A method for separating rhodium and ruthenium metals from a mixture of noble metals

Abstract

The application discloses a method for separating rhodium and ruthenium from a mixed liquid of noble metals in the field of chemical waste liquid recovery, and steps of the method comprise the following steps: analyzing the types and contents of noble metals in the mixed liquid, and selecting and adjusting the mixed liquid; preparing a carrier with a mesoporous silica coating layer as an outer shell and Fe3O4 nanoparticles as an inner core, and then modifying the carrier with thiourea-pyridine groups and 4-amino-1,2,4-triazole groups in sequence to obtain an adsorbent; loading the adsorbent into an adsorption column to perform dynamic adsorption; then performing step-by-step desorption and collecting desorption liquid; and taking the desorption liquid to recover metal rhodium and metal ruthenium respectively. The carrier modified with bifunctional chelating groups is used as a selective adsorbent, the selective adsorbent has high selectivity, strong anti-interference ability of impurities, and is helpful to improve the separation and recovery efficiency, and the process cycle is short, the operation is convenient, and the recyclability is good; the Fe3O4 nanoparticles are used as the inner core, the magnetic separation operation is facilitated, and the structural stability of the adsorbent is improved.

Description

Technical Field

[0001] This invention relates to the field of chemical waste recovery, and specifically to a method for separating rhodium and ruthenium metals from a mixture of precious metals. Background Technology

[0002] In many catalyst waste liquids (such as acidic leachate produced after the deactivation of rhodium-based catalysts, and waste acid washing liquid of ruthenium-based catalysts in hydrogenation reactions), electronic electroplating waste liquids (such as ruthenium plating waste liquid of hard disks, and rhodium plating waste liquid of semiconductors), precious metal refining by-product liquids (such as residual liquid after platinum / palladium purification), alloy processing waste liquids (such as acidic waste liquid produced by etching or dissolving rhodium-ruthenium alloys), and other precious metal mixtures, there are certain contents of rhodium and ruthenium precious metals. Separating and recycling these rhodium and ruthenium precious metals has the following significance: (1) High economic value: The price of rhodium is about RMB 80 / gram, and the price of ruthenium is about RMB 80 / gram (data from 2024). Recycling can significantly reduce industrial costs. The value of a single ton of waste catalyst can reach several thousand US dollars, and the recycling benefits are significant. (2) Resource scarcity: 80% of the world's rhodium and ruthenium are produced in South Africa, and the supply is unstable. The abundance of rhodium in the earth's crust is only 0.001 ppm, and recycling is the key to sustainable supply. (3) Environmental protection and regulatory requirements: direct landfill will lead to heavy metal pollution, and the number of available landfills worldwide has decreased by 75% in the past 20 years. In addition, some Chinese regulations also require the harmless treatment of precious metal waste.

[0003] Currently, the main method for separating and recovering rhodium and ruthenium precious metals is chemical precipitation. For example, Chinese patent document CN110218867B discloses a method for separating rhodium and ruthenium from a mixture of precious metals. First, aqua regia is used to dissolve the solid containing rhodium and ruthenium to obtain a liquid containing rhodium and ruthenium. Then, a rhodium precipitation agent is added to precipitate and enrich the precious metal rhodium. In order to improve the purity of rhodium separation, the solid precipitated each time is dissolved in aqua regia and then the rhodium precipitation agent is added again for precipitation and enrichment until the concentration of Ru in the precipitation tail liquid is detected to be 0.001 g / L. This concentration has no effect on the purity of the recovered rhodium. Then, the precipitation tail liquids at each stage are collected and zinc powder is added for reduction, thereby achieving the purpose of separating rhodium and ruthenium.

[0004] However, when using the existing chemical precipitation method, rhodium needs to be precipitated multiple times (usually 3 times) to achieve high purity. The operation is cumbersome, the rhodium loss rate is high, the cycle is long, and the precipitate is easily contaminated. Summary of the Invention

[0005] The purpose of this invention is to provide a method for separating rhodium and ruthenium metals from a mixture of precious metals, which solves the problems of cumbersome operation, high rhodium loss rate, long cycle, and easy contamination of precipitates in existing chemical precipitation methods for separating rhodium and ruthenium metals.

[0006] The present invention achieves the above objectives through the following technical solutions:

[0007] A method for separating rhodium and ruthenium metals from a precious metal mixture, comprising the steps of:

[0008] S1. Preprocessing:

[0009] Take a mixture of precious metals, analyze the types and contents of precious metals in the mixture, select the mixture with rhodium and ruthenium metal contents that meet the preset range as the target for separation, add NaCl to the mixture until the concentration reaches 0.08-0.12M, and then adjust the pH of the mixture to 1.5±0.2 with hydrochloric acid.

[0010] S2, Adsorbent Preparation

[0011] Fe3O4@mSiO2 support with a mesoporous silica coating and Fe3O4 nanoparticles as the core was prepared. After activation, the support was dispersed in anhydrous ethanol, and aminopyridine and ammonium thiocyanate were added. The reaction was carried out at 75±2℃ for 10-15 h. The support was then separated, activated, and dispersed in dimethylformamide, and 4-amino-1,2,4-triazole was added. The reaction was carried out at 85±2℃ for 25-30 h. The support was then separated and purified to obtain the rhodium-ruthenium selective adsorbent.

[0012] S3, Dynamic Adsorption

[0013] Rhodium-ruthenium selective adsorbent was packed into an adsorption column, and the flow rate of the mixed solution was controlled at 2.5-3.5 BV / h for dynamic adsorption at room temperature. The total throughput of the mixed solution was controlled at 10-15 BV.

[0014] S4, Stepwise desorption

[0015] First, 0.4-0.6M thiourea and 1.2-1.5M HCl are added to pure water as a solvent to obtain a rhodium desorbent. The rhodium desorbent is pumped into the column for circulation desorption and the rhodium desorbed solution is collected. The column is then rinsed with pure water. Next, 8-12% H2O2 and 0.15-0.2M NaOH are added to pure water as a solvent to obtain a ruthenium desorbent. The ruthenium desorbent is pumped into the column for circulation desorption and the ruthenium desorbed solution is collected.

[0016] S5, Rhodium-Ruthenium Recycling

[0017] Rhodium and ruthenium were recovered from the rhodium and ruthenium desorption solutions, respectively.

[0018] A further improvement is that, in step S1, the types and contents of precious metals in the waste liquid are analyzed by inductively coupled plasma mass spectrometry or X-ray photoelectron spectroscopy, and the preset range refers to Rh 3+ 500-5000 mg / L, Ru 3+ : 100-500mg / L.

[0019] A further improvement is made in step S2, where the specific operation for preparing the Fe3O4@mSiO2 support is as follows: Fe3O4 nanoparticles with a particle size of 400±20nm are taken, dispersed in an ethanol solution, and ultrasonically treated until no agglomeration occurs. Then, hexadecyltrimethylammonium bromide is added and stirred to dissolve. Next, tetraethyl orthosilicate and ammonia are added, and the temperature is controlled at 40±2℃. The mixture is stirred at 300-350rpm for 4-6h. After the reaction, the product is magnetically separated and washed, and then extracted with 0.08-0.12M HCl-ethanol solution by Soxhlet extraction for 24-28h to remove hexadecyltrimethylammonium bromide. Finally, the product is calcined and activated at 350-400℃ in a nitrogen atmosphere for 1.8-2.2h to obtain the Fe3O4@mSiO2 support.

[0020] The ratio of Fe3O4 nanoparticles, ethanol solution, hexadecyltrimethylammonium bromide, tetraethyl orthosilicate and ammonia is 1g:180-220mL:0.9-1.2g:2.4-2.6mL:4-6mL.

[0021] A further improvement is that the pore size of the Fe3O4@mSiO2 support is 40-50 nm.

[0022] A further improvement is that, after the Fe3O4@mSiO2 support is prepared, a poly(acrylamide-co-acrylonitrile) thermosensitive layer is grafted onto its surface and pore walls. The specific operation is as follows: Fe3O4@mSiO2 support is refluxed with 1M HCl for 4 hours, washed with water until neutral and dried. Fe3O4@mSiO2 support is then dispersed in dimethylformamide at a ratio of 1g / 250mL. Acrylamide and acrylonitrile monomers are then added. The mixture is heated to 60℃ under nitrogen protection, and then 0.5% of azobisisobutyronitrile (AIBN) is added. The reaction is carried out for 6 hours. After the reaction is completed, the mixture is washed with dimethylformamide and ethanol alternately and then dried.

[0023] A further improvement is that the total mass of the monomers is 2.2 times the mass of the Fe3O4@mSiO2 carrier, and the molar ratio of acrylamide to acrylonitrile is 10:1, resulting in a UCST temperature of 40±2℃ for the poly(acrylamide-co-acrylonitrile) thermosensitive layer.

[0024] A further improvement is that, in step S2, the amount of anhydrous ethanol used is 100-120 mL / g, the amount of aminopyridine used is 0.18-0.24 mol / g, the amount of ammonium thiocyanate used is 0.22-0.26 mol / g, the amount of dimethylformamide used is 120-150 mL / g, and the amount of 4-amino-1,2,4-triazole used is 0.35-0.42 mol / g.

[0025] A further improvement is that, in step S2, the activation treatment refers to: first, dehydrating the carrier at 100-110℃ for 1.5-2.5h, then dissolving 3-propyltriethoxysilane in toluene to obtain an activation solution with a concentration of 0.005-0.01mol / mL, then placing the carrier in the activation solution, controlling the temperature at 112±2℃, refluxing under nitrogen protection for 24-28h, and finally cooling, magnetically separating, washing and drying.

[0026] A further improvement is that, in step S2, the purification refers to: first, Soxhlet extraction of the carrier with ethanol as solvent for 24-36 hours, and then vacuum drying at 55-65℃ for 10-15 hours.

[0027] A further improvement is that, in step S4, the pumping flow rate of the rhodium desorbent is 1.8-2.4 BV / h, the column temperature is controlled at 58-62℃, and when the Rh in the outlet rhodium desorbate... 3+ Desorption was terminated when the concentration of Ru in the ruthenium desorbent was <5 mg / L. The pumping flow rate of the ruthenium desorbent was 1.4-1.6 BV / h, the column temperature was controlled at 75-85℃, and the concentration of Ru in the outlet ruthenium desorbent was <5 mg / L. 3+ Desorption was terminated when the concentration was <5 mg / L.

[0028] The beneficial effects of this invention are as follows:

[0029] (1) The present invention uses a carrier modified with bifunctional chelating groups (thiourea-pyridine group and 4-amino-1,2,4-triazole group) as a selective adsorbent. It has high selectivity for rhodium and ruthenium, strong resistance to impurity interference, and helps to improve separation and recovery efficiency. In addition, the process cycle is short, the operation is convenient, and the recyclability is good.

[0030] (2) The adsorbent carrier of the present invention uses Fe3O4 nanoparticles as the core, which facilitates magnetic separation operation and can improve the structural stability of the adsorbent and extend the cycle life.

[0031] (3) In a preferred embodiment of the present invention, a poly(acrylamide-co-acrylonitrile) thermosensitive layer is grafted onto the surface and pore walls of the adsorbent carrier. During the grafting process, the process parameters are strictly controlled to ensure that the pores of the carrier are fully preserved after grafting, so as to avoid affecting the modification of chelating groups and adsorption efficiency. At the same time, by controlling the copolymer molar ratio, the UCST temperature of the thermosensitive layer is kept at about 40°C. This allows it to be in a hydrophobic shrinkage state when adsorbing at room temperature, so that the pore depth and volume are large, which is conducive to large-capacity adsorption. When desorbing at high temperature, it is in a hydrophilic swelling state, so that the pore depth and volume are reduced, which is conducive to desorption and can improve the desorption efficiency and final yield.

[0032] (4) The process of the present invention can also be coupled with membrane separation and other electrochemical technologies to further shorten the process and reduce energy consumption. Attached Figure Description

[0033] Figure 1 This is a scanning electron microscope image of the Fe3O4@mSiO2 support grafted with a thermosensitive layer in Example 4 of the present invention;

[0034] Figure 2 This is a graph showing the test results of the high critical dissolution temperature of the temperature-sensitive layer in Embodiment 4 of the present invention. Detailed Implementation

[0035] The present application will now be described in further detail with reference to the accompanying drawings. It should be noted that the following specific embodiments are only used to further illustrate the present application and should not be construed as limiting the scope of protection of the present application. Those skilled in the art can make some non-essential improvements and adjustments to the present application based on the above application content.

[0036] I. Main Materials

[0037] Fe3O4 nanoparticles: particle size 400±20nm, purchased from Shanghai Yaotian New Materials Technology Co., Ltd.;

[0038] Cetyltrimethylammonium bromide: purchased from Henan Licheng Fine Chemical Co., Ltd.;

[0039] Ethyl orthosilicate: purchased from Shandong Silicon Science New Materials Co., Ltd.;

[0040] Ammonia solution: purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.

[0041] 3-Propyltriethoxysilane: purchased from Hubei Yongkuo Technology Co., Ltd.;

[0042] Aminopyridine: purchased from Anhui Xingyu Chemical Co., Ltd.;

[0043] Ammonium thiocyanate: purchased from Hunan Ruipinsheng New Materials Co., Ltd.;

[0044] Dimethylformamide: purchased from Jinan Feiyue Chemical Co., Ltd.;

[0045] 4-Amino-1,2,4-triazole: purchased from Shanghai Qiao Chemical Technology Co., Ltd.;

[0046] Thiourea: purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.;

[0047] Acrylamide: purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.;

[0048] Acrylonitrile: Purchased from Chengdu Aikeda Chemical Reagent Co., Ltd.;

[0049] Azobisisobutyronitrile: Purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.

[0050] II. Conducting the Experiment

[0051] The object of the precious metal mixed liquid treatment: the petrochemical catalytic waste liquid of a factory. According to the inductively coupled plasma mass spectrometry, its initial rhodium concentration was 2421.8 mg / L, the ruthenium concentration was 315.4 mg / L, and it also contained heavy metal impurities of Ni, Cu and Fe, all of which were <0.5 mg / L.

[0052] Example 1

[0053] A method for separating rhodium and ruthenium metals from a precious metal mixture, characterized by the following steps:

[0054] S1. Preprocessing:

[0055] Take a mixture of precious metals and analyze the types and contents of precious metals in the waste liquid by inductively coupled plasma mass spectrometry or X-ray photoelectron spectroscopy. Select the mixture with rhodium and ruthenium metal contents that meet the preset range as the target separation object (the initial rhodium concentration of the object of this invention is 2421.8 mg / L and the ruthenium concentration is 315.4 mg / L). Add NaCl to the mixture until the concentration reaches 0.08 M, and then adjust the pH of the mixture to 1.3 with hydrochloric acid.

[0056] S2, Adsorbent Preparation

[0057] The Fe3O4@mSiO2 support with a mesoporous silica coating and Fe3O4 nanoparticles as the core was prepared as follows: Fe3O4 nanoparticles with a particle size of 400±20 nm were dispersed in an ethanol solution and sonicated until no agglomeration occurred. Then, hexadecyltrimethylammonium bromide was added and stirred to dissolve. Next, tetraethyl orthosilicate and ammonia were added, and the reaction was carried out at 38℃ and stirred at 300 rpm for 6 h. After the reaction, the product was magnetically separated and washed, and then Soxhlet extracted with 0.08M HCl-ethanol solution for 28 h to remove hexadecyltrimethylammonium bromide. Finally, it was calcined and activated at 350℃ for 2.2 h in a nitrogen atmosphere to obtain Fe3O4@mSiO2 support with a pore size of 40-50 nm. The ratio of Fe3O4 nanoparticles, ethanol solution, hexadecyltrimethylammonium bromide, tetraethyl orthosilicate and ammonia was 1 g:180 mL:0.9 g:2.4 mL:4 mL.

[0058] The carrier was dehydrated at 100℃ for 2.5 h. Then, 3-propyltriethoxysilane was dissolved in toluene to obtain an activation solution with a concentration of 0.005 mol / mL. The carrier was then placed in the activation solution and refluxed at 110℃ under nitrogen protection for 28 h. Finally, the mixture was cooled, magnetically separated, washed, and dried. The carrier was then dispersed in anhydrous ethanol, and aminopyridine and ammonium thiocyanate were added. The reaction was carried out at 73℃ for 15 h. The carrier was then separated and activated (using the same procedure), and then dispersed in dimethylformamide. 4-Amino-1,2,4-triazole was added, and the reaction was carried out at 83℃ for 30 h. The carrier was then separated and purified (first, the carrier was Soxhlet extracted with ethanol as a solvent for 24 h, and then vacuum dried at 55℃ for 15 h) to obtain the rhodium-ruthenium selective adsorbent.

[0059] Specifically, based on the carrier mass, the amount of anhydrous ethanol used is 100 mL / g, the amount of aminopyridine used is 0.18 mol / g, the amount of ammonium thiocyanate used is 0.22 mol / g, the amount of dimethylformamide used is 120 mL / g, and the amount of 4-amino-1,2,4-triazole used is 0.35 mol / g.

[0060] S3, Dynamic Adsorption

[0061] Rhodium-ruthenium selective adsorbent was packed into an adsorption column, and the flow rate of the mixed solution was controlled at 2.5 BV / h for dynamic adsorption at room temperature. The total throughput of the mixed solution was controlled at 10 BV.

[0062] S4, Stepwise desorption

[0063] First, 0.4 M thiourea and 1.2 M HCl were added to pure water as a solvent to obtain a rhodium desorbent. This rhodium desorbent was pumped into a column for circulation desorption, and the rhodium eluent was collected. The column was then rinsed with pure water. Next, 8% H₂O₂ and 0.15 M NaOH were added to pure water as a solvent to obtain a ruthenium desorbent. This ruthenium desorbent was pumped into a column for circulation desorption, and the ruthenium eluent was collected. The pumping flow rate of the rhodium desorbent was 1.8 BV / h, the column temperature was controlled at 58℃, and the concentration of Rh in the outlet rhodium eluent was... 3+ Desorption was terminated when the Ru content was <5 mg / L. The pumping flow rate of the ruthenium desorbent was 1.4 BV / h, the column temperature was controlled at 75°C, and the Ru content in the outlet ruthenium desorbate was determined by the concentration of Ru. 3+ Desorption was terminated when the concentration was <5 mg / L.

[0064] S5, Rhodium-Ruthenium Recycling

[0065] Rhodium and ruthenium desorption solutions were recovered to obtain metallic rhodium and metallic ruthenium, respectively (specifically, existing technology was used; for example, the pH of the rhodium desorption solution was adjusted to neutral with ammonia water to obtain [Rh(NH3)5Cl]Cl2 precipitate, which was then filtered and calcined (800℃ / 2h) to obtain metallic rhodium with a purity >99.5%; the ruthenium desorption solution was concentrated by distillation, and then saturated KCl solution was added to obtain K2[RuO4] crystals, which were then reduced with hydrogen (300℃ / H2) to obtain metallic ruthenium with a purity >99.2%, the same below).

[0066] Example 2

[0067] A method for separating rhodium and ruthenium metals from a precious metal mixture, characterized by the following steps:

[0068] S1. Preprocessing:

[0069] Take a mixture of precious metals and analyze the types and contents of precious metals in the waste liquid by inductively coupled plasma mass spectrometry or X-ray photoelectron spectroscopy. Select a mixture with rhodium and ruthenium metal contents that meet the preset range as the target separation object (the initial rhodium concentration of the object of this invention is 2421.8 mg / L and the ruthenium concentration is 315.4 mg / L). Add NaCl to the mixture until the concentration reaches 0.1M, and then adjust the pH of the mixture to 1.5 with hydrochloric acid.

[0070] S2, Adsorbent Preparation

[0071] The Fe3O4@mSiO2 support with a mesoporous silica coating and Fe3O4 nanoparticles as the core was prepared as follows: Fe3O4 nanoparticles with a particle size of 400±20 nm were dispersed in an ethanol solution and sonicated until no agglomeration occurred. Then, hexadecyltrimethylammonium bromide was added and stirred to dissolve. Next, tetraethyl orthosilicate and ammonia were added, and the reaction was carried out at 40℃ and stirred at 320 rpm for 5 h. After the reaction, the product was magnetically separated and washed, and then Soxhlet extracted with 0.1M HCl-ethanol solution for 26 h to remove hexadecyltrimethylammonium bromide. Finally, it was calcined and activated at 380℃ for 2 h in a nitrogen atmosphere to obtain Fe3O4@mSiO2 support with a pore size of 40-50 nm. The ratio of Fe3O4 nanoparticles, ethanol solution, hexadecyltrimethylammonium bromide, tetraethyl orthosilicate and ammonia was 1 g: 200 mL: 1 g: 2.5 mL: 5 mL.

[0072] The carrier was dehydrated at 105℃ for 2 h. Then, 3-propyltriethoxysilane was dissolved in toluene to obtain an activation solution with a concentration of 0.008 mol / mL. The carrier was then placed in the activation solution and refluxed at 112℃ under nitrogen protection for 26 h. Finally, the mixture was cooled, magnetically separated, washed, and dried. The carrier was then dispersed in anhydrous ethanol, and aminopyridine and ammonium thiocyanate were added. The reaction was carried out at 75℃ for 12 h. The carrier was then separated and activated (using the same procedure), dispersed in dimethylformamide, and 4-amino-1,2,4-triazole was added. The reaction was carried out at 85℃ for 28 h. The carrier was then separated and purified (first, the carrier was Soxhlet extracted with ethanol as a solvent for 30 h, then vacuum dried at 60℃ for 12 h) to obtain the rhodium-ruthenium selective adsorbent.

[0073] Specifically, based on the mass of the carrier, the amount of anhydrous ethanol used is 110 mL / g, the amount of aminopyridine used is 0.2 mol / g, the amount of ammonium thiocyanate used is 0.24 mol / g, the amount of dimethylformamide used is 135 mL / g, and the amount of 4-amino-1,2,4-triazole used is 0.4 mol / g.

[0074] S3, Dynamic Adsorption

[0075] Rhodium-ruthenium selective adsorbent was packed into an adsorption column, and the flow rate of the mixed solution was controlled at 3 BV / h for dynamic adsorption at room temperature. The total throughput of the mixed solution was controlled at 12 BV.

[0076] S4, Stepwise desorption

[0077] First, 0.5 M thiourea and 1.4 M HCl were added to pure water as a solvent to obtain a rhodium desorbent. This rhodium desorbent was pumped into a column for circulation desorption, and the rhodium eluent was collected. The column was then rinsed with pure water. Next, 10% H₂O₂ and 0.18 M NaOH were added to pure water as a solvent to obtain a ruthenium desorbent. This ruthenium desorbent was pumped into a column for circulation desorption, and the ruthenium eluent was collected. The pumping flow rate of the rhodium desorbent was 2.2 BV / h, the column temperature was controlled at 60℃, and the concentration of Rh in the outlet rhodium eluent was... 3+ Desorption was terminated when the concentration of Ru in the ruthenium desorbent was <5 mg / L. The pumping flow rate of the ruthenium desorbent was 1.5 BV / h, the column temperature was controlled at 80°C, and the concentration of Ru in the outlet ruthenium desorbent was determined by the concentration of Ru in the ruthenium desorbent. 3+ Desorption was terminated when the concentration was <5 mg / L.

[0078] S5, Rhodium-Ruthenium Recycling

[0079] Rhodium and ruthenium were recovered from the rhodium and ruthenium desorption solutions, respectively.

[0080] Example 3

[0081] A method for separating rhodium and ruthenium metals from a precious metal mixture, characterized by the following steps:

[0082] S1. Preprocessing:

[0083] Take a mixture of precious metals and analyze the types and contents of precious metals in the waste liquid by inductively coupled plasma mass spectrometry or X-ray photoelectron spectroscopy. Select the mixture with rhodium and ruthenium metal contents that meet the preset range as the target separation object (the initial rhodium concentration of the object of this invention is 2421.8 mg / L and the ruthenium concentration is 315.4 mg / L). Add NaCl to the mixture until the concentration reaches 0.12M, and then adjust the pH of the mixture to 1.7 with hydrochloric acid.

[0084] S2, Adsorbent Preparation

[0085] The Fe3O4@mSiO2 support with a mesoporous silica coating and Fe3O4 nanoparticles as the core was prepared as follows: Fe3O4 nanoparticles with a particle size of 400±20 nm were dispersed in an ethanol solution and ultrasonically treated until no agglomeration occurred. Then, hexadecyltrimethylammonium bromide was added and stirred to dissolve. Next, tetraethyl orthosilicate and ammonia were added, and the reaction was carried out at 42℃ and stirred at 350 rpm for 4 h. After the reaction, the product was magnetically separated and washed, and then Soxhlet extracted with 0.12M HCl-ethanol solution for 24 h to remove hexadecyltrimethylammonium bromide. Finally, it was calcined and activated at 400℃ for 1.8 h in a nitrogen atmosphere to obtain Fe3O4@mSiO2 support with a pore size of 40-50 nm. The ratio of Fe3O4 nanoparticles, ethanol solution, hexadecyltrimethylammonium bromide, tetraethyl orthosilicate and ammonia was 1 g: 220 mL: 1.2 g: 2.6 mL: 6 mL.

[0086] The carrier was dehydrated at 110℃ for 1.5 h. Then, 3-propyltriethoxysilane was dissolved in toluene to obtain an activation solution with a concentration of 0.01 mol / mL. The carrier was then placed in the activation solution and refluxed at 114℃ under nitrogen protection for 24 h. Finally, the mixture was cooled, magnetically separated, washed, and dried. The carrier was then dispersed in anhydrous ethanol, and aminopyridine and ammonium thiocyanate were added. The reaction was carried out at 77℃ for 10 h. The carrier was then separated and activated (using the same procedure), and then dispersed in dimethylformamide. 4-Amino-1,2,4-triazole was added, and the reaction was carried out at 87℃ for 25 h. The carrier was then separated and purified (first, the carrier was Soxhlet extracted with ethanol as a solvent for 36 h, and then vacuum dried at 65℃ for 10 h) to obtain the rhodium-ruthenium selective adsorbent.

[0087] Specifically, based on the mass of the carrier, the amount of anhydrous ethanol used is 120 mL / g, the amount of aminopyridine used is 0.24 mol / g, the amount of ammonium thiocyanate used is 0.26 mol / g, the amount of dimethylformamide used is 150 mL / g, and the amount of 4-amino-1,2,4-triazole used is 0.42 mol / g.

[0088] S3, Dynamic Adsorption

[0089] Rhodium-ruthenium selective adsorbent was packed into an adsorption column, and the flow rate of the mixed solution was controlled at 3.5 BV / h for dynamic adsorption at room temperature. The total throughput of the mixed solution was controlled at 15 BV.

[0090] S4, Stepwise desorption

[0091] First, 0.6 M thiourea and 1.5 M HCl were added to pure water as a solvent to obtain a rhodium desorbent. This rhodium desorbent was pumped into a column for circulation desorption, and the rhodium eluent was collected. The column was then rinsed with pure water. Next, 12% H₂O₂ and 0.2 M NaOH were added to pure water as a solvent to obtain a ruthenium desorbent. This ruthenium desorbent was pumped into a column for circulation desorption, and the ruthenium eluent was collected. The pumping flow rate of the rhodium desorbent was 2.4 BV / h, the column temperature was controlled at 62℃, and the concentration of Rh in the outlet rhodium eluent was... 3+ Desorption was terminated when the Ru content was <5 mg / L. The pumping flow rate of the ruthenium desorbent was 1.6 BV / h, the column temperature was controlled at 85°C, and the Ru content in the outlet ruthenium desorbate was determined by the concentration of Ru. 3+ Desorption was terminated when the concentration was <5 mg / L.

[0092] S5, Rhodium-Ruthenium Recycling

[0093] Rhodium and ruthenium were recovered from the rhodium and ruthenium desorption solutions, respectively.

[0094] Example 4

[0095] A method for separating rhodium and ruthenium metals from a precious metal mixture, characterized by the following steps:

[0096] S1. Preprocessing:

[0097] Take a mixture of precious metals and analyze the types and contents of precious metals in the waste liquid by inductively coupled plasma mass spectrometry or X-ray photoelectron spectroscopy. Select a mixture with rhodium and ruthenium metal contents that meet the preset range as the target separation object (the initial rhodium concentration of the object of this invention is 2421.8 mg / L and the ruthenium concentration is 315.4 mg / L). Add NaCl to the mixture until the concentration reaches 0.1M, and then adjust the pH of the mixture to 1.5 with hydrochloric acid.

[0098] S2, Adsorbent Preparation

[0099] The Fe3O4@mSiO2 support with a mesoporous silica coating and Fe3O4 nanoparticles as the core was prepared as follows: Fe3O4 nanoparticles with a particle size of 400±20 nm were dispersed in an ethanol solution and sonicated until no agglomeration occurred. Then, hexadecyltrimethylammonium bromide was added and stirred to dissolve. Next, tetraethyl orthosilicate and ammonia were added, and the reaction was carried out at 40℃ and stirred at 320 rpm for 5 h. After the reaction, the product was magnetically separated and washed, and then Soxhlet extracted with 0.1M HCl-ethanol solution for 26 h to remove hexadecyltrimethylammonium bromide. Finally, it was calcined and activated at 380℃ for 2 h in a nitrogen atmosphere to obtain Fe3O4@mSiO2 support with a pore size of 40-50 nm. The ratio of Fe3O4 nanoparticles, ethanol solution, hexadecyltrimethylammonium bromide, tetraethyl orthosilicate and ammonia was 1 g: 200 mL: 1 g: 2.5 mL: 5 mL.

[0100] The specific procedure for grafting a poly(acrylamide-co-acrylonitrile) thermosensitive layer onto the surface and pore walls of the Fe3O4@mSiO2 support is as follows: The Fe3O4@mSiO2 support is refluxed with 1M HCl for 4 hours, washed with water until neutral, and dried. Then, the Fe3O4@mSiO2 support is dispersed in dimethylformamide at a ratio of 1 g / 250 mL. Acrylamide and acrylonitrile monomers are added, and the mixture is heated to 60°C under nitrogen protection. Then, 0.5% (by mass) of azobisisobutyronitrile (AIBN) is added, and the reaction is carried out for 6 hours. After the reaction, the mixture is washed alternately with dimethylformamide and ethanol, and then dried. The total mass of the monomers is 2.2 times the mass of the Fe3O4@mSiO2 support, and the molar ratio of acrylamide to acrylonitrile is 10:1.

[0101] The basic morphology of the Fe3O4@mSiO2 support was observed using a scanning electron microscope (JEM-7800F, JEOL). The morphology is as follows: Figure 1 As shown in the figure, it can be seen that the size uniformity, roundness and dispersibility are good. The specific surface area, pore volume and pore size of the Fe3O4@mSiO2 support were analyzed by a specific surface area and pore size analyzer (BELSORP-maxII). The final results are shown in Table 1 below. The results show that the support after grafting the temperature-sensitive layer still has a high specific surface area and good pore structure, which enables it to have sufficient adsorption performance.

[0102] Table 1: Specific surface area, pore volume, and pore size of Fe3O4@mSiO2 support

[0103]

[0104] To determine the UCST temperature of the prepared poly(acrylamide-co-acrylonitrile) thermosensitive layer, an acrylamide-co-acrylonitrile thermosensitive solution was prepared using the same monomer ratio and initiator dosage as described above (i.e., without the addition of Fe3O4@mSiO2 support). A 760CRT dual-beam UV-Vis spectrophotometer was used in single-wavelength scanning mode at 700 nm to measure the light transmittance of the thermosensitive solution at different temperatures to characterize the turbidity changes in the solution system, thereby determining its phase transition temperature (high critical solution temperature, UCST). The results are as follows: Figure 2 As shown, its UCST temperature is 40±2℃.

[0105] Next, the support was dehydrated at 105℃ for 2 hours. Then, 3-propyltriethoxysilane was dissolved in toluene to obtain an activation solution with a concentration of 0.008 mol / mL. The support was then placed in the activation solution and refluxed at 112℃ under nitrogen protection for 26 hours. Finally, the solution was cooled, magnetically separated, washed, and dried. The support was then dispersed in anhydrous ethanol, and aminopyridine and ammonium thiocyanate were added. The reaction was carried out at 75℃ for 12 hours. The support was then separated and activated (using the same procedure), dispersed in dimethylformamide, and 4-amino-1,2,4-triazole was added. The reaction was carried out at 85℃ for 28 hours. The support was then separated and purified (first, the support was Soxhlet extracted with ethanol as a solvent for 30 hours, and then vacuum dried at 60℃ for 12 hours) to obtain the rhodium-ruthenium selective adsorbent.

[0106] Specifically, based on the mass of the carrier, the amount of anhydrous ethanol used is 110 mL / g, the amount of aminopyridine used is 0.2 mol / g, the amount of ammonium thiocyanate used is 0.24 mol / g, the amount of dimethylformamide used is 135 mL / g, and the amount of 4-amino-1,2,4-triazole used is 0.4 mol / g.

[0107] S3, Dynamic Adsorption

[0108] Rhodium-ruthenium selective adsorbent was packed into an adsorption column, and the flow rate of the mixed solution was controlled at 3 BV / h for dynamic adsorption at room temperature. The total throughput of the mixed solution was controlled at 12 BV.

[0109] S4, Stepwise desorption

[0110] First, 0.5 M thiourea and 1.4 M HCl were added to pure water as a solvent to obtain a rhodium desorbent. This rhodium desorbent was pumped into a column for circulation desorption, and the rhodium eluent was collected. The column was then rinsed with pure water. Next, 10% H₂O₂ and 0.18 M NaOH were added to pure water as a solvent to obtain a ruthenium desorbent. This ruthenium desorbent was pumped into a column for circulation desorption, and the ruthenium eluent was collected. The pumping flow rate of the rhodium desorbent was 2.2 BV / h, the column temperature was controlled at 60℃, and the concentration of Rh in the outlet rhodium eluent was... 3+Desorption was terminated when the concentration of Ru in the ruthenium desorbent was <5 mg / L. The pumping flow rate of the ruthenium desorbent was 1.5 BV / h, the column temperature was controlled at 80°C, and the concentration of Ru in the outlet ruthenium desorbent was determined by the concentration of Ru in the ruthenium desorbent. 3+ Desorption was terminated when the concentration was <5 mg / L.

[0111] Comparative Example 1

[0112] Based on Example 4, only the specific operation of grafting poly(acrylamide-co-acrylonitrile) thermosensitive layer onto the surface and pore walls of the Fe3O4@mSiO2 support was adjusted: The Fe3O4@mSiO2 support was refluxed with 1M HCl for 4 hours, washed with water until neutral, and dried. Then, the Fe3O4@mSiO2 support was dispersed in dimethylformamide at a ratio of 1 g / 250 mL. Acrylamide and acrylonitrile monomers were added, and the mixture was heated to 60°C under nitrogen protection. Then, 1% (by mass) of azobisisobutyronitrile was added, and the reaction was carried out for 10 hours. After the reaction, the mixture was washed alternately with dimethylformamide and ethanol, and then dried. The total mass of the monomers was 3.5 times the mass of the Fe3O4@mSiO2 support, and the molar ratio of acrylamide to acrylonitrile was 10:1.

[0113] Comparative Example 2 and Comparative Example 3

[0114] Based on Example 4, only the molar ratio of acrylamide to acrylonitrile in the poly(acrylamide-co-acrylonitrile) thermosensitive layer was adjusted to obtain Comparative Example 2 and Comparative Example 3, as shown in Table 2 below:

[0115] Table 2: Molar ratio of acrylamide to acrylonitrile in Comparative Examples 2 and 3

[0116]

[0117] III. Effect Test

[0118] The rhodium and ruthenium content in the precious metal mixtures treated in Examples 1-4 and Comparative Examples 1-3 was determined by inductively coupled plasma mass spectrometry. The specific detection process is as follows:

[0119] (1) Sample pretreatment: Take 1.0 mL of the mixture into a 15 mL polypropylene centrifuge tube, add 5% aqua regia (HNO3:HCl:H2O=1:3:16) to make up to 10.0 mL, mix well (if organic matter is present, first add 1 mL of concentrated HNO3 and digest at 95℃ for 30 min, then cool and dilute), filter through a 0.45 μm PTFE membrane, and store the filtrate at 4℃ (≤24 h);

[0120] (2) Standard and internal standard: Rh / Ru calibration curves (0, 1, 5, 10, 50, 100 μg / L) were prepared fresh with 5% aqua regia; the internal standard solution was 10 μg / L. 115 In (or 193 Ir).

[0121] (3) Instrument preparation: ICP-MS was preheated for 30 min and the sensitivity was optimized with tuning solution. 89 Y signal > 500000cps, oxide CeO ＋ / Ce ＋ <3%, double charge Ba 2＋ / Ba ＋ <3%.

[0122] (4) Sample analysis: ① Initial cleaning: Inject 5% aqua regia blank solution and clean the system for 90 seconds; ② Calibration curve analysis: Inject samples in order of increasing concentration: 0 μg / L → 1 μg / L → 5 μg / L → 10 μg / L → 50 μg / L → 100 μg / L standard solution; ③ Sample analysis: Inject the sample solution to be tested. The instrument automatically mixes the internal standard solution online. Pay attention to the cleaning between samples, that is, inject the sample immediately after completing each sample. Mix the cleaning solution and rinse for 90 seconds. Additionally, after every 10 samples analyzed, insert: 1 certified reference material (CRM) (known concentration) and 1 spiked recovery sample (sample matrix + known concentration of standard).

[0123] Instrument parameter monitoring: RF power 1500W, carrier gas flow rate 0.90L / min, DRC mode CH4 flow (0.7mL / min), monitoring 102 Ru (main) 101 Ru (verification) 103 Rh.

[0124] Based on the above test results, the adsorption separation rate and rhodium-ruthenium recovery rate of each embodiment and comparative example were calculated using the following formulas:

[0125]

[0126] In the formula, C0 is the initial concentration of rhodium or ruthenium metal in the mixture, in mg / L; C1 is the residual concentration of rhodium or ruthenium metal in the mixture after treatment, in mg / L.

[0127]

[0128] In the formula, M0 is the initial mass of rhodium or ruthenium metal in the mixture, in mg; M1 is the final mass of recovered rhodium or ruthenium metal, in mg.

[0129] IV. Results Analysis

[0130] The calculated results of adsorption separation rate and rhodium-ruthenium recovery rate of Examples 1-4 and Comparative Examples 1-3 are summarized in Table 3 below:

[0131] Table 3: Adsorption separation rate and rhodium-ruthenium recovery rate of Examples 1-4 and Comparative Examples 1-3

[0132]

[0133] As can be seen from Table 3 above, Examples 1-4 of this invention demonstrate outstanding effects in separating and recovering rhodium and ruthenium from precious metal mixtures. The rhodium adsorption separation rate is ≥95.0%, the rhodium recovery rate is ≥91.3%, the ruthenium adsorption separation rate is ≥93.0%, and the ruthenium recovery rate is ≥89.3%, all exceeding industry standards. Furthermore, the overall solution has a short cycle time and good recyclability. Example 4, in particular, further enhances the process by grafting a poly(acrylamide-co-acrylonitrile) temperature-sensitive layer onto the surface and pore walls of the adsorbent carrier, resulting in a rhodium adsorption separation rate of 99.1%, a rhodium recovery rate of 95.2%, a ruthenium adsorption separation rate of 98.7%, and a ruthenium recovery rate of 94.8%, demonstrating even more significant results.

[0134] Comparative Examples 1-3 were based on the process adjustments made in Example 4. In Comparative Example 1, some parameters in the grafting process of poly(acrylamide-co-acrylonitrile) thermosensitive layer were changed, which ultimately reduced the rhodium adsorption separation rate to 91.2%, the rhodium recovery rate to 87.5%, the ruthenium adsorption separation rate to 89.7%, and the ruthenium recovery rate to 86.1%. The overall effect was significantly reduced, even significantly worse than that of Example 2. This shows that the grafting process requires strict control of process parameters to ensure that the carrier pores are fully preserved after grafting, and to avoid affecting the modification of chelating groups and adsorption efficiency. Otherwise, it will be counterproductive. Comparative Examples 2 and 3 altered the molar ratio of acrylamide to acrylonitrile in the monopolymerized (acrylamide-co-acrylonitrile) thermosensitive layer. Comparative Example 2 significantly increased the amount of acrylonitrile, resulting in the worst separation and recovery performance. This may be because excessive acrylonitrile led to a significant decrease in the UCST temperature of the thermosensitive layer, causing it to prematurely enter a hydrophilic swelling state during room-temperature adsorption, occupying the pores and affecting the adsorption effect. Comparative Example 3 significantly reduced the amount of acrylonitrile, resulting in a certain degree of decrease in separation and recovery performance, especially for rhodium. This may be related to the significantly increased UCST temperature of the thermosensitive layer, which prevented the desorption temperature from fully triggering the phase transition of the thermosensitive layer, thus affecting the desorption process. In contrast, the desorption process of ruthenium, which occurs at a higher temperature, was less affected.

[0135] The embodiments described above are merely examples of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention.

Claims

1. A method for separating rhodium and ruthenium metals from a precious metal mixture, characterized in that the steps include... include: S1. Preprocessing: Take a mixture of precious metals, analyze the types and contents of precious metals in the mixture, select the mixture with rhodium and ruthenium metal contents that meet the preset range as the target for separation, add NaCl to the mixture until the concentration reaches 0.08-0.12M, and then adjust the pH of the mixture to 1.5±0.2 with hydrochloric acid. S2, Adsorbent Preparation Fe3O4@mSiO2 support with a mesoporous silica coating and Fe3O4 nanoparticles as the core was prepared. After activation, the support was dispersed in anhydrous ethanol, and aminopyridine and ammonium thiocyanate were added. The reaction was carried out at 75±2℃ for 10-15 h. The support was then separated, activated, and dispersed in dimethylformamide, and 4-amino-1,2,4-triazole was added. The reaction was carried out at 85±2℃ for 25-30 h. The support was then separated and purified to obtain the rhodium-ruthenium selective adsorbent. The Fe3O4@mSiO2 support has a pore size of 40-50 nm. The specific steps for preparing the Fe3O4@mSiO2 support are as follows: Fe3O4 nanoparticles with a particle size of 400±20 nm are dispersed in an ethanol solution and ultrasonically treated until no agglomeration occurs. Then, hexadecyltrimethylammonium bromide is added and stirred to dissolve. Next, tetraethyl orthosilicate and ammonia are added, and the reaction is carried out at 40±2℃ with stirring at 300-350 rpm for 4-6 hours. After the reaction, the product is magnetically separated and washed, then placed in a 0.08-0.12M HCl-ethanol solution for Soxhlet extraction for 24-28 hours to remove hexadecyltrimethylammonium bromide. Finally, the product is calcined and activated at 350-400℃ for 1.8-2.2 hours under a nitrogen atmosphere to obtain the Fe3O4@mSiO2 support. The surface and pore walls were grafted with a poly(acrylamide-co-acrylonitrile) thermosensitive layer. The specific procedure was as follows: Fe3O4@mSiO2 support was refluxed with 1M HCl for 4 hours, washed with water until neutral, and dried. Fe3O4@mSiO2 support was then dispersed in dimethylformamide at a ratio of 1 g / 250 mL. Acrylamide and acrylonitrile monomers were added, and the mixture was heated to 60°C under nitrogen protection. Then, 0.5% of azobisisobutyronitrile (AIBN) was added, and the reaction proceeded for 6 hours. After the reaction, the mixture was washed alternately with dimethylformamide and ethanol, and then dried. The total mass of the monomers was 2.2 times the mass of the Fe3O4@mSiO2 support, and the molar ratio of acrylamide to acrylonitrile was 10:

1. The UCST temperature of the resulting poly(acrylamide-co-acrylonitrile) thermosensitive layer was 40±2°C. The ratio of Fe3O4 nanoparticles, ethanol solution, hexadecyltrimethylammonium bromide, tetraethyl orthosilicate, and ammonia is: 1g:180-220mL:0.9-1.2g:2.4-2.6mL:4-6mL. S3, Dynamic Adsorption Rhodium-ruthenium selective adsorbent was packed into an adsorption column, and the flow rate of the mixed solution was controlled at 2.5-3.5 BV / h for dynamic adsorption at room temperature. The total throughput of the mixed solution was controlled at 10-15 BV. S4, Stepwise desorption First, 0.4-0.6M thiourea and 1.2-1.5M HCl are added to pure water as a solvent to obtain a rhodium desorbent. The rhodium desorbent is pumped into the column for circulation desorption and the rhodium desorbed solution is collected. The column is then rinsed with pure water. Next, 8-12% H2O2 and 0.15-0.2M NaOH are added to pure water as a solvent to obtain a ruthenium desorbent. The ruthenium desorbent is pumped into the column for circulation desorption and the ruthenium desorbed solution is collected. S5, Rhodium-Ruthenium Recycling Rhodium and ruthenium were recovered from the rhodium and ruthenium desorption solutions, respectively.

2. The method for separating rhodium and ruthenium metals from a precious metal mixture according to claim 1, characterized in that, In step S1, the types and contents of precious metals in the waste liquid are analyzed by inductively coupled plasma mass spectrometry or X-ray photoelectron spectroscopy, and the preset range refers to Rh 3+ 500-5000 mg / L, Ru 3+ : 100-500mg / L.

3. The method for separating rhodium and ruthenium metals from a precious metal mixture according to claim 1, characterized in that, In step S2, based on the mass of the carrier, the amount of anhydrous ethanol used is 100-120 mL / g, the amount of aminopyridine used is 0.18-0.24 mol / g, the amount of ammonium thiocyanate used is 0.22-0.26 mol / g, the amount of dimethylformamide used is 120-150 mL / g, and the amount of 4-amino-1,2,4-triazole used is 0.35-0.42 mol / g.

4. The method for separating rhodium and ruthenium metals from a precious metal mixture according to claim 1, characterized in that, In step S2, the activation treatment refers to: first, dehydrating the carrier at 100-110℃ for 1.5-2.5h, then dissolving 3-propyltriethoxysilane in toluene to obtain an activation solution with a concentration of 0.005-0.01mol / mL, then placing the carrier in the activation solution, controlling the temperature at 112±2℃, and refluxing under nitrogen protection for 24-28h, and finally cooling, magnetically separating, washing and drying.

5. The method for separating rhodium and ruthenium metals from a precious metal mixture according to claim 1, characterized in that, In step S2, the purification refers to: first, Soxhlet extraction of the carrier with ethanol as solvent for 24-36 hours, and then vacuum drying at 55-65℃ for 10-15 hours.

6. The method for separating rhodium and ruthenium metals from a noble metal mixture according to claim 1, characterized in that, In step S4, the pumping flow rate of the rhodium desorbent is 1.8-2.4 BV / h, the column temperature is controlled at 58-62℃, and the Rh concentration in the outlet rhodium desorbate is... 3+ Desorption was terminated when the concentration of Ru in the ruthenium desorbent was <5 mg / L. The pumping flow rate of the ruthenium desorbent was 1.4-1.6 BV / h, the column temperature was controlled at 75-85℃, and the concentration of Ru in the outlet ruthenium desorbent was <5 mg / L. 3+ Desorption was terminated when the concentration was <5 mg / L.

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