Review on the mineral processing in ionic liquids and deep eutectic solvents

Mineral processing is one of the important methods of resource utilization, and flotation and leaching are the main methods of mineral processing. The conventional reagents used in these methods usually show that they may lead to health, environment, safety, and other related problems. In order to make these methods safer and cleaners, it is necessary to explore the use of more green and environmentally friendly reagents. Ionic liquids (ILs) and deep eutectic solvents (DESs) are known as green solvents because of their wide liquid temperature range, good solubility, high thermal and chemical stability, almost nonvolatile and low toxicity. The application of ILs and DESs as agents in mineral flotation and extraction of valuable metal can provide new alternatives to traditional methods and processes and realize green and clean production. ILs and DESs have been successfully used to high-efficient float some minerals that are difficult to float, such as rare-earth minerals, quartz, and quartz hematite, as well as carbonate asphalt during recent years. Here we focus on the application progress, existing problems, and development direction of ILs and DESs in mineral processing. We introduced characteristics of ILs and DESs, and the research progress of ILs and DESs in green flotation of rare-earth ore, quartz and quartz hematite. The research works of ILs and DESs in the green leaching of chalcopyrite, sulfide ore, gold, and silver ore is summarized. Interactions of ILs and DESs with common minerals of soil also discussed to help understand the impact of ionic liquids on soil and groundwater. Compared with the traditional flotation and leaching reagents, the amount of ILs and DESs used is obviously smaller, and the selectivity and efficiency are better than that of the traditional system. After further research and optimization, it is expected to be developed into a new efficient and green mineral processing technology.