Lasers secure rare raw materials
Lasers play an important role in the recycling of high-quality metal alloys. Scientists are now working on new processes to secure rare earths.
The technology of the future needs rare earths. There is growing demand for scandium, yttrium, lanthanum, and another 14 elements in this group. Since additional requirements from electric mobility, lightweight construction, 3D printing, and photonics is inevitable, market observers expect to see enormous increases in demand in the coming decades. There is a threat of supply bottlenecks and increasing prices.
Europe has no large deposits of these high-tech metals. So as not to rely completely on imports, scientists are looking for recycling solutions and innovative methods to recover rare earths from waste material. Photonics plays a key role in the research.
High-quality recycling with LIBS
Lasers already ensure clean separation of plastics and metals. For example, in laser induced breakdown spectroscopy (LIBS): For fractions of a second, strong laser pulses heat metals to several tens of thousands of degrees. Light-emitting plasma forms—the spectroscopic analysis of this plasma provides clear conclusions about the material composition. Imaging systems follow the analyzed metal parts and ensure that they are sorted automatically. What Fraunhofer ILT, InnoLas Laser, Raylase and partners began in 2008 in the LASMET project is now used in industry. The latest LIBS systems analyze 6,000 objects per minute at belt speeds of up to five meters per second and also sort out very small chopped metal scrap.
This reliable clean separation allows high-quality aluminum, titanium, magnesium, and nickel alloys to be reused with no losses in value or quality. ILT scientists are now using the LIBS method in the recovery of rare earths from electronic scrap. In the EU-funded “ADIR” project, together with nine research and industry partners from Poland, France, Italy, Austria, and Germany, they apply a process chain that should disassemble smartphones and computer circuit boards cleanly. If the laser spectroscopy indicates typical spectra of expensive raw ma-terials, the respective components are desoldered by laser and removed. The consortium will optimize the process and adapt it for the rough industrial conditions in a pilot plant. The yield outlook appears good: In electronic hardware, rare earths are much more concentrated than in nature.
Scandium from Greece
The low natural concentration is also a cost driver for scandium. At present, kilo prices are fluctuating between USD 1.500 and 3.000; at the beginning of this decade, it was above USD 15,000 in some cases. The metal is used for fuel cells, special optics, and as a light-weight construction enabler in the aerospace industry. The latter mainly because, in aluminum alloys, scandium contributes to much higher strength and corrosion resistance and simplifies processing. In combination with 3D printing, these alloys are regarded as the key to efficient lightweight construction. Increasing demand from optics and 3D printing brought material specialists, such as II-VI Incorporated, into the game. As part of a large consortium, the company is currently working in the EU project SCALE to develop new processes to recover scandium from waste materials in aluminum and titanium oxide production.
II-VI has developed a new process which should halve the costs of scandium recovery compared to current metallurgical methods. The patented selective ion recovery (SIR) is a continuous process in which scandium accumulates on chemically modified polymer resin and is dis-solved with a stripper material. The resin and stripper can be reused. In the laboratory, II-VI has shown that the process works even if the scandium concentration in liquid residues from aluminum production are in single-digit PPM (parts per million) ranges. On this basis, the SCALE consortium will now implement a pilot plant in Greece. In the SIR process it will process sludge containing 80 to 130 mg scandium per kilogram. Photonics does not play a role in the selective ion process. But, according to II-VI, it can’t work without: Scandium is detected with inductively coupled plasma-optical emission spectrometry (ICP-OES).