Nucleophilic/Oxidizing Degradation of Paraoxon and Thioanisole using NH3 Modified Aqueous H2O2 Solution

Degradation of paraoxon and thioanisole (PhSMe) were studied using NH3 modified H2O2 solution as decontaminant. Degradation rates of paraoxon depend exponentially on pH of the modified solution. Nucleophilic substitution mediated by HOO- is the major degradation mechanism and at least two orders of magnitude faster than hydrolysis. Proton catalytic oxidation and solvent-aided oxidation contribute differently to the primary oxidation of PhSMe (PhSMe -> PhS(O)Me), and the apparent kinetic constants (k(ap)) of the primary oxidation show a three-stage profile with pH of the NH3-modified H2O2 solution. Secondary oxidation of PhSMe (PhS(O) Me -> PhS(O)(2)Me) is much slower than the primary oxidation in the modified H2O2 solution, and the yield of PhS(O)(2)Me depended exponentially on pH too. The best pH range for the NH3 modified H2O2 solution as a broad-spectrum decontaminant is at 9.5-10.0 since a balance of nucleophilic/oxidizing decontamination reactivity could be achieved.