title: Surface complexation of organic arsenic on nanocrystalline titanium oxide.
abstract: The adsorption mechanisms of monomethylarsonic acid (MMA) and dimethylarsinic acid (DMA) on nanocrystalline titanium oxide (TiO2) were investigated with X-ray absorption spectroscopy (XAS), surface charge and zeta potential measurements, adsorption edge, and surface complexation modeling. XAS data demonstrated that MMA and DMA formed bidentate and monodentate inner sphere complexes with the TiO2 surface, respectively. The charge and zeta potential behaviors of TiO2 as a function of ionic strength suggested that the point of zero charge (PZC) and isoelectric point (IEP) of TiO2 were identical at pH 5.8. Adsorption of MMA and DMA on TiO2 shifted the IEP to pH 4.1 and 4.8, respectively, indicating the formation of negatively charged surface complexes. A satisfactory interpretation of the experimental data was provided by the charge distribution (CD) multi-site complexation (MUSIC) model with the triple plane option under the constraint of the XAS evidence.
authors.affiliation: Center for Environmental Systems, Stevens Institute of Technology, Hoboken, NJ 07030, USA. cjing@stevens.edu
authors.forename: Chuanyong
authors.initials: C
authors.lastname: Jing
authors.forename: Xiaoguang
authors.initials: X
authors.lastname: Meng
authors.forename: Suqin
authors.initials: S
authors.lastname: Liu
authors.forename: Salem
authors.initials: S
authors.lastname: Baidas
authors.forename: Ravi
authors.initials: R
authors.lastname: Patraju
authors.forename: Christos
authors.initials: C
authors.lastname: Christodoulatos
authors.forename: George P
authors.initials: GP
authors.lastname: Korfiatis
mesh_terms: D000327:Adsorption; D001152:Arsenicals / Q000737:chemistry*; D003460:Crystallization; D006863:Hydrogen-Ion Concentration; D015394:Molecular Structure; D049329:Nanostructures / Q000737:chemistry*; D012680:Sensitivity and Specificity; D013052:Spectrometry, X-Ray Emission / Q000379:methods; D013499:Surface Properties; D014025:Titanium / Q000737:chemistry*
chemical_list: D001152:Arsenicals; C009495:titanium dioxide; D014025:Titanium