Review on advances in mineral processing technologies suitable for critical metal recovery from mining and processing wastes

Demand for technologies delivering renewable energy and improving energy efficiencies are set to increase with the worldwide movement towards low carbon economies. Many of these technologies are reliant on “critical metals”: metals considered both important to society and vulnerable to supply disruption. Significant concentrations of critical metals have reported to mining and processing wastes over time; thus, an opportunity exists to meet critical metal demand through re-processing of these wastes. Mining and processing wastes have significantly different properties to run of mine ores. This means that while the overall mineral processing sequence for mining and processing wastes is the same as run of mine ore, the best technologies to achieve the liberation, separation, and concentration of critical metals is different. There are a range of innovative technologies that can be used to liberate and separate critical metals from mining and processing waste. Mineral liberation can be achieved using stirred milling, which breaks up particles and removes hydrophilic surface that can prevent particle flotation. Particle separation based on size can be achieved using semi-inverted cyclones and hybrid classification technologies. Separation of minerals from gangue can be achieved using flotation, with fluidised bed reactors and reactor-separator induced air reactors being suitable for coarse and fine particles, respectively. Gravity concentration using counter flow fluidised bed separators is also suitable for separating minerals from gangue. This review provides an overview of these technologies, as well as an introduction to the sequence of events when undertaking mineral processing, for an audience not specialised in this discipline. However, extraction of any metal value from tailings is contingent on detailed mineralogical characterisation. Three case studies are presented to demonstrate the analysis that is necessary as a crucial first step towards valorisation. Ultimately, implementation of these technologies to extract critical metals from mining and processing wastes will not only aid in meeting future critical metal demand but is essential for achieving a sustainable circular mining system with near-zero waste.