- Mining rare earth elements from recycled LEDs
A method to mechanically separate LEDs could expedite processes to recycle them. The technique was developed by researchers in Germany at the Fraunhofer Project Group for Materials Recycling and Resource Strategies IWKS, which is under the mantle of the Fraunhofer Institute for Silicate Research ISC, based in Würzburg.
“Right now recyclers are starting to receive LED products, but currently they are often simply stored as there is no suitable recycling process available yet,” said researcher Jörg Zimmermann. “The main goal is to recover the valuable materials. It’s only a matter of time until recyclers will have to start processing LEDs.”
To recycle LED-based lighting elements efficiently, they must first be broken down into their constituent parts. When recycling the LED diodes themselves, it is important that they remain as intact as possible for collection. Courtesy of Fraunhofer ISC/IWKS.
The researchers adapted their experimental mechanical separation setup for use on retrofit LED lamps. However, they said the method works in principle also for other sizes, such as for LEDs from television sets or from automobile headlights, as well as from other electronic products.
LED lamps are manufactured with a variety of materials, including glass or plastic for the housing, ceramic or aluminum for the heat sink, copper for the resistors and cables — and more expensive elements such as indium and gallium inside the semiconductor diode, and rare earths such as europium and terbium in the phosphor material.
“To efficiently separate and recycle all components of a LED lamp, an entirely different approach is necessary — one that produces large quantities of semiconductor and phosphor materials.” If the entire retrofit is shredded, it is much more difficult to separate the materials.
To break the LED lamps into their component parts without destroying the LEDs themselves, the researchers used a process called “electrohydraulic comminution.” They separated the components at their predetermined break points with the help of shock waves created by electrical impulses in a water bath. They are continuing to test whether the comminution process can be repeated until the desired materials have been separated.
The group is able to adjust parameters of the setup — such as type and quantity of fluid, container size and electric pulse voltage — so that separation occurs precisely at the specified break points.
“In particular it is the number of pulses that determines how the components will separate,” Zimmermann said.
The researchers expect that the electrohydraulic comminution process could be used in other LED application areas following further study and improvement.
Breaking LED lamps down to the component level makes it easier to recover greater quantities of the materials contained in them, Zimmermann said. It enables recyclers and manufacturers to collect large quantities of similar components in which the concentration of individual elements is already higher. The reprocessing needs to involve larger quantities to be profitable for recyclers and manufacturers.
“Our research has demonstrated that mechanical separation is a viable method for improving the economics of LED lamp recycling.”
MORE FROM PHOTONICS MEDIA