The platinum group metals, Pt, Pd, Rh, have been used in numerous applications, ranging from production of chemicals to dental material construction, while the extensive use of automotive vehicles accounts for the majority of the consumption of these precious metals. Unfortunately, their continuously increasing demand and the simultaneous gradual depletion of their natural resources paint a bleak picture with regard to the future satisfaction of said demand. Although recycling of these metals from secondary sources has become a common practice, which could bridge the gap between their supply and demand, it is plagued by significant shortcomings, i.e., incomplete metal recovery and significant environmental impact.On the one hand, achieving complete metal recovery from end-of-life materials will further assist the conservation of natural resources, which are fairly limited and strictly localized. On the other hand, environmental impact of processes is nowadays, perhaps more than ever, a pressing issue that needs to be carefully evaluated and properly addressed. The scientific community has certainly developed, within the last decades, a heightened sensibility toward environmental protection, which is reflected in the strives it is making to minimize the detrimental effect of products and developed processes. In the same spirit, the following doctoral thesis was perceived and performed.The thesis focuses on the recovery of platinum group metals (Pt, Pd, Rh) from spent materials, specifically car catalysts, with the aid of ionic liquids and deep eutectic solvents. The topic addressed in this thesis was perceived and performed within the frame of the EU Project Platirus; the multinational project aimed to investigate novel and alternative recovery processes for platinum group metals from secondary raw materials. Key focus of the project was the development of novel extraction and separation technologies with potential for industrial upscaling, aiming for a sustainable process with high metal recovery and minimized environmental impact.Deep eutectic solvents based on the choline cation were investigated and successfully applied to the quantitative leaching/extraction of Pt and Pd and partial leaching (50%) of Rh, at mild process conditions. The possibility to increase Rh leachability was additionally explored, which was feasible (increase by approx. 20%) by pre-treatment of the car catalyst material at high temperature and inert gas atmosphere.Further separation of the platinum group metals by co-extracted metals, which are present in the car catalyst matrix, was evaluated by two different approaches, namely, liquid-liquid and solid-liquid separation. Commercially available and in-house synthesized hydrophobic ionic liquids were employed for the liquid-liquid separation via bi-phasic system formation with P66614Cl, yielding quantitative extraction of all three target metals and significant separation from the main interfering metal, i.e., Al. Although complete separation of platinum group metals was not achieved with this approach, it still offers two major advantages; recovery and reuse of the deep eutectic solvent for subsequent leaching cycles and a hydrophobic environment for platinum group metals which ideally serves for their recovery via electrodeposition. Direct recovery of the metals from the deep eutectic solvent with the aid of gas-diffusion electrocrystallization is also a distinct possibility, as demonstrated within the Platirus project.Alternatively, the immobilization of an ionic liquid on silica support via polymerization (polymerized supported ionic liquid phase) allowed for the fast and simple separation of Pt and Pd, leached in an acidic liquor, from other interfering elements, whereas the removal of Rh from the sorbent material is a topic that still needs to be addressed.