Metal Recovery from E-Waste via Supercritical CO2 Delamination
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Solution Overview
Problem
Current methods for recycling electronic waste, particularly printed circuit boards (PCBs), face challenges such as high energy and labor intensity, metal losses during mechanical processing, and the release of toxic gases and dioxins, with existing hydrometallurgical and pyrometallurgical processes being inefficient and environmentally harmful.
Innovation Solution
A method involving the treatment of waste materials with supercritical CO2 and acids to separate metals and polymers, followed by the use of organic ligands to form metal-ligand complexes, and electrochemical separation to recover metals like copper, gold, and rare earth elements, reducing the need for corrosive acids and high temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional mechanical processing (crushing, shredding, grinding) is used to separate metals from PCBs, then metal separation is achieved, but energy and labor intensity increase and metal losses occur
Solution Approach 1:
The patent replaces mechanical processing (crushing, shredding, grinding) with a chemical hydrometallurgical process using selective leaching agents. The chemical process dissolves metals from PCBs into solution, eliminating the need for energy-intensive mechanical size reduction while achieving complete metal recovery without losses.
Solution Approach 2:
The patent changes the state of metal recovery from solid mechanical separation to chemical dissolution. By using selective leaching agents that dissolve specific metals into aqueous solution, the process transforms solid-solid separation into liquid-phase extraction, achieving higher efficiency with lower energy input.
2Productivity
If pyrometallurgy (incineration and smelting) is used to treat PCBs, then metal recovery is achieved, but toxic gases and dioxins are released
Solution Approach 1:
The patent replaces pyrometallurgical heating and smelting processes with a hydrometallurgical chemical leaching process. This substitution eliminates high-temperature combustion that generates toxic gases and dioxins, while still achieving effective metal recovery through selective chemical dissolution.
Solution Approach 2:
The patent converts the harmful effect of high-temperature processing into a beneficial controlled chemical process. Instead of uncontrolled combustion generating toxins, the process uses selective leaching agents to dissolve metals under mild conditions, transforming a harmful thermal process into a clean chemical extraction.
3Productivity
If conventional hydrometallurgical processes are used, then metal extraction is achieved, but corrosive acids and high temperatures are required
Solution Approach 1:
The patent changes the chemical parameters of the leaching process by using selective leaching agents that operate under milder conditions. Instead of requiring highly corrosive acids and high temperatures, the process uses agents that selectively dissolve specific metals under controlled, less harsh conditions, reducing corrosion and safety hazards.
Solution Approach 2:
The patent applies local quality by using selective leaching agents that target specific metals within the PCB composition. Different leaching agents are chosen for different metal types, allowing selective extraction without requiring harsh conditions for all metals simultaneously, thus reducing overall corrosivity and temperature requirements.
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 enhances metal recovery efficiency, reduces energy consumption, minimizes toxic emissions, and allows for the selective extraction of valuable metals, offering a more sustainable and environmentally friendly recycling process for electronic waste.
Implementation Method 1
treating a waste feed stock with supercritical CO2 (scCO2) and at least one acid to produce a solid delaminated waste and a liquid delaminated waste
Implementation Method 2
treating the enriched-metal solid delaminated waste, liquid delaminated waste, or combinations thereof, with a solvent including one or more organic ligands to form a solution, the organic ligands configured to bind at least one target metal in the enriched-metal solid delaminated waste to form at least a first-metal-ligand complex
Implementation Method 3
electrochemically separating a first product from the solution, the first product including a first metal from the first-metal-ligand complex
Data Source
AI summary
A plurality of different metals, including precious metals, platinum group metals, rare earth elements, alkaline earth metals, etc., can be electrochemically recovered from waste materials such as ashes and e-waste, e.g., printed circuit boards. Waste feed stocks are treated with supercritical CO2 (scCO2) and acid to produce a solid delaminated waste and a liquid delaminated waste for recovery of elemental metals and metal compounds from each. Carbonation reactions can be used to convert and recover alkaline earth metals from the liquid delaminated waste. The solid delaminated waste can yield a solid gold product, and be further treated along with the liquid delaminated waste via a solvent including one or more organic ligands that bind target metals to form metal-ligand complexes. Electrochemical separation of the different metals, e.g., via stepwise variation of pH to release the metals from organic ligands having different pKa values, yields high purity metal product streams.