A method for continuously detecting the pH value, sulfuric acid and zinc ion content of electroplating solution or conductive roller cleaning solution

Abstract

The application belongs to the technical field of analysis and detection, and discloses a method for continuously detecting pH value, sulfuric acid content and zinc ion content of electroplating liquid or conductive roller cleaning liquid. The method comprises the following steps: 1) selecting the "pH" block in "pH / mV" on the potential titrator, setting the instrument parameters, inserting the electrode into the to-be-detected liquid, and reading the pH value displayed by the potential titrator; 2) selecting the "mV" block in "pH / mV" on the potential titrator, selecting the dynamic pH titration mode, setting the instrument parameters, diluting the to-be-detected liquid after the pH value is detected, inserting the electrode into the diluted to-be-detected liquid, and adopting the sodium hydroxide standard solution titration, and ending the titration after two equivalent points appear; and 3) calculating the pH value, sulfuric acid content and zinc ion content of the to-be-detected liquid through a formula. The application can realize the continuous detection of the three indexes by adopting one instrument and one standard titration solution, is simple, fast and high in accuracy, and can effectively reduce the influence of chemical reagents on the health of workers.

Description

Technical Field

[0001] This invention belongs to the field of analytical testing technology, and specifically relates to a method for continuously detecting the pH value, sulfuric acid and zinc ion content of electroplating solution or conductive roller cleaning solution. Background Technology

[0002] Electroplating solution is the solution used in cold-rolled electroplating zinc units to deposit zinc coatings on metal surfaces using electrochemical methods. The pH value, sulfuric acid content, and zinc ion content of the electroplating solution directly affect the thickness and quality of the zinc coating on the electroplated surface. Conductive roller cleaning solution is a solution used to clean the surface of conductive rollers to prevent zinc from sticking to them. The pH value, sulfuric acid content, and zinc ion content also need to be monitored.

[0003] Generally, laboratories need to use three independent analytical methods to complete the detection of three indicators. pH value is usually measured using a pH meter; sulfuric acid content is detected using the acid-base reaction principle, either by manual titration or potentiometric titration; and zinc ion content is detected using the EDTA complexometric titration principle, also either by manual titration or potentiometric titration. Detecting these three indicators requires preparing two different standard titration solutions and various reagents for analysis, which is not only cumbersome but also inefficient. In particular, the detection of zinc ion content involves the use of ammonia and ammonia buffer solutions, which are highly irritating and can affect the occupational health of employees.

[0004] Therefore, developing more convenient and safer detection methods is of great significance to this field. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to address the shortcomings of the existing technology by providing a method for continuously detecting the pH value, sulfuric acid and zinc ion content of electroplating solution or conductive roller cleaning solution. This method uses an instrument and a standard titration solution to achieve continuous detection of the three indicators. It is simple, fast and accurate, and also effectively reduces the impact of chemical reagents on the health of employees.

[0006] To address the technical problems proposed in this invention, this invention provides a method for continuously detecting the pH value, sulfuric acid content, and zinc ion content of electroplating solutions or conductive roller cleaning solutions, comprising the following steps:

[0007] 1) On the potentiometric titrator, select the "pH" setting under "pH / mV" and set the instrument parameters; insert the electrode into the solution to be tested and read the pH value displayed on the potentiometric titrator;

[0008] 2) On the potentiometric titrator, select the "mV" setting under "pH / mV", select the dynamic pH titration mode, and set the instrument parameters; dilute the test solution after measuring the pH value, insert the electrode into the diluted test solution, and titrate with sodium hydroxide standard solution. End the titration after two equivalence points appear.

[0009] 3) Calculate the pH value, sulfuric acid content, and zinc ion content of the test solution using the following formulas:

[0010] pH = k × pH' + b

[0011]

[0012]

[0013] In the formula:

[0014] pH is the pH value of the test solution, and pH' is the pH value displayed by the potentiometric titrator;

[0015] k and b are correction coefficients, where k = 1.187 and b = -0.122;

[0016] c(H2SO4) represents the sulfuric acid content of the test solution, and c(Zn) represents the sulfuric acid content of the test solution. 2+ The value represents the zinc ion content of the test solution, expressed in g / L.

[0017] c(NaOH) is the concentration of the sodium hydroxide standard solution, in mol / L;

[0018] V0 is the volume of the test solution taken in step 2), and V1 and V2 are the volumes of sodium hydroxide standard solution consumed when the first and second equivalence points are reached, respectively, in mL.

[0019] α is a correction coefficient, when c'(Zn) 2+ When α < 60, α is 1; when 60 ≤ c'(Zn) 2+ When α ≤ 90, α is 0.975~0.989; when 90 <c’(Zn 2+ When α ≤ 125, α is 0.98~0.995.

[0020] In the above scheme, the test liquid is an electroplating solution or a conductive roller cleaning solution.

[0021] In the above scheme, the electrode of the potentiometric titrator is a pH composite electrode.

[0022] In the above scheme, the potentiometric titrator needs to use the two-point calibration method to calibrate the electrode before measuring the pH value. The calibration frequency is once a day. The instrument parameters are set as follows during calibration: signal drift 2-4 mV / min, minimum waiting time 10-15s, and maximum waiting time 80-100s.

[0023] In the above scheme, in step 1), the instrument parameters are set as follows: signal drift 2-4 mV / min, minimum waiting time 10-15 s, and maximum waiting time 80-100 s.

[0024] In the above scheme, in step 2), the instrument parameters are set as follows: signal drift 40-50mV / min, maximum waiting time 20-30s, measurement point density 1-2; there are 2 stop equivalence points, the equivalence point identification standard is set to ERC≥10, and the equivalence point identification mode is all.

[0025] In the above scheme, in step 2), the dilution ratio is 30 to 50 times when the test liquid is an electroplating solution, and 3 to 5 times when the test liquid is a conductive roller cleaning solution.

[0026] In the above scheme, the concentration of the sodium hydroxide standard solution is 0.1-0.2 mol / L.

[0027] The technical concept of this invention is as follows:

[0028] 1) The pH composite electrode in the potentiometric titrator lacks the function of measuring temperature and performing temperature coefficient compensation correction. The pH value detected by it deviates significantly from the actual pH value of the sample. Therefore, it is mainly used to detect the acid or alkali concentration of the sample. The pH value detected by it is only used to monitor the pH value change of the acid-base reaction process or to monitor the endpoint by pH value. It is not used for pH value detection of production samples. In order to realize the detection of pH value of production samples by potentiometric titrator, this invention corrects the pH value detected by potentiometric titrator to improve the accuracy of pH measurement.

[0029] 2) Potentiometric titration for sulfuric acid content determination generally uses acid-base reaction titration, while zinc ion content determination generally uses EDTA complexometric titration. This requires two different standard titration solutions, which is cumbersome. To reduce the number of operations during the determination and improve the continuity of the determination, this invention uses sodium hydroxide standard solution to titrate sulfuric acid and zinc ions sequentially. However, there is always a slight deviation between the detection result of zinc ion content and the true content. Therefore, this invention introduces a correction factor to correct the detection result and improve the accuracy of zinc ion content detection.

[0030] 3) In the measurement process of potentiometric titrator, the control of instrument parameters is very important. The signal drift parameter is the criterion for finding the best measurement value during the test. If the setting is reasonable, the measurement will be fast and accurate. The minimum waiting time is the minimum reference value to ensure the stability of the signal drift parameter. If the setting is too small, the accurate measurement value cannot be guaranteed. If the setting is too large, the instrument will not be able to find the endpoint using this condition. The maximum waiting time is related to the signal drift. The measurement finds the value under the signal drift parameter set in the experiment. If the signal drift is unstable, the instrument will automatically take the value at the set maximum waiting time. Therefore, its setting is also critical. Therefore, this invention sets different instrument parameters for different indicators to maximize the accuracy of the results.

[0031] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0032] This invention establishes a continuous detection method for pH value, sulfuric acid, and zinc ion content in electroplating solutions and conductive rollers using a potentiometric titrator. Specifically, it enables accurate detection of pH value in electroplating solutions and conductive rollers using a potentiometric titrator, and continuous titration detection of sulfuric acid and zinc ion content using a single standard titration solution. By introducing correction coefficients or adjustment coefficients to correct or adjust the detection results, serious deviations between the measured results and actual results are avoided. Thus, continuous detection of these three indicators can be achieved using a single instrument and a single standard titration solution. This method is simple, rapid, and highly accurate, and also effectively reduces the impact of chemical reagents on employee health. Detailed Implementation

[0033] To better understand the present invention, the following embodiments further illustrate the content of the present invention, but the content of the present invention is not limited to the following embodiments.

[0034] In the following examples, the potentiometric titrator used is an Omnis model, and its electrode is a pH composite electrode.

[0035] In the following embodiments, before measuring the pH value, the potentiometric titrator uses a two-point calibration method to calibrate the pH composite electrode. The calibration parameters are set as follows: signal drift of 2.0 mV / min, minimum waiting time of 10 s, and maximum waiting time of 80 s. The specific steps are as follows: first, prepare two pH standard buffer solutions with pH values ​​of 4.01 and 7.00; clean the pH composite electrode and dry it; insert the pH composite electrode into the 4.01 standard buffer solution; select the pH calibration program to start running; the instrument automatically completes the calibration of the 4.01 standard buffer solution; remove the pH composite electrode as prompted by the instrument, clean it, dry it, and then insert the pH composite electrode into the 7.00 standard buffer solution. Continue running to complete the calibration of the 7.00 standard buffer solution, giving a calibration slope of 99.75%.

[0036] For pH multi-electrode verification, set the parameters as follows: signal drift 4.0 mV / min, minimum wait time 15 s, maximum wait time 100 s. Insert the pH multi-electrode into a 4.01 standard buffer solution, select the pH verification program to start running, and the instrument will automatically complete the measurement of the 4.01 standard buffer solution, displaying 4.00. Insert the pH multi-electrode into a 7.00 standard buffer solution, select the pH verification program to start running, and the instrument will automatically complete the measurement of the 7.00 standard buffer solution, displaying 7.01.

[0037] Example 1

[0038] The pH value, sulfuric acid content, and zinc ion content of a 20℃ electroplating solution are continuously measured, including the following steps:

[0039] 1) On the potentiometric titrator, select the "pH" setting under "pH / mV" and set the instrument parameters as follows: signal drift 2.0mV / min, minimum waiting time 10s, maximum waiting time 80s; insert the electrode into 30mL of electroplating solution, and the potentiometric titrator displays pH' = 1.425;

[0040] 2) On the potentiometric titrator, select the "mV" setting under "pH / mV", select the dynamic pH titration mode, and set the instrument parameters as follows: signal drift 40mV / min, maximum waiting time 20s, measurement point density 1, stop equivalence points 2, equivalence point identification standard set to ERC≥10, and equivalence point identification mode set to all. Take 1.00mL of the test solution after pH measurement and dilute it 30 times. Insert the electrode into the diluted test solution and titrate with 0.1mol / L sodium hydroxide standard solution (calibrated to 0.1006mol / L). Stop the titration after two equivalence points appear, and record V1 = 1.20mL and V2 = 27.83mL.

[0041] 3) Calculate the pH value, sulfuric acid content, and zinc ion content of the test solution using the following formulas:

[0042] pH=k×pH'+b=1.187×1.425-0.122=1.57

[0043]

[0044]

[0045] Taking α as 0.983, we calculate c(Zn) 2+ )=α×c'(Zn 2+ = 0.983 × 87.60 = 86.11 g / L

[0046] Example 2

[0047] The pH value, sulfuric acid content, and zinc ion content of a 23℃ conductive roller cleaning solution were continuously measured. The steps are as follows:

[0048] 1) On the potentiometric titrator, select the "pH" setting under "pH / mV" and set the instrument parameters as follows: signal drift 3.0mV / min, minimum waiting time 12s, maximum waiting time 100s; insert the electrode into 30mL of conductive roller cleaning solution, and the potentiometric titrator displays pH' = 1.198;

[0049] 2) On the potentiometric titrator, select the "mV" setting under "pH / mV", select the dynamic pH titration mode, and set the instrument parameters as follows: signal drift 45mV / min, maximum waiting time 30s, measurement point density 2, stop equivalence points 2, equivalence point identification standard set to ERC≥10, and equivalence point identification mode set to all. Take 10.00mL of the test solution after pH measurement and dilute it 5 times. Insert the electrode into the diluted test solution and titrate with 0.1mol / L sodium hydroxide standard solution (calibrated to 0.1006mol / L). Stop the titration after two equivalence points appear, and record V1 = 9.93mL and V2 = 20.42mL.

[0050] 3) Calculate the pH value, sulfuric acid content, and zinc ion content of the test solution using the following formulas:

[0051] pH=k×pH'+b=1.187×1.198-0.122=1.30

[0052]

[0053]

[0054] Taking α as 1, we can calculate c(Zn) 2+ )=α×c'(Zn 2+ = 3.45 g / L

[0055] Example 3

[0056] The pH value, sulfuric acid content, and zinc ion content of a 26℃ electroplating solution are continuously measured, including the following steps:

[0057] 1) On the potentiometric titrator, select the "pH" setting under "pH / mV" and set the instrument parameters as follows: signal drift 4.0mV / min, minimum waiting time 15s, maximum waiting time 90s; insert the electrode into 30mL of electroplating solution, and the potentiometric titrator displays pH' = 1.552;

[0058] 2) On the potentiometric titrator, select the "mV" setting under "pH / mV", choose the dynamic pH titration mode, and set the instrument parameters as follows: signal drift 50mV / min, maximum waiting time 30s, measurement point density 2, stop equivalence points 2, equivalence point identification standard set to ERC≥10, and equivalence point identification mode set to all. Take 2.00mL of the test solution after pH measurement and dilute it 40 times. Insert the electrode into the diluted test solution and titrate with 0.2mol / L sodium hydroxide standard solution (calibrated to 0.1995mol / L). Stop the titration after two equivalence points appear and record V1 = 1.20mL and V2 = 36.70mL.

[0059] 3) Calculate the pH value, sulfuric acid content, and zinc ion content of the test solution using the following formulas:

[0060] pH=k×pH'+b=1.187×1.552-0.122=1.72

[0061]

[0062]

[0063] Taking α as 0.990, we can calculate c(Zn) 2+ )=α×c'(Zn 2+ = 114.63 g / L

[0064] Precision test

[0065] To verify the precision of the method of the present invention, the electroplating solution in Example 1 was tested 5 times. The results are shown in Table 1. As can be seen from the data in the table, the difference between the 5 test results is very small, indicating that the precision of the method of the present invention is good.

[0066] Table 1 Precision test results

[0067]

[0068] Accuracy test

[0069] To verify the accuracy of the method of the present invention, the pH value, sulfuric acid content, and zinc ion content of the test solutions in each embodiment were sequentially detected using conventional methods. The pH value was measured using a Mettler S210 pH meter; the sulfuric acid content was determined using the GB / T9736-2008 method; and the zinc ion content was determined using EDTA complexometric titration. The results are shown in Table 2. As can be seen from the data in the table, the detection results of the method of the present invention are in good agreement with those of conventional methods, and the method of the present invention can be used for quantitative analysis.

[0070] Table 2 Accuracy Test Results

[0071]

[0072] The above embodiments are merely examples for clear illustration and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations, and any obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A method for continuously detecting the pH value, sulfuric acid content, and zinc ion content of electroplating solution or conductive roller cleaning solution, characterized in that, Includes the following steps: 1) On the potentiometric titrator, select the "pH" setting under "pH / mV" and set the instrument parameters as follows: signal drift 2~4mV / min, minimum waiting time 10~15s, maximum waiting time 80~100s; insert the electrode into the test solution and read the pH value displayed on the potentiometric titrator. 2) On the potentiometric titrator, select the "mV" setting under "pH / mV", choose the dynamic pH titration mode, and set the instrument parameters as follows: signal drift 40~50 mV / min, maximum waiting time 20~30s, measurement point density 1~2; stop equivalence points 2, equivalence point identification standard set ERC≥10, equivalence point identification mode set to all; take the test solution after pH measurement and dilute it, insert the electrode into the diluted test solution, and titrate with sodium hydroxide standard solution. Stop the titration after two equivalence points appear. 3) Calculate the pH value, sulfuric acid content, and zinc ion content of the test solution using the following formulas: In the formula: pH is the pH value of the test solution, and pH' is the pH value displayed by the potentiometric titrator; k and b are correction coefficients, where k = 1.187 and b = -0.122; c(H2SO4) represents the sulfuric acid content of the test solution, and c(Zn) represents the sulfuric acid content of the test solution. 2+ The value represents the zinc ion content of the test solution, expressed in g / L. c(NaOH) is the concentration of the sodium hydroxide standard solution, in mol / L; V0 is the volume of the test solution taken in step 2), and V1 and V2 are the volumes of sodium hydroxide standard solution consumed when the first and second equivalence points are reached, respectively, in mL. α is a correction coefficient, when c'(Zn) 2+ When α < 60, α is 1; when 60 ≤ c'(Zn) 2+ When α ≤ 90, α is 0.975~0.989; when 90 <c’(Zn 2+ When α ≤ 125, α is 0.98~0.

995.

2. The method for continuously detecting the pH value, sulfuric acid content, and zinc ion content of electroplating solution or conductive roller cleaning solution according to claim 1, characterized in that, Before measuring pH, the potentiometric titrator needs to use the two-point calibration method to calibrate the electrodes. The calibration frequency is once a day. During calibration, the instrument parameters are set as follows: signal drift 2~4mV / min, minimum waiting time 10~15s, and maximum waiting time 80~100s.

3. The method for continuously detecting the pH value, sulfuric acid content, and zinc ion content of electroplating solution or conductive roller cleaning solution according to claim 1, characterized in that, In step 2), the dilution ratio is 30 to 50 times when the test solution is an electroplating solution, and 3 to 5 times when the test solution is a conductive roller cleaning solution.

4. The method for continuously detecting the pH value, sulfuric acid content, and zinc ion content of electroplating solution or conductive roller cleaning solution according to claim 1, characterized in that, The electrode of the potentiometric titrator is a pH composite electrode.

5. The method for continuously detecting the pH value, sulfuric acid content, and zinc ion content of electroplating solution or conductive roller cleaning solution according to claim 1, characterized in that, The concentration of the sodium hydroxide standard solution is 0.1~0.2 mol / L.

Images