American researchers have devised a new way to fish rare earths, crucial for many electrical appliances, from various types of waste.

You will find them in every mobile phone: rare earths, also known as rare earths. Most of these silver-white, rather soft metals are not really rare. However, they are so scattered in the earth’s crust that they are difficult to extract. Moreover, this is currently happening in a limited number of places: more than 80 percent of rare earths are mined in China.

That is why it would be great if we could properly recycle rare earths. Scientists at Rice University in Houston, Texas, now have a new method developed who can help with that.

Twice as much

The process the Americans work with is called flash Joule heating† In 2020, the researchers already showed that you can extract the ‘wonder material’ graphene – carbon that consists of layers only one atom thick – from coal and other materials. It now appears that the same ‘trick’ can also be used to remove rare earths from waste.

The researchers start with ash that is produced when burning coal, ‘red mud’ (a substance that arises during the production of aluminum), or electronic waste. They mix that with carbon black, a substance that consists of soot particles, so that the waste conducts electricity better. Then an electric shock goes through the material, which heats it to about 3000 degrees Celsius in one second.

Why is that useful? In waste, other substances form a glass layer around the rare earths, explains research leader James Tour in a press release† If you make that waste hot by means of flash Joule heating, the glass layer will break and the rare earths will be much easier to recover.

This recovery is done by bringing the material into contact with an acid. And, as the researchers showed: if you use their process, you can get by with a much less concentrated acid than with other methods. Moreover, with this you remove about twice as much of the most rare earths from your waste.

From cylinder to fabric

Yongxiang Yang, who leads the Metals Production, Refining and Recycling research group at TU Delft, says he has confidence in the scientific principles behind the method and its operation. As far as he knows, this way of recycling rare earths is also really new. “I haven’t read about it in scientific papers before.”

However, he doubts the economic feasibility. To heat a ton of fly ash in this way, 600 kilowatt hours of energy is needed. According to the researchers, that costs about 12 dollars (as a Dutch energy consumer you pay a lot more† “That gives you less than a kilo of rare earths,” says Yang. The question then, he continues, is whether a kilogram of recycled rare earths yields enough to make those energy costs worth it.

From the lab to the real world

Yang also has doubts about scaling up the method. “If you apply this method to a large amount of material, you are essentially making a stone cylinder with a diameter of one to five meters. You will first have to break them into pieces, and those pieces you have to pulverize into dust again.” And that will require some brute force.

Anyway, recycling remains a noble pursuit – and when it comes to these kinds of sought-after, hard-to-win elements, the importance is quite clear. Now it’s a question of waiting to see if the method can overcome all the hurdles on the long road from the lab to the ‘real world’.