Funded by the Audi Environmental Foundation, a team at TU Bergakademie Freiberg is researching new ways of recovering raw materials through recycling. Metals such as indium, gallium and tin are limited - and essential for modern technologies such as fibre optics, photovoltaics and semiconductors. Almost every electronic device consists of components containing these elements. Using selective extraction, these raw materials are to be recovered from the fly ash produced during waste incineration.

The challenge is to develop specific molecules that specifically bind the desired metal ions. Put simply, the team is developing specially shaped "tweezers" that pick out only very specific metal ions from a fly ash solution, thus enabling separation. Each customised pair of "tweezers" - also known as a ligand - only fits exactly one metal ion, such as indium. The researchers use an acid to make the ligand release the ions again. In this way, the different metal ions can be separated from the mixture step by step and brought to a technologically usable purity. Once optimised, the process can be scaled up. The metals from the fly ash left over from the incineration of household waste are to be recovered so that they can be reused later in the manufacture of new products.