括：本发明公开了一种焦磷酸盐-柠檬酸盐铜镍合金镀液中铜和镍的滴定分析方法,用双氧水氧化铜镍合金镀液中的柠檬酸盐,加强酸使焦磷酸水解生成正磷酸,消除其对测定的干扰。用硫脲和抗坏血酸联合掩蔽铜离子,以抗坏血酸掩蔽铁,用pH＝5.4的六次甲基四胺-盐酸缓冲溶液调节试液的pH,加入EDTA标准溶液,以二甲酚橙作指示剂,用硫酸锌返滴定过量的EDTA,计算镀液中的镍含量。按上述方法破坏柠檬酸盐和焦磷酸盐,加抗坏血酸掩蔽铁,然后加氢氧化钠溶液调节试液至弱酸性,再加pH＝10的氨-氯化铵缓冲溶液调节试液的pH,以紫脲酸铵作指示剂,用EDTA标准溶液滴定铜和镍的总量,用差减法计算铜的含量。(The invention discloses a titration analysis method for copper and nickel in pyrophosphate-citrate copper-nickel alloy plating solution. Masking copper ions by combining thiourea and ascorbic acid, masking iron by using the ascorbic acid, adjusting the pH of the test solution by using a hexamethylenetetramine-hydrochloric acid buffer solution with the pH being 5.4, adding an EDTA standard solution, using xylenol orange as an indicator, back-titrating excessive EDTA by using zinc sulfate, and calculating the nickel content in the plating solution. The citrate and pyrophosphate are destroyed according to the method, ascorbic acid is added to mask iron, then sodium hydroxide solution is added to adjust the test solution to weak acidity, ammonia-ammonium chloride buffer solution with pH of 10 is added to adjust the pH of the test solution, ammonium prussiate is used as indicator, EDTA standard solution is used to titrate the total amount of copper and nickel, and the content of copper is calculated by differential subtraction.)

1. The titration analysis method for copper and nickel in pyrophosphate-citrate copper-nickel alloy plating solution is characterized in that the determination of the content of nickel sulfate comprises the following steps:

(a) absorbing pyrophosphate-citrate copper-nickel alloy plating solution to be detected into a conical flask, adding hydrogen peroxide and sodium hydroxide solution, heating for reaction for 1min to completely destroy citrate, then adding dilute sulfuric acid, heating to boil for 0-20 s to hydrolyze pyrophosphate to generate orthophosphoric acid, cooling, adding water for dilution, dropwise adding 25% by mass of sodium hydroxide solution until the test solution is slightly turbid, adding thiourea solution, ascorbic acid and hexamethylenetetramine-hydrochloric acid buffer solution, and then sequentially adding EDTA standard solution A and xylenol orange indicator to obtain a yellowish green test solution; sucking the volume ratio of the plating solution to be detected to the added sodium hydroxide solution, the diluted sulfuric acid, the thiourea solution, the hexamethylenetetramine-hydrochloric acid buffer solution and the EDTA standard solution A to be 1: 5, and sucking the volume mass ratio of the plating solution to be detected to the added ascorbic acid to be 1: 0.1-0.2;

(b) titrating with a zinc sulfate standard solution until the yellow-green test solution in the step (a) is converted into purple red as an end point;

(c) calculating the mass concentration of nickel sulfate hexahydrate in the pyrophosphate-citrate copper-nickel alloy plating solution: rho (NiSO)₄·6H₂O)＝262.8(c₁V₁-c₂V₂)/V₀Where ρ (NiSO)₄·6H₂O) represents the mass concentration (g/L) of nickel sulfate hexahydrate in the plating solution, 262.8 is the molar mass (g/mol) of nickel sulfate hexahydrate, c₁The quantity concentration (mol/L) of a substance which is an EDTA standard solution A, V₁Volume (mL) for EDTA Standard solution A, c₂The quantity concentration (mol/L) of a substance which is a standard solution of zinc sulfate, V₂Volume (mL) of standard solution of zinc sulfate to be consumed, V₀To draw up the volume (mL) of pyrophosphate-citrate copper nickel alloy plating solution to be tested.

2. The titration analysis method for copper and nickel in pyrophosphate-citrate copper-nickel alloy plating solution is characterized in that the determination of the copper sulfate content comprises the following steps:

(d) absorbing pyrophosphate-citrate copper-nickel alloy plating solution to be detected into a conical flask, adding hydrogen peroxide and sodium hydroxide solution, heating for reaction for 1min, then adding dilute sulfuric acid, heating to boil for 0-20 s, cooling, adding water for dilution, dropwise adding 25% of sodium hydroxide solution until the sample solution is turbid, adding ascorbic acid, adding ammonia-ammonium chloride buffer solution, and adding an ammonium diuranate indicator to obtain a yellow-green sample solution; sucking the volume ratio of the plating solution to be detected to the added sodium hydroxide solution, the diluted sulfuric acid and the ammonia-ammonium chloride buffer solution to be 1: 5, sucking the volume mass ratio of the plating solution to be detected to the added ascorbic acid to be 1: 0.1-0.2, and sucking the volume of the pyrophosphate-citrate copper-nickel alloy plating solution to be detected to be the same as the sucking amount in the step (a);

(e) titrating by using an EDTA standard solution B until the yellow-green test solution in the step (d) is converted into purple red as an end point;

(f) calculating the mass concentration of copper sulfate pentahydrate in the pyrophosphate-citrate copper-nickel alloy plating solution: rho (CuSO)₄·5H₂O)＝249.7(c₃V₃-c₁V₁+c₂V₂)/V₀Where ρ (CuSO)₄·5H₂O) represents the mass concentration (g/L) of copper sulfate pentahydrate, 249.7 is the molar mass (g/mol) of copper sulfate pentahydrate, c₃The quantity concentration (mol/L) of the substance being EDTA standard solution B, V₃To consume volume (mL) of EDTA Standard solution B, c₁Is the quantity concentration (mol/L) of the substance of the EDTA standard solution A in step (a), V₁Volume (mL) of EDTA Standard solution A added in step (a), c₂The quantity concentration (mol/L) of a substance which is a standard solution of zinc sulfate, V₂Volume (mL), V, of standard solution of zinc sulfate to be consumed in step (b)₀To draw up the volume (mL) of pyrophosphate-citrate copper nickel alloy plating solution to be tested.

3. The method for the titrimetric analysis of copper and nickel in a pyrophosphate-citrate copper nickel alloy plating bath as set forth in claims 1 to 2, characterized in that: the sodium hydroxide solution is 8-12 g/L sodium hydroxide aqueous solution, the hydrogen peroxide is 30% hydrogen peroxide in mass fraction, the dilute sulfuric acid is 180-220 mL/L sulfuric acid aqueous solution in volume concentration, and the ascorbic acid is solid.

4. The method for the titrimetric analysis of copper and nickel in a pyrophosphate-citrate copper nickel alloy plating bath as set forth in claim 1, characterized in that: the thiourea solution is a thiourea aqueous solution with the mass concentration of 40-80 g/L, and the xylenol orange indicator is prepared by the following method: 0.15-0.25 g of xylenol orange is weighed and dissolved in 100mL of water.

5. The method for the titrimetric analysis of copper and nickel in a pyrophosphate-citrate copper nickel alloy plating bath as set forth in claim 1, characterized in that: the hexamethylene tetramine-hydrochloric acid buffer solution is prepared by the following method: 160g of hexamethylenetetramine was dissolved in 400mL of water, and 40mL of concentrated hydrochloric acid was added.

6. The method for the titrimetric analysis of copper and nickel in a pyrophosphate-citrate copper nickel alloy plating bath as set forth in claim 1, characterized in that: the substance quantity concentration of the EDTA standard solution A is 0.08 mol/L.

7. The method for the titrimetric analysis of copper and nickel in a pyrophosphate-citrate copper nickel alloy plating bath as set forth in claim 1, characterized in that: the mass concentration of the zinc sulfate standard solution is 0.05 mol/L.

8. The method for the titrimetric analysis of copper and nickel in a pyrophosphate-citrate copper nickel alloy plating bath as set forth in claim 2, characterized in that: the ammonium diuranate indicator is prepared by the following method: 0.15-0.25 g of ammonium diuranate and 100g of sodium chloride are ground and mixed uniformly.

9. The method for the titrimetric analysis of copper and nickel in a pyrophosphate-citrate copper nickel alloy plating bath as set forth in claim 2, characterized in that: the ammonia-ammonium chloride buffer solution is prepared by the following method: dissolving 15g of ammonium chloride in 300mL of water, adding 100mL of concentrated ammonia water with the mass fraction of 25-28%, uniformly mixing, and adding water to 500 mL.

10. The method for the titrimetric analysis of copper and nickel in a pyrophosphate-citrate copper nickel alloy plating bath as set forth in claim 2, characterized in that: the substance quantity concentration of the EDTA standard solution B is 0.05 mol/L.

Technical Field

The invention relates to a method for analyzing a plating solution, in particular to a method for titrating and analyzing copper and nickel in a copper-nickel alloy plating solution containing pyrophosphate and a citrate complexing agent.

Background

The pyrophosphate-citrate copper-nickel alloy plating solution has more complex components, and has certain difficulty in analyzing copper and nickel in the plating solution. For the analysis of the mixed solution of copper and nickel, documents [1-3] report an EDTA volumetric method for measuring nickel, document [1] uses thiourea to mask copper, uses xylenol orange as an indicator, and directly titrates nickel by using an EDTA standard solution under the condition of pH 5.5. Document [2] discloses that the method is also not applicable when the determination of nickel is interfered by pyrophosphate and citrate, as shown by experiments, in which copper is first masked by ascorbic acid and thiourea, PAN-6S is used as an indicator, nickel is titrated by EDTA under the condition that the pH is 2.3, then copper is deblocked by adding hydrogen peroxide, and then copper is titrated by EDTA. Document [3] reports a method for measuring nickel by zinc sulfate back titration using xylenol orange as an indicator under a condition of pH 5.4; tests have shown that citrate interferes strongly with the determination of nickel, and this method is not feasible.

The citrate has strong oxidation resistance, and the citrate is difficult to be effectively damaged by ammonium persulfate, hydrogen peroxide and sodium hypochlorite solution, thereby bringing great difficulty to the analysis of the content of copper and nickel in the pyrophosphate-citrate copper-nickel alloy plating solution.

Among them, references:

[1] xuhong was turned, Zhoudu electroplating solution analysis technique [ M ]. Beijing chemical industry Press, 2003: 300-302.

[2] Sanyusheng (PAN-6S) as a complexometric titration indicator for continuous copper and nickel determination [ J ]. proceedings of the chemical institute of sheng, 2004, 18 (4): 309-312.

[3] Analysis of nickel sulfate in mucigera, guo chongwu pyrophosphate copper-nickel alloy baths [ J ] plating and finishing, 2016, 38 (6): 36-38.

Disclosure of Invention

Based on this, it is necessary to develop a titration analysis method for copper and nickel in pyrophosphate-citrate copper-nickel alloy plating solution.

The citric acid has strong oxidation resistance, and the citrate can not be effectively destroyed by using a strong oxidant ammonium persulfate under the acidic and heating conditions; under the condition of no copper ion catalysis, the citrate can not be effectively destroyed by hydrogen peroxide under the heating condition; citrate is also not effectively destroyed with sodium hypochlorite.

The invention utilizes the catalytic action of copper ions to destroy citric acid by using hydrogen peroxide with higher concentration under the conditions of alkalinity and heating.

The pyrophosphate-citrate copper-nickel alloy plating solution is used for electroplating metal coins, the used metal is steel, the plating solution contains iron impurities, and the interference of the iron impurities on the measurement is eliminated by masking the iron with ascorbic acid.

The invention discloses a titration analysis method of copper and nickel in pyrophosphate-citrate copper-nickel alloy plating solution, which comprises the steps of destroying citrate by using hydrogen peroxide, strengthening acid to hydrolyze pyrophosphoric acid to generate orthophosphoric acid, jointly masking copper ions by using thiourea and ascorbic acid, masking iron by using ascorbic acid, adjusting the pH of the test solution by using hexamethylenetetramine-hydrochloric acid buffer solution with the pH being 5.4, adding EDTA standard solution, using xylenol orange as an indicator, back titrating excessive EDTA by using zinc sulfate, and calculating the content of nickel in the plating solution. The citric acid and pyrophosphoric acid are destroyed by the method, then sodium hydroxide solution is added to adjust the test solution to be weakly acidic, ascorbic acid is added to mask iron, ammonia-ammonium chloride buffer solution with the pH value of 10 is added to adjust the pH value of the test solution, ammonium prussiate is used as an indicator, EDTA standard solution is used for titrating the total amount of copper and nickel, and the content of copper is calculated by a differential subtraction method.

The invention solves the problem that the prior art can not use an EDTA volumetric method to measure the content of copper and nickel in the pyrophosphate-citrate copper-nickel alloy plating solution.

The technical scheme of the invention is realized as follows: the titration analysis method for copper and nickel in pyrophosphate-citrate copper-nickel alloy plating solution comprises the following steps:

(a) absorbing pyrophosphate-citrate copper-nickel alloy plating solution to be detected into a conical flask, adding hydrogen peroxide and sodium hydroxide solution, heating for reaction for 1min to completely destroy citrate, then adding dilute sulfuric acid, heating to boil for 0-20 s to hydrolyze pyrophosphate to generate orthophosphoric acid, cooling, adding water for dilution, dropwise adding 25% by mass of sodium hydroxide solution until the test solution is slightly turbid, adding thiourea solution, ascorbic acid and hexamethylenetetramine-hydrochloric acid buffer solution, and then sequentially adding EDTA standard solution A and xylenol orange indicator to obtain a yellowish green test solution; sucking the volume ratio of the plating solution to be detected to the added sodium hydroxide solution, the diluted sulfuric acid, the thiourea solution, the hexamethylenetetramine-hydrochloric acid buffer solution and the EDTA standard solution A to be 1: 5, and sucking the volume mass ratio of the plating solution to be detected to the added ascorbic acid to be 1: 0.1-0.2;

(b) titrating with a zinc sulfate standard solution until the yellow-green test solution in the step (a) is converted into purple red as an end point;

(c) calculating the mass concentration of nickel sulfate hexahydrate in the pyrophosphate-citrate copper-nickel alloy plating solution: rho (NiSO)₄·6H₂O)＝262.8(c₁V₁-c₂V₂)/V₀Where ρ (NiSO)₄·6H₂O) represents the mass concentration (g/L) of nickel sulfate hexahydrate in the plating solution, 262.8 is the molar mass (g/mol) of nickel sulfate hexahydrate, c₁The quantity concentration (mol/L) of a substance which is an EDTA standard solution A, V₁Volume (mL) for addition of EDTA Standard solution, c₂The quantity concentration (mol/L) of a substance which is a standard solution of zinc sulfate, V₂Volume (mL) of standard solution of zinc sulfate to be consumed, V₀To draw up the volume (mL) of pyrophosphate-citrate copper nickel alloy plating solution to be tested.

The titration analysis method of copper and nickel in pyrophosphate-citrate copper-nickel alloy plating solution comprises the following steps:

(d) absorbing pyrophosphate-citrate copper-nickel alloy plating solution to be detected into a conical flask, adding hydrogen peroxide and sodium hydroxide solution, heating for reaction for 1min, then adding dilute sulfuric acid, heating to boil for 0-20 s, cooling, adding water for dilution, dropwise adding 25% of sodium hydroxide solution until the sample solution is turbid, adding ascorbic acid, adding ammonia-ammonium chloride buffer solution, and adding an ammonium diuranate indicator to obtain a yellow-green sample solution; sucking the volume ratio of the plating solution to be detected to the added sodium hydroxide solution, the diluted sulfuric acid and the ammonia-ammonium chloride buffer solution to be 1: 5, sucking the volume mass ratio of the plating solution to be detected to the added ascorbic acid to be 1: 0.1-0.2, and sucking the volume of the pyrophosphate-citrate copper-nickel alloy plating solution to be detected to be the same as the sucking amount in the step (a);

(e) titrating by using an EDTA standard solution B until the yellow-green test solution in the step (d) is converted into purple red as an end point;

(f) calculating the mass concentration of copper sulfate pentahydrate in the pyrophosphate-citrate copper-nickel alloy plating solution: rho (CuSO)₄·5H₂O)＝249.7(c₃V₃-c₁V₁+c₂V₂)/V₀Where ρ (CuSO)₄·5H₂O) represents the mass concentration (g/L) of copper sulfate pentahydrate, 249.7 is the molar mass (g/mol) of copper sulfate pentahydrate, c₃The quantity concentration (mol/L) of the substance being EDTA standard solution B, V₃To consume volume (mL) of EDTA Standard solution B, c₁The quantity concentration (mol/L) of a substance which is an EDTA standard solution A, V₁Volume (mL) of EDTA Standard solution A added in step (a), c₂The quantity concentration (mol/L) of a substance which is a standard solution of zinc sulfate, V₂Volume (mL), V, of standard solution of zinc sulfate to be consumed in step (b)₀To draw up the volume (mL) of pyrophosphate-citrate copper nickel alloy plating solution to be tested.

In some embodiments, the sodium hydroxide solution is 8-12 g/L sodium hydroxide solution.

In some embodiments, the hydrogen peroxide is 30% by mass of hydrogen peroxide.

In some embodiments, the dilute sulfuric acid is an aqueous sulfuric acid solution with a volume concentration of 180-220 mL/L.

In some of these embodiments, the ascorbic acid is a solid.

In some embodiments, the thiourea solution is a thiourea aqueous solution with a mass concentration of 40-80 g/L.

In some of these embodiments, the xylenol orange indicator is formulated as follows: 0.15-0.25 g of xylenol orange is weighed and dissolved in 100mL of water.

In some of these examples, the hexamethylenetetramine-hydrochloric acid buffer solution is prepared as follows: 160g of hexamethylenetetramine was dissolved in 400mL of water, and 40mL of concentrated hydrochloric acid was added.

In some of the embodiments, the substance of the EDTA standard solution A is in a concentration of 0.08 mol/L.

In some of these examples, the zinc sulfate standard solution has a mass concentration of 0.05 mol/L.

In some of these embodiments, the ammonium diuranate indicator is formulated as follows: 0.15-0.25 g of ammonium diuranate and 100g of sodium chloride are ground and mixed uniformly.

In some of these embodiments, the ammonia-ammonium chloride buffer solution is formulated as follows: dissolving 15g of ammonium chloride in 300mL of water, adding 100mL of concentrated ammonia water with the mass fraction of 25-28%, uniformly mixing, and adding water to 500 mL.

In some of the embodiments, the substance of the EDTA standard solution B is in a concentration of 0.05 mol/L.

The invention has the beneficial effects that:

1. the invention utilizes the catalytic action of copper ions, and uses hydrogen peroxide with higher concentration to completely destroy citrate under the alkaline and heating conditions, thereby effectively eliminating the interference of the citrate on the determination of copper and nickel;

2. according to the method, pyrophosphoric acid is hydrolyzed by strong acid under the heating condition to generate orthophosphoric acid, so that the interference of pyrophosphate on the measurement is effectively eliminated;

3. according to the invention, thiourea and ascorbic acid are adopted to jointly mask copper, an EDTA standard solution is added under the condition that the pH value is 5.4, then xylenol orange is used as an indicator, and the content of nickel is determined by a zinc sulfate back titration method, so that the blocking effect of nickel ions on the xylenol orange indicator is effectively eliminated;

4. the method fills the blank of the titration analysis method of copper and nickel in the pyrophosphate-citrate copper-nickel alloy plating solution, and has the advantages of simplicity and high accuracy.

Detailed Description

The present invention will be further specifically illustrated by the following examples for better understanding, but the present invention is not to be construed as being limited thereto, and certain insubstantial modifications and adaptations of the invention by those skilled in the art based on the foregoing disclosure are intended to be included within the scope of the invention.

The chemical reagents used were as follows:

1. sodium hydroxide solution: the mass concentration is 10 g/L;

2. 25% sodium hydroxide solution: 100g of sodium hydroxide is dissolved in 300g of water;

3. hydrogen peroxide: the mass fraction is 30 percent;

4. dilute sulfuric acid: the volume concentration is 200 mL/L;

5. thiourea solution: the mass concentration is 50 g/L;

6. ascorbic acid: a solid;

7. xylenol orange indicator: weighing 0.2g of xylenol orange to dissolve in 100mL of water;

8. ammonium taurocyanate indicator: 0.2g of ammonium diuranate and 100g of sodium chloride are ground and mixed uniformly;

9. hexamethylenetetramine-hydrochloric acid buffer solution: 160g of hexamethylenetetramine is dissolved in 400mL of water, and 40mL of concentrated hydrochloric acid is added;

10. ammonia-ammonium chloride buffer solution: dissolving 15g of ammonium chloride in 300mL of water, adding 100mL of concentrated ammonia water with the mass fraction of 25-28%, uniformly mixing, and adding water to 500 mL;

11. EDTA standard solution a: the mass concentration of the substance is 0.08 mol/L;

12. EDTA standard solution B: the mass concentration of the substance is 0.05mol/L

13. Zinc sulfate standard solution: the mass concentration of the substance is 0.05 mol/L;