Rare earths are at the heart of almost every everyday electronic device. With expected growth in the areas of wind energy and electromobility, demand is expected to increase dramatically again in the coming years. China is currently the main supplier of rare earths. The European Commission wants to significantly reduce its dependence on Chinese raw materials. The Commission proposal stipulates that 15% of demand for critical raw materials should be covered by recycling by 2030.
rare earth
Rare earths include the elements cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium, and the chemically similar element yttrium.
But the goal still seems a long way off, at least for now. According to the German Leibnitz Association, only one percent of rare earths is currently recycled. Economically attractive and environmentally friendly recycling methods are lacking, says Dominik Schild from the Institute of Biotechnology at the International Management Centers and the University of Applied Sciences Krems (IMC FH Krems). Once it reaches a certain size, e-waste can no longer be sorted manually. However, rare earths only occur in small quantities and therefore cannot be easily extracted. They are generally crushed and deposited in landfill along with ceramic, plastic and other metal waste.
Gut bacteria can absorb rare earth elements
The team from the Krems University of Applied Sciences, together with colleagues from the Czech Academy of Sciences Třeboň, the Krems University of Advanced Education and the Karl Landsteiner Private University, are researching a method to be able to put the valuable metals back into production. Scientists have found a promising ally in the bacteria E.coli. Bacteria that occur naturally in the human colon, also called coli bacteria, can absorb rare earth elements.
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Shredded e-waste is fed to bacteria in the form of dissolved acid. The bacteria then absorb the rare earths inside the cell, and some of the earths also adhere to the cell wall. The reason why bacteria absorb metals is still controversial in the scientific community. The most likely explanation is that bacteria cannot chemically distinguish between substances that are useful to them, such as magnesium or calcium, or rare earths, says Schild.
Coliform bacteria test winner
One thing is certain: the method works in the laboratory without damaging the bacteria. In numerous experiments with a wide variety of bacteria, the most surprising successes have been achieved with coli bacteria, reports Schild. “Coli bacteria were the winners of our test, achieving an absorption rate of up to 85 percent.” Furthermore, intestinal bacteria are impressive due to their high availability: they are easy to cultivate, inexpensive and, above all, they have already been scientifically tested. described in detail.
The bacteria now grow in the reactor for a certain period of time and have the opportunity to absorb rare earth elements. The cells are then opened mechanically. “Then we have biomass and the metallic form of rare earths,” explains Schild.
IMC FH Krems coli bacteria under the microscope
Goal: First prototype by 2030
To separate the different types of metal, researchers at IMC FH Krems are working, among other things, with electrochemical deposition. To do this, the metals are placed in an electrolysis tank. The positively charged metal ions are attracted to the negatively charged cathode. Depending on the voltage (potential) applied, different elements are deposited on the cathode.
However, it will take some time before the laboratory’s research results are used in industry. Schild expects the first industrial prototype to appear by the end of the decade. However, some waste companies in Lower Austria have already expressed initial interest, it is said.