Surface speciation of yttrium and neodymium sorbed on rutile: Interpretations using the change distribution model.
Journal Article
·
· Geochimica et Cosmochimica Acta
- Texas Tech University, Lubbock
- Oak Ridge National Laboratory (ORNL)
- Illinois State Water Survey, Champaign, IL
- ORNL
- Wageningen University and Research Centre, The Netherlands
The adsorption of Y3+ and Nd3+ onto rutile has been evaluated over a wide range of pH (3 11) and surface loading conditions, as well as at two ionic strengths (0.03 and 0.3 m), and temperatures (25 and 50 C). The experimental results reveal the same adsorption behavior for the two trivalent ions onto the rutile surface, with Nd3+ first adsorbing at slightly lower pH values. The adsorption of both Y3+ and Nd3+ commences at pH values below the pHznpc of rutile. The experimental results were evaluated using a charge distribution (CD) and multisite complexation (MUSIC) model, and Basic Stern layer description of the electric double layer (EDL). The coordination geometry of possible surface complexes were constrained by molecular-level information obtained from X-ray standing wave measurements and molecular dynamic (MD) simulation studies. X-ray standing wave measurements showed an inner-sphere tetradentate complex for Y3+ adsorption onto the (110) rutile surface (Zhang et al., 2004b). TheMDsimulation studies suggest additional bidentate complexes may form. The CD values for all surface species were calculated based on a bond valence interpretation of the surface complexes identified by X-ray and MD. The calculated CD values were corrected for the effect of dipole orientation of interfacial water. At low pH, the tetradentate complex provided excellent fits to the Y3+ and Nd3+ experimental data. The experimental and surface complexation modeling results show a strong pH dependence, and suggest that the tetradentate surface species hydrolyze with increasing pH. Furthermore, with increased surface loading of Y3+ on rutile the tetradentate binding mode was augmented by a hydrolyzed-bidentate Y3+ surface complex. Collectively, the experimental and surface complexation modeling results demonstrate that solution chemistry and surface loading impacts Y3+ surface speciation. The approach taken of incorporating molecular-scale information into surface complexation models (SCMs) should aid in elucidating a fundamental understating of ion-adsorption reactions.
- Research Organization:
- Oak Ridge National Laboratory (ORNL)
- Sponsoring Organization:
- SC USDOE - Office of Science (SC)
- DOE Contract Number:
- AC05-00OR22725
- OSTI ID:
- 1050939
- Journal Information:
- Geochimica et Cosmochimica Acta, Journal Name: Geochimica et Cosmochimica Acta Vol. 95; ISSN GCACAK; ISSN 0016-7037
- Country of Publication:
- United States
- Language:
- English
Similar Records
Surface Complexation of Neodymium at the Rutile-Water Interface: A Potentiometric and Modeling Study in NaCl Media to 250°C
inner-sphere complexation of cations at the rutile-water interface: A concise surface structural interpretation with the CD and MUSIC model
Rb+ and Sr2+ adsorption at the TiO2 (110) - electrolyte interface observed by resonant X-ray reflectivity.
Journal Article
·
Fri Dec 31 23:00:00 EST 2004
· Geochimica et Cosmochimica Acta
·
OSTI ID:978261
inner-sphere complexation of cations at the rutile-water interface: A concise surface structural interpretation with the CD and MUSIC model
Journal Article
·
Wed Dec 31 23:00:00 EST 2008
· Geochimica et Cosmochimica Acta
·
OSTI ID:1045879
Rb+ and Sr2+ adsorption at the TiO2 (110) - electrolyte interface observed by resonant X-ray reflectivity.
Journal Article
·
Thu Dec 31 23:00:00 EST 2009
· Langmuir
·
OSTI ID:1045874