Reactions of Cu(I) and Cu(II) with H2O2 in natural waters: kinetics, mechanism and the generation of reactive oxidizing intermediates

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Copyright: Xing, Guowei
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Abstract
The kinetics of reactions of nanomolar concentrations of Cu(I) and Cu(II) with H2O2 have been investigated in 0.7 M NaCl and 2.0 mM NaHCO3 at pH 8.0. At these low concentrations of Cu(II), the reaction between Cu(II) and H2O2 was found to occur via the free radical mechanism in which Cu(II) was utilized through one-electron reduction that converted H2O2 into the intermediate reactive radical species O2 with a rate constant of 4.6 x 102 M-1s-1. Measurements of both hydroxylated phthalhydrazide (PhthOH) CL product and the degradation of radiolabelled formate in the absence and presence of known HO scavengers indicated that the reaction between Cu(I) and H2O2 did not occur via a Fenton-like mechanism under the experimental conditions investigated here but involved the formation of a higher oxidation state of copper, Cu(III), with a rate constant of 74 M-1s-1. HO plays an insignificant role because the decomposition of Cu(III) to yield HO is very slow (occurring with an upper limit of 1.6 x 10-4s-1). Cu(III) however, acting as the dominant oxidant, reacts with the substrates that were present (although at much lower rates compared to those of HO ). A kinetic model based on the CuL approach has been developed and shown to satisfactorily describe the reaction kinetics of the inorganic Cu(I)/Cu(II)/H2O2/O2 system over a range of experimental conditions. Key reactions in this kinetic model have been determined by sensitivity analysis.
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Author(s)
Xing, Guowei
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Waite, T. David
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Publication Year
2012
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Thesis
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Masters Thesis
UNSW Faculty
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