Method for recovering rhodium from rhodium-containing waste residues

Abstract

This invention relates to the field of precious metal recycling technology and provides a method for recovering rhodium from rhodium-containing waste residue. The method includes the following steps: (1) roasting the rhodium-containing waste residue to obtain rhodium ash; (2) reacting the rhodium ash with a treatment agent, followed by filtration and drying, wherein the treatment agent is selected from at least one of alcohol and N,N-dimethylformamide; (3) subjecting the treated rhodium ash obtained in step (2) to a hydrogen reduction reaction under a hydrogen-containing gas atmosphere to obtain reduced rhodium ash; and (4) dissolving the reduced rhodium ash with an acid solution. The method of this invention is simple to operate, highly efficient, with minimal rhodium loss, and a yield greater than 96.9%.

Description

Technical Field

[0001] This invention relates to the field of precious metal recycling technology, and provides a method for recovering rhodium from rhodium-containing waste residue. Background Technology

[0002] Carbonyl synthesis (also known as hydroformylation) is one of the most important reactions in the chemical industry, including the hydroformylation of olefins, the carbonylation of methanol to acetic acid, and the carbonylation of methyl acetate to acid anhydrides. Rhodium-phosphine complex catalysts prepared from the precious metal rhodium are the most commonly used catalysts for carbonyl synthesis reactions. Rhodium, as a precious metal, has wide applications not only in the petrochemical and metallurgical industries but is also indispensable in automotive electronics, aerospace, and fuel cells. The mining and purification of rhodium is extremely difficult and its price is very high; therefore, rhodium recovery has attracted the attention of many countries.

[0003] In the hydroformylation reaction, rhodium-phosphine complex catalysts have the characteristics of high catalytic activity and good selectivity. However, these catalysts are easily deactivated by trace impurities and high temperatures during the reaction. Every year, a large number of spent rhodium-phosphine complex catalysts need to be recycled. These spent rhodium catalysts are valuable secondary resources, and recovering the precious metal rhodium from them has significant economic and social benefits.

[0004] In the process of recycling waste rhodium, the waste rhodium catalyst contains high levels of impurities and many high-boiling-point organic compounds, making the processing and purification of rhodium extremely difficult. Currently, the main recycling methods include incineration, wet processing, and extraction. Incineration is commonly used in industry, but it suffers from problems such as poor temperature control leading to significant rhodium loss and over-burning, which complicates subsequent processing. Chinese patent CN108950233A proposes a method that melts transition metals, reducing agents, and rhodium residue together to form an alloy, which is then obtained through electrolysis or acid hydrolysis. However, this method requires the addition of large amounts of other transition metals, has a long recovery cycle, and ultimately affects the yield.

[0005] Therefore, it is very important to develop an efficient and economical method for recovering rhodium from rhodium-containing slag. Summary of the Invention

[0006] This invention addresses the shortcomings of existing technologies by providing a method for recovering rhodium from rhodium-containing waste residue. This method can efficiently and economically recover rhodium, achieving both economic and social benefits.

[0007] To achieve the above objectives, the present invention provides a method for recovering rhodium from rhodium-containing waste residue, the method comprising the following steps:

[0008] (1) Rhodium-containing waste residue is roasted to obtain rhodium ash;

[0009] (2) The rhodium ash is reacted with a treatment agent, and then filtered and dried in sequence. The treatment agent is selected from at least one of alcohol and N,N-dimethylformamide.

[0010] (3) The treated rhodium ash obtained in step (2) is subjected to a hydrogen reduction reaction in a hydrogen-containing gas atmosphere to obtain reduced rhodium ash;

[0011] (4) Dissolve the reduced rhodium ash in an acid solution.

[0012] Compared with the prior art, the present invention has the following advantages and effects:

[0013] (1) The method described in this invention uses a method of first roasting the rhodium-containing waste residue, then reacting it with a treatment agent, and then performing hydrogenation reduction to treat the rhodium ash. The treatment agent can react away the organic matter remaining in the rhodium-containing waste residue after roasting, and can also reduce some of the rhodium ash. Combined with the hydrogenation reduction method, it is more conducive to improving the solubility of rhodium.

[0014] (2) The method used in this invention is simple to operate, highly efficient, with little rhodium loss and a yield greater than 96.9%. At the same time, it efficiently removes residual metal ions and impurities such as high-boiling-point organic matter. Detailed Implementation

[0015] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0016] This invention provides a method for recovering rhodium from rhodium-containing waste residue, the method comprising the following steps:

[0017] (1) Rhodium-containing waste residue is roasted to obtain rhodium ash;

[0018] (2) The rhodium ash is reacted with a treatment agent, and then filtered and dried in sequence. The treatment agent is selected from at least one of alcohol and N,N-dimethylformamide.

[0019] (3) The treated rhodium ash obtained in step (2) is subjected to a hydrogen reduction reaction in a hydrogen-containing gas atmosphere to obtain reduced rhodium ash;

[0020] (4) Dissolve the reduced rhodium ash in an acid solution.

[0021] The method provided by this invention is suitable for rhodium-containing waste obtained through various existing methods, such as spent rhodium-phosphine complex catalysts obtained in carbonyl synthesis reactions. This invention does not particularly limit the impurities in the rhodium-containing waste, which may include residual iron, calcium, nickel, and other metal ions, as well as high-boiling-point organic compounds.

[0022] This invention is applicable to the recovery of rhodium of different mass concentrations from rhodium-containing waste residue; the higher the mass concentration, the greater the amount of rhodium recovered. According to this invention, preferably, the rhodium content in the rhodium-containing waste residue is ≥0.1% by weight.

[0023] According to the present invention, the range of selection for the roasting conditions is relatively wide, as long as the high-boiling-point organic matter in the rhodium-containing waste residue can be removed. Preferably, the roasting conditions include: a temperature of 700-1000℃ and a time of 4-8 hours.

[0024] According to the present invention, the alcohol can be a C1-C5 alcohol, and can be a monohydric alcohol, a dihydric alcohol, or a polyhydric alcohol. Preferably, the treatment agent is selected from at least one of methanol, ethanol, and N,N-dimethylformamide. The preferred treatment agent is more conducive to reacting away the organic matter remaining after roasting in the rhodium-containing waste residue, and also reduces part of the rhodium ash, which is beneficial for further reduction of rhodium and improving the solubility of rhodium. Preferably, the treatment agent is N,N-dimethylformamide. N,N-dimethylformamide is more effective as a treatment agent and requires less dosage, thus saving costs. According to the present invention, preferably, the amount of N,N-dimethylformamide used is 10-15 mL relative to 1 g of rhodium ash.

[0025] According to the present invention, preferably, the amount of the treatment agent used is 5-20 mL, more preferably 10-15 mL, relative to 1 g of rhodium ash.

[0026] According to the present invention, preferably, the reaction conditions in step (2) include: a temperature of 80-150°C, more preferably 100-130°C, and a time of 0.3-2.5 hours, more preferably 0.5-2 hours. Under these preferred conditions, the reaction between the treatment agent and rhodium ash is accelerated, which is more conducive to saving reaction time.

[0027] Preferably, the reaction in step (2) is carried out under stirring conditions. Stirring ensures that the treatment agent reacts fully with the rhodium ash. The present invention does not impose a particular limitation on the stirring speed; those skilled in the art can make an appropriate selection based on specific circumstances.

[0028] According to a preferred embodiment of the present invention, the method further includes washing after filtration in step (2) and then drying. The present invention does not particularly limit the washing conditions and agents used; for example, the washing conditions are such that the pH of the resulting washing solution is neutral. Deionized water can be used as the washing agent. The present invention does not particularly limit the drying conditions; the washed rhodium ash can be dried. Preferably, the drying is carried out at a temperature of 60-120°C.

[0029] According to the present invention, preferably, the conditions for the hydrogenation reduction reaction in step (3) include: a temperature of 600-900°C and a time of 3-8 hours.

[0030] According to the present invention, preferably, pure hydrogen gas is used to reduce the treated rhodium ash. This preferred method results in a better reduction effect of the rhodium ash.

[0031] According to the present invention, preferably, the acid solution in step (4) is selected from at least one of hydrochloric acid, sulfuric acid and nitric acid, and preferably hydrochloric acid.

[0032] Preferably, the concentration of the acid solution is 35-98 wt%. Those skilled in the art can appropriately select the concentration of the acid solution based on the specific type of acid. Preferably, the concentration of hydrochloric acid is 35-37 wt%, the concentration of sulfuric acid is 90-98 wt%, and the concentration of nitric acid is 65-68 wt%.

[0033] Preferably, the amount of acid solution used is 10-25 mL, more preferably 15-18 mL, relative to 1 g of the reduced rhodium ash.

[0034] According to the present invention, there are no particular limitations on the conditions for dissolution in step (4). For example, it can be carried out at room temperature (25-30°C) or under heating conditions.

[0035] According to the present invention, preferably, the method further includes: mixing the rhodium-containing material obtained by dissolving in the acid solution in step (4) with an oxidant. This preferred embodiment is more conducive to improving the solubility of rhodium. The oxidant is selected from at least one of hydrogen peroxide, nitric acid, and perchloric acid, preferably hydrogen peroxide. Hydrogen peroxide is an environmentally friendly green oxidant, and the reduction product is only water, which reduces subsequent processing steps and lowers costs.

[0036] Preferably, the concentration of the hydrogen peroxide is 30-50 wt%.

[0037] More preferably, the amount of oxidant (preferably hydrogen peroxide) used is 1-2 mL, more preferably 1.2-1.7 mL, relative to 1 mL of the acid solution.

[0038] According to the present invention, preferably, the conditions for mixing the rhodium-containing material obtained by acid solution dissolution in step (4) with the oxidant include: a temperature of 80-120°C.

[0039] According to the present invention, preferably, the mixing method includes adding an oxidant (preferably hydrogen peroxide) dropwise to the rhodium-containing material obtained by dissolving the acid solution in step (4). The present invention does not impose a particular limitation on the rate of addition; those skilled in the art can make appropriate selections according to specific circumstances, ensuring that a violent reaction between the oxidant (hydrogen peroxide) and the rhodium-containing material obtained by dissolving the acid solution is avoided throughout the addition process.

[0040] According to the present invention, preferably, the mixing is carried out under stirring conditions. This method enables the rhodium-containing material obtained by dissolving the oxidant and acid solution to be mixed uniformly.

[0041] According to the present invention, preferably, the method further includes a reflux reaction after the mixing is completed, with the reflux time being 2-5 hours. This preferred embodiment is more conducive to the uniform mixing of the rhodium-containing material obtained by dissolving in hydrogen peroxide and acid solution, further improving the solubility of rhodium.

[0042] According to the present invention, preferably, the method further includes filtering the rhodium-containing material obtained by dissolving the acid solution in step (4).

[0043] According to a preferred embodiment, the method further includes collecting the rhodium-containing filtrate obtained by filtration, and repeating the steps of dissolving the filter residue in acid solution, stirring and heating, adding hydrogen peroxide dropwise and then refluxing the reaction 2-5 times.

[0044] According to the present invention, preferably, the method further includes removing impurities from the rhodium-containing filtrate obtained by filtration. The impurity removal can be performed using conventional techniques in the art. Preferably, the impurity removal is performed using ion exchange.

[0045] This invention offers a wide range of ion exchange resins that can be self-made or commercially available, as long as the purpose of impurity removal is achieved. Preferably, the rhodium-containing filtrate obtained from filtration is sequentially passed through a first cation exchange resin column and a second cation exchange resin column. The first cation exchange resin column is used to remove nickel ions, and the second cation exchange resin column is used to remove iron ions. Preferably, the first cation exchange resin column uses LX-110 cation exchange resin, and the second cation exchange resin column uses LSD-396 cation exchange resin. This preferred embodiment will also remove some calcium ions. However, since calcium ions do not interfere with the recovery and determination of rhodium in rhodium-containing waste, this invention does not specifically remove calcium ions.

[0046] It should be noted that the terms "first" and "second" in this invention do not serve a limiting function, but are only used to distinguish the operations performed at different stages and the substances used.

[0047] The present invention will be described in detail below through examples. In the following examples, LX-110 cation exchange resin and LSD-396 cation exchange resin are both commercially available products manufactured by Xi'an Lanxiao Technology Co., Ltd.

[0048] In the following examples, the mass percentage of rhodium in the rhodium-containing waste residue was analyzed by ICP after digestion, and the rhodium content in rhodium trichloride was analyzed by X-ray fluorescence spectroscopy.

[0049] The rhodium yield is calculated using the following formula:

[0050] Rhodium yield = (mass of rhodium trichloride × percentage of rhodium content in rhodium trichloride) / (percentage of rhodium content in rhodium-containing waste × mass of rhodium-containing waste) × 100%.

[0051] The rhodium-containing waste residue described in the example originates from the waste rhodium-phosphine complex catalyst obtained in the carbonyl synthesis reaction. It includes rhodium, more than 50% by weight of high-boiling-point organic compounds such as triphenylphosphine and triphenylphosphine oxide generated in the carbonyl synthesis reaction, and less than 1% by weight of impurities such as iron and nickel metal ions. The rhodium content is 0.4257% by weight.

[0052] Example 1

[0053] 40g of rhodium-containing waste residue was transferred to a muffle furnace for calcination at 800℃ for 4 hours to obtain 25.77g of rhodium ash. 258mL of N,N-dimethylformamide was added to the rhodium ash, and the mixture was stirred and heated to 100℃ for 2 hours. After filtration, the treated rhodium ash filter cake was washed with deionized water until the pH of the resulting washing solution was neutral. After drying, the treated rhodium ash was placed in a hydrogen reduction furnace and reacted at 750℃ for 4 hours under a pure hydrogen atmosphere to obtain 14.94g of reduced rhodium ash. 240mL of 37wt% hydrochloric acid was added to the reduced rhodium ash, and the mixture was stirred and heated to 80℃. 336mL of 40wt% hydrogen peroxide was added dropwise, and the mixture was refluxed for 2 hours. After filtration, the filtrate was collected. The filter residue was subjected to the same steps of adding acid, stirring and heating, adding hydrogen peroxide, and then refluxing three times. The filtrates from the four filtrations were combined to obtain a crude rhodium chloride solution. The obtained crude rhodium chloride solution was passed sequentially through an LX-110 cation exchange resin column and an LSD-396 cation exchange resin column, concentrated, and dried to obtain 0.4453 g of rhodium trichloride with a rhodium content of 37.24% by weight and a rhodium yield of 97.39%.

[0054] Example 2

[0055] 40g of rhodium-containing waste residue was transferred to a muffle furnace for calcination at 700℃ for 7 hours to obtain 24.61g of rhodium ash. 370mL of N,N-dimethylformamide was added to the rhodium ash, and the mixture was stirred and heated to 120℃ for 1.5 hours. After filtration, the rhodium ash filter cake was washed with deionized water until the pH of the washing liquid was neutral. After drying, the rhodium ash was placed in a hydrogen reduction furnace and reacted at 600℃ for 5 hours under a pure hydrogen atmosphere to obtain 16.27g of reduced rhodium ash. 244mL of 36wt% hydrochloric acid was added to the reduced rhodium ash to dissolve it, and the mixture was stirred and heated to 80℃. 293mL of 50wt% hydrogen peroxide was added dropwise, and the mixture was refluxed for 5 hours. After filtration, the filtrate was collected. The filter residue was subjected to the same steps of adding acid, stirring and heating, adding hydrogen peroxide, and then refluxing three times. The filtrates from the four filtrations were combined to obtain a crude rhodium chloride solution. The obtained crude rhodium chloride solution was passed sequentially through an LX-110 cation exchange resin column and an LSD-396 cation exchange resin column, concentrated, and dried to obtain 0.4447 g of rhodium trichloride with a rhodium content of 37.35% by weight and a rhodium yield of 97.54%.

[0056] Example 3

[0057] 40g of rhodium-containing waste residue was transferred to a muffle furnace for calcination at 750℃ for 5 hours to obtain 25.04g of rhodium ash. 300mL of N,N-dimethylformamide was added to the rhodium ash, and the mixture was stirred and heated to 130℃ for 0.5 hours. After filtration, the treated rhodium ash filter cake was washed with deionized water until the pH of the resulting washing solution was neutral. After drying, the treated rhodium ash was placed in a hydrogen reduction furnace and reacted at 800℃ for 3 hours under a pure hydrogen atmosphere to obtain 15.38g of reduced rhodium ash. 262mL of 35wt% hydrochloric acid was added to the reduced rhodium ash, and the mixture was stirred and heated to 80℃. 445mL of 30wt% hydrogen peroxide was added dropwise, and the mixture was refluxed for 4 hours. After filtration, the filtrate was collected. The filter residue was subjected to the same steps of adding acid, stirring and heating, adding hydrogen peroxide, and then refluxing three times. The filtrates from the four filtrations were combined to obtain a crude rhodium chloride solution. The obtained crude rhodium chloride solution was passed sequentially through an LX-110 cation exchange resin column and an LSD-396 cation exchange resin column, concentrated, and dried to obtain 0.4367 g of rhodium trichloride with a rhodium content of 38.01% by weight and a rhodium yield of 97.48%.

[0058] Example 4

[0059] 40g of rhodium-containing waste residue was transferred to a muffle furnace for calcination at 900℃ for 8 hours to obtain 24.36g of rhodium ash. 317mL of N,N-dimethylformamide was added to the rhodium ash, and the mixture was stirred and heated to 120℃ for 1.5 hours. After filtration, the treated rhodium ash filter cake was washed with deionized water until the pH of the resulting washing solution was neutral. After drying, the treated rhodium ash was placed in a hydrogen reduction furnace and reacted at 900℃ for 6 hours under a pure hydrogen atmosphere to obtain 14.73g of reduced rhodium ash. 265mL of 37wt% hydrochloric acid was added to the reduced rhodium ash, and the mixture was stirred and heated to 80℃. 400mL of 30wt% hydrogen peroxide was added dropwise, and the mixture was refluxed for 5 hours. After filtration, the filtrate was collected. The filter residue was subjected to the same steps of adding acid, stirring and heating, adding hydrogen peroxide, and then refluxing three times. The filtrates from the four filtrations were combined to obtain a crude rhodium chloride solution. The obtained crude rhodium chloride solution was passed sequentially through an LX-110 cation exchange resin column and an LSD-396 cation exchange resin column, concentrated, and dried to obtain 0.4486 g of rhodium trichloride with a rhodium content of 36.92% by weight and a rhodium yield of 97.27%.

[0060] Example 5

[0061] 40g of rhodium-containing waste residue was transferred to a muffle furnace for calcination at 1000℃ for 5.5 hours to obtain 24.68g of rhodium ash. 247mL of N,N-dimethylformamide was added to the rhodium ash, and the mixture was stirred and heated to 100℃ for 2 hours. After filtration, the treated rhodium ash filter cake was washed with deionized water until the pH of the resulting washing solution was neutral. After drying, the treated rhodium ash was placed in a hydrogen reduction furnace and reacted at 800℃ for 8 hours under a pure hydrogen atmosphere to obtain 14.81g of rhodium ash. 222mL of 37wt% hydrochloric acid was added to the reduced rhodium ash, and the mixture was stirred and heated to 80℃. 333mL of 35wt% hydrogen peroxide was added dropwise, and the mixture was refluxed for 3 hours. After filtration, the filtrate was collected. The filter residue was subjected to the same steps of adding acid, stirring and heating, adding hydrogen peroxide, and then refluxing three times. The filtrates from the four filtrations were combined to obtain a crude rhodium chloride solution. The obtained crude rhodium chloride solution was passed sequentially through an LX-110 cation exchange resin column and an LSD-396 cation exchange resin column, concentrated, and dried to obtain 0.4439 g of rhodium trichloride with a rhodium content of 37.69% by weight and a rhodium yield of 98.25%.

[0062] Example 6

[0063] The method of Example 1 was followed, except that N,N-dimethylformamide was replaced with an equal volume of methanol, the mixture was heated to reflux, reacted for 2 hours, and then filtered. 0.4441 g of rhodium trichloride was obtained, with a rhodium content of 37.18% by weight and a rhodium yield of 96.97%.

[0064] As can be seen from the results of the above embodiments, the method for recovering rhodium using the present invention is simple to operate, highly efficient, with minimal rhodium loss and a yield greater than 96.9%, while also efficiently removing residual metal ions and impurities such as high-boiling-point organic matter.

[0065] 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 inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A method for recovering rhodium from rhodium-containing waste residue, characterized in that, The method includes the following steps: (1) Rhodium-containing waste residue is roasted to obtain rhodium ash; (2) The rhodium ash is reacted with a treatment agent, and then filtered and dried in sequence. The treatment agent is N,N-dimethylformamide. (3) The rhodium ash obtained in step (2) is subjected to a hydrogenation reduction reaction in a hydrogen-containing gas atmosphere to obtain reduced rhodium ash; (4) Dissolve the reduced rhodium ash in an acid solution; The amount of the treatment agent used is 10-15 mL relative to 1 g of rhodium ash; The reaction conditions in step (2) include: a temperature of 100-130℃ and a time of 0.5-2 hours.

2. The method according to claim 1, wherein, The roasting conditions include a temperature of 700-1000℃ and a time of 4-8 hours.

3. The method according to claim 1, wherein, The reaction described in step (2) is carried out under stirring conditions.

4. The method according to any one of claims 1-3, wherein, The conditions for the hydrogenation reduction reaction in step (3) include: a temperature of 600-900℃ and a time of 3-8 hours.

5. The method according to any one of claims 1-3, wherein, The acid solution in step (4) is selected from at least one of hydrochloric acid, sulfuric acid and nitric acid.

6. The method according to claim 5, wherein, The acid solution mentioned in step (4) is hydrochloric acid.

7. The method according to any one of claims 1-3, wherein, The concentration of the acid solution is 35-98 wt%.

8. The method according to any one of claims 1-3, wherein, The amount of acid solution used is 10-25 mL relative to 1 g of the reduced rhodium ash.

9. The method according to claim 8, wherein, The amount of acid solution used is 15-18 mL relative to 1 g of the reduced rhodium ash.

10. The method according to any one of claims 1-3, wherein, The method further includes: mixing the rhodium-containing material obtained by dissolving it in an acid solution with an oxidant, wherein the oxidant is selected from at least one of hydrogen peroxide, nitric acid and aqua regia.

11. The method according to claim 10, wherein, The oxidant is hydrogen peroxide.

12. The method according to claim 11, wherein, The concentration of the hydrogen peroxide is 30-50 wt%.

13. The method according to claim 11, wherein, The amount of hydrogen peroxide used is 1-2 mL relative to 1 mL of the acid solution.

14. The method according to claim 13, wherein, The amount of hydrogen peroxide used is 1.2-1.7 mL relative to 1 mL of the acid solution.

15. The method according to claim 10, wherein, The conditions for mixing the rhodium-containing material obtained by acid solution dissolution in step (4) with the oxidant include: a temperature of 80-120℃.

16. The method of claim 10, wherein, The mixing method includes adding the oxidant dropwise to the rhodium-containing material obtained by dissolving the acid solution in step (4).

17. The method according to claim 10, wherein, The mixing is carried out under stirring conditions.

18. The method according to claim 10, wherein, The method also includes a reflux reaction after the mixing is completed, with a reflux time of 2-5 hours.

19. The method according to any one of claims 1-3, wherein, The method also includes filtering the rhodium-containing material obtained by dissolving the acid solution in step (4).

20. The method according to claim 19, wherein, The method also includes removing impurities from the rhodium-containing filtrate obtained by filtration.

21. The method according to claim 20, wherein, The impurity removal method used is ion exchange.

22. The method according to claim 21, wherein, The rhodium-containing filtrate obtained from filtration is passed sequentially through a first cation exchange resin column and a second cation exchange resin column. The first cation exchange resin column is used to remove nickel ions, and the second cation exchange resin column is used to remove iron ions.