From waste to windfall: Engineers' new method extracts valuable materials from mining discards

Ores that contain metals such as nickel, cobalt, and copper are widely used to produce products like cables and batteries needed in the energy industry. Once those elements have been harvested through mining, leftover remnants are usually discarded. Johns Hopkins engineers believe that these less commercially valued members of the mineral world, called "gangue," are a potential resource for the creation of cleaner energy.

Chao Wang, associate professor in the Department of Chemical and Biomolecular Engineering and a member of the Ralph S. O'Connor Sustainable Energy Institute, is leading a team that has developed a system that uses robust acid-base chemistry and renewable electricity to cull valuable elements–including manganese, cobalt, nickel, and copper—from mining gangue. These extracted materials have many uses, including in the production of lithium-ion batteries used in electric vehicles.

"We use renewable energy to make acid and base, then we use the acid to leach the gangue minerals. Then we use the alkali strain to titrate the leached solutions. The result is valuable enriched materials," said Wang, who calls the new system "an electrosynthesizer."

The explicit mining of these kinds of minerals can be expensive and environmentally destructive, and as electric vehicles become more popular, there are concerns about looming shortages of the materials used to make them. Experts say that the metals and mining industry accounts for about 8% of greenhouse gas emissions globally. Wang's team's approach is less invasive and uses less energy, avoiding high-temperature thermochemical processing, minimizing the discharge of hazardous chemical wastes, and substantially reducing the carbon emissions usually produced by mining. It can also mesh with the current infrastructure.

"We can plug it into the existing mining industry—that's the whole point," Wang said.

This research is supported by a $2 million U.S. Department of Energy Advanced Research Projects Agency-Energy award as part of the E Mining Innovations for Negative Emissions Resource Recovery program, which aims to develop market-ready technologies that will increase domestic supplies of critical elements required for the clean energy transition.

The team includes Jonah Erlebacher, professor in the Department of Materials Science and Engineering; Rafael Santos, of the University of Guelph (Canada); and Christopher P. Kolodziej, of the Argonne National Laboratory. EDAC Labs is also the technology-to-market partner of this project.