title: Adsorption and desorption of U(VI) on functionalized graphene oxides: a combined experimental and theoretical study.
abstract: The adsorption and desorption of U(VI) on graphene oxides (GOs), carboxylated GOs (HOOC-GOs), and reduced GOs (rGOs) were investigated by batch experiments, EXAFS technique, and computational theoretical calculations. Isothermal adsorptions showed that the adsorption capacities of U(VI) were GOs > HOOC-GOs > rGOs, whereas the desorbed amounts of U(VI) were rGOs > GOs > HOOC-GOs by desorption kinetics. According to EXAFS analysis, inner-sphere surface complexation dominated the adsorption of U(VI) on GOs and HOOC-GOs at pH 4.0, whereas outer-sphere surface complexation of U(VI) on rGO was observed at pH 4.0, which was consistent with surface complexation modeling. Based on the theoretical calculations, the binding energy of [G(···)UO2](2+) (8.1 kcal/mol) was significantly lower than those of [HOOC-GOs(···)UO2](2+) (12.1 kcal/mol) and [GOs-O(···)UO2](2+) (10.2 kcal/mol), suggesting the physisorption of UO2(2+) on rGOs. Such high binding energy of [GOs-COO(···)UO2](+) (50.5 kcal/mol) revealed that the desorption of U(VI) from the -COOH groups was much more difficult. This paper highlights the effect of the hydroxyl, epoxy, and carboxyl groups on the adsorption and desorption of U(VI), which plays an important role in designing GOs for the preconcentration and removal of radionuclides in environmental pollution cleanup applications.
authors.affiliation: †School of Environment and Chemical Engineering, North China Electric Power University, Beijing 102206, P. R. China.|⊥Collaborative Innovation Center of Radiation Medicine of Jiangsu Higher Education Institutions, Suzhou, Jiangsu, P. R. China.
authors.forename: Yubing
authors.initials: Y
authors.lastname: Sun
authors.affiliation: †School of Environment and Chemical Engineering, North China Electric Power University, Beijing 102206, P. R. China.
authors.forename: Shubin
authors.initials: S
authors.lastname: Yang
authors.affiliation: ‡Fukui Institute for Fundamental Chemistry, Kyoto University, Takano-Nishihiraki-cho 34-4, Sakyo-ku, Kyoto 606-8103, Japan.
authors.forename: Yue
authors.initials: Y
authors.lastname: Chen
authors.affiliation: §Key Lab of New Thin Film Solar Cells, Institute of Plasma Physics, Chinese Academy of Sciences, P.O. Box 1126, Hefei, 230031 Anhui, P. R. China.
authors.forename: Congcong
authors.initials: C
authors.lastname: Ding
authors.affiliation: §Key Lab of New Thin Film Solar Cells, Institute of Plasma Physics, Chinese Academy of Sciences, P.O. Box 1126, Hefei, 230031 Anhui, P. R. China.
authors.forename: Wencai
authors.initials: W
authors.lastname: Cheng
authors.affiliation: †School of Environment and Chemical Engineering, North China Electric Power University, Beijing 102206, P. R. China.
authors.forename: Xiangke
authors.initials: X
authors.lastname: Wang
mesh_terms: D000327:Adsorption; D006108:Graphite / Q000737:chemistry*; D007700:Kinetics; D008962:Models, Theoretical; D010087:Oxides / Q000737:chemistry; D014501:Uranium / Q000737:chemistry*; D014874:Water Pollutants, Chemical / Q000737:chemistry
chemical_list: D010087:Oxides; D014874:Water Pollutants, Chemical; D014501:Uranium; D006108:Graphite