Recycling rare earth metals has just gotten easier.
Rare earth metals (REEs), a set of 17 elements -including neodymium, cerium, and yttrium- that are found in the two rows at the bottom of the periodic table, are critical for the development of many modern-day technologies, such as telephones, hard-drives, electric cars, and flat-screen monitors. As natural reserves of REEs decrease, scientists have turned to recovering REEs from existing products, creating a closed circle of REE use.
Many older electronics and gadgets are full of REEs and recycling them can be environmentally hazardous. However, reclaiming REEs involves long purifications, lots of waste, and generally yields low results.
There is a need for a more efficient way to recycle REEs, and a new study published this week in Science Advances may have the solution. The team, led by James Tour of Rice University, proposed a simpler solution for extracting REEs from existing products using a quick flash of heat.
The proposed technique is ingeniously simple: shocking industrial waste with a pulse of electrical heat can make it easier to extract the REEs. The method is also twice as efficient as current methods and uses fewer hazardous chemicals. The strategy is versatile, too, efficiently extracting REEs from coal fly ash (produced from pulverized coal burning), red mud (also known as bauxite residue, an industrial waste created from extracting aluminum from bauxite ore), and electronic waste.
The researchers first combined their REE-containing-waste with a conductor and placed it in quartz tubes to begin the extraction. Then, they sent an electrical shock through the tube, which caused the tube’s internal temperature to spike to 3000 °C within a second and then cool down rapidly. The flash of electric heat releases REEs by chemically reducing them, making them more soluble and easier to extract.
The REEs are converted into soluble salts using diluted acid to treat the product while impurities precipitate out of the solution. Tour’s group’s technique uses acid 120 times less concentrated than the current method yet extracts twice the amount of REEs.
The researchers still have a long way to go before this technique can make a real-world impact, other experts in the field say. After the REEs are extracted, there is still the challenge of separating them into their individual elements if they are reused in other products. However, the technique is promising, and the study cites the low cost and high efficiency of the process. With just 600 kWh of energy ($12 per ton of fly ash), these researchers make REE recycling seem like a sustainable and achievable future.
Sources: Science News, Science Advances, American Geosciences Institute