Hydrogen peroxide chemical decay

The study of the chemical behavior of concentrated preparations of short-Hved isotopes is compHcated by the rapid production of hydrogen peroxide ia aqueous solutions and the destmction of crystal lattices ia soHd compounds. These effects are brought about by heavy recoils of high energy alpha particles released ia the decay process. 

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). 

The self radiolysis of a solution may change the chemical equilibria of the solution components. For example, the a-decay of plutonium decomposes water in a solution containing 1 mole of Pu, ca. 0.01 mole of H2O2 is produced per day. This hydrogen peroxide can react with the plutonium to form a precipitate of plutonium peroxide. To avoid this precipitation, nitrite ions are added to the solution to react with the hydroxyl radicals formed by the radiolysis and to eliminate the H2O2. 

Several pathways can account for the decomposition of hydrogen peroxide In natural waters. Some of these decay processes not only remove H2O2, but also result In the oxidation of chemicals, possibly Including various pollutants, that are present In natural waters. These processes Include direct oxidation (5), peroxidase-catalyzed oxidation (6), and free radical oxidation Initiated by photochemical or metal-catalyzed decomposition (7). Little Is known about the significance and rates of these various processes under environmental conditions, but they have all been shown to occur rapidly with certain organic substrates In the laboratory. 

---