This primary study was undertaken to assess the use of EPR spectroscopy at different microwave frequencies to characterize the potential of geochemical materials as adsorbents for environmental remediation. Three sets of experiments were performed. In the first, a multifrequency EPR approach was used to study changes in the Fe signal corresponding to changes in Fe valence in two clay minerals containing structural iron. Spectra were collected at L-, S-, and X-band before and after treatment by buffered dithionite solutions. In the second set of experiments, a stopped-flow X-band resonator with attached mixer was used to estimate the homogeneous kinetics of the reaction between dithionite and chromate. Dithionite and chromate solutions at the same and widely differing ionic strengths were used and demonstrated a strong effect of ionic strength/viscosity on the reaction rate. The third set of experiments was conducted at X-band to attempt to identify surface Mn on single calcite crystals that had been treated with MnCl2 solutions. A strong signal from Mn impurities in the bulk crystal, however, shrouded the weak signal, if any, from the surface Mn.
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