Anode Sludge Hydrometallurgical Treatment via Sequential Acid Leaching
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Solution Overview
Problem
Current hydrometallurgical methods for separating precious metals from anode sludge obtained from copper electrolysis are complex and difficult to control, and they are not compatible with the electrolytic refining process, leading to environmental emissions and process delays.
Innovation Solution
A method that uses sulfuric acid for leaching anode sludge to remove chlorides, followed by pressure leaching and subsequent leaching with hydrochloric acid to dissolve silver, selenium, gold, and platinum-group metals, eliminating the need for selenium calcination and slimes smelting, allowing for recirculation of solutions and reducing environmental emissions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If nitric acid is used for leaching anode sludge to achieve high silver solubility, then silver recovery is improved, but compatibility with the electrolytic copper refining process deteriorates and environmental emissions increase
Solution Approach 1:
The invention changes the chemical parameter from nitric acid to sulfuric acid leaching, maintaining effective silver dissolution while ensuring compatibility with the sulfate-based electrolytic copper refining process. This parameter substitution resolves the contradiction between high silver recovery and process compatibility
Solution Approach 2:
The invention converts the previously harmful nitrate waste stream into a beneficial component by using sulfuric acid leaching that produces sulfate solutions compatible with electrolytic refining. The sulfuric acid system transforms potential environmental harm into process synergy, allowing sludge treatment to support rather than hinder the main electrolytic operation
2Productivity
If mechanical grinding is performed finer to improve leaching efficiency with nitrate, then leaching success is improved, but process complexity and time consumption increase
Solution Approach 1:
The invention changes the chemical parameter from nitrate to sulfuric acid leaching, which achieves effective silver dissolution without requiring excessive mechanical grinding. The sulfuric acid system provides adequate leaching efficiency at coarser grind sizes, thereby reducing process complexity and milling time
Solution Approach 2:
The invention substitutes mechanical intensity (fine grinding) with chemical effectiveness (sulfuric acid leaching parameters). By optimizing the chemical leaching conditions, the process achieves high silver recovery without relying on excessive mechanical size reduction, thus reducing overall process complexity
3Manufacturing precision
If selenium calcination and slimes smelting are performed to recover metals, then metal recovery is improved, but environmental emissions and process delay increase
Solution Approach 1:
The invention merges the selenium recovery step with the main sulfuric acid leaching process. Selenium is dissolved simultaneously with silver in the sulfuric acid leach, eliminating the need for separate calcination and smelting steps. This integration maintains metal recovery while significantly reducing process time and environmental emissions
Solution Approach 2:
The invention extracts selenium from the sludge matrix during the primary sulfuric acid leaching step, removing it as a soluble component in the leach solution. This early extraction eliminates the need for subsequent high-temperature calcination and smelting operations, thereby reducing process delay and environmental impact while maintaining recovery efficiency
4Manufacturing precision
If multiple leaching steps with different acids are used to separate precious metals, then separation completeness is improved, but process complexity and control difficulty increase
Solution Approach 1:
The invention changes the acid system from multiple different acids (nitric, hydrochloric, sulfuric) to a unified sulfuric acid-based system with varying concentrations and conditions. This single-acid approach achieves effective separation of silver, selenium, gold, and platinum group metals through controlled leaching parameters, significantly simplifying process operation and control while maintaining separation completeness
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This method simplifies the process, reduces environmental emissions, and enables the recirculation of solutions, thereby improving the efficiency and reducing the total process delay while maintaining high recovery rates of precious metals.
Implementation Method 1
leaching the anode sludge in an aqueous sulfuric acid solution to remove leachable chlorides
Implementation Method 2
pressure leaching the first leaching residue to dissolve Ag and Se
Implementation Method 3
leaching the second leaching residue with an aqueous hydrochloric acid solution to dissolve Au and PGMs
Data Source
Figure 1
AI summary
The present invention provides a method of separating precious metals from anode sludge obtained from copper electrolysis, comprising (a) leaching the anode sludge in an aqueous sulfuric acid solution to remove leachable chlorides and to obtain a first leaching residue depleted of chlorides; (b) pressure leaching the first leaching residue to dissolve Ag and Se and to obtain a first filtrate compris¬ ing Ag and Se and a second leaching residue depleted of Ag and Se; and (c) leaching the second leaching residue with an aqueous hydrochloric acid solution to dissolve Au and PGMs to obtain a second filtrate comprising Au and PGMs and a final leaching residue.