Fenton's oxidation of pentachlorophenol.

The combination of H(2)O(2) and Fe(II) (Fenton's reaction) has been demonstrated to rapidly degrade many organics via hydroxyl radicals. However, few studies have related hydroxyl radical generation rates with measured organic chemical degradation data. The goals of this work were to investigate the kinetics, stoichiometry, and intermediates of pentachlorophenol (PCP) degradation in the Fenton's reaction and to develop a mathematical model of this reaction system. Batch reaction experiments were performed to assess both initial transients and steady states, and special attention was given to the analysis of intermediates. Solutions of PCP (55 microM) and Fe(II) (200 microM) were treated with variable levels of H(2)O(2) (<850 microM), and the concentrations of these reactants and their products were measured. Partial PCP degradation and near stoichiometric dechlorination were observed at low initial H(2)O(2) concentrations. Higher H(2)O(2) doses achieved at most 70% dechlorination even though nearly all of the PCP was degraded. The reaction intermediates tetrachlorohydroquinone and dichloromaleic acid accounted for up to 5% of the PCP degraded. Organic carbon mineralization (transformation to CO(2)) was not observed. The ()OH scavenging effects of the PCP-by-products mixture were characterized as a lumped parameter in the reaction kinetics model, which provided reasonable predictions of experimental results at different oxidant concentrations and reaction time.