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MEASUREMENT OF HYDROXYL RADICAL ACTIVITY IN A SOIL SLURRY USING THE SPIN TRAP A-(4-PYRIDYL-1-OXIDE)-N-TERT-BUTYLNITRONE
Citation:
Huling*, S G., R. G. Arnold, R. A. Sierka, AND M. R. Miller. MEASUREMENT OF HYDROXYL RADICAL ACTIVITY IN A SOIL SLURRY USING THE SPIN TRAP A-(4-PYRIDYL-1-OXIDE)-N-TERT-BUTYLNITRONE. ENVIRONMENTAL SCIENCE & TECHNOLOGY 32(21):3436-3441, (1998).
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Description:
The spin trap compound a-(4-pyridyl-1-oxide)N-tert-butylnitrone (4-POBN) served as a probe to estimate the activity of Fenton-derived hydroxyl radicals (.OH) in a batch suspension comprised of silica sand and crushes goethite ore. The rate of probe disappearance was used to analyze system kinetics and oxidation efficiency under heterogeneous, Fenton-driven conditions. The .OH-(4-POBN) adduct produced by the reaction of 4-POBN with .OH was observed vua electron paramagnetic resonance to confirm the mechanism of 4-POBN transformation. The disappearance of 4-POBN with .OH in the sand/goethite slurry amended with H2O2 (150mM) was first-order in 4-POBN. Under the conditions of this experiments, the effective steady-state .OH concentration ([.OH]ss) was estimated at 1.2 x 10-15 and 6.5 x 10-16 M, when 4-POBN was initially present at 7-00 and 1440 uM, respectively. Observed kinetics were in qualitative agreement with a conceptual model in which H2O2 is consumed in both Fenton and non-Fenton reactions and 4-POBN competes with other slurry constituents for .OH. Reaction of H2O2 with .OH was an appreciable sink for .OH, but the reaction did not contribute significantly to H2O2 depletion. Nonproductive reactions involving H2O2 (those that did not contribute to .OH production) represented a significant source of overall reaction inefficiency, as defined.
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MEASUREMENT OF HYDROXYL RADICAL ACTIVITY IN A SOIL SLURRY USING THE SPIN TRAP A-(4-PYRIDYL-1-OXIDE)-N-TERT-BUTYLNITRONE