Ionometallurgy: an academic exercise or promising approach?

Abstract

Metals and functional metal-containing compounds are indispensable mass products. Metals are produced from low-reactive resources that are activated by very high temperatures (pyrometallurgy) or aggressive chemicals (hydrometallurgy). These traditional and highly optimized processes are often environmentally problematic because they require a lot of energy and generate large quantities of waste. Nowadays, numerous metal oxides and sulfides can be dissolved in ionic liquids (ILs) or deep eutectic solvents (DESs) at moderate temperatures below 200 °C, at least on a laboratory scale. Some of these solutions are thermally and electrochemically stable enough to enable galvanic metal deposition. Moreover, valuable metal-containing compounds can by synthesized from them. This review discusses whether such ionometallurgical metal extraction could be a viable and sustainable alternative to conventional processes, focusing on the examples of copper, cobalt and aluminum. Among the various factors that are crucial for the sustainability and economic feasibility of ionometallurgical processes, we mainly focus on the chemical aspects, but also take a look at the availability, environmental impact and reusability of the new solvents. Although the challenges associated with ionometallurgy are great, especially when it comes to upscaling, ionometallurgy could contribute to a more sustainable production of metals and metal compounds and also provide rewarding results in other areas, e.g. battery applications.