Method for determining copper content in electronic waste circuit board

Abstract

The invention relates to a method for determining the copper content in an electronic waste circuit board. A computer board and a television board are subjected to first-stage and second-stage crushing and then pass through a 100-mesh standard sieve, the particle size of a sample is larger than 100 microns, the sample weighing amount is increased, the copper content of the computer board and the television board is measured through an iodometric method, the precision and accuracy of a copper analysis result detected through a new method are verified by referring to GB / T3884.1-2012, and the requirements for repeatability and reproducibility in the standard are met. The RSD (Relative Standard Deviation) of copper analysis results in a computer board and a television board is respectively between 0.381% and 0.0.506%, and 0.491% and 0.604%; the analysis result of the copper in the computer board and the standard recovery rate of the copper in the television board are 99.68%-100.97% and 99.67%-100.35% respectively; the precision is good, the accuracy is high and the recovery rate is excellent.

Description

Technical Field

[0001] This application relates to the technical field of copper content determination, and particularly relates to a method for determining the copper content in electronic waste printed circuit boards. Background Art

[0002] Electronic waste printed circuit boards (computer boards, TV boards) are the core components of electronic products, which contain a large amount of valuable metal elements. Some research indicates that the composition of waste electronic waste printed circuit boards is 30% plastic, 30% refractory oxides, and 40% metal. Among the 40% metal, the copper content accounts for about 15%-25%. By adopting appropriate methods for copper recovery, the utilization rate of secondary copper resources can be improved. At present, GB / T3884.1-2012 is a widely used method for the determination of copper content in the copper smelting industry, and GB / T14263-2010 is a method for sampling and sample preparation of copper concentrates in the copper smelting industry. The requirements for the test samples in both standards are that the particle size of the samples should not be greater than 100μm, that is, it must pass through a 160-mesh standard sieve in the sample preparation process. However, the nature of electronic waste printed circuit boards determines the complexity of their components and the large differences in composition. It is inevitable that there are many difficulties in accurately determining their copper content by using traditional sampling, sample preparation, and analysis methods.

[0003] When using GB / T 3884.1-2012 for traditional sampling, sample preparation, and analysis of computer boards and TV boards, the analysis timeliness is poor, and the repeatability of the analysis results is poor, with low accuracy. Although the public document HG / T5965-2021 "Sampling and Sample Preparation Methods for Waste Printed Circuit Boards" is an industry standard, the evaluation method is the mainstream. Due to the lack of experience and immaturity in sampling and inspection by the evaluation method, the popularity of this method is not wide. There are problems with high business risks when using the above method for sample preparation of waste printed circuit boards. The repeatability of the analysis results in the public document HS / T62-2019 "Determination Method of Copper Content in Printed Circuit Board (PCB) Scrap - Wavelength Dispersive X-ray Fluorescence Spectrometry" is ±0.8%, and the reproducibility is ±1.5%. Copper in waste printed circuit boards is the main valuation element. According to the computer board grade calculation, the repeatability of the determination of copper content in GB / T3884.1-2012 is ±0.15%, and the reproducibility is ±0.22%. There are problems with poor repeatability and low accuracy of the analysis results when using the above determination methods.

[0004] Therefore, accurately determining the copper content in electronic waste printed circuit boards and establishing relevant analysis methods have important practical significance and guiding significance for copper metal recovery and copper resource recycling. Summary of the Invention

[0005] To solve or partially solve the problems existing in the related technologies, this application provides a method for determining the copper content in electronic waste printed circuit boards, which can solve the problems of poor repeatability and accuracy of the analysis results caused by the existing detection technologies and methods.

[0006] This application provides a method for determining the copper content in electronic waste printed circuit boards, including the following steps:

[0007] S1: Preparation of electronic waste printed circuit board samples.

[0008] S2: Sample pretreatment:

[0009] S21: Weigh 1 g of the sample (accurate to 0.0001 g) and place it in a 250 mL beaker. Moisten it with a small amount of water, add 5 drops of hydrofluoric acid, disperse the sample, add 10 mL of hydrochloric acid, cover it with a watch glass, and place it on a hot plate to heat at a low temperature until the remaining acid is about 5 mL. Remove it and let it cool slightly;

[0010] S22: Add 20 mL of nitric acid drop by drop while shaking and heat. Wait until the brown fumes disappear completely, remove it and let it cool slightly. Add 5 mL of saturated bromine water, continue to heat until there is about 1 mL of residual acid at the bottom of the cup, remove it and let it cool slightly. Add 15 mL of a nitric acid-sulfuric acid mixture (7+3), and continue to heat until a large amount of elemental sulfur appears;

[0011] S23: Heat 20 mL of perchloric acid, shake well, and heat at a low temperature. After the sulfur mass in the sample is completely decomposed, continue to heat and evaporate to dryness. Remove it and let it cool;

[0012] S24: Add 5 mL of hydrochloric acid, continue to heat to dissolve the soluble salts, rinse the cup wall and the watch glass with 30 mL of water, cover it with a watch glass, and boil it on a hot plate until the solution is clear to completely dissolve the soluble salts. Remove it and rinse the cup wall and the watch glass with a small amount of water, and cool it to room temperature.

[0013] S3: Make up the volume and take aliquots of the test solution.

[0014] S4: Titration: Add ammonium acetate solution (300 g / L) drop by drop until the red color no longer deepens and an excess of 4 mL is added. Add ammonium bifluoride solution (250 g / L) until the red color of the solution disappears and an excess of 3 mL is added. Shake well, rinse the cup wall with a small amount of water, add 2 g of potassium iodide, gently shake to mix it evenly, immediately titrate with a standard sodium thiosulfate titrant until it turns light yellow, add 2 mL of starch solution (5 g / L), continue to titrate until it turns light blue, add 2 mL of potassium thiocyanate solution (400 g / L), shake well, and continue to titrate until the blue color just disappears, which is the end point.

[0015] S5: Result calculation: The mass fraction of copper in the electronic waste printed circuit board is calculated using the following formula:

[0016]

[0017] In the above formula: V - the volume of the standard sodium thiosulfate solution consumed in the titration, in mL; V0 - the volume of the standard sodium thiosulfate solution consumed in the blank experiment, in mL; V 定- Volume of the test solution, in mL; V1—Aliquot volume of the test solution, in mL; C—Concentration of the sodium thiosulfate standard solution, in mol / L; M—Molar mass of copper ions, (M = 63.546) in g / mol; m—Mass of the test sample, in g.

[0018] Optionally, in some embodiments, the sample preparation in S1 includes the following steps:

[0019] S11: First-stage crushing: Crush the taken circuit board by a shredder to a particle size of 1 - 3 cm, and use the coning and quartering method for reduction. The reduction is carried out no less than three times, and discard two diagonals and enter the second-stage crushing;

[0020] S12: Second-stage crushing: Put all the samples after the first-stage crushing into an impact crusher for crushing, and perform reduction after crushing. The reduction is carried out no less than three times to the required preparation amount;

[0021] S13: Put the reduced samples into the mortar in batches, with the loading amount each time not exceeding 2 / 3 of the mortar volume, and carry out grinding. The grinding time each time does not exceed 180 s, and perform sieving. Repeat the above steps until all the samples pass through the sieve;

[0022] S14: Place the sieved samples on a clean mixing cloth and mix them evenly. Use the corner-lifting method to mix the samples, and transfer the mixed samples to a pile no less than 3 times, and evenly divide them into 9 equal parts, with each part having a sample amount of no less than 50 g.

[0023] Optionally, in some embodiments, the required preparation amount in S12 is no less than 1000 g.

[0024] Optionally, in some embodiments, the performance of continuing to heat and evaporate to dryness in S23 is: the cup body is transparent, and there is only a small amount of white smoke.

[0025] Optionally, in some embodiments, the specific method for volume fixing and aliquoting the test solution in S3 is: Transfer the solution to a 100 mL volumetric flask, fix the volume to the graduation line, shake well, and set aside. Accurately pipette 25 mL of the sample solution and place it in a 30 mL beaker.

[0026] Optionally, in some embodiments, during the process of adding acetic acid - ammonium acetate solution dropwise until the red color no longer deepens in S4, if the iron content is low, add 1 mL of ferric chloride solution (150 g / L).

[0027] The technical solutions provided by this application may include the following beneficial effects:

[0028] This application increases the sample weighing amount of waste computer boards and TV boards, making the samples more representative and improving the accuracy of the analysis method. According to the data statistics of this application, the precision RSD (n = 7) of the copper analysis results in GB / T3884.1-2012 is between 2.05% and 2.84%. After using the new method to measure waste computer boards and TV boards, the precision RSD (n = 7) of the obtained analysis results is between 0.446% and 0.755%, meeting the analysis requirements.

[0029] It should be understood that the above general description and the following detailed description are only exemplary and explanatory, and cannot limit this application. Description of the Drawings

[0030] By describing the exemplary embodiments of this application in more detail in combination with the drawings, the above and other purposes, features, and advantages of this application will become more obvious. Among them, in the exemplary embodiments of this application, the same reference numerals generally represent the same components.

[0031] Figure 1 It is a broken line graph of the stability test of the computer board sample;

[0032] Figure 2 It is an analysis graph of copper in computer boards and TV boards measured by the method of this article and the copper content determination method of GB / T3884.1-2012;

[0033] Figure 3 It is a broken line graph comparing the measurement results of the method of this article with those of other laboratories;

[0034] Figure 4 It is a broken line graph of the analysis results of the reference material of this method;

[0035] Figure 5 It is a broken line graph of the experimental results of the influence of calcium, iron, and zinc ion amounts on the determination of copper ion content;

[0036] Figure 6 It is a broken line graph of the test results of the precision experiment of this method;

[0037] Figure 7 It is a broken line graph of the measurement results of the accuracy experiment of this method. Detailed Embodiments

[0038] The embodiments of this application will be described in more detail below with reference to the drawings. Although the embodiments of this application are shown in the drawings, it should be understood that this application can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided to make this application more thorough and complete, and to fully convey the scope of this application to those skilled in the art.

[0039] It should be understood that although the terms "first", "second", "third", etc. may be used in this application to describe various information, such information should not be limited to these terms. These terms are only used to distinguish information of the same type from each other. For example, without departing from the scope of this application, the first information may also be referred to as the second information, and similarly, the second information may also be referred to as the first information. Thus, features defined with "first" and "second" may explicitly or implicitly include one or more of such features. In the description of this application, the meaning of "a plurality" is two or more, unless otherwise specifically defined.

[0040] In view of the above problems, an embodiment of this application provides a method for determining the copper content in electronic waste printed circuit boards, which can solve the problems of poor repeatability and accuracy of analysis results caused by existing detection technologies and methods.

[0041] The method for determining the copper content in the electronic waste printed circuit boards includes the following steps:

[0042] S1: Preparation of electronic waste printed circuit board samples.

[0043] S2: Sample pretreatment:

[0044] S21: Weigh 1 g of the sample (accurate to 0.0001 g) and place it in a 250 mL beaker. Moisten it with a small amount of water, add 5 drops of hydrofluoric acid, disperse the sample by shaking, add 10 mL of hydrochloric acid, cover with a watch glass, and place it on a hot plate to heat at a low temperature until the remaining acid is about 5 mL. Remove it and let it cool slightly;

[0045] Hydrofluoric acid has extremely strong corrosiveness and can strongly corrode metals, glass, and silicon-containing objects;

[0046] S22: Add 20 mL of nitric acid dropwise while shaking and heat. Wait until the brown fumes disappear completely, remove it and let it cool slightly. Add 5 mL of saturated bromine water, continue to heat until there is about 1 mL of residual acid at the bottom of the cup, remove it and let it cool slightly. Add 15 mL of a nitric acid-sulfuric acid mixture (7 + 3), and continue to heat until a large amount of elemental sulfur appears;

[0047] S23: Heat 20 mL of perchloric acid, shake well, and heat at a low temperature. After the sulfur mass in the test sample is completely decomposed, continue to heat and evaporate to dryness, remove it and let it cool;

[0048] S24: Add 5 mL of hydrochloric acid and continue to heat to dissolve the soluble salts (there is about 1 mL of residual acid at the bottom of the cup). Rinse the cup wall and the watch glass with 30 mL of water, cover with a watch glass, and boil on a hot plate until the solution is clear to completely dissolve the soluble salts. Remove it and rinse the cup wall and the watch glass with a small amount of water, and cool to room temperature.

[0049] S3: Make up the volume and aliquot the test solution.

[0050] S4: Titration: Add ammonium acetate - acetic acid solution (300 g / L) until the red color no longer deepens and then add an excess of 4 mL. Add ammonium bifluoride solution (250 g / L) until the red color of the solution disappears and then add an excess of 3 mL. Shake well, rinse the inner wall of the cup with a small amount of water, add 2 g of potassium iodide, gently shake to mix evenly, immediately titrate with a standard sodium thiosulfate titrant until it turns light yellow, add 2 mL of starch solution (5 g / L), continue titrating until it turns light blue, add 2 mL of potassium thiocyanate solution (400 g / L), shake well, and continue titrating until the blue color just disappears, which is the end point.

[0051] 2Cu2+ + 4I - = 2CuI + I2

[0052] I2 + 2S2O 2- = S4O6 2- + 2I -

[0053] The ammonium acetate - acetic acid solution has the characteristics of strong stability and small change in pH value.

[0054] S5: Result calculation: The following formula is used to calculate the mass fraction of copper in the electronic waste printed circuit board:

[0055]

[0056] In the above formula: V - the volume of the standard sodium thiosulfate solution consumed in the titration, unit: mL; V0 - the volume of the standard sodium thiosulfate solution consumed in the blank experiment, unit: mL; V 定 - the volume of the test solution, unit: mL; V1 - the aliquot volume of the test solution, unit: mL; C - the concentration of the standard sodium thiosulfate solution, unit: mol / L; M - the molar mass of copper ions, (M = 63.546) unit: g / mol; m - the mass of the test sample, unit: g.

[0057] Optionally, in some solutions, the sample preparation in S1 includes the following steps:

[0058] S11: First - stage crushing: Crush the taken circuit board by a shredder to a particle size of 1 - 3 cm, and use the coning and quartering method for reduction. The reduction is carried out no less than three times, discard two opposite corners and enter the second - stage crushing;

[0059] S12: Second - stage crushing: Put all the samples after the first - stage crushing into an impact crusher for crushing, and then carry out reduction. The reduction is carried out no less than three times until the required preparation amount is reached. The samples to be prepared are pre - dried according to the sample situation to meet the preparation requirements;

[0060] S13: Put the quartered samples into the mortar in batches, with the loading amount each time not exceeding 2 / 3 of the mortar volume, grind them, with the grinding time each time not exceeding 180 s, sieve them, and repeat the above steps until all the samples pass through the sieve;

[0061] S14: Place the sieved samples on a clean sample mixing cloth and mix them evenly. Use the corner-lifting method to mix the samples, transfer the mixed samples in a pile no less than 3 times, and evenly divide them into 9 equal parts, with the amount of each part no less than 50 g.

[0062] In some embodiments, the required preparation amount in S12 is not less than 1000 g.

[0063] In some embodiments, the manifestation of continuing heating and evaporating to dryness in S23 is that the cup body is transparent and there is only a small amount of white smoke.

[0064] In some embodiments, the specific method for volume fixing and aliquoting test solution in S3 is: transfer the solution to a 100 mL volumetric flask, fix the volume to the graduation line, shake well, reserve it, accurately pipette 25 mL of the sample solution, and place it in a 30 mL beaker.

[0065] In some embodiments, during the process of dropping acetic acid - ammonium acetate solution until the red color no longer deepens in S4, if the iron content is low, add 1 mL of ferric chloride solution (150 g / L).

[0066] The present application is further elaborated through experiments below:

[0067] Experiment 1 Homogeneity experiment of electronic waste circuit board (computer board, TV board) samples

[0068] Experiment scheme:

[0069] (A) Specimen requirements: After completely crushing the computer board, pass it through a 100-mesh standard sieve. Spread the samples flat on the sample preparation tabletop, divide the samples into 24 equal parts using the grid method, extract 10 samples (take samples at intervals, with each grid as a sample), control the total amount of the samples at 50 g, and the sampling amount is 50 * weight. Under repeatability conditions, detect the element Cu and repeat the determination 2 times. Use one-way ANOVA for sample homogeneity test. Complete the homogeneity test of the TV board according to the above method, and the analysis results are shown in Table 1 and Table 2.

[0070] (B) Sampling amount: Weigh 1 g of each sample, accurate to 0.0001 g.

[0071] Table 1 Homogeneity experiment of computer board samples

[0072]

[0073] As can be seen from Table 1, at the m = 10 level, each level was analyzed 2 times repetitively, n = 2, with a total of 20 data, and N = 20. The degree of freedom f1 = m - 1 = 9, f2 = N - m = 10, the sum of squares between samples Mean square Sum of squares within samples Mean square Statistic At the significance level a = 0.05, the critical value F 0.05 (9, 10) = 3.02. In this experiment, F = 2.22 < F 0.05 (9, 10), so there is no significant difference in the detection results of Cu in the whole batch of samples, and they are uniform. It shows that the uniformity of the computer board samples is very good and representative.

[0074] Table 2 Uniformity experiment of TV board samples

[0075]

[0076] As can be seen from Table 2, at the m = 10 level, each level was analyzed 2 times repetitively, n = 2, with a total of 20 data, and N = 20. The degree of freedom f1 = m - 1 = 9, f2 = N - m = 10, the sum of squares between samples Mean square Sum of squares within samples Mean square Statistic At the significance level a = 0.05, the critical value F 0.05 (9, 10) = 3.02. In this experiment, F = 1.94 < F 0.05 (9, 10), so there is no significant difference in the detection results of Cu in the whole batch of samples, and they are uniform. It shows that the uniformity of the TV board samples is very good and representative.

[0077] Experiment 2 Stability experiment of electronic waste circuit board (computer board, TV board) samples

[0078] Experiment scheme:

[0079] Taking the results of copper in computer boards and TV boards as examples, 3 samples were randomly selected at each interval day (the 0th, 5th, 9th, 18th, 30th days), and the method of this application was used. Each sample was measured 2 times repetitively. According to the ability verification uniformity and stability formula The t value was calculated, and the measurement results and the summary results of data calculation are shown in Table 3 and Table 4. Figure 1 It is the broken line graph of the stability test of computer board samples.

[0080] Table 3 Determination results of copper content in computer boards

[0081]

[0082] Analysis of the Determination Results of Copper Content in the Computer Board

[0083]

[0084] Look up the t value in the table 0.05 t(10)=2.230, and the t values at each time point in the table are all less than t 0.05 (10) critical value, indicating that the sample is stable at the 0.05 significance level.

[0085] Experiment 3: Comparative Experiment on the Effects of Different Determination Methods

[0086] Experimental Scheme:

[0087] Method 1: The results of measuring waste computer boards and TV boards according to the method in this article are shown in Table 5;

[0088] Method 2: The results of copper content determination according to GB / T3884.1-2012 are shown in Table 6;

[0089] The analysis diagrams of copper in computer boards and TV boards measured by the method in this article and the copper content determination method of GB / T3884.1-2012 are as Figure 2 shown.

[0090] Table 5 Copper Analysis Results of the Method in This Article

[0091]

[0092] Table 6 Copper Content Determination Results of GB / T3884.1-2012

[0093]

[0094]

[0095] As can be seen from Table 5 and Table 6, the standard deviations of the copper analysis results in computer boards and TV boards measured by the method in this article are 0.446% and 0.755% respectively, indicating that the precision of the method in this article is high.

[0096] Experiment 4: Comparative Experiment Among Different Laboratories

[0097] Experimental Scheme:

[0098] Respectively take the above 5 computer board and TV board samples, and compare and analyze the measured values by the method in this article with the measured values of other 3 laboratories. The analysis results are shown in Table 7, and the broken line diagram of the comparison between the method in this article and the measured results of other laboratories is as Figure 3 shown.

[0099] Table 7 Comparison Results of the Method in This Article and the Measured Results of Other Laboratories

[0100]

[0101] As shown in the results of Table 7, by comparing the copper content measured by this method with the copper content measured by the other three laboratories, it is found that the extreme difference is within the acceptable range, indicating that the precision and accuracy of this method are good.

[0102] Experiment 5 Verification Experiment of Certified Reference Materials

[0103] Experimental Scheme:

[0104] Traceability of the copper analysis results was carried out for two certified copper concentrate reference materials numbered GSB04-2709-2011 series ZBK338 and ZBK339 by this method. For ZBK338, Cu = 20.56%, and for ZBK339, Cu = 8.46%. The traceability results are shown in Table 8, and the line graph of the analysis results of the reference materials by this method is as Figure 4 shown.

[0105] Table 8 Analysis Results of Reference Materials by This Method

[0106]

[0107] From the traceability results in Table 8, it can be seen that the analysis results of the copper content in computer boards and TV boards measured by this method are close to the standard values. Thus, it can be seen that both the accuracy and precision of this method are relatively good.

[0108] Experiment 6 Experiment on the Influence of Lead, Calcium, Iron, and Zinc Ion Contents on the Determination of Copper Ions

[0109] Experimental Scheme:

[0110] In the electronic waste circuit board (computer board, TV board) samples, the contents of lead (about 20%), calcium (about 10%), iron (about 40%), and zinc (about 3%) were used to further verify whether they would interfere with the determination of copper content. The following experiment was carried out: 0.2 g of lead, 0.1 g of calcium, 0.4 g of iron, and 0.03 g of zinc were successively added to the fixed copper amounts (0.5 mg, 1.0 mg, 10.0 mg). The results are listed in Table 9, and the subsequent process was carried out according to this method. The line graph of the experimental results of the influence of calcium, iron, and zinc ion amounts on the determination of copper ion content is as Figure 5 shown.

[0111] Table 9 Influence of Lead, Calcium, Iron, and Zinc Ion Amounts on the Determination of Copper Ion Content

[0112]

[0113] From the data in Table 9, it can be concluded that the measured values of the standard solutions (1.0 mg, 5.0 mg, 10.0 mg, 20 mg) are highly consistent with the background values, indicating that lead, calcium, iron, and zinc ions in the electronic waste circuit board (computer board, TV board) have no influence on the determination of copper ion content.

[0114] Experiment 7 Precision Experiment of This Method

[0115] Experimental Scheme:

[0116] Take 5 different samples, and each sample is independently measured 7 times according to this method. The test results are shown in Table 10, and the line graph of the test results is as shown in Figure 6 .

[0117] Table 10 Precision Test of This Method

[0118]

[0119] Experiment 8 Accuracy Experiment of This Method

[0120] Experimental Scheme:

[0121] Select two samples of computer board and TV board, add different masses of pretreated high-purity copper sheets [ω(Cu)≥99.999%], and measure them by this method. The measurement results are shown in Table 11, and the line graph of the measurement results is as shown in Figure 7 .

[0122] Table 11 Standard Addition Recovery Test of This Method

[0123]

[0124] It can be seen from Table 11 that the standard addition recovery rates of the copper analysis results in the computer board and TV board measured by this method are between 99.68% and 100.97%, and between 99.67% and 100.35% respectively. This method has high precision and high accuracy, meeting the requirements of analysis and detection.

[0125] The method of the present invention has innovation, feasibility and practicability:

[0126] Innovation: After all the computer boards and TV boards are broken, they are passed through a 100-mesh standard sieve, and then decomposed by hydrochloric acid, nitric acid, perchloric acid and sulfuric acid. After accurately transferring the volume of the solution, the acidity is adjusted with acetic acid-ammonium acetate solution, and ammonium bifluoride is used to mask iron. In a slightly acidic solution with a pH value of 3.0 - 4.0, potassium iodide is added to react with divalent copper, and the precipitated iodine is titrated with a standard sodium thiosulfate titration solution using starch as an indicator.

[0127] Feasibility: On the premise of precise control of experimental conditions, precision, accuracy and standard addition recovery experiments are carried out for verification. The results show that the RSD of this experimental method is less than 2.00%, the standard addition recovery rate is 99.01% - 101.16%, and the RE is 0.06% - 0.27%. It has high precision and high accuracy, meeting the requirements of analysis and detection.

[0128] Practicality: The research makes up for the deficiencies in the treatment methods of HS / T 62-2019 and HG / T 5956-2021, reduces business risks, optimizes the method principle by combining the component content and physical and chemical properties, and provides a low-cost, simple-to-operate and widely applicable method for the determination of constant copper in waste printed circuit board samples.

[0129] Finally, it should also be noted that in this article, relationships such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "including", "comprising" or any other variant are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements not only includes those elements, but also includes other elements not explicitly listed, or further includes elements inherent to such process, method, article or device.

[0130] The embodiments of the present application have been described above. The above description is exemplary, not exhaustive, and is not limited to the disclosed embodiments. Many modifications and variations are obvious to those of ordinary skill in the art in the technical field without departing from the scope and spirit of the described embodiments. The choice of terms used herein is intended to best explain the principles of the embodiments, the practical application or the improvement of the technology in the market, or to enable other ordinary technical personnel in the technical field to understand the disclosed embodiments.

Claims

1. A method for determining the copper content in electronic waste circuit boards, characterized in that: The method for determining the copper content in the electronic waste circuit board comprises the following steps: S1: Preparation of electronic waste circuit board samples; S2: Sample preparation: S21: Weigh 1 g of the sample (accurate to 0.0001 g) and place it in a 250 mL beaker, moisten it with a small amount of water, add 5 drops of hydrofluoric acid, shake the sample, add 10 mL of hydrochloric acid, cover with a watch glass, place on a hot plate and heat at low temperature until the acid residue is about 5 mL, then remove and cool slightly; S22: Add 20 mL of nitric acid while shaking and heat until the brown smoke disappears, remove and cool slightly, add 5 mL of saturated bromine water, continue heating until a small amount of acid (about 1 mL) remains at the bottom of the cup, remove and cool slightly, add 15 mL of nitric acid and sulfuric acid mixture (7+3), and continue heating until a large amount of elemental sulfur appears; S23: Heat 20 mL of perchloric acid, shake well, heat at low temperature, and continue heating and evaporating to dryness after the sulfur groups in the sample are completely decomposed, then remove and cool; S24: Add 5 mL of hydrochloric acid, continue heating to dissolve soluble salts, rinse the cup wall and the watch glass with 30 mL of water, cover the watch glass, boil on the hot plate until the solution is clear and the soluble salts are completely dissolved, remove the cup wall and the watch glass with a small amount of water, and cool to room temperature; S3: fix volume and take test solution; S4: Titration: Add acetic acid-ammonium acetate solution (300 g / L) dropwise until the red color no longer deepens and the excess is 4 mL, add ammonium bifluoride solution (250 g / L) dropwise until the red color of the solution disappears, and the excess is 3 mL, shake thoroughly, rinse the cup wall with a small amount of water, add 2 g of potassium iodide, shake gently to mix, immediately titrate with sodium thiosulfate standard titration solution to light yellow, add 2 mL of starch solution (5 g / L), continue to titrate to light blue, add 2 mL of potassium thiocyanate solution (400 g / L), shake thoroughly, and continue to titrate until the blue color just disappears, which is the end point; S5: Result calculation: The following formula is used to calculate the mass fraction of copper in electronic waste circuit boards: In the above formula: V-the volume of sodium thiosulfate standard solution consumed in titration, in mL; V0-the volume of sodium thiosulfate standard solution consumed in blank experiment, in mL; V 定 - volume of the test solution, in mL; V1—volume of the test solution, in mL; C-concentration of sodium thiosulfate standard solution, in mol / L; M-molar mass of copper ion, (M=63.546) in g / mol; m-mass of the sample, in g.

2. The method for determining the copper content in electronic waste circuit boards according to claim 1, characterized in that: The sample preparation in S1 comprises the following steps: S11: First stage crushing: The circuit boards are crushed to a particle size of 1-3 cm by a shredder, and then reduced by cone quartering method for no less than three times, and two diagonal parts are discarded for second stage crushing; S12: Secondary crushing: all samples after primary crushing are crushed in an impact crusher, and then reduced for at least three times to the required preparation amount; S13: Put the shrunken samples into the material bowl in batches, with the sample amount each time not exceeding 2 / 3 of the volume of the material bowl, grind them, and the grinding time each time does not exceed 180s, sieve them, and repeat the above steps until all the samples are sieved; S14: Place the sieved sample on a clean mixing cloth and mix it evenly. Use the angle-lifting method to mix the sample. Turn the mixed sample over for no less than 3 times and evenly divide it into 9 equal parts, with each sample weighing no less than 50g.

3. The method for determining the copper content in electronic waste circuit boards according to claim 2, characterized in that: The amount of preparation required in the S12 is not less than 1000g.

4. The method for determining the copper content in electronic waste circuit boards according to claim 3, characterized in that: The performance of continuing heating and evaporating to dryness in S23 is that the cup body is transparent and only a small amount of white smoke is present.

5. The method for determining the copper content in electronic waste circuit boards according to claim 4, characterized in that: The specific method of adjusting the volume and taking the test solution in S3 is as follows: transfer the solution to a 100mL volumetric flask, adjust the volume to the scale line, shake well, set aside, accurately transfer 25mL of sample solution, and place it in a 30mL beaker.

6. The method for determining the copper content in electronic waste circuit boards according to claim 5, characterized in that: In the process of adding acetic acid-ammonium acetate solution to S4 until the red color no longer deepens, if the iron content is low, add 1 mL of ferric chloride solution (150 g / L).

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