Method for determining rhodium content in rhodium-containing waste residue

Abstract

The invention relates to the field of rhodium determination methods, and discloses a method for determining the content of rhodium in rhodium-containing waste slag, which comprises the following steps: (1) roasting the rhodium-containing waste slag, washing for the first time, and drying for the first time to obtain rhodium slag; (2) the rhodium slag is subjected to reduction treatment, and rhodium ash a is obtained; (3) sequentially performing soaking, secondary washing and secondary drying on the rhodium ash a to obtain rhodium ash b; (4) adding strong acid into the rhodium ash b to carry out second reaction, then adding a strong oxidant to carry out third reaction, and fixing the volume after post-treatment to obtain a rhodium dissolving solution; (5) measuring the rhodium concentration of the rhodium dissolving solution; in the step (1), the first washing comprises the step of carrying out first reaction on the rhodium-containing waste residue and a first solvent; the first solvent is selected from N, N-dimethylformamide, N, N-dimethylacetamide, N-methylformamide or formamide, and the second solvent is selected from N, N-dimethylformamide, N, N-dimethylacetamide, N-methylformamide or formamide. According to the scheme, the rhodium metal can be dissolved from the rhodium-containing waste residues as much as possible, so that the rhodium content can be measured more accurately.

Description

Technical Field

[0001] The present invention relates to a method for the determination of rhodium, and particularly to a method for determining the rhodium content in rhodium-containing waste residues. Background Art

[0002] As a precious metal, rhodium has a wide range of uses in the industrial society. It can be prepared into rhodium-phosphine complex catalysts and applied in the field of olefin hydroformylation carbonylation synthesis. Moreover, it also has important applications in fields such as methanol carbonylation to acetic acid. Not only that, in terms of environmental protection, rhodium is also an important component element of the three-way catalyst in motor vehicle exhaust purification devices. Because the price of rhodium is high and the demand is large, the recovery of rhodium from rhodium-containing waste materials has become an important source of rhodium. Therefore, the determination of the rhodium content in rhodium-containing waste residues has important value for the recovery of rhodium.

[0003] At present, the commonly used methods for analyzing the rhodium content in waste rhodium residues include microwave digestion method, electrochemical dissolution method, alloy activation dissolution method, etc. Among them, the alloy activation dissolution method is relatively widely used. This method is to melt base metals such as zinc and aluminum with precious metals at high temperature to form an alloy, and then use acid to dissolve to obtain a precious metal salt solution, and then analyze and determine the precious metal salt solution. This analysis method is not easy to precipitate trace rhodium in the material, and the reaction process is relatively complex with many interference factors.

[0004] CN114427998A discloses a method for determining the rhodium content in rhodium-containing waste residues, which includes the following steps: subjecting the waste rhodium slag to aerobic roasting, and then obtaining rhodium ash I after washing and drying; performing a reduction treatment on rhodium ash I to obtain rhodium ash II; adding an acid solution to rhodium ash II for reaction to obtain a rhodium-containing liquid; adding a strong oxidant to the rhodium-containing liquid for reaction, and performing post-treatment and volume fixing to obtain a rhodium dissolution solution; detecting the concentration of rhodium in the rhodium dissolution solution. However, when determining the rhodium content in waste three-way catalysts, its accuracy is relatively low. Summary of the Invention

[0005] The purpose of the present invention is to overcome the above technical problems and provide a method for determining the rhodium content in rhodium-containing waste residues. This method can easily precipitate trace rhodium in the rhodium-containing waste residues, improve the dissolution rate of rhodium, and thus make the determination result more accurate.

[0006] To achieve the above purpose, the inventors of the present invention have conducted a large number of studies and found that treatment with N,N-dimethylformamide, N,N-dimethylacetamide, N-methylformamide or formamide, and subsequent immersion in hydrofluoric acid, the two cooperate synergistically, can effectively destroy the embedding structure of the rhodium-containing waste residues, release the embedded rhodium metal, and make the rhodium metal easier to dissolve.

[0007] Based on this, the first aspect of the present invention provides a method for determining the rhodium content in rhodium-containing waste residues, wherein the method includes:

[0008] (1) Roast the rhodium-containing waste residue, conduct the first washing and the first drying to obtain a rhodium residue;

[0009] (2) Conduct a reduction treatment on the rhodium residue to obtain rhodium ash a;

[0010] (3) Soak, conduct the second washing and the second drying on the rhodium ash a in sequence to obtain rhodium ash b;

[0011] (4) Add a strong acid to the rhodium ash b for a second reaction, then add a strong oxidant for a third reaction, and after post-treatment, make up the volume to obtain a rhodium dissolution solution;

[0012] (5) Measure the rhodium concentration of the rhodium dissolution solution;

[0013] In step (1), the first washing includes conducting a first reaction between the rhodium-containing waste residue and a first solvent;

[0014] The first solvent is selected from N,N-dimethylformamide, N,N-dimethylacetamide, N-methylformamide or formamide.

[0015] Through the above technical solution, the method of the present invention can precipitate trace rhodium in the rhodium-containing waste residue, improve the dissolution rate of rhodium, so that the measurement result is more accurate, and this method is simple to operate and less interfered. Detailed implementation mode

[0016] In the ranges disclosed herein, the endpoints and any values are not limited to the exact ranges or values, and these ranges or values should be understood to include values close to these ranges or values. For numerical ranges, between the endpoint values of each range, between the endpoint values of each range and a single point value, and between single point values, they can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be regarded as specifically disclosed herein.

[0017] In the present invention, without special circumstances, the "first", "second" and "third" neither represent the order nor limit each material or step, but are only used to distinguish that these are not the same material or step. For example, in "the first drying" and "the second drying", "first" and "second" are only used to indicate that these are not the same drying.

[0018] The first aspect of the present invention provides a method for measuring the rhodium content in a rhodium-containing waste residue, wherein the method includes:

[0019] (1) Roast the rhodium-containing waste residue, conduct the first washing and the first drying to obtain a rhodium residue;

[0020] (2) Conduct a reduction treatment on the rhodium residue to obtain rhodium ash a;

[0021] (3) Soak the rhodium ash a successively, conduct the second washing and the second drying to obtain rhodium ash b;

[0022] (4) After adding strong acid to rhodium ash b for the second reaction, add strong oxidant for the third reaction, and after post-treatment, make up the volume to obtain a rhodium dissolution solution;

[0023] (5) Measure the rhodium concentration of the rhodium dissolution solution;

[0024] In step (1), the first washing includes conducting the first reaction between the rhodium-containing waste residue and the first solvent;

[0025] The first solvent is selected from N,N-dimethylformamide, N,N-dimethylacetamide, N-methylformamide or formamide.

[0026] In the present invention, after conducting the first reaction with the above-mentioned first solvent, it is beneficial to the subsequent dissolution of rhodium, thereby improving the accuracy and stability of the rhodium content determination.

[0027] According to the present invention, in step (1), the roasting is aerobic roasting.

[0028] According to the present invention, the temperature of the roasting is 800 - 1000 °C, and the time of the roasting is 6 - 10 h.

[0029] Further, the temperature of the roasting is 850 - 950 °C, and the time of the roasting is 7 - 9 h.

[0030] According to the present invention, the first washing includes washing the rhodium-containing waste residue after the first reaction with water until the pH value of the obtained filtrate is neutral; specifically, mixing the rhodium-containing waste residue after the first reaction with water and filtering, and this step can be repeated multiple times until the pH value of the filtrate obtained after filtering is neutral.

[0031] According to the present invention, the mass ratio of the rhodium-containing waste residue to the first solvent is 1:5 - 40; when the mass ratio is within this range, it is more beneficial to the reduction of high-valent rhodium and improves the dissolution rate of rhodium.

[0032] Further, the mass ratio of the rhodium-containing waste residue to the first solvent is 1:10 - 20.

[0033] Further, the first solvent is N,N-dimethylformamide. After treatment with N,N-dimethylformamide and using hydrofluoric acid for soaking in subsequent steps, it can more effectively destroy the embedding structure of the rhodium-containing waste residue, release the embedded rhodium metal, make the rhodium metal easier to dissolve, and thus make the determination accuracy of the rhodium content higher.

[0034] According to the present invention, in step (1), the temperature of the first reaction is 90 - 150 °C, and the time of the first reaction is 0.5 - 3 h. When these reaction conditions are met, it is more conducive to the reduction of high-valent rhodium and improves the dissolution rate of rhodium.

[0035] Further, in step (1), the temperature of the first reaction is 100 - 120 °C, and the time of the first reaction is 1 - 2 h.

[0036] In the present invention, there is no specific limitation on the first drying, and it can be a conventional drying method in the art. For example, drying is carried out at 80 - 110 °C for 1 - 2 h.

[0037] According to the present invention, in step (2), the reduction treatment is carried out under a hydrogen atmosphere.

[0038] According to the present invention, the temperature of the reduction treatment is 700 - 1000 °C, and the time of the reduction treatment is 3 - 8 h.

[0039] Further, the temperature of the reduction treatment is 800 - 850 °C, and the time of the reduction treatment is 5 - 7 h.

[0040] According to the present invention, in step (3), the soaking is carried out using hydrofluoric acid. For the rhodium-containing waste residue treated with N,N-dimethylformamide, hydrofluoric acid can remove the organic matter in rhodium ash a, release the embedded rhodium metal, improve the dissolution rate of rhodium, and thus make the measurement result more accurate.

[0041] According to the present invention, the temperature of the soaking is 25 - 50 °C, and the time of the soaking is 6 - 48 h.

[0042] Further, the temperature of the soaking is 35 - 45 °C, and the time of the soaking is 12 - 24 h.

[0043] According to the present invention, the dosage of hydrofluoric acid is 25 - 45 mL / g of rhodium ash a, preferably 30 - 40 mL / g of rhodium ash a. That is, relative to 1 g of rhodium ash a, the dosage of hydrofluoric acid is 25 - 45 mL, preferably 30 - 40 mL.

[0044] According to the present invention, the concentration of hydrofluoric acid is 10 - 40 wt%, preferably 35 - 40 wt%.

[0045] According to the present invention, the second washing includes washing with water until the pH value of the obtained filtrate is neutral; specifically, the soaked rhodium ash a is mixed with water multiple times and filtered until the pH value of the filtrate obtained after filtration is neutral.

[0046] In the present invention, there is no specific limitation on the second drying in step (3), and it can be a conventional drying method in the art. For example, drying is carried out at 80 - 110 °C for 60 - 120 min.

[0047] According to the present invention, in step (4), the strong acid includes concentrated sulfuric acid and concentrated nitric acid.

[0048] According to the present invention, the volume ratio of the concentrated sulfuric acid to the concentrated nitric acid is 1:1.1 - 2. When the volume ratio is within this range, the dissolution rate of rhodium is increased, thereby making the measurement result more accurate.

[0049] Further, the volume ratio of the concentrated sulfuric acid to the concentrated nitric acid is 1:1.4 - 1.6.

[0050] According to the present invention, the dosage of the concentrated sulfuric acid is 10 - 15 mL / g of rhodium ash a; preferably 11 - 13 mL / g of rhodium ash a. That is, relative to 1 g of rhodium ash a, the dosage of the concentrated sulfuric acid is 10 - 15 mL, preferably 11 - 13 mL.

[0051] According to the present invention, in step (4), the strong oxidant includes perchloric acid and / or sodium perchlorate, preferably perchloric acid.

[0052] According to the present invention, the dosage of the strong oxidant is 15 - 30 mL / g of rhodium ash a. When the dosage is within this range, rhodium metal ions can be effectively dissolved. That is, relative to 1 g of rhodium ash a, the dosage of the strong oxidant is 15 - 30 mL.

[0053] Further, the dosage of the strong oxidant is 20 - 25 mL / g of rhodium ash a. That is, relative to 1 g of rhodium ash a, the dosage of the strong oxidant is 20 - 25 mL.

[0054] According to the present invention, in step (4), the temperature of the second reaction is 80 - 120 °C, and the time of the second reaction is 4 - 8 h.

[0055] Further, in step (4), the temperature of the second reaction is 100 - 110 °C, and the time of the second reaction is 5 - 7 h.

[0056] According to the present invention, the second reaction is a reflux reaction.

[0057] According to the present invention, the temperature of the third reaction is 80 - 120 °C, and the time of the third reaction is 4 - 8 h.

[0058] Further, the temperature of the third reaction is 100 - 110 °C, and the time of the third reaction is 5 - 7 h.

[0059] According to the present invention, in step (4), the post-treatment sequentially includes: cooling and filtration.

[0060] The present invention will be described in detail below through embodiments.

[0061] The rhodium content is calculated using the following formula:

[0062] Rhodium content = (Volume V of the rhodium-containing solution made up to volume × Concentration C of rhodium) / (Rhodium-containing material M) × 100%

[0063] The rhodium content of the rhodium dissolution solution is determined and analyzed using an inductively coupled plasma optical emission spectrometer.

[0064] In the following examples and comparative examples, the normal temperature is 25 °C.

[0065] In the following examples and comparative examples, the rhodium-containing waste residue comes from spent ternary catalysts. Using the traditional detection method for preparing rhodium solutions with hydrochloric acid / sulfuric acid and peroxides, the measured rhodium content is 0.098 wt%.

[0066] The raw materials used in the examples and comparative examples are all commercially available products.

[0067] Example 1

[0068] Transfer 1 g of rhodium-containing waste residue (rhodium content 0.098 wt%) into a muffle furnace for incineration, ashing at 900 °C for 8 hours. Transfer the ashed product into 15 g of N,N-dimethylformamide, heat and react at 100 °C for 1 hour. After the reaction is completed, cool to room temperature and wash with deionized water until the pH value of the obtained filtrate is neutral, then dry to obtain rhodium residue.

[0069] Place the rhodium residue into a hydrogen reduction furnace, react at 825 °C for 5 hours under a hydrogen atmosphere to obtain 0.5628 g of rhodium ash (rhodium ash a).

[0070] Add 20 mL of 40 wt% hydrofluoric acid to the obtained rhodium ash, soak at 40 °C for 24 h, filter and wash with deionized water until the pH value of the obtained filtrate is neutral, then dry to obtain rhodium ash b.

[0071] Add 6.75 mL of concentrated sulfuric acid to the obtained rhodium ash b, then add 10.13 mL of concentrated nitric acid, heat to 110 °C and react for 6 hours. Then add 12.94 mL of 70 wt% perchloric acid, heat to 100 °C and react for 6 hours. Stop the reaction and cool to room temperature. After filtering the rhodium-containing solution, make up to volume with deionized water, and the measured rhodium content is 0.121 wt%.

[0072] Example 2

[0073] Transfer 1 g of rhodium-containing waste residue (rhodium content 0.098 wt%) into a muffle furnace for incineration, ashing at 900 °C for 8 hours. Transfer the ashed product into 15 g of N,N-dimethylformamide, heat and react at 120 °C for 2 hours. After the reaction is completed, cool to room temperature and wash with deionized water until the pH value of the obtained filtrate is neutral, then dry to obtain rhodium residue.

[0074] Place the rhodium residue into a hydrogen reduction furnace, react at 825 °C for 5 hours under a hydrogen atmosphere to obtain 0.5582 g of rhodium ash (rhodium ash a).

[0075] Add 20 mL of 40 wt% hydrofluoric acid to the obtained rhodium ash, soak at 40 °C for 24 h, filter and wash with deionized water until the pH value of the obtained filtrate is neutral, then dry to obtain rhodium ash b.

[0076] Add 6.70 mL of concentrated sulfuric acid to the obtained rhodium ash b, then add 33.49 mL of concentrated nitric acid, heat to 110 °C and react for 6 hours. Then add 12.84 mL of 70 wt% perchloric acid, heat to 100 °C and react for 6 hours. Stop the reaction and cool to room temperature. Filter the rhodium-containing solution, make up the volume with deionized water, and measure the rhodium content to be 0.116 wt%.

[0077] Example 3

[0078] Transfer 1 g of rhodium-containing waste residue (rhodium content 0.098 wt%) into a muffle furnace for incineration, ashing at 800 °C for 6 hours. Transfer the ashed product into 15 g of N,N-dimethylformamide, heat and react at 100 °C for 1 hour. After the reaction is completed, cool to room temperature and wash with deionized water until the pH value of the obtained filtrate is neutral, then dry to obtain rhodium residue.

[0079] Place the rhodium residue into a hydrogen reduction furnace, react at 1000 °C for 3 hours under a hydrogen atmosphere to obtain 0.5607 g of rhodium ash (rhodium ash a).

[0080] Add 20 mL of 40 wt% hydrofluoric acid to the obtained rhodium ash, soak at 40 °C for 24 h, filter and wash with deionized water until the pH value of the obtained filtrate is neutral, then dry to obtain rhodium ash b.

[0081] Add 6.73 mL of concentrated sulfuric acid to the obtained rhodium ash b, then add 10.09 mL of concentrated nitric acid, heat to 110 °C and react for 6 hours. Then add 22.43 mL of 70 wt% perchloric acid, heat to 100 °C and react for 6 hours. Stop the reaction and cool to room temperature. Filter the rhodium-containing solution, make up the volume with deionized water, and measure the rhodium content to be 0.118 wt%.

[0082] Example 4

[0083] Transfer 1 g of rhodium-containing waste residue (rhodium content 0.098 wt%) into a muffle furnace for incineration, ashing at 950 °C for 9 hours. Transfer the ashed product into 40 g of N,N-dimethylformamide, heat and react at 100 °C for 1 hour. After the reaction is completed, cool to room temperature and wash with deionized water until the pH value of the obtained filtrate is neutral, then dry to obtain rhodium residue.

[0084] Place the rhodium residue into a hydrogen reduction furnace, react at 850 °C for 5 hours under a hydrogen atmosphere to obtain 0.5578 g of rhodium ash (rhodium ash a).

[0085] Add 20 mL of 40 wt% hydrofluoric acid to the obtained rhodium ash, soak at room temperature for 24 h, filter and wash with deionized water until the pH value of the obtained filtrate is neutral, then dry to obtain rhodium ash b.

[0086] Add 7.81 mL of concentrated sulfuric acid to the obtained rhodium ash b, then add 12.5 mL of concentrated nitric acid, heat to 100 °C and react for 5 hours. Then add 11.16 mL of 70 wt% perchloric acid, heat to 100 °C and react for 4 hours. Stop the reaction and cool to room temperature. Filter the rhodium-containing solution, make up the volume with deionized water, and measure the rhodium content to be 0.114 wt%.

[0087] Example 5

[0088] Transfer 1 g of rhodium-containing waste residue (rhodium content 0.098 wt%) into a muffle furnace for incineration, ashing at 900 °C for 10 hours. Transfer the ashed product into 20 g of N,N-dimethylformamide, heat and react at 100 °C for 1 hour. After the reaction is completed, cool to room temperature and wash with deionized water until the pH value of the obtained filtrate is neutral, then dry to obtain rhodium residue.

[0089] Place the rhodium residue into a hydrogen reduction furnace, react at 1000 °C for 4 hours under a hydrogen atmosphere to obtain 0.5606 g of rhodium ash (rhodium ash a).

[0090] Add 20 mL of 40 wt% hydrofluoric acid to the obtained rhodium ash, soak at room temperature for 24 h, filter and wash with deionized water until the pH value of the obtained filtrate is neutral, then dry to obtain rhodium ash b.

[0091] Add 6.73 mL of concentrated sulfuric acid to the obtained rhodium ash b, then add 10.1 mL of concentrated nitric acid, heat to 100 °C and react for 5 hours. Then add 11.2 mL of 70 wt% perchloric acid, heat to 100 °C and react for 8 hours. Stop the reaction and cool to room temperature. Filter the rhodium-containing solution, make up the volume with deionized water, and measure the rhodium content to be 0.117 wt%.

[0092] Example 6

[0093] Transfer 1 g of rhodium-containing waste residue (rhodium content 0.098 wt%) into a muffle furnace for incineration, ashing at 850 °C for 7 hours. Transfer the ashed product into 5 g of N,N-dimethylformamide, heat and react at 100 °C for 1 hour. After the reaction is completed, cool to room temperature, wash with deionized water until the pH value of the obtained filtrate is neutral, and dry to obtain rhodium residue.

[0094] Place the rhodium residue into a hydrogen reduction furnace, react at 800 °C for 4 hours under a hydrogen atmosphere to obtain 0.5639 g of rhodium ash (rhodium ash a).

[0095] Add 20 mL of 40 wt% hydrofluoric acid to the obtained rhodium ash, soak at room temperature for 24 h, filter, wash with deionized water until the pH value of the obtained filtrate is neutral, and dry to obtain rhodium ash b.

[0096] Add 7.33 mL of concentrated sulfuric acid to the obtained rhodium ash b, then add 13.2 mL of concentrated nitric acid, heat to 90 °C, react for 4.5 hours, then add 14.1 mL of 70 wt% perchloric acid, heat to 100 °C, react for 5 hours. Stop the reaction and cool to room temperature. Filter the rhodium-containing solution, make up the volume with deionized water, and measure the rhodium content to be 0.112 wt%.

[0097] Example 7

[0098] Transfer 0.5 g of rhodium-containing waste residue (rhodium content 0.098 wt%) into a muffle furnace for incineration, ashing at 1000 °C for 7 hours. Transfer the ashed product into 10 g of N,N-dimethylformamide, heat and react at 100 °C for 1 hour. After the reaction is completed, cool to room temperature, wash with deionized water until the pH value of the obtained filtrate is neutral, and dry to obtain rhodium residue.

[0099] Place the rhodium residue into a hydrogen reduction furnace, react at 800 °C for 8 hours under a hydrogen atmosphere to obtain 0.2784 g of rhodium ash (rhodium ash a).

[0100] Add 10 mL of 40 wt% hydrofluoric acid to the obtained rhodium ash, soak at room temperature (25 °C) for 24 h, filter, wash with deionized water until the pH value of the obtained filtrate is neutral, and dry to obtain rhodium ash b.

[0101] Add 4.18 mL of concentrated sulfuric acid to the obtained rhodium ash b, then add 4.60 mL of concentrated nitric acid, heat to 120 °C, react for 8 hours, then add 4.18 mL of 70 wt% perchloric acid, heat to 120 °C, react for 6 hours. Stop the reaction and cool to room temperature. Filter the rhodium-containing solution, make up the volume with deionized water, and measure the rhodium content to be 0.109 wt%.

[0102] Example 8

[0103] Transfer 0.5 g of rhodium-containing waste residue (rhodium content 0.098 wt%) into a muffle furnace for incineration, and ashing at 800 °C for 6 hours; transfer the obtained ashed product into 40 g of N,N-dimethylformamide, heat and react at 100 °C for 1 hour. After the reaction is completed, cool to room temperature, wash with deionized water until the pH value of the obtained filtrate is neutral, and dry to obtain rhodium residue.

[0104] Place the rhodium residue into a hydrogen reduction furnace, react at 700 °C for 3 hours under a hydrogen atmosphere to obtain 0.2861 g of rhodium ash (rhodium ash a).

[0105] Add 10 mL of 40 wt% hydrofluoric acid to the obtained rhodium ash, soak at room temperature for 24 h, filter, wash with deionized water until the pH value of the obtained filtrate is neutral, and then dry to obtain rhodium ash b.

[0106] Add 2.86 mL of concentrated sulfuric acid to the obtained rhodium ash b, then add 5.72 mL of concentrated nitric acid, heat to 80 °C, react for 4 hours, then add 8.58 mL of 70 wt% perchloric acid, heat to 80 °C, react for 4 hours. Stop the reaction and cool to room temperature. Filter the rhodium-containing solution, make up the volume with deionized water, and measure the rhodium content to be 0.108 wt%.

[0107] Example 9

[0108] Transfer 1 g of rhodium-containing waste residue (rhodium content 0.098 wt%) into a muffle furnace for incineration, and ashing at 900 °C for 8 hours. Transfer the ashed product into 15 g of N,N-dimethylacetamide reagent, heat and react at 100 °C for 1 hour. After the reaction is completed, cool to room temperature, wash with deionized water until the pH value of the obtained filtrate is neutral, and dry to obtain rhodium residue.

[0109] Place the rhodium residue into a hydrogen reduction furnace, react at 825 °C for 5 hours under a hydrogen atmosphere to obtain 0.5504 g of rhodium ash (rhodium ash a).

[0110] Add 20 mL of 40% hydrofluoric acid to the obtained rhodium ash, soak at 40 °C for 24 h, filter, wash with deionized water until the pH value of the obtained filtrate is neutral, and then dry to obtain rhodium ash b.

[0111] Add 6.60 mL of concentrated sulfuric acid to the obtained rhodium ash b, then add 9.91 mL of concentrated nitric acid, heat to 110 °C, react for 6 hours, then add 12.66 mL of 70 wt% perchloric acid, heat to 100 °C, react for 6 hours. Stop the reaction and cool to room temperature. Filter the rhodium-containing solution, make up the volume with deionized water, and measure the rhodium content to be 0.106 wt%.

[0112] Example 10

[0113] Transfer 1 g of rhodium-containing waste residue (rhodium content 0.098 wt%) into a muffle furnace for incineration, ashing at 900 °C for 8 hours. Transfer the ashed product into 45 g of N,N-dimethylformamide, heat and react at 100 °C for 1 hour. After the reaction is completed, cool to room temperature and wash with deionized water until the pH value of the obtained filtrate is neutral, then dry to obtain rhodium residue.

[0114] Place the rhodium residue into a hydrogen reduction furnace, react at 825 °C for 5 hours under a hydrogen atmosphere to obtain 0.5592 g of rhodium ash (rhodium ash a).

[0115] Add 20 mL of 40 wt% hydrofluoric acid to the obtained rhodium ash, soak at 40 °C for 24 h, filter and wash with deionized water until the pH value of the obtained filtrate is neutral, then dry to obtain rhodium ash b.

[0116] Add 6.75 mL of concentrated sulfuric acid to the obtained rhodium ash b, then add 10.13 mL of concentrated nitric acid, heat to 110 °C and react for 6 hours. Then add 12.94 mL of 70 wt% perchloric acid, heat to 100 °C and react for 6 hours. Stop the reaction and cool to room temperature. Filter the rhodium-containing solution, make up the volume with deionized water, and measure the rhodium content to be 0.109 wt%.

[0117] Comparative Example 1

[0118] Transfer 0.5 g of rhodium-containing waste residue (rhodium content 0.098%) into a muffle furnace for incineration, ashing at 900 °C for 8 hours; transfer the obtained ashed product into 8 g of anhydrous ethanol reagent, heat and react at 100 °C for 1 hour. After the reaction is completed, cool to room temperature and wash with deionized water until the pH value of the obtained filtrate is neutral, then dry to obtain rhodium residue.

[0119] Place the rhodium residue into a hydrogen reduction furnace, react at 825 °C for 5 hours under a hydrogen atmosphere to obtain 0.3046 g of rhodium ash (rhodium ash a).

[0120] Add 10 mL of 40% hydrofluoric acid to the obtained rhodium ash, soak at 40 °C for 24 h, filter and wash with deionized water until the pH value of the obtained filtrate is neutral, then dry to obtain rhodium ash b.

[0121] Add 3.5 mL of concentrated sulfuric acid to the obtained rhodium ash b, then add 5.6 mL of concentrated nitric acid, heat to 110 °C and react for 6 hours. Then add 7.5 mL of 70 wt% perchloric acid, heat to 100 °C and react for 6 hours. Stop the reaction and cool to room temperature. Filter the rhodium-containing solution, make up the volume with deionized water, and measure the rhodium content to be 0.103 wt%.

[0122] Comparative Example 2

[0123] Transfer 0.5 g of rhodium-containing waste residue (rhodium content 0.098%) into a muffle furnace for incineration, and ashing at 600 °C for 3 hours; transfer the obtained ashed product into absolute ethanol reagent and deionized water in sequence to wash the obtained rhodium ash until the pH value of the washed deionized water is neutral, and then dry to obtain rhodium residue.

[0124] Place the rhodium residue into a hydrogen reduction furnace, and react at 700 °C for 6 hours under a hydrogen atmosphere to obtain 0.2981 g of rhodium ash.

[0125] Add 5.96 mL of concentrated sulfuric acid to the obtained rhodium ash, then add 11.92 mL of concentrated nitric acid, heat to 150 °C, react for 4 hours, then add 8.94 mL of 70 wt% perchloric acid, heat to 150 °C, react for 4 hours, stop the reaction and cool to room temperature. Filter and wash the rhodium-containing solution, and then make up the volume to 200 mL with deionized water in a volumetric flask. The measured rhodium content is 0.101 wt%.

[0126] Comparative Example 3

[0127] Transfer 1 g of rhodium-containing waste residue (rhodium content 0.098 wt%) into a muffle furnace for incineration, and ashing at 900 °C for 8 hours. Transfer the ashed product into 15 g of N,N-dimethylformamide, heat and react at 100 °C for 1 hour. After the reaction is completed, cool to room temperature and wash with deionized water until the pH value of the obtained filtrate is neutral, and then dry to obtain rhodium residue.

[0128] Place the rhodium residue into a hydrogen reduction furnace, and react at 825 °C for 5 hours under a hydrogen atmosphere to obtain 0.5491 g of rhodium ash (rhodium ash a).

[0129] Add 6.59 mL of concentrated sulfuric acid to the obtained rhodium ash, then add 9.88 mL of concentrated nitric acid, heat to 110 °C, react for 6 hours, then add 12.63 mL of 70 wt% perchloric acid, heat to 100 °C, react for 6 hours, stop the reaction and cool to room temperature. Filter the rhodium-containing solution and make up the volume with deionized water. The measured rhodium content is 0.105 wt%.

[0130] Table 1

[0131]

[0132] As can be seen from Table 1, compared with the comparative examples, the solution of the present invention can dissolve rhodium metal from the rhodium-containing waste residue as much as possible, thus making the determination of rhodium content more accurate. According to the examples and Comparative Examples 1 and 3, when the sintered rhodium ash is treated with the first solvent and then soaked in hydrofluoric acid, the rhodium content measured by the combined use of the two is high, significantly higher than that of Comparative Example 1 using absolute ethanol and higher than that of Comparative Example 3 without soaking in hydrofluoric acid. This shows that the combined use of the first solvent and hydrofluoric acid in the present invention can destroy the embedding structure of the rhodium-containing waste residue, release rhodium metal, make rhodium metal more easily dissolved, and thus make the test results more accurate. It can be seen from Examples 1 and 10 that when the dosage of the first solvent is within the preferred range, better effects can be obtained. When the first solvent is N,N-dimethylformamide, the effect of its combination with hydrofluoric acid is better.

[0133] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited thereto. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, including any other suitable combination of each technical feature. These simple modifications and combinations should also be regarded as the content disclosed by the present invention and fall within the protection scope of the present invention.

Claims

1. A method for determining the rhodium content in rhodium-containing waste residue, characterized in that, The method includes: (1) Roasting, first washing, and first drying the rhodium-containing waste residue to obtain rhodium residue; (2) Subjecting the rhodium residue to a reduction treatment to obtain rhodium ash a; (3) Soaking, second washing, and second drying the rhodium ash a in sequence to obtain rhodium ash b; (4) Adding strong acid to the rhodium ash b for a second reaction, then adding a strong oxidant for a third reaction, and performing post-treatment and volume fixing to obtain a rhodium dissolution solution; (5) Measuring the rhodium concentration of the rhodium dissolution solution; In step (1), the first washing includes subjecting the rhodium-containing waste residue to a first reaction with a first solvent; The first solvent is selected from N,N-dimethylformamide, N,N-dimethylacetamide, N-methylformamide, or formamide.

2. The method according to claim 1, wherein In step (1), the roasting is aerobic roasting; Preferably, the temperature of the roasting is 800-1000 °C, preferably 850-950 °C; the roasting time is 6-10 h, preferably 7-9 h.

3. The method according to claim 1 or 2, wherein In step (1), the first washing includes washing the rhodium-containing waste residue after the first reaction with water until the pH value of the obtained filtrate is neutral; Preferably, the first solvent is N,N-dimethylformamide; Preferably, the mass ratio of the rhodium-containing waste residue to the first solvent is 1:5-40, preferably 1:10-20.

4. The method according to any one of claims 1-3, wherein, In step (1), the temperature of the first reaction is 90-150 °C, preferably 100-120 °C; the time of the first reaction is 0.5-3 h, preferably 1-2 h.

5. The method according to any one of claims 1-4, wherein In step (2), the reduction treatment is carried out under a hydrogen atmosphere; Preferably, the temperature of the reduction treatment is 700-1000 °C, preferably 800-850 °C; the reduction treatment time is 3-8 h, preferably 5-7 h.

6. The method according to any one of claims 1-5, wherein In step (3), the soaking is carried out using hydrofluoric acid; Preferably, the dosage of the hydrofluoric acid is 25-45 mL / g of rhodium ash a, preferably 30-40 mL / g of rhodium ash a; Preferably, the concentration of the hydrofluoric acid is 10-40 wt%, preferably 35-40 wt%; Preferably, the temperature of the soaking is 25-50 °C, preferably 35-45 °C; the soaking time is 6-48 h, preferably 12-24 h; Preferably, the second washing includes washing with water until the pH value of the obtained filtrate is neutral.

7. The method according to any one of claims 1-6, wherein, In step (4), the strong acid includes concentrated sulfuric acid and concentrated nitric acid; Preferably, the volume ratio of the concentrated sulfuric acid to the concentrated nitric acid is 1:1.1-2; preferably 1:1.4-1.6; Preferably, the dosage of the concentrated sulfuric acid is 10-15 mL / g of rhodium ash a; preferably 11-13 mL / g of rhodium ash a.

8. The method according to any one of claims 1-7, wherein, In step (4), the strong oxidant includes perchloric acid and / or sodium perchlorate, preferably perchloric acid; Preferably, the dosage of the strong oxidant is 15-30 mL / g of rhodium ash a, preferably 20-25 mL / g of rhodium ash a.

9. The method according to any one of claims 1-8, wherein, In step (4), the temperature of the second reaction is 80-120 °C, preferably 100-110 °C; the time of the second reaction is 4-8 h, preferably 5-7 h; Preferably, the second reaction is a reflux reaction; Preferably, the temperature of the third reaction is 80-120°C, preferably 100-110°C; the time of the third reaction is 4-8 h, preferably 5-7 h.

10. The method according to any one of claims 1-9, wherein, In step (4), the post-treatment sequentially includes: cooling and filtration.

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