Method for determining rhodium in crude silver

Abstract

The invention provides a method for measuring rhodium in crude silver, and belongs to the technical field of precious metal analysis. The method for measuring the rhodium in the crude silver comprises the following steps: mixing the crude silver with nitric acid, digesting, and then separating to obtain a silver nitrate solution and a precipitate; mixing the precipitate with aqua regia, and then removing nitrate to obtain a solid substance; mixing the solid substance, an inorganic solvent and a gold reducing agent, and reducing to obtain gold and rhodium solutions; and determining the content of rhodium in the rhodium solution by atomic absorption spectrometry. According to the method, nitric acid is adopted for digestion, silver and palladium in crude silver can be dissolved with other nonferrous metals such as copper and lead, and precious metals such as gold and rhodium are not dissolved, so that separation is achieved; then dissolving precious metals such as gold and rhodium by using aqua regia, removing nitrate, removing nitrate ions, and avoiding generation of toxic gas during subsequent reduction; gold is reduced by adopting a gold reducing agent, so that gold is separated from rhodium, the interference on rhodium content measurement is avoided, and the rhodium content can be accurately measured.

Description

Technical Field

[0001] The invention belongs to the technical field of precious metal analysis, and in particular relates to a method for determining rhodium in crude silver. Background Art

[0002] In the purification of silver, it is very important to accurately analyze the rhodium content in the material. Rhodium is a rare metal with high economic value and is widely used in aerospace, chemical catalysis, automobile manufacturing, jewelry and other industries. The existing rhodium analysis method is mainly to convert the rhodium in the material into a soluble compound through wet digestion treatment, and then analyze it through various detection methods. For example, the material is mixed with aqua regia, heated to boiling, the rhodium is dissolved, and then quantitative analysis is performed by a spectrophotometer or an inductively coupled plasma emission spectrometer. However, this method has poor accuracy. Therefore, how to accurately determine the rhodium content in crude silver has become a technical problem that needs to be solved in this field. Summary of the invention

[0003] The object of the present invention is to provide a method for determining rhodium in crude silver. The method provided by the present invention can accurately determine the content of rhodium in crude silver.

[0004] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0005] The present invention provides a method for determining rhodium in crude silver, comprising the following steps:

[0006] (1) mixing crude silver with nitric acid, digesting the mixture, and then separating to obtain a silver nitrate solution and a precipitate;

[0007] (2) mixing the precipitate obtained in step (1) with aqua regia, and then removing the nitrate to obtain a solid substance;

[0008] (3) mixing the solid substance obtained in step (2), an inorganic solvent and a gold reducing agent, and reducing the mixture to obtain a gold and rhodium solution;

[0009] (4) using atomic absorption spectrophotometry to measure the rhodium content in the rhodium solution obtained in step (3).

[0010] Preferably, the silver content in the crude silver in step (1) is ≥ 98.5 wt%.

[0011] Preferably, the particle size of the coarse silver in step (1) is less than 20 mesh.

[0012] Preferably, the digestion temperature in step (1) is 70-80°C.

[0013] Preferably, the temperature of mixing the precipitate and aqua regia in step (2) is 70-80°C.

[0014] Preferably, the temperature of removing the nitrate in step (2) is 50-60°C.

[0015] Preferably, concentrated hydrochloric acid is used to remove nitrate in step (2).

[0016] Preferably, the gold reducing agent in step (3) is a hydroquinone solution.

[0017] Preferably, the mass fraction of the hydroquinone solution is 1-10%.

[0018] Preferably, the reduction temperature in step (3) is 60-70° C., and the reduction time is 1-10 min.

[0019] The present invention provides a method for determining rhodium in crude silver, comprising the following steps: mixing crude silver with nitric acid, digesting, and then separating to obtain a silver nitrate solution and a precipitate; mixing the precipitate with aqua regia, and then removing the nitrate to obtain a solid substance; mixing the solid substance, an inorganic solvent and a gold reducing agent, and reducing to obtain a gold and rhodium solution; and determining the rhodium content in the rhodium solution by atomic absorption spectrophotometry. The present invention uses nitric acid for digestion, which can dissolve silver palladium and other non-ferrous metals such as copper and lead in crude silver, but does not dissolve precious metals such as gold and rhodium, thereby achieving separation and avoiding interference with the determination of rhodium content; then aqua regia is used to dissolve precious metals such as gold and rhodium, remove the nitrate, and avoid the generation of toxic gases during subsequent reduction; gold is reduced by a gold reducing agent, thereby separating it from rhodium, avoiding interference with the determination of rhodium content, and then atomic absorption spectrophotometry is used to determine the rhodium content, thereby accurately determining the rhodium content. Experimental results show that the error of the method provided by the present invention in determining rhodium in crude silver is not higher than 4%. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 The present invention is a process flow chart of the method for determining rhodium in crude silver. DETAILED DESCRIPTION

[0021] The present invention provides a method for determining rhodium in crude silver, comprising the following steps:

[0022] (1) mixing crude silver with nitric acid, digesting the mixture, and then separating to obtain a silver nitrate solution and a precipitate;

[0023] (2) mixing the precipitate obtained in step (1) with aqua regia, and then removing the nitrate to obtain a solid substance;

[0024] (3) mixing the solid substance obtained in step (2), an inorganic solvent and a gold reducing agent, and reducing the mixture to obtain a gold and rhodium solution;

[0025] (4) using atomic absorption spectrophotometry to measure the rhodium content in the rhodium solution obtained in step (3).

[0026] The method provided by the invention is applicable to crude silver containing rhodium.

[0027] The present invention has no particular limitation on the sources of the raw materials, and commercially available products known to those skilled in the art may be used.

[0028] The invention mixes crude silver with nitric acid, performs digestion, and then separates to obtain a silver nitrate solution and a precipitate.

[0029] In the present invention, the silver content in the crude silver is preferably ≥98.5wt%; the rhodium content in the crude silver is preferably 10g / t; and the palladium and gold contents in the crude silver are independently preferably 1000g / t.

[0030] In the present invention, the particle size of the crude silver is preferably less than 20 meshes. The present invention limits the particle size of the crude silver to the above range to facilitate subsequent digestion.

[0031] In the present invention, the crude silver is preferably pretreated before use. The present invention uses pretreatment for sample preparation.

[0032] In the present invention, the pretreatment is preferably:

[0033] 1) drilling the crude silver ingot to obtain drill cuttings;

[0034] 2) Powdering the drill cuttings obtained in step 1) to obtain crude silver.

[0035] In the present invention, the crude silver ingot is preferably drilled to obtain drill cuttings.

[0036] In the present invention, the drilling is preferably performed by using an electric drill for sampling. The present invention has no particular limitation on the model of the electric drill, and any instrument or equipment well known to those skilled in the art can be used.

[0037] After obtaining the drill cuttings, the present invention preferably powders the drill cuttings to obtain crude silver.

[0038] The present invention has no special limitation on the powdering operation, as long as the particle size of the coarse silver meets the requirements.

[0039] In the present invention, the nitric acid is preferably dilute nitric acid; the volume ratio of nitric acid to water in the dilute nitric acid is preferably 1: (2-4), more preferably 1: 3. The present invention has no special limitation on the amount of nitric acid, as long as the material does not change after the addition of nitric acid. The present invention uses nitric acid for digestion, which can dissolve silver, palladium and other non-ferrous metals such as copper and lead in crude silver, but does not dissolve precious metals such as gold and rhodium, thereby achieving separation.

[0040] The present invention has no particular limitation on the operation of mixing the crude silver with nitric acid, and a technical solution for preparing a mixed material well known to those skilled in the art may be used.

[0041] In the present invention, the digestion temperature is preferably 70-80° C., more preferably 75° C. The present invention has no particular limitation on the digestion time, as long as the material is guaranteed to be non-reactive.

[0042] In the present invention, the digestion is preferably carried out under stirring conditions. The present invention has no particular limitation on the stirring speed, and operations well known to those skilled in the art can be used.

[0043] The present invention has no particular limitation on the separation operation, and any operation well known to those skilled in the art may be used.

[0044] After separation is completed, the present invention preferably washes the solid product obtained by separation to obtain a precipitate.

[0045] In the present invention, the detergent used in the washing is preferably hot water; the temperature of the hot water is preferably 60-80° C., more preferably 70° C.; the number of washings is preferably 2. The present invention uses washing to remove nitrates in the precipitate.

[0046] After obtaining the precipitate, the present invention mixes the precipitate with aqua regia, and then removes nitrate to obtain a solid substance. The present invention uses aqua regia to dissolve gold and rhodium, and then removes nitrate in the solution to avoid the generation of toxic gas during subsequent gold reduction.

[0047] In the present invention, the volume ratio of nitric acid to hydrochloric acid in the aqua regia is preferably 1: 3. The present invention has no particular limitation on the amount of the aqua regia, as long as the precipitate is completely dissolved.

[0048] In the present invention, the temperature for mixing the precipitate with aqua regia is preferably 70-80° C., more preferably 75° C. The present invention has no particular limitation on the mixing time, as long as the precipitate is completely dissolved.

[0049] In the present invention, the temperature of the nitrate removal is preferably 50-60°C, more preferably 55°C; the nitrate removal method is preferably concentrated hydrochloric acid; the mass concentration of the concentrated hydrochloric acid is preferably 30-40%, more preferably 36%; the number of nitrate removal is preferably 2 times. The present invention has no particular limitation on the amount of the concentrated hydrochloric acid, as long as the nitrate in the solution obtained by mixing the precipitate with aqua regia is removed.

[0050] After the removal of nitrate, the present invention preferably evaporates the product obtained by removing nitrate to dryness to obtain a solid substance.

[0051] The present invention has no particular limitation on the evaporation operation, and any operation well known to those skilled in the art may be used.

[0052] After obtaining the solid substance, the present invention mixes the solid substance, an inorganic solvent and a gold reducing agent to obtain a gold and rhodium solution.

[0053] In the present invention, the inorganic solvent is preferably water. The present invention has no particular limitation on the amount of water used, as long as the solid matter can be completely dissolved.

[0054] In the present invention, the gold reducing agent is preferably a hydroquinone solution; the solvent of the hydroquinone solution is preferably water; the mass fraction of the hydroquinone solution is preferably 1-10%, more preferably 5%.

[0055] In the present invention, 1 mL of hydroquinone solution is preferably used to reduce 6 mg of gold. The present invention has no particular limitation on the amount of the hydroquinone solution, as long as the gold is completely reduced.

[0056] The present invention has no special limitation on the operation of mixing the solid substance, the inorganic solvent and the gold reducing agent, and the technical scheme for preparing the mixed material well known to those skilled in the art can be adopted.

[0057] In the present invention, the reduction temperature is preferably 60-70°C, more preferably 65-70°C; the reduction time is preferably 1-10 min, more preferably 5 min. The present invention limits the reduction temperature and time within the above ranges to ensure complete reduction of gold.

[0058] After the reduction is completed, the present invention preferably filters the product obtained by the reduction to obtain a gold and rhodium solution.

[0059] The present invention has no particular limitation on the filtering operation, and any operation well known to those skilled in the art may be used.

[0060] After obtaining the rhodium solution, the present invention adopts atomic absorption spectrophotometry to measure the rhodium content in the rhodium solution.

[0061] In the present invention, the rhodium solution is preferably fixed to volume before the determination; the solution used for the fixed volume is preferably hydrochloric acid; the mass concentration of the hydrochloric acid is preferably 5-15%, more preferably 10%. The present invention has no special limitation on the amount of the fixed volume, as long as the content of rhodium in the rhodium solution is guaranteed to be within the range of 0.5-5 μg / mL.

[0062] In the present invention, the atomic absorption spectrophotometry preferably uses a rhodium hollow cathode lamp. The present invention has no special limitation on the operation of the atomic absorption spectrophotometry, and the operation well known to those skilled in the art can be used.

[0063] In the method provided by the invention, silver, gold and palladium do not interfere with rhodium; meanwhile, the error of rhodium in crude silver is no higher than 4%.

[0064] The advantages of the present invention mainly lie in that: by adopting a specific analysis method and technical route, the content of rhodium in crude silver can be accurately determined, the problems of low determination accuracy and complicated operation in the existing method are solved, and a new technology is provided for the determination of the rhodium content in crude silver; a new method is proposed for the separation and enrichment of precious metals in crude silver, the precious metal rhodium can be efficiently separated from the crude silver, the problems of low separation efficiency, complicated operation, interference between precious metals in the traditional method are solved, and a new technical support means is provided for the recovery and utilization of precious metals in crude silver.

[0065] The process flow chart of the method for determining rhodium in crude silver of the present invention is as follows Figure 1 shown.

[0066] from Figure 1 It can be seen that the crude silver is sequentially sampled by electric drill, sampled by powder making machine, sampled for analysis, and digested with nitric acid to obtain silver nitrate solution and precipitate; the precipitate is dissolved in aqua regia, and then the gold is separated to obtain gold powder and rhodium solution, which are then fixed to volume and measured by instruments.

[0067] The technical solutions in the present invention will be described clearly and completely below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0068] In the embodiment, the silver content in the crude silver is ≥98.5wt%, the rhodium content is 10g / t, and the palladium and gold contents are both 1000g / t.

[0069] Example 1

[0070] The method for determining rhodium in crude silver is as follows:

[0071] (1) Using an electric drill to sample the crude silver ingot along the diagonal line on the ingot surface, three points are taken on each surface, each point is drilled through, and the drill cuttings are collected. Then, a metal powder machine is used to make fine silver with a particle size of less than 20 mesh, which is collected and bagged. Then, 5.0000 g of the crude silver sample is weighed and placed in a 50 mL beaker. 30 mL of dilute nitric acid is added and stirred and dissolved at 70° C. After the material has no reaction, the silver nitrate solution is poured out. The precipitate is washed twice with 10 mL of ionized water at 70° C., and the washing water is poured into the silver nitrate solution to recover silver and other metals; wherein, the volume ratio of nitric acid to water in the dilute nitric acid is 1:3;

[0072] (2) mixing and dissolving the precipitate obtained in step (1) with 20 mL of aqua regia at 70° C., then evaporating the mixture at 60° C. to dryness, and adding 36% concentrated hydrochloric acid twice, 5 mL each time, to remove nitrate, to obtain a solid substance; wherein the volume ratio of nitric acid to hydrochloric acid in the aqua regia is 1:3;

[0073] (3) adding 20 mL of water to the solid substance obtained in step (2), heating to 70° C., adding 1 mL of a 5% hydroquinone aqueous solution to perform gold reduction for 5 min, separating the gold, and adding 2.5 mL of 10% hydrochloric acid to make up to 25 mL to obtain a rhodium solution;

[0074] (4) The rhodium content in the rhodium solution was determined to be 9.98 g / t by atomic absorption spectrophotometry using a rhodium hollow cathode lamp at a wavelength of 343.5 nm, a slit of 0.2 nm, and a rhodium standard linear range of 0.5 to 5 μg / mL.

[0075] Example 2

[0076] The method for determining rhodium in crude silver is as follows:

[0077] (1) Using an electric drill to sample the crude silver ingot along the diagonal line on the ingot surface, three points are taken on each surface, each point is drilled through, and the drill cuttings are collected. Then, a metal powder machine is used to make fine silver with a particle size of less than 20 mesh, which is collected and bagged. Then, 8.0000 g of the crude silver sample is weighed and placed in a 50 mL beaker. 40 mL of dilute nitric acid is added and stirred and dissolved at 75° C. After the material has no reaction, the silver nitrate solution is poured out. The precipitate is washed twice with 10 mL of ionized water at 70° C., and the washing water is poured into the silver nitrate solution to recover silver and other metals; wherein, the volume ratio of nitric acid to water in the dilute nitric acid is 1:3;

[0078] (2) mixing and dissolving the precipitate obtained in step (1) with 20 mL of aqua regia at 75° C., then evaporating the mixture at 60° C. to dryness, and adding 36% concentrated hydrochloric acid twice, 5 mL each time, to remove nitrate, to obtain a solid substance; wherein the volume ratio of nitric acid to hydrochloric acid in the aqua regia is 1:3;

[0079] (3) adding 20 mL of water to the solid substance obtained in step (2), heating to 70° C., adding 1.5 mL of a 5% hydroquinone aqueous solution to perform gold reduction for 5 min, separating the gold, and adding 5.0 mL of 10% hydrochloric acid to make up the volume to 50 mL to obtain a rhodium solution;

[0080] (4) The rhodium content in the rhodium solution was determined to be 9.95 g / t by atomic absorption spectrophotometry using a rhodium hollow cathode lamp at a wavelength of 343.5 nm, a slit of 0.2 nm, and a rhodium standard linear range of 0.5 to 5 μg / mL.

[0081] Example 3

[0082] The method for determining rhodium in crude silver is as follows:

[0083] (1) Using an electric drill to sample the crude silver ingot along the diagonal line on the ingot surface, three points are taken on each surface, each point is drilled through, and the drill cuttings are collected. Then, a metal powder machine is used to make fine silver with a particle size of less than 20 mesh, which is collected and bagged. Then, 10.0000 g of the crude silver sample is weighed and placed in a 75 mL beaker, and 40 mL of dilute nitric acid is added and stirred and dissolved at 80° C. After the material has no reaction, the silver nitrate solution is poured out, and the precipitate is washed twice with 10 mL of ionized water at 70° C., and the washing water is poured into the silver nitrate solution to recover silver and other metals; wherein, the volume ratio of nitric acid to water in the dilute nitric acid is 1:3;

[0084] (2) mixing the precipitate obtained in step (1) with 20 mL of aqua regia and dissolving it at 80° C., then evaporating it at 60° C. to dryness, and adding 36% concentrated hydrochloric acid twice, 5 mL each time, to remove the nitrate, to obtain a solid substance; wherein the volume ratio of nitric acid to hydrochloric acid in the aqua regia is 1:3;

[0085] (3) adding 20 mL of water to the solid substance obtained in step (2), heating to 70° C., adding 2 mL of a 5% hydroquinone aqueous solution to perform gold reduction for 5 min, separating the gold, and adding 5.0 mL of 10% hydrochloric acid to make up the volume to 50 mL to obtain a rhodium solution;

[0086] (4) The rhodium content in the rhodium solution was determined to be 10.02 g / t by atomic absorption spectrophotometry using a rhodium hollow cathode lamp at a wavelength of 343.5 nm, a slit of 0.2 nm, and a standard linear range of rhodium of 0.5 to 5 μg / mL.

[0087] It can be seen from the above examples that the method provided by the present invention can accurately determine the content of rhodium in crude silver.

[0088] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for measuring rhodium in crude silver, comprising the following steps: (1) mixing crude silver with nitric acid, digesting the mixture, and then separating to obtain a silver nitrate solution and a precipitate; (2) mixing the precipitate obtained in step (1) with aqua regia, and then removing the nitrate to obtain a solid substance; (3) mixing the solid substance obtained in step (2), an inorganic solvent and a gold reducing agent, and reducing the mixture to obtain a gold and rhodium solution; (4) using atomic absorption spectrophotometry to measure the rhodium content in the rhodium solution obtained in step (3).

2. The method according to claim 1, characterized in that The silver content in the crude silver in step (1) is ≥ 98.5 wt%.

3. The method according to claim 1 or 2, characterized in that: The particle size of the coarse silver in the step (1) is less than 20 meshes.

4. The method according to claim 1, characterized in that: The digestion temperature in step (1) is 70-80°C.

5. The method according to claim 1, characterized in that The temperature of mixing the precipitate and aqua regia in step (2) is 70-80°C.

6. The method according to claim 1, characterized in that The temperature of removing the nitrate in step (2) is 50-60°C.

7. The method according to claim 1 or 6, characterized in that: In the step (2), concentrated hydrochloric acid is used to remove nitrate.

8. The method according to claim 1, characterized in that In the step (3), the gold reducing agent is a hydroquinone solution.

9. The method according to claim 8, characterized in that The mass fraction of the hydroquinone solution is 1-10%.

10. The method according to claim 1, characterized in that The reduction temperature in step (3) is 60-70° C., and the reduction time is 1-10 min.

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