Method for determining rhodium content in a platinum-rhodium alloy

Abstract

The present invention provides a method for determining the rhodium content in a platinum-rhodium alloy, the method comprising: completely dissolving the platinum-rhodium alloy, then mixing and reacting with nitrite, adjusting the pH, performing solid-liquid separation, and obtaining a platinum-rhodium mixed solution; mixing the platinum-rhodium mixed solution with a coordination precipitant and a polar solvent in turn, performing solid-liquid separation, obtaining a rhodium precipitate, and calculating the rhodium content in the platinum-rhodium alloy by mass calculation of the rhodium precipitate. The determination method of the present invention avoids the measurement error introduced by metal impurities in the platinum-rhodium alloy, and also avoids trace residues of rhodium precipitates in the solution and other interfering metal co-precipitations. The process and reagents used are simple, the operation is safe, and the efficiency is high. The use of high-cost and complex precipitants such as metal elements or hexaammine cobalt nitrate in the prior art is avoided. The rhodium precipitation is complete, the determination result is accurate, and the relative standard deviation is especially less than 0.21%. At the same time, there is no need to rely on expensive analytical equipment, and it has great application value.

Description

Technical Field

[0001] The present invention belongs to the technical field of metal material testing, and relates to a method for determining noble metal elements, and particularly to a method for determining the rhodium content in a platinum-rhodium alloy. Background Art

[0002] Noble metal rhodium and its alloys and compounds are widely used in fields such as petrochemical industry, glass fiber, electroplating, green catalysis, and jewelry. During the application and recycling of rhodium metal resources, it is necessary to accurately measure its weight percentage.

[0003] Currently, the detection methods for the rhodium content in rhodium alloys and compounds mainly include spectrometry, titration method, gravimetric method, etc. The spectrometry method generally dissolves the rhodium alloy or compound and uses a spectrometer to determine the rhodium content in the solution, such as atomic absorption spectrometry (AAS), X-ray fluorescence spectrometry (XRF), inductively coupled plasma atomic emission spectrometry (ICP-AES), etc., such as CN111999150A, CN115452807A, CN117054401A, etc. However, the spectrometry method often relies on expensive analytical equipment, and the result analysis is relatively complex, and there are problems such as element interference. The titration method usually has problems in endpoint judgment, and the error of manual judgment is relatively large. The gravimetric method mainly uses the methods of liquid-phase reduction or coordination compounds, and calculates the rhodium content through the precipitation of rhodium metal or rhodium complex. The gravimetric method has a wide measurement range, high measurement accuracy, and less equipment dependence, and is a widely recognized measurement method.

[0004] The industry standard method YS / T 561-2009 (Chemical analysis method for noble metal alloys - Determination of rhodium content in platinum-rhodium alloys) uses cobalt hexammine nitrate to generate a double salt precipitate with rhodium for determination. This method is generally applicable to samples with a single system, not suitable for the analysis of samples with a high impurity content, and has disadvantages such as the preparation process of the raw and auxiliary material cobalt hexammine nitrate requires the use of explosive chemicals, the preparation process is complex, and the yield is low. The rhodium complex has a certain solubility in the solution, and it cannot ensure complete precipitation. CN113075200A discloses a method for determining the platinum and rhodium contents in a platinum-rhodium mixed solution. The platinum-rhodium mixed solution is precipitated and calcined multiple times through a saturated ammonium chloride solution to first obtain sponge platinum, then the rhodium precipitate is obtained through reduction with magnesium powder, and then the rhodium metal is obtained through calcination and reduction with hydrogen, and the weights are calculated separately. The process of this method is relatively complex, and there are problems such as the metal reducing agent is easily wrapped in the rhodium precipitate, rhodium coprecipitation is easily caused when separating platinum by ammonium chloride precipitation, and rhodium evaporation loss is caused by multiple dissolutions of rhodium.

[0005] Therefore, due to the deficiencies of the existing technology, the present invention provides a method for determining the rhodium content with high measurement accuracy and simplified processes based on the precipitation method. Summary of the Invention

[0006] In view of the shortcomings of the prior art, the purpose of the present invention is to provide a method for determining the rhodium content in a platinum-rhodium alloy, which determines the rhodium content in the platinum-rhodium alloy based on the weight method, effectively eliminates the interference of impurity metals in the platinum-rhodium alloy, and has high determination accuracy.

[0007] To achieve this object, the present invention adopts the following technical solutions:

[0008] The present invention provides a method for determining the rhodium content in a platinum-rhodium alloy, the method comprising the following steps:

[0009] (1) completely dissolving the platinum-rhodium alloy to obtain a metal chloric acid solution;

[0010] (2) mixing the metal chlorate solution obtained in step (1) with nitrite, adjusting the pH, standing for reaction, and then performing a first solid-liquid separation to obtain a platinum-rhodium mixed solution;

[0011] (3) The platinum-rhodium mixed solution obtained in step (2) is mixed with a coordination precipitant for precipitation, and then mixed with a polar solvent. After standing for precipitation, a second solid-liquid separation is performed to obtain a rhodium precipitate. The rhodium precipitate is dried to a constant weight, and the rhodium content in the platinum-rhodium alloy is calculated based on the mass of the rhodium precipitate.

[0012] The determination method provided by the present invention dissolves the platinum-rhodium alloy, and after obtaining the solution, first uses nitrite to react the impurity metal ions in the platinum-rhodium alloy such as iron, copper and nickel in the solution to generate feasible nitroso complexes to form precipitation, separate and remove, and eliminate the interference of subsequent impurity metals; then uses a coordination precipitant to form a rhodium compound into a rhodium complex hexanitrorhodate (potassium hexanitrorhodate or ammonium hexanitrorhodate) to selectively precipitate rhodium, at this time, the platinum compound is in a dissolved state, and then by adding a polar solvent, the solubility difference of the rhodium complex in the solution and the polar solvent is used to completely precipitate the rhodium complex remaining in the solution, and finally all rhodium is converted into a rhodium complex precipitate and separated, and the rhodium content in the platinum-rhodium alloy is calculated by the total mass of the final rhodium complex precipitate. The determination method of the present invention has simple procedures and reagents, safe operation, high efficiency, avoids the use of high-cost and complex precipitants such as metal elements or hexaammine cobalt nitrate in the prior art, platinum and rhodium are completely separated, rhodium is completely precipitated, loss is small, and the determination result is accurate. At the same time, it does not need to rely on expensive analytical equipment, and has great application value.

[0013] Preferably, the dissolving method in step (1) comprises: mixing the platinum-rhodium alloy powder with a mixed acid, performing microwave digestion, and then fixing the volume with water.

[0014] Preferably, the mixed acid comprises hydrochloric acid and hydrogen peroxide.

[0015] In the present invention, the mass concentration of the hydrochloric acid is 36%.

[0016] Preferably, the volume ratio of the hydrochloric acid to the hydrogen peroxide is (1 - 3):1. For example, it can be 1:1, 1.5:1, 2:1, 2.5:1, or 3:1, but is not limited to the listed values. Other unlisted values within the numerical range are equally applicable.

[0017] Preferably, the mass ratio of the platinum-rhodium alloy powder to the mixed acid is (1 - 50):400. For example, it can be 1:400, 5:400, 10:400, 20:400, 30:400, 40:400, or 50:400, but is not limited to the listed values. Other unlisted values within the numerical range are equally applicable.

[0018] Preferably, the temperature of the microwave digestion is 100 - 200 °C. For example, it can be 100 °C, 110 °C, 120 °C, 130 °C, 140 °C, 150 °C, 160 °C, 170 °C, 180 °C, 190 °C, or 200 °C, but is not limited to the listed values. Other unlisted values within the numerical range are equally applicable.

[0019] Preferably, the time of the microwave digestion is 0.5 - 2 days. For example, it can be 0.5 days, 1 day, 1.5 days, or 2 days, but is not limited to the listed values. Other unlisted values within the numerical range are equally applicable.

[0020] Preferably, the mass ratio of the mixed acid to the water is (1 - 10):50. For example, it can be 1:50, 2:50, 3:50, 4:50, 5:50, 6:50, 7:50, 8:50, 9:50, or 10:50, but is not limited to the listed values. Other unlisted values within the numerical range are equally applicable.

[0021] Preferably, the mass ratio of the nitrite to the platinum-rhodium alloy in step (2) is (10 - 50):1. For example, it can be 10:1, 15:1, 20:1, 25:1, 30:1, 35:1, 40:1, 45:1, or 50:1, but is not limited to the listed values. Other unlisted values within the numerical range are equally applicable.

[0022] Preferably, the nitrite in step (2) includes sodium nitrite.

[0023] Preferably, the temperature of the mixing in step (2) is 50 - 90 °C. For example, it can be 50 °C, 55 °C, 60 °C, 65 °C, 70 °C, 75 °C, 80 °C, 85 °C, or 90 °C, but is not limited to the listed values. Other unlisted values within the numerical range are equally applicable.

[0024] Preferably, the pH adjustment in step (2) is 6 - 10. For example, it can be 6, 6.5, 7, 7.5, 8, 8.5, 9, 9.5 or 10, but is not limited to the listed values. Other unlisted values within the numerical range are equally applicable.

[0025] Preferably, the pH regulator used in step (2) includes any one or a combination of at least two of sodium carbonate, sodium hydroxide or sodium bicarbonate. Typical but non - restrictive combinations include the combination of sodium carbonate and sodium hydroxide, the combination of sodium hydroxide and sodium bicarbonate, the combination of sodium carbonate and sodium bicarbonate, or the combination of sodium carbonate, sodium hydroxide and sodium bicarbonate.

[0026] Preferably, the time for the static reaction in step (2) is 0.5 - 3 h. For example, it can be 0.5 h, 1 h, 1.5 h, 2 h, 2.5 h or 3 h, but is not limited to the listed values. Other unlisted values within the numerical range are equally applicable.

[0027] Preferably, a glass - sand - core funnel is used for the first solid - liquid separation in step (2).

[0028] Preferably, the complexing precipitant in step (3) includes any one or a combination of at least two of ammonium chloride, potassium chloride, potassium carbonate, ammonium carbonate or potassium hydroxide. Typical but non - restrictive combinations include the combination of ammonium chloride and potassium chloride, the combination of potassium chloride and potassium carbonate, the combination of potassium carbonate and ammonium carbonate, the combination of ammonium carbonate and potassium hydroxide, the combination of ammonium chloride, potassium chloride and potassium carbonate, or the combination of potassium carbonate, ammonium carbonate and potassium hydroxide.

[0029] Preferably, the mass ratio of the complexing precipitant to the platinum - rhodium alloy in step (3) is (10 - 50):1. For example, it can be 10:1, 15:1, 20:1, 25:1, 30:1, 35:1, 40:1, 45:1 or 50:1, but is not limited to the listed values. Other unlisted values within the numerical range are equally applicable.

[0030] Preferably, the temperature of the precipitation in step (3) is 60 - 100 °C. For example, it can be 60 °C, 65 °C, 70 °C, 75 °C, 80 °C, 85 °C, 90 °C, 95 °C or 100 °C, but is not limited to the listed values. Other unlisted values within the numerical range are equally applicable.

[0031] Preferably, the polar solvent in step (3) includes any one or a combination of at least two of absolute ethanol, acetonitrile or methanol. Typical but non - restrictive combinations include the combination of absolute ethanol and acetonitrile, the combination of acetonitrile and methanol, the combination of absolute ethanol and methanol, or the combination of absolute ethanol, acetonitrile and methanol.

[0032] Preferably, the volume ratio of the polar solvent to the platinum-rhodium mixed solution in step (3) is 1:(5-20), for example, it can be 1:5, 1:8, 1:10, 1:12, 1:15, 1:18 or 1:20, but is not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0033] Preferably, the temperature for static precipitation in step (3) is 0-20°C, for example, it can be 0°C, 2°C, 5°C, 8°C, 10°C, 12°C, 15°C, 18°C or 20°C, but is not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0034] Preferably, the time for static precipitation in step (3) is 0.5-3 h, for example, it can be 0.5 h, 1 h, 1.5 h, 2 h, 2.5 h or 3 h, but is not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0035] Preferably, the temperature for drying in step (3) is 70-150°C, for example, it can be 70°C, 80°C, 90°C, 100°C, 110°C, 120°C, 130°C, 140°C or 150°C, but is not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0036] Preferably, the calculation formula for the rhodium content in step (3) is as follows:

[0037]

[0038] Wherein, ω is the rhodium content in the platinum-rhodium alloy; m 1 is the weight of the rhodium precipitate, in g; m is the weight of the platinum-rhodium alloy, in g; α is the factor for converting the rhodium precipitate into rhodium element.

[0039] In the present invention, when the rhodium precipitate is potassium hexanitrorhodate complex, α is 0.20736; when the rhodium precipitate is ammonium hexanitrorhodate complex, α is 0.23761.

[0040] As a preferred technical solution of the determination method provided by the present invention, the determination method includes the following steps:

[0041] (1) Mix the platinum-rhodium alloy powder with a mixed acid for microwave digestion. The composition of the mixed acid includes hydrochloric acid and hydrogen peroxide. The volume ratio of hydrochloric acid to hydrogen peroxide is (1-3):1. The mass ratio of the platinum-rhodium alloy powder to the mixed acid is (1-50):400. The temperature of the microwave digestion is 100-200°C, and the time of the microwave digestion is 0.5-2 days. After microwave digestion, dilute the digested solution with water to a fixed volume. The mass ratio of the mixed acid to water is (1-10):50 to obtain a metal chloric acid solution.

[0042] (2) Mix the metal chloric acid solution obtained in step (1) with sodium nitrite. The mass ratio of sodium nitrite to the platinum-rhodium alloy powder is (10-50):1. The mixing temperature is 50-90°C. Add a pH regulator to adjust the pH to 6-10. The pH regulator includes any one or a combination of at least two of sodium carbonate, sodium hydroxide, or sodium bicarbonate. Let it stand and react for 0.5-3 h. The impurity metals in the platinum-rhodium alloy form nitroso complexes and precipitate. Then use a glass sand core funnel for solid-liquid separation to obtain a platinum-rhodium mixed solution.

[0043] (3) Mix the platinum-rhodium mixed solution obtained in step (2) with a coordination precipitant. The coordination precipitant includes any one or a combination of at least two of ammonium chloride, potassium chloride, potassium carbonate, ammonium carbonate, or potassium hydroxide. The mass ratio of the coordination precipitant to the platinum-rhodium alloy powder is (10-50):1. Carry out a coordination reaction at 60-100°C to obtain a mixture. Then mix the mixture with a polar solvent. The polar solvent includes any one or a combination of at least two of anhydrous ethanol, acetonitrile, or methanol. The volume ratio of the polar solvent to the platinum-rhodium mixed solution is 1:(5-20). After mixing, let it stand and precipitate at 0-20°C for 0.5-3 h. After the standing precipitation ends, carry out solid-liquid separation to obtain a precipitate. Dry the precipitate to a constant weight. The drying temperature is 70-150°C. After drying, obtain a rhodium precipitate.

[0044] (4) Weigh the rhodium precipitate obtained in step (3), and calculate the rhodium content in the platinum-rhodium alloy through the mass of the rhodium precipitate. The calculation formula is as follows:

[0045]

[0046] Among them, ω is the rhodium content in the platinum-rhodium alloy; m 1 is the weight of the rhodium precipitate, in g; m is the weight of the platinum-rhodium alloy, in g; α is the factor for converting the rhodium precipitate into rhodium element.

[0047] Compared with the prior art, the beneficial effects of the present invention are:

[0048] The determination method of the present invention avoids the measurement error introduced by metal impurities such as copper and iron in the platinum-rhodium alloy, and also avoids trace residues of rhodium precipitate in the solution and co-precipitation of other interfering metals. The process and reagents used are simple, the operation is safe, and the efficiency is high. The use of high-cost and complex precipitants such as metal elements or hexaamminecobalt nitrate in the prior art is avoided. The rhodium precipitation is complete, the determination result is accurate, and the relative standard deviation is especially less than 0.21%. At the same time, there is no need to rely on expensive analytical equipment, and the method has great application value. DETAILED DESCRIPTION

[0049] The technical solution of the present invention is further illustrated below through specific implementation methods. Embodiment 1

[0050] This embodiment provides a method for determining the rhodium content in a platinum-rhodium alloy, the method comprising the following steps:

[0051] (1) 0.2 g of platinum-rhodium alloy powder was placed in a microwave digestion apparatus, and a mixed acid of 15 mL of hydrochloric acid and 5 mL of hydrogen peroxide was added, wherein the volume ratio of hydrochloric acid to hydrogen peroxide was 3:1, and the mass ratio of platinum-rhodium alloy powder to mixed acid was 1:126. The mixture was heated to 160° C. for digestion until the material was completely dissolved, and then 300 mL of pure water was added to make up the volume, wherein the mass ratio of mixed acid to pure water was 1:12, to obtain a metal chloride solution;

[0052] (2) Weigh 8 g of sodium nitrite and add it to a metal chloric acid solution, with the mass ratio of sodium nitrite to platinum-rhodium alloy powder being 40:1. Heat to 50° C., stir, add sodium hydroxide to adjust the pH to 8, and allow to react for 3 h.

[0053] (3) Filter the solution after the reaction using a G4 glass sand core funnel to remove metal impurities, repeat this step twice until no precipitate remains in the solution to obtain a platinum-rhodium metal filtrate;

[0054] (4) Weigh 10 g of potassium chloride as a coordination precipitant, add the platinum-rhodium metal filtrate, the mass ratio of the coordination precipitant to the platinum-rhodium alloy powder is 50:1, heat to 90° C. until no more precipitate continues to precipitate, and then cool to room temperature;

[0055] (5) Measure 20 mL of polar solvent anhydrous ethanol and add it to the solution of step (4), the volume ratio of the polar solvent to the platinum-rhodium mixed solution is 1:20, stir evenly, control the solution temperature at 0°C, and let it stand for 0.5 h;

[0056] (6) All materials in step (5) are filtered to obtain a precipitate, which is placed in an oven at 150° C. and dried to constant weight. The weight of the rhodium precipitate after drying is weighed. The composition of the rhodium precipitate is potassium hexanitrorhodate. The rhodium content is calculated according to the formula:

[0057]

[0058] Among them, ω is the rhodium content in the platinum-rhodium alloy; m 1 is the weight of the rhodium precipitate, in g; m is the weight of the platinum-rhodium alloy, in g; 0.20736 is the factor for converting the rhodium precipitate to rhodium. Example 2

[0059] This example provides a method for determining the rhodium content in a platinum-rhodium alloy. The determination method includes the following steps:

[0060] (1) Place 0.2 g of platinum-rhodium alloy powder in a microwave digestion instrument, add a mixed acid of 20 mL of hydrochloric acid and 15 mL of hydrogen peroxide. The volume ratio of hydrochloric acid to hydrogen peroxide is 1.3:1, and the mass ratio of platinum-rhodium alloy powder to the mixed acid is 1:228. Heat to 200 °C for digestion. After the material is completely dissolved, add 300 mL of pure water for constant volume. The mass ratio of the mixed acid to pure water is 1:6.6 to obtain a metal chloric acid solution;

[0061] (2) Weigh 3 g of sodium nitrite and add it to the metal chloric acid solution. The mass ratio of sodium nitrite to platinum-rhodium alloy powder is 15:1. Heat to 85 °C, stir, add sodium hydroxide to adjust the pH to 10, and then let it stand for reaction for 1 h;

[0062] (3) Filter the solution after standing reaction using a G4 glass sand core funnel to remove metal impurities. Repeat this step 4 times until there is no precipitate residue in the solution to obtain a platinum-rhodium metal filtrate;

[0063] (4) Weigh 4 g of the coordination precipitant potassium hydroxide and add it to the platinum-rhodium metal filtrate. The mass ratio of the coordination precipitant to platinum-rhodium alloy powder is 20:1. Heat to 100 °C. After no more precipitate precipitates, cool to room temperature;

[0064] (5) Measure 20 mL of the polar solvent anhydrous ethanol and add it to the solution in step (4). The volume ratio of the polar solvent to the platinum-rhodium mixed solution is 1:15. Stir evenly, control the solution temperature at 5 °C, and let it stand for precipitation for 2 h;

[0065] (6) Filter all the materials in step (5) to obtain a precipitate. Place it in an oven at 100 °C and dry to constant weight. Weigh the weight of the dried rhodium precipitate. The composition of the rhodium precipitate is potassium hexanitrorhodate. Calculate the rhodium content according to the formula. The calculation formula is as follows:

[0066]

[0067] Among them, ω is the rhodium content in the platinum-rhodium alloy; m 1 is the weight of the rhodium precipitate, in g;m is the weight of the platinum-rhodium alloy, in g; 0.20736 is the factor for converting rhodium precipitate to rhodium. Example 3

[0068] This example provides a method for determining the rhodium content in a platinum-rhodium alloy. The determination method includes the following steps:

[0069] (1) Place 0.2 g of platinum-rhodium alloy powder in a microwave digestion instrument, add a mixed acid of 20 mL of hydrochloric acid and 10 mL of hydrogen peroxide. The volume ratio of hydrochloric acid to hydrogen peroxide is 2:1, and the mass ratio of platinum-rhodium alloy powder to the mixed acid is 1:192. Heat to 120 °C for digestion. After the material is completely dissolved, add 300 mL of pure water for volume fixation. The mass ratio of the mixed acid to pure water is 1:7.8 to obtain a metal chloric acid solution;

[0070] (2) Weigh 10 g of sodium nitrite and add it to the metal chloric acid solution. The mass ratio of sodium nitrite to platinum-rhodium alloy powder is 50:1. Heat to 90 °C, stir, add sodium hydroxide to adjust the pH to 6, and then let it stand and react for 0.5 h;

[0071] (3) Filter the solution after standing reaction using a G4 glass sand core funnel to remove metal impurities. Repeat the operation of this step 2 times until there is no precipitate residue in the solution to obtain a platinum-rhodium metal filtrate;

[0072] (4) Weigh 2 g of the coordination precipitant potassium chloride and add it to the platinum-rhodium metal filtrate. The mass ratio of the coordination precipitant to platinum-rhodium alloy powder is 10:1. Heat to 60 °C. After no more precipitate precipitates, cool to room temperature;

[0073] (5) Measure 20 mL of the polar solvent anhydrous ethanol and add it to the solution in step (4). The volume ratio of the polar solvent to the platinum-rhodium mixed solution is 1:15. Stir evenly, control the solution temperature at 20 °C, and let it stand and precipitate for 3 h;

[0074] (6) Filter all the materials in step (5) to obtain a precipitate. Place it in an oven at 70 °C and dry to constant weight. Weigh the weight of the dried rhodium precipitate. The composition of the rhodium precipitate is potassium hexanitrorhodate. Calculate the rhodium content according to the formula. The calculation formula is as follows:

[0075] Where, ω is the rhodium content in the platinum-rhodium alloy; m 1 is the weight of the rhodium precipitate, in g; m is the weight of the platinum-rhodium alloy, in g; 0.20736 is the factor for converting rhodium precipitate to rhodium. Example 4

[0076] This embodiment provides a method for determining the rhodium content in a platinum-rhodium alloy. Compared with Embodiment 1, the coordination precipitant in step (4) is replaced with ammonium chloride in an equal mass to potassium chloride, and the rest is the same as in Embodiment 1. The composition of the rhodium precipitate is ammonium hexanitrorhodate, and the rhodium content is calculated according to the formula. The calculation formula is as follows:

[0077]

[0078] Wherein, ω is the rhodium content in the platinum-rhodium alloy; m 1 is the weight of the rhodium precipitate, in g; m is the weight of the platinum-rhodium alloy, in g; 0.23761 is the factor for converting the rhodium precipitate into rhodium. Embodiment Five

[0079] This embodiment provides a method for determining the rhodium content in a platinum-rhodium alloy. Compared with Embodiment 1, the polar solvent in step (5) is replaced with acetonitrile in an equal volume to absolute ethanol, and the rest is the same as in Embodiment 1. Embodiment Six

[0080] This embodiment provides a method for determining the rhodium content in a platinum-rhodium alloy. Compared with Embodiment 1, the pH in step (2) is adjusted to 11, and the rest is the same as in Embodiment 1. Embodiment Seven

[0081] This embodiment provides a method for determining the rhodium content in a platinum-rhodium alloy. Compared with Embodiment 1, the heating temperature in step (4) is controlled at 50 °C, and the rest is the same as in Embodiment 1. Comparative Example One

[0082] This comparative example provides a method for determining the rhodium content in a platinum-rhodium alloy. Compared with Embodiment 1, sodium nitrite is not added in step (2), and the rest is the same as in Embodiment 1. Comparative Example Two

[0083] This comparative example provides a method for determining the rhodium content in a platinum-rhodium alloy. Compared with Embodiment 1, no polar solvent is added in step (5), and the rest is the same as in Embodiment 1. Comparative Example Three

[0084] This comparative example provides a method for determining the rhodium content in a platinum-rhodium alloy. Compared with Embodiment 1, the coordination precipitant in step (4) is replaced with sodium chloride in an equal mass to potassium chloride, and the rest is the same as in Embodiment 1. Comparative Example Four

[0085] This comparative example provides a method for determining the rhodium content in a platinum-rhodium alloy. Compared with Embodiment 1, step (3) filtration is not carried out, and the rest is the same as in Embodiment 1. Comparative Example 5

[0086] This comparative example provides a method for determining the rhodium content in a platinum-rhodium alloy. According to the "Chemical Analysis Method of Platinum-Rhodium Alloy", GB1485-79, the nitric acid hexammine cobalt precipitation method is used for determination. The specific steps are as follows:

[0087] (1) Completely dissolve the platinum-rhodium alloy powder according to step (1) of Example 1 to obtain a sample solution;

[0088] (2) Heat the sample solution to 60°C, add sodium nitrite, heat to boiling, add a saturated solution of nitric acid hexammine cobalt under vigorous stirring, then age on a sand bath, cool, filter, wash, and dry the solution to obtain a double salt precipitate of rhodium, and calculate the percentage content of rhodium based on the mass of the double salt precipitate.

[0089] The determination methods of the examples and comparative examples were used for 3 parallel experiments, and the average value was calculated. The results are listed in Table 1.

[0090] Table 1

[0091]

[0092] "-" in the table indicates no data.

[0093] As can be seen from Table 1, the method for determining the rhodium content provided by the present invention has simple procedures, and the results of three parallel determinations are all accurate and reliable, with a small standard deviation. In Examples 1-5, the standard deviation is controlled below 0.036. Compared with Example 1, in Example 6, the pH adjustment in step (2) is too high, causing some rhodium to form hydroxide precipitates, resulting in more loss of rhodium elements when removing metal impurities and a large deviation in the determination results; in Example 7, the heating temperature in step (4) is too low, making the reaction of rhodium double salt slower, resulting in incomplete precipitation of rhodium and affecting the accuracy of the determination results.

[0094] In Comparative Example 1 and Comparative Example 2, rhodium cannot be completely precipitated, so accurate determination results cannot be obtained; in Comparative Example 3, using sodium chloride cannot form a hexanitrorhodate precipitate and cannot precipitate rhodium elements, so determination cannot be carried out; in Comparative Example 4, without filtration, the interference of impurity metals in the platinum-rhodium alloy is not excluded, and the impurity metals co-precipitate with the rhodium double salt, resulting in inaccurate determination results; in Comparative Example 5, using the standard rhodium content determination method, the deviation of its determination results is slightly increased compared with the present invention, and using nitric acid hexammine cobalt has a complex preparation process and is not convenient for operation.

[0095] In summary, the determination method of the present invention avoids the measurement error introduced by metal impurities such as copper and iron in the platinum-rhodium alloy, and also avoids trace residues of rhodium precipitate in the solution and co-precipitation of other interfering metals. The process and reagents used are simple, the operation is safe, and the efficiency is high. It avoids the use of high-cost and complex precipitants such as metal elements or hexaamminecobalt nitrate in the prior art. The rhodium precipitation is complete, the determination results are accurate, and the relative standard deviation is especially less than 0.21%. At the same time, there is no need to rely on expensive analytical equipment, and it has great application value.

[0096] The specific embodiments described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for determining the rhodium content in a platinum-rhodium alloy, characterized in that: The determination method comprises the following steps: (1) completely dissolving the platinum-rhodium alloy to obtain a metal chloric acid solution; (2) mixing the metal chlorate solution obtained in step (1) with nitrite, adjusting the pH to 6-10, standing for reaction, and then performing a first solid-liquid separation to obtain a platinum-rhodium mixed solution; (3) The platinum-rhodium mixed solution obtained in step (2) is mixed with a coordination precipitant for precipitation, wherein the coordination precipitant comprises any one of potassium chloride, potassium carbonate or potassium hydroxide or a combination of at least two thereof, and the precipitation temperature is 60-100°C. The mixed solution is then mixed with a polar solvent, and after standing and settling at 0-20°C, a second solid-liquid separation is performed to obtain a rhodium precipitate, wherein the rhodium precipitate is potassium hexanitrorhodate. The rhodium precipitate is dried to a constant weight, and the rhodium content in the platinum-rhodium alloy is calculated based on the mass of the rhodium precipitate.

2. The measuring method according to claim 1, characterized in that The dissolving method in step (1) comprises: mixing platinum-rhodium alloy powder with a mixed acid, wherein the mixed acid comprises hydrochloric acid and hydrogen peroxide, performing microwave digestion, and then fixing the volume with water; The mass ratio of the platinum-rhodium alloy powder to the mixed acid is (1-50):400; The volume ratio of hydrochloric acid to hydrogen peroxide is (1-3):1; The temperature of the microwave digestion is 100-200°C; The microwave digestion time is 0.5-2 days; The mass ratio of the mixed acid to water is (1-10):

50.

3. The measuring method according to claim 1, characterized in that The mass ratio of the nitrite to the platinum-rhodium alloy in step (2) is (10-50):1; The nitrite in step (2) includes sodium nitrite; The mixing temperature in step (2) is 50-90°C.

4. The measuring method according to claim 1, characterized in that The pH regulator used in step (2) includes any one of sodium carbonate, sodium hydroxide or sodium bicarbonate, or a combination of at least two of them.

5. The measuring method according to claim 1, characterized in that The standing reaction time in step (2) is 0.5-3h.

6. The measuring method according to claim 1, characterized in that The mass ratio of the coordination precipitant to the platinum-rhodium alloy in step (3) is (10-50):

1.

7. The measuring method according to claim 1, characterized in that The volume ratio of the polar solvent to the platinum-rhodium mixed solution in step (3) is 1:(5-20); The polar solvent in step (3) includes any one of anhydrous ethanol, acetonitrile or methanol, or a combination of at least two of them.

8. The measuring method according to claim 1, characterized in that The static sedimentation time in step (3) is 0.5-3h.

9. The measuring method according to claim 1, characterized in that The calculation formula of the rhodium content in step (3) is as follows: ； in, ω is the rhodium content in the platinum-rhodium alloy; m 1 is the mass of rhodium precipitate, in g; m is the mass of platinum-rhodium alloy, in g; α Factor for converting rhodium precipitate into rhodium element.

10. The measuring method according to claim 1, characterized in that The determination method comprises the following steps: (1) mixing platinum-rhodium alloy powder with a mixed acid for microwave digestion, wherein the mixed acid comprises hydrochloric acid and hydrogen peroxide, wherein the volume ratio of the hydrochloric acid to the hydrogen peroxide is (1-3):1, and the mass ratio of the platinum-rhodium alloy powder to the mixed acid is (1-50):

400. The microwave digestion temperature is 100-200° C., and the microwave digestion time is 0.5-2 days. After microwave digestion, the digested solution is fixed to volume with water, wherein the mass ratio of the mixed acid to water is (1-10):50, to obtain a metal chloride solution; (2) mixing the metal chlorate solution obtained in step (1) with sodium nitrite, wherein the mass ratio of the sodium nitrite to the platinum-rhodium alloy powder is (10-50):1, the mixing temperature is 50-90° C., adding a pH adjuster to adjust the pH to 6-10, wherein the pH adjuster comprises any one of sodium carbonate, sodium hydroxide or sodium bicarbonate or a combination of at least two thereof, standing for reaction for 0.5-3 h, and the impurity metals in the platinum-rhodium alloy generate nitroso complex precipitates, and then using a glass sand core funnel for solid-liquid separation to obtain a platinum-rhodium mixed solution; (3) mixing the platinum-rhodium mixed solution obtained in step (2) with a coordination precipitant, wherein the coordination precipitant includes any one of potassium chloride, potassium carbonate or potassium hydroxide or a combination of at least two thereof, and the mass ratio of the coordination precipitant to the platinum-rhodium alloy powder is (10-50):1, and performing coordination reaction at 60-100°C to obtain a mixture; and then mixing the mixture with a polar solvent, wherein the polar solvent includes any one of anhydrous ethanol, acetonitrile or methanol or a combination of at least two thereof, and the volume ratio of the polar solvent to the platinum-rhodium mixed solution is 1:(5-20); after mixing, standing and settling at 0-20°C for 0.5-3h, and after the standing and settling is completed, performing solid-liquid separation to obtain a precipitate, and drying the precipitate to constant weight at a drying temperature of 70-150°C to obtain a rhodium precipitate; (4) Weigh the rhodium precipitate obtained in step (3), and calculate the rhodium content in the platinum-rhodium alloy based on the mass of the rhodium precipitate. The calculation formula is as follows: ； in, ω is the rhodium content in the platinum-rhodium alloy; m 1 is the weight of rhodium precipitate, in g; m is the weight of platinum-rhodium alloy, in g; α Factor for converting rhodium precipitate into rhodium element.

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