Zeta potentials of the rare earth element fluorcarbonate minerals focusing on bastnäsite and parisite.
Advances in Colloid and Interface Science
© 2018 The Author(s). Open Access. This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made.
Rare earth elements (REE) are critical to a wide range of technologies ranging from mobile phones to wind turbines. Processing and extraction of REE minerals from ore bodies is, however, both challenging and relatively poorly understood, as the majority of deposits contain only limited enrichment of REEs. An improved understanding of the surface properties of the minerals is important in informing and optimising their processing, in particular for separation by froth flotation. The measurement of zeta potential can be used to extract information regarding the electrical double layer, and hence surface properties of these minerals. There are over 34 REE fluorcarbonate minerals currently identified, however bastnäsite, synchysite and parisite are of most economic importance. Bastnäsite-(Ce), the most common REE fluorcarbonate, supplies over 50% of the world's REE. Previous studies of bastnäsite have showed a wide range of surface behaviour, with the iso-electric point (IEP), being measured between pH values of 4.6 and 9.3. In contrast, no values of IEP have been reported for parisite or synchysite. In this work, we review previous studies of the zeta potentials of bastnäsite to investigate the effects of different methodologies and sample preparation. In addition, measurements of zeta potentials of parisite under water, collector and supernatant conditions were conducted, the first to be reported. These results showed an iso-electric point for parisite of 5.6 under water, with a shift to a more negative zeta potential with both collector (hydroxamic and fatty acids) and supernatant conditions. The IEP with collectors and supernatant was <3.5. As zeta potential measurements in the presence of reagents and supernatants are the most rigorous way of determining the efficiency of a flotation reagent, the agreement between parisite zeta potentials obtained here and previous work on bastnäsite suggests that parisite may be processed using similar reagent schemes to bastnäsite. This is important for future processing of REE deposits, comprising of more complex REE mineralogy.
This research was conducted thanks to funding by the UK's Natural Environment Research Council SoS RARE Grant Agreement No. NE/M 011429/1 and Mkango Resources Ltd. Support was also provided by Kroll Institute for Extractive Metallurgy, Department of Metallurgy and Materials Engineering, Colorado School of Mines. Work could not have been conducted without collaboration between the Critical Materials Institute and the SoS RARE project. Special thanks to Hao Cui and Dylan Everly of Colorado School of Mines for support on the Microtrac Stabino equipment and XRF. Travel costs for visiting researcher collaboration provided by a Camborne School of Mines Travel Trust Grant.
This is the final version of the article. Available from Elsevier via the DOI in this record.
Vol. 256, pp.152-162
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