A method for rapidly determining ferrous iron in copper electrolyte

Abstract

A method for rapidly determining ferrous iron in copper electrolyte relates to the technical field of ferrous iron detection. It comprises the following specific steps: taking two 250mL conical flasks, adding 10mL of copper sulfate solution equivalent to the content in the sample to be tested to one of the conical flasks, and adding 10mL of the sample to be tested to the other conical flask; adding 10mL of concentrated hydrochloric acid respectively, adding water to 75mL; adding 20mL of sulfur-phosphorus mixed acid, adding 5 to 6 drops of sodium diphenylamine sulfonate indicator, and titrating with potassium dichromate standard solution until the solution suddenly changes to purple, which is the end point. The beneficial effects of the present invention are: the Fe2+ amount in the copper electrolyte can be determined simply, quickly and at low cost by using the present invention, the copper sulfate matrix does not affect the determination of Fe2+, 10 samples can be detected in about 40min, and the Fe2+ amount in the copper electrolyte obtained by the present invention has a spiked recovery rate of 92% to 110%, and a relative standard deviation of <3%.

Description

Technical Field

[0001] The invention relates to the technical field of ferrous iron detection, and in particular to a method for rapidly determining ferrous iron in a copper electrolyte. Background Art

[0002] The complexity of copper ore resources has resulted in a relatively complex chemical composition in copper electrolyte, especially the content of impurity iron, which has a significant negative impact on the production of electrolytic copper. During the electrolysis process, the iron in the anode enters the electrolyte as Fe2+, which reduces the solubility of copper sulfate, increases the resistance, viscosity and density of the electrolyte, reduces the sedimentation rate of the anode mud, and increases the content of suspended matter in the electrolyte, increasing the pollution of the cathode copper by the electrolyte and suspended matter, resulting in a decrease in the quality of the cathode copper; on the other hand, Fe2+ and Fe3+ in the copper electrolyte repeatedly consume power between the anode and the cathode, reducing the current efficiency. Due to the electrolysis process, the iron electrode potential is more negative than that of copper, so it can enter the electrolyte in the form of Fe2+. Therefore, in order to control the iron content in the electrolyte and ensure the normal operation of copper electrolysis, it is necessary to determine the content of Fe2+ and total iron, and select a suitable method for iron removal in the process. The copper electrolyte is blue due to the high copper content, so it is impossible to use colorimetry. At present, there is no ideal analysis method. Therefore, in order to meet the needs of rapid detection in production and scientific research, it is of great significance to seek a low-cost, fast, and accurate method that can meet the needs of production and scientific research for the determination of the amount of Fe2+ in the electrolyte. Summary of the invention

[0003] The purpose of the present invention is to provide a method for quickly determining ferrous iron in copper electrolyte in view of the shortcomings and disadvantages of the prior art, realize the rapid pretreatment of Fe2+ samples in the electrolyte, greatly shorten the detection time, and the method has good accuracy, precision and applicability.

[0004] To achieve the above purpose, the present invention adopts the following technical scheme: a method for quickly determining ferrous iron in a copper electrolyte, which comprises the following specific steps: taking two 250mL conical flasks, adding 10mL of a copper sulfate solution having a content equivalent to that in a sample to be tested into one of the conical flasks, and adding 10mL of the sample to be tested into the other conical flask; adding 10mL of concentrated hydrochloric acid respectively, and adding water to 75mL; adding 20mL of sulfuric acid and phosphoric acid mixed acid, adding 5 to 6 drops of sodium diphenylamine sulfonate indicator (5g / L), and titrating with a potassium dichromate standard solution (T(Fe / K2Cr2O7)≈0.8g / L) until the solution suddenly turns purple, which is the end point.

[0005] As the present invention is more specific: the main reaction formula is as follows: Cr2O72-+6Fe2++14H+→2Cr3++6Fe3++7H2O.

[0006] As a more specific embodiment of the present invention, the preparation steps of the sulfur-phosphorus mixed acid are as follows: 200 mL of phosphoric acid is added into about 500 mL of water while stirring, and then 300 mL of sulfuric acid is added while stirring, mixed, and cooled with running water.

[0007] The working principle of the present invention is as follows: a blank sample with the same matrix as sulfuric acid and copper concentration in a copper electrolyte is prepared; under acidic conditions, sodium diphenylamine sulfonate is used as an indicator and a potassium dichromate standard solution is used to titrate Fe2+ in the copper electrolyte; the content of Fe2+ in the sample is calculated by the amount of potassium dichromate consumed, and the main reaction formula is as follows: Cr2O72-+6Fe2++14H+→2Cr3++6Fe3++7H2O.

[0008] After adopting the above technical scheme, the beneficial effects of the present invention are as follows: the present invention can be used to simply, quickly and inexpensively determine the amount of Fe2+ in a copper electrolyte, the copper sulfate matrix does not affect the determination of Fe2+, 10 samples can be tested in about 40 minutes, and the spiked recovery rate of the amount of Fe2+ in the copper electrolyte obtained by the present invention is between 92% and 110%, and the relative standard deviation is <3%. DETAILED DESCRIPTION

[0009] Embodiment 1:

[0010] The technical solution adopted in this specific implementation method is: it includes the following specific steps: take two 250mL conical flasks, add 10mL of copper sulfate solution with the content equivalent to that in the sample to be tested into one of the conical flasks, and add 10mL of the sample to be tested into the other conical flask; add 10mL of concentrated hydrochloric acid respectively, add water to 75mL; add 20mL of sulfuric acid and phosphoric acid mixture, add 5 to 6 drops of sodium diphenylamine sulfonate indicator (5g / L), and titrate with potassium dichromate standard solution (T(Fe / K2Cr2O7)≈0.8g / L) until the solution suddenly turns purple, which is the end point.

[0011] The main reaction formula is as follows: Cr2O72-+6Fe2++14H+→2Cr3++6Fe3++7H2O, and the preparation steps of the sulfur-phosphorus mixed acid are: adding 200mL of phosphoric acid into about 500mL of water while stirring, then adding 300mL of sulfuric acid while stirring, mixing, and cooling with running water.

[0012] Embodiment 2:

[0013] Preparation of potassium dichromate standard solution (T(Fe / K2Cr2O7)≈0.8g / L): Accurately weigh 0.7500g of potassium dichromate (benchmark) that has been dried at 140℃~150℃ for 2h, add water to dissolve, add a few drops of sulfur (1+1), transfer to a 1000mL volumetric flask, add water to dilute to the scale, and shake well.

[0014] Test solution treatment: Pipette 10.00 mL of test solution (sample after dilution when the content is high) into a 250 mL conical flask, add 10 mL of concentrated hydrochloric acid, and add water to 75 mL.

[0015] Determination: Add 20mL of sulfuric and phosphoric acid mixture (add 200mL of phosphoric acid into about 500mL of water while stirring, then add 300mL of sulfuric acid while stirring, mix well, and cool with running water), add 5 to 6 drops of sodium diphenylamine sulfonate indicator (5g / L), and titrate with potassium dichromate standard solution (T(Fe / K2Cr2O7)≈0.8g / L) until the solution turns a distinct and stable purple color, which is the end point.

[0016] Result calculation: Calculate the Fe2+ content according to the following formula, in g / L:

[0017]

[0018] Where:

[0019] T——Titer of potassium dichromate standard solution on iron, in grams per liter (g / L);

[0020] V 2 ——The volume of potassium dichromate standard solution consumed in titrating the sample test solution, in milliliters (mL);

[0021] V 1 ——The volume of potassium dichromate standard solution consumed in titrating the blank test solution, in milliliters (mL);

[0022] V 0 ——Sample volume, in milliliters (mL).

[0023] The calculation result is expressed to two decimal places.

[0024] Embodiment three:

[0025] Determine the recovery rate of Fe2+ in the copper sulfate matrix solution: prepare copper sulfate blank solution according to the concentrations of sulfuric acid and copper in the actual sample, transfer 10mL of copper sulfate solution respectively, and add the amount of Fe2+ according to Table 1.

[0026] Table 1

[0027]

[0028] The results show that the recovery rate of Fe2+ content determined directly by titration in copper electrolyte is between 92% and 110%, and the copper sulfate matrix does not interfere with the determination of Fe2+.

[0029] Embodiment 4:

[0030] The Fe2+ content in the actual copper electrolyte sample was determined with a blank consumption of 0.10 mL of pure copper sulfate. The results are shown in Table 2.

[0031] Table 2

[0032]

[0033] The results show that the precision of directly determining the content of Fe2+ in copper electrolyte by titration is good, and the content of Fe2+ can be determined quickly and accurately to meet the production requirements. The above is only used to illustrate the technical solution of the present invention rather than to limit it. Other modifications or equivalent substitutions made by ordinary technicians in this field to the technical solution of the present invention should be included in the scope of the claims of the present invention as long as they do not depart from the spirit and scope of the technical solution of the present invention.

Claims

1. A method for rapidly determining ferrous iron in a copper electrolyte, characterized in that: It includes the following specific steps: 1) Take two 250mL conical flasks, add 10mL of copper sulfate solution with the same content as the sample to be tested to one conical flask, and add 10mL of the sample to be tested to the other conical flask; add 10mL of concentrated hydrochloric acid to each, and add water to 75mL; 2) Add 20 mL of sulfuric acid and phosphoric acid, add 5-6 drops of 5 g / L sodium diphenylamine sulfonate indicator, and titrate with potassium dichromate standard solution until the solution suddenly turns purple, which is the end point; calculate the Fe content in the sample based on the amount of potassium dichromate consumed. 2+ Content; Calculate Fe according to the following formula 2+ Content, in g / L: ； Where: T——Titer of potassium dichromate standard solution on iron, in g / L; ——The volume of potassium dichromate standard solution consumed in titrating the sample test solution, in mL; ——The volume of potassium dichromate standard solution consumed in titrating the blank test solution, in mL; ——Sample volume, in mL; The calculation results are expressed to two decimal places; The main reaction formula is as follows: Cr2O7 2- +6Fe 2+ +14H + →2Cr 3+ +6Fe 3+ +7H2O.

2. A method for rapidly determining ferrous iron in a copper electrolyte according to claim 1, characterized in that: The preparation steps of the sulfur-phosphorus mixed acid are as follows: 200 mL of phosphoric acid is added into about 500 mL of water while stirring, and then 300 mL of sulfuric acid is added while stirring, mixed, and cooled with running water.

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