Method for determining the recovery of rhodium and iridium in a carbonylation alloy

Abstract

The application provides a method for determining the recovery rate of rhodium and iridium in carbonylation alloy, which comprises the following steps: sample processing, drawing of a working curve, optimization of test conditions, accuracy experiment and the like, and the carbonylation alloy sample is dissolved by using a full-automatic graphite digestion instrument, so that the problem that noble metal loss is caused by the need for copper removal treatment in the determination of rhodium and iridium in a high-copper matrix by using a nickel-matrix assay is solved, and the application can quickly and accurately detect the content of rhodium and iridium in the carbonylation alloy, thereby providing a basis for material settlement.

Description

Technical Field

[0001] This invention belongs to the field of precious metal detection technology and relates to a method for determining the recovery rate of rhodium and iridium in carbonyl alloys. Background Technology

[0002] Carbonylated alloys are solid residues remaining after nickel is extracted from water-quenched alloys through a carbonylation process. Since water-quenched alloys contain 60% nickel and 20% copper, during the carbonylation process, after the nickel in the raw materials is separated into gaseous carbonyl compounds, the remaining metal elements such as copper, iron, cobalt, sulfur, gold, silver, platinum, palladium, osmium, ruthenium, rhodium, and iridium are enriched in the tailings residue. Among them, the nickel content is 6-22%, the copper content is 55-75%, the sulfur content is 8-19%, the iron and cobalt content is 0.5%-7%, and the content of precious metals such as gold and silver is as high as hundreds of grams per ton. It is also rich in platinum group metals such as platinum, palladium, osmium, ruthenium, rhodium, and iridium.

[0003] Currently, carbonyl alloys are important settlement materials, especially since the content of precious metal elements in carbonyl alloys is related to the calculation of metal balance and carbonylation efficiency. Carbonyl alloys have a high copper content. When analyzing rhodium and iridium using existing nickel matte assay methods, the sample dissolution process requires a long time on a hot plate to remove copper. During the copper removal process, the combination of precious and base metals will cause a small amount of rhodium and iridium to dissolve, resulting in loss. At the same time, if traditional lead assays are used to enrich rhodium and iridium, these two elements are difficult to alloy due to their high melting points, making accurate determination impossible. Therefore, it can be seen that the existing technology cannot solve the above technical problems. Summary of the Invention

[0004] The purpose of this invention is to address the problems existing in the prior art by providing a method for determining the recovery rate of rhodium and iridium in carbonyl alloys, which solves the problem that existing nickel matte assay methods and traditional lead assay techniques cannot accurately determine the content of rhodium and iridium in carbonyl alloys.

[0005] Therefore, the present invention adopts the following technical solution:

[0006] A method for determining the recovery rate of rhodium and iridium in carbonyl alloys includes the following steps:

[0007] Step 1: Prepare the test solution: Weigh 0.500g of the sample into a polytetrafluoroethylene digestion tube, add 3mL of hydrofluoric acid (1.15g / mL), 8mL of nitric acid (1.42g / mL), and 3mL of perchloric acid (1.67g / mL) sequentially. Place the tube in a graphite furnace digester and heat to 80℃ for 20min, then to 120℃ for 30min, and finally to 180℃ for 160min. Evaporate the solution to a wet salt state, cool for 5min, add 10mL of hydrochloric acid (1.19g / mL) and 5mL of high-purity water, and heat for 5min. After cooling, transfer the solution to a 100mL volumetric flask, dilute to volume with water, and shake well. Transfer 5.00mL of the solution to a 100mL volumetric flask, add 5mL of hydrochloric acid (1.19g / mL), and dilute to volume with high-purity water to obtain the test solution.

[0008] Step 2: Prepare the standard solution: Take 10.00 mL of a 100 μg / mL rhodium and iridium mixed standard solution into a 100 mL volumetric flask, add 5 mL of 1.19 g / mL hydrochloric acid, dilute with water to the mark, and mix well. The rhodium and iridium concentration of this solution is 10 μg / mL.

[0009] Transfer 1.00 mL of a rhodium and iridium mixed standard solution with a mass concentration of 10 μg / L to a 100 mL volumetric flask, add 5 mL of hydrochloric acid with a mass concentration of 1.19 g / L, dilute with water to the mark, and mix well. The mass concentration of rhodium and iridium in this solution is 100 μg / L.

[0010] Transfer 0 mL, 1.00 mL, 2.00 mL, 5.00 mL, 10.00 mL, and 20.00 mL of a 100 μg / L rhodium and iridium mixed standard solution to a 100 mL volumetric flask, add 5 mL of 1.19 g / mL hydrochloric acid, dilute to volume with high-purity water, and shake well.

[0011] Step 3: Calculate the mass concentration of the analyte in the standard solution: Measure the mass concentration of the analyte in the standard solution using inductively coupled plasma mass spectrometry (ICP-MS).

[0012] The operating parameters of the inductively coupled plasma mass spectrometer used in step three are as follows: nebulizer flow rate of 0.90 L / min, sampling depth of 130.0 mm, cooler flow rate of 13.00 L / min, auxiliary flow rate of 0.80 L / min, and sample liquid lifting volume of 1.0 mL / min.

[0013] Step 4: Determination of Rhodium and Iridium Content in Carbonyl Alloy: The solution to be tested in Step 1, with Re as an internal standard, is injected simultaneously with the solution to be tested for determination. Data is collected using inductively coupled plasma mass spectrometry, and the determination results are calculated.

[0014] The beneficial effects of this invention are as follows:

[0015] During the use of this invention,

[0016] The invention includes steps such as sample processing, plotting working curves, optimizing experimental conditions, and accuracy experiments. It uses a fully automated graphite digester to dissolve carbonyl alloy samples, solving the problem that existing nickel matte assays require copper removal treatment to determine the content of rhodium and iridium in high-copper matrices, thus causing the loss of precious metals. This invention can quickly and accurately detect the content of rhodium and iridium in carbonyl alloys, providing a basis for material settlement. Detailed Implementation

[0017] The technical solution of the present invention will be described below in conjunction with the implementation method.

[0018] Example

[0019] Reagent preparation:

[0020] All reagents, unless otherwise specified, are of analytical grade. The solutions prepared and the water used for analysis are all high-purity water. Hydrochloric acid ρ = 1.19 g / mL; nitric acid ρ = 1.42 g / mL; perchloric acid ρ = 1.67 g / mL; hydrofluoric acid ρ = 1.15 g / mL; Rhodium and iridium mixed standard solution: a mixed element standard storage solution with a valid certificate is used, with a mass concentration of 100 μg / mL.

[0021] Rhenium standard solution: A single-element standard storage solution with a valid certificate was used, with a mass concentration of 1000 μg / mL;

[0022] Rhenium standard solution with a mass concentration of 10 μg / mL: Transfer 1 mL of rhenium standard solution to a 100 mL volumetric flask, add 5 mL of hydrochloric acid with a mass concentration of 1.19 g / mL, dilute with water to the mark, and mix well;

[0023] Internal standard solution: Transfer 1 mL of 10 μg / mL rhenium standard solution to a 1000 mL volumetric flask, add 5 mL of 1.19 g / mL hydrochloric acid, dilute with water to the mark, and mix well. This internal standard solution contains 10 μg of rhenium per L.

[0024] Instrument preparation:

[0025] The ICAP-Q inductively coupled plasma mass spectrometer manufactured by Thermo Fisher Scientific; the XS204 electronic balance manufactured by Mettler Toledo Ltd.; and the S60 fully automated graphite digester manufactured by LabTech.

[0026] A method for determining the recovery rate of rhodium and iridium in carbonyl alloys includes the following steps:

[0027] Step 1: Prepare the test solution: Weigh 0.500g of the sample into a polytetrafluoroethylene digestion tube, add 3mL of hydrofluoric acid (1.15g / mL), 8mL of nitric acid (1.42g / mL), and 3mL of perchloric acid (1.67g / mL) sequentially. Place the tube in a graphite furnace digester and heat to 80℃ for 20min, then to 120℃ for 30min, and finally to 180℃ for 160min. Evaporate the solution to a wet salt state, cool for 5min, add 10mL of hydrochloric acid (1.19g / mL) and 5mL of high-purity water, and heat for 5min. After cooling, transfer the solution to a 100mL volumetric flask, dilute to volume with water, and shake well. Transfer 5.00mL of the solution to a 100mL volumetric flask, add 5mL of hydrochloric acid (1.19g / mL), and dilute to volume with high-purity water. This is the test solution. Perform a blank test with the same sample.

[0028] The above steps use hydrofluoric acid with a mass concentration of 1.15 g / mL, nitric acid with a mass concentration of 1.42 g / mL, and perchloric acid with a mass concentration of 1.67 g / mL, which is sufficient to completely dissolve the sample. Since the noble metal in the carbonyl alloy exists in alloy form, and noble metals in alloy form are more easily dissolved by acid, the above dissolution method is applicable to carbonyl alloys.

[0029] In addition, since sufficient digestion time is retained at 180°C, the duration of temperature program holding time at 80°C and 120°C will not affect the sample dissolution state. In order to reduce the viscosity in the sample, perchloric acid needs to be removed as much as possible after the sample is completely decomposed. For the sake of fully dissolving the carbonyl alloy and the convenience of sample preparation, this embodiment selects the following digestion conditions: heating to 80°C and holding for 20 min, heating to 120°C and holding for 30 min, and heating to 180°C and holding for 160 min.

[0030] Step 2: Prepare the standard solution: Take 10.00 mL of a 100 μg / mL rhodium and iridium mixed standard solution into a 100 mL volumetric flask, add 5 mL of 1.19 g / mL hydrochloric acid, dilute with water to the mark, and mix well. The rhodium and iridium concentration of this solution is 10 μg / mL.

[0031] Specifically, the rhodium and iridium mixed standard solution refers to a mixed element standard storage solution with a valid certificate and a mass concentration of 100 μg / mL.

[0032] Transfer 1.00 mL of a rhodium and iridium mixed standard solution with a mass concentration of 10 μg / L to a 100 mL volumetric flask, add 5 mL of hydrochloric acid with a mass concentration of 1.19 g / L, dilute with water to the mark, and mix well. The mass concentration of rhodium and iridium in this solution is 100 μg / L.

[0033] Transfer 0 mL, 1.00 mL, 2.00 mL, 5.00 mL, 10.00 mL, and 20.00 mL of a 100 μg / L rhodium and iridium mixed standard solution to a set of 100 mL volumetric flasks, add 5 mL of 1.19 g / mL hydrochloric acid, dilute to volume with high-purity water, and shake well.

[0034] Step 3: Plotting the working curve: Calculate the mass concentration of the analyte in the standard solution: Measure the mass concentration of the analyte in the standard solution using inductively coupled plasma mass spectrometry (ICP-MS); Under the selected instrument operating conditions, add the internal standard to the test solution and the accompanying blank solution online. The instrument automatically calculates the mass concentration of the analyte in the test solution based on the working curve.

[0035] The operating parameters of the inductively coupled plasma mass spectrometer used in step three are as follows: nebulizer flow rate of 0.90 L / min, sampling depth of 130.0 mm, cooler flow rate of 13.00 L / min, auxiliary flow rate of 0.80 L / min, and sample liquid lifting volume of 1.0 mL / min.

[0036] Step 4: Determination of Rhodium and Iridium Content in Carbonyl Alloys: Ignite the instrument and, after stabilization, adjust all instrument parameters to optimal settings using tuning fluid. Use Re as an online internal standard, injecting it simultaneously with the sample to be tested. Introduce reagent blanks, standard series, and sample solutions into the instrument respectively. The computer collects data, plots a standard curve, calculates the regression equation, and provides the determination results.

[0037] During the operation of an inductively coupled plasma mass spectrometer, the settings of parameters such as nebulizer flow rate and sample liquid lift directly affect the determination of the analyte. The effects of each parameter on sensitivity were tested, and the instrument operating parameters were selected based on a comprehensive consideration of all factors, as shown in Table 1.

[0038] Table 1. Selection of Instrument Operating Parameters

[0039]

[0040] The carbonyl alloy comparative sample Gan C15926 was analyzed. This sample contains 400-500 g / t of silver, 200-300 g / t of gold, 500-600 g / t of platinum, and 330-400 g / t of palladium. The effect of the time of programmed temperature rise at different temperatures on the dissolution state of the sample was analyzed. The results are shown in Table 2.

[0041] Table 2. Effect of temperature program time on sample dissolution state at different temperatures.

[0042]

[0043] Table 2 shows that as long as sufficient digestion time is maintained at 180℃, the duration of the temperature program at 80℃ and 120℃ will not affect the sample's dissolution state. To reduce the viscosity of the sample, perchloric acid needs to be removed as much as possible after complete decomposition. For the sake of fully dissolving the carbonyl alloy and for ease of sample preparation, the following digestion conditions were selected: heating to 80℃ and holding for 20 min, heating to 120℃ and holding for 30 min, and heating to 180℃ and holding for 160 min.

[0044] To ensure complete dissolution of the sample, 3 mL of hydrofluoric acid (1.15 g / mL), 8 mL of nitric acid (1.42 g / mL), and 3 mL of perchloric acid (1.67 g / mL) were added. These are the dosages used in the graphite digester to dissolve the silver sample. Experiments show that these dosages are sufficient to completely dissolve the sample. The noble metal in carbonyl alloys exists in alloy form, which is more easily dissolved by acid. Therefore, this dissolution method is suitable for carbonyl alloys.

[0045] Different sample amounts of carbonyl alloy comparison sample Gan C15926 were weighed, and the influence of different sample amounts on the results was analyzed according to the analytical procedure, as shown in Table 3.

[0046] Table 3. Effect of different sample sizes on the results

[0047]

[0048] Different sample sizes did not show significant differences in results; however, when the sample size reached 2 grams, the added acid could not completely digest the sample due to its large volume. To ensure the concentration after fractionation was as close as possible to the middle of the curve, this embodiment selected a sample size of 0.500 grams.

[0049] When analyzing samples using ICP-MS, selecting appropriate spectral lines is crucial for ensuring analytical accuracy and precision. Typically, spectral interference in ICP-MS arises from the carrier gas, impurity gases within the carrier gas, and atomic and molecular ions formed by the solvent dissolving the sample in the plasma environment. Since the carbonyl alloy contains trace amounts of elements such as Y, In, Cd, and Bi, conventional elements cannot be used as internal standards. After full-spectrum elemental analysis, rhenium was found to be absent from the carbonyl alloy; therefore, Re187 was selected as the internal standard.

[0050] This embodiment uses the measurement mode in Table 2, and the spectral line selection results of all measured elements are shown in Table 4.

[0051] Table 4 Spectral lines of the elements being measured

[0052]

[0053] Carbonyl alloys mainly contain copper and nickel. The copper content can reach up to 65%, and the nickel content up to 15%. Standard solutions of copper, nickel, and rhodium / iridium with the same content as the test solution were prepared. Based on the principle of elemental interference in ICP-MS, the interference of copper and nickel solutions on rhodium and iridium elements in the standard mode and KED mode was analyzed. The results are shown in Table 5. Simultaneously, carbonyl alloy sample 15926 was selected as the research object to analyze the influence of different modes on the results of rhodium and iridium element determination in the carbonyl alloy. The results are shown in Table 6 below.

[0054] Table 5. Interference of copper and nickel solutions on rhodium and iridium elements in standard mode and KED mode.

[0055]

[0056] Table 6. Effects of different determination modes on the results of carbonyl alloys

[0057]

[0058] The test solution contained approximately 16 mg of copper and 4 mg of nickel. When using the standard mode, the presence of the matrix interfered with the determination of rhodium, resulting in an overestimation of the rhodium value. Iridium, however, was not affected by copper or nickel. Using the KED mode eliminated the interference from copper on rhodium. When determining rhodium in carbonyl alloys using the standard addition method, the results were consistent with those obtained using the KED mode. Iridium results remained unaffected regardless of the determination mode used. When the instrument lacks a KED mode, the standard addition method can be used to eliminate interference from the matrix.

[0059] The experiment used a blank sample and performed 11 measurements under the selected experimental conditions. The standard deviation σ of the analysis results was calculated, and the limit of detection was set at 3σ and the limit of determination was estimated at 10σ. The results are shown in Table 7.

[0060] Table 7 Detection limits for rhodium and iridium content in carbonyl alloys

[0061]

[0062] Following the analytical procedure, 11 parallel determinations were performed on rhodium and iridium in carbonyl alloy 15926, and the relative standard deviations (RSD) of each element were calculated. The results are shown in Table 8.

[0063] Table 8. Determination of Rhodium and Iridium Content and Precision Experiments in Carbonyl Alloys

[0064]

[0065] The relative standard deviation of Rh in the carbonyl alloy is 1.68%, and the relative standard deviation of iridium is 1.25%, indicating that the precision of this embodiment is relatively good.

[0066] Four portions of the same carbonyl alloy 15926 were taken. One portion was not spiked, and the other three portions were spiked. The samples were measured in parallel three times. The spiked recovery rate and relative standard deviation (RSD) were calculated based on the spiked amount and the measurement results. The results are shown in Table 9.

[0067] Table 9 Results of Spiked Recovery Experiment

[0068]

[0069]

[0070] The spiked recoveries of rhodium in the carbonyl alloy ranged from 95.86% to 104.71%, and the spiked recoveries of iridium ranged from 92.90% to 100.76%, which were good results.

[0071] Since there were no relevant rhodium and iridium standard samples for carbonyl alloys, this embodiment used a secondary alloy management sample with definite rhodium and iridium results. Both are alloy samples with similar properties. Accuracy experiments were conducted according to the analytical procedures. This sample contained the same amount of copper, but the silver content was higher than that of the carbonyl alloy. As long as the secondary alloy management sample is completely decomposed according to this embodiment and its rhodium and iridium content is accurately determined, the accuracy and reliability of this embodiment can be proven. The rhodium and iridium results of the secondary alloy management sample are shown in Table 10.

[0072] Table 10 Results of secondary alloy sample testing

[0073]

[0074] As shown in Table 10, the results of the secondary alloy management sample analysis using the method for analyzing rhodium and iridium elements in carbonyl alloys are consistent with the determined values, indicating that this embodiment is accurate and reliable.

[0075] The carbonyl alloy comparison samples C15915 and H34192 were compared using secondary alloy rhodium and iridium analysis methods, and the results are shown in Table 11.

[0076] Table 11 Comparison Results of Carbonyl Alloys

[0077]

[0078] The comparison results in Tables 10 and 11 show that the results of determining rhodium and iridium in carbonyl alloys using the wet direct dissolution-KED method are in good agreement with the results of the secondary alloy analysis method, and the results of rhodium and iridium are within the allowable error.

[0079] In summary, this embodiment is simple and easy to operate, eliminating the need for copper removal treatment required for determining rhodium and iridium in a high-copper matrix using the nickel matte assay method as in the original method. This saves time and effort. Furthermore, several experimental analyses have shown that the spiked recovery rate of rhodium in the carbonyl alloy is 95.86%–104.71%, and the spiked recovery rate of iridium is 92.90%–100.76%. The results of this embodiment are satisfactory and can meet the analytical testing requirements.

Claims

1. A method for determining the recovery rate of rhodium and iridium in carbonyl alloys, characterized in that, Includes the following steps: Step 1: Prepare the test solution: Weigh the sample and place it in a polytetrafluoroethylene digestion tube. Add hydrofluoric acid, nitric acid, and perchloric acid in sequence, then place it in a graphite furnace digester. Evaporate until it becomes a wet salt. After cooling, add hydrochloric acid and high-purity water, heat, and cool again. Transfer the test solution to a volumetric flask, dilute to volume with water, shake well, and aliquot the test solution into a volumetric flask. Add hydrochloric acid and dilute to volume with high-purity water to obtain the test solution. Step one includes: Weigh 0.500 g to 0.800 g of the sample into a polytetrafluoroethylene digestion tube. Add 3 to 8 mL of hydrofluoric acid (1.15 g / mL), 8 to 15 mL of nitric acid (1.42 g / mL), and 3 to 10 mL of perchloric acid (1.67 g / mL) sequentially. Place the tube in a graphite furnace digester and heat to 80°C for 20 to 60 min, then heat to 120°C for 30 to 60 min, and finally heat to 180°C and maintain the temperature. Evaporate the solution to a wet salt state for 160-200 minutes. After cooling for 5-20 minutes, add 10-30 mL of hydrochloric acid with a mass concentration of 1.19 g / mL and 5-20 mL of high-purity water and heat for 5 minutes. After cooling, transfer the test solution to a volumetric flask, dilute to volume with water, shake well, and take 5-10 mL of the test solution into a 100 mL volumetric flask. Add 5-12 mL of hydrochloric acid with a mass concentration of 1.19 g / mL and dilute to volume with high-purity water to obtain the test solution. Step 2: Preparation of standard solution: Take a portion of the rhodium and iridium mixed standard solution into a volumetric flask, add hydrochloric acid, dilute with water and mix well, continue to add hydrochloric acid, dilute with water and mix well, add hydrochloric acid again, make up to volume with high-purity water, and shake well. Step two includes: Take 10-20 mL of a 100 µg / mL rhodium and iridium mixed standard solution into a 100 mL volumetric flask, add 5-10 mL of 1.19 g / mL hydrochloric acid, dilute with water to the mark, and mix well. Transfer 1-10 mL of a 10 µg / mL rhodium and iridium mixed standard solution into a 100 mL volumetric flask, add 5-10 mL of 1.19 g / mL hydrochloric acid, dilute with water to the mark, and mix well. Transfer 0 mL, 1.00 mL, 2.00 mL, 5.00 mL, 10.00 mL, and 20.00 mL of a rhodium and iridium mixed standard solution with a mass concentration of 100 µL to 200 g / L to different volumetric flasks, add 5 to 10 mL of hydrochloric acid with a mass concentration of 1.19 g / mL, dilute to volume with high-purity water, and shake well. Step 3: Calculate the mass concentration of the analyte in the standard solution: Measure the mass concentration of the analyte in the standard solution using inductively coupled plasma mass spectrometry (ICP-MS). Step 4: Determination of Rhodium and Iridium Content in Carbonyl Alloy: The solution to be tested in Step 1, with Re as an internal standard, is injected simultaneously with the solution to be tested for determination. Data is collected using inductively coupled plasma mass spectrometry, and the determination results are calculated.

2. The method for determining the recovery rate of rhodium and iridium in carbonyl alloys according to claim 1, characterized in that, The operating parameters of the inductively coupled plasma mass spectrometer used in step three are as follows: nebulizer flow rate of 0.9~3L / min, sampling depth of 130~200mm, cooler flow rate of 13~20L / min, auxiliary flow rate of 0.8~2L / min, and sample liquid lifting volume of 1~2mL / min.

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