Electrostatic Origin of Element Selectivity during Rare Earth Adsorption

Mitchell Miller, Yihao Liang, Honghao Li, Miaoqi Chu, Sangjun Yoo, Wei Bu, Monica Olvera De La Cruz, Pulak Dutta*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

9 Scopus citations


Rare earths, which are fundamental components of modern technologies, are often extracted from aqueous solutions using surfactants at oil-water interfaces. Heavier lanthanides are more easily extracted, even though all lanthanides are chemically very similar. Using x-ray fluorescence measurements and theoretical arguments, we show that there is a sharp bulk-concentration-dependent transition in the interfacial adsorption of cations from aqueous solutions containing Er3+ or Nd3+ in contact with a floating monolayer. The threshold bulk concentration of erbium (Z=68) is an order of magnitude lower than that of neodymium (Z=60), and erbium is preferentially adsorbed when the solution contains both ions. This implies that elemental selectivity during separation originates at the surfactant interface. Electrostatic effects arising from the interface dielectric mismatch, ionic correlations, and sizes of the ions explain the sharp adsorption curve and selectivity.

Original languageEnglish (US)
Article number058001
JournalPhysical review letters
Issue number5
StatePublished - Feb 8 2019

ASJC Scopus subject areas

  • Physics and Astronomy(all)


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