title: Enhanced adsorption of Eu(III) on mesoporous Al2O3/expanded graphite composites investigated by macroscopic and microscopic techniques.
abstract: Mesoporous Al(2)O(3) was intercalated into an expanded graphite (EG) interlayer to prepare mesoporous Al(2)O(3)/EG composites. The basal spacing of mesoporous Al(2)O(3)/EG composites was enlarged as compared to raw graphite from the X-ray diffraction analysis. The massive surface functional groups and wedge-shaped pores were observed in terms of potentiometric acid-base titration analysis and scanning electron microscope, respectively. The pH-dependent adsorption of Eu(III) on mesoporous Al(2)O(3)/EG composites was evidently independent of ionic strength. The maximum adsorption capacity of Eu(III) on mesoporous Al(2)O(3)/EG composites at pH 6.0 and T = 293 K was calculated to be 5.14 mg g(-1). Desorption kinetics and cyclic operation results showed that mesoporous Al(2)O(3)/EG composites presented high hydrothermal stability in aqueous solution. The thermodynamic parameters suggested that Eu(III) adsorption on mesoporous Al(2)O(3)/EG composites is an endothermic and a spontaneous process. The decrease of Eu-O bond distance with the increasing pH demonstrated that the adsorption mechanism between Eu(III) and mesoporous Al(2)O(3)/EG composites would shift from outer-sphere surface complexation to inner-sphere surface complexation in terms of extended X-ray absorption fine structure spectroscopy analysis.
authors.affiliation: Key Lab of Novel Thin Film Solar Cells, Chinese Academy of Sciences, P.O. Box 1126, Hefei 230031, PR China.
authors.forename: Yubing
authors.initials: Y
authors.lastname: Sun
authors.forename: Changlun
authors.initials: C
authors.lastname: Chen
authors.forename: Xiaoli
authors.initials: X
authors.lastname: Tan
authors.forename: Dadong
authors.initials: D
authors.lastname: Shao
authors.forename: Jiaxing
authors.initials: J
authors.lastname: Li
authors.forename: Guixia
authors.initials: G
authors.lastname: Zhao
authors.forename: Shubin
authors.initials: S
authors.lastname: Yang
authors.forename: Qi
authors.initials: Q
authors.lastname: Wang
authors.forename: Xiangke
authors.initials: X
authors.lastname: Wang
mesh_terms: D000327:Adsorption; D000537:Aluminum Oxide / Q000138:chemical synthesis / Q000737:chemistry*; D005063:Europium / Q000737:chemistry*; D006108:Graphite / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D007477:Ions / Q000737:chemistry; D009994:Osmolar Concentration; D016062:Porosity; D013816:Thermodynamics
chemical_list: D007477:Ions; D005063:Europium; D006108:Graphite; D000537:Aluminum Oxide