A method for recovering iridium from wastewater with low iridium content

Abstract

This invention relates to a method for recovering iridium from low-iridium wastewater, comprising the following steps: (1) Heating oxidation: adding a strong oxidant to the low-iridium wastewater for oxidation treatment, followed by mixing and stirring reaction; (2) pH adjustment: slowly adding sodium hydroxide solution under stirring conditions; (3) Sulfide precipitation: slowly adding a sulfide precipitant under stirring conditions, heating to 70-80℃, reacting at a constant temperature, and then cooling to room temperature; (4) Flocculation and filtration: slowly adding a mixed flocculant under stirring conditions, allowing to stand, filtering, washing the filter residue until neutral, and then draining the water; (5) Sulfuric acid leaching: placing the filter residue in a reaction vessel, slowly adding a dilute sulfuric acid solution under stirring conditions for leaching, cooling to room temperature after the reaction is completed, filtering, washing the filter residue until neutral, and then draining the water; (6) Calcination: calcining the filter residue, and obtaining iridium oxide after calcination. This method has good recovery capability for low-content, high-impurity iridium wastewater.

Description

Technical Field

[0001] This invention relates to the field of iridium recovery technology, and specifically to a method for recovering iridium from wastewater with low iridium content. Background Technology

[0002] Iridium is a rare metal with very low abundance in the Earth's crust, making its recycling and processing costly. Due to its excellent corrosion resistance and other chemical properties, it is widely used in aerospace, electronics, and medical fields. Therefore, the importance of iridium recycling and processing is receiving increasing attention.

[0003] The most commonly used methods for iridium recovery are chemical precipitation and solvent extraction. These methods are effective for wastewater with high iridium content and low impurities. However, chemical precipitation lacks selectivity, and the reaction process can lead to co-precipitation with impurity metals, resulting in low recovery rates. Solvent extraction, on the other hand, requires strict control of the extraction solution parameters, including the concentration of the extracted metal and the impurities in the solution system. When dealing with wastewater with low iridium content and high impurities, both chemical precipitation and solvent extraction methods result in low recovery rates and low product purity. Currently, there is a lack of methods for treating wastewater with low iridium content and high impurities. Summary of the Invention

[0004] The purpose of this invention is to design a method for recovering iridium from wastewater with low iridium content, so as to achieve good recovery capability for wastewater with low iridium content and high impurities.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] A method for recovering iridium from wastewater with low iridium content includes the following steps:

[0007] (1) Heating oxidation: Place the low-iridium wastewater in a reaction vessel, slowly add a strong oxidant for oxidation treatment, mix and stir the reaction, control the reaction temperature at 70-80℃ during the reaction, keep the ORP potential value of the reaction system at +900-+1000mV to ensure that the iridium valence state is high under this condition, and react for 1-2 hours; the reaction temperature should not be lower than 75℃. The higher the temperature, the faster the reaction efficiency. However, since the side reactions of high impurity solutions are more complex, excessively high temperature may cause boiling during the reaction, which is not conducive to safe operation.

[0008] (2) pH adjustment: Add sodium hydroxide solution slowly to the iridium solution after the reaction in step (1) under stirring to adjust the pH to 1 to 2, and cool to room temperature; the purpose of using sodium hydroxide solution to adjust the pH to 1 to 2 is to reduce the consumption of sulfide precipitant in subsequent steps, and at the same time avoid the co-precipitation effect of other impurities due to the excessive use of sulfide precipitant; if the pH is lower than 1, a large amount of sulfide precipitant will be consumed and the best effect cannot be achieved; if the pH is higher than 2, a large amount of impurities will be generated in the co-precipitation reaction, reducing the purity of the recovered iridium;

[0009] (3) Sulfide precipitation: Slowly add the sulfide precipitant to the iridium solution after cooling in step (2) under stirring. After the sulfide precipitant is added, heat to 70-80℃ and react at a constant temperature for 2-3 hours. After the sulfide precipitation is completed, cool to room temperature. The reaction temperature of the sulfide complexation process should not be lower than 75℃, but excessively high temperatures may cause a boiling reaction. It should not be higher than 80℃.

[0010] (4) Flocculation and Filtration: The mixed flocculant is slowly added to the iridium sulfide precipitate solution after cooling in step (3) under stirring. The solution volume: mixed flocculant volume = 1000: 1~2. The pH of the solution system is controlled at 2~3. The flocculation time is 4~5h. After standing, the solution is filtered. The filter residue is washed until neutral and then the water is drained. The amount of mixed flocculant needs to be controlled. Too much will form a large amount of colloidal clumps, which is not conducive to filtration and separation. Too little will result in a low recovery rate. The pH of the solution system is controlled by adding auxiliary materials such as sodium hydroxide, ammonia, hydrochloric acid, and sulfuric acid.

[0011] (5) Sulfuric acid immersion: Place the filter residue obtained in step (4) into a reaction vessel and slowly add dilute sulfuric acid solution under stirring conditions for immersion. The solid-liquid volume ratio is 1:2-3. During the reaction, control the reaction temperature at 50-60℃ to accelerate the reaction rate. The reaction time is 1-2 hours. After the reaction is completed, cool to room temperature, filter, wash the filter residue until neutral, and then drain the water.

[0012] (6) Calcination: The filter residue obtained in step (5) is calcined. The calcination temperature is 200℃ for 1 hour in the first stage, 400℃ for 1 hour in the second stage, and 650℃ for 1 hour in the third stage. After calcination, iridium oxide is obtained.

[0013] Furthermore, in the above-mentioned method for recovering iridium from low-iridium wastewater, the strong oxidant in step (1) is one or more of potassium permanganate, sodium chlorate, and sodium persulfate. The purpose is to convert the solution system into a strong oxidizing state and oxidize the metal ions in the solution to a high valence, thus providing the basic conditions for subsequent sulfide precipitation.

[0014] Furthermore, in the above-mentioned method for recovering iridium from low-iridium wastewater, the amount of strong oxidant used in step (1) is 2 to 5 times the amount of iridium. If too much strong oxidant is used, it will cause over-oxidation and waste; if too little is used, the oxidation will be insufficient and the sulfidation effect will be poor.

[0015] Furthermore, in the above-mentioned method for recovering iridium from low-iridium wastewater, the stirring speed in step (1) is 110-150 r / min.

[0016] Furthermore, in the above-mentioned method for recovering iridium from low-iridium wastewater, the mass fraction of sodium hydroxide solution in step (2) is 30% to 40%. The sodium hydroxide solution at this concentration has moderate alkalinity, which facilitates pH adjustment and does not result in a significant increase in water content.

[0017] Furthermore, in the above-mentioned method for recovering iridium from low-iridium wastewater, in step (2), the solution pH value is stabilized for 1 hour before being cooled to room temperature. The pH measurement is affected by the reaction rate, and the measurement result is only accurate after the reaction is completed. Maintaining a constant pH value for a certain period of time is the closest to the true value of the solution system.

[0018] Furthermore, in the above-mentioned method for recovering iridium from low-iridium wastewater, the amount of sulfide precipitant used in step (3) is 1 to 2 times the amount of iridium.

[0019] Furthermore, in the above-mentioned method for recovering iridium from low-iridium wastewater, the sulfide precipitant in step (3) is one or more of sodium sulfide, ammonium sulfide, and thiourea.

[0020] Furthermore, in the above-mentioned method for recovering iridium from low-iridium wastewater, the mixed flocculant in step (4) consists of 0.01% polyacrylamide and 1% ferric sulfate by mass, with the remainder being water. Compared with any single polymeric flocculant, the mixed flocculant has a better agglomeration effect and can quickly agglomerate fine particles in the solution for sedimentation, resulting in high filtration efficiency and high recovery rate.

[0021] Furthermore, in the above-mentioned method for recovering iridium from low-iridium wastewater, the mass fraction of the dilute sulfuric acid solution in step (5) is 5-10%. This concentration of sulfuric acid can effectively remove impurities without dissolving iridium complexes.

[0022] Compared with the prior art, the beneficial effects of the present invention are as follows: the iridium recovery process in the method of the present invention is simple, the pH of the reaction system is in the range of 1 to 2, the metal ions are basically not in the form of precipitation, the high-valence sulfide complexation reaction has a high complexing ability for platinum group metals, but no such characteristic for other heavy metals. Therefore, the metal selectivity is strong, the iridium recovery effect is good and the purity is high. Attached Figure Description

[0023] Figure 1 This is a flowchart of the method for recovering iridium from low-iridium wastewater according to the present invention. Detailed Implementation

[0024] This invention can be implemented in many variations and in various ways, but as one example, a specific embodiment will be described in detail below. The embodiments are not limited to the specific embodiments of the invention disclosed herein, and all variations, equivalents, and alternatives implemented within the scope expressed in the appended claims are included in this scope. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without inventive effort are within the scope of protection of this invention.

[0025] Example 1

[0026] A method for recovering iridium from wastewater with low iridium content includes the following steps:

[0027] (1) Heating oxidation: Place the low-iridium wastewater in a reactor and slowly add a strong oxidant for oxidation treatment. The strong oxidant is potassium permanganate, and the amount of strong oxidant is twice the amount of iridium. Mix and stir to react. During the reaction, control the reaction temperature at 75℃, the stirring speed at 110r / min, and keep the ORP potential value of the reaction system at +900mV. React for 2h.

[0028] (2) pH adjustment: Slowly add 30% sodium hydroxide solution to the iridium solution after the reaction in step (1) under stirring to adjust the pH to 1. After the pH value of the solution stabilizes for 1 hour, cool to room temperature.

[0029] (3) Sulfide precipitation: In the iridium solution cooled in step (2), a sulfide precipitant is slowly added under stirring. The amount of sulfide precipitant is 1 times the amount of iridium. The sulfide precipitant is sodium sulfide. After the sulfide precipitant is added, the solution is heated to 78°C and reacted at a constant temperature for 3 hours. After the sulfide precipitation is completed, the solution is cooled to room temperature.

[0030] (4) Flocculation and Filtration: The mixed flocculant is slowly added to the iridium sulfide precipitate solution after cooling in step (3) under stirring conditions. The volume of the solution and the volume of the mixed flocculant are 1000:1. The mixed flocculant consists of 0.01% polyacrylamide and 1% ferric sulfate by mass, with the remainder being water. The pH of the solution system is controlled to be 2. The flocculation time is 5 hours. After standing, the solution is filtered. The filter residue is washed until neutral and then drained.

[0031] (5) Sulfuric acid immersion: The filter residue obtained in step (4) is placed in a reaction vessel and a 5% mass fraction of dilute sulfuric acid solution is slowly added under stirring conditions for immersion. The solid-liquid volume ratio is 1:2. During the reaction, the reaction temperature is controlled at 50℃ and the reaction time is 2h. After the reaction is completed, the mixture is cooled to room temperature, filtered, and the filter residue is washed until neutral and then drained.

[0032] (6) Calcination: The filter residue obtained in step (5) is placed in a program furnace for calcination. The calcination temperature is 200℃ for 1 hour in the first stage, 400℃ for 1 hour in the second stage, and 650℃ for 1 hour in the third stage. After calcination, iridium oxide is obtained.

[0033] Example 2

[0034] A method for recovering iridium from wastewater with low iridium content includes the following steps:

[0035] (1) Heating oxidation: Place the low-iridium wastewater in a reactor and slowly add a strong oxidant for oxidation treatment. The strong oxidant is sodium chlorate, and the amount of strong oxidant is 3 times the amount of iridium. Mix and stir to react. During the reaction, control the reaction temperature at 70℃, the stirring speed at 115r / min, and maintain the ORP potential value of the reaction system at +950mV. The reaction time is 1.5h.

[0036] (2) pH adjustment: Slowly add 35% sodium hydroxide solution to the iridium solution after the reaction in step (1) under stirring to adjust the pH to 1.5. After the pH of the solution stabilizes for 1 hour, cool to room temperature.

[0037] (3) Sulfide precipitation: In the iridium solution cooled in step (2), sulfide precipitant is slowly added under stirring. The amount of sulfide precipitant is 1.6 times the amount of iridium. The sulfide precipitant is a mixture of sodium sulfide, ammonium sulfide and thiourea. After the sulfide precipitant is added, the solution is heated to 75°C and reacted at a constant temperature for 3 hours. After the sulfide precipitation is completed, the solution is cooled to room temperature.

[0038] (4) Flocculation and Filtration: The mixed flocculant is slowly added to the iridium sulfide precipitate solution after cooling in step (3) under stirring conditions. The volume of the solution is 1000:1.5 of the mixed flocculant. The mixed flocculant consists of 0.01% polyacrylamide and 1% ferric sulfate by mass, with the remainder being water. The pH of the solution system is controlled to be 2.5. The flocculation time is 4.5 h. After standing, the solution is filtered. The filter residue is washed until neutral and then drained.

[0039] (5) Sulfuric acid immersion: The filter residue obtained in step (4) is placed in a reaction vessel and a dilute sulfuric acid solution with a mass fraction of 8% is slowly added under stirring conditions for immersion. The solid-liquid volume ratio is 1:2.5. During the reaction, the reaction temperature is controlled at 55℃ and the reaction time is 1.5h. After the reaction is completed, the mixture is cooled to room temperature, filtered, and the filter residue is washed until neutral and then drained.

[0040] (6) Calcination: The filter residue obtained in step (5) is placed in a program furnace for calcination. The calcination temperature is 200℃ for 1 hour in the first stage, 400℃ for 1 hour in the second stage, and 650℃ for 1 hour in the third stage. After calcination, iridium oxide is obtained.

[0041] Example 3

[0042] A method for recovering iridium from wastewater with low iridium content includes the following steps:

[0043] (1) Heating oxidation: Place the low-iridium wastewater in a reactor and slowly add a strong oxidant for oxidation treatment. The strong oxidant is a mixture of potassium permanganate and sodium chlorate. The amount of strong oxidant is 5 times the amount of iridium. Mix and stir to react. During the reaction, control the reaction temperature at 80℃, the stirring speed at 140r / min, and maintain the ORP potential value of the reaction system at +980mV. React for 1h.

[0044] (2) pH adjustment: Slowly add 40% sodium hydroxide solution to the iridium solution after the reaction in step (1) under stirring to adjust the pH to 2. After the pH of the solution stabilizes for 1 hour, cool to room temperature.

[0045] (3) Sulfide precipitation: In the iridium solution cooled in step (2), a sulfide precipitant is slowly added under stirring. The amount of sulfide precipitant is twice the amount of iridium. The sulfide precipitant is thiourea. After the sulfide precipitant is added, the solution is heated to 80°C and reacted at a constant temperature for 2 hours. After the sulfide precipitation is completed, the solution is cooled to room temperature.

[0046] (4) Flocculation and Filtration: The mixed flocculant is slowly added to the iridium sulfide precipitate solution after cooling in step (3) under stirring conditions. The volume of the solution is 1000:2 of the volume of the mixed flocculant. The mixed flocculant consists of 0.01% polyacrylamide and 1% ferric sulfate by mass, with the remainder being water. The pH of the solution system is controlled to be 3. The flocculation time is 4 hours. After standing, the solution is filtered. The filter residue is washed until neutral and then drained.

[0047] (5) Sulfuric acid immersion: The filter residue obtained in step (4) is placed in a reaction vessel and a 10% mass fraction dilute sulfuric acid solution is slowly added under stirring conditions for immersion. The solid-liquid volume ratio is 1:3. During the reaction, the reaction temperature is controlled at 60℃ and the reaction time is 1h. After the reaction is completed, the mixture is cooled to room temperature, filtered, and the filter residue is washed until neutral and then drained.

[0048] (6) Calcination: The filter residue obtained in step (5) is placed in a program furnace for calcination. The calcination temperature is 200℃ for 1 hour in the first stage, 400℃ for 1 hour in the second stage, and 650℃ for 1 hour in the third stage. After calcination, iridium oxide is obtained.

[0049] Comparative Example 1

[0050] A method for recovering iridium from wastewater with low iridium content includes the following steps:

[0051] (1) Heating oxidation: Place the low-iridium wastewater in a reactor and slowly add a strong oxidant for oxidation treatment. The strong oxidant is potassium permanganate, and the amount of strong oxidant is twice the amount of iridium. Mix and stir to react. During the reaction, control the reaction temperature at 75℃, the stirring speed at 110r / min, and keep the ORP potential value of the reaction system at +900mV. React for 2h.

[0052] (2) Sulfide precipitation: Sulfide precipitant is slowly added to the iridium solution after the reaction in step (1) under stirring. The amount of sulfide precipitant is 4 times the amount of iridium. The sulfide precipitant is sodium sulfide. After the sulfide precipitant is added, the solution is heated to 78°C and reacted at a constant temperature for 3 hours. After the sulfide precipitation is completed, the solution is cooled to room temperature.

[0053] (3) Flocculation and Filtration: The mixed flocculant is slowly added to the iridium sulfide precipitate solution after cooling in step (2) under stirring conditions. The volume of the solution and the volume of the mixed flocculant are 1000:1. The mixed flocculant consists of 0.01% polyacrylamide and 1% ferric sulfate by mass, with the remainder being water. The pH of the solution system is controlled to be 2. The flocculation time is 5 hours. After standing, the solution is filtered. The filter residue is washed until neutral and then drained.

[0054] (4) Sulfuric acid immersion: The filter residue obtained in step (3) is placed in a reaction vessel and a 5% mass fraction of dilute sulfuric acid solution is slowly added under stirring conditions for immersion. The solid-liquid volume ratio is 1:2. During the reaction, the reaction temperature is controlled at 50℃ and the reaction time is 2h. After the reaction is completed, the mixture is cooled to room temperature, filtered, and the filter residue is washed until neutral and then drained.

[0055] (5) Calcination: The filter residue obtained in step (4) is placed in a program furnace for calcination. The calcination temperature is 200℃ for 1 hour in the first stage, 400℃ for 1 hour in the second stage, and 650℃ for 1 hour in the third stage. After calcination, iridium oxide is obtained.

[0056] Comparative Example 2

[0057] A method for recovering iridium from wastewater with low iridium content includes the following steps:

[0058] (1) Heating oxidation: Place the low-iridium wastewater in a reactor and slowly add a strong oxidant for oxidation treatment. The strong oxidant is potassium permanganate, and the amount of strong oxidant is twice the amount of iridium. Mix and stir to react. During the reaction, control the reaction temperature at 75℃, the stirring speed at 110r / min, and keep the ORP potential value of the reaction system at +900mV. React for 2h.

[0059] (2) pH adjustment: Slowly add 30% sodium hydroxide solution to the iridium solution after the reaction in step (1) under stirring to adjust the pH to 1. After the pH value of the solution stabilizes for 1 hour, cool to room temperature.

[0060] (3) Sulfide precipitation: In the iridium solution cooled in step (2), a sulfide precipitant is slowly added under stirring. The amount of sulfide precipitant is 1 times the amount of iridium. The sulfide precipitant is sodium sulfide. After the sulfide precipitant is added, the solution is heated to 78°C and reacted at a constant temperature for 3 hours. After the sulfide precipitation is completed, the solution is cooled to room temperature.

[0061] (4) Flocculation and filtration: In the iridium sulfide precipitate solution cooled in step (3), flocculant is slowly added under stirring. The volume of solution: volume of mixed flocculant = 1000: 1. The flocculant consists of 1.01% polyacrylamide by mass fraction and the remainder is water. The pH of the solution system is controlled to be 2. The flocculation time is 5h. After standing, the solution is filtered. The filter residue is washed until neutral and then the water is drained.

[0062] (5) Sulfuric acid immersion: The filter residue obtained in step (4) is placed in a reaction vessel and a 5% mass fraction of dilute sulfuric acid solution is slowly added under stirring conditions for immersion. The solid-liquid volume ratio is 1:2. During the reaction, the reaction temperature is controlled at 50℃ and the reaction time is 2h. After the reaction is completed, the mixture is cooled to room temperature, filtered, and the filter residue is washed until neutral and then drained.

[0063] (6) Calcination: The filter residue obtained in step (5) is placed in a program furnace for calcination. The calcination temperature is 200℃ for 1 hour in the first stage, 400℃ for 1 hour in the second stage, and 650℃ for 1 hour in the third stage. After calcination, iridium oxide is obtained.

[0064] Comparative Example 3

[0065] A method for recovering iridium from wastewater with low iridium content includes the following steps:

[0066] (1) Heating oxidation: Place the low-iridium wastewater in a reactor and slowly add a strong oxidant for oxidation treatment. The strong oxidant is potassium permanganate, and the amount of strong oxidant is twice the amount of iridium. Mix and stir to react. During the reaction, control the reaction temperature at 75℃, the stirring speed at 110r / min, and keep the ORP potential value of the reaction system at +900mV. React for 2h.

[0067] (2) pH adjustment: Slowly add 30% sodium hydroxide solution to the iridium solution after the reaction in step (1) under stirring to adjust the pH to 1. After the pH of the solution stabilizes for 1 hour, cool to room temperature.

[0068] (3) Sulfide precipitation: In the iridium solution cooled in step (2), a sulfide precipitant is slowly added under stirring. The amount of sulfide precipitant is 1 times the amount of iridium. The sulfide precipitant is sodium sulfide. After the sulfide precipitant is added, the solution is heated to 78°C and reacted at a constant temperature for 3 hours. After the sulfide precipitation is completed, the solution is cooled to room temperature.

[0069] (4) Flocculation and Filtration: In the iridium sulfide precipitate solution cooled in step (3), flocculant is slowly added under stirring conditions. The volume of solution: volume of mixed flocculant = 1000: 1. The composition of flocculant includes 1.01% polypyrrolidone by mass, with the remainder being water. The pH of the solution system is controlled to be 2. The flocculation time is 5 hours. After standing, the solution is filtered. The filter residue is washed until neutral and then drained.

[0070] (5) Sulfuric acid immersion: The filter residue obtained in step (4) is placed in a reaction vessel and a 5% mass fraction of dilute sulfuric acid solution is slowly added under stirring conditions for immersion. The solid-liquid volume ratio is 1:2. During the reaction, the reaction temperature is controlled at 50℃ and the reaction time is 2h. After the reaction is completed, the mixture is cooled to room temperature, filtered, and the filter residue is washed until neutral and then drained.

[0071] (6) Calcination: The filter residue obtained in step (5) is placed in a program furnace for calcination. The calcination temperature is 200℃ for 1 hour in the first stage, 400℃ for 1 hour in the second stage, and 650℃ for 1 hour in the third stage. After calcination, iridium oxide is obtained.

[0072] The iridium content in the final iridium oxides of Examples 1-3 and Comparative Examples 1-3 was detected, and the iridium purity and direct iridium recovery rate were calculated.

[0073] The method for calculating the purity of iridium is as follows: first, iridium oxide is digested and then analyzed using an ICP instrument;

[0074] The method for calculating the direct recovery rate of iridium is as follows: first, iridium oxide is digested, and then the iridium content in the iridium oxide is detected by an ICP instrument. The direct recovery rate of precious metals = iridium content in iridium oxide / iridium content in low-iridium wastewater.

[0075] The test results are shown in Table 1 below:

[0076] Table 1

[0077]

[0078] Analysis of the data in Table 1 shows that Examples 1-3 are generally superior to Comparative Examples 1-3. Compared to Example 1, Comparative Example 1 did not use sodium hydroxide solution to adjust the pH to 1-2, resulting in higher consumption of sulfide precipitant in subsequent steps. This excessive use of sulfide precipitant led to the co-precipitation effect of other impurities. Compared to Example 1, Comparative Example 2 used a single polyacrylamide flocculant, resulting in inferior flocculation, lower filtration efficiency, and lower recovery rate. Compared to Example 1, Comparative Example 3 used a single polypyrrolidone flocculant, resulting in inferior flocculation, lower filtration efficiency, and lower recovery rate.

[0079] This application uses low-iridium wastewater as the source, adding a strong oxidant for oxidation treatment to transform the solution system into a strongly oxidizing state, laying the foundation for subsequent sulfide precipitation. Secondly, the pH is adjusted using sodium hydroxide solution to reduce the consumption of the sulfide precipitant in step three, avoiding the co-precipitation effect of other impurities due to excessive use of the sulfide precipitant. Then, the sulfide precipitant is added to carry out a sulfide complexation reaction, obtaining an iridium sulfide precipitate solution. Next, a mixed flocculant is added to rapidly agglomerate fine particles in the solution for sedimentation, improving filtration efficiency and recovery rate. Finally, sulfuric acid leaching effectively removes impurities without dissolving the iridium complex, followed by calcination to obtain iridium oxide. The iridium recovery process in this invention is simple, the reaction system pH is in the range of 1-2, and metal ions are basically not precipitated. The high-valence sulfide complexation reaction has high complexing activity for platinum group metals but not for other heavy metals, thus exhibiting strong metal selectivity, good iridium recovery effect, and high purity.

[0080] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A method for recovering iridium from wastewater with low iridium content, characterized in that: The following steps are included: (1) Heating oxidation: Place the low-iridium wastewater in a reaction vessel, slowly add a strong oxidant for oxidation treatment, mix and stir the reaction, control the reaction temperature at 70-80℃ during the reaction, keep the ORP potential value of the reaction system at +900-+1000mV, and react for 1-2 hours; (2) pH adjustment: Add sodium hydroxide solution slowly to the iridium solution after the reaction in step (1) under stirring to adjust the pH to 1 to 2, and cool to room temperature; (3) Sulfide precipitation: Slowly add the sulfide precipitant to the cooled iridium solution in step (2) under stirring. After the sulfide precipitant is added, heat to 70-80°C and react at a constant temperature for 2-3 hours. After the sulfide precipitation is completed, cool to room temperature. (4) Flocculation and filtration: The mixed flocculant is slowly added to the iridium sulfide precipitate solution after cooling in step (3) under stirring conditions. The solution volume: mixed flocculant volume = 1000: 1~2. The pH of the solution system is controlled to be 2~3. The flocculation time is 4~5h. After standing, the solution is filtered. The filter residue is washed until neutral and then the water is drained. (5) Sulfuric acid immersion: Place the filter residue obtained in step (4) into a reaction vessel and slowly add dilute sulfuric acid solution under stirring conditions for immersion. The solid-liquid volume ratio is 1:2-3. During the reaction, control the reaction temperature at 50-60℃ and the reaction time at 1-2h. After the reaction is completed, cool to room temperature, filter, wash the filter residue until neutral, and then drain the water. (6) Calcination: The filter residue obtained in step (5) is calcined. After calcination, iridium oxide is obtained.

2. The method for recovering iridium from low-iridium wastewater according to claim 1, characterized in that: In step (1), the strong oxidizing agent is one or more of potassium permanganate, sodium chlorate, and sodium persulfate.

3. The method for recovering iridium from low-iridium wastewater according to claim 1, characterized in that: In step (1), the amount of strong oxidant used is 2 to 5 times the amount of iridium.

4. The method for recovering iridium from low-iridium wastewater according to claim 1, characterized in that: In step (1), the stirring speed is 110-150 r / min.

5. The method for recovering iridium from low-iridium wastewater according to claim 1, characterized in that: In step (2), the mass fraction of the sodium hydroxide solution is 30% to 40%.

6. The method for recovering iridium from low-iridium wastewater according to claim 1, characterized in that: In step (2), the solution pH value is stabilized for 1 hour before being cooled to room temperature.

7. The method for recovering iridium from low-iridium wastewater according to claim 1, characterized in that: In step (3), the amount of sulfide precipitant used is 1 to 2 times the amount of iridium.

8. The method for recovering iridium from low-iridium wastewater according to claim 1, characterized in that: In step (3), the sulfide precipitant is one or more of sodium sulfide, ammonium sulfide, and thiourea.

9. The method for recovering iridium from low-iridium wastewater according to claim 1, characterized in that: The components of the mixed flocculant in step (4) include 0.01% polyacrylamide and 1% ferric sulfate by mass.

10. The method for recovering iridium from wastewater with low iridium content according to claim 1, characterized in that: In step (5), the mass fraction of the dilute sulfuric acid solution is 5-10%.

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