Method for enriching rhodium and iridium from neutralization slag of rhodium and iridium refining wastewater

Abstract

The invention discloses a method for enriching rhodium and iridium from neutralization slag of rhodium and iridium refining wastewater, which comprises the following steps of: dissolving the neutralization slag of the rhodium and iridium refining wastewater into mixed acid for acidification to obtain an intermediate product, feeding the intermediate product into a rotary furnace to obtain dissociation slag, feeding the dissociation slag into an enamel reaction kettle, adding water for slurrying, and carrying out solid-liquid separation to obtain the rhodium and iridium enriched in the neutralization slag of the rhodium and iridium refining wastewater. The preparation method comprises the following steps: adding an enamel reaction kettle into a reaction kettle, simultaneously adding an acid to control the pH value of the solution to be 0.5-1.5, then adding hydrazine hydrate and sodium hydrogen sulfite to obtain an enriched solution, and finally heating the enamel reaction kettle to remove base metal impurities in the enriched solution to obtain the enriched rhodium-iridium material. The neutralization slag of the rhodium-iridium refining wastewater is treated by adopting an acidification dissociation method, so that the condition of burning loss of rhodium and iridium in the treatment process is avoided, the rhodium and iridium can be better enriched while the separation of precious metals and base metals is realized, the enrichment multiple of the rhodium-iridium material is more than 10 times after the rhodium-iridium material is put into use, and the removal rate of the base metals reaches more than 90%; and the enriched rhodium-iridium material can be flexibly linked with the subsequent rhodium-iridium separation and refining process according to the specific content of the rhodium-iridium material, so that the refining period is shortened.

Description

Technical Field

[0001] The present invention relates to the technical field of platinum group metal refining and recovery, and specifically relates to a method for enriching rhodium and iridium from the neutralization slag of rhodium-iridium refining wastewater. Background Art

[0002] Rhodium and iridium are rare transition metals. Due to their high catalytic activity and high selectivity, they are widely used in fields such as petroleum industry catalysts, automotive three-way tail gas purifiers, catalytic hydrogenation, methanol carbonylation, and hydroformylation of olefins, and the market demand is very large.

[0003] In the process of separating and purifying rhodium and iridium metals, wastewater is generated in varying amounts in multiple steps, and these wastewaters will be centrally neutralized later. Due to the large volume of wastewater during the centralized neutralization process, rhodium and iridium will gradually accumulate in the neutralization slag, and at the same time, base metals in this part of the material will also continuously accumulate, resulting in an increase in the content of base metals in the rhodium-iridium material. Usually, the treatment method for this part of the rhodium-iridium material is to transfer it into a calcination furnace for calcination. However, a temperature of over a thousand degrees is extremely likely to cause the burning loss of the rhodium-iridium material. At the same time, such treatment will increase the refining cycle of the rhodium-iridium material, increase the labor intensity, and is not conducive to the enrichment, recovery, and utilization of this part of the rhodium-iridium material. Summary of the Invention

[0004] The present invention provides a method for enriching rhodium and iridium from the neutralization slag of rhodium-iridium refining wastewater, aiming to treat the neutralization slag of rhodium-iridium refining wastewater by means of acid dissociation and rhodium-iridium enrichment method to increase the enrichment multiple of precious metals, reduce the refining treatment steps, and shorten the refining cycle of rhodium-iridium materials.

[0005] To achieve its purpose, the present invention adopts the following technical solutions: A method for enriching rhodium and iridium from the neutralization slag of rhodium-iridium refining wastewater, comprising the following steps: S1: Dissolve the neutralization slag of rhodium-iridium refining wastewater in mixed acid for acidification to obtain an intermediate product; S2: Feed the intermediate product obtained in step S1 into a rotary furnace, and then slowly heat the rotary furnace to 550 - 560 °C and keep it warm for 2.5 - 3 h to obtain a dissociation slag; S3: Feed the dissociation slag obtained in step S2 into an enamel reaction kettle, add water for pulping, then add acid to control the solution to pH = 0.5 - 1.5, and then add hydrazine hydrate and sodium bisulfite to obtain an enrichment solution; S4: Heat the enamel reaction kettle to 60 - 65 °C and keep it warm for 2 - 2.5 h to remove the base metal impurities in the enrichment solution obtained in step S3, conduct rhodium-iridium enrichment to obtain an enriched rhodium-iridium material, and finally comprehensively treat the enriched rhodium-iridium waste liquid.

[0006] Further, in step S1, the mass fraction of the mixed acid is 75 - 80%. The mixed acid is prepared by adding formic acid to a 98% sulfuric acid solution, and the formic acid accounts for 2% of the total mass of the mixed acid.

[0007] Further, the solid - liquid ratio of the neutralization residue in step S1 to the mixed acid is 3:2 to 2.2.

[0008] Further, the solid - liquid ratio of the dissociation residue to water in step S3 is 1:6 to 8.

[0009] Further, the acid used in step S3 is 98% sulfuric acid.

[0010] Further, in the enrichment liquid of step S3, the mass fraction of hydrazine hydrate is 1.5 - 2%, and the mass fraction of sodium bisulfite is 0.5 - 1%.

[0011] The beneficial effects of the present invention are as follows: The present invention uses a milder acid dissociation method to treat the neutralization residue of rhodium - iridium refining wastewater, avoiding the loss of rhodium and iridium during the treatment process. While achieving the separation of noble and base metals, it can better enrich rhodium and iridium. After being put into use, the enrichment multiple of rhodium - iridium materials is more than 10 times, and the removal rate of base metals reaches more than 90%. The enriched rhodium - iridium materials can be flexibly connected to the subsequent rhodium - iridium separation and refining processes according to their specific contents, eliminating the impurity removal steps and shortening the refining cycle. The overall process is simple, the operation is convenient, the working intensity is small, and it is easy to realize industrial production, having popularization and application value for the treatment of neutralization residues of other precious metal refining wastewaters. Brief Description of the Drawings

[0012] Figure 1 It is the process flow chart of the present invention. Detailed Embodiments

[0013] The following further illustrates the present invention with specific embodiments: In the following embodiments of the present invention, two indicators, namely the enrichment multiple of rhodium - iridium materials and the removal rate of base metals, are used to characterize the enrichment effect of the method of the present invention. Among them, the enrichment multiple of rhodium - iridium materials = the content of rhodium and iridium elements in the neutralization residue after enrichment treatment / the content of rhodium and iridium elements in the neutralization residue of rhodium - iridium refining wastewater, and the removal rate of base metals = (the content of base metal elements in the neutralization residue of rhodium - iridium refining wastewater - the content of base metal elements in the neutralization residue after enrichment treatment) / the content of base metal elements in the neutralization residue of rhodium - iridium refining wastewater.

[0014] Example 1 The present invention is a method for enriching rhodium and iridium from the neutralization residue of rhodium - iridium refining wastewater. As Figure 1 shown, it includes the following steps: S1: Dissolve the neutralization slag of rhodium-iridium refining wastewater in a mixed acid with a mass fraction of 75% for acidification, control the solid-liquid ratio at 3:2 to obtain an intermediate product; among them, the mixed acid is obtained by adding formic acid to a 98% sulfuric acid solution, and the formic acid accounts for 2% of the total mass of the mixed acid. S2: Feed the intermediate product obtained in step S1 into a rotary kiln, and then slowly heat the rotary kiln to 550 °C and keep it warm for 2.5 h to obtain a dissociation slag. S3: Feed the dissociation slag obtained in step S2 into an enamel reaction kettle, add water for pulping, control the solid-liquid ratio at 1:6, then add 98% sulfuric acid to control the solution to pH = 0.5, and then add hydrazine hydrate with a mass fraction of 1.5% and sodium bisulfite with a mass fraction of 0.5% to obtain an enriched solution. S4: Heat the enamel reaction kettle to 60 °C and keep it warm for 2 h to remove the base metal impurities in the enriched solution in step S3, perform rhodium-iridium enrichment to obtain an enriched rhodium-iridium material, and then comprehensively treat the enriched rhodium-iridium waste liquid. Subsequently, the subsequent rhodium-iridium separation and refining process can be flexibly connected according to the specific content of the enriched rhodium-iridium material.

[0015] First, analyze the elements of the neutralization slag of rhodium-iridium refining wastewater, and the results are shown in Table 1. Then, analyze the elements after enrichment of the neutralization slag of rhodium-iridium refining wastewater treated by this method, and the results are shown in Table 2. It can be seen from Tables 1-2 that the rhodium-iridium enrichment rate of the enriched rhodium-iridium material treated by this method is as high as 10 times, and the removal of base metals is as high as 91%.

[0016] Table 1 Element content (%) of the neutralization slag of rhodium-iridium refining wastewater

[0017] Table 2 Element content (%) after enrichment treatment of the neutralization slag

[0018] Example 2 The present invention is a method for enriching rhodium and iridium from the neutralization slag of rhodium-iridium refining wastewater, as Figure 1 shown, including the following steps: S1: Dissolve the neutralization slag of rhodium-iridium refining wastewater in a mixed acid with a mass fraction of 78% for acidification, control the solid-liquid ratio at 3:2.2 to obtain an intermediate product; among them, the mixed acid is obtained by adding formic acid to a 98% sulfuric acid solution, and the formic acid accounts for 2% of the total mass of the mixed acid. S2: Feed the intermediate product obtained in step S1 into a rotary kiln, and then slowly heat the rotary kiln to 560 °C and keep it warm for 3 h to obtain a dissociation slag. S3: Feed the dissociation residue obtained in step S2 into an enamel reaction kettle, add water for pulping, control the solid-liquid ratio to be 1:7, then add 98% sulfuric acid to control the solution to pH = 1, and then add hydrazine hydrate with a mass fraction of 1.8% and sodium bisulfite with a mass fraction of 0.8% to obtain an enriched solution; S4: Heat the enamel reaction kettle to 65 °C and keep it warm for 2.5 h to remove the base metal impurities in the enriched solution in step S3, perform rhodium and iridium enrichment to obtain an enriched rhodium and iridium material, then comprehensively treat the enriched rhodium and iridium waste liquid, and subsequently, the subsequent rhodium and iridium separation and refining processes can be flexibly connected according to the specific content of the enriched rhodium and iridium material.

[0019] First, analyze the elements in the neutralization slag of rhodium and iridium refining wastewater, and the results are shown in Table 3. Then, analyze the elements in the neutralization slag of rhodium and iridium refining wastewater after enrichment treated by this method, and the results are shown in Table 4. Analyzing Tables 3 - 4 shows that the rhodium and iridium enrichment rate of the enriched rhodium and iridium material treated by this method is as high as 10 times, and the removal of base metals is up to 91.7%.

[0020] Table 3 Element content in the neutralization slag of rhodium and iridium refining wastewater (%)

[0021] Table 4 Element content after enrichment treatment of the neutralization slag (%)

[0022] Example 3 The present invention is a method for enriching rhodium and iridium from the neutralization slag of rhodium and iridium refining wastewater, as Figure 1 shown, including the following steps: S1: Dissolve the neutralization slag of rhodium and iridium refining wastewater in a mixed acid with a mass fraction of 80% for acidification, control the solid-liquid ratio to be 3:2 to obtain an intermediate product; wherein, the mixed acid is obtained by adding formic acid to a 98% sulfuric acid solution, and the formic acid accounts for 2% of the total mass of the mixed acid; S2: Feed the intermediate product obtained in step S1 into a rotary kiln, and then slowly heat the rotary kiln to 550 °C and keep it warm for 2.5 h to obtain a dissociation residue; S3: Feed the dissociation residue obtained in step S2 into an enamel reaction kettle, add water for pulping, control the solid-liquid ratio to be 1:8, then add 98% sulfuric acid to control the solution to pH = 1.5, and then add hydrazine hydrate with a mass fraction of 2% and sodium bisulfite with a mass fraction of 1% to obtain an enriched solution; S4: Heat the enamel reaction kettle to 60 °C and keep it warm for 2 h to remove the base metal impurities in the enriched solution in step S3, perform rhodium and iridium enrichment to obtain an enriched rhodium and iridium material, then comprehensively treat the enriched rhodium and iridium waste liquid, and subsequently, the subsequent rhodium and iridium separation and refining processes can be flexibly connected according to the specific content of the enriched rhodium and iridium material.

[0023] First, analyze the elements in the neutralization slag of rhodium-iridium refining wastewater. The results are shown in Table 5. Then, analyze the elements in the neutralization slag of rhodium-iridium refining wastewater after enrichment by the method proposed in this paper. The results are shown in Table 6. By analyzing Tables 5-6, it can be seen that the rhodium-iridium enrichment rate of the enriched rhodium-iridium material treated by the method proposed in this paper is as high as 11 times, and the removal rate of base metals is as high as 91%.

[0024] Table 5 Element content in the neutralization slag of rhodium-iridium refining wastewater (%)

[0025] Table 6 Element content after enrichment treatment of the neutralization slag (%)

Claims

1. A method for enriching rhodium and iridium from the neutralization slag of rhodium and iridium refining wastewater, characterized in that: The following steps are involved: S1: dissolving the neutralized residue of rhodium-iridium refining wastewater in mixed acid for acidification to obtain an intermediate product; S2: The intermediate product obtained in step S1 is fed into a rotary kiln, and the rotary kiln is slowly heated to 550-560° C. and kept warm for 2.5-3 hours to obtain dissociated slag; S3: sending the dissociated slag obtained in step S2 into an enamel reactor, adding water to slurry, then adding acid to control the solution to pH=0.5-1.5, and then adding hydrazine hydrate and sodium bisulfite to obtain an enriched solution; S4: heating the enameled reactor to 60-65°C and keeping it warm for 2-2.5h, removing base metal impurities in the enriched liquid of step S3, enriching rhodium and iridium to obtain enriched rhodium and iridium material, and finally comprehensively treating the enriched rhodium and iridium waste liquid.

2. A method for enriching rhodium and iridium from the neutralization slag of rhodium and iridium refining wastewater as claimed in claim 1, characterized in that: The mass fraction of the mixed acid in step S1 is 75-80%. The mixed acid is prepared by adding formic acid to a 98% sulfuric acid solution, and the formic acid accounts for 2% of the total mass of the mixed acid.

3. A method for enriching rhodium and iridium from the neutralization slag of rhodium and iridium refining wastewater as claimed in claim 2, characterized in that: The solid-liquid ratio of the neutralized slag to the mixed acid in step S1 is 3:2 to 2.

2.

4. A method for enriching rhodium and iridium from the neutralization slag of rhodium and iridium refining wastewater as claimed in claim 3, characterized in that: In step S3, the solid-liquid ratio of the dissociated slag to water is 1:6-8.

5. A method for enriching rhodium and iridium from the neutralization slag of rhodium and iridium refining wastewater as claimed in claim 4, characterized in that: The acid used in step S3 is 98% sulfuric acid.

6. A method for enriching rhodium and iridium from the neutralization slag of rhodium and iridium refining wastewater as claimed in claim 5, characterized in that: In the enriched solution of step S3, the mass fraction of hydrazine hydrate is 1.5-2%, and the mass fraction of sodium bisulfite is 0.5-1%.

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