Method for recovering iridium from wastewater with low iridium content

Abstract

The invention relates to a method for recovering iridium from low-iridium-content wastewater, which comprises the following operation steps: (1) heating oxidation: adding a strong oxidant into the low-iridium-content wastewater for oxidation treatment, and mixing and stirring for reaction; (2) pH adjustment: slowly adding a sodium hydroxide solution under a stirring condition; (3) sulfuration precipitation: slowly adding a sulfuration precipitator under a stirring condition, heating to 70-80 DEG C, carrying out a constant temperature reaction, and cooling to room temperature; (4) flocculation and filtration: slowly adding a mixed flocculant under a stirring condition, standing, filtering, cleaning filter residues to be neutral, and draining water; (5) sulfuric acid digestion: putting the filter residues into a reaction container, slowly adding a dilute sulfuric acid solution under a stirring condition for soaking, cooling to room temperature after the reaction is completed, filtering, washing the filter residues to be neutral, and draining water; and (6) calcining: calcining the filter residues to obtain the iridium oxide. The method has good recovery capability on the low-content and high-impurity iridium wastewater.

Description

Technical Field

[0001] The invention relates to the technical field of iridium recovery, and in particular to a method for recovering iridium from low-content iridium wastewater. Background Art

[0002] Iridium is a rare metal with a very low content in the earth's crust, so the cost of recycling and processing is high. Due to its excellent chemical properties such as corrosion resistance, it is widely used in aerospace, electronics, medical and other fields. Therefore, the importance of recycling and processing iridium has received increasing attention.

[0003] In the process of recovering iridium, the most commonly used methods are chemical precipitation and solvent extraction. These methods are effective for high-content iridium and low-impurity iridium wastewater, but the chemical precipitation method is non-selective, and the reaction process will form a co-precipitation reaction with the impurity metal, and the recovery rate is low. The solvent extraction method has high requirements for the extraction liquid parameters, and the content concentration of the extracted metal and the impurities in the liquid system must be strictly controlled. When faced with low-content, high-impurity iridium wastewater, the chemical precipitation method and solvent extraction method have low recovery rates and low product purity. There is a lack of methods for treating low-content, high-impurity iridium wastewater in the prior art. Summary of the invention

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

[0005] To achieve the above object, the present invention provides the following technical solutions:

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

[0007] (1) Heating oxidation: placing low-content iridium wastewater in a reaction vessel, slowly adding a strong oxidant for oxidation treatment, mixing and stirring the reaction, controlling the reaction temperature at 70-80°C during the reaction, maintaining the ORP potential value of the reaction system at +900-1000mV to ensure that the valence state of iridium is high under this state, and reacting for 1-2h; the reaction temperature is preferably not less than 75°C, the higher the temperature, the faster the reaction efficiency, but since the side reactions of high-impurity solutions are more complicated, excessively high temperatures will easily lead to violent boiling during the reaction, which is not conducive to safe operation;

[0008] (2) pH adjustment: slowly adding sodium hydroxide solution to the iridium solution after the reaction in step (1) under stirring conditions to adjust the pH to 1-2, and cooling to room temperature; the sodium hydroxide solution is used to adjust the pH to 1-2, the purpose of which is to reduce the consumption of the sulfide precipitant in the subsequent steps and to avoid the co-precipitation effect of other impurities caused by excessive use of the sulfide precipitant; if the pH is lower than 1, a large amount of the sulfide precipitant will be consumed and the optimal effect cannot be achieved; if the pH is higher than 2, a large amount of impurities will produce a co-precipitation reaction, reducing the purity of the recovered iridium;

[0009] (3) Sulfide precipitation: slowly add the sulfide precipitant to the iridium solution cooled in step (2) under stirring conditions. After the addition of the sulfide precipitant, heat to 70-80°C and react at constant temperature for 2-3 hours. After the sulfide precipitation is completed, cool to room temperature. The reaction temperature of the sulfide complex process is preferably not less than 75°C, but too high a temperature will cause a bumping reaction, and it should not be higher than 80°C.

[0010] (4) Flocculation and filtration: Slowly add a mixed flocculant to the iridium sulfide precipitation solution cooled in step (3) under stirring conditions, the solution volume: mixed flocculant volume = 1000: 1-2, control the solution system pH = 2-3, the flocculation time is 4-5 hours, let it stand and filter, wash the filter residue to neutrality and then filter out the water; the amount of mixed flocculant needs to be controlled, too much will form a large number of colloidal masses, which is not conducive to filtration and separation, too little will result in low recovery rate, the solution system pH is controlled by adding sodium hydroxide, ammonia, hydrochloric acid, sulfuric acid and other auxiliary materials for adjustment and control;

[0011] (5) Sulfuric acid digestion: the filter residue obtained in step (4) is placed in a reaction vessel, and a dilute sulfuric acid solution is slowly added under stirring conditions for soaking, with a solid-liquid volume ratio of 1:2-3. During the reaction, the reaction temperature is controlled at 50-60°C to accelerate the reaction speed. The reaction time is 1-2 hours. After the reaction is completed, it is cooled to room temperature, filtered, and the filter residue is washed to neutrality and then filtered to dry the water;

[0012] (6) Calcination: Calcinate the filter residue obtained in step (5), wherein the calcination temperature is kept at 200° C. for 1 h in the first stage, 400° C. for 1 h in the second stage, and 650° C. for 1 h in the third stage. After the calcination is completed, iridium oxide is obtained.

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

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

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

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

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

[0018] Furthermore, in the above method for recovering iridium from low-content 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 method for recovering iridium from low-content iridium wastewater, the sulfide precipitating agent 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-content iridium wastewater, the components of the mixed flocculant in step (4) include 0.01% by mass of polyacrylamide + 1% by mass of ferric sulfate, and the balance is water. Compared with any single polymer flocculant, the mixed flocculant has a better coagulation effect and can quickly cluster fine particles in the solution for sedimentation, thereby achieving high filtration efficiency and high recovery rate.

[0021] Furthermore, in the above method for recovering iridium from low-content iridium wastewater, the mass fraction of the dilute sulfuric acid solution in step (5) is 5-10%. Sulfuric acid of this concentration can effectively remove impurities and does not dissolve iridium complexes.

[0022] Compared with the prior art, the present invention has the following beneficial effects: the iridium recovery process in the method of the present invention is simple, the pH value of the reaction system is in the range of 1 to 2, there is basically no precipitation of metal ions, the high-valent sulfide complex reaction has a higher complexing property for platinum group metals, but not for other heavy metals, so the metal selectivity is strong, the iridium recovery effect is good and the purity is high. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 The present invention is a flow chart of the method for recovering iridium from low-content iridium wastewater. DETAILED DESCRIPTION

[0024] The present invention can be implemented in a variety of variations and in various ways, but as an example, a specific implementation is described in detail below. The implementation is not limited to the specific way of the present invention disclosed herein, and all variations, equivalents, and alternatives implemented within the scope explicitly stated in the attached claims are included in the object. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0025] Example 1

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

[0027] (1) Heating oxidation: low-content iridium wastewater is placed in a reactor, and a strong oxidant is slowly added for oxidation treatment. The strong oxidant is potassium permanganate, and the amount of the strong oxidant is twice the amount of iridium. Mix and stir to react. During the reaction, the reaction temperature is controlled at 75°C, the stirring speed is 110r / min, and the ORP potential value of the reaction system is maintained at +900mV. The reaction is continued for 2h;

[0028] (2) pH adjustment: slowly add a 30% by mass sodium hydroxide solution to the iridium solution after the reaction in step (1) under stirring conditions to adjust the pH to 1. After the pH value of the solution is stable for 1 hour, cool it to room temperature;

[0029] (3) sulfide precipitation: slowly add a sulfide precipitant to the iridium solution cooled in step (2) under stirring conditions, wherein the amount of the sulfide precipitant is 1 times the amount of iridium, and the sulfide precipitant is sodium sulfide. After the sulfide precipitant is added, heat to 78° C. and react at this temperature for 3 hours. After the sulfide precipitation is completed, cool to room temperature;

[0030] (4) Flocculation and filtration: slowly add a mixed flocculant to the iridium sulfide precipitation solution cooled in step (3) under stirring conditions, the volume of the solution: the volume of the mixed flocculant = 1000:1, the composition of the mixed flocculant includes 0.01% polyacrylamide by mass + 1% ferric sulfate by mass, the balance is water, the pH of the solution system is controlled to be 2, the flocculation time is 5 hours, and the solution is allowed to stand for 5 hours before filtering. The filter residue is washed until it is neutral and then the water is dried;

[0031] (5) Sulfuric acid digestion: the filter residue obtained in step (4) is placed in a reaction kettle, and a 5% by mass dilute sulfuric acid solution is slowly added under stirring conditions for soaking, with a solid-liquid volume ratio of 1:2. During the reaction, the reaction temperature is controlled at 50° C. and the reaction time is 2 h. After the reaction is completed, the filter residue is cooled to room temperature, filtered, and washed to neutrality and then drained to dry the water;

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

[0033] Example 2

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

[0035] (1) Heating oxidation: low-content iridium wastewater is placed in a reactor, and a strong oxidant is slowly added for oxidation treatment. The strong oxidant is sodium chlorate, and the amount of the strong oxidant is 3 times the amount of iridium. Mix and stir to react. During the reaction, the reaction temperature is controlled at 70°C, the stirring speed is 115r / min, and the ORP potential value of the reaction system is maintained at +950mV. The reaction is carried out for 1.5h;

[0036] (2) pH adjustment: slowly add a 35% by mass 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 value of the solution is stable for 1 hour, cool it to room temperature;

[0037] (3) Sulfide precipitation: slowly add a sulfide precipitant to the iridium solution cooled in step (2) under stirring conditions. The amount of the 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 addition of the sulfide precipitant, heat to 75° C. and react at this temperature for 3 hours. After the sulfide precipitation is completed, cool to room temperature.

[0038] (4) Flocculation and filtration: slowly add a mixed flocculant to the iridium sulfide precipitation solution cooled in step (3) under stirring conditions, the volume of the solution: the volume of the mixed flocculant = 1000:1.5, the composition of the mixed flocculant includes 0.01% polyacrylamide by mass + 1% ferric sulfate by mass, and the balance is water, the pH of the solution system is controlled to be 2.5, the flocculation time is 4.5 hours, and the solution is allowed to stand and then filtered, and the filter residue is washed to neutrality and then the water is filtered out;

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

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

[0041] Example 3

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

[0043] (1) Heating oxidation: low-content iridium wastewater is placed in a reactor, and a strong oxidant is slowly added for oxidation treatment. The strong oxidant is a mixture of potassium permanganate and sodium chlorate, and the amount of the strong oxidant is 5 times the amount of iridium. Mix and stir to react. During the reaction, the reaction temperature is controlled at 80°C, the stirring speed is 140r / min, and the ORP potential value of the reaction system is maintained at +980mV. The reaction is carried out for 1h;

[0044] (2) pH adjustment: slowly add a 40% by mass sodium hydroxide solution to the iridium solution after the reaction in step (1) under stirring to adjust the pH to 2. After the pH value of the solution is stable for 1 hour, cool it to room temperature;

[0045] (3) Sulfide precipitation: slowly add a sulfide precipitant to the iridium solution cooled in step (2) under stirring conditions. The amount of the sulfide precipitant is twice the amount of iridium. The sulfide precipitant is thiourea. After the addition of the sulfide precipitant, heat to 80° C. and react at this temperature for 2 hours. After the sulfide precipitation is completed, cool to room temperature.

[0046] (4) Flocculation and filtration: slowly add a mixed flocculant to the iridium sulfide precipitation solution cooled in step (3) under stirring conditions, the volume of the solution: the volume of the mixed flocculant = 1000:2, the composition of the mixed flocculant includes 0.01% polyacrylamide + 1% ferric sulfate by mass, and the balance is water, the pH of the solution system is controlled to be 3, the flocculation time is 4 hours, and the solution is allowed to stand for 4 hours before filtering, and the filter residue is washed to neutrality and then the water is dried;

[0047] (5) Sulfuric acid digestion: the filter residue obtained in step (4) is placed in a reaction kettle, and a 10% by mass dilute sulfuric acid solution is slowly added under stirring conditions for soaking, with a solid-liquid volume ratio of 1:3. During the reaction, the reaction temperature is controlled at 60° C. and the reaction time is 1 h. After the reaction is completed, the filter residue is cooled to room temperature and filtered. The filter residue is washed until neutral and then the water is dried;

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

[0049] Comparative Example 1

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

[0051] (1) Heating oxidation: low-content iridium wastewater is placed in a reactor, and a strong oxidant is slowly added for oxidation treatment. The strong oxidant is potassium permanganate, and the amount of the strong oxidant is twice the amount of iridium. Mix and stir to react. During the reaction, the reaction temperature is controlled at 75°C, the stirring speed is 110r / min, and the ORP potential value of the reaction system is maintained at +900mV. The reaction is continued for 2h;

[0052] (2) Sulfide precipitation: slowly add a sulfide precipitant to the iridium solution after the reaction in step (1) under stirring conditions. The amount of the sulfide precipitant is 4 times the amount of iridium. The sulfide precipitant is sodium sulfide. After the addition of the sulfide precipitant is completed, heat to 78° C. and react at this temperature for 3 hours. After the sulfide precipitation is completed, cool to room temperature.

[0053] (3) Flocculation and filtration: slowly add a mixed flocculant to the iridium sulfide precipitation solution cooled in step (2) under stirring conditions, the volume of the solution: the volume of the mixed flocculant = 1000:1, the composition of the mixed flocculant includes 0.01% polyacrylamide + 1% ferric sulfate by mass, and the balance is water, the pH of the solution system is controlled to be 2, the flocculation time is 5 hours, and the solution is allowed to stand for 5 hours before filtering, and the filter residue is washed to neutrality and then the water is dried;

[0054] (4) Sulfuric acid digestion: the filter residue obtained in step (3) is placed in a reactor, and a 5% by mass dilute sulfuric acid solution is slowly added under stirring conditions for soaking, with a solid-liquid volume ratio of 1:2. During the reaction, the reaction temperature is controlled at 50°C and the reaction time is 2 hours. After the reaction is completed, it is cooled to room temperature and filtered. The filter residue is washed until it is neutral and then the water is drained;

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

[0056] Comparative Example 2

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

[0058] (1) Heating oxidation: low-content iridium wastewater is placed in a reactor, and a strong oxidant is slowly added for oxidation treatment. The strong oxidant is potassium permanganate, and the amount of the strong oxidant is twice the amount of iridium. Mix and stir to react. During the reaction, the reaction temperature is controlled at 75°C, the stirring speed is 110r / min, and the ORP potential value of the reaction system is maintained at +900mV. The reaction is continued for 2h;

[0059] (2) pH adjustment: slowly add a 30% by mass sodium hydroxide solution to the iridium solution after the reaction in step (1) under stirring conditions to adjust the pH to 1. After the pH value of the solution is stable for 1 hour, cool it to room temperature;

[0060] (3) sulfide precipitation: slowly add a sulfide precipitant to the iridium solution cooled in step (2) under stirring conditions, wherein the amount of the sulfide precipitant is 1 times the amount of iridium, and the sulfide precipitant is sodium sulfide. After the sulfide precipitant is added, heat to 78° C. and react at this temperature for 3 hours. After the sulfide precipitation is completed, cool to room temperature;

[0061] (4) Flocculation and filtration: slowly add a flocculant to the iridium sulfide precipitation solution cooled in step (3) under stirring conditions, the volume of the solution: the volume of the mixed flocculant = 1000:1, the composition of the flocculant includes 1.01% polyacrylamide by mass, the balance is water, the pH of the solution system is controlled to be 2, the flocculation time is 5 hours, and the solution is allowed to stand for 5 hours before filtering. The filter residue is washed until it is neutral and then the water is dried;

[0062] (5) Sulfuric acid digestion: the filter residue obtained in step (4) is placed in a reaction kettle, and a 5% by mass dilute sulfuric acid solution is slowly added under stirring conditions for soaking, with a solid-liquid volume ratio of 1:2. During the reaction, the reaction temperature is controlled at 50° C. and the reaction time is 2 h. After the reaction is completed, the filter residue is cooled to room temperature, filtered, and washed to neutrality and then drained to dry the water;

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

[0064] Comparative Example 3

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

[0066] (1) Heating oxidation: low-content iridium wastewater is placed in a reactor, and a strong oxidant is slowly added for oxidation treatment. The strong oxidant is potassium permanganate, and the amount of the strong oxidant is twice the amount of iridium. Mix and stir to react. During the reaction, the reaction temperature is controlled at 75°C, the stirring speed is 110r / min, and the ORP potential value of the reaction system is maintained at +900mV. The reaction is continued for 2h;

[0067] (2) pH adjustment: slowly add a 30% by mass sodium hydroxide solution to the iridium solution after the reaction in step (1) under stirring conditions to adjust the pH to 1. After the pH value of the solution is stable for 1 hour, cool it to room temperature;

[0068] (3) sulfide precipitation: slowly add a sulfide precipitant to the iridium solution cooled in step (2) under stirring conditions, wherein the amount of the sulfide precipitant is 1 times the amount of iridium, and the sulfide precipitant is sodium sulfide. After the sulfide precipitant is added, heat to 78° C. and react at this temperature for 3 hours. After the sulfide precipitation is completed, cool to room temperature;

[0069] (4) Flocculation and filtration: slowly add a flocculant to the iridium sulfide precipitation solution cooled in step (3) under stirring conditions, the volume of the solution: the volume of the mixed flocculant = 1000:1, the composition of the flocculant includes 1.01% polypyrrolidone by mass, the balance is water, the pH of the solution system is controlled to be 2, the flocculation time is 5 hours, and the solution is allowed to stand for 5 hours before filtering. The filter residue is washed until it is neutral and then the water is dried;

[0070] (5) Sulfuric acid digestion: the filter residue obtained in step (4) is placed in a reaction kettle, and a 5% by mass dilute sulfuric acid solution is slowly added under stirring conditions for soaking, with a solid-liquid volume ratio of 1:2. During the reaction, the reaction temperature is controlled at 50° C. and the reaction time is 2 h. After the reaction is completed, the filter residue is cooled to room temperature, filtered, and washed to neutrality and then drained to dry the water;

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

[0072] The iridium content in the final iridium oxide in the above Examples 1-3 and Comparative Examples 1-3 was detected, and the iridium purity and iridium direct yield were calculated.

[0073] The detection and calculation method of iridium purity is: firstly, iridium oxide is treated by digestion and then analyzed and determined by ICP instrument;

[0074] The detection and calculation method for the direct recovery of iridium is: first treat iridium oxide by digestion, and then use an ICP instrument to detect the iridium content in the iridium oxide. The direct recovery of precious metals = iridium content in iridium oxide / iridium content in low-content iridium wastewater.

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

[0076] Table 1

[0077]

[0078] From the data analysis of Table 1, it can be seen that Examples 1-3 are better than Comparative Examples 1-3 as a whole. Compared with Example 1, Comparative Example 1 does not use sodium hydroxide solution to adjust pH=1-2, and the consumption of sulfide precipitant in the subsequent steps is large. Due to the excessive use of sulfide precipitant, the coprecipitation effect of other impurities is generated. Compared with Example 1, Comparative Example 2 uses a single polyacrylamide flocculant, and the flocculation effect is not as good as that of Example 1, the filtration efficiency is low, and the recovery rate is low. Compared with Example 1, Comparative Example 3 uses a single polypyrrolidone flocculant, and the flocculation effect is not as good as that of Example 1, the filtration efficiency is low, and the recovery rate is low.

[0079] In this application, low-content iridium wastewater is used as the source, and a strong oxidant is added for oxidation treatment, and the solution system is converted into a strong oxidation state, which is the basic condition for subsequent sulfidation precipitation; secondly, the pH is adjusted by sodium hydroxide solution to reduce the consumption of sulfidation precipitant in step three, and avoid the co-precipitation effect of other impurities caused by excessive use of sulfidation precipitant; then the sulfidation precipitant is added for sulfidation complex reaction to obtain iridium sulfidation precipitation solution; again, a mixed flocculant is added to quickly cluster fine particles in the solution for sedimentation, thereby improving the filtration efficiency and recovery rate; finally, sulfuric acid is used to effectively remove impurities and insoluble iridium complexes, and calcined to obtain iridium oxide. The iridium recovery process in the method of the present invention is simple, the reaction system pH is in the range of 1 to 2, the metal ions are basically not precipitated, the high-valent sulfidation complex reaction has a high complexation for platinum group metals, but not for other heavy metals, so the metal selectivity is strong, the iridium recovery effect is good, and the purity is high.

[0080] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Although the present invention has been disclosed as a preferred embodiment as above, it is not used to limit the present invention. Any technical personnel in this field can make some changes or modify the technical contents disclosed above into equivalent embodiments without departing from the scope of the technical solution of the present invention. However, any brief modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. A method for recovering iridium from low-content iridium wastewater, characterized in that: The steps are as follows: (1) Heating oxidation: Place low-content iridium wastewater in a reaction vessel, slowly add a strong oxidant for oxidation treatment, mix and stir to react, control the reaction temperature at 70-80°C during the reaction, maintain the ORP potential value of the reaction system at +900-+1000mV, and react for 1-2h; (2) pH adjustment: slowly adding sodium hydroxide solution to the iridium solution after the reaction in step (1) under stirring to adjust the pH to 1-2, and cooling to room temperature; (3) sulfide precipitation: slowly adding a sulfide precipitant to the iridium solution cooled in step (2) under stirring conditions; after the sulfide precipitant is added, heating to 70-80° C. and reacting at this temperature for 2-3 hours; after the sulfide precipitation is completed, cooling to room temperature; (4) Flocculation and filtration: slowly add a mixed flocculant to the cooled iridium sulfide precipitation solution in step (3) under stirring conditions, the solution volume: mixed flocculant volume = 1000: 1-2, control the solution system pH = 2-3, the flocculation time is 4-5 hours, let stand and then filter, wash the filter residue until it is neutral and then filter out the water; (5) Sulfuric acid digestion: the filter residue obtained in step (4) is placed in a reaction vessel, and a dilute sulfuric acid solution is slowly added under stirring conditions for soaking, with a solid-liquid volume ratio of 1:2-3. During the reaction, the reaction temperature is controlled at 50-60°C, and the reaction time is 1-2 hours. After the reaction is completed, the filter residue is cooled to room temperature, filtered, and the filter residue is washed until neutral and then drained to dryness; (6) Calcination: Calcinate the filter residue obtained in step (5) to obtain iridium oxide.

2. The method for recovering iridium from low-content iridium waste water according to claim 1, wherein: In step (1), the strong oxidant is one or more of potassium permanganate, sodium chlorate and sodium persulfate.

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

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

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

6. The method for recovering iridium from low-content iridium waste water according to claim 1, characterized in that: The pH value of the solution in step (2) is stabilized for 1 hour and then cooled to room temperature.

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

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

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

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

Images