‘Metal whispering’ enables recovery of pure and precious metals from electrical waste

April 12, 2021

April 12, 2021

Left: The technology brings the most reactive components to the surface, forming stalagmite-like spikes. Right: The least reactive components are left in the core surrounded by metal-oxide spikes, creating a ‘ship-in-a-bottle’ structure (Courtesy Martin Thuo/Iowa State University)

Researchers at the Iowa State University, Ames, USA, have developed a technology capable of recovering pure and precious metals from the alloys found in electrical waste. The process, which the team refers to as ‘metal whispering’, uses controlled applications of oxygen at relatively low temperatures to de-alloy a metal by slowly moving the most reactive components to the surface.

The technique leaves the least reactive components in a purified, liquid core surrounded by brittle metal-oxide spikes “to create a so-called ‘ship-in-a-bottle structure,’” states Martin Thuo, the leader of the research project and an associate professor of materials science and engineering at Iowa State University.

“The structure formed when the metal is molten is analogous to filled cave structures such as stalactites or stalagmites,” Thuo added. “But instead of water, we are using oxidation to create these structures.”

Thuo and the engineers in his research group want to control exactly how and where alloy components fall apart, or de-alloy. “It’s like being a metal whisperer,” he said. “We make things go the way we want.”

The engineers offered a more precise description in their paper ‘Passivation-driven speciation, dealloying and purification,’ published by the journal Materials Horizons. “This work demonstrates the controlled behaviour of surface oxidation in metals and its potential in design of new particle structures or purification/dealloying. By tuning oxidation via temperature, oxidant partial pressure, time and composition, a balance between reactivity and thermal deformation enables unprecedented morphologies.”

The technology works at lower temperatures of between 260°C and 370°C. Thuo continued, “What we demonstrate here is that the traditional electrochemical or high-temperature methods (above 1000°C) may not be necessary in metal purification as the metal’s reactivity can be used to drive separation.”

Besides metal purification and recovery, this new idea could also be applied to metal speciation – the ability to dictate creation and distribution of certain metal components. One use could be production of complex catalysts to drive multi-stage reactions.


April 12, 2021

In the latest issue of PM Review…

Download PDF

Extensive Powder Metallurgy industry news coverage, and the following exclusive deep-dive articles and reports:

  • Phoenix Sintered Metals: A story of transformation, growth and community from America’s PM heartland
  • World PM2024 Yokohama: The stage is set for the PM industry to find a path to sustainable growth
  • The state of Europe’s hard magnets industry and the challenge of optimising the mass production of Nd2Fe14B permanent magnets

The latest news from the world of metal powders, delivered to your inbox

Don't miss any new issue of PM Review, and get the latest industry news. Sign up to our weekly newsletter.

Sign up

Join our community

Discover our magazine archive…

The free-to-access PM Review magazine archive offers unparalleled insight into the world of Powder Metallurgy from a commercial and technological perspective through:

  • Reports on visits to leading PM part manufacturers, metal powder manufacturers and industry suppliers
  • Articles on technology and application trends
  • Information on materials developments
  • Reviews of key technical presentations from the international conference circuit
  • International industry news

All past issues are available to download as free PDFs or view in your browser.


Browse the archive


Looking for PM production equipment, metal powders, R&D support and more?

Discover suppliers of these and more in our
advertisers’ index and buyer’s guide, available in the back of PM Review magazine.

  • Powders & materials
  • Powder process, classification & analysis
  • PM products
  • Atomisers & powder production technology
  • Compaction presses, tooling & ancillaries
  • Sintering equipment & ancillaries
  • Post-processing
  • Consulting & toll sintering
View online
Share via
Copy link