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

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.


Latest Industry News

Download the latest issue of PM Review

Our latest issue is now available to download in PDF format, free of charge.

As well as an extensive Powder Metallurgy industry news section, this 116-page issue includes the following exclusive articles and reports:

  • Technical trends in metal-cutting tools: An overview of ongoing innovation in one of PM’s key markets
  • Fatigue data for PM steels: How the world’s largest PM part producer is facing the challenges of data generation and organisation
  • Reducing CO2 emissions in the PM industry: A lifecycle analysis of servo-electric versus hydraulic powder presses
  • Nickel-free steel powders: Paving the way for sustainable Powder Metallurgy
  • Euro PM2020: PM functional materials in energy management and magnetic applications
  • More information

Industry News


Sign up to our free e-newsletter, sent weekly to industry professionals around the world. We'll also let you know each time a new issue of PM Review magazine is available.

Subscribe for a FREE digital magazine

PM Review is the leading international magazine for the Powder Metallurgy industry.
Published four times a year, it is available as a free download or through a print subscription

Connect with us

Powder Metallurgy: The original net-shape production process

Powder Metallurgy components are relied upon by a wide variety of manufacturing industries, from automotive to power tools, household appliances, chemical engineering, filtration and more.

The main reason for the technology’s success is its cost-effectiveness at producing high volumes of net-shape components, combined with its ability to allow the manufacture of products that, because of the production processes, simply cannot be manufactured by other methods.

To discover more about how the technology has revolutionised component production, browse our Introduction to Powder Metallurgy.

Latest industry news

Copy link