Quantitative X-ray Analysis of Montmorillonite and Kaolinite Mixtures using Zinc Oxide and Corundum Intensity Standards
Poster Number
29
College
College of Arts and Sciences
Department
Chemistry, Physics, Geology, & the Environment
Faculty Mentor
Maria Gelabert, Ph.D.
Abstract
Mixtures of crystalline solids can be quantified using carefully collected X-ray data and least- squares refinement of structures, in order to match calculated to experimental data. Rietveld methods are commonly found in a variety of software programs that enable crystal structure refinement. Integrated intensities of different components in a mixture are proportional to the amounts present, thus providing a powerful, nondestructive method for quantitative analysis. Layered compounds, such as clay materials in soils, often exhibit significant preferred orientation, modifying X-ray intensities and introducing challenges to quantitative analysis of samples containing clays, minerals, and amorphous components. For all samples, X-ray powder diffraction data are collected over 3-4 hours, and component structures refined. Here, we present the exploration of different techniques toward a standard procedure for soil samples. For this project, initial experiments were done with quantitative mixtures of montmorillonite or kaolinite, and goethite. After refining each component structure with Rigaku PDXL2 software, integrated intensities produced weight percents within approximately 1% (kaolinite-goethite) and 10% (montmorillonite-goethite) of lab preparations. Current experiments incorporate intensity standards by quantitative addition of zinc oxide or corundum, and these samples are being analyzed with two software programs: PDXL2 (with a FullProf software core) and the Excel-based RockJock. The former software is packaged with the diffractometer software, and the latter is freeware developed specifically for clay-containing samples. Different sample preparations to minimize the effects of preferred orientation are also being examined. All of these analyses serve the development of best practices toward gaining reliable quantitative information on clay mixtures.
Course Assignment
CHEM351 – Hanna
Grant Support?
Supported by a grant from the Winthrop University Research Council
Start Date
21-4-2017 2:15 PM
Quantitative X-ray Analysis of Montmorillonite and Kaolinite Mixtures using Zinc Oxide and Corundum Intensity Standards
Richardson Ballroom
Mixtures of crystalline solids can be quantified using carefully collected X-ray data and least- squares refinement of structures, in order to match calculated to experimental data. Rietveld methods are commonly found in a variety of software programs that enable crystal structure refinement. Integrated intensities of different components in a mixture are proportional to the amounts present, thus providing a powerful, nondestructive method for quantitative analysis. Layered compounds, such as clay materials in soils, often exhibit significant preferred orientation, modifying X-ray intensities and introducing challenges to quantitative analysis of samples containing clays, minerals, and amorphous components. For all samples, X-ray powder diffraction data are collected over 3-4 hours, and component structures refined. Here, we present the exploration of different techniques toward a standard procedure for soil samples. For this project, initial experiments were done with quantitative mixtures of montmorillonite or kaolinite, and goethite. After refining each component structure with Rigaku PDXL2 software, integrated intensities produced weight percents within approximately 1% (kaolinite-goethite) and 10% (montmorillonite-goethite) of lab preparations. Current experiments incorporate intensity standards by quantitative addition of zinc oxide or corundum, and these samples are being analyzed with two software programs: PDXL2 (with a FullProf software core) and the Excel-based RockJock. The former software is packaged with the diffractometer software, and the latter is freeware developed specifically for clay-containing samples. Different sample preparations to minimize the effects of preferred orientation are also being examined. All of these analyses serve the development of best practices toward gaining reliable quantitative information on clay mixtures.
