TURNING RED MUD GREEN
Electronic devices pose a challenge for efficient recycling and careful separation of all the myriad materials for proper disposal or additional use. In addition to electronics and electrical devices, rare earths can be abundant in certain forms of industrial production waste that is now typically landfilled. One form currently being targeted by Center for Resource Recovery and Recycling (CR3) researchers is red mud, the caustic material left over after aluminum is extracted from bauxite.
“Nearly three billion tons of this highly caustic material sits in holding ponds all over the world, often in developing countries,” says Marion Emmert, PhD, assistant professor of chemistry and biochemistry. “When those ponds leak, it kills the surrounding ecosystems.”
In her lab, Emmert is just beginning to explore various approaches to chemically treat red mud to extract the rare earths. As with the approach taken with vehicle drive units, the solution will likely be a multistep process that separates the rare earths from the many other components of red mud. She is collaborating on the project with Brajendra Mishra, PhD, Kenneth G. Merriam Professor of Mechanical Engineering and director of CR3, whose target is another of those components: iron oxide (also known as magnetite). The material is used in pigments for construction materials and in a variety of agricultural products, and depending upon its purity, it can sell for $300 to $6,000 per ton. Since magnetite can make up as much as 60 percent of red mud, a viable recovery method could be lucrative.
“We’re the only ones who have developed a process for producing magnetite from red mud and converting it to a saleable product,” Professor Brajendra Mishra says.
Mishra and his students have developed a process that involves chemically reducing the iron in red mud by exposing it to carbon monoxide. The processed material is then poured into a device that exposes it to a strong, revolving magnet. The magnetic iron oxide is pulled from the solution, while the remaining residue is recovered for further processing (including the recovery of titanium in the Mishra Lab and rare earths in the Emmert Lab). Having demonstrated the process in the lab, Mishra is currently working with Paul Kennedy ’67, president of Kennedy Affiliated Industries, to explore how to scale it up.
“We’re the only ones who have developed a process for producing magnetite from red mud and converting it to a saleable product,” Mishra says.
Adds Emmert, “this is exciting work, because if we come up with processes that work, we can have a huge impact, not just on the aluminum industry, but also in terms of environmental remediation."