(450e) Scale-up of Laminar Co-Flow Separation Technology

In 2024, the U.S. economy imported a net $77 billion of processed mineral materials and had more than 50% import reliance for 40 of the 50 mineral commodities identified in the “2022 Final List of Critical Minerals” [1,2]. Included in those 40 critical minerals are magnesium (Mg) and 14 rare earth elements (REEs) which are of importance to technologies that build energy security. As global production of these elements has been largely restricted to China [1], there is growing interest in developing independent extraction processes from abundant and low-cost feedstocks such as Mg from seawater [3] and REEs from end-of-life REE magnets and electronic waste [4], thus mitigating potential supply risks. These feedstocks experience similar technical and economic challenges for separation due to variable and complex aqueous mixtures of ions in the feedstocks, and common ion separation and purification methods are energy-intensive and add costly reagents to the process.

The laminar co-flow method (LCM) is a promising separation process in which critical minerals can be selectively precipitated from complex feedstocks without the need for heat energy, electric fields, or complex chemical reagents. Recent work at Pacific Northwest National Laboratory successfully demonstrated the separation of high purity Mg(OH)₂ from seawater [3] and dysprosium precipitates from simulated leachate feedstocks [5]. Process development is currently limited to experiments in microfluidic devices at low flowrates, but commercial implementation of LCM technology for critical mineral separation will require the scale-up of co-flow channels for industrially relevant feedstock flowrates. Using Mg extraction from seawater as a representative system, we herein combined experiments, computational fluid dynamics, and cost modeling to identify important cost and scalability parameters for LCM. From experiments, we derived precipitation rates and selectivities as functions of Reynolds number, flow channel diameter, and residence time. Computational fluid dynamics models of the LCM system were in good agreement with experimental results and showed that a <5% difference in fluid densities is a limit for maintaining a well-defined reactive interface for critical mineral precipitation. We compared relative costs associated with numbering-up microreactors versus scaling-out the dimensions of the flow channel and identified Reynolds number (1/Re²) as a critical parameter in LCM scale-up economics. This work is a first-of-a-kind scale-up analysis of a laminar co-flow system of miscible fluids for mineral separation.

References

[1] U.S. Geological Survey, Mineral commodity summaries 2025, 2025. https://doi.org/10.3133/mcs2025.

[2] U.S. Department of Energy, 2023 Critical Materials Assessment, 2023. https://www.energy.gov/sites/default/files/2023-05/2023-critical-materi….

[3] Q. Wang, E. Nakouzi, E.A. Ryan, C.V. Subban, Flow-Assisted Selective Mineral Extraction from Seawater, Environ. Sci. Technol. Lett. 9 (2022) 645–649. https://doi.org/10.1021/acs.estlett.2c00229.

[4] A.B. Patil, V. Paetzel, R.P.W.J. Struis, C. Ludwig, Separation and Recycling Potential of Rare Earth Elements from Energy Systems: Feed and Economic Viability Review, Separations 9 (2022) 56. https://doi.org/10.3390/separations9030056.

[5] Q. Wang, Flow-driven enhancement of neodymium and dysprosium separation from aqueous solutions, RSC Sustainability 2 (2024) 1400. https://doi.org/10.1039/d3su00403a.