The sorption of Ce(III) on three abundant environmental
minerals
(goethite, anatase, and birnessite) was investigated. Batch sorption
experiments using a radioactive 139Ce tracer were performed
to investigate the key features of the sorption process. Differences
in sorption kinetics and changes in oxidation states were found in
the case of the sorption of Ce(III) on birnessite compared to that
on other minerals. Speciation of cerium onto all of the studied minerals
was investigated using spectral and microscopic methods: high-resolution
transmission electron microscopy (HRTEM), electron energy loss spectroscopy
(EELS), and X-ray absorption spectroscopy (XAS) in conjunction with
theoretical calculations. It was found that during the sorption process
onto birnessite, Ce(III) was oxidized to Ce(IV), while the Ce(III)
on goethite and anatase surfaces remained unchanged. Oxidation of
Ce(III) by sorption on birnessite was also accompanied by the formation
of CeO2 nanoparticles on the mineral surface, which depended
on the initial cerium concentration and pH value.