Aqueous Electrolyte Solutions at Solid-Liquid Interfaces
This project is supported, in part, by the US Department of Energy.
Mr. Dimitrios Argyris is primarily responsible for conducting this research.
Objectives
Radioactive waste remediation is one of the most compelling technological challenges facing humanity. One of the methods currently available for treating liquid waste streams consists in ion-exchange processes in which the heavy metal radioactive ions are trapped within organic or inorganic materials and subsequently properly disposed of (e.g., by vitrification). For this process to be effective it is necessary to selectively adsorb all the radionuclides from the aqueous solution to the solid matrix, and prevent leakage. Unfortunately, the available theories for aqueous electrolyte solutions at interfaces, or confined within narrow pores do not provide a description of the systems sufficiently accurate for securing the design of effective decontamination processes.
Methods
To improve our predictive capabilities we will conduct a number of molecular simulations to design more efficient ion exchangers. We are studying the equilibrium and transport properties of thin (1-10 molecular layers) films of aqueous solutions containing radionuclides (Cs +, Sr 2+, and Th 4+) at contact with SiO 2, analcite clays, titania oxides, and ZSM-5 zeolites. These materials are used as ion exchangers or as back fillers in nuclear waste sites.
Potential Outcomes
Our research is aimed at (1) improving the selective radionuclide adsorption in ion exchangers by incorporating organic macromolecules (SDS surfactants, polystyrenes containing –SO 3 - functional groups, short fragments of keratin and casein); (2) developing a novel application for the atomic force microscope that will allow us to sample experimentally the structure of the systems considered in our simulations; and (3) understand the molecular phenomena responsible for the diffusion of heavy metal ions through the narrow pores present in rocks and clays, so that to prevent leakage of radionuclides to the environment. History teaches that answering fundamental questions yields revolutionary scientific advances with an array of practical applications. Understanding the equilibrium and transport properties of aqueous electrolyte solutions at interfaces will allow us, in the short term, to improve the design of ion-exchange processes for nuclear-waste remediation, and in the long term, to implement a number of engineering applications (e.g., self-assembly of nanometer-scale chemical factories, molecular pumps, and responsive self-healing devices).