MICROFLUIDIC SOLVENT EXTRACTION OF RARE EARTH ELEMENTS
Frederik H. Kriel1, Rik Catthoor1, Elisabeth Kolar1, John Ralston1, Scott Middlemas2, Gareth Hatch3, and
Craig Priest1*
1
University of South Australia, Mawson Lakes, SA, 5095, Australia.
Army Research Laboratory, Aberdeen Proving Ground, MD 21005-5069, USA.
3
Technology Metals Research, 180 S Western Ave #150, Carpentersville, IL 60110, United States.
*Corresponding author: craig.priest@unisa.edu.au
2
ABSTRACT
Liquid-liquid solvent extraction (SX) of rare earth elements (REEs) is carried out using hundreds of extract,
scrub, and strip stages. Microfluidic SX, which is the focus of this study, offers process intensification and
precise time-resolved investigations of extraction performance. We have previously shown that base metal
leach solutions can be extracted in a Y-Y design microfluidic device.1-2 Here, the extraction rate and
selectivity for REEs using Cyanex 572 is studied in a custom microchip. The approach relies on continuous
streams of aqueous and organic phases contacting one another in a microscale environment, such that the
flow is laminar and droplets are not formed. Figure 1(a) shows the extraction of various elements from a
rare earth oxide (REO) leach solution. The initial pH (0.7) was chosen to achieve a heavy-light REE split.
The extraction efficiency of the heavy REEs increases from Tb to Lu, as one would expect. Figure 1(b)
shows that the extraction of the REEs was rapid (selected elements shown here; Dy, Yb, and Lu) and,
compared to lab-scale bulk extractions, the extraction rates were generally faster (clearer difference for the
heaviest elements) These higher extraction rate may be attributed to the higher surface/volume ratios
involved. Our results indicate that micro SX is a powerful academic tool and may be useful in industry
where enhanced separation rates, process control, and/or selectivity are required.
(a)
(b)
Figure 1 – (a) Microfluidic SX from REO leach solution at pH 0.7 (initial) using Cyanex 572. (b)
Extraction efficiency versus contact time for Dy, Yb, and Lu using the micro and bulk SX methods.
REFERENCES
[1] Priest, C., Zhou, J., Sedev, R., Ralston, J., Aota, A., Mawatari, K., Kitamori, T., Chemical Engineering
& Technology 2012, 35, 1312-1319.
[2] Priest, C., Zhou, J., Klink, S., Sedev, R., Ralston, J., International Journal of Mineral Processing 2011,
98, 168-173.
KEYWORDS
microfluidics, rare earth elements, solvent extraction, separation, process intensification