10.1021/acs.est.7b00946.s001
Bin Ma
Bin
Ma
Alejandro Fernandez-Martinez
Alejandro
Fernandez-Martinez
Sylvain Grangeon
Sylvain
Grangeon
Christophe Tournassat
Christophe
Tournassat
Nathaniel Findling
Nathaniel
Findling
Francis Claret
Francis
Claret
Ayumi Koishi
Ayumi
Koishi
Nicolas C. M. Marty
Nicolas C. M.
Marty
Delphine Tisserand
Delphine
Tisserand
Sarah Bureau
Sarah
Bureau
Eduardo Salas-Colera
Eduardo
Salas-Colera
Erik Elkaïm
Erik
Elkaïm
Carlo Marini
Carlo
Marini
Laurent Charlet
Laurent
Charlet
Evidence
of Multiple Sorption Modes in Layered Double
Hydroxides Using Mo As Structural Probe
American Chemical Society
2017
edge sites complexes
sorption isotherm
CaMoO 4 precipitation
Mo geometry
anion uptake mechanisms
CaAl LDHs
batch isotherm experiments
control anion uptake
time-resolved synchrotron-based X-ray diffraction
Mo K-edge X-ray absorption spectra
anion exchange mechanisms
anion exchange process
Layered Double Hydroxides
Multiple Sorption Modes
Structural Probe Layered
interlayer anion exchange
2017-04-18 00:00:00
Journal contribution
https://acs.figshare.com/articles/journal_contribution/Evidence_of_Multiple_Sorption_Modes_in_Layered_Double_Hydroxides_Using_Mo_As_Structural_Probe/4928681
Layered
double hydroxides (LDHs) have been considered as effective
phases for the remediation of aquatic environments, to remove anionic
contaminants mainly through anion exchange mechanisms. Here, a combination
of batch isotherm experiments and X-ray techniques was used to examine
molybdate (MoO<sub>4</sub><sup>2–</sup>) sorption mechanisms
on CaAl LDHs with increasing loadings of molybdate. Advanced modeling
of aqueous data shows that the sorption isotherm can be interpreted
by three retention mechanisms, including two types of edge sites complexes,
interlayer anion exchange, and CaMoO<sub>4</sub> precipitation. Meanwhile,
Mo geometry evolves from tetrahedral to octahedral on the edge, and
back to tetrahedral coordination at higher Mo loadings, indicated
by Mo K-edge X-ray absorption spectra. Moreover, an anion exchange
process on both CaAl LDHs was followed by in situ time-resolved synchrotron-based
X-ray diffraction, remarkably agreeing with the sorption isotherm.
This detailed molecular view shows that different uptake mechanismsedge
sorption, interfacial dissolution-reprecipitationare at play
and control anion uptake under environmentally relevant conditions,
which is contrast to the classical view of anion exchange as the primary
retention mechanism. This work puts all these mechanisms in perspective,
offering a new insight into the complex interplay of anion uptake
mechanisms by LDH phases, by using changes in Mo geometry as powerful
molecular-scale probe.