jz0c01091_si_liveslides.zip (7.52 MB)
Anions Enhance Rare Earth Adsorption at Negatively Charged Surfaces
online resource
posted on 2020-06-05, 15:06 authored by Srikanth Nayak, Kaitlin Lovering, Wei Bu, Ahmet UysalAnions
are expected to be repelled from negatively charged surfaces.
At aqueous interfaces, however, ion-specific effects can dominate
over direct electrostatic interactions. Using multiple in
situ surface sensitive experimental techniques, we show that
surface affinities of SCN– anions are so strong
that they can adsorb at a negatively charged floating monolayer at
the air–aqueous interface. This extreme example of ion-specific
effects may be very important for understanding complex processes
at aqueous interfaces, such as chemical separations of rare earth
metals. Adsorbed SCN– ions at the floating monolayer
increase the overall negative charge density, leading to enhanced
trivalent rare earth adsorption. Surface sensitive X-ray fluorescence
measurements show that the surface coverage of Lu3+ ions
can be triple the apparent surface charge of the floating monolayer
in the presence of SCN–. Comparison to NO3– samples shows that the effects are strongly dependent
on the character of the anion, providing further evidence of ion-specific
effects dominating over electrostatics.