Method for determining recovery rate of rhodium and iridium in carbonylation alloy

Abstract

The invention provides a method for determining the recovery rate of rhodium and iridium in carbonylation alloy, which comprises the steps of sample treatment, working curve drawing, test condition optimization, accuracy test and the like, and comprises the following steps: dissolving a carbonylation alloy sample by adopting a full-automatic graphite digestion instrument; the method solves the problem of precious metal loss caused by copper removal treatment required for determination of rhodium and iridium in a high-copper matrix through nickel sulfonium assaying in the prior art, can rapidly and accurately detect the content of rhodium and iridium in the carbonylation alloy, and provides a basis for material settlement.

Description

Technical Field

[0001] The invention belongs to the technical field of precious metal detection and relates to a method for determining the recovery rate of rhodium and iridium in a carbonylation alloy. Background Art

[0002] Carbonyl alloy is the solid residue remaining after nickel is extracted from water-quenched alloy through carbonylation reaction in the carbonylation process. Since the water-quenched alloy contains 60% nickel and 20% copper, in the carbonylation process, the nickel in the raw material generates gaseous carbonyl and is separated, and the remaining metal elements such as copper, iron, cobalt, sulfur, gold, silver, platinum, palladium, osmium, ruthenium, rhodium, iridium, etc. are enriched in the tailings residue, wherein 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%, the content of precious metals such as gold and silver is as high as hundreds of grams per ton, and it is rich in platinum group precious metals such as platinum, palladium, osmium, ruthenium, rhodium, iridium, etc.

[0003] At present, carbonyl alloy is an important settlement material, especially the content of precious metal elements in carbonyl alloy involves the calculation of metal balance and carbonylation efficiency. The copper content in carbonyl alloy is relatively high. When the existing nickel matte assay method is used to analyze rhodium and iridium elements, the sample needs to spend a long time on the electric hot plate to dissolve the sample and remove copper. In the process of removing copper, the combination of precious metals and base metals will cause a small amount of rhodium and iridium elements to dissolve, resulting in losses. At the same time, if the traditional lead assay is used to enrich rhodium and iridium, these two elements are difficult to alloy due to their high melting points and cannot be accurately determined. Therefore, it can be seen that the existing technology cannot solve the above technical problems. Summary of the invention

[0004] The purpose of the present invention is to provide a method for determining the recovery rate of rhodium and iridium in carbonyl alloy in view of the problems existing in the prior art, thereby solving the problem that the existing nickel matte gold assay analysis method and the traditional lead gold assay technology cannot accurately determine the content of rhodium and iridium in carbonyl alloy.

[0005] To this end, the present invention adopts the following technical solutions:

[0006] A method for determining the recovery rate of rhodium and iridium in a carbonyl alloy comprises the following steps:

[0007] Step 1, prepare the test solution: weigh 0.500g sample into a polytetrafluoroethylene digestion tube, add 3mL of hydrofluoric acid with a mass concentration of 1.15g / mL, 8mL of nitric acid with a mass concentration of 1.42g / mL, and 3mL of perchloric acid with a mass concentration of 1.67g / mL in sequence, put it into a graphite furnace digestion instrument and heat it to 80℃ and keep it for 20min, heat it to 120℃ and keep it for 30min, heat it to 180℃ and keep it for 160min, evaporate the solution to wet salt, cool it for 5min, add 10mL of hydrochloric acid with a mass concentration of 1.19g / mL, 5mL of high-purity water and heat it for 5min, transfer the test solution to a 100mL volumetric flask after cooling, make up to volume with water, shake well, take 5.00mL of the test solution in a 100mL volumetric flask, add 5mL of hydrochloric acid with a mass concentration of 1.19g / mL, and make up to volume with high-purity water as the test solution.

[0008] Step 2, prepare standard solution: take 10.00mL of 100μg / mL rhodium and iridium mixed standard solution in a 100mL volumetric flask, add 5mL of 1.19g / mL hydrochloric acid, dilute to scale with water, mix well, the rhodium and iridium mass concentration of this solution is 10μg / mL;

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

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

[0011] Step 3: Calculate the mass concentration of the element to be measured in the standard solution: Use inductively coupled plasma mass spectrometry to measure the mass concentration of the element to be measured in the standard solution;

[0012] The operating parameters of the inductively coupled plasma mass spectrometer used in the inductively coupled plasma mass spectrometer method in step three are: a nebulizer flow rate of 0.90 L / min, a sampling depth of 130.0 mm, a cooler flow rate of 13.00 L / min, an auxiliary flow rate of 0.80 L / min, and a test solution lift of 1.0 mL / rain.

[0013] Step 4: Determination of rhodium and iridium content in carbonyl alloy: The solution to be tested in step 1 is injected with Re as the internal standard substance at the same time as the solution to be tested for determination, and data is collected using an inductively coupled plasma mass spectrometer to calculate the determination results.

[0014] The beneficial effects of the present invention are:

[0015] During use of the present invention,

[0016] The method comprises the steps of sample processing, drawing working curve, optimizing test conditions, accuracy experiment and the like, adopts a fully automatic graphite digester to dissolve the carbonyl alloy sample, solves the problem that the existing nickel matte assay for determining rhodium and iridium in a high-copper matrix requires copper removal treatment, thereby causing loss of precious metals. The method can quickly and accurately detect the content of rhodium and iridium in the carbonyl alloy, and provide a basis for material settlement. DETAILED DESCRIPTION

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

[0018] Example

[0019] Reagent preparation:

[0020] All reagents are of analytical grade unless otherwise specified. High-purity water is used for preparing solutions and analyzing 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: use a mixed element standard storage solution with a certificate within the validity period, with a mass concentration of 100 μg / mL.

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

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

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

[0024] Instrument preparation:

[0025] ICAP-Q inductively coupled plasma mass spectrometer manufactured by Thermo Fisher Scientific; XS204 electronic balance manufactured by Mettler-Toledo Ltd.; S60 fully automatic graphite digestion instrument manufactured by Labtech.

[0026] A method for determining the recovery rate of rhodium and iridium in a carbonyl alloy comprises the following steps:

[0027] Step 1, prepare the test solution: weigh 0.500g sample into a polytetrafluoroethylene digestion tube, add 3mL of hydrofluoric acid with a mass concentration of 1.15g / mL, 8mL of nitric acid with a mass concentration of 1.42g / mL, and 3mL of perchloric acid with a mass concentration of 1.67g / mL in sequence, put it into a graphite furnace digestion instrument and heat it to 80℃ and keep it for 20min, heat it to 120℃ and keep it for 30min, heat it to 180℃ and keep it for 160min, evaporate the solution to wet salt, cool it for 5min, add 10mL of hydrochloric acid with a mass concentration of 1.19g / mL, 5mL of high-purity water and heat it for 5min, transfer the test solution to a 100mL volumetric flask after cooling, make up to volume with water, shake well, take 5.00mL of the test solution in a 100mL volumetric flask, add 5mL of hydrochloric acid with a mass concentration of 1.19g / mL, make up to volume with high-purity water, as the test solution, and carry out a blank test with the sample.

[0028] In the above steps, 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 are used, which are sufficient to completely dissolve the sample. Since the precious metals of the carbonyl alloy exist in the form of alloys, the precious metals in the form of alloys are more easily dissolved by acid. Therefore, the above dissolution method is suitable for carbonyl alloys.

[0029] In addition, since sufficient digestion time is retained at 180° C., the length of the program temperature retention time at 80° C. and 120° C. will not affect the state of sample dissolution. In order to reduce the viscosity in the sample, it is necessary to drive out the perchloric acid as much as possible when the sample is completely decomposed. In order to fully dissolve the carbonyl alloy and facilitate sample preparation, the present embodiment selects the digestion conditions of heating to 80° C. and holding for 20 minutes, heating to 120° C. and holding for 30 minutes, and heating to 180° C. and holding for 160 minutes.

[0030] Step 2, prepare standard solution: take 10.00mL of 100μg / mL rhodium and iridium mixed standard solution in a 100mL volumetric flask, add 5mL of 1.19g / mL hydrochloric acid, dilute to scale with water, mix well, the rhodium and iridium mass concentration of this solution is 10μg / mL;

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

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

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

[0034] Step 3. Drawing of working curve: Calculation of mass concentration of the measured element in the standard solution: Use inductively coupled plasma mass spectrometry to measure the mass concentration of the measured element in the standard solution; Under the selected instrument working conditions, online addition of internal standard measurement test solution and accompanying sample blank solution is adopted. The instrument automatically calculates the mass concentration of the measured element in the test solution according to the working curve.

[0035] The operating parameters of the inductively coupled plasma mass spectrometer used in the inductively coupled plasma mass spectrometer method in step three are: a nebulizer flow rate of 0.90 L / min, a sampling depth of 130.0 mm, a cooler flow rate of 13.00 L / min, an auxiliary flow rate of 0.80 L / min, and a test solution lift of 1.0 mL / rain.

[0036] Step 4, determination of rhodium and iridium content in carbonyl alloy: ignite the instrument, and after stabilization, use tuning solution to adjust the instrument indicators to the optimal state, use Re as the online internal standard substance, and inject it at the same time as the sample to be tested for determination. Introduce the reagent blank, standard series, and sample solution into the instrument respectively, collect data by computer, draw standard curve, calculate regression equation, and give the determination result.

[0037] During the operation of the inductively coupled plasma mass spectrometer, the settings of parameters such as the nebulizer flow rate and the test solution lifting amount have a direct impact on the determination of the elements to be measured. The influence of each parameter on the sensitivity was tested. Comprehensively considering various factors, the instrument working parameters are selected as shown in Table 1.

[0038] Table 1 Instrument working parameter selection

[0039]

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

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

[0042]

[0043] As can be seen from Table 2, as long as sufficient digestion time is retained at 180℃, the retention time of the program temperature rise at 80℃ and 120℃ will not affect the state of sample dissolution. In order to reduce the viscosity of the sample, it is necessary to drive out the perchloric acid as much as possible when the sample is completely decomposed. In order to fully dissolve the carbonyl alloy and facilitate sample preparation, the experiment selected the digestion conditions of heating to 80℃ and holding for 20 minutes, heating to 120℃ and holding for 30 minutes, and heating to 180℃ and holding for 160 minutes.

[0044] In order to completely dissolve the sample, 3 mL of hydrofluoric acid with a mass concentration of 1.15 g / mL, 8 mL of nitric acid with a mass concentration of 1.42 g / mL, and 3 mL of perchloric acid with a mass concentration of 1.67 g / mL were added respectively. This is the dosage of the graphite digester to dissolve the silver sample. Experiments show that these dosages of reagents are sufficient to completely dissolve the sample. The precious metals of the carbonyl alloy exist in the form of alloys, and the precious metals in the form of alloys are easier to be dissolved by acid. Therefore, this dissolution method is suitable for carbonyl alloys.

[0045] Weigh different amounts of carbonyl alloy comparison sample Gan C15926 and analyze the influence of different sample amounts on the results according to the analysis steps. See Table 3.

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

[0047]

[0048] The results of different sample weights are not very different. When the sample weight reaches 2 grams, the added acid cannot completely digest the sample because of its large sample volume. Considering that the concentration after fractionation is as close to the middle of the curve as possible, 0.500 grams of sample is selected in this embodiment.

[0049] When using ICP-MS to analyze samples, choosing the right spectrum is an important prerequisite to ensure the accuracy and precision of the analysis. Under normal circumstances, the types of spectrum interference in ICP-MS include the spectrum interference of the atomic ions and molecular ions formed by the carrier gas, impurity gases in the carrier gas, and the solvent that dissolves the sample in the plasma environment on the measured elements. Since carbonyl alloys contain a small amount of Y, In, Cd, Bi and other elements, conventional elements cannot be used as internal standards. After full spectrum analysis of the elements, there is no rhenium element in the carbonyl alloy, so Re187 is selected as the internal standard.

[0050] This example adopts the mode in Table 2 for determination, and the spectral line selection results of all the measured elements are shown in Table 4.

[0051] Table 4 Spectral lines of measured elements

[0052]

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

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

[0055]

[0056] Table 6 Effect of different measurement modes on carbonyl alloy results

[0057]

[0058] There are about 16 mg of copper and 4 mg of nickel in the solution to be tested. When the standard mode is used, the presence of the matrix will interfere with the determination of rhodium, and the result of rhodium will be high. The iridium element is not interfered by copper and nickel. The KED mode can eliminate the interference of copper on rhodium. When the standard addition method is used to determine rhodium in carbonyl alloy, the result is consistent with the KED mode determination result. The result of iridium element is not affected by which determination mode is used. When the instrument does not have the KED mode, the standard addition method can be used to eliminate the interference caused by the presence of the matrix.

[0059] The test selected a sample blank and carried out 11 measurements under the selected test conditions. The standard deviation σ of the analysis results was calculated, 3σ was used as the detection limit, and 10σ was used to estimate the lower limit of determination. The results are shown in Table 7.

[0060] Table 7 Detection limits of rhodium and iridium in carbonyl alloy

[0061]

[0062] According to the analytical method, rhodium and iridium in carbonyl alloy 15926 were measured 11 times in parallel, and the relative standard deviation (RSD) of each element was calculated. The results are shown in Table 8.

[0063] Table 8 Determination of rhodium and iridium content in carbonyl alloy and precision experiment

[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%. The precision of this embodiment is relatively good.

[0066] Four portions of the same sample of carbonyl alloy 15926 were taken, one portion was not spiked, and the other three were spiked. The sample was measured three times in parallel, and the spike recovery 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 Spike recovery test results

[0068]

[0069]

[0070] The recovery rates of the rhodium element in the carbonyl alloy by adding standard addition were between 95.86% and 104.71%, and the recovery rates of the iridium element by adding standard addition were between 92.90% and 100.76%, and the results were good.

[0071] Since there is no relevant carbonyl alloy rhodium and iridium element standard sample, this embodiment uses a secondary alloy management sample with a fixed rhodium and iridium result. Both are alloy samples with similar properties. According to the analysis steps, the accuracy experiment is carried out. The sample contains the same content of copper element and the silver element content is 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 proved. The rhodium and iridium results of the secondary alloy management sample are shown in Table 10.

[0072] Table 10 Test results of secondary alloy management samples

[0073]

[0074] As can be seen from Table 10, the results of dissolving and measuring the secondary alloy management sample according to the analytical method of rhodium and iridium elements in carbonyl alloy are consistent with the set value, and this embodiment is accurate and reliable.

[0075] The carbonyl alloy comparison samples Gan C15915 and Gan H34192 were compared according to the secondary alloy rhodium and iridium analysis method. The results are shown in Table 11.

[0076] Table 11 Carbonyl alloy comparison results

[0077]

[0078] From the comparison results of Table 10 and Table 11, it can be seen that the results of the determination of rhodium and iridium in carbonyl alloy by wet direct dissolution-KED are consistent with the results of the secondary alloy analysis method, and the results of rhodium and iridium are within the allowable error.

[0079] In summary, the present embodiment is simple and easy to operate, and does not require the step of copper removal for determining rhodium and iridium in a high-copper matrix by nickel matte gold assay as in the original method, which saves time and effort. At the same time, after several experimental analyses, the recovery rate of the rhodium element in the carbonyl alloy is 95.86% to 104.71%, and the recovery rate of the iridium element is 92.90% to 100.76%. The results of the present embodiment are satisfactory and can meet the analysis and testing requirements.

Claims

1. A method for determining the recovery rate of rhodium and iridium in carbonyl alloy, characterized in that: The following steps are involved: Step 1, prepare the test solution: weigh the sample, put it into a polytetrafluoroethylene digestion tube, add hydrofluoric acid, nitric acid, and perchloric acid in sequence, and put it into a graphite furnace digestion instrument, steam until wet salt, add hydrochloric acid and high-purity water after cooling, heat, cool again, transfer the test solution to a volumetric flask, make up to volume with water, shake well, take the test solution into a volumetric flask, add hydrochloric acid, and make up to volume with high-purity water as the test solution; Step 2, prepare standard solution: take the mixed standard solution of rhodium and iridium in 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 3: Calculate the mass concentration of the element to be measured in the standard solution: Use inductively coupled plasma mass spectrometry to measure the mass concentration of the element to be measured in the standard solution; Step 4: Determination of rhodium and iridium content in carbonyl alloy: The solution to be tested in step 1 is injected with Re as the internal standard substance at the same time as the solution to be tested for determination, and data is collected using an inductively coupled plasma mass spectrometer to calculate the determination results.

2. The method for determining the recovery rate of rhodium and iridium in a carbonyl alloy according to claim 1, characterized in that: The step one comprises: Weigh 0.500g~0.800g of sample into a polytetrafluoroethylene digestion tube, add 3~8mL of hydrofluoric acid with a mass concentration of 1.15g / mL, 8~15mL of nitric acid with a mass concentration of 1.42g / mL, and 3~10mL of perchloric acid with a mass concentration of 1.67g / mL in sequence, put it into a graphite furnace digestion instrument, heat it to 80℃ and keep it for 20~60min, heat it to 120℃ and keep it for 30~60min, heat it to 180℃ and keep it for 160-200 min, evaporate the solution to wet salt state, cool for 5-20 min, add 10-30 mL of 1.19 g / mL hydrochloric acid and 5-20 mL of high-purity water and heat for 5 min. After cooling, transfer the test solution to a volumetric flask, make up to volume with water, shake well, take 5-10 mL of the test solution in a 100 mL volumetric flask, add 5-12 mL of 1.19 g / mL hydrochloric acid, make up to volume with high-purity water, and use the test solution.

3. The method for determining the recovery rate of rhodium and iridium in a carbonyl alloy according to claim 1, characterized in that: The second step comprises: Take 10-20 mL of a mixed standard solution of rhodium and iridium with a mass concentration of 100 μg / mL in a 100 mL volumetric flask, add 5-10 mL of hydrochloric acid with a mass concentration of 1.19 g / mL, dilute to the scale with water, and mix well; Pipette 1-10 mL of a 10 μg / mL mixed standard solution of rhodium and iridium into a 100 mL volumetric flask, add 5-10 mL of 1.19 g / mL hydrochloric acid, dilute to the mark with water, and mix well. Pipette 0mL, 1.00mL, 2.00mL, 5.00mL, 10.00mL, and 20.00mL of a mixed standard solution of rhodium and iridium with a mass concentration of 100μ~200g / L into different volumetric flasks, add 5~10mL of hydrochloric acid with a mass concentration of 1.19g / mL, make up to volume with high-purity water, and shake well.

4. The method for determining the recovery rate of rhodium and iridium in a carbonyl alloy according to claim 1, characterized in that: The working parameters of the inductively coupled plasma mass spectrometer used in the inductively coupled plasma mass spectrometer method in step three are: a nebulizer flow rate of 0.9 to 3 L / min, a sampling depth of 130 to 200 mm, a cooler flow rate of 13 to 20 L / min, an auxiliary flow rate of 0.8 to 2 L / min, and a test solution lifting amount of 1 to 2 mL / rain.

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