Technical and Environmental Considerations for Valorisation of Mine Tailings.

Technical and Environmental Considerations for Valorisation of Mine Tailings. Abstract This thesis investigates the valorisation of copper mine tailings, focusing on their potential as a valuable secondary resource. This study explores the recovery of residual minerals and the transformation of residual waste into commercially viable products, such as cement, ceramics and geopolymers. Various case studies are analysed, evaluating the technical and environmental feasibility of different reprocessing methodologies. Chapter 1 introduces the problem of tailings management and the importance of developing efficient strategies for resource recovery. In Chapter 2, the scope of copper tailings valorisation is defined, with a detailed review of the available literature on the subject, highlighting gaps and opportunities for innovation. Chapter 3 focuses on the technical aspects of tailings valorisation, exploring both pyrometallurgical and hydrometallurgical routes. Case studies, such as copper and iron recovery from Taltal Tailings (Chile) and heap bioleaching of tailings from Zambia and China, are presented to assess the scalability and technical feasibility of the processes. A comparison of flotation, magnetic separation, and bioleaching techniques is made, with copper recoveries ranging from 57% to 66%, depending on the separation method. Chapter 4 shifts to the environmental implications of reprocessing copper tailings. A life cycle assessment (LCA) framework is developed, examining the environmental impacts of different reprocessing routes across various indicators, including climate change potential, cumulative energy demand (CED), and freshwater ecotoxicity. Case studies in Portugal and the EU provide insights into the environmental benefits and trade-offs of reprocessing sulfidic copper tailings. The analysis highlights the potential for significant greenhouse gas (GHG) reductions when substituting secondary materials in the production of ceramics and CSA cement, but also addresses challenges such as high energy consumption during secondary metal recovery processes.