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What is the characteristic gold content percentage in high-gold materials?
What is the characteristic gold content percentage in high-gold materials?
What is the primary characteristic of high-silver doré?
What is the primary characteristic of high-silver doré?
Which base metals are most commonly found in high-silver doré?
Which base metals are most commonly found in high-silver doré?
What is the Miller process primarily used for in gold refining?
What is the Miller process primarily used for in gold refining?
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What is the primary result of the Wohlwill process?
What is the primary result of the Wohlwill process?
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Which chemical combination is referred to as aqua regia?
Which chemical combination is referred to as aqua regia?
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What impacts the variability of doré materials in terms of composition?
What impacts the variability of doré materials in terms of composition?
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Which of the following is a common byproduct of the Miller process?
Which of the following is a common byproduct of the Miller process?
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What is a common method used to harvest gold deposited on titanium cathodes in Wohlwill operations?
What is a common method used to harvest gold deposited on titanium cathodes in Wohlwill operations?
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Which challenge must be managed daily during electrolytic refining?
Which challenge must be managed daily during electrolytic refining?
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What is one method used to prevent manual separation of deposited gold from cathode blanks?
What is one method used to prevent manual separation of deposited gold from cathode blanks?
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What reaction describes the cathodic reduction process in the electrowinning of gold?
What reaction describes the cathodic reduction process in the electrowinning of gold?
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What is the minimum required concentration of gold in the electrolyte for Wohlwill operations?
What is the minimum required concentration of gold in the electrolyte for Wohlwill operations?
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Which insoluble material commonly needs to be captured and removed during electrolysis?
Which insoluble material commonly needs to be captured and removed during electrolysis?
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What occurs due to the imbalance during the electrolysis process?
What occurs due to the imbalance during the electrolysis process?
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What factor primarily drives the abundance of gold and silver refining services?
What factor primarily drives the abundance of gold and silver refining services?
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Why do most mining companies choose not to operate their own refineries?
Why do most mining companies choose not to operate their own refineries?
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What is a common characteristic of independent gold and silver refiners?
What is a common characteristic of independent gold and silver refiners?
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What operational challenges led Harmony Gold Mine to discontinue its on-site refining?
What operational challenges led Harmony Gold Mine to discontinue its on-site refining?
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How does the structure of PGM refining typically differ from gold and silver refining?
How does the structure of PGM refining typically differ from gold and silver refining?
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What is a typical purity level for the gold produced by Harmony Gold Mine's refining operation?
What is a typical purity level for the gold produced by Harmony Gold Mine's refining operation?
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What typically characterizes the fees charged by independent refiners for processing doré?
What typically characterizes the fees charged by independent refiners for processing doré?
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How long does it typically take for clients to receive most of their value from a refining transaction?
How long does it typically take for clients to receive most of their value from a refining transaction?
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What is the primary advantage of using a particulate anode in automated silver operations?
What is the primary advantage of using a particulate anode in automated silver operations?
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What is the primary function of nitric acid in the electrolyte during gold refining?
What is the primary function of nitric acid in the electrolyte during gold refining?
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Which reducing agent is mentioned as commonly used for reducing silver chloride to metallic silver?
Which reducing agent is mentioned as commonly used for reducing silver chloride to metallic silver?
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Which reaction characterizes the aqua regia-based electrolysis process?
Which reaction characterizes the aqua regia-based electrolysis process?
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What notable feature does the EMEW cell offer for silver recovery?
What notable feature does the EMEW cell offer for silver recovery?
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What process is primarily used to completely leach silver-bearing feedstock?
What process is primarily used to completely leach silver-bearing feedstock?
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Which of the following reducing agents can effectively recover gold from spent electrolyte?
Which of the following reducing agents can effectively recover gold from spent electrolyte?
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How does the traditional electrorefining process compare to the alternative leaching and precipitation method?
How does the traditional electrorefining process compare to the alternative leaching and precipitation method?
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What role do PGMs play in the refining process mentioned?
What role do PGMs play in the refining process mentioned?
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What is required to dissolve gold effectively, given its chemical nobility?
What is required to dissolve gold effectively, given its chemical nobility?
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What are the common results obtained from the direct electrowinning of silver?
What are the common results obtained from the direct electrowinning of silver?
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What is a potential drawback of reducing metallic silver from a solution in the presence of base metals?
What is a potential drawback of reducing metallic silver from a solution in the presence of base metals?
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What does the term 'red salt process' refer to in gold refining?
What does the term 'red salt process' refer to in gold refining?
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What is nitric acid's effect on the production of gold mud?
What is nitric acid's effect on the production of gold mud?
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Which of the following methods is NOT typically used for silver recovery?
Which of the following methods is NOT typically used for silver recovery?
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What is the function of excess chloride in the gold dissolution process?
What is the function of excess chloride in the gold dissolution process?
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What is one of the primary benefits of the mentioned refining processes?
What is one of the primary benefits of the mentioned refining processes?
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What aspect of doré refining is expected to see incremental improvements?
What aspect of doré refining is expected to see incremental improvements?
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Why is process knowledge and judgment important in handling mining doré?
Why is process knowledge and judgment important in handling mining doré?
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What is currently well established in the applications of refining schemes?
What is currently well established in the applications of refining schemes?
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What is the significance of process robustness and flexibility in gold and silver refineries?
What is the significance of process robustness and flexibility in gold and silver refineries?
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What does the future hold for the methods of gold refining mentioned?
What does the future hold for the methods of gold refining mentioned?
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How do process controls affect labor requirements in refining?
How do process controls affect labor requirements in refining?
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What is the main focus of ongoing improvements in doré refining?
What is the main focus of ongoing improvements in doré refining?
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Study Notes
Refining of Gold and Silver-Bearing Dore
- This chapter describes the treatment of gold and silver-bearing doré materials to produce refined gold and silver bullion.
- Doré processing methods include pre-refining (pyrometallurgical or hydrometallurgical) followed by electrorefining or dissolution followed by precipitation.
- Doré refining differs from industrial precious metals scrap and old jewelry refining due to the variability of the doré feedstock.
- Recent developments in doré refining processes are described, even though basic flowsheets have not changed much in 100 years.
Industry Structure and Refining Business
- Gold and silver refining is separate from PGM refining, usually not integrated with mining companies.
- Gold and silver refiners often focus on old jewelry and industrial scrap. This contrasts with PGM refineries that often are part of larger companies.
- The gold and silver refining industry is characterized by high competition, low refining fees, and advance payments.
- Mining companies rarely operate their own refineries due to lower costs and easier access to independent refineries.
Operations of a Precious Metals Refiner
- The precious metals refining process has three key elements: evaluation, separation, and conversion.
- Evaluation, the most important aspect, involves sampling and assaying the customer's material to determine precise precious metals content.
- Separation involves the chemical processing to separate gold, silver, and other precious metals.
- Conversion involves converting the separated precious metals into a saleable form (bars, coins, chemicals, alloys and other products).
Gold and Silver Dore
- Refiners typically receive doré from mining or recycling of precious metals.
- Dore from jewelry or fabrication scrap is more consistent than from mining, differing in high base metal content from mining doré and generally containing larger amounts of silver, zinc, copper.
- High-gold doré has 30% to 98% gold with varying amounts of silver and base metals; high-silver doré contains over 50% silver, with gold between 1% and 30%, and base metals.
Refining High-Gold Dore
- Two basic refining schemes
- Prerefining/electrorefining: involves melting the impure material, injection of chlorine to convert base metals and silver into chlorides, followed by electrolysis to further purify the gold.
- Dissolution/precipitation: involves dissolving the impure material in concentrated hydrochloric acid (with nitric acid as an oxidizing agent), selectively precipitating the gold (then, processing the byproduct solutions/materials), and producing a high-purity gold product.
Refining High-Silver Dore
- Hydrometallurgical or pyrometallurgical refining schemes are used.
- Hydrometallurgical: Base metals are leached from the feed using sulfuric acid; soluble silver is then removed or recovered.
- Pyrometallurgical: Base metals are oxidized in a furnace to form a slag; the silver is then recovered.
Future Developments in Dore Refining
- Existing refining processes have changed little, but automation, new materials, process controls, improved analytical tools and techniques (for analysis of precious metals and contaminants) have transformed the operation.
- New acidless processes and methods for handling deleterious elements have promise
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Description
This quiz explores the processes involved in refining gold and silver-bearing doré materials, detailing both pyrometallurgical and hydrometallurgical methods. It also distinguishes between doré processing and industrial precious metal refining, highlighting recent advancements in technology. Gain insights into the competitive landscape of the gold and silver refining industry.
