Microwave-Assisted Ionic Liquid Leaching for Waste Circuit Board Metal Recovery
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Solution Overview
Problem
Current methods for recycling precious metals from waste circuit boards, such as pyrometallurgical and hydrometallurgical technologies, face challenges including long process flows, low efficiency, environmental pollution, and the use of toxic reagents, making them inefficient and hazardous.
Innovation Solution
A microwave-assisted leaching method using imidazole ionic liquids for the extraction of precious metals from waste circuit boards, which allows for rapid digestion without crushing the boards, controlling heating, and achieving high selectivity and recovery rates while avoiding co-extraction of nickel and copper ions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If pyrometallurgical technology is used for waste circuit board recycling, then metal recovery is achieved, but environmental pollution from furan and dioxins occurs and temperature control is strict
Solution Approach 1:
The patent replaces the thermal field of pyrometallurgy with a chemical field using ionic liquids as leaching agents. The microwave heating system provides controlled thermal energy to activate the chemical leaching process, avoiding the uncontrolled high-temperature combustion that produces dioxins and furans. This substitution achieves metal recovery through selective chemical dissolution rather than thermal decomposition.
Solution Approach 2:
The patent changes the fundamental parameter of the recycling process from high-temperature thermal processing (pyrometallurgy) to controlled-temperature chemical processing with microwave assistance. By using ionic liquids with specific melting points and leveraging microwave heating's selective heating capability, the process operates at lower temperatures with precise control, eliminating the formation of harmful substances while maintaining effective metal recovery.
2Reliability
If hydrometallurgical technology is used for precious metal extraction, then metal transfer to solution is achieved, but the process is complicated and requires large amounts of reagents
Solution Approach 1:
The patent employs ionic liquids that serve multiple functions simultaneously: they act as leaching agents to dissolve metals, as extracting agents to separate precious metals from base metals, and as green solvents that can be recycled. This multi-functionality consolidates what would traditionally require multiple separate chemical processes into a single integrated system, reducing overall process complexity while maintaining high extraction efficiency.
Solution Approach 2:
The ionic liquid serves as an intermediary substance that facilitates the selective transfer of precious metals from the solid circuit board matrix into the liquid phase. Its unique properties enable it to selectively complex with precious metal ions while leaving base metals behind, and the same ionic liquid can then be used to back-extract and purify the precious metals, simplifying the overall flowchart compared to traditional multi-step hydrometallurgical processes.
3Reliability
If traditional leaching process is used, then metal dissolution is achieved, but leaching time is long and efficiency is low
Solution Approach 1:
The patent utilizes periodic microwave heating cycles to enhance the leaching process. The microwave energy is applied in controlled intervals, creating periodic thermal stress that accelerates the dissolution kinetics. This periodic heating combined with the chemical action of ionic liquids significantly reduces leaching time compared to continuous conventional heating, thereby improving productivity while maintaining complete metal dissolution.
4Area of stationary object
If crushing is performed before leaching, then surface area is increased, but energy consumption increases and environmental impact worsens
Solution Approach 1:
The patent applies local quality enhancement by using microwave radiation to create localized heating zones directly at the surface of the circuit board pieces during leaching. This localized thermal energy concentration accelerates the chemical reaction at the solid-liquid interface without requiring mechanical crushing to increase overall surface area, thereby avoiding the energy consumption and environmental impact associated with size reduction operations.
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
The method achieves high recovery rates of gold (98.5%), nickel (99%), and copper (99.5%) with minimal environmental impact and no secondary pollution, utilizing a clean and green extraction process.
Implementation Method 1
whole component microwave fast digestion
Implementation Method 2
precious metal extraction from ionic liquid
Data Source
AI summary
The invention discloses Method for whole component microwave fast digestion and precious metal extraction from ionic liquid of waste circuit board, and belongs to the field of hydrometallurgy. Based on the theory that microwaves can directly penetrate through a leaching medium to directly heat a circuit board, microwave-assisted leaching can reinforce mass transfer and heat transfer in the traditional leaching process, the leaching time is greatly shortened, and the leaching efficiency is improved. Before leaching, a waste circuit board does not need to be smashed, and environmental protection is achieved while energy is saved. The temperature rising process and reaction time of the reaction can be controlled, the whole process is conducted under the airtight condition, heat loss in the leaching process is avoided, the valuable leaching rate is high, the selectivity is high, and efficient leaching of valuable metal can be achieved. Precious metal leachate is extracted through imidazolium ionic liquid, the selectivity of the imidazolium ionic liquid to gold is high, and the co-extraction phenomenon of gold, nickel, copper and other ions is avoided. The method for extracting the precious metal leachate through ionic liquid is a green and clean recycling method, and the overall recycling rate of gold, nickel and copper can reach 99% or above.