Method for detecting the circulating liquid acidity of an electrowinning cobalt

Abstract

The application discloses a method for detecting the acidity of a circulating solution of electro-deposited cobalt, which comprises the following steps: removing oxidizing substances in the circulating solution of electro-deposited cobalt by potassium iodide in an acidic medium; reacting the potassium iodide with potassium iodate and acid to generate iodine molecules; titrating with a sodium thiosulfate standard solution until the solution changes from blue or blue-black to the original color of the solution, which is the end point; and calculating the acidity content according to the mass balance. The method can effectively remove the oxidizing substances in the solution to be measured, avoid the interference with the determination of the acidity content, and make the detection result more accurate. The sodium thiosulfate is innovatively applied to the detection of the acidity of the circulating solution of electro-deposited cobalt, and the sodium thiosulfate titration is used to replace the commonly used sodium hydroxide titration method, so that the interference of the original color of the light red solution with the color judgment of the end point of the sodium hydroxide (phenolphthalein as an indicator) is avoided.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of detecting acidity content, and particularly relates to a detection method for the acidity of cobalt electrowinning circulating liquid. BACKGROUND

[0002] In the prior art, the conventional method for detecting the acidity of cobalt electrowinning circulating liquid is as follows: sodium hydroxide standard solution is used to titrate the cobalt electrowinning circulating liquid, phenolphthalein is used as an indicator, and then the acidity of the cobalt electrowinning circulating liquid is calculated according to the amount of sodium hydroxide consumed. However, cobalt is contained in the cobalt electrowinning circulating liquid, and cobalt reacts with sodium hydroxide to generate precipitates, and also consumes sodium hydroxide, which affects the accuracy of the acidity detection result. Moreover, the solution is light red in color due to the presence of cobalt in the cobalt electrowinning circulating liquid, and the light red color of the solution affects the judgment of the titration end point when the sodium hydroxide standard solution is used to titrate the acidity content, which further affects the accuracy of the detection result. SUMMARY

[0003] In order to solve the problems existing in the prior art, the application provides a detection method for the acidity of cobalt electrowinning circulating liquid, the acidity refers to the molar concentration of hydrogen ions in the cobalt electrowinning circulating liquid, and specifically includes the following contents:

[0004] A detection method for the acidity of cobalt electrowinning circulating liquid, comprising the following steps:

[0005] (1) adding deionized water to cobalt electrowinning circulating liquid with a volume of V1 to obtain a to-be-detected liquid a;

[0006] (2) adding 10g / L-20g / L (for example, 12g / L, 14g / L, 16g / L, 18g / L, etc.) of potassium iodide solution to the to-be-detected liquid a, shaking well, and then adding 5-10g / L (for example, 6g / L, 7g / L, 8g / L, 9g / L, etc.) of starch solution to obtain a blue mixed liquid b, and the volume ratio of the to-be-detected liquid a, the potassium iodide solution and the starch solution is controlled to be (80-100):(5-20):1, for example, 85:8:1, 90:10:1, 100:15:1, etc.;

[0007] (3) titrating the mixed liquid b with a sodium thiosulfate standard solution until the solution is light red in color, and then adding 40-50g / L (for example, 42g / L, 44g / L, 46g / L, 48g / L, etc.) of potassium iodate solution to the solution according to the volume ratio of the mixed liquid b:potassium iodate solution=(15-20):1 (for example, 16:1, 17:1, 18:1, 19:1, etc.) to obtain a mixed liquid c;

[0008] (4) titrate the mixed solution c with sodium thiosulfate standard solution until the solution is colorless, record the volume V2 of sodium thiosulfate standard solution consumed in this titration, and calculate the acidity of the electrowinning cobalt circulating liquid according to V2.

[0009] Preferably, the volume ratio of the electrowinning cobalt circulating liquid to deionized water in step (1) is 1: (10-20) (for example, 1:12, 1:14, 1:16, 1:18, etc.).

[0010] Preferably, the method for calculating the acidity of the electrowinning cobalt circulating liquid according to V2 in step (4) is:

[0011]

[0012] In the formula: C H+ - is the amount-of-substance concentration of hydrogen ions in the electrowinning cobalt circulating liquid, mol / L;

[0013] C (Na2S2O3) - is the amount-of-substance concentration of the sodium thiosulfate standard titration solution, mol / L;

[0014] V2 - is the volume of sodium thiosulfate standard titration solution consumed, mL;

[0015] V1 - is the volume of the electrowinning cobalt circulating liquid to be measured, mL.

[0016] The beneficial effects of the present application are:

[0017] (1) The method for detecting the acidity of the electrowinning cobalt circulating liquid provided by the present application first removes the oxidizing substances in the electrowinning cobalt circulating liquid in an acidic medium with potassium iodide, and then the potassium iodide reacts with potassium iodate and acid to generate iodine molecules, with starch as an indicator, and the solution is titrated with sodium thiosulfate standard solution until the solution changes from blue or blue-black to colorless, which is the end point, and then the acidity content is calculated according to the mass balance. This method can effectively remove the oxidizing substances in the liquid to be measured, avoid interference with the determination of the acidity content, and make the detection result more accurate.

[0018] (2) The method for detecting the acidity of the electrowinning cobalt circulating liquid disclosed by the present application innovatively applies sodium thiosulfate to the detection of the acidity of the electrowinning cobalt circulating liquid, and replaces the commonly used sodium hydroxide titration method with sodium thiosulfate titration, avoiding the interference of the light red solution color with the judgment of the end point color of sodium hydroxide (phenolphthalein as an indicator).

[0019] (3) The method for detecting the acidity of the electrowinning cobalt circulating liquid disclosed by the present application accurately limits the concentration and ratio of the solution at each step, which is conducive to improving the accuracy of titration and ensuring the accuracy of the finally determined acidity value. DETAILED DESCRIPTION

[0020] The application will be described in detail below with reference to specific embodiments. The embodiments shown below do not limit the invention described in the claims in any way. In addition, the entire content of the embodiments shown below is not limited to being necessary for the solution of the invention described in the claims.

[0021] A method for detecting the acidity of a cobalt electrowinning circulating solution, comprising the following steps:

[0022] (1) adding deionized water to a cobalt electrowinning circulating solution with a volume of V1 to obtain a test solution a; the volume ratio of the cobalt electrowinning circulating solution to the deionized water is 1:(10-20) (for example, 1:12, 1:14, 1:16, 1:18, etc.);

[0023] (2) adding a 10g / L-20g / L (for example, 12g / L, 14g / L, 16g / L, 18g / L, etc.) potassium iodide solution to the test solution a, shaking well, and then adding a starch solution with a concentration of 5-10g / L (for example, 6g / L, 7g / L, 8g / L, 9g / L, etc.) to obtain a blue mixed solution b, and the volume ratio of the test solution a, the potassium iodide solution, and the starch solution is controlled to be (80-100):(1-2):1, for example, 85:1:1, 90:1.5:1, 100:2:1, etc.;

[0024] (3) titrating the mixed solution b with a sodium thiosulfate standard solution until the solution is the original color, and then adding a 40-50g / L (for example, 42g / L, 44g / L, 46g / L, 48g / L, etc.) potassium iodate solution to the solution according to a volume ratio of the mixed solution b:potassium iodate solution=(15-20):1 (for example, 16:1, 17:1, 18:1, 19:1, etc.) to obtain a mixed solution c;

[0025] (4) titrating the mixed solution c with the sodium thiosulfate standard solution until the solution is the original color, and recording the volume V2 of the sodium thiosulfate standard solution consumed this time, and calculating the acidity of the cobalt electrowinning circulating solution according to V2, the calculation method being:

[0026]

[0027] In the formula: C H+ is the molar concentration of hydrogen ions in the cobalt electrowinning circulating solution, mol / L;

[0028] C(Na2S2O3) is the molar concentration of the sodium thiosulfate standard titration solution, mol / L;

[0029] V2 is the volume of the sodium thiosulfate standard titration solution consumed, mL;

[0030] V1 is the volume of the cobalt electrowinning circulating solution to be tested, mL.

[0031] Example 1

[0032] Accurately pipette 4 portions of 5 ml of the cobalt electrowinning circulating solution into 1#, 2#, 3# and 4# triangular flasks (300 ml) respectively, add 80 mL of water, and then add 2.5 mL, 5 mL, 10 mL and 15 mL of 10 g / L potassium iodide solution into the flasks respectively, add 1 mL of 10 g / L starch solution, and then shake well and titrate with sodium thiosulfate standard titration solution until the solution is colorless (light red) (the purpose is to remove oxidizing substances in the test solution).

[0033] Add 5.0 mL of potassium iodate solution (50 g / L) into the above solution, and titrate with sodium thiosulfate standard titration solution until the solution is colorless (light red), which is the end point of titration.

[0034] The acid content in the test solution is calculated according to the following formula:

[0035]

[0036] In the formula, C H+ is the molar concentration of hydrogen ions in the cobalt electrowinning circulating solution, mol / L;

[0037] C (Na2S2O3) is the molar concentration of the sodium thiosulfate standard titration solution, mol / L;

[0038] V2 is the volume of the sodium thiosulfate standard titration solution consumed, mL;

[0039] V1 is the volume of the cobalt electrowinning circulating solution to be measured, mL.

[0040] The calculated test results are as follows:

[0041] Table 1 Test results of Example 1

[0042] Sample No. 1# (Comparative Example) 2# 3# 4# Potassium iodide addition amount (g) 0.25 0.5 1.0 2.0 Detection value (mol / L) 0.3586 0.2990 0.2979 0.3000

[0043] As can be seen from the test results, the addition of 2.5 mL of potassium iodide solution fails to completely remove metal oxidizing substances, resulting in a high acid result. When 5 mL, 10 mL and 15 mL of potassium iodide solution are added, the test results are consistent.

[0044] Example 2

[0045] Accurately pipette 4 portions of 5 ml of the cobalt electrowinning circulating solution into 1#, 2#, 3# and 4# triangular flasks (300 ml) respectively, add 80 mL of water, and then add 2.5 mL, 5 mL, 10 mL and 15 mL of 10 g / L potassium iodide solution into the flasks respectively, add 1 mL of 10 g / L starch solution, and then shake well and titrate with sodium thiosulfate standard titration solution until the solution is colorless (light red) (the purpose is to remove oxidizing substances in the test solution).

[0046] To the above solution, 2.5 mL, 5.0 mL, 10.0 mL, 15.0 mL of potassium iodate solution (50 g / L) was added in sequence, and the solution was titrated with a standard titration solution of sodium thiosulfate until the solution was colorless (light red), which was the end point of titration.

[0047] The acid content in the test solution was calculated according to the following formula:

[0048]

[0049] In the formula, C H+ is the molar concentration of hydrogen ions in the electrolytic cobalt circulating solution, mol / L;

[0050] C (Na2S2O3) is the molar concentration of the standard titration solution of sodium thiosulfate, mol / L;

[0051] V2 is the volume of the standard titration solution of sodium thiosulfate consumed, mL;

[0052] V1 is the volume of the electrolytic cobalt circulating solution to be measured, mL.

[0053] The detection results are as follows:

[0054] Table 2 Detection results of Example 2

[0055]

[0056]

[0057] As can be seen from the detection results, the addition of 2.5 mL of potassium iodate did not completely react, resulting in a low acid detection result. When 5.0 mL, 10.0 mL, 15.0 mL of potassium iodate was added, the detection results were consistent. Considering cost savings, it is recommended to add 5 mL of potassium iodate.

[0058] Example 3

[0059] The purpose of this example is to detect the recovery rate of the method described in the application.

[0060] (1) Hydrochloric acid standard solution: C (HCl) = 0.5 mol / L.

[0061] Preparation: 41.66 mL of hydrochloric acid (ρ = 1.19 g / mL) was measured and dissolved in a 1000 mL volumetric flask. After cooling, it was diluted to constant volume.

[0062] Calibration:

[0063] Accurately weigh 0.8000 g of anhydrous sodium carbonate dried at 105°C for 2 h, dissolve in 300 mL of a triangular flask, dissolve in 50 mL of boiled and cooled water, add 3 drops of methyl orange indicator solution (10 g / L), titrate with the standard hydrochloric acid solution to be calibrated from yellow to red.

[0064] Calculation of the concentration of the standard hydrochloric acid solution:

[0065]

[0066] In the formula: V1 is the volume of the standard hydrochloric acid titration solution consumed by the titration of the anhydrous sodium carbonate reference solution, mL.

[0067] 53 is the molar mass of the 1 / 2 anhydrous sodium carbonate reference material, g / mol.

[0068] (2) Spiking

[0069] Accurately transfer 4 portions of 5 ml of the electrodeposited cobalt circulating solution into 1#, 2#, 3#, and 4# triangular flasks (300 ml), respectively, and transfer 0.5 ml, 1.0 ml, and 2.0 ml of the standard hydrochloric acid solution (C(HCl) = 0.5012 mol / L) into 2#, 3#, and 4# triangular flasks, respectively, add 80 mL of water and 5 mL of potassium iodide solution with a concentration of 10 g / L in sequence, add 1 mL of starch solution (10 g / L), and titrate with the standard sodium thiosulfate titration solution until the solution is colorless (light red), which is the end point of titration (remove oxidizing substances in the test solution).

[0070] Add 5.0 mL of potassium iodate solution (50 g / L) to the above solution, and titrate with the standard sodium thiosulfate titration solution until the solution is colorless (light red), which is the end point of titration.

[0071] Calculate the acid content in the test solution according to the following formula:

[0072]

[0073] In the formula: C is the molar concentration of hydrogen ions in the electrodeposited cobalt circulating solution, mol / L. H+

[0074] C(Na2S2O3) is the molar concentration of the standard sodium thiosulfate titration solution, mol / L.

[0075] V2 is the volume of the standard sodium thiosulfate titration solution consumed, mL.

[0076] V1 is the volume of the electrodeposited cobalt circulating solution to be measured, mL.

[0077] The detection results are as follows:

[0078] ​Table 3 detection results of Example 3

[0079] Sample No. 1# 2# 3# 4# Acid addition amount (mol) / 0.2506 0.5012 1.0024 Detection value (mol / L) 0.2996 0.5278 0.7886 1.3108 Recovery rate (%) 1.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0. / 91.06 96.97 100.01

[0080] From the detection results, the recovery rate is in the qualified interval.

[0081] Example 4

[0082] The purpose of this example is to detect the precision of the detection method of the application.

[0083] Accurately transfer 6 portions of 5ml of the electrodeposited cobalt circulating solution (batch number 230512001) into 1#, 2#, 3#, 4#, 5# and 6# triangular flasks (300ml) respectively, add 80ml of water, add 5ml of 10g / L potassium iodide solution in turn, add 1ml of starch solution (10g / L), and titrate with sodium thiosulfate standard titration solution until the solution is colorless (light red) (remove oxidizing substances in the test solution).

[0084] Add 5.0ml of potassium iodate solution (50g / L) to the above solution in turn, and titrate with sodium thiosulfate standard titration solution until the solution is colorless (light red), which is the end point of titration.

[0085] The content of acid in the test solution is calculated according to the following formula:

[0086]

[0087] In the formula, C H+ The amount-of-substance concentration of hydrogen ions in the electrodeposited cobalt circulating solution is mol / L;

[0088] C(Na2S2O3) is the amount-of-substance concentration of sodium thiosulfate standard titration solution, mol / L;

[0089] V2 is the volume of sodium thiosulfate standard titration solution consumed, mL;

[0090] V1 is the volume of the electrodeposited cobalt circulating solution to be measured, mL.

[0091] The detection results are as follows:

[0092] Table 4 detection results of Example 4

[0093]

[0094] From the detection results, the relative standard deviation of the method disclosed in the application is 0.38%, which meets the precision requirement.

[0095] The foregoing description of the disclosed embodiments enables a person skilled in the art to make or use the application. Modifications of these embodiments will occur to persons of skill in the art, and that the appended claims are intended to cover all such modifications that do not depart from the true spirit and scope of the application. Therefore, the application is not limited to the embodiments shown but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for detecting the circulation liquid acidity of an electrowinning cobalt, characterized in that, The method comprises the following steps: (1) adding deionized water to the electrodeposition cobalt circulating liquid with a volume of V1 to obtain a test liquid a; (2) adding a 10g / L-20g / L potassium iodide solution to the test liquid a, shaking well, and then adding a 5-10g / L starch solution to obtain a blue mixed liquid b, and the volume ratio of the test liquid a, the potassium iodide solution and the starch solution is controlled to be (80-100):(5-15):1; (3) titrating the mixed liquid b with a sodium thiosulfate standard solution until the solution is colorless, which is used to remove oxidizing substances in the test solution, and then adding a 40-50g / L iodate potassium solution to the solution according to the volume ratio of the mixed liquid b:the iodate potassium solution = (15-20):1 to obtain a mixed liquid c; (4) titrating the mixed liquid c with the sodium thiosulfate standard solution until the solution is colorless, recording the volume V2 of the sodium thiosulfate standard solution consumed in the titration, and calculating the acidity of the electrodeposition cobalt circulating liquid according to V2.

2. The method of claim 1, wherein the circulating electrolytic cobalt solution has a pH of about 1.5 to about 2.

5. The volume ratio of the electrodeposition cobalt circulating liquid to the deionized water in step (1) is 1:(10-20).

3. The method for detecting the cycle liquid acidity of electrowinning cobalt according to any one of claims 1 or 2, characterized in that, The method for calculating the acidity of the electrodeposition cobalt circulating liquid according to V2 in step (4) is: wherein: C H+ — is the molar concentration of hydrogen ions, mol / L, in the electrolytic cobalt circulating liquid; C (Na2S2O3) is the amount-of-substance concentration mol / L of the sodium thiosulfate standard solution; V2 is the volume mL of the sodium thiosulfate standard solution consumed; V1 is the volume mL of the electrodeposition cobalt circulating liquid to be tested.

Images