Indium Arsenic Separation via Segmented Leaching
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Solution Overview
Problem
Current methods for separating indium and arsenic from zinc-containing materials, such as those obtained from the Ausmelt TSL furnace process, often result in co-precipitation of arsenic with indium, requiring additional treatment steps and posing safety and environmental concerns due to the use of toxic substances like hydrogen sulfide and unstable arsenic sulfide.
Innovation Solution
A method involving a low acid leaching step to separate zinc and arsenic while leaving indium behind, followed by a high acid leaching step to selectively extract indium, with subsequent steps for arsenic removal and indium recovery, utilizing sulphuric acid and solvent extraction to achieve separation and purification.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If indium is precipitated from the leaching liquor by raising the pH of the solution, then indium can be recovered, but arsenic is co-precipitated with indium requiring further separation steps
Solution Approach 1:
The patent divides the leaching process into two separate stages: a first leaching step that selectively dissolves zinc and arsenic while leaving indium in the residue, and a second leaching step that recovers indium from the residue. This segmentation prevents co-precipitation of arsenic with indium by separating their extraction processes, thereby simplifying the overall purification process while maintaining high indium recovery purity.
2Manufacturing precision
If hydrogen sulfide is used to precipitate arsenic without precipitating indium, then arsenic can be separated, but occupation hygiene and safety concerns arise due to toxicity
Solution Approach 1:
The patent extracts arsenic from the leaching solution in the first leaching step by selective dissolution, separating it from indium before any precipitation operations. This approach removes arsenic from the solution stream that would otherwise require H2S treatment, thereby eliminating the need to handle toxic hydrogen sulfide gas while achieving effective arsenic separation.
Solution Approach 2:
The patent converts the potential harm of arsenic contamination into a benefit by using the first leaching step to selectively dissolve arsenic along with zinc, thereby concentrating arsenic in the leach solution away from indium in the residue. This transforms arsenic from a contaminant that requires dangerous handling into a component that is easily separated through selective leaching.
3Manufacturing precision
If arsenic is precipitated together with iron to form iron residue, then arsenic can be removed from solution, but arsenic returns to the process through fume leaching when iron residue is recycled
Solution Approach 1:
The patent extracts arsenic from the solid residue in the first leaching step by selective dissolution, removing it before the residue is recycled to the furnace. This ensures that when the iron-rich residue is recycled and subsequently leached, arsenic is not present to re-contaminate the process, thereby preventing arsenic re-entry while maintaining effective arsenic removal.
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 allows for the effective separation of indium and arsenic as separate streams, enabling the recovery of indium with high yield and purity, while routing arsenic to a stream free of indium, facilitating further treatment and reducing environmental hazards.
Implementation Method 1
a first leaching step, in which a starting material is contacted with a first leaching liquor in pH of 2.5 - 5 for obtaining a first leach solution comprising in leached form zinc and a first part of arsenic
Implementation Method 2
a second leaching step, in which the solid matter is contacted with a second leaching liquor in pH of below 2.5 for obtaining a second leach solution comprising in leached form indium
Implementation Method 3
The indium is separated from the second leach solution by solvent extraction
Data Source
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AI summary
A method and process arrangement of separating indium and arsenic from a zinc-containing starting material, comprising - low acid leaching, wherein the starting material is contacted with a first leaching liquor for obtaining a first leach solution comprising in leached form a first part of arsenic and zinc, - solid-liquid separation for separating solid matter from the first leach solution, - high acid leaching, wherein the solid matter is contacted with a second leaching liquor for obtaining a second leach solution comprising in leached form indium and a second part of zinc and arsenic and separating and recovering indium from the second leach solution.