3 research outputs found
Exploring the Utility of Compound-Specific Isotope Analysis for Assessing Ferrous Iron-Mediated Reduction of RDX in the Subsurface
This work determines isotope enrichment factors for RDX during reduction by iron minerals. The values determined are used to assess the transformation of RDX at a site with groundwater contamination and in laboratory column reactors simulating in situ chemical reduction treatment
Facet-Dependent Oxidative Goethite Growth As a Function of Aqueous Solution Conditions
Nitroaromatic
compounds are groundwater pollutants that can be
degraded through reactions with FeÂ(II) adsorbed on iron oxide nanoparticles,
although little is known about the evolving reactivity of the minerals
with continuous pollutant exposure. In this work, FeÂ(II)/goethite
reactivity toward 4-chloronitrobenzene (4-ClNB) as a function of pH,
organic matter presence, and reactant concentrations was explored
using sequential-spike batch reactors. Reaction rate constants were
smaller with lower pH, introduction of organic matter, and diluted
reactant concentrations as compared to a reference condition. Reaction
rate constants did not change with the number of 4-ClNB spikes for
all reaction conditions. Under all conditions, oxidative goethite
growth was demonstrated through X-ray diffraction, magnetic characterization,
and transmission electron microscopy. Nonparametric statistics were
applied to compare histograms of lengths and widths of goethite nanoparticles
as a function of varied solution conditions. The conditions that slowed
the reaction also resulted in statistically shorter and wider particles
than for the faster reactions. Additionally, added organic matter
interfered with particle growth on the favorable {021} faces to a
greater extent, with statistically reduced rate of growth on the tip
facets and increased rate of growth on the side facets. These data
demonstrate that oxidative growth of goethite in aqueous systems is
dependent on major groundwater variables, such as pH and the presence
of organic matter, which could lead to the evolving reactivity of
goethite particles in natural environments