Molten-Salt Electrorefiner for Indium Recovery
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Solution Overview
Problem
Current methods for recovering indium, such as solvent extraction and electrolytic refining, are complex and environmentally detrimental, and molten salt containing indium chloride reacts with air, degrading its quality and reducing recoverability.
Innovation Solution
A molten-salt electrolytic refining apparatus and method using a reaction container with a molten-salt electrolytic solution, an anode crucible, and a cathode crucible, where the temperature is adjusted above the melting point of the indium-tin alloy, and an electric current is applied using a fluoride-based electrolyte like LiF and KF to improve thermodynamic stability and reactivity, allowing continuous refining of high-purity indium.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If conventional methods (solvent extraction, stripping, cementation) are used to recover indium, then indium can be recovered, but the processes become complicated and environmental problems arise due to large amounts of acids used
Solution Approach 1:
The invention changes the fundamental parameters of the refining process by using molten salt electrolysis instead of conventional aqueous chemical methods. This involves changing the phase from liquid to molten state, using electric current instead of chemical reagents, and operating at elevated temperatures to simplify the process and eliminate environmental issues associated with acid usage
Solution Approach 2:
The invention replaces chemical mechanisms (solvent extraction, cementation reactions) with an electrochemical mechanism. Instead of using chemical reagents and complex chemical reactions, the process uses electric current to directly deposit indium from the molten salt electrolyte, simplifying the overall process flow
2Quantity of substance
If molten salt containing indium chloride is used, then electrolytic refining can be performed, but the molten salt reacts with air causing denaturation and quality deterioration
Solution Approach 1:
The invention creates an inert environment by conducting the electrolytic refining process in a sealed crucible that prevents contact between the molten salt electrolyte and air. This inert environment maintains the stability of the molten salt containing indium chloride, preventing oxidation and denaturation while allowing continuous operation
Solution Approach 2:
The invention uses a crucible as an intermediary barrier between the reactive molten salt and the air. The crucible material is selected to be chemically inert and resistant to molten salt corrosion, mediating the interaction and preventing direct contact that would cause degradation
3Quantity of substance
If electrolytic refining is performed with molten salt, then indium can be recovered, but reactivity issues with crucibles and electrodes reduce recoverability and industrial applicability
Solution Approach 1:
The invention changes the temperature parameter to maintain the crucible and electrode materials in a solid state while the electrolyte is in a molten state. This temperature control prevents unwanted reactions and material degradation, improving the ease of manufacture and industrial applicability
Solution Approach 2:
The invention uses composite or specially selected materials for the crucible and electrodes that exhibit both chemical inertness and thermal stability. These materials are designed to resist reaction with the molten salt electrolyte while maintaining structural integrity at operating temperatures
4Productivity
If a continuous electrolytic refining process is implemented, then productivity improves, but process control and stability become more challenging
Solution Approach 1:
The invention implements continuous electrolytic refining where the molten salt electrolyte continuously dissolves indium from the anode and deposits it on the cathode. This continuous operation eliminates idle time between batches, improving productivity while the sealed crucible design maintains process stability
Solution Approach 2:
The invention incorporates process monitoring and control mechanisms that provide feedback on the electrolytic refining process. This allows real-time adjustment of parameters such as current density and temperature to maintain optimal conditions for continuous operation
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 approach effectively recovers high-purity indium by improving process yield and productivity while minimizing environmental impact and avoiding reactivity issues with crucibles and electrodes.
Implementation Method 1
adjusting the temperature of a molten-salt electrolytic solution to be equal to or greater than the melting temperature of a raw-material alloy using a heater
Implementation Method 2
applying an electric current to an anode and a cathode, thus performing an electrolytic refining process
Implementation Method 3
applying an electric current to an anode and a cathode, thus performing an electrolytic refining process
Data Source
AI summary
The present invention provides a molten-salt electrolytic refining apparatus for refining a raw-material alloy containing indium using a molten-salt electrolytic refining method. The molten-salt electrolytic refining apparatus includes a reaction crucible provided in a reaction container so as to be filled with a molten-salt electrolytic solution, an anode and a cathode immersed in the molten-salt electrolytic solution, an anode crucible in which a liquid raw-material alloy is contained, a cathode crucible in which at least one raw-material metal included in the raw-material alloy is recovered in a liquid phase, and a heater provided so that the temperature of the molten-salt electrolytic solution is adjusted to be equal to or greater than the melting temperature of the raw-material alloy. The present invention also provides a molten-salt electrolytic refining method which includes recovering indium (In) from an indium-tin (In—Sn) alloy using a molten-salt electrolytic solution containing fluoride.