Cyanobacteria could help in the extraction of rare earths from secondary sources.
The recycling of critical raw materials is becoming more important in view of Germany’s heavy dependence on imports. In addition to the extraction of rare earths and technology metals from electronic waste, residues from industry and mining are also developing into a source of materials. For example, the Helmholtz Institute Freiberg for Resource Technology and the TU Bergakademie Freiberg are researching so-called bioleaching processes, in which microorganisms extract raw materials from secondary sources such as slags and mining dumps.
The Technical University of Munich, in cooperation with Kaiserslautern University of Applied Sciences, is taking a different approach: it has successfully tested the suitability of cyanobacteria for biosorption. Instead of a dissolution process, a binding of the raw materials to the bacteria takes place here. This is because the bacterial biomass used in the experiment has a high proportion of sugar compounds with a negative charge. It attracts the positively charged rare earth particles.
This process is reversible, the researchers say, because the biomass can be reused after the metallic raw materials have been washed out. The process also takes place very quickly, they said. Just five minutes after the reaction begins, most of the rare earth element cerium contained in the solution has been bound, they said.
The practical suitability of the process is now to be tested in larger-scale trials.