Recovery of metals from mining tailings by eco-friendly hydrometallurgical processes

Metal´s demand and price are increasing due to the global trend towards urbanisation and industrialisation. Metals and raw materials are crucial to Europe’s society, economy and industry. However, some of them show a high-supply risk due to high dependence of imports, being necessary to find alternative materials or new sources for their recovery. Additionally, the overall global reserves of high-grade ores are close to depletion. In this context, low-grade, complex ores like sulphide minerals and old waste deposits related to past mining activities have received much more attention in recent years as new metal sources. The main objective of the present work is the recovery of metals from mining tailings, mainly post-flotation wastes, by eco-friendly hydrometallurgical processes. The presence of low-grade minerals hinders metal extraction by traditional pyrometallurgical processes. Spanish mining tailings show different compositions depending on their origin. However, complex ores like sulphide minerals (pyrite; sphalerite; chalcopyrite; arsenopyrite and other polymetallic sulphides) are generally present. It is known that metals in the form of complex sulphide precludes their chemical leaching.  For this reason, some carbon materials have been studied during last years as efficient catalysts for the leaching of metals from complex sulphides. The present work will be performed during the project RTI2018-096695-B-C31 (Ministerio de Economía y Competitividad). Different mining taillings will be selected from Spanish mining areas and mix with corresponding carbon catalysts. Leaching experiments will be performed during 96 hours at 60 and 90ºC under continuous agitation. The results obtained in the project will contribute to better understanding of the influence of catalysts in the leaching of metals from mineral sulphides. 
Authors wish to thank Spanish Ministerio de Economía y Competitividad for economic support (RTI2018-096695-B-C31)