Much is made of the scarcity of rare earth materials that are important for energy technologies like solar panels, wind turbines (for magnets), and battery storage. It’s important to understand that those materials are critical for the entire landscape of technologies that make up the high tech, computer enabled, microchip world – including, significantly, defense industries.
I’ve posted in the past about how increasing market demand has spurred creativity in squeezing exotic materials out of pollution streams such as coal ash and E-waste.
Here’s another pathway that clearly has a future.
In the late fall in Montana, the early evening quiet is often pierced by a cacophony of honking from Snow Geese flying high overhead. Hundreds of thousands of the magnificent birds stop at lakes in the state to rest and refuel on their annual trek from breeding grounds in the far north to their overwintering sites in the south. Last week as many as 10,000 geese, likely forced to land amid a snowstorm, settled on the toxic waters of the Berkeley Pit in Butte.
Officials are still tallying the death toll, but they estimate that thousands of geese have died from ingesting the contaminated waters of the former open-pit copper mine. Telescopes, drones, and aircraft are all being employed to count carcasses on the lake (unstable mine walls have prevented boat access for the last few years), and local residents have also found a handful of dead birds around town.
While methods to remove metals from water have been around a long time, in recent years the global scramble for metals critical to manufacturing and technology advances has given birth to a new generation of extraction technologies and processes.
One of the mineral-rich sources researchers are focused on is wastewater, including the brine from desalination plants, oil and gas fracking water and wastewater from mining. Researchers at Oregon State University estimate the brine from desalination plants alone contains metals valued at about $2.2 trillion.
“Water is the ore body of the 21st century,” said Peter S. Fiske, director of the National Alliance for Water Innovation at the Department of Energy’s Lawrence Berkeley National Lab California. “Technology now is allowing us to pick through the garbage piles of wastewater and pick out the high-value items.”
Research on the extraction of rare earths, a set of metallic elements, from waste is widespread as the need for them increases significantly. Researchers at Indiana Geological and Water Survey at Indiana University, for example, are studying the potential for mining rare earths in coal waste, including fly ash and coal tailings. And researchers at the University of Texas at Austin have created membranes that mimic natural ones to separate rare earths from waste.
Not only is mining wastewater more economical and faster than starting new mines, it is also cleaner.
Acid mine drainage is a highly toxic pollutant created when sulfur-bearing pyrite in rock is exposed to oxygen and water during mining. The drainage then oxidizes and creates sulfuric acid and poisons waterways. It’s one of the country’s biggest environmental problems, and tens of thousands of abandoned mines have contaminated 12,000 miles of streams.
However, the acid also dissolves zinc, copper, rare earths and other minerals out of the rock and into the water, providing an opportunity for the right technology to extract them — which didn’t exist until recently.
Paul Ziemkiewicz, director of the water research institute at West Virginia University, has researched the pit water in Butte for 25 years. He and a team of researchers from Virginia Tech and L3 Process Development, a chemical engineering firm, developed a method to extract critical metals from acid mine drainage in West Virginia’s coal mines, the same process used in Butte. Large, densely woven plastic bags are filled with a mudlike sludge from the water treatment plant. The water slowly percolates out, leaving a preconcentrate of about 1 to 2 percent rare earths that need further refinement, with chemical processes. The final step in the patented process is an extraction with solvents that creates pure rare-earth elements.
“One of the nice things about acid mine drainage is the concentrates we get are particularly enriched in heavy rare earths,” Dr. Ziemkiewicz said. “The light ones aren’t as valuable.”
The Butte project is awaiting word on a Department of Defense grant of $75 million to build a concentrator, the last step needed to refine the preconcentrate to rare earths and begin full-scale production.
Zinc is also plentiful in the acid-mine-drainage mix here and, because it fetches a higher price, is important as a way to pay for the process. Nickel and cobalt are also extracted.
While rare-earth elements are much in demand, China produces a majority and manipulates prices to keep them low, which forces out competition. That’s why the Defense Department is funding much of the work on rare-earth elements and other metals. The United States has just one operational rare-earths mine, in Mountain Pass, Calif., which produces around 15 percent of the global supply of rare earths.