Look in the second row at the bottom of most periodic tables and you’ll find lanthanides separated from an archive of items that don’t know what to do with them. Lanthanides are a cohesive group that is difficult to distinguish from each other because of their similar colors and properties. Even for most scientists, they live in a cold and distant country, completely inorganic and far from the comfort of hydrogen, carbon and oxygen.
But these metals are crucial in order to make the modern world head. They are members of a group known as rare earth elements or rare earth elements that support everything from magnets that power clean energy technology to telescope lenses and to the screen of the device on which you read it. And to extract them is difficult and environmentally friendly.
Thus, chemists and engineers are trying to make the best use of rare earth substances that have already been processed by recycling them from industrial waste and old electronics. In a new study published Feb. 9 Advances in sciencethey show how they try to do it with bright flashes of electricity.
Most rare earth elements aren’t really that rare (certainly not compared to really rare elements like iridium), but they’re not easy to get. Once their ore is extracted from the ground, they need to be separated to make specialized products – a tedious process given their similar properties. Most homes for the extraction of rare earth products are made of lanthanum and cerium, but heavier metals such as neodymium and dysprosium are especially desirable for magnets used in clean energy technologies.
The vast majority (by some estimates, more than 90 percent) of world supplies today come from China, making the resource more vulnerable to geopolitical tensions. In 2010, after a Chinese fishing boat collided with Japan’s coast guard boat in disputed waters, China stopped exporting rare earths to Japan. The blockade did not continue, but since then Japan has spent years aggressively searching for alternative sources of rare earths. So are other countries.
More importantly, the extraction of rare earths comes at an environmental cost. “It’s energy- and chemically intensive,” says Simon Jovit, a geochemist at the University of Nevada in Las Vegas who hasn’t been involved in recent research. “Depending on how you process them, this includes high strength acids.” These acids can be leached into the environment.
[Related: How shape-shifting magnets could help build a lower-emission computer]
One way to reduce weight is to recycle products that already contain these elements, but this is still not common. Callie Babbitt, a professor of sustainability at the Rochester Institute of Technology in upstate New York, who also did not participate in the new study, says only 1 to 5 percent of the world’s rare earth elements are recycled.
This is why researchers are looking for new ways to split rare earths. Some tried bacteria, but feeding these microbes proved to be energy-intensive.
Now one group from Rice University has developed a method of recycling that relies on intense electricity, called “flash heating of joules.” Researchers behind it have previously tested it on old, shredded PCBs to rid them of precious metals such as palladium and gold, and heavy metals such as chromium and mercury before safely dumping them into agricultural soil.
This time, they applied rapid joule heating to other industrial by-products: coal ash, which is a pollutant from fossil fuel power plants, red mud, which is a toxic substance left over from the conversion of bauxite to aluminum, and , indeed, more e-waste. .
Their process looked something like this. They placed the substance they were smashing into a finger-sized quartz tube, where the electricity “flashed” to a temperature of about 5,400 degrees Fahrenheit. The separated components were then dissolved in solution for production by chemists later.
The process does emit some toxic compounds, but the system aims to capture them and prevent them from getting into the air. “If you do it industrially, you don’t just release these compounds into the air,” says James Tour, a chemist at Rice University and one of the study’s authors. “You would have captured them.”
“Our waste flow is very different,” explains Tour. Unlike strong nitric acid, which is often used to extract rare earth elements from the earth, their solution is a much weaker, more dilute hydrochloric acid. “If it had happened to you, I don’t think you would have even felt it,” says Tour.
However, even if you take a step forward in this study, it will be some time before heaps of industrial waste can be recycled to produce rare earth elements. “There’s been a lot of activity in this area, but I haven’t seen anything in the way of breakthroughs,” Jovit says.
[Related: You throw out 44 pounds of electronic waste a year. Here’s how to keep it out of the dump.]
According to Joey, one of the problems with heating flash-joules is that rare earth elements still need to be separated before they can be molded into gadgets. Moreover, the use of pollutants such as coal ash means that there will be other harmful residues in the process. “Extraction and recovery [rare earths] they contain only part of the bigger problem of managing this waste, ”says Babbitt.
When it comes to e-waste, it will be difficult to extract mountains of obsolete computers and phones for valuable components. For example, the number of rare earth items in an average smartphone is up to a fraction of a gram. And many consumers would not know where and how to recycle them.
However, Jovit believes that the solution may lie in products that increase the demand for rare earths. “One obvious thing is to change the way things are designed to make them more recyclable.”