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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. [ABSTRACT FROM AUTHOR]

The short-lived 146Sm–142Nd isotope system traces key early planetary differentiation processes that occurred during the first 500 million-years of the solar system history. The variations of 142Nd/144Nd in terrestrial samples, typically within a range of ±20 ppm, are determined using high-precision mass spectrometry that requires quantitative separation of Nd from all other elements in the sample, including the neighboring lanthanides. Recent improvements in mass spectrometry have pushed the analytical precision of 142Nd/144Nd measurements down to ∼2 ppm. Non-mass-dependent isotope fractionation produced during Nd separation, however, is a major factor limiting the quality of the 142Nd data. Popular chemical separation methods using Ln resins have unpredictable nuclear field shift effects that generate anomalous Nd isotope ratios. In order to solve this problem and potentially resolve small 142Nd/144Nd variations within ±5 ppm, in this study, we present a new two-step column separation method that effectively removes the isobaric interferents of Ce, Pr and Sm, with a recovery rate of Nd greater than 98%. JNdi-1 standard solutions doped with these interfering elements and geological reference materials are tested to document the performance of this method. A set of titanite samples from the Pilbara Craton in western Australia were also investigated to test the potential isotope fractionation effects. The same samples were processed using our method and the widely used Ln method. In contrast to the nuclear field shift effects observed from the samples using the Ln method, the results based on our new method show no detectable isotope fractionation, which further confirms the reliability of this new column chemistry scheme that is optimized for ppm-level precision Nd isotope ratio measurement, especially for resolving small variations in 142Nd/144Nd caused by the decay of 146Sm. [ABSTRACT FROM AUTHOR]