Uranyl Adsorption at the Muscovite (Mica)/Water Interface Studied by Second Harmonic Generation

作者：Gomez Sarah A Saslow; Jordan David S; Troiano Julianne M; Geiger Franz M^*

来源：Environmental Science & Technology, 2012, 46(20): 11154-11161.

DOI：10.1021/es302879y

Uranyl adsorption at the muscovite (mica)/water interface was studied by second harmonic generation (SHG). Using the nonresonant chi(3) technique and the Gouy-Chapman model, the initial surface charge density of the mica surface was determined to be -0.022(1) C/m(2) at pH 6 and in the presence of dissolved carbonate. Under these same conditions, uranyl adsorption isotherms collected using nonresonant chi(3) experiments and resonantly enhanced SHG experiments that probe the ligand-to-metal charge transfer bands of the uranyl cation yielded a uranyl binding constant of 3(1) x 10(7) M-1, corresponding to a Gibbs free energy of adsorption of -52.6(8) kJ/mol, and a maximum surface charge density at monolayer uranyl coverage of 0.028(3) C/m(2). These results suggest favorable adsorption of uranyl ions to the mica interface through strong ion-dipole or hydrogen interactions, with a 1:1 uranyl ion to surface site ratio that is indicative of monovalent cations ((UO2)(3)(OH)(5)(+), (UO2)(4)(OH)(7)(+), UO2OH+, UO2Cl+, UO2(CH3COO-)(+)) binding at the interface, in addition to neutral uranyl species (UO2(OH)(2) and UO2CO3). This work provides benchmark measurements to be used in the improvement of contaminant transport modeling.

• 出版日期2012-10-16
• 单位西北大学