Hydrogen peroxide decay rate constants

Figure 5. Hydrogen peroxide decay rate constants in surface-water samples from Sharpes Bay (in June and September), Jacks Lake, Ontario, Canada, from the East (Station 23), Central (Station 84), and West Basin (Station 357) of Lake Erie and the Chesapeake Bay, plotted as a function of bacteria...

The first detailed investigation of the reaction kinetics was reported in 1984 (68). The reaction of bis(pentachlorophenyl) oxalate [1173-75-7] (PCPO) and hydrogen peroxide cataly2ed by sodium saUcylate in chlorobenzene produced chemiluminescence from diphenylamine (DPA) as a simple time—intensity profile from which a chemiluminescence decay rate constant could be determined. These studies demonstrated a first-order dependence for both PCPO and hydrogen peroxide and a zero-order dependence on the fluorescer in accord with an earher study (9). Furthermore, the chemiluminescence quantum efficiencies Qc) are dependent on the ease of oxidation of the fluorescer, an unstable, short-hved intermediate (r = 0.5 /is) serves as the chemical activator, and such a short-hved species "is not consistent with attempts to identify a relatively stable dioxetane as the intermediate" (68). 

Lepidocrocite (-y-FeOOH) has also been used as a catalyst for Fentonlike reactions [54]. First-order decomposition of hydrogen peroxide was observed in the presence of this catalyst. Peroxide decay at 20 g/L catalyst was found to be pseudo-first-order and pH-dependent, with rate constant values reported from 0.102 hr-1 at pH 3.3 to 0.326 hr-1 at pH 8.9. In this system benzoic acid degradation was fastest at the low pH value. Under these conditions, acid dissolution of the lepidocrocite was observed to produce... 

In a second serie of experiments the concentration of hydrogen peroxide in the droplets was varied in the range from 2 x 10 5 to 5 x 10 3 mol l l while the other experimental conditions were kept constant. The pH of the droplets was set to 4.0. Again the S(IV)aq decay showed a pseudo-first-order kinetic. The measured rate constants are plotted in a log-log diagram in Figure 5 in dependence of the respective H2O2-concentration. 

Hydrogen peroxide, cuprum perchloride, and perchloric acid were used as acceptors in aqueous solutions. The experimentally observed process of hydrated electron decay in solutions of these three substances obeyed the first-order reaction law. Kinetic characteristics of observed processes were calculated by the method of the least squares using 15-20 photo-oscillograms. Values of rate constants of corresponding pseudo-first order reactions are shown in Table I. There one can see also values of bimolecular rate constants calculated on the basis of above data. The rate constant does not vary occasionally within some limits but it changes monotonously with the variation of concentration. This may mean that some process of the decay of the intermediates was not taken into consideration. It was shown in earlier work (J), that we had satisfactory agreement with the experiment supposing that the process was the mono-molecular intermediates decay. 

Figure 3. Dependence of first-order rate constant for decay of hydrogen peroxide on concentration of Chiamydomonas sp.

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