Surface structural ion adsorption modeling of competitive binding of oxyanions by metal (hydr)oxides
- Wageningen Univ. and Research Centre (Netherlands)
An important challenge in surface complexation models (SCM) is to connect the molecular microscopic reality to macroscopic adsorption phenomena. This study elucidates the primary factor controlling the adsorption process by analyzing the adsorption and competition of PO{sub 4}, AsO{sub 4}, and SeO{sub 3}. The authors show that the structure of the surface-complex acting in the dominant electrostatic field can be ascertained as the primary controlling adsorption factor. The surface species of arsenate are identical with those of phosphate and the adsorption behavior is very similar. On the basis of the selenite adsorption, The authors show that the commonly used 1pK models are incapable to incorporate in the adsorption modeling the correct bidentate binding mechanism found by spectroscopy. The use of the bidentate mechanism leads to a proton-oxyanion ratio and corresponding pH dependence that are too large. The inappropriate intrinsic charge attribution to the primary surface groups and the condensation of the inner sphere surface complex to a point charge are responsible for this behavior of commonly used 2pK models. Both key factors are differently defined in the charge distributed multi-site complexation (CD-MUSIC) model and are based in this model on a surface structural approach. The CD-MUSIC model can successfully describe the macroscopic adsorption phenomena using the surface speciation and binding mechanisms as found by spectroscopy. The model is also able to predict the anion competition well. The charge distribution in the interface is in agreement with the observed structure of surface complexes.
- OSTI ID:
- 316353
- Journal Information:
- Journal of Colloid and Interface Science, Vol. 210, Issue 1; Other Information: PBD: 1 Feb 1999
- Country of Publication:
- United States
- Language:
- English
Similar Records
Adsorption Equilibrium and Kinetics at Goethite-Water and Related Interfaces
Adsorption mechanisms of selenium oxyanions at the aluminum oxide/water interface