ABSTRACT
Most commercial processes are based on the photochemical generation of hydroxyl radicals, which then attack and oxidize the pollutants. However, there are some refractory pollutants, such as halogenated alkanes, that are slow to react. The hydrated electrons are detected indirectly using an electron paramagnetic resonance spectrometer in conjunction with the spin-trap 5,5-dimethyl-l-pyrroline N-oxide (DMPO). DMPO reacts with hydrated electrons in the presence of water to form the spin-adduct DMPO-H, whose nine-line spectrum is easily monitored, even in the presence of the hydroxyl radical adduct (DMPO-OH) which is often produced along with DMPO-H. The rate constant for a given pollutant molecule is deduced by measuring the initial rate of production of DMPO-H as a function of pollutant concentration. Since the pollutant and DMPO compete for the scarce species, the initial rate of production of DHPO-H decreases as the pollutant concentration increases.
