A method for bromine-catalyzed oxidation of pressurized noble metal sulfide slag

Abstract

This invention relates to the field of precious metal extraction technology and discloses a method for catalytic oxidation of pressurized precious metal sulfide slag with bromine, comprising the following steps: S1, catalytic oxidation with sodium bromide under near-neutral conditions; S2, reduction of the leachate with oxalic acid; S3, enrichment of platinum and palladium in the reduced solution after a first stage; and S4, addition of ozone or electrolysis to the tail liquid formed after the reduction of platinum and palladium. This invention selectively leaches pressurized precious metal sulfide slag using sodium chloride solution supplemented with sodium bromide, and uses oxalic acid to reduce the leachate to extract gold. Then, it reduces the reduced solution with sulfur dioxide flue gas to extract platinum and palladium. The use of a near-neutral medium for selective leaching of rare and precious metals reduces equipment corrosion, thereby significantly reducing production and maintenance costs. Furthermore, the addition of a process to produce acid from the reduction tail gas reduces tail gas emissions and produces an acidic solution, which not only reduces environmental pollution but also improves the utilization rate of reducing materials, effectively solving the problem of difficult wastewater treatment in current processes.

Description

Technical Field

[0001] This invention relates to the field of precious metal extraction technology, specifically a method for bromine-catalyzed oxidation of pressurized precious metal sulfide slag. Background Technology

[0002] Precious metal recycling and refining is a technology used to purify and recover precious metals. Several different methods exist for refining precious metals, but the two main methods are pyrometallurgy, which involves heating, and hydrometallurgy, which involves dissolving the metal in a solvent. After purification, the metal is washed to complete the recycling and refining process.

[0003] Current precious metal extraction processes generally employ high-chlorine, high-acid leaching, which generates a large amount of perchloric acid waste liquid. Direct treatment of this waste liquid is costly, and it also corrodes equipment, increasing maintenance costs. Therefore, we need to propose a method for pressurized precious metal sulfide slag oxidation using bromine catalytic oxidation. Summary of the Invention

[0004] The purpose of this invention is to provide a method for the catalytic oxidation of pressurized precious metal sulfide slag with bromine. This method involves selectively leaching the pressurized precious metal sulfide slag with a sodium chloride solution supplemented with sodium bromide solution, and then using oxalic acid to reduce the leaching solution to extract gold. The reduced solution is then further reduced with sulfur dioxide flue gas to extract platinum and palladium. The selective leaching of rare and precious metals using a near-neutral medium effectively solves the problem of corrosion in the system equipment, thereby significantly reducing production and maintenance costs. Furthermore, the addition of a process to produce acid from the reduction tail gas reduces tail gas emissions and produces an acidic solution, which not only reduces environmental pollution but also improves the utilization rate of the reducing materials. This effectively solves the problem of difficult wastewater treatment in current processes, thus addressing the issues raised in the background section.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a method for catalytic oxidation of pressurized noble metal sulfide slag with bromine, comprising the following steps:

[0006] S1. Using sodium bromide catalytic oxidation, under near-neutral conditions, chloride salt medium is added to selectively leach gold, platinum, and palladium from pressurized precious metal sulfide slag, yielding a precious metal leachate and catalytic oxidation slag.

[0007] S2. The catalytic oxidation residue is sent to the comprehensive utilization workshop. The leachate is reduced with oxalic acid to obtain a first-stage reduced gold and a first-stage reduced solution. Crude gold powder is extracted and refined to obtain high-grade gold powder.

[0008] S3. Enriching platinum and palladium through a first-stage reduction solution: Sulfur dioxide flue gas is passed through the first-stage reduction solution to obtain reduced platinum and palladium and reduction tail gas. Crude platinum powder and crude palladium powder are extracted, and the generated reduction tail gas is sent to the acid production process to produce acid solution.

[0009] S4. Ozone or electricity is added to the tail liquid formed after the reduction of platinum-palladium extraction to oxidize the low-valence bromide ions to high-valence bromide ions, and then the tail liquid is sent to the leaching solution of step S1 for cyclic leaching.

[0010] Preferably, in step S1, sodium bromide acts as a catalyst and strong oxidant to catalytically oxidize the pressurized precious metal sulfide slag under slightly neutral conditions, thereby accelerating the leaching process of precious metals in the pressurized precious metal sulfide slag. The chloride salt medium helps to regulate the ionic strength and chemical properties of the reaction system, thereby improving the leaching efficiency of precious metals. The catalytic oxidation slag is composed of non-precious metal components in the pressurized precious metal sulfide slag and byproducts generated in the reaction.

[0011] Preferably, in step S1, the chloride salt medium is a sodium chloride solution, and the leaching parameters for selective leaching of precious metals are: the concentration of sodium chloride solution is 200 g / L, the concentration of sodium bromide is 28 g / L, the leaching temperature is 60-85℃, the reaction time is 120-210 min, the initial oxidation potential is 900-1000 mV, and the final oxidation potential is 360-540 mV.

[0012] Preferably, in step S2, after the catalytic oxidation slag is sent to the comprehensive utilization workshop, the useful components can be recovered or it can be rendered harmless. The reduced liquid contains unreduced platinum ions, palladium ions, and other unreacted components. The steps for producing high-grade gold powder are as follows:

[0013] S21. Filtration: The reduced gold element is filtered out from the reduced solution using a filter medium.

[0014] S22. Washing: The surface of the filtered gold elemental will be covered with impurities and unreacted oxalic acid. Wash the gold elemental with clean water multiple times to remove the attached impurities and unreacted oxalic acid.

[0015] S23. Drying: Remove the moisture from the surface of the gold element by means of hot air or an oven, so that the gold element is in a dry and loose state;

[0016] S24. Smelting: The dried gold element is placed in a smelting furnace and melted at high temperature to further remove impurities;

[0017] S25. Electrolytic refining: During the electrolysis process, liquid gold serves as the anode. Under the action of electrolysis, impurities remain in the anode, while pure gold is deposited on the cathode to obtain high-grade gold powder.

[0018] Preferably, in step S3, sulfur dioxide flue gas acts as a reducing agent to react chemically with palladium and platinum ions in the first-stage reduction liquid. Palladium ions are reduced to elemental palladium, and platinum ions are reduced to elemental platinum. The elemental palladium and platinum precipitate at the bottom of the first-stage reduction liquid. The elemental palladium and platinum are then extracted and purified.

[0019] Preferably, in step S3, the main component of the reduction tail gas is sulfur dioxide gas, which can be converted into sulfuric acid. The conversion method is as follows:

[0020]

[0021] Preferably, in step S3, when enriching platinum and palladium, the leaching parameters are: temperature 95-99℃, reaction time 120-210min.

[0022] Preferably, in step S4, ozone oxidizes low-valence bromide ions: ozone, as a strong oxidant, rapidly reacts with low-valence bromide ions in the tail liquid, oxidizing the low-valence bromide ions to high-valence bromide ions, while ozone is reduced to oxygen ions and water; electrolytic oxidation of low-valence bromide ions: the tail liquid serves as the electrolyte, and an electric current is applied in the electrolytic cell for electrolysis, causing the low-valence bromide ions to lose electrons at the anode and be oxidized to high-valence bromide ions.

[0023] Compared with the prior art, the beneficial effects of the present invention are:

[0024] This invention selectively leaches pressurized precious metal sulfide slag using a sodium chloride solution supplemented with sodium bromide solution, and extracts gold by reducing the leaching solution with oxalic acid. Platinum and palladium are then extracted by reducing the reduced solution with sulfur dioxide flue gas. The selective leaching of rare and precious metals using a near-neutral medium effectively solves the problem of corrosion in the system equipment, thus significantly reducing production and maintenance costs. Furthermore, the addition of a process to produce acid from the reduction tail gas reduces tail gas emissions and produces an acidic solution, which not only reduces environmental pollution but also improves the utilization rate of the reducing materials, effectively solving the problem of difficult wastewater treatment in current processes. Attached Figure Description

[0025] Figure 1 This is a flowchart of the present invention;

[0026] Figure 2 This is a flowchart of the present invention;

[0027] Figure 3 This is a flowchart illustrating the process of producing high-grade gold powder from coarse gold powder according to the present invention. Detailed Implementation

[0028] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Example 1

[0029] Please see Figure 1-3 This invention provides a technical solution: a method for catalytic oxidation of pressurized noble metal sulfide slag with bromine, comprising the following steps:

[0030] S1. Using sodium bromide catalytic oxidation, under near-neutral conditions, chloride salt medium is added to selectively leach gold, platinum, and palladium from pressurized precious metal sulfide slag, yielding a precious metal leachate and catalytic oxidation slag. The catalytic oxidation slag is then used to extract other valuable elements.

[0031] In step S1, sodium bromide acts as a catalyst and strong oxidant to catalytically oxidize the pressurized precious metal sulfide slag under slightly neutral conditions, accelerating the leaching process of precious metals in the pressurized precious metal sulfide slag. That is, the leachate contains a high concentration of precious metal ions. The chloride salt medium helps to regulate the ionic strength and chemical properties of the reaction system, thereby improving the leaching efficiency of precious metals. The chloride salt medium can also react with certain components in the sulfide slag to promote the release of precious metals. The catalytic oxidation slag is composed of non-precious metal components in the pressurized precious metal sulfide slag and by-products generated by the reaction.

[0032] In step S1, sodium chloride solution is selected as the chloride salt medium. The leaching parameters for selective leaching of precious metals are as follows: the concentration of sodium chloride solution is 200 g / L, the concentration of sodium bromide is 28 g / L, the leaching temperature is 60℃, the reaction time is 120 min, the initial oxidation potential is 900 mV, the final oxidation potential is 360 mV, the initial pH of the leachate is 5.5, and the final pH is 2.0.

[0033] S2. The catalytic oxidation residue is sent to the comprehensive utilization workshop. The leachate is reduced with oxalic acid to obtain a first-stage reduced gold and a first-stage reduced solution. Crude gold powder is extracted and refined to obtain high-grade gold powder.

[0034] In step S2, after the catalytic oxidation slag is sent to the comprehensive utilization workshop, it can be processed to recover useful components or undergo harmless treatment. The reduced solution contains unreduced platinum ions, palladium ions, and other unreacted components. Oxalic acid reacts with the precious metal ions in the leaching solution under appropriate conditions, reducing them to gold particles. The steps for producing high-grade gold powder are as follows:

[0035] S21. Filtration: The reduced gold element is filtered out from the reduced solution using a filter medium. Filter paper or filter cloth can be used as the filter medium to effectively trap gold powder particles while allowing the solution to pass through.

[0036] S22. Washing: The surface of the filtered gold will have impurities and unreacted oxalic acid adhering to it. Wash the gold repeatedly with clean water to remove the adhering impurities and unreacted oxalic acid, ensuring that most impurities and residual reducing agents are removed. This step is crucial for improving the purity of the gold powder.

[0037] S23. Drying: Remove the moisture from the surface of the gold element by means of hot air or an oven, so that the gold element is in a dry and loose state, which facilitates subsequent refining and processing.

[0038] S24. Smelting: The dried gold element is placed in a smelting furnace and melted at high temperature to further remove impurities; precise temperature control is ensured to obtain pure liquid metal.

[0039] S25. Electrolytic refining: During the electrolysis process, liquid gold serves as the anode. Under the action of electrolysis, impurities remain in the anode, while pure gold is deposited on the cathode to obtain high-grade gold powder.

[0040] S3. Enrichment of Platinum and Palladium through a first-stage reduction solution: The first-stage reduction solution contains ions of precious metals such as platinum and palladium. To extract these precious metals from the solution, a reducing agent is needed to convert them from their ionic state to elemental metals. Sulfur dioxide flue gas is passed through the first-stage reduction solution to obtain reduced platinum and palladium and reduction tail gas. Crude platinum powder and crude palladium powder are extracted, and the generated reduction tail gas is sent to the acid production process to produce an acid solution.

[0041] In step S3, sulfur dioxide flue gas acts as a reducing agent and reacts chemically with palladium and platinum ions in the first-stage reduction liquid. Palladium ions are reduced to elemental palladium, and platinum ions are reduced to elemental platinum. The elemental palladium and platinum precipitate at the bottom of the first-stage reduction liquid. The elemental palladium and platinum are then extracted and purified. The purification process for elemental palladium and platinum can be found in the refining process of elemental gold described above.

[0042] In step S3, the main component of the reduction exhaust gas is sulfur dioxide gas, which can be converted into sulfuric acid. This not only reduces environmental pollution but also allows for the recovery and reuse of useful components from the exhaust gas. The conversion method is as follows:

[0043]

[0044] Converting sulfur dioxide in exhaust gas into sulfuric acid not only helps reduce environmental pollution, but also enables resource recycling and reuse, resulting in significant environmental and economic benefits.

[0045] In step S3, when enriching platinum and palladium, the leaching parameters are: temperature 95℃ and reaction time 120min.

[0046] S4. Ozone or electricity is added to the tail liquid formed after the reduction of platinum-palladium extraction to oxidize the low-valence bromide ions to high-valence bromide ions, and then the tail liquid is sent to the leaching solution of step S1 for cyclic leaching.

[0047] After platinum and palladium are extracted from the tailings of platinum-palladium reduction, low-valence bromide ions remain in the tailings. These low-valence bromide ions no longer possess sufficient oxidizing power to effectively leach the precious metals.

[0048] In step S4, ozone oxidizes low-valence bromide ions: ozone, as a strong oxidant, rapidly reacts with low-valence bromide ions in the tail liquid, oxidizing them to high-valence bromide ions, while ozone is reduced to oxygen ions and water; electrolytic oxidation of low-valence bromide ions: the tail liquid serves as the electrolyte, and an electric current is applied in the electrolytic cell for electrolysis, causing low-valence bromide ions to lose electrons at the anode and be oxidized to high-valence bromide ions.

[0049] Please refer to the table below for the extraction rates of each precious metal element:

[0050] Table 1. Precious metal element content (%)

[0051]

[0052] Calculations show that the extraction rates of Au, Pt, and Pd were 99.23%, 98.21%, and 97.42%, respectively. Example 2

[0053] The similarities with Example 1 will not be repeated here; the differences are...

[0054] In step S1, sodium chloride solution is selected as the chloride salt medium. The leaching parameters for selective leaching of precious metals are as follows: the concentration of sodium chloride solution is 200 g / L, the concentration of sodium bromide is 28 g / L, the leaching temperature is 72℃, the reaction time is 165 min, the initial oxidation potential is 950 mV, and the final oxidation potential is 450 mV.

[0055] In step S3, when enriching platinum and palladium, the leaching parameters are: temperature 97℃ and reaction time 165min.

[0056] Please refer to the table below for the extraction rates of each precious metal element:

[0057] Table 2. Precious metal element content (%)

[0058]

[0059] Calculations show that the extraction rates of Au, Pt, and Pd were 99.54%, 98.57%, and 98.06%, respectively. Example 3

[0060] The similarities with Examples 1 and 2 will not be repeated here; the differences are...

[0061] In step S1, sodium chloride solution is selected as the chloride salt medium. The leaching parameters for selective leaching of precious metals are as follows: the concentration of sodium chloride solution is 200 g / L, the concentration of sodium bromide is 28 g / L, the leaching temperature is 85℃, the reaction time is 210 min, the initial oxidation potential is 1000 mV, and the final oxidation potential is 540 mV.

[0062] In step S3, when enriching platinum and palladium, the leaching parameters are: temperature 99℃ and reaction time 210min.

[0063] Please refer to the table below for the extraction rates of each precious metal element:

[0064] Table 3. Precious metal element content (%)

[0065]

[0066] Calculations show that the extraction rates of Au, Pt, and Pd were 99.38%, 97.86%, and 97.74%, respectively.

[0067] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for catalytic oxidation of pressurized noble metal sulfide slag with bromine, characterized in that: Includes the following steps: S1. Using sodium bromide catalytic oxidation, under near-neutral conditions, chloride salt medium is added to selectively leach gold, platinum, and palladium from pressurized precious metal sulfide slag, yielding a precious metal leachate and catalytic oxidation slag. The chloride salt medium used is sodium chloride solution. The leaching parameters for selective leaching of precious metals are as follows: sodium chloride solution concentration of 200 g / L, sodium bromide concentration of 28 g / L, leaching temperature of 60-85℃, reaction time of 120-210 min, initial oxidation potential of 900-1000 mV, and final oxidation potential of 360-540 mV. S2. The catalytic oxidation residue is sent to the comprehensive utilization workshop. The leachate is reduced with oxalic acid to obtain a first-stage reduced gold and a first-stage reduced solution. Crude gold powder is extracted and refined to obtain high-grade gold powder. S3. Enriching platinum and palladium through a first-stage reduction solution: Sulfur dioxide flue gas is passed through the first-stage reduction solution to obtain reduced platinum and palladium and reduction tail gas. Crude platinum powder and crude palladium powder are extracted, and the generated reduction tail gas is sent to the acid production process to produce acid solution. S4. Ozone or electricity is added to the tail liquid formed after the reduction of platinum-palladium extraction to oxidize the low-valence bromide ions to high-valence bromide ions, and then the tail liquid is sent to the leaching solution of step S1 for cyclic leaching.

2. The method for catalytic oxidation of pressurized noble metal sulfide slag by bromine according to claim 1, characterized in that: In step S1, sodium bromide acts as a catalyst and strong oxidant to catalytically oxidize the pressurized precious metal sulfide slag under slightly neutral conditions, thereby accelerating the leaching process of precious metals in the pressurized precious metal sulfide slag. The chloride salt medium helps to regulate the ionic strength and chemical properties of the reaction system, thereby improving the leaching efficiency of precious metals. The catalytic oxidation slag is composed of non-precious metal components in the pressurized precious metal sulfide slag and byproducts generated in the reaction.

3. The method for catalytic oxidation of pressurized noble metal sulfide slag by bromine according to claim 1, characterized in that: In step S2, the catalytic oxidation residue is sent to the comprehensive utilization workshop for treatment to recover useful components or to undergo harmless treatment. The reduced liquid contains unreduced platinum ions, palladium ions, and other unreacted components. The steps for producing high-grade gold powder are as follows: S21. Filtration: The reduced gold element is filtered out from the reduced solution using a filter medium. S22. Washing: The surface of the filtered gold elemental will be covered with impurities and unreacted oxalic acid. Wash the gold elemental with clean water multiple times to remove the attached impurities and unreacted oxalic acid. S23. Drying: Remove the moisture from the surface of the gold element by means of hot air or an oven, so that the gold element is in a dry and loose state; S24. Smelting: The dried gold element is placed in a smelting furnace and melted at high temperature to further remove impurities; S25. Electrolytic refining: During the electrolysis process, liquid gold serves as the anode. Under the action of electrolysis, impurities remain in the anode, while pure gold is deposited on the cathode to obtain high-grade gold powder.

4. The method for catalytic oxidation of pressurized noble metal sulfide slag by bromine according to claim 1, characterized in that: In step S3, sulfur dioxide flue gas acts as a reducing agent and reacts chemically with palladium and platinum ions in the first-stage reduction liquid. Palladium ions are reduced to elemental palladium, and platinum ions are reduced to elemental platinum. The elemental palladium and platinum precipitate at the bottom of the first-stage reduction liquid. The elemental palladium and platinum are then extracted and purified.

5. The method for catalytic oxidation of pressurized noble metal sulfide slag by bromine according to claim 1, characterized in that: In step S3, the main component of the reduction tail gas is sulfur dioxide gas. The sulfur dioxide gas is converted into sulfuric acid, and the conversion method is as follows: SO2 + H2O H2SO3 2H2SO3 + O2 2H2SO4; or 2SO2 + O2 2SO3 SO3 + H2O H2SO4.

6. The method for catalytic oxidation of pressurized noble metal sulfide slag by bromine according to claim 1, characterized in that: In step S3, when enriching platinum and palladium, the leaching parameters are: temperature 95-99℃, reaction time 120-210min.

7. The method for catalytic oxidation of pressurized noble metal sulfide slag by bromine according to claim 1, characterized in that: In step S4, ozone oxidizes low-valence bromide ions: ozone, as a strong oxidant, rapidly reacts with low-valence bromide ions in the tail liquid, oxidizing them to high-valence bromide ions, while ozone is reduced to oxygen ions and water; electrolytic oxidation of low-valence bromide ions: the tail liquid serves as the electrolyte, and an electric current is applied in the electrolytic cell for electrolysis, causing low-valence bromide ions to lose electrons at the anode and be oxidized to high-valence bromide ions.

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