Strontium in Inorganic Materials Studied with High-Field Solid-State NMR Spectroscopy
EMSL Project ID
25440
Abstract
During prior research at PNNL, we found that DFS-QCPMG NMR on the 21.14 T spectrometer provides significant sensitivity enhancement for 87Sr, permitting studies of strontium bound in anhydrous strontium-selective micas. Unfortunately, strontium in hydrated versions of these same materials has proven non-detectable by NMR, even when an adequate quantity of strontium is present. Strontium has also proven non-observable in hydrated strontium-rich crystalline materials, natural phyllosilicate minerals, titanates, and tectosilicates. Our preliminary data suggests that this "invisible strontium" phenomenon is either the result of (i) extreme quadrupolar broadening due to distortions in the strontium coordination environment produced by the hydrating water, (ii) a dynamic process with a correlation time such that the strontium signal is invisible at room temperature, or (iii) strong multi-spin heteronuclear couplings with nearby 1H or 19F nuclei. In order to investigate these processes, it is necessary to perform 87Sr NMR experiments at varying temperatures, with high-power decoupling, and at the highest available homogeneous magnetic field. The sensitivity afforded by the high magnetic field will make it possible to (i) identify if dynamic processes play a critical role in 87Sr NMR of hydrated minerals, (ii) characterize any dynamic behaviors, and (iii) identify the strontium binding environment in hydrated materials. This research will have a direct impact on the design of strontium remediation methods and reactive transport models, leading to numerous peer-reviewed publications.
Project Details
Project type
Large-Scale EMSL Research
Start Date
2007-07-01
End Date
2010-09-30
Status
Closed
Released Data Link
Team
Principal Investigator
Team Members
Related Publications
NMR Studies of Heat-Induced Transitions in Structure and Cation Binding Environments of a Strontium-Saturated Swelling Mica Appl. Mag. Reson. (2007) 32, 595-612 DOI 10-1007/s00723-007-0042-z Printed in the Netherlands