Method for recovering rhodium, ruthenium or iridium from wastewater by combining vulcanization and ultraviolet treatment

Abstract

The invention belongs to the field of wastewater treatment and rare and noble metal resource recovery, and particularly relates to a method for recovering rhodium, ruthenium or iridium from wastewater by combining vulcanization and ultraviolet treatment. The method comprises the following steps: 1) adding a vulcanizing agent into wastewater containing rhodium, ruthenium or iridium, and fully mixing and reacting to obtain a mixed solution; (2) placing the mixed solution obtained in the step (1) under ultraviolet light, illuminating for a certain time under a stirring state, and reacting; and 3) carrying out solid-liquid separation to respectively obtain precipitates containing rhodium, ruthenium or iridium and treated wastewater. According to the method, the rhodium, the ruthenium or the iridium can be recovered from the wastewater by sequentially adopting vulcanization treatment and ultraviolet treatment.

Description

Technical Field

[0001] The invention belongs to the field of wastewater treatment and rare metal resource recovery, and specifically relates to a method for recovering rhodium, ruthenium or iridium from wastewater by combining sulfidation and ultraviolet treatment. Background Art

[0002] Platinum group metals such as rhodium, ruthenium and iridium play an important role in catalysis, aerospace and even the broader industrial field due to their unique physical and chemical properties, especially as manufacturing materials for high-end catalysts and key components.

[0003] Methanol carbonylation is the main method for producing acetic acid at present. In order to promote the efficient reaction, this method requires the use of precious metals such as rhodium, ruthenium, and iridium as catalysts. However, these precious metal catalysts will gradually be lost into the production waste acid liquid during the long catalytic process. During the purification process of acetic acid production, acidic complex wastewater rich in organic acids and trace precious metals is produced. This type of organic acid wastewater is mainly composed of small molecule organic acids such as acetic acid, formic acid, and propionic acid, with organic acids accounting for as high as 40-80%. The concentration of high-value precious metals such as rhodium, ruthenium, and iridium is about 1-5ppm. Although the content of rare precious metals such as rhodium, iridium, and ruthenium is low, their value is extremely high.

[0004] Since the amount of organic acid wastewater produced is large and the concentration of rhodium, ruthenium and iridium in it is low, in order to reduce the treatment volume, the conventional method in the field of water treatment is to first enrich and concentrate the components to be recovered in the wastewater. For acetic acid production wastewater, the current main method for enriching rhodium, ruthenium and iridium is to use multi-stage distillation to utilize the difference in boiling points to distill formic acid, acetic acid and propionic acid and then recover them, while rhodium, iridium and ruthenium follow other impurity components in the wastewater, such as high molecular polymers, iron, manganese and other metal ions into the distillation residue, and then use extreme conditions such as hot melting and high-strength acid dissolution to achieve the initial extraction of rhodium, iridium and ruthenium from the distillation residue, and then separate and purify rhodium, iridium and ruthenium from the extract by complex chemical means such as precipitation, extraction, adsorption, ion exchange, etc. There are also some methods for enriching rhodium, ruthenium and iridium from solid catalyst leachate. For example, some studies use zinc or aluminum as a replacement agent to recover ruthenium from the waste catalyst leachate. After the spent catalyst is calcined at 600°C, hydrochloric acid or sulfuric acid is added, and then excess aluminum is added to the solution to replace ruthenium. After filtration, the solid needs to be dried, then reacted with 10% NaClO solution and concentrated H 2 SO 4 Dissolve ruthenium; Some studies have used organic extractants such as dioctyl urea and trimethyl urea to separate rhodium, ruthenium or iridium from the catalyst leachate, but the metal replacement method and extraction method are not suitable for the recovery of rhodium, ruthenium or iridium in the organic acid system. One reason is that the replacement method requires excessive base metals and subsequent separation is difficult. The other reason is that the extraction method is mostly suitable for inorganic acid systems and is not suitable for organic acid environments.

[0005] In view of the above situation, it is urgent to develop an efficient and environmentally friendly recovery technology specifically for precious metals such as rhodium, ruthenium, and iridium in acetic acid production wastewater. This technology must be able to effectively overcome the limitations of existing methods, achieve efficient extraction and purification of precious metals, and reduce the impact on the subsequent recovery process of organic acids such as acetic acid and propionic acid, providing strong support for the sustainable development of the acetic acid industry. Summary of the invention

[0006] In order to solve the shortcomings of the prior art, the present invention provides a method for recovering rhodium, ruthenium or iridium from waste water by combining sulfidation and ultraviolet treatment. The present invention can recover rhodium, ruthenium or iridium from waste water by sequentially using sulfidation treatment and ultraviolet treatment.

[0007] The technical solution provided by the present invention is as follows:

[0008] A method for recovering rhodium, ruthenium or iridium from waste water by combining sulfidation and ultraviolet treatment, comprising the following steps:

[0009] 1) adding a sulfiding agent to wastewater containing rhodium, ruthenium or iridium, mixing and reacting the mixture to obtain a mixed solution;

[0010] 2) placing the mixed solution obtained in step 1) under ultraviolet light, irradiating it for a certain period of time under stirring, to react;

[0011] 3) Solid-liquid separation to obtain precipitate containing rhodium, ruthenium or iridium and treated wastewater respectively.

[0012] In the above technical solution:

[0013] Firstly, the treatment with sulfiding agent can greatly enrich the types and abundance of reducing free radicals in the reaction system, which is specifically manifested as: sodium dithionite (Na 2 S 2 O 4 ) or sodium sulfite (Na 2 SO 3 ) solution can produce SO 2 - , ·S 2 O 3 - , ·S, ·H, ·HSO 2 、SO 3 - Free radicals and hydrated electrons (e aq - )(Eq.1~Eq.7); sodium sulfide (Na 2 S) or thiourea (CH 4 N 2 S) solution can produce ·HS or ·H (Eq.8~Eq.10) when irradiated with ultraviolet light;

[0014] Directly applying ultraviolet light to acetic acid production wastewater can stimulate the inherent small molecular organic acids such as formic acid and acetic acid in the wastewater to produce strong reducing hydrogen free radicals (·H) and carbon dioxide free radicals (·CO 2 ). Under the continuous action of ultraviolet light, these free radicals can reduce rhodium, ruthenium or iridium ions in wastewater to metal elements and precipitate them in the form of precipitation. However, due to the limitations of free radical yield and survival time, the reaction time of the system with only ultraviolet light is relatively long. Through the synergistic effect of the above-mentioned free radicals, the reduction and recovery efficiency of rhodium, ruthenium or iridium in acetic acid wastewater can be jointly promoted, shortening the treatment time.

[0015] The main reaction formula is as follows:

[0016] 2S 2 O 4 2- +2H + →S 2 O 3 2- +2SO 2 +H 2 O (Eq.1)

[0017] S 2 O 4 2- +hv→2·SO 2 - (Eq.2)

[0018] S 2 O 3 2- +hv→·SO 3 - +e aq - (Eq.3)

[0019] S 2 O 3 2- +hv→·SO 3 - +·S - (Eq.4)

[0020] ·SO 2 - +H + → HSO 2 (Eq.5)

[0021] ·HSO 2 → H+SO 2 (Eq.6)

[0022] SO 32- +hv→·SO 3 - +e aq - (Eq.7)

[0023] S 2- +2H + →H 2 S (Eq.8)

[0024] CH 4 N 2 S+4H + →H 2 S+CO 2 +2NH 3 (Eq.9)

[0025] H 2 S+hv→·HS+·H (Eq.10)

[0026] Specifically: in step 1), the wastewater is industrial wastewater containing rhodium, ruthenium or iridium, including but not limited to: wastewater generated by the acetic acid production industry; leaching solution containing rhodium, ruthenium or iridium.

[0027] Based on the above technical solution, the present invention can utilize organic components such as acetic acid in wastewater, and can also recover rhodium, ruthenium or iridium without these organic components.

[0028] Specifically: in step 1), the vulcanizing agent is selected from any one of sodium sulfide, sodium sulfite, sodium dithionite or thiourea.

[0029] Specifically, in step 1):

[0030] When the wastewater contains only any one of rhodium, ruthenium or iridium, the molar ratio of the sulfiding agent to rhodium, ruthenium or iridium is (1-100):1;

[0031] When the wastewater contains only any two or three of rhodium, ruthenium or iridium, the molar ratio of the sulfiding agent to rhodium, ruthenium or iridium is (2-100):1.

[0032] Specifically, in step 1), the mixing reaction is carried out by one or more of stirring, shaking or ultrasound.

[0033] Specifically, in step 2): the ultraviolet light includes but is not limited to single-wavelength, multi-wavelength or continuous-wavelength ultraviolet light with an effective wavelength of 190 to 400 nm.

[0034] Specifically, in step 2), the illumination intensity of the ultraviolet light is 0.5 mW / cm 2 -5000mW / cm 2 .

[0035] Specifically, in step 2), the ultraviolet light irradiation time is 2-60 min.

[0036] Specifically, the rhodium, ruthenium or iridium in the wastewater exists in the form of dissolved ions.

[0037] Specifically, the wastewater contains any one, any two or three of rhodium, ruthenium or iridium.

[0038] Specifically, the solid-liquid separation is a combination of one or more of sand filtration, filter press, membrane filtration and centrifugal separation.

[0039] The present invention also provides a product recovered by the above method, which may contain:

[0040] Rhodium sulfur compound precipitation and elemental substance;

[0041] and / or, precipitates of sulfur-containing compounds and simple substances of ruthenium;

[0042] and / or, precipitate of sulfur-containing compounds and elemental iridium.

[0043] The recovery rate of rhodium can be as high as 99%.

[0044] The recovery rate of ruthenium can be as high as 99%.

[0045] The recovery rate of iridium can be as high as 99%.

[0046] The beneficial effects of the present invention are as follows:

[0047] 1) Significantly shortened the recovery time;

[0048] 2) Rhodium, ruthenium or iridium can be recovered with extremely low energy consumption;

[0049] 3) The recovered product can be easily obtained through simple treatment to obtain a high-purity single substance. DETAILED DESCRIPTION

[0050] The principles and features of the present invention are described below. The examples given are only used to explain the present invention and are not used to limit the scope of the present invention.

[0051] Unless otherwise specified, the test methods used in the examples are conventional methods; the materials and reagents used are commercially available reagents and materials unless otherwise specified.

[0052] Example 1

[0053] S1. Detecting the concentrations of rhodium, ruthenium and iridium in the acetic acid production wastewater to be treated;

[0054] The acetic acid production wastewater to be treated in this example contains 5% (wt%) formic acid, 34% (wt%) acetic acid, 20% (wt%) propionic acid, a rhodium concentration of 1.12 mg / L, and no ruthenium and iridium are detected.

[0055] S2. Take 50 mL of wastewater sample and stir it with a magnetic stirrer; at the same time, add thiourea solid according to the molar ratio of thiourea to rhodium of 1:1 to 100:1.

[0056] S3, 500W high pressure mercury lamp is used for irradiation, and the irradiation intensity is 900mW / cm 2 After 10 minutes of irradiation, precipitation occurred in the acidic wastewater.

[0057] S4. Filter the precipitate produced by the treatment in step S3 using a 0.22 μm filter membrane to obtain the precipitate and treated acetic acid wastewater.

[0058] The recovery rate of rhodium under different dosage of reagents is as follows

[0059]

[0060]

[0061] Through the above-mentioned condition optimization experiment, it was found that under the condition of thiourea to rhodium molar ratio of 2:1-100:1, the residual rhodium concentration in acetic acid production wastewater was below 0.028 mg / L, and the recovery rate of rhodium was greater than 97.50%.

[0062] Example 2

[0063] S1. Detecting the concentrations of rhodium, ruthenium and iridium in the acetic acid production wastewater to be treated;

[0064] The acetic acid production wastewater to be treated in this example contains 3% (wt%) formic acid, 52% (wt%) acetic acid, 30% (wt%) propionic acid, and a ruthenium concentration of 5.3 mg / L, while rhodium and iridium are not detected.

[0065] S2. Take 50 mL of wastewater sample and stir it with a magnetic stirrer; at the same time, add thiourea solid at a molar ratio of thiourea to rhodium of 2:1.

[0066] S3, 500W high pressure mercury lamp is used for irradiation, and the irradiation intensity is 900mW / cm 2 After irradiation for 1 to 10 minutes, precipitation occurs in the acidic wastewater.

[0067] S4. Filter the precipitate produced by the treatment in step S3 using a 0.22 μm filter membrane to obtain the precipitate and treated acetic acid wastewater.

[0068] The recovery rate of ruthenium under different illumination times is as follows

[0069]

[0070]

[0071] Through the above-mentioned condition optimization experiment, it was found that after ultraviolet light irradiation for 2-10 minutes, the residual ruthenium concentration in the acetic acid production wastewater was below 0.032 mg / L, and the recovery rate of ruthenium was greater than 99.47%.

[0072] Example 3

[0073] S1. Detecting the concentrations of rhodium, ruthenium and iridium in the acetic acid production wastewater to be treated;

[0074] The acetic acid production wastewater to be treated in this example contains 4% (wt%) formic acid, 45% (wt%) acetic acid, 35% (wt%) propionic acid, iridium concentration of 2.1 mg / L, and neither rhodium nor ruthenium is detected.

[0075] S2. Take 50 mL of wastewater sample and stir it with a magnetic stirrer; at the same time, add thiourea solid according to the molar ratio of thiourea to rhodium of 1:1 to 100:1.

[0076] S3, 500W high pressure mercury lamp is used for irradiation, and the irradiation intensity is 900mW / cm 2 After 10 minutes of irradiation, precipitation occurred in the acidic wastewater.

[0077] S4. Filter the precipitate produced by the treatment in step S3 using a 0.22 μm filter membrane to obtain the precipitate and treated acetic acid wastewater.

[0078] The recovery rates of iridium under different dosages are as follows

[0079]

[0080]

[0081] Through the above-mentioned condition optimization experiment, it was found that under the condition of thiourea to iridium molar ratio of 10:1-100:1, the residual iridium concentration in acetic acid production wastewater was below 0.034 mg / L, and the iridium recovery rate was greater than 98.38%.

[0082] Example 4

[0083] S1. Detecting the concentrations of rhodium, ruthenium and iridium in the acetic acid production wastewater to be treated;

[0084] The acetic acid production wastewater to be treated in this example contains 5% (wt%) formic acid, 34% (wt%) acetic acid, 20% (wt%) propionic acid, a rhodium concentration of 1.12 mg / L, and no ruthenium and iridium are detected.

[0085] S2. Take 50 mL of wastewater sample and stir it with a magnetic stirrer; at the same time, add thiourea solid at a molar ratio of thiourea to rhodium of 2:1.

[0086] S3, irradiation with 36W 254nm single wavelength low pressure UV lamp, irradiation intensity is 10mW / cm 2 After irradiation for 1-60 minutes, precipitation occurs in the acidic wastewater.

[0087] S4. Filter the precipitate produced by the treatment in step S3 using a 0.22 μm filter membrane to obtain the precipitate and treated acetic acid wastewater.

[0088] The recovery rate of rhodium under different illumination time is as follows

[0089]

[0090] Through the above-mentioned condition optimization experiment, it was found that after ultraviolet light irradiation for 30-60 minutes, the residual rhodium concentration in the acetic acid production wastewater was below 0.024 mg / L, and the rhodium recovery rate was greater than 97.86%.

[0091] Example 5

[0092] S1. Detecting the concentrations of rhodium, ruthenium and iridium in the acetic acid production wastewater to be treated;

[0093] The acetic acid production wastewater to be treated in this example contains 3% (wt%) formic acid, 52% (wt%) acetic acid, 30% (wt%) propionic acid, and a ruthenium concentration of 5.3 mg / L, while rhodium and iridium are not detected.

[0094] S2. Take 50 mL of wastewater sample and stir it with a magnetic stirrer; at the same time, add thiourea solid at a molar ratio of thiourea to ruthenium of 2:1.

[0095] S3, irradiation with 36W 254nm single wavelength low pressure UV lamp, irradiation intensity is 10mW / cm 2 After irradiation for 60 minutes, precipitation was produced in the acidic wastewater.

[0096] S4. Filter the precipitate produced by the treatment in step S3 using a 0.22 μm filter membrane to obtain the precipitate and treated acetic acid wastewater.

[0097] After the above treatment, the residual ruthenium concentration in the acetic acid production wastewater of this embodiment is 0.028 mg / L, and the recovery rate of ruthenium is 99.47%.

[0098] Example 6

[0099] S1. Detecting the concentrations of rhodium, ruthenium and iridium in the acetic acid production wastewater to be treated;

[0100] The acetic acid production wastewater to be treated in this example contains 4% (wt%) formic acid, 45% (wt%) acetic acid, 35% (wt%) propionic acid, iridium concentration of 2.1 mg / L, and neither rhodium nor ruthenium is detected.

[0101] S2. Take 50 mL of wastewater sample and stir it with a magnetic stirrer; at the same time, add sodium dithionite solid at a molar ratio of sodium dithionite to iridium of 2:1.

[0102] S3, irradiation with 36W 254nm single wavelength low pressure UV lamp, irradiation intensity is 10mW / cm 2 After irradiation for 60 minutes, precipitation was produced in the acidic wastewater.

[0103] S4. Filter the precipitate produced by the treatment in step S3 using a 0.22 μm filter membrane to obtain the precipitate and treated acetic acid wastewater.

[0104] After the above treatment, the residual iridium concentration in the acetic acid production wastewater of this embodiment is 0.030 mg / L, and the recovery rate of iridium is greater than 98.57%.

[0105] Example 7

[0106] S1. Detecting the concentrations of rhodium, ruthenium and iridium in the acetic acid production wastewater to be treated;

[0107] The acetic acid production wastewater to be treated in this example contains 0.8% (wt%) formic acid, 50% (wt%) acetic acid, 32% (wt%) propionic acid, 3.4 mg / L ruthenium concentration, 1.8 mg / L rhodium concentration, and no iridium is detected.

[0108] S2. Take 50 mL of wastewater sample and stir it with a magnetic stirrer; at the same time, add thiourea solid at a total molar ratio of thiourea to ruthenium and rhodium of 2:1.

[0109] S3, irradiation with 36W 254nm single wavelength low pressure UV lamp, irradiation intensity is 10mW / cm 2 After irradiation for 60 minutes, precipitation was produced in the acidic wastewater.

[0110] S4. Filter the precipitate produced by the treatment in step S3 using a 0.22 μm filter membrane to obtain the precipitate and treated acetic acid wastewater.

[0111] After the above treatment, the residual ruthenium concentration in the acetic acid production wastewater of this embodiment is 0.023 mg / L, and the recovery rate of ruthenium is 99.32%; the residual rhodium concentration is below 0.020 mg / L, and the recovery rate of rhodium is 98.89%.

[0112] Example 8

[0113] S1. Detecting the concentrations of rhodium, ruthenium and iridium in the acetic acid production wastewater to be treated;

[0114] The acetic acid production wastewater to be treated in this embodiment contains 3.5% (wt%) formic acid, 45% (wt%) acetic acid, 25% (wt%) propionic acid, 4.3 mg / L ruthenium concentration, 2.1 mg / L rhodium concentration and 1.1 mg / L iridium concentration.

[0115] S2. Take 50 mL of wastewater sample and stir it with a magnetic stirrer; at the same time, add thiourea solid at a total molar ratio of thiourea to ruthenium, rhodium and iridium of 2:1.

[0116] S3, irradiation with 36W 254nm single wavelength low pressure UV lamp, irradiation intensity is 10mW / cm 2 After irradiation for 60 minutes, precipitation was produced in the acidic wastewater.

[0117] S4. Filter the precipitate produced by the treatment in step S3 using a 0.22 μm filter membrane to obtain the precipitate and treated acetic acid wastewater.

[0118] After the above treatment, the residual ruthenium concentration in the acetic acid production wastewater of this embodiment is 0.026 mg / L, and the recovery rate of ruthenium is 99.39%; the residual rhodium concentration is below 0.025 mg / L, and the recovery rate of rhodium is 98.81%; the residual iridium concentration is 0.032 mg / L, and the recovery rate of iridium is greater than 97.09%.

[0119] Comparative Example 1

[0120] For three types of wastewater containing rhodium, ruthenium and iridium, thiourea was added at a molar ratio of 1:1-100:1 and reacted in the dark for 60 minutes. No precipitate was generated under all dosage conditions.

[0121] Comparative Example 2

[0122] For three types of wastewater containing rhodium, ruthenium and iridium respectively, no reagent is added, and ultraviolet light is irradiated using a 500W high-pressure mercury lamp and a single-wavelength low-pressure ultraviolet lamp in the embodiment. The ultraviolet light reaction lasts for 2-60 minutes, and the recovery rate of rhodium, ruthenium or iridium is only 30-50%.

[0123] It can be seen from the above embodiments and comparative examples that the recovery method of the present invention can efficiently recover rhodium, iridium and ruthenium, realize the resource recovery of rhodium, ruthenium and iridium, and also ensure the smooth progress of the subsequent recovery process of organic acids such as acetic acid and propionic acid.

[0124] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for recovering rhodium, ruthenium or iridium from waste water by combining sulfidation and ultraviolet treatment, characterized in that: The following steps are involved: 1) adding a sulfiding agent to wastewater containing rhodium, ruthenium or iridium, mixing and reacting the mixture to obtain a mixed solution; 2) placing the mixed solution obtained in step 1) under ultraviolet light, irradiating it for a certain period of time under stirring, to react; 3) Solid-liquid separation to obtain precipitate containing rhodium, ruthenium or iridium and treated wastewater respectively.

2. The method for recovering rhodium, ruthenium or iridium from waste water by combined sulfidation and ultraviolet treatment according to claim 1, characterized in that: In step 1), the wastewater is industrial wastewater containing rhodium, ruthenium or iridium, including but not limited to: wastewater generated by the acetic acid production industry; leaching solution containing rhodium, ruthenium or iridium.

3. The method for recovering rhodium, ruthenium or iridium from waste water by combined sulfidation and ultraviolet treatment according to claim 1, characterized in that: In step 1), the vulcanizing agent is selected from any one of sodium sulfide, sodium sulfite, sodium dithionite or thiourea.

4. The method for recovering rhodium, ruthenium or iridium from waste water by combined sulfidation and ultraviolet treatment according to claim 3, characterized in that: In step 1): When the wastewater contains only any one of rhodium, ruthenium or iridium, the molar ratio of the sulfiding agent to rhodium, ruthenium or iridium is (1-100):1; When the wastewater contains only any two or three of rhodium, ruthenium or iridium, the molar ratio of the sulfiding agent to rhodium, ruthenium or iridium is (2-100):

1.

5. The method for recovering rhodium, ruthenium or iridium from waste water by combined sulfidation and ultraviolet treatment according to claim 1, characterized in that: In step 1), the mixing reaction is carried out by one or more of stirring, shaking or ultrasound.

6. The method for recovering rhodium, ruthenium or iridium from waste water by combined sulfidation and ultraviolet treatment according to claim 1, characterized in that: In step 2), the ultraviolet light includes but is not limited to single-wavelength, multi-wavelength or continuous-wavelength ultraviolet light with an effective wavelength of 190 to 400 nm.

7. The method for recovering rhodium, ruthenium or iridium from waste water by combined sulfidation and ultraviolet treatment according to claim 6, characterized in that: In step 2), the intensity of the ultraviolet light is 0.5 mW / cm 2 -5000mW / cm 2 .

8. The method for recovering rhodium, ruthenium or iridium from waste water by combined sulfidation and ultraviolet treatment according to claim 6, characterized in that: In step 2), the ultraviolet light irradiation time is 2-60 min.

9. A method for recovering rhodium, ruthenium or iridium from waste water by combining sulfidation and ultraviolet treatment according to any one of claims 1 to 8, characterized in that: The rhodium, ruthenium or iridium in the wastewater exists in the form of dissolved ions; The wastewater contains any one, any two or three of rhodium, ruthenium or iridium.

10. A product recovered according to the method according to any one of claims 1 to 9, characterized in that contain: Rhodium sulfur compound precipitation and elemental substance; and / or, precipitates of sulfur-containing compounds and simple substances of ruthenium; and / or, precipitate of sulfur-containing compounds and elemental iridium.

Images