Critical elements: opportunities for microfluidic processing and potential for ESG-powered mining investments

Abstract

Critical minerals are those minerals containing elements, typically metals, and element allotropes which play an irreplaceable role in the ongoing revolution in technology and manufacturing needed to progress society to a high-tech, clean-energy future. The global market for critical minerals is highly vulnerable due to supply chain monopoly risks. Moreover, the mining, processing and refining of these elements involves substantial environmental and health risks, including, but not limited to, ecosystem degradation, chemical pollution, and hazards related to chemical and particulate exposure. Countries such as Australia, therefore, have developed national critical minerals strategies, which include investment in research to develop improved recovery methods and processing technologies. Australia has escalated continuous flow chemistry and critical minerals as critical priorities of national interest. In lieu of this, this review paper assesses the role of solvent extraction and other processing innovations using microchannel systems for the recovery of critical minerals. Microfluidic devices have captured worldwide attention for miniaturising reactor dimensions and, hence, provide huge potential for advancing the application of chemical processes that require precise control, enhanced mixing and rapid reactions. For mineral processing, continuous-flow operation can lead to advantages for extraction efficiency, processing time (productivity), and selectivity. Thus, this review summarises the up-to-date extraction performance of microfluidic devices along classes of critical minerals, as defined by their grouping in the periodic table. Attention is given to the fluidic concept used, e.g. the flow patterns, and how the microfluidic system is configured. From there, the achieved performance is reviewed, both for model and real world extractant solutions, the latter includes multiple minerals and issues of selectivity. Finally, a proposed recommendation is that microfluidics used should aim to impact the whole processing and supply chain, and to support and contribute to ESG (Environmental, Social, and Governance) profiling, a crucial demand faced by the mining industry. The enabling technologies not only have the potential to change the environmental profile, but will also require a highly skilled and trained workforce, and hence can create new employment opportunities.