GEOC 85 |
| Proton and metal ion binding to humic acids(HA) was recognized as an important factor in the control of metal speciation and mobility in aqueous and soil environments. However, their binding and competition behaviour on humic surface was not fully described due to the polydisperse mixtures of natural organic polyelectrolytes with different functional groups in humic materials. The simplified discrete binding group type of the model (Model A) was employed in this study. Model A was applied to describe three single metals and their competition binding on the humic surface. Model A considers only single carboxylic group type and phenolic hydroxyl group type, and a variable electrostatic interaction factor, expressed as polynomial equation. Meltal binding experiments were carried out with the batch type dialysis equilibrium method. Mass and charge balance experessions were used to calculate individual components of the system. The fit of Model A suggested that the major binding site for the three ions tested (Cd, Zn and Cu) was a bidentate chelate of the carboxyl groups. The model employed in this study presented good descriptions of the the two metals competions. However, the model showed weaknesses when applied to multi-metal systems, especially when metals with substantially different binding characteristics were present. ModelA presented a better prediction with adjusted Cu concentration (2:1:1 = Cu:Cd:Zn). |
|
Physical Chemistry of Soil and Aquifer Systems: A Symposium in Honor of Garrison Sposito
1:30 PM-5:10 PM, Monday, 11 September 2006 Moscone Center -- Room 256, Oral
Division of Geochemistry |