The process of gold extraction from electronic waste

Here’s a detailed overview of the extraction methods highlighted in recent research:

1. Initial Preparation
   Dismantling: E-waste, such as old circuit boards and electronic components, is manually or mechanically dismantled to separate valuable parts.
   Shredding: The dismantled components are shredded into smaller pieces to increase the surface area for subsequent chemical processes.
2. Chemical Extraction Methods
   A. Electrochemical Liquid-Liquid Extraction (e-LLE)
   Developed by researchers at the University of Illinois, this method uses electrochemical reactions to extract gold and platinum group metals from e-waste solutions. The process involves:
   Dissolving e-waste in an organic solvent.
   Streaming the solution through specialized electrodes in three columns for oxidation, leaching, and reduction.
   Converting metal ions into solid forms via electroplating, allowing for recycling of the solvent and minimizing waste1.
   B. Protein Sponge Method
   Researchers at ETH Zurich utilized whey protein byproducts to recover gold:
   The proteins were denatured in acidic conditions to create a sponge that attracts gold ions.
   After dissolving the electronic components in an acid bath, the sponge was introduced to capture gold ions effectively.
   The sponge was then heated to convert these ions into metallic gold flakes, yielding a high-purity nugget23.
   C. Hydrometallurgical Processes
   This approach involves leaching metals from e-waste using acidic or alkaline solutions:
   Acidic solutions dissolve metals, which are then recovered through precipitation or solvent extraction methods.
   Researchers have achieved up to 95% recovery rates using optimized processes that avoid toxic solvents78.
3. Biological Methods
   Some studies explore using microorganisms (like certain bacteria and fungi) to bioleach metals from e-waste. These organisms can selectively extract precious metals while minimizing environmental impact6.
4. Flash Joule Heating
   A cutting-edge method developed at Rice University employs intense electric pulses to vaporize metals from e-waste:
   The process heats the material rapidly, allowing for the condensation of metals into a liquid form for easy separation9.
5. Final Recovery and Purification
   After extraction, the recovered gold undergoes further purification processes such as melting and refining to achieve high purity levels suitable for commercial use.
   These methods not only enhance the recovery of precious metals from e-waste but also emphasize sustainability by reducing environmental impacts associated with traditional mining practices. As research progresses, these techniques are expected to become more efficient and widely adopted in e-waste recycling operations.