Europe faces major challenges to guarantee its future raw-materials supply chain and as indicated in the EC’s new Circular Economy Action plan, a diversified and sustainable access to critical raw materials (CRMs) must involve maximizing the potential of our own resources. As Europe does not have unfettered access to ore deposits rich in CRMs, SOCRATES aims at laying the foundations of a diversified and sustainable supply chain for critical metals, with a focus on Ge, In, Ga and Sb. SOCRATES develops game-changing technology combinations: 1) to extract metals from distinct industrial-process residues, 2) to recover the metals from the extraction process, 3) to valorise the residual matrix into engineered products, while simultaneously performing an integrated assessment of the new flow sheets.
The objective of this project is to carry out a detailed characterization of low-grade industrial-process residues (i.e., Cu flotation tailings, iron (Fe) -rich sludges from electrolytic zinc refining, fayalite slags and incineration bottom ashes) before and after metal extraction, with the aim to determine the chemical composition, the mineralogical phase composition, distribution of phases and elements, porosity and oxidation states of the metal ions. It is important to know not only the concentrations of the different metals, but also in which mineral phases they occur, how these phases are distributed throughout the matrix and the size of the mineral grains. It is also crucial to evaluate the concentrations and the mineral phases after leaching, in order to know if the leaching was successful. Furthermore, an advanced in situ/operando characterization of waste residues will lead to a breakthrough in knowledge for structure-performance relationships, which will aid in improving their catalytic/binder potential. Last but not least, in-line with the catalytic valorisation side of the SOCRATES project, an additional objective of this project is to synthesize, characterize and evaluate zeolites based on wastes. Zeolites are aluminosilicates of alkaline elements, rare earth elements or other monovalent or multivalent metals and they are classified as microporous materials (a material containing well-defined pores with diameters less than 2 nm). Due to the presence of strong acidic sites, large specific surface area, high ion-exchange ability, high thermal stability and a defined system of micropores and channels, zeolites find application in catalysis. The high silica content of low-grade industrial-process residues (i.e Cu flotation tailings and incineration bottom ashes) makes them a potential source for the synthesis of zeolites. Given the chemical complexity of the waste residues and the method used to prepare the zeolites, it is important to investigate the presence of metal impurities and how they affect the zeolite framework, catalytic activity and its deactivation.