Review on metal extraction technologies suitable for critical metal recovery from mining and processing wastes

The transition to low-carbon economies, advancements in high-tech and rapid uptake of electronic equipment will see increased demand over the coming decades for so-called “critical” metals: metals considered important to society and that are vulnerable to supply disruption. Consequently, there is now a global drive to find and develop critical metal resources. Significant concentrations of critical metals have reported to mining and processing wastes over time due to a range of factors, including unfavourable economics and unsuitable processing infrastructure. With expanding scope and scale of markets, mining and processing wastes now represent a largely un-tapped resource of critical metals. The reclamation of critical metals from solid mining and processing wastes involves mineral processing, metal extraction, and metal recovery. Metal extraction involves the separation of metals from a metal-bearing material using chemical reactions. Metal extraction from solid mining and processing wastes largely relies on established processing techniques. However, the overall process configuration can differ greatly from conventional primary production methods, and there is often an opportunity to streamline the reprocessing of wastes where the original production process has already done some of the required physical or chemical work. This review provides an overview of seven technologies: atmospheric leaching, pressure leaching, bioleaching, resin-in-pulp, pyrometallurgy, phytomining and solvometallurgy, that are suitable for extracting specific critical metals from solid mining and processing wastes. Eleven critical metals are considered in this review: cobalt, gallium, germanium, indium, lithium, nickel, rhenium, tellurium, tin, tungsten, and vanadium. The approaches discussed are important for the extraction of critical metals from mining and processing wastes now and into the future.