title: Sorption of Eu(III) on humic acid or fulvic acid bound to hydrous alumina studied by SEM-EDS, XPS, TRLFS, and batch techniques.
abstract: To identify the effect of humic acid (HA) and fulvic acid (FA) on the sorption mechanism of Eu(III) on organic--inorganic colloids in the environment at a molecular level, surface adsorbed/ complexed Eu(III) on hydrous alumina, HA-, and FA-hydrous alumina hybrids were characterized by using X-ray photoelectron spectroscopy (XPS) and time-resolved laser fluorescence spectroscopy (TRLFS). The experiments were performed in 0.1 mol/L KNO3 or 0.1 mol/L NaClO4 under ambient conditions. The pH values were varied between 2 and 11 at a fixed Eu(III) concentration of 6.0 x 10(-7) mol/L and 4.3 x 10(-5) mol/L. The different Eu(III)/FA(HA)/hydrous alumina complexes were characterized by their fluorescence emission spectra ((5D0-F1)/ (5D0 --> 7F2)) and binding energy of Eu(III). Inner-sphere surface complexation may contribute mainly to Eu(III) sorption on hydrous alumina, and a ternary surface complex is formed at the HA/ FA-hydrous alumina hybrid surfaces. The sorption and species of Eu(III) in ternary Eu-HA/FA-hydrous alumina systems are not dominated by either HA/FA or hydrous alumina, but are dominated by both HA/FA and hydrous alumina. The results are important for understanding the sorption mechanisms and the nature of surface adsorbed Eu(III) species and trivalent chemical homologues of Eu(III) in the natural environment.
authors.affiliation: Institute of Plasma Physics, Chinese Academy of Sciences, P.O.Box 1126, 230031, Hefei, PR China.
authors.forename: X L
authors.initials: XL
authors.lastname: Tan
authors.forename: X K
authors.initials: XK
authors.lastname: Wang
authors.forename: H
authors.initials: H
authors.lastname: Geckeis
authors.forename: Th
authors.initials: T
authors.lastname: Rabung
mesh_terms: D000537:Aluminum Oxide / Q000737:chemistry*; D001578:Benzopyrans / Q000737:chemistry*; D005063:Europium / Q000737:chemistry*; D006812:Humic Substances; D008855:Microscopy, Electron, Scanning; D013057:Spectrum Analysis / Q000379:methods; D014965:X-Rays
chemical_list: D001578:Benzopyrans; D006812:Humic Substances; D005063:Europium; D000537:Aluminum Oxide; C005023:fulvic acid