Rapid colorimetric analysis method for content of thiourea in copper electrolyte

Abstract

The invention relates to the technical field of copper electrolysis, in particular to a rapid colorimetric analysis method for the content of thiourea in copper electrolyte, which comprises the following steps: preparation before detection: preparing a reagent and preparing a sample; preparing a standard color card: taking different volumes of thiourea standard solutions, respectively adding reagents for reaction, inserting starch potassium iodide test paper for color development, and making the standard color card according to different color development conditions; treating a sample: taking a certain sample, diluting to a detection range, and adding a reagent for reaction; and colorimetric analysis of the thiourea content in the sample: inserting the starch potassium iodide test paper into a solution obtained after the reaction of the iodine solution and the thiourea, carrying out colorimetric analysis with a standard color card after color development so as to obtain the content range of the thiourea in the sample to be detected, and analyzing the gray value after photographing the color development test paper so as to further determine the accurate content of the thiourea in the sample. According to the method, the content of the thiourea in the copper electrolyte can be quickly, efficiently, simply and conveniently obtained on site without an instrument, and the content of the thiourea in the copper electrolyte can be judged in time.

Description

Technical Field

[0001] The invention relates to the technical field of copper electrolysis, in particular to a rapid colorimetric analysis method for thiourea content in a copper electrolyte. Background Art

[0002] Adding an appropriate amount of additives during copper electrolytic deposition can effectively avoid various crystal defects, improve the crystal density of copper and the product quality of cathode copper. Common additives in the copper electrolysis process include industrial gelatin, thiourea, Avitron, chloride ions, etc. The appropriate amount and ratio of additives can also prevent the roughness of the cathode surface from causing the inclusion of electrolyte, anode mud and suspended particles in the cathode copper, thereby avoiding problems such as reduced conductivity and ductility of copper products, making the grains refined and the deposits bright.

[0003] Thiourea is a white crystal that can refine the grains and depolarize the cathode during copper electrolytic refining. When thiourea is used together with gelatin, a cathode copper with a smoother surface and a denser structure can be obtained than when gelatin is used alone. However, when the thiourea content is high, more copper sulfide is produced on the cathode copper plate, and the copper sulfide will become the growth center of the nodules, thus making the surface of the deposit rough. In addition, thiourea can be 2+ Oxidation forms disulfide and adsorbs on the cathode copper surface. It can also react with Cu 2+ Cu + Complexation, Cu 2+ The complex further reacts with SO4 2- Combined to form [Cu(NH4CS)4]2SO4. The copper complex film not only has an adsorption effect on the cathode surface, but also a desorption effect. The desorption effect causes the thiourea adsorbed in the complex on the cathode surface to not completely enter the lattice, and most of it is desorbed and re-formed into a complex, causing the accumulation of thiourea in the electrolyte. When the thiourea in the electrolyte accumulates to a certain concentration, it affects the electrolysis efficiency and reduces the quality of the cathode copper product. Therefore, it is very necessary to judge the level of thiourea in the copper electrolyte in a timely manner.

[0004] The existing detection methods for thiourea in electrolyte mainly include:

[0005] (1) Ultraviolet spectrophotometry. For example, on May 30, 1998, Duan Mengjiao, Huang Jian, and Yong Fu published a paper titled “Determination of Thiourea in Copper Electrolyte by Extraction-Spectrophotometry” in Electroplating and Environmental Protection. The study used ethyl acetate to extract excess iodine in an acetic acid-sodium acetate buffer solution (pH = 4.2) system, and measured the absorbance at 450 nm with ethyl acetate as a blank. The linear regression equation y = 0.4822-5.185×10 -3x, regression coefficient r = 0.9999. This method can accurately measure thiourea in the electrolyte, but the method has a narrow linear range (between 0-4 mg / L), requires extraction and separation steps, consumes organic reagents, and takes a long time to detect, and cannot achieve rapid detection of thiourea content in copper electrolyte. For example, Chinese patent application No. 202210790951.8, with an application publication date of October 4, 2022, discloses a method for detecting the content of thiourea in a copper electrolyte. The patent method includes step 1): first prepare a thiourea standard solution, then measure the absorbance of different volumes of thiourea standard solution at 235nm, and draw a standard curve based on the relationship between thiourea concentration and absorbance; step 2): add perchloric acid and hydrogen peroxide to the electrolyte and digest it on a hot plate until dry, add water to boil after the smoke is exhausted and cooled, then use ethanol solution as mobile phase and washing liquid, and finally use LD-150 polishing mixed bed resin to adsorb the electrolyte and measure the absorbance; step 3): calculate the thiourea concentration by checking the standard curve based on the absorbance value. Although this method can directly use an ultraviolet spectrophotometer to detect the concentration of thiourea in the treated electrolyte, the electrolyte treatment process is complicated, requiring digestion, rinsing, adsorption, etc., and the steps are cumbersome, which is not suitable for rapid detection on site.

[0006] (2) Electrochemical detection method. For example, Chinese patent application No. 202011577618.6, with a publication date of May 7, 2021, discloses a method for rapidly detecting thiourea content in a copper electrolyte. The patent method comprises the following steps: step 1): detecting Cu in an unknown copper electrolyte; 2+ concentration and sulfuric acid concentration; Step 2): take the Cu 2+ The copper electrolyte with the same sulfuric acid concentration but different thiourea concentration is used to detect Cu 2+ The AC impedance of the reduction reaction is obtained by fitting the charge transfer resistance R ct Step 3): Establish the charge transfer resistance R under the acid and copper concentration ct and the linear relationship between thiourea concentration; Step 4): Take a copper electrolyte with unknown thiourea concentration, obtain the charge transfer resistance and calculate the thiourea concentration according to the linear relationship. This method can determine the thiourea content in the copper electrolyte, but an instrument is required to measure the charge transfer resistance, and when sulfuric acid and Cu 2+ When the electrolysis conditions change, the linear relationship needs to be recalculated.

[0007] Colorimetric analysis can analyze the relative content of specific substances in unknown samples, and has the advantages of simple operation, fast and convenient. Colorimetric analysis can quickly, easily and on-site detect the content range and changes of thiourea in copper electrolyte. The introduction of image processing software can also avoid errors caused by low resolution of the human eye and obtain the accurate content of thiourea in the sample, which is particularly suitable for rapid judgment of thiourea content at the electrolytic copper production site. Summary of the invention

[0008] In order to solve the problems that the content of thiourea as an additive in the copper electrolysis process is difficult to detect quickly and timely in the prior art, as well as the hysteresis and empirical problems existing in manual adjustment, the present invention proposes a rapid colorimetric analysis method for the thiourea content in a copper electrolyte. Based on the principle of color development by the reaction of starch and iodine, a colorimetric method is used to achieve instrument-free on-site instant detection, and the content range of thiourea in the copper electrolyte is obtained by rapid analysis.

[0009] In order to achieve the above purpose, the technical solutions provided are as follows:

[0010] A rapid colorimetric analysis method for thiourea content in a copper electrolyte, characterized in that it comprises the following steps:

[0011] Step 1: Preparation of reagents, specifically including the following:

[0012] Prepare a thiourea standard solution with a concentration of 1000 mg / L;

[0013] Prepare iodine solution with iodine concentration of 250 mg / L and potassium iodide concentration of 500 mg / L;

[0014] Prepare acetic acid-sodium acetate buffer with a pH of 4.2;

[0015] Step 2: Preparation of standard color cards, specifically including the following steps:

[0016] Step (1), taking different volumes of thiourea standard solution, adding water to 1 mL, obtaining solutions with different thiourea contents, adding buffer to adjust the pH, and then adding iodine solution to react with thiourea;

[0017] Step (2), immersing starch potassium iodide test paper in reaction solutions with different residual iodine contents for 3 seconds to obtain color test paper with different color development conditions, photographing the color test paper, and arranging them to obtain a standard color card;

[0018] Step (3), using image processing software to perform grayscale analysis on the standard color card, obtain the grayscale values ​​corresponding to the standard color card at different thiourea contents, draw a standard curve, and obtain a linear relationship;

[0019] Step 3, sample processing, the samples include but are not limited to copper sulfate simulated electrolyte containing thiourea, industrial copper electrolyte containing thiourea and additive solution containing thiourea in industrial on-site additive preparation tank, specifically comprising the following steps: taking different samples, adding water to dilute to the detection range, taking 1 mL of the diluted sample solution, adding buffer to adjust the pH, and then adding iodine solution to react with thiourea;

[0020] Step 4, colorimetric analysis of the thiourea content in the sample, specifically comprising the following steps: taking a starch potassium iodide test paper and inserting it into the solution after the reaction of iodine and thiourea in the sample for 3 seconds to develop color to obtain a color test paper, and performing a colorimetric analysis on the color test paper and the standard color card obtained in step (2) of step 2, and visually comparing the color to quickly obtain the content range of thiourea in the sample solution; taking a photo of the color test paper and processing it with image processing software, performing grayscale analysis, and further determining the accurate content of thiourea.

[0021] Preferably, in step one, the preparation steps of the thiourea standard solution are as follows: dry thiourea at 105° C. for 2 h, accurately weigh 1.000 g of thiourea into a 250 mL beaker, add deionized water to dissolve it, transfer it into a 1000 mL volumetric flask, add water to the scale line, and obtain a thiourea standard solution with a concentration of 1000 mg / L.

[0022] Preferably, in step one, the preparation steps of the iodine solution are as follows: accurately weigh 0.500 g of potassium iodide and 0.250 g of iodine into a 500 mL beaker, add deionized water and vigorously stir at 40° C. for 2 h, transfer to a 1000 mL brown volumetric flask after complete dissolution, and store in a dark place to obtain an iodine solution with an iodine concentration of 250 mg / L and a potassium iodide concentration of 500 mg / L.

[0023] Preferably, in step one, the preparation steps of the buffer solution are as follows: weigh 33.0 g of anhydrous sodium acetate and dissolve it in 200 mL of deionized water, transfer it into a 1000 mL volumetric flask, then add 50.0 mL of glacial acetic acid, add water to the scale line, shake well, and obtain an acetic acid-sodium acetate buffer solution with a pH of ≈ 4.2.

[0024] Preferably, in step (1) of step 2, 0.0, 20.0, 40.0, 60.0, 80.0 μL of thiourea standard solution are taken in a 25 mL colorimetric tube, 1000.0, 980.0, 960.0, 940.0, 920.0 μL of deionized water are added to obtain thiourea solutions with thiourea concentrations of 0.0, 20.0, 40.0, 60.0, 80.0 mg / L, respectively; 10.0 mL of acetic acid-sodium acetate buffer solution is added, mixed, and then 5.0 mL of iodine solution is added to react for 5 minutes.

[0025] Preferably, in step (2) of step 2, the starch potassium iodide test paper is immersed in sample solutions with different residual iodine contents for 3 seconds to obtain color test papers with different color development conditions. The color test paper is photographed, and the RGB value of the photo is obtained using ImageJ image processing software, and a standard color card is prepared according to the RGB value.

[0026] Preferably, in step (3) of step 2, the color test paper is photographed and processed into 8-bit format using ImageJ software, and the background grayscale is unified to 195. A rectangular tool is used to select a 5×12 mm area 4 mm from the top of the color test paper and 2 mm from the left and right sides to measure the average grayscale value of the test paper. A standard curve is drawn with the grayscale value as the ordinate and the thiourea content as the abscissa, and a linear relationship is calculated.

[0027] Preferably, in step three, the sample solution is diluted 4 to 10 times according to the approximate content of thiourea in the sample, 1.0 mL of the diluted sample solution is taken, 10.0 mL of buffer is added to adjust the pH, and then 5.0 mL of iodine solution is added to react with the thiourea in the sample for 5 minutes.

[0028] Preferably, in step 4, starch potassium iodide test paper is taken, and the sample solution after the reaction of iodine and thiourea in the sample is inserted for 3 seconds to obtain a color test paper strip, and the color test paper is compared with the standard color card obtained in step (2) of step 2, and the content range of thiourea in the sample solution is obtained by visual colorimetry;

[0029] Preferably, in step 4, the colorimetric test paper is photographed and processed into 8-bit format using ImageJ image processing software, and the background grayscale is unified to 195. A rectangular tool is used to select a 5×12 mm area 4 mm from the top of the colorimetric test paper and 2 mm from the left and right sides to measure the average grayscale value of the test paper. The grayscale value is substituted into the linear relationship obtained in step (3) of step 2 to calculate the accurate content of thiourea in the sample solution.

[0030] The beneficial effects of the present invention are as follows: the present invention is based on the principle that thiourea can be oxidized by iodine under acidic conditions. The amount of iodine remaining after the copper electrolyte with different thiourea contents reacts with the iodine solution is different. Test strips with different color development conditions are prepared according to the different color development conditions of the reaction of the remaining iodine and the starch potassium iodide test paper. The standard color card under different thiourea contents and its corresponding standard gray value are obtained by using ImageJ image processing software, and the linear relationship between the thiourea content and the gray value is obtained by linear regression. The sample is simply processed, and the starch potassium iodide test paper is inserted into the sample solution for color development. By comparing the test strip with the standard color card, the visual colorimetric analysis can quickly, efficiently, simply and on-sitely judge the content range of thiourea in the copper electrolyte, and realize the instant detection on-site without instrument. In addition, by taking a photo of the color development test paper for gray analysis, the gray value obtained is brought into the linear relationship to calculate the accurate content of thiourea in the sample solution, and the detection range of the method is 0-80.0mg / L. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 This is a color development photograph of starch potassium iodide test paper used to make a standard color card of the present invention;

[0032] Figure 2 The standard color card used for thiourea content detection of the present invention;

[0033] Figure 3 This is a schematic diagram of the gray value measurement area of ​​the color test paper used for thiourea content detection of the present invention;

[0034] Figure 4 is the standard gray value corresponding to the standard color card used for thiourea content detection in the present invention;

[0035] Figure 5 This is a colorimetric photograph of a test paper for detecting the thiourea content in a copper sulfate simulated electrolyte according to the present invention;

[0036] Figure 6 This is a grayscale data diagram corresponding to the color test paper for detecting thiourea content in different electrolytes according to the present invention;

[0037] Figure 7 This is a color development photograph of the spiked test paper for detecting the thiourea content in the copper sulfate simulated electrolyte of the present invention;

[0038] Figure 8 This is a colorimetric photograph of a test paper for detecting the thiourea content in a solution containing a thiourea additive at an industrial site according to the present invention;

[0039] Fig. 9 This is a colorimetric photograph of the test paper for detecting the thiourea content in industrial electrolytes according to the present invention. DETAILED DESCRIPTION

[0040] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0041] Example 1

[0042] A rapid colorimetric analysis method for thiourea content in a copper electrolyte comprises the following steps:

[0043] (1) Reagent preparation

[0044] Preparation of thiourea standard solution: Dry thiourea at 105℃ for 2h, accurately weigh 1.000g of thiourea into a 250mL beaker, add deionized water to dissolve, transfer to a 1000mL volumetric flask, and add water to the scale line;

[0045] Preparation of iodine solution: Accurately weigh 0.500g of potassium iodide into a 500mL beaker, add deionized water to dissolve, accurately weigh 0.250g of iodine, add to the beaker, vigorously stir at 40℃ for 2h, transfer to a 1000mL brown volumetric flask after complete dissolution, and store away from light;

[0046] Preparation of buffer solution: weigh 33.0 g of anhydrous sodium acetate and dissolve it in 200 mL of water, transfer it to a 1000 mL volumetric flask, add 50.0 mL of glacial acetic acid, add water to the scale, shake well, and obtain acetic acid-sodium acetate buffer solution, pH ≈ 4.2;

[0047] Preparation of copper sulfate simulated electrolyte: weigh 7.8g of copper sulfate pentahydrate into a 50mL beaker, add deionized water to dissolve, then add 5.4mL of concentrated sulfuric acid (98%) and transfer to a 50mL volumetric flask, add 5.0mL of thiourea standard solution to the volumetric flask, add water to make up to volume to obtain Cu 2+ The sample solution has a concentration of 40g / L, a sulfuric acid concentration of 190g / L, and a thiourea concentration of 100mg / L.

[0048] (2) Preparation of standard color cards

[0049] Use a pipette to accurately transfer 0.0, 20.0, 40.0, 60.0, and 80.0 μL of thiourea standard solution into a 25 mL colorimetric tube, and then add 1000.0, 980.0, 960.0, 940.0, and 920.0 μL of deionized water to obtain thiourea solutions with thiourea concentrations of 0.0, 20.0, 40.0, 60.0, and 80.0 mg / L, respectively. Add 10.0 mL of buffer, mix well, and then add 5.0 mL of iodine solution to react with thiourea for 5 minutes. Insert starch potassium iodide test paper into the reaction solution with different residual iodine content for 3 seconds to develop color, and obtain the following: Figure 1 The original color test paper of the standard color card shown in the figure gradually changes from purple to colorless as the concentration of thiourea increases. The color test paper is photographed, and the RGB value of the photo is obtained using ImageJ image processing software. The following is prepared based on the RGB value: Figure 2 Then use ImageJ software to convert the standard color card into 8-bit format, unify the background grayscale to 195, and use the rectangle tool to select Figure 3 The grayscale value measurement area shown in the figure is 4mm from the top of the color test paper and 2mm from the left and right sides. The size is 5×12mm. The measurement results are as follows Figure 4 The standard gray value data corresponding to the standard color card under different thiourea contents are shown. The darker the color of the color card, the smaller the gray value. As the thiourea content increases, the gray value increases in a step-by-step manner. The standard curve is drawn with the gray value as the ordinate and the thiourea content as the abscissa, and the linear relationship y=0.704x+135.94 is obtained. 2 =0.9947.

[0050] (3) Detection of thiourea content in copper sulfate simulated electrolyte samples

[0051] Dilute the copper sulfate simulated electrolyte sample 5 times to within the detection range, take 1.0 mL of the diluted sample solution, add 10.0 mL of buffer to adjust the pH, and then add 5.0 mL of iodine solution to react with the thiourea in the copper sulfate simulated electrolyte sample for 5 minutes. Insert the starch potassium iodide test paper into the solution after the iodine reacts with the thiourea in the sample for 3 seconds to develop color, and perform parallel detection 3 times to obtain the following results: Figure 5 The color test paper shown is used for visual colorimetric analysis with the standard color card obtained in step (2), and the content of thiourea in the sample solution is in the range of 10-20 mg / L, which is close to the theoretical value.

[0052] The color test strip was photographed and processed into 8-bit format using ImageJ software. The background grayscale was unified to 195. A 5×12 mm area with a distance of 4 mm from the top of the color test strip and 2 mm from the left and right sides was selected using the rectangular tool to measure the average grayscale value of the test strip. Figure 6 The grayscale values ​​of the three test strips shown in "Simulated Electrolyte" in Figure 1. The average grayscale value of the parallel determination is 149.2. Substituting it into the linear relationship formula, the thiourea content in the sample solution is calculated to be close to 18.8 mg / L, which is close to the theoretical value of 20 mg / L.

[0053] (4) Spike-addition test

[0054] After diluting the prepared electrolyte 5 times, take 3 portions and add 0, 25, and 50 mg / L thiourea respectively, and use the color card colorimetric analysis to detect the thiourea concentration. Figure 7 The colorimetric analysis results are shown in Table 1. From the color development and colorimetric detection results, it can be seen that when the electrolyte contains different concentrations of thiourea, the color card colorimetry can achieve semi-quantitative rapid detection.

[0055] Table 1 Results of spiked experiments

[0056]

[0057] Example 2

[0058] (1) Reagent preparation

[0059] Iodine solution: use the iodine solution prepared in step (1) of Example 1;

[0060] Buffer: Use the buffer prepared in step (1) of Example 1;

[0061] Additive solution containing thiourea in industrial site additive preparation tank: The sample was taken from the industrial site copper electrolyte additive preparation tank, containing additives such as thiourea, gelatin, and Avitron, with a theoretical thiourea content of 9500 mg / L.

[0062] (2) Preparation of standard color cards

[0063] The standard color card prepared in step (2) of Example 1 was used.

[0064] (3) Detection of thiourea content in thiourea-containing additive solution

[0065] Take the thiourea solution in the additive preparation tank and dilute it 200 times. Take 1.0 mL of the diluted sample solution, add 10.0 mL of buffer to adjust the pH, and then add 5.0 mL of iodine solution to react with the thiourea in the additive solution for 5 minutes. Insert the starch potassium iodide test paper into the solution after the iodine and thiourea in the additive react for 3 seconds to develop color. Perform the test three times in parallel to obtain the color test paper as shown in the figure. Figure 8 The color test paper was compared with the standard color card in step (2), and the thiourea content range was 40-60 mg / L by visual colorimetry.

[0066] After taking a photo of the color test strip, use ImageJ software to process it into 8-bit format, and unify the background grayscale to 195. Use the rectangular tool to select a 5×12mm area 4mm from the top of the color test strip and 2mm from the left and right sides to measure the average grayscale value of the test strip. The grayscale values ​​of the three test strips are as follows: Figure 6 As shown in the "Additive solution in the preparation tank", the average grayscale value of the parallel measurements is 170.4. Substituting it into the linear relationship equation, the thiourea content in the sample solution is calculated to be close to 48.9 mg / L. The test result is close to the theoretical concentration of thiourea in the additive solution containing thiourea at the industrial site (47.5 mg / L).

[0067] Example 3

[0068] (1) Reagent preparation

[0069] Iodine solution: use the iodine solution prepared in step (1) of Example 1;

[0070] Buffer: Use the buffer prepared in step (1) of Example 1;

[0071] Industrial electrolyte containing thiourea: The industrial electrolyte was sampled from a copper electrolytic cell of a certain enterprise. After 200 days of continuous production, the thiourea content was unknown and there was an accumulation phenomenon.

[0072] (2) Preparation of standard color cards

[0073] The standard color card prepared in step (2) of Example 1 was used.

[0074] (3) Detection of thiourea content in industrial electrolyte

[0075] Take industrial electrolyte and dilute it 10 times. Take 1.0mL of the diluted solution, add 10.0mL of buffer to adjust the pH, and then add 5.0mL of iodine solution to react with the industrial electrolyte for 5 minutes. Insert starch potassium iodide test paper into the solution after the reaction of iodine and thiourea in the industrial electrolyte for 3 seconds to develop color. The color development result is as follows: Fig. 9 The color test paper was visually compared with the standard color card in step (2), and the test was performed in parallel for 3 times, and the content of thiourea in the industrial electrolyte was found to be in the range of 20-40 mg / L.

[0076] After taking a photo of the color test strip, use ImageJ software to process it into 8-bit format, and unify the background grayscale to 195. Use the rectangular tool to select a 5×12mm area 4mm from the top of the color test strip and 2mm from the left and right sides to measure the average grayscale value of the test strip. The grayscale values ​​of the three test strips are as follows: Figure 6 As shown in "Industrial Electrolyte", the average grayscale value of the parallel measurements is 161.6. Substituting it into the linear relationship equation, the thiourea content in the sample solution is calculated to be close to 36.5 mg / L.

[0077] The method of the present invention has many advantages over other methods for detecting the thiourea content in the electrolyte, such as a simple detection method, a fast color development speed, a short detection time, and the detection of the thiourea content can be completed within 15 minutes, realizing instrument-free on-site instant detection. 2+ Does not affect the color development of the test paper.

[0078] It will be apparent to those skilled in the art that the invention is not limited to the details of the exemplary embodiments described above and that the invention can be implemented in other specific forms without departing from the spirit or essential features of the invention. Therefore, the embodiments should be considered exemplary and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is intended that all variations falling within the meaning and scope of the equivalent elements of the claims be included in the invention. Any reference numeral in a claim should not be considered as limiting the claim to which it relates.

Claims

1. A rapid colorimetric analysis method for thiourea content in a copper electrolyte, characterized in that: The steps include: Step 1: Preparation of reagents, specifically including the following: Prepare a thiourea standard solution with a concentration of 1000 mg / L; Prepare iodine solution with an iodine concentration of 250 mg / L and a potassium iodide concentration of 500 mg / L; Prepare acetic acid-sodium acetate buffer with a pH of 4.2; Step 2: Preparation of standard color cards, specifically including the following steps: Step (1), taking different volumes of thiourea standard solution, adding water to 1 mL, obtaining solutions with different thiourea contents, adding buffer to adjust the pH, and then adding iodine solution to react with thiourea; Step (2), immersing starch potassium iodide test paper in reaction solutions with different residual iodine contents for 3 seconds to obtain color test paper with different color development conditions, photographing the color test paper, and arranging them to obtain a standard color card; Step (3), using image processing software to perform grayscale analysis on the standard color card, obtain the grayscale values ​​corresponding to the standard color card at different thiourea contents, draw a standard curve, and obtain a linear relationship; Step 3, sample processing, the samples include but are not limited to copper sulfate simulated electrolyte containing thiourea, industrial copper electrolyte containing thiourea and additive solution containing thiourea in industrial on-site additive preparation tank, specifically comprising the following steps: taking different samples, adding water to dilute to the detection range, taking 1 mL of the diluted sample solution, adding buffer to adjust the pH, and then adding iodine solution to react with thiourea; Step 4, colorimetric analysis of the thiourea content in the sample, specifically comprising the following steps: taking a starch potassium iodide test paper and inserting it into the solution after the reaction of iodine and thiourea in the sample for 3 seconds to develop color to obtain a color test paper, and performing a colorimetric analysis on the color test paper and the standard color card obtained in step (2) of step 2, and visually comparing the color to quickly obtain the content range of thiourea in the sample solution; taking a photo of the color test paper and processing it with image processing software, performing grayscale analysis, and further determining the accurate content of thiourea.

2. The rapid colorimetric analysis method for thiourea content in a copper electrolyte according to claim 1, characterized in that: In step 1, the preparation steps of the thiourea standard solution are as follows: dry thiourea at 105° C. for 2 h, accurately weigh 1.000 g of thiourea into a 250 mL beaker, add deionized water to dissolve it, transfer it into a 1000 mL volumetric flask, add water to the scale line, and obtain a thiourea standard solution with a concentration of 1000 mg / L.

3. The rapid colorimetric analysis method for thiourea content in a copper electrolyte according to claim 1, characterized in that: In step 1, the preparation steps of the iodine solution are as follows: accurately weigh 0.500 g of potassium iodide and 0.250 g of iodine into a 500 mL beaker, add deionized water and stir vigorously at 40°C for 2 hours, transfer to a 1000 mL brown volumetric flask after complete dissolution, and store away from light to obtain an iodine solution with an iodine concentration of 250 mg / L and a potassium iodide concentration of 500 mg / L.

4. The rapid colorimetric analysis method for thiourea content in a copper electrolyte according to claim 1, characterized in that: In step 1, the preparation steps of the buffer solution are as follows: weigh 33.0 g of anhydrous sodium acetate and dissolve it in 200 mL of deionized water, transfer it into a 1000 mL volumetric flask, then add 50.0 mL of glacial acetic acid, add water to the scale line, shake well, and obtain an acetic acid-sodium acetate buffer solution with a pH of ≈ 4.

2.

5. The rapid colorimetric analysis method for thiourea content in a copper electrolyte according to claim 1, characterized in that: In step (1) of step 2, 0.0, 20.0, 40.0, 60.0, and 80.0 μL of thiourea standard solution are taken in a 25 mL colorimetric tube, and 1000.0, 980.0, 960.0, 940.0, and 920.0 μL of deionized water are added to obtain thiourea solutions with thiourea concentrations of 0.0, 20.0, 40.0, 60.0, and 80.0 mg / L, respectively; 10.0 mL of acetic acid-sodium acetate buffer solution is added, mixed, and then 5.0 mL of iodine solution is added to react with thiourea for 5 minutes.

6. The rapid colorimetric analysis method for thiourea content in a copper electrolyte according to claim 1, characterized in that: In step (2) of step 2, the starch potassium iodide test paper is immersed in the solution of step (1) of step 2 for 3 seconds to obtain color test strips with different color development conditions. The test strips are photographed, and the photos are processed using ImageJ image processing software to obtain the RGB values ​​of the color test strips. A standard color card is prepared based on the RGB values.

7. The rapid colorimetric analysis method for thiourea content in a copper electrolyte according to claim 1, characterized in that: In step (3) of step 2, the colorimetric test paper was photographed and processed into 8-bit format using ImageJ software, and the background grayscale was unified to 195. A rectangular tool was used to select a 5*12 mm area 4 mm from the top of the colorimetric test paper and 2 mm from the left and right sides to measure the average grayscale value of the test paper. A standard curve was drawn with the grayscale value as the ordinate and the thiourea content as the abscissa, and a linear relationship was calculated.

8. The rapid colorimetric analysis method for thiourea content in a copper electrolyte according to claim 1, characterized in that: In step three, the sample solution is diluted 4 to 10 times according to the approximate content of thiourea in the sample, 1.0 mL of the diluted sample solution is taken, 10.0 mL of buffer is added to adjust the pH, and then 5.0 mL of iodine solution is added to react with the thiourea in the sample for 5 minutes.

9. The rapid colorimetric analysis method for thiourea content in a copper electrolyte according to claim 1, characterized in that: In step 4, a starch potassium iodide test paper is inserted into the solution after the reaction of iodine and thiourea in the sample for 3 seconds to obtain a color test paper, and the color test paper is compared with the standard color card obtained in step (2) of step 2, and the content range of thiourea in the sample solution is obtained by visual colorimetry.

10. The rapid colorimetric analysis method for thiourea content in a copper electrolyte according to claim 1, characterized in that: In step 4, the colorimetric test paper is photographed and processed into 8-bit format using ImageJ software, and the background grayscale is unified to 195. A rectangular tool is used to select a 5×12 mm area 4 mm from the top of the colorimetric test paper and 2 mm from the left and right sides to measure the average grayscale value of the test paper. The obtained grayscale value is substituted into the linear relationship in claim 7 to calculate the accurate content of thiourea in the sample solution.

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