Development of Microscopically-Based Models for Prediction of the Impact of Surface Grain Coating on Mineral Dissolution and Leaching Rates
EMSL Project ID
18422
Abstract
Over the past two decades, molecular level information on the composition, structure, and nature of impurities in naturally occurring mineral phases and anthropogenic subsurface materials has become available in unprecedented detail. Unfortunately, our ability to use this information to predict the adsorption properties or dissolution rates of complex heterogeneous materials has not evolved as far. In particular, the ability to accurately predict the long-term dissolution and leaching rates of natural and anthropogenic heterogeneous materials remains as one of the "grand challenges" facing subsurface science. This inability to predict long-term dissolution and leaching rates can result in conservative modeling of the dissolution of complex waste forms based either on short term experiments or complete solid dissolution assumptions. This conservative approach in turn can result in the costly design and construction of contained engineered systems.One of the key factors limiting the ability to extrapolate mineral dissolution rates into the future is the changing surface properties of the subsurface materials principally as a result of the evolving nature of the surface grain coatings. The purpose of this project is to use and refine our knowledge of the microscopic processes leading to blockage of reactive dissolution sites on selected mineral surfaces and how this microscopic information can be used in macroscopic dissolution and release models. This research will be conducted under three specific tasks: 1) studies of selective site blockage and the impact on dissolution rates; 2) studies of surface phase formation using AFM, FTIR and SEM; and 3) development of dissolution models that incorporate the impact of key reactive site blockage and the microscopic form and extent of the mineral surface coverage. Finally, these microscopically-based dissolution models are fully integrated into our current geochemical modeling capability, specifically surface complexation models that have been previously incorporated into subsurface reactive transport models used at Hanford and elsewhere. This integrated capability will allow the microscopic information on mineral dissolution to be seamlessly integrated into field scale simulation.
Project Details
Project type
Large-Scale EMSL Research
Start Date
2006-07-26
End Date
2007-11-05
Status
Closed
Released Data Link
Team
Principal Investigator
Team Members