Method for recovering rhodium and iridium from precious metal refining mother liquor containing rhodium and iridium

Abstract

The invention relates to a method for recovering rhodium and iridium from precious metal refining mother liquor containing rhodium and iridium, which comprises three procedures of oxidation pretreatment, purification and impurity removal and deep precipitation, and in the oxidation pretreatment procedure, sodium chlorate is used for oxidizing the precious metal refining mother liquor, so that organic matters in the solution are removed; base metal ions in the solution are oxidized into high valence states which are easy to remove, so that conditions are created for purification and impurity removal; most of base metal ions in the solution are removed by utilizing the properties that benzoate of base metals such as nickel, copper, iron and cobalt is low in solubility and benzoic acid does not react with rhodium and iridium in the solution, and meanwhile, the loss of rhodium and iridium is avoided; and finally, efficient precipitation of rhodium and iridium in the solution is achieved through a precipitator, the content of impurities in the obtained rhodium and iridium precipitate is low, and after the precipitate is dissolved by aqua regia, a refining process can be linked to produce rhodium powder and iridium powder.

Description

Technical Field

[0001] The invention relates to the technical field of noble metal hydrometallurgy, and in particular to a method for recovering rhodium and iridium from noble metal refining mother liquor containing rhodium and iridium. Background Art

[0002] The traditional rhodium-iridium refining process involves more than 60 process links, each of which will produce mother liquor containing trace amounts of rhodium-iridium. Due to the high continuity and irreversibility of the refining process, these mother liquors are difficult to be effectively reintegrated into the refining process for further processing. With the continuous advancement of the process, impurities such as nickel, copper, iron, selenium, silicon, sulfur, calcium, sodium and various organic substances in the mother liquor gradually accumulate and increase, making the mother liquor system more complex and more difficult to handle. At present, the recovery of rhodium-iridium in the traditional rhodium-iridium refining mother liquor usually adopts the zinc-magnesium powder replacement process. The replacement efficiency of this process is low, and it is difficult to completely remove the zinc and magnesium elements during the recovery of rhodium-iridium, resulting in a high impurity content in the recovered rhodium-iridium product, which cannot meet the high quality requirements. At the same time, the zinc-magnesium powder replacement process also has the problem of no open circuit, that is, it is impossible to effectively separate zinc and magnesium impurities from rhodium and iridium, so that zinc and magnesium impurities continue to accumulate in the refining process of the recovered rhodium-iridium product, which seriously interferes with the refining process and product quality of the recovered rhodium-iridium product. Summary of the invention

[0003] In view of the problems in the above-mentioned prior art of low rhodium-iridium recovery rate, high impurity content in the recovered rhodium-iridium product, and low product quality of the recovered rhodium-iridium product after refining, the present invention provides a method for recovering rhodium-iridium from precious metal refining mother liquor containing rhodium-iridium, which can achieve efficient precipitation of rhodium-iridium through oxidation pretreatment, purification and impurity removal and deep precipitation steps.

[0004] To achieve the above object, the technical solution of the present invention is as follows:

[0005] A method for recovering rhodium and iridium from precious metal refining mother liquor containing rhodium and iridium comprises the following steps:

[0006] (1) Oxidation pretreatment: add saturated sodium chlorate solution to the precious metal refining mother liquor and react at 90-95°C for 1.5-2h;

[0007] (2) Purification and impurity removal: sodium hydroxide is added to the pretreated solution to adjust the pH value of the solution, and benzoic acid, an impurity remover, is added to react at 60-65° C. for 1-2 hours, and filtered. The filtrate obtained is the purified solution;

[0008] (3) Deep precipitation: adding a precipitant to the purified liquid and reacting at 70-75° C. for 2-3 hours to obtain a rhodium-iridium precipitate, wherein the precipitant is a mixed solution of sodium hydroxyacetate and sodium hydroxide.

[0009] Furthermore, the amount of the saturated sodium chlorate solution added in step (1) is 1-2% of the volume of the precious metal refining mother liquor.

[0010] Furthermore, in step (2), sodium hydroxide is added until the pH value of the pretreated solution is 1-2.

[0011] Furthermore, the amount of the impurity remover benzoic acid added in step (2) is 1.8-2.1 times the total content of nickel, copper, iron and cobalt in the precious metal refining mother liquor.

[0012] Furthermore, the precipitant in step (3) is sodium hydroxyacetate and sodium hydroxide mixed in a mass ratio of 1:0.8-1.2 to prepare a mixed solution with a concentration of 20-25%.

[0013] Furthermore, in step (3), a precipitant is added to the purified liquid until the pH value of the solution is 8-9.

[0014] The reaction principle involved in the present invention is as follows:

[0015] In the oxidation pretreatment, adding saturated sodium chlorate solution to the precious metal refining mother liquor can consume the residual organic matter in the precious metal refining mother liquor, and at the same time oxidize the metal ions in the solution to a high-valent state, which is convenient for subsequent purification and impurity removal.

[0016] During the purification and impurity removal, the impurity remover benzoic acid can react with high-valent base metal ions such as nickel, copper, iron, and cobalt in the solution to form insoluble benzoates, thereby achieving the purpose of purification and impurity removal; benzoic acid does not react with rhodium and iridium in the solution, so it will not cause the loss of rhodium and iridium metal content.

[0017] During deep impurity removal, sodium hydroxyacetate and sodium hydroxide in the precipitant can react with rhodium and iridium in the solution to generate rhodium hydroxyacetate / iridium and rhodium / iridium hydroxide, thereby achieving efficient precipitation of rhodium and iridium.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] The invention provides a method for recovering rhodium and iridium from a noble metal refining mother liquor containing rhodium and iridium. In an oxidation pretreatment process, sodium chlorate is used to oxidize the noble metal refining mother liquor, so that organic matter in the solution is removed and base metal ions in the solution are oxidized to a high-valent state that is easy to be removed, thereby creating conditions for purification and impurity removal. The benzoate of base metals such as nickel, copper, iron, and cobalt has low solubility, and benzoic acid does not react with rhodium and iridium in the solution, so that most of the base metal ions in the solution are removed and the loss of rhodium and iridium is avoided. Finally, a precipitant is used to realize efficient precipitation of rhodium and iridium in the solution, so that the impurity content in the obtained rhodium and iridium precipitate is low, and the precipitate can be connected to a refining process to produce rhodium powder and iridium powder after being dissolved in aqua regia. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The embodiments of the present invention are further described below with reference to the accompanying drawings, in which:

[0021] Figure 1 A process flow chart for recovering rhodium and iridium from precious metal refining mother liquor is shown. DETAILED DESCRIPTION

[0022] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below through specific embodiments in conjunction with the accompanying drawings. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0023] Example 1

[0024] A method for recovering rhodium and iridium from precious metal refining mother liquor containing rhodium and iridium comprises the following steps:

[0025] (1) Oxidation pretreatment: add 2% of the mother liquor volume of saturated sodium chlorate solution to the precious metal refining mother liquor and react at 95°C for 1.5h;

[0026] (2) Purification and impurity removal: sodium hydroxide was added to the pretreated solution to adjust the pH value of the solution to 1, and benzoic acid, an impurity remover, was added in an amount of 1.8 times the total content of nickel, copper, iron and cobalt, and reacted at 60° C. for 2 h, and filtered. The obtained filtrate was the purified solution;

[0027] (3) Deep precipitation: adding a precipitant to the purified liquid until the pH value of the solution is 9, reacting at 75° C. for 2 hours to obtain a rhodium-iridium precipitate, wherein the precipitant is sodium hydroxyacetate and sodium hydroxide mixed in a mass ratio of 1:1.2 to prepare a mixed solution with a concentration of 20%.

[0028] In this embodiment, the precious metal refining mother liquor contains 0.211 g / L of rhodium, 0.085 g / L of iridium, 2.67 g / L of copper, 1.92 g / L of nickel, 1.34 g / L of iron, and 0.87 g / L of cobalt. After the treatment of steps (1) and (2), the metal contents in the solution are: 0.204 g / L of rhodium, 0.083 g / L of iridium, 0.023 g / L of copper, 0.015 g / L of nickel, and 0.009 g / L of iron. L, cobalt 0.014g / L; the metal content in the solution after treatment in step (3) is: rhodium 0.0041g / L, iridium 0.0039g / L, copper 0.024g / L, nickel 0.009g / L, iron 0.007g / L, cobalt 0.010g / L; the metal content in the rhodium-iridium precipitate is: rhodium 1.53%, iridium 1.04%, copper 0.07%, nickel 0.06%, iron 0.07%, cobalt 0.06%.

[0029] Example 2

[0030] A method for recovering rhodium and iridium from precious metal refining mother liquor containing rhodium and iridium comprises the following steps:

[0031] (1) Oxidation pretreatment: add 1% of the mother liquor volume of saturated sodium chlorate solution to the precious metal refining mother liquor and react at 90°C for 2h;

[0032] (2) Purification and impurity removal: sodium hydroxide was added to the pretreated solution to adjust the pH value of the solution to 2, and benzoic acid, an impurity remover, was added at 2.1 times the total content of nickel, copper, iron and cobalt, and reacted at 65° C. for 1 h, and filtered. The filtrate obtained was the purified solution;

[0033] (3) Deep precipitation: adding a precipitant to the purified liquid until the pH value of the solution is 8, reacting at 70° C. for 3 hours to obtain a rhodium-iridium precipitate, wherein the precipitant is sodium hydroxyacetate and sodium hydroxide mixed in a mass ratio of 1:0.8 to prepare a mixed solution with a concentration of 25%.

[0034] In this embodiment, the precious metal refining mother liquor contains 0.13 g / L rhodium, 0.068 g / L iridium, 2.54 g / L copper, 1.74 g / L nickel, 1.87 g / L iron, and 0.85 g / L cobalt; after being treated in steps (1) and (2), the metal contents in the solution are: 0.124 g / L rhodium, 0.066 g / L iridium, 0.017 g / L copper, 0.011 g / L nickel, and 0.008 g / L iron. , cobalt 0.013g / L; the metal content in the solution after treatment in step (3) is: rhodium 0.0038g / L, iridium 0.0037g / L, copper 0.012g / L, nickel 0.008g / L, iron 0.0067g / L, cobalt 0.011g / L; the metal content in the rhodium-iridium precipitate is: rhodium 1.34%, iridium 0.98%, copper 0.06%, nickel 0.04%, iron 0.02%, cobalt 0.07%.

[0035] The invention provides a method for recovering rhodium and iridium from a noble metal refining mother liquor containing rhodium and iridium. In an oxidation pretreatment process, sodium chlorate is used to oxidize the noble metal refining mother liquor, so that organic matter in the solution is removed and base metal ions in the solution are oxidized to a high-valent state that is easy to be removed, thereby creating conditions for purification and impurity removal. The benzoate of base metals such as nickel, copper, iron, and cobalt has low solubility, and benzoic acid does not react with rhodium and iridium in the solution, so that most of the base metal ions in the solution are removed and the loss of rhodium and iridium is avoided. Finally, a precipitant is used to realize efficient precipitation of rhodium and iridium in the solution, so that the impurity content in the obtained rhodium and iridium precipitate is low, and the precipitate can be connected to a refining process to produce rhodium powder and iridium powder after being dissolved in aqua regia.

[0036] Some exemplary embodiments of the present invention are described above. It can be understood that the above embodiments are only used to explain the present invention and do not constitute a limitation on the protection scope of the present invention. The features in these embodiments can be recombined in a suitable manner, and the scheme obtained thereby is still within the protection scope required by the present invention. Based on the above embodiments, all other embodiments obtained by those skilled in the art without making creative work, that is, all modifications, equivalent substitutions and improvements made within the spirit and principles of this application, fall within the protection scope required by the present invention.

Claims

1. A method for recovering rhodium and iridium from precious metal refining mother liquor containing rhodium and iridium, characterized in that: The steps include: (1) Oxidation pretreatment: add saturated sodium chlorate solution to the precious metal refining mother liquor and react at 90-95°C for 1.5-2h; (2) Purification and impurity removal: sodium hydroxide is added to the pretreated solution to adjust the pH value of the solution, and benzoic acid, an impurity remover, is added to react at 60-65° C. for 1-2 hours, and filtered. The filtrate obtained is the purified solution; (3) Deep precipitation: adding a precipitant to the purified liquid and reacting at 70-75° C. for 2-3 hours to obtain a rhodium-iridium precipitate, wherein the precipitant is a mixed solution of sodium hydroxyacetate and sodium hydroxide.

2. A method for recovering rhodium and iridium from a precious metal refining mother liquor containing rhodium and iridium according to claim 1, characterized in that: The amount of the saturated sodium chlorate solution added in step (1) is 1-2% of the volume of the precious metal refining mother liquor.

3. A method for recovering rhodium and iridium from a precious metal refining mother liquor containing rhodium and iridium according to claim 1, characterized in that: In step (2), sodium hydroxide is added until the pH value of the pretreated solution is 1-2.

4. A method for recovering rhodium and iridium from a precious metal refining mother liquor containing rhodium and iridium according to claim 1 or 3, characterized in that: The amount of benzoic acid added as the impurity remover in step (2) is 1.8-2.1 times the total content of nickel, copper, iron and cobalt in the precious metal refining mother liquor.

5. A method for recovering rhodium and iridium from a precious metal refining mother liquor containing rhodium and iridium according to claim 1, characterized in that: The precipitant in step (3) is sodium hydroxyacetate and sodium hydroxide mixed in a mass ratio of 1:0.8-1.2 to prepare a mixed solution with a concentration of 20-25%.

6. A method for recovering rhodium and iridium from a precious metal refining mother liquor containing rhodium and iridium according to claim 1 or 5, characterized in that: In step (3), a precipitant is added to the purified liquid until the pH value of the solution is 8-9.

Images