Jihae Yoon Stanford University

Event Info

Title:  Characteristics of Organobentonite and Study of Iodine Adsorption on Organobentonite Using X-Ray Adsorption Spectroscopy

Date: Oct 20, 2008
Location: 3105 Etcheverry Hall
Time: 4-5pm

Abstract

The adsorption of iodide on untreated bentonite and bentonites modified with organic cation (i.e., hexadecylpyridinium chloride monohydrate (HDP+)) was investigated, and the organobentonites were characterized using uptake measurements, micro X-ray diffraction (μ-XRD), and electrophoretic mobility measurements prior to reaction with KI solutions. I found significant differences in adsorption capacities of iodide depending on the bentonite properties as follows: iodide adsorption capacities were 439 mmol/kg for the bentonite modified with HDP+ at an equivalent amount corresponding to 200% of the CEC of bentonite whereas no adsorption of iodide was observed for the untreated bentonite. The molecular environments of iodine adsorbed on organobentonites were further studied using x-ray absorption spectroscopy (XAS). Quantitative analysis of EXAFS spectra of organobentonite samples indicates that iodine is bound to carbon and the coordination number and interatomic distances between I–C varied depending on the organic concentration on bentonite. In this study, we observed significant differences in the adsorption environments of iodide depending on the property of the bentonite, and suggest that these molecular-level differences result in an organobentonite that has potential as reactive barrier material around a nuclear waste repository containing radioactive iodide.

Speaker Biography

Dr. Yoon is a visiting scholar at Surface and Aqueous Geochemistry Group at Stanford University. Her research interests include characteristics of bentonite modified with organic compounds and its potential application as reactive barrier material around a nuclear waste repository containing radioactive iodine, which generated during the processing of nuclear energy and nuclear testing and were consisted of spent nuclear fuel as a fission-product are released into the environment as contaminants, which results in a serious environmental problem. For investigating the molecular environments of iodine adsorbed on organobentonites, synchrotron based technique (i.e., x-ray absorption spectroscopy (XAS)) was used. Before coming to Stanford, she worked as a lecturer at universities and a researcher at Institute of Geological Hazards and Industrial Resources in Pusan National University in Korea. During her dissertation research, she studied about some anionic contaminants (i.e., phosphate, nitrate, and sulfate) adsorption properties of organobentonites. Also, during graduated student she investigated the clay veins and clay minerals (i.e., illite, smectite, kaolin minerals) in the Paleogene granite in Kyeongju, Korea.