Western Kentucky University

Enhanced Nanoporous Minerals for Energy Processes

Institution

Western Kentucky University

Abstract

The nanoporous crystalline mineral sitinakite (crystalline titanium silicate) is a highly selective fast ion conductor that is being used for targeted removal of cesium and strontium from high-level waste solutions at DoE facilities. In addition to environmental concerns, titanium silicates and similar zirconium and yttrium silicates, have a wide range of evolving applications from battery materials, hydrogen storage, and rare earth and transition element catalyst for gasses and petrochemicals. Sitinakite is stable under a wide range of pressure, temperature, and chemical conditions which make it an ideal host material to perform selective chemistries in extreme environments. Therefore, our investigation was to determine the fundamental structural properties of this unique mineral for exploitation toward other energy related applications. This research led to several discoveries that reveal multiple ion exchange steps that serve to enhance ion selectivity, and the host crystalline framework control these steps as well as the chemistry and hydration state of the native compound. To determine the exchange mechanisms, we collected high temporal resolution in situ spectroscopy data, coupled with diffraction and computational studies, to capture the ion exchange process from the natural sodium form, to the enhanced hydrogen form, and finally to the cesium exchanged structure. Recent advances to this century old puzzle in crystal engineering of rare minerals as well as new materials for hydrogen and REE catalysis, and how understanding the atomic scale properties can be used for novel designer nanostructured compounds are presented.

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Enhanced Nanoporous Minerals for Energy Processes

The nanoporous crystalline mineral sitinakite (crystalline titanium silicate) is a highly selective fast ion conductor that is being used for targeted removal of cesium and strontium from high-level waste solutions at DoE facilities. In addition to environmental concerns, titanium silicates and similar zirconium and yttrium silicates, have a wide range of evolving applications from battery materials, hydrogen storage, and rare earth and transition element catalyst for gasses and petrochemicals. Sitinakite is stable under a wide range of pressure, temperature, and chemical conditions which make it an ideal host material to perform selective chemistries in extreme environments. Therefore, our investigation was to determine the fundamental structural properties of this unique mineral for exploitation toward other energy related applications. This research led to several discoveries that reveal multiple ion exchange steps that serve to enhance ion selectivity, and the host crystalline framework control these steps as well as the chemistry and hydration state of the native compound. To determine the exchange mechanisms, we collected high temporal resolution in situ spectroscopy data, coupled with diffraction and computational studies, to capture the ion exchange process from the natural sodium form, to the enhanced hydrogen form, and finally to the cesium exchanged structure. Recent advances to this century old puzzle in crystal engineering of rare minerals as well as new materials for hydrogen and REE catalysis, and how understanding the atomic scale properties can be used for novel designer nanostructured compounds are presented.